Analysis of Geochemical Data for the Unsaturated Zone Rev 00, ICN 00

ANL-NBS-HS-000017

April 2000

1. PURPOSE 
Geochemical data and models that are important for site characterization purposes and for 
evaluations of site performance are discussed in this report. Geochemical and isotopic data for 
present-day fluids and for fracture minerals which reflect past water chemistries at the site are 
reviewed and evaluated with respect to the development and testing of models to explain 
variations in water chemistry and their implications for the development and testing of site-scale 
hydrologic flow models for the unsaturated zone. Such models are required to derive bounds on 
future variations in the chemical compositions of waters in the Yucca Mountain flow system. 
These bounds are required to model the transport behavior of radionuclides in the flow system. 
More specifically, this report: 
 Identifies fluid geochemical parameters that are relevant to site characterization and 
repository evaluations (Section 6.1). 
 Reviews the methods that were used in investigating fluid geochemistry (Section 6.2). 
 Discusses available data on the geochemical and isotopic compositions of local 
precipitation (Section 6.3) and surface water (Section 6.4). The compositions of these 
waters define the starting point for the geochemical evolution of water in the unsaturated 
zone. 
 Discusses available data on the geochemical and isotopic compositions of unsaturatedzone 
pore waters and perched water (Sections 6.5 and 6.6), unsaturated-zone gases 
(Section 6.7), secondary fracture minerals (Section 6.10), and fluid inclusions (Section 
6.11). 
 Discusses relevant geochemical data for saturated-zone groundwaters (Section 6.8) 
because the similarity between geochemical compositions of local perched water and 
waters from the saturated zone suggests common controls. 
 Provides overviews of processes that control fluid compositions and the limitations of 
the existing data for each category (throughout Section 6). 
 Summarizes a conceptual model for the evolution of fluid geochemistry in Yucca 
Mountain (Section 7.1). 
 Discusses how these data bear on site characterization and repository performance issues 
(Section 7). 
Constraints, caveats, and limitations associated with the analyses and models in this report are 
identified within the sections that discuss the analyses and models themselves. 
This report has been prepared according to the requirements of OCRWM Procedure AP-3.10Q, 
Rev 2, ICN 0, Analyses and Models. Planning efforts for this report were outlined in the

ANL-NBS-HS-000017, Rev 00 Page 15 of 156 
Analysis and Modeling Report (AMR) Development Plan TDP-NBS-HS-000040, U0085 
Analysis of Geochemistry Data, Rev 00 (CRWMS M&O 1999a). 
2. QUALITY ASSURANCE 
The activities documented in this AMR were evaluated in accordance with QAP-2-0, Conduct of 
Activities, and were determined to be subject to the requirements of the U.S. Department of 
Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM) Quality Assurance 
Requirements and Description (QARD) (DOE 2000). This evaluation is documented in 
CRWMS M&O (1999b), and Wemheuer (1999, activity evaluation for work package WP 
140123UM1). This AMR has been prepared in accordance with procedure AP-3.10Q, Analyses 
and Models. 
3. COMPUTER SOFTWARE AND MODEL USAGE 
Standard spreadsheet and visual display graphics programs were used to prepare this report, as 
listed below, but they are not subject to software quality assurance requirements. 
Microsoft Excel 97 (Version SR-1, for Windows 95 and Windows NT 4.0) is a standard 
spreadsheet program that was used to organize and sort data, calculate averages and standard 
deviations, and to perform linear regressions on specific geochemical data sets using standard 
built-in Excel functions available with the software on a PC. In addition, the following visual 
display graphical programs were used to plot and illustrate the results of data analyses shown in 
this report. These programs were not used to develop data used in quality affecting work. 
 PlotchemWin, Version 7.9, for Windows 95, is a graphical program used to prepare 
trilinear (Piper) diagrams of dissolved ion concentrations of water samples (TECSOFT 
1997) 
 Adobe Illustrator, Version 7.0, for Windows 95 and Windows NT 4.0 
 Corel Draw 9, Version 9.337, for Windows 95 and Windows NT 
All plots and figures were compared against the original data or other sources for correctness. 
4. INPUTS 
4.1 DATA AND PARAMETERS 
This document is a compilation and synthesis of data and other information collected under 
various activities and reported in publications, YMP reports, the YMP Technical Data 
Management System (TDMS), and other databases. The qualification status of input data used in 
this report is tracked in the electronic YMP Document Input Reference System (DIRS) database.

ANL-NBS-HS-000017, Rev 00 Page 16 of 156 
The primary input data used in this report are geochemical and isotopic analyses of pore waters, 
perched water, gases and fracture minerals collected from the unsaturated zone at Yucca 
Mountain; and analytical data for surface waters and groundwaters in the area. Section 6.2 lists 
the major chemical and isotopic parameters used as input to the analyses in this report and 
provides an overview discussion of their appropriateness and relevance for these analyses. The 
data listed below are appropriate to be used as input for this report because they directly bear on 
values of these parameters applicable to the Yucca Mountain site. 
Data used in this report that were acquired or developed as part of the Yucca Mountain Program 
are contained in data packages with unique Data Tracking Numbers (DTNs) that permit the data 
to be tracked in the YMP Automated Technical Data Tracking (ATDT) Database. DTNs for 
primary input datai.e., data that are directly used to support the reports conclusionsare listed 
below. Because this list is organized to parallel the structure of this report, many DTNs are listed 
more than once. Data sources are listed in the reference section (Section 8.3). 
4.1.1 Precipitation Geochemical Data Inputs 
Chloride concentrations in local and regional precipitation, along with associated precipitation 
quantities, are considered to be primary input data, and provide the basis for estimating 
infiltration rates by the chloride mass balance method (sections 6.3.2, 6.3.3, and 6.9.2). 
LA0003JF12213U.001 Precipitation-weighted average monthly concentrations (mg/l) of 
precipitation in Red Rock Canyon, Nevada, 1985 to 1998 
GS930108315214.003 Chemical analysis of surface water, spring, and precipitation samples 
collected from Kawich and Stewart Creek Basins from September, 
1984, to April, 1989. 
GS930108315214.004 Chemical analysis of surface water, spring, and precipitation samples 
collected from Kawich and Stewart Creek Basins from May, 1989, to 
September, 1991 
GS930908315214.030 Chemical analysis of surface water, spring, and precipitation samples 
collected from Kawich and Stewart Creek Basins from February, 
1992, to September, 1992. 
LAJF831222AQ95.003 Halide analyses of rainwater from Yucca Mountain 
All other precipitation chemistry data are used in a corroborative manner, to characterize local 
and regional precipitation chemistry in terms of average concentrations and relative ion ratios. 
These precipitation trend data provide a baseline against which to compare and contrast chemical 
compositions of the various sources of water at Yucca Mountain, and to illustrate general trends 
of relative enrichment or depletion of one element compared to another (sections 6.3.2 and 
6.3.3).

ANL-NBS-HS-000017, Rev 00 Page 17 of 156 
4.1.2 Surface-water Geochemical Data Inputs 
None of the surface-water geochemical and isotopic data used in this report are considered to be 
primary input data. Surface-water data presented in this report are used solely to characterize 
local and regional surface water chemistry in terms of concentration averages and ranges, relative 
ion ratios, and isotopic characteristics. These calculations provide a means to compare chemical 
compositions of surface water and runoff at Yucca Mountain to those of unsaturated-zone pore 
waters and perched water, so as to illustrate general trends of relative enrichment or depletion of 
one element compared to another (section 6.4.3). 
4.1.3 Pore-water Geochemical Data Inputs 
The following primary input data are used in Section 6.5.3 to characterize pore-water chemistry: 
GS950608312272.001 Chemical Data For Pore Water From Tuff Cores Of USW NRG-6, 
NRG7/7a, UZ-14 and UZ-N55, and UE-25 UZ#16 
GS961108312261.006 Gas Chemistry, ESF Alcoves 2 And 3, 11/95 - 4/96; Water 
Chemistry, Alcove 2 (Tritium), Alcove 3, And ESF Tunnel; And 
Pneumatic Pressure Response From Boreholes In Exploratory 
Studies Facility Alcoves 2 and 3, 10/95 - 5/96 
GS961108312271.002 Chemical And Isotopic Composition Of Pore Water And Pore Gas, 
1994-96, From Boreholes USW UZ-1, USW UZ-14, UE-25 UZ#16, 
USW NRG-6, USW NRG-7a, USW SD-7 USW SD-9, ESF-AL#3- 
RBT#1, And ESF-AL#3-RBT#4, And ESF Rubble 
GS970208312271.002 Unsaturated Zone Hydrochemistry Data, 10-1-96 To 1-31-97, 
Including Chemical Composition And Carbon, Oxygen And 
Hydrogen Isotopic Composition 
GS970908312271.003 Unsaturated Zone Hydrochemistry Data, 2-1-97 to 8-31-97, 
Including Chemical Composition and Carbon, Oxygen, And 
Hydrogen Isotopic Composition: porewater from USW NRG-7A, 
SD-7, SD-9, SD-12 and UZ-14; and gas from USW UZ-14 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9810----2272.004, Analysis for chemical composition of 
pore water from boreholes USW UZ-7A, USW WT-24, USW SD-6, 
USW SD-7, and USW SD-12 during FY 1997 and 1998 
Data set 9902----2272.001, Analysis for chemical composition of 
pore water from borehole USW UZ-14 and groundwater from USW 
UZ-16 
LA9909JF831222.004 Chloride, bromide, and sulfate analyses of Busted Butte and Cross 
Drift tunnel porewaters in FY99 
LA9909JF831222.010 Chloride, bromide, sulfate and chlorine-36 analyses of ESF 
porewaters

ANL-NBS-HS-000017, Rev 00 Page 18 of 156 
LA9909JF831222.012 Chloride, bromide, and sulfate analyses of porewater extracted from 
ESF Niche 3566 (Niche #1) and ESF 3650 (Niche #2) drillcore 
4.1.4 Perched-water Geochemical Data Inputs 
The following primary input data are used in Section 6.5.3 to characterize perched-water 
chemistry: 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9512----2272.004, Chemical composition of perched water 
samples from boreholes NRG-7A, SD-9, UZ-14, ONC#1, USW G-2, 
and SD-7, and for water samples from UE-25 UZ-N2 and UZ-N46 
LAJF831222AQ98.011 Chloride, bromide, sulfate and chlorine-36 analyses of springs, 
groundwater, porewater, perched water and surface runoff 
4.1.5 Tritium Data Inputs 
The following primary input data are used in Section 6.6.2 to characterize the distribution of 
tritium in surface water, porewater, perched water and groundwater: 
GS940308312133.002 Water quality data for samples taken in Fortymile Wash, Nevada, 
during the 1993 water year 
GS960308312133.001 Water quality data from samples collected in the Fortymile Wash 
Watershed, Yucca Mountain area, Nevada, Water year 1995 
GS961108312261.006 Gas Chemistry, ESF Alcoves 2 And 3, 11/95 - 4/96; Water 
Chemistry, Alcove 2 (Tritium), Alcove 3, And ESF Tunnel; And 
Pneumatic Pressure Response From Boreholes In Exploratory 
Studies Facility Alcoves 2 And 3, 10/95 - 5/96 
GS961108312271.002 Chemical And Isotopic Composition Of Pore Water And Pore Gas, 
1994-96, From Boreholes USW UZ-1, USW UZ-14, UE-25 UZ#16, 
USW NRG-6, USW NRG-7a, USW SD-7 USW SD-9, ESF-AL#3- 
RBT#1, And ESF-AL#3-RBT#4, And ESF Rubble 
GS970108312232.001 Sulfur hexafluoride gas chemistry data and shut-in pressure 
monitoring data from the radial boreholes in Alcove 1 of the ESF, 
4/95; and tritium data from borehole ESF-AL#2-HPF#1 in alcove 2 
GS970208312271.002 Unsaturated Zone Hydrochemistry Data, 10-1-96 To 1-31-97, 
Including Chemical Composition And Carbon, Oxygen And 
Hydrogen Isotopic Composition 
GS970283122410.002 Gas and water chemistry data from samples collected at boreholes 
UE-25 NRG#5 and USW SD-7 on Yucca Mountain, Alcove 5, and 
borehole ESF-NAD-GTB#1a in Alcove 6, ESF, between 8-11-96 
and 1-14-97

ANL-NBS-HS-000017, Rev 00 Page 19 of 156 
GS970608312272.005 Tritium Data From ESF Alcove #5 Cores For Single Heater Test 
GS970908312271.003 Unsaturated Zone Hydrochemistry Data, 2-1-97 to 8-31-97, 
Including Chemical Composition and Carbon, Oxygen, And 
Hydrogen Isotopic Composition: porewater from USW NRG-7A, 
SD-7, SD-9, SD-12 and UZ-14; and gas from USW UZ-14 
GS980908312322.008 Field, Chemical, And Isotopic Data From A Precipitation Sample 
Collected Behind The Service Station In Area 25 And Ground Water 
Samples Collected At Boreholes UE-25 C #2, UE-25 C #3, USW 
UZ-14, UE-25 WT #3, UE-25 WT #17 And USW WT-24, Between 
10/06/97 And 07/01/98 
GS990608312133.001 Ground-water quality data 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9512----2272.002, Tritium analyses of perched waters from 
SD-7, SD-9, UZ-14, and NRG-7A; and of porewaters from core from 
UZ-14, UZ#16, NRG-6 and NRG-7A 
Data set 9911----2272.004, Tritium analyses for porewater samples 
from UZ-14, WT-24, SD-12, SD-6, SD-7, SD-9, UZ-7A and NRG- 
7A 
4.1.6 Chlorine-36 Data Inputs 
The following primary input data are used in Section 6.6.3 to characterize the distribution of 
chlorine-36 in precipitation (using fossil packrat urine samples), surface water, soil, porewater, 
borehole cuttings and drillcore, perched water and groundwater: 
LA000000000062.002 Halide and chlorine-36 analyses of cuttings from borehole USW UZN27. 
LA9909JF831222.001 Chloride, bromide, sulfate and chlorine-36 analyses of groundwater 
and runoff in FY99 
LA9909JF831222.003 Chloride, bromide, sulfate and chlorine-36 analyses of salts leached 
from Cross Drift rock samples in FY99 
LA9909JF831222.005 Chlorine-36 analyses of ESF and Busted Butte porewaters in FY99 
LA9909JF831222.010 Chloride, bromide, sulfate and chlorine-36 analyses of ESF 
porewaters 
LAJF831222AQ95.005 Halide and chlorine-36 analyses of soils from the UE25 NRG#5 
drillpad. 
LAJF831222AQ95.006 Halide and chlorine-36 analyses of soils from Midway Valley pits 
and trenches. 
LAJF831222AQ96.005 Halide and 36Cl analyses of cuttings from boreholes NRG-4, NRG- 
6, and NRG 7/7A

ANL-NBS-HS-000017, Rev 00 Page 20 of 156 
LAJF831222AQ96.006 Halide and 36Cl analyses of soil from Midway Valley Pit MWV-P2 
LAJF831222AQ96.008 Halide and 36Cl analyses of cuttings from boreholes UZ-N15, UZN16, 
UZ-N17, UZ-N36, UZ-N38, UZ-N39, UZ-N61, UZ-N62, and 
UZ-N64 
LAJF831222AQ96.009 Halide and 36Cl analyses of cuttings from borehole UZ-N11 
LAJF831222AQ96.010 Halide and 36Cl analyses of cuttings from borehole UZ-N37 
LAJF831222AQ96.011 Halide and 36Cl analyses of cuttings from borehole UZ-N53 
LAJF831222AQ96.012 Halide and 36Cl analyses of cuttings from borehole UZ-N54 
LAJF831222AQ96.013 Halide and 36Cl analyses of cuttings from borehole UZ-N55 
LAJF831222AQ96.014 Halide and 36Cl analyses of cuttings from borehole UZ#16 
LAJF831222AQ96.015 Halide and 36Cl analyses of cuttings from borehole UZ-14 
LAJF831222AQ97.002 Chlorine-36 analyses of packrat urine 
LAJF831222AQ97.006 Halide, sulfate and chlorine-36 analyses of soils from Midway Valley 
soil pits MWV-P31 and NRSF-TP-19 
LAJF831222AQ97.007 Halide, sulfate and chlorine-36 analyses of cuttings from borehole 
SD-12 
LAJF831222AQ98.004 Chloride, bromide, sulfate and chlorine-36 analyses of salts leached 
from ESF rock samples 
LAJF831222AQ98.009 Chlorine-36 analyses of salts leached from ESF Niche 3566 (Niche 
#1) drillcore 
LAJF831222AQ98.011 Chloride, bromide, sulfate and chlorine-36 analyses of springs, 
groundwater, porewater, perched water and surface runoff 
LA9909JF831222.010 Chloride, bromide, sulfate and chlorine-36 analyses of ESF 
porewaters 
LA9912JF831222.001 Halide and chlorine-36 analyses of drillcore from USW UZ-N55 
4.1.7 Carbon-14 and Carbon-13 Data Inputs for Unsaturated-zone Water 
The following primary input data are used in Section 6.6.4 to characterize the distribution of 
carbon isotopes in pore water and perched water: 
GS961108312261.006 Gas Chemistry, ESF Alcoves 2 And 3, 11/95 - 4/96; Water 
Chemistry, Alcove 2 (Tritium), Alcove 3, And ESF Tunnel; And 
Pneumatic Pressure Response From Boreholes In Exploratory 
Studies Facility Alcoves 2 And 3, 10/95 - 5/96 
GS961108312271.002 Chemical And Isotopic Composition Of Pore Water And Pore Gas, 
1994-96, From Boreholes USW UZ-1, USW UZ-14, UE-25 UZ#16, 
USW NRG-6, USW NRG-7a, USW SD-7 USW SD-9, ESF-AL#3- 
RBT#1, And ESF-AL#3-RBT#4, And ESF Rubble

ANL-NBS-HS-000017, Rev 00 Page 21 of 156 
GS970208312271.002 Unsaturated Zone Hydrochemistry Data, 10-1-96 to 1-31-97, 
Including Chemical Composition And Carbon, Oxygen, And 
Hydrogen Isotopic Composition 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9512----2272.003, Isotopic composition (13C, 14C) of 
porewater from UZ-14, UZ-16, NRG-6 and NRG-7a during FY93- 
95, and isotopic composition (13C, 14C, 2H, 18O) of perched water 
from SD-7, SD-9, UZ-14 and NRG-7a 
4.1.8 Carbon-14 and Carbon-13 Data Inputs for Gases from Open Boreholes 
None of the data collected for samples from open boreholes are considered primary input data for 
characterization of the chemical composition of gas at Yucca Mountain. These data are 
discussed in Sections 6.6.4 and 6.7.2 but are only used to corroborate interpretations based on 
isotopic data for instrumented borehole samples (section 4.1.9). 
4.1.9 Carbon-14 and Carbon-13 Data Inputs for Gases from Instrumented Boreholes 
The following primary input data are used in Sections 6.6.4 and/or 6.7.2 to characterize the 
distribution of carbon isotopes in borehole gas from instrumented boreholes: 
GS961108312271.002 Chemical And Isotopic Composition Of Pore Water And Pore Gas, 
1994-96, From Boreholes USW UZ-1, USW UZ-14, UE-25 UZ#16, 
USW NRG-6, USW NRG-7a, USW SD-7 USW SD-9, ESF-AL#3- 
RBT#1, And ESF-AL#3-RBT#4, And ESF Rubble 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9112----2271.009, Laboratory results of carbon-14 analysis 
of gas samples from borehole UZ1 
Data set 9112----2271.010, Laboratory results of carbon-13/carbon- 
12 isotope ratio from gas samples from borehole UZ1 
Data set 9301----2271.009, Laboratory results of carbon-13/carbon- 
12 isotope ratio from gas samples from borehole USW UZ-1 
Data set 9301----2271.010, Laboratory results of carbon-14 analysis 
of gas samples from borehole USW UZ-1 
Data set 9304----2271.019, Laboratory results of carbon-13/carbon- 
12 isotope ratio from gas samples from borehole USW UZ-1, May 
1989 December 1989, and January 1991 
Data set 9304----2271.020, Laboratory results of carbon-14 analysis 
of gas samples from borehole USW UZ-1, collected May 1989 
December 1989, and January 1991

ANL-NBS-HS-000017, Rev 00 Page 22 of 156 
Data set 9404----2271.004, Laboratory results of carbon 13/carbon 
12 and oxygen 18/oxygen16 isotope ratios from gas samples from 
borehole USW UZ-1 taken 12/93 
Data set 9404----2271.005, Laboratory results of carbon 14 analysis 
of gas samples from borehole USW UZ-1 collected 12/3/93 - 12/7/93 
Data set 9404----2271.008, Laboratory results of carbon 14 analysis 
of gas samples from borehole USW UZ-1 collected 1/19/93 - 1/29/93 
Data set 9404----2271.009, Laboratory results of carbon 13/carbon 
12 and oxygen 18/oxygen16 isotope ratios from gas samples from 
borehole USW UZ-1 (collected January 1993) 
Data set 9507----2271.001, Laboratory results of analyses of UZ-1 
gas samples for CO2, CH4, SF6, C-13, O-18 and C-14 (collected 
February 1995) 
4.1.10 Stable Hydrogen and Oxygen Isotopic Data Inputs 
None of the stable hydrogen and oxygen isotopic data used in this report are considered to be 
primary input data. These data are used solely to corroborate interpretations of water flow paths 
and the timing of recharge that are based on other geochemical and isotopic signatures. 
4.1.11 Strontium Isotopic Data Inputs for Waters, Rocks, and Minerals 
The following primary input data are used in Sections 6.6.6 and 6.10 to characterize the 
distribution of strontium isotopes in soils, borehole cuttings, porewaters, perched water, and 
groundwater, and associated mineralogic analyses: 
GS910508315215.005 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 5/3/89 to 5/9/91 
GS920208315215.008 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 5/10/91 to 2/28/92 
GS930908315215.027 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 3/2/92 to 11/18/92 
GS931008315215.029 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 11/19/92 to 12/3/93 
GS941108315215.010 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 12/6/93 to 8/17/94 
GS950608315215.002 Strontium isotope ratios and isotope dilution data for rubidium and 
strontium collected 9/7/94 to 5/4/95 
GS970908315215.011 Strontium isotope ratios and strontium concentrations in USW SD-7 
rocks and soils, and ESF calcite

ANL-NBS-HS-000017, Rev 00 Page 23 of 156 
GS980108312322.004 Strontium Isotope Ratios And Strontium Concentrations In Water 
Samples From USW WT-24 And UE-25 J-13 Collected In October 
1997 
GS990308315215.003 X-ray fluorescence elemental compositions of rock core samples 
from USW SD-9 and USW SD-12 
GS990308315215.004 Strontium isotope ratios and strontium concentrations in rock core 
samples and leachates from USW SD-9 and USW SD-12 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data 
Data set MOL.20000104.0012, Strontium isotope ratios and isotope 
dilution data for rubidium and strontium collected 5/11/95 to 8/5/96 
4.1.12 Uranium Isotopic Data Inputs for Waters 
The following primary input data are used in Section 6.6.7 to characterize the distribution of 
uranium isotopes in soils, borehole cuttings, porewaters, perched water, and groundwater: 
GS930108315213.004 Uranium isotopic analyses of groundwaters from SW Nevada  SE 
California. 
GS960908315215.013 Uranium and thorium isotope data for waters analyzed between 1/94 
and 9/96. 
GS970508312272.001 Uranium Isotopic Data From ESF Alcove 5 Pore-Water Leaches And 
UZ Heater-Test Water Collected Between April And May, 1997. 
GS980108312322.003 Uranium isotopic data for saturated- and unsaturated-zone waters 
collected between 12/96 and 12/97 
GS980208312322.006 Uranium isotopic data for saturated- and unsaturated-zone waters 
collected by non-YMP personnel between May 1989 and August 
1997 
GS980908312322.009 Uranium concentrations and 234U/238U ratios from spring, well, 
runoff, and rain waters collected from the Nevada Test Site and 
Death Valley vicinities and analyzed between 01/15/98 AND 
08/15/98. 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data 
Data set MOL.20000104.0007, Uranium concentration and isotopic 
composition of SZ and UZ waters in the Yucca Mountain vicinity 
4.1.13 Chemical Data Inputs for Gases from Open Boreholes 
None of the data collected for samples from open boreholes are considered primary input data for 
characterization of the chemical composition of gas at Yucca Mountain. These data are only 
used to corroborate interpretations based on chemical data for instrumented borehole samples 
(section 4.1.14).

ANL-NBS-HS-000017, Rev 00 Page 24 of 156 
4.1.14 Chemical Data Inputs for Gases from Instrumented Boreholes 
The following primary input data are used in Section 6.7.2 to characterize the chemical 
composition of gases in instrumented boreholes: 
GS991299992271.001 Preliminary hydrochemical data 
Data set 9301----2271.004, Gas chromatograph analysis of gas 
composition (CO2, CH4, SF6) of syringe samples taken during USW 
UZ-1 borehole gas sampling, 12/9/91 - 12/19/91 
Data set 9304----2271.013, Gas chromatograph analysis of gas 
composition (SF6, CH4) of syringe samples taken during USW UZ-1 
borehole gas sampling, May 1989, December 1989, and January, 
1991 
Data set 9404----2271.001, Gas chromatograph analysis of gas 
composition (CO2, CH4, SF6) of syringe samples taken during USW 
UZ-1 borehole gas sampling, December 1993 
Data set 9404----2271.006, Gas chromatograph analysis of gas 
composition (CO2, CH4) of syringe samples taken during USW UZ- 
1 borehole gas sampling, January 1993 
4.1.15 Groundwater Geochemical and Isotopic Data Inputs 
Uranium activity ratios in local groundwater are considered to be primary input data, and provide 
the technical basis for identifying the presence of local recharge beneath Yucca Mountain 
(section 6.6.8). These input data are listed in section 4.1.12. 
Carbon-14 activities in groundwater beneath Yucca Mountain are primary input data used to 
establish the boundary condition at the water table for the unsaturated-zone gas diffusion model 
cited in section 6.7.2. These input data are reported in the following DTNs: 
GS980908312322.008 Field, Chemical, And Isotopic Data From A Precipitation Sample 
Collected Behind The Service Station In Area 25 And Ground Water 
Samples Collected At Boreholes UE-25 C #2, UE-25 C #3, USW 
UZ-14, UE-25 WT #3, UE-25 WT #17 And USW WT-24, Between 
10/06/97 And 07/01/98 
GS990608312133.001 Ground-water quality data 
All other groundwater chemistry and isotopic data are used in a corroborative manner, to 
characterize local groundwater chemistry in terms of average concentrations and relative ion 
ratios. These groundwater trend data provide a baseline against which to compare and contrast 
chemical compositions of the various sources of water at Yucca Mountain, and to illustrate 
general trends of relative enrichment or depletion of one element compared to another (sections 
6.8.2 and 6.8.3).

ANL-NBS-HS-000017, Rev 00 Page 25 of 156 
4.1.16 Data Inputs Used for Chloride Mass Balance Calculations 
Precipitation data used in Section 6.9.2 to estimate bounds on present-day average chloride 
deposition rates at Yucca Mountain are listed in section 4.1.1. Pore-water chloride data analyzed 
by the chloride mass balance analysis are listed in section 4.1.3. Determination of the 
background 36Cl/Cl ratio for the Yucca Mountain vicinity, which is used to estimate the longterm 
average chloride deposition rate at Yucca Mountain, uses the following input data: 
LAJF831222AQ95.006 Halide and chlorine-36 analyses of soils from Midway Valley pits 
and trenches. 
LAJF831222AQ96.006 Halide and 36Cl analyses of soil from Midway Valley Pit MWV-P2 
LAJF831222AQ96.008 Halide and 36Cl analyses of cuttings from boreholes UZ-N15, UZN16, 
UZ-N17, UZ-N36, UZ-N38, UZ-N39, UZ-N61, UZ-N62, and 
UZ-N64 
LAJF831222AQ96.010 Halide and 36Cl analyses of cuttings from borehole UZ-N37 
LAJF831222AQ96.012 Halide and 36Cl analyses of cuttings from borehole UZ-N54 
LAJF831222AQ96.014 Halide and 36Cl analyses of cuttings from borehole UZ#16 
LAJF831222AQ96.015 Halide and 36Cl analyses of cuttings from borehole UZ-14 
LAJF831222AQ97.002 Chlorine-36 analyses of packrat urine 
LAJF831222AQ97.006 Halide, sulfate and chlorine-36 analyses of soils from Midway Valley 
soil pits MWV-P31 and NRSF-TP-19 
GS960308315131.001 Woodrat midden radiocarbon (C14) 
4.1.17 Uranium, Thorium and Lead Isotopic Data Inputs for Minerals 
The following primary input data are used in Section 6.10 to characterize the uranium, thorium, 
and lead isotopic compositions of subsurface secondary mineral deposits from ESF and drill hole 
locations: 
GS960208315215.001 Uranium and thorium isotope data determined by mass spectrometry 
for dating subsurface secondary deposits from ESF and drill hole 
locations, 8/1/95 to 2/15/96 
GS960908315215.014 Uranium and thorium isotope data for ESF secondary minerals 
collected between 3/96 and 7/96. 
GS970208315215.001 Uranium and thorium isotope data collected between 9/96 and 2/97 
from secondary minerals in the ESF 
GS970208315215.002 U-Pb isotope data for ESF secondary minerals, 9/12/96  2/15/97 
GS970808315215.012 Uranium and thorium isotope data from secondary minerals in the 
ESF collected between 2/15/97 and 9/15/97 
GS970908315215.013 U-Pb isotope data for ESF secondary minerals, 7/12/97 - 8/24/97

ANL-NBS-HS-000017, Rev 00 Page 26 of 156 
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. 
GS980908315215.016 Uranium and thorium isotope data determined at the Royal Ontario 
Museum between 07/12/97 and 01/29/98 and calculated 230Th/U 
ages and initial 234U/238U ratios for secondary silica from the 
exploratory studies facility 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data 
Data set MOL.20000104.0009, Depths of microsamples for the U-Pb 
dating 
4.1.18 Data Inputs for Abundances of Subsurface Secondary Minerals 
The following primary input data are used in Section 6.10 to characterize the abundances of 
subsurface secondary minerals in ESF and drill hole locations: 
GS971108314224.020 Revision 1 of detailed line survey data, station 0+60 to station 4+00, 
north ramp starter tunnel, Exploratory Studies Facility. 
GS971108314224.021 Revision 1 of detailed line survey data, station 4+00 to station 8+00, 
north ramp, Exploratory Studies Facility. 
GS971108314224.022 Revision 1 of detailed line survey data, station 8+00 to station 
10+00, north ramp, Exploratory Studies Facility. 
GS971108314224.023 Revision 1 of detailed line survey data, station 10+00 to station 
18+00, north ramp, Exploratory Studies Facility. 
GS971108314224.024 Revision 1 of detailed line survey data, station 18+00 to station 
26+00, north ramp, Exploratory Studies Facility. 
GS971108314224.025 Revision 1 of detailed line survey data, station 26+00 to station 
30+00, north ramp and main drift, Exploratory Studies Facility. 
GS971108314224.026 Revision 1 of detailed line survey data, station 45+00 to station 
50+00, main drift, Exploratory Studies Facility. 
GS971108314224.028 Revision 1 of detailed line survey data, station 55+00 to station 
60+00, main drift and south ramp, Exploratory Studies Facility. 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data 
Data set MOL.20000104.0008, Calcite contents in WT-24 cuttings 
Data set MOL.20000104.0013, Line survey information from the 
Exploratory Studies Facility obtained to estimate secondary mineral 
abundance

ANL-NBS-HS-000017, Rev 00 Page 27 of 156 
4.1.19 Carbon and Oxygen Isotopic Data Inputs for Minerals 
The following primary input data are used in Section 6.11 to characterize the carbon-14, stable 
carbon, and stable oxygen isotopic compositions of calcite minerals from soil, ESF and drill hole 
locations: 
GS931008315215.030 Carbon and oxygen isotope analyses of cavity- and fracture-coating 
calcite and soil carbonate from drill holes and outcrops, May '89 - 
Oct. '93. 
GS931108315215.034 Carbon 14 ages from drill holes USW G-1, G-2, GU-3, and G-4, 
April 92 - Jan. 93. 
GS931108315215.035 Oxygen stable isotope analyses of opal from drill holes and outcrops, 
June 92 - Aug. 92. 
GS940608315215.006 Oxygen stable isotope analyses of opal from drill holes and outcrop, 
June 1994 
GS950708315215.005 Delta 13C and delta 18O stable isotope data from the Yucca 
Mountain region, July 1992 to September 1994 
GS960408315215.002 Carbon and oxygen stable isotope analyses of calcite from drill holes 
and the Exploratory Studies Facility (ESF), February 1995 to April 
1996 
GS960408315215.003 Oxygen stable isotope analyses of opal from drill holes, the 
Exploratory Studies Facility (ESF), and outcrop, April 1996. 
GS960808315215.006 14-C analyses of calcite from ESF, 12/95 - 2/96 
GS960908315215.010 C and O stable isotope KIEL analyses of calcite from ESF and USWG2; 
10/27/94 - 6/22/96 
GS970208315215.003 14-C analyses of calcite from ESF fracture coatings, 12/2/96 - 
2/13/97 
GS970208315215.004 C and O stable isotope 252 analyses of calcite from ESF and USW 
G-2, SD-7, UE-25 a#7; 11/19/96 - 1/27/97 
GS970208315215.005 C and O stable isotope KIEL analyses of calcite from ESF and USW 
G-2, G-2, G-4, UE-25 a#1, USW NRG-6, NRG-7/7a, UE-25 UZ#16; 
4/8/96 - 1/17/97 
GS970808315215.010 Carbon and oxygen stable isotope analyses of calcite from the ESF 
and USW G-1, G-2, and G-3/GU-3, from 01 /16/97 to 07/18/97 
GS980408315215.010 Corrected data for carbon and oxygen isotope analyses of cavity- and 
fracture-coating calcite for one sample from drill hole USW G-2. 
GS980908315213.002 Carbon and oxygen stable isotopic compositions of Exploratory 
Studies Facility secondary calcite occurrences, 10/1/97 to 8/15/98 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data

ANL-NBS-HS-000017, Rev 00 Page 28 of 156 
Data set MOL.20000104.0014, Stable carbon and oxygen isotope 
macro- and microanalyses of calcite from the ESF and UZN-35, 2/96 
 4/99 
4.1.20 Other Data Inputs for Minerals 
The following primary input data are used in Section 6.11 to characterize the uranium, thorium, 
and lead isotopic compositions of subsurface secondary mineral deposits from ESF and drill hole 
locations: 
GS931108315215.033 Fluid inclusion temperatures from drill holes USW G-1 and G-2, 
Oct. 92  Sept. 93. 
GS991299995215.001 Preliminary unsaturated zone borehole hydrochemistry data 
Data set MOL.20000104.0011, X-ray fluorescence elemental 
compositions acquired 4/14/95 to 7/26/96 
4.1.21 Other Data Inputs 
The following data are used to establish the range of temperatures in the unsaturated zone at 
Yucca Mountain: 
GS980408312232.001 Deep unsaturated zone surface-based borehole instrumentation 
program data from boreholes USW NRG-7a, UE-25 UZ#4, USW 
NRG-6, UE-25 UZ#5, USW UZ-7a and USW SD-12 for the time 
period 10/01/97  03/31/98 
Accepted data used in this report are atomic masses of elements, and radioactive half-lives of 
radionuclides such as tritium, carbon-14, chlorine-36, rubidium-87, uranium isotopes, and 
thorium isotopes. These data are tabulated in numerous readily available sources (e.g. Parrington 
et al. 1996, pp. 18, 19, 22, 46 to 49, and 61). 
4.2 CRITERIA 
This AMR complies with the DOE interim guidance (Dyer 1999). Subparts of the interim 
guidance that apply to this analysis or modeling activity are those pertaining to the 
characterization of the Yucca Mountain site (Subpart B, Section 15), the compilation of 
information regarding geochemistry and hydrology of the site in support of the License 
Application (Subpart B, Section 21(c)(1)(ii)), and the definition of hydrologic and geologic 
parameters and conceptual models used in performance assessment (Subpart E, Section 114(a)). 
4.3 CODES AND STANDARDS 
No specific formally established codes or standards have been identified as applying to this 
analysis and modeling activity. This activity does not directly support License Application 
design.

ANL-NBS-HS-000017, Rev 00 Page 29 of 156 
5. ASSUMPTIONS 
Underlying assumptions used to perform the analyses of fluid and mineral geochemical and 
isotopic data are listed in Table 2, together with the rationale for accepting them. Assumptions 
that are indicated as To Be Verified (TBV) in Table 2 are also identified as such in the locations 
of the report where they are used. 
6. ANALYSIS AND MODELS 
6.1 GEOGRAPHIC AND GEOLOGIC SETTING 
Yucca Mountain is in the northern Mojave Desert and lies 150 km northwest of Las Vegas in 
southern Nevada (Figure 1). It consists of a series of fault-bounded blocks of ash-flow and ashfall 
tuffs and a smaller volume of lava deposited between 14 and 11 Ma (million years before 
present) from a series of calderas located a few to several tens of kilometers to the north (Table 1 
and Figure 1 in Sawyer et al. 1994). Yucca Mountain itself extends northward to the southern 
end of the Claim Canyon caldera and southward toward U.S. Highway 95 where the tuffs thin 
and pinch out beneath the alluvium in the northern Amargosa Desert (Figure 2). The tuffs dip 5 
to 10 degrees to the east over most of Yucca Mountain. Crater Flat is west of Yucca Mountain 
and separated from it by Solitario Canyon, which is the surface expression of the Solitario 
Canyon Fault - a steeply dipping scissors fault with down-to-the-west displacement of as much as 
500 m in southern Yucca Mountain (Day et al. 1996, pp. 6 to 7). Underlying Crater Flat is a 
thick sequence of alluvium, lavas and tuffs that have been locally cut by faults and subvolcanic 
dikes. East of Yucca Mountain and separated from it by Fortymile Wash is Jackass Flats, which 
is underlain by a thick sequence of alluvium and volcanic rocks. Timber Mountain, 
approximately 25 km to the north of the potential repository area, is a resurgent dome within the 
larger caldera complex that erupted the tuffs at Yucca Mountain. 
The central block of Yucca Mountain, into which waste would be emplaced if the site were 
licensed, is bounded by Drill Hole Wash on the north, the Solitario Canyon Fault on the west, 
and the Bow Ridge Fault on the east, and is dissected by the Ghost Dance and Dune Wash Faults. 
Topography is pronounced and, north of the central block, is dominated by long, northwesttrending, 
fault-controlled washes (Figure 3). Within and south of the central block, washes are 
shorter and trend eastward. Topography in the southern part of Yucca Mountain is dominated by 
south-trending faults (Figure 4). 
6.2 GEOCHEMICAL PARAMETERS AND METHODS 
Fluid geochemical parameters of importance to site characterization and repository evaluations 
include the following, although not necessarily in order of importance: 
 Major, minor and trace species 
 Redox-sensitive elements

ANL-NBS-HS-000017, Rev 00 Page 30 of 156 
 Oxidation/reduction potential (ORP, usually expressed as Eh, for Electrode potential, on 
the hydrogen scale) 
 Colloids and particulates 
 Dissolved organic carbon 
 Microbial populations 
 Gases (dissolved in aqueous phase as well as present in gas phase) 
 Stable isotopes (hydrogen, carbon and oxygen) 
 Cosmogenic and atmospheric radionuclides (tritium, carbon-14, chlorine-36) 
 Radiogenic isotopes (isotopes of strontium, uranium, and uranium decay products) 
 Temperature and pressure 
 Ages of fracture minerals 
Some of the parameters on this list are primarily pertinent to site characterization issues, others 
are primarily pertinent to radionuclide transport issues, and some are pertinent to both sets of 
issues. Data on stable isotopes, cosmogenic and atmospheric radionuclides, and radiogenic 
isotopes are used primarily for site characterization purposes. More specifically, data for these 
isotopes have been used to develop and calibrate models for the hydrologic flow system. Most of 
the remaining parameters are primarily used in repository performance evaluations of 
radionuclide dissolution, mobilization and transport. The major constituent and trace-element 
concentration data are used in both areas. These parameters are discussed in this report. 
The parameters pertinent to repository performance evaluations are used in various ways. For 
example, data on oxidation/reduction potentials, pH, major constituents, major species, gas 
concentrations, redox-sensitive elements, dissolved organic carbon, and microbial populations 
are all used to constrain predictions of the corrosion behavior of the waste packages and the 
solubility of the waste forms. Most of these parameters are also used to constrain predictions for 
the sorption behavior of the radionuclides released from the waste forms. 
The rest of this section reviews the sampling or measurement locations and collection methods 
for the different types of fluid samples analyzed in Yucca Mountain studies including 
precipitation, surface waters, pore waters, gases from the unsaturated zone, and perched water. 
Also reviewed are collection and analysis methods used for secondary fracture minerals at Yucca 
Mountain. For detailed descriptions of sampling or measurement locations and collection 
methods, the original publications cited in the discussion below should be consulted.

ANL-NBS-HS-000017, Rev 00 Page 31 of 156 
6.2.1 Sampling Locations 
A summary of the types of unsaturated-zone geochemical and isotopic data available from 
boreholes at Yucca Mountain is provided in Table 3. Surface-based boreholes from which water 
and gas samples were collected in the Yucca Mountain area are shown in Figure 3. 
Lithostratigraphy of the samples that were collected was determined using the sources listed in 
Table 4. For subsurface-based boreholes, hydrochemical sampling was conducted in the Busted 
Butte Field Test facility (Figure 2); niches, alcoves and drifts in the Exploratory Studies Facility 
(ESF); and the East-West Cross Drift (Figures 3 and 4). The alcoves from which samples were 
collected include the Upper Tiva Canyon Alcove (ESF Alcove 1), the Bow Ridge Fault Alcove 
(ESF Alcove 2), the Upper Paintbrush Contact Alcove (ESF Alcove 3), the Thermal Test Facility 
(Alcove 5) and the Northern Ghost Dance Fault Access Drift (ESF Alcove 6) (Figure 4). 
6.2.2 Gas Samples 
Gas samples have been collected from a limited set of surface-based boreholes at Yucca 
Mountain. Borehole UZ-1 was instrumented for temperature and other probes at 33 levels, 
which allowed sampling of gas compositions from 15 distinct intervals (Montazer et al. 1985, p. 
439). Additional boreholes were cased from the surface down to some depth and are open below 
this depth. These included UZ-6, UZ-6S, UZ#16, NRG-6, NRG-7a, SD-7, SD-9 and SD-12 
(Thorstenson et al. 1990, p. 256; Yang et al. 1996, p. 11; Yang, Yu et al. 1998, p. 6). In 
boreholes UZ#16, NRG-6, SD-7, SD-9 and SD-12, packers were installed to isolate specified 
intervals for gas sampling. In addition, gases were collected from radial and horizontal boreholes 
drilled from alcoves driven from the Main Drift of the ESF (LeCain and Patterson 1997, p. 3). 
Sulfur hexafluoride, SF6, was used in each of these boreholes as a gaseous tracer to identify 
drilling-air contamination of the rock gas (Yang et al. 1996, pp. 9 to 11). Based on ten years of 
records and the stabilized value in borehole UZ-1, the tracer (SF6) concentration of less than 0.1 
ppmv (parts per million on a volume basis) in the borehole air is used to define uncontaminated 
rock gas. In some instances, such as boreholes in Alcoves 2 and 3, SF6 tracer concentrations did 
not decrease even after several days of gas pumping (LeCain et al. 1997, p. 38; LeCain and 
Patterson 1997, p. 3). These residual tracer concentrations are believed to reflect the propensity 
of SF6 to adsorb onto clays and zeolites in nonwelded units (Rattray et al. 1995, p. 1). Gas 
samples were collected from surface-based boreholes using a 500 cm3-per-min peristaltic pump 
connected through short silicone tubing to within hole gas-sampling tubes (Yang et al. 1996, p. 
8). Sampling tubes were pumped overnight to purge any atmospheric air. 
Two different methods were used to collect CO2 for isotopic analysis (Yang et al. 1996, pp. 8 to 
11). A molecular-sieve method was used from 1984 to 1991, and involved passing the gas 
stream through a silica-gel tower to remove moisture, then through an anhydrous 50-nm 
molecular sieve to trap to CO2 gas. Starting in 1991, a whole-gas method was used for batch 
sampling, which involved collection of the gas in a flow-through glass container (or in a Mylar 
balloon). Separation of CO2 from the air sample took place in the laboratory using a trap cooled 
with dry-ice alcohol to trap water vapor, followed by a liquid-nitrogen trap to trap the CO2. The 
whole-gas method is the preferred technique because the molecular-sieve method depletes 13C 
relative to 12C, such that d13C values reported for gas samples collected by this method represent

ANL-NBS-HS-000017, Rev 00 Page 32 of 156 
depleted samples and are not representative of in-situ conditions (DTN: GS970908312271.003, 
footnote for SEP Table S97576.018). Consequently, d13C data obtained for molecular-sieve 
samples are not included in this report. 
Investigations in the ESF alcoves were intended to provide a better understanding of gas flow in 
the upper part of the unsaturated zone; provide evidence of gas flow direction, gas flux, and 
travel time; determine the degree of fracture connectivity in the rocks; and support conceptual 
models of fluid flow in the unsaturated zone (LeCain et al. 1997, pp. 18 to 20). In general, stable 
CO2 concentrations, at levels significantly higher than atmospheric or alcove (350 ppmv) 
concentrations, were an indication that the gas being pumped from the borehole was 
representative of rock gas. Gas samples for CO2 and SF6 concentrations were collected in glass 
syringes with three-way stopcocks so that the syringes could be filled and purged a minimum of 
three times before the actual sample was obtained. Three duplicate samples were collected from 
each borehole interval and then transported to the laboratory for analysis by gas chromatograph. 
Gas samples for 14C analysis were collected by pumping the borehole gas through molecular 
sieves designed to collect the CO2. Gas samples for d13C analysis were collected in Mylar 
balloons. 
In addition to the analysis of C isotopes in CO2, other isotopic analyses sometimes included O 
isotopes in CO2 (as an indicator of the degree of isotopic exchange with pore water), and H and 
O isotopes in water vapor. Geochemical and isotopic data for gases are presented in section 6.7. 
6.2.3 Pore-water Samples 
For drillcore samples intended for pore-water analysis, each core was wrapped in plastic, placed 
in a Lexan liner, sealed inside an aluminum foil bag, and stored under cool conditions (6 to 9  C) 
until ready for analysis (Yang et al. 1996, p. 6). Despite all subsequent precaution to preserve the 
integrity of these samples for pore-water characterization, some geochemical and isotopic 
characteristics of these fluids may have been perturbed due to the fact that drilling was conducted 
using air and the cores were exposed to ambient atmospheric conditions for some time before 
they were hermetically sealed (Assumptions 2 (TBV), 4, 9 (TBV), 12 and 14 in Table 2). Thus, 
pore-water analyses should be used with appropriate caution in subsequent interpretations. 
Water samples were extracted from drillcore using one of three methods: compression, 
ultracentrifugation, or vacuum distillation (for analysis of tritium and stable isotopes of hydrogen 
and oxygen). In many cases, following extraction of pore water by compression or high-speed 
centrifugation, residual water was extracted from the core by vacuum distillation and analyzed 
for tritium and stable isotopes of hydrogen and oxygen. 
The advantages and disadvantages of different compression methods for extracting pore water 
from drillcore, and of the effects of each on the major-ion chemistry of the extracted water, was 
investigated by Mower et al. (1994, pp. 1 to 7, 60 to 62). The method used to extract most of the 
pore-water samples obtained from surface-based boreholes was high-pressure uni-axial 
compression, applying an initial pressure of 103.4 MPa which was gradually increased to a final 
pressure of 827 MPa (Yang, Yu et al. 1998, pp. 6 to 7). To protect against atmospheric 
contamination, particularly with regard to carbonate species, the system is air tight throughout the

ANL-NBS-HS-000017, Rev 00 Page 33 of 156 
extraction process. Additional pore water was extracted in some cases by injecting dry nitrogen 
gas into the porespace and by forcing out pore water at the end of the compression. The 
compression extraction technique was applied to core samples recovered from several dry-drilled 
boreholes (LeCain et al. 1997, p. 14; Yang et al. 1988, pp. 29 to 30, 33 to 34; Yang et al. 1996, p. 
12; Yang, Yu et al. 1998, p. 6). 
Extracted pore waters were filtered through Nucleopore filters (0.45 m) before chemical 
analysis (Yang, Yu et al. 1998, p. 7). Cation concentrations were measured using inductively 
coupled plasma emission spectroscopy, and anion concentrations were measured using ion 
chromatography. Analytical errors were "5% (one-sigma) for all major ions except sulfate, for 
which the error was "10%. Reported aluminum values reflect the presence of both dissolved and 
particulate components less than 0.45 :m. Yang et al. (1988, pp. 38 to 41) determined that the 
chemical composition of extracted water changed under increasing stress in a triaxial 
compression cell operating with an axial stress between 41 and 190 MPa and a lateral confining 
stress between 34 and 69 MPa. However, with a few exceptions, the range of variation was 
generally less than 20% for calcium, sodium, magnesium, potassium, chloride, sulfate and silica 
(DTN: GS90090123344G.001). 
Analyses of chloride, bromide and sulfate were performed on pore waters extracted from ESF 
and Cross Drift drill core by ultracentrifugation (Fabryka-Martin, Wolfsberg, Roach et al. 1998, 
pp. 264 to 265). Centrifugation methods were also used on some samples to test whether a 
compression method modified the chemistry of the pore-water samples. Yang et al. (1990, p. 
250) analyzed pore waters extracted from adjacent samples of nonwelded tuff using a triaxial 
compression system (operating up to 152 MPa axial stress and 62 MPa confining stress) and a 
high-speed centrifuge (operating up to 18,000 rpm). These authors concluded that both methods 
produced reliable data, with similar results from each under the operating conditions used in the 
test. In general, differences in chemical concentrations of the major ions (calcium, sodium, 
magnesium, chloride, and sulfate) within each pair were less than 15% (Yang et al. 1990, p. 258). 
However, other chemical species were not analyzed in the study. For example, it is likely that insitu 
concentrations of bicarbonate and carbonate would be influenced to different extents by the 
extraction methods used. However, these concerns do not affect the conclusions in this report 
that are based on general geochemical trends, although they are an important consideration for 
interpretation of carbon isotopic data for pore waters. 
Pore-water data are discussed in Section 6.5.3 (geochemistry) and 6.6 (isotopes). For densely 
welded tuff core samples, which generally have moisture contents less than 5% by weight, only a 
few samples produced sufficient pore water by the compression or centrifugation methods to 
permit a complete chemical analysis. For these samples, vacuum distillation was used to extract 
water (as vapor) for analyses of tritium and stable isotopes of hydrogen and oxygen (Yang et al. 
1996, p. 6). This method was applied to core from some of the surface-based boreholes. In 
addition, in the Bow Ridge Fault Alcove (Alcove 2), water samples were extracted from cores of 
boreholes HPF#1 and HPF#2 by vacuum distillation and analyzed for tritium to assess the rate of 
infiltration of water from the land surface (LeCain et al. 1997, p. 40). In the Upper Paintbrush 
Contact Alcove, water samples were obtained by vacuum distillation from cores of boreholes 
RBT#1 and RBT#4 (Alcove 3) (LeCain and Patterson, 1997, p. 15). These water samples were 
analyzed for tritium to provide an indication of the spatial distribution of percolation flux near

ANL-NBS-HS-000017, Rev 00 Page 34 of 156 
the PTn-TSw contact between the Paintbrush nonwelded (PTn) and underlying Topopah Spring 
welded (TSw) hydrogeologic units (LeCain and Patterson, 1997, p. 17) (unit stratigraphy shown 
in Table 1). 
6.2.4 Perched Water and Groundwater Samples 
Samples of perched waters were obtained from deep surface-based boreholes UZ-14, NRG-7a, 
SD-7, and SD-9 (Yang et al. 1996, pp. 34 to 37) as well as from WT-24 (DTNs: 
GS980108312322.004 and GS991299992271.001, data set 9911----2272.004). These samples 
were collected with a bailer or from the surface output of a downhole pump. As with the porewater 
extraction methods, these methods of sampling perched water make it very difficult to 
derive reliable values for some parameters of interest such as pH, ORP/Eh, and the major species 
of redox-sensitive elements such as ferrous and total iron. Geochemical and isotopic analyses of 
perched waters are discussed in Sections 6.5 and 6.6, respectively. 
Groundwater samples from the saturated zone were generally obtained either with a downhole 
pump or a bailer (Ogard and Kerrisk 1984, pp. 5 and 7; Benson and McKinley 1985, p. 1). 
Geochemical data for these samples are discussed in Section 6.8, and isotopic data are discussed 
in Section 6.7. 
6.2.5 Fracture Minerals 
Fracture minerals consisting primarily of calcite and opal were extracted from surface-based and 
ESF drillcore, as well as being collected directly from rocks exposed along the ESF tunnels and 
alcoves. Analyses conducted on these minerals included stable isotopes of carbon, oxygen, and 
strontium, as well as 14C and members of the uranium and thorium adecay chains. These data 
are presented in sections 6.6.6, 6.10 and 6.11, in which they are interpreted in terms of evidence 
for paleoclimatic and paleohydrologic conditions in the unsaturated zone. 
6.2.6 Sample Processing for Isotopic Analyses 
Methods of processing samples for isotopic analyses include leaching salts from unsaturated rock 
cores or cuttings for 36Cl and Sr isotopic analysis, distillation or compression of core to extract 
water for analysis of tritium or stable isotopes of hydrogen and oxygen, compression of core to 
extract water for carbon isotopic analysis, and digestion of mineral samples for analyses of Sr 
isotope ratios or of U series nuclides. Centrifugation of core has also been used to extract water 
for some of these isotopic analyses. All uncertainties quoted below are one standard deviation 
unless stated otherwise. 
Tritium.Hydrogen-3 (tritium) was analyzed by liquid scintillation counting, with an 
uncertainty of "4 tritium units (TU) (one-sigma) (Yang, Yu et al. 1998, p. 7). Section 6.6.2 
provides a statistical evaluation of the tritium data to show that only results above 25 TU can be 
interpreted unambiguously as containing a component of bomb-pulse tritium. When sufficient 
water was available, some samples from ESF boreholes were isotopically enriched prior to 
analysis by liquid scintillation, a method with an uncertainty of 0.7 TU or better (Clark and 
Fritz 1997, p. 17).

ANL-NBS-HS-000017, Rev 00 Page 35 of 156 
Stable hydrogen and oxygen isotope ratios.Ratios of hydrogen-2 to hydrogen-1 (2H/1H) and 
of oxygen-18 to oxygen-17 (18O/16O) were measured by gas source mass spectrometry. These 
data are reported as delta (d) 2H and d18O, which express the samples degree of enrichment or 
depletion of the heavy isotope relative to the Vienna Standard Mean Ocean Water (VSMOW) 
standard (Clark and Fritz 1997, pp. 6 to 8). Uncertainties were 0.2 per mil () for d18O and 
1.0  for d2H (Yang et al. 1996, p. 8). 
Stable carbon isotope ratio.The ratio of carbon-13 to carbon-12 (13C/12C) was measured by 
conventional mass spectrometry. It is reported as d13C with a precision of about 0.2 (Yang, Yu 
et al. 1998, p. 7). d13C is measured relative to the Vienna Pee Dee Belemnite (VPDB) standard 
(13C/12C = 0.011237) (Clark and Fritz 1997, pp. 6 and 9). 
Carbon-14.Carbon-14 was analyzed either by conventional liquid scintillation or tandem 
accelerator mass spectrometry (TAMS) (Yang, Yu et al. 1998, p. 7). Both methods have 
analytical uncertainties on the order of 0.7 percent modern carbon (pmc). The advantage of 
TAMS, however, is its capability to analyze extremely small samples (less than 5 mg of carbon), 
whereas conventional scintillation counting requires between 1 and 3 g of carbon, depending 
upon the samples age (Clark and Fritz 1997, p. 19). 
Chlorine-36.Chlorine-36 was analyzed by accelerator mass spectrometry (as 36Cl/Cl), with 
typical uncertainties of 5% (Sharma et al. 1990, p. 410). 
Stable strontium isotope ratio.The ratio of strontium-87 to strontium-86 (87Sr/86Sr) was 
measured using solid-source thermal ionization mass spectrometry. The ratios are commonly 
expressed as d87Sr relative to the ratio of reference seawater strontium (87Sr/86Sr = 0.7092) 
(Paces, Marshall et al. 1997, p. C-1). 
Uranium, thorium and lead isotope ratios.Solid-source thermal ionization mass spectrometry 
with isotope dilution was used to obtain 234U/238U, 230Th/U, 207Pb/235U and 206Pb/238U ratios 
(Paces, Neymark et al. 1996, p. 16; Paces, Marshall, Whelan and Neymark 1997, p. E-2). 
Sections 6.6, 6.10 and 6.11 provide additional details on sample processing methods for specific 
isotopes. 
6.3 CHEMICAL COMPOSITION OF PRECIPITATION 
Chloride concentrations in local and regional precipitation, along with associated precipitation 
quantities, are considered to be primary input data, and provide the basis for estimating 
infiltration rates by the chloride mass balance method (sections 6.3.2 and 6.9.2). These input 
data are listed in section 4.1.1. All other precipitation chemistry data are used in a corroborative 
manner, to characterize local and regional precipitation chemistry in terms of average 
concentrations and relative ion ratios. These precipitation trend data provide a baseline against 
which to compare and contrast chemical compositions of the various sources of water at Yucca 
Mountain, and to illustrate general trends of relative enrichment or depletion of one element 
compared to another (sections 6.3.2 and 6.3.3).

ANL-NBS-HS-000017, Rev 00 Page 36 of 156 
6.3.1 Processes Controlling Precipitation Chemistry 
The initial chemical and isotopic composition of Yucca Mountain groundwater is largely 
established by that of local precipitation and dry fallout. Once the precipitation enters the soil 
zone, absolute and relative concentrations of the various constituents are shifted to varying 
degrees by evapotranspiration and by interactions with minerals, organic matter, and the gas 
phase. The effects of these latter processes are described in subsequent sections. Isotopic data 
for precipitation are discussed in Section 6.6. 
Several processes control the initial composition of precipitation or fallout. Some examples are: 
 Salts from marine and terrestrial sources. For example, ions such as Na and Cl in 
precipitation derive predominantly from the ocean, whereas terrestrial sources contribute 
to Ca and Mg concentrations. 
 Anthropogenic sources. Acid rain resulting from industrial releases of sulfur is an 
example of an anthropogenic source that impacts the chemical reactivity of precipitation. 
Other examples of anthropogenic sources are freons and fallout of radioactivity from 
above-ground nuclear tests. Global fallout nuclides (tritium, 14C, and 36Cl) in 
precipitation are discussed in Section 6.6.2, 6.6.3 and 6.6.4. 
 Wet and dry deposition processes. For example, between one-third and two-thirds of the 
Cl deposition in Southern Nevada is from dry deposition of aerosols and particulates, a 
process also known as dry fallout (Eriksson 1960, p. 82; Dettinger 1989, p. 62). 
 Atmospheric processes (for example, chemical transformation of molecular species). 
Different chemical species can be present as inorganic or organic gases or as aerosols, 
with each species having different average residence times in the atmosphere. 
 Season, frequency and cycles of precipitation events. 
 Evaporation prior to deposition will concentrate many solutes, as well as affect the 
fractionation of hydrogen and oxygen isotopes in moisture. 
 Air temperature affects H and O isotopic fractionation, with the greatest fractionation 
observed for cold temperatures. Air temperature also controls gas solubilities. 
Many problems complicate the collection and analysis of precipitation data. These include 
evaporation of rain or sublimation of snow in the collector, bacterial modification, and CO2 
uptake or loss. Even major elements may be below instrumental detection limits, and the charge 
imbalance for these analyses often exceeds 10%. 
6.3.2 Present-Day Regional Characteristics 
The largest database available for characterizing regional precipitation chemistry is that 
maintained by the National Atmospheric Deposition Program/National Trends Network 
(NADP/NTN), which was established in 1978 (National Atmospheric Deposition Program 1996,

ANL-NBS-HS-000017, Rev 00 Page 37 of 156 
pp. 1 to 4). The network is a cooperative effort between many different groups, including the 
State Agricultural Experiment Stations, U.S. Geological Survey, U.S. Department of Agriculture, 
and numerous other governmental and private entities. This network presently consists of 200 
rural stations throughout the United States that monitor wet-only deposition. A limited number 
of stations also monitor dry deposition, but none of these stations are in Nevada. Chemical 
analyses on weekly precipitation samples are conducted by the Central Analytical Laboratory 
operated by the Illinois State Water Survey. Summary records are available for annual, quarterly, 
and monthly periods. The data are subject to the quality assurance program of the NADP/NTN. 
Within the YMP, the NADP/NTN regional database has been used to characterize Cl deposition 
rates in the Southwestern United States. Cl is the most conservative dissolved chemical species 
in Yucca Mountain groundwaters, insofar as its origin is strongly dominated by atmospheric 
sources and the contribution from water-rock interactions generally appears to be negligible. 
Increases in its subsurface concentrations relative to that in precipitation (including dry fallout of 
aerosols and particulates) are attributed to evapotranspiration in the soil zone, including 
sublimation of snow. Because of this characteristic, various pore-water constituents are 
commonly plotted as a function of Cl concentration to assess the direction and magnitude of 
rock-water interactions in the subsurface (Section 6.5.3). 
Chloride pore-water concentrations have also been used as a surrogate measure of infiltration 
rates, an approach called the chloride mass-balance method (Scanlon 1991, p. 138). Total Cl 
deposition is a key parameter in the Cl mass-balance method. In general, Cl concentrations in 
precipitation decrease with increasing distance from the ocean (Eriksson 1960, p. 87). However, 
dry deposition of Cl is quite variable, showing no clear trend, possibly because dry fallout is 
largely dependent upon local sources of Cl in addition to distance from the ocean and wind 
patterns, which control the regional distribution of aerosol particles and their deposition rates 
(Winchester and Duce 1967, p. 110; Eriksson 1960, p. 88). Eriksson (1960, p. 82) studied the 
ratio of Cl concentrations in runoff to those in precipitation and suggested that, as a rule of 
thumb, precipitation chloride constitutes about one third of the total chloride deposition, with dry 
fallout accounting for the remaining two-thirds. In a local study of the Great Basin of Nevada 
and Utah, Dettinger (1989, p. 62) calculated an average bulk-precipitation concentration of 0.6 
mg/L (for 8 sites) and an average wet-precipitation concentration of 0.4 mg/L (for 66 sites), 
implying that dry deposition comprises about 33 percent of the total Cl input in this region. A 
crude estimate of the contribution of dry fallout to total Cl deposition rates in Southern Nevada 
can also be derived by comparing the average annual Cl concentration in wet fallout at Red Rock 
Canyon (0.16 mg/L, unweighted average calculated from Cl data in DTN: 
LA0003JF12213U.001) to the average annual Cl concentration in precipitation at 3 Springs 
Basin, which includes both wet and dry fallout (0.51 mg/L, calculated from data in DTN: 
GS930108315214.003, GS930108315214.004, and GS930908315214.030). This comparison 
indicates that dry fallout comprises about 70 percent of the total fallout in this area. 
6.3.3 Present-Day Site Characteristics 
The isotopic and chemical composition of precipitation at the Yucca Mountain site is largely 
inferred from measurements made at other local sites. Seven years of record (1984 to 1992) are 
available for precipitation chemistry in the semiarid 3 Springs Basin located east of Kawich Peak

ANL-NBS-HS-000017, Rev 00 Page 38 of 156 
in the Kawich Range east of Tonopah, Nevada, and about 130 km due north of Yucca Mountain 
(McKinley and Oliver 1994, pp. 1 to 3; 1995, pp. 1 to 3) (Figure 1). Major ion chemistries of 
precipitation for the two precipitation chemistry monitoring stations at this location (3 Springs 
Basin and Kawich Peak) were used to derive average annual weighted concentrations for major 
constituents and regression lines for these constituents relative to Cl concentrations (Table 5). 
The regression lines are used in Sections 6.4 and 6.5 to illustrate subsequent changes in water 
chemistry as it flows through the subsurface. 
Chemical data for precipitation are also available for Red Rock Canyon, the desert observation 
station closest to Yucca Mountain in the NADP/NTN network (Figure 1). This site is about 
120 km southeast of Yucca Mountain. The record used for the analysis in this report spans 12 
years, from 1985 to 1997, which includes two El Nio episodes, one in 1986 to 1987, and a long 
episode from autumn 1989 through the summer of 1995 (chemistry data in DTN: 
LA0003JF12213U.001; Fabryka-Martin, Turin et al. 1996, section 4.1.2.2). Neither alkalinity 
nor carbonate species are reported in this database. 
The chemistry of precipitation is important for modeling the composition of waters at Yucca 
Mountain because precipitation represents the starting point in the evolution of groundwater 
chemistry. Subsequent changes in the water chemistry as it enters the subsurface are illustrated 
by three types of diagrams: 
 Trilinear (Piper) diagrams show the relative concentrations of major ionic species. 
Figure 5 is a trilinear diagram for the precipitation samples from 3 Springs Basin, to be 
compared against other trilinear diagrams for surface waters and subsurface waters in 
later sections. Because bicarbonate concentrations are not available for the Red Rock 
Canyon data (DTN: LA0003JF12213U.001), these data are not presented on a trilinear 
diagram. Bicarbonate concentrations could be estimated for these samples based on 
charge-balance calculations although the uncertainties in relative anion proportions 
would probably be large for these dilute fluids. 
 Frequency distributions (histograms) of major elements are used to contrast the 
distributions of specific dissolved species in different parts of the hydrologic system. 
Frequency distributions for precipitation data have been included on the figures in 
Section 6.5.3, so that they can be directly compared to analogous data for surface and 
subsurface waters. 
 Scatterplots of various major constituents as a function of some conservative species are 
a common method for evaluating the role of water-rock interactions in changing 
concentrations along a flow path. Chloride is usually considered to be the most 
conservative species, and a common assumption is that its concentration in surface and 
subsurface pore waters reflects increases due solely to evapotranspiration (Assumption 3 
in Table 2). Figure 6 presents a set of plots of sodium, calcium, sulfate, bicarbonate, and 
silica as a function of Cl. Only samples with less than 1 mg/L Cl have been included. 
The regression lines plotted for each constituent on this figure represent least-squares fits 
to the precipitation data from the two 3 Springs Basin sites. These lines have also been 
plotted on analogous figures in Section 6.5.3 (chemistry of waters from the unsaturated

ANL-NBS-HS-000017, Rev 00 Page 39 of 156 
zone) as a basis for a discussion of the direction and magnitude of rock-water 
interactions in the subsurface. 
Other than the monitoring studies at 3 Springs Basin and Red Rock Canyon, only a few studies of 
Yucca Mountain precipitation chemistry have been conducted, and the coverage of these studies 
was limited in time, space, and/or analytical data. Chloride, bromide and sulfate were measured 
in a suite of about 100 samples collected from rain gauges at several neutron-monitoring 
boreholes at Yucca Mountain in the spring of 1995 (DTN: LAJF831222AQ95.003 and 
LAJF831222AQ97.009). The purpose of these analyses was to provide independent 
corroboration for estimates of the Cl deposition rate, a parameter used in the Cl mass-balance 
method (Section 6.9.2), and to characterize the Cl/Br and SO4/Cl ratios of precipitation. These 
ratios can be useful qualitative tracers of groundwater origins and flow paths. Histograms 
showing the frequency distributions of Cl and SO4 from this work are presented in Section 6.5.3 
(Figures 18 and 19), in which they are compared to the concentrations of these species in waters 
from the unsaturated and saturated zones. 
6.3.4 Representativeness of the Available Data 
An important issue to address is the extent to which these precipitation data are representative of 
precipitation at Yucca Mountain, both past and present. Monitoring at the site at the present time 
may not produce valid data because it may not be possible to separate out the effects of site 
disturbance from natural conditions. Present-day compositions may also not be representative of 
past (pre-industrial) compositions, for example, because of the widespread effects of air 
pollution. This raises the question, then, of which of the two available data sets is more 
representative of natural conditions at Yucca Mountain. The compositions differ in both absolute 
as well as relative concentrations of major ions (for example, compare annual average values for 
Na/Cl, SO4/Cl, and Ca/Cl in Figure 6). The Red Rock Canyon data have the advantage of 
providing a comparatively long (12-year) record, with details available for individual storms if 
desired. However, the proximity of Las Vegas may influence dust loadings and chemical 
compositions, and the lack of alkalinity analyses is a significant shortcoming that also makes it 
impossible to calculate a charge balance. In addition, only wet deposition chemistry is measured. 
The 3 Springs Basin data, although further removed from Yucca Mountain and representing a 
shorter period of time (seven years), have the advantages of a reduced influence from urban 
activities associated with Las Vegas and of the inclusion of both wet and dry deposition data. 
These precipitation data are considered adequate for the purposes for which they are used, i.e., as 
input data for simple correlation plots and as corroborative data to support independent estimates 
of the chloride deposition rate at Yucca Mountain. For the saturated zone, the geochemical 
evolution of the water is not very sensitive to uncertainties in the precipitation chemistry. 
However, for the unsaturated zone, the dominant input function is the composition of 
precipitation following evapotranspiration, and hence, predictions of the unsaturated-zone porewater 
compositions based on precipitation inputs can be more sensitive to the precipitation 
uncertainties because errors may be magnified as the water becomes more concentrated.

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6.4 CHEMICAL COMPOSITION OF SURFACE WATERS 
This section describes the data available on the chemistry of surface water in the region. Three 
types of surface-water chemistry exist, depending on the source of the water: 
 Relatively dilute waters from runoff during precipitation or snowmelt 
 Relatively saline waters from groundwater discharge at springs 
 A mixture of the two preceding types. 
After an overview of the occurrence of surface water in the basin, the following discussion 
focuses on the chemical composition of the first category of surface waters, and particularly on 
surface waters from potential recharge areas and along flow paths through the Yucca Mountain 
area. Isotopic data for surface waters are discussed in Section 6.6. 
None of the surface-water geochemical and isotopic data used in this report are considered to be 
primary input data. The surface-water data are used solely to characterize local and regional 
surface water chemistry in terms of concentration averages and ranges, relative ion ratios, and 
isotopic characteristics. These calculations provide a means to compare chemical compositions 
of surface water and runoff at Yucca Mountain to those of unsaturated-zone pore waters and 
perched water, so as to illustrate general trends of relative enrichment or depletion of one 
element compared to another (section 6.4.3). 
6.4.1 Overview of Regional and Local Surface-Water Bodies and Drainage Areas 
Local drainages on Yucca Mountain ultimately enter the Amargosa River. The eastern slope 
drains via Yucca Wash, Drill Hole Wash, and Dune Wash to Fortymile Wash; Fortymile Wash 
spreads out into a distributary system in the Amargosa Desert, joining the Amargosa River about 
18 km north of Death Valley Junction, California (Figure 2). An unnamed ephemeral channel in 
Crater Flat collects drainage from the western and southern slopes of Yucca Mountain, draining 
to the Amargosa River near its confluence with Fortymile Wash. In addition, the tributary 
Carson Slough enters the Amargosa River as it flows southward through the Amargosa Desert. 
Carson Slough drains spring flow from the Ash Meadows regional groundwater discharge area in 
the eastern portion of the Franklin Lake Playa (also known as Alkali Flat), a discharge area for 
Yucca Mountain regional groundwater. However, the Amargosa River and its tributaries are 
ephemeral streams except for short distances where spring discharges enter the channel system; 
flow throughout its entire reach occurs rarely (Malmberg and Eakin 1962, p. 7; Walker and Eakin 
1963, pp. 14 to 15) because of losses to infiltration and evaporation from the streambed. 
Savard (1995, p. F241; 1998, pp. 9 and 24) and Grasso (1996, pp. 11 to 13) discuss climatic and 
weather patterns responsible for Yucca Mountain area streamflow and associated flooding. 
Winter/spring stream flow occurs during El Nio events when the track of Pacific cyclonic fronts 
crosses the Yucca Mountain area. Summer streamflow occurs from thunderstorms, often when 
the summer monsoon in the southwestern United States extends into the Yucca Mountain area. 
Occasionally, remnant hurricanes from the Pacific Ocean move into the Yucca Mountain area, 
causing stream flow in the late summer and fall. These climatic factors influence the initial 
chemical and isotopic composition of the local precipitation.

