PB96-964612
EPA/ROD/R10-96/147
March 1997
EPA Superfund
Record of Decision:
Idaho National Engineering Lab,
(USDOE) Operable Unit 26
(Stationary Low-Power Reactor-1 and
Boiling Water Reactor Experiment-I Burial
Grounds), Idaho Falls, ID
12/1/1995
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FEB 1 2 1996
Wcnruwl1
DIVISION OF
ENVIRONMENTAL
QUM.ITY
INEL-95/0282
January, 1996
Record of Decision
Stationary Low-Power Reactor-1 and
Boiling Water Reactor Experiment-I Burial
Grounds
(Operable Units 5-05 and 6-01),
and 10 No Action Sites
(Operable Units 5-01,5-03, 5-04, and 5-11)
u
\
-•>
Idaho National Engineering Laboratory • Idaho Falls, Idaho
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Declaration of the Record of Decision
Site Name and Location
Stationary Low-Power Reactor-1 Burial Ground,
Boiling Water Reactor Experiment-I Burial Ground, and
10 No Action Sites Within the
Auxiliary Reactor Area and the Power Burst Facility
Idaho National Engineering Laboratory
Idaho Falls, Idaho
Statement of Basis and Purpose
This document presents the selected remedial action for the Stationary Low-Power Reactor-1 (SL-1) burial
ground, the Boiling Water Reactor Experiment-I (BORAX-I) burial ground, and 10 no action sites in Waste
Area Group 5. The remedial actions were selected in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) as amended by the Superfund Amendments and
Reauthorization Act (SARA) (hereafter referred to collectively as "CERCLA"), and is consistent, to the extent
practicable, with the National Oil and Hazardous Substances Pollution Contingency Plan. Information sup-
porting the selection of the remedies for the burial grounds is contained in the Administrative Record for the
SL-1 and BORAX-I burial grounds (Operable Units 5-05 and 6-01). The Administrative Record for Track 1
sites in Waste Area Group 5 contains information regarding the 10 no action sites (Operable Units 5-01, 5-03,
5-04, and 5-11).
The U.S. Department of Energy (DOE) is the lead agency for this decision. The U.S.
Environmental Protection Agency (EPA) and the Idaho Department of Health and Welfare (IDHW)
have participated in the evaluation of the final action alternatives. The EPA and IDHW both concur
with the selection of the preferred remedy for the SL-1 and BORAX-I burial grounds and with the no
action determinations for the 10 Track 1 sites.
Assessment of the Sites
Actual or threatened releases of hazardous substances from die 6L-1 and BORAX-I burial grounds,
if not addressed by implementing the response action selected in this Record of Decision, may present a
current or potential threat to public health, welfare, or the environment.
The 10 no action sites do not present a threat to human health or the environment.
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Description of the Selected Remedy
The Idaho National Engineering Laboratory (INEL) has been subdivided into 10 waste area groups
for investigation pursuant to the Federal Facility Agreement and Consent Order between the DOE,
EPA, and IDHW. The SL-1 burial ground is designated Operable Unit 5-05, one of 13 operable units
in Waste Area Group 5; the BORAX-I burial ground is Operable Unit 6-01, one of five operable units
in Waste Area Group 6. The major components of the selected remedy for both sites are:
• Containment by capping with an engineered barrier constructed primarily of native materials
• For BORAX-I implementation will include consolidation of surrounding contaminated surface
soils for containment under the engineered cover
• Contouring and grading of surrounding terrain to direct surface water runoff away from the caps
• Periodic above-ground radiological surveys following completion of the caps to assess the
effectiveness of the remedial action
• Periodic inspection and maintenance following completion of the caps to ensure cap integrity
and surface drainage away from the barriers
• Access restrictions consisting of fences, posted signs, and permanent markers
• Restrictions limiting land use to industrial applications for at least 100 years following comple-
tion of the caps
• Review of the remedy no less often than every five years until determined by the regulatory
agencies to be unnecessary.
The selected remedy addresses the principal threats posed by the burial grounds by providing
shielding from ionizing radiation, a barrier to inhibit ecological and human intrusion, and a long-lasting
cover to diminish the effects of wind and water erosion.
Statutory Determination
The selected remedies are protective of human health and the environment, comply with federal
and state requirements that are legally applicable or relevant and appropriate requirements (ARARs) to
law ieuiedial actions, and are cost effective. These remedies utilize permanent solutions and alternative
treatment technologies to the maximum extent practicable. However, because treatment of the princi-
pal threats of the two burial grounds was not found to be practicable, this remedy does not satisfy the
statutory preference for treatment as a principal element of the remedy. The EPA's preference for sites
that pose relatively low long-term threats or where treatment is impracticable is engineering controls,
such as containment. The radioactivity at each burial ground precludes a remedy in which contami-
nants could be readily excavated and treated without unacceptable exposures to workers. The primary
contributor to risk is a short half-lived radionuclide more effectively managed by providing engineered
containment while allowing the radionuclide to decay naturally.
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Because these remedies will result in radionuclide-contaminated substances remaining on site at the
burial grounds in excess of health-based levels, reviews will be conducted within five years after com-
mencement of the remedial actions. Subsequent reviews will be conducted no less often than every five
years thereafter to ensure that the remedies continue to provide adequate protection of human health and
the environment. The periodic reviews will be discontinued when the regulatory agencies determine the
sites no longer pose an unacceptable risk to human health or the environment.
iii
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Signature sheet for the foregoing Stationary Low-Power Reactor-1 Burial Ground, the Boiling
Water Reactor Experiment-I Burial Ground, and 10 no further action sites in Waste Area Group 5 at the
Idaho National Engineering Laboratory Record of Decision between the U.S. Department of Energy
and the U.S. Environmental Protection Agency, with concurrence by the Idaho Department of Health
and Welfare.
M.
ohn M.WcynskQ . Date
anager
U.S. Department of Energy, Idaho Operations Office
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Signature sheet for the foregoing Stationary Low-Power Reactor-1 Burial Ground, the Boiling
Water Reactor Experiment I Burial Ground, and 10 no further action sites in Waste Area Group 5 at the
Idaho National Engineering Laboratory Record of Decision between the U.S. Department of Energy
and the U.S. Environmental Protection Agency, with concurrence by the Idaho Department of Health
and Welfare.
ick Clarke
Regional Administrator, Region 10
U. S. Environmental Protection Agency
Date
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Signature sheet for the foregoing Stationary Low-Power Reactor-1 Burial Ground, the Boiling
Water Reactor Experiment I Burial Ground, and 10 no further action sites in Waste Area Group 5 at the
Idaho National Engineering Laboratory Record of Decision between the U.S. Department of Energy
and the U.S. Environmental Protection Agency, with concurrence by the Idaho Department of Health
and Welfare.
Wallace N. Cory T Date
Administrator
Division of Environmental Quality
Idaho Department of Health and Welfare
VI
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Contents
Declaration of the Record of Decision
Acronyms and Abbreviations Jx
1. Site Name, Location, and Description 1
2. Site History and Enforcement Activities 5
2.1 SL-1 6
2.2 BORAX-I 7
3. Highlights of Community Participation 8
4. Scopes and Roles of Operable Units and
Response Actions 10
5. Site Characteristics 11
5.1 SL-1 11
5.1.1 Previous Investigations . 11
5.1.2 Nature and Extent 12
5.1.3 Fate and Transport 16
5.2 BORAX-I 16
5.2.1 Previous Investigations 17
5.2.2 Nature and Extent 17
5.2.3 Fate and Transport 19
6. Summary of Site Risks 20
6.1 Human Health Risks 21
6.1.1 Contaminant Identification 21
.2 Exposure Assessment 22
.3 Toxicity Assessment 24
.4 Human Health Risk Characterization
25
6. .5 Uncertainty 35
6. .6 Conclusions 37
6.2 Ecological Concerns 38
6.2.1 Species of Concern 38
6.2.2 Exposure Assessment 39
6.2.3 Risk Characterization 39
6.3 Basis for Response 39
7. Description of Alternatives 40
7.1 Remedial Action Objectives and Applicable
or Relevant and Appropriate Requirements .... 40
7.1.1 Remedial Action Objectives 40
7.1.2 Applicable or Relevant and Appropriate
Requirements 41
7.2 Summary of Alternatives 42
7.2.1 No Action 42
7.2.2 Containment 43
7.2.3 Removal and Disposal 45
8. Summary of Comparative Analysis of
Alternatives 46
8.1 Threshold Criteria 46
8.1.1 Overall Protection of Human Health
and the Environment 46
8.1.2 Compliance with Applicable or Relevant
and Appropriate Requirements 47
8.2 Balancing Criteria 47
8.2.1 Long-Term Effectiveness and Permanence ... 47
8.2.2 Reduction of Toxicity, Mobility, or
Volume through Treatment 48
8.2.3 Short-Term Effectiveness 48
8.2.4 Implementability 48
8.2.5 Cost 49
8.3 Modifying Criteria 51
8.3.1 State Acceptance 52
8.3.2 Community Acceptance 52
9. Selected Remedy 52
9.1 Description of Selected Remedy 53
9.2 Remediation Goals 55
9.3 Estimated Cost Details for the Selected Remedy 56
10. Statutory Determinations 59
10.1 Protection of Human Health and the
Environment 59
10.2 Compliance with ARARs 60
10.2.1 ARARs 60
10.2.2 To-Be-Considered Guidance 61
10.3 Cost Effectiveness 61
10.4 Use of Permanent Solutions and Alternative
Treatment Technologies to the Maximum
Extent Practicable 61
10.5 Preference for Treatment as a Principal Element . 63
11. Documentation of Significant Changes 63
11.1 Surface Soil Consolidation 63
11.2 Monitoring 64
11.2.1 Groundwater Monitoring 64
11.2.2 Air Monitoring 64
11.2.3 Soil Monitoring 65
11.3 Cost Refinements 65
11.4 Operable Unit 5-05 Boundary 65
11.5 Other Changes to the Proposed Plan .66
12. Decision Summary for No Action Sites 66
12.1 Site Name, Location, and Description 66
12.2 Site History and Enforcement Activities 67
12.3 Highlights of Community Participation 68
12.4 Scope and Role of Operable Unit or
Response Action 68
12.4.1 Auxiliary Reactor Area Sites 68
12.4.2 Power Burst Facility Sites 68
12.5 Site Characteristics 69
12.6 Summary of Site Risks 69
12.6.1 Wastewater Disposal Sites 69
12.6.2 Soil-Contamination Sites 71
12.6.3 Underground Storage Tanks 71
12.7 Description of the No Action Alternative 72
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Appendices
Appendix A A-l
Responsiveness Summary A-3
Figures
1. Location of the SL-1 and BORAX-I burial grounds
at the INEL .2
A.I Overview A-3 2. SL-1 burial ground site map 3
A.2 Background on Community 3. BORAX-I burial ground site map 3
Involvement A-3 4. 1990 isoplethic map of SL-1 13
A.3 Summary of Comments with Responses A-5 5. 1990 isoplethic map of BORAX-I 13
A.4 Comment and Response Index A-16 6. Graphical summary of risk for SL-1 31
Appendix B B-l 7. Graphical summary of risk for BORAX-I 33
Administrative Record File Index . .B-3 8. Graphical summary of external exposure risk based
AR1.1 Background B-3 on measured radiological fields and natural
AR1.7 Initial Assessments B-5 background, SL-1, and BORAX-I 35
AR3.8 Risk Assessment B-5 9. Waste Area Group 5 facilities and no further
AR3.10 Scope of Work B-6 action sites 67
AR3.12 Remedial Investigation/Feasibility
Study B-6
AR4.3 Proposed Plan B-6
Tables
1. Contaminants of concern and surface soil
concentrations at SL-1 14
2. Potential contaminants of concern and estimated
subsurface concentrations at SL-1 for non-
groundwater pathways 15
3. Contaminants of concern and surface soil
concentrations at BORAX-I 18
4. Potential contaminants of concern and estimated
subsurface concentrations at BORAX-I for
non-groundwater pathways .19
5. Summary of risks for the potential exposure scenarios
and pathways at SL-1 27
6. Summary of risks for the potential exposure scenarios
and pathways at BORAX-I 29
7. Summary of risk assessment assumptions and
associated uncertainties 36
8. Summary of ARARs and criteria to be considered for
alternatives 41
9. SL-1 alternative cost estimates 51
10. BORAX-I alternative cost estimates .. . . 51
11. SL-1 selected remedy detailed cost estimate 57
12. BORAX-1 selected remedy detailed
cost estimate 58
A-l Estimates of dose for the 30-year residential
intrusion scenario A-6
A-2 Minimum and maximum vadose zone water travel
times (years) considered in the sensitivity/
uncertainty analysis . . .'. A-8
A-3 Index of comments A-17
viii
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Acronyms and Abbreviations
ARA Auxiliary Reactor Area
ARAR applicable or relevant and appropriate requirements
BORAX-I Boiling Water Reactor Experiment-I
°C degree(s) Celsius
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
cm centimeter(s)
DOE U.S. Department of Energy
DOE-ID U.S. Department of Energy, Idaho Operations Office
EPA U.S. Environmental Protection Agency
°F degrees Fahrenheit
g gram(s)
IDAPA Idaho Administrative Procedures Act
IDHW Idaho Department of Health and Welfare
INEL Idaho National Engineering Laboratory
km kilometer(s)
m meter(s)
m2 square meter(s)
mg milligram(s)
mR milliroentgen
firem/hr microroentgen equivalent man per hour
nCi nanocurie(s)
PBF Power Burst Facility
pCi picocurie(s)
RI/FS Remedial Investigation/Feasibility Study
SARA Superfund Amendments and Reauthorization Act
sec second
SL-1 Stationary Low-Power Reactor-1
TBC To-Be-Considered
WAG Waste Area Group
yr year
ix
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Decision Summary
1. Site Name, Location, and Description
The Idaho National Engineering Laboratory (INEL) is a government facility managed by the
U.S. Department of Energy (DOE). The main security gate in the southern portion of the site is located
44 miles (71 km) west of Idaho Falls, Idaho. The INEL occupies 890 square miles (2,305 km2) of the
northeastern portion of the Eastern Snake River Plain. The Stationary Low-Power Reactor-1 (SL-1)
and Boiling Water Reactor Experiment-I (BORAX-I) burial grounds are approximately 38 and 52 miles
(61 and 84 km) west of Idaho Falls (Figure 1).
The SL-1 site is located about 1,600 feet (488 m) northeast of the Auxiliary Reactor Area n and
includes the surface-soil area surrounding a 600- by 300-foot (182.9- by 91.4-m) fenced burial ground
(Figure 2). Approximately 99,000 cubic feet (2,800 m3) of radionuclide-contaminated debris, soil, and
gravel are disposed of in the burial ground. An estimated 2 feet (0.6 m) of soil with a thick grass cover
lies over the waste.
The BORAX-I burial ground is located about 2,730 feet (832 m) northwest of the Experimental
Breeder Reactor-1, a national monument. The BORAX-I site includes a 200- by 420-foot (61- by
128-m) surface-soil contamination area surrounding the 100- by 100-foot (30- by 30-m) fenced burial
ground (Figure 3). The volume of buried radionuclide-contaminated soil and debris is approximately
6,336 cubic feet (180 m3). The 84,000-square foot (7,800-m2) area was covered with 6 inches of
gravel in 1954, but grass, sagebrush, and other plants have reseeded the area since then.
The INEL was originally established as the National Reactor Testing Station by the U.S. Atomic
Energy Commission in 1949. The National Reactor Testing Station's mission was to build, test, and
operate nuclear reactors, fuel processing plants, and support facilities. The INEL's current mission, as
directed by the DOE, is the integration of engineering, applied science, and operations in an environ-
mentally conscious, safe, and cost-effective manner.
The SL-1 and BORAX-I burial grounds are historical disposal areas and do not host any current
programs. Current activities are limited to periodic observations for maintenance of the fences and
grounds and monitoring for radioactivity.
Of the approximately 11,700 people employed at the INEL, none work full time at either burial
ground. There are no residential communities within the INEL boundaries. The nearest residential
community is Atomic City, located approximately 1 mile (1.6 km) south of the INEL boundary, with a
population of 25. Larger communities near the INEL include Idaho Falls, located approximately 44
miles (71 km) to the east of the main gate, with a population of 43,973; Blackfoot, located approxi-
mately 37 miles (60 km) to the southeast, with a population of 9,646; and Arco, located approximately
19 miles (31 km) to the west, with a population of 1,016.
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ARA Auxiliary Reactor Area
ANL-W Argonne National Laboratory-West
BORAX-I Boiling Water Reactor Experiment I
CFA Central Facilities Area
EBR-I Experimental Breeder Reactor I
EBR-II Experimental Breeder Reactor II
ICPP Idaho Chemical Processing Plant
IET Initial Engine Test
LOFT Loss-of-Fluid Test (facility)
NRF Naval Reactor Facility
PBF Power Burst Facility
RWMC Radioactive Waste Management Complex
SL-1 Stationary Low-Power Reactor No. 1
TAN Test Area North
TRA Test Reactor Area
TSF Technical Support Facility
WRRTF Water Reactor Research Test Facility
INEL boundary
Roads
Facilities
Towns
Pioneer Basin
boundary
To Salmon
ToDubois
INEL
890 square miles
2,305 square kilometers
ICPP
PBF
CFA /"ARA ill
ARA
14 mi
11
Approximate scale
22km
INEL boundary groundwater INEL Atomic City *N.
receptor location for BORAX I boundary groundwater To Blackfoot
receptor location for SL-1
Pioneer Basin
Figure 1. Location of the SL-1 and BORAX-I bur^l grounds at the INEL.
2
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Operable Unit 5-05
LEGEND
Fence
Exclusion Fence
Estimated boundwy of OU 5-05
^••••M Area of surface soil evaluated
in the taase(tn« nsk assessment
- — - — Estimated boundary of ARA-23
M950332
Figure 2. SL-1 burial ground site map.
Figure 3. BORAX-I burial ground site map.
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Most of the area surrounding the INEL is either unimproved rangeland or farmland, and approxi-
mately 330,000 acres (1,300 km2) of the INEL are open to grazing by permit. However, grazing is
prohibited within 2 miles (3 km) of any nuclear facility, and no dairy cows are allowed. Approximately
95% of the INEL site has been withdrawn from the public domain by land transfer from the U.S.
Bureau of Land Management to the DOE.
The climate of the region is arid to semiarid. Average annual precipitation is 8.71 inches (22 cm),
wind is generally from the southwest with average speeds of 5 to 9 miles per hour (8 to 15 km/hour),
and average air temperatures are 64.6°F (18.1°C) in the summer and 18.8°F (-7.3°C) in the winter.
The INEL lies in the Pioneer Basin, a closed topographic depression located on the Eastern Snake
River Plain. Elevations range from approximately 4,800 to 5,400 feet (1,463 to 1,646 m) with a total
relief of about 600 feet (183 m). The area receives surface water from rainfall, snowmelt, and stream-
flow. The streamflow sources are the Big Lost River, the Little Lost River, and Birch Creek.
Streamflow that reaches the INEL goes to the Big Lost River playa or the Birch Creek playa and is lost
to evaporation and infiltration. Consequently, there is little available surface water within the INEL site
boundaries and none available at the SL-1 and BORAX-I sites.
The Eastern Snake River Plain is a broad, flat plain composed of thick basaltic flows covering rhy-
olitic calderas. The flows occur as layers of lava, ranging from a few inches to a few feet thick, inter-
spersed with cinders, breccia, and unconsolidated sediments. Much of the INEL's land surface consists
of basalt flows. The western and central portions of the INEL lie within the floodplain of the Big Lost
River, which extends across the site from the southwest to the northeast. Alluvial deposits from the
Big Lost River grade into lacustrine (lake) deposits in the northern portion of the INEL where the Big
Lost River enters
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The variety of habitats on the INEL support numerous species of reptiles, birds, and mammals. Ten
reptiles, including the short-horned lizard, the gopher snake, the sagebrush lizard, and the western rat-
tlesnake, and one amphibian species, the Great Basin spadefoot toad, have been observed on the site.
A total of 164 species of birds inhabit the INEL, including sparrows, raptors, waterfowl, swallows,
American kestrels, killdeers, American robins, sage thrashers, sage sparrows, western meadowlarks,
house sparrows, and mallards during the breeding season and sage grouse, rock doves, horned larks,
and black-billed magpies year-round. The 37 species of mammals found on the site include 18 species
of rodents, four species of leporids, and six species of carnivores. The most common rodents are the
Townsend's ground squirrel, the least chipmunk, the Great Basin pocket mouse, and Ord's kangaroo
rat; the dominant leporid is the rabbit; common carnivores are the coyote and the long-tailed weasel.
Pronghorn antelope and mule deer are frequently observed.
Only two species have been identified at the INEL that are classified as endangered or threatened:
the bald eagle and the American peregrine falcon. The bald eagle has been seen in the winter months
at or around the INEL, and the peregrine falcon has been observed in the northern portion of the INEL
on rare occasions.
2. Site History and Enforcement Activities
The SL-1 and BORAX-I burial grounds were constructed to dispose of contaminated debris, soils,
and gravel generated by the destruction of a small nuclear reactor at each location. The BORAX-I bur-
ial ground was established in 1954; the SL-1 burial ground was established in 1961. Both sites were
identified in the Consent Order and Comph'ance Agreement which was signed by the EPA and the DOE
and promulgated in 1987 pursuant to the Resource Conservation and Recovery Act Section 3008(h).
Under this agreement, the DOE initially assessed and screened the identified sites and established a
procedure for conducting corrective actions. Both burial grounds were identified as solid waste man-
agement units. The INEL was proposed for listing on the National Priorities List in July 1989. The
listing was proposed by the EPA under authorities granted by the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980. This act is also referenced by the acronym
"CERCLA" or as the "Superfund." The act was amended by the Superfund Amendments and
Reauthorization Act of 1986. References to CERCLA include the amendments of 1986. The National
Priorities List identifies the highest risk sites, as determined by a screening and ranking process, which
are to be remediated via the CERCLA process. The INEL was officially placed on the National
Priorities List in November 1989.
Subsequent to the CERCLA listing, the DOE, the EPA, and the IDHW (collectively referred to as
the agencies) negotiated a Federal Facility Agreement and Consent Order and an Action Plan for reme-
diation of the INEL. The documents were signed in December 1991. Both burial grounds were classi-
fied as Track 2 operable units, described in the Action Plan as operable units that may require field data
collection before a remedial decision could be reached. A Track 2 investigation would determine if no
further action, an interim action, or a remedial investigation/feasibility study was warranted.
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Results of the 1993 Track 2 preliminary scoping for the SL-1 burial ground led the agencies to con-
clude that the evaluation of the site should be elevated to a remedial investigation/feasibility study. The
scope of the investigation was limited to existing data, considered sufficient by the agencies to deter-
mine a remedial action for the site, and a feasibility study focused on examining remedial alternatives
selected in other Records of Decision for similar sites. In addition, because of the similarities of the
BORAX-I burial ground to the SL-1 burial ground, the agencies determined that both sites would be
assessed in the same remedial investigation/feasibility study.
This Record of Decision documents the remedy selected based on the results of the remedial inves-
tigation/feasibility study and additional information contained in the Administrative Record for
Operable Units 5-05 and 6-01. Additional details concerning the history of each of the two burial
grounds follow in the next two subsections.
2.1 SL-1
The SL-1 was a small nuclear power plant designed for the military to generate electric power and
heat for remote arctic installations. The reactor was operated from August 1958 until January 3, 1961,
as a test, demonstration, and training facility. On the evening of January 3, 1961, the SL-1 reactor
accidentally achieved a prompt critical nuclear reaction, which caused a steam explosion that destroyed
the reactor and resulted in the deaths of the three operators on duty. The reactor vessel and building
were severely damaged and highly contaminated, and a massive cleanup operation ensued to dismantle
and dispose of the reactor and building.
A burial ground was constructed approximately 1,600 feet (488 m) northeast of the original site of
the reactor. This was done to minimize radiation exposure to the public and site workers that would
have resulted from transport of contaminated debris from SL-1 to the Radioactive Waste Management
Complex over 16 miles (26 km) of public highway. Original cleanup of the site took about 18 months.
The entire reactor building, contaminated materials from nearby buildings, and soil and gravel contami-
nated during cleanup operations were disposed of in the burial ground. The majority of buried materi-
als consists of soils and gravel.
Recovered portions of the reactor core, including the fuel and all other parts of the reactor that were
important to the accident investigation, were taken to the ENEL's Test Area North for study. After the
accident investigation was complete, the reactor fuel was sent to the Idaho Chemical Processing Plant
for reprocessing. The reactor core minus the fuel, along with the other components sent to Test Area
North for study, was eventually disposed of at the Radioactive Waste Management Complex.
The SL-1 burial ground consists of three excavations, in which a total volume of 99,000 cubic feet
(2,800 m3) of contaminated material was deposited. The excavations were dug as close to basalt as the
equipment used would allow and ranged from 8 to 14 feet (2.4 to 4.3 m) in depth. At least 2 feet
(0.6 m) of clean backfill was placed over each excavation. Shallow mounds of soil over the excava-
tions were added at the completion of cleanup activities in September 1962. Operable Unit 5-05 is
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defined as the surface and subsurface soils and debris within the 600- by 300-foot (183- by 91-m) SL-1
burial ground exclusion fence and the surface area surrounding the burial ground (see Figure 2). Other
residual surface contamination from the SL-1 accident is being investigated in Waste Area Group 5
under Operable Unit 5-12, site code Auxiliary Reactor Area (ARA)-23, which is southwest of and adja-
cent to Operable Unit 5-05 (see Figure 2). ARA-23 includes the original location of the SL-1 reactor.
