An Update of Hydrologic Conditions and Distribution of 

Selected Constituents in Water, Snake River Plain 

Aquifer and Perched Groundwater Zones, Idaho 

National Laboratory, Idaho, Emphasis 2006–08

Scientific Investigations Report 2010–5197

Prepared in cooperation with the U.S. Department of Energy

U.S. Department of the Interior

U.S. Geological Survey

DOE/ID-22212
Cover: Photographs of the U.S. Geological Survey multi-level water sampling setup, 

and U.S. Geological Survey employees deploying water sampling bottles into the well 

equipped with a WestbayTM packer sampling system at the Idaho National Laboratory, 

Idaho. (Photographs courtesy of the U.S. Geological Survey Idaho National Laboratory 

Project Office, 2008.)
An Update of Hydrologic Conditions and 

Distribution of Selected Constituents in 

Water, Snake River Plain Aquifer and 

Perched Groundwater Zones, 

Idaho National Laboratory, Idaho, 

Emphasis 2006–08

By Linda C. Davis

Prepared in cooperation with the 

U.S. Department of Energy DOE/ID-22212

Scientific Investigations Report 2010–5197

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Davis, L.C., 2010, An update of hydrologic conditions and distribution of selected constituents in water, Snake River 

Plain aquifer and perched groundwater zones, Idaho National Laboratory, Idaho, emphasis 2006–08: U.S. Geological 

Survey Scientific Investigations Report 2010–5197 (DOE/ID-22212), 80 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................3

Purpose and Scope ..............................................................................................................................3

Previous Investigations........................................................................................................................3

Groundwater Monitoring Networks ...........................................................................................................7

Water-Level Monitoring Network ......................................................................................................7

Water-Quality Monitoring Network ...................................................................................................7

Waste-Disposal Sites at the Idaho National Laboratory ......................................................................19

Advanced Test Reactor Complex .....................................................................................................19

Idaho Nuclear Technology and Engineering Center.....................................................................20

Radioactive Waste Management Complex ....................................................................................20

Test Area North ...................................................................................................................................20

Central Facilities Area........................................................................................................................21

Hydrologic Conditions.................................................................................................................................21

Surface Water.....................................................................................................................................21

Groundwater........................................................................................................................................22

Perched Groundwater .......................................................................................................................23

Methods and Quality Assurance of Water Sample Analyses ..............................................................27

Guidelines for Interpreting Results of Radiochemical Analyses ................................................27

Guidelines for Interpreting Results of Chemical Analyses ..........................................................28

Selected Radiochemical and Chemical Constituents and Physical Properties of 

Water in the Snake River Plain Aquifer......................................................................................29

Tritium ..................................................................................................................................................29

Strontium-90.........................................................................................................................................32

Cesium-137...........................................................................................................................................36

Plutonium..............................................................................................................................................36

Americium-241.....................................................................................................................................37

Gross Alpha- and Beta-Particle Radioactivity...............................................................................37

Chromium .............................................................................................................................................37

Sodium..................................................................................................................................................39

Chloride.................................................................................................................................................39

Sulfate ..................................................................................................................................................44

Nitrate (as N) ......................................................................................................................................47

Fluoride.................................................................................................................................................53

Trace Elements....................................................................................................................................53

Volatile Organic Compounds.............................................................................................................53

Total Organic Carbon..........................................................................................................................57

Specific Conductance, Temperature, and pH................................................................................57
iv

Contents—Continued

Selected Radiochemical and Chemical Constituents and Physical Properties of 

Water in Perched Groundwater...................................................................................................59

Advanced Test Reactor Complex .....................................................................................................59

Tritium .........................................................................................................................................59

Strontium-90................................................................................................................................63

Gamma Spectrometry ...............................................................................................................63

Chromium ....................................................................................................................................65

Sodium.........................................................................................................................................65

Chloride........................................................................................................................................65

Sulfate .........................................................................................................................................65

Idaho Nuclear Technology and Engineering Center.....................................................................69

Well PW 4....................................................................................................................................69

Well USGS 50..............................................................................................................................69

Radioactive Waste Management Complex ....................................................................................69

Summary........................................................................................................................................................71

Acknowledgments.......................................................................................................................................74

References Cited..........................................................................................................................................74

Figures

Figure 1. Map showing location of the Idaho National Laboratory, surface-water gaging 

stations, and selected facilities, Idaho ................................................... 4

Figure 2. Map showing location of wells in the U.S. Geological Survey aquifer water-level 

monitoring network at and near the Idaho National Laboratory (INL), Idaho, and 

frequency of water-level measurements, as of December 2008 ..................... 8

Figure 3. Map showing location of wells in the U.S. Geological Survey aquifer water-level 

monitoring network at the Advanced Test Reactor Complex (ATRC), Idaho 

Nuclear Technology and Engineering Center (INTEC), and Radioactive Waste 

Management Complex (RWMC), Idaho National Laboratory (INL), Idaho, and 

frequency of water-level measurements, as of December 2008 ..................... 9

Figure 4. Map showing location of wells in the U.S. Geological Survey perched 

groundwater-level monitoring network at the Advanced Test Reactor Complex 

(ATRC), Idaho Nuclear Technology and Engineering Center (INTEC), and 

Radioactive Waste Management Complex (RWMC), Idaho National 

Laboratory (INL), Idaho, and frequency of water-level measurements, 

as of December 2008 ........................................................................ 10

Figure 5. Map showing location of wells in the U.S. Geological Survey aquifer 

water-quality monitoring network, Idaho National Laboratory (INL) and vicinity, 

Idaho, and frequency of water-sample collections, as of December 2008 ......... 11

Figure 6. Map showing location of wells in the U.S. Geological Survey aquifer 

water-quality monitoring network at the Advanced Test Reactor Complex 

(ATRC), Idaho Nuclear Technology and Engineering Center (INTEC), and 

Radioactive Waste Management Complex (RWMC), Idaho National Laboratory 

(INL), Idaho, and frequency of water-sample collections, as of December 2008 ... 12
v

Figures—Continued

Figure 7. Map showing location of wells in the U.S. Geological Survey perched 

groundwater-quality monitoring network at the Advanced Test Reactor 

Complex (ATRC), Idaho Nuclear Technology and Engineering Center (INTEC), 

and Radioactive Waste Management Complex (RWMC), Idaho National 

Laboratory (INL), Idaho, and frequency of water-sample collections, 

as of December 2008 ........................................................................ 13

Figure 8. Graphs showing streamflow at gaging stations along the Big Lost River ............ 22

Figure 9. Map showing altitude of the water table in the Snake River Plain aquifer at 

and near the Idaho National Laboratory, Idaho, March–May 2008 .................. 24

Figure 10. Map showing generalized rise or decline in groundwater levels in the Snake 

River Plain aquifer at and near Idaho National Laboratory (INL), Idaho, 

March–May 2005 to March–May 2008 ................................................... 25

Figure 11. Hydrographs showing water levels in four wells (USGS 12, 17, 20, 23) in the 

central part of the Idaho National Laboratory, Idaho, 1952–2008 ..................... 26

Figure 12. Map showing distribution of tritium in water from wells at and near the 

Advanced Test Reactor Complex, Idaho Nuclear Technology and Engineering 

Center, Central Facilities Area, and Radioactive Waste Management Complex 

at the Idaho National Laboratory, Idaho, April or October 2008........................ 30

Figure 13. Graphs showing tritium concentrations in water from six wells at and near the 

Central Facilities Areas (CFA) and Idaho Nuclear Technology and Engineering 

Center (INTEC), 1980–2008.................................................................. 31

Figure 14. Map showing distribution of strontium-90 in water from wells at and near the 

Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and 

Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive 

Waste Management Complex (RWMC), Idaho National Laboratory (INL), Idaho, 

April and October 2008 ..................................................................... 34

Figure 15. Graphs showing strontium-90 concentrations in water from seven wells at 

and near the Idaho Nuclear Technology and Engineering Center (INTEC), 

1980–2008 .................................................................................... 35

Figure 16. Graphs showing vertical distribution of dissolved chromium in water from 

six wells equipped with multi-level WestbayTM packer sampling systems, 

2006–08 ....................................................................................... 38

Figure 17. Graphs showing dissolved sodium concentrations in water from seven wells at 

and near the Idaho Nuclear Technology and Engineering Center (INTEC), 

1980–2008 .................................................................................... 40

Figure 18. Graphs showing vertical distribution of dissolved sodium in water from six wells 

equipped with multi-level WestbayTM packer sampling systems, 2006–08 ......... 41

Figure 19. Map showing distribution of chloride in water from wells at and near the 

Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and 

Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive 

Waste Management Complex (RWMC), Idaho National Laboratory (INL), 

Idaho, April or October 2008 ............................................................... 42

Figure 20. Graphs showing dissolved chloride concentrations in water from seven wells 

at and near the Idaho Nuclear Technology and Engineering Center (INTEC), 

1980–2008 .................................................................................... 43
vi

Figures—Continued

Figure 21. Graph and map showing amount of chloride in wastewater discharged to the 

disposal well and percolation ponds at the Idaho Nuclear Technology and 

Engineering Center (INTEC), flow direction, and the location and amount of 

chloride in water from wells USGS 37 and USGS 57, Idaho National Laboratory 

(INL), Idaho, 1971–2008 ..................................................................... 45

Figure 22. Graphs showing vertical distribution of dissolved chloride in water from 

six wells equipped with multi-level WestbayTM packer sampling systems, 

2006–08 ....................................................................................... 46

Figure 23. Graphs showing vertical distribution of dissolved sulfate in water from 

six wells equipped with multi-level WestbayTM packer sampling systems, 

2006–08 ....................................................................................... 48

Figure 24. Graphs showing concentration of nitrate (as N) in water from wells at and 

near the Idaho Nuclear Technology and Engineering Center (INTEC), 

1981–2008 .................................................................................... 49

Figure 25. Graphs showing concentration of nitrate (as N) in water from wells south of

 the Idaho Nuclear Technology and Engineering Center (INTEC), 1981–2008 ...... 50

Figure 26. Map showing distribution of nitrate (as N) in water from wells at and near the 

Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and 

Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive 

Waste Management Complex (RWMC), Idaho National Laboratory (INL), 

Idaho, April or October 2008 ............................................................... 51

Figure 27. Graphs showing vertical distribution of nitrate (as N) in water from six wells 

equipped with multi-level WestbayTM packer sampling systems, 2006–08 ......... 52

Figure 28. Graphs showing vertical distribution of fluoride in water from six wells 

equipped with multi-level WestbayTM packer sampling systems, 2006–08 ......... 54

Figure 29. Graph showing carbon tetrachloride concentrations in water from the 

Radioactive Waste Management Complex (RWMC) Production Well, 

Idaho National Laboratory (INL), Idaho, 1987–2008 .................................... 56

Figure 30. Map showing distribution of specific conductance of water from wells at 

and near the Advanced Test Reactor Complex (ATRC), Naval Reactors 

Facility (NRF), and Idaho Nuclear Technology and Engineering Center (INTEC), 

Central Facilities Area (CFA), and Radioactive Waste Management Complex 

(RWMC), Idaho National Laboratory (INL), Idaho, April or October 2008 ............ 58

Figure 31. Map showing concentrations of tritium in water from wells completed in 

deep perched groundwater, Advanced Test Reactor Complex, Idaho National 

Laboratory, Idaho, April or October 2008 ................................................ 60

Figure 32. Map showing concentrations of strontium-90 in water from wells completed 

in deep perched groundwater, Advanced Test Reactor Complex, Idaho National 

Laboratory, Idaho, April or October 2008 ................................................ 64

Figure 33. Map showing concentrations of dissolved chromium in water from wells 

completed in deep perched groundwater, Advanced Test Reactor Complex,

 Idaho National Laboratory, Idaho, April or October 2008 .............................. 68
vii

Tables

Table 1. Summary of selected previous investigations on geology, hydrology, and water 

characteristics of groundwater and perched groundwater, Idaho National 

Laboratory, Idaho, 1961–2010 ............................................................ 5

Table 2. Construction of wells in the U.S. Geological Survey aquifer water-quality 

monitoring network and water sample-collection method, eastern Snake River 

Plain aquifer, Idaho National Laboratory, Idaho, as of December 2008 ............... 14

Table 3. Construction of wells in the U.S. Geological Survey perched groundwaterquality monitoring network and water sample-collection method at the 

Advanced Test Reactor Complex, Idaho Nuclear Technology and Engineering 

Center, and Radioactive Waste Management Complex, Idaho National 

Laboratory, Idaho, as of December 2008 ................................................ 18

Table 4. Average annual streamflow at U.S. Geological Survey streamflow-gaging 

stations along the Big Lost River, Idaho, water years 2006–08 ........................ 21

Table 5. Tritium concentrations in water sampled at multiple depths in six wells 

equipped with multi-level WestbayTM packer sampling systems, 2006–08 ......... 33

Table 6. Trace elements disposed during various periods, number of wells sampled, and 

range of concentrations detected, Idaho National Laboratory, Idaho, 2006–08 ... 55

Table 7. Concentrations of tritium, strontium-90, and cesium-137 in perched 

groundwater from selected wells, Advanced Test Reactor Complex, Idaho 

National Laboratory, Idaho, 2006–08 ...................................................... 62

Table 8. Concentrations of selected dissolved ions in perched groundwater from 

selected wells, Advanced Test Reactor Complex, Idaho National Laboratory, 

Idaho, 2006–08 .............................................................................. 66

Table 9. Concentrations of tritium, strontium-90, cesium-137, selected transuranic 

elements, and dissolved chloride in perched groundwater from well USGS 92, 

Radioactive Waste Management Complex, Idaho National Laboratory, Idaho, 

2006–08 ....................................................................................... 70

Table 10. Concentrations of selected volatile organic compounds in perched 

groundwater from well USGS 92, Radioactive Waste Management Complex, 

Idaho National Laboratory, Idaho, April 23, 2007 ....................................... 71
viii

Conversion Factors, Datums, and Abbreviations and 

Acronyms

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Area

acre 0.4047 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

million gallons (Mgal) 3,785 cubic meter (m3)

Flow rate

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per month (gal/mo) 3.785 liter per month (L/mo) 

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

pound per year (lb/yr) 0.4536 kilogram per year (kg/yr) 

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Transmissivity*

foot squared per day (ft2/d) 0.09290 Meter squared per day (m2/d)

SI to Inch/Pound

Multiply By To obtain

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

Radioactivity

picocurie per liter (pCi/L) 0.037 Becquerel per liter (Bq/L)
ix

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Concentrations of radiochemical constituents in water are given in picocuries per liter (pCi/L).

*Transmissivity: The standard unit is cubic foot per day per square foot times foot of aquifer 

thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot squared per day 

(ft2/d), is used for convenience.

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Altitude, as used in this report, refers to distance above the vertical datum.

Abbreviations and Acronyms

Abbreviation or 

Acronym Definition

ATRC Advanced Test Reactor Complex (formerly RTC, Reactor Technology Complex, and TRA, 

Test Reactors Facility)

CFA Central Facilities Area

DOE Department of Energy

ICPP Idaho Chemical Processing Plant

INEL Idaho National Engineering Laboratory (1974–97)

INEEL Idaho National Engineering and Environmental Laboratory (1997–2005)

INL Idaho National Laboratory

INTEC Idaho Nuclear Technology and Engineering Center

LRL laboratory reporting level

LT-MDL long-term method detection level

MCL maximum contaminant level

MFC Materials and Fuels Complex

MRL minimum reporting level

NRF Naval Reactors Facility

NRTS National Reactor Testing Station (1949–74)

NWIS National Water Information System

NWQL National Water Quality Laboratory (USGS)

PBF Power Burst Facility

RESL Radiological and Environmental Sciences Laboratory (DOE)

RWMC Radioactive Waste Management Complex

RWMC PROD RWMC production well

s sample standard deviation

SDA Subsurface Disposal Area

TAN Test Area North

TSF Technical Support Facility

TOC total organic carbon

USGS U.S. Geological Survey

VOC volatile organic compound
x

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Abstract

Since 1952, radiochemical and chemical wastewater 

discharged to infiltration ponds (also called percolation 

ponds), evaporation ponds, and disposal wells at the Idaho 

National Laboratory (INL) has affected water quality in the 

eastern Snake River Plain aquifer and perched groundwater 

zones underlying the INL. The U.S. Geological Survey, in 

cooperation with the U.S. Department of Energy, maintains 

groundwater monitoring networks at the INL to determine 

hydrologic trends, and to delineate the movement of 

radiochemical and chemical wastes in the aquifer and in 

perched groundwater zones. This report presents an analysis 

of water-level and water-quality data collected from aquifer 

and perched groundwater wells in the USGS groundwater 

monitoring networks during 2006–08. 

Water in the Snake River Plain aquifer primarily moves 

through fractures and interflow zones in basalt, generally 

flows southwestward, and eventually discharges at springs 

along the Snake River. The aquifer primarily is recharged 

from infiltration of irrigation water, infiltration of streamflow, 

groundwater inflow from adjoining mountain drainage basins, 

and infiltration of precipitation. 

From March–May 2005 to March–May 2008, water 

levels in wells generally remained constant or rose slightly in 

the southwestern corner of the INL. Water levels declined in 

the central and northern parts of the INL. The declines ranged 

from about 1 to 3 feet in the central part of the INL, to as 

much as 9 feet in the northern part of the INL. Water levels in 

perched groundwater wells around the Advanced Test Reactor 

Complex (ATRC) also declined. 

Detectable concentrations of radiochemical constituents 

in water samples from wells in the Snake River Plain aquifer 

at the INL generally decreased or remained constant during 

2006–08. Decreases in concentrations were attributed to 

decreased rates of radioactive-waste disposal, radioactive 

decay, changes in waste-disposal methods, and dilution from 

recharge and underflow. In April or October 2008, reportable 

concentrations of tritium in groundwater ranged from 810±70 

to 8,570±190 picocuries per liter (pCi/L), and the tritium 

plume extended south-southwestward in the general direction 

of groundwater flow. Tritium concentrations in water from 

wells completed in shallow perched groundwater at the ATRC 

were less than the reporting levels. Tritium concentrations 

in deep perched groundwater exceeded the reporting level in 

11 wells during at least one sampling event during 2006–08 

at the ATRC. Tritium concentrations from one or more zones 

in each well were reportable in water samples collected 

at various depths in six wells equipped with multi-level 

WestbayTM packer sampling systems. 

Concentrations of strontium-90 in water from 24 of 

52 aquifer wells sampled during April or October 2008 

exceeded the reporting level. Concentrations ranged from 

2.2±0.7 to 32.7±1.2 pCi/L. Strontium-90 has not been 

detected within the eastern Snake River Plain aquifer 

beneath the ATRC partly because of the exclusive use of 

waste‐disposal ponds and lined evaporation ponds rather than 

using the disposal well for radioactive-wastewater disposal at 

ATRC. At the ATRC, the strontium-90 concentration in water 

from one well completed in shallow perched groundwater 

was less than the reporting level. During at least one sampling 

event during 2006–08, concentrations of strontium-90 in water 

from nine wells completed in deep perched groundwater at 

the ATRC were greater than reporting levels. Concentrations 

ranged from 2.1±0.7 to 70.5±1.8 pCi/L. At the Idaho Nuclear 

Technology and Engineering Center (INTEC), the reporting 

level was exceeded in water from two wells completed in 

deep perched groundwater. During 2006–08, concentrations 

of cesium-137, plutonium-238, and plutonium-239, 

-240 (undivided), and americium-241 were less than the 

reporting level in water samples from all wells and all zones in 

wells equipped with multi-level WestbayTM packer sampling 

systems at the INL. 

An Update of Hydrologic Conditions and Distribution of 

Selected Constituents in Water, Snake River Plain 

Aquifer and Perched Groundwater Zones, Idaho 

National Laboratory, Idaho, Emphasis 2006–08

By Linda C. Davis
2 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

The concentration of chromium in water from one well 

south of the ATRC steadily decreased from 2006 to 2008 and 

was 93 micrograms per liter (μg/L) in 2008, just less than 

the maximum contaminant level (MCL). Concentrations in 

water samples from other wells ranged from 1.2 to 28.3 μg/L. 

During 2006–08, chromium was detected in one well 

completed in shallow perched groundwater at a concentration 

of 3 μg/L. Dissolved chromium was detected in water from 

14 wells completed in deep perched groundwater at the ATRC 

during 2006–08. 

Concentrations of sodium in water from wells south of 

the INTEC during 2006–08 generally were equal to or less 

than sodium concentrations detected in October 2005, with 

the exception of concentrations in water from well USGS 47 

which was slightly higher in 2008 than in 2005. In October 

2008, sodium concentrations in water from two wells near 

the Radioactive Waste Management Complex (RWMC) were 

45 and 26 milligrams per liter (mg/L), slightly higher than 

the October 2005 concentrations. During 2006–08, analyses 

were not made for dissolved sodium concentrations in shallow 

perched groundwater at the ATRC. During April or October 

2008, dissolved sodium concentrations in water from 16 wells 

completed in deep perched groundwater ranged from 6 to 

23 mg/L; concentration in water from one well was 476 mg/L. 

The vertical distribution of sodium concentrations in wells 

equipped with WestbayTM systems were fairly consistent with 

depth, with the exception of sodium concentrations in water 

from well USGS 132, which were much higher (26–30 mg/L) 

in the uppermost zone than in the deeper zones (9–12 mg/L).

Chloride concentrations in water from wells near the 

INTEC generally decreased since the late 1990s. During 

2006–08, concentrations in most wells either generally were 

constant or increased slightly. Trends in concentrations in 

water from wells downgradient from the percolation ponds 

correlated with discharge rates into the ponds when travel 

time was considered. During 2008, chloride concentrations in 

water from wells USGS 88 and 89 at the RWMC were 91 and 

41 mg/L. Concentrations of chloride in all other wells near the 

RWMC ranged from 11 to 25 mg/L. In 2008, concentrations 

in water from all wells at or near the ATRC ranged between 

10 and 18 mg/L. During April 2008, dissolved chloride 

concentrations in shallow perched groundwater near the ATRC 

ranged from 11 to 13 mg/L; concentrations in deep perched 

groundwater during April or October 2008 ranged from 4 to 

43 mg/L. 

In 2008, sulfate concentrations ranged from 40 to 

157 mg/L in water samples from nine aquifer wells in the 

south-central part of the INL, which exceeds the 40-mg/L 

background concentration of sulfate. The greater-thanbackground concentrations of sulfate in water from these 

wells probably resulted from sulfate disposal at the ATRC 

infiltration ponds. In October and April 2008, sulfate 

concentrations in water samples from two wells near the 

RWMC were greater than background levels and could have 

resulted from the well construction and (or) waste disposal 

at the RWMC. During 2007–08, sulfate concentrations from 

three wells southwest of the INTEC were 45, 47, and 46 mg/L. 

The maximum dissolved sulfate concentration in shallow 

perched groundwater near the ATRC was 399 mg/L in well 

CWP 1 in November 2006. During April–October 2008, the 

maximum concentration of dissolved sulfate in deep perched 

groundwater was 1,477 mg/L in well USGS 68, which is 

located west of the chemical-waste pond. Concentrations of 

sulfate in two wells completed in deep perched groundwater 

near the INTEC were 36 and 39 mg/L. Overall the vertical 

distribution of sulfate in water from wells equipped with 

WestbayTM systems generally was consistent in most zones in 

wells during 2006–08.

The regional background concentration for nitrate (as N) 

is about 1 mg/L. In October 2008, concentrations of nitrate 

(as N) in water from most wells at and near the INTEC 

exceeded the background concentration and ranged from 2.2 

to 5.97 mg/L. Near the ATRC, the concentration of nitrate 

(as N) in water from well USGS 65 was 1.5 mg/L. In 2008, 

concentrations of nitrate (as N) in water from wells USGS 

88, 89, and 119 were 0.9, 1.7, and 1.4 mg/L, respectively. All 

concentrations measured in aquifer wells at the INL in 2008 

were less than the MCL for drinking water of 10 mg/L as N, 

with the exception of a concentration of 18.9 mg/L from well 

USGS 50 at the INTEC.

During April or October 2008, fluoride concentrations 

in water samples from four aquifer wells ranged from 0.2 to 

0.3 mg/L. These concentrations are similar to the background 

concentrations, which indicate that wastewater disposal has 

not appreciably affected fluoride concentrations in the Snake 

River Plain aquifer near the INTEC.

During 2006–08, water samples from 30 aquifer wells 

were collected and analyzed for volatile organic compounds 

(VOCs). Twelve VOCs were detected. Concentrations of from 

1 to 10 VOCs were detected in water samples from 11 wells. 

Primary VOCs detected included carbon tetrachloride, 

trichloromethane, 1,1-dichloroethane, 1,1,1-trichloroethane, 

trichloroethylene, and tetrachloroethylene. 

During April or October 2008, water samples from 

50 wells completed in the Snake River Plain aquifer at the 

INL were analyzed for total organic carbon (TOC); detected 

concentrations ranged from 0.43 to 1.9 mg/L. 

Well USGS 92 is in the Subsurface Disposal Area (SDA) 

at the RWMC and is completed in a sedimentary interbed 

214 ft below land surface. Perched groundwater in this well 

has moved through overlying sediments and basalt, and may 

contain waste constituents leached from radiochemical and 

organic chemical wastes buried in the SDA. During 2006–08, 

tritium concentrations in water samples from well USGS 92 

exceeded the reporting level and ranged from 490±110 pCi/L 

in April 2006 to 300±80 pCi/L in June 2008. Water from well 
Introduction 3

USGS 92 was sampled for VOCs in April 2007, and 9 VOCs 

were detected which was a decrease from the 15 compounds 

detected in 2002–03. Additionally, all VOC concentrations 

detected in 2007 were significantly lower than those detected 

during 2002–03, with the exception of toluene, which was not 

detected in 2002–03. 

Introduction

The Idaho National Laboratory (INL), operated by 

the U.S. Department of Energy (DOE), encompasses about 

890 mi2 of the eastern Snake River Plain in southeastern 

Idaho (fig. 1). Names formerly used for this site, from 

earliest to most recent, were National Reactor Testing Station 

(NRTS, 1949–1974), Idaho National Engineering Laboratory 

(INEL, 1974–1997), and Idaho National Engineering and 

Environmental Laboratory (INEEL, 1997–2005). The 

INL facilities are used in the development of peacetime 

atomic-energy applications, nuclear safety research, defense 

programs, environmental research, and advanced energy 

concepts. 

Radiochemical and chemical wastewater generated at 

these facilities has been discharged to onsite infiltration ponds, 

evaporation ponds, disposal wells, or a combination thereof 

since 1952. Wastewater disposal has resulted in detectable 

concentrations of several waste constituents in water from 

the eastern Snake River Plain aquifer underlying the INL. 

Disposal of wastewater to infiltration ponds and infiltration of 

surface water at waste-burial sites resulted in the formation 

of perched groundwater in basalts and in sedimentary 

interbeds that overlie the Snake River Plain aquifer. Perched 

groundwater is an integral part of the pathway for wasteconstituent migration to the aquifer.

The DOE requires information about the mobility of 

dilute radiochemical- and chemical-waste constituents in 

the Snake River Plain aquifer and in perched groundwater 

above the aquifer to assess the impact of INL facility 

operations on water quality, and to aid in remediation 

activities. Waste‐constituent mobility is determined, in 

part, by (1) the rate and direction of groundwater flow, 

(2) the locations, quantities, and methods of waste disposal, 

(3) waste‐constituent chemistry, and (4) the geochemical 

processes taking place in the aquifer. This study was 

conducted by the U.S. Geological Survey (USGS) in 

cooperation with the DOE Idaho Operations Office.

Purpose and Scope

In 1949, the U.S. Atomic Energy Commission, which 

later became the DOE, requested that the USGS describe 

the water resources of the area now known as the INL. 

The purpose of the resulting study was to characterize 

these resources before the development of nuclear-reactor 

testing facilities. Since that time, the USGS has maintained 

water‐level and water-quality monitoring networks at the INL 

to determine hydrologic trends and to delineate the movement 

of radiochemical and chemical wastes in the Snake River Plain 

aquifer and in perched groundwater.

Most of the wells in the USGS monitoring network were 

constructed as open boreholes and are open to the aquifer 

through their entire depth below the water table. Beginning 

in 2005, the USGS and the INL contractor collaborated to 

instrument two wells (Middle 2050A and Middle 2051) with 

multi-level WestbayTM packer sampling systems to collect 

water samples for analysis in order to describe the vertical 

distribution of constituents in the eastern Snake River Plain 

aquifer. The USGS expanded the program in 2006 and 2007 to 

include four additional wells (USGS 103, 132, 133, and 134). 

Various data were collected from these multi-level sampling 

systems during 2005–08 (Bartholomay and Twining, 2010). 

This report presents an analysis of water-level and waterquality data collected from wells in the USGS groundwater 

monitoring networks during 2006–08 as part of the continuing 

hydrogeologic investigations conducted by the USGS at the 

INL. This report describes the distribution and concentration 

of selected radiochemical and chemical constituents in 

groundwater and perched groundwater at the INL, the vertical 

distribution of selected constituents from samples collected 

with multi-level WestbayTM systems, and the changes in the 

regional water-levels since 2005. The report also summarizes 

the history of waste disposal at the Advanced Test Reactor 

Complex (ATRC; formerly known as the Test Reactor Area, 

TRA; and the Reactor Technology Complex, RTC), Idaho 

Nuclear Technology and Engineering Center (INTEC; 

formerly known as the Idaho Chemical Processing Plant, 

ICPP), Radioactive Waste Management Complex (RWMC), 

Test Area North (TAN), and the Central Facilities Area (CFA). 

Perched groundwater has been detected beneath infiltration 

ponds and ditches at other facilities at the INL in the past, but 

is not discussed in this report. 

Previous Investigations

Hydrologic conditions and the distribution of selected 

wastewater constituents in groundwater and perched 

groundwater are discussed in a series of reports describing 

the INL. Table 1 summarizes selected previous investigations 

on the geology, hydrology, and water characteristics at and 

near the INL, and periods included in those investigations. 

Numerous previous investigations on the hydrology and 

geology at the INL have been done by INL contractors, 

state agencies, and the USGS. Copies of published reports 

for previous USGS studies at the INL are available from 

the USGS INL Project Office or the USGS Publications 

Warehouse Web site at http://pubs.er.usgs.gov/ (U.S. 

