Unsaturated Zone Flow and Transport Model Process Model Report Rev 00, ICN 02 

TDR-NBS-HS-000002

August 2000

EXECUTIVE SUMMARY 
The Unsaturated Zone (UZ) Process Model Report (PMR) describes the modeling, analysis and 
current understanding of fluid flow and chemical (solute and colloidal) transport through the UZ 
at Yucca Mountain. The UZ PMR is supported by 24 Analysis/Model Reports (AMRs) which 
provide detailed descriptions of the various UZ models and analyses. The primary purpose of 
the UZ PMR is to document models and analyses for Total System Performance Assessment 
(TSPA) that evaluate the post-closure performance of the UZ. The models in the UZ PMR 
consider two principal factors (factors identified by the Yucca Mountain Project that greatly 
affect the performance of the potential repository), which are seepage into drifts and radionuclide 
retardation in the UZ. Seven other factors (factors of secondary importance) that relate to 
climate/infiltration, percolation flux, and coupled processes are also considered. The other 
factors are climate, net infiltration into the mountain, UZ flow above the repository, coupled 
processes-effects on UZ flow, advective pathways in the UZ, colloid-facilitated transport in the 
UZ and coupled processes-effects on UZ transport. 
The UZ PMR models are built upon the Integrated Site Model (ISM) and conceptual models for 
flow and transport through the UZ that have been developed from site-specific data, together 
with scientific and technical knowledge associated with flow and transport at analog sites and 
other UZ studies. The construction of mountain- and drift-scale numerical grids for the models is 
based upon the geological characterization of the site at scales relevant to the intended purpose 
of, or process(es) described by, the specific model. Most of the models in the UZ PMR are 
based on continuum approximations and employ the dual-permeability approach with van 
Genuchten equations to describe characteristic curves of both the fracture and matrix continua. 
The models are supported by site data collected since the early 1980s and the results of field 
testing in boreholes and underground drifts, which allow for model calibration against field 
observations, and validation using independent data sets and/or field tests. Uncertainties 
associated with the models range from uncertainties in individual parameters and processes, to 
uncertainties in the conceptual and numerical models employed. Some of these uncertainties are 
due to the fact that the UZ at Yucca Mountain is very heterogeneous. Uncertainty is included in 
the models for use in TSPA. 
The major hydrogeologic units identified at Yucca Mountain are, in order from the land surface 
to the water table, the Tiva Canyon welded unit (TCw), the Paintbrush nonwelded unit (PTn), the 
Topopah Spring welded unit (TSw), the Calico Hills nonwelded unit (CHn), and the Crater Flat 
undifferentiated unit (CFu). These units are partially saturated with water. Generally, water 
occupies about half of the pore space in the TCw and the PTn, except for values near 90% at the 
transition between the TCw and PTn. Within the TSw, water saturations range from 60% to 
almost fully saturated, and saturations in the CHn are mostly greater that 90%. The water table 
elevation is approximately 400 to 800 meters (m) below ground surface. 
Current climate is expected to persist for approximately the next 600 years, followed by a 
warmer and wetter monsoon climate for another 1,400 years, and then a cooler, still wetter 
glacial-transition climate for the remainder of the 10,000-year compliance period. The current 
best estimate of average net-infiltration of 4.6 mm/yr is expected to increase to an average of 
12.2 and 17.8 mm/yr for the monsoon climate and glacial-transition climate, respectively. 
Percolating water derived from precipitation flows primarily in fractures in the welded units
(e.g., TCw and TSw), and in the rock matrix in the nonwelded units (e.g., PTn and CHn (vitric)). 
Although infiltration is highly episodic, with significant amounts expected to infiltrate for only a 
few days every 3 to 5 years, the PTn is expected to dampen these pulses, so that water flow 
below the PTn is assumed to be steady. 
The potential repository will reside at a depth ranging from 200 to 425 m below ground surface, 
and from 175 to 365 m above the water table, in three geological units within the TSw. About 
ten percent of the potential repository volume is located in the middle nonlithophysal unit, 78% 
in the lower lithophysal unit, and 12% in the lower nonlithophysal unit. More than 80% of water 
flow at the potential repository horizon is through fractures, while the remainder flows through 
the low permeability (10-16 to 10-18 m2) rock matrix. In general, as the infiltration/percolation flux 
increases, the fraction of the total water flow in the fractures also increases. Bomb-pulse 36Cl 
data have verified the existence of fast flow from the land surface to the potential repository 
horizon; most of the fast flow is associated with known faults. The fracture network 
permeability in the upper nonlithophysal unit is high but scale-dependent, with large-scale 
(100 m scale) permeability on the order of 5  10-11 m2, and smaller-scale (1 m scale) 
permeability ranging from 10-14 to 10-11 m2. Preliminary field tests show that the average 
permeability of the lower lithophysal unit may be an order of magnitude higher than that of the 
upper nonlithophysal unit. Geochemical data such as total chloride (Cl), nonbomb-pulse 36Cl 
and calcite fillings in fractures are used to build confidence in the conceptual and numerical 
models of flow and transport processes occurring in the mountain, and to constrain the 
predictions of local and global percolation flux. 
As a result of the varied geology, critical flow and transport processes differ between the 
northern and southern parts of the potential repository. Below the horizon of the potential 
repository, perched water bodies have been found primarily in the northern part of the potential 
repository area, where low permeability zeolitic rock units are abundant. The presence of the 
perched water bodies creates the potential for the lateral flow of water to nearby highpermeability 
vertical features, such as faults. The three-dimensional (3-D) simulations of flow 
and radionuclide transport in the northern part indicate that flow down the faults increases with 
depth below the repository, resulting in over 40% of the groundwater recharge occurring through 
faults. The potential lateral flow and flow through faults have important implications for 
radionuclide transport, by allowing rapid advective transport from the potential repository to the 
water table and bypassing of the rock matrix where matrix diffusion and sorption could promote 
retardation. Larger-size colloids (e.g., plutonium (Pu) colloids) that cannot diffuse into the matrix 
are particularly susceptible to rapid transport. Beneath the southern part of the potential 
repository, vitric rock units are present; the vitric rocks potentially provide efficient sorption of 
some radionuclides such as neptunium (237Np). Technetium (99Tc) and iodine (129I) are nonsorbing 
and potentially may provide the highest dose rates for the first 10,000 years of the 
potential repositorys life. Daughter products of plutonium (239Pu) such as uranium (235U) 
become important after 10,000 years, and therefore must be considered in the abstractions and 
models for Total System Performance Assessment (TSPA). 
The rate of water seepage into drifts is expected to be considerably less than the prevailing 
percolation flux and may be zero for areas where the percolation flux is lower than the seepage 
threshold for that location. This is because the drifts act as capillary barriers which divert most of 
the flowing water around the drifts. The seepage threshold, defined as the percolation flux below
which no seepage occurs (for a given location within a hydrogeological unit), depends upon 
various hydrological parameters, especially fracture permeability and the fracture van Genuchten 
alpha value. The average seepage threshold of the upper nonlithophysal unit is estimated to be 
200 mm/yr. Based on limited hydrological data and understanding of seepage processes, it is 
expected that the seepage behavior of the lower lithophysal and lower nonlithophysal units is 
similar to that of the upper nonlithophysal unit. Changes in the drift shape due to rock fall may 
increase seepage; however, estimates based on the current rock fall model show negligible 
effects on seepage. 
As the radioactive waste emits heat, coupled thermal-hydrological-chemical (THC) processes in 
the UZ rock mass may be important for time periods of up to about 10,000 years. The energy 
emitted will heat up the entire UZ extending 600 m from the potential repository footprint, with 
estimated temperature increases of 30 to 35C at the water table, and up to 5C at the ground 
surface. With the assumed design options (Enhanced Design Alternatives II and 50-year 
ventilation, currently under revision), boiling will occur around the drifts; the region 
experiencing the boiling temperature (~97C) will extend out to a maximum of 50 meters into the 
rock. Temperatures in the mid-pillar regions will increase to 80 to 85C, but sufficient drainage 
of condensate is predicted because of the relatively high fracture permeabilities of the potential 
repository hydrogeological units. As a result, the percolation flux during the thermal period will 
not greatly exceed the ambient percolation flux for most locations within the potential repository. 
The drift-scale models of THC coupled processes predict the chemistry of water and gases 
entering and occurring around the drifts, and the changes in hydrological properties expected 
from precipitation/dissolution processes. The results from the models indicate that the water 
entering the drifts will have relatively neutral pH values, ranging from 7 to 9, and total chloride 
concentrations that increase to a maximum of about four times the concentrations in the ambient 
pore water. The precipitation/dissolution of various chemical species and/or minerals was found 
to have negligible effects on fracture and matrix hydrological properties. 
The UZ PMR process models, specifically the Flow Model, the Seepage Model, the Drift-Scale 
THC Model and the Transport Model, are abstracted for use in TSPA. The degree of abstraction 
of these models varies from direct use of the process model in TSPA to using the model to justify 
neglecting certain processes. In the development of the process models, the uncertainties in 
parameters, processes, and conceptual models are identified and qualified where possible; TSPA 
then evaluates the importance of these uncertainties on the performance of the potential 
repository. 
In addition to the treatment of the various technical issues on UZ flow and transport, the UZ 
PMR summarizes concerns and comments by various overseeing bodies such as the Nuclear 
Regulatory Commission (NRC), the Nuclear Waste Technical Review Board (NWTRB), various 
peer review groups convened by the Yucca Mountain Site Characterization Project (YMP), and 
from various internal YMP workshops discussed in Section 2.5. The issues raised by the NRC 
are of particular interest. In support of the Site Recommendation (SR), the NRC will review 
current information about the Yucca Mountain site in the UZ PMR, as part of their statutory role 
in the high-level waste management program. The NRC issues are discussed in detail in Chapter 
4 of the UZ PMR.


1. INTRODUCTION 
The United States (US) Department of Energy (DOE) is evaluating Yucca Mountain, Nevada, 
for the development of a potential geological repository for the permanent disposal of the 
nations commercial and defense spent nuclear fuel and high-level radioactive waste. This 
evaluation includes analyses of the ability of the natural geologic and engineered barrier systems 
of this potential repository to prevent the migration of radionuclides to the accessible 
environment. The primary pathway to the accessible environment has been determined to be via 
the groundwater aquifer below the potential repository (CRWMS M&O 2000b). 
As the site-characterization effort at Yucca Mountain (YMP) is near completion, and the 
preliminary design of an Engineered Barrier System (EBS) and the potential repository layout 
are completed, the DOE is deciding whether to recommend the site. This activity is termed Site 
Recommendation (SR), and if the site is recommended, a License Application (LA) may be 
submitted to the Nuclear Regulatory Commission (NRC). A series of project documents that 
include the Yucca Mountain Site Description (YMSD), the Total System Performance 
Assessment (TSPA), and Process Model Reports (PMRs) will support any SR. The PMRs 
provide the technical basis for the higher-level YMSD and TSPA documents. Figure 1-1 is a 
schematic diagram that shows the relationships amongst all of these project documents. 
Regulatory requirements and the SR/LA design feed the allocation analysis and the Repository 
Safety Strategy (RSS) (CRWMS M&O 2000b). The RSS identifies the most important factors 
(principal factors) that are expected to affect the performance of the potential repository. 
TSPA is conducted to evaluate the postclosure performance of a potential repository at Yucca 
Mountain. Nine Process Models Reports (PMRs), of which this document is one, are being 
developed to summarize the technical basis for each of the process models supporting the TSPA. 
These reports cover the following areas: 
 Integrated Site Model 
 Unsaturated Zone Flow and Transport 
 Near Field Environment 
 Engineered Barrier System Degradation, Flow, and Transport 
 Waste Package Degradation 
 Waste Form Degradation 
 Saturated Zone Flow and Transport 
 Biosphere 
 Disruptive Events 
These PMRs are supported by Analysis/Model Reports (AMRs) that contain the more detailed 
technical information to be input into each PMR and the TSPA. This technical information 
consists of data, analyses, models, software, and supporting documentation that will be used to 
show the applicability of each process model for its intended purpose of evaluating the 
postclosure performance of the potential Yucca Mountain repository system. The PMR process 
will ensure the traceability of this information from its source through the AMRs, PMRs, and 
eventually to how that information is used in the TSPA. The PMRs also support the Site 
Description, a document that contains detailed information about the various aspects of the 
Yucca Mountain Site (see Figure 1-1).

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 2 August 2000 
This document is the PMR for unsaturated zone (UZ) flow and transport, hereafter referred to as 
the UZ PMR. The UZ PMR considers those features, events, and processes (FEPs) concerning 
flow and transport through the UZ that are expected to be important for evaluating the 
performance of the potential repository system; the FEPs are discussed in detail in Section 1.2.3. 
The UZ PMR is supported by 24 AMRs that cover all aspects of UZ flow and transport (see 
Figure 1-1). 
Some of these AMRs are, in essence, data reports with limited in-depth analysis; others primarily 
discuss development and documentation of computer codes and models, and the remainder 
document Performance Assessment (PA) abstractions of the models for subsequent use in TSPA. 
The main models included in the UZ PMR and the citations for their respective AMRs are listed 
in Table 1-1. The models form the basis of the UZ PMR both as integration and performance 
evaluation tools. Figure 1-2 is a graphic illustration of the interrelations of the models and their 
connections to TSPA. 
Table 1-1. The Main Models of the UZ PMR 
Model Title Acronym AMR Reference Dimensionality Abstracted 
for PA 
UZ PMR 
Section 
Climate Model CM USGS 2000, U0005 N/A Yes 3.5 
Infiltration Model IM USGS 2000, U0010 3-D Yes 3.5 
Calibrated 
Properties Model 
CPM CRWMS M&O 2000, U0035 1-D and 2-D No 3.6 
Flow Model FM CRWMS M&O 2000, U0050 3-D Yes 3.7 
Ambient 
Geochemistry 
Model 
AGM CRWMS M&O 2000, U0050 Analytical and 
3-D 
No 3.8 
Seepage 
Calibration 
Model 
SCM CRWMS M&O 2000, U0080 2-D and 3-D No 3.9.4 
Seepage Model 
for Performance 
Assessment 
SMPA CRWMS M&O 2000, U0075 3-D Yes 3.9.5 
Drift Scale Test 
Thermal- 
Hydrological- 
Chemical Model 
DST 
THCM 
CRWMS M&O 2000, 
N0120/U0110 
2-D No 3.10 
THC Seepage 
Model 
THCM CRWMS M&O 2000, 
N0120/U0110 
2-D Yes 3.10.5 
Transport Model TM CRWMS M&O 2000, U0060 2-D, 3-D No 3.11 
Mountain-Scale 
Thermal- 
Hydrological 
Model 
THM CRWMS M&O 2000, U0105 2-D, 3-D No 3.12 
NOTE: N/ANot applicable

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TDR-NBS-HS-000002 REV00 ICN02 3 August 2000 
The basic approach of the UZ PMR is to provide a comprehensive summary of UZ flow and 
transport issues discussed in the UZ AMRs as well as to provide the following additional 
information: 
1. New data and analyses that are important to one or more of the main models, and 
have been collected or compiled since the AMRs were prepared. 
2. Information from journal references to other sites worldwide that address issues 
considered in the AMRs and the UZ PMR. 
Table 1-2. Roadmap for the UZ PMR 
Information Icon (Examples) Report 
Chapter/Section 
Cross-Referencing 
Objectives and scope of 
the PMR 
UZ PMR UZ PMR 
UZ PMR Sections 1.1 and 
1.2 
N/A 
Features, Events, and 
Processes and their 
screening 
N/A Section 1.2.3 N/A 
Key hypotheses and 
alternative hypotheses 
for the UZ PMR 
N/A Section 1.2.4 Pointers to sections of 
PMR for detailed 
discussions 
Key issues from NRC, 
NWTRB, Peer Review 
Groups, and others 
N/A Section 2.5 Pointers to sections of 
the PMR where each 
issue is discussed 
Software used in AMRs 
that support the PMR 
iTOUGH2 
Code Code 
TOUGH2 
Section 1.3.2 Pointers to sections of 
the PMR supported 
by AMRs using the 
software 
Evolution of field testing 
and model development 
N/A Chapter 2 N/A

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TDR-NBS-HS-000002 REV00 ICN02 4 August 2000 
Information Icon (Examples) Report 
Chapter/Section 
Cross-Referencing 
Geological data, 
conceptual models and 
numerical grids 
Geologic Framework 
Model 
Conceptual 
Model 
Numerical Grids 
Sections 3.2 to 
3.4 
N/A 
Key UZ PMR models 
and analyses 
Climate 
Model 
Flow and Transport 
Model 
Transport 
Model 
Thermal-Hydrological 
Model 
Sections 3.5 to 
3.12 
For each model, the 
data inputs, 
relationships to other 
models, the data 
outputs, and intended 
use in TSPA are 
described. 
Key NRC issues and 
subissues 
N/A Chapter 4 Pointers to sections in 
PMR where each 
issue is discussed 
Summary and 
conclusions 
N/A Chapter 5 N/A 
Summary of field and 
laboratory data used in 
AMRs and PMR 
3H 
36Cl 
Cl 
Sr 
Perched Water Data 
Geochemistry Data 
Transport Data 
Seepage Data 
Attachment I A brief description of 
the different data sets 
with appropriate DTN 
numbers is given. 
NOTE: N/ANot applicable 
Table 1-2 provides a roadmap for the UZ PMR, indicating the chapters/sections in which key 
points of information are located. Most of this chapter (Chapter 1) describes the objectives and 
scope of the PMR, the principal factors, and other factors addressed by this PMR. Features, 
Events, and Processes (FEPs) and the key hypotheses for the PMR are also described.

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Section 1.3 summarizes the Quality Assurance (QA) status and issues regarding the data and 
software used in this PMR. Chapter 1 concludes with a brief section describing the relationships 
between the UZ PMR and other key Project documents. 
Chapter 2 summarizes the evolution of field and laboratory testing, data-collection activities and 
process/TSPA modeling of flow and transport in the UZ, and UZ flow and transport issues raised 
by various overseeing bodies, peer review groups, PA and UZ Workshops, NRC, and others. The 
Chapter describes the rationale for the evolution of the testing program and the major advances 
that have been made in modeling of the UZ. Chapter 2 refers to Attachment I, which summarizes 
the various data sets used in the UZ AMRs with appropriate pointers to Data Tracking Numbers 
(DTNs). 
Chapter 3 contains the main technical sections of the UZ PMR. This chapter describes and 
summarizes all of the models that are considered in the UZ PMR. These include models on 
calibrated properties, 3-D flow fields, seepage, ambient chemistry, radionuclide transport, 
mountain-scale thermal-hydrological (TH) processes, and drift-scale thermal-hydrologicalchemical 
(THC) processes (see Figure 1-2). In addition, Chapter 3 provides the necessary 
framework for the models in terms of the geological information, conceptual models, and 
numerical grids. 
Chapter 4 deals with the Key Technical Issues (KTIs) on UZ flow and transport identified by the 
NRC. Each of the subissues is identified and pointers are provided to the relevant 
chapters/sections in the UZ PMR that address it. Finally, Chapter 5 gives the summary and 
conclusions of the UZ PMR, primarily focusing on the models that feed TSPA. 
Table 1-2 shows examples of the various icons used in this PMR. The icons were developed to 
provide the reader with easily identifiable representations of the various components of the UZ 
PMR. Data icons are represented by diamond shapes, and model icons as squares. The icons are 
used in the various subsections of Chapter 3 to show the flow of data and information, as well as 
the interrelations among the various models. 
1.1 OBJECTIVES 
The following are the main objectives of the UZ PMR: 
1. To synthesize all important data, analyses, models, and model abstractions of flow 
and transport within the UZ in a single document 
2. To document the development of key models used to analyze the various data sets 
from the UZ 
3. To document the development of key models for UZ flow and transport used in 
TSPA 
4. To document the abstraction process and results for key UZ flow and transport 
models used by TSPA

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TDR-NBS-HS-000002 REV00 ICN02 6 August 2000 
5. To summarize the key products that are provided to TSPA for performance 
analysis. 
The various AMRs that support the UZ PMR and the PMR itself are key documents that the 
Yucca Mountain Site Characterization Project (YMP) will rely upon and reference in the SR and 
LA documents. 
1.2 PMR SCOPE AND BACKGROUND INFORMATION 
1.2.1 Scope of UZ Flow and Transport PMR 
The UZ Flow and Transport Model generates numerical simulations of spatial and temporal 
distributions of water flow and potential radionuclide transport through the UZ, and of water 
seepage into the potential repository waste emplacement drifts. The UZ models account for 
infiltration processes near the ground surface of the mountain, and the effect of climate changes. 
The spatial and temporal variability of net infiltration is specified as the main boundary condition 
for the UZ Flow and Transport Model. Numerical grids for the UZ models are developed based 
on the Geologic Framework Model (GFM, CRWMS M&O 2000, I0035), the Rock Properties 
Model (CRWMS M&O 2000, I0040), the Mineralogic Model (CRWMS M&O 2000, I0045) and 
Hydrological Property Data (CRWMS M&O 2000, U0090). 
The Calibrated Properties Model (CPM) uses the estimated infiltration rates at various boreholes 
and adjusts various hydrological properties (CRWMS M&O 2000, U0090), such as permeability, 
to match observed matrix saturations, water potentials and pneumatic signals, using inverse 
modeling techniques. The calibrated property sets produced by this analysis are used for a wide 
variety of downstream models, including the 3-D Flow Model (FM), the Transport Model (TM), 
the Seepage Calibration Model (SCM), the Seepage Model for Performance Assessment 
(SMPA), the Thermal-Hydrological Model (THM), and the Thermal-Hydrological-Chemical 
Model (THCM). 
The 3-D Flow Model and its submodels use the calibrated property sets (CRWMS M&O 2000, 
U0035) as initial values for further 3-D calibrations against various geochemical, temperature, 
and perched water data. These models generate numerous 3-D flow fields for TSPA that are 
based upon different assumptions regarding important hydrological properties, conceptual 
models, and infiltration cases. These 3-D flow fields are used as input to the Seepage Model for 
PA and for transport calculations. 
The Seepage Calibration Model (SCM) (CRWMS M&O 2000, U0080) uses the calibrated 
property sets (CRWMS M&O 2000, U0035) as initial values to match the observed seepage data 
from the niche studies (CRWMS M&O 2000, U0015). The SCM supports the Seepage Model for 
PA, which evaluates the relationships between seepage and important hydrological parameters as 
a function of percolation flux. The results of the Seepage Model for PA are further abstracted to 
predict the fraction of waste packages that will encounter water seeping into open drifts and the 
flow rate of seepage into a drift (CRWMS M&O 2000, U0120). 
Transport calculations (Transport Model) are performed using particle trackers (CRWMS M&O 
2000, U0155; CRWMS M&O 2000, U0065; CRWMS M&O 2000, U0160), as well as numerical 
solutions of the conventional advection/dispersion equations. Comparison among these different

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numerical approaches yield estimates for their accuracy and the extent to which they are 
conservative. Transport properties are mostly derived from laboratory data and from the Busted 
Butte transport test (CRWMS M&O 2000, U0100). Potential radionuclide transport in the 
colloidal phase is evaluated using various models and formulations for colloid transport 
mechanisms (CRWMS M&O 2000, U0070; CRWMS M&O 2000, U0060). 
This PMR is intended for providing models and analyses to TSPA for their evaluation of the 
overall system behavior. In general, the PMR uses a more realistic approach in its treatment of 
processes identified as principal factors (see Section 1.2.2) and bounding or conservative values 
for processes controlling other factors, such as climate and coupled processes (see Table 1.2-1) 
related to unsaturated zone flow and transport. This is in accordance with the Repository Safety 
Strategy (CRMWS M&O 2000b). For these reasons, the results presented in this PMR should 
not be used to directly evaluate regulatory or other requirements. 
Heat released by the emplaced waste potentially affects both the 3-D flow fields and the seepage 
rates into underground openings. Mountain-scale models (CRWMS M&O 2000, U0105) of the 
TH conditions near the emplacement drifts are included in the UZ PMR to evaluate the impact of 
these coupled processes on two-phase (water and gas) flow. These models investigate the extent 
of two-phase and dry-out zones, water drainage between pillars, and critical temperature 
conditions, occurring at various locations, such as at the drift walls, within mid-pillar regions, 
and within perched water bodies and zeolitic rocks. THC models (CRWMS M&O 2000, 
N0120/U0110) investigate the chemistry of water and gases entering drifts, and associated 
changes in important hydrological properties near the emplacement drifts. 
1.2.2 Principal Factors and Other Factors Considered 
The YMP has identified those factors most important to performance, hereafter named the 
principal factors, based on the Repository Safety Strategy (RSS) (CRWMS M&O 2000b). A 
series of workshops were conducted to develop the RSS (including the list of principal factors), 
review of each modeling area and discuss sensitivities from the perspective of the process 
models and TSPA. Project personnel from each of the scientific areas and from performance 
assessment took part in these workshops. The RSS lists seven principal factors and twenty other 
factors of second-order importance. The selection of the principal factors was based on 
preliminary TSPA analyses and expert judgment, which showed that these factors significantly 
affected the performance of the potential repository. The other factors were deemed to have 
second-order effects on the repository performance in terms of dose to the accessible 
environment (CRWMS M&O 2000b, Section 3.1). Table 1.2-1 lists the seven principal factors, 
the twenty other factors, and the PMRs that address each factor.

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Table 1.2-1. Principal Factors, Other Factors, and the PMRs where Addressed 
Factor Process Model Report 
Seepage into drifts Unsaturated Zone Flow and Transport 
Performance of the drip shield Waste Package Degradation 
Performance of the waste package barriers Waste Package Degradation 
Solubility limits of dissolved radionuclides Waste Form Degradation 
Retardation of radionuclide migration in the 
unsaturated zone 
Unsaturated Zone Flow and Transport 
Retardation of radionuclide migration in the 
saturated zone 
Saturated Zone Flow and Transport 
Principal 
Factors 
(Nominal 
Scenario) 
Dilution of radionuclide concentrations during 
migration 
Saturated Zone Flow and Transport 
Climate Unsaturated Zone Flow and Transport 
Net infiltration into the mountain Unsaturated Zone Flow and Transport 
Unsaturated zone flow above the repository Unsaturated Zone Flow and Transport 
Coupled processes - effects on unsaturated zone 
flow 
Unsaturated Zone Flow and Transport 
Coupled processes - effects on seepage Near-Field Environment 
Environments on the drip shield Engineered Barrier System Degradation, Flow, 
and Transport 
Environments on the waste package Engineered Barrier System Degradation, Flow, 
and Transport 
Environments within the waste package Waste Form Degradation 
CSNF waste form performance Waste Form Degradation 
DHLW glass waste form performance Waste Form Degradation 
DSNF, Navy fuel, Pu disposition waste form 
performance 
Waste Form Degradation 
Colloid-associated radionuclide concentrations Waste Form Degradation 
In-package radionuclide transport Waste Form Degradation 
Transport through the drift invert Engineered Barrier System Degradation, Flow, 
and Transport 
Advective pathways in the unsaturated zone Unsaturated Zone Flow and Transport 
Colloid-facilitated transport in the unsaturated 
zone 
Unsaturated Zone Flow and Transport 
Coupled processes  effects on unsaturated zone 
transport 
Unsaturated Zone Flow and Transport 
Advective pathways in the saturated zone Saturated Zone Flow and Transport 
Colloid-facilitated transport in the saturated zone Saturated Zone Flow and Transport 
Other Factors 
(Nominal 
Scenario) 
Biosphere transport and uptake Biosphere 
Factors for 
Disruptive Event 
Scenarios 
To be determined. See Disruptive Event PMR for 
preliminary considerations 
Disruptive Events 
SOURCE: CRWMS M&O 2000b

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The UZ PMR addresses the following principal factors: 
1. Seepage into drifts (see Section 3.9) 
2. Retardation of radionuclide migration in the UZ (see Sections 3.3 and 3.11). 
Seepage into drifts is a principal factor as the amount of water entering the drift affects waste 
mobilization rates and transport of radionuclides out of the drifts into the UZ. Retardation of 
radionuclide migration in the UZ is a principal factor as this process is effective in delaying the 
migration of many radionuclides due to matrix diffusion and sorption (see Sections 3.3 and 3.11 
for descriptions of these processes.) 
In addition, the following seven other factors are within the scope of the UZ PMR: 
1. Climate (Section 3.5) 
2. Net infiltration into the mountain (Section 3.5) 
3. UZ flow above the repository (Section 3.7) 
4. Coupled processes-effects on UZ flow (Section 3.12) 
5. Advective pathways in the UZ (Sections 3.3 and 3.11) 
6. Colloid-facilitated transport in the UZ (Sections 3.3 and 3.11) 
7. Coupled processes-effects on UZ transport (Section 3.12). 
The general guidelines for addressing the seven other factors are to use conservative bounding 
analysis for the safety case. The two principal factors will be studied and evaluated using 
rigorous realistic numerical evaluations as well as bounding analyses. 
1.2.3 Features, Events, and Processes (FEPs) 
The Yucca Mountain Project has established a database of all features, events, and processes 
(FEPs) that could affect the potential repository performance. Rev. 00C of the database 
(CRWMS M&O 1999d) contains 1786 entries, derived from the following sources: 
 General FEPs from other international radioactive waste disposal programs 
 YMP-specific FEPs identified in YMP literature 
 YMP-specific FEPs identified in technical workshops 
The YMP FEPs list was initially populated with FEPs compiled by other international 
radioactive waste programs. The Nuclear Energy Agency (NEA) of the Organization for 
Economic Co-operation and Development (OECD) maintains an electronic FEP database that 
currently contains 1261 FEPs from seven programs, representing the most complete attempt 
internationally at compiling a comprehensive list of FEPs potentially relevant to radioactive 
waste disposal.

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The YMP FEP list was supplemented with YMP-specific FEPs identified in past YMP work 
during site characterization and preliminary performance assessments. Because the YMP is the 
only repository proposed for an unsaturated fractured tuff, many of these FEPs represent events 
and processes not otherwise included in the international compilation. A search of YMP 
literature identified these 443 additional FEP entries. 
Relevant FEPs from the 1704 entries identified from the NEA database and YMP literature were 
taken from a series of technical workshops convened between December, 1998 and April, 1999. 
At these workshops, the relevant FEPs were reviewed and discussed by subject matter experts 
within the project. As a result of these discussions, workshop participants proposed 82 
additional YMP-specific FEPs. 
From this project-wide list, there are 515 FEPs identified for UZ flow and transport. FEPs were 
selected for the UZ based on the processes identified in each FEP and the processes that are 
known to affect the UZ. UZ flow and radionuclide transport are components of the natural 
geologic barriers that affect the overall performance (including engineered barriers) of the 
potential repository. The UZ flow and transport FEPs were evaluated systematically to determine 
their relevance to UZ subsystem performance. Models were developed to address the FEPs 
identified as potentially important to performance. These models are the subject of the AMRs 
supporting the UZ PMR. This report summarizes the scientific bases for these models. The 
TSPA model and underlying process models of the natural barrier capture some, but not all, of 
the 515 FEPs that are associated with this natural barrier. The reasons for exclusion of a FEP are 
low probability and/or low consequence, discussed further below. The identification and 
treatment of all 515 FEPs are given in CRWMS M&O (2000, U0170). 
A large degree of overlap exists among these 515 FEPs, and this overlap has been used to group 
FEPs into two broad categories, primary and secondary FEPs. Eighty-one primary FEPs that 
incorporate the topics represented by the entire list of 515 FEPs have been identified. Thus, the 
434 secondary FEPs are subsets of the primary FEPs. 
The primary FEPs have been further subdivided into the categories identified and described in 
Table 1.2-2. Both primary and secondary FEPs are discussed in CRWMS M&O 2000 (U0170).

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Table 1.2-2. FEPs for the UZ PMR 
FEP Category Description YMP Primary FEP Numbers 
Included FEPs Those FEPs that are completely 
included in the TSPA. 
1.3.01.00.00, 1.3.07.02.00, 2.1.08.01.00, 2.1.08.02.00, 
2.2.03.01.00, 2.2.03.02.00, 2.2.07.01.00, 2.2.07.02.00, 
2.2.07.03.00, 2.2.07.04.00, 2.2.07.08.00, 2.2.07.09.00, 
2.2.08.04.00, 2.2.08.08.00, 2.2.08.09.00, 2.2.08.10.00, 
2.2.10.03.00, 2.2.10.10.00, 2.3.01.00.00, 2.3.11.01.00, 
2.3.11.02.00, 3.1.01.01.00 
Boreholes and 
Repository Seals 
FEPs concerning site 
characterization boreholes and 
repository drift openings generally 
excluded from TSPA. 
1.1.01.01.00, 1.1.01.02.00, 1.1.02.01.00, 1.1.04.01.00, 
1.1.11.00.00, 1.4.04.02.00, 2.1.05.01.00, 2.1.05.02.00, 
2.1.05.03.00 
Extreme 
Climate/Episodic 
Transient Flow 
FEPs concerning major changes in 
climate and/or episodic transient 
flow driven by episodic infiltration or 
thermal-hydrologic effects. 
Generally excluded from TSPA. 
1.3.04.00.00, 1.3.05.00.00, 1.3.07.01.00, 1.4.01.01.00, 
2.2.07.05.00, 2.2.07.06.00, 2.2.07.07.00, 2.3.11.03.00 
Erosion/ 
Dissolution/ 
Subsidence 
FEPs concerning surface erosion 
and deposition, large-scale rock 
dissolution, and subsidence. 
Generally excluded from TSPA. 
1.2.07.01.00, 1.2.07.02.00, 1.2.09.02.00, 2.2.06.04.00 
Human Influences 
on Climate/Soil 
FEPs concerning effects of 
greenhouse gas emissions, 
destruction of ozone layer, and 
changes in soil chemistry due to 
human activities. Excluded from 
TSPA. 
1.4.01.00.00, 1.4.01.02.00, 1.4.01.03.00, 1.4.01.04.00, 
1.4.06.01.00 
Natural Gas/Gas 
Generation Effects 
FEPs concerning formation of 
gases in the emplacement drifts 
due to interactions with repository 
materials, intrusion of natural gas. 
Excluded from TSPA. 
2.1.12.01.00, 2.2.10.11.00, 2.2.11.01.00, 2.2.11.02.00, 
2.2.11.03.00 
Seismic/Igneous/ 
Rock 
Characteristics 
FEPs concerning existing geologic 
characteristics and the effects of 
seismic or igneous activity on these 
characteristics. Mixture of items 
included in and excluded from 
TSPA. 
1.2.02.01.00, 1.2.02.02.00, 1.2.03.01.00, 1.2.04.02.00, 
1.2.06.00.00, 1.2.10.01.00, 1.2.10.02.00, 2.2.06.02.00, 
2.2.06.03.00, 2.2.12.00.00 
Repository 
Perturbed 
Thermal- 
Hydrologic- 
Mechanical- 
Chemical (THMC) 
FEPs concerning coupled effects of 
thermal-hydrologic-mechanicalchemical 
processes in the 
repository environment. Effects of 
repository heat and materials on 
hydrology and geochemistry. 
Mixture of items included in and 
excluded from TSPA. 
1.1.02.00.00, 2.2.01.01.00, 2.2.01.05.00, 2.2.07.10.00, 
2.2.07.11.00, 2.2.08.01.00, 2.2.08.02.00, 2.2.08.03.00, 
2.2.08.05.00, 2.2.08.06.00, 2.2.08.07.00, 2.2.09.01.00, 
2.2.10.01.00, 2.2.10.04.00, 2.2.10.05.00, 2.2.10.06.00, 
2.2.10.07.00, 2.2.10.09.00 
SOURCE: CRWMS M&O 2000, U0170

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FEPs designated as included are those directly represented in TSPA models and process-level 
models that support TSPA. Therefore, the treatment of these FEPs is described in other 
chapters/sections of this document and the corresponding supporting AMRs. Some FEPs 
(representing broad categories) are not fully in the included FEP category, but are also not 
fully excluded; these broad-category FEPs address some aspects that are included and some 
aspects that are excluded from TSPA. In other words, different aspects of the same FEP have 
different treatments. A summary of the included FEPs that affect UZ flow and transport is given 
in Section 1.2.4. FEPs in the other categories are mostly (but not entirely) excluded from the 
TSPA. The exclusion of FEPs from the TSPA is based on arguments demonstrating low 
probability or low consequence of occurrence. Most of the exclusion arguments are based on low 
consequence. For example, the FEP Flow and Transport in the UZ from Episodic Infiltration is 
argued to have low consequence. This is based on the findings by existing studies of episodic 
infiltration and percolation showing that flow through one of the hydrogeologic units above the 
potential repository (the Paintbrush nonwelded unit (PTn)) damps out the transient nature of the 
percolation. Consequently, UZ flow near the potential repository and below is essentially steady. 
In some cases, the low-consequence argument takes the form of a conservative assumption that 
bounds the potential effects of the FEP. For example, the FEP Human Influences on Climate is 
treated by assuming the onset of a wetter climate (the glacial-transition climate) early (after 2000 
years) in the 10,000-year regulatory period. This bounds the impact of human activity on the 
climate by using a much earlier transition to the wetter climate than would be expected from the 
climate cycles indicated by the paleoclimate record. A few of the excluded FEPs, such as the 
FEP on glaciers, are excluded on the basis of low probability as shown by the paleoclimate 
record. An event may be excluded on the basis of low probability if the probability of 
occurrence is less than 0.0001 in 10,000 years. 
Six assumptions used in the FEPs exclusion arguments are based on scientific rationale, but 
never-the-less may continue to be verified. These six assumptions are identified as to be 
verified (TBV). The six TBV assumptions and a brief description of their bases (CRWMS 
M&O 2000, U0170) follow. All FEPs excluded on the basis of TBV assumptions are identified 
in CRWMS M&O (2000, U0170, Chapter 7). 
Assumption 1 (assumption 10 in CRWMS M&O 2000, U0170, Sections 6.3.8 and 6.8.6): 
Changes in aqueous geochemistry in the repository environment are dominated by thermalchemical 
interactions associated with the potential repository. 
Basis: With the exception of climate change, the potential repository is the only perturbation that 
will potentially affect the aqueous geochemistry of the UZ over the 10,000 year regulatory 
period. The assumption that the effects of climate change on the geochemistry will be smaller 
than the effects of the potential repository is based on the fact that temperature changes driven by 
the potential repository will be much larger than temperature changes that occur as a result of 
climate change. Also, the potential repository introduces a large number of new materials (some 
of them are in substantial quantities) that will influence the geochemistry. Climate change may 
influence the concentrations of dissolved salts in water that percolates, but will not introduce 
new materials. This is a reasoned argument based on the knowledge that temperature and 
chemical components affect the system chemistry. Temperature changes and introduction of 
new materials will be more drastic as a result of the repository than due to climate change.

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Because the effects of climatic factors that affect the chemistry will be smaller, the resulting 
changes in chemistry are assumed to also be less. 
Assumption 2 (assumption 11 in CRWMS M&O 2000, U0170, Sections 6.8.7, 6.8.8, 6.8.10, 
6.8.17, and 6.8.18): Results from the near-field THC coupled processes model can be used to 
bound the effects of similar coupled processes on far-field flow and radionuclide transport. 
Basis: Model results show that THC coupled processes in the near-field have a negligible effect 
on flow and transport. The effects of coupled processes in the far-field unsaturated zone are 
expected to be less severe than in the near-field. This is caused by the higher temperatures that 
will occur near the waste emplacement drifts, including boiling of the rock-water and the 
associated precipitation of minerals and condensation of water. The near-field temperatures 
clearly bound the temperatures in the far field. Further THC process modeling at the mountain 
scale may be conducted, and data showing thermal-chemical effects on minerals in the Calico 
Hills will be considered, as appropriate, for further verification. 
Assumption 3 (assumption 12 in CRWMS M&O 2000, U0170, section 6.8.12): The quantities 
of organic matter and microbes either emplaced or generated (through microbial growth 
processes) in the waste emplacement drifts are sufficiently small that they are unlikely to be of 
significance for far-field flow and transport processes. 
Basis: This assumption is based on the limited use of organic matter in the emplacement drifts 
and the limited quantities of natural organic matter and nutrients, such as phosphorus, in the 
unsaturated zone. Analyses conducted for the viability assessment (CRWMS M&O 1998i; pp. 
4-108 and 4-109) and the analysis of in-drift microbial communities (CRWMS M&O 2000, 
E0040, Section 7.3) provide additional support for this assumption. This assumption relies on 
the premise that organic and microbial material will interact with dissolved metals in a relatively 
uniform way. Although this assumption is qualitatively reasonable, it is important to show that 
microbial and organic matter that may be present in the potential repository environment does 
not have specific affinity for interaction with particular radionuclides, such as plutonium, which 
requires an investigation of existing data. 
Assumption 4 (assumption 13 in CRWMS M&O 2000, U0170, Sections 6.3.5, 6.8.4, and 6.8.5): 
TH flow processes will have a minimal effect on radionuclide transport. 
Basis: The major effects of TH flow processes will be near the emplacement drifts in the early 
part (first 10,000 years) of the postclosure time period. Radionuclide releases will likely be after 
the main portion of the thermal pulse (after waste heat begins to dissipate), and a large part of the 
radionuclide transport process in the UZ will take place at locations outside the envelope of the 
main TH effects. Therefore, the effect of TH flow processes on radionuclide transport is 
expected to be negligible, i.e. TH effects on flow will be small by the time radionuclide transport 
occurs. These qualitative arguments require quantitative verification with transport calculations 
using mountain-scale TH flow fields. 
Assumption 5 (assumption 14 in CRWMS M&O 2000, U0170, Section 6.8.14): Thermalmechanical 
effects on hydrogeologic properties near waste emplacement drifts will be limited to 
a time period (first 1000 years) occurring before any significant seepage occurs into the drifts.

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Basis: The main compressive stresses caused by thermal-mechanical effects will occur during the 
period when temperatures are increasing. Drift seepage is not expected during this time period 
when temperatures are increasing because water boils and is removed as vapor from the vicinity 
of the waste emplacement drifts. The effects of thermal-mechanical stress around the waste 
emplacement drifts are expected to be small by the time water is present to seep into the drifts. 
Additional thermal-hydrologic-mechanical process modeling will be performed to verify this 
assumption. 
Assumption 6 (assumption 15 in CRWMS M&O 2000, U0170, Section 6.7.1): Mechanical 
stresses around waste emplacement drifts after the thermal period are dominated by the existing 
in-situ stresses created by the presence of the opening. Therefore, changes to mechanical stresses 
due to fault movement around waste emplacement drifts are negligible. 
Basis: Drift stability analyses have found that seismic activity has only a minor influence on 
rockfall in drifts (CRWMS M&O 2000b, Section 7). Therefore, the effects of fault movements 
on stresses around the emplacement drifts are expected to be minor. Additional hydrologicmechanical 
process modeling will be performed to verify this assumption. 
1.2.4 Summary of Current Understanding of Flow and Transport at Yucca Mountain 
The UZ PMR considers many parameters, processes, and models that describe UZ flow and 
transport at Yucca Mountain. Current understanding of flow and transport issues have been 
gained through collections of site data and modeling of the relevant processes. Table 1.2-3 is 
intended to summarize the current understanding of flow and transport parameters and processes, 
and to provide pointers for each statement to the relevant section(s) of the PMR, where a more 
detailed discussion is given. This summary given here describes the aspects of the included FEPs 
(Section 1.2.3) that are believed to be important for UZ flow and transport processes. The 
specific titles used here are different than those in the formal FEPs database to allow for a more 
uniform and detailed discussion of the relevant FEPs. However, the content of all FEPs discussed 
below fall within the framework of the formal list of included FEPs. The statements listed under 
the column Current Understanding are a mixture of observations, hypotheses, and modeling 
insights and should only be considered as brief summary information. This column also includes 
alternative views to the current understanding that were either investigated in analyses or models, 
or previously proposed. A more detailed summary of the current understanding is given in 
Section 3.3 and in other sections identified in the table below. 
Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
Climate/infiltration Rainfall for the modern mean climate is about 190 mm/yr resulting in 
average steady-state net infiltration of 4.6 mm/yr. 
3.5.1.8, 3.5.2.10 
Climate/infiltration After 600 years, the average rainfall is forecast to increase to about 300 
mm/yr for monsoon climate; in response the average net infiltration is 
predicted to increase to 12.2 mm/yr. 
3.5.1.8, 3.5.2.10

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
Climate/infiltration After 2,000 years, the average rainfall is predicted to increase to about 320 
mm/yr for a glacial-transition climate; in response the average net 
infiltration is predicted to increase to 17.8 mm/yr. 
3.5.1.8, 3.5.2.10 
Infiltration The net infiltration is episodic with a significant amount infiltrating only 
every few years. 
3.3.2 
Infiltration There is large spatial variability of infiltration, with most water infiltrating on 
ridgetops and in the upper reaches of washes where there is little alluvial 
cover. 
Alternative View: 
Use of different models of groundwater/surface interaction results in 
different spatial distribution. 
3.3.2, 3.5.2.5, 
Figures 3.5-4c, 
3.5-5a and b 
3.5.2.7 
Flow through TCw Flow through Tiva Canyon welded hydrogeologic unit (TCw) is episodic as 
controlled by infiltration. 
3.3.3.1, 3.7.3.1 
Flow through TCw Fracture flow dominates in TCw. 3.3.3.1, 3.7.3.1 
Flow through TCw Fracture permeability of TCw is high (~10-11 to 10-10 m2). 3.6.5.1, 
Figure 3.6-6 
Flow through TCw Water flow is transmitted rapidly through TCw. 3.3.3.1, 3.7.3.1 
Flow through PTn Flow through Paintbrush tuff nonwelded hydrogeologic unit (PTn) is 
primarily porous medium flow. 
Alternative View: 
Flow through the PTn is primarily fracture flow. 
3.3.3.2 , 3.7.3.1 
3.3.3.2 
Flow through PTn The PTn consists of 5 to 10 bedded units with different degrees of welding 
and alterations and different hydrological properties. 
3.2.2.2 
Flow through PTn The average matrix permeability of the PTn is about 10-13 m2, with 
estimated variability of the major layers from 7 x 10-14 to 3 x 10-12 m2. 
3.6.5.1, 
Figure 3.6-6 
Flow through PTn Limited lateral flow occurs in the PTn. 
Alternative View: 
Significant lateral flow occurs in the PTn. 
3.3.3.2, 3.7.3.1, 
3.7.3.2 
2.4, 3.3.3.2 
Flow through PTn Most of the fast flow through the PTn occurs via faults, and this represents 
only a very small fraction of the total flow. 
Alternative View: 
Fast flow through the PTn occurs via fractures and faults, and this 
represents a large fraction of the total flow. 
3.3.7, 3.11.8 
3.7.3.1 
Flow through TSw Episodic flow through Topopah Spring welded hydrogeologic unit (TSw) is 
damped by the PTn to the extent that flow can be considered steady-state 
when it enters the TSw. The exception is at or near major faults where 
episodic flow may still persist through the PTn. 
Alternative View: 
Episodic flow through the TSw is pervasive. 
3.3.3.2, 3.3.3.3, 
3.3.5, 3.3.6, 
3.7.3.1, 3.7.3.2 
3.7.3.1

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
Flow through TSw Fracture flow dominates in the TSw because this unit is densely welded 
and highly fractured; additionally, the low-permeability matrix is incapable 
of transmitting the percolation flux estimated to be moving through the unit. 
3.3.3.3, 3.7.4.3 
Flow through TSw Fracture flow in the potential repository horizon, which intersects the 
Topopah Spring middle nonlithophysal, lower lithophysal and lower 
nonlithophysal stratigraphic units, is estimated to range from 84-94% of the 
total water flow for the three present-day climate scenarios. For the three 
scenarios of the two future climates, the percentage of fracture flow 
increases to 87%96% of the total water flow. 
3.7.4.2, 3.7.4.3 
Flow through TSw Water drainage in the potential repository units, Topopah Spring middle 
nonlithophysal, lower lithophysal and lower nonlithophysal stratigraphic 
units, is expected to be good due to the generally high fracture 
permeability (~10-11 to 10-10 m2). 
3.6.5.1, 
Figure 3.6-6 
Flow through TSw Current average percolation flux in the potential repository horizon is 
estimated to be about 5 mm/yr, with spatial variability between 0 and 60 
mm/yr. 
Alternative View: 
Chloride data suggest that the percolation flux at the potential repository 
horizon is more uniform with values ranging from 1 to 10 mm/yr. 
3.7.4.1, 3.7.4.2, 
3.7.4.5 
3.8.2, 
Figure 3.8-4 
Flow through TSw Long-term average percolation flux at the potential repository horizon, 
averaged over the last 1000 to 10,000 years, is estimated to be about 6 
mm/yr based on calcite abundances, with a range of 2 to 20 mm/yr. 
3.8.4.2 
Flow through TSw Evidence for fast/preferential flow is seen at the potential repository 
horizon, primarily near major faults. It is estimated that the fast component 
of flow is a less than a few percent of the total flow. 
Alternative View: 
Fast flow is the major component of the total flow. 
2.2.3.3, 3.3.7, 
3.8.3, 3.11.8 
Perched water Several perched water bodies have been found below the potential 
repository horizon, with the perching layer generally being the basal 
vitrophyre of the TSw or the zeolitic part of the Calico Hills nonwelded 
hydrogeologic unit (CHn). 
3.3.3.4, 3.3.8, 
3.7.3.3 
Perched water Perched water bodies formed due to permeability barriers (basal vitrophyre 
of the TSw or zeolitic portion of the CHn) and an absence of water-draining 
fractures. 
Alternative View: 
The perched water bodies in the northern region resulted from a 
historically elevated water table. 
3.7.3.3 
3.7.3.3 
Perched water The largest perched water body is found in the vicinity of borehole UZ-14, 
north of the potential repository region; this perched water body may be 
connected to those found in boreholes WT-24, SD-9 and SD-12. 
Alternative View: 
The perched water bodies found in the northern part of the potential 
repository region at boreholes UZ-14, WT-24, SD-9 and SD-12 are all 
disconnected. 
3.7.3.3 
3.7.3.3

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
Perched water A very small perched water body is found in the southern part of the 
potential repository region at borehole SD-7. This perched water body is 
expected to have little impact on the performance of the potential 
repository. 
3.7.3.3 
Perched water The perched water bodies contain a mixture of Pleistocene and Holocene 
water, with average ages ranging from 3,500 to 11,000 years old. 
2.2.3.3, 3.3.3.3, 
3.8.3, 3.10.3.4 
Perched water Infiltration rates needed to form perched water bodies are higher than 
present-day values 
3.8.2, 3.8.3 
Perched water The minute fractions of bomb-pulse 36Cl and tritium in perched water 
suggest that the fast flow fraction over the last 50 years is very small. 
3.8.3 
Flow through CHn The CHn consists of unaltered vitric zones, primarily in the south, and 
altered zeolitic zones, primarily in the north. Water flow through the zeolitic 
units is primarily fracture flow, but mostly or all matrix flow through the vitric 
units. 
3.7.3.3, 3.3.3.4 
Flow through CHn Lateral flow in perched water bodies toward faults and other major 
permeable features causes partial bypassing of the low permeability 
zeolitic units of the CHn. 
Alternative View: 
Flow from the perched water bodies is primarily vertical through the zeolitic 
CHn, partly through fractures and partly through the low permeability 
matrix. 
3.7.3.2, 3.7.3.3 
3.7.3.3 
Flow through CHn Water entering the CHn vitric unit from the TSw transitions from discrete 
fracture flow to heterogeneous matrix flow 
3.11.4 
Perched water Perched water is formed when percolation flux exceeds the capacity of the 
geologic media to transmit vertical flux through underlying low-permeability 
units. Water may either flow through the units, or laterally to major faults or 
other vertical conduits for flow. 
Alternative View: 
Perched water bodies are primarily formed by water infiltrating in the 
Solitario Canyon area flowing vertically downward until the water 
encounters low permeability units, such as the basal vitrophyre of the TSw, 
and then flows laterally to form the observed perched water bodies. 
3.7.3.2, 3.7.3.3 
3.7.3.3, 3.7.4.7 
Flow through faults Fault properties are variable, and generally controlled by rock type and 
stratigraphic displacement. 
3.2.3, 3.3.5 
Flow through faults Faulting enhances fracturing in the fault zones contributing to increased 
permeability. Permeability in the TCw and TSw fault zone is 6 to 9 x 10-11 
m2. In the PTn fault zone it is ~2 x 10-11 m2. 
3.7.3.2, 3.6.5.1 
Flow through faults Faults are high permeability features through the CHn and Crater Flat 
undifferentiated hydrogeologic unit (CFu), provide a fast flow path from the 
TSw to the water table, and allow discharge from perched water bodies. 
Alternative View: 
Alteration of faulted rocks in the CHn and CFu causes them to be of low 
permeability, slowing travel time from the TSw to the water table. 
3.3.5 
3.3.5 
Seepage Open emplacement drifts act as capillary barriers, impeding water from 
seeping into the drifts and diverting some fraction of the prevailing 
3.3.9, 3.9.1, 
3.9.9, 3.9.3.5

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
percolation flux around the drifts. 
Alternative View: 
1) Seepage is governed by local heterogeneity and ponding probability. 
2) Weep-type flow will be unaffected by the presence of the drift. 
3.9.8.2 
Seepage A critical percolation flux (seepage threshold) exists below which no 
seepage occurs. The distribution of seepage thresholds depends on the 
hydrological characteristics and variability of the unit, especially the 
fracture permeability and the van Genuchten alpha values. 
3.9.3.5 
Seepage Seepage flux is always smaller than the percolation flux as a result of 
partial flow diversion around the drift. 
Alternative View: 
Seepage flux is equal to percolation flux. 
3.9.1, 3.9.6.1 
3.9.6.1 
Seepage Ventilation reduces seepage of liquid water. Neglecting ventilation effects 
in seepage models is conservative. 
Alternative View: 
Neglecting ventilation may not be conservative, because ventilation 
increases vapor flow, which may condense in the drift. 
3.9.3.3 
3.9.3.3 
Seepage Seepage percentages are expected to be similar for all potential repository 
units because permeability and capillary strength are inversely related, 
canceling their respective effects on seepage. 
3.9.6.2 
UZ transport The main geological units below the potential repository expected to retard 
selected radionuclides are the Calico Hills vitric units, and the Prow Pass 
unit (in certain areas). 
3.11.4 
UZ transport A small fraction of the expected nuclear waste inventory consists of 
radionuclides that are soluble in water and non-sorbing. These include 
iodine, technetium and others; they are not retarded as they migrate 
through the UZ. 
Table 3.11-1, 
3.11.5, 3.11.6 
UZ transport The bulk of the expected nuclear waste inventory consists of radionuclides 
that have very low solubility in water, and commonly have large sorption 
capacity in the UZ rocks. These radionuclides, including plutonium and 
others, will migrate very slowly through the UZ and do not contribute 
significantly to dose for tens of thousands of years. 
Alternative View: 
Discrete flow along fast paths from the repository to the water table will 
bypass the majority of the sorbing capacity and contribute to dose soon 
after release. 
3.11.5, 3.11.6 
3.11.9.1 
UZ transport The UZ contributes to the retardation of several important radionuclides 
that are rather soluble in water, including neptunium, strontium and others. 
For most radionuclides the sorptivity of the CHn zeolitic rocks is the 
highest, followed by CHn vitric and TSw. 
Table 3.11-1, 
3.11.4

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
UZ transport The retardation processes are matrix diffusion and sorption in the rock 
matrix. Sorption in the fractures is not considered because of limited data 
and conservative nature of the assumption. 
Alternative View: 
Matrix diffusion is not effective in retarding radionuclides. 
3.11.2.4, 
3.11.2.5 
3.11.9.1 
UZ transport The most efficient retardation of radionuclides is found in the CHn vitric 
unit, which behaves as a porous medium. In spite of its large sorption 
potential, the low matrix permeability of the CHn zeolitic rock, causes water 
flow through fractures, thus limiting the amount of radionuclide sorption. 
Thermal alteration of zeolites was excluded as an alternative view because 
mountain-scale TH modeling indicates that temperatures in the zeolites will 
not exceed 70C (CRWMS M&O 2000, U0105, Section 6.8.2.1). 
3.11.4, 3.11.5, 
3.11.6 
UZ transport Significant colloidal transport may occur for radionuclides such as 
plutonium, americium, and others. Colloidal transport is believed to be 
most critical and important in the fracture-dominated flow. Furthermore, the 
larger size colloids pose the greatest threat for rapid transport as they 
cannot diffuse into the adjacent matrix. 
3.3.11, 3.11.2.7, 
3.11.3.5, 3.11.7, 
3.11.9.2 
Coupled processes The heat released by the emplaced waste will have an important impact on 
water flow around the drifts in the potential repository, seepage into drifts, 
and the chemistry of water and gases entering the drifts. 
3.3.12, 3.10.2, 
3.12.1 
Coupled processes The heat released by the emplaced waste will increase wall temperatures 
of the drift to boiling conditions of approximately 97C; some localized 
drifts in low percolation flux areas may completely boil off all fracture water 
and consequently reach higher peak temperatures (generally below 
120C). 
3.12.3.1 
Coupled processes Peak temperature conditions in the drift walls will be reached after about 
500 years, but closer to 1,000 years in the mid-pillars. 
3.12.3.1, 
Figure 3.12.7 
Coupled processes Peak temperatures in the mid-pillars will reach 85 to 90C depending upon 
the location and the prevailing percolation flux. Water saturation in the 
entire pillar will decline significantly primarily due to boiling near the drifts, 
and capillary suction further away. 
3.12.3.1, 
3.12.3.2, 
3.12.3.3, 
Figure 3.12.7 
Coupled processes The extent of the maximum boiling zone around the drifts is estimated to 
be on the order of 10 m in all directions from the drifts. No significant water 
accumulation is found above or below the drifts. 
3.12.3 
Coupled processes The water that may seep into the drifts will be near neutral in pH and 
mostly reflect the chemical composition of condensate waters mixed with 
infiltration waters at elevated temperatures. The predicted pH is about 7.2 
to 9.0. 
3.10.5.4 
Coupled processes Gas is mostly expected to flow away from drifts due to gas pressure 
gradients induced by increased temperatures. In specific locations, and at 
certain times during the thermal load period, the CO2 concentration in the 
gas phase may increase to about 10 % (~ 100 times ambient 
concentrations). 
3.10.5.3, 
Figure 3,10-8

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Table 1.2-3. Summary of Current Understanding Used to Develop Conceptual and Numerical Models 
for UZ Flow and Transport at Yucca Mountain 
Feature, Event or 
Process 
Current Understanding Section(s) 
Addressed 
Coupled processes Thermal-hydrological-chemical processes resulting in precipitation and 
dissolution of minerals will not significantly alter important fracture and 
matrix hydrological properties. 
Alternative View: 
Thermal-hydrological-chemical processes resulting in precipitation and 
dissolution of minerals significantly alter important fracture and matrix 
hydrological properties. 
3.10.5.5 
3.10.7, 3.10.9 
Coupled processes The thermal-hydrological processes will affect percolation fluxes and 
seepage in a beneficial way. No seepage will occur into any of the 
emplacement drifts for the bulk of the first 1,000 years after emplacement. 
A small spike in the percolation flux will occur, which will then quickly drop 
to the ambient system flux. After that, the percolation fluxes will slowly 
reach those of the ambient system. 
3.12.3.3 
Coupled processes Excavation of the emplacement drifts will increase fracture permeability 
around the drifts up to two orders of magnitude due to mechanical stress 
release. 
2.2.2, 2.2.2.2 
Coupled processes The coupled processes due to heat released from the emplaced waste will 
have insignificant effects on radionuclide transport through the UZ. 
Alternative View: 
The changing flow patterns around drifts will have significant effects on 
radionuclide transport in the UZ. 
3.3.12.1 
3.11 
1.3 QA STATUS OF DATA AND SOFTWARE 
Pursuant to evaluations (CRWMS M&O 1999a, 1999b, Wemheuer 1999) performed in 
accordance with QAP-2-0, Conduct of Activities (now superseded by AP-2.16Q, Activity 
Evaluation), it was determined that activities supporting development of the UZ PMR, its 
component models, and their documentation are quality-affecting activities subject to the quality 
assurance (QA) requirements of the Quality Assurance Requirements and Description (DOE 
2000). The UZ PMR was produced by the Civilian Radioactive Waste Management System 
(CRWMS) Management and Operating (M&O) Contractor in accordance with the CRWMS 
M&O quality assurance program, using Office of Civilian Radioactive Waste Management 
(OCRWM) Administrative Procedures (APs) identified in the Development Plan for the UZ 
Flow and Transport PMR (CRWMS M&O 2000a). 
The UZ PMR was prepared in accordance with AP-3.11Q, Technical Reports, the Development 
Plan for the UZ PMR (CRWMS M&O 2000a), and the Work Package Planning Summary for UZ 
Flow and Transport Process Model Report FY00 (CRWMS M&O 1999c). It was reviewed at 
LBNL in accordance with YMP-LBNL-QIP-6.1, Document Review, prior to checking and 
review per AP-3.11Q and AP-2.14Q, Review of Technical Products, respectively. The electronic 
management of data complied with procedural requirements identified in the Development Plan 
(CRWMS M&O 2000a). The QA procedures under which the supporting Analysis/Model

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Reports (AMR) were developed are identified in the respective AMRs and associated planning 
documents. The AMRs were prepared in accordance with AP-3.10Q, Analyses and Models. 
This document may be affected by technical product input information that requires 
confirmation. Any changes to the document that may occur as a result of completing the 
confirmation activities will be reflected in subsequent revisions. The status of the input 
information quality may be confirmed by review of the Document Input Reference System 
(DIRS) database. The QA status of technical inputs to this PMR and the supporting AMRs are 
provided in the DIRS. The DIRS database is updated to indicate changes to the QA status of 
these data. 
1.3.1 Acquired and Developed Data 
The acquired data used in the development of the UZ AMRs are discussed in Attachment I. 
The QA status of the acquired and developed data supporting the UZ PMR is provided in the 
DIRS Database for each of the AMRs supporting the UZ PMR. These data reside in the 
Technical Data Management System (TDMS) and are tracked by Data Tracking Numbers 
(DTNs). Their status is further classified depending on whether or not the data are relied upon to 
support a principal factor for the postclosure safety case. For the UZ PMR, there are two 
principal factorsSeepage into drifts and Retardation of radionuclide migration in the 
unsaturated zone (Section 1.2.2). These are discussed in Section 1.2.2 and listed in Table 1.2-1. 
These principal factors will be the focus of postclosure safety considerations for the SR and LA 
decision-making process, and therefore data supporting these principal factors require 
confirmation of their QA status. Approximately fifty data sets have been identified as relied upon 
to support the two principal factors for the UZ. These data sets are being confirmed in 
accordance with AP-3.15Q, Managing Technical Inputs. 
The DTNs for the figures and tables in this document are listed separately in Attachment II. The 
QA status of these data can also be found in the DIRS Database. 
1.3.2 Software 
The software codes used in the AMRs that support the UZ PMR and their version number, and 
software tracking number, are listed in Table 1.3-1. These codes were managed in accordance 
with AP-SI.1Q, Software Management, or used under Section 5.11 of AP-SI.1Q. All software 
codes and routines are listed in the supporting AMRs. In the following subsections, the primary 
software codes used in the development of the models supporting the UZ PMR are discussed. 
1.3.2.1 TOUGH2 
TOUGH2 (Transport Of Unsaturated Groundwater and Heat) is an integral finite difference 
numerical simulator for nonisothermal flow of multi-component, multiphase fluids in porous and 
fractured media. It is used for numerical simulation of unsaturated and saturated flow, under both 
isothermal (constant temperature) and nonisothermal (variable temperature) conditions. 
When considering flow in fractured porous media, a key issue is how to evaluate the interface 
area for fluid exchange between the matrix and fracture continua. The preferred method now

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employed in TOUGH2 is the active fracture model (see Section 3.3.4). It was developed to 
describe gravity-dominated, nonequilibrium, preferential liquid flow in fractures, which is 
expected to be similar to flow fingering in unsaturated porous media. In this model, the fractures 
contributing to liquid flow are referred to as active fractures. 
1.3.2.2 iTOUGH2 
iTOUGH2 provides forward and inverse modeling capabilities for the numerical simulator 
TOUGH2. All TOUGH2 input parameters can be considered unknown or uncertain. The 
parameters are estimated based on any type of observation for which a corresponding TOUGH2 
output is available, including prior information about the parameters to be estimated. One of the 
key features of iTOUGH2 is its extensive error analysis, which provides statistical information 
about residuals, estimation uncertainties, and the ability to discriminate among model 
alternatives. 
The key elements of iTOUGH2 are (1) a simulation program to model flow and transport in the 
hydrogeologic system (forward modeling), (2) the objective function, which measures the 
misfit between the model output and the data, (3) the minimization algorithm, which reduces the 
objective function by automatically updating parameter values, and (4) the error analysis, which 
allows one to judge the accuracy of the estimates. 
1.3.2.3 TOUGHREACT 
TOUGHREACT is a numerical code designed to simulate coupled thermal-hydrologicalchemical 
processes. It was developed for the Drift Scale Test and Single Heater Test, to simulate 
boiling conditions and fracture-matrix interactions (diffusion and advection of aqueous and 
gaseous species across fracture-matrix interfaces). The core of TOUGHREACT is the EOS3 
module of the TOUGH2 code which solves the equations for the flow of water, air, and heat 
under nonisothermal and variably saturated conditions. 
In TOUGHREACT, a transport module and a geochemical speciation module are sequentially 
coupled to the TOUGH2 module. The transport module solves for transport of dissolved species 
in water and transport of gases such as CO2 and O2 in a carrier gas phase consisting of H2O 
and air. Transport of the latter two gas phases is computed by the TOUGH2 module. The 
geochemical module incorporated in TOUGHREACT simultaneously solves a set of chemical 
mass-action and mass-balance equations under equilibrium and/or kinetic conditions to compute 
the extent of reaction and mass transfer between a set of given aqueous species, minerals, and 
gases at each gridblock of the flow model. 
1.3.2.4 Transport Codes 
EOS9nT 
EOS9nT is a TOUGH2 module for simulating flow and transport of an arbitrary number (n) of 
tracers (solutes and/or colloids) in the subsurface. The module first solves Richards equation, 
which describes saturated or unsaturated water flow in subsurface formations, and obtains the 
flow regime. A second set of transport equations, corresponding to the n tracers/colloids, is then 
solved sequentially. The very low concentrations of the tracers are considered to have no effect

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on the density of the liquid phase, thus allowing the decoupling of transport from the flow 
equations. 
The tracer transport equations account for sorption, radioactive decay, advection, hydrodynamic 
dispersion, molecular diffusion, filtration (for colloids only), first-order chemical reactions, and 
colloid-facilitated tracer transport. A total of n-1 daughter products of radioactive decay or of a 
chemical reaction chain can be tracked. EOS9nT can handle gridblocks of irregular geometry in 
3-D domains and offers the option of a Laplace space formulation of the transport equations (in 
addition to conventional time-stepping) after the flow field becomes time-invariant. The Laplace 
transform formulation eliminates the need for time discretization and the problems stemming 
from the treatment of the time derivatives in the transport equations, and it yields solutions semianalytical 
in time. This allows an unlimited time step size without loss of accuracy. 
T2R3D 
T2R3D has been developed to handle transport of sorbing and nonsorbing tracers in fractured 
media. A special module of T2R3D has been created for efficient simulation of radionuclide 
transport in porous media, in which the transport process is decoupled from fluid and heat flow. 
This module can be used when flow fields are established or reached steady state. The mass 
balance equation for the tracer/radionuclide component solved in this case is exactly the same as 
that of the coupled case. However, flow fields needed for calculating tracer or radionuclide 
transport are treated as input parameters, determined by a previous EOS9 or EOS3 flow 
simulation under the same boundary condition(s). This option provides substantial savings in 
both execution times and storage requirement for large problems of flow and transport in 
fractured rock. The coupled version of T2R3D as well as the decoupled version are both 
modified for implementation of a new computational scheme for handling the dispersion tensor. 
FEHM 
FEHM (Finite Element Heat and Mass Transfer) calculates hydrological flow and the transport 
of radionuclides, the latter by a particle-tracking algorithm. The particle-tracking method in 
FEHM views the computational domain as an interconnected network of fluid storage volumes. 
The two steps in the particle-tracking approach for steady-state flow fields are: (1) determine the 
time a particle spends in a cell, and (2) determine which cell the particle travels to next. The 
domain can consist of a single-continuum or dual-continua (e.g., fracture plus matrix) 
representation of the flow field. FEHM can be used to model transport breakthrough times in 
porous and fractured media. 
DCPT 
DCPT (Dual Continuum Particle Tracker) is a particle-tracking code used for modeling transport 
in dual-continuum media, such as fractured porous media. It receives as input the flow field 
calculated by another code, such as TOUGH2, and a grid developed by a mesh generator, such as 
WinGridder. It simulates transport by particle-tracking incorporating advection, dispersion, and 
linear sorption. Dispersion can be expressed as a tensor. The grid may be an irregular 3-D grid.

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WinGridder 
WinGridder is a Windows-based grid-generating software program that generates 1-D, 2-D, or 
3-D grids for numerical modeling of flow and transport problems based on the integral finite 
difference method. For a given geological model and engineering-structure information, this 
software can be used to design, generate, and visualize discrete 1-D, 2-D, or 3-D grids for 
numerical modeling of flow and transport problems. The generated grid can be designed to 
describe special geological and engineering features (e.g., inclined faults, potential repository 
horizons). The major output file contains all the data required for the TOUGH2 input file MESH. 
WinGridder also allows users to produce other ASCII and EPS output files as well as hard copies 
of grid figures, for inspection or other purposes. 
Table 1.3-1. Software for UZ Flow and Transport Model and Abstractions for TSPA-SR 
Software 
Name/Version 
Software Tracking Number Short Description Used in AMR(s) 
Supporting PMR 
Section 
AMESH V1.0 10045-1.0-00 Generates numerical grids used 
for modeling drift-scale 
processes 
3.9 
DCPT V1.0 10078-1.0-00 Transport modeling with particle 
tracking 
3.11 
EARTHVISION V4.0 30035-2 V4.0 Graphical display in 3-D 3.4, 3.7 
EOS9nT (TOUGH2 
V1.11 Module 
EOS9nT V1.0) 
10065-1.11MEOS9NTV1.0-00 EOS for TOUGH2 with tracers 
and colloids for transport 
modeling 
3.11 
EXT V1.0 10047-1.0-00 Extracts data from TOUGH2 for 
visual display 
3.7, 3.9 
FEHM V2.00 10031-2.00-00 Flow and transport modeling 
with particle tracking 
3.11 
FEHM V2.10 10086-2.10-00 Flow and transport modeling 
with particle tracking (new) 
3.11 
FRACL V1.0 10191-1.0-00 Semi-analytical solution for 
transport in heterogeneous 
fractured media 
3.11 
GSLIB V1.0 Module 
GAMV2 V1.201 
10087-1.0MGAMV2V1.201-00 Analyzes spatial correlation of 
2-D data 
3.9 
GSLIB V1.0 Module 
SISIM V1.203 
10001-1.0MSISIMV1.203-00 Generates 3-D spatially 
correlated fields 
3.9 
GSLIB V2.0 Module 
SISIM V2.0 
10098-2.0MSISIMV2.0-00 Generates 3-D spatially 
correlated fields 
3.9 
INFIL V2.0 10127-2.0-00 Calculates field water balance 
and net infiltration 
3.5 
INFIL2GRID V1.6 10077-1.6-00 Maps infiltration onto grids for 
simulating flow and transport 
3.6, 3.7, 3.8 
iTOUGH2 V3.2 10054-3.2-00 Inverse calculations for 
TOUGH2 
3.6

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Software 
Name/Version 
Software Tracking Number Short Description Used in AMR(s) 
Supporting PMR 
Section 
iTOUGH2 
V3.2_DRIFT 
10055-3.2_DRIFT-00 Inverse calculations for 
TOUGH2 (for drift calculations) 
3.9 
iTOUGH2 V4.0 10003-4.0-00 Inverse calculations for 
TOUGH2 with additional 
features 
3.9 
LAGRIT V1.0 10212-1.0-00 Developing grid for Busted 
Butte 
3.11 
LHS V2.50 10205-2.50-00 Monte Carlo simulation using 
Latin Hypercube Sampling 
3.5 
SOLVEQ/CHILLER 
V1.0 
10057-1.0-00 SOLVEQ calculates species, 
CHILLER simulates equilibria 
3.10 
STO-UNSAT V1.0 10292-1.0-00 Stochastic method simulations 
for Busted Butte 
3.11 
SUPCRT92 V1.0 10058-1.0-00 Calculation of thermodynamic 
properties to 500 MPa, 1,000C 
3.10 
T2R3D V1.4 10006-1.4-00 Transport modeling with active 
fracture concept 
3.7, 3.11 
TOUGH2 V1.3 10061-1.3-00 TOUGH2 with fracture-matrix 
interaction and enhancements 
2.3 
TOUGH2 V1.4 10007-1.4-01 TOUGH2 with active fracture 
concept and further upgrades 
3.7, 3.8, 3.11 
TOUGHREACT V2.2 10154-2.2-00 TOUGH2 with reactive transport 
chemistry 
3.8, 3.10 
TOUGHREACTE9 
V1.0 
10153-1.0-00 EOS9 for TOUGHREACT 3.8 
WinGridder V1.0 10024-1.0-00 Interactive mesh generator for 
TOUGH2 family 
3.4 
1.4 RELATIONSHIP TO OTHER PROCESS MODEL REPORTS AND KEY 
PROJECT DOCUMENTS 
Figure 1-1 shows the relationship between the UZ PMR and other key project documents; this 
relationship is also briefly described in the beginning of this chapter. The UZ PMR uses directly 
the geological framework, mineralogical and rock properties information from the ISM PMR. 
The UZ PMR is also closely connected to three other PMRs, the Near-Field Environment (NFE), 
Engineered Barrier System (EBS) and Saturated Zone (SZ) Flow and Transport PMRs through 
analysis performed in TSPA. The NFE models describe the evolving thermodynamic conditions 
near the emplacement drift using fine-grid, drift-scale, coupled process models. The EBS models 
in TSPA utilize information on water seepage and chemistry as well as gas chemistry from 
models provided to TSPA from the UZ PMR and the NFE PMR. Finally, the models developed 
within the UZ PMR provide temporal and spatial distributions of water recharge and 
radionuclide concentrations at the water table to the flow and transport models developed within 
the SZ PMR. All of these interfaces and data flows occur in the TSPA and not within the 
individual PMRs.

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The specifications for the reference repository design used in the development of the UZ PMR 
and its supporting AMRs were from design input transmittals (CRWMS M&O 1999e; CRWMS 
M&O 1999f). These designs were based on the technical requirements baseline of Enhanced 
Design Alternative II (Wilkins and Heath 1999; CRWMS M&0 2000, EBS PMR, Section 2.5). 
Since that time, a number of modifications to the repository design have been under 
consideration. For example, backfill is no longer part of the design (Stroupe 2000) and the final 
design may extend the northern boundary of the repository approximately 600 meters. These 
design changes were not issued when the analysis and modeling work for the UZ was being 
performed and therefore could not be incorporated into the UZ AMRs. Evaluation of the impact 
of all of these design changes may require modification of models and additional simulations. 
The impact of these, or any, design changes will have to be evaluated once all of the design 
changes are finalized. The impact of excluding backfill is briefly discussed qualitatively at the 
end of Section 3.10.2.1.

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2. EVOLUTION OF THE UZ SITE CHARACTERIZATION PROGRAM  DATA 
COLLECTION AND MODEL DEVELOPMENT SUPPORTING THE UZ PMR 
This chapter summarizes the evolution of data-collection activities and the development of 
models for the unsaturated zone (UZ) of Yucca Mountain. The testing and modeling activities 
are used to characterize the site, evaluate the processes, and assess the viability of Yucca 
Mountain as a site for a potential nuclear waste repository. This chapter also summarizes issues 
identified by overseeing bodies, peer review groups, and other parties. The Department of 
Energy (DOE) Yucca Mountain Site Characterization Project (YMP) has evaluated the Yucca 
Mountain site for over two decades. The data-collection activities have evolved from intensive 
surface-based investigations in the early 1980s to the current focus on testing in underground 
drifts. The models have evolved from early conceptual descriptions of the site to current 
numerical model representations at relevant site- and drift-scales. The Yucca Mountain site 
investigations have contributed to the improved scientific understanding of UZ processes, and 
have benefited from studies at other analog sites and from the technical developments in the 
earth science disciplines. 
Section 2.1 presents the chronology of the site characterization activities and a summary of the 
main characteristics of the Yucca Mountain site. Section 2.2 describes the specific activities 
associated with geological mapping, hydrological studies, geochemical samplings, and thermal 
testing activities. Information used as corroborative evidence obtained from analog studies is 
summarized in Section 2.3. The site-specific data, together with scientific and technical 
knowledge associated with flow and transport at analog sites and UZ studies, form the basis for 
the Yucca Mountain UZ model formulation, calibration, and validation. The evolution of the UZ 
models is summarized in Section 2.4. UZ flow and transport issues raised by peer review groups 
and panels, Nuclear Regulatory Commission (NRC), and Nuclear Waste Technical Review 
Board (NWTRB), and in the TSPA-VA, PA Workshop and UZ Model Workshop are presented 
in Section 2.5. The overview presented in this section provides some background and context 
for the detailed discussion of the current UZ models and analyses in Section 3. Any inferred 
conclusions in this section will be substantiated in detailed analyses in Section 3 or in cited 
Analysis/Model Reports (AMRs). 
2.1 UZ CHARACTERIZATION PROGRAM AT YUCCA MOUNTAIN 
This section summarizes the development of the site characterization program in Section 2.1.1, 
presents the chronology of the site characterization activities in Section 2.1.2, discusses some 
specific process issues for the UZ in Section 2.1.3, and summarizes characteristics, boreholes 
and underground facilities at the Yucca Mountain site in Section 2.1.4. 
As a site for a potential nuclear waste repository, Yucca Mountain is considered to have the 
favorable hydrogeological characteristics: (1) a desert setting with arid climate and (2) a deep 
water table with a thick UZ. In a desert environment, the total amount of available water is small. 
The potential UZ repository will be designed to complement the hydrological environment of 
limited water flux by further diverting the small flow of water that does occur away from the 
wastes emplaced between the ground surface and the deep water table. Multiple natural barriers 
and engineered barriers are expected to contribute to limiting the contact between water and 
waste packages, and retarding radionuclide migration.

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2.1.1 Development and Documentation of the Site Characterization Program 
The concept of emplacing nuclear waste in the UZ in the arid region in and around the Nevada 
Test Site (NTS) was first proposed by the U.S. Geological Survey (USGS) (McKelvey 1976; 
Winograd 1981, pp. 14571464). DOE selected Yucca Mountain, near the southwest corner of 
NTS, for detailed study and extensive surface-based drilling and investigations in the 1980s. The 
Nuclear Waste Policy Act of 1982 was amended in 1987 to focus the U.S. effort on the Yucca 
Mountain site. A Site Characterization Plan (SCP) was completed in 1988 for systematic 
surface-based investigations, underground testing, laboratory studies, and modeling activities 
(DOE 1988). The in situ field testing was planned to be conducted in boreholes and in an 
underground tunnel, the Exploratory Studies Facility (ESF). 
The Yucca Mountain Site Description (YMSD, CRWMS M&O 1998a through 1998f) 
summarizes the results of the site characterization program up to 1998. The Viability Assessment 
of a Repository at Yucca Mountain (VA, DOE 1998, Section 3.1) applies the available data to 
(and discusses the uncertainties in) a total system performance assessment (TSPA). This UZ 
Process Model Report (PMR), together with eight other PMRs and associated AMRs, is being 
developed to support the TSPA for Site Recommendation (SR) and Licensing Application (LA) 
with traceable and verifiable data. The VA (DOE 1998, p. 25) and the repository safety strategy 
(CRWMS M&O 2000b, p. 32) identify four attributes for safe disposal: limited water contact 
with waste packages, long waste-package lifetime, low rate of radionuclide release from 
breached waste packages, and reduction of radionuclide concentration during transport. Seepage 
into drifts and the reduction in radionuclide concentration by matrix diffusion and sorption in the 
UZ are two principal factors evaluated by this UZ PMR for assessment of the potential 
repository performance and safety. 
2.1.2 Chronology of Drilling/Excavation, Testing, and Modeling 
The evolution of the UZ site characterization activities in (1) drilling/excavation, (2) testing, and 
(3) modeling are summarized in Figure 2.1-1. The activities in Figure 2.1-1 are discussed 
throughout Section 2 of this PMR. Figure 2.1-2 illustrates the locations of the main deep surfacebased 
boreholes and the underground ESF drifts in the vicinity of the potential repository block 
at Yucca Mountain. 
The evolution of the drilling/excavation, testing, and modeling activities are closely coupled in 
the site characterization program. In the following discussion, the focus of each category of 
activities is described in terms of four distinct periods: (1) the early 1980s, (2) the period from 
1986 to 1991, (3) the early 1990s, and (4) the current period (mid-1990s to the present). Specific 
references to technical advances and highlights of testing and modeling activities are not cited 
here; further details follow this discussion of the chronology of the site characterization program. 
(1) Drilling/Excavation. To characterize the site and to conduct in situ testing, extensive 
borehole drilling and excavation have been conducted at Yucca Mountain to characterize the tuff 
layers and structures and to access the potential repository underground environment. During the 
first period, the drilling of boreholes from the land surface was the main focus of activity. The 
second period was devoted to the development of characterization plans, including the 
formulation of the quality assurance (QA) programs. The design of the original shaft access for

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the ESF in the SCP (DOE 1988) was revised to adopt ramp access by the end of this period. The 
third period launched the specific design, preparation, and excavation of the ESF for 
underground access to the rock units surrounding the potential repository emplacement drifts. 
Borehole drilling was resumed over the site for UZ hydro-chemical investigations and along the 
North Ramp of the ESF for design and geotechnical evaluations. During the current period, the 
excavation of the main loop of the ESF and the Cross Drift was completed, alcoves and niches 
were excavated, and boreholes were drilled for enhanced characterization of the repository block 
(ECRB). 
(2) Testing. Surface-based investigations and underground tests have been conducted to 
characterize and to evaluate the suitability of the site for a potential repository. The surfacebased 
reconnaissance era of the first period collected most of the data used to establish the 
geological framework of Yucca Mountain. During the near-surface monitoring era of the second 
period, intensive laboratory measurements of flow and transport parameters were conducted. In 
the deep-borehole testing era in the third period, collections of samples for hydrological and 
geochemical characterization (especially for 36Cl and calcite studies) were intensified and 
networks of boreholes were instrumented for pneumatic and moisture monitoring. As the project 
has matured, it has identified key scientific studies that are required to increase the understanding 
of hydrologic and transport processes. In the current underground testing era, the main focus of 
testing activities is on the UZ processes that control seepage into the drifts, heat transfer around 
the drifts, and transport through the UZ. Section 2.2 describes the data collection activities. 
(3) Modeling. The scientific studies have included testing and modeling for a range of processes 
and for a range of scales. The conceptual models for Yucca Mountain site were formulated in the 
early 1980s. The heat transfer and thermal-hydrological (TH) modeling methodologies were 
established in the late 1980s. During the third period, the integration of site data into models was 
initiated and the basic probabilistic approach for TSPA was improved. In the current period, the 
calibration, validation, and integration of UZ process models and the direct inputs to TSPA 
models were conducted. The process models include UZ site scale flow and transport models, 
drift-scale seepage models, and coupled models for various combination of thermal, 
hydrological, mechanical, and chemical processes in site and in drift scales. The integration of 
UZ modeling with testing and the interaction of UZ process models with TSPA models illustrate 
how scientific methods have worked for the evaluation of UZ flow and transport at Yucca 
Mountain. Section 2.4 describes the evolution of the modeling activities. 
2.1.3 Stimulating Issues for the UZ 
The basic issues of limited water flow to the potential repository horizon and retarded 
radionuclide transport through the UZ were formulated in the early 1980s and were assessed 
consistently for over two decades. In the course of site characterization of this unique system, 
new concepts and hypotheses were developed and controversial issues were evaluated and 
resolved (or uncertainties addressed). The topics of focus within the site characterization 
program evolved dynamically, especially in the early period before the SCP. The stimulating 
topics in the 1980s include the origins of near-surface caliches, the possibility of water table rise 
under conditions of wet climates and seismic events, and the potential benefit of a hot potential 
repository with high temperatures induced by concentrated waste-loading. The topics of focus in 
the 1990s include the detection of bomb-pulse signals from chloride-36 (36Cl) measurements in

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borehole and ESF samples, the estimation of higher percolation fluxes than previously modeled, 
and the field observation of seepage thresholds that may limit the water flux into drifts. 
Currently, the YMP also places more emphasis on the potential benefit of the engineered barrier 
system (EBS) with drip shield and/or backfill protecting the waste packages, and with ventilation 
and wide-drift spacing maintaining the temperature of most of the water in the potential 
repository rock below its boiling point. 
These topics are related to issues associated with keeping the water away from the waste 
packages and reducing the radionuclide concentration that could reach the accessible 
environment. The UZ processes and mechanisms addressing these and related topics are 
discussed in sections of this chapter on the evolution of the UZ site characterization program and 
in sections of Chapter 3 on UZ flow and transport models. A brief summary of relevant sections 
for the topics evolved in the site characterization program is given below. 
The origin of near-surface caliches and the potential for water-table rise are discussed in Section 
2.2.1. The possibility of upward movement of water from the deep water table was evaluated 
extensively in the 1980s. 
The possibility of keeping water out of the vicinity of waste packages by boiling it away 
motivated the hot repository concept, as discussed in Section 2.2.4.1 on TH modeling. The driftscale 
thermal-hydrological-chemical (THC) processes induced by the heat released by emplaced 
wastes are discussed in Section 3.10. 
The detection of 36Cl bomb-pulse signals stimulated the evaluation of fast flow paths, as 
discussed in Section 2.2.3. Since the water flows through the UZ in the matrix and in the 
fractures, most of the hydrological tests and geochemical studies discussed in Sections 2.2.2 and 
2.2.3 are related to the quantification of the partitioning of total flux between fracture flow 
component and matrix flow component. 
Over the site scale, percolation-flux magnitude and distribution are evaluated and updated as 
more site characterization data are collected. The evolution of percolation-flux estimate from low 
to high values is discussed in Section 2.4. The diversion of infiltrating water to steeply dipping 
and near-vertical faults above the potential repository horizon can reduce the percolation flux 
reaching the potential emplacement drifts. The perching of water and the diversion of percolation 
flux to faults at tuff unit interfaces below the repository horizon can affect the effectiveness of 
zeolites and clays for radionuclide retardation. 
In the drift scale, the seepage into drifts can be a fraction of percolation, as discussed in Section 
2.2.2.2 on tests conducted at the potential repository horizon. The capillary forces arising from 
unsaturated conditions can prevent water from entering waste emplacement drifts. If the 
percolation flux is less than a seepage threshold, no seepage into drifts occurs. The seepage 
models and analyses are discussed in Section 3.9. 
To protect waste packages further from seepage into drifts, engineered barriers with drip shields 
and/or backfill are being evaluated. The performance of engineered barriers is closely related to 
the amount of water available to contact the waste packages.

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In addition to seepage from the ceiling, lateral influx through the walls may also contribute to the 
water available in the drifts. Some of tests discussed in Section 2.2.2.2 evaluate the lateral flows 
at tuff unit interfaces. Perching at the tuff interface can enhance the potential of lateral flow and 
lateral seepage for drifts intercepted by tuff unit interfaces. The drainage below the drifts is 
another important process for fluid to move away from the waste packages and transport through 
the UZ. The monitoring of water migration is discussed in Section 2.2.2.2. 
One of the more recent topics addressed by the site characterization program is on the benefits of 
keeping the water in tuff rocks surrounding the waste emplacement drifts from boiling, with 
wide drift spacing to allow bulk of flow moves through the pillars and with long-term ventilation 
to remove heat from the emplaced wastes. The TH analyses of multiple drifts are presented in 
Section 3.12. 
The topics listed in this section are subsets of issues for the UZ addressed in the site 
characterization program. Most of these topics are also identified by overseeing bodies, peer 
review groups, and other interested parties, as discussed in Section 2.5. 
2.1.4 Yucca Mountain Boreholes and ESF Drifts 
This section describes the surface-based boreholes and the ESF drifts. A summary of the Yucca 
Mountain site characteristics is also presented. 
Over two hundred vertical boreholes have been drilled from the surface for the YMP. These 
boreholes are referred to as surface-based boreholes. The first YMP borehole was drilled in 
1978. Over one-fourth of the surface-based boreholes are over 300 m deep, with 80% of deep 
boreholes drilled in the early 1980s and 20% drilled in the 1990s. Most of the early boreholes 
penetrating the entire UZ were drilled away from the potential repository block along nearby 
washes. The geological (G) series, hydrological (H) series, water table (WT) series, and 
unsaturated zone (UZ) series of boreholes were all initiated in the late 1970s or early 1980s. 
(Additional official prefixes UE25 for boreholes located within the NTS and USW for boreholes 
outside the NTS boundary are omitted in this section.) 
The early deep boreholes are used to define the stratigraphy, to locate the water table, to collect 
cores, and to test in situ borehole monitoring techniques. The main tuff units in the UZ at Yucca 
Mountain are the Tiva Canyon welded hydrogeologic unit (TCw), the Paintbrush nonwelded 
hydrogeologic unit (PTn), the Topopah Spring welded hydrogeologic unit (TSw), and the Calico 
Hills nonwelded hydrogeologic unit (CHn). The nomenclature of hydrogeologic units is adapted 
from Montazer and Wilson (1984, pp. 919) and explained in Section 3.2 of this PMR. 
Nearly one hundred shallow boreholes were drilled with depths less than 100 m for near-surface 
infiltration studies, with three-quarters of the infiltration boreholes drilled in the early 1980s and 
the remainder in the early 1990s. The infiltration study collected water-content profile data for 
over ten years and provided input data to the UZ flow and transport models at the upper UZ 
boundary. 
The construction of the starter tunnel for the ESF was initiated in 1992. Construction of the ESF 
was supported by additional surface-based boreholes drilled along the North Ramp (NRG series 
of boreholes) and along the Main Drift for systematic drilling (SD series of boreholes) in the

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potential repository block. Pneumatic and moisture monitoring sensors were installed in most of 
the boreholes in the NRG and SD series, together with selected boreholes in the UZ series. 
Figure 2.1-2 includes the main deep boreholes in the vicinity of the Yucca Mountain potential 
repository block. A borehole drilled by the Nye County (borehole ONC-1) was also instrumented 
with sensors for monitoring. 
The 8 km long, 8 m diameter ESF main loop was excavated with a Tunnel Boring Machine 
(TBM) from 1994 to 1997. The 2.7 km long, 5 m diameter ECRB Cross Drift was excavated 
with a smaller TBM in 1997 and 1998. Underground testing, calcite and 36Cl sampling, and 
moisture monitoring studies were initiated during the ESF North Ramp excavation in 1995, 
intensified in 1998, and continued to the present time. 
The ESF is the largest effort of the site characterization program and provides direct 
underground access to the upper tuff units. Yucca Mountain is a flat-topped ridge running 10 km 
from north to south and rising approximately 300 m above the adjacent valleys. With the ridgetop 
and underlying tuff layers gently tilted to the east, the middle of the UZ can be accessed by 
nearly horizontal ramps of the ESF from the base of the eastern slopes. The ESF ramps penetrate 
TCw, PTn, and the upper lithophysal zone of TSw. 
The primary potential repository block is located between the north-south trending ESF Main 
Drift and Solitario Canyon to the west. The Main Drift is at the depth of the potential repository. 
Most of the Main Drift is located in the middle nonlithophysal zone of TSw (Tptpmn, the 
stratigraphic nomenclature of Buesch et al. 1996, pp. 58, labeled as tpmn in figures of this 
section). During and after the construction of the ESF, seven alcoves and four niches were 
excavated along the ESF for in situ testing and monitoring of UZ processes, as illustrated in 
Figure 2.1-3. 
Photographs and schematic illustrations of the test sites are presented in Section 2.2. The ESF 
tests include air-injection tests in all alcoves (including Alcove 2 for the Bow Ridge fault and 
Alcove 6 for the Ghost Dance fault) and niches, the infiltration test at Alcove 1, the faultdamping 
test at Alcove 4, the Single Heater Test (SHT) and Drift-Scale Test (DST) at Alcove 5, 
seepage tests at Niches 3650, 3107, and 4788, the fracture-matrix interaction test at Alcove 6, 
and moisture monitoring in sealed Niche 3566, in sealed Alcove 7, and along open (ventilated) 
tunnel segments. 
Figure 2.1-4 illustrates the stratigraphic units penetrated by the ECRB Cross Drift and the 
locations of two test sites (Alcove 8 and Niche 1620) under excavation for testing of seepage. 
The ECRB Cross Drift provides underground access to the lower lithophysal and lower 
nonlithophysal tuff zones of TSw (tpll and tpln in Figure 2.1-4) respectively, and to the Solitario 
Canyon fault. Approximately 10% of the potential repository area is located in the middle 
nonlithophysal zone of TSw, 78% in the lower lithophysal zone, and 12% in the lower 
nonlithophysal zone. 
Figure 2.1-4b also illustrates that PTn and the upper lithophysal zone (tpul in Figure 2.1-4) of 
TSw are exposed on the steep outcrop below the crest of Yucca Mountain on the Solitario 
Canyon wall. Some of the lower tuff units can be seen at outcrops of other more remote ridges to 
the east and to the southeast of Yucca Mountain. At one of these locations, Fran Ridge, the

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fractures of middle nonlithophysal zone of TSw were mapped, and an above ground thermal test 
was conducted in a block carved from the outcrop of middle nonlithophysal zone of TSw (the 
large block test or LBT). At Busted Butte, the vitric CHn is exposed. A test facility was 
excavated for UZ transport testing at Busted Butte. (A photograph presented in Figure 2.2-12 in 
Section 2.2 illustrates the locations of Fran Ridge and Busted Butte relative to the Yucca 
Mountain ridge.) The deeper units, including the zeolitic CHn, can only be accessed by the 
available deep boreholes. 
2.2 DATA COLLECTION AND IN SITU FIELD TESTING 
This section describes the evolution of activities for geological data collection in Section 2.2.1, 
the hydrological testing and data collection in Section 2.2.2, the geochemical data collection in 
Section 2.2.3, and the thermal testing in Section 2.2.4. The surface-based data collection 
activities have evolved from surface surveys, trench studies, and infiltration studies with shallow 
boreholes, to testing and monitoring of deeper boreholes. The underground data collection 
activities have evolved from sampling and testing in short horizontal and slanted boreholes to 
seepage, thermal, and transport testing in niches, alcoves, and test beds. 
2.2.1 Geological Reconnaissance and Data Collection 
The stability of the geological structures and spatial distribution of the tuff units and faults were 
the focus of early geological studies. This section focuses on the UZ, delineated by the upper 
ground surface and the deep water table. 
The stability of the geological environment is one of the early issues addressed in the study of 
Yucca Mountain. The tuff units from TCw to TSw were formed 12.7 to 12.8 million years (Ma) 
ago by eruptions from volcanic vents associated with calderas to the north. The Yucca Mountain 
landform has changed little since its formation. The erosion in the Yucca Mountain region 
generally has proceeded slowly. The modern landforms of ridges and valleys had been 
established 11.6 Ma ago when the Rainier Mesa tuff was deposited (Sawyer et al. 1994, 
pp. 13041318). Most of the surface deposits are alluvium in the washes and valleys. Only rock 
rubbles and a very thin to nonexistent veneer of colluvium cover the bedrock ridges and slopes. 
Near-surface carbonate deposits (caliche) extend to shallow depths as fracture fillings. Evidence 
from trench studies indicates that the caliche deposits are pedogenic in origin, related to the 
formation of soil under arid and semi-arid climates. In the pedogenic process, downward 
infiltrating rainwater dissolves carbonate minerals at the surface and reprecipitates them at 
shallow depth as a result of evapotranspiration. The speculation that caliche forms from seismic 
pumping from the water table has not been substantiated (Stuckless et al. 1991, pp. 551554; 
CRWMS M&O 1998d, Section 3.4.3.4.2). 
The bedrock of Yucca Mountain is mainly in the fractured TCw hydrogeological unit. The 
bedrock is incised by a series of east-to-southeast-trending stream channels. In the north, the 
ridge is cut by northwest-to-southeast trending washes associated with faults. The early 
geological mapping of Yucca Mountain by Scott and Bonk (1984) was updated and refined by 
Day et al. (1998) to include additional small faults on the surface (e.g., the Sundance fault in the 
potential repository block, Spengler et al. 1994, pp. 911; Potter et al. 1999, pp. 115). The 
fracture patterns in the bedrock were also mapped in pavement studies (with thin soil covers

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removed) and in shallow-pit studies of fractures exposed on the walls. Mapping and sampling 
data along transects, especially along washes and valleys, together with regional geophysical 
surveys were used to construct early stratigraphic and structural models for Yucca Mountain. 
The stratigraphic description of the tuff units were refined with coring, mapping, and 
geophysical logging data from surface-based boreholes, and confirmed by data collected in the 
underground drifts. The division of tuff units into members, zones, and subzones is based on 
variations in degree of welding (compaction and fusion at high temperatures), abundance of 
lithophysae (cavities formed by bubbles of volcanic gases trapped in the tuff matrix during 
cooling), depositional features, crystal content, mineral composition, pumice and rock fragment 
abundance, and fracture characteristics (Moyer et al. 1996, pp. 779; Buesch et al. 1996, pp. 4 
16) (see Section 3.2 of this PMR). Detailed line surveys and full peripheral mapping of fracture 
networks were conducted along the ESF drifts (Barr et al. 1996, pp. 133135; Albin et al. 1997, 
pp. 161163; see data sources listed in Appendix I of this PMR). New features were mapped, 
including the observations of an intensely fractured zone in the southern part of the ESF Main 
Drift (Buesch and Spengler 1998, p. 19) and several new faults in the western part of the ECRB 
Cross Drift (see data sources listed in Appendix I of this PMR). The geologic mapping and 
geophysical studies conducted on the surface and in the ESF are summarized in Figure 2.2-1. 
The water table defines the lower boundary of the UZ. The water table at Yucca Mountain is 
approximately 500 to 750 m below the ground surface. A large hydraulic gradient just north of 
the potential repository area was inferred from the relatively high water tables observed in three 
boreholes north of the Pagany Wash (Luckey et al. 1996, pp. 2137; CRWMS M&O 2000, 
U0000, Section 4.1). Alternative hypotheses have been proposed to interpret the large gradient, 
involving either the de-coupling of the northern aquifer system from the southern aquifer system 
or the existence of perched water bodies (Ervin et al. 1994, pp. 512; Czarnecki et al. 1994, pp. 
249250; 1995, pp. 191192). The other issue associated with the water table is its potential rise 
in response to wetter climates or to seismic events. Analyses of the mineral alternations indicate 
that the highest water rise of the ancient water table was less than 120 m above the current water 
table. 
The results of the geological data collection for Yucca Mountain are summarized in the YMSD 
(CRWMS M&O 1998d, Section 3), incorporated in the Geologic Framework Model 
(GFM)/Integrated Site Model (ISM) (CRWMS M&O 1997a and CRWMS M&O 2000, ISM 
PMR), and used in developing the numerical grid for the UZ Model (CRWMS M&O 2000, 
U0000, Sections 6.5, 6.6, 6.7; see Section 3.2 of this PMR). 
2.2.2 Hydrological Testing and Data Collection 
YMP hydrological testing and data collection evaluate climate/infiltration, percolation, seepage, 
and migration. The net infiltration into the tuff layers is a small fraction of the precipitation at the 
ground surface and represents the inflow to the UZ model at the upper boundary. The percolation 
process redistributes the infiltration, determines the fluxes throughout the UZ and at the potential 
repository horizon, and provides the source of recharge to the saturated zone below the potential 
repository. Diversions to the boundary faults (steeply dipping to near vertical faults at the 
boundaries of the potential repository block) reduce the percolation flux through the potential 
repository block from the net infiltration value. The seepage process determines the fraction of

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percolation dripping or seeping into the drifts. Seepage into drifts occurs at the interface between 
the natural geological barriers of the UZ and engineered barriers within the drift. As such, 
seepage depends not only on rock characteristics, but also on the drift opening size and shape, as 
well as excavation-induced perturbations in the vicinity of the drift. Water drainage through the 
drift floor and radionuclide transport through the UZ constitutes the migration process. 
The climate/infiltration studies were initiated in the mid-1980s. The percolation studies were 
intensified in the 1990s with more data collected and finer models developed, as discussed in 
Section 2.4 of this PMR. The seepage tests and moisture monitoring in the ESF were conducted 
in the late 1990s. The transport test at Busted Butte is summarized in Section 2.2.3 and the 
thermal tests in the ESF are summarized in Section 2.2.4. Before discussing the thermal and 
transport tests and modeling, the following sections focus on hydrological testing and monitoring 
activities. Section 2.2.2.1 is on the surface-based investigations and hydrological property 
measurements. Section 2.2.2.2 is on the underground testing and monitoring of drift seepage, 
fracture-matrix interaction, fault flow, large-scale infiltration and seepage tests, air-permeability 
tests and potential monitoring. 
2.2.2.1 Surface-Based Investigations and Hydrological Property Measurements 
Modern climate data have been collected in and around the Yucca Mountain site since 1988. The 
climate at Yucca Mountain is arid. On average, Yucca Mountain receives about 190 mm of rain 
and snow per year; nearly all the precipitation (about 95 percent) is either run-off or lost to 
evaporation (Hevesi et al. 1994, pp. 25202529). The climate study also evaluates the long-term 
records of analog sites, e.g., calcite dating data from Devils Hole (Winograd et al. 1992, pp. 255 
260), and microfossil records from Owens Lake (Forester et al. 1999). Geological information 
indicates that the regional climate has changed over the past million years and that long-term 
average precipitation is somewhat greater than modern conditions. Future climate scenarios use 
available climate data from wetter analog sites in western states (CRWMS M&O 1998a, Section 
4.3; USGS 2000, U0005, Section 6.6; see Section 3.5 of this PMR). 
The infiltration study at Yucca Mountain was initiated in 1984. To date, the infiltration study has 
used nearly 100 shallow boreholes across washes and on the crest to measure the changes in 
water-content profiles in response to precipitation and snow-melt events (Flint and Flint 1995; 
USGS 2000, U0010, Sections 6.3 and 7.1; see Section 3.5 of this PMR). Weekly or monthly 
measurements were collected from 1984 through 1995. The Pagany Wash and three other washes 
were instrumented for run-on and run-off measurements. Water-balance calculations from 
precipitation, evapotranspiration, run-on, and run-off along washes are used to derive the net 
infiltration flux values over the ridge top, side slopes, and stream channels. Areas with exposed 
bedrock and no soil cover have a different infiltration flux compared to areas with soil covers 
that have substantial storage capacity for excess water. Figure 2.2-2 provides a summary of the 
surface infiltration studies performed. The net infiltration distributions for different climate states 
over the bedrock are used as upper boundary conditions for the UZ Flow and Transport Model 
and TSPA models. 
The collection and processing of drill cores began with the surface-based borehole program. The 
characteristic curves of water content (saturation times porosity) as a function of water potential, 
together with permeability, porosity, and rock densities, were measured in the laboratory on

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samples and cores collected from bedrock transects, surface-based boreholes, and alcove, drift, 
and niche boreholes in the ESF. The laboratory measurements indicate that the matrix of the PTn 
and CHnv units have high-enough permeabilities to conduct net infiltration, while the TCw, 
TSw, and CHn (zeolitic) units have low matrix permeabilities that could promote a larger 
fracture flow component. The laboratory techniques for tuff samples have evolved from the 
adoption of established soil-testing methods (e.g., submerged pressure cell, chilled-mirror 
psychrometer, transient diffusivity measurements) to the use of an ultracentrifuge for relative 
permeability measurements. The matrix properties of thousands of samples are used to define 
hydrogeological units (Flint 1998, pp. 34; CRWMS M&O 2000, U0090, Section 6.2; see 
Sections 3.2 and 3.6 of this PMR). Soil properties were also measured to support geotechnical 
evaluation of the near surface, especially during the ESF preparation period. 
The surface-based borehole testing program in the early 1980s included the instrumentation of 
the first UZ borehole, UZ-1, in the Drill Hole Wash (Montazer 1987, pp. 3142) and the 
measurement of pneumatic signals in a pair of boreholes, UZ-6 and UZ-6a, on the crest near the 
Solitario Canyon cliff (Weeks 1987, pp. 165170). Eight deep boreholes were instrumented in 
the 1990s for extensive testing and monitoring. This program included the measurement of 
barometric pressures in sealed borehole intervals or in the borehole annulus with an inflatable 
borehole sealing system (Rousseau et al. 1999, pp. 55122). The pneumatic data (damping and 
lag of barometric signals) were used to derive the effective parameters for the PTn unit and the 
properties of the Ghost Dance fault (CRWMS M&O 2000, U0035, Sections 6.1, 6.2, 6.3). Air 
permeability was measured along four surface-based boreholes with straddle packers (LeCain 
1997, pp. 923). In situ moisture potentials and temperatures were also measured in sealed 
borehole intervals. The data sets obtained through the surface-based borehole testing program, 
specifically pneumatic signals between boreholes, core saturation data from laboratory 
measurements, and in situ moisture potential profiles, were used to calibrate the Flow Model for 
the UZ and determine the effective fracture-flow component of the total flow through the 
hydrogeological units (CRWMS M&O 2000, U0050, Section 6.6; see Sections 3.6 and 3.7 of 
this PMR). 
The partitioning of total flux between fracture flow component and matrix flow component is 
one of the most important processes to determine in the UZ flow field. Percolation or UZ flow 
distribution determines the amount of water that could potentially contact the waste packages 
and other components of the Engineered Barrier System (EBS). The magnitude of percolation 
flux and its distribution between the fractures and matrix are predicted by the UZ Flow and 
Transport Model based on calibration against all available data. Early estimates of percolation 
flux were based on the assumption of matrix-dominated flow that was calibrated by saturation 
profile data alone (see Section 2.4 of this PMR on early percolation flux estimates of < 1 mm/yr). 
Subsequent investigations have shown that the welded tuff matrix has low permeability and that 
therefore matrix flow is a small fraction of the percolation flux in the TCw and TSw units. 
Currently, the estimates of percolation flux range from 1 to 10 mm/yr. These higher values result 
from the inclusion of temperature, age-dating, and geochemical data together with pneumatic and 
hydrological data. The additional field data that indicate higher values of percolation flux include 
the prevailing low geothermal gradient associated with convective heat transfer, the relatively 
young water found at depth, and the low concentration of dissolved salts in pore water and in 
perched water bodies. The evolution of the percolation flux estimate dramatically illustrates its

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close coupling with the evolution of data-collection activities in the UZ site characterization 
program (see Sections 3.6 and 3.7 of this PMR). 
Perched water information is one of the most important pieces of hydrological data for UZ sitescale 
model calibration. While most of the tuff units are unsaturated, perched water bodies exist 
in the north below the potential repository horizon and in the south in the vicinity of the Ghost 
Dance fault. Perched water bodies (i.e., localized zones that are fully water-saturated) can occur 
either above a low-permeability barrier or above a capillary barrier. Perched water bodies have 
been encountered in boreholes at both the vitrophyre between the TSw and CHn units and at the 
vitric-zeolitic interface (CHnv-CHnz) within the CHn unit. Pumping tests were conducted to 
evaluate the spatial extent of the perched water bodies, and water samples were collected for age 
dating. When water perches at tilted interfaces, lateral redistribution of percolation flux can 
occur. The absence of perched water bodies at the boundaries of the PTn unit and the presence of 
perched water bodies at interfaces within the CHn unit suggest that lateral redistribution is 
relatively ineffective above the potential repository horizon, but significant below. The process 
of lateral diversion by the CHn interfaces and the mechanism of mixing within the perched water 
bodies greatly affect radionuclide transport in terms of both the retardation potential of the CHn 
and the capacity for dilution within the UZ (see Sections 3.3.8, 3.7 and 3.11 of this PMR). 
2.2.2.2 Underground Testing and Monitoring 
The ESF provides direct access to the UZ environment. The locations of the alcoves and niches 
for underground studies were shown previously in Figure 2.1-3. The underground studies have 
evolved rapidly through three stages as they develop new emphases and different approaches. 
For the first stage during the North Ramp excavation period, methodologies developed and 
deployed in surface-based borehole testing were applied to the underground ESF. Four alcoves 
were excavated in the first part of the ESF North Ramp to provide access to specific features and 
hydrogeological units. Alcove 1 provides access to the upper TCw unit, Alcove 2 to the Bow 
Ridge fault, Alcove 3 to the upper PTn contact, and Alcove 4 to the lower PTn contact. These 
alcoves were largely used in the mid-1990s as drill bays for horizontal and slanted boreholes to 
collect cores, measure air permeability, and sample gases (LeCain 1998, pp. 1228; Rousseau et 
al. 1999, pp. 55122). In the second stage, three alcoves were excavated along the Main Drift. 
Alcove 5 was dedicated to thermal testing. Alcoves 6 and 7 were designed to measure the 
properties of the Ghost Dance fault located to the east of the Main Drift. The thermal tests are 
discussed in Section 2.2.4 and Section 3.10 of this PMR. 
In the third stage, four niches (Niches 3566, 3650, 3107, and 4788niches are short drifts, 
typically 10 m long) were excavated along the ESF Main Drift in the northwest direction into the 
potential repository block to test the drift seepage processes. Two test beds with slot undercuts 
were constructed in Alcoves 4 and 6 to conduct fracture-matrix and fault-matrix interaction tests. 
Alcove 1 was instrumented with seepage collectors and wall sensors for a large-scale infiltration 
and seepage test. The tests in these sites have one feature in common: the use of water and 
aqueous phase tracers to directly evaluate hydrological processes. This is a drastic departure 
from the previous approach in UZ testing, where the concerns about contamination and 
perturbation of the ambient unsaturated states discouraged the use of water in surface-based 
drilling and testing. The change in approach arises from the fact that it is much easier to control 
water releases and quantify water movement in the underground (ESF) environment compared to

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injection into deep boreholes. In addition, while boreholes could be drilled dry, the use of 
construction water to control dust during TBM excavation already perturbed the ambient 
saturation state. Evaluating the migration of the construction water itself provided useful site 
data. This was done by coring below the ESF and by monitoring below the ECRB Cross Drift, at 
the starter tunnel of the Cross Drift and at the crossover point (where the Cross Drift passes ~20 
m over the ESF Main Drift) (CRWMS M&O 2000, U0015, Section 6.9). 
The underground testing and monitoring activities are discussed in the following four sections, 
with Section 2.2.2.2.1 on drift seepage tests and moisture monitoring, Section 2.2.2.2.2 on 
fracture-matrix interaction and fault flow tests, Section 2.2.2.2.3 on large-scale infiltration and 
seepage tests, and Section 2.2.2.2.4 on air-permeability tests and potential monitoring. 
2.2.2.2.1 Drift Seepage Tests and Moisture Monitoring 
A number of drift seepage studies are the current focus of underground ESF testing. The seepage 
tests were motivated by the observed absence of continuous seepage in the ESF drifts following 
their excavation. The capillary barrier mechanism may explain the lack of seepage in 
underground drifts in the UZ. Under unsaturated conditions, capillary forces can hold the water 
within the rock mass. For seepage or dripping into a drift opening to occur, the percolation flux 
must be greater than the seepage threshold. Above the seepage threshold, the local accumulation 
of water is large enough to overcome capillarity. The absence of seeping water in the ESF may 
indicate that the prevailing percolation flux, on the order of 10 mm/yr (CRWMS M&O 2000, 
U0050, Section 6.6), may not be large enough to break the capillary barrier (see Section 3.9 of 
this PMR). 
Seepage tests involve the release of liquid water above the niche ceiling and collection of seeps if 
they occur. Niche seepage tests are designed to evaluate the capillary barrier mechanism and to 
quantify seepage and the seepage threshold. Aqueous dye tracer are released as pulses above the 
niche ceiling to represent episodic percolation events, as illustrated in Figure 2.2-3 for the 
seepage tests at Niche 3650. Tracers used in the seepage tests are sampled to evaluate the spatial 
distribution of flow paths. The seepage flow paths indicated by the presence of dyes on the niche 
ceilings are associated with transient wetting-front movement through the fractures. The seepage 
threshold data and the wetting-front movement data are used to derive characteristic curves for 
the fractures for in situ conditions. The seepage threshold for releases at a given borehole interval 
is determined by a series of tests with decreasing flow rates until no seep occurs. The wettingfront 
arrival at the niche ceiling is determined by visual or video observations. Available seepage 
test data and seepage calibration model results indicate that the seepage threshold could be larger 
than the percolation flux for releases above the niche ceiling (CRWMS M&O 2000, U0015; 
Section 6.2; CRWMS M&O 2000, U0080, Section 6.6; see Section 3.9 of this PMR). 
Ventilation, needed for underground operations and construction activities, may also explain the 
lack of observed seepage. Ventilation can remove a large amount of moisture, dry the rock 
behind the drift walls, and suppress seepage. Ventilation is also being considered as an important 
component in potential repository design to remove heat during the thermal periods. The concept 
of constructing niches along the ESF Main Drift was originally motivated by the need to isolate a 
drift-size opening with a bulkhead from the ventilation in the Main Drift. The niches were 
excavated by an Alpine Miner, a mechanical device (shown in Figure 2.2-5) with no water

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spreading upward at the cutter head into the ceiling. Drift seepage tests at Niche 3107 near the 
crossover point and at Niche 4788 in the intensely fractured zone are conducted behind 
bulkheads and under high humidity conditions. 
With dry excavation, it is possible to observe flow paths visually. In the dry excavation of Niche 
3566 in the vicinity of the Sundance fault, a damp feature was observed in 1997, as illustrated in 
Figure 2.2-4. The 0.3 m wide by over 3 m long, nearly vertical feature dried up before the 
bulkhead could be installed. The full rewetting of this feature was not observed after over two 
years of bulkhead closure at this niche site. Figure 2.2-4 also illustrates that the Sundance fault is 
one of several faults and features with bomb-pulse signals detected by 36Cl/Cl measurements 
along the ESF. The 36Cl/Cl measurements are further discussed in Section 2.2.3.3. 
In addition to the niches, two additional drift-sealing studies are ongoing. The first study is at 
Alcove 7 in an over 100 m long segment intersecting the Ghost Dance fault. The second study is 
in the second half of the ECRB Cross Drift for a 1,000 m scale segment that intersects the 
Solitario Canyon fault. Both sealing studies deploy double bulkheads for better isolation from 
ventilation. No continuous seeps have been observed so far in either of these two long drift 
segments. 
Most of the potential repository area is located in the lower lithophysal zone of TSw (tpll in 
Figure 2.1-4). The lower lithophysal tuff is more permeable than the middle nonlithophysal tuff, 
the fractures are shorter, and large lithophysal cavities are pervasive. Figures 2.2-5c and d show 
an example of a large lithophysal cavity in the lower lithophysal tuff and a borehole image of 
lithophysal cavities intersected by a borehole for the test site of Niche 1620 in the ECRB Cross 
Drift. Figure 2.2-5 also summarizes the objective and results of the seepage testing in this niche. 
The presence of lithophysal cavities makes packer installation and test setup in the lower 
lithophysal zone more challenging than in the middle nonlithophysal zone. 
The larger permeability of the lower lithophysal tuff may enhance the capillary barrier effect, i.e. 
reduce seepage, either by the presence of permeable fractures that can divert flow around the 
drift opening, or by higher porosity in the matrix rock that can absorb more water. Geological 
mapping along the Cross Drift indicates that the lower lithophysal zone is very heterogeneous. 
The effects of spatial heterogeneity on pneumatic and seepage characteristics are evaluated by 
systematic hydrological testing along the Cross Drift, using slanted boreholes drilled into the 
crown of the drift ceiling. 
2.2.2.2.2 Fracture-Matrix Interaction and Fault Flow Tests 
Two tests were conducted to evaluate the contribution of the rock matrix to overall flow and 
tracer transport. If the contact time between the water flowing along fractures or faults and the 
unsaturated matrix is long, water can imbibe into the matrix. Fracture-matrix interaction refers to 
the flow of water from the fracture to the matrix. While the results of the niche seepage tests for 
episodic flow conditions are adequately analyzed with fracture parameters alone, analysis of the 
long-term tests requires the quantification of fracture-matrix interaction. 
The dominance of fracture flow and the dependence of the fraction of flow occurring through the 
fractures on the total flux magnitude were evaluated in a test bed in Alcove 6, as illustrated in

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Figure 2.2-6. The slot below the test bed was used to collect the fast fracture flow component. 
The amount of water imbibed into the welded tuff matrix was estimated from mass balance of 
the water injected and collected. A series of tests were conducted over time periods longer than 
the episodic releases in the niche tests, and with larger volumes of traced water. The approach to 
steady-state outflow occurred in irregular steps, which reflect the intrinsic instability of the flow 
field. The fracture flow fractions have an oscillatory dependence on injection rates, ranging from 
60% to 80% for this test bed in the TSw middle nonlithophysal unit for large flow rates 
(Figure 2.2-6). 
The first fault test with liquid water in the ESF was conducted at Alcove 4. (The Bow Ridge fault 
and Ghost Dance fault were characterized by air injection tests before the Alcove 4 liquid test.) 
The same mass-balance approach used in Alcove 6, with a slot for recovery of the outflow, was 
adopted. The Alcove 4 test bed includes a small fault and the PTn layers, as illustrated 
schematically in Figure 2.2-7c and in the photograph in Figure 2.2-7b. Figure 2.2-7 also 
summarizes the testing performed in Alcove 4. In contrast to the TSw unit occurring in Alcove 6 
and in the niches, the matrix of the PTn unit has a large capacity to absorb water and to dampen 
the flow pulses along the fault. The data in Figure 2.2-7 show a slow decline in water intake rates 
with time. One hypothesis to explain the slow decline is the possible swelling of the PTn argillic 
layers and subsequent reduction of fault permeability. With sequential wetting, the wetting front 
moves faster, with more water introduced into the flow system. These preliminary findings help 
determine the behavior of flow through the PTn layers. 
2.2.2.2.3 Large-Scale Infiltration and Seepage Tests 
The first of two large-scale infiltration and seepage tests is located in Alcove 1 near the North 
Portal and is illustrated in Figure 2.2-8. In this test, a drip irrigation system on the outcrop 
directly above Alcove 1 is used to simulate large infiltration events associated with the El Nio 
conditions of high precipitation. The test results have shown that matrix diffusion is important in 
diluting the tracer concentration and reducing the tracer breakthrough times in the TCw unit. 
At the location where the ECRB Cross Drift crosses over the ESF Main Drift, the migration of 
construction water from the excavation of the Cross Drift was monitored below at the Main Drift 
near Niche 3107, as illustrated in Figure 2.2-9. No seepage was observed when the Tunnel 
Boring Machine passed over the Main Drift. A new Alcove 8 has been excavated in the Cross 
Drift for controlled liquid-release tests directly above the Niche 3107 which is instrumented for 
seepage detection. The test bed includes the interface between the upper lithophysal zone and the 
middle nonlithophysal zone of the TSw unit. The test results can be used to understand largescale 
flow and seepage processes across a tuff layer interface at the potential repository horizon. 
2.2.2.2.4 Air-Permeability Tests and Potential Monitoring 
Air-injection tests with multiple packers were conducted at all hydrological test sites to measure 
the air permeability and characterize the formation heterogeneity. With fast responses and a 
benign impact on the rock mass, air-injection tests are an effective method for site 
characterization. Air-permeability profiles were used for selecting liquid test intervals. Repeated 
air-injection tests were conducted before and after niche excavation to quantify the excavation

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induced permeability changes (Wang and Elsworth 1999, pp. 751757; CRWMS M&O 2000, 
U0015, Section 6.1). 
Air-injection testing is one of many examples where methods deployed in surface-based testing 
programs are successfully adopted, improved, and enhanced for underground studies. Other 
examples include neutron logging used for infiltration studies in the ESF boreholes to measure 
saturation changes associated with drying, heat-dissipation probes and psychrometers in 
boreholes used to monitor water-potential along drifts and into the walls, and relative humidity 
sensors from meteorological studies used to monitor the effects of ventilation on moisture 
monitoring. These methods, together with extensive mapping and sampling, enable the 
confirmation and verification of many site attributes, the improved evaluation of drift-scale 
processes, and the definition and quantification of interactions between natural barriers and 
engineered barriers. 
2.2.3 Geochemical Data Collection 
Geochemical and solute transport studies include major laboratory components to analyze 
samples collected in the field. Geochemical data collection is closely associated with 
hydrological data collection, especially with regard to the rock and water sample collection 
activities in recent years. The early efforts involved samples collected from surface mapping and 
analyses of drill-cuttings and cores of the rock samples (collected in the surface-based boreholes) 
to establish the mineralogic character of the tuff units. With the ESF access in the mid-1990s, 
sampling focused in the ESF drifts to elucidate the distributions of calcite, 36Cl, and fracture 
fillings. 
2.2.3.1 Mineral and Solubility Measurements 
The mineral and petrologic studies identified the locations of altered zones, especially the 
presence of zeolites in the CHn units below the TSw potential repository units. The spatial 
distributions of vitric CHn (CHnv) and zeolitic CHn (CHnz), along with the characterization of 
the vitrophyre sublayer between the TSw and CHn units, are important for understanding the 
distribution of perched water bodies and determining potential flow paths for radionuclides. 
The solubility and retardation factors of weakly sorbing radionuclides were measured 
extensively in the laboratory. Most of the UZ geochemical and transport property measurements 
performed in the laboratory used water from the well J-13 in the saturated zone (CRWMS M&O 
2000, U0100). Dissolution and rock-water interaction parameters are determined in batch 
experiments with tuff fragments mixed with water. Column experiments are also conducted to 
determine various transport parameters. The transport test results form the basis of the minimum 
sorption coefficient approach used in radionuclide transport calculations. 
2.2.3.2 Geochemical Measurements 
In the boreholes and along the ESF drifts, samples have been collected for geochemical and 
isotopic measurements. Pore water is used for chemical analyses and age dating. The techniques 
to collect pore water from tight matrix evolved from mechanical squeeze (tri-axial compression) 
to ultracentrifuge spin. The total dissolved solids and chloride contents are mainly measured in 
nonwelded tuff samples that generally can yield sufficient amounts of water for chemical

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analyses (Yang et al. 1998, pp. 67). Relatively high concentrations of dissolved-solid contents 
are used to indicate low infiltration fluxes. The total chloride distributions, especially along the 
ECRB Cross Drift, are shown to be an important data set for determining the percolation flux 
distribution (see Section 3.7 of this PMR). 
The chemical composition and carbon dioxide concentrations are measured in pore-water 
samples to elucidate the saturation states, to determine the origin of pedogenic calcite and 
amorphous silica, and to measure the evolution of inorganic carbonate concentrations. Ionexchange 
reactions along the flow paths generally cause an increase in the cation abundances in 
deep tuff units. Deviation from the general trend of geochemical evolution with depth may 
provide information about the effects of faults and other structural features. The calcite and opal 
studies along fracture surfaces (Paces et al. 1998b, pp. 3639) and within lithophysal cavities 
(CRWMS M&O 2000, U0085, Section 6.5; see Section 3.9 of this PMR) are used to evaluate the 
alternation of flow paths and seepage into cavities, averaged over millions of years. Strontium 
participates in ion-exchange with zeolites, and concentrations may be significantly depleted in 
the CHnz unit (Sonnenthal and Bodvarsson 1999, pp. 143147; see Section 3.8 of this PMR). 
Examples of geochemical studies of tuff samples are illustrated in Figure 2.2-10. 
2.2.3.3 Isotopic Measurements 
The environmental isotope data are used to infer the presence of fast flows from the ground 
surface into and through the UZ. High 36Cl/Cl ratios well above background levels are related to 
global fallout from thermonuclear tests in the Pacific Ocean. The presence of greater-thanbackground 
concentrations of bomb-pulse 36Cl therefore suggests travel times from the ground 
surface of 50 years or less. The 36Cl signals, first observed in infiltration boreholes and later in 
the ESF at faults and other features, have received great attention and continue to be evaluated 
(Fabryka-Martin et al. 1993, pp. 5868; CRWMS M&O 2000, U0085, Section 6.6). The 36Cl/Cl 
data along the ESF are presented in Figure 2.2-4 in Section 2.2.2.2.1. Additional boreholes were 
recently drilled in the ESF around the Sundance fault and the Drillhole Wash fault for 
verification of the bomb pulse signals. 
Other environmental isotope data are also collected. Bomb-pulse tritium (3H) concentrations are 
also present at several locations at depth, associated with both liquid and pneumatic flow paths. 
The carbon-14 (14C) age of the gas phase increases with depth in borehole UZ-1, with less 
obvious trends in other boreholes. The deuterium (2H) and oxygen-18 (18O) data reflect climatic 
conditions at time of groundwater recharge. Based on the analysis of these two isotopes, pore 
water in the CHn unit with lighter isotopic compositions is inferred to originate either during 
winter precipitation or during a time of colder climate. Perched water appears to be up to 11,000 
years old, based on 14C and 36Cl ages. The perched water does not appear to have equilibrated 
with matrix water, based on major constituent concentrations and uranium isotope data (Paces et 
al. 1998a, pp. 185188; CRWMS M&O 2000, U0085, Section 6.6). Examples of isotopic studies 
of tuff samples are illustrated in Figure 2.2-11. 
2.2.3.4 UZ Transport Tests 
Retardation of radionuclides can reduce the concentrations along the flow paths. Transport 
processes through the CHnv unit are currently under investigation at the Busted Butte

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underground facility. This facility consists of a drift complex excavated 70 m below the ground 
surface. Tracer-injection tests, partial mine-out, and geophysical measurements (groundpenetrating 
radar, electric-resistivity tomography, neutron logging) were performed to map 
solute migration patterns, as illustrated in Figure 2.2-12. The available test results from the 
ongoing tests are documented in CRWMS M&O (2000, U0100, Section 6.8) (see Section 3.11 of 
this PMR). 
The Phase 1A results indicated that the transport through the CHnv unit could be dominated by 
capillary-driven flow, with a well-defined plume developed following tracer injection (see 
Section 3.11). The plumes from the ongoing larger-scale Phase 2 test are tracked by sorbing pads 
in monitoring boreholes and by geophysical imaging techniques. Examples of a fluorescent 
plume photograph from Phase 1A test and a ground-penetrating radar tomograph from Phase 2 
are illustrated in Figure 2.2-12. The results of transport tests with sorbing tracers that represent 
the sorbing radionuclides will indicate whether or not laboratory-measured retardation factors 
can be used to predict field-scale transport processes. 
2.2.4 Thermal Testing 
Thermal tests evaluate thermally induced effects on flow and transport. The thermal test is 
different from hydrological and geochemical tests that evaluate ambient conditions and UZ 
processes intrinsic to the system (see model discussion in Section 2.4). The waste heat represents 
an external perturbation to the system subjected to design and control. This section starts with a 
brief summary of the influence of modeling results on the design of thermal testing and waste 
loading in Section 2.2.4.1. The tests outside and inside the ESF are summarized in Sections 
2.2.4.2 and 2.2.4.3, respectively. 
2.2.4.1 Thermal-Hydrological Modeling 
Early multiphase studies identified the importance of heat-pipe effects on TH conditions near the 
heaters. The heat pipe refers to the counter-flow mechanism with vapor flowing in one direction 
and liquid flowing in the opposite direction. The heat-pipe phenomenon is associated with 
regions under boiling conditions where the temperature is maintained at the nominal boiling 
point (approximately 97oC at Yucca Mountain). This can occur if sufficient liquid can be 
transported back toward the heat source to sustain the boiling (Pruess et al. 1990a, pp. 1235 
1248). 
After the rock becomes dry, temperature is determined by a heat-conduction mechanism and the 
thermal power of the heat source. The temperature can reach hundreds of degrees Celsius, if the 
heat load is high. If the heat load of the waste packages is high enough to keep the liquid away 
from the waste packages, it should in principle improve their performance (Buscheck and Nitao 
1992, pp. 10031017; 1993, pp. 418448). 
The hot and dry potential repository concept has been a motivating factor in waste loading 
designs. YMP has designed large waste packages to contain multiple spent fuel assemblies. The 
large waste packaging with high thermal outputs is developed for drift-emplacement, as opposed 
to borehole-emplacement, as the basis for waste loading. With planar heat sources (used in early 
models) to represent a closely spaced drift configuration, large condensate zones are predicted

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(Buscheck and Nitao 1992, pp. 10031017), with drainage occurring through shedding away 
from the high temperature regions, outside the boiling zones. 
2.2.4.2 Thermal Characterization and Pre-ESF Testing 
Concurrent with the thermal-modeling studies, the thermal properties of potential repository rock 
samples have been measured in the laboratory (Rautman and McKenna 1997, pp. 1630). These 
data provide the basis for the development of thermal-mechanical (TM) stratigraphic 
descriptions and their comparison with geological and hydrological definitions of the tuff units. 
Thermal test designs in the UZ have also benefited from the data from the prototype tests in the 
G-tunnel at Rainier Mesa at the NTS. The focus of the G-tunnel tests was on TM processes. 
However, measured temperature signatures could be interpreted as resulting from TH coupling. 
The thermal-hydrological-mechanical (THM) results of the G-tunnel tests are documented in 
reports by Zimmerman et al. (1986, Sections 6.0, 8.0, 9.0) and Ramirez et al. (1991). 
The first heater test in the middle nonlithophysal zone of TSw was initiated to develop the testing 
approaches for TH and other coupled processes. The Large Block Test (LBT) is located in the 
large outcrop welded tuff at Fran Ridge (Lin et al. 1998, pp. 4951). The LBT used five line 
heaters to represent a planer heat source. Sensors were emplaced to detect changes in 
temperature and water saturation above and below the heater plane. Temperatures were 
significantly affected by infiltration from the top of the block. 
2.2.4.3 Underground Thermal Tests 
Two underground thermal tests were conducted at Alcove 5 near the north end of the ESF Main 
Drift, in the top of the middle nonlithophysal zone of the TSw unit. 
The Single Heater Test (SHT) was conducted near the entrance of Alcove 5 to evaluate the 
thermal-hydrological-chemical-mechanical (THCM) coupled processes in fractured tuff, as 
illustrated in Figure 2.2-13. Drainage of condensate to the region below the heater was observed 
(Tsang and Birkholzer 1999, pp. 411415). Ambient percolation flux through the block was 
derived from the UZ site-scale evaluation. Condensate induced by heating was transported in the 
fractures and collected in packed borehole intervals. Cross-hole air-permeability tests, radar 
tomography, neutron logging, and electrical resistivity tomography were used to detect the 
changes in rock moisture content in the test block. Measurements showed that the dry-out zone 
extended about 1 m from the heater hole and that the condensate zone below the heater horizon 
was larger than above the heater. Cores collected from drill-back after the heating phase below 
the heater had higher saturation values than cores collected above the heater. 
The DST, illustrated in Figure 2.2-14, is the largest test in the ESF. The testing methodologies 
developed in LBT and SHT were applied, improved, and expanded in the DST. Nine full-scale 
heaters are used to simulate waste packages emplaced in the potential repository. Two panels of 
wing heaters are used to simulate the thermal environments of multiple drifts. The heating phase 
is ongoing and has lasted for over two years, since December 1997, with the temperature at the 
drift wall reaching 190oC (see Section 3.10 of this PMR).