ANL-NBS-HS-000017, Rev 00 Page 41 of 156 
Once the water contacts the ground, the chemistry of ephemeral surface waters evolves based 
upon the type of geologic materials with which the water comes into contact and the length of 
time of the contact period. Factors that influence the chemistry of ephemeral surface waters 
include: 
 Site topography (for example, slope, ridgetop, terrace, sideslope, channel), 
 Soil development (for example, depth of regolith, porosity, soil stratification/profile 
development, infiltration rates), 
 Soil mineralogy and chemistry, 
 Biota and vegetative coverage, and 
 Evaporative concentration of solutes during flow. 
In addition to ephemeral flows following precipitation events, perennial surface water in the 
Amargosa River drainage basin is associated with springs (Malmberg and Eakin 1962, p. 8). 
Flowing water occurs in the Oasis Valley, Ash Meadows, Tecopa, and Badwater areas after 
infrequent precipitation/runoff events, as well as during winter months when evapotranspiration 
is at a minimum. Some of these areas dry up almost entirely during high evapotranspiration 
periods during the summer. Perennial surface waters are found at the following locations: 
 Numerous permanent or nearly permanent springs discharge along or near the Amargosa 
River channel in Oasis Valley. Although the flow in the channel is ephemeral through 
the Amargosa Desert, short reaches of persistent flow occur between the desert and the 
location at which the channel enters Death Valley. Wet playas occur in the eastern 
(Amargosa or Peters Playa) and southernmost (Franklin Lake Playa or Alkali Flat) parts 
of Amargosa Desert. 
 The Ash Meadows regional groundwater system, which drains the region east of Yucca 
Mountain, discharges at several perennial springs that sustain small pools at Ash 
Meadows in southeastern Amargosa Desert. Crystal Reservoir, a man-made structure, 
captures discharge from Crystal Spring and several springs in the Point of Rocks area 
and drains to the Amargosa River by Carson Slough. 
 Four small perennial ponds occur in the Amargosa Desert in former clay mining pits. 
 Badwater is a spring discharge pool in the terminal area of the Amargosa River in Death 
Valley. 
The following section presents chemical data only for ephemeral surface waters (runoff). 
6.4.2 Relevance of Surface-Water Chemistry to Flow and Transport Models 
Chemical and isotopic compositions of some of the surface waters described above may be 
relevant to flow and transport modeling for two major reasons. First, infiltration of surface

ANL-NBS-HS-000017, Rev 00 Page 42 of 156 
runoff into the beds of large channels such as Fortymile Wash may contribute significantly to 
local recharge and may thereby influence the chemistry of saturated-zone fluids. Although such 
fluids do not have the potential to contact waste packages and are, furthermore, unlikely to lie 
along the direct flow path between the potential repository and the accessible environment, 
characterizing their chemical and isotopic compositions is nonetheless necessary in order to be 
able to use these constituents as groundwater tracers for the regional flow system. Secondly, 
infiltration from runoff events collected from small channels above the potential repository, at 
locations where soil cover is negligible, may contribute to seeps that have the potential to directly 
contact the repository backfill and the waste canisters. Runoff water chemistry is discussed in 
Section 6.4.3. 
6.4.3 Surface-Water Chemistry Data 
Samples have been collected to document stream flow chemistry during the occasional runoff 
event as part of Yucca Mountain site characterization studies. Sampling locations are plotted on 
the map in Figure 7. Water-quality data are also taken from a compilation of hydrochemical data 
collected in the Death Valley region during the period from 1910 to 1990, including baseline data 
from rivers and playas in addition to springs and wells (Perfect et al. 1995, pp. 1 and 3). 
Although the main objective of the Perfect et al. (1995) report was to document groundwater 
quality in the Yucca Mountain area, surface-water quality was also documented. The chemical 
analyses in the compilation by Perfect et al. are taken from four general sources: USGS 
unpublished data files, USGS National Water Information System database, published reports 
from Federal and State agency investigations, and unpublished data. 
The following general observations are made from the chemical data for channel flow and 
surface runoff. Major ion chemistry for these samples is plotted in the trilinear diagram in Figure 
8. The sampling sites fall into three general categories: channel flow fed by springs and seeps, 
channel flow from runoff events and surface runoff, and overland runoff mixed with spring 
discharge. 
Nineteen samples were analyzed for major and minor ions between 1984 and 1995 from 
15 locations within 15 km of Yucca Mountain along its eastern side. These data were collected 
during three series of runoff events: 
 Surface water samples collected in Fortymile Wash, Drill Hole Wash, and Busted Butte 
Wash in August 1984 were the first surface-water samples collected during site 
characterization studies in the Yucca Mountain area (Perfect et al., 1995, attached file 
dataedit.wk1). 
 Emett et al. (1994, p. 550) document analyses from dip samples of surface water in the 
Amargosa River drainage basin from six sampling sites during stream flow conditions in 
January and February 1993. Two of the sitesStockade Wash at Airport Road and 
Yucca Wash near its mouthrepresent local overland runoff during precipitation. 
(Note: Three of the other sitesAmargosa River near Beatty, Carson Slough at 
Stateline Road, and Amargosa River near Eagle Mountainrepresent spring discharge 
from groundwater or mixing of overland runoff and spring discharge and are not relevant

ANL-NBS-HS-000017, Rev 00 Page 43 of 156 
to this discussion. The remaining sample of runoff is from Cane Spring Wash below 
Skull Mountain but is not included here because it is not representative of runoff in the 
vicinity of Yucca Mountain.) 
 During periods of stream flow in 1994 and 1995, surface-water quality samples were 
collected on Yucca Mountain and in Fortymile Canyon during overland runoff and 
channel flow following precipitation (DTN: GS940308312133.002 and 
GS960308312133.001; the latter data are also presented in Savard 1996, p. 28). Some of 
the overland runoff from the hillslopes in the drainage basins infiltrated soil and volcanic 
rock layers and then re-emerged as overland runoff. Some of the overland runoff also 
originated from disturbed areas in the drainage basins such as roads and drill pads where 
compaction of the surface material reduced infiltration and increased overland runoff. 
Some of the surface-water quality samples in Fortymile Canyon were taken during 
overland runoff of precipitation and or snowmelt, whereas others were taken during the 
recession period after peak discharge. All samples probably represent a mixing of 
overland runoff and shallow infiltration waters that discharge along the hillslopes. 
Among the dilute runoff samples described above, total dissolved solids range from 45 to 122 
mg/L. These waters have similar ionic chemistries when plotted on a trilinear diagram (Figure 
8). The cation field is dominated by calcium, which accounts for 50 to 60 percent of the cation 
charge, whereas the anion field is dominated by carbonate species, which account for 70 to 
90 percent of the total anion charge. The average Cl content of these local runoff waters is 
3.5 mg/L. 
In addition to surface-water samples from the general vicinity of Yucca Mountain, water quality 
data are also available for 3 Springs Basin and East Stewart Basin, sites that are considered 
representative of potential recharge areas in central Nevada (Figure 1) (McKinley and Oliver 
1994, pp. 1 to 3; 1995, pp. 1 to 3). The 3 Springs Basin is a semiarid basin in the Kawich Range 
east of Tonopah; sampling locations are at elevations of 7,070 to 9,040 feet. East Stewart Basin 
is a subalpine basin in the Toiyabe Range north of Tonopah with sampling occurring at 
elevations of 9,455 to 10,240 feet. The two basins were studied as analog sites to Yucca 
Mountain during wetter and cooler periods (Section 6.4.1). Water quality samples were collected 
from precipitation, springs, and other surface waters during the period 1986 to 1992. Chemical 
data for precipitation at the 3 Springs Basin sites were discussed previously in Section 6.3.3. 
Springs in the basins are probably above the regional groundwater system and do not represent 
discharge from large groundwater basins, in contrast to springs at Ash Meadows in the Amargosa 
Desert. The water chemistry of the spring discharges does reflect modification due to movement 
of water through unsaturated volcanic rock layers in the basins. Surface-water samples can 
represent overland runoff from precipitation or snow melt and also mixing of spring discharge 
with overland runoff. 
Major ion compositions of some of the 3 Springs Basin and Stewart Basin samples are plotted in 
the trilinear diagram shown in Figure 9, and the major constituents are plotted versus chloride 
concentrations in Figure 10. These waters are very similar to the Yucca Mountain runoff 
samples with respect to their relative proportions of the major ions; that is, they are 
Ca-bicarbonate waters with a significant component of Na. However, the central Nevada

ANL-NBS-HS-000017, Rev 00 Page 44 of 156 
samples have slightly higher proportions of Na and Cl, and lower proportions of Ca and 
carbonate species, than the Yucca Mountain waters. 
Figure 10 shows various major constituents plotted against Cl concentrations for channel flow 
and surface runoff at Yucca Mountain and for surface waters from 3 Springs Basin and Stewart 
Basin. Also shown on the plots are the regression lines obtained for 3 Springs Basin 
precipitation chemistry from Table 5 in Section 6.3.3. The surface-water plots illustrate the 
direction and magnitude of changes in water chemistry in response to evaporation, dissolution of 
dry-fall salts accumulated since the last infiltration event, and water-rock interactions. Sulfate in 
these waters increases to a similar extent as does Cl, as shown by the fact that the surface-water 
compositions cluster about the regression line shown for these two anions on Figure 10. This 
observation suggests that sulfate concentrations in these waters are fairly conservative and are 
mostly a function of evaporative concentration and dissolution of dry-fall salts. In contrast, both 
Na and Ca concentrations plot considerably above the precipitation regression lines, suggesting 
that their concentrations are increased by dissolution of carbonate minerals and weathering 
reactions of soil minerals. Dissolution of carbonate minerals also leads to a large gain in 
bicarbonate concentrations, which is also apparent in a comparison of the trilinear plot of Figure 
5 (precipitation) with those in Figures 8 (Yucca Mountain runoff) and 9 (surface waters from 3 
Springs Basin and Stewart Basin). Finally, the most dramatic constituent increase is observed for 
silica, which increases by two orders of magnitude over its concentration in precipitation due to 
fast dissolution of opaline silica in the soil (Chadwick et al. 1987, p. 977). 
Another source of chemical data for surface-water samples is the compilation of analyses of 
springs and tunnel seeps from Rainier Mesa (location shown on Figure 2) (McKinley et al. 1991, 
Tables 5 and 6 on pp. 26 to 33). Because of the similarity in geologic settings for Yucca 
Mountain and Rainier Mesa, these samples expand the database used to develop a conceptual 
model for the early stages of the geochemical evolution of waters contacting tuff. A trilinear plot 
of these data is presented in Figure 11, in which some of the tunnel seeps (points 8, 9, A) are 
observed to have similar compositions to those of perched waters at Yucca Mountain (Figure 17). 
These surface-water chemical data are also included in the discussion on the geochemical 
evolution of Yucca Mountain waters (Section 6.5.3.2) in which frequency histograms for some of 
the major ion species are presented (Figures 18 to 23). 
6.4.4 Representativeness of the Data 
A key question is, to what extent are the Yucca Mountain runoff samples representative of 
surface water at this location? Surface waters under current climatic conditions at Yucca 
Mountain are an infrequent occurrence, thereby making it difficult to build a chemical database. 
Re-aeration of surface water as it proceeds down the channel may also affect the chemistry of the 
collected samples. Some samples were analyzed for bicarbonate in the laboratory instead of at 
the site during collection, such that the reported bicarbonate concentrations may not represent 
field conditions. 
Some of the samples may also be affected by site activities because man-made disturbances 
influence sediment concentrations in surface water. For example, runoff from the ESF pad and

ANL-NBS-HS-000017, Rev 00 Page 45 of 156 
tunnel waste piles during light precipitation events goes down the Drill Hole Wash channel. 
During some periods of runoff from the ESF pad, no other runoff was noted in the area, leading 
to the hypothesis that the ESF pad and tunnel waste piles were influencing water quality and 
runoff. Fine sediment probably originating from the ESF pad and tunnel waste piles has been 
transported down the channel system and has clogged infiltration pathways in the channel 
alluvial material. Because of greatly reduced infiltration in the channel bottom, surface-water 
runoff and sediment were both transported much greater distances than they would have been 
under natural conditions. 
However, none of these concerns affect the conclusions in this report that are based on general 
geochemical trends. These surface-water data are considered adequate for the purposes for 
which they are used, i.e., as input data for simple correlation plots and histograms for comparison 
against the chemistry of water in the unsaturated zone. Including the more extensive data from 
the 3 Springs Basin is useful to develop and test concepts about geochemical evolution in this 
environment. The surface geology at the two central Nevada sites is similar to that at Yucca 
Mountain insofar as both are dominated by silicic volcanic rocks, and the precipitation chemistry 
is also expected to be similar. The prevailing climatic regime at the central Nevada sites differs 
from that at Yucca Mountain, leading to differences in soil chemistry, in particular less calcic 
soils. The central Nevada sites also have higher precipitation rates and higher infiltration rates, 
such that ionic concentrations should be slightly lower for these surface waters than for the 
Yucca Mountain samples. Nonetheless, general geochemical trends should be the same. These 
data are used in the following section as corroborative evidence that the description of 
geochemical evolution of subsurface waters is consistent with general trends observed in surface 
waters. 
6.5 CHEMICAL COMPOSITION OF PORE WATERS AND PERCHED WATER 
Primary input data for the chemical compositions of unsaturated-zone waters at Yucca Mountain 
are listed in sections 4.1.3 (pore water) and 4.1.4 (perched water). Primary input data for 
subsurface temperatures are listed in section 4.1.21. Boreholes for which chemical data are 
available for pore waters and perched water are listed in Table 3. Assumptions 1, 2 (TBV) and 3 
in Table 2 apply to discussions in this section. 
6.5.1 Processes Controlling the Chemistry of Unsaturated-Zone Waters 
The major processes that could influence the chemistry of waters in the unsaturated zone, 
including perched water, include the following: 
 Dry and wet deposition (precipitation). This refers to the compositions of rain, snow, and 
dust deposited on the surface of Yucca Mountain. These compositions provide the 
starting point (that is, input composition) for unsaturated-zone water chemistry. 
Chemical data available for wet and dry deposition were discussed in Section 6.3. 
 Surface-water chemistry. Under some conditions, surface waters may be a significant 
source of recharge to the unsaturated zone in the Yucca Mountain region (see Section 
6.4). Therefore, the chemistry of surface waters is potentially an important factor in the

ANL-NBS-HS-000017, Rev 00 Page 46 of 156 
control of unsaturated-zone water compositions. Chemical data available for surface 
waters were discussed in Section 6.4.3. 
 Soil-zone processes. Soil-zone processes of importance to unsaturated-zone water 
chemistry include evapotranspiration, deposition of pedogenic mineral horizons, reaction 
of infiltrating precipitation waters with soil minerals, and biogenic processes. 
 Infiltration paths and rates. The pathways by which waters infiltrate Yucca Mountain 
impact water chemistry not only because they determine the rock/mineral types that the 
waters contact but also because they determine the contact times for waters with the 
various rock/mineral types. These contact times in turn determine the extent of reaction 
between the waters and the rocks/minerals. Particularly significant to solute transport 
rates is the distribution of flow between fractures and matrices in each lithologic unit. 
 Rock-water interactions. The extent to which infiltrating waters react with the 
rocks/minerals with which they come into contact will have a major impact on water 
chemistry. These interactions can include rock/mineral-dissolution reactions, ionexchange 
reactions, hydrolysis reactions, precipitation reactions, and possibly other 
alteration reactions. 
 Mineral-substrate-water interactions. These interactions are a subset of rock/mineral 
interactions but are separated out here because of their potential significance with respect 
to radionuclide retardation reactions (for example, sorption). 
 Water-air interactions. The composition of the gas phase in the unsaturated zone is an 
important factor in the control of unsaturated-zone water chemistry. For example, the 
carbon-dioxide partial pressure influences the carbonic-acid system and the oxygen 
partial pressure influences the oxidation state of redox-sensitive elements such as 
carbon, sulfur, iron, and manganese. 
 Microbial influences. The existence of various microbial populations in the unsaturated 
zone implies that water chemistry could be altered by microbial activity. For example, 
microbial metabolic activity could influence pH, the concentrations of redox-sensitive 
species, and the concentrations of organic acids in unsaturated-zone waters. 
 Temperature. Variations in temperature can influence the composition of unsaturatedzone 
waters by increasing or decreasing the rates of important reactions (for example, 
dissolution or precipitation reactions) and by changing the composition of the 
equilibrium assemblage in the system. Temperature variations beneath Yucca Mountain 
between depths of about 40 feet to the top of the water table range from about 18C to 
34C (based on data for NRG-6, NRG-7a, UZ#4, UZ#5 and SD-12 in DTN: 
GS980408312232.001; corroborated by data for H-1, H-3, H-4, H-5, G-4, UE-25 b#1, 
UZ-1, WT-2, and WT#4 reported in DTN: GS950408318523.001) and likely have only 
small although measurable impacts on water chemistry.

ANL-NBS-HS-000017, Rev 00 Page 47 of 156 
 Pressure. Pressure variations will have a minor effect on water chemistry through its 
effect on the dissolution of gases such as CO2 in water. More significant, however, is its 
effect on gas flow patterns, including water vapor transport. 
6.5.2 Significance and Occurrence of Perched Water 
6.5.2.1 Significance 
Perched water is a zone in which the rocks are locally saturated above the regional water table. 
The presence of perched water implies that, at least at some time in the past, the percolation rate 
through the unsaturated zone has exceeded the saturated hydraulic conductivity of the perching 
layer. The perched-water reservoir may be a remnant from a time during which percolation rates 
were higher or may reflect long-term steady-state conditions. Perched-water reservoirs of large 
volume could indicate that structural or stratigraphic traps are present that allow infiltrating 
waters to accumulate. Perched water in proximity to the waste-emplacement tunnels in a 
repository is a potential source of water.in addition to pore water.that may become mobilized 
as vapor resulting from waste-generated heat, a fact that needs to be considered when attempting 
to analyze the impact of that mobilized water on repository performance. 
6.5.2.2 Perched Water Occurrences 
Perched water has been identified below the potential repository horizon in six boreholes in the 
Yucca Mountain Site area: UZ-1, UZ-14, and NRG-7a in Drill Hole Wash; and SD-7, SD-9, and 
SD-12 along the ESF Main Drift (Rousseau et al. 1999, pp. 170 to 171; OBrien 1997, p. 23; 
Rautman and Engstrom 1996a, p. 32; Rautman and Engstrom 1996b, p. 8 and 32). The perchedwater 
bodies identified are at elevations significantly below (100 to 200 m) the potential 
repository horizon. Although other boreholes in the site area did not detect perched water, this 
may be because they were not drilled to sufficient depth to intercept the geologic units where 
perched water has been identified or because they were drilled with water or foam that obscured 
the perched water when it was encountered. In all cases, accumulation of perched water seems to 
be caused by either the basal vitrophyre of the Topopah Spring Tuff or the vitric-zeolitic 
boundary in the Calico Hills Formation acting in concert with a lateral structural barrier 
(Rousseau et al. 1999, pp. 171 to 172). Although not detected in all boreholes, based on field 
observations and the apparent prerequisite conditions, perched water beneath the site area seems 
to be a common occurrence and is probably nearly everywhere near the base of the Topopah 
Spring Tuff in the vicinity of the North Ramp (Rousseau et al. 1999, p. 170). 
The following discussion summarizes aspects of the perched water occurrences relevant to 
interpretation of their geochemical and isotopic constituents. 
UZ-1 and UZ-14.These two boreholes penetrate perched water in Drillhole Wash about 190 m 
above the water table (Rousseau et al. 1999, pp. 170 to 171). The top of the perched water is 
within the lower nonlithophysal zone of the Topopah Spring Tuff (Tptpln) about 8 m (for UZ-1) 
and 9 m (for UZ-14) above the contact with the crystal-poor vitric zone (Tptpv). Chemical 
analysis of the water showed that it was contaminated by water used to drill G-1, a borehole 
located about 305 m to the southeast (Whitfield et al. 1990, p. 6). During the drilling of G-1,

ANL-NBS-HS-000017, Rev 00 Page 48 of 156 
approximately 8.7 million liters of drilling fluid was lost into the rock (Whitfield 1986, p. 418). 
Pumping tests of UZ-14 indicated that this perched-water reservoir may be extensive (Rousseau 
et al. 1999, pp. 170 to 171). 
NRG-7a.This borehole is located in Drill Hole Wash. Water was first noticed in the borehole at 
a depth of 461.3 m (Rousseau et al. 1999, p. 171), below the contact between the bedded tuff 
(Tpbt1) and the crystal-poor vitric zone (Tptpv) at the base of the Topopah Spring Tuff. The 
water level in the borehole then rose about 30 m to stand at a depth of 428 m (elevation of 855 
m), which is 4 m above the base of the lower nonlithophysal zone (Tptpln). The perched water 
was initially detected about 91 m above the predicted water table at this borehole (Ervin et al. 
1994, Plate 1). The perched water was encountered near the contact of a series of highly fractured 
welded tuffs overlying relatively unfractured, nonwelded tuffs. This is similar to the situation at 
boreholes UZ-1 and UZ-14 where perched water may be entrapped in fractures while slowly 
imbibing into the matrix of the less fractured, underlying rock unit. 
SD-7.This borehole is located on the eastern slope of Yucca Mountain near the ESF Main Drift 
and near the southern extent of the potential repository area. Water was first observed during 
coring at a depth of 488 m in the bedded tuffs (Tacbt) at the base of the Calico Hills Tuff 
(O'Brien 1997, p. 23). This level is 4.5 m above the top of the Prow Pass Tuff and about 150 m 
above the regional water table. The perched-water level subsequently rose 8 m, apparently having 
been confined by the low-permeability zeolitic materials in this interval (Rautman and Engstrom 
1996b, p. 32). The stratigraphically complex bedded-tuff zone is a well-sorted volcanic sandstone 
layer with argillically altered pumice in all layers, predominantly horizontal fractures, and some 
lamination below 487 m (Rautman and Engstrom 1996b, p. 60). 
SD-9.This borehole is located in Drillhole Wash. Standing water was first noticed at a depth of 
about 449 m (Rousseau et al. 1999, p. 171). Television logs revealed that water was seeping 
through a fracture into borehole SD-9 at a depth of 413 m (elevation of 890 m), which is 3 m 
above the contact between the lower nonlithophysal unit (Tptpln) and the crystal-poor vitric unit 
(Tptpv) of the Topopah Spring Tuff and about 157 m above the predicted regional water table 
(Ervin et al. 1994, Plate 1). The perched-water reservoir is in fractured welded tuff (Tptpv) 
underlain by less-fractured nonwelded and bedded tuffs that comprise the uppermost part of the 
CHn. Because no pumping tests have been conducted on this perched-water reservoir, its areal 
extent is uncertain. 
SD-12.Although no perched-water reservoir of sufficient magnitude to cause standing water in 
the borehole was detected during the drilling of SD-12 (Rautman and Engstrom 1996a, p. 8), the 
video-camera log of this borehole indicates that a perched-water zone of limited extent probably 
is present in the densely welded vitric unit (Tptpv3) of the Topopah Spring Tuff, extending from 
the top of this unit down to the base of the moderately welded vitric unit of the CHn (Rousseau et 
al. 1997, p. 21). Perched water over this interval is also indicated by the in-situ pneumaticpressure 
responses observed in the instrument station immediately below this zone. Fracture 
densities measured for the core indicate intense fracturing within the lower nonlithophysal unit 
(Tptpln) and sparse fracturing in the underlying crystal-poor vitric unit (Tptpv) (Rautman and 
Engstrom 1996a, p. 25).

ANL-NBS-HS-000017, Rev 00 Page 49 of 156 
WT-24.This borehole is north of the repository block, approximately 1.5 km north of UZ-14. 
Based on saturation data, water appeared to be perched above either the moderately welded base 
of the Topopah Spring Tuff (Tptpv2, depth to top of unit is 512 m) or the basal vitrophyre of the 
Topopah Spring Tuff (Tptpv3, depth to top of unit is 524.5 m) (DTN: GS980708312242.011). 
The perching layer was difficult to determine with more precision because of inadequate core 
preservation for moisture analysis. The regional water table was encountered at a depth of 670 
m. No published reports have discussed the nature of the apparent perched layer. 
6.5.3 Major Constituents in Unsaturated-Zone Pore Waters and Perched Waters 
This section discusses the data available on the major ion chemistry of pore waters and perched 
waters in the unsaturated zone. Interpretation of the chemical data in a geochemical framework 
is based largely on the groundwater chemistry discussion in Triay et al. (1997, Section II). 
The compositions of pore waters above the potential repository horizon are of significance to 
transport modeling because they represent the types of waters that could enter the near field of 
the potential repository. They are also significant because they can be used to constrain models 
for the rock/mineral-water-gas interactions that occur in the soil zone and the unsaturated zone 
above the potential repository horizon. Such models can be used to derive estimates of future 
variations in unsaturated zone water chemistry. Data on major constituents can also be used to 
evaluate potential flow paths for flow modeling. 
Trilinear (Piper) diagrams are used to characterize the relative distributions of major cations and 
anions in these waters as a function of their stratigraphic depths. Figures 12 through 16 present 
such plots for pore waters from the PTn, TSw, and CHn hydrogeologic units, as well as from the 
combined Prow Pass (Tcp), Bullfrog (Tcb) and Tram (Tct) lithostratigraphic units. Figure 17 
presents a trilinear plot for perched-water samples. These plots are referenced in the subsequent 
discussion of the geochemical evolution of pore fluids in the unsaturated zone. 
Frequency histograms of chloride concentration data are plotted in Figure 18 for pore waters 
from the Tiva Canyon welded (TCw), PTn, CHn, TCw and TSw hydrogeologic units. These 
concentrations are compared against data for precipitation, surface waters, perched waters, and 
saturated-zone waters in order to elucidate general trends. 
6.5.3.1 Major-Ion Chemistry 
PTn Pore-water ChemistryPore waters extracted from bedded tuff of the PTn are calciumchloride 
or calcium-sulfate-type waters, i.e. samples plot near the top part of the diamond in a 
trilinear diagram (Figure 12). This characteristic becomes more pronounced for samples collected 
deepest within the PTn. Pore-water samples near the top of the PTn have not yet acquired the 
calcium-chloride or calcium-sulfate signature (e.g., point H from UZ-14 and point Y from 
UZ#16, on Figure 12). 
TSw Pore-water ChemistryData for TSw pore waters are sparse due to the difficulty of 
extracting sufficient water for analysis from densely welded core. In general, the waters have 
equal quantities of Na and Ca, with negligible Mg; the dominant anion is bicarbonate, with a

ANL-NBS-HS-000017, Rev 00 Page 50 of 156 
much smaller proportion of sulfate than is typical of PTn waters (Figure 13). In terms of relative 
proportions of anions, the chemical composition of TSw waters is intermediate between those of 
the PTn and CHn. The fields occupied by PTn, TSw, and CHn pore waters on a trilinear diagram 
are distinctly different with only slight overlaps. 
CHn Pore-water ChemistryPore waters extracted from the Calico Hills nonwelded unit are 
sodium carbonate-bicarbonate-type waters that plot near the lower part of a trilinear diagram 
(Figures 14, 15 and 16). Waters become more strongly sodium carbonate-bicarbonate types with 
increasing depth within the Calico Hills Formation (compare Figure 14 to Figure 16). 
Total Dissolved SolidsThe total concentration of constituents in pore waters as shown by total 
dissolved solid contents (Table 6) is highly variable, and is often greater near contacts than in the 
middle of stratigraphic units (Yang et al. 1996, p. 24). Unsaturated-zone pore waters from 
surface-based boreholes have significantly larger concentrations of total dissolved solids than 
either perched water (Tables 7 and 8) or saturated-zone water (Benson and McKinley 1985, p. 5). 
The larger concentrations suggest either a greater degree of evapotranspiration near the surface 
(e.g., for PTn pore-water samples from UZ-14), or a greater degree of rock-water interaction 
which could indicate a prolonged contact of percolating water with silicate rocks. 
Chloride and Sulfate ConcentrationsChloride and sulfate are generally conservative 
constituents in oxidizing groundwater and hence are commonly used as indicators of water 
origins, flow paths, and mixing. The concentrations of chloride and sulfate in many pore-water 
samples from surface-based boreholes are one to two orders of magnitude greater than those of 
either perched water or saturated-zone water. For example, chloride concentrations of deep 
perched waters lie between 4.1 and 15.5 mg/L (Table 8) with a mean of 6.8 mg/L, which is 
similar to that of the saturated zone water from the volcanic rocks beneath Yucca Mountain (9.5 
mg/L). In contrast, the chloride concentration of matrix pore water from surface-based boreholes 
ranges from 10 to 245 mg/L with a mean of 49 mg/L (calculated from data in Table 6). If matrix 
pore water had contributed significantly to the perched-water bodies, the chloride concentration 
of perched water should be similar to that of the pore water. The smaller concentration of 
chloride in perched water implies that pore waters and perched waters have distinctly different 
histories of geochemical evolution, undergoing different degrees of evaporation and/or of waterrock 
interactions. 
Figure 19 shows that sulfate concentrations are similarly elevated in PTn pore waters relative to 
those for the other waters plotted. The higher proportions of chloride and sulfate concentrations 
in PTn pore waters relative to the other waters at the site are also evident by comparing the 
trilinear plot in Figure 12 to the trilinear plots in Figure 14 (upper Calico Hills pore waters), 
Figure 15 (lower Calico Hills pore waters), Figure 16 (Prow Pass pore waters), and Figure 17 
(perched waters). 
Silica ConcentrationsThe frequency distribution for silica shown in Figure 20 indicates that 
silica is low in precipitation but substantially higher in surface waters. By the time precipitation 
and surface waters infiltrate into the unsaturated zone, the silica concentrations have reached a 
limit. This limit is presumably the result of saturation with a silica phase as discussed further in 
Section 6.5.3.2.

ANL-NBS-HS-000017, Rev 00 Page 51 of 156 
Major Cation ConcentrationsThe concentrations of sodium and calcium are also elevated in 
pore waters relative to other waters at the site as shown in Figures 21 and 22. Sodium is elevated 
in most of the pore-water samples whereas calcium is elevated only in the PTn and TSw samples. 
The trilinear diagram for PTn pore waters (Figure 12) shows that PTn pore-water compositions 
extend to higher calcium proportions than observed in either precipitation compositions (Figure 
5) or surface-water compositions (Figures 8 and 9). This enhancement presumably reflects 
water-soil/rock reactions that release calcium to solution preferentially to the release of sodium 
and magnesium. The pore waters in the Calico Hills and Prow Pass units show high proportions 
of sodium (Figures 14, 15 and 16). This shift in dominance from divalent to monovalent cations 
primarily reflects the ion-exchange reactions with zeolites in the CHn unit. The zeolites 
preferentially take up calcium and magnesium while releasing sodium to the water. 
Vertical Trends in Ion ConcentrationsThe chemical composition of pore waters within the 
nonwelded units does not change in a simple or predictable fashion in a given borehole. 
Chloride and sulfate show large concentration changes within the CHn, even by as much as a 
factor of two for samples separated by less than 0.5 m (e.g., compare two SD-7 samples from 791 
m, three UZ-14 samples at 477 m, two WT-24 samples from 532 m, all in Table 6). Similar 
large contrasts are noted for sodium and total carbonate within the PTn. If flow within these 
units were dominated by vertical percolation of pore water, a monotonic increase in sodium and a 
monotonic decrease in calcium should be noted in the CHn because of cation exchange by 
zeolites (replacement of Na with Ca or Mg on ion-exchange sites). Although pore waters for SD- 
9 show a continual increase in the sodium content with depth, the data set is limited to only four 
samples. Data for UZ#16 show a decrease in calcium with depth, but changes are fairly erratic 
and the concentration of calcium rebounds sharply at the top of the Prow Pass Tuff. The data, 
therefore, suggest at least some component of lateral flow within the nonwelded units. 
6.5.3.2 Geochemical Evolution 
A convenient method for assessing the magnitude and direction of rock/mineral-water 
interactions experienced by percolating infiltration waters transported through the soil and 
unsaturated zones is to plot the concentrations of the major constituents in these waters relative 
to a conservative constituent (that is, a highly soluble and nonsorbing constituent), such as 
chloride, in an x-y plot. In the absence of other geochemical processes, evaporation or 
transpiration of a given water sample will result in proportional increases in all constituent 
concentrations, describing a linear trend in this plot starting at the origin. If processes other than 
evapotranspiration significantly influence the concentration of a particular constituent, the 
resulting data point will lie off the evapotranspiration trend. The selection of chloride as the 
normalizing constituent for such a plot assumes that its concentration is not affected significantly 
by leakage from fluid inclusions or by geochemical reactions along the flow path (Assumption 3 
in Table 2). 
Calcium and BicarbonatePlots showing the concentrations of calcium and bicarbonate versus 
chloride for various pore-water, perched-water, and saturated-zone samples are presented as 
Figures 24 and 25, respectively. Included on each plot is a regression line representing a leastsquares 
fit to the weighted annual precipitation data from the 3 Springs Basin monitoring sites 
(regression lines from Table 5). These plots show that both calcium and bicarbonate

ANL-NBS-HS-000017, Rev 00 Page 52 of 156 
concentrations in PTn pore waters generally plot on or below the evapotranspiration lines 
(Figures 24a and 25a). This observation implies that calcium and bicarbonate were lost from 
these waters relative to chloride. Given the fact that soils on Yucca Mountain contain abundant 
caliche horizons, this loss likely reflects the precipitation of calcite as the result of 
evapotranspiration and possibly other reactions in the soil zone. 
Pore waters from the Calico Hills and Prow Pass units show even greater depletions of calcium 
relative to the precipitation trend (Figures 24b and 24c). These greater depletions likely reflect 
ion-exchange processes in which sodium in the ion-exchanger phase (for example, zeolite or 
clay) was replaced by calcium from the water and vice versa. Unlike the PTn pore waters, many 
of the Calico Hills and Prow Pass pore waters are enriched in bicarbonate relative to the 
precipitation trend (Figures 25b and 25c). This fact most likely reflects carbonic acid weathering 
reactions which start with the dissociation of carbonic acid in the water as follows: 
H2CO3 . H+ + HCO3
- . (Eqn 1) 
SodiumIn the weathering of aluminosilicate rocks and minerals, weathering reactions include 
the exchange of the hydrogen ions produced in the carbonic acid reaction with sodium or other 
cations on the rock or mineral. This step leads to an increase in sodium as well as bicarbonate 
concentrations in the water. The overall reaction is approximated as follows: 
>SONa + H2CO3 . >SOH + Na+ + HCO3
- , (Eqn 2) 
where >SO is a mineral substrate with a surface-complexation site at which ions can be 
exchanged. As shown in Figures 26b and 26c, sodium concentrations in pore waters from the 
Calico Hills and Prow Pass units generally plot well above the precipitation trendline. This result 
is attributed to the sodium/hydrogen ion-exchange reaction and to ion-exchange reactions 
involving calcium, magnesium, and sodium ion exchange on zeolites and clays. Assuming the 
sodium/hydrogen ion-exchange reaction is accompanied by the formation of an equimolar 
amount of bicarbonate, the increase in bicarbonate levels over and above the amount predicted by 
the precipitation trend line (Figure 25b and 25c) would imply a large proportion of the increase in 
sodium concentrations shown in Figure 26 is due to the sodium/hydrogen ion reaction. 
In contrast to the increase in sodium relative to the precipitation trend line for the Calico Hills 
and Prow Pass units, data for PTn pore waters (Figure 26a) plot below the regression line 
calculated from the 3 Springs Basin precipitation data. As explained previously, sodium is 
generally leached from minerals and rocks during low-temperature weathering reactions. Such 
leaching would lead to compositions that plot above the evapotranspiration line, not below it. 
Furthermore, the PTn pore waters also have low values of bicarbonate relative to chloride (Figure 
25a). These trends would seem to preclude reactions similar to that proposed above for the 
Calico Hills and Prow Pass units to explain the geochemistry of pore waters for the PTn. 
Analytical error is not considered a likely explanation for the Na vs. Cl trend because of qualitycontrol 
measures and because nearly all the samples plot below the line, implying they would all

ANL-NBS-HS-000017, Rev 00 Page 53 of 156 
have to be in error, and because the charge balances for the analyses generally agree within 10% 
(Table 6, last column). 
Several explanations could account for the observed Na versus Cl trend in the PTn pore waters. 
 The average Na/Cl ratios in precipitation may have been lower in the past (i.e., closer to the 
halite line) than those measured in the 3 Springs Basin samples at the present day. This 
possibility is supported by the fact that the weighted-average Na/Cl ratio in precipitation at 
the Red Rock site near Las Vegas (1.1 molar ratio) is about half of that for the 3 Springs 
Basin data (2.4 molar ratio). (The Red Rock Na/Cl ratio is calculated from precipitationweighted 
average annual Na and Cl concentrations using data reported in DTN: 
LA0003JF12213U.001. The 3 Springs Basin Na/Cl ratio is calculated from precipitationweighted 
average annual Na and Cl concentrations using summary data shown in Table 5.) 
 Sodium may be taken up by some sort of rock-water interaction not generally considered. 
However, smectites in the PTn are generally low in sodium and high in potassium and 
calcium. Although present in the PTn, zeolites do not appear to be particularly common in 
this unit, and limited analytical data also show them to be calcium-rich. 
 Sodium may have been sequestered in the soil zone as some other sodium salt such as sodium 
sulfate. 
The last hypothesis is the preferred one, insofar as it also accounts for the observed depletion in 
sulfate relative to chloride for PTn pore waters (Figure 27a). 
SulfateLike chloride, sulfate is considered to be a generally conservative constituent in dilute 
oxidizing waters such as the unsaturated-zone pore waters in Yucca Mountain. However, as 
shown in Figures 27a, 27b, and 27c, unsaturated-zone pore waters show sulfate-to-chloride ratios 
consistently lower than the ratios observed in recent precipitation. Because all the unsaturatedzone 
pore-water analyses are grossly undersaturated with chloride phases and with gypsum and 
other possible sulfate phases involving the major cations, it is unlikely that solid chloride or 
sulfate phases are precipitated in the unsaturated zone (Triay et al. 1997, p. 29). Although 
anthropogenic sulfate may have elevated the modern-day SO4/Cl ratio in precipitation, the data 
used to calculate parameters of the precipitation regression line do not appear to have been 
significantly influenced by this source because perched waters and saturated-zone waters plot 
near the precipitation regression line (Figure 27d). 
Drever and Smith (1978, p. 1452) presented a model that offers one potential explanation for the 
low sulfate-to-chloride ratios in the unsaturated-zone pore waters (Triay et al. 1997, p. 29). Their 
model involves drying and wetting cycles in the soil zone. During the drying phase, 
concentrations of dissolved solutes are increased in soil waters by evapotranspiration to the 
degree that phases such as calcite, gypsum, silica, and the more soluble salts precipitate. During 
occasional heavy rains, the phases precipitated during the drying phase are partially redissolved. 
Because the dissolution rates for highly soluble salts, such as sodium chloride, are higher than the 
rates for less-soluble salts, such as calcite, gypsum, and silica, a portion of the less-soluble salts 
may remain undissolved after the occasional heavy rains infiltrate through the soil zone. In terms

ANL-NBS-HS-000017, Rev 00 Page 54 of 156 
of sulfate and chloride concentrations, this process could lead to soil waters with lower sulfateto-
chloride ratios than those observed in precipitation. The actual concentrations of sulfate and 
chloride in these waters would depend on the details of the processes involved, including the 
dissolution kinetics of the sulfate and chloride phases, the residence time of the waters in the soil 
zone, and the original masses of sulfate and chloride in the soil zone. 
An alternative hypothesis to account for the low sulfate-to-chloride ratio is the microbial 
reduction of sulfate ions in the soil (e.g., initially to hydrogen sulfide, or more likely to a mixture 
of organic sulfides such as methyl disulfide and dimethyl disulfide). These volatile compounds 
are commonly produced in soils and are readily lost to the atmosphere. However, decreased 
SO4/Cl are not observed in up-gradient saturated-zone waters. Because up-gradient waters 
recharge in regions with more vegetation and wetter soils, one might expect the likelihood of 
microbial reduction of sulfate to be even greater for those waters than for infiltrating waters at 
Yucca Mountain. Hence, this hypothesis is considered improbable for the Yucca Mountain site. 
Although differences in the dissolution kinetics of sulfate and chloride salts may be part of the 
explanation for the low sulfate-to-chloride ratios in pore waters from the unsaturated zone at 
Yucca Mountain, these differences are likely augmented, and perhaps even dominated, by 
crystallization-sequence effects. For example, it is possible that minerals (such as calcite and 
gypsum) that precipitate from evaporating soil pore waters early in a crystallization sequence, are 
partially or completely sequestered by minerals that precipitate later in the sequence (such as 
being coated by opal-A). Alternatively, early crystallized phases may completely fill smaller 
pores in the rocks and, therefore, be less accessible to infiltrating waters than minerals 
crystallized later in the sequence in larger pores (for example, Chadwick et al. 1987, p. 975). 
During subsequent infiltration events, the latest-formed phases in pores accessible to infiltrating 
waters would preferentially dissolve, leading to soil solutions enriched in the more soluble salts 
relative to the less soluble salts. 
SilicaA plot of silica versus chloride concentrations in pore waters, perched waters, and 
saturated-zone waters is shown in Figure 28. Most of the water samples from the Yucca 
Mountain area plot above the precipitation trend line. This result suggests that a process other 
than evapotranspiration is contributing to the increase in silica concentrations in these waters. 
According to Gifford and Frugoli (1964, pp. 386 to 388) and Chadwick et al. (1987, p. 977), 
silica is added to soil waters as a result of the dissolution of opaline silica in soil horizons in arid 
regions. This explanation would be consistent with the presence of opal in the soils of Yucca 
Mountain and opal deposits on fracture surfaces exposed in the ESF (section 6.11.1). It is also 
consistent with the fact that surface waters have much higher silica concentrations than 
precipitation compositions (Figure 20). 
Perched WaterPerched-water compositions are generally distinct from the compositions of 
pore waters although they are very similar to saturated-zone water compositions (Section 6.8). 
These relationships are readily seen by comparing the trilinear plots of each category of water: 
perched water (Figure 17), unsaturated-zone pore waters (Figures 12 to 16), and groundwater 
from the saturated zone (Figure 48). The similarity of perched and saturated-zone water 
compositions suggests that these waters are subject to similar water-rock interactions. As

ANL-NBS-HS-000017, Rev 00 Page 55 of 156 
discussed in Section 6.8, these reactions predominantly involve mineral/rock dissolution and ion 
exchange. 
pHpH values shift from slightly acidic values for precipitation (pH 6), to increasingly basic 
values with depth in the unsaturated zone (pH 9 for the deepest pore-water samples, Table 6) 
(Figure 23). Controls on pH in ambient unsaturated-zone pore waters and perched waters are 
dominated by the carbonic-acid system and the interaction of hydrogen ions with the host 
rock/mineral. As discussed above, hydrogen ions can replace sodium ions in the host 
rock/mineral (for example, volcanic glass, feldspar) under most conditions. As hydrogen ions are 
used up, carbonic-acid dissociation produces additional hydrogen ions and bicarbonate ions. If 
hydrogen/sodium exchange is inhibited, the pH of a given pore-water sample will depend 
primarily on the partial pressure of carbon dioxide in the gas phase in contact with the water and 
on whether or not the gas phase has equilibrated with the water phase. This process will buffer 
the pH of the (dilute) pore waters at near-neutral levels. If both the carbonic-acid dissociation 
and hydrogen/sodium exchange reactions are important, the control of pH becomes a kinetic 
problem. For example, if the rate at which hydrogen ions react with the host rock is fast relative 
to the rate at which the carbon-dioxide partial pressure changes or the rate at which the carbon 
dioxide in the gas phase equilibrates with the water phase, the pH of the water phase could 
increase above the equilibrium level for the carbon-dioxide partial pressure of interest. 
Conversely, if the hydrogen reaction rate is slow relative to the carbon-dioxide equilibration rate, 
the pH of the water phase would more directly reflect the carbon-dioxide partial-pressure 
variations. 
Because the sodium-versus-chloride concentration data for pore waters from units above the 
Calico Hills nonwelded (CHn) unit (Figure 26) suggest little or no evidence for the 
hydrogen/sodium ion-exchange reaction, the pH of these pore waters likely is controlled in part 
by the carbon-dioxide partial pressure with which they are in contact. Measured pH values in 
PTn pore waters average 7.2. In contrast, the CHn pore waters and perched waters show clear 
evidence of sodium/hydrogen ion exchange. The average pH values for these waters are 8.1 for 
perched water, 8.3 for pore waters from the CHn unit above the Prow Pass Tuff, and 9.0 for pore 
waters from the Prow Pass Tuff and below. Analytical uncertainties in pH measurements are 
about "0.2 to "0.3 pH units. Whether the higher pH values for deeper samples reflect the 
cation/hydrogen-ion exchange rate or simply a lower partial pressure of carbon dioxide in the gas 
phase has not yet been resolved although there may be sufficient CO2 gas data available to do so. 
However, it is also possible that the pore-water pH changes when it is exposed to air during 
sample collection, or that it is affected by the compression of the rock during the pore-water 
extraction process; both processes could vary according to rock type. 
Redox StateThe oxidation/reduction state of unsaturated-zone waters is likely dominated by 
the presence of oxygen in the unsaturated-zone gas phase. At the two locations where such 
measurements have been made, the unsaturated-zone gas phase has atmospheric levels of 
oxygen: 21% reported for UZ-6S gas in Thorstenson et al. (1990, p. 256); and 18.5 to 21.1% 
reported for UZ-1 gas (DTN: GS991299992271.001, data sets 9507----2271.002 and 9512---- 
2271.010; also Yang et al. 1996, p. 42). These results confirm that unsaturated-zone pore waters 
would generally be oxidizing. Measured Eh would typically be high (400 to 600 mV) even 
though in low-temperature natural systems this value does not always indicate equilibrium

ANL-NBS-HS-000017, Rev 00 Page 56 of 156 
insofar as some oxidation/reduction reactions may not have gone to completion. It is possible 
that lower oxidation/reduction potentials could be present locally (that is, in microenvironments) 
as a result of microbial activity or the presence of a reducing compound (for example, pyrite). 
Microbial ActivityThe influence of microbes on the chemistry of waters in the unsaturated 
zone is not well defined. At a minimum, microbes could produce organic acids and locally alter 
pH and oxidation/reduction states. Microbial activity could also affect concentrations of sulfate, 
bromide, and other dissolved species, as well as fractionate isotopes of light elements such as 
carbon. According to Kieft et al. (1997, p. 3128), microbial cell counts and microbial biomasses 
were low at all the locations sampled in the ESF. Kieft et al. (1997, p. 3128) suggest that this 
result was likely due to low water contents and low nutrient availability. However, they note that 
the potential for microbial activity was high. That is, microbial populations were present but not 
active. They concluded that if sufficient water and nutrients were added to the system, microbial 
populations could increase dramatically. 
6.5.4 Representativeness of Available Data 
The data available on pore-water and perched-water chemistry are limited in several ways. First, 
complete pore-water analyses are available mainly for those horizons in Yucca Mountain that 
contain nonwelded tuffs with relatively high porosities. Very few complete pore-water analyses 
are available for well-indurated, low-porosity rocks (for example, welded tuffs in the repository 
horizon). Second, pore-water and perched-water analyses are only available for samples from a 
limited number of boreholes (Table 3). Third, the procedure for extraction of water from the 
pores may have an impact on the water chemistry. For example, the release of carbon dioxide 
from pore-water samples could change the pH of the samples. Similarly, the pH of perchedwater 
samples could shift due to degassing as the bailer is brought to the surface or at the pump 
outlet. 
Despite these restrictions, the major ion chemistry of the pore waters is sufficiently consistent 
and the controls on this chemistry are sufficiently well understood that bounds can be placed on 
the likely range of variations to be expected. An important parameter in estimation of these 
bounds is the net infiltration rate (that is, the degree of evapotranspiration) over the period of 
interest. Bounds on the pH of the pore waters are more difficult to derive because the variations 
in carbon-dioxide partial pressures within the unsaturated-zone gas phase are not well defined at 
the present time. However, model calculations assuming saturation with calcite would allow this 
parameter to be bounded. Lower bounds on the oxidation/reduction state cannot be derived 
without additional field data. 
The compositional variations of pore waters and perched waters in the unsaturated zone at Yucca 
Mountain reflect a variety of infiltration rates, rock-water interactions, gas-water interactions, 
and other effects. The range of these processes and effects will likely not change greatly within 
the potential range of climatic regimes likely to affect Yucca Mountain. What may change is the 
relative importance of these processes and effects. For example, under climatic regimes 
involving higher infiltration rates, the ion-exchange processes represented by pore waters from 
the Calico Hills nonwelded unit and by the perched waters may become more dominant. This 
scenario would result in more dilute pore waters with higher proportions of sodium ions and

ANL-NBS-HS-000017, Rev 00 Page 57 of 156 
possibly higher pH. However, as these types of waters are present in the ambient system, they do 
not present an unanticipated change in water chemistry. 
6.6 ISOTOPIC COMPOSITION OF FLUIDS 
The purpose of this section is to summarize available aqueous-phase isotopic data for 
precipitation, surface waters, pore waters and perched waters recovered from the unsaturated 
zone, and groundwaters. These data provide constraints for water and solute transport rates and 
mechanisms. Examples of specific issues addressed by these data include spatial and temporal 
variability in net fluxes, lateral diversion in specific stratigraphic units, role of faults in 
controlling flow paths, fracture-matrix interactions, and distribution of water travel times. 
The types of isotopic data available for borehole samples from the unsaturated zone are presented 
in Table 3. Borehole and tunnel alcove locations are plotted in Figures 3 and 4. 
6.6.1 Overview of Isotopic Methods 
Isotopes measured in unsaturated-zone fluids as part of YMP site characterization activities fall 
into five general categories as described below. It would be incorrect to assume that the various 
methods in each category provide redundant information. Rather, each method yields very 
different types of information (see reviews of isotopic methods in IAEA 1983, sections 5 to 8, 
10, 11 and 13; Davis and Murphy 1987, pp. 4 to 9; Clark and Fritz 1997, Chapters 1, 7 and 8). 
Hence, a large suite of different approaches has been critical to the development and testing of 
conceptual models for flow and transport through the unsaturated zone at Yucca Mountain. 
Anthropogenic MaterialThis category of environmental tracers includes radioactive species 
present in global fallout from nuclear weapons testing and from releases from nuclear-fuel 
reprocessing plants. Tritium, 14C, and 36Cl produced in the atmosphere during above-ground 
nuclear testing activities, primarily between 1952 and 1963, have been widely used in hydrologic 
studies. The presence of these nuclides above background levels in subsurface fluids is generally 
accepted as a clear indication that some proportion of the water was transported to that depth in 
less than 50 years. If the sampled depth is more than a few meters in an arid environment, the 
presence of global fallout nuclides implies a component of fracture flow. Hence, these isotopic 
data provide a means for constraining the extent to which solute transport is retarded by diffusion 
from fractures into the adjacent matrix. Fission products 99Tc and 129I in a subsurface sample 
(above natural background) would also provide a clear indication of a component of recent water. 
However, a robust analytical protocol for these species in unsaturated-zone fluids has not yet 
been developed. Other radionuclides in global fallout, such as 137Cs and plutonium isotopes, 
sorb strongly onto most mineral surfaces and hence are largely immobilized in the near-surface 
soil. Tritium, 36Cl, and 14C data acquired as part of the YMP site characterization activities are 
discussed in Sections 6.6.2, 6.6.3, and 6.6.4, respectively. Fluorocarbon compounds have also 
been used as tracers of gas movement at Yucca Mountain but are not discussed in this report 
because their primary use is to characterize how the presence of boreholes can alter natural gas 
flow patterns and rates (Thorstenson et al. 1998, p. 1507).

ANL-NBS-HS-000017, Rev 00 Page 58 of 156 
Atmospheric RadionuclidesTritium, 36Cl, and 14C also exist naturally in the atmosphere as 
the result of the interactions of cosmic rays with atmospheric gases. To the extent that the 
original concentrations at the surface can be reconstructed, these nuclides are useful indicators of 
water residence times, with water ages based on the extent of radioactive decay of the 
atmospheric component. As part of YMP site characterization activities, 14C and 36Cl have been 
used to constrain water age estimates. Chlorine-36 and 14C data acquired as part of the YMP site 
characterization activities are discussed in Sections 6.6.3 and 6.6.4, respectively. 
Climatic ReconstructionStable isotopic compositions of hydrogen and oxygen can be used to 
infer paleoclimatic conditions. Hydrogen and oxygen isotopic analyses of water samples acquired 
under Yucca Mountain site characterization activities are summarized in Section 6.6.5. Noble 
gases are another indicator of the paleotemperature of recharge waters but are relevant mostly to 
saturated-zone water and have not been measured in YMP site characterization activities. 
Water-Rock InteractionsGroundwater is commonly out of chemical and isotopic equilibrium 
with the rocks through which it moves (Davis and Murphy 1986, Section 8). The extent of 
disequilibrium provides a qualitative method for establishing flow paths and flow chronologies. 
Furthermore, if the kinetics of chemical or isotopic exchange between the water and minerals 
along its flow path are sufficiently well known, then semi-quantitative estimates of water travel 
times may be possible. Sections 6.6.6 and 6.6.7 address the hydrologic implications of trends 
observed in isotopic ratios for strontium and uranium in pore waters. 
Dating of Secondary Fracture MineralsWaters percolating through the unsaturated zone at 
Yucca Mountain deposit secondary minerals in areas where solutions exceed chemical saturation 
with respect to various mineral phases, most commonly calcite and opal (Paces, Neymark et al. 
1998, p. 36). These minerals provide evidence of past percolation flow paths and preserve 
physical and isotopic records related to fracture solutions). As part of site characterization 
activities, measurements of 14C activities, 230Th/U activity ratios, and 207Pb/235U ratios were 
obtained to provide the basis for estimating mineral formation ages. These age data, combined 
with the physical and isotopic data, can be used to derive constraints on water flow through the 
mountain (Section 6.10.3). 
6.6.2 Tritium 
Primary input data used to characterize the distribution of tritium in the unsaturated zone at 
Yucca Mountain, which provide a basis for water travel time estimates, are listed in section 4.1.5. 
Assumption 4 in Table 2 applies to discussions in this section. 
6.6.2.1 Background 
Natural tritium (3H or T) is produced in the upper atmosphere by the bombardment of nitrogen by 
the flux of neutrons in cosmic radiation (Clark and Fritz, 1997, p. 174): 
H C n N 3
1 
12 
6 
1 
0 
14 
7 + . + (Eqn 3) 
where n is a neutron. Once produced, tritium oxidizes rapidly to tritiated water (HTO). Transfer 
of tritium to the troposphere occurs during spring in mid-latitude zones. Tritiated water has a

ANL-NBS-HS-000017, Rev 00 Page 59 of 156 
short residence time in the troposphere (less than one year) and is eventually removed from the 
atmosphere in precipitation or through isotopic exchange. Historical concentrations in rain water 
in the middle latitudes have been estimated to be on the order of 10 tritium units (TU) with one 
TU being equal to one tritium atom per 1018 atoms of 1H and corresponding to 3.19 pCi/L (IAEA 
1983, p. 58). Tritium values in precipitation prior to the 1950s were between 2 and 25 TU 
(Yang et al. 1996, p. 51). Because of the relatively short half-life of tritium (12.3 yr, Parrington 
et al. 1996, p. 18), groundwater infiltrating prior to 1952 with an initial tritium content of 10 TU 
would have a present-day tritium content of 0.7 TU or less. 
Above-ground testing of nuclear devices in the Northern Hemisphere between 1952 and 1963 
produced significant amounts of tritium in the Earths atmosphere. Tritium from powerful 
thermonuclear blasts was injected into the stratosphere during that time. Bomb-pulse tritium 
overwhelmed natural background levels by as much as several orders of magnitude (Figure 29). 
Peak concentrations in precipitation, expressed as annual precipitation-weighted averages, were 
reached in 1963 when the annual average measured values at Albuquerque, NM, and Salt Lake 
City, UTthe two stations probably most representative of fallout at Yucca Mountainwere 
about 1,900 TU and 3,600 TU, respectively (IAEA 1981, pp. 134 and 154). Seasonal variations 
in post-bomb tritium concentrations in precipitation are quite significant (Davis and Murphy 
1987, pp. 36 to 37; Clark and Fritz 1997, pp. 177 to 178). These variations are caused by 
changes in atmospheric circulation between the troposphere and the stratosphere, which is a 
major reservoir of tritium. During the early 1960s in the Northern Hemisphere, early summer 
maxima at many monitoring locations were ten times as large as the winter minima. Even in the 
early 1980s, 20 years after the cessation of atmospheric nuclear tests, summer maxima were still 
more than twice winter minima at many stations. Consequently, the seasonal timing of 
precipitation is a critical determinant of the magnitude of the tritium signal introduced into the 
subsurface. 
A nuclear-test ban treaty signed in 1963 largely stopped further nuclear testing activity in the 
atmosphere, although some small atmospheric releases of tritium continued from nuclear reactors 
and testing by countries that had not signed the treaty (Carter and Moghissi 1977, p. 58). Tritium 
concentrations have gradually decreased since 1963 to about 10 to 40 TU measured in 
precipitation at the Nevada Test Site between November 1983 to June 1985 (DTN: 
GS920908315214.032). Precipitation samples from 3 Springs Basin in Central Nevada, slightly 
north of the Nevada Test Site, showed slightly lower tritium concentrations in samples collected 
between 1985 and 1991, ranging from 19 to 71 pCi/L (6 to 22 TU) (McKinley and Oliver 1994, 
pp. 27 and 74). Annual mean values and monthly maximum values for monitoring stations in 
states surrounding Nevada likewise were in this range (i.e., still elevated above pre-1952 
background levels) during 1988 to 1993 (Yang et al. 1996, p. 51). In the winter of 1992, the 
tritium content of surface runoff collected from several sites in the vicinity of Yucca Mountain 
ranged from 19 to 33 pCi/L (6 to 10 TU) (Emett et al. 1994, p. 550; Savard 1996, p. 28); values 
of tritium during the winter are typically the lowest of the year. 
It is possible that venting of tritium from subsurface nuclear detonations on the Nevada Test Site 
may also have contributed to tritium in precipitation at Yucca Mountain. For example, the 
Project Plowshare Schooner event on December 8, 1968, was a shallow cratering experiment 
conducted in Area 20 (Pahute Mesa, shown on Figure 2) of the Nevada Test Site, about 40 km

ANL-NBS-HS-000017, Rev 00 Page 60 of 156 
due north of Yucca Mountain, and was known to have vented tritium to the atmosphere (EPA 
1971, pp. i, ii, 34 and 42). Immediately following the event, tritium concentrations of 5,200 to 
10,000 pCi/L (1,630 to 3,135 TU) were reported for snow samples from three sites in Nevada. 
However, trajectories for this particular event were mostly northerly and northeasterly, such that 
Yucca Mountain precipitation was unlikely to have been influenced by it. 
The extent to which detectable quantities of tritium enter the subsurface is dependent upon the 
spatial and temporal variations in precipitation. If precipitation is insufficient to lead to net 
infiltration following a storm event, then the tritium is lost back to the atmosphere by 
evapotranspiration. Consequently, because 1958 to 1964 experienced below-average levels of 
precipitation at Yucca Mountain (Precipitation Station 4JA) (French 1985, pp. 52 to 56), it is 
entirely possible that much of the peak tritium concentrations were never transported into the 
bedrock at Yucca Mountain. In this regard, the behavior of tritium as a tracer of modern water 
differs substantially from that of 36Cl. In the latter case, all global fallout 36Cl eventually is 
carried into the subsurface. 
6.6.2.2 Statistical Analysis of Tritium Data 
As part of YMP site-characterization activities, tritium has been analyzed in over 800 pore-water 
fluids extracted from unconsolidated material in shallow surface-based boreholes, from drill core 
from deep surface-based boreholes, and from ESF drillholes. Analyses are also available for 
water samples bailed and pumped from perched-water bodies (Table 9) and from the saturated 
zone. Detectable levels of tritium have been observed in the Bow Ridge fault zone in ESF 
Alcove 2 and in pore waters extracted from core samples from surface-based boreholes. These 
detections occur within the TCw, PTn and TSw, and also in some samples from the CHn, as deep 
as the Prow Pass member of the Crater Flat Tuff. 
Because of the implications of post-bomb tritium for the presence of fast transport paths and 
large fracture fluxes, it is important to define the threshold at which a given signal can be 
considered as being above background. Although the analytical uncertainty is 4 TU (for 1- 
sigma) based on counting statistics, other factors contribute to a larger uncertainty in the 
measured value. For this analysis report, Chauvenet's criterion for identifying outliers was the 
basis of the statistical test used to establish the cutoff tritium value above which a sample result 
is considered to be elevated over background (Bevington and Robinson 1992, p. 58), i.e., the 
minimum tritium activity that would indicate the presence of bomb-pulse water in a sample. The 
approach taken in this report is to rank the tritium data from lowest to highest value and to 
calculate a cumulative average and standard deviation for each step of the ranking. One then 
calculates the number of standard deviations that the highest-value data point lies above the mean 
as each new data point is included in the cumulative average. These standard deviations are 
plotted in Figure 30, in which they are compared against Chauvenet's criterion for identifying 
outliers (solid line) as a function of ranking. This criterion states that a data point is an outlier of 
a Gaussian (normal) distribution if the probability of such a value being that far from the 
cumulative mean of the ranked data set is less than 0.5% (Bevington and Robinson 1992, p. 58). 
The plot of sample standard deviations versus sample rank (Figure 30) varies smoothly within 
the region of background. Sample 730, with 25.7 TU, exceeds the cumulative mean of 5.3 by 3.4 
standard deviations, which exceeds Chauvenet's criterion for identifying statistical outliers for a

ANL-NBS-HS-000017, Rev 00 Page 61 of 156 
population of this size. Hence, all values above 25 TU (the value for the preceding sample) are 
considered to lie outside the range of the population of background samples. The limitation of 
this approach is that background in this case includes post-bomb waters which have returned to 
pre-bomb tritium levels. A more appropriate statistical analysis would compare the sample data 
against the results obtained for analytical blanks since the objective is to identify the presence of 
any tritium with non-zero concentrations as indicative of any component of water less than 50 
years old, post-bomb as well as bomb-pulse. 
Following this simple statistical analysis, Table 10 summarizes the distribution of pore-water 
samples in each borehole, according to the total number of samples analyzed for each 
hydrogeologic unit and the number that exceeded the threshold of 25 TU. Of the 718 samples 
included in this summary table, 51 had tritium contents above 25 TU. These individual samples 
are listed in Table 11. These tritium results are summarized below. 
6.6.2.3 Summary of Tritium Data 
The following discussion summarizes tritium data for drillcore samples from surface-based and 
ESF boreholes, with respect to the identification of samples containing bomb-pulse tritium 
(Tables 10, 11 and 12). 
TCw samples.Some of the highest tritium concentrations at Yucca Mountain were in TCw 
samples from the vicinity of the Bow Ridge fault zone. Samples were collected from drillhole 
HPF#1, which was drilled into the fault zone from the ESF Bow Ridge Fault Alcove (Alcove 
#2). A concentration of 155 TU was measured for pore water 3.4 m west of the fault within the 
pre-Rainier Mesa Tuff (LeCain et al. 1997, p. 40). Values of 118 and 128 TU were found in pore 
waters within the fault breccia. The high values indicate minimal mixing of the percolating 
fluids with older fluids and may be a consequence of the width of the fault zone at the surface, 
the lack of alluvium up-slope from the fault, and the shallow depth of the fault where sampled 
(approximately 20 to 30 m). 
None of the 40 TCw samples from seven surface-based boreholes included in the Table 10 
summary showed tritium levels above 25 TU. 
In UZ#5, a zone of samples with levels above 30 TU occurred in the interval of 28.3 to 36.7 m, at 
the base of the Tiva Canyon unit, with a peak of 75 TU (corroborative data, Table 12). 
Collection of these data preceded the establishment of the YMP quality assurance program. 
PTn samples.Bomb-pulse tritium was detected in PTn samples from two out of 10 surfacebased 
boreholes. One UZ#16 sample from the Tpcpv2 (48 m), near the top of the PTn, contained 
148.5 TU. Five of the 13 PTn samples from NRG-6 contained tritium above 25 TU; these were 
from the Tpp and Tpbt2 units and spanned a 55-ft interval. In UZ-14, one out of 35 PTn samples 
contained tritium above the threshold (32 TU in a Tpp sample). 
No bomb-pulse tritium was detected in the 104 PTn samples from NRG-7a, UZ-7a, SD-6, SD-7, 
SD-9, SD-12, or UZ-1, nor in the 3 PTn samples from ESF Alcove 3. PTn samples from three

ANL-NBS-HS-000017, Rev 00 Page 62 of 156 
ESF South Ramp drillholes (at stations 6720, 6721 and 6679) also were below the threshold 
(corroborative data in DTN: GS990183122410.001). 
A cluster of four PTn samples with levels of 38 to 45 TU occurred in the interval of 44.8 to 49.5 
m in UZ#4, within and below the Yucca Mountain unit (corroborative data, Table 12). Collection 
of these data preceded the establishment of the YMP quality assurance program. 
TSw samples.Bomb-pulse tritium was detected in TSw samples from five out of 10 surfacebased 
boreholes, representing nearly 10% of the 244 samples from this unit. Half of the bombpulse 
results were in UZ#16 samples, in which tritium peaks were observed at several depths: 80 
m, 204 m, and the interval of 317 to 357 m. Seven out of 10 WT-24 samples from the Tptpv3 
unit contained 26 to 50 TU (depth interval, 1689 to 1703 ft). SD-6, which is located in the 
bottom of a small wash, had a cluster of elevated tritium values (27 to 30 TU) from a 3-ft interval 
in the Tptpln at a depth of about 1440 ft. Single occurrences of bomb-pulse tritium were 
detected in UZ-1 (28 TU at 621 ft) and NRG-7a (47 TU at the top of the TSw at 357 ft). 
No bomb-pulse tritium was detected in 7 TSw samples from the drillhole transecting the Ghost 
Dance fault in the Northern Ghost Dance Fault Access Drift (Alcove 6) (DTN: 
GS970283122410.002), despite the fact that elevated levels of 36Cl were measured in Alcove 6 
(see section 6.6.3). This negative result is corroborated by analyses of 9 other samples from this 
drillhole (DTN: GS9901083122410.001). 
Seventeen samples from ESF boreholes were analyzed following isotope enrichment, resulting in 
analytical uncertainties of 0.2 TU or less, more than an order of magnitude lower than analytical 
uncertainties for conventional counting without enrichment. Of this set, the highest tritium 
activity was 1 TU in ESF-SR-MOISTSTDY#7; other samples were from ESF Alcove #6, ESFNDR-
MF#1, South Ramp holes #1, 2, 5, 6, and 7, and North Ramp holes #4, 13 and 16 (DTN: 
GS990183122410.004). Because of the potential for isotopic exchange with tunnel air, this 
result is not considered to indicate the presence of bomb-pulse or post-bomb tritium 
CHn unit above the Prow Pass.Of 144 CHn samples above the Prow Pass from seven 
surface-based holes, bomb-pulse tritium was detected in two samples from UZ#16 (about 43 and 
104 TU), separated by 37 ft. 
Prow Pass Tuff.In the Prow Pass portion of the CHn at about 1752 ft (30 to 43 TU). One 
sample from the Prow Pass in SD-12 contained 39 TU (Table 11). All tritium analyses from SD- 
7 and SD-9 are less than 25 TU. 
Perched water. Isotopic compositions have been measured in perched water from four Yucca 
Mountain boreholes (Table 9). None of the tritium analyses were above the 25 TU threshold 
indicating the presence of bomb-pulse tritium. 
Summary.Tritium data for some of the unsaturated-zone boreholes show several inversions in 
which samples with larger tritium concentrations occur below background values in a vertical 
profile (Yang et al. 1996, p. 31). These inversions suggest that vertical water percolation through 
the rock matrix is not the predominant flow mechanism in the unsaturated zone for all

ANL-NBS-HS-000017, Rev 00 Page 63 of 156 
stratigraphic units at Yucca Mountain. The occurrence of detectable tritium in waters below nontritium-
bearing water (and hence older water) in a vertical profile is strong evidence for the 
occurrence of fracture and lateral flow at Yucca Mountain. 
6.6.3 Chlorine-36 
Primary input data used to characterize the distribution of chlorine-36 at Yucca Mountain, which 
provides a basis for water travel time estimates, are listed in section 4.1.6. Assumptions 5, 6 and 
7 in Table 2 apply to discussions in this section. 
6.6.3.1 Background 
Measurements of chloride (Cl-) concentrations and 36Cl/Cl for salts extracted from water, soil, 
and rocks have been used to provide information on characteristics of water movement and 
solute transport through the unsaturated zone at Yucca Mountain (Fabryka-Martin, Wolfsberg et 
al. 1997, pp. 75, 77 to 79; Fabryka-Martin, Wolfsberg, Levy, Roach et al. 1998, p. 93; Fabryka- 
Martin, Wolfsberg, Roach et al. 1998, p. 264; Wolfsberg et al. 1998, p. 81). Chlorine-36 is a 
radioactive isotope of chlorine, with a half-life of 3.01 x 105 years (Parrington et al. 1996, p. 22), 
and in nature, it occurs primarily as the chloride anion. As such, it is relatively inert in the 
subsurface environment and behaves conservatively. This radionuclide is present in infiltrating 
waters as a natural tracer produced mainly in the upper atmosphere by the bombardment of argon 
gas by cosmic radiation (Clark and Fritz, 1997, p. 232):
p Cl n Ar 
n Cl p Ar 
+ . + 
+ + . + 
36 36 
36 40 a 
(Eqn 4) 
where n = neutron, p = proton, and " = alpha particle. Common Cl in the atmosphere is also 
irradiated by the atmospheric neutron flux to produce Cl and gamma radiation: 
. + . + Cl n Cl 36 35 (Eqn 5) 
The relatively long half-life of 36Cl theoretically permits the detection of travel times up to 
several hundred-thousand years. To normalize the data for the variable effects of 
evapotranspiration, the 36Cl concentration is generally reported relative to that of stable Cl-. 
Expressed in this manner, the present-day background level of 36Cl/Cl is 502 ( 53) x 10-15 
(Table 25, discussed in Section 6.9.2.3). 
Global fallout from thermonuclear tests conducted primarily in the Pacific Proving Grounds 
resulted in a 36Cl bomb pulse with maximum meteoric ratios in excess of 200,000 x 10-15 
(Figure 29). These extremely high values were diluted by mixing processes in the soil zone and 
subsurface and are not observable today. Nevertheless, high 36Cl/Cl (those greater than about 
1250 x 10-15) indicate some bomb-pulse component, and their appearance in an environmental 
sample signals the presence of at least a small component of bomb-pulse 36Cl. Present day 
36Cl/Cl in surface soils at Yucca Mountain are generally in the range of 1500 x 10-15 to 3000 x

ANL-NBS-HS-000017, Rev 00 Page 64 of 156 
10-15 (CRWMS M&O 1998, p. 3-5). In subsurface water, high ratios suggest travel times from 
the ground surface of 50 years or less. 
Although the existence of bomb-pulse 36Cl enables the study of solute transport with travel times 
of 50 years or less, the natural cosmogenic background permits analysis of much longer-term 
transport processes. However, the use of 36Cl/Cl for dating older waters is not as straightforward 
as the case for bomb-pulse signals due to the time-varying input signal. Both theoretical 
considerations as well as measurements of soil profiles and fossil urine from ancient pack-rat 
middens support the hypothesis that the present-day background ratio has remained relatively 
constant during the Holocene (last 10 ka) (Plummer et al. 1997, Figure 3B). Expected lower 
rates of stable Cl deposition during the Pleistocene (10 ka to 2 Ma), in combination with higher 
rates of cosmogenic 36Cl deposition as a result of Southern shifts in the jet stream, would have 
led to higher local meteoric 36Cl/Cl, relative to those that were present throughout the Holocene 
(Plummer et al. 1997, p. 540). Superimposed on this effect are varying atmospheric 36Cl 
production rates caused by variations in the Earths geomagnetic field. Based on these two 
factors, the meteoric 36Cl/Cl at Yucca Mountain has been reconstructed for the last 1.8 Ma 
(Fabryka-Martin, Wolfsberg et al. 1997, pp. 4 to 5). Analyses of 36Cl/Cl in pack-rat midden 
samples dated by the 14C technique are generally consistent with the reconstruction, although 
these data can only cover the last 40 ka due to the comparatively short half-life of 14C (Figure 
31). 
Chlorine-36 is also produced in rocks due to a low but ubiquitous neutron flux resulting from the 
decay of uranium and thorium isotopes and their daughters, but these background levels are low 
relative to those that have been measured in Yucca Mountain water samples (Fabryka-Martin, 
Wolfsberg et al. 1997, pp. 8 and 13, and Table 5-3). Although uranium concentrations reach 
several hundred ppm in some silica deposits lining fractures in the unsaturated zone at Yucca 
Mountain, such concentrations do not elevate the local neutron flux (or 36Cl production rates) 
because the flux is determined by uranium and thorium concentrations averaged on a much larger 
scale (e.g., 104 cm3). 
Together the bomb-pulse record and the long-term reconstruction allow 36Cl/Cl observations in 
subsurface fluids at Yucca Mountain to be divided into four classes: 
 Ratios over 1250 x 10-15 provide clear evidence of bomb-pulse influence, and indicate 
the presence of some rapid transport pathways (Fabryka-Martin, Wolfsberg et al. 1997, 
p. 18). 
 Ratios near the present-day value of 500 x 10-15 suggest Holocene precipitation of prenuclear-
age (from 1950, extending back to about 10 ka before the present) (Figure 31a). 
A value of 500 x 10-15 is very unlikely to indicate extremely young (post-1980) 
precipitation because bomb-pulse 36Cl is still widely prevalent in surface soils at Yucca 
Mountain, based on analyses of surface soils and surface runoff. 
 Ratios that are elevated above present-day background but less than 1250 x 10-15 cannot 
be interpreted unambiguously in terms of water travel time, in the absence of additional 
geochemical or isotopic information. These may be attributed to Pleistocene-aged water

ANL-NBS-HS-000017, Rev 00 Page 65 of 156 
that is not so old as to unequivocally demonstrate radioactive decay (note elevated ratios 
at the end of the Pleistocene in Figure 31b; Fabryka-Martin, Wolfsberg et al. 1997, pp. 4 
to 5). Alternatively, these ratios may reflect the presence of a small component of bombpulse 
36Cl, possibly as low as a percent of the total flow. 
 Ratios significantly less than 350 x 10-15 clearly show the effects of radioactive decay of 
36Cl. Actual estimates of water age will depend on the past meteoric ratios, which must 
be considered highly speculative for the period before the earliest packrat data (40 ka). 
However, based on the current reconstruction, these ratios imply ages in excess of 200 
ka. 
Unfortunately, the interpretation of a given sample in one of the above categories is not always 
clear-cut. Only interpretation of the highest ratios (indicating bomb-pulse water) and the lowest 
ratios (indicating radioactively decayed ancient water) may usually be considered relatively 
unequivocal. Intermediate ratios may represent Holocene or Pleistocene input with 
corresponding travel times or may represent mixtures of waters of different ages. Nonetheless, 
the intermediate ratios shed light on the interpretation of water ages when considered in 
conjunction with other independent lines of evidence, such as other isotopic measurements and 
infiltration studies and results of flow and transport simulations of alternative conceptual models. 
Over 900 36Cl measurements have been conducted thus far for the Yucca Mountain Project. 
Analyzed samples include surface soils and soil profiles; rock samples collected from surfacebased 
boreholes, the ESF, and the Cross Drift; water samples including surface runoff, 
unsaturated-zone pore water, perched water, and saturated-zone water; and fossilized urine from 
pack-rat middens. Observations from these sample analyses are summarized in Table 13 and 
discussed below. 
6.6.3.2 Chlorine-36 in Shallow Samples 
Analyses of bomb-pulse 36Cl and Cl profiles in soil and alluvial profiles show that thick alluvium 
is generally effective at reducing net infiltration to levels less than 1 mm/yr (Fabryka-Martin, 
Turin et al. 1996, section 5.1.2) (e.g., see data for soil from pits and trenches in DTN: 
LAJF831222AQ95.006 and LAJF831222AQ96.006). An exception to this generalization may 
be in channels and at the base of sideslopes, as illustrated by the penetration of bomb-pulse 36Cl 
into the soil exposed at the NRG#5 drill pad (DTN: LAJF831222AQ95.005) and in samples as 
deep as 3.3 m in the soil-test pit NRSF-TP-19 at the North Portal (DTN: 
LAJF831222AQ97.006). 
Similarly, borehole samples collected from the PTn when this rock unit is overlain by thick 
alluvium do not show any evidence for the presence of bomb-pulse 36Cl (e.g., data for UZ-N37, 
UZ-N54, UZ#16, and UZ-14 in DTN: LAJF831222AQ96.010, LAJF831222AQ96.012, 
LAJF831222AQ96.014, and LAJF831222AQ96.015, respectively). 
In contrast, where alluvial cover is thin (for example, less than a few meters thick) or missing, 
water is able to readily enter fractures of the bedrock, as shown by the detection of bomb-pulse 
36Cl measurements in samples from such locations (e.g., see data for neutron boreholes in DTN:

ANL-NBS-HS-000017, Rev 00 Page 66 of 156 
LAJF831222AQ96.008, LAJF831222AQ96.009, LAJF831222AQ96.011 and 
LAJF831222AQ96.013). For example, fast transport through the welded Tiva Canyon (TCw) is 
indicated by bomb-pulse 36Cl/Cl ratios measured in several boreholes that intersect the 
nonwelded Paintbrush Tuff (PTn), which lies below the TCw. Bomb-pulse levels of 36Cl were 
also observed in drillcore samples from the top of the Calico Hills unit in the shallow Busted 
Butte Field Transport Facility (DTN: LA9909JF831222.005). 
6.6.3.3 Bomb-Pulse 36Cl in the Exploratory Studies Facility and Cross Drift 
Evidence for fast pathways that persist into the TSw is provided by bomb-pulse 36Cl/Cl ratios 
measured at locations in the ESF and Cross Drift (Figure 32 and Table 14). Over 250 samples 
have been analyzed from the 8-km ESF tunnel including two of its niches and alcoves. Of these, 
more than 40 had 36Cl levels sufficiently elevated as to be interpreted as unambiguous evidence 
for the presence of bomb-pulse 36Cl (DTN: LAJF831222AQ98.004, LAJF831222AQ98.009 and 
LA9909JF831222.010). For example, bomb-pulse 36Cl was detected in the Drillhole Wash fault 
zone, in the vicinity of the Sundance fault zone in the Main Drift and ESF Niche #1, and near the 
Sundance fault zone and the Ghost Dance fault zone where they were intersected by the Northern 
Ghost Dance Fault Access Drift (Alcove 6). Similar to the ESF results, five out of 15 Cross Drift 
samples had ratios above 1250 x 10-15, and nine were above 1000 x 10-15 (DTN: 
LA9909JF831222.003; data not yet qualified). 
The correlation of the elevated 36Cl measurements with the surface expression of faulting 
indicates that the pathway and travel time may involve locally modified PTn fracture properties 
(Fabryka-Martin, Wolfsberg et al. 1997, p. 78; Fabryka-Martin, Flint et al. 1997, pp. 6-22 and 8- 
18). These data support the hypothesis that faulting or other disturbances increase PTn fracture 
permeability, thereby generating a local environment in the PTn that supports fracture flow and 
hence rapid transport of solutes. Once through the PTn, flux distributions favor fracture flow in 
the TSw, thereby providing a continuous pathway to the sampled depths. 
6.6.3.4 Non-Bomb-Pulse 36Cl in the Exploratory Studies Facility 
Most of the ESF sample analyses had ratios less than the threshold for indicating bomb-pulse 
36Cl (Figure 32). In the southern part of the ESF, beyond station 45+00, most samples had 
36Cl/Cl ratios typical of Holocene water, which could suggest travel times less than 10 ka to this 
depth. (Averages of water with greater and lesser values provide a less likely explanation 
because the mixing proportions would have to be the same for the large number of samples). A 
number of samples from this part of the system also had 36Cl signals that were significantly 
below the present-day background value, suggesting the possible presence of zones of relatively 
stagnant water. 
Many of the samples from the northern part of the ESF, up to station 45+00, had 36Cl/Cl ratios 
variably above the present-day background and provide a striking contrast to the nearly-constant 
ratios measured in the southern part of the ESF (Figure 32). The largest signalsthose above a 
ratio of 1250x10-15are attributed to global fallout 36Cl. Fabryka-Martin, Wolfsberg et al. (1997, 
pp. 19 and 21) discuss alternative hypotheses to account for these highly elevated signals and rule 
out sample contamination as well as in-situ production of 36Cl either at the surface or deeper in

ANL-NBS-HS-000017, Rev 00 Page 67 of 156 
the profile. The favored hypothesis is that fast hydrologic paths capable of conducting bombpulse 
36Cl to the level of the ESF are more prevalent in the northern part of the ESF than in the 
southern part, due to a greater number of faults in the north that cut through the comparatively 
unfractured PTn where it overlies the ESF. With regard to those intermediate samples with ratios 
greater than present-day background but less than 1250 x 10-15, it is not presently possible to 
assess whether or not these intermediate signals indicate the presence of a very small component 
of bomb-pulse 36Cl or whether the elevated signals reflect travel times exceeding 10 ka, the most 
recent time when the signal in infiltrating water would have been high enough to provide the 
36Cl/Cl signatures found in water from this area. 
6.6.3.5 Chlorine-36 in Deep Boreholes 
Measured 36Cl/Cl ratios for samples of moderately to densely welded tuff from boreholes are 
systematically lower than the values for ESF samples. This apparent discrepancy is probably 
attributable to differences in the sample collection techniques (Fabryka-Martin, Turin et al. 1996, 
section 6.2). Borehole samples are obtained from ream cuttings. Rock Cl is released to the 
cuttings during drilling and, subsequently, is leached together with the pore-water Cl during 
sample preparation for 36Cl analysis. This source of Cl has a 36Cl/Cl ratio on the order of 40 x 
10-15. The extent to which rock Cl contributes to the total amount of Cl leached from the rock 
can be estimated from its Br/Cl ratio (Fabryka-Martin, Wolfsberg et al. 1997, pp. 30 to 32; 
Fabryka-Martin, Turin et al. 1996, section 6.2.1). Because of the low 36Cl/Cl of the rock Cl, the 
36Cl/Cl calculated for the meteoric component of Cl in the borehole samples is always equal to or 
higher than the measured ratio. Samples collected from tunnel walls are not as greatly affected by 
rock Cl as are borehole samples because the manual method of collection used in the tunnel does 
not pulverize the rock as does the ream bit. Borehole samples from nonwelded units (PTn, CHn, 
Prow Pass) also do not appear to be greatly affected by the release of rock Cl, probably because 
the concentration of leachable rock Cl in these particular units is negligibly small relative to that 
in the pore-water fluids. Differences between uncorrected 36Cl/Cl ratios for borehole samples 
from welded units and those from the ESF demonstrate the importance of recognizing the 
magnitude of the influence of rock Cl to the 36Cl/Cl values measured for borehole samples. After 
correcting for this effect, the two sets of analyses are consistent (Fabryka-Martin, Wolfsberg et 
al. 1997, p. 33). None of the few 36Cl/Cl measurements available for samples collected below 
the potential repository horizon are sufficiently high as to indicate the unambiguous presence of 
bomb-pulse 36Cl (Table 13, Observations for TSw and CHn samples). The maximum ratio 
measured for a surface-based borehole sample in or below the Tptpul unit was 843 x 10-15 for 
SD-12 (1940 to 1941 ft, Tcp2 unit; LAJF831222AQ97.007). 
6.6.3.6 Chlorine-36 in Perched Water 
The variation of input signal for 36Cl/Cl over time enables 36Cl/Cl measurements in perched 
water (Table 9) to be interpreted in support of 14C ages. Figure 31b shows that co-variation of 
14C and 36Cl/Cl is irregular but can be smoothed as a meteoric water curve (Figure 33). This 
co-variation can be used as corroborative data to support interpreted 14C ages as being less than 
or greater than about 10,000 years. For example, 14C activity is plotted against 36Cl/Cl for 
perched water samples on the same curve (Figure 33). The data match the meteoric water curve 
well and the ages of the perched water can be estimated by interpolation along the meteoric water

ANL-NBS-HS-000017, Rev 00 Page 68 of 156 
curve. Chlorine-36 and other isotopic analyses of perched water provide a consistent estimate of 
the age of the perched water bodies. Ages of the perched water can be estimated by interpolation 
along a characteristic curve based on a predicted correlation between reconstructed 14C and 36Cl 
input functions for the past 25 ka. By this approach, the 36Cl analyses indicate ages ranging from 
2 to 12 ka for the different perched-water bodies sampled, which is in general agreement with 
14C-based ages. However, there is substantial uncertainty in attributing 36Cl/Cl data to particular 
ages above 10,000 years, as well as uncertainty in the quantitative interpretation of ages from 14C 
data. 
6.6.3.7 Consistency of Data with Site-Scale Flow and Transport Models 
A flow and transport model using the FEHM code was used to simulate transport of 36Cl into the 
ESF tunnel (Fabryka-Martin, Wolfsberg et al. 1997, pp. 78 to 79). Modeling results show that 
observed 36Cl signals are consistent with the above site-scale conceptual model and with 
reasonable parameter estimates. The overall picture from these studies is that: 
 Infiltration is spatially variable and, on the average, exceeds 1 mm/year over the 
potential repository block. 
 Fracture transport can be critical, permitting rapid transport through otherwise lowconductivity 
materials. 
 Isolated fast paths associated with faults and fractures may penetrate deep into the 
mountain. 
These modeling studies showed that the arrival of even small (1 percent of the input flux) 
amounts of bomb-pulse 36Cl at the ESF and Cross Drift horizon in under 50 years generally 
required percolation fluxes of at least 1 to 10 mm/year, depending on the characteristics of the 
secondary permeability assumed for the model layers corresponding to the PTn (Fabryka-Martin, 
Wolfsberg et al. 1997, Tables 8-4 to 8-6). This modeling study considered the stratigraphy at 
two locations within the ESF, one where the thickness of the PTn was large (ESF station 35+00) 
and one where the PTn was relatively thin (ESF station 59+00). Conclusions drawn from the 
one-dimensional modeling study included the following (Fabryka-Martin, Flint et al. 1997, 
section 8.3): 
 Generally, fracture flow through the PTn could be sustained more readily with increases 
in percolation flux and secondary permeability, and when fractures contributing to the 
secondary permeability were assumed to be sparse (thereby minimizing fracture-matrix 
interactions) and have large apertures. 
 Increases to the assumed water retention capacity of the fractures by adjusting poorly 
constrained parameters that described the fracture's capillary properties also resulted in 
more sustained fracture or fault flow through the PTn at lower fluxes. 
 Fluxes insufficient to sustain fracture flow in the densely welded Tiva Canyon and 
Topopah Spring Tuffs resulted in water samples at the ESF that were very old, with

ANL-NBS-HS-000017, Rev 00 Page 69 of 156 
predicted 36Cl/Cl ratios that indicated significant decay (approximately 300 x 10-15 to 
600 x 10-15) and which were generally too small relative to those obtained for what were 
considered to be non-bomb-pulse samples (500 x 10-15 to 1,500 x 10-15). 
 The predicted ratios for non-bomb-pulse samples were generally consistent with those 
predicted using assumed percolation fluxes of 1 to 10 mm/year. Just as fluxes on the 
order 0.1 mm/year led to 36Cl/Cl ratios at the ESF horizon that displayed considerable 
decay of the meteoric signal, fluxes greater than 10 mm/year resulted in short travel 
times that led to introduction of Holocene water with 36Cl/Cl ratios lower (500 x 10-15) 
than observed for the non-bomb-pulse samples. 
6.6.4 Carbon Isotopes 
Primary input data used to characterize the distribution of carbon-14 at Yucca Mountain, which 
provides a basis for water and gas travel time estimates, are listed in section 4.1.7 (pore water 
and perched water), 4.1.8 (gas from open boreholes), 4.1.9 (gas from instrumented boreholes), 
and 4.1.15 (groundwater). Table 3 lists the locations for which these data are available. 
Relevant assumptions that apply to discussions in this section are Assumptions 8, 9 (TBV) and 
10 in Table 2. 
6.6.4.1 Background 
The best-developed isotopic method for dating groundwater is that using 14C, an application that 
began with Munnichs study in 1957 (Davis and Murphy 1987, pp. 29 to 34; Clark and Fritz 
1997, pp. 200 to 231). Carbon-14 is produced naturally in the upper atmosphere by 
bombardment of nitrogen by the secondary neutron flux (Clark and Fritz 1997, p. 202): 
p C n N 1
1 
14 
6 
1 
0 
14 
7 + . + (Eqn 6) 
The modern atmospheric activity of 14C is set by convention to 13.56 decays per minute per gram 
of carbon in the year A.D. 1950, which is considered to have an activity of 100 Percent Modern 
Carbon (pmc) (Clark and Fritz 1997, p. 18). Based on a half-life of 5,715 years (Parrington 
1996, p. 19), this specific activity corresponds to a 14C/C ratio of about 1.2 x 10-12. The effect of 
above-ground testing of nuclear devices was to temporarily increase the 14C content by as much 
as a factor of two (Figure 29). The decrease since 1964 is due to the exchange of 14C for 
nonradioactive carbon from the biosphere and hydrosphere, predominantly the ocean. Other 
secondary influences on the atmospheric 14C inventory are releases of 14C from nuclear fuel 
reprocessing plants and dilution by releases of nonradioactive carbon from the burning of fossil 
fuels. 
Despite its extensive use in hydrologic studies, numerous processes related to carbon 
geochemical reactions complicate the interpretation of 14C analyses in water. These processes 
involve the isotopic exchange between carbonate species dissolved in pore water, and carbonates 
in soil and fracture minerals along the flow path, as well as with CO2 in the gas phase. Hence, 
the successful use of 14C to date groundwater is dependent upon a thorough understanding of 
geochemical reactions involving carbon species in the hydrologic system. This stipulation is

ANL-NBS-HS-000017, Rev 00 Page 70 of 156 
even more important in the case of unsaturated-zone fluids. Stable carbon isotope ratios (d13C 
values) are invaluable for evaluating the likelihood and magnitude of subsurface reactions 
involving carbon. Delta 18O has been measured in CO2 gases in YMP studies for a similar 
reason. Detailed discussions of geochemical modeling of carbon reactions, which clearly have 
implications for 14C ages of Yucca Mountain pore waters, are provided in numerous publications 
(Davis and Murphy 1987, pp. 29 to 34; Clark and Fritz 1997, pp. 200 to 231). 
6.6.4.2 Carbon-14 in Pore-water Samples 
As is the case for tritium, post-bomb levels of 14C have been observed in a few samples collected 
above and within the PTn unit. None of the pore-water samples from surface-based boreholes 
have shown post-bomb levels of 14C, that is, activities above 100 pmc (Table 15; corroborative 
data in Table 16). However, it is possible that the presence of a relatively small volume of postbomb 
water could be obscured by mixing with a large volume of old water, such that the 
resulting mixture would have an activity less than 100 pmc. For the 14 pore-water samples 
extracted from the PTn unit, 14C activities range from 74 pmc (NRG-7a and SD-7) to 96 pmc 
(UZ-14) (Table 15). The 33 samples extracted from the CHn unit range from 53 pmc (UZ#16) to 
98 pmc (UZ#16) (Table 15). A histogram of the data from these two hydrogeologic units (Figure 
34) shows that the PTn values cluster tightly about the range of 80 to 90 pmc, whereas the CHn 
values spread more evenly across the range, presumably reflecting a larger spread in groundwater 
travel times to this depth as would be expected if fracture flow were mixing to variable extents 
with slower matrix flow. Stable carbon isotope ratios for these same pore waters show a wide 
range in both hydrogeologic units (Figure 34), which may be a consequence of a variety of 
processes but which is also consistent with spatially and temporally variable infiltration rates and 
mixing between fast fracture flow and slow matrix flow. The extent of contamination with 
drilling air for some of the samples has not yet been resolved (see discussion below). 
The 14C pore-water data do not show any trend with stratigraphic depth, with larger 14C activities 
interspersed among smaller 14C activities in a vertical profile (Tables 15). These irregular 
profiles are consistent with a conceptual model in which fracture flow and perhaps lateral flow 
occur in some of the stratigraphic units at Yucca Mountain (Yang et al. 1996, p. 32; Yang, Yu et 
al. 1998, p. 23). In general, 14C activities in pore waters from both the PTn and CHn suggest 
apparent ages that are less than 6,000 years. Apparent ages are based on the assumption that the 
initial 14C activity is 100 pmc, and that the carbon isotopic composition of the sample has not 
been significantly altered by any geochemical processes such that changes relative to the initial 
atmospheric activity are solely the result of radioactive decay (Assumption 10 in Table 2). This 
assumption is supported by the high 14C activities measured in the annulus of shallow boreholes 
(Table 17). 
Detailed evaluations of the various processes that could affect 14C activities and stable carbon 
isotope ratios in Yucca Mountain pore waters are presented in Yang et al. (1996, pp. 31 to 34) 
and in Yang, Yu et al. (1998, pp. 21 and 23). These processes include: 
 Atmospheric contamination of pore-water samples during drilling could shift 14C 
activities to higher values.