Numerous radiation surveys and cleanup of the surface of the burial ground and surrounding area
have been performed in the years since the SL-1 accident. Aerial surveys were performed by EG&G
Las Vegas in 1974, 1982, 1990, and 1993. The Radiological and Environmental Sciences Laboratory
conducted gamma radiation surveys every 3 to 4 years between 1973 and 1987 and every year between
1987 and 1994. Particle-picking at the site was performed in 1985 and 1993. Results from the surveys
indicate that cesium-137 and its progeny (decay product) are the primary surface-soil contaminants.
During a survey of surface soil in June 1994, "hot spots," areas of higher radioactivity, were found
within the burial ground with activities ranging from 0.1 to 50 milliroentgen (mR)/hour. On
November 17, 1994, the highest radiation reading measured at 2.5 feet (0.75 m) above the surface at
the SL-1 burial ground was 0.5 mR/hour; local background radiation was 0.2 mR/hour. A dose equiva-
lent rate survey was conducted in 1995; all locations surveyed within Operable Unit 5-05 yielded read-
ings at or below the background value of 20 u,rem/hr.
Today the SL-1 burial ground is defined by a three-strand, barbed-wire exclusion fence posted with
radiological control signs. Inside the burial ground the ends of the excavations are identified by con-
crete markers. The surface of the burial ground is covered with various grass species. The two
mounds and several minor depressions due to subsidence are visible within the fenced area. A second
radiological-control fence encompasses the burial ground, a larger contaminated surface soil area, and
the Auxiliary Reactor Area I and n facilities. The fences, posted with radiological-control signs, and
restricted access protect INEL workers and the public from exposure.
2.2 BORAX-I
The BORAX-I reactor was a small experimental reactor used in the summer months of 1953 and
1954 for testing boiling-water reactor technology. In 1954, the design mission of BORAX-I was com-
pleted, and the decision was made to make one final test, whirv TS"lted in the intentional destruction
of the reactor. The destruction of the reactor contaminated approximately 84,000 square feet of the
surrounding terrain. Immediately following the final test of the BORAX-I reactor, much of the
radioactive debris, including some fuel residue, was collected and buried on site in the reactor shield
tank. Recovered fuel fragments and fuel residue were sent to the Idaho Chemical Processing Plant and
Oak Ridge National Laboratory in Tennessee. Reusable equipment associated with the reactor was
successfully decontaminated and used in the construction of BORAX-II. However, the cleanup did not
sufficiently reduce the radioactivity at the site; therefore, the 84,000-square foot (7,800-m2) contami-
nated area was covered with approximately 6 inches (15 cm) of gravel to reduce radiation levels at the
ground surface.
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Buried materials at the site consist of unrecovered uranium fuel residue, irradiated metal scrap, and
contaminated soil and debris. Part of the waste was buried in the bottom half of the shield tank; the top
half of the tank was collapsed into the bottom and the void space was filled with debris. The burial
ground is contained within the foundation of the BORAX-I installation, the dimensions of which are 18
by 32 by 11 feet (5.5 by 9.8 by 3.4 m). A mounded gravel and dirt cover approximately 5 feet (1.5 m)
high and 30 feet (9 m) in diameter is centered over the buried shield tank. Operable Unit 6-01 includes
the buried debris, as well as the 84,000-square feet (7,800-m2) of contaminated surface soil.
Field radiation surveys conducted in 1978 and 1980 detected radiation at about three times the
background levels in the central portion of the gravel-covered 84,000-square foot (7,800-m2) area
south-southeast of the buried reactor. Radiation in adjacent areas was at background levels. Surface
and subsurface soil sampling of the 84,000-square foot (7,800-m2) gravel-covered area in 1978 and
1980 indicated that radioactive contamination exists and is highest at a depth of approximately 6 inches
(15 cm) at the interface of the gravel cover and the original ground surface. Ongoing monitoring of the
site through the use of radiation dosimeters shows that radiation levels are slightly above background
levels. On November 18, 1994, the radiological field measured at 2.5 feet (0.75 m) above the surface
of the BORAX-I burial ground was 0.1 mR/hour; local background radiation was also 0.1 mR/hour.
Today, the ground surface at the site looks very much like the surrounding terrain. Abundant native
vegetation has grown over the mound and surrounding area. A large stake about 5 feet (1.5 m) tall marks
the reactor location. A 6-foot (1.8-m)-high chain-link fence surrounds the burial ground, forming an
enclosed area approximately 100 feet (30 m) on each side. The contaminated surface soil area outside of
the chain-link fence is bounded by a two-wire exclusion fence. The fences, posted with radiological-control
signs, and restricted access protect INEL workers and the public from unacceptable exposures.
3. Highlights of Community Participation
In accordance with the CERCLA §113(k)(2)(B)(i-v) and §117, a series of opportunities for public
information and participation in the remedial investigation and decision process for the SL-1 and
BORAX-I burial grounds was provided to the public from September 1994 through May 1995. For the
public, notifications included fact sheets that briefly discussed the investigation to date, INEL Reporter
art'~'es nnd updates, a proposed plan, telephone briefings, and public meetings. The INEL Reporter is
a periodic, public information publication of the INEL's Environmental Restoration Program.
In September 1994, a fact sheet concerning the SL-1 and BORAX-I remedial investigation/feasibil-
ity study was sent to about 6,700 individuals of the general public and to 650 INEL employees on the
INEL Community Relations Plan mailing list.
The project was discussed at informal semiannual briefings in Twin Falls (October 11, 1994),
Pocatello (October 13, 1994), Moscow (October 18, 1994), Boise (October 19, 1994), and Idaho Falls
(October 20, 1994). During these briefings, representatives from the DOE and the INEL discussed the
project, answered questions, and listened to public comments.
8
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Regular reports concerning the status of the project were included in the INEL Reporter and were
mailed to those who were on the mailing list. Reports also appeared in two issues of Citizens' Guide
(a supplement to the INEL Reporter).
In April 1995, another fact sheet concerning the project was sent to about 6,700 individuals of the general
public and to 650 INEL employees on the INEL Community Relations Plan mailing list. On April 11, 1995,
the DOE issued a news release to more than 100 contacts concerning the beginning of a 30-day public com-
ment period, which began May 3, 1995, and ended June 3, 1995, pertaining to the SL-1 and BORAX-I pro-
posed plan. Many of the news releases resulted in a short note in community calendar sections of newspa-
pers and in public service announcements on radio stations. Both the fact sheet and news release gave notice
to the public that SL-1 and BORAX-I documents would be available before the beginning of the comment
period in the Administrative Record section of the INEL Information Repositories located in the INEL
Technical Library of Idaho Falls, in the INEL Boise Office, and in public libraries in Idaho Falls, Fort Hall,
Pocatello, Twin Falls, Boise, and Moscow. Also, table top displays were set up at the Grand Teton Mall in
Idaho Falls (May 15-20), Burley Public Library (April 24-May 5), Twin Falls Public Library (May 5-26),
Boise Towne Square Mall (April 29), and the Pocatello City Building (April 24-May 15).
Opportunities for public involvement in the decision process for the SL-1 and BORAX-I project
began in May 1995. For the public, the activities included receiving the proposed plan, receiving tele-
phone calls, attending the availability sessions at public meetings to informally discuss the issues, and
submitting verbal and written comments to the agencies during the 30-day public comment period.
Copies of the proposed plan for SL-1 and BORAX-I were mailed to about 6,700 members of the pub-
lic and to 650 INEL employees on the INEL Community Relations Plan mailing list on April 28, 1995,
urging citizens to comment on the proposed plan and to attend public meetings. Display advertisements
announcing the same information and the locations of public meetings on May 16, 17, and 18, 1995, in
Idaho Falls, Boise, and Moscow, respectively, appeared in seven major Idaho newspapers. Large adver-
tisements appeared in the following newspapers on April 26: the Post Register (Idaho Falls); the Idaho
State Journal (Pocatello); the South Idaho Press (Burley); the Times News (Twin Falls); the Idaho
Statesman (Boise); the Lewiston Morning Tribune (Lewiston); and the Daily News (Moscow).
Post cards were mailed on May 10, 1995, to about 6,700 members of the public and to 650 INEL
employees on the INEL Community Relations Plan mailing list to encourage them to attend the public
meetings and to provide verbal or written comments. News releases and newspaper advertisements
gave public notice of public involvement activities. Offerings for briefings and the 30-day public com-
ment period that was to begin May 3 and run through June 3, 1995 were also announced. Personal
calls were made to stakeholders in Idaho Falls, Pocatello, Twin Falls, Boise, and Moscow the weeks of
May 8 and 15 to remind individuals about the meetings.
Written comment forms, including a postage-paid business-reply form, were made available to
those aftending the public meetings. The forms were used to submit written comments either at a
-------
meeting or by mail. The reverse side of the meeting agenda contained a form for the public to evaluate
the effectiveness of the meetings. A court reporter was present at each meeting to keep transcripts of
discussions and public comments. The meeting transcripts were placed in the Administrative Record
sections for SL-1 and BORAX-I, Operable Units 5-05 and 6-01, in five INEL Information
Repositories. For those who could not attend the public meetings but wanted to make formal written
comments, a postage-paid written comment form was attached to the proposed plan.
A Responsiveness Summary has been prepared as part of the Record of Decision. All formal verbal
comments, as given at the public meetings, and all written comments, as submitted, are included in
Appendix A and in the Administrative Record for the Record of Decision. Those comments are annotated
to indicate which response in the Responsiveness Summary addresses each comment.
A total of about 10 people not associated with the project attended the SL-1/BORAX-I public
meetings. Overall, 10 provided formal comment; of these 10 people, three provided oral comments,
and seven provided written comments. All comments received on the proposed plan were considered
during the development of this Record of Decision. The decision for this action is based on the infor-
mation in the Administrative Record for these operable units.
On August 2, 1995, the project manager from the Idaho Department of Health and Welfare Division
of Environmental Quality gave a brief presentation on the projects to the Environmental Management
Site Specific Advisory Board — Idaho National Engineering Laboratory. The advisory board is a
group of individuals representing the citizens of Idaho, making recommendations to DOE, EPA, and
the state of Idaho regarding environmental restoration activities at the INEL.
4. Scopes and Roles of Operable Units and Response Actions
Under the Federal Facility Agreement and Consent Order, the INEL is divided into ten waste area
groups. Each waste area group is further subdivided into operable units, each of which may contain one or
more sites. The first nine waste area groups correspond to particular operating facilities on the INEL; the
tenth waste area group represents the entire INEL and the Snake River Plain Aquifer. The SL-1 site is part
of Waste Area Group 5, which contains 13 operable units and is the only site in Operable Unit 5-05. The
BORAX-I site is in Waste Area Group 6 and is the only site in Operable Unit 6-01. A complete evaluation
of all cumulative risks associated with CERCLA action in Waste Area Groups 5 and 6 will be addressed in
the respective comprehensive remedial investigation/feasibility study for each waste area group.
Cumulative risks for the entire INEL will be addressed in the Waste Area Group 10 risk assessment.
Existing data from past operating and disposal activities were available to expedite the evaluation of
these sites. Therefore, the scope of the remedial investigation for the SL-1 and BORAX-I burial
grounds did not include any sampling or acquisition of new data, and a Work Plan was not produced.
A focused feasibility study, one that examined only those alternatives that had been previously selected
in Records of Decision for similar sites, was performed.
10
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The SL-1 site is defined as the buried waste in the SL-1 burial ground plus the surface soils in the sur-
rounding area shown in Figure 2. The BORAX-I site is defined as the buried waste in the BORAX-I burial
ground plus the surface soil in the surrounding 84,000-square foot (7,800-m2) area illustrated in Figure 3.
This Record of Decision addresses the contaminated surface soils and buried wastes at both burial grounds.
Both of these sites pose unacceptable risk to human health and the environment, primarily because of the
risks from direct exposure to ionizing radiation from the buried wastes. There is also a lesser but still unac-
ceptable nsK due to soil ingestion. The purpose of this response is to inhibit current or future exposure to
the buried waste and to reduce risks from soil ingestion.
5. Site Characteristics
This section summarizes the historical data used to evaluate contamination at the SL-1 and BORAX-I
burial grounds. The agencies determined that sufficient data exist to recommend a remedial action for
each site, therefore, no sampling was conducted for the remedial investigation. A complete discussion of
the site characteristics for the SL-1 and BORAX-I burial grounds can be found in the remedial investiga-
tion/feasibility study and the Administrative Record for Operable Units 5-05 and 6-01.
5.1 SL-1
On January 3, 1961, the SL-1 reactor was destroyed by an accidental nuclear excursion that resulted in
a steam explosion. Very little contamination was released to the environment at the time of the accident
due to the containment provided by the reactor building; however, demolition and cleanup activities result-
ed in the spread of contamination over surface soils from Auxiliary Reactor Area n to the SL-1 burial
ground. Numerous radiological surveys, surficial soil sampling, and particle-picking activities have been
conducted in the years since the accident. The following section summarizes the results of these activities.
5.1.1 Previous Investigations
The DOE's Radiological and Environmental Sciences Laboratory conducted gamma radiation sur-
veys in the vicinity of Auxiliary Reactor Areas I and n and the SL-1 burial ground every 3 to 4 years
between 1973 and 1991. The areas north of Auxiliary Reactor Areas I and II and northeast of the SL-1
burial ground had the highest gamma radiation intensities. Soil sampling in 1977 found that
cesium-137 was the primary contaminant.
The INEL's Waste Management Group surveyed areas in the vicinity of Auxiliary Reactor Area O
and outside of the SL-1 burial-ground fence in 1985. The survey identified and mapped 236 radioactive
particles, of which 219 had maximum surface readings of 20 mR/hour or greater. Of these, 16 had read-
ings greater than 200 mR/hour (the maximum reading possible for the instruments used in the survey).
A total of 44 of the particles were removed. Particles with readings greater than 200 mR/hour that were
located on the road between Auxiliary Reactor Area n and the burial ground or were located in the dis-
turbed area across Fillmore Boulevard from Auxiliary Reactor Area n were removed.
The INEL's Environmental Monitoring Unit conducted annual radiological surveys of surface soils
within the SL-1 burial ground fence from 1987 through 1992. One-third of the area was surveyed each
11
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year; at the end of each three-year period, the entire area had been surveyed. From 1987 to 1989, read-
ings ranged from 0.05 to 11.0 mR/hour measured at contact. From 1990 to 1992, readings ranged from
0.04 to 4.42 mR/hour measured at contact.
In 1993, the Environmental Monitoring Unit performed a surface-soil radiological survey and parti-
cle-picking at the SL-1 burial ground. There were 874 particles identified with readings from 0.01 to
200 mR/hour at contact. Particles reading greater than 0.15 mR/hour were removed if they were locat-
ed hi the top 3 inches (7.6 cm) of soil. Of the 874 particles, 709 were removed for disposal at the
Radioactive Waste Management Complex. Activity levels of the particles deeper than 3 inches
(7.6 cm) and left in place ranged from 0.01 to 50 mR/hour.
As part of the 1993 effort, an area immediately adjacent and northeast of the burial ground was
investigated. Of the 163 particles identified, 66 were removed. The remaining particles were located
at a depth of greater than 3 inches (7.6 cm) and had activities ranging from 1.0 to 250 mR/hour. Three
soil samples were collected from a depth of 0 to 1 foot (0 to 0.3 m).
Four soil samples were collected from the vicinity of the SL-1 burial ground in a separate, unrelat-
ed sampling effort conducted in 1993 as part of the Waste Area Group 3 and Waste Area Group 10 soils
treatabih'ty study. The soil samples were analyzed for gross alpha, gross beta, and cesium-137.
A surface-soil survey in June 1994 found 217 particles within the burial-ground fence, with activi-
ties ranging from 0.1 to 50 mR/hour. There were 51 particles identified in the area just northeast of the
burial ground, with activities ranging from 0.2 to 250 mR/hour. In November 1994, a survey was con-
ducted to determine radiation levels within the burial ground at a height of 2.5 feet (0.8 m). A maxi-
mum of 0.5 mR/hour was detected at two locations; the remainder of the area was at the local back-
ground of 0.2 mR/hour.
Aerial surveys of the SL-1 burial ground were conducted in 1974, 1982, 1990, and 1993. The sur-
veys detected gamma radiation from man-made sources in the area, with cesium-137 the primary con-
tributor. The 1990 survey, which was used to define the site boundary, is illustrated in Figure 4. A risk
assessment was completed in August 1995 on the basis of soil samples and dose equivalent rate mea-
surements within the isopleth defined by the 1990 aerial survey (see Section 11.1).
5.1.2 Nature and Extent
5.1.2.1 Surface Contamination. Operable Unit 5-05 comprises the area illustrated in Figure 2.
Based on the original source of surface contamination (aerial distribution of contaminants during
demolition and cleanup of the SL-1 reactor) and the limited mobility of radionuclides in the soil at the
INEL, it is believed that contamination is restricted to the upper 0.5 foot (0.15 m) of soil. For the
remedial investigation, identification of the contaminants of concern associated with surface soils at
SL-1 was based on comparison of analytical data with background concentrations. Concentrations of
12
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Mill I
fflSL-1 Burial
ound
Figure 4. 1990 isoplethic map of SL-1.
BORAX-V
B
Letter
Label
Counts per
second
A
B
C
D
E
G < 1,100
1,100-3,500
3,500-11,000
11,000 - 35,000
35,000-110,000
Preliminary Data Results. The data shown
here have been processed in a manner
that suppresses the natural background.
The results are displayed as relative levels
of manmade radionudide activity. It is
nearly impossible to convert the relative
levels of activity to a meaningful exposure
rate because of the complex distribution
of the nudides.
Feet
0 1,000 2,000 3,000
I ' i i
I ' ' ^r
0 300 600 900
Meters
Letter Counts per
Label second
< 1,100
B LJ 1,100-3,500
C BUD 3,500 -11,000
D | 11,000 - 35,000
Preliminary Data Results. The data shown
here have been processed in a manner
that suppresses the natural background.
The results are displayed as relative levels
of manmade radionudide activity. It is
nearly impossible to convert the relative
levels of activity to a meaningful exposure
rate because of the complex distribution
of the nudides.
Feet
0 1,000 2,000 3,000
0 300 600
Meters
900
Figure 5. 1990 isoplethic map of BORAX-I.
13
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the contaminants of concern for surface soils were based on the 95% upper confidence limit of the ana-
lytical data, and the assumption was made that each contaminant is uniformly distributed across the
site. Table 1 presents the contaminants of concern for surface soils.
An assessment of the surface soils surrounding the SL-1 burial ground was concluded in August
1995 subsequent to the remedial investigation and proposed plan. Based on the results of this assess-
ment, all dose equivalent rates within the Operable Unit are at or below the background value of 20
uxem/hr.
Table 1. Contaminants of concern and surface soil concentrations at SL-1.
Concentration (pCi/g)
Radionuclide 95% upper confidence limit INEL Backgrounda
Cobalt-60
Cesium-137
Europium-154
Strbntium-90
Thorium-228
Thorium-230 and/or uranium-234
Thorium-232
0.36
904
2.68
1,370
1.6
2.7
1.4
No data available
1.28
No data available
0.76
2.1b
1.88, 1.95
2.1b
a. 95%/95% upper tolerance limit, grab sample background concentrations from Background Dose Equivalent Rates and
Surficial Soil Metal and Radionuclide Concentrations for the Idaho National Engineering Laboratory, INEL-94/0250,
S. M. Rood, G. A. Harris, G. J. White, February 1995.
b. Thorium-228 and -232 were retained for evaluation based on background data that were available when the remedial investiga-
tion was prepared; the above-referenced background document was released after the remedial investigation was finalized.
5.1.2.2 Subsurface Contamination. Subsurface contamination at the SL-1 burial ground is
restricted to the excavations that received contaminated building debris, equipment, and gravel and soil
from the demolition and cleanup following the SL-1 reactor accident. The estimated volume of buried
contaminated material is 99,000 cubic feet (2,800 m3).
The inventory and activities of radionuclides in the subsurface of the SL-1 burial ground were estimated
using the computer model ORIGEN2. Because 93% of the uranium-235 fuel was recovered during the acci-
dent investigation and cleanup, it was assumed that only 7% of the original quantity of fuel was disposed of in
the SL-1 burial ground. Inventories of radionuclide activities were generated for 1961, 1994, 2024, and 2094
and were utilized in the baseline risk assessment to calculate risks for current, 30-year future, and 100-year
future scenarios. Inventories were calculated for specific times to account for the decay (decrease through
time) of parent radionuclides and the ingrowth (an increase through time) of radioactive progenies. The con-
centration of each contaminant of concern for each time evaluated was estimated using the assumption that
7% of the model-generated activity for each contaminant of concern was uniformly distributed throughout the
source volume. Table 2 presents contaminants of concern for the subsurface and estimated concentrations.
14
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Table 2. Potential contaminants of concern and estimated subsurface concentrations at SL-1 for
non-groundwater pathways.
Radionuclide
Cesium- 137
Strontium-90
Krypton-85
Samarium- 151
Promethium-147
Plutonium-241
Europium- 154
Europium- 155
Plutonium-239
Technetium-99
Plutonium-238
Arnericium-241
Plutonium-240
Zirconium-93
Niobium-93m
Antimony- 125
Europium- 152
Uranium-235
Cesium- 135
Uranium-236
Tellurium- 125m
Antimony- 126m
Tin- 126
Cesium- 134
Tin-121m
Antimony- 126
Neptunium-237
Iodine- 129
Palladium- 107
Uranium- 234
Uranium-238
Protactinium-231
Americium-242m
Actinium-227
Americium-243
Protactinium-234
Curium-243
Francium-223
Concentration (pCi/g)
July 1994 July 2024 July 2094
2.29E+04
2.15E+04
6.91E+02
5.20E+02
2.62E+01
1.96E+01
1.84E+01
1.24E+01
1.04E+01
6.85E+00
6.72E+00
2.57E+00
1.56E+00
1.04E+00
8.09E-01
7.30E-01
7.11E-01
4.60E-01
4.34E-01
2.32E-01
1.78E-01
1.78E-01
1.78E-01
9.12E-02
2.70E-02
2.49E-02
2.14E-02
1.12E-02
7.38E-U-;
6.28E-03
5.64E-03
3.34E-04
2.40E-04
1.31E-04
3.55E-05
7.33E-06
6.83E-06
1.81E-06
1.14E+04
1.05E+04
9.94E+01
4.13E+02
9.46E-03
4.62E+00
1.64E+00
1.87E-01
1.04E+01
6.85E+00
5.30E+00
2:93E+00
1.56E+00
1.04E+00
9.46E-01
4.01E-04
1.54E-01
4.60E-01
4.34E-01
2.32E-01
9.78E-05
1.78E-01
1.78E-01
3.81E-06
1.78E-02
2.49E-02
2.14E-02
1.12E-02
7.38E-03
6.79E-03
5.64E-03
6.26E-04
2.09E-04
3.60E-04
3.54E-05
7.33E-06
3.29E-06
4.96E-06
2.27E+03
1.99E+03
1.08E+00
2.41E+02
8.78E-11
1.59E-01
5.80E-03
1.05E-05
1.04E+01
6.85E+00
3.05E+00
2.76E+00
1.55E+00
1.04E+00
9.83E-01
9.89E-12
4.35E-03
4.60E-01
4.34E-01
2.32E-01
2.41E-12
1.78E-01
1.78E-01
2.30E-16
6.76E-03
2.49E-02
2.15E-02
1.12E-02
7.38E-03
7.60E-03
5.64E-03
1.31E-03
1.52E-04
l.OOE-03
3.52E-05
7.33E-06
6.00E-07
1.39E-05
15
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5.1.3 Fate and Transport
Potential pathways for contaminant migration at the SL-1 burial ground are limited by site condi-
tions. The SL-1 site is fairly isolated, is gently sloped, is in a desert climate, and has a great depth to
groundwater [approximately 667 feet (203 m)]. Although there is surface contamination at the site, the
majority of contamination is subsurface. In general, the potential pathways for contaminant migration
include atmospheric transport and transport via surface water and groundwater.
There is a potential for windblown migration of radionuclides present in the surface soil at the SL-1
burial ground, although the presence of a thick grass cover minimizes mobilization of dust and its dis-
persion by wind.
No surface-water migration pathway exists at the site, and there are no surface-water features. The
SL-1 burial ground is in a topographic low, minimizing the chance for significant erosion due to sur-
face water but increasing infiltration from precipitation. Flooding of the Big Lost River is not a con-
cern at SL-1 because of topography, distance from the river, and the INEL's flood diversion system.
No groundwater sampling data are available for the SL-1 burial ground, therefore the groundwater
pathway was evaluated using the GWSCREEN (version 2.02) computer model. Concentrations in the
groundwater were modeled for three hypothetical locations: the edge of the burial grounds, the down-
gradient boundary of the waste area group (Figure 2), and the nearest downgradient INEL site-bound-
ary (Figure 1). Groundwater flow is generally from northeast to southwest. The groundwater model-
ing performed in support of the remedial investigation indicates that vertical migration of contaminants
from the SL-1 burial ground is limited. The tendency of the contaminants to chemically react with nat-
urally occurring minerals in the soil and low annual precipitation result in long transit times within the
vadose zone (typically hundreds of years or more). It is assumed that no lateral migration of contami-
nants has occurred within the subsurface because there is no mechanism or driving force to move cont-
aminants horizontally. Infiltration of precipitation is primarily vertical within the vadose zone and
therefore would not contribute significantly to the horizontal migration of radionuclides.
5.2 BORAX-I
In 1954, the design mission of the BORAX-I reactor was completed and the decision was made to
conduct one final experiment that would result in the destruction of the reactor. The excursion contam-
inated approximately 84,000 square feet (7,800-m2) of ground, in a strip approximately 200 feet (61 m)
wide and 420 feet (128 m) long, extending south-southeast from the reactor. Following cleanup, the
contaminated area of approximately 84,000 square feet (7,800-m2) was covered with gravel to a depth
of 6 inches (15 cm). Soil sampling of the 84,000-square foot (7,800-m2) area of surface contamination
was conducted in 1978 and 1980. Results of these activities are summarized in the following section.
