NUREG/CR-5737 

PNL-7688 

Hydrogeologic Performance 

j'Assessment Analysis of the 

Commercial Low-Level 

Radioactive Waste Disposal Facility 

near West Valley, New York 

Prepared by M. P. Bergeron, J. L Smoot, M. L Kemner, W. E. Cronin 

Pacific Northwest Laboratory 

Operated by 

Battelle Memorial Institute 

Prepared for 

U.S. Nuclear Regulatory Commission

1=
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NUREG/CR-5737 

PNL-7688 

Hydrogeologic Performance 

Assessment Analysis of the 

Commercial Low-Level 

Radioactive Waste Disposal Facility 

near West Valley, New York 

Manuscript Completed: April 1991 

Date Published: June 1991 

Prepared by K. P. Bergeron, 3. L Smoot, K. L Kenmer, W. E. Cronin 

Pacific Northwest Laboratory Richiand, WA 99352 

Prepared for 

Division of Low-Level Waste Management and Decommissioning 

OMce of Nuclear Material Safety and Safeguards 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555 

NRC FIN B2485
ABSTRACT

A hydrogeologic performance assessment of the commercial low-level waste site 

near West Valley, New York, was performed for two pathways: a shallow lateral path

way where trench water can potentially migrate laterally through fractured and 

weathered till to nearby streams and a deep vertical pathway where leachate can 

migrate downward through unweathered till and laterally offsite in a lacustrine unit. 

Along the shallow pathway, little physical site evidence is available to Indicate 

what the degree of lateral migration can be. Past modeling showed that overflowing 

trench water would migrate laterally some distance before migrating downward into 

the unweathered till. If water did reach a nearby stream, calculations show that decay, 

adsorption, and stream dilution would reduce leachate concentration to acceptable 

levels. 

Within the deep pathway, tritium and 14C were the only radionuclides released in 

any significant concentrations. Predicted tritium levels are well below regulatory limits; 

however, predicted peak 14C concentrations, while meeting the 25 mrem/yr limit using the drinking-water-only exposure scenario, exceed the limit for the full garden sce

nario. Site Information on 14C release rates and geochemical behavior has con

siderable uncertainty and would need to be more fully evaluated in a licensing 

situation.

iii
SUMMARY 

The West Valley Low-Level Radioactive Waste burial site, which is located in Cat

taraugus County In western New York, about 40 miles south of Buffalo, began opera

tions in 1963. Fourteen trenches excavated at the site contain a variety of wastes 

Interred primarily In steel drums. Tritium, 9oSr, and 14C constitute the primary radio

nuclides in the Inventory. Operation was terminated In 1975, and the site is now under 

the custodianship of New York State Environmental Research and Development 

Authority. 

The trenches at the site are excavated about 5 m into glacial till that has a thick

ness of about 28 m. The upper few meters of the till Is fractured, oxidized, and 

weathered, while the underlying till is unweathered, contains few fractures, and reduc

ing conditions prevail. Laboratory and field measurements Indicate that the hydraulic 

conductivity of the unweathered till ranges between 2 x 10-8 and 6 x 10-8 cm/s. The till 

is underlain by a sequence of lacustrine sediments that are sandy at the top and grade 

Into slits and varved clays with depth. The upper portion of the lacustrine unit is par

tially saturated. 

Ground-water movement through the till Is predominantly downward as indicated 

by measurements of hydraulic head. Computer simulations of ground-water flow ade

quately reproduce the measured configuration of hydraulic head at the site based on a 

hydraulic conductivity distribution that decreases with depth. In the best-fit simulation, 

hydraulic conductivity of the shallow, weathered, fractured till is 5 to 10 times higher 

than the deeper unweathered till. In addition, hydraulic conductivity at depth Is 

reduced to 0.75 and 0.80 of the base value to account for compaction of the unweath

ered till. Previous work has calculated ground-water velocities of I to 8 cm/yr through 

the unweatherec! till assuming an effective porosity of 0.30. 

Computer simulations of tritium, 90Sr,'and 14C migration reproduced the observed 

concentration In the till beneath selected trenches. One-hundred-year projections 

Indicate that tritium may migrate as far as 10 m beneath the trench floor and 9OSr as far 

as 6 m beneath the trench floor. 

In this hydrogeologic performance fssessment, we evaluated two pathways for 

radionuclide migration: a shallow lateral pathway where trench water can potentially 

migrate laterally through the upper 1 to 2 m of fractured and weathered till to nearby 

streams and a deep vertical pathway where leachate can migrate downward through 

unweathered till and laterally offsite In a lacustrine unit. 

While this previous modeling indicates the lateral pathway through the fractured 

till eventually moves downward before reaching nearby streams, the occurrence of 

migration of kerosene at the nearby burial area would seem to indicate that migration

V
could be significant. To evaluate this pathway, we made conservative estimates of the 

potential Impact of the contaminated water overflowing from the trench to nearby 

Frank's Creek. Using trench leachate concentrations and conservative estimates of 

travel time to Frank's Creek, we evaluated which key radionuclides could be released 

from the site. With the exception of tritium and 14C, the effects of decay and adsorption 

eliminated the majority of radionuclides in the Inventory. The combined effect of decay 

and dilution offered by the annual average flow of Frank's Creek reduces levels of 

tritium and 14C to below regulatory concern. 

In the assessment of the deep vertical pathway, a one-dimensional streamtube 

transport code, TRANSS, was used in the analysis to predict radionuclide concentra

tions at 10 and 100 m downgradlent of the site. The area of the trenches was used as 

a guideline to develop the overall dimensions of the streamlines that defined the 

streamtube of the model. Different streamlines were used for the north and south 

trenches, respectively. A period of 14 years corresponding to the operational rife of the 

site was allowed before release to the environment; the only attenuation of activity dur

ing this time was due to radioactive decay. Travel times from the bottom of the 

trenches through 23 m of till to the lacustrine unit ranged between 300 to 2300 years 

according to Prudic's work. In this analysis, 300 years was used as a conservative 

estimate. Because of the relatively slow movement of water through the till, the effect 

of the waste containment was not considered, and the waste was assumed to be 

uniformly distributed throughout the bottom of the trenches. 

The results of the performance assessment analysis Indicate that tritium and 14C 

would potentially be the only radionuclides, released from the West Valley site in any 

significant concentrations. Peak tritium levels estimated In the assessment that ranged 

from 4.0 to 7.4 pCI/L 10 m downgradlent of the site are well below regulatory limits. 

For 14C, predicted peak concentrations meet the U.S. Nuclear Regulatory Commission 

limit for a 25-mrem dose using the drinking-water-only exposure scenario at 10 and 

100 m downgradient of the site. However, predicted concentrations exceed the limit 

for the full garden scenario at both 10 m and 100 m downgradient of the trenches. 

The release rate of 14C from the Individual trenches is the most sensitive param

eter In the overall performance assessment. For this analysis, the release rate to the 

flow system is estimated from maximum measured trench water concentrations and 

the estimated Infiltration rate. Experimental data on solubility for these radionuclides 

are generally not directly available for the West Valley site otherrthan what can be 

inferred from direct measurements In trench leachate. The use of this Information was 

based on the assumption that, because the trenches have historically had water in 

contact with the waste over a number of years, the measured concentrations of radio

nuclides in the trench leachate could possibly reflect reasonable solubility limits for the 

radionuclides in question. However, the validity of this assumption is not known in the

vi
context of the performance period. We acknowledge that If these concentrations con

tinue to Increase or decrease, the results of this performance assessment would not be 

valid and would need to be reevaluated. 

Once released to the flow system, we have assumed that all forms of 14C (organic and Inorganic) have the same geochemical behavior. The validity of this assumption 

Is unknown given the limited amount of geochemical Information on the 14C In the 

Inventory. It is generally known that the 14C can originate from a variety of sources, Including organic wastes, such as pesticides; solvents, resin materials, and biological 

wastes, and Inorganic wastes such as activated charcoal filters. The approach used in 

this study, which assumes minimal adsorption and retardation, in all probability pre

sents an overly conservative case for transport. The range of geochemical behavior in 

the context of these complexities is the subject of much uncertainty and certainly would 

need to fully evaluated in a licensing situation.

vii
ACKNOWLEDGMENTS

The authors wish to express their gratitude and appreciation to L. Deering, F. Ross, and R. J. Starmer of the U.S. Nuclear Regulatory Commission, Office of 

Nuclear Material Safety and Safeguards, for providing useful comments and sug

gestions In their review of this report. We also would like to acknowledge the 

assistance of the following persons who provided reports and/or information that were 

useful In preparing this report: David Prudic, U.S. Geological Survey, Carson City, 

Nevada; Alan Randall, U.S. Geological Survey, Albany, New York; Dr. James 

Albanese, New York State Geological Survey, Albany, New York; and Carol Hor

nibrook, New York State Energy Research and Development Authority, Albany, New 

York.

ix
ABBREVIATIONS

CEC 

CFR 

CFS 

LLW 

NFS 

NRC 

NYSDEC 

NYSDOH 

NYSDOL 

NYSDPW 

NYSERDA 

NYSGS 

PNL 

USGS 

WMGB 

WNYNSC 

WRD

Cation Exchange Capacity 

Code of Federal Regulations 

Cubic Feet per Second 

Low-Level Waste 

Nuclear Fuel Services. 

U.S. Nuclear Regulatory Commission 

New York State Department of Environmental Conservation 

New York State Department of Health 

New York State Department of Labor 

New York State Department of Public Works 

New York State Environmental Research Development Authority 

New York State Geological Survey 

Pacific Northwest Laboratory 

U.S. Geological Survey 

Waste Management Geotechnical Branch 

Western New York Nuclear Service Center 

USGS Water Resources Division

xi
CONTENTS 

ABSTRACT .. iii 

ACK•N=O EN •• •L.iEDG •• . . . •.S . . . • .•o . . .• . . . . . . lx SUMMARY ................................................ v 

ACKNOWLEDGMENTS .... ;.......... ..... .. ix 

ABBREVIATIONS . xi 

1.0 INTRODUCTION ....................................... 1.1 

2.0 DESCRIPTION OF DISPOSAL FACILITY ....................... 2.1 

2.1 TOPOGRAPHY AND DRAINAGE ......................... 2.4 

2.2 CLIMATE .............................. 2.4 

2.3 SITE OWNERSHIP AND DISPOSAL HISTORY ............... 2.4 

2.3.1 Trench Construction .............................. 2.6 

2.3.2 Waste Volume and Characteristics .................... 2.9 

3.0 PREVIOUS INVESTIGATIONS .............................. 3.1 

3.1 GEOLOGY ........................................ 3.1 

3.1.1 Bedrock Characteristics ........................... 3.1 

3.1.2 Glacial Sediment Characteristics ..................... 3.4 

3.2 GROUND-WATER HYDROLOGY ......................... 3.10 

3.2.1 Major Hydrogeologic Units .......................... 3.10 

3.2.2 Direction and Rate of Ground-Water Movement ........... 3.11 

3.3 SUBSURFACE RADIONUCUDE MIGRATION ................ 3.15 

3.3.1 Infiltration Through Trench Covers .................... 3.15 

3.3.2 Waste Leachate Characteristics ...................... 3.16 

3.3.3 Extent of Measured Migration ....................... 3.18 

4.0 HYDROLOGIC AND RADIONUCLIDE TRANSPORT ANALYSIS 

OF THE GROUND-WATER PATHWAY ........... . o 4.1 

4.1 PREVIOUS WORK. * * * ... 4.1 

4.1.1 Ground-Water Flow Modeling ....................... 4.1 

4.1.2 Radionuclide Transport Modeling .................... 4.5 

4.2 HYDROGEOLOGIC PERFORMANCE ASSESSMENT .......... 4.12 

4.2.1 Performance Objectives ........................... 4.13 

4.2.2 Analysis and Results of Shallow Lateral Pathway 

Assessment ................................... 4.13

xiii
4.2.3 Analysis and Results of Deep Vertical Pathway 

Assessment .............. ..................... 4.17 

5.0 DISCUSSION OF PERFORMANCE ASSESSMENT RESULTS....... 5.1 

5.1 COMPARISON OF RESULTS WITH PERFORMANCE 

OBJECTIVES ..................................... 5.1 

5.2 UNCERTAINTIES IN PERFORMANCE ASSESSMENT 

ANALYSIS ......................................... 5.1 

5.2.1 Ground-Water Movement .......................... 5.3 

5.2.2 Radionuclide Release and Transport Analysis ............. 5.6 

6.0 SUMMARY AND CONCLUSIONS ............................ 6.1 

7.0 REFERENCES .......................................... 7.1

xiv
2.1 Location of Western New York Nuclear Service Center, Streams, and 

Selected Wells Within Cattaraugus Creek Basin ................. 2.1 

2.2 Overview of Major Physiographic Features and Major Western 

New York Nuclear Service Center Facilities .................. 2.2 

2.3 Detailed View of Major Physiographic Features and Major Western 

New York Nuclear Service Center Facilities ..... .......... 2.... 2.3 

2.4 Location of Commercial Low-Level Waste Site, Fuel Reprocessing 

'Plant, Streams, Wells, Test Holes, and Geologic Sections Within the 

Western New York Nuclear Service Center .......... ........... 2.5 

2.5 Locations of Waste-Burial Trenches and Nearby Test Holes and 

W ells ............................................... 2.7 

2.6 ;North-South Cross Section of North End of Commercial Low-Level 

Radioactive Waste Burial Grounds at Nuclear Fuel Services, West 

Valley, New York ...................................... 2.8 

3.1 Generalized Stratigraphic Column for the Vicinity of Western New 

York Nuclear Service Center ........................ ......... 3.2 

3.2 Bedrock-Surface Altitude In Buttermilk Creek Valley .............. 3.3 

3.3 Idealized Cross Section In Vicinity of Burial Site West of Buttermilk 

'Creek Showing Inferred Distribution of Saturated and Unsaturated 

Material and General Directions of Ground-Water Flow .............. 3.5 

3.4 Vertical Sections Through Trenches Showing Head Distribution 

During February 1976: Section C-C' Through North Trenches ........ 3.11 

3.5 Vertical Sections Through Trenches Showing Head Distribution 

During February 1976: Section D-D' Through South Trenches ....... 3.13 

3.6 Map Showing Lateral Direction of Ground-Water Flow in Lacustrine 

Sequence . ................. ............ 3.14 

3.7 Water Level Changes In Trench 5 in Relation to Precipitation 

from May Through September 1975 and from January Through 

July 1976 ........................................... 3.17

xv
3.8 Water Level Trends In the North Trenches Showing the Effects of 

Regrading the Trench Caps ................................ 3.19 

3.9 Changes in Tritium Concentrations with Depth in Test Holes Near the Burial Site .................... q..............0........ 3.21 

4.1 Vertical Section C-C' Through North Trenches Showing Computer 

Model Design Used In Best-Fit Simulation ...................... 4.2 

4.2 Vertical Section C-C' Through North Trenches Showing 

Computer-Simulated Distribution of Heads ....................... 4.6 

4.3 Vertical Section D-D' Through South Trenches Showing Computer Model Design . . . . . . . . . . . . . . . . . . .. 4.7 

4.4 Vertical Section E-E' from Trench 4 Northward to Small Stream Showing 

Computer Model Design ................................ 4.8 

4.5 Comparison of Simulated and Observed Tritium Concentrations Beneath 

Trenches 5 and 8 .4............................... . 4.10 

4.6 Comparison of Observed and Calculated 9oSr Concentrations Beneath 

Trench 8 In Test Hole 8-2B ................................ 4.11 

4.7 Predicted 9OSr Concentration in Till Beneath Trench 4 After 10, 100, 

and 500 Years ........................................ 4.12 

4.8 Vertical Section C-C' Through North Trenches Showing Computer 

Simulated Distribution of Heads for a Scenario of High Water Levels 

in the Trench ......................................... 4.15 

4.9 Depiction of the Streamtube Approach to Transport Through 

the Till Zone and Lacustrine Unit as Incorporated Into the 

TRANSS Code ........................................ 4.18 

4.10 Streamlines and Streamtubes Used for Transport Modeling ........ 4.20 

4.11 Cross-Sectional View of Flow Path Used In Transport. Modeling..... 4.21 

4.12 Tritium Concentrations at a Hypothetical Well Located Approximately 

10 m and 100 m Downgradlent (Northeast) of the North Trenches .... 4.31 

4.13 Tritium Concentrations at a Hypothetical Well Located Approximately 

10 m and 100 m Downgradlent (Northeast) of the South Trenches .... 4.31

xv!
4.14 Carbon-14 Concentrations at a Hypothetical Well Located Approximately 10 m and 100 m Downgradient (Northeast) of the North Trenches .... 4.32 

4.15 Carbon-14 Concentrations at a Hypothetical Well Located Approximately 

10 m and 100 m Downgradient (Northeast) of the South Trenches .... 4.33 

5.1 Sensitivity of Predicted Peak 14C Concentrations to Changes In the 1111 Travel Time ........ . . ................ .......... 5.4 

5.2 Sensitivity of Predicted Peak 14C Concentrations to Changes in the 

Distribution Coefficient .... ............... .............................. 5.7

ýxvii
TABLES

2.1 Estimated Inventory for Low-Level Waste Burial Trenches ........... 2.10 

2.2 Volume of Waste Containers In Trenches 8 Through 14 ............ 2.11 

3.1 Stratigraphy of Quatemary Sediments in Central Buttermilk Creek 

Valley, Cattaraugus County, New York ........................ 3.6 

3.2 Dates of Trench Completion and Regrading .................... 3.18 

3.3 Radionuclide Content of Water In Trenches ..................... 3.20 

3.4 Concentration of Selected Radionuclides Beneath Trenches 4, 5, 

and 8, November- December 1977 .......................... 3.25 

4.1 Differences Between Heads Observed in February 1976 and 

Simulated Heads for Assumed Conditions ..................... 4.3 

4.2 Factors Used to Convert Concentration for Selected Radionuclides 

to Dose for the Drinking Water and Full Garden Exposure Scenarios ... 4.14 

4.3 Summary of Effects of Decay and River Dilution on Maximum Trench 

Concentrations for Tritium and 14C ........................... 4.17 

4.4 Selected Retardation Factors for Various Radionuclides ............ 4.22 

4.5 West Valley Trench Inventory ............................... 4.24 

5.1 Equivalent Doses from Modeled Peak Concentrations for Tritium 

an d 14C ............................................. 5.2

xv;ili
1.0 INTRODUCTION

In December 1982, the U.S. Nuclear Regulatory Commission (NRC) published regulations setting forth specific evaluation criteria for licensing the land disposal of 

low-level radioactive waste (LLW). These regulations are contained In Title '10 of the 

Code of Federal Regulations, Part 61 (10 CFR 61), "Ucensing Requirements for Land 

Disposal of Radioactive Waste." A specific requirement of these regulations, Indicated 

in Section 61.5, Subpart D, states that land disposal of LLW "... shall be capable of 

being characterized, modeled, analyzed, and monitored...'. Implicit in these require ments are that applications for future LLW sites would include sufficient information 

and analyses to provide reasonable assurance that performance objectives In the 

regulations be met. These analyses will likely Include the use of transport models for prediction of radionuclide transport along the ground-water pathway from the prospec tive facility. To date, no LLW sites have been licensed under 10 CFR 61; the NRC 

technical staff can only speculate on the degree of complexity needed to model the 

performance of future LLW sites along the ground-water pathway with respect to the 

evaluation criteria of 10 CFR 61. 

The Pacific Northwest Laboratory (PNL)(a) provides technical assistance to the 

NRC in developing performance assessment capabilities that will enable the NRC to 

evaluate the adequacy of future LLW sites following the congressional mandate In the 

Low-Level Radioactive Waste Policy Amendments Act of 1985. The overall objective of this project is to provide technical support to the NRC on the geologic, hydro geologic, geochemical, and geophysical aspects of LLW disposal. Specific goals of 

this project are to 

" Develop detailed reports describing the geoscience characteristics and 

general disposal design for existing commercial LLW disposal sites. Initial 

sites being evaluated are the commercial low-level radioactive waste 

disposal facilities at Sheffield, Illinois, and West Valley, New York. 

* Develop a computerized geoscience data base for the existing commercial 

LLW disposal sites. This data base will be used by the NRC staff to analyze ground-water flow and transport at existing sites and to provide pre-licensing guidance for LLW.disposal to states based on past experience. 

" Select and apply hydrogeologic codes to existing commercial LLW disposal sites to gain insight into modeling strategies, data needs, and levels of detail 

needed to adequately model proposed LLW sites with respect to 10 CFR 61. 

(a) Pacific Northwest Laboratory Is operated for the U.S. Department of Energy by Battelle Memorial Institute.

1.1
Recommend and supply modeling codes as needed for NRC staff to evalu

ate the performance of proposed LLW sites. These performance assess

ment capabilities will be used to support findings on specific licensing 

requirements of 10 CFR 61. 

This report summarizes the relevant environmental characteristics and the past 

performance of the LLW disposal facility situated near West Valley, New York. The 

purpose of the report Is to present a summary of past investigations that are pertinent 

to performance assessment at the West Valley LLW site and to describe the perform

ance assessment approach that was used to evaluate the long-term transport of 

radionuclides through the subsurface at the site. This report includes a review of 

pertinent past Investigations and studies that have been conducted at the West Valley 

site by the site operator and various state and federal agencies over the operational 

and post-closure period of the facility. The Information compiled In this report is also 

contained In a computerized geoscience data base developed for the West Valley site. 