Geological Survey, 2010a).
4 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Figure 1. Location of the Idaho National Laboratory, surface-water gaging stations, and selected facilities, Idaho.

tac10-0506_fig01

Mud

Lake

Big

Lost

River

Little

Lost

River

Birch

Creek

Mackay

Reservoir

Camas

Creek

Big 

Southern

Butte

East

Butte

Middle Butte

BITTERROOT

RANGE

LEMHI RANGE

LOST RIVER RANGE

PIONEER MOUNTAINS

WHITE KNOB

MOUNTAINS

Atomic

City

Howe

Arco

Mud

Lake

Terreton

Mackay

26

93

20

26

33

22

28

20

93

TAN

ATRC

INTEC

CFA

NRF

RWMC

MFC

PBF

Big Lost River

playas and sinks

Birch Creek

sinks

SPREADING

AREAS

13132565

Big Lost River above

Big Lost River sinks 

near Howe, ID

13132520

Big Lost River below INL 

diversion near Arco, ID

13132513

INL diversion at head near Arco, ID

13132500

Big Lost River near Arco, ID

13127000

Big Lost River below 

Mackay Reservoir, 

near Mackay, ID

13132513

MFC

CFA

INTEC

NRF

RWMC

TAN

ATRC

PBF

Selected facilities at the Idaho National Laboratory

 Materials and Fuels Complex 

 Central Facilities Area

 Idaho Nuclear Technology and Engineering Center

 Naval Reactors Facility

 Power Burst Facility

 Radioactive Waste Management Complex

 Advanced Test Reactor Complex—formerly known as

 Reactor Technology Complex (RTC) and Test Reactor

 Area (TRA)

 Test Area North

Boundary of Idaho National Laboratory

USGS gaging station and number

EXPLANATION

IDAHO

BOISE

Eastern 

Snake River

Idaho Plain

National

Laboratory

Twin

Falls

Pocatello

Idaho

Falls

113° 45’

44°

45’

43°30’

113°30’ 15’ 30’ 112°15’

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

0

0 10

10

20 Kilometers

20 Miles
Introduction 5

Table 1. Summary of selected previous investigations on geology, hydrology, and water characteristics of groundwater and perched 

groundwater, Idaho National Laboratory, Idaho, 1961–2010.

[Abbreviations: NRTS, National Reactor Testing Station; RWMC, Radioactive Waste Management Complex; INEL, Idaho National Engineering Laboratory; 

INEEL, Idaho National Engineering and Environmental Laboratory; INL, Idaho National Laboratory; TRA, Test Reactor Area; ICPP, Idaho Chemical 

Processing Plant]

Reference Investigation

period Summary

Groundwater

Jones (1961) Hydrology of waste disposal at the NRTS, Idaho.

Olmsted (1962) Chemical and physical character of groundwater at the NRTS, Idaho.

Morris and others (1963, 1964, 1965) Hydrology of waste disposal at the NRTS, Idaho.

Barraclough and others (1967a) 1965 Hydrology of the NRTS, Idaho.

Barraclough and others (1967b) 1966 Hydrology of the NRTS, Idaho.

Nace and others (1975) Generalized geologic framework of the NRTS, Idaho.

Robertson and others (1974) Effects of waste disposal on the geochemistry of groundwater at the NRTS, 

Idaho.

Barraclough and others (1976) Hydrology of the solid waste burial ground (now the RWMC).

Barracough and Jenson (1976) 1971–73 Hydrologic data for the Idaho INEL, Idaho.

Barraclough and others (1981) 1974–78 Hydrologic conditions for the INEL, Idaho.

Lewis and Jensen (1985) 1979–81 Hydrologic conditions for the INEL, Idaho.

Pittman and others (1988) 1982–85 Hydrologic conditions for the INEL, Idaho.

Orr and Cecil (1991) 1986–88 Hydrologic conditions and distribution of selected chemical constituents in 

water at the INEL, Idaho.

Bartholomay and others (1995) 1989–91 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in water, INEL, Idaho.

Bartholomay and others (1997) 1992–95 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in water, INEL, Idaho.

Bartholomay and others (2000) 1996–98 Hydrologic conditions and distribution of selected constituents in water, 

INEEL, Idaho.

Davis (2006b)

http://pubs.usgs.gov/sir/2006/5088/

1999–2001 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in water, INL, Idaho.

Ackerman and others (2006)

http://pubs.usgs.gov/sir/2006/5122/

Conceptual model of groundwater flow in the eastern Snake River Plain 

aquifer, INL, with implications for contaminant transport.

Davis (2008)

http://pubs.usgs.gov/sir/2008/5089/

2002–05 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in groundwater and perched groundwater, INL, 

Idaho.

Bartholomay and Twining (2010)

http://pubs.usgs.gov/sir/2010/5116/

2006–08 Vertical distribution of selected constituents in water from wells equipped 

with WestbayTM packer sampling systems.

Perched groundwater

Barraclough and others (1967a) 1965 Extent of perched groundwater and distribution of selected wastewater 

constituents in perched groundwater at the TRA.

Barraclough and others (1967b) 1966 Extent of perched groundwater and distribution of selected wastewater 

constituents in perched groundwater at the TRA.
6 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Reference Investigation

period Summary

Perched groundwater—Continued

Robertson and others (1974) Analysis of perched groundwater and conditions related to the disposal of 

wastewater to the subsurface at the INEL.

Barraclough and Jensen (1976) Extent of perched groundwater and distribution of selected wastewater 

constituents in perched groundwater at the ATRC.

Robertson (1977) Numerical model simulating flow and transport of chemical and 

radionuclide constituents through perched groundwater at the ATRC.

Barraclough and others (1981) 1974–78 Hydrologic conditions for the INEL, Idaho.

Lewis and Jensen (1985) 1979–81 Hydrologic conditions for the INEL, Idaho.

Pittman and others (1988) 1982–85 Hydrologic conditions for the INEL, Idaho.

Hull (1989) Conceptual model that described migration pathways for wastewater and 

constituents from the radioactive-waste infiltration ponds at the TRA.

Anderson and Lewis (1989) Correlation of drill cores and geophysical logs to describe a sequence 

of basalt flows and sedimentary interbeds in the unsaturated zones 

underlying the RWMC.

Anderson (1991) Correlation of drill cores and geophysical logs to describe a sequence 

of basalt flows and sedimentary interbeds in the unsaturated zones 

underlying the RTC, and INTEC.

Ackerman (1991) Analyzed data from 43 aquifer tests conducted in 22 wells to estimate 

transmissivity of basalts and sedimentary interbeds containing perched 

groundwater beneath the TRA and INTEC.

Cecil and others (1991) 1986-88 Mechanisms for formation of perched water at the TRA, ICPP, and 

RWMC, INEL, Idaho; distribution of chemical and radiochemical 

constituents in perched groundwater at the TRA, ICPP and RWMC.

Tucker and Orr (1998) 1989–91 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in perched groundwater, INEL, Idaho.

Bartholomay (1998) 1992-95 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in perched groundwater, INEL, Idaho.

Orr (1999) Transient numerical simulation to evaluate a conceptual model of flow 

through perched water beneath wastewater infiltration ponds at the TRA.

Bartholomay and Tucker (2000) 1996-98 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in perched groundwater, INEEL, Idaho.

Davis (2006a)

http://pubs.usgs.gov/sir/2006/5236/

1999-2001 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in perched groundwater, INL, Idaho.

Davis (2008)

http://pubs.usgs.gov/sir/2008/5089/

2002-05 Hydrologic conditions and distribution of selected radiochemical and 

chemical constituents in groundwater and perched groundwater, INL, 

Idaho.

Table 1. Summary of selected previous investigations on geology, hydrology, and water characteristics of groundwater and perched 

groundwater, Idaho National Laboratory, Idaho, 1961–2010.—Continued

[Abbreviations: NRTS, National Reactor Testing Station; RWMC, Radioactive Waste Management Complex; INEL, Idaho National Engineering Laboratory; 

INEEL, Idaho National Engineering and Environmental Laboratory; INL, Idaho National Laboratory; TRA, Test Reactor Area; ICPP, Idaho Chemical 

Processing Plant]
Groundwater Monitoring Networks 7

Groundwater Monitoring Networks

The USGS maintains groundwater monitoring networks 

at the INL to characterize the occurrence, movement, and 

quality of water, and to delineate waste-constituent plumes in 

the Snake River Plain aquifer and perched groundwater zones. 

Periodic water-level and water-quality data are obtained from 

these networks. In addition, selected data are collected from 

multi-level WestbayTM packer sampling systems in order to 

describe the vertical distribution of selected constituents. Data 

from these monitoring networks are on file at the USGS INL 

Project Office and are available via the USGS National Water 

Information System (NWIS) Web site at http://waterdata.usgs.

gov/id/nwis/nwis (U.S. Geological Survey, 2010b).

Water-Level Monitoring Network

The USGS aquifer water-level monitoring network 

was designed to determine hydraulic-gradient changes that 

affect the rate and direction of groundwater and wasteconstituent movement in the Snake River Plain aquifer, to 

identify sources of recharge to the aquifer, and to measure 

the effects of recharge. During 2005–07, six wells were 

equipped with multi-level WestbayTM packer sampling 

systems that allow pressure and temperature measurements 

to be acquired at isolated depths in each of the wells. This 

multi‐level monitoring provided data used to describe the 

vertical distribution of pressure and temperature gradients 

in addition to the horizontal distribution information 

previously gathered from open boreholes. Water levels 

were monitored in 181 aquifer wells during 2006–08. Water 

levels were measured annually in 26 wells, semiannually in 

59 wells, quarterly in 78 wells, monthly in 13 wells, and are 

continuously recorded in 5 wells. Figures 2 and 3 show the 

locations of aquifer wells and the frequency of water-level 

measurements as of December 2008. 

The USGS perched groundwater-level monitoring 

network was designed so that the extent of perched 

groundwater and the volume of perched groundwater in 

storage could be estimated. Water levels in 30 wells (fig. 4) 

were monitored during 2006–08. At the ATRC, the network 

included 18 wells to monitor deep perched groundwater 

levels and 10 wells to monitor shallow perched groundwater 

levels. Shallow perched groundwater is considered to be 

water perched in surficial sediment deposits, and deep 

perched groundwater is water perched at greater depth. 

Perching mechanisms are attributed to contrasting hydraulic 

properties between sedimentary interbeds and basalts or 

between low-permeability basalt-flow interiors and overlying 

fractured basalt. At the INTEC, the network included one 

well to monitor deep perched groundwater levels around the 

INTEC disposal well. Perched groundwater at the RWMC 

was measured in one well. Well locations and frequency of 

water-level measurements as of December 2008 are shown in 

figure 4.

Water-Quality Monitoring Network

The radiochemical and chemical character of 

groundwater and perched groundwater in the Snake River 

Plain aquifer was determined from analyses of water samples 

collected as part of a comprehensive sampling program to 

identify contaminant concentrations and to define patterns 

of waste migration in the aquifer and perched zones. Water 

samples were collected from wells that penetrate the aquifer 

at various depths and with differing well completions, and 

the water samples were analyzed to identify trends in water 

quality. Numerous water samples were collected from 

groundwater and perched groundwater wells near areas of 

detailed study, such as the ATRC, INTEC, RWMC, TAN, and 

CFA. Water samples from the Naval Reactors Facility (NRF) 

were collected and analyzed as part of a separate study, and 

the results of that study are presented in series of separate 

reports (Bartholomay and others, 2001a, 2001b). Beginning 

in 2005, the USGS and the INL contractor collaborated to 

instrument two wells (Middle 2050A and Middle 2051; figs. 5

and 6) with multi-level WestbayTM packer sampling systems 

to collect water samples for analysis in order to describe the 

vertical distribution of constituents in the eastern Snake River 

Plain aquifer. The USGS expanded the program in 2006 and 

2007 to instrument four additional wells (USGS 103, 132, 133, 

and 134; figs. 5 and 6). North Wind (2006) and B.V. Twining 

and J.C. Fisher, U.S. Geological Survey, written commun., 

(2010) give detailed descriptions of the installation of each 

well. Bartholomay and Twining (2010, table 1) describe the 

water sample port depth and associated intervals sampled with 

the WestbayTM packer sampling systems. Various data were 

collected from these multi-level sampling systems during 

2005–08 (Bartholomay and Twining, 2010).

The type, frequency, and depth of groundwater 

sampling generally depend on the information needed in 

a specific area. Water samples were routinely collected 

and analyzed for concentrations of tritium, strontium-90, 

cesium-137, plutonium-238, plutonium-239, -240 (undivided), 

americium-241, gross alpha- and beta-particle radioactivity, 

chromium, sodium, chloride, sulfate, nitrate (as N), and 

volatile organic compounds, and measurements of specific 

conductance, pH, and temperature. Additionally, as part of 

the INL groundwater monitoring program adopted in 1994 

(Sehlke and Bickford, 1993), water samples from several wells 

also were analyzed for fluoride, an extensive suite of trace 

elements, and total organic carbon. A sample schedule that 

lists the constituents typically analyzed for is given in a report 

by Knobel and others (2008, appendix A). 

The location and construction of wells, and the water 

sample collection method in the aquifer water-quality 

monitoring network as of December 2008, are shown in 

figures 5 and 6, and in table 2. Well location and construction 

of wells in the USGS water-quality monitoring network 

for perched groundwater beneath INL facilities as of 

December 2008 are shown in figure 7 and table 3. All wells 

were scheduled to be sampled annually. 
8 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig02

Big Lost 

River

playas 

and 

sinks

SPREADING

AREAS

33

26

26

20

20

Mud

Lake

Big

Lost

River

Little

Lost

River

Birch

Creek

Camas

Creek

Atomic

City

Howe

Arco

Mud

Lake Terreton

Big 

Southern

Butte

East

Butte

Middle

Butte

BITTERROOT

RANGE

LEMHI RANGE

LOST RIVER RANGE

11 Q

125 Q

109 S

103 Q

108 S

105 S

129 M

14 Q

104 Q

131 M

9 M

86 Q

8 Q

RWMC

M14S S

22 Q

RWMC

M13S S RWMC

M12S S

RWMC

M11S S

127 Q

83 Q

107 S

Site 9 Q

Area 2 S

NPR Test Q

5 Q

110A S 1 R,M

2 Q

100 Q Arbor 

Test Q

101 M

6 Q

17 Q

Site 14 Q

18 Q

7 Q

PSTF Test S

No Name 1 Q 

ANP 6 S IET 1 Disp S 26 Q

27 M

31 S

32 S

4 Q

29 S

P&W 2 S

19 M

12 M

15 Q

23 Q

Site 17 M

WS INEL 1 S

98 S

99 Q

 126A Q 

126B Q

13 A

INEL 1 A Site 6 A

ANL MW 13 A

ANL-OBS-A-014 A Site 16 A

Corehole 1 Q

30A,B,C Q

28 S

21 R,M

DH 1B Q Corehole 2A Q

DH 2A Q

2nd Owsley A

ANP 9 Q

ANP 10 A

GIN 5 A

GIN 2 A

GIN 4 A

GIN 3 A

GIN 1A TAN CH2B Q

TAN 8 Q

24 R,M FET Disp 3 A

ANP 5 A 

P&W 1 A 25 R,M

P&W 3 A

ANP 7 A 

Highway 2 Q

Highway 1A,B,C Q

04N 35E 31daa1 A

04N 35E 20caa1 A

USBR Site 15 A

97 M

102 S

106 S

124 S

Cerro 

Grande Q

130 M

TAN 15 Q

TAN 18 Q

TAN 13A Q

TAN 23A Q

TAN 17 Q

TAN 19 Q

TAN 13 Q

TAN 14 Q

FIRE STATION 2 Q ANL-OBS-A-001 A

See figure 3 

See figure 3

ATRC

INTEC

RWMC

EXPLANATION

M14S S

14 Q

Frequency of measurements

A, annually; 

S, semiannually; 

M, monthly; 

Q, quarterly; 

R, well is equipped with a recorder

Well in the usgs aquifer water-level 

monitoring network and identifier

Local well identifierNumber only shows 

USGS well, other 

names are local well 

names

Inset areas for selected facilities at the Idaho National Laboratory—See figure 3.

RWMC Radioactive Waste Management Complex

ATRC Advanced Test Reactor Complex

INTEC Idaho Nuclear Technology and Engineering Center

Idaho National Laboratory boundary

113°15’ 113°00’ 45’

44°

43°30’

45’

112°30’ 112°15’

0 5 10 MILES

0 5 10 KILOMETERS

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

Figure 2. Location of wells in the U.S. Geological Survey aquifer water-level monitoring network at and near the Idaho 

National Laboratory (INL), Idaho, and frequency of water-level measurements, as of December 2008.
Groundwater Monitoring Networks 9

tac10-0506_fig03

Lincoln Boulevard

Big

Lost

River

Advanced Test

Reactor Complex

Idaho Nuclear

Technology and

Engineering Center

Radioactive

Waste

Management

Complex

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste

ponds

Cold-waste ponds

Subsurface

disposal area

Transuranic

storage

area

Spreading area

89 Q

87 Q

RWMC M1SA S

RWMC M3S S

RWMC M7S S

88 Q

117 Q

119 Q

120 M

RWMC M6S A

RWMC M4D A

118 Q

A11A31 A

33

MTR TEST M Site 19 S

65 Q

79 S

76 S

TRA

DISP S

58 Q

MIDDLE 1823 M

84 Q

39 Q

35 S 34 S

36 Q 37 S

38 S

112 Q 113 Q

85 Q

128 Q

CFA LF 2-10 Q CFA LF 3-9 S

77 S

111 S

57 Q

CFA LF 2-11 A

ICPP 1798 Q

ICPP-MON-A-167 Q

CFA 1932 S

ICPP-MON-A-166 Q

82 Q

67 S

116 Q

115 Q

20 Q

114 Q

51 S

123 S

52 S

59 S

121 S

41 S

42 S

43 S

44 S

45 S

46 S 47 S

48 S

40 Q

122 S

Percolation

ponds

EXPLANATION

ICPP 1798 Q

20 Q

Frequency of measurements

A, annually; 

S, semiannually; 

M, monthly; 

Q, quarterly; 

R, well is equipped with a recorder

Well in the USGS aquifer water-level 

monitoring network and identifier

Local well identifierNumber only shows 

USGS well, other 

names are local well 

names

Idaho 

National 

Laboratory

Map areas

112°58' 57' 56' 55' 112°54'

43°35'

34'

43°33'

113o03’

43o30’

113o02’

0

0

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

3,000 Feet

1,000 Meters

0 1,000 Meters

0 3,000 Feet

Figure 3. Location of wells in the U.S. Geological Survey aquifer water-level monitoring network 

at the Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and Engineering Center 

(INTEC), and Radioactive Waste Management Complex (RWMC), Idaho National Laboratory (INL), 

Idaho, and frequency of water-level measurements, as of December 2008.
10 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig04

Big

Lost

River

Lincoln Boulevard

Idaho Nuclear

Technology and

Engineering Center

Advanced Test Reactor Complex

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste ponds

Cold-waste ponds

Percolation ponds

PW 9 Q (D)

PW 8 Q (D)

 78 R,M (D)

 73 Q (D)

72 Q (D)

 70 Q (D)

 69 Q (D)

 68 Q (D)

 66 M (D)

 63 Q (D)

62 Q (D)

56 S (D) 55 Q (D)

TRA A 77 Q (S)

 60 Q (D)

 53 Q (D)

61 Q (D)

 50 S(D)

INTEC

DISPOSAL

WELL

 71 S (D)

EXPLANATION

CWP 9 A (S) 71 S (D)

Frequency of measurements as of December 2008—

A, annually; 

S, semiannually; 

M, monthly; 

Q, quarterly; 

R, well is equipped with a recorder

(S), well completed in shallow perched groundwater

(D), well completed in deep perched groundwater

Well in the USGS aquifer water-level 

monitoring network and identifier

Local well identifierNumber only shows 

USGS well, other 

names are local well 

names

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

0

0

3,000 Feet

1,000 Meters

43°35’

43°34’

112°58’ 112°56’

Idaho 

National 

Laboratory

Map areas

CWP 8 S (S)

CWP 6 A (S)

CWP 7 A (S)

CWP 9 A (S)

CWP 5 A (S) CWP 4 A (S)

CWP 3 S (S)

CWP 1 S (S)

CWP 2 A (S)

 54 Q (D)

 92 Q (D)

Radioactive Waste

Management Complex

Subsurface

Disposal 

Area Transuranic

Storage

Area

113°03’ 113°02’30”

43°30’

43°29’30”

0

0

3,000 Feet

1,000 Meters

Figure 4. Location of wells in the U.S. Geological Survey perched groundwater-level monitoring network at the Advanced 

Test Reactor Complex (ATRC), Idaho Nuclear Technology and Engineering Center (INTEC), and Radioactive Waste 

Management Complex (RWMC), Idaho National Laboratory (INL), Idaho, and frequency of water-level measurements, as of 

December 2008.
Groundwater Monitoring Networks 11

tac10-0506_fig05

Big 

Southern

Butte

East

Butte

Middle

Butte

BITTERROOT

RANGE

LEMHI RANGE

LOST RIVER RANGE

33

26

26

20

20

See figure 6 

See figure 6

ATRC

INTEC

RWMC

IDAHO NATIONAL 

LABORATORY BOUNDARY

Mud

Lake

Big

Lost

River

Little

Lost River

Birch

Creek

Camas

Creek

Atomic

City

Howe

Arco

Mud

Lake Terreton

Big Lost River

playas and 

sinks

SPREADING

AREAS

Atomic City Well 

11 

Crossroads

124 

125 

109 103 105 108 

14 

104 

9 

86 

8 

RWMC M14S 

22 

Highway 3 Rifle 

Range 

RWMC

M13S 

EBR 1 

RWMC

M12S RWMC M11S MIDDLE 2051 

106 

127 

131 83 

CFA 1 

CFA 2 

107 

Badging

Facility 

Site 9 

SPERT 1 Area 2 

NPR Test 

5 

Leo Rodgers 1 

110A 1 

2 

100 Arbor Test 

101 

6 

134 

17 

Site 14 

18 

7 PSTF Test 

No Name 1 

ANP 6 

ANP 9 

IET 1 Disp 

26 

27 

31 

32 

4 

29 

P&W 2 

19 

12 

15 

23 

Site 17 

Site 4 

102 

WS INEL 1 97 

98 

99 

 126A 

126B 

TAN Disposal Well

(not sampled in 2008)

133 

EXPLANATION

M14S

14

Well in the USGS aquifer water-quality 

monitoring network and identifier

Local well identifierNumber only shows 

USGS well, other 

names are local well 

names

Frequency of water-sample collections—All 

wells sampled annually except WestbayTM packer 

sampling system

Well equipped with multilevel 

WestbayTM packer sampling system

TAN Test Area North

Inset areas for selected facilities at the Idaho National Laboratory—See figure 6.

RWMC Radioactive Waste Management Complex

ATRC Advanced Test Reactor Complex

INTEC Idaho Nuclear Technology and Engineering Center

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°15’ 113°00’ 45’

44°00’

43°30’

45’

112°30’ 112°15’

0 5 10 Miles

0 5 10 Kilometers

IDAHO

BOISE

EASTERN 

SNAKE RIVER

IDAHO PLAIN

NATIONAL

LABORATORY

Twin

Falls

Pocatello

Idaho

Falls

Figure 5. Location of wells in the U.S. Geological Survey aquifer water-quality monitoring network, Idaho National 

Laboratory (INL) and vicinity, Idaho, and frequency of water-sample collections, as of December 2008.
12 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Figure 6. Location of wells in the U.S. Geological Survey aquifer water-quality monitoring network 

at the Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and Engineering Center 

(INTEC), and Radioactive Waste Management Complex (RWMC), Idaho National Laboratory (INL), 

Idaho, and frequency of water-sample collections, as of December 2008.

tac10-0506_fig06

33

Lincoln Boulevard

Transuranic

storage

area

Subsurface

disposal area

Radioactive Waste 

Management Complex

Advanced Test

Reactor Complex

Idaho Nuclear

Technology and

Engineering Center

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste

ponds

Cold-waste ponds

Percolation ponds Big

Lost

River

Spreading area

Not sampled

in 2008

89 

87 

RWMC M3S 

RWMC M7S 

RWMC

PRODUCTION

88 

117 

119 

90 

120 

132 

MTR TEST 

Site 19 

TRA 3 

TRA 4 TRA 1 

65 

79 

76 

58 

39 

35 

34 

36 

37 

38 

112 113 

85 

128 

CFA LF 2-10 

77 

111 

57 

ICPP-MON-A-166 

82 

67 

116 

115 

20 

114 

51 

123 

52 

59 

121 

CPP 2 

CPP 4 

41 

42 

43 44 

45 

46 

47 

48 

40 

84 

RWMC M1SA 

MIDDLE 2050A 

TRA

DI SP

CPP 1 

EXPLANATION

CPP 1

77

Well in the USGS aquifer water-quality 

monitoring network and identifier

Local well identifier—Number only 

shows USGS well, other names 

are local well names

Well equipped with multilevel 

WestbayTM packer sampling 

system

Frequency of water-sample collections—All 

wells sampled annually except WestbayTM packer 

sampling system

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

Idaho 

National 

Laboratory

Map areas

0 1,000 Meters

0 3,000 Feet

0

0 3,000 Feet

1,000 Meters

113 ̊03’

43 ̊30’

43 ̊29’

113 ̊02’

112°58' 57' 56' 55' 112°54'

43°35'

34'

43°33'
Groundwater Monitoring Networks 13

Figure 7. Location of wells in the U.S. Geological Survey perched groundwater-quality monitoring network at the 

Advanced Test Reactor Complex (ATRC), Idaho Nuclear Technology and Engineering Center (INTEC), and Radioactive 

Waste Management Complex (RWMC), Idaho National Laboratory (INL), Idaho, and frequency of water-sample collections, 

as of December 2008.

tac10-0506_fig07

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste ponds

Cold-waste ponds

INTEC

DISPOSAL

WELL

Idaho Nuclear

Technology and

Engineering Center

Advanced Test Reactor Complex

Percolation ponds

Tank farm

(approximately

located) Big

Lost

River

PW 9

PW 8

 78

 73

72

 70

 69

 68

 66

 63 

 62

56 55

TRA A 77

 60

 53

61

 71

PW 6 

PW 4 PW 1 

 50

EXPLANATION

CWP 1

71

Well in the USGS perched groundwater-quality 

monitoring network and identifier

Local well identifier—Number only 

shows USGS well, other names 

are local well names

Frequency of water-sample collections—All 

wells sampled annually

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

0

0

3,000 Feet

1,000 Meters

43°35’

43°34’

112°58’ 112°56’

Idaho 

National 

Laboratory

Map areas

 92

Radioactive Waste

Management Complex

Subsurface

Disposal 

Area Transuranic

Storage

Area

113°03’ 113°02’30”

43°30’

43°29’30”

0

0

3,000 Feet

1,000 Meters

Lincoln Boulevard

TRA A 13 

CWP 8

CWP 3

CWP 1

 54
14 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Table 2. Construction of wells in the U.S. Geological Survey aquifer water-quality monitoring network and water sample-collection 

method, eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, as of December 2008. .

[All wells are sampled annually except those whose sample collection method is WestbayTM. WestbayTM sample schedule is subject to change from year to year. 

Well No.: Well locations are shown in figures 5 and 6. Sample-collection method: Pump, sampled from pumping well (pumping rate in gallons per minute); Tap, 

sampled from faucet; WestbayTM, sampled with multi-level thief sampler. //, hole diameter is not required for borehole volume calculations with multi‐level thief 

samplers. Abbreviations: USGS, U.S. Geological Survey]

Well No. USGS site No.

Well construction

Sample-collection

Diameter method

(inches)

Depth

 (feet)

ANP 6 435152112443101 10 305 Pump (26)

ANP 9 434856112400001 8 322 Pump (18)

ARBOR TEST 433509112384801 10 790 Pump (20)

AREA 2 433223112470201 16 877 Pump (18)

ATOMIC CITY 432638112484101 8 639 Tap

BADGING FACILITY 433042112535101 8 644 Pump (35)

CFA 1 433204112562001 16 639 Pump (1,000)

CFA 2 433144112563501 16 681 Pump (1,400)

CFA LF 2-10 433216112563301 6 716 Pump (8.2)

CPP 1 433433112560201 16 586 Pump (3,000)

CPP 2 433432112560801 16 605 Pump (3,000)

CPP 4 433440112554401 16 700 Pump (400)

CROSSROADS 432128113092701 8 607 Pump (35)

EBR 1 433051113002601 10 1,075 Pump (25)

HIGHWAY 3 433256113002501 8 750 Tap

ICPP-MON-A-166 433300112583301 6 527 Pump (3)

IET 1 DISP 435153112420501 12 324 Pump (3)

LEO RODGERS 1 432533112504901 20 720 Pump (20)

MIDDLE 2050A-514.9 FT 433409112570515 // 1,376 Westbay

MIDDLE 2050A-641.9 FT 433409112570512 // 1,376 Westbay

MIDDLE 2050A-790.2 FT 433409112570509 // 1,376 Westbay

MIDDLE 2050A-997.6 FT 433409112570506 // 1,376 Westbay

MIDDLE 2050A-1178.8 FT 433409112570503 // 1,376 Westbay

MIDDLE 2051-604.2 FT 433217113004912 // 1,175 Westbay

MIDDLE 2051-750.1 FT 433217113004909 // 1,175 Westbay

MIDDLE 2051-827.8 FT 433217113004906 // 1,175 Westbay

MIDDLE 2051-1092.5FT 433217113004903 // 1,175 Westbay

MIDDLE 2051-1142.5 FT 433217113004901 // 1,175 Westbay

MTR TEST 433520112572601 8 588 Pump (26)

NO NAME 1 435038112453401 12 550 Pump (45)

NPR TEST 433449112523101 6 599 Pump (23)

PSTF TEST 434941112454201 10 319 Pump (30)

P&W 2 435419112453101 10 386 Pump (30)

RIFLE RANGE 433243112591101 5 620 Pump (25)

RWMC M1SA 432956113030901 6 638 Pump (3.5)

RWMC M3S 433008113021801 6 633 Pump (5)

RWMC M7S 433023113014801 6 628 Pump (5)

RWMC M11S 433058113010401 6 624 Pump (14)

RWMC M12S 433118112593401 6 572 Pump (6)

RWMC M13S 433037113002701 6 643 Pump (6)

RWMC M14S 433052113025001 6 635 Pump (14)

RWMC PROD 433002113021701 10,14 685 Pump (200)

SITE 4 433617112542001 8 495 Pump (500)

SITE 9 433123112530101 10 1,057 Pump (30)

SITE14 434334112463101 8,12 717 Pump (36)
Groundwater Monitoring Networks 15

Well No. USGS site No.

