An Update of the Distribution of Selected 

Radiochemical and Chemical Constituents in 

Perched Ground Water, Idaho National Laboratory, 

Idaho, Emphasis 1999-2001

Scientific Investigations Report 2006–5236

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

U.S. Department of the Interior

U.S. Geological Survey

DOE/ID-22199
Cover: Photograph of U.S. Geological Survey well and sampling apparatus at the Idaho National Laboratory, Idaho. 

View looking southwest.

(Photograph courtesy of the U.S. Geological Survey Idaho National Laboratory Project Office.)
An Update of the Distribution of Selected 

Radiochemical and Chemical Constituents 

in Perched Ground Water, Idaho National 

Laboratory, Idaho, Emphasis 1999–2001

By Linda C. Davis

Prepared in cooperation with the 

U.S. Department of Energy DOE/ID-22199 

Scientific Investigations Report 2006–5236

U.S. Department of the Interior

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

DIRK A. KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Davis, L.C., 2006, An update of the distribution of selected radiochemical and chemical constituents in perched ground 

water, Idaho National Laboratory, Idaho, emphasis 1999–2001: U.S. Geological Survey Scientific Investigations Report 

2006-5236, 48 p.
iii

Contents

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

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Previous Investigations........................................................................................................................4

Ground-Water Monitoring Networks ................................................................................................4

Water-Level Monitoring Network .............................................................................................4

Water-Quality Monitoring Network ..........................................................................................4

Water-Quality Sampling Methods and Quality Assurance...................................................8

Geohydrologic Setting...................................................................................................................................8

Guidelines for Interpreting Results of Radiochemical Analyses ...........................................................8

Guidelines for Interpreting Results of Chemical Analyses .....................................................................9

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water...10

Reactor Technology Complex ...........................................................................................................10

Tritium .........................................................................................................................................10

Strontium-90................................................................................................................................18

Cesium-137..................................................................................................................................21

Chromium-51...............................................................................................................................21

Cobalt-60......................................................................................................................................21

Chromium ....................................................................................................................................21

Sodium.........................................................................................................................................27

Chloride........................................................................................................................................27

Sulfate .........................................................................................................................................27

Idaho Nuclear Technology and Engineering Center.....................................................................28

Tritium .........................................................................................................................................30

Strontium-90................................................................................................................................30

Cesium-137..................................................................................................................................35

Sodium.........................................................................................................................................35

Chloride........................................................................................................................................37

Sulfate .........................................................................................................................................39

Nitrate .........................................................................................................................................39

Radioactive Waste Management Complex ....................................................................................39

Summary........................................................................................................................................................42

Acknowledgments.......................................................................................................................................44

References Cited..........................................................................................................................................44
iv

Figures

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

gaging stations, and selected facilities, Idaho .......................................... 3

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

monitoring network at the Reactor Technology Complex, Idaho Nuclear

Technology and Engineering Center, and Radioactive Waste Management

Complex, Idaho National Laboratory, Idaho, and frequency of water-level

measurements, as of December 2001 ................................................... 5

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

monitoring network at the Reactor Technology Complex, Idaho Nuclear

Technology and Engineering Center, and Radioactive Waste Management

Complex, Idaho National Laboratory, Idaho, and frequency of water-sample

collections, as of December 2001 ......................................................... 6

Figure 4. Graphs showing amount of tritium discharged, tritium as a percentage of

total radioactive constituents in wastewater discharged, and volume of

wastewater discharged to the radioactive-waste infiltration and lined

evaporation ponds at the Reactor Technology Complex, Idaho National 

Laboratory, Idaho, 1962–2001 ............................................................ 12

Figure 5. Map showing concentrations of tritium in water from wells completed in

deep perched ground water, Reactor Technology Complex, Idaho National

Laboratory, Idaho, July–October 2001 ................................................... 13

Figure 6. Graphs showing water-level changes in selected wells, Reactor Technology

Complex, Idaho National Laboratory, Idaho, 1960–2001 .............................. 19

Figure 7. Map showing concentrations of strontium-90 in water from wells completed

in deep perched ground water, Reactor Technology Complex, Idaho

National Laboratory, Idaho, July–October 2001.......................................... 20

Figure 8. Map showing concentrations of dissolved chromium in water from wells

completed in deep perched ground water, Reactor Technology Complex,

Idaho National Laboratory, Idaho, July–October 2001 ................................. 26

Figure 9. Map showing concentrations of dissolved sulfate in water from wells

completed in deep perched ground water, Reactor Technology Complex,

Idaho National Laboratory, Idaho, July–October 2001 ................................. 28

Figure 10. Graphs showing amount of tritium discharged, tritium as a percentage of

total radioactive constituents in wastewater discharged, and volume of

wastewater discharged to the disposal well and infiltration ponds at the

Idaho Nuclear Technology and Engineering Center, Idaho National

Laboratory, Idaho, 1962–2001 ............................................................ 29

Figure 11. Map showing concentrations of tritium in water from wells completed in

deep perched ground water, Idaho Nuclear Technology and Engineering

Center, Idaho National Laboratory, Idaho, October 2001 .............................. 33

Figure 12. Map showing concentrations of strontium-90 in water from wells completed

in deep perched ground water, Idaho Nuclear Technology and Engineering

Center, Idaho National Laboratory, Idaho, October 2001 .............................. 34

Figure 13. Map showing concentrations of dissolved chloride in water from wells

completed in deep perched ground water, Idaho Nuclear Technology and

Engineering Center, Idaho National Laboratory, Idaho, October 2001 ............... 38
Multiply By To obtain

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

foot squared per day (ft2/d) 0.09290 meter squared per day

gallon (gal) 3.785 liter

mile (mi) 1.609 kilometer

million gallons (Mgal) 3,785 × 106 liter

million gallons per year (Mgal/yr) 3,785 × 106 liter per year

picocurie per liter (pCi/L) 0.037 becquerel per liter

picocurie per milliliter (pCi/mL) 0.037 becquerel per milliliter

pound, avoirdupois (lb) 0.4536 kilogram

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

square mile (mi2) 2.590 square kilometer

ton per year (ton/yr) 0.9072 metric ton per year

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

°F=(1.8×°C)+32

Conversion Factors, Datums, and Abbreviations, 

Acronyms, and Symbols

Conversion Factors

Tables

Table 1. Location and construction of wells in the U.S. Geological Survey perched

ground water-quality monitoring network and sample-collection method

and frequency, Idaho National Laboratory, Idaho, as of December 2001 ............ 7

Table 2. Concentrations of tritium, strontium-90, and cesium-137 in perched ground

water from selected wells, Reactor Technology Complex, Idaho National

Laboratory, Idaho, 1999–2001 ............................................................ 14

Table 3. Concentrations of selected dissolved ions in perched ground water from

selected wells, Reactor Technology Complex, Idaho National Laboratory,

Idaho, 1999–2001 ........................................................................... 22

Table 4. Concentrations of tritium, strontium-90, and cesium-137 in perched ground

water from selected wells, Idaho Nuclear Technology and Engineering

Center, Idaho National Laboratory, Idaho, 1999–2001 ................................. 31

Table 5. Concentrations of selected dissolved ions in perched ground water from

selected wells, Idaho Nuclear Technology and Engineering Center, Idaho

National Laboratory, Idaho, 1999–2001 ................................................... 36

Table 6. Concentrations of tritium, strontium-90, cesium-137, selected transuranic

elements, and dissolved chloride in perched ground water from well USGS

92, Radioactive Waste Management Complex, Idaho National Laboratory,

Idaho, 1999–2001 ........................................................................... 40

Table 7. Concentrations of selected volatile organic compounds in perched ground

water from well USGS 92, Radioactive Waste Management Complex, Idaho

National Laboratory, Idaho, 1996–2001 ................................................... 41
vi

Datums

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

(NAVD 29).

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

Transmissivity: The standard unit for transmissivity 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.

Abbreviations, Acronyms, and Symbols

Abbreviations, 

Acronyms, and Symbols Definition

Ci Curie

CFA Central Facilities Area

DOE U.S. Department of Energy

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

INEL Idaho National Engineering Laboratory (1974-97)

INL Idaho National Laboratory

INTEC Idaho Nuclear Technology and Engineering Center

LRL laboratory reporting level

LT-MDL long-term method detection level

mg/L milligram per liter

MRL minimum reporting level

NRTS National Reactor Testing Station (from 1949-74)

NWIS National Water Information System (USGS)

NWQL National Water Quality Laboratory

pCi/L picocurie per liter

pCi/mL picocurie per milliliter

RESL Radiological and Environmental Sciences Laboratory

RTC Reactor Technology Complex

RWMC Radioactive Waste Management Complex

s sample standard deviation

SDA Subsurface Disposal Area

SWP Sanitary-waste pond

TAN Test Area North

TRA Test Reactor Area

μg/L microgram per liter

USGS U.S. Geological Survey

VOC volatile organic compound

< less than

± plus or minus

Conversion Factors, Datums, and Abbreviations, 

Acronyms, and Symbols—continued
Abstract

Radiochemical and chemical wastes generated at facilities 

at the Idaho National Laboratory (INL) were discharged since 

1952 to infiltration ponds at the Reactor Technology Complex 

(RTC) (known as the Test Reactor Area [TRA] until 2005), 

and the Idaho Nuclear Technology and Engineering Center 

(INTEC) and buried at the Radioactive Waste Management 

Complex (RWMC). Disposal of wastewater to infiltration 

ponds and infiltration of surface water at waste burial sites 

resulted in formation of perched ground water in basalts and 

in sedimentary interbeds above the Snake River Plain aquifer. 

Perched ground water is an integral part of the pathway for 

waste-constituent migration to the aquifer.

The U.S. Geological Survey (USGS), in cooperation 

with the U.S. Department of Energy, maintains ground-water 

monitoring networks at the INL to determine hydrologic 

trends, and to monitor the movement of radiochemical and 

chemical constituents in wastewater discharged from facilities 

to both perched ground water and the aquifer. This report 

presents an analysis of water-quality and water-level data 

collected from wells completed in perched ground water at the 

INL during 1999–2001, and summarizes historical disposal 

data and water-level-and water-quality trends.

At the RTC, tritium, strontium-90, cesium-137, dissolved 

chromium, chloride, sodium, and sulfate were monitored in 

shallow and deep perched ground water. In shallow perched 

ground water, no tritium was detected above the reporting 

level. In deep perched ground water, tritium concentrations 

generally decreased or varied randomly during 1999–2001. 

During October 2001, tritium concentrations ranged from 

less than the reporting level to 39.4±1.4 picocuries per 

milliliter (pCi/mL). Reportable concentrations of tritium 

during July-October 2001 were smaller than the reported 

concentrations measured during July–December 1998. 

Tritium concentrations in water from wells at the RTC were 

likely affected by: well’s distance from the radioactive-waste 

infiltration ponds (commonly referred to as the warm-waste 

ponds); water depth below the ponds; the amount of tritium 

discharged to radioactive-waste infiltration ponds in the 

past; discontinued use of radioactive-waste infiltration 

ponds; radioactive decay; and dilution from disposal of 

nonradioactive water.

During 1999–2001, the strontium-90 concentrations in 

two wells completed in shallow perched water near the RTC 

exceeded the reporting level. Strontium-90 concentrations in 

water from wells completed in deep perched ground water 

at the RTC varied randomly with time. During October 

2001, concentrations in water from five wells exceeded the 

reporting level and ranged from 2.8±0.7 picocuries per liter 

(pCi/L) in well USGS 63 to 83.8±2.1 pCi/L in well USGS 54. 

No reportable concentrations of cesium-137, chromium-51, 

or cobalt-60 were present in water samples from any of the 

shallow or deep wells at the RTC during 1999–2001.

Dissolved chromium was not detected in shallow perched 

ground water at the RTC during 1999–2001. Concentrations 

of dissolved chromium during July–October 2001 in 

deep perched ground water near the RTC ranged from 10 

micrograms per liter (μg/L) in well USGS 61 to 82 μg/L in 

well USGS 55. The largest concentrations were in water from 

wells north and west of the radioactive-waste infiltration 

ponds. During July–October 2001, dissolved sodium 

concentrations ranged from 7 milligrams per liter (mg/L) in 

well USGS 78 to 20 mg/L in all wells except well USGS 68 

(413 mg/L). Dissolved chloride concentrations in shallow 

perched ground water ranged from 10 mg/L in wells CWP 

1, 3, and 4 to 53 mg/L in well TRA A 13 during 1999–2001. 

Dissolved chloride concentrations in deep perched ground 

water ranged from 5 mg/L in well USGS 78 to 91 mg/L in 

well USGS 73. The maximum dissolved sulfate concentration 

in shallow perched ground water was 419 mg/L in well CWP 

1 during July 2000. Concentrations of dissolved sulfate in 

water from wells USGS 54, 60, 63, 69, and PW 8, completed 

in deep perched ground water near the cold-waste ponds, 

ranged from 115 to 285 mg/L in July–October 2001. The 

maximum concentration of dissolved sulfate in water during 

July–October 2001 was 1,409 mg/L in well USGS 68 west of 

the chemical-waste pond.

An Update of the Distribution of Selected Radiochemical 

and Chemical Constituents in Perched Ground Water, 

Idaho National Laboratory, Idaho, Emphasis 1999–2001

By Linda C. Davis
At the INTEC, tritium, strontium-90, cesium-137, 

dissolved sodium, chloride, sulfate, and nitrite plus nitrate 

(as nitrogen) were monitored in shallow and deep perched 

ground water. No reportable concentrations of tritium were 

measured in shallow perched ground water during 1999–2001. 

The tritium concentration in water from wells completed in 

deep perched ground water beneath the infiltration ponds 

ranged from less than the reporting level in wells PW 1 

and PW 5 to 9.7±0.5 pCi/mL in well PW 6 during 1999–

2001. The strontium-90 concentration in water from well 

SWP 8, completed in shallow perched ground water, was 

2.1±0.7 pCi/L in July 2001. In October 2001, strontium-90 

concentrations in deep perched ground water in wells closest 

to the ponds were less than the reporting level, not sampled 

because of access problems, or the wells were dry.

Dissolved sodium, chloride, and sulfate concentrations 

in shallow and deep perched ground water at the INTEC 

infiltration ponds during 1999–2001 were similar to or less 

than the average annual effluent monitoring data.

At the RWMC, tritium, strontium-90, cesium137, plutonium-238, plutonium-239, -240 (undivided), 

americium-241, dissolved chloride, and a suite of volatile 

organic compounds were monitored in deep perched ground 

water at well USGS 92. Radiochemical constituents in all 

water samples from well USGS 92 were less than the reporting 

level with the exception of the April 2000 and October 2001 

samples analyzed for tritium. The tritium concentration was 

at the reporting level at 0.3±.0.1 pCi/mL in April 2000 and 

slightly above the reporting level at 0.45±0.14 pCi/mL in 

October 2001. Samples contained concentrations greater 

than the minimum reporting levels of 15 volatile organic 

compounds.

Introduction

The Idaho National Laboratory (INL) 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, 

1949–74), Idaho National Engineering Laboratory (INEL, 

1974–97), and Idaho National Engineering and Environmental 

Laboratory (INEEL, 1997–2005). Facilities at the INL are 

operated by the U.S. Department of Energy (DOE) and 

are used in the development of peacetime atomic-energy 

applications, nuclear-safety research, defense programs, 

advanced energy concepts, and environmental research. Since 

1952, radiochemical and chemical wastes generated at these 

facilities have been contained in wastewater discharged to 

infiltration ponds, lined evaporation ponds, disposal wells, or 

a combination thereof. Liquid and solid radiochemical and 

chemical wastes also have been buried at the INL. Disposal 

of wastewater to infiltration ponds and infiltration of surface 

water at waste-burial sites resulted in formation of perched 

ground water in basalts and in sedimentary interbeds that 

overlie the Snake River Plain aquifer. Perched ground water is 

an integral part of the pathway for waste-constituent migration 

to the aquifer.

The U.S. Department of Energy (DOE) requires 

information about the dilute radiochemical- and 

chemical-waste constituent mobility in perched ground 

water at the INL to monitor the possible movement 

of these constituents to the Snake River Plain aquifer. 

Waste-constituent mobility in part is determined by 

(1) hydraulic properties of saturated and unsaturated basalts 

and sedimentary interbeds, (2) location, quantity, and method 

of waste disposal, (3) waste-constituent chemistry, and 

(4) geochemical processes taking place in perched ground 

water. This study was conducted by the U.S. Geological 

Survey (USGS) in cooperation with the DOE’s 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 INL. The study’s 

purpose was to characterize the water resources before 

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 ground water and in the Snake River Plain 

aquifer.

This report presents an analysis of water-level and 

water-quality data collected from selected wells completed in 

perched ground water at selected INL facilities during 1999–

2001 as part of the continuing hydrogeologic investigations 

by the USGS at the INL. The report describes the distribution 

and concentration of selected radiochemical and chemical 

constituents in perched ground water and the history of 

waste disposal at the Reactor Technology Complex (RTC) 

(known as the Test Reactor Area [TRA] until 2005), Idaho 

Nuclear Technology and Engineering Center (INTEC), and 

Radioactive Waste Management Complex (RWMC). Perched 

ground water also has been detected beneath infiltration 

ponds and ditches at other facilities at the INL, but is not 

discussed in this report because of the relatively small quantity 

of wastewater and associated radiochemical and chemical 

constituents discharged. An analysis of water-quality and 

water-level data collected from wells completed in the Snake 

River Plain aquifer during 1999–2001 is described in Davis 

(2006).

   Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
ID19-0022_fig01

13132513

ANL-W

CFA

INTEC

NRF

RWMC

TAN

RTC

PBF

Idaho National Laboratory boundary

USGS gaging station and number

EXPLANATION

Selected Facilities at the Idaho National Laboratory

Argonne National Laboratory-West

Central Facilities Area

Idaho Nuclear Technology and Engineering Center

Naval Reactors Facility

Power Burst Facility

Radioactive Waste Management Complex

Reactor Technology Complex—also known as Test

 Reactor Area (TRA)

Test Area North

IDAHO

BOISE

EASTERN

SNAKE RIVER

PLAIN IDAHO

NATIONAL

LABORATORY

Twin

Falls

Pocatello

Idaho

Falls

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

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

13132565

Big Lost River above

Big Lost River sinks 

near Howe

13132520

Big Lost River below 

INL diversion near Arco

13132513

INL diversion at head near Arco

13132500

Big Lost River near Arco

13127000

Big Lost River below 

Mackay Reservoir

28

22

33

20

26

93

20

26

93

TAN

RTC

INTEC

CFA

NRF

ANL-W

PBF

BIG LOST RIVER

PLAYAS AND SINKS

SPREADING

AREAS

RWMC

113°00’ 45’

44°00’

45’

43°30’

113°30’ 15’ 30’ 112°15’

Atomic

City

Howe

Arco

Mud

Lake Terreton

WHITE KNOB

MOUNTAINS

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

Introduction 
Previous Investigations

The extent of perched ground water at the RTC and the 

distribution of selected wastewater constituents in perched 

ground water are discussed in a series of reports describing 

the hydrology of the INL. This series includes reports by 

Barraclough, Teasdale, and Jensen (1967), Barraclough, 

Teasdale, and others (1967), and Barraclough and Jensen 

(1976). An analysis of perched ground water at the RTC 

is presented in a comprehensive discussion of conditions 

related to the disposal of wastewater to the subsurface at the 

INL (Robertson and others, 1974). Later reports present data 

on perched ground water at the RTC, INTEC, and RWMC: 

hydrologic conditions during 1974–78 were described by 

Barraclough and others (1981); during 1979–81 by Lewis 

and Jensen (1985); and during 1982–85 by Pittman and 

others (1988). Cecil and others (1991) discussed mechanisms 

responsible for formation of perched ground water and 

described the distribution of chemical and radiochemical 

constituents in perched ground water at the RTC, INTEC, 

and RWMC during 1986–88. Distribution of selected 

radiochemical and chemical constituents in perched ground 

water during 1989–91 was described by Tucker and Orr 

(1998); during 1992–95 by Bartholomay (1998); and during 

1996–98 by Bartholomay and Tucker (2000).

Robertson (1977) used a three-segment numerical 

model to simulate flow and transport of chemical and 

radionuclide constituents through perched ground water 

at the RTC. The model included effects of convection, 

hydrodynamic dispersion, radioactive decay, and adsorption. 

Hull (1989) developed a conceptual model that described 

migration pathways for wastewater and constituents from the 

radioactive-waste infiltration ponds (commonly referred to 

as the warm-waste ponds) at the RTC. Orr (1999) described 

the development of a transient numerical simulation used 

to evaluate a conceptual model of flow through perched 

ground water beneath wastewater infiltration ponds at the 

RTC. Anderson and Lewis (1989) and Anderson (1991) 

correlated drill cores and geophysical logs to describe a 

complex sequence of basalt flows and sedimentary interbeds 

in the unsaturated zone underlying the RWMC, RTC, and 

INTEC. This stratigraphic sequence provides the geologic 

framework where perched ground water formed. Ackerman 

(1991) analyzed data from 43 aquifer tests conducted in 22 

wells to estimate transmissivity of basalts and sedimentary 

interbeds containing perched ground water beneath the RTC 

and INTEC.

Ground-Water Monitoring Networks

Ground-water monitoring networks at the INL are 

maintained by the USGS to characterize the occurrence, 

movement, and quality of perched ground water beneath INL 

facilities. Periodic water–level and –quality data are obtained 

from these networks. Data from these monitoring networks are 

on file at the USGS INL Project Office and are available on 

the USGS National Water Information System (NWIS) Web 

site at http://waterdata.usgs.gov/id/nwis/nwis.

Water-Level Monitoring Network

The USGS perched water-level monitoring network 

was designed to estimate the extent of perched ground water 

and the volume of perched water in storage. Water levels 

in 42 wells (fig. 2) were monitored during 1999–2001. At 

the RTC, the network included 22 wells to monitor deep 

perched ground-water levels and 11 wells to monitor shallow 

perched ground-water levels. Shallow perched ground water is 

considered water perched in surficial sediment deposits, and 

deep perched ground water is water perched at greater depths. 

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 seven 

wells to monitor perched ground-water levels around the 

INTEC infiltration ponds and one well to monitor the waterlevel changes in deep perched ground water beneath the 

INTEC. Perched ground water at the RWMC was monitored 

in one well. Well locations and frequency of water-level 

measurements as of December 2001 are shown in figure 2.

Water-Quality Monitoring Network

The radiochemical and chemical character of perched 

ground water beneath INL facilities was determined from 

analyses of water samples collected as part of the USGS 

water-quality monitoring network to identify contaminant 

concentrations and define the pattern of waste migration in 

perched ground water and in the Snake River Plain aquifer.

Type, frequency, and depth of ground-water sampling 

generally depend on the information needed in a specific area. 

Water samples routinely are collected from selected wells 

and analyzed for concentrations of tritium, strontium-90, 

cesium-137, cobalt-60, plutonium-238, plutonium-239 

and plutonium-240 (undivided), americium-241, dissolved 

chromium, sodium, chloride, sulfate, nitrate, volatile 

organic compounds (VOCs), and measurements of specific 

conductance, pH, and water temperature. Water samples were 

analyzed for concentrations of radiochemical constituents 

at the Radiological and Environmental Sciences Laboratory 

(RESL) and for chemical constituents at the National Water 

Quality Laboratory (NWQL) in Lakewood, Colo. Well 

locations in the USGS water-quality monitoring network for 

perched ground water beneath INL facilities during 1999–

2001 and the frequency of sample collection are shown in 

figure 3 and table 1. A sample schedule that lists constituents 

analyzed at each site is available in a report by Mann (1996, 

attachment 1).

 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
USGS 71 Q

IDAHO NUCLEAR

TECHNOLOGY AND

ENGINEERING CENTER

REACTOR TECHNOLOGY COMPLEX

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste ponds

Cold-waste ponds

Infiltration ponds

Big

Lost

River

USGS 92 Q

RADIOACTIVE WASTE

MANAGEMENT COMPLEX

Subsurface

Disposal

Area Transuranic

Storage

Area

0

0

3,000 FEET

1,000 METERS

0

0

3,000 FEET

1,000 METERS

PW 9 Q

PW 8 Q

PW 7 S

USGS 78 R

USGS 75 A

USGS 74 S

USGS 73 Q

USGS 72 Q

USGS 70 Q

USGS 69 Q

USGS 68 Q

USGS 66 M

USGS 64 A

USGS 63 Q

USGS 62 Q

USGS 56 Q

USGS 55 Q

TRA A 77 Q

USGS 60 Q

USGS 53 Q

USGS 61 Q

CWP 8 A

CWP 9 A

CWP 5 A

CWP 7 A

CWP 6 A

CWP 4 A

CWP 3 A

CWP 1 A

CWP 2 A

TRA A 13 Q

USGS 54 Q

PW 6 Q PW 3 S

USGS 50 Q

PW 5 S

PW 4 Q

PW 2 S

PW 1 R

SWP 8 A

Disposal

Well

113°03’ 113°02’30”

43°35’

43°34’

112°58’ 112°56’

43°30’

43°29’30”

EXPLANATION

PW 6 Q Well In The USGS Water-level Monitoring Network— 

Entry, PW 6, is local well identifier; letter following 

identifier is frequency of water level measurement as of 

December 2001: A, annually; S, semiannually; M, monthly; 

and Q, quarterly; R, recorder

Figure 2. Location of wells in the U.S. Geological Survey water-level monitoring network at the Reactor Technology 

Complex, Idaho Nuclear Technology and Engineering Center, and Radioactive Waste Management Complex, Idaho National 

Laboratory, Idaho, and frequency of water-level measurements, as of December 2001.

Introduction 
ID19-0022_fig03

IDAHO NUCLEAR

TECHNOLOGY AND

ENGINEERING CENTER

REACTOR TECHNOLOGY COMPLEX

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

Radioactive-waste ponds

Cold-waste ponds

Infiltration ponds

Big

Lost

River

RADIOACTIVE WASTE

MANAGEMENT COMPLEX

Subsurface

Disposal

Area Transuranic

Storage

Area

0

0

3,000 FEET

1,000 METERS

0

0

3,000 FEET

1,000 METERS

PW 9 Q

PW 8 Q

PW 7 S

(Sampling

discontinued

October 2001)

USGS 78 A

USGS 74 S

(Sampling

discontinued

October 2001)

USGS 73 S

USGS 72 A

USGS 70 S

USGS 69 A

USGS 68 S

USGS 66 A

USGS 63 S

USGS 62 S

USGS 56 S

USGS 55 S

TRA A 77 S

USGS 60 S

USGS 53 S

USGS 61 S

CWP 8 A

CWP 5 A

CWP 7 A

CWP 6 A

CWP 4 A

CWP 3 A

CWP 1 A

CWP 2 A

TRA A 13 S

USGS 54 Q

PW 6 Q PW 3 S

USGS 50 S

PW 5 S

PW 4 Q

PW 2 S

PW 1 Q SWP 8 A

Disposal

Well

SWP 13 A

USGS 92 S

USGS 71 S

113°03’ 113°02’30”

43°35’

43°34’

112°58’ 112°56’

43°30’

43°29’30”

EXPLANATION

PW 6 Q Well In The USGS Water-quality Monitoring Network— 

Entry, PW 6, is local well identifier; letter following identifier 

is frequency of water sample collection as of December 

2001: A, annually; S semiannually; Q, quarterly

Figure 3. Location of wells in the U.S. Geological Survey water-quality monitoring network at the Reactor Technology 

Complex, Idaho Nuclear Technology and Engineering Center, and Radioactive Waste Management Complex, Idaho National 

Laboratory, Idaho, and frequency of water-sample collections, as of December 2001.

 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Well

No. USGS site No.

Well construction Sample collection

Diameter 

(inches)

Depth 

(feet) Method Frequency

CWP 1 433459112572601 10 66.0 Bail (65) A

CWP 2 433458112572401 10 52.5 Bail (52) A

CWP 3 433455112572501 10 60.5 Bail (60) A

CWP 4 433454112572601 10 61.0 Bail (60) A

CWP 5 433455112572901 10 53.5 Bail (53) A

CWP 6 433456112573301 10 52.5 Bail (52) A

CWP 7 433458112573201 10 53.5 Bail (53) A

CWP 8 433500112573001 10 66.0 Bail (65) A

PW 1 433349112560701 10 117 Pump (3) Q

PW 2 433344112555601 10 131 Bail (115) S

PW 3 433351112555701 10 125 Bail (121) S

PW 4 433348112554901 10 136 Pump (6) Q

PW 5 433348112555701 10 124 Pump (8) S

PW 6 433353112562201 10 125 Bail (125) Q

PW 8 433456112572001 10 166 Pump (8) Q

PW 9 433500112575401 10 200 Pump (5) Q

SWP 8 433351112555401 2 26 Bail (26) A

SWP 13 433349112555702 2 32 Bail (32) A

TRA A 13 433502112572802 2 59 Bail (59) S

TRA A 77 433507112573801 2 33 Bail (33) S

USGS 50 433419112560201 6 405 Pump (<1) S

USGS 53 433503112573401 6 90 Bail (75) S

USGS 54 433503112572801 6 91 Pump (4) Q

USGS 55 433508112573001 6 79 Pump (1) S

USGS 56 433509112573501 6 80 Pump (1) S

USGS 60 433456112571901 6 117 Pump (6) S

USGS 61 433453112571601 10 123 Pump (6) S

USGS 62 433446112570701 8 165 Pump (5) S

USGS 63 433455112574001 10 97 Pump (5) S

USGS 66 433436112564801 6 475 Bail (214) A

USGS 68 433516112573901 10 128 Pump (1) S

USGS 69 433450112573001 10 115 Pump (5) A

USGS 70 433504112571001 8 100 Pump (6) S

USGS 71 433439112571501 8 184 Bail (175) S

USGS 72 433519112574601 6 177 Pump (1) A

USGS 73 433502112575401 6 127 Pump (1.5) S

USGS 78 433413112573501 7 204 Bail (160) A

USGS 92 433000113025301 6 214 Bail (213) S

Table 1. Location and construction of wells in the U.S. Geological Survey perched ground water-quality monitoring network and 

sample-collection method and frequency, Idaho National Laboratory, Idaho, as of December 2001.

[Well No.: Locations of wells are shown in figure 3. 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). Sample-collection frequency: A, annually, S, 

semiannually; Q, quarterly. Abbreviation: USGS, U.S. Geological Survey. Symbol: <, less than]

Introduction 
Water-Quality Sampling Methods and Quality 

Assurance

Methods used to sample and analyze for selected 

constituents generally followed guidelines established by the 

USGS (Goerlitz and Brown, 1972; Stevens and others, 1975; 

Wood, 1981; Claassen, 1982; W.L. Bradford, USGS, written 

commun., 1985; Wershaw and others, 1987; Fishman and 

Friedman, 1989; and Wilde and others, 1998).

Water samples were collected according to a qualityassurance plan for water-quality activities conducted by 

personnel at the INL Project Office (Mann, 1996). Water 

samples collected for dissolved constituent analysis are filtered 

through a 0.45-micron membrane filter. About 10 percent 

of samples collected generally are for quality assurance. 

Quality-assurance samples collected by the USGS INL 

Project Office include equipment blanks, splits, and replicates. 

Nine quality-assurance replicates were collected for wells 

sampled for this study; results are included in the tables in 

this report. Comparative studies to determine agreement 

between analytical results for individual water-sample pairs 

by laboratories involved in the INL Project Office qualityassurance program were summarized by Wegner (1989), and 

Williams (1996, 1997). Additional quality-assurance studies 

by personnel at the INL Project Office included:

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); and

An analysis of two analytical methods to determine gross 

alpha- and beta-particle activity (Bartholomay and others, 

1999).

Geohydrologic Setting

The eastern Snake River Plain is a northeast oriented 

structural basin about 200-mi long and 50- to 70-mi wide. 

The plain consists of surficial alluvial and eolian sediments 

and basalt outcrops underlain by a layered sequence of basalt 

flows and sedimentary interbeds. Individual basalt flows are 

from 10- to 50-ft thick, although the average thickness is from 

20 to 25 ft (Mundorff and others, 1964, p. 143). Surficial 

sediments and sedimentary interbeds consist of sand, silt, clay, 

and lesser amounts of gravel. Locally, rhyolitic flows and tuffs 

are exposed at land surface or are present at depth.

1.

2.

3.

4.

5.

The top of the Snake River Plain aquifer is about 450 

ft below land surface at the RTC and INTEC and about 600 

ft below land surface at the RWMC. The unsaturated zone 

beneath these facilities consists of alluvial and eolian surficial 

sediments, basalt flows, and sedimentary interbeds and is 

typical of the stratigraphy at the INL. Anderson and Lewis 

(1989), Anderson (1991), Anderson and Bowers (1995), and 

Anderson and Liszewski (1997) described the stratigraphic 

sequence of the unsaturated zone and uppermost part of the 

Snake River Plain aquifer at selected INL facilities and at 

and near the INL. This sequence was formed by extrusion 

and cooling of basaltic lava followed by periods of volcanic 

quiescence and sedimentary deposition (Nace and others, 

1975, p. 16; Anderson and others, 1997). Vertical and 

horizontal fractures developed as lava flows cooled. These 

fractures and interflow rubble zones are primary conduits 

through which water is transmitted.

Locally, perched ground water formed in the basalt and in 

sedimentary interbeds in response to recharge from wastewater 

infiltration ponds and localized infiltration of snowmelt and 

rain. Perched ground water also formed from streamflow 

infiltration of the Big Lost River (fig. 1). Transmissivity 

estimates from 22 wells completed in perched ground water 

ranged from 1.0 to 15,000 ft2/d.(Ackerman, 1991, p. 10). 

Differences in the vertical hydraulic conductivity of basalt 

layers and sedimentary interbeds in the unsaturated zone 

provide mechanisms for development of perched ground 

water (Cecil and others, 1991, p. 17). The vertical hydraulic 

conductivity of a sedimentary interbed typically is smaller 

than an overlying fractured basalt layer. Perched ground water 

is closely associated with sedimentary interbeds beneath the 

RTC, INTEC, and RWMC. Several perched water zones exist 

below each facility. A more detailed description of the perched 

zones is available in Cecil and others (1991). Alterations in 

the baked zones between two basalt layers may contribute to 

decreased vertical hydraulic conductivity. Dense, unfractured 

basalt or sediment and chemical filling of fractures near the 

upper contact of a basalt layer limit the capability of the basalt 

to transmit water.

Guidelines for Interpreting Results of 

Radiochemical Analyses

Radionuclide concentrations are reported with an 

estimated sample standard deviation, s, which is obtained by 

propagating sources of analytical uncertainty in measurements. 

Guidelines for interpreting analytical results are based on an 

extension of a method proposed by Currie (1984).

During 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 larger than the signal observed 

 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
for the blank before the decision can be made that a 

radionuclide was detected; and (2) an estimate must be made 

of the minimum radionuclide concentration that will yield a 

sufficiently large observed signal before the correct decision 

can be made for detection or non-detection of a radionuclide. 

The first aspect of the problem is a qualitative decision based 

on an observed signal and a definite detection criterion. The 

second aspect of the problem is an estimation of detection 

capabilities of a given measurement process.

In the laboratory, instrument signals must exceed a 

critical level of 1.6s before the qualitative decision can be 

made regarding whether a radionuclide was detected. At 1.6s, 

the correct conclusion—not detected—is about a 95-percent 

probability. Given a large number of samples, as many as 5 

percent of the samples with measured concentrations greater 

than or equal to 1.6s, which were determined 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 is defined, the minimum 

detectable concentration may be determined. Concentrations 

that equal 3s represent measurements at the minimum 

detectable concentration. For true concentrations equal to or 

greater than 3s, the probability is 95 percent or higher that 

the radionuclide was detected in a sample. In a large number 

of samples, the conclusion—not detected—will be made in 

5 percent of samples that contain true 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.

True radionuclide concentrations between 1.6s and 3s

have larger errors of the second kind. That is, there is a largerthan-5-percent probability of false negative results for samples 

with true 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 concentration 

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 below a “reporting level.” The critical 

level, minimum detectable concentration, and reporting level 

help the reader interpret analytical results and do not represent 

absolute radioactivity concentrations, which may or may not 

have been detected.

Many analytical results of environmental radioactivity 

measurements are at or near zero. If the true concentration for 

a given radionuclide is zero, a given set of analytical results 

for that radionuclide should be distributed about zero, with an 

equal number of negative and positive measurements. Negative 

analytical results occur if the radioactivity of a water sample 

is less than background radioactivity or the radioactivity of the 

prepared blank sample in the laboratory (American Society for 

Testing and Materials, 1992, p. 126; Knobel and others, 1992, 

p. 51).

