United States
Environmental Protection
Agency
Off ice of
Emergency and
Remedial Response
EPA/ROD/R10-93/056
December 1992
SEPA Superfund
Record of Decision:
US DOE Idaho National
Engineering Laboratory
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50272-101
REPORTDOCUMENTA~ON 11. REPORT NO.. 2 3. Recipient'. AccM8lon No.
PAGE EPA/ROD/R10-93/056
4. TItle snd Subtitle S. Report Date
SUPERFUND RECORD OF DECISION ' 12/07/92
USDOE Idaho National Engineering Laboratory (Operable 6.
Unit 12), ID
Fifth Remedial Action
7. AUlhor(.) I. Performing Org8nlzatlon Repe. No.
II. Performing Org8nlzatlon N81118 snd Add,.. 10 Project TuklWork Unit No.
r
11. ContI'llCt(C) or Gr8n1(0) No.
(e)
(0)
12. ~Ing Orpnlzatlon N81118 snd Add.... 13. Type of Report & Period Cov8l'8cl
U.S. Environmental Protection Agency
401 M Street, S.W. 800/800
Washington, D.C. 20460 14.
15. SI'PPlsments'Y Nell.
PB94-964610
16.. AbetI'8Ct (Umlt: 200 words)
The USDOE Idaho National Engineering Laboratory (Operable Unit 12), site part of the
890-square mile U.S. Department of Energy (USDOE) facility, located in Idaho Falls,
Idaho. The primary mission of the Idaho National Engineering Laboratory (INEL) is
nuclear reactor technology development and waste management. Land use in the area is
predominantly industrial, with some restricted agricultural and recreational uses. The
site is contained within the northeastern portion of the Eastern Snake River Plain
(ESRP) and overlies the Snake. River Plain Aquifer, which is a sole-source aquifer. The
site, also known as the Auxiliary Reactor Area (ARA), consists of four separate
facilities that were used for research reactor operations and support activities. -From
1970 to 1988, the Chemical Evaporation Pond, an unlined surface impoundment, was used
to dispose of laboratory wastewater consisting of nonradioactive acids and VOCs,
radioactively-contaminated acids, and other laboratory wastewater through a discharge
pipe. The pond is now typically dry except after precipitation events. All ARA
reactors have been removed, and each facility has undergone partial decontamination and
decommissioning. In 1987, studies conducted by DOE identified releases of radioactive
~r hazardous contaminants to the Chemical Evaporation Pond. In 1990, DOE conducted
(See Attached Page)
17. Document AnsIy8la s. D88crIplOI'8
Record of Decision - USDOE Idaho National Engineering Laboratory (Operable
Unit 12), ID
Fifth Remedial Action
Contaminated Medium: None
Key Contaminants: None
b. 1dentlll81'81Open
-------
EPA/ROD/R10-93/056
USDOE Idaho National Engineering Laboratory (Operable Unit 12), ID
Fifth Remedial Action
Abstract (Continued)
additional studies to define the extent of contamination at the site. These
investigations indicated that concentrations of metals in the sediment were at or below
background levels, and only a small number of samples indicated concentrations of VOCs and
gamma-emitting radionuclides above background levels. Previous 1992 RODs addressed
sediment at the Warm Waste Pond, ordnance and contaminat~d soil, contaminated ground water
at the Technical Support Facility, and contaminated sediment and sludge in the evaporation
pond, discharge pipe, and waste sump as OUs 5, 23, 2, and 22 respectively. This ROD
addresses the Chemical Evaporation Pond, as OU12. Other 1993 RODs address the Perched
Water System, the CFA Motor Pool Pond, and pit 9 of the Subsurface Disposal Area, as OUs
4, 9, and 18 respectively. Any impacts from past releases to the pond that may affect the
subsurface or ground water will be evaluated in a future investigation that will be
completed before the site-wide ROD is finalized; therefore, there are no contaminants of
concern affecting this site.
.
The selected remedial action for this site is no further action because results of the
risk assessment indicate that the sediment within the Chemical Evaporation Pond and under
the discha?ge ,pipe poses no unacceptable.risk to human health and the environment. There
are no present worth or O&Mcosts associated with this no action remedy.
PERFORMANCE STANDARDS OR GOALS:
Not applicable.
.
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,
.I -
December 1992
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IDo1IHO 0EPAAnIIM'
OF--1MIMD W8J'ME
DIVISION OF
ENVIRONMENTAL QUAlITY
kaho
National
Eng;"..rinll
uboratory
Record of Decision
Auxiliary Reactor Area-I Chemical Evaporation Pond
Operable Unit 5-10
Idaho National Engineering Laboratory
Idaho Falls, Idaho
The Auxiliary Reactor Area-I Facility in the foreground, with the Chemical Evaporation
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.
ii
.-.-.-- - --~--
-~_._._---_...- .-. .-..
.
.
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. . _... - -- - --. -.-. -- --_. ---_..- --. .----. - _._...~ ... .-_-~.
DECLARA nON OF THE RECORD OF DECISION
Site Name and Location
Auxiliary Reactor Area-I Chemical Evaporation Pond
Operable Unit 5-10
Waste Area Group 5
Idaho National Engineering Laboratory
Idaho Falls. Idaho
Statement of Basis and Purpose
TI1is decision document presents the remedial action selected for the Auxiliary Reactor Area-I (ARA-l) Chemical
Evaporation Pond. Idaho National Engineering Laboratory Operable Unit 5-10. TI1is alternative was selected in
accordance with the Comprehensive Environmental Response. Compensation. and Uability Act, as amended by
the Superfund Amendments and Reauthorization Act. and to the extent practicable. the National Oil and
Hazardous Substances Pollution Contingency Plan. This decision was based on the information in the site
Administrative Record. which is located in the INEL Technical Ubrary in Idaho Falls. Idaho.