Well construction

Sample-collection

Diameter method

(inches)

Depth

 (feet)

SITE 17 434027112575701 15 600 Pump (30)

SITE 19 433522112582101 8,10 860 Pump (15)

SPERT-1 433252112520301 14 653 Pump (400)

TRA 1 433521112573801 18 600 Pump (3,400)

TRA 3 433522112573501 20 602 Pump (3,800)

TRA 4 433521112574201 16, 18 965 Pump (2,000)

TRA DISP 433506112572301 6,8 1,267 Pump (25)

USGS 1 432700112470801 5 636 Pump (14)

USGS 2 433320112432301 5 686 Pump (18)

USGS 4 434657112282201 6 553 Pump (36)

USGS 5 433543112493801 6 494 Pump (3)

USGS 6 434031112453701 4 620 Pump (30)

USGS 7 434915112443901 4, 6 903 Pump (45)

USGS 8 433121113115801 6 812 Pump (13)

USGS 9 432740113044501 6 632 Pump (15)

USGS 11 432336113064201 6 704 Pump (20)

USGS 12 434126112550701 10 563 Pump (36)

USGS 14 432019112563201 5 751 Pump (18)

USGS 15 434234112551701 10 610 Pump (30)

USGS 17 433937112515401 5, 6 498 Pump (15)

USGS 18 434540112440901 4 329 Pump (26)

USGS 19 434426112575701 6 399 Pump (17)

USGS 20 433253112545901 6 658 Pump (18)

USGS 22 433422113031701 6 657 Pump (5)

USGS 23 434055112595901 5, 6 463 Pump (18)

USGS 26 435212112394001 6 266 Pump (20)

USGS 27 434851112321801 6 312 Pump (30)

USGS 29 434407112285101 6 426 Pump (30)

USGS 31 434625112342101 8, 10 428 Pump (45)

USGS 32 434444112322101 5.5, 6 392 Pump (36)

USGS 34 433334112565501 10 700 Pump (20)

USGS 35 433339112565801 7 579 Pump (12)

USGS 36 433330112565201 6 567 Pump (18)

USGS 37 433326112564801 6 572 Pump (8)

USGS 38 433322112564301 4 612 Pump (18)

USGS 39 433343112570001 8 493 Pump (25)

USGS 40 433411112561101 4 483 Pump (6)

USGS 41 433409112561301 6 674 Pump (15)

USGS 42 433404112561301 6 678 Pump (18)

USGS 43 433415112561501 6 676 Pump (6)

USGS 44 433409112562101 6 650 Pump (18)

USGS 45 433402112561801 6 651 Pump (18)

USGS 46 433407112561501 6 651 Pump (18)

USGS 47 433407112560301 6 652 Pump (15)

Table 2. Construction of wells in the U.S. Geological Survey aquifer water-quality monitoring network and water sample-collection 

method, eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, as of December 2008.—Continued

[All wells are sampled annually except those whose sample collection method is WestbayTM. WestbayTM sample schedule is subject to change from year to year. 

Well No.: Well locations are shown in figures 5 and 6. Sample-collection method: Pump, sampled from pumping well (pumping rate in gallons per minute); 

Tap, sampled from faucet; WestbayTM, sampled with multi-level thief sampler. //, hole diameter is not required for borehole volume calculations with multi‐level 

thief samplers. Abbreviations: USGS, U.S. Geological Survey]
16 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Well No. USGS site No.

Well construction

Sample-collection

Diameter method

(inches)

Depth

 (feet)

USGS 48 433401112560301 6 750 Pump (18)

USGS 51 433350112560601 6 647 Pump (5)

USGS 52 433414112554201 6 602 Pump (12)

USGS 57 433344112562601 6 582 Pump (9)

USGS 58 433500112572502 6 503 Pump (15)

USGS 59 433354112554701 6 657 Pump (18)

USGS 65 433447112574501 4 498 Pump (9)

USGS 67 433344112554101 4, 6 694 Pump (6)

USGS 76 433425112573201 6 718 Pump (30)

USGS 77 433315112560301 6 586 Pump (10)

USGS 79 433505112581901 6 702 Pump (30)

USGS 82 433401112551001 6 693 Pump (18)

USGS 83 433023112561501 6 752 Pump (20)

USGS 84 433356112574201 6 505 Pump (20)

USGS 85 433246112571201 6 614 Pump (12)

USGS 86 432935113080001 8 691 Pump (20)

USGS 87 433013113024201 4 673 Pump (1.5)

USGS 88 432940113030201 4 662 Pump (8)

USGS 89 433005113032801 6 637 Pump (1.5)

USGS 97 433807112551501 4 510 Pump (30)

USGS 98 433657112563601 4 505 Pump (7.5)

USGS 99 433705112552101 4 440 Pump (25)

USGS 100 433503112400701 6 750 Pump (18)

USGS 101 433255112381801 4, 6 842 Pump (12)

USGS 102 433853112551601 6 445 Pump (30)

USGS 103

USGS 103—678.4 FT

USGS 103—799.8 FT

USGS 103—906.7 FT

USGS 103—990.4 FT

USGS 103—1083.9 FT

USGS 103—1205.6 FT

USGS 103—1254.0 FT

432714112560701

432714112560723

432714112560720

432714112560716

432714112560712

432714112560708

432714112560702

432714112560704

8

//

//

//

//

//

//

//

760 Pump (21) 2006, Westbay 

2007-08

Westbay 2007-08

Westbay 2007-08

Westbay 2007-08

Westbay 2007-08

Westbay 2007-08

Westbay 2007-08

USGS 104 432856112560801 8 700 Pump (18)

USGS 105

USGS 105—725.7 FT

USGS 105—849.0 FT

USGS 105—949.4 FT

USGS 105—1069.6 FT

USGS 105—1240.5 FT

432703113001801

432703113001818

432703113001815

432703113001811

432703113001807

432703113001803

4

//

//

//

//

//

800 Pump (24) 2006-07

Westbay installed 2008

Westbay installed 2008

Westbay installed 2008

Westbay installed 2008

Westbay installed 2008

USGS 106 432959112593101 8 760 Pump (23)

Table 2. Construction of wells in the U.S. Geological Survey aquifer water-quality monitoring network and water sample-collection 

method, eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, as of December 2008.—Continued

[All wells are sampled annually except those whose sample collection method is WestbayTM. WestbayTM sample schedule is subject to change from year to year. 

Well No.: Well locations are shown in figures 5 and 6. Sample-collection method: Pump, sampled from pumping well (pumping rate in gallons per minute); 

Tap, sampled from faucet; WestbayTM, sampled with multi-level thief sampler. //, hole diameter is not required for borehole volume calculations with multi‐level 

thief samplers. Abbreviations: USGS, U.S. Geological Survey]
Groundwater Monitoring Networks 17

Table 2. Construction of wells in the U.S. Geological Survey aquifer water-quality monitoring network and water sample-collection 

method, eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, as of December 2008.—Continued

[All wells are sampled annually except those whose sample collection method is WestbayTM. WestbayTM sample schedule is subject to change from year to year. 

Well No.: Well locations are shown in figures 5 and 6. Sample-collection method: Pump, sampled from pumping well (pumping rate in gallons per minute); 

Tap, sampled from faucet; WestbayTM, sampled with multi-level thief sampler. //, hole diameter is not required for borehole volume calculations with multi‐level 

thief samplers. Abbreviations: USGS, U.S. Geological Survey]

Well No. USGS site No.

Well construction

Sample-collection

Diameter method

(inches)

Depth

 (feet)

USGS 107 432942112532801 8 690 Pump (25)

USGS 108 432659112582601 8 760 Pump (20)

USGS 109 432701113025601 4 800 Pump (15)

USGS 110A 432717112501502 6 644 Pump (6)

USGS 111 433331112560501 8 560 Pump (12)

USGS 112 433314112563001 8 563 Pump (12)

USGS 113 433314112561801 6 564 Pump (15)

USGS 114 433318112555001 6 560 Pump (8)

USGS 115 433320112554101 6 581 Pump (5)

USGS 116 433331112553201 6 572 Pump (12)

USGS 117 432955113025901 6.5 655 Pump (12)

USGS 119 432945113023401 6.5 705 Pump (15)

USGS 120 432919113031501 6.5 705 Pump (18)

USGS 121 433450112560301 6 475 Pump (10)

USGS 123 433352112561401 6 481 Pump (12)

USGS 124 432307112583101 4 800 Pump (20)

USGS 125 432602113052801 5 774 Pump (18)

USGS 126A 435529112471301 5 648 Pump (30)

USGS 126B 435529112471401 6 452 Pump (11)

USGS 127 433058112572201 6 596 Pump (25)

USGS 128 433250112565601 4.5 615 Pump (6)

USGS 131 433036112581601 6 797 Pump (20)

USGS 132—636.4 FT

USGS 132—763.9 FT

USGS 132—825.8 FT

USGS 132—917.2 FT

USGS 132—1010.3 FT

USGS 132—1172.2 FT

432906113025022

432906113025018

432906113025014

432906113025010

432906113025006

432906113025001

//

//

//

//

//

//

1238 Westbay

Westbay

Westbay

Westbay

Westbay

Westbay

USGS 133—468.0 FT

USGS 133—568.5 FT

USGS 133—684.9 FT

USGS 133—744.3 FT

433605112554312

433605112554308

433605112554305

433605112554301

//

//

//

//

798 Westbay

Westbay

Westbay

Westbay

USGS 134—577.5 FT

USGS 134—644.5 FT

USGS 134—705.5 FT

USGS 134—805.5 FT

USGS 134—845.5 FT

433611112595819

433611112595815

433611112595811

433611112595807

433611112595804

//

//

//

//

//

894 Westbay

Westbay

Westbay

Westbay

Westbay

WS INEL1 433716112563601 6, 8 490 Pump (20)
18 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Well No. USGS Site no.

Well construction

Sample-collection 

Diameter method

(inches)

Depth 

(feet)

CWP 1 433459112572601 6 58 Bail (46)

CWP 3 433455112572501 6 55 Bail (49)

CWP 8 433500112573001 6 64 Bail (58)

PW 1 433349112560701 6 117 Bail (115)

PW 4 433348112554901 6 150 Bail (126)

PW 6 433353112562201 6 125 Bail (125)

PW 8 433456112572001 6 166 Pump (6)

PW 9 433500112575401 6 200 Pump (3)

TRA A 13 433502112572802 2 59 Bail (bottom of well)

TRA A 77 433507112573801 2 34 Bail (bottom of well)

USGS 50 433419112560201 6 405 Pump (0.5)

USGS 53 433503112573401 6 71 Bail

USGS 54 433503112572801 6 82 Pump (4)

USGS 55 433508112573001 6 81 Pump (1)

USGS 56 433509112573501 6 80 Pump (1)

USGS 60 433456112571901 6 117 Pump (3.5)

USGS 61 433453112571601 4 123 Pump (2)

USGS 62 433446112570701 8 165 Pump (3)

USGS 63 433455112574001 10 97 Pump (3.5)

USGS 66 433436112564801 4 475 Bail (188)

USGS 68 433516112573901 10 128 Pump (1)

USGS 69 433450112573001 4 115 Pump (4)

USGS 70 433504112571001 8 100 Pump (6)

USGS 71 433439112571501 5 171 Bail (157)

USGS 72 433519112574601 6 200 Bail (148)

USGS 73 433502112575401 6 127 Pump (1)

USGS 78 433413112573501 7 204 Bail (178)

USGS 92 433000113025301 3.5 214 Bail (212)

Table 3. Construction of wells in the U.S. Geological Survey perched groundwater-quality monitoring network and water samplecollection method at the Advanced Test Reactor Complex, Idaho Nuclear Technology and Engineering Center, and Radioactive Waste 

Management Complex, Idaho National Laboratory, Idaho, as of December 2008.

[Well No.: Well locations are shown in figure 7. Sample-collection method: Pump, sample collected with a pump (pumping rate in gallons per minute); Bail, 

sample collected with a bailer (sample collection depth in feet below land surface). All wells sampled annually. Abbreviation: USGS, U.S. Geological Survey]
Waste-Disposal Sites at the Idaho National Laboratory 19

Waste-Disposal Sites at the Idaho 

National Laboratory 

Wastewater disposal at INL facilities (fig. 1) has been 

the principal source of radioactive- and chemical-waste 

constituents in water from the Snake River Plain aquifer and 

in perched-groundwater zones at and near the INL. In the 

past, wastewater disposal sites included infiltration ponds 

(percolation ponds) and ditches, evaporation ponds, drain 

fields, and disposal wells. Solid and liquid wastes buried at 

the RWMC (fig. 1) also are sources of some constituents in 

groundwater. 

Contractors at each INL facility collected radioactiveand chemical-waste-disposal data from 1976 to 1998. 

Historical radioactive-waste-disposal data presented in this 

report were obtained from the most recent radioactive-wastemanagement information report (French and others, 1999b). 

Chemical-waste-disposal data were obtained from the most 

recent nonradiological-waste-management information report 

(French and others, 1999a). Since 1999, no formal program 

has been in place to compile annual amounts of constituents 

discharged at each facility (Richard Kauffman, U.S. 

Department of Energy, oral commun., 2005); however, the 

INEEL Site Environmental Reports (S.M. Stoller Corporation, 

2002a, 2002b, and 2002c) provide some radioactive waste 

disposal data for 1999–2001. The amounts and types of 

radioactive- and chemical-wastes discharged at the various 

INL facilities are not published for 1999–2008 and are not 

presented in this report. Highlights of the waste disposal 

history at INL facilities are summarized below; a more 

comprehensive summary of waste disposal at the INL can be 

found in Davis (2008).

Advanced Test Reactor Complex

Since 1952, low-level radioactive, chemical, and sanitary 

wastewater has been discharged to infiltration and lined 

evaporation ponds (fig. 3). Nonradioactive cooling-tower 

wastewater was discharged to radioactive-waste infiltration 

ponds from 1952 to 1964, to the Snake River Plain aquifer 

through a 1,267-ft-deep disposal well (TRA DISP, fig. 3) from 

1964 until March 1982, and into two cold-waste infiltration 

ponds from 1982 to the present. 

In 1976, the DOE contractor at the ATRC began a 

three‐phase program to reduce radioactivity in wastewater. 

The first phase was from 1976 to 1980 and the second phase 

was from 1981 to 1987. The contractor finished the final phase 

of the program in 1993. In August 1993, the radioactivewaste infiltration ponds at the ATRC were replaced with lined 

evaporation ponds. During 1993–98, about 515 Ci (or about 

85 Ci/yr) (French and others, 1999b) were discharged at the 

INL. This represents a significant decrease in discharge of 

radioactivity since the program began. The evaporation ponds 

may prevent radioactive wastewater from entering the aquifer.

During 1974–79, about 10 percent of radioactivity in 

wastewater discharged was attributed to tritium; most other 

radioactivity consisted of radionuclides with half-lives of 

about several weeks, as well as small amounts of strontium-90, 

cesium-137, and cobalt-60 (Barraclough and others, 1981). 

In 1980, about 50 percent of radioactivity was attributed to 

tritium, and during 1981–85, about 90 percent was attributed 

to tritium (Pittman and others, 1988, p. 22). From 1986–2000, 

about 97 percent of radioactivity in wastewater discharged at 

the ATRC has been attributed to tritium (Davis, 2008, fig. 8). 

Tritium data are not available for 2001–08.

A chemical-waste infiltration pond was used for disposal 

of chemical wastewater from an ion-exchange system at 

the ATRC (fig. 3) from 1962 to 1999. The average annual 

discharge to this pond was about 17.5 Mgal during 1962–98. 

Sulfate and sodium hydrate were the predominant constituents 

in the chemical wastewater. During 1996–98, average 

annual amounts of about 210,280 lb of sulfate and 98,800 lb 

of sodium hydrate were discharged to the chemical-waste 

infiltration pond (Bartholomay and others, 2000). Additionally, 

about 11,100 lb of sodium ion was discharged in October 

1996 (French and others, 1997). In 1999, the chemical-waste 

infiltration pond was closed and covered with a protective cap 

(S.M. Stoller Corporation, 2002a).

The TRA disposal well was used from 1964 to March 

1982 to inject nonradioactive wastewater from cooling-tower 

operations at the ATRC into the Snake River Plain aquifer. 

Since March 1982, this wastewater has been discharged to two 

cold-waste infiltration ponds (fig. 3). The disposal well has 

been used as an observation well since 1982.

Sewage effluent discharged to sanitary-waste ponds 

(fig. 3) at the ATRC was about 28 Mgal/yr during 1996–98 

(Bartholomay and others, 2000), about 17 Mgal in 2000, and 

about 52 Mgal in 2001 (Richard Kauffman, U.S. Department 

of Energy, written commun., 2005). Data are unavailable for 

the amount of effluent discharged from 2002–08. Prior to 

1990, the major constituents in the effluent were chloride and 

hypochlorite. Chloride and hypochlorite were not reported as 

part of the sewage effluent after February 1990 (Bartholomay 

and others, 2000). 
20 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Idaho Nuclear Technology and 

Engineering Center

From 1952 to February 1984, the INTEC discharged 

most low-level radioactive, chemical, and sanitary 

wastewater into the Snake River Plain aquifer through a 

600-ft-deep disposal well. Two percolation ponds (also 

called infiltration ponds) were used for wastewater disposal 

from 1984 through August 25, 2002 (fig. 6). The first pond 

was completed in February 1984 and the second pond was 

completed in October 1985. On August 26, 2002, the existing 

percolation ponds were taken out of service, and wastewater 

was discharged to the new percolation ponds southwest of 

INTEC. The new percolation ponds were designed to be a 

rapid infiltration system, and each pond can accommodate 

as much as 3 Mgal/d of continuous discharge (S.M. Stoller 

Corporation, 2004).

Tritium accounted for most of the radioactivity in 

wastewater discharged to the disposal well and percolation 

ponds at the INTEC since 1970. During 1986–95, a total of 

about 559 Ci of tritium was discharged at the INTEC, except 

1989, 1993, and 1994, when tritium was not discharged. 

Tritium was not discharged during 1996–99 and 0.03 Ci was 

discharged during 2000 (Davis, 2008). Data were not available 

for tritium discharged during 2001–08.

During 1996–98, chloride, fluoride, nitrate, sodium, 

and sulfate were the predominant chemical constituents in 

wastewater discharged to the INTEC percolation ponds. 

During this period, average annual amounts of about 

1,166,000 lb of chloride; 1,070 lb of fluoride; 86,700 lb of 

nitrate; 708,000 lb of sodium, and 146,000 lb of sulfate were 

in wastewater discharged at the INTEC (Bartholomay and 

others, 2000). Data have not been compiled for predominant 

constituents and amounts in wastewater discharged during 

1999–2008.

In 1972, about 18,100 Ci of strontium-90 and 19,100 Ci 

of cesium-137 were released to soil at the INTEC Tank Farm 

(fig. 7) (Cahn and others, 2006). In 1972, during a failed 

transfer of waste between two underground storage tanks, 

about 18,600 gal of sodium-bearing waste was leaked at an 

INTEC Tank Farm site. This accounts for about 88 percent 

(approximately 15,900 Ci) of the source of strontium-90 to 

groundwater at the Tank Farm. Three other locations at the 

Tank Farm are the source of the remaining 12 percent of 

strontium-90 (Cahn and others, 2006). 

Radioactive Waste Management Complex

Solid and liquid radioactive and chemical wastes 

have been buried in trenches and pits at the Subsurface 

Disposal Area (SDA) at the RWMC (fig. 3) since 1952. 

These include transuranic wastes, other radiochemical and 

inorganic chemical constituents, and organic compounds. The 

transuranic wastes were buried in trenches until 1970, and 

stored above ground at the RWMC after 1970. Only low‐level 

mixed waste has been buried at the RWMC since 1970. 

Before 1970, little or no sediment was retained between the 

excavation bottoms and the underlying basalt. Since 1970, a 

layer of sediment has been retained in excavations to inhibit 

downward migration of waste constituents. 

About 17,100 Ci of plutonium-238, 64,900 Ci of 

plutonium-239, 17,100 Ci of plutonium-240, and 183,000 Ci 

of americium-241 were buried in the SDA during 1952–99 

(Holdren and others, 2002, table 4-1). An estimated 88,400 gal 

of organic waste was buried before 1970 (Mann and Knobel, 

1987, p. 1). These buried wastes included about 24,400 gal 

of carbon tetrachloride; 39,000 gal of lubricating oil; and 

about 25,000 gal of other organic compounds, including 

trichloroethane, trichloroethylene, perchloroethylene, toluene, 

and benzene.

Test Area North

From 1953 to 1972, low-level radioactive, chemical, 

and sanitary wastewater was discharged at TAN (fig. 1) into 

the Snake River Plain aquifer through a 310-ft-deep disposal 

well (TAN Disposal Well, fig. 5). In 1972, the disposal well 

was replaced by a 35-acre infiltration pond. Records are not 

available to indicate the amount of radioactivity in wastewater 

discharged at TAN before 1959. During 1959–93, about 61 Ci 

of radioactivity in wastewater were discharged to the disposal 

well and infiltration pond. Radioactive wastewater has not 

been discharged since 1993 (Bartholomay and others, 2000). 

Information is not available about constituents in wastewater 

discharged since 1998.

Chemical wastewater containing predominantly 

chloride and sodium was discharged to the infiltration pond 

at the Technical Support Facility (TSF) near TAN during 

1996–98, with average annual amounts of 6,900 and 4,500 lb, 

respectively. The average annual amount of all other chemical 

constituents in the wastewater was about 760 lb (Bartholomay 

and others, 2000). Data were not available for total amounts of 

individual constituents disposed in wastewater for 1999–2007. 

A closure plan for the pond was submitted to the Idaho 

Department of Environmental Quality in November 2007, and 

wastewater discharge to the pond ceased on November 29, 

2007. All activities proposed in the plan were completed by 

February 2008 (S.M. Stoller Corporation, 2009).
Hydrologic Conditions 21

Central Facilities Area

About 65 Ci of radioactivity in about 1,500 Mgal of 

wastewater were discharged to the sewage-plant tile drain field 

at the CFA (fig. 1) during 1952–93. Most radioactive wastes 

discharged to this drain field were from aquifer water pumped 

from well CFA 1 (fig. 5), which obtains water from within the 

INTEC contaminant plume in the Snake River Plain aquifer. 

Most radioactivity in wastewater discharged at the CFA was 

attributed to tritium. During 1993–98, no radioactivity was 

recorded in wastewater discharged at the CFA (Bartholomay 

and others, 2000). Data were not available for radioactivity in 

wastewater at the CFA for 1999–2008.

Chloride and sodium were the predominant chemical 

constituents in wastewater at the CFA during 1996–98. 

Average annual amounts of about 7,800 lb of chloride 

and 5,300 lb of sodium were discharged during 1996–98. 

The average annual amount of all other constituents in the 

wastewater was about 6,300 lb; about 5,400 lb was from 

disposal of janitorial supplies (Bartholomay and others, 

2000). Data were not available for total amounts of individual 

constituents disposed in wastewater for 1999–2008.

Hydrologic Conditions

The Snake River Plain aquifer is one of the most 

productive aquifers in the United States (U.S. Geological 

Survey, 1985, p. 193). The aquifer consists of a thick sequence 

of basalts and sedimentary interbeds filling a large, arcuate, 

structural basin in southeastern Idaho (fig. 1). Recharge to 

the Snake River Plain aquifer is primarily from infiltration 

of applied irrigation water, infiltration of streamflow, 

groundwater inflow from adjoining mountain drainage basins, 

and infiltration of precipitation. 

Surface Water

The Big Lost River drains more than 1,400 mi2 of 

mountainous area that includes parts of the Lost River Range 

and the Pioneer Mountains west of the INL (fig. 1). Flow in 

the Big Lost River infiltrates to the Snake River Plain aquifer 

along the river channel and at sinks and playas at its terminus. 

To avoid flooding at the INL facilities, excess runoff has been 

diverted since 1965 to spreading areas in the southwestern 

part of the INL (Bennett, 1990, p. 15), where much of the 

water rapidly infiltrates to the aquifer. Other surface drainages 

that provide recharge to the Snake River Plain aquifer at the 

INL include Birch Creek, Little Lost River, and Camas Creek 

(fig. 1).

The average streamflow recorded at USGS gaging station 

13127000, Big Lost River below Mackay Reservoir near 

Mackay, ID (fig. 1) for complete water years (October 1–

September 30) 1905–2008 was 219,400 acre-ft/yr (U.S. 

Geological Survey, 2006, 2007, 2008) (fig. 8). Streamflow at 

gaging stations at and downstream of gaging station 13127000 

(fig. 1) for water years 2006–08 are shown in table 4 and 

figure 8. 

Recharge to the Snake River Plain aquifer downstream 

of Arco, Idaho, is substantial during wet years because of 

streamflow infiltration from the Big Lost River channel, 

diversion areas, sinks, and playas. For example, infiltration 

losses at various discharges measured during 1951–85 

ranged from 1 (ft3/s)/mi in the river channel to 28 (ft3/s)/mi 

in the sinks (Bennett, 1990, p. 24-26). Bennett considered 

streamflow losses to evapotranspiration minor as compared to 

infiltration losses. However, infiltration can be zero in years 

when there is little or no flow in the Big Lost River channel 

as was the case during 2002–04 (Davis, 2008), and 2008 at or 

downstream of gaging station 13132500 (table 4).

USGS streamflowgaging station

Streamflow 

(in acre-feet)

WY 2006 WY 2007 WY 2008

13127000 Big Lost River below 

Mackay Reservoir, near Mackay, 

Idaho

278,600 153,600 158,100

13132500 Big Lost River near 

Arco, Idaho

35,810 728 0

13132513 INL diversion at head, 

near Arco, Idaho

3,840 0 0

13132520 Big Lost River below the 

INL Diversion, near Arco, Idaho

24,030 0 0

13132565 Big Lost River above 

Big Lost River Sinks, near Howe, 

Idaho

12,840 0 0

Table 4. Average annual streamflow at U.S. Geological Survey 

streamflow-gaging stations along the Big Lost River, Idaho, water 

years 2006–08.

[Gaging station: Station locations are shown in figure 1. Streamflow:

Data are from U.S. Geological Survey (USGS), 2006, 2007, and 2008. 

Abbreviations: INL, Idaho National Laboratory; WY, water year]
22 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Groundwater

Water in the Snake River Plain aquifer primarily moves 

through interflow and fracture zones in the basalt. A large 

proportion of groundwater moves through the upper 200 to 

800 ft of basaltic rocks (Mann, 1986, p. 21). Ackerman (1991, 

p. 30) and Bartholomay and others (2000, p. 15) reported 

a range of transmissivity of basalt in the upper part of the 

aquifer of 1.1 to 760,000 ft2/d. Anderson and others (1999) 

reported a range of hydraulic conductivity at the INL of 0.01 

to 32,000 ft/d. The hydraulic conductivity of rocks underlying 

the aquifer is from 0.002 to 0.03 ft/d (Mann, 1986, p. 21). 

The effective base of the Snake River Plain aquifer probably 

ranges from about 815 to 1,710 ft below land surface in 

the western half of the INL based on data from wells that 

penetrate the base of the aquifer (Anderson and others, 1996, 

table 3). Wells in the eastern half of the INL do not penetrate 

the base of the aquifer, so the effective base of the aquifer 

cannot be estimated in that area.

tac10-0506_fig08

Station 13127000 

Big Lost River below Mackay Reservoir, 

near Mackay, Idaho

Streamflow, in thousands of acre-feet per water year 100

200

300

400

500

0

Partial water year

93-year average:

219,400 acre-feet per year

196519701980199020002008

Streamflow, in thousands of acre-feet per water year

0 0 0 0 0 0 0 0

100

200

300

400

0 0 0 0

2.0

0

Water year

19041910192019301940195019601970198019902000

2008

Water year

Big

Lost

Big Lost River below

Mackay Reservoir,

near Mackay, Idaho

13127000

Mackay

Reservoir

Spreading

areas

13132513

INL diversion at head,

near Arco, Idaho 

13132520

Idaho National

Laboratory

Arco

Mackay

River

Big Lost River below

INL diversion,

near Arco, Idaho

13132513 INL diversion at 

head, near Arco, Idaho

13132520 Big Lost River below 

INL diversion, near Arco, 

Idaho

Total streamflow above diversion

Figure 8. Streamflow at gaging stations along the Big Lost River: Big Lost River below Mackay Reservoir, water years 1905, 1913–14, 

and 1920–2008; Big Lost River below the Idaho National Laboratory (INL) diversion, near Arco; and INL diversion at head, near Arco, 

Idaho, water years 1965–2008.
Hydrologic Conditions 23

Depth to water in wells completed in the Snake River 

Plain aquifer ranges from about 200 ft in the northern part of 

the INL to more than 900 ft in the southeastern part. During 

March–May 2008, the altitude of the water table was about 

4,560 ft in the northern part of the INL (fig. 9) and about 4,410 

to 4,420 ft in the southwestern part. Water flowed south and 

southwestward beneath the INL (fig. 9) at an average hydraulic 

gradient of about 4 ft/mi. 

Water levels in wells generally remained 

constant or declined in the INL area from March–May 2005 

to March–May 2008 (fig. 10). In the southwestern part 

of the INL, most water levels were unchanged from the 

March–May 2005 reporting period or rose slightly (fig. 10). In 

the central part of the INL, water levels declined about 1–3 ft, 

and in the northern part of the INL, water levels declined as 

much as 9 ft. Water levels monitored in wells USGS 12, 17, 

and 23 (fig. 2), and 20 (fig. 3) show long-term water-level 

changes in the Snake River Plain aquifer in the central part 

of the INL in response to infiltration of streamflow (fig. 11). 

Long-term water-level fluctuations have ranged from about 

18 ft in well USGS 20 to about 36 ft in well USGS 12. Water 

levels in these wells rose during 2006, but declined overall 

from 2007 to 2008 mostly because of lack of streamflow 

infiltration from the Big Lost River.

Groundwater moves southwestward from the INL 

and eventually discharges to springs along the Snake River 

near Twin Falls, Idaho, about 100 mi southwest of the INL. 

Discharge from the springs estimated by methods given by 

Kjelstrom (1995) was about 3.64 million acre-ft/yr for water 

year 2008 (Tom Brennan, U.S. Geological Survey, written 

commun., 2009). Historically, the discharge to these springs 

has ranged from 2.97 million acre-ft/yr in 1904 to 4.94 million 

acre-ft/yr in 1951 (Daniel J. Ackerman, U.S. Geological 

Survey, written commun., 2007).