16
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5.2.1 Previous Investigations
In 1978, the Radiological and Environmental Sciences Laboratory performed a multiphase study to
assess the distribution of radioactivity at the BORAX-I reactor burial ground. Exposure rates at 3 feet
(1m) above the ground were determined.
A portable gamma-ray spectroscopy system was used to identify gamma-emitting radionuclides. In
situ gamma-ray spectrums were obtained from nine locations. Surface-soil samples were also collected
at nine locations outside of the graveled area in order to assess the extent of contamination. The col-
lection locations were chosen to include samples down range of the major debris and surface deposi-
tion zones. Soil samples were collected from five locations within the gravel-covered area and were
analyzed by gamma ray spectroscopy in order to assess the deposition and migration activity. Analyses
of the soil samples showed that cesium-137 and uranium-235 were the only detectable gamma-emitting
radionuclides present. Samples collected from the gravel covering showed that 98% of the radioactive
contamination was located within 2 inches (5 cm) of the gravel/soil interface.
An investigation of the BORAX-I reactor area was conducted in June and November 1980. The
investigation consisted of a gridded radiation survey of the BORAX-I site, including high-resolution
gamma spectrometer measurements of the surface soil, soil samples from trenches, and sodium-iodide
gamma spectrometer profiles of selected boreholes. The purpose of the radiological characterization
was to identify the radionuclides present within the area and to specify their concentrations and distrib-
utions. Cesium-137 was the only man-made gamma emitter detected during the radiological surveys.
Soil-sample analyses detected cesium-137, strontium-90, uranium-235, and plutonium-239. Results
indicate that surface contamination was limited to relatively small areas, mainly along a south-south-
east line from the reactor location.
Aerial surveys of the BORAX-I burial ground were conducted in 1974, 1982, 1990, and 1993. The
surveys detected gamma radiation from man-made sources in the area, with cesium-137 being the pri-
mary contributor. Figure 5 illustrates the results of the 1990 survey.
5.2.2 Nature and Extent
5.2.2.1 Surface Contamination. Operable Unit 6-01 comprises an area approximately 200 by 420
feet (61 by 128 m). Based on the original source of surface contamination (aerial distribution of conta-
minants resulting from the final experiment of the BORAX-I reactor) and the limited mobility of
radionuclides in the soil at the INEL, it is believed that contamination is restricted to the upper 1 foot .
(0.3 m) including 0.5 foot (0.15 m) of contaminated soil and 0.5 foot (0.15 m) of gravel cover.
Identification of the contaminants of concern associated with surface soils at BORAX-I was based
on comparison of analytical data with background concentrations. Concentrations of the contaminants
of concern for surface soils were based on the 95% upper confidence limit of the analytical data, and
the assumption was made that each contaminant is uniformly distributed throughout the 200- by
420-foot (61- by 128-m) area. Table 3 presents the contaminants of concern for surface soils.
17
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Table 3. Contaminants of concern and surface soil concentrations at BORAX-I.
Concentration (pCi/g)
Radionuclide 95% upper confidence limit INEL Background2
Cesium-137 1,817 1.28
Strontium-90 2.0 0.76
Uranium-235 68.6 0.055 - 0.059b
a. 95%/95% upper tolerance limit, grab sample background concentrations for cesium-137 and strontium-90 from
Background Dose Equivalent Rates and Surficial Soil Metal and Radionuclide Concentrations for the Idaho National
Engineering Laboratory, INEL-94/0250, S. M. Rood, G. A. Harris, G. J. White, February 1995.
b. Range of background for uranium-235 from the remedial investigation/feasibility study, Attachment 1 of Appendix B.
5.2.2.2 Subsurface Contamination. Subsurface contamination at the BORAX-I burial ground is
restricted to the contaminated soil and materials deposited in the concrete foundation of the reactor
structure. The estimated volume of contaminated material in the subsurface is 6,336 cubic feet
(180 m3).
The BORAX-I inventory and activities of buried radionuclides were estimated using the computer
model RSAC-5. Decontamination documents prepared after the cleanup of the BORAX-I facility in
1954 reported that 12% of the uranium-235 fuel had been recovered. Based on this figure, it was
assumed that 88% of each of the associated radionuclides remained unrecovered and was disposed of
in the burial ground. Inventories of radionuclides were generated for 1954, 1994, 2024, and 2094 and
were used in the baseline risk assessment to calculate risks for current, 30-year future, and 100-year
future scenarios. Inventories were calculated for specific times to account for the decay (a decrease
through time) of parent radionuclides and for ingrowth (an increase through time) of radioactive proge-
nies. The concentration of each contaminant of concern for each time evaluated was estimated using
the assumption that 88% of the model-generated activity for each contaminant of concern was uniform-
ly distributed throughout the source volume. Table 4 presents the contaminants of concern for the sub-
surface.
18
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Table 4. Potential contaminants of concern and estimated subsurface concentrations at BORAX-I for
non-groundwater pathways.
Radionuclide
Concentration (pCi/g)
July 1994 July 2024 July 2094
Cesium- 137
Strontium-90
Uranium-234
Samarium- 151
Uranium-235
Krypton-85
Technetium-99
Thorium-230
Promethium-147
Uranium-238
Zirconium-93
Niobium-93m
Protactinium-23 1
Tin- 126
Actinium-227
Cesium- 135
Antimony- 125
Radium-226
Lead-210
Iodine- 129
Protactinium-234
Europium- 154
Niobium-94
1.20E+03
1.10E+03
9.29E+02
5.05E+01
2.94E+01
1.90E+01
4.27E-01
3.34E-01
2.77E-01
1.91E-01
6.35E-02
5.57E-02
2.18E-02
1.10E-02
9.51E-03
8.29E-03
8.14E-03
2.88E-03
8.99E-04
6.02E-04
2.48E-04
1.12E-04
6.35E-07
6.02E+02
5.39E+02
9.29E+02
4.01E+01
2.94E+01
2.73E+00
4.27E-01
5.83E-01
l.OOE-04
1.91E-01
6.35E-02
6.21E-02
3.83E-02
1.10E-02
2.29E-02
8.29E-03
4.46E-06
8.77E-03
4.01E-03
6.02E-04
2.48E-04
9.96E-06
6.32E-07
1.19E+02
1.01E+02
9.29E+02
2.34E+01
2.94E+01
2.95E-02
4.27E-01
1.17E+00
9.25E-13
1.91E-01
6.35E-02
6.35E-02
7.65E-02
1.10E-02
5.95E-02
8.29E-03
1.10E-13
3.48E-02
2.25E-02
6.02E-04
2.48E-04
3.53E-08
6.32E-07
5.2.3 Fate and Transport
Potential pathways for contaminant migration at the BORAX-I burial ground are limited by condi-
tions at the site. The site is fairly isolated, is gently sloped, is in a desert climate, and has a great depth
to groundwater [approximately 596 feet (181 m)]. Although there is surface contamination at the site,
the majority of contamination is in the subsurface. In general, the potential pathways for contaminant
migration include atmospheric transport and transport by surface water and groundwater.
There is a potential for windblown migration of radionuclides present in the surface soil at the
BORAX-I burial ground, although the existing vegetative cover minimizes the mobilization of dust and
its dispersion by wind.
19
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No surface-water migration pathway exists at the site and there are no surface-water features. Although
the BORAX-I burial ground is located on a slight rise, the slope of the ground immediately adjacent to the
site is fairly gentle, minimizing the likelihood of erosion. Hooding of the Big Lost River is not a concern at
BORAX-I because of topography, distance from the river, and the INEL's flood diversion system.
No groundwater sampling data are available for the BORAX-I burial ground, therefore the ground-
water pathway was evaluated using the GWSCREEN (version 2.02) computer model. Concentrations
in the groundwater were modeled for three hypothetical locations: the edge of the burial grounds, the
downgradient boundary of the waste area group (Figure 3), and the nearest downgradient EVEL site-
boundary (Figure 1). Regional groundwater flow is generally from northeast to southwest. Results of
the modeling indicate that vertical migration of contaminants from the BORAX-I burial ground is lim-
ited. The tendency of the contaminants to chemically react with naturally occurring minerals in the soil
and low annual precipitation result in long transit times within the vadose zone (typically hundreds of
years or more). It is assumed that no lateral migration of contaminants has occurred within the subsur-
face because there is no mechanism or driving force to move contaminants horizontally. Infiltration of
precipitation is primarily vertical within the vadose zone and therefore would not contribute significant-
ly to the horizontal migration of radionuclides.
6. Summary of Site Risks
A baseline risk assessment was conducted to evaluate current and future potential risks to human
health. The risk assessments were conducted in accordance with the EPA Risk Assessment Guidance
for Superfund, Volume I: Human Health Evaluation Manual and other EPA guidance. Risk scenarios
and default parameters used in the risk assessment were selected with the concurrence of the agencies.
Radionuclides are the only contaminants of concern at the SL-1 and BORAX-I burial grounds.
Although nonradioactive contaminants may be present at either site, it was determined that, if present, they
probably represent an insignificant contribution to the total risk. Radionuclides present in surface soils at
BORAX-I and subsurface soils at both sites pose potential carcinogenic (cancer causing) risks to occupa-
tional workers and future residents. Carcinogenic risks are generally a much greater concern than noncar-
cinogenic risks from radionuclides. Therefore, the baseline risk assessment focused on a quantitative
assessment of carcinogenic risks. Noncarcinogenic risks were subjected to a qualitative evaluation and were
eliminated from further assessment. The assessment considered the carcinogenic health effects that could
result from exposure to the contaminants under current occupational and future occupational and residential
land use scenarios. The health effects differ depending on whether the sites are used for light industry or
residential development. Effects could result from direct exposure to radiation, from inhalation of contami-
nated dust, or from ingestion of contaminated soil or groundwater. Section 6.1 summarizes the results of
the baseline risk assessment.
The baseline risk assessment for Operable Unit 5-05 evaluated potentially contaminated surface
soils in an area 1,200 by 1,500 feet (366 by 457 m). Subsequent to finalization of the remedial investi-
gation/feasibility study report and the proposed plan, an evaluation of new data in conjunction with his-
20
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torical sampling and survey data determined that surface soils within Operable Unit 5-05 do not pose
an unacceptable risk to human health or the environment (see Section 11.1). Support documentation
for this determination can be found in the Administrative Record for Operable Units 5-05 and 6-01.
A qualitative ecological risk assessment was performed to evaluate potential risks to the environ-
ment due to contamination at the SL-1 and BORAX-1 burial grounds. Section 6.2 summarizes results
of the ecological risk assessment.
6.1 Human Health Risks
A baseline risk assessment was performed to evaluate the risks associated with taking no further
action at a site. Thus, it was assumed in the assessment, as instructed in EPA guidance, that no remedi-
ation will take place. Potential risks for specified land use scenarios were assessed.
The risk assessment consisted of contaminant identification, exposure assessment, toxicity assess-
ment, and human health risk characterization. The contaminants identified at the SL-1 and BORAX-I
burial grounds were based on historical soil-sampling data and radionuclide inventories calculated
using computer models. The exposure assessment identified the potential exposure pathways for cur-
rent workers and for future workers and residents. The toxicity assessment evaluated the potential
health effects to an individual as a result of exposure to contaminants. Exposure scenarios were chosen
to reflect a range of potential future land uses. Industrial land use is assured for the next 100 years,
after which residential use is considered possible. Specifically, scenarios included the current use of
the SL-1 and BORAX-I burial grounds (current occupational land use) and potential future land use
scenarios (occupational and residential land use) in which the onset of exposures are delayed for 30
and 100 years.
The baseline risk assessment was presented in two parts: (1) an evaluation of deterministic risk
based on standard EPA methodology and (2) an evaluation of the uncertainty associated with the mean
risk using probabilistic risk assessment. The first quantity (deterministic risk) is a point estimate that
represents a quantified upper bound of risk. Deterministic risks are used by decisionmakers to define
the estimated excess risk that must be addressed in remedial decisions. Probabilistic methods are used
in the second evaluation to quantify the uncertainty associated with the deterministic risk. These meth-
ods provide a more complete understanding of the excess risk potential at a site by examining the like-
lihood of over- or under-estimation of risk.
6.1.1 Contaminant Identification
Historical soil sampling analytical data were used to identify radionuclides present in surface soils
at both sites. The lists of radionuclides were screened based on comparison with background concen-
trations determined for the INEL. The range of sample concentrations was compared to the range of
background concentrations. If the maximum sample concentration exceeded the maximum background
concentration, the radionuclide was retained and assessed in the risk assessment (Tables 1 and 3).
21
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Computer models were used to generate lists of radionuclides with estimated activities for the sub-
surface at each site. The radionuclides were screened based on availability of lexicological data and
potential for posing a significant risk. Radionuclides evaluated in the risk assessment for the subsur-
face are presented in Tables 2 and 4.
6.1.2 Exposure Assessment
The objective of the exposure assessment was to estimate the magnitude of exposure to contami-
nants of concern at SL-1 and BORAX-I. The magnitude of exposure was determined by measuring or
estimating the quantities of the contaminants available for contact at an exposure point during a speci-
fied time period. The results of the exposure assessment were then combined with contaminant-specif-
ic toxicity information to characterize potential risks.
6.1.2.1 Exposure Scenarios. Only those exposure pathways where a plausible route of exposure
can be demonstrated from the site to an individual were quantitatively evaluated in the risk assessment.
The populations at risk due to exposure from wastes at the SL-1 and BORAX-I burial grounds were
identified by considering both current and future land use scenarios. For each of the two sites, 10
potential exposure scenarios (five residential scenarios and five occupational scenarios) were examined
in the baseline risk assessment.
The residential scenarios model a person living on the site 350 days a year for 30 years, beginning
in 2024 and 2094 (30 and 100 years from 1994). The intrusive scenarios reflect conditions if the
buried waste is exposed. The nonintrusive scenarios model the risk to an individual who lives on the
surface above the wastes in 2024 and 2094 and to a subsistence farmer on the site beginning in 2094.
The five occupational scenarios model nonintrusive daily industrial use without restrictions in 1994,
two 1994 site-specific evaluations reflecting occupational activities over the last few years, and daily
industrial use 30 and 100 years in the future in the years 2024 and 2094. Section 6.1.2.3 lists exposure
parameters for each scenario.
6.1.2.2 Media Concentrations. Limited sampling and analytical data were available regarding
contaminants present in the surface and subsurface soil at the SL-1 and BORAX-I sites. Surface-soil
samples from the burial grounds and adjacent areas were used to evaluate the risk for soil ingestion,
inhalation of dust, and ingestion of crops, meat, and milk for the nonintrusion scenarios. Surface-sam-
ple data were also used to evaluate the external exposure pathway for the subsistence farmer scenarios.
Subsurface contamination was evaluated based on radionuclide inventories and activities estimated
using computer models. All pathways for the intrusion scenarios and the groundwater and external
exposure pathways for the nonintrusion scenarios were evaluated using the computer-generated
radionuclide inventories and activities. The radionuclides and concentrations evaluated in the baseline
risk assessment are listed in Tables 1 through 4.
22
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To provide an understanding of the external exposure risk present at the surface at the two sites,
risk attributable to the radiological field measurements taken within the fence at each burial grounds
was also evaluated. A radiological field survey conducted in November 1994 found levels of 0.5
mR/hour at the SL-1 burial ground and 0.1 mR/hour at the BORAX-I burial ground. Measurements
were taken at 2.5 feet (0.8 m) above the ground surface. Local backgrounds were 0.2 mR/hour for
SL-1 and 0.1 mR/hour at BORAX-I. However, dose equivalent rates measurements taken in 1995 in
the area around SL-1 yielded readings at or below the background value of 20 (irem/hr.
6.1.2.3 Quantification of Exposure. The following exposure pathways were considered applica-
ble to the evaluation of human exposure to contaminants at the sites: ingestion of soil; inhalation of
fugitive dust; ingestion of groundwater (residential scenarios only); ingestion of crops, meat, and milk
(subsistence farmer scenario only); and external exposure from radionuclides. The future residential
setting included a hypothetical well, which could provide contaminated groundwater for use as drink-
ing water. For the subsistence farmer scenario, the resident was also assumed to consume homegrown
produce, meat, and milk produced on site.
Adult exposures were evaluated for all scenarios and pathways (external exposure; inhalation of
dust; and ingestion of soil, groundwater, and foods); child exposures (0 to 6 years old) were considered
separately only for the soil ingestion pathway in the residential scenarios. Children were included
because children ingest more soil than adults, significantly increasing their exposure rate.
The exposure parameters used in the risk assessment were obtained from EPA and DOE guidance.
The exposure parameter default values used in the risk assessment are designed to estimate the reason-
able maximum exposure at a site. The EPA defines reasonable maximum exposure as the highest
exposure at a site. Use of this approach makes under-estimation of the actual cancer risk highly unlike-
ly. Concentrations of the radionuclides evaluated in the baseline risk assessment are listed in Tables 1
through 4. The exposure parameters used in the risk assessment were:
• All pathways
- Exposure frequency, residential: 350 days/year
- Exposure frequency, occupational, current: 2." J. ys/year
- Exposure frequency, occupational, site-specific #1: 30 days/year
- Exposure frequency, occupational, site-specific #2: 5 days/year
- Exposure duration, occupational, current: 25 years
- Exposure duration, occupational, site-specific #1 and #2: 3 years
• External exposure pathway
- Exposure time, residential: 24 hour/day
- Exposure time, occupational: 8 hour/day
- Exposure duration, residential: 30 years
23
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• Soil ingestion pathway
- Soil ingestion rate, residential, adult: 100 mg/day
- Soil ingestion rate, residential, child: 200 mg/day
- Soil ingestion rate, occupational: 50 mg/day
- Exposure duration, residential, adult: 24 years
- Exposure duration residential, child: 6 years
• Dust inhalation pathway
- Inhalation rate: 20 m3 of air/day
- Exposure duration, residential: 30 years
• Groundwater ingestion pathway
- Groundwater ingestion rate, residential: 2 liters/day
- Exposure duration, residential: 30 years.
The parameters and distributions used in the probabilistic risk assessment are presented in Tables
6-9 through 6-11 of the Remedial Investigation/Feasibility Study Report for Operable Units 5-05 and 6-
01 (SL-1 and BORAX-I Burial Grounds), INEL-95/0027 (K. J. Holdren, R. G. Filemyr, D. W. Vetter,
Idaho National Engineering Laboratory, March 1995), which is included in the Administrative Record
for Operable Units 5-05 and 6-01.
6.1.3 Toxicity Assessment
A toxicity assessment was conducted to identify potential adverse effects to humans from
contaminants at SL-1 and BORAX-I. A toxicity value is the numerical expression of the substance
dose-response relationship used in the risk assessment. Carcinogenic values (slope factors) for the
sites were obtained from EPA's Health Effects Assessment Summary Tables: Annual FY-93,
ECAO-CIN-909, 1993. The slope factors selected for the soil ingestion, inhalation of dust, and
external exposure pathways include progenies when available. Slope factors used to evaluate the
groundwater pathway do not always include daughters because the groundwater model GWSCREEN
specifically accounts for up to five daughters.
Slope factors have been developed by the EPA for estimating excess lifetime cancer risks associated
with exposure to potentially carcinogenic chemicals. Slope factors for radionuclides are expressed in
units of risk/pCi for ingestion and inhalation and risk/year per pCi/gram for external exposure. Slope
factors are multiplied by the estimated intake of a potential carcinogen, in pCi (pCi-year/gram for
external exposure), to provide an upper-bound estimate of the excess lifetime cancer risk associated
with the exposure at that intake level. Slope factors are derived from the results of human epidemio-
logical studies or chronic animal bioassays to which animal-to-human extrapolation and uncertainty
factors have been applied.
24
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6.1.4 Human Health Risk Characterization
Excess lifetime cancer risks are estimated by multiplying the intake level, developed using the
exposure assumptions, by the slope factor (see Section 6.1.3). These risks are probabilities that are
generally expressed in either scientific notation (1x10"^) or exponential notation (1E-06). An excess
lifetime cancer risk of 1E-06 indicates that, as a plausible upper bound, an individual has a one in one
million chance of developing cancer as a result of site-related exposure to a carcinogen over a 70-year
lifetime under the specific exposure conditions at a site. Excess cancer risks estimated below 1E-06
typically indicate that no further action is appropriate. Risks estimated in the range of 1E-04 to 1E-06
(1 in 10,000 to 1 in 1,000,000) indicate that further investigation or remediation may be needed, and
risks estimated above 1E-04 typically indicate that further action is appropriate. However, the upper
boundary of the risk range is not a discrete line at 1E-04, although EPA generally uses 1E-04 in mak-
ing risk management decisions. A specific risk estimate around 1E-04 may be considered acceptable if
justified based on site-specific conditions.
6.1.4.1 Deterministic and Probabilistic Risk Summary. The results of the deterministic and
probabilistic risk calculations are summarized in Table 5 for SL-1 and in Table 6 for BORAX-I and
presented graphically in Figures 6 and 7. For the probabilistic simulations, the risk summary tables
and figures present the 50th percentile, representing the average individual risk, and the 95th percentile,
representing the reasonable maximum exposure individual risk.
The probablistic risk assessment showed that the greatest contributors to uncertainty in the overall
risk for the site (that is, the risk due to external exposure) are associated with the exposure duration,
concentration of cesium-137, and the external exposure slope factor for cesium-137. A number of sce-
narios and pathways utilized source terms estimated from computer models. Because of the lack of a
sample population from which to estimate statistical parameters for use in the probablistic simulations,
it was necessary to assume specific values for the parameters. Increases in the amount of actual data
used for input into the probablistic assessment would result in increased value and usefulness of the
results.
At both sites, the primary contributor to risk is cesium-137 (plus progeny) in the external exposure
pathway. Cesium-137 has a half-life of about 30 years. The decreasing concentration through time
results in decreased risk through time. External exposure risk will remain above 1E-04 for approxi-
mately the next 400 years at the SL-1 burial ground and will decrease to 2E-04 after approximately 320
years at the BORAX-I burial ground. Due to the long half-life of uranium-235 (7E+08 years), the
external exposure risk at BORAX-I will essentially never decrease below 2E-04.
For SL-1, the only radionuclides predicted to reach the aquifer in concentrations of potential con-
cern were tritium and technetium-99, with associated risks of 2E-07 and 6E-07, respectively. Summed
with the risks from the remaining radionuclides, the total risk due to groundwater ingestion associated
with the SL-1 burial ground is 1E-06. For BORAX-I, uranium-234 and its progenies were the only
radionuclides predicted to reach the aquifer in concentrations of potential concern, with a risk sum of
25
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2E-06. Summed with the risks from the remaining radionuclides, the total risk due to groundwater
ingestion associated with BORAX-I is 3E-06.
For SL-1, an evaluation of risks due to surface soils defined by the 1990 aerial survey isopleth was
performed. It was determined that there are no unacceptable risks via the soil ingestion, inhalation of
dust, groundwater ingestion, or external exposure pathways within Operable Unit 5-25. Section 11.1
contains specific references contained in the Administrative Record in support of this assessment.
6.1.4.2 Radiological Field Risk. Surface radiological field measurements taken within the fences
at the burial grounds provide exposure levels that account for shielding of radiation provided by the
soil cover. Based on the reported maximum, single point radiological field measurements of 0.5
mR/hour at SL-1 and 0.1 mR/hour for BORAX-I, the 30-year residential risk at the surface was esti-
mated at 9E-02 for SL-1 and 2E-02 for BORAX-I. The risk associated with local background is 3E-02
at SL-1 and 2E-02 at BORAX-I. The risk associated with the average background radiological field at
the ENEL is 3E-03 (0.02 mR/hour). The 30-year residential risk from national average natural back-
ground radiation ranges from 2E-03 (0.011 mR/hour) to 6E-03 (0.034 mR/hour). Risks based on radio-
logical field measurements taken within the fences are shown graphically in Figure 8.
A more comprehensive data set for SL-1 was acquired in 1995 and an assessment of the surface
soils within Operable Unit 5-05 was completed in August 1995. Dose equivalent rate measurements,
all below the background value of 20 urem/hr, indicate no unacceptable external exposure risks due to
surface soils within Operable Unit 5-05.
26
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Table 5. Summary of risks for the potential exposure scenarios and pathways at SL-1.
Scenario
Pathway
Residential (30-year, intrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (30-year, nonintrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (100-year, intrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (100-year, nonintrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Subsistence farmer (100-year)
(water independent pathways)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of plants
Ingestion of meat
Ingestion of milk
Total scenario risk
Occupational (current)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Deterministic
risk
5E-01
9E-04
8E-07
1E-06
5E-01a
5E-01
5E-05
4E-07
1E-06
5E-01a
1E-01
2E-04
4E-07
1E-06
lE-01a
1E-01
9E-06
3E-07
1E-06
IE-OP
1E-03
4E-07
2E-06
1E-05
4E-05
1E-05
1E-038
2E-01
2E-05
4E-07
2E-018
Probabilistic
50th percentile
risk
1E-01
4E-05
2E-07
NCb
1E-01
1E-01
3E-07
7E-08
NCb
1E-01
3E-02
8E-06
1E-07
NCb
3E-02
3E-02
6E-08
7E-08
NCb
3E-02
NCC
NCC
NCC
NCC
NCC
NCC
NCC
8E-02
8E-08
9E-08
6E-02
Probabilistic
95th percentile
risk
6E-01
1E-04
9E-07
NCb
6E-01
6E-01
8E-07
2E-07
NCb
6E-01
2E-01
2E-05
5E-07
NCb
2E-01
2E-01
2E-07
2E-07
NCb
2E-01
KG*
NCC
NCC
NCC
NCC
NCC
NCC
4E-01
4E-07
3E-07
3E-01
Refer to footnotes at end of table.