The information provided the basis for the selection and application of appropriate 

codes for analyses of the ground-water pathway at the West Valley site. 

Section 2.0 describes the disposal facility at the West Valley site and provides 

background on the physical and climatic setting. Previous investigations of the site's 

geology, hydrology, and subsurface radionuclide migration are discussed In Sec

tion 3.0. Section 4.0 describes the hydrologic and radionuclide transport analysis and 

results, Section 5.0 is a discussion of the results of the performance assessment, and 

Section 6.0 provides a summary and conclusions. References are listed In Sec

tion 7.0.

1.2
2.0 DESCRIPTION OF DISPOSAL FACILITY

SThe West Valley site is located on the grounds of the Western New York Nuclear 

Service Center (WNYNSC) In northern Cattaraugus County, New York (Figure 2.1). 

The site Is contained within the glaciated Allegheny portion of the Appalachian 

Plateau Physiographic Province. The WNYNSC Is about 6 km northwest of the town of 

West Valley and about 48 km south of Buffalo. The WNYNSC covers 13.5 km2, of 

which about 4 ha (0.4 km2) is allocated to the LLW burial site. 

In addition to the commercial site, the WNYNSC contains a number of other 

facilities related to fuel reprocessing plant that operated within the center from the mid

1960s to the early 1970s (Figures 2.2 and 2.3). These facilities include a fuel repro

cessing plant, a facility disposal area (FDA) used by the previous site operations for 

selected site radioactive waste, a high-level radioactive waste-storage tank complex, 

and a LLW water treatment plant and lagoon, as well as other related facilities.

£ STREAM-GAGING STATION 

WELL - Seiceds of latitude 

followed by seconds of Iongitude 

idejitlfiu well sampled for 

mvcala ,analysIs (table 11. 

Bass from U S Geological Survey 

Buffalo 1:250000. 1962 0 4 B KILOMETERS 

0 SMILES

Location of Western New York Nuclear Service Center, Streams, and 

Selected Wells Within Cattaraugus Creek Basin (after Prudic 1986)

2.1
Base from U S Geological Sungey 

Ashford Hollow. 1979 1.24 000

FIGURE 2.2. Overview of Major Physiographic Features and Major Western 

New York Nuclear Service Center Facilities 

2.2
78'391. 76*39 00

(S"" FRENCH DRAIN 

CONTINUOUS-RECORDING 

STATION (A• PARTIAL-RECORD STATION 

RAIN GAGE 

( i WATERSHED BOIJNDARY 

-~ ~ ~ Vetland. P-fr3 

.4/ 

HIUH LEVEL &-\ . ;-T::- RADIOACTIVE 

WAStE -STORAGE I~ . TANK COMPLEX( ~J ,,.. 

.- LOW-LEVEL WASTE-WATER "TREATMENT LAGOONS 

f ;f qEPRO("ESSING k 

42'p 

00WASTE IULk~\\~ 

LAG/- ROAD 

N \\% 

'A %]• 

Al, D IS-OSAL 

STATF LICENdSED Vt.14E 

~cDISPOSAL AREA 

5;. U,,-. _.$ 

e a fsrp , U C ,- v. aT , 

FIGURE 2.3. Detailed View of Major Physiographic Features and Major Western 

New York Nuclear Service Center Facilities

2.3
2.1 TOPOGRAPHY AND DRAINAGE

The glaciated terrain near West Valley is a gentle, rolling topography that is 

moderately dissected by streams. The surface is generally covered by glacial till com

posed predominantly of fine-grained silts and clays but also includes some gravel and 

cobbles. The vegetation in the area is deciduous hardwood forest, although much of 

the land In the area has been farmed for many years. The waste burial site sits on a 

knoll bordered by Intermittent creeks and a small, swampy area on lowlands to the 

north. The LLW site is located on the west side of the Buttermilk Creek Valley in the 

Cattaraugus Creek drainage basin (Figure 2.4). Frank's Creek and a tributary called 

Erdman Brook drain the east and west sides of the burial area. Frank's Creek drains 

into Buttermilk Creek, which flows several kilometers north from the burial site to its 

confluence with Cattaraugus Creek. Cattaraugus Creek then flows about 50 km north

west before reaching its mouth at Lake Erie (Figure 2.1). 

2.2 CLIMATE 

The West Valley area has a moist continental climate owing to the proximity of the 

Atlantic Ocean and Lake Ontario. The prevailing winds are from the west with south

westerly winds prevalent during the warmer months and northwesterly winds during 

the cooler months. Wind speeds are moderate, generally less than 15 km per hour. 

The mean annual temperature at West Valley is about 70C with mean monthly 

temperatures of -60C for the January-February period and 200C in July. Annual 

temperatures commonly range between -260C and 320C. Several days may be 

expected to be near each extreme annually. Approximately 100 to 120 frost-free days 

can commonly be expected during the growing season. 

The average annual precipitation In the West Valley area is about 100 cm. 

Precipitation is distributed relatively evenly throughout the year. Rates of 9 cm/mo are 

common in the spring, early summer, and late fall. Winter precipitation, which aver

ages about 7 cm/mo, commonly occurs as snow; accumulations of 30 cm or more may 

result from a single storm. Accumulations of 125 cm during two consecutive months 

during the winter are not uncommon, and continuous snow cover may be expected 

from mid-December to mid-March., 

2.3 SITE OWNERSHIP AND DISPOSAL HISTORY 

The West Valley site is owned by the State of New York. Nuclear Fuel Services, 

Inc. (NFS), who was the sole site operator under permit from the state, began site 

operations in 1963. The permit was Initially administered by the New York State 

Department of Labor (NYSDOL) and the New York State Department of Health

2.4
4'739' W8 783 Wn*17 .... * '1 7

EXPLANATION

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003 Burls 

: '. 0546 . ;; Wree S 

*• ' , ' , '" ;i" I- "1 .' .. 

I. -. * "I" f " 

, / • .. '\ . 61 "Poo-, :

L STREAM-GAGING STATION 

L MEASURED GEOLOGIC SECTION WITH 

IDENTIFICATION-Some sections am de. 

icribed In Randall 119801. wthers are unpub. 

lishled 

o WELL OR TEST HOLE 

DH6 

82 Geologic test hoto 

V 

. 20-59 Seconds of latitude followed by seconds of 

"longitude, Identifies wells sampled for ehemical Snalysis (with degrees and minutes in table 1) 

r LINE OF GEOLOGIC SECTIONS-Shown in 

figure 9 "WESTERN NEW YORK NUCLEAR SERVICE 

CENTER BOUNDARY 

4 N 

I. 

'. B , 

04 * I I 

''A 

*j ,..~ i

SE

ean from U L 5eologece Sur&wy Ashford Hollow 1:24.000, 1964

0 0.2 0.4 0.6

FIGUREL2.4. Location of Commercial Low-Level Waste Site, Fuel Reprocessing Plant, Streams, Wells, Test Holes, and Geologic Sections Within the 

Western New York Nuclear Service Center 

2.5

I --

42 27'

4f26'

KILOMETER 

MILE

78" 40' 78"38' • j•!• •7;,

! I I

i
(NYSDOH) until 1974. The New York State Department of Environmental Conserva

tion (NYSDEC) assumed control from the NYSDOH in October 1974. Radioactively 

contaminated water was discovered overflowing several of the trench covers in 1975, 

and operation of the site was terminated through a joint agreement between NFS and 

NYSDEC (Envirosphere 1986). As part of the agreement, a closure plan was devel

oped that enabled the eventual transfer of responsibility for the site to the New York 

State Energy Research and Development Authority (NYSERDA) (Envirosphere 1986). 

Fourteen waste budal trenches were excavated and filled over the period of 

operation (Prudic 1986) as shown in Figure 2.5. Trenches are numbered consecu

tively as they were constructed. Trenches 1 through 7 were constructed and filled 

during the first 6 years of operation and are known as the north trenches. Trenches 8 

through 14, the south trenches, were constructed and filled during the next 6 years of 

operation. Major customers served during the operational period included medical 

and educational Institutions, industrial clients such as radiopharmaceutical and instru

ment manufacturers, various levels of federal and state government, commercial 

nuclear power plants, and commercial haulers (Envirosphere 1986). 

In a recent report of site status, Envirosphere (1986) indicated that NYSERDA is 

developing comprehensive site management plans for the site. The trench covers 

now support a thick stand of grass. Maintenance surveys are conducted semiannually 

to monitor the conditions of the trench covers. Water levels in each trench, except 6 

and 7, are monitored monthly along with the condition of the fence around the perim

eter of the site. Trench leachate is being occasionally pumped from a number of 

trenches to maintain leachate levels at acceptable levels. 

2.3.1 Trench Construction 

The trenches at the West Valley site have been excavated using the cut-and-fill 

method, which Is schematically illustrated In Figure 2.6. The land that the trenches 

occupy was cleared and graded before excavation. Trenching proceeded several 

tens of meters at a time to minimize the amount of time that any given portion of a 

trench was exposed to the elements. The excavated till was set to the side and used 

to cover the wastes when the trenches were full. As trenching proceeded, completed 

trenches were temporarily covered with the excavated material. Experience gained 

with the construction and maintenance of the north trenches has improved the quality 

of trench construction over time. Because less than 2 m separates the north trenches, 

the resulting thin trench walls tended to be unstable, causing slumping of the till side

wall into the trenches. In addition, the trench covers consisted of a relatively thin and 

poorly graded soil, leading to a reduced effectiveness at preventing infiltration. The 

south trenches were spaced at least 3 m apart and have thicker, well-graded caps. 

These two aspects have contributed to better overall performance of the south 

trenches, which have experienced much reduced infiltration.

2.6
EXPLANATION 

e E Test hole drilled 

1975-76 

4 2C Test hole augered 

1973-74 

C Test hole hand augered 

1977.80

0 Pipe from sump In trench / 

Well driven Into trench I 

1976-77 

V Teti hole driven through trench 

1977-78 

10 Trench number 

C swami 

I Cross-sectlon profile IG H D 

I used m.odel• In computer C. 1 1o,1 

C& IN 

4 Fr 

N Fence al ,1

K

4//

q'O 

/

I

/

ESwamp* 

E S -.

A/ 

*O R 

A2 1

I

s,. North 

trenches

.6 I,

I

I

(

ES 10 0 

E.70 EP\ 

0S- I 0

f -,

0 25 50 75 METERS Based on plane-table survey 

,, , U S Geological Survey. 1975-78 

0 100 200 FEET 

FIGURE 2.. Locations of Waste-Burial Trenches and Nearby Test Holes and Wells 

(after Prudic 1986)

2.7

-A-
UNWEATHERED 

TILL

A ORIGINAL GEOLOGIC AND TOPOGRAPHIC CONDITIONS

UNWEATHERED 

TILL 

B SITE AFTER GRADIIr, AND PREPARATION FOR BURIAL 

OPERATIONS

5*LU.WASTES 

? ?,Wb LOCATION OF 

END OF TRENCH 

? I 1 UNCERTAIN

UNWEATHERED 

TILL

C SITE AF rER BURIAL OPERATIONS COMPLETED

EI.GU.B,2.6. North-South Cross-Section of the North End of Commercial Low-Level 

Radioactive Waste Burial Grounds at Nuclear Fuel Services, West 

Valley, New York. The cross-sections interpret the geology of the north 

end of the burial grounds based on data from core holes, topographic 

maps and field observations (after U.S. Department of Energy 1979).

2.8
2.3.2 Waste Volume and Characteristics

Waste emplacement and burial at the site was relatively constant during the 

period of operation. About 67,000 m3 of waste is interred at the site. Inventories for 

the waste burial trenches, listed In Table 2.1, are estimated Inventories at the time of 

disposal developed by Kelleher and Michaels (1973). Tritium Is generally the most 

abundant radionuclide followed by 14C. The remaining radionuclides are generally listed in order of decreasing abundance In the inventory. The distribution of radio

nuclides for trenches 12 through 14 reflect average distributions from trenches 1 and 

11. The distribution of 90Sr In the inventcry is not provided In Table 2.1. Most of the 9OSr Interred at the site Is located In trench 4 where approximately 15,763 Ci were 

buried (Giardina et al. 1977). Only minor amounts of O0Sr were buried In most of the 

other trenches; thus, they are listed separately In Table 2.1. 

Several sources exist for the 14C buried in the trenches. Some may be the result 

of disposal of activated charcoal filters used during the nuclear fuel cycle (Kelleher and Michaels 1973). Giardina et al. (1977) report on the shipment of pesticides con

taining organic 14C to several of the trenches. 

Table 2.2 lists the volume and types of waste containers for trenches 8 through 14 

as described In Prudic (1986). The total waste volumes presented here differ slightly from those given in Table 2.1. At least half of the Inventory is housed In metal con

tainers. The next most abundant type of container Is either cardboard or wood, depending on the trench. Each trench may contain up to several hundred cubic 

meters of both concrete containers and loose rubble. A few cubic meters of plastic con

tainers are found In trenches 8 and 12.

2.9
IABLE 2.1. Estimated Inventory for Low-Level Waste Burial Trenches (after Ford et al. 1978)

Total 

Truich Acavity 

No. (C)

11 

10 

9 

8 

5 

4 

3 

2 

1 

7 

6 

12tO 

13) 

146) 

Total 

Ave

5.35 x 104 

549 x 104 

3.42 x 104 

3.87 x 104 

9.29 x 104 

6.71 x 104 

1.71 x 104 

2.2 x 103 

4.12 x 103 

1.57 x 103 

1.02 x 104 

1.12 x 104 

9.40 x 103 

1.23 x 104 

4.09 x 105

Waste 

Volume 

(cm3 ) 3H 14C WCo 

5.18 x 109 7.0 6.6 x 10-2 5.1 x 10.2 

5.17 x 109 6.1 64 x 193 3.5 x 104 

4.92 x 109 1.6 3.6 x 10-3 2.8 x 10-2 

7.15 x 109 2.2 4.9 x 103 1.8 

7.88 x 109 14 3.8 x 104 5.9 

7.77 x 109 3.5 x 104 1.0 x 104 2.2 x 10-2 

5.62 x 109 1.2 x 104 8.9 x 104 7.1 x 104 

3.24 x 19 2.5 x 104 - 4.9 x 10-2 

1.56 x 109 1.1 x 10 6.4 x 104 2.2 x 10.2 

7.00 x 107 - 3.6 

2.10 x 106 - - 4.9 x 103 

5A9 x 109 2.2 9.8 x 104 1.6 

5.82 x 109 2.2 9.8 x 10 1.6 

4.72 x 109 2.2 9.8 x 103 1.6 

646 x 1010 

- 2.2 9.8 x 104 1.6

Nuclide Concentration m Waste (uCici 

137CS 2 26 Ra ___Am_

5.8 x 10`4 1.9 x 10-3 

5.8 x 104 5.8 x 10

1.8 x 104 2.8 x 10-6 

1A x 104 2.3 x 104 

1.3 x 10-5 5.6 x 10-5 

3.9 x 104 2.1 x 104 

- 8.9 x 10.6 

- 6.2 x 10-5 

5.0 x 104 1.1 x 104 

5.0 x 104 1.1 x 104 

5.0 x 10-4 1.1 x 104 

5.0 x 104 1.1 x 104

1.3 x 103 

7.7 x 10-7 

1.0 x 103 

2.1 x 104 

8A x 104 

SA x 104 

8.4 x 104 

84 x 104

2UPu 239pu 23SU 232Th 

7.6 x 10- 1.2 x 10- 2.3 x 10-6 9.9 x 10.6 

1.7 x 104 7.5 x 104 9.1 x 10-7 2.5 x 10,6 

2.1 x 10-2 1.2 x 10-3 1.6 x 10-6 5.7 x 106 

3.1 x 10-2 3.9 x 10-3 3.8 x 10-6 5.2 x 10-5 

1.7 x 10-2 2.3 x 104 8.5 x 10-7 3.3 x 10

- 3.8 x 10-3 2.2 x 10-6 

7.2 x 104 1.1 x 10"i" 6.8 x 10-7 1.6 x 10-6 

- 1.7 x 104 4.3 x 10-7 

- - 3.9 x 10-6 2.0 x 10-5 

- - 9.0 x 10-6 -

6.2 x 10-2 

6.2 x 10-2 

6.2 x 10-2

7.3 x 10-3 1.7 x 10-6 2.0 x 10-5 

7.3 x 10- 1.7 x 10,6 2.0 x 10

7.3 x 10-3 1.7 x 104 2.0 x 104

6.2 x 10-2 2.0 x 10-3 1.7 x 10-6 2.0 x 105

(a) Nuwcld. Concea'aziowa for Treche 12.13, sod 14 taken to be average of Tieachei 1-11 (emiWig 6 and 7).

I
TABLE 2.2. Volume of Waste Containers in Trenches 8 Through 14 (after Prudic 1986) 

Trench 8 Treh9 Trench 10 Trench 11 I .in 1Trench 13 Trench 14 

Volume Peretwg Volume Percentage Volume Percentage Volume Percentage Volume Penmtge Volume Percentage Volume Percentage 

TMeof Cotainer JmO. o[otuL _(r3L of Total _(ill3 of _(Mnft - Total 1_ -of Total - _(M3)_ -oJts

Metal 

Dnum 3279 

Tanks and boxes 164 

Madubiesyequipmemt 4 

Php bei m, other 

loose pleces 1

Lumber, other items 

Casks 

Pqr. cant m fiberboawd 

Boxes

Plastic

1081 

1 

119 

1712 

342

46 

2

2543 

39 

165

53 

1 

3

-9 1

15 

2 

24 

5

718 

17 

161 

11 

769 

24

15 

3 

16 

1

2467 

84 

135 

6 

889 

10

32 

1

47 

2 

3

3034 

165

15

17

I

1016 2D 

73 1

952 

11 

67 

6 

423 

31

59 3 3400 61 3893 

266 5 46 

4 - 35

- 216 4 23 

18 908 1 1030 

- 1 - 3

1 

8 

1

4

Loose dirt, gravel, slag, 

rubble 383

168 3 457 

22 -

294 5 240 

52 1 65

1

17 

8 

4 

1

4057 63 

408 6 

1 -

1061 17 

7 -

442 

146 

137

7 

2 

2

2 -

5 231 5 461 9 419 8 175 3 M1 1 101 2

MiceUlleu 

Boxes, type unknown 56 

Ofrx 32

Total volume 7178

- indates neliible amount.

1 21 2

21 22 

6

4838

- 41 

- 19 

52M2 5183

1 29 1 5 36 35

5558

1 

1

59M4

27 

27

6439
3.0 PREVIOUS INVESTIGATIONS

Numerous Investigations have covered many aspects of the West Valley site. 

The following discussion focuses on previous Investigations related to the site 

geology, hydrology, and subsurface radionuclide migration that has occurred. 

3.1 GEOLOGY 

The West Valley site Is found In the northwest Appalachian Basin. The geology is 

characterized by early Paleozoic marine sediments that form a broad syncline and are 

overlain by Pleistocene glacial deposits. The paleozoic sediments consist primarily of 

shales and siltstones with smaller amounts of sandstones and limestones, while the 

overlying glacial deposits are Interlayered tills, lacustrine deposits, and lenses of 

coarser sediments Indicative of several episodes of glaciation. A generalized strati

graphic column for the vicinity of the West Valley site is provided in Figure 3.1. 

The site Is located structurally on the north limb of a broad syncline. The rocks 

dip to the south at 6 to 8 m/km. The rocks exhibit regular bedding with little folding or 

faulting apparent. However, a well-developed set of approximately vertical joints or 

fractures Is evident. In the few places where bedrock Is exposed (Figure 3.2), individ

ual joints tend to be about 30 cm long and 60 cm apart. The common orientations of 

the joints are N 680 E and N 450 W. 

3.1.1 Bedrock Characteristics 

According to Colton (1961) and Eardley (1962), who provide detailed discussions 

of the bedrock stratigraphy in western New York, approximately 2300 m of Paleozoic 

rocks consisting predominantly of shales, limestones, and sandstones is present in the 

vicinity of the site. The upper bedrock in this portion of the Appalachian Basin is com

prised of shales and siltstones of the Devonian Canadaway Group (Chadwick 1933). 

In the vicinity of the burial site, the Canadaway Group is highly jointed and about 

300 m in thickness. 

The Caneadea-Machias Formation comprises the upper 120 m of bedrock that 

underlies the glacial deposits and consists of moderately hard, thin-bedded shales 

and slltstones that are gray to black in color. Prudic (1986) describes the upper 180 m 

of bedrock as containing thin beds of gray shale and silty shale with a few scattered 

thin beds of light-gray calcareous siltstone. 

The bedrock surface in the vicinity of the site displays a well-dissected paleo

topography with as much as 300 m of relief between hills and valleys. A structural

3.1
.1 I rApprox. Thickness Depth System Series Unit I (a) I ()

QuaternaryI

Solocene

Pleistocene

Alluvial fans; floodplain alluvium

Glacial till; fluvial sands a gravel$

0-S

0-160

Canadaway Group Up Java'&Vest Falls Grdup (shales) 58. 