The lead agency in this decision was the U.S. Department of Energy (DOE). The U.S. Environmental Protection
Agency (EPA) and the Idaho Department of Health and Welfare (IDHW) participated in scoping the site
investigations and evaluating the remedial investigation data. The IDHW concurs with the selected remedy.
Description of the Selected Remedy
The DOE has determined that no further remedial action is necessary at the ARA-I Chemical Evaporation Pond to
ensure protection of human health and the environment This decision is based on the results of the human health
and ecological risk assessments. which indicate that co.nditions at the ARA-I Chemical Evaporation Pond pose no
unacceptable risk to human health or the environment. The EP A approves of the DOE decision. and the IDHW
concurs.
Declaration
No remedial action is necessary at Operable Unit 5-10 to ensure protection of human health and the environment
A statutory 5-year review will not be required because hazardous substances do not remain onsite above health-
based levels. Subsurface conditions and the groundwater pathway need further evaluation; consequently.
additional investigations will be conducted in another Operable Unit within Waste Area Group 5.
. .
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Signature sheet for the foregoing Record of Decision for Operable Unit 5-10 at the Idaho National
Engineering Laboratory by the United States Departmem of Energy and approved by the U irited
States Environmental Protection Agency. with concurrence by the Idaho Department of Health and
Welfare. The operable unit consistS of the Auxiliary Reactor Area-! Chemical Evaporation Pond at
the Idaho National Engin~ring Laboratory.
".
q{? Ji.~
1/ / Jd/9 <..
Augustine A. Pitrolo
Manager.
U.S. Department of Energy Idaho Field Office
Date
. r.
.
.;
iv
-"----_.__..- .."~.- ---------.--... --~-_._-----
-------
.- " ~ ..~. --------~-- ..- --",,--"~._'.'-'-_¥- .-~'...~--
.- - -... .-.-. .... -. -
Signature sheet'for the foregoing Record of Decision for Operable Unit 5-10 at the Idaho National
Engineering LaboratOry by the United States Department of Energy and approved by the United
States Environmental Protection Agency. with concurrence by the Idaho Department of Health and
Welfare. The operable unit consistS of the Auxiliary ReaCtOr Area-I Chemical Evaporation Pond at
the Idaho National Engineering Laboratory.
~~
DEC
i 19~
Dana Rasmussen
Regional Administrator, Region 10
U.S. Environmental Protection Agency
Date
" .
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SignatUre sheet for the foregoing Record of Decision for Operable Unit 5-10 at the Idaho National
Engineering LaboratOry by the United States Department of Energy and approved by the United
Scates Environmental Protection Agency. with concurrence by the Idaho Department of Health and
Welfare. The operable unit consists of the Au."tiliary ReactOr Area-I ChemiC3l Evaporation Pond at
the Idaho National Engine--..ring Laboratory .
a/d/~-
~ Richard Donovan
DirectOr
Idaho Department of Health and Welfare
/ Z io ~z
I '
Date
. "
vi
-,.--.."---.---,.- ..---_. 0.'- --------------- -.. -,_.- ..-. .
. . - - - - -.-
-------
-- -- ----
- -- ----- - --- ... -- - -- ---. - n-- -
._- ..---...- -_.__.~---_.-~.~--..___h___.-._.. .__.
.- - U -. -. - -.-
TABLE OF CONTENTS
DECLARATION OF THE RECORD OF DECISION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii
DESCRIPTION OF THE SELECTED REMEDY .................................................iii
DECLARATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . iii
,
DECISION SUMMARY
. 1. SITE NAME. LOCATION. AND DESCRIPTION.. .......................................... ..1
2. SITE HISTORY AND ENFORCEMENT ACTIVITIES ..........................................4
3. HIGHLIGHTS OF COMMUNITY PARTICIPATION.......................................... 5
4. SCOPE AND ROLE OF OPERABLE UNIT AND RESPONSE ACTION... ........... .............6
5. SITE C.HARACTERISTICS [[[ ........... 7
6. SUMMARY OF SITE RISKS. . . . . . . . . . . ... . . . . .' '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. DECISION[[[ 12
8. EXPLANATION OF SIGNIFICANT CHANGES. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .12
Appendix A - Responsiveness Summary. [[[ .A-l
Appendix B - Public Comment/Response List. . . .. .. . . . . . . . . . . .. . . . .. . . . . . .. . .. . . .... .. . . . .. .. . . B-1
Appendix C - Administrative Record Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-l
FIGURES
Figure 1.
Figure 2.
Figure 3.
Location of the Auxiliary Reactor Area (ARA) ..........................................1
Map of the ARA-I facility and the ARA-I O1emical Evaporation Pond. . . . . . . . . . . . . . . . . . . . . . . .2
Map of the ARA-I Chemical Evaporation Pond and sediment sample locations. . . . . . . . . . . . . . . . . 3
TABLES
Table 3.
Analytical results for random. biased. and background samples. .............................7
Contaminant concentrations in ARA-I O1emical Evaporation Pond used in
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ARA
ACRONYMS AND ABBREVIATIONS
Auxiliary Reactor Area
CERCLA Comprehensive Environmental Response. Compensation. and Liability Act
COCA Consent Order and Compliance Agreement
DOE
DOE-ID
EPA
FF AlCO
FR
IDHW
INEL
Ilg/kg
mg/kg
NCP
NPL
OU
pCilg
UCL
voc
WAG
u.s. Department of Energy
U.S. Department of Energy Idaho Field Office
.