27
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Table 5. (continued)
Scenario
Pathway
Deterministic
risk
Probabilistic
50th percentile
risk
Probabilistic
95th percentile
risk
Occupational (site-specific #1)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (site-specific #2)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (future - 30 years)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (future - 100 years)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
4E-03
3E-07
6E-09
4E-03a
6E-04
6E-08
9E-10
6E-048
1E-01
1E-05
2E-07
lE-01a
3E-02
2E-06
2E-07
3E-02"
2E-03
2E-09
NCd
2E-03
3E-04
3E-10
NCd
3E-04
4E-02
4E-08
5E-08
4E-02
9E-03
8E-09
5E-08
9E-03
1E-02
5E-09
NCd
1E-02
2E-03
9E-10
NCd
2E-03
3E-01
2E-07
2E-07
3E-01
6E-02
3E-08
2E-07
6E-02
a. Cesium-137 (plus barium-137m) is the primary contributing radionuclide.
b. A probabilistic risk assessment was not performed for the groundwater pathway due to its small contribution to total risk
and to the absence of published probability distribution functions for input parameters.
c. A probabilistic risk assessment was not performed for the subsistence farmer scenario due to the absence of published
probability distribution functions for input parameters.
d. A probabilistic risk assessment was not performed due to its small contribution to total risk.
NC = Not calculated.
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Table 6. Summary of risks for the potential exposure scenarios and pathways at BORAX-I.
Scenario
Pathway
Residential (30-year, intrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (30-year, nonintrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (100- year, intrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Residential (100-year, nonintrusive)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of groundwater
Total scenario risk
Subsistence farmer (100-years)
(water independent pathways)
External exposure
Ingestion of soil
Inhalation of dust
Ingestion of plants
Ingestion of meat
Ingestion of milk
Total scenario risk
Occupational (current)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Deterministic
risk
3E-02
7E-05
9E-07
3E-06
3E-02a
3E-02
3E-05
8E-07
3E-06
3E-028
7E-03
3E-05
9E-07
3E-06
7E-03*
7E-03
8E-06
8E-07
3E-06
7E-038
5E-03
2E-06
4E-06
1E-04
1E-04
4E-05
6E-03a
1E-02
2E-05
5E-07
1E-028
Probabilistic
50th percentile
risk
7E-03
3E-06
2E-07
NCb
7E-03
7E-03
4E-09
5E-09
NCb
7E-03
1E-03
1E-06
2E-07
NCb
1E-03
IE-03
2E-09
5E-09
NCb
IE-03
NCC
NCC
NCC
NCC
. NCC
NCC
NCC
4E-03
1E-09
4E-09
4E-03
Probabilistic
95th percentile
risk
5E-02
8E-06
1E-06
NCb
5E-02
5E-02
1E-08
5E-08
NCb
5E-02
1E-02
4E-06
1E-06
NCb
1E-02
1E-02
1E-08
5E-08
NCb
1E-02
NCC
NCC
NCC
NCC
NCC
NCC
NCC
3E-02
4E-09
3E-08
3E-02
Refer to footnotes at end of table.
29
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Table 6. (continued)
Scenario
Pathway
Occupational (site-specific #1)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (site-specific #2)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (future - 30 years)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Occupational (future - 100 years)
External exposure
Ingestion of soil
Inhalation of dust
Total scenario risk
Deterministic
risk
2E-04
2E-07
7E-09
2E-04a
3E-05
4E-08
1E-09
3E-058
7E-03
8E-06
5E-07
7E-038
IE-OS
2E-06
5E-07
1E-038
Probabilistic
50th percentile
risk
9E-05
1E-11
NCd
9E-05
2E-05
2E-12
NCd
2E-05
2E-03
6E-10
4E-09
2E-03
5E-04
3E-10
4E-09
5E-04
Probabilistic
95th percentile
risk
5E-04
4E-11
NCd
5E-04
8E-05
6E-12
NO1
8E-05
2E-02
3E-09
4E-08
2E-02
3E-03
2E-09
4E-08
3E-03
a. Cesium-137 (plus barium-137m) is the primary contributing radionuclide.
b. A probabilistic risk assessment was not performed for the groundwater pathway due to its small contribution to total risk
and to the absence of published probability distribution functions for input parameters.
c. A probabilistic risk assessment was not performed for the subsistence farmer scenario due to the absence of published
probability distribution functions for input parameters.
d. A probabilistic risk assessment was not performed due to its small contribution to total risk.
NC = Not calculated.
30
-------
•Q^ 1E+OO —
g 1E-02 —
o
lE-oe -
£ 1E'1°-
SL-1 Residentia
1 (30-year, intrusive risk) r-j o««mini,tic
1 1 SOthp.ro.nUta'
f~~ 1 95th pwonrttto '
""• " External exposure Ingeston of soil Inhalation of dust ngestion of
groundwater
•5- 'E*oo —
CO
0 1E-02-
o
a
§> IE-OS -
=-
X 1E-10 —
CO
SL
-1 Residential (30-year, non-intrusive risk) £-, o^^nini.,*
I 1 SOttifMrantil*'
I 1 95th p«rc«ntil« '
"• External exposure Ingestion of soil Inhalation of dust Ingestion of
groundwater
-•• 1E*00 — ,-
S
| «•*-
ed
g> 1E-06-
^T 1E-10 —
S
•L-1 Residential (100-year, intrusive risk) £-3 tM.rminMic
I — I SOtti pwnntito '
1 1 95th p«rc«ntil« *
"- External exposure Ingestion of soil Inhalation o dust Ingestion of
groundwater
^ 'E*«° — .
,**-
£
1E-M -
g 1E-0-
SL-
..*.'.
•:•:•:•
1 Residential (100-year, non-intrusive risk) CD DM»mini*tic
I 1 SOtllpwcwitll*'
1 1 Mttl pwcwitil* *
External exposure Ingestion of soil Inhaationo dust Ingestion of
groundwater
~& 1E«00 — ,
g 1E-02 —
O
8" 1E-08 -
^ 1E-10 —
W
SL-1 Subsistence Far
mer Ri
sk
"• External Ingestion inhalation Ingestion Ingestion Ingestion
exposure of soil of dust ofplams of meat 61 milk
Refer to notes at end of figure
Figure 6. Graphical summary of risk for SL-1.
31
-------
•«• 1E«00 —
a
g 1E-02-
u
a
g> lE-oe -
¥ 1E-10 —
CO
SL-1 Occupational (current) Risk CD Deterministic
I — l 50th percentile •
I — l 9Sth percentile '
• • •. . ;•._••."," • •'.-;.;
c External exposure Ingestion of soil Inhalation of dust
"5T 1E»00 —
o
§" 1E-M
X 1E-10 —
W
SL-1 Occupational Risk (site-specific #1) en Deterministic
l — l 50th percentile •
l — l 95th percentfle '
"~ ~ * External axposure Ingestion of soil Inhalation of dust
•y tE»oo — |
S ,e4s-
^ 1E06-
1E-08 -
^ IE-10 —
CO
SL-1 Occupational Risk (site-specific #2) a Deterministic
_ l — I 50th percentile •
l — l BSth percentile '
"• External exposure Ingestion of soil Inhalation of dust
. .
•J" 1E«00 — ,
I
8 1602-
o
g> 1E-08 -
^ 1E-10 —
CO
SL-
1 Occupational Risk (future - 30-year) en Drt.rmini.tic
Cn 50th percentile •
l — l 95th percentile '
' 1 1 1 '1
External exposure Ingestion of soil Inhalation of dust
of 1E+00 —
1E^2 -
u
.c
§* 'E-08 —
^ tE-IO —
CO
SL-1 Occupational Risk (future - 100-year) en Deterministic
I — I 50th percentile*
I — l 95th percentile'
~ External exposure Ingestion of soil Inhalation of dust
a. The 50th percentile is the average individual risk.
b. The 95th percentile is the reasonable maximum exposure individual risk.
Figures, (continued)
32
-------
•0* 1E+00 —
CD
a IE-OJ -
.c
1E-06 -
^ 1E-10 —
CO
BORAX-I Residential Risk (30-year, intrusive) a D*t.r™r,«tic
,— l~~l 50th fwrcintil* *
I — I 9001 Mmntll* '
**" External exposure Ingestion of soil Inhalation of
dust Ingestion of
groundwater
-J- 1E*00 -
Jj 1E-02 —
o
a
J> IE-OS -
£ 1E'1°-
BORAX-I Residential
Risk
(30-year, non-intrusive) ^ o«.m,nittic
I I SOth p»rc»ntfl«"
I 1 •Mh p«re«ntil« '
"• External exposure Ingestion of soil
Inha ation o dust Ingestion of
groundwater
-5- 'E*oo -,
(0
U lt-miMic
I I SOIh pcrcwilil* "
1 1 85th p*rc*ntil« '
"- External exposure Ingestion of soil Inhalation of
dust Ingestion of
groundwater
5~ 1E»00 — |
0
SL
R
g1 IE-OS
*: IE-ID —
w
i
3ORAX-I Residential Risk (100-year, non-intrusive) a D.«rmmi.«c
I~~l 50ttip»rc«ntil*'
1 — 1 Win p«re«ntil« *
External exposure Ingestion of soil
Inhalation of dust
Ingestion of
groundwater
BORAX-I Subsistence Farmer Risk
~0 1E-.00 — ,
as
a
§ IE-OB -
^ 1E-10 —
CO
- j— |
! [•
"• External Ingestion inhalation Ingestion Ingestion Ingestion
exposure of soil of dust or plants of meat of milk
Refer to notes at end of figure
Figure 7. Graphical summary of risk for BORAX-I.
33
-------
-J- 1£tOO —
^
3 1E-02
5!
Q
O
g> 1E-08-
¥ 1E-10 —
CO
BORAX-I Occupational Risk (current) en o^rmin^c
_ CD SOthpwewrtfto'
I — I «Sth pwiantito "
I
^ * External exposure Ingestion of soil Inhalation of dust
"a IE.OO —
8 'E-02 -
g" 1E-08 -
•X. 1E-10 —
CO
BORAX-I Occupational Risk (site-specific #1) a M»mini«tie
.— I I 5Oth p«re«ntil«"
I — 1 99th pcrewitil* *
?>&— ^— 1 \^
~ External exposure Ingestion of soil Inhalation of Oust
•y IE*00 —
"a
8 'E"02 -
o
O
8" IE-" -
J£ 16-10 —
«
BORAX-I Occupational Risk (site-specific #2) GO oMnmnMe
1 — 1 50ttip«rcMrtil«"
f~1 9Sth pcrcwitil* '
External exposure Ingestion of soil Inhalation of dust
s 1E<0°-
§ 16-02 -
0 16-04 -
a.
g> 1E-OB -
^ 16-10 —
CO
BORAX-I Occupational Risk (future - 30-year) EH D**m 16-06 -
~~
CO
BORAX-I Occupational Risk (future - IOC year) en oMenum* .c
_ 1 1 S0thp»re»ntil«"
1 — I 9Sth ptnmnu* *
.*.'.( • . .
°- E " External exposure Ingestion of soil Inhalation of dust
a. The 50th percentile is the average individual risk.
b. The 95th percentile is the reasonable maximum exposure individual risk.
Figure?, (continued)
34
-------
Residential (current)
1E+00
1E-02
5 1E-04
1E-06
i
1E-10-
1E-12-
9E-2
3E-2
2E-2
2E-2
\
National National
Natural Background Natural Background
(without radon) (with radon)
Highest Local
Reading Background
SL-1
Highest Local
Reading Background
BORAX-I
Figure 8. Graphical summary of external exposure risk based on measured radiological fields and natural background, SL-1,
and BORAX-I.
The residential risk (30-year duration) estimated from radiological field measurements at the SL-1
burial ground, 9E-02, is only slightly higher than the risk due to the local background of 3E-02. At
BORAX-I, the risk based on radiological field measurements is equal to local background (2E-02) and
is only slightly higher than the national average natural background, which ranges from 2E-03 to
6E-03.
6.1.5 Uncertainty
Risk assessments are subject to uncertainty from assumptions about inventory estimates, fate and
transport estimation, exposure estimation, and radiotoxicity data. Uncertainty was addressed by using
health-protective assumptions that systematically overstate the magnitude of health risks. This process
bounds the plausible upper limits of risk and facilitates an informed risk management decision. Table 7
is a summary of risk assessment assumptions and associated uncertainties.
In addition to uncertainty directly associated with the baseline risk assessment, two other issues
were considered. The first was estimation of risk associated with the radiological field actually mea-
sured at the sites to evaluate the effectiveness of the soil shielding currently on the sites (the baseline
risk assessment requires exposure of the receptor directly to the waste). The second issue was explored
as a result of public comment received on the proposed plan and involved estimating the soil concentra-
tion of uranium-235 based on the quantity of unrecovered fuel.
35
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Table 7. Summary of risk assessment assumptions and associated uncertainties.
Assumption
Description of uncertainty
Effect of uncertainty on
risk estimates
Soil sample analytical results
are representative of surface
contamination.
Many samples at both sites were collected
from hot spots, as opposed to a strictly
random sampling strategy. Concentrations
based on the 95% upper confidence limit
of these biased results were assumed uniformly
distributed throughout surface soil.
Computer-modeled radionuclide
inventories (curies) converted
to subsurface concentrations of
radionuclides (pCi/g) are
representative of subsurface
contamination.
Radionuclide inventories were assumed uniformly
distributed throughout the reported volumes at a
material density of 1.5 g/cm-*.
Results in higher
estimated concentrations
in surface soils and thus
increased risk. (Note that
Operable Unit 5-05 surface
soils were found to not
present an unacceptable
risk subsequent to the base-
line risk assessment in the
remedial investigation.)
The actual nature and
density of buried materials
is not homogeneous. Areas
of both higher and lower
concentrations (and thus
risk) within the waste are
expected.
Modeled inventories reduced by The reduced quantities are upper-bound estimates Results in higher estimated
percent of uranium-235 recovered of inventories originally deposited on each site. concentrations in the sub
are representative of actual surface and thus increased
concentrations. risk.
No migration of contaminants has Maximizes concentrations (no dilution) and
occurred. minimizes volume.
Significant quantities of
nonradioactive contaminants are
not present at either site.
If any nonradioactive contaminants are present,
they would represent an insignificant contribution
to the total risk at each site.
Modeled receptor is in direct Shielding provided by existing soil cover is
contact with the surface or excluded from consideration; the EPA-default time
subsurface contamination for time and duration of exposure values are formulated
periods specified in the remedial for sensitive individuals.
investigation report
Groundwater modeling parameters Parameters and assumptions were selected to
and assumptions generic to the maximize concentrations of contaminants in the
INEL are adequate to model groundwater.
groundwater impacts.
Results in higher estimated
concentrations in the sub-
surface and thus increased
risk.
May underestimate risk
slightly.
Results in substantially
higher exposure
values for all receptors,
and thus higher risks.
Results in overestimation of
concentrations in aquifer
and minimizes vadose zone
travel times, resulting in
higher estimated risk.
36
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The uncertainties related to the measurement of radiological data in the field can lead to an under-
or over-estimation of risk. Field measurements are accurate at the time and location the reading is
taken. However, factors such as detection limits, correlation of field measurements to specific radionu-
clide concentrations, and perturbations resulting from radioactive fragments or particles add significant
uncertainty to these risk estimates.
To address remarks received during the public comment period, hypothetical soil concentrations of
uranium-235 were estimated for the surface soil at BORAX-I using the assumption that the entire 3.7
kg of uranium-235 unrecovered at the site was uniformly distributed through two soil volumes. The
first, 84,000 cubic feet (2,400 m3) was based on the extent of gravel-covered area and a depth of one
foot. A second volume, 14,700 cubic feet (416 m3) by one foot deep, was based on the portion of the
gravel-covered area which had a radiological field greater than 0.02 mR/hour during a survey conduct-
ed in 1980. Concentrations resulting from these calculations were 2.2 pCi/g (1 mg uranium-235/kg
soil) and 13 pCi/g (6 mg uranium-235/kg soil). Although, these estimates were developed under the
assumption that the entire 3.7 kg of uranium-235 was distributed in the surface soil, historical docu-
mentation indicates that some of the fuel remaining at the site was buried in the reactor structure foun-
dation. In the risk assessment, the 95% upper confidence limit for uranium-235 (68.6 pCi/g), based on
analytical results of biased samples, was used to represent surface soil concentrations. This concentra-
tion is much higher than either 2.2 or 13 pCi/g, demonstrating that use of the 95% upper confidence
limit of biased sampling can result in over-estimation of actual soil concentrations, and therefore over-
estimation of the risk.
6.1.6 Conclusions
An inspection of the risk values shows several important facets of the investigation:
• At the SL-1 burial ground, scenario total risks range from 6E-04 to 5E-01. At BORAX-I the
scenario risks range from 3E-05 to 3E-02. The risks are dominated by cesium-137 plus its
daughter barium-137m in the external exposure pathway for both sites.
• The risks due to external exposures estimated by deterministic or probabilistic methods are all
greater than 1E-06, and in nearly all scenarios, greater than 1E-04; the only exception was the
occupational site-specific #2 scenario for BORAX-I. Values greater than 1E-04 are considered
indicative of conditions that may pose a threat to human health and the environment if not
addressed by a response action.
• The risks attributable to soil ingestion for all radionuclides are generally one or more orders of
magnitude lower than the risks from external exposure and considered a secondary concern;
however, for the residential intrusion scenarios at SL-1, the risk from the soil ingestion pathway
exceeds 1E-04.
• The risks of soil inhalation and groundwater ingestion for all scenarios are less than 1E-05 and
generally less than 1E-06, and thus negligible.
• Decay of cesium-137 (plus its progeny) will result in a decrease of risk through time at both
sites. After about 400 years, the risk will reach 1E-04 at SL-1; after 320 years, the risk at
37
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BORAX-I will be dominated by the long-lived uranium-235 in the external exposure pathway,
and the risk will not drop below 2E-04.
• The external radiation exposure risks estimated using deterministic and probabilistic methods
dominate the total risk. Although this calculated upper limit of the risk notably exceeds the
1E-04 risk value, the external exposure risks estimated from radiological field measurements
were not much greater than the risk due to background radiation. The primary difference is that
the baseline risk assessment was based on the assumption that the individual is exposed directly
to the waste; that is, the dose that the individual receives is not adjusted to account for the
shielding provided by the soil cover. The risk estimated from the field measurements was based
on the actual measured dose that an individual at the surface receives.
• Although Operable Unit 5-05 surface soils were evaluated in the baseline risk assessment pre-
sented in the remedial investigation/feasibility study report and summarized in this section, a
subsequent determination found the surface soils do not present an unacceptable risk to human
health or the environment (see Section 11.1).
The main contributor to the deterministic and probabilistic risk is from external exposure to
cesium-137 plus its daughter barium-137m. All other contributions to the total risk are very small, usu-
ally two, three, or more orders of magnitude below the risk due to external exposure to ionizing radia-
tion and generally below the acceptable risk level of 1E-04.
6.2 Ecological Concerns
The ecological assessment of the SL-1 and BORAX-I burial grounds is a qualitative evaluation of
the potential effects of the sites on plants and animals other than people and domesticated species. A
quantitative ecological assessment is planned in conjunction with the ENEL-wide comprehensive reme-
dial investigation/feasibility study tentatively scheduled for 1998. There are no critical or sensitive
habitats on or nearby the burial grounds, and no endangered species or habitats of endangered species
are known to exist on either site. Based on the present contaminant and ecological information and the
qualitative eco-evaluation performed for this Record of Decision, the preferred alternative remedial
action presented herein will serve to further reduce the ecological risks posed by these sites. It is
unlikely the 1998 INEL-wide comprehensive remedial investigation/feasibility study quantitative eco-
logical assessment will result in the need for any additional actions at these sites.
6.2.1 Species of Concern
The only federally listed endangered species known to frequent the INEL is the peregrine falcon.
The status of the bald eagle in the lower 48 United States was changed from endangered to threatened
in July 1995. Several other species observed on the INEL are the focus of varying levels of concern by
either federal or state agencies. Animal and avian species include the ferruginous hawk, the northern
goshawk, the sharp-tailed grouse, the loggerhead shrike, the Townsend's big-eared bat, the pygmy rab-
bit, the gyrfalcon, the boreal owl, the flammulated owl, the Swainson's hawk, the merlin, and the bur-
rowing owl. Plant species classified as sensitive include Lemhi milkvetch, plains milkvetch, wing-seed
evening primrose, nipple cactus, and oxytheca.
38
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6.2.2 Exposure Assessment
Three potential routes of exposure were identified for terrestrial and avian species: ingestion of
soil, vegetation, or prey; inhalation of fugitive dust; and external exposure to radiation. Ingestion of
contaminated water was not considered because there are no surface-water features on either burial
ground and because groundwater is not accessible to ecological receptors. For plants, the uptake of
contaminants through roots systems was considered.
The amount of exposure is directly related to the amount of time spent and the fraction of diet taken
on the sites. Therefore exposures are greatest for permanent ecological residents, particularly plants and
small burrowing animals. The small size of the burial grounds minimizes the exposures received by
migratory species, which include most avian and large mammal species that inhabit the INEL.
6.2.3 Risk Characterization
The contaminants of concern at the burial grounds consist of radionuclide-contaminated soil and
debris, most of which is buried beneath a minimum of 2 feet (0.6 m) of soil. Both sites are relatively
small. Some amounts of contamination may be brought to the surface through plant uptake and bur-
rowing animals and insects, be ingested by herbivores and animals who take prey from the sites, and
enter the food web. Individuals representing a small portion of the total population of burrowing and
ground-dwelling animals may also receive direct exposures. However, risks due to these exposures
would be limited to a small number of individual ecological receptors and would have little impact on
total populations. As a result, the potential for risk to ecological receptors is very small. In addition,
the inaccessibility of contamination supports the conclusion that the sites do not present a significant
risk to plant and animal life.
The small areas of the sites will not support sizeable populations relative to the area and popula-
tions of the entire INEL. The potential for cumulative effects throughout each waste area group and
INEL-wide are of much greater concern than the effects from the individual burial grounds. These
issues will be addressed in the comprehensive remedial investigation/feasibility studies for each waste
area group and for the entire ENEL.
6.3 Basis for Response
Actual or threatened releases of contaminants from these burial grounds, if not addressed by imple-
menting the response action selected in this Record of Decision, present a potential threat to public
health, welfare, or the environment.
The results of the baseline risk assessment indicate that unacceptable risk exists at both burial
grounds. The primary risk at both sites is from external exposure to cesium-137 and its daughter bari-
um-137m. Decay of cesium-137 (plus its daughter) will result in a decrease of risk to acceptable levels
after about 400 years at SL-1, and after 320 years at BORAX-I. Risk at both sites results from direct
exposure to the contaminants. The shielding and control of intrusion can be accomplished through
construction of a long-term engineered cap at each site designed to contain the radionuclides as they
decay with time.
39
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The risk to ecological receptors at both sites is associated with intrusion into the wastes. This risk
will decrease through time as the radionuclides decay. Long-term engineered caps can inhibit intrusion
by plant roots, insects, and burrowing animals.
7. Description of Alternatives
7.1 Remedial Action Objectives and
Applicable or Relevant and Appropriate Requirements
The description of alternatives includes discussion of how remediation goals are satisfied by the
actions undertaken. Similarly, the descriptions explain how compliance with federal and state environ-
mental laws is achieved. The remedial action objectives and environmental laws associated with the
alternatives considered in the remedial investigation/feasibility study for the SL-1 and BORAX-I burial
grounds are summarized below to support the description of alternatives.
7.1.1 Remedial Action Objectives
As part of the remedial investigation/feasibility study process, remedial action objectives were
developed in accordance with the National Contingency Plan and EPA guidance. The intent of the
remedial action objectives is to set goals for protecting human health and the environment. The goals
are designed specifically to mitigate the potential adverse effects associated with the burial grounds.
Results of the remedial investigation and baseline risk assessment indicate that exposure to pene-
trating radiation from contaminated soils and materials within the burial grounds presents the most sig-
nificant future risk to human health. Therefore, the primary remedial action objectives and the focus of
the remedial action alternative development are to inhibit exposure to radioactive materials. Remedial
action objectives established for protection of human health are:
• Inhibit exposure to radioactive materials that would result in a total excess cancer risk (for all
contaminants) of greater than 1 in 10,000 to 1 in 1,000,000 (1E-04 to 1E-06)
• Inhibit ingestion of radioactive materials that would result in a total excess cancer risk (for all
contaminants) of greater than 1 in 10,000 to 1 in 1,000,000 (1E-04 to 1E-06)
• Inhibit inhalation of suspended radioactive materials that would result in a total excess cancer
risk (for all contaminants) of greater than 1 in 10,000 to 1 in 1,000,000 (1E-04 to 1E-06)
• Inhibit degradation of the burial grounds that could result in exposure of buried wastes or
migration of contaminants to the surface that would pose a total excess cancer risk (for all cont-
aminants) of greater than 1 in 10,000 to 1 in 1,000,000 (1E-04 to 1E-06).
The remedial action objective for protection of the environment focuses on preservation of the local
ecology by inhibiting the potential for contaminant migration. The remedial action objective estab-
lished for protection of the environment is:
• Inhibit adverse effects to resident species from exposure to contaminants at the burial grounds.
40
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7.1.2 Applicable or Relevant and Appropriate Requirements
CERCLA requires that remedial actions comply with federal and state laws that are applicable to
the action being taken. Remedial actions must also comply with the requirements of laws and regula-
tions that are not directly applicable but are relevant and appropriate; in other words, the requirements
pertain to situations sufficiently similar to those encountered at a CERCLA site so that their use is
well-suited to the site. Combined, these are referred to as applicable or relevant and appropriate
requirements (ARARs). State ARARs are limited to those requirements that are (a) promulgated, (b)
uniformly applied, and (c) are more stringent than federal requirements. Compliance with ARARs
requires evaluation of the remedial alternatives for compliance with chemical-, location-, and action-
specific ARARs or justification for a waiver.