Guidelines for Interpreting Results of 

Chemical Analyses

Historically, the NWQL 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 constituent concentration that may be reliably 

reported using a given analytical method (Timme, 1995). This 

was the “less than” value reported by the NWQL. However, 

the NWQL determined that establishment of MRLs often 

was inconsistent, undefined, undocumented, and subjective 

(Childress and others, 1999). In 1998, the NWQL began 

implementing 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 the NWQL:

“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 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 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 <LRL for 

samples in which the analyte was either not detected or did 

not pass identification. Analytes 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 1999–2001. 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).

Guidelines for Interpreting Results of Chemical Analyses   
Distribution of Selected Radiochemical 

and Chemical Constituents in Perched 

Ground Water

Wastewater-disposal sites at INL facilities are the 

principal sources of radiochemical and chemical constituents 

in the Snake River Plain aquifer. These sites included 

infiltration ponds and ditches, lined evaporation ponds, drain 

fields, pits, and disposal wells. During 1999–2001, wastewater 

was discharged to infiltration and lined-evaporation ponds. 

Liquid and solid waste materials buried at the RWMC (fig. 1) 

also are sources of some constituents in ground water.

Radiochemical and chemical constituents in wastewater 

migrate to the Snake River Plain aquifer through perched 

ground water beneath wastewater infiltration ponds at the RTC 

and INTEC. Perched ground water beneath the RWMC formed 

from infiltration of snowmelt and rain and recharge from the 

Big Lost River and INL spreading areas. This perched water 

contains constituents leached from buried radioactive and 

organic-chemical wastes. The extent of this perched ground 

water is affected by the waste-disposal practices.

Contractors at each INL facility collect radioactive- and 

chemical-waste-disposal data. Historical radioactive-wastedisposal data presented in this report were obtained from a 

series of radioactive-waste-management information reports 

(French and others, 1997b; French and Taylor, 1998, and 

French and others, 1999b). Chemical-waste-disposal data were 

obtained from a series of nonradiological-waste-management 

information reports (French and others, 1997a; 1998; 

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 (Stoller Corp., 2002a, b, and c) provide some 

radioactive waste disposal data for 1999–2001. Effluent 

monitoring and wastewater discharge raw data for some INL 

facilities were provided by DOE contractor personnel (Teresa 

Meachum, CH2M-WG Idaho, LLC, written commun., 2005), 

however compilation of those data was beyond the scope of 

this report. Therefore, this report does not present amounts 

and types of most radioactive and chemical wastes discharged 

at the various facilities for 1999–2001. Davis (2006) presents 

a more detailed description of the waste-disposal history at 

selected facilities.

Reactor Technology Complex

Shallow and deep perched ground water formed at the 

RTC in response to wastewater disposal to radioactive-, 

chemical-, cold-, and sanitary-waste ponds (fig. 2). During 

2001, about 293 Mgal/yr of wastewater was discharged 

to infiltration and lined evaporation ponds at the RTC. 

Selected radiochemical and inorganic chemical constituents 

in wastewater have been monitored in the shallow and deep 

perched ground water since the early 1960s.

Water samples from seven wells (CWP 1, 2, 3, 4, 5, 8, 

TRA A 13) (fig. 3) completed in shallow perched ground 

water near the RTC routinely were collected and analyzed 

for selected radiochemical and chemical constituents during 

1999–2001. No water was present in wells CWP 6, 7, and 

TRA A 77 during this period. Water samples also were 

collected from 16 wells (PW 8 and 9, USGS 54, 55, 60 

through 63, 66, 68 through 73, 78) (fig. 3) completed in deep 

perched ground water beneath the RTC. No samples were 

collected from wells USGS 53, 56, 74, and PW 7 because 

either the well was dry or water was below the level of 

the pump intake. Selection of radiochemical and chemical 

constituents for analyses was based on waste-disposal history 

at the RTC. Selected radiochemical constituents were tritium, 

strontium-90, cesium-137, and gamma analyses; chemical 

constituents were dissolved chromium, sodium, chloride, and 

sulfate.

Tritium

Tritium has a half-life of 12.3 years (Walker and 

others, 1989, p. 20). During 1952–93, about 10,500 Curies 

(Ci) of tritium was contained in wastewater discharged to 

the radioactive-waste infiltration ponds at the RTC. Since 

August 1993, tritium in wastewater has been discharged to 

two lined evaporation ponds, replacing the radioactive-waste 

infiltration ponds (fig. 3) (Orr, 1999), which probably prevents 

radioactive wastewater from entering the ground. Before 

1980, tritium generally accounted for less than 20 percent of 

the total radioactivity discharged to the ponds; most of the 

rest consisted of radionuclides with half-lives on the order 

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

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

After 1980, tritium generally accounted for more than 90 

percent of the total radioactivity. About 191 Ci of tritium was 

released in wastewater to the RTC lined evaporation ponds 

10 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
during 1999–2000 (Stoller Corp., 2002a, 2002b). Data are 

not available for the total amount of tritium in wastewater 

discharged in 2001. Figure 4 shows annual wastewater and 

tritium discharged to the radioactive-waste infiltration and 

lined evaporation ponds during 1962–2001.

Well TRA A 77 (fig. 3) is completed in shallow perched 

ground water in alluvium near the RTC retention basin 

(fig. 5), where radioactive wastewater flowed before it was 

discharged to the radioactive-waste infiltration ponds (figs. 3

and 5). 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 largest 

tritium concentration in water from well TRA A 77 during 

1989–91 was 3,790±50 pCi/mL (Tucker and Orr, 1998, p. 15). 

In 1992, the largest tritium concentration increased slightly 

to 3,940±60 pCi/mL (Bartholomay, 1998, p. 41). In October 

1995, the tritium concentration in water from well TRA A 77 

had decreased to 22.4±0.9 pCi/mL (Bartholomay, 1998, p. 41) 

and by April 1997 to 1.0±0.15 pCi/mL (Bartholomay, 1998, 

table 2). Historically, tritium concentrations were variable 

in water from well TRA A 77. Because of the shallow depth 

of well TRA A 77 and its proximity to the leaking retention 

basin, the variability in tritium concentrations in this well 

could have been the result of changes in tritium disposal rates 

(Bartholomay, 1998, p. 10). No samples were collected from 

this well since April 1997 because no water was 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.

Maximum concentrations of tritium in water from well 

TRA A 13 decreased from 158±2 pCi/mL during 1982-85 

to 1.1±0.3 pCi/mL 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. 3), likely is attributed to the large quantity of 

nonradioactive water discharged to the cold-waste ponds 

(Bartholomay and Tucker, 2000).

Wells CWP 1 through CWP 9 monitor shallow perched 

ground water around the cold-waste ponds at the RTC. During 

1982–2001, tritium was less than the reporting level in water 

from wells CWP 1 through CWP 7. A tritium concentration of 

0.8±0.2 pCi/mL was measured in water from well CWP 8 in 

November 1988, and since then, concentrations have been less 

than the reporting level. Tritium concentrations in water from 

well CWP 9 (fig. 2) decreased from 6.3±0.2 pCi/mL during 

1982–85 to 1.1±0.2 pCi/mL during 1986–88 (Cecil and others, 

1991, p. 35). No samples have been collected at CWP 9 since 

1988. Discharge of cooling-tower wastewater to the TRA 

disposal well ceased in 1982 and this water subsequently was 

discharged to the cold-waste ponds. 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).

Tritium concentrations in water from nine wells 

completed in deep perched ground water (PW 8, PW 9, USGS 

54, 55, 61, 66, 70, 71, and 73) generally were greater than the 

reporting levels during 1999–2001. Concentrations decreased 

in some wells and varied randomly in other wells (table 2), 

and all reportable concentrations were less than the 1998 

concentrations. Tritium concentrations in water from four 

wells (USGS 60, 68, 69, and 78) were less than the reporting 

level during 1999–2001 (table 2). Tritium concentrations 

varied between reportable and nonreportable concentrations 

in water from two wells, USGS 62 and 63, during 1999-2001. 

Tritium concentrations in water from well USGS 62 were 

greater than the reporting level in October 1999 and April 

2000, but the concentration decreased to less than the 

reporting level by October 2001. Concentrations in water from 

well USGS 63 were greater than the reporting level in October 

2000, however, the concentration decreased to less than the 

reporting level by October 2001 (table 2). An obstruction in 

well USGS 53 in 1996 prevented water-level measurement 

or water-quality sampling. The water level in well USGS 56 

decreased below the pump intake in 1997 and no samples 

have been collected at this well since January 1997 due to 

lack of water. No samples were collected at wells USGS 74 

and PW 7 because they have been dry since 1993 and 1994, 

respectively. The decreases in concentration and lack of water 

in wells USGS 53 and 56 may be attributed to discontinuing 

wastewater disposal to the radioactive-waste infiltration ponds. 

Variations in tritium concentrations in water from these wells 

likely are attributed to fluctuations in disposal rates and to 

mixing of water from the radioactive- and cold-waste ponds 

(Bartholomay and Tucker, 2000).

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 11
ID19-0022_fig04

No Data

Annual dicharge of tritium to the radioactive-waste infiltration and 

lined evaporation ponds at the Reactor Technology Complex, 1962-2001

No Data

Tritium as a percentage of total radioactive constituents

in wastewater discharged at the Reactor Technology Complex, 1962-2001

(1970 percentage based on disposal data for January-June)

Wastewater discharged to the radioactive-waste infiltration and 

lined evaporation ponds at the Reactor Technology Complex, 1962-2001

No Data

August 1993 through 2001,

wastewater discharged only

to lined evaporation ponds

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0

20

40

60

80

100

0

100

200

300

400

500

600

700

ANNUAL DISCHARGE OF TRITIUM, IN CURIES PERCENT COMBINED ANNUAL DISCHARGE, IN MILLIONS OF GALLONS

19651970197519801985199019952000

Figure 4. Amount of tritium discharged, tritium as a percentage of total radioactive constituents in wastewater 

discharged, and volume of wastewater discharged to the radioactive-waste infiltration and lined evaporation ponds at the 

Reactor Technology Complex, Idaho National Laboratory, Idaho, 1962–2001.

12 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
During July–October 2001, the most recent tritium 

concentrations in water from eight wells completed in deep 

perched ground water at the RTC exceeded the reporting levels 

(fig. 5; table 2). Tritium concentrations ranged from 0.49±0.14 

pCi/mL (well PW 8) to 39.4±1.4 pCi/mL (well PW 9). During 

July–October 2001, reportable tritium concentrations in water 

from wells completed in deep perched ground water (fig. 5) 

were less than concentrations measured during July–December 

1998 (Bartholomay and Tucker, 2000, fig. 5).

Water samples collected in October 2001 from wells 

USGS 73 and PW 9 contained tritium concentrations 

of 9.3±0.5 and 39.4±1.4 pCi/mL, respectively. These 

concentrations represent generally steady decreases since 

1993 when the radioactive-waste infiltration ponds were 

taken out of service. Water in well USGS 74 contained 

93.1±1.7 pCi/mL in April 1992; however, no samples have 

been collected since 1992 because the well has been dry. 

0.14±0.13

0±0.12

2±0.2

0.4±0.14

0.49±0.14

0.08±0.12

4.5±0.3

0.23±0.13

1.8±0.2

NSEQ

0.03±0.13

39.4±1.4

9.3±0.5

Dry

25±1

WBP

4.8±0.3

WBP

NSEQ

PW 7

(Sampling

discontinued

October 2001)

USGS 63

USGS 69

USGS 71

USGS 54

PW 8

USGS 60

USGS 61

USGS 62

USGS 66

Cold-waste ponds

USGS 72

USGS 68

USGS 74

(Sampling

discontinued

October 2001)

USGS 73

PW 9

USGS 53

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

USGS 55

USGS 56

Retention

basin Radioactive-waste ponds

USGS 70

REACTOR TECHNOLOGY COMPLEX

Extent of deep perched ground water zone—

October 2001. Approximately located

Water level below pump, could not sample

Not sampled, equipment problems

Well completed in deep perched ground water—Entry,

PW 8, is local well identifier; 0.49±0.14, is tritium 

concentration and associated uncertainty in picocuries per 

milliliter. Concentration equal to or greater than the 3s 

reporting level in bold. Values represent most recent data 

collected during July–October 2001

Lincoln Boulevard

0.49±0.14

PW 8

Monroe Boulevard

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

EXPLANATION

0

0

2,000 FEET

500 METERS

Figure 5. Concentrations of tritium in water from wells completed in deep perched ground water, Reactor Technology 

Complex, Idaho National Laboratory, Idaho, July–October 2001.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 13
Table 2. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Reactor Technology 

Complex, Idaho National Laboratory, Idaho, 1999–2001.

[Well No.: Locations of wells are shown in figure 3. Analyses completed by the 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 water; QA-3, quality assurance replicate sample, number indicates 

the replicate sequence number during a sampling event; SP, well completed in shallow perched water; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSO, not sampled because of obstruction in well; NSA, not sampled because of well access problems; 

NSEQ, not sampled because of equipment problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter; SL, sample lost in analysis; USGS, U.S. 

Geological Survey. Symbol: ±, plus or minus]

Well No. Date sampled Tritium 

(pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

CWP 1 (SP) 06-30-99 0.02±0.12 3.1±0.7 NR

07-17-00 0.03±0.12 1.4±0.8 NR

07-26-01 0±0.12 1±0.7 NR

CWP 2 (SP) 06-30-99 NS NS NS

07-17-00 0.03±0.12 0.4±0.7 NR

07-17-00 QA-3 0.01±0.12 0±0.7 NR

07-26-01 -0.07±0.12 -0.1±0.6 NR

CWP 3 (SP) 06-30-99 0.01±0.12 0.4±0.7 NR

06-30-99 QA-1 0.03±0.12 1±0.8 NR

07-17-00 NS NS NS

07-26-01 -0.05±0.12 -0.1±0.6 NR

CWP 4 (SP) 06-30-99 0.02±0.12 1.7±0.7 NR

07-17-00 NS NS NS

07-26-01 -0.02±0.12 -0.7±0.6 NR

CWP 5 (SP) 06-30-99 NS NS NS

07-17-00 NS NS NS

07-26-01 -0.01±0.12 0±0. 6 NR

CWP 6 (SP) 06-30-99 NS NS NS

07-17-00 NS NS NS

07-19-01 NS NS NS

CWP 7 (SP) 06-30-99 NS NS NS

07-17-00 NS NS NS

07-19-01 NS NS NS

CWP 8 (SP) 06-30-99 0.02±0.12 0±0.7 NR

07-17-00 0.04±0.12 0±0.8 NR

07-26-01 0.05±0.13 0±0.6 NR

PW 7 (DP) 04-22-99 NS NS NS

10-19-99 NS NS NS

04-06-00 NS NS NS

10-02-00 NS NS NS

04-18-01 NS NS NS

PW 8 (DP) 01-21-99 0.93±0.16 12.4±0.7 NR

04-06-99 0.57±0.14 12.8±0.9 24±30

07-15-99 1.15±0.16 11.8±0.9 NR

10-19-99 0.55±0.16 13±0.9 NR

01-26-00 0.88±0.15 13±1 NR

04-05-00 0.9±0.2 15.4±0.9 10±30

07-20-00 1.25±0.17 15.5±1 NR

10-04-00 0.84±0.16 16.5±1.1 NR

01-23-01 0.67±0.15 13.8±0.8 NR

04-03-01 0.37±0.15 10.4±0.9 -60±40

07-26-01 0.22±0.14 7.9±0.8 NR

10-09-01 0.49±0.14 9.3±0.8 NR

14  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Well No. Date sampled Tritium 

(pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

PW 9 (DP) 01-20-99 80.4±2.8 -0.8±0.7 NR

04-06-99 75.3±2.6 0.69±0.7 8±30

07-14-99 65.3±2.3 0.4±0.7 NR

10-06-99 62.7±2.2 0.6±0.8 NR

01-26-00 53.3±1.9 1.2±0.7 NR

04-05-00 53.9±1.9 1±1 -40±20

07-06-00 53.6±1.9 0.7±0.8 NR

10-04-00 49.1±1.7 0.4±0.9 NR

04-03-01 51.3±1 2.3±0.7 20±30

07-26-01 47.1±0.9 -0.12±0.65 NR

10-09-01 39.4±1.4 0.7±0.6 NR

TRA A 13 (SP) 04-26-99 0.18±0.12 32.8±1 7±30

10-06-99 0.02±0.13 38±1.4 10±30

04-13-00 0.07±0.12 34.6±1.2 20±30

09-27-00 NS NS NS

04-18-01 -0.08±0.13 22.1±1.1 -60±40

10-14-01 NSO NSO NSO

TRA A 77 (SP) 05-26-99 NSA NSA NSA

07-21-99 NS NS NS

10-19-99 NS NS NS

10-18-00 NS NS NS

04-16-01 NS NS NS

11-10-01 NS NS NS

USGS 53 (DP) 04-21-99 NS NS NS

10-09-99 NS NS NS

04-06-00 NS NS NS

10-02-00 NS NS NS

04-18-01 NS NS NS

10-04-01 NS NS NS

USGS 54 (DP) 01-20-99 0.6±0.15 77±2 NR

04-21-99 0.11±0.12 68.2±2 -7±40

07-14-99 0.79±0.15 79±2 NR

10-06-99 0.24±0.14 70±2 10±30

01-26-00 0.69±0.14 85±4.1 NR

04-11-00 0.01±0.12 76.1±1.9 -20±30

07-06-00 1.7±0.2 82.1±2.2 NR

10-04-00 0.44±0.14 85.7±2.2 10±40

01-18-01 -0.01±0.12 86.3±2.1 NR

04-12-01 0.16±0.14 63±1.8 -40±40

07-30-01 0.16±0.13 68.4±1.9 NR

10-23-01 0.4±0.14 83.8±2.1 40±40

USGS 55 (DP) 04-21-99 30.7±1.2 44±2 6±20

10-26-99 45.8±1.6 33±1.2 NR

04-13-00 36.8±1.3 26.4±1.1 -10±40

10-05-00 NS NS NS

04-19-01 17.3±0.5 44.4±1.4 -10±20

10-23-01 25±1 58.1±1.6 NR

Table 2. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Reactor Technology 

Complex, Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figure 3. Analyses completed by the 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 water; QA-3, quality assurance replicate sample, number indicates 

the replicate sequence number during a sampling event; SP, well completed in shallow perched water; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSO, not sampled because of obstruction in well; NSA, not sampled because of well access problems; 

NSEQ, not sampled because of equipment problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter; SL, sample lost in analysis; USGS, U.S. 