ANL-NBS-HS-000017, Rev 00 Page 71 of 156 
 14CO2 in the gaseous phase may exchange with bicarbonate species in the groundwater. 
 Seasonal variations in d13C in soil gas as a function of the stage of vegetative growth 
affect the isotopic signature in infiltrating waters. 
 Dissolution of caliche and calcites in fractures, with their wide variations in 14C ages, 
can dilute the initial 14C activity of infiltrating pore water and shift its d13C value. 
To some extent, the significance of these processes can be evaluated by examining the d13C and 
14C data for trends as a function of borehole, depth, and stratigraphic unit and by comparing porewater 
data to those for the gas phase, perched water and groundwaters for which some of the 
above processes can be assumed to be negligible. Figure 35 plots d13C versus 14C for these 
different categories. This plot suggests the idea that some of the high 14C pmc values and young 
apparent ages may be the result of contamination from 14CO2 in the drilling air (about 120 pmc, d 
13C about -8 ). Although the total mass of carbon in pore water is orders of magnitude higher 
than that in subsurface air, it is possible that the injection of large volumes of drilling air may 
alter the carbon isotopic composition of pore waters under some conditions. 
6.6.4.3 Carbon-14 in Gas Samples 
Gas samples were collected from open surface-based boreholes following overnight pumping to 
remove atmospheric air from the well bore (Tables 18 and 19). Gas samples have also been 
collected from two instrumented surface-based boreholes, with records available from 1984 to 
1995 for UZ-1, and for 1996 for SD-12 (Table 20). Finally, gas samples from ESF drillholes 
were collected after CO2 and SF6 concentrations had stabilized (Table 21) (section 6.2.2). 
The carbon isotope data for gas samples are discussed in greater detail in Section 6.7.2. The 
observed distribution can be summarized as follows: 
Gas samples in open surface-based boreholes (Tables 18 and 19).Uncorrected radiocarbon 
ages range from modern to 2600 years in the TCw, modern to 3100 years in the PTn, 650 to 7200 
years in the Tptpul and Tptpmn, and modern to 11,200 years in the CHn. Radiocarbon profiles 
generally do not show any clear trend, with apparently younger gas often underlying older gas. 
However, for gas collected from open boreholes, it is often difficult to discern a clear trend with 
respect to the spatial distribution of 14C activities in unsaturated-zone gases. The downhole 
packer system did not completely seal against the borehole wall for all of these samples. Thus 
trends are obscured by the inclusion of data that probably show the effects of atmospheric 
contamination. Although d13C and CO2 concentrations can often be used to identify such 
contamination, there is no simple rule by which to identify which 14C activities represent in-situ 
conditions because d13C and CO2 also vary in the subsurface as a function of surface conditions 
(e.g., soil thickness and vegetative activity). Nor are 14C activities in nearby pore waters a good 
guide. If the CO2 in the gas phase were in isotopic equilibrium with CO2 in the aqueous phase of 
the pore water, then the 14C activities in the two phases should be comparable; however, the pore 
waters themselves may have been contaminated by the drilling air. Because of these various 
unresolved issues, Yang et al. (1996, p. 32) conclude it would be difficult to make a good age 
correction. However, a possible range of ages with some uncertainty can be assigned in the

ANL-NBS-HS-000017, Rev 00 Page 72 of 156 
future when more data become available. At present, apparent ages will be used to make 
preliminary interpretation. 
Gas samples in instrumented surface-based boreholes (Table 20).Carbon-14 data from 
samples from the two instrumented boreholes are the most reliable indicators of in-situ 
conditions. Uncorrected radiocarbon ages for UZ-1 are modern at the probe near the top of the 
PTn (62 ft), about 3600 years at the probe closest to the base of the PTn (266 ft), about 7000 
years at a depth of 621 ft in the Tptpmn, and about 7800 and 16,000 years at the bottom two 
probes, in the Tptpll (1100 and 1207 ft). Uncorrected ages for SD-12 of similar magnitude 
although the profile is not as smooth. The gas age is about 1000 years at the top of the PTn and 
about 2100 years at its base. The age increases to nearly 8000 years in the Tptpul, and to about 
11,000 years at probe B near the top of the CHn. 
Gas samples from instrumented boreholes in ESF alcoves (Table 21).Carbon-14 isotope 
results are available for gases from boreholes in ESF Alcove 1 and 6. Samples from three 
boreholes in Alcove 1, all tapping intervals within the TCw unit, contained 93, 101 and 107 pmc 
indicating the presence of young CO2. Ten samples from the Alcove 6 borehole, which 
penetrated the Ghost Dance fault zone in the TSw unit, ranged from 75.1 to 58.1 pmc, 
corresponding to uncorrected 14C ages of 2400 to 4500 years, somewhat younger than those 
obtained for similar stratigraphic depths in UZ-1 and SD-12. Activities measured for gas samples 
from boreholes ESF-NDR-MF#1 and ESF-NDR-MF#2 ranged from 73.8 to 64.8 pmc, 
corresponding to ages of 2500 to 3600 years (DTN: GS981283122410.006, corroborative data). 
6.6.4.4 Carbon-14 and d13C in Perched Waters 
Carbon-14 activities and d13C values of perched waters are shown in Table 9. The 14C values 
range from 67 to 27 pmc, corresponding to apparent 14C residence times of about 3300 to 11,000 
years (Yang et al. 1996, p. 34). Water 14C ages can be affected by the dissolution of older carbon 
in the carbonate minerals, which would result in anomalously old apparent ages. Reaction with 
or incorporation of gas-phase CO2 from deep in the unsaturated zone can also result in an 
anomalous apparent age. Recent input of post-bomb 14C is expected to be minor because all 
perched-water samples contain background tritium concentrations. If post-bomb water is present 
in the perched bodies, the component is too small to be detectable. 
The d13C values measured for perched water are quite variable, ranging from -9.2 to -16.6  
(Table 9). A weak correlation is observed between these values and the surface material in 
which the drillhole is located. Perched water in SD-7, a borehole that is essentially started in 
bedrock, has heavy values of about -9.5 , only slightly lighter than atmospheric CO2. In 
contrast, perched water from NRG-7a, which was drilled through soil, has the lightest value of 
-16.6 , presumably reflective of the isotopic composition of soil CO2 gas. This observation is 
similar to that made for strontium isotopic data, which show a less radiogenic input for bedrock 
and fracture coatings where there is no soil and for pore waters from a drillhole that was started 
in bedrock (Section 6.6.6). In summary, d13C data show that most of the bicarbonate in 
unsaturated-zone matrix pore fluids originated in the soil zone. In contrast, most of the 
perched-water bodies and groundwater in the Yucca Mountain area have heavier (less negative) d

ANL-NBS-HS-000017, Rev 00 Page 73 of 156 
13C values that do not show the same degree of soil influence as do the unsaturated-zone pore 
waters (Figure 35). 
6.6.5 Stable Hydrogen and Oxygen Isotopes 
None of the stable hydrogen and oxygen isotopic data used in this report are considered to be 
primary input data. These data are used solely to corroborate interpretations of water flow paths 
and the timing of recharge that are based on other geochemical and isotopic signatures. Table 3 
lists the locations for which stable isotope data are available. Assumptions 11, 12, 13 and 14 
from Table 2 apply to discussions in this section. 
6.6.5.1 Background 
Large differences in hydrogen and oxygen isotopic ratios (d2H and d18O) in water arise from 
phase changes that do not go to completion, that is, partial evaporation, condensation, 
crystallization, or melting (Davis and Murphy 1987, p. 119). Such incomplete processes are 
typical of rainfall, snowfall, evapotranspiration, and sublimation of snow and ice. As a 
consequence, regional differences arise in surface waters as a function of elevation, distance from 
water sources (such as the ocean), orographic (rain shadow) effects, degree of evaporation, and 
air temperature during precipitation. If the first four of these factors stay relatively constant for a 
given location, then variations in d2H and d18O in infiltrating water may be related to temperature 
variations during precipitation events. Factors that might complicate simple interpretations of 
such data at Yucca Mountain include shifts in d18O in pore waters due to: alteration, dissolution, 
or precipitation of minerals containing oxygen; isotopic exchange; and sorption of water by clays 
and zeolites (Yang, Yu et al. 1998, p. 24). 
6.6.5.2 Isotopic Characteristics of Precipitation, Surface Waters, Perched Water and 
Groundwater 
The standard method for presenting stable isotope data is by plotting d2H versus d18O, as has 
been done in Figure 36 for precipitation, surface waters, perched water, and regional 
groundwater. The following observations are made from this figure: 
 Precipitation data from 3 Springs Basin and Stewart Basin are plotted in Figure 36a. 
These data illustrate how fractionation of oxygen and hydrogen isotopes in atmospheric 
moisture results in a well-defined correlation line, called the meteoric water line. 
Interpretations of isotopic data for other waters are all based upon the extent to which 
their compositions shift along or away from this line. Based on its lower elevation and 
warmer temperatures, modern precipitation at Yucca Mountain is generally expected to 
fall along the upper end of the range shown, with heavier (less negative) compositions as 
demonstrated by four local precipitation samples plotted in Figure 36. 
 Surface water data from 3 Springs Basin and Stewart Basin (Figure 36b) illustrate how 
stable isotopes reflect average climatic conditions prevailing during infiltration events. 
The cooler climate at Stewart Basin results in lighter (more negative) isotopic 
compositions. These surface waters have not undergone much evaporation, based on the 
fact that the isotopic data plot on the meteoric line. Such a conclusion is supported by

ANL-NBS-HS-000017, Rev 00 Page 74 of 156 
the dilute chemical compositions of these waters (Section 6.4.3). Data for two Yucca 
Mountain surface runoff samples, both collected in February 1993, also show negligible 
evaporation. Their heavy isotopic signatures overlap with those of the four precipitation 
samples collected at Yucca Mountain in 1984 (Figure 36a). 
 Stable isotopic data of the perched-water samples also lie close to the meteoric water 
line, indicating little evaporation occurred before infiltration (Figure 36c). 
 Groundwaters beneath Fortymile Wash (Figure 36d) have stable isotope values similar 
to those for perched water beneath Yucca Mountain. Both of these data sets are 
consistent with recharge during the Holocene (that is, post-glacial climate), as suggested 
by the 14C data for these waters (Section 6.6.4; Figures 35c and 35d). 
 Among the groundwaters in the Yucca Mountain area, the lightest waters are from wells 
in the southwestern most portion of the site (for example, VH-1, WT#10, H-3). Local 
groundwaters with the heaviest isotopic values overlap with the values measured for 
perched waters and for wells in Fortymile Wash. 
 Groundwaters from Pahute Mesa have lighter isotopic values than do the perched waters 
and groundwaters from Fortymile Wash. This difference is consistent with recharge of 
the Pahute Mesa waters under colder climatic conditions than those that prevailed for the 
perched waters and samples from Fortymile Wash, and subsequent modification of the 
Pahute Mesa waters by water-rock interactions that shift d18O to heavier values. 
Although isotopic shifts due to evaporative loss cannot be altogether ruled out, this 
process seems unlikely to be significant for the Pahute Mesa recharge waters. 
6.6.5.3 Isotopic Characteristics of Pore Waters 
Extraction of Pore Waters for Isotopic AnalysisIn contrast with the above types of samples, 
hydrogen and oxygen isotope data for unsaturated-zone pore waters are more difficult to 
interpret, presumably due to complications related to the methods used to extract the fluids for 
analysis. Vacuum distillation and compression extraction (squeezing) were the two methods of 
pore-water extraction for stable-isotope analysis of d2H and d18O used in the site-characterization 
investigation (Yang, Yu et al. 1998, pp. 25 to 27). Vacuum distillation involves heating the rock 
sample under vacuum in a distillation apparatus and collecting and condensing the evolved water 
vapor in a separate flask. Compression extraction is similar to the procedures described 
previously for pore-water extraction for chemical compositions and 14C analyses. Water samples 
were collected in glass syringes attached to the compression cell. For both extraction methods, 
stable isotope ratios are determined by mass spectrometer. 
Testing for isotopic effects resulting from the two different water-extraction procedures was 
accomplished by analyzing adjacent core samples (Yang, Yu et al. 1998, pp. 30 to 33). The two 
methods yielded comparable results for samples from the PTn. However, isotopic compositions 
of water obtained by vacuum distillation are more depleted in d2H and d18O than water obtained 
by the compression method for cores containing clay or zeolite minerals, particularly for samples 
from CHn, Prow Pass Tuff, and Bull Frog Tuff (Yang, Yu et al. 1998, Figures 15 and 16).

ANL-NBS-HS-000017, Rev 00 Page 75 of 156 
Subsequent tests have shown that vacuum distillation of pore waters for stable isotope analysis 
produced reliable results from tuffs free of clay and zeolite minerals but not for tuffs with large 
contents of hydrated minerals (Yang, Yu et al. 1998, p. 44). The compression-extraction process 
only extracts pore water, whereas the vacuum-distillation process extracts both pore water as 
well as water held by zeolites or clays. Percolating water can replace the water in the large pore 
spaces as well as undergo isotopic exchange with water in zeolites. Isotopic exchange rates 
range from days to months. Pore waters extracted from zeolitic core by compression may, 
therefore, reflect the most recently infiltrated water but may lose the record of past percolating 
water. 
Interpretation of Isotopic Characteristics of Pore WatersThe oxygen and hydrogen 
isotopic compositions of pore waters can yield information about infiltrating waters, provided 
that sampling has not disturbed the original compositions. Significant amounts of drilling air 
were injected into the formation during borehole drilling that could cause drying of the core 
samples. The potential magnitude of this effect can be examined by plotting the stable isotope 
compositions of the pore water on the d2H versus d18O diagram, as has been done for UZ-14 in 
Figure 37. Data for unsaturated-zone pore-water samples obtained by squeezing the core, plot on 
or slightly below the meteoric precipitation line, indicating minor evaporative loss (Figure 37b). 
This evaporation may have occurred either prior to recharge or during drilling. Alternatively, the 
shift away from the meteoric water line may reflect oxygen isotopic exchange with the host rock. 
In contrast, the composition of the CHn pore waters extracted by distillation is significantly 
lighter than that of the PTn pore waters (Figure 37a). The lighter values for CHn pore waters do 
not result from incomplete recovery by the distillation method because more than 96% of the 
water was recovered by vacuum distillation in laboratory tests in which tap water of known mass 
and isotopic composition was imbibed into an oven-dried core (Yang, Yu et al. 1998, Table 13). 
On the basis of these experiments, Yang, Yu et al. (1998, pp. 41 to 43) concluded that these 
extremely light oxygen isotopic signatures are not representative of in-situ pore waters but rather 
are caused by isotopic fractionation induced by the distillation technique. 
Comparison of isotopic compositions of unsaturated-zone pore waters (Figures 37b) with those 
of the saturated-zone groundwaters (Figures 36d) beneath Yucca Mountain show that the CHn 
pore waters are similar to the heaviest (least negative isotopic values) groundwaters in the Yucca 
Mountain area, whereas the PTn pore waters are significantly heavier (less negative) than either 
of these data sets. Again, this difference is consistent with recharge of the CHn pore waters and 
Yucca Mountain groundwaters occurring under colder climatic conditions than recharge for the 
PTn pore waters. In the TSw basal vitrophyre, d2H values in pore water from three boreholes 
(SD-7, SD-9, SD-12) are consistently shifted to more negative values, implying that waters were 
infiltrated during the colder climate of the last ice age (Yang, Rattray et al. 1998, p. 27 and 
Figure 2). The d2H values in pore waters from the underlying CHn are heavier than those for 
pore waters from the basal vitrophyre and similar to those for waters above the basal vitrophyre 
zone, indicating post-ice-age water. 
Isotopic Characteristics of Pore Waters with Large Concentrations of Dissolved SolidsA 
few pore-water samples have very large dissolved-solid concentrations, exceeding 800 ppm and 
indicating very large evapotranspirative losses. The isotopic compositions of pore waters for

ANL-NBS-HS-000017, Rev 00 Page 76 of 156 
three of these samples plot to the right of the Yucca Mountain precipitation line, which would 
also indicate evaporation after precipitation (Yang, Yu et al. 1998, p. 51). The extent of 
evaporation for sample NRG-6 (256 feet), which has the largest apparent loss of moisture by 
evaporation, can be approximated assuming a temperature of 20C for evaporation, equilibrium 
Rayleigh fractionation, and an initial starting isotopic composition equal to that of the average 
winter precipitation. However, the results of this latter calculation suggest that the pore waters 
were subjected to a maximum evaporation of only 12 percent. The different estimates obtained 
for evaporative losses from salt content and from isotopic characteristics reflect the fact that the 
two measures apply to different period of time. The salt concentration in infiltrating water 
reflects evaporative losses integrated over all precipitation events that occurred since the last 
event that resulted in infiltration below the soil zone. In contrast, the isotopic ratios of 
infiltrating water reflect the evaporative losses for the particular storm event that resulted in the 
net infiltration. 
Diffusion Controls on Isotopic Exchange RatesWater within tuffs at Yucca Mountain 
undergoes isotopic exchange, particularly between pore water and percolating infiltration. 
Isotopic exchange appears to be diffusion controlled and the equilibration time is dependent on 
the mean travel distance and the diffusion coefficient (Yang, Yu et al. 1998, pp. 38 to 43). 
Zeolites contain loosely held water which is referred to as channel water, and as noted above, its 
presence can contribute to analytical results for pore water. The channel water of pure 
clinoptilolite powder exchanges with the water percolating through laboratory columns within 
several hours to days. For ground tuffs from Yucca Mountain, the exchange rate is also several 
hours to days, whereas exchange for zeolites within intact cores take longer, depending on the 
core size and grain size of the zeolites within the core. The exchange processes for zeolitebearing 
core can be divided into two steps: the exchange between the pore water and the 
percolating water, and the exchange between the pore water and channel water. If the system 
reaches equilibrium, the stable isotopic compositions of pore water should equal those of 
percolating water, and those of channel water will differ from pore water by a fractionation 
factor. The second mechanism is still unknown, but the reaction is fast, as shown by column 
experiments. Therefore, the equilibration time is determined by the first process (Yang, Yu et al. 
1998, p. 54). For Topopah Spring Tuff, which bears no zeolites, the stable isotope composition 
of pore water will be controlled by exchange occurring through diffusion mechanisms. 
6.6.5.4 Isotopic Characteristics of Perched Waters 
Stable isotopic data of the perched water are generally between -12.8  and -13.8  for d18O 
and -94  and -99.8  for d2H (Table 9). These values are slightly greater than those for the 
saturated-zone values and similar to values for pore waters. They are generally close to the Yucca 
Mountain precipitation line, indicating little evaporation before infiltration (Figure 36c). All 
stable-isotopic values are similar to modern precipitation and are, therefore, consistent with 
recharge during the Holocene as suggested by the 14C data for the perched waters and consistent 
with the 36Cl data for these samples. 
6.6.6 Strontium Isotopes 
Primary input data used to characterize the distribution of strontium isotopes in rocks, minerals,

ANL-NBS-HS-000017, Rev 00 Page 77 of 156 
pore waters, and groundwater are listed in section 4.1.11. Assumptions 15 and 16 from Table 2 
apply to discussions in this section. 
Background.Calcite is ubiquitous at Yucca Mountain, occurring in soils and as fracture and 
cavity coatings within the volcanic tuff section. Strontium is a trace element in calcite, with 
concentrations generally at the tens to hundreds of ppm level. Decay of rubidium-87 (87Rb) is the 
source of stable 87Sr. Because calcite contains very little rubidium and the half-life of the 87Rb 
parent is 4.9 x 1010 years (Parrington et al. 1996, p. 29), 87Sr/86Sr ratios of calcite record the ratio 
in the water from which the calcite precipitated. Dissolution and reprecipitation do not alter 
strontium isotopic compositions. Thus, in the absence of other sources of strontium, one would 
expect the strontium ratios along a flow path to preserve variations inherited from strontium in 
the soil zone (Marshall, Futa et al. 1998, pp. 55 to 56). 
Strontium isotope compositions of calcites from various settings in the Yucca Mountain region 
have contributed to our understanding of the unsaturated zone, especially in distinguishing 
unsaturated zone calcite from saturated zone calcite. Different populations of calcite have been 
compared, either to group them together or distinguish them from each other in terms of their 
strontium isotope compositions. Ground water and perched water have also been analyzed. This 
section focuses on strontium isotope data obtained from pore water. 
Methods.Although pore water can be squeezed from the nonwelded tuffs at Yucca Mountain, 
the volumes recovered from reasonable lengths of drill core are small (Marshall, Futa et al. 1998, 
pp. 55 to 56). We have used dry-drilled core samples that have dried during storage, as 
repositories of pore water salts that can be carefully leached with deionized water for analysis of 
strontium isotope ratios. Crushed core is sieved to obtain a coarse sand (30-60 mesh) fraction that 
is then leached for less than an hour with deionized water to redissolve the pore-water salts. This 
water sample is then centrifuged and filtered; strontium is separated by standard techniques for 
analysis by thermal ionization mass spectrometry (TIMS). Strontium isotope ratios are reported 
as differences from modern seawater in parts per thousand using 
d87Sr = [((87Sr/86Sr) / 0.7092)  1] x 1000 (Eqn 7) 
A single comparison between d87Sr from water-leached pore-water salts and that of water 
squeezed in adjacent core from UZ-14 suggests that the extraction method is valid, at least for 
non-welded samples. 
Results for SD-7.Strontium isotope compositions in the host volcanic rocks differ significantly 
from those of the pore waters, indicating that pore water has not reached equilibrium with the 
tuffs. Core was sampled from SD-7, excluding core containing macroscopic calcite coatings. The 
pore water strontium data obtained from SD-7 (Figure 38) are remarkable in their systematic 
variation with depth and their distinction from whole rock compositions. At the top of the core, 
the d87Sr in the pore water is 3.6 , matching the d87Sr found in surface coatings of calcite at the 
drill pad. Delta-87Sr increases with depth; this increase is especially evident within the 
nonwelded units of the Paintbrush Tuff (PTn) and is only slightly discernible in the underlying 
welded Topopah Spring Tuff (TSw).

ANL-NBS-HS-000017, Rev 00 Page 78 of 156 
Interpretation.Although the data preclude local equilibrium between pore-water and rock, the 
rock data can predict the strontium isotope composition of the pore water if recalculated as a 
down-hole cumulative value weighted according to strontium content of the rock samples and the 
associated depth interval. An additional weighting factor that takes into account the higher 
reactivity of the PTn provides a close match to observed pore-water strontium values throughout 
most of the TSw. Deviations of the pore-water d87Sr from the predicted values are likely due to 
the presence of clays or zeolites which may contain a long-lived record of pore-water strontium 
compositions and could have been partially leached in the laboratory. 
A working model assumes that strontium is added to infiltrating water by dissolution of calcite in 
the soil zone (Marshall, Futa et al. 1998, pp. 55 to 56). During times of increased surface 
vegetation, soil waters are more acidic and volcanic detritus in the soil zone can contribute 
radiogenic strontium into infiltrating water, thus increasing the 87Sr/86Sr ratio in the thick 
calcretes formed during these times. There are two separate populations of soil carbonate that can 
contribute strontium to infiltrating water; one is dominated by eolian carbonate with a d87Sr = 3.6 
 and the other is dominated by calcretes in thick alluvial soils with d87Sr = 4.5  (Marshall 
and Mahan 1994, Figure 7). Although the eolian signal, represented by soil A/B horizons and 
calcite coatings on bedrock surfaces, exists throughout the Yucca Mountain region, the strontium 
signal from calcretes may dominate over the eolian component the strontium when both sources 
are present. 
Water infiltrating into welded tuff (Tiva Canyon Tuff or Topopah Spring Tuff) tends to retain the 
strontium isotope composition of the overlying soil. However, the pore-water data indicate that 
water infiltrating into or percolating through nonwelded tuff (PTn) reacts readily and acquires a 
strontium isotope signature reflecting interaction with this unit. The strontium isotope 
composition of the volcanic rocks changes systematically over millions of years due to the decay 
of 87Rb. As a result, pore waters interacting with these rocks would have d87Sr values that 
decrease linearly with age. Delta-87Sr of pore waters in the TSw unit are predicted to change from 
a modern value of 4.9  to about 0.4  at the time of TSw emplacement (12.7 Ma). The 
observation that d87Sr varies with microstratigraphic position within thick calcite coatings that 
occur in the TSw and the match between these ratios and the predicted values strongly suggests 
that the calcite coatings derive their strontium from the same source as the pore waters; in other 
words, both pore water and the fracture water leading to calcite deposition within the TSw derive 
strontium from water-rock interaction in the overlying section, dominantly in the nonwelded 
units. This model indicates that pore waters in the PTn are redistributed between pore and 
fracture water that subsequently percolates through the TSw. 
6.6.7 Uranium Isotopes 
Primary input data used to characterize the distribution of uranium isotopes in rocks, minerals, 
pore waters, and groundwater are listed in section 4.1.12. No assumptions are listed in Table 2 
that apply to discussions in this section. 
Background.Uranium isotopic ratios have been used to address the question of local recharge 
to the water table through the unsaturated zone at Yucca Mountain, and the prevalence and 
frequency of fracture flow. The presence of calcite and opal lining fractures and cavities in the

ANL-NBS-HS-000017, Rev 00 Page 79 of 156 
lowest units of the TSw exposed in the East-West Cross Drift and in core from underlying 
unsaturated-zone units suggests that water moving through fractures has reached these depths. 
Flow through the matrix also accounts for some portion of the total infiltration. However, the 
fraction of the shallow ground water beneath Yucca Mountain that is locally versus regionally 
derived, and the ratio of fracture flow versus matrix flow contributing to local recharge, are 
poorly known. Uranium isotopic compositions of unsaturated-zone fracture minerals, pore 
water, perched water, and shallow ground water contribute to the conceptualization of these 
issues (Paces, Ludwig et al. 1998, pp. 187 and 188; Paces and Peterman 1999, pp. 134 to 138), 
which is summarized in this section. 
Unlike oxygen-, carbon-, and strontium-isotope signatures that are largely inherited during 
infiltration through soils, uranium isotopic compositions of percolating water are significantly 
modified from values observed in soil- and surface-water, which usually have 234U/238U activity 
ratios of 1.4 to 1.8 (Table 24; Figure 3 of Muhs et al. 1990; Paces et al. 1994, p. 2400; Figures 9, 
10, 13, 16, 17, 20, 21, 25, 26, 27, 32, 36, 39, 42, 45, 46, and 53 of Paces et al. 1995), to 234U/238U 
activity ratios as large as 9 at the potential repository horizon (Figure 66, discussed in section 
6.10.2) (Figure 3.7 of Paces, Neymark et al. 1996; Figure D3 of Paces, Marshall et al. 1997). As 
a consequence of radioactive decay, 234U is preferentially enriched relative to 238U in migrating 
ground water (Figure 9.1 of Osmond and Cowart 1992). The primary causes for this enrichment 
are the greater solubility of 234U due to radiation-damage of crystal lattice sites containing 234U 
atoms (Szilard-Chalmers effect) and the greater probability that these 234U atoms have been 
converted to the more soluble uranyl ion due to the effects of radiation-induced ionization 
(Section 2.5.1 in Gascoyne 1992). In addition, decay of 238U can cause the displacement of the 
intermediate 234Th daughter (which rapidly decays to 234U) off of crystal surfaces into the 
adjacent water by alpha-recoil processes. The amount of excess 234U relative to 238U is controlled 
by 234U decay, water/rock ratios, flow path length, and the amount of bulk-rock dissolution in the 
aquifer. 
Meteoric water that interacts with readily soluble soil components results in infiltration 
containing relatively large amounts of both 234U and 238U derived by bulk dissolution (Table 23). 
As infiltrating water descends through the fracture network, small amounts of 234U that have 
become available from radioactive decay will be incorporated into these solutions. If water 
fluxes are large relative to the amount of 234U produced along fracture surfaces, then the 
234U/238U ratio will remain relatively unchanged from its initial infiltration value. If water fluxes 
are small and only occur infrequently, 234U can build up in sufficient amounts along the fracture 
surface between infiltration events such that the 234U/238U activity ratio in the water becomes 
elevated. The large 234U/238U ratios in unsaturated fracture flow at Yucca Mountain imply that 
volumes of percolation are small relative to shallow environments that receive larger amounts of 
percolation. 
Results.Data supporting this conceptual model of 234U/238U evolution were obtained from 
water samples collected during the single heater test conducted in the Thermal Test Facility (ESF 
alcove 5) (Figure 39). Water derived from the welded tuffs proximal to the heater was mobilized 
and flowed through a connected fracture network for several months into a nearby borehole. 
Uranium concentrations decreased from about 0.1 to 0.03 ppb between late November 1996 and 
late May 1997. In the same samples, 234U/238U activity ratios dropped from a value of 8.03 in the

ANL-NBS-HS-000017, Rev 00 Page 80 of 156 
first water collected, to values of 4.56 and 4.13 in the two subsequent collections. These data are 
interpreted as evidence that the fracture pathways used by mobilized water during the test had not 
experienced recent natural flow, and had built up substantial amounts of 234U on their surfaces. 
Fracture water mobilized during the early stages of the test incorporated the more labile 234U en 
route to the collection site. Once the most reactive components were dissolved, later water 
flowing along the same flow paths incorporated less total uranium as well as less 234U, resulting 
in smaller uranium concentrations and 234U/238U activity ratios with time. A longer duration test 
would presumably have resulted in water with 234U/238U activity ratios approaching either secular 
equilibrium (234U/238U activity ratio of 1.0) or values that are characteristic of readily 
exchangeable pore water (234U/238U activity ratio between 1 and 4). Although large 234U/238U 
activity ratios were not observed in early water from the much larger and more complex Drift 
Scale Heater Test, a similar pattern of decreasing values with time is present in water mobilized 
from volumes of rock much larger than the Single Heater Test (Figure 40). This pattern 
illustrates, in a qualitative sense, the likelihood that frequent flushing of fracture surfaces may 
not allow sufficient accumulation of 234U on fracture surfaces to substantially alter the 234U/238U 
ratios in fracture water. 
Uranium isotope data from other areas of the Nevada Test Site that receive recharge sufficient to 
support small-volume spring discharge can also be interpreted to indicate that small fluxes and 
infrequent flux events are required to attain the large 234U/238U ratios observed at Yucca 
Mountain. Springs and seeps discharging from perched water zones at Comb Peak, Shoshone 
Mountain, Skull Mountain and Rainier Mesa have 234U/238U activity ratios ranging between 1.9 
and 3.8 (Figure 41). These values are larger than those associated with surface water and 
pedogenic minerals (Paces et al. 1995, Figures 9, 10, 13, 16, 17, 20, 21, 25, 26, 27, 32, 36, 39, 
42, 45, 46, and 53), but are lower than 234U/238U ratios in most of the perched water at Yucca 
Mountain (Table 9) as well as the initial 234U/238U ratios in young calcite and opal in the deep 
unsaturated zone (Paces, Neymark et al. 1996, Figure 3.6). Water discharging from NTS springs 
have relatively large volume to path-length ratios and either continuous or frequent flow that 
does not permit accumulation of substantial excess 234U on solid surfaces along flow paths. As a 
result, uranium in water from these systems has isotopic compositions that are only slightly 
greater than values observed in the infiltrating water. In contrast, waters perched within the 
welded TSw at Yucca Mountain (boreholes WT-24, UZ-14, NRG-7a) have larger 234U/238U 
activity ratios (Table 9). These values (5.2 to 8.4) are in the range of initial 234U/238U activity 
ratios observed for young calcite and opal from the potential repository horizon in the ESF. 
Ground water from the saturated zone beneath Yucca Mountain also has elevated 234U/238U ratios 
compared to well water in adjacent areas (compare Figure 42 to Figure 43) (Ludwig et al. 1993, 
Figure 2; Paces, Ludwig et al. 1998, p. 185). Regional saturated-zone ground water in carbonaterock, 
alluvial, and Precambrian-rock aquifers from Oasis Valley, Amargosa Valley, Spring 
Mountains, and the easternmost Nevada Test Site have 234U/238U activity ratios between 1.5 and 
4. Ground water 234U/238U activity ratios from volcanic-rock aquifers in the region are commonly 
between 4 and 6; however, shallow saturated-zone ground water beneath Yucca Mountain has 
anomalously large 234U/238U activity ratios between 6 and 8.5. Groundwater obtained from 
Paleozoic carbonate rocks at depth beneath Yucca Mountain (UE-25 p#1) has a much smaller 
234U/238U ratio of 2.32, typical of the regional carbonate aquifer and indicative of the 
stratification of shallow and deep aquifers at the site. Up-gradient regions including Timber

ANL-NBS-HS-000017, Rev 00 Page 81 of 156 
Mountain, Pahute Mesa, and Rainier Mesa (locations shown on Figures 1 and 2) are at higher 
topographic elevations and receive greater amounts of recharge. Although the number of 
analyzed wells in these areas is relatively small, observed 234U/238U activity ratios are equal to or 
less than about 5. Smaller 234U/238U ratios (activity ratios less than 6) are also characteristic of 
ground water in the volcanic-rock aquifer in the Fortymile Wash and Crater Flat areas east and 
west of Yucca Mountain, and in down-gradient water wells along Highway 95 and in the 
Amargosa Valley. Uranium concentrations in ground waters from most of these areas range from 
about 0.5 to 3 ppb. 
The anomalous uranium isotopic compositions of shallow saturated-zone water beneath Yucca 
Mountain are similar to the elevated initial 234U/238U compositions measured for deep 
unsaturated-zone minerals and perched water bodies within the welded TSw. The similarity of 
the unsaturated and saturated-zone uranium reservoirs at Yucca Mountain is interpreted as an 
indication of a genetic linkage between the two. Therefore, some component of recharge through 
the thick unsaturated zone at Yucca Mountain is required. If this recharge made up only a small 
proportion of the saturated-zone ground water beneath Yucca Mountain, a 234U/238U value that is 
only slightly larger than the presumed up-gradient signature would be expected. Instead, the 
observed value is near the upper end of the range observed in the unsaturated-zone materials, 
implying that the local recharge has not been highly diluted by through-flow from the north. 
Likewise, ground water down-gradient from Yucca Mountain should have a relatively large 
234U/238U signature if the local recharge contributed significantly to the uranium budget. 
Groundwater containing elevated 234U/238U ratios is not observed in either Fortymile Wash (with 
the exception of J-13, the main supply well for activities in NTS Area 25) or along the southern 
margin of Yucca Mountain at Highway 95. More-or-less uniform U concentrations in waters 
throughout this area indicate that the different ground waters should have roughly equal 
weighting when mixed on a volume basis. Because of this similarity, small volumes of ground 
water in adjacent areas should not rapidly mask the uranium isotopic contributions of Yucca 
Mountain saturated-zone ground water. Therefore, local recharge is considered an important 
component to the saturated zone immediately below Yucca Mountain; however, this component 
does not contribute significantly to the regional water budget in the Fortymile or Crater Flat 
hydrologic flow systems. These conclusions are consistent with major ion data, as well as d2H, 
d18O, and d87Sr data from the shallow groundwaters at Yucca Mountain that are interpreted to 
indicate km-scale heterogeneities over the same areas (Peterman and Patterson 1998, pp. 277 to 
278; Paces and Peterman 1999, p. 137). 
Preliminary uranium isotopic data from pore water extracted by centrifugation may indicate that 
most of the local recharge flows through fracture pathways rather than through the matrix. 
Several samples of pore water (1.5 to 3.0 mL) have been extracted from the upper lithophysal 
unit of the welded Tpt. Pore water has uranium concentrations of about 1 ppb and 234U/238U 
activity ratios of 2.5 to 3.0. These ratios are slightly larger than most of the pore water squeezed 
from nonwelded tuff near the top of the PTn (234U/238U activity ratios of 1.5 to 2.5), but are 
smaller than water collected from boreholes associated with in-situ heater tests (234U/238U activity 
ratios of 2.5 to 5.6). Larger values approaching those that are indicative of fracture water (initial 
234U/238U in fracture minerals as well as water perched within the Tpt) or characteristic of 
shallow saturated-zone ground water have not been observed. Substantial differences in

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234U/238U compositions between pore water and fracture water indicate a general lack of 
equilibration between the two unsaturated-zone water sources and implies minimal liquid 
exchange. These differences also indicate that fracture water is likely the most dominant 
contributor to recharge of the shallow saturated zone beneath Yucca Mountain. 
6.7 CHEMICAL AND ISOTOPIC COMPOSITION OF GASES 
Only chemical and isotopic data collected for gas samples from instrumented boreholes are 
considered primary input data for characterization of the chemical composition of gas at Yucca 
Mountain. These data are listed in sections 4.1.14 (gas chemistry) and 4.1.9 (carbon isotopes). 
Chemical and isotopic data for gas samples collected from open boreholes are only used to 
corroborate interpretations based on data for instrumented borehole samples. Table 3 lists 
locations for which gas chemical data are available. Assumptions 17 and 18 from Table 2 apply 
to discussions in this section. 
6.7.1 Processes Controlling Gas Chemistry 
The major processes that control the chemistry of the gas phase include: 
 Atmospheric gas chemistry. The composition of air is the primary control on 
unsaturated-zone gas chemistry. 
 Soil-zone processes. Soil-zone processes such as plant respiration can alter the chemistry 
of the gases that diffuse into the unsaturated zone. Carbon-dioxide partial pressures are 
particularly susceptible to modification by these processes. 
 Water-air interactions. Once gases diffuse from the soil zone into the unsaturated zone, 
the gas-phase composition will tend to equilibrate with the waters present in the 
unsaturated zone. For example, CO2 will tend to dissolve or exsolve from the waters 
depending on the partial pressures of CO2 in the soil zone versus the upper unsaturated 
zone. 
 Upward gas flow. Gases can migrate upward through the unsaturated zone along various 
gradients including concentration gradients and temperature and pressure gradients. The 
gases migrating along these gradients may have a nonatmospheric composition. 
Therefore, as they mix with the indigenous gases in the unsaturated zone, they alter the 
overall gas composition in the unsaturated zone. 
 Matrix, fractures, and fault structures. Because gas permeabilities of matrix, fractures, 
and faults are very different, the composition of the gas phase in a certain part of Yucca 
Mountain at a given time may deviate from the average composition. 
 Microbial influences. Microbial metabolic activity may locally influence the 
composition of the gas phase in the unsaturated zone. 
 Temperature. Temperature can influence the composition of the gas phase in the 
unsaturated zone primarily through its influence on the kinetics of the various reactions

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involved controlling the composition of the gas phase. In addition, temperature controls 
the equilibrium fractionation of light stable isotopes, particularly oxygen. A summary of 
temperature data available for the unsaturated zone at Yucca Mountain is presented in 
Section 6.5.1. 
 Pressure. Variations in total gas pressure can influence the composition of unsaturatedzone 
waters through their effect on the partial pressures of separate gases in the gas 
phase. For example, the partial pressure of carbon dioxide in the gas phase varies 
directly with total gas pressure. Such variations in the CO2 partial pressure directly 
affect the concentration of CO2 in water, which in turn, affects the dissociation of 
carbonic acid and, thereby, the pH. More significant, however, is its effect on gas flow 
patterns, including water vapor transport. 
6.7.2 Site Characteristics 
6.7.2.1 Gas Compositions 
Data exist on the abundances of the major atmospheric gases in the unsaturated-zone gas phase at 
Yucca Mountain, including data obtained from the instrumented borehole UZ-1 (Yang et al. 
1996, Table 8) as well as from other boreholes. To a depth of 368 m in UZ-1, the concentrations 
of oxygen, nitrogen, and argon are within analytical error of atmospheric compositions (DTN: 
GS991299992271.001, data set 9507----2271.002 for O2 and N2, corroborated by data in data set 
9512----2271.010). According to Thorstenson et al. (1990, p. 260), samples of gases from UZ- 
6S, UZ-6, and the neutron boreholes also showed concentrations of O2, N2, and Ar that were 
identical to the concentrations of these gases in atmospheric air to the limits of precision of the 
analyses. The authors report that soil gases sampled on and near Yucca Mountain showed 
methane concentrations that were depleted relative to the atmospheric value of about 1.7 ppm by 
volume (ppmv), but still greater than 0.5 ppmv (Thorstenson et al. 1990, p. 267). In contrast, 
neutron hole and UZ-6S gases generally showed methane concentrations near zero, ranging up to 
a maximum value of 0.5 ( 0.1) ppmv, suggesting that methane consumption occurs in the 
subsurface, even below the soil zone (Figure 4 of Thorstenson et al. 1990). 
CO2 concentrations are generally larger in the rock gas (about 0.1 percent) than in air (0.035 
percent) (UZ-1 gas data from DTN: GS930408312271.014 for 1989, and GS991299992271.001, 
data sets 9301----2271.004 for 1991, 9404----2271.001 and 9404----2271.006 for 1993, and 
9507----2271.001 for 1995). CO2 gas concentrations in boreholes ranged from 0.01 to 1.3 percent 
by volume (Thorstenson et al. 1990, Figure 4; Yang et al. 1996, Table 8) compared to an 
atmospheric value of approximately 0.035 percent by volume. The CO2 concentration profiles as 
a function of time in UZ-1 show that relatively low CO2 concentrations were measured in 1983 
shortly after completion of the borehole, and that, except for probe 13, concentrations steadily 
increased until 1987 (Yang et al. 1996, Table 8 and Figure 18). Thus the early CO2 samples were 
probably diluted by drilling air (Yang et al. 1996, p. 40). As the semiannual gas sampling process 
proceeded, most of the drilling air was removed from the hole. Halfway down the hole in the 
1994 data set, carbon dioxide dropped to 0.08 percent by volume but increased with increasing 
depth to 0.36 percent by volume at the lowest sampling point in the hole (367.9 m). The more 
recent samples probably represent uncontaminated rock gas. This conclusion is supported by data

ANL-NBS-HS-000017, Rev 00 Page 84 of 156 
collected from 1986 through 1994, which show CO2 concentration from 100 m to 360 m changed 
very little (Yang et al. 1996, Figure 18). 
The CO2 concentrations on the upper portions of UZ-1 are elevated due to their proximity to the 
soil zone where biologic activity increases CO2 concentrations (Yang et al. 1996, p. 40). The 
increased CO2 concentrations at the bottom of the borehole probably represent breakdown of 
organic polymers from drilling fluids. The consistently low values for CO2 concentrations at 
Probe 13 cannot be explained by currently available data. If probe 13 is sensing a fracture 
connected to the atmosphere, the concentrations would indeed be anomalously low, but the d13C 
composition would also be anomalously heavy, which is not the case (Figure 19 in Yang et al. 
1996). 
Essentially all gas data indicate that the partial pressure of CO2 in the unsaturated-zone gas phase 
is higher by factors of three or more than that in the atmosphere. This conclusion is based on 
analyses of CO2 concentrations in open boreholes NRG#4, NRG#5, NRG-6, NRG-7A, SD-9, 
SD-12, UZ-7, UZ#16, WT-4, WT-18, UZ-6, and UZ-6s as well as in instrumented borehole UZ- 
1 (DTN: GS941208312261.008, GS950808312261.004, GS951208312261.008 and 
GS9912299992271.001, data set 9507----2271.001). Some of these data are listed in Tables 18 
and 20. 
6.7.2.2 Carbon Isotopes in Gases 
Carbon isotopes were monitored at the different sampling depths in UZ-1 starting in 1984 (Yang 
et al. 1996, Figures 19 and 20). Early data show the effects of contamination by drilling air, as 
evidenced by shifts in the radiocarbon profile from one sampling period to the next (DTN: 
GS930508312271.021 for 1984 and 1985, and GS991299992271.001, data set 9512----2271.010 
for 1986 and 1987, and data set 9112----2271.009 for 1988). The 14C activities have stabilized 
since 1989 (top part of Figure 44) and these more recent data sets are more representative of in 
situ conditions, although some of the d 13C values still show fluctuations at a given sampling 
depth that lie outside the range of analytical uncertainty (e.g., Probe 11 in the bottom part of 
Figure 44). Most values for d 13C lie within the range of -16  to -22  (Table 20 and Figure 
44). SD-12 gases are lighter, ranging from 20  to 25  (two samples with values of 16  
and 17  are believed to have been contaminated with atmospheric air, based on their 14C 
activities) (Table 20). Slightly heavier d 13C values ranging from -13.5  to -16.5  were 
obtained for gas samples from boreholes in ESF alcoves 1 and 6 (Table 21). There is very little 
overlap between the d 13C values for UZ-1 and SD-12 gases and those obtained for the gases 
from the ESF boreholes. However, the slightly heavier d 13C values observed in the ESF alcoves 
are likely to be due to contamination by atmospheric CO2 as a result of ESF ventilation through 
highly fractured TSw tuff. Hence, the UZ-1 d 13C values that were obtained before the excavation 
of the ESF are considered to be more representative of in-situ rock gas d 13C values. 
The 14C data for UZ-1 have been very consistent for the last seven years of monitoring, with a 
gradual decrease in 14C activity with depth to about 23 pmc at 368 m (Figure 44). The 14C 
profile shows an abrupt change in the slope within the Pah Canyon interval of the PTn. The gas 
transport velocity (14C concentration gradient over distance) within the PTn unit is smaller than 
the transport velocity in the TSw unit (Yang et al. 1993, p. 404). The smaller transport velocity

ANL-NBS-HS-000017, Rev 00 Page 85 of 156 
may be due to a greater degree of water saturation in this unit. An estimate of the minimum 
travel time of gas in the TSw unit based on the apparent 14C ages and depths in the borehole 
yields gas movement of 3.26 cm/year. This rate, as well as results of gas-transport modeling 
(Yang et al. 1996, pp. 47 and 49), is nominally consistent with downward movement of 
atmospheric CO2 by simple Fickian diffusion. The fact that the 14C values of rock gas in the 
closed (i.e., instrumented) borehole decrease steadily with depth indicates that inhalation and 
exhalation of gases in response to changes in atmospheric pressure, as observed in open 
boreholes, is not a significant process under undisturbed conditions. If such a topographic effect 
were to be significant, then 14C values would not decrease steadily as seen in UZ-6 and UZ-6s. 
Although diffusion may not be the only mechanism for gas movement in the TSw unit at UZ-1, it 
seems to be the dominant mechanism and can account for the observed distribution of gaseous 
14C with depth. 
The extent to which rock gas is in isotopic equilibrium with the pore waters is not clear. The 
isotopic composition of pore waters is highly variable, with d 13C ranging from -9  to -27  
(Table 15, Figure 34). Unsaturated-zone gases show a nearly identical range, with d 13C ranging 
from 8  to -26  (Tables 18 to 21). At equilibrium, carbon in bicarbonate in water should be 
about 8.5  heavier than carbon in CO2 in the gas phase at 25C (Clark and Fritz 1997, Figure 
5-4 on p. 120). For the example shown in this reference, d 13C would be -15.1  for aqueousphase 
HCO3 in equilibrium with gas-phase CO2 with d 13C of -23 . Although no data exist for 
gas and pore water extracted from the same sample, Table 22 compares samples that were 
collected from the same general depth ranges in Yucca Mountain boreholes. These samples show 
apparent disequilibrium insofar as the differences for d 13C in gas and pore water are much less 
than 8.5  for all but a couple samples from the CHn unit in UZ-14. After coexisting for 
hundreds or even thousands of years, CO2 gas in pore spaces would have to be in isotopic 
equilibrium with inorganic carbon species in the pore water. Therefore, the apparent 
disequilibrium between the two phases is probably not representative of in situ conditions, but 
rather a consequence of the drilling or sampling technique; e.g., in a fractured rock, the pore 
water may have been contaminated by drilling air, or the sampled gas may not derive from the 
immediate vicinity of the packed-off-interval. 
Although the data sets are less extensive, data for NRG-6 and NRG-7a (Table 15) yield different 
results from those for UZ-1 and SD-12 (Table 20). In these drillholes, 14C activity does not 
appear to decrease with depth, and in fact, all three gas analyses from NRG-7a show post-bomb 
carbon. However, leakage of air through poor sealing of the packer system against the borehole 
wall could account for these large 14C activities. 
The 14C activity of gas in borehole SD-12 is similar to that of UZ-1 in that there is a decrease 
from surface to depth, but with some irregularly large deviations from the trend (Table 20). 
Another striking difference is the markedly lighter carbon in SD-12 and the strong correlation 
between d13C and 14C activities. Rousseau et al. (1997, p. 64) noted that the pneumatic pressures 
in the two deepest stations of SD-12 (both within the CHn) were lower than predicted by 
extrapolation of the static-pressure profile developed across the overlying TSw. This gaspressure 
deficiency could be due to the presence of hydrocarbons, perhaps breakdown organic 
products from the drilling operation. The oxidation of hydrocarbons, such as methane, could

ANL-NBS-HS-000017, Rev 00 Page 86 of 156 
account for the anomalously light carbon in the drillhole. Assuming that the methane is older 
than 50,000 years, this source would also account for the low 14C activity of the sample at 407 m. 
Because the postulated methane would be affecting both carbon isotopes, the two isotopic 
compositions would tend to be correlated. 
The smooth 14C trends observed in the SD-12 data are consistent with the data obtained from 
UZ-1, supporting the concept of gas transport by a diffusion mechanism as previously concluded. 
However, the large fluctuations towards greater percentages of modern carbon at a couple of the 
SD-12 stations probably represent a fracture-flow component. Alternatively, the component in 
the bottom of the hole could be modern atmospheric carbon, given the sharp increase in both d 
13C and 14C (Table 20). Tests conducted on SD-12 instrument stations in January 1997 revealed 
a leak between one of the monitoring stations (Station C at a depth of 385.6 m in the Tptplnc 
unit) and the open fiberglass support pipe (Rousseau et al. 1997, p. 21), which probably allowed 
gas samples from this station to be contaminated with atmospheric air (Yang, Yu et al. 1998, p. 
21). Monitoring data suggest that atmospheric contamination of the lowest station (A) may have 
occurred prior to instrumentation and sealing of the borehole (Yang, Yu et al. 1998, p. 21). 
6.7.3 Representativeness of Available Data 
Gas chemical and isotopic data reported for boreholes UZ-1 and SD-12 are considered to be 
representative of in-situ conditions at specific depths. Data obtained in annual sampling events of 
borehole UZ-1 for gas compositions over a decade have established that variability in gas 
compositions (that is, CO2 partial pressure and isotopic compositions) tends to decrease with 
time in instrumented boreholes. This fact suggests that reported gas compositions reflect distinct 
zones in the borehole and that the compositions reflect in-situ (that is, natural) compositions. 
Data for samples collected from open boreholes are less useful because the gas samples are 
subject to contamination from atmospheric gas as a result of drilling and because most of these 
gas samples were obtained from open boreholes and thus reflect an averaging of gas 
characteristics over large depth intervals. This approach makes it difficult to associate a given 
gas analysis with a pore water from a specific depth interval. 
The number of boreholes for which gas data are available is limited in terms of both areal 
coverage and depth. This fact makes it difficult to evaluate the d 13C variations in gas 
compositions in the unsaturated zone of Yucca Mountain. 
6.8 CHEMICAL AND ISOTOPIC COMPOSITION OF SATURATED-ZONE 
GROUNDWATER 
Uranium activity ratios in local groundwater are considered to be primary input data, and provide 
the technical basis for identifying the presence of local recharge beneath Yucca Mountain 
(section 6.6.8). These input data are listed in section 4.1.12 and are discussed in section 6.6.7. 
All other groundwater chemistry and isotopic data are used in a corroborative manner, to 
characterize local and regional groundwater chemistry in terms of average concentrations and 
relative ion ratios. These groundwater trend data provide a baseline against which to compare 
and contrast chemical compositions of the various sources of water at Yucca Mountain, and to

ANL-NBS-HS-000017, Rev 00 Page 87 of 156 
illustrate general trends of relative enrichment or depletion of one element compared to another 
(sections 6.8.2 and 6.8.3). No assumptions are listed in Table 2 that apply to discussions in this 
section. 
6.8.1 Processes That Control Saturated-Zone Water Chemistry 
The chemistry of saturated-zone waters is determined by a series of processes that are linked in 
space and time. In this section, the primary focus will be on processes that control the chemistry 
of groundwaters along flow paths from recharge areas north of Yucca Mountain, through Yucca 
Mountain, and downgradient from Yucca Mountain to the accessible environment. A discussion 
of saturated-zone geochemistry has been included in this report on unsaturated-zone 
geochemistry because the similarities in compositions between groundwater and perched water 
suggest that similar geochemical processes control their compositions, and that these processes 
differ from those controlling the geochemistry of unsaturated-zone pore waters. The chemistry 
of local saturated-zone water is compared to that of perched waters in section 6.8.3. 
The main processes that determine groundwater chemistry along its flowpaths are: 
 Precipitation quantities and compositions (Section 6.3) 
 Surface-water quantities and compositions at recharge areas and along flow paths 
between recharge areas and the accessible environment (Section 6.4) 
 Soil-zone processes at recharge areas and along flow paths between recharge areas and 
the accessible environment, including the effects of evapotranspiration 
 Rock-water-gas interactions in the unsaturated zone at recharge areas 
 Rock-water-gas interactions in the unsaturated zone (Section 6.7) 
 Rock-water interactions in the saturated zone along flowpaths between the recharge 
areas and the accessible environment 
 Temperature and pressure along flow paths between recharge areas and the accessible 
environment 
 Mixing of groundwaters from different flow systems 
Recharge areas for saturated-zone waters in Yucca Mountain are located to the north of Yucca 
Mountain in the direction of Buckboard Mesa, Rainier Mesa, and Pahute Mesa (Figure 2). The 
rock types dominating the recharge areas are silicic and basaltic volcanic units (Byers et al. 1976, 
pp. 6, 7, and 19). Although Paleozoic limestones and other sedimentary units are present at great 
depth, they do not appear to influence the compositions of waters that occur in the volcanic units 
in the saturated zone beneath Yucca Mountain. 
Climatic conditions in the recharge areas are somewhat different from those that prevail at Yucca 
Mountain. Specifically, they receive more precipitation and are cooler on average than the Yucca

ANL-NBS-HS-000017, Rev 00 Page 88 of 156 
Mountain area and support a greater abundance of vegetation. Accordingly, infiltration rates on 
Pahute Mesa are also expected to be higher on average than infiltration rates on Yucca Mountain. 
Higher infiltration rates imply that dissolved salts and other constituents that may accumulate in 
the soil zone as a result of evapotranspiration of infiltrating waters (that is, precipitation) have 
shorter residence times in this zone. This process is likely the reason that soils on Pahute Mesa 
and adjacent areas contain much less pedogenic calcite and/or silica than is the case at Yucca 
Mountain. The higher infiltration rates also imply that waters infiltrating into the saturated zone 
will have lower salt and silica concentrations than is the case at Yucca Mountain. This dilute 
composition makes these waters more reactive with respect to the rock units through which they 
may subsequently migrate. 
As discussed in Section 6.5, water-rock reactions that occur in the soil zone or the unsaturated 
zone include mineral dissolution, mineral precipitation, mineral alteration, and ion exchange on 
charged surfaces. Because the waters percolating downward from the soil zones in recharge 
areas are likely more reactive than soil waters percolating into the unsaturated zone in Yucca 
Mountain, dissolution reactions are likely more important in the unsaturated zones of the 
recharge areas. The dominant changes to the water compositions that result from these reactions 
are major increases in silica, sodium, and bicarbonate (White et al. 1980, pp. Q15 to Q17). 
Once the water has undergone the initial dissolution reactions, the rate of change in water 
composition would likely decrease. This decrease is because the rate of dissolution is a function 
of the degree to which the water has approached thermodynamic equilibrium with the rock units 
with which it is in contact. The closer the water is to thermodynamic equilibrium with the host 
rock, the slower the rate of reaction. 
Actual calculation of the degree to which the reaction approaches thermodynamic equilibrium is 
difficult because the reactions involved are commonly incongruent. For example, in the case of 
feldspar equilibration with a given water composition, the feldspar crystals do not simply 
dissolve into the solution. It appears that the cation/hydrogen ion-exchange reaction discussed 
previously (Section 6.5.3.2) causes the feldspar surface layers to be converted (that is, 
hydrolyzed) into a poorly structured hydrogen aluminosilicate solid phase. Sodium, potassium 
and calcium are the major cations that participate in this exchange. The solubility of this solid 
phase would then control the rate of disappearance of the feldspar crystal (Brantley and 
Stillings 1996, p. 101). Unfortunately, the thermodynamic properties of this solid phase are 
not well defined. The same situation occurs with the hydrolysis of volcanic glass at ambient 
temperatures. 
The dominant water-rock reactions that impact the water chemistry after the initial dissolution 
reactions are silica precipitation and ion exchange involving minerals such as zeolites and clays. 
The cation/hydrogen ion-exchange reaction will also continue to be of significance. The ionexchange 
reactions will tend to lead to increased sodium concentrations and decreased calcium, 
magnesium, and potassium concentrations in the waters. However, changes in the concentrations 
of these ions will only occur if zeolites and/or clays are present in adequate quantities in rock 
units through which the waters migrate. The sodium/hydrogen ion-exchange reaction will 
continue to increase the sodium content of the waters until thermodynamic equilibrium is

ANL-NBS-HS-000017, Rev 00 Page 89 of 156 
achieved with the host rock (although the formation of metastable phases may cause the approach 
to equilibrium to be very slow). 
The degree to which alteration reactions involving silicates and aluminosilicates in the host rock 
control water compositions is unclear. For example, volcanic glass is thermodynamically 
unstable in contact with water at ambient conditions, and given enough time, it will alter to 
secondary minerals such as clays, zeolites, silica polymorphs, and other minerals. However, 
glass is still present in great abundance in the volcanic units that make up Pahute Mesa and 
Rainier Mesa (Byers et al. 1976, pp. 6, 7 and 19). Although glass alteration reactions are taking 
place at some rate, this rate appears to be much slower than the rate of the initial dissolution 
reactions and ion-exchange reactions. For purposes of predicting water compositions, restricting 
the discussion to the latter reaction is probably adequate given the current state of knowledge. 
Controls on the pH of groundwaters in the saturated zone are similar to those discussed in 
Section 6.5.3.2. In brief, the primary controls on pH are the partial pressure of CO2 and the rate 
at which hydrogen ions are consumed by the rock/mineral matrix. In the saturated zone, access 
to the CO2 reservoir in the gas phase of the unsaturated zone becomes progressively more 
difficult with depth. Therefore, unless a secondary source of carbonic acid or another source of 
acidity (for example, sulfide minerals) exist in the saturated zone, the reaction of hydrogen ions 
with the rock/mineral matrix will eventually consume the available acidity, leading to increased 
pH. The high pH value observed in H-3 (pH 9.4) (Ogard and Kerrisk 1984, p. 9) likely reflects 
this process. 
Controls on reduction/oxidation (redox) states in the saturated zone are more difficult to define. 
Potential redox reactions in the saturated zone include various redox couples such as 
oxygen/water, ferrous/ferric iron, sulfide/sulfate, nitrite/nitrate, and other couples. The methane/ 
CO2 couple is not likely to be of significance where methane abundances are very low because 
this redox couple only becomes active at low temperatures if it is microbially mediated. If 
dissolved oxygen is higher than approximately 0.1 mg/L, it could produce a relatively high redox 
potential (Eh > 600 mV). The redox state of saturated-zone waters as calculated from the 
concentrations or activities for respective couples may or may not be at equilibrium. Lindberg 
and Runnels (1984, p. 925) have argued that ground and surface waters are rarely in equilibrium 
in terms of redox couples and that different couples may give different redox potentials (that is, 
Eh). However, this conclusion is based primarily on measurements on young groundwaters. 
Deep groundwaters such as those in the saturated zone at Yucca Mountain have had longer 
residence times during which to reach equilibrium. 
In summary, the dominant processes that are likely to control water compositions along the flow 
paths from recharge areas to the saturated zone beneath Yucca Mountain are dissolution 
reactions, silica and calcite precipitation reactions, and ion-exchange reactions. The pH of these 
waters will be controlled primarily by the partial pressure of CO2 and the rate at which the rocks 
consume hydrogen ions. Controls on the redox state in the saturated zone are poorly defined at 
the present time.

ANL-NBS-HS-000017, Rev 00 Page 90 of 156 
6.8.2 Present-Day Regional Characteristics 
This section summarizes the available data for groundwater chemistry in volcanic aquifers and 
tuffaceous valley fill in the saturated zone in the Yucca Mountain region extending from recharge 
areas north of Yucca Mountain along flow paths through Yucca Mountain and to the accessible 
environment boundary south of Yucca Mountain. 
Figure 45 shows the locations of several wells on Pahute Mesa from which water samples have 
been obtained. All of these wells were completed in Tertiary volcanic rocks (McKinley et al. 
1991, Table 5). Full identifiers for these wells are shown in Figure 47. Based on regional flow 
models, only those wells in the eastern part of Pahute Mesa are likely to lie along flow paths that 
pass through the Yucca Mountain area. Those wells located in the western part of Pahute Mesa 
apparently lie along flow paths that pass through Oasis Valley. Water samples from springs 
located in the area of Rainier Mesa may reflect the compositions of waters recharging the 
saturated zone in the Pahute Mesa area. 
The available data on saturated-zone waters from the recharge areas consist primarily of analyses 
of the major constituents, although a limited number of isotopic analyses have been reported. 
A trilinear plot of relative major-ion abundances in saturated-zone waters from eastern Pahute 
Mesa and southern Rainier Mesa is shown in Figure 47. The data indicate that the waters are 
dominated by sodium bicarbonate. These waters have pH values ranging from 7.4 to 8.2 and 
total dissolved solids ranging from 169 to 578 mg/L. Claassen (1985, p. F13) noted that these 
waters are chemically relatively evolved. By this he was apparently referring to the fact that the 
ratio of sodium to other major cations was high. Because these waters occur in the recharge area 
(that is, they are the youngest waters in the flow system), this is an important observation. 
The locations of wells in the vicinity of Yucca Mountain from which groundwater samples were 
taken to obtain geochemical data are shown in Figure 46. Physical data for these wells are listed 
in Table 24. The relative abundances of major ionic constituents in saturated-zone waters from 
wells in the vicinity of Yucca Mountain are plotted in Figure 48. Comparison of Figures 47 to 48 
shows saturated-zone waters from volcanic aquifers to be very similar in both areas. Data for 
down-gradient waters were not plotted in the cations/anions versus chloride plots (Figures 24 to 
28) because they directly overlap data points for Yucca Mountain area saturated-zone waters. The 
down-gradient waters show a pH range from 7.5 to 8.2 and a range in total dissolved solids from 
217 to 233 mg/L, depending on where the southern boundary is placed (Excel file yucca.xls in 
Oliver and Root 1997). The fact that the down-gradient waters are even farther from the recharge 
areas than those in the Yucca Mountain area again suggests these waters are close to equilibrium 
with their host rocks. 
6.8.3 Present-Day Characteristics of Groundwaters in the Yucca Mountain Area 
As pointed out in the last section, saturated-zone waters from volcanic aquifers in the recharge 
area are compositionally very similar to saturated-zone waters from the Yucca Mountain area 
(compare Figures 47 and 48). Analyses of groundwater from drillholes that penetrate the host 
rock and other volcanic units in the area of the exploration block indicate that they are principally 
sodium-bicarbonate waters (Figure 48) with low contents of total dissolved solids (200 to 400

ANL-NBS-HS-000017, Rev 00 Page 91 of 156 
mg/L, based on data in DTN: GS930308312323.001, GS980908312322.008, 
GS990608312133.001 and Excel file yucca.xls in Oliver and Root 1997). Compared to waters in 
the recharge areas, the Yucca Mountain area waters show a greater range in pH values from 6.6 
to 9.2 and total dissolved solids ranging from 181 to 887 mg/L (DTN: GS930308312323.001, 
GS980908312322.008, GS990608312133.001 and Excel file yucca.xls in Oliver and Root 1997). 
Plots of the major cations versus chloride show that saturated-zone waters (as well as perched 
waters, based on data from Sections 6.5.3 and 6.6.5) are generally distinct from unsaturated-zone 
pore waters in the Yucca Mountain area in several ways: 
 First, saturated-zone waters and perched waters have much lower chloride 
concentrations than the pore waters (Figure 18). This result suggests the saturated-zone 
and perched waters were subject to less evapotranspiration than the pore waters. An 
alternative explanation, loss of chloride from solution by reactions with glass or 
hydroxyl phases in tuff, is improbable for unsaturated-zone pore waters at Yucca 
Mountain. 
 Second, saturated-zone waters are either on or above the precipitation trend line in a 
sulfate versus chloride plot suggesting they gained sulfate, perhaps by dissolving some 
sulfate mineral(s) such as gypsum (Figure 27). Among the unsaturated-zone pore 
waters, only some samples from the PTn unit show a similarly high SO4/Cl ratio. The 
vast majority of pore waters plot well below the trend line. 
 Third, unlike unsaturated-zone waters, all of the perched waters and a significant 
proportion of the saturated-zone waters plot above the precipitation trend line in a 
calcium-versus-chloride plot (Figure 24). This result suggests some of these waters 
gained calcium while others lost calcium. The fact that nearly all of these waters gained 
bicarbonate (Figure 25) suggests the calcium gained may have come from the dissolution 
of calcite. The loss of calcium likely reflects ion-exchange reactions on clays and 
zeolites. This possibility is supported by the fact that these waters have all gained 
sodium (Figure 26). 
 Finally, silica concentrations in these waters are slightly lower than those measured in 
most pore waters. However, nearly all waters are oversaturated with alpha-cristobalite 
(Figure 28), suggesting that a different silica phase may control their concentrations. 
On trilinear diagrams, local groundwater and perched waters show distributions of major ions 
that are quite similar to one another (Figures 17 and 48), and considerably different from those of 
unsaturated-zone pore waters. The relative abundances of cations in saturated-zone waters show 
considerable variation from east to west across Yucca Mountain, with perched water being most 
like groundwater from wells in Fortymile Wash (e.g., J-13). Wells on Yucca Mountain and just 
to the west (USW H-3, USW H-5, and USW H-6) plot nearest the sodium apex of Figure 48. 
Wells on the eastern slopes and washes (USW H-1, USW H-4, USW G-4, J-13, and UE-25 b#1) 
show increasing levels of calcium. The Na+K / Ca+Mg molar ratio increases from 3.8 in J-12 to 
263 in H-3. This result most likely reflects ion-exchange reactions involving the zeolites and 
clays in the saturated-zone units beneath Yucca Mountain and the sodium/hydrogen ion

ANL-NBS-HS-000017, Rev 00 Page 92 of 156 
exchange reaction. The fact that bicarbonate concentrations also increase from east to west 
suggests a significant contribution from the latter reaction. 
The anionic constituents of the Yucca Mountain groundwaters show a relatively uniform 
distribution in all the wells, with about 80 percent bicarbonate and the remainder as sulfate and 
chloride (usually present in nearly equal molar concentrations) and fluoride (in varying 
concentrations). Perched waters have a slightly higher molar proportion of bicarbonate (about 
85% of total anions) and more than twice the proportion of sulfate relative to chloride (Figure 
17). 
6.8.4 Representativeness of Available Data 
Because the analyses of major constituents in saturated-zone groundwaters from volcanic 
aquifers in the Yucca Mountain region show only limited variability (compare Figures 47 and 
48), the available data are sufficiently representative for characterization and modeling purposes. 
For pH, bounds can be placed on the likely variability to be expected based on observations and 
hydrochemical models. 
6.9 FLUID GEOCHEMICAL INDICATORS OF FLOW AND TRANSPORT 
PROCESSES 
6.9.1 Chloride as a Hydrologic Tracer 
Chloride pore-water concentrations obtained from unsaturated core samples serve several 
purposes within the Yucca Mountain investigation: 
 Infiltration estimates. Cl concentrations provide independent corroboration of surface 
infiltration rates estimated by modeling. The Cl mass balance (CMB) method estimates 
infiltration as a proportion of precipitation based upon the enrichment of Cl in pore 
water relative to its concentration in precipitation. 
 Perched water origin. The origin and age of perched water bodies underlying Yucca 
Mountain have been problematic because their Cl concentrations (4 to 10 mg/L) are 
generally considerably lower than those of pore waters from the unsaturated zone above 
the bodies. Expanding the spatial coverage of the pore-water data helps constrain the 
various hypotheses on the derivation of the perched water. 
 Mixing of waters. Cl, Br, and SO4 pore-water concentrations indicate the extent to 
which water geochemistry is homogenized as it percolates through the nonwelded 
Paintbrush unit. Fracture-dominated flow in the overlying low-permeability, highly 
fractured TCw unit is expected to transition to matrix-dominated flow in the highpermeability, 
comparatively unfractured PTn (Wolfsberg et al. 1998, p. 82). The 
transition process from fracture to matrix flow in the PTn, as well as the transition from 
low to high matrix storage capacity, could damp out most of the seasonal, decadal, and 
secular variability in surface infiltration. This process could also result in the 
homogenization of the variable geochemical and isotopic characteristics of pore water

ANL-NBS-HS-000017, Rev 00 Page 93 of 156 
entering the top of the PTn. In contrast, fault zones that provide continuous fracture 
pathways through the PTn may damp climatic and geochemical variability only slightly 
and may provide fast paths from the surface to the sampled depths, whether within the 
PTn or in underlying welded tuffs (Wolfsberg et al. 1998, p. 82 and Figure 2). If this 
concept can be validated, then it would suggest that repository design and performance 
assessment efforts can be based on fluxes that are uniform in time, except near fault 
zones. 
 Lateral diversion. Variability in Cl, Br, and SO4 pore-water concentrations can be used 
to assess the extent to which water may be laterally diverted due to contrasting 
hydrologic properties of the various stratigraphic units above the potential repository 
horizon (although it is recognized that this aspect may be obscured by climatic 
variability in the geochemistry of infiltrating fluids). 
 Model calibration. To the extent that the Cl pore-water database can be extended to a 
wide spatial and stratigraphic coverage, it is an increasingly valuable data set for sitescale 
modelers to use in calibrating flow and transport models of Yucca Mountain. 
6.9.2 Infiltration Estimates using the Chloride Mass Balance Method 
Precipitation data used in Section 6.9.2 to estimate bounds on present-day average chloride 
deposition rates at Yucca Mountain are listed in section 4.1.1. Pore-water chloride data analyzed 
by the CMB analysis are listed in section 4.1.3. Determination of the background 36Cl/Cl ratio 
for the Yucca Mountain vicinity, which is used to estimate the long-term average chloride 
deposition rate at Yucca Mountain, uses input data listed in section 4.1.16. Assumptions 1, 2 
(TBV), 3, 19 (TBV), 20 (TBV), and 21 (TBV) from Table 2 apply to discussions in this section. 
6.9.2.1 Chloride mass balance model 
The CMB approach is based on the premise that the flux of Cl deposited at the surface equals the 
flux of Cl carried beneath the root zone by infiltrating water. With increasing depth, as water is 
extracted by evapotranspiration, Cl concentrations in pore waters increase and apparent 
infiltration rates decrease. Net infiltration is the flux of water moving below the zone of 
evapotranspiration, at which depth Cl concentrations remain relatively constant (Figure 49a). 
Infiltration rates can thus be estimated from measured Cl concentrations using the relationship: 
I = (P C0)/Cp, (Eqn 8) 
where I is average net infiltration (mm/yr), P is average annual precipitation (mm/yr), C0 is the 
effective average Cl concentration in precipitation (mg/L), including the contribution from dry 
fallout, and Cp is the measured Cl concentration in pore water (mg/L). 
This approach has been widely used to estimate water transport rates in alluvial profiles through 
the unsaturated zone and basin-wide recharge (e.g., see reviews by Dettinger 1989, pp. 57 to 61; 
Herczeg and Edmunds 2000, pp. 49 to 50; Phillips 1994, pp. 19 to 21; Scanlon et al. 1997, pp. 
470 to 472). Estimates of recharge using the CMB technique for 15 groundwater basins in 
Nevada were found to be in fairly good agreement with estimates obtained by the Maxey-Eakin

ANL-NBS-HS-000017, Rev 00 Page 94 of 156 
linear step function (Dettinger 1989, p. 75). Using a 6-year study of two upland basins selected as 
analog wetter climate sites for Yucca Mountain, Lichty and McKinley (1995, p. 1) showed the 
CMB method to be more robust than a water balance modeling approach using a deterministic 
watershed model for estimating basin-wide recharge for two comparatively wet sites in the 
Kawich Range north of Yucca Mountain. They attributed the robustness of the CMB method to 
the small number of measured parameters required as compared to the number of parameters 
needed for defining a deterministic watershed model. Point estimates of net infiltration or 
recharge using the CMB technique tend to be less robust than basin-wide estimates because of 
additional assumptions concerning vertical ground water flow and surface water flow. 
6.9.2.2 Model assumptions 
The CMB method is based on the following simplifying assumptions (Assumptions 19, 20, 21 in 
Table 2, all TBV): 
 the average annual Cl deposition rate (the product of precipitation and Cl concentration in 
precipitation), is known and constant (or can be bounded) throughout the time period of 
interest, 
 run-on or run-off is negligible, 
 lateral subsurface flow, such as along the bedrock/alluvial contact, is negligible, 
 precipitation (dry and wet fallout) is the only source of Cl, 
 there is no sink for Cl, 
 transport of Cl in soil can be approximated as piston flow (i.e., uniform downward movement 
of water without dispersion), 
 preferential flow allowing a portion of dilute infiltrating water to bypass the root zone (e.g., 
via root channels or fractures) is negligible, and 
 extracted pore water is representative of in-situ infiltrating water. 
Applicability of the CMB method to the specific conditions at Yucca Mountain (e.g., shallow 
soil cover over fractured rock) is an assumption to be verified (TBV) (Assumption 19 in Table 
2). It is possible that relatively dilute water that has infiltrated rapidly through fracture pathways 
may be inadequately represented by matrix pore water because of incomplete mixing. If this is 
the case, matrix pore-water samples might be biased toward the slower moving, more 
concentrated matrix component of flow; and percolation estimates based on these samples would 
constitute lower bounds on the actual percolation rates. In the PTn, some component of the flux 
can bypass the matrix as fracture or fault flow, as evidenced by the presence of bomb-pulse 
tracers in the ESF. However, based on the discussion of these assumptions, the method appears 
to be valid for a first-approximation of infiltration at Yucca Mountain (Fabryka-Martin, Flint et 
al. 1997, section 6.3.1).