During the remedial investigation/feasibility study for SL-1 and BORAX-I, ARARs were specified
for the remedial action alternatives under consideration. Potential ARARs initially identified were
screened on the basis of review by the DOE-ID, the EPA, and the IDHW. Table 8 provides a summary
of the ARARs for the three alternatives considered. These regulations focus on protection of the public
from radiation and control of emissions that may result from any remediation activities. As ARARs,
these regulations govern potential radionuclide emissions and dust-generating activities (such as exca-
vation, earth-moving, and heavy-equipment operation). Although DOE orders are not ARARs, estab-
lished DOE orders would be considered to ensure radiation protection for the environment and the pub-
lic. Such DOE orders are identified as "To-Be-Considered" (TBC) criteria. Currently no EPA or State
of Idaho regulations exist that establish cleanup levels for radionuclide contaminants in soil. Based on
the contaminants of concern at SL-1 and BORAX-I, the location of the burial grounds, and the remedi-
al actions evaluated, no other ARARs were identified.
Table 8. Summary of ARARs and criteria to be considered for alternatives.
Alternative 1 Alternative 2 Alternative 3
Statute Regulations No Action Containment Removal
NESHAP National Emission Standards for NA NA A
Radionuclide Emissions Other than
Radon from DOE Facilities (40 CFR §61.90)
IDAPA Idaho Rules for Control of Fugitive Dust NA A A
(IDAPA 16.01.01.650 and .651)
IDAPA Idaho Rules for Toxic Air Pollutants NA NA A
(IDAPA 16.01.01.585 and .586)
DOE Order 5400.5, "Radiation Protection of TBC TBC TBC
the Public and Environment"
DOE Order 5820.2A, "Radioactive Waste TBC TBC TBC
Management"
A = Applicable; NA = Not applicable or relevant and appropriate; R = Relevant and appropriate; TBC = To be considered
41
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7.2 Summary of Alternatives
The three types of alternatives submitted to detailed analysis include:
Alternative 1: No action
Alternative 2: Containment by capping with an engineered long-term barrier comprised
primarily of natural materials
Alternative 3: Removal by conventional excavation with disposal at the Radioactive Waste
Management Complex.
The no action alternative and the two alternatives that passed the screening criteria are described
below. Remedial action at BORAX-I is expected to include management of contaminated surface soils.
Surface soils presenting a potential human health excess risk of over 1 in 10,000 will be included in the
remedial action. Action levels for the radionuclides of concern in BORAX-I soils are based on the
Remedial Investigation/Feasibility Study for Operable Unit 10-06 (Radionuclide-Contaminated Soils at
the INEL) and are identified as 16.7 pCi/g for cesium-137, 10.8 pCi/g for strontium-90, and 13.2 pCi/g
for uranium-235. These activity concentrations correspond to a 1 in 10,000 risk level based on the
external exposure and ingestion pathways and a residential scenario beginning in 100-years. Costs pre-
sented for remedial actions at BORAX-I are based on the assumption that all potentially contaminated
surface soils will be included in the remedial action. A surface area as large as 84,000 square feet
(7,800 m^) would require management as part of the remedial action at BORAX-I. As presented in the
proposed plan, remedial action at the SL-1 operable unit may have also required management of poten-
tially contaminated surface soils. An assessment of those soils has since been completed that supports
a no action decision for the surface soils within Operable Unit 5-05 outside of the exclusion fence.
Section 11 contains more details regarding this assessment.
7.2.1 No Action
Under Alternative 1, no attempt would be made to contain, treat in place, or remove contaminated
materials. Instead, environmental monitoring would be performed to assess contaminant miration
from the burial grounds. Environmental monitoring would consist of those methods used to identify
contaminant migration within environmental media (air, groundwater, and soil) and to identify the
exposure resulting from those contaminated media. Monitoring results would be used to determine the
need for any future remedial actions necessary to protect human health and the environment.
Environmental monitoring would be conducted until future reviews of the remedial action determine
such activities are no longer necessary. There were no ARARs identified for the no action alternative.
The estimated cost for implementing environmental monitoring for 30 years under this alternative is
$188,000 at SL-1 and $180,000 at BORAX-I. Environmental monitoring may be required beyond 30
years, however CERCLA guidance specifies costing such activities for only 30 years.
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To the extent practicable, environmental monitoring activities would be performed under WAG-
wide and INEL-wide comprehensive monitoring programs. Radiological surveys would be performed
at both SL-1 and BORAX-I as part of this remedial action until WAG-wide comprehensive environ-
mental monitoring programs are in place. Groundwater monitoring needs would be identified in the
WAG 5 Comprehensive RI/FS and the WAG 10 Comprehensive RI/FS (which encompasses WAG 6).
Air monitoring at both site« would be conducted as part of the INEL-wide air monitoring program.
7.2.2 Containment
Alternative 2 is a containment action that consists of installing a long-term engineered barrier (cap)
over a burial site to provide shielding from penetrating radiation, to inhibit contaminant migration, and
to limit intrusion. Barrier technology is currently in use at several waste sites to provide long-term iso-
lation of radioactive wastes that are disposed of in place, as is the case for both burial grounds. The
cap can be designed for longevity and would be of sufficient thickness to provide a shield from pene-
trating radiation, inhibit intrusion by burrowing animals and insects into the waste, and discourage
human intrusion. Contaminant migration would be inhibited by reducing erosion by wind and water.
The barrier would be designed to provide shielding from penetrating radiation for at least 400 years at
SL-1 and 320 years at BORAX-I. A multiple-layer cap comprised primarily of natural materials would be
designed during the remedial design phase of the remedial action. Cap layers would likely consist of a
combination of sand, gravel, silt, basalt, cobbles, or native soil. Construction details for the engineered
barrier would be identified during the remedial design phase. The barrier design would be based on site-
specific characteristics and conditions at the INEL such that maintenance requirements are minimized.
Site-specific considerations, such as annual precipitation, frost depth, and anticipated soil erosion, would
be used to design the optimum barrier configuration for application at the SL-1 and BORAX-I burial
grounds during the remedial action phase. Each cap system would also include surface-water diversion
controls to direct runoff away from the burial grounds.
The capping system would be combined with institutional controls consisting of access and land
use restrictions to prevent intrusion into the SL-1 and BORAX-I burial grounds. The DOE would be
responsible for establishing and maintaining land use and access restrictions for at least 100 years.
Access restrictions in the form of fences, warning signs, and permanent markers would be used to
determine unauthorized entry into the burial grounds. Institutional controls would include placing writ-
ten notification of the remedial action in the facility land use master plan; the notification would pro-
hibit any activities that would interfere with the remedial activity. A copy of the notification would be
given to the Bureau of Land Management, together with a request that a similar notification be placed
in the Bureau of Land Management property management records. The DOE would provide EPA and
IDHW with written verification that notification, including Bureau of Land Management notification,
have been fully implemented.
Cap integrity monitoring and radiological survey programs would be established to verify the con-
tinued functionality of the containment systems and provide early detection of potential contaminant
migration. Cap integrity monitoring for cracks, erosion, and other observable degradation would be
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conducted to identify maintenance requirements. Institutional controls and monitoring requirements
would be the responsibility of the DOE and would be evaluated for adequacy, effectiveness, and neces-
sity during each five-year review of the remedial actions.
The area requiring containment at SL-1 is the region extending from the trench to pit 1 in Figure 2.
The area requiring containment at BORAX-I is based on the assumption that consolidation of all conta-
minated surface soil is necessary. The minimum area requiring containment at BORAX-I is the 100-
by 100-foot (30- by 30-m) fenced area of the burial ground, or 10,000 square feet (929 m2). The maxi-
mum area of containment required at BORAX-I is based on the assumption that the entire 84,000
square foot (7,800 m2) area of contaminated surface soil would require containment. Although protec-
tive covers over this entire area are feasible, consolidation of contaminated surface soil to a location
near the existing buried wastes is proposed. Consolidation of contaminated surface soil would ensure
that the size of a protective cover is limited to the area containing the majority of contamination
(e.g., the reactor foundation).
The ARAR identified for this alternative is the Idaho Rules for Control of Fugitive Dust
(IDAPA 16.01.01.650 and .651). This ARAR would be met during soil consolidation activities at
BORAX-I and construction of a barrier at either site by application of appropriate engineering controls
to minimize generation of airborne contamination and dust.
The estimated cost of Alternative 2 is $1.9 million at SL-1 and $1.5 million at BORAX-I. These
costs are based on refinements to the estimates presented in the proposed plan for Alternative 2. The
primary refinements include a cap design specific to the INEL and elimination of groundwater monitor-
ing requirements. "The cap design is based on research performed at the INEL by the Environmental
Science and Research Foundation. Environmental monitoring has been specified by the agencies to
consist of radiological surveys. Groundwater monitoring costs have not been included because ground-
water monitoring needs will be determined by the WAG 5 Comprehensive RI/FS for WAG 5 as a whole
and the WAG 10 Comprehensive RI/FS for WAG 6. Responsibility for radiological surveys at SL-1 will
be assumed by the WAG 5 Comprehensive RI/FS once the comprehensive program is in place. Similarly,
responsibility for radiological surveys at BORAX-I will be assumed by the WAG 10-04 Comprehensive
RI/FS once the comprehensive program is in place. The cost estimates include 30 years of radiological
surveys at SL-1 and BORAX-I. (Air monitoring at both sites would be conducted as part of the ENEL-
wide air monitoring program to eliminate that cost component from this remedial action.)
Direct costs for equipment and construction are approximately $0.90 million at SL-1 and $0.61
million at BORAX-I (including soil consolidation). Indirect costs for engineering design and manage-
ment, construction management, and contractor overhead and profit are approximately $0.47 million at
SL-1 and $0.45 million at BORAX-I. A contingency cost to account for the conceptual level of design
for Alternative 2 is approximately $0.27 million at SL-1 and $0.18 million at BORAX-I. Net present
value cost to perform post-closure monitoring and maintenance activities for 30 years are approximately
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$0.33 million at SL-1 and $0.21 million at BORAX-I. Monitoring and maintenance may be required
beyond 30 years, however CERCLA guidance specifies costing such activities for no more than 30 years.
7.2.3 Removal and Disposal
Alternative 3 is the complete removal of all contaminated materials from the burial grounds using
conventional excavation techniques, with cleanup levels established on the basis of excess risk at the
INEL. Conventional excavation techniques utilize commercially available earth-moving equipment.
The volume of contaminated media at the SL-1 is approximately 265,182 cubic feet (7,509 m3).
The total volume of contaminated media at the BORAX-I is approximately 93,421 cubic feet
(2,645 m3). These estimates are based on the volumes of buried waste, backfill, and potentially conta-
minated surface soils at BORAX-I. Once removed, contaminated materials would be packaged and
transported to the Radioactive Waste Management Complex for disposal.
Following the removal of contaminated soil and solid waste, the excavated area would be backfilled
with clean fill material and compacted to prevent future subsidence or settling. A layer of topsoil
would be placed over the compacted backfill, contoured to match the surrounding landscape, and seed-
ed with an appropriate mixture of native grasses and shrubs to facilitate revegetation.
The ARARs identified for this alternative include the National Emissions Standards for
Radionuclide Emissions Other than Radon from DOE Facilities (40 CFR §61.90), Idaho Rules for
Toxic Air Pollutants (IDAPA 16.01.01.585 and .586), and Idaho Rules for Control of Fugitive Dust
(IDAPA 16.01.01.650 and .651). All three ARARs would be met by conducting excavation activities
within an enclosed structure fitted with a filtered ventilation system and by implementing dust-suppres-
sion measures.
The estimated costs of Alternative 3 are approximately $68.9 million at SL-1 and $20.5 million at
BORAX-I. The estimated cost for SL-1 is based on the no action decision for soils outside of the
600- by 300-foot (182.9- by 91.4-m) exclusion fence but inside the boundary of Operable Unit 5-05.
The lower end of the cost range presented in the proposed plan for Alternative 3 at SL-1 reflects this
situation. The estimated cost for BORAX-I is based on the anticipated need to include up to 84,000
square feet (7,800 m2) of contaminated surface soil in the remedial action. The upper end of the cost
range presented in the proposed plan for Alternative 3 at BORAX-I is representative of this scenario.
The estimates include an assumption that no additional costs are incurred once the contaminated
materials are removed from the sites and disposed at the Radioactive Waste Management Complex.
Therefore, post-closure activities such as monitoring are not required. Direct costs for equipment, con-
struction, and disposal at the Radioactive Waste Management Complex are approximately $34.0 mil-
lion at SL-1 and $10.1 million at BORAX-I. Indirect costs for engineering design and management,
construction management, and contractor overhead and profit are approximately $24.7 million at SL-1
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and $7.4 million at BORAX-I. The contingency cost to account for the conceptual level of design for
Alternative 3 is approximately $10.2 million at SL-1 and $3.0 million at BORAX-I.
8. Summary of Comparative Analysis of Alternatives
Each of the three alternatives subjected to the detailed analysis were evaluated against the nine evalu-
ation criteria identified under CERCLA. The criteria are subdivided into three categories: (a) threshold
criteria that mandate overall protection of human health and the environment and compliance with
ARARs; (b) primary balancing criteria that include long- and short-term effectiveness, implementability,
reduction in toxicity, mobility or volume through treatment, and cost; and (c) modifying criteria that mea-
sure the acceptability of alternatives to state agencies and the community. The following sections sum-
marize the evaluations of the three alternatives against the nine evaluation criteria.
8.1 Threshold Criteria
The remedial alternatives were evaluated in relation to the two threshold criteria: overall protection
of human health and the environment, and compliance with ARARs. The selected remedial action
must meet the threshold criteria. Although the no action alternative does not meet the threshold crite-
ria, this alternative was used in the detailed analysis as a baseline against which the other alternatives
were compared, as directed by EPA guidance.
8.1.1 Overall Protection of Human Health and the Environment
This criterion addresses whether a remedy provides adequate protection of human health and the
environment and describes how risks posed through each exposure pathway are eliminated, reduced, or
controlled through treatment, engineering controls, or institutional controls.
Results of the baseline risk assessment indicate that upper limit of exposure risk will decrease to
below 1 in 10,000 after approximately 400 years at SL-1. This upper limit will further decrease to 3 in
1,000,000 after approximately 650 years and remain constant thereafter. The upper limit of exposure
risk at BORAX-I will decrease to approximately 2 in 10,000 after 320 years, then remain essentially
unchanged far into the future.
Alternative 1 (no action) would not satisfy the criterion of overall protection of human health and
the environment because access to the site and contact with the waste is not prevented. The contain-
ment alternative, Alternative 2, would provide overall protection of human health and the environment.
A protective cover would provide shielding from penetrating radiation, limit contaminant migration,
and inhibit inadvertent intrusion into the wastes by humans, insects, and animals. Consolidated surface
soil at BORAX-I would also be contained beneath the protective cover. Long-term protection would be
ensured by incorporating design features engineered to last a minimum of 400 years at SL-1 and 320
years at BORAX-I. Alternative 3 (removal by conventional excavation with disposal at the Radioactive
Waste Management Complex) would provide effective long-term protection of human health and the
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environment but could result in potentially significant short-term exposures for workers removing the
radionuclide-contaminated wastes during the remedial action.
Both of the action alternatives would result in a reduction of excess lifetime cancer risk. Alternative 2
would result in an excess lifetime cancer risk of less than 1 in 1,000,000 for as long as the cap remains
functional. A cap minimizes potential risks by shielding, limiting migration of contamination, and inhibit-
ing intrusion into the waste. Alternative 3, the removal action, would reduce risk by managing contaminat-
ed materials removed from the burial grounds within an operating radioactive waste disposal facility.
8.1.2 Compliance with Applicable or Relevant and Appropriate Requirements
There are no ARARs identified for the no action alternative. The two action alternatives meet the
identified ARARs through engineering controls and operating procedures. Section 7.2, Summary of
Alternatives, discusses the primary ARARs considered in this study. These ARARs focus on control-
ling exposures to the public and air emissions that may result from remediation activities at the SL-1
and BORAX-I operable units.
8.2 Balancing Criteria
Once an alternative satisfies the threshold criteria, five balancing criteria are used to evaluate other
aspects of the remedial alternatives and weigh major trade-offs among alternatives. The balancing cri-
teria are used in refining the selection of the candidate alternatives for the site. The five balancing cri-
teria are: (1) long-term effectiveness and permanence; (2) reduction in toxicity, mobility or volume
through treatment; (3) short-term effectiveness; (4) implementability; and (5) cost.
8.2.1 Long-Term Effectiveness and Permanence
This criterion evaluates the long-term effectiveness of alternatives in maintaining protection of
human health and the environment after remedial action objectives have been met.
Alternative 1 (no action) provides the least possible level of long-term effectiveness and permanence
because unacceptable risks would remain at both burial grounds. The long-term effectiveness and perma-
nence of containment, Alternative 2, depends on the design-life 01 caca protective cover. As described pre-
viously, the cover can be designed to last for the period of time required to allow radionuclide decay to
decrease exposure risks to acceptable levels. Risks at SL-1 will fall below the 1 in 10,000 risk range in
about 400 years. Risks at BORAX-I will decrease to about 2 in 10,000 in approximately 320 years and
will remain constant, essentially forever, due to the presence of long-lived uranium-235. The Alternative 3
removal action provides the highest degree of long-term effectiveness and permanence because contami-
nated materials would be completely removed. However, removing and transporting contaminated materi-
als from one place to another within the INEL (from SL-1 or BORAX-I to the Radioactive Waste
Management Complex) simply transfers the risk from one place to another.
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8.2.2 Reduction of Toxicity, Mobility, or Volume through Treatment
This criterion addresses the statutory preference for selecting remedial actions that employ treat-
ment technologies that permanently reduce toxicity, mobility, or volume of the hazardous substances as
their principal element. Treatment to reduce the toxicity of radionuclides is presently not feasible;
therefore none of the remedial alternatives developed for the burial grounds involve the use of treat-
ment to reduce the toxicity, mobility, or volume of contaminated materials.
8.2.3 Short-Term Effectiveness
Short-term effectiveness addresses the period of time needed to implement remediation methods to
reduce any adverse impacts on human health and the environment that may be posed during the con-
struction and implementation period until cleanup goals are achieved.
The short-term effectiveness for any remedial action taken at the burial grounds would be enhanced
to the maximum extent practicable through adherence to strict health and safety protocols for worker
protection and use of engineering controls to prevent potential contaminant migration. However, the
alternative that requires the least amount of disturbance of contaminated materials ranks the highest in
terms of short-term effectiveness. As such, Alternative 1 (no action) provides the highest degree of short-
term effectiveness because no additional on-site activities are required. Implementation of Alternative 2
(containment) would require disturbance to the surface of the burial grounds, however, no contact with
buried waste would be involved. Alternative 2 does require contaminated surface soil at BORAX-I to
be consolidated near the location of the reactor foundation. Assuming no protective measures were in
place, workers installing the Alternative 2 cap would receive external exposure to penetrating radiation
until sufficient construction material (such as soil, sand, and gravel) was placed over the burial ground to
provide adequate shielding. Based on modeling and field measurements, approximately 3 inches (0.1 m)
of additional soil placed over the SL-1 burial ground and 9 inches (0.2 m) of additional soil placed over
the BORAX-I burial ground would reduce external exposures to background radiation levels.
Consequently, the soil required to form the foundation for a protective cover is likely to reduce external
exposures to background levels. Alternative 3 (conventional excavation) offers the least short-term effec-
tiveness due to direct contact with contaminated materials during excavation of the burial grounds and
transport to the Radioactive Waste Management Complex. Short-term effectiveness for Alternatives 2 and
3 would be equally diminished if surface-soil consolidation is required at BORAX-I.
8.2.4 Implementability
The implementability criterion has the following three factors requiring evaluation: (a) technical
feasibility, (b) administrative feasibility, and (c) the availability of services and materials. Technical
feasibility requires an evaluation of the ability to construct and operate the technology, the reliability of
the technology, the ease of undertaking additional remedial action (if necessary), and monitoring con-
siderations. The ability to coordinate actions with other agencies is one factor for evaluating adminis-
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trative feasibility, and the agencies have demonstrated this ability throughout the project to date. Other
administrative activities that would be readily implementable include planning, use of administrative
controls, and personnel training. In terms of services and materials, an evaluation of the following
availability factors is required: necessary equipment and personnel, prospective technologies, and
cover materials.
Alternative 1 (no action) is the simplest remedial action to implement from a technical perspective
because environmental monitoring is all that is required. Monitoring would be required until future
reviews of the remedial action indicate such activities are no longer necessary. Environmental monitor-
ing services and equipment are readily available. However, Alternative 1 is administratively unaccept-
able due to the potential risks to human health and the environment posed by SL-1 and BORAX-I.
The containment option of Alternative 2 is technically implementable. Consolidation of contami-
nated surface soils at BORAX-I would involve standard earth moving equipment to perform excavation
activities and water spray vehicles for dust suppression. Construction capabilities for engineered barri-
ers are commercially available, and such barriers have been used at many similar sites in both private
industry and at government facilities. Specialized construction equipment and materials would not be
required. The engineering required to design and construct a cap meeting the requirements necessary
to ensure protection of human health and the environment at SL-1 and BORAX-I would be specified
during the remedial design phase. The general performance requirements of the cap are established in
this Record of Decision.
Alternative 3 (excavation and removal) would be the most difficult remedial option to implement
because of the complexity of the remediation process. Containment of contamination during excava-
tion and handling contaminated materials removed from the burial grounds would be required.
Conventional excavation techniques to perform removal operations are commercially available and
commonly used for earth moving applications. Administratively this alternative would require signifi-
cant time and resources to perform environmental assessments, safety analyses, designs, and demon-
strations prior to initiating any removal activity.
8.2.5 Cost
In evaluating project costs, an estimation of the direct and indirect costs in present-worth dollars is
required. Direct costs include the estimated dollars for equipment, construction, and operation activi-
ties to conduct a remedial action. Indirect costs include the estimated dollars for activities that support
the remedial action (such as construction management, project management, and management reserve).
In accordance with remedial investigation/feasibility study guidance, the costs presented are estimates
(-30% to +50%). Actual costs will vary based on the final design and detailed cost itemization.
Table 9 for SL-1 and Table 10 for BORAX-I summarize the estimated costs for each remedial
action alternative. The costs presented are based on a specific set of assumptions and as those assump-
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tions change so will the cost estimates. For example, CERCLA guidance specifies monitoring and
maintenance costs to be estimated for 30 years. However, these activities may be required beyond 30
years and as a result may cost significantly more than estimated.
The cost estimates presented for Alternative 3 (excavation and removal) are based on the proposed
plan and the remedial investigation/feasibility study prepared for 5T.-1 and BORAV-I. As indicated in
Section 7.2.1, the estimated cost for no action (Alternative 1) differs from the proposed plan because
monitoring requirements for the sites have been refined.
The cost estimates presented for Alternative 2 (containment) have been revised since the proposed
plan. As part of the CERCLA process, estimated costs for the selected remedy have been refined based
on further developments in the level of design detail for Alternative 2. Estimated costs for Alternative
2 have been revised based on a cap design specific to the conditions at the INEL and identification of
specific environmental monitoring requirements at both sites. The cap design is based on research per-
formed at the INEL by the Environmental Science and Research Foundation. Environmental monitor-
ing has been specified by the agencies to consist of radiological surveys. Groundwater monitoring
costs have not been included because groundwater monitoring needs will be determined by the WAG 5
Comprehensive RI/FS for WAG 5 as a whole and the WAG 10 Comprehensive RI/FS for WAG 6.
Responsibility for radiological surveys at SL-1 will be assumed by the WAG 5 Comprehensive RI/FS
once the comprehensive program is in place. Similarly, responsibility for radiological surveys at
BORAX-I will be assumed by the WAG 10-06 Comprehensive RI/FS once the comprehensive program
is hi place. The cost estimates included 30 years of radiological surveys at both sites. (Air monitoring
at both sites will be conducted as part of the INEL-wide air monitoring program. Therefore air moni-
toring costs are not included in the estimates.) The estimated costs presented for Alternative 2 reflect
these refinements.
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Table 9. SL-1 alternative cost estimates.a
Cost Elements
Construction and construction operations"
Post-closure maintenance0
Post-closure monitoring*1
Contingency
Total6
Alternative 1
No Action
NA
NA
150,000
38,000
$188,000
Alternative 2
Containment
$1,368,000
115,000
150,000
337,000
$1,970,000
Alternative 3
Removal
$58,724,000
NA
NA
10,149,000
$68,870,000
a. Costs are for 1995 for Alternatives 1 and 2 and 1994 for Alternative 3.
b. Includes operating costs (net present value) during remedial
action.
c. Net present value assuming 5% interest (net of inflation) for 30 years.
d. Changed from proposed plan to include soil monitoring only. See Section 1 1 .
e. Rounded to ten thousands.
NA = Not applicable (item is not included in the scope for the
alternative).
Table 10. BORAX-I alternative cost estimates.3
Cost Elements
Construction and construction operationsb
Post-closure maintenance0
Post-closure monitoringd
Contingency
Total6
Alternative 1
No Action
NA
NA
144,000
36,000
$180,000
Alternative 2
Containment
$1,058,000
27,000
144,000
225,000
$1,450,000
Alternative 3
Removal
$17,518,000
NA
NA
3,020,000
$20,540,000
a. Costs are for 1995 for Alternatives 1 and 2 and 1994 for Alternative 3.
b. Includes operating costs (net present value) during remedial action.
c. Net present value assuming 5% interest (net of inflation) for 30 years.
d. Changed from proposed plan to include «oil monitoring only. See Section 11.
e. Rounded to ten thousands.
NA = Not applicable (item is not included in the scope for the alternative).