Sony•t Group 

Genesee Group 

Devonian 

Tally Formation 5 

iddle Iamiltos Group (shale a limestone) 110 

Onondaga Limestone 50 

Upper Akron-Irtiea 

Salina Group 230 

-1 

Silurian Lockport Group 70 

'ftddie 

Clinton Group 45 

Lover hedums (sandstone) 30 

Upper queenston Formatios (red shales) 300 

Osvego Foruation (sandstone) 35 ' 

Ordovician 

Lorraine Group 250 

Utica Formation 

liddle 

Trenton-Mlack liver Group 253 

Tribes Hill-Beekinantows 30 

Little Falls Dolomite 60 Cambrian Upper 

Theresa Formation 213 

Fotsdam Formation 30

Precambrian

3

610 

615 

725 

775 

005 

T07S 

1120 

1150 

1450 

14253 

1735 

1996 

2020 

2080

2295 

2323

FIGURE 3.1. Generalized Stratigraphic Column for the Vicinity of Western New York 

Nuclear Service Center (modified from U.S. Department of Energy 1982)

3.2
7 07 978'38' 70* -A 4

EXPLANATION 

400 BEDROCK SURFACE CONTOUR - Shows alti 

rude of bedrock surface Contour Interval b 

50 meters Datum ieea level 

297 0 WELL OR TEST HOLE - Number Is altitude of 

bedrock surace. in meters above ues level 

4%- WELL OR TEST HOLE - Number Is altitude of 

45 bottom of hole, In metars above sea evel 

a SEISMIC SHOT POINT OR POINT FROM A 

SEISMIC CROSS SECTION - Number Is 

attitude of bedrock surface. In meters above "•- a level INuclear Fuels Services, Inc , 1962) 

* :l BEDROCK OUTCROP - fin Part fromLaFleur. 

1979)

42" 29' 

4f 28' 

42" 27' 

4262

IN1

IN

* 4S7 

o . 4402 

* N. 

4 

00 

.404? 

4 "

II.N 

-'A"

454 

0

- 1..

Base from U S Geological Survey 

Ashford Hollow 1:24.000.1964

0 '2 1 0*I 

0, 02 04 06

FIGURE 3.2. Bedrock-Surface Altitude In Buttermilk Creek Valley (modified from 

Randal11980)

3.3

i

I I

KILOMETER 

MILE

78" 40' 71" 39' 7B'311'

9 I

] ! ,

L_
contour map of the bedrock surface in the vicinity of the burial site (Figure 3.2) indi

cates that the thalweg of the bedrock valley occurs at a depth of 90 to 120 m when it 

coincides with the current stream channel (Randall 1980). Directly east of the waste 

burial trenches, the thalweg Is west of Buttermilk Creek in an area where the glacial fill 

may be about 150 m thick. 

3.1.2 Glacial Sediment Characteristics 

Broughton and Stewart (1963) and Stewart (in two letters to J. D. Anderson, New 

York State Office of Atomic Development dated April 3. 1962, and July 10, 1962) 

describe initial investigations of the glacial till and lacustrine sediments that comprise 

the valley fill. Subsequent work on the glacial deposits is documented in a number of 

reports which include Coates (1976), Muller (1977a, 1977b), and most notably LaFleur 

(1979, 1980) and Randall (1980). 

According to LaFleur (1979), the unconsolidated sediments at the site are inter

bedded layers of glacial till, lacustrine, alluvial, and colluvial deposits formed in melt

water lakes and streams during glacial recesses. A generalized cross section 

representing the vicinity of the burial site, Illustrated in Figure 3.3, shows pre-Lavery 

age tills as undifferentiated older deposits. More complete descriptions, thicknesses, 

and stratigraphic correlation of these deposits taken from LaFleur (1979) are given in 

Table 3.1. 

Information about Olean, Kent, and Defiance (Lavery-Hiram) aged glacial till over

lying Paleozoic bedrock has been revealed by wells drilled by the New York State 

Department of Public Works (NYSDPW), the New York State Geological Survey 

(NYSGS), and the U.S. Geological Survey (USGS) in the West Valley Area. A more 

recent till called the Valley Heads till is Identified in the Cattaraugus Creek Basin but 

has either been eroded or was never deposited in the vicinity of the West Valley site. 

Geologic logs and construction details of test holes that have been drilled at the com

mercial site as well as all others drilled within the WNYNSC and several geologic sec

tions measured along Buttermilk Creek are documented in Bergeron et al. (1985). 

Much of the upper 2 m of the geologic section, given in Table 3.1, consists of 

reworked till (units 1 through 4). Slumping and soil creep have altered much of the till 

along the steeper slopes. The alluvium within these units is predominantly derived 

through the reworking of the underlying till by Buttermilk Creek and tributaries. Both 

valley fill and fan deposits exist along the present stream channels; alluvium-covered 

terraces developed as the streams down-cut through the till. Unit 4 Is the only 

reworked till found In the area occupied by the trenches and is mappable only In the 

northern portion of the waste burial area.

3.4
Precipitation Precipitation

Evapotranspiration 

.I

3

Buttermilk 

. Creak 2

t 10

Not To Scale

EXPLANATION 

j SATURATED 

0 UNSATURATED 

S DIRECTION OF WATER MOVEMENT 

Length and number of arrows 

suggest relative magnitude. 

.... WATER TABLE 

-CONTACT BETWEEN UNITS 

STRATIGRAPHIC UNITS From table 4 

2,3,4,7 Gravel, coarse sand 9 Silt, clay 

S Fine sand, silt S. 10 Till

FIGURE 3.3. Idealized Cross-Section in Vicinity of Burial Site West of Buttermilk Creek 

Showing Inferred Distribution of Saturated and Unsaturated Material and 

General Directions of Ground-Water Flow 

Lavery Till (unit 5) is exposed across much of the surface in the vicinity of the 

burial site. The till is approximately 28 to 30 m in thickness (Prudic 1986). LaFleur 

(1979) divides the Lavery Till into three facies: 1) a silty clay till matrix containing 10% 

to 20% stones, 2) a similar till matrix with occasional wisps of light-gray quartz silt 

containing less than 5% stones, and 3) lenticular, stratified, discontinuous deposits of 

sand and clay containing recognizable portions of the first till facies. The till matrices 

of facies one and two are similar in composition; grain size and mineralogical ana

lyses indicate compositions on the order of 40% clay, 48% silt, and about 12% sand 

with the predominant mineralogies of the silt and clay being quartz, illite, and chlorite 

(Whitney 1977). The first facies accounts for about 70% of the Lavery Till. The second

3.5
TABLE 31 Stratigraphy of Quaternary Sediments in Central Buttermilk Creek Valley, 

Cattaraugus County, New York (after Prudic 1986) 

[Locations (Riceville Station, Bond Rd., etc.) are shown in Figure 2.21

(1) Slopes: typically 0.3 -1 m 

Elsewhere: 0 

(2) Valley bottoms: 0.6-2 m 

Elsewhere: 0 

(3) Terraces: 0.6-2mtypical 

Elsewhere: 0 

(4) 0-6.2m 

(5) 5 m (Riceville Station) 

22 m (Buttermilk Rd.) 

28 m (burial site) 

37 m (RR bridge over 

Buttermilk Cr.) 

40 m (mouth of Frank's 

Cr to Bond Rd.)

Llthol and Distnbution 

A layer of chiefly soft, plastic pebbly 

silt (reworked till) 0.3 to 1 m thick on 

all slopes, also local slump blocks 

several meters thick. 

Gravel, pebbles to large cobbles, 

and sand, moderately silty; In part 

overlaln by clayey silt with organic 

matter; Includes local masses of 

colluvium, chiefly reworked till. 

Ferruginous gravel and silt, under

lies terraces along Buttermilk Creek 

Gravel and sand, moderately silty; 

coarser and siltlier on alluvial fans 

formed where streams enter Butter

milk Valley at about 437 m altitude. 

Till, composed predominantly of 

clay and silt. Sixteen cores from 

drill holes near the burial site con

tained 50% clay, 27% silt, 13% 

sand, and 10% fine gravel on the 

average. LaFleur (1979) reports 

that 10-20% pebbles and cobbles 

is characteristic of most exposures. 

Typical non-sorted till Interfingers 

randomly with a similar tilt contain

Ing many tiny blebs and torn, 

deformed wisps of quartz silt 

Although these two sublacles form 

crudely horizontal layers, each is 

internally deformed. Distributed 

throughout (at least within bound

ary of the center) are randomly

Colluvlurn, formed by soil creep 

and local shallow-seated rational' 

slumps. 

Stream alluvium (channel point-bar 

gravel, and silt deposited by over

bank floods or in channel reaches 

ponded by mudslides) locally 

interbedded with mudslide 

deposits. 

Older alluvium of Buttermilk Creek 

Deposited by upland streams that 

flowed onto the freshly exposed 

till plain, then northwestward, 

before significant Incision by the 

present system. Alluvial-fan depo

sition near the valley wall probably 

continued after incision by 

Buttermilk Creek had begun. 

Absent on some higher areas of 

the till plain and where lingering 

ice blocks diverted flow. 

Deposited by a tongue of ice that 

readvanced as far south as West 

Valley through ponded water as 

much as125 m deep in Buttermilk 

Valley. During this readvance, 

which has been correlated by 

LaFleur (1979) with the Lavery 

readvance in Ohio, the glacier 

apparently floated free from the 

substrate periodically and allowed 

beds of silt and clay to accumulate 

Resettling of the ice to the lake 

floor, possibly in response to low

ering of lake water by subglacial 

*drainage or to more rapid ad

vance of the glacier, would explain 

renewed till deposition as well as

3.6
i 11111 IIII

(6) 0-2.5 m

TALE .31•I. (contd) 

Lfthogo, and DistrWbin 

oriented pods and Irregular lenses 

of stratified sand and gravel and 

rhythmic sit and clay. Excavations 

at the burial site and between Frank's 

Creek and Buttermilk Creek (Davis 

and Fakundiny 1978) consistently 

demonstrate that these stratified 

deposits are discontinuous, de

formed, and rotated or transported 

from their original point of deposi tion. Although these lenses con

stitute only about 7% of core foot

age logged (Prudic and Randall 

1979). two-thirds of the U.S. Geo

logical Survey test holes In 1962 

and 1975-78 near the burial site 

penetrated one or more lenses at 

depths of 3 to 11 m below natural 

grade. The tM Is present through

out Buttermilk Valley below about 

437 m altitude. 

Layered clay or clay-slit rhythmites; 

may contain pebbles or grade 

upward Into layered silty clay with 

scattered pebbles and then Into 

till. 

Gravel composed of pebbles and 

small cobbles, and sand; typically 

poorly sorted and moderately silty. Absent near the burial site and fuel

reprocessing plant (Figure 2.3); 

present consistently (but possibly discontinuous) near Buttermilk 

Creek. Where more than 3 m thick, 

Interbedded with pebbly coarse 

sand, fine sand, and slit.

3.7

(7) 0-8m

the structural deformation ob

served In both the till and 

lacustdne-till subfacles. The 

apparent abundance of fragments 

of water-laid deposits In the upper 

part of the till led LaFleur (1979) to 

suggest a minor Ice withdrawal 

and readvance across Ice-frontal 

deposits near the end of this 

glaciation. 

Deposited In proglaclal lake 

dammed by advancing Ice 

Missing In some places; not 

easily recognized unless well 

exposed. May be grouped with 

the overlying unit on basis of 

similar grain size and frequency 

with which the till grades Into or 

Incorporates lacustrine beds at 

various depths. 

At least three modes of deposition 

are plausible. Deposits east and 

southeast of the burial ground 

may have originated as deltas In a 

declining post-glacial lake, and (or) 

as an alluvial blanket spreading 

across the former lake floor. De

posits near the mouth of Franks 

Creek are thin, 15 m lower in alti

tude, and rest on unit 9 rather 

than unit 8; they might have 

formed along stream channel(s) 

during Interglacial Incision (Erie 

Interstade) (LaFleur 1979).
(8) 0-3m

Unt

Till, similar to unit 5, perhaps darker, 

rare Inclusions of grayish-red till; 

facies with tom, deformed wisps, 

slivers, or masses of coarse silt and In 

part with low pebble content predomi

nates south of Buttermilk Road.

3.8

Sand, very fine to fine, well-sorted 

and stratified, Interbedded with 

much silt that becomes predomni

nant with depth. Grades into 

underlying unit. Absent near 

mouth of Frank's Creek and 

generally along the west side of 

the valley. 

Interbedded coarse silt, fine silt, and 

day, generally in rhythmic layers up 

to several mm thick; some fine silt 

layers are as thick as 30 cm, but close 

inspection commonly reveals regular 

partings of coarse silt; olive-gray 

except clay layers commonly pale 

grayish-red. At most locations, some 

intervals are marked by widely scat

tered pebbles, disturbed bedding, 

and (or) thin layers, blebs, and Ir

regular masses of reddish-brown or 

greenish-gray pebbly sandy silt. 

This unit Is present everywhere 

from Riceville Station to mouth of 

Frank's Creek, except close to sides 

of valley.

Deltaic sediments deposited in a 

persistent glacial lake, probably by 

local streams, as indicated by 

distribution; northward flow Indi

cated in two exposures, and grada

tion into underlying lake-bottom 

deposits without an intervening till 

or truncation. 

Units 9 and 11 consist of bottom 

deposits in a glacial take character

ized by Icebergs and occasional 

readvances of a floating or occa

sionally grounded Ice tongue. 

The Kent age (LaFleur 1979); it 

Intervening till layer (unit 10) is 

inferred to be of appears to be a 

continuous unit but south of 

Buttermilk Road incorporates 

fragments of lacustrine sediment 

and may grade Into or interfinger 

with lacustrine sediment that con

tains detritus dropped from float

ing Ice. Furthermore, some 

borehole logs and geologic 

sections seem Inconsistent with 

this simple threefold division of 

units (Randall 1980), perhaps 

because floating ice tongues that 

dropped scattered pebbles and 

sandy clay blebs In one locality 

may have been grounded in 

another locality and deposited till 

In any case, the deposits below 

the top of unit 9 were formed 

during repeated Ice advance and 

retreat through proglacial lake 

water.

(9) 6-16(?)m

(1 0)3-10 m

TA L . (contd)
Ut Litholok= and Distrlxbtn 

(11) ? Predominantly clay, clayey sit, and 

sit in rhythmic layers, commonly 

disturbed much the same as unit 9; 

layered fine sand, coarse sand, and 

gravels locally present. 

(12)? Till, much more sandy and stony May be an upland facies of unit 10, 

than units 5 and 10; exposed and or an older till sheet; may inoorpo

reported in test holes near the side rate or grade to silty gravel. 

of the valley, atop or close to 

bedrock. 

till facies comprises much of the remaining 30% of the till, with the third facies 

encountered only at shallow depths (2 to 4 m) (LaFleur 1979). 

Fractures occur In the till, particularly In the upper few meters. Dana et al. (1 979f) 

describe the orientation and spacing of fractures along the wall of a research trench 

excavated near the burial site. Most fractures are oriented approximately vertically, 

and major fractures are several meters apart. Several small fractures may occur 

locally within a meter of each other, particularly within the upper 2 m of till. Fractures 

are not evident beyond a depth of about 5 m In the till. 

Approximately 80% to 90% of the till is derived from the local bedrock, which is 

composed of shales and siltstones of sodium-magnesium-silicate composition. How

ever, the remaining 10% to 20% of the till contains allocthonous crystalline rocks from 

the Canadian Shield and sandstones and carbonates from northern New York. The 

small amount of carbonate is significant because the resulting ground-water chemistry 

is predominantly a calcium-carbonate regime rather than the sodium-chloride regime 

that would otherwise occur. 

Underlying the Lavery Till is a sequence of lacustrine and deltaic deposits. 

These are described as units 6 through 9 In Table 3.1. Underlying these deposits are 

tills In units 10 and 12; the intervening unit 10 is a lacustrine deposit similar to unit 9. 

Prudic (1986) Indicates that unit 10 Is Kent-aged till based on work of LaFleur (1979). 

The underlying till (unit 12) Is similar In composition to unit 10 and may also be Kent in 

age.

3.9

TAL .. (contd)
3.2 GROUND-WATER HYDROLOGY

Information on ground-water conditions of the West Valley site is available from a 

number of sources. Prudic and Randall (1977) conducted the most recent and signif

icant ground-water investigations at the site. Their work Included extensive test drilling 

and the Installation of numerous plezometers to determine ground-water levels and 

analyze water samples for the presence of radionuclides. Other hydrogeologic 

evaluations on the trenches, trench covers, and surrounding till by the USGS are sum

marized In Prudic (1979a, 1979b, 1980, 1982). Prudic (1986) is a summary document 

that incorporates the results of all previous investigations at the site. Bergeron et al. 

(1987) provides descriptions of geohydrologic conditions at the WNYNSC site that 

includes the commercial waste site. 

3.2.1 Major Hydrogeologic Units 

Major hydrogeologic units in the vicinity of the waste burial trenches are the 

Lavery Till, the underlying lacustrine units, and the basal till. The Lavery Till is satu

rated In the vicinity of the waste burial site and Is sufficiently impermeable to cause 

water infiltrating through trench covers to build up in the trenches. Prudic (1982) 

conducted extensive hydraulic tests of the till, employing both field and laboratory 

methods, that Indicated that the till Is approximately Isotropic; average hydraulic con

ductivitles ranged between 2 x 10-08 and 6 x 10-08 cm/s based on slug tests conducted 

in the field. Laboratory tests provided a wider range of values but generally were in 

agreement with the field tests. 

The lacustrine sediments that underlie the Lavery Till are relatively coarse 

grained compared to the till. These sediments grade from fairly sandy near the contact 

with the Lavery till to silts and varied clays at their base. Lateral drainage In this unit 

coupled with a small water flux draining from the till tends to produce partially satu

rated conditions in the upper portions of the lacustrine sediments. No direct hydraulic 

testing of the lacustrine sediments has been done. The compositional difference 

between these sediments and the till Indicates that the hydraulic conductivity Is prob

ably several orders of magnitude higher in the lacustrine sediments. 

The basal tills and shale bedrock that underlie the lacustrine sediments are 

primarily finer-grained material with hydraulic conductivities likely to be similar to the 

Lavery till. The similarities of unit 10 (Table 3.1) to the Lavery till support this. The 

pressure exerted from overlying layers may significantly compact the till, producing 

even lower hydraulic conductivity. The underlying shale is probably about the same 

order of magnitude of hydraulic conductivity as the till. Although no direct hydraulic 

tests have been conducted at the site, hydraulic conductivity of shale commonly 

ranges between I x 10-7 and 1 x 10-11 cm/s (Freeze and Cherry 1979), which com

pares favorably with measured values for the till.

3.10
3.2.2 Direction and Rate of Ground-Water Movement 

Prudic and Randall (1977, 1979), Prudic (1986), and Bergeron et al. (1987) 

indicate that much of the precipitation that falls on the site may be accounted for by evapotranspiration and runoff. The low hydraulic conductivity of the till allows very little deep percolation. Water tends to pond on the surface and run off. Steep slopes exist over much of the till surface causing precipitation to run off those areas before 

significant infiltration can occur. 

A distribution of heads measured In piezometers at the site, Illustrated in Fig

ure 3.4, shows that Infiltrating water moves In two primary directions. Although most of 

the precipitation that falls on the site either evapotranspires or runs off, some water in

filtrates Into the upper few meters of weathered, oxidized till and moves laterally

tSil 

.5 

g 

I-. 

'Si 

'a 

a4

J

EAST

30 60 90 120 150 180 

DISTANCE FROM WEST EDGE OF BURIAL SITE. IN METERS

210

Backfill 

Weathered till 

r Tilt with oxidized fractures 

Unw~eahered till

EXPLANATION 

Water level In trench 

... $Z.. Assumed water table 

-414- Line of equlpoten flat head 

Interval 2 meters Dashed where till 

may be unsaturated

I Test hole

Vertical Sections Through Trenches Showing Head Distribution During February 1976: Section C-C' Through North Trenches (after Prudic 

1986)

3.11

FIUE 34.
toward nearby streams. A small fraction of this water will Infiltrate the underlying 

unweathered till and continue moving downward under a predominantly vertical 

hydraulic gradient. 

3.2.2.1 Shallow Pathb 

Within the shallow till, physical processes act on the till to Increase its overall 

hydraulic character. These processes Include wetting and desiccation, freezing as 

well as biological activity such as plant rooting and animal burrowing. These proc

esses combine to create secondary features that cause the majority of water entering 

the upper till to flow laterally rather than Infiltrate Into the unweathered till at depth. 

Prudic (1986) notes an occasion where water discharged from a mole run during a 

period of high precipitation, indicating the reduced ability of the unweathered till to 

accept Infiltration. 

In modeling of the site, Prudic (1986) estimated that the upper weathered and 

fractured till was about 5 to 10 times more permeable than the unweathered till. How

ever, other evidence at a nearby disposal area suggests that hydraulic properties of 

this unit could b6 higher. Bergeron et al. (1987) reported the lateral migration of kero

sene from shallow disposal pits within the shallow till west of the site. In 1983, kero

sene disposed In one of the pits In 1970 was detected In a monitoring well about 18 m 

away. This evidence is an Indication that lateral migration rates may approach a few 

meters per year in the upper till layer, although these rates have yet to be coraborated 

at the commercial waste site. 