ANL-NBS-HS-000017, Rev 00 Page 95 of 156 
6.9.2.3 Model parameter values 
Two approaches can be used to estimate the deposition rate of meteoric Cl onto the land surface 
at Yucca Mountain: (a) measuring Cl concentrations in precipitation and dry fallout, and (b) 
dividing the natural 36Cl fallout at the site, which varies with latitude, by the prebomb 36Cl/Cl 
ratio (Phillips 1994, pp. 22 to 23; Scanlon et al. 1997, p. 471). Both approaches have been taken 
for Yucca Mountain. Deposition is highly variable on short time scales, such that long-term 
monitoring records are needed that cover all seasons for several years or more. Section 6.3.2 
summarizes the availability of precipitation records for the area: 
 In his study of desert basins in Nevada, Dettinger (1989, p. 62) calculated an average bulkprecipitation 
concentration of 0.6 mg/L (using data from 8 sites). For his study of recharge in 
Las Vegas Valley, this author used an average concentration of 0.4 mg/L (for 74 sites) but 
noted that 66 of the sites only had wet fallout data (Dettinger 1989, pp. 63 and 66). 
 At 3 Springs Basin north of Yucca Mountain (Figure 1), the average annual Cl concentration 
was 0.51 mg/L with an average annual precipitation rate of 335 mm (calculated from data in 
DTN: GS930108315214.003, GS930108315214.004, and GS930908315214.030; these data 
were also published in McKinley and Oliver 1994, pp. 23 to 27, 66 to 74, and McKinley and 
Oliver 1995, pp. 17, 18, 29 and 30). 
 Cl data for the Red Rock Canyon site outside of Las Vegas (Figure 1) average 0.16 mg/L for 
an average annual precipitation of 162 mm, but only include wet fallout (data from DTN: 
LA0003JF12213U.001). 
 The concentration of Cl in 111 samples collected from Yucca Mountain for the present study 
during the Spring of 1995 ranged from 0.3 to 1.8 mg/L, averaging 0.5 mg/L (DTN: 
LAJF831222AQ95.003). 
A longer-term record is provided by the second approach in which the Cl deposition rate (DCl) is 
estimated from: 
DCl = D36 / (36Cl/Cl)0, (Eqn 9) 
where D36 is the deposition rate of prebomb 36Cl, and (36Cl/Cl)0 is the prebomb 36Cl/Cl ratio. 
The prebomb 36Cl/Cl ratio is 502 x 10-15, based on analyses of 41 samples of soil, alluvium and 
fossil packrat urine (Table 25). The data for radiocarbon-dated packrat samples indicate that this 
ratio has been fairly constant throughout the Holocene. For the latitude at which Yucca 
Mountain is located, Phillips (2000, Figure 10.2 on p. 308) presents an empirical equation for 
estimating 36Cl deposition rate as a function of precipitation: 
D36 = 0.047 P + 8.09, (Eqn 10) 
where D36 has units of atoms m-2 s-1, and P is average annual precipitation in mm. The average 
annual precipitation over Yucca Mountain is 172 mm and ranges from 128 mm at the lower 
elevations (3000 ft) to over 231 mm at higher elevations (6000 ft) (Hevesi et al. 1992, p. 677 and 
equation 5 on p. 685). Using these precipitation bounds, estimates for D36 range from 14

ANL-NBS-HS-000017, Rev 00 Page 96 of 156 
atoms/m2/s (for an average annual precipitation of 128 mm), to 19 atoms/m2/s (for 231 mm), 
averaging 16 atoms/m2/s for Yucca Mountain itself (172 mm). Estimates for DCl thus range from 
52 to 70 mg/m2/yr (for precipitation of 128 and 231 mm/yr, respectively), corresponding to 
effective Cl concentrations of 0.40 and 0.31 mg/L for these two precipitation rates. In general, 
however, the spatial distribution of precipitation directly over the repository site is fairly uniform, 
with high rates over the crest (e.g., 184 mm/yr at UZ-6), decreasing to 160 or 150 mm/yr in the 
lower washes (Hevesi et al. 1992, Table 3). Assuming an average precipitation of 170 mm/yr, 
the Cl deposition rate for Yucca Mountain is 60 mg/m2/yr with an effective concentration of 0.35 
mg/L. 
From this discussion, the following is concluded: 
 The rate of Cl deposition is proportional to the precipitation rate and is probably fairly 
constant on the timescales of interest for estimating infiltration at Yucca Mountain (i.e., 
hundreds or thousands of years). 
 Estimates of average annual Cl concentrations in precipitation at Yucca Mountain range from 
0.3 to 0.6 mg/L, with 0.35 mg/L being the best estimate for a long-term average. 
The relationship between measured pore-water concentration and inferred infiltration rate is 
plotted in Figure 49b for this range of concentrations and a precipitation rate of 170 mm/yr. 
6.9.2.4 Infiltration rates at Yucca Mountain 
Values of net infiltration estimated at Yucca Mountain using the CMB technique range from less 
than 0.1 mm/yr to nearly 20 mm/year (Tables 26 and 27). Table 26 lists Cl pore-water 
concentrations for boreholes in the ESF, Cross Drift and Busted Butte, together with the 
associated apparent infiltration rates. Average concentrations for the Yucca Mountain samples 
are tabulated in Table 27. Average Cl concentrations for the North Ramp (23 mg/L) and Main 
Drift (20 mg/L) are similar to that for the Cross Drift (22 mg/L) and about a third of the average 
value for the South Ramp (64 mg/L). Assuming precipitation of 170 mm/yr with an average Cl 
concentration of 0.35 mg/L, these pore-water concentrations correspond to infiltration rates of 5 
to 14 mm/yr above the North Ramp, Main Drift, and Cross Drift, and 1 to 2 mm/yr above the 
South Ramp. Despite variable Cl concentrations in the easternmost South Ramp samples, the 
corresponding infiltration rates calculated for individual samples cover a narrow range, 0.4 to 4 
mm/yr (Table 26), because of the insensitivity of the CMB method to concentrations above about 
20 mg/L (Figure 49b). 
Table 27 lists average Cl pore-water concentrations for surface-based boreholes, together with 
the associated apparent infiltration rates. In the north part of the study area, Cl concentrations are 
higherand associated infiltration rates lowerfor pore waters from these boreholes as 
compared to pore waters from tunnel boreholes. This difference is probably due to the location 
of the surface-based boreholes in washes with thick alluvial cover. On the basis of chloride 
concentration data from alluvium and from nonwelded PTn, along with supporting information 
from neutron moisture logging and 36Cl analyses, the alluvium is, in most cases, a significant 
barrier to water movement and infiltration is indeed higher where alluvium is thin or absent.

ANL-NBS-HS-000017, Rev 00 Page 97 of 156 
Some channel boreholes, as well as soil samples collected from sideslopes, display chloride 
profiles that suggest recent flushing of chloride from the soil profile (as evidenced by low 
concentrations in the surficial layers). Based on Cl concentrations, infiltration through the 
alluvium is less than 0.05 mm/year at UZ#16 and UZ-N54, which are located on alluvial terraces, 
and 0.4 to 0.8 mm/year at UZ-N37, which is located in a channel. Pore-water chloride 
concentrations from the PTn at UZ#16 yield an estimated percolation flux of 2 to 3 mm/year. 
Pore-water chloride concentrations from the top of the PTn at UZ-14 yield an estimated 
percolation flux of 0.2 to 0.4 mm/year. Estimates of percolation flux in the PTn using the CMB 
equation were 0.6 to 1.0 mm/year at UZ#4 and 1.4 to 2.4 mm/year at UZ#5. 
6.9.3 Origin, Age and Continuity of Perched-Water Bodies 
Hydrochemical and isotopic data are useful in the evaluation of alternative hypotheses for the 
origin of perched water at Yucca Mountain. Among possible alternative hypotheses are the 
following: 
 They represent a transient rise in the water level in the saturated zone. 
 They represent a remnant from a time during which percolation rates were higher and 
locally exceeded the hydraulic conductivity of the rock units in the unsaturated zone. 
 They reflect long-term steady-state conditions. 
Although analyses of major chemical constituents in perched water and saturated zone waters 
suggest a close similarity (Section 6.8.2), isotopic data generally do not. The d13C values, d87Sr 
values, and 234U/238U activity ratios for perched waters are generally distinct from those obtained 
for saturated zone waters (Section 6.6). Further, there are consistent trends in d13C values, d87Sr 
values, and 234U/238U activity ratios in water and secondary mineral samples from the soil zone 
down through the unsaturated zone and into the upper-most saturated zone (Sections 6.6 and 
6.10). These observations strongly suggest that the water in the perched zones originated at the 
surface of Yucca Mountain and do not represent upwelling from the saturated zone. 
Assuming the water in the perched-water bodies originated at the surface of Yucca Mountain, the 
next important question is how the water accumulated in the perched-water bodies. Did it 
accumulate in a steady-state process that may be on-going or did it accumulate during a transient 
period of increased infiltration at some time in the past? Analyses of major chemical 
constituents in perched water samples and pore waters squeezed from core samples indicate that 
these two water types are generally different in composition. The pore waters have much higher 
concentrations of most constituents compared to the perched water samples (Tables 6 and 8; 
Figures 18 to 20). This observation suggests that the infiltration mechanism for matrix pore 
water is different from that feeding the perched water bodies. The higher ionic strength of the 
pore waters can be explained by higher rates of evapotranspiration at the infiltration points for 
these waters, as compared to the locations at which perched waters infiltrate the subsurface. 
Thus, perched waters appear, on average, to have spent less time in the near-surface zones than 
did unsaturated-zone pore waters.

ANL-NBS-HS-000017, Rev 00 Page 98 of 156 
The mechanism proposed to explain the chemical differences in pore waters and perched waters 
is one in which pore waters flow primarily through the rock matrix while perched waters 
accumulate from flow that occurred primarily through the fractures in the host rock. For perched 
waters, isotopic data suggest that the flux of water through fractures is likely episodic and of 
small volume compared to the hydraulic conductivity of the fracture. For example, 234U/238U 
activity ratios measured in perched water samples are much higher than the ratios in pore waters 
(Section 6.6.7). The high activity ratios in perched waters would be most readily produced when 
there are episodic fluxes through many small fractures. Under these conditions of rare episodic 
fracture flow, 234U that has accumulated on the fracture surfaces between fracture flow events is 
preferentially leached into the water relative to 238U. If the original concentration of uranium in 
the water is small or if the flux of water is small, a high 234U/238U activity ratio can be produced 
in the percolating water. Clearly, the higher the fracture surface area to water volume ratio, the 
higher the resulting 234U/238U activity ratio, assuming all other factors remain constant. 
The identification of bomb-pulse constituents at depth within Yucca Mountain (Sections 6.6.2, 
6.6.3 and 6.6.4 for tritium, 36Cl and 14C, respectively) suggests that flow along fractures can be 
rapid. However, the absence of a clear bomb-pulse signal for any of these radionuclides in 
perched water samples (Table 9, Section 6.6.3) indicates that the present-day flux of water from 
the surface downward through fractures to perched water bodies must be small. 
In summary, the hydrochemical evidence suggests that pore waters and perched waters in the 
unsaturated zone at Yucca Mountain originated at the surface of the mountain. Perched waters 
appear to form as a result of episodic fracture flow involving small volumes of water. The travel 
time of waters percolating from the surface to the depth of the perched water bodies can be short 
(i.e., less than 40 years). The matrix pore waters apparently represent a more continuous 
percolation of water infiltrated at the surface and moving slowly downward after enough 
residence time in the soil zone to gain the major-ion constituent concentrations observed in the 
pore waters. 
Data bearing on the age of perched water were discussed in Section 6.7.4. The 14C values range 
from 67 to 27 pmc, corresponding to residence times of 3,500 to 11,000 years. These 
residence times have not been corrected for dead carbon that may have been gained by the 
waters due to the dissolution of carbonate minerals along flowpaths from the surface. 
6.9.4 Ion Exchange in the Calico Hills Tuff 
Data on major-ion concentrations in unsaturated-zone waters beneath the proposed repository 
horizon are of great significance as corroborative data for radionuclide transport calculations. 
For example, the fact that pore waters in the lower portions of the zeolitized Calico Hills tuff 
have negligibly low calcium and magnesium concentrations compared to pore waters in the 
overlying units indicates that ion-exchange processes operate on the pore waters that percolate 
through the zeolitic tuffs. These processes tend to remove calcium and magnesium from the 
percolating waters, replacing them with equimolar concentrations of sodium. When combined 
with 14C age data suggesting relatively young ages (up to 100 pmc) for CHn pore waters, these 
data indicate that ion-exchange processes operate on vertically migrating young pore waters in 
the CHn. This suggests ion-exchange processes would also operate on any radionuclides

ANL-NBS-HS-000017, Rev 00 Page 99 of 156 
released from the potential repository into aqueous solutions that migrate vertically into the 
zeolitic CHn. 
6.10 FRACTURE MINERALS 
Calcite and opal are present as fracture and cavity coatings within the unsaturated zone at Yucca 
Mountain. These mineral coatings provide a record of past water percolation through the 
connected fracture network in areas where solutions exceed chemical saturation with respect to 
various mineral phases. Calcite and opal are typically present in the form of 0.1-cm to 6-cm-thick 
coatings in high- to low-angle fractures where apertures exceed several millimeters and on floors 
of lithophysal cavities intersected by fractures allowing the ingress of fracture flow. A small 
proportion of the calcite and opal deposits are present as cements coating breccia fragments in 
narrow rubble zones, or as thin (1-mm to 5-mm-thick) filled veins with low porosity. 
The following sources of primary input data are used to support the conclusions in section 6.10: 
 uranium, thorium and lead isotopic data for minerals (section 4.1.17), 
 abundances of secondary minerals in the subsurface (section 4.1.18), 
 carbon and oxygen isotopic data for minerals (section 4.1.19), and 
 strontium isotopic data for minerals (section 4.1.11). 
6.10.1 Occurrences of Mineral Coatings 
6.10.1.1 Spatial Distribution of Mineral Coatings 
The abundance of mineral coatings measured in the ESF ranges from zero to 0.65 percent (DTN: 
GS991299995215.001, data set MOL.20000104.0013). In general, nonwelded tuffs (PTn) with 
large matrix permeability and few open fractures or cavities have small abundances compared to 
values in the overlying welded TCw and underlying welded TSw tuffs. Abundance data for all 
intervals in welded tuffs have an arithmetic mean of 0.084 percent; however, the frequency 
distribution is strongly skewed, as shown in Figure 50. The data are better represented by a 
lognormal distribution with a geometric mean of 0.034 percent. A number of factors may control 
the distribution of hydrogenic minerals in the subsurface, including topography, infiltration, 
fracture density, fault and shear frequency, and depth. None of these factors are highly correlated 
to the measured mineral abundances in Figure 51. Instead, abundances measured by visual 
examination in the ESF show an apparent decrease with increasing stratigraphic depth in Figure 
52 and appear to be associated, at least qualitatively, with fault density (Figures 51C and 51D). 
Preferred estimates of mineral abundances grouped by stratigraphic position show an apparent 
decrease with depth in the welded tuffs of the Tpt-welded with log means of 0.14 percent for the 
crystal-rich nonlithophysal unit, 0.06 percent for the crystal-poor upper lithophysal unit, and 0.03 
percent for the crystal-poor middle nonlithophysal unit. Uncertainties for percentages in these 
groups have substantial overlap.

ANL-NBS-HS-000017, Rev 00 Page 100 of 156 
Preliminary calcite abundance data from WT-24 cuttings indicate large abundances in the nearsurface 
welded TCw that decrease progressively downwards into the PTn (Figure 53). These 
data imply a progressively smaller amount of evaporation and CO2 loss from the open fracture 
network with increasing depth in the TCw (see assumption 22 in Table 2). These data also 
indicate the likelihood of an inequality between estimates of net infiltration and the amount of 
recharge to the PTn. Abundances are uniformly low in the lower part of the PTn and shallow part 
of the underlying welded TSw, but increase with depth below the base of the PTn, especially in 
the upper and lower lithophysal units. These data will be used to help evaluate the 3-D model of 
fracture mineral distribution and will provide fundamental information to be used in modeling 
fracture fluxes based on mineral data. 
Mineral coatings in fractures are generally restricted to depositional sites where apertures exceed 
several millimeters (Paces, Neymark et al. 1996, Section 2.1.1). Individual fractures that vary in 
aperture along their lengths commonly lack deposits in the narrow-aperture (typically less than 1 
mm) portions but may contain coarse sparry calcite and opal in wide-aperture segments (typically 
greater than 5 mm). Calcite and opal deposits are present on both high-angle and low-angle 
fractures; however, the nature of the coatings differs between these two fracture settings. 
Coatings on high-angle fracture surfaces are generally less than 1 to 5 mm in thickness, whereas 
coatings on low-angle fracture surfaces may attain thicknesses up to several centimeters. Opal is 
most abundant in coatings on low-angle fractures and is commonly rare or absent in deposits on 
high-angle fracture surfaces. Fracture coatings are present almost exclusively on the footwalls 
(lower surface) of open-aperture fractures. Hanging wall (upper) surfaces of the same 
mineralized fracture, unless near vertical, are almost invariably barren of mineral deposits. 
Mineral coatings have outer surfaces that clearly grew into the open space. Completely filled 
fractures, typically between 1 mm and 5 mm in width, constitute a small volume of the total 
calcite deposited exposed in the ESF, in contrast to veins from the saturated zone that are 
commonly filled with coarse calcite. 
Floors of lithophysal cavities (primary spheroidal cavities, typically 5 to 50 cm in diameter) in 
and subjacent to the upper lithophysal unit of the TSw can contain coatings of calcite and opal up 
to 5 to 6 cm thick (Paces, Neymark et al. 1996, Section 2.1.2). More commonly, coatings vary 
between 0.5 and 3 cm thick. Mineral coatings are present in only a small number of the total 
lithophysae. Unlike the vapor-phase minerals that cover all surfaces of these cavities, calcite and 
opal deposits are confined to the floors of the cavities. Walls and ceilings of lithophysal cavities 
are barren of calcite and opal deposits. Even though the coatings are topographically irregular, 
forming mound- and lump-like shapes rather than smooth, uniform layers, they typically follow 
the slope of the floor. In those cases with dipping floors, coatings do not extend up the walls or 
ceiling on the down-slope end of the cavity. 
In most cases, lithophysae are intersected by thin-aperture fractures that could serve as fluid 
pathways (Paces, Neymark et al. 1996, Section 2.1.2). These can either be high-angle, fractures 
cutting the cavity ceiling, or bedding-plane partings that extend only short distances away from 
the lithophysae. In some cases, ridges or valleys preserved in the mineral coatings may correlate 
with the lower extension of the fracture. Obvious connections to a fracture network are not 
always apparent; however fractures may have been removed by the tunneling process, or may 
remain unexposed. Determination of the actual mechanisms of seepage into the cavities remains

ANL-NBS-HS-000017, Rev 00 Page 101 of 156 
as one of the significant uncertainties of these deposits. 
In addition, most calcite and opal deposits do not completely fill lithophysal cavities (Paces, 
Neymark et al. 1996, Section 2.1.2). Typically the thickness of the mineral coating is small 
relative to the height of the lithophysae. In small or flattened lithophysae with heights of only 
several centimeters, bladed calcite may extend from the bottom to the top of the cavity. 
However, even in these instances, the voids between calcite blades remained unfilled and highly 
porous. Calcite from completely filled thin veins (typically less than several mm thick), which 
are scattered throughout the rockmass, constitutes only a small proportion of the total volume of 
fracture minerals. 
6.10.1.2 Mineral Morphology 
Calcite forms coarse, sparry crystals ranging from equant prisms to thin upright, blades 
commonly having flaring-upward overgrowths at the blade tips (scepter-head overgrowths) 
(Figures 2.3 and 2.8 and Section 2.3 of Paces, Neymark et al. 1996; Figures 3 and 4d and p. 8 of 
Whelan et al. 1998). Opal in post-cooling mineral coatings is present as thin sheets or lacey 
patchworks veneering calcite crystals or as small hemispheres present at the tips of calcite blades. 
Both opal and calcite are finely layered (micrometer or finer) and are commonly intergrown at 
very fine scales. These features contrast markedly with occurrences in the saturated zone where 
large-aperture fractures are typically completely filled with coarse, banded calcite, and opal is 
absent. The coatings are also distinct from the granular assemblage of tridymite/cristobalite and 
minor alkali feldspar and hematite that formed from a high-temperature vapor phase during 
cooling of the tuffs and uniformly coats floors, walls, and ceilings of lithophysal cavities. 
Mineral coatings commonly show a systematic sequence of growth that involves changes in both 
mineral compositions and textures (Figure 2.8a and Section 2.4 of Paces, Neymark et al. 1996). 
The oldest parts of the coating commonly include an early silica phase with or without calcite 
and fluorite. The early silica phase commonly is represented by both chalcedony and euhedral 
prisms of quartz, which are restricted to basal positions within individual mineral coatings. 
Main-stage deposits consist of calcite that commonly has blocky to tabular textures in older parts 
of the coating and delicate thin-bladed textures in the later parts. Opal is the dominant silica 
phase throughout this main-stage sequence, and commonly is most abundant near outer surfaces. 
6.10.1.3 Geochronological Observations 
Outermost growth surfaces have been dated using radiocarbon (calcite), 230Th/U (calcite and 
opal) and 207Pb/235U (opal) methods (Appendices 1 and 2 of Paces, Neymark et al. 1996; Tables 
B1, D1, and 3E of Paces, Marshall et al. 1997; Figures 2 and 3 of Neymark et al. 1998; Section 
IV of Paces, Neymark et al. 1998). Radiocarbon dates range from 44 to 16 ka whereas 230Th/U 
ages range from greater than 500 ka to 28 ka (see assumptions 24 and 25 in Table 2) (Figure 54). 
Subsamples of opal at or near outer growth surfaces have 207Pb/235U ages that commonly range 
from about 100 ka to just over 1 Ma. Growth surfaces of mineral coatings show no systematic 
230Th/U age differences between calcite and opal regardless of the depositional setting of a 
mineral coating indicating that lithophysal cavities are just as likely to receive percolating water 
as the fractures. Mineral coatings from both settings have outer surfaces with ages that are young

ANL-NBS-HS-000017, Rev 00 Page 102 of 156 
(typically less than 500 ka) compared to the age of the host rocks (12.7 Ma). However, there are 
systematic differences between younger radiocarbon ages, intermediate 230Th/U, and older 
207Pb/235U ages determined from outer surfaces of the same sample. It is also common for 
multiple subsamples from the same outer surfaces to have different rather than similar ages. 
Typically, the thinnest subsamples from a given surface tend to have the youngest ages. Where 
multiple 230Th/U ages were obtained from different levels within the outer portions of a mineral 
coating, deeper layers have older ages indicating progressive, outward growth of minerals. At 
one site (sample HD2074 from ESF station 30+50.7), half-millimeter-radius hemispheres of opal 
showing distinct micrometer-scale layering have 230Th/U ages of about 152 to 226 ka (Figure 55, 
Table 28). Microdigestions of the outer layers (10 to 50 m thicknesses) of these hemispheres 
have distinctly younger ages between about 4 and 12 ka. Differences in age between the whole 
hemispheres and their outer layers indicate that deposition of these small opal hemispheres was 
not geologically instantaneous. 
Uranium-lead isotopic systems can also be used to date older layers within mineral coatings 
(Neymark et al. 1998, p. 86). Opal layers within the interiors of mineral coatings have 207Pb/235U 
ages that range from about 2 to 8 Ma (Figure 56). Ages were calculated from 207Pb/235U ratios 
given in DTN: GS970208315215.002 and GS970908315215.013, using the following formula 
(Dickin 1995, p. 105): 
1 
* 235 
235 
207 
- = . .
.
. 
. .
.
. t 
t 
e 
U
Pb . (Eqn. 11) 
where 207Pb* is radiogenic Pb resulting from the a-decay of 235U and its daughters, and .235 is the 
decay constant of 235U, with a value of 9.8485 x 10-10 yr-1 (Steiger and Jager 1977, p. 359). Ages 
become progressively older with increasing depth below outer surfaces. Ages of opal near the 
base of mineral coatings are variable, typically from about 4 to 7 Ma implying that not all 
mineral coatings were initiated at the same time. Chalcedony has somewhat older ages than opal 
ranging between about 7.5 to 10 Ma. These results are consistent with paragenetic (depositional 
sequence) observations. Neither opal nor chalcedony has yielded 207Pb/235U ages older than 
about 10 Ma resulting in an apparent time gap of over two and a half million years between the 
deposition of the host tuffs and the oldest fracture mineral ages. It is not clear whether this time 
gap represents a real period of non-deposition, or whether it represents a thermal signature after 
which these silica phases were capable of remaining closed to the decay products of uranium. 
The latter explanation is supported by radiometric ages between 10 and 11 million years for 
illite/smectite clay minerals from boreholes G-2 and G-1 that formed at temperatures as high as 
200 to 275 EC in the deep unsaturated and saturated zones beneath northern Yucca Mountain 
(Bish and Aronson 1993, p. 148). 
6.10.2 Isotopic Compositions of Calcite and Opal 
Oxygen, carbon, and strontium isotopic compositions of subsurface calcite were initially 
determined from fracture coatings in drill core both above and below the water table (Table 1 of 
Szabo and Kyser 1990; p. 930 and Figure 2 of Whelan and Stuckless 1990; Table 1 and Figure 3

ANL-NBS-HS-000017, Rev 00 Page 103 of 156 
of Whelan and Stuckless 1992; Table 1 of Marshall et al. 1992; p. 1583 and Figure 2 of Peterman 
et al. 1992; Marshall et al. 1993, p. 1949; Figure 3 of Whelan et al. 1994). Most of the reported 
d18O values vary systematically with depth from the surface (Figure 57) and are consistent with 
temperature-controlled water-calcite isotope fractionation factors responding to modern-day 
geothermal gradients of 30 to 40C per kilometer measured at Yucca Mountain (Szabo and Kyser 
1990, p. 1718) (see assumption 23 in Table 2). Variations of both d13C and 87Sr/86Sr values in 
drill hole calcite are limited within the unsaturated zone, overlapping the values observed in soil 
carbonate (Whelan et al. 1994, p. 2738; p. 1950 and Figure 5 of Marshall et al. 1993). However, 
d13C and 87Sr/86Sr values for unsaturated-zone calcites are distinct from values for calcites in the 
saturated zone, precluding an upwelling source of water in the unsaturated zone (Figures 58 and 
68). 
Calcites from mineral coatings in the ESF have a much wider range of d13C, d18O and d87Sr 
values than those characterized from deposits sampled from drill core (Sections 4.1 and 4.2 of 
Paces, Neymark et al. 1996; Whelan et al. 1998, p. 13). Values of d13C vary from about -8.2 to 
+8.5 per mil and d18O vary from about 21 to less than 10 per mil (Figure 59). Compared to 
previous determinations of stable isotope compositions of drill core calcite, a larger percentage of 
ESF calcite analysis have d13C values greater than 0 per mil and d18O values less than 15 per mil. 
This difference is likely related to differences between the quality of the mineral coatings 
available for subsampling between the drilling and tunneling programs. Both d13C and d18O in 
calcite are negatively correlated such that subsamples with large d13C values tend to have small 
d18O values (Figure 60). Systematic microsampling across individual mineral coatings indicates 
that d13C values in calcite shifted from larger values (+2  to +9 ) early in the depositional 
history to intermediate values (-3  to 0 ) and finally to smaller values (-8  to -5 ) with 
time (Figure 61). Calcite microsamples show similar correlations between age and composition. 
Late calcite d18O values from coatings within the Tiva Canyon Tuff typically range from 18  to 
21  whereas coatings from deeper in the Topopah Spring Tuff have d18O that varies from 16  
to 18 . Early calcite has d18O values less than 16 , and even less than 10  for some of the 
earliest calcite from basal positions within mineral coatings. 
Opal, quartz and chalcedony also show shifts in both abundance and d18O compositions with 
time (Figure 62: data from Moscati and Whelan 1996, Table 1; Whelan et al. 1998, Appendix 3). 
Massive chalcedony, deposited early in the depositional sequence, has the smallest d18O values 
(7.9  to 17.3 ). Quartz also formed early in the mineralization sequence although it is 
commonly deposited on top of, and slightly later than, chalcedony. Values for d18O in quartz are 
substantially larger than in chalcedony (16.8  to 22.8 ). Opal deposited throughout the 
intermediate and late stages of the depositional history of mineral coatings overlaps the values for 
early quartz but extends the range of d18O to even larger values (18.0  to 27.9 ). 
Strontium isotope ratios from ESF calcite overlap the range reported previously from drill core 
samples, but extend the range to much smaller values (Figure 4.7 of Paces, Neymark et al. 1996). 
Variations in 87Sr/86Sr are crudely correlated with microstratigraphic positions within individual 
mineral coatings showing a general trend of decreasing ratios with relative age (Figure 63). Late 
calcite has 87Sr/86Sr values of 0.7115 to 0.7127 directly overlapping previously published values 
from pedogenic calcite deposits (Figure 5 of Marshall and Mahan 1994). Early calcite generally

ANL-NBS-HS-000017, Rev 00 Page 104 of 156 
has the least radiogenic 87Sr/86Sr ratios between 0.7105 and 0.7120 whereas intermediate-aged 
calcite has 87Sr/86Sr between these two ranges. Strontium concentrations show a less welldefined 
variation with time; however, calcite from the early and intermediate groups typically has 
concentrations less than about 130 g/g (Figure 63) whereas late calcite commonly has larger 
concentrations. Strontium isotope ratios from subsamples across mineral coatings show distinct 
correlations with carbon and oxygen isotopes that are probably related to a gradual evolution of 
isotopic compositions in water percolating through fractures (Figure 64). The relatively large 
amount of scatter observed in these correlations indicate that separate, time-dependent processes 
most likely control the resulting isotopic composition of fracture water. 
An initial 234U/238U ratio can be calculated from the measured uranium isotopic composition and 
the 230Th/U age of a given mineral, assuming the mineral has behaved as a closed isotopic 
system. This initial 234U/238U represents the isotopic composition of percolating waters at the 
time of mineral deposition. Values for initial 234U/238U activities in outermost opal and calcite 
span a wide range from about 1 to over 9. When plotted against their associated 230Th/U age, 
initial 234U/238U ratios show a scattered but distinct negative correlation (Figure 65) indicating 
that older subsamples tend to have smaller initial ratios (section 3.2.3 of Paces, Neymark et al. 
1996). This relation generally is true for both multiple subsamples from a single mineral coating 
as well as for the entire set of data. Taken at face value, this trend suggests that fracture water 
has become progressively enriched in 234U over the last 500 ka; however, mechanisms causing 
this type of long-term trend are difficult to imagine. Other natural reservoirs of uranium, such as 
soil (Figure 2D and p. 2400 of Paces et al. 1994; Figures 9, 10, 13, 16, 17, 20, 21, 25, 26, 27, 32, 
36, 39, 42, 45, 46, and 53 of Paces et al. 1995) and ground water (Figure 5 of Ludwig et al. 1992; 
Figure 20 of Paces, Forester et al. 1996; Figures 4, 11, and 13 of Paces, Whelan et al. 1997) have 
234U/238U that appear to remain relatively uniform over similar time periods. The observed 
negative correlation between age and initial 234U/238U ratios has been explained using a constant 
234U/238U in fracture water at a given depositional site but by the presence of both older layers 
with small present-day 234U/238U and younger layers with larger present-day 234U/238U in 
individual subsamples (section 3.4 of Paces, Neymark et al. 1996). The resulting initial 
234U/238U in opal and calcite subsamples is therefore strongly influenced by the age of the oldest 
layer present in the analyzed subsample, and the proportion of older and younger materials mixed 
together. 
Outermost calcite with ages less than 100 ka are minimally impacted by this analytical artifact. 
Initial 234U/238U activity ratios observed in these younger materials still span a large range from 4 
to 9.5 implying isotopic heterogeneity of fracture water in different unsaturated-zone flow paths. 
In addition, available isotopic data indicates that 234U/238U in fracture water has varied 
systematically with depth in the unsaturated zone (Figure 66; also Figure 3 of Paces, Neymark et 
al. 1998). Calcite and opal within the shallow unsaturated zone (Tpc and PTn) have maximum 
initial 234U/238U ratios similar to those values observed in soils and surface runoff (about 1.5 to 
slightly greater than 2). In contrast, maximum initial 234U/238U ratios attained by calcite and opal 
from below the PTn increase with depth in the TSw, reaching activity ratios up to 9 at the level 
of the potential repository (Figure 66). Therefore, 234U-enrichment with depth is a function of 
the percolation process and contains information related to the history and mechanisms of 
unsaturated-zone flow. This issue is discussed in greater detail in section 6.6.7.

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6.10.3 Interpretation of Isotopic Data for Fracture Minerals 
Assumption 23 in Table 2 applies to discussions throughout this section. 
6.10.3.1 Interpretation of Ages 
Conventional age models (Ivanovich and Harmon 1992, p. 781) assume that mineral deposition 
occurs instantaneously and that the resulting deposit consists of a layer of finite thickness, 
constant age, and uniform initial isotopic compositions. However, even the finest scale of 
subsampling is unable to resolve this layering, and therefore, subsamples represent mixtures of 
both younger and older layers and the resulting measured isotopic ratios will be intermediate 
between the values of the end members. A depositional model that is more consistent with 
observed data is based on the observation of very thin layers at a micrometer scale that are likely 
added more or less continuously (Section 3.4 of Paces, Neymark et al. 1996). The model predicts 
many of the features observed in the geochronological data sets including subsample thickness 
and resulting age, wide-ranging ages from a single outer surface, the discordance between 
isotopic systems with different half-lives, the negative correlation between 230Th/U age and 
initial 234U/238U ratios, and ages that are less than those at which secular equilibrium or complete 
decay is attained (Figures 3.13 and 3.14, and Table 1 of Paces, Neymark et al. 1996). 
6.10.3.2 Growth Rates 
Slow long-term rates of deposition (less than about 5 mm of mineral per million years) are 
inferred from subsamples of outermost calcite and opal. Measurements of 230Th/U age and 
estimates of the thickness for subsample of individual opal hemispheres and microdigestions of 
their outermost surfaces yield estimated growth rates of between 0.4 and 6 mm/Ma (Table 28). 
Growth rates estimated from both millimeter and micrometer scales are similar. Rates of the 
same order of magnitude calculated assuming a continuous deposition model of mineral growth 
closely match the observed U and Th isotopic data (Section 3.4 of Paces, Neymark et al. 1996). 
In addition, similar rates are obtained for the generalized case assuming that the 0.5- to 3-cmthick 
mineral coatings accumulated over a 12.7 million year period (Section 3.4 of Paces, 
Neymark et al. 1996). 
Long-term growth rates over the last 8 million years can also be calculated from the U-Pb ages of 
interior opal layers within mineral coatings (Table 4E of Paces, Marshall et al. 1997; Neymark et 
al. 1998, p. 86). Average long-term growth rates of 1 to 4 mm/Ma are calculated using 
thicknesses measured between dated layers in mineral coatings within the Topopah Spring Tuff 
(Figure 67). Although this range of rates varies by only a factor of about 3 between different 
mineral coatings, rates calculated for different layers within individual coatings are even more 
uniform, typically within a factor of 40%, regardless of relative position within the coating. In 
contrast, mineral coatings from the Tiva Canyon Tuff have more complex depositional relations 
including more rapid growth rates and obvious depositional hiatuses (Neymark et al. 1998, p. 
86). Growth rates during the early stages of mineral deposition throughout the unsaturated zone 
remain uncertain because of the absence of opal with ages older than about 8 Ma as well as the 
smaller number and lower precision of chalcedony dates between 8 and 10 Ma. The similarity of 
mineral growth rates based on independent methods of 230Th/U dating for outer layers and 
207Pb/235U dating for interior layers, plus the uniformity of rates within and between mineral

ANL-NBS-HS-000017, Rev 00 Page 106 of 156 
coatings over the last 8 million years, indicate that fracture flow systems in the deep unsaturated 
zone have been buffered from Neogene and Quaternary climate variations (see Section 6.10.3.7 
on long-term isotopic shifts). 
6.10.3.3 Source of Unsaturated-Zone Water 
Isotopic data from unsaturated zone minerals strongly support a descending meteoric water 
source that has interacted with soil at Yucca Mountain, and refute a saturated-zone source. 
Textural gradations in the upper 10 to 30 meters of the unsaturated zone provide a genetic link 
between the fine-grained, detritus-rich pedogenic deposits, and the detritus-free, coarse calcite 
and opal present in the deeper unsaturated zone. Isotopic compositions of oxygen, carbon and 
strontium in late unsaturated-zone calcite also completely overlap the isotopic compositions of 
calcite observed within Yucca Mountain soils (Figure 5 of Marshall and Mahan 1994; Figure 4 of 
Vaniman and Whelan 1994; Figure 4.11 of Paces, Neymark et al. 1996; Whelan et al. 1998, p. 
13). Values of d13C and d18O in late unsaturated-zone calcites are also consistent with the 
present-day carbon isotopic compositions of CO2 and HCO3
- in unsaturated-zone gas and PTn 
pore waters. Carbon dioxide gas in isotopic equilibrium with late calcite has calculated d13C 
compositions between about -5  to -18  (enrichment factor for low temperature CO2(g)- 
calcite, from Clark and Fritz 1997, inside front cover), overlapping the heavy end of d13C values 
measured in unsaturated-zone gas (Figure 35b). 
The amount of fractionation between oxygen isotopes is more sensitive to mineral formation 
temperature than are carbon isotopes. Temperature gradients calculated from d18O compositions 
of calcite and depth relations are similar to measured unsaturated-zone geothermal gradients in 
several boreholes at Yucca Mountain, yielding average values of about 35C/km (Sass et al. 
1980, 1988; Szabo and Kyser 1990, p. 1718). Water in equilibrium with late calcite in the Tiva 
Canyon Tuff (calcite d18O values of 18  to 21 ) at temperatures between 18 C and 21C 
should have d18O values of about -10  to -12 . Warmer temperatures at the repository 
horizon (ESF main drift temperatures of about 27C) result in similar estimates of water d18O 
values in equilibrium with calcite d18O values of +16.5  to +18 . Conditions during pluvial 
episodes throughout the Quaternary would yield somewhat cooler subsurface temperatures and 
slightly more negative water d18O estimates (-11  to -14 ). Modern precipitation (individual 
rain events dropping more than 0.25 cm and snowfalls at Yucca Mountain) has d18O values 
ranging between about -9  and -18  (Figures 14 and 16 of Benson and Klieforth 1989) with 
mean d18O values of -8  to -10. Mean d18O values for precipitation during the cooler pluvial 
conditions of the Pleistocene were likely to be somewhat more negative. Unsaturated-zone pore 
waters distilled from the welded tuffs or squeezed from the non-welded tuffs have d18O values 
that generally range from -14  to -12 (Figure 37b), also suggesting a pluvial origin. 
In contrast, carbon and oxygen isotope values in unsaturated-zone calcite are difficult to 
reconcile with a saturated-zone source of water. Ground water from the shallow part of the 
saturated zone beneath Yucca Mountain has dissolved inorganic carbon d13C values of about - 11 
 to - 7 , and d18O values of - 13  to - 14  (Table 6 of Claassen 1985; Table 1a of Benson 
and Klieforth 1989; Table 1 of White and Chuma 1987). Although waters with these 
compositions would yield calcite with d13C similar to those observed in unsaturated-zone calcite,

ANL-NBS-HS-000017, Rev 00 Page 107 of 156 
the d18O values of -13  to -14  and present-day ground water temperatures of 30 C would 
result in calcite with d18O values of +13  to +14 . 
Shallow ground water from the saturated zone beneath Yucca Mountain has 87Sr/86Sr ratios 
between 0.7093 and 0.7116 (Figure 2 of Peterman and Stuckless 1993; Peterman and Patterson 
1998, p. 277 to 278). These values are less radiogenic than either late unsaturated-zone calcite or 
pedogenic calcite. In addition, saturated-zone ground water beneath Yucca Mountain is 
undersaturated with respect to calcite and would tend to dissolve rather than precipitate material 
in unsaturated-zone fractures (Section 6.2 of Paces, Neymark et al. 1996). Calcite-saturated 
ground water from the deeper Paleozoic-carbonate aquifer has the same problems with d18O and 
87Sr/86Sr, but also has a carbon isotopic composition that would result in d13C values that are 
much larger than those observed in the late unsaturated-zone calcite. Field, morphologic, 
chemical and isotopic arguments have been used previously to refute a saturated-zone water 
source for pedogenic calcite deposits (Muhs et al. 1990, p. 928 and Figure 3; Stuckless et al. 
1991, p. 553; Stuckless 1991, p. 1429; National Research Council 1992, p. 5; Whelan and 
Stuckless 1992, p. 1580; Vaniman et al. 1994, p. 15; Vaniman and Whelan 1994, p. 2736; Taylor 
and Huckins 1995, Table 5 and pp. 19 to 24; Stuckless et al. 1998, p. 76). Strontium and calcium 
concentrations within the zeolitized Calico Hills formation above the modern water table vary 
vertically and also support a descending water source (Vaniman et al. 1999, p. S5). In addition, a 
defensible physical mechanism responsible for saturated-zone ground water upwelling more than 
a few meters above the static water table has not been identified (National Research Council 
1992, pp. 136 to 139 and p. 212; Rojstaczer 1999, p. S4). 
Although fracture water percolating through the unsaturated zone has not been sampled at Yucca 
Mountain, its major element composition is probably intermediate between runoff and perched 
water intercepted in boreholes at depth. Precipitation rapidly interacts with calcite- and opal-rich 
materials in surface deposits, typically reaching chemical saturation with respect to calcite and 
opal after only brief overland flow (Figure 6.2 of Paces, Neymark et al. 1996). Fracture water is 
likely to have compositions that are similar to or even more chemically evolved than runoff 
samples considering the interactions that take place during infiltration through calcite- and opalrich 
soils and possible silicate/water interaction that occurs within the nonwelded tuffs of the 
PTn. Chemistries of perched-water bodies, presumably recharged largely by fracture flow, 
support this expectation. Therefore, descending fracture water is likely to be at or very near 
levels of saturation with respect to both calcite and opal. Chemical and textural arguments imply 
that once fracture water reaches mineral saturation, it is not likely to later become undersaturated 
during further descent through the unsaturated zone. 
6.10.3.4 Mechanisms of Mineral Deposition 
The process of unsaturated-zone mineral deposition is initiated during infiltration where meteoric 
water interacts with materials in the soil, after which a portion may then enter the bedrock 
fracture network. Fracture water is distributed into connected pathways in response to gravitycontrolled 
downward percolation as thin films that do not require complete water saturation of 
the fractures within the welded tuff (Tokunaga and Wan 1997, p. 1287). Physical and textural 
evidence indicates that these coatings of calcite and opal must have formed in hydrologically 
unsaturated environments with the additional requirement of the presence of open space

ANL-NBS-HS-000017, Rev 00 Page 108 of 156 
(Sections 2.1 and 2.5 of Paces, Neymark et al. 1996). Textures indicate that mineral growth 
commonly occurs at the tips of calcite blades and that a mechanism is required to transport 
dissolved ions to these sites where solutions reach supersaturation. Differences in textures 
between near-horizontal substrates and high-angle fractures indicate that slowing of downwardmigrating 
water may play an important role. 
These observations plus the presence of mineral coatings in open cavities imply a depositional 
mechanism involving liquid/gas exchange including loss of both CO2 and water vapor. Other 
mechanisms of mineral precipitation do not provide adequate explanations of the observed 
textural and mineralogical features. Although an increase in temperature in response to the 
geothermal gradient may explain some of the calcite deposition, it does not account for the 
distribution of calcite with depth in either the ESF or WT-24 drill cuttings (Figures 52 and 53). 
It also does not provide an explanation for opal precipitation, which should be more soluble at 
greater temperatures. Silicate hydrolysis may provide an alternative mechanism for opal 
deposition; however, the devitrified welded tuffs consist of quartz and potassium feldspar which 
are not particularly reactive at low temperatures, and the calcite/opal coatings lack evidence of 
aluminosilicate phases required to balance the hydrolysis reactions. Both thermal and hydrolysis 
mechanisms would permit mineral precipitation in narrow aperture fractures and small pores 
which generally are not observed. Also, neither of these mechanisms readily explains the 
mineral textures observed in many of the open cavities (delicate calcite blades, opal 
concentrations at blade tips, fine-scale intergrowths of calcite and opal, and textural differences 
between steep and shallow fracture cavities). 
A more likely depositional mechanism for calcite precipitation involves transport of both CO2 
and water vapor in an independently migrating gas phase (see assumption 22 in Table 2). Such a 
mechanism also accounts for simultaneous deposition of calcite and opal from a single solution. 
Rates of mass transfer of both water vapor and CO2 from deeper parts of the unsaturated zone are 
likely to be small; however, operation over long time periods may explain the very slow growth 
rates observed in the calcite-opal coatings at the level of the potential repository. A depositional 
mechanism involving interactions between liquid and gas phases also offers possible 
explanations for the observed textural features. Because physical evidence indicates that the 
coatings formed in locally unsaturated environments, thin films of water seeping into fracture and 
lithophysal cavities are the likely source of solutions. Water films may only be present on some 
fraction of the total surface area at any given time. An uneven distribution of wetted surfaces 
likely contributes to the age heterogeneities observed for different subsamples of the same outer 
surfaces of a mineral coating. Thin water films must also be capable of wicking up the outside 
surfaces of elongated calcite blades by capillary processes similar to those that form anthoditic 
speleothems. Water that moves out of cavities and back into the fracture network can form 
additional calcite and opal at sites deeper in the unsaturated zone by further losses of CO2 and 
water vapor as the fracture water descends toward the water table. 
6.10.3.5 Conceptualization of Seepage into Cavities from Secondary Calcite 
Seepage of water into emplacement drifts is a major factor contributing to a calculated release of 
radionuclides, but estimates of seepage flux based on hydrologic parameters have large 
uncertainties. Densely welded Topopah Spring Tuff in the thick unsaturated zone at Yucca

ANL-NBS-HS-000017, Rev 00 Page 109 of 156 
Mountain is the host rock for a potential high-level radioactive waste repository. Observations in 
the ESF show that the welded tuffs contain both large-aperture fractures and lithophysal cavities 
containing secondary calcite and opal deposited from downward-percolating water that has 
seeped into these openings in the past (DTN: GS991299995215.001, data set 
MOL.20000104.0013). Uranium-lead dating indicates that these minerals formed throughout 
most of the timespan since the tuffs were emplaced 12.7 million years ago. 
The percentage of lithophysae containing secondary minerals within the upper lithophysal zone 
of the Topopah Spring Tuff is variable, ranging from 1 to 40 percent per 30 m of tunnel length 
(DTN: GS991299995215.001, data set MOL.20000104.0013). Because essentially all the 
cavities are intersected by fractures, the lack of secondary mineral coatings in some cavities is 
interpreted to indicate a lack of flow in some of the fractures. Calcite typically composes 90 
percent of the low-temperature mineral assemblage. Calcite is abundant in the calcic soils at 
Yucca Mountain, leading to rapid saturation of infiltrating water with respect to calcite. The 
volcanic rocks are calcium (Ca)-poor so infiltrating water is essentially the only source of Ca 
available to form the calcite in the unsaturated zone. Therefore, the calcite that has formed in a 
cavity can be related directly to an amount of water required to transport that amount of Ca into 
the cavity (Marshall et al. 1999, p. S5; Marshall, Paces et al. 1998, pp. 127 to 129). The 
calculated amount of water would be a minimum estimate of the amount of water that actually 
seeped into the cavity unless the water evaporated completely within the cavity. However, 
calculation of the total seepage flux for the whole unsaturated zone based on measurements of 
total calcite abundance in the ESF indicates a flux of about 2 millimeters per year, which is 
within an order of magnitude of the estimated long-term infiltration flux at the surface. 
Calculated rates of water flow into cavities over the past 10 million years, using 0.3 to 2-cm 
coating thicknesses in hypothetically spherical cavities ranging from 12 to 40 cm in diameter, 
would range from about 0.007 milliliters per year to about 20 milliliters per year. Scaling of 
detailed line survey data to the 5-meter diameter of the potential emplacement drifts, the 
estimated seepage rate per 5-m length of drift is 0.1 to 1000 milliliters per year. 
Observations of calcite and opal in cavities in the unsaturated zone at Yucca Mountain indicate 
that: 1) seeps are not regularly spaced in underground workings and there has been no change in 
seepage locations over time, 2) not all fractures sustain flow, 3) there is no evidence (such as 
dripstone) for seepage dripping into cavities from their ceilings, and 4) an actively flowing 
fracture intersecting a 5-m diameter tunnel is not likely to produce more than about 1 liter of 
water per year based on calcite abundances observed in the ESF. This estimate of seepage is 
significantly lower than that used for performance assessment. 
6.10.3.6 Thermal Evolution of the Unsaturated Zone 
Patterns of d18O variations in both silica phases and calcite preserve a record of decreasing 
temperatures as deposition progressed with time in the unsaturated zone. Early chalcedony and 
quartz have d18O values that imply elevated unsaturated-zone temperatures (as high as about 
80C) with respect to the modern geothermal gradient. Heat sources included the cooling tuffs 
themselves during the first few thousands to hundreds of thousands of years, as well as the 
steeper geothermal gradients associated with regional magmatism during the first several million

ANL-NBS-HS-000017, Rev 00 Page 110 of 156 
years after tuff emplacement. Small d18O values in early calcite also support the notion of higher 
temperatures as indicated by early silica phases. Larger d18O values in quartz and subsequent 
opal and calcite indicate that geothermal gradients reached near-modern values by the time that 
the bulk of the mineral coatings were deposited. 
6.10.3.7 Long-Term Isotopic Shifts 
Isotopic compositions of fluids continued to evolve after Yucca Mountain reached modern-like 
thermal gradients by the end of the episode of early chalcedony/quartz deposition between 8 and 
10 million years ago. Carbon isotopic compositions are relatively enriched in 13C in intermediate 
calcite with d13C values of about +3  to - 5  compared to late calcite with d13C values of 
about - 5  to - 9  (Figure 4.6 of Paces, Neymark et al. 1996; Figures 1 and 2 of Whelan and 
Moscati 1998). This shift in composition is presumably caused by changes in the composition of 
the corresponding plant communities at the surface, which are in turn a function of changes in 
climate, as discussed in Boutton (1996, pp. 50 to 57). Carbon isotopic data indicate that the 
earlier plant community was dominated by C4 plants (using the Hatch-Slack photosynthetic 
pathway), which produced soil CO2 gas enriched in 13C. Water infiltrating through this soil 
deposited subsurface calcite with characteristic d13C compositions of - 3  to 0 . Carbon 
isotopic compositions in the late calcite indicate that the plant community had evolved to one 
with a larger C3 (using the Calvin photosynthetic pathway, Boutton 1996, pp. 50 to 57) 
component in more recent times. Dating by the U-Pb method indicates that this major shift in 
d13C values occurred between about 2 and 4 million years ago (p. 14 and Figure 3 of Whelan and 
Moscati 1998). During this same time, climate conditions were undergoing a major change from 
milder, wetter conditions characteristic of the Tertiary to the more severe, semi-arid conditions of 
the Quaternary. Despite this major shift from wetter to drier conditions, mineral growth rates in 
the deep unsaturated zone remained unchanged, suggesting that the deep fracture flow may be 
buffered from substantial variations in infiltration. 
Strontium isotopic compositions of fracture water have also changed over the last 8 million 
years. Early calcite has 87Sr/86Sr ratios of about 0.7105 to 0.7120 whereas late calcite has more 
radiogenic values of 0.7118 to 0.7127. Two different factors may have affected this temporal 
shift in 87Sr/86Sr ratios. Large Rb/Sr ratios in the felsic tuffs cause the 87Sr/86Sr ratio of the wall 
rocks to evolve to larger values over time through decay of 87Rb to 87Sr. Strontium in fracture 
fluids that is derived from water/rock reaction in the more reactive portions of the flow paths 
(nonwelded tuffs of the PTn) will therefore have larger 87Sr/86Sr values in more recent calcite 
relative to early calcite. In addition, development of calcite-rich soils at Yucca Mountain in 
response to increased aridity during the Quaternary provides a large reservoir of readily leachable 
Sr during infiltration. The similarity of 87Sr/86Sr compositions in late ESF calcite to values in 
pedogenic deposits (Figure 64) is probably not a coincidence. 
6.10.3.8 Mineral Growth Rates and Quaternary Climate Variations 
Geochronological and isotopic data show no strong evidence of the effects of pluvial-interpluvial 
climate variations during the last several glacial cycles (Section 7 of Paces, Neymark et al. 1996). 
Although evidence throughout the Great Basin suggests cooler conditions and greater amounts of 
precipitation were common during pluvial episodes (Haynes 1967, pp. 77 to 82; Mifflin and

ANL-NBS-HS-000017, Rev 00 Page 111 of 156 
Wheat 1979, pp. 37 to 50; Spaulding 1985, pp. 27 to 45; Quade et al. 1995, pp. 213 to 228; 
Bradbury 1997, pp. 99 and 109 to 111), 230Th/U ages of calcite and opal show neither an increase 
nor decrease in frequency during these intervals (see assumption 25 in Table 2) (Figure 54). 
Records of late calcite and opal show no obvious evidence of dissolution during periods of 
greater meteoric precipitation. Carbon and oxygen isotopes also show a range of two to three per 
mil in late calcite; similar to the entire range of variation seen in pluvial and interpluvial records 
from saturated-zone calcite at nearby Devils Hole (Figure 2 of Winograd et al. 1992; Figure 2 of 
Coplen et al. 1994). If deposition of unsaturated-zone calcite was affected by Quaternary climate 
variation, a more restricted range of d13C and d18O values at either the larger or smaller end of 
the range observed in late calcite might be expected. These observations are consistent with the 
concept that the average rate of deposition of unsaturated-zone opal and calcite at the potential 
repository horizon may be relatively constant over long periods of time 
6.10.3.9 Implications of Mineral Data for Long-Term Unsaturated-Zone Hydrologic 
Behavior 
Observations of slow, uniform, average growth rates over long periods of time imply that the 
unsaturated zone fracture network has maintained a large degree of hydrologic stability over 
time. Evidence from mineral coatings implies that fracture flow in the deep unsaturated zone is 
buffered from climate-induced variations in precipitation and infiltration. Buffering may be 
accomplished by a number of different processes that operate at different stratigraphic levels 
within the unsaturated zone as well as on a spectrum of magnitude scales. Because these 
processes are complex, the concept that net infiltration equates directly to recharge to the water 
table is probably an oversimplification at Yucca Mountain. 
Numerous processes occurring in the near-surface environment are likely to damp net infiltration 
in response to climate-induced variations in meteoric precipitation. Long-term variations in 
mean annual precipitation result in changes to the plant community. Consequently, the plant 
biomass and its associated evapotranspiration may be able to utilize much of the mean annual 
effective moisture available during any given climate state. A proportion of shallow infiltration 
that is not capable of being utilized by plants is diverted down-slope along the tuff/colluvium 
interface. The presence of massive calcrete deposits in thicker colluvial or alluvial surface 
deposits on the down-thrown side of normal faults provides evidence of a greater accumulation 
of soil water at these sites. The large permeability contrast between colluvium and welded TCw 
over most of the site is likely sufficient to provide an effective mechanism for downslope lateral 
diversion. In addition, many of the near-surface fractures in the welded TCw are largely filled 
with pedogenic calcite and opal, and although their permeability may still be greater than the 
welded tuff, direct ingress into the fracture network is likely to be further restricted. Surface 
runoff from the slopes into alluvial-filled drainages further diverts infiltration during extreme 
precipitation events. 
Once net infiltration enters the subsurface fracture network, hydrogeologic processes may further 
dissipate, divert, or reduce downward fluxes. Calcite abundances show a systematic decrease 
with depth through the TCw in cuttings from borehole WT-24 (Figure 53), requiring a hydrologic 
process that results in a progressively smaller mass of Ca2+ at greater depths from the surface (see 
assumption 22 in Table 2). One way to achieve this result is through non-steady-state net

ANL-NBS-HS-000017, Rev 00 Page 112 of 156 
infiltration that frequently provides fluxes to the shallowest bedrock fractures and only 
infrequently provides fluxes to deeper levels of the TCw. This process implies that not all net 
infiltration events ultimately result in local recharge to the saturated zone. The data could also be 
explained under a steady-state flux environment if the degree of gas loss decreased progressively 
within the TCw such that greater amounts of CO2 and water vapor are removed from the 
shallowest levels within the bedrock. In the latter scenario, rates of mineral deposition are also 
likely to decrease with depth and may help explain the gradual transition of textures from 
microcrystalline calcite and turbid opal in near-surface veins to the coarse, sparry calcite and 
transparent, glassy opal observed at depths below about 10 to 20 meters. Both of these scenarios 
imply that the amount of percolation through the TCw fracture network contributing percolation 
to the PTn is less than the amount of net infiltration at the base of the root zone. 
Most water flowing through fractures in the welded TCw is intercepted by nonwelded tuffs of the 
PTn where flow occurs dominantly through the high permeability matrix. The PTn decreases in 
thickness from north to south at Yucca Mountain (p. 8 and Figure 4 of Moyer et al. 1996) and has 
a large capacity to store water recharging through the TCw . Therefore, short-term variations in 
percolation flux are likely to be buffered by fluctuations in the degree of saturation within this 
unit. In addition, a portion of the matrix flow may be diverted down dip towards the east to 
structurally disturbed zones where greater amounts of vertical flow may be focused. 
6.10.3.10 Comparisons of Fracture Minerals with 36Cl/Cl Data 
The concept of slow and more-or-less uniform growth of fracture minerals over long periods of 
time implies that the fracture flow system in the deep unsaturated zone tends to be sluggish in 
response to short-term variations in meteoric precipitation and infiltration. This conclusion 
appears to conflict with those based on elevated 36Cl/Cl signals in the ESF that are interpreted as 
evidence of rapid (50 years or less) liquid flow through fractures to the level of the potential 
repository (Section 6.6.3). Possible explanations for this apparent discrepancy have been 
proposed in Fabryka-Martin, Flint et al. (1997, Section 6.2.4) including: 
 The possibility that the two different methods have sampled two different flow networks. 
 The possibility that fast paths transmit water that is unsaturated with respect to calcite or 
silica and leave no mineralogical records of this hydrologic activity. 
 The possibility that youngest mineral ages record cessation of flow due to blocking or 
diversion of individual flow channels along the fracture surface as a result of mineral 
deposition. 
 Slow, long-term mineral growth rates may not form deposits on time scales relevant to 
decade- to century-scale flow that are sufficiently thick for petrographic or 
geochronological resolution. 
Although these reasons may represent possible explanations, the two interpretations may not be 
mutually exclusive. Both conceptual models imply that relatively small volumes of fracture fluid 
are responsible for the observed phenomena. The absence of elevated 36Cl/Cl signatures in

ANL-NBS-HS-000017, Rev 00 Page 113 of 156 
perched water or saturated-zone ground water beneath Yucca Mountain constrains the fast-path 
contribution to a very limited component of the total fracture flux. In addition, dating of calcite 
and opal places constraints on the time at which the solid phase became closed to mobilization of 
parent and daughter isotope. However, there is no inherent information on the unsaturated-zone 
travel times preserved in these analyses. Waters from which the minerals were deposited could 
have been 50 or 50,000 years old at the time of mineral formation, yet geochronological 
information would be the same in both cases. Large volumes of water or extremely rapid 
percolation are expected to yield consistently small 234U/238U ratios at the sampling site at depth. 
However, the uranium isotopic response to percolation of very small volumes of rapid flow 
might not be noticed if it is spatially restricted, and if the small amounts of 238U inherited from 
the surface source are still able to be assimilate sufficient 234U from flow-path surfaces. 
In order to provide additional confirmation, work is currently underway to more thoroughly 
evaluate the distribution of 36Cl/Cl across two structural zones within the ESF that exhibited 
bomb-pulse signatures in previous reports (Drill Hole Wash Fault and Sundance Fault) using a 
suite of bomb-pulse indicators including 36Cl/Cl, 3H, 99Tc and 129I. In addition, samples of 
fracture surfaces are being analyzed for uranium isotopic disequilibrium for evidence of recent 
hydrologic activity. 
6.11 THERMAL HISTORY OF THE UNSATURATED ZONE 
The following sources of primary input data are used to support the conclusions in section 6.11: 
 uranium, thorium and lead isotopic data for minerals (section 4.1.17), 
 abundances of secondary minerals in the subsurface (section 4.1.18), 
 carbon and oxygen isotopic data for minerals (section 4.1.19), and 
 other input data for minerals (section 4.1.20). 
6.11.1 Isotopic and Fluid Inclusion Evidence of Unsaturated-Zone Temperature 
At present, models of future flow through the potential repository assume that this zone will 
remain, as it is today, well above the water table. This assumption is based in large part on 
evidence collected from deposits of calcite and opal found in cavities and open fractures of the 
unsaturated zone (Whelan et al. 1994, p. 2744; Whelan et al. 1999, p. S-8; Paces, Neymark et al. 
1996, Section 2.1; Paces et al. 1999, p. S-4). Taken in its entirety, this evidence argues strongly 
that the water table has always remained well below the level of the potential repository and that 
the modern extent of the unsaturated zone is representative of past conditions, at least since uplift 
and tilting of the volcanic sequence. This interpretation, however, has been disputed. Hill et al. 
(1995, p. 86), Dublyansky et al. (1996, pp. 38 to 39), Dublyansky (1999, p. S-4), and Dublyansky 
and Reutsky (1998, p. A-79) have suggested that most, perhaps all, of this calcite and opal was 
deposited by repeated, and possibly recent, flooding of the potential repository by heated fluids 
upwelling from below.

ANL-NBS-HS-000017, Rev 00 Page 114 of 156 
The upwelling hypothesis is based, in part, on a limited amount of data from calcite-hosted fluid 
inclusions. Minimum formation temperatures estimated from calcite-hosted fluid inclusions 
cluster between 35 and 55C but locally range up to 70 to 85C (Dublyansky et al. 1996, pp. 38 
to 39; Dublyansky 1999, p. S-4; Dublyansky and Reutsky 1998, p. A-79). The position of these 
inclusions within the respective calcite samples, that is, whether they represent old or recent 
depositional conditions, is generally not described although the warmest temperatures (70 to 
80C) are ascribed to the oldest portion of that sample. Calcite d18O values, coupled with 
paragenetic and age relations, provide independent evidence of past temperatures in the 
unsaturated zone. This evidence indicates that the tuffs experienced an episode of elevated 
temperature (perhaps up to about 100C) during the earliest stage of calcite formation. 
6.11.2 Paragenetic Relations and Sampling Protocols 
Previous studies (e.g., Whelan et al. 1994, p. 2738) have shown that the unsaturated-zone calcite 
d13C and d18O coincide with those of pedogenic carbonate in the overlying soils (Figure 68). 
Inasmuch as the d13C of soil carbonate is a function of the types of plants present, and thus of the 
climate, the d13C of the unsaturated zone calcite is a record of climate at the time of infiltration. 
The steady decrease of calcite d18O with depth is a reflection of the depositional temperature. 
The fractionation of oxygen isotopes between calcite and water is temperature sensitive. Figure 
69 plots this fractionation against temperature and shows, for low temperatures, a change of 
about 0.18/C (ONeil et al. 1969, p. 5552; Kim and ONeil 1997, p. 3467). If any two of the 
variablesd18O of calcite, d18O of water, or temperatureare known, then the third can be 
estimated. This relation permits some useful inferences to be made from the calcite d18O values. 
It also explains the gradual decrease of calcite d18O with depth as a reflection of warming of the 
calcite-depositing water down the local geothermal gradient. 
Roughly 300 samples of calcite and opal deposits have been collected from ESF exposures by the 
Environmental Science Team of the USGS; input data resulting from these samples are listed in 
Sections 4.1.17 and 4.1.19. Mineralization sequences (parageneses) exhibited by these samples 
define the following generalized paragenesis for post-cooling mineral deposition. Calcite is 
found throughout the paragenesis. Earliest calcite is typically found underlying or associated with 
chalcedony and (or) drusy quartz; the end of the early stage is tentatively placed at the end of 
chalcedony/quartz deposition. Both intermediate- and late-stage deposition consist mainly of 
calcite and opal. Whereas intermediate-stage calcite may be riddled with tiny liquid and solid 
inclusions and is, hence, often murky, late-stage calcite contains fewer inclusions and often forms 
clear, sparry overgrowths. Such textural distinctions, however, are often lacking and 
distinguishing between intermediate and late stages on their basis is frequently impractical. As 
discussed in section 6.11.3, the intermediate- to late-stage boundary is best defined by a shift in 
d13C values. 
Most ESF samples were sampled to determine the range of calcite stable-isotope compositions. 
Moreover, those occurrences that display a simple paragenesis were also the object of detailed 
microsampling to determine the time/space d13C and d18O systematics of the calcite. 
Microsamples were milled from the polished surface of samples at magnifications of 30-40x. For 
each sample, the oldest calcite (closest to the tuff host rock) was designated early and the

ANL-NBS-HS-000017, Rev 00 Page 115 of 156 
youngest calcite (usually free-growing crystal faces) was designated late. Intermediate-stage 
boundaries were based on changes in mineralogy or texture. This approach led to some 
misclassification of calcite stage (e.g., those samples missing a stage) but ensured objectivity. 
6.11.3 ESF Calcite d13C and d18O Values 
Calcite d13C values decrease markedly during the paragenetic sequence, from nearly +10 in the 
early stage to less than -9 in the late stage. Frequency diagrams of early, intermediate, and late 
calcite d13C values display this time dependence (Figure 61) and show that calcite d13C values 
provide a coarse indication of relative age. Figure 70, a plot of calcite d13C vs. age, shows a sharp 
decrease of d13C between 3 and 4 Ma that defines the boundary between the late and intermediate 
stages. This shift probably reflects a change in the d13C of plant organic matter in the overlying 
soils caused by a change in regional climate. The higher d13C values of the intermediate-stage 
calcite suggest a greater dominance by C4 plants such as grasses, perhaps indicating a prairie or 
savanna climate, in contrast to the high desert to pygmy conifer climate zones of the late stage 
(e.g. Quade et al. 1989, p. 467). 
Calcite d18O values also change with time. A plot of d13C vs. d18O for the microsamples (Figure 
71) shows late-stage d18O was fairly constant between 16 and about 20, but gradually 
decreasing values during the intermediate and early stages. A small subset of the early-stage 
calcite displays anomalously low d18O values. 
6.11.3.1 Late-Stage Calcite d18O Variations 
Three important observations can be made from the distribution of late stage calcite d18O values. 
First, when plotted versus age based on 207Pb/235U or 230Th/238U (Figure 72), late-stage deposits 
(roughly the last 4 million years) from the Tiva Canyon Tuff and the Topopah Spring Tuff both 
display ranges of 1.5 to 2.0. These ranges are comparable to that of the 500 thousand year (ky) 
record from Devils Hole in southwestern Nevada (Winograd et al. 1992, p. 256). At Devils Hole, 
where calcite deposits provide a detailed record of groundwater d18O and regional climate during 
the last 500 ky, a similar range of values is observed. This similarity indicates that the scatter 
shown by late-stage calcite d18O values is probably also a reflection of regional climate 
variability. Second, plotting late-stage calcite d18O versus depth below surface shows two 
distinct trends (Figure 73). In the Tiva Canyon Tuff, calcite d18O decreases steeply, at a rate of 
about 2.5/100m. Assuming that calcite d18O changes by about 0.18/C, this decrease is 
equivalent to an unreasonably high geothermal gradient of nearly 140C/km. However, because 
the Tiva Canyon Tuff is highly fractured and open to the atmosphere, it seems likely that 
evaporation, not a high geothermal gradient, increased the d18O of the water and, hence, of the 
calcite. Evaporation enriches the remaining water in 18O, and the d18O values increase towards 
the surface where evaporative loss would be greatest. Topopah Spring Tuff calcite deposits, on 
the other hand, are beneath the PTn which would at least limit evaporation rates. Although there 
is some scatter to the data, late-stage calcite d18O values in the Topopah Spring Tuff have a bestfit 
slope of about 36C/km with an r2 of 0.48, in relatively good agreement with geothermal 
gradients measured in the unsaturated zone which range between 15 and 60C/km (Sass et al.

ANL-NBS-HS-000017, Rev 00 Page 116 of 156 
1988, p. 38). If some percolation water d18O values were less than -11 , the calculated 
geothermal gradients would be lower. 
6.11.3.2 Intermediate Through Early-Stage d18O Decrease 
Although intermediate and early-stage calcite d18O values scatter somewhat more than the late 
stage, they tend to cluster within a similar overall range of about 3. This similarity suggests 
that the scatter of d18O in the older stages is also a reflection of climate variability. Nonetheless, a 
gradual decrease of calcite d18O with age is apparent in Figure 72. Plotting only data from the 
middle non-lithophysal unit of the Topopah Spring Tuff (Tptpmn) (Figure 74) clarifies the 
relation by restricting the depth interval (i.e., limiting the temperature variable). The calcite of the 
older stages must reflect either water with lower d18O values, warmer temperatures, or both. 
Lowering the water d18O to produce the decrease requires a more or less monotonic shift in 
climate between 3 and 10+ my. A reasonable average d18O for waters in the unsaturated zone 
and at Devils Hole is 111. Ascribing the 4 lowering of past d18O entirely to a climate 
change indicates meteoric waters with d18O of -151 at 10 Ma. Meteoric waters with this 
range of d18O today are characteristic of southern Canada. Even though Quaternary climates in 
the region may have hit such extremes during glacial maxima, no published regional climate 
records indicate such a long-term shift to such colder conditions. 
The long history of volcanism in the region suggests that past geothermal gradients may have 
been higher than today and that higher geothermal gradients may have caused the lower d18O 
values of the intermediate and early-stage calcite. Intermediate and early stage percolation-water 
d18O values are presently unconstrained. However, assuming that they have remained within the 
same range as for the late stage, and that calcite d18O values decrease about 0.18/C, the 4 
lower values found in the early stage equate to a temperature increase to about 46C at the level 
of the Tptpmn. If we assume a depth of ~300 meters to the Tptpmn and a surface mean annual 
temperature of 15C, this indicates geothermal gradients of around 100C/km during the early 
stage and perhaps around 60C/km at the beginning of the intermediate stage. 
6.11.3.3 Possible Early Stage Thermal Event 
Oxygen isotopic evidence from drill core samples indicating warmer temperatures of deposition 
during formation of the earliest calcite was reported in a milestone report to DOE in 1996 
(Whelan et al. 1998, p. 21). Although the number of occurrences in the ESF displaying low d18O 
values of early-stage calcite is small, detailed study has revealed some stratigraphic and 
paragenetic controls on their distribution. Figure 75 plots data from the different stages against 
distance in the ESF from the North Portal. Early-stage calcite with low d18O values occurs 
exclusively in the North and South Ramp portions of the tunnel. Stratigraphically, it is restricted 
to the Tiva Canyon Tuff and upper part of the Topopah Spring Tuff. Although the early-stage 
calcite d18O values are lower in the lower part of the Topopah Spring Tuff (Tptpmn), none are 
lower than about 12. Furthermore, these low d18O calcite occurrences are typically associated 
with, but older than, the early-stage silica stage of chalcedony and (or) quartz in those samples. 
They do not compose the entire early stage but typically represent only a thin layer near the base 
of the early calcite stage.