8.3 Modifying Criteria
Two modifying criteria are used in the final evaluation of remedial alternatives: state acceptance
and community acceptance. For both of these criteria, the factors that are considered include the ele-
ments of the alternatives that are supported, the elements of the alternatives that are not supported, and
the elements of the alternatives that have strong opposition.
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8.3.1 State Acceptance
The EDHW concurs with the selected remedial alternative, containment with an engineered cover
comprised primarily of native materials. The IDHW has been involved in the development and review
of the remedial investigation/feasibility study, the proposed plan, and this Record of Decision.
Comments received from EDHW were incorporated into these documents, which have been issued with
IDHW concurrence.
8.3.2 Community Acceptance
This assessment evaluates the general community response to the proposed alternatives presented in
the proposed plan. Specific comments are addressed in the Responsiveness Summary portion of
Appendix A in this document.
Nine individuals provided comments on the proposed plan during the public comment period. One
additional comment was received after the comment period. A total of nineteen comments were
received. Public opinion on the preferred alternative, in no particular order, included, but was not lim-
ited to (a) Alternative 3, Removal, should have been selected; (b) Alternative 2, Containment, was the
best choice; (c) models for groundwater fate and transport should be benchmarked and validated before
proceeding; (d) maximum doses should be compared to maximum dose limits; (e) how were the laws
addressing disposal of spent fuel, transuranic wastes, greater-than-Class-C wastes, and low-level wastes
accounted for; (f) trials regarding partial cleanup, including ground scraping and removal, should be
conducted and considered; (g) future land uses should be considered; (h) results of other capping stud-
ies should be used in this evaluation; (i) no further out-of-state shipments of radioactive wastes should
be allowed to be deposited there; and (j) publications and the expenditures directed toward low-risk
projects are a total waste of taxpayers' dollars.
In summary, three commentors favored the preferred alternative, two preferred Alternative 3, and
the others either requested additional or clarifying information or provided comments not specifically
associated with the two sites in question. The additional information requested appears in the
Responsiveness Summary in Appendix A.
9. Selected Remedy
Based upon consideration of the requirements of CERCLA, on detailed analysis, and on public com-
ments, the DOE-ID, the EPA, and the IDHW have selected Alternative 2, Containment, as the most
appropriate remedy for both the SL-1 and BORAX-I burial grounds. The agencies believe that this alter-
native represents the best balance of trade-offs with respect to the evaluation criteria. Alternative 2 pro-
vides overall protection of human health and the environment, complies with ARARs, provides long- and
short-term effectiveness, is readily implementable, and is cost-effective. An engineered barrier can effec-
tively isolate contaminated materials from the accessible environment. Isolation both inhibits migration
of contaminants from the burial grounds and allows time for radioactive decay of the primary contributor,
cesium-137 and progeny, to the overall risk. Engineered barriers can also inhibit biotic and inadvertent
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human intrusion into the burial grounds. The agencies believe that an engineered cover system can main-
tain isolation of contaminated materials while the overall risks decrease. Engineered barriers have been
used extensively for remedial actions involving radionuclide-contaminated wastes.
Results of the baseline risk assessment indicate that the direct exposure pathway dominates the
overall risk for both burial grounds. The primary contributor to this risk at both sites is cesium-137 and
its progeny. Based on the time required for radionuclide decay to reduce the direct exposure risk to 1
in 10,000 at SL-1 and 2 in 10,000 at BORAX-I, a protective cover must be effective for approximately
400 years at SL-1 and for approximately 320 years at BORAX-I.
9.1 Description of Selected Remedy
The selected remedial action for both burial grounds is Alternative 2, containment by capping with
an engineered long-term barrier comprised primarily of natural materials. The cover will be designed
to maintain effective long-term isolation of contaminants. The number and thicknesses of layers
designed in the cover depend on local climatic and geographic conditions, including precipitation rate,
freeze depth, indigenous plant and animal species, and local topography. A 25-foot (7.5-meter) buffer
zone will be established around the perimeter of the containment structures at each site. Additional
design considerations will include the engineered lifetime of each cap, a minimum of 400 years at SL-1
and a minimum of 320 years at BORAX-I, to allow decay of cesium-137 and to reduce exposure risks.
Surface-water diversion measures, including contouring and grading, will be used as necessary to direct
runoff away from the burial grounds and into nearby, naturally occurring drainage formations. The
specific cover design for each burial ground will be defined during final remedial design.
The cover system design will provide:
• Shielding from penetrating radiation
• A barrier to inhibit biotic and inadvertent human intrusion
• Longevity through the predominant use of naturally occurring materials
• Resistance to erosion that could expose buried waste and contribute to contaminant migration
• Containment of contaminated surface soils which pose an excess risk greater than 1 in 10,000 at
BORAX-I
• Low maintenance requirements.
The capping system will be combined with instititional controls consisting of access and land use
restrictions to discourage intrusion into the SL-1 and BORAX-I burial grounds. The DOE would be
responsible for establishing and maintaining land use and access restrictions for at least 100 years.
Access restrictions in the form of fences, warning signs, and permanent markers would be used to deter
unauthorized entry into the burial grounds. Institutional controls would include placing written notifi-
cation of the remedial action in the facility land use master plan; the notification will prohibit any
activities that would interfere with the remedial activity. A copy of the notification, will be given to the
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Bureau of Land Managment, together with a request that a similar notification be placed in the Bureau
of Land Management property management records. The DOE will provide EPA and IDHW with writ-
ten verification that notification, including Bureau of Land Managment notification, have been fully
implemented.
Cap integrity monitoring and radiological survey programs will be established to ensure the func-
tionality of the containment systems and provide early detection of potential contaminant migration.
These programs will be implemented annually for the first five years following completion of the caps.
The necessity for continued monitoring will then be reevaluated and defined as determined appropriate
by the agencies during subsequent five-year reviews. Groundwater monitoring needs at WAG 5 will be
determined by the WAG 5 Comprehensive RI/FS. Radiological surveys at SL-1 will be conducted as
part of this Record of Decision until such time the surveys can be included as part of the environmental
monitoring program established for the WAG 5 Comprehensive RI/FS. Similarly, groundwater moni-
toring needs at WAG 6 will be determined during the WAG 10 Comprehensive RI/FS. Radiological
surveys at BORAX-I will be conducted as part of this Record of Decision until such time the surveys
can be included as part of the environmental monitoring program established for the WAG 10
Comprehensive RI/FS. Air monitoring will be conducted as part of the INEL-wide air monitoring pro-
gram. Cap integrity monitoring for cracks, erosion, and any observable degradation will be conducted
to identify maintenance requirements. Institutional controls and monitoring requirements will be the
responsibility of the DOE and will be evaluated for adequacy, effectiveness, and necessity during each
five-year review of the remedial actions.
During implementation dust suppression measures such as water sprays will be used to minimize
dust generation and thereby ensure compliance with ARARs (IDAPA 16.01.01.650 and .651). Health
and safety plans will be established to identify training requirements, specify personal protection equip-
ment requirements, and define general safe work practices. The remedial design will include measures
to ensure mitigation of potential contaminant migration during implementation.
Implementation of the selected remedy at BORAX-I includes consolidation of contaminated surface
soils which pose an excess risk greater than 1 in 10,000 to a location near the reactor foundation. Any
surface soils consolidated will then be isolated beneath the engineered barrier. Action levels for the
radionuclides of concern in BORAX-I surface soils are identified as 16.7 pCi/g for cesium-137, 10.8
pCi/g for strontium-90, and 13.2 pCi/g for uranium-235.
Because this remedy will result in wastes remaining on site, five-year reviews of this Record of
Decision and reviews of monitoring data will be conducted. Evaluation will be performed within five
years of the Record of Decision signature and will be conducted at least every five years thereafter until
such evaluations are determined by the agencies to be no longer necessary. The purpose of these
reviews is to ensure that the remedy achieves the remedial action objectives set forth in this Record of
Decision and continues to provide adequate protection of human health and the environment.
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9.2 Remediation Goals
The purpose of this response action is to inhibit potential exposure for human and environmental
receptors and to minimize the spread of contamination. This will be accomplished by constructing
long-term covers (caps) and restricting access to the sites.
Performance standards will be implemented to ensure that the cover system provides protection
against direct exposure to the wastes at the two sites. The performance standards identified for the con-
tainment alternative include:
• Installation of caps that are designed to remain in existence for at least 400 years at SL-1 and
320 years at BORAX-I to discourage any individual from inadvertently intruding into the buried
waste or from contacting the waste at any time after active institutional controls over the dispos-
al sites are removed up to the design life of the cap.
• Application of maintenance and surface monitoring programs for the containment systems capa-
ble of providing early warning of releases of radionuclides from the disposal site before they
leave the site boundary.
• Institution of restrictions limiting land use to industrial applications for at least 100 years.
• Implementation of surface water controls to direct surface water away from the disposed
wastes.
• Elimination, to the extent practicable, of the need for ongoing active maintenance of the dispos-
al sites following closure so that only surveillance, monitoring, or minor custodial care are
required.
• Placement of adequate cover to inhibit erosion by natural processes for the specified design
lives of the caps.
• Incorporation of features to inhibit biotic intrusion into the waste disposal pits and trench at the
SL-1 burial ground.
The inspection and maintenance of the cover system will be conducted concurrent with the radiolog-
ical survey program. Implementation of the maintenance and survey programs will ensure protection of
human health and the environment from any unacceptable risks. These programs will be implemented
annually for the first five years following completion of the caps. The necessity for continued monitor-
ing will then be reevaluated and defined as determined appropriate by the agencies during subsequent
five-year reviews.
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9.3 Estimated Cost Details for the Selected Remedy
A summary of the costs for each of the remedial action alternatives evaluated was presented in
Tables 9 and 10. As noted in Section 8.2.5, additional design details for the engineered barrier and
environmental monitoring requirements have enabled subsequent refinements in the original cost esti-
mates for Alternative 2 (containment). Tables 11 and 12 provide detailed breakdowns of the estimated
costs for the selected remedy, based on refinements in the costs presented previously in the proposed
plan. Post-closure costs for maintenance and monitoring of the sites are net present value dollars for
1994. These costs are calculated based on a 5 percent interest rate (net of inflation).
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Table 11. SL-1 selected remedy detailed cost estimate.3
Cost Elements Estimated Cost
Construction
Mobilize/demobilize cap subcontractor $ 95,000
Construction of cap 543,000
Subsidence prevention 22,000
Surface water control 51,000
Air monitoring 50,000
Miscellaneous 141,000
Construction management 234,000
Engineering design and inspection 111,000
Contractor overhead and profit 121,000
Contingency 271,000
Construction subtotal $1,639,000
Post-closure costs
Cap monitoring and maintenance $ 108,000
Fence maintenance 7,000
Environmental monitoring 150,000
Post-closure contingency 66,000
Post-closure costs subtotal0 $331,000
Totald $1,970,000
a. Costs are for 1995.
b. Includes net present value operating costs during remedial action.
c. Net present value assuming 5% interest (net of inflation) over 30 years.
d. Rounded to ten thousands.
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Table 12. BORAX-I selected remedy detailed cost estimated
Cost Elements
Estimated Cost
Construction
Mobilize/demobilize cap subcontractor
Construction of cap
Surface soil consolidation*3
Subsidence prevention
Surface water control
Air monitoring
Miscellaneous
Construction management
Engineering design and inspection
Contractor overhead and profit
Contingency
Construction subtotal0
Post-closure costs
Cap monitoring and maintenance
Fence maintenance
Environmental monitoring
Post-closure contingency
Post-closure costs subtotal*1
Total*
$ 95,000
274,000
5,000
20,000
50,000
162,000
233,000
79,000
140,000
182,000
$1,240,000
$ 24,000
3,000
144,000
43,000
$214,000
$1,450,000
a. Costs are for 1995.
b. Costs for soil consolidation are covered by the other cost elements.
c. Includes net present value operating costs during remedial action.
d. Net present value assuming 5% interest (net of inflation) over 30 years.
e. Rounded to ten thousands.
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10. Statutory Determinations
Remedy selection is based on CERCLA and the regulations contained in the National Oil and
Hazardous Substances Pollution Contingency Plan. All remedies must meet the two threshold criteria
(see Section 8.1) established in the National Oil and Hazardous Substances Pollution Contingency
Plan: protection of human health and the environment, and compliance with ARARs. In addition,
CERCL/ requires that th? remedy uses permanent solutions and alternative treatment technologies to
the maximum extent practicable, and that the implemented action is cost-effective. Finally, the statute
includes a preference for remedies that employ treatment that permanently and significantly reduce the
volume, toxicity, or mobility of hazardous wastes as their principal element. The following sections
discuss how the selected remedy addresses these statutory requirements.
10.1 Protection of Human Health and the Environment
As described in Section 9, the selected remedy for both SL-1 and BORAX-I satisfies the criterion
of overall protection of human health and the environment by isolating contaminated materials from the
accessible environment. The remedy will maintain isolation for a sufficient period of time to allow
short-lived radionuclides to decay, thereby decreasing direct exposure risks. Decay of short-lived
radionuclides (primarily cesium-137 and its progeny) will reduce direct exposure risks to 1 in 10,000 at
SL-1 after approximately 400 years and to 2 in 10,000 at BORAX-I after approximately 320 years.
The risk level at SL-1 will continue to decrease to a lower limit of 3 in 1,000,000 after approximately
650 years, where it will remain due to the presence of long-lived uranium-235. The risk level at
BORAX-I will decrease to 2 in 10,000 in about 320 years and will stabilize due to long-lived
uranium-235.
Although the National Oil and Hazardous Substances Pollution Contingency Plan established the
acceptability of risk to be within a range of 1 in 10,000 to 1 in 1,000,000, the estimated long-term risk
levels cited above for SL-1 and BORAX-I are considered acceptable for several reasons. First, the
Office of Solid Waste and Emergency Response Directive 9255.0-30, dated April of 1991, states that
the upper boundary of this risk range is not a discrete line at 1 in 10,000 and that a specific risk esti-
mate around 1 in 10,000 may be considered acceptable if justified based on site-specific conditions.
On this basis, risk levels around 1 in 10,000 have been determined to be acceptable for remedial
actions implemented at other INEL operable units. Second, there are no practical, safe, and cost-effec-
tive methods of removing the uranium-235 and its progenies from the contaminated materials associat-
ed with the burial grounds. Any uranium-235 and its progenies removed would still require long-term
isolation because there are no technologies for accelerating radionuclide decay. Finally, the methodolo-
gy used in the baseline risk assessment to determine potential risks at SL-1 and BORAX-I resulted in
upper bound estimates; uncertainty analysis indicates that risk is likely over-estimated, not under-esti-
mated. Therefore it is probable that the long-term risJcs at BORAX-I, estimated at 2 in 10,000, may
actually be within the 1 in 10,000 to 1 in 1,000,000 range.
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Several assumptions, as discussed in Section 6.1.4, were incorporated into the methodology of the
baseline risk assessment to ensure an upper-bound estimate would be computed. The assessment of
residential scenarios was based on the assumption that direct contact with buried waste would be main-
tained for 24 hours a day, 350 days per year, for 30 years. Similarly, occupational scenarios included
the assumption that direct contact with buried waste would be maintained for 8 hours a day, 250 days
per year, for 25 years. For surface exposures, the assessments also included an assumption of homoge-
neous contamination within soils, based on the highest radionuclide concentrations detected during
sampling activities. The result of these assumptions is most likely an over-estimation of the potential
risks associated with the SL-1 and BORAX-I burial grounds.
The remedy selected for both SL-1 and BORAX-I is containment by capping, with engineered bar-
riers comprised primarily of natural materials. The selected remedy will include consolidation of cont-
aminated surface soils at BORAX-I for isolation beneath the engineered barrier. The engineered barri-
ers will shield against penetrating radiation, discourage human and biotic intrusion, resist erosion,
require low maintenance, and provide long-term performance and durability. Until determined by the
agencies to be no longer necessary, radiological surveys will be performed to ensure effective isolation
of contamination at both sites. Monitoring of the engineered barriers will be performed until deter-
mined by the agencies to be no longer necessary to ensure the integrity of the caps is not compromised
by erosion or other deteriorating mechanisms. Additionally, institutional controls consisting of access
restrictions (e.g., fencing, warning signs, and permanent markers) and runoff controls (e.g., contouring
and grading as determined necessary) will be implemented to enhance isolation of the burial grounds.
Land use will be restricted to industrial applications for the duration of DOE operations at the INEL.
The DOE will request that the U.S. Department of Interior, Bureau of Land Management imposes simi-
lar restrictions.
Because this remedy will result in wastes remaining on site at both SL-1 and BORAX-I, reviews of
this Record of Decision and monitoring data will be conducted. The initial review will be performed
within five years of this Record of Decision signature with subsequent reviews conducted at least every
five years thereafter until determined by the agencies to be no longer necessary. The purpose of these
five-year reviews is to ensure the remedy provides adequate protection of human health and the envi-
ronment.
10.2 Compliance with ARARs
The engineered caps for SL-1 and BORAX-I will be designed to meet all state and federal ARARs.
The ARARs that will be satisfied by the selected remedy are explained below.
10.2.1 ARARs
No chemical- or location-specific ARARs were identified for the remedial action at either SL-1 or
BORAX-I. A single action-specific ARAR was identified for the selected remedy at both SL-1 and
BORAX-I (see Section 7.1.2, Table 8). The requirements of the rules for Control of Fugitive Dust
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(IDAPA 16.01.01.650 and .651) will be satisfied at both SL-1 and BORAX-I by application of appro-
priate engineering controls to minimize generation of airborne contamination and dust during installa-
tion of the engineered barriers and consolidation of surface soil at BORAX-I:
10.2.2 To-Be-Considered Guidance
In implementing the selected remedy, the agencies have agreed to consider a number of procedures
and guidance documents that are not legally binding. The following list of DOE orders are to be con-
sidered as guidance documents:
• DOE 5400.5, "Radiation Protection of the Public and Environment"
• DOE 5820.2A, "Radioactive Waste Management."
These DOE orders provide guidance to ensure radiation protection for the environment and the
public. DOE Order 5400.5 provides radiation protection standards to protect the general public from
activities conducted at DOE sites. DOE Order 5820.2A addresses future control of sites; the DOE
intends to maintain active institutional control of low-level radioactive waste disposal sites for 100
years following closure.
10.3 Cost Effectiveness
The selected remedy is cost-effective based on the overall protection to human health and the envi-
ronment relative to the costs incurred. Due to the persistent toxicity associated with radionuclides,
removing waste from SL-1 and BORAX-I simply results in the transfer of risk from one location to
another with a significant increase in cost and short-term risk. Therefore, compared to other potential
remedial actions, the selected remedy provides the best balance between cost and effectiveness in pro-
tecting human health and the environment.
10.4 Use of Permanent Solutions and Alternative Treatment Technologies to
the Maximum Extent Practicable
The selected remedy utilizes permanent solutions to the maximum extent practicable for the SL-1
and BORAX-I burial grounds. The National Oil and Hazardous Substances Pollution Contingency
Plan prefers a permanent solution whenever possible. However, guidance established in the National
Oil and Hazardous Substances Pollution Contingency Plan to assist in the selection and implementation
of appropriate remedial actions states that EPA encourages the use of containment for waste that poses
a relatively low long-term threat or where treatment is impracticable. Therefore, the selected remedy
focuses on long-term containment, radiological monitoring, and institutional control of the burial
grounds, due to the persistent radiotoxicity associated with radionuclides. The selected remedy pro-
vides protection by isolating contaminated materials from the accessible environment for a sufficient
period of time to reduce potential exposure risks to acceptable levels. Based on analysis of the
CERCLA remedial alternative evaluation criteria and in particular the five balancing criteria (see
Section 8.2), containment provides the best remedy for both the SL-1 and BORAX-I burial grounds in
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terms of long- and short-term effectiveness, cost, implementability, and reduction of toxicity, mobility,
and volume. The following discussion highlights the tradeoffs among the alternatives considered for
SL-1 and BORAX-I relative to the five balancing criteria.
Long-term effectiveness is equally achieved by either containment or removal and disposal, because
both remedial actions involve isolation from the accessible environment to ensure long-term protection
of human health and the environment. However, removal actions would involve significantly increased
worker exposures during the short-term period of implementation. No action would not be effective in
the short- or long-term.
The toxicity of radionuclides associated with the burial grounds can only be reduced by natural
decay; there are currently no technologies available to accelerate the decay process. Therefore, evalua-
tion of the remedial actions considered with respect to reduction in toxicity is not applicable. In
addition, the alternatives evaluated do not affect the volume of contaminated material existing at the
burial grounds. However, both the selected remedy and the removal and disposal alternative would
result in significantly reduced mobility based on long-term isolation from the accessible environment.
No action would not have an impact on toxicity, volume, or mobility of contaminants at SL-1 or
BORAX-I.
Lmplementability and cost are directly related to the complexity of the remedial actions considered.
Removal and disposal is the most complex alternative due to health and safety concerns associated with
handling the contaminated materials buried at SL-1 and BORAX-I. As a result, removal and disposal
is the most difficult to implement and the most expensive alternative. Although no action would be
unacceptable to the agencies, this alternative is technically easy to implement and the least expensive.
The selected remedy is not complex and therefore is not difficult to implement and is much less expen-
sive than removal and disposal.
Relative to the five balancing criteria, short-term effectiveness, implementability, and cost were the
decisive factors in selecting the containment alternative. The containment alternative does not require
intrusion into the burial grounds and therefore does not require worker exposure to the contaminated
waste buried at SL-1 and BORAX-I. Furthermore, the containment alternative is not difficult to imple-
ment and does not involve significant cost when compared to the removal and disposal alternative. No
action was not considered a viable option.
State and community acceptance were also included in the decision-making process for remedy
selection. The IDHW participated in the development and review of all required CERCLA documenta-
tion, including the remedial investigation/feasibility study, the proposed plan, and this Record of
Decision, and supports the selected alternative. The Environmental Management Site Specific
Advisory Board for the INEL concurred with the selection of the containment alternative at both burial
grounds and recommended that construction and monitoring costs be reduced to the extent possible to
reflect the costs for similar actions performed within the private sector. In addition, public meetings
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were held at various locations throughout the state, and publications were made available to inform,
educate, and. encourage participation of the community regarding remedial activities associated with the
SL-1 and BORAX-I burial grounds.
10.5 Preference for Treatment as a Principal Element
Treatment was not considered in the formulation of potential alternatives for SL-1 and BORAX-I
based on review of remedial actions previously selected for similar CERCLA sites. In addition, the
nonhomogeneous characteristics associated with the wastes buried at SL-1 and BORAX-I rendered
standard treatment techniques inappropriate. Contaminated materials buried at these sites include con-
struction debris, with physical properties ranging in size, shape, and material. Furthermore, based on
the inability of treatment to reduce the toxicity of radionuclides, the remedy selected did not consider
treatment as a principal element.
11. Documentation of Significant Change
Several refinements have been identified for the selected remedial action at the SL-1 and BORAX-I
burial grounds. These refinements are related to surface soil consolidation, monitoring, cost refine-
ments, the boundaries of Operable Unit 5-05, and other changes to the proposed plan and are described
in the following subsections.
11.1 Surface Soil Consolidation
The information in the proposed plan indicated that the surface soils around the burial grounds
could require consolidation due to the presence of wind-dispersed contamination. Costs in the pro-
posed plan were developed as ranges to accommodate the potential for consolidation of surface soils
and the types of caps under consideration. Refined cost estimates were prepared for this Record of
Decision based on no surface soil consolidation at SL-1, and consolidation of the entire 84,000-square
foot (7,800-square meter) area at BORAX-I.
Subsequent to finalization of the proposed plan an evalua*' - ^r new data in conjunction with his-
torical sampling and survey data determined that surface soils surrounding the SL-1 burial ground do
not pose an unacceptable risk to human health or the environment. Soil ingestion, dust inhalation,
groundwater ingestion, and external exposure were evaluated for current occupational and 30-year
future residential scenarios. Surface soil concentrations of identified contaminants of concern outside
of the exclusion fence are at or below background values within Operable Unit 5-05. Dose equivalent
rate measurements of the Operable Unit 5-05 surface soils indicate radiological field levels at or below
the average INEL level of 20 }irem/hr. The agencies have reviewed this information and concur that no
further action is appropriate for the surface soils outside of the exclusion fence within Operable
Unit 5-05. Documentation in support of the decision can be found in the Administrative Record for
Operable Units 5-05 and 6-01 specifically in an engineering design file titled "ARA Windblown Area
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Risk Evaluation" and an associated letter report titled "Assessment of Surface Soils Surrounding the
SL-1 Burial Ground".
It is expected that surface soil consolidation will be necessary at BORAX-I to appropriately man-
age soil contamination and minimize the potential for human or environmental exposure to unaccept-
able risks. Therefore the refined cost estimate for capping the BORAX-I site incorporates the consoli-
dation of surface soil option discussed in the proposed plan.
11.2 Monitoring
Long-term monitoring to confirm isolation of the buried contaminants for the accessible environ-
ment and groundwater was described in the proposed plan. Environmental monitoring of air, soil, and
groundwater, and cap integrity monitoring to assess erosion, cracking, or other observable deterioration
were included. In the effort to refine costs the monitoring component was critically examined. It was
determined that large components of the environmental monitoring could be incorporated into larger
programs on the INEL at significant cost savings. Monitoring costs for the no action alternative were
revised to be consistent with monitoring estimated for the selected Alternative 2. Therefore the no
action alternative includes only soil monitoring. Alternative 3 did not include monitoring, and esti-
mates have not changed.
11.2.1 Groundwater Monitoring
The results of the baseline risk assessment indicate risks via ingestion of groundwater of 1E-06 at
the SL-1 burial ground and 3E-06 for the BORAX-I burial ground. These estimates, very low in the
acceptable risk range, are upper bounds on risk because parameters for the groundwater modeling were
selected to maximize the potential risk estimates. These estimates also represent the summation of
risks due to all contaminants, regardless of modeled peak concentration time in the aquifer.