U.S. Environmental Protection Agency
Federal Facility Agreement and Consent Order.
Federal RegiSter
Idaho Department of Health and Welfare
Idaho National Engineering Laboratory
micrograms per kilogram
milligrams per kilogram
. National Oil and Hazardous SubStances Pollution Contingency Plan .
National Priorities List
Operable Unit
picocuries per gram
upper confidence limit.
volatile organic compound
WaSte Area Group
. .,
viii
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DECISION SUMMARY
1. SITE NAME, LOCATION, AND DESCRIPTION
.
The Idaho National Engineering Laboratory (INEL) is a U.S. Depamnent of Energy (DOE) facility that
encompasses approximately 2,305 sq Ian (890 sq mi) in southeastern Idaho. The nearest permanent residents are
located in Atomic City (population 34) about 11 km (7 mi) south of the Auxiliary Reactor Area (ARA) facilities.
The nearest large population center is Idaho Falls (population 46.(00), located approximately 48 kIn (32 mi) to
the east. INEL land is currently classified for industrial and mixed use (restricted agricultural and recreational) by
the U.S. Bureau of Land Management. It has been designated as a National Environmental Research Park. The
ARA is located in Butte County on the southern portion of the INEL site (Figure 1). .
The INEL is part of the Eastern Snake River Plain, a volcanic plateau consisting of a series of basaltic
lava flows with sedimentary interbeds. The topography of the INEL is generally flat to gently rolling, with an
elevation range of 1,732 m (4,750 ft)to 1,896 m (5,200 ft). The topography at the ARA is relatively flat with a
gradual slope to the south. Soils in the vicinity of the ARA are shallow and poorly developed and are composed
of windblown (eolian) sediments exhibiting a sandy loam or loamy composition. The majority of the soils are
Aridisols with calcic horizons (accumulations of calcium carbonate).
The Snake River Plain Aquifer underlies the INEL and has been designated as a sole source aquifer
pursuant to the Safe Drinking Water Act. The depth to the aquifer varies from 61 m (200 ft) in the northern
portion of the INEL to 270 m (900 ft) in the southern portion; the depth to the aquifer at the ARA is
approximately 183 m (600 ft). Regional groundwater flow is generally to the southwest.
. J
t
.,
~-~
- 118-
. "..-..::: au..
- .-
-.
-.0
oz..,
~ ---.oy
o . . .z
ICILCIIETSIS
--
Figure 1. Location of the Auxiliary Reactor Area (ARA).
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x-x-x-x 0 Fire hose
.. ~
I house
..
Building
ARA- Scale: (meter) ,
627 627 I I I I I I
addition 0 25
Septic
leach
field
To Fillmore
Boulevard
I I
Area of
highest
concentration
K92 0340
Figure 2. Map of the ARA-I facility and the ARA-I Chemical Evaporation Pond.
The ARA consists of four separate facilities; ARA-I is the southernmoSt and oldest fadlity. The ARA
facilities have been used for research reactor operations and suppon activities. All ARA reactors have been
removed. and each facility has undergone partial decont:tmination and decommissioning. ARA-I was a suppon
facility and has not been used for operations since 1988.
The ARA-I Chemical Evaporation Pond is listed as Operable Unit (QU) 5-10 in Waste Area Group
(WAG) 5 under the Federal Facility Agreement and Consent Order (FF NCQ) for the INEL. QU 5-10 is an
unlined SUIface impoundment that was previousiy used to dispose of laboratory wasteWater from building ARA-627
(Figure 2). The pond is now typically dry except after precipitation events. The pond was constructed in 1970 by
excavating native soil to create a topographic depression. Basaltoutcrops are present within the pond and
immediately adjacent to the pond. Field sampling conducted on the pond in 1990 found a maximum pond soil
depth of 1.1 m (3.5 ft) and an average soil depth of approximately 0.5 m (1.5 ft). The ARA-I facility is
approximately 3 m (10 ft) higher in elevation than the pond. The dimensions of the area sampled were
approxiinately 40 x 140 m (130 x 460 ft), but the ponded area was approximately 20 m (66 ft) in diameter (Figme 3).
.. .
2
...-. - -.- - -'---.-'- -'_._--~_.__._,-- -----.- --..
."--. - "--.-.-.------.- -_._-.. - ---.- --., __.0.
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_. ...40----- ---.--....----.---- -- - .....--
~
~
Scale: (meter)
I 1 I 1 I I
o 25
((ceee c.
(
--
Ponded area /'
I
/
I
\
\
f---------......
,... - -3~4 81702 8'
8 1802 1704 J
404 1804 /
1404 /
81703 -_/
/'
303 /
/
/
/
. 81701)
7038 ---------
...----
............... .----------.---"'"
---
8704
. Explanation
8 = Sample location (the number
shown to the side is the reference
number of the sample taken in and
around the pond)
. .
Background samples
8101
8102
8103
8104
8105
8106
8107
8108
8109
8110
R92 1638
Figure 3. Map of the ARA-I Chemical Evaporation Pond and sediment sample locations (quality assurance samples
not shown on map).
3
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2. SITE IDSTORY AND ENFORCEMENT AcrIVITIES
2.1 Enforcement Activities
Under the INEL Consent Order and Compliance Agreement (COCA) signed by the U.S. Environmental
Protection Agency (EPA), DOE, and U.S. Geological Survey in July 1987, the ARA-I Chemical Evaporation
Pond was classified as a Land Disposal Unit and was listed as COCA Unit ARA"()1. Releases ofradioactiye or
hazardous contaminants to the ARA-I Chemical Evaporation Pond were first identified and evaluated during
investigations conducted in "accordance with the COCA.