3.2.2.2 Dee2 Pathway 

A small amount of water Is able to migrate downward from the weathered till zone 

into the unweathered till. Water levels from profiles of the north and south trenches at 

the West Valley site are shown in Figures 3.4 and 3.5. The distribution of hydraulic 

head indicate that ground water in the vicinity of the trenches moves predominantly 

downward; hydraulic head gradients locally may approach unity. 

Test drilling and outcrop observation have indicated that the till contains 

numerous lenses and pods of stratified sands, gravels, and silts that vary in size and 

shape as well in their degree of saturation. The behavior of water movement in and 

around sand and silt lenses and pods found within the till matdx and the effect of these 

features on the overall flow system is not well understood. Characterization efforts 

have suggested that they represent disconnected units which do not have much effect 

in short circuiting or enhancing hodzontal or vertical water movement. Although the 

distribution and continuity or connectivity of these units has not been completely

3.12
E425 ESTAST 

D 

~420 

0i0 

4 1. 13 12 I 1 0 9 8 9 

CO 415 

I 

- ----- ---- -- - - -_ - - " 2 

S410 

•40808-"-J -.. 

i- 405 "•Piezometer .1tIv Vertical exaggeration-x 5 

-< 0 30 60 90 120 150 180 210 240 270 300 

DISTANCE FROM HOLE K, IN METERS 

EXPLANATION 

Backfill Water level in trench 

Weathered till ... R.,. Assumed water table 

with oxidized fractures - 414- Line of equipotentlal head 

Interval 2 meters Dashed where till 

EJ Unweathered till M may be unsaturated 

Test hole 

EIGU.E_3.5. Vertical Sections Through Trenches Showing Head Distribution During February 1976: Section D-D' Through South Trenches (after Prudic 

1986) 

verified, the clay and silt-rich till matrix Is accepted as the unit which dominates the 

flow system, and the impact of these lenses and pods on the water movement is 

minimal. 

Prudic and Randall (1979) Indicate the possibility that portions of the till are 

slightly to moderately unsaturated. Test holes L and 0 west of trench 14 contain 

plezometers that have never Intercepted measurable amounts of water. However, 

neutron moisture measurements do not differ significantly from those for proven saturated till, and the lack of water in the plezometers may indicate only that the till is 

slightly lower in hydraulic conductivity. 

The lacustrine units that underlie the till serve as a drain to the till with water 

collecting In the lower portion of the lacustrine units (Prudic 1986). Once in the 

lacustrine unit, water moves laterally very slowly in a northeasterly direction before 

discharging In outcrop areas along the Buttermilk Creek Valley (Figure 3.6). The finer

grained till is unable to transmit as much water as the underlying lacustrine units are 

capable of receiving; consequently, the water supplied by the till is insufficient to 

maintain saturated conditions in the upper portion of the lacustrine units. Ground

3.13
K '---= •,r 

Bass from U. S. Geological Survey 

Ashford Hollow 1:24,000. 1964

0 300 . 600 METERS 

o 1000 2000 FEET I 

EXPLANATION V 

e TEST HOLE - Number is altitude of water level 379 In plezometer, In meters above sea level 

FIGURE 3.6. Map Showing Lateral Direction of Ground-Water Flow in Lacustrine 

Sequence (after Prudic 1986)

3.14
water from the lacustrine units discharges to seeps along Buttermilk Creek, but 

discharge of these seeps Is small, and no significant springs are apparent (Prudic and 

Randall 1979). 

3.3 SUBSURFACE RADIONUCLIDE MIGRATION 

State and federal agencies have carefully monitored the performance of the 

trenches at the West Valley burial site throughout its operational and post-closure history. Radionuclides mobilized by Infiltrating water have migrated several meters 

both laterally and vertically from the trenches into the surrounding till. Tritium in the 

form of tritiated water has migrated the farthest. Favorable soil properties In the till 

have served to limit the migration of radionuclides. The most significant performance problems at the West Valley site have been related to the infiltration of precipitation 

through trench covers, which In turn caused a buildup of leachate In many of the 

trenches. Site closure resulted when overflowing leachate was detected in trench 5 at 

the north end of the burial ground. 

3.3.1 Infiltration Through Trench Covers 

Standing water in the trenches resulting from Infiltration through the trench covers 

Is the most serious performance problem at the West Valley site. A number of proc

esses have contributed to this problem, which has reduced the effectiveness of the site 

trench covers In Isolating wastes from precipitation. 

One of the processes that has reduced trench cap effectiveness has been the 

compaction of trench wastes over time, which has led to collapses within the trench 

cover material. This compaction process has resulted in the creation of both smaller 

scale cracks and larger scale area of subsidence In the trench covers. Large-scale compaction of the wastes has probably contributed to the development of cracks cor

responding to the edges of the trenches. Both Dana et al. (1978) and Prudic and 

Randall (1979) note that cracks commonly are parallel to the sides and ends of the 

trenches. Other cracks In trench covers have resulted from repeated wetting and 

desiccation of the fine-grained till that makes up the cover material. These types of 

cracks result from shrinkage of the till as It looses water to evaporation. Prudic (1986) 

measured cracks In the trench covers as deep as 60 cm using a steel measuring tape; 

cracks of 30 cm In depth were very common throughout the trench caps. Cracks that 

penetrate the entire thickness of the trench covers may result from the Intersection of 

subsidence cracks developing from below with desiccation cracks developing at the 

surface. 

Prudic (1986) tested the ability of cracks In several of the trenches to transmit 

water. He siphoned 2000 L of water Into two sets of cracks at the south end of 

trenches 4 and 5 with no overflow observed. Similar observations resulted from the

3.15
application of 110 L to a crack in the north end of trench 4. Other cracks required very 

little water before overflow was observed, however. Consequently, Prudic (1986) 

concluded that some of the cracks fully penetrated the trench caps. 

Prudlc (1986) indicated that the water-level rises in some of the trenches corre

late with precipitation at the site (Figure 3.7). To circumvent Infiltration problems with 

the trench covers, most of the covers have been regraded. Table 3.2 lists the approxi

mate completion dates of each trench followed by the approximate date that regrading 

occurred. Regrading was accomplished during three phases: trenches I through 5 

were regraded in August 1969, trenches 8 through 11 were regraded in July 1973, 

and trenches 12 through 14 were regraded in June 1975. All north trenches were also 

regraded in 1975. The effectiveness of regrading the north trenches In reducing the 

rate of trench filling Is Illustrated in Figure 3.8. Consequently, the high accumulation 

rates in the trenches appear to be directly related to the condition of the trench caps. 

Because forces such as subsidence, desiccation, and erosion will continue to act on 

the trench covers, periodic regrading will likely be necessary to maintain the integrity 

of the trench covers. 

The water-level rises may also be the result of ground water infiltrating through 

the sides or bottom of a trench, but the low hydraulic conductivity of the till and the pre

dominantly downward hydraulic gradient Indicate that seepage from the till probably 

would not be nearly sufficient to produce the water-level rises observed in the 

trenches. 

The high precipitation at West Valley coupled with the low hydraulic conductivity 

of the till tends to produce severe erosion in the vicinity of the site. Boothroyd et al. 

(1979, 1982) investigated the potential that erosion of the steep slopes adjacent to the 

trenches could compromise integrity of the trench covers and enhance contaminant 

migration. Their analyses of the sediment load In Buttermilk Creek Indicate that 

erosion Is actively occurring at the site. Consequently, erosion Is a long-term manage

ment concern at the site, although Nicholson and Hurt (1985) conclude that given the 

depth of burial of the waste, sheet-wash erosion is not likely to disturb the waste for 

centuries. 

3.3.2 Waste Leachate Characteristics 

Sophisticated and in-depth studies of trench waters conducted by Brookhaven 

National Laboratory (Weiss and Columbo, 1979) and the NYSDOH Radiological 

Sciences Laboratory have shown that leachate present In the trenches are complex 

mixtures of inorganic and organic compounds because of the presence of various 

natural organic materials, organic solvents and pesticides, inorganic wastes, and 

radionuclides. Prudic (1986) notes that the nonradioactive constituents are similar to 

those described for several municipal landfills in Illinois and Indiana. Prudic (1986)

3.16
A

.j 

W 4196 > 

IJl 050 

Corrected hydrograph, us w Uj ~ trench 5B -045~ 

005" 

4195 >. 2 -J Uj > 4 1 8 . * , 05 

0 040- >--.- Rrf volum 2 wt Days In January.March when 

Recor of volume~ i. L 0 maximum temperature 16 omalunctionedl - 0 35l' v 418w4 04 1 nCorrected hydrograph, / No record 04 : 

SI. 1-4194 03 0u -3-o -, > trech J 

2 Precipitation cc < " 

"" 4 25193 w 4183 0.3 " 3 419 us C -> W 

> I

91 70 20 W " 

-J E• UA Uj w os -015J 2 4182 Preciitatin 0? U 

l 4192 M :.j U. oloU' FJF": 

J'-. 4181 01..i 0 05XD 419 1 .,. -E 5LI¢: 

2 < / r F rnkllnville records -I, I I *" O0* 4180 Preipitin estimae from ! , 

21 31 15 30 15 31 15 31 IS 4 00 

1 15 31 15 29 15 31 15 30 15 31 15 30 15 31 

MAY JUNE JULY AUG SEPT 

JAN FEE MAR APR MAY JUNE JULY 

1975 

1976 

EFUE3.7 Water Level Changes In Trench 5 in Relation to Precipitation from May Through September 1975 and from January Through July 1976 

also Indicates that nonradioactive constituents from the West Valley leachate equal or 

exceed those measured at Maxey Flats, Kentucky, and Sheffield, Illinois. 

Tritium, 9

OSr, and 14C are the radionuclides that are present in the largest quan tities in the trench waters sampled. A compilation from several sources listing the radionuclides found in a series of water samples taken from the trenches is presented In Table 3.3.

3.17
TABLE3.2. Dates of Trench Completion and Regrading (after Prudic 1986) 

Date Completed and Date Cover was Regraded 

Trench Totally Covered to Level of 1975-78 

1 August 1969 

2 ? August 1969 

3 1966 August 1969 

4 1967 August 1969 

5 1969 August 1969 

8 October,1970 July 1973 

9 June 1971 July 1973 

10 May 1972 July 1973 

11 January 1973 July 1973 

12 October 1973 June 1975 

13 June 1974 June 1975 

14 May 1975 June 1975 

3.3.3 Extent of Measured Migration 

Prudic and Randall (1977, 1979) and Prudic (1978, 1979a, 1979b, 1981, 1982, 

1986) have conducted extensive Investigations into the extent of radionuclide move

ment through the subsurface about the trenches. Dana et al. (1978, 1979a, 1979b, 

1980) investigated the containment effectiveness of the site through the analysis of 

migration pathways. Monitoring wells around the waste burial trenches Indicate that 

radionuclides have migrated from the trenches into the surrounding till; radionuclides 

do not appear to have penetrated more than 3 m either laterally or vertically into the till. 

Following Is a discussion of the measured migration of specific radionuclides including 

Tritium, 9OSr, 140, and a few others. 

3.3.3.1 Tritium 

Twenty-nine monitoring wells were drilled adjacent to the trenches during the 

period 1973 to 1975 (Prudic 1986). The holes were located between 2.5 and 5.0 m 

from the edges of the trenches (holes A-G, I-N, and P-R; see Figure 2.5). Core 

samples were obtained for each hole using the procedure described in Prudic 

(1979a). The samples Indicate generally decreasing radionuclide concentration with 

depth. Profiles of tritium from selected wells are shown In Figure 3.9. Common to all 

of the profiles Is a relatively high concentration of radionuclides near the surface that 

decreases with depth. The rate of vertical migration within the till appears to exceed 

the rate of lateral migration, which is in agreement with the predominantly vertical 

gradients through the till.

3.18
A

421 

Range in altitude of 

-J 420 lop of undisturbed 

> etill west of trench I 

.j flange In altitude of 

top o of undisturbed 

3 &W 419 il east oftrench of 27 Addition oil 13 mo~tors cover >/ material, tece . 

0 

Cover reshaped into individual More cOver, S418 mounds over trenches 1-4 / trenches 1-5 I 

M previously, one large I 

umbrella mound) - . - I -I -- • 

S416 

. TreTrench3 

415 Trench5 5 . _ 

I - - " it,1 ,,-- ~Trench 2 .. 

414 -, ,- " • , 

"'w-Water pumped from * trench 2 before 1966= 

413 

I

0.6 

:' "; i • i0.2,. 049 

Ut 

166 1967 1968 1969 11970 1971 1972 19'73 119'74 1 9e'75 i 197 1977 19781 197.9 , 

FIGURE•3.6,. Water Level Trends In the North Trenches Showing the Effects of 

Regrading the Trench Caps

3.1 0
TABU3,1.Radfionuclide Content of Water in Trenches

TMO&d Numbar and Daew of Sample CoIeiamsm 

1 2 3 4 5 8 9 10 It 12 13 14 

Rndi~nellde .JwJý 97 Nvebe l Ig QjbL QflAbr17 ittg 99QgrL DDdL= ~J AUSaagj AMggg= -JAUnLM- 4DJIML ln luang IM

1.42-06* 11 8L92-7*11 

1.75402* 1 4.72-44*

3SAM4* 1 2.3*3I 

SAM-0* 10 1.5204410 

3.42-0 * 5 7.4M5* 5 

9.82-09*40 1247* 10 

1.5548W* 32 8.15-0* 12 

NIX NAD 

1.3247*31 4.3247* 8 

1.5246*20 NAD 

9.9W4 * 6 3-99-M* 10 

9.354 * 65 2.72407*k57 

6.454* 49 1.7246* 3 

1.12-05* 1 3.3"*1I

1.311-04*1I 2.72.07*15 1.339-03* 3 5.221-0* 3 1.811-0* 11 

4.70-04 * 1 1.211,04 * 3 1.426w4 * 4 - 2.3543* 1 

3.7 *1 4.6411* 1 4.27 *3 2.77 13 3A6-01 *1 

1.48-04 *10 3.8M 0* 10 6.0044* 5 1.615-44*3 

S.2.044* 3 L4205 * 5 - - 3R6044* 5 

1.92- * 5 2.29-055 3.322-5* 5 1.449544* 5 5.80-46 *5 

1.62.4*10 2AH-04410 2.-044* 15 3.148 * 19 

3.A2-07 *20 4.0L0 UR047 * 35 5.024 * 37 

2.09-07*57 N.D. N.D. 2.1548*31 N.D. 

2.79V07*11 3.924* 9 2.13245 *5 L 471146*34 1.1246*24 

3.98-07 *53 3.111-7 *62 M.D. X.D. 

2.02.07 * 18 9.72.07* 6 3.15407 *45 (L72-07 * 19 6.224 * 6 

4.5H-07 *23 LOE048* 52 --

9.41147 *6 9.647* 5 2.1206 * 14 3246 * 9 132.05 *6 

1IA2-04 * I 2.6-0 *1I 5.460545 * 4 4.23244 * 3 9.00-04 * I

3.100*3 

4.9"-1*1I

M.D. 

554 * 25

IJ42.0 * 1 

4247 *32

2.3546*k10 1.454 * 14 

62M7* 49 3.35-5* 2 

4.91146 * 5 2.42-W4 * I

(a) Dew fanm fdlowwsq aaam: Truac 1. DavuwA Fala Lakudy (1978, usbl IV.6) utueacb 2-.9 Wesw wan Coambo (1980. table 5.30X. Imanch 10 wAd 11. Do& et &L (1950 table 5U siendia 12.14. 

Wet"s awl Calmba (1980 table 4.10) 

(b) Iaespomawdinmehculeiafwa&er OMN Same addkmaal uwlum may be preaensiimad"an (014) and Ww ownce nwnplu waaime mckode& 

(a) Ana~jaeaby sheYSDOILRadlelosacaScoaenULabwaty.fmcin samples eolecdnSepWAmet 1977 sacepiixemche 10 and 11, wl aeda tepaad =nDama Metl (1950,tableUs)

CO,

iabais 

Tniimaa0 

14C OneqMo 

14C Oowwm 

2341% 

=.%wp

1.-626* 25 

7.654O6k * 

3.1I2-44* 3 

4.5246 * 9 

2.3246* 17 

13249 *52 

N.D. 

Ma * 46* 

N.D. 

NIA 

M.A 

NM.. 

N.D.

1.W4 * 10 

2.492-02 * 5 

3.4250 * 10 

3324 * 24 

NA 

4.75&07 * 35 

33H-.32* 12 

M.D. 

2.7E40 * I

7.3247*314 

2.9M4 * 1 

4.85401 * 1 

8.52-44* 10 

7.6248 * 14 

LIM20* 12 

M.D. 

1.5247 *40 

4.524 * 72 

7.024 * 1 

MAX 

M.D. 

1.-023*I
A. North of north trenches.

422 LITHOLOGY 

c .L. Trench 4. March 175I 

420 C C2 C2 .Trench 3. March 1975 ! Wat'r 

a .r Trench 3.4. October ln v 1975 

-J I Cover 

SOxidizedtill. - - oend a till with oxidized fractures 

S415 EXPLA--NATOT-r- Trench 2. March and 415 eT whIr X th ONr -October 1975. water levelo 

Lu~~~ ~~~~~~~Ts holesthoesybl C2 Sny rve lttd nor Trenches 2.3.4 011. bottom 

40I I 

BL West side of trench 5 LITHOLOGY 

422 -' 'u 

"0 

t-mhGrave sybo plotte att 

415 - -J 

0 

S40Test holes EXPLANATION jtill anbundant 0 

>• 41 litwe onlotiuu 

-"' • ~F I'TISilt and very fine sandbed-s 

S95-percent gonfidence ilimits for tritium 

({ •Tritium acltiviy less tha detectable: 

test-hole symbol plotted at helf of maximum 

405 confidence limit 

107 10-6 10to0 4 10.3 10.2 10"1 4 X 10"1 

TRITIUM CONCENTRATION, 'IN MICROCURIES PER MiLLiLITER 

EI.Jfl.BE_3. Changes in Tritium Concentrations with Depth in Test Holes Near the 

Burial Site (after Prudic 1986)

3.21
C. East side of trench 2.

us > 

A tu 

Cos LITHOLOI 

C, 

415 

Ca 

I

Test holes EXPLANATION 

2 O I Silt and very line sand beds 

d114r13 Till 03 41 A2 

I- V 

Sactivity. 95-percent where confidence limits for trtium Iarfler than test hole symbol 

Tritium activity less than detectable: test hole symbol plotted at hall of 

maximum confidence limit 

40I I 

0. Vicinity of south to 

423N' T 

.j 

4C 

Ca 

us 'p' 

0 LITHOLO 

4C 

VII 

1,- 415 551EXPLANATION 

Tow holes Sit 

a L Sandy gravel V M 0 N J•::•Sand D• A P "- Till 

- 95 percent confidence limits for tritium 

activily, where larger Ihan test hole symi 

4 Tritium activity less than detectable: 1 

maiu test hole symbol cniece plotted at hall of lImill 

4061 

10-7 106 10-5 10 4 I1 

TRITIUM CONCENTRATIOIN. IN MICRC 

FIGU IE-3 . (contd)

)CURIES PER MILLILITER

3.22
E Otitlying test holes.

w J 

> G 

-j 

> 4151 

0 V 

z 

4 1Test 

hole EXPLANATION 

£G W) Sit 

/j *l Fine Sand /"r-lTill R' 

,--,95.per•-V confldence limits for tritium 

ativty where lamer then test-hole symbol 

,,-.Trlitum activity less than detectable: 405 test-hole symbol plotted at half of maximum 

confidence limit 

403 Al l l I 

•. 10-8 10-7 10-6 10-5 ' 10-4 10-3 10-2 

TRITIUM CONCENTRATION, IN MICROCURIES PER MILLILITER 

FIGURE .1 (contd) 

Prudic (1986) Indicates that the high concentrations evident near the surface 

(Figure 3.9) are most likely not the result of post-emplacement waste migration in ground water. He states that the most reasonable explanation appears to be " ...some 

combination of surface processes such as 1) spills during emplacement of refuse or 

during removal of excess water from trenches, 2) redistribution of contaminated water 

by excavation equipment that entered the trenches, or 3) fallout from the stack at the 

nearby fuel-reprocessing plant." 

Investigations at the site did not find the same level of shallow lateral migration for 

the trenches as was detected with the kerosene migration at the nearby FDA. Analy ses of core samples reveal only two cases where tritium has migrated more than 2.5 m 

In the lateral direction. This occurred In holes D and E located just west of Trench 5 

(see Figure 2.5). Highest subsurface concentrations of about 1 x 10-03 j±Ci/mL are 

found In hole D at an elevation of about 412 m corresponding to the bottom of trench 5. 

A less pronounced peak of 1 x 10-05 gCi/mL is evident in hole E at a similar elevation. 

Water levels may have risen sufficiently to produce head gradients able to move water 

laterally through silty till present near the bottom of the trench.