Geological Survey. Symbol: ±, plus or minus]

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 15
Well No. Date sampled Tritium 

(pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

USGS 56 (DP) 04-26-99 NS NS NS

10-19-99 NS NS NS

10-18-00 NS NS NS

04-16-01 NS NS NS

10-10-01 NS NS NS

USGS 60 (DP) 04-06-99 -0.04±0.11 0.4±0.8 20±20

10-19-99 0.06±0.14 3.7±0.8 NR

04-05-00 0.09±0.12 4±1 13.5±34.2

10-04-00 0.12±0.13 8.3±1 NR

10-04-00 QA-2 0.13±0.13 7.1±1 NR

04-03-01 0.37±0.15 10.4±0.9 -60±40

10-09-01 0.08±0.12 0.7±0.6 NR

USGS 61 (DP) 04-13-99 8.1±0.4 0.5±0.8 10±20

04-13-99 QA-1 8.4±0.4 1.6±0.8 -10±20

10-06-99 7.5±0.4 1.1±0.8 NR

04-06-00 6.3±0.4 1.9±0.7 20±40

09-27-00 5.4±0.3 0.1±0.9 NR

04-12-01 5.8±0.3 0.4±0.8 -20±40

10-04-01 4.5±0.3 -1.1±0.7 NR

USGS 62 (DP) 04-13-99 0.17±0.12 4.36±0.8 7±30

10-06-99 2±0.2 3.6±0.8 NR

04-03-00 0.3±0.1 3±1 10±30

09-27-00 0.16±0.13 2.9±0.9 NR

09-27-00 QA-1 0.05±0.12 3.3±0.9 NR

04-17-01 0.2±0.14 1.6±0.8 52±38

10-09-01 0.23±0.13 1.4±0.6 NR

USGS 63 (DP) 04-13-99 0.16±0.12 4.9±0.9 -10±20

10-25-99 0.4±0.15 5.5±0.8 NR

04-06-00 0.07±0.12 6±1 -13.4±44.1

10-04-00 0.79±0.16 4±0.9 NR

04-19-01 0.15±0.14 3.2±0.7 0±50

10-15-01 0.14±0.13 2.8±0.7 NR

USGS 66 (DP) 07-08-99 3.3±0.2 1.4±0.7 NR

07-25-00 2.6±0.2 0.7±0.9 NR

07-25-00 QA-8 2.6±0.2 0.3±0.8 NR

07-25-01 1.8±0.2 0.3±0.7 NR

USGS 68 (DP) 05-26-99 NSA NSA NSA

07-21-99 0.01±0.12 0.4±0.8 15±33

10-19-99 -0.08±0.13 0.5±0.8 14.8±33.8

10-18-00 0.1±0.1 0.4±1.1 13.1±20.5

04-16-01 0±0.13 -0.3±0.9 0±40

10-10-01 0.03±0.13 1.4±1.3 30±30

Table 2. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Reactor Technology 

Complex, Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figure 3. Analyses completed by the 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 water; QA-3, quality assurance replicate sample, number indicates 

the replicate sequence number during a sampling event; SP, well completed in shallow perched water; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSO, not sampled because of obstruction in well; NSA, not sampled because of well access problems; 

NSEQ, not sampled because of equipment problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter; SL, sample lost in analysis; USGS, U.S. 

Geological Survey. Symbol: ±, plus or minus]

16  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Well No. Date sampled Tritium 

(pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

USGS 69 (DP) 07-13-99 0.04±0.12 0.5±0.7 NR

07-12-00 0.02±0.12 1.1±0.7 NR

07-31-01 0±0.12 0.3±0.6 NR

USGS 70 (DP) 04-13-99 5.7±0.3 42.5±2 7±20

10-26-99 5.9±0.3 47±1.4 NR

04-06-00 8.6±0.4 50.6±1.5 10±40

10-04-00 11.8±0.5 47.8±1.5 NR

04-19-01 4.5±0.3 40.6±1.3 -30±20

10-15-01 4.8±0.3 50.4±1.5 NR

USGS 71 (DP) 04-27-99 2.9±0.2 SL 18±20

10-21-99 2.6±0.2 0±0.8 NR

04-13-00 NS NS NS

10-03-00 2±0.2 1.1±0.8 NR

04-17-01 NS NS NS

10-10-01 2±0.2 0.4±0.7 NR

USGS 72 (DP) 07-21-99 NSEQ NSEQ NSEQ

10-19-99 -0.12±0.13 -0.5±0.7 20±20

08-03-00 NSEQ NSEQ NSEQ

07-19-01 NSEQ NSEQ NSEQ

USGS 73 (DP) 04-15-99 37.9±1.4 2.0±0.8 58±30

10-21-99 25.9±1 0.7±0.8 NR

04-13-00 26.1±1 0.3±0.8 42±30

09-27-00 29.9±1.1 0±0.9 NR

04-02-01 19.9±0.6 0.88±0.67 56±39

10-10-01 9.3±0.5 0.5±0.6 NR

USGS 74 (DP) 04-22-99 NS NS NS

10-19-99 NS NS NS

04-10-00 NS NS NS

10-02-00 NS NS NS

04-18-01 NS NS NS

USGS 78 (DP) 07-08-99 0.05±0.12 -0.4±0.8 NR

07-25-00 0.08±0.12 0.74±0.71 NR

07-25-01 -0.07±0.12 -0.3±0.6 NR

Table 2. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Reactor Technology 

Complex, Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figure 3. Analyses completed by the 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 water; QA-3, quality assurance replicate sample, number indicates 

the replicate sequence number during a sampling event; SP, well completed in shallow perched water; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSO, not sampled because of obstruction in well; NSA, not sampled because of well access problems; 

NSEQ, not sampled because of equipment problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter; SL, sample lost in analysis; USGS, U.S. 

Geological Survey. Symbol: ±, plus or minus]

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 17
The well was removed from the sampling schedule in October 

2001. These three wells are more than 1,500 ft west of the 

radioactive-waste infiltration ponds (fig. 5). Historically 

large tritium concentrations in water from these wells 

indicate that the chemistry of perched ground water west of 

the RTC was affected by radioactive-waste infiltration pond 

disposals. Discontinuation of wastewater discharge to the 

radioactive-waste infiltration ponds and subsequent use of 

lined evaporation ponds, together with the radioactive decay 

process, may account for the decreased tritium concentrations 

in this area and could indicate an eastward migration of the 

extent of deep perched water relative to well USGS 74.

Water-level hydrographs for wells USGS 60 and 73 

(fig. 6) indicate that wastewater disposal to the cold-waste 

ponds since 1982 has hydraulically affected perched ground 

water flow to the west and east. Disposal to the cold-waste 

ponds affected water levels much less in wells USGS 54 

and 70, to the north and northeast of the cold-waste ponds 

(fig. 6). Water levels in all four wells decreased significantly 

in 1992 (fig. 6), when wastewater discharge to the cold-waste 

ponds was much less than during other years (Bartholomay 

and Tucker, 2000). Because of the effect of disposal to the 

cold-waste ponds on water levels and the removal of the 

radioactive-waste infiltration ponds as a water source, tritium 

concentrations in perched ground water at the RTC likely 

decreased as nonradioactive wastewater from the cold-waste 

ponds mixed with water derived from earlier radioactive-waste 

infiltration pond disposal (Bartholomay and Tucker, 2000).

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 is also demonstrated by the fact 

that 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.

Bartholomay (1998) noted that increases and decreases 

in tritium concentrations in water from well USGS 73 lagged 

from 3 to 13 months behind increases and decreases in well 

USGS 56. This time lag indicated that tritium in ground 

water moved from the radioactive-waste infiltration ponds to 

well USGS 73 during that period. Bartholomay (1998) also 

determined that changes in tritium concentrations in water 

from well USGS 54 did not correspond directly to monthly 

changes in tritium disposal. The lack of correspondence 

indicated that other factors, including hydraulic effects 

and dilution from the cold-waste ponds, affected tritium 

concentrations in water from that well.

Several factors have affected the distribution of tritium 

in perched ground water at the RTC. These factors include 

proximity of the wells to the radioactive-waste infiltration 

ponds, depth of the water below the ponds, variations in 

the 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 

ground water and decreases in the amount of perched water 

in some wells. Infiltration from the Big Lost River during 

1999 and early 2000 may have contributed to diluted tritium 

concentrations in perched ground water southeast of the 

RTC . Tritium concentrations in wells USGS 62, 66, and 71 

decreased slightly during 1999–2001.

Strontium-90

Strontium-90 has a half-life of 29.1 years (Walker 

and others, 1989, p. 29). During 1952–93, about 93 Ci of 

strontium-90 was in wastewater discharged to the radioactivewaste infiltration ponds at the RTC, an average of 2.3 Ci/yr 

(Bartholomay and Tucker, 2000). During 1996–98, about 

0.03 Ci was discharged to the lined evaporation ponds 

(Bartholomay and Tucker, 2000). During 1999, less than 

0.001 Ci of strontium-90 was discharged at the RTC (Stoller 

Corp., 2002a, table 7-2); during 2000, 0.21 Ci of strontium-90/

yttrium-90 was discharged at the RTC (Stoller Corp., 

2002b, table 6-2). Data are not available for the amount of 

strontium-90 discharged in 2001.

During 1996–98, strontium-90 concentrations in water 

from wells TRA A 77 and TRA A 13, completed in shallow 

perched ground water, were above the reporting levels 

(Bartholomay and Tucker, 2000, table 2). Concentrations in 

water from well TRA A 77 ranged from 4,710±140 pCi/L 

in October 1996 to 6,800±200 pCi/L in April 1997. Well 

TRA A 77 was not sampled during 1999–2001 because of well 

access problems or lack of water in the well. In October 1998, 

the concentration of strontium-90 in water from well TRA A 

13 was 23.5±1.2 pCi/L. Water from well TRA A 13 exceeded 

the reporting level during 1999–2001 and in April 2001 the 

concentration was 22.1±1.1 pCi/L (table 2), consistent with 

the October 1998 concentration. The well was not sampled in 

October 2001 because of an obstruction in the well. Well CWP 

1, also completed in shallow perched ground water, exceeded 

the reporting level in June 1999 with a concentration of 

3.1±0.7 pCi/L, however, by July 2001, the concentration was 

less than the reporting level.

In October 2001, concentrations of strontium-90 in water 

from wells PW 8, USGS 54, 55, 63, and 70, completed in deep 

perched ground water at the RTC were greater than reporting 

levels (table 2 and fig. 7); concentrations ranged from 

2.8±0.7 pCi/L in well USGS 63 to 83.8±2.1 pCi/L in well 

USGS 54. The distribution of strontium-90 concentrations 

in water from these wells during 1999–2001 is attributed to 

exchange reactions between strontium-90 in solution and 

sediments beneath the radioactive-waste infiltration ponds. 

18  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
ID19-0022_fig06

USGS 60

USGS 73

USGS 70

USGS 54

0

20

40

60

80

100

120

0

20

40

60

80

100

120

0

20

40

60

80

100

120

20

40

60

80

100

120

0

196019651970197519801985199019952000

WATER LEVEL, IN FEET BELOW LAND SURFACE

No Data

Figure 6. Water-level changes in selected wells, Reactor Technology Complex, Idaho National Laboratory, Idaho, 1960–2001.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 19
Strontium-90 was not detected in water from the Snake River 

Plain aquifer beneath the RTC (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. Study 

of strontium distribution coefficients for samples of surficial 

sediment, sedimentary interbeds, and sediment-filled fractures 

in basalts (Liszewski and others, 1997, 1998; Pace and others, 

1999) at the INL support this theory.

Water in wells PW 9 and USGS 62 contained 

strontium-90 at concentrations less than reporting levels in 

some samples collected during 1999–2001, but greater than 

reporting levels in other samples (table 2). Because 2001 

strontium-90 disposal data were not available, fluctuations 

could not be correlated with disposal during 1999–2001. In 

addition, lined evaporation ponds were in use, which probably 

prevented contaminated water from percolating into the 

ground.

ID19-0022_fig07

2.8±0.7

0.3±0.6

0.4±0.7

83.8±2.1

9.3±0.8

0.7±0.6

-1.1±0.7

1.4±0.6

0.3±0.7

NSEQ

1.4±1.3

0.7±0.6

0.5±0.6

Dry

58.1±1.6

WBP

50.4±1.5

WBP

NSEQ

PW 7

(Sampling

discontinued

October 2001)

USGS 63

USGS 69

USGS 71

USGS 54

PW 8

USGS 60

USGS 61

USGS 62

USGS 66

Cold-waste ponds

USGS 72

USGS 68

USGS 74

(Sampling

discontinued

Ocober 2001)

USGS 73

PW 9

USGS 53

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

USGS 55

USGS 56

Retention

basin Radioactive-waste ponds

USGS 70

REACTOR TECHNOLOGY COMPLEX

Extent of deep perched ground water zone—

October 2001. Approximately located

Water level below pump, could not sample

Not sampled, equipment problems

Well completed in deep perched ground water—Entry,

PW 8, is local well identifier; 9.3±0.8, is strontium-90 

concentration and associated uncertainty in picocuries per 

milliliter. Concentration equal to or greater than the 3s 

reporting level in bold. Values represent most recent data 

collected during July–October 2001

Lincoln Boulevard

9.3±0.8

PW 8

Monroe Boulevard

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

EXPLANATION

0

0

2,000 FEET

500 METERS

Figure 7. Concentrations of strontium-90 in water from wells completed in deep perched ground water, Reactor 

Technology Complex, Idaho National Laboratory, Idaho, July–October 2001.

20 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Cesium-137

Cesium-137 has a half-life of 30.17 years (Walker and 

others, 1989, p. 34). About 138 Ci of cesium-137 was in 

wastewater discharged to the radioactive-waste infiltration 

ponds at the RTC during 1952–93. The average disposal 

rate decreased from 2.0 Ci/yr during 1979–81 (Lewis and 

Jensen, 1985) to 0.65 Ci/yr during 1982–85 (Pittman and 

others, 1988, p. 35). The average disposal rate of cesium137 during 1986–88 was 0.23 Ci/yr (Cecil and others, 1991, 

p. 36). The rate decreased during 1989–91 to 0.02 Ci/yr 

(Tucker and Orr, 1998, p. 17), and averaged 0.7 Ci/yr during 

1992–93 (Bartholomay, 1998, p. 16). After 1993, wastewater 

was discharged to lined evaporation ponds, which probably 

prevents any cesium-137 from percolating into the ground.

During 1999–2001, no reportable concentrations of 

cesium-137 were detected in water from any wells completed 

in either shallow or deep perched ground water. The general 

absence of reportable concentrations of cesium-137 in perched 

ground water at the RTC probably is due to decreasing 

cesium-137 disposal rates, change from using the radioactivewaste infiltration ponds to lined evaporation ponds, and 

sorption and (or) exchange of cesium-137 to minerals in 

sediments. During 1996–97, cesium-137 concentrations in 

water from shallow well TRA A 77 exceeded the reporting 

level and ranged from 42,300±1,800 pCi/L in April 1996 to 

1,200±110 pCi/L in April 1997. No samples were collected 

from well TRA A 77 during 1998–2001 because the well was 

dry. The intermittent presence of cesium-137 in water from 

well TRA A 77 may have been due to the proximity of the 

well to the retention basin and to the amount of suspended 

sediment in water samples collected onto which cesium-137 

may have sorbed.

Chromium-51

Chromium-51 has a half-life of 27.7 days (Walker and 

others, 1989, p. 24). About 2,390 Ci of chromium-51 was in 

wastewater discharged to the radioactive-waste infiltration 

and lined evaporation ponds during 1979–98. Data are not 

available for the amount of chromium-51 discharged during 

1999–2001. The average disposal rate of chromium-51 during 

1979–81 was 766 Ci/yr (Pittman and others, 1988, p. 35). 

A total of 25.7 Ci of chromium-51 was discharged during 

1986-88, an average of 8.6 Ci/yr (Cecil and others, 1991, 

p. 35). During 1989–91,11.6 Ci was discharged for an average 

of 3.9 Ci/yr (Tucker and Orr, 1998, p. 17). During 1992–95, 

10 Ci was discharged, an average of 2.5 Ci/yr (Bartholomay, 

1998, p. 16). During 1996–98, 6.2 Ci was discharged, an 

average of 2.1 Ci/yr (Bartholomay and Tucker, 2000).

Because of the decreased amount of chromium-51 

discharged and the relatively short half-life, this radionuclide 

was not detected in water from wells completed in deep 

perched ground water during 1986–88 (Cecil and others, 1991, 

p. 35). Chromium-51 was not detected in shallow perched 

ground water from wells TRA A 13 and CWP 1 through 

CWP 9 during 1982–88. During 1989–91, chromium-51 

was detected in water from wells TRA A 77, USGS 53, and 

USGS 56 (Tucker and Orr, 1998, p. 17). During 1992–95, 

chromium-51 was detected only in shallow well TRA A 77; 

concentrations ranged from 2,700±500 to 24,500±1,300 pCi/L 

(Bartholomay, 1998, p. 16). Chromium-51 was not detected in 

any wells during 1996–2001.

Cobalt-60

Cobalt-60 has a half-life of 5.27 years (Walker and 

others, 1989, p. 25). About 442 Ci of cobalt-60 was in 

wastewater discharged to the radioactive-waste infiltration 

ponds at the RTC during 1952–88. The average cobalt-60 

disposal rate decreased from 2.3 Ci/yr during 1979–81 to 

1 Ci/yr during 1982–85 (Pittman and others, 1988). The 

average disposal rate was 2.2 Ci/yr during 1986–88, 0.15 Ci/yr 

during 1989–91, 0.8 Ci/yr during 1992–95 (Bartholomay, 

1998, p. 16) and about 0.3 Ci/yr during 1996–98.

During 1996–98, cobalt-60 concentrations in water 

from wells TRA A 77 and USGS 56 exceeded the reporting 

level. Concentrations of cobalt-60 in water from well TRA 

A 77 ranged from 7,700±260 to 44,000±1,400 pCi/L. The 

concentration in water from well USGS 56 was 220±30 pCi/L 

(Bartholomay and Tucker, 2000). The presence of cobalt-60 in 

these wells probably is due to their proximity to the ponds and 

retention basin. During 1999–2001, no samples were collected 

from these two wells because well TRA A 77 was dry and 

water was below the pump intake level in well USGS 56. 