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Nearly one hundred boreholes were drilled for thermal, hydrological, mechanical, and chemical 
measurements in the DST. Most of the boreholes are located within the middle nonlithophysal 
zone of the TSw, with the upper portions of some boreholes drilled into the upper lithophysal 
zone of TSw. The ongoing test results indicate that the heat-pipe signature is prominent in 
temperature measurements. Condensates increased the saturation below the wing heater early on. 
Air-permeability reduction from increased liquid saturation in fractures is measured by periodic 
cross-hole air-injection tests. Drying in rock matrix is monitored by geophysical imaging 
techniques. 
Substantial increases of gas-phase CO2 concentration are measured in large regions around the 
heaters in the DST. Chemical analyses of water collected in boreholes elucidate the interactions 
of calcite and silicate minerals with water. Temperature changes in the rocks and observations of 
dripping from condensation of hot air through the bulkhead indicate significant redistribution of 
moisture due to thermal effects. Various AMRs summarize data from the DST. The Drift-Scale 
Coupled Processes (DST and THC Seepage Models) (CRWMS M&O 2000, U0110/N0120, 
Section 6.2) evaluates changes in the chemistry of seepage and porosity arising from thermally 
induced precipitation. ESF and LBT TH thermal test results are summarized in an AMR for the 
Near Field Environment PMR. Mountain-Scale TH Models (CRWMS M&O 2000, U0105, 
Sections 6.10 and 6.11) assesses the temperature rises, saturation changes, and thermally induced 
fluxes toward the drifts and drainage between the drifts. See Sections 3.10 and 3.12 of this PMR 
for TH and THC analyses. 
2.3 NATURAL ANALOGS AS CORROBORATIVE INFORMATION 
Natural analogs with geological records can be used to support the long-time predictions of 
future performance of the potential repository. The ambient characterization of the UZ and the 
model prediction based on calibrations against short-term tests can greatly benefit from 
integration with natural-analog studies. 
The AMR on Natural Analogs for the Unsaturated Zone (CRWMS M&O 2000, U0135) has 
evaluated analogs for the nuclear waste potential repository processes and Revision 1 of the 
YMSD will include a chapter on natural analogs. Winograd (1986) and ongoing studies use 
archeological artifacts preserved over thousands of years in underground structures as 
collaborative evidences for UZ potential repository performance. Table 2.3-1 lists the analog 
sites and the processes related to UZ flow and transport in the southwestern and western U.S., 
Mexico, and many geothermal, uranium deposit, and archeological sites worldwide. The sites in 
North America are listed first, followed by sites in the Pacific Rim, Asia, Europe, and Africa. 
Selected references are listed. Discussions of sites without cited references in the Table can be 
found in above-mentioned reports. 
Table 2.3-1. Natural Analogs for Process Evaluation 
Analog Site Data and/or Process 
Yucca Mountain as self-analog Mineral reaction rates (Bish and Aronson 1993) 
Rainier Mesa, NTS, Nevada Seepage into drifts, discrete fractures, percolation, perched 
water (Thordarson 1965; Russell et al. 1987; Wang et al. 
1993) 
Papoose Lake sill, Paiute Ridge, NTS, Nevada Magma intrusion, THC (Crowe et al. 1983; Matyskiela 
1997; Lichtner et al. 1999)

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Table 2.3-1. Natural Analogs for Process Evaluation 
Analog Site Data and/or Process 
Caves and rock shelters, NTS and vicinity Packrat midden preservation (Spaulding 1985) 
Weapon tests, NTS, Nevada Radionuclide transport (Hoffman and Daniels 1981; 
Buddemeier and Hunt 1988; Kersting et al. 1999) 
Devils Hole, Nevada Paleoclimate, calcite deposit (Winograd et al. 1992) 
Beowawe, Nevada Climate  glacial transition period lower bound analog 
(USGS 2000, U0005) 
Uranium deposits in Northwestern Nevada and 
Southeastern Oregon - McDermitt caldera (Moonlight, 
Bretz, Opalite mines), Virgin Valley, Painted Hills 
Uranium deposits, UZ radionuclide transport (Wallace and 
Roper 1981; Castor et al. 1996) 
Archeological finds - preservation of cave arts in 
France and Germany, preserved seeds and Dead Sea 
Scrolls in Israel, wood, textiles, and plants in Peruvian 
cave, mummies in Chilean pits, manuscripts in Gobi 
desert, Chinese cave temples, etc. 
Demonstrating the efficacy of an unsaturated environment 
in isolating nuclear wastes (Winograd 1986) 
Caves, western North America Biotic remains preservation (Davis 1990) 
Ancient glass Glass degradation (Kaplan and Mendel 1982; Miller and 
Chapman 1995) 
Dixie Valley, Nevada Geothermal, THC, preferential flow, fracture-matrix 
interaction, mineral precipitation and dissolution, mineral 
alteration 
Apache Leap, Arizona Seepage into drifts, discrete fractures, transient flow 
Nogales, Arizona Climate  monsoon period upper bound analog (USGS 
2000, U0005) 
Pea Blanca (Nopal I Mine), Mexico Uranium ore deposits, secondary mineral formation and 
sequestration, plant uptake of radionuclides, seepage into 
drifts, discrete fractures, transient flow, sorption and matrix 
diffusion, (Pearcy et al. 1994, 1995; Pickett and Murphy 
1997, 1999) 
Cerro Prieto, Mexico Geothermal, preferential flow, fracture network 
permeability, mineral reaction rates, self-sealing 
Mitchell Caverns, California Infiltration, dripping water deposits 
Owens Lake, California Paleoclimate (Forester et al. 1999) 
East Mesa, California Geothermal, preferential flow, mineral reaction rates 
Heber, California Geothermal (Lippmann and Bodvarsson 1985) 
Long Valley, California Geothermal, fracture-matrix interaction, mineral 
precipitation and dissolution 
Geysers, California Geothermal, preferential flow, fracture network 
permeability, heat pipes, boiling and condensation, selfsealing 
Hobbs, New Mexico Climate  monsoon period upper bound analog, (USGS 
2000, U0005) 
Valles Caldera, New Mexico Magma intrusion, fossil hydrothermal reactions (Stockman 
et al. 1994) 
Grants Ridge, New Mexico Magma intrusion, fossil hydrothermal reactions 
(WoldeGabriel et al. 1999) 
Fenton Hill, New Mexico Geothermal, mineral precipitation and dissolution

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Table 2.3-1. Natural Analogs for Process Evaluation 
Analog Site Data and/or Process 
Delta, Utah Climate (glacial transition period lower bound analog, 
USGS 2000, U0005) 
Newberry Volcano, Oregon Geothermal (Sammel et al. 1988) 
INEEL Box Canyon, Idaho Seepage, discrete fractures, transient flow (Faybishenko et 
al. 1998; CRWMS M&O 2000, U0135) 
Yellowstone, Wyoming Geothermal, fracture-matrix interaction, mineral alteration 
Eldora stock and Alamosa River stock, Colorado Deep hydrothermal intrusions (Brookins 1986; Wollenberg 
and Flexser 1986) 
Spokane, Rosalia and St. John, Washington Climate  glacial transition period upper bound analog 
(USGS 2000, U0005) 
Wanapum basalt, Hanford, Washington Basalitic glass (Jercinovic et al. 1986) 
Hanford, Washington Radionuclide migration (Barnett et al. 1997) 
Alligator Rivers (Koongara deposit), Australia Transient flow, uranium ore deposits (partially UZ) (Airey 
1986; Isobe et al. 1992; Murakami et al. 1997) 
Wairakei, New Zealand Geothermal, hydrological properties, preferential flow, 
fracture network permeability, mineral precipitation and 
dissolution, mineral alteration, THM subsidence (Mercer 
and Faust 1979; Glassley and Christensen 1992; Bruton et 
al. 1993) 
Broadlands, New Zealand Geothermal, mineral precipitation and dissolution, mineral 
alteration 
Kamojang, Indonesia Geothermal, hydrological properties, fracture network 
permeability, heat pipes, boiling and condensation, selfsealing 
Bulalo, Philippines Geothermal, THM subsidence 
Tianjin, China Geothermal, hydrological properties 
Oguni, Japan Geothermal, hydrological properties 
Sumikawa, Japan Geothermal, hydrological properties, fracture network 
permeability 
Matsukawa, Japan Geothermal, fracture network permeability, heat pipes, 
boiling and condensation, self-sealing 
Krasnoyarsk, Russia Radionuclide transport at deep injection sites 
(Rybal'chenko et al. 1998) 
Lake Karachai, Russia Radionuclide contamination (Drozhko et al. 1997; Rumynin 
et al. 1998) 
Chernobyl, Ukraine Radionuclide contamination (Belyaev et al. 1997) 
Negev Desert, Israel Infiltration (Nativ et al. 1995) 
Amman, Jordan Seepage 
Maqarin, Jordan Alkaline water (Khoury et al. 1992) 
Cappadocia, Turkey Drift stability and insulation (Aydan et al. 1999) 
Santorini, Greece Trace-element transport (Murphy et al. 1998) 
Larderello, Italy Geothermal, fracture network permeability, heat pipes, 
boiling and condensation, mineral precipitation and 
dissolution, self-sealing

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Table 2.3-1. Natural Analogs for Process Evaluation 
Analog Site Data and/or Process 
Altamira, Spain Cave seepage (Villar et al. 1985) 
Chauvet, Cosquer, Lascaux, France Cave painting preservation 
Iceland Basaltic glass (Jercinovic and Ewing 1987) 
Krafla, Iceland Geothermal, fracture network permeability, THM 
subsidence (Bodvarsson et al. 1984) 
Reykjanes, Iceland Geothermal, self-sealing 
Oman Alkaline plume, THC (McKinley et al. 1988) 
Shinkolobwe mine, Zaire Uranium oxidation (Finch and Ewing 1991) 
Olkaria, Kenya Geothermal, fracture network permeability, fracture-matrix 
interaction (Bodvarsson et al. 1987) 
Angola Rock shelter painting preservation 
Bangomb, Gabon Uranium ore deposits, secondary mineral formation and 
sequestration, criticality (Gauthier-Lafaye et al. 1989) 
The YMP has used analogs for testing conceptual models and evaluating coupled processes. 
Yucca Mountain is viewed as a self-analog, using the past thermally driven hydrologicalchemical 
processes of secondary mineral formation and alteration zones as a key to future 
alteration. Within the NTS, there are examples of waste emplacement in the Climax Stock; 
underground testing at G-tunnel; hydrological evaluations of seepage, percolation, perched 
water, and tunnel discharges at Rainier Mesa tunnel complexes; and a basalt intrusion study at 
Paiute Ridge. In Nevada and the surrounding southwestern/western states and Mexico, 
paleoclimatic analog, uranium ore deposit, and geothermal site evaluation have contributed to 
knowledge about hydrological and coupled processes. 
The geothermal system at Wairakei, New Zealand, was endorsed by the YMP for study of THC 
processes. NRC sponsored the field studies at Apache Leap, Arizona, Las Cruces, New Mexico, 
and Pea Blanca, Mexico. Yucca Mountain, Apache Leap, and Las Cruces are test cases 
evaluated by the INTRAVAL project. Participation in international cooperative projects, such as 
the ongoing DEvelopment of COupled models and their VALidation against EXperiments in 
nuclear waste isolation (DECOVALEX) for THCM coupled-processes modeling, is an effective 
forum for YMP to assemble useful information on nuclear waste potential repository studies. 
Geothermal reservoir studies address many thermally driven coupled processes and phenomena 
associated with nuclear waste disposal. The natural analog AMR (CRWMS M&O 2000, U0135) 
and Revision 1 of the YMSD also review analog information for waste package and waste form 
degradation. Some well-studied saturated zone sites are included for specific processes of 
interest. 
The Pea Blanca site evaluation of uranium migration and the Idaho National Engineering and 
Environmental Laboratory (INEEL) infiltration test modeling are two examples of analog studies 
presented in the natural analog AMR (CRWMS M&O 2000, U0135, Section 6.5). For collecting 
corroborative evidences for radionuclide migration and drift seepage, YMP is conducting 
additional field sampling of borehole cores and assessing seepage into mine adits and migration 
from veins at the Nopal I mine at Pea Blanca. For the INEEL Box Canyon site, the modeling

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approach used in the UZ Model for Yucca Mountain is used to interpret ponded-infiltration test 
results. These examples illustrate the approach for selecting and applying natural analog 
information for future use in SR and LA, and in performance confirmation. The confidence in 
the safe emplacement of nuclear wastes in the UZ can be greatly enhanced with natural analog 
studies to supplement field testing and UZ modeling at Yucca Mountain. 
In addition to scientific/technical data and geological records from analog sites, archeological 
records can be more comprehensible to the public than hydrological/geochemical data and 
mathematical/numerical models (Winograd 1986). Paintings and tools preserved in caves, manmade 
opening and rock shelters (partial openings), structural integrity of underground dwellings, 
artifacts found in underground chambers, and even biotic remains from ancient animals can be 
used to demonstrate the possibility of preserving man-made materials surrounded by dry air over 
geological time scales. Model predictions and short-term experiments indicating flow diversion 
around openings can be demonstrated to be valid over very long time periods by archeological 
records. 
2.4 EVOLUTION OF UZ AND TSPA MODELS 
The conceptual model for the UZ flow at Yucca Mountain was first presented by Montazer and 
Wilson (1984, pp. 3649). The basic geological framework with alternating welded and 
nonwelded tuff units, the hydrological perching and lateral flow diversions at tilted tuff 
interfaces, and the potential for flow and transport through faults were components of the model. 
Site characterization data were collected to modify, refine, and improve the understanding of the 
model of the UZ system. The evolution of the model was strongly influenced by the available 
data and information. The key parameters and processes included the magnitude of the 
infiltration flux, the partitioning between fast fracture-flow and slow matrix-flow components, 
and the redistribution of percolation flux over the potential repository horizon and at the water 
table. 
Mathematical models were recognized at the onset of YMP as the tools needed to represent the 
system, interpret the observations and testing results, and make long-term predictions. Numerical 
modeling techniques developed within the context of geothermal reservoir research and in the 
petroleum industry were adopted and modified for the UZ at Yucca Mountain. The doubleporosity, 
double-permeability model concepts evolved to describe fractured reservoirs with 
storage in the matrix and flow and transport through the fractures. The multiple interacting 
continuum formulation was developed for fractured medium representations (Pruess and 
Narasimhan 1985, pp. 1426). 
A description of the Yucca Mountain UZ utilizes many concepts developed in the field of soil 
physics. The water content (or saturation) and matrix densities are the first basic measurements 
in soil physics to characterize the unsaturated state. Water potential and permeability are the 
other essential parameters needed to characterize flow. The constitutive relationships between 
saturation and water potential, and between relative permeability and potential, are represented 
empirically with sets of functional relationships, also known as the characteristic curves. The van 
Genuchten functions are the most popular functions used in the scientific literature that treats 
flow through soil and tuffs. If the matrix continuum and the fracture continuum are in 
equilibrium, the fractured tuff can be represented by a composite characteristic curve (Montazer

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and Wilson 1984, pp. 3649; Peters and Klavater 1988, pp. 416430; Pruess et al. 1990b, 
pp. 12491261). The composite-porosity model was first used by Rulon et al. (1986), the doublecontinuum 
model by Wittwer et al. (1995, p. 8), and the double-permeability model by Robinson 
et al. (1996, pp. 6769) for site-scale models. 
Montazer and Wilson (1984, pp. 3649) suggested that the value of net infiltration ranged from 
0.5 to 4.5 mm/yr, with the upper bound corresponding to 3% of precipitation. Weeks and Wilson 
(1984) estimated that downward flux in the matrix of the TSw unit was less than 0.2 mm/yr. It 
was suggested that most of the water (4 mm/yr) was diverted laterally within the PTn unit and 
flowed down the faults, with 0.5 mm/yr moving downward through the TSw. Sinnock et al. 
(1987) presented the first TSPA model and Klavetter and Peters (1986) and Peters and Klavetter 
(1988, pp. 416430) presented numerical analyses to evaluate the conceptual model that 
consisted of low infiltration, lateral PTn flow and matrix-dominated flow. The transient 
transition from fracture-dominated flow to matrix dominated flow was theoretically evaluated by 
Wang and Narasimhan (1985, pp. 18611874) in a small fractured block, with fracture 
characteristic curves related to the fracture-matrix contact areas. Episodic pulse propagation and 
other alternative models to sustain fracture flow through unsaturated matrix blocks were 
presented by Pruess (1999, pp. 10391051) and Pruess et al. (1999, pp. 281322). 
One-dimensional column simulations for three different conceptual models are shown in 
Figure 2.4-1. The first 2-D site-scale model for Yucca Mountain was presented by Rulon et al. 
(1986). Using only the water-content profiles available at that time, multiple simulations were 
carried out for ranges of infiltration rates imposed on the surface boundary of the columns in the 
2-D vertical cross section. The simulations indicated that as much as 50% of the infiltration was 
diverted for infiltration rates less than 1 mm/yr. For infiltration rates of 4.5 mm/yr, only 1 mm/yr 
of lateral flow was predicted. Because of the equilibrium constraint between matrix and fracture 
under steady-state conditions, water resided preferentially in the matrix. To keep the matrix 
unsaturated, only very small infiltration rates (< 1 mm/yr) could be accommodated through a tuff 
column (Figure 2.4-1a). 
Because fractures are free to accept more water, the infiltration rate is believed to be much larger 
than the matrix flow component. High infiltration rates for short-term climate changes could be 
easily drained through high-permeability fractures, which would minimize the contact time 
between water and waste canisters (Roseboom 1983). Episodic pulses instead of steady 
infiltration rates were simulated to determine flow transmission in transient mode. The 
nonwelded tuff units had large damping capacities to smear the pulses. Instead of trying to 
transmit flows through the tuff layers, the TSPA-1991 (Barnard et al. 1992) used the weep model 
(Gauthier et al. 1992, pp. 891898), which assumed that the fracture flows were decoupled from 
the matrix flow. The travel times of the weeps through the UZ were not modeled. 
Using weep size and spacing as parameters, the extent of water contact with the waste packages 
was determined from geometrical considerations. The weep component could accommodate 
additional infiltration beyond the amount carried by the matrix. TSPA simulations from 1991 
(Barnard et al. 1992) used six 1-D columns along the G-4 to H-5 transect and the weep model to 
accept 1 mm/yr infiltration (Figure 2.4-1b). In the TSPA-1993 (Wilson et al. 1994), the 
Infiltration Model was generalized to have a dry period and a wet period (Figure 2.4-1c). The

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explicit representation of weeps contacting individual waste packages was accounted for in the 
eight areas covering the primary and secondary potential repository areas. 
The first 3-D UZ model (UZ-1995) that faithfully honors the geology was presented by Wittwer 
et al. (1995). The nodal centers were aligned with major faults. Each major borehole was also 
located at the nodal center, as illustrated in Figure 2.4-2. Vertically, the layers were represented 
by fine gridding near layer interfaces. Fault offsets were accurately represented. Both fracture 
flow and matrix flow components were calculated with the effective-continuum model. With the 
3-D model to redistribute the flow, percolation flux was no longer equivalent to infiltration on 
the surface boundary. The results of the 3-D flow field were used to select 1-D columns for 
TSPA-1995 (CRWMS M&O 1995). A five-fold increase (from 0.5 mm/yr to 2.5 mm/yr) was 
assumed to differentiate the dry years from the wet years. This ratio is probably conservative, 
although the magnitudes are not necessarily conservative. 
Concurrently with the development of the UZ site scale flow models, UZ site-scale transport 
models were developed (Robinson et al. 1995, 1996, 1997). The UZ transport models took the 
outputs from the UZ site-scale flow models, transferred them to a finite-element mesh, and 
performed particle-tracking calculations for the transport of major radionuclides. The dualporosity 
formulation was generalized to the dual-permeability formulation (Robinson et al. 1995, 
pp. 6769; Zhou and Apted 1995, pp. 160162). The first site-scale transport model with dualpermeability 
formulation is illustrated in Figure 2.4-3. The particle-tracking technique used is 
conservative in predicting early breakthrough. The AMR on Analysis Comparing Advective- 
Dispersive Solution to Particle Tracking (CRWMS M&O 2000, U0155) quantifies some of the 
differences in various approaches to modeling transport. The Flow Model and Transport Model 
were consolidated in 1999. 
In TSPA-VA (DOE 1998), the flow fields from a further-refined UZ site-scale model (UZ-1997 
model) were directly imported into the TSPA calculations. The refinement included a 100-fold 
increase in spatial resolution (from 103 nodes in UZ-1995 model to 105 nodes in UZ-1997 
model), explicit gridding of the ESF drift, and incorporation of tilted faults, as illustrated in 
Figure 2.4-4. The UZ-1997 model was also expanded to incorporate a drift-scale model for the 
assessment of seepage into drifts. The preliminary test results of seepage at Niche 3650 in the 
ESF were used to confirm that the drift-scale model represents the capillary barrier mechanism 
well (Wang et al. 1999, pp. 323347; Birkholzer et al. 1999, pp. 349384). Thirty-nine calibrated 
flow fields were generated for inputs to TSPA. The corresponding drift-scale model results for 
each of the 39 flow fields were also provided to the TSPA. 
Beside refinements and applications, the philosophy of the UZ Flow and Transport model to 
incorporate all available data was implemented in the UZ-1997 model (Bandurraga and 
Bodvarsson 1999, pp. 2546; Wu et al. 1999a, pp. 185215). Pneumatic responses were used to 
derive effective fracture and fault properties (Ahlers et al. 1999, pp. 4768). Temperature 
profiles were used to derive the advective contribution to heat transfer. The perched water 
information at the interfaces within the CHn unit constrained the nature of flow field below the 
potential repository by diverting a large portion of flow away from the zeolitic tuff below the 
perched water bodies (Wu et al. 1999b, pp. 157184). The infiltration models also evolved to 
using more accurate data and calculations to derive higher infiltration fluxes. The climate studies 
refined the future climate scenarios and designated three climate states (DOE 1998). The

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infiltration ratios were 3 and 1/3 for the upper and lower bounds, respectively, for each of the 
climate periods. The effects of future climate and infiltration changes were modeled (Ritcey and 
Wu 1999, pp. 257279). The UZ-1997 model was also used in thermal loading studies (Haukwa 
et al. 1999, pp. 217255). TSPA-VA (DOE 1998) carried out systematic sensitivity analyses 
with probabilistic formulation for dose calculations. Compliance with regulations was more 
transparently presented. 
The UZ PMR supporting the SR continues the refinement and improvement of modeling efforts 
with calibrations using traceable and verifiable data. The active fracture model (Liu et al. 1998, 
pp. 26332646; CWRMS M&O 2000, U0035), with saturation-dependent formulation for the 
fracture-matrix contact area, is used in model calibration. Validations against data from in situ 
tests and from new borehole data further establish the reasonableness of UZ models to represent 
the features, events, and processes (FEPs) in the UZ natural barriers. In addition to the AMRs, 
which analyze and model different UZ characteristics and processes, the abstraction of UZ model 
results for inputs to TSPA is an integral part of this UZ PMR. This UZ PMR, together with 
PMRs for other system components, lead to a more refined TSPA for SR and LA. Chapter 3 of 
this PMR describes the UZ model components in details. 
2.5 KEY ISSUES FOR UNSATURATED ZONE FLOW AND TRANSPORT 
This section discusses the key issues that have been identified by external peer reviews and 
oversight bodies and YMP workshops on unsaturated zone flow and transport. Section 2.5.1 
summarizes major comments on the representation of unsaturated zone flow and transport in the 
TSPA-VA from the TSPA Peer Review Panel, the UZ Transport Panel (Independent Evaluation 
Panel), the Drift Seepage Peer Review, and others. NRC Key Technical Issues are discussed in 
Chapter 4 and not repeated in this Section 2.5.1. Section 2.5.2 summarizes key issues identified 
in the TSPA-VA (DOE 1998) and from YMP workshops on unsaturated zone flow and transport. 
2.5.1 Summary of Key Issues from External Reviewers 
This section summarizes comments from external reviewers of the representation of unsaturated 
zone flow and transport in the TSPA-VA and an expert elicitation completed during 
development of the TSPA-VA. Table 2.5-1 summarizes the key issues from these reviews and 
provides an explanation of how these issues are addressed in the UZ PMR. Because of NRC 
statutory role in the review of the technical basis for the SR, NRC issues are summarized 
separately in Chapter 4. 
2.5.1.1 Summary of the TSPA Peer Review Panel 
The YMP convened a peer-review panel to review the TSPA-VA (Budnitz et al. 1999). This 
panel recognized the importance of environmental tracers (36Cl) as evidence of fast pathways and 
recommended their use in developing conceptual models of UZ flow. The existence of fast 
pathways in fractures was accounted for by using a dual-permeability model, and transport times 
between the surface and the repository were addressed in sensitivity analyses. The TSPA Peer 
Review Panel also recommended studies to improve the hydrologic characterization of the UZ 
and the understanding of fracture-matrix interactions. The TSPA Peer Review Panel also 
emphasized the need to better understand seepage into drifts, including the characterization of

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heterogeneity and fracture capillary properties in the region around the drift wall. They also 
noted that many of the assumptions underlying the representation of seepage in the TSPA-VA, 
such as constant drift geometry, may not be valid. 
The TSPA Peer Review Panel questioned the TSPA-VA assumption that the effects of THC 
processes will be short lived and can be neglected. They also recommended that the TH 
abstraction method be tested against real data, noting that the drift-scale heater test would 
provide a major step forward in understanding the thermal effects on the repository system. They 
were concerned with the uncertainties in the representation of water chemistry in the near-field 
environment. 
With respect to transport in the UZ, the TSPA Peer Review Panel recommended validation of the 
assumption that flow is diverted around perched water zones. They also recommended obtaining 
field data that would support the modeling of colloid transport to assess the importance of 
processes such as colloid filtration and remobilization. They recommended a more careful 
analysis of the source term for radionuclides released from the potential repository. Additional 
issues raised by the Panel included the effect of grid scale on flow and sorption properties, 
upscaling in a fracture-matrix dual continuum, and the effect of episodic flow. They also 
recommended using the same approach to modeling transport in the unsaturated and saturated 
zones. 
Table 2.5-1. Key External Issues for the Unsaturated Zone Flow and Transport Process Model Report 
Issue Source PMR Approach 
Climate and Infiltration 
The TSPA-VA model, using three distinct 
climate was simplistic and without a firm 
basis. A more robust justification for the 
duration of climate states would strengthen 
the analysis. 
PARP1 Section 3.5.1 provides a more defensible 
justification for the duration of climate states, 
based on the paleoclimate record. 
In the TSPA-VA, the justification for the 
range infiltration for each climate state was 
weak. A better justification of the range in 
infiltration under a given climate state would 
strengthen the analysis. 
PARP The Infiltration Model provides an improved 
justification for the range in net infiltration under a 
given climate state (Section 3.5.2). Infiltration for 
future climate states is based on analog climate 
sites. 
The project could provide a stronger 
justification for 1-dimensional versus 3- 
dimensional infiltration modeling and grid 
resolution than was provided in TSPA-VA. 
PARP This issue is addressed in USGS (2000, U0010). 
The TSPA-VA model for infiltration did not 
include the effects of processes such as 
runoff/run on, snowpack/snowmelt, 
seasonality, and cloudiness on infiltration. 
Addition of the effects of these processes in 
the Infiltration Model would improve 
estimates of infiltration. 
PARP, DSPR2 The Infiltration Model now includes effects of 
additional processes on infiltration, such as runoff/
run-on, temperature, and vegetation (Section 
3.5.2). 
The YMP should study the hydrology of at 
least one drainage basin at Yucca Mountain. 
UZEE3, DSPR This proposed study is not planned. Eleven years 
of infiltration data are available from up to 98 
boreholes and in at least five washes. It is not 
clear that additional field studies at new sites 
would improve the model significantly.

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Table 2.5-1. Key External Issues for the Unsaturated Zone Flow and Transport Process Model Report 
Issue Source PMR Approach 
Unsaturated Zone Flow 
Alternative conceptual models for 
fracture/matrix interaction and perched water 
that were not considered in TSPA-VA should 
be evaluated. 
PARP The active fracture model (Section 3.3) provides 
a new, more defensible conceptual model for 
fracture/matrix interaction. Different conceptual 
models for perched water are being considered 
(Sections 3.7 and 3.11). 
The YMP uses 1-dimensional (versus 3- 
dimensional) inversions for parameter 
estimation; The YMP should proceed with 3- 
dimensional inversions and incorporate 
additional measured data. 
PARP 3-dimensional inversions are under consideration 
for future work; additional hydrologic data on flow 
and transport have been collected in the ECRB 
and the Busted Butte facility and are considered 
in current models (Section 3.7 and 3.11). 
The TSPA-VA did not adequately evaluate 
episodic, transient percolation. 
PARP, NWTRB4 Model studies have shown that the PTn 
effectively damps episodic, transient flow 
(Doughty 1999). 
More information is needed to analyze the 
spatial distribution and rate of percolation 
flux in fast pathways. 
DSPR , NWTRB Limited available data and model studies suggest 
that fast pathways carry only a small fraction of 
the total flow, so that fast pathways may have 
little effect on system performance (Section 3.7 
and 3.8). 
The YMP should implement subgrid 
modeling using different discretization and 
including re-calibration of properties on a 
smaller scale for comparison to base-case 
calibrated properties. 
UZFTEP5 This modeling approach is under consideration 
for future study. 
The YMP should complete comparisons of 
the single gridblock and multiple grid 
approaches with the standard grid 
discretization used in the UZ model. 
UZFTEP These comparisons are under consideration for 
future study. 
The YMP should study matrix flow within the 
PTn. 
UZEE, DSPR The proposed study is not planned. Percolation 
flux through the matrix has been estimated with a 
combination of integrated measures of total 
chloride content, geothermal gradient, and 
Darcy-flux estimations with borehole saturation 
data. 
The YMP should complete focused 
investigations of site characteristics in the 
Cross Drift 
NWTRB Current data from focused investigations in the 
Cross Drift are summarized in Section 2.2. 
The inversion process should account for 
appropriate ranges of parameters, given 
nonuniqueness of inverse method. 
PARP The Calibrated Properties Model (CPM) does 
specify an allowable range of parameters during 
the inversion process that is based upon the 
uncertainty of that specific parameter (Section 
3.6). 
Drift Seepage 
The TSPA-VA may have underestimated the 
amount of seepage into drifts, considering 
the recent results of testing in the ESF. 
NC6 The testing in the ESF was an artificial infiltration 
experiment in the Tiva Canyon. The results are 
not comparable to expected seepage below the 
PTn. 
The TSPA-VA did not account for the effects 
of drift deformation, collapse, and backfill on 
seepage. 
PARP, NWTRB The effects of partial collapse of drifts have been 
evaluated (Section 3.9).

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Table 2.5-1. Key External Issues for the Unsaturated Zone Flow and Transport Process Model Report 
Issue Source PMR Approach 
The YMP should analyze the effects of 
episodic, transient percolation on seepage. 
PARP This issue has only been partially addressed by 
repeated seepage tests (Section 2.2), and limited 
modeling studies (Section 3.9). 
The YMP should evaluate the 
representativeness of continuum fracture 
flow model and should implement discrete 
fracture modeling. 
PARP, UZFTEP Partial evaluation of the continuum approach for 
seepage models has been completed; an active 
fracture model has been implemented (Section 
3.9). 
Additional work is needed to evaluate the 
effectiveness of the capillary barrier in 
diverting/preventing seepage. 
DSPR Seepage data (Section 2.2) and modeling 
studies (Section 3.9) have shown the 
effectiveness of the capillary barrier concept. 
The YMP should plan experiments to 
measure amount of moisture diverted 
around drifts. 
DSPR Long-term drift-scale testing with wing slots to 
collect diverted water is one possible approach to 
measure the amount of water diverted around 
drifts. Geophysical techniques from surrounding 
boreholes can help to delineate the plume. 
These types of tests will be assessed as part of 
performance confirmation. 
The YMP should consider fractures with a 
trace length of less than one meter in drift 
seepage analysis. 
DSPR Fractures with trace lengths of less than 1 m 
have been mapped in drift segments in the ESF. 
Drift seepage analyses use air-injection test 
results which capture the contributions from all 
fractures around test intervals, including fractures 
with a trace length of less than I meter. Seepage 
models do not rely on fracture mapping 
information. Microfractures are accounted for 
through the estimation of effective, seepagespecific 
formation parameters (Section 3.9). 
Although the impact of small-scale fractures is 
not likely to be great, the impact will be evaluated 
in future studies. 
Unsaturated Zone Transport 
The YMP should refine EBS/UZ transport 
interface to appropriately treat localized 
releases of radionuclides. 
PARP Changes in radionuclide releases from the EBS 
over time are now directly input to the UZ 
transport model abstraction. Releases are 
assigned to individual blocks within the model. 
The YMP has limited data from the Calico 
Hills directly beneath the potential repository 
at Yucca Mountain. The applicability of the 
results of testing in the Calico Hills at Busted 
Butte to the site has been questioned. 
NC, NWTRB Busted Butte provided readily accessible 
exposures of the hydrological units that are 
directly beneath the potential repository. The 
tests performed in the Calico Hills in the Busted 
Butte Test Facility generated data to evaluate 
flow and transport bounds in the Calico Hills. 
The YMP should develop a more defensible 
colloid transport model, including irreversible 
capture of radionuclides by colloids. 
NWTRB The development of the colloid model continues 
with addition of irreversible capture of 
radionuclides by colloids (Section 3.11). 
The YMP should continue testing to define 
the sorption characteristics to improve 
estimates of transport. 
NC Additional work on sorption in the Calico Hills is 
ongoing at Busted Butte. 
The YMP should provide better 
documentation for basis of matrix sorption 
model. 
PARP Better documentation and model studies of 
matrix sorption have been completed (Section 
3.11).

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Table 2.5-1. Key External Issues for the Unsaturated Zone Flow and Transport Process Model Report 
Issue Source PMR Approach 
The YMP should consider thermal effects in 
radionuclide transport modeling. 
UZFTEP Evaluation of the thermal effects in radionuclide 
transport modeling is under consideration for 
future study. 
Complete benchmark tests to evaluate 
advection; advection and diffusion; 
advection and multiple diffusion; decay, 
advection, and multiple diffusion for model 
verification. 
UZFTEP Benchmark tests are underway, but the results 
were not available for inclusion in the UZ PMR. 
The YMP should complete comparisons of 
the single gridblock and multiple grid 
approaches for matrix diffusion. 
UZFTEP This comparison is under consideration for future 
study. 
Coupled Processes 
The YMP needs to consider the effects of 
thermal-hydrologic processes on UZ flow 
and transport in the early postclosure period, 
including how to treat transient flow during 
the first 10,000 years with respect UZ 
transport. 
PARP Thermohydrological effects on UZ flow have 
been quantified (Section 3.12). Thermal effects 
on flow were not found to be significant and were 
not included in UZ transport simulations (Section 
3.11). 
The YMP should consider the effects of 
THCM processes on post-thermal period 
geochemistry for drift seepage and 
radionuclide transport. 
PARP, NWTRB, 
DSPR 
Effect of THC processes on geochemistry of drift 
seepage has been addressed (Section 3.10). 
Effects of THC processes on porosity and 
permeability were small. THC effects on 
radionuclide transport were not analyzed 
(Section 3.10). 
The YMP should complete coupled THC 
modeling. 
UZFTEP Coupled THC modeling has been performed as 
summarized in Section 3.10. 
The YMP should use a discrete fracture 
network model to evaluate coupled THC 
processes at smaller scales to improve the 
understanding of the repository system. 
UZFTEP Work to address this issue is ongoing, but the 
results were not available for inclusion in the UZ 
PMR. 
The YMP should complete bench mark tests 
for THC to evaluate a heat pipe with 
calcite/silica precipitation using a 1-D dual 
permeability approach for model verification. 
UZFTEP The suggested bench mark tests are under 
consideration for future study. 
The YMP should complete bench mark tests 
to evaluate chemical: microbial degradation 
and complexation of EDTA, copper leaching, 
and acid mine drainage for model 
verification. 
UZFTEP The suggested bench mark tests are under 
consideration for future study. 
The YMP should consider modeling smallscale 
THC processes. 
UZFTEP The suggested modeling is under consideration 
for future study. 
NOTES: 1 PARP: Total System Performance Assessment Peer Review Panel (Budnitz et al. 1999) 
2 DSPR: Drift Scale Peer Review (Chandler et al. 1999) 
3 UZEE: Unsaturated Zone Flow Expert Elicitation (CRWMS M&O 1997b) 
4 NWTRB: Nuclear Waste Technical Review Board (NWTRB 1999, 2000) 
5 UZFTEP: Unsaturated Zone Flow and Transport Evaluation Panel (YMP 1999) 
6 NC: Nye County (Bradshaw 1999)

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Finally, the TSPA Peer Review Panel noted that there are two types of processes that should be 
analyzed in future TSPAs: those for which analytical models are available and those that may be 
essentially intractable, given current analytical capabilities or the Projects time constraints. 
They recommended the following approach to analyze these processes: 
 Update models 
 Increase the quality and quantity of data input to the analyses 
 Use bounding analyses 
 Implement design changes. 
The TSPA Peer Review Panel also recommended using the defense-in-depth concept in 
conjunction with the approaches listed above to increase confidence that the potential repository 
system will meet regulatory requirements. This approach is being implemented as models are 
developed for the postclosure safety case as defined under the Repository Safety Strategy 
(CRWMS M&O 2000b). 
2.5.1.2 Summary of the UZ Flow and Transport Model Independent Evaluation Panel 
In 1999, the YMP convened an independent evaluation panel to review the UZ Flow and 
Transport Model using the TOUGH2 family of codes and determine the adequacy of this effort 
to meet the project goals within specified time frames. The panels review (YMP 1999) focused 
on the conceptual model basis, water-flow capability, reactive-transport capability, and nuclidetransport 
capability. The panel concluded that the TOUGH2 models represent a capability at the 
leading edge of development in many areas. The panel also noted that the reactive-transport and 
nuclide-transport capabilities of the models are limited and have not yet been validated with site 
data. Accordingly, these capabilities should be primarily used for sensitivity studies. The panel 
also made several recommendations for future work to support the UZ flow and transport 
modeling effort. They noted that no proven best conceptual model for Yucca Mountain has been 
established, and a variety of methods using different conceptual perspectives, such as discrete 
fracture flow with particle tracking, could contribute to a better understanding of system 
performance. Key issues identified by the panel are listed in Table 2.5-1. The panels report was 
issued after analyses supporting the UZ PMR had been initiated so some of their 
recommendations for new testing and analyses are not addressed in the UZ PMR; these 
recommendations are under consideration for future study. 
2.5.1.3 Summary of the Drift-Scale Seepage Peer Review 
In 1999, the YMP completed a peer review of the drift seepage studies (Chandler et al. 1999). 
The panel did not believe that it is realistic to develop models that predict current and future rates 
and locations of seepage into drifts. This panel also concluded that there is insufficient 
information and inadequate models to accurately predict the spatial and temporal distribution of 
moisture that will enter drifts in a potential repository at Yucca Mountain. Instead, they 
recommended that the project should develop models that provide reliable statistical bounds for 
estimating rates and locations of drift seepage. The panel recommended that the YMP develop a 
thorough plan for ongoing and future experimental and modeling work that is well integrated 
with developments in repository design and engineered barriers. The experiments should include 
a comprehensive program of drift seepage experiments in the ESF. The testing should include

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acquisition of site data for a wide range of spatial scales, focusing on the rocks of the potential 
repository horizon, that can be used to develop multiscale relationships for geologic 
heterogeneity controlling movement of moisture through the rocks. Key issues are listed in 
Table 2.5-1. 
2.5.1.4 Summary of the Unsaturated Zone Flow Expert Elicitation 
In 1997, the YMP conducted a UZ Flow Model Expert Elicitation, in which project data and 
models were presented to a group of experts (mostly from outside YMP) so that they could 
provide assessments of uncertainties in key parameters and processes in the UZ (CRWMS M&O 
1997b). Specific emphasis was placed on infiltration and deep percolation. Each expert estimated 
probability distribution functions for these processes. The panel also evaluated spatial and 
temporal variability in net infiltration and percolation flux, partitioning of fracture and matrix 
flow, seepage into drifts, modeling issues, and additional testing that might reduce uncertainty. 
The panel generally agreed that infiltration maps capture the general spatial variability of 
infiltration, but several experts suggested that more infiltration occurs beneath washes with thin 
alluvial cover. The experts also agreed that temporal variability in net infiltration was 
characterized by episodic events from major storms, but that most of the transient flux was 
attenuated within the system. 
With regard to lateral diversion above the potential repository, most of the experts agreed that 
contrasts in hydrologic properties between units could cause lateral flow, particularly at the 
contact of the TCw with the PTn. However, they concluded that the distance of diversion would 
be limited to scales of several meters to tens of meters. This was consistent with the results of 
TSPA-VA UZ flow simulations showing nearly vertical flow above the repository. The experts 
did not address lateral diversion caused by perched water beneath the repository. The experts 
also estimated that the flow in the TSw was predominantly in fractures and that the fast-flow 
component likely represents only a small part of the total flux. This was consistent with 
simulated results in TSPA-VA. 
With regard to seepage into drifts, the experts agreed that a capillary barrier would exist around 
the drifts and that it would likely divert the water flow in the matrix around the drifts. This 
behavior is also consistent with the results of TSPA-VA. Finally, the experts recommended a 
number of additional testing and modeling activities to address uncertainties in estimates of 
infiltration, percolation, and seepage. Their recommendations for additional testing were 
considered in planning tests in the ECRB. These recommendations included concerns with net 
infiltration, percolation flux in matrix and fractures at the repository horizon, temperature 
gradients, saturations and water potentials, chloride mass balance and isotopic evidence for fast 
paths, water balance, hydraulic properties of faults and fault zones, and fracture coating minerals 
(see Section 2.2). Two recommendations for additional testing have not been implemented (see 
Table 2.5-1) 
2.5.1.5 Summary of Nuclear Waste Technical Review Board Issues 
The Nuclear Waste Technical Review Board (NWTRB) has commented on the importance of 
understanding the spatial distribution and rate of percolation flux in fast pathways and the need 
to evaluate episodic, transient percolation. In recent meetings, the NWTRB has focused on the

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importance of refining the understanding of seepage into drifts through the collection of site 
specific data and improving seepage models. They have emphasized the importance of focused 
testing in the lower lithophysal and lower nonlithophysal units of the Topopah Spring that may 
host the potential repository. They have encouraged the YMP to continue ongoing work in the 
Cross Drift, including systematic sampling, geologic mapping and small-scale fracture mapping, 
36Cl/Cl analyses, fracture mineralogy geochemistry and geochronology, and moisture 
monitoring. They have also expressed concern with extrapolating the results of testing at Busted 
Butte to the Calico Hills formation beneath the potential repository block, and the need to 
determine the thermal, hydrologic, mechanical, and chemical properties of the rock units that 
may host the potential repository (NWTRB 1999, 2000). These issues are summarized in Table 
2.5-1. 
2.5.1.6 Summary of Nye County Issues 
In their review of the VA, Nye County provided some comments related to UZ flow and 
transport (Bradshaw 1999). They were concerned that seepage into drifts was underestimated in 
the VA, compared to the recent results of seepage testing in Alcove 1 in Tiva Canyon welded 
tuff in the ESF. The seepage model predicted the seepage observed in the Alcove 1 tests. 
However, the values determined are not directly applicable to the Topopah Spring welded tuff at 
the potential repository horizon. They also noted that there are limited data from the Calico Hills 
directly beneath the potential repository. They do not think that recent results from testing 
Busted Butte will resolve the lack of data because Busted Butte is not an analog for the Calico 
Hills beneath the potential repository. They believe that more data are needed from the Calico 
Hills at this location to confirm bounds on flow and transport in this formation. Finally, they 
noted that additional data are needed to define site-specific sorption characteristics. They believe 
that the treatment of sorption as a potential retardation mechanism may be underestimated in 
fractures and overestimated in the matrix. These issues are summarized in Table 2.5-1. 
2.5.2 Summary of Key Project Issues 
This section summarizes key findings identified in the TSPA-VA (DOE 1998) and at subsequent 
YMP workshops including the PA Workshop on UZ Flow and Transport (Houseworth and Ho 
1999) and UZ Model Workshop (Cushey and Liu 1999). The issues identified in the TSPA-VA 
were further addressed in the PA Workshop and the UZ Model Workshop to identify direct 
strategies for addressing these and other issues. 
2.5.2.1 TSPA-VA 
The data and analyses in TSPA-VA (DOE 1998) provided an evaluation of repository 
performance, given the information available at that time. The analysis included an assessment 
of model enhancements and analyses that may improve future assessments of repository 
performance, including the representation of UZ flow and transport (DOE 1998, Section 6.5.1). 
The discussion below summarizes the key issues that were identified as having the potential to 
enhance the confidence in future assessments of UZ flow and transport. The manner in which 
these were incorporated or addressed in the UZ PMR is discussed in the sections on the PA and 
UZ Model Workshops.

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Precipitation and infiltration. The TSPA-VA model evaluated three distinct climate states. This 
approach was simplistic and did not have a strong technical basis. The analysis of future climate 
states could have been improved by developing a more defensible basis for the number, timing, 
and duration of climate states. The timing of transitions from one climate to another is not 
known. Noninstantaneous climate transitions may lead to lower peak doses. Climate analogs 
were used as a basis for infiltration modeling; the analogs were defined simply by precipitation. 
Taking into account temperature and other factors would have provided a better definition of 
climate analogs. Section 3.5 summarizes the current evaluation of climate states; this evaluation 
provides a more defensible basis for the duration of each climate state and uses climate analog 
sites to define ranges of temperature and precipitation for infiltration modeling. 
Percolation to depth. The adequacy of the TSPA-VA modeling using the continuum approach 
with coarse spatial discretization has not been fully established. The effect of localized 
channeling, or specifically the effect of flow in discrete fractures, is an important uncertainty in 
UZ flow modeling. Better integration of geochemical, isotopic, and temperature data could have 
improved the calibration procedure and provide insights into the importance of flow through 
fractures. Another uncertainty in the Flow Model is the role of perched water. The TSPA-VA 
model assumed that flow is diverted around water that is perched on an impermeable layer. 
Investigation of alternative models, such as mixing and flow through the perched zones, could 
have been analyzed. The effects of localized channeling and discrete fractures are evaluated in 
Section 3.9; an alternative model for perched water is presented in Section 3.7. 
Effects of heat and excavation on flow. For the conceptual models of flow, differences had been 
noted between the dual-permeability flow model and the equivalent continuum model. The dualpermeability 
model provides for greater mobility of water in fractures, which has a great effect 
on the buildup of condensate and drainage. Current approaches to modeling UZ flow are 
described in Section 3.7. In addition, channelized flow, especially in fractures, could increase the 
spatial variability in the results by increasing the range of water-flow rates onto waste packages. 
These processes are addressed in Section 3.9. Coupling of TH and TC processes was not fully 
addressed in TSPA-VA. These processes are addressed in Section 3.10. In addition, TH effects 
could have been more closely coupled with mountain-scale UZ flow and transport. Section 3.12 
summarizes TH effects on the mountain scale. 
Almost all of the data on matrix hydrologic properties have been obtained from drying 
experiments. Data obtained from wetting experiments would be more appropriate for modeling 
the TH behavior during rewetting and condensate drainage in the potential repository. These data 
have not yet been obtained. 
In situ thermal tests will continue to provide data to improve TH modeling. Ongoing tests are 
located in the Topopah Spring middle nonlithophysal hydrologic unit. In the current repository 
design, most of the drifts are in the Topopah Spring lower lithophysal unit with some drifts in the 
middle nonlithophysal unit and others in the lower nonlithophysal unit. Obtaining thermalresponse 
data in these units could provide additional confidence in these models. These data 
have not yet been obtained. 
Seepage. Several improvements to the approach to modeling seepage in TSPA-VA were 
suggested. The model could be tested by comparisons between field data and model predictions

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to enhance the current confidence in the model. The number of waste packages that are contacted 
by seepage water relates to the average spacing of seeps along the drift, which is, in turn, related 
to parameters such as fracture spacing and permeability distribution. Field data that relate these 
parameters to the spacing of seeps could increase confidence in the seepage model. Seepage into 
drifts is also potentially strongly affected by channeling of flow and discrete-fracture effects. The 
adequacy of fracture-continuum models to represent these effects is uncertain. These 
improvements to the seepage models are summarized in Section 3.9. 
For the TSPA-VA, seeps were assumed to occur at the same locations through time. Varying the 
location of seeps could result in more waste packages failing through time, but over a longer 
time. This effect had not been analyzed in TSPA-VA. Other effects that had not been analyzed in 
the seepage model include drift collapse and thermal alteration of hydrologic properties around 
the drifts. These effects could significantly impact seepage. Finally, the potential for episodic 
percolation at the repository and increases in seepage from drainage of thermally mobilized 
water were not considered. Section 3.9 summarizes the current seepage model that includes 
partial drift collapse; Section 3.10 summarizes TH effects on seepage. 
UZ flow and transport. The TSPA-VA model did not account for the effects of thermal alteration 
of minerals, chemical interactions of repository materials, mineral dissolution and precipitation 
on UZ flow and transport. Development of a coupled, reactive transport representation would 
help assess these effects. The effect of colloid filtration was not included in TSPA-VA because 
there was insufficient information available to bound this mechanism. Colloid filtration is 
particularly important for the fraction of radionuclides that are irreversibly bound to colloids. 
The effects of higher infiltration evaluated in TSPA-VA imply that transport may be fracturedominated 
in many units in the UZ. More data on the character and distribution of fracture 
materials would allow consideration of sorption onto fracture surfaces in future analyses. 
Radionuclide transport in the UZ may be sensitive to changes in matrix diffusion depending on 
the nature of the releases from the engineered barrier system. The current models for UZ flow 
and transport address thermal alteration of minerals, mineral dissolution and precipitation 
(Section 3.10) and colloid filtration (Section 3.11). Sorption on fractures is still conservatively 
neglected. 
2.5.2.2 Summary of PA Workshop on UZ Flow and Transport 
A YMP workshop to address the treatment of UZ flow and transport for TSPA-SR was held in 
December 1998. The participants developed work plans that address the remaining issues 
identified as requiring additional development in preparation for the TSPA-SR (Houseworth and 
Ho 1999). The workshop focused on the following topics: climate, infiltration, UZ flow, drift 
seepage, radionuclide transport, and thermal-hydrological-chemical-mechanical coupled 
processes. Issues considered included those from the NRCs Issue Resolution Status Reports, 
TSPA-VA and the TSPA Peer Review Panel (as discussed in previous sections), as well as 
comments from within the program. At the time of the workshop, the Issue Resolution Status 
Report on Radionuclide Transport was not available for review. 
The issues presented at the workshop were discussed, modified, and agreed upon by the 
workshop participants. These issues are summarized below.

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Climate and Infiltration. Issues centered on the justification for the results obtained in TSPAVA. 
Improved justification for the magnitude and duration of climate states and changes in the 
water-table elevation were specifically identified as issues. For infiltration, improvements to the 
treatment of uncertainty, justification for the modeling approach, and explicit inclusion of 
additional processes were identified. Many of these processes have already been incorporated 
into the Infiltration Model. Stochastic simulations were identified as a more rigorous way to 
establish uncertainty in infiltration as compared to the TSPA-VA analyses based on observations 
of thermal gradients and water composition in the deep UZ. 
UZ Flow. Issues included questions on physical processes such as alternative conceptual models 
for fracture-matrix interaction and perched water, transient flow, and coupled processes 
(THCM). Methodological issues were also identified, including parameter estimation from 
inverse methods, applicability of gas-phase measurements to hydraulic properties, and grid 
resolution. Uncertainty in the appropriate range of percolation flux was also raised as an issue. 
Drift seepage. A mixture of issues on physical processes and methodology were identified. 
Specifically, drift collapse, which was not evaluated in TSPA-VA, was identified as an issue. 
Coupled processes (THCM) were identified as important to seepage. Additional physical 
processes of concern included episodic transient flow and the influence of matrix permeability. 
Methodological issues included representation of heterogeneity in models, coupling between the 
mountain-scale and drift-scale models, and continuum versus discrete representations of 
fractures. 
UZ Transport. Documentation of existing work was raised as a key question for issues related to 
radionuclide sorption, radionuclide decay, matrix diffusion, and gas-phase radionuclides. Issues 
regarding physical processes were identified for colloid-facilitated radionuclide transport and 
THC coupled processes. Issues on methodology included interfacing of the engineered barrier 
system and the UZ, grid refinement, the abstraction of matrix diffusion, radionuclide screening, 
and particle tracking. 
In conjunction with the technical issues, the workshop participants discussed issues related to the 
completeness and traceability of documentation, and quality assurance. These included the 
appropriate procedures to be followed for conducting and documenting work, qualification of 
existing data, tracking of existing data in technical reports, and software configuration 
management and verification. 
The issues discussed above were addressed in work plans for the modeling and analyses that 
were completed for the UZ PMR. 
2.5.2.3 Summary of the UZ Flow and Transport Model Workshop 
In March 1999, the UZ Flow and Transport Model Workshop was held to discuss the current 
status of ongoing field studies at Yucca Mountain related to the UZ Flow and Transport Model 
and to discuss the model development strategies for TSPA-SR (Cushey and Liu 1999). The 
workshop included presentations of the recent work being performed by YMP scientists from 
LBNL, LANL, SNL, USGS, and PA. This work included the collection, analyses, and 
interpretation of field data, the development and use of conceptual models, the current and

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planned use of calibration techniques, the interpretation of geochemical data, and the modeling 
of flow, transport, and coupled processes on the drift and mountain-scale. Each presentation was 
followed by discussions resulting in key decisions to direct the further development of the UZ 
Flow and Transport Model. The following summarizes these key decisions grouped by (1) those 
directed at the conceptual models that provide the framework for the UZ Flow and Transport 
Model and, (2) those related to the direct modeling approach, model inputs, and use of field data. 
For each key decision, a reference to the applicable section in this PMR and the AMR(s) that 
further discuss this information or approach is also provided. 
1. Conceptual Models: 
 The dual-continuum approach is the most appropriate for simulating flow and transport 
at the site or mountain scale for Yucca Mountain. Discrete fracture models are more 
appropriate for subscale analyses (alcove-, niche- or drift-scale) (see Sections 3.4.1.1, 
3.4.1.2 and 3.4.1.3 and CRWMS M&O 2000, U0030, Section 6.4.1.1). 
 There is adequate evidence that the van Genuchten model is applicable for welded tuffs 
and is defensible given the lack of better alternatives (see CRWMS M&O 2000, U0030, 
Sections 5 and 6.4.4). 
 The active fracture model will be used for the UZ Flow and Transport Model and TSPA 
(see Section 3.4.1.4.1 and CRWMS M&O 2000, U0030, Section 6.4.5; U0035, Section 
6; U0050, Section 6.1.2). 
 It is not necessary to include film flow because it is most likely limited to active 
fractures and will only represent a small fraction of the total water flowing in the UZ 
(see CRWMS M&O 2000, U0030, Section 6.1.3). 
 Alternative conceptual models for perched water (see Section 3.7.3.3 and CRWMS 
M&O 2000, U0050, Section 6.2.2) and distribution of percent zeolitic alteration in vitric 
zones (see Section 3.4.2.1 and 3.4.2.2 and CRWMS M&O 2000, U0000, Section 6.6.3) 
should be fully evaluated to determine their potential impact on performance. 
 The percent alteration in the vitric zone within the CHn hydrogeological unit and the 
corresponding changes in permeability and sorption are primary components for 
understanding and modeling of radionuclide transport and evaluating repository 
performance. Once these data are available from Busted Butte test facility, the results 
will be used as an analog for the CHn hydrogeological unit below the repository. 
 A consensus technical opinion on whether or not the perched water in G-2, UZ-14, SD- 
12, and SD-9 are the same chemically (i.e., do these form one continuous perched-water 
body) is needed. 
2. Modeling Approach, Model Inputs and Use of Field Data: 
 The 1999 infiltration map will be used for the UZ Model (see Section 3.5.2, 3.6.4, and 
3.7.2 and, USGS 2000 U0010, Section 1; CRWMS M&O 2000 U0035, Section 4.1; 
U0050, Section 4.1).

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 For the UZ Flow and Transport Model grid, the distribution of the percent zeolitic 
alteration for the CHn hydrogeological unit will be derived from the Rock Properties 
Model, a component of the Integrated Site Model (see Section 3.4.2.1 and 3.4.2.2 and 
CRWMS M&O 2000, U0000, Section 6.6.3). 
 At the workshop, it was recommended that for a design drift spacing of 28 m that a grid 
spacing of 56 m x 56 m x 15 m, with 15 m being the maximum vertical height, be used. 
Subsequent to this workshop, the design drift spacing was changed to 81 m and, 
therefore, the grid spacing was changed. In addition, TSPA requested that a coarser, less 
computationally intensive grid be provided, resulting in a grid spacing of 81 m x 270 m 
x 5 m in the potential repository horizon and 81 m x 270 m x 20 m (or less) below the 
potential repository horizon (see Section 3.4.2.3 and CRWMS M&O 2000, U0000, 
Attachment VI). 
 The fracture porosity used for the Tptpmn will be on the order of 0.01 (based on gas 
tracer data) rather than using calculated fracture porosities based only on fracture 
mapping data, which are on the order of 0.0001 (see Section 3.6.3.2 and CRWMS M&O 
2000, U0090, Section 6.1.3). 
 The proposal presented at this workshop for incorporating shorter trace length fractures 
(less than 1 m in length) will be utilized in determining the fracture properties for the UZ 
Model (see CRWMS M&O 2000, U0090, Section 6.1.2.3). 
 Water potential measurements will be made in deep boreholes (approximately 5 m deep) 
in the ESF Main Drift and Cross Drift to provide additional data for comparison with the 
measurements already made from shallow boreholes (approximately 2 m deep). 
 The calibrated mean properties (the layered approach) will be used in the UZ Flow and 
Transport Model and for the base-case flow fields (see Section 3.6.4 and CRWMS M&O 
2000, U0035, Section 6). A geostatistical representation of matrix properties for the 
CHn hydrogeological unit will be evaluated as part of a sensitivity study in Revision 1 of 
the UZ PMR. 
 Pneumatic data will continue to be used in performing calibration for the UZ Flow and 
Transport Model (see Section 3.6.4 and CRWMS M&O 2000, U0035, Sections 6.1, 6.2, 
and 6.3). 
 Results from in situ field tests in the ESF provide bounds for several hydrological 
parameters, including fracture alpha and fracture porosities, and will be used to 
corroborate model values (see CRWMS M&O 2000, U0090, Section 6.5). 
 Chloride data should be used for confirmation of the Infiltration Model, and bomb pulse 
data (36Cl) should be used for determining the presence of fast flow paths (see Section 
3.8.2 and 3.8.3 and CRWMS M&O 2000, U0050, Section 6.4). 
These key decisions were used to direct the development of the UZ Flow and Transport Model 
and its supporting AMRs.

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3. UZ FLOW AND TRANSPORT MODEL AND ABSTRACTIONS 
3.1 INTRODUCTION 
The Unsaturated Zone Process Model Report (UZ PMR) describes many models and analyses, 
all of which are aimed to gain a thorough understanding of flow and transport at Yucca 
Mountain. Some of these models are developed to explain certain specific data sets, others are 
used to evaluate parameter and process sensitivities, and the remainder provide TSPA with 
needed information. The UZ models developed for TSPA are the Calibrated Properties Model 
(CPM), the 3-D Flow Model (FM), the Seepage Model for Performance Assessment (SMPA), 
the Drift-Scale Thermal-Hydrological-Chemical Model (THCM), and the Transport Model 
(TM). The SMPA and TM directly evaluate the principal factors Seepage into Drifts and UZ 
Transport (see Section 1.2.2 for discussion of principal factors). Figure 1-2 shows the 
interrelation between the various UZ PMR models. 
The term model is used throughout the UZ PMR as a generic term for a conceptualization or 
numerical analysis. However, the YMP distinguishes between models and analyses in 
implementing its quality-assurance program. In the terminology of the YMP, a model is a 
representation of a process, system, or phenomenon, along with any hypotheses required to 
describe the process or system or explain the phenomenon, often mathematically (AP-3.10Q, 
Section 3.13). An analysis is defined by the YMP to be a scientific investigation that 
quantitatively or qualitatively describes, interprets, explains, or models a natural system, process, 
or phenomenon (AP-3.10Q, Section 3.1). Analyses may be performed in constructing a model, 
in developing data sets for input to a model or an analysis, or in applying a model to generate 
output that, in turn, may be used as input to another model or analysis. Models and analyses are 
documented in Analysis/Model Reports (AMRs) that are prepared in accordance with the 
requirements set forth in AP-3.10Q. Different documentation requirements apply, depending on 
whether the purpose of an AMR is to document the development of a model or the performance 
of an analysis. The UZ PMR, on the other hand, is being prepared in accordance with AP-3.11Q 
and provides summary documentation of the models, submodels, and analyses that constitute the 
UZ Flow and Transport Model and its abstraction to support TSPA. The UZ PMR, in turn, 
provides reference to the individual supporting AMRs in which the detailed technical 
documentation of the models and analyses is presented. 
This chapter is the main technical chapter of the UZ PMR and describes all of the models and 
analyses supporting the PMR. For each of the process models discussed, the following aspects 
of that particular model are addressed: 
 Description of the model and submodels 
 Relevant data and data uncertainties 
 Assumptions and conceptual bases 
 Model results (outputs) 
 Abstraction of the model for TSPA (if applicable; see Table 1-1) 
 Information on model validation 
 Alternative models and interpretations

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In addition, where appropriate, corroborative/supportive information is given, relevant journal 
articles are referenced, and natural analogs are discussed. 
This chapter starts with sections on geology as it relates to flow and transport, descriptions of 
physical processes, and a discussion of numerical approaches and grid development. Then the 
various flow-related models are discussed, including those on climate and infiltration, calibrated 
properties, and 3-D flow fields. The ambient geochemistry model follows, describing modeling 
of geochemical data to ensure consistency between the flow fields and radionuclide transport 
models. Then the seepage models are discussed as well as THC models that evaluate seepage 
during the thermal period, chemistry of water entering drifts, and modifications of hydrological 
properties resulting from THC processes. Finally, the transport models and the mountain-scale 
TH models are described. The last section of Chapter 3 provides a high-level summary of the 
uncertainties of the various process models of the UZ Flow and Transport Model.

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3.2 GEOLOGICAL CONSIDERATIONS FOR FLOW AND TRANSPORT 
3.2.1 Overview 
Located in southern Nevada, Yucca Mountain is composed of a thick sequence of volcanic rock 
units that were deposited as a result of a series of volcanic eruptions in the vicinity of Yucca 
Mountain during the Miocene Epoch (about 14 to 9.5 million years ago; Sawyer et al. 1994, 
pp. 13041318). Variations in lithostratigraphy within this sequence reflect the type of eruption, 
the rate of cooling and crystallization of the deposits, and the postdepositional processes of 
mineral alteration and tectonics. Sculpted by the slow but continual forces of erosion, Yucca 
Mountain is marked by washes and ridges that reflect the underlying structure of the mountain. 
Situated in one of the most arid regions of the United States (see Section 3.5.1.4), Yucca 
Mountain is underlain by a thick unsaturated zone (UZ). Depth to the nearly flat water table 
ranges from approximately 500 to 750 meters (m) below ground surface. The current, potential 
repository design calls for waste emplacement at a depth ranging from 200 to 425 m below 
ground surface and from 175 to 365 m above the water table (DOE 1999, pp. S-9S-10). 
Table 3.2-1 summarizes the key geological issues related to unsaturated flow and transport 
performance of the potential repository site. 
Table 3.2-1. Geological Issues Related to Performance 
Performance 
Aspect 
Key Geological Issues 
Liquid, Gas, and 
Heat Flow 
 Fracture connectivity (fracture networks) in the welded units 
 Occurrence of fast pathways in the welded and nonwelded units 
 Layer continuity and heterogeneity 
 The occurrence and location of faults 
 Fault displacement and fault hydrological properties 
 Location of altered zones 
 Thermal properties of variably welded / fractured zones 
Seepage  Fracture connectivity 
 Breakouts and drift collapse due to rock stress, fracture orientation, 
and lithophysal zones 
 Location of major faults 
Radionuclide 
Transport 
 Tuff mineralogy (sorptive potential) 
 Effective surface area for matrix diffusion 
 Faulting and fracturing providing fast pathways 
 Groundwater travel times and focused flow below the potential 
repository 
Repository 
Design 
 Rock stability in fractured nonlithophysal and lithophysal zones 
 Location of major faults 
 Waste isolation/seepage into drifts

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In the UZ, flow and transport phenomenacontrolled by rock hydrogeological characteristics 
such as porosity, permeability, saturation, and moisture contentare closely linked to the 
depositional and postdepositional history of Yucca Mountain. It is important, therefore, to 
understand the distinguishing depositional characteristics of the volcanic rocks and any 
significant changes in rock properties resulting from hydrothermal and tectonic processes, as 
well as ongoing geochemical processes in variably saturated rocks. 
The UZ at Yucca Mountain consists primarily of gently dipping pyroclastic flow and fall 
deposits (Figure 3.2-1). These tuffs grade from nonwelded to densely welded, reflecting 
differences in the rate of cooling and in the compressional stresses exerted on the tuffs during 
cooling caused by the weight of the overlying material. Typically, the degree of welding is 
inversely proportional to porosity and directly proportional to fracture frequency. The nonwelded 
tuffs usually have large porosities (typically 30 to 50%) and few fractures (less than 1 per meter), 
while the densely welded tuffs generally have greatly reduced pore space (generally less than 15 
percent) and abundant fractures (approximately 1 to 4 per meter) (Flint 1998, p. 44, Table 7; 
CRWMS M&O 2000, U0090, p. 36). Fracturing within the stratigraphic layers that comprise 
Yucca Mountain is typically confined within each layer (i.e., most fractures terminate at layer 
boundaries) (Spengler et al. 1994, pp. 1-11; Rousseau et al. 1999, p. 23). 
In some cases, gases trapped during the cooling process form cavities (lithophysae) of varying 
diameter, shape, and roughness within the welded tuff matrix, resulting in an increase in total 
porosity. Degree of welding and presence of lithophysal cavities govern fracture geometry and 
surface roughness. Fractures within densely welded tuffs have a more planar geometry and a 
smoother surface than less welded units. However, in lithophysal zones, fractures are less 
planar, and fracture surfaces are typically rougher than in nonlithophysal zones (Buesch et al. 
1996, p. 15, Table 2 and Figure 5; Rousseau et al. 1999, p. 24) as shown in the photos and 
schematics in Figure 3.2-4. The occurrence of small fractures may be important in 
nonlithophysal zones because of the relative absence of abundant through-going or long-length 
fractures. Conceptually, small fractures may add to the bulk permeability of the rock. 
Other important aspects of the geological setting at Yucca Mountain include layer continuity and 
heterogeneity. Layer thickness and lateral continuity initially depend on three principal factors: 
location of the source area, volume of deposited material, and shape of the pre-existing 
topographic surface (Rousseau et al. 1999, p. 30). On a regional scale, volcanic deposits thicken 
closer to the source area and pinch out in distal regions. Locally, layers thicken to fill existing 
topographic lows and thin (or even pinch out) around existing topographic highs. During 
volcanic deposition and cooling, variations in layer thickness, in addition to local moisture 
conditions, give rise to internal heterogeneity within the tuff layers. Margins of thick ash flows 
(including top, bottom, and lateral boundaries) cool quickly and under different pressures 
compared to the interior of the flow units, thus producing rock fabrics with different hydraulic 
characteristics. For instance, the upper and lower margins of the highly fractured, moderately to 
densely welded potential repository host rock, the Topopah Spring Tuff, grade into sparsely 
fractured, partially welded and nonwelded tuffs (Figure 3.2-2b and Figure 3.2-5). A similar 
trend is seen within the Paintbrush nonwelded unit (PTn), where two ash-flow members thin 
dramatically to the south across Yucca Mountain, with observed lateral and vertical increases in 
matrix porosity corresponding to reduced welding. These transitions between welded to

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nonwelded intervals of rock can significantly impact vertical flow, leading to accumulation of 
water and focusing of flow. 
Postdepositional processes such as mineral alteration, tectonics, and erosion further modify the 
hydrological characteristics and continuity of the tuffs beneath Yucca Mountain. The slow, 
continual process of mineral alteration resulting from prolonged rock-water interaction and 
weathering at the land surface (in addition to hydrothermally induced mineral changes that 
occurred during cooling of the welded tuffs) has led to the formation of clays, zeolites, and 
vapor-phase minerals in the rock layers (Bish and Chipera 1989, pp. 115; Bish and Aronson 
1993, pp. 148161). These alteration products are important because of their potential to reduce 
permeability and to sorb radionuclides. Also important to flow and transport are interruptions in 
layer continuity attributed to fault displacement and erosion. Faulting may further affect the 
hydrological properties of the tuffs by establishing a secondary high-permeability network 
through intense fracturing (Figure 3.2-5d), or, conversely, by reducing permeability through the 
formation of fault gouge (Figure 3.2-5e). 
3.2.2 Major Hydrogeological Units 
Tuffs occurring within the UZ beneath Yucca Mountain are identified by lithostratigraphic name 
and by major and detailed hydrogeological unit nomenclatures in Table 3.2-2. This table also 
provides the correlation between these units and UZ model layers. Most layers are laterally 
continuous across the site, except where eroded or interrupted by faults whose displacement 
exceeds layer thickness. The following discussion summarizes units of principal importance to 
flow and transport in the UZ at Yucca Mountain. Definition of major hydrogeological units 
comes from Montazer and Wilson (1984, pp. 919). Their abbreviation of each of the five major 
hydrogeological units (i.e., TC, P, TS, CH, and CF) has been modified slightly for use in this 
PMR. In order to be more descriptive, a lowercase letter has been added indicating whether the 
unit is welded (w), nonwelded (n), or undifferentiated (u).

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Table 3.2-2. Major Hydrogeological Unit, Lithostratigraphic Unit, Detailed Hydrogeological Unit, and UZ 
Model Layer Nomenclatures (adapted from CRWMS M&O 2000, U0000, Table 10) 
Major 
Hydrogeological 
Unit 
Lithostratigraphic Unit Detailed 
Hydrogeological 
Unit 
UZ Model 
Layer 
Tpcr CCR, CUC tcw11 
Tpcp CUL, CW tcw12 
Tpcpv3 
Tiva Canyon 
welded (TCw) 
Tpcpv2 
CMW tcw13 
Tiva Canyon 
Tuff 
Tpcpv1 CNW ptn21 
Bedded tuff Tpbt4 BT4 ptn22 
TPY ptn23 
Yucca 
Mountain 
Tuff 
Tpy 
Bedded tuff Tpbt3 BT3 ptn24 
Pah Canyon 
Tuff 
Tpp TPP ptn25 
Bedded tuff Tpbt2 
Tptrv3 
Paintbrush 
nonwelded (PTn) 
Tptrv2 
BT2 ptn26 
Tptrv1 TC tsw31 
Tptrn TR tsw32 
Tptrl 
Tptpul 
TUL tsw33 
Tptpmn TMN tsw34 
Tptpll TLL tsw35 
TM2 (upper 2/3) tsw36 Tptpln 
TM1 (lower 1/3) tsw37 
Tptpv3 PV3 tsw38 
Topopah Spring 
welded (TSw) 
Tptpv2 PV2 tsw39 
Topopah 
Spring Tuff 
Tptpv1 
Bedded tuff Tpbt1 
BT1 or 
BT1a (altered) 
ch1 (vit, zeo) 
ch2 (vit, zeo) 
ch3 (vit, zeo) 
ch4 (vit, zeo) 
Calico Hills 
Formation 
Tac CHV (vitric) 
or 
CHZ (zeolitic) 
ch5 (vit, zeo) 
Bedded tuff Tacbt BT ch6 
Tcpuv PP4 (zeolitic) pp4 
Tcpuc PP3 (devitrified) pp3 
Calico Hills 
nonwelded (CHn) 
Prow Pass 
Tuff 
Tcpmd PP2 (devitrified) pp2

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Major 
Hydrogeological 
Unit 
Lithostratigraphic Unit Detailed 
Hydrogeological 
Unit 
UZ Model 
Layer 
Tcplc 
Tcplv 
Bedded tuff Tcpbt 
Tcbuv 
PP1 (zeolitic) pp1 
Tcbuc 
Tcbmd 
Tcblc 
BF3 (welded) bf3 
Bullfrog Tuff 
Tcblv 
Bedded tuff Tcbbt 
Tctuv 
BF2 (nonwelded) bf2 
Tctuc 
Tctmd 
Tctlc 
Not Available tr3 
Crater Flat 
undifferentiated 
(CFu) 
Tram Tuff 
Tctlv & below Not Available tr2 
3.2.2.1 Tiva Canyon Welded (TCw) Hydrogeological Unit 
The TCw is the most prevalent hydrogeological unit exposed at the land surface. The unit is 
composed of moderately to densely welded, highly fractured pyroclastic flow deposits of the 
Tiva Canyon Tuff. The deposits are of variable thickness resulting from erosion. Within the 
potential repository area, the maximum thickness of the TCw is about 150 m along Yucca Crest 
(which runs along the western half of the potential repository footprint; see Figure 3.2-1), 
whereas in alluvial washes east of Yucca Crest, the TCw may be completely eroded (Montazer 
and Wilson 1984, p. 14; Rousseau et al. 1999, p. 30). Vapor-phase corrosion of volcanic glass 
and pumice in the lower TCw imparts a secondary porosity beneath central and northern Yucca 
Mountain (Buesch et al. 1996, pp. 3536; Flint 1998, p. 21). The lower boundary of the TCw 
has been defined as the contact between the densely welded, vitric subzone (Tpcpv3) and the 
moderately welded, vitric subzone (Tpcpv2) of the Tiva Canyon Tuff. Because Tpcpv3 is 
typically very thin and only observed beneath southeastern Yucca Mountain, the base of Tpcpv2 
is selected as the lower TCw boundary for the purpose of defining layers within the mountainscale 
numerical grids discussed in this report. 
TCwPTn transitionTuffs grade gently downward over a few tens of centimeters from 
densely welded (Tpcpv3, where present, otherwise the lower nonlithophysal zone of the TCw or 
the upper portion of Tpcpv2) to nonwelded (Tpcpv1), accompanied by an increase in matrix 
porosity and a decrease in fracture frequency (Figure 3.2-2a). Many fractures in the lower TCw 
terminate at the contact between TCw and PTn, or their apertures are greatly reduced across this 
boundary. Alteration to clay minerals is common at the base of the TCw (Moyer et al. 1996, 
pp. 12, 1617, 88, Table 3; Buesch et al. 1996, pp. 3536) and is correlated with observed 
increases in saturation (Flint 1998, p. 8 and Figures 6, 7). Changes in fracture characteristics and

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the occurrence of alteration minerals at the TCw-PTn contact may have important implications 
for downward flow of water at this interface. 
3.2.2.2 Paintbrush Nonwelded (PTn) Hydrogeological Unit 
The PTn consists of layers of predominantly nonwelded and bedded tuffs (particularly in the 
potential repository footprint) with high matrix porosity and low fracture frequency (Moyer et al. 
1996). The layers include the nonwelded vitric (i.e., glassy) subzone at the base of the Tiva 
Canyon Tuff (Tpcpv1), the bedded tuff Tpbt4, the Yucca Mountain Tuff (Tpy), the bedded tuff 
Tpbt3, the Pah Canyon Tuff (Tpp), the bedded tuff Tpbt2, and the non- to moderately welded 
vitric tuffs at the top of the Topopah Spring Tuff (Tptrv3, Tptrv2). Thickness of the PTn 
hydrogeological unit ranges from about 110 to 20 m (north to south) across the potential 
repository area and thickens to over 160 m beneath the northernmost part of Yucca Mountain 
(Figure 3.2-3a). Lateral variation in welding associated with the substantial thickening of two 
PTn units (Tpy and Tpp), in addition to the variable distribution of altered (e.g., smectitic and 
zeolitic) intervals, make rock-hydrological properties within the PTn highly heterogeneous. 
Through-going fracture networks are rare and are typically associated with faults (Rousseau et al. 
1999, p. 54). The bottom of the PTn is defined as the contact between the moderately and 
densely welded, crystal-rich vitric subzones (Tptrv2 and Tptrv1, respectively). Given the overall 
large storage capacity of the highly porous rock matrix, the PTn unit may effectively dampen 
transient pulses of infiltration and more evenly distribute the downward flow of water. 
PTnTSw transitionA thin, but prevalent layer of argillic alteration is observed in the pre-Pah 
Canyon bedded tuff (Tpbt2), near the base of the PTn (Moyer et al. 1996; pp. 53, 80), and may 
behave as a capillary or permeability barrier to flow (Rousseau et al. 1999, p. 25). Below this 
horizon, crystal-rich vitric tuffs grade sharply downward from nonwelded (Tptrv3) to densely 
welded (Tptrv1), accompanied by a sharp decrease in matrix porosity and an increase in fracture 
frequency (Figure 3.2-2b). These changes in porosity and fracture characteristics may create 
saturated conditions above this contact that may reinitiate fracture flow into the TSw. 
3.2.2.3 Topopah Spring Welded (TSw) Hydrogeological Unit 
Sharing many characteristics of the TCw, the TSw is composed of moderately to densely welded, 
pyroclastic flow deposits with intense fracturing (Buesch et al. 1996, pp. 1921). A key 
difference between the TSw and the TCw is the existence of a well-developed, densely welded, 
crystal-poor vitrophyre (i.e., rock with a glassy groundmass) near the base of the TSw (Buesch et 
al. 1996, p. 23; Rousseau et al. 1999, p. 22). (The densely welded, basal vitrophyre of the TCw is 
very thin and occurs only beneath southeastern Yucca Mountain.) Thickness of the TSw ranges 
from about 280 to 350 m in the potential repository area (Figure 3.2-3b). The base of the TSw is 
defined as the contact between the densely and moderately welded, crystal-poor vitric subzones 
(Tptpv3 and Tptpv2, respectively). In descending lithostratigraphic order (using the 
nomenclature of Buesch et al. 1996, Table 2), the key units within the TSw are (refer to 
Figure 3.2-4): 
 Tptrv1 and/or uppermost Tptrnthin (~ 2 m thick), crystal-rich upper vitrophyre of 
the TSw, characterized by very low porosity and intense fracturing.

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 Tptrncrystal-rich nonlithophysal unit with well developed secondary porosity 
imparted by vapor-phase corrosion of volcanic glass and pumice clasts. 
 Tptrl & Tptpulcrystal-rich and crystal-poor upper lithophysal units. 
 Tptpmncrystal-poor middle nonlithophysal unit (potential repository layer). 
 Tptpllcrystal-poor lower lithophysal unit (potential repository layer). 
 Tptplncrystal-poor lower nonlithophysal unit; contains a highly fractured subzone 
and frequent clay alteration near base of unit (potential repository layer). Perched water 
is observed in several locations within the lower part of this unit. 
 Tptpv3crystal-poor basal vitrophyre, characterized by very low porosity and intense 
fracturing near unit top; alteration minerals (e.g., smectite, zeolite) commonly found at 
top of unit. 
TSwCHn transitionTuffs grade downward from densely welded to nonwelded over several 
meters, accompanied by an increase in matrix porosity and a decrease in fracture frequency 
(Figure 3.2-5). Furthermore, much of the vitric material occurring above and below this 
boundary has been altered to clays or zeolites. Alteration occurs (although not ubiquitously) 
along fractures in the densely welded basal vitrophyre (Tptpv3) of the TSw as well as within the 
high porosity, nonwelded matrix of the CHn (Broxton et al. 1987, pp. 89110; Bish and Chipera 
1989, Appendix A; CRWMS M&O 2000, I0045, Section 6.3). Alteration near this contact has 
been linked to the occurrence of perched water and has important implications for transport and 
retardation of radionuclides. 
3.2.2.4 Calico Hills Nonwelded (CHn) Hydrogeological Unit 
Comprised of predominantly nonwelded pyroclastic flow and fall deposits, the CHn extends 
from the base of the crystal-poor, densely welded vitrophyre to the water table, except where 
units below the base of the upper vitric portion of the Bullfrog Tuff (Tcbuv) lie above the water 
table (which occurs in certain areas beneath Yucca Crest). The key units of the CHn include the 
moderately welded to nonwelded vitric subzones at the base of the Topopah Spring Tuff (Tptpv2 
and Tptpv1, respectively), the bedded tuff Tpbt1, the Calico Hills Formation (Tac), the bedded 
tuff Tacbt, the entire Prow Pass Tuff (Tcpuvupper vitric, Tcpucupper crystalline, Tcpmd 
moderate/densely welded, Tcplclower crystalline, Tcplvlower vitric, and Tcpbtbedded tuff), 
and the upper vitric portion of the Bullfrog Tuff (Tcbuv). Within the potential repository 
footprint, the thickness of the CHn ranges from about 180 to 320 m, as shown in Figure 3.2-3c. 
Many different lithologies, distinguished by depositional history and degree of welding, by 
matrix color, and by the size, amount, and composition of pumice and lithic material, are 
contained within this interval. In a hydrogeological context, however, the most significant 
features in the CHn are the abundance and distribution of zeolites. The distribution of abundance 
of clays and zeolites beneath the potential repository horizon is difficult to determine because 
mineral data from only a small number of boreholes are available and because the degree of 
alteration is highly variable. Mineral alteration is discussed in greater detail in Section 3.2.4.

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3.2.2.5 Crater Flat Undifferentiated (CFu) Hydrogeological Unit 
The CFu consists of any units that occur above the water table and below the base of the upper 
vitric portion of the Bullfrog Tuff (Tcbuv). This includes portions of welded and nonwelded 
units from the Bullfrog and Tram tuffs. Within the potential repository area, the thickness of the 
CFu ranges from 0 (in the northern and eastern portions) to about 140 m (along the southwestern 
edge of the potential repository) (Figure 3.2-3d). Because of the limited number of deep 
boreholes, sufficient data are not available to fully characterize these tuffs. Nevertheless, the 
volume of CFu material is small and restricted to the southwestern area of Yucca Mountain. 
3.2.2.6 Water Table Configuration 
Several interpretations exist for the configuration of the water table beneath Yucca Mountain 
(Robison 1984; Wittwer et al. 1992; Ervin et al. 1994; Tucci and Burkhardt 1995). They range 
from an approximately flat interpretation (at an altitude of about 730 masl) to maps showing a 
steep hydraulic gradient linking observed water levels below southern Yucca Mountain (at about 
730 masl in several boreholes) with water levels beneath northern Yucca Mountain (up to about 
1,020 masl in borehole G-2). Given the limited amount of water level data in the north and the 
possibility that the few high altitudes observed represent perched water, either interpretation is 
valid. 
Regardless of altitude, the potentiometric surface intersects many lithostratigraphic units because 
of faulting and the gentle eastward dip of the strata. Figure 3.2-6 shows the occurrence of the 
Topopah Spring Tuff, Calico Hills Formation, Prow Pass Tuff, Bullfrog Tuff, and Tram Tuff at 
the water table east of the Solitario Canyon fault. 
3.2.3 Structural Setting 
Major faults at Yucca Mountain are of two basic types: north-trending normal faults (whose 
principal direction of movement is vertical) and northwest-trending strike-slip faults (whose 
principal direction of movement is lateral). The Solitario Canyon and Bow Ridge faults are the 
two major block-bounding faults in the Yucca Mountain area (see Figure 3.2-6) (Day et al. 1998, 
p. 6). The volume of rock lying between these faults is referred to as the central block. Both 
the Solitario Canyon and Bow Ridge faults are north-trending normal faults characterized by 
small (few meters) vertical displacement in the northern Yucca Mountain area and by large 
(several hundreds of meters) vertical displacement to the south. The zone of deformation along 
the western boundary of the central block associated with the Solitario Canyon fault is as much 
as 550 m wide (Day et al. 1998, p. 7). Numerous fault splays (three of which are shown in 
Figure 3.2-6) branch off from the main trace of the Solitario Canyon fault. Structural 
deformation associated with the Bow Ridge fault within the eastern part of the central block 
takes the form of a series of discontinuous, steeply-dipping normal faults, represented 
collectively as the Imbricate fault in Figure 3.2-6. 
Located within the central block are other north-trending normal faults, including the Ghost 
Dance and Dune Wash faults. Currently, the potential repository footprint is located between the 
Solitario Canyon and Ghost Dance faults (Figure 3.2-6), in an area referred to as the Yucca Crest 
structural subdomain (Rousseau et al. 1999, p. 47). The Ghost Dance fault dips steeply to the

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west and shows variable displacement and rock deformation along its trace (Day et al. 1998, 
pp. 910). Within the Yucca Crest structural subdomain lies a wide zone of minor northwesttrending 
faults referred to as the Sundance fault zone (represented by a single trace in 
Figure 3.2-6). The nature and continuity of the Sundance fault is described by Potter et al. 1999, 
pp. 115). 
Northwest-trending strike-slip faults are the prevailing structures in the northern part of the 
central block. These include the Sever Wash, Pagany Wash, and Drill Hole Wash faults, whose 
surface expression/projection parallels elongated, northwest-trending alluvial washes. Vertical 
displacement along these faults is typically less than 10 m (Day et al. 1998, p. 8). 
As described in the following section, faults may be important features in the UZ flow and 
transport regime given their potential role in the alteration history of Yucca Mountain. The 
effect faults may have on groundwater flow is also discussed in Section 3.3.5. 
3.2.4 Mineral Alteration and the Vitric-Zeolitic Boundary 
In the context of UZ flow and transport modeling, the abundance and distribution of clays and 
zeolites between the potential repository horizon and the water table are of particular interest 
because these alteration products can affect flow paths and sorb radionuclides. The potential for 
mineral alteration is affected by several factors: (1) rock fabric and composition, (2) proximity to 
structural features such as through-going fractures and faults, and (3) presence of water (rockwater 
interaction) (Broxton et al. 1987, pp. 89110). The rock units at Yucca Mountain most 
susceptible to mineral alteration are vitric tuffs with high porosity and high permeability. High 
porosity and permeability provide a large surface area of particles for interaction with passing 
groundwater and can be established either through the process of deposition and subsequent 
cooling or through secondary fracturing. 
Smectitic and zeolitic alteration has been observed in the highly porous nonwelded tuffs of the 
PTn and CHn, not only in the matrix, but along faults and well-connected fractures. Alteration 
to smectite and zeolite is also seen in fractures of the densely welded basal vitrophyre of the TSw 
and at the bottom of the lower nonlithophysal zone of the TSw, just above the contact with the 
basal vitrophyre (see schematic, Figure 3.2-5) (Broxton et al. 1987, p. 93). 
Below the potential repository horizon, the most abundant type of alteration (and the most 
important to radionuclide transport and sorption) is zeolitic. The degree of zeolitic alteration of 
vitric material is highly variable between the potential repository horizon and the water table 
large areas are considerably altered (zeolitic), while other areas remain unaltered (vitric) 
(Figure 3.2-7). Interpreted as an ancient water table (Broxton et al. 1987, p. 104; Bish and 
Aronson 1993, p. 150), the vitric-zeolitic boundary has been mapped as a three-dimensional 
surface that cross cuts several lithostratigraphic boundaries (Rousseau et al. 1999, pp. 40-43). 
This representation does not include the complex features of the vitric-zeolitic boundary such as 
transitions along fault zones and through-going fracture networks, local alteration associated 
with bodies of perched water, and areas of saturation transition, such as the capillary fringe of the 
water table.

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Although many complexities in the vitric-zeolitic transition have been observed at Yucca 
Mountain (in outcrop mapping and borehole logging), limited amounts of data are available over 
the three-dimensional, site-scale domain of the UZ model to fully understand this transition and 
to numerically simulate its effects on flow and transport processes. Nevertheless, the general 
geometry of the vitric-zeolitic boundary has been identified using various types of data analyses, 
including mineralogic x-ray diffraction (XRD) analyses of core samples (CRWMS M&O 2000, 
I0045, Section 4.1.1) and rock property measurements of matrix porosity and matrix 
permeability (Flint 1998; CRWMS M&O 2000, I0040, Section 4.1). In most cases, rock 
hydrological measurements are consistent with mineralogic analyses and indicate a trend of 
increasing alteration to the north and east across the potential repository area, and with depth 
from the base of the TSw to the water table (Figure 3.2-7). 
Within the welding transition from the base of the TSw into the upper CHn (Tptpv3 to Tptpv1), 
the occurrence of unaltered, vitric tuffs occupies much of the southern half of Yucca Mountain 
(Figure 3.2-7) (CRWMS M&O 2000, I0045, Section 6.3.2). A thin, vitric layer is observed in the 
area surrounding boreholes G-1, SD-9, G-4, and H-5 within the moderately welded, crystal-poor 
subzone (Tptpv2) at the base of the TSw. Given that this area is underlain by low-permeability 
zeolites (in layers Tptpv1 and Tpbt1), lateral diversion may occur within layer Tptpv2 beneath 
the northernmost part of the ESF. 
Within the Calico Hills Formation (lithostratigraphic unit Tac which has been subdivided into 
four layers of equal thickness in the Integrated Site Model (ISM3.1) Mineralogy Model; 
CRWMS M&O 2000, I0045, Section 6.2.2), the areal extent of predominantly vitric material 
appears to diminish with depth as boreholes SD-12 and SD-7 show increased zeolite content 
(Figure 3.2-7). The transition into zeolitic material is not easily characterized and may be 
gradual or abrupt in vertical and lateral directions, with lenses or fingers of zeolitic material 
occurring in otherwise predominantly vitric zones, and vice versa. 
The bedded tuff directly beneath the Tac is more pervasively altered to zeolites than the 
lithostratigraphic unit above it. The vitric area within the bedded tuff (Tacbt) appears limited in 
extent to an area surrounding boreholes SD-6, H-3, and G-3 (though an increase in smectite 
abundance is observed in borehole SD-6) (CRWMS M&O 2000, I0045, Section 6.3.2). 
The upper vitric interval of the Prow Pass Tuff (Tcpuv) has a distribution of zeolite abundance 
similar to layer Tacbt, with vitric material encountered in boreholes SD-6, H-3, and G-3. The 
remainder of the Prow Pass Tuff is moderately to densely welded, except at the base of the unit, 
which is nonwelded and pervasively zeolitized (CRWMS M&O 2000, I0045, Section 6.3.2). 
The maximum thickness of the largely unaltered, vitric rocks in the CHn is approximately 130 m 
and occurs just south of the potential repository footprint in an area surrounding borehole H-3 
(Rousseau et al. 1999, p. 41, Figure 16). 
Although not considered in the Mineralogy Model of ISM3.1, the location of and displacement 
along faults appear to affect the geometry of the vitric-zeolitic boundary. The Yucca Crest 
structural domain, within which lies the potential repository site, is bound in the west and east by 
two major faults: the Solitario Canyon and the Drill Hole Wash faults, respectively. Nearly all of 
the boreholes from which vitric samples in the CHn have been collected are located in the 
southern and western part of this structural domain. Boreholes intersecting predominantly

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zeolitized tuffs within the CHn lie in the northern and eastern part of the Yucca Crest structural 
domain and beyond its boundaries. The lateral transition from predominantly altered tuffs to 
unaltered tuffs within the CHn occurs in an area cross cut by the Sundance fault. Though 
modeled in the ISM as a single fault plane, the Sundance fault is actually a system comprised of 
many small northwest-trending faults. It has been hypothesized that the Sundance and Ghost 
Dance fault systems may have acted as barriers to the alteration process by either ponding 
southward migrating zeolitizing waters (i.e., faults behaving as low-permeability barriers) or by 
diverting water downward through high-permeability fracture networks associated with the 
faulting (Buesch et al. 1995, pp. 800804). 
3.2.5 Summary 
Potential repository performance is affected by key geological issues such as fracture 
connectivity in welded units, occurrence of fast flow pathways in nonwelded units, layer 
continuity and heterogeneity, distribution of mineralogically altered horizons and their sorptive 
potential, and rock stability in fractured nonlithophysal and lithophysal zones. Understanding the 
distinguishing depositional characteristics of the volcanic rocks, as well as any significant 
changes in rock properties resulting from postdepositional process (e.g., mineral alteration and 
tectonics), is the key to estimating rock hydrogeological characteristics (needed to simulate flow 
and transport phenomena) within the UZ at Yucca Mountain. 
The UZ has be divided into five major hydrogeological units, whose primary characteristics are 
as follows (listed in order from land surface to water table): 
1. TCwvariably eroded (0 to 150 m thick in the potential repository area), moderately to 
densely welded unit with high fracture frequencies. 
2. PTnpredominantly nonwelded unit (20 to 110 m thick in the potential repository 
area) with large matrix porosity, low fracture frequency, and variable distribution of 
low-permeability clays and other alteration minerals. 
3. TSwmoderately to densely welded unit (280 to 350 m thick in the potential 
repository area) with high fracture frequencies; contains potential repository horizon in 
the middle nonlithophysal, lower lithophysal, and lower nonlithophysal layers; perched 
water frequently occurs above the altered contact between the lower nonlithophysal unit 
and the densely welded, intensely fractured basal vitrophyre of the TSw. 
4. CHnmostly nonwelded tuffs (180 to 320 m thick in the potential repository area) 
with highly variable zeolite distribution; zeolite abundance increases to the north and 
east across the potential repository area, as well as with depth; major vitric (unaltered) 
areas in the CHn lie in the southern half of the potential repository area (maximum 
thickness of vitric material is about 130 m in an area just south of the potential 
repository footprint). 
5. CFua relatively small volume of rock (up to about 140 m thick in the potential 
repository footprint) occurring just above the water table beneath the westernsouthwestern 
portion of the potential repository area; includes portions of welded and 
nonwelded units from the Bullfrog and Tram tuffs.

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Subdivision of these five major hydrogeological units into detailed hydrogeological layers for the 
purpose of simulating flow and transport in the UZ is described in Section 3.4.2.2 of this report.

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3.3 PHYSICAL PROCESSES 
The UZ at Yucca Mountain is a complex system with a variety of flow and transport processes 
occurring at different scales. These processes include infiltration under different climate 
conditions, liquid and gas flow, chemical transport, and energy transport. The flow and transport 
processes occur within fracture networks, major faults, and the rock matrix. Fracture-matrix 
interactions, or the flow and transport between fractures and rock matrix, present additional 
process complexity. In addition, the potential repository for nuclear waste will introduce a large 
thermal perturbation (resulting from radioactive decay) that will drastically alter flow and 
transport processes. This section highlights some of these processes, which have relevance to 
Yucca Mountain UZ flow and transport modeling, with an emphasis on the current conceptual 
ideas. The discussion in this section is also closely related to some identified FEPs that could 
affect the potential repository performance (see Section 1.2.3). More detailed discussions on 
each process can be found in Sections 3.4 through 3.12 of this PMR that describe the relevant 
models and analyses. 
3.3.1 Climate 
Climate process refers to quantifying the precipitation rate and temperature at the surface of 
Yucca Mountain. This is used to determine the net infiltration into Yucca Mountain and hence 
water percolation at the repository horizon. These climate processes are used as indicators of 
climate change over the next 10,000 years at Yucca Mountain and are based upon paleoclimate 
reconstruction of an analogous time interval that occurred approximately 400,000 years ago. 
Three climates are forecast to occur within this time interval: the current modern climate, a 
monsoon climate and a glacial-transition climate. A range of precipitation rates and temperatures 
for each of these three climates is derived from analog meteorological stations within the 
contiguous US. Section 3.5.1 describes the Climate Model used to represent the climate process. 
3.3.2 Infiltration 
The infiltration process refers to the penetration of liquid water through the ground surface and 
to a depth where it can no longer be removed by evaporation or transpiration by plants. Net 
infiltration is the source of groundwater recharge and water percolation at the potential 
repository horizon and provides the water for flow and transport mechanisms that could move 
radionuclides from the potential repository to the water table. 
The overall framework of the conceptual model for infiltration is based on the hydrological 
cycle. Important processes that affect net infiltration include precipitation (rain and snow), runoff 
and run-on (flow of surface water off one place and onto another), evaporation, transpiration, and 
moisture redistribution by flow in the shallow subsurface (USGS 2000, U0010, Section 5.1). As 
shown in Figure 3.3-1, infiltration is spatially and temporally variable because of the nature of 
the storm events that supply precipitation (Section 3.5.1 of this PMR) and variation in soil cover 
and topography (CRWMS M&O 2000, U0030, Section 6.1.1). Infiltration rates are believed to 
be high on sideslopes and ridgetops where bedrock crops are exposed, and fracture flow in the 
bedrock is able to move liquid water away from zones of active evaporation (Flint and Flint 
1995, p. 15).

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Significant infiltration occurs only every few years (USGS 2000, U0010, Section 5.3). In these 
years, the amount of infiltration still varies greatly, depending on storm amplitudes, durations, or 
frequencies. In very wet years, infiltration pulses into Yucca Mountain may occur over a 
relatively short time period. A detailed discussion of infiltration processes can be found in USGS 
(2000, U0010) and in Section 3.5, which describe the Infiltration Model. 
3.3.3 Fracture and Matrix Flow Component 
Figure 3.3-2 schematically shows the overall conceptualized water flow behavior in the UZ, 
including the relative importance of fracture and matrix flow components in the different 
hydrogeologic units, as defined in Section 3.2. Accurate determination of the flow components is 
especially important for chemical transport processes. Flow in fractures (fracture flow) is 
typically much faster than flow in the matrix (matrix flow), leading to much shorter travel times 
for radionuclides and other chemicals in fractures compared to the matrix. The characteristic 
flow behavior in each of the major hydrogeologic units is described in the following subsections. 
3.3.3.1 Flow Through the TCw Unit 
The high density of interconnected fractures and low matrix permeabilities in the TCw 
hydrogeologic unit (CRWMS M&O 2000, U0090, Sections 6.1 and 6.2) are considered to give 
rise to significant water flow in fractures and limited matrix imbibition (water flow from 
fractures to the matrix). Thus, episodic infiltration pulses are expected to move rapidly through 
the fracture system with little attenuation by the matrix. This is partially supported by pneumatic 
data in the TCw showing little attenuation of the barometric signal in monitoring boreholes 
relative to the barometric signal observed at the land surface (Rousseau et al. 1999, p. 89), as 
discussed in CRWMS M&O (2000, U0030, Section 6.1.2). The presence of relatively high 
fractional abundances of 36Cl measured in TCw samples from boreholes (CRWMS M&O 2000, 
U0085, Section 6.6.3) also supports this conceptual model regarding water flow within the TCw. 
The source of the elevated (bomb-pulse) 36Cl has been attributed to nuclear testing conducted in 
the 1950s, and its occurrence in the TCw indicates the presence of fast pathways for water flow 
within the unit (CRWMS M&O 2000, U0030, Section 6.1.2). 
3.3.3.2 Flow Through the PTn Unit 
The relatively high matrix permeabilities and porosities, and low fracture densities of the PTn 
unit (CRWMS M&O 2000, U0090, Sections 6.1 and 6.2) should convert the predominant 
fracture flow in the TCw to dominant matrix flow within the PTn (CRWMS M&O 2000, U0030, 
Section 6.1) (Figure 3.3-3). The dominance of matrix flow and the relatively large storage of the 
matrix resulting from its high porosity and low saturation give the PTn significant capacity to 
attenuate infiltration pulses. This will result in water flow below the PTn being approximately at 
steady state, as demonstrated by the modeling study of Wang and Narasimhan (1993, 
pp. 354-361). 
In an early conceptual model of Yucca Mountain, Montazer and Wilson (1984, pp. 45-48) 
hypothesized that significant lateral flow occurs within and above the PTn unit. They argued 
that the contrast in hydraulic properties at the contact of the two units could cause lateral flow. 
Furthermore, the transient water flow from the TCw unit to the PTn promotes air entrapment,

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which could further reduce the vertical liquid flux to the PTn. The current understanding is that 
local heterogeneities, vertical fractures in the upper portion of the PTn, and gradual transitions in 
hydraulic properties across the PTn/TCw interface may prevent lateral flow from occurring over 
extensive distances. 
Montazer and Wilson (1984, p. 47) also showed that vertical heterogeneities within the PTn unit 
may result in a much larger effective permeability of the unit in the direction of dip, compared 
with the effective permeability in the direction normal to the bedding plane. They argued that 
combination of this factor and capillary barrier effects might introduce considerable lateral flow 
within the unit. Recent modeling studies (CRWMS M&O 2000, U0030, Section 6.1), however, 
indicate that lateral flow is reduced with increasing infiltration rate, and becomes significant only 
when infiltration rates are far lower than the current estimated values. This is because a lower 
infiltration rate corresponds to a larger capillary pressure gradient in the vertical direction, which 
enhances the strength of capillary barrier and limits vertical flow. Therefore, the current 
conceptual model is that lateral water flow above and within the PTn does occur, but is not 
significant. 
An alternative conceptual model for water flow through the PTn is one which assumes pervasive 
fracture flow through this unit. While this conceptual model cannot be completely excluded, the 
pneumatic and the bomb-pulse 36Cl data support the preferred conceptual model of 
predominately matrix flow through the PTn, as discussed above. A more detailed discussion of 
water flow within the PTn is given in Section 3.7.3.1. 
3.3.3.3 Flow Through the TSw Unit 
Unsaturated flow in the TSw hydrological unit is primarily through the fractures (Figure 3.3-2). 
One piece of supporting evidence for this comes from the magnitude of matrix hydraulic 
conductivity values of the TSw relative to the estimated average infiltration rate. The maximum 
matrix percolation rate is the same as the matrix hydraulic conductivity if the hydraulic gradient 
is assumed to be unity under unsaturated conditions. Because the matrix hydraulic conductivity 
is much lower than the average estimated infiltration rate (CRWMS M&O 2000, U0030, 
Section 6.1.2), the remainder of the flow must be distributed in the fracture network. The 
extensive fracture flow in this unit is also supported by other field observations (CRWMS M&O 
2000, U0030, Section 6.1.2). 
Other evidence for fracture flow comes from calcite-coating data, which are signatures of water 
flow history and indicate that most of the deposition is found within the fractures in the welded 
units (Paces et al. 1998b, p. 37). As discussed in CRWMS M&O (2000, U0030, Section 6.1.2), 
14C ages of the perched water bodies below the TSw unit also suggest fracture-dominant flow 
within the TSw. These ages approximately range from 3,500 to 11,000 years (Yang et al. 1996, 
p. 34), which is much younger than if the major path for water flow within the TSw was the 
matrix (CRWMS M&O 2000, U0030, Section 6.1.2). Therefore, fracture flow is considered as 
the dominant water flow mechanism within the TSw in the Flow Model.

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3.3.3.4 Flow Below the Potential Repository 
Flow behavior below the potential repository is especially important for modeling radionuclide 
transport from the repository to water table, because transport paths follow the water flow 
pattern. The main hydrogeologic units below the potential repository are the CHn and CFu. Both 
of these units have vitric and zeolitic components that differ by the degree of hydrothermal 
alteration and subsequent hydrological properties. The zeolitic rocks have low matrix 
permeabilities and some fracture permeability, and therefore a relatively small amount of water 
may flow through the zeolitic units, with most of the water flowing laterally in perched water 
bodies and then vertically down faults (Figure 3.3-2). On the other hand, similar to the PTn unit, 
the vitric units have relatively high matrix porosity and permeability, and therefore porousmedium-
type flow dominates. This is supported by the test results within the CHn (defined in 
Table 3.2-2) at the Busted Butt underground facility, as discussed in Section 3.11.10.2 of this 
PMR. The results showed that water flow and tracer transport mainly occur within the matrix of 
the CHn. Fracture flow is believed to be limited in these units. 
One distinctive feature below the potential repository is the existence of perched water zones, 
which have been reported from a number of boreholes at the lower portion of the TSw and the 
upper portion of the CHn (CRWMS M&O 2000, U0050, Section 6.2.2). The occurrence of 
perched water bodies indicates that the layers of the TSw basal vitrophyre and the CHn serve as 
barriers to vertical flow. Perched water is further discussed in Sections 3.3.8 and 3.7.3.3. 
3.3.4 Fracture-Matrix Interaction 
Fracture-matrix interaction refers to flow and transport between fractures and the matrix. Owing 
to their different hydrological properties, distinct flow and transport behavior occurs in each 
component. The extent of fracture-matrix interaction is therefore a key factor in modeling flow 
and transport processes in the UZ. 
Modeling results and field observations show limited fracture-matrix interaction within welded 
units at Yucca Mountain (CRWMS M&O 2000, U0030, Section 6.1.3). The chloride 
concentration data indicate that perched water is recharged mainly from fracture water, with a 
small degree of interaction with matrix water (CRWMS M&O 2000, U0030, Section 6.1.3). The 
small degree of interaction between fractures and the matrix at locations associated with geologic 
features is also suggested by the presence of bomb-pulse 36Cl (CRWMS M&O 2000, U0085, 
Section 6.6.3) at the potential repository level in the ESF. Studies by Ho (1997b, pp. 401-412) 
show that the match between simulations and observed matrix saturation and water potential data 
is improved by reducing the fracture-matrix interaction significantly. 
The occurrence of limited fracture-matrix interaction is also supported by observations from 
Rainier Mesa and other sites. The Rainier Mesa site is characterized by thick sequences of 
alternating welded and nonwelded unsaturated tuffs and has been considered an analog to Yucca 
Mountain. Thordarson (1965, pp. 67 and pp. 7580) noted that typically only portions of 
fractures carried water, and that the chemical composition of water obtained from fractures was 
substantially different from that of water samples extracted from the nearby rock matrix at that 
site. At a field site in the Negev Desert, Israel, man-made tracers were observed to migrate with 
velocities of several meters per year across a 20 to 60 m thick UZ of fractured chalk (Nativ et al.

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1995, pp. 253261). Such high velocities could only occur for conditions of limited fracturematrix 
interaction. 
The concept of limited fracture-matrix interaction at the Yucca Mountain site is also supported 
by many other independent laboratory tests as well as theoretical and numerical studies 
(CRWMS M&O 2000, U0030, Section 6.1.3). In a number of laboratory experiments without 
considering matrix imbibition, Glass et al. (1996, pp. 67) and Nicholl et al. (1994, pp. 2533 
2546) demonstrated that gravity-driven fingering flow is a common flow mechanism in 
individual fractures. This can reduce the wetted area in a single fracture to fractions as low as 
0.01 to 0.001 of the total fracture area (Glass et al. 1996, pp. 67), although the matrix imbibition 
can increase wetted areas of fingering flow patterns in individual fractures (Abdel-Salam and 
Chrysikopoulos 1996, pp. 15371538). A theoretical study by Wang and Narasimhan (1993, 
pp. 329335) indicated that the wetted area in a fracture under unsaturated flow conditions is 
generally smaller than the geometric interface area between fractures and the matrix, even in the 
absence of fingering flow. This results from the consideration that liquid water in an unsaturated 
fracture occurs as saturated segments that cover only a portion of the fracture-matrix interface 
area. Liu et al. (1998, p. 2645) suggested that in unsaturated, fractured rocks, fingering flow 
occurs at both a single fracture scale and a connected fracture-network scale (Figure 3.3-4), 
which is supported by the field observations from the Rainier Mesa site, as discussed above, and 
by a numerical study of Kwicklis and Healy (1993, pp. 40974099). They found that a large 
portion of the connected fracture network played no role in conducting the flow. Studies have 
also shown that fracture coatings can either reduce or increase the extent of fracture-matrix 
interaction. Thoma et al. (1992, pp. 1357-1367) performed experiments on coated and uncoated 
tuff fractures and observed that the low-permeability coatings inhibited matrix imbibition 
considerably. In contrast, fracture coatings may in some cases increase the fracture-matrix 
interaction when microfractures develop in the coatings (Sharp et al. 1996, p. 1331). 
Based on the above discussion, it is believed that fingering flow in fractures is a common flow 
mechanism in unsaturated fractured rocks and a major reason for limiting fracture-matrix 
interaction, although some other mechanisms exist. To incorporate the effects of fingering flow 
into modeling flow and transport in unsaturated fractured rocks, the active fracture model was 
developed by Liu et al. (1998, pp. 26332646) and documented in CRWMS M&O (2000, 
U0030, Section 6.4). In the model, only a portion of connected fractures are considered to 
actively conduct liquid water as a result of fingering flow at a fracture network scale. 
Note that the active fracture model was developed to consider the average effects of subgrid 
channels within the context of the dual-continua approach, and could not be used to explicitly 
simulate individual subgrid channels (fingers or weeps) without additional channel-scale 
parameters. In addition to the active fracture model, several other models have been proposed to 
simulate the fracture-matrix interaction (Liu et al. 1998, p.2635), with the fracture-matrix 
interface area reduction factor set empirically to a constant, to a power function of liquid 
saturation, or set equal to the liquid phase relative permeability. The relative permeability for the 
fracture continuum does not consider the fingering flow mechanism explicitly either. 
The fracture-matrix interface area reduction factor from the active fracture model, together with 
fracture spacing, weep width, and fracture set dimensionality, can be used to estimate the weep 
spacing. The fracture-matrix interaction is one of the important factors for the TSPA abstractions

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of flow focusing in the drift seepage abstraction (Section 3.9.6.3; CRWMS M&O 2000, U0120, 
Section 6.3.3). It also is taken into account in the radionuclide transport abstraction (CRWMS 
M&O 2000, U0065, Section 6.2.1). In addition to area, fracture coating distribution, matrix 
imbibition capacity and other flow path characteristics and transport processes control the spatial 
and temporal variations of the fracture-matrix interaction. 
3.3.5 Effects of Major Faults 
Different kinds of faults with varying amounts of displacements exist at Yucca Mountain, as 
discussed in Section 3.2.3. Fault properties are variable and generally controlled by rock type 
and stratigraphic displacement. Because major faults are important features of the UZ, they may 
have the potential to significantly affect the flow processes at Yucca Mountain. 
A fault can act as a fast-flow conduit for liquid water (Figure 3.3-5). In this case, transient water 
flow may occur within the fault as a result of temporally variable infiltration. Note that major 
faults cut through the PTn, and therefore the attenuating effect of the PTn on water flow 
transience is significantly reduced within the faults. This is supported by the correlation of 
observed bomb-pulse 36Cl data and localized geologic features in the depth of the UZ of Yucca 
Mountain (CRWMS M&O 2000, U0085, Section 6.6.3). However, this fast flow along the major 
faults is expected to carry only a small amount of water and may not contribute significantly to 
the liquid flow above the potential repository horizon in the UZ, as will be discussed in Section 
3.3.7. Faults intercepting the perched water bodies, however, can correspond to significant 
vertical water flow as a result of lateral flow within perched water bodies to the faults (see 
Section 3.3.3.4). 
Alternatively, a fault can act as a barrier for water flow (Figure 3.3-5b). Where a fault zone is 
highly fractured, the corresponding coarse openings will create a capillary barrier for lateral 
flow. On the other hand, a fault can displace the surrounding geologic units such that a unit with 
low permeability abuts one with relatively high permeability within the fault zone. In this case, 
the fault will act as a permeability barrier to lateral flow within the units with relatively high 
permeability. Montazer and Wilson (1984, p. 20) hypothesized that permeability would vary 
along faults, with higher permeability in the brittle, welded units and lower permeability in the 
nonwelded units where gouge or sealing material may be produced. While a fault sealed with 
gouge or other fine-grained material has much higher capillary suction (driving imbibition), it 
also has low permeability, retarding the movement of water. 
Since lateral flow is considered to be small above the repository (Section 3.3.3.2) and focusing of 
infiltration near faults may not be significant (Section 3.3.7), it is assumed that faults will not 
significantly alter the percolation pattern from the surface to the repository level. Large lateral 
flow to the faults and/or focusing of infiltration near the fault zone on the ground surface are 
required to generate significant water flow in faults. Below the repository, low-permeability 
layers in the CHn channel some flow to faults that act as conduits to the water table. However, it 
is also possible that alteration of faulted rocks in the CHn and CFu causes them to be of low 
permeability, slowing water travel time from the TSw to the water table. The effects of major 
faults on flow processes are further discussed and analyzed in Section 3.7.3.2 within the context 
of the UZ flow submodels.

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3.3.6 Transient Flow 
Temporal variation in the infiltration rate drives the time-dependent or transient nature of flow in 
the UZ. The temporal variation of the infiltration may be short term due to weather fluctuations 
that drive episodic flow, or over much longer time periods corresponding to climate change. As 
discussed in Section 3.3.3, the PTn is believed to greatly attenuate episodic infiltration pulses 
such that water flow below the PTn is approximately steady. However, water flow in a relatively 
small area near the Solitario Canyon fault may be transient because the PTn is not present in that 
area. Some transience is also expected for liquid flow through isolated fast flow paths that cut 
through the PTn because of the lack of a significant attenuation mechanism. However, these 
isolated flow paths are believed to carry only a small amount of water, as will be discussed in 
Section 3.3.7. Based on these considerations, the FEP Flow and Transport in the UZ from 
Episodic Infiltration is believed to have low consequence, and therefore transient flow behavior 
is not considered in the UZ Model (Section 1.2.3). 
3.3.7 Flow Focusing 
Flow focusing refers to occurrence of significant water flow through a very small area and/or 
zone. Depending on geologic conditions and the magnitude of the flux, flow focusing leading to 
fast flow pathways across the PTn may occur. A number of samples obtained from the ESF show 
bomb-pulse signatures of 36Cl (CRWMS M&O 2000, U0085, Section 6.6.3). They are 
generally associated with localized fault structures that cut through the PTn. These pathways are 
possibly responsible for the presence of high levels of 36Cl within the TSw at the repository 
horizon. However, the Flow Model assumes for the following reasons that these fast and 
transient flow paths probably carry a small amount of water (CRWMS M&O 2000, U0030, 
Section 6.1): (1) bomb-pulse samples are found from only a few locations in the ESF, (2) no 
significant correlation between high matrix saturation and elevated 36Cl has been reported, (3) 
these discrete fast paths are not associated with large catchment areas involving large volumes of 
infiltrating water, (4) bomb-pulse signatures of 36Cl were not found in the perched water bodies 
(CRWMS M&O 2000, U0085, Section 6.6.3), and (5) post-bomb tritium was detected only in 
one sample from the perched water (in borehole NRG-7a), but not in any of the other samples 
(CRWMS M&O 2000, U0085, Section 6.6.2). 
Fingering flow through the matrix is an alternative fast flow mechanism through the PTn 
(CRWMS M&O 2000, U0030, Section 6.1.7). Occurrence of fingering flow has been often 
reported for unsaturated soils (e.g., Yao and Hendrickx 1996, p. 20; Glass et al. 1991, pp. 1947 
1956; Flury et al. 1994, pp. 19451954; Selker et al. 1992, pp. 13461350). However, fingering 
flow is a gravity-driven phenomenon and cannot occur when capillary forces are dominant (e.g., 
Yao and Hendricks 1996, p. 21). The tuff matrix at Yucca Mountain is subject to much greater 
capillary pressures, characterized by orders of magnitude higher absolute air-entry values than 
soils (Wang and Narasimhan 1993, pp. 374-377). Therefore, fingering flow through the matrix 
within the PTn is not considered to be a significant flow focusing mechanism. 
While extensively fractured, observations indicate that the fracture water flow paths in the TSw 
are dispersed and not focused (CRWMS M&O 2000, U0030, Section 6.1.7; Bodvarsson et al. 
1999, p. 13). Average measured matrix saturations suggest relatively uniform values for most of 
the units, and in situ water potential measurements also show little variability within the TSw for

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different boreholes. It was also observed that temperature within the TSw unit is fairly uniform 
(CRWMS M&O 2000, U0030, Section 6.1.7). These observations are consistent with a 
conceptual model in which fracture flow is dispersed, resulting in relatively uniform conditions 
within the geologic formation. 
3.3.8 Perched Water 
Perched water is defined as saturated zones that are above or not directly connected to the 
groundwater table. It may occur when large permeability differences exist between geological 
units. Perched water zones at Yucca Mountain are reported from a number of boreholes (UZ-14, 
NRG-7a, SD-7, SD-9, SD-12 and G-2) at the lower portion of the TSw and the upper portion of 
the CHn (CRWMS M&O 2000, U0050, Sections 6.2.1 and 6.2.2). The hydraulic tests indicate 
that the perched water zones having very different water volumes exist at Yucca Mountain 
(CRWMS M&O 2000, U0030, Section 6.1.4). 
The presence of perched water has important implications for the travel times and flow paths of 
water through the UZ of Yucca Mountain. First, perched water 14C age data suggest dominant 
fracture flow in the TSw unit (see Section 3.3.3.3). Second, the occurrence of perched water 
bodies indicates that the layers of the TSw basal vitrophyre and the CHn serve as barriers to 
vertical flow and cause lateral flow (Figure 3.3-6). 
3.3.9 Seepage into Drifts 
Seepage refers to the flow of liquid water into emplacement drifts. The amount of water seeping 
into the drifts is crucial for the performance of the potential repository, since this affects the 
corrosion rates of the waste packages and the mobilization rate of radionuclides. While limited 
by the percolation flux occurring at the repository horizon, seepage into drifts is mainly 
determined by the capillary barrier effects of the underground openings to divert water around 
them. This condition is analogous to capillary barriers formed by fine-grained soils overlying 
coarse-grained soils (e.g., Frind et al. 1997, pp. 31333163; Ross 1990, pp. 26252629; 
Oldenburg and Pruess 1993, pp. 10451056). Here, the controlling physical mechanism is that 
the capillary pressure developed in the fine-grained material prevents water from entering the 
larger pores of the underlying coarse-grained material (Birkholzer et al. 1999, p. 350). If a drift is 
conceptualized as very coarse-grained with essentially zero capillarity, seepage into the drift 
can only occur if the capillary pressure in the rock close to the drift walls increases to positive 
values; i.e., the flow field becomes locally saturated. It can become locally saturated by either 
disturbance to the flow field caused by the drift opening (Philip et al. 1989, pp. 1628) or spatial 
heterogeneities that create channelized flow and local ponding (Birkholzer et al. 1999, pp. 349 
351). The capillary barrier effect has been tested in the ESF by niche tests in which water is 
injected above a niche (see Section 2). Results from the tests indicate that most of the water does 
not seep into niches, confirming the existence of the capillary barrier. A more detailed discussion 
of the seepage into drifts and associated modeling and analysis is given in Section 3.9. 
3.3.10 Gas Flow Processes 
Gas flow at Yucca Mountain depends primarily on the characteristics of fracture networks 
because fractures are generally much more permeable for the gas phase than the matrix. This is

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particularly true for the welded units. However, in the nonwelded units, the matrix is also an 
important gas flow path because the gas permeability of the matrix continuum is much higher 
than that in the welded units, due to lower liquid saturation and larger pore sizes. 
The ambient gas flow processes occurring at Yucca Mountain include barometric pumping, i.e., 
the response of subsurface pneumatic pressure to changes in atmospheric pressure. Because this 
is a transient process, both the permeability and storage of the media affect the subsurface 
response. In the welded units, this translates into little change in the pneumatic pressure signal 
with depth (CRWMS M&O 2000, U0030, Section 6.1.8). In the PTn, though, the high gas-filled 
porosity serves to attenuate and lag the response to barometric pumping between the top and the 
bottom of the unit. Ahlers et al. (1999, p. 58) showed a close correlation between the PTn 
thickness and pneumatic response below the PTn. They also showed that faults are fast pathways 
for gas flow but affect subsurface response only on a relatively local scale (Ahlers et al. 1999, 
p. 47; also see Sections 3.6.3.3 and 3.6.4.2). Gas flow also occurs under ambient conditions as a 
result of density- and wind-driven processes (Weeks 1987, pp. 165170), while their effects on 
the overall flow and transport processes in UZ of Yucca Mountain are minor (CRWMS M&O 
2000, U0030, Section 6.1). In general, under ambient conditions, it is believed that significant 
gas flow processes occur only in the shallow zone of the UZ, but not in the deep zone, as implied 
from the gas age data, showing that the rock gas is old at depth within the UZ, where its 14C age 
is about 10,000 years (Yang et al. 1996, p. 47). 
Thermal loading is expected to greatly impact gas flow processes. The modeling studies of Wu et 
al. (1995, p. 41) show that the average gas flux at the ground surface is increased by many orders 
of magnitude in response of the thermal loading, and that Solitario Canyon fault and Ghost 
Dance fault both serve as major pathways for heated gas. A more detailed discussion of the 
impact of thermal loading on gas flow is given in Section 3.12.3. 
3.3.11 Radionuclide Transport Processes 
Radionuclide transport processes are closely tied to water flow behavior, because liquid water is 
considered to be the principal medium in which solutes are transported through the UZ. 
Figure 3.3-7 schematically shows important radionuclide transport processes in the UZ, 
including advection, matrix diffusion, sorption, dispersion, and colloid-facilitated transport 
processes. Radionuclides also undergo radioactive decay, but this is not shown explicitly in 
Figure 3.3-7. These processes are briefly reviewed in this section, with a more detailed 
discussion given in Section 3.11. 
Advection refers to the movement of dissolved or colloidal materials because of the bulk flow of 
fluid (Fetter 1993, p. 47). Transport is strongly related to water flow through advection, and 
advective transport pathways are consistent with the flow pathways discussed in Section 3.3.3. 
Matrix diffusion refers to solute transport from fracture networks to surrounding matrix blocks 
resulting from molecular diffusion (Neretnieks 1993, pp. 4748). Mass transfer between 
fractures and the tuff matrix plays an important role in transport within Yucca Mountain. 
Because flow velocity in the matrix is much slower than that in fractures, matrix diffusion and 
sorption (for sorbing radionuclides) can significantly retard the overall transport of radionuclides 
to the water table.

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Dispersion is a transport mechanism that promotes dilution and spreading of the solute due to 
mixing caused by localized variations in flow velocity and heterogeneity (de Marsily 1986, pp. 
234-235; p. 244). Dispersion is not expected to play an important role in UZ transport (CRWMS 
M&O 2000, U0030, Section 6.2). In the rock matrix, dispersion is also considered to be minor 
compared with diffusion because of low pore velocity in the matrix (de Marsily 1986, pp. 
236-238). 
Sorption describes a combination of chemical interactions between dissolved solutes and the 
solid phases (immobile rock matrix or colloids) (Fetter 1993, p. 117). Radionuclide sorption to 
the rock matrix can act to retard its movement relative to the bulk flow of the groundwater. 
Strongly sorbing radionuclides are relatively immobile. 
Colloids, on the other hand, can facilitate the transport of radionuclides. Colloids are particles 
that are small enough to become suspended and transported in a liquid (Fetter 1993, p. 149). 
They can interact with radionuclides through sorption mechanisms (James and Chrysikopoulos 
1999, p. 707). Unlike sorption of radionuclides to the rock matrix, however, radionuclides sorbed 
on colloids are potentially mobile. Therefore, colloids can facilitate radionuclide transport 
through the UZ at a faster rate than the aqueous phase alone (de Marsily 1986, pp. 270-271). 
Another form of colloidal movement occurs when the radionuclide is an integral component of 
the colloid structure. In this case, the radionuclide is irreversibly bounded to the colloid 
(Figure 3.3-7). 
Radioactive decay affects the concentration of radionuclides during transport through the UZ. 
For simple decay, radionuclide concentration decreases exponentially with time (de Marsily 
1986, p. 265), creating stable decay products. In chain-decay, radioactive daughters are produced 
from the decay of a parent radionuclide, with each daughter product having potentially different 
sorption and transport behavior. 
3.3.12 Effects of Coupled Processes 
Radioactive wastes potentially emit a significant amount of decay heat that can influence 
hydrological, mechanical, and chemical conditions in both the near field (drift scale) and far field 
(mountain scale) environments. Consequently, the corresponding coupled processes, including 
thermal-hydrological (TH), thermal-mechanical (TMe), and thermal-chemical (TC) processes, 
will affect flow and transport within the UZ of Yucca Mountain. TH, TMe and TC processes are 
also coupled among themselves, although they are discussed separately for simplicity. In this 
section, we briefly review these processes with an emphasis on their effects on flow and 
transport in the UZ. More detailed discussions of coupled processes are given in Sections 3.10 
and 3.12 that describe the Drift-Scale THC and Mountain-Scale TH Models, respectively. 
3.3.12.1 TH Processes 
The TH response of the unsaturated fractured tuff to decay heat involves a number of processes 
(Tsang and Birkholzer 1999, pp. 389-390; Buscheck and Nitao 1993, pp. 418448). As the 
formation temperatures are increased around the waste packages, pore water boils and vaporizes. 
Most of the generated vapor moves into the fractures, where it becomes highly mobile. The 
heated dry-out zone can prevent the infiltrating water from moving down through the potential

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repository, resulting in a drop in the net water flux at the potential repository horizon. When the 
water vapor encounters cooler rock above and below the potential repository, it condenses, and 
the local fracture and matrix saturations increase, resulting in a liquid reflux toward the drier 
region. Between the dry-out and condensation zones, a heat-pipe zone may develop (Tsang and 
Birkholzer 1999, pp. 389390). A heat-pipe is indicated by the persistence of liquid-vapor 
counter flow over a region of small temperature gradient, where temperatures are approximately 
at the nominal boiling point. 
TH effects drive processes at two physical scales (CRWMS M&O 2000, U0030, Section 6.3), as 
indicated in Figure 3.3-8. At the drift scale (near-field scale), flow and transport is affected by 
decay-generated heat from each of the individual waste packages in an emplacement drift. 
Variability of heat output from waste packages could result in large variabilities in the extent of 
dry-out, rewetting, and of liquid-phase flux along drifts. Heat driven features at the mountain 
scale include thermally altered, large-scale water flow fields both above and below the potential 
repository, which may affect radionuclide transport. Thermal loading may also potentially alter 
the characteristics of perched water bodies (e.g., volume) because of the thermally induced vapor 
flow from the perched water bodies. However, the major effects of TH processes are expected to 
be near the emplacement drifts in the early part of the postclosure time period. Radionuclide 
releases will likely be after the main portion of the thermal pulse (after waste heat begins to 
dissipate), and a large part of the radionuclide transport process in the UZ will take place at 
locations outside the envelop of the main TH effects. Therefore, it is reasonable to assume for 
simplicity that the effects of TH processes on radionuclide transport are not significant. As 
discussed in Section 1.2.3, this reasoning is a basis for an assumption used in the FEPs exclusion 
arguments. 
3.3.12.2 TMe Processes 
Elevated temperatures of the host rock surrounding the potential repository will mechanically 
change the physical properties of the rock within the UZ (CRWMS M&O 2000, U0030, 
Section 6.3). Expansion of the rock matrix caused by heating will affect stress distribution in the 
rock and induce changes in the fracture apertures. These changes can affect the amount of flow 
through the fractures and subsequently through the entire system. Hydrological changes can, in 
turn, affect the thermal behavior, which governs the mechanical changes of the rock. 
Thermal expansion of the matrix surrounding drifts tends to close fractures and reduce fracture 
aperture and permeability while increasing capillary forces. However, non-uniform deformation 
of heterogeneous matrix rock blocks will promote sliding or relative movement along two 
adjacent matrix block surfaces, which may lead to an increase in fracture permeability. During 
the cooling phase, the fracture apertures near the drifts would generally increase. 
3.3.12.3 TC Processes 
Chemical reactions in response to a high thermal load in the potential repository can alter 
hydrological properties of the rock matrix and fractures (CRWMS M&O 2000, U0030, 
Section 6.3; N0120/U0110). Above the potential repository horizon, the temperature is projected 
to be sufficiently high to vaporize water and cause the precipitation of minerals in fractures. 
Condensate may dissolve mineral phases from the walls of fractures and flow back to zones

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where precipitation occurs. Mineral dissolution at one point in the fracture network, and 
redeposition at another, could lead to the formation of a precipitate cap over the potential 
repository. In the precipitate cap, porosities and permeabilities of fractures and portions of the 
matrix near the fractures will be reduced. The significance of this reduction depends on the 
abundance of readily dissolved fracture-lining minerals, relative to fracture porosity, and the 
dissolution and precipitation rates for the relevant minerals. Other potential effects of thermal 
loading include hydrothermal alteration of glasses in the PTn, Topopah Spring basal vitrophyre, 
and the CHn units. TC processes may also alter the chemical composition of seeping water and 
the sorption capacity of the formations below the potential repository. A more detailed 
discussion is given in Section 3.10. In general, as discussed in Section 1.2.3, the effects of TC 
and other coupled processes in the near-field are expected to be more severe than in the far-field. 
This is caused by the high temperatures that will occur near the waste emplacement drifts, 
including boiling of the rock-water and associated precipitation of the minerals and condensation 
of dilute water. This reasoning is a basis for an assumption used in the FEPs exclusion arguments 
(Section 1.2.3). 
3.3.13 Current and Alternative Conceptual Models 
Based on the above discussions of physical processes, the current conceptual model of flow in 
the UZ can be summarized as follows. Infiltration is spatially and temporally variable to a large 
extent. Infiltration pulses move rapidly through fractures in the TCw unit with little attenuation 
by the matrix. Because of the attenuative capacity of the PTn unit, water flow below this unit is 
approximately at steady-state under ambient conditions. Lateral flow in the PTn tends to be 
insignificant. Fracture flow dominates in the welded units and matrix flow in the nonwelded 
units. Fracture flow paths are dispersed. Isolated fast flow paths exist, but carry only a small 
amount of liquid water. Fracture-matrix interaction in the welded units is limited. Perched water 
bodies introduce three-dimensional, lateral flow. Flow through the major faults does not 
significantly alter the percolation pattern from the surface to the potential repository horizon. 
Below the potential repository, low-permeability layers in the CHn channel some flow to faults 
that act as conduits to the water table. 
While the current conceptual model is largely based on the model originally presented by 
Montazer and Wilson (1984, pp. 3649), the major difference between these two models are the 
roles of the PTn unit and structural features, or faults, in conducting water through the UZ. 
Montazer and Wilson (1984, pp. 5051) hypothesized that the combination of dipping beds, 
permeability layering, and capillary-barrier effects results in significant lateral flow within the 
PTn toward the bounding structural features that transmit most of the infiltrated water downward 
to the water table. As discussed in Sections 3.3.3.2 and 3.3.5, more recent studies indicate that 
lateral flow in the PTn may not be as significant as previously thought, and faults are not likely 
to act as flow paths that significantly alter the flow pattern above the potential repository in the 
UZ. 
Other conceptual models of flow in the UZ have been published in the literature. Since the mid- 
1980s, the prevailing view has held that under ambient conditions, water flow mainly occurs 
through the rock matrix, even in the welded, densely fractured TSw unit (Wang and Narasimhan 
1993, pp. 327339; Peters and Klavetter 1988, pp. 416430; Nitao and Buscheck 1991, 
pp. 20992112; Rulon et al. 1986). It was believed that under unsaturated conditions, water

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would essentially be excluded from fractures because of the strong capillarity in the matrix. 
However, as more site characterization data are available, it has become evident that unsaturated 
flow in the welded units is primarily through the fractures, as discussed in Section 3.3.3.3. 
In a recent study, Pruess (1999, pp. 10401051) proposed a conceptual model for flow in thick, 
unsaturated, fractured rock zones. Key elements of the model are (Pruess 1999, p. 1041): (1) 
most water flow in thick UZs of fractured rock proceeds by way of episodic, transient, and 
localized flow through fractures, (2) water flow can remain localized even in the presence of 
dispersive effects that would tend to cause lateral spreading, and (3) several mechanisms 
combine to severely reduce the effects of matrix imbibition. While both the model of Pruess 
(1999, pp. 10401051) and the current conceptual model of flow in the UZ consider fracturematrix 
interactions to be limited and that only a portion of fractures are active in conducting 
liquid water, they differ in the spatial distribution and time-dependent features of fracture flow. 
The former hypothesizes that fracture flow paths in unsaturated, fractured rocks are sparse 
(Pruess 1999, p. 1049) and transient (Pruess 1999, p. 1041). As discussed in Section 3.3.7, it is 
more likely that water flow below the PTn unit is approximately at steady state and that fracture 
flow paths are dispersed. 
3.3.14 Summary and Conclusions 
A variety of flow and transport processes are involved in the UZ at Yucca Mountain. Based on 
the discussions of physical processes in the UZ, a conceptual model of flow in the UZ has been 
developed, as summarized in Section 3.3.13. Because water is considered to be the principal 
medium in which solute is transported, solute transport is closely tied to flow processes. Major 
radionuclide transport processes include advection, matrix diffusion, sorption, radioactive decay 
and colloid-facilitated transport. Flow and transport will be affected by coupled TH, TMe and 
TC processes resulting from potential repository heat release.

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3.4 NUMERICAL MODELS AND GRIDS 
Based on available data, an understanding of the complex flow and transport processes occurring 
within the UZ at Yucca Mountain requires simplification of the real-world system. This is done 
by applying a set of numerical equations (believed to represent the behavior of the physical 
process under investigation) to a model volume that has been discretized into a finite number of 
nodes, or elements, for which certain rock properties are known or estimated. 
Section 3.4.1 provides a general overview of numerical models for simulating flow and transport 
processes in the unsaturated, fractured porous media at Yucca Mountain. The process of 
numerical grid development and discretization, which is discussed at length in CRWMS M&O 
(2000, U0000), is summarized in Section 3.4.2. 
3.4.1 Numerical Models for UZ Flow and Transport 
A variety of numerical models have been proposed in the literature to deal with flow and 
transport processes in fractured media at the field scale. When classified according to the manner 
in which fracture networks are treated in the model structure, the models fall into one of three 
groups: continuum models, discrete fracture-network models, and other models. The other types 
of numerical models (e.g., Clemo and Smith 1997, pp. 17631783) can be considered as 
variations and/or combinations of the first two basic models. Excellent reviews on these models, 
which have been developed and used in different fields (including oil reservoir engineering, 
groundwater hydrology, geothermal engineering, and soil physics), can be found in Bear et al. 
(1993, pp. 267320, 396428) and the National Research Council (1996, pp. 307394). The 
numerical models that can be used for unsaturated, fractured rocks will be briefly reviewed, and 
the rationale for determining the numerical models used in the UZ Flow and Transport Model 
PMR will be presented. 
3.4.1.1 Continuum Models 
In continuum models, fractures are considered to be sufficiently ubiquitous and distributed in 
such a manner that they can be described statistically in a meaningful way (Bear et al. 1993, 
pp. 395396). The role of individual fractures in fractured media is considered to be similar to 
that of individual pores in porous media. Connected fractures and rock matrix are viewed as two 
or more overlapping interacting continua. In other words, at a point, two or more continua are 
considered to co-exist. In this case, the continuum-mechanics formulations, such as those used 
for porous media, can be used to describe flow and transport in each continuum. Coupling of 
processes between different continua is determined by interaction mechanisms at a subgrid scale 
(Figure 3.4-1). Depending on the number of continua and methodologies used to treat fracturematrix 
interaction, continuum models can be classified further as effective-continuum (ECM), 
dual-continua, and multiple-interacting-continua (MINC) models. 
In ECM models (Pruess et al. 1990b, pp. 12491261), fractures and rock matrix are replaced 
with a single effective continuum (Figure 3.4-1). Liquid saturation is partitioned into the matrix 
and fractures in accordance with the principle of local thermodynamic equilibrium, which 
requires capillary pressure in the matrix and fracture components of a gridblock to be equal. The 
ECM approach also assumes that fluids in the fractures and matrix have the same chemical

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concentration and temperature (Doughty 1999, pp. 69106). ECM models provide a substantial 
simplification for describing flow and transport in fractured porous media and is computationally 
efficient in handling a model with a large number of gridblocks (>103). However, the 
assumptions on which ECM models are based may break down when long times are needed to 
reach local equilibrium conditions between the fracture and matrix continua. This is especially 
true for a very tight and low-permeability rock matrix with rapid fracture flow (CRWMS M&O 
2000, U0030, Section 6.4.4.1). 
In the dual-continua models, fractures and matrix are treated as two separate, yet interacting 
continua, and each gridblock is subdivided into one fracture block and one matrix block 
(Doughty 1999, pp. 69106) (Figure 3.4-1). The fracture-matrix flow and transport are 
approximated as quasi-steady. This treatment is the numerical equivalent of the Warren and Root 
(1963, pp. 245255) formulation. If global flow occurs only between fracture gridblocks, the 
model is known as a dual-porosity model. If global flow occurs within both fracture and matrix 
continua, the model is known as a dual-permeability model (Doughty 1999, p. 76). Compared 
with ECM models, dual-continua models will more accurately predict flow and transport, 
because nonequilibrium is allowed between fracture and matrix continua. Since there is only one 
matrix block used for each gridblock and a quasi-steady fracture-matrix flow assumption is 
employed, gradients of matrix capillary pressures, temperature, and concentration near a 
fracture-matrix interface may be poorly predicted using dual-continua schemes. Under steadystate 
conditions, however, the gradients near the matrix surface become minimal, and the models 
are expected to generate acceptable solutions (CRWMS M&O 2000, U0030, Section 6.4.4.1). 
Using a more general and rigorous approach, multiple interacting continua (MINC) models 
(Pruess and Narasimhan 1985, pp. 1426), were developed to overcome the limitation of dualcontinua 
models. Specifically, MINC models further subdivide the matrix into more than one 
matrix continuum to consider the nonequilibrium of flow and transport within the matrix. 
Compared with dual-continua models, MINC models can more accurately predict flow and 
transport in fractured media, but have larger computational requirements in both CPU times and 
storage space. 
3.4.1.2 Discrete Fracture-Network Models 
Discrete fracture-network models are based on an assumption that flow and transport behavior 
can be predicted from knowledge of the fracture geometry and data on hydraulic properties of 
individual fractures (National Research Council 1996, p. 332). These models involve 
computational generation of synthetic fracture networks and (subsequently) modeling of flow 
and transport in each individual fracture. These models have been extensively used for singlephase 
flow and transport, with deterministic, stochastic, artificial, or site-specific fracture 
networks in two or three dimensions (National Research Council 1996, pp. 333350). Recently, 
the same models have also been applied to unsaturated conditions (e.g., Kwicklis and Healy 
1993, pp. 40914102; Rasmussen 1991, pp. 6776; Karasaki et al. 1994, pp. 26332638; 
Zimmerman and Bodvarsson 1996, pp. 433438). 
While discrete fracture-network models are useful as tools for concept evaluation or model-based 
process studies, they have several limitations. First, the models require geometric parameters that 
may strongly impact flow and transport, such as fracture apertures and conductivity, but typically

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cannot be well constrained by field observations (Pruess et al. 1999, p. 308). Second, it is 
difficult to separate the conductive fracture geometry from the nonconductive fracture geometry 
(National Research Council 1996, p. 350). Third, flow and transport simulations with these 
models can be complex and computationally intensive for realistic fracture densities (National 
Research Council 1996, p. 350). Fourth, so far, the studies based on discrete fracture-network 
models have rarely considered fracture-matrix interaction because of computational complexity 
(Pruess et al. 1999, p. 308). The capability to simulate fracture-matrix interaction is essential 
because of its important effects on flow and transport in unsaturated, fractured rocks. 
3.4.1.3 Numerical Models for UZ Flow and Transport at Yucca Mountain 
Appropriateness of the currently available numerical models for the flow and transport 
simulations at Yucca Mountain depends on several important factors, including flow and 
transport behavior at the Yucca Mountain site, the scale of the problem, data availability, and 
computational feasibility. 
The overall flow and transport behavior in the UZ at Yucca Mountain are characterized by two 
important features. The first feature is that the isolated fast flow paths only carry small amounts 
of water and do not significantly contribute to the overall flow and transport patterns in the UZ 
(see Section 3.3.7), and fracture flow paths are many and dispersed. This makes the continuum 
model a reasonable choice for simulations of flow and transport in the UZ at Yucca Mountain. 
The second feature is the coexistence of matrix-dominant flow and transport in nonwelded units 
and fracture-dominant flow and transport in welded units. This feature can be easily handled by 
continuum models, but not by other models, such as a fracture-network model. The scale of the 
problem is an important factor for assessing appropriateness of numerical schemes for flow and 
transport in the UZ. Because continuum models are relatively simple and straightforward to 
implement, they are preferred for most applications that are encountered in practice (National 
Research Council 1996, p. 331). Estimates of the number of potentially water-conducting 
fractures at Yucca Mountain are on the order of 109 (Doughty 1999, p. 77). Considering data 
availability and computational feasibility, it is practically impossible to construct and calibrate a 
discrete fracture-network site-scale model with so many fractures. 
Based on the above considerations, continuum models are considered appropriate for use in the 
unsaturated flow and transport models at Yucca Mountain (CRWMS M&O 2000, U0030). As a 
compromise between accuracy and feasibility, dual-permeability models have become the main 
modeling approach currently used to simulate unsaturated water flow, heat transfer, and chemical 
transport at Yucca Mountain. Details of the numerical approaches utilized such as the use of 
upstream and downstream weighting are discussed in the individual AMRs documenting the 
particular model (e.g., CRWMS M&O 2000, U0050, Section 6.1 and CRWMS M&O, U0035, 
pp. 2734). 
3.4.1.4 Some Important Issues for Flow and Transport Modeling 
While detailed discussions of dual-permeability models have been well documented in the 
literature (e.g., Doughty 1999, pp. 7576), this section discusses some important issues 
specifically for modeling unsaturated flow and transport at Yucca Mountain.

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3.4.1.4.1 Porous Medium Equivalence and Active Fracture Model 
In dual-continua models, porous-medium equivalence has been used for describing water flow in 
the fracture continuum (National Research Council 1996, p. 380). Specifically, Darcys law is 
used to determine water flux within the fracture continuum, and constitutive relations between 
relative permeability, capillary pressure, and saturation are employed for modeling water flow. 
The van Genuchten (1980, pp. 892898) relations widely used for porous media are employed as 
approximate constitutive relations for water flow in the active fracture continuum. The active 
fracture continuum consists of fractures that actively conduct water. This represents only a 
portion of the whole fracture continuum because of fingering flow in fractures at different scales. 
Considering that fingering flow is a common flow mechanism in unsaturated fractures, its effects 
on overall flow and transport processes in the fracture continuum and between the fracture and 
matrix continua are considered by using the newly developed active fracture model (Liu et al. 
1998, pp. 26332646). The active fracture model is documented in CRWMS M&O (2000, 
U0030, Section 6.4.5). 
3.4.1.4.2 Particle Tracking and Conventional Algorithms for Transport Modeling 
In general, two kinds of numerical algorithms are used for modeling chemical transport in the 
subsurface (Liu and Dane 1996, p. 359). One is the conventional algorithm based on finitedifference 
and/or finite-element methods, and the other is the particle-tracking algorithm. In the 
particle-tracking algorithm, chemical mass is divided into a large number of particles (Tompson 
and Gelhar 1990, pp. 25412562; LaBolle et al. 1996, pp. 583593). Chemical transport is 
simulated by calculating particle movement, which is determined by velocity fields, 
dispersion/diffusion coefficients, and fracture-matrix interaction formulations. Particle tracking 
has the following two advantages, when compared with conventional approaches. First, it can 
significantly reduce or eliminate numerical dispersion, a common numerical problem for coarse 
grid simulations of chemical transport problems (artificially smearing concentration fronts in 
simulations). Second, the particle-tracking algorithms generally compute more efficiently. 
However, one shortcoming of particle-tracking algorithms is that they can only be used for 
chemical transport with simple chemical reactions (such as linear sorption and decay). Therefore, 
for unsaturated transport modeling at Yucca Mountain, particle-tracking algorithms are used for 
modeling chemical transport with simple reactions, and conventional algorithms are used for 
transport with complex reactions. A detailed comparison between the particle-tracking 
algorithms and a conventional approach is given in CRWMS M&O (2000, U0155). 
3.4.1.4.3 Modeling the Dispersion Process in the Fracture Continuum 
Although it is generally recognized that dispersion in a fractured medium is physically different 
than dispersion in a porous medium, the porous medium form of the dispersion tensor is 
generally used for lack of a more appropriate expression (Bear et al. 1993, p. 419). Since 
dispersion may not be a major transport mechanism for the UZ at Yucca Mountain 
(Section 3.3.11), it is believed that the use of the dispersion tensor is adequate for approximating 
dispersion processes in the fracture continuum.

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3.4.1.4.4 Heterogeneity and Parameterization 
Heterogeneities exist at different scales within both the fracture and matrix continua in the UZ at 
Yucca Mountain. Parameterization refers to the use of a number of parameters to represent the 
heterogeneous distribution. Treatment of subsurface heterogeneity and parameterization are 
important for modeling flow and transport processes. A variety of approaches are available for 
constructing subsurface heterogeneous property distributions, as reviewed by Koltermann and 
Gorelick (1996, pp. 26172658). 
A geology-based, deterministic approach, in which an entire model layer is assigned uniform 
properties, is used mainly for characterizing subsurface heterogeneity and modeling flow and 
transport in the UZ. The justification for use of this approach is based on the following 
considerations (CRWMS M&O 2000, U0030, Section 6.4.3). First, it is expected that the overall 
behavior of site-scale flow and transport processes is determined mainly by relatively large-scale 
heterogeneities associated with the geologic stratification of the mountain. Stratification and 
faulting, which places units with highly different properties against each other, are the major 
heterogeneities within the UZ at Yucca Mountain. Within the same geologic unit, hydrological 
properties are relatively uniformly distributed because of the intra-strata homogenization induced 
by the tuff depositional environments (CRWMS M&O 2000, I0040, Section 6.3.1.1). In the 
geology-based, deterministic approach, subunits are defined within the major hydrogeologic 
units to capture variability in the vertical stratification. Within these subunits, important lateral 
heterogeneity can be accounted for by defining lateral boundaries, differentiating areas with 
significant differences in hydrological properties (Section 3.4.2.2). Second, the complexity of a 
heterogeneity model needs to be consistent with the availability of the data. More complicated 
models introduce larger degrees of uncertainties in rock property estimations when data are 
limited. Third, the layered approach is also supported by field observations, such as the relatively 
uniform matrix water saturations within a given layer. Fourth, flow and transport models based 
on a layered approach can be relatively easily calibrated with multiple data sets and provide a 
means to incorporate a significant amount of the available site data. Fifth, it is straightforward to 
upscale using inverse modeling when a layered approach is employed. 
3.4.2 Development of Numerical Grids 
Using the continuum approach (specifically, the dual-permeability method) described and 
justified above (Section 3.4.1.3), numerical grids of the UZ at Yucca Mountain were developed 
to simulate flow and transport processes. The following subsections discuss the process of 
numerical grid development, summarizing the input data, the key steps involved in data 
integration and grid generation, and the resulting numerical grids and their end uses. The flow of 
information is described schematically in Figure 3.4-2. 
3.4.2.1 Input 
Mountain-scale dual-permeability numerical grids of the UZ are developed using geologic and 
hydrogeologic data, including information from the Integrated Site Model (ISM) of Yucca 
Mountain as well as data describing fracture characteristics for each grid layer. 
The ISM consists of three component models: the Geologic Framework Model (GFM), the 
Mineralogical Model (MM), and the Rock Properties Model (RPM). Several different versions

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of the ISM have been developed, as new information allows for modification of the previous 
interpretation. ISM3.1 is the current version of the Integrated Site Model (containing GFM3.1, 
MM3.0, and RPM3.1). Details of this model and its components are given in the ISM Process 
Model Report (CRWMS M&O 1999, ISM PMR) and in CRWMS M&O (2000, I0035, I0045, 
I0040). During the development of numerical grids used in the UZ Flow and Transport Model 
PMR, the most recent ISM data consisted of GFM3.1, MM2.0, and RPM3.0. MM3.0 and 
RPM3.1 became available subsequent to numerical grid development, and the differences 
between these model versions and those used to generate the grids are discussed below. 
The GFM describes the three-dimensional orientation of geologic layers and faults (CRWMS 
M&O 2000, I0035, Section 6). Layers explicitly defined within GFM3.1 correspond to 
lithostratigraphic units differentiated according to depositional history, to variations in degree of 
welding, crystallization, and alteration, and to fracture characteristics (see Section 3.2). The key 
difference between GFM3.1 (from ISM3.1) and its predecessor GFM3.0 (from ISM3.0) is the 
inclusion of new lithology data from boreholes SD-6 and WT-24. Data extracted from GFM3.1 
form the basis of the numerical grids developed for the mountain-scale models described in this 
report. Of the 48 geologic units and 42 faults represented in GFM3.1, approximately 40 of these 
units and 18 faults (those that lie within the UZ mountain-scale domain) are incorporated into the 
model grids. 
The MM provides three-dimensional interpretations of the distribution of mineral abundances, 
including smectite and zeolite (CRWMS M&O 2000, I0045, Section 6). Changes between 
MM2.0 (from ISM3.0) and MM3.0 (from ISM3.1) that may be important for unsaturated flow 
and transport include the incorporation of new data from boreholes SD-6 and WT-24, and the 
subdivision of an MM2.0 model layer (that combined geologic layers Tptpv3 and Tptpv2) into 
two layers of equal thickness to better represent a zone of intense smectitic and zeolitic alteration 
at the base of the TSw (CRWMS M&O 2000, I0045, Section 6.1). The procedure for modeling 
mineral abundance distributions was also improved in MM3.0. The deterministic inversedistance-
weighting function used to calculate the distribution of mineral abundances in MM2.0 
produced certain point anomalies (centered at data point locations) determined inappropriate for 
use in defining vitric-zeolitic boundaries in the mountain-scale numerical grids described in this 
PMR (for more details, refer to CRWMS M&O 2000, U0000, Section 6.6.3). More recent 
mineral abundance distributions calculated for MM3.0 show more extensive regions of vitric 
material surrounding borehole SD-6 (Figure 3.4-3). The presence of more vitric material would 
lead to more matrix flow in the models and, consequently, slower radionuclide breakthrough 
times (beneficial to repository performance). 
The RPM provides a three-dimensional geostatistical interpretation of the distribution of matrix 
porosity (CRWMS M&O 2000, I0040, Section 6). The model also describes the distribution of 
derivative properties (using porosity as a surrogate), including saturated hydraulic conductivity, 
bulk density, and thermal conductivity. Differences between RPM3.0 (from ISM3.0) and 
RPM3.1 (from ISM3.1) that may be important for unsaturated flow and transport include higher 
matrix permeabilities in the vitric areas in RPM3.1, although the overall pattern of the property 
distribution is similar in both versions (Figure 3.4-4). [Note that in light of the newer MM and 
RPM data, the current representation of the vitric-zeolitic boundary used in the flow and 
transport models can be considered conservative.]

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RPM3.0 does not contain data from newly drilled boreholes SD-6 or WT-24 that suggest a 
greater extent of vitric material (corresponding to areas of higher matrix permeability) beneath 
the southern half of the potential repository footprint and a thin vitric interval within pervasively 
zeolitic tuffs beneath northern Yucca Mountain. Data used in numerical grid development 
discussed herein for defining low permeability, zeolitic volumes of rock within certain model 
layers were obtained from the most current rock properties model available at the time, RPM3.0. 
The key assumption related to the use of these data was that matrix permeability could be 
correlated with sorptive alteration minerals (e.g., clays and zeolites). Sharp gradients between 
areas of high and low matrix permeability, calculated for the CHn hydrogeological unit in 
RPM3.0, were assumed to correspond to the boundary between unaltered (vitric) and altered 
(zeolitic) materials (see Section 3.2.4). Polygons were created along these sharp gradients within 
the CHn for five model layers in the mountain-scale numerical grids. The polygons were then 
used during grid development to distinguish between vitric and zeolitic areas in each of these 
five model layers. 
The final data input, used to formulate the dual-permeability grids described in this PMR, is 
fracture hydrogeologic properties (CRWMS M&O 2000, U0000, Table 5). Fracture 
hydrogeologic properties consist of calculated fracture porosity, fracture frequency, and fracturematrix 
interaction parameters for each model layer in the mountain-scale grids. Fracture 
hydrogeologic properties are summarized in Sections 3.6.3.2 and 3.6.5.1 of this PMR and are 
described in greater detail in CRWMS M&O (2000, U0090, Section 6.1). 
3.4.2.2 Data Integration and Grid Generation 
Data integration and numerical grid generation consist of three main steps: 
1. Defining a hydrogeologic layering scheme appropriate for capturing important 
unsaturated flow and transport processes, and extracting relevant data from 
GFM3.1 based on this scheme. 
2. Determining vitric-zeolitic boundaries within several model layers in the CHn 
hydrogeologic unit and incorporating these boundaries into the numerical grids. 
3. Generating ECM and dual-permeability numerical grids using WinGridder 
software. 
Although variations in rock hydrogeologic properties (such as porosity and permeability) often 
correspond to changes in lithostratigraphy, a strictly geologic model cannot adequately capture 
all of the important features that affect flow and transport processes in the UZ. For instance, 
materials with similar porosity but with highly contrasting saturations and matrix permeabilities, 
such as the nonwelded vitric and zeolitic tuffs, are found within the single GFM3.1 unit Tac (see 
Section 3.2.4). Similarly, hydrological property variations exist within lithostratigraphic unit Tpy 
(see Section 3.2.2.2), caused by porosity changes resulting from variations in the degree of 
welding. Hydrogeologic rock property data, therefore, were considered during the process of 
defining hydrogeologic layers for the mountain-scale numerical grids, as discussed in CRWMS 
M&O (2000, U0000, Section 4) and Chapter 2 of this PMR.