Uncertainty analyses support the conclusion that there is no risk to groundwater from either burial
ground; therefore, costs for groundwater monitoring have been eliminated. Installation of groundwater
monitoring wells specific to these sites, at an approximate cost of $200,000 per well, is not necessary.
Therefore, groundwater monitoring needs will be determined under the Waste Area Group 5
Comprehensive Remedial Investigation/Feasibility Study for WAG 5 and the Waste Area Group 10
Comprehensive Remedial Investigation/Feasibility Study for WAG 6. This approach will be more cost
eiiiw-ieiit because groundwater monitoring plans can be designed to cover much larger areas. Five-year
reviews of monitoring data will be defined for the comprehensive remedial investigation/feasibility
studies. In the unlikely event that either burial ground is suspected of contributing to groundwater con-
tamination, additional site-specific monitoring wells or other means of contaminant migration detection
can be installed in the future.
11.2.2 Air Monitoring
Costs for long-term monitoring of air have been eliminated for both burial grounds for Alternatives
1 and 2. An INEL-wide program is in place that would make additional monitoring specific to either
site redundant. In compliance with the identified ARARs, site-specific air monitoring will be per-
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formed during the construction of the caps; after the remedial action is complete, responsibility for air
monitoring at each site will be assumed by the site-wide program.
11.2.3 Soil Monitoring
Under Alternative 2, surface soils will be monitored by radiological surveys. For SL-1, cost esti-
mates include radiological monitoring until the Waste Area Group 5 Comprehensive Remedial
Investigation/Feasibility Study monitoring program is in place. At that time, long-term responsibility
for these surveys will be placed under the Waste Area Group 5 program. Monitoring results and the
need for continued monitoring will be evaluated during subsequent five-year reviews by the agencies.
Because there will be no long term monitoring plan for Waste Area Group 6, estimates in this
Record of Decision include costs for radiological monitoring of the BORAX-I site. The need for con-
tinued monitoring will be assessed periodically in the five-year reviews conducted by the agencies.
Estimates for monitoring under the No Action Alternative 1 were revised to be consistent with the
approach formulated for Alternative 2.
11.3 Cost Refinements
The estimated costs for the selected remedy were presented in the proposed plan as ranges;
$3,684,000 to $8,775,000 for SL-1, and $2,340,000 to $4,690,000 for BORAX-I. The refined cost esti-
mates presented in this Record of Decision are $1,970,000 for SL-1 and $1,450,000 for BORAX-I.
The cost refinements result from the soil consolidation issues discussed in Section 11.1, monitoring
discussed in Section 11.2, and refinements in general design parameters applied to the extent possible
without specific engineering designs. Further refinements of costs will be achieved when the remedial
design is finalized and well-defined.
Removing costs for goundwater and air monitoring (see Section 11.2) results in estimates for the
No Action Alternative 1 of $188,000 for SL-1 and $180,000 for BORAX-I.
11.4 Operable Unit 5-05 Boundary
In the proposed plan the boundary of OU 5-05 was defined as the 1,200- by 1,500-foot (366- by
477-m) area around the SL-1 burial ground. The investigation of the surface soils and the external
exposure pathway discussed above in Section 11.1 was not limited to this region, but encompassed the
entire area defined by the isopleth illustrated in Figures 2 and 4. Rather than assess a region in the
middle of one end of this isopleth, the agencies have agreed to expand the boundary of Operable
Unit 5-05 to include the northeast portion, about 40% of the entire area defined by the aerial isopleth.
This approach avoids the necessity for future reassessment and expenditure of additional funds for the
administration of the additional evaluation. Based on recently acquired dose equivalent rates, there are
no unacceptable external exposure risks due to surface soil outside the exclusion fence but inside the
revised Operable Unit 5-05 boundary. There are no other pathways of concern for the surface soils in
the defined area. Therefore no remedial actions will be necessary. Expanding Operable Unit 5-05 to
include the surrounding surface soils efficiently addresses the region and saves significant time and
funds. The remaining 60% of the area defined by the aerial isopleth will be addressed in the WAG 5
comprehensive RI/FS as site ARA-23.
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11.5 Other Changes to the Proposed Plan
Several other minor changes have been made due to refinement of elements presented in the pro-
posed plan.
• Institutional control: Institutional control will be maintained by DOE for at least 100 years to
limit land use to industrial applications. Institutional controls will include placing written noti-
fication of the remedial action in the facility land use master plan; the notification will prohibit
any activities that would interfere with the remedial activity. A copy of the notification will be
given to the Bureau of Land Management, together with a request that a similar notification be
placed in the Bureau of Land Management property management records. The DOE will pro-
vide EPA.and IDHW with written verification that notification, including Bureau of Land
Management notification, have been fully implemented.
• Remedial action objectives: The word "prevent" has been replaced with the word "inhibit" to
more realistically describe each of the remedial action objectives.
• Biotic intrusion at BORAX-I: In the development of preliminary cap design, the agencies have
reviewed the available data and concluded that a biotic barrier is not necessary for protection of
human health and the environment at BORAX-I.
• Biotic intrusion at SL-1: In the development of preliminary cap design, the agencies have
reviewed the available data and concluded that a biotic barrier is not necessary over the entire
SL-1 burial ground. Layers to inhibit biotic intrusion will be placed only directly over the dis-
posal pits and trench.
12. Decision Summary for No Action Sites
This Record of Decision includes determinations for 10 Track 1 sites. The agencies have evaluated
each site and support decisions for no further action. Much of the information discussed in previous
sections, particularly Sections 1 through 5, also applies to these 10 sites. Additional information specif-
ic to these sites is discussed in the remainder of this section, with individual descriptions of the 10 sites
in Section 12.6. Further details can be found in the Administrative Record for Waste Area Group 5.
12.1 Site Name, Location, and Description
Waste Area Group 5 contains two groups of facilities: the Auxiliary Reactor Area and the Power
Burst Facility (see Figure 9). The Auxiliary Reactor Area is comprised of four inactive facilities located
along Fillmore Boulevard north of Highway 20. The Power Burst Facility is just north of the Auxiliary
Reactor Area and consists of a total of five facilities spread radially around the Power Burst Facility
Control Area at the end of Jefferson Boulevard. Section 1 describes the topography, meteorology, sur-
face-water hydrology, geology, ecology, demography, and land use for both areas. The general descrip-
tion of groundwater hydrology is also the same, with site-specific depths to groundwater of approximate-
ly 667 feet (203 m) at the Auxiliary Reactor Area and 483 feet (147 m) at the Power Burst Facility.
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12.2 Site History and Enforcement Activities
The Auxiliary Reactor Area was originally constructed in 1957 for U.S. Army research and devel-
opment of a compact power reactor. The area consisted of four facilities called Auxiliary Reactor
Areas I through IV. In 1965 the Army program was discontinued. Technical support services, not
including reactor operations, were continued until 1985, when the facilities were shut down. Three
Track 1 sites, two at Auxiliary Reactor Area I and one at Auxiliary Reactor Area IJJ, are included in
this Record of Decision.
The Power Burst Facility was originally called the Special Power Excursion Reactor Test area.
Built in the late 1950s for reactor behavior and safety experiments, the facility consisted of five areas,
the Control Area and Special Power Excursion Reactor Test Areas I through IV. After this series of
experiments terminated, all of the reactors were removed, and the individual facilities within the area
were converted to other uses. With the construction of a new reactor in 1970, the area was renamed the
Power Burst Facility. The Special Power Excursion Reactor Test Control Area became the Power Burst
Facility Control Area; Special Power Excursion Reactor Test Areas I through IV became, respectively,
the Power Burst Facility Reactor Area, the Waste Engineering Development Facility, the Waste
Experimental Reduction Facility, and the Radioactive Mixed Waste Storage Facility. Seven Track 1
sites located at the Power Burst Facility are included in this Record of Decision.
PBF-24 Drainage Area
PBF-19 Underground
Tank Site
PBF-14 Underground
Tank Site
PBF-13 Rubble Pit'
PBF-28 Overspray.
Area and Ditch
PBF-06 Drainage Area
PBF-07 Oil Drum
Storage Area
Power Burst
Facility Area
r
Auxiliary Reactor Area
ARA-1 3 Sanitary
Sewer Tank and
Leach Field
ARA-17 Drainage Area
ARA-05 Evaporation
Pond
1. Power Burst Facility Reactor Area
4. Power Burst Facility Control Area
7. Auxiliary Reactor Area-Ill
2. Waste Engineering Development Facility
5. Radioactive Mixed Waste Storage Facility
8. Auxiliary Reactor Area-ll
Not to scale
3. Waste Experimental Reduction Facility
6. Auxiliary Reactor Area-IV
9. Auxiliary Reactor Area-l
Figure 9. Waste Area Group 5 facilities and no further action sites.
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12.3 Highlights of Community Participation
All 10 Track 1 sites were included in the proposed plan for the SL-1 and BORAX-I burial grounds.
Public comments were solicited at the same meetings and in the same comment periods discussed pre-
viously. No comments were received.
12.4 Scope and Role of Operable Unit or Response Action
Ten sites in Waste Area Group 5 are presented in this Record of Decision with no further action
determinations. As illustrated in Figure 9, three are located in the Auxiliary Reactor Area, and seven
are within the Power Burst Facility. Of the twelve operable units in Waste Area Group 5, four have one
or more individual Track 1 sites presented here for no further action.
All 10 sites were identified in the Federal Facility Agreement and Consent Order and evaluated
according to ENEL-specific guidance for Track 1 sites. Qualitative Track 1 risk assessments evaluate
all available existing information and data, including site operating, waste, and disposal histories, engi-
neering drawings, and anecdotal evidence. These assessments examine only potential hazards to
human health, utilizing the assumption that actions taken to protect human health will also be protec-
tive of the environment. The information was evaluated by representatives of the DOE, the IDHW, and
the EPA, who agreed that the sites did not warrant remediation or further study.
As previously described, cumulative risks from each operable unit will be further evaluated in the
comprehensive remedial investigation/feasibility study for Waste Area Group 5. Final evaluation of
site-wide impacts will be performed in the Waste Area Group 10 assessment.
12.4.1 Auxiliary Reactor Area Sites
Operable Unit 5-01, located at the Auxiliary Reactor Area I, contains six sites; two of the six,
ARA-05 and ARA-17, are included in this Record of Decision. Also addressed is site ARA-13, the
only site in Operable Unit 5-11. This Operable Unit is located at the ARA-III.
12.4.2 Power Burst Facility Sites
All of the five sites in Operable Unit 5-03 (PBF-06, PBF-07, PBF-13, PBF-24) and PBF-28, are
included in this Record of Decision. Of these five sites, four are located at the Power Burst Facility
Reactor Area and the fifth, PBF-24, is at the Radioactive Mixed Waste Storage Facility. The other two
Power Burst Facility sites are two of the three sites in Operable Unit 5-04, site codes PBF-14 and
PBF-19. PBF-14 is located at the Waste Engineering Development Facility. PBF-19 is adjacent to the
Waste Experimental Reduction Facility.
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12.5 Site Characteristics
The complete Track 1 Decision Documentation Packages and other information supporting the
evaluations for these sites can be found in the Administrative Record. Standard exposure pathways and
scenarios were evaluated according to the INEL-specific guidance for assessing Track 1 sites. Potential
exposure routes considered were external exposure to ionizing radiation, soil ingestion, inhalation of
dust, inhalation of volatiles, and groundwater ingestion. Both current occupational and future residen-
tial scenarios were qualitatively evaluated. The following section summarizes the contaminants consid-
ered for each site and the results of the qualitative risk assessments.
12.6 Summary of Site Risks
The 10 sites were categorized for discussion and summary into three different types: wastewater
disposal sites, soil contamination sites, and underground storage tanks.
12.6.1 Wastewater Disposal Sites
The six sites discussed in the following subsections were associated with liquid waste discharges.
During the initial site identifications, several of these sites were only suspected of receiving hazardous
or radioactive wastes. Subsequent evaluation determined that no disposal activities had occurred.
Other sites were identified as recipients of contaminated wastes, but evaluation determined that dis-
charges were neutralized, biodegraded, or in quantities too small to pose an unacceptable risk.
12.6.1.1 ARA-05. ARA-05 in Operable Unit 5-01 was originally described in the initial site iden-
tification as an evaporation pond northeast of ARA-I. The area is a shallow natural depression in the
ground that may have received some runoff from an adjacent small parking lot. There are no records
of waste generation or disposal processes associated with this site, nor are there any records indicating
that the site was ever the intended destination of any waste stream. Historical monitoring surveys
detected the presence of random radioactive particles in both the pond area and the general vicinity
around ARAs I and II. These hot particles were probably a result of the SL-1 accident and cleanup
efforts. This site was prepared in 1993 for removal of radioactive particles, but the survey indicated
that the area was free of radioactivity above the ambient background.
12.6.1.2 ARA-17. ARA-17 in Operable Unit 5-01 is a nearly flat drainage area south of ARA-I
that received drainage from two sources: the boiler room blow-down from the Hot Cells building and
the raw-water storage tank and pump house at the southwestern corner of the facility. Surface dimen-
sions are approximately 150 by 150 feet (46 by 46 m). There are no known concentrations of radiolog-
ical contamination above background levels at this site, as confirmed by radiological surveys, and no
evidence of nonradiological constituents. Historical documents and process information pertinent to
ARA-I do not indicate that this site was the intended destination of any waste stream except uncontam-
inated water.
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12.6.1.3 PBF-28. PBF-28 in Operable Unit 5-03 consists of an overspray area of surface soils
north of the drainage ditch that is south and west of the Power Burst Facility Reactor Area cooling
tower. The reactor cooling tower began service in 1976 and received reactor secondary cooling water
until 1985. The drainage ditch was constructed in the early 1970s and is approximately 600 feet (183
m) in length. This drainage ditch was used for surface runoff drainage from the reactor area. It also
received water from the boiler blow-down tank and discharge or overflow of secondary cooling water
from the cooling towers. Soil samples were collected along the entire length of the drainage ditch and
the cooling tower area and analyzed for chromium, the primary contaminant of concern. Results indi-
cated a 100- by 100-foot (30- by 30-m) area was contaminated by aerosol overspray from the cooling
tower. However, the concentrations of chromium found at this site are substantially below risk-based
contaminant levels and surveys indicate no radiological activity above background levels for the cool-
ing tower area or the drainage ditch.
12.6.1.4 PBF-06. PBF-06 in Operable Unit 5-03 is a ditch located west of the Power Burst
Facility reactor building. A pipe running from the oil-fired boiler has emptied approximately 30 gal-
lons (114-liters) per day of blow-down water into the pit since 1970. Although the reactor was placed
in a standby status in 1985, the boiler is still being used to support ongoing activities at the facility,
which require continued release of the boiler blow-down water. The blow-down water contains some
chemicals that are used to inhibit corrosion in the boiler. However, the corrosion inhibitors used con-
tain no hazardous chemicals, are nontoxic, and are used in very small quantities. A radiological survey
conducted in 1991 found no radiological contamination above background levels at this site.
12.6.1.5 PBF-24. PBF-24 in Operable Unit 5-03 is a boiler blow-down pit that was used for
drainage of the reactor building boiler waters from 1960 to 1971. The 2- by 2- by 6-foot (0.6- by 0.6- by
1.8-m) pit, located 30 feet (9 m) north of the reactor building, is a subsurface reinforced concrete struc-
ture and has an open gravel base for drainage. A pipe running from the oil-fired boiler emptied approxi-
mately 30 gallons (114 liters) per day of blow-down water into the pit. The blow-down water contained
some chemicals that were used to inhibit corrosion in the boiler. However, the corrosion inhibitors used
contained no hazardous chemicals, were relatively nontoxic, and were used in very small quantities.
Radiological surveys show no radiological contamination above background levels at this site.
12.6.1.6 ARA-13. ARA-13 in Operable Unit 5-11 consists of a septic tank, a distribution box, and
a drain field at Auxiliary Reactor Area ID. Sanitary wastes were disposed into the system from 1969 to
1980. Between 1980 and 1983, in addition to sanitary wastes, small quantities of hazardous laboratory
wastes were diverted to this system. Sampling and analysis yielded low-level concentrations of arsenic,
barium, beryllium, mercury, nickel, selenium, and thallium in four samples taken from the leach field.
The metals were detected at depths from 1 to 6 feet (0.3 to 1.8 m). However, concentrations were lower
than background metal concentrations found in soils at other operable units at the INEL. The contents
of the system were sampled and analysis showed concentrations were below levels that would present an
unacceptable risk.
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12.6.2 Soil-Contamination Sites
The following two Track 1 sites were classified as potential soil-contamination sites. One site was
suspected of having received hazardous waste and possible oil spillage, but subsequent site evaluation
determined that no such disposal activities had occurred. The other site was a dump for a variety of
materials, including piping with asbestos insulation and some heavy metals. The asbestos has been
removed, and subsequent evaluation of the site indicated that remaining contaminant concentrations do
not pose an unacceptable risk to human health or the environment.
12.6.2.1 PBF-07. PBF-07 in Operable Unit 5-03 is the location of an oil drum storage area at the
Power Burst Facility Reactor Area. The site consists of a wholly enclosed 4- by 8-foot (1.2- by 2.4-m)
concrete pad, which is used to temporarily store two or three 55-gallon (208-liter) drums of used oil
and lubricant until pick up for recycling. The site initially only had a steel roof covering the oil drums,
but in 1990, the pad was enclosed with metal corrugated siding, and a drip pan was installed. There
have been no recorded oil spills and the site shows no physical evidence of spillage. No hazardous
substances have been stored on the site, and a radiological survey conducted in 1991 detected no radio-
logical activity above background.
12.6.2.2 PBF-13. PBF-13 in Operable Unit 5-03 is a rubble pit located north of the Power Burst
Facility Reactor Area cooling tower. The rubble pit was first used to dispose of soil and basalt pieces
excavated during facility construction in the late 1960s and was later used as a dump for a variety of
construction materials until approximately the mid-1970s. Fence posts mark the location of the 75- by
45- by 10-foot (23- by 14- by 3-m) dumping area. The dump received lumber, rusting empty barrels
and cans, cable, concrete, and piping with asbestos insulation. All visible materials containing asbestos
were removed from the pit in 1993. Any small quantity that remains was covered when the pit was
backfilled with 3 to 12 feet (0.9 to 3.7 m) of clean soil and basalt rubble. Soil samples indicated the
presence of cadmium, chromium, lead, nickel, and zinc in small amounts consistent with background
levels. Volatile organic compounds detected at very low concentrations were acetone and toluene.
12.6.3 Underground Storage Tanks
The following two Track 1 sites were associated with underground storage tanks. One of the tanks,
its contents, associated piping, and contaminated soil have been removed. This site is now paved and
used for storage. The other tank was filled with sand, disconnected from the associated piping, and
abandoned in place. Risk evaluations determined that possible residual soil contamination would not
pose an unacceptable risk.
12.6.3.1 PBF-14. PBF-14 in Operable Unit 5-04 is the site of a buried 500-gallon (1,893-liter)
gasoline tank once used to power an emergency generator. The tank was in service from 1960 to 1964,
when the Special Power Excursion Reactor Test II reactor was functional. The tank was filled with
sand and abandoned in place with the fuel line disconnected. Two posts prevent parking on the tank
site. The top of the tank is about 2 feet (0.6 m) below the surface. During the Track 1 investigation,
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soils were excavated down to the top of the tank to a depth of 2 to 2.5 feet (0.6 to 0.8 m). No stained
soils were visible, volatile organic compounds were not detected and there were no holes observed in
either the tank or associated piping.
12.6.3.2 PBF-19. PBF-19 in Operable Unit 5-04 was a 3,000-gallon (11,355-liter) underground
fuel oil storage tank associated with the furnace in the reactor building at the Special Power Excursion
Test Reactor ffl. Documentation from 1986 indicates that the tank and any contaminated soil associat-
ed with the tank were scheduled for removal, but post-removal records were not found. Although evi-
dence that the tank was removed versus abandoned in place is not confirmed, it is likely that the tank
and any associated contaminated soil were removed in 1986. The area has since been paved and is
now used for outside storage.
12.7 Description of the No Action Alternative
Based on the information summarized above from the supporting documents placed in the
Administrative Record, the 10 Track 1 sites described do not pose an unacceptable risk to either human
health or the environment. No further action is warranted. Although no additional efforts will be
expended to remediate or assess these sites individually, each will be considered again for cumulative
effects in the comprehensive remedial investigation/feasibility study for Waste Area Group 5 and the
site-wide assessment for Waste Area Group 10.
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Appendix A
Responsiveness Summary
A-1
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Appendix A
Responsiveness Summary
A.1 Overview
Operable Unit 5-05 is within Waste Area Group 5 of the Power Burst Facility/Auxiliary Reactor
Area at the ENEL. The unit comprises the SL-1 burial ground and surrounding area. Operable Unit
6-01 is within Waste Area Group 6 of the Experimental Breeder Reactor-I/Boiling Water Reactor
Experiment at the INEL and comprises the BORAX-I burial ground and surrounding area. Both of
these operable units are described in the Record of Decision to which this Responsiveness Summary is
attached. Due to the similarities of the two operable units, they were investigated together. A proposed
plan was released April 28, 1995, with a public comment period from May 3 to June 3, 1995. The pre-
ferred alternative recommended in the proposed plan is containment by capping with an engineered
long-term barrier comprised primarily of natural materials. This Responsiveness Summary recaps and
responds to the comments received during the comment period. Generally, the comments reflect a
broad range of views, from strong support for the selected alternative to opposition and support for
Alternative 3, Removal and Disposal.
A.2 Background on Community Involvement
In accordance with CERCLA §113(k)(2)(B)(i-v) and 117, a series of opportunities for public infor-
mation and participation in the remedial investigation and decision process for the SL-1 and BORAX-I
burial grounds were provided to the public from September 1994 througn May 1995. For the public,
the activities included receiving fact sheets that briefly discussed the investigation to date, INEL
Reporter articles and updates, a proposed plan, an availability session and public meetings. A few
members of the public received telephone briefings
In September 1994, a kickoff fact sheet concerning the SL-1 and BORAX-I remedial
investigation/feasibility study was sent to about 6,700 individuals of the general public and to 650
INEL employees on the INEL Community Relations Plan mailing list. The fact sheet contained a
postage-paid comment form to solicit early public input on the investigations.
The investigations were discussed at informal semiannual briefings in Twin Falls (October 11,
1994), Pocatello (October 13, 1994), Moscow (October 18, 1994), Boise (October 19, 1994), and Idaho
Falls (October 20, 1994). During these briefings, representatives from the DOE and INEL discussed
the projects with members of the community, answered questions, and listened to public comments.
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Regular reports concerning the status of the project were included in the INEL Reporter and mailed
to those who were on the mailing list. Reports also appeared in two Citizens' Guides.
In April 1995, a fact sheet concerning the project was sent to about 6,700 individuals of the general
public and 650 ENEL employees on the INEL Community Relations Plan mailing list. On April 11,
1995, the DOE issued a news release to more than 100 news media contacts concerning the beginning
of a 30-day public comment period, which began May 3, 1995 and ended June 3, 1995, pertaining to
the proposed plan for SL-1 and BORAX-I. Many of the news releases resulted in a short note in com-
munity calendar sections of newspapers and as public service announcements on radio stations. Both
the fact sheet and news release gave notice to the public that documents for SL-1 and BORAX-I would
be available before the beginning of the comment period in the Administrative Record section of the
INEL Information Repositories located in the INEL Technical Library of Idaho Falls, the INEL Boise
Office, as well as in public libraries in Idaho Falls, Fort Hall, Pocatello, Twin Falls, Boise, and the
University of Idaho Library in Moscow. Also, table top displays were set up at the Grand Teton Mall
in Idaho Falls (May 15-20), Burley Public Library (April 24-May 5), Twin Falls Public Library (May
5-26), Boise Towne Square Mall (April 29), and the Pocatello City Building (April 24-May 15).
Opportunities for public involvement in the decision process for SL-1 and BORAX-I were provided
beginning in May 1995. For the public, the activities ranged from receiving the proposed plan, con-
ducting one teleconference call, and attending open houses and public meetings to informally dis-
cussing the issues and offering verbal and written comments to the agencies during the 30-day public
comment period.
Copies of the proposed plan for the burial grounds were mailed to about 6,700 members of the pub-
lic and 650 INEL employees on the INEL Community Relations Plan mailing list on April 28, 1995,
urging citizens to comment on the proposed plan and to attend public meetings. Display advertise-
ments announcing the same information and the location of public meetings on May 16, 17, and 18,
1995, in Idaho Falls, Boise, and Moscow, respectively, appeared in seven major Idaho newspapers. All
of the public meetings were held on the scheduled days. Large advertisements appeared in the follow-
ing Idaho newspapers on April 26: Post Register (Idaho Falls); Idaho State Journal (Pocatello); South
Idaho Press (Burley); Times News (Twin Falls); Idaho Statesman (Boise); Lewiston Morning Tribune
(Lewiston); and The Daily News (Moscow).
Personal calls were made to stakeholders in Idaho Falls, Pocatello, Twin Falls, Boise, and Moscow
the week of May 8 and 15 to remind individuals about the meetings. A post card was mailed on May
10, 1995, to about 6,700 members of the public and 650 INEL employees on the INEL Community
Relations Plan mailing list to encourage them to attend the public meetings and provide verbal or writ-
ten comments. Both media, the news release and newspaper advertisements, gave public notice of pub-
lic involvement activities and offerings for briefings, and the beginning of a 30-day public comment
period that was to begin May 3 and run through June 3, 1995.