Cobalt-60 was not detected in any other water samples 

analyzed during 1999–2001.

Chromium

An estimated 24,000 lb of nonradioactive chromium 

in wastewater from RTC cooling-tower operations was 

discharged to the radioactive-waste infiltration ponds during 

1952–64 (Mann and Knobel, 1988, p. 7–10). During 1964–72, 

a disposal well at the RTC was used to dispose chromium 

directly to the Snake River Plain aquifer. In October 1972, 

chromium was replaced by polyphosphate as a corrosion 

inhibitor in cooling-tower operations. No disposal of 

chromium to the subsurface was reported after 1972.

During 1996–98, dissolved chromium concentrations in 

shallow perched ground water ranged from less than 5 μg/L in 

several wells to 26 μg/L in well TRA A 77 (Bartholomay and 

Tucker, 2000). During 1999–2001, wells TRA A 77, CWP 6, 

and CWP 7 could not be sampled because the wells were dry. 

During 1999–2001, dissolved chromium was not detected in 

shallow perched ground water (table 3).

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 21
Table 3. Concentrations of selected dissolved ions in perched ground water from selected wells, Reactor Technology Complex, 

Idaho National Laboratory, Idaho, 1999–2001.

[Well No.: Locations of wells are shown in figures 3, 8, and 9. Analyses completed by the National Water Quality Laboratory. Abbreviations: DP, well 

completed in deep perched water; SP, well completed in shallow perched water; QA-3, quality assurance replicate sample, number indicates the replicate 

sequence number during a sampling event; μg/L, microgram per liter; mg/L, milligram per liter; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSA, not sampled because of well access problems; NSEQ, not sampled because of equipment 

problems; E, estimated; 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) 06-30-99 <14 NR 26 332

07-17-00 <14 NR 31 419

07-26-01 <10 NR 10 31

CWP 2 (SP) 06-30-99 NS NS NS NS

07-17-00 <14 NR 17 123

07-17-00 QA-3 <14 NR 17 123

07-26-01 <10 NR 12 78

CWP 3 (SP) 06-30-99 <14 NR 24 295

06-30-99 QA-1 <14 NR 24 293

07-17-00 NS NS NS NS

07-26-01 <10 NR 10 35

CWP 4 (SP) 06-30-99 <14 NR 12 74

07-17-00 NS NS NS NS

07-26-01 <10 NR 10 48

CWP 5 (SP) 06-30-99 NS NS NS NS

07-17-00 NS NS NS NS

07-26-01 <10 NR 11 58

CWP 6 (SP) 06-30-99 NS NS NS NS

07-17-00 NS NS NS NS

07-19-01 NS NS NS NS

CWP 7 (SP) 06-30-99 NS NS NS NS

07-17-00 NS NS NS NS

07-19-01 NS NS NS NS

CWP 8 (SP) 06-30-99 <14 NR 13 78

07-17-00 <14 NR 15 134

07-26-01 <10 NR 11 48

PW 7 (DP) 04-22-99 NS NS NS NS

10-19-99 NS NS NS NS

04-06-00 NS NS NS NS

10-02-00 NS NS NS NS

04-18-01 NS NS NS NS

PW 8 (DP) 01-21-99 E12 NR 20 200

04-06-99 <14 NR 11 NR

07-15-99 <14 NR 18 203

10-19-99 E12 17 19 206

01-26-00 E13 NR 21 220

04-05-00 E11 NR 22 NR

07-20-00 <14 NR 22 270

10-04-00 E7 19 24 293

01-23-01 14 NR 22 283

04-03-01 E7 NR 20 NR

07-26-01 E7 NR 15 129

10-09-01 E6 15 20 179

22 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Well No. Date sampled

Chromium,

dissolved

(μg/L)

Sodium,

dissolved

(mg/L)

Chloride, 

dissolved

(mg/L)

Sulfate, 

dissolved

(mg/L)

PW 9 (DP) 01-20-99 90 NR 27 107

04-06-99 80 NR 10 NR

07-14-99 57 NR 26 110

10-06-99 57 20 27 110

01-26-00 52 NR 28 108

04-05-00 48 NR 26 NR

07-06-00 45 NR 27 110

10-04-00 43 21 29 110

01-23-01 53 NR 30 104

04-03-01 47 NR 32 NR

07-26-01 47 NR 31 105

10-09-01 35 20 33 107

TRA A 13 (SP) 04-26-99 <14 NR 41 NR

10-06-99 <14 23 48 222

04-13-00 <14 NR 53 NR

09-27-00 NS NS NS NS

04-18-01 <10 NR 27 NR

TRA A 77 (SP) 05-26-99 NSA NSA NSA NSA

07-21-99 NS NS NS NS

10-19-99 NS NS NS NS

10-18-00 NS NS NS NS

04-16-01 NS NS NS NS

11-10-01 NS NS NS NS

USGS 53 (DP) 04-21-99 NS NS NS NS

10-09-99 NS NS NS NS

04-06-00 NS NS NS NS

10-02-00 NS NS NS NS

04-18-01 NS NS NS NS

10-04-01 NS NS NS NS

USGS 54 (DP) 01-20-99 E9 NR 18 170

04-21-99 <14 NR 41 NR

07-14-99 E8 NR 21 252

10-06-99 E7 16 16 125

01-26-00 E11 NR 24 276

04-11-00 E9 NR 16 NR

07-06-00 E11 NR 24 297

10-04-00 E6 21 25 321

01-18-01 E9 NR 23 308

04-12-01 E5 NR 17 NR

07-30-01 E5 NR 13 107

10-23-01 14 18 25 285

USGS 55 (DP) 04-21-99 44 NR 19 NR

10-26-99 72 19 20 125

04-13-00 63 NR 21 NR

10-05-00 NS NS NS NS

04-19-01 33 NR 17 NR

10-23-01 82 18 27 149

Table 3. Concentrations of selected dissolved ions in perched ground water from selected wells, Reactor Technology Complex, 

Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figures 3, 8, and 9. Analyses completed by the National Water Quality Laboratory. Abbreviations: DP, well 

completed in deep perched water; SP, well completed in shallow perched water; QA-3, quality assurance replicate sample, number indicates the replicate 

sequence number during a sampling event; μg/L, microgram per liter; mg/L, milligram per liter; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSA, not sampled because of well access problems; NSEQ, not sampled because of equipment 

problems; E, estimated; USGS, U.S. Geological Survey. Symbol: <, less than respective reporting level]

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 23
Well No. Date sampled

Chromium,

dissolved

(μg/L)

Sodium,

dissolved

(mg/L)

Chloride, 

dissolved

(mg/L)

Sulfate, 

dissolved

(mg/L)

USGS 56 (DP) 04-26-99 NS NS NS NS

10-19-99 NS NS NS NS

10-18-00 NS NS NS NS

04-16-01 NS NS NS NS

10-10-01 NS NS NS NS

USGS 60 (DP) 04-06-99 <14 NR 10 NR

10-19-99 E9 14 16 146

04-05-00 E12 NR 21 NR

10-04-00 E7 19 23 282

10-04-00 QA-2 <10 18 24 282

04-03-01 E6 NR 16 NR

10-09-01 E6 13 17 124

USGS 61 (DP) 04-13-99 <14 NR 20 NR

04-13-99 QA-1 E10 NR 20 NR

10-06-99 25 13 19 178

04-06-00 <14 NR 19 NR

09-27-00 10 14 18 181

04-12-01 16 NR 21 NR

10-04-01 10 14 20 182

USGS 62 (DP) 04-13-99 <14 NR 20 NR

10-06-99 E13 17 21 231

04-03-00 <14 NR 21 NR

09-27-00 E9 18 22 262

09-27-00 QA-1 E8 18 22 260

04-17-01 E7 NR 20 NR

10-09-01 <10 16 20 189

USGS 63 (DP) 04-13-99 <14 NR 19 NR

10-25-99 18 17 21 220

04-06-00 19 NR 22 NR

10-04-00 35 19 23 244

04-19-01 11 NR 20 NR

10-15-01 E9 16 20 196

USGS 66 (DP) 07-08-99 <14 16 21 217

07-25-00 <14 15 18 197

07-25-00 QA-8 <14 15 18 189

07-25-01 <10 16 21 224

Table 3. Concentrations of selected dissolved ions in perched ground water from selected wells, Reactor Technology Complex, 

Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figures 3, 8, and 9. Analyses completed by the National Water Quality Laboratory. Abbreviations: DP, well 

completed in deep perched water; SP, well completed in shallow perched water; QA-3, quality assurance replicate sample, number indicates the replicate 

sequence number during a sampling event; μg/L, microgram per liter; mg/L, milligram per liter; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSA, not sampled because of well access problems; NSEQ, not sampled because of equipment 

problems; E, estimated; USGS, U.S. Geological Survey. Symbol: <, less than respective reporting level]

24  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Well No. Date sampled

Chromium,

dissolved

(μg/L)

Sodium,

dissolved

(mg/L)

Chloride, 

dissolved

(mg/L)

Sulfate, 

dissolved

(mg/L)

USGS 68 (DP) 05-26-99 NSA NSA NSA NSA

07-21-99 E8 NR 21 NR

10-19-99 19 623 22 2,184

10-18-00 42 504 22 1,835

04-16-01 45 NR 23 NR

10-10-01 55 413 23 1,409

USGS 69 (DP) 07-13-99 <14 12 19 145

07-12-00 <14 12 17 135

07-31-01 E6 11 16 115

USGS 70 (DP) 04-13-99 <14 NR 17 NR

10-26-99 15 16 17 150

04-06-00 26 NR 21 NR

10-04-00 32 18 19 196

04-19-01 12 NR 17 NR

10-15-01 15 15 19 165

USGS 71 (DP) 04-27-99 20 NR 19 NR

10-21-99 47 12 19 169

04-13-00 NS NS NS NS

10-03-00 32 12 19 173

04-17-01 NS NS NS NS

10-10-01 27 12 21 176

USGS 72 (DP) 07-21-99 NSEQ NSEQ NSEQ NSEQ

10-19-99 <14 25 13 32

08-03-00 NSEQ NSEQ NSEQ NSEQ

07-19-01 NSEQ NSEQ NSEQ NSEQ

USGS 73 (DP) 04-15-99 37 NR 14 NR

10-21-99 37 18 39 62

04-13-00 33 NR 70 NR

09-27-00 28 17 46 55

04-02-01 21 NR 91 NR

10-10-01 <10 14 30 47

USGS 74 (DP) 04-22-99 NS NS NS NS

10-19-99 NS NS NS NS

04-10-00 NS NS NS NS

10-02-00 NS NS NS NS

04-18-01 NS NS NS NS

USGS 78 (DP) 07-08-99 <14 7 5 19

07-25-00 <14 7 5 20

07-25-01 <10 7 5 19

Table 3. Concentrations of selected dissolved ions in perched ground water from selected wells, Reactor Technology Complex, 

Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figures 3, 8, and 9. Analyses completed by the National Water Quality Laboratory. Abbreviations: DP, well 

completed in deep perched water; SP, well completed in shallow perched water; QA-3, quality assurance replicate sample, number indicates the replicate 

sequence number during a sampling event; μg/L, microgram per liter; mg/L, milligram per liter; NR, analysis not requested; NS, not sampled due to lack 

of water or because water level was below pump intake; NSA, not sampled because of well access problems; NSEQ, not sampled because of equipment 

problems; E, estimated; USGS, U.S. Geological Survey. Symbol: <, less than respective reporting level]

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 25
Figure 8. Concentrations of dissolved chromium in water from wells completed in deep perched ground water, Reactor 

Technology Complex, Idaho National Laboratory, Idaho, July–October 2001.

E9

E6

27

14

E6

E6

10

<10

<10

NSEQ

55

35

<10

Dry

82

WBP

15

WBP

NSEQ

PW 7

(Sampling

discontinued

October 2001)

USGS 63

USGS 69

USGS 71

USGS 54

PW 8

USGS 60

USGS 61

USGS 62

USGS 66

Cold-waste ponds

USGS 72

USGS 68

USGS 74

(Sampling

discontinued

October 2001)

USGS 73

PW 9

USGS 53

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

USGS 55

USGS 56

Retention

basin Radioactive-waste ponds

USGS 70

REACTOR TECHNOLOGY COMPLEX

Extent of deep perched ground water zone—

October 2001. Approximately located

Water level below pump, could not sample

Not sampled, equipment problems

Well completed in deep perched ground water—Entry,

PW 8, is local well identifier; E6, is dissolved chromium 

concentration in micrograms per liter; E, indicates the 

concentration was estimated; <, indicates the concentration 

was less than the minimum reporting level. Values represent 

most recent data collected during July–October 2001

Lincoln Boulevard

E6

PW 8

Monroe Boulevard

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

EXPLANATION

0

0

2,000 FEET

500 METERS

The LRL for dissolved chromium varied from 14 μg/L 

in October 1998 to 0.8 μg/L in October 2001; consequently, 

concentrations within that range were designated according to 

those LRLs as detections or nondetections during 1999–2001. 

Estimated concentrations (table 3) 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).

Dissolved chromium was detected in water from 10 wells 

(PW 8, 9, USGS 54, 55, 61, 63, 68, 70, 71, and 73) completed 

in deep perched ground water at the RTC during 1999–2001 

(table 3). During 1996–98, the maximum concentration of 

dissolved chromium was 200 μg/L in well USGS 56 in April 

1996; this well was not sampled during 1999–2001 because 

the water level was below the pump intake. During 1999–

2001, the maximum concentration of dissolved chromium 

in deep perched ground water was 90 μg/L in well PW 9 in 

January 1999. This concentration decreased to 35 μg/L by 

October 2001. During July–October 2001, the most recent 

concentrations of dissolved chromium in wells completed 

in deep perched ground water near the RTC ranged from 10 

μg/L in well USGS 61 to 82 μg/L in well USGS 55 (table 3

and fig. 8). The largest concentrations were in water from 

26  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
wells north and west of the radioactive-waste infiltration 

ponds (PW 9 and USGS 55, 68). The presence of dissolved 

chromium in water from wells completed in perched water 

indicates that water from these wells contains chromium and 

other constituents that were discharged to the radioactivewaste infiltration ponds before 1965, when disposal practices 

changed to injection of cooling-tower blowdown water to the 

disposal well.

Sodium

During 1962–70, wastewater containing about 500 

tons/yr of sodium hydroxide and 50 tons/yr of sodium chloride 

were discharged to the chemical-waste pond (Robertson and 

others, 1974). Average annual sodium disposal was 188,000 lb 

during 1971–73 (Barraclough and Jensen (1976); 117,600 lb 

during 1974–78 (Barraclough and others, 1981); 101,000 lbs 

during 1979–81 (Lewis and Jensen, 1985); 85,000 lb during 

1982–85 (Pittman and others, 1988); 183,000 lbs during 

1986–88 (Cecil and others, 1991); 171,000 lb during 1989–91 

(Tucker and Orr, 1998); and 168,000 lbs during 1992–95 

(Bartholomay, 1998). An estimated 173,000 lb of sodium 

was contained in wastewater discharged to the chemicalwaste pond during 1996–98. Average dissolved sodium 

concentration in wastewater discharged to the chemical-waste 

pond was about 2,000 mg/L (Bartholomay and Tucker, 2000). 

Total sodium discharged at the RTC is the amount of sodium 

ion estimated from the discharged sodium hydrate solution 

(Bartholomay and Tucker, 2000). The total amount of sodium 

in wastewater discharged at the RTC from 1999 to 2001 has 

not been compiled.

During 1999–2001, only one analysis was made for 

dissolved sodium concentrations (23 mg/L) in shallow 

perched ground water from well TRA A 13. Concentrations of 

dissolved sodium in other wells completed in shallow perched 

ground water were not available because (1) wells were dry 

during 1999–2001, (2) wells could not be sampled because 

of access problems, or (3) analyses for dissolved sodium 

were not requested from the laboratory (table 3). Dissolved 

sodium concentrations in water from 16 wells completed in 

deep perched ground water also were determined. During 

July–October 2001, dissolved sodium concentrations ranged 

from 7 to 20 mg/L in all wells except well USGS 68, with 

a concentration of 413 mg/L (table 3), a decrease from 

December 1998 when the concentration was 662 mg/L 

(Bartholomay and Tucker, 2000, table 3). The decreased 

concentration of dissolved sodium in water from well USGS 

68 may be attributed to the closure of the chemical-waste pond 

in 1999.

Chloride

Robertson and others (1974, pg. 92) estimated that 

chloride (in the form of sodium chloride) was discharged to 

the chemical-waste pond at a rate of about 50 tons/yr during 

1962–70. Negligible chloride concentrations were discharged 

in wastewater during 1974–78 (Barraclough and Jensen, 

1976). Average annual disposal of chloride to the chemicalwaste pond was 1,540 lb during 1979–81 and 2,000 lb during 

1982–85 (Pittman and others, 1988). About 1,975 lb/yr of 

chloride were discharged to the chemical- and sanitary-waste 

ponds during 1986–88 (Cecil and others, 1991). About 1,215 

lb/yr of chloride were discharged to the chemical-waste pond 

during 1989–91; discharge of chloride to the sanitary-waste 

pond was curtailed after 1989 (Tucker and Orr, 1998). About 

4,430 lb of chloride contained in wastewater was discharged 

to the cold-waste ponds during 1992–95 (Bartholomay, 1998). 

During 1996–98, about 3,600 lb of chloride was in wastewater 

discharged to the cold-waste ponds. Data are not available for 

chloride in wastewater discharged during 1999–2001.

During 1999–2001, dissolved chloride concentrations in 

shallow perched ground water ranged from 10 mg/L in wells 

CWP 1, 3, and 4 to 53 mg/L in well TRA A 13. Dissolved 

chloride concentrations in deep perched ground water ranged 

from 5 mg/L in well USGS 78 to 91 mg/L in well USGS 73 

(table 3).

Sulfate

Compiled data are not available for sulfate in wastewater 

discharged during 1999–2001. During 1996–98, about 833,000 

lb of sulfate was in wastewater discharged to the chemicaland cold-waste ponds at RTC, an average of 278,000 lb/yr 

(Bartholomay and Tucker, 2000). This represents a decrease 

from the sulfate discharge of 920,000 lb/yr during 1989–1991 

(Tucker and Orr, 1998) and 595,500 lb/yr discharged during 

1992–95 (Bartholomay, 1998).