Perched Groundwater

Disposal of wastewater to infiltration ponds and 

infiltration of surface water at waste-burial sites resulted 

in formation of perched groundwater in basalts and in 

sedimentary interbeds that overlie the Snake River Plain 

aquifer. Perched groundwater has formed in a complex 

sequence of basalt flow and sedimentary interbeds beneath 

the ATRC, the INTEC, and the RWMC. Anderson and Lewis 

(1989) and Anderson (1991) correlated geophysical logs 

to describe the stratigraphic sequences in which perched 

groundwater has formed. Although the subsurface stratigraphy, 

geohydrologic characteristics, and waste disposal practices 

at each of these areas differs, the features controlling the 

formation of perched groundwater at these sites are similar 

(Cecil and others, 1991). Sedimentary interbeds in the 

subsurface may have smaller vertical hydraulic conductivities 

than overlying basalt flows, and alteration between 

basalt flows may contribute to reduced vertical hydraulic 

conductivity in the interflow rubble zones. Dense, unfractured 

basalt flows may have a decreased vertical hydraulic 

conductivity and inhibit downward flow, and sedimentary or 

chemical infilling of fractures in basalt may reduce vertical 

hydraulic conductivity by limiting the interconnectivity of 

fractures reducing the water transmitting capability of the 

basalts (Cecil and others, 1991). Any combination of these 

factors may disrupt the downward vertical movement of water 

and contribute to the formation of perched groundwater zones.

At the ATRC, deep and shallow perched groundwater 

zones have formed in response to disposal of wastewater to 

infiltration ponds (Tucker and Orr, 1998). South of the INTEC, 

perched groundwater zones also have formed in response 

to wastewater disposal to two infiltration ponds. Perched 

groundwater also has been found in other areas at the INTEC 

and may be attributed to leaking pipelines, leach fields, 

damaged casing in the upper part of the disposal well, other 

infiltration ponds, or landscape irrigation (Tucker and Orr, 

1998). Perched groundwater beneath the RWMC formed from 

infiltration of snowmelt and rain and recharge from the Big 

Lost River and INL spreading areas. This perched groundwater 

contains constituents leached from buried radioactive and 

organic-chemical wastes. Perched groundwater beneath 

wastewater infiltration ponds and buried waste is an integral 

part of the pathway for waste-constituent migration to the 

eastern Snake River Plain aquifer. The extent of perched 

groundwater is affected by the waste-disposal practices.

During March–May 2008, water levels in perched 

groundwater wells around the ATRC declined since the 

March–May 2005 reporting period. Water-level declines 

ranged from about 0.7 ft in well CWP 8 to about 21.5 ft 

in well USGS 54 (fig. 4). Well CWP 8 is completed in 

shallow perched groundwater and the water level in this 

well is influenced by discharge to the cold waste ponds. Well 

USGS 54 is completed in deep perched groundwater and the 

water level probably is influenced by the cold waste ponds, 

radioactive waste ponds, and chemical waste ponds. Waterlevel declines may be attributed to lack of infiltration of water 

in the Big Lost River channel during 2007–08 (table 4), an 

overall decrease in recharge at the INL during 2006–08, or a 

decrease in wastewater discharge to the different ponds. 
24 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig09

Big 

Southern

Butte

East

Butte

Middle

Butte

BITTERROOT

RANGE

LEMHI RANGE

LOST RIVER RANGE

33

26

26

20

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Mud

Lake

Big

Lost

River

Little

Lost

River

Birch

Creek

Camas

Creek

4470

4440

4400

4410

4420

4430

4460

4450

4480

4490

4510

4500

4540

4530

4520

4550

4560

Atomic

City

Howe

Arco

Mud

Lake Terreton

Big Lost River

playas and 

sinks

Spreading

areas

EXPLANATION

4400 Water-table contour—Shows altitude of the water table, March−

May 2008. Contour intervals are 10 and 100 feet. Datum is 

National Geodetic Vertical Datum of 1929. Contours 

approximately located.

Well in the USGS water-level monitoring network at which 

water level was measured

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°15’ 113°00’ 45’

44°00’

43°30’

45’

112°30’ 112°15’

0 5 10 Miles

0 5 10 Kilometers

Figure 9. Altitude of the water table in the Snake River Plain aquifer at and near the Idaho National Laboratory, Idaho, 

March–May 2008.
Hydrologic Conditions 25

tac10-0506_fig10

Big 

Southern

Butte

East

Butte

Middle

Butte

BITTERROOT

RANGE

LEMHI RANGE

LOST RIVER RANGE

33

26

26

20

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Mud

Lake

Big

Lost

River

Little

Lost

River

Birch

Creek

Camas

Creek

-1

-7

-2

0

-4

-5

-6

-2

-8

-1

-6

0

0

0

-3

-3

-1

-1 -1

Atomic

City

Howe

Arco

Mud

Lake Terreton

Big Lost River

playas and 

sinks

Spreading

areas

EXPLANATION

4 Line of equal water-level rise or decline—March−May 2005 to 

March−May 2008. Interval, in feet, is variable. Positive numbers 

indicate water-level rise; negative numbers indicate water-level 

decline. Contours approximately located

Well in the USGS water-level monitoring network at which 

water level was measured

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°15’ 113°00’ 45’

44°00’

43°30’

45’

112°30’ 112°15’

0 5 10 Miles

0 5 10 Kilometers

Figure 10. Generalized rise or decline in groundwater levels in the Snake River Plain aquifer at and near Idaho National 

Laboratory (INL), Idaho, March–May 2005 to March–May 2008.
26 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig11

USGS 12

USGS 434126112550701

USGS 17

USGS 433937112515401

USGS 20 

USGS 433253112545901

USGS 23

USGS 434055112595901

300

310

320

330

340

350

305

315

325

335

345

4,515

4,510

4,505

4,500

4,495

4,490

4,485

4,480

4,475

4,470

340

345

350

355

360

365

370

4,490

4,485

4,480

4,475

4,470

4,465

450 4,465

455 4,460

460 4,455

465 4,450

470 4,445

475 4,440

375

380

385

390

395

400

405

410

415

420

4,505

4,500

4,495

4,490

4,485

4,480

4,475

4,470

4,465

Water level, in feet below land surface (scale variable)

Water level, in feet above National Geodetic Vertical Datum of 1929 (scale varable)

1952196019701980199020002008

1952196019701980199020002008

1952196019701980199020002008

1952196019701980199020002008

Calendar year

Figure 11. Water levels in four wells (USGS 12, 17, 20, 23) in the central part of the Idaho National Laboratory, Idaho, 1952–2008.
Methods and Quality Assurance of Water Sample Analyses 27

Methods and Quality Assurance of 

Water Sample Analyses

Water samples were analyzed for radiochemical 

constituents at the DOE Radiological and Environmental 

Sciences Laboratory (RESL) at the INL and for chemical 

constituents at the USGS National Water Quality Laboratory 

(NWQL) in Lakewood, Colorado. Until 2008, water samples 

analyzed by the RESL reported an uncertainty of 2s, where 

s is the sample standard deviation, and were entered into the 

USGS National Water Information System (NWIS) database 

with this uncertainty. In 2008, RESL began reporting the 

uncertainty as 1s, and data are now entered into NWIS with 

the 1s uncertainty. Analytical uncertainties in this report 

are reported as 1s for consistency with conventions used in 

previous USGS reports.

Methods used to sample and analyze for selected 

constituents generally follow the guidelines established by 

the USGS (Goerlitz and Brown, 1972; Stevens and others, 

1975; Wood, 1976; Claassen, 1982; Wershaw and others, 

1987; Fishman and Friedman, 1989; Faires, 1993; Fishman, 

1993; and Wilde and others, 1998). Water samples were 

collected according to a quality-assurance plan for waterquality activities conducted by personnel at the USGS INL 

Project Office. The plan was finalized in June 1989, revised 

in March 1992, in 1996 (Mann, 1996), in 2003 (Bartholomay 

and others, 2003), and in 2008 (Knobel and others, 2008). 

The plan is available for inspection at the USGS INL Project 

Office. 

Water samples collected for dissolved constituent 

analysis are filtered through a 0.45-micron membrane filter. 

About 10 percent of water samples collected generally are for 

quality assurance. Quality-assurance water samples collected 

by the USGS INL Project Office include equipment blanks, 

splits, and replicates. 

Water samples were collected from six wells equipped 

with dedicated multi-level WestbayTM packer sampling 

systems using pre-cleaned stainless-steel thief sampling bottles 

which were lowered to the zone to be sampled, connected 

to the sampling port, and filled with formation water. The 

stainless-steel bottles were then raised to the surface and 

emptied into a pre-cleaned container; the water was then 

processed to fill appropriate bottles for analyses. Field 

measurements also were taken from the pre-cleaned container 

(Bartholomay and Twining, 2010).

Field processing of water samples differed depending 

on the constituents for which analyses were requested. Water 

samples analyzed by the NWQL were placed in containers 

and preserved in accordance with laboratory requirements 

specified by Timme (1995) and Knobel and others (2008, 

appendix A). Containers and preservatives used for this 

study were supplied by the NWQL and were processed using 

a rigorous quality-control procedure (Pritt, 1989, p. 75) to 

minimize sample contamination. Water samples requiring 

filtration consisted of filtering the water through a disposable 

0.45-μm filter cartridge that had been pre-rinsed with at least 

1 L of deionized water. Water samples analyzed by the RESL 

were placed in containers and were preserved in accordance 

with laboratory requirements specified by Bodnar and Percival 

(1982) and Knobel and others (2008, appendix A).

Comparative studies to determine agreement 

between analytical results for individual water-sample 

pairs by laboratories involved in the INL Project Office 

quality‐assurance program were summarized by Wegner 

(1989), and Williams (1996, 1997). Additional qualityassurance studies by USGS INL Project Office personnel 

include:

• An evaluation of field sampling and preservation 

methods for strontium-90 (Cecil and others, 1989);

• A study comparing pump types used for sampling 

VOCs (Knobel and Mann, 1993);

• An analysis of tritium and strontium-90 concentrations 

in water from wells after purging different borehole 

volumes (Bartholomay, 1993);

• An analysis of effects of various preservation types on 

nutrient concentrations (Bartholomay and Williams, 

1996); 

• An analysis of two analytical methods to determine 

gross alpha- and beta-particle activity (Bartholomay 

and others, 1999); 

• An evaluation of well-purging effects on water-quality 

results (Knobel, 2006); 

• An evaluation of the 2006–08 WestbayTM quality 

assurance data is given in Bartholomay and Twining 

(2010).

Guidelines for Interpreting Results of 

Radiochemical Analyses

Concentrations of radionuclides are reported with an 

estimated sample standard deviation, s, which is obtained by 

propagating sources of analytical uncertainty in measurements. 

The following guidelines for interpreting analytical results are 

based on an extension of a method proposed by Currie (1984).

In the analysis for a particular radionuclide, laboratory 

measurements are made on a target sample and a prepared 

blank. Instrument signals for the sample and the blank vary 

randomly. Therefore, it is essential to distinguish between two 

key aspects of the problem of detection: (1) the instrument 

signal for the sample must be greater than the signal 
28 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

observed for the blank before a decision can be made that the 

radionuclide was detected, and (2) an estimation must be made 

of the minimum radionuclide concentration that will yield a 

sufficiently large observed signal before a correct decision can 

be made for detection or nondetection of the radionuclide. The 

first aspect of the problem is a qualitative decision based on 

an observed signal and a definite criterion for detection. The 

second aspect of the problem is an estimation of the detection 

capabilities of a given measurement process.

In the laboratory, instrument signals must exceed a 

critical level of 1.6s, where s is the sample standard deviation, 

before the qualitative decision can be made as to whether the 

radionuclide was detected. At 1.6s, there is about a 95-percent 

probability that the correct conclusion—not detected—will 

be made. Given a large number of water samples, as many as 

5 percent of the water samples with measured concentrations 

greater than or equal to 1.6s, concluded as detected, might not 

contain the radionuclide. These measurements are referred to 

as false positives and are errors of the first kind in hypothesis 

testing.

Once the critical level of 1.6s has been defined, the 

minimum detectable concentration may be determined. 

Concentrations that equal 3s represent a measurement at the 

minimum detectable concentration. For actual concentrations 

equal to or greater than 3s, there is a 95 percent or higher 

probability that the radionuclide was detected in a water 

sample. In a large number of water samples, the conclusion—

not detected—will be made in 5 percent of the water samples 

that contain actual concentrations at the minimum detectable 

concentration of 3s. These measurements are referred to as 

false negatives and are errors of the second kind in hypothesis 

testing.

Actual radionuclide concentrations between 1.6s and 

3s have larger errors of the second kind. That is, there is a 

larger-than-5-percent probability of false negative results 

for water samples with actual concentrations between 1.6s

and 3s. Although the radionuclide might have been detected, 

such detection may not be considered reliable; at 1.6s, the 

probability of a false negative is about 50 percent.

The critical level and minimum detectable concentrations 

are based on counting statistics alone and do not include 

systematic or random errors inherent in laboratory procedures. 

The values 1.6s and 3s vary slightly with background or 

blank counts, with the number of gross counts for individual 

analyses, and for different radionuclides. 

In this report, radionuclide concentrations less than 3s

are considered to be less than a “reporting level.” The critical 

level, minimum detectable concentration, and reporting 

level aid the reader to interpret analytical results and do not 

represent absolute concentrations of radioactivity, which may 

or may not have been detected. Analytical uncertainties in this 

report are reported as 1s for consistency with conventions used 

in previous reports.

Guidelines for Interpreting Results of 

Chemical Analyses

Historically, the NWQL has used a minimum reporting 

level (MRL) to report nondetected concentrations or 

concentrations less than the MRL. The MRL for chemical 

constituents is the lowest measured concentration of a 

constituent (the “less than” value reported by NWQL) that may 

be reliably reported using a given analytical method (Timme, 

1995). However, NWQL determined that establishment of 

MRLs often was inconsistent, undefined, undocumented, and 

subjective (Childress and others, 1999). Therefore, in 1998, 

NWQL implemented new reporting procedures for some 

analytical methods based on long-term method detection levels. 

Childress and others (1999, p. 16) explained the new reporting 

procedures used by NWQL as: 

The USGS National Water Quality Laboratory 

collects quality-control data on a continuing basis 

to evaluate selected analytical methods to determine 

long-term method detection levels (LT–MDLs) and 

laboratory reporting levels (LRLs). These values are 

re-evaluated each year on the basis of the most recent 

quality control data and, consequently, may change 

from year to year. 

This reporting procedure limits the occurrence of 

false positive error. The chance of falsely reporting a 

concentration greater than the LT–MDL for a water 

sample in which the analyte is not present is 1 percent 

or less. Application of the LRL limits the occurrence 

of false negative error. The chance of falsely 

reporting a non-detection for a water sample in which 

the analyte is present at a concentration equal to or 

greater than the LRL is 1 percent or less. 

Accordingly, concentrations are reported as less than 

(<) the LRL for water samples in which the analyte 

was either not detected or did not pass identification. 

Analytes that are detected at concentrations between 

the LT–MDL and LRL and that pass identification 

criteria are estimated. Estimated concentrations will 

be noted with a remark code of “E.” These data 

should be used with the understanding that their 

uncertainty is greater than that of data reported 

without the “E” remark code. 

New LRLs were established for some analytical methods 

during 2006–08. In this report, concentrations determined 

using these methods are reported as greater than the LRL; 

concentrations determined using other methods are reported as 

greater than the MRL. Estimated concentrations less than the 

LRLs are treated as nondetected concentrations for consistency 

with treatment in previous publications, and because an 

estimated concentration is considered a “qualitatively detected 

analyte” (Childress and others, 1999, p. 7). 
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 29

Selected Radiochemical and Chemical 

Constituents and Physical Properties of 

Water in the Snake River Plain Aquifer

Contaminant plumes of radiochemical and chemical 

constituents in the Snake River Plain aquifer at the INL are 

attributed to waste-disposal practices. Areal distribution 

of the plumes was interpreted from analyses of water 

samples collected from a three-dimensional flow system. 

Concentrations of these constituents represent water 

samples collected during April or October 2008 from 

wells completed at various depths in the aquifer and with 

differing well completions. For example, single and multiple 

screened intervals and open boreholes. No attempt was 

made to determine the vertical extent and distribution of 

these plumes. However, beginning in 2006, water samples 

were collected from six wells with dedicated multi-level 

WestbayTM packer sampling systems that may allow for the 

description of the vertical distribution of selected constituents 

in the aquifer. Radiochemical and chemical constituents 

analyzed for in groundwater samples collected from wells 

at the INL during 2006–08 include tritium, strontium-90, 

cesium-137, plutonium-238, plutonium-239, -240 (undivided), 

americium-241, gross alpha- and beta-particle radioactivity, 

chromium and other trace elements, sodium, chloride, sulfate, 

nitrate (as N), fluoride, VOCs, and total organic carbon. 

Physical properties of water measured during sampling events 

included specific conductance, temperature, and pH.

Tritium

A tritium plume has developed in the Snake River 

Plain aquifer from discharge of wastewater at the INL since 

the 1950s. Tritium has a half-life of 12.3 years (Walker and 

others, 1989, p. 20). The MCL for tritium is 20,000 pCi/L 

(U.S. Environmental Protection Agency, 2001). The primary 

sources of tritium in the aquifer have been the injection of 

wastewater through the disposal well at INTEC and the 

discharge of wastewater to the percolation ponds at the INTEC 

(fig. 4). Routine use of the disposal well at the INTEC ended 

in February 1984; subsequently, radioactive wastewater has 

been discharged to the percolation ponds. About 31,620 Ci 

of tritium in wastewater was discharged to the well and 

percolation ponds from 1952 to 1995 (Bartholomay and 

others, 2000). During 1996–99, tritium was not discharged to 

the ponds at the INTEC; during 2000, 0.03 Ci of tritium was 

discharged (S.M. Stoller Corporation, 2002a, 2002b). Data 

have not been compiled for the total amount of tritium in 

wastewater discharged at the INTEC during 2001–08. 

Since 1993, tritium in wastewater at the ATRC has been 

discharged to lined evaporation ponds, which should prevent 

migration to the aquifer. About 191 Ci of tritium were released 

in wastewater to the ATRC lined evaporation ponds during 

1999–2000 (S.M. Stoller Corporation, 2002a, 2002b). Data 

are unavailable for the total amount of tritium in wastewater 

discharged at the ATRC during 2001–08. 

Reportable concentrations of tritium in water samples 

collected in April or October 2008 ranged from 810±70 to 

8,570±190 pCi/L and the tritium plume extended southsouthwestward in the general direction of groundwater 

flow (fig. 12). In 1991, the area of the plume in which 

concentrations exceeded the MCL was about 2.4 mi2

(Bartholomay and others, 1995). Since 1997, tritium 

concentrations of water samples collected by the USGS from 

the Snake River Plain aquifer have not exceeded the MCL.

Long-term radioactive-decay processes and an overall 

decrease in tritium disposal rates since the 1960s (Davis, 

2008) contributed to decreased concentrations of tritium in 

water from most wells at the INL during 2006–08. Tritium 

concentrations in water from several wells at and southsouthwest of the INTEC decreased or remained relatively 

constant during 2006–08 (fig. 13). Concentrations in water 

from well USGS 123 (fig. 6), southwest of the INTEC, 

decreased from 4,600±300 pCi/L in October 2005 to 

3,600±120 pCi/L in October 2008. Although the tritium 

concentration in water from well USGS 114 (fig. 6) was 

highest in 2008 (8,570±190 pCi/L), it was a decrease in 

concentration from the concentration of 10,500±500 pCi/L 

in October 2005. Tritium concentrations in water from well 

CFA LF 2-10 (fig. 6) decreased from 3,060±320 pCi/L in 

October 2005 to 1,390±100 pCi/L in 2008. The decrease 

in tritium concentrations in water from wells at and 

south‐southwest of the INTEC likely is the result of decreased 

discharge of tritium to the percolation ponds since the early 

1990s (Davis, 2008, fig. 9).

Tritium concentrations in water from well USGS 59, near 

the INTEC percolation ponds (figs. 6 and 13), have decreased 

since 1980, but were unusually high in October 1983, 1985, 

1991, and 1995, and 2002 (fig. 13). The higher concentrations 

in 1983 and 1985 correlate with higher annual discharge 

rates of tritium; however, annual discharge of tritium was 

low in 1991 and 1995 (Davis, 2008, fig. 9). In 1986, perched 

groundwater was detected outside the casing in well USGS 59. 

Following modifications to the well to prevent seepage of 

water into the well, a video log showed that some water from 

the perched zone was still seeping into the well. The higher 

concentrations in 1991, 1995, and 2002 could be the result of 

seepage from a perched zone. The higher concentrations also 

correlate with the use of the east infiltration pond and with 

disposal of tritium to the ponds. The lower concentrations in 

water from well USGS 59 in 1989, 1993, 1994, and from 1996 

to 2000 correlate with years in which little or no tritium was 

discharged to the percolation ponds (Davis, 2008, fig. 9). 
30 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig12

26

20

Advanced Test

 Reactor Complex

33

26

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Big

Lost

River

500

1000

2000

1000

5000

2000

3000

3000

2000

2000

5000

8000

1000

500

1000

4000

Lincoln Boulevard

Idaho Nuclear

Technology and 

Engineering Center

Central 

Facilities

Area

Radioactive

Waste

Management

Complex

Spreading areas

EXPLANATION

500 Line of equal tritium concentration—April and October 2008. Lines of equal 

concentration were interpreted from analyses of water samples collected 

from a 3-dimensional flow system. Mapped concentrations represent water 

samples collected from various depths in boreholes with differing well 

completions; for example, single- and multiple-screened intervals, and 

open boreholes. Location is approximate. Interval, in picocuries per liter, is 

variable

Well in the USGS water-quality monitoring network—Water samples 

analyzed for tritium

0 1 2 3 Miles

0 1 2 3 Kilometers

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°05' 113°00' 112°55'

43°35'

43°30'

Idaho 

National 

Laboratory

Map area

Figure 12. Distribution of tritium in water from wells at and near the Advanced Test Reactor Complex, Idaho Nuclear 

Technology and Engineering Center, Central Facilities Area, and Radioactive Waste Management Complex at the Idaho 

National Laboratory, Idaho, April or October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 31

tac10-0506_fig13

0 0

0 0

10,000

20,000

30,000

40,000

50,000

0 0

20,000

40,000

60,000

80,000

100,000

19801985199019952000200520081980198519901995200020052008

19801985199019952000200520081980198519901995200020052008

19801985199019952000200520081980198519901995200020052008

Tritium concentration, in picocuries per liter (scale variable)Tritium concentration, in picocuries per liter (scale variable)

CFA 1 USGS 59

USGS 38 USGS 77

USGS 47 USGS 111

20,000

40,000

60,000

80,000

100,000

20,000

40,000

60,000

80,000

100,000

20,000

40,000

60,000

80,000

100,000

20,000

40,000

60,000

80,000

100,000

Figure 13. Tritium concentrations in water from six wells at and near the Central Facilities Areas (CFA) and Idaho Nuclear 

Technology and Engineering Center (INTEC), 1980–2008. Locations of wells are shown in figures 5 and 6.
32 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

The slight increase in tritium concentrations in wells USGS 

38, 47, 59, 77, and 111 between 2000 and 2001 (fig. 13), could 

have resulted from disposal of 0.03 Ci of tritium (S.M. Stoller 

Corporation, 2002b) to the INTEC percolation ponds and 

from the lack of dilution by groundwater recharge because of 

low streamflows in the Big Lost River during 2000 (Davis, 

2008). The lower concentrations in 2003–08 occur after the 

percolation ponds were taken out of service.

The greatest decrease in tritium concentrations in 

wells south of the INTEC disposal well during the 2006–08 

reporting period was in well USGS 77, which decreased from 

11,500±600 pCi/L in October 2005 to 5,620±150 pCi/L 

in October 2008. Concentrations of tritium in well CFA 1 

(fig. 5) decreased from 8,700±400 pCi/L in April 2005 

to 6,300±200 in April 2008. Figure 13 shows graphs of 

tritium concentrations in other wells south of INTEC. Most 

concentrations were relatively constant during 2005–08 when 

uncertainties were considered. 

Tritium concentrations in water from wells USGS 83 and 

EBR 1 (fig. 5) south and west of the INTEC, and in and near 

the tritium plume (fig. 12), were less than the reporting level 

during 2006–08. Well USGS 83 penetrates about 250 ft of the 

Snake River Plain aquifer and well EBR 1 penetrates about 

490 ft of the aquifer. Most of the other wells in the tritium 

plume penetrate only the uppermost 50–200 ft of the aquifer. 

Tritium concentrations in water from wells USGS 83 and 

EBR 1 were less than the reporting level, possibly because of 

dilution by water from deeper zones, a phenomena described 

by Mann and Cecil (1990, p. 18) for these wells.

Prior to 1999, concentrations of tritium in water from 

wells near the southern boundary of the INL (USGS 1, 103, 

105, 108, 109, 110A) (fig. 5), varied between exceeding and 

not exceeding the reporting levels (Pittman and others, 1988; 

Mann and Cecil, 1990; Bartholomay and others, 1997, 2000). 

During 1999–2005, concentrations of tritium in water from 

these wells and all wells sampled south of the INL boundary 

were less than the reporting level. During 2006 and 2007, 

water from well USGS 105 exceeded the reporting level with 

concentrations of 210±60 and 270±80 pCi/L, respectively. 

Well USGS 105 was not sampled in 2008 because the well 

was deepened and equipped with a multi-level WestbayTM

packer sampling system. Water from the multi-level sampling 

system installed in well USGS 103 showed concentrations less 

than the reporting level in 2008 in the upper two zones that 

represent the zone of water sampled through 2005 (table 5), 

but did show concentrations greater than the reporting level in 

four deeper levels of the aquifer.

Water from various depths in all six wells equipped with 

the multi-level WestbayTM packer sampling system (figs. 5

and 6, table 5) was sampled and analyzed for tritium during 

2006–08. Results showed that water from one or more zones 

in each well contained concentrations of tritium greater 

than the reporting level. The concentrations greater than 

the reporting levels are attributed to wastewater disposal at 

NRF, INTEC, and ATRC (Bartholomay and Twining, 2010). 

Bartholomay and Twining (2010) give a comprehensive 

analysis of the vertical variation in tritium concentrations and 

possible sources of the tritium for the different zones in each 

well.

Strontium-90

A strontium-90 plume developed in the Snake River Plain 

aquifer from wastewater disposal at the INL. Strontium-90 

has a half-life of 29.1 years (Walker and others, 1989, p. 29). 

The MCL for strontium-90 in drinking water is 8 pCi/L (U.S. 

Environmental Protection Agency, 2001). During 1952–98, 

about 24 Ci of strontium-90 was in wastewater that was 

injected directly into the aquifer through the disposal well 

and was discharged to percolation ponds at the INTEC 

(Bartholomay and others, 2000). During this period, about 

93 Ci of strontium-90 also was discharged to radioactivewaste infiltration and evaporation ponds at the ATRC. During 

1962–63, more than 33 Ci of strontium-90 in wastewater was 

discharged into a pit at the INTEC (Robertson and others, 

1974, p. 117). In 1972, about 18,100 Ci of strontium-90 was 

leaked at the INTEC Tank Farm (fig. 7) (Cahn and others, 

2006). During 1996–98, about 0.03 Ci of strontium-90 was 

discharged to percolation ponds at the INTEC (Bartholomay 

and others, 2000). During 1999, less than 0.001 Ci of 

strontium-90 was discharged at the INTEC or at the ATRC 

(S.M. Stoller Corporation, 2002a, table 7-2); during 2000, 

0.21 Ci of strontium-90/yttrium-90 was discharged at the 

ATRC (S.M. Stoller Corporation, 2002b, table 6-2). Data are 

not available for strontium-90 discharged during 2001–08. 

During April or October 2008, water from 52 aquifer 

wells was sampled for strontium-90 throughout the INL. 

Concentrations of strontium-90 in water from 24 wells 

exceeded the reporting level. Reportable concentrations of 

strontium-90 in the aquifer wells ranged from 2.2±0.7 pCi/L 

in water from well Site 9, to 32.7±1.2 pCi/L in water from 

well USGS 47. The area of the strontium-90 plume near the 

INTEC extended south-southwestward in the general direction 

of groundwater flow (fig. 14). The concentrations in water 

from wells near and southwest of INTEC have varied since 

1980; however, all wells have shown an overall decrease in 

strontium-90 concentration (fig. 15). Six WestbayTM equipped 

wells were sampled in August and September 2008 and did 

not contain reportable concentrations of strontium-90.

Concentrations in water from wells at and near the 

INTEC exceeded the reporting level in most years during 

1980–2008 (Davis, 2008, table 6; this report). Figure 15 shows 

how the concentration in these wells has varied since 1980. 
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 33

Well No. 

Sampling 

port depth

(ft BLS)

Date Concentration

USGS 103 681.9 10-02-07 -70 ± -60

USGS 103 681.9 08-20-08 -10 ± 60

USGS 103 805.2 10-02-07 -80 ± -60

USGS 103 805.2 08-19-08 50 ± 60

USGS 103 913.8 10-01-07 160 ± -70

USGS 103 913.8 08-19-08 90 ± 60

USGS 103 999.5 10-01-07 290 ± -70

USGS 103 999.5 08-18-08 370 ± 70

USGS 103 1,095.1 10-01-07 350 ± -80

USGS 103 1,095.1 08-18-08 440 ± 70

USGS 103 1,220.2 09-25-07 380 ± -80

USGS 103 1,220.2 08-18-08 320 ± 70

USGS 103 1,269.4 09-25-07 400 ± -80

USGS 103 1,269.4 08-19-08 430 ± 70

USGS 132 825.8 09-05-06 190 ± 60

USGS 132 825.8 09-18-07 140 ± 60

USGS 132 825.8 08-13-08 120 ± 50

USGS 132 917.2 08-31-06 330 ± 70

USGS 132 917.2 09-17-07 150 ± 60

USGS 132 917.2 08-12-08 340 ± 70

USGS 132 1,010.3 08-30-06 300 ± 60

USGS 132 1,010.3 09-17-07 210 ± 70

USGS 132 1,010.3 08-12-08 301 ± 9

USGS 132 1,172.2 08-29-06 270 ± 60

USGS 132 1,172.2 09-17-07 310 ± 70

USGS 132 1,172.2 08-12-08 300 ± 70

USGS 133 468.0 09-24-07 50 ± 60

USGS 133 468.0 09-02-08 210 ± 70

USGS 133 568.5 09-24-07 -50 ± 60

USGS 133 568.5 09-02-08 -10 ± 60

USGS 133 684.9 09-24-07 -30 ± 60

USGS 133 684.9 09-02-08 40 ± 60

USGS 133 744.3 09-24-07 -50 ± 60

USGS 133 744.3 09-02-08 20 ± 60

USGS 134 577.5 09-27-06 390 ± 70

USGS 134 577.5 09-10-07 -20 ± 60

USGS 134 577.5 09-04-08 10 ± 60

USGS 134 644.5 09-28-06 110 ± 60

USGS 134 644.5 09-06-07 180 ± 70

Table 5. Tritium concentrations in water sampled at multiple depths in six wells equipped with multi-level WestbayTM packer sampling 

systems, 2006–08.