ANL-NBS-HS-000017, Rev 00 Page 117 of 156 
Nothing is known about the d18O of the early-stage water. Nonetheless, we have argued that late 
stage *18O was relatively constant around -11 and that, in concert with a change in geothermal 
gradient in the past, meteoric waters may have remained in that range for the last 10 my or more. 
Recognizing beforehand that it is a long-range extrapolation, assuming a value of -11 for the 
water does, however, provide an initial constraint on the maximum temperature during the early 
stage. 
Early-stage calcite d18O values range down to 3.2. This calcite would form from -11 water at 
a temperature of about 114C (ONeil et al. 1969, p. 5552). The fact that this estimate is above 
the boiling temperature, and there is no evidence from fluid inclusion observations for boiling 
during calcite deposition (as discussed in section 6.11.4), indicates that the d18O of the depositing 
water was at least 1 to 2 less than 11. So, assuming a water d18O of 12.5 yields an 
estimated temperature of about 102C for formation of the calcite with the lowest d18O value 
(3.2) and a temperature of 55C for calcite with a d18O of 10. Temperatures of 55 to 100C 
are significantly warmer than those estimated for normal early-stage calcite and represent a 
thermal anomaly. The stratigraphic distribution of calcite with low d18O values may provide a 
clue to the heat source for this thermal pulse. 
So far, calcite with low values of d18O has been found only sporadically, only in the Tiva Canyon 
Tuff or the top of the Topopah Spring Tuff, only in volumetrically minor amounts, and only in 
the earliest part of the early stage. These conditions are all consistent the hypothesis that 
deposition of the Tiva Canyon Tuff caused conductive heating of the underlying tuffs. These 
conditions do not appear to be consistent with a heat source at depth or with upwelling of heated 
fluids. However, fluid inclusion evidence of warmer depositional temperatures, which appears to 
be at least in partial accord with the distribution of calcite with low values of d18O, has been 
interpreted as proof of the upwelling of heated groundwater (Dublyansky et al. 1996, pp. 38 to 
39; Dublyansky 1999, p. S-4; Dublyansky and Reutsky 1998, p. A-79). 
6.11.4 Fluid Inclusion Studies of Unsaturated-Zone Calcite 
Fluid inclusions are tiny (generally =100 micrometers) cavities in minerals that trap samples of 
the liquids and (or) gases (i.e., fluids) present at the time the cavity was sealed by subsequent 
mineral growth. They may form in many ways (Roedder 1984, pp. 12 to 25; Goldstein and 
Reynolds 1994, pp. 5 to 9), but most commonly by ongoing mineral precipitation sealing 
imperfections in the surface of mineral grains (primary fluid inclusions) or by trapping of fluids 
present during healing of microfractures in mineral grains (secondary fluid inclusions). The 
contents of fluid inclusions are as variable as the multitude of geologic settings in which minerals 
may form. Several common inclusion types are germane to the origin of unsaturated zone calcite. 
Inclusions formed in a vadose setting (i.e., the unsaturated zone) may trap the gas phase 
(typically dominated by atmospheric gases), the liquid (dominantly water), or mixtures of the two 
in varying proportions. Inclusions formed in saturated settings will trap the liquid phase present 
(e.g., groundwater, hydrothermal fluid, or brine). If this trapping occurs at near-ambient 
temperatures, a single-phase, all-liquid inclusion will result. However, if trapping occurs at 
elevated temperatures, the fluid density will increase during cooling and the fluid will shrink. If it 
shrinks enough, a vapor bubble will nucleate in the inclusion to offset the decrease in fluid

ANL-NBS-HS-000017, Rev 00 Page 118 of 156 
volume. These are termed two-phase inclusions and are particularly useful because they permit 
estimates of the temperature of mineral formation. However, any fluid inclusion must meet many 
petrographic criteria (too numerous to discuss here but listed in Chapter 2 of Roedder 1984, pp. 
43 to 45) before it can be considered a reliable source of temperature data. 
Estimates of mineral formation temperatures from two-phase fluid inclusions are made by 
gradually heating the two-phase inclusion and observing the temperature at which vapor and 
liquid re-homogenize to a single phase. If the inclusion was trapped at atmospheric pressure, this 
temperature of homogenization (Th) is essentially the temperature of trapping; to the extent that 
the inclusion was formed at >1 atmosphere (i.e., at depth), Th is an underestimate of the 
formation temperature and must be corrected for the hydrostatic or lithostatic pressure on the 
fluid. Calcite formed in an unsaturated zone setting would require no pressure correction and that 
formed in a shallow saturated zone, <200 m below the water table, a trivial correction of only 
several degrees. 
6.11.4.1 Fluid Inclusion Evidence for the Origin of Unsaturated Zone Calcite 
Several researchers have examined the fluid inclusions present in the calcite from the unsaturated 
zone of Yucca Mountain (Bish and Aronson 1993, pp. 152 to 154; Roedder et al. 1993, p. A-184; 
1994, pp. 1854 to 1860; Roedder and Whelan 1998, p. 56; Dublyansky et al. 1996, pp. 38 to 39; 
Dublyansky 1999, p. S-4; Dublyansky and Reutsky 1998, p. A-79) and, in general, all have 
reported three types of inclusions: liquid-filled or vapor-filled single phase, and two phase, 
consisting of varying proportions of liquid plus vapor. They have not, however, agreed on the 
genetic implications of those observations. 
Liquid-Filled and Small Vapor-Liquid Ratio Two-Phase InclusionsUnsaturated-zone 
calcite from Yucca Mountain contains numerous fluid inclusions. The majority of these are 
liquid filled and indicative of relatively low formation temperatures, although how low is 
uncertain. Ideally, only inclusions trapped at room temperature or less, would be all liquid at 
room temperature. In reality, many all-liquid inclusions formed at 60-70C or less will fail to 
nucleate a shrinkage bubble but will metastably remain a single, liquid, phase. This behavior by 
low-temperature inclusions is caused by the small decrease of internal pressure during cooling 
being insufficient to overcome the surface tension of the liquid. Failure to nucleate a vapor 
bubble is most common for small inclusions, trapped at low temperature, and containing lowsalinity 
fluidstypical attributes of the unsaturated zone calcite all-liquid inclusions. 
The unsaturated-zone calcite also contains two-phase inclusions consisting of liquid plus vapor. 
The vapor:liquid ratios in these inclusions range from nearly all liquid to all vapor, but can be 
divided into two types: (1) small groups of inclusions with small, but consistent, vapor:liquid 
ratios, and (2) scattered vapor-dominated inclusions with large and highly variable vapor:liquid 
ratios. The first type provides evidence of the formation temperatures of the calcite; the second, 
through estimates of internal pressure and gas composition, can permit inferences regarding the 
depositional setting. 
Fluid inclusion studies of secondary calcite occurrences sampled from drill core by YMP 
scientists revealed many two-phase inclusions with large and variable vapor:liquid ratios and

ANL-NBS-HS-000017, Rev 00 Page 119 of 156 
many all-vapor inclusions but very few two-phase inclusions that met the petrographic 
requirements to yield reliable temperature data (Roedder et al. 1994, pp. 1857 to 1858). Roedder 
and Whelan (1998, p. 56) reported Th ranging from about 50 to 100C for seven calcite-hosted 
inclusions from four occurrences sampled from the unsaturated zone of boreholes USW G-1 and 
USW G-2 (data are in DTN: GS931108315215.033). It now appears that this sample set may 
have been adversely affected by core and sample handling procedures. Core from these boreholes 
was not always protected from extremes of temperature (e.g., core sometimes remained at the 
drill site during the summer when temperatures may have exceeded 40C). Also, procedures used 
to prepare the sections could have inadvertently heated the samples to temperatures of 40 to 50 
C. Just as fluid inclusions that trapped only a liquid phase may metastably fail to nucleate a 
vapor bubble on cooling, low-temperature two-phase inclusions with small vapor:liquid ratios 
will homogenize to a single phase if accidentally heated above their Th and then fail to renucleate 
the vapor bubble on cooling. Thus, accidental heating can erase evidence of formation conditions 
below the maximum temperature reached. 
Subsequent studies of calcite samples from the ESF have described the limited occurrence of 
two-phase inclusions with Th ranging from 35 to 55C, and the rare existence of fluid inclusions 
with Th up to at least 80C (Dublyansky et al. 1996, pp. 38 to 39; Dublyansky 1999, p. S-4; 
Dublyansky and Reutsky 1998, p. A-79). The scarcity of similar fluid inclusions in drill core 
samples examined by Roedder et al. (1993, p. A-184; 1994, pp. 1857 to 1858), suggests that 
thermal mishandling could have rehomogenized the previously two-phase inclusions that had 
been trapped at <50C. Why the higher Ths were not observed is uncertain although, if their 
distribution is restricted like that of the calcite with low values of d18O, reconnaissance sampling 
of drill core could have easily missed them. 
Vapor-Filled or Large Vapor-Liquid Ratio InclusionsAlthough not as abundant as allliquid 
inclusions, vapor-filled or vapor-rich inclusions are common. The most common 
depositional settings that produce minerals having inclusions of widely-ranging vapor:liquid 
ratios are where the depositing fluids have boiled, or where mineral deposition took place in an 
unsaturated (vadose) environment. Inclusions formed in these two settings are, however, easily 
distinguished by their internal pressures. Vapor-rich inclusions formed in a boiling environment 
that trap steam or a mixture of steam and fluid will, when cooled to room temperature, have an 
internal pressure that is a near vacuum (unless they contain large amounts of CO2). Inclusions 
formed in a vadose setting trap a mixture of the gases present (dominated by atmospheric gases) 
and the liquid; these inclusions should have internal pressures near or just slightly less than 
atmospheric pressure (depending on the trapping temperature). Dublyansky (1999, p. S-4) has 
offered a third explanation for the vapor-rich inclusions: exsolution of gases from a fluid in a 
saturated zone (i.e., sub-water-table) setting. In this case, the inclusions should have an internal 
pressure equivalent to the height of the overlying water column and which would be considerably 
greater than atmospheric pressure. 
Fortunately, a simple device called a crushing stage permits qualitative estimates of the internal 
pressure of fluid inclusions (Roedder 1970, pp. 41 to 42). A mineral grain containing an 
inclusion of interest is placed in an immersion medium (oil, glycerol, etc.) between two glass 
plates on a microscope stage. Squeezing of the mineral chip between the two plates generates 
fractures which ultimately rupture the fluid inclusion. If the internal pressure is much less than

ANL-NBS-HS-000017, Rev 00 Page 120 of 156 
atmospheric, as in a high-temperature or boiling inclusion, the immersion fluid will be sucked 
into and fill the inclusion. If the internal pressure is near atmospheric, as in vadose zone mineral 
formation, little or no immersion fluid will enter the inclusion. Lastly, if the internal pressure is 
greater than atmospheric, the inclusion gases will expand into and form a bubble in the 
immersion fluid. 
Analysis of the vapor-rich inclusions in the unsaturated zone calcite fluid inclusions has 
produced conflicting results. Roedder et al. (1993, p. A-184) reported that small amounts of 
immersion oil entered the vapor-rich fluid inclusions when they were crushed. Subsequent 
qualitative analyses of the gases released during crushing (Roedder et al. 1994, p. 1859), 
however, indicated large quantities of CH4 and CO2, with N2 and O2 in roughly atmospheric 
proportions. These results lead to a re-evaluation of the initial crushing experiments because 
CH4, which is locally present in concentrations of tens of percent, is readily soluble in the 
immersion oil used in the experiment. Solution of the CH4 into the immersion oil at the time of 
inclusion rupture would lower the internal pressure in the inclusion and result in oil entering the 
inclusion cavity. The crushing test was therefore repeated using glycerol as the immersion fluid, 
in which CH4 is insoluble. In these tests no glycerol entered the inclusions and they appeared to 
have ~atmospheric internal pressure, indicating that they had likely formed in the same vadose 
setting that they are found in today. 
Again, however, Dublyansky (1999, p. S-4) has reported crushing and gas composition results 
from the vapor-rich inclusions that are at odds with those of Roedder et al. (1994, p. 1859). He 
reported that immersion fluids, including glycerol, entered the inclusions during crushing tests, 
thus indicating a less-than-atmospheric internal pressure. Furthermore, although he reported 
qualitative gas compositions that were similarly rich in CH4, CO2, and N2 he found no O2; and he 
inferred the presence of traces of aromatic hydrocarbons, based on Raman spectroscopy. 
6.11.4.2 Percolation vs. Upwelling Origins for Unsaturated-Zone Calcite 
Not surprisingly, these two research groups have come to distinctly different conclusions 
regarding the formation of the secondary calcite deposits in the unsaturated zone. 
Roedder et al. (1994, pp. 1859 to 1860) concluded that the calcite and associated silica 
mineralization (early chalcedony/quartz, intermediate and late opal) had formed from meteoric 
water. This water infiltrated through the soil zone, picking up its C, Sr, and U geochemical 
signatures, and then percolated through the unsaturated zone depositing calcite and silica along 
its fracture and cavity flowpath. Roedder et als (1994, pp. 1859 to 1860) and Roedder and 
Whelans (1998, p. 56) interpretations were based largely on the following observations: 
 The majority of fluid inclusions are liquid-filled, indicating low formation temperature. 
 The liquid-filled inclusions are closely associated with vapor-rich inclusions in which 
crushing tests have indicated near atmospheric pressure and quadrupole mass 
spectrometry has revealed atmosphere-like N2/O2 ratios.

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 As discussed in Section 6.10, all stages of calcite-silica deposition are largely restricted 
to the footwalls of fractures or the floors of lithophysal cavities and typically mineralize 
only a small percentage of suitable fracture or lithophysal surfaces. This arrangement of 
occurrences is more compatible with deposition controlled by the distribution of discrete 
flowpaths in the unsaturated zone than with the pervasive mineralization that would be 
expected from wholesale flooding of the tuffs. 
Dublyansky (1999, p. S-4) disputed these conclusions and argued that the calcite and silica 
deposits have formed from the upwelling of relatively low-temperature, but deep-seated, thermal 
fluids. These fluids, he contended, have repeatedly invaded the UZ, possibly recently, depositing 
calcite and silica. His conclusions are based primarily on the following observations: 
 The common occurrence of two-phase inclusions that have Th typically of 35 to 55C but 
which range up to ~80C in some of the early stage calcite. Dublyansky insists that these 
temperatures, which are well above the present-day ambient temperature, require 
upwelling of heated fluids and flooding of the unsaturated zone to form the calcite. 
 Vapor-rich inclusions from which crushing tests have indicated less than atmospheric 
internal pressure and in which other analytical studies have suggested the presence of 
traces of aromatic hydrocarbons. Again, this evidence is presented as conclusive proof of 
the upwelling hypothesis. 
6.11.4.3 Alternative Interpretations of Fluid Inclusion Data 
The possibility that thermal water has flooded the unsaturated zone in the past and might do so 
again in the future, no matter how unlikely, must be evaluated carefully. Independent but parallel 
studies of the occurrence and paragenetic distribution of two-phase fluid inclusions, and of the 
timing of deposition of the host calcite, were begun in April 1999 by the US Geological Survey 
(USGS) and the University of Nevada at Las Vegas (UNLV). These studies will be based on a 
comprehensive set of approximately 200 samples jointly collected by the participants from the 
underground workings, and are scheduled for completion in the Spring of 2001. 
Sample collection for the parallel studies is nearly complete. Preliminary reviews of the existing 
data by representatives of the USGS, the UNLV, and the State of Nevada, coupled with 
observations of the new samples appear to support the following inferences: 
 Primary two-phase inclusions are more common than originally reported by Roedder et 
al. (1994, pp. 1857 to 1858). This may reflect the uncertain storage history and sample 
preparation procedures of the drill core samples used in that study. 
 Fluid inclusion Th measurements indicate temperatures of 35 to 55C may have been 
common, and temperatures up to 80C occur at least locally in the early stage 
paragenesis. These temperatures are consistent with those inferred from calcite d18O 
values (Whelan et al. 1999, p. S-8) which record a thermal event in the oldest calcite and 
a progressive decline of the geothermal temperature gradient with time. Geochronologic

ANL-NBS-HS-000017, Rev 00 Page 122 of 156 
studies in conjunction with the fluid inclusion Th measurements will test the thermal 
history of the unsaturated zone inferred from calcite d18O values. 
 Warmer temperature does not, in and of itself, necessitate upwelling fluids or saturated 
conditions. Early stage calcite is still restricted to fracture footwalls and cavity floors. 
Calcite of unquestioned hydrothermal origin formed in tuffs deep below the water table 
about 10.4 Ma (Bish and Aronson 1993, p. 148) and it is isotopically, texturally, and 
chemically distinct from the unsaturated zone calcite (Whelan et al. 1994, pp. 2738 to 
2739 and Figure 3). As long as temperatures were below 100C, unsaturated-zone fluids 
were liquid, and inclusion Th measurements do not necessitate a saturated environment. 
7. SUMMARY AND CONCLUSIONS 
An extensive database of geochemical and isotopic characteristics has been established for pore 
waters and gases from the unsaturated zone, perched water, and saturated-zone waters in the 
Yucca Mountain area. The analytical work has been driven by diverse needs of the YMP site 
characterization, process modeling and performance assessment communities. Water and gas 
chemistries influence the sorption behavior of radionuclides and the solubilities of the 
radionuclide compounds that form. The chemistry of waters that may infiltrate the potential 
repository will be determined in part by that of water present in the unsaturated zone above the 
potential repository horizon, while pore-water compositions beneath the potential repository 
horizon will influence the sorption behavior of the radionuclides transported towards the water 
table. However, more relevant to the discussion in this report, development and testing of 
conceptual flow and transport models for the Yucca Mountain hydrologic system are 
strengthened through the incorporation of natural environmental tracer data into the process. 
Chemical and isotopic data are used to establish bounds on key hydrologic parameters and to 
provide corroborative evidence for model assumptions and predictions. Examples of specific 
issues addressed by these data include spatial and temporal variability in net fluxes, lateral 
diversion in specific stratigraphic units, role of faults in controlling flow paths, fracture-matrix 
interactions, age and origin of perched water, and distribution of water travel times. This section 
summarizes the types of data available and their implications for key hydrologic processes at 
Yucca Mountain. 
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 a subsequent revision. The status of the input 
information quality may be confirmed by review of the Document Input Reference System 
database. 
The following assumptions are identified as to be verified: 
 Chemical data for pore waters extracted from drillcore are representative of in situ conditions 
(Assumption 2 in Table 5; impacts conclusions in Section 7.1, 7.3, 7.4, and 7.7).

ANL-NBS-HS-000017, Rev 00 Page 123 of 156 
 Carbon isotopic data for pore waters and gases are representative of in situ conditions, and 
have not been affected significantly by laboratory or field sources of contamination, including 
drilling air (Assumption 9 in Table 5; impacts conclusions in Section 7.2 and 7.3). 
 The chloride mass balance (CMB) method is assumed to be applicable to the estimation of 
infiltration rates at Yucca Mountain, for samples obtained above the CHn (Assumption 19 in 
Table 5; impacts conclusions in Section 7.4). 
 The estimated range of annual deposition rates for chloride at Yucca Mountain encompasses 
the present-day rate as well as the rates that prevailed when the sampled pore waters 
infiltrated below the soil zone (Assumption 20 in Table 5; impacts conclusions in Section 
7.4). 
 Pore-water samples that have been analyzed for chloride are representative of the full 
spectrum of significant flow paths in the unsaturated zone at Yucca Mountain (Assumption 
21 in Table 5; impacts conclusions in Section 7.4). 
For these reasons, quantitative values and bounds provided in this report and summarized below, 
are subject to change but the general trends are judged to be valid. 
7.1 CHEMICAL COMPOSITION 
Total Dissolved Solids and ChloridePore-water samples were extracted by tri-axial 
compression and by centrifugation from unsaturated core samples recovered from dry-drilled 
boreholes. Only nonwelded to poorly welded tuffs generally yield sufficient water for complete 
chemical analysis, and analyses of pore water from densely welded units are scarce. In general, 
unsaturated-zone pore waters have higher total dissolved solid concentrations than perched or 
saturated-zone waters, reflecting low surface infiltration rates. The variability in the dissolvedsolids 
content of the shallow-most nonwelded unit (PTn) is a direct consequence of the spatial 
variability of surface infiltration rates. Chloride concentrations in this unit are highest beneath 
the terraces of large washes, and lower elsewhere. This inverse relationship between infiltration 
rates and pore-water chloride concentrations is reflected in the fact that infiltration rates 
calculated on the basis of the CMB method are generally consistent with rates calculated on the 
basis of physical methods. 
Geochemical Evolution of Major Ion ChemistryThe relative concentrations of ions in porewater 
samples also provide information about percolation processes. Most of the major chemical 
characteristics of the pore waters appear to be established by soil-zone processespredominantly 
evapotranspiration and dissolution or precipitation of pedogenic calcite and amorphous silica 
such that pore waters entering the bedrock are nearly always saturated with respect to these two 
phases. The infiltrating water compositions range from calcium-sodium bicarbonate type to 
calcium-sodium sulfate-chloride types, depending upon the residence time of the water in the soil 
zone. During large rainfall events that lead to percolation of soil waters directly into the 
unsaturated zone, the waters may be predominantly of the calcium-sodium bicarbonate type. 
During smaller rainfall or snowfall events, waters that percolate into the unsaturated zone may be 
closer to the calcium-sodium chloride-sulfate type.

ANL-NBS-HS-000017, Rev 00 Page 124 of 156 
Major-ion compositions of deeper pore waters indicate that water-rock reactions are very 
restricted during percolation through the unsaturated zone. Relative abundances of cations are 
altered through ion-exchange reactions with clays and zeolites along the flow paths. As a result 
of these reactions, pore waters extracted from the Calico Hills nonwelded (CHn) unit are sodium- 
(carbonate+bicarbonate) type waters, a characteristic that becomes stronger with increasing 
depth. In contrast to PTn pore waters, chemical compositions in the CHn are generally similar 
within a given stratigraphic unit and markedly different between different host lithologies in any 
given borehole, implying significant lateral movement of water within the CHn unit. 
Samples that deviate from this general geochemical evolution may provide insight into the role 
of other factors that can influence water chemistry, such as faults as pathways. 
7.2 ISOTOPIC COMPOSITION 
The isotopic data that are summarized in this section bear on the paleoclimatology of Yucca 
Mountain as well as on the details of the flow system. The paleoclimatic information is largely 
contained in the stable isotopes of hydrogen, oxygen, and carbon. Details of flow, in particular 
evidence for recent flow at depth, is provided by the tritium, carbon-14 and chlorine-36 data. In 
addition, evidence for the presence of local recharge is provided by uranium activity ratios. The 
Sr isotope data largely reflect water-rock interactions, and therefore is pertinent to discussion of 
transport processes. 
TritiumTritium has been analyzed in over 800 pore-water fluids extracted from 
unconsolidated material in shallow surface-based boreholes, from drill core from deep surfacebased 
boreholes, and from ESF drillholes. Analyses are also available for water samples bailed 
and pumped from perched-water bodies and from the saturated zone. Statistical analysis was 
used to define 25 tritium units (TU) as the threshold at which a given signal can be considered as 
being above background. (One of the limitations of this approach is that background in this 
case includes post-bomb waters which have returned to pre-bomb tritium levels.) By this 
criterion, detectable levels of tritium have been observed in the Bow Ridge fault zone in ESF 
Alcove 2 and in about 6% of the pore waters extracted from core samples from 11 surface-based 
boreholes. These detections occur predominantly within the TSw and the Prow Pass member of 
the Crater Flat Tuff. No bomb-pulse tritium was detected in TSw samples from the drillhole 
transecting the Ghost Dance fault in the Northern Ghost Dance Fault Access Drift (Alcove 6), 
despite the fact that elevated levels of 36Cl were measured in Alcove 6. Bomb-pulse tritium was 
not detected in any of the perched-water samples, as all of these were well below 25 TU. 
Tritium data for some of the unsaturated-zone boreholes show several inversions in which 
samples with larger tritium concentrations occur below samples with background values in a 
vertical profile. The occurrence of detectable tritium in waters below non-tritium-bearing water 
(and hence older water) in a vertical profile is strong evidence for the occurrence of fracture and 
lateral flow at Yucca Mountain. 
Chlorine-36Chlorine-36 analyses exist for several hundred rock samples from surface-based 
boreholes and the ESF. Bomb-pulse concentrations are present in the PTn at several locations 
and in the vicinity of some fault zones in the ESF. Bomb-pulse chlorine-36 is not present in

ANL-NBS-HS-000017, Rev 00 Page 125 of 156 
perched water or groundwater from the site (other than in shallow recharge from UE-29 a#2 in 
Fortymile Wash). 
Carbon-14Uncorrected carbon-14 ages of unsaturated-zone pore waters range from modern to 
5,200 years. These data do not show any trend with stratigraphic depth. In fact, larger 14C 
activities are interspersed among smaller 14C activities in a vertical profile. These irregular 
profiles are consistent with a conceptual model in which fracture flow and perhaps lateral flow 
occur in some of the units. Radiocarbon ages for PTn pore-water samples span a narrower range 
than for CHn pore waters, as expected if the CHn unit were fed by fracture flow mixing to 
variable extents with slower matrix flow. 
For carbon isotopes in gases, samples collected from instrumented boreholes (UZ-1, SD-12, and 
drillholes in ESF Alcoves 1 and 6) are considered to be the most reliable indicators of in-situ 
conditions. Gas ages for these samples range from modern in the upper 100 feet, to 15,900 years 
near the water table in UZ-1. The measured gas profiles generally increase smoothly with depth 
and appear to be consistent with gas-transport modeling of downward movement of atmospheric 
CO2 by simple diffusion. In the potential repository horizons, between the TSw upper 
lithophysal and lower lithophysal units, radiocarbon ages for gases range from 6,100 to 9,500 
years in UZ-1 and SD-12. A slightly younger range of 2,400 to 4,500 years was obtained for 
gases from the Alcove 6 drillhole, which intersected the Ghost Dance fault zone. 
Ages for perched waters are 3,300 years for the sample from NRG-7a, and between 7,200 and 
10,700 years for samples from three other boreholes (SD-7, SD-9, UZ-14). If post-bomb water is 
present in the perched bodies, the component is too small to be detectable by any of the three 
bomb-pulse isotope signals (tritium, 14C and 36Cl). 
Questions regarding corrections to the radiocarbon ages remain to be resolved. The extent of 
contamination of pore-water samples with drilling air has not been quantified; such 
contamination would shift the isotopic signature to apparently younger ages. Pore-water and 
perched-water 14C activities can also be diluted by the dissolution of older carbon in the 
carbonate minerals, which would result in anomalously old apparent ages. Reaction with or 
incorporation of gas-phase CO2 from deep in the unsaturated zone can also result in an 
anomalous apparent age. However, although questions can be raised about the representativeness 
of individual samples, the general trends shown by the samples support the conclusion that 
average travel times through the unsaturated zone are on the order of 5,000 to 10,000 years. 
Carbon-13Relative to stable carbon isotope ratios in the atmosphere, most pore-water samples 
are isotopically light. This signature indicates that these pore waters have been influenced by 
biogenic processes, and that most of the bicarbonate in unsaturated-zone matrix pore fluids 
originated in the soil zone. In contrast, most of the perched-water bodies and groundwater in the 
Yucca Mountain area have heavier (less negative) d13C values that do not show the same degree 
of soil influence as do the unsaturated-zone pore waters. Stable carbon isotope ratios for pore 
waters show a wide range in both the Ptn and CHn units, which may be a consequence of a 
variety of processes but which is also consistent with spatially and temporally variable 
infiltration rates and mixing between fast fracture flow and slow matrix flow.

ANL-NBS-HS-000017, Rev 00 Page 126 of 156 
Deuterium and oxygen-18Stable isotopic compositions of hydrogen and oxygen reflect 
climatic conditions that prevailed when the pore water infiltrated below the root zone. Lighter 
isotopic values for CHn pore waters suggest that much of the water in this unit originated either 
during winter precipitation or during a time of colder climate, as compared to the origin of pore 
water in the PTn. This timing may also be the explanation for the more dilute nature of the CHn 
pore waters, because waters are subject to less evapotranspiration during winter precipitation or 
during a colder climate. Spatial differences in Yucca Mountain groundwater samples from the 
saturated zone are not large, but the general trend is that groundwaters to the south of the site 
tend to be isotopically lighter than those farther to the north or east, suggesting that recharge 
occurred under cooler climatic conditions. 
Strontium-87Strontium isotope compositions in the host volcanic rocks differ significantly 
from those of the unsaturated-zone pore waters, indicating that pore water has not reached 
isotopic equilibrium with the tuffs. Near the top of borehole SD-7, the d87Sr in the pore water 
matches the d87Sr found in calcite surface coatings at the drillpad. Delta-87Sr increases with 
depth; this increase is especially evident within the PTn and is only slightly discernible in the 
underlying TSw. A working model assumes that strontium is initially added to infiltrating water 
by dissolution of calcite in the soil zone. During subsequent percolation through the PTn, the 
pore water interacts with the rocks in this unit, which changes its strontium signature. 
Uranium activity ratios Uranium isotopic ratios have been used to address the prevalence and 
frequency of fracture flow through the unsaturated zone at Yucca Mountain and the issue of local 
recharge to the water table. Substantial differences in 234U/238U activity ratios between pore 
water and fracture water imply that, once water is entrained in fractures, there may be minimal 
liquid exchange between these two types of flow pathways. Anomalously large 234U/238U activity 
ratios in shallow saturated-zone water beneath Yucca Mountain are similar to the elevated initial 
234U/238U ratios measured for deep unsaturated-zone minerals and perched water bodies at the 
site. The similarity of the signals for shallow groundwaters, fracture water, and perched waters 
supports the concept of recharge through the thick unsaturated zone at Yucca Mountain, and that 
much of the local recharge derives from flow through fracture pathways in the deep unsaturated 
zone rather than from percolation through the matrix column. Furthermore, the fact that the 
234U/238U values in the groundwater are near the upper end of the range observed in the 
unsaturated-zone materials, implies that the local recharge has not been highly diluted by 
through-flow from the north. 
7.3 FLOW PATHS 
Geochemical and isotopic data in waters from the unsaturated and saturated zones at Yucca 
Mountain are consistent with a flow model in which all unsaturated-zone waters, including 
perched waters, originate at the surface of the mountain. Although flow paths appear to be 
predominantly vertical, there is evidence that suggests lateral flow in some units. For example, 
the observation that samples from the PTn with tritium values well above background are found 
beneath samples with tritium at background values is difficult to explain without calling upon 
some type of lateral flow mechanism. The isotopic data further provide evidence of water that 
has flowed rapidly to at least the depth of the ESF. This water presumably flowed along 
pathways that included fractures and/or faults. To account for the data, there must also be

ANL-NBS-HS-000017, Rev 00 Page 127 of 156 
fractures and/or faults through the PTn. How much of the total percolation flux is due to this 
fracture flow is difficult to quantify. The available hydrochemical data, in toto, suggest the 
proportion is small. This implies that the bulk of water in the unsaturated zone moves through 
the matrix. However, the fact that CHn pore waters are considerably more dilute than pore 
waters in the overlying tuffs suggests that the fracture flow component can dominate the 
chemistry of the deeper unsaturated-zone waters. Alternatively, the more dilute nature of the CHn 
fluids could reflect infiltration under cooler climates than the present climate at Yucca Mountain. 
7.4 INFILTRATION RATES 
Apparent infiltration rates were estimated by the CMB method, using chloride concentrations for 
pore-water samples from 11 surface-based boreholes, 53 ESF drillholes, and 24 Cross Drift 
drillholes. Alluvium in washes or forming terraces had apparent infiltration rates less than 0.5 
mm/yr. Apparent infiltration rates in the PTn were generally higher than the rates estimated for 
alluvium, even for samples from the same boreholes, presumably due to lateral flow and mixing 
within this unit. Nonetheless, the rates appear to be roughly correlated with surface topography. 
PTn samples beneath deep alluvium had infiltration rates between 0.6 and 3.3 mm/yr. PTn and 
TSw pore waters beneath sideslopes and ridgetops, which have thin alluvial cover, had average 
infiltration rates between 5 and 8 mm/yr in the northern half of the study area (e.g., Cross Drift, 
North Ramp, main drift up to station 45+00), but only about 1 mm/yr in the southern half (ESF 
South Ramp). The overall average infiltration rate for pore-water samples collected along the 
Main Drift and Cross Drift (30 samples) is about 6 mm/yr. 
7.5 PERCHED WATER 
The existence of perched water bodies beneath Yucca Mountain is of interest because of 
potential implications for flow and transport in the unsaturated zone. With respect to flow issues, 
the existence of the perched water bodies could reflect an earlier period(s) of increased 
infiltration rates or it could reflect some sort of steady-state phenomenon. The fact that perched 
water samples appear to be up to 11,000 years old based on 14C and 36Cl ages favors the former 
explanation. Major ion concentrations and uranium isotope data suggest that these bodies were 
formed by water flowing through fractures in the unsaturated zone rather than through the matrix. 
The fact that these waters do not appear to have equilibrated with water in the matrix of units in 
which the perched water bodies are found also supports a distinct origin (e.g., fracture flow) for 
these waters and very slow exchange between fracture and matrix reservoirs. 
7.6 PALEOHYDROLOGIC CONSTRAINTS ON FRACTURE FLOW 
Deposits of calcite and opal lining fractures and cavities in the ESF contain spatial and temporal 
information on past migration of water through the unsaturated zone. Mineral textures, the fact 
that less than 10% of all fractures and open spaces contain coatings of calcite and opal, and 
restriction of minerals to fracture footwalls and cavity floors, are consistent with deposition from 
thin films of descending fracture water at sites where solutions lose carbon dioxide and water 
vapor. Carbon, oxygen, and strontium isotopic compositions of the unsaturated zone calcite and 
silica phases also support a source of water from downward-percolating meteoric water. Oxygen

ANL-NBS-HS-000017, Rev 00 Page 128 of 156 
isotopic data on secondary fracture minerals indicate that geothermal gradients during the last 
eight million years have been relatively constant. 
Geochronological data indicate that calcite and opal grew at extremely slow and relatively 
uniform rates for millions of years. Radiocarbon, uranium-thorium, and uranium-lead ages for 
outer (youngest) mineral surfaces range from less than ten thousand to about 1.5 million years. 
Uranium-lead ages for interior (older) layers of opal and chalcedony range from 0.5 to 10 million 
years and result in calculated long-term average deposition rates of about 1 to 5 mm/million 
years. These rates are consistent with estimates based on uranium-thorium ages for subsamples 
deposited over the last half million years. 
Stable isotope compositions (d13C and d18O) of calcite deposited over the last several million 
years span a wide range of values indicating deposition from water originating from both pluvial 
and interpluvial precipitation, consistent with climate fluctuations documented throughout the 
region. However, uniform mineral growth rates imply that fracture flow in the deep unsaturated 
zone at Yucca Mountain did not vary substantially despite these climate variations. In addition, 
230Th/U ages do not show clustering that can be correlated with cycles of pluvial-interpluvial 
climate over the last 200 ka. Initial 234U/238U ratios calculated for opal and calcite deposited 
within the potential repository horizon also imply that deep unsaturated zone fracture flow at 
Yucca Mountain was low volume and/or infrequent. 
Hydrologic buffering of the deep fracture-flow system is attributed to a number of hydrogeologic 
factors including increased runoff and surface drainage in response to additional precipitation, 
downslope diversion along the colluvium-bedrock interface, increased vegetation during wetter 
climates leading to greater rates of evapotranspiration, and the presence of nonwelded tuffs with 
large matrix permeabilities in the PTn overlying the fractured, densely welded tuffs of the 
potential repository horizon. A combination of these factors has resulted in the long-term 
hydrologic stability of the fracture-flow system at the level of the potential repository horizon. 
7.7 IMPLICATIONS FOR REPOSITORY PERFORMANCE 
The chemistry of water is a potentially important factor in radionuclide transport because it 
influences the solubilities of radionuclide compounds that form and because it influences the 
sorption behavior of the radionuclides. In addition, the chemistry of waters that may infiltrate the 
potential repository will be determined largely by the chemistry of water present in the 
unsaturated zone above the potential repository horizon. 
Variations expected in water compositions that intersect the near-field environment will be 
strongly dependent on the climatic regime and on flow paths. Because most flow paths that 
would produce water in the repository horizon will likely represent fracture flow paths, the water 
compositions may be more dilute than those of matrix pore waters extracted from welded and 
nonwelded tuffs. If infiltration rates increased in the site area as a result of a climatic shift, these 
compositions would likely become even more dilute, presumably more like the perched-water 
compositions. 
Data on major ion concentrations in unsaturated zone waters beneath the proposed repository

ANL-NBS-HS-000017, Rev 00 Page 129 of 156 
horizon are of great significance to radionuclide transport. For example, the fact that pore waters 
in the lower portions of the zeolitized Calico Hills tuff have very low calcium and magnesium 
concentrations compared to pore waters in the overlying units indicates that ion exchange 
processes operate on the pore waters that percolate through the zeolitic tuffs. These processes 
tend to remove calcium and magnesium from the percolating waters replacing them with 
equivalent concentrations of sodium. When combined with 14C age data suggesting relatively 
young ages (up to 100 pmc) for CHn pore waters, these data indicate ion exchange processes 
operate on vertically migrating young pore waters in the CHn. This suggests ion exchange 
processes would also operate on radionuclides released from the potential repository into 
aqueous solutions that subsequently migrated vertically into the zeolitic CHn. 
8. REFERENCES 
8.1 CITED REFERENCES 
Benson, L. and Klieforth, H. 1989. "Stable Isotopes in Precipitation and Ground Water in the 
Yucca Mountain Region, Southern Nevada: Paleoclimatic Implications." Geophysical 
Monograph, 55, 41-59. Washington, D.C.: American Geophysical Union. TIC: 224413. 
Benson, L.V. and McKinley, P.W. 1985. Chemical Composition of Ground Water in the Yucca 
Mountain Area, Nevada, 1971-84. Open-File Report 85-484. Denver, Colorado: U.S. Geological 
Survey. ACC: NNA.19900207.0281. 
Bevington, P.R. and Robinson, D.K. 1992. Data Reduction and Error Analysis for the Physical 
Sciences. 2nd Edition. New York, New York: McGraw-Hill. TIC: 243514. 
Bish, D.L. and Aronson, J.L. 1993. "Paleogeothermal and Paleohydrologic Conditions in Silicic 
Tuff from Yucca Mountain, Nevada." Clays and Clay Minerals, 41, (2), 148-161. Long Island 
City, New York: Pergamon Press. TIC: 224613. 
Boutton, T.W. 1996. "Stable Carbon Isotope Ratios of Soil Organic Matter and Their Use as 
Indicators of Vegetation and Climate Change." Chapter 2 of Mass Spectrometry of Soils. 
Boutton, T.W. and Yamasaki, S., eds. New York , New York : Marcel Dekker. TIC: 246834. 
Bradbury, J.P. 1997. "A Diatom-Based Paleohydrologic Record of Climate Change for the Past 
800 k.y. from Owens Lake, California." Chapter 9 of An 800,000-Year Paleoclimatic Record 
from Core OL-92, Owens Lake, Southeast California. Smith, G.I. and Bischoff, J.L., eds. Special 
Paper 317. Boulder, Colorado: Geological Society of America. TIC: 236857. 
Brantley, S.L. and Stellings, L. 1996. "Feldspar Dissolution at 25C and Low pH." American 
Journal of Science, 296, (2), 101-127. New Haven, Connecticut: Yale University, Kline Geology 
Laboratory. TIC: 239822. 
Buesch, D.C.; Spengler, R.W.; Moyer, T.C.; and Geslin, J.K. 1996. Proposed Stratigraphic 
Nomenclature and Macroscopic Identification of Lithostratigraphic Units of the Paintbrush 
Group Exposed at Yucca Mountain, Nevada. Open-File Report 94-469. Denver, Colorado: U.S.

ANL-NBS-HS-000017, Rev 00 Page 130 of 156 
Geological Survey. ACC: MOL.19970205.0061. 
Byers, F.M., Jr.; Carr, W.J.; Orkild, P.P.; Quinlivan, W.D.; and Sargent, K.A. 1976. Volcanic 
Suites and Related Cauldrons of Timber Mountain-Oasis Valley Caldera Complex, Southern 
Nevada. Professional Paper 919. Washington, D.C.: U.S. Geological Survey. TIC: 201146. 
Carter, M.W. and Moghissi, A.A. 1977. "Three Decades of Nuclear Testing." Health Physics, 33, 
55-71. New York, New York: Health Physics Society. TIC: 239141. 
Chadwick, O.A.; Hendricks, D.M.; and Nettleton, W.D. 1987. "Division S-5Soil Genesis, 
Morphology, and Classification, Silica in Duric Soils: I. A Depositional Model." Soil Science 
Society of America Journal, 51, 975-982. Madison, Wisconsin: Soil Science Society of America. 
TIC: 236964. 
Claassen, H.C. 1985. Sources and Mechanisms of Recharge for Ground Water in the West- 
Central Amargosa Desert, Nevada  A Geochemical Interpretation. Professional Paper 712-F. 
Washington, D.C.: U.S. Geological Survey. TIC: 204574. 
Clark, I.D. and Fritz, P. 1997. Environmental Isotopes in Hydrogeology. Boca Raton, Florida: 
Lewis Publishers. TIC: 233503. 
Coplen, T.B.; Winograd, I.J.; Landwehr, J.M.; and Riggs, A.C. 1994. "500,000-Year Stable 
Carbon Isotopic Record from Devils Hole, Nevada." Science, 263, 361-365. Washington, D.C.: 
American Association for the Advancement of Science. TIC: 234269. 
CRWMS M&O 1998. Evaluation of Flow and Transport Models of Yucca Mountain, Based on 
Chlorine-36 and Chloride Studies for FY98. BA0000000-01717-5700-00007 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.19981208.0119. 
CRWMS M&O 1999a. Analysis of Geochemistry Data. TDP-NBS-HS-000040 REV 00. Las 
Vegas, Nevada: CRWMS M&O. ACC: MOL.19990824.0142. 
CRWMS M&O 1999b. M&O Site Investigations -- (Q). Activity Evaluation, September 28, 
1999. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990928.0224. 
Davis, S.N. and Murphy, E. 1987. Dating Ground Water and the Evaluation of Repositories for 
Radioactive Waste. NUREG/CR-4912. Washington, D.C.: U.S. Nuclear Regulatory Commission. 
ACC: NNA.19900522.0260. 
Day, W.C.; Potter, C.J.; Sweetkind, D.S.; Dickerson, R.P.; and San Juan, C.A. 1996. Bedrock 
Geologic Map of the Central Block Area, Yucca Mountain, Nye County, Nevada. Preliminary 
Manuscript. Denver, Colorado: U.S. Geological Survey. 
Dettinger, M.D. 1989. "Reconnaissance Estimates of Natural Recharge to Desert Basins in 
Nevada, U.S.A., by Using Chloride-Balance Calculations." Journal of Hydrology, 106, 55-78.

ANL-NBS-HS-000017, Rev 00 Page 131 of 156 
Amsterdam, The Netherlands: Elsevier Science. TIC: 236967. 
Dickin, A.P. 1995. Radiogenic Isotope Geology. New York, New York: Cambridge University 
Press. TIC: 242869. 
Drever, J.I. and Smith, C.L. 1978. "Cyclic Wetting and Drying of the Soil Zone as an Influence 
on the Chemistry of Ground Water in Arid Terrains." American Journal of Science, 278, 1448- 
1454. New Haven, Connecticut: Yale University, Kline Geology Laboratory. TIC: 237357. 
Dublyansky, Y.; Reutsky, V.; and Shugurova, N. 1996. "Fluid Inclusions in Calcite from the 
Yucca Mountain Exploratory Tunnel." Sixth Biennial Pan American Conference on Research in 
Fluid Inclusions, May 30 - June 1, 1996. Brown, P.E. and Hagemann, S.G., eds. Madison, 
Wisconsin: Department of Geology, University of Wisconsin. TIC: 237704. 
Dublyansky, Y.V. 1999. "Fluid Inclusions in Calcite from the ESF, Yucca Mountain, Nevada: 
Evidence of Saturated Environments and Elevated Temperatures." EOS, Transactions, American 
Geophysical Union 1999 Spring Meeting. S4. Washington, D.C.: American Geophysical Union. 
TIC: 246467. 
Dublyansky, Y.V. and Reutsky, V.N. 1998. "Epigenetic Quartz-Opal-Calcite Crusts in the Yucca 
Mountain Subsurface: Fluid Inclusion and Stable Isotopic Evidence of Hydrothermal Origin." 
Abstracts with Programs, Geological Society of America 1998 Annual Meeting, October 26-29, 
1998, 30, (7), A-79. Boulder, Colorado: Geological Society of America. TIC: 246483. 
Dyer, J.R. 1999. "Revised Interim Guidance Pending Issuance of New U.S. Nuclear Regulatory 
Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada." 
Letter from J.R. Dyer (DOE/YMSCO) to D.R. Wilkins (CRWMS M&O), September 3, 1999, 
OL&RC:SB-1714, with enclosure, "Interim Guidance Pending Issuance of New NRC 
Regulations for Yucca Mountain (Revision 01)." ACC: MOL.19990910.0079. 
Emett, D.C.; Hutchinson, D.D.; Jonson, N.A.; and O'Hair, K.L. 1994. Water Resources Data, 
Nevada, Water Year 1993. Water-Data Report NV-93-1. Carson City, Nevada: U.S. Geological 
Survey. TIC: 236836. 
Engstrom, D.A. and Rautman, C.A. 1996. Geology of the USW SD-9 Drill Hole, Yucca 
Mountain, Nevada. SAND96-2030. Albuquerque, New Mexico: Sandia National Laboratories. 
ACC: MOL.19970508.0288. 
EPA (Environmental Protection Agency) 1971. Final Report of Off-Site Surveillance for Project 
Schooner. PNE-524. Pages i, ii, 34, 42. Las Vegas, Nevada: Environmental Protection Agency. 
TIC: 246092. 
Eriksson, E. 1960. "The Yearly Circulation of Chloride and Sulfur in Nature: Meteorological, 
Geochemical, and Pedalogical Implications. Part II." Tellus, 12, (1), 63-109. Stockholm, Sweden: 
Swedish Geophysical Society. TIC: 236893.

ANL-NBS-HS-000017, Rev 00 Page 132 of 156 
Ervin, E.M.; Luckey, R.R.; and Burkhardt, D.J. 1994. Revised Potentiometric-Surface Map, 
Yucca Mountain and Vicinity, Nevada. Water-Resources Investigations Report 93-4000. Denver, 
Colorado: U.S. Geological Survey. ACC: NNA.19930212.0018. 
Fabryka-Martin, J.T.; Turin, H.J.; Wolfsberg, A.V.; Brenner, D.; Dixon, P.R.; and Musgrave, 
J.A. 1996. Summary Report of Chlorine-36 Studies. LA-CST-TIP-96-003. Draft. Los Alamos, 
New Mexico: Los Alamos National Laboratory. ACC: MOL.19970103.0037. 
Fabryka-Martin, J.; Wolfsberg, A.V.; Dixon, P.R.; Levy, S.; Musgrave, J.; and Turin, H.J. 1996. 
Summary Report of Chlorine-36 Studies: Sampling, Analysis and Simulation of Chlorine-36 in 
the Exploratory Studies Facility. 3783M. Los Alamos, New Mexico: Los Alamos National 
Laboratory. ACC: MOL.19970103.0047. 
Fabryka-Martin, J.T.; Flint, A.L.; Sweetkind, D.S.; Wolfsberg, A.V.; Levy, S.S.; Roemer, G.J.C.; 
Roach, J.L.; Wolfsberg, L.E.; and Duff, M.C. 1997. Evaluation of Flow and Transport Models of 
Yucca Mountain, Based on Chlorine-36 Studies for FY97. LA-CST-TIP-97-010. Los Alamos, 
New Mexico: Los Alamos National Laboratory. ACC: MOL.19980204.0916. 
Fabryka-Martin, J.T.; Wolfsberg, A.V.; Dixon, P.R.; Levy, S.S.; Musgrave, J.A.; and Turin, H.J. 
1997. Summary Report of Chlorine-36 Studies: Sampling, Analysis, and Simulation of Chlorine- 
36 in the Exploratory Studies Facility. LA-13352-MS. Los Alamos, New Mexico: Los Alamos 
National Laboratory. ACC: MOL.19980812.0254. 
Fabryka-Martin, J.T.; Wolfsberg, A.V.; Levy, S.S.; Roach, J.L.; Winters, S.T.; Wolfsberg, L.E.; 
Elmore, D.; and Sharma, P. 1998. "Distribution of Fast Hydrologic Paths in the Unsaturated 
Zone at Yucca Mountain." High-Level Radioactive Waste Management, Proceedings of the 
Eighth International Conference, Las Vegas, Nevada, May 11-14, 1998. Pages 93-96. La Grange 
Park, Illinois: American Nuclear Society. TIC: 237082. 
Fabryka-Martin, J.T.; Wolfsberg, A.V.; Roach, J.L.; Winters, S.T.; and Wolfsberg, L.E. 1998. 
"Using Chloride to Trace Water Movement in the Unsaturated Zone at Yucca Mountain." High- 
Level Radioactive Waste Management, Proceedings of the Eighth International Conference, Las 
Vegas, Nevada, May 11-14, 1998. Pages 264-268. La Grange Park, Illinois: American Nuclear 
Society. TIC: 237082. 
Flint, A.L.; Hevesi, J.A.; and Flint, L.E. 1996. Conceptual and Numerical Model of Infiltration 
for the Yucca Mountain Area, Nevada. Milestone 3GUI623M. Denver, Colorado: U.S. 
Geological Survey. ACC: MOL.19970409.0087. 
Flint, L.E. and Flint, A.L. 1995. Shallow Infiltration Processes at Yucca Mountain, Nevada 
Neutron Logging Data 1984-93. Water-Resources Investigations Report 95-4035. Denver, 
Colorado: U.S. Geological Survey. ACC: MOL.19960924.0577. 
French, R.H. 1985. Daily, Seasonal, and Annual Precipitation at the Nevada Test Site, Nevada.

ANL-NBS-HS-000017, Rev 00 Page 133 of 156 
DOE/NV/10384-01. Las Vegas, Nevada: Desert Research Institute, Water Resources Center. 
TIC: 206773. 
Gascoyne, M. 1992. "Geochemistry of the Actinides and Their Daughters." Chapter 2 of 
Uranium-Series Disequilibrium: Applications to Earth, Marine, and Environmental Sciences. 
Ivanovich, M. and Harmon, R.S. eds. 34-61. Oxford, England: Clarendon Press. TIC: 246658. 
Geslin, J.K.; Moyer, T.C.; and Buesch, D.C. 1995. Summary of Lithologic Logging of New and 
Existing Boreholes at Yucca Mountain, Nevada, August 1993 to February 1994. Open-File 
Report 94-342. Denver, Colorado: U.S. Geological Survey. ACC: MOL.19940810.0011. 
Gifford, R.O. and Frugoli, D.M. 1964. "Silica Source in Soil Solutions." Science, 145, 386-388. 
Washington, D.C.: American Association for the Advancement of Science. TIC: 239118. 
Goldstein, R.H. and Reynolds, T.J., eds. 1994. "Fluid Inclusions and Their Origin." SEPM short 
Course 31 Systematics of Fluid Inclusions in Diagenetic Minerals. 5-9. Tulsa, Oklahoma: 
Society for Sedimentary Geology. TIC: 246523. 
Grasso, D.N. 1996. Hydrology of Modern and Late Holocene Lakes, Death Valley, California. 
Water-Resources Investigations Report 95-4237. Denver, Colorado: U.S. Geological Survey. 
ACC: MOL.19970204.0218. 
Haynes, C.V. 1967. "Quaternary Geology of the Tule Springs Area, Clark County Nevada." 
Pleistocene Studies in Southern Nevada. Anthropological Papers No. 13. Carson City, Nevada: 
Nevada State Museum. TIC: 225695. 
Herczeg, A.L. and Edmunds, W.M. 2000. "Inorganic Ions as Tracers." Chapter 2 of 
Environmental Tracers In Subsurface Hydrology. Cook, P.G. and Herczeg, A.L., eds. Boston, 
Massachusetts: Kluwer Academic Publishers. TIC: 247093. 
Hevesi, J.A.; Flint, A.L.; and Istok, J.D. 1992. "Precipitation Estimation in Mountainous Terrain 
Using Multivariate Geostatistics. Part II: Isohyetal Maps." Journal of Applied Meteorology, 31, 
(7), 677-688. Boston, Massachusetts: American Meteorological Society. TIC: 225248. 
Hill, C.A.; Dublyansky, Y.V.; Harmon R.S.; and Schluter, C.M. 1995. "Overview of 
Calcite/Opal Deposits at or Near the Proposed High-Level Nuclear Waste Site, Yucca Mountain, 
Nevada, USA: Pedogenic, Hypogene, or Both?." Environmental Geology, 26, 69-88. New York, 
New York: Springer-Verlag. TIC: 222318. 
IAEA (International Atomic Energy Agency) 1981. Statistical Treatment of Environmental 
Isotope Data in Precipitation. Technical Reports Series No. 206. Pages xi-xx, 2, 3, 134-137, 154, 
155, and 245-255. Vienna, Austria: International Atomic Energy Agency. TIC: 246103. 
IAEA (International Atomic Energy Agency) 1983. Isotope Techniques in the Hydrogeological 
Assessment of Potential Sites for the Disposal of High-Level Radioactive Wastes. Technical

ANL-NBS-HS-000017, Rev 00 Page 134 of 156 
Report Series No. 228. Vienna, Austria: International Atomic Energy Agency. TIC: 238099. 
Ivanovich, M. and Harmon, R.S. 1992. Uranium-Series Disequilibrium: Applications to Earth, 
Marine, and Environmental Sciences. New York, New York: Oxford University Press. TIC: 
234680. 
Kieft, T.L.; Kovacik, W.P., Jr.; Ringelberg, D.B.; White, D.C.; Haldeman, D.L.; Amy, P.S.; and 
Hersman, L.E. 1997. "Factors Limiting Microbial Growth and Activity at a Proposed High-Level 
Nuclear Repository, Yucca Mountain, Nevada." Applied and Environmental Microbiology, 63, 
(8), 3128-3133. Washington, D.C.: American Society for Microbiology. TIC: 236444. 
Kim, S.T. and O'Neil, J.R. 1997. "Equilibrium and Nonequilibrium Isotope Effects in Synthetic 
Carbonates." Geochimica et Cosmochimica Acta, 61, (16), 3461-3475. New York, New York: 
Pergamon Press. TIC: 236999. 
LeCain, G.D. and Patterson, G.L. 1997. "Milestones  Submittal of Milestone SPH35EM4." 
Memorandum from G.D. LeCain and G.L. Patterson (USGS) to R. Craig (USGS-TPO), March 
11, 1997, with attachment. ACC: MOL.19980224.0146. 
LeCain, G.D.; Patterson, G.L.; and Severson, G.R. 1997. Results from Pneumatic Monitoring, 
Hydrochemistry Sampling, Air-Injection, and Tracer Testing in the Upper Tiva Canyon, and 
Bow Ridge Fault Alcoves, Yucca Mountain, Nevada, November,1994 to July,1996. Milestone 
3GUS619M-1996. Denver, Colorado: U.S. Geological Survey. ACC: MOL.19970415.0387. 
Lichty, R.W. and McKinley, P.W. 1995. Estimates of Ground-Water Recharge Rates for Two 
Small Basins in Central Nevada. Water-Resources Investigations Report 94-4104. Denver, 
Colorado: U.S. Geological Survey. ACC: MOL.19960924.0524. 
Lindberg, R.D. and Runnells, D.D. 1984. "Ground Water Redox Reactions: An Analysis of 
Equilibrium State Applied to Eh Measurements and Geochemical Modeling." Science, 225, 925- 
927. Washington, D.C.: American Association for the Advancement of Science. TIC: 224111. 
Ludwig, K.R.; Peterman, Z.E.; Simmons, K.R.; and Gutentag, E.D. 1993. "234U/238U as a 
Ground-Water Tracer, SW Nevada-SE California." High Level Radioactive Waste Management, 
Proceedings of the Fourth Annual International Conference, Las Vegas, Nevada, April 26-30, 
1993. 1567-1572. La Grange Park, Illinois: American Nuclear Society. TIC: 208542. 
Ludwig, K.R.; Simmons, K.R.; Szabo, B.J.; Winograd, I.J.; Landwehr, J.M.; Riggs, A.C.; and 
Hoffman, R.J. 1992. "Mass-Spectrometric 230[Th]-234[U]-238[U] Dating of the Devils Hole 
Calcite Vein." Science, 258, 284-287. Washington, D.C.: American Association for the 
Advancement of Science. TIC: 237796. 
Malmberg, G.T. and Eakin, T.E. 1962. Ground-Water Appraisal of Sarcobatus Flat and Oasis 
Valley, Nye and Esmeralda Counties, Nevada. Ground-Water Resources  Reconnaissance 
Series Report 10. Carson City, Nevada: State of Nevada, Department of Conservation and

ANL-NBS-HS-000017, Rev 00 Page 135 of 156 
Natural Resources. TIC: 208666. 
Marshall, B.D. and Mahan, S.A. 1994. "Strontium Isotope Geochemistry of Soil and Playa 
Deposits Near Yucca Mountain, Nevada." High Level Radioactive Waste Management, 
Proceedings of the Fifth Annual International Conference, Las Vegas, Nevada, May 22-26, 1994. 
4, 2685-2691. La Grange Park, Illinois: American Nuclear Society. TIC: 210984. 
Marshall, B.D.; Futa, K.; and Peterman, Z.E. 1998. "Hydrologic Inferences from Strontium 
Isotopes in Port Water from the Unsaturated Zone at Yucca Mountain, Nevada." Proceedings of 
FTAM: Field Testing and Associated Modeling of Potential High-Level Nuclear Waste Geologic 
Disposal Sites, December 15-16, 1997. Bodvarsson, G.S., ed. LBNL-42520, 55-56. Berkeley, 
California: Lawrence Berkeley National Laboratory. TIC: 243019. 
Marshall, B.D.; Neymark, L.A.; Paces, J.B.; Peterman Z.E.; and Whelan, J.F. 1999. "Seepage 
Flux Conceptualized from Secondary Calcite in Lithophysal Cavities in the Topopah Spring 
Tuff, Yucca Mountain, Nevada." EOS, Transactions, American Geophysical Union 1999 Spring 
Meeting. S5. Washington, D.C.: American Geophysical Union. TIC: 246466. 
Marshall, B.D.; Paces, J.B.; Neymark, L.A.; Whelan, J.F.; and Peterman, Z.E. 1998. "Secondary 
Minerals Record Past Percolation Flux at Yucca Mountain, Nevada." High-Level Radioactive 
Waste Management, Proceedings of the Eighth International Conference, Las Vegas, Nevada, 
May 11-14, 1998. Pages 127-129. La Grange Park, Illinois: American Nuclear Society. TIC: 
237082. 
Marshall, B.D.; Peterman, Z.E.; and Stuckless, J.S. 1993. "Strontium Isotopic Evidence for a 
Higher Water Table at Yucca Mountain." High Level Radioactive Waste Management, 
Proceedings of the Fourth Annual International Conference, Las Vegas, Nevada, April 26-30, 
1993. 2, 1948-1952. La Grange Park, Illinois: American Nuclear Society. TIC: 208542. 
Marshall, B.D.; Whelan, J.F.; Peterman, Z.E.; Futa, K.; Mahan, S.A.; and Stuckless, J.S. 1992. 
"Isotopic Studies of Fracture Coatings at Yucca Mountain, Nevada, USA." Proceedings of the 
7th International Symposium on Water-Rock Interaction, Park City, Utah, July 13-18, 1992. 
Kharaka, Y.K. and Maest, A.S., eds. 1, 737-740. Rotterdam, The Netherlands: A.A. Balkema. 
TIC: 208527. 
McKinley, P.W. and Oliver, T.A. 1994. Meteorological, Stream-Discharge, and Water-Quality 
Data for 1986 through 1991 from Two Small Basins in Central Nevada. Open-File Report 93- 
651. Denver, Colorado: U.S. Geological Survey. ACC: NNA.19940114.0099. 
McKinley, P.W. and Oliver, T.A. 1995. Meteorological, Stream-Discharge, and Water-Quality 
Data for Water Year 1992 from Two Basins in Central Nevada. Open-File Report 94-456. 
Denver, Colorado: U.S. Geological Survey. ACC: MOL.19950124.0284. 
McKinley, P.W.; Long, M.P.; and Benson, L.V. 1991. Chemical Analyses of Water from Selected 
Wells and Springs in the Yucca Mountain Area, Nevada and Southeastern California. Open-File

ANL-NBS-HS-000017, Rev 00 Page 136 of 156 
Report 90-355. Denver, Colorado: U.S. Geological Survey. ACC: NNA.19901031.0004. 
Mifflin, M.D. and Wheat, M.M. 1979. Pluvial Lakes and Estimated Pluvial Climates of Nevada. 
Bulletin 94. Reno, Nevada: Nevada Bureau of Mines and Geology. TIC: 200724. 
Montazer, P.; Weeks, E.P.; Thamir, F.; Yard, S.N.; and Hofrichter, P.B. 1985. "Monitoring the 
Vadose Zone in Fractured Tuff, Yucca Mountain, Nevada." Proceedings of the NWWA 
Conference on Characterization and Monitoring of the Vadose (Unsaturated) Zone, November 
19-21, 1985, Denver, Colorado. Pages 439-469. Worthington, Ohio: National Water Well 
Association. TIC: 201366. 
Moscati, R.J. and Whelan, J.F. 1996. Origins of Secondary Silica Within Yucca Mountain, Nye 
County, Southwestern Nevada. Open-File Report 95-289. Denver, Colorado: U.S. Geological 
Survey. TIC: 225888. 
Mower, T.E.; Higgins, J.D.; Yang, I.C.; and Peters, C.A. 1994. Pore-Water Extraction from 
Unsaturated Tuff by Triaxial and One-Dimensional Compression Methods, Nevada Test Site, 
Nevada. Water-Resources Investigations Report 93-4144. Denver, Colorado: U.S. Geological 
Survey. ACC: NNA.19940621.0002. 
Moyer, T.C. and Geslin, J.K. 1995. Lithostratigraphy of the Calico Hills Formation and Prow 
Pass Tuff (Crater Flat Group) at Yucca Mountain, Nevada. Open-File Report 94-460. Denver, 
Colorado: U.S. Geological Survey. ACC: MOL.19941208.0003. 
Moyer, T.C.; Geslin, J.K.; and Flint, L.E. 1996. Stratigraphic Relations and Hydrologic 
Properties of the Paintbrush Tuff Nonwelded (PTn) Hydrologic Unit, Yucca Mountain, Nevada. 
Open-File Report 95-397. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19970204.0216. 
Muhs, D.R.; Whitney, J.W.; Shroba, R.R.; Taylor, E.M.; and Bush, C.A 1990. "Uranium-Series 
Dating of Secondary Carbonates near Yucca Mountain, Nevada: Application to Tectonic, 
Paleoclimatic, and Paleohydrologic Problems." High Level Radioactive Waste Management, 
Proceedings of the International Topical Meeting, Las Vegas, Nevada, April 8-12, 1990. 2, 924- 
929. La Grange Park, Illinois: American Nuclear Society. TIC: 202058. 
National Atmospheric Deposition Program 1996. "National Atmospheric Deposition 
Program/National Trends Network: A Descriptive Summary." Fort Collins, Colorado: National 
Atmospheric Deposition Program. Accessed August 16, 1996. TIC: 246211. 
http://nadp.nrel.colostate.edu/NADP/ documentation/progdesc.txt.html 
National Research Council 1992. Ground Water at Yucca Mountain: How High Can It Rise?, 
Final Report of the Panel on Coupled Hydrologic/Tectonic/Hydrothermal Systems at Yucca 
Mountain. Washington, D.C.: National Academy Press. TIC: 204931. 
Neymark, L.A.; Amelin, Y.V.; Paces, J.B.; and Peterman, Z.E. 1998. "U-Pb Age Evidence for

ANL-NBS-HS-000017, Rev 00 Page 137 of 156 
Long-Term Stability of the Unsaturated Zone at Yucca Mountain." High-Level Radioactive 
Waste Management, Proceedings of the Eighth International Conference, Las Vegas, Nevada, 
May 11-14, 1998. Pages 85-87. La Grange Park, Illinois: American Nuclear Society. TIC: 
237082. 
O'Brien, G.M. 1997. Analysis of Aquifer Tests Conducted in Boreholes USW WT-10, UE-25 
WT#12, and USW SD-7, 1995-96, Yucca Mountain, Nevada. Water-Resources Investigations 
Report 96-4293. Denver, Colorado: U.S. Geological Survey. ACC: MOL.19980219.0822. 
O'Neil, J.R.; Clayton, R.N.; and Mayeda, T.K. 1969. "Oxygen Isotope Fractionation in Divalent 
Metal Carbonates." The Journal of Chemical Physics, 51, (12), 5547-5558. New York, New 
York: American Institute of Physics. TIC: 216938. 
Ogard, A.E. and Kerrisk, J.F. 1984. Groundwater Chemistry Along Flow Paths Between a 
Proposed Repository Site and the Accessible Environment. LA-10188-MS. Los Alamos, New 
Mexico: Los Alamos National Laboratory. ACC: HQS.19880517.2031. 
Oliver, T. and Root, T. 1997. Hydrochemical Database for the Yucca Mountain Area, Nye 
County, Nevada. Denver, Colorado: U.S. Geological Survey. ACC: MOL.19980302.0367. 
Osmond, J.K. and Cowart, J.B. 1992. "Ground Water." Chapter 9 of Uranium-Series 
Disequilibrium: Applications to Earth, Marine, and Environmental Sciences. Invanovich, M. and 
Harmon, R.S.; eds. 2nd Edition. New York, New York: Oxford University Press. TIC: 234680. 
Paces, J.B. and Peterman, Z.E. 1999. "Isotope Hydrology of Ground-Water Flow Systems, 
Southern Nevada." Proceedings of the International Symposium on Dynamics of Fluids in 
Fractured Rocks Concepts and Recent Advances held February 10-12, 1999, LBNL-42718. 
Faybishenko, Boris, ed. 134-138. Berkeley, California: Lawrence Berkeley National Laboratory. 
TIC: 246681. 
Paces, J.B.; Forester, R.M.; Whelan, J.F.; Mahan, S.A.; Bradbury, J.P.; Quade, J.; Neymark, 
L.A.; and Kwak, L.M. 1996. Synthesis of Ground-Water Discharge Deposits Near Yucca 
Mountain. Milestone 3GQH671M. Las Vegas, Nevada: U.S. Geological Survey. ACC: 
MOL.19970205.0007. 
Paces, J.B.; Ludwig, K.R.; Peterman, Z.E.; Neymark, L.A.; and Kenneally, J.M. 1998. 
"Anomalous Groundwater 234U/238U Beneath Yucca Mountain: Evidence of Local Recharge?." 
High-Level Radioactive Waste Management, Proceedings of the Eighth International 
Conference, Las Vegas, Nevada, May 11-14, 1998. Pages 185-188. La Grange Park, Illinois: 
American Nuclear Society. TIC: 237082. 
Paces, J.B.; Mahan, S.A.; Ludwig, K.R.; Kwak, L.M.; Neymark, L.A.; Simmons, K.R.; Nealey, 
L.D.; Marshall, B.D.; and Walker, A. 1995. Progress Report on Dating Quaternary Surficial 
Deposits. Milestone 3GCH510M. Final Draft. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19960611.0220.

ANL-NBS-HS-000017, Rev 00 Page 138 of 156 
Paces, J.B.; Marshall, B.D.; Whelan, J.F.; and Neymark, L.A. 1997. "Submission of Milestone: 
SPC23FM4, Due March 14, 1997." Memorandum from J.B. Paces, B.D. Marshall, J.F. Whelan, 
and L.A. Neymark (USGS) to R.W. Craig, March 14, 1997, with attachment, "Progress Report 
on Unsaturated Zone Stable and Radiogenic Isotope Studies." ACC: MOL.19980224.0119. 
Paces, J.B.; Marshall, B.D.; Whelan, J.F.; Neymark, L.A.; and Peterman, Z.E. 1998. Summary of 
Subsurface Secondary Mineralization and Predictions of the Distribution and Isotopic Nature of 
Mineralization Along the East-West Cross Drift Alignment, Yucca Mountain, Nevada. 
SPC237M4. Denver, Colorado: U.S. Geological Survey. Submit to RPC 
Paces, J.B.; Menges, C.M.; Widmann, B.; Wesling, J.R.; Bush, C.A.; Futa, K.; Millard, H.T., Jr.; 
Maat, P.B.; and Whitney, J.W. 1994. "U-Series Disequilibrium and Thermoluminescence Ages 
of Paleosols Associated with Quaternary Faults, East Side of Yucca Mountain." High Level 
Radioactive Waste Management, Proceedings of the Fifth Annual International Conference, Las 
Vegas, Nevada, May 22-26, 1994. 4, 2391-2401. La Grange Park, Illinois: American Nuclear 
Society. TIC: 210984. 
Paces, J.B.; Newmark, L.A.; Marshall, B.D.; Whelan, J.F.; and Peterman, Z.E. 1998. "Inferences 
for Yucca Mountain Unsaturated-Zone Hydrology from Secondary Minerals." High-Level 
Radioactive Waste Management, Proceedings of the Eighth International Conference, Las 
Vegas, Nevada, May 11-14, 1998. Pages 36-39. La Grange Park, Illinois: American Nuclear 
Society. TIC: 237082. 
Paces, J.B.; Neymark, L.A.; Marshall, B.D.; Whelan, J.F.; and Peterman, Z.E. 1996. Letter 
Report: Ages and Origins of Subsurface Secondary Minerals in the Exploratory Studies Facility 
(ESF). Milestone 3GQH450M. Las Vegas, Nevada: U.S. Geological Survey. ACC: 
MOL.19970324.0052. 
Paces, J.B.; Neymark, L.A.; Whelan, J.F.; Marshall, B.D.; and Amelin, Y.V. 1999. 
"Characteristics of Unsaturated-Zone Fracture Flow Interpreted from Calcite and Opal Deposits 
at Yucca Mountain, Nevada." EOS, Transactions, American Geophysical Union 1999 Spring 
Meeting. S4. Washington, D.C.: American Geophysical Union. TIC: 246468. 
Paces, J.B.; Whelan, J.F.; Forester, R.M.; Bradbury, J.P.; Marshall, B.D.; and Mahan, S.A. 1997. 
Summary of Discharge Deposits in the Amargosa Valley. Milestone SPC333M4 . Denver, 
Colorado: U.S. Geological Survey. ACC: MOL.19981104.0151. 
Parrington, J.R.; Knox, H.D.; Breneman, S.L.; Baum, E.M.; and Feiner, F. 1996. Nuclides and 
Isotopes, Chart of the Nuclides. 15th Edition. San Jose, California: General Electric Company 
and KAPL, Inc. TIC: 233705. 
Perfect, D.L.; Faunt, C.C.; Steinkampf, W.C.; and Turner, A.K. 1995. Hydrochemical Data Base 
for the Death Valley Region, California and Nevada. Open-File Report 94-305. Denver, 
Colorado: U.S. Geological Survey. ACC: MOL.19940718.0001.

ANL-NBS-HS-000017, Rev 00 Page 139 of 156 
Peterman, Z.E. and Patterson, G. 1998. "Isotopes Aid in Understanding the Yucca Mountain 
Flow System." High-Level Radioactive Waste Management, Proceedings of the Eighth 
International Conference, Las Vegas, Nevada, May 11-14, 1998. Pages 182-184. La Grange 
Park, Illinois: American Nuclear Society. TIC: 237082. 
Peterman, Z.E. and Stuckless, J.S. 1993. "Isotopic Evidence of Complex Ground-Water Flow at 
Yucca Mountain, Nevada, USA." High Level Radioactive Waste Management, Proceedings of 
the Fourth Annual International Conference, Las Vegas, Nevada, April 26-30, 1993. 2, 1559- 
1566. La Grange Park, Illinois: American Nuclear Society. TIC: 208542. 
Peterman, Z.E.; Stuckless, J.S.; Marshall, B.D.; Mahan, S.A.; and Futa, K. 1992. "Strontium 
Isotope Geochemistry of Calcite Fracture Fillings in Deep Core, Yucca Mountain, Nevada -- A 
Progress Report." High Level Radioactive Waste Management, Proceedings of the Third 
International Conference, Las Vegas, Nevada, April 12-16, 1992. 2, 1582-1586. La Grange Park, 
Illinois: American Nuclear Society. TIC: 204231. 
Phillips, F.M. 1994. "Environmental Tracers for Water Movement in Desert Soils of the 
American Southwest." Soil Science Society of America Journal, 58, 15-24. Madison, Wisconsin: 
Soil Science Society of America. TIC: 240651. 
Phillips, F.M. 2000. "Chlorine-36." Chapter 10 of Environmental Tracers In Subsurface 
Hydrology. Cook, P.G. and Herczeg, A.L. eds. Norwell, Massachusetts: Kluwer Academic 
Publishers. TIC: 247021. 
Plummer, M.A.; Phillips, F.M.; Fabryka-Martin, J.; Turin, H.J.; Wigand, P.E.; and Sharma, P. 
1997. "Chlorine-36 in Fossil Rat Urine: An Archive of Cosmogenic Nuclide Deposition During 
the Past 40,000 Years." Science, 277, 538-541. Washington, D.C.: American Association for the 
Advancement of Science. TIC: 237425. 
Quade, J.; Cerling, T.E.; and Bowman, J.R. 1989. "Systematic Variations in the Carbon and 
Oxygen Isotopic Composition of Pedogenic Carbonate Along Elevation Transects in the 
Southern Great Basin, United States." Geological Society of America Bulletin, 101, 464-475. 
Boulder, Colorado: Geological Society of America. TIC: 224797. 
Quade, J.; Mifflin, M.D.; Pratt, W.L.; McCoy, W.; and Burckle, L. 1995. "Fossil Spring Deposits 
in the Southern Great Basin and Their Implications for Changes in Water-Table Levels Near 
Yucca Mountain, Nevada, During Quaternary Time." Geological Society of America Bulletin, 
107, (2), 213-230. Boulder, Colorado: Geological Society of America. TIC: 234256. 
Rattray, G.W.; Striegl, R.G.; and Yang, I.C. 1995. Adsorption of Sulfur Hexafluoride onto 
Crushed Tuffs from the Yucca Mountain Area, Nye County, Nevada. Water-Resources 
Investigations Report 95-4057. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19970331.0042.

ANL-NBS-HS-000017, Rev 00 Page 140 of 156 
Rautman, C.A. and Engstrom, D.A. 1996. Geology of the USW SD-12 Drill Hole Yucca 
Mountain, Nevada. SAND96-1368. Albuquerque, New Mexico: Sandia National Laboratories. 
ACC: MOL.19970613.0101. 
Rautman, C.A. and Engstrom, D.A. 1996. Geology of the USW SD-7 Drill Hole Yucca Mountain, 
Nevada. SAND96-1474. Albuquerque, New Mexico: Sandia National Laboratories. ACC: 
MOL.19971218.0442. 
Roedder, E. 1970. "Application of an Improved Crushing Microscope Stage to Studies of the 
Gases in Fluid Inclusions." Schweizerische Mineralogische und Petrographische Mitteilungen, 
50, (1), 41-58. Zurich, Switzerland: Institut fur Mineralogie und Petrographie. TIC: 243697. 
Roedder, E. 1984. Fluid Inclusions. Reviews in Mineralogy, Volume 12. Washington, D.C.: 
Mineralogical Society of America. TIC: 236874. 
Roedder, E. and Whelan, J.F. 1998. "Ascending or Descending Water Flow Through Yucca 
Mountain Tuffs? - Fluid Inclusion Evidence." PACROFI VII, Pan-American Conference on 
Research On Fluid Inclusions, Las Vegas, Nevada, June 1-4, 1998. Open-File Report 98-4, 56. 
Reno, Nevada: Nevada Bureau of Mines and Geology. TIC: 247943. 
Roedder, E.; Whelan, J.F.; and Vaniman, D.T. 1993. "Environment of Formation of Calcite 
Veins from Yucca Mountain, Nevada, Tuffs as Evidenced by Fluid Inclusion Crushing Studies." 
Abstracts with Programs, Geological Society of America, 25, (6), A-184. Boulder, Colorado: 
Geological Society of America. On Order Library Tracking Number-248233 
Roedder, E.; Whelan, J.F.; and Vaniman, D.T. 1994. "Fluid Inclusion Studies of Calcite Veins 
from Yucca Mountain, Nevada, Tuffs: Environment of Formation." High Level Radioactive 
Waste Management, Proceedings of the Fifth Annual International Conference, Las Vegas, 
Nevada, May 22-26, 1994. 4. 1854-1860. La Grange Park, Illinois: American Nuclear Society. 
TIC: 210984. 
Rojstaczer, S. 1999. "Stress Dependent Permeability and Its Political Consequences at Yucca 
Mountain." EOS, Transactions, American Geophysical Union 1999 Spring Meeting. 80, S4. 
Washington, D.C.: American Geophysical Union. TIC: 246513. 
Rousseau, J.P.; Kwicklis, E.M.; and Gillies, D.C., eds. 1999. Hydrogeology of the Unsaturated 
Zone, North Ramp Area of the Exploratory Studies Facility, Yucca Mountain, Nevada. Water- 
Resources Investigations Report 98-4050. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19990419.0335. 
Rousseau, J.P.; Loskot, C.L.; Thamir, F.; and Lu, N. 1997. Results of Borehole Monitoring in the 
Unsaturated Zone Within the Main Drift Area of the Exploratory Studies Facility, Yucca 
Mountain, Nevada. Milestone SPH22M3. Denver, Colorado: U.S. Geological Survey. ACC: 
MOL.19970626.0351.

ANL-NBS-HS-000017, Rev 00 Page 141 of 156 
Sass, J.H.; Lachenbruch, A.H.; and Mase, C.W. 1980. Analysis of Thermal Data from Drill 
Holes UE25a-3 and UE25a-1, Calico Hills and Yucca Mountain, Nevada Test Site. Open-File 
Report 80-826. Denver, Colorado: U.S. Geological Survey. ACC: HQS.19880517.1429. 
Sass, J.H.; Lachenbruch, A.H.; Dudley, W.W., Jr.; Priest, S.S.; and Munroe, R.J. 1988. 
Temperature, Thermal Conductivity, and Heat Flow Near Yucca Mountain, Nevada: Some 
Tectonic and Hydrologic Implications. Open-File Report 87-649. Denver, Colorado: U.S. 
Geological Survey. ACC: MOL.19971027.0303. 
Savard, C.S. 1995. "Ground-Water Recharge from Small to Large Streamflow Events During El 
Nio Periods Under Fortymile Wash near Yucca Mountain, Nevada." American Geophysical 
Union 1995 Fall Meeting December 11-15, 1995 San Francisco, California. F241. Washington, 
D.C.: American Geophysical Union. TIC: 237433. 
Savard, C.S. 1996. Selected Hydrologic Data from Fortymile Wash in the Yucca Mountain Area, 
Nevada, Water Years 1993-94. Open-File Report 95-709. Denver, Colorado: U.S. Geological 
Survey. ACC: MOL.19980226.0548. 
Savard, C.S. 1998. Estimated Ground-Water Recharge from Streamflow in Fortymile Wash Near 
Yucca Mountain, Nevada. Water-Resources Investigations Report 97-4273. Denver, Colorado: 
U.S. Geological Survey. TIC: 236848. 
Sawyer, D.A.; Fleck, R.J.; Lanphere, M.A.; Warren, R.G.; Broxton, D.E.; and Hudson, M.R. 
1994. "Episodic Caldera Volcanism in the Miocene Southwestern Nevada Volcanic Field: 
Revised Stratigraphic Framework, 40Ar/39Ar Geochronology, and Implications for Magmatism 
and Extension." Geological Society of America Bulletin, 106, (10), 1304-1318. Boulder, 
Colorado: Geological Society of America. TIC: 222523. 
Scanlon, B.R. 1991. "Evaluation of Moisture Flux from Chloride Data in Desert Soils." Journal 
of Hydrology, 128, 137-156. Amsterdam, The Netherlands: Elsevier Science. TIC: 224126. 
Scanlon, B.R.; Tyler, S.W.; and Wierenga, P.J. 1997. "Hydrologic Issues In Arid, Unsaturated 
Systems and Implications for Contaminant Transport." Reviews of Geophysics, 35, (4), 461-490. 
Washington, D.C.: American Geophysical Union. TIC: 246881. 
Sharma, P.; Kubik, P.W.; Fehn, U.; Gove, H.E.; Nishiizumi, K.; and Elmore, D. 1990. 
"Development of (36)Cl Standards for AMS." Nuclear Instruments and Methods in Physics 
Research, B52, 410-415. Amsterdam, The Netherlands: Elsevier Science Publishers. TIC: 
224755. 
Spaulding, W.G. 1985. Vegetation and Climates of the Last 45,000 Years in the Vicinity of the 
Nevada Test Site, South-Central Nevada. Professional Paper 1329. Washington, D.C.: U.S. 
Geological Survey. TIC: 203210. 
Steiger, R.H. and Jager, E. 1977. "Subcommission on Geochronology: Convention on the Use of

ANL-NBS-HS-000017, Rev 00 Page 142 of 156 
Decay Constants in Geo- and Cosmochronology." Earth and Planetary Science Letters, 36, 359- 
362. Amsterdam, The Netherlands: Elsevier Scientific Publishing Company. TIC: 236817. 
Stuckless, J.S. 1991. "An Evaluation of Evidence Pertaining to the Origin of Vein Deposits 
Exposed in Trench 14, Nevada Test Site, Nevada." High Level Radioactive Waste Management, 
Proceedings of the Second Annual International Conference, Las Vegas, Nevada, April 28-May 
3, 1991. 2, 1429-1438. La Grange Park, Illinois: American Nuclear Society. TIC: 204272. 
Stuckless, J.S.; Marshall, B.D.; Vaniman, D.T.; Dudley, W.W.; Peterman, Z.E.; Paces, J.B.; 
Whelan, J.F.; Taylor, E.M.; Forester, R.M.; and O'Leary, D.W. 1998. "Comments on Overview 
of Calcite/Opal Deposits at or Near the Proposed High-Level Nuclear Waste Site, Yucca 
Mountain, Nevada, USA: Pedogenic, Hypogene, or Both by C.A. Hill, Y.V. Dublansky, R.S. 
Harmon, and C.M. Schluter." Environmental Geology, 34, (1), 70-78. New York, New York: 
Springer-Verlag. TIC: 238097. 
Stuckless, J.S.; Peterman, Z.E.; and Muhs, D.R. 1991. "U and Sr Isotopes in Ground Water and 
Calcite, Yucca Mountain, Nevada: Evidence Against Upwelling Water." Science, 254, 551-554. 
Washington, D.C.: American Association for the Advancement of Science. TIC: 224423. 
Szabo, B.J. and Kyser, T.K. 1990. "Ages and Stable-Isotope Compositions of Secondary Calcite 
and Opal in Drill Cores from Tertiary Volcanic Rocks of the Yucca Mountain Area, Nevada." 
Geological Society of America Bulletin, 102, 1714-1719. Boulder, Colorado: Geological Society 
of America. TIC: 221927. 
Taylor, E.M. and Huckins, H.E. 1995. Lithology, Fault Displacement, and Origin of Secondary 
Calcium Carbonate and Opaline Silica at Trenches 14 and 14d on the Bow Ridge Fault at Exile 
Hill, Nye County, Nevada. Open-File Report 93-477. Denver, Colorado: U.S. Geological Survey. 
ACC: MOL.19940906.0001. 
Thorstenson, D.C.; Weeks, E.P.; Haas, H.; Busenberg, E.; Plummer, L.N.; and Peters, C.A. 1998. 
"Chemistry of Unsaturated Zone Gases Sampled in Open Boreholes at the Crest of Yucca 
Mountain, Nevada: Data and Basic Concepts of Chemical and Physical Processes in the 
Mountain." Water Resources Research, 34, (6), 1507-1529. Washington, D.C.: American 
Geophysical Union. TIC: 246315. 
Thorstenson, D.C.; Weeks, E.P.; Hass, H.; and Woodward, J.C. 1990. "Physical and Chemical 
Characteristic of Topographically Affected Airflow in an Open Borehole at Yucca Mountain, 
Nevada." Focus 89, Proceedings of the Topical Meeting on Nuclear Waste Isolation in the 
Unsaturated Zone, Las Vegas, Nevada, September 17-21, 1989. 256-270. La Grange Park, 
Illinois: American Nuclear Society. TIC: 216833. 
Tokunaga, T.K. and Wan, J. 1997. "Water Film Flow along Fracture Surfaces of Porous Rock." 
Water Resources Research, 33, (6), 1287-1295. Washington, D.C.: American Geophysical 
Union. TIC: 242739.