~
In July 1989, the INEL was proposed for inclusion on the National Priorities List (NPL) in 54 Federal
Register (FR) 29820. The listing was proposed by the EP A under the authority granted by the Comprehensive
Environmental Response, Compensation, and LiabilityAct (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986. The final rule placing the INEL on the NPL was published in
November 1989 in 54 FR 44184.
In December 1991 the EP A. DOE, and Idaho Department of Health and Welfare (IDHW) signed the F.F AlCO.
" The FF AlCO and Action Plan supersede the COCA and provide schedules and strategies for implementing the
Nation3l Oil and Hazardous Substances Pollution Contingency Plan (NCP) at the INEL. Under the FFAiCO the
ARA-I Chemical Evaporation Pond is listed as OU 5-10. """ "'
2.2 Site History and Investigations
ARA~I is a surplus facility that was used as a nuclear research area, as research laboratories, and for
various operations related to the examination or storage of radioactively contaminated materials. The ARA-I
fadlity is comprised of tWo main buildings, ARA.;626 and ARA-627." ARA-626 was a hot cell used to support
materials research. and it contained a small laboratory area for sample preparation and inspection. ARA-626 was
not connected to the pond
ARA-627 served many purposes following its constnlctionin 1955. Between 1955 and 1971,ARA-627
was a print shop. Beginning in 1970. the building was expanded and modified to serve as a research laboratory
for materials development and testing. During this expansion, the ARA-I Chemical Evaporation Pond and the
waste line from ARA-627 were constructed. From "1970 to 1984, small amounts of volatile organic compounds
(VOCs) and mineral acids were used for material testing operations at ARA-627. On rare occasions when large
amounts of acids or VOCs were used on a specific project. they were retained and sent to the Idaho Chemical
Processing Plant for processing. Small amounts of acids and VOCs were used on a more routine basis and were
disposed of in the following mJ'lnner:
.
Radioactively contJ'lminJ'lted acids were placed into the radioactive waste sewer and retained in the
radioactive waste tank (ARA-729) before disposal. "
.
Nonradioactively contaminated acids and VOCs were discharged through the waste line to the ARA-I
Chemical Evaporation Pond (ARA-745).
. .
In 1980. ARA-627 was further modified to iJicorporate a radiochemistry laboratory that operated until
1988. The laboratory performed extractions to determine potential leaching characteristics and concentrations of
radionuclides in various waste forms and environmental media. 1be laboratory testing performed resulted in
approximately 95 to 99% of the low-level radioactive material leached from the analytical samples to be retained
on fIlter paper. The contaminated filter papers were periodically sent to the Radioactive Waste Management
4
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.. - -..- -'." . - .--.-...--.---'
.. ~ .. - .... -----_._- ---. ------- --. -" . .-..-.-. .
Complex for disposal. The small amounts of radioactive material DOt captured on the filter paper and the VOCs
used in the extraction process (xylene, heptane, 2-ethyl hexanol, and methanol) were discharged with other
laboratory wastewater to the ARA-I Chemical Evaporation Pond. In 1988, the radiochemistry laboratory was
moved to the Test Reactor Area; except for janitorial rinsewater from ARA-627 discharges to the pond ceased.
.
A sampling effon was conducted in 1990 to better characterize the ARA-I Chemical Evaporation Pond in
suppon of Resource Conservation and Recovery Act dosme activities under the COCA Previous characterization
activities did not define the extent of contamination; therefore. additional sampling was necessary to better
charaCterize the pond and discharge pipe. The 1990 sampling results are documented in the ReTI'U!dial
Investigation Reportfor the ARA Chemical Evaporation Pond (Operable Unit 5-10). which is available in the
Administrative Record. Upon the signing of the FF AlCO in 1991. the EP A. DOE, and IDHW agreed that these
data would be used for CERCLA site characterization and risk assessmenL
4
The sampling strategy developed to detect chemical and radioactive contaminants in the pond sediments
was based on process knowledge and a previous investigation that determined limited quantities of materials were
discharged over the 17 years of pond use. A total of 25 biased and 23 random sediment samples (including
quality assurance samples) were collected at the surface and basalt interface from within the pond and discharge
pipe area. Ten biased soil samples were collected approximately 30 m (100 ft) to the south of the poIld in an area
unaffected by ARA activities. These 10 samples were used to determine background metal concentrations (Figure 3).
3. IDGHLIGHTS OF COMMUNITY PARTICIPATION
On June 26. 1992, a document containing proposed plans for three INEL sites. including the ARA-I
Chemical Evaporation Pond. was released to the public. The plan was mailed to approximately 6.500 individuals
on the INEL mailing list, with a cover letter from ihe Director of the Environmental Restoration Division, U.S.
Department of Energy Idaho Field Office (DOE-ID). The public comment period for the proposed plan was from
July 6 to August 5. 1992. Community participation activities have been conducted as required by CERCLA
sections 113(k)(2)(B) (i-v) and 117 and pan XXIV of the FFAICO.
The ARA-I Chemical Evaporation Pond proposed plan summarized the results of the human health risk
assessment, which was based on modeled exposures to the pond cont:.mi n:.nts. The modeling indicated that the
cont:.min:.nts at the site pose no unacceptable risk to human health and the environmenL Therefore, the DOE,
EP A. and IDHW recommended No Action for the Chemical Evaporation Pond in the proposed plan.