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Based on hydrogeologic properties information presented in Flint (1998), certain GFM3.1 
lithostratigraphic layers were combined, while others were subdivided for the purpose of 
developing a set of hydrogeologic model layers for the UZ Flow and Transport Model PMR (see 
Table 3.2-2). The details of these modifications are given in CRWMS M&O (2000, U0000, 
Section 6.4.1). The resulting scheme subdivides the TCw into 3 layers, the PTn into 6 layers, the 
TSw into 8 layers, the CHn (including the Prow Pass) into 11 layers, and the CFu into 4 layers. 
Data describing the thickness of each hydrogeologic layer (i.e., corresponding to a combined, 
subdivided, or unchanged GFM3.1 layer) retain the regular horizontal spacing of 61 m in both X 
and Y directions used in the GFM. Calibrated fracture and matrix hydrogeologic properties are 
determined for each of the 32 UZ model layers (see Sections 3.6.4 and 3.6.5). Fault gridblocks 
are identified by major hydrogeologic intervals (i.e., TCw, PTn, TSw, and CHn/CFu), and fault 
hydrogeologic properties are determined for each of these intervals (see Sections 3.6.4.2 and 
3.6.5). 
Because of the importance of mineral (especially zeolitic) alteration on flow and transport 
calculations, lateral boundaries between vitric and zeolitic areas are defined within model grid 
layers ch1 through ch5 (refer to Table 3.2-2). Zeolitic alteration reduces permeability (Loeven 
1993, pp. 1819, 22; Flint 1998, p. 32) and increases the rocks ability to sorb radionuclides 
(CRWMS M&O 2000, I0045, Section 1.2). As stated above, data used in numerical grid 
development for defining low-permeability, zeolitic volumes of rock are obtained from RPM3.0. 
The details of extracting permeability rock properties data in order to delineate the vitric-zeolitic 
boundary in model layers are provided in CRWMS M&O (2000, U0000, Section 6.6.3). 
Resulting distributions of vitric and zeolitic material in layers ch1 to ch5 of the mountain-scale 
numerical grids used in the UZ Flow and Transport Model PMR are shown in Figure 3.4-5. 
The computer code WinGridder (WinGridder V1.0, STN: 10024-1.0-00) was used to generate 
the numerical grids for the model domain. WinGridder has the capability of designing complex, 
irregular grids with large numbers of gridblocks and connections, and can incorporate 
nonvertical faults and other embedded refinements, such as waste emplacement drift spacing 
within the potential repository area at Yucca Mountain. 
Numerical grid development begins with the arrangement of node-centered gridblocks in map 
view (Figure 3.4-6). The map-view, nodal-point array establishes the location of vertical 
columns that comprise either 1-, 2-, or 3-D numerical grids. These columns either coincide with 
important calibration points (e.g., boreholes), or are aligned along the lateral trace of major 
faults, potential emplacement drifts, and/or the exploratory tunnels, or conform to specified 
boundaries (e.g., the repository outline). All columns within the grids are vertical, except within 
certain fault zones where the average slope of the fault plane is less than approximately 80 
degrees (detailed criteria establishing vertical/nonvertical columns of gridblocks along faults are 
given in CRWMS M&O (2000, U0000, Section 6.3)). The vertical component of all grids 
contains the subdivision of the UZ into hydrogeologic layers according to their thickness and 
stratigraphic position. 
Generation of the numerical grids requires specification of three reference horizons: an upper 
and lower model boundary (usually the bedrock surface and water table, respectively) and a 
structural reference horizon (in this case, the top of unit Tpbt4) that defines layer displacement 
along major fault traces and sets the elevation of the remaining layer interfaces (for 1-D grids,

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fault displacement is irrelevant). Isochore maps (consisting of GFM3.1 data files that contain 
layer thickness data) are then added to or subtracted from the structural reference horizon to 
build the vertical component of the numerical grids. 
The primary grid generated by WinGridder represents only a single (matrix) continuum and is, 
therefore, referred to as an ECM grid. The incorporation of fracture characteristics is determined 
from fracture data analyses summarized in Section 3.6.3.2 of this PMR. It allows for 
modification of the ECM grid to create a dual-permeability grid that distinguishes between 
fracture and matrix components of flow. Fracture characteristics include fracture porosity, 
frequency, aperture, and fracture-matrix interaction area. The details of dual-permeability grid 
generation are explained in CRWMS M&O (2000, U0000, Section 6.7). 
3.4.2.3 Output 
The resulting numerical grids include: (1) a set of 1-D, vertical columns of gridblocks centered at 
the location of boreholes used to calibrate rock hydrogeological properties that, in turn, are 
assigned to layers within the mountain-scale numerical models of the UZ; (2) a 2-D grid 
consisting of columns of gridblocks aligned along an east-west transect through borehole UZ-7a 
used for fault hydrogeologic property calibrations; (3) a 3-D grid used for mountain-scale model 
calibrations; and (4) a 3-D grid used to generate ambient and predictive flow fields for PA. 
Table 3.4-1 summarizes the purpose, general description, and users of the four different 
numerical grids. CRWMS M&O (2000, U0000, Section 6) presents a detailed description of the 
steps involved in the generation of these grids. 
Table 3.4-1. Summary of Grids Developed for UZ Flow and Transport Model PMR Activities (Adapted 
from CRWMS M&O 2000, U0000, Table 6) 
Purpose Grid Description Grid User 
1-D hydrogeologic 
property set inversions 
and calibrations 
Consists of 1-D columns centered at borehole locations. 
Includes boreholes: SD-6, SD-7, SD-9, SD-12, NRG#5, 
NRG-6, NRG-7a, UZ#4, UZ-14, UZ#16, and WT-24. 
Calibrated Properties 
Model 
Fault hydrogeologic 
property calibration 
East-west cross-sectional grid through borehole UZ-7a and 
the Ghost Dance fault. 
Calibrated Properties 
Model (for faults) 
3-D UZ Model 
calibration 
Consists of a plan-view grid with discretization along major 
faults, the ESF, and the ECRB. Also contains columns of 
gridblocks centered at borehole locations. Vertical resolution 
in potential repository footprint is 5 m. 
Flow Model 
Transport Model 
Ambient 
Geochemistry Model 
Generation of 3-D flow 
fields for PA 
Consists of a plan-view grid with repository refinement, but 
no ESF or ECRB discretization. Rows of gridblocks (width  
length: 81  270 m) established along repository drift 
alignment. Vertical resolution in potential repository footprint 
is 5 m. Contains columns of gridblocks centered at certain 
borehole locations. 
Flow Model 
Transport Model 
Mountain-Scale 
Thermal-Hydrological 
Model

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Figures 3.4-7 through 3.4-9 show 2-D, cross-sectional grids extracted from the mountain-scale 
numerical grids. Cross sections from GFM3.1, corresponding to the approximate location of the 
grid profiles, are shown for comparison in each figure. 
3.4.2.4 Grid Refinement Studies 
Numerical grids must achieve a proper balance between desired numerical accuracy and 
computational time controlled by the total number of gridblocks. Gridblock size should reflect 
the scale of the process to be modeled and the availability of data. For reasons stated in 
Section 3.4.1.3, the mountain-scale models of Yucca Mountain do not attempt to capture isolated 
fast flow paths. Instead, the models focus on overall UZ characteristics and processes potentially 
affecting repository performance on a mountain scale. 
Simulations of the UZ at Yucca Mountain with coarse and refined 2-D, cross-sectional grids 
have helped to determine the appropriate numerical grid resolution to be used in the mountainscale 
numerical grids. Results of grid resolution sensitivity studies are described in CRWMS 
M&O (2000, U0000, Section 6.8). In summary, these results indicate that moisture flow is 
predominantly vertical, except where zeolites are present, suggesting that modeling results are 
less sensitive to lateral gridblock dimensions than to vertical changes in grid resolution, unless a 
sudden change in rock hydrogeologic properties occurs at a layer contact (resulting in significant 
lateral diversion). Below the repository horizon, lateral diversion is most likely to occur above 
zeolites in the CHn. Calculated saturation and percolation flux distribution can be adequately 
resolved by adding a few grid layers at the PTn-TSw interface and at the vitric-zeolitic interfaces 
within the CHn, since these are transitional areas where rock properties change rapidly over short 
vertical distances. 
The current UZ mountain-scale models are vertically resolved with about 44 layers in the 
potential repository footprint; about 15 of these layers are above the repository horizon, 5 layers 
(each with 5 m vertical resolution) are within the repository horizon, and about 24 layers lie 
between the repository horizon and the water table. The transitional areas at the PTn-TSw 
interface and the TSw-CHn interface are generally captured by several thin model layers. 
Also analyzed were results from tracer simulations at different grid resolutions and under 
different perched water scenarios. Results showed that differences in grid resolution were 
minimal, thus supporting the use of a relatively coarse numerical grid (CRWMS M&O 2000, 
U0000, Section 6.8). 
3.4.3 Summary 
Numerical simulation of performance-related flow and transport issues in the UZ at Yucca 
Mountain first requires an evaluation of numerical models and selection of the best approach 
based on the characteristic flow and transport behavior specific to the site, the scale of the 
problem, data availability, and computational feasibility. Dual-permeability (continuum) models 
have been determined to be the best approach for simulating flow and transport in the UZ at 
Yucca Mountain. 
Geological and hydrogeological data, predominantly from the Integrated Site Model (ISM) of 
Yucca Mountain, are used to develop numerical grids of the UZ mountain-scale domain.

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GFM3.1 provides key layer and fault-orientation data for establishing the structural and 
stratigraphic framework in the numerical grids of the UZ. Definition of detailed hydrogeologic 
units further refines the layering scheme used in the unsaturated flow and transport models. This 
hydrogeologic layering scheme subdivides the TCw into 3 layers, the PTn into 6 layers, the TSw 
into 8 layers, the CHn (including the Prow Pass) into 11 layers, and the CFu into 4 layers. 
Distribution of saturated hydraulic conductivity from RPM3.0 is used to differentiate between 
vitric and zeolitic regions within portions of the CHn hydrogeologic unit. 
The resulting dual-permeability numerical grids include: 
 A set of 1-D, vertical columns of gridblocks centered at the location of boreholes; used 
in the Calibrated Properties Model for determining calibrated fracture and matrix 
hydrogeologic properties. 
 A 2-D grid consisting of columns of gridblocks aligned along an east-west transect 
through borehole UZ-7a; used in the Calibrated Properties Model for fault 
hydrogeologic property calibrations. 
 A 3-D numerical grid for mountain-scale model calibrations; used in the Flow Model, 
Transport Model, and Ambient Geochemistry Model. 
 A 3-D grid for generating ambient and predictive flow fields for PA; used in the Flow 
Model, Transport Model, and Mountain-Scale Thermal-Hydrological Model.

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3.5 CLIMATE AND INFILTRATION 
This section describes issues related to future climate states and resulting net infiltration for the 
Yucca Mountain region over the next 10,000 years. Issues, modeling methodology and data, and 
results are summarized in Figure 3.5-1 for both the climate and infiltration models to provide 
perspective within the entire Yucca Mountain Project. In Section 3.5.1, three potential future 
climates are identified: modern, monsoon, and glacial transition with durations of 600, 1,400, 
and 8,000 years, respectively. Estimates for lower-bound, mean, and upper-bound precipitation 
and temperature are determined using analog meteorological stations. These are used as input 
for the Infiltration Model discussed in Section 3.5.2, which includes the processes of 
precipitation, evapotranspiration, snowmelt, and surface water run-on. This model provides 
estimates of the net infiltration over the Yucca Mountain region for the future climate scenarios 
for input into the flow and transport process models for the unsaturated zone (UZ) which are 
presented in Sections 3.7 and 3.11, respectively. The abstraction of climate and infiltration, 
which quantifies uncertainty in output results from the Climate Model and Infiltration Model for 
the Viability Assessment, is described in Section 3.5.3. This work is supported by the AMRs 
Future Climate Analysis (USGS 2000, U0005), Simulation of Net Infiltration for Modern and 
Potential Future Climates (USGS 2000, U0010), and Analysis of Infiltration Uncertainty 
(CRWMS M&O 2000, U0095). 
Anderson et al. (1998, pp. 1215) provide a critical summary of the previous VA Climate Model. 
This model was constructed from three elements: the dry present-day climate (P-climate); the 
long-term average climate (LTA-climate) which is colder and wetter than the present; and the socalled 
super pluvial climate (SP-climate) which is wetter and colder still. The P-climate occurs 
once every 100,000 years, lasts for 10,000 years, and has a present-day precipitation rate of 170 
mm/yr. The LTA-climate lasts for 80,000 to 90,000 years out of every 100,000 years and has 
twice the P-climate precipitation rate. The SP-climate occurs very infrequentlyjust twice per 
million years and lasts for 10,000 yearsand has almost three times the P-climate precipitation 
rate. The infiltration rates from the corresponding TSPA base-case Infiltration Model were 
8 mm/yr for the P-climate, 42 mm/yr for the LTA-climate, and 110 mm/yr for the SP-climate. 
They argue that the climate and infiltration models were overly conservative given evidence 
from precipitated secondary minerals in Yucca Mountain, regional shoreline and other 
geomorphic features, and lack of any past record of SP-climate. They further argue that evidence 
indicates that the Yucca Mountain region has become increasingly arid over the past million 
years. The Climate and Infiltration Models presented in this analysis provide an alternative 
methodology to that reviewed by Anderson et al. (1998, pp. 1215). Precipitation and netinfiltration 
rates estimated by the previous VA Climate Model provide an upper bound to those 
estimated using the Climate and Infiltration Models in this work. Despite these differences, 
similarity in the precipitation and net-infiltration rates estimated by the two independent 
methodologies indicate that the Climate and Infiltration Models are conservative as well. In 
particular, the Climate Model is based on an analysis of natural analog sites intended to represent 
the Quaternary paleoclimate of the Southern Great Basin as requested by Anderson et al. (1998, 
p. 15).

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3.5.1 Future Climate Analysis 
3.5.1.1 Introduction 
An analysis of potential future climate conditions for Yucca Mountain was conducted to estimate 
the timing and nature of climate change over the next 10,000 years. This is the imposed time 
interval appropriate for the analysis of future climates required for compliance with a regulatory 
standard as stated in NCRs proposed 10CFR63 (see Federal Register for February 22, 1999, 
64FR8640). The approach involves estimating the upper and lower bounds for precipitation and 
air-temperature for each future climate scenario as well as estimated mean annual values. This 
analysis is documented in the USGS (2000, U0005) and is used to provide input for the 
Infiltration Model (USGS 2000, U0010) discussed in Section 3.5.2. Paleoclimate reconstruction 
was used to estimate future climate conditions. The timing and nature of climate change is 
primarily based on Devils Hole, Nevada, delta oxygen-18 (d18O) and Owens Lake, California, 
microfossil data. Past climates were then used to select representative meteorological stations as 
future climate analogs. 
Devils Hole is an active extensional fracture (located approximately 90 km south of Yucca 
Mountain) in the Paleozoic limestone that composes the regional Paleozoic aquifer. During the 
last 500,000 or more years, calcite has precipitated on the walls of the fracture leaving a d18O 
record of the precipitation-derived infiltrating water flowing through the fracture. The isotopic 
values of infiltration are related to the temperature of the source water (the tropical and 
subtropical Pacific Ocean), the path that the water vapor takes from the source to the recharge 
area (and the amount of precipitation that occurs along the path), and the temperature at which 
the precipitation in the recharge area forms. The Owens Lake Basin is located on the eastern side 
of the Sierra Nevada Mountain Range east of Los Angeles, California. Microfossil records of 
diatoms and ostracodes from cores drilled at Owens Lake are used to reconstruct the climate 
history. Ostracode and diatom species environmental tolerances provide a way to interpret the 
relative total dissolved solids (TDS) of the Owens paleolake, and the relative temperature of its 
water. The TDS and water-temperature information are then interpreted in climate terms. Thus 
the stratigraphic profiles of microfossil species provide a way to interpret regional climate 
history from their implied paleoenvironments, provide insight into glacial and interglacial 
climate change, and provide a means to compare past climates with each other. 
The present-day earth climate system is illustrated in Figure 3.5-2a and consists of two active 
components, the tropical (Hadley Cell) and polar air masses, and one more passive component or 
mixing zone, the westerlies (Ferell Cell). Yucca Mountain is currently dominated by the northern 
region of the tropical air masses, the Subtropical Highs. These consist of high-pressure 
descending air that creates a hot low-precipitation and high-evaporation climate. In general, the 
Subtropical Highs define the global desert belts. Specifically, in the late spring through early fall 
at Yucca Mountain, there is a northward movement and intensification of the Subtropical Highs 
that do not intensify to the point of creating monsoonal weather patterns as in southern Arizona, 
New Mexico, and Mexico. Typically, there are local thunderstorms and high evaporation. From 
late fall to early spring, the Subtropical Highs weaken and retreat south, leaving the region 
largely under the influence of the westerlies. The westerlies represent the mixing zone between 
the tropical and polar air masses and consist of both high- and low-pressure air masses. The 
precipitation and temperature in this zone are typically seasonal. The moisture potential of the

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westerlies is greatly reduced by the Sierra Nevada Mountains and to a lesser extent by the 
Transverse Range. The wettest winters are attributed to El Nio years (USGS 2000, U0005, 
Section 6.2). The Subtropical Highs have dominated this region over the past 7,000 to 8,000 
years. Figures 3.5-2b and 3.5-2c show the daily precipitation over a 15-year period and an aerial 
view of Yucca Mountain, respectively. Currently, Yucca Mountain is one of the more arid 
regions in the U.S. 
The climate at Yucca Mountain for the last 8,000 years is not entirely representative of climate 
patterns that have existed for the past several hundred thousand years. Past climates exhibited a 
great deal of variability, alternating between glacial and interglacial periods. During glacial 
climates, winter seasons were longer and summers shorter, with the general climate conditions 
dominated by Polar Lows and Arctic Highs. Subtropical highs were less persistent and meanannual 
temperature, summer temperature, and evaporation were lower. Polar Lows represent the 
southern region of the polar-air masses and consist of low-pressure rising air, resulting in cool 
temperatures and high precipitation and low evaporation climates. The average position of the 
Polar Lows roughly defines the current position of the Boreal Forests. Arctic Highs consist of 
cold dry air, low precipitation, and low evaporation climates that at times result in large 
continental ice sheets. 
The following subsections provide a brief summary of the assumptions used in developing the 
future climate scenarios, the timing of future climate change, and the selection of analog 
meteorological stations (USGS 2000, U0005). 
3.5.1.2 Analyses and Assumptions 
The analysis of future climate change was based on examining paleoclimate records to find a 
past climate series that is expected to be repeated in the future. Four key assumptions are 
utilized (USGS 2000, U0005, Section 5) and described below. 
The first assumption is that climate is cyclical with several alternating glacial and interglacial 
periods occurring during an approximate period of 400,000 years. Furthermore, this pattern is 
expected to continue into the future, so that future climates may repeat, or at least approximate, 
past climates. Analysis of d18O from Devils Hole, Nevada, is the basis for this assumption 
(USGS 2000, U0005, Section 6.3). 
The second assumption is that a relationship exists between the timing of long-term past climates 
and timing of earth orbital parameters. Orbital parameters can be calculated from basic celestial 
mechanics, which can be used to estimate the timing of future climates once established. A 
correspondence was found between climate change chronology from Devils Hole and the earth 
orbital parameters of precession and eccentricity (USGS 2000, U0005, Section 6.4). 
The third assumption is that there is a relationship between the characteristics of past climates 
and the sequence of those climates. Past climates are assumed to repeat in a systematic order. 
Thus the analysis can focus on this particular climate sequence rather than all past climates and 
need not take the conservative approach of using the climates that generate the highest 
infiltration as being those expected in the next 10,000 years. Therefore, the microfossil record

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from cores drilled at Owens Lake, California, was used to reconstruct the projected climate 
history for the next 10,000 years. 
The fourth assumption is that long-term earth-based climate-forcing functions, such as tectonic 
change, have remained relatively constant over the past 500,000 years or so and will remain 
constant for the next 10,000 or more years. This is important to climate forecasting because such 
forcing functions change climate in noncyclic ways, invalidating the first three assumptions. 
Furthermore, it is assumed that anthropogenic influences (global warming due to green house 
gases) and other natural catastrophic events (volcanic eruptions, meteorite impact etc.) will not 
significantly induce noncyclic climate change. 
Using these four assumptions, which are intended to establish a defensible means for climate 
forecasting, the Owens Lake climate record is used to describe the climate conditions of the 
interval selected as the past/future climate analog. The past/future climate analog shows three 
distinct climates, each of which is described in terms of an upper-bound and a lower-bound 
climate value. The upper and lower bounds of each climate are described from what are believed 
to be representative meteorological stations, with the data at those stations then serving as input 
to the Infiltration Model. 
3.5.1.3 Timing of Climate Change 
The orbital clock as derived from the Devils Hole chronology (USGS 2000, U0005, Figures 7a, 
7b, and 8) was used to approximately identify the past/present point in the Owens Lake record 
(USGS 2000, U0005, Figure 11). The past/present point is the point in the past climate series 
representing the equivalent to the present-day climate. The future climate analog is then defined 
as the paleoclimate reconstruction of a 10,000-year sedimentary record interval beginning at the 
past/present point. Chronological correlation between the Owens Lake sedimentary record and 
the Devils Hole d18O record is based on a sediment mass-accumulation curve that is a function of 
climate and is discussed in USGS (2000, U0005, Section 6.5.1) 
From the past/present point at Owens Lake (about 400,000 years ago), the timing of the climate 
change intervals is further refined from the sediment mass-accumulation methodology on the 
basis of the abundance intervals for the ostracode species and the corresponding climatic 
conditions necessary to support these species (USGS 2000, U0005, Figure 14). The 
environmental tolerances of ostracode species provide a methodology to interpret the relative 
TDS of the Owens paleolake, and the relative temperature of the water. The TDS and water 
temperature are then interpreted in climatic terms. The time between the Limnocythere 
sappaensis abundance peak 403,970 years ago and the first appearance of L. bradburyi is about 
600 years in Owens Lake time. This corresponds to the length of time before the transition 
occurs from the remaining modern-like climate into the enhanced monsoon climate at Yucca 
Mountain. The length of the L. bradburyi abundance interval representative of monsoon climate 
conditions is about 1,400 years. The monsoon interval is followed by more than 8,000 years of 
glacial transition climate as indicated by the Candona caudata. This completes a 10,000 year 
interval from the past/present point in the Owens Lake record for use as the future climate analog 
(USGS 2000, U0005, Section 6.6.1).

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3.5.1.4 Nature of Future Climates 
The nature of future climate and, in particular, the annual and seasonal precipitation and 
temperature provide the input terms for the Infiltration Model, discussed in Section 3.5.2. The 
nature of future climate, as discussed below, is forecast in terms of upper- and lower-bound 
precipitation rates and temperatures. The mean values of precipitation and temperature are 
obtained from these bounding values. The upper- and lower-bound values are quantified by 
selecting meteorological stations at locations that currently have similar climatic conditions to 
past climates observed in the Owens Lake chronological record. These analog stations are in 
areas with some or all of the common ostracodes and diatoms found in Owens Lake, thus 
potentially integrating the biology, hydrology, and climate linkages that were expressed in the 
past at Owens Lake. The selected stations are discussed below and listed in Table 3.5-1. 
Stations with complete and long records were given priority. 
Table 3.5-1. Meteorological Stations Selected as Analogs for Future Climate States 
Climate State Duration 
Representative 
Meteorological Stations Locations of Meteorological Stations 
Modern Climate 600 years 
Site and regional 
meteorological stations 
Yucca Mountain region 
Average Upper Bound: North Latitude West Longitude 
Nogales, Arizona 31 21' 110 55' 
Hobbs, New Mexico 32 42' 103 08' 
Average Lower Bound: 
Monsoon 
Climate 1,400 years 
Site and regional 
meteorological stations 
Yucca Mountain region 
Average Upper Bound: North Latitude West Longitude 
Spokane, Washington 47 38' 117 32' 
Rosalia, Washington 47 14' 117 22' 
St. John, Washington 47 06' 117 35' 
Average Lower Bound: North Latitude West Longitude 
Beowawe, Nevada 40 35' 25" 116 28' 29" 
Glacial 
Transition 
Climate 
8,000 years 
Delta, Utah 39 20' 22" 112 35' 45" 
SOURCE: Adapted from USGS 2000, U0005, Table 6-1

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Modern Climate 
The modern-like climate interval consists of Owens Lake being supported by groundwater 
discharge and with Owens River predominately at base flow. Summers are warm to hot and very 
evaporative, with evaporation greatly exceeding precipitation at low elevations. Owens Lake 
remains saline and at a low lake level for long periods of time. The wettest years that are 
representative of the upper-bound present-day climate are characterized by Pacific airflow 
focused toward the high Sierra Nevada mountains. This results in an increase in snowpack and 
hence the seasonal duration of surface-water flow in the Owens River and its potential to dilute 
the salt content of Owens Lake. El Nio climates that have been common during the last couple 
of decades also focus Pacific moisture toward southern Nevada. Dry years representative of the 
lower-bound present-day climate are characterized by minimal winter precipitation when the 
polar front remains largely north of the region. Summer precipitation is dominated by subtropical 
high activity, but not to the degree necessary to generate a monsoon-type climate. 
Meteorological data for the upper and lower bounds come from available stations in the region, 
including Yucca Mountain Project and non-Project data. Regional averaged meteorological data 
from the National Oceanic and Atmospheric Administration (NOAA) reported in USGS 2000 
(U0005, Section 6.6.2) indicate that areas largely north of Yucca Mountain within central 
Nevada have had a range of mean annual precipitation from about 75 mm to one value as high as 
360 mm for the period of record (about 100 years). Similarly, areas largely south of Yucca 
Mountain have had a range of mean annual precipitation from less than 50 mm to one value as 
high as 325 mm for the period of record. Notably, more low-precipitation years have occurred 
than extremely high ones (i.e., the typical value is in the lower half of the range). By contrast, 
the mean annual temperature in both regions falls into a smaller range, within 1620C for the 
area south of Yucca Mountain and about 812C for the area north of Yucca Mountain. 
Monsoon Climate 
The second climate interval, the monsoon climate, is characterized in the Owens Lake record by 
a mixture of the ostracodes Limnocythere bradburyi and L. sappaensis. The existence of L. 
bradburyi in Owens Lake implies a relatively lower total dissolved solids (less than about 10,000 
mg/L) and source water derived from expansion and intensification of the summer rain system, 
diluting surface flow in the Owens River. 
Accordingly, an analog meteorological station for monsoon climate would be located to the 
south of Owens Lake in either Mexico or the southernmost U.S. to meet these conditions. The 
meteorological stations at Hobbs, New Mexico, and at Nogales, Arizona, with mean annual 
precipitations of 418 mm and 414 mm, respectively, were selected (USGS 2000, U0005, Section 
6.6.2). Two stations were selected to minimize the influence of local meteorological 
phenomena. Meteorological stations in the Yucca Mountain region were selected as the lower 
bound for the monsoon climate. 
Glacial Transition Climate 
The change from the monsoon climate to the glacial transition climate in the Owens Lake record 
occurs rapidly within a time interval of 100 to 200 years. The glacial-transition climate in the

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Owens Lake record is characterized by the appearance of Candona caudata as well as by the 
diatom Stephanodiscus asteroides, and diatom species belonging to Campylodiscus spp. and 
Anomoeneis spp. Candona caudata lives in the Owens Lake area today as well as in many 
places north of Owens Lake including sites within Canada and Alaska. In the Owens Lake area 
it lives in the Owens River as well as in freshwater lakes at higher elevation, and thus is tolerant 
of the regions seasonal temperature variability, but is not tolerant of saline water that would be 
typical for Owens Lake today under natural conditions. Candona caudata only enters Owens 
Lake when the TDS falls and remains below about 3,000 mg/L, and that typically implies that 
the lake is full and spilling. The presence of Stephanodiscus asteroides, a cool and freshwater 
planktic diatom, also implies a deep spilling lake. Conversely, the sporadic appearance of 
Limnocythere sappaensis as well as the diatoms Campylodiscus spp. and Anomoeneis spp imply 
that there were also episodes during this climate period that were relatively warm and dry, thus 
demonstrating some degree of climate variability. 
Selecting analog meteorological stations for the glacial transition climate requires identifying 
sites with cool winter wet seasons, and warm to cool and dry summers. The analog sites should 
be in the semi-arid west and lie on the eastern side of large mountain ranges so that they are in 
the rain shadow. The absence of the Cytherissa lacustris ostracode within the Owens Lake 
record is indicative of a cold Canadian-like climate and implies that a suitable analog should lie 
within the contiguous U.S. Lastly, because the mean annual temperature at Yucca Mountain 
during the last full-glacial period was about 8oC (USGS 2000, U0005, Section 6.6.2), the analog 
for the glacial transition climate should have a mean annual temperature no colder than and 
preferably warmer than 8oC. This would support current ostracode populations (at the analog 
site) with identical temperature preferences to those that existed at the Owens paleolake. 
Meteorological stations used to characterize an upper-bound analog for the glacial transition 
climate should be located in a region with a higher mean annual precipitation than observed 
during periods of high Owens Lake discharge. Given all of the conditions described above and 
the length and completeness of the record, the upper-bound glacial transition analog 
meteorological stations were selected from eastern Washington (namely Spokane, Rosalia, and 
St. John). The stations are all close to each other, but do not have identical records. Selecting 
multiple meteorological stations is intended to minimize local effects on the climate. 
For the lower-bound glacial transition climate analog, the meteorological stations should be in a 
place where mean annual temperature is higher than for the upper bound and thus would be south 
of the upper-bound localities. The temperature should also be lower than that for the present-day 
Owens Lake Basin, so that effective moisture levels are higher and consistent with a fill-and-spill 
lake. The stations should have a lower mean annual precipitation than the upper-bound sites, 
because the record from the Owens Lake Basin shows episodes when either saline diatoms or 
ostracodes or both are present, implying less surface flow in the Owens River. Few 
meteorological sites meet all of these conditions. The one set of meteorological data that fits all 
of these criteria and also has a long and complete record of weather data are those at Delta, Utah. 
The site at Beowawe, Nevada meets most of the requirements noted above and was added as an 
additional lower-bound meteorological station to avoid using a single site for input (USGS 2000, 
U0005, Section 6.6.2).

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3.5.1.5 Uncertainties 
Uncertainty in climate impact is addressed by the use of upper and lower bounds for each climate 
state. These bounding climates provide a range of precipitation and temperature to the 
subsequent infiltration calculations. The other uncertainty of interest is in the timing of the 
climate changes. 
Many uncertainties exist that may affect the timing of the three climate states. These include 
uncertainties in the Owens Lake sediment-accumulation rate, in Devils Hole age data, in the 
exact time when the Devils Hole record implies climate is changing, and in the exact location of 
the past/present point in the Owens Lake record (analog climate proxy record). In addition, the 
selection and timing of a particular past climatic sequence to forecast the future is problematic, 
given the chaotic nature of climate and the possibility that human activity may change the 
cyclical patterns. 
A quantitative estimate has been made of the first uncertainty (the Owens Lake sedimentaccumulation 
rate), leading to a range of 400600 years for the duration of the modern climate 
and 9001,400 years for the duration of the monsoon climate, with the glacial-transition climate 
extending for the balance of the 10,000-year period in each case (USGS 2000, U0005, 
Section 6.6.1). No simple or objective way of assessing the other uncertainties exists 
quantitatively. However, the impact of those uncertainties on TSPA results can be assessed by 
means of sensitivity analysis; see Section 3.5.3. 
Both the monsoon and glacial-transition climate states are expected to be wetter than the presentday 
climate, and, as a result, the water table is expected to rise. However, uncertainty exists 
regarding the amount of water-table rise for each climate state. Therefore, as discussed in 
Section 3.7.5.2, a conservative water-table rise of 120 m is used for all flow fields using future 
climate states. 
3.5.1.6 Alternative Conceptual Models 
The analysis presented in USGS (2000, U0005) focused on predicting climate change over the 
next 10,000 years based upon paleoclimate reconstruction of an analogous time interval that 
occurred approximately 400,000 years ago. An alternative approach would be to focus instead on 
the paleoclimate record for the last 18,000 years since glaciation. The climate within this time 
interval is known with significantly greater confidence than that which occurred 400,000 years 
ago. Trends in climate change over the last 18,000 years could be used to extrapolate expected 
future climates for the next 10,000 years. Uncertainty in any predictions will increase 
dramatically by the end of the 10,000-year time period, and in fact predictions may become 
wholly unreliable. Global climate circulation models could be used to provide a physical basis 
for predicting climate change for the next 10,000 years, although their reliable use is currently 
restricted to short time periods given limitations in current knowledge of the mechanisms forcing 
climate change. 
3.5.1.7 Corroborative Evidence 
This analysis is based on meteorological data collected at natural analog sites for the monsoon 
and glacial-transition climates expected to occur at Yucca Mountain. These analogs provide

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corroborative evidence for anticipated precipitation rates. Plant macrofossils recovered from 
packrat middens throughout the Yucca Mountain region, representing conditions since the last 
glacial climate (18,000 years), provide corroborative evidence for the glacial-transition climate 
predicted by the Climate Model (USGS 2000, U0005, Section 6.5.1). 
3.5.1.8 Summary and Conclusions 
The future climate at Yucca Mountain is treated as a sequence of three states whose timing and 
characteristics are described in detail in USGS (2000, U0005). Each climate state is defined in 
terms of climate analogs, with the monsoon and glacial-transition climates being bounded by a 
range of climate values that have wetter-than-modern upper-bound values and modern-like or 
wetter-than-modern lower-bound values. Tables 3.5-2 and 3.5-3 list the mean annual 
precipitation and temperature inferred from the lower- and upper-bound analog data for use in 
calculating infiltration over the area of the UZ Flow and Transport Model domain. Note that 
lower and upper refer to precipitation rate, not temperature. 
The upper-bound precipitation values for the monsoon and glacial-transition climates exceed the 
upper bound of the regions present-day climate by about 150 mm/yr. The glacial-transition 
climate's lower bound exceeds the modern lower-bound values by about 15 mm/yr. Thus the 
future climate (based on this method of analysis) is wetter than the modern climate. 
Temperature, however, defines an important difference between the modern climate and the 
glacial-transition climate. The glacial-transition climate is cooler than the modern climate, so 
evaporation is substantially lower than during modern times. A lower level of evaporation means 
that precipitation will be more readily stored, and hence available for infiltration, than is true in 
today's climate. 
Uncertainty in climate impact for use in the TSPA is addressed by the upper and lower 
precipitation and temperature values. The other uncertainty of interest is in the timing of the 
climate change with durations of 400600 years for the modern climate, 9001,400 years for the 
monsoon climate, and with the glacial-transition climate extending for the balance of the 10,000- 
year period in each case. 
Table 3.5-2. Mean Annual Precipitation for Analogs for the Lower and Upper Bound of the 
Three Climate Scenarios 
Climate Lower Bound 
(mm/yr) 
Mean 
(mm/yr) 
Upper Bound 
(mm/yr) 
Modern 186.8 190.6 268.6 
Monsoon 190.6 302.7 414.8 
Glacial Transition 202.2 317.8 433.5 
SOURCE: Adapted from USGS 2000, U0010, Tables 7-3 (modern), 7-7 (monsoon), and 7-12 (glacial 
transition)

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Table 3.5-3. Mean Annual Temperature for Analogs for the Lower and Upper Bound of the 
Three Climate Scenarios 
Climate Lower Bound 
(C) 
Mean 
(C) 
Upper Bound 
(C) 
Modern (not provided) (not provided) (not provided) 
Monsoon 17.3 17.2 17.0 
Glacial Transition 10.2 9.8 9.4 
SOURCE: Adapted from USGS 2000, U0010, Tables 7-6 (monsoon), and 7-11 (glacial transition) 
3.5.2 Infiltration Model 
3.5.2.1 Introduction 
The Infiltration Model provides spatially distributed time-averaged estimates of net infiltration 
for defining the upper boundary of the UZ Flow and Transport Model and its associated sitescale 
process models. The approach used in this model is documented in USGS (2000, U0010) 
and its results are summarized here. Net infiltration is the component of infiltrated precipitation, 
snowmelt, or surface water run-on that has percolated below the zone of evapotranspiration as 
defined by the depth of the effective root zone. Estimates of net infiltration are based on the 
upper bound, mean and lower bound precipitation rates for the modern, monsoon and glacialtransition 
climates provided by USGS (2000, U0005) and given in Table 3.5-2. Field data were 
obtained at the Yucca Mountain site to monitor the transient response of infiltrating groundwater 
as well as overland and stream flow resulting from episodic precipitation events. These data are 
then used to calibrate a watershed-scale volume-balance model (i.e., the Infiltration Model) that 
simulates groundwatersurface water interaction on the slopes of Yucca Mountain. The scope of 
the model is limited to surficial hydrological processes, with estimates of net infiltration limited 
to depth of the root zone only. These estimates of net infiltration then provide direct input into 
the UZ Flow and Transport Model. 
3.5.2.2 Analyses and Assumptions 
The first assumption in USGS (2000, U0010, Section 5.1.2) involves the development of the 
conceptual model of net infiltration. Net infiltration is defined here as water that has percolated 
from the land surface through the entire thickness of the root zone. The root zone is defined as 
the zone from the ground surface to some variable depth in soil or bedrock from which infiltrated 
water is readily removed on an annual or seasonal basis by evapotranspiration. In the conceptual 
Infiltration Model, the hydrological cycle is used to identify, define, and separate the various 
field-scale components and controlling processes (see Figure 3.5-3a). The hypothetical starting 
point of the hydrological cycle is precipitation, which for the current (modern) climate at Yucca 
Mountain occurs primarily as rain but can also occur as snow. Precipitation can accumulate on 
the ground surface, infiltrate the soil or exposed bedrock surfaces, contribute to runoff, or 
accumulate as snow. The contribution of precipitation to runoff generation depends on 
precipitation intensity relative to soil and exposed bedrock permeability, as well as on the 
available storage capacity of soil and shallow bedrock with thin or no soil cover. Water

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accumulated in the snowpack can sublimate into the atmosphere or become snowmelt, which can 
then infiltrate, evaporate, or contribute to runoff. Rain or snowmelt that becomes runoff either 
accumulates in surface depressions and basins or contributes to surface water flow, which is 
routed to downstream locations as run-on. Note that runoff is defined here as the volume or 
depth of water accumulation on the ground surface prior to being routed as surface-water flow, 
whereas run-on is defined as the volume or depth of the routed surface flow. Run-on contributes 
to either infiltration or accumulated surface-water run-on at downstream locations. Infiltrated 
water percolates through the root zone as either saturated or unsaturated ground water and is 
subject to evapotranspiration. Water percolating through the root zone is available as potential 
net infiltration, but the actual net-infiltration rate is limited by the bulk (or field-scale) saturated 
permeability of the bedrock or soil underlying the root zone. When infiltration from rain, 
snowmelt, or surface-water run-on occurs at a rate greater than the bulk saturated hydraulic 
conductivity of a subsurface layer, water will begin to fill the available storage capacity of the 
overlying soil. When the total storage capacity is exceeded, runoff is generated. 
The second assumption involves the numerical representation of the conceptual model. This 
involves simplifying physical processes while maintaining a sufficient level of accuracy in the 
mathematical approximation. In most cases, an exact mathematical formulation of the physical 
process being modeled is not required, and deference is given to computational efficiency and 
practical applicability. 
The third assumption involves calibration and verification of the numerical model. This involves 
assuming that the model was adequately calibrated using a variety of data collected at Yucca 
Mountain. These data include soil and bedrock hydrological properties, vertical water-content 
profiles in soil and bedrock, meteorological data, and streamflow measurements and are 
described in detail in Section 3.5.2.3. 
The fourth and final assumption is that climate conditions at Yucca Mountain as estimated in 
USGS (2000, U0005) are valid (USGS 2000, U0010, Section 5.4). 
3.5.2.3 Hydrological Data Collected at Yucca Mountain 
A significant body of hydrological data has been collected at Yucca Mountain to characterize the 
response of the hydrological system to precipitation events (USGS 2000, U0010, Section 5.3). 
These data include soil and bedrock hydrological properties, meteorological data, and 
streamflow measurements. Water-content profiles were measured using a network of 98 neutronmoisture 
probes at monthly or weekly intervals from 1984 through 1995. These data indicate that 
the episodic nature of precipitation events at Yucca Mountain with short periods of heavy 
precipitation (and/or snowmelt) result in highly transient surface run-on and stream flow events. 
Furthermore, thin soils and the fractured nature of the underlying tuff rock result in rapid 
percolation of infiltrated water below the root zone. In general, the average annual potential 
evapotranspiration rate is approximately six times greater than the average annual precipitation 
rate for the current climate, resulting in the arid condition of Yucca Mountain between episodic 
precipitation events.

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3.5.2.4 Conceptual Model for Net Infiltration 
Figure 3.5-3b provides a generalized illustration of the various model components required for 
simulating spatially distributed net-infiltration rates. In general, the main components of net 
infiltration are precipitation, evapotranspiration, and surface water run-on. These components are 
incorporated into a watershed-scale volume-balanced model using a snowpack submodel, an 
evaporation and net radiation submodel, one-dimensional (vertical) root-zone infiltration 
submodels, and a two-dimensional (plan view) surface-water flow-routing submodel. 
Precipitation rate is provided by the analog meterological stations discussed in Section 3.5.1 and 
is spatially distributed based on an empirical precipitation-elevation correlation relationship. 
Evapotranspiration is the combined process of bare-soil evaporation and transpiration (excluding 
evaporation from open bodies), which is the uptake and transfer of water to the atmosphere by 
vegetation. The potential evapotranspiration is determined by an energy balance and is primarily 
dependent on net radiation, air temperature, ground heat flux, the saturation-specific humidity 
curve, and wind. Temperature is also spatially distributed for the model by using an empirical 
temperature-elevation correlation relationship. Net infiltration is modeled through soil layers of 
the root zone only. The change in root zone water content is calculated instantaneously as a total 
daily change in water content using a simple water balance approach. The amount of daily net 
infiltration is limited by the bulk saturated hydraulic conductivity of the soil and storm duration. 
Water that exceeds the infiltration capacity of a soil column is routed to lower elevation nodes 
for subsequent infiltration. 
The modeling process is discussed in detail in USGS (2000, U0010, Section 6). 
3.5.2.5 Net Infiltration for the Three Climate Scenarios 
Results in USGS (2000, U0010) provide net-infiltration estimates over a 123.7 km2 area, termed 
the infiltration model domain. Results are also discussed for the 38.7 km2 area used as the 
modeling domain for the UZ Flow and Transport Model and the 4.7 km2 area corresponding to 
the potential repository area. Results presented in this section focus on those for the UZ Flow 
and Transport Model only. Net-infiltration rates estimated by the Infiltration Model for the UZ 
Flow and Transport Model domain differ slightly from those actually implemented in the UZ 
Flow and Transport Model due to plan-view discretization effects in the UZ Flow and Transport 
Model and the need to spatially average net-infiltration rates over each node in the UZ Flow and 
Transport Model domain. 
Modern climate 
Figure 3.5-4 illustrates precipitation, surface run-on, and net infiltration for the mean modern 
climate scenario. For the model domain area of the UZ Flow and Transport Model, the average 
precipitation rate is 190.6 mm/yr; the average outflow rate is -0.2 mm/yr, and the average netinfiltration 
rate is 4.6 mm/yr (USGS 2000, U0010, Section 6.11.1). The negative outflow rate 
indicates that more surface water flows into the UZ Flow and Transport Model area than flows 
out (primarily because of inflow from Yucca Wash). 
For the UZ Flow and Transport Model domain, the spatial distribution of estimated precipitation 
for the mean modern climate scenario indicates minimum values occurring along the eastern and

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southern portions and the maxima occurring in the northwestern region (see Figure 3.5-4a). The 
minima and maxima for the Infiltration Model occur outside the UZ Flow and Transport Model 
domain. Estimated evapotranspiration rates in general reflect the distribution of precipitation, 
but also reflect local terrain and surface-water flow effects (see Figure 3.5-4b). Minimum 
evapotranspiration rates of less than 100 mm/yr occur for steep north-facing sideslopes and areas 
with minimal soil cover, such as the west-facing slope of Solitario Canyon and the rugged terrain 
in the northern part of Yucca Wash. On the other hand, maximum evapotranspiration rates of 
240 mm/yr and higher are indicative of locations subject to a high volume or frequency of 
infiltrated surface-water run-on. This is particularly the case immediately downslope from areas 
receiving higher precipitation (as well as rugged terrain conducive to runoff generation) such as 
the northern part of Yucca Wash. Infiltrated surface-water run-on indicates the contribution of 
surface-water flow to potential net infiltration and evapotranspiration. Maximum infiltrated 
surface-water run-on rates of more than 100 mm/yr occur mostly along the Yucca Wash channel 
but also at more isolated locations in the upper sections of drainages, such as Drill Hole Wash, 
Solitario Canyon, Pagany Wash, and Abandoned Wash. 
The spatial distribution of estimated net-infiltration rates for the mean modern climate indicates 
most net infiltration occurs in upland areas. Relatively high net-infiltration rates of 100 mm/yr 
and higher occur throughout the steep north, north-east facing slope of the Prow, caused by a 
combination of higher precipitation rates, reduced potential evapotranspiration, frequent surfacewater 
run-on resulting from very thin soils, and high bedrock permeability associated with nonwelded 
tuffs. Areas of relatively high net-infiltration rates also include the upper channel 
locations of Solitario Canyon, Drill Hole Wash, Pagany Wash, and Abandoned Wash. Variability 
in net infiltration caused by topographic effects on potential evapotranspiration are illustrated by 
the higher net-infiltration rates for the north slopes of washes compared to south facing slopes 
(this is well illustrated by the west-to-east drainages along the east slope of Yucca Mountain and 
bisected by the ESF main drift). Maximum net-infiltration rates of more than 100 mm/yr occur 
within the UZ Flow and Transport Model domain for isolated areas that include side-slope and 
channel locations with thin soils and high permeability bedrock. The contribution to the total netinfiltration 
volume over the area of the UZ Flow and Transport Model is dominated, however, by 
the lower rates of 120 mm/yr covering wider areas of sideslope and ridgetop locations because 
of a much greater total area of coverage. 
The distribution of net infiltration for the upper-bound modern climate (USGS 2000, U0010, 
Figure 7-6) is similar to that of the mean but with an increase of net-infiltration rate directly over 
the proposed repository (along the ridge crest) from 1020 mm/yr to 2050 mm/yr. For the 
lower-bound modern climate (USGS 2000, U0010, Figure 7-5), the net-infiltration rate along the 
ridge crest decreases to 510 mm/yr without any net-infiltration over the majority of the potential 
repository and UZ Flow and Transport Model area. 
Monsoon Climate 
Net-infiltration results for the mean monsoon climate are shown in Figure 3.5-5a. For the UZ 
Flow and Transport Model area, results for the mean monsoon climate scenario include an 
average precipitation rate of 302.7 mm/yr, an average outflow rate of 4.6 mm/yr, and an average 
net-infiltration rate of 12.2 mm/yr (USGS 2000, U0010, Section 6.11.2). The maximum netinfiltration 
rate is 629 mm/yr. For the lower-bound monsoon climate scenario, average net

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infiltration is 4.6 mm/yr for the UZ Flow and Transport Model area (the mean modern climate 
result). Estimation results for the upper-bound monsoon climate scenario include a precipitation 
rate of 414.8 mm/yr, a snowfall rate of 6.8 mm/yr, an average outflow rate of 9.5 mm/yr, and a 
net-infiltration rate of 19.8 mm/yr. The maximum net-infiltration rate for the upper-bound 
monsoon climate scenario is greater than 1,000 mm/yr. The minimum is no net infiltration for all 
three scenarios. 
For the mean monsoon climate scenario, estimated net-infiltration rates along the crest of Yucca 
Mountain are in the range of 2050 mm/yr. Within the potential repository area, maximum netinfiltration 
rates occur in the active channel of Drill Hole Wash and for outcrop locations of 
permeable, nonwelded tuffs in the middle section of the west-facing slope of Solitario Canyon. 
Relatively high net-infiltration rates (100500 mm/yr) also occur at many steep side-slope 
locations in the northern part of the UZ Flow and Transport Model area. In contrast, net 
infiltration at upland locations with thin soils underlain by bedrock with low bulk permeability is 
less than 1 mm/yr. 
The distribution of net infiltration for the upper-bound monsoon climate (USGS 2000, U0010, 
Figure 7-8) is almost identical to that of the mean but with a slight increase of net-infiltration rate 
directly over the proposed repository (along the ridge crest) and UZ Flow and Transport Model 
area. Results are not presented in USGS (2000, U0010) for the lower-bound monsoon climate 
and are not discussed here. 
Glacial Transition Climate 
Net-infiltration results for the mean glacial-transition climate are shown in Figure 3.5-5b. For 
the area of the UZ Flow and Transport Model domain, results for the mean glacial-transition 
climate scenario include an average precipitation rate of 317.8 mm/yr, an average annual 
infiltrated surface-water run-on depth of 15.6 mm/yr, an average outflow rate of -0.2 mm/yr, and 
an average net-infiltration rate of 17.8 mm/yr (USGS 2000, U0010, Section 6.11.3). For the 
lower- and upper-bound glacial-transition scenarios, the average net-infiltration rate is estimated 
to be 2.5 mm/yr and 33.0 mm/yr, respectively. The maximum net-infiltration rates are 
approximately 220 mm/yr, 1,280 mm/yr, and 2,560 mm/yr for the lower-bound, mean, and 
upper-bound scenarios, respectively, for the UZ Flow and Transport Model domain. The 
minimum is no net infiltration for all three scenarios. 
For the mean glacial-transition climate scenario, the spatial distribution of net-infiltration rates is 
slightly greater than those of the mean monsoon climate, given their similar distribution of 
precipitation rates. Infiltration rates are slightly higher for the mean glacial-transition climate 
because annual temperatures are lower, resulting in reduced evapotranspiration. The netinfiltration 
rates along the crest of Yucca Mountain are also within 2050 mm/yr. 
The distribution of net infiltration for the upper-bound glacial-transition climate (USGS 2000, 
U0010, Figure 7-17) is similar to that of the mean but with an increase of net-infiltration rate 
directly over the potential repository (along the ridge crest) from 2050 mm/yr to 50100 mm/yr. 
For the lower-bound glacial-transition climate (USGS 2000, U0010, Figure 7-15), the netinfiltration 
rate along the ridge crest decreases to 020 mm/yr with the net-infiltration rate

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predominantly in the lower range of this interval over the majority of the potential repository and 
UZ Flow and Transport Model area. 
3.5.2.6 Uncertainties 
A detailed analysis of infiltration uncertainty was conducted using the Monte Carlo method 
(CRWMS M&O 2000, U0095). This analysis shows that the lower-bound and upper-bound 
infiltration rates are not truly bounds when all uncertainties are taken into account, and the mean 
infiltration rate is not the statistical mean when the appropriate probabilistic weighting factors 
are applied. In the rest of this subsection the three infiltration cases will be referred to as low, 
medium, and high to simplify terminology. 
The uncertainty in net-infiltration results from imperfect knowledge of input parameters used by 
the Infiltration Model. The uncertainty analysis focused on twelve key input parameters for 
which uncertainty distributions were developed. The key parameters include precipitation, 
bedrock and soil hydrological properties, and potential evapotranspiration. Latin Hypercube 
Sampling (LHS) was used to sample values from the twelve uncertainty distributions. LHS is a 
form of stratified sampling whereby the sampling interval is divided into a number of 
subintervals of equal probability. An equal number of samples is then drawn from each of these 
intervals. The result is greater confidence in the output distribution than would be obtained using 
the classical random-sampling approach. 
The Infiltration Model was run with 100 realizations to sampling each of the twelve input 
parameters. The glacial-transition climate was used for the analysis because that climate state is 
in effect most of the time, and it is in effect at later times when radionuclide releases are more 
likely. The mean infiltration over the repository area (actually, over a rectangular area slightly 
larger than the loaded portion of the repository) was computed for each realization. The 
distribution of mean infiltration values has an approximately log-normal shape; a histogram of 
the log values is shown in Figure 3.5-6. Also shown on the plot are the logs of mean infiltration 
for the three reference infiltration cases that are actually used for subsequent process and TSPA 
modeling. Incorporation of this infiltration uncertainty distribution into TSPA simulations, 
including a discussion on the derivation of the weighting factors shown on Figure 3.5-6, is 
discussed in Section 3.5.3. 
3.5.2.7 Alternative Conceptual Models 
Fully coupled groundwatersurface water flow models have been developed to simulate the 
hydrological cycle within watersheds. They involve using Richards equation to simulate variably 
saturated groundwater flow and shallow water flow equations (i.e. Saint Venant equations of 
overland flow, such as a kinematic wave model using Mannings equation) to simulate overland 
and stream flow. These models are designed to resolve spatial and temporal variations in net 
infiltration stemming from episodic precipitation events within a wide variety of watersheds. 
They could be used to simulate net infiltration on the slopes of Yucca Mountain in a manner 
physically identical to that used to simulate UZ flow. Specifically, the ability of precipitation to 
infiltrate the extremely dry soils on the slopes of Yucca Mountain is limited until they absorb 
sufficient water to become permeable enough to permit downward flow of the infiltrating water. 
Given the high intensity and short duration of storm events, a significant volume of water may

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flow along the surface or within streams before finally infiltrating in the lower elevation reaches 
of a given watershed. Therefore, the transient nature of groundwatersurface water interaction 
may be a significant mechanism controlling net infiltration. The distribution of net infiltration 
may then appear dramatically different that that shown on Figures 3.5-4a and 3.5-5 where 
infiltration occurs predominantly at the higher elevation reaches of a given watershed. The 
temporal and spatial distribution of net-infiltration fronts observed in the neutron-moisture probe 
data along with the stream flow data would then help constrain the transient response of such a 
model to precipitation from storm events. Use of alternative models such as the one proposed 
may provide confidence in the applicability of the assumptions used to simulate net infiltration in 
USGS (2000, U0010) and generate the net-infiltration maps shown on Figures 3.5-4a and 3.5-5 
for the UZ Flow and Transport Model and the TSPA. 
3.5.2.8 Corroborative Evidence 
Corroborative evidence that the mean modern net-infiltration rate of 4.6 mm/yr is a 
representative average value for the UZ Flow and Transport Model is provided by examining 
alternative approaches to estimating the net-infiltration rate. These include discharge (water 
balance), transfer function (based on variables such as precipitation), and geochemistry 
techniques. Winograd and Thordarson (1975, pp. 1126) used discharge from springs at Ash 
Meadows (south of Yucca Mountain near the Nevada-California border) to estimate net 
infiltration for the lower carbonate aquifer. They estimated that 3% of the precipitation falling on 
carbonate-rock uplands within the boundaries of the Ash Meadows basin becomes infiltration. 
The Infiltration Model estimated that 2.4% of precipitation becomes net infiltration over the UZ 
Flow and Transport Model domain indicating excellent agreement with the water balance 
methodology. Watson et al. (1976, pp. 335357) used a Maxey-Eakin transfer function approach 
to estimate net infiltration for basins in Nevada. They found that for precipitation rates between 
0300 mm/yr, approximately 03% becomes net infiltration further substantiating the Infiltration 
Model. Chloride concentrations measured in pore waters for the ESF and ECRB provided 
calibration targets for the UZ Flow and Transport Model by adjusting net-infiltration rates. 
Results on Figure 3.8-4 indicate a range of net-infiltration rates from 310 mm/yr. Furthermore, 
calcite abundances in the TSw were also used to estimate percolation fluxes (CRWMS M&O 
2000, U0085) with a net-infiltration rate of 6 mm/yr capturing the approximate average 
abundances in the TSw. Therefore, the geochemistry data also supports the mean modern netinfiltration 
rate calculated by the Infiltration Model for the UZ Flow and Transport Model 
domain. 
Long-term net-infiltration rates based upon analysis of sulfate and chloride data originating in 
water from the late Pleistocene to early Holocene epochs imply a spatially averaged infiltration 
rate of 21 mm/yr over the area of the UZ Flow and Transport Model (USGS 2000, U0010, 
Section 7). This value is similar to the upper-bound monsoon and glacial-transition climate 
values and provides qualitative validation of infiltration rates estimated by the Infiltration Model, 
assuming prevalence of these climates during the late Pleistocene to early Holocene epochs. 
3.5.2.9 Model Validation 
Validation of the Infiltration Model is supported by its ability to correctly estimate the top 
boundary condition for use in the calibration of the UZ Flow and Transport Model. Net

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infiltration rates comprising this boundary condition are integral to the successful calibration of 
the unsaturated zone flow parameter data set using one- and two-dimensional sections extracted 
from the UZ Models as described in Section 3.6. The unsaturated zone data set consists of water 
saturation as well as moisture tension measurements from all available boreholes. Calibration of 
the three-dimensional UZ Flow and Transport Model to the occurrence and distribution of 
perched water zones and the ambient temperature profile (see Section 3.7), and geochemistry 
data (chloride, strontium, calcitesee Section 3.8) further substantiate that the Infiltration Model 
is valid for its intended use. 
3.5.2.10 Summary and Conclusions 
Table 3.5-4 lists the average net-infiltration rates for the nine climate scenarios. As stated 
earlier, net-infiltration rates estimated by the Infiltration Model differ slightly from those actually 
implemented in the UZ Flow and Transport Model (see Table 3.7-1) due to plan-view 
discretization effects in the UZ Flow and Transport Model and the need to spatially average netinfiltration 
rates over each node in the UZ Flow and Transport Model domain. In general, the 
net-infiltration rates increase with time as climate changes from modern to monsoon to glacial 
transition. The exception is the lower bound of the glacial transition, where the estimated net 
infiltration decreases because of lower surface water run-on than in the lower-bound monsoon 
climate scenario. The highest net-infiltration rates occur on the steep north, north-east facing 
slope of the Prow, the upper channel locations of Solitario Canyon, Drill Hole Wash, Pagany 
Wash, and Abandoned Wash, and generally in the northern portion of the site. 
Table 3.5-4. Average Net-Infiltration Rates over the UZ Flow and Transport Model Domain 
Climate Lower Bound 
(mm/yr) 
Mean 
(mm/yr) 
Upper Bound 
(mm/yr) 
Modern 1.3 4.6 11.1 
Monsoon 4.6 12.2 19.8 
Glacial Transition 2.5 17.8 33.0 
SOURCE: Adapted from USGS 2000, U0010, Tables 7-3 (modern), 7-7 (monsoon), and 7-12 (glacial 
transition) 
The uncertainty in infiltration for use in the TSPA is determined by varying twelve key input 
parameters in the Infiltration Model and constructing a histogram of calculated infiltration rates 
for each climate. The resulting histogram yields the expected log-normal distribution of 
infiltration rates, combining the lower-bound, mean, and upper-bound climate and infiltration 
maps for the glacial transition climate only. This histogram is then used to incorporate 
infiltration uncertainty into TSPA simulations. 
3.5.3 Abstraction of Climate and Infiltration 
3.5.3.1 Climate 
The abstraction of climate for use in TSPA simulations has largely been discussed already in 
Section 3.5.1. Future climate is represented as a sequence of three climate states: modern for

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600 years, monsoon for 1,400 years (i.e., from 600 to 2,000 years in the future), and then glacialtransition 
for the balance of the 10,000-year period. 
Climate-properties uncertainty (e.g., precipitation and temperature) within each climate state is 
included by use of upper- and lower-bound climate analogs. These climate properties are not, 
however, used directly in TSPA simulations but only indirectly through their effects on UZ flow 
and thermal hydrology. Uncertainty in the timing of climate changes is not included in the base 
TSPA simulations and in fact is not well understood (see Section 3.5.1.5). However, the impact 
of the uncertainty in climate-change times on TSPA results can be assessed by arbitrarily varying 
the climate-change times within a TSPA simulation to determine whether the TSPA results are 
sensitive to such changes. Based on sensitivity analyses performed for the Viability Assessment 
(DOE 1998, Volume 3, Section 5.1.1), it is anticipated that climate-change time will not be 
found to have significant impact on repository performance. 
3.5.3.2 Infiltration 
As with climate, infiltration is not included directly in TSPA simulations, but only indirectly 
through its use as a boundary condition for the UZ flow and thermal hydrology models. As 
described in Section 3.5.2, three infiltration maps were generated for each climate state. The 
three will be referred to here as the low, medium, and high infiltration cases. To conduct a 
probabilistic TSPA simulation, we must assign weighting factors, or probabilities, to the three 
infiltration cases. These weighting factors were derived from the results of the infiltration 
uncertainty analysis (see Section 3.5.2.6). The weighting factors were chosen so as to make the 
log mean and standard deviation of the three-point discrete distribution (that is, the distribution 
consisting of three infiltration cases with defined weights) equal to the log mean and standard 
deviation of the distribution from the Monte Carlo simulation (shown in Figure 3.5-6). Log 
values were used in deriving the weighting factors because the distribution has a more normal 
shape in log space than in linear space (CRWMS M&O 2000, U0095, Section 6.3). The 
weighting factors derived in this manner are 0.17, 0.48, and 0.35 for the low, medium, and high 
cases, respectively (CRWMS M&O 2000, U0095, Section 6.5). Those weights are used for 
sampling in TSPA simulationsthat is, the low-infiltration case is used in approximately 17% of 
the TSPA realizations, the medium-infiltration case is used in 48% of the realizations, and the 
high-infiltration case is used in 35% of the realizations.

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3.6 UZ PROPERTIES DEVELOPMENT 
The development of hydrologic properties is a critical step for the UZ Flow and Transport 
Model. Property development integrates a large amount of data collected at Yucca Mountain 
(described in Section 2.2) with the conceptual model of UZ flow and transport (described in 
Sections 3.2, 3.3, and 3.4.1) to produce properties that are suitable for numerical simulations and 
predictions of present and future behavior of the UZ. Figure 3.6-1 shows the diverse data and 
models that are integrated for development of UZ properties. In addition to the raw data and the 
conceptual model, the Geologic Framework Model (GFM) (CRWMS M&O 2000, I0035), 
numerical grid (described in Section 3.4.2), and Infiltration Model (described in Section 3.5) are 
also used as input for the development process. The broad use, and therefore importance, of the 
developed UZ properties is indicated by the numerous analyses and models, also shown in 
Figure 3.6-1, to which the properties are input. 
3.6.1 Introduction 
Development of properties for the UZ Flow and Transport Model is a complex, multistep 
process. In this section, the framework for this process and the theory behind the process will be 
discussed. The process consists of two major steps. The first of these is the analysis of the 
hydrologic properties data, which is documented by CRWMS M&O (2000, U0090). In the 
second major step, in which the properties are calibrated as documented by CRWMS M&O 
(2000, U0035), the output of the first major step is integrated with other models and data, as 
shown in Figure 3.6-1, to produce properties that are suitable for numerical simulations and 
predictions of present and future behavior of the UZ. 
Using input from the conceptual model and the GFM (CRWMS M&O 2000, I0035), the 
hydrologic properties data are analyzed to provide an initial estimate of properties that will be 
used by numerical models. The conceptual model specifies that properties may be characterized 
by dividing the mountain into essentially horizontal layers, based on geology, and assuming that 
the properties within each layer are homogeneous (see Section 3.4.1.4.4). The conceptual model 
and the GFM (CRWMS M&O 2000, I0035) give the framework for grouping the data by layer. 
The data are then analyzed to estimate effective properties for each layer. The data analysis 
considers, with input from the conceptual model, not only how best to statistically describe the 
data, but also whether upscaling is appropriate. Upscaling is an adjustment to the estimate of the 
effective property when the property data are collected on one support scale but the estimate is 
intended for use in simulations and predictions on a much larger scale. Support scale refers to the 
size of the rock volume on which measurements are made (e.g., for measurements made on 
borehole core, the support scale is the size of the core). 
The hydrologic properties estimates are passed to the Calibrated Properties Model (CPM). The 
CPM integrates these estimates with a numerical model and data on the ambient conditions at 
Yucca Mountain using a technique called data inversion. The numerical model is used to attempt 
to simulate the ambient conditions. Input to the numerical model includes the Infiltration Model, 
which provides an estimate of the amount of water that is infiltrating into the UZ from the 
surface of the mountain; the numerical grid, which provides a representation of the geology for 
the numerical model; and hydrologic properties estimates. Data on the ambient conditions 
observed in the UZ are provided for comparison to the output of the numerical model. For the

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inversion, some element or elements of the numerical model (e.g., selected hydrologic properties 
or net infiltration rates) must be selected to be varied, or calibrated, so that the output from the 
numerical model can be matched, as well as possible, to the ambient conditions data. 
Here, it is appropriate to make the distinction between properties and parameters. Properties are 
those qualities of the real world that give rise to its behavior; in this case the real world may be 
confined to the UZ of Yucca Mountain. When this behavior is modeled, either analytically or 
numerically, the model is, by necessity, a simplification of the real world. So the properties of 
the real world are simplified to a limited set of parameters that are used to define the model. As 
much as possible, it is best to have a one-to-one correspondence between the properties and the 
model parameters because this simplifies the initial estimation of the parameters. 
The choice of which elements, or parameters, of the numerical model are to be calibrated is 
governed by several criteria. Any of the elements of the numerical model can be selected for 
calibration. Some model parameters will have a larger impact on the match to the data than 
others. Without any other information, these would be the obvious choices for the model 
parameters to be calibrated. However, it must also be considered that some of the model 
parameters have been estimated with a low uncertainty. To retain the best correspondence 
possible between the model parameters and the actual properties of the UZ (here properties not 
only mean hydrologic properties but any element of the model, such as geologic information and 
net infiltration rates), it is best to select parameters that have been estimated with higher 
uncertainty. For this case, some of the hydrologic properties are selected as the model parameters 
to be calibrated. These model parameters have a relatively high uncertainty, but are also 
parameters that will have a significant impact on the match to the ambient conditions data. All 
other model parameters remain unchanged or fixed. The initial estimates of the model parameters 
being calibrated, called prior information, are another type of data to be included in the 
inversion. 
When the selected model parameters are calibrated to the ambient conditions data and prior 
information, the changes to these parameters reflect biases in the initial estimates of the 
properties that the parameters represent, and they also reflect the inaccuracies that are inherent in 
the model because of simplifications. Additionally, biases in the property estimates for 
parameters that are fixed will also be compensated for by adjustments to the parameters being 
calibrated. In other words, biases, inaccuracies, and uncertainties in the fixed portion of the 
model will be compensated for by changes to the parameters that are being calibrated. 
The parameter calibration is performed using iTOUGH2 V3.2 (see Section 1.3.2), a code that 
provides data inversion capabilities for the TOUGH2 V 1.4 (see Section 1.3.2) simulator. The 
misfit between the ambient conditions calculated by the models and the ambient conditions data, 
as well as the misfit between the prior information and the parameters being calibrated, is 
evaluated based on the least-squares objective function. The objective function is then minimized 
using the Levenberg Marquardt algorithm (Finsterle 1999, pp. 44-45). Sensitivity coefficients are 
evaluated by means of finite differences. 
The end product is a calibrated set of model parameters that can be used to predict the present 
ambient conditions anywhere in the UZ at Yucca Mountain. These parameters can also be used

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to predict future conditions that may arise because of climate changes and/or emplacement of 
heat generating radioactive waste as well as other potential future scenarios. 
For simplification of the discussion in the remainder Section 3.6, the calibrated model 
parameters will be referred to as calibrated properties or calibrated hydrologic properties. The 
other model parameters are assumed to represent the real properties of the system. In the case of 
the GFM (CRWMS M&O 2000, I0035) and the numerical grid constructed from it as well as the 
conceptual and numerical model used to represent the processes at work in the UZ, this is 
probably a good assumption. In any case, uncertainties in these models are, as indicated above, 
incorporated into the calibrated hydrologic properties. Note that the uncertainties in other model 
parameters have been incorporated into the calibrated hydrologic properties. Thus, they are only 
appropriate for predicting present and future behavior when the other elements of the model are 
applied in the same way (e.g., the scale on which the processes are being represented must not be 
changed dramatically). In the case of the Infiltration Model, uncertainty is incorporated by 
estimating calibrated hydrologic properties for the mean, or expected, infiltration rates as well as 
for upper and lower bounds of expected infiltration. 
3.6.2 Issues 
Several important issues arise with regard to developing properties for the downstream models 
shown in Figure 3.6-1. These issues are summarized in Figure 3.6-2. 
 Calibrated hydrologic properties are required for two types of models. The first type, the 
mountain-scale model, is used to predict mountain-scale (or site-scale) behavior under 
ambient and future conditions. The second type, the drift-scale model, is used to predict 
system behavior within the potential repository horizon at the scale of the emplacement 
drifts. As discussed in Section 3.6.1, the models used to calibrate properties for use at 
these two different scales must be carefully chosen to properly represent the processes at 
those scales. 
 In situ water potential data have shown that water potential data from core may indicate 
drier or stronger matrix water potentials than actually exist in the UZ. Flint (1998, 
pp. 1819) also believes that the core data may have reflected drier than actual 
conditions and proposes a correction to the data. Flint (1998, p. 19) also states that the 
laboratory water potential and saturation data give a lower bound estimate of the matrix 
van Genuchten a parameter. The combination of these two situations gave rise to 
calibrated estimates of the a parameter for VA (CRWMS M&O 1998g, Chapter 2) that 
were probably too low. 
 The conceptual model of flow in the UZ indicates that water flow will occur mainly in 
the fractures in the welded units and mainly in the matrix in the unaltered nonwelded 
units (see Section 3.3.3). In addition to the ambient conditions data and the prior 
information, this element of the conceptual model must be considered in the property 
calibration.

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 The uncertainty of the calibrated properties is important for downstream analysis of the 
models that use the calibrated properties, particularly TSPA. However, estimating the 
uncertainty of the 196 independent calibrated properties is at best a difficult task. 
3.6.3 Analysis of Hydrologic Properties Data 
Hydrologic properties are estimated from measurements made on core and from in situ 
measurements. These estimates are either used directly for modeling flow and transport or are 
used as initial estimates of properties to be calibrated. For those properties to be calibrated, 
statistical data about the estimate are also calculated to provide a basis for evaluating the 
uncertainty of the initial estimate. Development of hydrologic properties data for input to the 
Calibrated Properties Model and numerical grids is summarized here and fully documented by 
CRWMS M&O (2000, U0090). 
The dual-permeability conceptual and numerical model is used for simulations (see 
Section 3.4.1.3), so hydrologic properties are developed for the matrix and for the fractures. 
Permeability and porosity are the primary hydrologic properties necessary for simulations of 
flow and transport. In the UZ, partially saturated flow processes are important. Relative 
permeability and water potential are described as a function of saturation using the van 
Genuchten (1980) relationships (see Section 3.4.1.4.1). Two additional hydrologic properties are 
necessary to describe the frequency of the fractures (which also describes the average size of the 
matrix blocks) and the geometrical interface area between the fractures and the matrix (which 
can also be thought of as the surface area of the matrix blocks). One set of thermal properties is 
developed for the rock itself. All of these properties are developed for the formation rock, and a 
second set is developed for the rock in fault zones. 
3.6.3.1 Matrix Property Data 
Matrix properties estimates are based on data from laboratory analysis of core recovered from 
nine deep boreholes, which penetrate to at least the bottom of the TSw, and 33 relatively shallow 
boreholes, which generally penetrate only to the top of the TSw. Collection, processing, and 
preliminary analysis of the core data are described by Flint (1998). Additional data from in situ 
water potential measurements are used to estimate the a parameter of the van Genuchten 
relationship. Collection and preliminary analysis of these data are described by Rousseau et al. 
(1997, pp. 3945; 1999, pp. 143151). 
Several other sources of data were considered but not included in the analysis. The bulk 
properties data (i.e., porosity and grain density) from the 42 boreholes indicated above are 
numerous and considered sufficient to describe those properties, so it was not necessary to 
include more recent data from the tunnels and recently drilled boreholes. Geophysical data 
characterizing porosity were not used because they include both the inter-grain porosity and 
porosity resulting from lithophysal cavities. The core data only represent the inter-grain porosity, 
and this is the property that is important for the downstream models. Data from samples 
collected at the surface of the mountain were not used because weathering of the rock can alter 
the properties so that they are not representative of properties deep in the mountain.

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Data from the Busted Butte test site, which significantly adds to the permeability characterization 
for the top of the vitric portion of the Calico Hills Formation, were not yet available at the time 
the analysis was done. Preliminary review of these data (DTN: GS990708312242.008) indicate 
that they are consistent with the calibrated permeability for this layer, shown in Figure 3.6-6. 
The data are divided by stratigraphic location corresponding to the 29 detailed hydrogeologic 
units shown in Table 3.2-2. Effective properties are calculated for each of these layers. Data from 
core are not available for Tram tuff layers (model layers tr3 and tr2), so the overlying Bullfrog 
tuff layers (model layers bf3 and bf2, respectively) are used as analogs. 
Permeability is commonly accepted to be a log-normally distributed property (de Marsily 1986, 
p. 80; Domenico and Schwartz 1990, p. 66; Freeze and Cherry 1979, p. 31). But it must also be 
considered that the core samples on which permeability is measured are much smaller than the 
average size of matrix blocks in situ, so an upscaling factor proposed by Paleologos et al. (1996, 
p. 1336) is used to correct for the size discrepancy. Thus the effective permeability is estimated 
as an upscaled geometric mean. Several layers include samples with permeability that is below 
the detection limit of the permeameters; these data are also considered when estimating the 
effective permeability. Figure 3.6-6 shows the initial estimates of matrix permeability that are 
input to the calibration process described below in Section 3.6.4. Note that while the PTn and 
vitric CHn have very high matrix permeability, the welded and zeolitic layers have much lower 
permeability. In some welded or zeolitic layers, the matrix permeability is insufficient to carry 
the estimated site average net infiltration which is 4.6 mm/yr (see Section 3.5.2.5). This net 
infiltration value is approximately equal to a permeability of 1.5  10-17 m2 under vertical 
percolation conditions. In these layers, a portion of the percolation must be carried by the 
fractures. 
Porosity is measured twice on each sample, once after drying in a low-temperature, humiditycontrolled 
oven that does not remove bound water or water hydrating clays and again after 
drying in an above-boiling oven that removes all water. Total porosity is estimated as the 
arithmetic average of data from the second measurement. Residual water content is estimated as 
the total porosity minus the arithmetic average of porosity data from the first measurement. 
Residual saturation is residual water content divided by total porosity. 
The parameters of the van Genuchten relationship, a, m, residual saturation, and satiated 
saturation, are estimated using both core and in situ data. Residual saturation, in the context of 
the van Genuchten relationship, is the amount of water that remains after the pores are fully 
drained under ambient conditions, and is calculated as indicated above. Satiated saturation, or the 
amount of water present in the matrix when zero water potential and full relative permeability 
are reached, is not measured and is assumed to be equal to full saturation. The other two 
parameters, a and m, are estimated by first fitting them to drainage data measured on core. These 
data are obtained by measuring the water potential at several points, starting with a fully 
saturated sample and gradually reducing the saturation. This gives a lower bound estimate for a. 
Second, in situ water potential data are used to give a better effective estimate of a. Figure 3.6-7 
shows that the initial estimate of the a parameter for the welded and zeolitic layers, like 
permeability, is generally lower than that of the unaltered, nonwelded layers, though there is not 
as marked a difference. Note that model layer ptn23, analogous to the detailed hydrogeologic 
unit Tpy, while in the generally nonwelded PTn, represents the partially to moderately welded

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interior of the Yucca Mountain tuff (Tpy) lithostratigraphic unit (Flint 1998, p. 27), and this is 
reflected in the value of the a parameter (i.e., it is lower than the other a parameter values in the 
PTn and similar to values in the TCw and TSw). 
3.6.3.2 Fracture Property Data 
Fracture properties estimates are based on permeability data from in situ air-injection tests 
conducted in four surface based boreholes and boreholes in alcoves of the ESF, porosity data 
from gas tracer tests in boreholes in Alcove 5, and fracture mapping from the ESF, ECRB, and 
surface based boreholes. Air-injection testing is described by LeCain (1997; 1998) and Rousseau 
et al. (1999) and in CRWMS M&O (2000, U0015). 
As with the matrix property data, some fracture property data were considered but not used. In 
particular, fracture frequency data from the surface of the mountain, measured on outcrops and at 
the Large Block Test area, are not considered representative of fracture frequencies in the deep 
subsurface because unloading, or the absence of overburden at the surface, is likely to have 
enhanced fracturing. Permeability data from air-injection testing in the Main Drift Niches (1-4) 
were not used because the support scale is 0.3 meters (one foot), and thus the data may not be 
representative of the fracture permeability at the scale of interest. The support scale of the airinjection 
test data that were used is from 1 to 12 meters (CRWMS M&O 2000, U0090, 
Section 6.1.1.1) 
There are also two new data sets that have become available since the analysis was performed. 
First, small-scale fracture data (DTN: GS990908314224.009) (data on fractures shorter than the 
0.3 and 1.0 meter cutoff lengths of Detailed Line Survey fracture data) are likely to significantly 
affect only the estimate of the interfacial area between the fractures and matrix. If the interfacial 
area is underestimated, the calibrated active fracture parameter (see Section 3.3.4 for discussion 
the active fracture model for which this is the parameter) will be affected and will correct for it. 
Inclusion of these data may also affect the estimate of the van Genuchten a parameter, but it will 
not be a very large change because the van Genuchten a parameter is proportional to the cube 
root of fracture frequency (CRWMS M&O 2000, U0090, Section 6.1.2). Second, air injection 
data from Niche 5 in the ECRB Cross Drift (DTN: LB002181233124.001) show larger 
permeabilities for the Tptpll than previously measured in tests with a larger support scale. 
Reevaluation of the decision to exclude these small support-scale data is appropriate, though, 
preliminary evaluation of these data indicate that the impact on the calibrated properties is not 
likely to be large. 
Air injection and gas tracer test intervals are grouped by lithostratigraphic unit (see Table 3.2-2) 
for analysis. Similarly the fracture mapping data are divided at lithostratigraphic unit contacts. 
Data are only available to the top of the CHn. Fracture properties in this unit and below are 
assigned on the basis of analogous layers. 
Like matrix permeability, fracture permeability is estimated as the geometric mean of the data. 
Figure 3.6-6 shows that the initial estimates of fracture permeability are much higher than the 
initial estimates of matrix permeability in the welded layers, but in the nonwelded layers they are 
nearly equal to and sometimes lower than the matrix permeability. The deeper, nonwelded layers

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have the lowest permeability, but the initial estimates of fracture permeability only cover a range 
of about three orders of magnitude, which is much less than the range of matrix permeability. 
Fracture frequency and intensity and the interfacial area between fractures and matrix are 
estimated using fracture mapping data from the tunnels and boreholes. Fracture intensity is the 
length of fractures per unit area, while frequency is the number of fractures per unit length. 
Intensity is the better number to use because it accounts for both the number of fractures and the 
length of those fractures, but it is only available where a tunnel is present. For deeper layers, 
borehole data, which only give frequency, are used. The intensity or frequency data are used to 
estimate the interfacial area between the fractures and matrix, which can also be thought of as the 
surface area of the matrix blocks. 
Analysis of gas tracer tests in the Tptpmn suggests that the fracture porosity in this layer is 1% 
(CRWMS M&O 2000, U0090, Section 6.1.3). This porosity datum is extrapolated to other layers 
using the cubic law (CRWMS M&O 2000, U0090, Section 6.1.3) to relate porosity, fracture 
intensity or frequency, and permeability. This method was chosen so that all possibly relevant 
fracture data were considered when estimating fracture porosity. An alternative approach would 
have been to use the gas tracer estimate of fracture porosity in the Tptpmn directly for at least the 
TSw if not all layers. This would ignore any information about fracture porosity contained in the 
fracture intensity (and/or frequency) and permeability data. CRWMS M&O (2000, U0090, 
Section 6.1.4) further discusses the defensibility of the approach used. 
No water potential or relative permeability data are available for fractures at Yucca Mountain, so 
these relationships are based on theory. The van Genuchten relationships are used for the 
fractures as they are for the matrix. The van Genuchten m parameter is estimated from fracture 
permeability and intensity data for the Tptpmn, and capillary theory (CRWMS M&O 2000, 
U0090, Section 6.1.2). The van Genuchten a parameter is assumed to be equal to the inverse of 
the air-entry pressure, again calculated using fracture permeability and frequency or intensity 
data and capillary theory (CRWMS M&O 2000, U0090, Section 6.1.2). Figure 3.6-7 shows that 
like fracture permeability, the estimate of the a parameter for the fractures has much less 
variability than in the matrix. Unlike permeability, the a parameter for the fractures is 
consistently higher than that of the matrix. The impact of assumptions used to estimate fracture 
van Genuchten parameters is insignificant because any estimation biases due to these 
assumptions are corrected for during the calibration phase of property development described in 
Section 3.6.4. 
3.6.3.3 Fault Property Data 
As discussed in Section 3.4.2.2, faults are divided into just four layers, corresponding to the 
major units (CHn and CFu are combined into one major unit for the faults). Very few property 
data specifically about faults exist. A small number of permeability measurements from airinjection 
tests have been performed and are described by LeCain (1998). These data indicate 
that, at least within the welded units, the fractures in the faults are more permeable and porous 
than the fractures in the formation (or nonfaulted rock). 
Matrix properties for faults are estimated by calculating the layer thickness weighted averages 
for each major unit from the matrix properties estimated for the formation. As appropriate to

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flow perpendicular to bedding, the harmonic mean is used to estimate the effective permeability 
and thermal conductivity. The effective a parameter is also estimated using the harmonic mean. 
All other matrix properties except specific heat for faults are estimated using the arithmetic 
mean. Specific heat is estimated as documented by CRWMS M&O (2000, U0090, Section 6.3). 
Fracture permeability estimates for faults are based on cross-hole air-injection tests performed in 
Alcoves 2 and 6. However, these estimates are only available for the TCw and TSw major 
hydrogeologic units. For the PTn and CHn/CFu major hydrogeologic units, the fault fracture 
permeability is estimated by assuming that the permeability structure of the major hydrogeologic 
units is the same in the faults and in the formation (outside faults). Permeability structure can be 
reasonably assumed to be correlated to rock type (i.e., welded or nonwelded). The impact of this 
assumption is minimized by the subsequent property calibration. 
Fracture frequency is estimated as the inverse of the layer thickness weighted average spacing. 
Fracture aperture is then calculated in the same manner as for the formation, using the cubic law. 
The increase in the fault fracture aperture as compared to the formation fracture aperture is 
applied to the major unit average fracture porosity to estimate fracture porosity for faults. 
3.6.3.4 Thermal Property Data 
Rock thermal properties, wet and dry conductivity and specific heat, are estimated from thermal 
measurements made on core (Brodsky et al. 1997) and porosity and grain density estimates made 
by Flint (1998). Unlike the hydrologic properties, these properties are not calibrated and are used 
directly by the downstream models. 
3.6.4 Calibrated Properties Model 
The Calibrated Properties Model incorporates many different data from analyses and models into 
one model to develop calibrated properties for the UZ Flow and Transport Model that are 
consistent with all these sources. Figure 3.6-1 shows the inputs to the Calibrated Properties 
Model (CPM). At the heart of the calibrated properties model is the conceptual and numerical 
model of Yucca Mountain. This specifies how it is thought that the system behaves under 
ambient conditions and how to simulate that behavior with a numerical model. The numerical 
grids provide a model of the geologic layering on which the simulations are performed. The 
Infiltration Model provides the infiltration rates for the upper boundary condition. Hydrologic 
properties data, described above, are used to specify properties for each of these layers. The 
model is calibrated to saturation, water potential, and pneumatic pressure data by varying some 
of the properties. Initial estimates of these properties are included as prior information (Carrera 
and Neuman 1986, pp. 199210). 
The properties that are calibrated are fracture and matrix permeability (kf and km), the fracture 
and matrix van Genuchten a and m parameters ( af, am, mf, and mm), and the active fracture 
parameter ( .) (see Section 3.3.4 for discussion the active fracture model for which this is the 
parameter). Except for ., these are also the properties for which prior information is provided. 
All other properties are used unchanged from the initial hydrologic properties estimates 
described in Section 3.6.3.

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Figure 3.6-3 shows the sequence of numerical grids and data that is used to produce the 
calibrated properties. The 1-D model, which is actually a collection of 1-D columns, is used to 
first calibrate some of the formation properties to saturation and water potential data. The same 
model, with the updated properties, is then used to calibrate the remaining formation properties 
(fracture permeabilities from the surface to the bottom of the TSw) to pneumatic data. The fully 
updated properties are then again checked against the saturation and water potential data, and 
any further calibration that is needed is performed. If the properties are updated, they are 
checked against the pneumatic data and refined if needed. In general, this process is iterated until 
no further property changes are needed to maintain the match to all the data. The use of this type 
of iterative process for model calibration is not limited to the YMP. Bullivant and OSullivan 
(1998, pp. 5358) have followed a similar iterative procedure for calibrating a geothermal 
reservoir model to data gathered prior to and during reservoir development. They have then 
successfully used the calibrated model in a predictive mode. 
These calibrated mountain-scale formation properties are then used as input to the 2-D model, 
which is used to calibrate the fault properties. The 2-D model is also alternately calibrated to 
saturation and water potential data and then to pneumatic data until a final fault property set is 
produced. The combination of the mountain-scale formation properties and the fault properties 
gives a comprehensive, mountain-scale calibrated property set. 
The calibrated mountain-scale formation properties are also used as input for development of 
drift-scale properties. These are developed by recalibrating fracture permeabilities to the smallscale 
(drift-scale) saturation and water potential data and air permeability prior information. 
Calibrated properties, both mountain scale and drift scale, are produced for three different 
present-day infiltration scenarios. As described in Section 3.5, the base case infiltration scenario 
provides the most likely estimate of present-day infiltration. The upper and lower bound 
infiltration scenarios are intended to provide reasonable bounds of possible present-day 
infiltration. By providing property sets calibrated using each of these scenarios, the impact of 
future climate variability on flow and transport can be evaluated in light of the uncertainty of 
present-day infiltration. 
Development of saturation, water potential, and pneumatic data; prior information; and 1-D and 
2-D inversions are documented by CRWMS M&O (2000, U0035). The misfit between the 
ambient conditions calculated by the models and the ambient conditions data as well as the misfit 
between the prior information and the parameters being calibrated all contribute to the objective 
function, which is the quantitative measure that the inversion code, iTOUGH2 V3.2, attempts to 
minimize. Saturation and water potential data are evaluated after steady-state conditions are 
reached. Pneumatic data are evaluated after a 30-day, barometric pumping initialization period. 
During the inversion of saturation and water potential data for the mountain-scale formation 
property calibration, the parameter selection feature of iTOUGH2 V3.2 is used. When this 
feature is used parameters (hydrologic properties being calibrated) that have an insignificant 
impact on the objective function are automatically deselected for a short period during the 
inversion. The inversion can then be performed more quickly because the complete set of 
hydrologic properties being calibrated is not being continuously evaluated.

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3.6.4.1 1-D Inversions 
The 1-D submodel is used for the calibration of formation properties because there are 173 
separate formation properties to be calibrated. This requires numerous forward simulations, and a 
1-D model provides the most efficient way to perform them. The 1-D submodel consists of 11 
vertical columns, shown schematically in Figure 3.6-4, that reflect the stratigraphy at the 11 
boreholes for which there are saturation, water potential, and/or pneumatic data suitable for 
inversion. 
The use of a 1-D, vertical model implicitly assumes that flow can be adequately approximated as 
one-dimensional and vertical, i.e., that lateral flow is not important. In the TCw, PTn, and TSw, 
this assumption is substantiated by the lack of perched water. The presence of perched water is 
an indicator of potential lateral flow in the UZ (see Sections 3.3.2 and 3.7.3.3). It is believed that 
in the PTn, small amounts of lateral flow may occur because of capillary gradients from areas 
under high infiltration to areas under low infiltration. To compensate for this, the source term at 
the upper boundary, representing infiltration, is calculated as an average of the infiltration rates 
within 200 m of the borehole. At the bottom of the TSw and below, perched water does exist in 
some areas, especially to the north. However, the presence of perched water and the potential for 
lateral flow is ignored while calibrating properties using a 1-D model. Perched water is 
investigated with the 3-D model (see Section 3.7.3.3). 
Saturation data measured on core from seven boreholes are included in the inversion. The 
saturation data are much more numerous than the model layers, so the data are averaged for each 
model layer before being included in the inversion. Water potential data measured in situ in four 
boreholes and pneumatic data measured in situ in five boreholes are included in the inversion. 
Several other sources of data were considered but not included in the inversion. Water potential 
data measured on core are not used. Core recovered from boreholes undergo a small amount of 
drying due to drilling with air and handling at the surface. While this drying is not significant for 
the saturation data and can be easily quantified and accounted for in the data uncertainty, it 
appears to be more significant for the water potential data. More importantly, it is not easily 
quantified. Saturation data from shallow boreholes were not used because they generally 
represent only the upper layers and would give only marginal improvement to the calibrated 
properties for a significantly increased computational burden. Geophysical saturation data are not 
used because lithophysal porosity cannot be easily separated out of the measurement. 
3.6.4.1.1 Calibrated, Mountain-Scale Properties 
As discussed above, the saturation and water potential data are inverted first. Additionally, a 
subjective criterion is used to evaluate the adequacy of the calibrated, mountain-scale properties 
to honor the conceptual model of flow partitioning between the fracture and matrix. Water flow 
is required by the conceptual model to be predominantly in the fracture continuum in the welded 
and zeolitic layers and predominantly in the matrix in the nonwelded layers (see Section 3.3.3). 
After a suitable initial match is obtained between the simulation and the saturation and water 
potential data, the pneumatic data are inverted to calibrate the fracture permeability. Pneumatic 
data inversion is itself a two-step process. First, the permeabilities of each layer in the TCw and

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PTn are calibrated. Then the permeabilities of layers tsw31 through tsw37 are calibrated as a 
whole. One factor is estimated to modify all the initial fracture permeabilities. This is done 
because the pneumatic data show insignificant attenuation and lag between sensors in the TSw. 
This means that inversion of these data can at best provide a minimum permeability necessary to 
match the data. The permeabilities are modified by a single factor to retain the permeability 
structure of the TSw indicated by the initial estimates. 
The calibrated properties are rechecked against the saturation and water potential data, and any 
adjustments to the calibrated properties that are necessary are made (e.g., to keep the water flow 
in the matrix through the unaltered, nonwelded layers). The new properties are then checked 
against the pneumatic data. For all three property sets, corresponding to the three infiltration 
scenarios, this check showed that no further calibration was necessary. Figure 3.6-4 shows the 
match between the final calibrated simulations and the saturation, water potential, and pneumatic 
data for the base case infiltration scenario. 
3.6.4.1.2 Calibrated, Drift-Scale Properties 
The calibrated properties produced using mountain-scale data are not appropriate for simulation 
of processes at the drift scale such as the seepage models (Section 3.9) or the THC Seepage 
Model (Section 3.10). Specifically, the use of pneumatic data that represent the mountain-scale 
process of barometric pumping of the UZ produces fracture permeabilities for the potential 
repository horizon and neighboring layers that are larger than appropriate for drift-scale 
modeling. 
To provide drift-scale properties, the fracture permeabilities for model layers tsw32 through 
tsw37 are recalibrated to saturation and water potential data and to air-injection derived fracture 
permeability prior information. The calibrated mountain-scale formation properties are used for 
all other properties. With the pneumatic data taken out of the inversion, the fracture 
permeabilities return to near their initial estimate values (i.e., prior information values). 
3.6.4.2 2-D Inversions 
Fault properties are calibrated using a 2-D model of an east-west cross section at borehole USW 
UZ-7a, shown schematically in Figure 3.6-5. Use of a 2-D model implies that flow constrained to 
the vertical and east-west directions adequately approximates ambient conditions. The dip of the 
bedding is approximately parallel to the cross section, and since bedding is most likely to control 
lateral flow, the assumption is reasonable. It is also reasonable to assume that flow in the fault, 
which strikes perpendicular to the cross section and dips nearly vertical, is adequately 
represented by a 2-D model. 
Borehole USW UZ-7a penetrates the Ghost Dance fault, and data from it represent ambient 
conditions in a fault at Yucca Mountain. This is the only borehole that provides a range of data 
with respect to faults. Data are available only from the upper portion of the TSw to the surface. 
Because of the lack of data for the lower layers, properties for faults in the CHn/CFu major unit 
are not included in the calibration. 
The same property types as were calibrated for the mountain-scale formation properties are 
calibrated for the faults. The same approach is also followed, with the exception that the

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proportion of flow in the fractures and matrix is not a criterion for an acceptable calibration 
because this criterion is only applicable to the formation. Figure 3.6-5 shows the match between 
the calibrated simulation and the saturation, water potential, and pneumatic data for base case 
infiltration. 
Note that Figure 3.6-5 shows that even though a single set of properties is used for each of the 
major hydrogeologic units, the results of the simulation still vary significantly. This is because 
the fault is narrow and the simulated conditions are controlled by the properties of the 
surrounding formation. Because this is the case, the calibrated fault properties for the base case 
infiltration are evaluated for the upper and lower bound infiltration scenarios and are found to be 
suitable for all three infiltration scenarios. 
3.6.5 Results and Discussion 
3.6.5.1 Results 
Simulations using the calibrated properties show a significant improvement in the match between 
the simulated ambient conditions and the data. In general, there is less than an order of 
magnitude difference between the calibrated properties and the prior information. The calibrated 
matrix permeability shows nearly the same structure as the initial estimates as shown in 
Figure 3.6-6. The most pronounced changes are those of more than an order of magnitude. At the 
top of the PTn and again at the top of the CHn, the matrix permeability increases approximately 
one and a half orders of magnitude. These changes result from the criterion discussed above for 
matrix dominated flow in the PTn and vitric CHn layers. For flow to transition from the fractures 
in the welded TCw and TSw, the respective underlying layers must have a high permeability, so 
that percolating water can be imbibed quickly. The matrix permeability of layers tsw36 and 
tsw37 near the bottom of the TSw also increases more than one order of magnitude. In these 
layers, as well as tsw34, the initial estimate is extremely low and causes nearly fully saturated 
conditions to develop in the simulations. The increased permeability allows the saturations to be 
reduced to match the data, as shown above in Figure 3.6-4. 
The most widespread exception to the generally small property changes are the calibrated 
mountain-scale fracture permeabilities in the TCw and TSw, which are increased significantly 
over the initial estimates. These high permeabilities are necessary to reproduce the pneumatic 
pressure data that show little or no attenuation or lag of the barometric signal as it crosses these 
units. This increase can be attributed to upscaling. The scale of the data from which the initial 
estimates of fracture permeability were made is on the order of 10 meters (the scale of the drifts). 
The scale on which the process of barometric pumping of the thick unsaturated zone occurs is 
hundreds of meters (the scale of the mountain). Note that for the drift-scale properties, the 
pneumatic data are not considered so that the calibrated fracture permeabilities reflect the scale 
of the initial estimate. 
Like the calibrated matrix permeabilities, generally only small differences appear between the 
initial estimates and the calibrated mountain-scale fracture and matrix van Genuchten a 
parameter values, as shown in Figure 3.6-7. The larger changes are observed in the same layers 
and for the same reasons as stated above for the matrix permeabilities. Matrix a at the top of the 
PTn is reduced, increasing the suction into the matrix, so that water will be imbibed into the

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matrix as it percolates into the PTn. At the bottom of the PTn and top of the TSw, fracture a is 
reduced so that flow will transition into the fractures through the TSw. Near the bottom of the 
TSw, matrix a is increased to reduce suction and consequently reduce the nearly saturated 
conditions initially predicted by the simulations. 
The difference between the fracture and matrix van Genuchten a parameter is approximately two 
orders of magnitude, where previous calibrated property sets (e.g., for VA (CRWMS M&O 
1998g, Chapter 2)) indicated approximately three orders of magnitude difference. This is a direct 
result of using only in situ water potential data for both the initial estimate of the matrix van 
Genuchten a parameter and in the data inversion, whereas the previous models had included core 
data. Use of the current calibrated properties produces thermal-hydrologic simulation results that 
closely match the expected performance (CRWMS M&O 2000, N0120/U0110, Section 6.2). 
The calibrated mountain-scale properties for the upper and lower bound infiltration scenarios are 
similar to those shown and discussed here (CRWMS M&O 2000, U0035, Section 6.1). 
3.6.5.2 Uncertainty 
With a total of 194 calibrated properties (all calibrated formation and fault properties), 
determining estimation uncertainty is conceptually and numerically difficult. Cross-correlations 
between the properties make the uncertainties of individual properties very large. Furthermore, 
the linearity and normality assumption underlying the error analysis implemented in iTOUGH2 
V3.2 is invalid if the estimation uncertainties become very large as a result of cross-correlations. 
However, as shown above, the calibrated properties generally do not vary much from their initial 
estimates. Where the calibrated properties have changed significantly with respect to the prior 
information, the data influencing the change reflect processes not completely accounted for in 
the initial model setup. For example, water flow transition from fractures to matrix at welded to 
nonwelded interfaces is likely a result of processes which occur at a subgrid scale, so the changes 
of calibrated properties at these interfaces incorporate the effects of these processes. Because the 
initial and calibrated properties are generally similar, the uncertainty of the initial property 
estimates is assumed to be an approximate surrogate for the uncertainty of the calibrated 
properties. Further confirmation of the appropriateness of this approach is warranted and can be 
achieved with sensitivity studies and/or Monte Carlo simulations. However, either of these 
confirmation approaches will still be of a limited nature because of the extremely large number 
of properties calibrated. 
3.6.5.3 Validation 
Validation of the Calibrated Properties Model, in the strict sense of validation being comparison 
to data not used for calibration, is performed by using the 3-D model. This is documented by 
CRWMS M&O (2000, U0050, Section 6.8). In situ water potential data measured in boreholes 
off the ECRB Cross Drift compare well with the predicted water potentials as shown in 
Figure 3.6-8. Although the predicted water potentials are generally lower, the difference is only a 
few tenths of a bar (1 bar = 105 Pa). The difference is exaggerated by the logarithmic scale 
because the water potentials are so close to zero. Pneumatic pressure data also compare well to 
the predicted pneumatic pressures as shown in Figure 3.6-8. These data partially show that the 
calibrated properties are valid for predicting ambient conditions and that the assumptions of one

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and two-dimensional flow are suitable for use in the calibration process. That the Calibrated 
Properties Model works for ambient thermal simulations (Section 3.12), drift heating simulations 
(Section 3.10.4), and ambient geochemistry simulations (Section 3.8) also builds confidence in 
the validity of the model under a wider range of conditions. However, these simulations also 
allow other elements of their models to vary in order to match data, which might hide 
inaccuracies in the Calibrated Properties Model. 
Validation of the Calibrated Properties Model, in the regulatory sense of building confidence that 
the model is appropriate for its intended use, is also partially satisfied by meeting the following 
criteria. 
 The model is calibrated within experimental data sets. 
 The calibrated properties are reviewed for reasonableness and consistency with respect 
to the prior information. For large differences between the calibrated properties and the 
prior information, consistency with respect to other data is necessary (see 
Section 3.6.5.1). 
 Calibration exercises for previous incarnations of calibrated properties for the UZ at 
Yucca Mountain have been published in open literature (i.e., Bandurraga and 
Bodvarsson 1999, pp. 2546; Ahlers et al. 1999, pp. 4768). 
Meeting these criteria builds confidence that the Calibrated Properties Model is appropriate for 
its intended use, in particular for predicting ambient conditions in the UZ for the present-day 
climate. The appropriateness for the other intended uses of predicting conditions under possible 
future scenarios, including changed climate and potential repository heating, is not as certain. 
This is because the properties were calibrated using present-day net infiltration estimates and 
were checked against present-day thermal and geochemical conditions. The drift-scale calibrated 
properties have also been checked against thermally perturbed conditions. Because there is less 
data about conditions under possible future scenarios (which is one of the reasons that 
predictions are necessary), and because the properties cannot be calibrated to these data, the 
confidence in the appropriateness of the calibrated properties for predictions of conditions under 
possible future scenarios is necessarily less than the confidence in the appropriateness of the 
calibrated properties for predictions of conditions under the present-day scenario. However, the 
calibrated properties do represent the best estimate of properties that are valid for all intended 
uses. 
3.6.5.4 Alternative Conceptual Models 
The main element of the conceptual model for the properties of Yucca Mountain developed as 
documented here is that the thermal-hydrologic system can be described by homogeneous layers. 
An alternative to this conceptual model is that the properties are heterogeneous and distributed 
three-dimensionally within the UZ. The Rock Properties Model (CRWMS M&O 2000, I0040) 
documents properties developed in such a way. The spatial variability of matrix porosity, the 
most numerous data available, is calculated and used to predict the spatial distribution not only 
of matrix porosity, but also matrix permeability, bulk density, and thermal conductivity. The

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distributions of these three other properties are predicted by developing correlations between 
them and porosity. 
The advantage of this type of model is that properties vary not only from layer to layer but also 
within layers. It is thus a more accurate representation of the properties data. However, several 
disadvantages arise from using this type of model as opposed to the homogeneous layer model. 
Distributed properties models need numerous data points to develop and support the choice of 
the spatial distribution. When data are sparse, correlations are necessary, but these correlations 
are simplifications of complex relationships between properties, which may lead to 
misrepresentation of the distribution. For example, the Rock Properties Model develops a 
correlation between porosity data, which are very numerous, and permeability data, which are 
not nearly as numerous (CRWMS M&O 2000, I0040, Section 6.4.5). While this correlation 
captures the trend of the relationship between the two properties, the data do not show an exact 
one-to-one correlation. Thus the distributed model of permeability that is produced has lost some 
of the original information about the distribution of permeability. Distributed properties models 
are also difficult to calibrate to other data (e.g., saturation, water potential, and pneumatic 
pressure data). Several approaches can be used to calibrate distributed properties models, but 
each has its pitfalls. In one approach, only the properties in the local area of a data point are 
varied, but this will have no effect on predictions where there are no data because the properties 
there are not changed. This approach also involves calibration of many more properties than the 
approach used for producing calibrated properties for the current UZ Flow and Transport Model. 
A second approach, which is a variant on the first approach, is to use the calibrated properties to 
re-estimate the property distributions iteratively during the data inversion, but this has the 
disadvantage of being a very computationally intensive approach. A third approach is to group 
the properties together, such as by layer, so that the mean of the group can be varied to match a 
set of data. However, this is very much like the approach used here and is not likely to be a 
significant improvement. 
A distributed properties model is an important alternative conceptual model to consider 
especially where a homogeneous boundary condition, such as potential repository heating or 
release of radionuclides from the potential repository horizon is applied. Work is currently being 
performed to address evaluation of this model. 
Deterministic models of the hydrologic properties are also an alternative, but are not favored 
because they only use properties data and do not incorporate other data, such as ambient 
conditions data. Related to the deterministic model would be the alternative of using Monte 
Carlo simulations based on parameter distributions developed from the properties data. In 
addition to having the same disadvantage of not using as much data as possible, Monte Carlo 
simulations evaluate unlikely parameter combinations with the same weight as more likely ones, 
and they are computationally intensive. 
3.6.6 Summary and Conclusions 
The UZ properties are developed for use in flow, seepage, transport, and coupled process 
simulations. Figure 3.6-9 shows the resolution of the important issues to property development 
raised at the beginning of this section. Mountain-scale and drift-scale properties are developed 
for use in flow, transport, and coupled process simulations at mountain-scales and drift-scales,

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respectively. The key difference between the two scales is in the fracture permeabilities and only 
those of the TSw are of interest for the drift-scale calibrated properties. Fracture permeabilities 
of 10 to 70  10-12 in the TSw are estimated for the mountain-scale calibrated properties, while 
for the drift-scale calibrated properties, the TSw fracture permeabilities are close to their initial 
estimate range of 0.1 to 1  10-12. 
The use of only in situ water potential data has significantly improved results compared to 
previous calibrations that included core data. Predicted water potentials in the TSw are 
approximately -105 Pa (1.0 bar). Calibrated van Genuchten a parameter values for the TSw 
fractures and matrix differ by approximately two orders of magnitude. These results are a large 
change from results reported for VA (CRWMS M&O 1998g, Chapter 2) and provide calibrated 
properties for thermal-hydrologic simulations such that they are in better agreement with 
expected and observed results. 
The conceptual model of water flow that is dominantly in the matrix in the unaltered, nonwelded 
layers and dominantly in the fractures in the welded layers is satisfied by the calibrated 
properties. 
Calibrated properties uncertainties are difficult to estimate. In general, the calibrated properties 
do not change significantly with respect to the initial estimates, except where the calibrated 
properties must compensate for model simplifications, such as those required to obtain flow 
repartitioning between fractures and matrix. The assumption that the uncertainty of the calibrated 
properties equals the uncertainty of the initial estimates of those properties is based on the small 
changes in the calibrated properties relative to the prior information, but further substantiation of 
this assumption is necessary. 
The calibration of hydrologic properties for the UZ Flow and Transport Model is an important 
step in the models development. This is true not only because of the number of users of these 
properties but also because it allows the large amount of data from the UZ at Yucca Mountain to 
be combined. With the calibrated properties that result from these combined data, the UZ Flow 
and Transport Model can provide the best estimates of present and future conditions in the UZ at 
Yucca Mountain.

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3.7 FLOW MODEL 
The Flow Model for the UZ, as described in this section, is divided into two categories: (1) UZ flow 
submodels (Section 3.7.3) and (2) site-scale flow analysis (Section 3.7.4). The submodels consist of 
studies of PTn, CHn/perched water, and major fault effects developed for specific studies and 
analyses. The site-scale flow analysis includes the results of modeled percolation fluxes and flow 
fields, and fracture and matrix flow components. 
3.7.1 Introduction 
The Flow Model and its submodels have been developed to simulate past, present, and future 
hydrological, geothermal and geochemical conditions in the UZ of Yucca Mountain. Over the 
past decade, Yucca Mountain has been studied extensively, and many types of data have been 
collected. These data have been used to develop conceptual and numerical models for the 
hydrological, geothermal and geochemical behavior of the site. These models have been used to 
simulate ambient conditions and perform predictive studies of changes in the mountain caused by 
climate-related, thermal, and geochemical perturbations. The comprehensive model that 
integrates all pertinent data from the UZ at Yucca Mountain is the 3-D, site-scale UZ Flow and 
Transport Model (e.g., Bodvarsson et al. 1999, pp. 324; Wu et al. 1999a, pp. 185215). 
3.7.1.1 Objectives 
The primary objectives in developing the Flow Model for the UZ are: 
 To integrate the available data from the UZ system into a single, comprehensive, and 
calibrated 3-D model for simulating the ambient hydrological, thermal, and geochemical 
conditions and predicting system response to future climate conditions 
 To develop a number of submodels with representative boundary and initial conditions 
specifically for detailed studies of perched water, percolation through the PTn, flow 
through CHn zeolitic units, and thermal effects from the potential repository heat after 
waste emplacement 
 To quantify the flow of moisture, heat, and gas through the UZ, under present-day and 
estimated future climate scenarios 
 To predict groundwater flow patterns from the potential repository to the water table 
 To contribute model parameters and model conditions for other specific studies, such as 
seepage into drifts 
 To provide Performance Assessment and Repository Design with a defensible and 
credible model that accounts for relevant UZ flow processes.

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3.7.1.2 UZ Flow Issues 
The Flow Model is an integrated process model for the YMPs Repository Safety Strategy and 
for support of the License Application (LA). The Total System Performance Assessment for Site 
Recommendation (TSPA-SR) will use the UZ flow simulations to provide input to other models 
such as ambient and thermal drift-scale models, the Mountain-Scale Thermal-Hydrological (TH) 
model, and the Transport Model. The Flow Model and its submodels provide estimates of 
important processes relevant to UZ flow regarding the performance of the potential repository, all 
of which contribute to the TSPA-SR and TSPA-LA. 
The important issues regarding UZ flow and transport are illustrated in Figure 3.7-1, including 
the following: 
 The spatially and temporally averaged values of the percolation flux at the potential 
repository horizon 
 The components of fracture and matrix flow and interactions within and below the 
potential repository horizon 
 The effects of observed perched water zones, and associated flow barriers and lateral 
flow diversion 
 The probable flow paths from the potential repository to the water table 
 The effects of faults on flow and transport processes 
 The role played by the PTn unit in lateral flow diversion and damping of infiltration 
pulses 
 Groundwater flow and potential radionuclide migration paths from the potential 
repository to the water table or from the land surface to the repository level, and 
breakthrough curves and collection areas at the water table. 
In developing the Flow Model, much emphasis has been placed on addressing these issues and 
preparing a defensible and credible UZ model for Yucca Mountain to evaluate its potential as an 
underground radioactive waste repository. Major activities, as discussed in this report, include 
the model calibration studies of 3-D UZ flow, perched water, geochemistry, and geothermal 
conditions, and model validation efforts.

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3.7.2 Description of the Flow Model 
The fundamental goal of developing the Flow Model is to conceptualize and represent the UZ 
system of Yucca Mountain using a computer model. The Yucca Mountain is a complex, 
heterogeneous hydrogeological system and is subject to many physical and geochemical 
processes. The Flow Model and its submodels are designed to capture these processes. The 
development of the Flow Model and its submodels consists of the following steps: 
 Development of a conceptual hydrogeological model for moisture, gas and heat flow, 
and tracer/chemical transport processes in the UZ system 
 Representation of the hydrogeological system using a 3-D computer model 
 Integration and incorporation of available field and laboratory observations and data into 
the model 
 Model calibration and sensitivity studies, including both inverse and direct modeling 
efforts, to estimate model input parameters and conditions and evaluate different 
conceptual models 
 Model applications including predictive and sensitivity studies. 
Geological Model and Numerical GridsThe Flow Model and its submodels are built on the 
current geological conceptual model of the GFM 3.1 and ISM 3.0, as discussed in Section 3.2 of 
this PMR. The development and features of the 3-D model grids with the geological model are 
discussed and documented in the AMR Development of Numerical Grids for UZ Flow and 
Transport Modeling (CRWMS M&O 2000, U0000, Section 6.1). In this geological model and 
the associated numerical grids, the geologic formations within the UZ have been reorganized into 
layered hydrogeologic units, based primarily on the degree of welding of the Yucca Mountain 
tuffs (see Section 3.2.2). These are the Tiva Canyon welded (TCw) hydrogeologic unit, the 
Paintbrush nonwelded unit (PTn) (consisting primarily of the Yucca Mountain and Pah Canyon 
Tuffs and their bedded tuffs), the Topopah Spring welded (TSw) unit, the Calico Hills 
nonwelded (CHn) unit, and the Crater Flat undifferentiated (CFu) unit (see Figure 3.7-2a). 
The 3-D UZ Flow Model domain (Figure 3.7-2a) is represented using a 3-D numerical grid, as 
shown in Figure 3.7-2b (CRWMS M&O 2000, U0000, Section 6.7). The plan view of the model 
grid (as well as represented model domain) is given in Figure 3.7-3. The 3-D UZ model grid, 
designed for simulations of 3-D flow fields delivered for use in TSPA-SR calculations, uses 
relatively refined meshes in the vicinity of the proposed repository, located near the center of the 
model domain. Also, shown in Figure 3.7-3 are the locations of several boreholes, used in model 
calibrations and analyses. The model domain is selected to focus on studies at and near the 
potential repository area and to investigate effects of different infiltration scenarios and major 
faults on fluid and heat flow and radionuclide migration around and below the potential 
repository.

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Modeling ApproachThe numerical modeling approach used in the Flow Model, as discussed in 
details in Section 3.4.1, is based on a mathematical formulation of the TOUGH2 code V1.4 
(STN:10007-1.4-01) (Pruess 1991) for coupled multiphase, multicomponent fluid and heat flow 
through porous and fractured rock. The numerical scheme of the TOUGH2 family of codes is 
based on the integral finite-difference method. The mass conservation equations for air, water 
and chemical constituents and thermal energy equations are discretized in space using the 
integral finite-difference method, without any reference to a global system of coordinates. This 
offers the advantage of being applicable to regular and irregular geometries of gridding in one, 
two, and three dimensions. The method also makes it possible, by means of simple preprocessing 
of geometric data, to implement double- and multiple-porosity, or dual-permeability methods for 
treatment of flow in fractured porous media. In the TOUGH2 formulation, time discretization is 
fully implicit using a first-order backward finite-difference scheme. The resulting discretized 
finite-difference equations for mass and energy balances are nonlinear and are solved 
simultaneously using the Newton/Raphson iterative scheme. 
Fracture-Matrix InteractionFracture and matrix flow in the UZ model and its submodels is 
treated using the dual-permeability conceptual model. In this dual-continua modeling approach, 
as discussed in Section 3.4.1.1, flow and transport processes at Yucca Mountain are simulated by 
two overlapping fracture-matrix systems with interactions between them. The dual-permeability 
concept represents each grid block by a fracture and matrix element. Because each fracture grid 
block is associated with only one matrix element, fracture-matrix flow must be approximated as 
quasi-steady state (Warren and Root, 1963, pp. 245255). Global flow occurs within both 
fracture and matrix continua. When applied to the Flow Model, the traditional dual-permeability 
concept is further modified using the active fracture model (Liu et al. 1998, pp. 26332646) to 
represent effects of liquid flow channeling and fingering through fractures, which may limit flow 
into the matrix system (CRWMS M&O 2000, U0030, Section 6.4.5). 
Model ConditionsIn the Flow Model, the UZ system is represented by a multilayer sequence of 
hydrogeologic units, with rock properties estimated from field measurements and modeling 
studies (Section 3.5). The UZ model domain (Figure 3.7-2 and 3.7-3) covers a total area of 
approximately 40 km2. Boundary conditions for the Flow Model are discussed in the AMR UZ 
Flow Models and Submodels (CRWMS M&O 2000, U0050, Section 6.1.3). The ground surface 
of the mountain (or the tuff-alluvium contact in areas of significant alluvial cover) is defined as 
the top model boundary, and the water table is treated as the bottom model boundary. Both the 
top and bottom boundaries of the model are described as Dirichlet-type boundaries with 
temperature, gas pressure, and liquid saturation values specified along these surfaces. Surface 
infiltration of different climatic scenarios is applied using a source term in the gridblocks within 
the second grid layer from the top. All the lateral boundaries, as shown in Figure 3.7-3 are treated 
as no-flow (closed) boundaries. The constant temperatures and their spatially distributed values, 
along the top and bottom boundaries, were based on field observation. The pressure conditions at 
the bottom boundary of the model are calculated using observed gas-pressure values. The water 
table, which is the bottom boundary of the site-scale model, is treated as a flat, stable surface 
(CRWMS M&O 2000, U0000, Section 6.4). East of the Solitario Canyon fault, the water table 
elevation is about 730 meters above sea level (masl); however, the water table elevation increases 
by 46 meters when it crosses the Solitario Canyon fault to the west. The gas pressures are 
approximated by the atmospheric pressure of 0.92 bars at an elevation of 730 m.

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Infiltration ScenariosNet infiltration of water, resulting from precipitation that penetrates the 
top-soil layer of the mountain, is the most important factor affecting the overall hydrological 
behavior of the UZ. Net infiltration is the ultimate source of groundwater recharge and 
percolation through the UZ and provides water as a transport medium for potential advective 
transport of radionuclides from the repository to the water table. A total of nine net infiltration 
maps (Section 3.5.2) are implemented by the UZ model and its submodels (USGS 2000, U0010; 
CRWMS M&O 2000, U0050, Section 6.1.3). The nine infiltration scenarios include present-day, 
monsoon, and glacial transitionthree climates, each of which consists of lower-, mean, and 
upper-bound maps. The statistics of the nine infiltration rates are summarized in Table 3.7-1 for 
average values over the model domain. These values (as well as the infiltration rates listed in 
Tables 3.7-3 and 3.7-4) are slightly different from what are estimated in Table 3.5-4 and 
Figure 3.5-1 of Section 3.5, due to using different grids. The flux distributions of the three mean 
infiltration maps over the model domain are shown in Figure 3.7-4. 
Table 3.7-1. The Average Value (mm/yr) of Infiltration Rates over the UZ Model Domain (Adapted from 
CRWMS M&O 2000, U0050, Table 6-3) 
Climate Scenario Lower Infiltration Mean Infiltration Upper Infiltration 
Present-day 1.2 4.6 11.2 
Monsoon 4.6 12.4 20.1 
Glacial transition 2.4 18.0 33.5 
Model Parameters and Rock PropertiesThe key input parameters for rock and fluid flow used 
in UZ model development include (1) fracture properties (frequency, permeability, van 
Genuchten a and m parameters, aperture, porosity, and interface area) for each UZ model layer; 
(2) matrix properties (porosity, permeability, and the van Genuchten a and m parameters) for 
each UZ model layer; (3) thermal and transport properties (grain density, wet and dry thermal 
conductivity, grain specific heat, and tortuosity coefficients) for each UZ model layer; and (4) 
fault properties (matrix and fracture parameters) for each of the major hydrogeologic unitsTCw, 
PTn, TSw, and CHn. The development and estimation of these parameters are presented in the 
AMRs Calibrated Properties Model (CRWMS M&O 2000, U0035, Sections 6.1, 6.2 and 6.3), 
Analysis of Hydrologic Properties Data (CRWMS M&O, 2000, U0090, Section 6), and UZ Flow 
Models and Submodels (CRWMS M&O, 2000, U0050, Section 6.1.4) as well as in Section 3.6 
of this PMR. 
The rock parameter specification in the Flow Model and its submodels is, in general, by layer 
averages, but certain parts of grid layers in the CHn unit are altered to vitric or zeolitic regions. 
In these property-altered layers, zeolitic and vitric tuff properties are specified to correspond to 
actual geologic properties according to the alterations, instead of layers (CRWMS M&O 2000, 
U0000, Section 6.6.3). All the geological units, including fault zones, are treated as fracturematrix 
systems using the dual-permeability approach described above. The van Genuchten 
relative permeability and capillary pressure functions (van Genuchten 1980, pp. 892898) are 
used to describe unsaturated flow in both fractures and matrix.

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UZ Flow Model Input and OutputThe key input data to (CRWMS M&O 2000, U0050, 
Section 6.1), and output models from, the UZ Flow Model are illustrated in Figure 3.7-5. As 
shown in this diagram, the Flow Model uses input from the perched water and matrix properties, 
calibrated properties models, the conceptual model, the geological and numerical grid model, and 
the climatic/infiltration model, as well as the geochemistry model. The output of the Flow Model 
directly feeds many process models, such as the TSPA UZ Flow Model, the Transport Model, the 
Ambient Geochemistry Model, the Mountain-Scale TH Model, the Seepage Model for PA, and 
the Drift-Scale THC Model. 
3.7.3 UZ Flow Submodels 
The submodels of the Flow Model, described in this section, include the studies of the PTn, 
effects of major faults submodel, and the CHn and perched water occurrence. These 
investigations are made to specifically study the effects of these geological units or features on 
flow and transport in the UZ system. In addition to the submodels of the Flow Model of this 
section, the Seepage Calibration Model is discussed in Section 3.9.4 and the Seepage Model for 
PA is presented in Section 3.9.5. 
3.7.3.1 PTn Flow Studies 
The PTn studies of this section are based mainly on the site-scale, 3-D UZ modeling efforts of 
the AMR UZ Flow Models and Submodels (CRWMS M&O 2000, U0050, Section 6.6). The 
focus of this investigation is on understanding the flow behavior through the Paintbrush Tuff 
nonwelded (PTn) unit. The role of the PTn in altering the pattern of percolation into the 
underlying Topopah Spring welded (TSw) unit is of great significance in assessing repository 
performance. A key issue is whether the PTn effectively damps pulses of transient infiltration, 
resulting in a generally uniform percolation flux into the underlying repository rocks of the TSw, 
or whether preferential flow paths within the PTn serve to focus flow above or around potential 
repository drifts. 
The present conceptual model for UZ flow at Yucca Mountain, as discussed in Section 3.3.3, 
considers that net infiltration at the bedrock surface (top of the TCw unit) is episodic, with 
significant pulses probably occurring only once every few years. These spatially and temporally 
variable pulses of moisture percolate rapidly through the highly fractured tuffs of the TCw, as 
indicated by the numerous bomb-pulse 36Cl signatures measured within the TCw (CRWMS 
M&O 2000, U0085, Section 6.6.3). However, at the TCw-PTn interface, where welded tuffs 
grade sharply into nonwelded tuffs, flow behavior changes from fracture-dominated to matrixdominated 
flow. The highly porous PTn matrix significantly attenuates the episodic infiltration 
flux; however, in localized areas such as around faults and zones with high infiltration rates, 
fracture flow within the PTn may predominate. In general, the high storage capacity of the PTn 
matrix damps moisture flow through the unit so that percolation flux across the bottom of the 
PTn into the TSw is more uniformly distributed spatially and temporally. Therefore, the net 
episodic surface infiltration, once crossing the PTn, may be effectively approximated as steadystate 
and the alternative view that the episodic flow through the TSw unit is pervasive is unlikely, 
except along the major faults.

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Figure 3.7-6 presents two vertical cross sections along the south-north and west-east of the UZ 
model domain, showing lithostratigraphic horizons and geological unit thicknesses. The PTn unit 
consists of non- to partially welded tuffs, and it extends from the base of the densely welded and 
devitrified portion of the Tiva Canyon Tuff to the top of the densely welded portion of the TSw 
(Section 3.2.2). The combined thickness of these layers exceeds 150 m at the northern end of 
Yucca Mountain, while at the southern end, the PTn thins to less than 30 m. Above the potential 
repository area, the PTn thickness ranges from approximately 30 to 60 m. 
The PTn unit displays significantly different hydrogeological properties from the TCw and TSw 
units that bound it. Both the TCw and the TSw are characterized by dense welding and intense 
fracturing. Where exposed at the land surface, the TCw plays an important role in controlling 
surface infiltration, since fracturing through the low-porosity matrix may initiate rapid vertical 
percolation. During percolation through the PTn, the flow pattern changes from fracturedominated 
flow in the TCw, to matrix-dominated flow within the PTn, to the initiation of 
significant fracture flow in the upper layers of the TSw. 
In the Flow Model, the PTn unit is represented using six model layers, in general, using the 3-D 
TSPA grid (see Section 3.4.2). Calibrated parameters for the present-day, mean infiltration 
scenario and perched water conceptual model #1 (flow-through model), described in 
Section 3.7.3.3 are used in the PTn modeling studies. The infiltration maps incorporated are the 
three mean infiltration scenarios of the present-day, monsoon, and glacial transition climates. 
The distribution of simulated vertical percolation fluxes at the interface between the PTn and 
TSw units is demonstrated in Figure 3.7-7 for the mean, present-day infiltration scenario. In this 
and subsequent figures, the total flux is defined as total vertical liquid mass flux per year through 
both fractures and matrix, divided by a constant water density, converted to mm/yr, which is the 
commonly used unit for surface infiltration. Comparison of Figures 3.7-7 and 3.7-4a 
(corresponding surface infiltration map) shows that simulated percolation fluxes at the PTn-TSw 
interface are similar, in distribution patterns, to the surface infiltration map for the present-day 
case. The high percolation areas, located at the northern part and along the Solitario Canyon fault 
in the middle portion of the model domain, are especially preserved. The similarity between 
surface infiltration maps and percolation fluxes simulated at the bottom of the PTn unit, as 
shown in Figure 3.7-7, indicates that there may be only small lateral diversion of infiltrated water 
flowing through the PTn unit. A close look at the figure reveals that some lateral movement does 
occur in several areas when crossing the PTn. In particular, the percolation fluxes simulated 
under the high infiltration areas along the north-south mountain crest (east of the Solitario 
Canyon fault), at the middle portion of the model domain, show obvious differences from the 
infiltration maps. 
The simulations reveal two types of lateral flow diversion through the PTn: (1) up to a hundred 
meters movement to the east in the areas above the potential repository and (2) lateral diversion 
into majors faults (e.g., Solitario Canyon and Ghost Dance). In general, high infiltration zones of 
the mountain crest along the middle, north-south model domain are damped and spread into 
larger areas after crossing the PTn.

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Table 3.7-2 compares the fraction of vertical fracture and matrix flow at the middle of the PTn 
with that at the repository horizon below. Note that on the ground surface, infiltration is 
introduced into fractures only; therefore, it is 100% fracture flow at the top of model domain. 
The statistics in Table 3.7-2 show that matrix flow is dominant in the PTn unit, taking nearly 
90% of the total flow, with little variation among the three climate scenarios. This indicates that a 
dramatic transition takes place from fracture-dominant flow within the TCw to matrix-dominant 
flow in the PTn crossing the interface between the TCw and PTn units. While flowing down 
across the PTn and TSw interface, percolation flux changes back from matrix-dominated to 
fracture-dominated flow into the TSw, as indicated by the statistics in the table. 
Table 3.7-2. Comparison of the Water Flux through Matrix and Fractures as a Percentage of the Total 
Flux at the Middle PTn and at the Potential Repository (CRWMS M&O 2000, U0050, 
Section 6.6.3) 
Climate Flux at middle PTn 
(%) 
Flux at Potential Repository 
(%) 
Fracture Matrix Fracture Matrix 
Present-day 11.6 88.4 83.7 16.3 
Monsoon 12.1 87.9 89.5 10.5 
Glacial 
Transition 
11.8 88.2 91.4 8.6 
SummaryThe 3-D simulations with three climate scenarios have provided some key insights 
into the flow pattern alteration by the predominantly nonwelded PTn formation. The PTn studies 
indicate the following: 
 Percolation through the PTn is predominantly matrix flow, comprising nearly 90% of the 
total flow. This conclusion is consistent with the field-observed pneumatic responses, 
which are controlled by the porous-medium-like PTn unit (Ahlers et al. 1999, pp. 47 
66). Therefore, the alternative view that fracture flow is dominanted crossing the PTn 
unit is a very unlikely scenario. 
 In general, the model predicted insignificant lateral flow diversion by the PTn over the 
entire UZ model domain. However, some lateral, east-bound flow (up to 100 m) is 
predicted in the areas above the potential repository along the mountain crest. 
Occurrence of large-scale or significant lateral flow in the PTn, however, is unlikely due 
to existence of a large amount of faults in the PTn and these faults will intersect the 
lateral flow and provide downward flow paths. 
 Some flow is to be diverted into nearby faults when crossing the PTn unit. 
3.7.3.2 Effects of Major Faults 
IntroductionMajor faults may significantly affect the ambient hydrogeologic system and flow 
and transport processes at Yucca Mountain. Compared to the surrounding rock, the larger

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fracture apertures and higher fracture densities generally lead to increased permeability and 
reduced capillarity within and near faults and fault zones. Flow is also affected by the amount of 
offset at the fault, which can range from meters to hundreds of meters (see discussion in 
Sections 3.2.3 and 3.3.5). Figure 3.7-6b presents a vertical cross section along the east-west UZ 
model domain (EW-S on Figure 3.7-3), showing several vertical and inclined faults and fault 
displacements as well as lithostratigraphic horizons and geologic unit thicknesses. 
Faults may provide a direct path from the potential repository horizon to the water table. This is 
particularly significant to the problem of waste isolation because radionuclides released from the 
potential repository could bypass altered, zeolitic, or vitric layers within the CHn hydrogeologic 
unit, where they could be retarded by sorption. Consequently, dissolved radionuclides could enter 
the saturated zone where hydrologically significant faults and the water table intersect. 
Alternatively, faults might be considered a positive feature of the site if they divert water around 
waste emplacement drifts or prevent laterally flowing water from focusing at the area of waste 
emplacement. 
In this section, the site-scale, 3-D TSPA UZ model, as documented the AMR UZ Flow Models 
and Submodels (CRWMS M&O 2000, U0050, Sections 6.1 and 6.6), is used for analyzing 
effects of major faults on the UZ flow processes at Yucca Mountain. 
Conceptual ModelAs discussed in Section 3.2, Yucca Mountain is a structurally complex 
system of Tertiary volcanic rock. Faults at Yucca Mountain fall into three types: (1) northstriking 
block-bounding faults such as the Solitario Canyon and Bow Ridge faults, (2) northweststriking 
faults such as Drill Hole Wash, Sever Wash and Pagany Wash faults, and (3) intrablock 
faults (Day et al. 1998). Block-bounding faults are key structural features that dip steeply to the 
west and have large cumulative displacements of up to 500 m. Intrablock faults tend to be shorter 
and more discontinuous than block-bounding faults, and, with the exception of the Ghost Dance 
fault, generally have minor displacements of 5 to 10 meters (Day et al. 1998). Displacement 
along northwest-striking faults varies from small to moderate (30 m). 
Permeability is expected to vary along faults, with higher values in the brittle, welded units and 
lower values in the nonwelded units, where gouge or sealing material may exist (Montazer and 
Wilson 1984). Highly brecciated fault zones may act as capillary barriers to flow, as indicated by 
high pneumatic permeability measurements in portions of the faults, which suggest large fracture 
apertures and correspondingly low air entry pressure. However, if water does enter this type of 
zone, its high permeability could facilitate rapid transport to the water table (Wang and 
Narasimhan, 1988). 
The observed data show that the conceptual model for the effects of major faults on flow should 
depend upon the type of rock, the proximity of portions of the fault zone to the surface and/or to 
the water table, and the degree of offset along the fault. These factors affect the impact of the 
faults on fluid flow in the following ways (Sections 3.2.3 and 3.3.5): 
 Fault zones in the TCw are intensely fractured and therefore provide a major conduit for 
gas flow and high liquid flux or transient percolation.

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 Fault zones in the PTn are less likely to be intensely fractured because of the more plastic 
(non- to partially welded) character of the rock, but fracturing is more intense than in 
unfaulted areas of the PTn. PTn fracture zones may provide a conduit for gas and liquid 
flow. 
 The TSw, like the TCw, is intensely fractured within and around faults, mainly as a 
result of the brittle character of the rock. Fault zones in the TSw are major conduits for 
gas flow and may provide preferential water flow in certain areas. 
 Faults within the CHn behave like the PTn. The more plastic character of the CHn 
reduces the intensity of fracturing in comparison to the densely welded TCw and TSw. 
In addition, hydrothermal alteration may have reduced permeability of the fault zone. 
However, the fault zones are likely to be more permeable than the surrounding altered 
rock and thus are still the main drain from perched water or low-permeability zeolitic 
zones. 
In this section, the conceptual model of fault influence on the hydrogeologic system is 
investigated using the Flow Model, in which faults are represented using vertical or inclined 
walls 30 m thick. Vertically, faults are subdivided into four hydrogeologic units, according to 
their connections to the neighboring nonfaulting rocks, in the four major hydrogeologic units of 
TCw, PTn, TSw, and CHn. Therefore, each fault, as shown in Figures 3.7-3 and 3.7-8, is 
represented in the model as a vertical or inclined 3-D sheet of gridblocks. Fracture-matrix flow 
and interactions with fault elements are also treated using the dual-permeability approach. The 
fault properties are estimated using a two-dimensional inversion of saturation, water potential, 
and pneumatic data from borehole USW UZ-7a (CRWMS M&O 2000, U0035, Section 6.3). 
Model Results and Analyses of Effects of Major Faults on UZ FlowAn example of the 
effects of faults on UZ flow is presented in Figures 3.7-8 (a and b), using the simulation results 
with the present-day, mean infiltration map, showing (a) percolation flux at the water table and 
(b) vertical fracture flow along an east-west cross section. A comparison of the flux pattern 
between surface infiltration (Figure 3.7-4a) and the water table map (Figure 3.7-8a) clearly 
indicates that flow has been significantly converged to the faults after penetrating the UZ system. 
At the top boundary, infiltration rates or distributions, as shown in Figure 3.7-4a, are located 
independently of faults. However, on arriving at the water table, a large fraction of the water has 
been diverted to the Solitaro Canyon, Ghost Dance, and the other faults in the model domain. 
The effects of faults on the UZ flow under the current conceptual model can be analyzed using 
vertical flow path plots. Figure 3.7-8b displays such results, showing flow fields through 
fractures (flow through matrix is similar) along a west-east cross section. The flow path results 
shown along the 2-D cross section are extracted from the 3-D flow fields and the background 
contours show liquid saturation in the matrix. Figure 3.7-8b shows that flow paths for particles 
released in the surface areas close to faults either converge downward along or parallel to faults. 
No flow lines are seen to cross faults laterally. This indicates that faults can serve as either 
capillary barriers or downward flow conduits for UZ percolation. In addition, some lateral flow 
diversion can also be seen in the figure at the PTn in both matrix and fracture continua and at the 
CHn in the matrix continuum along this cross section.

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Analysis of the simulation results reveals that the fraction of flow occurring through the faults, as 
a percentage of the total flow (through the fractures, matrix and faults), increases with depth. 
Table 3.7-3 lists these percentages at four different horizons and for the three climate scenarios. 
At the ground surface, 4% of the total flow occurs through the faults. This percentage increases 
to 10 - 15% for flow through the PTn. At the water table, fracture flow accounts for 35 - 44% of 
the total flow. The percentage of fracture flow at the water table is the most sensitive to climate 
scenario as compared to the other horizons. It increases from 35% to 42% to 44% for the 
present-day, monsoon and glacial transition climates, respectively. In addition, Table 3.7-3 shows 
that flow percentages through faults at the water table are very different in the southern (through 
vitric zones) and northern (through zeolitic zones) part of the model domain. Fault flow consists 
of 42, 51 and 54% of the total flow in the northern model domain versus only 16, 22 and 24% in 
the south for the three infiltration scenarios. This indicates more lateral flow diversion occurring 
in the north when crossing the zeolitic zones. 
Table 3.7-3. Comparison of the Water Flux through Faults as a Percentage of the Total Flux at Four 
Different Horizons (1) on Ground Surface; (2) Interface between PTn and TSw; (3) at the Potential 
Repository; and (4) at the Water Table (Data from CRWMS M&O 2000, U0050, Section 6.6.3) 
Climate 
Scenarios 
Fraction of Total Flow through Faults 
(%) 
Ground surface PTn-TSw interface Potential 
Repository level 
Water table Mean 
Infiltration 
(mm/yr) Total South North Total South North Total South North Total South North 
Present-day 
4.6 
3.8 3.6 3.9 14.3 18.9 12.7 14.6 19.8 12.7 34.9 15.9 42.0 
Monsoon 
12.4 
4.1 3.8 4.2 10.5 13.0 9.6 10.5 13.3 9.5 42.4 21.9 51.3 
Glacial 
Transition 
18.0 
4.0 3.7 4.1 9.1 10.8 8.4 9.1 11.0 8.2 44.4 24.3 54.2 
NOTE: Total denotes flow over the entire model domain, South denotes flow over the southern 
part/half of the model domain; and North denotes flow over the northern part/half of the model 
domain. 
SummaryOverall, percolation fluxes in the UZ system of Yucca Mountain are predicted to 
converge into the faults as water flows downward through the geologic units. Faults serve as 
major focusing conduits for the downward unsaturated liquid flow in the UZ system. Lateral 
diversions of water into faults occur mainly in the CHn and some in the PTn unit. In addition, the 
percentage of fault flow increases as mean infiltration rates increases. 
3.7.3.3 Investigations of Calico Hills and Perched Water Occurrence 
In terms of groundwater flow paths, as well as radionuclide transport from the repository level, 
the CHn hydrogeologic unit may play a crucial role in the assessment of geologic repository 
performance. This unit separates the potential repository horizon from the saturated zone. The

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predominantly nonwelded nature of the CHn makes these initially high-porosity, vitric tuffs 
susceptible to hydrothermal alteration. Hydrothermal alteration produces low-permeability clays 
and zeolites that create complex, heterogeneous flow paths within the CHn (see Section 3.2.4). 
The observed, widespread alteration within the CHn has important implications for perched 
water, for groundwater flow paths, and for radionuclide transport because of the reduced 
permeability and the sorption potential associated with zeolitic and vitric rocks. 
The presence of perched water within the UZ, which is associated with the densely welded basal 
vitrophyre of the Topopah Spring Tuff or with zeolitic intervals of the CHn, has important 
ramifications for flow patterns. In perched water locations, vertical percolation flux locally 
exceeds the saturated hydraulic conductivity of the perching layers. Perched water bodies suggest 
that flow paths may not be completely vertical through the CHn unit to the water table. Instead, 
the water may be partially diverted laterally to a fault zone or another high-permeability channel 
that may serve to focus flow downward to the water table. The diverted flow may bypass zeolitic 
layers, reducing the potential sorption of radionuclides. 
CHn Geological ModelWithin the Flow Model, the CHn is represented with 14 model layers 
based on lithostratigraphy and available hydrogeologic properties, as discussed in CRWMS 
M&O (2000, U0000, Sections 6.1 and 6.3) and Section 3.2.2. The CHn unit extends from the 
base of the lower welded vitrophyre of the TSw to the top of the welded portion of the Bullfrog 
Tuff. The CHn consists of the non- to partially welded vitric subzone of the lower TSw (Tptpv1), 
the pre-Topopah Spring bedded tuffs (Tpbt1), the Calico Hills Formation (Tac), the pre-Calico 
Hills bedded tuffs (Tacbt), the entire Prow Pass Tuff (Tcp), and the upper nonwelded, vitric 
portions of the Bullfrog Tuff. More detailed description on the hydrogeological units can be 
found in Table 3.2-2 of Section 3.2 of this PMR. 
The cumulative, unsaturated thickness of the CHn ranges from about 400 m at the northern end 
of Yucca Mountain to approximately 200 m near the southern end. Figure 3.7-6a presents a 
north-south cross section through the UZ near borehole UZ-14, showing the major grouping of 
layers into hydrogeologic units. Governed by the water table elevation, the location of major 
faults, and the gentle eastward dip of the strata, the thickness of the CHn at Yucca Mountain, in 
general, increases to the east of the Solitario Canyon fault (Figure 3.7-6b). 
Perched Water Conceptual ModelConceptual models involving perched water occurrence in 
the UZ below the repository horizon are of particular interest in assessing the natural geologic 
system performance of the potential repository. The extent of radionuclide sorption within the 
zeolitically altered CHn and groundwater flow patterns between the repository horizon and the 
water table may be altered by perched water. The genesis of perched water at Yucca Mountain is 
much debated among Yucca Mountain project scientists, and several conceptual models have 
been proposed (e.g., Wu et al. 1999b, pp. 157184). 
Perched water may occur where percolation flux exceeds the capacity of the geologic media to 
transmit vertical flux in the UZ. At Yucca Mountain, perched water has been encountered in a 
number of boreholes, including UZ-14, SD-7, SD-9, SD-12, NRG-7a, G-2, and WT-24 (Figure 
3.7-3) (CRWMS M&O 2000, U0050, Sections 6.2 and 6.6). These perched water occurrences are 
found to be associated with low-permeability zeolites in the CHn or the densely welded basal

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vitrophyre of the TSw unit. It should be noted that the perched water body found at SD-7 is very 
small, as inferred from pumping tests and is not believed to impact the performance of the 
potential repository. Possible mechanisms of water perching in the UZ of Yucca Mountain may 
be permeability and/or capillary barrier effects. 
A permeability barrier conceptual model for perched water occurrence (model #1) has been used 
in the UZ flow modeling studies since 1996 (Wu et al. 1999b). The major assumptions of the 
permeability barrier conceptual model are: (1) no large-scale vertically connected fractures 
transect the underlying low-permeability units, (2) both vertical and horizontal permeabilities 
within and below the perched water zone are small compared with permeabilities outside 
perching zones, and (3) sufficient percolation flux (>1 mm/yr) exists. Previous modeling studies 
(Wu et al. 1999b, pp. 157184) concluded that this conceptual model is able to match the 
observed data of perched water in the UZ of Yucca Mountain. 
Another conceptual perched water model is an unfractured zeolite model (model #2). Similar to 
the permeability barrier model discussed above, this model presumes that the occurrence of 
perched water at Yucca Mountain results mainly from the lack of globally connected fractures 
within zeolitic units. This model can be considered a special case of the permeability barrier 
model, in which a water-perching mechanism is controlled by the low-permeability zeolitic 
matrix only, i.e., the existence of fractures in zeolites is ignored. In the present Flow Model, the 
occurrence of perched water is assumed to follow either model #1 or model #2. In other words, a 
perched water body is formed mainly as a result of permeability barrier effects. 
There are other alternative conceptual models for explaining perched water occurrence at Yucca 
Mountain. One of the alternative views considers that the perched water zones in the northern 
part of the model domain may have resulted from elevated water tables or steep water gradients 
there. Another alternative explanation is that water sources of perched water bodies have been 
supplied from the recharge in the Solitario Canyon area and then lateral flow along low 
permeability units, such as the basal vitrophyre of the TSw. The current perched water 
conceptual models have not included these two alternative concepts because they are not strongly 
supported neither by field-observed data nor by modeling results. 
To calibrate the Flow Model against observed perched-water conditions at Yucca Mountain, 
some local modification of rock properties is necessary. In general, permeability was adjusted 
only within the model layers associated with the perching zones (CRWMS M&O 2000, U0050, 
Section 6.2). For perched water conceptual model #1, calibrated parameters of fracture and 
matrix permeabilities within perched zones are results from a series of modeling studies of 3-D 
simulations. Matrix permeabilities of potential perched layers/zones are based on average values 
of the measured matrix permeabilities, while fracture permeabilities were manually calibrated so 
that modeled perched water results matched observed data. For perched water conceptual model 
#2, rock properties of all the fractures within the zeolitic layers/zones were replaced by the 
corresponding matrix properties of the same units. 
Model Results and AnalysesSimulations using the two conceptual perched water models 
incorporate all three climate scenarios (present-day, monsoon and glacial transition) and their 
associated mean or upper-bound infiltration maps (CRWMS M&O 2000, U0050, Section 6.6).