ANL-NBS-HS-000017, Rev 00 Page 143 of 156 
Triay, I.R.; Meijer, A.; Conca, J.L.; Kung, K.S.; Rundberg, R.S.; Strietelmeier, B.A.; Tait, C.D.; 
Clark, D.L.; Neu, M.P.; and Hobart, D.E. 1997. Summary and Synthesis Report on Radionuclide 
Retardation for the Yucca Mountain Site Characterization Project. LA-13262-MS. Los Alamos, 
New Mexico: Los Alamos National Laboratory. ACC: MOL.19971210.0177. 
Vaniman, D.T. and Whelan, J.F. 1994. "Inferences of Paleoenvironment from Petrographic, 
Chemical and Stable-Isotope Studies of Calcretes and Fracture Calcites." High Level Radioactive 
Waste Management, Proceedings of the Fifth Annual International Conference, Las Vegas, 
Nevada, May 22-26, 1994. 4, 2730-2737. La Grange Park, Illinois: American Nuclear Society. 
TIC: 210984. 
Vaniman, D.T.; Carey, J.W.; Bish, D.L.; and Chipera, S.J. 1999. "Cation Profiles Generated by 
Downward Transport Into Unsaturated Zeolitic Strata at Yucca Mountain, Nevada." EOS, 
Transactions, American Geophysical Union 1999 Spring Meeting. S5. Washington, D.C.: 
American Geophysical Union. TIC: 246464. 
Vaniman, D.T.; Chipera, S.J.; and Bish, D.L. 1994. "Pedogenesis of Siliceous Calcretes at Yucca 
Mountain, Nevada." Geoderma, 63, 1-17. Amsterdam, The Netherlands: Elsevier Science B.V. 
TIC: 212060. 
Walker, G.E. and Eakin, T.E. 1963. Geology and Ground Water of Amargosa Desert, Nevada 
California. Ground-Water Resources  Reconnaissance Series Report 14. Carson City, Nevada: 
State of Nevada, Department of Conservation and Natural Resources. TIC: 208665. 
Whelan, J.F. and Moscati, R.J. 1998. "9 M.Y. Record of Southern Nevada Climate from Yucca 
Mountain Secondary Minerals." High-Level Radioactive Waste Management, Proceedings of the 
Eighth International Conference, Las Vegas, Nevada, May 11-14, 1998. Pages 12-15. La Grange 
Park, Illinois: American Nuclear Society. TIC: 237082. 
Whelan, J.F. and Stuckless, J.S. 1990. "Reconnaissance [Delta]13C and [Delta]18O Data from 
Trench 14, Busted Butte, and Drill Hole G-4, Yucca Mountain, Nevada Test Site." High Level 
Radioactive Waste Management, Proceedings of the International Topical Meeting, Las Vegas, 
Nevada, April 8-12, 1990. 2, 930-933. La Grange Park, Illinois: American Nuclear Society. TIC: 
202058. 
Whelan, J.F. and Stuckless, J.S. 1992. "Paleohydrologic Implications of the Stable Isotopic 
Composition of Secondary Calcite Within the Tertiary Volcanic Rocks of Yucca Mountain, 
Nevada." High Level Radioactive Waste Management, Proceedings of the Third Annual 
International Conference, Las Vegas, Nevada, April 12-16, 1992. 2, 1572-1581. La Grange Park, 
Illinois: American Nuclear Society. TIC: 204231. 
Whelan, J.F.; Moscati, R.J.; Allerton, S.B.M.; and Marshall, B.D. 1998. Applications of Isotope 
Geochemistry to the Reconstruction of Yucca Mountain, Nevada, PaleohydrologyStatus of 
Investigations: June 1996. Open-File Report 98-83. Denver, Colorado: U.S. Geological Survey. 
ACC: MOL.19981012.0740.

ANL-NBS-HS-000017, Rev 00 Page 144 of 156 
Whelan, J.F.; Paces, J.B.; Moscati, R.J.; Neymark, L.A.; Marshall, B.D.; and Peterman, Z.E. 
1999. "Paragenesis and Oxygen Isotopes of Calcite in the Unsaturated Zone of Yucca Mountain, 
Nevada: Evidence of an Early Thermal Event." EOS, Transactions, American Geophysical Union 
1999 Spring Meeting. S8. Washington, D.C.: American Geophysical Union. TIC: 246462. 
Whelan, J.F.; Vaniman, D.T.; Stuckless, J.S.; and Moscati, R.J. 1994. "Paleoclimatic and 
Paleohydrologic Records from Secondary Calcite: Yucca Mountain, Nevada." High Level 
Radioactive Waste Management, Proceedings of the Fifth Annual International Conference, Las 
Vegas, Nevada, May 22-26, 1994. 4, 27382745. La Grange Park, Illinois: American Nuclear 
Society. TIC: 210984. 
White, A.F. and Chuma, N.J. 1987. "Carbon and Isotopic Mass Balance Models of Oasis Valley - 
Fortymile Canyon Groundwater Basin, Southern Nevada." Water Resources Research , 23, (4), 
571-582. Washington, D.C.: American Geophysical Union. TIC: 237579. 
White, A.F.; Claassen, H.C.; and Benson, L.V. 1980. "The Effect of Dissolution of Volcanic 
Glass on the Water Chemistry in a Tuffaceous Aquifer, Rainier Mesa, Nevada." Geochemistry of 
Water. Geologic Survey Water-Supply Paper 1535-Q. Washington, D.C.: U.S. Government 
Printing Office. TIC: 221391. 
Whitfield, M.S. 1986. "Vacuum Drilling of Unsaturated Tuffs at a Potential Radioactive-Waste 
Repository, Yucca Mountain, Nevada." Proceedings of the NWWA Conference on 
Characterization and Monitoring of the Vadose (Unsaturated) Zone, Denver, Colorado, 
November 19-21, 1985. 413-423. Worthington, Ohio: National Water Well Association. TIC: 
222624. 
Whitfield, M.S.; Thordarson, W.; Hammermeister, D.P.; and Warner, J.B. 1990. Drilling and 
Geohydrologic Data for Test Hole USW UZ-1, Yucca Mountain, Nye County, Nevada. Open-File 
Report 90-354. Denver, Colorado: U.S. Geological Survey. ACC: NNA.19900622.0450. 
Winchester, J.W. and Duce, R.A. 1967. "The Global Distribution of Iodine, Bromine, and 
Chlorine in Marine Aerosols." Naturwissenschaften, 54, (5), 110-113. New York, New York: 
Springer-Verlag. TIC: 226930. 
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. 
Wolfsberg, A.V.; Fabryka-Martin, J.T.; Roemer, G.J.C.; and Robinson, B.A. 1998. "Modeling 
Flow and Transport Pathways to the Potential Repository Horizon at Yucca Mountain." High- 
Level Radioactive Waste Management, Proceedings of the Eighth International Conference, Las 
Vegas, Nevada May 11-14, 1998. Pages 81-84. La Grange Park, Illinois: American Nuclear 
Society. TIC: 237082.

ANL-NBS-HS-000017, Rev 00 Page 145 of 156 
Yang, I.C. 1992. "Flow and Transport through Unsaturated Rock  Data from Two Test Holes, 
Yucca Mountain, Nevada." High Level Radioactive Waste Management, Proceedings of the 
Third International Conference, Las Vegas, Nevada, April 12-16, 1992. 1, 732-737. La Grange 
Park, Illinois: American Nuclear Society. TIC: 204231. 
Yang, I.C.; Davis, G.S.; and Sayre, T.M. 1990. "Comparison of Pore-Water Extraction by 
Triaxial Compression and High-Speed Centrifugation Methods." Proceedings of Conference on 
Minimizing Risk to the Hydrological Environment, American Institute of Hydrology. Pages 250- 
259. Dubuque, Iowa: American Institute of Hydrology. TIC: 224435. 
Yang, I.C.; Peters, C.A.; and Thorstenson, D.C. 1993. "Carbon Isotopic Data from Test Hole 
USW UZ-1 Yucca Mountain, Nevada." High Level Radioactive Waste Management, 
Proceedings of the Fourth Annual International Conference, Las Vegas, Nevada, April 26-30, 
1993. 401-406. La Grange Park, Illinois: American Nuclear Society. TIC: 208542. 
Yang, I.C.; Rattray, G.W.; and Scofield, K.M. 1998. "Carbon and Hydrogen Isotopic 
Compositions for Pore Water Extracted from Cores at Yucca Mountain, Nevada." High Level 
Radioactive Waste Management, Proceedings of the Eighth International Conference, Las 
Vegas, Nevada, May 11-14, 1998. Pages 27-32. La Grange Park, Illinois: American Nuclear 
Society. TIC: 237082. 
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.; Turner, A.K.; Sayre, T.M.; and Montazer, P. 1988. Triaxial-Compression Extraction 
of Pore Water from Unsaturated Tuff, Yucca Mountain, Nevada. Water-Resources Investigations 
Report 88-4189. Denver, Colorado: U.S. Geological Survey. ACC: NNA.19890309.0161. 
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. 
8.2 CODES, STANDARDS, REGULATIONS AND PROCEDURES 
AP-3.10Q, Rev. 2, ICN 0. Analysis and Models. Washington, D. C.: U.S. Department of 
Energy, Office of Civilian Radioactive Waste Management. ACC: MOL.20000217.0246. 
DOE (U.S. Department of Energy) 2000. Quality Assurance Requirements and Description. 
DOE/RW-0333P, Rev. 9. Washington, D.C.: U.S. Department of Energy, Office of Civilian 
Radioactive Waste Management. ACC: MOL.19991028.0012. 
QAP-2-0, Rev. 5. Conduct of Activities. Las Vegas, Nevada: CRWMS M&O. ACC: 
MOL.19980826.0209.

ANL-NBS-HS-000017, Rev 00 Page 146 of 156 
8.3 SOFTWARE 
TECSOFT, Inc 1997. Software Code: PLOTCHEM - WIN. 7.8. Amaganestt, New York: 
TECSoft. 
8.4 SOURCE DATA, LISTED BY DATA TRACKING NUMBER (DTN) 
GS90090123344G.001. Triaxial-Compression Extraction of Pore Water From Unsaturated Tuff, 
Yucca Mountain, Nevada. Submittal date: 09/17/1990. Submit to RPC 
GS910508315215.005. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 5/3/89 to 5/9/91. Submittal date: 05/15/1991. 
GS920208315215.008. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 5/10/91 to 2/28/92. Submittal date: 02/28/1992. 
GS920208315215.012. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 4/8/88 to 5/2/89. Submittal date: 02/28/1992. 
GS920408312272.002. Preliminary Isotopic Data for Tritium, Chemical Composition, Carbon- 
14, Carbon-13, Oxygen-18, and Deuterium in Pore Water in Cores Obtained from Two Test 
Holes in Pagany Wash, a Dry Channel on the East Side of Yucca Mountain. Submittal date: 
04/29/1992. 
GS920408312321.003. Chemical Composition of Groundwater in the Yucca Mountain Area, 
Nevada 1971 - 1984. Submittal date: 04/24/1987. 
GS920708315215.017. Carbonate Carbon and Oxygen Isotope Analyses of Samples from Trench 
14, Busted Butte, and Drill Hole USW G-4. Submittal date: 07/15/1992. 
GS920908315214.032. Isotope Content and Temperature of Precipitation in Southern Nevada, 
August 1983  August 1986. Submittal date: 01/07/1993. 
GS930108315213.004. Uranium Isotopic Analyses of Groundwaters from SW Nevada  SE 
California. Submittal date: 01/21/1993. 
GS930108315214.003. Chemical Analysis of Surface-Water, Spring, and Precipitation Samples 
Collected from Kawich and Stewart Creek Basins from September, 1984, to April, 1989. 
Submittal date: 01/07/1993. 
GS930108315214.004. Chemical Analysis of Surface-Water, Spring, and Precipitation Samples 
Collected from Kawich and Stewart Creek Basins from May, 1989, to September, 1991. 
Submittal date: 11/18/1992. 
GS930308312323.001. Chemical Composition of Groundwater and the Locations of Permeable 
Zones in the Yucca Mountain Area. Submittal date: 03/05/1993.

ANL-NBS-HS-000017, Rev 00 Page 147 of 156 
GS930408312271.014. Analysis Of CO2 Concentration Of Syringe Samples Taken During USW 
UZ-1 Borehole Gas Sampling, May, 1989, Thru Jan., 1991. Submittal date: 03/30/1993. 
GS930508312271.021. Analysis of Gaseous-Phase Stable and Radioactive Isotopes in the 
Unsaturated Zone, Yucca Mountain, Nevada. Submittal date: 04/30/1993. 
GS930908315214.030. Chemical Analysis of Surface-Water, Spring, and Precipitation Samples 
Collected from Kawich and Stewart Creek Basins from February, 1992, to September, 1992. 
Submittal date: 09/30/1993. 
GS930908315215.027. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 3/2/92 to 11/18/92. Submittal date: 09/29/1993. 
GS931008315215.029. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 11/19/92 to 12/3/93. Submittal date: 12/08/1993. 
GS931008315215.030. Carbon and Oxygen Isotope Analyses of Cavity- and Fracture-Coating 
Calcite and Soil Carbonate from Drill Holes and Outcrops, May '89 - Oct. '93. Submittal date: 
10/26/1993. 
GS931108315215.033. Fluid Inclusion Temperatures from Drill Holes USW G-1 and G-2, Oct. 
92 - Sept. 93. Submittal date: 11/17/1993. 
GS931108315215.034. Carbon 14 Ages From Drill Holes USW G-1, G-2, GU-3, and G-4, April 
92 - Jan. 93. Submittal date: 11/17/1993. 
GS931108315215.035. Oxygen Stable Isotope Analyses of Opal From Drill Holes and Outcrops, 
June 92  Aug. 92. Submittal date: 11/17/1993. 
GS940208314211.002. Table of Contacts in Boreholes USW UZ-N62. Submittal date: 
02/01/1994. 
GS940208314211.004. Table of Contacts in Borehole USW UZ-N27. Submittal date: 
02/10/1994. 
GS940208314211.008. Table of Contacts in Boreholes USW UZ-N57, UZ-N58, UZ-N59, and 
UZ-N61. Submittal date: 02/10/1994. 
GS940308312133.002. Water Quality Data for Samples Taken in Fortymile Wash, Nevada, 
During the 1993 Water Year. Submittal date: 03/02/1994. 
GS940308314211.011. Table of Contacts for the Tiva Canyon Tuff in Borehole USW UZ-N38. 
Submittal date: 03/10/1994.

ANL-NBS-HS-000017, Rev 00 Page 148 of 156 
GS940308314211.016. Table of Contacts for the Tiva Canyon Tuff in Borehole USW UZ-N64. 
Submittal date: 03/28/1994. 
GS940308314211.018. Table of Contacts for the Tiva Canyon Tuff in Borehole USW UZ-N36. 
Submittal date: 03/28/1994. 
GS940308314211.019. Table of Contacts for the Tiva Canyon Tuff in Boreholes USW UZ-N15, 
USW UZ-N16, and USW UZ-N17. Submittal date: 03/28/1994. 
GS940608315215.006. Oxygen Stable Isotope Analyses of Opal From Drill Holes and Outcrop, 
June 1994. Submittal date: 06/27/1994. 
GS941108315215.010. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 12/6/93 to 8/17/94. Submittal date: 11/30/1994. 
GS941208312261.008. Carbon Dioxide, Methane, Carbon 14, and Carbon 13/12 Data from 
USW NRG-6 and USW NRG-7 for May and June 1994; and Carbon 14 Data from USW Wells 
NRG#5, UZ-6S, UZ-N27, UZ-N62, UZ-N64, UZ-N93, UZ-N94, and UZ-N95 from March 1994. 
Submittal date: 12/16/1994. 
GS950408318523.001. Temperature, Thermal Conductivity, and Heat Flow Near Yucca 
Mountain, Nevada. Submittal date: 04/21/1995. 
GS950608312272.001. Chemical Data for Pore Water from Tuff Cores of USW NRG-6, 
NRG7/7a, UZ-14 and UZ-N55, and UE-25 UZ#16. Submittal date: 05/30/1995. 
GS950608315215.002. Strontium Isotope Ratios and Isotope Dilution Data for Rubidium and 
Strontium Collected 9/7/94 to 5/4/95. Submittal date: 05/12/1995. 
GS950708315131.001. Woodrat Midden and Pollen Core Radiocarbon (C14). Submittal date: 
07/21/1995. 
GS950708315131.002. Woodrat Midden Contents Comprised of Raw Counts of Plant 
Macrofossils from Northern and Southern Nevada. Submittal date: 07/21/1995. 
GS950708315131.003. Woodrat Midden Age Data in Radiocarbon Years Before Present. 
Submittal date: 07/21/1995. 
GS950708315215.005. Delta 13C and Delta 18O Stable Isotope Data From the Yucca Mountain 
Region, July 1992 to September 1994. Submittal date: 07/17/1995. Submit to RPC 
GS950708315215.006. Delta 13C and Delta 18O Stable Isotope Data From Non-Qualified 
Borehole Core of the Yucca Mountain Region, July 1988 to September 1994. Submittal date: 
07/17/1995.

ANL-NBS-HS-000017, Rev 00 Page 149 of 156 
GS950808312261.004. Carbon 14 Results from Gas Samples Collected in February and March 
1995. Submittal date: 08/29/1995. 
GS960208312261.002. Carbon-14 Results from Gas Samples Collected; Carbon Dioxide, 
Carbon 13/12, Oxygen 18/16, and Carbon-14 Results from Gas Samples Collected; and Carbon 
Dioxide, Methane, Carbon 13/12 and Oxygen 18/16 Results from Gas Samples Collected. 
Submittal date: 02/16/1996. 
GS960208315215.001. Uranium and Thorium Isotope Data Determined by Mass Spectrometry 
for Dating Sub-Surface Secondary Deposits from ESF and Drill Hole Locations. Submittal date: 
02/21/1996. 
GS960308312133.001. Water Quality Data from Samples Collected in the Fortymile Wash 
Watershed, Yucca Mountain Area, Nevada, Water Year 1995. Submittal date: 03/27/1996. 
GS960308315131.001. Woodrat Midden Radiocarbon (C14) . Submittal date: 03/07/1996. 
GS960408315215.002. Carbon and Oxygen Stable Isotope Analyses of Calcite From Drill Holes 
and the Exploratory Studies Facility (ESF), February 1995 to April 1996. Submittal date: 
04/18/1996. 
GS960408315215.003. Oxygen Stable Isotope Analyses of Opal from Drill Holes, The 
Exploratory Studies Facility (ESF), and Outcrop, April 1996. Submittal date: 04/18/1996. 
GS960708314224.008. Provisional Results: Geotechnical Data for Station 30 + 00 to Station 35 
+ 00, Main Drift of the ESF. Submittal date: 08/05/1996. 
GS960708314224.010. Provisional Results: Geotechnical Data for Station 40 + 00 to Station 45 
+ 00, Main Drift of the ESF. Submittal date: 08/05/1996. 
GS960808314224.011. Provisional Results: Geotechnical Data for Station 35+00 to Station 
40+00, Main Drift of the ESF. Submittal date: 08/29/1996. 
GS960808315215.006. 14-Carbon Analyses of Calcite from Exploratory Studies Facility (ESF) 
Fracture Coatings, 12/95 - 2/96. Submittal date: 08/21/1996. 
GS960908312211.003. Conceptual and Numerical Model of Infiltration at Yucca Mountain, 
Nevada. Submittal date: 09/12/1996. 
GS960908314224.014. Provisional Results - ESF Main Drift, Station 50+00 to Station 55+00. 
Submittal date: 09/09/1996. 
GS960908315215.010. Carbon and Oxygen Stable Isotope KIEL Analyses of Calcite from the 
ESF and USW-G2, October 1994 to June 1996. Submittal date: September 13, 1996.

ANL-NBS-HS-000017, Rev 00 Page 150 of 156 
GS960908315215.013. Uranium and Thorium Isotope Data for Waters Collected Between 
January 1994 and September 1996. Submittal date: 09/25/1996. 
GS960908315215.014. Uranium and Thorium Isotope Data for ESF Secondary Minerals 
Collected Between March 1996 and July 1996. Submittal date: 09/25/1996. 
GS961108312261.006. Gas Chemistry, ESF Alcoves 2 and 3, 11/95  4/96; Water Chemistry, 
Alcove 2 (Tritium), Alcove 3, and ESF Tunnel; and Pneumatic Pressure Response from 
Boreholes in Exploratory Studies Facility Alcoves 2 and 3, 10/95  5/96. Submittal date: 
11/12/1996. 
GS961108312271.002. Chemical and Isotopic Composition of Pore Water and Pore Gas, 1994 
96, from Boreholes USW UZ-1, USW UZ-14, UE-25 UZ#16, USW NRG-6, USW NRG-7A, 
USW SD-7, USW SD-9, ESF-AL#3-RBT#1, and ESF-AL#3-RBT#4, and ESF Rubble. 
Submittal date: 12/04/1996. 
GS970108312232.001. Sulfur Hexafluoride Gas Chemistry Data and Shut-in Pressure 
Monitoring Data from the Radial Boreholes in Alcove 1 of the ESF, 4/95; and Tritium Data from 
Borehole ESF-AL#2-HPF#1 in Alcove 2. Submittal date: 01/09/1997. 
GS970208312271.002. Unsaturated Zone Hydrochemistry Data, 10-1-96 to 1-31-97, Including 
Chemical Composition and Carbon, Oxygen and Hydrogen Isotopic Composition. Submittal 
date: 02/21/1997. 
GS970208314224.003. Geotechnical Data for Station 60+00 to Station 65+00, South Ramp of 
the ESF. Submittal date: 02/12/1997. 
GS970208315215.001. Uranium and Thorium Isotope Data Collected Between September 1996 
and February 1997 from Secondary Minerals in the ESF. Submittal date: 03/06/1997. 
GS970208315215.002. Uranium-Lead Isotope Data for ESF Secondary Minerals from Sep. 96 to 
Feb. 97. Submittal date: 03/06/1997. 
GS970208315215.003. 14-Carbon Analyses of Calcite from ESF Fracture Coatings, February 
1997. Submittal date: 02/27/1997. 
GS970208315215.004. Carbon and Oxygen Stable Isotope 252 Analyses of Calcite from the ESF 
and USW G-2 and SD-7, and UE-25 A#7, November 1996  January 1997. Submittal date: 
02/27/1997. 
GS970208315215.005. Carbon and Oxygen Stable Isotope Kiel Analyses of Calcite from the 
ESF and USW G-1, G-2 and G-4, UE-25 A#1, USW NRG-6 and NRG-7/7A, and UE-25 UZ#16, 
April 1996  January 1997. Submittal date: 02/27/1997. 
GS970283122410.002. Gas and Water Chemistry Data from Samples Collected at Boreholes

ANL-NBS-HS-000017, Rev 00 Page 151 of 156 
UE-25 NRG#5 and USW SD-7 on Yucca Mountain, Alcove 5, and Borehole ESF-NADGTB#
1A in Alcove 6, ESF, between 8-11-96 and 1-14-97. Submittal date: 02/21/1997. 
GS970508312272.001. Uranium Isotopic Data from ESF Alcove 5 Pore-Water Leaches and UZ 
Heater-Test Water Collected Between April and May, 1997. Submittal date: 05/30/1997. 
GS970608312272.005. Tritium Data from ESF Alcove #5 Cores for Single Heater Test. 
Submittal date: 06/06/1997. 
GS970708312323.001. Delta 18-O and Delta D Stable Isotope Analyses of a Bore-Hole Waters 
from GEXA Well 4 and VH-2. Submittal date: 07/22/1997. 
GS970808314224.008. Provisional Results: Geotechnical Data for Station 65+00 to Station 
70+00, South Ramp of the ESF. Submittal date: 08/18/1997. 
GS970808314224.010. Provisional Results: Geotechnical Data for Station 70+00 to Station 
75+00, South Ramp of the ESF. Submittal date: 08/25/1997. 
GS970808314224.012. Provisional Results: Geotechnical Data for Station 75+00 to Station 
78+77, South Ramp of the ESF. Submittal date: 08/25/1997. 
GS970808315215.010. Carbon and Oxygen Stable Isotope Analyses of Calcite from the ESF and 
USW G-1, G-2, and G-3/GU-3, from 01/16/97 to 07/18/97. Submittal date: 08/18/1997. 
GS970808315215.012. Uranium and Thorium Isotope Data from Secondary Minerals in the ESF 
Collected Between 02/15/97 and 09/15/97. Submittal date: 09/17/1997. 
GS970908312271.003. Unsaturated Zone Hydrochemistry Data, 2-1-97 to 8-31-97, Including 
Chemical Composition and Carbon, Oxygen, and Hydrogen Isotopic Composition: Porewater 
from USW NRG-7A, SD-7, SD-9, SD-12 and UZ-14; and Gas from USW UZ-14. Submittal 
date: 09/08/1997. 
GS970908315215.011. Strontium Isotope Ratios and Strontium Concentrations in USW SD-7 
Rock and Soils, and ESF Calcite. Submittal date: 09/11/1997. 
GS970908315215.013. Uranium-Lead Isotope Data for ESF Secondary Minerals from July 12, 
1997 to August 24, 1997. Submittal date: 09/17/1997. 
GS971108314224.020. Revision 1 of Detailed Line Survey Data, Station 0+60 to Station 4+00, 
North Ramp Starter Tunnel, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.021. Revision 1 of Detailed Line Survey Data, Station 4+00 to Station 8+00, 
North Ramp, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.022. Revision 1 of Detailed Line Survey Data, Station 8+00 to Station 10+00,

ANL-NBS-HS-000017, Rev 00 Page 152 of 156 
North Ramp, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.023. Revision 1 of Detailed Line Survey Data, Station 10 + 00 to Station 18 + 
00, North Ramp, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.024. Revision 1 of Detailed Line Survey Data, Station 18+00 to Station 
26+00, North Ramp, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.025. Revision 1 of Detailed Line Survey Data, Station 26+00 to Station 
30+00, North Ramp and Main Drift, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.026. Revision 1 of Detailed Line Survey Data, Station 45+00 to Station 
50+00, Main Drift, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS971108314224.028. Revision 1 of Detailed Line Survey Data, Station 55+00 to Station 
60+00, Main Drift and South Ramp, Exploratory Studies Facility. Submittal date: 12/03/1997. 
GS980108312322.003. Uranium Isotopic Data for Saturated- and Unsaturated-Zone Waters 
Collected Between December 1996 and December 1997. Submittal date: 01/29/1998. 
GS980108312322.004. Strontium Isotope Ratios and Strontium Concentrations in Water 
Samples from USW WT-24 and UE-25 J-13 Collected in October 1997. Submittal date: 
01/26/1998. 
GS980208312322.006. Uranium Isotopic Data for Saturated- and Unsaturated-Zone Waters 
Collected by Non-YMP Personnel Between May 1989 and August 1997. Submittal date: 
02/03/1998. 
GS980408312232.001. Deep Unsaturated Zone Surface-Based Borehole Instrumentation 
Program Data from Boreholes USW NRG-7A, UE-25 UZ #4, USW NRG-6, UE-25 UZ #5, 
USW UZ-7A and USW SD-12 for the Time Period 10/01/97 - 03/31/98. Submittal date: 
04/16/1998. 
GS980408315215.010. Corrected Data for Carbon and Oxygen Isotope Analyses of Cavity- and 
Fracture-Coating Calcite for One Sample from Drill Hole USW G-2. Submittal date: 04/10/1998. 
Submit to RPC 
GS980708312242.011. Physical Properties and Hydraulic Conductivity Measurements of Lexan- 
Sealed Samples from USW WT-24. Submittal date: 07/30/1998. 
GS980908312322.008. Field, Chemical, and Isotopic Data from Precipitation Sample Collected 
Behind Service Station in Area 25 and Ground Water Samples Collected at Boreholes UE-25 C 
#2, UE-25 C #3, USW UZ-14, UE-25 WT #3, UE-25 WT #17, and USW WT-24, 10/06/97 to 
07/01/98. Submittal date: 09/15/1998.

ANL-NBS-HS-000017, Rev 00 Page 153 of 156 
GS980908312322.009. Uranium Concentrations and 234U/238U Ratios from Spring, Well, 
Runoff, and Rain Waters Collected from the Nevada Test Site and Death Valley Vicinities and 
Analyzed Between 01/15/1998 and 08/15/1998. Submittal date: 09/23/1998. 
GS980908315213.002. Carbon and Oxygen Stable Isotopic Compositions of Exploratory Studies 
Facility Secondary Calcite Occurrences, 10/01/97 to 08/15/98. Submittal date: 09/16/1998. 
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. 
GS980908315215.016. Uranium and Thorium Isotope Data Determined at the Royal Ontario 
Museum Between 07/12/97 and 01/29/98 and Calculated 230TH/U Ages and Initial 234U/238U 
Ratios for Secondary Silica from the Exploratory Studies Facility. Submittal date: 09/23/1998. 
GS981108314224.005. Locations of Lithostratigraphic Contacts in the ECRB Cross Drift. 
Submittal date: 11/30/1998. 
GS981283122410.006. Gas Chemistry and Isotope Data from 3 ESF Boreholes. Submittal date: 
12/28/1998. 
GS990183122410.001. Tritium Data from Pore Water from ESF Borehole Cores, 1997 Analyses 
by USGS. Submittal date: 01/06/1999. 
GS990183122410.004. Tritium Data from Pore Water from ESF Borehole Cores, 1998 Analyses 
by University of Miami. Submittal date: 10/14/1999. 
GS990308315215.003. X-ray Fluorescence Elemental Compositions of Rock Core Samples from 
USW SD-9 and USW SD-12. Submittal date: 03/25/1999. 
GS990308315215.004. Strontium Isotope Ratios and Strontium Concentrations in Rock Core 
Samples and Leachates from USW SD-9 and USW SD-12. Submittal date: 03/25/1999. 
GS990608312133.001. Ground-Water Quality Data. Submittal date: 06/09/1999. 
GS990983122410.003. Carbon-14 Data from ESF/NAD/GTB#1A Gas. Submittal date: 
09/30/1999. 
GS991299992271.001. Preliminary Unsaturated Zone Borehole Hydrochemistry Data. Submittal 
date: 12/23/1999. 
GS991299995215.001. Preliminary Hydrochemical Data from Yucca Mountain. Submittal date: 
12/29/1999.

ANL-NBS-HS-000017, Rev 00 Page 154 of 156 
LA000000000062.002. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN27. 
Submittal date: 09/01/1993. 
LA0001JF12213U.001. Reconstructed Annual Record of Tritium in Atmospheric Moisture for 
Albuquerque, New Mexico, 1946-1993. Submittal date: 01/07/2000. 
LA0002JF831222.001. Apparent Infiltration Rates in Alluvium from USW UZ-N37, USW UZN54, 
USW UZ-14 and UE-25 UZ#16, Calculated by Chloride Mass Balance Method. Submittal 
date: 02/25/2000. 
LA0002JF831222.002. Apparent Infiltration Rates in PTN Units from USW UZ-7A, USW UZN55, 
USW UZ-14, UE-25 UZ#16, USW NRG-6, USW NRG-7A, and USW SD-6, SD-7, SD-9 
and SD-12 Calculated by the Chloride Mass Balance Method. Submittal date: 02/25/2000. 
LA0003JF12213U.001. Precipitation-Weighted Average Monthly Concentrations (MG/L) of 
Precipitation in Red Rock Canyon, Nevada, 1985 to 1998. Submittal date: 03/13/2000. 
LA9909JF831222.001. Chloride, Bromide, Sulfate and Chlorine-36 Analyses of Groundwater 
and Runoff in FY99. Submittal date: 09/29/1999. 
LA9909JF831222.003. Chloride, Bromide, Sulfate and Chlorine-36 Analyses of Salts Leached 
from Cross Drift Rock Samples in FY99. Submittal date: 09/29/1999. 
LA9909JF831222.004. Chloride, Bromide, and Sulfate Analyses of Busted Butte and Cross Drift 
Tunnel Porewaters in FY99. Submittal date: 09/29/1999. 
LA9909JF831222.005. Chlorine-36 Analyses of ESF and Busted Butte Porewaters in FY99. 
Submittal date: 09/29/1999. 
LA9909JF831222.006. Cation Analyses of ESF, Cross Drift 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. 
LA9909JF831222.012. Chloride, Bromide, and Sulfate Analyses of Porewater Extracted from 
ESF Niche 3566 (Niche #1) and ESF 3650 (Niche #2) Drillcore. Submittal date: 09/29/1999. 
LA9912JF831222.001. Halide and Chlorine-36 Analyses of Drillcore from USW UZ-N55. 
Submittal date: 12/16/1999. 
LAJF831222AN97.008. Halide, Sulfate and 36CL Analyses of Cuttings from Borehole ONC#1. 
Submittal date: 09/26/1997. 
LAJF831222AN97.012. Halide, Sulfate and 36CL Analyses of Surface Soils. Submittal date:

ANL-NBS-HS-000017, Rev 00 Page 155 of 156 
09/26/1997. 
LAJF831222AN98.013. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of Groundwater 
from USW UZ-1, UE#25-p1, UE25 UZN#2, and USW VH-1. Submittal date: 09/09/1998. 
LAJF831222AQ95.003. Halide Analyses of Rainwater from Yucca Mountain. Submittal date: 
09/26/1995. 
LAJF831222AQ95.005. Halide and Chlorine-36 Analyses of Soils from the UE25 NRG#5 
Drillpad. Submittal date: 09/26/1995. 
LAJF831222AQ95.006. Halide and Chlorine-36 Analyses of Soils Collected from Midway 
Valley Pits and Trenches. Submittal date: 09/26/1995. 
LAJF831222AQ95.007. Halide and Chlorine-36 Analyses of Soils from Test Cell C, NTS Area 
25. Submittal date: 09/26/1995. 
LAJF831222AQ96.005. Halide and Chlorine-36 Analyses of Cuttings from Boreholes UE25 
NRG -4, USW NRG -6, and USW NRG-7A. Submittal date: 09/30/1996. 
LAJF831222AQ96.006. Halide and Chlorine-36 Analyses of Soil From Midway Valley Pit 
MWV-P2. Submittal date: 09/30/1996. 
LAJF831222AQ96.008. Halide and Chlorine-36 Analyses of Cuttings from Boreholes USW UZN15, 
USW UZ-N16, USW UZ-N17, USW UZ-N36, USW UZ-N38, UE25 UZ-N39, USW UZN61, 
USW UZ-N62, and USW UZ-N64. Submittal date: 09/30/1996. 
LAJF831222AQ96.009. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN11. 
Submittal date: 09/30/1996. 
LAJF831222AQ96.010. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN37. 
Submittal date: 09/30/1996. 
LAJF831222AQ96.011. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN53. 
Submittal date: 09/30/1996. 
LAJF831222AQ96.012. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN54. 
Submittal date: 09/30/1996. 
LAJF831222AQ96.013. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZN55. 
Submittal date: 09/30/1996. 
LAJF831222AQ96.014. Halide and Chlorine-36 Analyses of Cuttings from Borehole UE25 
UZ#16. Submittal date: 09/30/1996.

ANL-NBS-HS-000017, Rev 00 Page 156 of 156 
LAJF831222AQ96.015. Halide and Chlorine-36 Analyses of Cuttings from Borehole USW UZ- 
14. Submittal date: 09/30/1996. 
LAJF831222AQ97.002. Chlorine-36 Analyses of Packrat Urine. Submittal date: 09/26/1997. 
LAJF831222AQ97.006. Halide, Sulfate and Chlorine-36 Analyses of Soils from Midway Valley 
Soil Pits MWV-P31 and NRSF-TP-19. Submittal date: 09/26/1997. 
LAJF831222AQ97.007. Halide, Sulfate and 36CL Analyses of Cuttings from Borehole SD-12. 
Submittal date: 09/26/1997. 
LAJF831222AQ97.009. Sulfate Analyses of Yucca Mountain Precipitation. Submittal date: 
08/26/1997. 
LAJF831222AQ97.010. Halide and Sulfate Analyses of Paintbrush Tuffs from Yucca Mountain. 
Submittal date: 09/26/1997. 
LAJF831222AQ98.003. Chloride, Bromide, Sulfate, and Chlorine-36 Analysis of Construction 
Water. Submittal date: 09/09/1998. 
LAJF831222AQ98.004. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of Salts Leached 
from ESF Rock Samples. Submittal date: 09/10/1998. 
LAJF831222AQ98.005. Chloride, Bromide, Sulfate, and Chlorine-36 Analyses of Soils 
Collected Above the ESF South Ramp. Submittal date: 09/09/1998. 
LAJF831222AQ98.009. Chlorine-36 Analyses of Salts Leached from ESF Niche 3566 (Niche 
#1) Drillcore. Submittal date: 09/09/1998. 
LAJF831222AQ98.011. Chloride, Bromide, Sulfate and Chlorine-36 Analyses of Springs, 
Groundwater, Porewater, Perched Water and Surface Runoff. Submittal date: 09/10/1998. 
MO9907YMP99025.001. YMP-99-025.01, List of Boreholes. Submittal date: 7/19/1999. 
SNF40060198001.001. Unsaturated Zone Lithostratigraphic Contacts in Borehole USW WT-24. 
Submittal date: 10/15/1998. 
SNF40060298001.001. Unsaturated Zone Lithostratigraphic Contacts in Borehole USW SD-6. 
Submittal date: 10/15/1998.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-1 
Table 1. Correlation of Lithostratigraphic Units with Hydrogeologic Units 
Lithostratigraphic Nomenclature1 Lithostratigraphic 
Abbreviations 
Hydrogeologic Units 
Alluvial and colluvial deposits (Quaternary) QTac 
TIMBER MOUNTAIN GROUP (Tm) 
Rainier Mesa Tuff (Tmr) Tmr Unconsolidated 
PAINTBRUSH GROUP (Tp) Surficial 
Tiva Canyon Tuff (Tpc) Materials 
Crystal-rich member Tpcr (UO) 
Vitric zone Tpcrv 
nonwelded Tpcrv3 
moderately welded Tpcrv2 
densely welded Tpcrv1 
Nonlithophysal zone Tpcm Tiva Canyon 
Lithophysal zone Tpcrl Welded 
Crystal-poor member Tpcp Hydrogeologic 
Upper lithophysal zone Tpcpul Unit 
Middle nonlithophysal zone Tpcpmn (TCw) 
Lower lithophysal zone Tpcpll 
Lower nonlithophysal zone Tpcpln 
Vitric zone Tpcpv 
Densely welded Tpcpv3 
Moderately welded Tpcpv2 
nonwelded Tpcpv1 Paintbrush 
Pre-Yucca Mountain Tuff bedded tuff Tpbt3 Nonwelded 
Pah Canyon Tuff Tpp Hydrogeologic 
Pre-Pah Canyon Tuff bedded tuff Tpbt2 Unit 
Topopah Spring Tuff Tpt (PTn) 
Crystal-rich member Tptr 
Vitric zone Tptrv 
nonwelded Tptrv3 
moderately welded Tptrv2 
densely welded Tptrv1 
Nonlithophysal zone Tptrn 
Lithophysal zone Tptrl Topopah Spring 
Crystal-poor member Tptp Welded 
Upper lithophysal zone Tptpul Hydrogeologic 
Middle nonlithophysal zone Tptpmn Unit 
Lower lithohysal zone Tptpll (TSw) 
Lower nonlithophysal zone Tptpln 
Vitric zone Tptpv 
Densely welded Tptpv3 
moderately welded Tptpv2 
Nonwelded Tptpv1 
Pre-Topopah Spring Tuff bedded tuff Tpbt1 Calico Hills 
CALICO HILLS FORMATION Tac Nonwelded 
Bedded tuff Tacbt Hydrogeologic 
Basal sandstone Tacbs Unit 
CRATER FLAT GROUP (Tc) (CHn) 
Prow PassTuff Tcp 
Pre-Prow Pass bedded tuff Tcpbt 
Bullfrog Tuff Tcb

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-2 
Table 1. Correlation of Lithostratigraphic Units with Hydrogeologic Units 
Lithostratigraphic Nomenclature1 Lithostratigraphic 
Abbreviations 
Hydrogeologic Units 
Tram Tuff Tct Crater Flat 
Hydrogeologic unit 
(CFu) 
Notes: Official Group and Formation names are shown in bold type. Member designations, zonal subdivisions, 
and unit abbreviations follow the usage of Buesch et al. (1996, Table 4) and Day et al. (1996, map sheet 
2). Correlation of lithostratigraphic and hydrogeologic units from Buesch et al. (1996, Table 4).

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-3 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
1. Reported chemical data for pore waters and perched 
waters are of sufficient quality (e.g., precision and 
accuracy) that meaningful inferences can be made 
regarding their variability in space. 
Standard quality-control measures used by the laboratories producing 
the chemical data include analyses of blanks, standards, replicates. 
When analyses of all major ions are available, charge balances are used 
to verify consistency. In addition, the data are used in this report to 
define general qualitative trends, such that outliers if present can be 
clearly distinguished from the population. 
No Sections 
6.5, 6.9.2; 
Tables 6, 8, 
26, 27 
2. Chemical data for pore waters and perched waters can be 
considered to be representative of in situ conditions. When 
data are reported for more than one aliquot in a given DTN, 
it is assumed that the published values represent the ones 
considered to be most representative of in situ conditions 
(e.g., that the author(s) averaged the available data in an 
appropriate manner). 
A laboratory study comparing pore water extracted from nonwelded tuff 
by the compression system to that extracted by a high-speed centrifuge 
found no significant difference in the major-ion chemistry (Yang et al. 
1990, p. 250). No verification studies have been conducted for pH or 
minor elements but chemical analyses of these parameters are not 
directly used for calculations in this report. Caution about aluminum data, 
which may contain particulate aluminum that passed through the 0.45 ..m 
filters, is noted in Section 6.2.3; this caution may also apply to silica 
concentrations but is expected to be negligible. The assumption of 
representativeness is TBV for pore-water data reported in Table 6 
because it is not clear, when data are reported for multiple aliquots of the 
same pore-water sample, whether the value to be used should be the 
result for the first aliquot, the aliquot with the largest volume, a straight 
average of all aliquots, a volume-weighted average, or (in the case of pH) 
a geometric volume-weighted average. It also is not clear when the 
reported pH and conductivity values are field analyses (i.e., measured 
in the pore water immediately following its extraction) and when they are 
laboratory analyses (i.e., submitted to an outside laboratory). Field 
analyses are more likely to be representative of in situ conditions for 
these parameters. The assumption is also TBV because chloride porewater 
concentrations are directly used for testing the flow and transport 
model. None of these concerns apply to perched water chemical 
analyses, for which this assumption is considered not TBV. 
Yes for porewater 
data 
No for 
perched 
water data 
Sections 
6.2.3, 6.5, 
6.9.2, 7; 
Tables 6, 8, 
26, 27 
3. Chloride concentrations in surface and subsurface pore 
waters and perched waters reflect increases due solely to 
evapotranspiration. Cl concentrations are not significantly 
affected significantly by leakage from fluid inclusions or by 
geochemical reactions along the flow path. 
Chloride is a conservative anion, and minerals containing it are rare in 
the Yucca Mountain environment. Br/Cl ratios are available to evaluate 
this assumption for many samples. 
No Sections 
6.3.3, 6.5, 
6.9.2; 
Tables 26, 
27

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-4 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
4. Reported tritium data for pore waters and perched waters 
are of sufficient quality (e.g., precision and accuracy) that 
meaningful inferences can be made regarding their 
variability in space. Tritium values above a statisticallydetermined 
threshold are assumed to indicate a component 
of water less than 50 years old at the sampling location. 
Cross-contamination of samples in the field, in storage 
facilities and in the laboratory can be ruled out as an 
explanation for elevated tritium levels. Similarly, sampling, 
storage and analytical protocols minimize loss of tritium due 
to evaporation or isotopic exchange. 
Precision and accuracy have been monitored through the analysis of 
duplicate samples and standards, and background levels of 
contamination have been monitored through the analysis of blanks and 
duplicate samples. The threshold value is evaluated through statistical 
analysis. The interpretation of the tritium data is not very sensitive to the 
precise threshold value that is calculated. 
No Sections 
6.2.3, 6.6.2; 
Tables 9, 
10, 11, 12 
5. Reported chlorine-36 data for surface waters, soils, pore 
waters, perched waters and groundwaters are of sufficient 
quality (e.g., precision and accuracy) that meaningful 
inferences can be made regarding their variability in space. 
Precision and accuracy have been monitored through the analysis of 
blind duplicate samples and blind standards. 
No Section 
6.6.3; 
Tables 9, 
13, 14 
6. Chlorine-36 data can be considered to be representative of 
in situ conditions, unless a statement to the contrary 
accompanies the data. Samples used for direct input for 
this report have not been significantly affected by sources 
of contamination in the field, storage areas or laboratory. 
Lack of any significant contamination has been verified through analysis 
of frequent blanks and replicates, and through the analysis of Cl/Br 
ratios. 
No Section 
6.6.3; 
Tables 9, 
13, 14 
7. 36Cl/Cl ratios elevated above a threshold of about 1250 x 
10-15 are attributable to the presence of bomb pulse fallout. 
This threshold value is evaluated through statistical analysis. The 
interpretation of these data is not very sensitive to the precise threshold 
value that is calculated. 
No Section 
6.6.3; 
Tables 9, 
13, 14 
8. Reported carbon isotopic data for pore waters, perched 
waters and gases are of sufficient quality (e.g., precision 
and accuracy) that meaningful inferences can be made 
regarding their variability in space. 
It is assumed that precision and accuracy have been monitored through 
the analysis of blind duplicate samples and blind standards. 
No Section 
6.6.4, 6.7; 
Tables 9, 
15, 16, 17, 
18, 19, 20, 
21, 22 
9. Carbon isotopic data for pore waters, perched waters and 
gases can be considered to be representative of in situ 
conditions, unless a statement to the contrary accompanies 
the data. These data have not been affected significantly 
by laboratory or field sources of contamination, including 
drilling air. 
This assumption is considered not TBV for perched water analyses. 
However, this assumption may not be valid for all pore-water and gas 
samples, some of which may have been contaminated with drilling air. 
Although the total mass of carbon in pore water is orders of magnitude 
higher than that in subsurface air, it is possible that the injection of large 
volumes of drilling air may alter the carbon isotopic composition of pore 
Yes for porewater 
and 
unsaturatedzone 
gas 
data from 
open 
Sections 
6.2.3, 6.6.4, 
6.7, 7; 
Tables 9, 
15, 16, 17, 
18, 19, 20,

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-5 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
waters under some conditions. In particular, gas data from open 
boreholes cannot be assumed to be representative of in situ conditions. 
Gas data from instrumented boreholes, however, appear to be reliable, 
with exceptions as noted in the text and tables. 
boreholes 
No for gas 
data from 
instrumented 
boreholes, 
perched 
water and 
atmospheric 
data 
21, 22 
10. Lower limits on pore-water and gas ages can be calculated 
based on the assumption that the initial 14C activity is 100 
pmc, and that decreases relative to the initial atmospheric 
activity are solely the result of radioactive decay. 
The assumption for an initial 14C activity of 100 pmc is supported by the 
high 14C activities measured in the annulus of shallow boreholes (Tables 
17 and 19). 
No Section 
6.6.4; 
Tables 9, 
15, 16, 18, 
19, 20 
11. Reported stable hydrogen isotopic data are of sufficient 
quality (e.g., precision and accuracy) that meaningful 
inferences can be made regarding their variability in space 
Precision and accuracy have been monitored through the analysis of 
duplicate samples and standards. 
No Section 
6.6.5; 
Table 9 
12. Stable hydrogen isotopic data for perched waters, pore 
waters, and groundwater can be considered to be 
representative of in situ conditions. 
Stable hydrogen and oxygen isotopes are well-established as 
conservative tracers of water provenance and evaporative history. 
However, experiments reported in Yang, Yu et al. (1998, pp. 28 to 48) 
show the extent to which different methods of pore-water extraction can 
fractionate isotopes of these two elements, such as by incomplete 
extraction in the presence of hydrated minerals such as clays and 
zeolites. They concluded that different extraction methods should be 
used for different samples depending upon their mineral contents (Yang, 
Yu et al., 1998, p. 44). Vacuum distillation is appropriate for samples 
with few hydrated minerals, provided extraction is complete. For zeolitebearing 
or clay-bearing samples, the compression method should be 
used. The method used for a given sample can be determined from its 
unique sample identifier. 
No Section 
6.2.3, 6.6.5; 
Table 9 
13. Reported stable oxygen isotopic data are of sufficient 
quality (e.g., precision and accuracy) that meaningful 
inferences can be made regarding their variability in space 
Precision and accuracy have been monitored through the analysis of 
duplicate samples and standards. 
No Section 
6.6.5; 
Table 9

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-6 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
14. Stable oxygen isotopic data for perched waters, pore 
waters, groundwater and minerals can be considered to be 
representative of in situ conditions. 
See rationale for assumption 12. No Section 
6.2.3, 6.6.5; 
Table 9 
15. Reported strontium isotopic data are of sufficient quality 
(e.g., precision and accuracy) that meaningful inferences 
can be made regarding their variability in space 
Precision and accuracy have been monitored through the analysis of 
duplicate samples and standards. 
No Section 
6.6.6; 
Table 9 
16. Strontium isotopic data for perched waters, pore waters, 
groundwater and minerals can be considered to be 
representative of in situ conditions. 
Extraction and analysis of strontium isotopes from water, rock and 
mineral samples are well-established protocols. 
No Section 
6.6.6; 
Table 9 
17. Reported chemical data for unsaturated-zone gases are of 
sufficient quality (e.g., precision and accuracy) that 
meaningful inferences can be made regarding their 
variability in space 
Precision and accuracy have been monitored through the analysis of 
duplicate samples and standards. 
No Section 6.7; 
Tables 18 
and 20 
18. Chemical data for unsaturated-zone gases can be 
considered to be representative of in situ conditions, unless 
a statement to the contrary accompanies the data. 
Unsaturated-zone gas chemical data are generally the same as that for 
the atmosphere, with the expected exception of CO2, which is 
considerably elevated in the subsurface. These elevated CO2 analyses 
cannot be attributed to contamination from the atmosphere or from 
drilling air. Stable carbon isotope ratios and 14C activities can be used to 
evaluate whether the gas chemical data are reasonable for in situ 
conditions. A more difficult problem to address, however, is the interval 
which the gas sample represents if it has been collected from a fractured 
rock with low matrix permeability. However, gas chemical data in this 
report have only been used to define general qualitative trends and so 
this assumption is not TBV for this limited purpose. 
No Section 6.7; 
Tables 18 
and 20 
19. The chloride mass balance (CMB) method is assumed to 
be applicable to the estimation of infiltration rates at Yucca 
Mountain, for samples obtained above the CHn. The CMB 
method assumes one-dimensional, downward piston flow, 
constant average annual precipitation rate, constant 
average annual Cl deposition rate, no run-on or run-off, no 
Cl source other than precipitation (e.g., it is assumed that 
the concentrations of Cl brought in by surface runoff and Cl 
released from weathering of surface rocks are negligible), 
and no Cl sink (e.g., it is assumed that removal of Cl 
through the formation of halite is negligible). 
The CMB method is well-established for estimating recharge rates on a 
watershed scale and for estimating infiltration rates in deep soil profiles in 
which one-dimensional porous media flow can be assumed to apply. 
What has not been clearly established, however, is the validity of 
applying this method to an intermediate scale in which runon and runoff 
may not be negligible, and in an environment where water is known to 
percolate through fractured rock. Of particular concern is the apparent 
discrepancy between infiltration estimates obtained by the CMB method 
and those obtained by the numerical infiltration model of Flint et al. 
(1996, Fig. 39). The assumption is TBV because chloride pore-water 
concentrations are directly used for testing the flow and transport model. 
Yes Section 
6.9.2, 7; 
Tables 26, 
27

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-7 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
20. The estimated range of annual deposition rates for chloride 
at Yucca Mountain encompasses the present-day rate as 
well as the rates that prevailed when the sampled pore 
waters infiltrated below the soil zone. 
This assumption is supported by several independent lines of evidence. 
However, what is still needed is an estimate of the uncertainties in the 
deposition rates, and propagation of that uncertainty through the resulting 
estimates of infiltration obtained by the CMB method. The assumption is 
TBV because the chloride deposition rate is directly used in the CMB 
method for determining infiltration boundary conditions for the flow and 
transport model. 
Yes Section 
6.9.2, 7; 
Tables 26, 
27 
21. Pore-water samples that have been analyzed for chloride 
are representative of the full spectrum of significant flow 
paths in the unsaturated zone at Yucca Mountain. 
It is possible that relatively dilute water that has infiltrated rapidly through 
fracture pathways may be inadequately represented by matrix pore water 
extracted for analysis because of incomplete mixing. If this is the case, 
matrix pore-water samples might be biased toward the slower moving, 
more concentrated matrix component of flow; and percolation estimates 
based on these samples would constitute lower bounds on the actual 
percolation rates. In the PTn, some component of the flux can bypass the 
matrix as fracture or fault flow, as evidenced by the presence of bombpulse 
tracers in the ESF. 
Yes Section 
6.9.2, 7; 
Tables 26, 
27 
22. Reported calcite concentrations for cuttings from borehole 
WT-24 are based on the assumption that the secondary 
calcite is the only source for Ca released from the rock and 
measured CO2 amounts. 
No significant source of CO2 other than calcite is present in the volcanic 
rock section. 
No Sections 
6.10.1.1, 
6.10.3.4, 
Figure 53 
23. Calculated estimates of mineral formation temperatures or 
isotopic compositions of formation water are based on the 
assumption that the mineral deposition was an equilibrium 
process. 
Typically these assumptions are clearly stated in text when made. They 
are not necessarily valid, but provide a means of comparing temperature 
conditions between mineralization stages or between variations in the 
isotopic compositions of formation waters at different depositional 
episodes. 
No Sections 
6.10.2, 
6.10.3 
24. Reported uncorrected 14C ages for fracture minerals are 
ased on the law of radioactive decay and on the 
assumption that carbon initially incorporated into the 
mineral during its deposition contained 100 percent modern 
carbon. 
Although this assumption is not strictly true, it allows comparisons of 14C 
data in a geochronological framework that can be compared to 230Th/U 
and U/Pb ages; and this simplification is considered acceptable for the 
limited purpose of such comparisons. Calculated 14C ages are likely to 
be maximum ages due to incorporation of dead carbon at the surface 
and decay of 14C in the percolating water during travel time to site of 
calcite formation. 
No Section 
6.10.1.3, 
Figure 54

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-8 
Table 2. Assumptions Used in This Report 
Assumption Rationale for considering assumption to be valid Assumption 
to be 
verified 
(TBV) 
Section in 
which 
assumption 
is used 
25. Reported ages calculated from 230Th/U and 207Pb/235U 
ratios are based on the law of radioactive decay and on the 
assumption that studied minerals behaved as closed 
systems with regard to uranium and its decay products. 
U-Th-Pb isotope ratios rarely show disruption of the systematic evolution 
that allows ages to be calculated. Calculated 230Th/U ages are 
particularly sensitive to U leaching resulting in 230Th/238U ratios greater 
than those allowed through closed-system decay. Lack of disturbed 
ratios supports the closed-system behavior of the U decay systems in 
calcite and opal. 
No Section 
6.10.1.3, 
6.10.3, 
Table 28, 
Figures 54, 
55, 56, 65, 
67, 70 and 
72

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-9 
Table 3. Types of Isotopic and Geochemical Data Collected for Unsaturated-zone Fluids at Yucca Mountain 
Analyses of pore waters or leached salts Shorthand 
Identifier 
Official Borehole 
Identifier (depth in m 
shown for surfacebased 
holes) 
Chem 3H 13, 14C 
(pore) 
2H  
18O 
36Cl Other 
Gas and 
water vapor 
analyses 
Perchedwater 
analyses 
NRG#4 UE-25 NRG#4 221         
NRG#5 UE-25 NRG#5 411         
NRG-6 USW NRG-6 335       CO2, CH4, 
13,14C, 18O 
 
NRG-7a USW NRG-7a 461      234,238U CO2 
, CH4, 
13.14C 
Chem, 3H, 
13,14C, 2H, 
18O, 36Cl, 
87Sr, 
234,238U 
ONC#1 UE-25 ONC#1 469         
SD-12 USW SD-12 660       CO2, CH4, 
13,14C, 18O 
SD-6 USW SD-6 774      87Sr   
SD-7 USW SD-7 815      87Sr 13,14C, CO2, 
18O 
Chem, 3H, 
13,14C, 2H, 
18O, 36Cl, 
234,238U 
SD-9 USW SD-9 678      234,238U CO2 
, CH4, 
13,14C, 18O 
Chem, 3H, 
13,14C, 2H, 
18O, 36Cl, 
87Sr, 
234,238U 
UZ#16 UE-25 UZ#16 514       13,14C, CO2, 
CH4, 18O 
 
UZ#4 UE-25 UZ#4 112         
UZ#5 UE-25 UZ#5 111         
UZ-1 USW UZ-1 387       CO2, atm 
gases, 
13,14C, 2H, 
18O, 3H 
3H, 13,14C, 
2H, 
18O, 36Cl 
UZ-13 USW UZ-13 18       CO2, CH4, 
13,14C, 18O 
 
UZ-14 USW UZ-14 678      234,238U 13,14C, CO2 Chem, 3H, 
13,14C, 2H, 
18O, 36Cl, 
87Sr, 
234,238U 
UZ-6 USW UZ-6 575       CO2, CH4, 
13,14C, 18O 
 
UZ-6s USW UZ-6s 158       CO2, 13,14C, 
18O, atm 
gases 
 
UZ-7a USW UZ-7a 235       CO2, CH4, 
13C, 18O 
 
UZN#1 UE-25 UZN#1 15        

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-10 
Table 3. Types of Isotopic and Geochemical Data Collected for Unsaturated-zone Fluids at Yucca Mountain 
Analyses of pore waters or leached salts Shorthand 
Identifier 
Official Borehole 
Identifier (depth in m 
shown for surfacebased 
holes) 
Chem 3H 13, 14C 
(pore) 
2H  
18O 
36Cl Other 
Gas and 
water vapor 
analyses 
Perchedwater 
analyses 
UZN#2 UE-25 UZN#2 15        Chem, 
36Cl 
UZN#39 UE-25 
UZN#39 
18         
UZN#8 UE-25 UZN#8 14         
UZN#91 UE-29 
UZN#91 
29        36Cl 
UZ-N11 USW UZ-N11 26         
UZ-N15 USW UZ-N15 18         
UZ-N16 USW UZ-N16 18         
UZ-N17 USW UZ-N17 18         
UZ-N27 USW UZ-N27 62       13,14C, 18O  
UZ-N36 USW UZ-N36 18         
UZ-N37 USW UZ-N37 83         
UZ-N38 USW UZ-N38 27         
UZ-N43 USW UZ-N43 14         
UZ-N46 USW UZ-N46 30        Chem 
UZ-N53 USW UZ-N53 72         
UZ-N54 USW UZ-N54 75         
UZ-N55 USW UZ-N55 78         
UZ-N61 USW UZ-N61 36         
UZ-N62 USW UZ-N62 18       13,14C, 18O  
UZ-N64 USW UZ-N64 18       13,14C, 18O  
UZ-N90 USW UZ-N90 14         
UZ-N93 USW UZ-N93 12       CO2, CH4, 
13,14C, 18O 
 
UZ-N94 USW UZ-N94 9       CO2, CH4, 
13,14C, 18O 
 
UZ-N95 USW UZ-N95 6       CO2, CH4, 
13,14C, 18O 
 
WT#18 UE-25 WT#18 623       CO2, CH4, 
13C, 18O 
 
WT#4 UE-25 WT#4 482       CO2, CH4  
WT-24 USW WT-24 Not 
avail. 
       Chem, 3H, 
13,14C, 2H, 
18O, 36Cl, 
87Sr, 
234,238U 
Busted 
Butte 
UZTT-BB-PH1-2         
Busted 
Butte 
UZTT-BB-PH1-3         
Busted 
Butte 
UZTT-BB-PH1-4        

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-11 
Table 3. Types of Isotopic and Geochemical Data Collected for Unsaturated-zone Fluids at Yucca Mountain 
Analyses of pore waters or leached salts Shorthand 
Identifier 
Official Borehole 
Identifier (depth in m 
shown for surfacebased 
holes) 
Chem 3H 13, 14C 
(pore) 
2H  
18O 
36Cl Other 
Gas and 
water vapor 
analyses 
Perchedwater 
analyses 
Busted 
Butte 
UZTT-BB-PH1-6         
Busted 
Butte 
UZTT-BB-PH1-7         
Cross Drift Cross Drift samples 
collected from walls 
(manually or with dry 
excavation method) 
        
Cross Drift ECRB-SYS-CSnnnn 
holes, where nnnn is 
distance in meters 
Cl, Br, 
SO4 
       
ESF ESF samples collected 
from walls of Main Drift 
or alcoves (manually or 
with dry excavation 
method) 
     87Sr   
ESF Alcove 
#1 
ESF-AL#1-RBT#1, #2, 
#3 
      13,14C, 18O  
ESF Alcove 
#1 
Seeps from infiltration 
test 
Cl, Br, 
SO4 
       
ESF Alcove 
#2 
ESF-AL#2-HPF#1         
ESF Alcove 
#2 
ESF-LPCAMOISTSTDY#
n 
Cl, Br, 
SO4 
       
ESF Alcove 
#3 
ESF-AL#3-RBT#1, #4         
ESF Alcove 
#5 
Single Heater Test 
(SHT) Hole 16 
     234,238U   
ESF Alcove 
#5 
ESF-AL#5 Sr     87Sr   
ESF Alcove 
#5 
ESF-HD-PERM-1, -3 Cl, Br, 
SO4 
    87Sr, 
234,238U 
  
ESF Alcove 
#5 
ESF-TMA-NEU-2         
ESF Alcove 
#5 
Drift Scale Heater Test 
Holes, DST-60 and 
DST-186 
     234,238U   
ESF Alcove 
#6 
ESF-NAD-GTB#1A       13,14C, 18O, 
CO2 
 
ESF Main 
Drift 
ECRB-CWAT#1, #2, #3 Cl, Br, 
SO4 
    87Sr   
ESF Main 
Drift 
ESF-MD-WATMOV#nn Cl, Br, 
SO4 
       
ESF Niche 
#1 
ESF-MDNICHE3566#
1, #2, 
LT#1 
Cl, Br, 
SO4 
      

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-12 
Table 3. Types of Isotopic and Geochemical Data Collected for Unsaturated-zone Fluids at Yucca Mountain 
Analyses of pore waters or leached salts Shorthand 
Identifier 
Official Borehole 
Identifier (depth in m 
shown for surfacebased 
holes) 
Chem 3H 13, 14C 
(pore) 
2H  
18O 
36Cl Other 
Gas and 
water vapor 
analyses 
Perchedwater 
analyses 
ESF Niche 
#1 
ESF-MDNICHE3650#
nn 
Cl, Br, 
SO4 
       
ESF North 
Ramp 
ESF-NRMOISTSTDY#
nn 
Cl, Br, 
SO4 
       
ESF South 
Ramp 
ESF-SRMOISTSTDY#
nn 
Cl, Br, 
SO4 
       
Notes: 
a. Data identified by this table include data that are directly used (listed in Section 4.1) as well as data used 
solely for corroborative purposes in this report. Not all data indicated in this table are discussed in this 
report; e.g., many data are not directly relevant to the discussions in this report. 
b. Borehole depths are reported in feet in DTN: MO9907YMP99025.001 and have been converted to meters 
in the table above. 
c. Abbreviations for types of analyses: Chem, pore-water chemistry; H, tritium, 13, 14C (pore), carbon-13 and 
carbon-14 analyses for pore waters; 2H18O, stable hydrogen and oxygen isotopes; 36Cl, chlorine-36

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-13 
Table 4. Sources of Stratigraphic Information Used to Classify Pore-water and Gas Samples in This 
Report 
Borehole Sources for stratigraphic information Table or figure in which information 
is used 
NRG#4 Moyer et al. (1996, Appendix 3) Table 13 
NRG#5 Geslin et al. (1994, Appendix 3) 
Rousseau et al. (1999, Figure 26) 
Tables 13 and 18 
NRG-6 Moyer et al. (1996, Appendix 3) for PTn 
Geslin et al. (1994, Appendix 3) 
Tables 6, 10, 11, 15, 18 and 22 
NRG-7a Geslin et al. (1994, Appendix 2), for upper part 
Moyer et al. (1996, Appendix 3) for PTn 
Rousseau et al. (1999, Figure 25) for TSw 
Tables 6, 10, 11, 13, 15 and 18 
SD-12 Rautman and Engstrom (1996a, Table 3) Tables 6, 10, 11, 13, 15, 18, 20 and 22 
SD-6 DTN: SNF40060298001.001 Tables 6, 10 and 11 
SD-7 Rautman and Engstrom (1996b, Table 3) Tables 6, 10, 13, 15, 18 and 22 
SD-9 Engstrom and Rautman (1996, Table 3) Tables 6, 10, 13, 15, 18 and 22 
UZ#16 Moyer et al. (1996, Appendix 3) for PTn 
Geslin et al. (1994, Appendix 3) 
Moyer and Geslin (1995, Tables 4 and 6) for CHn 
Tables 6, 10, 11, 13, 15 and 18 
UZ#4 Yang (1992, Figure 2) Tables 12 and 16 
UZ#5 Yang (1992, Figure 3) Tables 12 and 16 
UZ-1 Rousseau et al. (1999, Figure 92) Tables 10, 20 and 22 
UZ-14 Geslin et al. (1994, Appendix 2), for upper part of UZ-14 
Moyer et al. (1996, Appendix 3) for PTn 
Moyer and Geslin (1995, Tables 4 and 6) for CHn 
Tables 6, 10, 11, 13, 15, 18 and 22 
UZ-6 Thorstenson et al. (1998, p. 1510) Table 19 
UZ-6s Thorstenson et al. (1998, pp. 1509 to 1510) Table 19 
UZ-7a Moyer et al. (1996, Appendix 3) for PTn Tables 6 and 10 
UZ-N11 Moyer et al. (1996, Appendix 3) Table 13 
UZ-N15 DTN: GS940308314211.019 Table 13 
UZ-N16 DTN: GS940308314211.019 Table 13 
UZ-N17 DTN: GS940308314211.019 Table 13 
UZ-N27 DTN: GS940208314211.004 Table 13 
UZ-N36 DTN: GS940308314211.018 Table 13 
UZ-N37 Geslin et al. (1994, Appendix 2) Table 13 
UZ-N38 DTN: GS940308314211.011 Table 13 
UZN#39 Flint and Flint (1995, p. 34) Table 13 
UZ-N53 Geslin et al. (1994, Appendix 2) Table 13 
UZ-N54 Geslin et al. (1994, Appendix 2) Table 13 
UZ-N55 Geslin et al. (1994, Appendix 2) Tables 6 and 13 
UZ-N61 DTN: GS940208314211.008 Table 13 
UZ-N62 DTN: GS940208314211.002 Table 13 
UZ-N64 DTN: GS940308314211.016 Table 13 
WT-24 DTN: SNF40060198001.001 Tables 6, 10 and 11 
Note: These sources for stratigraphic information are used as corroborative data. Stratigraphic 
misclassification of a sample would not be expected to change the interpretation of the data.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-14 
Table 5. Average Annual Weighted Concentrations for Precipitation, 3 Springs Basin, Nevada 
Annual Weighted concentration (mg/L) Nominal Year Start End Total 
precip. 
(cm) 
Alkalinity 
as CaCO3 
Equiv. 
HCO3 
Ca Mg Na K SO4 Cl SiO2 
3 Springs Creek 
1986 850924 860930 13.93 2.67 3.26 0.61 0.06 0.40 0.15 0.73 0.34 0.13 
1987 860930 880109 15.58 2.04 2.49 0.46 0.04 0.34 0.13 0.63 0.31 0.08 
1988 880109 890223 14.24 2.93 3.57 0.98 0.09 0.78 0.28 1.12 0.47 0.13 
1989 890223 891108 5.85 4.30 5.25 1.06 0.18 1.03 0.15 1.41 0.59 0.19 
1990 891108 910130 12.62 1.40 1.70 0.81 0.08 0.79 0.20 1.12 0.56 N/C 
1991 910130 910925 11.65 N/C N/C 0.73 0.08 0.46 0.17 1.13 0.25 N/C 
1992 910925 920917 13.94 N/C N/C 0.49 0.05 0.23 0.15 0.81 0.17 N/C 
Kawich Peak 
1989 881001 891108 13.44 3.23 3.94 0.97 0.16 0.97 0.16 1.27 0.64 0.20 
1990 891108 910130 15.07 1.83 2.23 0.73 0.07 0.62 0.64 0.96 0.39 N/C 
1991 910130 920218 17.77 N/C N/C 0.68 0.07 0.95 0.15 0.95 0.31 N/C 
1992 920218 920917 6.8 N/C N/C 0.66 0.07 0.32 0.21 1.25 0.31 N/C 
Results of linear regression for Cl as the independent variable 
Y-intercept (assigned value of zero to force line through 
origin) 
0 0 0 0 0 0 0 N/A 0 
Standard error of y-intercept 0.91 1.11 0.15 0.03 0.18 0.16 0.30 N/A 0.02 
R squared 0.13 0.13 0.38 0.65 0.63 -0.22 -0.49 N/A 0.88 
No. Of observations 7 7 11 11 11 11 11 N/A 5 
X coefficient 5.433 6.628 1.787 0.220 1.578 0.489 2.431 N/A 0.313 
Standard error of X coefficient 0.707 0.863 0.111 0.019 0.127 0.116 0.213 N/A 0.016 
Source data: The above values were calculated from data reported in DTN: GS930108315214.003, GS930108315214.004 and GS930908315214.030. The 
calculated regression lines are used solely to provide a way to graphically compare and contrast chemical compositions of the various sources of water at 
Yucca Mountain, and to illustrate general trends of relative enrichment or depletion of one element compared to another. Precipitation data reported in the 
original source DTNs in inches have been converted to centimeters in the table above. 
Notes: N/C signifies not calculated; N/A signifies not applicable.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-15 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Concentration (mg/L) Bore 
hole 
Depth 
Interval 
(ft) 
Hydro- 
Geologic 
unit2 
Lithostratigraphic 
unit2 
Ave. 
depth 
(m) 
pH 
Spec. 
cond. 
(..S/cm) Ca Mg Na SiO2 K HCO3 CO3 Cl NO3 SO4 
Charge 
balance1 
NRG-6 158.2158.58 PTn Tpbt4 48 6.4 1070 122 23.3 35.6 97.4  34 0 185 32 159 -0.2 
NRG-6 160.8161.2 PTn Tpbt4 49 7.0 860 104 18 35.0 84.0  55 0 148 35 139 -2.0 
NRG-6 171.0171.3 PTn Tpbt3 52 7.0 620 70.5 11.5 29.2 79.4  48 13 58 43 94 2.1 
NRG-6 175.6175.95 PTn Tpp 54 6.6 520 49.2 8.6 29.4 78.1  60 0 47 42 64 1.4 
NRG-6 219.9220.2 PTn Tpp 67 7.0 660 24.3 4.2 99.3 61.4  92 0 77 47 77 -1.4 
NRG-6 244.6245.0 PTn Tpbt2 75 6.6 630 33 4.9 72.0 51.0  61 0 49 40 115 -2.2 
NRG-6 255.9256.1 PTn Tptrv3 78 6.7 1910 176 19 215.0 68.0  61 0 115 35 840 -6.2 
NRG-7A 165.75166.0 PTn Tpbt3 51 7.4 510 55.3 5.6 31.7 68.3  89 0 38.9 45.5 63.4 -0.1 
NRG-7A 258.0258.4 PTn Tpp 79 8.2 600 43 3.7 82 68.9  128 0 53.6 43.7 65.5 2.9 
NRG-7A 1483.5-1483.8 CHn Tptpv1 452 7.9 580 61 0.6 94 48.6  323 0 33.1 16.7 24.4 1.3 
NRG-7A 1492.7-1493.1 CHn Tptpv1 455 7.9 580 30.6 0.3 74.7 71.5  104 34 39 18 23 1.0 
NRG-7A 1498.6-1498.9 CHn Tac 457 7.5 500 28.7 0.5 73.2 83.0  156 0 50 17 18 0.5 
SD-6 430.3-430.6 PTn Tpcpv1 131 7.4 430 46 9.4 56.8 81.7 2.8 109 0 43 69 43 5.7 
SD-6 443.2-443.5 PTn Tpbt4 135 7.3 580 55.2 11.2 53.2 94.8 1.4 134 0 27 64 73 4.5 
SD-6 443.5-443.8 PTn Tpbt4 135 7.2 630 62.4 12 51.6 92.8 1.8 95 0 33 57 101 7.4 
SD-7 339.7340.2 PTn Tpbt3 104 7.4 690 110 15 20 82.8  220 0 77.2 1.5 76.7 1.3 
SD-7 370.3370.6 PTn No core 113 6.7 1420 289 0.2 39 25.9  73 0 133 0.6 650 -6.7 
SD-7 1498.41498.6 CHn Tac2 457 7.2 440 31 0.6 67 63.5  171 0 28.9 13.6 14.1 4.4 
SD-7 1524.61525.7 CHn Tac1 465 7.2 490 38.7 0.9 57.6 68.6 7 203 0 30.1 12.4 15.9 -0.2 
SD-7 1558.41558.6 CHn Tac1 475 7.2 390 39 0.9 43 69.3  171 0 25.1 9.0 14.9 -0.9 
SD-7 1600.1-1600.33 CHn Tacbt 488 7.6 380 23 0.6 59 66.7  150 0 31 5.7 12 1.2 
SD-7 1617.01617.2 CHn Tacbs 493 7.2 570 40.2 < 1 79 62.2  194 < 1 65 11.0 14 -0.3 
SD-7 1890.7-1891.1 CHn Tcp1 576 8.7 850 0 0.2 206 67  334 78 18 4.8 10 0.6 
SD-7 1952.4-1952.7 CHn Tcp1 595 8.8 980 0 0.3 251 67.4  353 120 22 6.7 11 0.9 
SD-7 2088.2-2088.5 CHn Tcp1 636 9.2 710 0 0 173 54.4  157 101 15 4.0 25 4.0 
SD-7 2170.1-2170.5 CHn Tcpbt 661 9.2 670 0 0 164 55.4  100 103 18 3.8 18 8.5 
SD-7 2596.12596.3 CHn Tcbts 791 9.0 670 < 1 < 1 158 64.3  79 65 83 3.2 12 5.9