The Notice of Availability for the proposed plan was published in the following newspapers:
. ,
- The Post Register (Idaho Falls) - July 1.1992
- The Idaho State Joumal (pocatello) - July 2, 1992
- Tunes News (Twin Falls) - July 1. 1992
- ldiJho Sttltesrrum (Boise) - July 2, 1992
- Daily News (Moscow-Pullman) - July 11 and 12, 1992
- South ldllho Press (Burley) - July 1. 1992
- The Lewiston Morning Tribune (Lewiston) - July 1. 1992.
Copies of the plan are available in the Administrative Record file in the INEL Technical library, 1776
Science Center Drive. Idaho Falls. Copies of the file also are available in the INEL Information Repository
sections of the public libraries in Idaho Falls, Pocatello, Twin Falls. Boise, and the University of Idaho library in
Moscow.
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Technical briefings on the proposed plan were held July 13 in Twin Falls. July 14 in Moscow. and July 15
in Pocatello. The Twin Falls briefing was presented to the Twin Falls City Council and was open to the public;
the Moscow and Pocatello briefings were presented to the public.
"
. Articles explaining the proposed plan for the ARA-I Chemical Enporation Pond were printed in the May
and July 1992 issues of the INEL Reporter newsletter. which is widely distributed within Idaho. Additionally.
during the public comment period (from July 6 to August 5). public meetings on the proposed plan were held in
Idaho Falls on July 20. Burley on July 21. Boise on July 22. and Moscow on July 23. An INEL press release
infomiing the public of the upcoming meeting in their area was distributed to State-wide media. Personal phone
calls were made by INEL Outreach Offices in Pocatello. Twin Fans. and Boise to inform key representatives from
community groups of the opportUnity for public comment.
~
The notices of the times and dates of public meetings were published in the following newspapers:
The Post Register (Idaho Falls) - July 17. 1992
- 17le Idaho State Journal (pocatello) - July 17. 1992
- Times News (Twin Falls) - July 20. 1992
- Idaho Statesman (Boise) - July 20. 1992
- Daily News (Moscow-Pullman) - July 21. 1992
- South Idaho Press (Burley) - July 20. 1992 .
- The Lewiston Morning Tribune (Lewiston) - July 21. 1992.
At the meetings; representatives from the DOE-ID. EPA. and IDHW discussed the proposed plan.
.answered queStions. and received public comment. . Verbatim transcripts of each public meeting were prepared by
a court reporter and are available. along with th.e written comments. in ta'1e Administrative Record. Comments
received from the public were considered in the final decision and have been summarized and addressed in the
Responsiveness Summary attached to this Record of Decision (Appendix A). . .
4. SCOPE AND ROLE OF OPERABLE UNIT AND RESPONSE ACTION
. Under the FFNCO. the INEL is divided into 10 WAGs; each WAG consists of several OUs. This
strategy allows the DOE-ID. EPA. and IDHW to investigate OUs and focus available cleanup resources on thoSe
areas that pose an unacceptable risk to human health and the environment.W AG 5 consists of 13 aUslocated at
the Power Burst Facility and the ARA As previously stated, the ARA-I Chemical Evaporation Pond is
designated as OU 5-10.
. au 5-10 includes the pond sediments and the sediments under the discharge pipe. The data collected to
characterize the pond's sediments were used in the remedial investigation baseline risk assessment. This risk
assessment indicates the sediments within the Chemical Evaporation Pond and under the discharge pipe pose no
unacceptable risk to human health and the environment. Based on these results and risk management
considerations. the three agencies agree that the ARA-I Chemical Evaporation Pond requires no remedial action to
protect human health and the environment. Any impacts from past releases to the pond that may affect the
subsurface (vadose zone) or groundwater will be evaluated in a future investigation that will be completed before
the INEL site-wide Record of Decision is fmalized. . . .
~ .
6
. .. - ." '---~--'-----'------'---.-
_u. -_..- + --.
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. ---.--. - . -' .4- ~- _...----_.~,-_._.._- ._-.- .~_._-----_.. .--..--.-
5. SITE CHARACTERISTICS
.
The ARA-I Chemica] Evaporation Pond sediments were investigated by DOE for the presence of
contamination between 1982 and 1990. Investigations before 1990 indicated that metals, VOCs, and
radionuclides existed in the sediments. Samples collected in 1990 were analyzed for metals, VQCs. and gamma- and
alpha-emitting radio nuclides. Analyses for metals and VOCs were performed as specified in the laboratory
manual Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (EP A. SW -846. 1986). Gamma-
emitting radionuclides were ana1yzed by gamma-spectroscopy methods specified in the EG&G Radiation
MeasurementS Laboratory Standard Operating Procedures (Procedure DM-l). and alpha emitting radio nuclides
were analyzed using the ''Total Spectrometric Alpha Determination" procedure used by the Radiation
Measurement Laboratory at the INEL. Analytical results for random, biased. and background samples are
summarized in Table I.
.