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Both perched water conceptual models can generally match the water perching conditions, as 
observed in Yucca Mountain. Figure 3.7-9 presents a simulated perspective view of 3-D perched 
water bodies and their volumetric extensions. This figure shows fracture-water saturations, 
simulated along the bottom of the TSw or the low basal vitrophyre layer for perched water 
model #1. The blue isosurfaces on the figure reflect the regions of 100% liquid saturations, or 
perched water zones, within fractures along the model layer, while the green isosurface 
represents a portion of the model layer with fracture liquid saturations less than 100%. Figure 
3.7-9 clearly shows several extensive perched water bodies, separated by faults, predicted in the 
northern part of the model domain. 
Effects of perched water zones on flow processes in the CHn unit is best explained by comparing 
percolation fluxes simulated at the repository level and the water table. Figure 3.7-10 presents 
three map views of the simulated percolation fluxes (a) at the repository horizon with model #1; 
(b) at the water table with Conceptual Model #1; and (c) at the water table with model #2. The 
map at the potential repository horizon is only shown for model #1 because model #2 is applied 
only to the zeolites in the CHn unit and consequently has minimal effect on flow at the repository 
and higher-elevation horizons. 
Figure 3.7-10 reveals large differences in the magnitude and distribution of percolation fluxes or 
their distributions at the water table and the repository horizon. This confirms significant lateral 
flow or diversion occurring above or within the CHn for both perched water models. Comparing 
the flux distribution in the northern part of the model domain in Figure 3.7-10a, b, and c shows 
that there is a large amount of the percolation flux at the water table, which is focused along the 
major faults. The water table flux maps, compared to the flow patterns at the repository level, 
show significantly lower fluxes (red zone) in the northern part of the potential repository area, 
directly below the perched water bodies and bounded by the Solitario Canyon and the Drillhole 
Wash faults. A large amount of water is diverted laterally to the east, along layer slopes, and 
intersects faults that focus flow downward to the water table. 
In the southern part below the potential repository area of the model domain, the majority of 
percolation flux at the water table is found to be contributed by high-permeability matrix flow in 
vitric zones. The analyses of the simulated fracture and matrix flow (e.g., near borehole SD-7) 
indicate that matrix flow dominates in those vitric zones, as predicted by both perched water 
conceptual models. Even in these areas, however, water is laterally diverted to the east and 
intercepted by faults along the thin zeolitic layers, when one compares the repository fluxes with 
the water table fluxes of Figure 3.7-10. 
SummaryThe CHn hydrological unit could play a critical role in controlling groundwater flow 
patterns and radionuclide transport pathways from the potential repository horizon to the 
saturated zone. One specific issue related to flow below the potential repository horizon is 
perched water. Its presence implies that vertical percolation flux locally exceeds the saturated 
hydraulic conductivity of the perching layer. Thus, predominant flow paths may not be vertical 
through the CHn from the potential repository horizon to the water table. Instead, water may be 
diverted laterally to a fault zone, fracture network, or relatively high-permeability vitric zone that 
focuses flow to the water table.

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The modeling results show that the flow patterns, or pathways, through the CHn are controlled 
mainly by fracture and matrix parameters in the CHn unit and by the presence of highpermeability 
flow channels, such as faults, that cross-cut the unit. All modeling scenarios, based 
on the two perched water conceptual models, indicate significant lateral flow diversion (40-50% 
of the total flow) at the CHn resulting from the presence of perched water or thick zeolitic layers. 
In addition, faults act as major flow paths in the northern part of the model domain under the 
current conceptualization. In the southern part of the model domain, flow through the vitric zone 
of the CHn is matrix flow dominated because of the high matrix permeability. 
3.7.4 Site-Scale Flow Analysis 
This section presents an in-depth analysis of site-scale 3-D UZ flow using the Flow Model for the 
UZ. The results, as discussed in the following subsections, represent the best estimates and the 
current understanding of the Yucca Mountain UZ flow system. 
3.7.4.1 Percolation Flux at the Potential Repository Horizon 
Percolation flux through the UZ is one of the most critical factors affecting the potential 
repository performance of the natural waste storage system as well as TSPA calculations. The 
quantity and spatial and temporal variations in percolation flux directly affect: (1) the amount of 
water flowing into waste emplacement drifts; (2) moisture conditions and corrosion environment 
of canisters within the drifts; (3) waste mobilization from the potential repository; (4) thermalhydrological 
behavior of the potential repository; and (5) radionuclide migration from the UZ to 
the saturated zone. However, because percolation fluxes of unsaturated flow cannot be readily 
measured in the field, we must rely on indirect data and model results to estimate these fluxes. 
The past modeling studies (Wu et al. 1999a, pp. 185215 and Wu et al. 1999b, pp. 157184) 
indicate that accurate model predictions of percolation fluxes at Yucca Mountain depend on 
many factors. The most important are (1) net infiltration rates over the surface boundary; (2) 
representative geological and conceptual models; (3) reliable distributed rock property values for 
fractures and matrix blocks; and (4) treatment of fracture-matrix flow and interactions. 
Percolation fluxes at the repository horizon, as predicted by the UZ Flow Model, have been 
analyzed using 28 3-D UZ flow simulation results, with nine infiltration maps and different 
perched water conceptual models (CRWMS M&O 2000, U0050, Section 6.6.3). 
Figures 3.7-11a, b, and c show samples of percolation fluxes simulated at the repository level for 
the three mean infiltration rates of mean present-day, monsoon and glacial-transition climate 
scenarios. As discussed for the perched water studies, percolation fluxes at the potential 
repository are nearly the same for the same infiltration map, regardless of the specific perched 
water conceptual models. Figure 3.7-11 displays a highly nonuniform pattern of flux distributions 
(the darker blue spots on the figure indicates the higher modeled percolation fluxes). The high 
percolation fluxes are located primarily at the northern part, but also along the Solitario Canyon 
fault in the middle portion of the model domain. A comparison of the modeled percolation fluxes 
to their corresponding surface infiltration maps (Figure 3.7-4) indicates very similar flux patterns, 
and therefore minimal lateral flow diversion between the surface and potential repository level.

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Percolation fluxes at the level of the potential repository horizon are largely a reflection of 
surface infiltration rates. Areas of higher infiltration rates (i.e., in the northern portion of the 
model domain and along the Yucca Mountain crest) have the highest percolation fluxes, and the 
low infiltration areas have correspondingly lower percolation. Beneath the potential repository 
horizon, the distribution of percolation fluxes is more diffuse and generally spread to the east as a 
function of lateral flow. 
The statistics of the averaged percolation fluxes within the potential repository footprint, 
extracted from the 3-D UZ model results for the three mean infiltration scenarios, are listed in 
Table 3.7-4. Table 3.7-4 indicates that the total percolation flux within the potential repository 
horizon is very similar to the average surface infiltration rate over the model domain of Table 
3.7-1. The only exception is the glacial-transition scenario, which predicts a higher average 
percolation flux within the potential repository footprint than the average value over the entire 
model domain. 
Table 3.7-4. Average Percolation Fluxes Simulated within the Potential Repository Footprint for the Three 
Mean Infiltration Scenarios (Data from CRWMS M&O 2000, U0050, Section 6.6.3) 
Climate Scenario Average Percolation Flux within Potential Repository 
(mm/yr) 
Mean Infiltration over the 
UZ Model Domain 
(mm/yr) 
Fracture Matrix Total 
Present-day 
4.6 
4.0 0.5 4.5 
Monsoon 
12.4 
12.1 0.8 12.9 
Glacial Transition 
18.0 
19.5 0.9 20.5 
3.7.4.2 Repository Percolation Flux Frequency Distribution 
Percolation fluxes within the potential repository footprint can be further analyzed using a 
frequency distribution plot, which displays the average percentage of the potential repository area 
subject to a particular percolation flux. This information is useful to drift-scale modeling studies 
of flow and transport at drifts. Figure 3.7-12 shows the frequency distribution of percolation flux 
within the potential repository horizon for the three mean infiltration scenarios of present-day, 
monsoon, and glacial-transition climates. The frequencies are generated by grouping the vertical 
flux results for the repository model nodal areas, counting the total area found in each flux group, 
and then calculating the percent contribution relative to the total potential repository area in each 
category. On the plots, a node in the 1 mm/yr category has a flux in the 0.0 to 1.0 mm/yr range. 
Figure 3.7-12a indicates that the highest flux frequencies have fluxes within the 1.0 to 4.0 mm/yr 
range and occur over about 50% of the potential repository area. The nodal area with percolation

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fluxes greater than 20.0 mm/yr comprises only about 1% of the total repository area. For the 
monsoon scenario, Figure 3.7-12b shows that the highest frequency of percolation fluxes is in a 
range of about 6 to 7 mm/yr, occurring over 18% of the total repository area. Less than 1% of the 
repository area is subject to 50 mm/yr or higher percolation rates. For the high-infiltration rates 
of the glacial-transition climate, the highest areal frequency of percolation fluxes is in the range 
of 8 to 13 mm/yr (Figure 3.7-12c), 25% of the total repository area, and less than 3% of the 
repository area is subject to 60 mm/yr or higher percolation flux. 
The areal frequency distributions of percolation fluxes at the potential repository are 
approximately log normal (see Figure 3.7-12) for the three base-case infiltration scenarios. The 
percolation flux with highest areal frequencies is lower than the average values of corresponding 
average infiltration rates. 
3.7.4.3 Fracture and Matrix Flow Components 
This subsection presents a modeling analysis of steady-state fracture and matrix flow components 
using the Flow Model. The objective of this section is to examine the effect of various climate 
scenarios and perched water conceptual models on fracture and matrix flow, especially at the 
repository level of the TSw unit. Fracture flow is predicted to control percolation where flux 
exceeds the hydraulic conductivity of the matrix. This is most likely to occur within the densely 
welded units, such as in the TSw. Fracture flow has important implications for flow into 
emplacement drifts and therefore may directly impact the long-term performance of the potential 
repository. In addition, fractures provide preferential fast flow paths from the ground surface to 
the repository level and from the repository level to the water table. For these reasons, the 
conceptual model of fracture flow is of major concern for TSPA-SR calculations of radionuclide 
releases from the potential repository. 
Similar to percolation fluxes, fracture and matrix flow components are difficult to measure 
directly at the site. The partitioning of flow between fractures and matrix must, therefore, be 
inferred from modeling results. Examples of simulated fracture and matrix flow at the repository 
horizon are shown in Figure 3.7-13. The terms fracture flow and matrix flow are defined as 
mass flux of water through fractures or matrix, respectively. Units are also given in mm/yr per 
unit area, a commonly used measurement for infiltration and percolation rates. Summation of 
fracture and matrix flows gives total percolation flux. 
Figure 3.7-13a and b shows that fracture flow is predominant, as compared to matrix flow for the 
same climate scenario at the level of the potential repository. Table 3.7-5 lists the percentage of 
fracture-matrix flow components at the potential repository horizon and the water table as a 
percentage of the total flux. These statistics were predicted using the 18 simulation results of nine 
infiltration maps and two perched water conceptual models. They show that fracture flow is 
dominant both at the potential repository horizon and at the water table in all the 18 flow fields. 
Specific predictions are as follows: 
 For three present-day climate scenarios, at the potential repository level, fracture flow 
consists of 84-94% of the total flow; at the water table, it consists of 7095% of the total 
flow.

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 For two future climate scenarios, the percentage of fracture flow increases relative to the 
present-day case at both the potential repository (8796%) and water table level (71 
97%). 
 Perched water conceptual model #2 predicts consistently lower fracture flow 
components at the water table (by 10% or more) for all three climate scenarios. 
Table 3.7-5. Comparison of the Water Flux through Fractures as a Percentage of the Total Flux at Two 
Different Horizons (1) at the Potential Repository and (2) at the Water Table, Using the Nine Infiltration 
Scenarios and Two Perched Water Conceptual Models (Data from CRWMS M&O 2000, U0050, 
Section 6.6.3) 
Climate Present-Day Monsoon Glacial Transition 
Perched 
Model 
Infiltration Potential 
Repository 
(%) 
Water 
Table 
(%) 
Potential 
Repository 
(%) 
Water 
Table 
(%) 
Potential 
Repository 
(%) 
Water 
Table 
(%) 
#1 Lower 86.6 84.7 90.0 90.1 86.9 87.2 
#2 Lower 86.4 69.4 89.9 76.6 86.8 71.4 
#1 Mean 83.7 86.7 89.5 90.2 91.4 90.5 
#2 Mean 83.7 71.2 89.5 80.9 91.4 83.4 
#1 Upper 94.5 95.4 95.6 96.5 96.5 96.9 
#2 Upper 94.3 82.1 95.5 83.9 96.4 89.0 
In addition, the Flow Model can also predict moisture conditions in fracture and matrix systems, 
respectively. In terms of moisture contents or liquid saturations of fracture and matrix continua, 
the modeled results of liquid saturations in matrix matched well with observations in all the 
units. For fractures, the Flow Model estimates fracture saturation at 1-2% at the potential 
repository level, which is lower than the previous estimates (Haukwa et al. 1999, pp.236). This is 
because the new values of van Genuchtens alpha for fractures, calibrated using newly measured 
in-situ water potentials, are higher than before. 
3.7.4.4 Model Validation and Confidence Building 
Validating the Flow Model and its submodels and confidence building for these models have 
been the top priority in the development of the UZ model over the past decade. The 
comprehensive model calibration and validation studies have been carried out and the main 
results and conclusions of these model validation efforts are summarized as follows. 
Previous Model Validation Efforts- As a critical step in developing the 3-D UZ Flow Model, 
borehole-measured saturation, water potential and temperature data were compared with the 
model predictions (Wu et al. 1999a, pp. 199206). This has been part of the important iterative 
processes of model calibration and verification to increase confidence in model predictions of the 
site condition. Liquid saturation data taken from five boreholes UZ-14, UZ#16, SD-7, SD-9 and 
SD-12 (Figure 3.7-3) were used to calibrate the 3-D simulation results. The modeling results

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indicated that the UZ Flow Model could generally reproduce the moisture condition in the UZ at 
Yucca Mountain. 
Temperature and heat flow calibrations with the Flow Model have also been carried out, in which 
the 3-D simulation results were compared with temperature profiles measured from 25 boreholes 
within and near the potential repository area (Wu et al 1999a, pp. 203206). The model results 
were found to match temperature data from the 25 boreholes and therefore the geothermal 
conditions were incorporated in the model. 
Another important step of model calibration is to match perched water occurrence at Yucca 
Mountain. Perched water data observed from boreholes UZ-14, NRG-7a, SD-7, SD-9, SD-12 and 
G-2 were compared with the UZ model predictions (Wu et al. 1999b, pp. 168174). It has been 
concluded that the simulation results were generally in good agreement with water perching 
locations at these boreholes and the pumping tests at boreholes UZ-14 and G-2 (Wu et al. 1999b, 
pp. 178180). 
In addition, calibrations using pneumatic and geochemical data have been performed, showing 
that the UZ model provides a good representation of gas flow and geochemical conditions at 
Yucca Mountain. The results have been documented (Ahlers et al. 1999, pp. 5464; Sonnenthal 
and Bodvarsson 1999, pp. 125150). 
Current, Continual Model Validation Results-During its continual development, as discussed 
in this section and documented in CRWMS M&O (2000, U0050, Sections 6 and 6.8.1), the Flow 
Model has been further calibrated and validated using all available, updated observation data. 
These updated model validation studies have further confirmed and enhanced the capability of 
the Flow Model. 
The first example of the current model validation efforts is based on the water infiltration test at 
the ESF Alcove 1 (CRWMS M&O 2000, U0050, Section 6.8.1). The test was conducted by 
applying water at the ground surface directly above Alcove 1 and measuring the amount of water 
flowing into the alcove with time. The experimental observations are directly related to the flow 
and transport processes in the unsaturated fractured rocks, and have been used for evaluating the 
continuum approaches used in the Flow and Transport Model. Comparisons between observed 
seepage data and the simulation results show fair agreement and indicate that the continuum 
approach, as used in the Flow Model, is valid for capturing the complex flow and transport 
processes in an unsaturated fractured porous medium. 
The Flow Model has been further examined against water-potential data collected along the wall 
of ECRB tunnel (CRWMS M&O 2000, U0050, Section 6.8.2) as well as liquid-saturation and 
water-potential data from the two new boreholes, WT-26 and SD-6 (CRWMS M&O 2000, 
U0050, Section 6.8.3). The modeling results were compared to these field observation data to 
check the accuracy of the modeling predictions. Even though the data available at the ECRB drift 
and the two boreholes are limited, the comparisons indicate that the Flow Model matches those 
from in situ measurements and accurately predicts the location of perched water occurrence at 
borehole WT-24.

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Furthermore, all the 3-D flow fields, as generated for TSPA calculations using the Flow Model, 
have been calibrated against the field observed data of matrix liquid saturations, water potentials, 
and perched water. One example of the calibrations is given in Figure 3.7-14, for comparisons at 
UZ-14 of the results using the three mean infiltration rates of the three climatic scenarios of the 
present-day, monsoon, and glacial transition with perched water conceptual model #1. The figure 
shows a good match between simulated and observed saturation and perched water data at this 
location from the three simulations. Overall, all the simulation results are generally consistent 
with the observed saturation, water potential and perched water data. 
As part of the model validation efforts, the 3-D pneumatic predictions using the Flow Model 
have been compared to pneumatic data from six boreholes, namely NRG#5, NRG-6, NRG-7a, 
SD-7, SD-12, and UZ-7a (CRWMS M&O 2000, U0050, Section 6.8.4). In these comparisons, 
the first 30 days of each data record are used for the inversion as documented in the AMR, 
Calibrated Properties Model (CRWMS M&O 2000, U0035, pp. 41 and 62), and the second 30 
days are compared to the prediction for validation. Comparisons of the 3-D prediction and the 
data for borehole UZ-7a are shown in Figure 3.7-15. The figure shows a good match between the 
prediction and the data. This validates the base-case infiltration-scenario calibrated properties for 
use in gas-flow simulations. 
Finally, geochemical modeling of Cl and calcite deposition has been used to build some 
constraints on hydrological parameters such as infiltration/percolation flux. These geochemical 
studies provide additional evidence for validation of flow and transport model (CRWMS M&O 
2000, U0050, Sections 6.4 and 6.5). 
In all these model calibration studies and validation efforts, it has been shown that the results of 
the Flow Model can match different types of data, such as water potentials, liquid saturation, 
seepage rate, breakthrough and in situ concentrations, and pneumatic pressures, as observed for 
the mountain. These modeling investigations and results have provided sufficient confidence in 
the Flow Model for its accuracy and reliability for its intended use in describing and predicting 
flow and transport processes in the UZ system of Yucca Mountain. 
3.7.4.5 Bounds on Percolation and Uncertainties/Limitations 
Upper-Bound of Net Infiltration RateBounds or upper limits of percolation fluxes or 
infiltration rates at the site can be estimated based on the studies of the AMR UZ Flow Models 
and Submodels (CRWMS M&O 2000, U0050, Section 6.2, 6.4, 6.5 and 6.6). The analysis of 
chloride data in the AMR indicates that the average percolation rate is about 4.6 mm/yr over the 
UZ model domain, which is further confirmed by the temperature analysis by matching steadystate 
temperature profiles in the UZ. Analysis of calcite deposition also gives us some estimates 
on infiltration near WT-24, which are 2 to 20 mm/yr. 
In the 3-D model calibrations using the perched water data, the average infiltration rate should be 
1 mm/yr or higher. Otherwise the model cannot match perched water occurrence, e.g., as 
observed in borehole UZ-14. Therefore, the upper limit of the average infiltration rate at Yucca 
Mountain is no more than three times the average base-case infiltration rate or less than 15

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mm/yr. This needs to be further investigated and verified, using the updated field data and 
understanding of the mountain system. 
Uncertainties/LimitationsThe Flow Model and its submodels are comprehensive and complex. 
These models have played an important role in characterizing flow and transport processes at 
Yucca Mountain. Limitations and uncertainties associated with these models should be 
recognized for their successful applications. The accuracy and reliability of the Flow Model 
predictions are critically dependent on the accuracy of estimated model properties, other types of 
input data, and hydrogeological conceptual models. These models are limited mainly by the 
current characterization of the mountain system, including the geological and conceptual models, 
the volume-average modeling approach, steady-state moisture flow, and available field and 
laboratory data. 
The past site investigations have shown that large variability exists in the flow and transport 
parameters over the spatial and temporal scales of the mountain. Even though considerable 
progress has been made in this area, the major remaining uncertainties in model parameters are: 
(1) accuracy in estimated current, past, and future net-infiltration rates over the mountain; (2) 
quantitative descriptions of welded and nonwelded tuff heterogeneity, their flow properties, and 
detailed spatial distributions within the mountain, especially below the potential repository; (3) 
sufficiency of field studies, especially for fracture properties in zeolitic units and faults; (4) 
alternative conceptual models of major-fault water-flow transmission; (5) evidence of lateral 
diversion due to zeolites in the CHn units; and (6) transport properties (e.g., adsorption or Kd 
coefficients in different rock types, matrix molecular diffusion coefficients in different units for 
different radionuclides, dispersivities in fracture and matrix systems). All of these uncertainties 
have been addressed in this report. 
3.7.4.6 Corroborative Evidence and Natural Analog 
The variably saturated fractured basalt at Box Canyon, Idaho, was used as a natural analog to 
Yucca Mountain to examine the applicability of conceptual and numerical modeling 
methodologies developed to represent preferential flow paths in variably saturated, fractured rock 
(CRWMS M&O 2000, U0135, Section 6.5.1). A dual-permeability model was constructed using 
TOUGH2 V1.4 representing both the matrix and fracture continua of the upper basalt flow at the 
Box Canyon site. A consistent set of hydrogeological parameters was obtained by calibrating the 
model to predict infiltration-front arrival times in the fracture continuum. These times were 
inferred from bromide samples collected from fracture/borehole intersections that were observed 
to conduct the infiltrating water. Parameters included the permeability of the fracture and matrix 
continua, the interfacial area between the fracture and matrix continua, and the porosity of the 
fracture continuum. The interfacial area was decreased by a factor of 0.01 during calibration to 
reduce imbibition of water from the fracture continuum into the matrix continuum during the 
infiltration pulses. Furthermore, the porosity of the fracture continuum, as calculated using the 
fracture aperture inferred from pneumatic-test permeabilities, was increased by a factor of 50. 
The fracture-continuum porosity was a highly sensitive parameter controlling the arrival times of 
the simulated infiltration fronts. Although the dual-permeability approach is also applied to 
explain groundwater flow at Yucca Mountain, the vastly different scales of Box Canyon and 
Yucca Mountain mean that upscaling is an issue when comparing parameter values.

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3.7.4.7 Alternative Conceptual Models 
The Flow Model, as summarized in this section, represents our current understanding of the UZ 
flow system of Yucca Mountain. The simulation results and the sensitivity analyses conducted in 
the Flow Model are based primarily on the conceptual hydrogeological model, the calibrated rock 
properties, the dual-permeability approach for fracture-matrix interactions, and the infiltration 
maps for present-day and two future climates. Many alternative conceptual models have been 
investigated and tested for describing the UZ flow processes at Yucca Mountain. Other 
alternative conceptual models are also possible and make the current model more uncertain, 
especially with regard to their impact on radionuclide transport from the repository to the water 
table. These alternative conceptual models include: 
1. Different conceptualization and numerical representation of faults 
2. Different numerical approaches for handling fracture and matrix interactions in 
different hydrogeological units or in faults 
3. Hybrid grid conceptual numerical models of a combination of dual-permeability, 
MINC, single- or double-porosity, ECM, and explicit-fracture models to represent 
the UZ system 
4. Transient infiltration rate model 
5. Alternative models of lateral flow diversion and perched water beneath the 
repository. 
3.7.5 UZ Flow Abstractions for TSPA-SR 
The previous sections have described the development, use, and results of the conceptual and 
process models for UZ flow. The Flow Model forms the basis for the model that is used (or 
abstracted) for TSPA-SR. This section summarizes the products of the UZ flow models and 
the abstractions that are carried forward to the TSPA-SR calculations. 
3.7.5.1 Abstraction of Flow Fields 
A total of 18 flow fields were originally defined for the base-case TSPA-SR calculations. These 
consisted of three infiltration cases (lower, mean, and upper) within each of the three climate 
states (present-day, monsoon, and glacial transition), along with two different perched water 
conceptual models. As discussed in Section 3.7.5.3, only one perched water model was selected 
for conservatism, so nine flow fields are carried forward to TSPA-SR. Each of the nine flow 
fields are used directly for TSPA-SR calculations, but the files are postprocessed so that the code 
used for transport simulations in TSPA-SR (FEHM V2.1, STN: 10086-2.10-00) can interpret the 
files (CRWMS M&O 2000, U0125; Section 6.1). This method maintains consistency with the 
three-dimensional UZ site-scale flow fields that have been calibrated using TOUGH2 V1.4. 
As discussed in Section 3.5, the three infiltration cases are weighted based on Monte Carlo 
analyses of the uncertainty in the infiltration input parameters. The flow fields that correspond to

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each of the three infiltration cases are assigned the same weightings (i.e., 0.17, 0.48, and 0.35 for 
the lower, mean, and upper infiltration cases, respectively). These weightings are the same for 
each climate state, and the infiltration cases are consistent among all three climates. For 
example, if the low-infiltration case were selected for a present-day climate realization, the lowinfiltration 
case would also be used for the monsoon and glacial-transition climates for that 
realization. 
3.7.5.2 Abstraction of Water-Table Rise 
The two future climate states (monsoon and glacial transition) are expected to be wetter than the 
present-day climate, and, as a result, the water table is expected to rise. However, uncertainty 
exists regarding the amount of water-table rise for each climate state. Therefore, as discussed in 
CRWMS M&O (2000, U0125, Section 6.2), a conservative water-table rise of 120 m is used for 
all flow fields using future climate states. All elements (nodes) located at or beneath an elevation 
of 850 m are modified by changing the liquid saturation to a value of one and applying a large 
mass-flow sink, which effectively removes particles from the UZ in FEHM V2.1 (for use as a 
source term for the SZ model). 
The impact of the water-table rise on groundwater flow and transport beneath the potential 
repository was evaluated in CRWMS M&O (2000, U0160, Section 6.2.4). Results of that 
analysis showed that the majority of particle paths between ~730 m and ~850 m were primarily 
vertical, and the higher water-table elevation decreased the median breakthrough time for a 
sorbing tracker (Np) by nearly a thousand years for the mean-infiltration case using perched 
water model #1. At ten thousand years, the cumulative breakthrough of particles increases from 
~70% to ~80%. 
3.7.5.3 Abstraction of Perched Water Models 
Section 3.7.3.3 introduced two perched water models: (1) a permeability-barrier model with 
reduced permeability in both fracture and matrix elements in the vicinity of the perched water 
and (2) an unfractured zeolite model that eliminated fractures in all zeolitic units. Figure 3.7-17 
shows that the breakthrough curves resulting from the two perched-water models are similar. As 
a result, only one of the two models is carried forward to TSPA-SR, and a PA analysis was 
performed to determine the most conservative model. 
In the analysis performed by PA (CRWMS M&O 2000, U0160 Sections 6.2.1 and 6.2.2), 
FEHM V2.1 was used to assess the particle breakthrough locations and flow patterns resulting 
from the two perched water models. Figure 3.7-16 shows the particle-breakthrough locations at 
the water table for an advective tracer (no diffusion, sorption, or dispersion) released uniformly 
as a pulse in the outlined repository region using the mean infiltration case, glacial-transition 
climate, and both perched water models. Both perched-water models show a significant amount 
of lateral diversion of particles in the northern part of the repository, but perched water model #2 
shows more diversion in the southern portion. Many of the diverted particles are concentrated in 
faults, which act as a conduit to the water table.

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Figure 3.7-17 shows the breakthrough curve for a nonsorbing tracer (Tc) released uniformly as a 
pulse in the repository region using the mean-infiltration case, glacial-transition climate, and both 
perched-water models (CRWMS M&O 2000, U0160, Section 6.2.2). Results of the two perched 
water models are similar, although perched water model #1 yields slightly more conservative 
results, especially for early breakthrough times (via fracture transport). Perched water model #1 
also yielded slightly more conservative results for the other flow fields as well. Therefore, only 
perched water model #1 is used in TSPA-SR. 
The difference in the calculated groundwater flow patterns using the PA model may be a 
consequence of the shorter travel paths in the southern portion of the repository, where more 
particles experience vertical flow rather than lateral diversion as in perched water model #2. As 
a result, particles may be experiencing less opportunity for matrix diffusion and subsequent 
matrix sorption in those vertical pathways. Although significant matrix flow can occur in the 
Calico Hills vitric unit (Section 3.7.3.3), it appears that at least some of the flow may still occur 
in the fractures, especially at higher infiltration rates during future climates, which results in 
faster and more direct travel paths in perched water model #1. 
3.7.5.4 Abstraction of Groundwater Flow Patterns 
The arrival at the water table of a nonsorbing tracer (Tc) released uniformly in the repository 
region is simulated using FEHM V2.1 to gain insight into the range of possible groundwater flow 
patterns that can result based on the different possible infiltration cases for the present-day 
climate. Breakthrough curves for future climates are also presented in CRWMS M&O (2000, 
U0160, Section 6.2.6), but they are not presented here. 
Figure 3.7-18 shows the breakthrough curves for Tc using the present-day climate and three 
infiltration cases. The median arrivals at the water table are approximately 400 years, 2,000 
years, and 600,000 years for the upper, mean, and lower infiltration cases, respectively. As 
expected, the higher infiltration rates yield shorter breakthrough times relative to lower 
infiltration rates. As a result, the range of median breakthrough times among the three different 
infiltration cases is large (nearly 600,000 years). 
3.7.6 Summary and Conclusions 
The Flow Model and its submodels are developed to simulate past, present, and future 
hydrogeologic, geothermal and geochemical conditions at the UZ of Yucca Mountain for 
supporting various TSPA activities, including the current TSPA-SR calculations. This section has 
presented the Flow Model and its submodels in terms of the methodology and key model results, 
summarized as follows (as well as in Figure 3.7-19). 
Model Calibration and ValidationModel calibration is part of the important iterative 
processes of the UZ model development to build and enhance the confidence in model 
predictions of the site condition. The Flow Model has been calibrated using the available data 
observed and measured from the site, including field-measured saturation, water potential and 
perched water data, temperature profiles, and geochemical data. These model-calibration efforts 
conclude that the Flow Model can accurately reproduce moisture conditions in the UZ of Yucca

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Mountain in terms of liquid saturations, water potentials, and perched water occurrence, as well 
as temperature conditions. 
Role of the PTn UnitThe 3-D PTn submodel (Section 3.7.3.1) has provided some important 
insights into the role played by the PTn unit to alter the flow pattern of the incoming moisture 
flux after the flux has traversed through the welded TCw unit and encounters the predominantly 
nonwelded PTn unit. The PTn submodel results indicate that (1) percolation flux at the middle of 
the PTn is predominantly matrix flow, comprising nearly 90% of the total flow; (2) the model 
predicted that lateral flow diversion by the PTn is insignificant over the entire UZ model domain. 
However, certain east-bound lateral flow (up to 100 m) is predicted in the areas above the 
potential repository from the mountain crest; and some flow is predicted to be diverted into 
nearby faults when crossing the PTn unit. 
Effects of Major FaultsFaults serve as major focusing conduits for and as a capillary barrier to 
the downward unsaturated liquid flow in the UZ system (Section 3.7.3.2). Lateral diversion of 
water into faults occurs mainly in the CHn and PTn units. Percentage of fault flow versus total 
percolation fluxes increases as mean infiltration rates increases. Under the present-day, mean 
infiltration scenario, the Flow Model predicts that fault flow will increase from 4% at the ground 
surface to 15% at the repository level and to 35% at the water table. 
CHn and Perched Water OccurrenceThe CHn hydrological unit plays a critical role in 
controlling groundwater flow patterns and radionuclide transport pathways from the potential 
repository horizon to the saturated zone (Section 3.7.3.3). The presence of perched water zones 
implies that vertical percolation flux locally exceeds the saturated hydraulic conductivity of the 
perching layer. Thus, the Flow Model predicts that water is significantly diverted laterally, when 
crossing the CHn to a fault zone, fracture network, or relatively high-permeability vitric zone that 
focuses flow to the water table. As indicated by modeling results, the flow patterns, or pathways, 
across the CHn, are controlled mainly by fracture and matrix parameters and their distributions in 
the CHn unit, and by the presence of high-permeability flow channels, such as faults. All 
modeling scenarios indicate significant lateral flow diversion at the CHn resulting from the 
presence of perched water or thick low-permeability zeolitic layers. In addition, the model 
indicates that faults act as major flow paths through the CHn in the northern part of the model 
domain under the current conceptualization. In the southern part of the model domain, flow 
through the vitric zone of the CHn is dominated by matrix flow. 
Percolation Fluxes at the Potential Repository HorizonRepository percolation fluxes 
(Section 3.7.4.1) are predicted largely as a reflection of surface infiltration rates, with areas of 
higher surface infiltration in the northern portion of the model domain and along the Yucca 
Mountain crest and with other areas having correspondingly lower fluxes. These percolation 
fluxes and their distributions indicate little large-scale lateral flow or diversion by the PTn unit 
and flow focusing into faults in the vicinity of the potential repository. 
The statistics of the averaged percolation fluxes within the potential repository footprint indicate 
that the total percolation fluxes within the repository are very similar to the average surface 
infiltration rates over the model domain, except for the glacial-transition scenario, which 
predicts higher average repository fluxes than the average over the entire model domain.

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Percolation Flux Frequency Distribution at the Potential Repository LevelThe areal 
frequency distributions of simulated percolation fluxes at the potential repository horizon are 
approximately log normal, and the fluxes with the highest areal frequency are lower than the 
average values of infiltration rates (Section 3.7.4.2). For the present-day, mean infiltration rate of 
4.6 mm/yr, the highest flux frequencies over 50% of the repository area have fluxes within the 
range of 1.0 to 4.0 mm/yr. 
Fracture-Matrix Flow ComponentsThe model shows that fracture flow is dominant in the 
welded tuff, both at the potential repository horizon and at the water table in all the UZ flow 
fields generated for TSPA-SR calculations (Section 3.7.4.3). For three present-day infiltration 
scenarios, fracture flow consists of 85 to 95% of the simulated fracture-matrix flow components 
at the potential repository level. At the water table fracture flow makes up 70 to 95%, of the total 
flow. For two future climate scenarios, a higher percentage of fracture flow occurs, at both the 
potential repository (8796%) and water table level (7197%), than for the case with of the 
present-day infiltration scenario. 
UZ Flow Abstractions for TSPA-SRNine flow fields are being used in the base-case TSPASR 
calculations (Section 3.7.5). These consist of the three infiltration cases (low, mean, and 
high) in each of the three climate states (present-day, monsoon, and glacial-transition), using a 
permeability-barrier perched water model (model #1, Section 3.7.3.3). (A second perched-water 
model was not used because it produced similar results.) In addition, the model selected 
produced slightly more conservative results in terms of calculated breakthrough times using the 
TSPA transport model. For the two future climate states, a conservative water-table rise of 120 m 
is implemented (water-table elevation = 850 m). Results showed that the increased water table 
decreases the duration of groundwater flow and transport beneath the repository, but it is not 
expected to be significant for TSPA calculations. Finally, an evaluation of the breakthrough 
times of a nonsorbing tracer revealed that the median present-day groundwater breakthrough time 
ranges from 400 years to 600,000 years, depending on the infiltration scenario.

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3.8 AMBIENT GEOCHEMISTRY ANALYSIS AND MODELS 
3.8.1 Introduction 
This section gives an overview of the modeling and analysis of the geochemistry of the Yucca 
Mountain unsaturated zone (UZ) as it pertains to flow and transport modeling. The conceptual 
models and analyses are here grouped together as the Ambient Geochemistry Model (AGM). 
The major emphasis of this work has been to quantitatively describe geochemical processes 
relevant to the task of refining bounds on infiltration rates and percolation fluxes to the potential 
repository. The data used for validation and calibration in this overview are pore-water chloride 
concentrations, 36Cl/Cl isotopic ratios in pore waters (or extracted salts), and calcite abundances. 
The measured geochemical data described in this section are considered to be the best 
understood and characterized within a much larger and more diverse body of information. 
Detailed descriptions and analysis of geochemical data in the UZ and other relevant data (e.g., 
precipitation and runoff water chemistry) are given in the Analysis/Model Report (AMR) 
Analysis of Geochemical Data for the Unsaturated Zone (CRWMS M&O 2000, U0085). More 
complete discussion of the modeling results is presented in the AMR UZ Flow Models and 
Submodels (CRWMS M&O 2000, U0050, Sections 6.4 and 6.5). 
Variations in water chemistry in the UZ can be quite large because of processes such as 
evapotranspiration, water-rock interaction, and climatic changes. Secondary mineral distributions 
and assemblages are also useful for testing hydrological models of the UZ because of their 
sensitivity to infiltration rate, percolation flux, and fracture-matrix interaction. The following 
discussion in the introduction presents the conceptual models for the analysis and modeling of 
Cl, 36Cl/Cl, and calcite. Sections 3.8.2 and 3.8.3 present discussion of modeling results and data 
for Cl and 36Cl/Cl, and Section 3.8.4 is focused on modeling of calcite abundances. Following 
these subsections, several aspects related to model uncertainties, limitations, validation, and 
corroborating evidence are discussed. 
The sensitivity of natural conservative tracers such as chloride (Cl) to infiltration rate is wellknown, 
i.e., the chloride mass-balance method (Phillips 1994, pp. 1524). For such 
constituents, the flux is related to the precipitation rate and additions from other sources such as 
windblown dust (Plummer et al. 1997, pp. 538541). The extent of evapotranspiration in the 
shallow soil zone then controls the concentration in infiltrating water. In arid environments, with 
significant topographic and soil cover thickness variations, the infiltration rate can vary by orders 
of magnitude over short distances (USGS 2000, U0010). Thus, it is expected that spatial 
distributions of a conservative tracer in the subsurface could also vary over a similar range. In 
contrast to using a method such as chloride mass balance and making assumptions about the 
absence of diffusion and lateral flow, limiting the system to one-dimensional piston-flow, it is 
preferable to incorporate such tracers directly into the calibrated flow model. One uncertainty 
concerns the actual scale of variability of net infiltration, because this determines the scale of 
concentration variations. 
A conceptual model illustrating the variations in Cl and 36Cl/Cl in the subsurface and the 
processes thought to control their distributions is shown in Figure 3.8-1. This diagram also 
relates the major issues to the available data that can be used to address these issues. This 
schematic diagram is based on geochemical data described in CRWMS M&O (2000, U0085).

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Hydrogenic calcite deposits in fractures and cavities at Yucca Mountain have been studied to 
estimate past percolation fluxes, flow pathways, and hydrological processes in the (CRWMS 
M&O 2000, U0085, Section 6.10). These deposits can provide an important understanding of 
the current and future UZ percolation, because direct measurements of infiltration fluxes over 
thousands of years are not possible. Using reaction-transport modeling, several factors were 
investigated that influenced calcite deposition (CRWMS M&O 2000, U0050, Section 6.5). 
Calcite deposition in the unsaturated fractured rock occurs through a complex interplay of fluid 
flow, chemical transport, and reaction processes. The following major processes were considered 
in the simulations presented in Section 3.8.4: (1) fracture-matrix interaction (dual permeability) 
for water flow and chemical constituents, (2) gaseous CO2 diffusive transport and partitioning in 
liquid and gas phases, (3) effect of temperature (geothermal gradient) on geochemical reactions, 
and (4) kinetics of fluid-rock chemical interaction. 
The flow of information between various models and data sources and the Ambient 
Geochemistry Model is presented in Figure 3.8-2. The Ambient Geochemistry Model takes its 
inputs from the UZ Flow Model (FM), the Calibrated Properties Model (CPM), and numerous 
sources of geochemical data (Geochemical Data). The results of geochemical modeling are also 
used for testing conceptual models of flow and transport and calibration of percolation fluxes and 
therefore feed back into the UZ FM. This information is then abstracted for use in Total System 
Performance Assessment (TSPA). 
Other geochemical data, such as Sr, isotopic ratios of Sr and U, and stable isotopes of carbon, 
oxygen, and hydrogen, 14C, and tritium, are also important for evaluation of UZ processes. 
However, the more limited number of samples, analytical uncertainties (in particular, tritium), 
and the more complex geochemical behavior (carbon) limit their direct use in a transport model 
at this time. Once the reaction-transport models are shown to capture the important 
mineralogical and geochemical aspects of the UZ, then the modeling of the Sr, U, and C isotopic 
systems will have a much stronger basis, because they are controlled by the nature and 
magnitude of water-rock reactions. 
3.8.2 Chloride and 36Cl/Cl Data and Analysis 
This subsection gives an overview of Cl data from pore waters in the UZ and the relations 
employed to model the concentration variations. The observed distribution of Cl is of 
moderately high values at the base of the TCw (> 100 mg/L) and near the top of the PTn, with a 
range of values in the bulk of the PTn and TSw units of approximately 10 to 120 mg/L (CRWMS 
M&O 2000, U0085, Table 4). Chloride concentrations of several thousand mg/L have been 
reported in the alluvial pore waters; the highest value found in pore waters from rocks in the UZ 
was 245 mg/L (CRWMS M&O 2000, U0085, Table 4). Chloride concentrations in the perched 
water bodies average around 7 mg/L (Sonnenthal and Bodvarsson 1999, p. 142) and reach values 
as low as 4 mg/L in borehole SD-7 (CRWMS M&O 2000, U0085, Table 7). Although some 
pore water in the TSw from the ECRB (Enhanced Characterization of Repository Block) have Cl 
concentrations of around 10 mg/L, most are in the 15 to 30 mg/L range, which are distinctly 
higher than that in the perched water (CRWMS M&O 2000, U0085, Table 5). There are 
differing interpretations to explain the difference between Cl concentrations in perched and pore 
waters. One explanation is that the perched water was derived from fracture water that is more 
dilute than that traveling through the matrix. Another explanation is that the perched water was

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derived from areas of higher infiltration (and lower Cl), which are found generally to the north of 
the potential repository area. A third explanation is that the perched water only forms during 
relatively short periods (thousands of years) of high infiltration associated with wetter glacial 
cycles. These hypotheses for the origin are not mutually exclusive, though. A fourth hypothesis 
(p.16 of this PMR) suggests that the perched water in the north is actually SZ water. However, 
the chemistry of perched water in UZ-14 and WT-24 (northern region) is unlike SZ water 
because it does not show the effect of cation exchange with zeolites (Sonnenthal and Bodvarsson 
1999, p. 119). 
The model used for the simulation of Cl considers that its source is the precipitation reaching the 
surface. The Cl concentration in precipitation is taken as 0.62 mg/L (Sonnenthal and Bodvarsson 
1999, p. 113) and is assumed to be spatially and temporally constant. The model must also 
consider runoff and runon because these processes can result in large changes in the local 
chloride flux. Although runoff may carry some Cl from the surface, the amounts are likely to be 
variable and difficult to quantify. Measurements of surface runoff have typically exhibited Cl 
concentrations of a few mg/L (CRWMS M&O 2000, U0085, Section 6.4), not much higher than 
the estimated effective concentration in precipitation. Therefore, it is assumed that runoff and 
runon are given the same Cl concentration as precipitation. The chloride flux can then be 
expressed as: 
Cl Flux = Concentration Cl (in precipitation)  (Precipitation Flux  Runoff Flux + Runon Flux) 
The model boundary condition is therefore the chloride flux and is not derived from 
measurements of chloride in pore waters from Yucca Mountain. Therefore, this boundary 
condition is independent of the measured pore water Cl concentrations to which the model 
simulations are compared. 
Pore-water chloride, 36Cl/Cl, and sulfate concentrations were analyzed using 3-D transport 
simulations and analytical methods. Water infiltration rate calibrations were performed by 
calculating infiltration rates with the measured pore-water Cl concentrations. As a result, 
modeled Cl and 36Cl/Cl concentrations compared more favorably with measured concentrations 
using the calibrated infiltration rates. An analytical method was applied to the transient transport 
analysis for Cl and 36Cl/Cl. This method, verified by the 3-D simulations under the same flow 
and transport conditions, was able to capture major Cl and background 36Cl/Cl trends under 
conditions of transient Cl input (CRWMS M&O 2000, U0050, Section 6.4). 
A base-case simulation was conducted using the present-day (modern), mean infiltration rate to 
compare the base-case model with observed Cl data. Chloride concentrations from the steadystate 
transport simulation were compared with measured pore-water Cl concentration data 
(CRWMS 2000, U0085, Section 6.5). Simulated and measured concentrations along the stations 
in the ESF and ECRB are shown in Figure 3.8-3; see also Figure 2.1-4 for locations. In 
comparison to the measured Cl concentrations, the simulated concentrations are higher in the 
North (0 to 2,000 m) and South (6,400 m to 8,000 m) ramps, and in the northeast side of the 
ECRB (left side of the figure); and are lower at the southwest end of the ECRB. At the entrance 
of the ECRB, higher simulated Cl concentrations correspond to very low infiltration rates, 
whereas near the western end of the ECRB, higher infiltration leads to lower simulated values of 
Cl concentrations. The results indicate that measured Cl concentrations show a smaller range

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than would be predicted by the modern infiltration rates under steady-state conditions. However, 
because many measured Cl concentrations are fit closely by the model results, it appears that the 
mean infiltration rate is approximately correct. 
Differences between measured and modeled Cl concentration in the high and low infiltration 
regions suggest that the time-averaged infiltration rates may be more uniform. Therefore, 
applying the simple chloride mass-balance approach, using the measured pore-water Cl 
concentration data, we developed a modified water percolation flux map, as shown in Figure 3.8- 
4. The domain was divided into nine regions based on measured Cl concentrations, and by 
inspection of the modern infiltration map. In those regions where pore-water data were 
unavailable (Regions I, II and VIII), the rate was approximated using an average value of the 
present-day, mean infiltration in that area of the map. This was done very coarsely, only to 
capture the mean percolation flux for a large area. The percolation fluxes obtained from this 
analysis are then assumed to be the infiltration rates. Note that this approach is in part an 
alternative interpretation of the distribution of percolation fluxes to that of USGS (2000, U0010). 
Because results from that AMR were used to guide the analysis, it cannot be considered 
completely independent. These percolation fluxes may represent more appropriate time-averaged 
values. The infiltration rates estimated by chloride mass balance are actually very close to the 
mean infiltration rates obtained by averaging the rates over the same area (CRWMS M&O 2000, 
U0050). Cl concentrations modeled using this distribution of infiltration rates are shown in 
Figure 3.8-3, compared to the measured concentrations and the simulated concentrations using 
the base-case infiltration map. 
The distribution of Cl concentrations in the ESF and the ECRB are closer to the mean of the 
measured data with the modified percolation flux map, as would be expected. If a smoother 
distribution of infiltration rates is qualitatively correct, then the modified percolation fluxes 
would have a positive impact on performance because of the lower maximum percolation fluxes 
near the crest of Yucca Mountain. 
To more efficiently assess the effect of the change in Cl and background 36Cl/Cl due to climate 
changes, a 1-D analytical solution was derived that approximates transport to the potential 
repository horizon. 36Cl/Cl ratios can be used as an approximate indicator of age if the samples 
can be shown to have had no bomb pulse 36Cl additions. The 36Cl/Cl ratio during the late 
Pleistocene (10-20 ka) was about 50 to 100% higher than present-day (pre-bomb) ratio of about 
50010-15. This latter modern ratio has been approximately constant for the past 10,000 years. 
Correlation of higher than modern 36Cl/Cl ratios with early Holocene ages determined by 14C and 
a lack of bomb-pulse tritium is good evidence for the older ages of the perched waters. Chloride 
and 36Cl concentrations at ESF and ECRB stations were calculated using a 1-D analytical 
solution to each column of the 3-D calibration grid over the model domain. An assumed glacial 
maximum infiltration rate, corresponding Cl and 36Cl fluxes, and zero initial Cl and 36Cl 
concentrations were first used to estimate a glacial steady-state distribution of Cl and 36Cl 
concentrations. Chloride concentrations and 36Cl/Cl ratios at different times after changing to a 
modern climate were then computed using the calibrated present-day infiltration rates and 
modern Cl and 36Cl fluxes, with the glacial steady-state Cl and 36Cl results as initial 
concentrations. Results of Cl simulations, including climate changes, are presented in CRWMS 
M&O (2000, U0050, Section 6.4), and do not change the overall conclusions presented in the

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preceding paragraph. Analytical results of 36Cl/Cl ratios, with a climate change, are discussed in 
the following paragraph. 
Travel times to the potential repository horizon in the UZ are dependent on the thickness of littlefractured 
PTn units (leading to longer times), and the infiltration rate that is dependent on 
climate. Models of 36Cl/Cl were used to explore these aspects for the UZ Flow and Transport 
Model. Modeled background 36Cl/Cl ratios for different simulation times are plotted in 
Figure 3.8-5 and show that after 18,000 years, the ratios in the South Ramp are much lower than 
the 36Cl/Cl ratios in the North Ramp. Measured background 36Cl/Cl ratios in extracted pore 
salts/waters (CRWMS M&O 2000, U0085, Table 13) are plotted in Figure 3.8-5 and, while 
highly variable, show uniformly low values over much of the South Ramp compared to those 
measured from the North Ramp (see Figure 2.1-3, also). This analysis supports the interpretation 
that the difference in the ratios is primarily a result of the thinner PTn in the South, which more 
than counteracts the lower infiltration rate in this area. Therefore, travel times to the potential 
repository horizon are expected to be greater in the northern region, relative to the southern 
region. The times for equilibration of pore waters (between Pleistocene and modern) at the 
potential repository horizon depend on many factors, including the initial 36Cl/Cl ratio during the 
Pleistocene, and the rate of transition to a modern 36Cl/Cl ratio (500  10-15). The 36Cl/Cl ratio of 
1,000  10-15 is close to a peak value for the last 20,000 years (CRWMS M&O 2000, U0085, 
Figure 31) and therefore the time of 18,000 years is probably overestimated, compared to what 
would be obtained with a time-varying 36Cl/Cl ratio in infiltrating water. 
3.8.3 Evidence for Fast Flow Paths and Transport from 36Cl/Cl and Tritium 
The magnitude and spatial distribution of flow through fast pathways is a critical question for the 
performance of the potential repository. Because flow through fast pathways may be prevalent 
only under transient infiltration events, that may be spaced in time by years or longer, it is 
difficult, if not impossible, to quantify the flux associated with fast flow paths through 
hydrological measurements. Several lines of geochemical evidence can be brought to bear on 
this question. The most recent fast flow path (within the last 50 years) can be investigated by the 
study of isotopes produced by the atmospheric testing of nuclear weapons during the 1950s and 
1960s. The most studied bomb-pulse isotopes at Yucca Mountain are 36Cl and 3H (tritium). 
Data collected from the ESF, ECRB, and surface-based boreholes are described in detail in 
CRWMS M&O (2000, U0085, Section 6.6). 
Locations of fast path flow at the depth of the potential repository in the ESF and ECRB, as 
evidenced by elevated 36Cl/Cl and tritium in pore waters, are generally limited to regions in and 
close to faults (CRWMS M&O 2000, U0085, Section 6.6). In samples collected in the tunnels, 
no evidence has been found for pervasive fast flow path water not associated with faults or 
fracture zones. At locations in the tunnels where bomb-pulse ratios of 36Cl/Cl were found (i.e., 
ratios greater than 1,250  10-15, there are also samples with lower ratios, indicating that the 
effect of fast flow path water has been limited in spatial extent. The latter observation could be 
interpreted as either a very limited degree of fracture-matrix interaction, resulting in highly 
confined transport pathways, or very small fluxes such that Cl has not diffused significantly into 
the matrix or dispersed widely through the fracture system. Locally higher pore-water Cl 
concentrations, however, could mask a bomb-pulse signature (Sonnenthal and Bodvarsson 1999, 
p. 150). However, in the ESF tritium values over the cutoff for bomb-pulse values of 25 TU

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(tritium units) are only found in the Bow Ridge fault zone (CRWMS M&O 2000, U0085, 
Table 10). Although waters having tritium below 25TU may have a bomb-pulse component, they 
have uncertainties that make them suspect. This observation validates the conceptual model of 
generally slow matrix flow through the PTn where it is undisturbed by faulting. 
Tritium values above 25 TU have been found in the TSw in some surface-based boreholes 
(UZ#16, NRG-7a, UZ-1, WT-24, and SD-6), as reported in CRWMS M&O (2000, U0085, Table 
10). Because inversions in tritium abundances with depth were found in samples collected from 
the surface-based boreholes, it has been suggested that fracture and lateral flow are important for 
fast flow path transport (CRWMS M&O 2000, U0085, Section 6.6.2.2). In the five boreholes in 
which perched waters were analyzed for tritium, the maximum tritium abundance was 10 TU 
found in NRG-7a in 1994 (CRWMS M&O 2000, U0085, Table 9). Because many UZ pore 
waters have over 100 TU in the PTn and TCw units (CRWMS M&O 2000, U0085, Table 11), 
the very low tritium abundances in the perched waters suggests that they are unlikely to have a 
significant component of very recent fast-path water. However, because of the short half-life of 
tritium (approximately 12 years) and the change in tritium abundances in precipitation to as low 
as 10 TU by the early 1990s (CRWMS M&O 2000, U0085, Section 6.6.2.2) it is not possible to 
calculate a maximum proportion of recent fast flow path water (i.e., very recent fast-path water 
could be lower in tritium). Pore waters in NRG-7a had up to 46.8 TU in the TSw (CRWMS 
M&O 2000, U0085, Table 11), indicating that the fast flow path waters could have raised the 
perched water tritium abundances significantly from their pre-bomb values that were most likely 
less than 1 TU. Because the 36Cl/Cl ratio in perched water from NRG-7a is approximately 500  
10-15 and the calculated 14C age is over 3,000 years, it is highly unlikely that there is a significant 
proportion (> 10%) of recent fast path water in NRG-7a perched water. However, it is also 
possible that the perched water consists of older fast path water emplaced under much wetter 
conditions or more intense storm events than has occurred over the past 30 years. 
36Cl/Cl ratios in perched waters are elevated above modern ratios in several boreholes, but are 
consistent with calculated ages based on 14C measurements. The highest 36Cl/Cl ratio in the 
perched water was found in UZ-1 (999  10-15) and had a tritium value of only 1.0 TU (CRWMS 
M&O 2000, U0085, Table 9). In fact, tritium abundances in perched water samples collected 
from UZ-14 over time decreased to 0 TU from a maximum of 3.1 TU, with the 36Cl/Cl ratios 
increasing to 690  10-15, which is well above the modern pre-bomb ratio of 500  10-15. In the 
latter sample the age calculated from 14C was over 10,000 years. If the 36Cl/Cl ratios in the 
perched waters were the result of mixing with fast path water, then the relationship between 
tritium would be opposite to what is observed. In summary, the perched waters could have no 
more than a small fraction of fast path water from flow in the past 50 years (probably less than a 
few percent, and certainly less than 10%). 
3.8.4 Calcite Simulation Results and Data 
The purpose of this study was to investigate the relationship between percolation flux and 
measured calcite abundances. Other factors that may be important in relating calcite abundance 
to the percolation flux were also considered, such as the infiltrating water chemistry, partial 
pressure of carbon dioxide, reactive surface areas of minerals, and the relevant model mineral 
assemblage. In CRWMS M&O (2000, U0050, Section 6.5), several simulations were performed 
using a range of infiltration rates, water, and gas chemistry (at the top boundary), and effective

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reaction rates. Two sets of initial mineralogical conditions were considered, so that the effect of 
uncertainties in thermodynamic and kinetic data for more complex minerals, such as zeolites and 
clay minerals, can be assessed. 
Two 1-D columns (representing boreholes NRG-7A and WT-24) were used for analysis of the 
calcite deposition in the Yucca Mountain UZ. There are no calcite data for NRG-7A, so these 
runs cannot be compared with measured data. Analyses of total calcite abundances (ppm by 
mass) in borehole WT-24 were recently reported (CRWMS M&O 2000, U0085, Figure 53) and 
made possible the refinement of the model parameters to better match the profile. The active 
fracture model (Liu et al. 1998, pp. 26332646) was used to describe gravity-dominated and 
preferential liquid flow in fractures. Because a constant infiltration and steady-state water flow 
were considered, percolation through the entire column is equal to net infiltration. Two types of 
water chemical compositions were used for the top boundary of the hydrochemical transport 
simulations. The first water in Table 3.8-1 is a calculated, average Topopah Spring tuff water 
(CRWMS M&O 2000, U0050, Table 6-14). The second water type is a pore water extracted 
from a core from Alcove 5 in the Tptpmn (CRWMS M&O 2000, N0120/U0110, Table 3.10-1). 
This pore water has a higher Ca concentration than the average TSw water. The initial water 
chemical composition used was uniform throughout the column for both the fracture and matrix 
blocks, and was adopted from the average TSw water (Type 1). 
In addition to aqueous species transport and reaction in water, diffusive transport of CO2 in the 
gas phase and equilibration with pore water were considered. The CO2 gas partial pressure used 
for initial and top boundary conditions is in equilibrium with the corresponding aqueous 
chemical composition (the bottom row of Table 3.8-1). These CO2 partial pressures were 
calculated based on the measured pH and calculated HCO3 concentration (by charge balance). 
Water Types 1 and 2 are slightly oversaturated with respect to calcite. The water chemical 
composition, especially pH, is controlled primarily by the CO2 partial pressure. Therefore, the 
boundary water type is also denoted by the characteristic CO2 partial pressure, meaning that the 
CO2 partial pressure is used to indicate the corresponding equilibrated water type as listed in 
Table 3.8-1.

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Table 3.8-1. Aqueous and Gaseous Chemical Concentrations (mg/L) Used for Initial and Boundary 
Conditions of Hydrochemical Transport Simulations (CRWMS M&O 2000, U0050, Table 6-14) 
Water type 1 2 
Component Average TSw water Measured TSw water 
Ca2+ 27 101 
Mg2+ 5 17 
Na+ 91 61.3 
K+ 4 8 
SiO2(aq) 60 70.5 
Al3+ 9.9210-7 (5) 9.9210-7 (1) 
HCO3
- (3) 219 200 
Cl- 41 117 
SO4
2- 40 116 
F- 0.86 0.86 
Fe3+ 6.4610-8 (5) 6.4610-8 (2) 
pH 8.2 (6) 8.32 
PCO2 (bar) (4) 1.32210-3 8.56510-3 
NOTES: (1) Calculated by equilibrating with Ca-smectite at 25C 
(2) Calculated by equilibrating with hematite at 25C 
(3) Total aqueous carbonate as HCO3
-, calculated from charge 
balance 
(4) Calculated at equilibrium with the solution at 25C 
(5) Total aqueous Al and Fe are set equal to those of Type 2 water 
(6) Measured 
A series of simulations examining the sensitivity of calcite deposition to infiltration (percolation) 
rate, boundary water and gas chemistry, and reaction rate are described in CRWMS M&O (2000, 
U0050, Section 6.5). Simulations were carried out for 10 million years based on mineral growth 
having remained approximately constant over the past eight million years (Ma) and the age of 
the rocks being over 12 Ma. This record of growth has been indicated by radiocarbon, 230Th/U, 
and U-Pb ages (CRWMS M&O 2000, U0085, Section 6.10.3.8). 
To compare with measured calcite abundances in WT-24 borehole cuttings and in the ESF, 
simulated calcite abundances (ppmV) were expressed as the average among the matrix and the 
fractures (calculated by calcite volume in the matrix and fractures divided by the total matrix and 
fracture solid volume). Difference in volume and mass abundances are slight for these rocks and 
would imperceptibly change the plots.

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Calcite precipitation generally increased as infiltration rate increased, especially in the TSw unit. 
An increased infiltration rate results in a slight change in the amount of calcite at the bottom of 
the PTn unit. Calcite precipitation is sensitive to the boundary water chemical composition and 
the CO2 partial pressure. Higher CO2 partial pressure results in lower pH and calcite dissolution 
or less calcite precipitation (Type 1 water with a partial pressure of 1.322  10-3 bar over Type 2 
water with a partial pressure of 8.565  10-4 bar). The decrease in pH (increase in H+) 
destabilizes calcite, as in the following reaction: 
CaCO3 (calcite) + H+ . Ca2+ + HCO3
- 
The Type 1 water with a partial pressure of 1.322  10-3 bar may represent the average water 
chemical composition and was used for most sensitivity simulations. 
The calcite distribution is also dependent on reaction rate. Sensitivity studies were performed by 
modification of the reactive surface area for all of the units by a constant factor (CRWMS M&O 
2000, U0050, Section 6.5.4). Close to the land surface in the TCw unit, the higher the reaction 
rate, the more calcite precipitation there was. For simulations using larger reactive surface areas, 
the results show less calcite precipitation in the deeper welded TSw unit because of more rapid 
calcite precipitation at shallower depths, such as in the TCw. Reactive surface areas reduced by 
one order of magnitude from the initial estimated data yielded calcite abundances closest to those 
measured in the TSw unit. 
The following analysis considers the effect of a different mineralogy on calcite deposition, based 
on the WT-24 column. A base-case infiltration rate of 5.92 mm/yr, and estimated bounding 
values of 2 mm/yr and 20 mm/yr at WT-24, respectively, were used in these simulations 
(CRWMS M&O 2000, U0035, Table 9), for consistency other UZ flow simulations. Two top 
boundary water chemical compositions, average TSw water and measured TSw water (Types 1 
and 2, respectively, in Table 3.8-1) were employed. Changes in calcite volume fraction are 
presented in Figure 3.8-6, together with measured calcite deposition data in the WT-24 well 
cuttings (CRWMS M&O 2000, U0085, Section 6.10). 
Modeled calcite abundances in the welded TCw unit are closer to the measured data (in terms of 
curve shape and range of values) with the calcite-silica system and the average TSw water 
(Type 1) than the abundances obtained with a more complex mineralogy (including 
aluminosilicates) and the measured TSw water. The simulations using the calcite-silica system 
also reproduce the calcite deposition in the nonwelded PTn unit more closely, except for the 
bottom layer. The improved agreement for the PTn unit is achieved by reducing the reactive 
surface area, which is consistent with the fact that fewer fractures occur in this unit. The 
simulated abundances at the bottom of the PTn unit are higher than those measured in the WT-24 
column, especially the values from the complex-mineralogy simulation. However, bulk rock 
analyses by X-ray diffraction in the USW G-2 borehole core have high calcite abundances at the 
base of the PTn, suggesting that high values are possible. Results for the middle nonlithophysal 
TSw unit and below for both mineralogy conditions generally fall in the wide range of measured 
calcite data. Between 1200 m and the PTn boundary there is a large discrepancy that cannot be 
explained.

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The simulated results are sensitive to the net infiltration rate (percolation flux). Modeled calcite 
abundances obtained from the highest net infiltration rate (20 mm/yr) are close to the highest of 
the measurements. Those from the base-case (5.92 mm/yr) and lower infiltration rate (2 mm/yr) 
fall in the middle of the TSw measured data range. This may imply that the 20 mm/yr 
percolation flux is an upper bound for the WT-24 location, whereas the base-case net infiltration 
rate (5.92 mm/yr) used in the flow model may be close to a mean value. The reactive surface 
area for calcite, reduced by one order of magnitude from the initial estimate, provides the most 
favorable condition for calcite formation in the deeper welded TSw unit. Therefore, the 
simulated values may be slightly overestimated. 
Calcite abundances provide constraints on percolation fluxes, but cannot give a definite value or 
even a narrow range of values. This is because calcite precipitation depends not only on the 
percolation flux, but also on the water and gas chemistry, reaction rate, geothermal gradient, and 
mineralogy considered. In addition, the uncertainty could rise from climate and infiltration 
variations over time, transient water flow condition, and possible lateral water recharge. 
Over a range of 2 to 20 mm/yr infiltration rates, the simulated calcite distributions using the 
simpler mineralogy (most relevant to calcite precipitation) agree reasonably well with the 
measured data from the WT-24 well cuttings. The amount of calcite precipitation generally 
increases as infiltration rate increases. The simulated calcite abundances are also sensitive to the 
model water and gas chemistry, reaction kinetics, and mineralogy. The analysis provides some 
constraints on hydrological parameters and the percolation flux, and additional evidence for 
validation of the flow and transport model. However, this analysis cannot give a definite value or 
a narrow range of values because of the dependence of calcite deposition on the other factors. 
The main reason for calcite precipitation with depth is its inverse solubility with temperature. 
However, the partial pressure of CO2 and Ca concentration in percolating water controls the 
abundances of calcite and its stability. The reaction rate, and therefore the reactive surface area, 
controls its distribution with depth. 
Measured calcite abundances vary significantly in the ESF as well as in the WT-24 borehole. 
According to the findings in CRWMS M&O (2000, U0085, Section 6.10.1.1), calcite 
abundances decrease with depth in the TSw unit in the ESF, which is not the case in WT-24. 
However, the mean calcite abundance in the ESF is 0.034% (CRWMS M&O 2000, U0085, 
Section 6.10.1.1), which is close to the lower bound of calcite observed in WT-24 borehole 
cuttings. Therefore, the ESF data are consistent with the overall rate of deposition on the UZ, as 
indicated by the WT-24 calcite abundances. The specific trends with depth may be more 
difficult to compare, because the ESF data are obtained over a large lateral distance that 
encompasses areas that may have experienced different percolation fluxes. 
3.8.5 Uncertainties and Limitations 
The use of chloride to estimate infiltration rates or percolation fluxes is directly related to the 
initial estimate of the effective Cl concentration in precipitation, its spatial variations and 
changes over time (Ginn and Murphy 1997, pp. 20652066). If the effective chloride 
concentration is twice the estimated value, then the infiltration rate necessary to produce a given 
subsurface Cl concentration would be twice as high. Studies on the range in chemistry of 
precipitation are given in CRWMS M&O (2000, U0085, Section 6.3). The spatial and temporal

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patterns of precipitation are also uncertain because they have been measured for less than one 
hundred years, which is short compared to the time period over which the chloride 
concentrations have developed in the UZ (tens of thousands of years; Sonnenthal and 
Bodvarsson 1999, p. 107). Therefore, given these uncertainties, the model can only be used to 
provide ranges in the infiltration rate. The percolation flux at the potential repository horizon is 
also influenced by lateral flow in the PTn or at unit boundaries, as well as diffusion and 
dispersion, and thus may not directly reflect the spatial distribution of infiltration. 
As has been investigated in CRWMS M&O (2000, U0050, Section 6.5), the amount of calcite 
precipitated over time is sensitive to the water and gas composition, the reactive surface area, 
and the thermodynamic and kinetic parameters used in the model. Because calcite abundances 
are highly variable within a single unit in the WT-24 borehole and in the ESF (CRWMS M&O 
2000, U0085, Section 6.10.1.1 and Figure 53), it is only possible to estimate a range of 
percolation fluxes (~220 mm/yr). 
3.8.6 Alternative Conceptual Models 
There are no clearly defined alternative conceptual models for the evolution of Cl abundances in 
the UZ. The problems with the model generally reflect the uncertainties and limitations 
described above. Elevated 36Cl/Cl values that are below the bomb-pulse cast-off could easily be 
mixtures of prebomb and postbomb fast path waters. 14C ages of the waters could help 
discriminate between these models; however, dilution with dead carbon from interaction with 
calcite could make the ages appear older. 
An alternative conceptual model for calcite deposition would consider its formation as an 
episodic rather than as steady-state process. Because of the kinetics of calcite precipitation, an 
episodic fluid pulse would tend to change the distribution of calcite with depth, possibly 
resulting in near-surface dissolution and deeper calcite deposition. During more typical smaller 
infiltration events, more precipitation might take place near the surface and little at depth. This 
does not necessarily change the underlying conceptual model for calcite precipitation (kinetic 
rate law), but would change the modeling method and the modification of parameters to match 
measured abundances. 
3.8.7 Corroborating Evidence 
The chloride model can be corroborated, in part, by the study of other conservative and also 
reactive species. Strontium (Sr) was used by Sonnenthal and Bodvarsson (1999, p. 146) 
similarly to Cl, except for undergoing exchange in deeper zeolitic units. The rough match of Sr 
in a few PTn samples and in perched waters is corroborating evidence, but much more data are 
needed to attempt a more quantitative modeling study. Sulfate (SO4) behaves similarly to Cl; 
however, calcium sulfate precipitation in soils may cause some shifts in the SO4/Cl ratio in 
infiltrating water. Differences in atmospheric contributions over time and space may also affect 
the initial SO4/Cl ratio in infiltrating waters (see CRWMS M&O (2000, U0085, Section 6.3) for 
a detailed discussion on precipitation chemistry).

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3.8.8 Analogs 
Other areas of similar climate and rock types provide the best analogs to the ambient 
geochemical system at Yucca Mountain. Analyses of Cl and 36Cl/Cl in thick alluvium elsewhere 
in the Nevada Test Site (Tyler et al. 1996, pp. 14811499) have been studied in detail and have 
been interpreted to represent a long climatic history (over 100,000 years). Chloride profiles from 
the base of the TCw through the PTn at Yucca Mountain and elsewhere in the Nevada Test Site 
(profiles in thick alluvium) show some similarities (Sonnenthal and Bodvarsson 1999, pp. 115 
116). 
The rate of stalagmite growth in caves, tunnels and mines around the world have been 
investigated for the purpose of correlating water supply rate and chemistry to calcite 
precipitation rate (Baker et al. 1998). Theoretically predicted growth rates (using calcite reaction 
kinetics) and calculated rates (based on calcite thickness and C-14 ages) compared favorably 
(Baker et al. 1998, p. 393). 
3.8.9 Model Validation 
The model for chloride concentrations can be tested on the basis of a prediction done in early 
1998 before the excavation of the ECRB (Sonnenthal and Bodvarsson 1999, Figure 14). The 
model used for the prediction differed little from the current Cl model. The predictive model 
used earlier estimates of infiltration rates and hydrologic properties but used the same initial Cl 
concentration in precipitation. It also did not consider runon and runoff. The main similarities 
between the models are the governing boundary condition of Cl fluxes at the surface, the scale of 
the model grids, and the rates of flow and mixing in the subsurface which are controlled by the 
hydrogeological properties. A comparison of the predicted concentrations and those measured in 
pore waters (CRWMS M&O 2000, U0085, Section 6.5) is shown in Figure 3.8-7. The measured 
concentrations generally fall within the range of those predicted for a glacial climate and for the 
modern climate, except in the western part of the ECRB where the model slightly underestimates 
the concentrations, and in the eastern part where they are overestimated. Compared to the range 
of Cl concentrations measured in the UZ (about 4 to 245 mg/L; CRWMS M&O 2000, U0085, 
Section 6.5), the range observed in the ECRB (about 13 to 38 mg/L, CRWMS M&O 2000, 
U0085, Section 6.5) is quite narrow. Given that the ECRB shows substantially lower average 
concentrations than were previously observed in the ESF and in boreholes (Sonnenthal and 
Bodvarsson, 1999, pp. 107156; CRWMS M&O 2000, U0085, Section 6.5), the model 
predictions capture the difference between this area and the other areas where Cl concentrations 
were measured. Differences in concentrations for fracture and matrix in transient climate change 
simulations, and in the matrix for the different climate scenarios, illustrates the sensitivity of 
chloride concentrations to changing boundary conditions. Because sufficiently detailed climate 
records and spatial variations of precipitation and its chemistry will never be obtainable, the 
model results can only be used to provide a range of infiltration rates or percolation fluxes. Thus, 
predictions using estimated glacial maximum precipitation and infiltration rates could have also 
have been similar conditions during the early Holocene. Given these uncertainties, the model can 
be considered validated for its intended use. 
The calcite model (AMR U0050, 2000) incorporated the important processes in the UZ that are 
thought to control calcite precipitation. The model is therefore adequate for its intended use.

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Validation of the calcite model for a quantitative estimate of percolation flux can only be done 
once significantly more data are available as a function of depth, such as at WT-24. This is 
because the reactive surface areas were modified to better match the data. The major uncertainty 
is the unknown effective reactive surface area for calcite, as well as uncertainties in the input 
thermodynamic and kinetic data, and the unknown water chemistry as a function of time for the 
several million years over which the calcite was precipitated. Thus, the parameters used to 
estimate calcite abundances in WT-24 have been modified somewhat to match these data and are 
nonunique because of the many parameters that could be modified simultaneously. Another 
complicating factor is that the development over time of the calcite abundances from WT-24 is 
unknown. Therefore, the model treats the system as at steady state, whereas calcite precipitation 
could have formed during many short transient events. However, the trends and absolute 
abundances of calcite were captured using reasonable modifications to the reactive surface areas, 
which gives confidence in the conceptual model and the range of values of the parameters used 
in the analysis. 
3.8.10 Summary and Conclusions 
Chloride concentrations measured in pore waters from the ESF and the ECRB can be roughly 
matched using the 3-D UZ FM using the base-case, present-day infiltration rates. However, a 
better match to the data is achieved by modifying the infiltration rates so that the percolation 
fluxes are more uniform. This results in lower infiltration rates in those areas over the potential 
repository footprint that are currently estimated to have significantly higher rates, yet 
maintaining roughly the same average rate as the Infiltration Model predicts. Differences in 
background 36Cl/Cl ratios in the ESF may be explained by the thinner PTn section above the 
South Ramp compared to the section above the North Ramp, even though infiltration rates are 
lower in the South Ramp. The higher 36Cl/Cl ratios in the North Ramp could therefore reflect a 
larger proportion of late Pleistocene/early Holocene water or it could be a result of mixing of 
bomb-pulse water and matrix pore water. Although bomb-pulse ratios of 36Cl/Cl, indicating fast 
flow paths, are found in several locations in the ESF and ECRB, they are confined to the 
immediate vicinity of faults and other structural discontinuities, strongly suggesting that large 
areas of the potential repository are unaffected by fast path flow. The lack of bomb-pulse levels 
of 36Cl and tritium in the perched waters supports this position. The results of the analyses are 
summarized in Figure 3.8-8. 
Calcite abundances and ages in the UZ have been used as a tool for estimating percolation fluxes 
(CRWMS M&O 2000, U0085, Section 6.10). Modeling studies, incorporating reaction-transport 
in UZ flow simulations, were used to investigate the relationship of calcite deposition to 
infiltration rate, water and gas compositions, and reactive surface area (CRWMS M&O 2000, 
U0050, Section 6.5). With some modification of the reactive surface area, the model results 
indicated that a range in infiltration rate from about 2 mm/yr to 20 mm/yr could bound the spread 
in calcite abundances, with approximately 6 mm/yr capturing the approximate average 
abundances in the TSw.

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3.9 DRIFT SEEPAGE MODELS 
3.9.1 Introduction 
This section summarizes modeling studies performed to estimate seepage of liquid water into 
waste emplacement drifts. These seepage-related studies are discussed in detail in three AMRs: 
(1) the development of a seepage process model and its calibration, described in AMR Seepage 
Calibration Model and Seepage Testing Data (CRWMS M&O 2000, U0080), (2) the application 
of the model to predict seepage under a variety of conditions, described in AMR Seepage Model 
for PA (CRWMS M&O 2000, U0075), and (3) the seepage abstraction process, described in 
AMR Abstraction of Drift Seepage (CRWMS M&O 2000, U0120). 
Potential seepage of water into waste emplacement drifts has been identified by YMP as a 
principal factor that may affect the overall performance of the potential high-level nuclear-waste 
repository at Yucca Mountain, Nevada (Section 1.2.2). The number of waste packages contacted 
by water, the corrosion rate of drip shields and waste packages, the dissolution and mobilization 
of radioactive contaminants, and their release and migration towards the accessible environment 
all depend on the rate, the chemical composition, and the spatial and temporal distribution of 
water seeping into the waste emplacement drifts. Consequently, the design requirements of the 
engineered barriers (CRWMS M&O, 1998h) are affected by the presence or absence, rate, and 
distribution of drift seepage. 
Seepage is defined here as flow of liquid water into an underground opening such as a niche, 
alcove, or waste emplacement drift. According to this definition, seepage does not include vapor 
diffusion into the opening or condensation of water vapor within the drift. Seepage flux is 
defined as the rate of seepage per unit area. Seepage percentage is defined as the ratio of seepage 
flux divided by percolation flux. In the context of liquid-release tests, seepage percentage is the 
ratio of the amount of water that seeped into the niche divided by the total amount of water 
released. Seepage threshold is defined as a critical percolation flux below which no seepage 
occurs. Seepage fraction is defined as the fraction of waste packages affected by seepage. This is 
equivalent to the number of 5 m drift sections that exhibit a nonzero seepage percentage. 
Estimating seepage into underground openings excavated from an unsaturated fractured 
formation requires process understanding on a wide range of scales, from the mountain-scale 
distribution of percolation flux to the intermediate-scale channeling or dispersion of flow in an 
unsaturated fracture network, to the small-scale capillary-barrier effect, to the micro-scale 
phenomena within fractures and specifically at the drift wall. Moreover, the thermodynamic 
environment in the drift (temperature, relative humidity, ventilation regime, etc.) must be 
considered. 
The schematic in Figure 3.9-1 illustrates some of the seepage-relevant phenomena and processes. 
The factors affecting drift seepage can be described as follows: 
1. Capillary-Barrier Effect, Flow Diversion: Under unsaturated conditions, the rate 
of water dripping into the opening is expected to be less than the downward 
percolation rate because the cavity acts as a capillary barrier (Philip et al. 1989, 
pp. 1628). (A capillary barrier is sometimes also referred to as a Richards barrier

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or cavity effect.) If percolating water encounters the cavity, the relatively strong 
capillary forces in the formation retain the water, preventing it from seeping into 
the drift. Water accumulates at the drift ceiling, where the increase in saturation 
leads to capillary pressures that are locally less negative than in the surrounding 
rock, allowing water to be diverted around the drift. If the lateral hydraulic 
conductivity is insufficient to divert the water, fully saturated conditions are 
reached locally, and seepage occurs as the capillary barrier fails. In an anisotropic 
fracture network, the orientation of an individual fracture determines which of its 
hydraulic properties affects seepage most. The effectiveness of the capillary 
barrier is determined by the capillarity of the vertical fractures and by the 
permeability and connectivity laterally within the fractures. Note that even though 
the capillary barrier fails and seepage occurs, the seepage flux is (perhaps 
significantly) lower than the percolation flux. The seepage threshold and the 
seepage rate are strongly affected by the drift geometry and formation properties, 
especially the capillary-pressure and unsaturated hydraulic-conductivity 
functions. The capillary-barrier effect generally leads to a saturation increase at 
the apex (crown) of the drift. Flow rates and liquid saturations below the drift are 
usually lower as a result of the capillary barrier effect, but may be locally 
increased depending on the drainage system. 
2. Distribution of Percolation Flux, Flow Channeling: As water percolates through 
the layered, unsaturated, fractured porous system at Yucca Mountain, it is likely 
to be redirected and focused into flow channels, which may again be dispersed at 
fracture intersections. The distribution of flow channels, their frequency, width, 
and hydrologic properties determine the seepage probability and thus the number 
of emplacement drifts and waste packages affected by seepage. The spatial 
distribution of flow channels may change with average percolation flux and 
potentially with time. Note that calcite deposits suggest that flow channels do not 
change significantly with time (CRWMS M&O 2000, U0085, Section 6.10.3). 
Flow focusing is estimated based on the active fracture concept (CRWMS M&O 
2000, U0120, Section 6.3.3); these estimates are consistent with an observation of 
a damped feature in Niche 3566 (Section 2.2.2.2.1). Depending on the flux within 
an individual flow channel, the seepage threshold may or may not be exceeded 
locally. A general discussion of channeling effects under unsaturated flow 
conditions can be found in Birkholzer and Tsang (1997, pp. 22212238). Flow 
focusing occurs and must be accounted for on a variety of scales, as discussed in 
Section 3.9.3.1. 
3. Hierarchical Fracture Network: The geometric and hydrologic characteristics of 
the fracture network affect seepage as they determine the flux distribution and the 
effectiveness of the capillary barrier. The intermediate-scale (between mountain 
and drift scale) characteristics of the fracture network affect seep development, 
potential compartmentalization of the flow field, and effective anisotropy. All 
these factors determine the spatial distribution of flow channels and the flux 
within one of those channels. Heterogeneities of the fracture network on different 
scales and within individual fractures affect local percolation fluxes, and therefore 
seepage. The capillary-barrier effect is governed by the connectivity of the

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fracture network and its capillary strength. Small fractures and microfractures, if 
interconnected, have the potential to reduce seepage because they have sufficient 
capillary strength to hold the water, preventing it from freely seeping into the 
opening. At the same time they haveunlike the matrixsufficient permeability 
to facilitate flow diversion around the drift. The question arises whether seepagerelevant 
fracture properties can be derived from fracture-trace maps, considering 
that the mapped geometric characteristics and hydraulic properties are not 
necessarily related. Model calibration is the approach relied upon to determine 
effective parameters that include the potential effects of individual fractures and 
microfractures on seepage. Simulations with multiple realizations of a 
heterogeneous property field are performed to account for the random nature of 
the fracture network (CRWMS M&O 2000, U0075). 
4. Drift Geometry, Roughness, Breakouts The geometry (shape, size) of the 
underground opening (waste emplacement drift, alcove, niche) determines the 
likelihood of encountering seeps and the ease with which water can be diverted 
around it as a result of the capillary barrier effect. Analytical solutions examining 
the impact of drift geometry on seepage threshold were developed by Philip et al. 
(1989, pp. 1628). The geometry of drift-wall roughness and the characteristics of 
the surface (wettability, micro-roughness, dust, and coating) partially control local 
water accumulation, droplet formation, the potential for film flow along the drift 
wall, and eventually dripping locations. The frequency, location, size, and 
geometry of breakouts (locations with a cavity in the drift wall because rock has 
fallen out) and partial drift collapse affect the integrity of the capillary barrier. 
Breakouts may lead to distinct topographic lows, which increase seepage, or they 
make the drift more cone-shaped, which promotes flow diversion and thus 
decreases seepage. 
5. Ventilation, Evaporation/Condensation: The temperature and humidity conditions 
in the drift and their regulation by ventilation determine evaporation and 
condensation effects. Evaporation at the drift wall generally reduces drop 
formation and dripping (Ho 1997a, pp. 26652671), and creates a dry-out zone 
around the drift. If relative humidity in the drift is kept below 100% by 
ventilation, seepage of liquid water is reduced, whereas vapor diffusion into the 
drift is increased. The moisture from the increased vapor influx is effectively 
removed by ventilation. Nevertheless, local differences or temporal changes in 
drift temperature may lead to condensation of vapor, causing droplet formation at 
the drift wall and other surfaces within the drift. Accumulation of condensate may 
lead to dripping. 
6. Excavation-Disturbed Zone, Dry-Out Zone: The properties of the fractured rock 
in the immediate vicinity of the drift wall control the capillary-barrier effect, 
which occurs within a relatively small region around the opening. The extent of 
this zone is approximately given by the height to which water rises on account of 
capillarity. The zone governing seepage is likely to be smaller than the zone 
affected by excavation-induced stress redistribution and related rock deformations 
(opening and closing of existing fractures, generation of new microfractures and

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cracks) resulting from drift excavation. Moreover, drift ventilation and/or heating 
lead to a dry-out zone with associated dissolution and precipitation of minerals 
(CRWMS M&O 2000, N0120/U0110). The hydrologic properties of this zone, its 
extent, and the characteristics of its transition to the undisturbed formation 
potentially impact seepage. 
7. Design: The layout and design of the potential repository and the engineered 
barrier system affect the probability of seepage water contacting waste packages. 
The complex physical processes affecting drift seepage cannot be addressed comprehensively in 
an analytical or numerical model, mainly because it is impossible to obtain sufficient 
characterization data over many scales to describe all the relevant geometric features and 
hydrologic properties. The characterization and modeling approach presented here focuses on 
obtaining effective parameters based on seepage-relevant hydraulic data. The abstraction of 
seepage for Total System Performance Assessment (TSPA) aims at yielding robust, conservative 
seepage estimates over a wide range of hydrologic conditions (CRWMS M&O 2000, U0120). 
3.9.2 Objectives and General Modeling Approach 
Seepage predictions are based on and provide information for a suite of models and analyses: 
 Site-Scale UZ Flow Model (UZFM) (CRWMS M&O 2000, U0050) 
 Calibrated Properties Model (CPM) (CRWMS M&O 2000, U0035) 
 Seepage Calibration Model (SCM) (CRWMS M&O 2000, U0080) 
 Thermal-Hydrological-Chemical Seepage Model (THC Seepage Model) (CRWMS 
M&O 2000, N0120/U0110) 
 Seepage Model for Performance Assessment (SMPA) (CRWMS M&O 2000, U0075) 
 Seepage abstraction (CRWMS M&O 2000, U0120) 
 TSPA 
The site-scale UZ Flow Model provides (among other quantities) the large-scale distribution of 
percolation fluxes at the potential repository horizon (Sections 3.7.4.1 through 3.7.4.3). The 
Calibrated Properties Model (Section 3.6) provides estimates for some of the parameters input to 
the drift-scale seepage process models. The purpose of the Seepage Calibration Model (SCM) is 
to present a methodology for the subsequent development of seepage process models (Section 
3.9.4). The purpose of the Seepage Model for PA (SMPA) is to provide seepage estimates for a 
variety of hydrologic properties and drift shapes (Section 3.9.5). The purpose of the THC 
Seepage Model (Section 3.10) is to analyze the impact of thermal and chemical effects on 
seepage and to predict the chemical composition of water and gas that may seep into waste 
emplacement drifts. The purpose of the seepage abstraction is to provide the framework for 
evaluating seepage into potential repository emplacement drifts for TSPA simulations and to

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generate probability distributions that represent the uncertainty and spatial variability of seepage 
(Section 3.9.6). This information is then used in TSPA calculations for SR. 
Figure 3.9-2 schematically shows the relationships between the different seepage models as well 
as data input and the exchange of information. Air-permeability and liquid-release-test data enter 
the development and calibration of the SCM, which also uses parameters developed by the CPM. 
The modeling approach and some of the seepage-relevant parameters from the SCM are used to 
develop the SMPA, which also evaluates various drift-degradation scenarios. The seepage data 
calculated with the SMPA enter the seepage abstraction process, which incorporates results from 
the mountain-scale percolation flux modeling as well as drift-scale THC modeling to arrive at 
defensible seepage values to be used in the TSPA calculation. This section of the PMR describes 
the SCM and SMPA as well as the seepage abstraction. 
Given the objectives outlined above, the current seepage models are not expected to accurately 
predict individual seepage events or the precise spatial distribution along the emplacement-drift 
axis or the drift ceiling. Instead, the seepage models are intended to provide estimates of the 
seepage flux averaged over a 5 m drift segment (the approximate length of a waste package) as a 
function of the percolation flux on the drift scale. Once seepage rates are known 
deterministically for a wide range of conditions, a probabilistic analysis is performed to include 
uncertainty and spatial variability. In addition, the seepage models improve our understanding of 
seepage in fractured formations and the relative importance of certain factors (such as drift 
deformation, variability in the permeability field, and the correlation between permeability and 
capillary strength). 
Seepage models are simplifications and abstractions of the recognized seepage-relevant 
processes and features summarized in Section 3.9.1. The selection of processes being included in 
a specific seepage model is guided by their expected significance. Experiments are designed to 
identify, understand, and characterize significant processes and parameters. Remaining 
uncertainties and property variabilities are considered either by stochastic simulations and 
uncertainty propagation analyses, or by assuming large parameter uncertainties in the TSPA 
calculations. Conservative assumptions are made for effects that cannot be accounted for because 
of a lack of characterization data. 
The following premises guide the seepage modeling approach: 
1. Seepage amounts and seepage locations are sensitive to magnitude and local 
distribution of percolation flux as well as the heterogeneity in fracture properties 
around the drifts. The heterogeneity cannot be captured deterministically, but 
rather through geostatistical description, stochastic simulations, and the estimation 
of effective parameters. 
2. Parameters affecting seepage are best derived from tests that reveal seepagerelevant 
processes. The effective parameters determined in such a manner are 
process specific, scale dependent, and model related.

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3. Uncertainties in the parameters defining the geostatistical model and mean 
hydrogeologic properties are accounted for in a probabilistic uncertainty 
propagation analysis. 
4. The seepage models must be consistent and compatible with the suite of UZ flow 
and transport models. 
Finally, independent evidence from analog sites is examined and alternative conceptual models 
are studied to guard against potential flaws in the conceptual models. 
As mentioned in Section 3.9.1, seepage is affected by features and processes occurring on a 
multitude of scales, which cannot be captured in a single model. The model hierarchy presented 
here assures that each scale is appropriately represented. The site-scale UZ Flow Model provides 
the large-scale distribution of percolation fluxes (Sections 3.7.4.1 through 3.7.4.3). Flow 
focusing factors are calculated (Section 3.9.6.3) to account for channeling effects occurring on 
the drift scale. The heterogeneity in the seepage process models (Sections 3.9.4 and 3.9.5) leads 
to further flow focusing down to the sub-meter scale. Finally, the estimation of effective 
parameters through calibration against seepage-relevant data (Section 3.9.4) takes into account 
the effects of sub-grid-block channeling and other small-scale flow phenomena. 
3.9.3 Key Issues and Corresponding Modeling Assumptions 
The following is a discussion of key issues pertaining to seepage (see Figure 3.9-3); their 
relevance (given the objectives described in Section 3.9.2) is discussed, and the simplifying 
assumptions made in the seepage process models and seepage abstraction are presented in the 
remainder of this subsection. 
3.9.3.1 Percolation Flux and Channeling Effects 
Flux and spatial distribution of downward percolating water is the most important factor 
affecting seepage rates and locations. Water movement is controlled by net infiltration at the 
surface and subsequent multiscale moisture redistribution either by channeling (flow focusing) or 
bifurcation (flow dispersion). Large-scale geological units and features such as the PTn and 
faults lead to a redistribution of percolation fluxes. On an intermediate scale, flow through the 
fracture network may be focused as a result of flow channeling effects. This leads to zones of 
locally higher percolation fluxes and (in between them) areas of reduced water flow. Water 
within such a high-flux zone (weep) may be further channeled by small-scale heterogeneities of 
the fracture network. Finally, heterogeneity and flow instabilities within individual fractures lead 
to small-scale flow channels (rivulets or fingers). Since flow diversion and average seepage flux 
are determined by the characteristics of these rivulets as they encounter the drift wall, it is 
important to estimate channeling effects on all scales. 
A single numerical model cannot possibly account for multiscale heterogeneity and channeling 
effectsfrom large-scale flow redistributions to small-scale rivulet formation. Therefore, a 
series of models was developed, each addressing flow channeling on its assigned scale. The 
model hierarchy can be described as follows:

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1. Flow redistribution on account of large-scale features is considered in the sitescale 
UZ Flow Model (Section 3.7.2). This model provides average percolation 
fluxes on the scale of hundreds of meters (CRWMS M&O 2000, U0050). 
2. Potential concentration of flow from the large-scale averages to the scale of an 
individual drift segment (an area of tens of square meters) is accounted for by 
multiplying the average flux with a stochastic flow-focusing factor, taking into 
account the fact that flow is reduced in other areas. These flow-focusing factors 
are estimated using the active fracture concept of Liu et al. (1998, pp. 26332646) 
and geometric arguments. The approach is described in Section 3.9.6.3 and 
CRWMS M&O (2000, U0120, Section 6.3.3). 
3. Flow redistribution on the scale of a few meters or less is simulated in the driftscale 
seepage process models (Sections 3.9.4 and 3.9.5), in which heterogeneities 
in the fracture continuum are explicitly represented based on geostatistical 
analysis of air-permeability values (Sections 3.9.4.4 and 3.9.5.2). Seepage is then 
calculated for multiple realizations of stochastically generated property fields. 
4. Phenomena and processes that occur on a scale smaller than the gridblock size of 
the numerical model are accounted for by estimating effective parameters through 
inverse modeling. The impact of rivulets on seepage and other small-scale effects 
are not modeled explicitly, but are implicitly considered by estimating seepagerelevant 
parameters. Specifically, if water from a small-scale rivulet or through 
film flow seeps into the opening during a liquid-release test, it is reflected in the 
corresponding seepage data point. By adjusting parameters during the calibration 
process to match these data points, the small-scale effects are automatically 
accounted for in an integrated way. 
In summary, percolation flux used in the seepage process models is taken to be the large-scale 
average flux multiplied by flow-focusing factors. This increased flux is applied uniformly at the 
top boundary of the model, and additional focusing occurs as water percolates through the 
heterogeneous property field of the model. The calculated seepage fraction is finally determined 
based on property values determined in an inversion of seepage-relevant data that include smallscale 
effects. 
3.9.3.2 Episodic Flow 
Percolation flux is not expected to be constant with time, but may increase episodically as a 
result of high-infiltration events, seasonal variations, and climate changes (Section 3.7.2). 
Episodic flow events may affect seepage in two ways: 
1. Episodic flow events lead to periods when percolation fluxes (and thus seepage 
rates) are greater than the corresponding average values. 
2. Episodic flow events lead to transient effects (such as storage and hysteresis). 
Temporally increased percolation fluxes can be handled by applying episodic-flow factors in a 
way similar to the flow-focusing factors discussed in Section 3.9.3.1 (see also CRWMS M&O

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(2000, U0120, Section 6.3.4)). Currently, there is no evidence that high-frequency fluctuations (a 
few years or shorter) penetrate to the depth of the potential repository. Flow simulations have 
shown that the PTn effectively damps out flow transients (Section 3.7.3.1). Note that increased 
percolation from long-term transients (climate change) is explicitly accounted for in the TSPA 
analysis (CRWMS M&O 2000, U0120). 
Seepage is controlled by the properties of a small zone surrounding the drift. Consequently, 
storage effects as a result of episodic flow events are negligible if the event is longer than the 
time required to change the saturation in the available pore space in that zone. High-frequency, 
large-amplitude net infiltration events are damped as they travel through the mountain to the 
extent that they arrive as diffuse fronts of small amplitude at the potential repository horizon, 
making storage effects in the seepage-controlling zone negligible. An episodic-flow scenario is 
discussed in CRWMS M&O (2000, U0075, Section 6.6.7). Additional documentation on the 
implications of episodic flow for seepage is presented in CRWMS M&O (2000, U0170, FEP 
number 2.2.07.05.00). 
The parameters of the capillary pressure curve are determined by inversion of liquid-release tests 
(Section 3.9.4). These tests are imbibition experiments, yielding a wetting branch of a hysteretic 
capillary pressure curve. If hysteresis were important, this approach would lead to a conservative 
estimate of capillary strength. Potential hysteresis effects, however, are neglected because these 
effects are considered to be small in comparison to the uncertainty inherent in the empirically 
determined capillary pressure relations. 
3.9.3.3 Ventilation, Evaporation, and Condensation Effects 
Ventilation leads to reduced relative humidity in the drift and forced advective removal of water 
vapor. The potential impact on seepage and seepage experiments are as follows: 
1. Water evaporates at the drift wall, reducing the rate of liquid water seeping into 
the opening. 
2. Diffusive vapor transport into the drift increases, potentially creating a dry-out 
zone around the opening. 
3. Water collected in the capture system during liquid-release tests evaporates, 
leading to apparently smaller seepage rates. 
4. Spatial or temporal temperature changes may lead to condensation of water at the 
drift wall. 
Evaporation of water at the drift wall reduces seepage. This effect may be significant during 
ventilation periods, when the evaporation rate exceeds the potential seepage rate, preventing the 
development of liquid droplets that drip into the opening. Ho (1997a, pp. 26652671) provides a 
detailed description of evaporation mechanisms on the scale of individual water droplets within 
or emerging from fractures. The fact that no natural seepage is currently observed in the ESF 
could be attributed to ventilation effects. (Note that, because of the capillary-barrier effect, zero 
seepage may result even if the relative humidity in the ESF were 100%.) Neglecting ventilation 
and evaporation effects in a numerical seepage prediction is conservative because omitting them

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increases predicted seepage of liquid water. Therefore, the assumption is made that the relative 
humidity in the drift is 100% (i.e., there is a zero-capillary-pressure boundary condition applied 
at the drift wall). In a ventilated drift, the development of a dry-out zone increases the capillary 
pressure and local storage volume and thus reduces the risk of reaching seepage conditions; the 
assumption of 100% relative humidity in the drift is again conservative. The assumption is also 
reasonable for the time when ventilation is stopped and the drift is closed. 
The reduced relative humidity in a ventilated drift increases diffusive vapor flow from the rock 
into the opening. However, the underestimation of diffusive vapor flow in a model with 100% 
relative humidity is irrelevant, because the assumption already implies that the moisture content 
in the drift environment is at its maximum. The assumption of 100% relative humidity is 
conservative since it maximizes the amount of moisture that can condense within the drift. While 
condensation is a potentially important effect, no estimates of drip formation as a result of 
condensation due to temperature variations or in-drift movement of moist air are presented here. 
Evaporation of water collected in the seepage-test capture system leads to an underestimation of 
seepage rates during a liquid-release test and is therefore not conservative. Parameters are 
adjusted during the inversion such that the model reproduces the observed seepage percentage, 
which is likely to be too small. This issue is currently addressed by monitoring relative humidity 
in the niche and directly measuring evaporation rates. Moreover, the estimation of seepagerelevant 
parameters is predominantly based on data from short-term liquid-release tests that were 
performed at rates significantly higher than the potential evaporation rate. 
For these reasons, drift ventilation effects are neglected in the current seepage process models. 
Note that evaporation and condensation in the rock as a result of waste-generated heat is 
accounted for in the THC Seepage Model (Section 3.10.5; CRWMS M&O 2000, N0120/U0110). 
In-drift evaporation and condensation effects are not considered here. 
3.9.3.4 Excavation Effects, Surface Roughness, and Drift Degradation 
Drift excavation induces mechanical disturbance and stress redistribution in the surrounding 
rock, creating a zone with altered formation properties. Surface roughness at the drift wall, 
breakouts and rock fall from the drift ceiling, and changes in drift geometry as a result of partial 
drift collapse may result in local topographic lows along the drift ceiling, where water tends to 
accumulate. These features have the following impact on seepage: 
1. Increased fracturing, fracture dilatation, and fracture compression affect the 
hydrologic properties of the excavation-disturbed zone (EDZ), and may increase 
or decrease seepage. 
2. Small-scale roughness increases local ponding probability and thus increases 
seepage. 
3. Depending on the location of rock fall along the drift perimeter and the geometry 
of the breakouts, these intermediate-scale changes in drift-wall geometry tend to 
promote seepage as water may be channeled into rock wedges from which it

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cannot escape. The frequency, location, and geometry of breakouts determine 
their overall impact on total seepage. 
4. Depending on the final shape of the drift, partial or complete drift collapse may 
either increase or decrease seepage into the remnants of the opening. Since 
breakouts tend to produce local topographic lows along the drift wall, it is more 
likely that drift collapse leads to an increase in seepage. 
Existing fractures may be opened or compressed as a result of drift excavation. The mechanism 
leading to either opening or closing of fractures depends on the location of the drift in relation to 
major geologic features, the position along the drift circumference (crown, spring line, invert), 
the local stress condition, the fracture orientation and fracture network characteristics, the rockmechanical 
properties of the fractures and the matrix, and the rock-mechanical behavior during 
the deformation (elastic, inelastic). Fracture dilatation leads to an increase in permeability, which 
tends to reduce seepage, and at the same time to a decrease in capillary strength, which tends to 
increase seepage. Conversely, reduced permeability as a result of fracture compression tends to 
promote seepage, but at the same time the increased capillary strength enhances the water 
retention capability, reducing seepage. This counteracting effects reduce the overall impact of 
fracture deformation on seepage. A detailed analysis of the coupled hydrologic-mechanical 
behavior as a result of drift excavation and its effect on seepage is difficult to perform. Note that 
the approach described in this section relies on the calibration of data from seepage experiments 
that were performed in the excavation-disturbed zone. The data thus reflect potential effects of 
fracture dilatation or compression on seepage. Matching these data through inverse modeling 
yields effective parameters that include potential excavation effects. 
The extent of the EDZ is likely to exceed the thickness of the zone that determines seepage. This 
is confirmed by modeling (Bidaux and Tsang 1991, pp. 29933008) and experimentation (Wang 
and Elsworth 1999, pp. 751757). The seepage-relevant properties of this zone are determined 
by calibration against liquid-release-test data. As a result of this approach, the potential impact of 
the EDZ on seepage is automatically accounted for in a calibrated seepage process model. Note 
that excavation-induced (micro-) fracturing around the drift increases permeability without 
significantly reducing the effective capillary strength. This reduces seepage by promoting flow 
diversion. On the other hand, dilatation of existing fractures is accompanied by a reduction in 
capillary strength, offsetting the advantage of increased permeability by a reduced strength of the 
capillary barrier. 
If the amplitude of small-scale surface roughness reaches a significant fraction of the capillary 
head, small-scale lateral flow diversion is impeded and saturation in the troughs of the wavy or 
jagged surface is elevated, leading to increased seepage. The impact of small-scale, subgridblock 
surface roughness is automatically accounted for through the estimation of effective 
seepage parameters. 
A breakout can be described as an intermediate-scale surface roughness. Water is accumulated in 
topographic lows created by the breakout, leading to increased local seepage if no opportunities 
or insufficient opportunities for flow diversion exist. The impact of breakouts on seepage 
depends on block size and rock fall frequency, which in turn is functions of fracturing and stress

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conditions. Examples of 3-D seepage simulations with discrete breakouts are presented by 
CRWMS M&O (2000, U0075, Sections 6.4.2 and 6.6.5). 
Extended rock failure and partial drift collapse may change the shape of the opening in a way 
that promotes or reduces seepage. One example yielding increased seepage is shown in 
Section 6.4.3 and CRWMS M&O (2000, U0075, Sections 6.43 and 6.6.5). The composite effects 
of drift degradation are accounted for in the seepage abstraction (Section 3.9.6) through 
application of a seepage-rate enhancement factor (CRWMS M&O 2000, U0120, Section 6.3.1). 
3.9.3.5 Capillary Barrier and Seepage Threshold 
The capillary-barrier effect has been described in Section 3.9.1, Point 1. While the development 
of a capillary barrier and the existence of a seepage threshold are the result of the fundamental 
behavior of fluids in unsaturated media and are well-understood features of a hydrogeologic 
system (see, for example, Frind et al. (1977, pp. 31333163); Philip et al. (1989, pp. 1628); 
Oldenburg and Pruess (1993, pp. 10451056); Birkholzer et al. (1999, pp. 349384)), the 
effectiveness of the capillary barrier at a specific location is difficult to determine. It specifically 
depends on the permeability and capillary strength near the opening. Moreover, the performance 
of a capillary barrier must be assessed as a total system (here on the scale of the cross section of 
a waste emplacement drift) that considers all the factors discussed in Sections 3.9.3.1 through 
3.9.3.4. 
A detailed characterization of seepage-relevant, small-scale hydrogeologic properties near the 
drift wall appears unfeasible. Fracture-trace maps are likely to be biased because they exclude 
small fractures and microfractures, which may be crucial for the performance of the capillary 
barrier. In addition, it is difficult to relate the mapped geometric characteristics to the hydraulic 
properties governing seepage. For these reasons, no use of geometric fracture network 
information is made, because it would require making numerous simplifying assumptions to 
arrive at the hydrogeologic properties controlling seepage. Instead, seepage-relevant properties 
are determined, and the overall performance of the drift as a capillary barrier is assessed by 
conducting and analyzing liquid-release tests. As water injected from a borehole reaches the 
opening at the drift crown, the capillary barrier comes into effect. Some of the water may seep 
into the opening, whereas the rest is diverted laterally, eventually flowing around the drift. 
Analyzing data from this experiment ensures that the capillary barrier is tested on the appropriate 
scale, in the relevant zone, and using the pertinent physical processes such as water retention and 
pressure build-up in the fractures, flow diversion through microfractures, local failing of the 
capillary barrier in discrete fracture segments intersected by the opening, and seepage as a result 
of film flow. Nevertheless, numerical modeling is required to estimate seepage under changed 
conditions, namely lower percolation fluxes. Currently, the validity of such an extrapolation 
cannot be assessed experimentally. The synthetic modeling study presented in CRWMS M&O 
(2000, U0080, Section 5.3) suggests that reasonable predictions of seepage for lower percolation 
fluxes can be obtained when following the approach described here and in Section 3.9.4 below. It 
should be realized that applying a numerical model to conditions and time scales different from 
those encountered during model calibration always bears a risk, because the underlying 
mechanisms significant to seepage may change.

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The seepage threshold may be considered a characteristic point describing the performance of a 
capillary barrier. It indicates whether or not water seeps into the opening for a given local 
percolation flux. However, performance assessment requires predicting seepage rates over the 
entire range of expected percolation fluxes. Even if seepage-threshold estimates remain 
uncertain, the reduction of drift influx at percolation fluxes above the seepage threshold is an 
important aspect of the seepage problem. The relative difficulty of accurately determining the 
seepage threshold does not invalidate the calculation of seepage fluxes. 
3.9.4 Seepage Calibration Model 
3.9.4.1 Objectives and General Approach 
In this section the development, calibration, and validation of the Seepage Calibration Model is 
described. The purpose of the SCM is to present a methodology for the subsequent development 
of seepage process models such as the Seepage Model for Performance Assessment 
(Section 3.9.5). The SCM is a template, heterogeneous fracture-continuum model that is 
developed based on air-permeability and liquid-release-test data from the experiments performed 
in Niche 3650 of the ESF at Yucca Mountain. The steps involved in the development of the SCM 
are schematically shown in Figure 3.9-4. A geostatistical analysis of post-excavation airpermeability 
data provides the basis for the generation of a heterogeneous property field, which 
is mapped onto the model grid. Liquid-release tests are simulated to calibrate the model against 
measured cumulative-seepage data. The calibrated SCM is then validated using data from 
additional liquid-release tests. The development of the SCM is documented in CRWMS M&O 
(2000, U0080). 
The scope of this modeling study is limited to an analysis of seepage data from Niche 3650. The 
parameters estimated by the SCM are thus only representative for isothermal seepage into an 
uncollapsed opening excavated in the middle nonlithophysal zone of the Topopah Spring welded 
tuffs at Yucca Mountain. 
3.9.4.2 Air-Permeability and Liquid-Release-Test Data 
Air-injection tests were performed in boreholes drilled above Niche 3650, and air-permeability 
values were determined (CRWMS M&O 2000, U0015, Section 6.1). A geostatistical analysis of 
these post-excavation air permeabilities provided a measure of statistical variability and spatial 
correlation (see variogram in the top panel of Figure 3.9-4). The air-permeability field is 
essentially random, without a noticeable spatial correlation. 
A series of short-duration liquid-release tests was performed at Niche 3650. The seepage tests 
were conducted after niche excavation by introducing water into select test intervals in boreholes 
located above the niche. The tests were performed by sealing a short section of borehole (using 
an inflatable packer system) and then releasing water at a constant rate into the isolated test 
interval. Any water that migrated from the borehole to the niche ceiling and dripped into the 
opening was captured and weighed. The seepage percentage, defined as the mass of water that 
dripped into the capture system divided by the mass of water released into the borehole interval, 
was used to quantify seepage into the drift from a localized water source of known duration and

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flow rate. Details about the liquid-release tests can be found in CRWMS M&O (2000, U0015, 
Section 6.2). 
The heterogeneous property field of the SCM was developed based on the geostatistical 
characteristics of the air-permeability data (Section 3.9.4.4). The seepage-relevant hydrologic 
properties were determined by calibrating the SCM against the liquid-release-test data 
(Section 3.9.4.5). 
3.9.4.3 Model Assumptions 
The basic assumptions of the SCM are consistent with those of other submodels of the UZ Flow 
and Transport Model (see Section 1 for list of submodels; see CRWMS M&O (2000, U0050, 
Sections 5 and 6.1.2) for assumptions and modeling approach); the submodel of specific concern 
is the SMPA described in Section 3.9.5. Consistency and compatibility are essential 
requirements because the concepts and parameters derived with the SCM are only valid and 
useful for subsequent seepage calculations if they refer to similar conceptual models. The key 
assumptions are summarized below; additional assumptions and a more detailed discussion of 
why they are considered valid or reasonable can be found in CRWMS M&O (2000, U0080, 
Section 5). 
It is assumed that the continuum approach is a valid concept to calculate percolation flux and 
drift seepage at Yucca Mountain. This assumption is based on the observation that the fracture 
network in the Topopah Spring middle nonlithophysal unit at Yucca Mountain is well connected 
(CRWMS M&O 2000, U0075, Section 6.7). In addition, the synthetic study presented in 
CRWMS M&O (2000, U0080, Section 5.3) demonstrates that simulating seepage into 
underground openings excavated from a highly fractured formation can be performed using a 
model that is based on the continuum assumption, provided that the model is calibrated against 
seepage-relevant data such as data from a liquid-release test. Synthetically generated data from a 
model that exhibits discrete flow and seepage behavior were used to calibrate a simplified 
fracture-continuum model. Seepage predictions for low percolation fluxes made with the 
calibrated fracture-continuum model were consistent with the synthetically generated data from 
the discrete-feature model. The appropriateness of using the continuum approach to simulate 
flow through fractured rock was also studied by Jackson et al. (2000, pp. 189202) using 
synthetic and actual field data. They concluded that heterogeneous continuum representations of 
fractured media are self-consistent, i.e., appropriately estimated effective continuum parameters 
are able to represent the underlying fracture network characteristics. 
Adopting the continuum approach, water flow under unsaturated conditions is assumed to be 
governed by Richards equation (Richards 1931, pp. 318333). Relative permeability and 
capillary pressure are described as continuous functions of effective liquid saturation according 
to the expressions given by the van Genuchten-Mualem model (Luckner et al. 1989, pp. 2191 
2192). Within the heterogeneous property field, capillary strength is correlated to absolute 
permeability according to the Leverett scaling rule (Leverett 1941, p. 159).

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3.9.4.4 Model Development 
Because the SCM was to be calibrated against liquid-release-test data obtained in Niche 3650, 
the model was discretized to include the approximate geometry of the niche and its boreholes. A 
permeability field was generated, conditioned on and following the geostatistical properties of 
the post-excavation air-permeability data measured in various intervals of the three boreholes 
drilled above the niche. The resulting permeability field was mapped onto the numerical grid of 
the SCM, and the capillary-strength parameter was correlated to the permeability in each grid 
block according to Leveretts scaling rule (Leverett 1941, p. 159). The location of Niche 3650, 
its layout, and the corresponding numerical grid and log-permeability field of the 3-D 
heterogeneous SCM are shown in Figure 3.9-5. Simplified versions of the SCM include a 2-D XZ 
cross section and homogeneous versions of the model in two and three dimensions. 
A free-drainage boundary condition was applied at the bottom of the model. The niche itself was 
set at a reference pressure of 1 bar. No capillary suction was applied in the niche, i.e., it was 
assumed that the air at the niche wall was of 100% relative humidity (see discussion in 
Section 3.9.3.3). Water was allowed to enter, but was prevented from exiting the niche. Thus, the 
temporal change of water in the niche element represented the cumulative seepage collected in 
the capture system installed during the liquid-release tests in Niche 3650. No-flow boundary 
conditions were specified at the left, right, back, and front sides of the model. Initial parameter 
estimates were obtained from the Calibrated Properties Model (CRWMS M&O 2000, U0035), 
and a steady-state simulation was performed to obtain the initial saturation distribution. More 
details about the development of the SCM can be found in Section 6.3 of CRWMS M&O (2000, 
U0080). 
3.9.4.5 Model Calibration 
Data from five liquid-release tests (CRWMS M&O 2000, U0080, Table 6) were selected for 
calibration of the seepage model by means of inverse modeling. The five tests were conducted in 
30 cm long borehole intervals at various injection rates (ranging from approximately 120 ml/min 
for the first test to 1 ml/min for the last test), revealing the dependence of seepage on flux. 
Approximately 1 liter of water was injected in each test. The inactive time between individual 
test events ranged from approximately 2 hours between the second and third test, to 20 days 
between the first and the second test. This reveals potential memory effects such as the increased 
seepage percentage in the third test, which is a result of reduced storage because the pore space is 
occupied by water injected during the previous test. The seepage percentages observed at the end 
of each test (ranging from approximately 56% for the third test to 0% for the last test) are thus 
expected to reveal a number of seepage-relevant processes, including storage effects and rates 
below and above the seepage threshold. 
Using the measured amount of water collected during the five seepage tests, two parameters 
were determined by inverse modeling. The two parameters are the porosity ( f) and the reference 
capillary-strength parameter (1/ a). These parameters were selected because of their sensitivity to 
the observed data and their correlation to other parameters. In a transient seepage experiment 
with only a small volume released, the amount of water seeping into the niche depends mainly 
on the following three factors:

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1. The ability of the formation to hold the water by capillary forces, here expressed 
through an effective van Genuchten parameter a 
2. The ability of the formation to store the finite amount of water released, here 
expressed through an effective porosity f, which may include effects of matrix 
imbibition 
3. The ability of the formation to divert water around the opening, here expressed 
through an effective permeability k. 
The simulated seepage mass can be increased by decreasing either capillary strength, 1/ a, 
porosity, f, or permeability, k. Consequently, all possible parameter pairs are negatively 
correlated if inversely determined from seepage data. Because only seepage-mass data are 
available for calibration, the parameter correlations are expected to be strong; that is, it is 
unlikely that they can be determined independently from one another and with a reasonably low 
estimation uncertainty. The parameters to be determined are the porosity ( f) and the reference 
capillary-strength parameter (1/ a) while permeability (k) is fixed at the value estimated from the 
air-injection tests. A joint inversion of all five tests using iTOUGH2 V4.0 (STN: 10003-4.0-00) 
(Section 1.3.3.2) yielded a good match and reasonable parameter estimates. As shown in Figure 
3.9-6, the heterogeneous three-dimensional SCM matches the observed seepage-mass data well 
and better than the two-dimensional or homogeneous alternatives. 
The estimated reference capillary-strength parameter of 1/ a = 66 Pa is low relative to values 
derived from calibration against saturation and water-potential data (CRWMS M&O 2000, 
U0035, Section 6.1.2). This is mainly because the injected water preferentially flowed through 
the relatively large fractures, which exhibit weak capillarity. In addition, the apertures of these 
fractures are likely to be larger in the excavation-disturbed zone as opposed to the undisturbed 
rock, leading to weaker capillarity. Moreover, the low estimate results from the fractures not 
being modeled as discrete features but as a continuum. Discrete fractures intersecting the niche 
promote seepage (i.e., for some flow paths, diversion around the drift is not possible). 
Consequently, the absence of discrete fractures in the model is partly compensated by a 
reduction of the estimated 1/ a value, which has the effect of weakening the capillary barrier and 
thus increasing seepage. The porosity estimate of f = 0.0013 seems reasonable (CRWMS M&O 
2000, U0090, Section 6.1); it comprises all fractures involved in the flow and seepage process, 
including microfractures and the pore space affected by matrix imbibition. Note that porosity is 
of no importance for the prediction of long-term, near-steady-state seepage. More details about 
the calibration of the SCM can be found in CRWMS M&O (2000, U0080, Section 6.4). 
3.9.4.6 Model Validation 
The purpose of the SCM is to provide a general modeling approach that can be used for the 
subsequent development of process models for seepage predictions. These predictions are 
performed with the Seepage Model for Performance Assessment (SMPA), which develops the 
data basis for the seepage abstraction. Confidence into the SCM and the modeling approach can 
be gained by demonstrating that seepage-relevant processes and seepage-relevant parameters are 
identified to the degree required by the objectives of the downstream models. The SMPA 
evaluates seepage over a wide range of parameter values to accommodate spatial variability and

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uncertainty (Section 3.9.5). Moreover, uncertainty is accounted for during the abstraction process 
by choosing appropriate distribution functions for the input parameters and by applying safety 
factors based on conservative assumptions (Section 3.9.6). 
Given the objectives of the downstream models, the following testing of the SCM was 
considered sufficient and appropriate. The calibrated SCM was used to make predictions of 
observed seepage percentages from liquid-release tests that were performed in a different 
borehole interval using different injection rates and varying inactive time periods in between the 
individual test events. The uncertainty of the model predictions was evaluated using linear error 
propagation analysis and Monte Carlo simulations. This approach reflects the intended use of the 
downstream models, in which seepage is treated as a stochastic process. The observed seepage 
percentages lay within the uncertainty range of the model predictions, i.e., a correct probabilistic 
statement would have been made regarding the predicted seepage value. This favorable result 
increased confidence in the appropriateness of the chosen approach to seepage modeling. The 
relevant processes are understood and the key factors affecting seepage are identified. The 
proposed modeling approach, which includes the conceptual model development and the 
calibration against seepage-relevant data, is appropriate for evaluating seepage into waste 
emplacement drifts. The model is thus validated for its intended use. More details about the 
testing of the SCM can be found in CRWMS M&O (2000, U0080, Section 6.5). 
3.9.4.7 Seepage Threshold Prediction 
Steady-state seepage simulations were performed with the calibrated SCM (CRWMS M&O 
2000, U0080, Section 6.6). The percolation flux applied at the top of the model was varied over a 
large range. Starting from a small value yielding zero seepage, the percolation flux was increased 
stepwise until seepage occurred, at which point the seepage threshold was identified. Further 
increasing the flux at the top model boundary provided estimates of seepage percentage as a 
function of percolation flux. A seepage threshold of approximately 200 mm/yr was obtained for 
the middle nonlithophysal unit of the Topopah Spring tuff. Note that this value applies to an 
opening of the size and geometry of Niche 3650; thus, the estimate cannot be directly applied to 
seepage into waste emplacement drifts because they are of a different geometry andmore 
importantlyare predominantly located in a different stratigraphic unit. Furthermore, seepage 
threshold predictions are expected to be highly uncertain and variable with location. 
Conservatively estimated distributions of seepage thresholds for the potential repository horizon 
are presented in Section 3.9.6.4. The preliminary seepage-threshold prediction obtained for 
Niche 3650 suggests that a potentially significant amount of water percolating under natural flow 
conditions is diverted around the drift. 
3.9.4.8 Summary 
The calibration and validation of the SCM demonstrate that simulations of seepage into 
underground openings excavated from a highly fractured formation can be performed using a 
heterogeneous fracture-continuum model, provided that the model is calibrated against seepagerelevant 
data. The calibration process yields scale-dependent, seepage-specific, and modelrelated 
effective parameters that partly reflect the discreteness of the fracture network. The 
modeling and calibration approach was successfully applied to seepage data from liquid-release

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tests performed in Niche 3650 in the ESF. The calibrated model can be used to predict seepage 
threshold and seepage percentages for different percolation fluxes, as described in Section 3.9.5. 
3.9.5 Seepage Model for PA 
3.9.5.1 Objectives and General Approach 
This section contains a description of the simulations performed with the Seepage Model or 
Performance Assessment (SMPA) and its submodel, the Disturbed Drift Seepage Model 
(DDSM). The main purpose of the SMPA is to evaluate long-term drift seepage over a large 
range of hydrogeologic parameters and for a variety of percolation fluxes. In addition to these 
parameter sensitivity studies, the SMPA is also used to examine certain scenarios described 
below (Section 3.9.5.3). The SMPA is run for multiple realizations of heterogeneous rock 
properties. Effects of episodic flow events and changed drift geometry on account of drift 
degradation are also evaluated. The results of these simulations are to be used by TSPA to 
develop the probability distributions of water seepage into waste emplacement drifts 
(Section 3.9.6). The SMPA is documented in CRWMS M&O (2000, U0075). 
The SMPA simulations are based on the current repository design, using hydrogeologic 
information and seepage-related data from the middle nonlithophysal unit of the Topopah Spring 
tuff. Moreover, it only considers seepage under ambient thermal conditions. These limitations 
require the use of relatively large uncertainties in the subsequent TSPA calculations 
(Section 3.9.6). 
3.9.5.2 Model Development 
The SMPA follows the approach of the SCM (see Section 3.9.4 and CRWMS M&O (2000, 
U0080)) and the modeling framework described in Birkholzer et al. (1999, pp. 358362) 
(CRWMS M&O 2000, U0075, Section 5). The model is based on the same assumptions already 
discussed in Section 3.9.4.3. The SMPA is a three-dimensional, heterogeneous fracturecontinuum 
model 5.23 m long (corresponding to the waste package length plus 0.1 m spacing), 
15 m wide (drift diameter is 5.5 m), and 20 m high. Gridblock size is 0.5 m  0.5 m  0.5 m. 
Additional information about the development of the SMPA can be found in CRWMS M&O 
(2000, U0075, Section 6.3). 
3.9.5.3 Selection of Parameter Ranges and Case Studies 
Table 3.9-1 shows four parameters identified as being relevant for long-term seepage predictions. 
Seepage is evaluated for each parameter combination at discrete points within the ranges 
indicated; three realizations of the heterogeneous property field were generated for each point in 
the four-dimensional parameter space. This can be considered an extensive sensitivity analysis. 
No probability distributions or parameter correlations need to be specified here; during the 
seepage abstraction (Section 3.9.6) and TSPA calculations, correlations are identified, and the 
seepage rates developed here are sampled following the probability distributions of the input 
parameters.

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Table 3.9-1. Parameter Ranges for Which Seepage Is Evaluated Using the SMPA (Adapted from 
CRWMS M&O 2000, U0075, Section 6.3) 
Parameter Minimum Maximum Parameter Description 
k, m2 0.9  10-14 0.9  10-11 Mean permeability of fracture-continuum 
1/ a, Pa 30 1000 van Genuchtens capillary-strength parameter 
sln(k) 1.66 2.50 Standard deviation of log-permeability field 
Qp, mm/yr 5 500 Percolation flux 
The permeability range is based on a review of air-permeability data from the niche studies 
(CRWMS M&O 2000, U0015, Section 6.1), the Single Heater Test area (Tsang and Birkholzer 
1999, p. 393), pneumatic pressure signal analyses (Ahlers et al. 1999, pp. 4768), and airinjection 
tests in four surface-based boreholes (LeCain 1997, pp. 2, 1114) (CRWMS M&O 
2000, U0075, Section 6.3.2). 
The range of the capillary-strength parameter 1/ a covers the values obtained with the SCM 
(CRWMS M&O 2000, U0080, Table 10) and previously published values by Birkholzer et al. 
(1999, p. 354) (CRWMS M&O 2000, U0075, Section 6.3.4). The lower bound for the sln(k) 
parameter, which reflects the degree of heterogeneity, is taken from the geostatistical analysis of 
post-excavation air-permeability data at Niche 3650 (CRWMS M&O 2000, U0080, 
Section 6.2.3). 
Seepage is expected to increase with increasing variability in the heterogeneous permeability 
field, because local channeling effects and ponding probabilities are increased. Consequently, the 
range of sln(k), which is a measure of heterogeneity, is examined for values higher than that 
obtained from the geostatistical analysis of the air-permeability data (CRWMS M&O 2000, 
U0075, Section 6.3.5). 
Finally, seepage is evaluated for percolation fluxes as low as 5 mm/yr and as high as 500 mm/yr 
(CRWMS M&O 2000, U0075, Section 6.3.6). The latter accounts for a pluvial climate scenario 
as well as spatial and temporal focusing effects (Sections 3.9.3.1, 3.9.3.2, and 3.9.6.4). The 
rationale for selecting the parameter ranges shown in Table 3.9-1 is further discussed in Sections 
6.3.2 through 6.3.4 of the AMR CRWMS M&O (2000, U0075). 
Two parameter combinations were singled out for additional sensitivity studies. Parameter Set A 
is close to the base-case set given in Birkholzer et al. (1999, Table 1); Set B is close to the bestestimate 
parameter set obtained with the SCM, reflecting parameters of the EDZ (CRWMS 
M&O 2000, U0075, Section 6.3.5). Sensitivity studies were performed to examine the following 
parameters, processes, and features: 
 The correlation length of the heterogeneous permeability field (three . values). 
 The van Genuchten parameter n (two n values). 
 Correlation between capillary-strength parameter and permeability (Leverett scaling). 
 Drift degradation (four scenarios). 
 Episodic flow events.

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Details about the different scenarios can be found in CRWMS M&O (2000, U0075, Sections 4.1, 
6.3.5, 6.4, and 6.5). 
3.9.5.4 Results 
The seepage percentagedefined as the seepage flux divided by the average percolation flux 
over the drift footprintis evaluated for three realizations of the permeability field at 240 points 
in the four-dimensional parameter space described in Section 3.9.5.3. The results confirm the 
expected behavior where seepage increases with decreasing permeability, decreasing capillary 
strength, and increasing percolation flux. The seepage flux is high and approaches the 
percolation flux only if the capillary barrier is weak (i.e., 1/ a is small), permeability is relatively 
low (smaller than 10-12 m2), or percolation flux is high. In all other cases, the capillary barrier 
effect results in seepage fluxes that are substantially lower than the corresponding percolation 
fluxes. Zero seepage is obtained for a relatively large portion of the examined parameter space. 
The various sensitivity studies indicate the following trends: 
 Seepage increases with increasing correlation length . (CRWMS M&O 2000, U0075, 
Section 6.6.2). Note that the geostatistical analysis of the post-excavation airpermeability 
data (CRWMS M&O 2000, U0080, Section 6.2.2) support the choice of the 
base-case value with the smallest correlation length. 
 Seepage is relatively insensitive to the van Genuchten parameter n (CRWMS M&O 
2000, U0075, Section 6.6.3). 
 Seepage tends to be higher if the capillary strength is correlated to permeability 
according to the Leverett scaling rule (CRWMS M&O 2000, U0075, Section 6.6.4). 
 Drift degradation leads to increased seepage (CRWMS M&O 2000, U0075, 
Section 6.6.5). 
 Episodic flow events result in averaged seepage fluxes that are higher than those 
obtained with constant percolation flux. However, transient effects from episodic flow 
events are not expected to be significant over most of the potential repository. 
The detailed results can be obtained from Tables 6 through 8 of the report CRWMS M&O (2000, 
U0075). They are summarized and condensed as part of the PA seepage abstraction (see 
CRWMS M&O (2000, U0120) and Section 3.9.6 below). 
3.9.6 Abstraction of Seepage into Drifts 
3.9.6.1 Introduction and Objectives 
Evaluating the impact of drift seepage on repository performance is complex because many of 
the effects previously discussed counteract one another. For example, seepage is more likely to 
occur (and seepage rate is generally higher) if the water percolating through the rock is focused 
into discrete flow channels. On the other hand, the stronger the focusing effect, the fewer

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channels are developed, reducing the number of waste packages being affected by seepage. 
Similarly, the ability of the capillary barrier forming at the drift wall to divert some of the water 
around the opening is reduced if permeability is low, leading to higher seepage rates. At the same 
time, low-permeability rocks tend to exhibit stronger capillary forces, which increase the 
capillary-barrier effect, leading to reduced seepage rates. Because of this negative correlation, it 
is difficult to predict whether competent rock with few fractures leads to higher or lower seepage 
than less competent rock with a high fracture density or larger fracture apertures. 
The situation is further complicated by the fact that the relationships between the degree of 
channeling and flow rate within an individual channel, the flow rate in a channel and seepage, 
seepage and corrosive damage, and finally corrosive damage and contaminant release are 
strongly nonlinear. Moreover, each of these relationships exhibits conceptual and parametric 
uncertainties. 
Figure 3.9-7 shows schematically the relationships between some of the major seepage-relevant 
factors and their impact on repository performance. For example, if a given percolation flux is 
focused into a few flow channels (i.e., low seep frequency) the flux in each flow channel is 
relatively high (Figure 3.9-7a). This has the following two effects: (1) the number of waste 
packages affected by seepage is relatively small (Figure 3.9-7b), potentially reducing the 
negative impact of seepage; on the other hand, (2) the seepage threshold is likely to be exceeded 
and seepage fluxes in the affected area are relatively high (Figure 3.9-7c). High seepage rates can 
promote corrosion of engineered barriers, waste dissolution, and contaminant release from the 
affected waste package (Figure 3.9-7d). The total release of radionuclides is the product of the 
relatively high release rate and the relatively small number of waste packages being affected by 
seepage. 
On the other hand, flow dispersion lead to relatively small local percolation fluxes that are 
potentially below the seepage threshold. As a result, seep flow rates can be expected to be low, 
anddepending on the distribution of percolation flux and seepage thresholdthe seepage 
fraction is smaller or larger compared to the scenario with strong flow focusing. A detailed 
performance-assessment calculation must determine which of these factors dominate. Moreover, 
local conditions, uncertainties, and spatial variabilities must be propagated through these models 
to arrive at seepage probabilities and distributions for use in downstream TSPA models. 
The seepage models discussed in Sections 3.9.4 and 3.9.5 focus on the determination of the 
seepage threshold and seepage rates for a given percolation flux (i.e., the relationship 
schematically shown in Figure 3.9-7c). Flow focusing and seep frequency (Figure 3.9-7a) and 
their impact on seepage fraction (Figure 3.9-7b) are accounted for in the abstraction 
(Section 3.9.6.4). 
The presumption that seepage events are not localized and occur everywhere in the waste 
emplacement drifts (i.e., all waste packages encounter seepage), and that the seepage rate is 
equal to the percolation rate (i.e., no capillary-barrier effect exists, leading to maximum seepage 
rates), would be overly conservative. Consideration of a seepage threshold is beneficial for 
TSPA even if the seepage threshold value remains highly uncertain. Essentially, the occurrence 
of seepage is the product of two probabilities, namely the probability of experiencing high local 
percolation fluxes and the probability of encountering a drift segment with a low seepage

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threshold. The situation is schematically shown in Figure 3.9-8. Given a certain percolation flux, 
the conditional probability for the capillary barrier to fail is indicated by the shaded area. While 
the failure probability increases with increasing percolation flux, the probability for reaching 
such high percolation fluxes decreases. The probability that the capillary barrier fails and 
seepage occurs can be determined by independently sampling from both the percolation-flux and 
seepage-threshold distribution, and by counting the number of realizations in which the 
percolation flux exceeded the seepage threshold. Even assuming a large uncertainty in the 
seepage threshold, the resulting seepage fraction will be less than one (the seepage fraction 
obtained by neglecting capillary-barrier effects). 
A good understanding of seepage processes, an accurate determination of seepage-relevant 
formation parameters, and a careful estimation of seepage rates and seepage distribution are 
therefore some of the main objectives of the experimental, numerical, and analytical UZ studies 
at Yucca Mountain. A more detailed discussion of PA-related aspects of seepage can be found 
in CRWMS M&O (2000, U0120). 
The purpose of the seepage abstraction is to put the information generated by the seepage 
process modeling in a form appropriate for use in TSPA for SR. The abstraction method is an 
extension of that employed for the TSPA for VA (DOE 1998, Sections 3.1.1.4, 3.1.2.4, and 
3.1.3.3; CRWMS M&O 1998g, Sections 2.2.4, 2.4.4, and 2.5.2). The objective is to develop the 
framework for evaluating the amount of seepage of liquid water into potential repository 
emplacement drifts for TSPA simulations. Seepage is treated as a stochastic quantity in TSPA 
simulations by sampling values from generated probability distributions that represent the 
uncertainty and spatial variability of seepage. The process is schematically shown in 
Figure 3.9-9. Seepage has been evaluated as a function of percolation flux and k/ a, a lumped 
parameter capturing the effectiveness of the capillary barrier. Probability density functions are 
prescribed for each of the two parameters. During a TSPA simulation, a large number of random 
values are generated based on these distributions. The seepage rate corresponding to each pair of 
random parameter values yields the probability density function of seepage into waste 
emplacement drifts. Note that the actual sampling procedure is more complicated as the potential 
repository is located in multiple units, and additional constraints and correlations must be 
observed. 
The Monte Carlo simulation is basically an uncertainty analysis: each realization is taken to be 
equally likely, so any one of the realizations could be the correct one. The differences between 
one realization and another are within the range of uncertainty about each parameter that is 
varied. Some parameters, like fracture permeability or a parameter, are uncertain, so they vary 
from one TSPA realization to another; but they are also spatially variable, so they vary from 
location to location within each TSPA realization. TSPA calculations thus account for both 
uncertainty and spatial variability. 
In Section 3.9.6.2, probability distributions of seepage are developed, combining the results of 
the SMPA with information about the relative likelihood of the various parameter combinations. 
In Section 3.9.6.3, adjustments for several perturbing physical processes are introduced. In 
Section 3.9.6.4, the results of the abstraction of drift seepage are summarized.

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3.9.6.2 Initial Abstraction of Seepage Results 
The SMPA was used to simulate seepage for a large number of parameter combinations (Section 
3.9.5). Examination of the results reveals that seepage percentages are not strongly dependent on 
the standard deviation of the heterogeneous permeability field. In addition, similar seepage 
percentages were obtained for simulations with the same value of k/a (and common values of 
other parameters). Thus, for the abstraction analysis, seepage is treated as a function of k/a rather 
than of k and a separately. With these simplifications, seepage can be treated as a function of just 
two variables, namely k/a and percolation flux q. 
The abstraction analysis focuses on two quantities: (1) the seepage fraction, fs, which is the 
fraction of waste-package locations (model simulations) that have seepage (i.e., that have 
nonzero seepage percentage); and (2) the seep flow rate, Qs, which is the volumetric flow rate of 
seepage in a drift segment. The seep flow rate is obtained from the seepage percentage by 
multiplying by the percolation flux and the area of a drift segment. For each modeled percolation 
flux q, and for all simulations with a common value of k/a, the seepage fraction and the mean 
and standard deviation of the seep flow rate are calculated. 
The next step in the abstraction is to assign probabilities, or weights, to the two parameters. The 
distribution for k/a is obtained from the means and standard deviations of k (based on 
air-injection data) and a (based on SCM calibration results). Details of this procedure can be 
found in CRWMS M&O (2000, U0120, Section 6.2.2). The mean of k/ a was determined to be 
6  10-11 m2 Pa. To account for uncertainty, a range of values is considered. The available 
information indicates that our uncertainty increases at higher values of k/a, so the range 
considered is skewed to higher values: values of k/a from one-half order of magnitude lower to 
one order of magnitude higher than 6  1011 m2 Pa are considered. This is the range of values 
for the geometric mean of the distribution of k/a from location to location; in each case the 
standard deviation of the distribution of log(k/a) from location to location is taken to be 0.32. As 
is implied by the use of logs, the spatial distribution of k/a values is taken to be log-normal. 
Percolation flux q is not weighted at this stage. Percolation information is supplied with the 
appropriate spatial and temporal distribution during the actual TSPA simulations. All the results 
are thus given as a function of percolation flux. Given a distribution for k/a, a corresponding 
distribution can be developed for seepage. When the seepage information from the Seepage 
Model for PA is combined with the discrete distribution of k/a, weighted seepage statistics are 
obtained, representing the distribution of spatial variability of seepage within a TSPA realization. 
3.9.6.3 Adjustments 
The following adjustment are made to account for certain effects: 
1. Distributions for the amount of seepage as a function of percolation flux are 
derived directly from seepage process-model results (CRWMS M&O 2000, 
U0075) and are constrained by measurements of permeability around three niches 
in the ESF (CRWMS M&O 2000, U0015, Section 6.1) and calibration of seepage 
tests conducted in one niche in the ESF (CRWMS M&O 2000, U0080,

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Section 6.4). The derived distributions are summarized in Section 3.9.6.4; more 
details can be found in CRWMS M&O (2000, U0120, Section 6.2.4). 
2. Seepage calculations for drifts with breakouts in the drift wall were performed 
with the SMPA (CRWMS M&O 2000, U0075, Section 6.4.3). These simulations 
suggested a moderate increase of drift seepage as a result of partial drift 
degradation. In the abstraction, seep flow rates calculated with the SMPA were 
increased by a conservative factor of 1.55 to account for the effects from partial 
drift degradation and rock bolts (CRWMS M&O 2000, U0120, Section 6.3.1). 
3. The impact of the correlation between permeability and capillary strength on 
seepage was evaluated by the SMPA (CRWMS M&O 2000, U0075, 
Section 6.6.4). Using the Leverett scaling rule (Leverett 1941, p. 159) to relate 
capillary strength to local permeability variations yielded slightly higher seepage 
rates as compared to the rates obtained with a spatially constant a value. Seep 
flow rates calculated with the SMPA were therefore increased by 10% as an 
adjustment for the potential correlation of k and a (CRWMS M&O 2000, U0120, 
Section 6.3.2). 
4. Distributions of the degree of flow focusing above the drifts are determined based 
on estimates of weep spacings implied by the active fracture model of UZ flow. 
Weep spacings were calculated by two methods to estimate lower and upper 
bounds for three net infiltration levels (mean, lower, and upper; see CRWMS 
M&O (2000, U0120, Section 6.3.3.1)). Both methods generate weep spacings that 
are approximately log-normally distributed. The distributions of weep spacings 
are used to define distributions of the flow-focusing factor, which is a 
multiplicative factor describing how much percolation flux might be increased 
over its average value at any given location. The flow-focusing factor is used to 
scale the percolation flux and the seepage fraction; it is log-uniformly distributed, 
with minimum of 1 in each case and maximum of 47 for the low-infiltration case, 
22 for the base-infiltration case, and 9.7 for the high-infiltration case. This 
distribution of flow-focusing factors is an uncertainty distribution, which means 
that one value of it is sampled for each TSPA realization. That value is then 
applied to modify the spatial variability of seepage within the realization. Details 
can be found in CRWMS M&O (2000, U0120, Section 6.3.3.2). 
5. Episodic flow could be accounted for through application of temporally varying 
percolation fluxes during the TSPA calculations in analogy to the use of spatial 
flow focusing factors. Since episodic flow events are damped by the PTn and are 
not expected to penetrate to the potential repository horizon, no adjustment is 
currently made. 
6. Coupled processes (thermal-hydrologic, thermal-hydrologic-mechanical, and 
thermal-hydrologic-chemical) have generally been found to have limited impact 
(in terms of magnitude and time scale) on seepage or are beneficial. Currently, no 
adjustments are being made (see Section 4.2.1.1 and CRWMS M&O (2000, 
U0120, Sections 5 and 6.3.5)).

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3.9.6.4 Abstraction Results 
As discussed in Section 3.9.6.2, seepage is mainly a function of the ratio of geometric-mean 
fracture permeability k to fracture a parameter, k/ a, and the uncertainty in this ratio is taken to be 
one order of magnitude above and one-half order of magnitude below the best-estimate value, 
which is 6  1011 m2 Pa. A triangular shape is chosen for the seepage uncertainty distributions. 
This distribution appropriately represents the key features desired, which are that seepage values 
for k/ a = 6  1011 m2 Pa are most likely and that k/ a could be higher or lower, but those values 
are less likely to be representative of potential repository conditions. 
Table 3.9-2 summarizes the seepage distributions as they vary with percolation flux. A seepage 
threshold of approximately 200 mm/yr, 15 mm/yr, and 5 mm/yr was found for minimum, peak, 
and maximum k/ a values, respectively. Note that these values are the abstracted, conservatively 
estimated seepage rates, seepage fractions, and seepage thresholds for a waste emplacement drift 
with a 5.5 m diameter, taking into account uncertainty and spatial variability of the entire 
potential repository horizon. This has to be distinguished from the previously reported seepagethreshold 
estimate of 200 mm/yr (Section 3.9.4.7), which referred to a single location in the 
middle nonlithophysal zone and for an opening smaller than a waste emplacement drift. 
Additional details on the derivation of the values in this table and their interpretation may be 
found in CRWMS M&O (2000, U0120, Section 6.4). For values of percolation flux not in the 
table, linear interpolation or extrapolation was used. 
Table 3.9-2. Uncertainty in Seepage Parameters as Function of Percolation (Table from CRWMS M&O 
2000, U0120, Table 11) 
Minimum Value of k/ a Peak Value of k/ a Maximum Value of k/ a 
q 
(mm/yr) 
fs Mean 
Qs (m3/yr) 
Std. Dev. 
Qs (m3/yr) 
fs Mean 
Qs (m3/yr) 
Std. Dev. 
Qs (m3/yr) 
fs Mean 
Qs (m3/yr) 
Std. Dev. 
Qs (m3/yr) 
5 0 0 0 0 0 0 1.97103 3.21103 3.16103 
14.6 0 0 0 2.45103 7.95103 7.09103 5.75102 2.26102 2.45102 
73.2 0 0 0 0.250 0.106 0.198 0.744 0.404 0.409 
213 4.91103 0.284 0.188 0.487 1.51 1.15 0.944 3.31 2.24 
500 6.01102 0.992 1.05 0.925 5.50 4.48 0.999 13.0 5.74 
NOTE: q is percolation flux, fs is seepage fraction, and Qs is seep flow rate. 
The standard deviations of seep flow rate in Table 3.9-2 are relatively large. These large standard 
deviations result from the large differences in seepage from one set of simulations to another. For 
example, the weighted mean and standard deviation for k/a = 6  1011 m2 Pa are a combination 
of the results for k/a values from 9  1012 to 2.7  1010 m2 Pa and over that range of k/a the 
mean seep flow rate at 73.2 mm/yr goes from zero to 0.408 m3/yr. Thus, an amount of spatial 
variability in k/a corresponding to a log standard deviation of 0.32 (Section 3.9.6.2) translates 
into a relatively large spatial variability of seepage. This is consistent with the concept of 
seepage as a random process.