3.23
A similar peak between 1 x 10-6 and 1 x 10-4 IiCi/mL was observed at an eleva

tion of about 409 m In test hole B located about 12 m north of trench 2. Subsequent 

holes drilled closer to the trench do not reveal a similar peak at the same depth (Prudic 

1986); consequently, the observed concentrations are probably not the result of lateral 

migration of tritium at depth. Other explanations for the reported concentration Include 

improper handling of the sample and migration of surface spills through a collapsed 

borehole several meters away. 

The absence of any large-scale (less than 3 to 5 m) lateral movement of con

taminants at the site Is reasonable based on the predominantly downward gradient at 

the site; wells drilled through trenches 4, 5, and 8 (Table 3.4) In 1977 indicate this 

downward movement. Figure 3.9 shows tritium concentrations below the tested 

trenches. Concentrations generally reach undetectable levels at depths of about 3 m 

below the trench floor for the 7 to 10 years since sampling occurred. Prudic (1986) 

indicated tritium detection at a depth of 3 m occurred In silty till but only 2 m In regular 

till. However, 3 m is probably a reasonable number for both cases because the trench 

floor elevation is inexactly known. 

3.3.3.2 Other Radlonuclides 

The holes were tested forla full suite of radionuclides In addition to tritium. Values 

are reported as g.Ci/g in Table 3.3. Other radionuclides contained within the trenches 

appear to be less mobile than tritium. Unlike tritium, most of these species are 

charged ions which will be adsorbed, to varying degrees, by the till matrix. Therefore, 

these radionuclides would be expected to migrate shorter distances than tritium. 

Chemical analyses of trench water (Table 3.3) indicated that 9OSr and 14C were 

the most abundant radionuclides after tritium. The greatest concentrations of 9OSr are 

found in Trench 4. Samples 0.7 m below trench 4 contained detectable levels of 9oSr. 

A zone of silty-till may have provided a high hydraulic conductivity conduit for move

ment of the 9OSr. Strontium-90 only penetrated 0.14 m into till beneath trench 5. 

Carbon-14 appears to have migrated about 1.0 m beneath trench 5. However, the 14C 

was difficult to measure because of the large number of carbon isotopes present and 

because the sampling procedure was intended primarily to detect tritium. 

Cesium, cobalt, and plutonium also were found in detectable quantities beneath 

the trenches. The concentrations are shown in Table 3.4. Cesium-137 was detected 

at greater depths than either 1

34Cs or 5oCo (Prudlc 1986). Cesium-134 was detected 

at 0.5 m versus 0.48 m for 137Cs. This may reflect a 134Cs:137Cs ratio of about 1:1000 

in trench 5. Prudic (1986) does not report the depth for SOCo. Plutonium-238 was 

detected In silty till about 1.06 m beneath the floor of trench 8 In hole 8.2A but only 

0.8 m deep in hole 8-1C.

3.24
iARLiE14. Concentration of Selected Radionuclides Beneath Trenches 4,5, and 8. November - December 1977 (after Data et al. 1979, 1980) 

nomibensfollowing ±arepercnwe M-samples nut analed for pareular radionudId 

Depths Isteval Depth of sample Matmial 

Below Midpownt Below m Each~ 

LAMAdSuffacel TrenIcho Cure~b Win (a0) "~~)5ST Z3ft 2st.240 dom 134CS lY7s Segm"ent 

9.22 0 - .5.45 -- 1.67E-04 14 88-06125 4.511-0414 WesirMdCmkdboud 

9.22-9.24 1 2.02M 153 -- 7I807 * 22 38-07*37 1.52M-015 TIM 

92.4930 5 -1.17E-05* 6 - -14807 *33 3.913-07*34 2.613-07*112 Tiln 9.30-9.37 12 -3.8813-06 1 4 - '8088-08 4.68-0* 17 7Ml 

9M5-9.58 34*7 - 6H-8 -08 08 48-08 1.08-75 so Sill/Clay 9.5"-.63 39* 7 - 2.5-07 * 31 -d- - 8.0 49-09 41308 t 63 Sib/clay 9.63-9.68 44* - 3.28-0 1 23 - <5 8-O 48-0 2S8-07 * 24 Sf/caw" 

9.6"..72 4 * 7 - 1.1313-06±10 - -13-07 *60 .c98.0 1.75&- * 10 Sift/dy 

8,nc OUea hole 9-2A 

9.96-9.99". 76*7 - - -- 1.266-05*7 - -d8-07 111 

9.99-10.02 79t±7 .88-0 -c1.18-O -IS - 1.8-7 -09 4C8-01 IlM 

10.02-10.0 82*±7 3.48-M7 * 2 9 E.9-08 4&8"-0 -809 <1.6E-07 <48-09 c78-M8 71 

10.0910.18 92*7 7E-07*183 <S8-0 - - -- 7Mil 

10.27-10.30 106t7 <1.68-07 <68-0 218-07* 13 2.011-08*138 <8M0 <48-08 8-08 SIf/lway 1031-10.43 115*7 <58.0 Id"8- - - 7Mil 

Irnch IMes hole 84IC 

10.09-10.11 80 *30 1.381-079 1.5-07 IAE-07 * 16 <8-0 41.5M-0 413-07 47B-08 7M! 

10311-10.14 833*30 4M-O 'cI.2-07 3.08-08*40 -c18-09 <1SE-07 4l.113-08 <51-M8 7Ml 

10.19-10.29 94* 30 <4.S-MM 4.411-M 1.7-0 * 88 -- Tl 780M 

10.29-10.38 104 *30 - -1.5-0 * 91 <5M0 - Ill 

10.38-10.40 109*3so .9R-07* 31 -I- 1.0* 46 1BE-09 c138-07 <4H.09 -78-08 7il 

10.5-10.66 130 *30 <5W0 -- 7M Tl 

(a) Hiorerassociaed with each vau above de" Ten lao praem Gnu".i standur n, o htwl.a 5 ofdneitraLWe tadr nsecessml oniiu 

backgvun come w~,esa vw osdrdblwdso ht n roasedaslestthan the atandu'd esrr. (b) Uncevialny as to the exact depth at which the bnchd floor was penetrated by.mos holes (Pmuwc 1979) remit fnw Micwiiy nsmpl4e depfths Inicte by *wulue FNrhole 4-4A. 

dedts of surnplesm in centanetess below hortwmnal pmojeoston of the brench floorpenetrte byneatby ole 4-3A- unceitafidy in trendw-floor depth eamuobe estimated fran drilling data 

for hoe 4-3A (Pmud& 1979) but tritrn profiles iA, Psed ms fth report suggest the depths gwen ame mainitan Values. 

Wc Moddes boshmoigmu mid oismo inbm 

SAboveeUfit~ huenclifloor. 

(d) Sameprlgdevic lowered throgh trench water befrebot dm'en inao brench floor to collect these samles 

(a) Com smple with impression of retractable pons.
4.0 HYDROLOGIC AND RADIONUCLIDE TRANSPORT ANALYSIS 

OF THE GROUNDWATER PATHWAY 

Hydrologic flow and transport models were used in the ground-water pathway analysis to simulate subsurface release of radionuclides and evaluate the perform

ance the West Valley site. Previous flow and transport modeling by-Prudic (1986) provided the primary basis for much of the work done In this assessment. Following is 

a brief description of the details of the previous model results relevant to this analysis. This background Information Is followed by a summary of the hydrogeologic perform

ance assessment analysis and results. 

4.1 PREVIOUS WORK 

The USGS conducted most of the significant ground-water flow and transport modeling at the site. The work focused primarily on the development of two

dimensional ground-water flow models along transects of the north and south trenches 

followed by simplified one-dimensional transport modeling of selected radionuclides. 

4.1.1 Ground-Water Flow Modeling 

Prudic (1981) completed the most comprehensive modeling study of ground water flow and transport at the West Valley site. He simulated ground-water flow at the 

West Valley site for both the north and south trenches by incorporating hydrogeologic 

data from the site with a two-dimensional finite-element hydrologic flow and transport code described by Reeves and Duguid (1975) and Duguld and Reeves (1976). The 

cross-section lines C-C' and D-D' are perpendicular to the trenches as shown in Fig

ure 2.5. 

Prudic (1986) Indicated that the code was particularly suited for evaluation of the 

West Valley Site because simulations could incorporate 1) cross-sectional modeling of 

saturated and unsaturated flow with a changing water table, 2) ground-water dis

charge along the, land surface, and 3) the existence of a solute transport code that 

could be coupled to the calculated flow distribution. The choice of a two-dimensional 

model for the trenches Implies several assumptions. The cross-section through each 

set of trenches Is assumed to be representative of conditions for any cross-section 

through that set of trenches. The cross sections at West Valley are probably reason

able approximations of conditions along the trenches, but do not Include the special burial areas contained In trenches 6 and 7. Ground-water flow Is also assumed to be 

effectively two-dimensional with no flow through the plane of the section. The predomi nantly downward gradient at the site supports this assumption. 

The modeled section for the north trenches with discretization and boundary con

ditions Is shown In Figure 4.1. No-flow boundaries were used at either end of the

4.1
430 WEST EAST

C Distribution of simulated infiltration rate relative to horizontal hydraulic conductivity of unweathered till Ce 

i-I 54-1-.15--4--0 8-4 110 5-l-. 21- i ----- 0----1 5-4 

Trenches: Fixed head for nodes below 

us trench water level; seepage 

Land surface D nodes above water level Constant Infiltration rat 

us I4 

420 .lo 991 99 9C ý111 IIQP 

5 44 3 "2 to10 

o ^1 I : "K- 

> 00 

00 0 o 0 oooooo 0 0 0 0 0o 

00 0 00 0 0 a 0 0 0 CI 0 ~ 0 

I 410 K-1 0000 o 00 

Lai 00 0 0 0 00 

Node associated with piezometer K-1 

00 0 06 0 00 000 0 0 000 0 0 a 0 :0 0 

0 oe 0 

M 400 Za 9 o * *C ** 

. 4K-0 70 K0a 

Fixed head (zero pressure) 

390 

0 25 50 7S METERS 

Vertical Exaggeration x 3 

FIGURE 4.1. Vertical -Section C-C' Through North Trenches Showing Computer 

Model Design Used in Best-Fit Simulation. Node arrangement, boun

dary conditions, relative hydraulic conductivity values, and relative 

infiltration rates (from Prudic 1986). 

section. Pressute heads are set to zero (atmospheric) along the bottom of the model, 

corresponding to the contact between the till and underlying lacustrine sediments. 

Constant infiltration Is applied to the land surface boundary corresponding approxi

mately to the net precipitation after evapotranspiration and runoff are accounted for. 

Sufficient infiltration was used to saturate the till to near land surface. The trenches 

are represented by constant head nodes corresponding to 1976 and 1978 water level 

measurements with seepage permitted at greater elevations within the trenches. 

Prudic (1981) modeled the site based on the hydrogeologlc framework described 

previously. Initial simulations incorporated a uniform hydraulic conductivity throughout 

the problem domain with subsequent simulations containing increasing complexity 

(Table 4.1). The complexity reflects the observed conditions of weathered and frac

tured till near the surface, underlain by unweathered till and compacted unweathered 

till at depth. The complexity seems reasonable based on the hydrogeologic frame 

work. These concepts are Incorporated in step-wise fashion beginning with case 1.

4.2

WEST EAST
TABLEA4.. Differences Between Heads Observed In February 1976 and Simulated 

Heads for Assumed Conditions (after Prudic and Randall 1979) 

Mean Absolute 

Departure from 

Observed Heads 

of February 1976 

Conditions 

One isotropic unit 

(a) Kx = Kz = 3.0 x 10-8 cm/s 201 

(b) Kx = Kz = 3.0 x 10-7 cm/s 201 

2 One unit with anisotropy 

(a) Kz=0.1 Kx 161 

(b) Kz= 0.01 Kx 114 

(c) Kz = 0.001 Kx 116 

3 Two Isotropic units (weathered and unweathered till) 

(a) K (weathered) = 10 K (unweathered) 123 

(b) K (weathered) = 100 K (unweathered) 127 

4 Two anlsotropic units (weathered and unweathered till) 

Kx (weathered) = 10 Kx (unweathered) 

(a) Kz = 0.1 Kx In each unit 93 

(b) Kz = 0.01 Kx In each unit 74 

5 Two anisotropic units (weathered and unweathered till) 

Kx (weathered) = 100 Kx (unweathered) 

(a) Kz = 0.1 Kx In each unit 90 

(b) Kz = 0.1 Kx (weathered) 

Kz = Kx (unweathered) 109 

(c) Kz = 0.01 Kx (weathered) 

Kz 0.01 Kx (unweathered) 92 

6 Two anisotropic units (weathered and unweathered till) 

Kx (weathered) = 10 Kx (unweathered) 

Kz = 0.01 Kx In each unit 

(a) Simulated sand and sift lenses near D, I, and J 65 

(b) As above plus Increased heads at base of model 60 

near G

4.3
TABLE 4.1. (contd) 

Mean Absolute 

Departure from 

Observed Heads 

of February 1976 

Conditions 

7 Three isotropic units (weathered, unweathered with 

fractures and unweathered till) 

(a) K (weathered) = 10 K (unweathered) 

K (weathered) = 100 K (unweathered) 

K (unweathered w/fractures) = 10 K (unweathered) 121 

8 Three anisotropic units (weathered, unweathered with 

fractures and unweathered till) with Kx the same as 

noted in case 7(a) above 

(a) Kz = 0.1 Kx in each unit 96 

(b) Kz = 0.01 Kx In each unit 93 

(c) Kz = 0.01 Kx in each unit plus simulated sand and 57 

silt lenses near D, I, and J; Increased head at base 

of model near G, and lower Infiltration near 

holes D and I 

(d) Same as 8(c) except Kz = 0.1 Kx for each unit 53 

9 Four isotropic units (weathered, unweathered with fractures, 

and 2 unweathered till units to compensate for overburden 

pressures) 

K (weathered) = 10 K (unwekthered) 

K (weathered w/fractures) - 5 K (unweathered) 

(a) K (lowest unweathered unit) = 0.5 K (unweathered) 120 

(b) K (lowest unweathered unit) = 0.7 K (unweathered) 104 

(c) K (lowest unweathered unit) = 0.85 K (unweathered) 107 

(d) K (lowest unweathered unit) = 0.7 K (unweathered) 

plus simulated sand and silt lenses near D, I and J; 

and reduced infiltration near D and I 31 

(e) as above, but 

K (lowest unweathered unit) = 0.85 K (unweathered) 

except beneath hole G where 

K (lowest unweathered unit) = 0.7 K (unweathered) 21

4.4
The case that incorporated the greatest amount of complexity (case 9) produced the smallest deviation from measured head values by Introducing layering into the till 

to account for the weathering of the upper portion of the till and the compaction of the 

deepest till. The resulting distribution of hydraulic conductivity for case 9 Is shown in Figure 4.1. The hydraulic conductivity of the unweathered till is 8 x 10-8 cm/s (Prudic 1981), although this was later revised (Prudic 1986) to about 4 x 10-8 cm/s. The 

hydraulic conductivity factors for the other layers are multipliers of the unweathered val

ues. Most of the Interior of the till is unweathered and has a relative hydraulic conduc

tivity of K = 1 corresponding to the 2 to 6 x 10-8 cm/s calculated for the till. Weathering of tihe till was considered to be degradational from the surface with a thin, highly oxi dized surficial layer with a relative hydraulic conductivity of 10 K underlain by a moder

ately weathered zone containing oxidized fractures, which has a relative hydraulicr conductivity of 5 K. The bulk of the till underlies the weathered zone, having a relative 

hydraulic conductivity of 1 K. The basal portion of the till is divided into several zones 

having hydraulic conductivities ranging between 0.70-K and 0.85 K primarily because 

of compaction of the sediments. 

Simulated distributions of hydraulic head for February, 1976, and February 1978, 

are shown In Figures 4.2, 4.3, and 4.4. These results agree well with measured water 

levels (see Figures 3.4 and 3.5). 

4.1.2 Radionuclide Transport Modeling 

Prudic developed a simple, one-dimensional method to calculate radionuclide 

migration rates from the trenches under the conditions of a downward gradient. His 

method is described in detail (Prudic 1986) and Incorporates convective transport, hydrodynamic dispersion, radioactive decay, and instantaneous but reversible 

equilibrium-controlled sorption. He modeled releases of 3H, 9oSr, and 14C. Prudic ruled out modeling additional radionuclides because of the relatively small concentra

tions measured In the trench water and the apparent small rates of migration Indicated 

from core samples. 

4.1.2.1 Tritium 

Prudic (1986) assumed that tritium will migrate as tritiated water; consequently, tritium is modeled as an unretarded species. The distribution coefficient (Kd) Is thus 

equal to zero, producing a calculated retardation factor (R) of 1. Other hydraulic and 

chemical coefficients Input for tritiated water Include a radioactive half-life (Th) of 

4.5 x 103 days, a diffusion coefficient (Dd) in water of 475 cm2/yr at 10°C after Wang et al. (1953), a porosity (n) of 0.3, and a tortuosity factor (A) ranging between 2.4 and 2.7. The diffusion coefficient, porosity, and tortuosity factor are used to estimate the 

coefficient of hydrodynamic dispersion (D') based upon Sherwood et al. (1975) as 

shown In Equation (4.1).

4.5
A

430

j ------ 412 Ul .-- 4110 4 8--,, 

4 090 408.7 I~ezo r • • ----- 0e 4------ _. 

> 400 

400 

.( 

I

U.1 430 

2 c 

U; 

T I 

14416 L.. q L...j LJ 15 4160 411 

414---ted 1a4e t3.0 - 4142Snltdlnele~Mh 

4105 414 

4104 

.mT.• • • • ''' • ''--405 ' '

09e i..a 4a7ti 3 404 

(from~ Prui0 986 

----._._ _- -.- 4046,4 2---. 

EXPLANATION 

Backfil ..... Compuedwatertable -414• Sknuated line of *mdhead SBacfillInterval 2 metemL 

SW eathered till v W ater level In t rnmc h T s h l 

[ Till wvith oxidized fracture 0 414 0 Observed head In plezometer 

a 25 50 METERS 

Vertical E~xamervi x 3 

FI.UtRE-4.. Vertical Section C-C' Through North Trenches Showing Computer_ 

Simulated Distribution of Heads, A) February, I1976, B) February, 1978 

(from Prudc 1986)

4.6
A

Simulated infiltration rate relative to the horijontal hydraulic conductivity of the urnweathewrd till

I 1 5 - I o6---4 

Constant infiltration rate Trenches 8 14: Fixed head for nodes 

along land surface below trench water level; seepage 

K nodes aboe trench water level 

,F#nU L L2

0 0 0 a 4 11 11311121 II•i •l18*4 1-

S0 0 00 I0 0 0 00000 0 a a0 0 a o 

K-I 0 K-I 0: 

0 0100 000 00000 0o 0 0 0 00 

Nod associated with piezo!meer I0 O. I 0 0 0 0 a00 0 0 acc00 00 coal 

Node 

'K0850 u l3.~m P O

Fixed head Iaero pressure)

E 3 Sackfill. Cover 

i•J Uiseathered till 

**.... Computed water table

EXPLANATION 

Weathered till 

MTill with oxidized fractures 

SWater level in trench

*4220 Obserd head in till 

K I Tosn bole 

-414- Simulated line of equal 

head Imtensl 2 meters

FIGUE4.E.. Vertical Section D-D' Through South Trenches Showing Computer 

Model Design, A) Node Arrangement, Boundary Conditions, Relative 

Hydraulic-Conductivity Values, and Relative Infiltration Rates Used In 

Best-Fit Simulations, B) Computer-Simulated Distribution of Heads for 

Till for February 1978 (from Prudic 1986) 

4.7

430

D,

K

Z

-a 

-1 

Go 

Go 

151

420 

410 

400

390 

430

B

-j 

W5 

Wi 

-I

420

410 1

400

D ly

-- 4004 4----

404 

402 2 

' 400 400 

0 go 100 METERS 

Vertical Exaggeration x 5 " I I I

4

i
EXPLANATION

Unweathered till with oxidized fractures 

Unweathered till 

Weathered till 

Alluvium 

Backfill

a Water level in trench 

....... Computed water table 

0 Observed head in 

4 1 piezometer * 

Simulated line of equal 

head interval I meter

0 I 10 20 p METERS 

F[GU RE 4. Vertical Section E-E' from Trench 4 Northward to Small Stream Showing 

Computer Model Design, A) Node Arrangement, Boundary Conditions, 

and Relative Hydraulic-Conductivity Values and Relative Infiltration 

Rates Used in Best-Fit Simulation, B) Computer-Simulated Distribution 

of Heads for February 1976 (from Prudlc 1986)

4.8

A .

430 

425

-C 

0

420 

415 

410 

405 

4WD 

395

B

390 

385

-a 

4 

0 

co 

4j

425 

420 

415 

410 

405 

400

EJ 

EM

Flow patk 

Teot hole
D'- (Dd.n)/A

The calculated range for D' was between 53 and 59 cm2/yr. Specific flux (q) was Input based on the results of the ground-water flow modeling. 