Table 1. Analytical results for random, biased. and background samples.a
Frequency of Frequency of Estimated upper Range of
Chemical detection greater range of detected Units
detectionb than background background concentrations
Metals
Antimony 40/40 ND 26.97 3.3-16.8 mg/kg
Arsenic 4/4 2/4 8.31 7.4-11.6 mg/kg
Barium 40/40 c 3/40 26129 105.0-293.0 mg/kg
Beryllium 40/40 1/40 1.70 053-22 mg/kg
Cadmium 40/40 8/40 2.42 0.95-3.8 mglkg
Chromium . 40/40 17/40 33.81 22.2-69.0 mg/kg
Lead 40/40 10/40 26.92 7.0-43.9 mgJkg
Mercury 4/4 2/4 0.06 O.02~2.8 mnk"
-"~-'e
Nickel 40/40 6/40 27.17 17.7-36.0 mg/kg
Selenium 4/4 2/4 0.31 0.15-1.2 mg/kg
Silver 40/40 8/40 8.08 4.3-15.0 mg/kg
Cyanide 4/4 ND 0.37 .28-.30 mglkg
Tin 40/40 2/40 20.09 9.6-21.7 mglkg
Vanadium 40/40 .1/40 56.44 39.6-68.0 mglkg
Zinc 40/40 7/40 80.18 25.3-312.0 ' mg/kg
Thallium 0/4 ND 0.35" 1/2 mglkg
VOCS
Methylene O1eloride 4/32 NA NA 8.0-26.0 ~g
Ace!one 2/32 NA NA 2.0-7.0 ~Lg/kg
Toluene 3/32 NA NA 3.0-4.0 J1g1kg
Radionuclides
Cesium-137 25/40 25/40 O.48d 0.11-297.0 pCilg
Cesium-l34 4/40 4/40 NO 0.22-11.4 pCilg
Cobalt-60 3/40 3/40 NO 0.13-8.14 pCilg
Plutonium-239 1/1 1/1 NO 2.6" . pCilg
Unmium-234 1/1 1/1 NO 1.6e pCilg
. .
a. NA - BackgroUDd concentrations are expected to be zero. ND - Not detected in concentrations above background. NO-BaclcgroUDd
concentrations not available.
b. Full gamma spectroscopy annual 40 samples. only those detected are present in the table.
.. . c. Instrument detection limit.
d. Arithmetic mean.
e. Only one sample collected.
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Because some of the constituents identified at the site also occur natUrally in the soil. it was necessary to
determine background concentrations specific to ARA-I. Background samples were taken approximately 30 m
(100ft) to the southeast of the pond Analysis of these soil samples indicated metal concentrations similar to
generally accepted background values for the western United States (EPA, Office of Solid Waste and Emergency
Response. Hazardous Waste Land Treatment. SW-874. April 1983):
..
The pond sediment samples were analyzed for 16 naturally occurring metals. All metals were detected;
however. as shown in Table 1. most metal concentrations were at or below the background concentration. The
samples with the highest metal concentrations were collected within a 9 sq m (approximately 100 sq ft) area
adjacent to the pond inlet (see Figure 2).
.
A full gamma spectroscopy analysis was performed. only three gamma-emitting radionuclides were
detected in the pond sediments: cesium-l 37 (25 of 40 samples). cesium-l 34 (4 of 40 samples). and cobalt-60 (3 of
40 samples). However. only two samples containing gamma-emitting radionuc1ides (biased sample and replicate)
had detections statistically greater than backgroUnd radioactivity as determined from samples collected within the
WAG 5 area and reponed in Environmental Monitoringfor EG&G Idaho Falls Facilities at the Idaho National
Engineering Laboratory. EG&G-2612(90). August 1991. The maximum concentration of radio nuclides in these
samples was 297 pCilg cesium-137. 11.4 pCilg cesium-I34. 8.14 pCilg cobalt-60, 2.6 pCilg plutonium-239, and
1.6 pCilg uranium-234. As with the metals, the samples with the highest radionuclide concentrations were
collected adjacent to the pond inlet. . .
Only one Sample was analyzed for alpha-emitting radionuclides. That sample was collected from the area
adjacent to the pond inlet, which was the area expected to exhibit the greatest contamination. The alpha-emitting
radionuclides. plutonium-239 and iJranium-234. were detected at low concentrations in that sample. Although
only one sample was targeted for alpha-emitting radionuclides. other data exist that indicate their absence.
Specifically. the alpha-emitting radionuclides plutonium-239 and plutonium-241 are co-produced from the decay
of a parent compound. Plutonium-241 quickly undergoes radioactive decay (14-year half-life) to produce
americium-241. which is a x-ray emitting radionuclide and is detectable by gamma spectroscopy. Gamma
spectroscopy analysis was performed on.the sediment samples collected throughout the rest of the pond. and
americium-241 was not detected The absence of americium-24I indicates that the parent plutonium-241 and the
associated plutonium-239 are also absent. and it supports the assUmption that the alpha contamination has limited
distribution in the pond sediments. .
Three VOCs (methylene chloride. acetone. and toluene) were detected in the pond sediments. Out of 32
total random and biased samples targeted for VOC analysis. methylene chloride was detected in four samples at
concentrations ranging from 8 to 26 Jiglkg. acetone was detected in two samples (2 and 7 Jigikg). and tOluene was
detected in three samples (3 to 4 Jiglkg).
'The fate and transport of the detected CODtaminants are affected by a variety of physical and chemical
processes. Radionuclides decay and VOCs dissipate; therefore. their concentrations will continue to decrease
over time. Metal contamination (including radionuclides) found in the sediments is relatively immobile; the
primary mode of transport is windblown dust Metals of potential concern in the sediments are:
. .
.
. -
Arsenic, chromium-VI, cesium-137. cesium-l34. cobalt-60. plutonium-239. and uranium-234. which
are classified as Group A human carcinogens .
. .
.
Cadmium, a Group B 1 probable human carcinogen
.
Beryllium, a Group B2 probable human carcinogen
8
"".-.----
----------_...__.--~- ..
-------
. . --.-. - - --.-.