[Well No.: Well locations are shown in figures 5 and 6. Concentrations and associated uncertainties in picocuries per liter. Analytical uncertainties are reported 

as 1 times the sample standard deviation. Concentrations equal to or greater than 3 times the sample standard deviation are considered greater than the reporting 

level and are bold. Symbol: ±, plus or minus. Abbreviations: ft BLS, feet below land surface; USGS, U.S. Geological Survey]

Well No. 

Sampling 

port depth

(ft BLS)

Date Concentration

USGS 134 644.5 09-04-08 390 ± 70

USGS 134 705.5 09-27-06 40 ± 50

USGS 134 705.5 09-05-07 -110 ± 60

USGS 134 705.5 09-03-08 40 ± 60

USGS 134 805.5 09-26-06 30 ± 50

USGS 134 805.5 09-05-07 -130 ± 60

USGS 134 805.5 09-03-08 16 ± 64

USGS 134 845.5 09-03-08 90 ± 70

Middle 2050A 514.9 09-19-06 90 ± 50

Middle 2050A 514.9 09-20-07 210 ± 70

Middle 2050A 514.9 08-27-08 220 ± 70

Middle 2050A 641.9 09-19-06 140 ± 50

Middle 2050A 641.9 09-20-07 70 ± 60

Middle 2050A 641.9 08-26-08 140 ± 70

Middle 2050A 790.2 09-20-06 160 ± 60

Middle 2050A 790.2 09-20-07 40 ± 60

Middle 2050A 790.2 08-26-08 90 ± 70

Middle 2050A 997.6 09-18-06 20 ± 50

Middle 2050A 997.6 09-19-07 -20 ± 60

Middle 2050A 997.6 08-26-08 16 ± 64

Middle 2050A 1,178.8 09-18-06 170 ± 60

Middle 2050A 1,178.8 09-19-07 70 ± 60

Middle 2050A 1,178.8 08-26-08 130 ± 70

Middle 2051 604.2 09-11-06 60 ± 50

Middle 2051 604.2 09-12-07 -50 ± 60

Middle 2051 604.2 08-25-08 50 ± 60

Middle 2051 750.1 09-13-06 700 ± 100

Middle 2051 750.1 09-12-07 450 ± 80

Middle 2051 750.1 08-25-08 680 ± 80

Middle 2051 827.8 09-12-06 660 ± 90

Middle 2051 827.8 09-11-07 610 ± 100

Middle 2051 827.8 08-21-08 630 ± 80

Middle 2051 1,092.5 09-11-06 360 ± 70

Middle 2051 1,092.5 09-11-07 230 ± 70

Middle 2051 1,092.5 08-21-08 470 ± 80

Middle 2051 1,142.5 09-7-06 320 ± 70

Middle 2051 1,142.5 09-11-07 210 ± 70

Middle 2051 1,142.5 08-21-08 460 ± 80
34 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig14

26

20

Advanced Test

 Reactor Complex

33

26

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Big

Lost

River

2

4

6

8

2

2

4

6

8

12

16

32

Lincoln

Boulevard

Idaho Nuclear

Technology and 

Engineering Center

Central 

Facilities

Area

Radioactive

Waste

Management

Complex

Spreading areas

EXPLANATION

2 Line of equal strontium-90 concentration—April and October 2008. Lines of 

equal concentration were interpreted from analyses of water samples 

collected from a 3-dimensional flow system. Mapped concentrations 

represent water samples collected from various depths in boreholes with 

differing well completions; for example, single- and multiple- screened 

intervals, and open boreholes. Location is approximate. Interval, in picocuries 

per liter, is variable

Well in the USGS water-quality monitoring network—Water samples 

analyzed for strontium-90

0 1 2 3 Miles

0 1 2 3 Kilometers

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°05' 113°00' 112°55'

43°35'

43°30'

Idaho 

National 

Laboratory

Map area

Figure 14. Distribution of strontium-90 in water from wells at and near the Advanced Test Reactor Complex (ATRC), Idaho 

Nuclear Technology and Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive Waste Management 

Complex (RWMC), Idaho National Laboratory (INL), Idaho, April and October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 35

tac10-0506_fig15

0

10

20

30

40

50

0

10

20

30

40

50

0

10

20

30

40

50

0

10

20

30

40

50

USGS 36

USGS 37

USGS 38

0

10

20

30

40

50

60

70

80

100

90 USGS 45

0

20

40

60

80

100

120

140

USGS 47

0

10

20

30

40

50

60

70

80

90

100

USGS 57

USGS 113

Strontium-90 concentration, in picocuries per liter (scale variable)

Strontium-90 concentration, in picocuries per liter (scale variable)

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

Figure 15. Strontium-90 concentrations in water from seven wells at and near the Idaho Nuclear Technology and Engineering 

Center (INTEC), 1980–2008. Location of wells shown in figure 6.
36 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Before 1989, strontium-90 concentrations in most wells 

had been decreasing likely because of factors including 

radioactive decay, diffusion, dispersion, changes in disposal 

methods, and dilution from natural recharge (Orr and Cecil, 

1991, p. 35). The fluctuating concentrations in water from 

most of the wells sampled during 2006–08 could have resulted 

at least partly from variations in recharge from the Big Lost 

River. An increase in disposal of other chemical constituents 

into the percolation ponds also could have affected the 

exchange capacity of strontium-90 in the unsaturated zone 

(Bartholomay and others, 1997). 

Strontium-90 has not been detected in the eastern Snake 

River Plain aquifer beneath the ATRC partly because of the 

exclusive use of waste-disposal ponds and lined evaporation 

ponds rather than the disposal well for radioactive-wastewater 

disposal at that facility. Sorption processes in sediments in the 

unsaturated zone beneath the radioactive waste-disposal pond 

could have minimized or prevented strontium-90 migration to 

the aquifer at the ATRC. Additionally, the stratigraphy beneath 

the ATRC includes more sediment than the stratigraphy 

beneath the INTEC (Anderson, 1991, p. 22–28). 

In 1988, a DOE contractor was given the responsibility 

for monitoring areas around TAN and the TAN disposal well 

as part of the Environmental Restoration Program. The USGS 

collected water samples from wells in the area for special 

studies in 1989, but the USGS has not collected any other 

water samples in this area since December 1989. During 

1988–96, four water samples analyzed for strontium-90 from 

well USGS 24, just south of the TAN, yielded one reportable 

concentration in 1990. 

Cesium-137

From 1952 to 2000, about 138 Ci of cesium-137 in 

wastewater was discharged to the ATRC radioactive-waste 

infiltration and lined evaporation ponds and about 23 Ci was 

discharged to the INTEC disposal well and infiltration ponds. 

In 1972, an additional 19,100 Ci of cesium-137 leaked at the 

INTEC Tank Farm (fig. 7) (Cahn and others, 2006). During 

1999–2000, about 0.009 Ci was discharged to the ATRC lined 

evaporation ponds, and less than 0.001 Ci/yr was discharged 

to the INTEC percolation ponds (S.M. Stoller Corporation, 

2002a). Data are not available for cesium-137 discharged 

during 2001–08. The half-life of cesium-137 is 30.17 years 

(Walker and others, 1989, p. 34).

Concentrations of cesium-137 in water from wells USGS 

40 and 47, near the INTEC (fig. 6) exceeded the reporting 

levels through 1985 (Orr and Cecil, 1991, p. 35) but they have 

not exceeded the reporting level since 1985. The absence of 

detectable concentrations of cesium-137 probably resulted 

from discontinuation of wastewater discharge to the INTEC 

disposal well and to sorption processes in the unsaturated and 

perched groundwater zones.

Before 1990, cesium-137 concentrations in water 

from the TAN disposal well (fig. 5) exceeded the reporting 

level because of wastewater discharge to the well. Water 

samples were not collected by the USGS after 1989, because 

the responsibility for monitoring the TAN disposal well 

was turned over to a DOE contractor. The cesium-137 

concentration in water from the TAN Disposal well at that 

time was 4,400±200 pCi/L (Davis, 2006b; U.S. Geological 

Survey, 2010c). 

During 2006–08, concentrations of cesium-137 were less 

than the reporting level in water from all 75 wells sampled 

by the USGS at the INL, including all zones sampled in wells 

equipped with WestbayTM systems.

Plutonium

In 1974, the USGS began monitoring plutonium-238 and 

plutonium-239, -240 (undivided) in wastewater discharged 

to the eastern Snake River Plain aquifer through the disposal 

well (fig. 6) at the INTEC. During 1974–2000, about 0.26 Ci 

of plutonium in wastewater was discharged to the disposal 

well and percolation ponds at the INTEC (Davis, 2008). 

Discharge data for plutonium in wastewater are not available 

for 2001–08. 

Before 1974, alpha radioactivity from disintegration 

of plutonium was not separable from the monitored, 

undifferentiated alpha radioactivity. The half-lives of 

plutonium-238, plutonium-239, and plutonium-240 are 87.7, 

24,100, and 6,560 years, respectively (Walker and others, 

1989, p. 46). Because of radioactive wastewater discharged 

to the disposal well at INTEC, concentrations of plutonium 

isotopes in some water samples from wells USGS 40 and 

47 near INTEC (fig. 6) through January 1987 exceeded the 

reporting level (Orr and Cecil, 1991, p. 37). Concentrations 

in water samples collected from these wells since 1987 have 

been less than the reporting level.

Plutonium isotopes in water from the TAN disposal 

well (fig. 5) exceeded the reporting level because of 

radioactive‐wastewater discharged before 1972. Because 

the responsibility for monitoring the TAN disposal well 

was turned over to a DOE contractor in 1988, the only 

water samples collected by the USGS since that time were 

collected in March and December 1989. The concentration 

of plutonium-238 in water from the TAN disposal well at 

that time was 0.26±0.04 pCi/L, and the concentration of 

plutonium-239, -240 (undivided) was 0.71±0.06 pCi/L 

(Bartholomay and others, 1995). 

During 2006–08, concentrations of plutonium-238 and 

plutonium-239, -240 (undivided) in water from all 28 wells 

sampled and all zones in wells equipped with WestbayTM

systems were less than the reporting level. 
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 37

Americium-241

Americium-241 is a decay product of plutonium-241. 

Plutonium isotopes have been detected in wastewater 

discharged to the Snake River Plain aquifer at the INL and 

they are in wastes buried at the RWMC. The half-life of 

americium-241 is 432.7 years (Walker and others, 1989, 

p. 46). Concentrations of americium-241 in water samples 

collected between September 1972 and July 1982 from 

wells USGS 87, 88, 89, and 90 at the RWMC (fig. 6) and 

in water samples collected through 1988 from the TAN 

disposal well (fig. 5) exceeded the reporting level (Orr and 

Cecil, 1991, p. 38–39). During 1992–95, concentrations of 

americium-241 in water samples from two wells were equal 

to the reporting level. On October 2, 1992, the concentration 

in water from well USGS 37 was 0.09±0.03 pCi/L; on April 

20, 1993, the concentration in water from well USGS 120 

was 0.06±0.02 pCi/L (Bartholomay and others, 1997). The 

concentration in one water sample collected on April 12, 

2001, from the RWMC Production Well (RWMC PROD) was 

0.003±0.001 pCi/L, equal to the reporting level (Davis, 2008). 

During 2006–2008, concentrations in water from all 28 wells 

sampled and all zones in WestbayTM equipped wells were less 

than the reporting level.

Gross Alpha- and Beta-Particle Radioactivity

Gross alpha- and beta-particle radioactivity is a 

measure of the total radioactivity given off as alpha and 

beta particles during the radioactive decay process. The 

radioactivity is usually reported as if it occurred as one 

radionuclide. Gross alpha and beta measurements are used to 

screen for radioactivity in the aquifer as a possible indicator 

of groundwater contamination. Water samples collected 

during 2006–08 were analyzed for gross alpha- and gross 

beta‐particle radioactivity by RESL. In 2008, RESL increased 

the sensitivity of the gross alpha- and gross beta- particle 

radioactivity and changed the radionuclide reported for gross 

alpha from plutonium-239 to thorium-230, and for gross beta 

from cesium-137 to strontium-90/yttrium-90. The minimum 

detectable activity decreased from about 1.6 to 1.5 pCi/L for 

gross alpha and from about 6.4 to 3.4 pCi/L for gross beta, 

allowing for increased detectable concentrations for 2008 data 

(Bartholomay and Twining, 2010).

During 2006–07, concentrations of gross alpha 

radioactivity in water from 58 wells sampled were less than 

the reporting levels. In 2008, reportable concentrations of 

gross alpha radioactivity were observed in 24 wells, and 

ranged from 2.3±0.7 to 6.6±1.3 pCi/L. This likely is a result of 

RESL increasing the sensitivity and changing the radionuclide 

reported for gross alpha radioactivity from plutonium-239 to 

thorium-230. 

During 2006, concentrations of gross beta radioactivity in 

water from ten wells were reportable; in 2007, concentrations 

in water from seven wells were reportable. During 2008, 

concentrations of gross beta radioactivity water from 37 wells 

were reportable ranging from 2.8±0.9 to 21.6±1.8 pCi/L, 

again likely reflecting the increase in sensitivity and change 

in the reporting radionuclide from cesium-137 to strontium-90/

yttrium-90 by RESL.

Chromium

Wastewater from ATRC cooling-tower operations 

contained an estimated 24,000 lb of chromium discharged 

to an infiltration pond during 1952–64 and an estimated 

31,000 lb discharged to an injection well during 1965–72 

(Mann and Knobel, 1988, p. 7). In October 1972, chromium 

used as a corrosion inhibitor in cooling-tower operations was 

replaced by a polyphosphate. No disposal of chromium to the 

subsurface at the ATRC was reported after 1972. 

During 1971–83, about 265 lb of chromium in 

wastewater were discharged to the disposal well at INTEC 

and 720 lb of chromate were discharged at the Power Burst 

Facility (PBF, fig. 1) (Cassidy, 1984, p. 3). About 130 lbs of 

chromium were discharged to the INTEC percolation ponds 

during 1992–98 (Bartholomay and others, 2000). Information 

is not available on the total amount of chromium discharged at 

the INL during 1984-1991 and 1999–2008.

Background concentrations of chromium in the Snake 

River Plain aquifer range from 2 to 3 μg/L (Orr and others, 

1991, p. 41). In April 2005, the MCL of 100 μg/L (U.S. 

Environmental Protection Agency, 2001) for total chromium 

in drinking water was equaled in water from one well, USGS 

65, south of ATRC (fig. 6). In 2008, the concentration of 

chromium in water from that well was 93 μg/L, just less 

than the MCL, and concentrations steadily decreased during 

2006–08. Concentrations in water samples from 75 other wells 

sampled ranged from 1.2 to 28.3 μg/L. The LRL for chromium 

ranged from 0.4 to 2 μg/L during 2006–08; consequently, 

concentrations within that range were designated according to 

those LRLs as detections or nondetections during 2006–08. 

Variation in chromium concentrations with depth in 

WestbayTM equipped wells during 2006–08 is shown in 

figure 16. In 2007 and 2008, chromium concentrations in 

water samples from well Middle 2050A were higher in the 

uppermost zone (7 to 8 μg/L) than concentrations in the four 

lower zones (1 to 4 μg/L). Chromium concentrations in water 

samples from well Middle 2051 were higher in the four lower 

zones, with concentrations ranging from about 6 to 8 μg/L, 

and a lower concentration in the uppermost zone (604.2 ft, 

about 1 μg/L). Concentrations in the water samples from the 

uppermost zone in well USGS 103 (681.9 ft) collected in 

2007 and 2008 were less than 1 μg/L , and the concentrations 

in the rest of the zones generally were consistent, with 

concentrations ranging from about 5 to 6 μg/L. The highest 
38 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig16

Chromium concentration, in micrograms per liter, scale variable

0 2 4 6 8 10

0 2 4 6 8 10

0 2 4 6 8 10

0 2 4 6 8 10

0 2 4 6 8 10

0 5 10 15 20

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 16. Vertical distribution of dissolved chromium in water from six wells (Middle 2050A, Middle 2051, USGS 103, 132, 

133, and 134) equipped with multi-level WestbayTM packer sampling systems, 2006–08.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 39

concentrations of chromium in water samples were from the 

uppermost zone of well USGS 132 (636.4 ft) at 16.7 μg/L in 

2008, and the concentrations in the rest of the zones generally 

were consistent with concentrations ranging from about 7.9 to 

8.4 μg/L in 2008. Chromium concentrations in water samples 

from wells USGS 133 in the uppermost zone (468.0 ft) were 

less than 1 μg/L and concentrations generally were consistent 

ranging from 4.2 to 5.5 μg/L in the deeper zones. In 2008, the 

highest concentration was in water samples from the fourth 

deepest zone of well USGS 134 (805.5 ft) and was 6.1 μg/L; 

the lowest concentration for that well was found in the deepest 

zone (845.5 ft) at 3.0 μg/L.

Sodium

During 1989–98, an estimated average annual 1.3 

million lb/yr of sodium in wastewater were discharged at 

the INL (Bartholomay and others, 1995, 1997, and 2000). 

During 1996–98 about 708,000 lb/yr of sodium were 

discharged to the INTEC percolation ponds; about 58,000 lb/

yr were discharged to the ATRC chemical-waste infiltration 

pond; about 524,000 lb/yr were discharged to the NRF 

industrial‐waste ditch; and about 5,000 lb/yr were discharged 

at CFA (Bartholomay and others, 2000). The total amount of 

sodium in wastewater discharged at individual facilities from 

1999–2008 has not been compiled.

The background concentration of sodium in water 

from the Snake River Plain aquifer near the INL generally is 

less than 10 mg/L (Robertson and others, 1974, p. 155). In 

October 2005, concentrations in water from most wells in the 

southern part of the INL were greater than 10 mg/L.

Concentrations of sodium in water from wells near 

the INTEC generally have varied since 1984 when disposal 

practices were changed from injection to the disposal well 

to discharge to percolation ponds (figs. 6 and 17). During 

1999–2008, the higher concentrations of sodium were in water 

from wells at or near INTEC. During 2006–08, the highest 

sodium concentration in water samples from aquifer wells near 

the INTEC was 40 mg/L in a water sample from well USGS 

77 (fig. 6). Concentrations of sodium in water from other 

wells south of the INTEC during 2006–08 generally were less 

than or equal to sodium concentrations detected in October 

2005, with the exception of well USGS 47, which was slightly 

higher in 2008 (fig. 17). Bartholomay (2009) noted iodine-129 

increases in several wells near INTEC during 2007 and 

attributed the increases to recharge from the Big Lost River 

in 2006 moving water from the perched groundwater bodies 

below INTEC into the aquifer. This also may be the reason for 

the variability in concentration of sodium in wells USGS 37 

and 47 during 2006–08 (fig. 17).

In October 2008, sodium concentrations in water from 

wells USGS 88 and 120 (fig. 6), near the RWMC, were 45 and 

26 mg/L, respectively, slightly higher than the October 2005 

concentrations. 

In May 2008, the sodium concentration in water from 

well MTR Test at the ATRC near the chemical waste pond 

(fig. 6) was 9 mg/L, significantly less than the concentration 

of 42 mg/L in 1998 and about the same as the concentration 

in March 2005. This concentration decrease may be a result of 

the discontinued use of the chemical waste pond in 1999.

The vertical distribution of sodium concentrations 

in wells equipped with WestbayTM systems are shown in 

figure 18. Concentrations in most wells generally were 

consistent with depth, except for well USGS 132. During 

2006–08, the concentration in the uppermost zone (636.4 ft) 

of well USGS 132 was much higher (about 26–30 mg/L) than 

concentrations in the deeper zones (9–12 mg/L).

Chloride

About 2.3 million lb/yr of chloride in wastewater was 

discharged to infiltration ponds at the INL during 1996–98, 

an increase from the estimated 1.5 million lb/yr discharged 

during 1992–95 (Bartholomay and others, 1997, p. 36). 

Of the 2.3 million lb/yr discharged during 1996–98, about 

1.17 million lb/yr were discharged to the INTEC percolation 

ponds (fig. 3; Bartholomay and others, 2000), which was 

about the same amount discharged during 1986–95 (Orr and 

Cecil, 1991, p. 40; Bartholomay and others, 1995, p. 31; 

Bartholomay and others, 1997, p. 36). Information has not 

been compiled for the total amount of chloride discharged in 

wastewater during 1999–2008.

The background chloride concentration in water from 

the Snake River Plain aquifer at the INL generally is about 

15 mg/L (Robertson and others, 1974, p. 150). In 2008, 

concentrations of chloride in most water samples from 

wells south of the INTEC and at the CFA (fig. 19) exceeded 

20 mg/L. The secondary MCL for chloride in drinking water is 

250 mg/L (U.S. Environmental Protection Agency, 2001).

Chloride concentrations in water from wells south of 

the INTEC generally increased because of increased chloride 

disposal to the percolation ponds since 1984 when discharge 

of wastewater to the INTEC disposal well was discontinued. 

Although variable, the concentrations show an overall increase 

through the late 1990s, and overall decrease since the late 

1990s, with the exception of well USGS 59 (fig. 20). Chloride 

concentrations in water from USGS 59, near the INTEC 

percolation ponds, varied during 1984–2005; concentrations 

were unusually high in October 1991, 1995, and 2002 

(fig. 20). The higher concentrations probably were caused by 

seepage down the well from the perched groundwater zone; 

chloride concentrations in perched groundwater wells near 

the percolation ponds were about 270 mg/L in 1991 and 1995 

(Bartholomay and others, 1997) and averaged about 175 mg/L 

in five perched groundwater wells in 2002 (Davis, 2008, table 

13).
40 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig17

USGS 47 USGS 113

0

20

40

60

80

100

10

30

50

70

90

0

10

20

30

40

60

50

0

10

20

30

40

50

60

80

70

90

100

0

20

40

60

80

10

30

50

70

90

100

0

10

20

30

40

50

60

0

10

20

30

40

50

60

0

10

20

30

40

50

60

70

80

100

90

Sodium concentration, in milligrams per liter (scale variable)

Sodium concentration, in milligrams per liter (scale variable)

USGS 40 USGS 111

USGS 37 USGS 59

USGS 57

19801985199019952000200520081980198519901995200020052008

19801985199019952000200520081980198519901995200020052008

19801985199019952000200520081980198519901995200020052008

1980198519901995200020052008

Figure 17. Dissolved sodium concentrations in water from seven wells at and near the Idaho Nuclear Technology and 

Engineering Center (INTEC), 1980–2008. Location of wells shown in figure 6.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 41

tac10-0506_fig18

0 2 4 6 8 10 12 14

0 2 4 6 8 10

0 5 10 15 20 25 30 35

0 2 4 6 8 10

0 2 4 6 8 10

Sodium concentration, in milligrams per liter, scale variable

0 5 10 15 20

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 18. Vertical distribution of dissolved sodium in water from six wells equipped with multi-level WestbayTM packer 

sampling systems, 2006–08.
42 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig19

26

20

Advanced Test

 Reactor Complex

33

26

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Big

Lost

River

40

20

40

60

80

100 120

140

100

60

20

60

80

40

80

Lincoln

Boulevard

Idaho Nuclear

Technology and 

Engineering Center

Central 

Facilities

Area

Radioactive

Waste

Management

Complex

Spreading areas

EXPLANATION

40 Line of equal chloride concentration—April and October 2008. Lines of equal 

concentration were interpreted from analyses of water samples collected 

from a 3-dimensional flow system. Mapped concentrations represent 

water samples collected from various depths in boreholes with differing 

well completions; for example, single- and multiple-screened intervals, and 

open boreholes. Location is approximate. Interval, in milligrams per liter, is 

variable

Well in the USGS water-quality monitoring network—Water samples 

analyzed for chloride

0 1 2 3 Miles

0 1 2 3 Kilometers

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°05' 113°00' 112°55'

43°35'

43°30'

Idaho 

National 

Laboratory

Map area

Figure 19. Distribution of chloride in water from wells at and near the Advanced Test Reactor Complex (ATRC), Idaho 

Nuclear Technology and Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive Waste Management 

Complex (RWMC), Idaho National Laboratory (INL), Idaho, April or October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 43

tac10-0506_fig20

USGS 37

0

50

100

150

200

250

USGS 40

USGS 47

0

50

100

150

200

250

USGS 57

USGS 59

USGS 111

0

50

100

150

200

250

USGS 113

Chloride concentration, in micrograms per liter (scale variable)

Chloride concentration, in micrograms per liter (scale variable)

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

0

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0 0

40

80

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160

200

0

0

40

80

120

160

200

0

0

40

80

120

160

200

0

Figure 20. Dissolved chloride concentrations in water from seven wells at and near the Idaho Nuclear Technology and 

Engineering Center (INTEC), 1980–2008. Location of wells shown in figure 6.
44 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

During 2002–05, concentrations decreased in some 

wells, but increased in others; during 2006–08, concentrations 

in most wells generally either were constant, or increased 

slightly (figs. 6 and 20). Trends in concentrations in water from 

wells downgradient from the percolation ponds correlated 

with discharge rates into the ponds when travel time was 

considered. For example, chloride concentrations in water 

from wells USGS 37 and 57 were lowest in 1985, during the 

period (1984–98) when the smallest amount of chloride was 

discharged to the ponds (fig. 21). Concentrations of chloride 

in water from well USGS 37 generally continued a decreasing 

trend through 2008. However, disposal data are not available 

for 1999–2008. These decreasing trends may indicate decreased 

disposal rates at some time prior to collection of the water 

samples or the redirection of discharge to the new percolation 

ponds to the southwest of these wells in 2002. Concentrations 

of chloride in water from well USGS 57 increased as discharge 

rates increased from 1985 through 1993; concentrations then 

decreased through 1995, increased in 1996, and decreased again 

in 1997 and 1998. Concentrations continued decreasing through 

October 2000, and then they increased through October 2003. 

Since 2003, concentrations have steadily decreased in well 

USGS 57 (figs. 20 and 21). 

Chloride concentrations in water from well USGS 113, 

south of the INTEC, generally decreased from January 1998, 

when the concentration was 240 mg/L, through October 

2008, when the concentration was 50 mg/L (fig. 20). The 

concentration in water from well CFA 1, also south of the 

INTEC, decreased in April 2006 from 114 mg/L to 88 mg/L in 

April 2008. Chloride concentrations in the Rifle Range well 

(fig. 5) increased from 9 mg/L in October 2002 to 42 mg/L in 

October 2008. This may be a result of discharge to the new 

percolation ponds southwest of INTEC beginning in 2002.

In April 2008, the chloride concentration in water from 

well USGS 65 south of the ATRC (fig. 6) was greater than 

background at 18 mg/L. Chloride concentrations in water from 

all other wells completed in the Snake River Plain aquifer at or 

near the ATRC were less than background and ranged between 

10 and 13 mg/L during 2008. 

During 2008, chloride concentrations in water from 

wells USGS 88 and 89 at the RWMC were 91 and 41 mg/L, 

respectively, nearly the same as the 2002–05 reporting period. 

Concentrations of chloride in all other wells near the RWMC 

ranged from 11 to 25 mg/L.

The vertical distribution of chloride concentrations in 

wells equipped with WestbayTM systems varied during 2006–08 

(fig. 22). The highest concentrations in water from well Middle 

2050A were in the uppermost and lowermost zones at about 

14 to 16 mg/L. Concentrations in the middle zones ranged 

from about 10 to 11 mg/L. Concentrations in well Middle 2051 

were lower in the uppermost zone (about 5.6 mg/L) than in 

the deeper zones at concentrations ranging from about 10 to 

12 mg/L. Concentrations in water from wells USGS 103 and 

132 were higher in their uppermost zone, ranging from 18 to 

21 mg/L and 19 to 35 mg/L, respectively. Concentrations in 

water from well USGS 133 generally were lower in the three 

upper zones and the concentration increased in the lowermost 

zone. Concentrations in well USGS 134 were high in the 

two upper zones and variable in the three lower zones. The 

concentrations in the two upper zones ranged from about 9 to 12 

mg/L, and concentrations ranged from about 7 to 10 mg/L in the 

three lower zones.

Sulfate

During 1996–98, about 0.8 million lb/yr of sulfate in 

wastewater was discharged at the INL, a decrease from the 

1.05 million lb/yr discharged during 1992–95 (Bartholomay 

and others, 2000). Of the 0.8 million lb/yr discharged during 

1996–98, about 610,000 lb/yr was discharged to infiltration 

ponds at the ATRC, 146,000 lb/yr was discharged to percolation 

ponds at the INTEC, and 45,000 lb/year was discharged to the 

NRF industrial-waste ditch (Bartholomay and others, 2000). 

Background concentrations of sulfate in the Snake River Plain 

aquifer in the south-central part of the INL range from about 10 

to 40 mg/L (Robertson and others, 1974, p. 72). Compiled data 

are not available for sulfate in wastewater discharged during 

1999–2008. The secondary MCL for sulfate in drinking water is 

250 mg/L (U.S. Environmental Protection Agency, 2001).

Because of the sulfate disposal history at the various 

facilities, water-sample collection for sulfate analyses at several 

wells was added to the USGS water-quality monitoring network 

in 1995. In 2008, sulfate concentrations in water samples 

from nine wells in the south-central part of the INL equaled or 

exceeded the 40-mg/L upper limit background concentration 

of sulfate and ranged from 40 to 157 mg/L. Concentrations 

in water samples from MTR Test, just east of the ATRC 

(fig. 6), decreased from 64 mg/L in October 2001 to 23 mg/L 

in March 2005; and have remained constant since then. The 

decrease in concentrations in this well is probably a result of 

the discontinued use of the chemical waste ponds in 1999. 

Concentrations in a water sample collected during 2008 from 

well USGS 65, just south of the ATRC, was 157 mg/L, similar 

to concentrations since 2001. The concentrations that are higher 

than background concentrations in water from these wells 

probably resulted from sulfate disposal at the ATRC infiltration 

ponds. 

In April or October 2008, sulfate concentrations in water 

samples from USGS 88 and USGS 119 (fig. 6), near the RWMC, 

were 50 and 39 mg/L, respectively, similar to concentrations 

in October 2005. The background concentration that is greater 

than the upper limit of 40 mg/L in water from these wells could 

have resulted from the well construction techniques (Pittman 

and others, 1988, p. 57–61). In October 2008, the sulfate 

concentration in well CFA 2, south of INTEC (fig. 5), 51 mg/L, 

also exceeded the background concentration. This was a slight 

increase from the concentration in October 2005 of 42 mg/L. 