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The effect of flow focusing is illustrated in Figures 3.9-10 and 3.9-11 for seepage fraction and 
mean seep flow rate, respectively. Each plot has four curves, for the flow-focusing factor F equal 
to 1 (no flow focusing), 5, 15, and 45. The F = 1 curves are based on the mean of the respective 
uncertainty distributions (for a triangular distribution, the mean is (min + peak + max)/3, with 
min, peak, and max as listed in Table 3.9-2). The curves with higher values of F are generated 
from the F = 1 curves as described in CRWMS M&O (2000, U0120, Section 6.3.3.2). Increased 
flow focusing results in lower seepage fractions and higher seep flow rates. Note, however, that 
at very low percolation fluxes the seepage fraction is higher for higher focusing factors, because 
a percolation flux below the threshold for seepage can be boosted above the threshold by the 
focusing multiplier (CRWMS M&O (2000, U0120, Section 6.3.4) 
3.9.7 Corroborative Evidence and Analog Studies 
3.9.7.1 Calcite Depositions in Lithophysal Cavities 
Observations of calcite and opal in lithophysal cavities in the Topopah Spring tuff were used to 
estimate long-term seepage rates into these small openings (CWRMS M&O 2000, U0085, 
Section 6.10.3). Calcite is assumed to precipitate from downward-percolating meteoric water 
because of (1) evaporation, (2) CO2 outgassing as a result of the geothermal gradient, and (3) 
interaction with a gas phase containing less CO2 than the gas with which the water was last 
equilibrated. Considering these calcite-precipitation mechanisms and assuming certain water-tocalcite 
ratios, seepage into lithophysal cavities was estimated from calcite-deposition data. This 
analysis shows that (1) not all lithophysal cavities encountered seepage and (2) seepage flux is a 
very small fraction of percolation flux. Both conclusions corroborate the general concept and the 
findings of the drift-seepage studies discussed in Sections 3.9.1 though 3.9.5. Specifically, they 
support the concept of a capillary barrier reducing seepage over percolation flux. Note that the 
seepage threshold for small cavities may be significantly higher than for a large waste 
emplacement drift. 
The presence of lithophysal cavities does not directly impact seepage into a waste emplacement 
drift. However, there is a second-order, indirect effect. On account of the capillary barrier effect, 
lithophysal cavities are partial obstacles to downward flow of water. Consequently, their 
presence may lead to local, small-scale flow channeling, which could induce increased seepage. 
Lithophysal cavities also increase the roughness of the drift wall. Both effects are accounted for 
through the use of conservative flow focusing factors and safety factors for drift roughness. 
3.9.7.2 Rainier Mesa 
Rainier Mesa, located approximately 30 km northeast of Yucca Mountain, is underlain be a 
sequence of welded and nonwelded tuffs similar to those that underlie Yucca Mountain. 
Precipitation is about double the mean at Yucca Mountain, and percolation is estimated to be 
about eight percent of precipitation (Wang et al. 1993, p. 676). Most of the Rainier Mesa tunnels 
were constructed in the zeolitic tuffs, which are believed to be near full saturation. Faults and 
joints are abundant in these zeolitic-bedded tuffs. When intersected by tunnels, some of these 
joints and especially through-going faults have yielded significant amounts of water. The seeping 
features are thought to be pathways for flow from a perched water zone above the zeolitic 
horizon. Seepage water is geochemically similar to meteoric water and is associated with fast

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flow paths. Seepage at Rainier Mesa occurs only in tunnels constructed in the zeolites; no 
seepage is observed in the tunnel intersecting the vitric tuff units. These observations suggest 
that seepage into tunnels may be localized and restricted to certain flow paths and units. This 
corroborates the modeling results, which indicate that the seepage fractions are less than one. 
More details can be found in CRWMS M&O (2000, U0135, Section 6.5.1.2) and Wang et al. 
(1993, pp. 675681). 
3.9.7.3 Altamira 
Seepage into caves can be used as a natural analog for seepage into waste emplacement drifts. 
Unfortunately, most caves are part of a karst system found in limestone formations in the 
saturated zone or in zones of significantly higher percolation fluxes than those expected at Yucca 
Mountain. The caves near Altamira, Spain are located in the unsaturated zone of a fractured 
limestone bedrock with clay-rich layers. Precipitation is approximately ten times higher than at 
Yucca Mountain. Nevertheless, seepage rates into the caves are estimated to be a small fraction 
of the expected percolation flux. Moreover, there are essentially no fluctuations in the observed 
seepage rates despite the fact that the unsaturated zone is only about 7 m thick and 
evapotranspiration is expected to exceed precipitation for a few months out of the year. More 
details can be found in Villar et al. (1985, pp. 2124). 
3.9.7.4 Absence of Seepage into Sealed Drift Segments 
Currently, no natural seepage into the ESF has been observed. Furthermore, no construction 
water was observed to seep into the ESF Main Drift as the tunnel boring machine passed the 
cross-over point during the excavation of the ECRB Cross Drift. However, evaporation and 
moisture removal through ventilation of the ESF is likely to be larger than potential seepage 
rates, preventing direct observation of liquid water dripping into the drift. 
As described in Section 2.2.2.2.1, an approximately 100 m long segment of Alcove 7 and an 
approximately 1,000 m long segment of the ECRB Cross Drift have been sealed by bulkheads to 
isolate them from ventilation. No seepage has been observed so far in either of these two drift 
segments. The absence of visible seepage in sealed-off drift segments corroborates the modeling 
results which estimate that present-day percolation fluxes are likely to be smaller than the 
prevailing seepage thresholds. 
3.9.8 Alternative Conceptual Models 
3.9.8.1 Discrete Fracture Network Model 
A discrete fracture network model (DFNM) is an alternative conceptual model to the 
heterogeneous fracture continuum model (Pruess et al. 1999, pp. 307309). The DFNM has the 
advantage of being intuitively more appealing for seepage predictions. A high-resolution DFNM 
model is capable of generating channelized flow and discrete seepage events. The development 
of a defensible DFNM requires collecting a very large amount of geometric and unsaturated 
hydrologic property data. While part of the required geometric information can be obtained from 
fracture mappings, the description of the network remains incomplete and potentially biased. 
Moreover, unsaturated hydrologic parameters on the scale of individual fractures are required, 
along with conceptual models and simplifying assumptions regarding unsaturated flow within

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fractures and across fracture intersections. These databases required to develop a DFNM are 
currently not available. As a result, the cumulative effect of all the input uncertainties is likely to 
outweigh the apparent advantage of a detailed representation of the fracture network. 
In general, the choice of a conceptual model for seepage predictions should be based on a careful 
consideration of the study objectives, the available database in comparison with the data needs, 
the uncertainties in the input parameters, and the corresponding prediction uncertainties, as well 
as computational aspects. The appropriateness of using a fracture-continuum model for the 
prediction of effective seepage quantities was demonstrated in CRWMS M&O (2000, U0080, 
Section 5.3). 
3.9.8.2 Seepage Governed by Ponding Probability 
As an alternative conceptual model to a seepage process model, Birkholzer et al. (1999, pp. 372 
379) related seepage to the local ponding probability, which was derived from the variability of 
the permeability field. Their approach assumed that in strongly heterogeneous formations, 
seepage is predominantly affected by pressure variations governed by local heterogeneity rather 
than the presence and geometry of the capillary barrier. This is different from the behavior in a 
homogeneous system, where the geometry of the capillary barrier has a strong impact on seepage 
(Philip et al. 1989, pp. 1628). Strong medium- to small-scale heterogeneities tend to increase 
seepage as they increase channeling and local ponding. This effect is included in the current 
seepage process models through the estimation of effective, seepage-specific parameters. While 
the approach presented by Birkholzer et al. (1999, pp. 372379) and discussed in CRWMS 
M&O (2000, U0075, Section 6.7) may provide guidelines for how to extrapolate seepage 
predictions to other units or drift geometries, it nonetheless requires a calibration step similar to 
that described in Section 3.9.4. 
3.9.9 Summary and Conclusions 
Seepage into waste emplacement drifts is considered a key factor affecting the performance of a 
potential high-level nuclear waste repository at Yucca Mountain, Nevada. Theoretical analyses, 
numerical modeling studies, field testing, and observations at analog sites suggest that seepage 
into underground openings excavated in unsaturated formations is smaller than the local 
percolation flux. This is mainly a result of capillary pressure holding water in the formation, 
diverting it around and preventing it from entering the openings. The effectiveness of this 
capillary barrier depends on the percolation flux itself, the hydrogeologic properties of the 
formation, and the geometry of the drift. 
A sequence of models was used to predict seepage fraction, seepage threshold, and seep flow 
rate for waste emplacement drifts. A seepage process model was calibrated against seepagerelevant 
data from liquid-release tests. Seepage rates were then calculated over a wide range of 
parameter values and compiled in an abstraction process. Finally, probability distributions of the 
key parameters were introduced and conservative assumptions were made to arrive at 
probabilities for seepage into waste emplacement drifts.

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These analyses indicate that seepage fluxes are lower than percolation fluxes, even under 
conservative assumptions, and that only a fraction of the waste packages will encounter seepage. 
However, seepage predictions remain uncertain. 
Figure 3.9-12 summarizes qualitative and quantitative results pertaining to the issues discussed 
in Section 3.9.3. The results reflect the values obtained after the TSPA abstraction.

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3.10 DRIFT-SCALE THERMAL-HYDROLOGICAL-CHEMICAL PROCESSES AND 
MODELS 
3.10.1 Introduction 
The purpose of this section is to describe (1) the conceptual model and input data for coupled 
thermal, hydrological, and chemical (THC) processes; (2) the Drift Scale Test (DST) THC 
Model; (3) the THC Seepage Model; and (4) the abstractions done by Performance Assessment 
on the results of the THC Seepage Model. The conceptual model for THC processes provides a 
comprehensive basis for modeling the pertinent mineral-water-gas reactions in the host rock 
under thermal loading conditions, as they influence the water and gas chemistry that may enter 
drifts over 100,000 years. The purpose of the DST THC Model is to validate the conceptual 
model and input data by comparison of measured gas and water chemistry from the DST to the 
results of simulations. The purpose of the THC Seepage Model is to evaluate the effects of THC 
processes in the rock around emplacement drifts on the possible seepage-water chemistry, gasphase 
composition, and the potential effects of THC processes on unsaturated zone (UZ) flow 
and transport. This model was used to evaluate the effects of mineral dissolution and 
precipitation, the effects of CO2 exsolution and transport in the region surrounding the drift, the 
potential for forming zones of calcite, silica, or other minerals, the resulting changes to porosity, 
permeability, and the potential effects on seepage. The THC Seepage Model and validation of 
the data and processes using the DST are treated in the Analysis/Model Report (AMR) Drift- 
Scale Coupled Processes (DST and THC Seepage) Models (CRWMS M&O 2000, 
N0120/U0110). 
3.10.2 Thermal-Hydrological-Chemical Conceptual Model 
The THC conceptual model underlies the numerical simulations of THC processes in the DST 
THC Model and in the THC Seepage Model. The conceptual model must be able to describe 
processes involving liquid and vapor flow, heat transport, and thermal effects resulting from 
boiling and condensation, transport of aqueous and gaseous species, mineralogical characteristics 
and changes, and aqueous and gaseous chemistry. A conceptual model of reaction-transport 
processes in the fractured welded tuffs of the potential repository host rock must also account for 
the different rates of transport in very permeable fractures compared to the much less permeable 
rock matrix (see for example, Steefel and Lichtner 1998, pp. 186187). 
In addition to the unsaturated hydrological properties required to simulate THC processes in the 
UZ, the data necessary for the evaluation of THC processes include the initial and boundary 
water and gas chemistry, the initial mineralogy, mineral volume fractions, reactive surface areas, 
equilibrium thermodynamic data for minerals, aqueous and gaseous species, kinetic data for 
mineral-water reactions, and diffusion coefficients for aqueous and gaseous species. The 
following subsections describe the conceptual model for thermal-hydrological (TH), 
geochemical, and coupled THC processes in the fractured tuffs. 
3.10.2.1 TH Processes 
TH processes in the fractured welded tuffs at Yucca Mountain have been examined theoretically 
and experimentally since the early 1980s (Pruess et al. 1984; Pruess et al. 1990a, pp. 12351248;

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Buscheck and Nitao 1993, pp. 418448; Pruess 1997, pp. 335372; Tsang and Birkholzer 1999, 
pp. 385425; Kneafsey and Pruess 1998, pp. 33493367). A conceptual model showing the 
important TH processes occurring around a drift (as derived through these studies and through 
observations of the Single Heater Test and the DST) is shown in Figure 3.10-1. To summarize 
the processes as depicted in the figure, heat conduction from the drift wall into the rock matrix 
results in vaporization and boiling, with vapor migration out of matrix blocks into fractures. The 
vapor moves away from the drift through the permeable fracture network by bouyancy, by the 
increased vapor pressure caused by heating and boiling, and through local convection. In cooler 
regions, the vapor condenses on fracture walls, where it drains through the fracture network 
either down toward the heat source from above or away from the drift into the zone underlying 
the heat source. Slow imbibition of water from fractures into the matrix gradually leads to 
increases in the liquid saturation in the rock matrix. Under conditions of continuous heat loading, 
a dryout zone may develop closest to the heat source separated from the condensation zone by a 
nearly isothermal zone maintained at about the boiling temperature. Where this nearly isothermal 
zone is characterized by a continuous process of boiling, vapor transport, condensation, and 
migration of water back to the heat source (either by capillary forces or gravity drainage), this 
zone may be termed a heat pipe (Pruess et al. 1990a, pp. 12351248). 
The design shown in Figure 3.10-1 includes backfill; however, this conceptual model is not 
dependent on the presence of backfill. A design change was made in January 2000 that removed 
backfill from the reference design. Qualitatitively, this change does not affect the THC 
processes occurring in the rock around the drifts; however, the absence of backfill may result in a 
different temperature distribution at the drift wall and different times of maximum drift-wall 
temperature, maximum dryout and rewetting. These different rates of heating would affect the 
time variation of water and gas chemistry around the drifts. 
3.10.2.2 Effects of TH Processes (Boiling, Condensation, and Drainage) on Water and 
Gas Chemistry and Mineral Evolution 
The chemical evolution of waters, gases, and minerals is intimately coupled to the TH processes 
discussed in the previous section. The distribution of condensate in the fracture system 
determines where mineral dissolution and precipitation can occur in the fractures and where 
there can be direct interaction (via diffusion) between matrix pore waters and fracture waters. 
Figure 3.10-2 shows schematically the relationships between TH and geochemical processes in 
the zones of boiling, condensation, and drainage in the rock mass outside of the drift and above 
the heat source. 
One important aspect of the system is the exsolution of CO2 out of the liquid phase as 
temperature increases. The exsolution and transport of CO2 out of the boiling zone results in a 
local increase in pH and a decrease in pH in the condensation zone into which the vapor enriched 
in CO2 is transported. The extent to which the pH is shifted depends strongly on the rates of 
mineral-water reactions, which can buffer the change in pH. Because the diffusivities of gaseous 
species are several orders of magnitude greater than those of aqueous species, and because the 
advective transport of gases can be more rapid than that of liquids, the region where CO2 
degassing affects water and gas chemistry could be much larger than the region affected by 
transport of aqueous species.

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Effects of TH processes on water chemistry are varied and depend on the behavior of the 
dissolved species and their relation to mineral-water reactions. Conservative species (i.e., those 
that are unreactive and nonvolatile), such as chloride (Cl-), become concentrated in waters 
undergoing vaporization or boiling, but are absent from the vapor condensing in the fractures. 
Therefore, the concentration in the draining condensate waters is determined by mixing with 
fracture pore waters and interaction with matrix pore waters via diffusion. Concentrations of 
aqueous species, such as Ca+2, are also affected by calcite dissolution or precipitation as well as 
reactions involving Ca-bearing zeolites, clays, and plagioclase feldspar. 
Zonation in the distribution of mineral species may occur as a result of varied temperature effects 
on mineral solubility. The inverse relation between temperature and calcite solubility (as 
opposed to the silica phases, which are much more soluble at higher temperatures) may cause 
zonation in the distribution of these phases in the condensation and boiling zones 
(Figure 3.10-2). Precipitation of amorphous silica or another silica phase is likely to be confined 
to a narrower zone where evaporative concentration from boiling exceeds its solubility. Hence, 
calcite may precipitate in fractures over a broad zone of elevated temperature and where CO2 has 
exsolved due to temperature increases or boiling. Alteration of feldspars to clays and zeolites is 
likely to be most rapid in the boiling zone because of their increased solubility (as well as 
dissolution and precipitation rates) at higher temperatures (Lasaga 1998, p. 66). In drainage 
zones, there may also be zonation in mineral alteration within the rock matrix adjacent to the 
fracture similar to that observed as a function of distance along the transport path (Steefel and 
Lichtner 1998, pp. 186199). 
3.10.2.3 Effects of Infiltration and Climate Changes on THC Processes 
Early in the thermal history of the potential repository, much of the chemistry of the UZ around 
drifts will be constrained by the chemistry of ambient fracture and matrix pore water, which may 
change the concentration as a result of boiling, by dilution with condensate water, or by mineralwater-
gas reactions. Once the peak thermal period has subsided, percolating water mixes with 
the condensate water above the potential repository and eventually rewets the dryout zone. The 
composition of the percolating waters (before mixing) may be similar to that presently found 
above the potential repository as matrix pore water, or it may reflect more dilute water, from a 
wetter climate, that has traveled through fractures. Changes in the percolation flux also affect the 
extent of mineral deposition and dissolution, because of the changes in the flux of dissolved 
species to the region around drifts. For example, the greater the flux of Ca, the more calcite 
would be precipitated, at a given concentration. Higher percolation fluxes could increase the 
dissolution rates of minerals that are undersaturated in the fluid, because it can increase the 
degree to which the mineral is undersaturated. 
3.10.2.4 Hydrologic Property Changes in Fractures and Matrix 
Mineral precipitation and dissolution in fractures and matrix have the potential for modifying the 
porosity, permeability, and unsaturated hydrologic properties of the system. Because the molar 
volumes of minerals created by hydrolysis reactions (i.e., anhydrous phases, such as feldspars, 
reacting with aqueous fluids to form hydrous minerals, such as zeolites or clays) are often larger 
than the molar volumes of the primary reactant minerals, dissolution-precipitation reactions can 
often lead to porosity reductions. The extent of mineral-water reactions is controlled by the

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surface areas of the mineral phases in contact with the aqueous fluid, and the distribution of 
minerals in the fractures is heterogeneous. Therefore, changes in porosity and permeability 
caused by these processes may also be heterogeneously distributed. Other factors that may lead 
to heterogeneity in property changes are the distribution of liquid saturation in fractures, the 
proportion of fractures having actively flowing water, and the rates of evaporative concentration 
due to boiling, which may change the dominant mechanisms of crystal growth and nucleation. 
As summarized in the preceeding subsection, the conceptual model for THC processes 
incorporates a wide range of coupled physical and chemical processes. The following subsection 
deals with the implementation of this conceptual framework into a quantitative numerical model. 
3.10.3 Modeling Approach, Assumptions, Inputs and Outputs 
The flow of information between various models and data sources and the DST THC Model and 
THC Seepage Model is presented in Figure 3.10-3. The DST THC Model takes its inputs from 
the DST TH Model, the Calibrated Properties Model (CPM; CRWMS M&O 2000, U0035), and 
numerous sources of geochemical data (Geochemical Data) as discussed in CRWMS M&O 
(2000, N0120/U0110). Geochemical Data include mineral abundances and compositions, and 
water and gas chemistry. The THC Seepage Model obtains its inputs from the Calibrated 
Properties Model (CPM), Geochemical Data, and also Repository Design (CRWMS M&O 
1999e; CRWMS M&O, EBS PMR, Section 2.5) and the UZ Flow and Transport Model (Flow 
and Transport; CRWMS M&O 2000, U0050). Repository Design provides the data on in-drift 
geometry and drift spacing, and the thermal and hydrological properties of Engineered Barrier 
System components. The UZ Flow and Transport Model provides the hydrogeologic layer 
boundaries and pressure and temperature boundary conditions. Results of sensitivity studies on 
mineral assemblages and conceptual model validation in the DST are used to guide the 
development and analysis of the THC Seepage Model. However, direct numerical output from 
the DST THC Model is not used in the THC Seepage Model. Output data from the THC 
Seepage Model are abstracted for use in Total System Performance Assessment (TSPA) and 
discussed further in Section 3.10.11. 
The following subsections describe in more detail the implementation of the conceptual model as 
a mathematical description of THC processes in the fractured tuffs. Data that form the basis of 
the DST THC and THC Seepage models are also discussed. 
3.10.3.1 Dual-Permeability Model For Reaction-Transport Processes 
To handle separate yet interacting processes in fractures and matrix, the dual-permeability 
method was adopted for all aspects of the system (flow, transport, and reaction). Transport rates 
greater than the rate of chemical equilibration via diffusion necessarily lead to disequilibrium in 
water chemistry between fractures and matrix. This can lead to differences in 
dissolution/precipitation rates and therefore the rate of change in porosity and permeability 
between the two media. Because the system is unsaturated and undergoes boiling, the transport 
of gaseous species is an important consideration. The model must also capture the differences 
between initial mineralogy in fractures and matrix and their evolution. In the dual-permeability 
method, each gridblock is separated into a matrix and fracture continuum, each of which is

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characterized by its own pressure, temperature, liquid saturation, water and gas chemistry, and 
mineralogy. 
The fracture continuum is considered as separate from but interacting with the matrix continuum, 
in terms of the flow of heat, water, and vapor through advection and conduction. Aqueous and 
gaseous species are transported via advection and molecular diffusion between fractures and 
matrix. It is assumed that the dual-permeability approach, with appropriate material and fracture 
properties and an appropriate discretization of time and space, is a sufficiently accurate 
approximation of the real world for the spatial scales of interest. The dual-permeability approach 
for modeling hydrologic processes in fractured porous media is also discussed in Section 3.4. 
This approach is validated by the comparison of measured geochemical data to results of 
simulations presented in CRWMS M&O (2000, N0120/U0110), and as discussed in 
Section 3.10.4. 
3.10.3.2 Active Fracture Model For Reaction-Transport Processes 
The active fracture model (Liu et al. 1998; CRWMS M&O 2000, U0030, Section 6.4.5) has been 
used in many of the modeling studies described in this report. Because a major intent of the 
method is to modify the fracture-matrix area for the liquid phase as a function of the liquid 
saturation, for consistency the active fracture model should also be used for the calculation of the 
surface area of minerals on fracture walls in contact with the liquid phase. The reference 
saturation for the active fracture model is the residual liquid saturation, below which flow is 
considered to be absent. However, mineral-water reactions are expected to occur at all 
saturations above zero. Therefore, a modification of the active fracture model was implemented 
for mineral-water reactions, such that the reference saturation was taken as a small value 
(1  10-4), consistent with that implemented for mineral-water reactions and transport near 
conditions of complete dryout. This value is approximately a cutoff at which evaporative 
concentration increases the ionic strength of the residual porewater to values outside the range of 
the validity of thermodynamic relationships for dilute systems. 
3.10.3.3 Equilibrium and Kinetic Models for MineralWaterGas Reactions 
Mineral-water reactions are considered to take place under kinetic or equilibrium conditions. The 
methods used to express the kinetic and equilibrium reactions are described in CRWMS M&O 
(2000, N0120/U0110) and are similar to those described in Reed (1982, pp. 513528) and 
Steefel and Lasaga (1994, pp. 529592). Because the dissolution rates of many mineral-water 
reactions are quite slow, most phases were treated using pseudo-first-order reaction kinetics. 
Data for kinetic mineral-water reactions were derived from published experimental data. Gas 
species, such as CO2, were treated as ideal mixtures of gases in equilibrium with the aqueous 
solution. 
3.10.3.4 Initial and Infiltrating Water and Gas Chemistry and Mineralogy 
The initial water chemistry for the DST THC Model and the THC Seepage Model was an 
average of measurements made of pore waters from Alcove 5, near the Drift Scale Test 
(CRWMS M&O 2000, N0120/U0110, Section 6.1.2). The chemistry of this water is given in 
Table 3.10-1.

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Table 3.10-1. TSw Porewater Composition and CO2 Partial Pressure (CRWMS M&O 2000, 
N0120/U0110, Table 3) 
Parameter Units Concentration 
pH (at 25C) pH Units 8.32 
Na mg/L 61.3 
SiO2(aq) mg/L 70.5 
Ca mg/L 101 
K mg/L 8.0 
Mg mg/L 17 
Al mg/L 9.92x10-7 (1) 
Fe mg/L 6.46x10-8 (2) 
HCO3 (3) mg/L 200 
Cl mg/L 117 
SO4 mg/L 116 
F mg/L 0.86 
CO2 (gas) (4) Pa 85.2 
NOTES: (1) Calculated by equilibrating with Ca-smectite at 25C. 
(2) Calculated by equilibrating with hematite at 25C. 
(3) Total aqueous carbonate as HCO3
-, calculated from 
charge balance. 
(4) Calculated at equilibrium with the solution at 25C. 
The infiltrating water chemistry could be chosen from either the porewater chemistry in the UZ 
at or above the potential repository horizon or from a more dilute composition found in the 
perched water or saturated zone (e.g., J-13 water). The perched waters are much more dilute 
than UZ pore waters (CRWMS M&O 2000, U0085, Tables 6 and 8), and isotopic compositions 
(36Cl/Cl, 18O/16O, D/H, 14C) and Cl concentrations also suggest the presence of a large proportion 
of late Pleistocene/early Holocene water (Levy et al. 1997, p. 906; Sonnenthal and Bodvarsson 
1999, pp. 107108; CRWMS M&O 2000, U0085, Table 9). Consequently, we assume that the 
infiltrating water and the water in the fractures have the same chemical composition as the 
matrix pore water. The sample chosen was collected from Alcove 5 near the DST and is listed in 
Table 3.10-1. Analyses of PTn pore waters (and some at the top of the TSw) and many Cl 
analyses of TSw pore waters are consistent with this interpretation (Sonnenthal and Bodvarsson 
1999, pp. 140141; CRWMS M&O 2000, U0085, Table 6). 
The minerals, aqueous and gaseous species shown in Table 3.10-2 include the major phases 
found in fractures and the matrix in the TSw and others that are likely to occur under thermally 
perturbed conditions, based on their occurrence in deeper zeolitized units (denoted Case 1). Two 
sets of geochemical species were chosen, so that the sensitivity to the mineral assemblage could 
be evaluated, and additional information could be obtained for PA abstractions. Case 2 
represents a smaller set of species and minerals (calcite, gypsum, silica phases) that captures

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many basic aspects of the DST water and gas chemical evolution, such as the pH and gas-phase 
CO2 concentrations, but neglects Al, Fe, and F-bearing aqueous species and minerals. 
Simulations of the DST and the THC Seepage Model considered both geochemical cases. 
Table 3.10-2. Model Mineral Assemblage, Aqueous and Gas Species (Full Geochemical System; 
CRWMS M&O 2000, N0120/U0110, Table 7) 
Species Minerals 
Aqueous: 
H2O Calcite 
H+ Tridymite 
Na+ a-Cristobalite 
K+ Quartz 
Ca+2 Amorphous Silica 
Mg+2 Hematite 
SiO2 Fluorite 
AlO2
- Gypsum 
HFeO2
+3 Goethite 
HCO3
- Albite 
Cl- Microcline 
SO4
-2 Anorthite 
F- Ca-Smectite 
Mg-Smectite 
Species Minerals 
Gas: Na-Smectite 
CO2 K-Smectite 
Illite 
Kaolinite 
Sepiolite 
Stellerite 
Heulandite 
Mordenite 
Clinoptilolite 
Volcanic Glass 
3.10.3.5 Relations for Mineral Reactive Surface Areas 
Reactive surface areas of minerals on fracture walls were calculated from the fracture-matrix 
interface area/volume ratio, the fracture porosity, and the derived mineral volume fractions 
(CRWMS M&O 2000, N0120/U0110, Section 6.1.5.1). The fracture-matrix interface areas and

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fracture porosities for each unit were taken from the drift-scale calibrated properties set 
(CRWMS M&O 2000, U0050, Section 6.2). These areas were based on the fracture densities, 
fracture porosities, and mean fracture diameter. The wall of the fracture is treated as a surface 
covered by mineral grains having the form of uniform hemispheres. 
Mineral surface areas in the rock matrix were calculated using the geometric area of a cubic 
array of truncated spheres that make up the framework of the rock (CRWMS M&O 2000, 
N0120/U0110, Section 6.1.5.2). Clay minerals are considered as coatings of plate-like grains. 
The grains forming the framework of the rock matrix are considered to be the primary hightemperature 
phases of the tuff (i.e., quartz, cristobalite, tridymite, and feldspars). The abundance 
of secondary phases (i.e., those that formed as alteration products or low-temperature coatings on 
the primary assemblage), such as clay minerals, is used to reduce the free surface area of the 
framework grains. 
3.10.3.6 Relations for Hydrological Property Changes 
Changes in porosity, permeability, and capillary pressure as a result of mineral precipitation and 
dissolution are treated in CRWMS M&O (2000, N0120/U0110, Sections 6.1.6.26.1.6.3). 
Porosity changes in matrix and fractures are directly tied to the volume changes resulting from 
mineral precipitation and dissolution. Fracture-permeability changes are approximated using the 
porosity change and an assumption of plane parallel, fractures of uniform aperture (cubic law; 
Steefel and Lasaga 1994, p. 556). Although this is a gross simplification of the fracture 
geometry, it is not possible to predict the actual form and distribution of mineral precipitates at a 
very small scale. This is because of the many complexities of the fracture geometry and the very 
complex nature of mineral nucleation and growth under changing physical and chemical 
conditions. Thus, the permeability changes are only approximate. Matrix permeability changes 
are calculated from changes in porosity using ratios of permeabilities calculated from the 
Carmen-Kozeny relation (Bear 1988, p. 166) and ignoring changes in grain size, tortuosity, and 
specific surface area. Because of the exceedingly small initial matrix permeabilities of the 
welded Topopah Spring tuff, simplification in the matrix relations is immaterial. If mineral 
precipitation caused very substantial changes in permeability, or the permeability of the fracture 
system was already very low, then it would be necessary to treat the relations between 
permeability changes and porosity changes more rigorously. Changing permeability and porosity 
also induces changes in the unsaturated flow properties of the rock. Therefore, the capillary 
pressure is modified using the Leverett scaling relation (Slider 1976, p. 280). 
3.10.3.7 Basis for Numerical Code TOUGHREACT V2.2 
The geochemical module incorporated in TOUGHREACT V2.2 (described in Section 1.3.2.3) 
simultaneously solves a set of chemical mass-action, kinetic-rate expressions for mineral 
dissolution/precipitation, and mass-balance equations. Implementation of multiphase flow and 
heat transport for dual-permeability media is equivalent to TOUGH2 V1.4, which was used for 
other UZ flow calculations and TH calculations (CRWMS M&O 2000, U0050) and for TH 
calculations of the DST. TOUGHREACT V2.2 provides the extent of reaction and mass 
transfer between a set of given aqueous species, minerals, and gases at each gridblock of the flow 
model (Xu and Pruess 1998; Xu et al. 1998). Equations for heat, liquid and gas flow, aqueous 
and gaseous species transport, chemical reactions, and permeability/porosity changes are solved

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sequentially (e.g., Steefel and Lasaga 1994, p. 550). It is assumed that the physical properties of 
the gas phase are unaffected by changes in the partial pressure of CO2 resulting from heating, 
calcite reactions, and gas-phase transport. This assumption is justified by the results of the DST 
and THC Seepage Model runs, which show that the volume fraction of CO2 is generally less than 
5% and always less than 10% (CRWMS M&O 2000, N0120/U0110). 
3.10.4 DST THC Model Results and Validation 
The DST is the second underground thermal test being carried out in the Exploratory Studies 
Facility (ESF) at Yucca Mountain, Nevada. The purpose of the test is to evaluate the coupled 
thermal, hydrological, chemical and mechanical processes that take place in unsaturated 
fractured tuff over a range of temperatures from approximately 25C to 200C. The heaters were 
activated in December 1997 and are planned to run for 4 years followed by a 4 year cooling 
period. 
Simulation of DST THC processes provides an important validation test for the THC conceptual 
models and input data used in the THC Seepage Model (Figure 3.10-3) for a much longer time 
scale. Geochemical input parameters have not been calibrated to measured data collected during 
the DST and therefore the DST THC Model simulations are an independent test of the 
conceptual model and input data used also in the THC Seepage Model. Detailed analysis of 
THC processes in the DST and validation tests are presented in CRWMS M&O (2000, 
N0120/U0110). This validation process involves examination of areas of modeled fracture 
drainage compared to the locations where water was collected during the test, the comparison of 
CO2 concentrations collected from sampled gases, and comparison of the chemistry of waters 
collected from boreholes over time. These validation exercises are continuing as more data are 
collected from the DST and the models are improved to represent the physical and chemical 
processes more accurately. The following subsection compares modeling results to measured 
CO2 concentrations collected from boreholes. Brief descriptions of the evolution of the water 
chemistry and mineralogy follow. 
3.10.4.1 Gas-Phase CO2 Evolution 
In the first test, CO2 concentrations measured in gas samples taken from boreholes during the 
DST are compared to simulation results using the DST THC Model. It is very important to 
capture changes in gas-phase CO2 concentrations because they strongly control the pH of 
condensate waters, they are sensitive to temperature, and CO2 transport is sensitive to the 
fracture hydrologic properties. CO2 also affects HCO3
- concentrations in fracture waters, which 
are important for the in-drift geochemical environment. Modeled distributions of CO2 
concentrations and temperature in fractures and matrix are shown after 6 and 20 months of 
heating (which are also times for which CO2 measurements are available) in Figure 3.10-4 for 
the calcite-silica-gypsum geochemical system (Case 2). At both times, and in both fractures and 
matrix, a halo of increased CO2 concentrations appears centered approximately at the 60C 
isotherm. Over the 14-month period, between 6 months and 20 months, the halo increases 
considerably in extent and magnitude. 
To evaluate how the model predicts the time evolution of CO2 concentrations in the gas phase, 
measured CO2 concentrations from intervals that were repeatedly sampled from February 1998

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to August 1999 (20 months) are compared to model results for the same times. Figure 3.10-5 
shows the time evolution of CO2 concentrations in borehole intervals 74-3, 75-3, 76-3, and 78-3 
(see Figure 3.10-4 for locations of borehole intervals). In borehole interval 74-3, there were only 
grid nodes above (cooler side) and below (hotter side) the interval, and therefore results from 
both nodes are plotted to see if they bracket the measured compositions. In borehole interval 78- 
3, two locations (center and end) were chosen, because of the strong thermal gradient across this 
region. The comparison shows that the simulations generally follow the trends in measured CO2 
concentrations. Two exceptions are when a known heater power loss occurred (around 19 
months; see slope change in 74-3 and 75-3 at 20 months) or when the samples were at boiling 
temperatures and were nearly all water vapor (instead of air) and had much of the water 
condensed out during sampling (76-3 and 78-3, largest peaks). In the latter case, the modeling 
results should diverge from the measured data, because they reflect the CO2 concentration for the 
full water vapor-air mixture. This effect is discussed in CRWMS M&O (2000, N0120/U0110, 
Section 6.2.7.2). 
3.10.4.2 Water Chemistry Evolution 
The modeled chemistry of waters in fractures is shifted from an initial pH of about 8.3 to 6.5, 
and is captured as changes in time and space. The lowest modeled pH values are in the region of 
highest gas-phase CO2 concentrations. The shift in pH in the modeled fracture water is similar to 
that observed in the water collected from hydrology boreholes at the same times and in the 
expected regions during the DST (CRWMS M&O 2000, N0120/U0110), which were also areas 
of high gas-phase CO2 concentrations. Chloride concentrations in waters collected from 
hydrology boreholes are considerably more dilute (a factor of 5 to 10) than the matrix pore 
water, which was also predicted by the modeling. Other species such as Ca and Si show similar 
trends in the modeled fracture water compositions compared to measured water compositions. 
Additional information on water chemistry can be found in CRWMS M&O (2000, 
N0120/U0110). 
3.10.4.3 Mineralogical Changes 
In the model simulations, calcite is the major phase forming in the zone above the heaters, 
although the abundances are exceedingly small. Secondarily, amorphous silica also precipitates, 
but is much less abundant compared to calcite. No direct observation of the precipitation or 
dissolution of calcite has been found because the DST is ongoing; however, trends such as 
decreasing Ca in water found in boreholes with increasing temperature, pH and silica 
concentrations are strongly suggestive of calcite precipitation (CRWMS M&O 2000, 
N0120/U0110, Table 9). Fracture porosity changes in the DST simulations are very small after 
20 months of simulation (on the order of 0.01%) and follow closely the area of calcite 
precipitation (CRWMS M&O 2000, N0120/U0110, Figure 17). Such small changes likely have 
no measurable effect on the hydrologic properties of the rock. More data are being collected 
from the DST, including 14C concentrations in gas-phase CO2 and hydrogen, carbon, oxygen, 
strontium, and uranium isotopic measurements that will allow for more careful testing of the 
DST THC Model.

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3.10.5 THC Seepage Model 
This subsection describes the THC Seepage Model and the results of predictions of water and 
gas chemistry that may seep into drifts over the next 100,000 years. This model also considers 
any changes in the hydrological properties as a result of mineral precipitation and dissolution. 
3.10.5.1 THC Seepage Model Description 
A THC Seepage Model incorporates the elements of the EDA II (Enhanced Design Alternatives; 
Wilkins and Heath 1999, Enclosure 2) to represent waste package heating over time, changes in 
heat load due to ventilation, the effective heat transfer within the drift, the addition of backfill 
after 50 years, and THC processes. This two-dimensional model incorporated the initial layering 
in hydrologic and thermal properties and mineralogy from the surface to the Calico Hills zeolitic 
unit, along with different initial mineralogy and reactive surface areas in fractures and matrix 
(Figure 3.10-6). A number of cases were evaluated for different calibrated property sets, climate 
change scenarios, and geochemical systems. The climate scenarios were constructed from 
average values of the present-day infiltration, monsoon and glacial transition climates along with 
the upper and lower bounds. These averages were calculated from about 30 TH chimney models 
in the potential repository footprint. Predictions were presented of the water and gas chemistry 
that may enter the drifts for a period of 100,000 years, including a preclosure period of 50 years 
with 70% heat removal by ventilation. 
3.10.5.2 TH Effects 
TH effects on liquid saturation and flow around drifts were investigated in CRWMS M&O 
(2000, N0120/U0110). The TH effects on liquid saturation and temperature around drifts are a 
function of the infiltration rate and the initial liquid saturations calculated from steady-state 
simulations using specific calibrated property sets (CRWMS M&O 2000, U0035). Liquid 
saturations and temperature are shown around the drifts at 600 years, which is approximately the 
time of maximum dryout extent for the three climate cases investigated (Figure 3.10-7). These 
climate cases considered three time periods (0600, 6002,000, and 2,000100,000 years) and 
different infiltration rates for each period (0.6/6/3, 6/16/25, and 15/26/47 mm/yr) for a lower, 
mean, and upper bound, respectively (CRWMS M&O 2000, N0120/U0110). The dryout zone is 
asymmetric around the drift as a result of the position of the waste package and backfill, and the 
effect of infiltration above the drift. The smaller dryout zone in the lowest infiltration case 
compared to the mean infiltration case is apparently the result of the differing property sets rather 
than differences in the infiltration rate. Higher liquid saturations in the pillar region are a result 
of water being diverted around the drift. 
3.10.5.3 Gas-Phase CO2 Evolution 
The CO2 evolution in the gas phase is a controlling factor for the pH and mineral-water 
reactions. Time profiles for gas-phase CO2 concentrations at three locations around the drift are 
shown in Figure 3.10-8 for the Case 2 (calcite-silica-gypsum) geochemical system. Carbon 
dioxide concentrations in fractures drop significantly during dryout and increase again during 
rewetting. The increase in CO2 concentrations in the gas phase during rewetting is likely a result 
of heating of these waters as they approach the drift wall, as suggested by the high-infiltration

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case showing the largest CO2 concentration after rewetting (near 12,000 ppmV). The highest 
concentrations are similar to those observed during the DST, although rewetting has not taken 
place in the DST because it is still in the heating phase. 
3.10.5.4 Water Chemistry Evolution 
Chloride is a useful indicator of the extent of boiling or dilution, and interaction of condensate 
waters in fractures that are low in Cl with matrix pore waters having much higher chloride 
concentrations. Chloride concentrations are plotted in Figure 3.10-9 as a function of time at three 
locations around the drift. The gap in concentrations between about 75 and 1,000 years reflects 
the dryout period when no aqueous phase is present at the drift wall. Upon rewetting, chloride 
concentrations drop relatively quickly below 400 mg/L toward ambient values near 110 mg/L. 
There is no evidence of water with high concentrations of chloride at liquid saturations above 
residual saturation during the reflux period (after about 1,000 years). Therefore, waters that are 
most likely to seep into drifts will not be significantly more concentrated in chloride than the 
ambient pore water. 
Predicted pH and total aqueous carbonate concentrations (as HCO3
-) in fracture pore water are 
shown in Figures 3.10-10 and 3.10-11 for the calcite-silica-gypsum system. The calculated pH is 
generally higher for the full geochemical system results (approximate range 8.5 to 9.8; shown in 
CRWMS M&O 2000, N0120/U0110, Figure 30) than for the calcite-silica-gypsum system 
(approximate range 7 to 8.5). The composition of waters reaching the drift wall during rewetting 
were roughly neutral in pH (7.2 to 8.3) for the smaller system, and approximately 8.6 to 9.0 for 
the full geochemical system. Total aqueous carbonate concentrations are higher in the full system 
at the drift crown (maximum, after rewetting, near 10,000 mg/L for the low infiltration case) than 
in the calcite-silica-gypsum system (near ambient values of 200 mg/L after rewetting). 
The pH-carbonate-CO2 data show different trends when aluminosilicates in the mineral 
assemblage are considered. The aluminosilicate reactions are sensitive to competing effects of 
infiltration rate and gas phase CO2 diffusion relative to calcite dissolution/precipitation, feldspar 
dissolution, and calcium-zeolite precipitation. The dissolution of feldspars to form zeolites and 
clays directly affects the pH. For example, the dissolution of albite (Na-feldspar) to form 
kaolinite (clay) results in an increase in pH, as follows: 
2 NaAlSi3O8 (albite) + H2O + 2H+ . Al2Si2O5(OH)4 (kaolinite) + 4SiO2 + 2Na+ 
Feldspar dissolution also indirectly causes an increase in pH when Ca-rich zeolites precipitate, 
depleting calcium from solution and destabilizing calcite, as in the following reaction: 
2 NaAlSi3O8 (albite) + SiO2 (aq) + CaCO3 (calcite) + H+ + 7H2O . 
CaAl2Si7O18  7H2O (stellerite) + 2Na+ + HCO3
- 
As a result, simulations that consider aluminosilicate reactions generally yield higher pH and 
total aqueous carbonate concentrations and generally lower CO2 partial pressures than 
simulations with the simpler calcite-silica-gypsum system. Simulations of the DST show that 
results from the calcite-silica-gypsum system matches the observed pH, bicarbonate, and calcium

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more closely than the more complex system. However, over longer and more stable periods of 
reflux and boiling, the system may trend toward the chemistry of the more complex system. 
3.10.5.5 Porosity and Permeability Changes and Assessment of Precipitation Cap 
Formation 
The calculated change in fracture porosity in the vicinity of the drift, at a simulation of 10,000 
years, is shown in Figure 3.10-12 for the three climate scenarios and the calcite-silica-gypsum 
system. The maximum porosity reduction (negative in the plots) occurs for the high-infiltration 
case and is predominantly above the drift, adjacent to the tsw33 and tsw34 hydrogeologic unit 
contact. In all cases, the porosity change is relatively small (less than 1% of the initial porosity) 
and mostly to smaller values. The porosity decrease results primarily from calcite precipitation 
(as in the DST simulations). In the full geochemical system, the fracture porosity change is 
similarly small, but is dominated by zeolite reactions. Because the fracture porosity changes are 
exceedingly small, and permeability changes are negligible, TH processes are not significantly 
affected by mineral precipitation or dissolution. 
3.10.6 Uncertainties and Limitations 
Many uncertainties exist in the thermodynamic and kinetic parameters used to describe mineral 
precipitation and dissolution. Limitations also arise under specific geochemical and/or physical 
conditions. For example, as the concentrations of dissolved solutes increase during boiling of 
porewater, the activity coefficients of the dissolved species may deviate significantly from unity, 
and the ionic strength at which the models yield reasonable results is exceeded. Rapid boiling 
can also lead to mineral supersaturation outside the range of the pseudo-first-order kinetic 
models employed, which are generally reasonable under near-equilibrium conditions. Mineral 
precipitation may then be controlled by nucleation kinetics and other surface-energy-related 
phenomena. These uncertainties and limitations are generally difficult to quantify, because the 
models also introduce simplifications in the process of using these data, and the physical regimes 
under which the model breaks down may not be important for the overall dynamics of the 
system. Geochemical reactions are a strong function of temperature and the presence of water, 
which are better constrained than the rates of reaction and may control the spatial distribution of 
mineral precipitation, even if the exact quantities of the minerals at a given time are uncertain. 
Relations between permeability changes and porosity changes are also highly uncertain. These 
uncertainties are difficult to quantify because they depend on the detailed geometry of the pore 
space and throats; however, some methods have succeeded in quantifying this effect in 
diagenetically altered rocks (Ehrlich et al. 1991, pp. 15791592). The effect of porosity 
reductions in fractures on the fracture permeability is even more uncertain. 
The model is also limited to the middle nonlithophysal unit of the Topopah Spring tuff. 
Lithophysal units may exhibit different TH behavior that would change the interaction of 
fracture and matrix waters. Differences in the mineralogy of fractures and lithophysae could 
change the chemistry of the system somewhat, although the bulk rock chemistry is very similar 
for all of the welded TSw units. More important than small differences in mineral abundances is 
the effective reactive surface area which could be larger in lithophysal units because of the

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greater abundance of vapor-phase minerals and as result of the interaction of waters flowing 
between fractures and lithophysae. 
These uncertainties do not, in general, limit the applicability of the models because of the ability 
to calibrate effective reaction rates to fit the results of laboratory and in-situ experiments (i.e., 
thermal tests). Some of the uncertainties inherent in the thermodynamic and kinetic data have 
been addressed by the consideration of a simplified and a more complex mineral assemblage. 
Validation of the model by comparison to geochemical data from the DST provides the best 
degree of confidence building, and these comparisons have shown that the model is reasonable. 
Differences in the model results between the two geochemical systems, showing that the pH and 
CO2 concentration in the gas phase for the simpler system compare more favorably to data from 
the DST shows that the model does provide important bounds on reaction rates. Results from the 
more complete system yield a higher pH than in the measured waters from the DST, which is due 
to a greater calculated reaction rate for feldspars. Therefore, porosity reductions as a result of 
feldspars altering to clays and zeolites likely take place at rates less than that given by model, 
giving an important upper bound. 
3.10.7 Alternative Conceptual Models 
A model proposed by Matyskiela (1997, pp. 11151118) suggests that silica precipitation in the 
rock matrix adjoining fractures will strongly reduce the permeability of the matrix, resulting in 
significantly decreased imbibition of percolating waters. The times for strong silica sealing of the 
matrix wall for a vitric tuff were 5 years for a solution having 350 ppm SiO2 and 105 years for a 
solution having 125 ppm SiO2. For a devitrified tuff, it was estimated that cristobalite 
dissolution followed by quartz precipitation would lead to a 1 mm thick quartz margin in about 
30 years. It is clear that several factors would immediately reduce the magnitude of the effects 
described. First, the potential repository would be located in a devitrified tuff where the rates of 
reaction are orders of magnitude slower than for volcanic glasses. Second, the proposed model 
considered the system as fully saturated, maximizing the reactive surface area, the water 
available for reaction, and the diffusion coefficient. In an unsaturated system, only a part of the 
fracture area would be contacted by water, so that the process would have to take place for much 
longer periods to actually affect a large part of the fracture surfaces. Third, it is considered that 
the fracture water will have higher silica concentrations than a matrix porewater, thus leading to 
a diffusion gradient into the matrix. However, no clear reason exists why the fracture water 
should have a higher silica concentration, because it originated as pure condensate (zero SiO2) 
that has drained back toward the heat source, increasing its silica content through wall rock 
reactions. Because the system is unsaturated, there is little driving force for convection as in a 
single-phase hydrothermal system. A quantitative analysis of this problem was explored by 
Lichtner et al. (1999) which also questioned the interpretations and conclusions presented in the 
Matyskiela (1997, pp. 11151118) paper (see CRWMS M&O 2000, U0135) and in 
Section 3.10.9 below. 
3.10.8 Corroborative Evidence 
Water and gas chemistry collected from the ongoing DST has been invaluable in the testing of 
the models developed for the prediction of potential long-term repository performance. No other 
data can be used to directly corroborate the model because of the uniqueness of the system.

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However studies from natural geothermal analogs has been used as corroborative evidence, as 
discussed in Section 3.10.9. 
3.10.9 Analogs 
THC processes are better constrained through analysis of selected intrusive complexes hosted in 
unsaturated tuffaceous rock. The ideal intrusion to serve as a natural analog to THC processes 
anticipated at a potential Yucca Mountain repository should have been emplaced above the water 
table, should be of sufficient size to have produced enough heat to sustain boiling conditions for 
times on the order of several thousand years (~30 m width), and should occur in host rock of 
similar composition and characteristics to the Topopah Spring tuff. 
An analogy for understanding future behavior of a potential repository is the fossil hydrothermal 
system at Yucca Mountain itself (Bish and Aronson 1993, pp. 148161). After formation of the 
major zeolitic horizons (1311.6 Ma), deep-seated hydrothermal activity persisted until about 10 
million years ago (Ma). This activity was limited to temperatures of 90100oC, the zeolite 
stability limit. Conceptual models for mineral evolution at Yucca Mountain (CRWMS M&O 
2000, I0045, Section 6.3) suggest that the most likely mineralogical reactions caused by potential 
repository heating would include dissolution of volcanic glass and precipitation of clinoptilolite, 
clay, and opal-CT; dissolution and precipitation of silica polymorphs (cristobalite, opal-CT, 
tridymite, and quartz); alteration of feldspars to clays; and, finally, reactions involving calcite 
and zeolites. Present-day temperatures in borehole G-3, within the potential repository block, 
compare closely to inferred paleotemperatures. In contrast, increasingly higher 
paleotemperatures are inferred for boreholes G-1 and G-2, which are closer to the center of the 
Timber Mountain caldera source of eruption (G-2 being the farthest north). Mineral abundances 
in G-1 and G-2 cores indicate a northward progression of an increasing abundance of clays and 
zeolites along with decreased abundance of glass. This is consistent with the reactions stated 
above. 
In addition to considering Yucca Mountain as a self-analog, contacts between igneous intrusions 
and host rock may provide useful information as coupled-process analogs. The Banco Bonito 
obsidian flow filled a steep-walled canyon cut in the Battleship Rock tuff on the southwest rim of 
the Valles Caldera, New Mexico, about 400,000 years ago. The obsidian, initially at 
temperatures of 850oC, heated the porous tuff in the canyon walls to 150350oC for decades, 
and, according to models, vaporized much of the pore water, and caused refluxing of water 
(Stockman et al. 1994). Contact effects include a reddish baked zone extending several meters 
into the tuffs. No evidence of hydrothermal alteration was noted, suggesting that the area was 
unsaturated at the time of contact. Apart from devitrification, the principal mineralogic change in 
tuff near the contact was the development of feldspar-silica linings on voids in the pumiceous 
tuff matrix; no significant development of zeolites was found. Stockman et al. (1994) concluded 
that overall, the effects of heating in this unsaturated environment appeared to have been slight 
and were limited to the tuff nearest the contact. 
At Grants Ridge, New Mexico, a 2.6 Ma basalt plug intruded into 3.3 Ma non-welded, pumicerich, 
compositionally homogeneous, rhyolitic tuff and volcaniclastic sediments (WoldeGabriel et 
al. 1999, pp. 389411). A 10 m wide aureole characterized by color variation, contact welding, 
brecciation, partial melting, and stoping developed around the 150 m wide basalt plug. Despite

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the high-temperature (> 700oC) basaltic intrusion, there was no evidence of pervasive 
hydrothermal circulation and alteration of the country rock. WoldeGabriel et al. (1999, pp. 389 
411) postulated that vapor-phase expulsion of elemental species could have been responsible for 
the minor depletion of elements at the contact during devitrification of the silicic glass at nearsolidus 
temperature related to the basaltic intrusion. Because devitrification is generally 
enhanced by the presence of aqueous fluids, the abundance of volcanic glass within a short 
distance (~10 m) from the plug is consistent with the inference of WoldeGabriel et al. (1999, 
pp. 389411) that the plug intruded into an unsaturated environment. 
In the Paiute Ridge area of the Nevada Test Site, late Miocene basaltic magma intruded a 
sequence of 22 to 11 Ma tuffs in a single magmatic pulse as dikes, sills, and lopoliths (Lichtner 
et al. 1999). A contact aureole ~3 m wide surrounds the intrusions. Matyskiela (1997, pp. 1115 
1118) studied alteration surrounding one intrusion, the 50 m wide Papoose Lake sill. His major 
finding was alteration of glass shards to cristobalite and clinoptilolite within 60 m of the 
intrusion, which he interpreted as resulting from emplacement of the intrusion. Most significant 
was his observation of complete filling of pore spaces with silica at fracture-matrix interfaces, 
thus reducing fracture-matrix interaction and facing infiltrating water to flow within fractures. 
Matyskiela (1997) estimated enhanced fracture flow to be as much as five times ambient 
conditions. This is the opposite behavior to formation of a silica cap, as predicted by recent 
simulations conducted for Yucca Mountain (Nitao 1998) in which fractures would become filled 
with quartz or chalcedony, thus inhibiting further flow. An issue is the extent to which a fracture 
can be filled by the silica contained in matrix pore water. Lichtner et al. (1999) shows that for a 
given matrix porosity, the degree of sealing of the fracture depends on the fracture porosity and 
the particular silica polymorph that precipitates. The two-phase numerical simulation results of 
Lichtner et al. (1999) suggest that at distances of tens of meters from the larger Paiute Ridge 
intrusion in their study (width > 39 m), prolonged boiling conditions were established for times 
on the order of several thousands of years. Amorphous silica, with its higher solubility, gives the 
largest fracture filling, followed by chalcedony and quartz. For complete sealing of the fracture, 
a very small fracture porosity is necessary. 
Some other questions arise regarding the effect of the sill on the host rocks. First, it is stated that 
the basaltic magma was particularly dry because hydrous phases (such as amphibole) were not 
found and because it was nonvesiculated (Matyskiela 1997, p. 1115). However, the absence of 
amphibole in this sill is not evidence for a lack of water in the melt because amphiboles are not 
stable phases at low pressures in basaltic melts (Ehlers 1972, p. 161). Also, this igneous body is 
a sill and not a flow; the slower cooling allows water degassing without obvious vesiculation (as 
in a lava flow). Basaltic magmas also can exsolve significant quantities of CO2 in addition to 
H2O, and therefore the geochemical environment was not clearly analogous to that around a 
potential repository drift. 
In summary, in both the Banco Bonito flow and the Grants Ridge basaltic intrusion, the effects of 
high temperature on unsaturated environments appeared to have been slight, were limited to 
within about 10 m of the contact, and showed no evidence of fluid-driven convective heat 
transfer or pervasive hydrothermal alteration of the country rock. These field studies provide a 
limiting-case natural analog for evaluating effects of heat from decay of radioactive waste in an 
unsaturated environment.

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3.10.10 Model Validation 
The drift-scale THC models have been extensively validated by comparison of gas and water 
geochemical data collected during the DST, as discussed in Section 3.10.4 and described in 
detail in CRWMS M&O (2000, N0120/U0110). These comparisons include gas-phase CO2 
concentrations as a function of time and space, the pH of waters collected in boreholes, and 
general observations on changes in concentrations of Cl and other aqueous species. The model 
can be considered validated for its intended use. 
The thermal tests provide the only field-scale experiments that have produced seepage under 
thermally perturbed conditions. Numerous samples of water have been collected from several 
borehole intervals during the DST, and previously a few samples were collected in the Single 
Heater Test. 
Prediction and comparison to data from thermal tests and experimental studies have allowed for 
validation of the models describing coupled THC processes. However, it is not possible to 
validate all aspects of the model over a 100,000 year period. Yet reasonable bounds on the 
system behavior were made based on validation over relatively short time scales using the DST 
as described in this section and in CRWMS M&O 2000, N0120/U0110. The model has provided 
bounds on the gas and water chemistry over time (i.e., CO2 and pH) as well as changes in 
porosity, as discussed in Section 3.10.6. For example, the composition of waters reaching the 
drift wall during rewetting was roughly neutral in pH (78.5) for the smaller geochemical system 
(without aluminosilicates) and had a pH of approximately 8.69.0 for the more complete 
geochemical system. 
3.10.11 Abstraction of Drift-Scale THC Modeling for TSPA-SR 
The THC water chemistry and gas-phase composition abstraction represents the fracture waters 
impinging at the crown and sides of the potential emplacement drifts. The abstraction uses the 
detailed time-history results of the process-level THC model and discretizes them into four 
distinct geochemical periods for which compositional boundary conditions are provided for the 
potential in-drift geochemical environment for TSPA models. The abstraction compositional 
boundary conditions include constituents represented by five cations, six anions, and pH. In 
addition, this abstraction includes the partial pressure of carbon dioxide in the gas phase in 
fractures adjacent to the potential drifts (and, during the abstraction boiling period, the 
equilibration temperature used for that gas with the condensate water composition). These 
boundary conditions to the potential drifts allow incorporation of time varying, thermally 
perturbed water and gas compositions within the assessment of chemical interactions of the indrift 
environment. 
The abstracted use of the THC process model results from the Case 2 mineralogy is based on the 
fact that it reproduces more accurately the observed changes to water and gas compositions in 
the drift-scale heater test (CRWMS M&O 2000, N0120/U0110; Sections 6.1.7 and 6.2.7). This 
corresponds to using the mineralogic phase constraints represented in Case 2 to set the major 
element composition of the water and gas. This decision is supported by the THC process-level 
model validation with the DST results, for which the Case 2 results provide closer description of 
the ambient and thermally perturbed geochemical system (CRWMS M&O 2000, N0120/U0110;

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Sections 6.1.7, 6.2.7 and 6.3.5). Therefore, the abstraction of aqueous water chemistry of the 
major chemical species (which are contained in both Case 1 and Case 2 representations) is from 
Case 2 only. 
For the constituents included in both those chemical systems, the major differences between 
results (for PA purposes this is defined as a factor of 10or one log unitor more) are limited 
to Ca2+, Na+, and HCO3
. These represent differences that result primarily from the more 
uncertain kinetic representation of the more complex chemical system (CRWMS M&O 2000, 
N0120/U0110; Sections 6.1.7, 6.2.7, and 6.3.5). As discussed therein, the uncertain precipitation 
rates of the alumino-silicates create a feedback to the carbonate system by removing Ca from 
solution, impacting the carbonate system through the changes in calcite saturation state. 
However, estimates of the additional constituents included only within the Case 1 results should 
be reasonably obtained from those results. This is because the primary differences in the systems 
are those constituents listed above and the variations in pH, that may impact mineral equilibria in 
the more complex chemical system, are of lesser magnitude. The process model Case 1 results 
for F- are assessed to be relatively insensitive to the possible changes (CRWMS M&O 2000, 
N0120/U0110; Section 6.3.5). The phase constraints applied within the Case 1 representation for 
these additional constituents should be largely unchanged (although more accurate kinetic 
parameter sets should prevent them from impacting the carbonate subsystem) and these are all 
trace constituents compared to the major constituents included within both Case 1 and Case 2. 
Given this, the values for the additional constituents from the Case 1 representation should 
provide at least order-of-magnitude estimates for incorporating abstracted first approximations 
for these constituents. In the abstraction these values are combined with the constituents from 
the Case 2 results to describe a more comprehensive water composition (Table 3.10.3). Addition 
of these values to these abstracted water compositions should have only minor effects on charge 
balance, because these additional aqueous species are trace constituents compared to the major 
elements given within the Case 2 representation. 
Table 3.10.3 represents the THC abstraction of water and gas compositions for the THC 
boundary conditions adjacent to the drift wall. Each of the time periods defined below has a 
defined composition of gas and water that represent those constituents that can enter the drift 
during those times based on the process-level THC models for the thermally perturbed 
geosphere. Four periods were defined based on the examination of the process-level results. Each 
of these periods was evaluated to define constant representative values (as discussed above) for 
all constituents during that period with step (i.e., instantaneous) changes between the periods. 
The first period defined goes from 0 to 50 years and is the entire preclosure period. This is 
followed by the defined boiling period 2, during which the fractures are calculated to have zero 
saturation. The water that may enter the drift through these fractures would be that moving 
rapidly down from the condensate zone. This boiling period is followed by a transitional 
cooldown period from 1000 to 2000 years during which the temperature is still high, but below 
boiling. Finally an extended cool-down period 4 is defined from 2000 to 100,000 years, over 
which the temperatures return to ambient and water compositions change gradually. 
Although the preclosure period (50 years) is included in the process models, the postclosure 
performance assessment starts at the end of this initial period. Abstracted results for Period 1 
preclosure are included only for complete coverage of the time of the process-level results. The 
process model results do not include the chemical effects of pre-closure ventilation, so the gas

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composition and water chemistry within this period may not be very representative of those that 
could enter the drifts. These abstracted values for Period 1 preclosure are not used within the 
performance assessment analyses. Because the preclosure period is not being used within the 
performance assessment, the values for the 0-50 year period are more coarsely abstracted and 
chosen to be roughly representative of the first 50 years. This period will not be used further in 
this abstraction. The abstracted boiling period 2 directly follows the preclosure abstraction period 
1. During the second abstraction period, the boiling period, the fracture saturation around the 
drifts is calculated to be zero in the THC process model results. The chemical composition of 
the condensate water, calculated to be in the zone of highest saturation above the fracture dryout, 
is used to represent the water that may flow rapidly through the fractures during the boiling 
period. The values for such water are given below in Table 3.10.3 with the value of the partial 
pressure of CO2 in the gas surrounding the drift wall during that dryout time. The flux of such 
water would be at a minimum during this period, so that the fracture gas composition at the drift 
wall during the dryout period should be the appropriate composition with which to equilibrate 
the condensate liquid. This value (log CO2, volume fraction = -6.5) is given in Table 3.10.3 
below. This gas composition, and associated boiling temperature, should be used to equilibrate 
with the abstracted condensate water composition shown for this period in Table 3.10.3. This 
represents the abstracted water that may flow rapidly down fractures into the dryout zone from 
the overlying condensate zone. 
It is re-emphasized that during the abstracted boiling period (50-1000 years), denoted as period 2 
in Table 3.10.3, the abstracted aqueous concentrations and pH are obtained from the processlevel 
model results from satmax_summary.xls (DTN: LB991200DSTTHC.002), not the results 
for locations at the drift wall. These latter water compositions are artifacts of the point at which 
the water chemistry representation was shut off either due to high ionic strength or low 
saturations. However, the gas composition (CO2, gas) is obtained from the appropriate results 
for the crown fractures at the drift wall because the process-level THC gas chemistry calculation 
is continuous through this period (see Figure 29, CRWMS M&O 2000, N0120/U0110). The 
boiling period abstracted water composition is based on the condensate water chemistry above 
the dryout zone, representing water that would flow rapidly down the fracture if possible. 
The remaining two THC periods, the transitional and extended cool-down periods, are 
abstractions of the chemistry results obtained from the process-level THC model in the same 
manner as that for the pre-closure period (0-50 years). However, because the changes are more 
gradual for most constituents in these time periods, it was possible to identify a result at a 
specific time given by the process model that corresponded to a reasonable representation for the 
compositional parameters needed in the abstraction. Using specific calculated results from the 
THC process model ensures that issues of charge balance and phase equilibria are maintained 
completely consistently within the abstracted representation. 
It is noted that the abstracted temperatures listed in Table 3.10.3 are given for use as a guide 
only, especially in Period 4 in which the temperature changes gradually from about 90oC to 25oC 
over 98,000 years. Only the temperature in the Boiling Period 2 should be used in process 
models to calculate re-equilibration of the condensate-zone water composition with the 
abstracted CO2 gas composition in the fractures at the drift crown for that period of time. For 
further Performance Assessment model abstractions, the temperatures given in Table 3.10.3 can 
be used as the representative values for the temperature of the abstracted compositions, but

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should be tied to the thermal variation of the repository system as abstracted for the total system 
performance assessment. 
The following should be noted for the abstraction shown in Table 3.10.3: 
 The first 50 years represents the repository preclosure period with 70% heat removal via 
ventilation. However, because the Performance Assessment only starts at closure, these 
values are not used there and are only provided for completeness of the time span. It is 
emphasized that the values probably would not be representative of preclosure 
conditions because the potential chemical effects of ventilation are not included in the 
process model. 
 The values for abstraction period 3, correspond to the process-level model results at 
2000 years after initial waste emplacement. This is because as soon as the drift wall 
rock resaturates, the CO2 very rapidly approaches about 1x10-3 bars and the pH and 
water composition are taken consistently with this gas chemistry. 
 The 10,000-year process-level model results are used for the abstraction values in the 
last period as a reasonable approximation of the water composition average for that 
whole period. 
 The additional constituents taken from the results of the more detailed chemical system 
are, in general, trace constituents compared to those taken from the less detailed 
chemical system. Even though combination of these results may lead to discrepancies of 
the trace constituents that could be large in a relative sense, their contributions to the 
absolute uncertainties will remain small because of their trace abundances. Only 
potassium approaches the concentrations of the constituents taken from the less detailed 
chemical system, and even it is one to two orders of magnitude lower in concentration 
than the major cation species Ca+2 and Na+ included in Case 2 results.

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Table 3.10-3. THC Abstraction for the Mean Infiltration Rate Case with Climate Change (CRWMS M&O 
2000, N0125, Table 3) 
Constituents from Simplified Chemical System (Calcite-Silica-Gypsum) 
Preclosure Boiling Transitional Cool- 
Down 
Extended Cool-Down 
Period 1 Period 2 Period 3 Period 4 
Parameter Abstracted Values Abstracted 
Values 
Abstracted Values Abstracted Values 
Time 0 - 50 years 50  1,000 years 1,000  2,000 years 2,000 - 100,000 years 
Temperature, C 80 96 90 50 
log CO2, vol. frac. -2.8 -6.5 -3.0 -2.0 
pH 8.2 8.1 7.8 7.3 
Ca2+, molal 1.7E-03 6.4E-04 1.0E-03 1.8E-03 
Na+, molal 3.0E-03 1.4E-03 2.6E-03 2.6E-03 
SiO2, molal 1.5E-03 1.5E-03 2.1E-03 1.2E-03 
Cl

, molal 3.7E-03 1.8E-03 3.2E-03 3.3E-03 
HCO3

, molal 1.3E-03 1.9E-04 3.0E-04 2.1E-03 
SO4
2
, molal 1.3E-03 6.6E-04 1.2E-03 1.2E-03 
Additional Constituents from Full Chemical System 
Mg2+, molal 4.0E-06 3.2E-07 1.6E-06 7.8E-06 
K+, molal 5.5E-05 8.5E-05 3.1E-04 1.0E-04 
AlO2

, molal 1.0E-10 2.7E-07 6.8E-08 2.0E-09 
HFeO2

, molal 1.1E-10 7.9E-10 4.1E-10 2.4E-11 
F

, molal 5.0E-05 2.5E-05 4.5E-05 4.5E-05 
3.10.12 Summary and Conclusions 
The conceptual model for THC processes provides a comprehensive basis for modeling the 
pertinent mineral-water-gas reactions in the host rock, under thermal loading conditions, as they 
influence the water and gas chemistry that may enter drifts over 100,000 years. Data are 
incorporated from the drift-scale calibrated property sets, the UZ Flow and Transport Model, 
geochemical data (fracture and matrix mineralogy, aqueous geochemistry, and gas chemistry), 
thermodynamic data (minerals, gases, and aqueous species), data for mineral-water reaction 
kinetics, and transport data. Simulations of THC processes included coupling between heat, 
water, and vapor flow, aqueous and gaseous species transport, kinetic and equilibrium mineralwater 
reactions, and feedback of mineral precipitation/dissolution on porosity, permeability, and 
capillary pressure (hydrologic properties) for a dual-permeability (fracture-matrix) system. The 
effect of these coupled THC processes on the time evolution of flow fields in the UZ around 
drifts has been investigated for different climate change scenarios, calibrated property sets, and 
initial mineralogy. Validation of the model was done by comparison of measured gas and water 
chemistry from the Drift Scale Test (DST) to the results of simulations using the DST THC

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Model. In particular, simulation results were compared to measured gas-phase CO2 
concentrations and the chemistry of waters collected from hydrology boreholes collected during 
the test. 
Comparisons of water chemistry (pH) and CO2 concentrations in the gas phase from the DST 
indicate that a smaller set of aqueous species and minerals (calcite, silica phases, gypsum), but 
including gaseous CO2, can describe the general evolution of DST water quite closely. Including 
a wide range of aluminosilicates, such as feldspars, clays, and zeolites yields information on 
additional species (i.e., Al, Fe, F), but their inclusion causes shifts in the water and gas chemistry 
that are more rapid than observed. These effects may be more important over longer time 
periods, leading to similar but less rapid changes (i.e., a slightly closer approach to equilibrium). 
However, over the time scale of the DST, the effective reaction rates and/or thermodynamic 
properties of these phases will clearly require some refinement. 
The THC Seepage Model incorporates the elements of the EDA II design to represent waste 
package heating over time, changes in heat load due to ventilation, the effective heat transfer 
within the drift, the addition of backfill after 50 years, and THC processes in the unsaturated 
zone. A number of cases were evaluated for different calibrated property sets, climate-change 
scenarios, and geochemical systems. The THC seepage simulations indicate that there may be an 
increase in the CO2 gas and aqueous carbonate concentrations around the drift during rewetting. 
The extent of the dryout zone and the time of rewetting were different for each climate history 
and calibrated property set, although the general character was unchanged. As in the Drift Scale 
Test THC simulations, some notable differences in the pH and CO2 concentrations appeared in 
the two geochemical systems. The composition of waters reaching the drift wall during 
rewetting were roughly neutral in pH (78.5) for the smaller geochemical system (without 
aluminosilicates) and approximately 8.69.0 for the more complete geochemical system. 
Predicted pH and HCO3
- concentrations in the smaller geochemical system simulations are 
supported by the data from the DST; however, the long term evolution could trend in the 
direction of the more complex system chemistry, if the slow reaction rates of the aluminosilicates 
limit the changes in water chemistry that can be observed over the short heating time of the DST. 
Even with the apparently overestimated reaction rates for the full mineral assemblage, the 
changes in porosity and permeability around drifts over 100,000 years were small (less than 1% 
of the total fracture porosity), and therefore effects on flow and transport are considered 
negligible. A summary of important results as related to the conceptual model of drift-scale 
THC processes is shown in Figure 3.10-13. 
In the abstraction for TSPA-SR calculations, the transient water and gas compositions are 
averaged over four discrete time periods from 0 to 100,000 years. Only the mean infiltration 
cases are selected because the results of the low and high infiltration cases showed similar 
behavior in general. The results that are passed to the in-drift geochemical models in TSPA are 
aqueous concentrations for five cations and six anions, pH, and partial pressure of carbon dioxide 
during the four discrete periods. These results are used to determine the in-drift environment and 
the corrosion of the drip shields and waste packages over time.

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3.11 UZ TRANSPORT MODEL 
3.11.1 Introduction 
The evaluation of possible radionuclide transport from the potential repository horizon to the 
groundwater in the saturated zone is key to assessing the performance of the potential repository. 
This section describes the issues, approach, assumptions, and understanding of the relevant 
physical processes, and input parameters used to develop the Transport Model in the UZ. The 
Transport Model utilizes the understanding of the complex flow processes from the Flow Model 
(Section 3.7) and accounts for the transport of aqueous/colloidal radionuclide species in both the 
fracture and matrix continua, with exchange between continua resulting from advective and/or 
diffusive processes, as well as sorption in the matrix. Results of 2-D vertical cross sections, 3-D 
site-scale simulations of the important radionuclides and daughter products, and 3-D simulations 
of tracer breakthrough at the water table are presented for different climate scenarios developed 
in Section 3.5. These results are analyzed to identify the major transport mechanisms and 
breakthrough times through the different hydrogeologic units and the effects of the major 
hydrogeologic features (faults and perched water). Model validation using the results of the ESF 
Alcove 1 and Busted Butte tracer tests is summarized. Review of known analog sites for UZ 
transport indicates that unsaturated systems in arid environments may provide favorable sites for 
geologic disposal of radioactive waste. The abstraction of the Transport Model used for 
calculations of radionuclide transport in TSPA is then discussed. Finally, this section ends with 
conclusions regarding the important issues identified for radionuclide transport at Yucca 
Mountain. 
3.11.1.1 Issues 
The Transport Model evaluates a suite of factors that control potential radionuclide transport to 
determine their effects on radionuclide breakthrough times and concentrations at the 
groundwater table. A schematic representation of the key issues for the Transport Model is 
shown in Figure 3.11-1. The flow of water from the potential repository horizon to the 
groundwater table can transport both aqueous and colloidal phase radionuclides. The 
concentration of radionuclides and their daughter products are diminished according to their 
radioactive decay rates, dilution due to mixing (i.e., dispersion), and the extent of sorption onto 
the solid phase. The flow pathways are determined by the characteristics of the faults, 
hydrogeologic units, and the presence of perched water. These characteristics control the extent 
of downward versus lateral flow, fracture-matrix interaction, and the partitioning of flow 
between fractures and rock matrix. Fractures and faults can be fast flow paths, where fluid 
contact time and surface area are small relative to the matrix and limit the extent of rock-water 
interaction relative to the slower-moving matrix flow. Fracture properties, such as aperture, 
frequency, mineralogy and saturation, affect fracture-matrix interactions, dispersion, sorption 
and the transport of aqueous and colloidal species. Matrix porosity, saturation, and mineralogy 
affect the extent of diffusion and sorption of species. The transport of colloidal species is further 
affected by their size, which determines the nature of pore exclusion, and filtration processes. 
More detailed discussions of these issues follow in Section 3.11.2.

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3.11.1.2 Approach 
Transport modeling studies of representative radionuclide and colloids are conducted in 2-D 
vertical cross sections and 3-D site-scale models of the UZ to: 
 Evaluate the effectiveness of matrix diffusion and sorption/filtration as retardation 
mechanisms in the various hydrogeologic units 
 Determine the dominant transport features and mechanisms 
 Estimate transport breakthrough from the potential repository to the water table 
 Evaluate the importance of decay daughter products on transport. 
Relationships of other models and data feeds to the Transport Model are schematically shown in 
Figure 3.11-2. 
3.11.1.3 Assumptions 
The key assumptions for the Transport Model in the UZ are listed here. The complete list of 
assumptions for the Transport Model and the discussion of the supporting rationale are in 
CRWMS M&O (2000, U0060, Section 5). 
 Flow component assumptions are the same as for the Flow Model described in Section 
3.7 (e.g., isothermal water flow, dual continuum, active fracture concept, van 
Genuchten-Mualem model for relative permeability and capillary-pressure constitutive 
relationships). 
 The processes governing the transport of dissolved and/or colloidal species include 
advection, molecular and surface diffusion, hydrodynamic dispersion, sorption, 
radioactive decay, colloid filtration, and colloid-assisted solute transport. 
 Colloid filtration does not affect the mediums porosity and permeability on account of 
the anticipated low colloid concentrations. 
 The initial radionuclide (solute or colloidal species) concentrations are constant in the 
gridblocks corresponding to the potential repository and zero throughout the rest of the 
UZ model domain. 
Section 3.11.2 provides a detailed discussion of the transport processes and other major factors 
affecting UZ transport.

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3.11.2 Physical Processes 
3.11.2.1 Flow Processes 
Transport is closely tied to water flow. A detailed discussion about hydrology in the UZ is 
presented in Section 3.3, and transport modeling is based on the Flow Model discussed in 
Section 3.7. In addition to the advective flow processes, transport of radioactive solutes and/or 
colloids involves hydrodynamic dispersion, sorption (solutes) or filtration (colloids), matrix 
diffusion, and radioactive decay. The effects of these processes on UZ transport are discussed 
below. 
3.11.2.2 Advection 
Advection is the movement of dissolved or colloidal species resulting from the bulk flow of fluid 
(Fetter 1993, p. 47). In advective transport, the flowing water carries contaminants, and 
transport pathways coincide with flow pathways determined by the characteristics of the faults, 
hydrogeologic units, and perched water (Section 3.3). As flow in Yucca Mountain is 
predominately downward because of gravity, so is advective transport. The presence of perched 
water bodies may result in lateral flow and subsequent transport of the radionuclides. 
Advection is probably the most important mechanism for fast radionuclide transport through the 
UZ to the water table. Advection through fractures is expected to dominate transport behavior in 
welded units because water flows largely through fracture networks. Dominant fracture flow in 
the zeolitic portions of the CHn and CFu also provides relatively short transport times to the 
water table, whereas the dominant matrix flow in the vitric CHn leads to much longer transport 
times. 
3.11.2.3 Hydrodynamic Dispersion 
Hydrodynamic dispersion includes both mechanical dispersion arising from local velocity 
variations and molecular diffusion driven by concentration gradients. Dispersion of the 
radionuclides occurs both along (longitudinal) and transverse to the average flow direction. 
Hydrodynamic dispersion dilutes and smears sharp concentration gradients and reduces the 
breakthrough time of radionuclides to the water table. The dispersion coefficient is a function of 
dispersivity and flow velocity. 
Values of dispersivity are difficult to determine without site-specific measurements. Dispersivity 
has been shown to increase as a function of observation scale, attributed mainly to mixing as 
more heterogeneities are sampled at larger scales (e.g., Gelhar et al. 1992, pp. 19551974; Fetter 
1993, pp. 6566). Furthermore, the reported field measurements of transverse dispersivity show 
it to be significantly less than longitudinal dispersivity (Fetter 1993, pp. 6566). 
Hydrodynamic dispersion is not expected to play an important role in UZ transport. First, 
dispersion effects are implicitly accounted for by the fracture-matrix dual-continuum approach, 
which explicitly models local velocity variations. Second, the potential repository emplacement 
area is very broad (relative to the distance to the water table), which tends to suppress dispersion 
effects (CRWMS M&O 2000, U0030, Section 6.2).

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3.11.2.4 Sorption 
Sorption is a general term to describe the binding of a solute (radionuclide) onto the sorbent 
(either the immobile rock matrix or colloids). As a result of sorption onto the rock matrix, the 
advancing rate of sorbing radionuclides is retarded. On the other hand, the attachment of sorbing 
radionuclides onto colloids can potentially facilitate their transport, which is to be discussed in 
Section 3.11.2.7. 
In Yucca Mountain studies, the effective sorption distribution coefficient (Kd) approach is 
employed to quantify the extent of radionuclide-sorbent interactions. This approach does not 
require identifying the specific underlying processes of sorption, such as surface adsorption, 
precipitation, and ion exchange. While the use of Kd to describe the complex radionuclide 
sorbent interactions in a flowing fluid of variable chemistry is a simplification, the results from 
numerous laboratory batch and column experiments have not produced recommendations to 
abandon the Kd approach for modeling radionuclide retardation in the YMP (CRWMS M&O 
2000, U0100, Sections 6.4 to 6.6). 
Experimentally determined Kd values have been predominantly derived from batch experiments 
using crushed tuff (with the sample size of 75500 m) under water-saturated conditions for a 
variety of rock types and radionuclides (Kd values are listed in Table 3.11-1 in Section 3.11.3.2). 
There are concerns that this experimental approach may overestimate the Kd values in UZ 
transport, as discussed in more detail in Section 3.11.10.2. 
Sorption onto fracture surfaces will retard radionuclide migration. The minerals coating the 
fracture surfaces generally differ from the host-rock mineralogy as a result of different exposure 
to precipitation of hydrothermal or meteoric waters, or alteration of the pre-existing minerals 
(CRWMS M&O 2000, U0100, Section 6.5.3). Laboratory sorption experiments showed that 
trace minerals might be quite effective at retarding 237Np (neptunium) transport when they are 
concentrated on fracture surfaces (CRWMS M&O 2000, U0100, Section 6.5.3). Numerical 
simulations also showed that the limited sorption on the fracture walls is sufficiently important to 
retard transport of strongly sorbing radionuclides [e.g., 239Pu (plutonium)] (CRWMS M&O 
2000, U0060, Section 6.17.1). However, sorption in the fractures is not considered in the TSPA 
transport evaluations because of the limited data and conservative nature of this assumption 
regarding the radionuclide transport to the water table. 
3.11.2.5 Matrix Diffusion 
Matrix diffusion can play an important role in radionuclide exchange between the fractures and 
the rock matrix. Radionuclide diffusion into the rock matrix and away from the fracture surface 
is driven by a concentration gradient, and it will slow the advance of radionuclides by removing 
them from the faster flowing fractures. The significance of matrix diffusion depends mainly on 
factors such as effective contact area between fracture and matrix, the diffusion coefficient of the 
species, and characteristics of fracture networks (CRWMS M&O 2000, U0030, Section 6.2). 
The presence of inactive and relatively dry fractures, accounted for with the active fracture 
model (Section 3.4), could serve as barriers for matrix diffusion.

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The effective diffusion coefficient, which is the product of the molecular diffusion coefficient, 
tortuosity, porosity, and water saturation, is used to account for rock geometry and saturation 
effects on matrix diffusion. Laboratory diffusion studies in porous geologic materials show that 
tortuosity values between about 0.5 and 0.01 are commonly observed (Fetter 1993, p. 44). Very 
limited experimental data exist on the tortuosity distribution in the various Yucca Mountain 
hydrogeologic units. CRWMS M&O (2000, U0060, Section 6.1.2) employed the approach of 
using the porosity value to approximate tortuosity, as suggested from the literature (Farrell et al. 
1994, p. 64; Grathwohl 1998, pp. 2835). Tortuosity measurements on devitrified tuffs showed 
good agreements with this approximation, thereby validating the approach (CRWMS M&O 
2000, U0060, Section 6.1.2). 
3.11.2.6 Radioactive Decay and Daughter Products 
The decay of the radioactive species of interest and their half-lives are completely predictable 
and well documented. The production of daughter products from chain-decay adds complexity 
because transport simulations must compute the total radioactivity distribution, i.e., the sum of 
the concentrations of all the members of the radioactive decay chain. This is especially 
significant if the daughters have long half-lives. Daughter products with short half-lives relative 
to the simulation periods may not need to be considered. 
The daughter products may have significantly different transport behavior than the parent 
radionuclide. Equation (1), for example, shows the 239Pu decay chain. 
239Pu . 235U (uranium) . 231Pa (protactinium) (Eq. 1) 
This equation includes only the most important radioactive chain members and omits daughters 
with short half-lives. The daughter 235U has significantly smaller Kd values compared to its 
parent 239Pu (see Table 3.11-1). 
3.11.2.7 Colloidal Transport 
Colloids are very fine particles such as clay minerals, metal oxides, viruses, bacteria, and organic 
macromolecules that range in size from 1 to 10,000 nm (McCarthy and Zachara 1989, pp. 496 
502). Generation and mobilization of colloids has become an important issue in the facilitated 
transport of radionuclides as intrinsic colloids [e.g., colloidal Pu (IV) and colloidal Pu (V)], or as 
radionuclide-bearing pseudocolloids for 239Pu and 243Am (americium). Colloidal transport 
differs from solute transport because of colloidal particle interactions (e.g., flocculation), pore 
exclusion, and surface reactions (e.g., deposition or attachment). 
There is some field evidence of colloid-facilitated transport of radionuclides. In one case, the 
rapid migration of Pu and Am, attributed to colloidal transport, was found more than 30 m 
downward through unsaturated tuff over the course of approximately 30 years from a low-level 
waste site at Los Alamos National Laboratory (Buddemeier and Hunt 1988, p. 536). In a 
saturated zone study at the Nevada Test Site (NTS), 240Pu/239Pu isotope ratio fingerprints of 
the source of Pu in groundwater showed that it had been transported more than 1.3 km over a 30- 
year period, although Pu is strongly sorbing at the NTS and assumed to be immobile (Kersting et 
al. 1999, pp. 5659). There was a direct finding that Pu was on colloidal material in samples

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taken from the NTS through filtration of the groundwater samples. Note that the Pu observed at 
the NTS originated from an underground nuclear bomb test and that the effects of the 
underground blast on Pu transport are not fully understood. Microspheres are used as a colloidal 
tracer at the saturated C-Wells tests (CRWMS M&O 2000, AMR U0100, Section 6.9) and at the 
Busted Butte transport test in the unsaturated vitric Calico Hills Formation (CRWMS M&O 
2000, AMR U0100, Section 6.8). 
Colloid concentrations have been measured in several groundwater samples from Yucca 
Mountain and from other areas at the Nevada Test Site. The measured particle concentrations 
vary between 1.05  106 and 2.72  1010 particles/mL, with the lowest being for water from well 
J-13 and the highest for water from well U19q on Pahute Mesa (CRWMS M&O 2000, U0070, 
Section 6.2.2.2). These values are consistent with what has been reported in the literature for 
various groundwaters around the world. 
In addition to natural colloids, anthropogenic colloids may be produced from the waste itself or 
from potential repository construction and sealing materials. This was demonstrated in a 
50-month-duration experiment on simulated weathering of a high-level nuclear waste glass, 
where the amounts of Pu and Am released from waste forms were orders of magnitude greater 
than their respective concentrations in the dissolved phase (Bates et. al 1992, pp. 649651). 
Constraints on these types of colloids are treated in the Waste Form Degradation (WFD) PMR 
(CRWMS M&O 2000, WFD PMR, Section 3.8). 
3.11.3 Transport Properties 
This section describes the transport properties used for the abstraction of UZ transport for TSPA 
evaluations, which is discussed in Section 3.11.13. Matrix diffusion and dispersivity values used 
for UZ transport modeling and validation, discussed in Sections 3.11.5-10, are different from 
those used for TSPA abstraction and will be explicitly identified. 
3.11.3.1 Dispersion 
No data are available to determine dispersivity in the UZ over the travel distance between the 
potential repository and the water table. In a transport simulation longitudinal dispersion results 
in earlier arrivals, but generally lower concentrations. Given this behavior, no simple 
conservative bound exists for the longitudinal dispersion. However, a dispersivity value of 20 m 
over the approximately 300 m UZ travel distance (in TSPA calculations) is consistent with the 
dispersivity versus scale correlation of Neuman (1990, pp. 17491758). Furthermore, the 
longitudinal dispersivity (primarily in the vertical direction) is not expected to have a large effect 
on radionuclide transport processes in the UZ because of the strong dispersive effects of fracturematrix 
interactions that are explicitly captured in the Finite Element Heat and Mass Transfer 
(FEHM) particle-tracking calculation (see Section 3.11.13). Transverse dispersion acts only to 
reduce concentrations, with generally little effect on breakthrough time. Therefore, a 
conservative value of zero for transverse dispersivity is used. The base-case distribution for 
longitudinal dispersivity has been selected to be normal, with a mean of 20 m and a standard 
deviation of 5 m, which captures a range of 7.5 m to 32.5 m within the 99 percent probability 
limits. This dispersivity distribution applies to transport in all model units for both the fracture

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and matrix continua, but values for fracture and matrix are sampled independently for TSPA 
calculations. 
3.11.3.2 Sorption Coefficients 
The main experimental program for sorption was carried out using batch sorption experiments. 
Table 3.11-1 gives the sorption distribution coefficients recommended for TSPA (CRWMS 
M&O 2000, U0100, Table 2a). For some radionuclides, specific sorption measurements using 
rock and water samples from Yucca Mountain have not been performed. For these 
radionuclides, sorption behavior has been evaluated on a theoretical basis. 
Three assumptions were made to develop values of Kd for use in performance assessment 
(CRWMS M&O 2000, U0100, Section 5). First, the water compositions from wells J-13 and 
UE-25 p#1 are assumed to provide an adequate range of compositions to capture the influence of 
water compositional variability on sorption in the UZ. Potentially perturbed fluid compositions 
moving as plumes out of the potential drifts are not included in the evaluation of this assumption. 
Second, the effects of mineral variations on sorption in the UZ may be approximated using three 
rock types: devitrified tuff, vitric tuff, and zeolitic tuff. Finally, the effects of temperature are 
bounded by measurements of sorption at ambient temperature. However, the effects of mineral 
alteration because of thermal history are not included in the evaluation of this assumption. 
The use of a linear, infinite-capacity sorption model is important for both describing sorption and 
for modeling the transport of sorbing radionuclides (see Section 3.11.13). Sorption of uranium 
shows nonlinear sorption behavior, in which the sorbed concentration is reduced from that of a 
linear model at higher concentrations (see CRWMS M&O 2000, U0100, Section 6.4.4.1.4.4). 
Linear sorption behavior is expected for the lower concentration levels that will constitute the 
earliest releases. At higher concentrations, nonlinear effects will act to self-sharpen the solute 
fronts (i.e., longitudinal dispersion is decreased). A linear sorption model may still be used for 
predicting radionuclide movements and breakthrough times in general, provided appropriate 
values of Kd are selected that account for the range of Kds represented by the data at different 
solute concentrations. In this case, the range of Kds as a function of concentration is incorporated 
as part of the frequency distribution defining the overall uncertainty in Kd.

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Table 3.11-1. Sorption Coefficient Distributions for UZ Units (Adapted from CRWMS M&O 2000, 
U0100, Table 2a) 
Element Rock type Min Kd (mL g-1) Max Kd (mL g-1) E[x]* COV* Distribution type 
Devitrified 100 2000   Uniform 
Vitric 100 1000 400 0.20 Beta 
Zeolitic 100 1000   Uniform 
Americium (also 
Actinium, 
Samarium, 
Thorium, 
Zirconium) Iron oxide 1000 5000   Uniform 
Plutonium Devitrified 5 70   Uniform 
Vitric 30 200 100 0.25 Beta 
Zeolitic 30 200 100 0.25 Beta 
Iron oxide 1000 5000   Uniform 
Uranium Devitrified 0 2.0 0.5 0.3 Beta 
Vitric 0 1.0 0.5 0.3 Beta 
Zeolitic 0 10.0 4.0 1.0 Beta (exp) 
Iron oxide 100 1000   Uniform 
Neptunium Devitrified 0 1.0 0.3 0.3 Beta 
Vitric 0 1.0 0.3 1.0 Beta (exp) 
Zeolitic 0 3.0 0.5 0.25 Beta 
Iron oxide 500 1000   Uniform 
Radium Devitrified 70 300   Uniform 
Vitric 50 100   Uniform 
Zeolitic 800 2000   Uniform 
Iron oxide 0 500 30 1.0 Beta (exp) 
Cesium Devitrified 10 700   Uniform 
Vitric 10 100   Uniform 
Zeolitic 300 3000   Uniform 
Iron oxide 0 300 30 1.0 Beta (exp) 
Strontium Devitrified 5 30   Uniform 
Vitric 0 20   Uniform 
Zeolitic 200 2000   Uniform 
Iron oxide 0 20 10 0.25 Beta 
Nickel Devitrified 0 200 50 0.33 Beta 
Vitric 0 50 30 0.33 Beta 
Zeolitic 0 200 50 0.33 Beta 
Iron oxide 0 500   Uniform 
Lead Devitrified 100 500   Uniform 
Vitric 100 500   Uniform 
Zeolitic 100 500   Uniform 
Iron oxide 100 1000   Uniform 
Tin Devitrified 20 200   Uniform 
Vitric 20 200   Uniform 
Zeolitic 100 300   Uniform 
Iron oxide 0 5000   Uniform 
Protactinium Devitrified 0 100   Uniform 
Vitric 0 100   Uniform 
Zeolitic 0 100   Uniform 
Iron oxide 500 1000   Uniform 
Selenium Devitrified 0 1 0.1 1.0 Beta (exp) 
Vitric 0 1 0.1 1.0 Beta (exp) 
Zeolitic 0 1 0.2 1.0 Beta (exp) 
Iron oxide 0 200 30 1.0 Beta (exp) 
Carbon Iron oxide 10 100   Uniform 
Chlorine, Technetium, Iodine 0 0    
NOTE: *Coefficient of variation: COV = s[x]/E[x]; E[x] is the expected value of Kd (mL g-1). 
 means this parameter is not applicable.

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3.11.3.3 Matrix Diffusion Coefficients 
The matrix diffusion values for radionuclides are based on measured diffusion coefficients of 
tritium and Tc (technetium) (CRWMS M&O 2000, U0100, Section 6.6.1). The measurements 
(in water-saturated rock) showed that tritium diffused at a rate between 1  10-10 m2/s and 3.5  
10-10 m2/s in several samples of devitrified tuff. For Tc, the matrix diffusion coefficient varied 
between 1  10-11 m2/s and 4.9  10-11 m2/s, which is lower than that of tritium (CRWMS M&O 
2000, U0100, Table 16). The lower diffusion rate is believed to be caused by exclusion from 
some matrix pores caused by the larger ion size and negative charge of the pertechnetate anion 
(TcO4
-
, the predominant aqueous species of Tc). 
A distribution for Tc diffusion coefficients has been assigned to account for variations in rock 
type and water content. Using the measured Tc diffusion coefficients as a rough guide to the 
variability in the diffusion coefficient for different rock types, the overall range is estimated to be 
about a factor of 10. This range is roughly captured by the distribution shown in Table 3.11-2 
for anionic radionuclides. 
Predictions of radionuclide transport for cationic radionuclides (Np, barium, strontium, Am, 
cesium) using the diffusion coefficient for tritium and measured batch sorption coefficients were 
found to be conservative (i.e., faster than) relative to measured diffusion behavior (CRWMS 
M&O 2000, U0100, Section 6.6.1.3). Diffusion coefficient measured for tritium has been 
assigned to cationic radionuclides, and the combination of using a batch-sorption Kd value and 
the tritium diffusion coefficient provides a conservative model. As described above, the 
variations in rock type and water content are expected to result in variations in the diffusion 
coefficient of about one order of magnitude. This range is roughly captured by the distribution 
shown in Table 3.11-2 for cationic radionuclides. 
Table 3.11-2. Summary of Diffusion Coefficient Data (CRWMS M&O 2000, U0100, Section 6.6.3) 
Radionuclide 
Type 
Mean 
(m2/s) 
Standard Deviation 
(m2/s) 
Maximum 
(m2/s) 
Minimum 
(m2/s) 
Distribution 
Type 
Anionic 3.2 x 10-11 1.0 x 10-11 1 x 10-9 0 Beta 
Cationic 1.6 x 10-10 0.5 x 10-10 1 x 10-9 0 Beta 
3.11.3.4 Fracture Aperture and Spacing 
Fracture aperture and spacing affect flow and transport between fractures and matrix. For a 
continuous, parallel fracture pattern, the inverse of the fracture aperture is half the area of contact 
between the fracture and matrix continua per unit volume of fracture pore space. Therefore, the 
larger the aperture, the less the diffusion (in a saturated system). For an unsaturated fracture the 
relevant volume (per unit matrix area) is not the fracture pore volume itself but the volume of 
water. In either case (saturated or unsaturated), specification of the aperture is necessary. 
Fracture spacing also affects the diffusion process because it sets the boundary for the depth of 
penetration from matrix diffusion.

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The fracture apertures are derived from the fracture porosity and fracture-matrix connection area 
(see CRWMS M&O 2000, U0065, Section 6.2.1). Aperture distributions are described using a 
log-normal distribution of apertures for all the model layers beneath the potential repository. 
Apertures are sampled stochastically in the transport calculations for TSPA. The sensitivity of 
transport to fracture spacing is low, so a constant value for each layer is used. 
3.11.3.5 Parameters for Colloid-Facilitated Radionuclide Transport 
The association of radionuclides with colloids is modeled using two end-member 
representations: reversible equilibrium exchange with the aqueous phase and irreversible 
attachment. Radionuclides associated with colloids in either condition (reversible or irreversible) 
may be subject to size exclusion for fracture-matrix exchange. Colloids are excluded from 
moving from a fracture into matrix pores smaller than the colloid diameter. This tends to keep 
colloids (and the associated radionuclides) in the fractures, which leads to more rapid transport 
of the radionuclide. The chance of exclusion of a colloid from the matrix during fracture-matrix 
exchange is computed using a probabilistic method that considers different colloid sizes and pore 
size distribution (CRWMS M&O 2000, U0070, Section 6.1.2). 
The description of reversible, colloid-facilitated radionuclide transport for the particle-tracking 
transport model used in performance assessment is quantified through two parameters (CRWMS 
M&O 2000, U0065, Section 6.1.4). One parameter, Kc, defines the equilibrium partitioning of 
radionuclides between the aqueous phase and colloids. The other parameter, Rc, is a retardation 
factor that captures the details of an equilibrium balance between colloid deposition and 
resuspension. The retardation factor in the colloid model abstraction applies to the transport 
through fractures. The distribution of retardation factors used is derived from C-Wells data for 
saturated-zone colloid transport (CRWMS M&O 2000, U0065, Section 6.2.5). 
3.11.4 Geological Layers below the Potential Repository 
The subsurface at Yucca Mountain consists of heterogeneous layers of anisotropic, fractured 
rocks consisting of alternating layers of welded and nonwelded ash flow and air fall tuffs. A 
more detailed discussion about the UZ geology is presented in Section 3.2; this section focuses 
on the effects of geological layers on transport. 
The potential repository will be located in the TSw. The fractures in the TSw typically have 
permeabilities several orders of magnitude larger than the matrix permeabilities. Unsaturated 
flow in the TSw is primarily through the fractures, because the matrix permeability in many of 
the TSw subunits can support flows of only a few millimeters per year (Bodvarsson et al. 1999, 
p. 13). 
The geological complexity of the underlying CHn results in heterogeneous distributions of 
fracture and matrix hydrological properties. These properties are expected to have pronounced 
effects on flow and transport of radionuclides in the UZ. The permeability of nonwelded tuffs is 
strongly dependent on the degree of alteration of the rock minerals into zeolites. The zeolitic 
alteration in the CHn (a common occurrence in its lower portions) can reduce the matrix 
permeability by orders of magnitude to the welded tuff permeability level (see Section 3.6).

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Flow in the zeolitic portions of the Calico Hills Formation and surrounding bedded tuffs (CH) 
(CHz) (see Table 3.2-2) is dominated by fracture flow (similar to that in the TSw layers), 
although the fracture density is smaller in the CHz than that in TSw layers. In vitric portions of 
the Calico Hills Formation and overlying bedded tuff (CHv), the matrix and fracture 
permeabilities are on the same order. Thus, these layers behave as porous (rather than fractured) 
media, and flow is matrix-dominated, as confirmed from the Busted Butte field test results 
(discussed in more detail in Section 3.11.11.2). Below the potential repository horizon, both 
vitric and/or zeolitic layers are present. The existence of CHv layers below the repository has 
important implications in radionuclide transport because fracture flow originating in the TSw 
will be strongly attenuated, transport velocities significantly reduced, and contact of dissolved 
radionuclides with the rock matrix enhanced (which leads to more retardation for sorbing 
radionuclides). 
Information about the zeolitic alteration of the Prow Pass Tuff and the underlying bedded tuffs 
(PP) is limited. Current understanding is that the model layers pp4 and pp1 are zeolitic and that 
pp3 and pp2 are devitrified and unaltered. Layers of pp4 and pp1, similar to the CHz layers, 
have small matrix permeabilities that are several orders of magnitude smaller than the fracture 
permeabilities (see Section 3.6). Permeability contrast between matrix and fracture in layers of 
pp3 and pp2 is small, similar to the CHv layers. Therefore, fracture flow may be dominant in 
pp4 and pp1 layers, while pp3 and pp2 behave like nonfractured porous media. 
At some locations in the UZ (e.g., near borehole SD-6), Bullfrog Tuff layers may be present 
above the water table. There is limited information about the flow and transport behavior in 
these layers. Current understanding is that the bf3 model layer is devitrified and unaltered while 
the bf2 layer is zeolitic. According to the Calibrated Properties Model in Section 3.6, the 
permeability contrast between matrix and fracture in the bf3 layer is small; the bf3 layer might 
behave like a nonfractured porous medium. The bf2 layer has small matrix permeabilities that 
are several orders of magnitude smaller than the fracture permeabilities, and fracture flow may 
be dominant in the bf2 layer. 
Based on the above discussions, conceptual schematics of flow and transport in two 
representative hydrogeologic sections are shown in Figure 3.11-3 to illustrate the effect of 
geologic layers on radionuclide migration below the potential repository. Borehole UZ-14 is 
located in the northern part of the potential repository site, while borehole SD-6 is located in the 
southern part. As radionuclides leave the potential repository, they could migrate through the 
TSw layers quickly, with limited matrix diffusion and sorption. CHv layers could be very 
effective in retarding migration because of the matrix-dominated flow in these layers. On the 
other hand, radionuclides could pass through CHz and zeolitic layers quickly, owing to the 
fracture-dominated flow. Devitrified layers pp3, pp2, and bf3 could also act as porous media and 
retard radionuclide migration effectively. 
3.11.5 2-D Radionuclide Transport Simulations 
Two vertical cross sections, representative of the geologic and mineralogical variability below 
the potential repository horizon, are used to study radionuclide transport from the potential 
repository to the groundwater of Yucca Mountain. These cross sections are located in the 
vicinity of the SD-6 and UZ-14 boreholes. The purpose of the transport simulations is to

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evaluate the integrated transport performance of the complete geologic system as well as the 
individual important hydrogeologic units (i.e., TSw, CHv, CHz, and PP) beneath the potential 
repository. The simulations account for fracture aperture, fracture frequency, active fracture 
spacing, and saturation distribution (in the fractures and the matrix) across geologic formation 
interfaces. 
3.11.5.1 2-D Semi-Analytical Code FRACL 
FRACL V1.0 (see Table 1.3-1) can analyze transport of reactive solutes and colloids through 
layers of fractured and porous media. The transport equations in the matrix account for 
molecular and surface diffusion, mass transfer between the mobile and immobile water fractions, 
and physical, chemical, or combined sorption following a linear equilibrium, kinetic or 
irreversible isotherm. Radioactive decay, first order chemical reactions, and tracking of up to 
five products of radioactive decay or chemical reactions are also included in the solution. The 
transport equations in the fractures account for the same processes, in addition to advection and 
hydrodynamic dispersion. FRACL V1.0 accounts for the effects of different fracture spacing 
and it can accommodate layers of fractured rocks or a combination of fractured rock and 
nonfractured strata (CRWMS M&O 2000, U0060, Section 6.3.2). 
3.11.5.2 Simulation Approach 
Three representative radionuclides are considered: 99Tc (nonsorbing), 237Np (moderately 
sorbing), and 239Pu (strongly sorbing). The radionuclides are released continuously at the top of 
the domain (which coincides with the location of the potential repository or the individual unit of 
interest), and the contaminant distribution is monitored over time. When occurring, sorption is 
assumed to follow a linear equilibrium isotherm (CRWMS M&O 2000, U0060, Section 6.5.2). 
Percolation rate is 6 mm/year, i.e., close to the mean present-day rate. 
It is assumed that advection occurs only in fractures with the longitudinal dispersivity of 1 m 
(CRWMS M&O 2000, U0060, Table 6.7). The only mechanism of radionuclide transport from 
the fracture to the matrix is by matrix diffusion. In the transition between layers with nonaligned 
fractures and/or different fracture spacing, it is assumed that transport in the fracture continuum 
is continuous. Thus, the results represent the worst-case scenario, yielding the shortest possible 
breakthrough times of radionuclide transport (CRWMS M&O 2000, U0060, Section 6.5.4). 
3.11.5.3 Transport in the Individual Hydrogeologic Unit 
The TSw does not effectively retard radionuclide transport because of the dominance of fracture 
flow that reduces matrix diffusion and sorption (see Section 3.11.4). The breakthrough time for 
the radionuclides is in the order of 99Tc < 237Np < 239Pu, which corresponds to their difference in 
sorptive strength, Kd. In borehole SD-6, for example, breakthrough of the nonsorbing 99Tc at the 
lower boundary of the TSw occurs in about 1 year. Breakthrough of the moderately sorbing 
237Np takes about 35 years, while for 239Pu it occurs at about 300 years (CRWMS M&O 2000, 
U0060, Section 6.6). 
Flow in the CHv is primarily matrix flow, and the unit behaves similarly to a nonfractured 
porous medium. The reduced flow velocity and increased contact time for matrix diffusion and 
sorption make the CHv an effective transport barrier (see Section 3.11.4). The CH in borehole

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SD-6 consists of five vitric layers (i.e., ch1v, ch2v, ch3v, ch4v, and ch5v) and one zeolitic layer 
(ch6z) at the bottom. The 99Tc front reaches the bottom of the ch5v in a few hundred years, 
while the 237Np takes several thousand years. Advancement of 239Pu is limited to the uppermost 
ch1v layer because of its strong sorptive tendency (CRWMS M&O 2000, U0060, Section 6.7). 
Flow in the CHz is dominated by the fractures, and radionuclide transport through the unit is 
expected to be rapid, similar to that in TSw (see Section 3.11.4). The CH in borehole UZ-14 
consists of six zeolitic layers (i.e., ch1z, ch2z, ch3z, ch4z, ch5z, and ch6z). The simulation 
results are consistent with the expected transport behavior. Both 99Tc and 237Np reach the bottom 
boundary in less than 10 years. Note that the value of Kd for 237Np is 4 mL/g in the zeolitic tuffs 
as compared to 1 mL/g in the vitrified tuffs. The larger Kd value does not lead to more 
retardation in the CHz than the CHv, since the contact time for 237Np with the tuffs is much 
shorter in the CHz because fracture flow is dominant. The strongly sorbing 239Pu needs several 
thousands years to cover this distance (CRWMS M&O 2000, U0060, Section 6.7). 
Within the PP, fracture flow may be dominant in pp4 and pp1 layers, while pp3 and pp2 layers 
behave like nonfractured porous media (Section 3.11.4). The top pp4 layer near SD-6 is breached 
in a short time, and then radionuclide transport is controlled by layers pp3 and pp2. These layers 
are quite efficient in retarding transport even for the nonsorbing 99Tc, which takes more than 
1,000 years. It takes several thousand years for 237Np to reach the pp1 layer. The 239Pu front 
does not cross the pp3 even after 105 years (CRWMS M&O 2000, U0060, Section 6.8). 
3.11.5.4 Transport Simulations below the Potential Repository 
Migration of radionuclides in borehole SD-6 is slow because of the presence of the CHv (see 
discussions in Section 3.11.4). The 99Tc front takes several thousand years to reach the water 
table. The 237Np breakthrough takes longer than 104 (but <105) years to reach the water table 
because of the moderate sorption (shown in Figure 3.11-4, where the right-side of the X-axis 
coincides with the location of water table). The strongly sorbing 239Pu does not advance past the 
ch1v layer, less than 60 m from the point of release, even after 105 years (CRWMS M&O 2000, 
U0060, Section 6.9.2). 
The 99Tc transport in borehole UZ-14 shows a drastically different profile from that of SD-6. 
The extensive zeolitic zones of the CH at this location, where fracture flow is dominant, result in 
very rapid transport with a significant amount of 99Tc reaching the water table in less than 103 
years. Similarly, the 237Np breakthrough at the water table takes substantially less than 104 years. 
Figure 3.11-4 compares the effects of the CHv and CHz on transport. The large portions of nearconstant 
concentrations indicate the substantial impact of fracture-flow dominated CHz layers on 
transport (Figure 3.11-4). Even the strongly sorbing 239Pu shows drastically enhanced migration 
by reaching a distance of about 255 m from the release point, yet it has not migrated past the pp3 
layer after 105 years (CRWMS M&O 2000, U0060, Section 6.9.6). 
3.11.6 3-D Site-Scale Radionuclide Transport 
Modeling of radionuclide transport using large-scale 3-D grids was documented by CRWMS 
M&O (2000, U0060, Sections 6.10 to 6.14). The release rate of radionuclides at the potential 
repository was considered constant over time. Radionuclides of 99Tc, 237Np, and 239Pu were

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investigated, as well as the important members in the decay chains of 237Np and 239Pu. The grids 
and flow fields used for present-day infiltration and perched water model #1 were identical to 
those discussed by CRWMS M&O (2000, U0065, Section 6.2). The longitudinal dispersivity 
used was 1 m in the fractures and 0.1 m in the matrix as there is advective-dispersive transport 
through the matrix block (CRWMS M&O 2000, U0060, Table 6.14). 
3.11.6.1 EOS9nT Code 
EOS9nT V1.0 (see Section 1.3.2) is a TOUGH2 (V1.11) module for the simulation of an 
arbitrary number of solutes and/or colloids in the subsurface. The tracer transport equations 
account for advection, hydrodynamic dispersion, molecular diffusion, mass transfer between the 
mobile and immobile water fractions, sorption, radioactive decay, filtration (for colloids only), 
first-order chemical reactions, and colloid-facilitated transport. EOS9nT V1.0 considers 
equilibrium (linear, Freundlich, or Langmuir) sorption and kinetic sorption (linear, Freundlich, or 
Langmuir). Daughter products of radioactive decay can also be tracked. 
EOS9nT V1.0 offers the option of a Laplace space formulation of the transport equations (in 
addition to conventional time-stepping) after the flow field becomes time-invariant. The Laplace 
transform formulation eliminates the need for time discretization, and an unlimited time-step size 
is thus possible without loss of accuracy or stability. It also completely linearalizes all the 
kinetic transport equations and, thus, does not increase the order of the matrix to be solved. 
Additionally, the Laplace transform alleviates accuracy problems that may arise from the 
inaccurate weighting of the radioactive decay (CRWMS M&O 2000, U0060, Section 6.3.1). All 
the 3-D transport simulations are conducted by using the DeHoog implementation of the Laplace 
transform formulation of EOS9nT V1.0. Simulations are very fast and efficient, requiring 
1,800-2,200 seconds of execution time to cover a simulation period of 106 years (CRWMS 
M&O 2000, U0060, Section 6.11.5). 
3.11.6.2 Transport Simulation of 99Tc 
Breakthrough is described by the normalized release rate R, i.e., the ratio of radionuclide mass 
release rates at the groundwater versus that at the potential repository. The normalized release 
rate in Figure 3.11-5 shows a very strong dependence of 99Tc transport on the infiltration regime. 
As the infiltration rate increases from lower bound to mean present-day level, the t10 time, 
defined as the time at which R = 0.1, decreases from about 104 years to about 300 years. The t50, 
the time at which R = 0.5, decreases from about 45,000 years to about 4,000 years. Upper bound 
infiltration rate further reduces t10 (see Table 3.11-3). Figure 3.11-5 also shows that the 
maximum attainable R decreases with the infiltration rate, because lower bound infiltration 
results in lower velocities and longer times for transport, thus higher radioactive decay. 
3.11.6.3 Transport Simulations of 237Np and its Daughters 
The sorption of 237Np retards its transport through the UZ system, as compared to 99Tc (Figure 
3.11-5). From the values of t10 and t50, the moderate sorption of 237Np is sufficient to increase the 
time to reach the water table by a factor of about 40 (Table 3.11-3). Because of significant 
retardation, the maximum attainable R varies over a large range, and R = 1.0 is not achieved

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within the simulation period. At t = 106 years, R is 0.98, 0.86, and 0.42 for the three infiltration 
rates, respectively (Figure 3.11-5). 
Table 3.11-3. Breakthrough Time of Radionuclides at the Water Table (Years) (CRWMS M&O 2000, 
U0060, Table 6.15) 
Present-Day Infiltration 
Lower Bound Mean Upper Bound 
t10 10,000 300 45 99Tc 
t50 45,000 4,000 1,000 
t10 220,000 10,000 1,700 237Np 
t50 >1,000,000 120,000 22,000 
t10 600,000 40,000 12,000 239Pu 
+ 
235U 
+ 
231Pa 
t50 >1,000,000 250,000 90,000 
Important members in the 237Np decay chain are shown in Equation 2. The relative flux fraction 
MR of each member of the chain, defined as the fraction of each radionuclide in the sum of the 
mass fluxes at the water table, shows that the daughter contribution only reaches a maximum of 
2% at 106 years (CRWMS M&O 2000, U0060, Section 6.13.1.2). As such, daughter 
contributions to the 237Np transport are rather insignificant and could be safely ignored. 
237Np . 233U . 229U (Eq. 2) 
3.11.6.4 Transport Simulations of 239Pu and its Daughters 
The value of R for 239Pu never reaches the 0.1 level even after 106 years of continuous release 
because of the strong sorption of 239Pu (Figure 3.11-5). The picture changes dramatically, 
however, if the daughter contributions to the release rate at the water table are accounted for in 
the computations. Given the half-life of 239Pu and the much longer one of 235U, the daughter 
contributions can become significant under the upper bound infiltration regime (Table 3.11-3). 
The relative flux fractions MR are also shown in Figure 3.11-5. The Pu contribution to the 
release rate starts declining rapidly after 100 years, and 235U is by far the dominant species after 
t = 20,000 years. Earlier emergence of 235U is associated with the lower bound infiltration rates 
because less 239Pu reaches the water table owing to strong sorption. Thus, after 1,000 years, the 
release at the water table consists mostly (over 95%) of 235U under lower bound present-day 
infiltration conditions. The 231Pa contribution is negligible because of the very long half-life of 
235U.

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3.11.6.5 Transport-Controlling Features 
The simulation results reveal that transport is controlled by the faults, especially at the early 
times. Splay G of the Solitario Canyon fault is the main transport-facilitating feature, as shown 
from the 99Tc distribution of the fracture mass fraction (normalized to that at the point of release 
in the potential repository) at the bottom of the TSw at t = 100 years (Figure 3.11-6). Once 
contaminants reach the TSw-CHn interface, they move in an easterly direction, moving with the 
draining water that hugs the downward sloping low-permeability interface (CRWMS M&O 
2000, U0060, Section 6.12). 
The Ghost Dance fault splay is the next most important transport-facilitating feature (Figure 
3.11-6). Though it facilitates downward migration, this fault appears to act as a barrier to the 
lateral migration of radionuclides, as evidenced both at the bottom of the TSw and at the water 
table. The Sundance fault and the Drill Hole Wash fault are also important. The Drill Hole 
Wash fault appears to act as a barrier to radionuclide migration laterally across it, while 
providing pathways for relatively fast transport to the water table (Figure 3.11-6). The main 
Ghost Dance fault does not play an important role in transport at the bottom of the TSw, as the 
99Tc does not reach the fault at this level even after 105 years (CRWMS M&O 2000, U0060, 
Section 6.12.2.2). This fault is more important at the water table, where it acts as a barrier to 
lateral transport while facilitating downward migration into the groundwater (Figure 3.11-6). 
As time progresses, contributions of fractures and matrix become important. Fractures act as the 
important pathways of transport, and diffusion from the fractures into the matrix is the main 
retardation process in radionuclide transport. By sorbing onto the matrix into which they diffuse, 
the migration of radionuclides is retarded (CRWMS M&O 2000, U0060, Section 7.2). 
The emerging transport pattern indicates that radionuclide transport to the groundwater is faster 
in the southern part of the potential repository block, where it is also areally concentrated. There 
are several reasons for this transport pattern (CRWMS M&O 2000, U0060, Section 6.12.2.3). 
First, the water flow pattern dictates the advective transport pattern, and the maximum water 
flow within the footprint of the potential repository is in its southern part in the Perched water 
model #1 (see Section 3.7.3.3). Second, the presence of the highly conductive faults (e.g., Splay 
G of the Solitario Canyon fault and the Ghost Dance fault splay) act as the venue for fast 
transport, despite the fact that the vitric CHn behaves as a porous medium (with relatively lower 
water velocities). This may be facilitated by flow focusing in the vitric CHn, whose vertical 
distribution shows a funnel-type structure in the south. Third, the low-permeability zones at the 
TSw-CHn interface in the northern part of the potential repository act as barriers to water 
drainage, and lead to low water velocities and presence of perched water bodies. Radionuclides 
move slowly through the perched water before reaching the underlying conductive zeolitic CHn, 
hence the delay in transport. 
3.11.7 3-D Site-Scale Transport of Pu True Colloids 
EOS9nT V1.0 is used for colloidal transport simulations, and the flow field and 3-D grid are 
identical to the ones discussed in Section 3.11.6.

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3.11.7.1 Colloidal Forms, Properties, and Filtration Model 
As concluded in CRWMS M&O 2000 (U0070, Section 7), the waste-form colloids (i.e., true 
colloids) will play a more significant role than natural colloids. True colloids are taken to have 
the properties of PuO2 and are subject to radioactive decay. Four colloids of different sizes (450 
nm, 200 nm, 100 nm, and 6 nm) are considered, with their accessibility factors into the 
geological units taken from CRWMS M&O (2000, U0070, Table 1). As reported by CRWMS 
M&O (2000, U0060, Section 6.16), the linear kinetic model of colloid filtration was used, with 
the forward kinetic coefficient, .+, directly computed. There is no information on the kinetic 
declogging (reverse) coefficient, .-, which was entered as a fraction of .+ to examine the 
sensitivity of this parameter on colloidal transport. 
3.11.7.2 Colloid Transport Simulations 
For a given .+, the transport of radioactive true colloids is strongly influenced by the .-. When 
no declogging is allowed, no colloids reach the groundwater (CRWMS M&O 2000, U0060, 
Section 6.16). Smaller values of .- (i.e., slow declogging) lead to significant retardation of 
colloids and longer times to reach the water table. In this case, t10 is more than 104 years, and t50 
cannot be reached because the maximum attainable R at the water table never exceeds 0.3 
(Figure 3.11-7). Larger values of .- (i.e., fast declogging) lead to dramatically different 
behavior, with very fast transport for the radioactive colloids to the water table. In this case, t10 
can be as low as 15 years (Figure 3.11-7). The extreme sensitivity of colloid filtration on .- and 
the dearth of any representative information on this value in the various UZ geologic units 
underline the need for attention to this subject. 
For a given .-, the colloid size has a significant effect on transport (Figure 3.11-7). Given the fact 
that fractures are the main transport conduit at Yucca Mountain, the inability of larger colloids to 
diffuse into the matrix, because of smaller diffusion coefficient values and size exclusion, result 
in fast transport to the groundwater. Smaller colloidal particles can diffuse more easily into the 
matrix, and their transport is thus more retarded. Size exclusion at the interfaces of different 
geologic units leads to colloid concentrations that can be significantly higher than that in the 
water released from the potential repository. These high concentrations are observed behind (i.e., 
they do not penetrate) the straining interfaces and are due to colloid accumulation because of 
their inability to move across these interfaces. This phenomenon is more pronounced for larger 
colloids (CRWMS M&O 2000, U0060, Section 6.16). 
3.11.8 Estimates of Mass Breakthrough 
This section summarizes the studies of tracer (conservative and reactive) transport using more 
than 20 3-D UZ flow fields and the T2R3D code V1.4 (see Section 1.3.2). The results provide 
insight to flow and transport processes from the repository to the water table (saturated zone) or 
from the land surface to the repository level and consider the potential effects of the major faults, 
different perched water conceptual models, infiltration scenarios, and sorption onto rocks. 
Estimates of breakthrough are based on calculations of a conservative (nonsorbing) tracer, using 
the properties of 99Tc and chloride-36 (36Cl), and a reactive (adsorbing) tracer, using the 
properties of 237Np (CRWMS M&O 2000, U0050, Section 6.7). Except for 36Cl, the mechanical

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dispersion effects through the fracture-matrix system are ignored, because sensitivity analyses 
show little effects of mechanical dispersion on cumulative tracer breakthrough curves at the 
water table. All transport simulations are run to 1 million years under steady-state flow and an 
initial, constant source concentration or constant mass flux conditions at the repository or surface 
fracture blocks. This assumes that all of the tracer is released instantaneously from the starting 
time of a simulation at the repository or land surface, while the radionuclides and/or colloids are 
released continuously at the potential repository for transport simulations discussed in Sections 
3.11.6 and 3.11.7. 
The fractional mass breakthrough is shown in Figures 3.11-8 and 3.11-9 and is defined as the 
cumulative mass of a tracer arrived at the water table or at the repository level over the entire 
bottom model boundary or the entire repository layer at the time, normalized by the total initial 
mass of the component at the source. Fifty percent mass breakthrough times for transport from 
the respository to the water table, estimated using 36 simulations are summarized in 
Figure 3.11-8. The figure correlates average infiltration rates with 50% cumulative massbreakthrough, 
including all the infiltration scenarios and two perched water conceptual models 
discussed in Section 3.7. As shown in Figure 3.11-8, the predominant factors are (1) infiltration 
rates or net water recharge and (2) adsorption effects. In addition, perched water conceptual 
models also affect transport. However, the overall impact of the perched water conceptual 
models on tracer breakthrough at the water table is insignificant compared to infiltration and 
adsorption effects. 
Analyses of mass breakthrough estimates at the water table indicate that: 
 Times for 50% mass breakthrough are inversely proportional to the average infiltration 
(net water recharge) rate over the model domain. When an average infiltration rate 
increases from 5 to 35 mm/yr, the time for 50% mass breakthrough decreases by one to 
two orders of magnitude. 
 Nonsorbing tracers migrate about one to two orders of magnitude faster than sorbing 
tracer when travelling from the repository to the water table under the same infiltration 
condition. 
The transport of 36Cl from the ground surface to the potential repository is also estimated using a 
fractional breakthrough curve, as shown in Figure 3.11-9, under the present-day, mean 
infiltration scenario. The figure shows a similar range of tracer transport times from the 
simulations with different surface source conditions (CRWMS M&O 2000, U0050, Section 6.7). 
Simulations 3 and 4 apply the 36Cl source over the entire upper boundary while simulations 1 and 
2 apply the source over the central area only to avoid lateral boundary effects. Simulations 1 and 
3 apply all the 36Cl at time = 0 while simulations 2 and 4 apply it as a constant mass fraction of 
the infiltrating water. There is about 1% or less total mass breakthrough during 10 to 100 years 
after tracer release on the ground. This indicates the existence of possible fast flow pathways 
with a transport time of 50 years, travelling from the ground surface to the repository level, under 
the steady-state UZ flow condition. However, the cumulative mass breakthrough is small (~1% 
of the total mass released on the ground) for the early breakthrough at 50 years. The average 
transport time from the surface to the repository level is estimated between 5,000 to 20,000 years 
using the 50% mass breakthrough curves of Figure 3.11-9 from the four simulation results.

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Simulated tracer concentration distributions along vertical cross sections, and the ESF and ECRB 
tunnels show that earlier breakthrough of the tracer at the repository level is associated only with 
high-permeability faults. 
3.11.9 Alternative Models 
As discussed above in Sections 3.11.6 and 3.11.7, the main mechanism of radionuclide 
retardation in the UZ is diffusion from the fractures into the matrix. This process transfers 
radionuclides from the fast pathways to the matrix, where their transport is retarded because of 
the much slower water velocities and matrix sorption for sorbing radionuclides. An alternative 
conceptual model that does not allow diffusion (but still allows advection) into the matrix was 
investigated by CRWMS M&O 2000 (U0060, Section 6.17); the results of the investigation are 
discussed below. 
3.11.9.1 Effects of Matrix Diffusion on Radionuclide Transport 
For the no-diffusion alternative model using mean present-day infiltration, the nonsorbing 99Tc 
and the moderately sorbing 237Np move unhindered in the fractures, with their t10 and t50 about 5 
and 30 years, respectively. A characteristic plateau at t = 50 years marks their arrival at the 
water table from fracture flow (Figure 3.11-10). The effects of the matrix flow become evident 
for t > 100 years, when matrix flow and contaminant transport begin to arrive at the water table. 
The nonsorbing 99Tc arrives at the water table earlier than the moderately sorbing 237Np. The 
phase of 237Np release from fracture flow lasts from 50 to about 2,000 years, after which time the 
matrix flow (and the 237Np it transports) arrives at the water table (Figure 3.11-10). 
The limited sorption on the fracture walls is, however, sufficiently important to retard transport 
of strongly sorbing 239Pu in the fractures (CRWMS M&O 2000, U0060, Section 6.17). If only 
239Pu is considered, the fracture release rate reaches a plateau at about 300 years, i.e., a very short 
time considering its half-life. There is no matrix flow contribution to the groundwater release of 
239Pu in the first 106 years. Accounting for the daughter products leads to matrix contributions to 
the water table after 104 years. These result (almost) exclusively from the release of the 235U 
daughter, which sorbs less strongly than 239Pu (Figure 3.11-10). 
3.11.9.2 Colloidal Transport Simulation 
Analysis of the alternative model indicates that diffusion is less significant in colloid transport 
than in solute transport, because (a) colloid diffusion is smaller than solute molecular diffusion 
because of the larger colloid size, and (b) size-exclusion effects at the interfaces of different 
geologic units further limit entry through diffusion into the matrix (especially for larger colloids) 
(CRWMS M&O 2000, U0060, Section 6.17). Its effect, however, becomes increasingly 
important for a decreasing colloid size (Figure 3.11-10). 
The colloid breakthrough curves do not exhibit the plateaus (denoting pure fracture transport 
with no matrix contribution) of the solute curves, but rather a section of milder slope (Figure 
3.11-10). This is attributed to the slower transport in the fractures (as a result of straining at the 
geologic unit interfaces) and the resulting evolution of concentrations larger than the one in the 
water released from the potential repository. Hence, the colloid concentration gradients across

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straining interfaces keep increasing over time (because of colloid accumulation behind them), 
and they do not reach a steady state as in solutes (CRWMS M&O 2000, U0060, Section 6.17.2). 
3.11.10 Uncertainty and Limitations 
This section discusses the uncertainties and limitations related to radionuclide transport analysis 
in the UZ. 
3.11.10.1 Assumptions 
The soundness of radionuclide transport analysis depends upon the validity of the assumptions 
discussed in Section 3.11.1.3. 
3.11.10.2 Sorption 
Experimentally determined Kd values in Yucca Mountain studies have been predominantly 
derived from batch experiments using crushed tuff (with the sample size of 75500 m) under 
saturated conditions. There are concerns that this experimental approach may overestimate the 
Kd values (CRWMS M&O 2000, U0060, Section 6.1.3.1). This is because: 
1. Batch experiment conditions may not be representative of the unsaturated 
conditions in the UZ. Little work has been reported for radionuclide sorption and 
transport in unsaturated rocks. Values of Kd may be invariant with respect to the 
water content, if similar experimental conditions (e.g., sample size, water 
chemistry, contact time) are employed. Experimental measurement of 
radionuclide sorption in unsaturated tuffs, however, deserves more attention. 
Laboratory studies of tracer penetration were presented to generate Kd values for 
core-sized samples under unsaturated conditions (CRWMS M&O 2000, U0015, 
Section 6.4). This approach could be adopted to generate Kd values of 
radionuclides in unsaturated solid tuff samples. 
2. Crushing of tuff may create new surfaces and also increase the accessibility of 
pores that may not be contributing to radionuclide sorption in the intact rocks. 
Using smaller-sized samples could likely generate larger Kd values. Some studies 
have compared the Kd values obtained from batch sorption with diffusion-sorption 
experiments that use multimillimeter scale samples. The results consistently 
show little agreement between Kd values from these two methods, which could be 
largely attributable to the difference in sample sizes used (CRWMS M&O 2000, 
U0060, Section 6.1.3.1). Removal of fines (particle sizes less than 75 .m) is a 
routine step used in the standard batch-sorption procedures of the YMP; however, 
this could serve as a compensating factor for this issue. 
Rate-limited sorption could be important, especially for fluid-radionuclide-rock systems with 
large sorption potential. Breakthrough curves for 237Np transport in tuffs from the column 
experiments cannot be analyzed without considering rate-limited sorption (Viswanathan et al. 
1998, p. 267). This result indicates the existence of rate-limited sorption under flowing 
conditions, possibly resulting from the slow diffusion of radionuclides into tuff pores. Ratelimited 
sorption may have a substantial effect on transport in fast fracture flow because it reduces

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the extent of sorption in the matrix, thus allowing larger radionuclide concentrations and longer 
migration in the fractures. Nonlinear and irreversible sorption are also evident from the diffusion 
and transport studies by CRWMS M&O (2000 U0100, Sections 6.5 and 6.6). Overall, ratelimited 
and nonlinear sorption can insert an element of uncertainty into the validity of the linear 
equilibrium isotherm assumed in UZ transport studies. 
There is limited information on sorption onto the fracture surfaces, which will retard migration 
of sorbing radionuclides. However, sorption in the fractures is not considered in the TSPA 
transport evaluations because of the limited data and conservative nature of this assumption. 
3.11.10.3 Matrix Diffusion 
Very limited experimental data exist on the tortuosity distribution in the various Yucca Mountain 
geologic units. In CRWMS M&O (2000, U0060), tortuosity is approximated by the value of 
porosity, an approach validated by the available, yet limited, experimental data 
(Section 3.11.2.5). Even less information exists on the effect of water content on effective 
diffusion coefficient, and the dependence could be much stronger than what could be expected 
from a linear relationship. This subject deserves more attention, because it could significantly 
affect transport estimates. 
No information exists on whether the UZ media support surface diffusion (a possibility in 
zeolites). Surface diffusion can be important in radionuclides that exhibit strong sorption (e.g., 
Pu). A larger Kd clearly indicates stronger sorption, but this does not mean immobilization of the 
dissolved species when the fractured porous medium supports surface diffusion (Moridis 1999, 
pp. 17291740). 
Different approaches to represent matrix diffusion could yield different transport behavior. 
Comparisons between FEHM V2.10 (see Section 1.3.2) particle-tracker and DCPT (see 
Section 1.3.2) were performed by CRWMS M&O (2000, U0155, Section 6.4.3). The two 
particle-tracking routines agree only if diffusion and dispersion are neglected. For the cases that 
include diffusion and dispersion, the median breakthrough for FEHM V2.10 occurs at times 
more than one or two orders of magnitude earlier. The difference is more pronounced for 
radionuclides undergoing sorption in the matrix. These differences stem from different 
implementations of the diffusive mass flow between fractures and the matrix in the two codes 
(CRWMS M&O, 2000, U0155, Section 7). 
3.11.10.4 Radioactive Decay and Daughter Products 
The . factor defines the fraction of the mass of the decayed sorbed parent that remains sorbed as 
a daughter (0 = . = 1). The term . is introduced to account for the different sorption behavior of 
parents and daughters, and the fact that daughters can be ejected from grain surfaces because of 
recoil (CRWMS M&O 2000, U0060, Section 6.2.8.1). The . factor is a function of the decay 
type as well as of the chemical form of the sorbed cation. In alpha decay (e.g., 237Np, 239Pu), 
. = 0 (CRWMS M&O 2000, U0060, Section 6.2.8.2). There is no information on the behavior 
of . for other types of decay. This issue can have significant implications for the transport 
behavior of daughters if (a) the large sorbed masses of strongly sorbing parents are ejected back

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into the aqueous phase after decay, (b) the daughter is a much weaker sorber, or (c) its sorption 
follows a kinetic isotherm (CRWMS M&O 2000, U0060, Section 6.2.8.2). 
3.11.10.5 Radionuclide Transport Simulations 
The importance of faults and perched water bodies in transport depends directly upon the 
underlying geologic and perched water conceptual models. In the simulations discussed in 
Section 3.11.6, the geological model discussed in Section 3.2 and implemented in Section 3.4.2 
and Perched water model #1 (see Section 3.7.3.3) were assumed. Changing geologic and 
perched water models may very well lead to different results (CRWMS M&O 2000, U0060, 
Section 6.11). 
3.11.10.6 Colloidal Transport 
Caution should be exercised in the interpretation of the colloid simulation results of Figure 3.11- 
7 because substantial knowledge gaps exist. The tremendous variation in behavior with the 
change in the kinetic declogging coefficient should only serve as an indication of the sensitivity 
of this parameter and to underline the need for more reliable information on this subject. The 
limits of the equations for the prediction of the forward kinetic filtration (clogging coefficient) 
have not been tested under the UZ conditions, and the subject of kinetic declogging coefficient 
has barely been raised (let alone studied). Additionally, it is unclear how representative the 
current size exclusion models are, because they are not based on laboratory measurements of 
filtered colloid suspension through rock samples but rather on predicted values obtained from 
retention curves and theoretical soil physics equations. The affinity of colloids for air-water 
interfaces could also have a potential effect on their transport (CRWMS M&O 2000, U0060, 
Section 6.15.8). The TSPA model only uses simple size exclusion filtering at fracture-matrix 
interfaces (Section 3.11.3.5). 
3.11.11 Model Validation 
This subsection discusses the validation of the Transport Model utilizing the results from Alcove 
1 and Busted Butte tracer tests, and it shows that the model can be considered valid for its 
intended use. 
3.11.11.1 Alcove Tracer Test 
This section is based on Section 6.8.1 of CRWMS M&O (2000, U0050), which includes more 
detailed discussions and references for data sources. An infiltration and tracer transport test was 
performed in Alcove 1, located near the North Portal of the ESF in the upper lithophysal zone of 
the Tiva Canyon Tuff (Tpcpul). The crown of Alcove 1 is approximately 30 m below the ground 
surface. The infiltration test at Alcove 1 involved applying water at the ground surface. At a late 
stage of the test, a conservative tracer, bromide, was introduced into the infiltrating water. The 
seepage into the alcove and the tracer arrival time were recorded. The tracer test was carried out 
over a 51-day period, beginning on May 18, 1999. First detection of the tracer within the 
seepage occurred after 28 days. 
Hydrological properties calibrated to earlier seepage data were used in the tracer simulation. The 
simulated breakthrough curve closely matches the tracer concentration data for a tortuosity value

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of 0.75, which is close to the value of 0.7 given by Francis (1997, p. 5). This relatively high 
tortuosity value (see Section 3.11.2.5) is possibly related to the nearly saturated conditions in the 
test. The results indicate that the continuum approach is valid for modeling flow and transport in 
unsaturated fractured rock. The use of an active fracture model can capture the major features of 
fingering flow and transport in fractures. The matrix diffusion has a significant effect on the 
overall transport behavior in unsaturated fractured rock, while the dispersion in fractures does 
not. 
3.11.11.2 Busted Butte Tracer Test 
3.11.11.2.1 Laboratory Kd Measurements 
The Busted Butte test facility was chosen based on the presence of a readily accessible exposure 
of the TSw and CHn and the similarity of these units at this location to their occurrence beneath 
the potential repository horizon (CRWMS M&O 2000, U0100, Section 6.8.1). Table 3.11-4 
presents the Kd results obtained on rock samples collected from the TSw and CHn at Busted 
Butte. Values of Kd for Np and Am in Table 3.11-4 are similar to these in Table 3.11-1. 
However, the sorption values for Pu are significantly larger. 
Table 3.11-4. Summary of Radionuclide Sorption Results from Busted Butte Tests (adapted from 
CRWMS M&O 2000, U0100, Tables 27-28) 
Approximate Average Kd (mL g-1) 
Sample Source 
Geologic Unit 
(Model Layer) 
Np Am Pu 
Phase 1A, BH 3 Tptpv1 (ch1v) 0.3 380 19 
Phase 1A, BH 4 Tac (ch2v) 1.4 470 2500 
Phase 1B, BH 7 Tptpv2 (tsw39) 1.1 460 1100 
3.11.11.2.2 Field Tracer Tests 
The Busted Butte Unsaturated Zone Transport Test is a long-term experiment conducted by the 
YMP. Numerical simulations were conducted for two components of the first phase (Phases 1A 
and 1B) by CRWMS M&O (2000, U0060, Section 6.10). The field work of the first phase has 
been completed, but the analysis of the experimental results is not yet complete. 
3.11.11.2.2.1 Phase 1A Test 
The location of Phase 1A test was the vitric CHn (i.e., layers ch1v and ch2v; CRWMS M&O 
2000, U0060, Figure VI.1). It involved injection rates of 10 mL/hr into boreholes 1 and 3, with 
borehole 3 located above and near the ch1v-ch2v interface and borehole 1 farther away from the 
interface. Injections were conducted continuously for 285 days, starting from April 2, 1998. At 
the end of the test, digital photographs were taken to evaluate tracer distribution, and rock 
samples were collected for moisture and tracer analysis. A 3-D modeling study, using the 
Calibrated Properties Model (Section 3.6) and hydraulic property measurements from fieldcollected 
samples, was conducted to predict the concentration of a nonreactive tracer and water 
saturation distributions (CRWMS M&O 2000, U0060, Section 6.10).

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The simulated Br distribution in borehole 1 exhibits symmetric, near-circular patterns, and 
indicates the dominance of capillary over gravitational forces in the vitric CHn. This is 
consistent with the experimental results and the expected flow and transport behavior in the vitric 
CHv discussed in Section 3.11.4. Borehole 3 simulations using the Calibrated Properties Model 
show that the flattening of tracer distribution occurs as the tracer moves preferentially laterally 
along the ch1v-ch2v interface. Experimental results also show the flattening behavior for 
borehole 3. When the hydraulic property measurements from field-collected samples are used, 
the Br distribution follows a more uniform pattern, which exhibits little flattening. This indicates 
that the permeability contrast from the limited number of core measurements is smaller than that 
suggested from the Calibrated Properties Model. 
3.11.11.2.2.2 Phase 1B Test 
In the Phase 1B field test, the tracers were injected into the lower portion of the TSw basal 
vitrophyre, which is a relatively low-permeability fractured rock. The tracer solution was 
injected at a rate of 10 mL/hr at the location x = 1.30 m from the rock surface into borehole 5. 
Injections began on May 12, 1998, and ceased on November 9, 1998. Liquid samples from 
collection borehole 6 were regularly collected and analyzed. For the 3-D numerical studies, the 
geologic model treated the domain as a homogeneous, unfractured rock matrix. Although this 
geologic layer is known to have fractures, the use of unfractured rock matrix as the domain 
model in the simulation was made possible by the system behavior during the injections, which 
did not show evidence of fracture flow. 
Experimental breakthrough data for both the nonsorbing and sorbing tracers can be found in 
CRWMS M&O (2000, U0100, Section 6.8.5.3.2). Peak concentrations are observed directly 
beneath the injection point of borehole 5. The measured concentrations indicate transport 
consistent with flow in the matrix (rather than in the fractures), which appears to quickly imbibe 
the injected solution. 
Visual inspection of the predicted breakthrough curves for nonsorbing tracer at several sampling 
locations indicates that the predictions are in good agreement with the measured data (CRWMS 
M&O 2000, U0060, Section 6.10). The breakthrough curves of sorbing tracer Li+ (lithium) 
follow a distinctively different pattern. Sorption of Li+ results in maximum relative 
concentrations significantly lower than the ones observed in the nonsorbing tracers. Predictions 
based on the laboratory-derived Kd = 1 mL/g are higher than the measured concentrations in 
CRWMS M&O (2000, U0100, Section 6.8.5.3.2). When Kd is increased to 2 mL/g, predictions 
are consistent with the measured Li+ concentrations (CRWMS M&O 2000, U0060, Section 
6.10). 
3.11.12 Analogs to Radionuclide Transport in the UZ 
This section is based on Section 6.5.2.1 of CRWMS M&O (2000, U0135), which includes more 
detailed discussions and references for data sources. Three UZ analogs are considered: (1) the 
Nopal I uranium deposit at Pea Blanca, Chihuahua, Mexico, (2) the collective northwestern 
Nevada-Southeastern Oregon uranium deposits, and (3) the trace metal migration study at 
Santorini, Greece.

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3.11.12.1 Natural Analog Studies at Pea Blanca, Mexico 
From the 1980s, the Nopal I uranium deposit at Pea Blanca has been recognized as a natural 
analog for the potential repository at Yucca Mountain. Transport of U-series nuclides at Pea 
Blanca has occurred over a range of time scales. From the U-Th (thorium) age data, it appears 
that the primary transport of U to the fractures occurred more than 300 ka (thousand years) ago. 
Subsequently, there has not been significant 238U or 235U redistribution. The 300 ka stability of 
uranium (235, 238), thorium, and protactinium in the fracture-filling minerals has apparently 
survived even recent hydrological disturbances from surface water infiltration of the fractures, as 
well as the infiltration of rainwater. 
Recent data obtained from U-series thermal ionization mass spectrometry indicate that the 
geochemical system at Nopal I restricts actinide mobility in the unsaturated environment. By 
analog, the tuffs at Yucca Mountain should have similar retentive properties to impede oxidized 
uranium mobility. The accumulation of natural analog data from Pea Blanca and similar sites 
would be of particular importance if such data demonstrated the general validity (or lack thereof) 
of low actinide mobility in unsaturated silicious tuffs under semi-arid climate conditions. 
3.11.12.2 Uranium Deposits in Northwestern Nevada/Southeastern Oregon 
The McDermitt Caldera uranium deposits and other uranium deposits in northwestern Nevada 
and southeastern Oregon have also been mentioned as possible analogs. Some of the uranium 
mineralization at these sites may constitute good analogs to aspects of radionuclide transport at 
Yucca Mountain, but this is questionable for several reasons. One reason is that the host 
volcanic rocks for these deposits are somewhat different. Another is that the uranium 
mineralization is fine-grained and low in concentration in these deposits. Also, age of deposition 
is poorly constrained for most of the deposits, and source-term information needed for models is 
lacking. Furthermore, hydrological data are sparse. Hence, in spite of their appealing proximity 
to Yucca Mountain for ease of study, these uranium deposits would require extensive additional 
characterization to build confidence in flow and transport process models. 
3.11.12.3 Akrotiri Archeological Site, Santorini, Greece 
Akrotiri is similar to Yucca Mountain in its silicic volcanic rocks, dry climate, and oxidizing, 
hydrologically unsaturated subsurface conditions. Bronze and lead artifacts were buried under 
1.5 to 2.0 meters of volcanic ash 3,600 years ago. Evidence for a plume of Cu (copper), Sn (tin), 
and Pb (lead) was investigated through selective leaching of packed earth and bedrock samples 
collected directly beneath the site where bronze and lead artifacts were excavated. Field data 
indicated that little of the bronze material had been transported away from its primary location. 
The total amount of Cu predicted to have been removed from the artifacts is roughly three orders 
of magnitude smaller than the volume of the artifacts. Neither Cu nor Pb was detected below a 
depth of 45 cm. The Akrotiri study shows preservation of artifacts for a long period of time in an 
oxidizing environment, indicating that unsaturated systems in arid environments may provide 
favorable sites for geologic disposal of radioactive waste.