The best fit to the observed tritium distribution profiles measured below trench 5 

and 8 was obtained using relatively low specific flux values between 0.30 and 

1.2 cm/yr. The tortuosity factor was varied both above and below the 2.4 to 2.7 range 

to Investigate sensitivity. Results of several runs are shown in Figure 4.5. 

Prudic (1986) uses the model to project tritium profiles beneath trench 5. The pro jections are based on the assumption of steady-state conditions in the trench. Water 

levels in the trench and the corresponding specific flux of 0.7 cm/yr are presumed 

constant. The tritium source term concentration In the trench water is assumed to be 

constant, Implying that the rate of radionuclide decay In the water will be exactly offset 

by the Influx of leachate from the waste. Other factors such as the effective porosity of 

0.3 and the tortuosity factor of 2.4 are also held constant. Based upon these assump tions, Prudic's model predicts that tritium will migrate about 10 m beneath the floor of 

the trench in 100 years. 

4.1.2.2 Stro.t~iuZm 

Prudic (1986) conducted similar simulations for 9OSr based on the tritium 

analysis. The majority of the Input coefficients used for tritium were used for 9

OSr sim

ulations with several exceptions. The half-life of 9oSr Is 28.1 years. The diffusion coeffi

cient of gOSr In water was assumed to be about 315 cm2/yr based on work performed by Sherwood et al. (1975). The distribution coefficient was also assumed to be greater than zero (retardation factor greater than 1) because 9oSr will undergo adsorption/ desorption reactions with most soils and particularly clay-rich tills such as those In 

which the waste burial trenches are excavated. Core samples taken beneath the 

trenches indicated OOSr migration to be less than tritium (Prudic 1986). Strontium-90 

will migrate In water as a cation with an electronic valence of +2; consequently, adsorp tion of 9OSr by the till may be expected through mechanisms such as Ion exchange, chemical precipitation-mineral formation, complexation-hydrolysis reactions, oxidation

reduction reactions, and colloid and polymer formation (Onishi et al. 1981). 

Prudic (1986) modeled 90Sr migration using distribution coefficient values 

ranging between 1 and 7 mug and similar ranges of specific discharge and tortuosity factor as used for tritium. Results are shown in Figure 4.6 for the 9oSr profile beneath 

trench 8. The calculated profiles are similar in shape to the calculated tritium profiles but do not match the measured -OSr values as well because of the higher degree of

4.9

(4.1)
H& Hole IC with cange In specific flux

flft'ERVPflI RITIUM itflIUM

TION 

'is uncartadenwt 

Oc*NION with 

rench lo0wc

L.

CONCENTRA• 

DatiV'U 

in sa"Pon It raspect toSa 

q 1 )cintyr 

7-.47S 

o04

g101 

Ub 

c 102 

£ 0 103 

z 104 

105 

I

I - . .6

0 40 30 120 160 200 240 0 s0 100 IS0 200 250 300 350 

DISTANCE BELOW TRENCH FLOOR IN CENTIMETERS

C Note 8 IC with changes in tcaruo.ty 0. Homs 5 2Dand E

1,u 

I 101 

o 

62 

S10.3 

i0 

i 101 

a 

I- 5 10 6

I I S I I l I I I p• e . , 

I * m/W 0 i,-.- OBSERVEOt~i COIMCENTRIAnk~qI NU 

"Bat.Sr nietwes uflel.nt 

in swampe Iocalta w.th 

epet"soa t0rench floor 

Contacts keween the a ItlIOg units awtle % 

Ithees ie flow h 

Sate intarbadded w eaps 

TII wmif tahlly c1ea of -CI 

a n d itI s-I I s lt w e d fine tlnd

FIUR . Comparison of Simulated and Observed Tritium Concentrations 

Beneath Trenches 5 and 8 (from Prudlc 1986) 

4.10

0 50 100 150 200 250 300 350 0 40 80 120 

DISTANCE BELOW TRENCH FLOOR. IN CENTIMETERS

160 200 240

\ T724 03a"lw 

27 . . -.

0 *Ll I -yr 

T24 I 

- " 

e--4 OBSERVED TRITJUM %\ 

CONCENTRATION- 'N 

S reepriunaanc~ts wnmtyvý\ 

in sarmpe location with 

assets to ti ien ira 

T- 24 .,.

S. . . . . . . i I i I I

A4 Holes 8-2A and 8-20
2 10-3 

o Weathered cardboard Weathered cardboard €•10-4 

'9• . q"3 0 cm/yr 

0 7-7 • a, "- 245 cm/yr 

10*6 KT 11m724 

*\N. Km1m9 

N, q - 3 0 a-2lyr 

K d. 3 mL/O 

o - \ 6 N q4m 

N7-24 cý 

Z K-------------.Kd-7.m g 

0 10-7 -0 45 cmyr 

7-27 \ \ \K Id'70m° \ \L19 -244 . 

4K 30mL/g \ I 73 m q 

o- L d .L --- j~30L d 

0 10 20 30 40 50 60 0 10 20 30 40 50 60 

DISTANCE BELOW TRENCH FLOOR. IN CENTIMETERS 

EXPLANATION 

MEASURED 90SR IN TILL 

Vertical bar represents 95-percent confidence limits for 90Sr activity 

Horizontal bar represents the uncertainty in location of sample with respect to the trench floor 

FIGUBE 4.6 Comparison of Observed and Calculated 90Sr Concentrations Beneath 

Trench 8 In Test Hole 8-2B (from Prudic 1986) 

nonlinearity in the measured 9oSr profile. Projections Indicate that 9OSr will migrate 

about 4 m below the trench floor after 100 years and about 6 m after 500 years 

(Figure 4.7). 

4.1.2.3 Cabon-14 

Changes were made In the model Input to analyze 14C transport that include 

changing the half-life to 5730 years. Calculation of the distribution and diffusion coef

ficients is difficult due to the wide range of values that carbon may assume in various 

organic and inorganic forms. Prudic assumed the 14C to be in the form of bicarbonate 

and assumed the same diffusion coefficient value as for 90Sr. Prudic (1986) reports 

that distribution coefficient values for organic 14C are relatively low, ranging from 0.7 to 

1.1 mug, while inorganic 14C ranged between 3 and 12 mUg. Prudic assumed a 

range of between 1 and 3 mUg. Utilizing specific discharge and tortuosity factor

4.11

A B
10-2

2 

cc 

10-4 LU 

2 

0 

cC 

z10.5 

I

u years 500 10

an 500 yeYms 

10"8 I t 

0 2 4 a 8 

DISTANCE BELOW TRENCH FLOOR, IN METERS 

F..GU.RE_•. Predicted 9oSr Concentration in Till Beneath Trench 4 After 10, 100, 

and 500 Years (from Prudic 1986) 

ranges similar to previous applications, projections of 14C movement indicate that 

between 1500 and 20000 years will be required for a migration of 23 m below the 

trench floor. 

4.2 HYDROGEOLOGIC PERFORMANCE ASSESSMENT 

Previous work provided the basis for the hydrogeologlc performance assessment 

of the West Valley site. The following discussion provides a description of the

4.12
performance objectives used In the assessment, details of the code and underlying assumptions used in the modeling analysis, and results of the assessment for key 

radionuclides released. 

4.2.1 Performance Objectives 

- The key performance objective as required by a low-level radioactive waste 

facility license in 10 CFR 61, "Licensing Requirements for Land Disposal of 

Radioactive Waste," states that: 

"... during operation and after site closure that concentrations of radioactive 

material which may be released to the general environment In ground water, 

surface water, air, soil, plants, or animals will not result In any member of the 

public receiving an annual dose equivalent of 25 millirems (2.5 x 10-4 Sv) to 

the whole body, 75 millirems (7.5 x 10-4 Sv) to the thyroid, and 25 millirems 

(2.5 x 10-4 Sv) to any organ of any member of the public." 

In this study, the performance assessment considered only the ground-water path

way. We also did not intend that this performance assessment analysis provide the 

basis for determination of compliance of the West Valley site with the licensing regula

tions put forth In 10 CFR 61. However, final model results for peak concentrations of 

the key radionuclides are transformed to dose. Factors used to convert concentration 

to dose for both the full garden and drinking water scenarios, presented in Table 4.2, 

are based on dose analysis performed with the GENII code (Napier et al. 1988). 

4.2.2 Analysis and Results of Shallow Lateral Pathway Assessment 

Prudic's cross-sectional modeling results of ground-water flow in the vicinity of 

the trenches appear to provide very reasonable Information about hydraulic heads 

and the direction of ground-water flow In the till about the trenches. Much of Prudic's 

modeling Involves comparisons between February 1976 water levels when the 

trenches were nearly three-quarters full and February 1978 when water was standing In only about the bottom quarter of the trenches. Subsequent modeling of the cross

section was conducted In this study to Investigate the flow-system under conditions of 

very high water levels. Such conditions may exist at the site in the event that the 

sumps are deactivated when Institutional control is lost. 

In this study, data sets obtained from Prudic (1981) were modified and analyzed 

with FEMWATER (Yeh 1987). FEMWATER was developed at Oak Ridge National 

Laboratory based on the finite element methodology of Reeves and Duguld (1975) 

and Duguid and Reeves (1976) that Prudic used in his analyses. Some rearran

gements of Prudic's data sets were necessary to obtain the proper format for Input to

4.13
IABLEA4.2. Factors Used to Convert Concentration for Selected Radionuclides to 

Dose for the Drinking Water and Full Garden Exposure Scenarios 

Radionuclide Drinklog .aera) Full Garden(b) 

3H 0.000042 0.000089 

14C 0.0014 0.041 

9OSr 0.088 4.9 

6oCo 0.0023 0.22 

137Cs 0.033 0.064 

226Ra 0.7 14 

232Th 0.2 9.2 

235U 0.019 0.41 

238U 0.017 0.17 

238Pu 0.24 0.68 

239Pu 0.27 7.2 

241Am 2.6 0.93 

(a) Drinking water scenario - 2 liters per day. 

(b) Full garden scenario - ground, external, inhalation 

uptake, drinking water Ingestion, terrestrial foods 

Ingestion, and animal product Ingestion. Assumes 

300 years of prior Irrigation. 

FEMWATER. The only change in the hydrologic content of the data sets was to 

change the ponding depths to raise water levels to the brim of the trenches. The 

model was operated for a four-layer, isotropic system as depicted In Figure 4.1. 

Results for the scenario where water levels rise to the very top of the trenches at 

an elevation of about 420 m are shown in Figure 4.8. The results seem reasonable in 

comparison to Prudic's results for the north trenches (Figure 4.2). Water levels several 

meters higher in the trenches than the February 1976 water levels appear to produce 

hydraulic heads several meters higher in the till immediately surrounding the trenches. 

Comparison with Figure 4.2 reveals that the increase In head is distributed within the 

potential field about the trenches. 

Of particular importance for long-term closure of the site is the potential for lateral 

movement of radionuclides through the weathered, fractured, oxidized till zone located 

in the upper few meters of the section. Water levels at or near the top of the trenches 

may provide the necessary driving force to move water through the weathered, 

fractured till. The modeling results reveal some Increase in lateral flow, particularly 

near the base of the trenches. However, the results seem to indicate that movement

4.14
EXPLANATION 

37 Water Level In trench

Weathered till 

Unweathered till 

Till with oxidized fractures

-402- Simulated lne of equal head. 

Interval 2 meters. 

D Test hole I

0 25 50 METERS 

Vertical Exaggeration x 3

S9011046 9

FIGURE 4.8. Vertical Section C-C' Through North Trenches Showing Computer 

Simulated Distribution of Heads for a Scenario of High Water Levels in 

the Trench

will still be predominantly downward through the till in the areas adjacent to the trench. 

Consequently, the hydraulic head gradient does not appear to exist to allow for sig

nificant, continuous lateral movement through the weathered, fractured till zone while 

moving laterally for a short distance to the nearest drainage. 

Below the soil cap covering the trenches and above the unweathered till Is the 

fractured, weathered, oxidized till zone where transport of water may occur in a rela

tively higher hydraulic conductivity zone. This zone Is about 2 m deep at about 4 to

4.15

== 

Q 

I

Backfill

EJ
5 m below the surface. Surface water coming through the trench cap may move later

ally through the surface zone to Frank's Creek to the east of the site. 

While hydrologic flow modeling done by Prudic (1986) and In this study indicates 

the lateral pathway through the fractured till may be attenuated to a large extent by the 

predominantly vertical gradient within the till, the occurrence of migration of kerosene 

at the nearby facility burial area would seem to Indicate that migration could be signifi

cant. To evaluate this pathway, we made conservative estimates of what the impact of 

the contaminated water overflowing from the trench might be to Frank's Creek. 

We first made the assumption that after the period of institutional control water 

levels in the trenches would rise in the trench covers and would begin to migrate Into 

the shallow weathered, fractured till. We also assumed that infiltration of rainfall would 

be sufficient to maintain these water levels within each trench. We also made an 

assumption contrary to the modeling studies done that contaminated water would in 

fact reach nearby Frank's Creek, and the rate of migration would be equivalent to that 

derived from the extent of lateral migration of kerosene at the FDA (i.e., 1.38 m/yr). The 

average travel time within the weathered fractured till to the creek, which is approxi

mately 140 m away from the trenches, would thus be about 100 years. Using the 

estimated elevation of the trench head for overflowing conditions (420 m), the approxi

mate elevation of Frank's Creek (410 m), and the approximate distance to Frank's 

Creek from the trenches (140 m), we calculated a hydraulic gradient of 0.07. Using the 

assumed velocity of 1.38 m/yr and a porosity of 0.3, we can calculate an effective 

hydraulic conductivity of 1.8 x 10-7 cm/s, which is about equivalent to values estimated 

In previous modeling. Using the approximate length of the trenches (370 m), an 

approximate thickness of the weathered and fractured till of 2 m, and an estimated 

porosity of 0.3, the cross-sectional area of flow can be estimated to be about 220 m2. 

Multiplying this area by the assumed linear velocity of 1.38 m/yr, we can calculate the 

average flux of water moving from the trenches to Frank's Creek to be about 300 m3/yr. 

Trench water entering the shallow till system would migrate for approximately 

100 years before entering Frank's Creiek. During this period, trench water concentra

tions would be reduced during transport by a number of factors including radioactive 

decay, diffusion and dispersion within the till, and eventually, dilution by the flow in 

Frank's Creek. Radioactive decay appears to allow concentrations of many radionu

clides to decline to negligible levels. This is particularly true for radionuclides that 

have an affinity to be absorbed to the till materials. The combination of decay and 

adsorption eliminate all radionuclides but tritium and 14C. 

Table 4.3 provides a summary of the effects of decay and river dilution on maxi

mum measured trench concentrations for tritium and 14C taken from Table 3.3. The 

concentrations given in column 2 would reflect the effect of decay of maximum concen

trations during transport up to the river. For tritium, the decay time would be 100 years;

4.16
TABLE 4.3. Summary of Effects of Decay and River Dilution on Maximum Trench 

Concentrations for Tritium and 140 

Maximum Decayed Diluted River 

Concentration Concentration Concentration 

Radionuclide 4DQieL) .4~i/L. JL 

Tritium North Trenches 2.3 x109 8.1 x 106 2,785 

South Trenches 4.3 x10 9 1.5 x 107 5,170 

Carbon-1 4 

North Trenches 7.4 x10 4 7.3 x 104 75 

South Trenches 5.2 x105 5.1 x 105 176 

for 14C, which Is assumed to have a retardation factor of about 7, the time was 

assumed to be 700 years. Concentration of tritium and 14C are further reduced by 

dilution from Frank's Creek. The average annual flow rate of 875,837 m3/yr measured 

in 1977 at a gauging station on Frank's Creek northeast of the site provides a dilution 

factor of 2920 when compared to the estimated flux through the shallow till of 

300 mS/yr. This dilution reduces the concentration of these radionuclides to levels 

below regulatory limits (see Table 4.2). Therefore, with the assumed conditions, move

ment of radionuclides along a lateral flow path through the till does not appear to pro

vide a significant loading to Frank's Creek. 

4.2.3 Analysis and Results of Deep Vertical Pathway Assessment 

The following section provides a discussion of the transport analysis for the deep 

vertical pathway. This discussion describes the modeling approach, model selection 

and design, modeling assumptions with regard to the site hydrogeologic characteris

tics, physical characteristics and setting of the site trenches, the waste inventory and 

related radionuclide release, and subsequent transport Into the environment to hypo

thetical offsite wells. 

4.2.3.1 Modeling Approach and Model Selection and Design 

The transport modeling approach was devised for the site to take advantage of 

the main attributes of the site conceptual model. Radionuclides were released from 

the site waste inventory and were transported downward In a vertical streamtube with 

a cross-sectional area equivalent to the surface areas of all trenches contained within 

the disposal facility through the total thickness of unweathered till to the underlying 

lacustrine unit. Once In the lacustrine, radionuclides were transported laterally in a 

horizontal streamtube defined by the length of the burial trenches and the saturated

4.17
thickness of the lacustrine unit. The transport was done to hypothetical off-site wells 

where an assessment of exposure through drinking water and full garden scenarios 

was made. Because of their physical separation, the north trenches and south 

trenches were treated separately in this analysis. 

The model selected for this analysis, the TRANSS code (Simmons et al. 1986), is 

designed for one-dimensional, convective transport in a streamtube. This approach is 

schematically Illustrated In Figure 4.9. The code, which Incorporates the theory of Sim

mons (1982) and relates dispersion directly to the variation observed in the travel time 

from the contaminant source, includes the following features: 

A probability-weighted summation of either the fluxes or concentration Is cal

culated along a streamline with a constant flow velocity determined from the 

travel time and length of the hydrologic streamline. 

One-dimensional transport is represented along each streamline by an 

analytical solution of the convective-dispersion equation. (This approach 

assumes a constant flow velocity, which varies with a local-scale dispersion 

coefficdent.) 

Lard Surface 

§ýVWý' q Waste Ve~rticw, al Pathlines

Till Unit

"of Infiltrating Water 

•A Water Table 

Pathlines of Ground-Water . RFlow Traced in the Aquifer

Saturated

Lacustrine Unit

Surface Water

S9104013 1

FIGURE 4.9 Depiction of the Streamtube Approach to Transport Through the Till 

Zone and Lacustrine Unit as Incorporated Into the TRANSS Code

4.18
* Decay of radioactive contaminants Is applied both during containment and 

after leaching from the waste source and entering the hydrologic flow path. 

* Retardation of the contaminant migration is based on a fixed distribution coef

ficient (Kd) for each nuclide. 

The model contains a general empirical description of contaminant release 

but also Includes the choice of three optional release models: 1) a constant 

fractional release rate, 2) a concentration-limited release rate based on 

chemical solubility, and 3) an adsorption equilibrium release rate based on 

the Kd value for the nuclide. 

4.2.3.2 Modeling Assumptions and Parameters 

Site Characteristics. The site has been divided vertically into two hydrologic 

zones, the near-surface weathered and fractured till, and the deeper unfractured till. 

Drainage in the subsurface is generally toward the north-northeast in the lacustrine 

unit, but flow paths are essentially vertical in the till. 

The area of the trenches was computed by measurement of the outlines of the 

trench boundaries from Smoot (1989). The cumulative area of the trenches receiving 

net infiltration is approximately 20,282 m2. Hydrologic and site information (Smoot 

1989) Includes the water influx and soil properties at West Valley. Net infiltration is 

approximately 0.023 m/yr. This infiltration rate will be assumed to be constant through

out the year. The porosity was assigned a value of 0.3, and the bulk density of the 

streamtube material was given a value of 1.8 g/cm3. 

To simulate the deep pathway scenario, two models were constructed, one from 

the southern trenches to wells 10 m and 100 m from the edge of the trenches In a 

direction downgradient from the waste site, and one from the northern trenches to 

wells 10 m and 100 m from the edge of the trenches. A map view of the trenches, 

wells, and streamtubes is shown in Figure 4.10. Streamlines from several different 

points along the streamtube In the trench area divide the inventory area. The width of 

the trenches projected In a direction along the hydraulic gradient was considered to be 

the streamtube width. 