. -. --- . - .--.. .
. ----~- -,_.' 0...
.--.----- - ---.. -. _...- ~-_#_-
-
Chromium-ill, a noncarcinogen that may have other adverse human health effects.
.
At the ARA-I Chemical Evaporation Pond, potential pathways for contaminant migration and exposure
to humans include (a) direct atmospheric transport. (b) indirect transport via game ammals, (c) direct transport via
groundwater, and (d) direct ingestion by workers or future residents. Direct exposure to ionizing radiation emitted
by pond contaminants constitutes another exposure route, but it is not a migration pathway. Exposure pathways
selected for the risk assessment include soil ingestion. inhalation. direct contact with contaminants, and exposure
to direct ionizing radiation.
..
Potential exposure scenarios based on the above pathways at the ARA-I Chemical Evaporation Pond were
limited to present occupational and future residential users. For the occupational scenario, the site worker was
assumed to be exposed to direct radiation and to inhale or ingest contaminants from the pond sediments.
Currently, exposure to the public is unlikely because of the strict security policy at the INEL. However, a future
residential scenario was evaluated because it is possible a home could be built on the site if existing land use
policy changes. Residential exposures may occur by inhalation. ingestion. dermal contact. or direct radiation
exposure. For the risk assessment, it was assumed residential development will not occur for at least 30 years. A
lOO-year residential scenario was also evaluated consistent with previously published FFAICO investigatiops.
6. SUl\1l\-IARY OF SITE RISKS
6.1 Human Health Risk
The contaminants found in.the ARA-I Chemical Evaporation Pond were evaluated to identify those that
contribute the greatest potential risk. A concentration-toxicity screen was used. which involved ranking each
contaminant by its highest detected concentration multiplied by a chemical-specific risk factor developed by the
EP A. Consistent with EP A guidance (Risk Assessment Guidance for Superfund. Part A), contaminants
contributing more than 1 % of the total calculated risk were retained in the baseline risk assessmenL The
concentration-toxicity screen identified chromium-ill as the main contributor of noncarcinogenic risk. while the
most significant carcinogenic risk drivers were chromium-VI, cadmium, beryllium, arsenic, and radionuclides
(Table 2).
.
,
Table 2. Contaminant concentrations in ARA-I Chemical Evaporation Pond used in the baseline risk assessmPnts.
.. .
Geometric Background Occupational Residential Residential
Contaminant (95% UCL)U (mean)¥ (present day)- (30-year)- (lOO-year)-
Cesium-137 0.54 0.54 0.09 0.05 0.01
Cesium-l34 0.10 NO 0.10 0.00 0.00
Cobalt~ 0.10 NO 0.10 0.00 0.00
Plutonium-239 2.60 NO 2.60. 2.60 2.60
Ur.mium-234 1.60 NO 1.60 1.60 1.60
Arsenic 10.70 5.46 524 S24 524
Beryllium 1.38 1.11 027 027 027
Cadmium . 2.15 1.60 O.5S 0.55 0.55
Chromium-VI 5.08 3.67 1.41 1.41 1.41
Chromium-ill 31.22 . 22.55 8.67 8.67 8.67
a. Units are pCilg for radionuclides aDd J.1g/kg for metals.
b. VCL = upper confidence limit
c. NO = background cooc:entration not available.
9
. -
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Table 2 gives the concentrations of the contaminants in the ARA-I Chemical Evaporation Pond that were
used in the baseline risk assessment for each scenario. Initial concentrations of contaminants measured in the
pond sediments were used to calculated the 95% upper confidence limit (UCL) for each identified risk driver.
Calculation of the 95% UCL is based on an apparent lognormal distribution on analytic results. using a one sided
t-test. For assessment of risk. the mean background concentration was then subtracted from the associated UCL.
and the resulting value was used for risk modeling. For nonradioactive analytes and long-lived radionuclides.
concentrations are considered to remain constant with time. The nonradioactive material may deteriorate over
time. but the decay is neither constant nor predictable. Radioactive material decays at a predictable rate. but the
activity reduction experie~ced by a long-lived radionuclide during a 30- or lOO-year period would be
insignificant. .
.
..
The human-health effects of the contaminants were evaluated for current occupational and future
residential scenarios (30 and 100 year). Two risk assessments for each scenario were developed: the first using
EPA default parameters and the second using site-specific parameters. ARA-I is a surplus facility that is not
normally occupied. Therefore~ occupational direct radiation and ingestion exposures were modeled for an
individual who would spend 2 hours at the site every 90 days. Occupational inhalation exposure was modeled for
an individual who spends 1 day/week at ARA-I [100 m (328 ft) from the pond].
Residential carcinogenic risks were calculated for both the 30- and lOO-year future-use scenarios for site-
specific and default parameters. The timing of the residential scenario is not important to the chemical risk
assessment. but it is considered in the radiological risk assessment because radio nuclide decay reduces risk over
time. Residential exposure at the site may occur by inhalation. ingestion. dermal contact. or direct radiation
exposure. .
Each scen:uiowas assessed using EP A default exposure parameters to establish a baseline risk value.
Site-specific risk assessment retlectssite conditions as they exist today and as they are likely to exist in the future.
The major difference between the default and site-specific conditions is the exposure frequency; a lower
frequency is more realistic for this site. The baseline risk assessment is included in the Remedial InveStigation
Reportfor the ARA Chemical Evaporation Pond (Operable Unit 5-10).
Contaminant intake rates for metals and radionuclides were calculated for inhalation. ingestion. and
dermal absorption in accordance with EP A methods found in the Risk Assessment Guidance for Superfund.