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3.11.13 Abstraction of Transport Model 
3.11.13.1 Introduction 
An abstraction of Transport Model in the UZ is used for calculations of radionuclide transport in 
performance assessment. In this case, the abstraction is also a process model in which simplified 
mathematical representations of the physical processes are used. The reason for using a model 
abstraction for performance assessment is that computational requirements for the process model 
are too demanding for performance assessment calculations that require a large number of 
calculations to address different scenarios and encompass the desired parameter ranges. 
Therefore, the transport model abstraction is computationally streamlined to allow for more rapid 
calculations. As a more streamlined computational tool, the transport model abstraction can be 
run concurrently with the TSPA model. Changes in radionuclide releases from the engineered 
barrier system over time are directly input to the transport model abstraction, which then 
determines the spatial and temporal distributions of the radionuclides at the water table. 
The transport model abstraction is a 3-D, dual-permeability, particle-tracking method (CRWMS 
M&O 2000, U0065). Flow fields derived using the 3-D site-scale flow model are input directly 
to the particle-tracking method and are used to compute transport velocities. The method 
explicitly accounts for transport in both the fracture and matrix continua, with exchange between 
continua resulting from advective or diffusive processes. The velocity fields from the flow 
model are also used for advective transport exchange between the fracture and matrix continua. 
The various aspects of the transport processadvection, diffusion, dispersion, sorption, 
radionuclide decay, and colloid-facilitated transportare all explicitly modeled. 
3.11.13.2 Assumptions 
As for any mathematical model of a physical process, there are assumptions associated with the 
model. These assumptions represent simplifications or idealizations that allow a specific 
mathematical treatment. 
Assumption 1: Sorption can be adequately represented by a linear model. 
Basis: The basis for this assumption is discussed in Section 3.11.3.2. 
Assumption 2: The effects of flow in the matrix are negligible with respect to radionuclide 
exchange between fractures and matrix through matrix diffusion. 
Basis: This is a simplifying assumption that allows for rapid computation of the effects of matrix 
diffusion on transport while including the specific effects of the radionuclide concentration 
gradients in the matrix (normal to the fracture planes). The details of this fracture to matrix 
concentration gradient are difficult to capture in a numerical model because of the fine spatial 
resolution of the grid required. This assumption allows for the treatment of this process with an 
analytical or semi-analytical model that captures the effects of this gradient without requiring the 
numerical gridding. Results from comparison calculations between the model abstraction and 
the process-level model suggest that this assumption is conservative for predictions of 
radionuclide transport (CRWMS M&O 2000, U0065, Section 6.3; CRWMS M&O 2000, U0160, 
Section 6.2.5).

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Assumption 3: Colloid-facilitated radionuclide transport can be approximated by two endmember 
representations for colloid-radionuclide associations: equilibrium, reversible exchange 
of radionuclides between colloids and the aqueous-phase radionuclides, and irreversible 
association of radionuclides with colloids. 
Basis: Any radionuclide/colloid association would lie somewhere between the bounds 
established by this assumption. Because transport behavior is expected to be conservatively 
bounded by radionuclides irreversibly attached to colloids, the effects of colloid transport can be 
conservatively bounded with a mixture of these end-member models. 
Assumption 4: Colloid filtration/resuspension processes can be represented as an equilibrium 
process in which colloids are partitioned between mobile and immobile conditions. 
Basis: Any opposing first-order rate reactions can be expressed in terms of an equivalent, 
equilibrium partitioning coefficient that is proportional to the ratio of the forward and reverse 
rate constants  if the process can be averaged over a sufficiently long time. The rate constants 
identified by CRWMS M&O (2000, U0070, Section 6.2.3) indicate that filtration/resuspension 
time scales are on the order of tens of days. Given typical UZ transport times of years to 
thousands of years, the use of an equilibrium-partitioning coefficient is reasonable. 
Assumption 5: Dispersive transport is small in comparison with advective transport. 
Basis: The criterion for applicability is based on the grid Peclet number a / x Peg . = , where x . 
is the characteristic length scale of the computational cell and . is the dispersivity, or dispersion 
length scale, associated with transport across the cell (Fetter 1993, pp. 4952). Dispersive 
transport over a computational cell in the numerical model is expected to be scale dependent, i.e., 
the appropriate value of dispersivity is proportional to the size of the computational cell. This 
Peg ratio is expected to be greater than 10 for a scale-dependent dispersivity, indicating 
advection-dominated transport. 
3.11.13.3 Approach 
The particle-tracking abstraction model follows particles through an interconnected network of 
computational cells that constitutes the computational domain. Particle locations are identified 
by the computational cell coordinates, which is the lower limit of spatial resolution in the model. 
This cell-to-cell particle tracking method is similar to that described by Desbarats (1990, 
pp. 153163). The basis for the method is described by CRWMS M&O (2000, U0065, 
Section 6.1.1). Briefly, particles are assigned a residence time randomly from a residence time 
distribution that is computed from the processes that affect residence time (e.g., advection, 
sorption, and matrix diffusion). For a cumulative probability distribution function of particle 
residence times, we compute the residence time of a particle in a cell by generating a random 
number between 0 and 1 to determine the corresponding residence time from the distribution 
function in Figure 3.11-11. The advection-dispersion equation was used to generate the 
schematic residence time transfer function (RTTF) curve, but other transport mechanisms can be 
incorporated as well. The particle moves from the resident cell to an adjoining cell randomly, 
with the probability of entering an adjoining cell set according to the proportion of efflux from 
the resident cell into each of the adjoining cells.

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This same methodology is extended to a dual-permeability grid with residence time distributions 
in a single cell determined through mathematical models for advection, sorption, matrix 
diffusion, dispersion, radionuclide decay, and colloid-facilitated transport. The dual-permeability 
transport model includes advective and diffusive transfers between the fracture and matrix 
continua. 
Colloid transport is included in the abstraction through two end-member representations of 
radionuclide/colloid associations (Assumption 3 in Section 3.11.13.2). Radionuclides that 
reversibly exchange between the aqueous phase and a sorbed phase on colloids are included in 
the transport abstraction as a separate aqueous species. It is shown in CRWMS M&O 2000 
(U0065, Section 6.1.4) that this type of colloid-facilitated radionuclide transport is 
mathematically equivalent to aqueous transport with appropriately modified transport 
coefficients. This approach assumes a linear partition coefficient between the mass concentration 
of radionuclide in the aqueous phase and the mass concentration of radionuclide attached to any 
given type of colloid. Colloids may be temporarily detained at the fracture/matrix interfaces, 
and this interaction is captured in the colloid transport model as a retardation factor for colloid 
transport in the fracture system. Finally, colloids are subject to size exclusion for entering the 
matrix from the fractures. This is represented by a size exclusion factor that multiplies the 
probability for a colloid to enter the matrix from the fractures. The size exclusion factor is 
computed based on the colloid sizes and matrix pore size distribution. 
Colloids that have a fixed radionuclide content represent the other end-member representation 
for colloid-facilitated radionuclide transport. In this case, the radionuclides may be considered 
permanently fixed in the colloid structure and do not partition with the aqueous phase. 
Radionuclides permanently attached to colloids are also tracked as separate species in the 
particle-tracking model. This colloid type is subject to retardation in the fracture system and size 
exclusion, as described above. In addition, this colloid type is subject to permanent filtration for 
cases in which the colloids are making a transition from one matrix unit to another. Permanent 
filtration is computed in a manner similar to the way colloid size exclusion is computed for 
movement between fractures and matrix. The colloid filtration is expressed as a factor that 
multiplies the probability for colloid movement between matrix units, which is again a function 
of the colloid size and matrix pore size distribution. It should be noted that this filtration 
mechanism is not applied to colloids with radionuclides that reversibly exchange with the 
aqueous phase because a permanently filtered colloid in this case will not remove the 
radionuclide from subsequent transport. 
3.11.13.4 Results 
The particle-tracking method has been compared to alternate solution methods for a variety of 
problems. Results for 1-D transport with diffusion and sorption are found to agree with wellestablished 
analytical solutions (CRWMS M&O 2000, U0065, Section 6.2.1). A good match is 
also obtained for transport in a dual-porosity system including matrix diffusion (CRWMS M&O 
2000, U0065, Section 6.2.2). 
Comparisons with numerical models for transport in a 1-D, dual-permeability model have also 
been performed (CRWMS M&O 2000, U0065, Section 6.3). The comparisons shown here are 
for a simplified, 1-D, dual-permeability flow model for the UZ of Yucca Mountain. The flow

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system consists of three significant hydrological units between the solute release point (the 
potential repository elevation) and the water table. Figure 3.11-12 shows the ability of the 
particle-tracking abstraction to match the full numerical solution for a dual-permeability model. 
The Y-axis is labeled the Cumulative RTD, which stands for Cumulative Residence Time 
Distribution. This is the fraction of particles that have traversed the UZ (between the potential 
repository and the water table) at any given time. This case, without matrix diffusion, shows 
how the model is able to capture advection and dispersion (the solid black line is the full dualpermeability 
numerical solution and the dashed red line is for dispersion with no diffusion using 
the particle-tracking algorithm). The dashed black line in Figure 3.11-12 shows that the particletracking 
algorithm is also able to produce sharp breakthrough curves when dispersion is zero, 
something that is difficult to do in a conventional numerical solution. 
Figure 3.11-13 shows comparisons for a 1-D dual-permeability solution when matrix diffusion is 
included. Here there is a discrepancy at early time, in which the conventional numerical 
simulation predicts an early breakthrough in the case where the matrix diffusion is nonzero. The 
conventional solution uses a single cell to represent the matrix adjacent to a fracture cell. Thus 
the concentration gradient in the matrix (in a direction normal to the fracture plane) is only 
roughly represented in the conventional model. This discrepancy results in an early 
breakthrough because the exact representation of this gradient can represent a steep but narrow 
gradient in the matrix near the fracture plane and therefore gives a larger fracture to matrix 
diffusive flux. This reduced diffusive flux into the matrix leads to an earlier breakthrough. 
Matrix diffusion in the particle-tracking algorithm is only exact if matrix advection is zero (see 
Assumption 2). To test this assumption, we performed calculations (CRWMS M&O 2000, 
U0160) using a particle-tracking method that does not use this assumption. The results shown in 
Figures 3.11-14 and 3.11-15 are for a 3-D simulation using the dual-permeability site-scale flow 
model. Transport is calculated for the 3-D, dual-permeability system using the model abstraction 
(FEHM V2.10) and a second particle-tracking routine, DCPT V1.0. The DCPT V1.0 code uses a 
Lagrangian approach that interpolates the velocity field onto a continuous space in which 
particles can travel. This routine simultaneously accounts for the effects of matrix diffusion and 
matrix advection. The breakthrough for the nonsorbing Tc is shown in Figure 3.11-14. The 
reason for the delayed breakthrough curve for DCPT V1.0 is thought to be a result of the 
inclusion of matrix advection in the treatment of matrix diffusion. Advective flow from the 
fractures to the matrix will reduce the flux of radionuclides from matrix to fractures through 
diffusion. Thus, radionuclides will tend to be retained for longer times in the matrix, leading to 
slower breakthrough. 
A similar comparison is also made for the sorbing Np in Figure 3.11-16. The differences in the 
two solution methods found in Figure 3.11-14 are accentuated for sorbing radionuclides. In 
these comparisons, we find that in the model abstraction solution FEHM V2.10 predicts 
radionuclide movement to the water table that is significantly faster than that predicted by the 
DCPT V1.0 solution. Although the differences can be large, the model abstraction solution is 
found to be conservative. These two particle tracking methodologies and the advectivedispersive 
approach utilized in T2R3D V1.4 are further compared in CRWMS M&O (2000, 
U0155).

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3.11.14 Summary and Conclusions 
Figure 3.11-16 corresponds to Figure 3.11-1, which shows key issues related to radionuclide 
transport in the UZ. The following conclusions can be drawn from this section: 
1. Two-dimensional simulations show that transport in the CHn is strongly 
dependent on the distribution of the vitric and zeolitic tuffs at the different 
locations. Occurrence of the zeolitic CHn leads to fast transport; on the other 
hand, the vitric CHn acts as an effective barrier to radionuclide transport, and its 
effectiveness increases with the sorptive tendencies of the radionuclides. 
2. Three-dimensional site-scale simulations indicate that radionuclide transport is 
both dominated and controlled by the faults (especially at early times). Faults 
provide fast pathways to downward migration to the water table, but also limit 
lateral transport across them. 
3. Fractures are also the main pathway of transport. Diffusion from the fractures 
into the matrix is the main retardation mechanism in radionuclide transport. By 
sorbing onto the matrix into which they diffuse, the migration of radionuclides is 
retarded. 
4. Three-dimensional site-scale simulations show that radionuclide breakthrough at 
the water table occurs early and over a large area in the southern part of the 
potential repository block. The maximum water flow within the footprint of the 
potential repository in the southern part in the Perched water model #1 contributes 
to this transport pattern. Also the low-permeability zones at the TSw-CHn 
interface in the northern part of the potential repository are barriers to water 
drainage and lead to low water velocities and formation of perched water bodies. 
The presence of the highly conductive Solitario Canyon fault Splay G and Ghost 
Dance fault splay also contributes to the dominance of the southern part as the 
main pathway. 
5. The members of the decay chain (239Pu, 235U, and 231Pa) must be considered in 
the transport of 239Pu. Uranium-235 will become the main contributor in the 
release at the water table after 10,000 years (at most) because of its weaker 
sorption onto the matrix and longer half-life. The contributions of 231Pa are not 
important. 
6. Colloidal transport is very sensitive to filtration parameters, and for the given 
parameters, the colloid size has a significant effect on transport. 
7. More than 40 tracer transport simulations indicate a wide range of time for mass 
breakthrough depending on infiltration rates, type of tracers/radionuclides, and 
perched water conceptual models. The most important of these factors for 
transport times are (1) surface infiltration rates and (2) adsorption effects in the 
CHn. Compared with the effects of infiltration and adsorption, perched water 
conceptual models are of secondary importance to the overall impact on transport,

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but have primary impact on determining breakthrough areas of 
tracers/radionuclides at the water table. 
8. The modeling results of tracer (36Cl) transport from the land surface to the 
repository level indicate the existence of possible fast flow pathways with 
transport times of 50 years. However, the cumulative mass breakthrough carried 
by the fast flow is relative small (about 1%) for the early times of 50 to 100 years. 
The 50% mass breakthrough times to the repository level since release from the 
surface is estimated between 5,000 to 20,000 years under the present-day, mean 
infiltration scenario. The fast flow breakthrough at the earlier time occurs mainly 
along faults. 
9. Available tracer transport results of the ESF Alcove 1 and Busted Butte tests are 
analyzed for model validation as a confidence-building process. The Alcove 1 
analyses indicate that the continuum approach is valid for modeling flow and 
transport in unsaturated fractured rock, an active fracture model can capture the 
major features of fingering flow and transport in fractures, and matrix diffusion 
has a significant effect on the overall transport behavior. Busted Butte tracer tests 
and simulations of the vitric CHn show that the unit behaves as a porous medium, 
which is consistent with the expected behavior. 
10. Known analog sites for UZ transport are reviewed as additional corroborative 
analyses with respect to radionuclide transport at Yucca Mountain. Analyses of 
the Nopal I uranium deposit in Mexico and the trace metal migration study in 
Greece indicate that unsaturated systems in arid environments may provide 
favorable sites for geologic disposal of radioactive waste. 
11. An efficient particle-tracking model abstraction for 3-D site-scale simulations of 
radionuclide transport in the UZ has been developed for TSPA analysis. This 
model abstraction utilizes simplified mathematical representations of advection, 
dispersion, sorption, matrix diffusion, colloid transport, and radionuclide chain 
decay in a dual-permeability system. Comparisons show that the TSPA particletracker 
will yield conservative transport calculations.

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3.12 MOUNTAIN-SCALE TH MODEL 
3.12.1 Introduction 
Unsaturated zone (UZ) flow and transport will be affected by the heat released from the decay of 
radioactive waste in emplacement drifts of the potential repository at Yucca Mountain. The 
Analysis/Model Report for mountain-scale coupled processes (CRWMS M&O 2000, U0105), 
documents the development of the Mountain-Scale Thermal-Hydrological (TH) Model. This 
model evaluates the effects of heat on UZ flow and the distribution of liquid and temperature 
over a period of 100,000 years and provides the necessary framework to test conceptual 
hypotheses of coupled heat and fluid flow in the UZ. This model can then be used to predict 
future behavior in the UZ under thermal loading. This section summarizes the results of the TH 
Model, identifies the performance issues addressed and provides resolutions of the issues in 
terms of input for Performance Assessment (PA). 
The Mountain-Scale UZ TH model complements the EBS MultiScale TH (MSTH) (CRWMS 
M&O 2000, E0120) model in the evaluation of the impact of thermal loading on the NFE TH 
conditions and the EBS system, at the potential repository. The MSTH model samples TH 
conditions at several locations at the potential repository and includes influence of alternative 
waste package configurations. The model is a localized alternative to a fully coupled 3-D driftscale 
and Mountain-Scale TH model, that provides detailed drift-scale processes at the repository 
under thermal loading, from a sampling of mountain-scale locations. The Mountain-Scale UZ 
TH model on the other hand provides an estimate of mountain-scale evolution of the flow field 
coupled to a simplified representation of the drift-scale processes. Detailed drift-scale TH and 
THC processes are modeled and discussed in CRWMS M&O (2000, N0120/U0110). 
Figure 3.12-1 presents design issues modeled by heating the volume of UZ rock surrounding the 
potential repository. The issues provide for qualitative and quantitative evaluation of the impact 
of potential repository heat on the UZ and include the following: 
 Extent of the two-phase zone 
 Liquid and gas flux in near field and far field 
 Moisture redistribution in the UZ 
 Temperature at drift walls and in pillars in between drifts 
 Potential for flow and transport property changes in the PTn and CHn 
 TH effects on water table and perched water bodies 
 Influence of climate and ventilation. 
The thermal load and the resulting temperature changes have a large influence on many related 
processes, which directly impact the performance of the potential repository. The emplacement 
of heat-generating high-level waste will elevate temperatures and cause the redistribution of the 
in situ moisture in the unsaturated zone. For example, if the temperature of the rocks near the 
emplacement drifts approaches or exceeds the boiling point of water (97oC at ambient pressure), 
boiling of formation water will take place, with the associated increase in vapor pressure and overall 
gas-phase pressure. This will result in forced convection of the gas phase, that is accompanied by 
large latent heat effects. Phase transformation and gas-phase flow will perturb the in situ fluid 
distribution in the fractures and matrix, thereby changing capillary pressure gradients, relative

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permeability and liquid-phase flow rates. The impact of heat on the TH processes will depend on 
the thermal load as well as its distribution in the emplacement drifts. 
The Mountain-Scale TH Model numerically simulates the potential impact of the heat that is 
released by radioactive decay on the natural hydrogeological system, including a representation 
of heat-driven processes occurring in regions far away from the potential repository (the far 
field). The simulations provide predictions for thermally affected liquid saturation, gas- and 
liquid-phase flux (together referred to as flow fields), and the distribution of temperature and 
saturation in the UZ. Of particular interest is the impact of thermal loading imposed by waste 
emplacement on water percolation at and near the potential repository host rock and the flow 
barrier effects in the basal vitrophyre of the Topopah Springs and the Calico Hills zeolites 
underlying the potential repository horizon. These rock units impede the transport of 
radionuclides from the potential repository to the water table due to their low permeability and 
high sorptivity. When heated for long periods of time at temperatures exceeding 90oC, the flow 
and transport properties of these rocks can be altered, thus directly impacting their ability to 
impede transport of radionuclides. 
The Mountain-Scale TH Model is developed based on the UZ Flow Model. This model uses 
input parameters based on the calibrated property set (CRWMS M&O 2000, U0035), a spatially 
varying mean infiltration rate, with varying climates during the thermal-loading period. The 
simulations were performed using the average initial thermal load of 72.7 kW/acre, scaled down 
by the natural decay curve over a total simulation period of 100,000 years. To account for 
ventilation, only 30% of this heat is used during the first 50 years. 
Prediction of the thermal-loading effect in such models in turn requires establishment and 
acceptance of mathematical models that accurately represent the physics of coupled heat and 
fluid flow in the UZ. The TH Model uses the mathematical formulation employed in the 
TOUGH2 family of codes (Pruess 1987, pp. 211; Pruess 1991), the dual-continua approach 
(Section 3.4) and the van Genuchten capillary pressure and relative permeability parameter 
values obtained from the calibrated properties data (CRWMS M&O 2000, U0035) to describe 
the behavior of the UZ under thermal-loading conditions. This formulation is based on the 
traditional energy- and mass-conservation relationships. 
During the development of the TH Model (CRWMS M&O 2000, U0105), the accuracy and 
validity of the model results were evaluated based on current understanding of fracture-matrix 
interactions, heat transfer, and two-phase flow in unsaturated subsurface systems. Calibration of 
modeled temperature against the measured temperature profiles in boreholes (CRWMS M&O 
2000, U0050, Section 6.3) provides a basis for assessing the effectiveness of the model to 
capture the ambient, mountain-scale temperature distribution, which is used as the initial 
temperature for TH modeling. 
3.12.2 Modeling Approach 
The TH Model is used to model the nonisothermal TH processes due to heat generated by the 
emplaced heat source. Figure 3.12-2 shows the relationship between the TH Model, the input 
data, and the models supporting its development. This section presents a brief discussion of the

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development of the TH conceptual model and numerical grids, as well as the selection of input 
data and the model boundary and initial conditions. 
3.12.2.1 Conceptual Model 
The conceptual model for describing the TH processes at Yucca Mountain is based on the 
conceptual model used for the UZ Flow Model, as discussed in Sections 3.3 and 3.7. In this 
hydrogeological conceptual model, the UZ system consists of multi-layered hydrogeologic units, 
with flow behavior determined primarily by the degree of welding of the Yucca Mountain tuffs 
(Sections 3.2 and 3.4). The heat transfer within the UZ system is fully coupled with other 
processes, such as liquid percolation and air circulation. 
The numerical approaches (Section 3.4) involve volume averaging and the continuum concept 
for modeling coupled fluid and heat flow and fracture-matrix interaction. The dual-permeability 
formulation described in Section 3.4 and CRWMS M&O (2000, U0000, Section 6.7) with a 
single fracture element and single matrix element representing each continuum is used in all the 
TH simulations. This dual-continua method allows for global flow through both the fracture and 
matrix continua. The fracture-matrix interaction is modeled using the active fracture concept 
(Liu et al. 1998, pp. 26332646) for liquid flow in dual-continua. 
The TH simulations were conducted using TOUGH2 V1.4 (Section 1.3), with the equation-ofstate 
module EOS3 (water, air and heat). The EOS3 module contains the constitutive 
relationships that describe the thermodynamic properties of water (enthalpy, density, viscosity) 
as functions of temperature and pressure. In all simulated cases the relationships between 
relative permeability and capillary pressure for unsaturated rock are estimated using documented 
relations of Brooks and Corey (1966, pp. 6188) and van Genuchten (1980, pp. 892898). 
3.12.2.2 Numerical Grids 
Several numerical grids were used for TH simulations, including (1) a 3-D submodel grid of the 
UZ 3-D grid and (2) two 2-D cross-section grids (NS#1 and NS#2). All the numerical grids are 
based on the Geologic Framework Model (GFM 3.1). Figure 3.12-3 shows a plan view of the UZ 
3-D grid and the location of the potential repository submodel grid and the 2-D cross-section 
grids NS#1 and NS#2. The numerical grid resolution and layers along the NS#2 cross section 
are shown in Figure 3.12-4. Most of the results presented in this section utilize this cross section, 
with the lateral grid spacing equal to 1/4 of the drift spacing. A detailed discussion of numerical 
grids is presented in Section 3.4 and in CRWMS M&O (2000, U0000) and CRWMS M&O 
(2000, U0105, Section 6.2). 
The design of the lateral grid spacing within the potential repository domain includes the 
proposed spacing and orientation of the drifts. For the 3-D grid, the lateral spacing over the 
potential repository domain is equal to the spacing between the drifts (81 meters). The vertical 
grid design uses a 5 m thick grid layer to represent the potential repository horizon, at the 
elevation of the proposed repository. This layer is bounded above and below by 5 m thick layers 
CRWMS M&O (2000, U0000, Section 6.6.2). This type of grid, although sufficient to resolve 
mountain-scale processes, does not provide sufficient resolution for detailed evaluation of TH 
conditions around and between drifts.

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In the 3-D grids discussed above and in CRWMS M&O (2000, U0000 and 2000, U0105), each 
potential repository drift is represented by elements aligned along the direction of drifts. For the 
2-D cross-section grids, each drift is represented by a single element (with both matrix and 
fracture continua). In the design for the potential repository, the heat-generating radioactive 
waste will be stored in widely spaced drifts (up to 81 m spacing) at the repository horizon. This 
physical separation of the drifts in the real world can be lost in numerical grids if large grid 
spacing is used. If the grid spacing within the potential repository is equal to the drift spacing, 
then although the drifts are physically separated, they are in fact numerically adjacent. This 
results in a laterally continuous (smeared) heat source across the potential repository. Such a 
numerical grid (although sufficient for resolution of UZ Mountain-Scale ambient flow processes) 
cannot provide adequate resolution to study TH processes in terms of temperature, saturation, 
and flux between the drifts. The discrete (drift-by-drift) grid provides a model in which such 
phenomena can be investigated and the effect on the mountain-scale TH processes to be 
documented. In the 3-D grids this requires development of a new, locally refined grid, with a 
large number of elements, which greatly increases numerical computation time. In the crosssection 
grids, locally refined drift elements can be added at the potential repository horizon, 
without a substantial increase in the total number of elements. 
To develop TH models that provide a detailed resolution of the ambient flux and resolve the TH 
conditions near and between the drifts, the locally refined grid NS#2 described in CRWMS 
M&O (2000, U0105, Section 6.2.2) was used. This grid incorporates individual drifts, and 
provides several nodes between the drifts so that evolution of TH conditions at the drifts and 
within the pillars can be modeled. Detailed discussion of the development of this numerical grid 
that provides a physically more accurate representation of the heat distribution at the potential 
repository is presented in CRWMS M&O (2000, U0105 Sections 6.2 and 6.3). 
3.12.2.3 Potential Repository Thermal Load 
Mountain-scale thermal-loading data, which include the initial thermal load and the natural 
radioactive decay rate, were used in all the TH models. The total initial thermal load for the 
base-case scenario is 72.7 kW/acre (18.0 W/m2), based on a potential repository area of 1,050 
acres (4.25106 m2). In the cross-section grids, the amount of heat to be applied to individual 
drifts was computed based on this initial thermal load, the decay curve, and the lateral spacing 
between the drifts. This thermal load was then applied as a heat source to the matrix continuum 
of the discrete drift elements at the potential repository, beginning with the maximum thermal 
load at time zero and scaling it down according the tabulated decay curve at subsequent times. 
This thermal load is included in the TOUGH2 input as a tabulated lookup of time versus heat for 
matrix elements representing the potential repository drifts. To include the effects of a 50 year 
pre closure period of ventilation, this heat load is further scaled down. In the ventilated drift 
thermal-loading scenario, 70% of the heat generated by the radioactive is removed by the 
ventilation system. Therefore, only 30% of the computed heat is included in the input during this 
period. After 50 years, the no-ventilation heat input is used. Since the practical and logistical 
details of ventilation and its efficiency have not been ascertained both the no-ventilation and 
ventilation scenarios were modeled in order to quantify the impact of ventilation.

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3.12.2.4 Boundary and Initial Conditions 
The UZ numerical grids (Section 3.4 and CRWMS M&O 2000, U0000) consider the top of Tiva 
Canyon (TCw) hydrogeological unit as the top boundary. This coincides with the ground surface 
in most areas, except in areas with thick alluvium cover, where the top of the model is at the 
alluvium-TCw contact. All TH numerical grids also use this surface as the reference top 
boundary. Fixed temperature, gas saturation and gas pressure corresponding to the near surface 
conditions are assigned along this boundary. 
The water table is used as the bottom boundary for fluid flow with a fixed liquid saturation and 
gas pressure prescribed. These conditions represent estimated gas pressure and capillary fringe 
saturation at the water table. Temperature changes at the water table are modeled by extending 
the bottom temperature boundary to 1,000 meters below the water table. The temperature at the 
extended boundary is then fixed at 65oC. A simulation of nonisothermal UZ flow under the fixed 
top temperature and saturation conditions, and fixed bottom temperature, pressure, and saturation 
boundary conditions, was conducted to obtain mountain-scale ambient conditions using the 
present-day mean infiltration. This simulation shows that the average temperature at the water 
table (730 masl) is between 30 to 33oC over the potential repository domain, which is in 
agreement with the calibrated temperature distribution at the water table (CRWMS M&O 2000, 
U0050, Section 6.3). The average temperature at the repository horizon is about 23oC. These 
mountain-scale ambient conditions are the initial conditions for the TH simulations. 
3.12.2.5 Input Data and Parameters 
Key input data used in the TH model development are summarized in CRWMS M&O (2000, 
U0105, Section 4) and include the following: 
 Fracture properties (frequency, permeability, van Genuchten a and m , and aperture, 
porosity, and surface area) for each UZ model layer. 
 Matrix properties (porosity, permeability, van Genuchten a and m ) for each UZ model 
layer. 
 Thermal properties (grain density, wet and dry thermal conductivity, grain specific heat, 
and tortuosity coefficients) for each UZ model layer. 
 Fault properties (matrix and fracture) for each hydrogeologic unit. 
 Repository thermal-load and ventilation scenarios. 
 Present-day infiltration and temporal changes in infiltration due to long-term climate 
changes. 
In the TH models, three infiltration rates based on three climate scenarios were used over the 
thermal loading period. These are discussed in detail in Sections 3.3 and 3.5, and in USGS 
(2000, U0010, Section 5.1). Net infiltration maps corresponding to the following climates were 
used for TH modeling:

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Present Day: The mean present-day climate was used. In the 3-D models and the 2-D model 
NS#1, this climate was used for the entire simulation period. For the refined 2-D cross-section 
NS#2 model, this climate was used for the period from 0 to 600 years. 
Monsoon: The mean monsoon climate was used for the 2-D NS#2 model and was applied for the 
period 600 to 2,000 years. 
Glacial Transition: The mean glacial transition climate was used for the rest of the simulation 
period beyond 2,000 years in the 2-D NS#2 models. Although models of climate only cover a 
period of 10,000 years, the glacial-transition climate is assumed to extend up to the total modeled 
period of 100,000 years. 
The average net infiltration rate along the NS#2 cross-section is 4.8 mm/yr for the mean presentday 
infiltration rate, 11.3 mm/yr for the mean monsoon climate average infiltration, and 
16.9 mm/yr for the mean glacial transition climate. These rates compare well with the net 
infiltration rates over the entire UZ model domain, as presented in Section 3.5, Table 3.5-4. 
3.12.3 Results of TH Simulations 
Table 3.12-1 summarizes the cases simulated to characterize the TH processes on the Mountain- 
Scale under thermal loading. The simulations of the non-isothermal fluid and heat flow were 
conducted for a thermal-loading period of 100,000 years. The simulations start at time zero using 
the ambient conditions of the UZ Flow Model as initial conditions. The simulations were stopped 
at 600 years and at 2,000 years to change the infiltration to that of the corresponding climate. 
The main purpose of the Mountain-Scale TH Model is to predict the extent of the thermally 
disturbed zone, i.e., the mountain-scale changes in temperature, saturation, and liquid and gas 
flux. In particular, attention is given the TH Model results that directly impact performance 
issues, as outlined in the introduction. This section presents a detailed discussion of the results 
only for the fine grid simulations (Cases 5 and 6). The reader is referred to CRWMS M&O 
(2000, U0105, Sections 6.10 and 6.11) for detailed discussions of the other cases.

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Table 3.12-1. Summary of Numerical Model Cases for Mountain-Scale TH. 
Case No. Numerical Grid Infiltration Thermal Load Temperature 
Boundary 
1 3-D Submodel, no drifts Mean present day 72.7 kW/acre; no 
ventilation 
1,000 m below the 
water table 
2 3-D Submodel, no drifts Mean present day 72.7 kW/acre; no 
ventilation 
At the water table 
3 2-D Cross-Section 
(NS#1), no drifts 
Mean present day 72.7 kW/acre; no 
ventilation 
1,000 m below 
water table 
4 2-D Cross-Section (NS#1) 
with locally refined drifts 
Mean present day 72.7 kW/acre; no 
ventilation 
1,000 m below 
water table 
5 2-D Cross-Section (NS#2) 
with locally refined drifts 
0-600 years, mean 
present day; 600- 
2,000 years, mean 
monsoon; 2,000+ 
years, glacial 
transition 
72.7 kW/acre; no 
ventilation 
1,000 m below 
water table 
6 2-D Cross-Section (NS#2) 
with locally refined drifts 
0-600 years, mean 
present day; 600- 
2,000 years, mean 
monsoon; 2,000+ 
years, glacial 
transition 
72.7 kW/acre; with 
ventilation: use 30% 
of the total heat for 
50 years 
1,000 m below 
water table 
SOURCE: Adapted from CRWMS M&O 2000, U0105, Table 5) 
3.12.3.1 Temperature 
The evolution of the temperature distribution provides an estimate of the volume and lateral 
extent the UZ that is affected by the heat at the potential repository, as well as the temperature in 
the drifts and in the pillars. The numerical model can provide the predicted distribution at any 
desired time during the thermal loading period. The average ambient temperature at the potential 
repository horizon is about 23 oC (CRWMS M&O 2000, U0105, Section 6.9). Figure 3.12-5 
shows the distribution of temperature along the cross-section NS#2 after 1,000 years of thermal 
load (a) without ventilation, and (b) with ventilation (for the first 50 years). The variations in net 
infiltration across the model strongly influence the evolution of temperature in both cases. 
Higher temperatures are predicted in the low infiltration areas. The plots show extensive boiling 
only in the area immediately above and at the potential repository horizon. At a lateral distance 
of 100 meters or more from the potential repository, no substantial increases in temperature are 
predicted. For example, the predicted maximum temperature is 37oC at 100 meters north of the 
potential repository and about 40oC at 100 meters south. The temperatures at 200 meters away 
from the potential repository remain near ambient conditions throughout the simulation. This 
response suggests that the convection mode of heat transfer, driven by extensive boiling and 
rapid fracture flow, is dominant near the potential repository. The ambient infiltration flux 
(predominantly vertical) controls the temperature changes outside the potential repository 
boundaries.

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A detailed evaluation of temperatures changes can be obtained by plotting the evolution of 
temperature profiles in a column within the potential repository domain. The plots of vertical 
temperature profiles in a column at the center of the potential repository (location #1, see 
Figure 3.12-4) are shown in Figure 3.12-6. The figure shows that TH processes at and near the 
potential repository are controlled by convection. Without ventilation (Figure 3.12-6a), the 
model predicts that temperature at the drift wall could rise to 250oC after both the matrix and the 
fracture elements of the drifts become completely dry. In this case, a two-phase boiling zone at 
97oC develops above the potential repository and extends out to 50 meters after 500 years. This 
zone expands to 200 meters after 1,000 years. With ventilation (Figure 3.12-6b) the two-phase 
boiling zone is small and is confined to within 20 meters above the potential repository drifts. In 
this case the average temperature within the drifts rises to boiling conditions (97oC), although in 
a few locations, temperatures rise to about 110oC (CRWMS M&O 2000, U0105, Section 6.11). 
A plot of the evolution of temperature along the middle section of the potential repository 
horizon is presented in Figure 3.12-7 (a) without ventilation, and (b) with ventilation. The peaks 
correspond to the individual drifts that are spaced about 21.4 m along this cross section. The 
maximum temperatures occur in the drifts and minimum temperatures occur in the pillars. 
Without ventilation, the temperatures at the potential repository horizon rise to above boiling 
conditions (97oC) between 5 and 10 years. At ten years, most of the drifts are at a temperature of 
100oC as shown in Figure 3.12-7a. However, at this time the temperatures rise to 260300oC in 
the completely dried out zone at the northern end of the potential repository, where the surface 
infiltration rate is nearly zero (CRWM M&O 2000, U0105, Section 6.11). At 50 years, the 
temperatures in most drifts decline to 210235oC. After 50 years, the temperatures in the drifts 
decline rapidly due to re-wetting, driven by strong capillary suction in the near-field 
environment. At 100 years, temperature within the drifts is 160180oC but continues to decline. 
After 500 years, the temperature range of the drifts is 120135oC and after 1,000 years the 
average temperature is about 97oC at the center of the pillars with peaks of 100oC to 110oC 
within the drifts. After 10,000 years the average is about 65oC between the pillars, but rises to 
about 70oC at the drifts. Therefore, even without ventilation, the predicted maximum 
temperatures at the center of the pillars between the drifts do not exceed boiling temperature. 
Figure 3.12-7b shows the temperatures in the middle section of the potential repository horizon 
with ventilation. Even with ventilation, the models predict the development of a small zone of 
two-phase counter-current flow of liquid towards the drifts and vapor away from the drifts (heatpipe) 
at the potential repository horizon. The model predicts much lower elevated temperatures 
within the drifts due to ventilation cooling. When the ventilation system is shut-off after 
50 years, the temperatures at the drift wall are predicted to rise. The models predict that 
maximum temperatures at most locations along the potential repository horizon will not exceed 
boiling temperature (Figure 3.12-7b), although at localized areas with low ambient infiltration 
the temperature may rise to 110oC after these zones dry out (CRWM M&O 2000, U0105, 
Section 6.11). In this case, the temperatures in the central pillars rise to a maximum of 85oC 
after 1,000 years. After 10,000 years this temperature drops to about 65oC at the center of the 
pillars and to about 70oC at the drifts. Similar temperature conditions are predicted at 10,000 
years without ventilation (Figure 3.12-7a), showing that the long-term temperature response is 
not affected by the 50 years of ventilation.

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At the top of the Calico Hills nonwelded hydrogeological unit (CHn), at an elevation of 907 masl 
(at location #1), the models predict a maximum temperature of 7075oC between 2,000 and 
7,000 years. This temperature range suggests minimal potential for temperature-induced 
mineralogical changes to occur within the zeolites of nonwelded hydrogeological Calico Hills 
unit. Therefore, the sorptive properties of these zeolites will not be altered significantly as a 
result of thermal load at the potential repository. At the water table the models predict a 
maximum temperature of 6570oC compared to the average ambient temperature of 30oC. 
Without ventilation, temperatures at the base of the PTn may rise to boiling conditions at an 
elevation of 1,2501,270 masl (Figure 3.12-5) and induce property changes within the low 
infiltration areas. Temperatures within the PTn are predicted to rise to a maximum of 7075oC. 
With ventilation, temperatures in the PTn are predicted to rise by 2025oC from the ambient 
condition to an average of 4045oC. The numerical simulations show that there is minimal 
potential for temperature induced property changes within the PTn. 
The elevated temperature at the drift wall during thermal loading may lead to significant changes 
in thermal-mechanical stresses that may alter permeability and other properties of the host rock 
in the vicinity of the drifts. The extent of permeability changes as a result of thermally induced 
stresses are not addressed in the Mountain-Scale TH Model, because the thermal-mechanical 
effects are expected to occur on smaller scale. In addition, there are few site-specific studies or 
data available for describing thermal-hydrological-mechanical processes at Yucca Mountain. 
3.12.3.2 Saturation 
Changes in liquid saturation are important for several reasons. First, they indicate how long the 
dryout period at the potential repository will be. Secondly, they are used to assess the potential 
desaturation-induced changes in porosity and hydraulic conductivity (for example, in the zeolitic 
units). Finally, they help identify the onset of re-wetting processes and the subsequent potential 
for corrosion at the potential repository horizon. The TH simulations begin with the ambient 
liquid saturation obtained by a steady-state simulation using the present day mean infiltration and 
the boundary conditions discussed in Section 3.12.2.4. The heat leads to mobilization of liquid 
and gas in both the matrix and fracture continua. 
Figure 3.12-8 shows contour plots of matrix liquid saturation at 1,000 years (a) without 
ventilation, and (b) with ventilation. The plots show large decreases in matrix liquid saturation 
only near the drifts. In both models all fractures in the drifts at the potential repository horizon 
are completely dry within the first few years of thermal loading and do no rewet until 1,000 years 
after thermal loading begins. Figure 3.12-9 shows the matrix liquid saturation at location #1 
whereas Figure 3.12-10 shows the corresponding matrix saturation along the entire repository 
horizon. Without ventilation, the models predict completely dry matrix conditions 
(Figures 3.12-9a and 3.12-10a) for all the drifts between 10 and 50 years, and an area of reduced 
matrix liquid saturation below and above the potential repository. This area of reduced matrix 
liquid saturation extends up to 100 m below and above the potential repository horizon without 
ventilation. In this case, the matrix liquid saturation in the pillars drops to a minimum of 0.4 
after 500 years. The fracture liquid saturation in pillars adjacent to drifts rises above ambient 
saturation at 10 years (CRWMS M&O 2000, U0105, Section 6.11) due to condensing of water 
vapor. After 10 years the fracture liquid saturation reduces to and remains at near ambient 
saturation controlled by the climate.

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With ventilation (Figures 3.12-9b and 3.12-10b), completely dry matrix conditions are predicted 
only at a few isolated locations having low percolation flux. Vertically (Figure 3.12-9b) the zone 
of reduced matrix saturation extends to about 50 m above and below the drifts. The matrix 
saturation in several drifts with high percolation flux recovers to above 0.9 at 1,000 years 
(Figure 3.12-10b). After 5,000 years the matrix liquid saturation is almost fully recovered to the 
liquid saturation controlled primarily by the prevailing climate. In this case the fracture and 
matrix liquid saturation within the pillars remains at near-ambient conditions and is controlled 
primarily by the changes in climate throughout the simulated period. With and without 
ventilation the simulations predict that the liquid saturation at a lateral distance more than 
50 meters away from the repository remains at near-ambient conditions. 
3.12.3.3 Water Flux 
Analysis of the liquid flux gives an estimate of the quantity and duration of enhanced liquid flux 
that may potentially contact the waste canisters (near-field environment) under thermal load. 
Flow at the potential horizon can be enhanced by a decrease in saturation, which leads to an 
increase the capillary suction. The liquid flux can also be enhanced by an increase in saturation 
due to drainage of condensate that leads to an increased liquid relative permeability. The suctioninduced 
increase in liquid flux is due to the intense boiling and vaporization of both fracture and 
matrix liquid at the potential repository drifts because the temperatures reach or exceed boiling 
conditions (about 97C) even with ventilation. The liquid vaporization results in increased gas 
flow at the potential repository, which dries up the fractures first and reduces matrix liquid 
saturation at the potential repository horizon. The dry-out of fractures and lower matrix 
saturation at the potential repository drifts creates a large capillary pressure gradient between the 
continua at the potential repository horizon and the adjacent formations. This promotes liquid 
flow toward the potential repository, i.e., enhances percolation flux. This liquid flux is directed 
toward the repository drifts, but there is ample heat to vaporize all the liquid, particularly at early 
times. The vaporization leads to increased gas flux, which may cause localized condensation and 
drainage through the fractures in the pillars and the drifts. Details of such processes are better 
resolved by the refined NS#2 grid, which is described Section 3.12.2.2 and used for the TH 
simulations described here. 
Figure 3.12-11 shows the evolution of predicted liquid flux through the fractures at location #1 at 
the center of the potential repository with and without ventilation. Because of an extensive lowsaturation 
zone within the drifts, both models predict high percolation fluxes near the drifts. 
Figure 3.12-11a, shows a plot the vertical liquid flux at this location without ventilation (the 
plots here show liquid flux scale of up to 200 mm/yr for clarity). The predicted maximum liquid 
flux rises 360 mm/yr at 10 years (CRWMS M&O 2000, U0105, Section 6.11), but declines to 
less than 30 mm/yr at 500 years. With ventilation (Figure 3.12-11b) the average vertical flux 
near the potential repository rises to only 60 mm/yr at 10 year. When ventilation is turned off at 
50 years, the increase in the available heat within the drifts leads to further decrease in matrix 
liquid saturation and increase in capillary pressure gradients. This in turn increases liquid flow 
toward the drier drifts. After 500 years the liquid flux is has only declined about 40 mm/yr. 
Figure 3.12-12a (the figures here show liquid flux scale of up to 100 mm/yr for clarity) shows 
the liquid flux through the fractures at the potential repository horizon, without ventilation. Note 
that vertical liquid flux at location #1 (Figure 3.12-11) is calculated based on the entire column

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area. In the locally refined NS#2 grid, 5 m drifts plus two equal elements represent the columns 
at the potential repository horizon in which drifts are located (CRWMS M&O 2000, U0105, 
Section 6.3.3.2). The liquid flux through an entire column above the drift is thus funneled 
toward the narrower drift by the high capillary gradients, because heat is applied only to the drift 
element. The figure shows that without ventilation, the liquid flux through the fractures toward 
the drifts, calculated based on this smaller drift area, rises to between 1,2501,600 mm/yr 
(CRWMS M&O 2000, U0105, Section 6.11) after 10 years. This liquid flux drops to zero, as the 
fractures in the drifts become completely dry (between 10 and 50 years). As the fractures begin 
to rewet between 500 and 1,000 years (see Figure 3.12-10a), the fracture liquid flux recovers 
(Figure 3.12-12a). Around 1,000 years, fracture liquid flux at several locations increases to 20 
50 mm/yr (2 to 5 times mean infiltration rate for the monsoon climate), controlled by the 
infiltration rate, capillary-pressure and the liquid-saturation gradients. This is the liquid flux that 
can potentially contact the canisters. The simulations also show increased fracture liquid flux in 
the pillars between the drifts. At around 500 years the average fracture flux between drifts is 
about 20 mm/yr, about 5 times higher than the infiltration rate. This is because the predicted 
boiling within the pillars in the no-ventilation case leads to a decrease in saturation and increased 
capillary suction. 
Although ventilation lasts only 50 years, it results in changes in flux patterns that last for several 
hundred years. This is because the heat removed by ventilation results in a delay in the dry-out of 
the matrix, and decreased gas flux at the potential repository horizon. Ventilation leads to much 
lower induced liquid and gas flux because the effective thermal load is only 30% of the total load 
during the period in which the heat yield of the emplaced waste is highest. With ventilation 
(Figure 3.12-12b, plot shows scale of up to 100 mm/yr for clarity) the predicted fracture flux at 
the potential repository horizon rises to maximum of 270300 mm/yr at 10 years, but 
subsequently declines due to decreased vaporization. When ventilation is shut off at 50 years, the 
retained heat leads to increased drying of the matrix and an increase liquid flux. However, this 
process is delayed because first the temperature of the rock-mass at the potential repository must 
rise to boiling conditions before liquid can be vaporized to create the large capillary pressure 
gradients. At 100 years (50 years after end of ventilation) the liquid flux is 10 mm/yr. However, 
flux recovers to over 150 mm/yr at 500 years (Figure 3.12-12b) as a result of increased heating, 
drying of matrix and re-wetting of the fractures. Because of the general decline in the heat 
released from the emplaced nuclear waste and the increased infiltration due to climate change, 
the fracture continuum at the potential repository horizon is almost completely re-wetted after 
5,000 years, and the fracture liquid flux recovers to the ambient percolation flux. With 
ventilation, the fracture flux through the pillars between the drifts remains at or above ambient 
conditions throughout the thermal-loading period. This is because temperatures do not rise to 
boiling conditions and condensation of liquid vapor gives rise to localized increase in fracture 
liquid saturation and a corresponding increase in liquid relative permeability. For example, the 
liquid flux between the drifts is 15 to 20 mm/yr, (about 2 to 3 times the ambient infiltration rate), 
at 500 years. Beyond 500 years the fracture liquid flux in the pillars is controlled primarily by the 
changes in ambient infiltration due to changes in the ambient climate, monsoon climate at 600 to 
2,000 years and glacial transition climate thereafter. 
Analysis of the liquid flux through the matrix gives an indication of the liquid that flows toward 
the potential repository primarily though the matrix during thermal loading. Figure 3.12-13 
shows the matrix liquid flux at the potential repository (a) without ventilation, and (b) with

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ventilation. Without ventilation (Figure 3.12-13a, plot shows scale of up to 100 mm/yr for 
clarity) the matrix liquid flux rises to a maximum of 400450 mm/yr after 500 years at the drifts, 
but stays at ambient conditions between the drifts. As the matrix continuum of the drifts becomes 
completely dry, this flux also drops to near zero between 500 to 1,000 years. With ventilation 
(Figure 3.12-13b) the matrix liquid flux rises to a maximum of 20 to 30 mm/yr at the drifts after 
500 years but remains at ambient conditions (about 0.25 mm/yr which is less than 6% of total 
liquid flux) between the drifts throughout the thermal-loading period. 
3.12.4 Model Validation 
Model validation here is discussed in terms of confidence building for the validity of the 
numerical and mathematical approaches used to model TH processes. There is no data for direct 
validation of the Mountain-Scale response to thermal loading. Validation data for a Mountain- 
Scale TH Model can only be obtained by monitoring the response of a fully operational 
repository. Numerical modeling of Mountain-Scale TH processes can provide a prediction of the 
performance of the potential repository under thermal loading. Such a model can then provide 
quantitative and qualitative evaluation of the issues discussed in Section 3.12.1, which are used 
to evaluate alternative designs for the potential repository. The validation process then becomes 
one of assuring that the numerical model adequately represents the physical processes, and that 
the results of such a model provide reliable data for decisions on the design of the potential 
repository. 
The problem to be modeled here is essentially that of coupled two-phase fluid and heat flow in a 
fractured geological medium. Approaches for the development of the numerical models for the 
simulation of the two-phase processes in such systems are generally based on geothermal and 
petroleum reservoir simulation methods. Numerical models of geothermal and petroleum 
systems can be validated from a wealth of field-scale tests and production data. The validity of 
model predictions based on this modeling approach is demonstrated using corroborative results 
from the modeling of these natural analog systems (Table 3.2-1), from the previously published 
UZ numerical modeling studies, and from small-scale underground thermal tests in the ESF 
discussed in Section 2.2.4. 
Validation of the TH Model, although incorporating results of the small-scale TH tests, relies 
mainly on the conceptual and mathematical validity of the models, the validity of flow and 
thermal properties, and the associated numerical grids. Performance Assessment of the effect of 
heat on the UZ flow, based on numerical simulation of fluid and heat flow, can include the 
physical processes affecting repository and host-rock behavior. The TH models explicitly 
represent the relevant thermal-hydrological conditions at the potential repository over the 
applicable time and space scale. These TH numerical models can then provide model predictions 
of the mountain-scale responses to thermal loading under the proposed design conditions. For 
example, the numerical models can be used to determine the effect of thermal loading on 
mountain-scale liquid and gas flux, temperature, and moisture distribution in the UZ. This 
coupled flow of heat and fluid in the UZ is modeled using TOUGH2 V1.4 (STN: 10007-1.4-0). 
Previous versions of this code have been used in the modeling of several natural analogs 
discussed in CRWMS M&O (2000, U0105, Section 6.12) and presented in Table 2.3-1 of this 
PMR. The table also documents the similarity between these natural analog systems and the UZ 
at Yucca Mountain that is modeled here. Applications include detailed studies, production

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history and future performance of geothermal fields. The justification for the modeling 
approaches employed in the TH Model and the validity of the TH predictions rely upon the 
successful modeling of fluid and heat transport in large natural sub-surface systems (for example 
geothermal systems) for which an extensive volume of field data is available for model 
validation. These natural analog models are validated by field measurements in several 
operating geothermal fields as discussed in Section 2.2.4. 
The predicted heat-pipe mode of heat transfer near the drifts in the Mountain-Scale TH Model, 
and its influence on temperature distribution agrees with the observations from the SHT results 
and the interim results of the thermal DST, discussed in Section 2.4 and documented in CRWMS 
M&O (2000, N0000). In addition, the modeled drift-scale THC response discussed in Section 
3.10 shows similar heat-pipe signatures and condensation in fractures. This response is validated 
by comparison to measured temperature at several observation points, by repeat air-injection 
tests, neutron logs and electrical-conductivity logs, which measure changes in liquid in liquid 
saturation. Both the results of the heater tests and the TH Model suggest no major adverse 
conditions in terms of temperature changes, moisture redistribution near the drifts, as well as 
liquid drainage towards the drifts and within the pillars. The TH Model shows no major 
moisture redistribution in the UZ except near the heated drifts. The simulations also show only 
moderate temperature increase within the zeolites and at the water table. We consider the TH 
Model developed here validated for the intended use because of this good agreement with the 
heater test models, the validity of the geothermal analog models, and the documented theoretical 
and physical validity of similar unsaturated flow studies with and without heat. 
3.12.5 Summary and Conclusions 
The TH modeling study investigates the effects of thermal loading on the UZ of Yucca 
Mountain. This study uses both 3-D and 2-D dual-permeability submodels of the 3-D UZ Flow 
Model and incorporates the calibrated model properties. Detailed investigation of the UZ 
response to thermal loading discussed in this PMR is conducted using refined 2-D cross-section 
models that include explicit representation of the drifts at the potential repository. 
These models simulate the mountain-scale TH response under the design base-case thermal load 
scenario. The models include expected future climatic changes in infiltration rate and the effects 
of drift ventilation. The numerical grids are sufficiently refined to determine Mountain-Scale, 
long-term TH behavior resulting from thermal load within the drifts, but do not explicitly include 
detailed heat transfer processes within the drifts. This is because such processes affect only small 
distances around the drift (a few meters) and at early times (less than 500 years) relative to the 
Mountain-Scale model spatial domain and the modeled temporal scale. Figure 3.12-14 
summarizes the results of the TH modeling in terms of the issues discussed in Section 3.12.1. 
The figure provides qualitative and quantitative data primarily based on the results of the detailed 
NS#2 cross-section UZ model. This study indicates that the available heat source and its 
distribution as well as the infiltration rates are the determining factors for boiling and re-wetting 
TH processes at the potential repository. 
With or without ventilation, heat-pipe conditions are developed in a region above the potential 
repository in the period of 10 to 100 years after thermal loading starts. Without ventilation, the 
TH models predict drift temperatures exceeding 100oC for hundreds of years. The results show

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that temperatures may be elevated to more than 250oC within the completely dry drift zone, 
when no ventilation is implemented. In this case, temperature within the pillars may rise to 
boiling temperature (about 97C) after 1,000 years of heating. With ventilation, temperatures 
only rise to boiling conditions in the immediate vicinity of the drifts, but may reach 110oC at 
drifts with low ambient liquid flux. In this case the temperatures in the pillars are predicted to 
rise to an average of 8085oC. In both cases the models predict a nearly 3035C temperature 
increase at the water table to an average of 6065oC. At the top of the CHn stratigraphic unit, 
the predicted maximum temperature rises to 7075C and occurs between 2,000 and 7,000 years. 
This suggests that temperature-induced property changes will be insignificant in the CHn 
because such changes are expected to occur if CHn zeolite temperatures remain above 90oC for 
prolonged periods of time. Without ventilation, temperatures within the PTn are predicted to rise 
to a maximum of 7075oC. With ventilation, temperatures within the PTn are predicted to rise by 
2025oC from the ambient condition to an average of 4045oC, indicating minimal potential for 
temperature-induced property changes within the PTn. In both cases, temperatures at a lateral 
distance of more than 100 m outside the potential repository are expected to remain at near 
ambient conditions. 
Therefore, thermal loading at the potential repository results in significant changes in the 
temperature conditions particularly near the drifts. The models predict that heating of the 
potential repository drifts will result in hot and dry conditions within the drifts that last for 
hundreds of years in the fractures with and without ventilation. Two-phase heat-pipe conditions 
will develop in a region above the potential repository. In areas with low surface infiltration this 
region may extend to the base of the PTn stratigraphic unit if no ventilation is implemented. 
Without ventilation most of the rock mass surrounding the drifts is predicted to become 
completely dry and remain so for over 1,000 years. With ventilation, although the TH Model 
does not predict completely dry conditions near all the drifts, the walls of the drifts are expected 
to remain dry for hundreds of years. In both cases the fractures at the potential repository drifts 
are predicted to completely dry and remain so for hundreds of years. With and without 
ventilation the matrix and fracture liquid saturation within the pillars remains high, and at several 
locations increases to above the ambient liquid saturation because of vapor condensation. 
Vertically, the zone of substantially reduced matrix liquid saturation extends to 50 m directly 
above and below the drifts with ventilation, and up to 100 m without ventilation, except in areas 
of high ambient liquid infiltration. 
With and without ventilation, large liquid and gas flow rates are predicted, primarily through the 
fractures. These flow rates are two to three orders of magnitude higher than the ambient flux at 
the repository drifts and are primarily driven by capillary pressure gradients due to drying of 
both the matrix and the fractures at the drifts. However, these large fluxes are confined to a 
period of less than 100 years. The liquid flux through the fractures towards the drifts may exceed 
1,2501,600 mm/yr without ventilation, and 270300 mm/yr with ventilation, particularly in the 
low infiltration areas due to these high capillary pressure gradients. However, in both cases there 
is ample heat within the potential repository drifts that immediately vaporizes this liquid flux, at 
this early period. Therefore, this liquid does not directly seep into the drifts and has little impact 
on the waste canisters in the drifts. The liquid flow through matrix towards the drifts rises to 
maximum of 400450 mm/yr without ventilation but is only 2030 mm/yr with ventilation. This 
liquid flux is also vaporized by the repository heat. The TH Model predicts continued liquid

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flow through the pillars, at a rate close to the ambient percolation flux for most of the thermalloading 
period. In some locations the flow may be enhanced by condensate drainage for several 
hundred years. The models predict little impact on liquid and gas flux outside the potential 
repository domain.

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3.13 OVERVIEW OF UNCERTAINTIES IN UZ FLOW AND TRANSPORT MODELS 
The models and components that comprise the UZ Flow and Transport Model contain inherent 
uncertainties. The identification and propagation of these uncertainties is important for the 
appropriate treatment of the models used in TSPA-SR calculations. Table 3.13-1 lists the major 
model components described in the UZ PMR and the uncertainties in the model inputs and 
outputs. Uncertainties in conceptual models are also identified. It is important to note that input 
and output parameters have both variability and uncertainty. For example, infiltration is spatially 
variable at the surface of Yucca Mountain, and there is also uncertainty in the rates that are 
simulated because of uncertainty in the input parameters such as precipitation, soil depth, and 
evapotranspiration. Spatial and temporal variability and uncertainty are included in the models 
where they are important and could potentially have a significant effect on TSPA calculations for 
repository performance. 
Table 3.13-1. Uncertainty in Major Model Components of the UZ Flow and Transport Model 
Model 
Component 
Input Parameter Uncertainty 
& Variability 
Conceptual and Numerical 
Model Uncertainty 
Output Parameter 
Uncertainty & Variability 
Climate 
(USGS, 2000, 
U0005; 
Section 3.5 
this PMR) 
Uncertainty in Owens Lake 
sediment-accumulation rate, 
Devils Hole age data, time 
when Devils Hole record 
implies climate has changed, 
exact location of the 
past/present point in the 
Owens Lake record (analog 
climate proxy record) 
Uncertainty in use of orbital 
cycles, interpretation of 
climate analogs 
Upper and lower bounds for 
precipitation and temperature 
using different meteorological 
stations as analogs; duration 
of climate periods 
Infiltration 
(USGS 2000, 
U0010; 
CRWMS M&O 
2000, U0095; 
Section 3.5 
this PMR) 
Uncertainty in precipitation, 
bedrock permeability, soil 
depth, evapotranspiration, 
etc.; variability in precipitation, 
temperature, etc. at surface 
Deterministic use of surface 
mass balance model 
Spatial and temporal variability 
of infiltration (USGS 2000, 
U0010); uncertainty in 
infiltration rates based on input 
parameters (CRWMS M&O 
2000, U0095) 
UZ Properties 
(CRWMS M&O 
2000, U0035; 
CRWMS M&O 
2000, U0090; 
Section 3.6 
this PMR) 
Uncertainty in measured core 
data parameters and crosscorrelation; 
spatial variability in 
properties 
Uncertainty in calibration 
method (non-uniqueness); 
initial estimates; upscaling 
Spatial variability in calibrated 
parameters; parameter 
calibration for different 
infiltration cases 
UZ Flow 
(CRWMS M&O 
2000, U0050; 
CRWMS M&O 
2000, U0125; 
CRWMS M&O 
2000, U0000; 
Section 3.7 
this PMR) 
Uncertainty and variability in 
hydrologic parameters 
(CRWMS M&O 2000, U0035); 
infiltration uncertainty 
(CRWMS M&O 2000, U0095) 
Uncertainty in dualpermeability 
model (Doughty, 
1999); active fracture model 
(Liu et al. 1998); perched 
water models, fault models 
(CRWMS M&O 2000, U0030; 
CRWMS M&O 2000, U0050); 
water table rise (CRWMS 
M&O 2000, U0125); 
refinement of mesh (CRWMS 
M&O (2000, U0000) 
Spatial and temporal variability 
and uncertainty in flow fields

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Model 
Component 
Input Parameter Uncertainty 
& Variability 
Conceptual and Numerical 
Model Uncertainty 
Output Parameter 
Uncertainty & Variability 
Ambient 
Geochemistry 
(CRWMS M&O 
2000, U0085; 
Section 3.8 
this PMR) 
Uncertainty and spatial 
variability in precipitation 
(chloride concentrations); 
reactive surface area; kinetic 
and thermodynamic 
parameters 
Uncertainty in thermodynamic 
and kinetic relationships; 
same conceptual uncertainties 
as UZ Flow Model 
Spatial prediction of 
percolation; uncertainty in 
estimate of infiltration rates 
Drift Seepage 
(CRWMS M&O 
2000, U0075; 
CRWMS M&O 
2000, U0080; 
CRWMS M&O 
2000, U0120; 
Section 3.9 
this PMR) 
Spatial variability of fracture 
permeability (CRWMS M&O 
2000, U0080); spatial 
variability and uncertainty in 
fracture permeability and van 
Genuchten a (CRWMS M&O 
2000, U0075; CRWMS M&O 
2000, U0080) 
Uncertainty in heterogeneous 
fracture continuum model 
(CRWMS M&O 2000, U0080); 
effects of drift degradation 
(CRWMS M&O 2000, U0075); 
episodic flow (CRWMS M&O 
2000, U0075); refinement of 
mesh; correlation of k and a 
Variability and uncertainty in 
seepage distributions 
(seepage fraction, mean seep 
flow rate, standard deviation of 
seep flow rate, flow focusing 
factor) (CRWMS M&O 2000, 
U0120) 
Drift-Scale 
THC 
(CRWMS M&O 
2000, 
N0120/U0110; 
Section 3.10 
this PMR) 
Variability in hydrologic 
parametersuse of calibrated 
parameters (CRWMS M&O 
2000, U0035); uncertainty in 
chemistry data 
(thermodynamic and kinetic 
data, chemistry of infiltrating 
water) (CRWMS M&O 2000, 
U0085) 
Uncertainty in dualpermeability 
model to capture 
THC changes in matrix at 
fracture wall; use of middlenonlithophysal 
parameters 
instead of lower-lithophysal 
parameters; refinement of 
mesh to capture THC changes 
in matrix at fracture wall 
Temporal and spatial 
variability of water and gas 
composition, as well as 
uncertainty from different 
infiltration cases (CRWMS 
M&O 2000, N0120/U0110); 
temporal variability in water 
and gas composition for 
TSPA-SR 
UZ Transport 
(CRWMS M&O 
2000, U0060; 
CRWMS M&O 
2000, U0065; 
CRWMS M&O 
2000, U0160; 
Section 3.11 
this PMR) 
Uncertainty and variability in 
transport parameters 
(CRWMS M&O 2000, U0100); 
spatial and temporal variability 
and uncertainty in flow fields 
(CRWMS M&O 2000, U0050; 
CRWMS M&O 2000, U0125) 
Uncertainty in matrix-diffusion 
model and particle tracking 
model (CRWMS M&O 2000, 
U0060; CRWMS M&O 2000, 
U0065; CRWMS M&O 2000, 
U0155; CRWMS M&O 2000, 
U0160); colloidal transport 
model (CRWMS M&O 2000, 
U0070); discretization of 
gradient for matrix diffusion 
(CRWMS M&O 2000, U0065); 
number of particles (CRWMS 
M&O 2000, U0160) 
Spatial and temporal 
radionuclide mass flux at 
water table (CRWMS M&O 
2000, U0065) 
Mountain- 
Scale Thermal 
Hydrology 
(CRWMS M&O 
2000, U0105; 
Section 3.12 
this PMR) 
Variability in hydrologic and 
thermal properties for different 
units (CRWMS M&O 2000, 
U0105) 
Uncertainty in dualpermeability 
model for 
transient TH simulations 
(Doughty, 1999); active 
fracture model (Liu et al., 
1998); perched water models, 
fault models (CRWMS M&O 
2000, U0030; CRWMS M&O 
2000, U0050); water table rise 
(CRWMS M&O 2000, U0125); 
Refinement of mesh (CRWMS 
M&O (2000, U0000) 
Spatial and temporal 
variations in temperature and 
hydrologic conditions 
(CRWMS M&O 2000, U0105)

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Table 3.13-2 provides a distilled list of uncertainties that are carried forward to TSPA 
calculations. The uncertainty in the parameters and models is included in TSPA calculations 
through the use of multiple realizations (statistically equivalent simulations) and stochastic 
sampling of parameters (i.e., a Monte Carlo approach). Each realization samples a set of 
parameters and/or models from given distributions for use in the TSPA calculation. The 
simulation of multiple realizations produces a range of performance results, with each outcome 
having a probability corresponding to its likelihood of occurrence. Thus, the uncertainty of the 
parameters and models leads to uncertainty in system performance. In the TSPA, the uncertainty 
in performance is analyzed, both in terms of its importance (i.e., is the uncertainty so great that it 
casts doubt on the safety of the repository?) and in terms of sensitivities (i.e., which parameter 
and submodel uncertainties have the greatest impact on the uncertainty in performance?). 
In addition, uncertainties in the process-model outputs can also be addressed in abstracted TSPA 
models and analyses that use conservative assumptions. If insufficient evidence exists to provide 
a defensible range of values for a given parameter, values that bound the physical behavior or 
provide conservative estimates of the range of physical behavior are used. For example, a 
conservative factor that increases the seep flow rate by over 50% is used in the TSPA seepageabstraction 
model to account for the uncertain impacts of drift degradation and rock bolts. For 
future climates, the water table is assumed to rise by a conservative amount in the abstracted UZ 
Flow Model, which will reduce travel times in the UZ. These conservative assumptions are 
intended to increase the defensibility of the models used in TSPA calculations given the inherent 
uncertainties in the actual system. 
The uncertainty and variability in the model parameters are due, in part, to the natural variability 
and heterogeneity in the geological, hydrological, chemical, and mechanical systems that are 
difficult to characterize in situ, such as the precise fracture network in the UZ. Uncertainties in 
models may also be due to conditions that are difficult to predict, such as future climate states. 
Nevertheless, the previous sections in this PMR have provided the basis and confidence (through 
data collection, field tests, and calibration exercises) for using these parameters and models. In 
addition, the models and analyses that are used in TSPA calculations address remaining 
uncertainties through probabilistic simulations or appropriate conservative bounding 
assumptions.

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Table 3.13-2. Uncertainties in UZ Flow and Transport Products for TSPA-SR 
Model 
Component 
Treatment of Uncertainty in Abstracted Product for TSPA-SR 
Climate  Future climates: three climates are assumed with uncertainty in precipitation 
and temperature (Section 3.5), which provide ranges of infiltration. 
 Duration of climates: Duration of the three climate states is assumed to be 
fixed and transitions are assumed to be instantaneous. Sensitivity studies of 
different climate durations are required. 
Infiltration  Three spatially variable infiltration maps (low, mean, and high) are used for 
each of the three climates (Section 3.5). 
 Monte Carlo simulations produced weightings for three infiltration cases used in 
each climate (Section 3.5). 
UZ Flow  Nine flow fields are used that correspond to low, mean, and high infiltration 
cases for each of the three climates (Section 3.7). 
 Assessment of uncertainty in the two perched water models revealed that both 
are similar. Only perched water model #1 is used for TSPA (Section 3.7). 
 Conservative estimate for water-table rise is used for future climates (Section 
3.5 and CRWMS M&O 2000, U0125). 
 Weightings for three infiltration cases are used for each corresponding flow 
field. 
Drift Seepage  Distributions are developed for seepage fraction, mean seep flow rate, standard 
deviation of seep flow rate, and flow focusing factor based on process model 
results (Section 3.9). 
 A conservative factor is applied to increase seepage due to drift degradation 
and rock-bolt effects. 
 A conservative factor is applied to increase seepage to account for potential 
parameter correlations not included in process models. 
Drift-Scale 
THC 
 Water and gas compositions are abstracted and prescribed at four discrete time 
periods following emplacement based on drift-scale THC process model results 
(Section 3.10). Sensitivity studies may be required. 
UZ Transport  Distributions of Kd and Kc (for reversible colloids), colloid filtration parameter, 
aperture parameter, and diffusion coefficient are used to capture uncertainty 
(CRWMS M&O 2000, U0100; CRWMS M&O 2000, U0065). 
 Weightings for three infiltration cases are used for each corresponding flow field 
during transport simulations. 
 Uncertainty in location of source term is implemented through random nodal 
release within bins in the repository region that are consistent with bins used in 
the near-field environment. 
 Uncertainty in dispersion of radionuclides within the UZ is treated conservatively 
by collecting mass flux at the water table in the UZ and releasing it at point 
locations at the water table in the SZ model. 
Mountain- 
Scale TH 
 Based on results of the process model (Section 3.12 and CRWMS M&O 2000, 
U0105), TH effects on far-field flow and transport are not considered. 
Sensitivity studies may be required. Note that thermal impacts on the near-field 
environment are considered in the Near-Field Environment PMR.

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4. RELATIONSHIP TO NRC ISSUE RESOLUTION STATUS REPORTS 
4.1 SUMMARY OF THE KEY TECHNICAL ISSUES 
As part of the review of site characterization activities, the Nuclear Regulatory Commission 
(NRC) has undertaken an ongoing review of information on Yucca Mountain site 
characterization activities to allow early identification and resolution of potential licensing 
issues. The principal means of achieving this goal is through informal, prelicensing consultation 
with the DOE. This approach attempts to reduce the number of, and to better define, issues that 
may be in dispute during the NRC licensing review, by obtaining input and striving for consensus 
from the technical community, interested parties, and other groups on such issues. 
The NRC has focused prelicensing issue resolution on those topics most critical to the postclosure 
performance of the potential geologic repository. These topics are called Key Technical 
Issues (KTIs). Each KTI is subdivided into a number of subissues. The KTIs are: 
 Activities Related to Development of the EPA Standard 
 Container Lifetime and Source Term 
 Evolution of the Near-field Environment 
 Igneous Activity 
 Radionuclide Transport 
 Repository Design and Thermal Mechanical Effects 
 Structural Deformation and Seismicity 
 Thermal Effects on Flow (TEF) 
 Total System Performance Assessment (TSPA) and Integration 
 Unsaturated Zone (UZ) and Saturated Zone (SZ) Flow under Isothermal Conditions 
Identifying KTIs, integrating their activities into a risk informed approach, and evaluating their 
significance for postclosure performance helps ensure that NRCs attention is focused on 
technical uncertainties that will have the greatest affect on the assessment of repository safety. 
Early feedback among all parties is essential to define what is known, what is not known, and 
where additional information is likely to make a significant difference in the understanding of 
future repository safety. The Issue Resolution Status Reports (IRSRs) are the primary mechanism 
that the NRC staff uses to provide feedback to the DOE on the status of the KTI subissues. 
IRSRs focus on NRC acceptance criteria for issue resolution and the status of issue resolution, 
including areas of agreement or when the staff has comments or questions. Open meetings and 
technical exchanges between NRC and DOE provide additional opportunities to discuss issue 
resolution, identify areas of agreement and disagreement, and develop plans to resolve any 
disagreements. 
KTIs are subdivided into a number of subissues. For most subissues, the NRC staff has identified 
technical acceptance criteria that the NRC may use to evaluate the adequacy of information 
related to the KTIs. The NRC has also identified two cross-cutting programmatic criteria that 
apply to all IRSRs related to the implementation of the Quality Assurance Program and the use of

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expert elicitation. The following sections provide a summary level discussion of the KTIs by 
subissues (Section 4.2) and a discussion of the specific NRC acceptance criteria (Section 4.3). 
4.2 RELATIONSHIP OF THE UZ FLOW AND TRANSPORT PMR TO THE KTIS 
The UZ PMR provides technical analyses that relate to six of the KTIs and their associated 
IRSRs. Table 4.2-1 shows these KTIs and their subissues; subissues that relate directly to this 
PMR, hereafter referred to as the UZ PMR, are shown in italics. The KTIs and subissues that 
relate directly to the UZ PMR are discussed in the following sections. 
4.2.1 Evolution of the Near-Field Environment 
The near field is considered to be the part of the site for which changes in the physical and 
chemical properties (that result from construction of the underground facility or from heat 
generated by the emplaced radioactive waste) affect performance of the repository (NRC 1999a). 
Evolution of the near field is expected to include coupling of thermal, hydrological, and chemical 
(THC) processes that could affect parts of the mountain. These coupled processes could affect 
components of the natural and engineered barrier system (EBS) and thereby affect repository 
system performance. The introduction of repository construction material and waste package 
materials may also perturb the near-field environment. 
The resolution of each of the subissues of this KTI (see Table 4.2-1) must adequately address 
four aspects of coupled processes: 
 Identify the potential effects of coupled processes on performance 
 Determine how the natural system will influence, and be influenced by, coupled 
processes 
 Evaluate how the engineered materials will influence, and be influenced by, coupled 
processes 
 Determine the adequacy of any representation of the effects of coupled processes in 
performance assessment. 
Two of the subissues for the near-field environment KTI relate to the UZ PMR (see Table 4.2-1), 
as described in the following subsections. PMRs on the EBS, the near-field environment, and 
waste-form degradation also provide information relevant to the evolution of the near-field 
environment. 
4.2.1.1 Effects of Coupled THC Processes on Seepage and Flow 
The NRC notes that previous performance assessments have included limited analyses of the 
effects of coupled processes for the representation of seepage and groundwater flow (NRC 
1999a, p. 15). For example, coupled THC processes that affect seepage and flow were not 
explicitly addressed in the Total System Performance Assessment (TSPA) that was completed

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for the Viability Assessment (VA) (DOE 1998). There was no abstraction of the effect of coupled 
THC on seepage and flow and no corresponding sensitivity and uncertainty analysis to evaluate 
the need for additional data (NRC 1999a, p. 107). The NRC also notes that use of homogeneous 
hydrological properties in modeling coupled processes did not account for the spatial and 
temporal variability in fracture flow. 
Table 4.2-1. Issue Resolution Status Report/Key Technical Issues (IRSR/KTI) Related 
to the UZ PMR 
NRC Key Technical Issues Subissues 
Evolution of the Near-field 
Environment 
Coupled thermal-hydrological-chemical (THC) processes effects on 
seepage and flow 
Coupled THC effects on the waste package chemical environment 
Coupled THC effects on the chemical environment for radionuclide release 
Coupled THC processes effects on radionuclide transport 
Coupled THC processes effects on potential nuclear criticality in the near 
field 
Radionuclide Transport Radionuclide transport through porous rock 
Radionuclide transport through alluvium 
Radionuclide transport through fractured rock 
Nuclear criticality 
Structural Deformation and 
Seismicity 
Faulting 
Seismic hazard 
Fracturing and structural framework of the geologic setting 
Tectonics and crustal conditions 
Thermal Effects on Flow (TEF) Is DOEs thermal testing program, including performance confirmation, 
sufficient to evaluate the potential for thermal reflux to occur in the near 
field? 
Is DOEs thermal modeling approach sufficient to predict the nature and 
bounds of TEF in the near field? 
Does DOEs total system performance assessment (TSPA) adequately 
account for TEF? 
Total System Performance 
Assessment (TSPA) and 
Integration 
System Description and demonstration of multiple barriers 
Scenario analysis 
Model abstraction 
Demonstration of the Overall Performance Objection 
UZ and SZ Flow Under 
Isothermal Conditions 
Future climates 
Hydrological effects of climate change 
Shallow infiltration 
Deep percolation 
Saturated zone 
Matrix diffusion UZ/SZ 
NOTE: Italicized subissues are addressed in the UZ PMR 

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Analyses have been completed to evaluate the effects of various coupled processes on seepage 
into drifts, including coupled THC processes (see Section 3.10). A fully coupled drift-scale THC 
model has been developed. Simulations using this model show only very small changes in 
hydrological properties, suggesting that thermal-chemical effects on seepage do not need to be 
represented in the abstraction of seepage. 
4.2.1.2 Effects of Coupled THC Processes on Radionuclide Transport 
The evolution of the near-field environment influences two abstractions of UZ flow and transport 
processes that are important to this subissue. These are (1) the distribution of mass flux between 
fracture and matrix and (2) radionuclide retardation in fractures in the UZ. The NRC staff has no 
major concerns with DOEs analyses of the distribution of mass flux between fracture and matrix 
and retardation in fractures in the UZ (NRC 1999a, p. 140). 
Section 3.13 summarizes modeling studies of transport in the UZ (see Section 4.2.2). Note that 
current transport models do not take credit for retardation in fractures because of relatively rapid 
travel times and limited data on the details of fracture mineralogy. This approach is conservative. 
4.2.2 Radionuclide Transport 
The primary objective of the Radionuclide Transport KTI is to evaluate the processes that may 
affect radionuclide transport from the repository to the biosphere (NRC 1999b). Transport in the 
near-field environment is considered in the IRSR/KTI for evolution of the near-field environment 
(Section 4.2.1). The key elements of the Radionuclide Transport KTI are retardation of 
radionuclides in fractures and the matrix in the UZ and retardation in the saturated zone (NRC 
1999b, p. 5). The IRSR focuses on sorption and other chemical processes that affect transport 
and colloid-facilitated transport. Two mechanisms that can reduce radionuclide concentrations 
along flow paths, matrix diffusion and dilution, are evaluated separately in the IRSR/KTI for UZ 
and SZ Flow under Isothermal Conditions (Section 4.2.6). Resolution of the KTI for radionuclide 
transport requires adequate characterization of the physical and chemical processes that affect 
radionuclide transport (NRC 1999b, p. 3). 
Two of the subissues for this KTI relate to the UZ PMR, as described in the following 
subsections. The PMR on SZ flow and transport also provides information relevant to 
radionuclide transport. 
4.2.2.1 Radionuclide Transport through Porous Rock 
This subissue focuses on the extent to which radionuclides can sorb onto minerals in the porous 
matrix and filtration of colloidal and particulate contaminants (NRC 1999b, p. 3). It addresses 
physical transport processes, chemical processes, and heterogeneities (NRC 1999b, p. 12). Issues 
related to physical transport processes include the appropriate conceptual models for fracturematrix 
interaction, the range and dependencies of parameters associated with fracture-matrix 
interactions, the effects of both long and short term transient flow conditions, and the expected 
magnitude of lateral and longitudinal dispersion. Chemical issues include the appropriateness of 
the minimum Kd approach, the amount of sorption expected in fractures, and the contribution of

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colloids to radionuclide flux. Issues related to heterogeneities in the UZ include the spatial 
distribution of infiltration, areal variations in amounts and compositions of zeolites, and the 
appropriate scale of heterogeneities. 
The NRC indicates that methods proposed to treat sorption are generally acceptable (NRC 
1999b, p. 80). In some cases, particularly for neptunium, adequate investigations have been 
completed. Additional work may be needed, such as batch sorption experiments for a few 
radionuclides, crushed tuff and intact rock column experiments for some radionuclides, and 
analyses using theoretical models and experimental data to demonstrate that sorption coefficients 
are compatible with the range of geochemical conditions expected in the postclosure time-frame. 
This PMR documents the current representation of UZ transport (see Section 3.11). It includes 
the following improvements to the UZ Transport Model: 
 Enhancement of the UZ/EBS transport interface and refinement of the UZ grid between 
the repository and the water table 
 A matrix diffusion algorithm that recognizes finite fracture spacing effects and an 
improved model for colloid transport 
 Improved justification for the treatment of sorption, chain decay, radionuclide screening, 
and gas-phase radionuclide transport. 
Current modeling provides better justification for coupling with the EBS transport at the 
potential repository and SZ transport at the water table, with releases spread over a more realistic 
area compared to the VA analysis. The effects of repository heating have also been considered in 
the UZ transport model. The improved colloid transport model was developed in conjunction 
with modeling conducted for the Nevada Test Site (NTS) (Section 3.11), using data from the 
NTS to calibrate the colloid model. 
The issue of heterogeneity requires proper scaling from laboratory-derived parameters; this has 
been evaluated with respect to the Calico Hills vitric unit (Section 3.8). 
4.2.2.2 Radionuclide Transport through Fractured Rock 
This subissue evaluates radionuclide transport in fractured rock where there is a potential for 
preferential pathways for transport and limited radionuclide-rock interactions. For the UZ, 
important factors include percolation rate, partitioning of flow between fractures and matrix, and 
sorption coefficients (NRC 1999b, p. 11). Many of the process parameters considered in this 
subissue are the same as those identified for the subissue on radionuclide transport through 
porous rock (Section 4.2.2.1). The NRC notes that preliminary experiments suggest that some 
sorption does occur in fractures (NRC 1999b, p. 94). 
Current transport models (Section 3.11) do not take credit for retardation in fractures because of 
relatively rapid travel times and limited data on the details of fracture mineralogy. This is a 
conservative assumption.

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4.2.3 Structural Deformation and Seismicity 
The objective of this KTI is to evaluate the tectonic features, events, and processes (FEPs) that 
may affect performance of the potential repository (NRC 1999c). One of the subissues for this 
KTI relates to the UZ PMR. The PMR on disruptive events provides information relevant to the 
remaining subissues. 
4.2.3.1 Fracturing and Structural Framework of the Geologic Setting 
The NRC will evaluate alternative modeling approaches for distribution and properties of 
fractures that are consistent with current data and geologic understanding. They will review 
representations of fracture data and properties in the UZ models and their abstractions to evaluate 
the degree to which data on fracture variability are honored, the justification for excluding data, 
and the degree to which there is adequate integration of fracture data into the UZ models (NRC 
1999c, p. 51). 
The NRC did not consider the values assigned to fracture-continuum hydraulic properties in the 
TSPA-VA (DOE 1998) parameter sets justified by the distribution of apertures in the model-grid 
scale. They were concerned with the limited fracture characterization in key stratigraphic units in 
the UZ, the potential bias in ESF fracture measurements by the one-meter cut-off, and low-angle 
fractures not being properly represented (NRC 1999c, pp. 113114). Thus, uncertainties in the 
representation of fractures and their properties were not reasonably bounded. Data used in the 
abstractions were not representative, and alternative modeling approaches were not adequately 
considered (NRC 1999c, p. 117). The NRC also states that the assumption of spatial 
homogeneity in fracture distribution in the UZ is not supported by sufficient field evidence (NRC 
1999c, p. 107). 
Section 2.2 of the UZ PMR documents current data and analyses from ambient field testing in the 
ESF. These data and analyses provide an enhanced framework in which to refine the conceptual 
model of matrix and fracture processes in the UZ. Fracture property estimates are based on 
permeability data from in situ air-injection tests conducted in four surface boreholes and 
boreholes in alcoves of the ESF, porosity data from gas-tracer tests in boreholes in Alcove 5, and 
fracture mapping from the ESF, the ECRB, and surface boreholes. The YMP is considering 
reevaluating the decision to exclude small-scale data, although the impact on the mountain-scale 
and the drift-scale calibrated properties is not likely to be large. 
4.2.4 Thermal Effects on Flow (TEF) 
This KTI focuses on the estimation of temperature, moisture content, and humidity at the waste 
package surface and estimation of temperature and thermally driven water flux with respect to 
transport of radionuclides away from failed waste packages (NRC 1999d, p. 3). This includes 
evaluating the redistribution of moisture driven by heat that may result in periods of dryness in 
the potential repository and in channeling of moisture towards waste packages. The UZ PMR 
evaluates parameters and processes that are key to understanding the TH behavior of the potential 
repository, such as percolation flux, seepage into drifts, and the effect of coupled TH processes

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on seepage. Other technical concerns related to this KTI are addressed in the Near-Field 
Environment and EBS PMRs. 
Two of the KTI subissues apply to this PMR, as discussed in the following subsections. The 
PMRs on the near-field environment and the EBS provide additional information related to these 
subissues and the remaining subissues. 
4.2.4.1 Is DOEs Thermal Modeling Approach Sufficient to Predict the Nature and 
Bounds of TEF in the Near Field? 
This subissue addresses the ability of the DOEs TH process models to represent thermally 
driven flow in the near field. For example, these models should adequately account for the effects 
of heterogeneities in the models (including focused recharge) and discrete geologic features 
(NRC 1999d, pp. 6667). The models do not adequately account for the effects of spatially 
variable infiltration coupled with the effect of variable heat load at the repository edge, seepage 
into drifts, and capillary diversion (NRC 1999d, pp. 6870). 
As discussed in Section 4.2.1.1, analyses have been completed to evaluate the effects of various 
coupled processes on seepage into drifts, including coupled THC processes (see Section 3.10). 
Current analyses consider the effects of mineral dissolution and precipitation, CO2 exsolution 
and transport in the region surrounding the drift, the potential for forming zones of calcite, silica, 
or other minerals, the resulting changes to porosity, and permeability, and the potential effects on 
seepage. 
4.2.4.2 Does DOEs TSPA Adequately Account for TEF? 
This subissue addresses adequate representation of TH processes in the TSPA. Model abstraction 
should conservatively bound the predictions from the process models. Process models in TSPAVA 
do not adequately incorporate processes such as seepage into drifts under ambient conditions 
and refluxing into drifts during and after the thermal period (NRC 1999d, p. 77). When these 
processes have been adequately represented in the process models and abstraction, sensitivity 
analyses should be completed to assess the need for additional data with respect to TEF (NRC 
1999d, p. 78). 
The UZ PMR summarizes a systematic modeling study that evaluates the effects of TH processes 
in the UZ (Section 3.12). The model provides mountain-scale thermal response (based on 
infiltration rate), thermal load, numerical discretization, and the effects of ventilation. It 
simulates the potential impact of thermal perturbations from emplaced waste on the natural 
hydrological system, including a representation of heat-driven processes in the far field. 
The seepage abstraction has been enhanced to include additional effects, such as changes in drift 
shape, preferential pathways resulting from degraded rock bolts, and focusing of flow. THC 
processes have been found to have little effect on seepage (Section 3.10.12).

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4.2.5 TSPA and Integration 
The objective of this KTI is to describe an acceptable methodology for conducting performance 
assessments of repository performance and using these assessments to demonstrate compliance 
with the overall performance objective and requirements for multiple barriers (NRC 2000, p.3). 
Three of the subissues for this KTI relate to the UZ PMR, as described in the following 
subsections. 
4.2.5.1 System Description and Demonstration of Multiple Barriers 
This subissue addresses the demonstration of multiple barriers. This includes the identification of 
natural and engineered barriers important to isolation, the capability of these barriers to isolate 
waste, and the identification of processes that may degrade the engineered barriers and thus 
adversely affect performance of the natural barriers (NRC 2000, p. 4). DOEs TSPA, including 
scenario analysis (Section 4.2.5.2), model abstractions (Section 4.2.5.3) and transparency and 
traceability (this section) will support the demonstration of multiple barriers (NRC 2000, p. 17). 
Specific technical acceptance criteria have not yet been developed for the demonstration of 
multiple barriers. 
This subissue also addresses the NRCs staff expectation on the contents of DOEs TSPA and 
supporting documents (NRC 2000, p. 4). It provides criteria to evaluate the transparency and 
traceability of the DOEs TSPA, of the identification and classification of features, events, and 
processes (FEPs), and of the abstractions for TSPA. Finally, this subissue focuses on the 
transparency, traceability and validity of data used to support TSPA and of code design and the 
flow of data in the TSPA (NRC 2000, pp. 10-17). 
With respect to transparency and traceability, the YMP is committed to improving the 
documentation of the technical analyses that support the TSPA. The development of this PMR, 
and the associated AMRs, focused on improving the transparency and traceability from initial 
data collection through the analysis and incorporation of data and analyses into the process model 
for UZ flow and transport to the abstraction of the process models for use in the TSPA. 
Attachment 1 to the UZ PMR summarizes the data used in the UZ PMR, including the major 
inputs and outputs with specific references to the technical data bases that store the data. Section 
1.3 summarizes the quality assurance status of data and software. 
4.2.5.2 Scenario Analysis 
This subissue focuses on the process of identifying, screening, and selecting FEPs for inclusion 
in the TSPA. FEPs that could affect future system performance are used to formulate scenarios. 
This includes construction of scenario classes, assignment of probabilities to scenario classes, 
and their incorporation into the TSPA. This is a key factor in ensuring the completeness of the 
TSPA (NRC 2000, p. 4). 
A systematic method was applied to identify and screen FEPs for UZ flow and transport 
phenomena. One hundred and fifteen FEPs have been identified and grouped into two broad 
categories of primary and secondary FEPs. The primary FEPs capture the issues associated with

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the secondary FEPs. The FEPs are further divided into included and excluded FEPs. 
Included FEPs are those directly represented in TSPA models and process models that support 
the TSPA. Analyses have focused on the identification and screening of FEPs; this work partially 
addresses this subissue (see Section 1.2.3). The construction and evaluation of scenario classes 
will be documented in TSPA-SR. 
4.2.5.3 Model Abstraction 
This subissue focuses on the information and technical approaches needed to develop defensible 
model abstractions and their integration into TSPA. The following aspects of model abstraction 
are addressed under this subissue: data used in the development of conceptual approaches or 
process models, the abstracted models, and estimates of system performance (NRC 2000, p. 4). 
Specifically, this subissue requires documentation of data used to develop conceptual or process 
models for model abstractions, verification of the consistency of the abstractions, and 
explanation of their integration (such as coupling and dependencies) into the TSPA. 
For each model abstraction for unsaturated zone flow and transport models, this PMR addresses 
the NRCs five general principles underlying the technical acceptance criteria: data and model 
justification, data uncertainty and verification, model uncertainty, model verification, and 
integration (NRC 2000, p. 32). The PMR summarizes: 1) data available to support the conceptual 
basis of process models and abstractions, 2) the basis for bounding assumptions and 
representations of uncertainties and parameter variabilities, 3) alternative conceptual models, 4) 
abstractions based on and consistent with the underlying process models, and 5) incorporation of 
design features, physical phenomena, and couplings and use of consistent assumptions 
throughout the abstraction process. To address consistency in assumptions, the AMRs that 
document assumptions have been subjected to interdisciplinary review to help ensure that 
assumptions are applied consistently to the extent practicable. In addition, the PMRs have been 
reviewed by a single team whose main objective was to identify inconsistencies among the 
PMRs. These measures provide confidence that consistent assumptions are used in the 
abstraction process, as appropriate. 
4.2.6 UZ and SZ Flow under Isothermal Conditions 
The main objective of this KTI is to evaluate all aspects of the ambient hydrological regime at 
Yucca Mountain that may adversely impact the performance of a potential repository (NRC 
1999e). Another objective is to assess the adequacy of the characterization of key hydrological 
processes and features at the site and in the region that may adversely affect performance. 
Four of the subissues for this KTI relate to the UZ PMR, as described in the following 
subsections. The PMR on SZ flow and transport provides information on the subissue for the SZ.

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4.2.6.1 Future Climates and Hydrological Effects on Climate Change: What Is the Likely 
Range of Future Climates at Yucca Mountain and What Are the Likely 
Hydrological Effects of Climate Change? 
The NRC considers all acceptance criteria for these subissues (NRC 1999e, pp. 170174) closed 
with the exception of the programmatic criterion on adequacy of the quality assurance program. 
This PMR summarizes improvements to the representation of future climate for the Yucca 
Mountain site since the VA. Section 3.5 provides a more defensible climate model that is focused 
on 10,000 years and includes upper- and lower-bound climate analogs as compared to TSPA-VA. 
4.2.6.2 Present-Day Shallow Infiltration: What Is the Estimated Amount and Spatial 
Distribution of Present-Day Shallow Infiltration? 
The NRC staff agrees with the use of multipliers of the mean annual infiltration (MAI) to 
incorporate the uncertainty of MAI estimates into the abstraction of the infiltration model (NRC 
1999e, p. 176). They note that the infiltration model does not account for surface runoff and 
shallow lateral flow, potentially impacting calculations of MAI. The NRC is also concerned that 
the methodology used to assign probabilities to the MAI multipliers is biased towards producing 
low values for the MAI. All other technical acceptance criteria are considered closed. 
The Infiltration Model (Section 3.5) has been refined to provide an improved surface water 
model and to enhance the ability to model future climate states by considering temperature 
dependence, vegetation dependence, and snow pack. These improvements provide a better 
representation of infiltration under future climates and a more defensible basis for the uncertainty 
in the Infiltration Model to address the NRC concerns. The methodology for assigning 
probabilities to the MAI multipliers has been enhanced to address the bias towards producing 
low values for the MAI. 
4.2.6.3 Deep Percolation: What Is the Estimated Amount and Spatial Distribution of 
Percolation through the Proposed Repository Horizon (Present Day and through 
the Period of Repository Performance)? 
The NRC has several concerns with respect to the representation of deep percolation in the UZ. 
The analyses do not provide a reasonable bound on the uncertainty in the distribution of UZ flow 
between fractures and the rock matrix (NRC 1999e, p. 181). In addition, fast-path contributions 
to flow are not adequately represented in the UZ Flow Model (NRC 1999e, p. 179). The effects 
of climate-induced change (temperature, soil, and vegetation) have not been addressed in 
defining the bounds on percolation flux and seepage. Uncertainty in flow paths below the 
repository needs to be addressed and incorporated into the TSPA. 
A new active fracture model for fracture-matrix interaction has been used to provide an improved 
theoretical basis for fracture-matrix interaction as compared to TSPA-VA (DOE 1998). The 
model describes gravity-dominated, nonequilibrium, preferential liquid-water flow through 
fractures, including a reduction factor for the interface area that conducts flow between fractures 
and matrix. As noted in Section 4.2.6.1, improvements have been made to the representation of 
climate states to address NRC concerns.

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The NRC is also concerned that the drift-scale seepage model in the VA did not incorporate 
several potentially important processes, such as multiple scales of heterogeneity in the hydraulic 
properties around the drift, modifications to drift geometry from rock fall, thermally induced 
geochemical changes, and episodic percolation flux (NRC 1999e, p. 180). This PMR summarizes 
the current seepage model (Section 3.9). This model has been enhanced to incorporate data from 
niche testing, establish a range of flux values for the upper boundary of the model, and provide a 
simplified representation of partial collapse of a drift. The model evaluates drift seepage under 
long-term, steady-state, and episodic conditions for a range of parameters and conditions. 
Alternative models of flow and transport around and through the perched water beneath the 
repository have been analyzed (Section 3.7). 
4.2.6.4 Matrix Diffusion: To what Degree Does Matrix Diffusion Occur in the UZ and SZ? 
If the DOE takes credit for matrix diffusion in the UZ, then the NRC will expect predictions of 
transport to be consistent with geochemical and isotopic data for the site (NRC 1999e, p. 191). 
The NRC is concerned about the application of matrix diffusion in the residence-time transfer 
function (RTTF) approach to modeling transport. This approach has a bias towards predicting 
faster diffusion from fractures into the matrix. If matrix diffusion is incorporated into UZ 
transport models, the DOE should (NRC 1999e, p. 192): 
 Implement small-scale discrete-fracture models to verify the RTTF approach 
 Scale the assumed value for the matrix diffusion coefficient for radionuclide diffusion to 
account for diminished transport resulting from reduced matrix saturation and reduced 
fracture-matrix interface area. 
The UZ PMR summarizes the current approach to modeling matrix diffusion in the UZ. The 
former model for matrix diffusion was based on the assumption that fracture spacing is large 
relative to the average diffusion penetration depth from fractures into the matrix. The matrixdiffusion 
model has been enhanced to account for the effects of finite fracture spacing. UZ 
transport modeling assumes that the active fracture model appropriately accounts for reduced 
fracture-matrix interaction. The current model also assumes that effects of flow in the matrix are 
negligible with respect to exchange between fractures and matrix through matrix diffusion. 
4.3 NRC ACCEPTANCE CRITERIA 
Specific technical acceptance criteria for each subissue that relates to this PMR are summarized 
in Table 4.3-1, along with the approach to addressing the criteria and sections of the PMR that 
describe these approaches. 
The UZ PMR also addresses the NRCs programmatic criteria for quality assurance and the use 
of expert elicitation. These programmatic criteria apply to all subissues and are not repeated 
under each subissue in Table 4.3-1. 
The acceptance criteria for quality assurance addresses DOEs implementation of an adequate 
quality assurance program. The UZ PMR was developed in accordance with project procedures

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for documenting data, analyses, models, and/or computer codes and preparing and reviewing 
technical reports (see Section 1.3). The programmatic criterion for expert elicitation specifies that 
expert elicitation should be conducted in accordance with NUREG-1563 (Kotra et al. 1996) or 
other acceptable approaches. An expert elicitation on the UZ flow model was completed in 1997 
(see Section 1.2). This elicitation was conducted and documented following the NRC guidance 
on the use of expert elicitation (Kotra et al. 1996). No additional expert elicitations have been 
completed for the UZ PMR.

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Table 4.3-1. Issue Resolution Status Reports, Subissues, Technical Acceptance Criteria, and PMR Approach (NRC 1997, 1999ae, 2000) 
NRC Technical Acceptance Criteria PMR Approach and Section Reference 
IRSR: Evolution of the Near-field Environment 
Subissue 1 - Effects of coupled THC processes on seepage and flow 
Data and model justification acceptance criteria for Subissue 1 
1 - Available data relevant to both temporal and spatial variations in conditions 
affecting coupled THC effects on seepage and flow were considered. 
The TSPA-VA did not explicitly consider the effects of coupled THC processes; 
the evaluation of coupled THC effects is documented in this PMR. Attachment I 
summarizes available site data. Section 3.10 documents the abstraction of 
coupled THC effects for TSPA, based on the process modeling results 
presented in the same section. 
2 - DOE's evaluation of coupled THC processes properly considered site 
characteristics in establishing initial and boundary conditions for conceptual 
models and simulations of coupled processes that may affect seepage and 
flow. 
Attachment I summarizes available data. These data on the site characteristics 
were used to establish initial and boundary conditions for the evaluation of THC 
effects on seepage and flow in the near field (Section 3.10). 
3 - Sufficient data were collected on the characteristics of the natural system 
and engineered materials, such as the type, quantity, and reactivity of material, 
to establish initial and boundary conditions for conceptual models and 
simulations of THC coupled processes that affect seepage and flow. 
Attachment I summarizes available data. The THC model incorporates site data 
to establish initial and boundary conditions and incorporates specific aspects of 
the design, including in-drift geometry, drift spacing, and the TH properties of 
the components of the EBS, such as waste packages and invert (Section 3.10). 
The current design does not include concrete liners in the emplacement drifts 
limiting the potential effects of interactions between concrete and tuff on 
seepage and flow. 
4 - Sensitivity and uncertainty analyses (including consideration of alternative 
conceptual models) were used to determine whether additional new data are 
needed to better define ranges of input parameters. 
Sensitivity and uncertainty analyses will be included in TSPA-SR. 
5 - If the testing program for coupled THC processes on seepage and flow is 
not complete at the time of license application, or if sensitivity and uncertainty 
analyses indicate additional data are needed, DOE will identify specific plans to 
acquire the necessary information as part of the performance confirmation 
program. 
The performance confirmation plan addresses coupled THC effects on seepage 
and flow. Rock mass cooling response, coupled process testing, and seepage 
testing under heated environments are planned for the pre-emplacement 
period. Longer term testing for seepage and near-field THC testing and 
monitoring around selected emplacement drifts and under simulated 
postclosure conditions is also addressed (CRWMS M&O 2000c, Appendix G). 
Data uncertainty and verification acceptance criteria for Subissue 1 
1 - Reasonable or conservative ranges of parameters or functional relations 
were used to determine effects of coupled THC processes on seepage and 
flow. Parameter values, assumed ranges, probability distributions, and 
bounding assumptions are technically defensible and reasonably account for 
uncertainties. 
The TSPA-VA did not explicitly consider the effects of coupled THC processes; 
the evaluation of the effects of coupled THC processes is documented in this 
PMR. Section 3.10.3 discusses ranges in the characteristics of the natural 
system that were used to evaluate the effects of THC processes on seepage 
and flow and the rationale for these ranges.

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Data uncertainty and verification acceptance criterion for Subissue 1, continued 
2 - Uncertainty in data due to both temporal and spatial variations in conditions 
affecting coupled THC effects on seepage and flow were considered. 
Section 3.10.6 discusses the uncertainty in data affecting THC coupled 
processes on seepage and flow. 
3 - DOEs evaluation of coupled THC processes properly considered the 
uncertainties in the characteristics of the natural system and engineered 
materials, such as type, quantity, and reactivity of material, in establishing initial 
and boundary conditions for conceptual models and simulations of THC 
coupled processes that affect seepage and flow. 
Section 3.10.6 discusses uncertainties in the characteristics of the natural 
system. Engineered materials are discussed in the PMR on the engineered 
barrier system. 
4 - The initial conditions, boundary conditions, and computational domain used 
in sensitivity analyses involving coupled THC effects on seepage and flow were 
consistent with available data. 
Sensitivity analyses will be included in TSPA-SR. 
5 - DOEs performance confirmation program should assess whether the 
natural system and engineered materials are functioning as intended and 
anticipated with regard to coupled THC effects on seepage and flow. 
The performance confirmation plan addresses coupled THC effects on seepage 
and flow. Rock mass cooling response, coupled process testing, and seepage 
testing under heated environments are planned for the pre-emplacement 
period. Longer term testing for seepage and near-field THC testing and 
monitoring around selected emplacement drifts and under simulated 
postclosure conditions is also addressed (CRWMS M&O 2000c, Appendix G). 
Model uncertainty acceptance criteria for Subissue 1 
1 - Appropriate models, tests, and analyses were used that are sensitive to the 
THC couplings under consideration for both natural and engineered systems, 
as described in the following examples. The natural setting data indicate 
processes that should be evaluated include: (i) zeolitization of volcanic glass, 
which could affect flow pathways; (ii) precipitation of calcite and opal on the 
footwall of fracture surfaces and the bottoms of lithophysal cavities, which 
indicates gravity-driven flow in open fractures that could affect permeability and 
porosity; and (iii) potential dehydration of zeolites and vitrophyre glass, which 
could release water affecting heat and fluid flow. The effects of THC coupled 
processes that may occur due to interactions with engineered materials or their 
alteration products include: (i) changes in water chemistry that may result from 
interactions between cementitious materials and groundwater, which, in turn, 
may affect seepage and flow; (ii) dissolution of the geologic barrier (e.g. tuff) by 
a hyperalkaline fluid that could lead to changes in the hydraulic properties of the 
geologic barrier; and (iii) precipitation of calcite or calcium-silica-hydrate phases 
along fracture surfaces as a result of migration of a hyperalkaline fluid that 
could affect hydraulic properties. 
Attachment I summarizes available site data. Section 3.10 summarizes data, 
analyses, and models that were used to evaluate THC processes on the natural 
system. The purpose of the THC seepage model is to evaluate the effects of 
THC processes in the rock around the emplacement drift on seepage water 
chemistry, gas-phase composition, and the potential effects of THC processes 
on UZ flow and transport. This model evaluates the effects of mineral 
dissolution and precipitation, the effects of CO2 exsolution and transport in the 
region surrounding the drift, the potential for forming zones of calcite, silica or 
other minerals, the resulting changes in porosity and permeability, and the 
potential effects on seepage. See also the PMR on the near field environment.

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2 - Given the current design of the repository, it will be acceptable to ignore the 
potential effects of microbial processes on seepage and flow. 
The DOE agrees that the potential effects of microbial processes on seepage 
and flow are not significant, given the current design (Section 1.2.3, Assumption 
3) (CRWMS M&O 2000, EBS PMR; CRWMS M&O 2000, WFD PMR). 
Model uncertainty acceptance criteria for Subissue 1, continued 
3 - Alternative modeling approaches consistent with available data and current 
scientific understanding were investigated, and their results and limitations were 
appropriately considered. 
Section 3.10.7 addresses the alternative conceptual model proposed by 
Matyskiela (1997). 
4 - DOE provided a reasonable description of the mathematical models 
included in its analyses of coupled effects on seepage and flow. The 
description should include a discussion of alternative modeling approaches not 
considered its final analysis and the limitations and uncertainties of the chosen 
model. 
Section 3.10 summarizes the mathematical models used; an alternative 
conceptual model is discussed in Section 3.10.7. 
Model verification acceptance criteria for Subissue 1 
1 -The mathematical models for coupled THC effects on seepage and flow are 
consistent with conceptual models based on inferences about near-field 
environment, field data and natural alteration observed at the site, and expected 
engineered materials. 
Section 3.10 summarizes the mathematical models used to evaluate coupled 
THC effects on seepage and flow. 
2 - DOE appropriately adopted accepted and well-documented procedures to 
construct and test the numerical models used to simulate coupled THC effects 
on seepage and flow. 
Procedures were followed, consistent with the governing quality assurance 
requirements (see Chapter 1). 
3 - Abstracted models for coupled THC effects on seepage and flow were 
based on the same assumptions and approximations shown to be appropriate 
for closely analogous natural or experimental systems. Abstracted model 
results were verified through comparison to outputs of detailed process models 
and empirical observations. Abstracted model results are compared with 
different mathematical models to judge robustness of results. 
Abstractions in Section 3.10 were derived from the underlying process models 
described in the UZ PMR. 
Integration acceptance criteria for Subissue 1 
1 - DOE has considered all the relevant features, events, and processes. The 
abstracted models adequately incorporated design features, physical 
phenomena, and couplings, and used consistent and appropriate assumptions 
throughout. 
Section 1.2.3 discusses the relevant features, processes and events. Included 
FEPS are directly represented in the process models and abstractions that 
support TSPA and discussed in other sections of the PMR corresponding to the 
specific models. 
2 - Models reasonably accounted for known temporal and spatial variations in 
conditions affecting coupled THC effects on seepage and flow. 
Section 3.10 summarizes the parameter ranges used in the THC model and 
provides a rationale for these ranges. Section 3.10.4 describes the process of 
validating the THC model with results from the drift scale test.

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Integration acceptance criteria for Subissue 1, continued 
3 - Not all THC couplings may be determined to be important to performance, 
and DOE may adopt assumptions to simplify PA analyses. If potentially 
important couplings are neglected, DOE should provide a technical basis for 
doing so. The technical basis could include activities, such as independent 
modeling, laboratory or field data, or sensitivity studies. 
The DOE agrees that simplifying assumptions may be appropriate if not all the 
THC couplings are determined to be important to performance and will provide 
the technical basis for the simplifying assumptions. 
4 - Where simplifications for modeling coupled THC effects on seepage and 
flow were used for PA analyses instead of detailed process models, the bases 
used for modeling assumptions and approximations were documents and 
justified. 
Section 3.10 11 documents the basis for the abstraction of coupled THC effects 
on seepage and flow. 
Subissue 2 - Waste package chemical environment ( Waste Package Degradation PMR) 
Subissue 3 - Effects of THC processes on the chemical environment for radionuclide release 
(Waste Form /Engineered Barrier System PMRs) 
Subissue 4 - Effects of coupled THC processes on the radionuclide transport through engineered and natural barriers 
Data and model justification acceptance criteria for Subissue 4 
1 - Available data relevant to both temporal and spatial variations in conditions 
affecting coupled THC effects on transport of radionuclides in the near field 
were considered. 
The TSPA-VA did not explicitly consider the effects of coupled THC processes; 
the evaluation of coupled THC effects are documented in this PMR. Attachment 
I summarizes available data; Section 3.10 describes how relevant data were 
incorporated into the modeling. 
2 - DOE's evaluation of coupled THC processes properly considered site 
characteristics in establishing initial and boundary conditions for conceptual 
models and simulations of coupled processes that may affect radionuclide 
transport in the near field. 
The evaluation of coupled THC processes in Section 3.10 considered site 
characteristics in establishing initial and boundary conditions for conceptual 
models and simulation of coupled processes. See also the PMRs on near field 
environment and EBS. 
3 - Sufficient data were collected on the characteristics of natural system and 
engineered materials, such as the type, quantity, and reactivity of material, in 
establishing initial and boundary conditions for conceptual models and 
simulations of THC coupled processes that affect transport of radionuclides in 
the near field. 
Attachment I summarizes available site data. The THC model incorporates site 
data to establish initial and boundary conditions and incorporates specific 
aspects of the design, including in-drift geometry, drift spacing, and the TH 
properties of the components of the EBS, such as waste packages and invert 
(Section 3.10). The current design does not include concrete liners in the 
emplacement drifts limiting the potential effects of interactions between 
concrete and tuff on seepage and flow (CRWMS M&O 2000, EBS PMR; 
CRWMS M&O 2000, WFD PMR). 
4 - A nutrient and energy inventory calculation should be used to determine the 
potential for microbial activity that could adversely affect radionuclide transport 
through engineered and natural barriers. 
The potential effects of microbial processes on transport away from a drift are 
not considered significant, given the current design (Section 1.2.3, Assumption 
3). See the PMRs on the engineered barrier system and waste form.

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Data and model justification acceptance criteria for Subissue 4, continued 
5 - Should microbial activity be sufficient to allow microbial effects on transport 
of radionuclides through engineered and natural barriers, then the time-history 
of temperature, humidity, and water saturation in engineered and natural 
materials should be used to constrain the probability for these effects. 
See the PMRs on the engineered barrier system and waste form. 
6 - Sensitivity and uncertainty analyses (including consideration of alternative 
conceptual models) were used to determine whether additional new data are 
needed to better define ranges of input parameters. 
Sensitivity and uncertainty analyses will be included in TSPA-SR. 
7 - If the testing program for coupled THC processes on the chemical 
environment for radionuclide release from the engineered barrier system is not 
complete at the time of license application, or if sensitivity and uncertainty 
analyses indicate additional data are needed, DOE has identified specific plans 
to acquire the necessary information as part of the performance confirmation 
program. 
Although THC effects on radionuclide transport have been determined not to be 
important to performance, the performance confirmation plan contains testing 
during the pre-emplacement period to confirm this assumption (CRWMS M&O 
2000c, Appendix G). 
Data uncertainty and verification acceptance criteria for Subissue 4 
1 - Reasonable or conservative ranges of parameters or functional relations 
were used to determine effects of coupled THC processes on transport of 
radionuclides in the near field. Parameter values, assumed ranges, probability 
distributions, and bounding assumptions are technically defensible and 
reasonably account for uncertainties. 
The TSPA-VA did not explicitly consider the effects of THC processes; the 
evaluation of coupled THC effects is documented in this PMR. Attachment 1 
summarizes available site data. Section 3.10 discusses the range of 
parameters in the characteristics of the natural system that were used to 
evaluate the effects of coupled processes along with the rationale for the range 
of parameters. 
2 - Uncertainty in data due to both temporal and spatial variations in conditions 
affecting coupled THC effects on radionuclide transport in the near field were 
considered. 
Section 3.10.6 discusses uncertainties in data due to temporal and spatial 
variations in conditions affecting THC processes. 
3 - DOEs evaluation of coupled THC processes properly considered the 
uncertainties in the characteristics of the natural system and engineered 
materials, such as type, quantity, and reactivity of material, in establishing initial 
and boundary conditions for conceptual models and simulations of THC 
coupled processes that affect transport of radionuclides in the near field. 
Section 3.10.6 discusses uncertainties in the characteristics of the natural 
system. See also the PMR on the engineered barrier system. 
4 - The initial conditions, boundary conditions, and computational domain used 
in sensitivity analyses involving coupled THC effects on radionuclide transport 
in the near field were consistent with available data. 
Sensitivity analyses will be included in the TSPA-SR. 
5 - DOEs performance confirmation program should assess whether the 
natural system and engineered materials are functioning as intended and 
anticipated with regard to coupled THC effects on transport of radionuclides in 
the near field. 
Although THC effects on radionuclide transport have been determined not to be 
important to performance, the performance confirmation plan contains testing 
during the pre-emplacement period to confirm this assumption (CRWMS M&O 
2000c, Appendix G).

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Model uncertainty acceptance criteria for Subissue 4 
1 - Appropriate models, tests, and analyses were used that are sensitive to the 
THC couplings under consideration for both natural and engineered systems, 
as described in the following examples. The effects of THC coupled processes 
that may occur in the natural setting or due to interactions with engineered 
materials or their alteration products include: (I) TH effects on gas and water 
chemistry in the unsaturated zone and saturated zone; (ii) precipitation of 
calcite and opal on the footwall of fracture surfaces and the bottoms of 
lithophysal cavities, which indicates gravity-driven flow in open fractures, and 
isolation of transport pathways from sorption sites in the rock matrix; (iii) 
zeolitization of volcanic glass, that could affect transport pathways; (iv) 
precipitation and dissolution of oxides and hydroxides on fracture surfaces, 
illitization of smectite, and recrystalization of zeolites to analcime, which could 
affect sorption characteristics; (v) effects of microbial processes; (vi) effects of 
corrosion products of container materials and waste forms on transport of 
radionuclides in the near field; and (vii) changes in hydraulic and sorptive 
properties of the natural system resulting from interactions between 
cementitious materials and groundwater. 
Attachment I summarizes available site data. Section 3.10 summarizes data, 
analyses, and models that were used to evaluate THC processes on the natural 
system. The purpose of the THC seepage model is to evaluate the effects of 
THC processes in the rock around the emplacement drift on seepage water 
chemistry, gas-phase composition, and the potential effects of THC processes 
on UZ flow and transport. This model evaluates the effects of mineral 
dissolution and precipitation, the effects of CO2 exsolution and transport in the 
region surrounding the drift, the potential for forming zones of calcite, silica or 
other minerals, the resulting changes in porosity and permeability, and the 
potential effects on seepage. See also the PMR on the near field environment. 
2 - Alternative modeling approaches consistent with available data and current 
scientific understanding were investigated, and their results and limitations were 
appropriately considered. 
Section 3.10.7 addresses the alternative conceptual model proposed by 
Matyskiela (1997). 
3 - DOE provided a reasonable description of the mathematical models 
included in its analyses of coupled effects on radionuclide transport in the near 
field. The description should include a discussion of alternative modeling 
approaches not considered its final analysis and the limitations and 
uncertainties of the chosen model. 
Section 3.10 summarizes the relevant mathematical models. 
Model verification acceptance criteria for Subissue 4 
1 - The mathematical models for coupled THC effects on radionuclide transport 
in the near field are consistent with conceptual models based on inferences 
about near-field environment, field data and natural alteration observed at the 
site, and expected engineered materials. 
Section 3.10 summarizes the basis for the mathematical models used to 
evaluate coupled THC effects. 
2 - DOE appropriately adopted accepted and well-documented procedures to 
construct and test the numerical models used to simulate coupled THC effects 
on transport of radionuclides in the near field. 
Procedures were followed, consistent with the governing quality assurance 
requirements (See Section 1).

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Model verification acceptance criteria for Subissue 4, continued 
3 - Abstracted models for coupled THC effects on radionuclide transport in the 
near field were based on the same assumptions and approximations shown to 
be appropriate for closely analogous natural or experimental systems. 
Abstracted model results were verified through comparison to outputs of 
detailed process models and empirical observations. Abstracted model results 
are compared with different mathematical models to judge robustness of 
results. 
Thermal effects on flow were not found to be significant and will not be included 
in UZ transport simulations for TSPA-SR (Sections 3.11.1.3, 3.11.2, and 5.2.4). 
Integration acceptance criteria for Subissue 4 
1 - DOE has considered all the relevant features, events, and processes. The 
abstracted models adequately incorporated design features, physical 
phenomena, and couplings, and used consistent and appropriate assumptions 
throughout. 
Section 1.2.3 discusses the relevant features, processes and events. Included 
FEPs are directly represented in the process models and abstractions that 
support TSPA and are discussed in sections of the PMR corresponding to the 
specific models. 
2 - Models reasonably accounted for known temporal and spatial variations in 
conditions affecting coupled THC effects on transport of radionuclides in the 
near field. 
Section 3.10 discusses temporal and spatial variations in conditions affecting 
THC effects. 
3 - Not all THC couplings may be determined to be important to performance, 
and DOE may adopt assumptions to simplify PA analyses. If potentially 
important couplings are neglected, DOE should provide a technical basis for 
doing so. The technical bases could include activities, such as independent 
modeling, laboratory or field data, or sensitivity studies. 
The DOE agrees that simplifying assumptions may be appropriate if not all the 
THC couplings are determined to be important to performance and will provide 
the technical basis for the simplifying assumptions. 
4 - The bases used for modeling assumptions and approximations were 
documented and justified, where simplifications for modeling coupled THC 
effects on radionuclide transport in the near field were used for performance 
assessment analyses instead of detailed process models. 
In general, the PMR documents the basis for modeling assumptions and 
approximations in the specific sections addressing the UZ flow and transport 
models. Also see Assumption 4 in Section 1.2.3. 
Subissue 5 - Coupled THC processes affecting potential nuclear criticality in the near field 
(covered in a topical report and supporting documents) 
IRSR: Radionuclide Transport 
Subissue 1 - Estimation of radionuclide transport through porous rock 
1 - For the estimation of radionuclide transport through porous rock DOE has: 
1.a - Determined, through PA calculations, whether radionuclide attenuation 
process such as sorption, precipitation, radioactive decay, and colloidal filtration 
are important to performance. 
Section 3.11.2 evaluates the effect of processes such as hydrodynamic 
dispersion, matrix diffusion, sorption (solutes), filtration (colloids), and 
radioactive decay. These processes are considered important to performance 
and are all explicitly modeled in the transport model abstraction (3.11.12).

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Subissue 1 - Estimation of radionuclide transport through porous rock, continued 
1.b - (i) Assumed Kd is zero and radionuclides travel at the rate of groundwater 
flow, if it has been found that radionuclide attenuation is unimportant to 
performance and it can be demonstrated that this assumption is conservative, 
in which case Acceptance Criteria 2 and 3 do not have to be met, or (ii) 
demonstrated that Criterion 2 or 3 has been met, if radionuclide attenuation in 
porous rock is important to performance, or if an assumption that K is zero in 
porous rock is not conservative 
This PMR uses an assumed Kd of zero, therefore acceptance criteria 2 and 3 
need to be evaluated. 
2 - For the valid application of the constant Kd approach, using equation (1) Rf 
=1 + .bKd/n, DOE has: 
2.a - Demonstrated that the flow path acts as a single continuum porous 
medium. If the flow can not be shown to be a single continuum porous medium, 
then the Acceptance Criteria for radionuclide transport in fractured rock apply. 
Section 3.4 summarizes numerical approaches for modeling UZ hydrology; 
transport modeling is based on the UZ flow model summarized in Section 3.7.2. 
2.b - Demonstrated that appropriate values for the parameters. Kd, n or ., and 
.b have been adequately considered (e.g., experimentally determined or 
measured). 
Details of the experimental program are provided in the Yucca Mountain Site 
Description. 
2.c - Demonstrated that the three implicit assumptions (i.e. linear isotherm, fast 
reversible sorption reaction, and constant bulk chemistry) are valid. 
Section 3.11 discusses these assumptions; the AMR on radionuclide transport 
models under ambient conditions provides the supporting rationale. 
3 - For the valid application of process models affecting radionuclide transport 
such as surface complexation, ion exchange, precipitation/dissolution, and 
processes involving colloidal material 
3.a - Demonstrated that the flow path acts as a single-continuum porous 
medium. See Subissue 4, page 312 of this PMR. 
Transport modeling is based on the UZ flow models discussed in Section 3.7. 
3.b - Demonstrated that values for the parameters used in process models are 
appropriate and sufficient. 
Transport parameters are summarized in Section 3.11.2. 
3.c - (i) Demonstrated that the three implicit assumptions (see 2c) are valid, if 
process models are intended to yield a constant Kd for use in the retardation 
equation (equation 1); or (ii) determined transport in a dynamic reactive 
transport system mode (e.g., PHREEQC, MULTIFLO, HYDROGEOCHEM, 
etc.). 
See 2 c) above. 
Subissue 2 - For the estimation of radionuclide transport through alluvium 
(covered in Saturated Zone Flow and Transport PMR) 
Subissue 3 - Radionuclide transport through fractured rock 
1 - For estimation of radionuclide transport through fractured rock, DOE has 
continued

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1a - Determined, through PA calculations, whether radionuclide attenuation 
processes such as sorption, precipitation, and radioactive decay, and colloidal 
transport are important to performance. 
Section 3.11 summarizes attenuation processes, such as sorption, precipitation, 
radioactive decay, and colloidal transport. These processes are considered 
important to performance. 
1b - Assumed Kd (or Ka) is zero and that radionuclides travel at the velocity of 
groundwater flow through fractures, if it has been found that radionuclide 
attenuation in fractures is unimportant to performance, and it can be 
demonstrated that this assumption is conservative. In this case, Acceptance 
Criterion 2 does not have to be met. 
There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption. 
1c - Justified the length of flow path to which these fracture transport conditions 
apply 
There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption (Section 3.11.10.2.). 
2 - If credit is taken for radionuclide attenuation in fractured rock, DOE has: There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption (Section 3.11.10.2.). 
2a - Demonstrated capability to predict breakthrough curves or reactive, 
nonreactive, and colloidal tracers in field tests. 
There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption (Section 3.11.10.2.). 
2b - Demonstrated nonradioactive tracers used in field tests are appropriate 
homologues for radioelements. 
There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption (Section 3.11.10.2.). 
2c - Justified the length of flowpath to which these fracture transport conditions 
apply. 
There is limited information on sorption onto the fracture surfaces, which will 
retard migration of sorbing radionuclides. However, sorption in the fractures is 
neglected in the PA transport evaluations because of limited data and the 
conservative nature of the assumption (Section 3.11.10.2.). 
Subissue 4 - Nuclear criticality in the far field 
(covered in a topical report and supporting documents) 
IRSR: Structural Deformation and Seismicity 
Subissue 1 - Fault displacement hazard (covered in Disruptive Events PMR) 
Subissue 2 - Seismic hazard (covered in Disruptive Events PMR)

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Subissue 3 - Fracturing and structural framework of the geologic setting 
1 - Data and model justification: Adequate field, borehole, and underground 
excavation data are acquired to sufficiently support conceptual models, 
assumptions, and boundary conditions of numerical abstractions of fracture 
data and fracture models of ambient and perturbed conditions. 
This information is provided in the Yucca Mountain Site Description. 
Attachment I summarizes data on the properties of fractures. Fracture property 
estimates are based on permeability data from in situ air injection tests 
conducted in four surface boreholes and boreholes in alcoves in the ESF, 
porosity data from gas tracer tests in boreholes in Alcove 5, and fracture 
mapping from the ESF, ECRB, and surface based boreholes (Section 3.6.3.2). 
2 - Data and uncertainty verification: Parameter values, assumed ranges, 
probability distributions, and bounding assumptions used to determine fracture 
distributions and properties reasonably account for uncertainties and 
variabilities. 
See above. Small-scale fracture data from detailed line surveys have become 
available since the analysis in this PMR was performed. Although the impact of 
small-scale fracture data on mountain-scale and drift-scale calibrated properties 
is not likely to be large, the impact will be evaluated in the future (Section 
3.6.3.2). 
3 - Model uncertainty: Alternative modeling approaches for fracture distribution 
and properties of fractures consistent with available data and current geologic 
understanding are investigated and results and limitations are appropriately 
considered in process, TSPA, or both models of ambient and perturbed 
repository conditions 
Physical processes, including a discussion of the fracture and matrix flow 
component for each major unit, are discussed in Section 3.3. Alternative 
numerical approaches for modeling are summarized in section 3.4. The 
representation of fractures in the UZ model is discussed in Section 3.7. Section 
3.7.3.2 analyzes the effects of major faults on UZ flow. The results indicate that 
faults serve as major focusing conduits for downward liquid flow in the UZ. 
For the seepage model (Section 3.9.) model calibration is used to determine the 
effective parameters, including potential effects of individual fractures and 
microfractures on seepage. Simulations with multiple realizations of a 
heterogeneous property field are completed to account for the random nature of 
the fracture field. 
4 - Model verification: Results of fracture data analyses and fracture models are 
verified by comparison with output of sensitivity studies, detailed process level 
models, natural analogs, and empirical observations, as appropriate. 
Physical processes, including a discussion of fracture and matrix flow 
component for each major unit, are discussed in Section 3.3. 
The representation of fractures in the UZ model is discussed in Section 3.7. 
5 - Integration: Results of abstractions of fracture data are consistent with 
physical and geological phenomena and coupled processes. 
Abstractions are based on available site fracture characteristics (Section 3.7). 
Subissue 4 - Tectonic framework of the geologic setting 
(covered in Disruptive Events PMR and the Yucca Mountain Site Description) 
IRSR: Thermal Effects on flow 
Subissue 1 - Is the U.S. Department of Energy TH testing program, including performance confirmation testing, sufficient to evaluate the potential for 
thermal reflux to occur in the near field? 
(covered in Near Field Environment PMR)

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Subissue 2 - Is the thermohydrologic modeling approach sufficient to predict the nature and 
bounds of thermal effects on flow in the near field? 
1 - Sufficient data are available to adequately define relevant parameters, 
parameter values, and conceptual models. Demonstrate that: 
1.1 - Uncertainties and variabilities in parameter values are accounted for using 
defensible methods. The technical bases for parameter ranges, probability 
distributions or bounding values used are provided. Parameter values (single 
values, ranges, probability distributions, or bounding values) are derived from 
site-specific data or an analysis is included to show the assumed parameter 
values lead to a conservative effect on performance. 
Section 3.10 summarizes the parameter ranges and the technical basis for 
these ranges. Parameter values derived from site data are specified. 
1.1.- Analyses are consistent with site characteristics in establishing initial 
conditions, boundary conditions, and computational domains for conceptual 
models evaluated. 
Analyses in Section 3.10 considered site characteristics in establishing initial 
conditions, boundary conditions, and computational domains. In addition to the 
required UZ hydrologic properties, the model includes initial and boundary 
water and gas chemistry, initial mineralogy, mineral volume fractions, reactive 
surface areas, equilibrium thermodynamic data for minerals, aqueous and 
gaseous species, kinetic data for mineral-water reactions, and diffusion 
coefficients for aqueous and gaseous species (Section 3.10.2). 
2 - Descriptions of process-level conceptual and mathematical models used in 
the analyses are reasonably complete. Demonstrate that: 
2.1 - Models are based on well-accepted principles of heat and mass transfer 
applicable to unsaturated geologic media. 
Sections 3.10 and 3.12 summarize TH models that are based on accepted 
principles of heat and mass transfer. 
2.2 - Models include, at a minimum, the processes of evaporation and 
condensation and the effects of discrete geologic features. 
Current models (Section 3.10.2) include processes of evaporation and 
condensation. Figure 3.10-2 shows schematically the relationships between TH 
and geochemical processes in zones of boiling, condensation, and drainage in 
the rock mass outside of the drift and above the heat source. Seepage models 
(Section 3.9) now include an active fracture model to describe fracture-matrix 
interactions.

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Subissue 2 - Is the thermohydrologic modeling approach sufficient to predict the nature and 
bounds of thermal effects on flow in the near field?, continued 
2.3 - Models include, at a minimum, an evaluation of important 
thermohydrological phenomena, such as: (I) multidrift dry-out zone 
coalescence, (ii) lateral movement of condensate, (iii) cold-trap effect, (iv) 
repository edge effects, and (v) condensate drainage through fractures. 
The current design has a lower thermal load that the VA design to eliminate 
dryout zone coalescence. Section 3.10 evaluates the extent of the dryout zone 
and time of rewetting for different calibrated property sets and climate 
scenarios. 
Section 3.12 summarizes TH mountain scale models of the effects of 
temperature changes over the mountain, including effects on flow around the 
drift. 
2.4 - Models include all significant repository design features. Sections 3.10 and 3.12 summarize the design features included in the TH 
model. For example, the THC model uses in-drift geometry and drift spacing, 
and the thermal and hydrologic properties of the EBS components, such as 
waste package and invert, from the current design. 
2.5 - Models are capable of accommodating variation in infiltration. The TH model incorporates variation in infiltration (Sections 3.10 and 3.12). 
2.6 - Conceptual model uncertainties have been defined and documented and 
effects on conclusions regarding performance assessed. 
Sections 3.10 and 3.12 summarize conceptual uncertainties. 
2.7 - Mathematical models are consistent with conceptual models, based on 
consideration of site characteristics. 
Sections 3.10 and 3.12 discuss mathematical models used to represent 
conceptual models and are based on site characteristics. 
2.8 - Alternative models and modeling approaches, which are consistent with 
available data and current scientific understanding, have been investigated, 
limitations defined, and results appropriately considered. 
Sections 3.10 .7 discusses an alternative model proposed by Matyskiela (1997). 
2.9 -Results from different mathematical models have been compared to judge 
robustness of results. 
Numerical approaches that can be used for unsaturated, fractured rock have 
been reviewed in the AMR on conceptual and numerical models for UZ flow and 
transport. 
2.10 - Models used to predict shedding around emplacement drifts are shown to 
contain an adequate level of heterogeneity in media properties. 
Sections 3.10 and 3.12 summarize the approach to evaluating heterogeneities 
in TH models. 
2.11 -TH models have been demonstrated to be appropriate for the temperature 
regime expected at the repository. 
TH models incorporated the anticipated thermal load for the current design 
(Sections 3.10 and 3.12). 
2.12. -Models include radiative heat transport unless it is shown that radioactive 
heat loss by a WP is not significant. 
TH models include radiative heat transfer at the drift scale (Section 3.10.5.1). 
2.13 - Models include the effect of ventilation particularly if ventilation could 
result in deposition or condensation of moisture on a WP surface. 
Effects of ventilation are included (Sections 3.10.5.1 and 3.12.1).

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Subissue 2 - Is the thermohydrologic modeling approach sufficient to predict the nature and 
bounds of thermal effects on flow in the near field?, continued 
2.14 - The media properties of a model contain an adequate level of 
heterogeneity so that mechanisms such as dripping are not neglected or 
misrepresented. 
The drift seepage model has been enhanced to account for heterogeneities 
(Section 3.9.3). 
2.15 - Drift wall representations in models contain sufficient physical detail so 
that processes predicted using a continuum model, such as capillary diversion, 
are appropriate for the geologic media at the proposed repository horizon. 
Models predicting seepage include partial drift collapse and multiple 
realizations of heterogeneous rock properties (Sections 3.9.3.4 and 3.9.4.5). 
See also the PMR on near field environment. 
2.16 - Physical mechanisms such as penetration of the boiling isotherm by flow 
down a fracture are not omitted from model predictions due to over 
simplification or the physical medium or the conceptual model. 
Section 3.9 summarizes the drift seepage models, including enhancements 
such as the evaluation of partial drift collapse and episodic percolation flux. 
Section 3.10 describes the seepage THC models. 
3 - Coupling of processes has been evaluated using a methodology in 
accordance with NUREG-1466 (Nataraja and Brandshaug, 1992) or other 
acceptable methodology. Coupled processes may be uncoupled, if it is shown 
that the uncoupled model results bound the predictions of the fully coupled 
model results. 
NUREG-1466 provides logical steps for the development of predictive models 
and their numerical representation of thermally induced TMHC behavior of the 
host rock. Models of coupled processes in Sections 3.10 and 3.12 present the 
current approach to modeling drift scale and mountain scale TH effects. The 
DOE agrees that coupled processes may be uncoupled if the models bound the 
effects of fully coupled processes. 
4 - The dimensionality of models, which include heterogeneity at appropriate 
scales and significant process couplings, may be reduced, if shown that the 
reduced dimension model bounds the predictions of the full dimension model. 
The DOE agrees with this approach, and has implemented a modeling 
approach with models of different dimensions and scales. See for example 
Section 3.10, Drift-Scale THC Processes and Models, and Section 3.12, 
Mountain-Scale TH Model. 
5 - Equivalent continuum models are acceptable for the rock matrix and small 
discrete features, if it can be demonstrated that water in small discrete features 
is in continuous hydraulic equilibrium with matrix water. Significant discrete 
features, such as fault zones, should be represented separately unless it can be 
shown that inclusion in the equivalent continuum model (ECM) produces a 
conservative effect on calculated overall performance. 
Section 3.10.3 summarizes the approach to modeling thermal-hydrologic 
processes. 
6 - Accepted and well-documented procedures have been adopted to construct 
and calibrate numerical models used. 
Procedures were followed, consistent with the governing quality assurance 
requirements (see Section 1). 
7 - Results of process-level models have been verified by demonstrated 
consistency with results/observations from field-scale, thermohydrologic tests. 
In particular, sufficient physical evidence should exist to support the conceptual 
models used to predict thermally driven flow in the near field. 
Process level models have been calibrated against field data and observations 
(Sections 3.9.4.5, 3.10.4, 3.12.4).

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Subissue 3: Does the DOEs TSPA adequately account for thermal effects on flow? 
1 - Abstractions of process-level models may be used if predictions from the 
abstracted model are shown to conservatively bound process-level predictions. 
In particular, DOE may use an abstracted model to predict water influx into an 
emplacement drift if the abstracted model is shown to bound process-level 
model predictions of the influx of water as liquid or vapor into an emplacement 
drift. 
Section 3.9 summarizes the abstraction of seepage into drifts. As noted in 
Section 3.9.6.3, distributions for the amount of seepage as a function of 
percolation flux are derived directly from process-model results and constrained 
by measurements of permeability around three niches in the ESF and 
calibration of seepage tests conducted in one niche in the ESF. 
2 - Sufficient data are available to adequately define relevant parameter values 
and conceptual models. Demonstrate that: 
2.1 - Uncertainties and variabilities in parameter values are accounted for using 
defensible methods. The technical bases for parameter ranges, probability 
distributions or bounding values used are provided. Parameter values (single 
values, ranges, probability distributions, or bounding values) are derived from 
site-specific data or an analysis is included to show the assumed parameter 
values lead to conservative effect on performance. 
The THC abstraction of the mean infiltration rate (with climate changes) 
includes both geochemical systems (full and calcite-silica-gypsum) considered 
in the THC process model (Section 3.10.11). 
2.2 - Analysis are consistent with site characteristics in establishing initial 
conditions, boundry conditions, and computational domains for conceptual 
models evaluated. 
Site characteristics have been considered in establishing initial conditions, 
boundary conditions, and computational domains (Sections 3.10 and 3.12). 
3 - Descriptions of conceptual and mathematical models used in DOEs TSPA 
are reasonably complete. 
3.1 - Performance affecting heat and mass transfer mechanisms, including 
processes observed in available thermohydrologic tests and experiments, have 
been identified and incorporated into the TSPA. Specifically, it is necessary to 
either demonstrate that liquid water will not reflux into the underground facility 
or incorporate refluxing water into the TSPA and bound the potential adverse 
effects of: (i) corrosion of the WP; (ii) accelerated transport of radionuclides; 
and (iii) alteration of hydraulic and transport pathways that result from refluxing 
water. 
Section 3.12 summarizes the evaluation of flow changes close to drifts and 
drainage in the pillars. 
3.2 - Significant Geologic Repository Operations Area underground facility 
design features, such as the addition of backfill of drip shields, that can result in 
changes in TSP have been identified and incorporated in to the TSPA. 
See the PMR for the engineered barrier system. 
3.3 - Conceptual model uncertainties have been defined and documented, and 
their effects on conclusions regarding TSP have been assessed. 
Section 3.12 summarizes the evaluation of flux into drifts during and after the 
thermal period. 
3.4 - Mathematical models are consistent with conceptual models, based on 
consideration of site characteristics. 
Modeling approaches for thermal effects are summarized in Sections 3.10 and 
3.12.

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3.5 - Alternative models and modeling approaches, consistent with available 
data and current scientific understanding, are investigated; limitations defined; 
and results appropriately considered. 
Alternative modeling approaches are discussed in Section 3.10.7. 
3.6 - Results from different mathematical models have been compared to judge 
robustness of results. 
Sensitivity analyses will be included in TSPA-SR. 
4 - Coupling of thermal processes has been evaluated using a methodology in 
accordance with NUREG-1466 (Nataraja and Brandshaug, 1992) or other 
acceptable methodology. Coupled processes may be uncoupled, if it is shown 
that the uncoupled model results bound the predictions of the fully-coupled 
model results. 
NUREG-1466 provides logical steps for the development of predictive models 
and their numerical representation of thermally induced THMC behavior of the 
host rock. Sections 3.10 and 3.12 summarize the approach to evaluating 
coupled processes at the drift-scale and mountain-scale. The DOE agrees that 
coupled processes may be uncoupled if the models bound the effects of fully 
coupled processes. 
5 - The dimensionality of models used to assess the importance of refluxing 
water on repository performance may be reduced if it is shown that the reduced 
dimension model bounds the predictions of the full dimension model in 
performance. 
The DOE agrees with this approach. Section 3.4.2.4 summarizes studies of grid 
refinement; Section 3.12.2.2 summarizes numerical grids for TH simulations. 
6 - Results of the TSPA related to TEF have been verified by demonstrating 
consistency with results of process-level models. 
TSPA analyses related to TEF were based on the process level models. 
7 - Sensitivity and importance analyses were conducted to assess the need for 
additional data or information with respect to TEF. 
Sensitivity analyses will be included in TSPA-SR. 
IRSR: Total System Performance Assessment and Integration 
Subissue 1  System description and demonstration of multiple barriers 
Total system performance assessment documentation style, structure, and organization 
Does approach to document structure and organization will be acceptable if: 
1 - Documents and reports are complete, clear, and consistent. The UZ PMR was carefully structured to be complete, clear, and consistent. 
The review of the draft document included checks for completeness, clarity and 
consistency. 
2 - Information is amply cross-referenced The UZ PMR contains ample references to data sources, codes, assumptions, 
and conclusions. 
Features, Events, and Processes Identification and Screening 
1 - The screening process by which FEPs were included or excluded from the 
TSPA is fully described. 
Section 1.2.3 summarizes excluded and included FEPs along with the rationale 
for these decisions. 
2. Relationships between relevant FEPs are fully documented. Section 1.2.3 describes the relationship between primary and secondary FEPs 
based on the overlap that exists among the FEPs for UZ flow and transport.

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Abstraction Methodology 
1- The levels and method(s) of abstraction are described starting from 
assumptions defining the scope of the assessment down to assumptions 
concerning specific processes and the validity of given data. 
For each model in the UZ PMR, the relevant chapter summarizes the data used 
to construction the process model, the process model, and the abstraction of 
that model, if the model is abstracted for TSPA. 
2 - A mapping (e.g., a road map diagram, a traceability matrix, a crossreference 
matrix) is provided to show what conceptual features (e.g., patterns of 
volcanic events) and processes are represented in the abstracted models, and 
by what algorithms. 
The UZ PMR provides a sufficient basis for the decisions and assumptions that 
were made during the abstraction process. 
3 - An explicit discussion of uncertainty is provided to identify which issues and 
factors are of most concern or are key sources of disagreement among experts. 
The UZ PRM provides a discussion of uncertainties and limitations for the major 
process models included in the report. 
Data Use and Validity 
1 - The pedigree of data from laboratory tests, natural analogs, and the site is 
clearly identified. 
Section 1.3 summarizes the quality assurance status of the data and software 
used in the component models. 
2 - Input parameter development and basis for their selection is described. The UZ PMR discusses input parameter development and the basis for using 
the parameters. For example, Section 3.6 summarizes the development of UZ 
properties, model calibration, and the results. 
3 - A thorough description of the methods used to identify performance 
confirmation program parameters. 
The DOE is developing a plan that will define the performance confirmation 
program. Performance confirmation testing is not covered in this PMR. 
Assessment results 
1 - PA results (i.e., the peak expected annual dose within the compliance 
period) can be traced back to applicable analyses that identify the FEPs, 
assumptions, input parameters, and models in the PA. 
The TSPA-SR will summarize UZ flow and transport features, processes and 
the conceptual model, and their implementation into the TSPA. This discussion 
will be based on the UZ PMR. 
2 - The PA results include a presentation of intermediate results that provide 
insight into the assessment (e.g., results of intermediate calculations of the 
behavior of individual barriers). 
Intermediate results for PA are not discussed in the UZ PMR. The TSPA-SR is 
planned to include sensitivity analysis, including uncertainty importance 
analyses, one-off analyses, and robustness analyses. 
Code design and data flow 
1 - The flow of information (input and output) between the various modules is 
clearly described. 
The flow of information (input and output) is documented in accordance with QA 
procedures to ensure traceability. 
2 - Supporting documentation (e.g., users manuals, design documents) clearly 
describes code structure and relations between modules. 
The codes used in the UZ PMR were documented in accordance with software 
QA procedures that include requirements for appropriate documentation. 
Demonstration of multiple barriers (acceptance criteria have not been included in this revision of the IRSR).

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Subissue 2  Scenario Analysis 
Identification of an initial set of processes and events 
1 - DOE has identified a comprehensive list of processes and events that: (i) 
are present or might occur in the Yucca Mountain region and (ii) includes those 
processes and events that have the potential to influence repository 
performance. 
Section 1.2.3 discusses the relevant FEPs for unsaturated zone flow and 
transport. Included FEPs are directly represented in the process models and 
abstractions that support TSPA, and discussed in sections of the PMR 
corresponding to the specific models. 
Classification of Processes and events 
1 - DOE has provided adequate documentation identifying how its initial list of 
processes and events has been grouped into categories. 
Section 1.2.3 discusses the identification and categories of relevant FEPs for 
unsaturated zone flow and transport. 
2 - Categorization of processes and events is compatible with the use of 
categories during the screening of processes and events. 
Section 1.2.3 discusses categories of relevant FEPs for unsaturated zone flow 
and transport and their use. 
Subissue 2  Scenario Analysis, continued 
Screening of processes and events 
1 - Categories of processes and events that are not credible for the Yucca 
Mountain repository because of waste characteristics, repository design, or site 
characteristics are identified and sufficient justification is provided for DOE's 
conclusions. 
Sections 1.2.3 discusses excluded FEPs and the rationale for exclusion. The 
exclusion of FEPs from TSPA is based on arguments of low probability or low 
consequence. 
2 - The probability assigned to each category of processes and events not 
screened based on criterion T1 or criterion T2 is consistent with site 
information, well documented, and appropriately considers uncertainty. 
Section 1.2.3 provides the rationale for excluding FEPs. 
3 - DOE has demonstrated that processes and events screened from the PA on 
the basis of their probability of occurrence, have a probability of less than one 
chance in 10,000 years of occurring over 10,000 years. 
Section 1.2.3 provides the rationale for excluding FEPs. 
4 - DOE has demonstrated that categories of processes and events omitted 
from the PA on the basis that their omission would not significantly change the 
calculated expected annual dose, do not significantly change the calculated 
annual dose. 
Section 1.2.3 summarizes information on FEPs that are directly and the 
rationale for their exclusion. 
Formation of scenarios (covered in TSPA-SR) 
Screening of scenario classes (covered in TSPA-SR) 
Subissue 3 - Model abstraction 
Engineered barrier system 
Engineered barrier degradation (to be covered in the Waste Package Degradation PMR) 
Mechanical disruption of engineered barriers (to be covered in the Disruptive Events PMR) 
Quantity and quality of water contacting waste packages and waste forms

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1 - Sufficient data (field, laboratory, and/or natural analog data) are available to 
adequately define relevant parameters and conceptual models necessary for 
developing the quantity and chemistry of water contacting WPs and waste 
forms abstraction in TSPA. Where adequate data do not exist, other 
information sources such as expert elicitation have been appropriately 
incorporated into the TSPA. 
Section 3.9 summarizes the available data and conceptual models for seepage 
into drifts. 
2 - Parameter values, assumed ranges, probability distributions, and bounding 
assumptions used in the quantity and chemistry of water contacting WPs and 
waste forms abstraction, such as pH, chloride concentration, and amount of 
water flowing in and out of the breached WP, are technically defensible and 
reasonably account for uncertainties and variability. 
See the PMRs on waste package degradation and waste form. 
3 - Alternative modeling approaches consistent with available data and current 
scientific understanding are investigated and results and limitations 
appropriately factored into the quantity and chemistry of water contacting WPs 
and waste forms abstraction. 
See the PMRs on waste package degradation and waste form. 
4 - Output of quantity and chemistry of water contacting WPs and waste forms 
abstraction are verified through comparison to output of detailed process 
models and/or empirical observations (laboratory testing or natural analogs, or 
both). 
See the PMRs on waste package degradation and waste form. 
5 - Important design features, physical phenomena and couplings, and 
consistent and appropriate assumptions are incorporated into the mechanical 
disruption of WPs abstraction. 
See the PMR for waste package degradation. 
Radionuclide release rates and solubility limits (to be covered in Waste Form PMR) 
Geosphere 
Unsaturated zone flow and transport 
Spatial and temporal distribution of flow 
1 - Sufficient data (field, laboratory, and/or natural analog data) are available to 
adequately define relevant parameters and conceptual models necessary for 
developing the spatial and temporal distribution of flow abstraction in TSPA. 
Where adequate data do not exist, other information sources such as expert 
elicitation have been appropriately incorporated into the TSPA. 
Attachment I summarizes available data used to define relevant parameters 
and conceptual models. Section 3.7.5 summarizes the abstraction of flow fields 
for TSPA-SR. The UZ flow model forms the basis for the model that is 
abstracted for TSPA-SR.