Results of the hydrologic flow modeling provided the basis for the conceptual model used in the TRANSS transport calculations. Figure 4.11 shows a cross

sectional view of the flow path through the unfractured till. Water infiltrating through 

the burial till moves vertically until it eventually reaches the underlying lacustrine unit, 

which acts as a drain to the till. The water then travels laterally downgradient to the 

wells. The average dispersion coefficient was chosen to be the largest found by

4.19
Based on plane-table survey 0 25 50 75 Meters S91040132 

US Geological Survey. 1975-78 ;;am= _ 

0 100 200 Feet 

Ei.aG.RE4.1il. Streamlines and Streamtubes Used for Transport Modeling 

4.20
Precipitation

I4I Precipitation 4,I

Exl~lnaron 

--] Saturated 

-" Unsaturated

Direction of Water Movement 

Length and number of arrows 

suggest relative magnitude 

Water Table 

-- Contact Between Units

St1rataphi Units 

2, 3. 4, 7 Gravel, coarse sand 

8 Fine sand, sift 

Lacustrine Unit

S9011046.6 

F.IGUE 4.11. Cross-Sectional View of Flow Path Used in Transport Modeling 

Prudic (1986) at 59 cm2/yr for tritium and about 47 cm2/yr for 14C In the till. The 

average bulk density and porosity was also taken from Prudic (1986) to be 1.8 g/cm3 

and 0.30, respectively. Retardation factors indicate the amount of retardation of the 

radionuclide, and are computed from

R = 1 + ( bulk density / porosity ) *'Kd. (4.2)

Table 4.4 shows the retardation values used in the transport simulations for the 

north and south trenches. Based on these figures, the only radionuclides not held

4.21

9 Silt, clay 5 Till
IABLE 4.4. Selected Retardation Factors for Various Radionuclides

ladionuclide R Comments-or Source 

3H 1 Conservative; moves with water 

137Cs 292 Prudlc 1986 

SOCo 6 Prudic 1986 

9OSr 43 Prudic 1986 

14C 7 Prudlc 1986 

226Ra 1168 Bergeron et al. 1987 

241Am >1200 Routson et al. 1987 

238Pu 338 Bergeron et al. 1987 

239Pu 338 Bergeron et al. 1987 

23sU 7. Bergeron et al., 1987 

232Th 219 Bergeron et al., 1987 

essentially Immobile as a result of retardation by adsorption are 3H and 14C. 

Cesium-1 37 along with 23MU, 6oCo, 226Ra, 241Am, 23sPu, 239 Pu, and 232Th, have been 

dropped from further consideration in model development. 

A period of 14 years was allowed for the inventory to decay corresponding to the 

operational life of the site before any release to the environment. This is important 

only for the inventory of 3H (53,272 Ci). With a half-life of 12.3 years, approximately 

half the inventory will have decayed before release Is allowed. The half-life of 14C 

(5730 years) Is so long as to make the reduction In inventory (212 C1) Insignificant. 

The areas over which net Infiltration contributed to the total flux through the waste 

were calculated to be 9313 m2 and 16386 m2, respectively. The waste was con

sidered to be concentrated at the bottom of the trenches, which were an average of 

6 m deep. Travel from the bottom of the trenches to the lacustrine unit took place over 

a distance of 23 m with travel times of 300 to 2300 years (Prudic 1986). The shorter 

time was used as a conservative estimate, which was based on a specific flux of 

2.3 cm/yr, a hydraulic conductivity of 6.0 x 10-a cm/s, and an effective porosity of 0.3. 

The areas used for the streamtubes In the TRANSS runs of the north and south 

trenches are 2038 m2 and 1727 m2 , respectively. Migration of the waste was assumed 

to take place equally along the entire width of the streamtube. The widths of the 

streamtubes for the north and south trenches were computed to be 198 and 172.7 m, 

respectively. The velocity of water In the lacustrine unit was determined to be 

1.68 m/yr based on a hydraulic conductivity of 1.0 x 10-4 cm/s and a hydraulic gradient 

of 0.014 (Prudlc 1986).

4.22
Trench Configuration and Waste Inventory. Information characterizing inventory 

was gathered for trenches 1 through 11 from Prudic (1986). Trenches 12, 13, and 14 

were not studied In detail. Information characterizing waste containment breakdown 

was compiled for trenches 8 through 14. Trenches I through 7 were not studied in 

detail. Only general Information on volume, operational life, and location were given for all trenches In the Prudic (1986) and Kelleher and Michael (1973) reports. The 

information from the studies were assumed to be Indicative of the types and amounts 

of waste being shipped to West Valley over the operational life of the she. To deter

mine a generalized Inventory and waste containment distribution for undocumented 

trenches, an average trench volume and Inventory was compiled. From this an 

Inventory and waste containment distribution was derived, based on documented 

trenches. The waste containment distribution was assumed to be that of the average 

trench, and the Inventory of each undocumented trench was corrected for the dif

ference in volume from the average trench. A similar method was used to approximate the waste containment breakdown for trenches with no Information available. A sum

mary of the estimated inventory for the West Valley site is provided in Table 4.5. 

The chemical or physical form (metal, liquid, etc.) of the Inventory can vary widely 

for each radionuclide In the trench. No attempts have been made in compiling the 

Inventory to break out parts of the radionuclide Inventory that would possibly have a 

significant effect on the availability and/or release of that radionuclide to the envi

ronment. Tritium, for example, was shipped to West Valley mostly as liquid tritium 

oxide (T20) or targets. However, forms of tritium exist that have a very low release rate 

as a consequence of their chemical form. Luminous paint containing tritium Is 

assumed to be nonleachable. No information on the possible presence of forms of 

tritium other than as targets or as byproducts of other wastes was provided. 

Solubilities of the different radionuclides depend on the chemical form taken. 

Little chemical Information exists describing radionuclide valences, oxidation states, 

complexation, etc., to apply solubility Information. Therefore, uncertainty exists in the 

solubility controls applied In the conceptual model. Carbon-14 was determined to be 

solubility controlled, and passed the screening process described in a later section. A 

maximum 14C value determined from the trench sumps was used as a limiting solubil

ity, even though it is several orders of magnitude below the theoretical maximum solu

bility of carbon in water. Additional chemical parameters unknown at this time are 

assumed to be-the source of the lower solubility In the trench leachates. 

Waste Containment Characteristics. Of all the different waste containment struc

tures shipped to the West Valley site, three either contained the bulk of the waste or 

provided an environmental barrier similar to the waste containment actually used. Sec

ondary waste containment structures within the primary waste containment may or 

may not be present; a conservative assumption of no secondary waste containment to 

the primary containment structure was made. These waste containment structures are 

described in Section 2.3.2.

4.23
TABLE 4.5. West Valley Trench Inventory 

laste Stream Breakdown

Tread Total 

umkbe Activity (CO)

Waste 

Vole. (m**4) 

1,589.9 

3,249.0 

5,82.60 

7,779.0 

7,511.3 

2.1 

7,155.9 

4,929.9 

6,175.0 

6,490.9 

4,721.0

Tot"l 

H-3 

(Ci) 

17.2 

6.1 

674.4 

2,719.6 

11,U52. 

15,731.0 

7,872.4 

31,537.4 

36,28.6 

12,978.0 

12,814.0 

1U,384.0

Boxes. 

Metal Concrete wood, etc.

18.43 

4.92 

415.94 

1,65,.46 

6,787.40 

7,659.40 

4,655.70 

16899.24 

22.481.25 

8,464.09 

8,678.8 

7,164.98

0.62 

1.29 

24.28 

97.99 

391.15 

314.U 

236.18 

315.U7 

382.89 

362.34 

1,624.32 

728.88

6.11 

2.88 

245.59 

988.14 

3,927.39 

7,u8.59 

14,822.39 

13,416.21 

3,2•1.U8 

3,261.99 

2,492.16

Total 

C-14

Waste Stream Breakdown

Metal Concrete

1 .61 

6 3.34 

7.77 4.72 

a 1.82

17.712 

U.eu 

63.U2 

67.M3 

46.268

16.82 

16.27 

17.21 

211.97 

U7.8 

38.21 

31.92

141,116.16 863,91.16 3,8U.1 63,272.59

4h.

1 

4 

6 

S 

7 

S 

9 

19 

11 

12 

13 

14

4,129 

2,2U9 

17.1" 

67.189 

92,9M9 

10,2U9 

'1,579 

38,789 

34.219 

11.2U9 

12,185

wood, etc.

';.3 

3.69 

1.78 

2.77 

1.57 

17.52 

6.91 

126.U 

14.•3 

14.26 

11.15

9.94 

5..g 

9.18 

0.28 

3.11 

0.70 

5.63 

5.33 

3.42 

1.61 

4.68 

3.24

Totalis 498943.04 "4,U2.1 U1.68 374.2116. IS 22.U•k
IABLE-4.5. (contd)

lusi. Streu Bmorftn

Total 

84.32 

19.293.69 

12,87.33 

187.76 

1,899.59 

264.10 

8,784.M6 

9,312.36 

7.552.M9

Dutes, 

metal Concret

23.8? 

96.53 

1,818.94 

198.93 

28,267.14 

8,177.69 

79.99 

946.94 

163.79 

6,148.86 

a,239.94 

5,219.68

1.24 

5.72 

197.61 

6.15 

1,7.71n 

25.49 

4.18 

16.16 

2.64 

M6.52 

744.95 

528. 64

12.22 

58.52 

1,364.51 

69.85 

16,551.15 

6,435.36 

53.73 

819.46 

97.75 

2,371.68 

2,28.M6 

1,812.48

ntast Stres Broskdmw

Total 

15,763.36

ornes 

Neta C"Conet wood etc

9.36 

6."9 

9.69 

9." 

9.09

6.99 

9.69 

9.99 

6.99 

9.33 

9.33 

9.36 

6.36 

9.3' 

9.36 

9.99 

9.86

9.39 

9.36 

0.3, 

9.69 

9.a

Totals 54,692.1 55,267.45 ~~~191.117.66 8,613.65 31,624.35 5739 .9 .993

Tmmnh 

*eAter

An

Total 

92,M3 

17139" 

34,M3 

54,93 

53.533 

11,23 

9,433 

12,333

1 

2 

a 

4 

14

71,569.9 

5,829.0 

4,929.9

ToUls 04,692.1 IS.M." 0." I.ff 0."
9~t,

C U i 0 .i. M bIf[

U I -----------

Wi a &E E I 

6 6 6 6 6

a . . 

mg-a-...-

... .m m S 

* baCCa

mom mace

... g- be5 * tE

-d m 

C

a 

I U 

I

a 

I

I -d

* a m m a mm 

* m a mm a a 

IEII9 

* a a m m em

mga m

-I 

U

flO 

I'r

U

IF 

IiF' 

ii 

SS 

Ii.In 

I 

8

I

4.

P4 

c
Total owna Total Dones, 

Aa-241 Metal Concrete woo. etc. P&n,-3 Mtal concrete od.ec

.Toil hWste 

tivity, (Cu) volus. (,-S).

3.96l g96 0.96 3.96 

6.96 0.11 

6.61 9.69 

3.13 N.A 

1.5 3.72 9.13 

4.92 2.85 3.15 

39A 2.67 0.94 

8.734 4.18 1.67 

4.6115 3.23 0.14 

4. 3.27 0.89 

8."064 2.74 0.26

9.96 

9.n 

.ON 

9.75 

1.92 

1.67 

2.49 

1.25 

1.22 

6.95

4.94 2.46 

233.96 81.45

'.96 

0.15 

0.02 

4.82

221.65 138.39 4.43 

163.32 59.93 3.13 

673.9 457.63 8.79 

39.68 244.96 3.94 

343.88 23.27 13.21 

383.84 241.78 28.87 

292.64 31.92 23.48

2,729.42 1,6.29 64.79 1,311.34

Trewh 

fteber

-N

1 

2 

3 

4 

6 

7 

a 

9 

13 

11 

12 

13 

14

4,123 

2,21W 

17,219 

67,119 

92,9M3 

34,233 

53,596 

11,210 

12,333

3,243.3 

56,21.3 

7,773.3 

7,893.3 

2.1 

7,123.0 

4,923.3 

5,173.9 

5,183.3 

5,493.3 

4,723.9

6.00 3.19 

1.44 

0.96 

47.89 

113.83 

43.29 

413.98 

145.86 

91.19 

"3.21 

73.23

Intostres ream , fn1e Strou Brekdown

Totals 4n,1s1.1 39.00 1.1. 1.n 19.45

TBE.5 (contd)
TABLE 4-5. (contd)

Trench Total last 

Number Activity (Ci) Volume (f..3)

1 

2 

a 

4 

6 

7 

8 

9 

12 

14

4,128 

2,211 

17, 11 

67.189 

92,98 

18,2U 

1,670 

34,2U 

64,91W 

63,589 

11,•21 

9,410 

12,388

1,51.1 

3,248.6 

7,173.9 

7,888.9 

2.1 

?a.# 

7,191.5 

4,929.0 

5,179.9 

6,499.9 

6,12.19 

4,720.0

last,. Stream Breakdown 

Pu-239 Metal Concret• wood, etc. lllllmmgg - -

11.6w 9.1 9.12 

6.182 3.76 0.22 

29.62 17.96 1." 

11.124 11.82 0.68 

27.886 15.88 9.65 

6.W84 3.42 0.18 

3.8776 2.52 6.54 

.5•2 9.54 1.01 

41.577 28.68 1.29 

42.488 28.47 8.41 

34.468 23.77 2.41

9.18 

0.21 

2.29 

19.61 

8.46 

18.94 

2.U 

1.62 

ICU2 

11.62 

8.27

Vaste Stream Breakdown 

Total Box" 

U-236 Metal Cnocret, wood, etc. 

1.1814 .184 0.18 0.4112 

3.1391U 2 6.591 6.6" $.Us 

I.1832 O.U2 0.99 0."1 

0.61759 6.61 9.81 0.6" 

9.118698 0.661 9.58" 9U2

5.527 9.013 0.611 

I.17872 9.185 9.5U 

0.64T 5.182 9.,18 

.9.119 a."?1 9.51 

0.589994 5.18 $."I1 

9.18•824 9.188 .1.81

Totals 49,&89.8 64,592.1

8.182 

9.88 

5.512 

9.55

269.12 1,12.2,2 9.74 U7.14 t.1 .57 a."J 0.14
I .' ?a.. . .e

-4 

a 

a

U P ! S

-4 -4,, g.

M P

m P m P P 

Me cap p "

0 P pPp 

EII!i 

3, g a 3 

P,!aP 

PP. P P

-4 

S 

I 

U

I-4

U 

p. -4. ? -3 0.

I
The initial competency of the waste containment structures was determined by 

the method of placement in the trench. All of the steel drums were assumed to be 

rolled or dropped into the trench, and thus suffered a 15% denting and/or breakage 

rate (MacKenzie et al. 1984). Fiberboard boxes, wood, plastic bags, and other simple 

waste containment structures were assumed not to be a barrier to the environment 

regardless of the emplacement method. 

The competence of the waste containment structures over time was determined 

by corrosion rates of the waste containment. MacKenzie et al. (1984) reports steel 

drum corrosion rates and expected lifetimes of waste containment structures in a soil 

environment similar to that of West Valley. The expected lifetime of a steel drum Is 

86 years, and a steel liner 215 years. Cardboard and wooden boxes do not have the 

ability to protect radionuclides from the environment. For the expected transport time 

of the radionuclides existing In the trenches (with the exception of 3H), waste contain

ment competency does not seriously affect eventual transport to off-site wells. 

In addition, little is known of the waste forms other than the general makeup of the 

container (metal, concrete, wood, etc.) or placement, so release scenarios would be 

speculative regarding the retardation or attenuation of radionuclides by the waste 

containment structure. Therefore, the conservative assumption has been made to 

disregard the effects of waste containment structures and release the total inventory of 

radionuclides to the trench environment at the end of the operational life of the site. 

Radioactive decay, however, Is still allowed to attenuate the inventory present in the 

trenches prior to release. 

4.2.2.3 Modeling Results 

Transport simulations were made for radionuclides in the trenches at West Valley 

for waste entering the unfractured zone at the bottoms of the trenches. The modeling 

assumptions discussed in Section 4.3.4 were used to model radionuclide transport 

and resulting concentrations of radionuclides reaching wells offsite. Travel times and 

concentration levels are discussed Individually for each radionuclide. 

Tritium. Because tritium Is a conservative species and travels with the water, it 

moves without attenuation or retardation through the subsurface. Tritium concentra

tions resulting from a release of tritium consisting of the maximum observed tritium 

concentration in trench water multiplied by the assumed Infiltration rate of 2.3 cm/yr are 

presented in Figures 4.12 and 4.13. Figure 4.12 represents predicted concentra

tions at a hypothetical well located approximately 10 m and 100 m downgradient of the 

north trenches; Figure 4.13 represents predicted concentrations at a hypothetical well 

located approximately 10 m and 100 m downgradlent of the south trenches. In both 

cases, the transport through the unweathered till in combination with the short half-life 

of tritium reduces the concentration of tritium to relatively low levels. Peak concentra

tion at 10 m downgradient from the north trenches is about 4 pCi/l respectively after

4.30
10 m Downgradient 100 m Downgradient

Time, in years

Tritium Concentrations at a Hypothetical Well Located Approximately 

10 m and 100 m Downgradient (Northeast) of the North Trenches

10 m Downgradient 100 m Downgrodient

lime, in years

_FIGRE4.13 Tritium Concentrations at a Hypothetical Well Located Approximately 

10 m and 100 m Downgradient (Northeast) of the SoUth Trenches

"-4.31

1000

100 

10 

1

01 

0.01 

0001 

0.0001 

0.00001

a0 

C 

0 

4.' 

C 

0 

E 

z. 

I0000001

1

1000 

100 

10 

1 

01 

0.01

0.001

0.0001 

0.00001 

0.000001

0. 

0 

0

E

i_, '.
about 310 years. Peak concentration at 100 m downgradlent of the trenches reach 

about 0.046 pCi/L after about 370 years. Peak concentrations decline after 

410 years at 10 m and about 500 yr at 100 m. Peak concentrations 10 m and 100 m 

downgradient of the south trenches rise to about 7.4 pCi/L after 310 years and 

0.086 pCVL after 370 years respectively. Peak concentrations decline after 

450 years at 10 m and 530 years at 100 m. 

Carbon-14. For 14C, solubility controls are a more Important limiting factor on the 

resultant concentration at a distant well than distribution coefficients. From chemical 

analyses of leachate waters In the trenches, a maximum value of 74,000 pCVIL for the 

north trenches and 520,000 pCi/L for the south trenches was obtained. These values 

were used In combination with the assumed infiltration rate of 2.3 cm/yr to determine 

the release of 14C from the Inventory and the subsequent transport to hypothetical 

offsite locations. 

Figure 4.14 represents predicted concentrations at a hypothetical well located ap

proximately 10 m and 100 m downgradient of the north trenches; Figure 4.15 repre

sents predicted concentrations at a hypothetical well located approximately 10 m and 

100 m downgradlent of the south trenches. In both cases, the transport through the un

weathered till In combination with the long half-life of 14C reduces the concentration of

10000 

1000 

100-. 

101 

0.1 

0.01 

0.001 

~.0001

0.00001

0

. Ij

10 M 

100 M

I ....I. I6 6 . . .g.... . .o 5 oo .... .1. I6 d Io .. #.. aiII " o' IIII " oo 10000 20000 30000 40000 50000 

Týime, in years

Carbon-14 Concentrations at a Hypothetical Well Located Approxi

mately 10 m and 100 m Downgradient (Northeast) of the North 

Trenches

4.32

C 

2 

r

0 

C 

C 

0 

0 

C-) 

C,)

0

I
10000

S 1000 o 

100 

S 

. 10 

4-. O*-*"-'•10 M 

o • 100 M 

,- 0.1 

0 001 0 

,.~ 0.001 

I 0.0001 

0.00001 1 

0 10000 20000 30000 40000 50000 

Time, in years 

FIG .15. Carbon-14 Concentrations at a Hypothetical Well Located Approxi mately 10 m and 100 m Downgradient (Northeast) of the South 

Trenches 

tritium to less significant levels. Peak concentration at 10 m downgradient from the north trenches Is about 1660 pCI/L, respectively after about 310 years. Peak con centration at 100 m downgradient of the trenches reach about 418 pCiIL after about 370 years. Peak concentrations 10 m and 1 00m downgradient of the south trenches 

rise to about 11680 pCI/L after 310 years and 2940 pCi/L after 370 years, respectively. In both cases, these peak concentrations are sustained by the Inventory and long half 

life for tens of thousands of years.

4.33
5.0 DISCUSSION OF PERFORMANCE ASSESSMENT RESULTS

This section of the report discusses the results of the simulated releases with the 

stated performance objectives and conclusions on the uncertainties associated with 

the overall site performance assessmbnt results. 

5.1 COMPARISON OF RESULTS WITH PERFORMANCE OBJECTIVES 

The results in the performance assessment suggests that tritium and 14C would 

be the only radionuclides released from the West Valley site in any significant concen

trations. To date, radionuclide migration has been limited to less than 3 m from the 

trenches at West Valley. 

As stated earlier, this performance assessment analysis was not intended to 

provide a definitive judgment of compliance of the West Valley site with the licensing regulations put forth in 10 CFR 61. No dose calculations were performed to assess 

site performance with regard to regulatory limits. For the sake of comparison, how

ever, we did make a comparison of peak concentrations of the key radionuclides from 

the model results to dose equivalent concentrations that would be consistent with the 

regulatory limit of 25 mrem/yr whole body dose. A comparison of peak concentrations 

from the transport modeling results and the relevant dose equivalent concentrations is 

given in Table 5.1. 

For the assumed simulated conditions, tritium levels are well below regulatory limits. For 14C, predicted peak concentrations meet the 25-mrem dose limit using the 

drinking water only exposure scenario but exceed the limit for full garden scenario. 

The limit was exceeded at both the 10-m and 100-m locations downgradient of the 

trenches. 

5.2 UNCERTAINTIES IN PERFORMANCE ASSESSMENT ANALYSIS 

Simulated concentrations of radionuclides (tritium and 14C) predicted In this study for the deep vertical pathway have many Inherent uncertainties that need to be con

sidered. These uncertainties can be categorized Into two basic areas: 1) the area of 

ground-water movement within the burial till medium and In the underlying lacustrine 

unit and 2) the area related to the release and transport of radionuclides from the 

waste inventory. Discussion of the uncertainties in these two areas is summarized 

below.