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-16 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Concentration (mg/L) Bore 
hole 
Depth 
Interval 
(ft) 
Hydro- 
Geologic 
unit2 
Lithostratigraphic 
unit2 
Ave. 
depth 
(m) 
pH 
Spec. 
cond. 
(..S/cm) Ca Mg Na SiO2 K HCO3 CO3 Cl NO3 SO4 
Charge 
balance1 
SD-7 2596.5-2596.9 CHn Tcbts 791 9.0 680 0 0 148 53.3  95 71 46 2.2 12 7.8 
SD-7 2598.32598.5 CHn Tct 792 8.7 630 < 1 < 1 152 94.8  231 59 22 4.0 18 -1.5 
SD-9 94.294.4 PTn Tpbt4 29 5.5 1050 125 24 43 74  37 0 170 11 260 -4.3 
SD-9 114.1-114.3 PTn Tpy 35 6.8 920 95 18 55 62.3  31 0 138 10.9 181 1.6 
SD-9 135.1-135.3 PTn NR 41 8.5 890 91 15 66 60.1  37 0 144 12 162 2.5 
SD-9 154.0154.2 PTn Tpbt3 47 6.8 650 72 13 36 55  90 0 93 4.7 106 -1.2 
SD-9 176.2-176.4 PTn Tpp 54 7.5 720 43 9.5 95 58.4  122 0 64 1.9 124 4.8 
SD-9 251.8-252.0 PTn Tpbt2 77 7.2 500 44 8 53 55.0  92 0 40 14.2 73 8.1 
SD-9 1452.61452.8 CHn Tptpv1 443 7.3 530 6.9 0 112 62.5  256 0 15.7 10.6 12.3 1.4 
SD-9 1535.21535.35 CHn Tac3 468 7.4 530 0.8 0.1 112 54.9 7 226 0 15.6 10.6 15.5 4.7 
SD-9 1619.91661.4 CHn Tac2 500 8.3 610 0.4 0 136.6 55.6 4 232 12 50.2 9.0 18.3 -0.7 
SD-9 1661.11661.3 CHn Tac2 506 8.1 660 0.7 0 164 48.8  317 0 42.0 8.2 18.9 1.8 
SD-9 1741.01741.2 CHn Tac1 531 8.7 520 0.2 0 125 52  185 41 19 4.4 10 2.2 
SD-9 1741.71741.9 CHn Tac1 531 8.4 310 0.2 0 74 53  113 12 15 3.8 8.7 5.0 
SD-9 1800.7-1800.9 CHn Tacbt1 549 9.3 790 0.8 0 180.7 59.6 6 137 106 32.3 4.6 20.9 5.6 
SD-12 265.8266.1 PTn Tpbt4 81 7.2 470 48.9 7.6 28.6 62.7 3 107 0 49.6 15.9 47.5 -0.1 
SD-12 278.6278.8 PTn Tpp 85 7.3 580 74 12.7 27 71.2  159 0 46 16.0 75 1.7 
SD-12 296.1296.6 PTn Tpbt2 90 6.9 490 75 8.0 21 72.2  163 < 1 60 18.0 21 2.2 
SD-12 1460.71461.0 CHn Tac4 445 8.5 490 31 0 89 65.5  98 30 55.9 7.3 30.1 4.8 
SD-12 1495.51495.8 CHn Tac3 456 8.5 550 16 0.2 108 87.3  49 57 57 8.1 55 -0.7 
SD-12 1517.01517.4 CHn Tac3 462 7.6 660 14 0 150 56.9  323 0 33.6 6.4 22.5 2.9 
SD-12 1558.9-1559.5 CHn Tac2 475 8.5 640 4.4 0.1 155 76.1  210 41 33 0.4 54 0.7 
SD-12 1582.5-1582.7 CHn Tac2 482 8.5 420 1.2 0.1 97 71.0  113 29 17 4.5 27 4.3 
SD-12 1600.61603.0 CHn Tac1 488 9.1 550 2.6 0 129 65.7  79 90 27.8 2.6 12.6 3.2 
SD-12 1636.8-1637.0 CHn Tacbt 499 9.1 520 3.8 0 129 64.6  67 102 15.2 1.7 11.2 5.6 
SD-12 1901.4-1901.5 CHn Tcp2 580 9.1 470 1.3 < 1 122 90.7  151 59 22 5.7 9.3 0.2 
SD-12 1938.5-1939.0 CHn Tcp2 591 8.7 650 1.4 0 165 55.0  171 66 34 1.0 26.1 5.2

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-17 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Concentration (mg/L) Bore 
hole 
Depth 
Interval 
(ft) 
Hydro- 
Geologic 
unit2 
Lithostratigraphic 
unit2 
Ave. 
depth 
(m) 
pH 
Spec. 
cond. 
(..S/cm) Ca Mg Na SiO2 K HCO3 CO3 Cl NO3 SO4 
Charge 
balance1 
SD-12 1942.2-1942.9 CHn Tcp2 592 8.9 550 1.3 0 140 60.1  134 66 24 3.5 24.4 4.3 
UZ-7A 203.3-203.7 PTn Tpbt4 62 7.3 830 115 20.6 16.6 69.7 5.6 120 0 70 105 140 -1.4 
UZ-7A 220.2-220.5 PTn Tpbt2 67 7.3 820 117 23.1 18.3 67.6 5.5 100 0 87 112 140 -0.7 
UZ-7A 241.4-241.7 PTn Tpbt2 74 6.9 930 116 21.9 39 52.2 10 70 0 60 83 240 2.0 
UZ-14 45.045.35 PTn Tpy 14 8.6 1340 19.6 6.1 249.3 59.5 6.1 245 18 245 35 33 -1.2 
UZ-14 85.285.6 PTn Tpbt3 26 6.9 630 49.9 13.2 43.5 89.8  131 0 60 22 66 -0.9 
UZ-14 91.091.25 PTn Tpbt3 28 7.6 530 40.7 10.1 37.1 80.6  87 0 47 26 81 -4.1 
UZ-14 95.595.9 PTn Tpbt3 29 7.2 600 53.3 13.2 38.1 81.5  73 0 79 29 83 -1.9 
UZ-14 96.296.6 PTn Tpbt3 29 6.9 550 46.9 12.7 33.6 79.6  79 0 59 26 75 -0.9 
UZ-14 100.4100.8 PTn Tpbt3 31 7.0 600 51.1 13.8 41.3 91.8  128 0 44 23 83 0.4 
UZ-14 114.75115.0 PTn Tpp 35 6.6 540 49.0 10.5 35.9 93.9  67 0 61 25 90 -2.2 
UZ-14 135.5135.8 PTn Tpp 41 6.9 690 68.5 14.3 56.2 92.0  105 0 83 23 96 4.5 
UZ-14 144.8145.2 PTn Tpp 44 7.7 650 65.5 12.0 48.2 81.5  118 0 77 22 102 -1.8 
UZ-14 147.79148.1 PTn Tpp 45 6.9 640 54.8 11.5 51.6 77.3  79 0 83 22 102 -1.5 
UZ-14 177.6177.9 PTn Tpp 54 6.5 730 67.8 11.3 48.7 77.5  49 0 100 23 130 -2.0 
UZ-14 178.1178.4 PTn Tpp 54 6.8 740 64.0 10.6 49.1 93.1  62 0 97 21 120 -3.0 
UZ-14 215.72216.1 PTn Tpp 66 6.8 670 65.5 10.7 39.4 97.8  55 0 85 14 130 -3.0 
UZ-14 225.9226.2 PTn Tpp 69 7.9 640 58.6 10.4 48.4 91.2  55 0 93 16 116 -2.5 
UZ-14 235.1235.4 PTn Tpp 72 7.1 630 67 10.5 29 63  96 N/S 84 15 94 -5.7 
UZ-14 240.8241.12 PTn Tpbt2 73 7.6 810 32 1 103 61  162 N/S 99 17 100 -11.8 
UZ-14 245.5245.8 PTn Tpbt2 75 6.8 580 65 12 9 46  66 N/S 77 12 79 -4.8 
UZ-14 1258.51258.8 TSw Tptpln 384   43 3.7 67 35  170 N/S 88 16 19 -4.9 
UZ-14 1277.41277.7 TSw Tptpln 389   62 4.5 49 44  170 N/S 87 17 45 -7.1 
UZ-14 1277.71278.0 TSw Tptpln 389   74 5.1 45 38  170 N/S 130 15 38 -10.4 
UZ-14 1409.41409.8 CHn Tpbt1 430 7.8 720 30 0.7 88 57  160 0 75 5 106 -13.2

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-18 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Concentration (mg/L) Bore 
hole 
Depth 
Interval 
(ft) 
Hydro- 
Geologic 
unit2 
Lithostratigraphic 
unit2 
Ave. 
depth 
(m) 
pH 
Spec. 
cond. 
(..S/cm) Ca Mg Na SiO2 K HCO3 CO3 Cl NO3 SO4 
Charge 
balance1 
UZ-14 1419.51419.8 CHn Tpbt1 433 8.3 410 20 0.6 68 60  166 0 24 6 21 0.9 
UZ-14 1461.91462.1 CHn Tac3 446 7.6 570 9.2 0.1 128 68.7  265 0 24.2 6.2 37.3 1.1 
UZ-14 1495.81496.0 CHn Tac2 456 8.4 500 2.1 0 122 56.7  228 0 28.0 10.8 14.3 3.9 
UZ-14 1524.551524.75 CHn Tac2 465 7.7 560 1.1 0.1 137 54.8  232 0 26.2 12.5 22.3 7.2 
UZ-14 1542.31542.8 CHn Tac2 470   3.6 0.5 207 143  384 46 20 4 28 1.0 
UZ-14 1563.61563.8 CHn Tac2 477 8.7 660 1.2 0.2 155 72.0  160 97 16 4 14 1.1 
UZ-14 1564.61564.75 CHn Tac2 477   1.3 0.2 129 140.4  61 113 16 4 17 0.5 
UZ-14 1564.91565.0 CHn Tac2 477 8.3 690 1.7 0.5 169 54.0  376 0 23 1 30 0.1 
UZ-14 1585.01585.15 CHn Tac2 483 9.7 560 0.9 0.3 106.8 74.5  98 67 14 7 10 1.7 
UZ-14 1585.31585.6 CHn Tac2 483 9.3 400 1.2 0.5 85 75.0  148 18 11 6 9 2.4 
UZ-14 1605.91606.1 CHn Tac2 490   1.0 0.3 87.8 67.2  178 0 18 6 9 2.4 
UZ-14 1644.31644.5 CHn Tac2 501 8.8 420 2.2 0.7 110 74.0  74 79 14 0 9 5.6 
UZ-14 1674.81675.05 CHn Tac1 511   1.8 0.6 58 64.6  104 0 10 4 9 8.6 
UZ-14 1695.41695.6 CHn Tabt1 517   1.4 1.1 115.8 55.9  203 18 21 5 26 0.5 
UZ-14 1715.01715.3 CHn Tabt1 523 7.3 390 0.2 0 88 52.9  168 0 11.9 3.1 16.0 5.0 
UZ-14 1734.51734.7 CHn Tabt1 529 8.7 750 2.0 0.3 184 50.7  211 79 39.4 5.6 17.5 3.0 
UZ-14 1735.31735.53 CHn Tabt1 529 9.0 700 1.7 0 158 46.9  288 18 37.4 3.4 15.4 1.5 
UZ-14 1804.51804.8 CHn Tcp4 550 8.0 480 0.5 0.2 111 43.0  181 12 25.1 15.3 14.9 2.5 
UZ-14 1825.81826.0 CHn Tcp3 557 9.4 590 0.6 0.1 138 47.9  42 112 23.5 11.8 12.9 4.3 
UZ-14 1854.91855.1 CHn Tcp3 565 8.0 460 0.5 0.2 107 34.5  181 23 18.8 13.7 15.9 -1.3 
UZ-14 1865.71865.9 CHn Tcp3 569 8.6 480 0.3 0 115 30.4  204 18 17.3 11.7 12.6 1.3 
UZ-14 2014.72014.9 CHn Tcp1 614 9.3 1520 3.2 0.2 392 37.7  409 219 32.1 1.8 22.2 5.6 
UZ-14 2015.22025.7 CHn Tcp1 616 9.4 1290 0.9 0 312.7 68.6  339 176 23.2 0.5 21.7 4.2 
UZ-14 2025.12025.3 CHn Tcp1 617 9.1 1550 4.0 0.2 414 54.8  493 189 36.5 6.9 26.3 6.3 
UZ-14 2095.12095.8 Cfu Tcb 639 8.8 540 0 0 112.8 63.0  143 29 30 0.3 29 1.3 
UZ#16 163.5163.85 PTn Tpbt4 50 6.8 420 42.5 13.4 21.5 77.5  94 45 32.4 23.1 72.3 -16.7 
UZ#16 180.9181.27 PTn Tpbt3 55 7.3 450 55 11 20 83 3 120 0 38 33 38 2.7

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-19 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Concentration (mg/L) Bore 
hole 
Depth 
Interval 
(ft) 
Hydro- 
Geologic 
unit2 
Lithostratigraphic 
unit2 
Ave. 
depth 
(m) 
pH 
Spec. 
cond. 
(..S/cm) Ca Mg Na SiO2 K HCO3 CO3 Cl NO3 SO4 
Charge 
balance1 
UZ#16 952.6-952.9 TSw Tptpln 290 8.2  2.2 13.7 99.5 31.7  179 --- 81 30 34 -7.1 
UZ#16 1166.191166.47 CHn Tptpv1 355 8.1 710 28.9 13.7 83.6 57.1  196 0 82 17 28 -1.4 
UZ#16 1206.33-1206.67 CHn Tptpv1 368 7.2 540 39.8 11.7 48.5 61.6  105 --- 43 28.4 31.1 11.2 
UZ#16 1227.351227.7 CHn Tac4 374 8.1 430 26.5 6.2 47.9 62.2  137 0 24 23 26 1.1 
UZ#16 1235.11235.4 CHn Tac4 377 7.7 480 33.5 7.9 51.3 52.9  154 0 52 26 29 -4.8 
UZ#16 1269.61269.95 CHn Tac3 387 8.5 430 14.1 2.4 67.5 57.1  139 13 27 18 14 -2.8 
UZ#16 1280.371280.75 CHn Tac3 390 8.3 530 20.5 3.7 92.0 71.8  192 0 28 19 19 6.9 
UZ#16 1296.81297.06 CHn Tac3 395 7.5 950 32.4 19.7 98.2 46.7  324 12 50 19 18 -1.9 
UZ#16 1317.861318.24 CHn Tac3 402 7.2 430 20.6 5.1 60.1 131.6  171 0 32 20 18 -4.0 
UZ#16 1358.051358.4 CHn Tac2 414 7.5 550 3.4 0.3 76.7 47.9  115 0 22.8 16.1 18.7 5.2 
UZ#16 1389.361389.64 CHn Tac2 424 9.4 480 3.6 0.9 114.6 62.5  100 36 23.5 18.5 23.8 9.9 
UZ#16 1395.51395.7 CHn Tac2 425 8.4 710 5.4 0.3 155 88.0  216 24 17 16 22 11.9 
UZ#16 1398.51398.7 CHn Tac2 427   5.0 0.4 145 123  237 31 14 16 20 4.8 
UZ#16 1412.91413.2 CHn Tac2 431 8.7 450 1.2 0.1 101 75.9  165 0 26 24 30 0.1 
UZ#16 1428.11428.4 CHn Tac2 435 8.8 570 1.9 0.1 134 80.5  160 43 23 19 23 3.8 
UZ#16 1442.891443.22 CHn Tac2 440 9.5 410 1.7 0.8 79.9 68.9  15 87.6 18.9 11.3 13.7 -7.0 
UZ#16 1486.91487.3 CHn Tcp4 453 8.9 370 6.3 0.8 79.5 233.3  137 0 38 6 11 2.6 
UZ#16 1601.11601.5 CHn Tcp3 488 9.0 580 10 0.3 100 36  181 0 53 13 27 -3.6 
UZ#16 1607.71608.05 CHn Tcp3 490 8.9 670 25 0.3 108 34  170 0 71 10 33 2.9 
UZ#16 1643.41647.2 CHn Tcp3 501 9.0 490 91 12 34 70  162 0 70 8 28 13.5 
UZ#16 1651.61651.7 CHn Tcp3 503 8.3 430 17.3 0.3 66 47.4  87 19 27 6 20 6.0 
UZ-N55 166.1-166.42 TCw Tpcplnc 51 7.8 845 28.7 7.6 126.9 47.7  136.6 --- 106.8 97.7 74.9 -5.1 
UZ-N55 195.27-195.47 PTn Tpcpv1 60 6.7 630 91.8 8.6 18.4 71.5  69.5 --- 77.1 93.3 80.7 -3.2 
UZ-N55 198.97-199.45 PTn Tpcpv1 61 6.7 765 91.2 9.5 39.9 76.4  35.4 --- 76.6 101.7 101 4.4 
WT#24 1734.3-1735.1 CHn Tptpv1 529 8.2 420 4.9 0 96 81.1 8.4 172 0 34 1.7 14 6.1 
WT#24 1744.2-1744.5 CHn Tptpv1 532 7.9 500 5.5 0.1 121 69.5 9.5 242 0 31 2.3 18 4.8 
WT#24 1744.5-1745.0 CHn Tptpv1 532 8.3 440 4.2 0 103 72.7 7.7 210 19 16 2.7 14 0.2

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-20 
Table 6. Chemical Composition of Unsaturated-zone Pore-water Samples from Surface-based Boreholes at Yucca Mountain 
Source for chemical data: DTN: GS950608312272.001, GS961108312271.002, GS970208312271.002, GS970908312271.003, and GS991299992271.001 (data 
sets 9810----2272.004 and 9902----2272.001). For 7 samples, data for more than one aliquot are reported in DTN: GS950608312272.001 (UZ-14: top depths 
85.2 and 100.4; UZ#16: top depths 1227.35, 1269.6, 1280.37, 1412.9, and 1442.89). For these samples, it is assumed that the data considered to be most 
representative of the sample are those reported in Yang et al. (1996, Tables 2 and 3). 
Relevant assumptions from Table 2: 1 and 2 (TBV) 
Notes:  data not available. 
0 values below detection limit 
No core No core available for stratigraphic examination 
1
Charge balance calculated from data shown using the following formula: [(meq cation/L - meq anion/L) / (meq cation/L + meq anion/L)] x 100 
2 
Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval from which each sample was collected was determined 
using the appropriate references listed in Table 4.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-21 
Table 7. Chemical Composition of Precipitation and Transient Shallow Perched-water at Yucca Mountain 
Concentration (mg/L) Bore 
Hole* 
Date 
Ca Mg Na SiO2 HCO3 CO3 Cl NO3 SO4 
Charge 
balance 
 
Precipitation samples 
NTS 
Area 251 
02-23-98 0.14 0.013 0.32 0.10 2.8 0 <0.1 --- 0.41 --- 
UZN#22 08-18-89 14 2.3 51 18 112 0 10 0 29 --- 
Shallow transient perched-water samples 
UZN#2 04-09-91 --- --- --- --- --- --- 19.9 --- 40.7 --- 
UZN#2 02-14-92 1.4 0.5 1.7 0 11.7 0 12 8.2 7.8 -63.4 
UZN#2 03-16-92 14 3.9 25 5.8 58.2 0 10 27.3 21 -0.1 
UZN#2 03-31-92 25 4.7 16 11.8 128 0 5.8 19.7 15.6 -10.9 
UZN#91 03-05-92 --- --- --- --- --- --- 19.5 --- 17.8 --- 
UZ-N46 02-14-92 0.8 0.5 1.6 0.2 23.3 0 3.3 1.6 4.7 -59.8 
Data sources: DTN: GS991299992271.001 (data set 9512----2272.004) for UZN#2 precipitation, UZN#2 
perched water for 1992, and UZ-N46 perched water; DTN: GS980908312322.008 for NTS Area 25 
precipitation; and DTN: LAJF831222AN98.013 for UZN#2 water from 1991 and UZN#91 perched water. 
These data are only used for corroborative purposes because of incomplete analyses and inadequate 
charge balances. 
Notes: 
 data not available. 
0 values below detection limit. 
*Sampling depths for perched water: UZN#2, 15.8 m; UZ-N46, 30.1 m (Yang et al. 1996, Table 2) 
Charge balance calculated from data shown using the formula: [(meq cation/L - meq anion/L) / (meq cation/L + 
meq anion/L)] x 100 
1 Sample from behind service station; pH 7.2, specific conductivity 4.5 S/cm (DTN: GS980908312322.008) 
2 pH 7.7, specific conductivity 308 S/cm (DTN: GS991299992271.001, data set 9512----2272.004)

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-22 
Table 8. Chemical Composition of Deep Perched Water at Yucca Mountain 
Concentration (mg/L) 
Sample 
Identifier 
Ave. 
Depth 
(m) 
Date Temp. 
(C) 
pH Spec. 
cond. 
(..S/cm) Al Ca Mg K Na SiO2 HCO3 CO3 Cl NO3 SO4 
Charge 
balance 
* 
NRG-7A 460.25 03-07-94  8.7 224 0.0 3 0 6.8 42 9 114  7 1 4 -0.4 
SD-9/TS 453.85 07-17-94 27.0 8.6 445 2.1 2.9 0.2 9.8 98 64.2 197 10 5.6 3.3 27.6 7.6 
UZ-14 A 384.60 08-02-93 27.1 7.6 312 0.7 23 1.8 5.6 39 34.2 150 0 7.9 8.6 14.3 0.3 
UZ-14 A2 384.60 08-02-93 27.1 7.8 308 1.0 24 1.8 3.9 38 36.4 148.8 0 9.1 12.5 13.8 -1.4 
UZ-14 B 387.68 08-03-93 23.8 8.1 335 6.1 31 2.7 4.4 40 51.4 147.6 0 8.3 16.9 16.3 5.2 
UZ-14 C 390.75 08-05-93 24.2 8.3 518 0.0 45 4.1 5.8 88 7.7 106.1 0 15.5 0 223 -1.9 
UZ-14 PT-1 390.75 08-17-93    0.0 37 3.1 6.3 40 21.4 144 0 7.2 12.7 57.3 0.5 
UZ-14 PT-2 390.75 08-19-93    0.0 30 2.4 3.3 35 25.7 144 0 7.0 15.4 22.9 0.3 
UZ-14 PT-4 390.75 08-27-93    0.0 27 2.1 1.8 34 32.1 141.5 0 6.7 14.5 14.1 0.2 
UZ-14 D 390.75 08-31-93  7.8  0.0 31 2.5 4.1 35 40.7 146.4 0. 7.0 17.1 24.2 0.1 
SD-7(3/8) 479.76 03-08-95    0.28 14.2 0.13 5.3 45.5 62.3 112 0 4.4 33.8 9.1 2.5 
SD-7(3/16) 488.29 03-16-95 21.8 8.1 239 0.44 13.3 0.13 5.3 45.3 57.4 128 0 4.1 33.8 9.1 -2.9 
SD-7(3/17) 488.29 03-17-95 22.6 8.2 285 0 12.8 0.08 5.5 45.8 50.9 130 0 4.1 22.8 8.6 -0.3 
SD-7(3/20) 488.29 03-20-95 23.3 8.0 265 0 12.9 0.07 5.4 45.5 55 127 0 4.1 13.4 8.5 3.3 
SD-7(3/21) 488.29 03-21-95 23.2 8.2 259 0 13.5 0.08 5.5 44.6 55.9 128 0 4.1 13.2 10.3 2.2 
Data source: DTN: GS991299992271.001 (data set 9512----2272.004). 
Relevant assumptions from Table 2: 1 and 2 
Notes: 
 data not available. 
0 values below detection limit. 
*Charge balance calculated from data shown using the following formula: [(meq cation/L - meq anion/L) / (meq cation/L + meq anion/L)] x 100.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-23 
Table 9. Isotopic Composition of Perched Water at Yucca Mountain 
Water 
sample 
Depth 
(m) 
Date d13C 
() 
14C 
(pmc) 
14C 
age1 
(yr) 
3H 
(TU
) 
d 2H 
() 
d 18O 
() 
234U 
/238U 
Activity 
ratio 
d 87Sr 
() 
36Cl/Cl 
(x 
10-15) 
SD-7 479.76 03-08-95 -10.4 34.4 8798 6.2 -99.8 -13.4   511 
488.29 03-16-95 -9.4 28.6 10321  -99.7 -13.3    
488.29 03-17-95 -9.5 28.4 10379  -99.6 -13.4 3.50  657 
488.29 03-20-95 -9.5 27.9 10525  -99.6 -13.4 3.58   
488.29 03-21-95 -9.5 28.4 10379  -99.6 -13.3 3.69  609 
635 
SD-9  03-07-94 -14.4 41.8 7192 0 -97.8 -13.3    
 07-07-94      2.42 (c)   
453.85 07-17-94 -14.4 41.8 7192 0 -97.8 -13.3   449 
 09-12-94      2.42 (c) 5.92  
UZ-14 A 384.60 08-02-93 -10.2 41.7 7212 0.3 -98.6 -13.8  4.51 559 
UZ-14 A2 384.60 08-02-93 -10.1 40.6 7432 3.1 -97.5 -13.5  4.47 538 
UZ-14 B 387.68 08-03-93 -9.5 36.6 8287 0 -97.1 -13.4  4.34 566 
UZ-14 C 390.75 08-05-93 -9.2 66.8 3327 0.4 -87.4 -12.1  4.37 389 
UZ-14 PT-1 390.75 08-17-93 -9.8 32.3 9318 1.8 -97.8 -13.3  3.91 
4.30 
644 
UZ-14 PT-2 390.75 08-19-93  28.9 10235 3.1 -97.9 -13.4  3.51 
4.19 
656 
UZ-14 PT-4 390.75 08-27-93 -9.6 27.2 10735 0 -97.3 -13.4 7.56 4.45 
4.49 
675 
UZ-14 D 390.75 08-31-93 -11.3 29.2 10150 0 -97.6 -13.1   690 
WT-24  10-06-97 
10-16-97 
10-17-97 
10-22-97 



 



 



 



 



 



 
4.36 (c) 
6.58 (c) 
8.33 
8.37 
4.08 
2.61 
3.88 
4.00 


 
586 
NRG-7a  03-04-94       5.17 (c) 4.94 518 
460.25 03-07-94 -16.6 66.9 3314 10. 
4 
-93.9 -12.8  2.54 
2.91 
474 
 03-08-94        11.68  
UZ-12 382 07-07-83 
to 
07-21-83 
-12.1 64.0 3680 1.0 -102 -13   999 
UZN#91 28.7 03-05-92         880 
UZN#2 15.2 04-09-91 
02-22-95 

 

 

 

 

 

 

 

 
20122 
3150 
Data sources: DTN: GS991299992271.001 (data sets 9512----2272.002 for tritium, and 9512----2272.003 for d13C, 
d2H, d18O, and 14C), GS980108312322.004 (d 87Sr), LAJF831222AQ98.011 (36Cl/Cl), LAJF831222AN98.013 
(36Cl/Cl for UZ-1 and UZN#2), and GS980108312322.003 (234U/238U activity ratios). 
Relevant assumptions from Table 2: 4 to 16 
Notes: 
(c) This result is not representative of in situ conditions due to sample contamination 
 not available

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-24 
1 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where t1/2 is the 
half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity (100 pmc). See 
assumption 10 in Table 2. 
2 Unqualified data because samples were collected prior to the establishment of a formal quality assurance 
program.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-25 
Table 10. Summary of Tritium Analyses in Unsaturated-zone Pore Waters at Yucca Mountain 
TCw and 
above 
PTn TSw CHn above 
Tcp 
Tcp and 
below 
Total ESF or borehole 
location 
Geomorphic 
Location 
Collar 
elevation 
(ft) Above 
25 TU 
Total Above 
25 TU 
Total Above 
25 TU 
Total Above 
25 TU 
Total Above 
25 TU 
Total Above 
25 TU 
Total 
ESF Alcove 2 Bow Ridge fault zone --- 8 9 --- --- --- --- --- --- --- --- 8 9 
ESF Alcove 3 --- --- --- --- --- 3 --- 7 --- --- --- --- --- 10 
ESF Alcove 5 --- --- --- --- --- --- --- 7 --- --- --- --- --- 7 
ESF Alcove 6 Ghost Dance fault zone --- --- --- --- --- --- 7 --- --- --- --- --- 7 
ESF North Ramp --- --- --- 3 --- --- --- 2 --- --- --- --- --- 5 
ESF Main Drift --- --- --- --- --- --- --- 4 --- --- --- --- --- 4 
Subtotals, ESF 8 12 --- 3 --- 27 --- --- --- --- 8 42 
UZ#16 Terrace, large wash 4000 --- 4 1 4 11 51 2 27 --- 13 14 99 
NRG-6 Hillslope 4092 --- --- 6 13 --- --- --- --- --- --- 6 13 
NRG-7A Hillslope 4207 --- 4 --- 9 1 22 --- 9 --- --- 1 44 
UZ-7a Small wash bottom 4228 --- --- --- 1 --- 13 --- --- --- --- --- 14 
SD-9 Small wash bottom 4273 --- 2 --- 15 --- 22 --- 26 --- 3 --- 68 
SD-12 Small wash bottom 4343 --- 13 --- 10 --- 27 --- 18 1 7 1 75 
UZ-1 Large channel (Drillhole Wash) 4425 --- 1 --- 5 1 9 --- --- --- --- 1 15 
UZ-14 Large channel (Drillhole Wash) 4425 --- --- 1 35 --- 53 --- 35 --- 14 1 137 
SD-7 Ridgetop 4472 --- 10 --- 7 --- 15 --- 18 --- --- --- 50 
WT-24 Ridgetop 4900 --- --- --- --- 7 10 --- --- 5 58 12 68 
SD-6 Small wash bottom 4905 --- 6 --- 17 3 22 --- 11 4 37 7 93 
Subtotals, boreholes --- 40 8 116 23 244 2 144 10 132 43 676 
Total, all samples 8 52 8 119 23 271 2 144 10 132 51 718 
Data sources: Tritium compositions of pore waters are from DTN: GS961108312271.002 (excluding data for UZ#16), GS991299992271.001 (data set 9512---- 
2272.002 (for UZ#16 data) and 9911----2272.004), GS961108312261.006, GS970108312232.001, GS970208312271.002, GS970283122410.002, 
GS970608312272.005, and GS970908312271.003. 
Relevant assumption from Table 2: 4 
Notes: 
1. Borehole elevations from DTN: MO9907YMP99025.001. These values are listed so as to provide a rough surrogate for average annual precipitation, which 
typically increases as a function of elevation (Hevesi et al. 1992, Fig. 7 on p. 685). 
2. The threshold for indicating the unambiguous presence bomb-pulse or post-bomb tritium is 25 TU, based on the application of Chauvenets criterion as 
described in the text (Section 6.6.2). This statistical test was applied to the 803 samples listed in the above DTNs, including 75 duplicate analyses but

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-26 
excluding ESF data that were reported more than once in DTN: GS970608312272.005, GS961108312261.006 and GS961108312271.002. Where duplicate 
analyses exist, the sample results were only tallied once in the summary table above. 
3. The stratigraphic interval from which each sample was collected was determined using the appropriate references listed in Table 4.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-27 
Table 11. Tritium Levels above 25 TU in Unsaturated-zone Pore Waters at Yucca Mountain 
Sampling location1 Top of 
Sampled 
Interval (ft) 
Hydrologic unit3 Stratigraphic unit3 Tritium 
(TU) 
ESF-AL#2-HPF#1 34.3 TCw Tpcpmn 28.8 
47.2 TCw Tpcpll 30.9 
50.5 TCw Tpcpll 118.3 
55.4 Bow Ridge fault zone --- 128.1 
58.9 TCw Tmbt1 78.6 
61.2 TCw Tmbt1 65.3 
68.6 TCw Tmbt1 154.6 
83.6 TCw Tmbt1 32.9 
NRG-6 175.6 PTn Tpp 30.9 
175.6 PTn Tpp 39.1 
210.4 PTn Tpp 117.3 
210.4 PTn Tpp 139.9 
229.4 PTn Tpbt2 (23.1) 
229.4 PTn Tpbt2 30.2 
NRG-7a 356.7 TSw Tptrv1 46.8 
UZ-1 621 TSw Tptprl+Tptpul 28.0 
UZ-14 135.5 PTn Tpp 32.0 
UZ#16 158.4 PTn Tpcpv2 142.2 
158.4 PTn Tpcpv2 148.5 
262.8 PTn Tptrn 27.0 
262.8 PTn Tptrn 31.2 
583.0 TSw Tptpmn 95.8 
583.0 TSw Tptpmn 105.9 
669.0 TSw Tptpmn (25.0) 
669.0 TSw Tptpmn 28.7 
945.0 TSw Tptpln 48.2 
945.0 TSw Tptpln 59.1 
1041.2 TSw Tptpln 44.4 
1041.2 TSw Tptpln 56.1 
1041.9 TSw Tptpln 28.7 
1090.6 TSw Tptpln (11.1) 
1090.6 TSw Tptpln 40.7 
1110.6 TSw Tptpln (21.3) 
1110.6 TSw Tptpln 30.2 
1113.2 TSw Tptpv3 35.0 
1113.2 TSw Tptpv3 42.7 
1113.2 TSw Tptpv3 51.5 
1113.6 TSw Tptpv3 42.8 
1122.2 TSw Tptpv3 26.1 
1122.2 TSw Tptpv3 26.2 
1122.2 TSw Tptpv3 35.7 
1129.5 TSw Tptpv3 58.7 
1397.7 CHn Tac2 41.3 
1397.7 CHn Tac2 44.4 
1434.3 CHn Tac2 98.1

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-28 
Table 11. Tritium Levels above 25 TU in Unsaturated-zone Pore Waters at Yucca Mountain 
Sampling location1 Top of 
Sampled 
Interval (ft) 
Hydrologic unit3 Stratigraphic unit3 Tritium 
(TU) 
1434.3 CHn Tac2 108.8 
SD-6 1437.5 TSw Tptpln 26.7 
1440.0 TSw Tptpln 27.9 
1440.7 TSw Tptpln 29.7 
1749.3 CHn Tcpuc 29.7 
1749.3 CHn Tcpuc 29.9 
1751.0 CHn Tcpuc 43.2 
1752.1 CHn Tcpuc 32.7 
1752.1 CHn Tcpuc 41.6 
1754.1 CHn Tcpuc 36.6 
SD-12 1722.5 CHn Tcp3 39.2 
WT-24 1688.8 TSw Tptpv3 37.6 
1689.3 TSw Tptpv3 35.6 
1690.5 TSw Tptpv3 28.3 
1690.5 TSw Tptpv3 29.1 
1694.4 TSw Tptpv3 25.8 
1694.4 TSw Tptpv3 29.9 
1697.6 TSw Tptpv3 42.8 
1697.6 TSw Tptpv3 50.0 
1699.7 TSw Tptpv3 29.7 
1699.7 TSw Tptpv3 30.7 
1702.9 TSw Tptpv3 45.1 
2515.9 CHn not available 28.3 
2515.9 CHn not available 31.2 
2515.9 CHn not available 34.3 
2519.1 CHn not available 30.2 
2522.2 CHn not available 25.7 
2522.2 CHn not available 32.6 
2525.3 CHn not available 29.0 
2526.0 CHn not available 33.0 
Data sources for tritium levels: DTN: GS961108312271.002 (excluding UZ#16 data), GS991299992271.001 
(data sets 9512----2272.002 for UZ#16 data and 9911----2272.004), GS951208312272.002, and 
GS961108312261.006. 
Relevant assumption from Table 2: 4 
Notes: 
1 Data listed in parentheses lie below the threshold for indicating the unambiguous presence of bomb-pulse or 
post-bomb tritium, but are included in this table because they are duplicate analyses for samples with tritium 
concentrations above the threshold. 
2 Distance from borehole collar for ESF boreholes, and depth from surface for surface-based boreholes 
3Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval from which 
each sample was collected was determined using the appropriate references listed in Table 4.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-29 
Table 12. Tritium Profiles in UZ#4 and UZ#5 
Sampling 
location 
Depth (m) Hydrologic 
Unit1 
Stratigraphic 
Unit1 
Tritium 
(TU)2 
UZ#4 1.0 2.3 Alluvium Alluvium 19 
2.5 4.5 Alluvium Alluvium 22 
5.5 6.5 Alluvium Alluvium 7 
8.8 10.3 Alluvium Alluvium 2 
11.0 11.8 Alluvium Alluvium 3 
24.7 24.8 TCw TCw 28 
25.5 25.6 TCw TCw 3 
33.5 33.6 PTn Tpy 22 
41.8 41.9 PTn Tpy 24 
44.8 44.9 PTn Tpy 41 
44.9 45.0 PTn Tpy 38 
46.3 47.9 PTn Tpy/Tpbt3 45 
49.4 49.5 PTn Tpbt3 45 
95.6 95.7 PTn Tpbt2 0 
UZ#5 28.3 28.4 TCw TCw 60 
28.8 28.9 TCw TCw 49 
29.8 30.0 TCw TCw 65 
30.4 30.6 TCw TCw 51 
31.4 31.5 TCw TCw 11 
32.6 32.8 TCw TCw 75 
33.6 33.7 TCw TCw 39 
34.0 34.1 TCw TCw 22 
34.8 34.9 TCw TCw 42 
36.0 36.1 PTn Tpbt4 66 
36.5 36.6 PTn Tpbt4 15 
36.6 36.7 PTn Tpbt4 36 
37.2 37.3 PTn Tpy 4 
37.6 37.7 PTn Tpy 13 
44.8 44.9 PTn Tpy 6 
68.6 68.8 PTn Tpp 10 
70.1 70.2 PTn Tpp 1 
72.4 72.5 PTn Tpp 0 
72.5 72.7 PTn Tpp 7 
75.3 75.5 PTn Tpp 0 
78.7 78.9 PTn Tpp 0 
82.4 82.6 PTn Tpp 4 
90.1 90.2 PTn Tpp 1 
94.1 94.3 PTn Tpp 6 
94.3 94.5 PTn Tpp 0 
98.3 98.4 PTn Tpbt2 1 
Data source: DTN: GS920408312272.002 
Relevant assumption from Table 2: 4 
Notes: 
These data are used to corroborate the limited penetration of infiltrating water into thick (13-m) alluvium (UZ#4), 
as contrasted with the deeper penetration of infiltrating water into a setting with negligible soil cover over 
densely welded fractured bedrock (UZ#5) (soil cover thickness described in Yang 1992, p. 733). The data 
also support an interpretation of lateral flow at the bedrock/alluvial interface in order to account for bombpulse 
tritium underlying pre-bomb tritium in UZ#4. 
1 Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval from which 
each sample was collected was determined using the appropriate references listed in Table 4. 
2 Typical uncertainties (one-sigma) for these sample data are 4 to 5 TU (Yang 1992, Table 1).

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-30 
Table 13. Summary of the Distribution of 36Cl in the Unsaturated Zone at Yucca Mountain 
Location Relevant sample sets Observed 36Cl distribution 
Soil Surface soils1 
Surface runoff 
Soil profiles 
Alluvial profiles for UZ-N37, 
UZ-N39, UZ-N54, UZ-N61, UZ- 
14, UZ#16 
In areas with sufficiently thick soil cover, bomb-pulse 36Cl is almost 
completely retained within the uppermost 2-3 m of soil. For thinner 
soils, some fraction of the bomb-pulse signal has moved down into 
the underlying bedrock. Elevated 36Cl/Cl ratios in shallow soils and 
surface runoff show that residual bomb-pulse 36Cl is still present on 
the surface. 
TCw Bomb-pulse in TCw: UZ-N11, 
UZ-N15, UZ-N16, UZ-N17, UZN27, 
UZ-N36, UZ-N38, UZN53, 
UZ-N55, UZ-N64 
No bomb-pulse in TCw: UZN37, 
UZ-N54, UZ#16 
ESF North Ramp 
ESF South Ramp 
Based on borehole data, bomb-pulse 36Cl appears to be widely 
present in the fractured welded TCw unit where it is overlain by thin 
soil cover (ridgetops and sideslopes) and absent where the soil 
thickness is at least 3 m. Fracture transport is also indicated by UZN53 
neutron logging data which have shown changes in moisture 
content down to a depth of 12 m, well into the TCw (Flint and Flint, 
1995, p. 29). The North Ramp data provide evidence of transport of 
bomb-pulse 36Cl through the TCw. 
PTn Bomb-pulse in PTn: 
UZ-N11, UZ-N53; UZ-N55; 
ESF North Ramp2 
Evidence for fast transport of water into the PTn is shown by 
elevated 36Cl/Cl ratios from this interval in boreholes with thin soil 
cover. Bomb-pulse 36Cl has also been measured in the PTn unit in 
several ESF samples from the North Ramp.2 
No bomb-pulse in PTn: most of 
PTn in UZ-N37, UZ-N53, UZN54, 
UZ#16, UZ-14 
ESF North Ramp 
ESF South Ramp 
No unambiguous evidence of bomb-pulse 36Cl is seen in the South 
Ramp despite infiltration rates and soil thicknesses that are similar 
to those over the North Ramp. 
TSw ESF Main Drift, Alcove #6, 
ESF Niche#1 
Cross Drift 
UE-25 NRG#4 
UE-25 NRG#5 
USW NRG-7a 
Perched water: UZ-14, NRG- 
7A, SD-7, SD-9 
Bomb-pulse 36Cl has been observed at several locations in the ESF 
and Cross Drift, and appears to be associated with faults.2 No 
unambiguous levels of bomb-pulse 36Cl are observed in any of the 
perched water bodies at the base of this unit or at the top of the 
CHn; values for these samples are at or slightly above present-day 
background. Borehole 36Cl data (from ream-bit cuttings) for this unit 
are usually too diluted by rock Cl to provide a reliable indication of 
the presence or lack of bomb-pulse 36Cl. 
CHn UZ-14 
UZ#16 
SD-12 
No unambiguous levels of bomb-pulse 36Cl have been observed in 
the CHn in surface-based boreholes. Measured 36Cl/Cl ratios are 
generally at or somewhat above present-day background. The 
highest ratios have been measured in SD-12, to a maximum value 
of 843 x 10-15. 
Saturated 
zone 
C#3, G-2, SD-7, J-13, SD-9, 
WT-10, WT-12 
The 36Cl/Cl ratio is uniformly at present-day background in the 
aquifer underlying the site, independent of location or depth 
Data sources: The above table is based on a review of data in the following DTNs: LA000000000062.002, 
LA9909JF0831222.001, LA9909JF831222.003, LA9909JF831222.005, LA9909JF831222.010, 
LAJF831222AQ95.005, LAJF831222AQ95.006, LAJF831222AQ95.007, LAJF831222AQ96.005, 
LAJF831222AQ96.006, LAJF831222AQ96.008, LAJF831222AQ96.009, LAJF831222AQ96.010, 
LAJF831222AQ96.011, LAJF831222AQ96.012, LAJF831222AQ96.013, LAJF831222AQ96.014, 
LAJF831222AQ96.015, LAJF831222AQ97.002, LAJF831222AQ97.006, LAJF831222AQ97.007, 
LAJF831222AQ98.003, LAJF831222AQ98.004, LAJF831222AQ98.005, LAJF831222AQ98.009, 
LAJF831222AQ98.011, LA9912JF831222.001. The stratigraphic interval from which each borehole sample was 
collected was determined using the appropriate references listed in Table 4. 
Relevant assumptions from Table 2: 5, 6 and 7 
Corroborative data: 
1 Numerous analyses of 36Cl in surface soil samples from Yucca Mountain confirm the continued presence of 
the bomb-pulse signal (DTN: LAJF831222AN97.012 and LAJF831222AN98.013). 
2 Numerous analyses of 36Cl in tunnel construction water confirm that this potential source of contamination 
cannot be the source of the elevated 36Cl/Cl used to identify the presence of bomb pulse (DTN: 
LAJF831222AN97.008).

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-31 
Table 14. Chlorine-36 in Faults and Fault Zones in the Cross Drift 
Cross Drift 
station (m) 
Sampling criterion Description of sampled feature 36Cl/Cl x 10-15 
(See note) 
CS1135.5 Systematic fault transect Breccia from Sundance fault zone 
zone 
347  16 
CS1137 Systematic fault transect Fractured wallrock adjacent to 
Sundance fault zone 
1206  98 
CS1317 Systematic fault transect Breccia 587  42 
CS1318 Systematic fault transect Breccia in fault zone 342  29 
CS2154 Systematic fault transect Breccia in fault zone 918  49 
CS2154.5 Systematic fault transect Breccia in fault zone 4890  174 
CS2238 Other through-going fault Breccia in fault zone 2361  106 
CS2348 Other through-going fault Fault with 3 m offset 1052  38 
CS2530.5 Systematic fault transect Fractured rock between 2 faults 1122  45 
CS2545 Opportunistic Highly fractured bedrock within 
Solitario Canyon fault zone 
854  43 
CS2550 Opportunistic Fractured rock and gouge within 
Solitario Canyon fault zone 
324  24 
CS2570 Systematic fault transect Solitario Canyon fault zone 2158  87 
CS2580 Systematic fault transect Solitario Canyon fault zone 890  55 
CS2585 Other through-going fault Brecciated footwall of fault 2460  103 
CS2586.5 Other through-going fault Brecciated hanging wall of fault 1233  41 
CS2590 Systematic fault transect Solitario Canyon fault zone 1379  58 
CS2621 Other through-going fault Solitario Canyon fault zone 974  50 
Data source: DTN: LA9909JF831222.003. 
Relevant assumptions from Table 2: 5, 6 and 7 
Note: Measured 36Cl/Cl ratios have been adjusted to correct for the presence of construction water, as 
estimated from the measured Br/Cl ratio.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-32 
Table 15. Carbon Isotopes in Unsaturated-zone Pore Waters from Surface-based Boreholes at Yucca Mountain 
Drill Hole Depth interval (ft) Processed 
length of 
core1 (ft) 
Hydrologic 
Unit2 Lithostratigraphic 
unit2 
d 13C 
()3 
14C 
(pmc)3 
Uncorrected 
14C age (yr)4 
ESF-AL#3- 
RBT#4 
72.0 74.2 2.2 TCw Tpcplnc -12.2 89 961 
ESF rubble from 
CS07+57.3 
--- --- --- TCw --- -16.2 84.7 1369 
NRG-6 219.9 256.1 1.2 PTn Tpbt2 -14.9 92.1 679 
NRG-7a 166.2 167.0 0.8 PTn Tpbt3 -12.9 92.6 634 
258.0 259.4 1.4 PTn Tpp/Tpbt2 --- 74.3 2449 
1492.7 1498.9 6.2 CHn Tpbt1 -18.6 58.4 4435 
SD-12 265.8 277.8 12.0 PTn Tpbt4 -14 80.3 1809 
1517.0 1517.9 0.9 CHn Tac3 -17.4 69.9 2953 
1637.4 1640.0 2.6 CHn Tacbt -16.9 66.5 3364 
1901.6 1901.8 0.2 CHn Tcp2 -12.2 63.7 3718 
1940.0 1942.6 2.6 CHn Tcp2 -16.3 59.2 4322 
SD-7 338.3 340.8 2.5 PTn Tpbt3 -18.1 74.1 2471 
1498.2 1498.9 0.7 CHn Tac2 -15.1 73.5 2539 
1524.6 1525.0 0.4 CHn Tac1 -17.5 62.8 3836 
1558.1 1558.9 0.8 CHn Tac1 -27.4 60.6 4130 
SD-9 1452.6 1453.0 0.4 CHn Tptpv1 -14.1 85.9 1253 
1535.2 1535.7 0.5 CHn Tac3 -15.3 88.9 970 
1619.7 1661.4 41.7 CHn Tac2 -14.5 95.3 397 
1800.7 1801.6 0.9 CHn Tacbt -16.4 82.3 1606 
UZ#16 158.1 158.4 0.3 PTn Tpcpv1 -9.3 87 1148 
180.9 --- --- PTn Tpbt3 -9.0 89.8 887 
219.4 219.6 0.2 PTn Tptrv3 -9.4 87.3 1120 
1344.1 1344.3 0.2 CHn Tac2 --- 87 1148 
1343.7 1379.9 0.6 CHn Tac2 -17.5 58.2 4463 
1380.0 1380.5 0.5 CHn Tac2 -23.3 71.8 2731 
1395.5 1398.7 0.6 CHn Tac2 -12.6 97.7 192 
1398.1 1398.3 0.2 CHn Tac2 --- 88.3 1026 
1408.2 1434.6 0.6 CHn Tac2 -16.6 53.1 5219 
1442.8 1443.2 0.4 CHn Tac2 -10.3 61.5 4008 
UZ-14 85.2 86.1 0.7 PTn Tpbt3 -17.1 83.2 1516 
91.0 100.8 1.45 PTn Tpbt3 -15.0 83.3 1507 
114.7 115.5 0.8 PTn Tpp --- 86.9 1158 
144.8 148.1 1.2 PTn Tpp --- 84.9 1350 
148.2 148.5 0.3 PTn Tpp -13.0 --- --- 
215.7 226.2 10.5 PTn Tpp -25.0 96.2 319 
235.1 246.4 6.9 PTn Tpbt2 -10.5 89.6 905 
254.9 255.7 0.8 PTn Tpbt2 -13.0 --- --- 
1409.35 1420.9 1.0 CHn Tpbt1 -12.4 81.8 1656 
1429.87 1430.15 0.28 CHn Tac3 -11.1 69.9 2953 
1460.8 1462.1 0.6 CHn Tac3 -13.4 96.3 311 
1524.55 1526.2 0.6 CHn Tac2 -11.8 93.4 563 
1563.6 1564.3 0.7 CHn Tac2 -15.8 76.8 2176 
1563.9 1565.1 1.2 CHn Tac2 -15.2 80 1840 
1585.0 1585.8 0.8 CHn Tac2 -11.3 93.7 537 
1605.6 1606.4 0.8 CHn Tac2 -14.6 81.1 1727 
1644.3 1645.2 0.8 CHn Tac2 -16.0 86.3 1215 
1674.3 1675.3 1.0 CHn Tac1 -13.7 91.3 750 
1694.9 1696.0 1.1 CHn Tacbt -10.3 92.3 661 
1714.5 1715.8 1.4 CHn Tacbt -11.6 96.3 311

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-33 
Table 15. Carbon Isotopes in Unsaturated-zone Pore Waters from Surface-based Boreholes at Yucca Mountain 
Drill Hole Depth interval (ft) Processed 
length of 
core1 (ft) 
Hydrologic 
Unit2 Lithostratigraphic 
unit2 
d 13C 
()3 
14C 
(pmc)3 
Uncorrected 
14C age (yr)4 
2014.5 2025.7 11.2 CHn Tcp1 -14.7 94.0 510 
2095.1 2096.0 0.9 CHn Tcb -15.7 84.6 1379 
Data sources: DTN: GS991299992271.001 (data set 9512----2272.003 for NRG-6, NRG-7A, UZ-14, UZ#16), 
GS961108312271.002 (NRG-7a, SD-7, SD-9, SD-12, UZ-14), GS961108312261.006 (ESF samples), and 
GS970208312271.002 (SD-12). 
Assumptions from Table 2: 8, 9 (TBV) and 10 
Notes: 
1 Total length of core processed is estimated from the lengths of individual core listed for each composite 
sample in the source DTNs. 
2 Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval from which 
each sample was collected was determined using the appropriate references listed in Table 4. 
3 Typical uncertainties (one-sigma) for these data are 0.3 to 0.7 pmc for 14C, and 0.2 for d 13C (Section 
6.2.5). 
4 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where t1/2 is the 
half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity (100 pmc). See 
assumption 10 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-34 
Table 16. Carbon Isotopes in Unsaturated-zone Pore Waters from UZ#4 and UZ#5 
Drill hole Hydrogeologic and 
lithostratigraphic unit1 
Depth (m) Processed 
length of core 
(m) 
d 13C 
() 
14C 
(pmc) 
Uncorrected 
14C age (yr) 
UZ#4 PTn Tpbt2 96.0  100.6 4.6 -20.0 88.6 998 
UZ#5 PTn Tpbt2 103.6  105.2 1.6 -26.7 55.1 4914 
Data source: DTN: GS920408312272.002 
Relevant assumptions from Table 2: 8, 9 (TBV) and 10 
Notes: 
1 Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval from which 
each sample was collected was determined using the appropriate references listed in Table 4. 
2 Typical uncertainties (one-sigma) for these data are 0.3 to 0.7 pmc for 14C, and 0.2 for d 13C (Section 
6.2.5). 
3 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where t1/2 is the 
half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity (100 pmc). See 
assumption 10 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-35 
Table 17. Carbon Isotopes in Unsaturated-zone Gases from the Atmosphere and Shallow Boreholes 
at Yucca Mountain 
Borehole Location of 
gas 
collection 
Collection date 14C 
(pmc) 
d 13C 
() 
UZ-1 Atmosphere Apr-84 125.6 -8.9 
UZ-1 Atmosphere Apr/May-85 124.4 -8.6 
UZ-13 Atmosphere 21-Mar-95 106.2 --- 
UZ-13 Atmosphere 26 & 29-Mar-95 115.4 -8.7 
UZ-N75 Atmosphere 15-Mar-94 114.6 --- 
UZ-1 Surface Apr-84 124.3 -16.6 
UZ-1 Surface Apr/May-85 123.4 -14.6 
UZ-6 Annulus 15-Mar-94 90.4 --- 
UZ-6 Annulus 21-Mar-95 93.0 --- 
UZ-6 Annulus 26 & 29-Mar-95 94.2 -17.4 
UZ-N93 Annulus 15-Mar-94 113.5 --- 
UZ-N93 Annulus 26 & 29-Mar-95 114.0 -17.4 
UZ-N94 Annulus 15-Mar-94 114.0 --- 
UZ-N94 Annulus 26 & 29-Mar-95 109.8 -17.6 
UZ-N95 Annulus 15-Mar-94 106.0 --- 
UZ-N95 Annulus 26 & 29-Mar-95 109.4 -17.2 
Data sources: DTN: GS930508312271.021, GS941208312261.008, GS950808312261.004, and 
GS960208312261.002 
Relevant assumptions from Table 2: 8 and 9 
Notes: 
These data are used to corroborate the present-day elevated 14C activity in the atmosphere due to global fallout, 
and that this activity is not greatly diluted by processes in shallow soil or bedrock although the effects of 
microbial activity and plant respiration on surface and subsurface samples result in a shift in d13C to more 
negative values.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-36 
Table 18. Carbon Isotopes in Unsaturated-zone Gases from Deep Open Surface-based Boreholes at 
Yucca Mountain (NRG#5, NRG-6, NRG-7, SD-7, SD-9, SD-12, UZ-14 and UZ#16) 
Bore- 
Hole 
Depth Hydrogeologic 
and 
lithostratigraphic 
unit1 
Collection 
date 
CO2 
(vol. 
%)2 
d 13C 
()3,4 
14C 
(pmc) 
3,4 
Uncorrected 
14C 
age (yr)5 
NRG#5 133 ft TCw Tpcpln 14&15-Aug-96  -16.7 88.82 978 
 -14.6   
 -14.6   
243 ft PTn Tpp 14&15-Aug-96  -16.7 68.56 3112 
 -14.9   
 -14.8   
 -9.7   
298 ft PTn Tpbt2 14&15-Aug-96  -15.5 69.57 2992 
 -14.6   
 -14.6   
354 ft TSw Tptrn 14&15-Aug-96  -15.3 54.19 5051 
 -14.4   
 -14.4   
410 ft TSw Tptrn 23-Aug-95  -14.9   
(Zone 5) 14&15-Aug-96  -15.7 65.77 3455 
 -14.6   
 -14.4   
 -13.1   
 -12.1   
466 ft TSw Tptrn 14&15-Aug-96  -16.4 77.47 2105 
 -15.6   
 -15.6   
475 ft TSw Tptrn Mar-94  -16.1 51.3 5503 
521 ft TSw Tptprl or 14&15-Aug-96  -16.8 69.95 2947 
Tptpul  -15.2   
 -15.2   
572 ft TSw Tptprl or 23-Aug-95  -15.4   
(Zone 9) Tptpul 14&15-Aug-96  -14.5 57.27 4596 
 -14.3   
 -14.1   
 -14.0   
 -11.3   
 -14.0   
633 ft TSw Tptprl or 14&15-Aug-96  -14.3   
Tptpul  -14.4   
 -15.7 61.31 4034 
744 ft TSw Tptpul 14&15-Aug-96  -15.7 58.41 4433 
799 ft TSw Tptpmn 14&15-Aug-96  -14.6 59.00 4350 
 -13.0   
 -13.0   
1225 ft TSw Tptpln Mar-94  -15.0 93.1 589

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-37 
Table 18. Carbon Isotopes in Unsaturated-zone Gases from Deep Open Surface-based Boreholes at 
Yucca Mountain (NRG#5, NRG-6, NRG-7, SD-7, SD-9, SD-12, UZ-14 and UZ#16) 
Bore- 
Hole 
Depth Hydrogeologic 
and 
lithostratigraphic 
unit1 
Collection 
date 
CO2 
(vol. 
%)2 
d 13C 
()3,4 
14C 
(pmc) 
3,4 
Uncorrected 
14C 
age (yr)5 
(Zone 13) 23-Aug-95  -15.0   
NRG-6 20 ft TCw Tpcpll 3-May-94 0.07 -15.2   
80 ft TCw Tpcpln Mar-94  -15.2 92.1 679 
24-May-94 0.11 -14.3   
200 ft PTn Tpp Mar-94  -14.9 91.0 778 
24-May-94 0.115 -14.3   
275 ft TSw Tptrn 3-May-94 0.06    
24-May-94  -15.1   
600 ft TSw Tptpul Mar-94  -15.5 83.2 1516 
24-May-94 0.115 -14.1   
725 ft TSw Tptpmn 3-May-94 0.06    
24-May-94  -14.8   
925 ft TSw Tptpll Mar-94  -16.1 94.2 493 
24-May-94 0.11 -14.2   
1000 ft TSw Tptpll 3-May-94 0.07 -14.5   
NRG-7 140 ft PTn Tpcpv2 Mar-94  -16.8 108.0 Modern 
29-Jun-94 0.12 -17.35   
490 ft TSw Tptrl Mar-94  -18.2 111.7 Modern 
29-Jun-94 0.19 -17.8   
890 ft TSw Tptpll Mar-94 0.15 -19.0 111.0 Modern 
29-Jun-94 0.15 -17.8   
1215 ft TSw Tptpll Mar-94  -18.0   
29-Jun-94 0.19 -17.7   
SD-7 300 ft PTn Tpcpv2 15-Aug-96  -17.6 100.27 Modern 
 -16.4   
 -16.3   
350 ft PTn Tpp 15-Aug-96  -16.4 91.38 743 
 -15.1   
 -14.1   
400 ft TSw Tptrn 15-Aug-96  -16.2 83.78 1459 
 -14.6   
 -14.5   
500 ft TSw Tptpul 15-Aug-96  -16.9 72.18 2688 
 -13.0   
 -13.0   
550 ft TSw Tptpul 15-Aug-96  -14.6 92.43 649 
 -12.3   
 -12.1   
600 ft TSw Tptpul 15-Aug-96  -14.6 79.40 1902 
 -12.7   
 -12.6  

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-38 
Table 18. Carbon Isotopes in Unsaturated-zone Gases from Deep Open Surface-based Boreholes at 
Yucca Mountain (NRG#5, NRG-6, NRG-7, SD-7, SD-9, SD-12, UZ-14 and UZ#16) 
Bore- 
Hole 
Depth Hydrogeologic 
and 
lithostratigraphic 
unit1 
Collection 
date 
CO2 
(vol. 
%)2 
d 13C 
()3,4 
14C 
(pmc) 
3,4 
Uncorrected 
14C 
age (yr)5 
650 ft TSw Tptpul 15-Aug-96  -9.1   
 -8.9   
700 ft TSw Tptpmn 15-Aug-96  -16.0 86.78 1169 
 -13.3   
 -13.3   
800 ft TSw Tptpmn 15-Aug-96  -15.6 84.18 1420 
 -12.3   
 -12.3   
508  633 m TSw Tptpul Not specified  -25.0 41.52 7247 
SD-9 0  454 m 
(Zone 1) 
TCw- 
CHn 
Tpcplnc/ 
Tac3 
Not specified  -16.1 96.70 277 
2/01/95 0.27 -13.7   
8/23/95  -15.2   
454  560 m 
(Zone 2) 
CHn Tac3- 
Tcp4 
Not specified  -19.1 51.04 5545 
2/01/95 0.092 -19.6   
8/23/95  -19.8   
UZ-14 1445 ft CHn Tac3 1997 0.05 -15.1 99.17 Modern 
1490 ft CHn Tac3 1997 0.06 -19.4 50.42 5646 
1540 ft CHn Tac2 1997 1.0 -8.4 48.76 5922 
1590 ft CHn Tac2 1997 0.04 -9.3 99.2* Modern 
1640 ft CHn Tac2 1997 0.06 -9.2 100.9* Modern 
1690 ft CHn Tac1 1997 1.2 -20.9 67.8 3204 
1738 ft CHn Tacbs 1997 1.1 -20.0 80.1 1830 
Data sources: DTN: GS941208312261.008 (NRG#5, NRG-6, NRG-7), GS950808312261.004 (SD-9), 
GS960208312261.002 (NRG#5, SD-9), GS961108312271.002 (SD-7, SD-9), 
GS970283122410.002 (NRG#5, SD-7), and GS970908312271.003 (UZ-14). Only the average CO2 
concentrations and 13C values are reported in the above table when replicate analyses are available. 
Data have been rounded to make it easier to compare them, although 14C ages have been 
calculated from the unrounded values reported in the DTNs. 
Relevant assumptions from Table 2: 8, 9 (TBV), 10, 17 and 18 
Notes: 
 data not available 
No report collection date not reported 
* Contamination with atmospheric air is suspected as indicated by 13C data, although there were no 
known leaks present during sample collection (DTN: GS970908312271.003, SEP Table 
S97576.003) 
1 Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. The stratigraphic interval 
from which each sample was collected was determined using the appropriate references listed in Table 4. 
2 In open boreholes, CO2 gas concentrations are often quite variable from one collection time to 
another, even when the samples are collected from the same packed-off borehole interval within 24

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-39 
hours of one another (e.g., CO2 data in DTN: GS941208312261.008). Thus, the CO2 values 
reported in this table should only be used as an approximate indication of in situ conditions. 
3 Yang, Yu et al. (1998, p. 16) warn that samples collected for SD-7, SD-9 and SD-12 by the wholegas 
balloon method varied from 10 to 25  for replicate samples (USGS data), probably due to 
problems with the balloon nozzle, and hence these data are not reported here. The values reported 
above were obtained by the Desert Research Institute (DRI); these were less variable than the 
USGS data although they also tend to be more negative by a few units per mil when collected with 
the molecular sieve. 
4 Typical uncertainties (one-sigma) for these data are 0.3 to 0.7 pmc for 14C, and 0.2 for d 13C 
(Section 6.2.5). 
5 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where 
t1/2 is the half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity 
(100 pmc). See assumption 10 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-40 
Table 19. Carbon Isotopes in Unsaturated-zone Gases from Boreholes UZ-6 and UZ-6s 
14C (pmc)1 Bore- 
Hole 
Depth 
(ft) 
Hydrogeologic 
unit4 
d 13C ()1 
26-Mar-95 
WGM2 
15-Mar-94 
WGM2 
21-Mar-95 
Mole. 
Sieve2 
29-Mar-95 
KOH2 
Uncorrected 
14C age (yr) 3 
29-Mar-95 
UZ-6 200 TCw -17.40 --- 88.47 88.15 1040 
800 TSw -17.14 --- 83.27 84.91 1349 
1195 TSw -17.18 --- 84.74 86.09 1235 
1800 CHn -16.62 --- 50.36 40.98 7355 
UZ-6s 20 TCw -16.68 107.90 90.67 106.81 Modern 
40 TCw -16.59 107.33 100.93 106.75 Modern 
60 TCw -16.90 106.09 96.17 105.24 Modern 
100 TCw -16.45 107.90 109.53 105.62 Modern 
200 TCw -16.42 109.07 102.03 107.82 Modern 
350 TCw -16.34 107.79 107.61 107.32 Modern 
400 TCw -15.16 100.73 101.90 99.45 Modern 
430 PTn -16.42 --- 95.00 94.72 447 
Data sources: DTN: GS950808312261.004 and GS960208312261.002. 
Relevant assumptions from Table 2: 8, 9 (TBV), and 10 
Notes: 
1 Typical uncertainties (one-sigma) for these data are 0.3 to 0.7 pmc for 14C, and 0.2 for d 13C 
(Section 6.2.5). 
2 Gas collection methods: WGM, whole gas balloon method; Mole. Sieve, molecular sieve method; 
KOH, gas bubbled through potassium hydroxide solution 
3 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where 
t1/2 is the half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity 
(100 pmc). See assumption 10 in Table 2. 
4 Hydrogeologic unit nomenclature from Table 1. The stratigraphic interval from which each sample was 
collected was determined using the appropriate references listed in Table 4.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-41 
Table 20. CO2 and Carbon Isotope Profiles in Unsaturated-zone Gases from Instrumented Boreholes 
UZ-1 and SD-12 
Bore 
hole Depth 
Probe 
or 
station 
Hydrogeologic and 
lithostratigraphic 
unit1 
CO2 
(vol. %)2 
d 13C 
() 
14C 
(pmc) 
Uncorrected 
14C age2 (yr) 
UZ-1 42 ft 1 Qtac UO 0.535 -18.9 108.5 Modern 
62 ft 2 PTn Tpy 0.581 -20.4 104.3 Modern 
93 ft 3 PTn Tpbt3 0.307 -20.8 96.2 319 
131 ft 4 PTn Tpp 0.428 -19.9 89.4 924 
201 ft 5 PTn Tpp 0.230 -20.3 67.2 3277 
266 ft 6 PTn Tptrv3 0.205 -17.4 64.7 3590 
348 ft 7 TSw Tptrn 0.104 -16.2 63.3 3770 
421 ft 8 TSw Tptrn 0.092 -15.7 61.1 4062 
501 ft 9 TSw Tptpul 0.082 -16.2 47.4 6155 
621 ft 10 TSw Tptpul 0.051 -16.1 42.6 7036 
747 ft 11 TSw Tptpmn 0.094 -14.6 47.2 6190 
871 ft 12 TSw Tptpll 0.121 -15.7 37.1 8175 
998 ft 13 TSw Tptpll 0.042 -16.9   
1100 ft 14 TSw Tptpll 0.091 -15.0 38.8 7806 
1207 ft 15 TSw Tptpll 0.216 -19.7 14.5 15921 
SD-12 24.7 m P TCw Tpcpmn/Tpcpll  -22.55 90.98 779 
43.9 m O TCw Tpcplnh  -20.20 49.17 5853 
65.2 m N TCw Tpcplnc  -21.99 87.39 1111 
91.7 m L PTn Tptrv1  -16.41 82.71 1565 
107.0 m K TSw Tptrn  -20.98 
-15.58 
77.75 
94.91 
2075 
431 
128.9 m J TSw Tptrn  -22.11 57.95 4498 
171.0 m I TSw Tptpul  -23.57 38.95 7774 
208.2 m H TSw Tptpmn  -24.71 36.92 8215 
236.8 m G TSw Tptpmn  -25.57 31.57 9506 
256.6 m F TSw Tptpll  -24.40 34.13 8863 
285.0 m E TSw Tptpll  -21.89 52.41 5327 
322.5 m D TSw Tptpln  -21.79 
-23.83 
46.65 
34.43 
6287 
8791 
385.6 m C TSw Tptpln  -22.86 88.69 990 
407.2 m B CHn Tptpv2  -24.63 
-23.65 
24.43 
26.89 
11620 
10829 
435.9 m A CHn Tac4  -17.17 84.47 1392 
Data sources: DTN: GS991299992271.001 (data set 9507----2271.001 for UZ-1 samples collected 
February 1995) and GS961108312271.002 (SD-12 samples collected October 1996) 
Relevant assumptions from Table 2: 8, 9 (TBV), 10, 17 and 18 
Note:   not available 
1 Hydrologic and lithographic nomenclature from Table 1. The stratigraphic interval from which each 
sample was collected was determined using the appropriate references listed in Table 4. UZ-1 
stratigraphy and UZ-1 probe depths from DTN: GS930508312271.021. 
2 Uncorrected 14C age calculated using the radioactive decay equation: t = (t1/2 / ln 2) ln (A/A0), where 
t1/2 is the half-life for 14C (5715 yr), A is the measured 14C activity, and A0 is the initial 14C activity 
(100 pmc). See assumption 10 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-42 
Table 21. Carbon Isotopes in Unsaturated-zone Gases from Boreholes in ESF Alcoves 
Borehole 
Sampled 
interval 
(m) 
Hydrogeologic 
unit1 
Lithostratigraphic 
unit1 
14C 
(pmc) 
d 13C 
() 
Alcove #1 air NA --- --- --- -9.13 
-9.07 
ESF-AL#1-RBT#1 30  32 TCw Tpcpul 101.35 -15.61 
35  42.5 TCw Tpcpul --- -13.49 
44  48 TCw Tpcpul --- -16.40 
49  55 TCw Tpcpul --- -13.60 
55.75  59 TCw Tpcpul --- -14.49 
60  73 TCw Tpcpul --- -14.42 
ESF-AL#1-RBT#2 6.5  9 TCw Tpcpul --- -18.35 
28  38 TCw Tpcpul --- -13.46 
62  65 TCw Tpcpul --- -16.20 
62  83 TCw Tpcpul 92.76 -14.69 
86  105 TCw Tpcpul --- -16.23 
-15.80 
ESF-AL#1-RBT#3 50.75  62.5 TCw Tpcpul 107.35 -15.79 
-10.22 
64  66.5 TCw Tpcpul --- -17.86 
85.5  92.8 TCw Tpcpul --- -15.83 
ESF-AL#6 ZONE 1 WGM 4.7 TSw Tptpmn 69.24 -14.14 
ESF-AL#6 ZONE 2 WGM 7.8 TSw Tptpmn 75.09 -14.06 
ESF-AL#6 ZONE 3 WGM 9.3 TSw Tptpmn 71.58 -14.11 
ESF-AL#6 ZONE 4 WGM 10.8 TSw Tptpmn 63.74 -15.08 
ESF-AL#6 ZONE 5 WGM 12.4 TSw Tptpmn 66.77 -15.45 
ESF-AL#6 ZONE 6 WGM 13.9 TSw Tptpmn 68.23 -15.38 
ESF-AL#6 ZONE 7 WGM 15.4 TSw Tptpmn 70.76 -15.55 
ESF-AL#6 ZONE 8 WGM 16.9 TSw Tptpmn 61.37 -14.78 
ESF-AL#6 ZONE 9 WGM 18.5 TSw Tptpmn 58.14 -16.17 
ESF-AL#6 ZONE 10 WGM 21.5 TSw Tptpmn 66.01 -15.89 
Data sources: DTN: GS960208312261.002 (ESF Alcove #1), GS970283122410.002 (..13C in ESF 
Alcove #6), and GS990983122410.003 (14C in ESF Alcove #6). The ..13C values in this table are the 
averages of those reported for each zone in the Alcove #6 borehole. 
Relevant assumptions from Table 2: 8 and 9 (TBV) 
1 Hydrologic and lithographic nomenclature from Table 1.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-43 
Table 22. Comparison of Carbon Isotopes in Pore-water and Gas Samples Collected from Similar Borehole 
Intervals 
Borehole Pore-water results Gas results 
Stratigraphic 
unit 
Depth 
(m) 
d13C 
() 
14C 
(pmc) 
Stratigraphic 
unit 
Depth 
(m) 
d13C 
() 
14C 
(pmc) 
NRG-6 PTn Tpbt2 71.6 -14.9 92.1 PTn Tpp 61 -14.1 to -14.9 91.0 
SD-7 PTn Tpbt3 103 -18.1 74.1 PTn Tpp 107 -14.1 to -16.4 91.4 
SD-9 CHn Tac3 468 -15.3 88.9 
CHn Tac2 494 to 
506 
-14.5 95.3 CHn 51.0 
CHn Tacbt 549 -16.4 82.3 
Tac3 
to 
Tcp4 
454 
to 
560 
-19.1 
to 
-19.8 
SD-12 PTn Tpbt4 82 -14 80.3 PTn Tptrv1 92 -16.4 82.7 
CHn Tac3 462 -17.4 69.9 CHn Tac4 436 -17.2 84.5 
UZ-14 CHn Tac3 436 -11.1 69.9 CHn Tac3 440 Variable 99.2 
CHn Tac3 445 -13.4 96.3 CHn Tac3 454 -19.45 50.4 
CHn Tac2 465 -11.8 93.4 CHn Tac2 469 -8.42 48.8 
CHn Tac2 477 -15.8 76.8 
CHn Tac2 477 -15.2 80.0 
CHn Tac2 483 -11.3 93.7 CHn Tac2 485 -9.3 99.2 
CHn Tac2 490 -14.6 81.1 
CHn Tac2 501 -16 86.3 CHn Tac2 500 -9.24 100.9 
CHn Tac1 510 -13.7 91.3 CHn Tac1 515 -20.89 67.8 
CHn Tacbt 517 -10.3 92.3 CHn Tacbs 530 -20.05 80.1 
CHn Tacbt 523 -11.6 96.3 
PTn Tpbt3 26 -17.1 83.2 PTn Tpbt3 28 -20.8 96.2 
PTn Tpbt3 29 -15.0 83.3 
PTn Tpp 45 -13.0 84.9 PTn Tpp 40 -19.9 89.4 
UZ-14 pore water 
(compared with 
UZ-1 gas from 
similar depth) 
PTn Tpp 67 -25.0 96.2 PTn Tpp 61 -20.3 67.2 
Data sources: Based upon a comparison of sampled intervals listed in Tables 15, 18 and 20, data 
were selected from DTN: GS991299992271.001 (data sets 9512----2272.003 for UZ-14 and NRG-6 
pore waters, and 9507----2271.001 for UZ-1 gas), GS941208312261.008 (NRG-6 gas), 
GS970283122410.002 (SD-7 gas), GS970908312271.003 (UZ-14 gas), and GS961108312271.002 
(SD-7, SD-9, and SD-12 pore waters; SD-9 and SD-12 gas). 
Relevant assumptions from Table 2: 8 and 9 (TBV)

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-44 
Table 23. Uranium Isotopic Data for Ephemeral Stream Flow in the Vicinity of Yucca Mountain 
Location Sample Name Collection Concentration Activity Ratios 
Date U g/l 2.. 234U/238U 2.. 
Fortymile Wash runoff CSS950106FMOV.4 01/06/95 0.0473 0.0002 3.670 0.081 
Pah Canyon SPC00009734 HOH 01/26/95 0.1111 0.0003 1.833 0.015 
Fortymile Canyon SPC00009805 HOH 01/25/95 0.2613 0.0007 1.497 0.015 
Upper Split Wash SPC00009732 HOH 01/25/95 0.3880 0.0010 1.501 0.009 
Yucca Wash near mouth SPC00009733 HOH 01/26/95 0.1086 0.0003 1.623 0.016 
Upper reach, Wren Wash SPC00009806 HOH 01/25/95 0.4868 0.0012 1.525 0.006 
Wren Wash SPC00529907-Wren Wash 02/20/98 0.2224 0.0007 1.543 0.005 
Pagany Wash SPC00529917-Pagany Wash 02/24/98 0.3766 0.0013 1.528 0.006 
Yucca Wash SPC00529927-Yucca Wash 02/24/98 0.1705 0.0005 1.721 0.01 
Data sources: DTN: GS960908315215.013 and GS980908312322.009 
Uranium isotopic data obtained by mass spectrometry at U.S. Geological Survey, Denver, Colorado. All errors 
are reported at the 95 percent confidence level.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-45 
Table 24. Locations and Other Physical Characteristics of Wells Sampled for Chemical and Isotopic Analyses of 
Groundwater in the Vicinity of Yucca Mountain. 
Site name UTM-x (m) UTM-y 
(m) 
Site 
elevation 
(m) 
Well 
depth 
(m) 
Water 
table 
depth 
(m) 
Aquifer1 
15S/49E-13dda 553312.5 4055302 796 174 90 Qal 
15S/49E-22a1 550086.3 4054974 796 174 90 Qal 
15S/49E-22dcc 549672.5 4053523 784 148 78 Qtal 
15S/49E-27acc 549552.9 4052722 777 467 73 Qal 
15S/50E-18ccc 553710.0 4055273 812 120 105 Qal 
15S/50E-18cdc 553934.3 4055151 812 120 105 Qal 
15S/50E-19b1 553862.5 4054720 --- 110 103 Qal 
16S/49E-05acc 546664.5 4049439 746 87 21 Qal 
Airport Well 553289.0 4055086 804 229 76 Qal 
BGMW-11 534410.9 4062631 786 --- 72 Qal 
Cind-R-Lite Well 544027.0 4059809 831 140 101 Tv 
Cowboy Joe's 554132.4 4055245 --- --- --- Qal 
Gexa Well 4 534068.9 4086110 1198 488 188 Tv 
JF-3 554498.3 4067974 944 347 216 Tv 
NDOT well 554132.4 4055245 810 151 105 Qal 
TW-5 562605.0 4054686 931 244 207 Qal 
UE-25 b#1 (0-1220 m) 549954.5 4078422 1201 1220 470 Th/Tct 
UE-25 b#1 (853-914 m) 549954.5 4078422 1201 1220 470 Tcb 
UE-25 c#1 550957.7 4075943 1131 914 401 Tcb/Tct 
UE-25 c#2 550944.0 4075867 1132 914 401 Tcb 
UE-25 c#3 550919.8 4075886 1132 914 402 Tcb/Tct 
UE-25 J-11 563816.0 4071049 1050 405 317 Tb 
UE-25 J-12 554435.8 4068767 953 347 226 Tv 
UE-25 J-13 554004.4 4073550 1011 1063 283 Tpt 
UE-25 ONC-1 550479.9 4076608 1163 469 433 Th/Tcp 
UE-25 p#1 (0-1200 m) 551508.7 4075663 1114 1805 382 Tcp 
UE-25 p#1 (1300-1800 m) 551508.7 4075663 1114 1805 382 DSlm 
UE-25 WT#12 550162.9 4070647 1075 399 345 Tpt/Th 
UE-25 WT#14 552638.0 4077337 1076 399 346 Th 
UE-25 WT#15 554033.7 4078702 1083 415 354 Tpt 
UE-25 WT#4 550445.9 4079420 1169 482 438 Th 
UE-25 WT-7 546148.2 4075461 1197 491 421 Tv 
UE-29 a#2 (250-355 m) 555753.3 4088351 1215 422 29 Th 
UE-29 a#2 (87-213 m) 555753.3 4088351 1215 422 28 Th 
USW G-2 548138.6 4082554 1554 1831 534 Th/Tct 
USW G-4 548938.0 4078590 1270 915 541 Tct 
USW H-1 (572-687 m) 548721.8 4079944 1303 1829 572 Tcp 
USW H-1 (687-1829 m) 548721.8 4079944 1303 1829 572 Tcb 
USW H-3 547537.0 4075762 1483 1219 751 Tct 
USW H-4 549195.0 4077322 1249 1219 519 Tcb/Tct 
USW H-5 547665.5 4078838 1477 1219 704 Tcb/Tct 
USW H-6 (525-1220 m) 546196.1 4077816 1302 1220 526 Tcb/Tct 
USW H-6 (600-650 m) 546196.1 4077816 1302 1220 526 Tcb/Tct 
USW H-6 (753-835 m) 546196.1 4077816 1302 1220 526 Tcb/Tct 
USW VH-1 539986.2 4071718 963 762 184 Tcb 
USW VH-2 537737.6 4073222 974 1219 164 Tv 
USW WT-10 545976.0 4073389 1123 431 347 Tpt 
Data source: Oliver and Root (1997, attached file yucca.xls)

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-46 
Table 24 continued 
1 Aquifer  Geologic unit from which water was obtained (Oliver and Root 1997, p. 5) 
Qal Quaternary alluvium 
Qtal Quaternary-Tertiary alluvium 
Tv Tertiary volcanic rocks 
Tpt Tertiary Topopah Spring Member of Paintbrush Tuff 
Tct Tertiary Crater Flat Tuff 
Th Tertiary Tuffaceous beds of Calico Hills 
Tcb Tertiary Bullfrog Member of Crater Flat Tuff