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2 - Parameter values, assumed ranges, probability distributions, and/or 
bounding assumptions used in the spatial and temporal distribution of flow 
abstraction, such as the effects of climate change on infiltration, near surface 
influences (e.g., evapotranspiration and runoff) on infiltration, structural controls 
on the spatial distribution of deep percolation, and thermal reflux owing to 
repository heat load, are technically defensible and reasonably account for 
uncertainties and variabilities. 
Sections 3.7.2 through 3.7.4 summarize UZ flow models and Section 3.7.5 
summarizes the results of abstractions of UZ flow. The abstraction considers 
three infiltration cases (low, mean, and high) within each of the three climate 
states (present-day, monsoon, and glacial transition). For the abstraction of TH 
processes, only the mean infiltration cases were selected since the results of 
the low and high infiltration cases showed similar behavior in general. 
3 - Alternative modeling approaches consistent with available data and current 
scientific understanding are investigated and results and limitations 
appropriately factored into the spatial and temporal distribution of flow 
abstraction. 
Section 3.7.4 summarizes alternative conceptual models. 
4 - Spatial and temporal distribution of flow abstraction output is justified 
through comparison to output of detailed process models, and/or empirical 
observations (laboratory testing or natural analogs, or both). 
The abstraction of flow was based on detailed process models (Section 3.7.5). 
5 - Important design features, physical phenomena and couplings, and 
consistent and appropriate assumptions are incorporated into the spatial and 
temporal distribution of flow abstraction. 
The abstraction of UZ flow is summarized in Section 3.7.5. 
Flow paths in the unsaturated zone 
1 - Sufficient data (field, laboratory and/or natural analog data) are available to 
adequately define relevant parameters and conceptual models necessary for 
developing the distribution of mass flux between fracture and matrix in the 
abstraction in TSPA. Where adequate data cannot be readily obtained, other 
information such as expert elicitation or bounding values have been 
appropriately incorporated in the TSPA. 
Attachment I describes available data used to define relevant parameters and 
conceptual models. The abstraction in Section 3.7.5. was based on available 
data and conceptual models. 
2 - Parameter values, assumed ranges, probability distributions, and bounding 
assumptions used in the flow paths in the UZ in the abstraction, such as 
hydrologic properties, stratigraphy, and infiltration rate, are technically 
defensible and reasonably account for uncertainties and variability. 
Abstraction results are summarized in Section 3.7.5. The abstraction considers 
three infiltration cases (low, mean, and high) within each of the three climate 
states (present-day, monsoon, and glacial transition), based on the processmodel 
results. 
3 - Alternative modeling approaches consistent with available data and current 
scientific understanding are investigated and results and limitations 
appropriately factored into the distribution of mass flux between fracture and 
matrix in the abstraction. 
Abstraction results are summarized in Section 3.7.5.

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4 - Flow paths in the UZ abstraction output is verified through comparison to 
output of detailed flow process models, or empirical observations (laboratory 
testing or natural analogs, or both). 
The abstraction was based on detailed process models (Sections 3.7.2 through 
3.7.4). 
5 - Important design features, physical phenomena and couplings, and 
consistent and appropriate assumptions are incorporated into the flow paths in 
the UZ abstraction. 
The results of the abstraction are summarized in Section 3.7.5. 
Radionuclide transport in the unsaturated zone 
1 - Sufficient data (field, laboratory and/or natural analog data) are available to 
adequately define relevant parameters and conceptual models necessary for 
developing the RT in the UZ abstraction in TSPA. Where adequate data do not 
exist, other information sources such as expert elicitation have been 
appropriately incorporated in the TSPA. Alternatively. The parameters or 
models lacking sufficient data have been replaced by bounding parameter 
values. 
Section 3.11.3 summarizes the transport properties that are used for the 
abstraction of radionuclide transport in the UZ. The AMR on UZ and SZ 
transport properties provides additional detail on transport properties for the UZ. 
2 - Parameter values, assumed ranges, probability distributions, and bounding 
assumptions used in the RT in the UZ in the abstraction, such as sorption on 
fracture surfaces, and Kd for the matrix, are technically defensible and 
reasonably account for uncertainties and variability. 
Section 3.11.3 summarizes parameter values, ranges, distributions, and 
bounding assumptions for the abstraction of radionuclide transport, as 
applicable. 
3 - Alternative modeling approaches consistent with available data and current 
scientific understanding are investigated and results and limitations 
appropriately factored into the RT in the UZ abstraction. 
Section 3.11.9 summarizes an alternative conceptual model for transport in the 
UZ. 
4 - RT in the UZ abstraction output is justified through comparison to output of 
detailed process models, or empirical observations (laboratory testing or natural 
analogs, or both). 
The abstraction of radionuclide transport is based on process models and 
compared to alternate solutions methods. 
5 - Important physical phenomena and couplings and consistent and 
appropriate assumptions are incorporated into the consideration of radionuclide 
transport in the UZ abstraction. 
Section 3.11.13 discusses the abstraction of radionuclide transport, including 
physical phenomena, couplings, and assumptions. 
Saturated zone flow and transport (to be covered in Saturated Zone Flow and Transport PMR) 
Radionuclide transport in the saturated zone (to be covered in Saturated Zone Flow and Transport PMR) 
Direct release and transport (to be covered in Disruptive Events PMR) 
Bioshpere (to be covered in the Biosphere PMR)

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Subissue 4  Demonstration of the overall performance objective (acceptance criteria not included in the IRSR) 
IRSR: Unsaturated and Saturated Zone Flow Under Isothermal Conditions 
Subissue 1 - Climate change 
1 - Climate projections used in performance assessments of the YM region are 
based on paleoclimate data, considering, at a minimum, information contained 
in Forester et al. (1996); Winograd et. al. (1992); Szabo et al. (1994) 
Climate projections are based on paleoclimate data (Section 3.5.1). The Yucca 
Mountain Site Description provides contains a detailed discussion of the 
paleoclimate data, including references to Forester, et al. (1996) and Szabo, et 
al. (1994) in Section 4 (Climatology and Meteorology). Winograd et al. (1992) is 
referenced in Section 5 (Hydrologic System). 
2 - DOE has evaluated long-term climate change based on known patterns of 
climatic cycles during the Quaternary, especially the last 500 k.y. 
Long term climate change is based on an analogous climate cycle that occurred 
approximately 400,000 years ago (Section 3.5.1). 
3 - If used, numerical climate models are calibrated with paleoclimate data and 
their use suitably simulates the historical record, before being used for 
projection of future climate. 
Numerical models of climate are not used in this PMR. 
4 - Climate-affected parameters (e.g., onset times for climate change, MAP, 
and MAT) used in YM performance assessment models include, as bounding 
condition, a return to full pluvial climate (higher precipitation and lower 
temperatures) for at least a part of the first 10-k.y. period, using parameter 
values that are supported by scientific data and analyses. 
The future climate at Yucca Mountain is treated as a sequence of three climate 
states, including a glacial transition at 1400 years (Section 3.5.1). Analog 
climate sites are used define the three climate states, including low, mean, and 
upper bound annual precipitation and temperature. 
Subissue 2 - Hydrologic effects of climate change 
1 - If bounding analyses are used to predict climate-induced effects (water table 
rise, for example), the analysis are based on a reasonably complete search of 
paleoclimate data pertinent to water-table rise and other effects (for example, 
changes in precipitation and geochemistry), including, at a minimum, 
information contained in Paces et al. (1996), Szabo et al. (1994), Forester et al. 
(1996). 
A comprehensive literature search of the paleoclimate data has been completed 
and documented in the Yucca Mountain Site Description. This description 
references Paces et al. (1996) in Section 5 (Hydrologic System). Szabo et al. 
(1994) and Forester et al. (1996) are referenced in Section 4 (Climatology and 
Meteorology). 
2 - Regional and sub-regional models for the SZ that are used to predict 
climate-induced consequences are calibrated with the paleohydrology data, and 
are consistent with evidence that the water-table rise during the late Pleistocene 
was up to 120 m. 
This acceptance criterion is addressed in the Saturated Zone PMR.

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NRC Technical Acceptance Criteria PMR Approach and Section Reference 
3 - DOE has incorporated future climate changes and associated effects in its 
performance assessments. For example, available information does not 
support an assumption that present-day climate will persist unchanged for 10 
k.y. or more. 
Future climate changes and associated effects have been incorporated into 
TSPA (Section 3.5). Three climate states are expected to occur over the next 
10,000 years: the current modern climate, a monsoon climate, and a glacial 
transition climate. 
Subissue 3 - Present day shallow infiltration 
1 - DOE has estimated present-day shallow infiltration at YM for use in TSPA 
using mathematical models that are reasonably verified with site-specific 
climatic, surface, and subsurface information, and the fundamental effects of 
heterogeneities, time-varying boundary conditions, evapotranspiration, depth of 
soil cover, and surface-water runoff have been considered in ways that do not 
underestimate infiltration. 
Section 3.5.2 summarizes models of present day infiltration and the site-specific 
parameters that are incorporated into the model. Important processes 
considered include precipitation, runoff and run-on, evapotransporation, 
transpiration, and moisture redistribution in the shallow subsurface. 
2- DOE has analyzed infiltration at appropriate time and space scales for 
performance assessment, and has tested the abstracted model against more 
detailed models to assure that it produces reasonable results. 
The infiltration model in Section 3.5.2 evaluates time and space scales for 
infiltration. 
3 - DOE has characterized shallow infiltration in the form of either probability 
distributions or deterministic upper-bound values for performance assessment, 
and provided sufficient data and analyses to justify the chosen probability 
distribution or bounding value. 
The methodology for assigning probabilities to the mean annual infiltration 
multipliers has been enhanced to address the NRC concern that the method 
used to assign probabilities to the mean annual infiltration multipliers is biased 
toward lower values of mean annual infiltration (Section 3.5.1). 
4 - If DOE can show through TSPA and associated sensitivity analyses that 
refinements of shallow infiltration estimates will not significantly alter 
performance predictions, no further refinement will be necessary. 
Sensitivity studies will be included in TSPA-SR. 
Subissue 4 - Deep percolation 
1 - Estimates of deep percolation flux rates and the fraction of flux that occurs in 
fractures will be acceptable provided that they are: (I) shown to constitute a 
conservative upper bound, or (ii) based on a technically defensible UZ flow 
model that reasonable represents the physical system, including flow in fracture 
systems and matrix-fracture interaction. The flow model has been calibrated 
using site-specific hydrologic, geologic, and geochemical data. 
The UZ flow model has been calibrated with available site data (Section 3.6). 
The representation of flow in the UZ is summarized in Section 3.7, including a 
discussion of fracture-matrix interaction. 
2 - To estimate deep-percolation flux, spatial and temporal variability of model 
parameters and boundary conditions must be considered. Model parameters 
must be averaged over appropriate time and space scales. DOE must also 
consider climate-induced change in soil depth and vegetation. 
Section 3.7 summarizes the UZ flow model, including the treatment of spatial 
and temporal variability of model parameters and boundary conditions. The 
infiltration model has been enhanced to include an improved surface-water 
model.

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NRC Technical Acceptance Criteria PMR Approach and Section Reference 
Subissue 4 - Deep percolation, continued 
3 - For estimates of the amount of water that may contact waste packages DOE 
must (i) demonstrate that coupled thermal-mechanical-chemical changes in 
rock mass properties will not focus deep percolation into the drifts; and (ii) 
rigorously justify estimated diversion of deep percolation away from the waste 
package footprints. This must include direct observations of dripping in test 
drifts or tunnels under ambient (unventilated) conditions in the repository 
horizon, or in an analog horizon with similar characteristics. Also needed are 
model calculations that account for the effects of backfill (if used), drift collapse, 
and coupled thermal-mechanical-chemical changes to rock properties. The 
models have been calibrated to niche studies and tracer tests in the ESF, or 
using an analog with characteristics similar to the repository horizon. 
Seepage models (Sections 3.9 and 3.10) evaluate partial drift collapse and 
coupled THM changes. These models have been calibrated to available data 
from the ESF and the cross drift. Direct observation of an unventilated segment 
of the ECRB is ongoing and dripping has not been observed. 
4 - In predicting likely flow and transport pathways beneath the proposed 
repository horizon, DOE must either (i) conservatively assume that all deep 
percolation below the repository level bypasses the bulk of the non-welded 
units, either by lateral movement above the units or through vertical flow 
through fractures and faults; or (ii) demonstrate that the estimated fraction of 
deep percolation that flows vertically through the matrix of the non-welded units 
is supported by (a) characterization data and (b) two-dimensional or threedimensional 
modeling that accounts for spatial and temporal variability that may 
result in lateral diversion of flow, and uses model parameter values appropriate 
for the scale of model discretization. 
Section 3.7 summarizes the approach to modeling flow through each of the 
major units below the repository horizon. Modeling results show that fracture 
flow is dominant both at the potential repository horizon and at the water table. 
The model uses input from perched water and matrix properties, calibrated 
properties model, the geologic and numerical grid model, the climate/infiltration 
model, and the geochemistry model. 
Subissue 5 - Saturated zone ambient flow (covered in Saturated Zone PMR) 
Subissue 6 - Matrix diffusion 
1 - If credit for matrix diffusion in the UZ is taken, then transport predictions 
must be consistent with site geochemical and isotopic data. 
The matrix diffusion model has been enhanced to account for the effects of 
finite fracture spacing (Section 3.11.3). 
2 - If credit for matrix diffusion in the SZ is take, rock matrix and solute diffusion 
parameters must be (i) based on a SZ transport model that reasonably matches 
the results of the field tracer tests that are conducted over different distance 
scales and flow rates with multiple tracers of different diffusive properties, and 
(ii) consistent with laboratory data. 
This acceptance criterion is addressed in the Saturated Zone PMR.

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5. SUMMARY AND CONCLUSIONS 
The Unsaturated Zone Flow and Transport Process Model Report (UZ PMR) documents the 
approach, development, and basis for the models and analyses that are used to understand and 
predict flow and transport processes in the unsaturated zone at Yucca Mountain. The models and 
analyses are supported by data collection, experiments, field tests, and calibration efforts that 
have been performed by project scientists for many years. The extensive studies provide 
confidence in the models and tools that will be used in Total System Performance Assessments 
for Site Recommendation and License Application. The following two sections provide a 
general summary of the contents of this PMR (Section 5.1), as well as a more detailed summary 
of the models and abstractions that will be used in TSPA-SR calculations (Section 5.2). 
5.1 SUMMARY OF THE UZ FLOW AND TRANSPORT PMR 
This section provides a concise summary and review of the contents of this PMR. More detailed 
summaries and conclusions can be found at the end of each chapter, as well as at the end of 
major subsections describing the process models. 
Chapter 1 provides an introduction to the scope and objectives of this PMR. Identification of 
key issues and FEPs (features, events, and processes) are presented to provide the motivation and 
requirements for this document. A summary of the quality assurance (QA) requirements for the 
data, software, models, and analyses in this PMR are also presented, and relationships to other 
relevant PMRs are discussed. 
Chapter 2 presents historical background on the evolution of site characterization and data 
collection at Yucca Mountain that support this PMR. This includes early surface-based testing 
and more recent underground testing and monitoring activities in the Exploratory Studies Facility 
(ESF). These characterization studies provide the basis for the geological, hydrological, 
geochemical, and thermal models presented in this PMR. Natural analogs to the processes and 
events at Yucca Mountain are also presented in Chapter 2, and an overview of the evolution of 
the conceptual and mathematical UZ Flow and Transport Model is given. 
Chapter 3 includes a description of the relevant process models and their underlying basis. 
Applicable abstractions for TSPA-SR are also presented. Section 3.2 begins with geological 
considerations for flow and transport. Geological issues important to repository performance 
(e.g., fracture characterization, mineralogy, and location of major faults) are listed and discussed. 
The hydrogeologic units at Yucca Mountain are identified, and their major features and impact to 
hydrology are presented. Mineralogy and locations of altered rock that may be important for UZ 
transport are also presented. 
Section 3.3 provides a summary of the physical processes and conceptual models relevant to UZ 
flow and transport. The components and processes that are described include climate, 
infiltration, flow through fractures and matrix in various hydrogeologic units, fracture-matrix 
interaction, effects of major faults, transient flow, focusing of flow, perched water, seepage into 
drifts, gas flow processes, radionuclide transport processes, and the effects of coupled processes. 
These process and component conceptualizations comprise the UZ Flow and Transport Model

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described in this PMR. Alternative conceptual models that are not used in this PMR are also 
presented. 
Section 3.4 documents the development of the numerical approaches and grids that are used in 
the development of the UZ Flow and Transport Model. Numerical modeling approaches that are 
discussed include continuum vs. discrete fracture-network modeling for flow through fractured 
rock, and a description of the current numerical approach is presented. Other numerical 
approaches that are discussed include the active fracture model, particle tracking, and methods 
for modeling dispersion and heterogeneities. The development of the numerical grids is then 
presented, starting with the required inputs and data for grid generation. The outputs are 
described, which include one-, two-, and three-dimensional grids for various aspects of the 
development of the UZ Flow and Transport Model. Grid-refinement studies were also 
performed that showed the refinement of the current grid used in the UZ Flow and Transport 
Model was adequate. 
Section 3.5 summarizes the development of the Climate and Infiltration Models, which provide 
the upper boundary condition (net infiltration) for the UZ Flow and Transport Model. The 
results and abstraction of the Climate Model reveal that a modern-like climate will persist for 
approximately 600 years, followed by a warmer and wetter monsoon climate for another ~1,400 
years. A cooler and wetter glacial-transition climate follows the monsoon climate for the 
remaining duration of the 10,000-year period analyzed in TSPA-SR. For each of these climates, 
three infiltration scenarios ranging from low to high are generated using different values for 
precipitation and temperature, as well as surface infiltration parameters such as soil depth, and 
evapotranspiration. The three infiltration cases are denoted as low, mean, and high (or upper); 
Section 3.5 provides a summary of how weightings are assigned to each case for TSPA-SR 
calculations. 
Section 3.6 documents the available hydrologic parameter data and the development of the 
calibrated hydrologic property sets for the UZ Flow and Transport Model. The data that were 
evaluated and used for property calibrations include information on measured matrix, fracture, 
and fault parameters. The calibration process is then presented to obtain calibrated parameter 
sets for mountain-scale and drift-scale applications. One- and two-dimensional numerical 
inversions were performed to estimate parameters that optimize the match between predicted 
results and measured data. Results and uncertainties of the calibration process are presented, and 
comparisons to additional data and alternative models are discussed. 
Section 3.7 provides a description of the site-scale UZ Flow Model, which simulates threedimensional 
flow fields that are used in transport calculations. This section begins with a 
summary of the inputs that are subsequently used in the Flow Model, which include the 
infiltration boundary conditions, the numerical grids, calibrated properties, and conceptual 
models of flow and fracture-matrix interaction. A description of the Flow Model and its 
submodels is provided, which include flow through the PTn, effects of major faults, flow through 
the Calico Hills, and the effects of perched water. Results of the site-scale Flow Model are then 
presented, which describe the flow fields for the nine infiltration scenarios (three infiltration 
cases for each of the three climates) and different perched water models. Flow predominantly 
occurs in the fractures in the welded units and in the matrix in the nonwelded units. Significant 
lateral diversion exists, especially in the northern portion of the potential repository, where

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perched water is simulated over zeolitized units. Abstractions include assessment of perched 
water models and water-table rise. 
Section 3.8 presents an analysis of the Ambient Geochemistry Model and its use in testing 
various components of the site-scale UZ Flow Model. The features and processes that can be 
analyzed using the Ambient Geochemistry Model include infiltration rate, percolation flux, 
partitioning between matrix and fracture flow, flow pathways, and travel times in the UZ. This 
section summarizes the geochemical data that are available for the analyses, and it describes the 
development of the model, which uses the calibrated properties (see Section 3.6) and available 
geochemical data as input. Results indicate that chloride concentrations in the ESF and ECRB 
can be qualitatively predicted by the model using the mean present-day infiltration rates. 
Modeling studies that investigated the relationship of calcite deposition to infiltration rate, water 
and gas compositions, and reactive surface area also revealed that the range of net infiltration 
rates used in the model could capture the calcite abundance in the TSw. 
Section 3.9 documents the development of the drift seepage models that are used to estimate the 
fraction of waste packages contacted by water and the amount of water that enters the drift as a 
function of several hydrologic parameters and boundary conditions. The relevant processes that 
impact drift seepage are detailed along with the inputs required for the model. Then, a sequence 
of seepage models is presented, beginning with the Seepage Calibration Model that provides 
seepage-related calibrated parameters. The Seepage Model for Performance Assessment is used 
to perform a wide range of seepage simulations using a combination of input parameters. 
Finally, seepage abstraction creates distributions for four seepage parameters that are sampled in 
TSPA-SR. Results indicate that seepage fluxes are likely to be significantly lower than 
percolation fluxes even under conservative assumptions, and that only a fraction of the waste 
packages will encounter seepage. 
Section 3.10 describes the thermal-hydrological-chemical drift-scale model, which is used to 
simulate the composition of the water and gas in the vicinity of the heated repository as well as 
any mineralogical alterations that result from precipitation and dissolution processes. A 
description of the conceptual model for coupled processes is provided, along with a complete 
description of the numerical approach, which is consistent with the approach taken by the Flow 
Model. The results of the drift-scale THC Model reveal that the water seeping into the drifts is 
likely to be neutral, and the concentration of chloride in the water will not be more than four 
times the concentration in ambient pore water. The fracture porosity decreases by less than 1% 
(e.g., from 0.01 to 0.0099) in the vicinity of the drifts, which suggests that the impacts of THC 
effects on fracture and matrix properties (and subsequently on UZ flow) are negligible. In the 
abstraction for TSPA-SR calculations, the transient water and gas compositions are averaged 
over four discrete time periods from 0 to 100,000 years. These results are used to determine the 
in-drift environment and the corrosion of the drip shields and waste packages over time. 
Section 3.11 presents the UZ Transport Model that is used to investigate radionuclide transport 
between the potential repository and the water table. This section presents two distinct transport 
models. The first is a process-oriented model used to investigate the importance of several 
features and processes that include advection, matrix diffusion, sorption, flow through faults, 
radioactive decay, colloidal transport, and perched water. Results of the process modeling 
indicate that (1) fast transport is controlled by faults at early times; (2) matrix diffusion and

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sorption can be effective retardation mechanisms; (3) the vitric Calico Hills layers can provide 
effective retardation via flow through the matrix; (4) decay products may be important for 
radionuclide transport; and (5) colloidal transport is very sensitive to filtration. The second 
model is the particle-tracking method that is used in TSPA-SR to simulate radionuclide transport, 
which also includes the same processes considered in the first model. The benefit of the particletracking 
method is its computationally efficiency, which is essential for TSPA calculations. 
Section 3.12 presents the mountain-scale Thermal-Hydrological (TH) Model, which is used to 
assess the importance of TH effects on far-field flow and transport. A description of the 
mountain-scale TH Model is presented, which consists of the conceptual model, input 
parameters, design configuration for heat load, and boundary conditions. The numerical 
approach for flow is consistent with that used in the Flow Model. Results are provided regarding 
the hydrologic and thermal behavior throughout the simulated two- and three-dimensional 
domains. The refined 2-D model predicts that vertical liquid flow crossing the interval between 
the drifts continues at a rate close to the ambient percolation flow for most of the thermal-loading 
period, although at some locations enhanced flow may occur as a result of condensate drainage 
for early times (less than a few hundred years). Based on these results, the effects of TH on farfield 
flow and transport are assumed negligible for TSPA-SR calculations, which simulate 
performance over a 10,000-year period. 
Section 3.13 summarizes the uncertainties associated with the UZ flow and transport models and 
components. A brief description of the uncertainties in the model inputs and outputs is presented, 
along with the uncertainties that are carried forward to TSPA-SR. A description of how 
uncertainties are treated in TSPA calculations is also summarized. 
Finally, Chapter 4 presents a detailed summary of the Key Technical Issues (KTIs) issued by the 
Nuclear Regulatory Commission that are relevant to this PMR. The six KTIs relevant to UZ 
flow and transport are the following: (1) Evolution of the Near-Field Environment; (2) 
Radionuclide Transport; (3) Structural Deformation and Seismicity; (4) Thermal Effects on 
Flow; (5) Total System Performance Assessment and Integration; and (6) Unsaturated Zone and 
Saturated Zone Flow Under Isothermal Conditions. Chapter 4 provides pointers to sections in 
this PMR that address each of these KTIs. 
5.2 SUMMARY OF MODELS AND ABSTRACTIONS FOR TSPA-SR 
This section summarizes the major components that comprise the UZ Flow and Transport Model 
for TSPA-SR. An overview of the process models is presented that highlights the primary 
inputs, outputs, and basis for each model. The subset of products that are actually used in TSPASR 
are also discussed along with a summary of the abstraction methodology. The reader is 
referred to the model sections (Section 3.53.12) for a more thorough discussion of the major 
conclusions from each process model component. 
The integrated UZ Flow and Transport Model for TSPA-SR is comprised of four major 
components: (1) UZ flow, (2) drift seepage, (3) drift-scale coupled thermal-hydrologic-chemical 
(THC) processes, and (4) UZ transport. Figure 5.2-1 shows the icons that represent these 
components along with a conceptual sketch of the UZ at Yucca Mountain. Additional sub

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components (e.g., infiltration, thermal-hydrology) are described within the four major 
components. 
5.2.1 UZ Flow 
The UZ Flow Model is a three-dimensional, site-scale numerical model that simulates 
groundwater flow from the surface of the mountain to the water table using a dual-permeability 
formulation to capture flow through fracture and matrix materials (see Section 3.7). The model 
is generated based on information from the Geologic Framework Model, Rock Properties Model, 
and Mineralogical Model. It is calibrated and tested against relevant data that include perchedwater 
data, matrix saturation, moisture potential, pneumatic data, air-permeability data, 
temperature data, and ambient geochemistry data. The 3-D Flow Model is also validated through 
percolation tests performed in Alcove 1 and comparisons to data from the ECRB, SD-6 and 
WT-24. 
Additional submodels that provide input to the Flow Model include climate and Infiltration 
Models (see Section 3.5). The Climate Model provides upper and lower bounds for precipitation 
and temperature for modern and future climates. The temperature and precipitation records are 
obtained through selected meteorological stations that are chosen based on interpretation of 
climate analogs and orbital cycles. In the TSPA-SR base-case calculations, the timing of the 
climate states following post-closure are deterministically prescribed and assumed to be as 
follows: (1) a modern climate lasting for 600 years; (2) a monsoon climate from 600 years to 
2,000 years; and (3) a glacial-transition climate for the remainder of the simulated 10,000-year 
period. Planned sensitivity studies using a different duration of the climate states are not 
expected to reveal a significant impact on performance. 
The Infiltration Model uses the precipitation and temperature data from the Climate Model, 
along with other inputs such as hydraulic permeability and soil depth, to determine the amount of 
net infiltration that penetrates beneath the surface of the mountain. The Infiltration Model 
implements a mass balance among flow processes at the surface such as precipitation, 
evapotranspiration, run-on, run-off, and net infiltration. The resulting products are maps of 
spatially variable infiltration rates that serve as the upper boundary condition for the 3-D Flow 
Model. Three infiltration maps, representing low, mean, and high infiltration cases, are produced 
for each of the three climates to capture the uncertainty in the infiltration parameters. Therefore, 
a total of nine infiltration maps are used in the Flow Model. 
The nine infiltration maps are used in the simulation of steady-state flow fields that are used in 
TSPA-SR calculations. Additional flow fields are generated for an alternative conceptual model 
of perched water. The alternative is a flow-through model (perched water model #1; Section 3.7) 
that allowed more water to percolate downward through the northern portion of the repository 
rather than being diverted above the basal vitrophyre. A comparison of the different perched 
water models revealed that the models produced similar results, although the flow-through model 
was slightly more conservative. As a result, only the flow-through perched water model was 
carried through to TSPA-SR, and the final product consisted of nine three-dimensional flow 
fields in the UZ (i.e., three infiltration cases for each of the three climate states).

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The flow fields are used directly in TSPA-SR calculations of transport. As part of the postprocessing 
of the flow fields, the water-table elevation is increased for the two future climate 
states, which are wetter than the modern climate. A conservative water-table elevation of 850 m 
is implemented by changing the liquid saturation of all elements (nodes) below 850 m to a value 
of one and adding a large sink to those nodes, effectively removing particles from the UZ. The 
cumulative mass of these particles leaving the UZ system are used as the source term for SZ 
modeling. 
To weight the three infiltration cases (low, mean, and high) within each climate for TSPA-SR 
calculations, a Monte Carlo analysis was performed using distributions for the input parameters 
(e.g., hydraulic permeability, soil depth, precipitation). The results of the uncertainty analysis 
yielded statistical weightings of 0.17, 0.48, and 0.35 for the low, mean, and high infiltration 
cases, respectively (see Section 3.5.3). The weightings are used to select a flow field 
(corresponding to one of the three infiltration cases) within each realization of the TSPA-SR 
calculation. In other words, for each realization, there is a 17% chance that the low infiltration 
case will be selected, a 48% chance that the mean infiltration case will be selected, and a 35% 
chance that the high infiltration case will be selected. A given realization uses the same 
infiltration case for all climate states (e.g., if a realization uses a high infiltration case for the 
modern climate, then a high infiltration case is used for the monsoon and glacial-transition 
climates as well). 
A final submodel that complements the ambient, steady-state flow simulations is the mountainscale 
Thermal-Hydrological Model (see Section 3.12). This model consists of two- and threedimensional 
submodels of the UZ Flow Model that include refinement around the repository to 
accommodate thermal loading. Temperatures and hydrologic conditions are simulated to 
determine the impact of repository heating on far-field flow. Currently, the impact of thermal 
effects on far-field transport remains to be rigorously tested, but based on results of the TH 
Model regarding increased flow through fractures due to condensate drainage, the changes to the 
far-field flow during the 10,000 period are not expected to be significant. 
A schematic of major inputs to and outputs from the UZ Flow Model and its submodels is shown 
in Figure 5.2-2. 
5.2.2 Drift Seepage 
The drift-scale seepage models consist of a sequence of models that are used to estimate the 
amount of water that can enter the waste emplacement drifts under a variety of conditions (see 
Section 3.9). The first model in the sequence of seepage models is the Seepage Calibration 
Model (SCM). The SCM is a three-dimensional heterogeneous fracture-continuum numerical 
model that contains small-scale variability and correlation structure in the hydrologic properties. 
The input parameters include permeabilities from air-injection tests and other hydrologic 
parameters from the Calibrated Properties Model. The SCM is calibrated to seepage data 
obtained from liquid-release tests in the ESF to produce model-related, seepage-relevant flow 
parameters. The calibrated model is then used to predict the behavior of additional liquid-release 
tests to validate the model. Results of the SCM include a conceptual seepage process model and 
calibrated parameters that are relevant to the seepage processes.

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The second model in the sequence of seepage models is the Seepage Model for Performance 
Assessment (SMPA). The SMPA is a three-dimensional, heterogeneous fracture-continuum 
numerical model that uses the conceptual model from the SCM as its basis. It implements a 
broader range of parameters from available data as well as drift-degradation scenarios. The 
SMPA considers variations in percolation flux, permeability, and capillarity (van Genuchten a). 
Results from the SMPA indicate that seepage decreases with increasing capillary strength and 
increasing permeability, which are conducive to greater capillary diversion around the drifts. 
The results also show that seepage increases with increasing permeability correlation length and 
drift degradation. 
The wide range of seepage rates calculated from the SMPA are then used in a PA abstraction 
model that creates distributions for seepage fraction, mean seep flow rate, standard deviation of 
seep flow rate, and a flow-focusing factor. The flow-focusing factor is based on estimates of 
discrete weep spacings implied by the active fracture model and percolation fluxes calculated 
by the Flow Model. It is used to scale the percolation flux and the seepage fraction. Greater 
amounts of flow focusing yield increased seep flow rates (where seepage exists) but lower 
seepage fractions. Additional effects of drift degradation, rock bolts, and possible correlation 
between hydrologic parameters are accounted for in the abstracted model by increasing the seep 
flow rates. The PA seepage abstraction also has provisions for episodicity, but because the PTn 
overlies the entire potential repository, transient effects of precipitation and infiltration are 
effectively dampened at the potential repository horizon. 
A schematic of major inputs to and outputs from the drift seepage models is shown in 
Figure 5.2-3. 
5.2.3 Drift-Scale THC 
The Drift-Scale THC Model is a two-dimensional dual-permeability chimney model that 
extends from the surface to the water table. It includes geologic layering consistent with the 
Flow Model. The model is more refined in and around the drift region, where it captures the 
features of the waste package, invert, and backfill (after 50 years; note that a design change was 
made in January 2000 that removed backfill from the reference design). It predicts transient 
water and gas chemistry, mineralogy, porosity, and permeability for 100,000 years (see Section 
3.10). A 50-year ventilation period is simulated, as well as three infiltration scenarios 
corresponding to the three climate states. The model is validated through predictions and 
comparisons to the measured gas and water chemistry from the Drift Scale Test. 
The results of the drift-scale THC process model reveal that the water seeping into the drifts is 
likely to be neutral (pH between 7 and 9), and the concentration of chloride in the water will not 
be more than a factor of four times the concentration in ambient pore water. The carbon dioxide 
concentrations increase with time in the drift, and the aqueous carbonate concentrations increase 
up to a few thousand mg/l. However, the fracture porosity decreases by less that 1% (e.g., from 
0.01 to 0.0099) in the vicinity of the drifts, which suggests that the impacts of THC effects on 
fracture and matrix properties (and subsequently on UZ flow) are negligible. 
In the abstraction for TSPA-SR calculations, the transient water and gas compositions are 
averaged over four discrete time periods from 0 to 100,000 years. Only the mean infiltration

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cases are selected since the results of the low and high infiltration cases showed similar behavior 
in general. The results that are passed to the in-drift geochemical models in TSPA are aqueous 
concentrations for five cations and six anions, pH, and partial pressure of carbon dioxide during 
the four discrete periods. These results are used to determine the in-drift environment and the 
corrosion of the drip shields and waste packages over time. 
A schematic of major inputs to and outputs from the drift-scale THC Model is shown in 
Figure 5.2-4. 
5.2.4 UZ Transport 
There are two distinct UZ transport modeling approaches: (1) a process model that tests and 
evaluates various transport processes and mechanisms, and (2) a TSPA particle-tracking model 
that incorporates the tested transport processes and mechanisms (see Section 3.11). The process 
model is used to gain confidence in understanding the impacts of various processes such as 
matrix diffusion, sorption, colloid filtration, and decay. It also serves as a basis for comparison 
to the TSPA model, which incorporates the same features and processes, but which uses an 
efficient particle-tracking algorithm that can be run in a few minutes for each TSPA realization. 
The UZ transport process model includes advection, dispersion, sorption, matrix diffusion, 
radioactive decay and daughter products, and colloid transport. The model uses geologic and 
hydrologic parameters from the Flow Model and transport parameters from CRWMS M&O 
(2000, U0100) and CRWMS M&O (2000, U0070). The model consists of 2-D and 3-D 
numerical simulations that can efficiently simulate radionuclide transport. Results of the process 
modeling indicate that (1) fast transport is controlled by faults at early times; (2) matrix diffusion 
and sorption can be effective retardation mechanisms; (3) the vitric Calico Hills layers can 
provide effective retardation via flow through the matrix; (4) the 239Pu daughter products are 
important to transport (at least for this subsystem analysis; full TSPA calculations must be 
performed to determine the overall importance to performance); and (5) colloidal transport is 
very sensitive to filtration. 
The TSPA transport model uses the FEHM particle-tracking algorithm. It also considers 
advection, dispersion, matrix diffusion, sorption, and colloidal transport. It uses the flow fields 
generated from the Flow Model, so the dual-permeability nature of flow through fractures and 
matrix is preserved. The individual components and processes of the FEHM particle-tracking 
algorithm have been compared to other process models and analytical solutions, and the basis for 
the particle-tracking method is substantiated. A notable discrepancy has been identified in the 
conceptualization for matrix diffusion. The FEHM particle-tracking method uses a dual-porosity 
semi-analytical solution for retardation due to matrix diffusion (i.e., no flow occurs in the matrix 
in the matrix diffusion model). Studies evaluating the use of a dual-permeability matrix 
diffusion model have shown that significantly longer travel times can result when particles that 
diffuse into the matrix are allowed to subsequently transport through the matrix. Thus, the dualporosity 
matrix diffusion model is considered to be a conservative choice. 
As presented earlier, the thermal effects on flow are not expected to be significant, so thermal 
effects are neglected in the UZ transport simulations for TSPA-SR. The influence of increased 
temperatures on transport parameters such as distribution coefficients are also neglected.

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TDR-NBS-HS-000002 REV00 ICN1 325 June 2000 
Uncertainty in the radionuclide source-term location is implemented by using discretized zones 
in the repository region. The zones are currently based on ranges of infiltration (03, 310, 10 
20, 2060, and > 60 mm/yr). The release of radionuclides occurs at a random location within one 
of these five zones depending on the zone in which the release occurs in the engineered barrier 
system (EBS) models. Four zones are also defined at the water table, where radionuclide mass is 
collected for release at a random point in the SZ model. 
A schematic of major inputs to and outputs from the UZ transport models is shown in 
Figure 5.2-5. 
5.2.5 Treatment of Uncertainties 
As discussed in Section 3.13, the models that comprise the UZ Flow and Transport Model for 
TSPA-SR contain inherent uncertainty and variability. The uncertainty and variability in the 
parameters are due, in part, to the natural variability and heterogeneity in the geological, 
hydrological, chemical, and mechanical systems that are difficult to characterize in situ, such as 
the precise fracture network in the UZ. Uncertainties in models may also be due to conditions 
that are difficult to predict, such as future climate states. 
This PMR presented the bases (data collection, field tests, and calibration exercises) for using 
these parameters and process models. In addition, the models and analyses that are used in TSPA 
calculations address remaining uncertainties through probabilistic simulations or appropriate 
conservative assumptions. 
The probabilistic simulations used in TSPA calculations consist of multiple realizations 
(statistically equivalent simulations) and stochastic sampling of parameters (i.e., a Monte Carlo 
approach). Each realization samples a set of parameters and/or models from given distributions 
for use in the TSPA calculation. The simulation of multiple realizations produces a range of 
performance results, with each outcome having a probability corresponding to its likelihood of 
occurrence. Thus, the uncertainty of the parameters and models leads to uncertainty in system 
performance. In the TSPA, the uncertainty in performance is analyzed, both in terms of its 
importance (i.e., is the uncertainty so great that it casts doubt on the safety of the potential 
repository?) and in terms of sensitivities (i.e., which parameter and submodel uncertainties have 
the greatest impact on the uncertainty in performance?). The probability distributions used in the 
TSPA uncertainty analyses reflect the degree of confidence in the input parameters and model 
assumptions. The resulting output distributions show whether input uncertainties have an 
acceptable or unacceptable impact on the calculated repository performance. The actual results 
of the TSPA calculations and uncertainty analyses will be included in the documentation for 
TSPA-SR. 
In addition to probabilistic analyses, uncertainties in the process-model outputs can be addressed 
in abstracted TSPA models and analyses that use conservative assumptions. If insufficient 
evidence exists to provide a defensible range of values for a given parameter, values that bound 
the physical behavior or provide conservative estimates are used. These conservative 
assumptions are intended to increase the defensibility of the models used in TSPA calculations 
given the inherent uncertainties in the actual system.

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TDR-NBS-HS-000002 REV00 ICN1 326 June 2000 
In summary, as detailed in this report, the confidence in the models and parameters is built on 
rigorous experimental and numerical studies; remaining uncertainties are addressed in the TSPA 
models and analyses through probabilistic simulations or appropriate conservative assumptions.

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TDR-NBS-HS-000002 REV00 ICN02 327 August 2000 
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CRWMS M&O 1999b. M&O Site Investigations. Activity Evaluation, January 23, 1999. Las 
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CRWMS M&O 1999c. Work Package Planning Summary, UZ Flow and Transport Process 
Model Report FY00. Work Package 1401213UM1, Rev. 00. WPP-NBS-HS-000002. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.19991020.0177. 
CRWMS M&O 1999d. Machine Readable Media Forms; Compact Disk YMP FEP Database 
Rev. 00C. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19991214.0518. 
CRWMS M&O 1999e. Request for Repository Subsurface Design Information to Support 
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Case to Support Yucca Mountain Site Recommendation and Licensing Considerations. TDRWIS-
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REV 00. Las Vegas, Nevada: CRWMS M&O. Submit to RPC URN-0019

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CRWMS M&O 2000 (EBS PMR). Engineered Barrier System Degradation, Flow, and 
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00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000121.0117. 
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GS-000003 REV 00 ICN 01. Las Vegas, Nevada: CRWMS M&O. ACC: 
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CRWMS M&O 2000 (N0120/U0110). Drift-Scale Coupled Processes (DST and THC Seepage) 
Models. MDL-NBS-HS-000001 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
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CRWMS M&O 2000 (N0125). Abstraction of Drift-Scale Coupled Processes. ANL-NBS-HS- 
000029 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000525.0371. 
CRWMS M&O 2000 (U0000). Development of Numerical Grids for UZ Flow and Transport 
Modeling. ANL-NBS-HS-000015 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: 
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CRWMS M&O 2000 (U0015). In-Situ Field Testing of Processes. ANL-NBS-HS-000005 REV 
00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.20000504.0304. 
CRWMS M&O 2000 (U0030). Conceptual and Numerical Models for Unsaturated Zone Flow 
and Transport. MDL-NBS-HS-000005 REV 00. Las Vegas, Nevada: CRWMS M&O. Submit 
to RPC URN-0036 
CRWMS M&O 2000 (U0035). Calibrated Properties Model. MDL-NBS-HS-000003 REV 00. 
Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990721.0520. 
CRWMS M&O 2000 (U0050). UZ Flow Models and Submodels. MDL-NBS-HS-000006 REV 
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CRWMS M&O 2000 (U0060). Radionuclide Transport Models under Ambient Conditions. 
MDL-NBS-HS-000008 REV 00. Las Vegas, Nevada: CRWMS M&O. Submit to RPC URN- 
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AAPG Studies in Geology No. 13, 73-80. Tulsa, Oklahoma: American Association of 
Petroleum Geologists. TIC: 245898. 
Wang, J.S.Y. and Elsworth, D. 1999. "Permeability Changes Induced by Excavation in 
Fractured Tuff." Rock Mechanics for Industry, Proceedings of the 37th U.S. Rock Mechanics 
Symposium, Vail, Colorado, June 6-9, 1999. Amadei, B., ed. 2, 751757. Rotterdam, The 
Netherlands: A.A. Balkema. TIC: 245246.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 351 August 2000 
Wang, J.S.Y. and Narasimhan, T.N. 1985. "Hydrologic Mechanisms Governing Fluid Flow in a 
Partially Saturated, Fractured, Porous Medium." Water Resources Research, 21, (12), 1861- 
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Wang, J.S.Y. and Narasimhan, T.N. 1988. Hydrologic Modeling of Vertical and Lateral 
Movement of Partially Saturated Fluid Flow Near a Fault Zone at Yucca Mountain. SAND87- 
7070. Albuquerque, New Mexico: Sandia National Laboratories. TIC: 202856. 
Wang, J.S.Y. and Narasimhan, T.N. 1993. "Unsaturated Flow in Fractured Porous Media." 
Chapter 7 of Flow and Contaminant Transport in Fractured Rocks. Bear, J., Tsang, C.F., and 
de Marsily, G., eds. San Diego, California: Academic Press. TIC: 235461. 
Wang, J.S.Y.; Cook, N.G.W.; Wollenberg, H.A.; Carnahan, C.L.; Javandel, I.; and Tsang, C.F. 
1993. "Geohydrologic Data and Models of Rainier Mesa and Their Implications to Yucca 
Mountain." High Level Radioactive Waste Management, Proceedings of the Fourth Annual 
International Conference, Las Vegas, Nevada, April 26-30, 1993. 1, 675-681. La Grange Park, 
Illinois: American Nuclear Society. TIC: 208542. 
Wang, J.S.Y.; Trautz, R.C.; Cook, P.J.; Finsterle, S.; James, A.L.; and Birkholzer, J. 1999. 
"Field Tests and Model Analyses of Seepage into Drift." Journal of Contaminant Hydrology, 
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Estimating Recharge to the Desert Basins of Nevada. Journal of Hydrology, 31, (3/4), 335-357. 
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Concepts and Observations. Flow and Transport Through Unsaturated Fractured Rock. Evans, 
D.D. and Nicholson, T.J., eds. Geophysical Monograph 42, 165-170. Washington, D.C.: 
American Geophysical Union. TIC: 223605. 
Weeks, E.P. and Wilson, W.E. 1984. Preliminary Evaluation of Hydrologic Properties of Cores 
of Unsaturated Tuff, Test Well USW H-1, Yucca Mountain, Nevada. Water-Resources 
Investigations Report 84-4193. Denver, Colorado: U.S. Geological Survey. ACC: 
NNA.19870407.0037. 
Wemheuer, R.F. 1999. "First Issue of FY00 NEPO QAP-2-0 Activity Evaluations." Interoffice 
correspondence from R.F. Wemheuer (CRWMS M&O) to R.A. Morgan, October 1, 1999, 
LV.NEPO.RTPS.TAG.10/99-155, with enclosures. ACC: MOL.19991028.0162. 
Wilkins, D.R. and Heath, C.A. 1999. "Direction to Transition to Enhanced Design Alternative 
II." Letter from Dr. D.R. Wilkins (CRWMS M&O) and Dr. C.A. Heath (CRWMS M&O) to 
Distribution, June 15, 1999, LV.NS.JLY.06/99-026, with enclosures, "Strategy for Baselining

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 352 August 2000 
EDA II Requirements" and "Guidelines for Implementation of EDA II." ACC: 
MOL.19990622.0126; MOL.19990622.0127; MOL.19990622.0128. 
Wilson, M.L.; Gauthier, J.H.; Barnard, R.W.; Barr, G.E.; Dockery, H.A.; Dunn, E.; Eaton, R.R.; 
Guerin, D.C.; Lu, N.; Martinez, M.J.; Nilson, R.; Rautman, C.A.; Robey, T.H.; Ross, B.; Ryder, 
E.E.; Schenker, A.R.; Shannon, S.A.; Skinner, L.H.; Halsey, W.G.; Gansemer, J.D.; Lewis, L.C.; 
Lamont, A.D.; Triay, I.R.; Meijer, A.; and Morris, D.E. 1994. Total-System Performance 
Assessment for Yucca Mountain  SNL Second Iteration (TSPA-1993). SAND93-2675. 
Executive Summary and two volumes. Albuquerque, New Mexico: Sandia National 
Laboratories. ACC: NNA.19940112.0123. 
Winograd, I.J. 1981. "Radioactive Waste Disposal in Thick Unsaturated Zones." Science, 212, 
(4502), 1457-1464. Washington, D.C.: American Association for the Advancement of Science. 
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Winograd, I.J. 1986. Archaeology and Public Perception of a Transscientific Problem  
Disposal of Toxic Wastes in the Unsaturated Zone. Circular 990. Denver, Colorado: U.S. 
Geological Survey. TIC: 237946. 
Winograd, I.J. and Thordarson, W. 1975. Hydrogeologic and Hydrochemical Framework, 
South-Central Great Basin, Nevada-California, with Special Reference to the Nevada Test Site. 
Professional Paper 712-C. Washington, D.C.: U.S. Geological Survey. TIC: 206787. 
Winograd, I.J.; Coplen, T.B.; Landwehr, J.M.; Riggs, A.C.; Ludwig, K.R.; Szabo, B.J.; Kolesar, 
P.T.; and Revesz, K.M. 1992. "Continuous 500,000-Year Climate Record from Vein Calcite in 
Devils Hole, Nevada." Science, 258, 255-260. Washington, D.C.: American Association for the 
Advancement of Science. TIC: 237563. 
Wittwer, C.; Chen, G.; Bodvarsson, G.S.; Chornack, M.; Flint, A.; Flint, L.; Kwicklis, E.; and 
Spengler, R. 1995. Preliminary Development of the LBL/USGS Three-Dimensional Site-Scale 
Model of Yucca Mountain, Nevada. LBL-37356. Berkeley, California: Lawrence Berkeley 
Laboratory. ACC: MOL.19960924.0538. 
Wittwer, C.S.; Bodvarsson, G.S.; Chornack, M.P.; Flint, A.L.; Flint, L.E.; Lewis, B.D.; Spengler, 
R.W.; and Rautman, C.A. 1992. "Design of a Three-Dimensional Site-Scale Model for the 
Unsaturated Zone at Yucca Mountain, Nevada." High Level Radioactive Waste Management, 
Proceedings of the Third International Conference, Las Vegas, Nevada, April 12-16, 1992. 1, 
263-271. La Grange Park, Illinois: American Nuclear Society. TIC: 204231. 
WoldeGabriel, G.; Keating, G.N.; and Valentine, G.A. 1999. "Effects of Shallow Basaltic 
Intrusion into Pyroclastic Deposits, Grants Ridge, New Mexico, USA." Journal of Volcanology 
and Geothermal Research, 92, 389-411. Amsterdam, The Netherlands: Elsevier Science. TIC: 
246037. 
Wollenberg, H.A. and Flexser, S. 1986. "Contact Zones and Hydrothermal Systems as 
Analogues to Repository Conditions." Chemical Geology, 55, 345-359. Amsterdam, The 
Netherlands: Elsevier Science B.V. TIC: 246171.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 353 August 2000 
Wu, Y.S.; Chen, G.; and Bodvarsson, G. 1995. Preliminary Analysis of Effects of Thermal 
Loading on Gas and Heat Flow Within the Framework of the LBNL/USGS Site-Scale Model. 
LBL- 37729. Berkeley, California: Lawrence Berkeley National Laboratory. TIC: 222270. 
Wu, Y-S.; Haukwa, C.; and Bodvarsson, G.S. 1999a. "A Site-Scale Model for Fluid and Heat 
Flow in the Unsaturated Zone of Yucca Mountain, Nevada." Journal of Contaminant 
Hydrology, 38, (1-3), 185-215. New York, New York: Elsevier. TIC: 244160. 
Wu, Y.S.; Ritcey, A.C.; and Bodvarsson, G.S. 1999b. "A Modeling Study of Perched Water 
Phenomena in the Unsaturated Zone at Yucca Mountain." Journal of Contaminant Hydrology, 
38, (1-3), 157-184. New York, New York: Elsevier. TIC: 244160. 
Xu, T. and Pruess, K. 1998. Coupled Modeling of Non-Isothermal Multi-Phase Flow, Solute 
Transport and Reactive Chemistry in Porous and Fractured Media: 1. Model Development and 
Validation. LBNL-42050. Berkeley, California: Lawrence Berkeley National Laboratory. TIC: 
243735. 
Xu, T.; Pruess, K.; and Brimhall, G. 1998. An Improved Equilibrium-Kinetics Speciation 
Algorithm for Redox Reactions in Variably Saturated Subsurface Flow Systems. LBNL-41789. 
Berkeley, California: Lawrence Berkeley National Laboratory. TIC: 240019. 
Yang, I.C.; Rattray, G.W.; and Yu, P. 1996. Interpretation of Chemical and Isotopic Data from 
Boreholes in the Unsaturated Zone at Yucca Mountain, Nevada. Water-Resources Investigations 
Report 96-4058. Denver, Colorado: U.S. Geological Survey. ACC: MOL.19980528.0216. 
Yang, I.C.; Yu, P.; Rattray, G.W.; Ferarese, J.S.; and Ryan, J.N. 1998. Hydrochemical 
Investigations in Characterizing the Unsaturated Zone at Yucca Mountain, Nevada. Water- 
Resources Investigations Report 98-4132. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19981012.0790. 
Yao, T-M and Hendrickx, J.M.H. 1996. "Stability of Wetting Fronts in Dry Homogeneous Soils 
Under Low Infiltration Rates." Soil Science Society of America Journal, 60, (1), 20-28. 
Madison, Wisconsin: Soil Science Society of America. TIC: 246692. 
YMP (Yucca Mountain Project) 1999. Unsaturated Zone Flow and Transport Model 
Independent Evaluation Panel Preliminary Report. Las Vegas, Nevada: Yucca Mountain Site 
Characterization Office. ACC: MOL.20000111.0135. 
Zhou, W. and Apted, M.J. 1995. "Flow and Transport Simulation in Yucca Mountain Using 
Dual-Porosity Model." High Level Radioactive Waste Management, Proceedings of the Sixth 
Annual International Conference, Las Vegas, Nevada, April 30-May 5, 1995. Pages 160-162. 
La Grange Park, Illinois: American Nuclear Society. TIC: 215781. 
Zimmerman, R.M.; Blanford, M.L.; Holland, J.F.; Schuch, R.L.; and Barrett, W.H. 1986. 
Nevada Nuclear Waste Storage Investigations Project, Final Report: G-Tunnel Small-Diameter 
Heater Experiments. SAND84-2621. Albuquerque, New Mexico: Sandia National 
Laboratories. ACC: HQS.19880517.2365.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 354 August 2000 
Zimmerman, R.W. and Bodvarsson, G.S. 1996. "Effective Transmissivity of Two-Dimensional 
Fracture Networks." International Journal of Rock Mechanics and Mining Sciences & 
Geomechanics Abstracts, 33, (4), 433-438. Oxford, United Kingdom: Pergamon Press. TIC: 
245649. 
6.2 CODES, STANDARDS, REGULATIONS, AND PROCEDURES 
64 FR (Federal Register) 8640. Disposal of High-Level Radioactive Waste in a Proposed 
Geologic Repository at Yucca Mountain. Proposed rule 10 CFR 63. Readily available. 
AP-2.14Q, Rev. 0, ICN 1. Review of Technical Products. Washington, D.C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: MOL.20000405.0477. 
AP-2.16Q, Rev. 0, ICN 0. Activity Evaluation. Washington, D.C.: U.S. Department of Energy, 
Office of Civilian Radioactive Waste Management. ACC: MOL.20000207.0716. 
AP-3.10Q, Rev. 2, ICN 1. Analyses and Models. Washington, D.C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: MOL.20000512.0066. 
AP-3.10Q, Rev. 2, ICN 2. Analyses and Models. Washington, D.C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: MOL.20000619.0576. 
AP-3.11Q, Rev. 1, ICN 1. Technical Reports. Washington, D.C.: U.S. Department of Energy, 
Office of Civilian Radioactive Waste Management. ACC: MOL.20000726.0216. 
AP-3.15Q, Rev. 1, ICN 1. Managing Technical Product Inputs. Washington, D.C.: U.S. 
Department of Energy, Office of Civilian Radioactive Waste Management. ACC: 
MOL.20000218.0069. 
AP-7.5Q, Rev. 0, ICN 1. Submittal, Review, and Acceptance of Deliverables. Washington, 
D.C.: U.S. Department of Energy, Office of Civilian Radioactive Waste Management. TIC: 
MOL.20000518.0343. 
AP-SI.1Q, Rev. 2, ICN 4. Software Management. Washington, D.C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: MOL.20000223.0508. 
DOE 2000. Quality Assurance Requirements and Description. DOE/RW-0333P, Rev. 10. 
Washington, D.C.: U.S. Department of Energy, Office of Civilian Radioactive Waste 
Management. ACC: MOL.20000427.0422. 
QAP-2-0, Rev. 5. Conduct of Activities. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.19980826.0209. 
YMP-LBNL-QIP-6.1, Rev. 5, Mod. 0. Document Review. Berkeley, California: Lawrence 
Berkeley National Laboratory. ACC: MOL.19991210.0091.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 355 August 2000 
6.3 SOURCE DATA, LISTED BY DATA TRACKING NUMBER 
GS990708312242.008. Physical and Hydraulic Properties of Core Samples from Busted Butte 
Boreholes. Submittal date: 07/01/1999. 
GS990908314224.009. Detailed Line Survey Data for Horizontal and Vertical Traverses, 
ECRB. Submittal date: 09/16/1999. 
LB002181233124.001. Air Permeability and Pneumatic Pressure Data Collected Between 
October 27, 1999 through November 7, 1999 from Niche 5 (ECRB Niche 1620) of the ESF. 
Submittal date: 02/18/2000. 
LB990501233129.004. 3-D UZ Model Calibration Grids for AMR U0000, "Development of 
Numerical Grids of UZ Flow and Transport Modeling". Submittal date: 09/24/1999. 
LB990701233129.001. 3-D UZ Model Grids for Calculation of Flow Fields for PA for AMR 
U0000, "Development of Numerical Grids For UZ Flow and Transport Modeling". Submittal 
date: 09/24/1999. 
MO9901MWDISMMM.000. ISM3.0 Mineralogic Models. Submittal date: 01/22/1999. Submit 
to RPC URN-0074. 
MO9901MWDISMRP.000. ISM3.0 Rock Properties Models. Submittal date: 01/22/1999. 
Submit to RPC URN-0075. 
MO9910MWDISMMM.003. ISM3.1 Mineralogic Models. Submittal date: 10/01/1999. 
Submit to RPC URN-0076. 
MO9910MWDISMRP.002. Rock Properties Model (RPM3.1). Submittal date: 10/06/1999. 
Submit to RPC URN-0080. 
6.3.1 Data Tracking Numbers Listed for Tables and Figures in Attachment II 
GS000399991221.002. Rainfall/Runoff/Run-on 1999 Simulations. Submittal date: 03/10/2000. 
GS000399991221.003. Preliminary Alcove 1 Infiltration Experiment Data. Submittal date: 
03/10/2000. 
GS000399991221.004. Preliminary Developed Matrix Properties. Submittal date: 03/10/2000. 
GS960308312232.001. Deep Unsaturated Zone Surface-Based Borehole Instrumentation 
Program Data from Boreholes USW NRG-7A, USW NRG-6, UE-25 UZ#4, UE-25 UZ#5, USW 
UZ-7A, and USW SD-12 for the Time Period 10/01/95 through 3/31/96. Submittal date: 
04/04/1996. 
GS960908315215.014. Uranium and Thorium Isotope Data for ESF Secondary Minerals 
Collected Between March 1996 and July 1996. Submittal date: 09/25/1996.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 356 August 2000 
GS980908312242.036. Water Potentials Measured With Heat Dissipation Probes in ECRB 
Holes from 4/23/98 to 7/31/98. Submittal date: 09/22/1998. 
GS980908315215.015. Uranium and Thorium Isotope Data Including Calculated 230TH/U 
Ages and Initial 234U/238U Activity Ratios for in Situ Microdigestions of Outermost Opal-Rich 
Mineral Coatings from the Exploratory Studies Facility Analyzed Between 12/01/97 and 
09/15/98. Submittal date: 09/23/1998. 
GS991299992271.001. Preliminary Unsaturated Zone Borehole Hydrochemistry Data. 
Submittal date: 12/23/1999. 
LA0003AM831341.001. Preliminary Revision of Probability Distributions for Sorption 
Coefficients (K_DS). Submittal date: 03/29/2000. Submit to RPC URN-0267 
LA0003JC831362.001. Preliminary Matrix Diffusion Coefficients for Yucca Mountain Tuffs. 
Submittal date: 4/10/2000. Submit to RPC URN-0305 
LA0004WS831372.002. Sorption of Np, Pu, and Am on Rock Samples From Busted Butte, NV. 
Submittal date: 04/19/2000. Submit to RPC URN-0304 
LA9909JF831222.005. Chlorine-36 Analyses of ESF and Busted Butte Porewaters in FY99. 
Submittal date: 09/29/1999. 
LA9909JF831222.010. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of ESF 
Porewaters. Submittal date: 09/29/1999. 
LAJF831222AQ98.004. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of Salts Leached 
from ESF Rock Samples. Submittal date: 09/10/1998. 
LAJF831222AQ98.011. Chloride, Bromide, Sulfate and Chlorine-36 Analyses of Springs, 
Groundwater, Porewater, Perched Water and Surface Runoff. Submittal date: 09/10/1998. 
LB980001233124.003. Liquid Release Tests Performed to Determine if a Capillary Barrier 
Exists in Niches 3566 and 3650. Submittal date: 04/23/1998. 
LB00032412213U.001. Busted Butte Ground Penetrating Radar Data Collected June 1998 
through February 2000 at the Unsaturated Zone Transport Test (UZTT): GPR Velocity Data. 
Submittal date: 03/24/2000. Submit to RPC URN-0303 
LB980901123142.006. Laboratory Test Results of Hydrological Properties from Post-Test Dry- 
Drilled Cores in the Single Heater Test Area for the Final TDIF Submittal for the Single Heater 
Test. Submittal date: 08/31/1998. 
LB980930123112.001. Surface to ESF Seismic Tomography. Submittal date: 09/30/1998. 
LB990051233129.001. Extent of Vitric Region Used to Assign Material Properties in FY 99 UZ 
Model Layers; Figure 5 From AMR U0000, Development of Numerical Grids for UZ Flow and 
Transport Modeling. Submittal date: 09/24/99.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 357 August 2000 
LB990501233129.004. 3-D UZ Model Calibration Grids for AMR U0000, Development of 
Numerical Grids of UZ Flow and Transport Modeling. Submittal date: 09/24/1999. 
LB990701233129.001. 3-D UZ Model Grids for Calculation of Flow Fields for PA for AMR 
U0000, Development of Numerical Grids for UZ Flow and Transport Modeling. Submittal 
date: 09/24/1999. 
LB990801233129.001. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #1). Submittal date: 11/29/1999. 
LB990801233129.003. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #3). Submittal date: 11/29/1999. 
LB990801233129.004. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #4). Submittal date: 11/29/1999. 
LB990801233129.005. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #5). Submittal date: 11/29/1999. 
LB990801233129.007. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #7). Submittal date: 11/29/1999. 
LB990801233129.009. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #9). Submittal date: 11/29/1999. 
LB990801233129.011. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #11). Submittal date: 11/29/1999. 
LB990801233129.013. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #13). Submittal date: 11/29/1999. 
LB990801233129.015. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #15). Submittal date: 11/29/1999. 
LB990801233129.017. TSPA Grid Flow Simulations for AMR U0050, UZ Flow Models and 
Submodels (Flow Field #17). Submittal date: 11/29/1999. 
LB990801233129.025. TSPA Grid Flow Simulations for AMR U0050, "UZ Flow Models and 
Submodels" Flow Field #25: Present Day Mean Infiltration for Flow-Through Perched-Water 
Conceptual Model. Submittal date: 3/11/2000. 
LB990831012027.001. Input to Seepage Calibration Model AMR U0080. Submittal date: 
08/31/1999. 
LB9908T1233129.001. Transport Simulations for the Low, Mean, and Upper Infiltration 
Scenarios of the Present-Day, Monsoon, and Glacial Transition Climates for AMR U0050, UZ 
Models and Submodels. Submittal date: 3/11/2000.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 358 August 2000 
LB990901233124.002. Alcove 6 Flow Data for AMR U0015, In Situ Field Testing of 
Processes. Submittal date: 11/01/1999. 
LB990901233124.005. Alcove 4 Flow Data for AMR U0015, In Situ Field Testing of 
Processes. Submittal date: 11/01/1999. 
LB990901233129.001. Input and Output Data for Verification of Dual-Continua Particle 
Tracker (DCPT) for AMR U0155,  Analysis Comparing Advect-Dispersion Transport Solution 
to Particle Tracking. Submittal date: 10/26/1999. 
LB991091233129.001. One-Dimensional, Mountain-Scale Calibration for AMR U0035, 
Calibrated Properties Model. Submittal date: 10/22/1999. 
LB991091233129.003. Two-Dimensional Fault Calibration for AMR U0035, Calibrated 
Properties Model. Submittal date: 10/22/1999. 
LB991101233129.001. Model Input/Output Files Supporting Seepage Model for PA in AMR 
U0075, Seepage Model for PA Including Drift Collapse. Submittal date: 11/30/1999. 
LB991121233129.007. Calibrated Parameters for the Present-Day, Mean Infiltration Scenario, 
Used for Simulations with Perched Water Conceptual Model #3 for the Mean Infiltration 
Scenarios of the Present-Day, Monsoon and Glacial Transition Climates. Submittal date: 
3/1/2000. 
LB991131233129.001. Modeling Calcite Deposition and Percolation. AMR U0050, UZ Flow 
Models and Submodels. Submittal date: 03/11/2000. 
LB991131233129.002. Modeling Seepage and Tracer Tests at Alcove 1. AMR U0050, UZ 
Flow Models and Submodels. Submittal date: 03/11/2000. 
LB991131233129.003. Analytical and Simulation Results of Chloride and Chlorine-36 Analysis. 
AMR U0050, UZ Flow Models and Submodels. Submittal date: 3/11/2000. 
LB991200DSTTHC.001. Pore Water Composition and CO2 Partial Pressure Input into 
Thermal-Hydrological-Chemical (THC) Simulations: Table 3 of AMR N0120/U0110, "Drift- 
Scale Coupled Processes (Drift-Scale and THC Seepage) Models". Submittal date: 03/11/2000. 
LB991200DSTTHC.002. Model Input and Output Files, Excel Spreadsheets and Resultant 
Figures Which are Presented in AMR N0120/U0110, Drift-Scale Coupled Processes (Drift- 
Scale Test and THC Seepage) Models. Submittal date: 3/11/2000. 
LB991201233129.001. The Mountain-Scale Thermal-Hydrologic Model Simulations for AMR 
U0105, Mountain-Scale Coupled Processes (TH) Models. Submittal date: 3/11/2000. 
LB991220140160.012. Model Prediction of 3-D Transport, Present-Day Infiltration, #1 Perched 
Water Model, Using EOS9nT Input and Output files. AMR U0060, Radionuclide Transport 
Models under Ambient Conditions. Submittal date: 3/11/2000.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN02 359 August 2000 
LB991220140160.017. Model Prediction of 3-D Colloid Transport, Present-Day Infiltration, #1 
Perched Water Model, using EOS9nT Input and Output files. AMR U0060, Radionuclide 
Transport Models under Ambient Conditions. Submittal date: 3/11/2000. 
LB997141233129.001. Calibrated Basecase Infiltration 1-D Parameter Set for the UZ Flow and 
Transport Model, FY99. Submittal date: 07/21/1999. 
MO9804MWDGFM03.001. An Update to GFM 3.0; Corrected Horizon Grids for Four Fault 
Blocks. Submittal date: 04/14/1998. 
MO9901MWDGFM31.000. Geologic Framework Model. Submittal date: 01/06/1999. 
MO9901MWDISMMM.000. ISM 3.0 Mineralogic Models. Submittal date: 01/22/1999. 
Submit to RPC URN-0074. 
MO9910MWDISMMM.003. ISM3.1 Mineralogic Models. Submittal date: 10/01/1999. Submit 
to RPC URN-0076. 
MO9901MWDISMRP.000. ISM3.0 Rock Properties Models. Submittal date: 01/22/1999. 
Submit to RPC URN-0075. 
MO9910MWDISMRP.002. Rock Properties Model (RPM3.1). Submittal date: 10/06/1999. 
Submit to RPC URN-0080. 
MO9912SPAPAI29.002. PA Initial Abstraction of THC Model Chemical Boundary Conditions. 
Submittal date: 01/11/2000. Submit to RPC URN-0282. 
SN0001T0581699.004. Supplemental Files to Support Base-Case Particle-Tracking Analysis for 
TSPA-SR (Total System Performance Assessment-Site Recommendation) (In Analysis/Model 
Report U0160, ANL-NBS-HS-000024). Submittal date: 01/06/2000. 
SN0003T0503100.001. Weighting Factors for Low, Middle and High Climate Infiltration Rate 
Maps. Submittal date: 03/20/2000. 
SN9908T0581699.001. Files to Support 1-D Comparison Between FEHM Particle Tracking and 
T2R3D Advective-Dispersive Transport Simulations Along SD-9. Submittal date: 08/16/1999. 
SN9912T0511599.002. Revised Seepage Abstraction Results for TSPA-SR (Total System 
Performance Assessment-Site Recommendation). Submittal date: 12/15/1999. 
SN9912T0581699.003. Files to Support Base-Case Particle-Tracking Analyses (AMR U0160) 
for TSPA-SR. Submittal date: 12/13/1999.

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TDR-NBS-HS-000002 REV00 ICN02 360 August 2000 
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7. ATTACHMENTS 
Attachment I  UZ Data and Associated Data Tracking Numbers (DTNs) 
Attachment II  List of DTNs for Figures and Tables 
Attachment III  Figures

Unsaturated Zone Flow and Transport Model Process Model Report 
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Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-1 June 2000 
ATTACHMENT I  UZ Data and Associated Data Tracking Numbers (DTNs) 
I.1 Available Site Data 
This section summarizes the data used in the AMRs supporting the UZ Flow and Transport 
PMR. The input data represent the current understanding of UZ flow and transport processes. 
Tables are presented to summarize the different data reviewed, analyzed, and developed in 
associated Analysis/Model Reports (AMRs). Some data sets are used in multiple analyses. The 
discussions associated with the tables cross-reference the relationships among data sets and 
AMRs. The details of analysis and modeling are given in individual AMRs and in Section 3. 
The Q-status of these data is provided in the DIRS database for the associated AMR. It should be 
noted that this Attachment is only intended to give the main data sets and the associated DTNs 
for the unsaturated zone, and is therefore not necessarily complete. 
I.2 Geologic Data 
The major inputs and outputs of the CRWMS M&O (2000, U0000), Development of Numerical 
Grids for UZ Flow and Modeling, are summarized in Table I-1 (with outputs presented in italic). 
Table I-1. Geologic Data for the UZ Model 
Data Description DTN or ACC 
Geologic Framework Model, GFM3.1 MO9901MWDGFM31.000 
Integrated Site Model, components MO9901MWDISMRP.000 
MO9804MWDGFM03.001 
Repository layout configuration MOL.19990409.001 
Mesh files for model calibrations, CRWMS M&O 2000, 
U0000 
Tables supporting UZ Model grid development LB990501233129.001 
1-D hydrogeologic property set inversions and 
model calibration 
LB990501233129.002 
2-D fault hydrogeologic property calibration LB990501233129.003 
3-D UZ Model calibration LB990501233129.004 
3-D UZ Model calibration grid for non-waterperching 
mode 
LB990701233129.002 
Mesh file for generating 3-D UZ flow fields, CRWMS 
M&O 2000, U0000 
LB990701233129.001 
The primary data input for UZ Flow and Transport Model grids is GFM3.1 (Geological 
Framework Model) for lithostratigraphic layering and major fault geometry at Yucca Mountain. 
The GFM contains information about layer thickness and layer contact elevation, and defines 
fault orientation and displacement. Approximately 40 geologic units and 18 faults are 
incorporated into the 3-D UZ Flow and Transport Model grids. RPM3.0 (Rock Properties 
Model) files are used to further define the units, especially the zeolitic zones of CHn. The 
repository layout data are used to locate areas for enhanced grid resolution.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-2 June 2000 
CRWMS M&O (2000, U0000) also uses inputs of hydrologic unit definitions, fracture data for 
hydrologic units, and elevation data on the water table and perched water bodies. The hydrologic 
unit definitions are based on matrix properties (Flint 1998) discussed in Section 2.2.3. Fracture 
data, discussed in Section 2.2.4, are used to formulate the dual-permeability (dual-k) meshes. 
The vertical columns in the meshes are from the TCw bedrock to the water table. Water table and 
perched water elevation data for the lower UZ boundary are discussed in Section 2.2.10. 
The final 3-D mesh files for UZ flow fields in Table I-1 are developed with inputs from 
calibrated property sets, summarized in Section 2.2.11. The areal domain of the UZ models 
encompasses approximately 40 km2 of the Yucca Mountain area. The areal grids are constructed 
with centers coinciding as close as practical with locations of surface-based boreholes, alcoves 
and niches, faults, ESF and ECRB drifts, and other domain nodes. 
I.3 Infiltration/Climate Data 
The USGS (2000, U0005) refines the climate estimates for the next 10,000 years. The climate 
AMR provides input to the USGS (2000, U0010), Simulation of Net Infiltration for Modern and 
Potential Future Climates. The major inputs and outputs are summarized in Table I-2. 
Table I-2. Infiltration/Climate Data for the UZ Model 
Data Description DTN or ACC 
Daily precipitation input for 1980-1995 calibration (file 
MOD3-PPT.DAT) 
GS950208312111.001 
GS950208312111.002 
GS960908312111.004 
GS970108312111.001 
Summary of the Day Data from the National Climatic 
Data Center (NCDC) for the Period Ending in 1995: 
for California, Nevada, Utah, Arizona, New 
Mexico, Colorado, and Wyoming. 
MO9811NCDCSDD0.000 
Streamflow records for 5 Yucca Mountain gauging 
stations (Upper Pagany Wash, Lower Pagany 
Wash, Wren Wash, Drill Hole Wash, Upper 
Split Wash). 
NWIS Database 
ATS#YD-200000269 
Parameters for SOLRAD subroutine for equations 
defined in Flint et al. (1996). 
GS960908312211.003 
Soil-depth-class map (Figure 13, Flint et al., 1996). GS960908312211.003 
Geospatial input parameters acquired from Flint et al. 
(1996) (elevation, slope, aspect, latitude, 
longitude, soil type, soil-depth class) (file 
30MSITE.INP). 
GS960908312211.003 
100-year stochastic daily precipitation input (files 
4JA.S01 and AREA12.S01). 
GS960908312211.003 
Calculated flux rates from neutron holes GS960508312212.008 
SO4 infiltration flux GS910908315214.003 
GS931008315214.032 
Infiltration map - base case, lower bound, upper 
bound, CRWMS M&O 2000, U0010 
GS000399991221.002

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-3 June 2000 
The climate USGS (2000, U0005) also used diatom and ostracode data from Owens Lake 1984- 
1992 cores, radiometric dating and d18O data from Devils Hole, and earth orbital parameter data 
for the last 10 million years and the next 100,000 years. The three climate states in VA are 
replaced by (1) the modern interglacial climate for about the next 400 to 600 years, (2) the 
monsoon climate for the duration of 900 to 1,400 years, and (3) the glacial-transition climate for 
the duration of 8,000 to 8,700 years. The modern climate uses data from site and regional 
meteorological stations. The monsoon climate uses data from Nogales, Arizona, and Hobbs, New 
Mexico, as upper-bound analogs and present-day site data as lower bound analog. The glacial 
transition climate uses data from Spokane, Rosalia, and St. John, all in Washington state, as 
upper-bound analogs and data from Beowawe, Nevada, and Delta, Utah, as lower-bound 
analogs. 
The infiltration USGS (2000, U0010) also used elevation data, bedrock permeability and 
property data, geology maps, and soil properties as documented in the AMR. Simulation results 
and averaged values were presented for 123.7 km2 area for the net infiltration model domain, for 
the 38.7 km2 area of the UZ Flow and Transport Model domain, and for the 4.7 km2 area of the 
1999 design potential repository area. Over the potential repository area, the mean net infiltration 
is 4.7 mm/yr for the modern climate (with 0.4 mm/yr for the mean lower bound and 11.6 mm/yr 
for the mean upper bound), 12.5 mm/yr for the monsoon climate (with 4.7 mm/yr for the mean 
lower bound and 20.3 mm/yr for the mean upper bound), and 19.8 mm/yr for the glacialtransition 
climate (with 2.2 mm/yr for the mean lower bound and 37.3 mm/yr for the mean upper 
bound). 
I.4 Matrix Properties 
Matrix properties include permeability, porosity, residual saturation, and the van Genuchten a 
and m parameters used to describe water retention and relative permeability relationships (van 
Genuchten 1980, pp. 892898). The input to the matrix properties for UZ Flow and Transport 
Model layers to the CRWMS M&O (2000, U0090), Analysis of Hydrologic Property Data, is 
based on the data transmittal listed in Table I-3. The data of Busted Butte cores are used in 
CRWMS M&O (2000, U0060), Radionuclide Transport Models under Ambient Conditions. 
Table I-3. Matrix Properties for the UZ Model 
Data Description DTN or ACC 
Matrix hydrologic property data GS960908312231.004 
Matrix saturation, water potential and hydrologic property 
data 
GS000399991221.004 
Physical and hydraulic properties of core samples from 
Busted Butte 
GS990308312242.007 
GS990708312242.008 
The sample collection and laboratory measurement methodologies are described by Flint (1998, 
pp. 1119) and Rousseau et al. (1999, pp. 1946). Core samples are grouped and analyzed 
according to the hydrogeologic units characterized by matrix properties (Flint 1998, pp. 1946, 
CRWMS M&O 2000, U0000, Section 6.3, CRWMS M&O 2000, U0090, Section 6.2). Matrix 
permeability has been measured on 750 core samples from eight surface-based boreholes. Some

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-4 June 2000 
samples with permeabilities too low to measure (nondetect results) were retested with a lowdetection-
limit permeameter. The nondetect results were included in defining the lowpermeability 
units, especially the zeolitic zones of CHn. Matrix porosity values are based on 
105C oven-dried measurements of 4,888 core samples, from 23 shallow boreholes and eight 
deep boreholes. The residual saturation is determined by relative humidity (RH) porosity and 
total porosity, with RH porosity determined in a 65C and 65% RH oven. The RH drying process 
is designed to remove water contributing flow, leaving only bound water and water in the 
smallest pores (Flint 1998, p. 17). The van Genuchten parameters are based on desaturation data 
from 75 samples. Desaturation data, with water potential and saturation measured several times 
while a core sample is drying, are used to calculate a and m by least-square fitting. 
I.5 Fracture Properties, Air Permeabilities, and Liquid Release/Seepage Data 
Fracture properties include fracture permeability, fracture porosity, van Genuchen fracture a and 
m parameters, fracture frequency, intensity, fracture interface area, and fracture aperture. 
Fracture properties are developed from analyzing fracture survey data and air-injection test data 
in CRWMS M&O (2000, U0090), Analysis of Hydrologic Property Data. The fracture 
permeability and van Genuchten parameters are updated in CRWMS M&O (2000, U0035), 
Calibrated Properties Model, after calibrations together with core saturation and in situ potential 
data, as summarized in Section 2.2.11. The fracture van Genuchten parameters and porosities are 
compared with ESF seepage test results for confirmation purposes. The seepage test results and 
other drift-scale hydrologic testing and air-permeability data are summarized in CRWMS M&O 
(2000, U0015), In Situ Field Testing of Processes. The seepage test results are used in CRWMS 
M&O (2000, U0080), Seepage Calibration Model and Seepage Testing Data. The major inputs 
and outputs from these AMRs related to fracture properties are tabulated in Table I-4.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-5 June 2000 
Table I-4. Fracture Geometry, Air Permeability, and Liquid Release/Seepage Data 
Data Description DTN or ACC 
Fracture type (location, strike, dip, length): 
Sta. 0+60 to 4+00 GS971108314224.020 
Sta. 4+00 to 8+00 GS971108314224.021 
Sta. 8+00 to 10+00 GS971108314224.022 
Sta. 10+00 to 18+00 GS971108314224.023 
Sta. 18+00 to 26+00 GS971108314224.024 
Sta. 26+00 to 30+00 GS971108314224.025 
Sta. 30+00 to 35+00 GS960708314224.008 
Sta. 35+00 to 40+00 GS960808314224.011 
Sta. 40+00 to 45+00 GS960708314224.010 
Sta. 45+00 to 50+00 GS971108314224.026 
Sta. 50+00 to 55+00 GS960908314224.014 
Sta. 55+00 to 60+00 GS971108314224.028 
Sta. 60+00 to 65+00 GS970208314224.003 
Sta. 65+00 to 70+00 GS970808314224.008 
Sta. 70+00 to 75+00 GS970808314224.010 
Sta. 75+00 to 78+77 GS970808314224.012 
Sta. 4+00 to 28+00, Alcoves 3 and 4 GS960908314224.020 
Alcove 5 GS960908314224.018 
Alcove 6 GS970808314224.014 
ECRB Cross Drift GS990408314224.001 
GS990408314224.002 
Fracture frequency: 
15 model units from 14 borehole locations GS970408314222.003 
NRG-7a SNF29041993002.084 
SD-12 TM000000SD12RS.012 
Fracture type: 
Outcrop survey of Calico Hills formation GS970308314222.001 
Line surveys in the Bullfrog Member of the 
Crater Flat Tuff from Raven Canyon 
GS930608312332.001 
Line surveys in the Bullfrog Member of the 
Crater Flat Tuff from east side of Little Skull 
Mountain in Yucca Mountain Area 
GS930608312332.002

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-6 June 2000 
Table I-4. Fracture Geometry, Air Permeability, and Liquid Release/Seepage Data (Continued) 
Data Description DTN or ACC 
Air-injection test data: 
surface-based boreholes GS960908312232.012 
GS960908312232.013 
Alcoves 1, 2, 3 (upper TCw, Bow Ridge fault, 
upper PTn) 
GS970183122410.001 
Alcove 4 lower PTn fault-matrix interaction test 
bed 
LB980901233124.009 
Alcove 5  single heater test area LB960500834244.001 
Alcove 5  drift scale test area LB970600123142.001 
LB980120123142.004 
LB980120123142.005 
Alcove 6 fracture-matrix interaction test bed LB980901233124.004 
Niches 3566 and 3650, pre-excavation and 
post-excavation data 
LB980001233124.002 
Niches 3107 and 4788, pre-excavation and 
post-excavation data 
LB980901233124.001 
Niches, pre-excavation and post-excavation 
analyses 
LB990601233124.001 
Niche 4788, Alcoves 4 and 6, cross-hole 
analyses, and 
4 niches and 2 alcoves, statistical analyses 
LB990901233124.004 
Niche 3107 and Alcove 5, air-injection , tracer 
test and fracture porosity data 
LB980912332245.002 
Fracture properties for the UZ Model grids and 
uncalibrated fracture and matrix properties for 
the UZ model layers, CRWMS M&O 2000, 
U0090 
LB99050501233129.001 
Seepage and liquid release data: 
Niches 3566 and 3650, pre-excavation liquidrelease 
data, and 
Niche 3566, post-excavation seepage data 
LB980001233124.003 
Niches 3566, 3650, 3107 and 4788, preexcavation 
liquid-release data and analyses, 
and 
Niche 3566, post-excavation seepage analyses 
LB980901233124.003 
Niche 3107, post-excavation seepage test data LB990601233124.002 
Seepage Calibration model, software routines and files, 
CRWMS M&O 2000, U0080 
LB990831012027.001

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-7 June 2000 
Table I-4. Fracture Geometry, Air Permeability, and Liquid Release/Seepage Data (Continued) 
Data Description DTN or ACC 
Infiltration and seepage data, Alcove 1 upper TCw El 
Nino test 
GS000399991221.003 
Water intake rate and wetting front detection data 
Alcove 4 lower PTn fault-matrix interaction test 
bed 
LB990901233124.005 
Alcove 6 fracture-matrix interaction test bed LB990901233124.002 
The precalibrated fracture permeabilities are based on air permeabilities from air-injection tests 
in vertical boreholes and ESF alcoves. For TCw, fracture permeabilities were based on tests in 
four vertical boreholes (NRG-7/7A, NRG-6, SD-12, and UZ-16) and Alcoves 1, 2, and 3. For 
PTn, permeability data are from one borehole (NRG-7/7A) and Alcove 3. For TSw, the 
permeability data are from the four boreholes and the tests at the Single Heater Test and the Drift 
Scale Test areas in Alcove 5. For CHn, permeability data are from a single sampled interval in 
borehole UZ-16. No air-injection data are available for the Prow Pass, Bullfrog, and Tram units. 
For model layers where no data are available, analogs to other units are used. The fracture 
properties in faults are based on air-injection tests in Alcove 2 for the Bow Ridge fault and in 
Alcove 6 for the Ghost Dance fault. The fracture permeabilities are used as prior information for 
the calibrated properties model CRWMS M&O (2000, U0035). 
The test-interval lengths between packers were approximately 4 m for vertical boreholes, 1 to 
3 m for Alcoves 1, 2, and 3, and 5 to 12 m in the Alcove 5 SHT and DST areas. Extensive airpermeability 
data on the scale of 0.3 m were measured in the niches (CRWMS M&O 2000, 
U0015). For Tptpmn, the niche data sets have approximately one order of magnitude lower mean 
values and two orders of magnitude higher range than the vertical borehole values. In this 
comparison, only the pre-excavation permeability values from the niche sites are used. The postexcavation 
data are used in the seepage calibration model CRWMS M&O (2000, U0080). 
The detailed line survey (DLS) data along ESF, together with air-permeability data, are the 
primary data sets used to derive other fracture properties. Borehole fracture data were used only 
when no data or incomplete data were available from the ESF DLS. Fracture spacing and 
frequency are calculated from averaging the DLS. The fracture intensity is calculated by dividing 
the trace length of the fracture by the area surveyed. Fracture interface area is calculated by 
dividing the fracture area by the volume of the interval surveyed. Fracture apertures are 
calculated by the cubic law relationship. The van Genuchten fracture m parameter is determined 
by fitting an analytical solution resulting from the aperture size distribution to the fracture 
saturation-capillary pressure curve. The fracture alpha parameter (af) is related to the aperture by 
the Young-LaPlace equation. For Tptpmn, the average of log(af) value is -3.17 from the fracture 
network estimation, compared to the value of -3.16 from averaging over seepage tests in five 
niche borehole intervals. 
Fracture porosities are derived from a combination of field gas-tracer-test data and estimates 
from the geometry of fracture network. The porosities from gas-tracer tests range from 0.6% to

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-8 June 2000 
2%. The porosities from drift seepage tests have the average value of 1.3% from three watercontent 
values determined from seepage front arrival times. The value of 1% is used as an orderof-
magnitude estimate for Tptpmn (model layer tsw34). For model layers without field test data, 
fracture porosities are estimated from aperture and frequency of the fracture network, and 
relative values are scaled to the tsw34 value. 
I.6 Pneumatic Data 
The CRWMS M&O (2000, U0035), Calibrated Properties Model, uses the borehole pneumatic 
data in the inversions to calibrate the tuff model-layer and fault properties. The CRWMS M&O 
(2000, U0015), In Situ Testing of Processes, compiled the moisture monitoring data collected 
along the drifts and in alcoves for the evaluation of moisture removal induced by ventilation 
operations. Both data sets are summarized in Table I-5. 
Table I-5. Pneumatic Data for the UZ Model 
Data Description DTN or ACC 
In situ data in surfaced-based boreholes: 
NRG-6 and NRG-7a, pneumatic pressure and 
temperature 
GS950208312232.003 
GS951108312232.008 
GS960308312232.001 
GS960808312232.004 
NRG#5, pneumatic pressure GS960208312261.001 
SD-7, pneumatic pressure GS960908312261.004 
UZ-7a, NRG-6, NRG-7a, and SD-12, pneumatic 
pressure and temperature 
GS960308312232.001 
UZ#4, UZ#5, UZ-7a, NRG-6, NRG-7a, and SD- 
12, pneumatic pressure, temperature, and water 
potential 
GS970108312232.002 
UZ#4, UZ#5, UZ-7a, NRG-7a, and SD-12, 
pneumatic pressure, temperature, and water 
potential: 
1/1/97 - 6/30/97 GS970808312232.005, MOL.19980226.0042-0045 
7/1/97 - 9/30/97 GS971108312232.007, MOL.19980226.0607-0614 
10/1/97 - 3/31/98 GS980408312232.001, MOL. 19980706.0269

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-9 June 2000 
Table I-5. Pneumatic Data for the UZ Model (Continued) 
Data Description DTN or ACC 
Moisture monitoring data in underground drifts: 
21+00/LB20, 28+30/LB50, 35+00/LB40 LB960800831224.001 
21+00/LB20, 28+30/LB50, 35+00/LB40, 
42+50/LB60, 47+00/LB70, 51+73/LB80, 
57+50/LB90, 64+59, 67+00, 73+50 10/1/96  
1/31/97 
LB970300831224.001 
Before and After the Completion of the ESF LB970801233124.001 
LB970901233124.002 
7+20/GS#3, 10+93/GS#4, 28+93, 51+64, 
67+20, 10/1/96  1/31/97 
GS970208312242.001 
2/1/97  7/3197 GS970708312242.002 
8/1/97  7/31/98 GS980908312242.024 
ECRB Cross Drift 0+25, 2+37, 2+88, 3+38, 
10+03, 21+07, 24+75, 4/8/98  7/31/98 
GS980908312242.035 
ECRB Cross Drift 14+35, 21+40, 25+55 LB990901233124.006 
Pneumatic pressure data measured in situ in five boreholes (NRG#5, NRG-6, NRG-7a, SD-7, 
and SD-12) are used in the 1-D inversion. These boreholes do not intersect known large faults, 
and thus the pneumatic pressure data are representative of the formation rock of Yucca 
Mountain. Pneumatic pressure data measured in borehole UZ-7a are used in the 2-D inversion 
for fault properties. This borehole intersects the Ghost Dance fault, and thus the pneumatic 
pressure data are representative of the faulted rock of Yucca Mountain. 
Thirty days of data from each borehole are used for either the simultaneous inversion of five 
borehole columns or for the 2-D inversion for fault properties. The data are selected from the 
time period prior to detection of any influence associated with construction of the ESF. Most of 
the attenuation and lag of barometric signal occurs within the PTn and not in the fractured TCw 
or TSw. The data from all PTn instrument stations or ports, along with data from one TCw port 
(nearest to the bottom) and two TSw ports (uppermost and lowest), are used in the inversions. 
PTn contains multiple layers and has heterogeneous permeability distributions calibrated by 
pneumatic inversion. 
With the penetration of the ESF drifts underground, atmospheric conditions were introduced into 
deep tuff units along the drifts. The barometric signals in the TSw ports became less attenuated 
as the ESF passed by the boreholes. In addition to barometric pressure, relative humidity, 
temperature, and/or air velocities are monitored along the drifts and in the alcoves, as 
summarized in Table I-5. The moisture conditions in the drifts are sensitive to the ventilation 
operations. Ventilation can remove the moisture, dry up the rock, and suppress the seepage. The 
perturbation to the ambient UZ conditions by the ESF drifts is de facto a mountain scale test at 
Yucca Mountain. UZ model calibration for the ambient conditions does not use the postpenetration 
data. Detected changes in pneumatic and moisture conditions can be used to validate

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-10 June 2000 
the models, assess the impacts of drift construction and operation, and provide inputs to 
repository design. 
I.7 Saturation Data 
The CRWMS M&O (2000, U0035), Calibrated Properties Model, uses the core saturation data 
summarized in Table I-6 in the inversions to calibrate the tuff model-layer and fault properties. 
The CRWMS M&O (2000, U0015), In Situ Testing of Processes, compiled the saturation data 
collected in alcoves and niches. The saturation data sets are summarized in Table I-6. 
Table I-6. Saturation Data for the UZ Model 
Data Description DTN or ACC 
Saturation data from surface-based borehole cores: 
UZ-7a, UZ-14, UZ#16, SD-7, SD-9, and SD-12 GS000399991221.004 
SD-6 GS980808312242.014 
WT-24 GS980708312242.010 
Saturation data from underground borehole cores 
Alcove 3, 1 borehole 
Alcove 4, 2 boreholes 
GS980908312242.033 
GS980908312242.032 
North Ramp, 7+27  10+70 
South Ramp, 59+65  76+33 
GS980308312242.005 
GS980308312242.003 
3 boreholes in Alcove 6, 
1 borehole in Alcove 7 
GS980908312242.029 
GS980908312242.028 
Niche 3566, 3 main boreholes, 6 lateral 
boreholes 
Niche 3650, 7 main boreholes 
GS980908312242.018 
GS980908312242.020 
ECRB Cross Drift Starter tunnel, 1 slant 
borehole below the invert 
GS980908312242.030 
Time domain reflectometry measurements: 
South Ramp, 8/1/97 - 1/4/98 GS980308312242.001 
Crossover point, ESF Main Drift 30+62 below the ECRB 
Cross Drift, 6/19/98 - 7/16/98 
LB980901233124.014 
Saturation data measured on core from seven deep boreholes (SD-6, SD-7, SD-9, SD-12, UZ-14, 
UZ#16, and WT-24) are used for the 1-D inversions. Saturation data measured on core from 
borehole UZ-7a are used for the 2-D inversions. 
Some of the cores from shallow boreholes in alcoves and niches are affected by the drying 
process, which can decrease the saturation several meters into the rock from the drift walls. The 
dry samples are not used in UZ model calibrations. The time-domain reflectometry (TDR) 
sensors are widely used in soil studies and are applied in the ESF boreholes or walls for detection

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TDR-NBS-HS-000002 REV00 ICN1 Attachment I-11 June 2000 
of saturation changes and wetting front arrivals. Not included in Table I-6 are neutron-hole 
surveys in the ESF, which were widely used in the infiltration study. 
I.8 Water Potential Data 
The CRWMS M&O (2000, U0035), Calibrated Properties Model, uses the borehole water 
potential data in the inversions to calibrate the tuff model-layer and fault properties. The 
CRWMS M&O (2000, U0015), In Situ Testing of Processes, compiled the water-potential data 
in the ESF to evaluate the extent of the drying into the rock and in situ profiles along the drifts. 
The water-potential data sets are summarized in Table I-7. 
Table I-7. Water-Potential Data 
Data Description DTN or ACC 
In situ water-potential data with psychrometer in surfacebased 
boreholes 
UZ#4, NRG-6, NRG-7a, SD-12, and UZ-7a GS950208312232.003 
GS951108312232.008 
GS960308312232.001 
GS960808312232.004 
GS970108312232.002 
GS970808312232.005 
GS971108312232.007 
GS980408312232.001 
Psychrometer data in underground drifts 
Niche 3566, 3 main boreholes, 5 lateral 
boreholes, 5/9/9710/21/97 
Niche 3650, 6 main boreholes, 7/1/977/28/97 
Niche 3107, 3 main boreholes, 12/22/971/8/98 
LB980001233124.001 
Cross over point, ESF Main Drift 30+62 below 
the ECRB Cross Drift, 6/19/987/16/98 
LB980901233124.014 
ECRB Cross Drift Starter tunnel, 1 slant 
borehole below the invert 
LB980901233124.014 
Heat dissipation probe (HDP) data in underground drifts: 
Niche 3566, 21 HDP, 11/4/977/31/98 GS980908312242.022 
Alcove 7, 12/9/971/31/98 GS980308312242.007 
South Ramp, 8/1/971/4/98 GS980308312242.002 
ECRB Cross Drift 0+507+75, 6 HDP, 4/23/98 
7/31/98 
GS980908312242.036 
ECRB Cross Drift GS000399991221.001 
Filter paper data on cores in underground drifts: 
Alcove 3, 1 core hole 
Alcove 4, 2 core holes 
GS980908312242.033 
GS980908312242.032 
North Ramp, 18 boreholes, Alcove 4, 3 
boreholes, and South Ramp, 46 boreholes, HQ, 
2-m length 
GS980308312242.004

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-12 June 2000 
Five surfaced-based boreholes have enabled continuous measurements of in situ water potential 
with psychrometer since 1997 (see also Table I-5 on pneumatic pressure data). Data measured in 
four boreholes (UZ#4, NRG-6, NRG-7a, and SD-12) are used in the 1-D inversions for rock 
formation outside the fault zones. Data from UZ-7a intercepting the Ghost Dance fault are used 
in the 2-D inversions. The inversions use the in situ water-potential data summarized in the first 
entry of Table I-7 and the core saturation data of Table I-6. 
Water-potential data measured in the ESF short boreholes and on cores generally have values 
substantially different from in situ values because of drying by drift ventilation or drying during 
drilling and/or handling. Drift-ventilation effects are minimized by bulkhead sealing in niches, 
Alcove 7, and in the second half of the ECRB Cross Drift. Preliminary data indicate that the 
water-potential values in the lower tuff units are in the range of -1 bar, substantially higher than 
values measured in the ESF Main Drift and/or sealed intervals in surface-based boreholes. 
I.9 Geochemical Data 
The CRWMS M&O (2000, U0085), Analysis of Geochemical Data for the Unsaturated Zone, 
and CRWMS M&O (2000, U0100), Unsaturated Zone and Saturated Zone Transport 
Properties, analyze and evaluate the UZ sorption and diffusion parameters for the UZ transport 
processes. 
Table I-8. Geochemical Data for the UZ Model 
Data Description DTN or ACC 
Mineralogic data: 
Model input and output files for mineralogic 
Model MM3.0 Version 3.0. 
LA9908JC831321.001 
Mineralogic characterization of the ESF SHT 
Block 
LASL831151AQ98.001 
Chloride, chlorine-36, bromide, sulfate data: 
Deep boreholes, halide and 36Cl analyses 
NRG-4, NRG-6, and NRG-7/7A 
UZ#16 
UZ-14 
SD-12 
LAJF831222AQ96.005 
LAJF831222AQ96.014 
LAJF831222AQ96.015 
LAJF831222AQ97.007 
ESF, Cl, 36Cl, Br, S LA9909JF831222.010 
LA9909JF831222.005 
LAJF831222AQ98.004 
ESF, CWAT#1, #2, and #3, Cl, Br, S LAJF831222AQ98.007 
Niches 3566 and 3650, Cl, Br, S LA9909JF831222.012 
Tritium data: 
SD-7, SD-9, UZ-14, NRG-7a 
Alcoves 2 and 3 
Alcove 5 SHT 
UZ-14, C#2, C#3, WT##, WT#17, WT-24, 
10/06/97  07/01/98 
GS951208312272.002 
GS961108312261.006 
GS970608312272.005 
GS991108312272.004

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-13 June 2000 
Table I-8. Geochemical Data for the UZ Model (Continued) 
Data Description DTN or ACC 
DST water and gas chemistry data: 
CO2 gas analyses LB991215123142.001 
DST, 4th, 5th, and 6th Qtr. CO2 data LB990630123142.003 
UZ diffusion and dispersivity coefficients: MO9807SPAAREST.000 
MO9810SPA00026.000 
MO9807SPATBDOC.000 
UZ retardation data: 
Np sorption column measurements 
Radionuclide elution data through crushed tuff 
columns and through fractured tuff columns 
Radionuclide retardation measurements of Ba, 
CE, Se, Sr, U, Pu, and. Np 
Kd for zeolitic rocks in UZ transport model 
LA000000000034.002 
LAIT831341AQ95.001 
LAIT831341AQ97.001 
LAIT831341AQ96.001 
LABR831371DN98.002 
Busted Butte UZ transport test data: 
Tracer Breakthrough Concentrations 
Radionuclide sorption coefficients of Np, Pu, U, 
Se 
Ground penetrating radar 
LA9909WS831372.001 
LA9909WS831372.002 
LA9909WS831372.003 
LB990423123112.001 
LB990423123112.002 
LB000123123112.001 
ESF tracer field test data: 
Alcove 6 fracture-matrix interaction test bed LB990901233124.001 
Niche 3650 drift seepage test LB990601233124.003 
Surface water data: 
Southern Nevada, 8/83  8/86, isotope content 
and temperature of precipitation 
GS920908315214.032 
Fortymile Wash, 1993 water year, water quality 
data 
GS940308312133.002 
Fortymile Wash, 1995 water year , water 
quality data 
GS960308312133.001

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-14 June 2000 
Table I-8. Geochemical Data for the UZ Model (Continued) 
Data Description DTN or ACC 
Pore water data: 
Triaxial-Compression Extraction GS90090123344G.001 
NRG-6, NRG7/7a, UZ-14 and UZ-N55, and 
UZ#16, chemical data from cores 
UZ-1, UZ-14, UZ#16, NRG-6, NRG-7a, SD-7, 
SD-9, Alcove 3 RBT#1, RBT#4, ESF rubble, 
94-96 
10/1/96  1/31/97 
NRG-7a, SD-7, SD-9, SD-12, UZ-14, 2/1/97  
8/31/97 
UZ-7a, WT-24, SD-6, SD-7, SD-12, 97  98 
UZ-14 and UZ-16 
GS950608312272.001 
GS961108312271.002 
GS970208312271.002 
GS970908312271.003 
GS980108312272.004 
GS990208312271.001 
Uranium isotopic data: 
SW NevadaSE California, U isotopic analyses 
U and Th analyzed 1/94  9/96 
Alcove 5, 4/97  5/97 
12/96  12/97 
5/89  8/97 
1/15/98  8/15/98 
GS930108315213.004 
GS960908315215.013 
GS970508312271.001 
GS980108312322.003 
GS980208312322.006 
GS980908312322.009 
Strontium isotope data: 
4/8/88  5/2/89 
5/3/89  5/9/91 
5/10/91  2/28/92 
11/19/92  12/3/93 
12/6/93  8/17/94 
9/7/94  5/4/95 
SD-7 and ESF calcite 
WT-24 and J-13 
SD-9 and Sd-12 
SD-9 and SD-12, X-ray fluorescence elemental 
compositions 
GS920208315215.012 
GS910508315215.005 
GS920208315215.008 
GS931008315215.029 
GS941108315215.010 
GS950608315215.002 
GS970908315215.011 
GS981008315222.004 
GS990308315215.004 
GS990308315215.003 
UZ-1 carbon and oxygen data: 
UZ-1, 14C 
UZ-1, 13C/12C 
UZ-1, 13C/12C and 18O/16O 
GS911208312271.009 
GS930108312271.010 
GS930408312271.020 
GS940408312271.005 
GS940408312271.008 
GS911208312271.010 
GS930108312271.009 
GS930408312271.019 
GS940408312271.004 
Geochemical data are used in the ambient geochemical model for CRWMS M&O (2000, 
U0050), UZ Flow Models and Submodels. Pore-water samples are mainly collected from eight 
boreholes (NRG-6, NRG-7A, SD-7, SD-9, SD-12, UZ#4, UZ-14, and UZ#16). Chloride 
concentrations are used in water-infiltration calibration to match the chloride distributions along 
the ESF and the ECRB Cross Drift. Hydro-geochemical simulations are carried out for the NRS- 
7A column and for the WT-24 column, with the calcite data available in the second borehole.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-15 June 2000 
The transport properties are used in the CRWMS M&O (2000, U0060), Unsaturated Zone 
Radionuclide Transport Model. The Kd values for radionuclides 99Tc, 237Np, 239U, and its 
daughter products (including the 235U with modest absorption and long half-life) are among the 
important parameters used for the transport calculations. Colloidal transport is sensitive to 
filtration mechanisms, which are evaluated in the CRWMS M&O (2000, U0070), Unsaturated 
Zone Colloid Transport Model. 
I.10 Temperature Data 
The CRWMS M&O (2000, U0050), UZ Flow Models and Submodels, uses temperature profiles 
for calibration. 
Table I-9. Temperature Data for the UZ Model 
Data Description DTN or ACC 
In situ temperature data in surface-based boreholes 
NRG-6, NRG-7a, UZ#4, SD-12, and UZ-7a GS950208312232.003 
GS951108312232.008 
GS960308312232.001 
GS960808312232.004 
GS970108312232.002 
GS970808312232.005 
GS971108312232.007 
GS980408312232.001 
Thermal conductivity, grain specific heat SNT05071897001.012 
Heat load data and repository footprint SN9907T0872799.001 
Hydrologic and thermal properties of drift design 
elements 
SN9908T0872799.004 
Effective thermal conductivity SN9907T0872799.002 
The recent data from six boreholes (NRG-6, NRG-7A, SD-12, UZ#4, UZ#5, UZ-7) are used for 
the calibration. The temperature profile data set (Sass et al. 1988) is one of the first sets of data 
used to indicate that the percolation flux is higher than the low value in the sub-mm/yr range. 
With low percolation flux, the convective contribution to heat transfer is suppressed. The 
deviation from conduction-only profiles is used to determine percolation flux. 
I.11 Perched Water Data 
The CRWMS M&O (2000, U0050), UZ Flow Models and Submodels, uses perched water data 
for calibration.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-16 June 2000 
Table I-10. Perched Water Data for the UZ Model 
Data Description DTN or ACC 
Water Table Elevations MO9609RIB00038.000 
Perched Water Elevations 
UZ-14 GS960308312312.005 
WT-24 GS98058312313.001 
G-2 GS970208312312.003 
G-2 GS981008312313.003 
SD-9 and NRG-7a MOL.19980220.0164 
SD-7 MOL.19971218.0442 
The perched water elevations are used together with matrix liquid saturations and water 
potentials for the calibration. Perched water may occur where percolation flux exceeds the 
capacity of the tuff units to transmit vertical flux in the UZ. A permeability-barrier model and an 
unfractured zeolite model are used to determine the calibrated parameters for the perched water 
zones. 
I.12 Calibrated Property Sets 
The CRWMS M&O (2000, U0035), Calibrated Properties Model, uses the saturation-potential 
inversion described in Section 2.3.7 and the pneumatic inversion in Section 2.3.5 to generate the 
calibrated properties sets summarized in Table I-11. The calibrated property sets are used as 
inputs to the AMRs on UZ Flow and Transport Field. 
Table I-11. Property Sets for the UZ Model 
Data Description DTN or ACC 
Flow fields and calibrated hydrologic property set LB971212001254.006 
Top and bottom boundary temperatures, pressure, and 
boundary elevations 
LB990701233129.002 
Calibrated 1-D parameter set for the UZ Flow and 
Transport Model, FY99 
for basecase infiltration LB997141233129.001 
for upper-bound infiltration LB997141233129.002 
for lower-bound infiltration LB997141233129.003 
Drift scale calibrated 1-D property set, FY99 
for basecase infiltration LB990861233129.001 
for upper-bound infiltration LB990861233129.002 
for lower-bound infiltration LB990861233129.003

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment I-17 June 2000 
Table I-11. Property Sets for the UZ Model (Continued) 
Data Description DTN or ACC 
Calibration for CRWMS M&O 2000, U0035 Calibrated 
Properties Model 
for 1-D, mountain-scale calibration LB991091233129.001 
for 1-D, draft-scale calibration LB991091233129.002 
for 2-D, fault calibration LB991091233129.003 
for 1-D, calibrated fault properties for the UZ 
Flow and Transport Model 
LB991091233129.001 
Calibration of the UZ Flow and Transport Model is carried out in a series of steps. For the 1-D, 
mountain-scale calibration of formation rock (nonfault) parameters and the 2-D fault calibration, 
first, saturation and potential data are inverted, with permeabilities fixed. Second, the pneumatic 
data are inverted to calibrate the permeabilities. Third, the calibrated parameters are checked 
against the saturation and potential data and calibrated if necessary. And fourth, a final check 
against the pneumatic data is performed. The iteration can in principle be carried out with 
repeated cycles. As a result of the pneumatic inversion, site-scale fracture permeabilities in most 
of the TSw model layers are increased by almost two orders of magnitude compared to the prior 
information determined from air-injection tests. The air-injection tests use packed intervals with 
length a few meters or less, which is closer to the range of drift scale than site scale. In drift-scale 
calibration, the pneumatic pressure data are excluded. The drift-scale calibrated permeabilities 
are closer to drift-scale measured values. 
The calibrated property sets are used as the starting point in other calibration models for different 
processes in different scales. The CRWMS M&O (2000, U0050), UZ Flow Models and 
Submodels, uses additional chloride, calcite, temperature and perched water data to formulate the 
UZ 3-D flow fields. The CRWMS M&O (2000, U0080), Seepage Calibration Model and 
Seepage Testing Data, uses UZ site-scale flow field as boundary conditions for additional drift 
scale calibration against niche seepage data. The CRWMS M&O (2000, N0120/U0110), Drift- 
Scale Coupled Processes (DST and THC Seepage) Models, uses the calibrated property and is 
validated against DST results. The CRWMS M&O (2000, U0060), Unsaturated Zone 
Radionuclide Transport Model, uses additional transport properties to evaluate radionuclide and 
colloid transport.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-1 June 2000 
ATTACHMENT II  List of DTNs for Figures and Tables 
The Q-status of the data listed in Tables II-1 and II-2 is provided in the DIRS database for this 
PMR. 
Table II-1. DTNs for Figures 
Figure Number Data Tracking Number (DTN) 
1-1. N/A 
1-2. N/A 
2.1-1. N/A 
2.1-2. MO9901MWDGFM31.000 
2.1-3. MO9901MWDGFM31.000 
2.1-4. MO9901MWDGFM31.000 
2.2-1. LB980930123112.001 
2.2-2. (a) N/A 
(b) GS000399991221.002 
2.2-3. N/A 
2.2-4. (a) N/A 
(b) N/A 
(c) LAJF831222AQ98.004 
LA9909JF831222.005 
LA9909JF831222.010 
2.2-5. N/A 
2.2-6. (a) N/A 
(b) N/A 
(c) N/A 
(d) LB990901233124.002 
2.2-7. (a) N/A 
(b) N/A 
(c) N/A 
(d) LB990901233124.005 
2.2-8. (a) N/A 
(b) N/A 
(c) LB991131233129.002 
GS000399991221.003 
2.2-9. N/A 
2.2-10. (a) GS000399991221.002 
LB990801233129.003 
(b) LB991131233129.001 
(c) GS991299992271.001 
2.2-11. (a) N/A 
(b) GS980908315215.015 
GS960908315215.014 
(c) LAJF831222AQ98.011 
GS991299992271.001 
2.2-12. (a) LB00032412213U.001 
(b) N/A 
(c) N/A 
2.2-13. (a) N/A 
(b) N/A 
(c) LB980901123142.006 
2.2-14. N/A 
2.4-1. N/A a 
2.4-2. N/A a 
a For historical perspective only.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-2 June 2000 
Table II-1. DTNs for Figures (Continued) 
2.4-3. N/A a 
2.4-4. N/A a 
3.2-1. MO9901MWDGFM31.000 
3.2-2. N/A 
3.2-3. MO9901MWDGFM31.000 
3.2-4. N/A 
3.2-5. N/A 
3.2-6. MO9901MWDGFM31.000 
3.2-7. MO9910MWDISMMM.003 
3.3-1. N/A 
3.3-2. N/A 
3.3-3. N/A 
3.3-4. N/A 
3.3-5. N/A 
3.3-6. N/A 
3.3-7. N/A 
3.3-8. N/A 
3.4-1. N/A 
3.4-2. N/A 
3.4-3. (a) MO9901MWDISMMM.000 
(b) MO9910MWDISMMM.003 
3.4-4. (a) MO9901MWDISMRP.000 
(b) MO9910MWDISMRP.002 
3.4-5. LB990051233129.001 
3.4-6. (a) N/A 
(b) LB990501233129.004 
(c) LB990701233129.001 
3.4-7 (a) MO9901MWDGFM31.000 
(b), (c) LB990701233129.001 
3.4-8 (a) MO9901MWDGFM31.000 
(b), (c) LB990701233129.001 
3.4-9 (a) MO9901MWDGFM31.000 
(b), (c) LB990501233129.004 
3.5-1. N/A 
3.5-2. (a) N/A 
(b) GS000399991221.002 
(c) N/A 
3.5-3. N/A 
3.5-4. GS000399991221.002 
3.5-5. GS000399991221.002 
3.5-6. SN0003T0503100.001 
3.6-1. N/A 
3.6-2. N/A 
3.6-3. N/A 
3.6-4 LB991091233129.001 
3.6-5 LB991091233129.003 
3.6-6. LB997141233129.001 
3.6-7. LB997141233129.001 
3.6-8. GS960308312232.001 
GS980908312242.036 
LB990801233129.003 
LB991121233129.007 
3.6-9. N/A 
3.7-1. N/A 
3.7-2. N/A 
3.7-3. LB990701233129.001

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-3 June 2000 
Table II-1. DTNs for Figures (Continued) 
3.7-4. (a) LB990801233129.003 
(b) LB990801233129.015 
(c) LB990801233129.009 
3.7-5. N/A 
3.7-6. MO9901MWDGFM31.000 
3.7-7. LB990801233129.003 
3.7-8. (a) LB990801233129.003 
(b) LB990801233129.003 
3.7-9. LB990801233129.025 
3.7-10. (a) LB990801233129.003 
(b) LB990801233129.003 
(c) LB990801233129.004 
3.7-11. (a) LB990801233129.003 
(b) LB990801233129.015 
(c) LB990801233129.009 
3.7-12. (a) LB990801233129.003 
(b) LB990801233129.015 
(c) LB990801233129.009 
3.7-13. (a) LB990801233129.003 
(b) LB990801233129.003 
3.7-14 LB990801233129.003 
LB990801233129.009 
LB990801233129.015 
GS000399991221.004 
3.7-15 LB991121233129.007 
GS960308312232.001 
3.7-16. SN9912T0581699.003 
SN0001T0581699.004 
3.7-17. SN9912T0581699.003 
3.7-18. SN9912T0581699.003 
SN0001T0581699.004 
3.7-19 N/A 
3.8-1. N/A 
3.8-2. N/A 
3.8-3 GS000399991221.002 
LB990801233129.003 
3.8-4. LB991131233129.003 
3.8-5 LB991131233129.003 
3.8-6. LB991131233129.001 
3.8-7. LB991131233129.003 
3.8-8 N/A 
3.9-1. N/A 
3.9-2. N/A 
3.9-3. N/A 
3.9-4. LB990831012027.001 
3.9-5. LB990831012027.001 
3.9-6. LB980001233124.003 
LB990831012027.001 
3.9-7. N/A 
3.9-8. N/A 
3.9-9. N/A 
3.9-10. SN9912T0511599.002 
3.9-11. SN9912T0511599.002 
3.9-12. N/A 
3.10-1. N/A 
3.10-2. N/A 
3.10-3. N/A

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-4 June 2000 
Table II-1. DTNs for Figures (Continued) 
3.10-4 LB991200DSTTHC.002 
3.10-5 LB991200DSTTHC.002 
3.10-6. LB991200DSTTHC.002 
3.10-7. LB991200DSTTHC.002 
3.10-8. LB991200DSTTHC.002 
3.10-9. LB991200DSTTHC.002 
3.10-10. LB991200DSTTHC.002 
3.10-11. LB991200DSTTHC.002 
3.10-12. LB991200DSTTHC.002 
3.10-13. N/A 
3.11-1. N/A 
3.11-2. N/A 
3.11-3. N/A 
3.11-4. LB991220140160.012 
3.11-5. LB991220140160.012 
3.11-6. LB991220140160.012 
3.11-7. LB991220140160.017 
3.11-8. LB9908T1233129.001 
3.11-9. LB9908T1233129.001 
3.11-10. LB991220140160.012 
LB991220140160.017 
3.11-11. N/A 
3.11-12. SN9908T0581699.001 
LB990901233129.001 
3.11-13. SN9908T0581699.001 
LB990901233129.001 
3.11-14. SN9908T0581699.001 
LB990901233129.001 
3.11-15. SN9908T0581699.001 
LB990901233129.001 
3.11-16. N/A 
3.12-1. N/A 
3.12-2. N/A 
3.12-3. LB990701233129.001 
3.12-4. LB991201233129.001 
3.12-5. LB991201233129.001 
3.12-6. LB991201233129.001 
3.12-7. LB991201233129.001 
3.12-8. LB991201233129.001 
3.12-9. LB991201233129.001 
3.12-10. LB991201233129.001 
3.12-11. LB991201233129.001 
3.12-12. LB991201233129.001 
3.12-13. LB991201233129.001 
3.12-14. LA0004WS831372.002 
5.1-1. N/A 
5.1-2. N/A 
5.1-3. N/A 
5.1-4. N/A 
5.1-5. N/A

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-5 June 2000 
Table II-2. DTNs for Tables 
Table Data Tracking Number (DTN) 
1-1. N/A 
1-2. N/A 
1.2-1 N/A 
1.2-2. N/A 
1.2-3. N/A 
1.3-1. N/A 
2.3-1. N/A 
2.5-1. N/A 
3.2-1. N/A 
3.2-2. N/A 
3.4-1. N/A 
3.5-1. N/A 
3.5-2. GS000399991221.002 
3.5-3. GS000399991221.002 
3.5-4. GS000399991221.002 
3.7-1. GS000399991221.002 
3.7-2. LB990801233129.003 
LB990801233129.009 
LB990801233129.015 
3.7-3. LB990801233129.003 
LB990801233129.009 
LB990801233129.015 
3.7-4. LB990801233129.003 
LB990801233129.009 
LB990801233129.015 
3.7-5. LB990801233129.001 
LB990801233129.003 
LB990801233129.005 
LB990801233129.007 
LB990801233129.009 
LB990801233129.011 
LB990801233129.013 
LB990801233129.015 
LB990801233129.017 
3.8-1. LB991131233129.001 
3.9-1. LB991101233129.001 
3.9-2. SN9912T0511599.002 
3.10-1. LB991200DSTTHC.001 
3.10-2. N/A 
3.10-3. MO9912SPAPAI29.002 
3.11-1. LA0003AM831341.001 
3.11-2. LA0003JC831362.001 
3.11-3. LB991220140160.012 
3.11-4. LA0004WS831372.002 
3.12-1. N/A 
3.13-1. N/A 
4.2-1. N/A 
4.3-1. N/A 
5.2-1. N/A

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-6 June 2000 
REFERENCES FOR ATTACHMENT II 
CRWMS M&O 2000 (U0100). Unsaturated Zone and Saturated Zone Transport Properties. 
ANL-NBS-HS-000019. Input Transmittal 00104.T. Las Vegas, Nevada: CRWMS M&O. 
ACC: 20000310.0366. 
CRWMS M&O 2000 (U0095). Analysis of Infiltration Uncertainty. ANL-NBS-HS-000027 
REV 00. Input Transmittal 00113.T. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.20000313.0632. 
DTN: GS000399991221.002. Rainfall/Runoff/Runon 1999 Simulations. Submittal date: 
03/10/2000. 
DTN: GS000399991221.003. Preliminary Alcove 1 Infiltration Experiment Data. Submittal 
date: 03/10/2000. 
DTN: GS000399991221.004. Preliminary Developed Matrix Properties. Submittal date: 
03/10/2000. 
DTN: GS960308312232.001. Deep Unsaturated Zone Surface-Based Borehole Instrumentation 
Program Data from Boreholes USW NRG-7A, USW NRG-6, UE-25 UZ#4, UE-25 UZ#5, USW 
UZ-7A, and USW SD-12 for the Time Period 10/01/95 through 3/31/96. Submittal date: 
04/04/1996. 
DTN: GS960908315215.014. Uranium and Thorium Isotope Data for ESF Secondary Minerals 
Collected Between March 1996 and July 1996. Submittal date: 09/25/1996. 
DTN: GS980908312242.036. Water Potentials Measured With Heat Dissipation Probes in 
ECRB Holes from 4/23/98 to 7/31/98. Submittal date: 09/22/1998. 
DTN: GS980908315215.015. Uranium and Thorium Isotope Data Including Calculated 
230TH/U Ages and Initial 234U/238U Activity Ratios for in Situ Microdigestions of Outermost 
Opal-Rich Mineral Coatings from the Exploratory Studies Facility Analyzed Between 12/01/97 
and 09/15/98. Submittal date: 09/23/1998. 
DTN: GS991299992271.001. Preliminary Unsaturated Zone Borehole Hydrochemistry Data. 
Submittal date: 12/23/1999. 
DTN: LA0003AM831341.001. Preliminary Revision of Probability for Sorption Coefficients 
(K_DS) . Submittal date: 03/29/2000. Submit to RPC URN-0267 
DTN: LA0003JC831362.001. Preliminary Matrix Diffusion Coefficients for Yucca Mountain 
Tuffs. Submittal date: 4/10/2000. 
DTN: LA9909JF831222.005. Chlorine-36 Analyses of ESF and Busted Butte Porewaters in 
FY99. Submittal date: 09/29/1999.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-7 June 2000 
DTN: LA9909JF831222.010. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of ESF 
Porewaters. Submittal date: 09/29/1999. 
DTN: LA0004WS831372.002. Sorption of Np,Pu, and Am on Rock Samples From Busted 
Butte, NV. Submittal date: 04/19/2000. Submit to RPC. 
DTN: LAJF831222AQ98.004. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of Salts 
Leached from ESF Rock Samples. Submittal date: 09/10/1998. 
DTN: LAJF831222AQ98.011. Chloride, Bromide, Sulfate and Chlorine-36 Analyses of 
Springs, Groundwater, Porewater, Perched Water and Surface Runoff. Submittal date: 
09/10/1998. 
DTN: LB980001233124.003. Liquid Release Tests Performed to Determine if a Capillary 
Barrier Exists in Niches 3566 and 3650. Submittal date: 04/23/1998. 
DTN: LB00032412213U.001. Busted Butte Ground Penetrating Radar Data 
Collected June 1998 through February 2000 at the Unsaturated Zone 
Transport Test (UZTT): GPR Velocity Data. Submittal date: 
03/24/2000. Submit to RPC 
DTN: LB980901123142.006. Laboratory Test Results of Hydrological Properties 
from Post-Test Dry-Drilled Cores in the Single Heater Test Area for the 
Final TDIF Submittal for the Single Heater Test. Submittal date: 
08/31/1998. 
DTN: LB980930123112.001. Surface to ESF Seismic Tomography. Submittal date: 
09/30/1998. 
DTN: LB990051233129.001. Extent of Vitric Region Used to Assign Material Properties in FY 
9 UZ Model Layers; Figure 5 From AMR U0000, Development of Numerical Grids for UZ 
Flow and Transport Modeling. Submittal date: 09/24/99. 
DTN: LB990501233129.004. 3-D UZ Model Calibration Grids for AMR U0000. 
Development of Numerical Grids of UZ Flow and Transport Modeling. Submittal date: 
09/24/1999. 
DTN: LB990701233129.001. 3-D UZ Model Grids for Calculation of Flow Fields for PA for 
AMR U0000, Development of Numerical Grids for UZ Flow and Transport Modeling. 
Submittal date: 09/24/1999. 
DTN: LB990801233129.001. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #1). Submittal date: 11/29/1999. 
DTN: LB990801233129.003. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #3). Submittal date: 11/29/1999.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-8 June 2000 
DTN: LB990801233129.004. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #4). Submittal date: 11/29/99. 
DTN: LB990801233129.005. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #5). Submittal date: 11/29/1999. 
DTN: LB990801233129.007. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #7). Submittal date: 11/29/1999. 
DTN: LB990801233129.009. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #9). Submittal date: 11/29/1999. 
DTN: LB990801233129.011. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #11). Submittal date: 11/29/1999. 
DTN: LB990801233129.013. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #13). Submittal date: 11/29/1999. 
DTN: LB990801233129.015. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #15). Submittal date: 11/29/1999. 
DTN: LB990801233129.017. TSPA Grid Flow Simulations for AMR U0050, UZ Flow 
Models and Submodels. (Flow Field #17). Submittal date: 11/29/1999. 
DTN: LB990801233129.025. TSPA Grid Flow Simulations for AMR U0050, "UZ Flow Models 
and Submodels." Flow Field #25: Present Day Mean Infiltration for Flow-Through Perched- 
Water Conceptual Model. Submittal date: 3/11/00. 
DTN: LB990831012027.001. Input to Seepage Calibration Model AMR U0080. Submittal 
date: 08/31/1999. 
DTN: LB9908T1233129.001. Transport simulations for the low, mean, and upper infiltration 
scenarios of the present-day, monsoon, and glacial transition climates. Submittal date: 3/11/00. 
DTN: LB990901233124.002. Alcove 6 Flow Data for AMR U0015, In Situ Field Testing of 
Processes. Submittal date: 11/01/99. 
DTN: LB990901233124.005. Alcove 4 Flow Data for AMR U0015, In Situ Field Testing of 
Processes. Submittal date: 11/01/99. 
DTN: LB990901233129.001. Input and Output Data for Verification of Dual-Continua Particle 
Tracker (DCPT) for AMR U0155,  Analysis Comparing Advect-Dispersion Transport Solution 
to Particle Tracking. Submittal date: 10/26/99. 
DTN: LB991091233129.001. One-Dimensional, Mountain-Scale Calibration for AMR U0035, 
Calibrated Properties Model. Submittal date: 10/22/1999.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-9 June 2000 
DTN: LB991091233129.003. Two-Dimensional Fault Calibration for AMR U0035, Calibrated 
Properties Model. Submittal date: 10/22/99. 
DTN: LB991101233129.001. Model Input/Output Files Supporting Seepage Model for PA in 
AMR U0075, Seepage Model for PA Including Drift Collapse. Submittal date: 11/30/99. 
DTN: LB991121233129.007. Calibrated parameters for the present-day, mean infiltration 
scenario, used for simulations with perched water conceptual model #3 (non-perching) for the 
mean infiltration scenarios of the present-day, Monsoon and Glacial transition climates. 
Submittal date: 3/11/00. 
DTN: LB991131233129.001. Modeling calcite deposition and percolation. Submittal date: 
3/11/00. 
DTN: LB991131233129.002. Modeling seepage and tracer tests at Alcove 1. Submittal date: 
3/11/00. 
DTN: LB991131233129.003. Analytical and Simulation Results of Chloride and Chlorine-36 
Analysis. Submittal date: 3/11/00. 
DTN: LB991200DSTTHC.001. Pore water composition and CO2 partial pressure input into 
THC simulations of the Drift Scale Test and the THC Seepage Model, Table 3 of AMR 
U0110/N0120. Submittal date: 3/11/00. 
DTN: LB991200DSTTHC.002. Model Input and Output Files, Excel Spreadsheets and 
Resultant Figures which are Presented in AMR N0120/U0110, Drift-Scale Coupled Processes 
(Drift-Scale Test and THC Seepage) Models. Submittal date: 12/15/99. 
DTN: LB991201233129.001. The Mountain-Scale Thermal-Hydrologic Model Simulations for 
AMR U0105, Mountain-Scale Coupled Processes (TH) Models. Submittal date: 12/15/99. 
DTN: LB991220140160.012. Model Prediction of 3-D Transport, Present-Day Infiltration, #1 
Perched Water Model, using EOS9nT Input and Output files. Submittal date: 3/11/00. 
DTN: LB991220140160.017. Model Prediction of 3-D Colloid Transport, Present-Day 
Infiltration, #1 Perched Water Model, using EOS9nT Input and Output files. Submittal date: 
3/11/00. 
DTN: LB997141233129.001. Calibrated Base-case Infiltration 1-D Parameter Set for the UZ 
Flow and Transport Model FY99. Submittal date: 07/21/1999. 
DTN: MO9901MWDGFM31.000. Geologic Framework Model. Submittal date: 01/06/1999. 
DTN: MO9901MWDISMMM.000. Mineralogy Models. Submittal date: 01/22/1999. Submit 
to RPC. 
DTN: MO9910MWDISMMM.003. ISM3.1 Mineralogic Models. Submittal date: 10/01/99.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN1 Attachment II-10 June 2000 
DTN: MO9901MWDISMRP.000. ISM3.0 Rock Properties Models. Submittal date: 
01/22/1999. Submit to RPC. 
DTN: MO9910MWDISMRP.002. Rock Properties Model (RPM3.1). Submittal date: 
10/06/1999. 
DTN: MO9912SPAPAI29.002. PA Initial Abstraction of THC Model Chemical Boundary 
Conditions. Submittal date: 01/11/2000. Submit to RPC URN-0282. 
DTN: SN0001T0581699.004. Supplemental Files to Support Base-case Particle-tracking 
Analysis for TSPA-SR (Total System Performance Assessment-Site Recommendation) (In 
Analysis/Model Report U0160, ANL-NBS-HS-000024). Submittal date: 01/06/2000. 
DTN: SN0003T0503100.001. Weighting Factors for Low, Middle and High Climate Infiltration 
Rate Maps. Submittal date: 03/20/2000. 
DTN: SN9908T0581699.001. Files to Support 1-D Comparison Between FEHM Particle 
Tracking and T2R3D Advective-Dispersive Transport Simulations along SD-9. Submittal date: 
08/16/99. 
DTN: SN9912T0511599.002. Revised Seepage Abstraction Results for TSPA-SR (Total 
System Performance Assessment-Site Recommendation). Submittal date: 12/15/99. 
DTN: SN9912T0581699.003. Files to Support Base-case Particle-tracking Analyses (AMR 
U0160) for TSPA-SR. Submittal date: 12/13/99.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-1 June 2000 
ATTACHMENT III  FIGURES

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-2 June 2000 
Figure 1-1. Schematic Diagram Showing the Relationships among Major YMP Documents, Including 
Analysis/Model Reports (AMRs), PMRs, SDs, SRR, and TSPA Documents AMRs Data Feeds 
 
In Situ Field Testing of Processes 
 Analysis of Geochemical Data for the UZ 
 UZ/SZ Transport Properties 
 Analysis of Hydrologic Properties 
AMRs Abstractions 
 Abstraction of Drift Seepage 
 Abstraction of Flow Fields 
 Particle Tracking Model and Abstraction of 
Transport 
AMRs Evaluations 
 Natural Analogs for the UZ 
 FEPs in UZ Flow and Transport 
 Analysis Comparing Advective-Dispersive 
Transport Solution to Particle Tracking 
 Analysis of Base-Case Particle Tracking 
Results for the Base-Case Flow Fields 
AMRs Model Development 
 Conceptual and Numerical Models for UZ 
Flow and Transport 
 Future Climate Analysis 
 Analysis of Infiltration Uncertainty 
 Development of Numerical Grids for UZ 
Flow and Transport Modeling 
 UZ Colloid Transport Model 
AMRs Models and Simulations 
 Simulation of Net Infiltration for Modern 
and Potential Future Climates 
 Calibrated Properties Model 
 Drift-Scale Coupled Processes Models 
 Seepage Calibration Model 
 Seepage Model for PA 
 UZ Flow Models and Submodels 
 Mountain-Scale TH Model 
 UZ Radionuclide Transport Model 
Repository 
Safety 
Strategy 
Allocation 
Analysis 
Regulatory 
Requirements 
Site 
Description 
TSPA 
UZ Flow and Transport 
PMR 
SR/LA 
Design

Cl-36 
Ambient Geochemistry 
Model 
Flow 
Model 
Transport 
Model 
Thermal-Hydrological 
Model 
Seepage Model for PA 
Model 
Thermal-Hydrological- 
Chemical 
Model 
Infiltration Climate 
TSPA 
Calibrated Properties Calibrated Properties 
Model 
Seepage Calibration 
Model 
Drift Scale Test THC 
Model 
UZ PMR Models 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-3 June 2000 
Figure 1-2. Main Models Included in the UZ PMR, Their Interrelations, and Their Connections to TSPA

1/2/80 1/1/85 1/1/90 1/1/95 
Time Line 
1/1/00 
UZ Boreholes UZ Boreholes UZ Boreholes 
Nye County Boreholes Nye County Boreholes 
LBT at Fran Ridge 
Seepage at Niches 
NRG Boreholes NRG Boreholes 
Mapping Mapping Mapping 
Calcite and Cl-36 Study 
Conceptual Model CM 
UZ Flow-1986 F-86 
TSPA-1991 TSPA-91 
UZ Flow-1994 F-94 
TSPA-1995 T-95 
UZ Flow-1997 F-97 
TSPA-1993 TSPA-93 
Drilling/Excavation Testing Modeling 
UZ Transport-1997 T-97 
TSPA-VA TSPA-VA 
SD Boreholes 
SD-6 
SD Boreholes 
H, WT Boreholes H, WT Boreholes WT-24 
NR and GDF Alcove Testing 
Logging and Geophysics 
Borehole Testing and Monitoring 
Infiltration Study 
NR and GDF Alcove Testing 
Infiltration Study 
Calcite and Cl-36 Study 
LBT at Fran Ridge 
Moisture Monitoring and 
Potential Measurements 
Transport at Busted Butte 
DST at Alcove 5 
SHT at Alcove 5 
ESF 
ECRB Cross Drift 
ESF and ECRB Cross Drift 
G Boreholes G Boreholes 
a, b, c, p, VH Boreholes a, b, c, p, VH Boreholes 
Neutron Boreholes Neutron Boreholes Neutron Boreholes 
Transport at Busted Butte 
Seepage at Niches 
DST at Alcove 5 
Moisture Monitoring and Potential Measurements 
SHT at Alcove 5 
Borehole Testing and Monitoring 
Logging and Geophysics Logging and Geophysics 
Legend 
Boreholes 
Tunnels (ESF and ECRB) 
Field Testing 
Reports 
TSPA Reports 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-4 June 2000 
Figure 2.1-1. Chronology of Drilling/Excavation, Testing, and Modeling Activities of the UZ Site 
Characterization Program at Yucca Mountain

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-5 June 2000 
Figure 2.1-2. Schematic Illustration of the Main Surface-Based Deep Boreholes and Underground Drifts 
of the ESF, and the Major Faults in the Vicinity of Yucca Mountain 
1400 
1000. 
600 
200 
168000 
169000 
170000 
171000 
172000 
173000 
EASTING 
(meters) 
.. 
239000. 
238000. 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000. 
NORTHING 
(meters) 
Elevation 
(masl) 
G-2 G-2 WT-24 WT-24 
WT#18 WT#18 
UZ#4 
UZ#5 
UZ#4 
UZ#5 
UZ-14 UZ-14 
G-1 G-1 
SD-9 SD-9 
G-4 G-4 
NRG-7A NRG-7A 
NRG#4 NRG#4 
WT#4 WT#4 
SD-6 SD-6 
UZ-6 UZ-6 
H-6 H-6 
H-6 
SD-12 SD-12
SD-7 SD-7
UZ-7A UZ-7A 
WT-1 WT-1 
UZ#16 UZ#16 ONC#1 ONC#1 
NRG-6 NRG-6 
Solitario 
Canyon 
Solitario 
Canyon 
Yucca 
Wash 
Yucca 
Wash 
Bow 
Ridge 
Fault 
Bow 
Ridge 
Fault 
Ghost 
Dance 
Fault 
Ghost 
Dance 
Fault 
Alluvium 
UZPMR2.1-2REV00 
ECRB 
Cross Drift 
Exploratory 
Studies Facility 
Tiva Canyon Tuff 
Yucca Mtn Tuff 
Bedded Tuff 
Pah Canyon Tuff 
Bedded Tuff 
Topopah Spring Tuff 
Borehole Location

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-6 June 2000 
Figure 2.1-3. Schematic Illustration of Alcove and Niche Locations in the Exploratory Studies Facility at 
Yucca Mountain 
Tpcp 
Tpcp 
Tpcr 
and 
above 
Tptrn 
Tptrl 
Tptpul 
Tptpmn 
Tptpll Tptrv (1-3) 
Tpbt2 
Tpp Tpbt3 
Tpy 
Tpbt4 
Tpcpv 
(1-3) 
Ghost Dance FaultGhost Dance Fault 
"Imbricate" Fault"Imbricate" Fault 
Dune Wash FaultDune Wash Fault 
Sundance FaultSundance 
Fault 
Drill Hole Wash Fault 
Drill Hole Wash Fault 
"Toe" Fault"Toe" Fault 
Bow Ridge FaultBow Ridge Fault 
Alcove 4 
(Sta. 10+27.8) 
Alcove 3 
(Sta. 7+54) 
Alcove 1 
(Sta. 0+42.5) 
Alcove 2 
(Sta. 1+68.2) 
171000 171500 172000 172500 173000 173500 
234500. 
234000. 
233500. 
233000. 
232500. 
232000. 
231500. 
231000. 
230500 
EASTING (meters) 
NORTHING (meters) 
Niche 3 
(Sta. 31+07) 
(Sta. 35+66 
& 36+50) 
Alcove 6 
(Sta. 37+37) 
Alcove 7 
(Sta. 50+64) 
Niche 4 
(Sta. 47+88) 
Alcove 5 
(Sta. 28+27) 
ESF 
Niches 1 & 2

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-7 June 2000 
Figure 2.1-4. Schematic Illustration of the ECRB Cross Drift, Geological Units and Test Sites. 
(a) Generalized geological map at the Cross Drift level. (b) Generalized geological 
cross-section along the ECRB Cross Drift, showing the potential repository horizon. 
Bulkhead 
28+00 24+00 20+00 16+00 12+00 8+00 4+00 0+00 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800. 
700 
Solitario 
Canyon 
fault 
Sundance 
fault 
ECRB Cross Drift 
Niche 5 
Sta. 16+20 
Alcove 8 
Sta. 8+00 
Bulkhead Bulkhead 
Sta. 25+03 Sta. 17+63 
ECRB Station at 
ESF Crossing 
Sta. 7+73 
Potential Repository Horizon 
Elevation (meters above sea level) 
ECRB Station (meters) 
Tpcr 
Tpcp 
Tpcpv3 
Tpcpv2 
Tpcpv1 
Tpbt4 
Tpy 
Tpbt3 
Tpp 
Tpbt2 
Tptrv3 
Tptrv2 
Tptrv1 
Tptrn 
Tptrl 
Tptpul 
Tptpmn 
Tptpll 
Tptpln 
Tptpv3 
Tptpv2 
Tptpv1 
Tpbt1 
Tac 
Tacbt 
Tcpuv 
Tcpuc 
Tcpmd 
Tcplc 
Tcplv 
Tcpbt 
Tcbuv 
Tcbuc 
Tcbmd 
Tcblc 
Tcblv 
Tcbbt 
Tctuv 
Tctuc 
Tiva Canyon 
(TCw) 
Paintbrush 
(PTn) 
Topopah Spring 
(TSw) 
Calico Hills 
(CHn) 
Crater Flat 
(CFu) 
Repository Outline 
Potential 
Ghost Dance fault 
Solitario Canyon fault 
Drill Hole Wash fault 
Pagany Wash fault 
Sever Wash fault 
Sundance 
fault 
"Imbricate" fault 
Dune Wash fault 
ECRB 
ESF 
Tptpll 
Tptpmn 
Tptpln 
Tptpln 
Tptpll 
Tptpmn 
Tptpul 
Tptpul 
Tptrn 
Tptrl 
Tptpv3 
Tptpv2 
Tptpv1 
Tac 
Tpcp 
170000 171000 172000 173000 
EASTING (meters) 
236000. 
235000. 
234000. 
233000. 
232000. 
231000 
NORTHING (meters) 
Tptrn 
Elev: ~1045 m Elev: ~1030 m 
Elev: ~1125 m Elev: ~1110 m 
Alcove 8 
Niche 5 
(a) 
(b)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-8 June 2000 
Figure 2.2-1. Geological and Geophysical Studies on the Surface and along the ESF 
(a) Drilling of Borehole SD-6 on the Crest of 
Yucca Mountain 
(b) Pavement Cleared for Ghost Dance Fault Mapping 
Geologic Mapping and Geophysical Studies on Surface and in ESF 
Objectives: 
 Determine lithology and 
structural features of tuff units. 
 Evaluate distribution of fractures 
and faults. 
Approaches: 
 Map features on bedrock, in 
trenches, and along ESF drifts. 
 Conduct geophysical logging 
along boreholes. 
 Deploy geophysical tomographic 
imaging techniques on the 
surface and in underground 
drifts. 
Results: 
 Refined geological maps of 
bedrock, washes and faults. 
 Improved geological framework 
of tuff layers and fault offsets. 
 Detailed line surveys and full 
peripheral maps along drifts. 
 Interpreted fracture density 
distributions between surface 
and underground drifts. 
(c) Fracture Density 
Distributions by 
Detailed Line Survey 
and Seismic Tomograph