The maximum dissolved sulfate concentration in shallow 

perched ground water was 419 mg/L in well CWP 1 in July 

2000. This concentration is attributed to sulfate disposal to 

nearby cold-waste ponds. The dissolved sulfate concentration 

in well CWP 1 decreased to 31 mg/L by July 2001. The most 

recent detected concentrations of dissolved sulfate in water 

from wells USGS 54, 60, 63, 69, and PW 8, completed in 

deep perched ground water near the cold-waste ponds, ranged 

from 115 to 285 mg/L during July–October 2001 (fig. 9). 

These large concentrations indicate that water in the wells 

also was affected by discharge into the cold-waste ponds. 

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 27
ID19-0022_fig09

196

115

176

285

179

124

182

189

224

NSEQ

1,409

107

47

Dry

149

WBP

165

WBP

NSEQ

PW 7

(Sampling

discontinued

October 2001)

USGS 63

USGS 69

USGS 71

USGS 54

PW 8

USGS 60

USGS 61

USGS 62

USGS 66

Cold-waste ponds

USGS 72

USGS 68

USGS 74

(Sampling

discontinued

October 2001)

USGS 73

PW 9

USGS 53

Chemical-waste pond

Sanitary-waste pond

Evaporation ponds

USGS 55

USGS 56

Retention

basin Radioactive-waste ponds

USGS 70

REACTOR TECHNOLOGY COMPLEX

Extent of deep perched ground water zone—

October 2001. Approximately located

Water level below pump, could not sample

Not sampled, equipment problems

Well completed in deep perched ground water—Entry,

PW 8, is local well identifier; 179, is dissolved sulfate

concentration in milligrams per liter. Values represent most 

recent data collected during July–October 2001

Lincoln Boulevard

179

PW 8

Monroe Boulevard

43°34’30’’

43°35’

43°35’30’’

112°58’ 112°57’

EXPLANATION

0

0

2,000 FEET

500 METERS

Figure 9. Concentrations of dissolved sulfate in water from wells completed in deep perched ground water, Reactor 

Technology Complex, Idaho National Laboratory, Idaho, July–October 2001.

Monitoring data for dissolved sulfate concentrations in 

wastewater discharged to the cold-waste pond for 1999–2001 

are summarized in Stoller Corp. (2002a, 2002b, 2002c).

During July–October 2001, the maximum concentration 

of dissolved sulfate in deep perched ground water was 1,409 

mg/L in well USGS 68 (table 3), west of the chemicalwaste pond (fig. 9). This dissolved sulfate concentration had 

decreased from 2,278 mg/L in December 1998 (Bartholomay 

and Tucker, 2000, table 3), which in part may be the result of 

the chemical-waste pond closure in 1999 (fig. 9) or a decrease 

in disposal rates.

Idaho Nuclear Technology and Engineering 

Center

Two wastewater-infiltration ponds were constructed south 

of the INTEC in 1984 and 1985 to replace the INTEC disposal 

well (fig. 3). Wastewater infiltrating from these ponds formed 

perched ground water in the basalt and sedimentary interbeds 

above the eastern Snake River Plain aquifer. The volumes of 

wastewater discharged to the well and infiltration ponds during 

1962–2001 are shown in figure 10.

28  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
ID19-0022_fig10

No Data

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0

20

40

60

80

100

0

100

200

300

400

500

600

700

ANNUAL DISCHARGE OF TRITIUM, IN CURIES PERCENT COMBINED ANNUAL DISCHARGE, IN MILLIONS OF GALLONS

19651970197519801985199019952000

No Data

No Data

Average discharge, 442 million

gallons per year, 1962-98

Routine use of the disposal well

was discontinued in 1984

No Data

0 0 0 0 0 0 0

0 0.5 2.2 0.2 0 0 0.1 0 0 0 0 0.03

Routine use of the disposal well

was discontinued in 1984

Volume of wastewater discharged to the disposal well and infiltration ponds 

at the Idaho Nuclear Technology and Engineering Center, 1962-2001

Tritium as a percentage of total radioactive constituents in wastewater discharged 

at the Idaho Nuclear Technology and Engineering Center, 1962-2001

Annual discharge of tritium to the disposal well and infiltration ponds 

at the Idaho Nuclear Technology and Engineering Center, 1962-2001

Figure 10. Amount of tritium discharged, tritium as a percentage of total radioactive constituents in wastewater discharged, 

and volume of wastewater discharged to the disposal well and infiltration ponds at the Idaho Nuclear Technology and 

Engineering Center, Idaho National Laboratory, Idaho, 1962–2001.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water 29
Annual discharge to the disposal well and ponds ranged 

from 260 Mgal in 1963 to 665 Mgal in 1993 and averaged 

about 442 Mgal (Bartholomay and Tucker, 2000). The 

average annual discharge during 1996–98 to the ponds was 

about 570 Mgal. Discharge to the ponds during 2001 was 

about 544 Mgal (Stoller Corp., 2002c, p 5–9); data for 1999 

and 2000 are not available. This report focuses on perched 

water derived from the INTEC infiltration ponds, however, 

perched ground water also has been identified in other areas 

beneath the INTEC and may be attributed to other infiltration 

ponds, leaking wastewater lines, leach fields, ruptured casing 

in the upper part of the INTEC disposal well, and 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 infiltration ponds. Two holes (SWP 8 and 13 [fig. 

3]) subsequently were used as monitoring wells to sample 

and measure water levels in shallow perched ground water in 

surficial sediment at the ponds. Attempts were made to sample 

wells SWP 8 and 13 annually during 1999–2001, however in 

some years, the wells were dry. 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 

infiltration ponds (fig. 3). Well USGS 50 was used to monitor 

deep perched ground water near the INTEC disposal well. All 

these wells were sampled quarterly or semiannually during 

1999–2001 (table 1). The following sections summarize 

concentrations of selected constituents in water from these 

wells and auger holes used to monitor water-quality changes 

related to infiltration of water from the INTEC infiltration 

ponds.

Tritium

Overall, most radioactivity in wastewater discharged to 

the infiltration ponds at the INTEC has been from tritium. 

About 960 Ci of tritium in wastewater was discharged to the 

INTEC infiltration ponds during 1984–88. During 1986–88, 

the average rate of tritium disposal was 185 Ci/yr (Cecil 

and others, 1991). During 1989–91, 2.7 Ci of tritium was 

discharged to the ponds and during 1992–95, 0.3 Ci was 

discharged (Bartholomay, 1998). There was no discharge 

during 1996–99; however, during 2000, 0.03 Ci of tritium was 

discharged (Stoller Corp., 2002a, 2002b) (fig. 10). Data are 

not available for the total tritium discharged in 2001.

Well SWP 13 (fig. 3), completed in shallow perched 

ground water, was not sampled in 1999 and 2000 because 

the well was dry. In 2001, the tritium concentration in well 

SWP 13 was less than the reporting level (table 4). Well SWP 

8 (fig. 3) was dry during 1999. During 2000–01, the tritium 

concentrations in well SWP 8 were less than the reporting 

level. During 1999–2001, tritium concentrations in water 

from wells completed in deep perched ground water beneath 

the infiltration ponds ranged from less than the reporting 

level in wells PW 1 and PW 5 to 9.7±0.5 pCi/mL in well 

PW 6 (table 4), the same concentration as in October 1998. 

Tritium concentrations in water from well PW 6 varied during 

1999–2000 and remained similar to concentrations reported 

during 1996–98 (Bartholomay and Tucker, 2000). No water 

was in well PW 6 in from July 2000 through October 2001. 

Tritium concentrations in water from wells near the infiltration 

ponds had decreased significantly from concentrations during 

1986–88, when disposal of tritium was about 185 Ci/yr (Orr 

and Cecil, 1991). During 1999–2001, tritium concentrations 

in perched ground water in the wells closest to the ponds (PW 

1 through 5, and SWP 8) decreased or remained less than 1 

pCi/mL (table 4). These concentration decreases likely are 

due to decreased tritium disposal to the ponds and radioactive 

decay. During 1999–2001, tritium concentrations in water 

from well USGS 50 (fig. 11), near the disposal well, decreased 

slightly from 37.5±1.4 pCi/mL in April 1999 to 31.7±1.2 

pCi/mL in October 2001 (table 4; fig. 11). The large tritium 

concentrations in water from well USGS 50 may be due to 

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 slight decrease in tritium 

concentrations can be attributed mostly to radioactive decay 

or dilution of well water from a nonradioactive source such as 

landscape irrigation. Figure 11 shows concentrations of tritium 

in wells near the INTEC as of October 2001. Many wells were 

dry or were not sampled because of well access problems.

Strontium-90

About 0.3 Ci of strontium-90 was in wastewater 

discharged to the INTEC infiltration ponds during 1984–

95 and about 0.03 Ci was discharged during 1996–98 

(Bartholomay and Tucker, 2000). During 1999–2000, less 

than 0.001 Ci/yr of strontium-90 was discharged at the INTEC 

(Stoller Corp., 2002a, table 7-2, footnote b; 2002b, table 6-2, 

footnote b); data are not available for the amount of strontium90 discharged in 2001. Additional sources of strontium-90 in 

perched ground water at the INTEC include more than 33 Ci 

of strontium-90 reportedly discharged to a shallow pit (fig. 12) 

in 1962–63 (Robertson and others, 1974, p. 119).

30 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Table 4. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, 1999–2001.

[Well No.: Locations of wells are shown in figures 3, 11, and 12. Analyses completed by the 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 water; SP, well 

completed in shallow perched water. QA-4, quality assurance replicate sample, number indicates the replicate sequence number during a sampling 

event. NR, analysis not requested; NS, not sampled due to lack of water or because water level was below pump intake; NSA, not sampled because of 

well access problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter. Symbol: ±, plus or minus]

Well No. Date Tritium

 (pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

PW 1 (DP) 01-14-99 0.03±0.12 1.5±0.6 NR

04-06-99 0.1±0.12 3.4±0.8 43±20 

07-20-99 0.08±0.12 1.7±0.7 NR

10-05-99 -0.08±0.13 2.6±0.8 NR

01-18-00 0.09±0.11 0.6±0.8 NR

05-01-00 NSA NSA NSA

07-19-00 NS NS NS

10-02-00 NS NS NS

01-18-01 NS NS NS

04-18-01 0.18±0.14 2±0.8 20±30 

07-31-01 0.09±0.13 0.3±0.6 NR

10-11-01 NS NS NS

PW 2 (DP) 04-22-99 0.13±0.12 2±0.8 30±30 

04-22-99 QA-4 0.14±0.12 2±0.8 -31±20 

10-19-99 0.03±0.13 2.3±0.8 NR

04-24-00 0.36±0.14 2.9±0.8 0±40 

10-03-00 0.16±0.13 2±0.9 NR

04-18-01 0.3±0.15 1.1±0.8 -20±30 

10-02-01 0.5±0.14 -0.1±0.8 NR

PW 3 (DP) 04-22-99 0.2±0.12 3.3±0.8 -48±30 

10-19-99 NS NS NS

04-24-00 0.73±0.15 2.5±0.8 -30±20 

10-03-00 0.19±0.13 1.9±0.9 NR

04-18-01 0.24±0.14 2.1±0.7 20±30 

10-02-01 0.34±0.14 -0.8±0.7 NR

PW 4 (DP) 01-19-99 0.56±0.14 2.2±0 .6 NR

04-13-99 0.48±0.14 2.2±0.7 -11±40 

07-15-99 0.79±0.15 3.6±0.8 NR

10-06-99 0.48±0.15 3.4±0.8 NR

10-06-99 QA-1 0.46±0.15 3.8±0.8 NR

01-18-00 0.51±0.13 2.1±0.8 NR

05-01-00 NSA NSA NSA

07-25-00 NSA NSA NSA

10-05-00 -0.06±0.12 2.4±0.9 NR

01-18-01 -0.04±0.12 1±0.6 NR

04-12-01 0.05±0.13 0.79±0.79 20±30 

07-24-01 0.05±0.13 0.8±0.6 NR

10-31-01 NSA NSA NSA

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  31
Table 4. Concentrations of tritium, strontium-90, and cesium-137 in perched ground water from selected wells, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figures 3, 11, and 12. Analyses completed by the 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 water; SP, well 

completed in shallow perched water. QA-4, quality assurance replicate sample, number indicates the replicate sequence number during a sampling 

event. NR, analysis not requested; NS, not sampled due to lack of water or because water level was below pump intake; NSA, not sampled because of 

well access problems; pCi/mL, picocurie per milliliter; pCi/L, picocurie per liter. Symbol: ±, plus or minus]

Well No. Date Tritium

 (pCi/mL)

Strontium-90 

(pCi/L)

Cesium-137

(pCi/L)

PW 5 (DP) 04-08-99 0.11±0.12 1.2±0.7 34±20 

10-25-99 -0.05±0.13 2.3±0.8 NR

10-25-99 QA-4 0±0.1 2.1±0.8 NR

05-01-00 NSA NSA NSA

10-26-00 0.04±0.12 2.5±0.8 NR

04-30-01 0.04±0.13 2.5±0.7 -50±40 

10-31-01 NSA NSA NSA

PW 6 (DP) 01-14-99 9.7±0.5 -0.4±0.7 NR

04-21-99 9.5±0.5 -0.92±0.9 25±20 

07-15-99 9.1±0.4 -0.4±0.7 NR

10-11-99 9.4±0.5 -0.1±0.8 NR

01-18-00 9±0.4 1.6±0.9 NR

04-24-00 8.6±0.4 -2±0.9 0±30

07-24-00 NS NS NS

10-02-00 NS NS NS

01-18-01 NS NS NS

04-08-01 NS NS NS

07-25-01 NS NS NS

10-11-01 NS NS NS

SWP 8 (SP) 07-15-99 NS NS NS

07-24-00 0.04±0.12 5.5±0.8 0±30 

07-25-01 0.07±0.13 2.1±0.7 60±30 

SWP 13 (SP) 07-15-99 NS NS NS

07-24-00 NS NS NS

07-25-01 0±0.13 -1.8±0.9 -20±20

USGS 50 (DP) 04-27-99 37.5±1.4 186±5 -16±23

10-20-99 35.2±1.3 204±5 20±20

05-02-00 NSA NSA NSA

10-10-00 28±1.1 172±4 10±30 

04-10-01 31.4±0.7 150±3 -10±30 

10-24-01 31.7±1.2 134±3 20±30 

32 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
ID19-0022_fig11

Infiltration Ponds

Shallow pit

Big

Lost

River

Lincoln Boulevard

Monroe Boulevard

PW 3

0.34±0.14

PW 4

NSA

PW 6

Dry

DISPOSAL

WELL

PW 1

Dry

PW 5

NSA

USGS 50

31.7±1.2

PW 2

0.5±0.14

43°33’30’’

43°34’

43°34’30’’

112°56’00’’ 112°56’ 112°55’30’’ 112°55’

EXPLANATION

0

0

2,000 FEET

500 METERS

Not sampled, well access problems

Well completed in perched ground water— 

Entry, PW 2, is local well identifier; 0.5±0.14, is 

tritium concentration and associated 

uncertainty in picocuries per milliliter.

Concentration equal to or greater than the 3s

reporting level in bold. Values represent data 

collected in October 2001.

NSA

PW 2

0.5±0.14

IDAHO NUCLEAR TECHNOLOGY

AND ENGINEERING CENTER

Figure 11. Concentrations of tritium in water from wells completed in deep perched ground water, Idaho Nuclear Technology 

and Engineering Center, Idaho National Laboratory, Idaho, October 2001.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  33
ID19-0022_fig12

Infiltration Ponds

Shallow pit

Big

Lost

River

Lincoln Boulevard

Monroe Boulevard

PW 3

-0.8±0.7

PW 4

NSA

PW 6

Dry

DISPOSAL

WELL

PW 1

Dry

PW 5

NSA

USGS 50

134±3

PW 2

-0.1±0.8

43°33’30’’

43°34’

43°34’30’’

112°56’00’’ 112°56’ 112°55’30’’ 112°55’

EXPLANATION

0

0

2,000 FEET

500 METERS

Not sampled, well access problems

Well completed in perched ground water— 

Entry, PW 2, is local well identifier; -0.1±0.8, is 

strontium-90 concentration and associated 

uncertainty in picocuries per milliliter.

Concentration equal to or greater than the 3s

reporting level in bold. Values represent data 

collected in October 2001

NSA

PW 2

-0.1±0.8

IDAHO NUCLEAR TECHNOLOGY

AND ENGINEERING CENTER

Figure 12. Concentrations of strontium-90 in water from wells completed in deep perched ground water, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, October 2001.

34  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
A strontium-90 concentration of 2.1±0.7 pCi/L in 

July 2001 in water from well SWP 8 (fig. 3) completed in 

shallow perched ground water continued the steady decrease 

in strontium-90 concentrations in water from this well since 

1991. During 1999–2001, concentrations of strontium-90 

varied in water from all wells completed in deep perched 

ground water beneath the INTEC infiltration ponds. In 

October 2001, strontium-90 concentrations in deep perched 

ground water in wells closest to the ponds were less than the 

reporting level, not sampled because of access problems, or 

the wells were dry (fig. 12).

The largest concentrations of strontium-90 in perched 

ground water at the INTEC were in well USGS 50 near the 

INTEC disposal well. During 1999–2001, strontium-90 

concentrations in water from well USGS 50 were variable 

and ranged from 204±5 pCi/L in October 1999 to 134±3 

pCi/L in October 2001 (table 4), indicating an overall 

decrease in strontium-90 concentrations since the mid–1980s. 

Strontium-90 concentrations in water from well USGS 50 

may be due to leakage of wastewater from ruptures in the 

disposal well casing or leakage from wastewater pipelines at 

the INTEC.

Cesium-137

Wastewater discharged to the INTEC infiltration ponds 

during 1984–95 contained about 0.5 Ci of cesium-137. During 

1996, wastewater discharged to the ponds contained about 

0.0006 Ci of cesium-137; no cesium-137 was discharged 

during 1997–98. During 1999–2000, less than 0.001 Ci/yr of 

cesium-137 was discharged to the INTEC infiltration ponds 

(Stoller Corp., 2002a, table 7-2, footnote b; 2002b, table 6-2, 

footnote b). Data are not available for cesium-137 discharged 

during 2001.

During 1999–2001, concentrations of cesium-137 did 

not exceed the reporting level in shallow or deep perched 

ground water in wells closest to the infiltration ponds or in 

well USGS 50. The absence of reportable concentrations of 

cesium-137 in perched ground water at the INTEC probably is 

due to decreased disposal and to sorption and (or) exchange of 

cesium-137 to minerals in sediments.