Volume I. "Human Health Evaluation Manual." .For noncarcinogens. the calculated contaminant intake rates and
absorbed doses for each contaminant and exposure route were compared to EP A reference doses. The hazard
quotients (the ratio of the calculated intake to the reference dose for each contaminant) were summed by exposure
route and scenario to obtain the h:1zard indices. A haz:1rd index value greater than 1 indicates possible adverse
human-health effects for sensitive subpopulations. For the modeled scenarios. no hazard indices greater than 1
were identified. This indicates the noncarcinogenic contaminants at the ARA-I Chemical Evaporation Pond pose
no unacceptable risk to human health (Table 3).
Carcinogenic health effects for each scenario were evaluated in accordance with EP A methodology using
calculated intake rates and absorption and slope factors for each carcinogen. The results were the calculated
excess cancer risks for each carcinogen. These risks were then summed to determine the total excess cancer risk
for that scenario. For the occupational scenario. the current total carcinogenic risk to workers near'the ARA-I
Chemical Evaporation Pond was 2 in 100.000 (2 x 10-5) using tbedefault parameters and 2 in 10.000.000 (2 x 10-7)
Using site-specific parameters. For the default 30-year future residential scenario. the total carcinogenic risk from
radionuclides and inorganic metals was I in 100.000 (1 x 10-5) and 2 in 1.000.000 (2 x 1O-~ for the site-specific
scenario. For the l00-year future residential scenario. the total carcinogenic risk for the default scenario was 4 in
1.000.000 (4 x 10~ and 1 in 1.000.000 (1 x 1O-~ for the site-specific scenario (Table 3).
. ~
. .
10
._~ -. ,-_..__.-.._-.._.._.__._-----_.__._-~----_.-..
-------
--.. -. -.
. -----. -,-,.'--'-.-..----' .-," .-.-.-...---.-.-..--
Table 3. Summary of risks at the ARA-I Chemical Evaporation Pond.
Carcinogenic risk Hazard index
Scenario Contaminants Default Site-specitk Default Site-specirac
. Occupational Radionuclides 2 in 100,000 2 in 10,000,000 NA" NA
(2E-05) (2E-07)
.. Chemicals 3 in 10,000,000 2 in 100,000,000 0.07 0.007
(3E-07) (2E-08)
Total 2 in 100,000 2 in 10,000,000 0.07 0.007
(2E-05) (2E-07)
Futux:e 30 year Radionuclides 9 in 1,000,000 2 in 1,000,000 NA NA
residential (9E-06) (2E-06)
Chemicals 8 in 10,000,000 4 in 10,000,000 0.09 0.09
(8E-07) (4E-07)
Total 1 in 100,000 . 2 in 1,000,000 0.09 0.09
(lE-05) (2E-06)
Future 100 year Radionuclides 3 in 1,000,000 1 in 1,000,000 NA NA
residential (3E-06) (4E-07)
Chemicals 8 in 10,000,000 4 in 10,000,000 0.09 0.09
Total 4 in 1,000,000 1 in 1,000,000 0.09 0.09
(4E-06) (IE-06)
a. Hazard indices are not applicable to radionuclides.
-
~
<
In summary, noncarcinogenic contaminants resulted in a hazard quotient ofless than 1 for the
occupational and residential scenarios. The calculated excess risk of carcinogenic effects from exposure to the
chemical and radioactive contaminants in the p
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risks associated with the pond is that a residence would be located at the pond site in the future. Because of
conditions at the pond t..'1e probability of a residence being located in close proximity to the pond is quite small.
The limited areal extent of contamination and the improbability of furore residents spending signiticant time in the
area indicates that the potential risks have probably been overestimated.
.
Because the potential effectS of the assumptions used in the risk assessment are not quantified, it is
difficult to measure the effect on total risk. However, the potential for over. and underestimation can be
qualitatively compared. On balance, it appears there is a greater potential for overestimation of exposures and
risks. Therefore, the estimates of total risk for this site can be considered conservative.
.
6.2 Environmental Risk
The remedial investigatio.n also addressed the effects the contaminants in the ARA-I Chemical .
Evaporation Pond sediments would have on the environment. The main contaminants of concern are metals and
radio nuclides, which typically are immobile in the soils and unlikely to be transferred through the food chain.
The contamination in the. pond has a limited distribution; therefore, any effect that could be identified would be on
an individual and not on a population or community. These factors, combined with the discontinued use of the
pond, semi-arid climate, sparse vegetation, and limited habitat for wildlife. minimize risks to the ecosystem.
However, environmental risk will be further evaluated in the WAG 10 Comprehensive Remedial Investigation!
Feasibility Study scheduled to begin in 1998.
7. DECISION
The DOE has determined no further remedial action is necessary at the ARA-I Chemical Evaporation
Pend to ensure protection of human health and the environment. 111is decision iso-:\.c;ed on the results of the
human health and ecological risk assessments that determined conditions at the site pose no unacceptable risk to
human health or the environmenL The EP A approves of the decision and the IDHW concurs.
8. EXPLANATION OF SIGNIFICANT CHANGES
The proposed plan for the ARA-I Chemical Evaporation Pond sediments was released for public
comment on June 26, 1992. The proposed plan identified No Action as the alternative preferred by the DOE,
EPA, and IDHW. The three agencies have reviewed and considered all written and verbal comments concerning
the proposed action that were submitted during the public comment period. The agencies determined that no
significant changes to the preferred alternative. as presented in the proposed plan, were necessary.
, "
. .
12
~ - -..-- -_..
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