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-9 June 2000 
Figure 2.2-2. Infiltration Study on the Bedrock and in Washes (USGS 2000, U0010, Sections 6.3 
and 7.1) 
(a) Location of Washes Instrumented for 
Watershed Study 
(b) Estimated Net Infiltration (mm/yr) for the Mean 
Modern Climate Scenario 
(c) Neutron Logging at Pagany Wash 
Infiltration Study on the Bedrock and in Washes 
Objectives: 
 Provide upper boundary 
conditions for UZ Flow and 
Transport Model. 
 Evaluate infiltration processes 
and mechanisms for determining 
net infiltration under current dry 
and future wet conditions. 
Approaches: 
 Conduct periodic neutron logging 
in network of shallow boreholes. 
 Record climate changes and 
evaluate evapotranspiration 
potentials. 
 Instrument washes to evaluate 
run-on and run-off processes. 
Results: 
 Improved infiltration maps for 
current, monsoon, and glacial- 
transition climates. 
 Quantification of relationships 
between precipitation and net 
infiltration. 
 Quantification of downward flux 
and lateral run-on and run-off 
processes. 
0
< 1 
1 - 5 
5 - 10 
10 - 20 
20 - 50 
50 - 100 
100 - 500 
500 - 1,000 
> 1,000 
Mean 
modern climate 
net 
infiltration 
(mm/year) 
UZPMR2.2-2REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-10 June 2000 
Figure 2.2-3. Drift Seepage Test at Niche 3650 (CRWMS M&O 2000, U0015, Section 6.2.) 
Niche 3650 
(a) Schematic of Niche 3650 in the ESF 
(b) Water Collection During a Drift Seepage Test 
(c) Flow Paths Indicated by Dye Tracers on Niche Ceiling 
Drift Seepage Test at Niche 3650 
Objectives: 
 Quantify seepage threshold 
below which no seepage occurs. 
 Evaluate capillary barrier 
mechanism and measure drift- 
scale parameters. 
Approaches: 
 Use air injection tests to 
characterize the niche site with 
resolution of 0.3-m scale (one 
tenth of drift dimensions). 
 Use pulse releases to represent 
episodic percolation events. 
 Determine seepage thresholds 
by sequences of liquid releases 
with reducing rates. 
 Derive in situ fracture 
characteristic curves with 
wetting front arrival analyses. 
Results: 
 Measured seepage threshold 
ranges from 200 mm/yr to 
136,000 mm/yr at localized 
release intervals. 
 Six out of sixteen tested intervals 
did not seep. 
 Observed both flow along high- 
angle fractures and flow through 
fracture network. 
 Derived fracture capillary 
parameters and characteristic 
curves, with equivalent fracture 
porosity as high as 2.4%. 
UZPMR2.2-3REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-11 June 2000 
Figure 2.2-4. Damp Feature Observed during Dry Excavation of Niche 3566 and Bomb-Pulse 36Cl/Cl 
Signals along the ESF (Wang et al. 1999, pp. 331332; CRWMS M&O 2000, U0085, 
Section 6.6) 
Sundance 
Fault 
Cooling 
Joint 
Pre-Excavation 
Boreholes 
Main Drift To North Portal 
Bulkhead Door 
35+94 35+58 35+66 
In SituWet Feature Observed at Niche 3566 
(a) Schematic of Sealed Niche 3566 in the ESF 
(b) Photograph of a Damp Feature 
in the Brecciated Zone at the 
Back of Niche 3566 
(c) Distribution of 36Cl/Cl in the ESF 
Objectives: 
 Characterize the hydrologic 
setting of a site with bomb- 
pulse 36Cl signals, the 
Sundance fault and its first 
cooling joint. 
 Quantify seepage processes. 
Approaches: 
 Mine the niche without 
spreading water to the ceiling 
during excavation. 
 Close the bulkhead to prevent 
moisture removal by 
ventilation. 
 Monitor the rock and drift over 
long time periods. 
Results: 
 One damp feature observed 
after dry excavation at end of 
the niche. It dried up before 
bulkhead installation and did 
not rewet after long-term 
monitoring over two years. 
Measured 36Cl/Cl Ratio (x 10-15) 
ESF Station (x 100m) 
North Ramp Main Drift South Ramp 
80 0 10 20 30 40 50 60 70 
0 
1000 
2000 
3000 
4000 
5000 
Dune Wash Fault 
Ghost Dance Fault 
Sundance Fault 
Diabolus Ridge Fault 
Drill Hole Wash Fault 
Bow Ridge 
Fault 
Estimated Range 
of Meteoric Signal 
Over Past 50 ka 
Present-day 
Meteoric 
Background 
Feature-based 
Rock Samples 
Systematic 
Rock Samples 
Porewater 
Samples

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-12 June 2000 
Figure 2.2-5. Lower Lithophysal Seepage Test at ECRB Cross Drift Niche 1620 
ECRB Cross Drift 
Access Drift 
Niche
Pre-Niche Excavation Boreholes 
Post-Excavation Boreholes 
Slot Cut with 
Injection Boreholes 
Drift Seepage Test at ECRB Cross Drift Niche 1620 
(a) Schematic of Niche 3107 
(b) Alpine Miner Excavating the Access Drift 
Objectives: 
 Quantify seepage into drift in the 
lower lithophysal unit at a cavity-rich 
zone. 
 Characterize the pneumatic and 
liquid flows in the presence of 
lithophysal cavities and porous tuff. 
 Determine the differences between 
lower lithophysal unit and middle 
non-lithophysal unit of the potential 
repository rock. 
 Quantify fracture-matrix interaction 
at lower lithophysal unit. 
Approaches: 
 Observe flow paths during dry 
excavation, use air-injection tests to 
characterize liquid release intervals, 
and conduct drift seepage tests with 
liquid releases at different rates. 
 Adopt, improve, and extend the 
methodologies used in tests 
conducted in the middle non- 
lithophysal niches and test beds. 
Results: 
 Pre-excavation air-injection test 
results suggest that lower 
lithophysal unit has higher 
permeability than middle non- 
lithophysal unit. 
 Access drift has been excavated 
with an Alpine Miner. 
 Seepage tests are prepared to be 
conducted after niche excavations. 
(c) Example of a 
Cavity in the 
Lower Lithophysal 
Tuff Unit 
(d) Scanner Image along Borehole AK-1 at Niche1620 
UZPMR2.2-5REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-13 June 2000 
Figure 2.2-6. Fracture-Matrix Interaction Test at Alcove 6 (CRWMS M&O 2000, U0015, Section 6.6) 
(a) Photograph of Alcove 6 Test Bed 
(c) Schematic of Liquid Release Test 
(d) Water Collected in the Slot 
Fracture-Matrix Interaction Test at Alcove 6 
Objectives: 
 Quantify fracture-matrix interaction 
and the fraction of fracture flow. 
Approaches: 
 Use a slot below boreholes to 
capture fracture flows. 
 Estimate the fracture/matrix flow 
partitioning by mass balance. 
 Use borehole sensors to detect 
wetting front arrivals. 
Results: 
 A maximum of 80% of injected 
water was recovered for high-rate 
injection tests (i.e. 80% fracture 
flow). 
 Out flows occurred in step increments which could 
be related to water stored in fracture flow paths. 
(b) Close-up of Trays on the Slot Tray 1-5 
Tray 1-6 
Tray 2-12 
Tray 2-13 
Liquid Injection 
Zone 
Injection 
Borehole 
Collection Trays 
0 
20 
40 
60 
80 
100
0 20 40 60 80 100 120 
Injection Rate (ml/min) 
% of Injected Fluid Recovered 
Tray 1-5 
Tray 1-6 
Tray 2-12 
Tray 2-13 
Tray-Total

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-14 June 2000 
Figure 2.2-7. Paintbrush Fault and Porous Matrix Test at Alcove 4 (CRWMS M&O 2000, U0015, 
Section 6.7) 
North Face Alcove 4 
Z 
(meters) 
Slot 
Fault 
Plane 
TppTpbt2D 
Contact 
Top 
of 
argillic 
layer 
Bottom 
of 
argillic 
layer 
G4 
G1 
G2 
G3 
C1-C5 
C6-C10 5 
6 7 8 
12 
1 
11 
4 
15 
16 3 
2 
X (meters) 
1 
1
2
3
4
5
6 
2 3 4 5 6 
(a) Photograph of Alcove 4 Test Bed 
(c) Schematic of Boreholes at Alcove 4 
(d) Water Intake Rate at a PTn Fault 
Fault Flow Damping Test at Alcove 4 
Objectives: 
 Evaluate flow mechanism in the 
Paintbrush nonwelded tuff unit. 
 Quantify the damping and lateral 
diversion processes along a fault 
and along bedded tuff 
interfaces. 
Approaches: 
 Select a test bed containing 
bedded tuff layers (including an 
argillic layer), a fault, and a 
fracture. 
 Release water under constant- 
head conditions to determine the 
intake rates. 
 Monitor wetting front arrivals and 
measure potential changes in 
boreholes. 
Results: 
 Water intake rate in the fault decreased as more 
water was introduced into the release zone. 
 Clay swelling is one mechanism proposed to 
interpret the field data. 
 Detection of down-gradient increases in saturation 
occurred over shorter time intervals with each 
liquid release test. 
UZPMR2.2-7REV00 
0 
50 
100 
150 
200 
250 
0 500 1000 1500 2000 2500 
Cummulative Injection Time (min) 
Intake Rate (ml/min)
Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 
(b) Close-up of Tray on the Left-Hand 
Side of the Slot

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-15 June 2000 
Figure 2.2-8. El Nio Infiltration and Seepage Test at Alcove 1 
El Ni.o Infiltration Test at Alcove 1 
Objectives: 
 Quantify large-scale infiltration and 
seepage processes in the bedrock. 
 Evaluate matrix diffusion 
mechanism in long-term flow 
and transport tests. 
Approaches: 
 Water applied on the surface 30 m 
directly above the alcove. 
 Tests conducted in two phases: 
March - August 1998 and May 
1999 - present, with Phase 1 
focusing on flow and Phase 2 
focusing on tracer transport. 
Results: 
 Over 100,000 liters infiltrated in 
Phase 1, with observed seepage 
rates of up to 300 liter/day. 
 First seepage was observed 58 
days after Phase 1 test initiation. 
Pressure/flow response of the 
system was observed to be ~2 
days once a nearly steady-state 
system had developed. 
 High concentrations of LiBr were 
used in Phase 2 tracer test. 
 First tracer breakthrough in Phase 
2 observed in 28 days with a nearly 
steady-state flow system using a 
conservative tracer. 
 Tracer recovery data were used to 
compare with model predictions 
and to evaluate the importance of 
matrix diffusion. 
(a) Photography of ESF North Portal and 
Infiltration Plot (Blue Cover) 
(b) Schematic of Alcove 1 Infiltration Test 
(c) Tracer Breakthoughs Test Results and Model Predictions 
with Matrix Diffusion 
Surface 
Infiltration 
Blue Cover 
Water 
Collection 
Grid 
Alcove 1 
ESF 
North Ramp 
30 m 
10-2 10-1 100 101 102 103 104 
Time (days) 
0.0 
0.2 
0.4 
0.6 
0.8 
1.0 
1.2 Relative tracer mass fraction (X/X0) 
threshold 
tracer test resuslts 
test results 
X X 
alpha-l=30.0m, Dm=2.0e-9, tortuosity=0.75 
alpha-l=30.0m,Dm=2.0e-9, tortuosity=0.5 
alpha-l=30.0m,Dm=2.0e-9,tortuosity=0.25 
alpha-l=0m,Dm=2.0e-9,tortuosity=0.5 
alpha-l=0m,Dm=1.0e-10,tortuosity=0.5 
X 
Note : in all cases, phi=0.03 and alpha-t=alpha-l/10

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-16 June 2000 
Figure 2.2-9. Cross-Drift Test between ECRB Cross Drift Alcove 8 and ESF Main Drift Niche 3107 
(CRWMS M&O 2000, U0015, Section 6.9) 
Alcove 8-Niche 3107 Cross-Drift Test 
Objectives: 
 Quantify large-scale infiltration 
and seepage processes in the 
potential repository horizon. 
 Evaluate matrix diffusion 
mechanism in long-term flow 
and transport tests across an 
lithophysal-nonlithophysal 
interface. 
Approaches: 
 Water releases are in Alcove 8 
and seepage collections are in 
Niche 3107. 
 Niche 3107 is instrumented with 
seepage collectors and wetting 
front sensors. 
 Geophysical tomographs are 
conducted in vertically slanted 
boreholes. 
Status: 
 Drill-and-blast phase of Alcove 8 
excavation was completed in 1999. 
 Tests are prepared to be 
conducted after alcove excavation. 
Supporting Results: 
 Seepage tests at Niche 3107 
behind bulkhead demonstrate the 
existence of seepage threshold 
under high humidity conditions. 
 During ECRB Cross Drift 
construction, no water was 
observed to seep into the ESF 
Main Drift 20 m below. 
(a) Schematic of the Cross Drift Test Bed 
(b) Photograph of Partial Excavated Alcove 8 in ECRB Cross Drift 
(c) Photograph of Water 
Collection Trays on the 
Ceiling of the ESF Main Drift 
ESF Niche 3107 
Existing Niche 3107 
Seepage Boreholes Niche 3 
Boreholes (4) 
ECRB 
Cross Drift 
Alcove 8 
Alcove 8 Boreholes (6) 
Blast 
Monitoring 
Boreholes (5) 
ESF Main Drift 
UZPMR2.2-9REV00

G-2 WT-24 
WT#18 UZ#4 
UZ#5 
UZ-14 
G-1 
SD-9 
G-4 
NRG-7A 
NRG#4 
WT#4 
SD-6 
UZ-6 
H-6 
SD-12
SD-7
UZ-7A 
WT-1 
UZ#16 ONC#1 
NRG-6 
Solitario Canyon 
Yucca Wash 
Bow Ridge fault 
Ghost Dance fault 
Exploratory 
Studies Facility 
ECRB 
Cross Drift 
Objectives: 
 Provide data to define geochemical 
evolution of water in the UZ. 
 Provide data to estimate 
percolation flux at depth. 
Approaches: 
 Collect gas and perched water 
samples by pumping. 
 Extract pore water by 
compression, ultracentrifuge, 
or vacuum distillation. 
 Determine major ion 
concentrations by chemical 
analyses. 
Results: 
 Total dissolved solid and chloride 
are used to estimate infiltration 
rates and percolation fluxes. 
 Pore waters are related to soilzone 
processes: 
evapotranspiration, dissolution 
and precipation of pedogenic 
calcite and amorphous silica. 
 Deep pore waters are used to 
evaluate restricted water-rock 
interactions and significant lateral 
movement within Calico Hills unit. 
(a) Total Chloride Contents Along the ECRB Cross Drift 
(b) Calcite Distributions Used for Infiltration and 
Percolation Evaluations 
(c) Strontium Profiles Used for Zeolite Quantification 
Geochemical Measurements on Borehole and ESF Samples 
0 
20 
40 
60 
0 500 1000 1500 2000 2500 
ECRB Station [m] 
Cl Concentration [mg/L] 
Field Data 
Simulation Using Present-day 
Mean Infiltration 
Simulation Using Calibrated 
Present-day Mean Infiltration 
-------------------- 
--------------------- 
1500 
1400 
1300 
1200 
1100 
1000 
900
1E+0 1E+1 1E+2 1E+3 
Change of Volume Fraction (ppmV) 
Elevation (m) 
1E+4 1E+5 1E+6 
PTn 
TCw 
TSw 
2 5.92 
Infiltration Rate (mm/yr) 
Water Type 1 
(Average TSw Water) 
20 
Field Data 
Model Result for 2 mm/yr 
Infiltration Rate 
Model Result for 5.92 
mm/yr Infiltration Rate 
Model Result for 20 mm/yr 
Infiltration Rate 
700 
800 
900 
1000 
1100 
1200 
1300 
1400
0.001 0.01 0.1 1 
Sr [mg/L] 
Elevation [m] 
UZ-14 
NRG-7A 
SD-9 
SD-7 
UZ-4 
perched water 
measurements 
UZ-14 
NRG-7A 
SD-9 
3-D Sr Profiles At 
Borehole Locations 
SD-7 
PTn UZ#4, 
UZ#5 
WT-24 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-17 June 2000 
Figure 2.2-10. Geochemical Studies of Tuff Samples (CRWMS M&O 2000, U0050, Section 6.5; 
Sonnenthal and Bodvarsson 1999, p. 146)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-18 June 2000 
Figure 2.2-11. Isotopic Studies of Tuff Samples (CRWMS M&O 2000, U0085, Section 6.6) 
(a) Photograph of a Fracture with Calcite Infill 
(b) Ages of Opal Indicate Long Term Flow in Fractures 
Isotopic Measurements on Fracture Minerals and Perched Waters 
Objectives: 
 Provide isotopic data to define 
age evolution of water in the UZ. 
 Provide data to delineate flow 
paths over geological time 
scales. 
Approaches: 
 Leach salts from UZ cores or 
cutting for 36Cl and Sr isotopic 
analyses. 
 Extract water for tritium, 
hydrogen and oxygen stable 
isotopes, and carbon isotopic 
analyses. 
 Digest mineral samples for 
analyses of Sr isotope ratios and 
of U series nuclides. 
Results: 
 Bomb-pulse 36Cl/Cl signals are 
present in the vicinity of some 
fault zones in the ESF. 
 Detectable levels of tritium are 
present in ~6% of pore waters 
sampled. 
 Bomb-pulse 36Cl/Cl and tritium 
signals are not present in 
perched waters. 
 Age of perched waters, mixing 
between fast and slow flows, 
climate of recharge are 
estimated by carbon and stable 
isotope analyses. 
 234U/238U activity ratios indicate 
recharge through fractures and 
minimal exchange between pore 
water and fracture water. 
UZPMR2 2 11REV00 
(c) Perched Water Ages Determined by 14C and 36Cl/Cl Data 
12 
10
8
6
4
2
0 50 100 150 200 250 
230Th / U Age, in ka 
Initial U/ U activity ratio 
234 238 
In situ HF 
digestion 
of outer 
surfaces 
Whole hemisphere 
digestion 
1.0 
1.0 
1.0 
0.5 
0.5 
0. 
5 
0.0 
0.0 
0.0 
mm 
1.5 
1.5 
2.5 
2.5 
3.0 3.5 4.0 2.0 
2.0 
HD2074 
ESF 30+50.7 
Opal hemisphere cut and etched 
0.05 mm 
1.0 mm 
= 2.5mm/ Ma 
= 2.5mm/Ma 
20 ka 
400 ka 
Observed age assumed to 
represent the average age of 
deposition. Actual duration 
equals twice the measured age.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-19 June 2000 
Figure 2.2-12. UZ Transport Test at Busted Butte (CRWMS M&O 2000, U0100, Section 6.8) 
(b) Schematic of Busted Butte Test Area 
Busted Butte 
Fran Ridge 
Yucca Mountain 
Solitario Canyon 
(c) Tracer Plume from Injection in the Side Wall of the 
Main Adit, Opposite to the Test Alcove (Phase 1A) 
(a) Ground Penetrating Radar Tomograph 
of Injected Plume (Phase 2) 
Objectives: 
 Quantify UZ transport processes 
in Calico Hills nonwelded unit. 
 Measure retardation coefficients in 
the field to compare with 
laboratory measured values. 
Approaches: 
 A test bed was excavated 70 m 
below the surface in mainly vitric 
CHn underlying the vitrophyre. 
 A mixture of conservative and 
sorbing tracers is used in tracer 
injection tests. 
 Absorbent pads are used to 
sample periodically the tracer 
distributions below injections. 
 Ground-penetrating radar 
tomography, together with 
electrical resistivity tomography 
and neutron logging, are used to 
track plume migrations. 
Results: 
 Phase 1A was conducted with 
single point injections from April 
1998 to mineback in 1999. 
Capillary driven flow mechanism 
is confirmed. 
 Phase 2 tests with areal injections 
are on-going with breakthroughs 
and plume migrations monitored. 
UZ Transport Test at Busted Butte 
Tptpv2 
Tptpv1 
Tac 
15 
m 
5 m 
7 m 
5 m 
2 m 
5m 
11 
46 
47 41
40 
7
8 5 
6 
14
17 
1823 
2427 
43 
44 
45 
10 
12 
9 48 
13 15 
Main Adit 
TestAlcove 
Legend 
Collection Boreholes 
Boreholes Used for GPR 
Injection Boreholes 
ERT Boreholes 
9 
18 
40 
10 
16 
42 
10 m 
Layout of Boreholes 
0.00 0.01 -0.01 
43 
27 
45 
Borehole 46-16 
(04/01/99 - 09/01/98) 
Change in Velocity (M/NS) 
18 
42 
44 
23 
22 
21 
20 
19 
24 
25 
26 
16 
46

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-20 June 2000 
Figure 2.2-13. Single Heater Test at Alcove 5 (Tsang and Birkholzer 1999, pp. 411-415) 
Objectives: 
 Evaluate THMC coupled 
processes around a line heater 
source in fractured tuff. 
 Develop testing methodologies 
and modeling approaches for high 
temperature conditions. 
Approaches: 
 Heating with a 5-m long 4-kW 
heater lasted 9 months in 1996 
and 1997. 
 Borehole sensing and cross-hole 
testing were used before, during, 
and after heating period. 
Results: 
 Extent of dry-out of about 1 m 
around the heater hole was 
measured with geophysical 
techniques (ERT, GRP and 
neutron). 
 Condensate zone below the 
heater was measured to be larger 
than above the heater horizon. 
 Chemical composition of water 
collected during heating in packed 
borehole intervals was analyzed. 
 Characterization data by air- 
injection tests and mechanical 
displacement measurements 
located high-k flow paths. 
(a) Schematic of Single Heater Test 
(b) Photograph of Single Heater Test Block Insulated 
(c) Distributed Liquid Saturation in Cores After Cooling Phase 
UZPMR2.2-13REV00 
Single Heater Test at Alcove 5 
-4 -3 -2 -1 0 1 2 3 4 5 6 7 
x (m) 
-4 
-3 
-2 
-1
0
1
2
3
4 
z (m) 
l iquid saturation 
0.9400 
0.8314 
0.7229 
0.6143 
0.5057 
0.3971 
0.2886 
0.1800 
r = 3m 
199 
200 
201 
* Cores 81, 83, and 86 not available for 
hydrological measurements. 
** Derived saturation is depressed because 
of the high porosity values (13 % - 17 %). 
80** 
97** 
02** 
82 84 
85 
87 
88 
89 
6 
7 
8 
9 
10 
11 
12 
90 
91 
95 
96 
03 
01 
92 
93 
94 
98 
99 
00 
* * * 
Heater 
Thermal 
Mechanical 
Hydrological 
Chemical 
TMA 
Extension 
Observation 
Drift 
Thermochemical 
Alcove

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-21 June 2000 
Figure 2.2-14. Drift Scale Test at Alcove 5 (CWRMS M&O 2000, U0110/N0120, Section 6.2) 
Drift Scale Test at Alcove 5 
Connecting 
Drift 
Wing 
Heaters 
Observation 
Drift 
Heated Drift 
Objectives: 
 Evaluate THCM coupled 
processes in emplacement drift 
scale with full-scale heaters. 
 Evaluate multi-drift heating effects 
with wing heaters to simulate 
multi-drift test conditions in 
fractured tuff. 
Approaches: 
 Install extensive borehole sensor 
arrays for monitoring of heating 
responses. 
 Perform periodic geophysical 
imaging, pneumatic testing, and 
fluid sampling to measure the 
thermally induced coupled effects. 
Results: 
 Drift wall temperature reached 
~190C after 2 years of heating 
(since December 1997 at 187 kW). 
 Condensate accumulated mainly 
below the wing heaters at early 
times. 
 Wetting and drying zones were 
identified by periodic air- 
injection tests and geophysical 
methods. 
 Gas phase CO2 concentration 
increased strongly in large 
region around the heaters. 
 Interactions of calcite and 
silicate minerals were indicated 
by chemical analyses of water 
collected. (c) Comparison of Measured and 
Modeled Temperature Distributions 
(b) Photograph of Full Scale Heaters within Heated Drift 
(a) Schematic of Drift Scale Test 
140 
130 
120 
110 
100 
90 
80 
70 
60 
50 
40 
30 
20 
10 
Hydrology 
Boreholes 
Measured 
Test Data 
(at x = 0m) 
Modeled Data 
(at y = 17m) C

PTn PTn 
CHv CHv 
TCw 
Q 0 
0.01 0.1 1.0 
0.001 
0 
0
100 
200 
300 
400 
500 
600 
0.2 0.4 
Degree of Liquid Saturation 
Infiltration Rate in mm/yr 
Depth Below Ground Surface (m) 
0.6 0.8 1.0 
TSw 
Bullfrog Bullfrog 
N 
0 0.5 1.0 0.75 2.0 
Distance (km) 
Outline of 
Potential Repository 
TSPA Transect 
Calico 
Hills 
Calico 
Hills 
Prow 
Pass 
Prow 
Pass Ghost Dance 
Fault 
6 
4 3 2 1 
5 
USW H-5 
UE-25 a#1 
4 
5 
3 
2 1 
6 
7 
8
Ghost 
Dance 
Fault 
Ghost 
Dance 
Fault 
(a) 1-D Model of ambient saturation 
conditions for different percolation 
flux values UZ Flow  1986 
(c) 8 1-D Columns from different areas, 
0-5 mm/yr infiltration during dry 
periods and 10 mm/yr during wet 
periods TSPA  1993 
(b) 6 1-D Columns in 1 transect with 
1mm/yr infiltration, composite-porosity 
and weep models TSPA  1991 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-22 June 2000 
Figure 2.4-1. One-Dimensional Column Simulations with the UZ-1986, the TSPA-1991, and the 
TSPA-1993 Models (Rulon et al. 1986, Barnard et al. 1992, and Wilson et al. 1994)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-23 June 2000 
Figure 2.4-2. The Mesh and Approximations Used in the UZ-1995 Model (Wittwer et al. 1995, 
pp. 46-47) 
(a) (b)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-24 June 2000 
Figure 2.4-3. Simulations of 237Np Transport by the UZ Transport-1995 Model (Robinson et al. 1995, 
p. 61, p. 125) 
Figure 2.4-3 DRAFT 
West 
Concentration 0 1 
East 
900,000 Years 
250,000 Years 
75,000 Years 
30,000 Years 
5,000 Years 
(a) Finite Element Grid of the Antler Ridge Cross Section 
(b) Simulations of Transport of 237Np from the Potential Repository

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-25 June 2000 
Figure 2.4-4. The Mesh and the Approximations Used in the UZ-1997 Model for TSPA-VA 
(adapted from Wu et al. 1999b, pp. 190-193) 
1.68E5 1.70E5 1.72E5 1.74E5 
2.30E5 
2.32E5 
2.34E5 
2.36E5 
2.38E5 
o 
o 
Model boundary 
Solitario 
Canyon 
fault 
Ghost 
dance 
fault 
Dune 
wash 
fault 
Bow 
Ridge 
fault 
UZ-14 
G-3
SD-7 
H-6 
G-2 
H-5 
WT-24 
Drillhole 
wash 
fault 
Imbricate 
fault 
UZ#16 
SD-12 
SD-6 
NRG-7a 
W E 
N 
S 
WT#18 
H-3 
Solitario 
West 
fault 
Sever 
wash 
fault 
P 
agany 
wash 
fault 
SD-9 
NORTH NEVADA COORDINATES (m) 
EAST NEVADA COORDINATES (m) 
169478 
800 
170365 
1100 
171243 
1400 
172121 172999 168609 
Elevation [m] 
East Nevada Coordinate [m] 
UZ-7a 
Solitario 
Canyon 
Fault 
Dune 
Wash 
Fault 
Ghost 
Dance 
Fault 
(a) Areal Grid 
(b) Vertical Grid

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-26 June 2000 
Figure 3.2-1. Yucca Mountain Site-Scale Geology: (a) in 3-D Perspective and (b) along an East-West 
Cross Section (adapted from GFM3.1 data, CRWMS M&O 2000, I0035) 
Borehole SD-6 
Borehole 
SD-12 
Borehole 
UZ#16 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault Dune 
Wash 
fault 
Elevation in meters above mean sea level 
Repository 
Horizon 
TCw 
CHn (zeolitic) 
CHn (vitric or 
devitrified) 
CFu 
230000 
232000 
234000 
236000 
238000 
240000 
Northing 
(meters) 
168000 
170000 
172000 
Easting 
(meters) 
Faults 
0 .25 .50 .75 1.0 
Distance (km) 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
(a) 
(b) 
Yucca 
Crest 
ucca 
Crest 
Yucca Crest 
Yucca 
Wash 
Sever 
Wash 
Drill 
Hole 
Wash 
Pagany 
Wash 
Potential Repository Potential Repository PTn 
TSw

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-27 June 2000 
Figure 3.2-2. Lithostratigraphic Transitions at the Upper and Lower Margins of the PTn Hydrogeological 
Unit. (a) Photos and schematic at the TCw-PTn interface, where tuffs grade downward 
from densely welded to nonwelded, accompanied by an increase in matrix porosity and a 
decrease in fracture frequency. (b) Photo and schematic at the PTn-TSw interface, where 
tuffs grade downward from nonwelded to densely welded, accompanied by a decrease in 
matrix porosity and an increase in fracture frequency. 
Tptpmn 
Tptpll 
Tptpln 
TCw 
PTn 
CHn 
CFu 
Solitario 
Canyon 
fault 
Ghost Dance Fault 
"Imbricate" 
Fault 
East-West Cross Section along N232,233 meters. 
Elevation in meters above mean sea level 
Tptrn 
Tptrl 
& 
Tptpul 
Base of TCw 
TCw 
Tpcpln 
Tpcpv2 
Tpcpv1 
Tpbt4 
TCw 
PTn 
TSw 
PTn 
TSw 
(b) 
(a) PTn 
PTn 
Fault 
Fractures 
Fractures 
Fractures 
Fault 
Vapor-Phase 
Corrosion 
Fault 
Clay Alteration 
Alteration 
Fault 
1 meter 
1 meter 
0 0.125 0.25 0.375 0.5 
Distance (m) 
0 0.25 0.50 0.75 1.0 
Distance (km) 
1 meter 
1 meter

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-28 June 2000 
Figure 3.2-3. Thickness Contour Plots of the (a) PTn, (b) TSw, (c) CHn, and (d) CFu Hydrogeological 
Units (Adapted from DTN: MO9901MWDGFM31.000). Contours are in meters. 
PTn Thickness (m) TSw Thickness (m) (a) (b) 
Easting (m) 
Northing (m) 
Easting (m) 
(c) (d) CHn Thickness (m) CFu Thickness (m) 
239000. 
238000. 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
Northing (m) 
239000. 
238000. 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
Northing (m) 
239000. 
238000. 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
Northing (m) 
239000. 
238000. 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
168000 169000 170000 171000 172000 173000 168000 169000 170000 171000 172000 173000 
168000 169000 170000 171000 172000 173000 168000 169000 170000 171000 172000 173000 
Easting (m) Easting (m) 
0 
80 
160 
40

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-29 June 2000 
Figure 3.2-4. Lithophysal Transitions within the TSw Unit. (a) Photo and schematic of the contact 
between the upper nonlithophysal (Tptpul) and the middle nonlithophysal (Tptpmn) zones 
showing a downward decrease in lithophysal volume. (b) Photo and schematic of the 
contact between the middle nonlithophysal (Tptpmn) and lower lithophysal (Tptpll) zones 
showing a downward increase in lithophysal volume. Fractures in the nonlithophysal unit 
are generally smoother, more planar, and more continuous than fractures in the 
lithophysal units. 
Tptpmn 
Tptpll 
Tptpln 
TCw 
PTn 
CHn 
CFu 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault 
"Imbricate" 
fault 
Elevation in meters above mean sea level 
Tptrn 
Tptrl 
& 
Tptpul 
1500 
1400 
1300 
1200 
1100 
1000 
900 
800. 
0 .25 .50 .75 1.0 
Distance (km) 
(a) 
(b) 
Lithophysae 
Lithophysae 
rock 
breakout 
fractures 
fractures 
Tptpmn 
Tptpll 
0.5 meters 0.5 meters 
Tptpmn 
Tptpul 
fractures 
Tptpul 
Tptpmn 
Tptpmn 
Tptpll 
Schematic Photo 
fractures

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-30 June 2000 
Figure 3.2-5. Lithostratigraphic Transitions at the TSw-CHn Interface. (a) Schematic with prevalent 
alteration at the TSw-CHn contact. (b) Schematic with variable alteration at the TSw-CHn 
contact. (c) Schematic with minimal alteration at the TSw-CHn contact. (d) Schematic 
representation of a fault zone as a well-connected fracture network that may represent a 
fast flow pathway. (e) Schematic representation of a fault zone showing alteration within 
the fracture network that creates a flow barrier. 
Tptpmn 
Tptpll 
Tptpln 
TCw 
PTn 
CHn (vitric) 
CFu 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault 
"Imbricate" 
fault 
Elevation in meters above mean sea level 
Tptrn 
Tptrl 
& 
Tptpul 
CHn (zeolitic) 
CHn 
(zeolitic) 
(a) (b) 
(c) 
0 .25 .50 .75 1.0 
Distance (km) 
(d) 
TSw (Tptpln) 
Basal Vitrophyre 
CHn (vitric) 
vitric 
vitric 
zeolitic 
TSw (Tptpln) 
Basal Vitrophyre 
(Tptpv3) 
CHn (vit / zeo) 
TSw 
(Tptpln) 
Basal 
Vitrophyre 
(Tptpv3) 
CHn 
(zeolitic) 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
(e) 
open 
fractures 
fractures 
filled w/ 
alteration 
minerals 
fault 
fractures 
scale: tens of meters 
scale: 
tens of centimeters 
scale: 
tens of centimeters 
scale: tens of meters 
scale: tens of meters

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-31 June 2000 
Figure 3.2-6. Occurrence of Lithostratigraphic Units at the Water Table (730 meters above sea level) 
(Adapted from DTN: MO9901MWDGFM31.000) 
Lithostratigraphic 
Units 
Potential 
Repository 
ESF 
ECRB 
Solitario 
Canyon 
fault 
Tptpln 
Tptpv3 
Tptpv2 - Tacbt 
Prow Pass Tuff 
Bullfrog Tuff 
Tram Tuff 
"Imbricate" 
fault 
Ghost 
Dance 
fault 
Dune 
Wash 
fault 
Drill 
Hole 
Wash 
fault 
Pagany 
Wash 
fault 
Bow 
Ridge 
fault 
170000 171000 172000 173000 174000
236000 
235000 
234000 
233000 
232000 
231000 
Easting (meters) 
Northing (meters) 
Sundance 
fault 
Sever 
Wash 
fault

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-32 June 2000 
Figure 3.2-7. Distribution of Zeolites in Certain Layers below the Potential Repository Horizon. 
(CRWMS M&O 2000, I0045, Section 6.3.2; DTN: MO9910MWDISMMM.003). Areas with 
less than or equal to 3% zeolite are considered vitric, or unaltered.

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-33 June 2000 
Figure 3.3-1. Schematic Showing Temporal and Spatial Variabilities of Net Infiltration Rates Resulting 
From the Nature of the Storm Events and Variation in Soil Cover and Topography. The 
size of the arrow indicates the relative magnitude of infiltration rates.
Evaporation 
Transpiration 
Infiltration 
Rate 
Run-on/Runoff 
Precipitation 
Soil 
Time 
Infiltration rate

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-34 June 2000 
Figure 3.3-2. Schematic Showing Overall Water Flow Behavior in the UZ Including the Relative 
Importance of Fracture and Matrix Flow Components in the Different Hydrogeologic Units. 
The blue and red colors on the land surface correspond to high and low infiltration rates, 
respectively, while the other colors correspond to intermediate infiltration rates 
(CRWMS M&O 2000, U0030, Figure 1). 
Episodic Fracture Flow 
Transition 
Fracture Flow 
Zeolitic 
Matrix Flow 
Saturated Zone 
Fault-DominatedFlow 
Vitric 
Cross Section West of Ghost Dance Fault 
Perched Water 
Matrix Flow 
CFu 
CHn 
TSw 
PTn 
TCw 
Evaporation 
Transpiration 
Run On/Run Off 
Potential Repository Horizon 
Yucca 
Crest 
Pagany 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Sundance 
Fault 
Solitario 
Canyon 
Fault 
Sever 
Wash 
Fault 
N

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-35 June 2000 
Figure 3.3-3. Schematic Showing Water Flow Behavior within the PTn Characterized by Dominant 
Matrix Flow and a Few Fast Flow Paths 
SD-6 
SD-12 
UZ#16 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault Dune 
Wash 
fault 
East-West Traverse through GFM 
Potential Repository 
TCw 
PTn 
TSw 
CHn 
TCw 
PTn 
An Isolated, Fast Flow Path 
Fracture Water 
Flow in the TCw 
Matrix Flow 
in the PTn 
TCw-PTn Interface 
Water Flow

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-36 June 2000 
Figure 3.3-4. Water Flow in Fractures Characterized by Fingering Flow at Different Scales 
Episodic Fracture Flow 
Transition 
Fracture Flow 
Zeolitic 
Matrix Flow 
Saturated Zone 
Fault-DominatedFlow 
Vitric 
Perched Water 
Matrix Flow 
Potential Repository Horizon 
Yucca 
Crest 
Pagany 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Sundance 
Fault 
Solitario 
Canyon 
Fault 
Sever 
Wash 
Fault 
Fracture 
Network 
Scale 
Single 
Fracture 
Scale 
Water Flow 
Water Flow 
Fingering Flow 
Matrix 
Fracture/Matrix 
Interface

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-37 June 2000 
Figure 3.3-5. Major Faults Can Act as Fast-Flow Conduits or Capillary Barriers. The size of the arrows 
in (a) and (b) indicates the relative magnitude of flow. 
SD-6 
SD-12 
UZ#16 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault 
Dune 
Wash 
fault 
East-West Traverse through GFM 
Repository 
TCw 
PTn 
TSw 
CHn 
(a) Fast Flow Pathway 
(b) Capillary Barrier 
Alteration 
Water Flow 
Water Flow 
in the Fault Zone 
Fault Zone 
Water Flow 
Alteration 
Fault Zone 
Water Flow 
in the Fault Zone

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-38 June 2000 
Figure 3.3-6. Schematic Showing Flow Patterns within and near a Perched Water Body Characterized 
by Strong Lateral Flow within the Perched Water Body and the Associated 
Fault-Dominated Flow 
Borehole SD-6 
Borehole 
SD-12 
Borehole 
UZ#16 
Solitario 
Canyon 
Fault 
Ghost Dance 
Fault 
Dune Wash 
Fault 
East-West Traverse through GFM 
Potential Repository 
TCw 
PTn 
TSw 
CHn 
Fault Zone 
Strong Lateral Flow 
Minor Fracture Flow 
Dominant 
Fracture Flow 
Perched Water 
Fault-dominated 
Flow 
Tsw 
CHn 
UZPMR3.3-6REV00

Figure 3.3-7. Important Radionuclide Transport Processes. (Note that the radionuclides also undergo 
radioactive decay, but this is not shown in the schematic.) 
Matrix 
Fluid Flow 
Fracture 
Fluid Flow 
Matrix 
Fluid Flow 
Matrix Fracture Matrix 
Flow between 
Fracture and 
the Matrix 
Mobile 
Radionuclide 
Immobile 
Radionuclide 
Mobile 
Colloid 
Immobile 
Colloid 
Attachment to the 
fracture surface 
Reversible and/or 
irreversible attachment 
to colloid 
Reversible and/or 
irreversible 
attachment to colloid 
Advection, dispersion, 
and diffusion 
Advection, 
dispersion, 
and diffusion 
Mass transfer between 
fractures and matrix 
Filtration 
Reversible sorption 
onto the fracture surface 
Reversible sorption 
onto matrix solid surface 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-39 June 2000

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-40 June 2000 
Figure 3.3-8. TH Processes at Mountain and Drift Scales 
Borehole 
SD-6 
Borehole 
SD-12 
Borehole 
UZ#16 
Solitario 
Canyon 
Fault 
Ghost 
Dance 
Fault 
Dune 
Wash 
Fault 
East-West Traverse through GFM 
TCw 
PTn 
TSw 
CHn 
Waste Package Waste Package 
Vapor Transport 
Percolation 
Heat-pipe Zone 
Potential Vapor 
Transport 
Dry-out Zone 
UZPMR3.3-8REV00 
Vapor Transport
Perched water 
Liquid 
Water 
Flow 
Drainage in Fractures 
Condensation 
Zone 
Vapor Transport 
Heat 
Transfer 
Heat 
Transfer 
Drift-Scale 
Condensation 
Zone 
Dryout Zone 
Heat-pipe 
Zone 
Heat-pipe 
Zone

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-41 June 2000 
Figure 3.4-1. Schematic Demonstrating (a) ECM, (b) Dual-Porosity with One Matrix Gridblock, 
(c) Dual-Permeability with One Matrix Gridblock per Fracture Gridblock, and (d) MINC with 
Three Matrix Gridblocks per Fracture Gridblock 
M21 
M23 
M22 
M31 
M33 
M32 
M41 
M43 
M42 
F1 M1 
F2 M2 
F3 M3 
F4 M4 
F5 
(b) 
M5 
F1 
F2 
F3 
F4 
F5
(a) 
F1 M1 
F2 M2 
F3 M3 
F4 M4 
F5 
(c) 
M5 
F1 
M11 
M13 
M12 
F2 
F3 
F4 
F5 
(d) 
M51 
M53 
M52 
Episodic Fracture Flow 
Transition 
Fracture Flow 
Zeolitic 
Matrix Flow 
Saturated Zone 
Fault-DominatedFlow 
Vitric 
Perched Water 
Matrix Flow 
Potential Repository Horizon 
Yucca 
Crest 
Pagany 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Sundance 
Fault 
Solitario 
Canyon 
Fault 
Sever 
Wash 
Fault 
Fracture-Matrix 
System 
Obliteration can be deduced from 
Figure 3.8-1, Attachment III-84

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-42 June 2000 
Figure 3.4-2. Flow Diagram Showing Key Input Data Used in Numerical Grid Development, the Types of 
Grids Generated, and their End Users 
Integrated Site Model, ISM INPUT 
OUTPUT 
END USERS 
Developed 
Fracture Data 
3-D Grids 2-D Grids 1-D Grids 
Data Integration and 
Grid Generation 
GFM RPM MM 
Flow and Transport 
Model 
Calibrated Pr operties 
Model 
Thermal-Hydrological 
Model 
Cl-36 
Ambient Geochemistry 
Model

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-43 June 2000 
Figure 3.4-3. Distribution of Percent Zeolite Mineral Abundance in the Calico Hills Formation 
(lithostratigraphic unit Tac): (a) MM2.0, (b) MM3.0. (DTNs: MO9901MWDISMMM.000, 
MO9910MWDISMMM.003, respectively). Areas with less than or equal to 3% zeolite by 
weight are considered vitric, or unaltered. 
(a) ISM3.0 Mineralogy Model Plots of % Zeolite 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
WT-2 
G-4 
G-2 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
WT-2 
G-2 
G-4 
UZ-14
G-1 
H-5
SD-7 
SD-12 
SD-9 
G-3 
UZ#16 
H-6 
WT-2 
G-2 
G-4 
UZ-14
G-1 
H-5
SD-7 
SD-12 
SD-9 
G-3 
UZ#16 
H-6 
WT-2 
G-4 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
WT-2 WT-2 WT-2 
G-2 G-2 
G-4 G-4 G-4 
G-2 
UZ-14
G-1 
H-5
SD-6 
SD-7 
SD-12 
SD-9 
G-3 
H-3 
UZ#16 
H-6 
WT-2 
G-4 
(b) ISM3.1 Mineralogy Model Plots of % Zeolite 
Tac4 (upper 1/4 of Tac) Tac3 Tac2 Tac1 (lower 1/4 of Tac) 
Tac4 (upper 1/4 of Tac) Tac3 Tac2 Tac1 (lower 1/4 of Tac) 
% by weight 
of zeolite 
Tac4 (upper 1/4 of Tac) Tac3 Tac2 Tac1 (lower 1/4 of Tac)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-44 June 2000 
Figure 3.4-4. Distribution of Matrix Permeability (m2) in Select Layers of the CHn Hydrogeologic Unit: 
(a) RPM3.0, (b) RPM3.1. (DTNs: MO9901MWDISMRP.000, MO9910MWDISMRP.002, 
respectively). In order to maintain consistent parameters within the UZ Flow and Transport 
Model PMR, saturated hydraulic conductivity (Ksat, m/s) from the RPM was converted to 
permeability (m2) by multiplying Ksat values by 10-7. 
Middle of Tptpv1_bt1 
Middle of Tptpv1_bt1 
(b) ISM3.1 Rock Properties Model (RPM3.1) Permeability Distribution 
Upper 1/4 Tac 
Upper 1/4 Tac 
Middle-Lower 1/4 Tac 
Middle-Lower 1/4 Tac 
Tacbt 
Tacbt 
Permeability 
(m ) 2 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
237000. 
236000. 
235000. 
234000. 
233000. 
232000. 
231000. 
230000 
169000 171000 173000 
10 
10 
10 
10 
10 
10 
10 
10
-12 
-13 
-14 
-15 
-16 
-17 
-18 
-19 
169000 171000 173000 169000 171000 173000 169000 171000 173000 
169000 171000 173000 169000 171000 173000 169000 171000 173000 169000 171000 173000 
(a) ISM3.0 Rock Properties Model (RPM3.0) Permeability Distribution

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-45 June 2000 
Figure 3.4-5. Extent of Vitric Region (Indicated by Pattern of Diagonal Lines) in Model Layers (a) ch1, 
(b) ch2, (c) ch3, (d) ch4, and (e) ch5. White areas indicate prevalent zeolitization 
(from CRWMS M&O 2000, U0000, Figure 5). 
f 
a a 
ff 
a 
a 
f 
f 
a 
(a) ch1 (b) ch2 (c) ch3 
(d) ch4 (e) ch5

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-46 June 2000 
Figure 3.4-6. Plan-View (a) Schematic Showing the UZ Model Boundary, the Repository Outline, Major 
Fault Locations Adapted from GFM3.1, Select Boreholes, the ESF, and the ECRB, (b) 
Numerical Grid Design for the Mountain-Scale Model Used for UZ Calibration (adapted 
from Figure V-1 of CRWMS M&O 2000, U0000), and (c) Numerical Grid Design for the 
Mountain-Scale Model Used for PA Calculations (Adapted from CRWMS M&O 2000, 
U0000, Figure VI-1). 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000 
168000 170000 172000 174000 
Map View, 53512 cells, 185245 connections, 1434 columns 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000 
168000 170000 172000 174000 
EASTING (m) 
NORTHING (m) 
Sever 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Solitario 
Canyon 
Fault 
Ghost 
Dance 
Fault 
Dune 
Wash 
Fault 
SD-12 
SD-7 
H-5 
SD-6 
UZ-6 
UZ#16 
UZ-14 
G-1
SD-9 
NRG-7a 
G-2
WT-24 
NORTHING (m) 
EASTING (m) 
NORTHING (m) 
EASTING (m) 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000 
168000 170000 172000 174000 
Map View, 50312 cells, 174553 connections, 1324 columns 
G-2
WT-24 
UZ-14 
Solitario 
Canyon 
fault 
G-1 
UZ-6 
SD-6 
SD-12 
SD-7 
H-5 
NRG-6 
SD-9 
Sever 
Wash 
fault 
NRG-7a UZ#4 
NRG#4 
UZ#16 
Pagany 
Wash 
fault 
Drill 
Hole 
Wash 
fault 
UZ-7a 
ESF 
ECRB 
Dune 
Wash 
flt 
Ghost 
Dance 
fault 
UZ 
Model 
Boundary 
(a) 
(b) (c)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-47 June 2000 
Figure 3.4-7. East-West Cross-Section through Borehole UZ-14: (a) Adapted from Data Contained in 
CRWMS M&O (2000, I0035) (b) from the 3-D UZ Model Numerical Grid for PA 
(Adapted from CRWMS M&O 1999a, Figure VI-2). The 3-D UZ Model Grid in plan view 
(c) shows the location of the cross section. Bottom elevation along cross sections is 730 m 
above mean sea level. 
Elevation (meters above mean sea level) 
tcw12 
tsw34 
tsw35 
tsw33 
tsw38 
tsw32 
ch2 
Potential Repository 
tcw11 
ch3 
ch4 
ptn25 
Northing (meters) 
Easting (meters) 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000
168000 170000 172000 174000 
G-1 
UZ-14 
3-D UZ Model Grid for 
Performance Assessment 
Solitario 
Canyon 
fault 
Drill 
Hole 
Wash 
fault 
Dune 
Wash 
fault 
Ghost 
Dance 
Fault 
ch2- 
ch5 
TCw 
PTn 
TSw 
CHn 
TCw 
PTn 
TSw 
CHn 
0 0.5 1.0 1.5 2.0 
Lateral distance (km) 
Elevation (meters above mean sea level) 
Solitario 
Canyon 
fault 
Drill Hole 
Wash 
fault 
Pagany 
Wash 
fault 
UZ-14 
G-1 
E-W Cross Section through GFM3.1 
E-W Cross Section through UZ Model PA Grid 
Solitario 
Canyon 
fault 
Drill Hole 
Wash 
fault 
Pagany 
Wash 
fault 
UZ-14 
G-1 
1600. 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
1600. 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
Tpcr 
Tpcp 
Tpbt3Tpp 
Tptrn 
Tptrl 
& 
Tptpul 
Tptpmn 
Tptpll 
Tptpln 
Potential Repository 
Tptpv3 
Tcbuc, Tcbmd, & Tcblc 
Tcpmd 
& 
Tcplc 
Tcplv, 
Tcpbt, 
& 
Tcbuv 
Tcpuv 
Tacbt 
Tac 
pp1 bf3 
pp2 
tsw36 
ch5 ch6 
(a) 
(b) 
(c)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-48 June 2000 
Figure 3.4-8. East-West Cross-Section through Boreholes SD-6, SD-12, UZ#16: (a) Adapted from Data 
Contained in CRWMS M&O (2000, I0035) (b) from the 3-D UZ Model Numerical Grid for 
PA (Adapted from CRWMS M&O 1999a, Figure VI-3). The 3-D UZ Model Grid in plan view 
(c) shows the location of the cross section. Bottom elevation along cross sections is 730 m 
above mean sea level. 
SD-6 
SD-12 
UZ#16 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault Dune 
Wash 
fault 
Elevation (meters above mean sea level) Elevation (meters above mean sea level) 
E-W Cross Section through UZ Model PA Grid 
E-W Cross Section through GFM3.1 
tcw11 
tcw12 
tsw32 
tsw33 
tsw34 
tsw35 
tsw36 
pp3 
pp1 
bf3 
bf2 
tsw37 
tsw38 
ch1 
ch2 
ch3 
ch4 
ch5 
ch6 
0 .25 .50 .75 1.0 
Lateral distance (km) 
Potential Repository 
Tpcr 
Tpcp 
Tptpmn 
Tptpll 
Tptpln 
Tptrl 
& 
Tptpul 
Tptrn 
Tcbuc, 
Tcbmd, 
& 
Tcblc 
Tcblv 
andbelow 
Tcpmd 
& 
Tcplc 
Tcplv, 
Tcpbt, 
& 
Tcbuv 
Tac 
Tacbt 
Tcpuc 
Tptpv3 
Tptpv1 
& 
Tpbt1 
SD-6 
SD-12 
UZ#16 
Solitario 
Canyon 
fault 
Ghost 
Dance 
fault Dune 
Wash 
fault 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
TCw
PTn 
TSw 
CHn 
TCw
PTn 
TSw 
CHn 
Northing (meters) 
Easting (meters) 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000 
168000 170000 172000 174000 
SD-12 
SD-6 UZ#16 
3-D UZ Model Grid for 
Performance Assessment 
Solitario 
Canyon 
fault 
Drill 
Hole 
Wash 
fault 
Dune 
Wash 
fault 
Potential Repository 
(a) 
(b) 
(c)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-49 June 2000 
Figure 3.4-9. North-South Cross-Section through Boreholes UZ-14, H-5, and SD-6: (a) Adapted from 
Data Contained in CRWMS M&O (2000, I0035) (b) from the 3-D UZ Model Calibration 
Grid (Adapted from CRWMS M&O 1999a, Figure V-4). The 3-D UZ Model Calibration Grid 
in plan view (c) shows the location of the cross sections. Bottom elevation along cross 
sections is 730 m above mean sea level. 
239000 
238000 
237000 
236000 
235000. 
.
234000. 
.
233000. 
.
232000. 
.
231000. 
.
230000. 
.
229000 
168000 170000 172000 174000 
Easting (meters) 
UZ-14 
H-5 
SD-6 
3-D Grid for UZ Model Calibration 
Solitario 
Canyon 
fault 
Drill 
Hole 
Wash 
fault 
Dune 
Washfault 
Ghost 
Dance 
fault 
(b) 
(c) 
N-S Cross Section through UZ Model Calibration Grid 
N-S Cross Section through GFM3.1 
0 .5 1.0 1.5 2.0 
Lateral distance (km) 
Tcbuc, 
Tcbmd, 
& 
Tcblc 
Tcplv, 
Tcpbt, 
& 
Tcbuv 
Drill Hole 
Wash 
fault 
UZ-14 
H-5 SD-6 
Drill Hole 
Wash 
fault 
UZ-14 
H-5 SD-6 UZ-6 
Elevation (meters above mean sea level) 
tcw12 
tsw34 
tsw35 
tsw33 
tsw32 
ch2 
Potential 
Repository 
tcw11 
ch3 
ch4 
ptn25 
ch6 
ch5 
ptn24 UZ-6 
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
Elevation (meters above mean sea level)
1500. 
1400. 
1300. 
1200. 
1100. 
1000. 
900. 
800 
(a) 
TCw 
PTn 
TSw 
CHn
TCw 
PTn 
TSw 
CHn 
Tptpmn 
Tptpll 
Tptpln 
Tac 
Tpcr 
Tpcp 
Tpp 
Tptrl & Tptpul 
Tptrn 
Tcpmd 
&Tcplc 
Tcpuc 
Tacbt 
(a) 
(b) 
Potential Repository

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-50 June 2000 
Figure 3.5-1. Summary of Issues, Modeling Methodology, Data, and Results for both the Climate and 
Infiltration Models 
UZPMR3.5-1REV00 
Issues 
 Predict Future Climate States and 
Durations at Yucca Mountain 
 Provide Lower, Mean and Upper 
Bound Values for Infiltration Model 
Results 
 Precipitation Rate (mean) and 
Duration 
Modern: 190.6 mm/yr  600 years 
Monsoon: 302.7 mm/yr  1400 years 
Glacial Transition: 317.8 mm/year  
8000 years 
Climate Model 
Model/Data 
 Precipitation and Temperature Data 
from Analog Sites 
 Monsoon:. 
Nogales, AZ; Hobbs, NM 
 Glacial Transition:. 
Spokane, Rosalia, St. John, WA;. 
Beowawe, NV; Delta, UT 
Issues 
 Estimate Infiltration Rates for UZ 
Flow and Transport Models 
 Lower, Mean, and Upper Boundary 
Values for Modern, Monsoon, and 
Glacial Transition Climates 
Results 
 Net Infiltration Rate (mean) 
Modern: 4.6 mm/yr 
Monsoon: 12.2 mm/yr 
Glacial Transition: 17.8 mm/year 
Infiltration Model 
Model/Data 
 Groundwater/Surface Water Models 
for Hydrologic Cycle 
 Calibrate to Hydrologic Properties, 
Water Content Profiles, and 
Streamflow Data

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-51 June 2000 
Figure 3.5-2. (a) Generalized View of Present-Day Atmospheric Circulation (USGS 2000, U0005, 
Figure 2) and (b) Daily Precipitation Record Between 1980 and 1995 at Yucca Mountain 
(USGS 2000, U0010, Figure 6-18) with (c) an Aerial View of the Arid Conditions at the 
Yucca Mountain Site 
0 
10 
20 
30 
40 
50 
60
1/1/80 1/1/82 1/2/84 1/2/86 1/3/88 1/3/90 1/4/92 1/4/94 
Date 
(b) 
Daily precipitation (mm) 
(a) (b) 
(c) 
UZPMR3.5-2REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-52 June 2000 
Figure 3.5-3. (a) Field-Scale Water Balance and Processes Controlling Net Infiltration 
(USGS 2000, U0010, Figure 5-1) and (b) Major Components of the Net Infiltration 
Modeling Process (USGS 2000, U0010, Figure 6-1) 
Transpiration 
Evaporation 
Precipitation 
Drainage 
Change in Storage 
Bedrock 
Soil 
Infiltration 
Run-on/runoff 
Redistribution 
Net 
Infiltration 
Boundary 
Percolation 
Recharge 
Unsaturated Zone 
Saturated Zone 
Geospatial Input Climate Input 
Precipitation 
Air Temperature 
Cloud Cover 
Day Number 
Location 
Geology 
Soil Type 
Root Zone Depth 
Vegetation Cover 
Vegetation Type 
Stream Channels 
Spatial- 
Temporal 
Distribution 
Model 
Parameter 
Table 
Input 
Estimation 
Potential 
Evapo- 
transpiration 
Model 
Water 
Balance 
Model 
Porosity 
Field Capacity 
Residual Water Content 
Soil Permeability 
Bedrock Permeability 
Root Zone Coefficients 
Output 
Water Content 
Evapotranspiration 
Streamflow 
Net Infiltration 
Initial 
Conditions 
Water Content 
Elevation 
(a) 
(b) 
UZPMR3.5-3REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-53 June 2000 
Figure 3.5-4. (a) Precipitation (USGS 2000, U0010, Figure 7-1), (b) Surface Run-On 
(USGS 2000, U0010, Figure 7-3) and (c) Net-Infiltration Rates 
(USGS 2000, U0010, Figure 7-4) for the Mean Modern Climate Scenario 
140 - 160 
160 - 180 
180 - 200 
200 - 220 
220 - 240 
240 - 260 
> 260 
0
0-1 
1 - 5 
5 - 10 
10 - 20 
20 - 50 
50 - 100 
100 - 500 
500 - 1,000 
> 1,000 
0
< 1 
1 - 5 
5 - 10 
10 - 20 
20 - 50 
50 - 100 
100 - 500 
500 - 1,000 
> 1,000 
(a) (b) (c) 
Average 
precipitation 
rate 
(mm/year) 
Infiltrated 
surface-water 
run-on 
(mm/year) 
Mean 
modern climate 
net 
infiltration 
(mm/year) 
UZPMR3.5-4REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-54 June 2000 
Figure 3.5-5. Net-Infiltration Rates for (a) Mean Monsoon (USGS 2000, U0010, Figure 7-7) and 
(b) Mean Glacial-Transition (USGS 2000, U0010, Figure 7-14) Climates 
0
0 - 1 
1 - 5 
5 - 10 
10 - 20 
20 - 50 
50 - 100 
100 - 500 
500 - 1,000 
> 1,000 
(a) (b) 
0
0 - 1 
1 - 5 
5 - 10 
10 -20 
20 -50 
50 -100 
100 - 500 
500 - 1,000 
> 1,000 
Mean 
monsoon 
climate net 
infiltration 
(mm/year) 
Mean glacial 
transition 
climate net 
infiltration 
(mm/year) 
UZPMR3.5-5REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-55 June 2000 
Figure 3.5-6. Histogram of Log of Potential Repository-Average Infiltration for Glacial-Transition Climate 
(adapted from CRWMS M&O 2000, U0095, Figure 6-2)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-56 June 2000 
Figure 3.6-1. Relationship of the Analysis of Hydrologic Properties Data and the Calibrated Properties 
Model to Input Data and Models and to Analyses and Models that use the Developed UZ 
Properties 
TSPA 
Data 
Data 
Data 
Data 
Data 
Data Data 
Data 
Geologic Framework 
Model 
Conceptual 
Model 
Infiltration 
Model 
Flow 
Model 
Transport 
Model 
Thermal-Hydrological 
Model 
Cl-36 
Ambient Geochemistry 
Model 
Pr operties 
Calibrated Model 
Thermal-Hydrological- 
Chemical 
Model 
Seepage Calibration 
Model 
U0080 
Matrix 
Properties 
Numerical 
Grid 
Water 
Potential 
Data 
Thermal 
Properties 
Saturation 
Data 
Pneumatic 
Data 
Fracture 
Mapping 
Thermal Properties 
Injection and 
Gas Tracer 
Testing 
Analysis of Hydrologic Properties Data 
Downstream Models 
Ambient Conditions Data

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-57 June 2000 
Figure 3.6-2. Issues for Development of UZ Properties 
SD-6 
SD-12 
Solitario 
Canyon 
fault 
Ghost 
Dance 
Fault 
Potential 
Repository 
TCw 
PTn 
TSw 
CHn 
UZ 
#16 
Dune 
Wash 
Fault 
PTn 
TCw 
CHn(v) 
TSw 
PTn 
TSw 
slog(k) 
Flow Repartioning at 
Welded/Nonwelded Interfaces 
Matrix 
Water Potential 
Mountain-Scale 
Properties 
Drift-Scale 
Properties 
Uncertainty of 
Calibrated Properties 
East-West Traverse through GFM

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-58 June 2000 
Figure 3.6-3. Calibrated Property Development 
Prior 
Information 1-D Grid 
Prior 
Information 1-D Grid 
Prior 
Information 
1-D Grid 
Prior 
Information 
Prior 
Information 
2-D Grid 2-D Grid 
Water 
Potential 
Data 
Saturation 
Data 
Pneumatic 
Data 
Formation Properties Calibrated 
km, kf(tsw38-bf2), am, af, mn, mf, . 
1-D Mountain-Scale Formation Property Calibration 
Water 
Potential 
Data 
Saturation 
Data 
Formation Properties Calibrated 
kf(tsw32-tsw37) 
1-D Drift-Scale 
Formation Property Calibration 
Drift-Scale 
Calibrated Formation Properties 
Mountain-Scale 
Calibrated Formation and 
Fault Properties 
Formation Properties Calibrated 
kf (tcw11-tsw37) 
Water 
Potential 
Data 
Saturation 
Data 
Pneumatic 
Data 
Fault Properties Calibrated 
(TCw, PTn, and TSw) 
km, am, af, mn, mf, . 
2-D Fault Property Calibration 
Fault Properties Calibrated 
(TCw, PTn, and TSw) 
kf

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-59 June 2000 
Figure 3.6-4. Calibrated 1-D Simulation Match to Saturation, Water Potential, and Pneumatic Data. 
Data from Borehole USW SD-12 for the Base Case Infiltration Scenario (adapted from 
CRWMS M&O 2000, U0035, Figures 2, 3, and 4) 
a 
0 5 1 0 1 5 2 0 2 5 3 0 
T im e [ d a y s f r o m 1 2 / 1 / 9 5 ] 
8 7 .0 8 7 .5 8 8 .0 8 8 .5 8 9 .0 8 9 .5 9 0 .0 
P r e s s u r e [ k P a ] 
T C w 
P T n 
T S w 
T S w 
s im u la t io n 
i n s i t u d a t a 
7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 
0 .2 0 .4 0 .6 0 .8 1 .0 
S a t u r a t i o n [ - ] 
E l e v a t io n [m ] 
c o r e d a t a 
s im u la t io n 
T C w 
P T n 
T S w 
C H n 
7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 
W a t e r P o t e n t i a l [ B a r s ] 
E l e v a t io n [m ] 
i n s i t u d a t a 
s im u la t io n 
T C w 
P T n 
T S w 
C H n 
- 1 0 0 - 1 0 - 1 - 1 0 1

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-60 June 2000 
Figure 3.6-5. Calibrated 2-D Simulation Match to Saturation, Water Potential, and Pneumatic Data from 
Borehole USW UZ-7a Base Case Infiltration Scenario (adapted from CRWMS M&O 2000, 
U0035, Figures 9, 10, and 11) 
0 5 1 0 1 5 2 0 2 5 3 0 
T im e [ d a y s a f t e r 1 2 / 1 / 9 5 ] 
8 7 8 8 8 9 9 0 9 1 
P r e s s u r e [ k P a ] 
T C w 
P T n 
P T n 
T S w 
T S w 
i n s i t u d a t a 
s im u la t io n 
7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 
0 .2 0 .4 0 .6 0 .8 1 .0 
S a t u r a t i o n [ - ] 
E l e v a t io n [m ] 
s im u la t io n 
c o r e d a t a 
G h o s t D a n c e 
F a u lt Z o n e 
T C w 
P T n 
T S w 
C H n 
7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 
W a t e r P o t e n t i a l [ B a r s ] 
E l e v a t io n [m ] 
s im u la t io n 
i n s i t u d a t a 
G h o s t D a n c e 
F a u lt Z o n e 
T C w 
P T n 
T S w 
C H n 
- 1 0 0 1 0- 1 - 1 0 1 
F ig u r e 3 . 6 - 5 R e v 0 0 C

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-61 June 2000 
Figure 3.6-6. Initial Estimate of and Calibrated Fracture and Matrix Permeability for the Base Case, 
Present-Day Infiltration Scenario (adapted from data in CRWMS M&O 2000, U0035, 
Table 13). The calibrated values for the vitric ch1 through ch5 layers are shown in a lighter 
color than the zeolitic. The prior information (initial estimate) is shown as a red line 
(green for the vitric ch1 through ch5). 
U Z P M R 3 .6 - 6 R E V 0 0 
F r a c t u r e P e r m e a b i l i t y ( m 2)
1 0- 9 1 0- 1 2 
M a t r i x P e r m e a b i l i t y ( m 2) 
1 0- 1 8 1 0- 1 5 1 0- 1 2 
c h 6 
p p 4 
p p 3 
p p 2 
p p 1 
b f3 
b f2 
C H n C F u T C w 
c h 2 
c h 3 
c h 4 
c h 5 
P T n T S w 
t c w 1 1 
t c w 1 2 
t c w 1 3 
p tn 2 1 
p tn 2 2 
p tn 2 3 
p tn 2 4 
p tn 2 5 
p tn 2 6 
t s w 3 1 
t s w 3 2 
t s w 3 3 
t s w 3 4 
t s w 3 5 
t s w 3 6 
t s w 3 7 
t s w 3 8 
t s w 3 9 
c h 1

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-62 June 2000 
Figure 3.6-7. Initial Estimate of and Calibrated Fracture and Matrix van Genuchten a Parameter for the 
Base Case, Present-Day Infiltration Scenario (adapted from data in CRWMS M&O 2000, 
U0035, Table 13). The calibrated values for the vitric ch1 through ch5 layers are shown in 
a lighter color than the zeolitic. The prior information (initial estimate) is shown as a red 
line (green for the vitric ch1 through ch5). 
U Z P M R 3 .6 - 7 R E V 0 0 
F r a c tu r e v a n G e n u c h te n 
a P a r a m e t e r ( P a - 1) 
M a t r ix v a n G e n u c h te n 
a P a r a m e t e r ( P a - 1) 
T C w P T n T S w C H n C F u 
1 0- 2 1 0- 4 1 0- 3 1 0- 6 
c h 6 
p p 4 
p p 3 
p p 2 
p p 1 
b f3 
b f2 
c h 2 
c h 3 
c h 4 
c h 5 
t c w 1 1 
t c w 1 2 
t c w 1 3 
p tn 2 1 
p tn 2 2 
p tn 2 3 
p tn 2 4 
p tn 2 5 
p tn 2 6 
t s w 3 1 
t s w 3 2 
t s w 3 3 
t s w 3 4 
t s w 3 5 
t s w 3 6 
t s w 3 7 
t s w 3 8 
t s w 3 9 
c h 1

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-63 June 2000 
Figure 3.6-8. Comparison of Predictions from the 3-D Model with In Situ Water Potential Data from the 
ECRB Cross Drift and Pneumatic Pressure Data from Borehole USW SD-12 (adapted 
from CRWMS M&O 2000, U0050, Figures 6-69 and 6-70) 
1 7 0 0 0 0 1 7 0 5 0 0 1 7 1 0 0 0 1 7 1 5 0 0 
N e v a d a S ta te P la n e E a s t in g [m ] 
- 1 0- 1 
- 1 00 
- 1 01 
W a t e r P o t e n t ia l [ B a r s ] 
i n s i t u d a t a 
s im u la t io n 
0 10 20 30 40 50 60 
T im e [d a y s f r o m 1 2 / 1 / 9 5 ] 
8 6 8 7 8 8 8 9 9 0 9 1 
P r e s s u r e [k P a ] 
1 - D c a l ib r a t io n p e r io d 
i n s i t u d a t a 
1 - D c a l ib r a t e d s im u la t io n 
3 - D p r e d ic t io n 
T S w 
P T n 
T S w 
T S w 
a

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-64 June 2000 
Figure 3.6-9. Important Results of Analysis of Hydrologic Properties Data and Calibrated Properties 
Model 
SD-6 
SD-12 
Solitario 
Canyon 
fault 
Ghost 
Dance 
Fault 
Potential 
Repository 
TCw 
PTn 
TSw 
CHn 
UZ 
#16 
Dune 
Wash 
Fault 
PTn 
TCw 
CHn(v) 
TSw 
PTn 
TSw 
slog(k) 
Use initial estimate of uncertainty to 
approximate calibrated properties 
uncertainty because of generally 
small parameter charge 
Use of only in situ 
water potential data 
results in ~2 orders of 
magnitude difference 
between fracture and 
matrix van Genuchten 
a parameters 
Fracture Flow 
~10% of total in PTn 
more where PTn 
is thin 
Fracture Flow ~85% 
of total in TSw 
Fracture Flow ~20% 
of total in vitric CHn 
TSw fracture permeability: 1 6 x 1011m2 
TSw matrix permeability: 4600 x 1018m2 
CHn vitric matrix permeability: 110 x 1013m2 
Flow Repartioning at 
Welded/Nonwelded 
Interfaces 
Matrix 
Water Potential 
Mountain-Scale Properties 
Uncertainty of 
Calibrated Properties 
East-West Traverse through GFM 
TSw fracture permeability: 
515 x 10
13 
m
2 
Drift-Scale Properties

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-65 June 2000 
Figure 3.7-1. Diagram Showing the Important UZ Flow and Transport Issues, Addressed by the Flow 
Model and Its Submodels 
Potential 
Repository 
 PTn Lateral Flow 
 Matrix Flow 
 Pulse Dampening 
 F/M Flow Through 
Vitric Zones  Flow Through Zeolites 
 Lateral/Vertical Flow 
Paths 
 Lateral Diversion 
 Perched Water Ages 
 Perched Body Extension 
 Preferential Water Flow 
 Capillary Barrier 
 Gas Flow 
 Variation in Percolation Flux 
 F/M Flow Component

UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
Solitario 
Splay 
S 
Solitario Canyon Fault 
Ghost Dance Fault West 
Bow 
Ridge 
Fault 
Dune 
Wash 
"X" 
Drillhole 
WashFault 
Pagany 
Wash 
Fault 
Sever 
Wash 
Fault 
Solitario 
WestFault 
Ghost Dance Fault 
Sundance 
Fault 
Dune Wash Fault 
Dune Wash West 1 
Imbricate 
Fault 
TSPA Mesh 
(a) (b) 
Faults 
Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-66 June 2000 
Figure 3.7-2. Perspective View of the UZ Model Domain of Yucca Mountain, Showing the 
Hydrogeological Units and Layers and Major Faults: (a) Geological Model and 
(b) Numerical Grid 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-67 June 2000 
Figure 3.7-3. Plan View of the 3-D UZ TSPA Model Grid, Showing the Model Domain at Yucca 
Mountain, Faults Incorporated and Borehole Locations (Adapted from 
CRWMS M&O, 2000, U0000, Figure VI-1) 
168000 170000 172000 174000 
EAST NEVADA COORDINATES (m) 
230000 
231000 
232000 
233000 
234000 
235000 
236000 
237000 
238000 
239000 
NORTH NEVADA COORDINATES (m) 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
Solitario 
Spla 
y 
S 
Solitario Canyon Fault 
Ghost Dance Fault West 
Bow 
Ridge 
Fault 
Dune 
Wash 
"X 
" 
DrillholeWashFault 
Pagany 
Wash 
Fault 
Sever 
Wash 
Fault 
EW-S 
SolitarioWest 
Fault 
Ghost Dance Fault 
S 
undance 
Fault 
Dune Wash Fault 
Dune Wash West 1 
Imbricate 
Fault 
EW-N 
NS 
TSPA Mesh

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-68 June 2000 
Figure 3.7-4. Three Base-Case Maps of Mean Surface Infiltration over the Flow Model Domain for 
(a) Present-Day Climate, (b) Monsoon Climate, (c) Glacial-Transition Climate 
(Adapted from CRWMS M&O, 2000, U0050, Figures 6-3, 6-4 and 6-5) 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
Solitario 
Spla 
yS 
Solitario Canyon Fault 
Ghost Dance Fault West 
BowRidge 
Fault 
DuneWash"X" 
DrillholeWash 
Fault 
PaganyWashFault 
SeverWash 
Fault 
Solita 
rioWest 
Fault 
Ghost Dance Fault 
Sundance 
Fault 
Dune Wash Fault 
Dune Wash West 1 
ImbricateFault 
TSPA Mesh 
40 
40 
15 
(a) 
(b) 
(c) 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-69 June 2000 
Figure 3.7-5. Schematic of the Major Input Data to, and Output Models from, the UZ Flow Model 
TSPA 
Data Data Data 
Seepage Model for PA 
Model 
Thermal-Hydrological- 
Chemical 
Model 
Transport 
Model 
Thermal 
Model 
Cl-36 
Geochemistry
Model 
Infiltration 
Model 
Pr operties 
Calibrated Model 
Conceptual 
Model 
Flow 
Model 
Numerical 
Grid 
Perched Water 
Properties 
Matrix 
Properties

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-70 June 2000 
Figure 3.7-6. Geological Profiles in Cross Sections Crossing the Model Domain, 
(a) North-South Transect at Yucca Mountain, Showing Thickness of the Hydrogeologic 
Units (b) East-West Transect at Yucca Mountain, Showing Incorporated Faults and 
Displacements as well as Hydrogeologic Units. 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-71 June 2000 
Figure 3.7-7. Simulated Vertical Percolation Fluxes at the PTn-TSw Interface with the Present-Day, 
Mean Infiltration Map (Data from CRWMS M&O, 2000, U0050, Section 6.6.3) 
170000 172000 174000 
Nevada Coordinate E-W (m) 
230000 
232000 
234000 
236000 
238000 
Nevada Coordinate N-S (m) 
15 
14.25 
13.5 
12.75 
12 
11.25 
10.5 
9.75 
9
8.25 
7.5 
6.75 
6
5.25 
4.5 
3.75 
3
2.25 
1.5 
0.75 
0 
TOTAL FLUX AT PTN-TSW INTERFACE (mm/year) 
(Conceptual Model #1 with Present Day Mean Infiltration) 

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-72 June 2000 
Figure 3.7-8. Effects of Faults on UZ Flow for the Present-Day, Mean Infiltration Rate; 
(a) Simulated Vertical Percolation Fluxes at the Water Table, (b) Simulated Groundwater 
Flow paths along the West-East Cross Section within Fracture-Fracture Flow Fields 
(Data from CRWMS M&O, 2000, U0050, Section 6.6.3) 
15 
(a) (b) 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
SolitarioSplay 
S 
Solitario Canyon Fault 
Ghost Dance Fault West 
BowRidgeFault 
Dune 
Wash"X" 
Drillhole 
WashFault 
Pagany 
Wash 
Fault 
SeverWashFault 
SolitarioWestFault 
Ghost Dance Fault 
SundanceFault 
Dune Wash Fault 
Dune Wash West 1 
ImbricateFault 
TSPA Mesh 
EW-S 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-73 June 2000 
Figure 3.7-9. Simulated 3-D View of Perched Water Bodies along the Base of the TSw, Using the 
Simulation Results of Conceptual Model #1 with Present-Day, Mean Infiltration Rate 
(the blue contours denote the domain with 100% water saturation and the green for the 
areas with less than 100% water saturation) (CRWMS M&O, 2000, U0050, Figure 6.9) 
WT-24 
UZ-14 
G-2 
UZ#4 
NRG-7a 
SD-9 
SD-6 
SD-12 
UZ-7a SD-7 
UZ#16 
1400 
1200 
1000 
800 
600 
169000 
170000 
171000 
172000 
173000

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-74 June 2000 
Figure 3.7-10. Comparison between Percolation Flux (mm/yr) Contours Simulated: (a) at the Potential 
Repository Horizon; (b) at the Water Table with Conceptual Model #1; and (c) at the Water 
Table with Conceptual Model #2, under the Present-Day, Mean Infiltration Rate 
(Data from CRWMS M&O, 2000, U0050, Section 6.6.3) 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
SolitarioSplay 
S 
Solitario Canyon Fault 
Ghost Dance Fault West 
Bow 
Ridge 
Fault 
Dune 
Wash"X" 
DrillholeWash 
Fault 
Pagany 
WashFault 
SeverWash 
Fault 
SolitarioWestFault 
Ghost Dance Fault 
SundanceFault 
Dune Wash Fault 
Dune Wash West 1 
Imbricate 
Fault 
TSPA Mesh 
15 
15 
15 
(c) (a) 
(b)
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-75 June 2000 
Figure 3.7-11. Simulated Percolation Fluxes at the Potential repository Under Three Mean Infiltration 
Rates: (a) Present-Day; (b) Monsoon; and (c) Glacial-Transition 
(Data from CRWMS M&O, 2000, U0050, Section 6.6.3) 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
Solitario 
Splay 
S 
Solitario Canyon Fault 
Ghost Dance Fault West 
Bow 
RidgeFault 
DuneWash"X" 
DrillholeWashFault 
Pagany 
WashFault 
SeverWash 
Fault 
S 
olitario 
WestFault 
Ghost Dance Fault 
Sundance 
Fault 
Dune Wash Fault 
Dune Wash West 1 
ImbricateFault 
TSPA Mesh 
(c) (a) 
(b) 
40 
40 
15 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-76 June 2000 
Figure 3.7-12. Areal Frequency and Distribution of Simulated Percolation Fluxes within the Potential 
Repository Horizon Under Three Mean Infiltration Rates: (a) Present Day; (b) Monsoon; 
and (c) Glacial Transition (Data from CRWMS M&O, 2000, U0050, Section 6.6.3) 
(a) 
(b) 
(c)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-77 June 2000 
Figure 3.7-13. (a) Matrix Flow (mm/yr) and (b) Fracture Flow at Potential Repository Horizon, Simulated 
Using the Present-Day, Mean Infiltration Rate. Data from CRWMS M&O, 2000, U0050, 
Section 6.6.3. 
UZ-14
NRG-7a 
SD-9 
WT-24 
G-2 
SD-12 
SD-7 
G-3 
UZ#16 
SD-6 
H-5 
UZ#4 
SolitarioSplayS 
Solitario Canyon Fault 
Ghost Dance FaultWest 
Bow 
Ridge 
Fault 
Dune 
Wash"X" 
DrillholeWash 
Fault 
Pagany 
WashFault 
Sever 
Wash 
Fault 
Solitario 
WestFault 
Ghost Dance Fault 
Sundance 
Fault 
Dune Wash Fault 
Dune Wash West 1 
Imbricate 
Fault 
TSPA Mesh 
(a) (b) 
1 5 
Illegible information can be deduced from 
Figure 3.7-3, Attachment III-67

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-78 June 2000 
Figure 3.7-14. Comparison to the Simulated and Observed Matrix Liquid Saturations and Perched Water 
Elevations for Borehole UZ-14, Using the Simulation Results for the Mean Infiltration 
Rates of the Three Climates Scenarios (Data from CRWMS M&O, 2000, U0050, 
Section 6.6.3, Figure 6-41) 
0.0 0.5 1.0 
Saturation 
700 
800 
900 
1000 
1100 
1200 
1300 
1400 
Elevation (m) 
Hydro. Unit 
pa-pchm1 
TSw 
TCw 
CHn 
Perched Water 
PTn
Field Data 
UZPMR3.7-14REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-79 June 2000 
Figure 3.7-15. Comparison of 3-D Pneumatic Prediction to Data from Borehole UZ-7a 
(CRWMS M&O 2000, U0050, Figure 6-70) 
0 10 20 30 40 50 60 
Time [days from 12/1/95] 
85 86 87 88 89 
Pressure [kPa] 
2-D calibration period 
observation 
2-D calibrated simulation 
TCw 
PTn 
PTn 
TSw 
TSw 
3-D prediction

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-80 June 2000 
Figure 3.7-16. Locations of Particle Breakthrough at the Water Table for the Mean Infiltration, 
Glacial-Transition Climate Using Two Perched Water Models 
(CRWMS M&O 2000, U0160, Figure 3) 
230000 
232000 
234000 
236000 
238000 
168000 170000 172000 174000 
Northing (m) 
Easting (m) 
230000 
232000 
234000 
236000 
238000 
168000 170000 172000 174000 
Northing (m) 
Easting (m) 
0.000 0.001  0.002 
Fraction of Total Particles Released at Repository 
(outlined) that Reached the Water Table 
Perched Water Model #1 Perched Water Model #2

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-81 June 2000 
Figure 3.7-17. Comparison of Cumulative Normalized Breakthrough Curves at the Water Table Using 
Perched Water Model #1 and #2 with a Non-Sorbing Tracer (Tc) for Mean-Infiltration, 
Glacial-Transition Climate (CRWMS M&O 2000, U0160, Figure 8. The data shown in this 
figure are based on a model that is appropriately conservative for TSPA analysis and 
consequently should not be used to evaluate expected breakthrough curves of 
radionuclides at the water table.) 
0 
0.2 
0.4 
0.6 
0.8
1
100 101 102 103 104 105 106 
FEHMv2-0_glam_Tc.qpc 
Perched Model #1 
Perched Model #2 
Cumulative Normalized Breakthrough 
Time (years) 
Mean, Glacial-Transition, Tc

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-82 June 2000 
Figure 3.7-18. Effect of Infiltration (lower, mean, and upper) on Cumulative Normalized Breakthrough 
Curves at the Water Table for a NonSorbing Tracer (Tc) Using FEHM V2.0 
(STN: 10031-2.00-00) with Present-Day Climate (CRWMS M&O 2000, U0160, Figure 12. 
The data shown in this figure are based on a model that is appropriately conservative for 
TSPA analysis and consequently should not be used to evaluate expected breakthrough 
curves of radionuclides at the water table.) 
0 
0.2 
0.4 
0.6 
0.8
1
100 101 102 103 104 105 106 
FEHMv2.0_present_Tc.qpc 
Cumulative Normalized Breakthrough 
Time (years) 
Present-Day Climate, Tc 
upper
mean 
lower

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-83 June 2000 
Figure 3.7-19. Summary of the UZ Flow Model Results and Issues to be Resolved 
Potential 
Repository 
 Variation in Percolation Flux 
Similar to Surface Infiltration Pattern 
 Fracture Flow (>80%) 
 PTn Lateral Flow (~100m) 
 Matrix Flow (90%) 
 Some Focusing into Faults 
 Dominant Matrix Flow 
Through Vitric Layers  Flow Partially Through 
Zeolites 
 Large Lateral Flow 
Along Zeolitic Layers 
 Significant Lateral 
Diversion 
 Perched Water Ages? 
 Extensive Body in the 
North 
 Focused Flow Pathways 
(Faults) 
 Capillary Barrier 
UZPMR3.7-19REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-84 June 2000 
Figure 3.8-1. Conceptual Model of Yucca Mountain Showing Major Processes Affecting Cl and 36Cl/Cl 
Distributions and Important Issues for Performance 
UZPMR3.8-1REV00 
Episodic Fracture Flow 
Transition 
Fracture Flow 
Zeolitic 
Matrix Flow 
Saturated Zone 
Fault-Dominated 
Flow 
Vitric 
Cross Section East of Ghost Dance Fault 
Perched Water 
Matrix Flow 
CFu 
CHn 
TSw 
PTn 
TCw 
Evaporation 
Transpiration 
Potential Repository Horizon 
Pagany 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Sundance 
Fault 
Solitario 
Canyon 
Fault 
Sever 
Wash 
Fault 
N 
Infiltration 
(mm/yr) 
20+ 
10-20 
5-15 
1-5 
<1 
Yucca 
Crest 
Run On/Run Off 
Perched Water: 
 Age (14C, 36Cl/Cl) 
 Lateral Flow 
 Zeolite Interaction (Sr) 
Water Age at 
Potential Repository 
36Cl/Cl 
Fast-Flow Path: 
 Fault-dominated 
3H, 36Cl/Cl 
Chloride Concentration: 
 Inverse Relation to Infiltration 
 Climate Effects 
 Lateral Flow in PTn

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-85 June 2000 
Figure 3.8-2. Model Diagram Showing Inputs and Outputs for Ambient Geochemistry Model. 
Icons are described in the text. 
TSPA 
Flow and Transport 
Flow and Transport 
3H 
36Cl 
Cl 
Sr 
Data 
Calibrated Pr 
Calibrated Pr 
operties 
Model 
Cl-36 
Ambient Geochemistry 
Model 
Geochemical Data

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-86 June 2000 
Figure 3.8-3. Infiltration Rates (USGS 2000, U0010) Plotted on UZ 3-D Calibration Grid. Simulated 
(using base-case infiltration rates), calibrated, and measured Cl concentrations in the ESF 
and the ECRB (Adapted from CRWMS M&O 2000, U0050, Figure 6-18). 
230000 
231000 
232000 
233000 
234000 
235000 
236000 
237000 
238000 
239000 
Northing [m] 
168000 169000 170000 171000 172000 173000 
Easting [m] 
0
2
4
6
8 
10 
12 
14 
16 
18 
20 
120 
FY99 3-D Calibration Grid; USGS-99 Modern Infiltration 
mm/yr 
0 
50 
100 
150 
200 
250 
0 1000 2000 3000 4000 5000 6000 7000 8000 
ESF Station [m] 
Cl Concentration [mg/L] 
0 
20 
40 
60 
0 500 1000 1500 2000 2500 
ECRB Station [m] 
Cl Concentration [mg/L] 
Field Data 
Present-day Mean Infiltration 
Calibrated Present-day Mean Infiltration 
Field Data 
Present-day Mean Infiltration 
Calibrated Present-day Mean Infiltration 
UZPMR3.8-3REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-87 June 2000 
Figure 3.8-4. Percolation Flux Map for 3-D Calibration Grid (Adapted from CRWMS M&O 2000, 
U0050, Figure 6-24) 
UZPMR3.8-4REV00 
230000 
231000 
232000 
233000 
234000 
235000 
236000 
237000 
238000 
239000 
Northing [m] 
168000 169000 170000 171000 172000 173000 
Easting [m] 
G-2 
NRG-6 
NRG-7A 
SD-12 
SD-7 
SD-6 
SD-9 
UZ-14 
UZ#16 
UZ#4,#5 
WT-24 
Percolation Flux 
Zone mm/year 
I 10.60 
II 2.32 
III 7.00 
IV 2.40 
V 3.00 
VI 1.00 
VII 1.50 
VIII 0.73 
IX 1.50 
I 
II III 
IV 
V 
VI 
VII 
VIII IX 
3-D Calibration Grid; Modified Percolation Flux Map

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-88 June 2000 
Figure 3.8-5. Analytical Results of 36Cl/Cl Along ESF (Using Calibrated Infiltration) for Transient 
Changes in Initial Ratios, Compared to Measured Ratios (CRWMS M&O 2000, 
U0050, Figure 6-31) 
UZPMR3.8-5REV00 
0 
200 
400 
600 
800 
1000 
1200 
0 1000 2000 3000 4000 5000 6000 7000 8000 
ESF Station [m] 
36Cl/Clx10-15 
Field Data 10,000 yrs 
15,000 yrs 18,000 yrs 
Analytical Solutions

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-89 June 2000 
Figure 3.8-6. Simulated Calcite Abundance (Lines) with Infiltration Rate After 10 Million 
Years in the WT-24 Column Together with Measured Calcite Mass Abundances 
(Diamond Symbols) (Data from CRWMS M&O 2000, U0085, Section 6.10, Figure 53; 
CRWMS M&O 2000, U0050, Figure 6-36) 
-------------------- 
--------------------- 
1500 
1400 
1300 
1200 
1100 
1000 
900
1E+0 1E+1 1E+2 1E+3 
Calcite Abundance (ppm) 
Elevation (m) 
1E+4 1E+5 1E+6 
PTn 
TCw 
TSw 
2 5.92 
Infiltration Rate (mm/yr) 
Water Type 1 
(Average TSw Water) 
20

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-90 June 2000 
Figure 3.8-7. Prediction of Cl Concentrations in Pore Waters Made Prior to Excavation of the ECRB 
Compared to Data Collected Subsequently (Adapted from Sonnenthal and Bodvarsson 
(1999, Figure 14) and CRWMS M&O 2000, U0050, Figure 6-23) 
0 4 0 0 8 0 0 1 2 0 0 1 6 0 0 2 0 0 0 2 4 0 S t a t i o n [m ] 
0 .0 
2 0 .0 
4 0 .0 
6 0 .0 
8 0 .0 
1 0 0 .0 
C h lo r id e [m g /L ]
M o d e r n C l im a t e : 3 D E C M 
M o d e r n C l i m a t e : 2 D M a t r i x 
G l a c i a l M a x im u m : 2 D M a t r C l im a t e C h a n g e : 2 D M a t r ix 
C l im a t e C h a n g e : 2 D F r a c t u M e a s u r e d P o r e W a t e r C l 
W E 

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-91 June 2000 
Figure 3.8-8. Conceptual Model of UZ Flow and Transport at Yucca Mountain, Showing Results Gained 
from Analysis of Geochemical Data and Modeling 
UZPMR3.8-8REV00 
Episodic Fracture Flow 
Transition 
Fracture Flow 
Zeolitic 
Matrix Flow 
Saturated Zone 
Fault-DominatedFlow 
Vitric 
Perched Water 
Matrix Flow 
CFu 
CHn 
TSw 
PTn 
TCw 
Evaporation 
Transpiration 
Potential Repository Horizon 
Pagany 
Wash 
Fault 
Drill 
Hole 
Wash 
Fault 
Sundance 
Fault 
Solitario 
Canyon 
Fault 
Sever 
Wash 
Fault 
N 
Infiltration 
(mm/yr) 
20+ 
10-20 
5-15 
1-5 
<1 
Yucca 
Crest 
Run On/Run Off 
Cross Section East of Ghost Dance Fault 
Fast-Flow Path: 
 Bomb-pulse 3H, 36Cl/Cl 
found near faults, and 
not in other areas, 
indicating only localized 
fast flow zones 
Proportion of matrix flow 
in zeolitic units still 
unresolved 
36Cl/Cl may indicate 
longer travel times to 
repository where PTn. 
is thicker 
Perched Water: 
 Lack of 3H and bomb-pulse 
36Cl, indicating no more 
than a small component of 
recent fast-flow water 
Predicated chloride concentrations 
in the ECRB are close to measured 
values, without calibration 
Cl Concentrations lower under 
repository than in North and South 
Ramps, as indicated by infiltration maps 
 Percolation fluxes more uniform than 
those predicted by infiltration maps 
and calibrated hydrologic properties

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-92 June 2000 
Figure 3.9-1. Schematic of Phenomena and Processes Affecting Drift Seepage. Numerals refer to list 
items in text. 
2 
1 
5 
4 6 
3 
1
2
3
4
5
6 
Capillary-Barrier Effect 
Percolation Flux Distribution 
Fracture Network 
Drift Geometry 
Evaporation/Condensation Effects 
Excavation-Disturbed Zone/Dry-out Zone

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-93 June 2000 
Figure 3.9-2. Schematic Showing Data Flow and Series of Models Supporting Evaluation of Drift 
Seepage 
TSPA 
Air-Permeability 
Data U0015 
Liquid-Release 
Test Data U0015 
PA 
Abstraction 
U0120 
EBS 
Drift Degradation 
Analysis 
E0080 
Seepage Calibration 
Model 
Thermal-Hydrological- 
Chemical 
Model 
Seepage Model for PA 
Model 
Calibrated Pr operties 
Model 
Data Data 
Flow 
Model

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-94 June 2000 
Figure 3.9-3. Seepage Issues 
 Flow Channeling 
 Locally Increased 
Percolation Flux 
 Episodic Flow Events 
Skin Zones 
 Excavation-Disturbed Zone 
 Dry-out Zone 
 Effectiveness of 
Capillary Barriers 
 Flow Diversion 
 Seepage Threshold 
 Ventilation Effects 
 In-Drift Condensation 
 Seep Flow Rate 
 Seepage Fraction 
 Drift Degradation 
 Increased Seepage at 
Topographic Lows Due to 
Roughness, Breakouts, 
Drift Collapse 
UZPMR3.9-3REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-95 June 2000 
Figure 3.9-4. Schematic Showing General Approach for the Development of the Seepage Calibration 
Model (Adapted from CRWMS M&O 2000, U0080, Section 6) 
0 1 2 3 4 5 6 
Lag-Distance [m] 
0 
0.1 
0.2 
0.3 
0.4 
0.5 
0.6 
0.7 
0.8 
Semi-Variogram 
Data from Post-Excavation 
Air-k Test Interpretations 
Spherical Semi-Variogram 
Nugget: 0.40 
Correlation length: 3.87 
Sill: 0.53 
-3 -2 -1 0 1 2 3 
X 
0
1
2
3
4
5 
Z 
Simulated 
Liquid-Release Test 
0 1 2 3 4 
Test 
0 
0.1 
0.2 
0.3 
0.4 
0.5 
0.6 
0.7 
0.8 
0.9
1 
Seepage Mass [kg] 
-
- 
-
- -
- - 
X X 
X 
X 
Test 4 Niche 3650 
Test #2 12-4-97 
Test #1 1-9-98 
Test #1 2-11-98 
Validation Tests Interval UM 5.49-5.79 m 
three-dimensional 
heterogeneous 
0
5
10 
15 
20 
Z 
0 
2 
4 
X 
0 
5 
10 
15 
Y 
Sliq 
0.95 
0.8 
0.6 
0.5 
0.4 
0.2 
0.05 
Partial Validation Using Additional 
Liquid-Release-Test Data 
Generation of Heterogeneous Property Field 
Seepage 
Predictions 
Geostatistical Analysis of Post-Excavation 
Air-Permeability Data 
Calibration Against 
Liquid-Release-Test Data

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-96 June 2000 
Figure 3.9-5. Schematic Showing Location and Layout of Niche 3650 as well as Log-Permeability Field 
of the Three-Dimensional Seepage Calibration Model (Adapted from CRWMS M&O 2000, 
U0080, Figures 12, 13, and 18) 
3.25 m 
C
L 
1.0 m 1.0 m 
0.5 m 0.5 m 
0.5 m 0.5 m 
MR ML 
BR BL 
UL UM UR 
1.0 m 1.15 m Niche 3650 0.65 m 
2.0 m 2.0 m 
E-W 
Drift 
Bedrock 
Exposed

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-97 June 2000 
Figure 3.9-6. Comparison between the Measured Seepage Mass (Circles) and That Calculated with 
Two- and Three-Dimensional, Homogeneous and Heterogeneous Models (Squares). 
The four models are visualized on the left. The uncertainty of the model predictions is 
shown as error bars on the 95% confidence level. The three-dimensional heterogeneous 
Seepage Calibration Model matches the data best (Adapted from CRWMS M&O 2000, 
U0080, Figure 19). 
1 2 3 4 5 
Test 
0 
0.1 
0.2 
0.3 
0.4 
0.5 
0.6 
0.7 
0.8 
0.9
1 
Seepage Mass [kg] 
-
- 
-
- 
-
- 
- - 
-
- 
-
- 
-
- 
-
- - 
-
- 
-
- 
-
- 
--
- 
-- 
-- 
-- 
-- 
-- 
Test 5 Niche 3650 
Test #1 12-3-97 
Test #2 12-3-97 
Test #1 1-7-98 
Test #2 2-10-98 
2D hom 
2D het 
3D hom 
3D het 
Data Point 
2D Homogeneous 
3D Homogeneous 
2D Heterogeneous 
3D Heterogeneous

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-98 June 2000 
Figure 3.9-7. Schematic Showing Relationships between Seepage-Relevant Factors. The red solid 
lines schematically indicate the expected behavior; uncertainty is schematically shown as 
blue dashed lines; the green dotted line shows the conservative assumption that no 
capillary-barrier effect exists. 
A 
Flux per Flow Channel 
Number of Flow Channels
B 
Number of Waste Packages 
Affected by Seepage 
Number of Flow Channels 
C
Flux per Flow Channel 
Seepage Rate 
Threshold 
D
Corrosive Damage 
Release 
Seepage Rate

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-99 June 2000 
Figure 3.9-8. Schematic Showing Percolation-Flux and Seepage-Threshold Distributions, Which 
Determine the Seepage-Fraction Probability 
Probability 
Percolation Flux 
Percolation Flux or Seepage Threshold 
Seepage Threshold

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-100 June 2000 
Figure 3.9-9. Schematic Illustrating Monte Carlo Sampling Approach for Seepage TSPA Calculations 
Percolation Flux q 
Percolation Flux q 
k/a 
k/a 
k/a 
Sample 
q 
Seepage Flux 
Low Seepage 
Flux 
Seepage Flux 
High Seepage 
Flux Probability 
Probability 
Probability 
Sample

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-101 June 2000 
Figure 3.9-10. Effect of Flow Focusing on Seepage Fraction (CRWMS M&O 2000, U0120, Figure 5) 
1.E-03 
1.E-02 
1.E-01 
1.E+00 
1 10 100 1000 
P e rco la tio n flux (m m /yr) 
Se e pa ge fra ction 
F = 1 
F = 5 
F = 15 
F = 45

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-102 June 2000 
Figure 3.9-11. Effect of Flow Focusing on Mean Seep Flow Rate (CRWMS M&O 2000, U0120, Figure 6) 
1.E-03 
1.E-02 
1.E-01 
1.E+00 
1.E+01 
1.E+02 
1.E+03 
1 10 100 1000 
P e rco la tio n flux (m m /yr) 
Me a n se e p flow ra te (m 3/yr) 
F = 1 
F = 5 
F = 15 
F = 45

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-103 June 2000 
Figure 3.9-12. Summary of Results 
 Average Percolation 
Flux from UZFM 
 Application of Flow- 
Focusing Factors. 
1 < F < 47 
 EDZ Effects Accounted for 
in Estimated Parameters 
 Conservative Assumption:. 
No Dry-out Zone 
 Estimation of Seepage- 
Relevant Parameters 
from Liquid-Release 
Test Data 
 30 < 1/a < 1000 Pa 
 Conservative Assumption of 100% 
Relative Humidity in Drift 
 Humidity Control During Seepage 
Tests 
 Calculation of Seep 
Flow Rate and Seep 
Fraction as a Function 
of Log (k/a) and Local 
Percolation Flux 
 Drift Degradation 
Increases Seep Flux Rate 
by 55% 
0 
1 
2 
4 
6 
8 
10 
12 
14 
Variability 
Uncertainty 
-12 -11 -10 -9 
log
10
(k/a) 
100 
200 
300 
400 
500 
Percolation Flux [mm/year] 
Seep Flow Rate [m
3
/year] 
0.0 
0.2 
0.6 
1.0 
Variability 
Uncertainty 
-12 -11 -10 -9 
log
10
(k/a) 
100 
200 
300 
400 
500 
Percolation Flux [mm/year] 
Seepage Fraction

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-104 June 2000 
Figure 3.10-1. Schematic Diagram of THC Processes Around a Heated Drift 
UZPMR3.10-1REV00 
Drainage 
Condensation Zone 
Vapor 
Waste 
Package Drip 
Shield 
Invert 
Backfill 
Mineral Precipitation in 
Fractures and Matrix 
Drift Wall: 
 Temperature 
 Liquid Saturation 
 Air Mass Fraction 
 CO2 
Concentration Other Issues: 
 Climate Changes 
 Mineral Assemblage 
 Water and Gas Initial 
Compositions 
Changes in Hydrological Properties 
Modification to UZ Flow and Transport 
Chemistry of Water and Gas 
Potentially Seeping into Drifts

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-105 June 2000 
Figure 3.10-2. Schematic Diagram Showing Relation Between TH Processes and Geochemical 
Processes 
Condensation and Coalescence 
of Droplets Through Surface 
Tension and Capture 
During Drainage 
T < Tboiling 
T ~ Tboiling 
Condensate Drainage 
Vapor Transport 
Conductive 
Heat Transfer 
Vapor Transport 
Heat Source 
Fracture 
Rock Matrix 
Imbibition
Diagram Showing TH Processes Diagram Showing THC Processes 
Condensate Drainage 
Boiling 
Zone 
Silica dissolution 
Aluminosilicate 
Dissolution-precipitation 
Zone of Active 
Calcite Precipitation 
Zone of Active 
Silica Precipitation 
Vapor 
Heat Source 
Fracture 
Rock Matrix 
CO2 
Vapor 
CO2 
CO2 
Vapor 
pH PCO2 
CO2 
Condensation- 
Drainage 
Zone 
Boiling 
Zone

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-106 June 2000 
Figure 3.10-3. Model Diagram Relating Inputs and Outputs for the THC Seepage Model and Drift Scale 
Test THC Model 
TSPA 
Geochemical Data 
Repository 
Design 
Thermal-Hydrological- 
Chemical 
Model 
Drift Scale Test THC 
Model 
Drift Scale Test TH 
Model 
Calibrated Pr operties 
Model 
3H 
36Cl 
Cl 
Sr 
Data 
Flow and Transport 
Model

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-107 June 2000 
Figure 3.10-4. Simulated CO2 Volume Fractions in Fractures and Matrix After 6 (a&b) and 20 (c&d) 
Months of Heating During the Drift Scale Test (adapted from CRWMS M&O 2000, 
N0120/U0110, Figures 5 and 6). Temperature contours are superimposed. "OD" refers to 
the Observation Drift. 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
[meters] 
-30 -20 -10 0 10 20 30 
[meters] 
-6.1 -5.5 -4.9 -4.3 -3.7 -3.1 -2.5 -1.9 -1.3 
LOG CO
2 
[Vol Fraction] 
40 
40 
40 
60 
60 
80 
80 
100 
100 
130 
140 
74
75 
76 
77 
78 
OD 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
[meters] 
-30 -20 -10 0 10 20 30 
[meters] 
-6.1 -5.5 -4.9 -4.3 -3.7 -3.1 -2.5 -1.9 -1.3 
LOG CO
2 
[Vol Fraction] 
40 
40 
40 
60 
60 
80 
80 
100 
100 
130 
140 
74
75 
76 
77 
78 
OD 
Twenty Months 
fracture 
matrix 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
[meters] 
-30 -20 -10 0 10 20 30 
[meters] 
-5.6 -5.0 -4.4 -3.8 -3.2 -2.6 -2.0 -1.4 
LOG CO
2 
[Vol Fraction] 
40 
40 
60 
60 
80 
80 
100 
130140 
74
75 
76 
77 
78 
OD 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
[meters] 
-30 -20 -10 0 10 20 30 
[meters] 
-5.6 -5.0 -4.4 -3.8 -3.2 -2.6 -2.0 -1.4 
LOG CO
2 
[Vol Fraction] 
40 
40 
60 
60 
80 
80 
100 
130140 
74
75 
76 
77 
78 
OD 
Six Months 
fracture 
matrix

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-108 June 2000 
Figure 3.10-5. Simulated CO2 Volume Fractions at Grid Nodes near Borehole (BH) Intervals Where 
Gas-Phase CO2 Measurements were Made (CRWMS M&O 2000, N0120/U0110, 
Figure 10). Filled circles are measured CO2 concentrations in the gas phase. Modeled 
data come from locations in 2-D grid close to center of borehole interval. 
0 3 6 9 12 15 18 21 
Time After Heating (Months) 
0 
5000 
10000 
15000 
20000 
25000 
30000 
CO2 (ppmV) 
74-3 Measured CO2 
74-3 Fracture Upper Node 
74-3 Matrix Upper Node 
74-3 Fracture Lower Node 
74-3 Matrix Lower Node 
0 3 6 9 12 15 18 21 
Time After Heating (Months) 
0 
5000 
10000 
15000 
20000 
25000 
30000 
CO2 (ppmV) 
75-3 Measured CO2 
75-3 Fracture 
75-3 Matrix 
0 3 6 9 12 15 18 21 
Time After Heating (Months) 
0 
5000 
10000 
15000 
20000 
25000 
30000 
35000 
40000 
45000 
CO2 (ppmV) 
78-3 Measured CO2 
78-3 Fracture BH Center 
78-3 Matrix BH Center 
78-3 Fracture BH End 
78-3 Matrix BH End 
0 3 6 9 12 15 18 21 
Time After Heating (Months) 
0 
5000 
10000 
15000 
20000 
25000 
30000 
35000 
CO2 (ppmV) 
76-3 Measured CO2 
76-3 Fracture 
76-3 Matrix 
(a) (b) 
(c) (d)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-109 June 2000 
Figure 3.10-6. THC Seepage Model Mesh Showing Hydrogeologic Units in Proximity of the Drift: 
Topopah Spring Tuff Upper Lithophysal (tsw33), Middle Nonlithophysal (tsw34), and 
Lower Lithophysal (tsw35) Units, and Blowup Showing Discretization of In-Drift Design 
Components (adapted from CRWMS M&O 2000, N0120/U0110, Figures 18 and 19) 
0 10 20 30 40 
X (m) 
-50 
-25
0 
25 
50 
Z (m) 
THC SEEPAGE MODEL MESH 
(top at +221m, bottom at -335m) 
tsw33 
tsw34 
tsw35 
0 1 2 3 
X (m) 
-3 
-2 
-1
0
1
2
3 
Z (m) 
DRIFT DISCRETIZATION 
Wallrock 
Outer Zone 
Backfill 
Inner Zone 
Invert 
Waste Package WP 
WP

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-110 June 2000 
Figure 3.10-7. Contour Plot of Modeled Liquid Saturations and Temperatures (Labeled Contour Lines) in 
the Matrix at 600 Years (Near Maximum Dryout) for Three Climate Change Scenarios: 
(a) Lower Bound, (b) Mean, and (c) Upper Bound (Calcite-Silica-Gypsum System) 
(CRWMS M&O 2000, N0120/U0110, Figure 26) 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
0.0 0.2 0.4 0.6 0.8 1.0 
Liquid Saturation 
90 
90 
95 
95 
95 
95 
100 
105 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
0.0 0.2 0.4 0.6 0.8 1.0 
Liquid Saturation 
90 
90 
95 
95 
95 
95 
100 
105 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
0.0 0.2 0.4 0.6 0.8 1.0 
Liquid Saturation 
85 
90 
90 
95 
95 
95 
100 
(a) (b) (c)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-111 June 2000 
Figure 3.10-8. Time Profiles of Modeled CO2 Concentrations in the Gas Phase in Fractures at Three Drift 
Wall Locations for Different Climate Change Scenarios (Calcite-Silica-Gypsum System) 
(CRWMS M&O 2000, N0120/U0110, Figure 29) 
Fractures 
Crown 
0 .1 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 0 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (ppmV) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
CO2 C a s e 2 
Side 
0 .1 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 0 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (ppmV) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
CO2 C a s e 2 
Base 
0 .1 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 0 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (ppmV) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
CO2 C a s e 2

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-112 June 2000 
Figure 3.10-9. Time Profiles of Modeled Total Aqueous Chloride Concentrations in Fracture Water at 
Three Drift Wall Locations for Different Climate Change Scenarios (Case 2). The dryout 
period is left blank. Numbers by each curve indicate the last output liquid saturation before 
dryout and the first output liquid saturation during rewetting (CRWMS M&O 2000, 
N0120/U0110, Figure 38). 
Fractures 
Crown 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
Cl- 
0 .1 0 3 
0 .1 0 1 
0 .1 1 8 
C a s e 2 
0 .1 0 1 
0 .1 0 0 
0 .0 1 4 
Side 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
Cl- 
0 .0 8 0 
0 .0 8 2 
0 .0 9 4 
C a s e 2 
0 .0 8 9 
0 .0 8 4 
0 .0 8 3 
Base 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
Cl- 0 .0 0 4 
0 .0 4 0 0 .0 2 6 
C a s e 2 
0 .0 1 3 
0 .0 2 0 
5 2 ,7 0 0 2 4 ,1 0 0

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-113 June 2000 
Figure 3.10-10. Time Profiles of the Modeled pH of Fracture Water at Drift Wall Locations for Different 
Climate Change Scenarios (Case 2 Calcite-Silica-Gypsum System). The dryout period is 
left blank. The last output liquid saturation before dryout and the first output liquid 
saturation during rewetting are noted on each curve (CRWMS M&O 2000, N0120/U0110, 
Figure 31). 
Fractures 
Crown 
7.0 
7.5 
8.0 
8.5 
9.0 
1 10 100 1000 10000 100000 
Time (yr) 
pH 
1 mm amb. 
0.6/6/3 mm 
6/16/25 mm 
15/26/47 mm 
Case 2 
0.103 
0.118 
0.101 
0.135 
0.101 
0.100
Side 
7.0 
7.5 
8.0 
8.5 
9.0 
1 10 100 1000 10000 100000 
Time (yr) 
pH 
1 mm amb. 
0.6/6/3 mm 
6/16/25 mm 
15/26/47 mm 
Case 2 
0.080 
0.082 
0.094 
0.083 
0.089 
0.084
Base 
7.0 
7.5 
8.0 
8.5 
9.0 
1 10 100 1000 10000 100000 
Time (yr) 
pH 
1 mm amb. 
0.6/6/3 mm 
6/16/25 mm 
15/26/47 mm 
Case 2 
0.004 
0.040 
0.026 
0.013 
0.020

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-114 June 2000 
Figure 3.10-11. Time Profiles of Modeled Total Aqueous Carbonate Concentrations (as HCO3
-) in Fracture 
Water at Drift Wall Locations for Different Climate Scenarios (Calcite-Silica-Gypsum 
System) (CRWMS M&O 2000, N0120/U0110, Figure 33) 
Fractures 
Crown 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
HCO3 
0 .1 0 3 
0 .1 0 1 
0 .1 1 8 
C a s e 2 
0 .1 0 1 
0 .1 0 0 
0 .0 1 4 
Side 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
HCO3 
0 .0 8 0 
0 .0 8 2 
0 .0 9 4 
C a s e 2 
0 .0 8 9 
0 .0 8 4 
0 .0 8 3 
Base 
1 
1 0 
1 0 0 
1 0 0 0 
1 0 0 0 0 
1 1 0 1 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 
Time (yr) 
Concentration (mg/l) 
1 m m a m b . 
0 . 6 / 6 / 3 m m 
6 / 1 6 / 2 5 m m 
1 5 / 2 6 / 4 7 m m 
HCO3 
0 .0 0 4 
0 .0 4 0 
0 .0 2 6 
C a s e 2 
0 .0 1 3 
0 .0 2 0 
-
- 
-

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-115 June 2000 
Figure 3.10-12. Contour Plot of Calculated Total Fracture Porosity Change at 10,000 Years for Three 
Climate Change Scenarios (Calcite-Silica-Gypsum System): (a) Lower Bound, 
(b) Mean, and (c) Upper Bound. Red areas indicate the maximum decrease in porosity as 
a result of mineral precipitation (CRWMS M&O 2000, N0120/U0110, Figure 42). 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
-0.14 -0.11 -0.08 -0.05 -0.02 0.02 
Porosity Change [%] 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
-0.10 -0.07 -0.04 -0.01 0.02 
Porosity Change [%] 
-40 
-35 
-30 
-25 
-20 
-15 
-10 
-5
0
5 
10 
15 
20 
25 
30 
35 
40 
[meters] 
0 10 20 30 40 
[meters] 
-0.24 -0.19 -0.14 -0.09 -0.04 0.02 
Porosity Change [%] 
(a) (b) (c) 
UZPMR3.10-12REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-116 June 2000 
Figure 3.10-13. Conceptual Model of TH Processes Around a Heated Drift and Summaries of Important 
Results of Drift-Scale THC Simulations and Analyses 
UZPMR3.10-13REV00 
Drainage 
Condensation Zone 
Vapor 
Waste 
Package Drip 
Shield 
Invert 
Backfill 
Minor Calcite, Amorphous 
Silica and Zeolite Precipitation 
in Fractures and Matrix 
Drift Wall Temperature: 
Maximum (base) ~180C 
Maximum (crown) ~120C 
Air Mass Fraction decreases to 
nearly zero during thermal period 
CO2 concentration increases up to 
a maximum of approximately 10% 
Different Mineral 
Assemblages affect results 
(e.g., shifts in pH), but not 
overall conclusions 
Increased infiltration during 
climate change results in 
more mineral deposition and 
smaller thermal effect 
Infiltration and Initial 
Water Composition was 
conservative for 
performance,because of 
its higher than average 
salinity 
Negligible Changes in Hydrological 
Properties and UZ Flow and Transport 
Chemistry of Water and Gas: 
pH ~7-9.5 
Low salinity

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-117 June 2000 
Figure 3.11-1. Key Issues Related to Potential Radionuclide Transport in the UZ 
Transport 
Rock Matrix 
Geological Layers 
Fractures 
Faults 
Climate 
Colloids 
Radioactive 
Decay 
Perched- 
Water 
Bodies 
 Matrix Diffusion and. 
Sorption 
 Properties (e.g., Kd, 
Permeability, Porosity) 
 Dispersion 
 Fast Pathways of 
Transport 
 Fracture-Matrix 
Interactions 
 Properties (e.g., Aperture, 
Frequency) 
 Sorption in Fractures 
 Dispersion 
 Fast Pathways of 
Transport 
 Limit Lateral Transport 
 Effects on Transport 
 Perched-Water Models 
 Infiltration Rates 
 Climate Regimes 
 Colloidal Transport 
 Colloids-facilitated 
Transport 
 Colloid Size 
 Size Exclusion 
 Filtration Models and 
Parameters 
 Fracture vs. Matrix Flow 
 Vitric CHn 
 Zeolitic CHn 
 Decay Rate 
 Fate of Daughter 
Products 
UZPMR3.11-1REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-118 June 2000 
Figure 3.11-2. Relationships of Other Models and Data Feeds to the Transport Model 
TSPA 
PA 
Abstraction 
U0065 
Colloid 
Transport 
U0070 
Transport 
Properties 
U0100 
Calibrated Pr operties 
Model 
Cl-36 
Ambient Geochemistry 
Model 
Transport 
Model 
Flow 
Model 
U0085 U0060 U0035 
U0050

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-119 June 2000 
Figure 3.11-3. Schematic Illustration of Flow and Transport in the UZ Model Layers below the Potential 
Repository (Boreholes SD-6 and UZ-14) 
UZPMR3.11-3REV00 
Potential Repository 
ch (1-5)v 
tsw 36-39 
ch6z 
pp4 
pp3 
pp2 
pp1 
bf3 
bf2 
tsw35 
tsw36 
tsw37 
tsw38 
tsw39 
ch6z 
ch5z 
ch4z 
ch3z 
ch2z 
ch1z 
pp4 
pp3 
pp2 
pp1 
Potential Repository 
UZ-14 
SD-6 
N

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-120 June 2000 
Figure 3.11-4. Concentration Profiles of 237Np in 2-D Cross Sections of SD-6 and UZ-14 (Adapted from 
CRWMS M&O 2000, U0060, Figures V.2 and V.8) 
1.E-12 
1.E-09 
1.E-06 
1.E-03 
1.E+00 
0 50 100 150 200 250 300 
Vertical Distance Below the Potential Repository (m) 
Relative Concentration (C/Co) 
10 yrs 
100 yrs 
1,000 yrs 
10,000 yrs 
100,000 yrs 
tsw36-39 bf3 ch(1-5)v pp4 pp3 pp2 ch6z pp1 bf2 
Effect of Vitric CHn Layers 
237Np, Near SD-6 
1.E-12 
1.E-09 
1.E-06 
1.E-03 
1.E+00 
0 50 100 150 200 250 300 
Vertical Distance Below the Potential Repository (m) 
Relative Concentration (C/Co) 
10 yrs 
100 yrs 
1,000 yrs 
10,000 yrs 
100,000 yrs 
tsw36 tsw37 
tsw38
tsw39
ch1z ch2z pp4 pp3 pp2 ch6z pp1 ch5z ch4z ch3z 
tsw35 
237Np, Near UZ-14 
Effect of Zeolitic CHn Layers 
UZ-14 
SD-6 
N

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-121 June 2000 
Figure 3.11-5. Concentration Profiles of 99Tc, 237Np, 239Pu and its Daughters at the Water Table for 
Varying Present-day Climatic Scenarios (Adapted from CRWMS M&O 2000, U0060, 
Figures 6.12.1, 6.13.1, 6.14.1, and 6.14.2. The data shown in this figure are based on a 
model that is appropriately conservative for TSPA analysis and consequently should not 
be used to evaluate expected breakthrough curves of radionuclides at the water table.) 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 
101 102 103 104 105 106 
Time (years) 
Mean 
Upper Bound 
Lower Bound 
Np-237 Transport 
Present-Day Infiltration 
0.1 fraction line 
0.5 fraction line 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 
101 102 103 104 105 106 
Time (years) 
Mean 
Upper Bound 
Lower Bound 
Tc-99 Transport 
Present-Day Infiltration 
0.1 fraction line 
0.5 fraction line 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 
101 102 103 104 105 106 
Time (years) 
Pu-239 Transport 
Present-Day Infiltration 
0.1 fraction line 
0.5 fraction line 
U, Pu+D 
M, Pu+D 
L, Pu+D 
L, Pu U, Pu 
M, Pu 
L: Lower Bound Infiltration 
M: Mean infiltration 
U: Upper Bound Infiltration 
Pu : Pu-239 only 
Pu+D : Pu-239+U-235+Pa-231 
10-9 
10-8 
10-7 
10-6 
10-5 
10-4 
10-3 
10-2 
10-1 
100 
MR of the Pu-239 chain in the watertable release 
101 102 103 104 105 106 
Time (years) 
Present-day Infiltration 
Pu-239 
Mean 
Lower Bound 
Upper Bound 
Pa-231 
Mean 
Lower Bound 
Upper Bound 
U-235 
Mean 
Lower Bound 
Upper Bound 
UZPMR3.11-5REV00 
239Pu 
237Np 
99Tc

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-122 June 2000 
Figure 3.11-6. Normalized Mass Fraction Distribution of 99Tc in the Fractures at the Bottom of the TSw 
and the Water Table (Adapted from CRWMS M&O 2000, U0060, 
Figures 6.12.2, 6.12.4, 6.12.12, and 6.12.14) 
1 7 0 0 00 1 7 2 0 0 0 1 7 40 0 0 
1
0 .95 
0 .9 
0 .85 
0 .8 
0 .75 
0 .7 
0 .65 
0 .6 
0 .55 
0 .5 
0 .45 
0 .4 
0 .35 
0 .3 
0 .25 
0 .2 
0 .15 
0 .1 
0 .05 
0 
Drill Hole 
Wash Fault 
1 7 0 0 00 1 7 2 0 0 0 1 7 40 0 0 
23 0 0 0 0 
23 2 0 0 0 
23 4 0 0 0 
23 6 0 0 0 
23 8 0 0 0 
Sundance 
Fault 
Splay,Ghost 
Dance Fault 
Solitario 
Canyon 
Splay G 
1 7 0 0 00 1 7 2 0 0 0 1 7 40 0 0 
1
0 .95 
0 .9 
0 .85 
0 .8 
0 .75 
0 .7 
0 .65 
0 .6 
0 .55 
0 .5 
0 .45 
0 .4 
0 .35 
0 .3 
0 .25 
0 .2 
0 .15 
0 .1 
0 .05 
0 
Main Ghost 
Dance Fault 
1 7 0 0 00 1 7 2 0 0 0 1 7 40 0 0 
23 0 0 0 0 
23 2 0 0 0 
23 4 0 0 0 
23 6 0 0 0 
23 8 0 0 0 
Drill Hole 
WashFault 
Splay,Ghost 
Dance Fault 
Fracture Mass Fraction at Water Table 
Fracture Mass Fraction at Bottom of TSw 
Nevada Coordinate E-W (m) 
Nevada Coordinate N-S (m) 
Nevada Coordinate N-S (m) 
(for Tc at 1,000 years) (for Tc at 10,000 years) 
(for Tc at 100 years) (for Tc at 1,000 years)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-123 June 2000 
Figure 3.11-7. Influence of Colloid Size and Kinetic Model Parameters on Colloidal Transport 
(Adapted from CRWMS M&O 2000, U0060, Figures 6.16.1 and 6.16.2. The data shown in 
this figure are based on a model that is appropriately conservative for TSPA analysis and 
consequently should not be used to evaluate expected breakthrough curves of 
radionuclides at the water table.) 
450 nm 
6 nm 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 
100 101 102 103 104 105 106 
Time (years) 
dc=450 nm 
dc=200 nm 
dc=100 nm 
dc=6 nm 
Mean Present-Day Infiltration 
0.1 fraction line 
0.5 fraction line 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 Normalized release rate at the watertable 
100 101 102 103 104 105 106 
Time (years) 
dc=450 nm 
dc=200 nm 
dc=100 nm 
dc=6 nm 
Mean Present-Day Infiltration 
0.1 fraction line 
0.5 fraction line 
Fast declogging 
Slow declogging 
450 nm 
6 nm 
UZPMR3.11-7REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-124 June 2000 
Figure 3.11-8. Correlations of Average Infiltration Rates and Tracer Transport Times at 50% Mass 
Breakthrough for 36 Simulation Scenarios (Data from CRWMS M&O, 2000, U0050, 
Section 6.7.3. The data shown in this figure are based on a model that is appropriately 
conservative for TSPA analysis and consequently should not be used to evaluate 
expected breakthrough curves of radionuclides at the water table.) 
UZPMR3.11-8REV00 
1.0E+01 
1.0E+02 
1.0E+03 
1.0E+04 
1.0E+05 
1.0E+06 
1.0E+07 
1 10 100 
Average Infiltration Rate Over the Model Domain (mm/year) 
Time for 50% Mass Breakthrough (years) 
Model 1, Non-adsorbing 
Model 2, Non-adsorbing 
Model 1, Adsorbing 
Model 2, Adsorbing 
Non-adsorbing 
Adsorbing

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-125 June 2000 
Figure 3.11-9. Simulated Breakthrough Curves of Cumulative Tracer (36Cl) Mass Arriving at the 
Repository Level, Since Release from the Ground Surface, Using the Present-Day, 
Mean Infiltration and Four Simulation Scenarios (Data from CRWMS M&O, 2000, U0050, 
Section 6.7.3. The data shown in this figure are based on a model that is appropriately 
conservative for TSPA analysis and consequently should not be used to evaluate 
expected breakthrough curves of radionuclides at the water table.)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-126 June 2000 
Figure 3.11-10. Effects of No Matrix Diffusion: Concentration of Radionuclides and Colloids at the Water 
Table for the No-diffusion Alternative Model (Adapted from CRWMS M&O 2000, U0060, 
Figures 6.17.1 and 6.17.2. The data shown in this figure are based on a model that is 
appropriately conservative for TSPA analysis and consequently should not be used to 
evaluate expected breakthrough curves of radionuclides at the water table.) 
99Tc 
99Tc 
Matrix 
Flow 
Fracture 
Flow 
237Np 
237Np 
239Pu 
239Pu 
No matrix diffusion 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 
10-1 100 101 102 103 104 105 106 
Time (years) 
Tc-99 
Np-237 
Pu-239 
Pu-239+U-235+Pa-231 
0.1 fraction line 
Mean present-day infiltration 
0.5 fraction line 
1.0 
0.8 
0.6 
0.4 
0.2 
0.0 
Normalized release rate at the watertable 10-1 100 101 102 103 104 105 106 
Time (years) 
450 nm 
200 nm 
100 nm 
6 nm 
0.1 fraction line 
Mean present-day infiltration 
0.5 fraction line 
Colloids 
No matrix diffusion 
UZPMR3.11-10REV00 
450 nm 
6 nm

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-127 June 2000 
Figure 3.11-11. Schematic of the RTTF Technique for Determining Particle Residence Time in a Cell 
(CRWMS M&O 2000, U0065, Figure 2)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-128 June 2000 
Figure 3.11-12. Comparison of the Particle-Tracking Solution and a Direct Finite-element Solution to the 
Transport (FEHM V2.10) for a 1-D, Dual-permeability Model (CRWMS M&O 2000, 
U0065, Figure 9. The data shown in this figure are based on a model that is appropriately 
conservative for TSPA analysis and consequently should not be used to evaluate 
expected breakthrough curves of radionuclides at the water table.) 
UZPMR3.11-12REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-129 June 2000 
Figure 3.11-13. Comparison of the Particle-Tracking Solution and a Direct Finite-element Solution to the 
Transport for a 1-D, Dual-permeability Model. Red curves: finite element solution, black 
curves: particle tracking (solid - no diffusion, dashed - diffusion) (CRWMS M&O 2000, 
U0065, Figure 10. The data shown in this figure are based on a model that is appropriately 
conservative for TSPA analysis and consequently should not be used to evaluate 
expected breakthrough curves of radionuclides at the water table.) 
UZPMR3.11-13REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-130 June 2000 
Figure 3.11-14. Comparison of Cumulative Normalized Breakthrough Curves at the Water Table Using 
FEHM V2.10 and DCPT V1.0 software with the Nonsorbing Tc for Mean-Infiltration, 
Glacial-Transition Climate (CRWMS M&O 2000, U0160, Figure 11. The data shown in this 
figure are based on a model that is appropriately conservative for TSPA analysis and 
consequently should not be used to evaluate expected breakthrough curves of 
radionuclides at the water table.) 
0 
0.2 
0.4 
0.6 
0.8
1
100 101 102 103 104 105 106 
FEHM v. 2.1 
DCPT 
Cu 
mu 
lati 
ve 
No 
rm 
aliz 
ed 
Br 
ea 
kth 
rou 
gh 
Time (years) 
Mean, Glacial-Transition, Tc 
Normalized Cumulative Breakthrough

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-131 June 2000 
Figure 3.11-15. Comparison of Cumulative Normalized Breakthrough Curves at the Water Table Using 
FEHM V2.10 and DCPT V1.0 software with the Sorbing Np for Mean-Infiltration, 
Glacial-Transition Climate (CRWMS M&O 2000, U0160, Figure 11. The data shown in this 
figure are based on a model that is appropriately conservative for TSPA analysis and 
consequently should not be used to evaluate expected breakthrough curves of 
radionuclides at the water table.) 
0 
0.2 
0.4 
0.6 
0.8
1
100 101 102 103 104 105 106 
FEHM v. 2.1 
DCPT 
Cumulative Normalized Breakthrough 
Time (years) 
Mean, Glacial-Transition, Np

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-132 June 2000 
Figure 3.11-16. Results Related to Radionuclide Transport in the UZ 
Transport 
Rock Matrix 
Geological Layers 
Fractures 
Faults 
Climate 
Colloids 
Radioactive 
Decay 
Perched- 
Water 
Bodies 
 Main Retardation 
Mechanism 
 Important 
 Not Significantly 
Important 
 Main Fast Pathways 
 Very Important 
 Important 
 Potentially Important 
 Not Significantly 
Important 
 Act as Fast Downward 
Pathways 
 Limit Lateral Transport 
 Lead to Lateral Diversion 
 Potentially Affect Transport 
 Critical in Release Rate 
 Potentially Affect 
Transport 
 Important for 
Radioactive Release 
 Potentially Important 
 Has a Significant Effect 
 Potentially Important 
 Very Sensitive 
 Very Important 
 Act as Effective Barriers 
 Lead to Fast Transport 
 Well Documented 
 Important for 239Pu 
Decay Chain

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-133 June 2000 
Figure 3.12-1. Schematic of the TH Modeling Issues 
Drifts and Pillars 
 Liquid Flow into Drifts 
 Liquid Flow in Pillars 
 Moisture Distribution 
 Temperature of Drifts 
and Pillars 
 Thermal Mechanical 
Coupling 
Ventilation 
 Influence on TH 
Water Table 
 Temperature 
Far Field 
 Liquid Flow Seepage 
 Extent of Thermally 
Affected Zone 
 Moisture Distribution 
CHn/Zeolites/Lower 
Lithophysal 
 Temperature Induced 
Mineralogic Change 
PTn 
 Temperature and 
Precipitation Induced 
Changes in Properties 
Climate 
 Influence of Climate 
and Changes in 
Ambient Infiltration 
Perched Water 
 Influence on TH and 
Temperature 
Figure 3.12-1 REV00C

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-147 June 2000 
Figure 5.1-1. Conceptual Sketch of the UZ with Icons Representing Major Model Components 
Seepage Model for PA 
Model 
Thermal-Hydrological- 
Chemical 
Model 
Flow 
Model 
Flow and Transport 
Model 
UZPMR5.1-1REV00 
Infiltration 
Model 
Climate 
Model 
Thermal-Hydrological 
Model

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-148 June 2000 
Figure 5.1-2. Schematic of Major Inputs and Outputs for UZ Flow Model and its Submodels 
Infiltration 
Model 
Climate 
Model 
Flow 
Model 
Thermal-Hydrological 
Model 
Climate 
(AMR U0005) 
Mountain-Scale TH 
(AMR U0105) 
UZ Flow 
(AMR U0050, AMR U0125) 
Infiltration 
Infiltration and Infiltration 
Uncertainty 
(AMR U0010, U0095) 
 Past Climate Data 
 Interpretation of Climate Cycles 
and Analogs 
 3-D UZ Site-scale Grid (AMR U0000) 
 Calibrated Properties (AMR U0035) 
 Conceptual and Numerical Models 
(AMR U0030) 
 3-D UZ Site-scale Grid (AMR U0000) 
 Calibrated Properties (AMR U0035) 
 Conceptual and Numerical Models 
(AMR U0030) 
 Design Information (Head Load, 
etc.) 
 Infiltration AMR U0010 
 Parameters for Precipitation, 
Bedrock Permeability, Soil Depth, 
Evapo-transpiration, etc. 
 Bounds on Temperature and 
Precipitation 
 Duration of Present-day, Monsoon, 
and Glacial-transition Climates 
 Spatial and Temporal Distribution 
of Flow Fields in UZ 
 Alteration to Flow Fields Used in 
Transport Simulations. 
(Screen out?) 
 Nine Infiltration Maps (low, "mean," 
and high for three climate states) 
 Weightings for Low, Mean, and 
Upper Infiltration Cases 
UZPMR5.1-2REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-149 June 2000 
Figure 5.1-3. Schematic of Major Inputs and Outputs of the Drift Seepage Models 
Drift Seepage 
(AMR U0075, AMR U0080, 
AMR U0120) 
Seepage Model for PA 
Model 
 Drift-seepage Tests (AMR U0015) 
 Conceptual and Numerical 
Models (AMR U0030) 
 Variability and Uncertainty in 
Seepage Distributions (Seepage 
Fraction, Mean Seep Flow Rate, 
Standard Deviation of Seep Flow 
Rate, Flow Focusing Factor)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-150 June 2000 
Figure 5.1-4. Schematic of Major Inputs and Outputs of the Drift-Scale THC Models 
Drift-Scale THC 
(AMR N0120/U0110, AMR N0125) 
Thermal-Hydrological- 
Chemical 
Model 
 UZ Flow Model (AMR U0050) 
 Calibrated Properties (AMR U0035) 
 Geochemistry Data (AMR U0085) 
 Design Parameters 
 Temporal and Spatial Distribution 
of Water and Gas Composition 
Around Drift 
 Influence of THC on Rock 
Properties Around Drift

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-151 June 2000 
Figure 5.1-5. Schematic of Major Inputs and Outputs of the UZ Transport Models 
Figure 5.1-5 
Transport 
Model 
UZ Transport Model 
(AMR U0065) 
 Transport Parameters (AMR U0100) 
 UZ Flow Fields (AMR U0050,. 
AMR U0125) 
 Conceptual Models (AMR U0060, 
AMR U0155, AMR U0160, . 
AMR U0170) 
 Spatial and Temporal Radionuclide 
Mass Flux at Water Table

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-134 June 2000 
Figure 3.12-2. Schematic Showing Input Data and the UZ Models that Support the Development of the 
TH Model 
Thermal 
Model 
TSPA 
Repository 
Design 
Numerical 
Grids 
Thermal 
Properties 
 Load/Decay 
U0035 
U0000 
U0105 
U0090 
Thermal 
Load 
Data 
 Potential Repository. 
Horizon 
 Drift Spacing 
 Load Distribution 
Data 
Data 
Infiltration/Climate 
Model 
Calibrated Pr 
operties 
Model 
Flow 
Model 
U0050 
UZPMR3.12-2REV00

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-135 June 2000 
Figure 3.12-3. Plan View of the UZ TSPA Grid, Showing the Location of the Potential Repository 
Submodel Domain (in Red) and the Cross Sections, NS#1 and NS#2. Locations #1 
and #2 are Used for Detail Plots. Large solid circles refer to boreholes; small circles refer 
to centers of grid columns (adapted from CRWMS M&O 2000, U0105, Figure 1). 
168000 169000 170000 171000 172000 173000 
239000 
238000 
237000 
236000 
235000 
234000 
233000 
232000 
231000 
230000 
229000 
Nevada State Plane Easting (m) 
Nevada State Plane Northing (m) 
Sever Wash fault 
Drill Hole Wash fault 
Solitario Canyon fault 
Ghost Dance fault 
Dune Wash 
fault 
SD-12 
SD-7 
H-5 
UZ-14 
SD-9 
NRG-7a 
G-2 
NS#2 
NS#1 
(170,700) 
H-3 
Imbricate fault 
Pagany Wash fault 
UZ-7a 
NRG-6 
Location #2 
E170,700 
N233,864 
Location #1 
E170,700 
N233,843.7

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-136 June 2000 
Figure 3.12-4. Lateral and Vertical Discretization at the NS#2 Cross-Section Based on the Refined 
Numerical Grid. Plot shows location of the potential repository and the hydrogeologic units 
layering (adapted from CRWMS M&O 2000, U0105, Figure 3). 
Nevada State Plane Northing (m) 
229,333 231,216 233,099 234,982 236,865 238,748 
1700. 
.
.
.
.
.
.
.
1400. 
.
.
.
.
.
.
.
1100. 
.
.
.
.
.
.
.
.
800 
Elevation (m) 
Pagany Wash 
fault 
Drill Hole Wash fault 
UZ-14 
Potential 
Repository 
tcw11 
tcw12
ptn24 
ptn25 
tsw32 
tsw33 
tsw34 
tsw35 
tsw36 
ch2 
ch3 
ch4 
ch5 
ch6 
pp3
pp2
pp1 
bf3 
tsw38 
NRG-7a 
SD-12 
Location #1 
Location #2 
Figure 3.12-4 REV00C

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-137 June 2000 
Figure 3.12-5. Temperature Distribution along NS#2 Cross-Section Grid at 1,000 Years (a) No 
Ventilation, (b) with Ventilation (Adapted from CRWMS M&O 2000, U0105, 
Figures 45 and 59). 
230000 232000 234000 236000 238000 
Nevada Coordinate (N-S) (m) 
800 
1000 
1200 
1400 
1600 
Elevation (m) 
30 
20 
40 
50 
60
70 
80 
90 
80 
70 
60 
50 
40 
90 
20 
90 
80 
90 
80 
50 
120 
110 
100 
90 
85 
80 
70 
60 
50 
40 
35 
30 
20 
(oC) 
230000 232000 234000 236000 238000 
Nevada Coordinate (N-S) (m) 
800 
1000 
1200 
1400 
1600 
Elevation (m) 
30 
20 
40 
50 
60 
70 
80 
85 
50 
60 
70 
80
40 
20 
85 
80 
70 
70 
60 
30 
120 
110 
100 
90 
85 
80 
70 
60 
50 
40 
35 
30 
20 
(oC) 
(a) No Ventilation 
(b) With Ventilation

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-138 June 2000 
Figure 3.12-6. Temperature at Location #1, NS#2 Cross-Section Grid (a) No Ventilation (b) with 
Ventilation (Adapted from CRWMS M&O 2000, U0105, Figures 46 and 60). 
0 1 0 0 2 0 0 
T e m p e r a t u r e ( oC ) 
8 0 0 
1 0 0 0 
1 2 0 0 
1 4 0 0 
E l e v a t io n (m ) e 
t im e = 0 . 1 y e a r s 
t im e = 1 0 y e a r s 
t im e = 5 0 y e a r s 
t im e = 1 0 0 y e a r s 
t im e = 5 0 0 y e a r s 
t im e = 1 0 0 0 y e a r s 
t im e = 1 0 0 0 0 y e a r s 
0 1 0 0 2 0 0 
T e m p e r a t u r e ( oC ) 
8 0 0 
1 0 0 0 
1 4 0 0 
1 4 0 0 
E l e v a t io n (m ) 
M a x im u m 
T e m p e r a t u r e 2 5 0 oC 
( a ) N o V e n t i l a t i o n 
( b ) W i t h V e n t i l a t i o n 
t im e = 0 . 1 y e a r s 
t im e = 1 0 y e a r s 
t im e = 5 0 y e a r s 
t im e = 1 0 0 y e a r s 
t im e = 5 0 0 y e a r s 
t im e = 1 0 0 0 y e a r s 
t im e = 1 0 0 0 0 y e a r s

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-139 June 2000 
Figure 3.12-7. Temperature along a Section of the Potential Repository Horizon of the NS#2 
Cross-Section Grid (a) No Ventilation, (b) with Ventilation (Adapted from 
CRWMS M&O 2000, U0105, Figures 48 and 62). 
232800 233000 233200 233400 233600 
North Nevada Coordinates (N-S) (m) 
0 
50 
100 
150 
200 
250 
300 time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
232800 233000 233200 233400 233600 
0 
50 
100 
150 
200 
Temperature ( C) o 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(a) No Ventilation 
(b) With Ventilation 
North Nevada Coordinates (N-S) (m) 
Temperature ( C) o

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-140 June 2000 
Figure 3.12-8. Matrix Liquid Saturation (Sl) along NS#2 Cross-Section Grid at 1,000 Years (a) No 
Ventilation, (b) with Ventilation (Adapted from CRWMS M&O 2000, U0105, 
Figures 50 and 64). 
230000 232000 234000 236000 238000 
800 
1000 
1200 
1400 
1600 
1.00 
0.95 
0.90 
0.85 
0.80 
0.75 
0.70 
0.65 
0.60 
0.55 
0.50 
0.45 
0.40 
0.35 
0.30 
0.25 
0.20 
0.15 
0.10 
0.05 
0.00 
SL
1.00 
0.95 
0.90 
0.85 
0.80 
0.75 
0.70 
0.65 
0.60 
0.55 
0.50 
0.45 
0.40 
0.35 
0.30 
0.25 
0.20 
0.15 
0.10 
0.05 
0.00 
SL 
Nevada Coordinate (N-S) (m) 
Elevation (m) 
Nevada Coordinate (N-S) (m) 
Elevation (m) 
(a) No Ventilation 
(b) With Ventilation 
800 
1000 
1200 
1400 
1600 
230000 232000 234000 236000 238000

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-141 June 2000 
Figure 3.12-9. Matrix Liquid Saturation at Location#1, NS#2 Cross-Section Grid (a) No Ventilation, 
(b) with Ventilation (Adapted from CRWMS M&O 2000, U0105, Figures 51 and 65). 
0.0 0.2 0.4 0.6 0.8 1.0 
Liquid Saturation 
800 
1000 
1200 
1400 
Elevation (m) 
time = 0.1 years 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
0.0 0.2 0.4 0.6 0.8 1.0 
Liquid Saturation 
800 
1000 
1200 
1400 
Elevation (m) 
time = 0.1 years 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(a) No Ventilation 
(b) With Ventilation

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-142 June 2000 
Figure 3.12-10. Matrix Liquid Saturation along a Section of the Potential Repository Horizon, 
NS#2 Cross-Section Grid (a) No Ventilation, (b) with Ventilation (Adapted from 
CRWMS M&O 2000, U0105, Figures 52 and 66). 
232800 233000 233200 233400 233600 
0.0 
0.5 
1.0 
1.5 
Liquid Saturation 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
232800 233000 233200 233400 233600 
0.0 
0.5 
1.0 
1.5 
Liquid Saturation 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(a) No Ventilation 
(b) With Ventilation 
North Nevada Coordinates (N-S) (m) 
North Nevada Coordinates (N-S) (m)

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-143 June 2000 
Figure 3.12-11. Fracture Liquid Flux at Location #1,NS#2 Cross-Section Grid (a) No Ventilation, 
(b) With Ventilation (Adapted from CRWMS M&O 2000, U0105, Figures 53 and 67). 
0 100 200 
Liquid Flux (mm/year) 
800 
1000 
1200 
1400 
Elevation (m) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
0 100 200 
Liquid Flux (mm/yr) 
800 
1000 
1200 
1400 
Elevation (m) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(a) No Ventilation 
(b) With Ventilation 
Maximum Flux 
= 360 mm/yr

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-144 June 2000 
Figure 3.12-12. Fracture Liquid Flux along a Section of the Potential Repository Horizon, 
NS#2 Cross-Section Grid (a) No Ventilation, (b) with Ventilation (Adapted from 
CRWMS M&O 2000, U0105, Figures 55 and 69). 
232800 233000 233200 233400 233600 
North Nevada Coordinates (N-S) (m) 
-20
0 
20 
40 
60 
80 
100 
Liquid Flux (mm/year) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
232800 233000 233200 233400 233600 
North Nevada Coordinates (N-S) (m) 
-20
0 
20 
40 
60 
80 
100 
Liquid Flux (mm/year) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(a) No Ventilation 
(b) With Ventilation 
Maximum Flux 
12501600 mm/yr at 10 years 
Maximum Flux 
270300 mm/yr at 10 years

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-145 June 2000 
Figure 3.12-13. Matrix Liquid Flux along a Section of the Potential Repository Horizon, 
NS#2 Cross-Section Grid (a) No Ventilation, (b) with Ventilation (Adapted from 
CRWMS M&O 2000, U0105, Figures 56 and 70). 
232800 233000 233200 233400 233600 
North Nevada Coordinates (N-S) (m) 
0 
20 
40 
60 
80 
100 
Liquid Flux (mm/year) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
232800 233000 233200 233400 233600 
North Nevada Coordinates (N-S) (m) 
0 
20 
40 
60 
80 
100 
Liquid Flux (mm/year) 
time = 10 years 
time = 50 years 
time = 100 years 
time = 500 years 
time = 1000 years 
time = 10000 years 
(b) With Ventilation 
(a) No Ventilation 
Maximum Flux 
400500 mm/yr at 10 years

Unsaturated Zone Flow and Transport Model Process Model Report 
TDR-NBS-HS-000002 REV00 ICN 1 Attachment III-146 June 2000 
Figure 3.12-14. Summary of TH Model Results 
Drifts 
 Completely Dry for up to 
1000 years 
 Temperature >250C with 
no Ventilation; up to 110C 
with Ventilation 
 Liquid Flux >400mm/year 
all Vaporized by Repository 
Heat 
Far Field 
 Boiling Zone up 200m above 
Repository if no Ventilation; 
with Ventilation less than 20m 
 Moisture Redistribution 
Significant if no Ventilation 
CHn/Zeolites/Lower Lithophysal 
 Temperature 70-75C 
 Low Potential for Mineralogic. 
Changes 
PTn 
 70-75C with no Ventilation 
 Less than 50C with 
Ventilation 
 Low Potential for Property 
Changes 
Climate/Infiltration 
 Distribution/Magnitude of 
Infiltration Controls 
Dryout/Rewetting 
Perched Water 
 Potential Vaporization for 
Perched Water Bodies 
Close to Repository 
Pillars 
 Temperature 80-85C 
 Sufficient Drainage 
Through Fractures 
Water Table 
 Temperature Increases by 
30-35C