Sodium

Robertson and others (1974, pg. 121) stated that the 

quantity of wastes disposed at the INTEC were not routinely 

monitored during 1952–70; however, the most abundant 

waste product discharged to the INTEC disposal well was 

sodium chloride. Barraclough and Jensen (1976) reported 

that 254,000 lb/yr of sodium were discharged to the INTEC 

disposal well during 1971–73. During 1974–78, about 

310,000 lb/yr of sodium were discharged to the disposal 

well (Barraclough and others, 1981); and 397,000 lb/yr were 

discharged during 1979–81 (Lewis and Jensen, 1984). About 

324,000 lb/yr of sodium were discharged at the INTEC 

during 1982–85; however, in 1984 the new INTEC infiltration 

ponds were put in use. About 72 percent of the sodium was 

discharged to the infiltration ponds and about 28 percent was 

discharged to the disposal well (Pittman and others, 1988). 

In 1985, nearly all sodium was discharged to the INTEC 

infiltration ponds (Pittman and others, 1988). During 1986–88, 

an estimated 22 million lb of sodium was discharged to the 

INTEC infiltration ponds (Cecil and others, 1991); during 

1989–91, no sodium discharge data were available, however 

chloride discharge records were used to estimate that about 

23 million lb of sodium may have been discharged to the 

INTEC infiltration ponds (Tucker and Orr, 1998); and during 

1992–95 about 3 million lb of sodium was discharged to the 

infiltration ponds (Bartholomay, 1998). About 708,000 lb of 

sodium was discharged to the INTEC infiltration ponds during 

1996–98 (Bartholomay and Tucker, 2000). No compilation 

was made of the total amount of sodium discharged to 

the INTEC infiltration ponds during 1999–2001. The 

concentration of sodium in wastewater decreased from an 

average of 127 mg/L in 1999 to 111 mg/L in 2001 (Stoller 

Corp., 2002a, table 7-3; 2002b, table 6-3; 2002c, table 5-6).

Water from well SWP 8, completed in shallow perched 

ground water, contained a maximum concentration of 133 

mg/L of dissolved sodium in July 2000. This concentration 

decreased to 102 mg/L in July 2001. Water from well SWP 13, 

also completed in shallow perched ground water, contained 

a dissolved sodium concentration of 92 mg/L in July 2001. 

This well was not sampled in 1999 or 2000 because the well 

was dry (table 5). During 1999–2001, dissolved sodium 

concentrations in deep perched ground water in wells closest 

to the infiltration ponds (PW 1 through 5) ranged from 109 

mg/L in well PW 2 in October 2001 to 164 mg/L in well PW 

5 in October 1999 (table 5). By October 2001, most wells 

could not be sampled due to lack of water in the well or well 

access problems. Dissolved sodium concentrations in shallow 

and deep perched ground water at the INTEC infiltration 

ponds during 1999–2001 were similar to or less than those in 

wastewater (Stoller Corp., 2002a, table 7-3; 2002b, table 6-3; 

2002c, table 5-6).

Dissolved sodium concentrations in two water samples 

from well USGS 50 were nearly constant during 1999–2000. 

The concentration in October 2000 was 60 mg/L (table 5), 

nearly the same as concentrations reported in Bartholomay 

and Tucker (2000, table 5) for 1996–98. Analysis for dissolved 

sodium in water from well USGS 50 was not requested in 

2001. These dissolved sodium concentrations may be due 

to leakage of wastewater from pipelines or infiltration of 

landscape irrigation at the INTEC.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  35
Table 5. Concentrations of selected dissolved ions in perched ground water from selected wells, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, 1999–2001.

[Well No.: Locations of wells are shown in figures 3 and 13. Analyses completed by the National Water Quality Laboratory. Analytical results 

in milligrams per liter. Abbreviations: DP, well completed in deep perched water; SP, well completed in shallow perched water. QA-4, quality 

assurance replicate sample, number indicates the replicate sequence number during a sampling event. NR, analysis not requested; NS, not 

sampled due to lack of water or because water level was below pump intake; NSA, not sampled because of well access problems]

Well No. Date Sodium, 

dissolved

Chloride, 

dissolved

Sulfate, 

dissolved 

Nitrite plus nitrate, 

as nitrogen,

dissolved 

PW 1 (DP) 01-14-99 NR 170 NR NR

04-06-99 NR 167 NR NR

07-20-99 NR 134 NR NR

10-05-99 132 196 27 NR

01-18-00 NR 152 NR NR

05-01-00 NSA NSA NSA NSA

07-19-00 NS NS NS NS

10-02-00 NS NS NS NS

01-18-01 NS NS NS NS

04-18-01 NR 151 NR NR

07-31-01 NR 148 NR NR

10-11-01 NS NS NS NS

PW 2 (DP) 04-22-99 NR 200 NR NR

04-22-99 QA-4 NR 198 NR NR

10-19-99 137 240 28 NR

04-24-00 NR 258 NR NR

10-03-00 130 212 25 NR

04-18-01 NR 148 NR NR

10-02-01 109 167 28 NR

PW 3 (DP) 04-22-99 NR 198 NR NR

10-19-99 NS NS NS NS

04-24-00 NR 258 NR NR

10-03-00 127 197 27 NR

04-18-01 NR 150 NR NR

10-02-01 NR 175 30 NR

PW 4 (DP) 01-19-99 NR 221 NR NR

04-13-99 NR 213 NR NR

07-15-99 NR 217 NR NR

10-06-99 152 316 29 NR

10-06-99 QA-1 152 308 29 NR

01-18-00 NR 210 NR NR

07-25-00 NSA NSA NSA NSA

10-05-00 124 188 25 NR

01-18-01 NR 79 NR NR

04-12-01 NR 152 NR NR

07-24-01 NR 155 NR NR

10-31-01 NSA NSA NSA NSA

PW 5 (DP) 04-08-99 NR 213 NR NR

10-25-99 163 348 27 NR

10-25-99 QA-4 164 344 27 NR

05-01-00 NSA NSA NSA NSA

10-26-00 137 227 25 NR

04-30-01 NR 149 NR NR

10-31-01 NSA NSA NSA NSA

36  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Table 5. Concentrations of selected dissolved ions in perched ground water from selected wells, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, 1999–2001.—Continued

[Well No.: Locations of wells are shown in figures 3 and 13. Analyses completed by the National Water Quality Laboratory. Analytical results 

in milligrams per liter. Abbreviations: DP, well completed in deep perched water; SP, well completed in shallow perched water. QA-4, quality 

assurance replicate sample, number indicates the replicate sequence number during a sampling event. NR, analysis not requested; NS, not 

sampled due to lack of water or because water level was below pump intake; NSA, not sampled because of well access problems]

Well No. Date Sodium, 

dissolved

Chloride, 

dissolved

Sulfate, 

dissolved 

Nitrite plus nitrate, 

as nitrogen,

dissolved 

PW 6 (DP) 01-14-99 NR 125 NR NR

04-21-99 NR 63 NR NR

07-15-99 NR 113 NR NR

10-11-99 108 151 18 NR

01-18-00 NR 99 NR NR

04-24-00 NR 37 NR NR

07-24-00 NS NS NS NS

10-02-00 NS NS NS NS

01-18-01 NS NS NS NS

04-08-01 NS NS NS NS

07-25-01 NS NS NS NS

10-11-01 NS NS NS NS

SWP 8 (SP) 07-15-99 NS NS NS NS

07-24-00 133 241 43 0.7

07-25-01 102 153 34 1.3

SWP 13 (SP) 07-15-99 NS NS NS NS

07-24-00 NS NS NS NS

07-25-01 92 157 30 .6

USGS 50 (DP) 04-27-99 NR 59 NR NR

10-20-99 63 57 39 58.4

05-02-00 NS NS NS NS

10-10-00 60 57 41 43.1

04-10-01 NR 55 NR NR

10-24-01 NR NR NR 4.7

Chloride

Robertson and others (1974, pg. 121) stated that the 

quantity of wastes disposed at the INTEC were not routinely 

monitored during 1952–1970, however, the most abundant 

waste product discharged to the INTEC disposal well was 

sodium chloride. Barraclough and Jensen (1976) reported 

that 386,000 lb/yr of chloride were discharged to the INTEC 

disposal well during 1971–73. During 1974–78, about 

548,000 lb/yr of chloride were discharged (Barraclough and 

others, 1981); about 875,000 lb/yr during 1979–81 (Lewis 

and Jensen, 1984); and about 735,000 lb/yr during 1982–85; 

however, in 1984, waste discharge ceased to the INTEC 

disposal well, and wastes were discharged to the INTEC 

infiltration ponds. About 35 million lb of chloride was 

discharged to the INTEC infiltration ponds during 1986–88 

(Cecil and others, 1991); 36 million lb was discharged during 

1989–91 (Tucker and Orr, 1998); 49 million lb was discharged 

during 1992–95 (Bartholomay, 1998); and 35 million lb 

was discharged during 1996–98 (Bartholomay and Tucker, 

2000). The total chloride discharged to the infiltration ponds 

at the INTEC was not compiled for 1999–2001; however, the 

concentration of dissolved chloride in wastewater decreased 

from an average of 193 mg/L in 1999 to 153 mg/L in 2001 

(Stoller Corp., 2002a, table 7-3; 2002b, table 6-3; 2002c, table 

5-6).

During 1999, well SWP 8 (fig. 3) was not sampled 

because the well was dry. The dissolved chloride concentration 

in well SWP 8 decreased from 241 mg/L in July 2000 to 153 

mg/L in July 2001. No samples were collected from well SWP 

13 during 1999–2000 because the well was dry; the dissolved 

chloride concentration in July 2001 was 157 mg/L. During 

1999–2001, dissolved chloride concentrations in deep perched 

ground water in wells closest to the infiltration ponds (PW 1 

through 5) ranged from 79 mg/L in well PW 4 to 348 mg/L 

in well PW 5 (table 5). In October 2001, wells PW 1 and 6 

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  37
Infiltration Ponds

Shallow pit

Big

Lost

River

Lincoln Boulevard

Monroe Boulevard

PW 3

175

PW 4

NSA

PW 6

Dry

DISPOSAL

WELL

PW 1

Dry

PW 5

NSA

USGS 50

NR

PW 2

167

43°33’30’’

43°34’

43°34’30’’

112°56’00’’ 112°56’ 112°55’30’’ 112°55’

EXPLANATION

0

0

2,000 FEET

500 METERS

Not sampled, well access problems

Well completed in perched ground water— 

Entry, PW 2, is local well identifier; 167, is 

dissolved chloride concentration in milligrams 

per liter. Values represent data collected in 

October 2001

NSA

PW 2

167

IDAHO NUCLEAR TECHNOLOGY

AND ENGINEERING CENTER

NR Analysis not requested

Figure 13. Concentrations of dissolved chloride in water from wells completed in deep perched ground water, Idaho Nuclear 

Technology and Engineering Center, Idaho National Laboratory, Idaho, October 2001.

were dry and wells PW 4 and 5 were not sampled because 

of well access problems. Dissolved chloride concentrations 

in water from wells PW 2 and 3 were 167 and 175 mg/L, 

respectively (table 5; fig. 13). When water was present, 

lower concentrations were measured in water from well PW 

6 than wells PW 1 through 5 (table 5). Dissolved chloride 

concentrations in shallow and deep perched ground water at 

the INTEC infiltration ponds were similar to or less than the 

dissolved chloride concentrations in wastewater (Stoller Corp., 

2002a, table 7-3; 2002b, table 6-3; 2002c, table 5-6).

During 1999–2001, dissolved chloride concentrations 

in water from well USGS 50 were consistent, ranging from 

59 mg/L in April 1999 to 55 mg/L in April 2001 (table 5). 

The dissolved chloride concentrations may be due to leakage 

of wastewater from ruptures in the disposal well casing or 

leakage from wastewater pipelines at the INTEC. Dissolved 

chloride concentrations in water from this well steadily 

decreased since sampling began in 1959.

38  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Sulfate

The quantity of wastes disposed at the INTEC was not 

routinely monitored during 1952–1970; however, high values 

of sulfate near the center of the INL may be associated with 

waste disposal (Robertson and others, 1974, p. 70, 121). The 

estimated average wastewater dissolved sulfate concentration 

was about 25 mg/L (Robertson and others, 1974, p. 124). 

About 73,000 lb/yr of sulfate were discharged to the INTEC 

disposal well during 1971–73 (Barraclough and Jensen, 1976), 

103,000 lb/yr during 1974–78, except during 1976 when 

no sulfate disposal was reported (Barraclough and others, 

1981), and 146,000 lb/yr during 1979–81. During 1982–85, 

575,000 lb/yr were discharged to the disposal well and INTEC 

infiltration ponds (Pittman and others, 1988). About 227,000 

lb/yr of sulfate were discharged to the infiltration ponds 

during 1986–88 (Cecil and others, 1991) and 575,000 lb/yr 

during 1989–91 (Tucker and Orr, 1998). During 1992–95, 

about 166,000 lb/yr of sulfate were discharged to the INTEC 

infiltration ponds (Bartholomay, 1998) and during 1996–98, 

about 146,000 lb/yr was discharged (Bartholomay and Tucker, 

2000). Total sulfate discharged to the infiltration ponds at the 

INTEC has not been compiled for 1999–2001. The average 

concentrations of dissolved sulfate in wastewater were about 

34 mg/L in 1999, 30 mg/L in 2000, and 34 mg/L in 2001 

(Stoller Corp., 2002a, table 7-3; 2002b, table 6-3; 2002c, table 

5-16).

Dissolved sulfate concentrations in shallow perched 

ground water from wells SWP 8 and 13 were 34 and 

30 mg/L, respectively, in July 2001 (table 5), which were 

similar to the average wastewater concentration. Dissolved 

sulfate concentrations in water from wells completed in the 

deep perched ground water closest to the INTEC infiltration 

ponds (PW 1 through 5) ranged from 28 to 30 mg/L in 2001 

(table 5). These concentrations also were consistent with 

the average concentration in the wastewater. Historically, 

dissolved sulfate concentrations in these wells have fluctuated 

between about 22 and 41 mg/L. The dissolved sulfate 

concentration in water from well PW 6 was 18 mg/L in 1999; 

this well was dry during 2000–01. Concentrations of dissolved 

sulfate in water from well PW 6 have historically fluctuated 

between 13 and 24 mg/L.

Concentrations of dissolved sulfate in samples from well 

USGS 50 (table 5) ranged from 39 to 41 mg/L during 1999–

2001. Historically, dissolved sulfate concentrations in water 

from well USGS 50 have fluctuated slightly around these 

values. The dissolved sulfate concentrations in water from this 

well are attributed to leakage from wastewater pipelines at the 

INTEC.

Nitrate

Robertson and others (1974, p. 121) reported that 

insignificant amounts of nitrate probably were discharged 

to the INTEC disposal well during 1952–70. In 1973, about 

101,000 lb of nitrate was discharged (Barraclough and Jensen, 

1976. During 1974–78, about 131,000 lb/yr was discharged to 

the disposal well (Barraclough and others, 1981) and 288,000 

lb/yr during 1979–81 (Lewis and Jensen, 1984). During 

1982–85, 274,000 lb/yr were discharged at the INTEC and 

after February 1984, most wastewater was disposed to the new 

INTEC infiltration ponds (Pittman and others, 1988). During 

1986-88, 160,400 lb/yr of nitrate were discharged to the 

infiltration ponds (Cecil and others, 1991); 56,000 lb/yr during 

1989–91; and 41,000 lb/yr during 1992–95 (Bartholomay and 

others, 1997). Wastewater discharged to the INTEC infiltration 

ponds during 1996–98 contained about 260,000 lb of nitrate; 

of that amount, about 221,000 lb was discharged in February 

1996. Annual discharge amounts of nitrate for 1999–2001 

have not been compiled. The concentration of nitrate (as 

nitrogen) in wastewater was nearly constant with an average of 

0.92 mg/L in 1999 to 0.91 mg/L in 2001 (Stoller Corp., 2002a, 

2002b, 2002c).

Dissolved nitrite plus nitrate (as nitrogen) analyses 

are done annually on water from shallow perched ground 

water wells at the infiltration ponds and on water from well 

USGS 50. Nitrite analyses indicated that almost all dissolved 

nitrite plus nitrate concentration is from nitrate. Well SWP 8, 

completed in shallow perched ground water, was not sampled 

in 1999 because the well was dry. The dissolved nitrite plus 

nitrate (as nitrogen) concentration in water from SWP 8 was 

0.7 mg/L in July 2000 and 1.3 mg/L in July 2001. Well SWP 

13 was not sampled in 1999 or 2000 because the well was dry; 

the dissolved nitrite plus nitrate (as nitrogen) concentration in 

July 2001 was 0.6 mg/L. During 1999–2001, dissolved nitrite 

plus nitrate (as nitrogen) concentrations in water from well 

USGS 50 ranged from 58.4 mg/L in October 1999 to 4.7 mg/L 

in October 2001 (table 5), a fluctuating but overall decreasing 

trend since sampling began in 1988. The nitrate concentrations 

may be due to leakage from wastewater pipelines at the 

INTEC.

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 (figs. 1, 3) since 1952. 

These include transuranic wastes, other radiochemical and 

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  39
Table 6. Concentrations of tritium, strontium-90, cesium-137, selected transuranic elements, and dissolved chloride in perched ground 

water from well USGS 92, Radioactive Waste Management Complex, Idaho National Laboratory, Idaho, 1999–2001.

[Well No.: Location of well is shown in figure 2. Analyses completed by the Radiological and Environmental Sciences Laboratory and the 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/mL, picocurie per milliliter; 

pCi/L, picocurie per liter; mg/L, milligram per liter. NR, analysis not requested; SL, sample lost prior to analysis; Insufficient sample, inadequate amount of 

sample collected for requested analysis; USGS, U.S. Geological Survey. Symbol: ±, plus or minus]

Well

No. Date Tritium(pCi/mL)

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 03-30-99 0.26±0.13 2.6±1 -15±20 0.005±0.005 0.005±0.005 0.03±0.02 81.2

10-21-99 0.33±0.15 1.4±0.9 -12±24 -0.015±0.011 -0.008±0 .013 0.02±0.02 79.7

04-17-00 0.3±0.1 0.2±0 .8 30±30 -0.007±0.007 -0.004±0 .006 -0.004±0.012 80.2

10-18-00 0.13±0.13 −0.8±1.1 0±40 Insufficient 

sample 

Insufficient 

sample

Insufficient 

sample

NR

04-17-01 0.42±0.15 0.6±0.7 0±30 −0.003±0.003 0.003±0.008 0.007±0.012 78.0

10-11-01 0.45±0 .14 NR −17±22 SL SL SL NR

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.