During 2007–08, concentrations were 45, 47, and 46 mg/L in 

water from wells USGS 34, 35, and 39, respectively, southwest 

of INTEC. Historically, concentrations in these wells were equal 

to or just less than the upper limit background value of 40 mg/L. 
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 45

tac10-0506_fig21

Idaho National 

Laboratory

Map

area

Idaho Nuclear

Technology and

Engineering Center

Percolation

ponds

112°57' 56' 112°55' 43°35'

43°33'

34'

Lincoln Boulevard

Lost

Big

River

INTEC

Disposal 

Well 

Flow

Direction

33

0

0 3,000 Feet

1,000 Meters

39 

35 

34 

36 

37 

38 

112 113 77 

111 

57 

82 

67 

116 

115 114 

51 

123 

52 

59 

121 

41 

42 

43 

44 

45 

46 

47 

48 

49 

40 

122 

Routine use of the disposal well 

was discontinued in 1984, and

discharge to percolation ponds

began.

USGS 37 chloride concentration

USGS 57 chloride concentration

Annual discharge of chloride

No discharge data

0

197119751980198519901995200020052008

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Annual discharge of chloride, in millions of pounds

50

100

150

200

250

Chloride concentration, in milligrams per liter

0

Water year

Figure 21. Amount of chloride in wastewater discharged to the disposal well and percolation ponds at the Idaho Nuclear 

Technology and Engineering Center (INTEC), flow direction, and the location and amount of chloride in water from wells 

USGS 37 and USGS 57, Idaho National Laboratory (INL), Idaho, 1971–2008.
46 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig22

Chloride concentration, in milligrams per liter, scale variable

0 5 10 15 20

0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14

0 10 20 30 40

0 5 10 15 20 25 0 2 4 6 8 10 12 14

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 22. Vertical distribution of dissolved chloride in water from six wells equipped with multi-level WestbayTM packer 

sampling systems, 2006–08.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 47

The vertical distribution of sulfate in water from wells 

equipped with WestbayTM systems is shown in figure 23. 

During 2006–08 sulfate concentrations in water from wells 

Middle 2050A were highest in the uppermost zone, and 

lowest in the lowermost zone, with concentrations ranging 

from 20 to 26 mg/L and 10 to 14 mg/L, respectively. Sulfate 

concentrations in water from wells Middle 2051, USGS 

103, and USGS 134 generally were consistent with depth 

that ranged from about 20 to 27 mg/L, 19 to 26 mg/L, and 

16 to 21 mg/L, respectively. Sulfate concentrations were 

highest in water from well USGS 132 in the uppermost 

zone, with concentrations ranging from 39 to 41 mg/L. 

Sulfate concentrations in the lower five zones in this well 

were consistent with depth and ranged from 23 to 26 mg/L. 

Sulfate concentrations in water from well USGS 133 were 

slightly variable in the two middle zones during 2007–08. 

Concentrations throughout all zones ranged from about 19 to 

22 mg/L. 

Nitrate (as N) 

Wastewater containing nitrate was injected into the Snake 

River Plain aquifer through the INTEC disposal well from 

1952 to February 1984 and was discharged to the INTEC 

percolation ponds after February 1984 (Orr and Cecil, 1991). 

About 260,000 lb of nitrate was discharged to the INTEC 

percolation ponds during 1996–98, 220,000 lb of which 

was discharged during February 1996 (Bartholomay and 

others, 2000). Discharge rates of nitrate for 1999–2008 are 

not available. Concentrations of nitrate in groundwater not 

affected by wastewater disposal from INL facilities generally 

are less than 1 mg/L (as N) (Robertson and others, 1974, 

p. 73). 

Concentrations of nitrate in this report are reported as 

nitrogen (N), a change from previous publications in which 

nitrate was reported as nitrate. To convert concentrations as 

N to concentrations as NO3

-

, the nitrate (as N) concentration 

should be multiplied by 4.4266 (Hem, 1989, table 8) so that 

concentrations reported here can be compared with those 

given in previous reporting-period publications. Historical 

nitrite analyses indicate that almost all nitrite plus nitrate 

concentrations in water are nitrate at and near the INL; the 

nitrite concentrations are almost always less than the LRL for 

analyses performed by NWQL.

All nitrate (as N) concentrations measured in 2008 

were less than the MCL for drinking water of 10 mg/L (as 

N) (U.S. Environmental Protection Agency, 2001). Nitrate 

concentrations at the INL have changed in response to reduced 

disposal rates and to the transition in 1984 from injection 

of wastewater to the INTEC disposal well to discharge to 

percolation ponds. In 1981, the maximum nitrate (as N) 

concentration for wells near the INTEC was 14 mg/L in water 

from well USGS 43 at the INTEC just west of the INTEC 

Disposal well (Lewis and Jensen, 1985) (figs. 6 and 24), and 

exceeded the MCL. Nitrate concentrations in water from wells 

in the vicinity of the INTEC disposal well and percolation 

ponds (wells USGS 40, 41, 43, 47, 48, 51, 52, and 67) have 

been variable through time (fig. 24). The variability could 

have resulted from periodic dilution by recharge from the Big 

Lost River and variation in discharge rates to the injection 

well prior to 1984 or percolation ponds later. Concentrations 

of nitrate (as N) in wells south of INTEC and further away 

from the influence of disposal areas and the Big Lost River 

[wells USGS 77, 111, 113, 114, 116, and CFA 1 (figs. 5 and 

6)] show much less variability and a general decrease in nitrate 

(as N) concentrations through time (fig. 25). In October 2008, 

concentrations of nitrate (as N) in water from most wells at 

and near the INTEC (wells USGS 40, 41, 47, 48, 51, 52, 67, 

77, 111, 113, 114, 116) exceeded the background concentration 

of 1 mg/L. Concentrations ranged from 2.2 mg/L (as N) in 

well USGS 113 to 5.97 mg/L (as N) in well USGS 47.

Historically, nitrate (as N) concentrations in water from 

wells near the RWMC have slightly exceeded the regional 

background concentration of about 1 mg/L as N (Robertson 

and others, 1974). In 1998, nitrate (as N) concentrations in 

water samples from wells USGS 88, 89, and 119, near the 

RWMC, exceeded the background and were 1.6, 2.0, and 

1.4 mg/L(as N), respectively (Bartholomay and others, 2000). 

Since 1998, the concentrations of nitrate (as N) in water from 

wells USGS 88, 89, and 119 remained relatively unchanged, 

with concentrations in 2008 of 0.9, 1.7, and 1.4 mg/L (as N), 

respectively. In 2005, near the ATRC, the concentration of 

nitrate (as N) in water from well USGS 65 was 1.6 mg/L , and 

remained constant in 2008 with a concentration of 1.5 mg/L. 

Figure 26 shows the generalized distribution of nitrate (as 

N) concentrations in water samples collected in April or 

October 2008. 

Figure 27 shows the vertical distribution of nitrate 

concentrations(as N) with depth in WestbayTM equipped wells 

during 2006–08. The vertical distribution of nitrate (as N) 

in wells Middle 2051, USGS 103, and USGS 133, showed 

similar patterns. Nitrate concentrations (as N) in all three of 

these wells were lower in the uppermost zone, and similar 

in all deeper zones in each well (fig. 27). Concentrations of 

nitrate (as N) from all zones in Middle 2051 and USGS 103 

were less than 1 mg/L. Concentrations in the deepest zone 

in well USGS 133 were slightly higher at about 1.2 mg/L. 

Nitrate (as N) concentrations in water from well USGS 132 

were higher in the upper zone than concentrations found in the 

deeper zones. Concentrations of nitrate (as N) in water from 

well Middle 2050A varied throughout the vertical sampling 

column (fig. 27), but concentrations generally were less than 

1 mg/L. In well USGS 134, concentrations of nitrate (as N) 

were variable between zones and all were less than 1 mg/L 

(fig. 27).
48 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig23

Sulfate concentration, in milligrams per liter, scale variable

0 5 10 15 20 25 30

0 5 10 15 20 25 30

0 10 20 30 40 50

0 5 10 15 20 25 30

0 5 10 15 20 25 30

0 5 10 15 20 25 30

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 23. Vertical distribution of dissolved sulfate in water from six wells (Middle 2050A, Middle 2051, USGS 103, 132, 133, 

and 134) equipped with multi-level WestbayTM packer sampling systems, 2006–08.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 49

tac10-0506_fig24

USGS 48

USGS 52

USGS 51

USGS 67

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

USGS 40

USGS 41

USGS 43

USGS 47

Nitrate concentration (as Nitrogen), milligrams per literNitrate concentration (as Nitrogen), milligrams per liter

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

Figure 24. Concentration of nitrate (as N) in water from wells at and near the Idaho Nuclear Technology and Engineering 

Center (INTEC), 1981–2008.
50 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig25

USGS 111 USGS 116

USGS 114

USGS 113

USGS 77

CFA 1

Nitrate concentration (as Nitrogen), in milligrams per literNitrate concentration (as Nitrogen), in milligrams per liter

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

0

4

8

12

16

20

24

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

1980198519901995200020052008

Figure 25. Concentration of nitrate (as N) in water from wells south of the Idaho Nuclear Technology and Engineering Center 

(INTEC), 1981–2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 51

tac10-0506_fig26

26

20

Advanced Test

 Reactor Complex

33

26

20

IDAHO NATIONAL 

LABORATORY BOUNDARY

Big

Lost

River

1

2

2

3

5

5

3

1

3

1

1

Lincoln

Boulevard

Idaho Nuclear

Technology and 

Engineering Center

Central 

Facilities

Area

Radioactive

Waste

Management

Complex

Spreading areas

EXPLANATION

5 Line of equal nitrate (as N) concentration—April and October 2008. Lines of 

equal concentration were interpreted from analyses of water samples 

collected from a 3-dimensional flow system. Mapped concentrations 

represent water samples collected from various depths in boreholes with 

differing well completions; for example, single- and multiple-screened 

intervals, and open boreholes. Location is approximate. Interval, in milligrams 

per liter as N, is variable

Well in the USGS water-quality monitoring network—Water samples 

analyzed for nitrate (as N)

0 1 2 3 Miles

0 1 2 3 Kilometers

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

113°05' 113°00' 112°55'

43°35'

43°30'

Idaho 

National 

Laboratory

Map area

Figure 26. Distribution of nitrate (as N) in water from wells at and near the Advanced Test Reactor Complex (ATRC), Idaho 

Nuclear Technology and Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive Waste Management 

Complex (RWMC), Idaho National Laboratory (INL), Idaho, April or October 2008.
52 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig27

Nitrate concentration, in milligrams per liter as N

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0 0.2 0.4 0.6 0.8 1 1.2 1.4

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 27. Vertical distribution of nitrate (as N) in water from six wells equipped with multi-level WestbayTM packer 

sampling systems, 2006–08.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 53

Fluoride

About 39,710 lb of fluoride in wastewater was 

discharged to percolation ponds at the INTEC during 1971–98 

(Bartholomay and others, 2000). Background concentrations 

of fluoride in the Snake River Plain aquifer in the 

southwestern part of the INL range from about 0.1 to 0.3 mg/L 

(Robertson and others, 1974, p. 75). Amounts of fluoride 

discharged since 1998 have not been compiled.

As part of the INL groundwater monitoring program 

adopted in 1994, the USGS began analyzing water samples 

collected near the INTEC for concentrations of fluoride. 

During April or October 2008, water samples from four 

wells (CPP 1, USGS 34, 38, and 77, fig. 6) were analyzed 

for fluoride; detected concentrations ranged from 0.2 to 

0.3 mg/L. These concentrations are similar to the background 

concentrations reported by Robertson and others (1974), 

which indicates that wastewater disposal has not had an 

appreciable effect on fluoride concentrations in the Snake 

River Plain aquifer near the INTEC. The LRL for fluoride 

ranged from 0.08 to 0.12 mg/L during 2006–08. 

Fluoride concentrations in water samples collected 

from all but two zones from wells equipped with WestbayTM

multi-level sampling systems during 2006–08 were within the 

range of background concentrations reported by Robertson 

and others (1974) (fig. 28). Fluoride concentrations in the two 

uppermost zones of well USGS 103 ranged from about 0.32 

to 0.47 mg/L. Concentrations in the rest of the lower zones in 

USGS 103 were consistent, with concentrations of about 0.21 

mg/L. Fluoride concentrations in the uppermost zones of wells 

USGS 132, 133, 134, and Middle 2051 were slightly higher 

than in deeper zones, but all concentrations were less than 

0.3 mg/L. The highest concentration of fluoride in well Middle 

2050A was in the deepest zone, although the concentration 

also was less than 0.3 mg/L (fig. 28).

Trace Elements

As part of the INL groundwater monitoring program 

adopted in 1994 and several special sampling programs, water 

samples from several wells were collected and analyzed for 

various trace elements during 2006–08. These trace elements 

were aluminum, antimony, arsenic, barium, beryllium, 

cadmium, cobalt, copper, iron, lead, lithium, manganese, 

mercury, molybdenum, nickel, selenium, silver, strontium, 

thallium, uranium, vanadium, and zinc. A summary of 

background concentrations of selected constituents in Snake 

River Plain aquifer water samples is presented in Knobel and 

others (1992, p. 52). Because the amounts of each constituent 

in wastewater discharged from INL facilities have not been 

compiled annually from monitoring data since 1998, these 

amounts are unavailable for 1999–2008. 

Beginning in 1998, NWQL began implementing new 

reporting procedures based on long-term method detection 

levels (LT-MDLs) for some analytical methods (Childress and 

others, 1999). This change in LRLs (as opposed to MRLs) 

for some elements accounts for concentrations of some 

elements detected during 1999–2008, although historically 

the concentrations were less than the MRL. Table 6 presents 

a summary of disposal data, disposal periods, and trace 

element concentration ranges in water samples analyzed 

during 2006–08 by the USGS. Bartholomay and Twining 

(2010, table 5) give a comprehensive summary of the vertical 

distribution of selected trace elements for each of the six 

wells equipped with multi-level WestbayTM packer sampling 

systems.

Volatile Organic Compounds

Volatile organic compounds (VOCs) are present in 

water from the Snake River Plain aquifer because of wastedisposal practices at the INL. From 1987–2005, water 

samples from many wells completed in the Snake River 

Plain aquifer at and near the INL were analyzed for VOCs 

for various water quality studies (Mann and Knobel, 1987; 

Mann, 1990; Liszewski and Mann, 1992; Greene and Tucker, 

1998; Bartholomay and others, 2000; Davis, 2006b, 2008). 

Analyses from these studies indicated that from 1 to 19 

VOCs in water samples from several wells exceeded their 

reporting levels during these years. The primary VOCs 

detected included carbon tetrachloride; 1,1-dichloroethane; 

1,1,1-trichloroethane; trichloroethylene; tetrachloroethylene; 

chloroform; and toluene. During 2006–08, water samples 

from 30 wells were collected and analyzed for VOCs. Twelve 

VOCs were detected. One to 10 VOCs were detected in water 

samples from 11 wells. 

A plume of 1,1,1-trichloroethane, a solvent used in 

industrial cleaning processes (Lucius and others, 1989, 

p. 450), has developed in the Snake River Plain aquifer near 

the INTEC because of waste-disposal practices (Bartholomay 

and others, 1995). During 1992–95, water samples were 

collected from 10 wells near the INTEC that previously 

contained water with concentrations of 1,1,1-trichloroethane 

exceeding the MRL. Concentrations in water from 8 of the 

10 wells exceeded the MRL (Bartholomay and others, 1997). 

During 1996–98, water samples were collected from three 

wells near INTEC that previously contained water with 

concentrations of 1,1,1-trichloroethane exceeding the MRL; 

concentrations in water from all three of the wells exceeded 

the MRL. 

During 2006–08, concentrations of 1,1,1-trichloroethane 

in water from wells USGS 34, 38, and 77, south of the 

INTEC, and well USGS 65, south of the ATRC (fig. 6), 

exceeded the MRL as during the 2002–05 reporting period. 
54 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig28

Fluoride concentration, in milligrams per liter, scale variable

0 0.05 0.1 0.15 0.2 0.25 0.3

0 0.05 0.1 0.15 0.2 0.25 0.3

0 0.05 0.1 0.15 0.2 0.25 0.3

0 0.05 0.1 0.15 0.2 0.25 0.3

0 0.1 0.2 0.3 0.4 0.5 0 0.05 0.1 0.15 0.2 0.25 0.3

Sample port depth, in feet below land surface, depth variableSample port depth, in feet below land surface, depth variable

Middle 2050A

Middle 2051

USGS 103

USGS 132

USGS 133

USGS 134

514.9

641.9

790.2

997.6

1178.8

604.2

750.1

827.8

1092.5

1142.5

636.4

763.9

825.8

917.2

1010.3

1172.2

468.0

568.5

684.9

744.3

577.5

644.5

705.5

805.5

845.5

681.9

805.2

913.8

999.5

1095.1

1220.2

1269.4

2006 2007 2008

EXPLANATION

Figure 28. Vertical distribution of fluoride in water from six wells (Middle 2050A, Middle 2051, USGS 103, 132, 133, and 134) 

equipped with multi-level WestbayTM packer sampling systems, 2006–08.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 55

Constituent

Approximate 

amount 

disposed 

(lb)

Disposal

period

Disposal

facility

Number of wells 

sampled at 

the INL during 

2006–08

Range of

concentrations 

(μg/L)

LRL(s) used 

during 2006–08 

(μg/L)

Aluminum 117 1995–98 INTEC 16 1.67-29.04 1.6, 4

Antimony NR NR INL 15 0.072-0.39 0.2,0.06,0.14,0.04

Arsenic 11 1971–98 INL 15 0.74-3.26 0.12, 0.06

Barium 4,740 1971–98 INL 16 15.4-138.5 0.2, 0.08, 0.4

Beryllium <1 1971–98 INL 16 ND 0.06, 0.008, 0.02

Cadmium 22 1971–98 INL 16 0.04-0.37 0.04, 0.02, 2.0, 0.06

Cobalt NR NR INL 16 0.02-2.36 0.4, 0.02, 2, 1.4

Copper 81 1995–98 INTEC 16 0.41-5.25 0.4, 1, 2

Iron 752 1995–98 INTEC 6 15.95-25.03 6, 8, 4

Lead 556 1971–98 INL 16 0.1-3.21 0.08, 0.12, 0.06

Lithium NR NR INL 6 1.12-4.15 0.6, 1

Manganese 44 1995–98 INTEC 16 0.2-476 0.1, 0.18, 0.2

Mercury 141 1971–98 INL 14 ND 0.010, 0.01

Molybdenum NR NR INL 16 0.98-6.3 0.4, 0.12, 0.2, 0.02

Nickel NR NR INL 16 0.12-4.16 0.06, 0.2,0.12

Selenium 9 1971–98 INL 10 0.61-2.07 0.08, 0.04, 0.12

Silver 190 1971–98 INL 16 ND 0.008, 0.1, 0.20

Strontium (stable) NR NR INL 6 200.9-305.9 0.4, 0.8

Thallium NR NR INL 10 ND 0.04

Uranium NR NR INL 15 0.45-2.68 0.04, 0.02, 0.006

Vanadium NR NR INL 6 0.07-6.36 0.04, 0.16

Zinc 5,240 1971–98 INL 16 0.77-330.98 0.6, 1.8, 2

Table 6. Trace elements disposed during various periods, number of wells sampled, and range of concentrations detected, Idaho 

National Laboratory, Idaho, 2006–08.

[Because the amounts of each constituent in wastewater discharged from INL facilities have not been compiled annually from monitoring data since 1998, no 

amounts are available for 1999–2008. Amount disposed, disposal period, and disposal facility from Bartholomay and others, 2000. Abbreviations: LRL, 

Laboratory Reporting Level; NR, none recorded; ND, not detected; INL, Idaho National Laboratory; INTEC, Idaho Nuclear Technology and Engineering 

Center; lb, pound; μg/L, microgram per liter. Symbol: <, less than]

The concentrations in water from wells USGS 34 and 38 

were both 0.17 μg/L, a slight increase from the 2004–05 

concentrations of 0.10 and 0.11 μg/L, respectively. The 

concentrations in water in wells USGS 65 and 77 were 0.10 

and 0.13 μg/L, respectively, in 2008, a slight decrease from 

the concentrations of 0.14 and 0.2 μg/L, respectively, from the 

2002–05 reporting period. The MRL for 1,1,1-trichloroethane 

varied between 0.1 and 1.0 μg/L during 2006–08. All 

1,1,1-trichloroethane concentrations were less than the 

MCL for drinking water of 200 μg/L (U.S. Environmental 

Protection Agency, 2001). In October 2006, the concentration 

of 1,1-dichloroethylene in water from well USGS 77 was 

0.16 μg/L, but was not detected during 2007–08. In April 

2008, water from well USGS 65 contained toluene with a 

concentration of 0.25 μg/L.

Historically, concentrations of VOCs in water samples 

from several wells at and near the RWMC exceeded the 

reporting levels (Bartholomay and others, 2000). For example, 

in October 1998, water from the RWMC Production Well 

contained 4.5 μg/L of carbon tetrachloride, 0.8 μg/L of 

chloroform, 0.5 μg/L of 1,1,1-trichloroethane, 2.1 μg/L of 

trichloroethylene, and 0.18 μg/L of tetrachloroethylene. 

In December 2005, nine VOCs were detected, and in 

December 2008, five VOCs were detected in water from 

the RWMC Production Well. Reported concentrations in 

2008 were 8.5 μg/L of carbon tetrachloride, 1.5 μg/L of 

trichloromethane, 0.54 μg/L of 1,1,1-trichloroethane, 3.1 μg/L 

of trichloroethylene, and 0.32 μg/L of tetrachloroethylene. 

Chloroform was not detected in 2008 although it was detected 

in 2005. The concentration of carbon tetrachloride was higher 

in December 2008 than the concentration in December 2005 

of 6.3 μg/L. A plot of carbon tetrachloride concentrations in 

water from the RWMC Production Well (fig. 29) indicates that 

concentration trends have increased with time from about 1 to 

8 μg/L since 1967.
56 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig29

0

2

4

6

8

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

10

12

Carbon tetrachloride concentraton, in micrograms per liter

Calendar year

Trendline derived by

linear regression

Figure 29. Carbon tetrachloride concentrations in water from the Radioactive Waste Management Complex (RWMC) 

Production Well, Idaho National Laboratory (INL), Idaho, 1987–2008.

In April 2008, VOCs were detected in three wells near 

the RWMC (fig. 6). Concentrations of carbon tetrachloride, 

1,1,1-trichloroethane, trichloromethane, trichloroethylene, and 

tetrachloroethylene in water from well USGS 87 exceeded the 

reporting levels. In October 2008, concentrations of carbon 

tetrachloride, trichloroethylene, and trichloromethane in water 

from well USGS 88 also exceeded the reporting levels, as did 

concentrations of carbon tetrachloride, 1,1,1-trichloroethane, 

trichloroethylene, and trichloromethane in water from well 

USGS 120. During 2006–08, water samples from three wells 

near TAN (ANP 9, No Name 1, and PSTF Test) (fig. 2) were 

sampled for VOCs. Concentrations of VOCs in water from 

these wells were all less than the MRL. Chloroform had 

been detected in all three wells during 2002–05, but was not 

detected during 2006–08. Historically, concentrations of from 

1 to 15 VOCs in water from wells near TAN exceeded the 

MRL (Davis, 2008).
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in the Snake River Plain Aquifer 57

Total Organic Carbon

Analyses of TOC are used to screen for organic 

compounds in the aquifer as a general indicator of 

groundwater contamination. As part of the INL groundwater 

monitoring program adopted in 1994, the USGS began 

collecting and analyzing water from several wells at the INL 

for TOC. During April or October 2008, water samples from 

50 wells completed in the Snake River Plain aquifer at the INL 

were analyzed for TOC; detected concentrations ranged from 

0.43 to 1.9 mg/L. The LRL for TOC ranged between 0.4 and 

0.6 mg/L during 2008.

Water samples were collected and analyzed for total 

organic carbon from six wells equipped with multi-level 

WestbayTM samplings systems. Results showed that the 

concentrations were variable between zones sampled in 

each well (Bartholomay and Twining, 2010). Bartholomay 

and Twining (2010) gives a comprehensive summary of 

concentrations in each zone in each well.

Specific Conductance, Temperature, and pH

Specific conductance is a measure of the electrical 

conductivity of water and is proportional to the quantities 

of dissolved chemical constituents in the water. Dissolved 

chemical constituents such as chloride, sodium, and sulfate 

in wastewater discharged to disposal wells and infiltration 

ponds at INL facilities generally have increased the specific 

conductance of groundwater through time. 

In 2008, the specific conductance of water from 135 wells 

ranged from 223 to 2,220 μS/cm; the highest value was in 

water from well NRF 6 located near the NRF waste ditch. 

Specific conductance measurements for water from most wells 

around the NRF area was around 500–600 μS/cm (fig. 30).

The general increase in specific conductance in 

groundwater attributed to wastewater discharged to the aquifer 

since the mid-1980s is apparent in groundwater downgradient 

from INL facilities. A plume of increased specific conductance 

originated from the INTEC percolation ponds (fig. 6) and 

extended downgradient from the INTEC to the CFA (fig. 30). 

The specific conductance of water from several wells within 

this plume increased from about 500 μS/cm in 1985 (Pittman 

and others, 1988, p. 64) to more than 1,000 μS/cm in 1998, 

but decreased to about 802 μS/cm by 2008 in water from well 

USGS 51. This decreasing trend in wells downgradient of INL 

facilities continued during 2006–08.

The specific conductance of water from several wells at 

the ATRC exceeded 400 μS/cm in 2005. Specific conductance 

of water from well USGS 65 (fig. 6), downgradient from the 

infiltration ponds at the ATRC, was 607 μS/cm in April 2005 

and 612 μS/cm in April 2008.

At the CFA, the specific conductance of water from well 

CFA 1 decreased from 700 μS/cm in 2006 to 609 μS/cm in 

2008; and in well CFA 2, the measurements increased from 

784 μS/cm in 2006 to 810 μS/cm in 2008.

The maximum specific conductance measured in water 

from well USGS 88, near the RWMC, was 580 μS/cm in 

October 2008, a slight increase from the measurement of 

570 μS/cm in October 2005.

Water temperature and pH were measured annually 

during 2006, 2007, and 2008 in water from 124, 127, 

and 127 wells at the INL, respectively. The lowest water 

temperatures consistently were measured in well P&W 2, 

northwest of the TAN (fig. 5) and ranged from 8.3 to 9.0°C, 

a slight increase from the 2002–05 reporting period (Davis, 

2008). The highest water temperatures consistently were 

measured in well USGS 7, ranging from 19.3 to 19.5°C. The 

median water temperature for all wells sampled annually 

from 2006 to 2008, was 12.7, 12.8, and 12.7°C, respectively, 

a slight decrease from the 2002–05 reporting period when the 

median was 12.9, 12.8, 12.8, and 12.9, respectively for each 

year. 

In 2006, pH ranged from 7.1 in well USGS 82 east of the 

INTEC to 8.5 in well USGS 119 south of the RWMC (fig. 6). 

In 2007, pH ranged from 7.3 in water from well USGS 29 on 

the eastern border of the INL (fig. 5) to 9.0 in water from well 

USGS 119, south of the RWMC (fig. 6). In 2008, pH ranged 

from 7.4 in water from well USGS 4 on the eastern border of 

the INL (fig. 5) to 9.1 in water from well USGS 119 (fig. 6). 

The median pH in water from all wells annually from 2006 

to 2008 was 7.8, 7.9, and 7.8, respectively, similar to the 

2002–05 reporting period when median pH ranged from 7.6 to 

8.0.

Field measurements of water temperature, pH, and 

specific conductance were made in all wells equipped with 

WestbayTM sampling systems during 2006–08. Bartholomay 

and Twining (2010, table 2) compiled field measurements 

taken from these wells during 2006–08.
58 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Figure 30. Distribution of specific conductance of water from wells at and near the Advanced 

Test Reactor Complex (ATRC), Naval Reactors Facility (NRF), and Idaho Nuclear Technology and 

Engineering Center (INTEC), Central Facilities Area (CFA), and Radioactive Waste Management 

Complex (RWMC), Idaho National Laboratory (INL), Idaho, April or October 2008.

tac10-0506_fig30

33

26

20

Lincoln Boulevard

26

20

400

IDAHO NATIONAL 

LABORATORY BOUNDARY

Big

Lost

River

400

500

600

400

600

500

600

700

400

300 2

200

500

600

600

300 2

500

2200

800

800

Advanced Test

Reactor Complex

Idaho Nuclear

Technology and 

Engineering Center

Central 

Facilities

Area

Radioactive

Waste

Management

Complex

Spreading areas

Naval

Reactors

 Facility

EBR 1

EXPLANATION

5 Line of equal specific conductance 

measurements—April and October 

2008. Lines of equal concentration 

were interpreted from measurements 

of water samples collected from a 

3-dimensional flow system. Mapped 

measurements represent water 

samples collected from various depths 

in boreholes with differing well 

completions; for example, single- and 

multiple-screened intervals, and open 

boreholes. Location is approximate, 

dashes indicate contour position is 

uncertain. Interval, in microsiemens 

per centimeter, is variable

Well in the USGS water-quality 

monitoring network—Water samples 

analyzed for specific conductance

113°05' 113°00' 112°55'

43°30'

43°35'

43°40'

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

0 1 2 3 Miles

0 1 2 3 Kilometers

Idaho 

National 

Laboratory

Map area
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 59

Selected Radiochemical and Chemical 

Constituents and Physical Properties of 

Water in Perched Groundwater

Disposal of wastewater to infiltration ponds and ditches, 

lined evaporation ponds, drain fields, and infiltration of 

surface water at waste-burial pits resulted in formation 

of perched groundwater in basalts and in sedimentary 

interbeds that overlie the Snake River Plain aquifer. Perched 

groundwater has formed in a complex sequence of basalt 

flow and sedimentary interbeds beneath the ATRC, the 

INTEC, and the RWMC. Anderson and Lewis (1989) and 

Anderson (1991) correlated geophysical logs to describe the 

stratigraphic sequences in which perched groundwater has 

formed. Although the subsurface stratigraphy, geohydrologic 

characteristics, and waste disposal practices at each of these 

areas differ, the features controlling the formation of perched 

groundwater at these sites are similar (Cecil and others, 

1991). Sedimentary interbeds in the subsurface may have 

smaller vertical hydraulic conductivities than overlying basalt 

flows, and alteration between basalt flows may contribute to 

reduced vertical hydraulic conductivity in the interflow rubble 

zones. Dense, unfractured basalt flows may have a decreased 

vertical hydraulic conductivity and inhibit downward flow, 

and sedimentary or chemical infilling of fractures in basalt 

may reduce vertical hydraulic conductivity by limiting the 

interconnectivity of fractures, reducing the water-transmitting 

capability of the basalts (Cecil and others, 1991). Any 

combination of these factors may disrupt the downward 

movement of water and contribute to the formation of perched 

groundwater zones. 