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-47 
Table 25. Background 36Cl/Cl in Precipitation at Yucca Mountain 
Field site Sample 
identifier 
Depth or age 36Cl/Cl x 10-15 
Midway Valley soil pits Depth (m) 
UE-25 MWV-P2 
UE-25 MWV-P6 
UE-25 MWV-P13 
UE-25 MWV-P23 
UE-25 MWV-P24 
UE-25 NRSF-TP-16 
ST033 
ST034 
ST035 
ST078 
ST079 
ST080 
ST081 
ST084 
ST085 
ST086 
ST087 
ST088 
ST089 
1.9 
2.0 
2.1 
3.1 
2.75 
3.0 
2.55 
2.6 
2.3 
2.9 
2.5 
2.4 
2.2 
494 " 16 
470 " 16 
490 " 10 
458 " 12 
462 " 7 
459 " 15 
475 " 14 
483 " 11 
459 " 11 
466 " 11 
524 " 10 
466 " 9 
468 " 13 
Alluvium from boreholes Depth (m) 
UZN#39 
UZ-N54 
UZ-14 
UZ#16 
R502 
R504 
R006 
R007 
R008 
R009 
R413 
R414 
R415 
R417 
R418 
R167 
R168 
R169 
R170 
R171 
R172 
R173 
R174 
12.5 
18.1 
4.9 
5.9 
7.3 
8.0 
3.7 
4.2 
5.5 
7.6 
9.1 
3.7 
4.2 
5.0 
5.5 
6.1 
6.6 
7.1 
7.7 
515 " 24 
557 " 29 
526 " 22 
501 " 21 
507 " 14 
474 " 13 
497 " 16 
526 " 13 
549 " 18 
429 " 16 
479 " 11 
526 " 16 
500 " 15 
528 " 24 
750 " 35 
494 " 21 
538 " 24 
601 " 26 
507 " 26 
Fossil packrat urine 14C age (ka) 
Owl Canyon PM-035 
PM-039 
PM-038 
PM-034 
PM-040 
PM-036 
PM-037 
0.69 
1.65 
3.12 
3.96 
4.00 
6.70 
9.31 
514 " 16 
518 " 43 
443 " 21 
442 " 15 
438 " 15 
505 " 31 
510 " 48 
Unweighted average, 39 samples 501 " 54 
Data sources: DTN: LAJF831222AQ95.006 (Midway Valley soil pits), LAJF831222AQ96.006 (MWVP2), 
LAJF831222AQ96.008 (UZ-N39), LAJF831222AQ96.010 (UZ-N37), LAJF831222AQ96.012 (UZN54), 
LAJF831222AQ96.014 (UZ#16), LAJF831222AQ96.015 (UZ-14), LAJF831222AQ97.002 
(packrat middens), and GS960308315131.001 (14C dates for Owl Canyon samples). 
Note: Corroborative data provided by Little Skull Mountain fossil packrat urine samples: PM-002, 14C 
age = 1.09 ka, 36Cl/Cl = 516 (" 19) x 10-15; PM004, 14C age = 6.68 ka, 36Cl/Cl = 509 (" 16) x 10-15 (DTN: 
GS950708315131.003 and LAJF831222AQ97.002) 
ka  thousand years

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-48 
Table 26. Chloride Concentrations and Infiltration Rates calculated for Tunnel Pore Waters by the 
Chloride Mass Balance Method 
Borehole Tunnel Tunnel 
distance 
(m) 
Hydrologic 
unit1 
Stratigraphic 
unit1 
mg/L 
Cl 
Apparent 
infiltration rate2, 
mm/yr 
Rate 1 Rate 2 
ECRB-SYS-CS150 Cross Drift 150 TSw Tptpul 25.0 2.4 4.1 
ECRB-SYS-CS200 Cross Drift 200 TSw Tptpul 19.1 3.1 5.3 
ECRB-SYS-CS200 Cross Drift 200 TSw Tptpul 19.2 3.1 5.3 
ECRB-SYS-CS400 Cross Drift 400 TSw Tptpul 11.8 5.0 8.6 
ECRB-SYS-CS450 Cross Drift 450 TSw Tptpul 33.6 1.8 3.0 
ECRB-SYS-CS550 Cross Drift 550 TSw Tptpul 20.2 2.9 5.0 
ECRB-SYS-CS600 Cross Drift 600 TSw Tptpul 17.9 3.3 5.7 
ECRB-SYS-CS650 Cross Drift 650 TSw Tptpul 16.0 3.7 6.4 
ECRB-SYS-CS750 Cross Drift 750 TSw Tptpul 24.6 2.4 4.2 
ECRB-SYS-CS800 Cross Drift 800 TSw Tptpul 15.0 4.0 6.8 
ECRB-SYS-CS850 Cross Drift 850 TSw Tptpul 26.3 2.3 3.9 
ECRB-SYS-CS900 Cross Drift 900 TSw Tptpul 24.9 2.4 4.1 
ECRB-SYS-CS950 Cross Drift 950 TSw Tptpul 24.9 2.4 4.1 
ECRB-SYS-CS1000 Cross Drift 1000 TSw Tptpul 36.6 1.6 2.8 
ECRB-SYS-CS1050 Cross Drift 1050 TSw Tptpmn 16.6 3.6 6.1 
ECRB-SYS-CS1550 Cross Drift 1550 TSw Tptpll 37.7 1.6 2.7 
ECRB-SYS-CS1600 Cross Drift 1600 TSw Tptpll 31.3 1.9 3.3 
ECRB-SYS-CS1650 Cross Drift 1650 TSw Tptpll 16.5 3.6 6.2 
ECRB-SYS-CS1750 Cross Drift 1750 TSw Tptpll 12.9 4.6 7.9 
ECRB-SYS-CS1950 Cross Drift 1950 TSw Tptpll 14.3 4.2 7.1 
ECRB-SYS-CS2000 Cross Drift 2000 TSw Tptpll 22.4 2.7 4.6 
ECRB-SYS-CS2100 Cross Drift 2100 TSw Tptpll 17.0 3.5 6.0 
ECRB-SYS-CS2150 Cross Drift 2150 TSw Tptpll 16.4 3.6 6.2 
ECRB-SYS-CS2300 Cross Drift 2300 TSw Tptpll 21.0 2.8 4.9 
ESF-NR-MOISTSTDY#1a ESF 727 TCw Tpcplnc 19.7 3.0 5.2 
ESF-NR-MOISTSTDY#2 ESF 750 TCw Tpcplnc/mw 18.4 3.2 5.5 
ESF/CS/07+57.53 ESF 758 PTn Unknown 34.2 1.7 3.0 
ESF-AL#3-RBT#1 32.1/UP ESF Alcove 3 758 PTn Unknown 40.9 1.5 2.5 
ESF-NR-MOISTSTDY#3 ESF 770 TCw Tpcplnc/mw 40.3 1.5 2.5 
ESF-NR-MOISTSTDY#4 ESF 772 PTn Tpcpv2 47.1 1.3 2.2 
ESF-NR-MOISTSTDY#5 ESF 783 PTn Tpcpv2 27.9 2.1 3.7 
ESF-NR-MOISTSTDY#6 ESF 821 PTn Tpcpv1 69.2 0.9 1.5 
ESF-NR-MOISTSTDY#7 ESF 867 PTn Tpbt4 15.1 3.9 6.8 
ESF-NR-MOISTSTDY#8 ESF 870 PTn Tpy 15.7 3.8 6.5 
ESF-NR-MOISTSTDY#9 ESF 873 PTn Tpbt3 5.7 10.4 17.9 
ESF-NR-MOISTSTDY#10 ESF 880 PTn Tpbt3 15.0 4.0 6.8 
ESF-NR-MOISTSTDY#11 ESF 892 PTn Tpp 6.7 8.9 15.2 
ESF-NR-MOISTSTDY#13 ESF 1008 PTn Tpbt2 12.0 5.0 8.5 
ESF-NR-MOISTSTDY#15 ESF 1054 PTn Tptrv3/rv2 20.8 2.9 4.9 
ESF-NR-MOISTSTDY#16 ESF 1069 TSw Tptrv2 12.9 4.6 7.9 
ESF-LPCA-MOISTSTDY#2 ESF Alcove 4 1130 PTn Tpbt2/argillic 17.7 3.4 5.8 
ESF-LPCA-MOISTSTDY#3 ESF Alcove 4 1130 PTn Tpbt2 17.5 3.4 5.8 
ESF-HD-PERM-3 ESF Alcove 5 ~2800 TSw Unknown 111.0 0.5 0.9

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-49 
Table 26. Chloride Concentrations and Infiltration Rates calculated for Tunnel Pore Waters by the 
Chloride Mass Balance Method 
Borehole Tunnel Tunnel 
distance 
(m) 
Hydrologic 
unit1 
Stratigraphic 
unit1 
mg/L 
Cl 
Apparent 
infiltration rate2, 
mm/yr 
Rate 1 Rate 2 
ESF-HD-PERM-3 ESF Alcove 5 ~2800 TSw Unknown 133.0 0.4 0.8 
ESF-MD-NICHE3566#1 ESF 3566 TSw Tptpmn 15.7 3.8 6.5 
ESF-MD-NICHE3566LT#1 ESF 3566 TSw Tptpmn 27.5 2.2 3.7 
ESF-MD-NICHE3650#6 ESF 3650 TSw Tptpmn 15.9 3.7 6.4 
ESF-MD-NICHE3650#7 ESF 3650 TSw Tptpmn 32.3 1.8 3.2 
ESF-SR-MOISTSTDY#10 ESF 6648 TSw Tptrv2 15.3 3.9 6.7 
ESF-SR-MOISTSTDY#11 ESF 6658 PTn Tptrv3 26.5 2.2 3.8 
ESF-SR-MOISTSTDY#12 ESF 6668 PTn Tpbt2 29.7 2.0 3.4 
ESF-SR-MOISTSTDY#13 ESF 6679 PTn Tpbt2 32.2 1.8 3.2 
ESF-SR-MOISTSTDY#14 ESF 6696 PTn Tpbt4 33.0 1.8 3.1 
ESF-SR-MOISTSTDY#15 ESF 6704 PTn Tpcpv1 26.8 2.2 3.8 
ESF-SR-MOISTSTDY#16 ESF 6721 PTn Tpcpv1 39.1 1.5 2.6 
ESF-SR-MOISTSTDY#17 ESF 6729 TCw/PTn Tpcplnc/Tpcpv1 55.3 1.1 1.8 
ESF-SR-MOISTSTDY#19 ESF 6826 TSw Tptpul 17.1 3.5 6.0 
ESF-SR-MOISTSTDY#21 ESF 7054 PTn Tpbt2 80.9 0.7 1.3 
ESF-SR-MOISTSTDY#22 ESF 7056 PTn Tpbt2 103.0 0.6 1.0 
ESF-SR-MOISTSTDY#22r ESF 7056 PTn Tpbt2 96.1 0.6 1.1 
ESF-SR-MOISTSTDY#27 ESF 7444 TSw Tptrv1 38.9 1.5 2.6 
ESF-SR-MOISTSTDY#28 ESF 7446 TSw Tptrv2 43.2 1.4 2.4 
ESF-SR-MOISTSTDY#29 ESF 7453 PTn Tptrv3 63.2 0.9 1.6 
ESF-SR-MOISTSTDY#30 ESF 7460 PTn Tpbt2 107.6 0.6 0.9 
ESF-SR-MOISTSTDY#31 ESF 7465 PTn Tpbt2 97.6 0.6 1.0 
ESF-SR-MOISTSTDY#32 ESF 7472 PTn Tpbt2 72.4 0.8 1.4 
ESF-SR-MOISTSTDY#33 ESF 7477 PTn Tpbt2 87.3 0.7 1.2 
ESF-SR-MOISTSTDY#34 ESF 7481 PTn Tpp 85.1 0.7 1.2 
ESF-SR-MOISTSTDY#35 ESF 7488 PTn Tpbt3 72.2 0.8 1.4 
ESF-SR-MOISTSTDY#36 ESF 7490 PTn Tpbt3 54.0 1.1 1.9 
ESF-SR-MOISTSTDY#37 ESF 7498 PTn Tpbt4 83.4 0.7 1.2 
ESF-SR-MOISTSTDY#38 ESF 7503 PTn Tpbt4 74.6 0.8 1.4 
ESF-SR-MOISTSTDY#39 ESF 7504 PTn Tpcpv1 85.0 0.7 1.2 
UZTT-BB-PH1-2 Busted Butte NA CHn Below 
Tptpv1/Tac 
70.6 0.8 1.4 
UZTT-BB-PH1-3 Busted Butte NA CHn Tptpv1 51.2 1.2 2.0 
UZTT-BB-PH1-4 Busted Butte NA CHn Tac 64.6 0.9 1.6 
UZTT-BB-PH1-6 Busted Butte NA CHn Tptpv2/pv1 36.7 1.6 2.8 
UZTT-BB-PH1-7 Busted Butte NA CHn Tptpv2 25.6 2.3 4.0 
Source for pore-water chloride data: DTN: GS961108312261.006, LA9909JF831222.004, 
LA9909JF831222.010, and LA9909JF831222.012. 
Relevant assumptions from Table 2: 1, 2 (TBV), 3, 19 (TBV), 20 (TBV) and 21 (TBV). 
1 Hydrogeologic unit and lithostratigraphic unit nomenclature from Table 1. Cross Drift lithostratigraphic 
contacts from DTN: GS981108314224.005. 
2 The CMB method for estimating infiltration is discussed in section 6.9.1. Rates 1 and 2 assume average 
annual precipitation of 170 mm with average chloride concentrations of 0.35 mg/L and 0.6 mg/L, respectively.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-50 
Table 27. Apparent Infiltration Rates Calculated From Pore-water Chloride Concentrations at Yucca 
Mountain 
Borehole location Topographic 
category1 
Sample 
stratigraphy 
Average chloride 
concentration2, 
mg/L 
Apparent 
infiltration rate3, 
mm/yr 
Rate 1 Rate 2 
UZ#4 A PTn 104 0.6 1.0 
UZ#5 A PTn 42 1.4 2.4 
UZ-N37 A Alluvium 133 0.4 0.8 
UZ-N54 A Alluvium 7400 0.01 0.01 
UZ-14 A Alluvium 520 0.1 0.2 
UZ-14 A PTn 245 0.2 0.4 
UZ#16 A Alluvium 3700 0.02 0.03 
UZ#16 A PTn 32 1.8 3.1 
NRG-6 A PTn 185 0.3 0.6 
SD-9 A PTn 170 0.4 0.6 
NRG-7a B PTn 39 1.5 2.6 
SD-12 B PTn 50 1.2 2.1 
SD-7 C PTn 77 0.8 1.3 
ESF North Ramp (16 
samples) 
C PTn 23 8 14 
ESF South Ramp (31 
samples) 
C PTn 64 1.2 2.1 
ESF Main Drift (6 samples) C TSw 20 7 12 
Cross Drift (24 samples) C TSw 22 5 9 
Sources for chloride data: DTN: LA0002JF831222.001 (alluvial samples), LA0002JF831222.002 (PTn samples), 
and Table 26 (ESF and Cross Drift samples) 
Relevant assumptions from Table 2: 1, 2 (TBV), 3, 19 (TBV), 20 (TBV) and 21 (TBV). 
1 Topographic categories for borehole locations 
A - Beneath deep alluvium (center of large wash, soil > 3 m thick) 
B - Terrace (side of large wash or near base of sideslope, soil 0.5 to 3 m) 
C - Beneath thin alluvium (ridgetop or sideslope, soil < 0.5 m thick) 
2 The average concentration for alluvial samples includes data only for samples below 5 meters, in 
order to ensure that the samples lie below the zone of evapotranspiration. Concentrations for PTn 
samples from surface-based boreholes are reported for the shallowmost PTn sample in each 
borehole because this sample is more likely to be representative of vertical infiltration at the 
borehole location than are deeper PTn samples, which are more likely to be affected by mixing with 
water transported laterally from adjacent zones. 
3 The CMB method for estimating infiltration is discussed in section 6.9.1. Rates 1 and 2 assume 
average annual precipitation of 170 mm with average chloride concentrations of 0.35 mg/L and 0.6 
mg/L, respectively.

ANL-NBS-HS-000017, Rev 00 Attachment I 
Page I-51 
Table 28. Estimates of Growth Rates For Opal Hemispheres On Calcite Blade Tips From Sample 
HD2074 (ESF station 30+50.7)1 
Measured 230Th/U 
age, in Ma 
Total duration of 
growth2, in Ma 
Estimated 
thickness3, in mm 
Growth rate4, 
in mm/Ma 
Microdigestions 
0.004 0.008 0.01 1.3 
0.004 0.008 0.05 6.3 
0.012 0.024 0.01 0.4 
0.012 0.024 0.05 2.1 
Whole hemispheres 
0.15 0.3 0.7 2.3 
0.15 0.3 1.3 4.3 
0.23 0.46 0.7 1.5 
0.23 0.46 1.3 2.8 
Data sources: DTN: GS960908315215.014 and GS980908315215.015 
Relevant assumption from Table 2: 25 
Notes: 
1 Rates are based on ranges of measured ages and ranges in estimated layer thicknesses from both 
whole hemispheres and microdigestions of hemisphere outer layers. 
2 Total duration of growth equals twice the measured age. Assumes the measured age represents 
an average between the oldest and youngest layers with a zero-age outermost layer. 
3 Thicknesses are not available for individual analyses. Values represent the typical range expected. 
4 Growth rates represent estimated thickness divided by total duration of growth.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-1 
Figure 1. Regional map showing Yucca Mountain and vicinity

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-2 
Figure 2. Regional map showing important physiographic features

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-3 
Figure 3. YMP boreholes. 
Note: This map shows the locations of surface-based boreholes for which isotopic and 
geochemical data are available for water and gas samples (Table 3). Boreholes that are not 
shown because they are outside the map area are UZ-N11, UZN#39 and UZN#91. 
NEVADA 
Quaternary 
deposits 
Tertiary 
volcanic rocks 
Trace of Exploratory 
Studies Facility (ESF), 
and ESF station number 
Borehole location 
and name 
116 26' 116 28' o o 
YUCCA MOUNTAIN 
SITE LOCATION 
20+00 
o 
o 
3 
6 
52' 
3 
6 5 
0 
' 
0 2000 4000 feet 
0 6 00 1200 meters 
Yu 
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c 
a 
M 
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in 
Yuc 
ca Wa 
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W 
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P 
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Wa 
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o 
lit 
ario Can 
y 
o 
n 
D 
rill H 
o 
le 
Was 
h 
W 
ha 
l 
e 
B 
ac 
k 
R 
i 
dg 
e 
60+ 00 
50+ 00 
40+ 00 
30+ 00 
78+ 77 70+ 00 
20+ 00 
10+ 00 
0+0 0 
Approximate 
trace of 
Cross-Drift 
UZ-N61 
UZ-N37 
UZ-6 
SD-7 
UZ-7a 
WT-2 
UZ-N27 
UZ-7 
UZ-14 
UZ-1 
SD-9 
SD-12 
NRG-7A 
UZ-N43 
ONC#1 
WT#4 
UZ#5 
UZ#4 
UZ#16 
UZ-N55 
UZ-N54 UZ-N53 
NRG#5 
NRG#4 
NRG-6 
UZ-N90 
UZ-6s 
UZN#1 
UZ-N46 
UZ-N64 
UZ-N38 
UZ-N62 
UZ-N36 
UZ-N17 
UZ-N15 
UZ-N16 
UZN#2 
UZN#8 
WT#18 
UZ-13 
UZ-N95 
UZ-N94 UZ-N93 
WT-24 
SD-6

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-4 
Ghost D ance 
Fault 
Ghost D ance 
Fault 
S 
o 
lita 
rio 
C 
a 
n 
yo 
n 
F 
a 
u 
l 
t 
B 
o 
w 
R 
id 
g 
e 
F 
a 
u 
l 
t 
NEVADA 
Trace o f Exp loratory 
Studies Facility (ESF), 
and ESF station number 
YUCCA MOUNTAIN 
S ITE LOCATION 
20+00 
o 
o 
36 
5 
2' 
36 
5 
0' 
0 2000 4000 feet 
0 6 00 1200 meters 
6 0+00 
5 0+00 
4 0+00 
3 0+00 
7 8+77 7 0+00 
2 0+00 
1 0+00 
0+0 0 
Approximate 
trace o f 
Cross-Drift 
UTCA Upper Tiva Canyon (0+70) 
BRFA Bow Ridge Fault (1+68) 
UPCA Upper Paintbrush (nonwelded) Contact (7+54) 
LPCA Lower Paintbrush (nonwelded) C ontact (10+28) 
TTF Thermal Test Facility (28+30) 
NGDFA Northern Ghost Dance Fault (37+37) 
SGDFA Southern Ghost Dance Fault (50+64) 
Alcove #1 
UTCA 
Alcove #2 
BRFA 
Alcove #3 
UPCA 
Alcove #4 
LPCA 
Alcove #5 
TTF 
Alcove #6 
NGDFA 
Alcove #7 
SGDFA 
11 6 2 6' 11 6 2 8' o o 
Figure 4. Locations of ESF test alcoves 
Note: Alcove locations are shown relative to faults mapped at the surface by Day et al. (1996, 
Plate 1). Not all faults on that map are shown here.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-5 
Legend 
Points Sample Location 
1-9, A-B 
C-J 
3 Springs Creek 
Kawich Peak 
Figure 5. Trilinear diagram for precipitation from the Kawich Range, Nevada. 
Note: Data sources are DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-6 
Figure 6. Constituents Plotted versus Chloride for Precipitation Samples. 
Note: Samples are from 3 Springs Basin and Red Rock Canyon, Nevada. Chloride versus: (a) 
Sodium, (b) calcium, (c) sulfate, (d) bicarbonate, and (e) silica. Data for 3 Springs Basin are from 
DTN: GS930108315214.003, GS930108315214.004, and GS930908315214.030. Data for Red 
Rock Canyon are reported in DTN: LA0003JF12213U.001. Only data with Cl concentrations less 
than 1 mg/L have been included in this figure. Regression lines for 3 Springs Basin data are from 
Table 5. The halite line on plot (a) is based on a 1:1 molar ratio of sodium to chloride in order to 
show the trend for halite dissolution.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-7 
Figure 6. (continued)

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-8 
Figure 7. Surface Water Collection Sites. 
Note: Surface water quality data collection sites in the vicinity of Yucca Mountain, Mountain, 
Nevada. Site numbers are identified on the legend of Figure 8.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-9 
Legend 
List of Plotted Points, Sample Locations and Site Numbers as Listed on Figure 7 
1-2 
3
4-5 
6
7
8-9 
A 
Tributary to Stockade Wash (22) 
Stockade Wash (23) 
Pah Canyon (52) 
Overland flow near Pah Canyon (53) 
Overland flow in Fortymile Canyon (56) 
Yucca Wash (26) 
Fortymile Wash above Drillhole Wash (57) 
B
C
D
E
F
G 
Wren Wash (31) 
Split Wash (33) 
Drillhole Wash (58) 
Fortymile Wash at H-Road (59) 
Busted Butte Wash (60) 
Fortymile Wash at J-12 (61) 
Figure 8. Trilinear Diagram for Surface Runoff from the Yucca Mountain Area. 
Note: Sampling locations shown on Figure 7. Data sources for the plotted points are DTN: 
GS940308312133.002 (sample 4) and GS960308312133.001 (samples 5, 6, 7, 9, B and C); 
Emett et al. 1994, p. 550 (samples 1, 2, 3 and 8); and Perfect et al. 1995, file dataedit.wk1 
(samples A, D, E, F, and G).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-10 
Legend 
List of Plotted Points and Sample Locations 
Stewart Basin, Toiyabe Range 3 Springs Basin, Kawich Range 
1-2 
3-4 
5-6 
Veg Spring 
East Stewart Creek 
Hellebore Spring 
7-8 
9, A 
B-C 
D-E 
3 Springs Creek near 3 Spring #3 
3 Springs Creek near Warm Springs 
3 Springs Creek near 3 Spring #2 
3 Springs Creek near Ledge Spring 
Figure 9. Trilinear diagram for surface waters from 3 Springs Basin and Stewart Basin, Nevada. 
Note: Data from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030. Because of the relative constancy of the chemical compositions, only two 
data points are plotted for each location.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-11 
Figure 10. Constituents Plotted versus Chloride for Surface-Water and Runoff Samples. 
Note: Surface-water and runoff samples are from Yucca Mountain, 3 Springs Basin, and Stewart 
Basin, Nevada. Chloride versus: (a) Sodium, (b) calcium, (c) sulfate, (d) bicarbonate, and (e) 
silica as SiO2. Data from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030, GS940308312133.002, and GS960308312133.001. Because of the 
constancy of their composition, only 3 data points are shown for each surface-water sampling 
location in 3 Springs Basin and Stewart Basin. Also shown are lines of best-fit to the 3 Springs 
Basin precipitation data, from Table 5. The halite line on plot (a) is based on a 1:1 molar ratio of 
sodium to chloride in order to show the trend for halite dissolution.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-12 
Figure 10. (continued)

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-13 
Legend 
List of Plotted Points, Sample Identifiers as Listed on Figure 45, and Sample Site Names 
1
2
3
4
5
6 
131 Captain Jack Spring 
137 Rainier Spring 
143 Tunnel Seep, U-12e.06 
144 Tunnel Seep, U-12n 
145 Tunnel Seep, U-12n.03 
146 Tunnel Seep, U-12t 
7
8
9
A
B 
147 Tunnel Seep, U-12t.03 
148 Tunnel Seep, U-12t.03 
149 Tunnel Seep, U-12t.03 
150 Tunnel Seep, U-12t.04 
206 Whiterock Spring 
Figure 11. Trilinear diagram for springs and seeps, Rainier Mesa, Nevada. 
Note: Data from McKinley et al. (1991, Table 6). Location of sampling sites shown on Figure 45.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-14 
Legend 
List of Plotted Points, Borehole Identifiers, and Tops of Sampled Intervals (feet) 
1
2
3
4
5
6
7
8
9 
NRG6-158.2 
NRG6-160.8 
NRG6-171 
NRG6-175.6 
NRG6-219.9 
NRG6-244.6 
NRG6-255.9 
NRG7A-165.8 
NRG7A-258 
A
B
C
D
E
F
G
H
I 
SD12-265.8 
SD12-278.6 
SD12-296.1 
SD7-339.7 
SD7-370.3 
SD9-94.2 
SD9-154 
UZ14-45 
UZ14-85.2 
J
K
L
M
N
O
P
Q
R 
UZ14-91 
UZ14-95.5 
UZ14-96.2 
UZ14-100.4 
UZ14-114.8 
UZ14-135.5 
UZ14-144.8 
UZ14-147.8 
UZ14-177.6 
S
T
U
V
W
X
Y
Z
a 
UZ14-178.1 
UZ14-215.7 
UZ14-225.9 
UZ14-235.1 
UZ14-245.5 
UZ#16-180.9 
SD9-114.1 
SD9-135.1 
SD9-176.2 
b
c
d
e
f
g
h
i
j
k
l 
SD9-251.8 
UZN55-195.3 
UZN55-199.0 
SD6-430.3 
SD6-443.2 
SD6-443.5 
UZ7a-203.3 
UZ7a-220.2 
UZ7a-241.4 
UZ14-240.8 
UZ#16-163.5 
Figure 12. Trilinear Diagram for Pore Waters from the Nonwelded Paintbrush Tuff (PTn) 
Hydrogeologic Unit. 
Note: The plotted data are listed in Table 6, and are reported in DTN: GS950608312272.001, 
GS961108312271.002, GS970208312271.002, GS970908312271.003, and 
GS991299992271.001 (data set 9810----2272.004).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-15 
Legend 
List of Plotted Points, Borehole Identifiers, and Tops of Sampled Intervals (feet) 
1
2
3 
UZ-14  1258.5 
UZ-14  1277.4 
UZ-14  1277.7 
4
5 
UZ#16  952.6 
UZN55  166.1 
Figure 13. Trilinear Diagram for Pore Waters from the Tiva Canyon welded (TCw) and Topopah 
Spring welded (TSw) Hydrogeologic Units. 
Note: Sample UZN55  166.1 is from the TCw; all other samples are from the TSw. The plotted 
data are listed in Table 6, and are reported in DTN: GS950608312272.001.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-16 
Legend 
List of Plotted Points, Borehole Identifiers, and Tops of Sampled Intervals (feet) 
1
2
3
4
5
6 
NRG7A  1483.5 
NRG7A  1492.7 
NRG7A  1498.6 
SD12  1460.7 
SD12  1495.5 
SD9  1452.6 
7
8
9
A
B
C 
SD9  1535.2 
UZ14  1419.5 
UZ14  1461.9 
UZ14  1495.8 
UZ14  1524.6 
UZ14  1542.3 
D
E
F
G
H
I 
UZ#16  1166.2 
UZ#16  1227.4 
UZ#16  1235.1 
UZ#16  1269.6 
UZ#16  1280.4 
UZ#16  1296.8 
J
K
L
M
N
O
P 
UZ#16  1317.9 
UZ#16  1358.1 
WT24  1734.3 
WT24  1744.2 
WT24  1744.5 
UZ14-1409.4 
UZ#16-1206.3 
Figure 14. Trilinear Diagram for Pore Waters from the Top 200 feet of the Calico Hills Nonwelded 
(CHn) Hydrogeologic Unit. 
Note: The plotted data are listed in Table 6, and are reported in DTN: GS950608312272.001, 
GS961108312271.002, GS970908312271.003, and GS991299992271.001 (data sets 9810---- 
2272.004 and 9902----2272.001).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-17 
Legend 
List of Plotted Points, Borehole Identifiers, and Tops of Sampled Intervals (feet) 
1
2
3
4
5
6
7
8 
SD12-1517 
SD12-1600.6 
SD12-1636.8 
SD7-1498.4 
SD7-1524.6 
SD7-1558.4 
SD7-1617 
SD9-1619.9 
9
A
B
C
D
E
F
G 
SD9-1661.1 
SD9-1741 
SD9-1741.7 
SD9-1800.7 
UZ14-1563.6 
UZ14-1564.6 
UZ14-1564.9 
UZ14-1585 
H
I
J
K
L
M
N
O 
UZ14-1585.3 
UZ14-1605.9 
UZ14-1644.3 
UZ14-1674.8 
UZ14-1695.4 
UZ14-1715 
UZ14-1734.5 
UZ14-1735.3 
P
Q
R
S
T
U
V
W
X 
UZ#16-1389.4 
UZ#16-1398.5 
UZ#16-1412.9 
UZ#16-1428.1 
UZ#16-1442.8 
SD12  1558.9 
SD12  1582.5 
SD7  1600.1 
UZ#161395.5 
Figure 15. Trilinear Diagram for Pore Waters Below the Top 200 Feet of the Calico Hills 
Nonwelded (CHn) Hydrogeologic Unit, and Above the Prow Pass Lithostratigraphic Unit. 
Note: The plotted data are listed in Table 6, and are reported in DTN: GS950608312272.001, 
GS961108312271.002, GS970208312271.002, and GS991299992271.001 (data sets 9810---- 
2272.004 and 9902----2272.001).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-18 
Legend 
List of Plotted Points, Borehole Identifiers, and Tops of Sampled Intervals (feet) 
1
2
3
4
5
6 
SD12-1901.5 
SD12-1942.4 
SD12-1938.8 
UZ#16-1486.9 
UZ#16-1601.1 
UZ#16-1607.7 
7
8
9
A
B
C 
UZ#16-1651.6 
UZ14-1804.5 
UZ14-1825.8 
UZ14-1854.9 
UZ14-1865.7 
UZ14-2014.7 
D
E
F
G
H
I 
UZ14-2015.2 
UZ14-2025.1 
UZ14-2095.6 
SD7-1890.7 
SD7-1952.4 
SD7-2596.1 
J
K
L
M
N 
SD7-2598.3 
SD7-2088.2 
SD7-2170.1 
SD7-2596.5 
UZ#16-1643.4 
Figure 16. Trilinear Diagram for Pore Waters from the Prow Pass, Bullfrog and Tram 
Lithostratigraphic Units 
Note: The plotted data are listed in Table 6, and are reported in DTN: GS950608312272.001, 
GS961108312271.002, GS970208312271.002, and GS970908312271.003.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-19 
Legend 
List of Plotted Points, Borehole Identifiers, and Sampled Depths (feet) 
1
2
3
4
5 
NRG7A 460.25 
SD9/TS 453.85 
UZ14 A 384.6 
UZ14 A2 384.6 
UZ14 B 387.68 
6
7
8
9
A 
UZ14 C 390.75 
UZ14 PT1 390.75 
UZ14 PT2 390.75 
UZ14 PT4 390.75 
UZ14 D 390.75 
B
C
D
E
F 
SD7 (3/8/95) 479.76 
SD7 (3/16/95) 488.29 
SD7 (3/17/95) 488.29 
SD7 (3/20/95) 488.29 
SD7 (3/21/95) 488.29 
Figure 17. Trilinear Diagram for Perched Water. 
Note: Data are listed in Table 8 and are reported in DTN: GS991299992271.001 (data set 9512--- 
-2272.004).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-20 
Figure 18. Histograms of chloride concentrations. 
Note: Histograms of chloride concentrations in precipitation, surface water, unsaturated zone porewater, 
perched water, and saturated-zone groundwater. (a) Chloride concentrations. (b) Log of chloride 
concentrations. Data are from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030 (3 Springs Basin precipitation and surface water); LA0003JF12213U.001 
(NADP/NTN data for Red Rock precipitation) and LAJF831222AQ95.003 (Yucca Mountain precipitation); 
GS940308312133.002, GS960308312133.001, Emett et al. 1994 (p. 550), and Perfect et al. (1995, file 
dataedit.wk1) (surface water); GS950608312272.001, GS961108312271.002, GS970208312271.002, 
and GS970908312271.003 (unsaturated zone porewater); GS991299992271.001 (data sets 9810---- 
2272.004 and 9902----2272.001 for unsaturated zone porewater, and 9512----2272.004 for perched 
water); and Oliver and Root (1997, attached file yucca.xls) (saturated zone).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-21 
Figure 19. Histograms of sulfate concentrations. 
Note: Histograms of sulfate concentrations in precipitation, surface water, unsaturated zone porewater, 
perched water, and saturated-zone groundwater. (a) Sulfate concentrations. (b) Log of sulfate 
concentrations. Data are from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030 (3 Springs Basin precipitation and surface water); LA0003JF12213U.001 
(NADP/NTN data for Red Rock precipitation) and LAJF831222AQ95.003 (Yucca Mountain precipitation); 
GS940308312133.002, GS960308312133.001, Emett et al. 1994 (p. 550), and Perfect et al. (1995, file 
dataedit.wk1) (surface water); GS950608312272.001, GS961108312271.002, GS970208312271.002, 
and GS970908312271.003 (unsaturated zone porewater); GS991299992271.001 (data sets set 9810---- 
2272.004 and 9902----2272.001 for unsaturated zone porewater, and 9512----2272.004 for perched 
water); and Oliver and Root (1997, attached file yucca.xls) (saturated zone).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-22 
Figure 20. Histograms of silica concentrations. 
Note: Histograms of silica concentrations in precipitation, surface water, unsaturated zone porewater, 
perched water, and saturated-zone groundwater. (a) Silica concentrations. (b) Log of silica 
concentrations. Data are from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030 (3 Springs Basin precipitation and surface water); GS940308312133.002, 
GS960308312133.001, Emett et al. 1994 (p. 550), and Perfect et al. (1995, file dataedit.wk1) (surface 
water); GS950608312272.001, GS961108312271.002, GS970208312271.002, and 
GS970908312271.003 (unsaturated zone porewater); GS991299992271.001 (data sets 9810----2272.004 
and 9902----2272.001 for unsaturated zone porewater, and 9512----2272.004 for perched water); and 
Oliver and Root (1997, attached file yucca.xls) (saturated zone). 
.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-23 
Figure 21. Histograms of sodium concentrations. 
Note: Histograms of sodium concentrations in precipitation, surface water, unsaturated zone porewater, 
perched water, and saturated-zone groundwater. (a) Sodium concentrations. (b) Log of sodium 
concentrations. Data are from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030 (3 Springs Basin precipitation and surface water); LA0003JF12213U.001 
(NADP/NTN data for Red Rock precipitation); GS940308312133.002, GS960308312133.001, Emett et al. 
1994 (p. 550), and Perfect et al. (1995, file dataedit.wk1) (surface water); GS950608312272.001, 
GS961108312271.002, GS970208312271.002, and GS970908312271.003 (unsaturated zone 
porewater); GS991299992271.001 (data sets set 9810----2272.004 and 9902----2272.001 for unsaturated 
zone porewater, and 9512----2272.004 for perched water); and Oliver and Root (1997, attached file 
yucca.xls) (saturated zone).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-24 
Figure 22. Histograms of calcium concentrations. 
Note: Histograms of calcium concentrations in precipitation, surface water, unsaturated zone porewater, 
perched water, and saturated-zone groundwater. (a) Calcium concentrations. (b) Log of calcium 
concentrations. Data are from DTN: GS930108315214.003, GS930108315214.004, and 
GS930908315214.030 (3 Springs Basin precipitation and surface water); LA0003JF12213U.001 
(NADP/NTN data for Red Rock precipitation); GS940308312133.002, GS960308312133.001, Emett et al. 
1994 (p. 550), and Perfect et al. (1995, file dataedit.wk1) (surface water); GS950608312272.001, 
GS961108312271.002, GS970208312271.002, and GS970908312271.003 (unsaturated zone 
porewater); GS991299992271.001 (data sets set 9810----2272.004 and 9902----2272.001 for unsaturated 
zone porewater, and 9512----2272.004 for perched water); and Oliver and Root (1997, attached file 
yucca.xls) (saturated zone).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-25 
Figure 23. Histograms of pH values. 
Note: Histograms of pH values in precipitation, surface water, unsaturated zone porewater, perched 
water, and saturated-zone groundwater. Data are from DTN: GS930108315214.003, 
GS930108315214.004, and GS930908315214.030 (3 Springs Basin precipitation and surface water); 
LA0003JF12213U.001 (NADP/NTN data for Red Rock precipitation); GS940308312133.002, 
GS960308312133.001, Emett et al. 1994 (p. 550), and Perfect et al. (1995, file dataedit.wk1) (surface 
water); GS950608312272.001, GS961108312271.002, GS970208312271.002, and 
GS970908312271.003 (unsaturated zone porewater); GS991299992271.001 (data sets set 9810---- 
2272.004 and 9902----2272.001 for unsaturated zone porewater, and 9512----2272.004 for perched 
water); and Oliver and Root (1997, attached file yucca.xls) (saturated zone).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-31 
Figure 29. Input functions for bomb-pulse nuclides. 
Note: (A) Estimated 36Cl/Cl ratio for global fallout at Yucca Mountain, as a function of average 
residence time in the soil zone, (B) tritium in atmospheric moisture in Albuquerque, NM, and (C) 
atmospheric concentrations of bomb-pulse 14C for the northern hemisphere. Reconstructed 
atmospheric tritium data from DTN: LA0001JF12213U.001; reconstructed 14C and 36Cl data from 
Fabryka-Martin, Turin et al. (1996, Appendix Tables C1 and C2).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-32 
Figure 30. Cutoff tritium value for the presence of bomb-pulse tritium 
Note: The plot illustrates the statistical determination of the cutoff tritium value for the presence of 
bomb-pulse tritium in unsaturated-zone fluid samples, using Chauvenets criterion. Analyses 
conducted using tritium composition of porewater from DTN: GS961108312271.002 (excluding 
data for UZ#16), GS991299992271.001 (for UZ#16 tritium data), GS961108312261.006, 
GS970108312232.001, GS970208312271.002, GS970283122410.002, GS970608312272.005, 
GS970908312271.003, and GS991299992271.001 (data sets 9512----2272.002and 9911---- 
2272.004). Chauvenets criterion is discussed in Bevington and Robinson (1992, p.58).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-33 
Figure 31. Reconstructed atmospheric 36Cl/Cl ratio. 
Note: The top plot compares the reconstructed 36Cl/Cl ratio to measured 36Cl/Cl ratios for 
fossilized packrat urine from southern Nevada (based on Plummer et al. 1997, Figure 2). The 
bottom plot compares the reconstructed 36Cl/Cl ratio (normalized to a present-day value of 500 x 
10-15) to the reconstructed 14C activity of Plummer et al. (1997, Figure 3B). 36Cl data from DTN: 
LAJF831222AQ97.002. Radiocarbon ages from DTN: GS950708315131.003 and 
GS960308315131.001 for top figure and DTN: GS950708315131.001 and 
GS950708315131.002, GS950708315131.003 and GS960308315131.001 for bottom figure.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-34 
Figure 32. Distribution of 36Cl/Cl in the ESF 
Note: This plot shows the distribution of 36Cl/Cl ratios measured for rock samples in the ESF. 
Faults in the ESF that correlate with mapped faults at surface are shown. ESF stations are 
labeled in 100-m increments. Analytical uncertainties are less than 10%. Data are from DTN: 
LAJF831222AQ98.004, LA9909JF831222.005 and LA9909JF831222.010.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-35 
Figure 33. Meteoric and atmospheric Carbon-14 and Chlorine-36 activities. 
Note: Reconstructed 14C and 36Cl activities in the atmosphere for the last 20 ka, compared with 
activities measured in perched water from UZ-14, SD-7, and NRG-7a. Perched water data are 
plotted with black squares, using 14C and 36Cl data shown in Table 9 and taken from DTN: 
LAJF831222AQ98.011 and GS991299992271.001 (data set 9512----2272.003). Reconstructed 
activities (gray squares) are plotted in the lower part of Figure 31. Key perched water data points 
are identified by borehole and sample identifier, and key reconstruction points are identified by 
age (ka is the abbreviation for thousand years).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-36 
Figure 34. Histogram of Carbon Isotopes in Pore Waters. 
Note: Frequency histograms comparing the distribution of carbon-14 activities and stable carbon 
isotope rations of unsaturated-zone porewaters in the PTn and CHn hydrogeologic units, Yucca 
Mountain. Data are shown in Table 15 and are from DTN: GS991299992271.001 (data set 9512- 
---2272.003), GS961108312271.002 and GS970208312271.002.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-37 
Figure 35. Carbon-14 versus Stable Carbon for Yucca Mountain Waters and Gases. 
Note: Plot of carbon-14 activity versus stable carbon isotopic ratio for (a) porewaters from the 
unsaturated zone, (b) gas from the unsaturated zone, (c) perched water, and (d) groundwaters. 
Data from DTN: GS991299992271.001 (data set 9512----2272.003), GS961108312271.002 and 
GS970208312271.002 (unsaturated zone porewaters); GS991299992271.001 (data set 9507---- 
2271.001), GS961108312271.002, GS960208312261.002, GS970283122410.002 and 
GS990983122410.003 (unsaturated zone gases from instrumented boreholes); 
GS991299992271.001 (data set 9512----2272.003 for perched water); GS930308313232.001 and 
Oliver and Root (1997, attached Excel file yucca.xls) (groundwater).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-38 
Figure 36. .. 2H and .. 18O Compositions of Yucca Mountain Waters 
Note: This plot shows .. 2H and .. 18O compositions of: (a) local precipitation, (b) local surface 
water, (c) perched water, and (d) Yucca Mountain ground waters. Data from DTN: 
GS930108315214.003, GS930108315214.004, and GS930908315214.030 (3 Springs Basin 
precipitation and surface waters); Yang, Yu et al. (1998, Figure 18) (1984 storms; corroborative 
data); DTN: GS940308312133.002 (surface water); GS991299992271.001 (data set 9512---- 
2272.003 for perched water); GS930308313232.001, GS970708312323.001 and Oliver and Root 
(1997, attached Excel file Yucca.xls) (groundwater); and Benson and Klieforth (1989, Table 3) 
(groundwater in the Amargosa Desert).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-39 
Figure 37. Plot of .. 2H versus .. 18O showing porewater compositions in UZ-14 
Note: This plot contrasts the stable isotopic signatures obtained for porewaters extracted using 
two different methods of extraction. (a) Porewater extracted by distillation. (b) Porewater 
extracted by squeezing (based on data shown in Yang, Yu et al. 1998, Figures 15 and 16). Data 
are from DTN: GS991299992271.001 (data set 9903----2272.002).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-40 
Figure 38. *87Sr in SD-7 Pore Waters and Rocks. 
Note: * 87Sr (per mil) of pore waters (black dots) and calcite fracture coatings (Xs) in SD-7 as a 
function of depth. Pore water Sr isotope compositions in SD-7 vary as a function of depth due to 
water-rock interaction, especially within the PTn. The range of strontium isotope compositions of 
calcite collected from soils in the vicinity of the SD-7 drill pad are shown by the bar at top. Sr 
isotopic ratios are reported in DTN GS970908315215.011, from which *87Sr values are 
calculated using equation (7) in section 6.6.6. 
V 
V
V
V 
V V V 
V
V 
V 
VV 
V V V V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V 
V V V 
V 
V
V 
500 
450 
400 
350 
300 
250 
200 
150 
100 
50
0 
0 2 4 6 8 10 12 14 
Depth (meters) 
Delta 87Sr 
V Rock 
Pore Water 
TCw 
PTn 
TSw 
CHn 
Range of Soil Carbonate at SD-7 Drill Pad

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-41 
0.02 
0.03 
0.04 
0.05 
0.06 
0.07 
0.08 
0.09 
0.10 
0.11
9/25/96 
12/9/96 
2/22/97 
5/7/97 
7/21/97 
Date of Collection 
Uranium Conc. (ppb) 
3.0 
4.0 
5.0 
6.0 
7.0 
8.0 
9.0 
234U/238U activity 
U conc. (ppb) 
234U/238U activity 
2/4/97 unacidified 5/22/97 
acidified 
11/25/96 
unacidified 2/4/97 acidified 
Figure 39. Uranium Concentrations and 234U/238U Activity Ratios of Water from the Single Heater 
Test. 
Note: Uranium concentrations and 234U/238U activity ratios in water collected from borehole ESFTMA-
NEU2, zone 4, associated with the Single Heater Test, ESF, Alcove #5. Data are from 
DTNs GS970508312272.001 (11/25/96 sample) and GS980908312322.009 (2/4/97 and 5/22/97 
samples).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-42 
0.00 
0.05 
0.10 
0.15 
0.20 
0.25 
0 
4 
/1 
5 
/ 
9 
8 
0 
6 
/0 
4 
/ 
9 
8 
0 
7 
/2 
4 
/ 
9 
8 
0 
9 
/1 
2 
/ 
9 
8 
11 
/0 
1 
/ 
98 
1 
2 
/2 
1 
/ 
9 
8 
0 
2 
/0 
9 
/ 
9 
9 
0 
3 
/3 
1 
/ 
9 
9 
0 
5 
/2 
0 
/ 
9 
9 
Date colle cte d 
U 
ra 
n 
iu 
m 
c 
o 
n 
c 
e 
n 
t 
ra 
t 
i 
o 
n 
, 
 
g 
/ 
l 
DST-186-3 
DST-60-2 
DST-60-3 
2
3
4
5
6 
0 
4/ 
1 
5 
/98 
0 
6/ 
0 
4 
/98 
0 
7/ 
2 
4 
/98 
0 
9/ 
1 
2 
/98 
11 
/01 
/9 
8 
1 
2/ 
2 
1 
/98 
0 
2/ 
0 
9 
/99 
0 
3/ 
3 
1 
/99 
0 
5/ 
2 
0 
/99 
Date colle cted 
2 
3 
4 
U 
/ 
238U 
a 
c 
t 
i 
v 
i 
ty 
rat 
i 
o 
DST-186-3 
DST-60-2 
DST-60-3 
Figure 40. Uranium concentrations and 234U/238U activity ratios in water from the Drift-Scale 
Heater Test 
. 
Note: Uranium concentrations and 234U/238U activity ratios in water collected from boreholes 
associated with the Drift-Scale Heater Test, ESF, Alcove #5. Data are reported in DTN: 
GS991299995215.001 (data set MOL.20000104.0007).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-43 
4,140,000 
4,120,000 
4,100,000 
4,080,000 
4,060,000 
4,040,000 
4,020,000 
4,000,000 
5000,000 520,000 540,000 560,000 580,000 600,000 
Comb 
Peak 
(2.23) 
Topopah (2.23) 
Water Pipe Butte (2.73) 
Cane (3.81) 
White 
Rock 
(1.92) 
Captain 
Jack 
(2.19) 
UTM - x, in meters 
U 
T 
M 
- 
y, 
i 
n 
m 
e 
t 
e 
r 
s 
Figure 41. 234U/238U activity ratios of water from perched springs 
Note: This map shows the locations of perched springs on the Nevada Test Site as well as the 
234U/238U activity ratios of the discharge. Yucca Mountain straddles the lower western boundary 
of the Nevada Test Site (boundary shown as yellow line). Data are from GS960908315215.013, 
GS980108312322.003 and GS991299995215.001 (data set MOL.20000104.0007).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-44 
1.0 to 3 .0 
3.0 to 4 .5 
4.5 to 6 .0 
6.0 to 8 .1 
0.0 to 1 .0 
1.0 to 2 .0 
2.0 to 4 .0 
4.0 to 18 
Figure 42. Uranium concentrations and 234U/238U activity ratios in regional ground water samples 
Note: Uranium concentrations and 234U/238U activity ratios of saturated-zone ground water 
samples from the vicinity of the Nevada Test Site. The highest activity ratios (right-hand figure) 
are beneath and slightly east of Yucca Mountain. Data are from DTNs GS930108315213.004, 
GS960908315215.013, GS980108312322.003, GS980208312322.006 and 
GS980908312322.009.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-45 
535000 540000 545000 550000 555000 560000 565000 
4050000 
4055000 
4060000 
4065000 
4070000 
4075000 
4080000 
4085000 
4090000 
234U / 238U activity ratio 
1.0 to 2.5 
2.5 to 4.0 
4.0 to 5.0 
5.0 to 6.0 
6.0 to 7.0 
7.0 to 8.5 
Figure 43. 234U/238U activity ratios of ground water in the Yucca Mountain vicinity. 
Note: Uranium isotopic compositions of regional saturated zone ground water samples from the 
Yucca Mountain vicinity. Yucca Mountain is the long ridge slightly west of the cluster of samples 
with the highest activity ratios on this map. Data from DTNs GS930108315213.004, 
GS960908315215.013, GS980108312322.003, GS980208312322.006, GS980908312322.009, 
and GS991299995215.001 (data set MOL.20000104.0007).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-46 
Figure 44. Carbon isotopes in UZ-1 gases 
Note: Isotopic data are from DTN: GS991299992271.001 (data sets 9301----2271.009, 9301---- 
2271.010, 9304----2271.019, 9304----2271.020, 9404----2271.004, 9404----2271.005, 9404---- 
2271.008, 9404----2271.009, and 9507----2271.001).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-47 
Figure 45. Nevada Test Site Wells and Springs. 
Note: Location of selected wells and springs in the Nevada Test Site area, for which isotopic and 
geochemical data for water samples are available (Figure 4 and Table 5 in McKinley et al. 1991). 
Identifiers for these samples are given in Figures 11 (for springs and seeps) and 47 (for wells).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-48 
Figure 46. Location of selected wells in the vicinity of Yucca Mountain 
Note: This map shows the location of selected wells in the vicinity of Yucca Mountain, for which 
geochemical data for groundwater samples are available. Well coordinates are from Table 24. 
H-5 and H-3 mark the ridgeline of Yucca Mountain.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-49 
Legend 
List of Plotted Points, Site Numbers as Listed on Figure 45, and Borehole Identifiers 
1
2
3
4
5 
152: U-20a#2 
161: UE-19b#1 
162: UE-19c 
163: UE-19d 
164: UE-19e 
6
7
8
9
A 
165: UE-19fs 
166: UE-19gs 
167: UE-19i 
141: TW-1 (0-171 m) 
142: TW-1 (0-1282 m) 
B
C
D 
198: Water Well 8 
181: UE-29 a#2 (250-355 m) 
182: UE-29 a#2 (87-213 m) 
Figure 47. Trilinear Diagram for Up-gradient Groundwaters. 
Note: This trilinear diagram is for groundwaters up-gradient of Yucca Mountain, for Pahute Mesa 
and Rainier Mesa, Nevada. Data from DTN: GS930308313232.001 (UE-29 a#2) and McKinley et 
al. (1991, Table 6).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-50 
Legend 
List of Plotted Points and Borehole Identifiers (locations shown in Figure 46) 
Yucca Mountain area 40 Mile Wash Other 
1
2
3
4
5
6
7
8 
b#1 
c#2 
G-2 
G-4 
H-1 (572-6887 m) 
H-1 (687-1829 m) 
H-3 
H-4 
9
A
B
C
D
E
F 
H-5 
H-6 
ONC#1 
p#1 (0-1200 m) 
p#1 (1300-1800 m) 
WT-7 
WT-10 
G
H
I
J
K
L 
a#2 (87-213 m) 
J-12 
J-13 
JF-3 
WT#14 
WT#15 
M
N
O
P 
Gexa 
VH-1 
VH-2 
WT#12 
Figure 48. Trilinear Diagram for Yucca Mountain Groundwaters 
Note: This trilinear diagram is for groundwaters from the vicinity of Yucca Mountain. Full 
identifiers for wells are given in Table 24. Well locations are shown in Figure 46. Data are from 
DTN: GS930308313232.001 (b#1, a#2, G-4, H-1, H-4, H-5, H-6, VH-1, J-12, J-13), 
GS980908312322.008 (c#2), GS990608312133.001 (WT#12, WT-10, and G-2), and Oliver and 
Root (1997, attached file yucca.xls).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-51 
Figure 49. Chloride Mass Balance (CMB) Method for Estimating Infiltration. 
Note: (a) Schematic diagram illustrating the underlying basis of the CMB method. (b) Plot 
showing Cl concentrations as a function of infiltration, assuming a range of average chloride 
concentrations for local precipitation and an average annual precipitation rate of 170 mm. See 
text in section 6.9.1 for discussion of the model, its assumptions, and the basis for these 
parameter values.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-52 
16 
16 
12 
12
8
8
4
4
0
0 
20 
20 
0 0.2 0.4 0.6 
0.0001 0.001 0.01 0.1 1 
HYDROGENIC-MINERAL ABUNDANCE, IN PERCENT 
HYDROGENIC-MINERAL ABUNDANCE, IN PERCENT 
NUMBER OF 30-METER INTERVALS 
Median 
Arithmettic M ean 
Arithmetic m ean = 0.084  0.027 
Standard deviation = 0.11 
Median = 0.050  0.013 
Log mean = 0.034 +0.017/-0.012 
Standard deviation = +0.16/-0.03 
NUMBER OF 30-METER INTERVALS 
B 
(Total number of surveys = 71. 
Uncertainties a re given a t the 95-percent 
confidence level.) 
(Total number of surveys = 71. 
Uncertainties a re given a t the 
95-percent confidence level.) 
Figure 50. Hydrogenic-mineral abundances. 
Note: Histograms showing hydrogenic-mineral abundances in welded tuffs in the Exploratory 
Studies Facility on A, linear, and B, log scales. Data are from DTN: GS991299995215.001 (data 
set MOL.20000104.0013).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-53 
18 
16 
14 
12 
10
8
6
4
2
0 
20 
15 
10
5
0 
0.4 
0.5 
0.6 
0.3 
0.2 
0.1 
0.0
6
8 
10 
12
4
2
0 
EXPLORATORY STUDIES FACILITY DISTANCE, IN METERS 
0 2,000 4,000 6,000 
A
B
C
D 
S 
I 
M 
U 
LA 
T 
E 
D 
I 
N 
F 
ILT 
R 
ATIO 
N 
, 
IN 
M 
I 
L 
LI 
ME 
TE 
R 
S 
/ 
YE 
A 
R 
N 
U 
MB 
E 
R 
O 
F 
F 
R 
A 
C 
- 
T 
U 
R 
E 
S 
PE 
R 
M 
E 
T 
E 
R 
N 
U 
M 
B 
ER 
O 
F FA 
U 
LT 
S P 
E 
R 
3 
3 
.3 
-M 
E 
T 
E 
R 
IN 
T 
E 
R 
VA 
L 
HY 
D 
R 
O 
G 
E 
N 
IC 
-M 
IN 
E 
R 
A 
L 
A 
B 
U 
N 
D 
A 
N 
C 
E 
, 
I 
N 
PE 
RCE 
N 
T 
Fracture and lithophysae 
Fracture only 
Figure 51. Infiltration, fracture, fault and shear densities, and hydrogenic-mineral abundances 
Notes: Estimates of A, simulated infiltration; B, fracture density; C, fault and shear; and D, 
hydrogenic-mineral abundance; plotted against distance from the north portal of the Exploratory 
Studies Facility. Data are from DTN: GS960908312211.003 (for plot A); DTN: 
GS960708314224.008, GS960708314224.010, GS960808314224.011, GS960908314224.014, 
GS970208314224.003, GS971108314224.022, GS971108314224.023, GS971108314224.024, 
GS971108314224.025, GS971108314224.026, GS971108314224.028, GS970808314224.008, 
GS970808314224.010, GS970808314224.012, GS971108314224.020, and 
GS971108314224.021 (for plots B and C) and DTN: GS991299995215.001 (data set 
MOL.20000104.0013) (for plot D).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-54 
Tpc - w All 
north ramp 
Tpt - welded 
Tpc - welded PTn Crystal-rich 
nonlithophysal 
Crystal-poor upper 
lithophysal 
Crystal-poor m iddle 
nonlithophysal 
Tpcpul - north ramp 
Tpcpln - north + 
south ramp 
Tpcrn - north ramp 
HYDROGENIC-MINERAL ABUNDANCE, 
IN LOG MEAN PERCENT 
south ramp 
all north ramp 
selected north ramp 
south ramp 
selected north ramp 
+ sou th ramp 
main drift 
south ramp 
0.01 0.1 1 
Tpcpmn - no rth + south ramp 
F illed circle s re presen t be st 
estim a tes of m ine ral abunda nces 
from ES F lin e surveys. 
Figure 52. Hydrogenic-mineral abundances in welded tuffs. 
Note: Summary of hydrogenic-mineral abundances in welded tuffs in the Exploratory Studies 
Facility. Stratigraphic units from Buesch et al. (1996). Data are from DTN: 
GS991299995215.001 (data set MOL.20000104.0013).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-55 
Nonwelded 
Tuff 
(PTn) 
Welded 
Tuff 
(Tpt) 
Tpy 
Tpp 
Tptrv1+Tptrn 
Tptrl + Tptf 
Tptpul 
Tptpmn 
Tptpll 
0 
50 
100 
150 
200 
250 
300 
350 
400 
450 
500 
550 
Depth, in meters 
Calcite concentration, in ppm 
100 101 102 103 104 105 
WT-24 Cuttings 
Welded Tuff (Tpc) 
Tiva Canyon welded 
PTn nonwelded 
Topopah Spring welded 
CalicoHills Formation 
Individual 5' 
intervals 
7-point running 
average 
Tptpln 
Figure 53. Calcite concentrations in cuttings from borehole WT-24. 
Note: Data are reported in DTN: GS991299995215.001 (data set MOL.20000104.0008). See 
assumption 22 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-56 
Figure 54. Radiometric ages for calcite and opal. 
Note: The frequency diagrams summarize the results of dating the outer surfaces of calcite and 
opal mineral coatings within the ESF. Data are from DTN: GS970208315215.003, 
GS960808315215.006 (14C ages); GS960908315215.014, GS970208315215.001, 
GS970808315215.012 (230Th/U ages); GS970208315215.002 and GS970908315215.013 
(207Pb*/235U ages). See assumptions 24 and 25 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-57 
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 
= 2.5 mm / Ma 
= 2.5 mm / Ma 
20 ka 
400 ka 
Observed age assumed to 
represent the average age of 
deposition. Actual duration 
equals twice the measured age. 
Figure 55. Dating of whole opal hemispheres and outer surfaces. 
Note: Results of 230Th / U dating of whole opal hemispheres and of selective removal of outer 
surfaces only. Data are from DTN: GS980908315215.015 and GS960908315215.014. See 
assumption 25 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-58 
Figure 56. Histogram of 207Pb / 235U ages for ESF mineral coatings. 
Note: Histogram of 207Pb / 235U ages for outer and interior layers of opal and basal chalcedony 
layers from ESF mineral coatings. Data are from DTN: GS970208315215.002 and 
GS970908315215.013. See assumption 25 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-59 
600 
500 
400 
300 
200 
100
0
-10 -5 0 5 10 15 20 25 
D 
E 
P 
T 
H 
, 
I 
N 
M 
E 
T 
E 
R 
S 
d d 13 18 C AND O, IN PER M IL 
d
d 
d d 
13 
18 
18 18 
water 
C values relative to PDB carbonate standard 
O values relative to VSMOW water standard 
Calculated O values for calcite in equilibrium with a percolation O 
of -12.5 per mil, a 10 Celsius mean annual surface temperature, and a 
geothermal g radient of: 
34 degrees Celsius per kilometer of depth (Szabo and Kyser, 1990) 
100 degrees Celsius per kilometer of depth (using fractionation fractors of 
O'Nield and others, 1969) 
Figure 57. Stable carbon and oxygen isotopic compositions of unsaturated-zone calcite 
Note: Stable carbon and oxygen isotopic compositions of subsamples of unsaturated-zone 
calcite from drill core at Yucca Mountain (modified from Whelan et al. 1998, Figure 5). Data from 
DTN: GS920708315215.017, GS950708315215.005, GS960408315215.002, 
GS97028315215.004, GS970808315215.010, and GS980408315215.010. Geothermal gradients 
shown in figure are based on Szabo and Kyser (1990, p. 1718) and ONeil et al. (1969, p. 5552).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-60 
UE-25 b #1 
USW G-1 
USW G-2 
USW G-3/GU-3 
USW G-4 
DEPTH RELATIVE TO THE WATER TABLE, 
IN METERS 
87 86 Sr / Sr 
0.7090 0.7100 0.7110 0.7120 0.7130 
600 
400 
200
0 
-200 
-400 
-600 
-800 
-1 ,000 
-1 ,200 
-1 ,400 
Unsaturated zone 
Saturated zone 
ESF 
Soil carbonate 
Water table 
EXPLANATION 
Boreholes 
(Data from Marshall 
and others, 1992) 
Figure 58. Strontium isotopic compositions of calcite 
Note: Strontium isotopic compositions of calcite subsamples from drill core and the Exploratory 
Studies Facility as a function of depth relative to the water table. Data are from DTN: 
GS930908315215.027, GS970908315215.011 and GS991299995215.001 (data set 
MOL.20000104.0012). 

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-62 
10 
12 
14 
16 
18 
20 
22 
24 
-10 -5 0 5 10 
d18O, IN PER MIL 
d13C, IN PER M IL 
Relative Age 
Late Early 
Calcite from PTn, Tiva Canyon 
and post-Tiva Canyon tuffs. 
Calcite from welded units o f the 
Topopah Spring Tuff. 
Linear regression of data from 
Topopah Spring Tuff. 
y = -0.241x + 15.7 
r = 0.65 2 
Figure 60. Scatterplot of stable carbon and oxygen isotopic compositions in calcite from the ESF 
Note: Isotopic compositions of carbon and oxygen in subsamples of calcite from the Exploratory 
Studies Facility (Whelan et al. 1998, Appendix 2). Data are from DTN: GS960908315215.010.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-63 
Figure 61. Histograms showing the distribution of *13C values. 
Note: Histograms showing the distribution of *13C values for microsamples of calcite from the 
Exploratory Studies Facility, classified by relative age determined by visual examination. Data 
from DTN: GS960908315215.010, GS970208315215.005, GS980908315213.002, and 
GS991299995215.001 (data set MOL.20000104.0014).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-64 
3
2
1
0 
5
4
3
2
1
0 
5
4
3
2
1
0 
10 15 20 25 30 
10 15 20 25 30 
10 15 20 25 30 
NUMBER OF VALUES NUMBER OF VALUES NUMBER OF VALUES 
d18O, IN PER MIL 
CHALCEDONY 
QUARTZ 
OPAL 
5
5
5 
Figure 62. ..18O values for chalcedony, quartz and opal from the unsaturated zone 
Note: Histograms showing the distribution of ..18O values for subsamples of unsaturated-zone 
chalcedony, quartz and opal from drill core and the Exploratory Studies Facility (Moscati and 
Whelan, 1996, Table 1; Whelan et al., 1998, Appendix 3). Data are from DTN: 
GS931108315215.035, GS940608315215.006, and GS960408315215.003.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-65 
0.7095 
0.7100 
0.7105 
0.7110 
0.7115 
0.7120 
0.7125 
0.7130 
0 
100 
200 
300 
400 
500 
600 
Early Intermediate Late 
Early Intermediate Late 
87 
8 
6 
S 
r 
/ 
S 
r 
S 
T 
R 
O 
N 
T 
I 
U 
M 
C 
O 
N 
C 
E 
N 
T 
R 
A 
T 
I 
O 
N 
, 
IN 
M 
IC 
R 
O 
G 
R 
A 
M 
S 
P 
E 
R 
G 
R 
AM 
RELATIVE AGE 
RELATIVE AGE 
Figure 63. Strontium isotopic compositions and concentrations for ESF calcite. 
Note: Strontium isotopic compositions and concentrations for subsamples of calcite from the 
Exploratory Studies Facility, classified by relative age. Data are from DTN: 
GS970908315215.011 and GS991299995215.001 (data set MOL.20000104.0012).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-66 
10
5
0 
-5 
-10 
18 
17 
16 
15 
14 
13 
12 
10
5
0 
-5 
-10
12 13 14 15 16 17 18 
0.030 
0.025 
0.020 
0.015 
0.010 
0.005 
0.000 
0.709 0.710 0.711 0.712 0.713 0.709 0.710 0.711 0.712 0.713 
0.709 0.710 0.711 0.712 0.713 
87 86 S r / S r 87 86 S r / S r 
d1 
3 
C 
, 
I 
N 
P 
E 
R 
M 
I 
L 
d13C 
, I 
N 
P 
E 
R 
M 
I 
L 
d18O, IN 
d1 
8O 
, 
I 
N 
P 
E 
R 
M 
IL 
R 
E 
C 
I 
P 
R 
O 
C 
A 
L 
S 
TR 
O 
N 
T 
IU 
M 
C 
O 
N 
C 
E 
N 
TR 
AT 
IO 
N 
, 
( 
 
g 
/ 
g 
) 
-1 
EXPLANATION 
Relative subsample age 
Late 
Intermediate 
Early 
Range of surficial calcite (carbon data 
from Vaniman and W helan, 1994; 
strontium data from Marshall and Mahan, 
1994) 
A C 
B D 
Figure 64. Carbon, oxygen and strontium isotopic compositions in ESF calcites 
Note: Relations between carbon, oxygen and strontium isotopic composition and reciprocal 
strontium concentration for subsamples of calcite from the Exploratory Studies Facility (modified 
from Figure 4.11 in Paces, Neymark, et al., 1996). Data are from DTN: GS910508315215.005, 
GS920208315215.008, GS920208315215.012, GS930908315215.027, GS931008315215.029, 
GS931008315215.030, GS941108315215.010, GS950608315215.002, GS960908315215.010, 
GS970908315215.011, GS960908315215.010, and GS991299995215.001 (data set 
MOL.20000104.0012). 
.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-67 
Figure 65. Covariance between initial 234U/238U activity ratios and 230Th/U ages for calcite and 
opal deposits 
Note: Covariance between initial uranium-234/uranium-238 (234U/238U) activity ratios and thorium- 
230/uranium (230Th/U) ages for calcite and opal deposits in the Exploratory Studies Facility. Data 
are from DTN: GS960908315215.014, GS970208315215.001, and GS970808315215.012. See 
assumption 25 in Table 2.
230Th/U AGE, IN THOUSANDS OF YEARS 
BEFORE PRESENT 
INITIAL U/ U ACTIVITY RATIO 234 238 
2 
10
8
6
4 
100 200 300 400 500 0 
TIE -LIN E S C ON NE C T IN G SUBSAM PLE S FROM TH E 
SAM E M IN E R A L C OA T IN GS 
HYPO TH ETICAL V A LUES ASSUM ING CO ND ITION S 
O F C O N T IN UOU S D EPO S ITIO N 
12

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-68 
-200 
-150 
-100 
-50
0 
50 
100 
150 
200
0 2 4 6 8 10 
V 
E 
RT 
IC 
A 
L D 
IS 
TA 
N 
C 
E 
FR 
O 
M 
T 
H 
E 
B 
AS 
E 
O 
F 
T 
H 
E 
P 
T 
n 
( 
h) 
, IN 
M 
E 
T 
E 
R 
S 
PTn 
Tpc - 
welded 
Tpt - 
welded 
INITIAL U/ U 234 238 
ACTIVITY 
Maximum value for 
pedogenic carbonates 
Maximum Initial 234U/238U 
= 1 .4e -0.013h 
Filled circles represent 
the analyses with 
greatest in itial U/ U 
activity ratios at various 
depths used to calculate 
the heavy curve . 
234 238 
Figure 66. Initial 234U/238U activity ratios for hydrogenic minerals 
Note: Initial uranium-234/uranium-238 (234U/238U) activity ratios for hydrogenic minerals from the 
Exploratory Studies Facility plotted against vertical distance from the base of the Paintbrush Tuff 
nonwelded hydrogeologic unit. Stratigraphic units from Buesch et al. (1996). Data are from DTN: 
GS960908315215.014, GS970208315215.001 and GS970808315215.012.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-69 
R 
e 
l 
a 
t 
iv 
e D 
e 
p 
th 
(D 
e 
p 
th 
t 
o 
L 
ay 
e 
r 
/ D 
e 
p 
th 
t 
o 
B 
a 
s 
e 
) 
Age of Layer, Ma 
1.0 
0.8 
0.6 
0.4 
0.2
0 
0 2 4 6 8 10 12 
HD2019 2,881 3.9  0.3 
HD2019A 2,880 1.3  0.4 
HD2055 2,911 2.06  0.08 
HD2059 3,018 2.6  0.09 
SAMPLE 
DISTANCE 
FROM ESF 
NORTH 
PORTAL 
(m) 
GROWTH 
RATE 
(mm/Ma) 
Figure 67. Growth rates of mineral coatings in the unsaturated zone 
Note: Growth rates determined from uranium-series and uranium-lead ages from individual 
mineral coatings in the densely welded, crystal-poor, middle nonlithophysal zone of the Topopah 
Spring Tuff. Analytical data are from DTN: GS970208315215.002, GS970908315215.013 and 
GS991299995215.001 (data set MOL.20000104.0009). Ages were calculated from the 
measured 207Pb/235U ratios reported in the DTNs. See assumption 25 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-70 
E E E E E E E EE 
E E E E E E EE E E 
E EEE E E E E E E
E E E E 
E E E E 
E E 
E E E EE EE EEE E EE E EE E E E E E E EE E E 
E E E E
E 
E E E E E
E E E EE E 
E E EEEE E E EE E
E E E E E EE E EEEE 
E E E E E E EE E 
E E 
E E E 
E EE
E E E E E E E E E E E EEE E E E E E EE E E EEE E EE EE E E EE EEE EE E EE E EE E E E E E EE E E 
E E 
E E E E EEE E EE E E E E 
E EEEE E E EE E E E E E EE E
E 
E E E E E E E EE E EE EEE
EEE E 
EE E E E E 
E E E E E 
E E E E 
E E E
E 
E 
EEE 
E E E E E E 
E 
E E 
E E E E E E E EE E E E 
E E E E E E 
EE E E E E E 
E E E 
EEEE E EE 
E EE E E 
E 
EE
EEE E E 
E E E 
EE E 
EE E E EE EE EEE E E E E E E E E E 
E E E E E E E E EE E EE E E E 
E EEEE E E E 
EE
E E E 
E E 
E EE E E E E EE E 
E EE E EEEEE E E EEE E E E EE 
E EE E E EEEE EE E E E E E E EEE E EE E E E E EE E E E E E E EE E 
E E E EE E E E EEEE
E 
E E E EE E E E
E E E 
EEEEE
EE E EE E E EE 
E 
EE E E 
E E 
E E E E 
E E E E EE E E 
E E E E E E E E E E E E
E E E 
E E E E 
EEE 
EE 
E E EE E E E EE E EE EE E EE E E E E E EE EE E E E E E E E E E E E 
-1500 
-1000 
-500
0 
500 
1000
-10 -5 0 5 10 15 20 25 
d13C -- Soil Carbonate -- d18O 
d13C -- Pz Carbonate -- d18O 
d13Cpdb & d18Osmow () 
Water Table 
Figure 68. The d13C and d180 values of unsaturated-zone calcite from boreholes at Yucca 
Mountain. 
Note: The d13C and d180 values of unsaturated-zone calcite sampled from boreholes at Yucca 
Mountain, plotted versus height above or below the water table. Ranges of d13C and d180 values 
encountered in the pedogenic carbonates of the overlying soils and the calcite that would 
precipitate from waters of the regional Paleozoic carbonate aquifer are also plotted. Data are from 
DTN: GS920708315215.017, GS931008315215.030, GS950708315215.005, 
GS950708315215.006, GS960408315215.002, GS97028315215.004, GS970808315215.010, 
and GS980408315215.010. Sample depths are part of the sample identifiers in these DTNs.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-71 
0.0 
5.0 
10.0 
15.0 
20.0 
25.0 
0 10 20 30 40 50 60 70 80 90 100 
Temperature 
-12.5 water 
-10 water 
-11 water 
Figure 69. Temperature dependence of the d180 value of calcite 
Note: Temperature dependence of the d180 value of calcite in equilibrium with waters having d180 
values of  12.5, -11.0, and 10.0 (based on information from ONeil et al. 1969, p. 5552; Kim 
and ONeil 1997, p. 3467). Shaded field is for typical late stage temperature of 15 to 30C and 
d180 values of 15 to 19.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-72 
1 1 1 1 1 1 
1 
1 
1 1 
1 1 
1 
1 1 1 -8 
-6 
-4 
-2 
0 
2 
4 
6 
8 
0 2 4 6 8 10 12 
Age, in millions of years 
Late Intermediate Early 
d13C() of calcite 
-Tiva Canyon 
-Topopah Spring Tuff 
1 
Figure 70. d13C value of calcite versus its age 
Note: Plot of the d13C value of calcite versus age for those samples with U-Pb age control. Ages 
were calculated based on measured 207Pb/235U ratios, using equation 11 in section 6.10.1. See 
section 6.10 for a discussion of geochronology. Data are from DTN: GS960408315215.002, 
GS970208315215.004, GS970808315215.010, GS980908315215.016, GS970908315215.013, 
GS970208315215.002, GS980908315215.015, GS970808215215.012, GS970208315215.001, 
GS960908315215.014, and GS96028315215.001. See assumption 25 in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-73 
-10 
-8 
-6 
-4 
-2 
0 
2 
4 
6 
8 
10 
0 5 10 15 20 25 30 
Early Calcite 
Intermediate Calcite 
Late Calcite 
d 
18 O () 
Higher 
Formation 
Temperatures? 
d13C() 
Figure 71. d13C versus d18O for the ESF calcite microsamples. 
Note: Stages are distinguished by different symbols. In general, calcite d13C values decrease and 
d18O values increase with time. Microsamples of early stages calcite with anomalously low d18O 
values are shown in the shaded field. Data are from DTN: GS96098315215.010, 
GS97028315215.005, GS980908315213.002, and GS991299995215.001 (data set 
MOL.20000104.0014).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-74 
10 
12 
14 
16 
18 
20 
22 
0 2 4 6 8 10 12 
Age, in millions of years 
Late Intermediate Ear ly 
-Tiva Canyon 
-Topopah Spring Tuff 
d18O() of calcite 
Figure 72. d18O value of calcite versus its age. 
Note: Plot of the d18O value of calcite versus age for those samples with U-Pb age control. Ages 
were calculated based on measured 207Pb/235U ratios, using equation 11 in section 6.10.1. See 
section 6.10 for discussion of calcite geochronology. Data are from DTN: 
GS960408315215.002, GS970208315215.004, GS970808315215.010, GS980908315215.016, 
GS970908315215.013, GS970208315215.002, GS980908315215.015, GS970808215215.012, 
GS970208315215.001, GS960908315215.014, and GS960208315215.001. See assumption 25 
in Table 2.

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-75 
J J J J 
J J J J J J 
J 
J J J J J J 
J J 
J J J J J J J J J 
J J J J J 
350 
300 
250 
200 
150 
100 
50 
0 
16 17 18 19 20 21 22 
Tiva Canyon 
J Topopah Spring 
d 
18 O () 
Depth in the ESF below the surface (m) 
Figure 73. Late-stage calcite d18O values plotted by depth below the surface. 
Note: Late-stage calcite d18O values from the ESF plotted by depth below the surface. 
Data are from DTN: GS960908315215.010, GS970208315215.005, GS98098315213.002, and 
GS991299995215.001 (data set MOL.20000104.0014).

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-76 
-10 
-8 
-6 
-4 
-2 
0 
2 
4 
6 
8 
10 
5 10 15 20 25 30 35 
d 
18 O () 
Intermediate 
Ear ly 
Late 
d13C () 
Figure 74. Plot of *13C versus *18O for calcite from the Tptpmn unit 
Note: Plot of *13C versus *18O for calcite microsamples from the middle nonlithophysal unit 
(Tptpmn) of the Topopah Spring Tuff, as exposed in the ESF between Stations 2634 and 6018 
(station distances in meters). Approximate trends of increasing *18O values from earliest to latest 
calcite are also shown (white line). Data are from DTN: GS960908315215.010, 
GS970208315215.005, GS980908315213.002, and GS991299995215.001 (data set 
MOL.20000104.0014)

ANL-NBS-HS-000017, Rev 00 Attachment II 
Page II-77 
E
E
EE 
EEE
EE E
E
E 
E
E
E
E
E 
E
EE
E
E E 
EE 
E
EE 
E
EE
E
EE E E 
E E
EEE 
EE E
EE E 
E
EEE E
E
EEE 
E
E
EEEEEE
E 
EE E 
E EE E E 
EE 
E
E
EE EE EE E E
EE 
E
E EE 
E
EE
EE 
E 
EE 
E EE 
EE E
E
E E
E
EE 
EE 
E 
E
E EE 
E
E E
EE 
EE
E E 
E
E
E
E
E
E
E
EE 
0
5 
10 
15 
20 
25 
Exploratory Studies Facility, distance from N. Portal (m) 
Early Calcite 
E Intermediate Calcite 
Late Calcite 
Tiva Canyon Tuff (welded) 
Paintbrush Group non-welded 
Topopah Spring Tuff (welded) 
North Ramp Main Drift South Ramp 
Figure 75. d18O values of calcite versus distance from the ESF North Portal 
Notes: The d18O values of ESF calcite microsamples plotted against distance from the North 
Portal of the ESF. Stratigraphic contacts and bends in the tunnel are shown. Data are from DTN: 
GS960908315215.010, GS970208315215.002, GS980908315213.002, and 
GS991299995215.001 (data set MOL.20000104.0014)