5.1
TAE.1 .Equivalent Doses from Modeled Peak Concentrations for Tritium and 14C

Tfitium Carbon-14

Downgradient 

Distance ,(m!-

i%3

North Trenches

South Trenches

10 

100 

10 

100

Thm Of 

Peak Anival 

310 

370

2,170 

2,590

Pe* 

Concentration 

4 

0.046

7.4 

0.086

Estimated Dose jffrem•_. 

DW Whole 

1.6E-4 3.6E-4 

1.9E-7 4.1E-6

3.1E-4 6.6E-4 

3.6E-6 7.6E-6

Pea 

Concentration 

1,660 

418

11,680 

2,940

Estimated Dose 

DW, Whole 

MOnly

223 

0.6

68..1 

17.1

16.6 478.9 

4.1 120.5
5.2.1 Ground-Water Movement

5.2.1.1 Burial Till Medium 

The flow system at the West Valley site within the burial till medium is charac

tedized as having two Interrelated hydrogeologic units: 1) a shallow fractured, weathered till within the top I to 2 m, and 2) a deeper unweathered till. The gradation between the two units Is typically fairly rapid over a meter or two where the level of 

fracturing and degree of weathering decreases with depth. 

In the shallow fractured, weathered system, the conceptual model of the site Indicates that flow is generally lateral away from the burial area towards nearby streams. However, little physical evidence is available at the site to Indicate what the 

degree of this migration can be under a variety of trench conditions. Modeling by Prudic (1986) would seem to support that the fractures and weathering have 

enhanced the hydraulic properties of the shallow till by a factor ol 10. Prudic also 

provided some simulation results that would I~ndicate that even under conditions where 

the trenches become filled with leachate that trench water would not migrate all the 

way to nearby streams. These model results showed that water originating from the 

trench would migrate laterally some distance before eventually migrating downward 

into the underlying unweathered till. Uttie direct evidence has been observed to refute 

this position other than the experience of kerosene migration at the nearby FDA. This evidence would seem to suggest that lateral migration through this shallow till unit can 

be rapid and far greater than could be estirhated using the results of the Prudic work. 

However, other factors related to the fluid properties (i.e., kerosene) could aid in 

explaining the discrepancies. 

Within the deeper till, the conceptual model Indicates that ground water moves 

very slowly (a few centimeters per year) In a vertical direction to an underlying lacustrine unit. This Is substantiated by the combination of measurement of hydraulic head and laboratory testing of till cores. However, the behavior of water movement in 

and around sand and silt lenses and pods found within the till matrix and the effect of 

these features on the overall flow system Is not well understood. These lenses vary in 

shape, size, and degree of saturation. Characterization efforts have suggested that 

they represented disconnected units that do not have much effect in short circuiting or 

enhancing horizontal or vertical water movement. Although the distribution and con

tinuity or connectivity of these units has not been completely verified, the matrix of the 

till Is accepted as the unit that dominates the flow system, and the impact of these lenses and pods on the water travel time and radionuclide migration through the till Is 

minimal. 

In this analysis, we used the most conservative estimate of travel time through the till [i.e., 300 years multiplied by a retardation factor of 7 (2100 years)] as the basis for 

the transport analysis. With this travel time estimate, predicted 14C concentrations

5.3
offsite exceed regulatory limits. To evaluate the sensitivity of this parameter on 

predicted concentrations, we examine the effect of the range of travel times proposed 

by Prudic (1986), 2100 to 16,100 years. Results of this evaluation at 10 m down

gradient of the north trenches, summarized In Figure 5.1, indicate the overall sensitivity 

of this parameter. For the longest travel time estimates, predicted concentrations are 

reduced by a factor of about 5.5 from the effect of increased decay. This would reduce 

the predicted concentrations from the north trenches well below regulatory limits but 

would do little to reduce predicted concentrations from the south trenches below the 

same limits. 

5.2.1.2 Underling Lacustrine Unit 

The lacustrine, unit below the burial till medium is characterized as being a sandy 

unit that increases in slit content with depth. The base of the unit has been found to 

contained varved clays. Because the downward water flux through the till is far less 

than the water-transmitting capability of the lacustrine unit, upper parts of the units are 

partially saturated. Based on limited borehole data, only the bottom 1 to 2 m of the unit 

appear to be saturated. 

In the analysis done for this study, the delay in water movement and radionuclide 

transport through the partially saturated upper part of the lacustrine unit was not con

sidered. To date, the flow system of the lacustrine unit is not well understood. Within 

the upper parts of the lacustrine, the sands are not entirely unsaturated. Silty parts of 

the unit have been found to be saturated. However, no laboratory measurements 

;. 1500.00 

2 100000 

0 =.., 

U 

o 0 500.00 

0 

a. 0 .00 - "- i rrT1, , ,, , , , *., , ,,,, ,, , 1" , 1 111"1" I I . . "11. 

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 

Till Travel Time, in Years 

FIGUE-5.L1. Sensitivity of Predicted Peak 14C Concentrations to Changes in the Till 

Travel Time

5.4
have been performed to Indicate what the actual range of hydraulic properties (i.e., saturated and unsaturated hydraulic conductivity, storage, and porosity) might be for 

this unit. 

SIf we make an assumption that the water travel time through the unsaturated part of the lacustrine unit can be approximated with a unit gradient approach, the travel 

time can be estimated with the following equation: 

TT= LOY/q (5.1) 

where L = length of the soil column 

0 = residual water content 

q = the assumed steady-state flux 

If we assume a soil column length of 20 m, a residual water content between 5 

and 10%, and a steady state flux equivalent to the infiltration through the till, 2.3 cm/yr, travel time through the lacustrine unit can be estimated to be between 45 and 

90 years. Based on the travel time sensitivity analysis illustrated In Figure 5.1, we 

postulate that while this additional time will have an impact in the final predicted results, the effect would not be expected to have a significant Impact on the overall 

analysis. 

Below the upper unsaturated parts of the lacustrine Is the saturated base of the 

unit. Although this part of the unit Is known to be saturated and probably composed of 

Increasingly siltler sand and varved clays, the exact nature and regional continuity of 

the sediments are not well understood. The data in these areas are limited and the 

range of hydraulic properties, like the upper part of the unit, have not been measured. 

Even the direction of movement within the unit cannot be considered very reliable 

because it Is based on three wells that are widely spaced regionally. However, pre vious analysis of rates of water movement through this unit have relied primarily on 

conservative assumptions and professional judgment. The hydraulic gradients meas

ured In the three wells that are completed were also assumed to be valid. In the final 

analysis, this part of the flow and transport, when compared to the much longer flow 

system estimated for the till, is expected to have little Impact on overall performance 

assessment results other than the dilution it offers.

5.5
5.2.2 Radionuclide Release and Transport Analysis

5.2.2.1 The Use of Leachate Concentrations in Source-Term Release 

The radionuclide release rate Is the most sensitive parameter in the overall 

performance assessment. For the 14C transport analysis, the radionuclide release rate 

to the flow system relied on measured trench water concentrations for initial condi

tions. Experimental data on solubility for these radionuclides are generally not directly 

available for the West Valley site other thari what can be inferred from direct measure

ments in trench leachate. The use of this information was based on the assumption 

that, because the trenches have historically had water in contact with the waste forms 

over a number of years, the measured concentrations of radionuclides in the trench 

leachate could possibly reflect reasonable solubility limits for the radionuclides In , . 

question. However, the validity of this assumption is not known In the context of the 

performance period. It is conceivable that these concentrations could continue to 

increase with time as waste forms continue to degrade or become compromised in the 

future. The use of the maximum measured concentration for 14C in the trench leachate 

was an attempt to add additional conservatism to the overall analysis. We acknow

ledge that if these concentrations are not valid and continue to Increase or decrease, 

the results of this performance assessment will need to be reevaluated. 

Model results change linearly with changes In solubility controlling concentration. 

For the range of measured concentrations of 14C In leachate for all trenches, the 

release concentrations range from 2100 pCI/L In trench 1 to 520,000 pCi/L In trench 8. 

Considering this range, predicted concentrations of 14C from individual trenches using 

the same release and transport scenario could potentially range over three orders of 

magnitude. 

5.2.2.2 Geochemical Behavior of Carbon-14 

In this analysis, we have assumed that all forms of 14C (organic and inorganic) 

has the same geochemical behavior. The validity of these conservative assumption Is 

unknown given the limited amount of geochemical Information on the 14C in the Inven

tory. In the case of 14C, it Is generally known that the form of carbon originates from a 

variety of sources, Including organic wastes, such as pesticides, solvents, resin mate

rials, and biological wastes, and inorganic wastes such as activated charcoal filters. 

The approach used in this study, which assumes minimal adsorption and retardation, 

in all probability presents an overly conservative case for transport. The range of geo

chemical behavior in the context these complexities Is the subject of much uncertainty 

and certainly would need to fully evaluated in a licensing situation. 

To evaluate the sensitivity of model results to changes in the affinity of 14C to 

adsorb to the site sediments,we examined the effect of retardation on model results.

5.8
Figure 5.2 presents the relationship of predicted peak 14C concentrations down

gradient of the north trenches over the measured range of distribution coefficients 

presented in Prudic (1986). This range, from 0.7 mUg to 12 mug, translates to 

retardation factors ranging from 5.25 to 73.8. The effect of Increased adsorption Is to 

delay the arrival time and increase the effect of radioactive decay. Over the range of 

measure adsorption, predicted peak 14C concentration are reduced by a factor of 

about 13. 

1500.00 

S1oo0o.00 

C 0 L 

U 500.00. U) 

0n 0 .0 0 0.00 , , , , ,,., 2.00 , , , ,,i, 4.00 , , , 6.00 , , , , , , ,,1, 8.00 , , , ,,1, 10.00 , , , 12.0C , , 

Distribution Coefficient, in ml/g 

FIUR .2 Sensitivity of Predicted Peak 14C Concentrations to Changes In the 

Distribution Coeficient

5.7
6.0 SUMMARY AND CONCLUSIONS

Results and conclusions of the hydrogeologic performance assessment of the 

commercial site near West Valley, New York are as follows: 

"Two primary ground-water pathways exists at the West Valley site. One 

pathway Is found In the top 1 to 2 m of burial medium where overflowing 

trench water can potentially migrate laterally through fractured and 

weathered till to nearby surface water drainages. Another pathway is a 

deep vertical pathway where trench leachate can migrate vertically down

ward through unweathered till and laterally within ground water to offsite 

locations In a more permeable lacustrine unit. 

" Though this and previous modeling done Indicate the lateral pathway 

through the fractured till eventually moves downward before reaching 

nearby streams, the occurrence of migration of kerosene at the nearby 

facility burial area would seem to Indicate that migration could be significant. 

To evaluate this pathway, we made conservative estimates of what the 

impact of the contaminated water overflowing from the trench might be to 

Frank's Creek. Using trench leachate concentrations and conservative 

estimates of travel time to nearby Frank's Creek, we evaluated what key 

radionuclides could be released from the site. With exception of Tritium and 

14C, the effects of decay and adsorption eliminated the majority of radio

nuclides in the Inventory. The combined effect of decay and dilution offered 

by the annual average flow of Frank's Creek reduces levels of tritium and 

14C to below regulatory concern. 

" Within the deep pathway, tritium and 14C would be the only radionuclides 

released from the West Valley site In any significant concentrations. To date, 

radionuclide migration has been limited to less than 3 m from the trenches at 

West Valley. Tritium levels are well below regulatory limits. For 14C, pre

dicted peak concentrations meet the NRC limit for a 25 mrem dose using the 

drinking-water-only exposure scenario but exceed the limit for the full gar

den scenario. The limit was exceeded at both the 1 0-m and 1 00-m loca

tions down-gradient of the trenches. 

Within the unweathered till, ground water moves very slowly (a few cm/yr) In 

a vertical direction to an underlying lacustrine unit. Although the distribution 

and continuity or connectivity of partially saturated and fully saturated sand 

and slit lenses and pods found In the till has not been completely verified, 

the matrix of the till is generally accepted as the unit which dominates the 

flow system, and the Impact of more permeable lenses and pods on the 

water movement and radionuclide migration through the till is minimal.

6.1
In this analysis, the delay in water movement and radionuclide transport 

through the partially saturated upper part of the lacustrine unit was not 

considered. To date, the flow system of the lacustrine unit is not well under

stood. The travel time through the lacustrine unit was conservatively esti

mated to be between 45 and 90 years. Based on the travel time sensitivity 

analyses, we postulate that while this additional time will have an Impact In 

the final predicted results for 14C, the effect would not be expected to have a 

significant Impact on the overall analysis. 

The exact nature and regional continuity of the saturated base of the lacust

rine sediments Is not well understood. Data In these areas are limited and 

the range of hydraulic properties, like the upper part of the unit, have not 

been measured. Even the direction of movement within the unit cannot be 

considered very reliable because it is based on three wells that are widely 

spaced regionally. However, in the final analysis, this part of the flow and 

transport, when compared to the much longer flow system estimated for the 

till, is expected to have little Impact on overall performance assessment 

results other than the dilution it offers. 

The release rate of 14C from the individual trenches Is the most sensitive 

parameter in the overall performance assessment. For this analysis, the 

release rate to the flow system Is estimated from maximum measured trench 

water concentrations and the estimated Infiltration rate. Experimental data 

on solubility for these radlonuclides are generally not directly available for 

the West Valley site other than what can be inferred from direct measure

ments in trench leachate. The use of this information was based on the 

assumption that, because the trenches have historically had water In contact 

with the waste over a number of years, the measured concentrations of radio

nuclides In the trench leachate could possibly reflect reasonable solubility 

limits for the radionuclides in question. However, the validity of this assump

tion Is not known In the context of the performance period. We acknowledge 

that if these concentrations continue to Increase or decrease that the results 

of this performance assessment would not be valid and would need to be 

reevaluated. 

Once released to the flow system, we have assumed that all forms of 14C 

(organic and inorganic) have the same geochemical behavior. The validity 

of this conservative assumption is unknown given the limited amount of geo-' 

chemical InfO'rmation on the 14C in the inventory. It is generally known that 

the 14C can originate from a variety of sources, Including organic wastes 

such as pesticides, solvents, resin materials, and biological wastes and 

Inorganic wastes such as activated charcoal filters. The approach used in 

this study, which assumes minimal adsorption and retardation, in all proba

bility presents an overly conservative case for transport. The range of

6.2
geochemical behavior in the context of these complexities is the subject of 

much uncertainty and certainly would need to fully evaluated In a licensing 

situation.

6.3
7.0 REFERENCES

10 CFR 61. 1982. U.S. Nuclear Regulatory Commission, "Ucensing Requirements for 

Land Disposal of Radioactive Waste." U.S. Code of Federal Regulations. 

Albanese, J. R., S. L. Anderson, L A. Dunne, and B. A. Weir. 1984. Glic and 

Hydrologic Research at the Western New York Nuclear Service Center West Valley. 

New-York. Annual Report August 1982 - December 1983. NUREG/CR-3782, New 

York State Geological Survey/State Museum, New York State Education Department, 

Albany, New York. 

Bergeron, M. P. 1985. Records of Wells. Test Borings. and Some Measured Geologic 

Sections Near the Western New York Nuclear Service Center. Cattaraugus County. 

New York. Open-File Report 83-682, U.S. Geological Survey, Albany, New York. 

Bergeron, M. P., W. M. Kappel, and R. M Yager. 1987. Geohydrologlc Conditions at 

the Nuclear Fuels Reprocessing Plant and Waste-Management Facilities at the 

Western New York Nuclear Service Center. Cattaraugus County. New York. Water

Resources Investigations Report 85-4145, U.S. Geological Survey, Reston, Virginia. 

Boothroyd, J. C., B. S. Timson, and R. H. Dana, Jr. 1979. Geomorphic and Erosion 

Studies at the Western New York Nuclear Service Center West Valley. New York. 

NUREG/CR-0795, NYSGS1792406, prepared by New York State Geological Survey 

for the U.S. Nuclear Regulatory Commission, Washington, D.C. 

Boothroyd, J. C., B. S. Timson, and L. A. Dunne. 1982. Geomorphic Processes and 

Evolution of Buttermilk Valley and Selected Tributaries West Valley. New York. Fluvial 

Systems and Erosion Study. Phase II. NUREG/CR-2862, prepared by New York State 

Geological Survey for the U.S. Nuclear Regulatory Commission, Washington, D.C. 

Broughton, J. G., and H. G. Stewart. 1963. "Geological and Hydrology of the Western 

New York Nuclear Service Center." Presented at the Geological Society of America 

Meetings, November 1963, New York. 

Chadwick, G. H. 1933. "Preliminary Ust of Titles and Abstracts of Papers to be Offered 

at 46th Annual Meeting." In Geological Society of America. 46th Annual Meeting. 

Chicago. IL. ProceedinMs, pp. 19, 82, 83, 84.

7.1'
Coates, D. G. 1976. "Quaternary Stratigraphy of New York and Pennsylvania." In 

Quaternary Stratigraphy of North America ed. Mahoney, W. C., Dowden, Hutchinson, 

and Ness, Inc. Stroudsberg, Pennsylvania. 

Colton, G. W. 1961. Geologic Summary of the Appalachian Basin. with Reference to 

the Subsurface Disposal of Radioactive Waste Solutions, U.S. Geological Survey 

Trace Elements Inv. Report 791, U.S. Geological Survey Open-File Report. 

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7.2
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7.4
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7.7
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NRC FORM 335 U S NUCLEAR REGULATORY COMMISSION I REPORT NUMBER 2891 IAi b NRC Add Voi. Supp, Rev. NRCM 1102, and Adnm Numb.r, I anyl 3201 3202 BIBUOGRAPHIC DATA SHEET 

ism i'st• u'ions on ft itverse NUREG/CR- 5737 

2 TITLE AND SUBTITLE I PNL-7688 

Hydrogeologic Performance Assessment Analysis of the Commercial 

Low-Level Radioactive Waste Disposal Facility near 3 DATE REPORT PUBLISHED 

West Valley, New York MONTH YEAR 

June 1991 

4 FIN OR GRANT NUMBER 

3B2485 

5 AUTHOR(S) 6 TYPE OF REPORT 

M. P. Bergeron, J. L. Smoot, H. L. Kemner, W. E. Cronin Technical 

7 PERIOD COVERED lnclus&w Dares)

8 PERFORMING ORGANIZATION - NAME AND ADDRESS (I INRC provide Diviion, Officeor R•agon US Nuclear Regulatory Commns ,on. ad maling address. l contractor provide -na and iihWg addr-sL)

Pacific Northwest Laboratory 

Richland, WA 99352

U SPONSORING ORGAflIZATION - NAME AND ADDRESS Ill NRC type Sama as above Iiconracter prouklt NRC Division. Office or Aeglon, US Nuclear Regulatory Conmi.slon 9 SPONSORING ORGANIZATION - NAME AND ADDRESS 01 NRC tye*gm " as bow llonrsgo provANRC~ikj~on, OfIkorRegon US NuclearRegulatry Camm~don 

and mniling addr*= I 

Division of Loty-Level Waste Management and Decommissioning 

Office of Nuclear Material Safety and Safeguards 

U.S. Nuclear Regulatory Commission 

Washington, DC 20555

10 SUPPLEMENTARY NOTES 

Prepared for U.S. NRC under contract .DE-AC06-76RL0 1830 

11 ABSTRACT O20 wortu 4w ml 

A hydrogeologic performance assessment of the commercial low-level waste site near West 

Valley, New York, was performed for two pathways: a shallow lateral pathway where 

trench water can potentially migrate laterally through fractured and weathered till to 

nearby streams and a deep vertical pathway where leachate can migrate downward through 

unweathered till and laterally offsite in a lacustrine unit. Along the shallow 

pathway, little physical site evidence is available to indicate what the degree of 

lateral migration can be. Past modeling showed that overflowing trench water would 

nigrate laterally some distance before migrating downward into the unweathered till. 

If water did reach a nearby stream, calculations show that decay, adsorption, and 

stream dilution would reduce leachate concentration to acceptable levels. Within the 

Jeep pathway, tritium and carbon-14 were the only radionuclides released in any 

significant concentration. Predicted tritium levels are well below regulatory limits; 

7owever, predicted peak I C concentrations, while meeting the 25 mrem/yr limit using 

the drinking-water-ol1y exposure scenario, exceed the limit for full garden scenario. 

Site information on C release rates and geochemical behavior has considerable 

incertainty and would need to be more fully evaluated in a licensing situation.

12 KEY WORDSIDESCRIPTORS (Lit weds or phrases har wil arsestearcea in locatkng merepon m 13 AVAILABILITY STATEMENT 

Performance Assessment unlimited 

Ground-Water Models 14 SECUPITY CLASSIFICATION 

Low-Level Waste Disposal ITIS Page 

Radioactive Waste unclassified 

Hydrogeology IT"i= 

West Valley LLW Site unclassified 

Radionucl ide Transport 15 NUMBER OF PAGES 

Pathway Analysis , i 

16 PRICE

NRC FORM 335 f2 891
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