Wastewater-disposal sites at INL facilities are the primary 

sources of radiochemical and chemical constituents in perched 

groundwater at the INL. During 2006–08, wastewater was 

discharged to infiltration and lined-evaporation ponds. Davis 

(2008) provides detailed information on waste disposal 

amounts and types of constituents discharged at each facility 

through 1998. Data for amounts and types of constituents 

discharged have not been compiled for 1998–2008.

Advanced Test Reactor Complex

Bodies of shallow and deep perched groundwater 

formed at the ATRC in response to wastewater disposal 

into radioactive-, chemical-, cold-, and sanitary-waste 

ponds (Tucker and Orr, 1998) (fig. 6). Radiochemical and 

chemical constituents in wastewater migrate to the Snake 

River Plain aquifer through perched groundwater beneath 

these wastewater infiltration ponds. The extent of perched 

groundwater is affected by the waste-disposal practices. 

Selected radiochemical and inorganic chemical constituents 

in wastewater have been monitored in the shallow and deep 

perched groundwater since the early 1960s.

Water samples from three wells (CWP 1, 3, and 8) 

completed in shallow perched groundwater near the ATRC 

(fig. 7) routinely were collected and analyzed for selected 

radiochemical and chemical constituents during 2006–08. 

Wells USGS 53, TRA A 13, and TRA A 77 were scheduled to 

be sampled, but were dry during the scheduled sampling runs; 

therefore, samples could not be collected. Water samples were 

collected from 17 wells (PW 8, 9, USGS 54 through 56, 60 

through 63, 66, 68 through 73, and 78) that were completed 

in deep perched groundwater beneath the ATRC. Sampling 

was discontinued at many perched groundwater wells during 

the 2002–05 reporting period because of lack of water in 

the wells (Davis, 2008, fig. 21). Selection of radiochemical 

and chemical constituents for analyses was based on wastedisposal history at the ATRC. Selected radiochemical 

constituents were tritium, strontium-90, and gamma analyses 

(which may yield detections of cesium-137, cobalt-60, 

or chromium-51); chemical constituents were dissolved 

chromium, sodium, chloride, and sulfate.

Tritium

The concentration of tritium in perched groundwater near 

the ATRC during April or October 2008 is shown in figure 31. 

Concentrations of tritium in wells near the ATRC historically 

have been high compared to 2008 values. The decrease in 

tritium concentrations in perched groundwater from wells 

near the ATRC likely is a result of changes in wastewater 

disposal practices near those wells. In some cases, the change 

in disposal practices also may have led to a decrease in the 

amount of perched groundwater available to sample. 

Well TRA A 77 (fig. 7) is completed in shallow perched 

groundwater in alluvium near the ATRC retention basin, 

where radioactive wastewater flowed before discharge to 

the radioactive-waste ponds. Some wastewater reportedly 

leaked to the subsurface through cracks in the retention 

basin (U.S. Department of Energy, 1991, p. 29). To prevent 

discharge of radioactive wastewater to the retention basin, 

the retention basin was isolated in 1993 when discharge 

to the lined evaporation ponds began (Bartholomay and 

Tucker, 2000). The highest tritium concentration in water 

from well TRAA 77 was 3,940,000±60,000 pCi/L in 1992 

(Bartholomay, 1998, p. 41). By April 1997 the concentrations 

had decreased to 1,000±150 pCi/L (Bartholomay, 1998, 

table 2). Historically, tritium concentrations varied in water 

from well TRA A 77. Because of the shallow depth of well 

TRAA 77 and its proximity to the leaking retention basin, the 

variability in tritium concentrations in this well could have 

resulted from changes in tritium disposal rates (Bartholomay, 

1998, p. 10). Water samples have not been collected from well 

TRA A 77 since April 1997 because water was not present in 

the well during scheduled sampling dates. The lack of water in 

this well may be the result of discontinued use of the retention 

basin for transfer of radioactive wastewater.
60 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig31

2900±130

120±50

USGS 63

30±50

USGS 69

1030±80

USGS 71

1030±80

USGS 71

DRY

USGS 74

220±60

USGS 54

280±70

PW 8

70±50

USGS 60

2610±120

USGS 61

120±60

USGS 62

500±60

USGS 66

30±60

USGS 72

60±60

USGS 68

12300±300

USGS 73

28700±500

PW 9 DRY

USGS 53

4880±170

USGS 55

DRY

USGS 56

USGS 70

40±50

USGS 78 (approx. located)

Advanced Test Reactor Complex

Lincoln Boulevard

Monroe Boulevard

Cold-waste

ponds

Chemical-waste pond

Sanitary-waste

pond Evaporation ponds

Retention

basin Radioactive-waste ponds

EXPLANATION

Extent of deep perched groundwater zone—April−October 2008. 

Approximately located

Well completed in deep perched groundwater—Entry, PW 8, is local 

well identifier; 280±70, is tritium concentration and associated uncertainty 

in picocuries per liter. Concentration equal to or greater than the 3s

reporting level in bold. Values represent most recent data collected 

during April–October 2008

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

0

0

2,000 Feet

500 Meters

Idaho 

National 

Laboratory

Map

area

Figure 31. Concentrations of tritium in water from wells completed in deep perched groundwater, Advanced Test Reactor 

Complex, Idaho National Laboratory, Idaho, April or October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 61

Maximum concentrations of tritium in water from well 

TRA A 13 (fig. 7) decreased from 158,000±2,000 pCi/L 

during 1982–85 to 1,100±300 pCi/L during 1986–88 

(Cecil and others, 1991, p. 33); during 1989–2001, tritium 

concentrations in water from this well were less than the 

reporting level. The decrease in tritium concentrations in well 

TRA A 13, between the radioactive-waste infiltration ponds 

and the cold-waste ponds (fig. 31), likely can be attributed to 

the large quantity of nonradioactive water discharged to the 

cold-waste ponds (Bartholomay and Tucker, 2000). Water 

samples were not collected from this well after April 2001 

because of well obstructions or because the well was dry 

during scheduled sampling events and sampling this well 

has been discontinued for the USGS water-quality sampling 

program.

Wells CWP 1 through CWP 9 (fig. 4) monitor shallow 

perched groundwater around the cold-waste ponds at the 

ATRC. During 2006–08, tritium concentrations in water 

samples collected from wells CWP 1, 3, and 8 were less than 

the reporting level.

Discharge of cooling-tower wastewater to the TRA 

disposal well ceased in 1982, and this water subsequently 

was discharged to the cold-waste ponds. During 1982–2005, 

tritium was less than the reporting level in water from 

wells CWP 1 through CWP 7. A tritium concentration of 

800±200 pCi/L was measured in water from well CWP 8 in 

November 1988; since then, concentrations have been less 

than the reporting level. Tritium concentrations in water from 

well CWP 9 decreased from 6,300±200 pCi/L during 1982–85 

to 1,100±200 pCi/L during 1986–88 (Cecil and others, 1991, 

p. 35). Water samples have not been collected from CWP 9 

since 1988. The absence of detectable tritium concentrations 

in most CWP wells was attributed to the large quantity of 

nonradioactive wastewater discharged to the cold-waste ponds 

since 1982 which has diluted any residual radioactive-waste 

infiltration pond water (Bartholomay and Tucker, 2000). Lack 

of available perched groundwater to sample and the history of 

non-reportable values of tritium in most of these wells resulted 

in the decision to remove wells CWP 2, 4, 5, 6, 7, and 9 from 

the sampling schedule at various times during 2002–05. 

Tritium concentrations in water from 11 wells completed 

in deep perched groundwater (PW 8, PW 9, USGS 55, 54, 

56, 61, 63, 66, 70, 71, and 73) generally were greater than 

the reporting level during at least one sampling event during 

2006–08 (table 7). Tritium concentrations in water from six 

wells (USGS 60, 62, 68, 69, 72, and 78) were less than the 

reporting level during 2006–08 (table 7). 

During April or October 2008, tritium concentrations in 

water from 10 wells completed in deep perched groundwater 

at the ATRC exceeded the reporting levels (table 7). Tritium 

concentrations ranged from 280±70 pCi/L in water from well 

PW 8 to 28,700±500 pCi/L in water from well PW 9 (fig. 31). 

Water samples collected in October 2008 from wells 

USGS 73 and PW 9 contained tritium concentrations 

of 13,100±300 and 28,700±500 pCi/L, respectively. 

Concentrations of tritium in these two wells have decreased 

significantly since October 1993 when concentrations were 

296,000±10,000 pCi/L in water from well USGS 73 and 

193,000±6,000 pCi/L in water from well PW 9. Water from 

well USGS 74 (fig. 31) contained 93,100±1,700 pCi/L of 

tritium in April 1992; however, water samples have not 

been collected since 1992 because the well was dry and 

was removed from the sampling schedule in October 2001. 

These three wells are located more than 1,500 ft west of 

the radioactive-waste infiltration ponds (fig. 31). In 1993, 

the radioactive-waste infiltration ponds were taken out of 

service and wastewater was discharged to lined evaporation 

ponds (Davis, 2008). Historically high tritium concentrations 

in water from these wells indicate that the chemistry of 

perched groundwater west of the ATRC was affected by 

radioactive-waste infiltration pond disposals. Discontinuation 

of wastewater discharge to the radioactive-waste infiltration 

ponds and the subsequent use of lined evaporation ponds, 

together with the radioactive decay process, may account 

for the decreased tritium concentrations in this area from 

1993–2008 and could indicate an eastward migration of the 

extent of deep perched groundwater relative to well USGS 74.

Bartholomay (1998) determined that increases in tritium 

concentrations in water from wells USGS 53, 56, and 70 

corresponded partly to tritium disposal rates. The hydraulic 

connection between the radioactive-waste infiltration ponds 

and wells USGS 53 and 56 also can be demonstrated because 

well USGS 53 dried up and the water level in well USGS 

56 declined below the pump intake subsequent to cessation 

of wastewater disposal to the ponds. Water was present and 

water samples were collected from well USGS 53 in October 

2003. The concentration of tritium in well USGS 53 was 

greater than the reporting level at 3,100±200 pCi/L; however, 

the decrease in concentration was significant compared to 

the concentration of 126,000±4,000 pCi/L for the water 

sample analyzed in October 1995. Water samples also were 

collected from well USGS 56 in October 2004 and 2005, with 

concentrations greater than the reporting level at 23,300±900 

and 23,300±1,100 pCi/L, respectively. The tritium 

concentration in a sample collected from water from well 

USGS 56 in October 2006 was 9,490±330 pCi/L, less than 

one-half of the October 2005 concentration. The decreases in 

concentrations were significant compared to the concentration 

of 148,000±5,000 pCi/L for the last water sample analyzed in 

April 1997.

Several factors affected the distribution of tritium in 

perched groundwater at the ATRC, including proximity of 

wells to the radioactive-waste infiltration ponds, depth of 

water below the ponds, variations in tritium disposal rate, and 

radioactive decay. Since 1982, tritium concentrations also 

have been affected by dilution from the cold-waste ponds. 

Replacement of the radioactive-waste infiltration ponds with 

the lined evaporation ponds in 1993 contributed to decreases 

in tritium concentrations in perched groundwater and 

decreases in perched groundwater in some wells. Infiltration 

from the Big Lost River during 1999, early 2000, 2005, and 

2006 may have contributed to diluted tritium concentrations in 

perched groundwater southeast of the ATRC. 
62 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Table 7. Concentrations of tritium, strontium-90, and cesium-137 in perched groundwater from selected wells, Advanced Test Reactor 

Complex, Idaho National Laboratory, Idaho, 2006–08.

[Well No.: Locations of wells are shown in figure 7. Analyses completed by the Department of Energy’s Radiological and Environmental Sciences Laboratory. 

Analytical uncertainties are reported as 1 times the sample standard deviation. Concentrations equal to or greater than 3 times the sample standard deviation are 

considered to be greater than the reporting level and are bold. Abbreviations: DP, well completed in deep perched groundwater; SP, well completed in shallow 

perched groundwater; NR, analysis not requested; NS-DRY, not sampled because the well was dry; NSEQ, not sampled because of equipment problems; pCi/L, 

picocurie per liter; USGS, U.S. Geological Survey. Symbol: ±, plus or minus]

Well No. Date

sampled

Tritium

(pCi/L)

Strontium-90

(pCi/L)

Cesium-137

(pCi/L)

CWP 1 (SP) 11-08-06 -40 ± 50 0.4 ± 0.7 40 ± 30

10-23-07 -30 ± 70 1 ± 0.7 NR

04-30-08 -30 ± 60 0.2 ± 0.7 NR

CWP 3 (SP) 05-15-06 80 ± 90 -2.2 ± 0.7 NR

04-30-07 -10 ± 110 0.2 ± 0.7 NR

04-30-08 90 ± 60 0.2 ± 0.8 NR

CWP 8 (SP) 11-08-06 10.1 ± 54 -0.9 ± 0.7 16 ± 21

10-22-07 -70 ± 60 2.1 ± 1 NR

04-30-08 70 ± 60 -0.1 ± 0.7 NR

PW 8 (DP) 05-05-06 250 ± 100 10 ± 30

04-11-07 410 ± 130 7.5 ± 0.9 0 ± 20

04-14-08 280 ± 70 7.8 ± 0.7 -17 ± 18

PW 9 (DP) 10-30-06 16,300 ± 500 -0.7 ± 0.7 20 ± 30

10-23-07 24,400 ± 2500 -1.2 ± 0.7 16 ± 33

10-06-08 28,700 ± 500 2.1 ± 0.7 -2 ± 15

USGS 54 (DP) 10-26-06 50 ± 60 48.8 ± 1.4 10 ± 20

10-04-07 100 ± 70 33.9 ± 1.2 -50 ± 30

10-06-08 220 ± 60 40.1 ± 1.2 10 ± 10

USGS 55 (DP) 04-25-06 5,600 ± 200 70.5 ± 1.8 20 ± 30

05-01-07 40,200 ± 1400 55.1 ± 1.6 -12 ± 25

04-15-08 4,880 ± 170 49.4 ± 1.5 40 ± 30

USGS 56 (DP) 10-26-06 9,490 ± 330 36.1 ± 1.2 -10 ± 30

10-16-07 NS-DRY NS-DRY NS-DRY

10-22-08 NS-DRY NS-DRY NS-DRY

USGS 60 (DP) 10-26-06 60 ± 60 0.5 ± 0.7 -20 ± 40

10-18-07 40 ± 70 0 ± 0.7 -10 ± 20

10-06-08 70 ± 50 4 ± 0.7 16 ± 8

USGS 61 (DP) 04-25-06 3,300 ± 200 -0.6 ± 0.7 30 ± 30

05-01-07 2,600 ± 200 0.8 ± 0.7 0 ± 3

04-14-08 2,610 ± 120 0.5 ± 0.7 10 ± 20

USGS 62 (DP) 04-25-06 240 ± 100 0.3 ± 0.7 12 ± 35

04-30-07 10 ± 110 2.2 ± 0.7 40 ± 40

04-14-08 120 ± 60 3.5 ± 0.7 -20 ± 30

USGS 63 (DP) 11-01-06 180 ± 60 0.9 ± 0.7 0 ± 30

10-23-07 -10 ± 70 -0.5 ± 0.7 0 ± 40

10-07-08 120 ± 50 3.3 ± 0.7 30 ± 10

USGS 66 (DP) 11-08-06 790 ± 70 0.8 ± 0.7 0 ± 20

10-22-07 460 ± 90 0.1 ± 0.7 -16 ± 34

10-23-08 500 ± 60 1.1 ± 0.7 -4 ± 10

USGS 68 (DP) 04-06-06 0 ± 1,500 1.1 ± 0.8 10 ± 30

04-25-07 -30 ± 60 0.8 ± 0.7 -30 ± 40

04-22-08 60 ± 60 2 ± 0.7 7 ± 16
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 63

Well No. Date

sampled

Tritium

(pCi/L)

Strontium-90

(pCi/L)

Cesium-137

(pCi/L)

USGS 69 (DP) 11-07-06 -60 ± 50 -0.1 ± 0.7 0 ± 40

10-23-07 -40 ± 60 0.7 ± 0.7 -80 ± 40

10-07-08 30 ± 50 1.7 ± 0.7 15 ± 12

USGS 70 (DP) 05-16-06 2,800 ± 200 5 ± 0.8 -30 ± 30

05-01-07 4,400 ± 300 42.1 ± 1.2 30 ± 20

4-14-2008 2,900 ± 130 34.7 ± 1.2 -20 ± 20

USGS 71 (DP) 11-08-06 1,130 ± 80 0.6 ± 0.7 -40 ± 20

10-22-07 NSEQ NSEQ NSEQ

10-23-08 1,030 ± 80 0 ± 0.6 -16 ± 8

USGS 72 (DP) 04-06-06 80 ± 90 0.3 ± 0.7 -60 ± 30

04-25-07 -60 ± 110 0.1 ± 0.7 15 ± 19

04-22-08 30 ± 60 1.8 ± 0.7 -10 ± 40

USGS 73 (DP) 11-08-06 9,470 ± 330 0.6 ± 0.7 0 ± 20

05-05-08 12,300 ± 300 1.6 ± 0.7 20 ± 20

10-07-08 13,100 ± 300 1.6 ± 0.7 2 ± 8

USGS 78 (DP) 11-08-06 0 ± 50 -0.2 ± 0.7 30 ± 40

10-22-07 0 ± 70 -0.5 ± 0.7 14 ± 23

10-23-08 40 ± 50 2.6 ± 0.7 -5 ± 11

Table 7. Concentrations of tritium, strontium-90, and cesium-137 in perched groundwater from selected wells, Advanced Test Reactor 

Complex, Idaho National Laboratory, Idaho, 2006–08.—Continued

[Well No.: Locations of wells are shown in figure 7. Analyses completed by the Department of Energy’s Radiological and Environmental Sciences Laboratory. 

Analytical uncertainties are reported as 1 times the sample standard deviation. Concentrations equal to or greater than 3 times the sample standard deviation are 

considered to be greater than the reporting level and are bold. Abbreviations: DP, well completed in deep perched groundwater; SP, well completed in shallow 

perched groundwater; NR, analysis not requested; NS-DRY, not sampled because the well was dry; NSEQ, not sampled because of equipment problems; pCi/L, 

picocurie per liter; USGS, U.S. Geological Survey. Symbol: ±, plus or minus]

Strontium-90

Some wells completed in shallow perched groundwater at 

the ATRC were not sampled during 2006–08 because the wells 

were dry. The concentration of strontium-90 in well CWP 1, 

completed in shallow perched groundwater, varied between 

reportable and non-reportable concentrations during 2000–05 

(Davis, 2008, table 10). Strontium-90 concentrations in water 

from wells CWP 1, 3, and 8 were less than the reporting level 

for all samples collected between 2006 and 2008 (table 7).

During at least one sampling event in the period 2006–08, 

concentrations of strontium-90 in water from wells PW 8, 

PW 9, USGS 54, 55, 56, 62, 63, 70, and 78, completed in 

deep perched groundwater at the ATRC, were greater than 

reporting levels (table 7, fig. 32). Concentrations ranged 

from 2.1±0.7 pCi/L in well PW 9 to 70.5±1.8 pCi/L in well 

USGS 55. The distribution of strontium-90 concentrations 

in perched groundwater from these wells during 2006–08 

is attributed to exchange reactions between strontium-90 

in solution and to sediments beneath the radioactive-waste 

infiltration ponds. Because data for strontium-90 disposal 

in 2006–08 were not available, fluctuations could not be 

correlated with disposal during this period. Strontium-90 has 

not been detected in water from the Snake River Plain aquifer 

beneath the ATRC possibly because of the exclusive use of 

waste disposal ponds and lined evaporation ponds rather than 

injection of waste directly to the aquifer (Bartholomay and 

others, 1997, p. 30). The absence of detectable concentrations 

indicates that strontium-90 in solution is removed possibly by 

sorption and (or) exchange reactions in the unsaturated zone. 

Studies of strontium distribution coefficients for samples of 

surficial sediment, sedimentary interbeds, and sediment-filled 

fractures in basalts at the INL (Liszewski and others, 1997, 

1998; Pace and others, 1999) support this theory.

Gamma Spectrometry

Water samples collected are routinely analyzed by 

gamma spectrometry and the results may yield concentrations 

of cesium-137, chromium-51, and cobalt-60. Water samples 

from wells completed in both shallow and deep perched 

groundwater at and near the ATRC have not yielded reportable 

concentrations of cesium-137 since 1997, chromium-51 since 

1995, or cobalt-60 since 1998 (Davis, 2008, table 10; this 

report, table 7).
64 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig32

34.7±1.2

3.3±0.7

USGS 63

1.7±0.7

USGS 69

0±0.6

USGS 71

7.8±0.7

PW 8

DRY

USGS 74

0±0.6

USGS 54

7.8±0.7

PW 8

4±0.7

USGS 60

0.5±0.7

USGS 61

3.5±0.7

USGS 62

1.1±0.7

USGS 66

1.8±0.7

USGS 72

2±0.7

USGS 68

1.6±0.7

USGS 73

2.1±0.7

PW 9 DRY

USGS 53

49±1.5

USGS 55

DRY

USGS 56

USGS 70

2.6±0.7

USGS 78 (approx. located)

Advanced Test Reactor Complex

Lincoln Boulevard

Monroe Boulevard

Cold-waste

ponds

Chemical-waste pond

Sanitary-waste

pond Evaporation ponds

Retention

basin Radioactive-waste ponds

EXPLANATION

Extent of deep perched groundwater zone—April−October 2008. 

Approximately located

Well completed in deep perched groundwater—Entry, PW 8, is local 

well identifier; 7.8±0.7, is strontium-90 concentration and associated 

uncertainty in picocuries per liter. Concentration equal to or greater 

than the 3s reporting level in bold. Values represent most recent data 

collected during April–October 2008

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

0

0

2,000 Feet

500 Meters

Idaho 

National 

Laboratory

Map

area

Figure 32. Concentrations of strontium-90 in water from wells completed in deep perched groundwater, Advanced Test 

Reactor Complex, Idaho National Laboratory, Idaho, April or October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 65

Chromium

Historically, dissolved chromium concentrations in 

shallow perched groundwater at the ATRC have been very low 

(less than or slightly greater than the LRL) because of lack of 

disposal of chromium in the cold waste ponds. Over the past 

decade, several wells were not sampled because they were dry 

and were removed from the USGS sampling program. During 

2006–08, three shallow perched groundwater wells (CWP 1, 3, 

and 8) were sampled for chromium. Chromium was detected 

only in well CWP 1 in April 2008 with a concentration of 

3 μg/L (table 8). The LRL for dissolved chromium varied 

from 1.2 to 2 μg/L during 2006–08. Estimated concentrations 

(table 8) less than the LRLs are treated as nondetected 

concentrations for consistency with treatment reported in 

previous publications and because an estimated concentration 

is considered a “qualitatively detected analyte” (Childress and 

others, 1999, p. 7).

Dissolved chromium was detected in water from 14 

wells (PW 8-9, USGS 54-56, 60-63, 66, 68, 70, 71, and 73) 

completed in deep perched groundwater at the ATRC during 

2006–08 (table 8). The highest concentrations during 2006–08 

were in water from wells north and west of the radioactivewaste infiltration ponds (PW 9 and USGS 55, 56, 68, and 73). 

During 2006–08 the maximum concentration of chromium 

in deep perched groundwater at the ATRC was 125 μg/L in 

well USGS 56 in October 2006. During April–October 2008, 

detectable concentrations of dissolved chromium in wells 

completed in deep perched groundwater near the ATRC ranged 

from 4 μg/L in well USGS 60 to 34 μg/L in well USGS 73; 

however, well USGS 56 was not sampled during 2008 because 

the well was dry (table 8 and fig. 33). 

Wastewater from ATRC cooling-tower operations 

contained an estimated 24,000 lb of chromium discharged 

to an infiltration pond during 1952–64 and an estimated 

31,000 lb discharged to an injection well during 1965–72 

(Mann and Knobel, 1988, p. 7). In October 1972, chromium 

used as a corrosion inhibitor in cooling-tower operations was 

replaced by a polyphosphate. No disposal of chromium to the 

subsurface at the ATRC was reported after 1972 (Bartholomay 

and Tucker, 2000). The presence of dissolved chromium in 

water from wells completed in perched groundwater indicates 

that water from these wells contains chromium discharged 

to the radioactive-waste infiltration ponds before 1965 when 

disposal practices changed to injection of cooling-tower 

blowdown water to the disposal well.

Sodium

During 2006–08, analyses were not made for dissolved 

sodium concentrations in shallow perched groundwater 

at the ATRC either because the wells were dry or because 

analyses for dissolved sodium were not requested from 

the laboratory (table 8). During April–October 2008, 

dissolved sodium concentrations in water from 17 wells 

completed in deep perched groundwater were determined. 

During April–October 2008, dissolved sodium concentrations 

ranged from 6 to 476 mg/L. The highest concentration was 

in well USGS 68 (table 8); the sodium concentration in well 

USGS 68 increased from 370 mg/L in October 2005 (Davis, 

2008, table 11). Sodium concentrations in this well have 

varied through time and ranged from 476 to 504 mg/L during 

2006–08. The reason for the variability of the concentrations 

in well USGS 68 probably is a result of movement of remnant 

water through the unsaturated zone from the chemical waste 

pond which was closed in 1999.

Chloride

Concentrations of chloride in most wells varied during 

2006–08 (table 8). During April 2008, dissolved chloride 

concentrations in shallow perched groundwater ranged 

from 11 mg/L in well CWP 8 to 13 mg/L in wells CWP 1 

and 3. Dissolved chloride concentrations in deep perched 

groundwater during April or October 2008 ranged from 

4 mg/L in well USGS 78 to 43 mg/L in well USGS 73. Higher 

concentrations in wells may be a result of movement of 

remnant water through the unsaturated zone from the chemical 

waste pond which was closed in 1999.

Sulfate

The maximum dissolved sulfate concentration in shallow 

perched groundwater was 399 mg/L in well CWP 1 in 

November 2006. Concentrations of dissolved sulfate in this 

well vary greatly. During 2002–05, the concentrations ranged 

from 26 to 396 mg/L and during 2006–08 concentrations 

ranged from 66 to 399 mg/L (table 8). The variable 

concentrations are probably a result of changes in the amount 

of sulfate disposal to the cold-waste ponds. Concentrations 

of dissolved sulfate ranged from 94 to 242 mg/L during 

April–October 2008 in water from wells USGS 54, 60, 

63, 69, and PW 8 that were completed in deep perched 

groundwater near the cold-waste ponds (table 8; fig. 7). 

These high concentrations indicate that water in the wells 

also was affected by discharge into the cold-waste ponds. 

During April–October 2008, the maximum concentration of 

dissolved sulfate in deep perched groundwater was 1477 mg/L 

in well USGS 68 (table 8), west of the chemical-waste pond 

(fig.7). The dissolved sulfate concentration in this well varied 

from 1240 to 1477 mg/L during 2006–08, an increase in 

concentrations from 951 mg/L in April 2005 (Davis, 2008, 

table 11). 
66 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Table 8. Concentrations of selected dissolved ions in perched groundwater from selected wells, Advanced Test Reactor Complex, 

Idaho National Laboratory, Idaho, 2006–08.

[Well No.: Locations of wells are shown in figure 7. Analyses completed by the USGS National Water Quality Laboratory. Abbreviations: DP, well completed 

in deep perched groundwater; SP, well completed in shallow perched groundwater; NR, analysis not requested; NS-DRY, not sampled due to lack of water or 

because water level was below pump intake; NSEQ, not sampled because of equipment problems; E, estimated, and followed by the estimated value; μg/L, 

microgram per liter; mg/L, milligram per liter; USGS, U.S. Geological Survey. Symbol: <, less than respective reporting level]

Well No. Date Sampled

Chromium, 

dissolved

(μg/L)

Sodium, 

dissolved

(mg/L)

Chloride, 

dissolved

(mg/L)

Sulfate, 

dissolved

(mg/L)

CWP 1 (SP) 11-08-06 <2 NR 29 399

10-23-07 E1 NR 15 117

04-30-08 3 NR 13 66

CWP 3 (SP) 05-15-06 <2 NR 19 175

04-30-07 <2 NR 25 323

04-30-08 E1 NR 13 63

CWP 8 (SP) 11-08-06 <2 NR 12 64

10-22-07 <1.2 NR 12 78

04-30-08 E1 NR 11 69

PW 8 (DP) 05-05-06 6 13 16 132

04-11-07 7 15 19 202

04-14-08 6 16 19 216

PW 9 (DP) 10-30-06 18 19 31 104

10-23-07 51 21 34 90

10-06-08 6 20 38 86

TRA A 13 (SP) 05-15-06 NSEQ NSEQ NSEQ NSEQ

10-03-07 NS-DRY NS-DRY NS-DRY NS-DRY

08 Sampling 

Discontinued

USGS 53 (DP) 05-15-06 NS-DRY NS-DRY NS-DRY NS-DRY

04-30-07 NS-DRY NS-DRY NS-DRY NS-DRY

10-06-08 NS-DRY NS-DRY NS-DRY NS-DRY

USGS 54 (DP) 10-26-06 4 13 13 101

10-04-07 6 15 15 122

10-06-08 5 16 19 208

USGS 55 (DP) 04-25-06 25 15 15 105

05-01-07 100 20 26 113

04-15-08 15 16 15 108

USGS 56 (DP) 10-26-06 125 42 18 80

10-23-07 NS-DRY NS-DRY NS-DRY NS-DRY

10-22-07 NS-DRY NS-DRY NS-DRY NS-DRY

USGS 60 (DP) 10-26-06 4 10 12 54

10-18-07 4 13 16 135

10-06-08 4 16 20 242
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 67

Well No. Date Sampled

Chromium, 

dissolved

(μg/L)

Sodium, 

dissolved

(mg/L)

Chloride, 

dissolved

(mg/L)

Sulfate, 

dissolved

(mg/L)

USGS 61 (DP) 04-25-06 7 12 14 92

05-01-07 8 12 14 86

04-14-08 11 12 15 116

USGS 62 (DP) 04-25-06 9 15 20 212

04-30-07 8 16 19 199

04-14-08 8 16 20 237

USGS 63 (DP) 11-01-06 22 14 16 127

10-23-07 7 15 16 144

10-07-08 11 17 21 241

USGS 66 (DP) 11-08-06 E11 14 17 146

10-22-07 7 16 17 158

10-23-08 5 15 18 173

USGS 68 (DP) 04-06-06 46 479 36 1240

04-25-07 36 504 34 1471

04-22-08 44 476 36 1477

USGS 69 (DP) 11-07-06 E2 9 12 62

10-23-07 E1 11 15 83

10-07-08 <1.2 11 15 94

USGS 70 (DP) 05-16-06 12 14 16 134

05-01-07 23 16 17 155

04-14-08 15 15 16 132

USGS 71 (DP) 11-08-06 14 12 18 164

10-22-07 NSEQ NSEQ NSEQ NSEQ

10-23-08 6 12 18 166

USGS 72 (DP) 04-06-06 1 32 17 28

04-25-07 2 34 21 32

04-22-08 1 23 16 26

USGS 73 (DP) 11-08-06 32 18 38 73

05-05-08 34 19 50 67

10-07-08 32 14 43 66

USGS 78 (DP) 11-08-06 <2 6 5 20

10-22-07 <1.2 6 5 20

10-23-08 <1.2 6 4 21

Table 8. Concentrations of selected dissolved ions in perched groundwater from selected wells, Advanced Test Reactor Complex, 

Idaho National Laboratory, Idaho, 2006-08.—Continued

[Well No.: Locations of wells are shown in figure 7. Analyses completed by the USGS National Water Quality Laboratory. Abbreviations: DP, well completed 

in deep perched groundwater; SP, well completed in shallow perched groundwater; NR, analysis not requested; NS-DRY, not sampled due to lack of water or 

because water level was below pump intake; NSEQ, not sampled because of equipment problems; E, estimated, and followed by the estimated value; μg/L, 

microgram per liter; mg/L, milligram per liter; USGS, U.S. Geological Survey. Symbol: <, less than respective reporting level]
68 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

tac10-0506_fig33

11

USGS 63

<1.2

USGS 69

6

USGS 71

5

USGS 54

6

PW 8

4

USGS 60

11

USGS 61

8

USGS 62

5

USGS 66

1

USGS 72

44

USGS 68

34

USGS 73

6

PW 9 DRY

USGS 53

15

USGS 55

DRY

USGS 56

<1.2

USGS 78 (approx. located)

USGS 70

15

Advanced Test Reactor Complex

Lincoln Boulevard

Monroe Boulevard

Cold-waste

ponds

Chemical-waste pond

Sanitary-waste

pond Evaporation ponds

Retention

basin Radioactive-waste ponds

EXPLANATION

Extent of deep perched groundwater zone—April−October 2008. 