Perched ground water beneath the RWMC is in 

sedimentary interbeds in basalts and can be attributed 

primarily to local snowmelt and rain infiltration and recharge 

from the Big Lost River and the INL spreading areas.

Well USGS 92 (fig. 3) 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 water 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 sample for all requested analyses. 

Adequate samples for requested analyses were collected 

during October 1999 and in the spring of 1996–98. The 

sample collected in October 2000 yielded only enough water 

for tritium, strontium-90, and cesium-137 analyses; part of the 

October 2001 sample was lost prior to analysis (table 6).

During 1999–2001, radiochemical constituents in all 

water samples from well USGS 92 (table 6) were less than 

the reporting level with the exception of the April 2000 and 

October 2001 samples analyzed for tritium. The tritium 

concentration was at the reporting level at 0.3±.0.1 pCi/mL in 

April 2000, and near the reporting level at .45±.14 pCi/mL in 

October 2001 (table 6). Tritium concentrations in water from 

well USGS 92 have been variable through time.

Historically, the concentration of americium-241 

was above the reporting level in October 1992, and the 

concentration of plutonium-238 was above the reporting level 

in November 1994 (Bartholomay, 1998).

Dissolved chloride concentrations in water from four 

samples collected from well USGS 92 ranged from 78.0 

to 81.2 mg/L during 1999–2001 (table 6). These dissolved 

chloride concentrations are consistent with concentrations 

measured historically.

40 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Table 7. Concentrations of selected volatile organic compounds in perched ground water from well USGS 92, Radioactive Waste 

Management Complex, Idaho National Laboratory, Idaho, 1996–2001.

[Analyses completed by the National Water Quality Laboratory using an analytical method that conforms to U.S. Environmental Protection Agency method 

524.2. Analytical results in micrograms per liter. Names in parentheses are alternate compound names. Abbreviations: NWIS, National Water Information 

System; E, estimated. Symbol: <, less than respective reporting level]

Date

Compound name

Carbon 

tetrachloride 

(Tetrachloromethane)

1,2-Dichloroethane

Chloroform

(Trichloromethane)

Methylene 

chloride 

(Dichloromethane)

Tetrachloroethylene 

(Tetrachloroethene)

1,1,-dichloroethane

1,1-Dichloroethylene 

(1,1-Dichloroethene)

1,1,-Trichloroethane

NWIS Parameter Code

 32102 32103 32106 34423 34475 34496 34501 34506

02-29-1996 1,800 1.8 920 <0.2 180 15 2.2 170

04-08-1997 990 1.2 633 .2 110 8.8 1.4 97.9

03-31-1998 260 1 540 5.3 50 7.7 1 55

03-30-1999 13.6 .5 285 3.5 22.9 4.5 .41 28.7

04-17-2000 291 .7 325 E2.4 43 6 E1.1 47.2

04-17-2001 377 1 602 22.4 125 8.5 .93 109

Date

Compound name

1,1,2-Trichloro-ethane1,2-Dichloropropane

Trichloroethylene 

(Trichloroethene)

Cis-1,2-

dichloroethene

Freon-113

(CFC-113)

(1,1,2-Trichloro1,2,2-Trifluoroethane)Toluene Benzene Chloroethane

NWIS Parameter Code

 34511 34541 39180 77093 77652 34010 34030 34311

02-29-1996 0.6 6.7 1,400 0.8 3.6 <0.2 <0.2 <0.2

04-08-1997 .3 4 786 .4 2.4 .3 <.4 <.4

03-31-1998 <.7 3.2 360 .3 1.3 <.2 <.2 <.2

03-30-1999 <.4 1.9 179 .3 .8 <.4 2.1 <.4

04-17-2000 .2 2.7 280 .4 1.3 <.2 .9 <.2

04-17-2001 .3 3.2 798 .7 1 <.2 .3 .2

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, water samples contained concentrations 

of 18 VOCs (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. Most of the same VOCs detected during 1996–98 were 

detected during 1999–2001, except toluene was not detected 

and benzene and chloroethane were detected. Table 7 lists the 

concentrations of 15 VOCs detected in 1999–2001 as well 

as VOCs detected during 1996–98. Most VOCs fluctuated 

through time and show no distinct trend. The MRL for some 

VOCs was changed from 0.2 to 0.1 μg/L during 1998–2001, a 

change that could result in detections of smaller concentrations 

and (or) different VOCs than detected in previous years.

Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water  41
Summary

Shallow and deep perched ground water is present 

in basalt and sediments beneath several facilities at the 

Idaho National Laboratory (INL) resulting from low-level 

radioactive, chemical, and sanitary wastewater discharge to 

infiltration ponds since 1952. During 2001, about 293 million 

gallons (Mgal) was discharged to infiltration and lined 

evaporation ponds at the Reactor Technology Complex (RTC), 

and 544 Mgal was discharged to infiltration ponds at the Idaho 

Nuclear Technology and Engineering Center (INTEC).

During 1952–93, about 10,500 Curies (Ci) of tritium 

was in wastewater discharged to the RTC radioactive-waste 

infiltration ponds. Since 1993, tritium in wastewater has been 

discharged to two lined evaporation ponds, which replaced the 

radioactive-waste infiltration ponds. About 191 Ci of tritium 

was released in wastewater to the RTC lined evaporation 

ponds during 1999–2000. Data are not available for the total 

amount to tritium in wastewater discharged in 2001.

In 2001, tritium concentrations in water from seven 

wells completed in shallow perched ground water near the 

cold-waste pond at RTC were less than the reporting level. 

Two wells completed in shallow perched water could not 

be sampled in 2001 because of either a lack of water or 

an obstruction in the wells. During July–October 2001, 

tritium concentrations in water from eight wells completed 

in deep perched ground water at the RTC were greater than 

the reporting levels. Tritium concentrations ranged from 

0.49±0.14 to 39.4±1.4 picocuries per milliliter (pCi/mL). 

During July–October 2001, reportable concentrations of 

tritium in water from wells completed in deep perched ground 

water were less than the reported concentrations measured 

during July–December 1998.

Several factors likely affected the distribution of tritium 

in perched ground water in wells at the RTC. These factors 

include proximity of the well to the radioactive-waste 

infiltration ponds, depth of water below the ponds, variations 

in tritium disposal rates, radioactive decay, dilution from 

infiltration from the cold-waste ponds, and infiltration of Big 

Lost River water. The replacement of the radioactive-waste 

infiltration ponds by lined evaporation ponds in 1993 also 

contributed to decreased tritium concentrations in perched 

ground water.

Less than 0.001 Ci of strontium-90 was discharged at 

the RTC during 1999; during 2000, 0.21 Ci of strontium90/yttrium-90 was discharged at the RTC. Data are not 

available for the amount of strontium-90 discharged in 2001. 

Water from well TRA A 13 completed in shallow perched 

ground water, exceeded the reporting level during 1999–2001, 

concentrations ranged from 38±1.4 to 22.1±1.1 pCi/L 

(picocuries per liter). Well CWP 1, also completed in shallow 

perched ground water, exceeded the reporting level in June 

1999 with a concentration of 3.1±0.7 pCi/L; however, by 

October 2001, the concentration was less than the reporting 

level.

Concentrations of strontium-90 in water from five 

wells completed in deep perched ground water at the RTC 

exceeded reporting levels in October 2001; concentrations 

ranged from 2.8±0.7 to 83.8±2.1 pCi/L. The distribution of 

strontium-90 concentrations in water from these wells during 

1999-2001 is attributed to sorption and (or) exchange reactions 

between strontium-90 in solution and sediments beneath the 

radioactive-waste infiltration ponds.

No reportable concentrations of cesium-137 were 

detected in water from any wells completed in either shallow 

or deep perched ground water at the RTC during 1999–2001. 

The general absence of reportable concentrations of cesium137 in perched ground water at the RTC probably is due to 

decreased cesium disposal rates, use of lined evaporation 

ponds instead of the radioactive-waste infiltration ponds, and 

sorption and (or) exchange reactions with sediments.

Chromium-51 and cobalt-60 were not detected in any 

water samples collected during 1999–2001. Decreased 

disposal and relatively short half-lives probably account for 

their absence.

Wastewater from RTC cooling-tower operations 

containing an estimated 24,000 lb of non-radioactive 

chromium was discharged to the radioactive-waste infiltration 

ponds during 1952–64. During 1964–72, chromium was 

discharged to a disposal well; no discharges of chromium 

were reported after 1972. During 1999–2001, no dissolved 

chromium was detected in shallow perched ground water. 

Dissolved chromium was detected in water from 10 wells 

completed in deep perched ground water at the RTC. The 

maximum concentration of dissolved chromium in deep 

perched ground water was 90 micrograms per liter (μg/L) in 

January 1999. This concentration decreased to 35 μg/L by 

October 2001. During July–October 2001, concentrations of 

dissolved chromium in deep perched ground water near the 

RTC ranged from 10 to 82 μg/L. The largest concentrations 

were in water from wells north and west of the radioactivewaste infiltration ponds, and the presence of dissolved 

chromium indicates that water from these wells contained 

constituents that were discharged to the radioactive-waste 

infiltration ponds before 1965.

About 173,000 pounds of sodium was discharged to 

the RTC chemical-waste pond during 1996–98. The total 

amount of sodium in wastewater discharged at the RTC from 

1999–2001 has not been compiled. During 1999–2001, the 

maximum concentration of sodium in water from wells in 

shallow perched ground water was 23 milligrams per liter 

(mg/L). During July–October 2001, sodium concentrations 

42 Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
in water from wells completed in deep perched ground water 

generally ranged from 7 to 20 mg/L in all wells except well 

USGS 68, with a concentration of 413 mg/L, a decrease from 

December 1998 when the concentration was 662 mg/L.

About 3,600 pounds of chloride was in wastewater 

discharged to the cold-waste ponds during 1996-98. Data are 

not available for chloride in wastewater discharged during 

1999–2001. During 1999–2001, chloride concentrations in 

shallow perched ground water ranged from 10 to 53 mg/L. 

Chloride concentrations in deep perched ground water ranged 

from 5 to 91 mg/L.

Wastewater that contained about 833,000 pounds of 

sulfate was discharged to the chemical- and cold-waste ponds 

at RTC during 1996–98. Compiled data are not available 

for the amount of sulfate in wastewater discharged during 

1999–2001. During July–October 2001, concentrations of 

dissolved sulfate in water from wells completed in deep 

perched ground water ranged from 115 to 1,409 mg/L. The 

maximum concentration of dissolved sulfate in deep perched 

ground water was from water from well USGS 68, west of the 

chemical-waste pond.

Two infiltration ponds were constructed south of the 

INTEC in 1984 and 1985 to replace the INTEC disposal well. 

Wastewater from these ponds formed perched ground water 

in the basalt and sedimentary interbeds above the Snake River 

Plain aquifer. The discharge to the ponds during 2001 was 

about 544 Mgal; data for 1999 and 2000 are not available. 

Perched ground water has been identified in other areas 

beneath the INTEC and may be attributed to other infiltration 

ponds, leaking wastewater lines, leach fields, ruptured casing 

in the upper part of the INTEC disposal well, and landscape 

irrigation.

Tritium discharged to the ponds decreased over the years 

from 960 Ci during 1984–88 to 0.03 Ci in 2000. Data are 

not available for tritium discharged in 2001. In 2001, tritium 

concentrations in water from wells completed in shallow 

perched ground water were less than the reporting level. 

During 1999–2001, the tritium concentration in water from 

wells completed in deep perched ground water beneath the 

infiltration ponds ranged from less than the reporting level to 

9.7±0.5 pCi/mL. Tritium concentrations have decreased in 

shallow and deep perched ground water near the INTEC since 

1986–88.

During 1999–2000, less than 0.001 Curie per year 

(Ci/yr) of strontium-90 was discharged at the INTEC; data 

are not available for strontium-90 discharged in 2001. A 

concentration of 2.1±0.7 pCi/L was detected in July 2001 in 

one well completed in shallow perched ground water. During 

1999–2001, concentrations of strontium-90 were variable in 

water from all wells completed in the deep perched ground 

water beneath the INTEC infiltration ponds. In October 2001, 

strontium-90 concentrations in deep perched ground water 

in wells closest to the ponds were less than the reporting 

level, not sampled because of access problems, or the wells 

were dry. Overall, concentrations of strontium-90 have been 

decreasing in wells near the INTEC.

During 1999–2000, less than 0.001 Ci/yr of cesium-137 

was discharged to the INTEC infiltration ponds. Data are 

not available for cesium-137 discharged during 2001. 

Concentrations of cesium-137 did not exceed the reporting 

level in perched ground water. The absence of reportable 

cesium-137 concentrations in perched ground water at the 

INTEC probably is due to decreased disposal and to sorption 

and (or) exchange of cesium-137 to minerals in sediments.

Estimates of sodium discharged at the INTEC are not 

available for 1999–2001. Sodium concentrations in water 

from two wells completed in shallow perched ground water 

ranged from 92 to 102 mg/L in July 2001, which was similar 

to the average wastewater concentration. During 1999–2001, 

dissolved sodium concentrations in deep perched ground 

water in wells closest to the infiltration ponds ranged from 

109 mg/L in October 2001 to 164 mg/L in October 1999. By 

October 2001, most wells could not be sampled due to lack of 

water in the well or well access problems. Dissolved sodium 

concentrations in shallow and deep perched ground water at 

the INTEC infiltration ponds during 1999–2001 were similar 

to or less than those in wastewater.

Estimates of chloride discharged at the INTEC are not 

available for 1999–2001. In July 2001, dissolved chloride 

concentrations in two wells completed in shallow perched 

ground water ranged from 153 to 157 mg/L. During 

1999-2001, dissolved chloride concentrations in deep perched 

ground water in wells closest to the infiltration ponds ranged 

from 79 to 348 mg/L. In October 2001, some wells were dry, 

some were not sampled because of well access problems, and 

water in two wells contained dissolved chloride concentrations 

of 167 mg/L and 175 mg/L. Dissolved chloride concentrations 

in shallow and deep perched ground water at the INTEC 

infiltration ponds were similar to or less than the dissolved 

chloride concentrations in wastewater. During 1999–2001, 

dissolved chloride concentrations in water from well USGS 

50 were consistent, ranging from 59 mg/L in April 1999 to 

55 mg/L in April 2001. Dissolved chloride concentrations in 

water from this well steadily decreased since sampling began 

in 1959.

Estimates of sulfate discharged during 1999–2001 are not 

available. Dissolved sulfate concentrations in water from two 

wells completed in shallow perched ground water ranged from 

30 to 34 mg/L in July 2001. Dissolved sulfate concentrations 

in water from wells completed in the deep perched ground 

water closest to the INTEC infiltration ponds ranged from 

28 to 30 mg/L in 2001. Historically, dissolved sulfate 

Summary  43
concentrations in these wells have fluctuated between about 22 

and 41 mg/L. Concentrations of dissolved sulfate in samples 

from well USGS 50 ranged from 39 to 41 mg/L during 

1999-2001. Historically, dissolved sulfate concentrations in 

water from well USGS 50 have fluctuated slightly around 

these values. These concentrations are consistent with the 

average concentration of dissolved sulfate in wastewater.

Estimates of dissolved nitrite plus nitrate (as nitrogen) 

discharged during 1999–2001 are not available. In July 

2001, the concentration of dissolved nitrite plus nitrate (as 

nitrogen) in wells completed in shallow perched ground water 

ranged from 0.6 to 1.3 mg/L. Dissolved nitrite plus nitrate (as 

nitrogen) concentrations in deep perched ground water near 

the INTEC disposal well ranged from 58.4 mg/L in 1999 to 

4.7 mg/L in 2001.

Perched ground water beneath the Radioactive Waste 

Management Complex (RWMC) is in sedimentary interbeds 

in basalts and can be attributed primarily to infiltration of 

snowmelt and rainfall and to recharge from the Big Lost River 

and the INL spreading areas and, therefore, may contain waste 

constituents leached from liquid and solid radiochemical 

and organic chemical wastes buried at the RWMC. During 

1999–2001, radiochemical constituents in all water samples 

from well USGS 92 were less than the reporting level with 

the exception of two samples analyzed for tritium. The 

tritium concentration in water from well USGS 92 was at the 

reporting level at 0.3±.0.1 pCi/mL in April 2000 and near the 

reporting level at 0.45±14 pCi/mL in October 2001. Tritium 

concentrations in water from well USGS 92 have been variable 

through time.

Dissolved chloride concentrations in water from four 

samples collected from well USGS 92 at the RWMC ranged 

from 78.0 to 81.2 mg/L during 1999–2001. These dissolved 

chloride concentrations are consistent with concentrations 

measured historically.

During 1999–2001, samples from well USGS 92 

contained concentrations greater than the reporting levels 

of 15 volatile organic compounds (VOCs). Water from well 

USGS 92 was analyzed for the same VOCs as in previous 

years. Mostly the same VOCs detected during 1996–98 were 

detected during 1999–2001, except that toluene was not 

detected and benzene and chloroethane were detected. Most 

VOCs have fluctuated through time and showed no distinct 

trend.

Acknowledgments

The U.S. Department of Energy’s Radiological and 

Environmental Sciences Laboratory at the Idaho National 

Laboratory provided radiochemical analyses of water samples. 

Technical staff at the Radiological and Environmental 

Sciences Laboratory during 1999–2001 were supervised 

by R. Douglas Carlson, Director. The author is grateful for 

technical review of the manuscript by Brennon R. Orr, North 

Wind Environmental, Inc., and Mark Hardy, Water Quality 

Specialist, U.S. Geological Survey.

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48  Radiochemical and Chemical Constituents in Perched Ground Water, Idaho National Laboratory, Idaho, 1999–2001
Manuscript approved for publication, September 15, 2006

Prepared by the USGS Publishing Network, 

Publishing Service Center, Tacoma, Washington

Bill Gibbs 

Bob Crist

Debra Grillo

Sharon Wahlstrom

Bobbie Jo Richey

For more information concerning the research in this report, contact the 

Director, Idaho Water Science Center 

U.S. Geological Survey, 230 Collins Road

Boise, Idaho 83702

http://id.water.usgs.gov/
SIR 2006–5236 Davis

An Update of the Distribution of Selected Radiochemical and Chemical Constituents in Perched Ground Water, 

Idaho National Laboratory, Idaho, Emphasis 1999-2001