Approximately located

Well completed in deep perched groundwater—Entry, USGS 66, is local 

well identifier; 5, is dissolved chromium concentration in micrograms 

per liter; <1.2, indicates the concentration was less than the 

laboratory reporting level. Values represent data collected during 

April–October 2008

5

USGS 66

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000

Universal Transverse Mercator projection, Zone 12

Datum is North American Datum of 1927

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

0

0

2,000 Feet

500 Meters

Idaho 

National 

Laboratory

Map

area

Figure 33. Concentrations of dissolved chromium in water from wells completed in deep perched groundwater, Advanced 

Test Reactor Complex, Idaho National Laboratory, Idaho, April or October 2008.
Selected Radiochemical and Chemical Constituents and Physical Properties of Water in Perched Groundwater 69

Idaho Nuclear Technology and 

Engineering Center

Two percolation ponds were constructed south of the 

INTEC in 1984 and 1985 to replace the INTEC disposal 

well (fig. 7). Wastewater infiltrating from these ponds 

formed perched groundwater in the basalt and sedimentary 

interbeds above the eastern Snake River Plain aquifer. Perched 

groundwater has been found in other areas at the INTEC as 

well and may be attributed to leaking wastewater pipelines, 

leach fields, damaged casing in the upper part of the disposal 

well, other infiltration ponds, or landscape irrigation (Tucker 

and Orr, 1998). 

Many auger holes were drilled in 1983 to obtain 

geohydrologic and engineering data at the site of the planned 

INTEC percolation ponds. Two holes, SWP 8 and 13 (Davis, 

2008, fig. 21) subsequently were used as monitoring wells 

to sample and to measure water levels in shallow perched 

groundwater in surficial sediment at the ponds. Wells PW 

1, 2, 3, 4, 5, and 6 were completed in 1986 to monitor deep 

perched groundwater levels and water-quality changes under 

the INTEC percolation ponds (Davis, 2008, fig. 21). Well 

USGS 50 was used to monitor deep perched groundwater near 

the INTEC disposal well (fig. 7). Lack of available perched 

groundwater to sample and the history of nonreportable values 

of tritium in most of these wells resulted in the decision to 

remove wells SWP 8 and 13, and PW 2, 3, and 5 from the 

sampling schedule at various times during 2002–05 (Davis, 

2008, fig. 21). During 2006–08, attempts were made to sample 

water from wells PW 1, 4, and 6, and USGS 50; however, 

wells PW 1 and PW 6 were dry. Only two water samples were 

collected from PW 4 in 2006 and 2007 and two water samples 

were collected from USGS 50 in 2007 and 2008. Davis (2008) 

gives a historical summary of water-sample analyses for wells 

completed in perched groundwater near the INTEC.

Well PW 4

A water sample collected from well PW 4 in November 

2006 yielded a reportable concentration of tritium of 

1,080±160 pCi/L, which was lower than the concentration 

in 2005 of 1,400±160 pCi/L. The water sample also 

contained a reportable concentration of strontium-90 of 

17.5±2.2 pCi/L, which was higher than the concentration 

in 2005 of 11.4±1 pCi/L. The cesium-137 concentration 

was less than the reporting level. Concentrations of sodium, 

chloride, and sulfate were 98, 155, and 36 mg/L, respectively. 

A water sample collected in October 2007 was analyzed only 

for sodium and the concentration was 95 mg/L, similar to the 

concentration in 2006. 

Well USGS 50

A water sample collected from well USGS 50 in 

October 2008 yielded a reportable concentration of tritium 

of 15,900±300 pCi/L, lower than the concentration in 

November 2004 of 22,000±700 pCi/L and continued the 

decreasing trend of tritium concentrations in that well. The 

high concentrations of tritium in water from well USGS 50 

may be a result of leakage of wastewater from ruptures in 

the upper part of the disposal well casing or to leakage from 

wastewater lines at the INTEC (Tucker and Orr, 1998). 

The decrease in tritium concentration may be attributed 

to radioactive decay or to the dilution of well water from 

a nonradioactive source such as landscape irrigation. 

The concentration of strontium-90 in water from well 

USGS 50 was 108±2 pCi/L in October 2008, a decrease 

from the concentration in November 2004 of 145±3 pCi/L. 

Concentrations of strontium-90 have been decreasing since 

the 1980s when concentrations were as high as 620±30 pCi/L 

in October 1982. Strontium-90 concentrations in water from 

well USGS 50 may be a result of the 1972 leak of 18,000 Ci 

of strontium-90 in soils at the INTEC Tank Farm (fig. 7) 

(Cahn and others, 2006), leakage of wastewater from ruptures 

in the disposal well casing, or leakage from wastewater 

pipelines at the INTEC. Cesium-137 concentrations in the 

water sample from October 2008 were less than the reporting 

level. The absence of reportable concentrations of cesium-137 

in perched groundwater at the INTEC is probably a result 

of decreased disposal and of sorption and (or) exchange 

of cesium-137 to minerals in sediments (Davis, 2008). 

Concentrations of sodium, chloride, and sulfate were 58, 52, 

and 39 mg/L, respectively, in April 2007, and in October 2008, 

concentrations changed little at 57, 52, and 39 mg/L, 

respectively. Concentrations of these constituents are similar 

to historical concentrations in water from this well. The 

nitrate (as N) concentration in the water sample from April 

2007 was 22.5 mg/L and 18.9 mg/L in the water sample from 

October 2008. These concentrations represent a decrease from 

the concentration of 33.3 mg/L (as N) in November 2004, 

maintaining an overall decreasing trend since 1988. Sodium, 

chloride, sulfate, and nitrate (as N) concentrations may be a 

result of leakage of wastewater from pipelines at the INTEC.

Radioactive Waste Management Complex

Perched groundwater beneath the RWMC is in 

sedimentary interbeds in basalts and can be attributed 

primarily to local snowmelt and rain infiltration and to 

recharge from the Big Lost River and the INL spreading 

areas. This perched groundwater contains constituents leached 
70 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

from buried radioactive and organic-chemical wastes. Liquid 

and solid waste materials buried at the RWMC (fig. 1) also 

are sources of some constituents in perched groundwater. 

Perched groundwater beneath buried waste can be an integral 

part of the pathway for waste-constituent migration to the 

eastern Snake River Plain aquifer. The extent of this perched 

groundwater is affected by the waste-disposal practices.

Well USGS 92 (fig. 4) is in the SDA at the RWMC and 

is completed in a sedimentary interbed (Anderson and Lewis, 

1989, p. 29) 214 ft below land surface. Perched groundwater 

in this well has moved through overlying sediments and 

basalt and may contain waste constituents leached from 

radiochemical and organic chemical wastes buried in the SDA. 

Small amounts of water in well USGS 92 frequently preclude 

collection of an adequate water sample for all requested 

analyses. Adequate water samples for most requested 

analyses were collected during April or June 2006–08. During 

2006–08, tritium concentrations in water samples from well 

USGS 92 (table 9) exceeded the reporting level ranging from 

490±110 pCi/L in April 2006 to 300±80 pCi/L in June 2008. 

Tritium concentrations in water from well USGS 92 have 

varied through time.

Historically, the concentration of americium-241 was 

greater than the reporting level in October 1992 and the 

concentration of plutonium-238 was greater than the reporting 

level in November 1994 (Bartholomay, 1998). Since the 

1990s, concentrations of these constituents have been less than 

the reporting levels.

Dissolved chloride concentrations in water from 

three water samples collected from well USGS 92 during 

2006–08 were all 98 mg/L (table 9). This dissolved 

chloride concentration is slightly higher than the April 2002 

concentration of 87 mg/L, but consistent with concentrations 

measured historically.

In 1987, 9 VOCs were detected in water from well USGS 

92 (Mann and Knobel, 1987, p. 16–17); in January 1990, 

6 VOCs were detected (Tucker and Orr, 1998); and in April 

1992, 18 VOCs were detected (Bartholomay, 1998, p. 28; 

Greene and Tucker, 1998). During 1996–98, 14 VOCs were 

detected (Bartholomay and Tucker, 2000). During 1999–2001, 

water from well USGS 92 was analyzed for the same VOCs as 

in previous years. During 2002–05, attempts were made each 

year to sample well USGS 92 that is completed in perched 

groundwater at the RWMC; however, lack of water in the well 

precluded obtaining an adequate water sample during most 

sampling events. Most of the same VOCs except chloroethane 

that were detected during 1999–2001 were detected during 

2002–03; additionally, bromodichloromethane was detected. 

Water from well USGS 92 was sampled for 

VOCs in April 2007. Table 10 lists the concentrations 

of nine VOCs detected. All of the VOCs detected in 

April 2007 had been detected in 2002–03. However, 

bromodichloromethane, 1,2-dichloroethane, benzene, 

methylene chloride (dichloromethane), 1,1,2-trichloroethane, 

cis‐1,2‐dichloroethene, and freon-113 (CFC-113) 

(1,1,2-trichloro-1,2,2-trifluoroethane), which were detected 

in 2002–03, were not detected in 2007. Additionally, all of 

the VOC concentrations detected in 2007 were significantly 

lower than those detected in 2002 or 2003, with the exception 

of toluene which was not detected in 2002–03 (table 10, 

this report; Davis, 2008, table 15). This decrease in VOC 

concentration may be a result of dilution by lateral infiltration 

of water flowing in the Big Lost River during water years 

2005–06 (table 4) or removal of VOCs from the subsurface 

at the SDA by vapor vacuum extraction processes conducted 

by the INL contractor from 1996–present. The MRL for most 

VOCs was between 0.1 and 0.2 μg/L during 2006–08.

Well No. Date Tritium

(pCi/L)

Strontium-90

(pCi/L)

Cesium-137

(pCi/L)

Plutonium-238

(pCi/L)

Plutonium-239,

240 (undivided)

(pCi/L)

Americium-241

(pCi/L)

Chloride

 (dissolved)

 (mg/L)

USGS 92 04-13-06 490 ± 110 -0.13 ± 0.76 40 ± 20 SL SL SL 98

04-23-07 480 ± 130 0.9 ± 0.7 -10 ± 20 0.006 ± 0.006 -0.006 ± 0.012 0.03 ± 0.02 98

06-12-08 300 ± 80 1.5 ± 0.7 -20 ± 20 -0.003 ± 0.007 -0.006 ± 0.004 0.02 ± 0.02 98

Table 9. Concentrations of tritium, strontium-90, cesium-137, selected transuranic elements, and dissolved chloride in perched 

groundwater from well USGS 92, Radioactive Waste Management Complex, Idaho National Laboratory, Idaho, 2006–08.

[Well No.: Location of well is shown in figure 7. Analyses completed by the Department of Energy’s Radiological and Environmental Sciences Laboratory 

and the USGS National Water Quality Laboratory. Analyses for radionuclides, analytical uncertainties are reported as 1 times the sample standard deviation. 

Concentrations equal to or greater than 3 times the sample standard deviation are considered to be greater than the reporting level and are bold. Abbreviations:

pCi/L, picocurie per liter; mg/L, milligram per liter. NR, analysis not requested or inadequate amount of sample; SL, sample lost at lab; USGS, U.S. Geological 

Survey. Symbol: ±, plus or minus]
Summary 71

Summary

Radiochemical and chemical wastewater discharged since 

1952 to infiltration ponds and disposal wells, and waste buried 

in pits and trenches at the Idaho National Laboratory (INL) 

has affected water quality in the Snake River Plain aquifer and 

in perched groundwater zones at the INL. The U.S. Geological 

Survey (USGS), in cooperation with the U.S. Department 

of Energy, maintains aquifer and perched groundwater 

monitoring networks at the INL to determine hydrologic 

trends and to delineate the movement of radiochemical and 

chemical wastes in the eastern Snake River Plain aquifer and 

in perched groundwater zones. 

Water in the Snake River Plain aquifer primarily moves 

through fractures and interflow zones in basalt, generally 

flows southwestward, and eventually discharges at springs 

along the Snake River. The aquifer is recharged primarily 

from infiltration of irrigation water, infiltration of streamflow, 

groundwater inflow from adjoining mountain drainage basins, 

and infiltration of precipitation.

During March–May 2008, the altitude of the water 

table in the Snake River Plain aquifer was about 4,560 ft 

in the northern part of the INL, and about 4,410 to 

4,420 ft in the southwestern part. Water flowed southward 

and southwestward beneath the INL at an average 

hydraulic gradient of about 4 ft/mi. Water levels in wells 

generally remained constant or declined in the INL area from 

March–May 2005 to March–May 2008. In the southwestern 

part of the INL, water levels were mostly unchanged from 

the March–May 2005 reporting period or rose slightly. In the 

central part of the INL, water levels declined about 1–3 ft and, 

in the northern part of the INL, water levels declined as much 

as 9 ft. Groundwater moves southwestward from the INL and 

eventually is discharged to springs along the Snake River 

near Twin Falls, Idaho, about 100 miles southwest of the INL. 

Estimated discharge from the springs was about 3.64 million 

acre-ft/yr for water year 2008.

Disposal of wastewater to infiltration ponds and 

infiltration of surface water at the Advanced Test Reactor 

Complex (ATRC) and Idaho Nuclear Technology and 

Engineering Center (INTEC) resulted in formation of perched 

groundwater in basalts and in sedimentary interbeds that 

overlie the Snake River Plain aquifer. Perched groundwater 

beneath the Radioactive Waste Management Complex 

(RWMC) formed from infiltration of snowmelt and rain and 

recharge from the Big Lost River and INL spreading areas. 

This perched groundwater contains constituents leached 

from buried radioactive and organic-chemical wastes. 

Perched groundwater is an integral part of the pathway for 

waste‐constituent migration to the aquifer.

During 2005–07, six wells were equipped with multilevel WestbayTM packer sampling systems that allow water 

samples and pressure and temperature measurements to be 

acquired at isolated depths in each of the wells. This multilevel monitoring helps to describe the vertical distribution of 

water chemistry and pressure and temperature gradients in 

addition to the horizontal distribution information previously 

gathered from open boreholes. Beginning in 2005, the USGS 

and the INL contractor collaborated to instrument two wells 

with multi-level WestbayTM packer sampling systems. The 

USGS expanded the program in 2006 and 2007 to include 

four additional wells that were equipped with the systems. 

The vertical distribution of radiochemical and chemical 

constituents is variable at depth.

A tritium plume developed in the Snake River Plain 

aquifer from discharge of wastewater at the INL since the 

1950s. In April or October 2008, reportable concentrations 

of tritium in water from aquifer wells ranged from 810±70 

to 8,570±190 pCi/L and the tritium plume extended southsouthwestward in the general direction of groundwater flow. 

In April or October 2008, concentrations of tritium in water 

samples generally decreased from the 2001–05 reporting 

period and all concentrations were less than the maximum 

contaminant level of 20,000 pCi/L. 

Volatile organic compound name

NWIS

parameter

code

Concentration

(μg/L)

Carbon Tetrachloride (Tetrachloromethane) 32102 43.7

Chloroform (Trichloromethane) 32106 72.3

Toluene 34010 0.5

Tetrachloroethylene (Tetrachloroethene) 34475 6

1,1-dichloroethane 34496 0.8

1,1-dichloroethylene (1,1,-dichloroethene) 34501 0.2

1,1,1-trichloroethane 34506 5.2

1,2-dichloropropane 34541 0.7

Trichloroethylene (Trichloroethene) 39180 50.3

Table 10. Concentrations of selected volatile organic compounds in perched groundwater from well USGS 92, Radioactive Waste 

Management Complex, Idaho National Laboratory, Idaho, April 23, 2007.

[Location of well is shown in figure 7. Analyses completed by the U.S. Geological Survey’s National Water Quality Laboratory using an analytical method that 

conforms to U.S. Environmental Protection Agency Method 524.2 (1995). Names in parentheses are alternate compound names. Abbreviations: NWIS, U.S. 

Geological Survey National Water Information System; μg/L, microgram per liter]
72 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

At the ATRC, three wells completed in shallow perched 

groundwater were sampled for tritium during 2006–08; all 

concentrations were less than the reporting level. Tritium 

concentrations in water from 11 wells completed in deep 

perched groundwater (PW 8, PW 9, USGS 54, 55, 56, 61, 63, 

66, 70, 71, and 73) generally were greater than the reporting 

level during at least one sampling event during 2006–08. 

Tritium concentrations in water from 6 wells (USGS 60, 62, 

68, 69, 72, and 78) were less than the reporting level during 

2006–08. 

At the INTEC, a water sample collected from well 

PW 4 in November 2006 yielded a reportable concentration 

of tritium of 1,080±160 pCi/L, which was lower than 

the concentration in 2005 of 1,400±160 pCi/L. A water 

sample collected from well USGS 50 in October 2008 

yielded a reportable concentration of tritium of 15,900±300 

pCi/L, lower than the concentration in November 2004 of 

22,000±700 pCi/L and continued the decreasing trend of 

tritium concentrations in that well.

During April or October 2008, water from 52 aquifer 

wells was sampled for strontium-90 throughout the INL. 

Concentrations of strontium-90 in water from 24 wells 

exceeded the reporting level. Six WestbayTM equipped 

wells were sampled in August and September 2008 and 

did not contain reportable concentrations of strontium-90. 

Reportable concentrations of strontium-90 in the aquifer 

wells ranged from 2.2±0.7 pCi/L in water from well Site 

9 to 32.7±1.2 pCi/L in water from well USGS 47. The 

area of the strontium-90 plume near the INTEC extended 

south‐southwestward in the general direction of groundwater 

flow. The concentrations in water from wells near and 

southwest of INTEC (USGS 36, 37, 38, 45, 47, 57, and 113), 

have varied since 1980; however, all wells have shown an 

overall decrease in strontium-90 concentration.

Strontium-90 has not been detected within the eastern 

Snake River Plain aquifer beneath the ATRC partly because 

of the exclusive use of waste-disposal ponds and lined 

evaporation ponds rather than use of the disposal well 

for radioactive-wastewater disposal at ATRC. Sorption 

processes in sediments in the unsaturated zone beneath the 

radioactive waste-disposal pond could have minimized or 

prevented strontium-90 migration to the aquifer at the ATRC. 

Additionally, the stratigraphy beneath the ATRC is different 

from that beneath the INTEC; more sediment is present below 

the ATRC than the INTEC.

During 2006–08, attempts were made to sample water 

from wells PW 1, 4, and 6, and USGS 50 near the INTEC; 

however, wells PW 1 and PW 6 were dry. Only two water 

samples were collected from PW 4 in 2006 and 2007, and 

two water samples were collected from USGS 50 in 2007 and 

2008. During 2006–07, water from well PW 4 contained a 

reportable concentration of strontium-90 of 17.5±2.2 pCi/L in 

November 2006, which was higher than the concentration in 

2005 of 11.4±1 pCi/L. The concentration of strontium-90 in 

water from well USGS 50 was 108±2 pCi/L in October 2008, 

a decrease from the concentration in November 2004 of 

145±3 pCi/L. Concentrations of strontium-90 have been 

decreasing since the 1980s when concentrations were as 

high as 620±30 pCi/L in October 1982. Strontium-90 

concentrations in water from well USGS 50 may be a result 

of the 1972 leak of 18,000 Ci of strontium-90 in soils at the 

INTEC Tank Farm, leakage of wastewater from ruptures in the 

disposal well casing, or leakage from wastewater pipelines at 

the INTEC.

During 2006–08, concentrations of cesium-137, 

plutonium-238, and plutonium-239, -240 (undivided), and 

americium-241 were less than the reporting level in water 

from all wells sampled by the USGS at the INL, including all 

zones sampled in wells equipped with WestbayTM systems.

Gross alpha- and beta-particle radioactivity is a 

measure of the total radioactivity given off as alpha and 

beta particles during the radioactive decay process. The 

radioactivity is usually reported as if it occurred as one 

radionuclide. Gross alpha and beta measurements are used to 

screen for radioactivity in the aquifer as a possible indicator 

of groundwater contamination. Water samples collected 

during 2006–08 were analyzed for gross alpha- and gross 

beta‐particle radioactivity by Radiological and Environmental 

Sciences Laboratory (RESL). In 2008, RESL increased 

the sensitivity of the gross alpha- and gross beta-particle 

radioactivity and changed the radionuclide reported for gross 

alpha from plutonium-239 to thorium-230, and for gross beta 

from cesium-137 to strontium-90/yttrium-90. The minimum 

detectable activity decreased from about 1.6 to 1.5 pCi/L for 

gross alpha and from about 6.4 to 3.4 pCi/L for gross beta, 

allowing for increased detectable concentrations for 2008 data.

During 2006–08, water samples from several aquifer 

wells were analyzed for chromium. In 2008, concentration 

of chromium in water from one aquifer well, USGS 65, 

south of ATRC, was 93 μg/L, just less than the MCL, 

and concentrations steadily decreased during 2006–08. 

Concentrations in water samples from other wells ranged from 

1.2 to 28.3 μg/L.

Historically, dissolved chromium concentrations in 

shallow perched groundwater at the ATRC have been very low 

(less than or slightly greater than the laboratory reporting level 

[LRL]) as a result of lack of recent disposal of chromium in 

the cold waste ponds. Over the past decade, several wells were 

not sampled because they were dry and were removed from 

the USGS sampling program. During 2006–08, chromium 

was detected only in well CWP 1 in April 2008 with a 

concentration of 3 μg/L. Dissolved chromium was detected 

in water from 14 wells (PW 8, 9, USGS 54-56, 60-63, 66, 68, 

70, 71, and 73) completed in deep perched groundwater at 

the ATRC during 2006–08. During 2006–08, the maximum 

concentration of chromium in deep perched groundwater at 

the ATRC was 125 μg/L in well USGS 56 in October 2006. 

During April–October 2008, detectable concentrations of 

dissolved chromium in wells completed in deep perched 

groundwater near the ATRC ranged from 4 μg/L in well USGS 

60 to 34 μg/L in well USGS 73; however, well USGS 56 was 

not sampled during 2008 because the well was dry. 
Summary 73

During 2006–08, the highest sodium concentration 

in water samples from aquifer wells near the INTEC 

was 40 mg/L in a water sample from well USGS 77. 

Concentrations of sodium in water from other wells south of 

the INTEC during 2006–08 generally were less than or equal 

to sodium concentrations detected in October 2005 with the 

exception of well USGS 47 which was slightly higher in 2008.

During 2006–08, analyses were not made for 

dissolved sodium concentrations in shallow perched 

groundwater at the ATRC. During April–October 2008, 

dissolved sodium concentrations in water from 17 wells 

completed in deep perched groundwater were determined. 

During April–October 2008, dissolved sodium concentrations 

ranged from 6 to 476 mg/L. 

The background chloride concentration in water from 

the Snake River Plain aquifer at the INL generally is about 

15 mg/L; the ambient chloride concentration near the INTEC 

is about 10 mg/L; and, near the Central Facilities Area (CFA), 

the ambient chloride concentration is about 20 mg/L. In 2008, 

concentrations of chloride in most water samples from wells 

closest to the INTEC and the CFA exceeded 20 mg/L.

During April 2008, dissolved chloride concentrations 

in shallow perched groundwater ranged from 11 mg/L in 

well CWP 8 to 13 mg/L in wells CWP 1 and 3. Dissolved 

chloride concentrations in deep perched groundwater during 

April or October 2008 ranged from 4 mg/L in well USGS 78 

to 43 mg/L in well USGS 73. Higher concentrations in wells 

may be a result of movement of remnant water through the 

unsaturated zone from the chemical waste pond which was 

closed in 1999. 

In 2008, sulfate concentrations in water samples from 

nine wells in the south-central part of the INL exceeded the 

40-mg/L background concentration of sulfate ranging from 40 

to 157 mg/L. 

In April or October 2008, sulfate concentrations in water 

samples from USGS 88 and USGS 119, near the RWMC, 

were 50 and 39 mg/L, respectively, similar to concentrations 

in October 2005. The sulfate concentrations that are greater 

than background concentration in water from these wells 

could have resulted from the well construction and (or) waste 

disposal at the RWMC.

The maximum dissolved sulfate concentration in shallow 

perched groundwater near the ATRC was 399 mg/L in well 

CWP 1 in November 2006. Concentrations of dissolved 

sulfate ranged from 94 to 242 mg/L during April–October 

2008 in water from wells USGS 54, 60, 63, 69, and PW 

8 that are completed in deep perched groundwater near 

the cold-waste ponds. These high concentrations indicate 

that water in the wells also was affected by discharge into 

the cold-waste ponds. During April–October 2008, the 

maximum concentration of dissolved sulfate in deep perched 

groundwater was 1,477 mg/L in well USGS 68, west of the 

chemical-waste pond. The dissolved sulfate concentration in 

this well varied from 1,240 to 1477 mg/L during 2006–08, an 

increase in concentrations from 951 mg/L in April 2005. 

Concentrations of nitrate (as N) in groundwater not 

affected by wastewater disposal from INL facilities generally 

are less than the regional background of 1 mg/L. In October 

2008, concentrations of nitrate (as N) in water from most 

wells at and near the INTEC (wells USGS 40, 41, 47, 48, 

51, 52, 67, 77, 111, 113, 114, 116) exceeded the background 

concentration. Concentrations ranged from 2.2 mg/L (as N) in 

well USGS 113 to 5.97 mg/L (as N) in well USGS 47.

Historically, nitrate (as N) concentrations in water from 

aquifer wells near the RWMC slightly exceeded the regional 

background concentration of about 1 mg/L. Since 1998, the 

concentrations of nitrate (as N) in water from wells USGS 88, 

89, and 119 have remained relatively unchanged, with 2008 

concentrations of 0.9, 1.7, and 1.4 mg/L, respectively.

In 2005, near the ATRC, the concentration of nitrate (as 

N) in water from well USGS 65 was 1.6 mg/L, and remained 

constant in 2008 with a concentration of 1.5 mg/L. All 

concentrations measured in 2008 were less than the MCL for 

drinking water of 10 mg/L (as N).

During April or October 2008, water samples from 

four wells (CPP 1, USGS 34, 38, and 77, were analyzed 

for fluoride; detected concentrations ranged from 0.2 to 

0.3 mg/L. These concentrations are similar to the background 

concentrations which indicates that wastewater disposal has 

not had an appreciable effect on fluoride concentrations in the 

Snake River Plain aquifer near the INTEC.

Detectable concentrations of nonradioactive trace 

elements in water from the Snake River Plain aquifer at the 

INL varied during 2006–08.

During 2006–08, water samples from 30 wells 

were collected and analyzed for VOCs. Twelve VOCs 

were detected. Concentrations of from 1 to 10 VOCs 

were detected in water samples from 11 wells. The 

primary VOCs detected included carbon tetrachloride; 

1,1-dichloroethane; 1,1,1-trichloroethane; trichloroethylene; 

and tetrachloroethylene. Most VOCs fluctuated through time 

and show no distinct trend. 

Water from well USGS 92 near the RWMC was sampled 

for VOCs in April 2007. Nine VOCs were detected. All of the 

VOCs detected in April 2007 had been detected in 2002–03. 

However, bromodichloromethane; 1,2-dichloroethane; 

benzene; methylene chloride (dichloromethane); 

1,1,2-trichloroethane; cis-1,2-dichloroethene; and freon-113 

(CFC-113) (1,1,2-trichloro-1,2,2-trifluoroethane), which were 

detected in 2002–03, were not detected in 2007. Additionally, 

all of the VOC concentrations detected in 2007 were 

significantly lower than those detected in 2002 or 2003 with 

the exception of toluene which was not detected in 2002–03. 

This may be a result of dilution by lateral infiltration of water 

flowing in the Big Lost River during water years 2005–06 

or removal of VOCs from the subsurface at the Subsurface 

Disposal Area (SDA) by vapor vacuum extraction processes 

conducted by the INL contractor. 
74 Hydrological Conditions and Distribution of Selected Constituents in Water, Idaho National Laboratory, Idaho, 2006–08

Acknowledgments

The Department of Energy Radiological and 

Environmental Sciences Laboratory (RESL) at the Idaho 

National Laboratory provided radiochemical analyses of water 

samples. R. Douglas Carlson, Director, supervised technical 

staff at the RESL during 2006–08. The author is also grateful 

to Betty J. Tucker and Flint Raben, Hydrologic Technicians, 

U.S. Geological Survey, for data verification review.

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Davis— Hydrologic Conditions and Distribution of Selected Constituents in Groundwater, Idaho National Laboratory, Idaho, 2006–08—Scientific Investigations Report 2010–5197