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Written comment forms, including a postage-paid business-reply form, were made available to
those attending the public meetings. The forms were used to turn in written comments at the meeting,
and by some, to mail in comments later. The reverse side of the meeting agenda contained a form for
the public to evaluate the effectiveness of the meetings. A court reporter was present at each meeting
to record transcripts of discussions and public comments. Transcripts from the three public meetings
were placed in the Administrative Record section for the SL-1 and BORAX-I burial grounds, Operable
Units 5-05 and 6-01, in five INEL Information Repositories. A total of about 10 people attended the
public meetings. Overall, eight provided formal comment; of these eight people, three provided oral
comments and five provided written comments. For those who did not attend the public meetings but
wanted to make formal written comments, a postage-paid comment form was attached to the proposed
plan. All comments received on the proposed plan were considered during the development of this
Record of Decision.
This Responsiveness Summary has been prepared as part of the Record of Decision. All formal
verbal comments, as given at the public meetings, and all written comments, as submitted, are included
in the Administrative Record for the Record of Decision. Those comments are annotated to indicate
which response in the Responsiveness Summary addresses each comment. The Record of Decision
presents the preferred alternative for the project, selected in accordance with CERCLA, as amended by
the Superfund Amendments and Reauthorization Act and, to the extent practicable, the National Oil
and Hazardous Substances Pollution Contingency Plan. The decision for this operable unit is based on
information contained in the Administrative Record.
A.3 Summary of Comments with Responses
Comments and questions raised during the public comment period on the SL-1 and BORAX-I bur-
ial grounds proposed plan are summarized below. The public meetings were divided into an informal
question-and-answer session and a formal public comment session. The meeting format was described
in published announcements and meeting attendees were reminded of the format at the beginning of
each meeting. The informal question-and-answer session was designed to provide immediate responses
to the public's questions and concerns.. Several questions were answered during the informal question-
and-answer period during the public meetings on the proposed plan. This Responsiveness Summary
does not attempt to summarize or respond to issues and concerns raised during that part of the public
meeting. However, the Administrative Record contains complete transcripts of these meetings, which
include the agencies' responses to these informal questions.
Comments received during the formal comment session of the meeting were addressed by the agen-
cies in this Responsiveness Summary. The public was requested to provide their comments in writing,
verbally during the public meetings, or by recording a message by calling the INEL's toll-free number.
Seven written comments were received and 12 verbal comments were offered during the public meet-
ings. This Responsiveness Summary responds to those comments.
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1. Comment: One commenter asked what the maximum doses are regardless of time, at least to
10,000 years, and how these compare to the maximum dose limits of Nuclear Regulatory
Commission and the DOE for an unrecognized abandoned radiation waste disposal facility.
Response: The annual dose was estimated for the SL-1 and BORAX-I burial grounds based on the
residential intrusion scenario beginning 30 years in the future. This scenario was selected because
it represents the "maximum dose" at the time of earliest possible public access to either site.
Selection of this exposure scenario from the 10 scenarios modeled in the baseline risk assessment
represents the highest risk to the public and is also consistent with the proposed plan.
Risk spreadsheets generated for the baseline risk assessment provided the starting point for the esti-
mation of dose. Radionuclides posing a risk less than 1 in 10,000,000 for a given pathway were
screened from this evaluation as insignificant contributors to the total dose. The methodology,
including formulae, source terms, and dose conversion factors used to estimate annual dose rates, is
presented in the technical memorandum titled Dose Conversions for the SL-1 and BORAX-I Burial
Grounds, and can be found in the Administrative Record for Operable Units 5 and 6.
Results of the calculations for the 30-year residential intrusion scenarios are summarized below. A
limit of 25 mrem/yr for members of the public has been established by the Nuclear Regulatory
Commission and by the DOE.
Table A-1. Estimates of dose for the 30-year residential intrusion scenario.
Estimated Annual Dose Rate
Site Pathway (mrem/yr)
SL-1 External exposure 34,000
Soil ingestion 69
Dust inhalation 0.31
Groundwater ingestion 0.043
Total (2 significant digits) 34,000
BORAX-I External exposure 1,800
Soil ingestion 7.0
Dust inhalation 0.14
Groundwater ingestion 0.64
Total (2 significant digits) 1,800
2. Comment: Two commenters feel that models used for groundwater fate and transport must be
benchmarked and validated before we can proceed with action or no action.
Response: GWSCREEN was the groundwater modeling code used to estimate groundwater concen-
trations and potential risks due to groundwater ingestion. This code was designed to EPA and IDHW
specifications to address conditions and uncertainties pertinent to the INEL. Worst case upper bounds
A-6
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of concentrations and risks were generated by using EPA and IDHW approved default input parame-
ters defined for evaluating Track 2 sites (sites about which little is known, and low risk is expected).
The code has been validated by benchmarking against the PORFLOW and GRDFLX codes, both of
which are well known and accepted codes in groundwater modeling. GWSCREEN results were
within 5% of both PORFLOW and GRDFLX results. Further information regarding the develop-
ment, validation, and benchmarking of GWSCREEN can be found in the following documents which
are available in the Administrative Record for Operable Units 5-05 and 6-01.
Rood, A. S. and R. C. Arnett, J. T. Barraclough. Contaminant Transport in the Snake River Plain
Aquifer: Phase I, Part 1: Simple Analytical Model of Individual Plumes" EGG-ER-8623, May 1989.
Matthews, S. D., "Software Configuration Management Plan for Controlled Code Support System",
EGG-CATT-10196, April 1992.
Rood, A. S., "Software Verification and Validation Plan for the GWSCREEN Code",
EGG-GEO-10798, May 1993.
Smith, C. S, and C. A. Whitaker, "Independent Verification and Limited Benchmark Testing of the
GWSCREEN Computer Code, Version 2.0", GEE-GEO-10799, June 1993.
Rood, A. S., "GWSCREEN: A Semi-Analytical Model for Assessment of the Groundwater Pathway
from Surface or Buried Contamination Theory and User's Manual Version 2.0", EGG-GEO-10797,
June 1994, Revision 2.
Rood, A. S, "GWSCREEN: A Semi-Analytical Model for Assessment of the Groundwater Pathway
from Surface or Buried Contamination: Theory and User's Manual", EGG-GEO-10158, March 1992.
DOE, Track 2 Sites: Guidance for Assessing Low Probability Hazard Sites at the INEL, DOE/ID-
10389, January 1994, Revision 6.
3. Comment: One commenter requested information regarding the water transport time from the sur-
face to the aquifer, and flow rate in the aquifer used in the groundwater modeling. The commenter
also inquired about the extremes examined in the uncertu^..^ ^...alysis, what kind of uncertainty
analyses were done, and the resultant extremes of dosage imposed by the more significant radionu-
clides in the aquifer plumes from SL-1 and BORAX-I.
. Response: Vadose zone water travel times used in the evaluation were 18 years for SL-1 and
66.3 years for BORAX-I. The GWSCREEN model (see comment #2) uses water travel times esti-
mated using only sediment thicknesses in the vadose zone. Water travel time through the basalts was
neglected because describing water movement through the basalts in the vadose zone is not scientifi-
cally well-defined. Neglecting the travel time through basalt results in conservative estimates. The
average linear water velocity in the aquifer was specified as 570 m/yr for both facilities.
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A parametric sensitivity/uncertainty analysis was performed for both SL-1 and BORAX-I for those
parameters that were thought to most significantly affect the results. Sensitivity calculations were
done only for the radionuclides with the highest estimated groundwater risk at each facility bound-
ary using base case parameters. The radionuclides were technetium-99 for SL-1 and U-234 for
BORAX-I. Parameters varied in the analysis were: infiltration rate, vadose zone sediment thick-
ness, sediment moisture content, distribution coefficient, aquifer porosity, aquifer dispersivity, and
well-screen thickness. Each parameter was varied over a range and only one parameter was varied
at a time, except infiltration rate and moisture content which were related through the moisture
characteristic curve for the sediment.
Vadose zone water travel times for base case calculations as well as minimum and maximum values
investigated as part of the sensitivity/uncertainty analysis are shown in Table A-2. The minimum
and maximum vadose zone water travel times were a result of varying the vadose zone thickness or
infiltration rate.
Table A-2. Minimum and maximum vadose zone water travel times (years) considered in the sensitiv-
ity/uncertainty analysis.
Facility/Location
SL-1
BORAX-I
Base Case Value
18
66.3
Minimum Value
10.2a
42.5a
Maximum Value
54.4b
156C
a. Using minimum value of vadose zone sediment thickness and base case infiltration.
b. Using maximum value of vadose zone sediment thickness and base case infiltration.
c. Using minimum value of infiltration rate and base case vadose zone sediment thickness.
The average linear groundwater velocity was not varied as part of the sensitivity/uncertainty analy-
sis because the burial ground boundary receptor is so close to the source that the concentration and
corresponding risk values are relatively insensitive to changes in this parameter. The term average
linear groundwater velocity is the average speed traveled by water in the aquifer, and is often
referred to as aquifer pore velocity.
TLe results of the sensitivity/uncertainty analysis were presented as a percent change from the base
case peak groundwater concentration. This comparison can be extended to risk because the rela-
tionship between concentration and risk is linear. For SL-1, the changes in concentration ranged
from a minimum of 19% (of base case concentration) using the maximum well screen thickness
(vertical mixing zone) to a maximum of 301% (of base case concentration) using the minimum
aquifer dispersivities. For BORAX-I, the changes ranged from a minimum of 8% to a maximum of
970%. Both of these are the result of using the minimum and maximum distribution coefficients.
A more complete discussion of the sensitivity/uncertainty analysis as well as a discussion of the
effect of each parameter and assumption can be found in Appendix C, Section C-5, of the remedial
investigation/feasibility study report.
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Because annual dose due to groundwater ingestion is insignificant (see Comment #1), sensitivity
analyses to generate the extremes of dose by radionuclide, as requested by this commenter, were
not generated.
4. Comment: One commenter requested more information regarding potential contaminant plumes and
stated that cumulative impacts from various facilities must be considered to at least 10,000 years in
the future, not contributions from individual sites for only 100 or 1,000 years. Specific questions
included "Will the SL-1 contaminant plume in the aquifer overlap the plume from BORAX-I?", and
"Will these plumes overlap the plume from the previously evaluated RWMC Pad A?"
Response: It is unlikely that potential groundwater plumes from SL-1 and BORAX-I will overlap
and cause significant concentrations. Figure 1 in the Record of Decision shows the locations of the
INEL site boundary receptors for SL-1 and BORAX-I. These locations were determined based on
the regional groundwater flow direction which is to the southwest. Radionuclide concentrations
from both SL-1 and BORAX-I were predicted to decrease several orders of magnitude by the time
they reached the INEL site boundary receptors. It is doubtful that the plumes would overlap on the
INEL unless there were an uncharacteristically large degree of spreading. Any plume overlap
would likely occur off the INEL site. At that point, the additive concentrations of any plume over-
lap would be much less than those predicted at the burial ground boundary, facility boundary, and
probably the INEL site boundary. Nevertheless, overlap of plumes will be considered in the
sitewide groundwater assessment in conjunction with the Waste Area Group 10 remedial investiga-
tion/feasibility study.
The possibility of potential groundwater plumes from other facilities was not evaluated It is likely
however, that a plume from BORAX-I would overlap a plume from Pad A given the relatively close
proximity of the two sites. Any impact of overlaps will be evaluated in Waste Area Group 10.
The peak radionuclide groundwater concentrations were calculated irrespective of any time frame.
Several radionuclides were predicted to take more than 10,000 years to reach the aquifer. For con-
servatism, the peak groundwater concentrations of each radionuclide were assumed to occur at the
same time for each receptor.
5. Comment: One commenter wanted to know how the requirements of 40 CFR 193, particularly
10,000 year disposal requirements, and the Low-Level Waste Policy Act of 1985 are being met for
these two sites, described by the commenter as "inactive disposal sites for spent fuel, transuranic
waste, greater than Class C waste, and low-level waste."
Response: The preproposal draft of 40 CFR 193 states explicitly that "The management and stor-
age standards are not intended to apply to remedial actions at LLW facilities which were closed
prior to the effective date of 40 CFR part 193...". The draft acknowledges that it may be years
before 40 CFR 193 is finalized. 40 CFR 193 does not qualify as an ARAR until it becomes law.
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Capping of the two burial grounds does, however, satisfy the intent of the preproposal draft. The
draft states that "The only practical method of reducing the radiation hazard from LLW is to isolate
it from people and the environment until the radioactivity has decayed," and the proposed standards
should consider "...the protection provided by the engineered and natural barriers of a disposal sys-
tem." The caps will be designed to prevent human or environmental exposure to the wastes for 400
years at SL-1 (when the external exposure risk will reach 1E-04) and 320 years at BORAX-I (when
the long-lived uranium-235 becomes the primary risk contributor at 2E-04).
In terms of possible intrusion into the waste, the draft states that "the standards have not been
devised to protect individuals who purposefully or inadvertently farm on the superjacent land or
penetrate into the waste. They do apply outside the area delineated by permanent markers and in
records of government ownership." It is anticipated that these restrictions will be specified in the
remedial design phase which follows the signing of this Record of Decision.
The EPA proposes a standard of 15 mrem committed effective dose per year (equivalent to a fatal
cancer risk of 5E-04) to the public, outside of the area delineated by permanent markers and
recorded government ownership. Shielding provided by the caps will be adequate to keep expo-
sures below 15 mrem/yr above background.
The commenter referred to disposal requirements for spent fuel, transuranic waste, and greater-
than-Class C waste. The wastes buried at both SL-1 and BORAX-I do not meet the definition of
these waste types. All wastes associated with the SL-1 and BORAX-I burial grounds are consid-
ered low-level waste. The following paragraphs clarify this point.
Spent nuclear fuel is defined in DOE Order 5820.2A (Radioactive Waste Management), Attachment
2, as "Fuel that has been withdrawn from a nuclear reactor following irradiation, but that has not
been reprocessed to remove its constituent elements." Neither the SL-1 or BORAX-I reactor oper-
ated for long enough to achieve burn-up to the design core lifetime prior to destruction of the facili-
ties. Thus, the fuel never became "spent".
Transuranic waste is defined in DOE Order 5820.2A, Attachment 2, as "Without regard to source or
form, waste that is contaminated with alpha emitting transuranium radionuclides with half-lives
greater than 20 years and concentrations greater than 100 nCi/g at the time of assay." The concen-
trations of transuranium radionuclides at SL-1 are estimated to be in the pCi/g range and no
transuranium radionuclides were identified as contaminants of concern at BORAX-I. Thus, no
transuranic wastes exist at either burial ground.
A comparison of the radionuclide concentrations associated with the SL-1 and BORAX-I burial
grounds with Class C waste determination criteria revealed that no waste containing concentrations
in excess of Class C levels exists at either site. This determination is based on the assumption of
uniform distribution of contaminants throughout the estimated volume. Therefore, it is possible
A-10
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that localized areas of higher concentrations could exceed Class C criteria. However, based on the
comparison performed, contaminant concentrations are below the lower end of the Class B criteria
range.
All the waste associated with both burial grounds does meet the definition of low-level waste, as
defined in DOE Order 5820.2A, Attachment 2:
"Waste that contains radioactivity and is not classified as high-level waste, transuranic waste,
or spent nuclear fuel or 1 l(e) byproduct material as defined by this Order. Test specimens of
fissionable material irradiated for research and development only, and not for the production of
power or plutonium, may be classified as low-level waste, provided the concentration of
transuranic is less that 100 nCi/g."
Therefore, only low-level radioactive waste management and disposal requirements are considered
relevant to the SL-1 and BORAX-I burial grounds.
The commenter also referenced disposal requirements specified in the Low-Level Waste Policy Act of
1985. The act specifically excludes low-level waste owned or generated by the DOE. DOE
Order 5820.2A specifies requirements for managing and disposing DOE owned and generated low-
level waste. This DOE Order specifies that inactive sites such as SL-1 and BORAX-I be managed in
conformance with CERCLA, which is the process currently being undertaken. The Order does not
specify retrofitting such inactive sites to meet the requirements that would apply for new or operating
disposal facilities.
6. Comment: One commenter calls the reports "excellent and interesting" but thinks cost estimates
are too high, especially for construction management and contractor u v erhead and profit. The com-
menter states that competitive bidding on a fixed price design that is simple and clear should reduce
estimated costs by 25 to 50%.
Response: Cost estimates for the alternatives analyzed were developed for comparison purposes
only, and will not likely reflect the actual cost of implementing the selected alternative. The cost
estimates were developed on the basis of a preliminary conceptual design, and therefore have omit-
ted many specific details of the alternatives that were not well defined. These specific details are
accounted for within a contingency cost element included in each estimate. However, the com-
menter judged the estimates as being excessive by 25 to 50 percent. This evaluation by the com-
menter is consistent with CERCLA guidance for preparing such cost estimates, which calls for
accuracy within the range of -30 to +50 percent.
The commenter specifically identified Construction Management and Contractor Overhead & Profit
costs as being "very high". These cost elements are computed on a percentage basis. The percent-
age rate used was developed from INEL-specific construction cost history.
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Costs were refined in preparation for public meetings with the EM Site-Specific Advisory
Board-INEL. These refined estimates include additional specific items, such as foundation prepara-
tion and acquisition and transportation of materials, thus reducing the contingency factor percentage.
These refinements result in estimates of $1.97 million for SL-1 and $1.45 million for BORAX-I.
Although these estimates are better than those that appeared in the proposed plan, they are still fairly
rough. Anticipated actual costs can not be presented until remedial design is complete.
7. Comment: Three commenters expressed opinions that Alternative 2 is the best choice.
Response: The agencies agree that Alternative 2, containment by capping with an engineered bar-
rier comprised primarily of natural materials, is the preferred alternative based on effectiveness,
cost, and the other evaluation criteria discussed in the proposed plan and Record of Decision.
Consequently, this alternative appears in the Record of Decision as the selected remedial action for
both the SL-1 and the BORAX-I burial grounds.
8. Comment: Two commenters favor Alternative 3. One commenter felt that Alternative 2 would
leave us vulnerable to natural disasters, vandalism, or cutbacks in monitoring. The other com-
menter was worried that the INEL, being situated above the Snake River Plain Aquifer and in an
earthquake sensitive area, is "a disaster awaiting its own fulfillment."
Response: The excavation and removal discussed in Alternative 3 does return the sites to natural
conditions; however, this remedy essentially moves the problem from one location to another with-
in the INEL with significant risks to workers and the public and at very high cost. This action
would only forestall a timely decision regarding the final disposition of the wastes and would not
alleviate the commenters' concerns. The prediction regarding "a disaster awaiting its own fulfill-
ment", refer: to events such as earthquakes and other natural disasters. A very small probability
exists that such events could occur; therefore design features such as slope minimization will be
evaluated and incorporated into the engineered covers as determined appropriate during the
Remedial Design phase.
9. Comment: One commenter stated that the Special Power Excursion Reactor Test I reactor pro-
gram was also concluded with a destructive test similar to the BORAX-I experiment. The com-
menter concludes that this experiment must also have resulted in contaminated debris and soil, and
wanted to know why it is not included in any proposed clean-up plan.
Response: The Special Power Excursion Reactor Test I facility was decommissioned in 1964. The
reactor pit was demolished in 1985 and the site returned to its original state. No known contami-
nated debris remains at the site. The Power Burst Facility reactor was built just north of the Special
Power Excursion Reactor Test I location, and the facility is now known as the Power Burst Facility
Reactor Area. The only two remediation sites identified within this facility are a seepage pit (site
code PBF-11) and a leach pond (site code PBF-12). Both have received no further action recom-
mendations.
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10. Comment: One commenter expressed the opinion that taxpayers money is being wasted by pro-
ducing publications and expending funds on "low risk projects."
Response: The SL-1 and BORAX-I burial grounds can not be considered low risk projects in view
of the risks estimated in the baseline risk assessment and summarized in the proposed plan. In
response to Superfund guidance and the INEL Community Relations Plan, the agencies have direct-
ed that program funds be used to communicate information concerning the investigations to the
public. The preparation of the INEL Reporter, fact sheets, and proposed plans are traditional meth-
ods of updating citizens on project specifics. The object of these publications is to describe how
the agencies are approaching the work outlined in the Federal Facility Agreement and what new
information is learned about the sites. The invitation for citizens to interact with the agencies con-
cerning this process is an important part of finding out what citizens think of the agencies' recom-
mendations. The result of interaction between the public and the agencies is the formulation of a
decision that considers the issues raised by citizens through a fair and reasonable process.
11. Comment: One commenter stated that trials should be conducted to determine if scraping surface
soils and extracting the uranium-235 results in recovery of significant amounts of uranium. If suc-
cessful, the method should be applied more extensively at the sites because recovery of the uranium
would return it to secure storage and reduce the long-term impacts from these sites.
Response: The commenter referred to the use of technologies which could be used to extract ura-
nium-235 from surface soils if soils were scraped from the areas surrounding the burial grounds.
The technology being referred to is called "soil washing". This technology has been demonstrated
for the removal of uranium from soil, but was not considered for application at either SL-1 or
BORAX-I. As described in Section 11, the surface soil associated with the SL-1 burial ground will
not require remedial action. In addition, uranium was not identified as a contaminant of concern in
SL-1 surface soils. This technique for BORAX-I is described below.
The effectiveness of soil washing is dependent on site-specific soil characteristics and the chemical
behavior of contaminants in the environment. Soil washing studies performed at the Hanford site
indicated that uranium would typically be concentrated in the smaller soil size fractions (silts and
clays). Therefore, removal of uranium from BORAX-I soils would initially require separation into
specific soil size fractions such as gravel, sand, silt, and clay. The larger soil size fractions, gravel
and sand, would then be analyzed and either returned to the site or treated, depending on the results
of the analysis. If necessary, mechanical agitation or scrubbing would be used to physically remove
uranium from the surfaces of the larger size soil fractions. The smaller soil size fractions, most
likely to contain the majority of uranium, would then be leached by a chemical extractant such as
sulfuric acid. Studies have shown such leaching processes can reduce uranium concentrations in
the smaller soil size fractions to levels between approximately 20 and 70 parts per million. The
chemical extractant and wash water would require additional treatment to remove uranium extract-
ed from the soils.
A-13
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Separating uranium from the soil surrounding BORAX-I is not considered feasible based on the
extremely low concentrations anticipated in the surface soils, and the small mass of uranium actually
contained in the soil. Scraping contaminated surface soils would result in considerable mixing of the
existing gravel cover and the clean soil immediately beneath the contaminated soil. Assuming the
entire mass of unrecovered uranium at BORAX-I, about eight pounds (3.7 kilograms), is uniformly
distributed throughout the 84,000 square feet of potentially contaminated soil area, removal of the top
foot of soil and gravel from this area would result in a maximum uranium concentration of one part
per million. For the sake of argument, assuming the smaller soil size fraction represented 20 percent
of this volume and was effectively separated by the initial soil washing stage, then a maximum of
only five parts per million could be obtained. Assuming the entire eight pounds (3.7 kilograms) were
distributed in a much smaller area, perhaps one-sixth the entire 84,000 square feet, the uranium con-
centration would be approximately six parts per million. If the smaller soil size fraction represented
20 percent of this volume and were effectively separated by the initial soil washing, then a maximum
of 30 parts per million could be obtained. Such low concentrations would not be amenable to effec-
tive leaching in the final stage of the soil washing process.
Soil washing could be effective for removing larger particles if the majority of uranium were not in the
form of uniformly distributed fine particles. However, historical documentation indicates the fuel frag-
ments (larger particles) were collected from the surface soils and the majority of remaining contamina-
tion interred in the reactor foundation. Therefore the actual mass of uranium in the BORAX-I surface
soils is probably significantly less than the unrecovered eight pounds (3.7 kilograms).
The focused remedial investigation/feasibility study performed for SL-1 and BORAX-I was based
on remedial actions identified in previous CERCLA Records of Decision, and although soil wash-
ing technology exists and is currently in use under the EPA Superfund Innovative Technology
Evaluation Program, the technology has not been specified for use in previous CERCLA Records
of Decision involving radionuclide contaminated soils.
12. Comment: One commenter suggested that selection of an alternative should be deferred until the
methods and costs associated with the Pit 9 action are available. The commenter felt the cost esti-
mates for SL-1 and BORAX-I and the decision for these two sites could change if some of the
waste could be processed through the Pit 9 treatment facilities.
Response: The situation at Pit 9 is sufficiently different from that at the SL-1 and BORAX-I burial
grounds to eliminate the possibility of similar treatment. The limited production tests at Pit 9 are
directed at transuranic wastes in concentrations greater than 10 nanocuries per gram; wastes at the
SL-1 and BORAX-I burial grounds are described in terms of picocuries, three orders of magnitude
smaller. In addition, Pit 9 wastes include hazardous substances and some mixed waste, unlike the
SL-1 and BORAX-I burial grounds where radionuclides are the only contaminants of concern.
Preliminary information regarding cost and effectiveness of the limited production tests being per-
formed for the Pit 9 treatments will not be available before January, 1997. The agencies do not
A-14
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anticipate that delaying this remedial action until the Pit 9 cost and effectiveness data are available
will alter their preference for capping the sites as described in Alternative 2 of the proposed plan.
13. Comment: One commenter stated that partial cleanup including ground scraping and removal of cont-
amination in excess of 10 CFR 61 Class A limits should be considered as an additional alternative.
Response: Removal of contaminated surface soil is a potential aspect of the final remedial design
phase. Three potential options for disposition of contaminated surface soils surrounding the burial
grounds were identified in the remedial investigation/feasibility study. These options include:
• No action or restricted access
• Removal followed by disposal at Radioactive Waste Management Complex
• Consolidation near the location of buried waste for inclusion beneath the protective cover.
10 CFR 61 defines the criteria under which the Nuclear Regulatory Commission issues licenses for
land disposal of radioactive waste. The disposal at the SL-1 and BORAX-I burial grounds took
place prior to the effective date of 10 CFR 61, so the licensing requirements do not apply.
14. Comment: Two commenters indicated that future land use scenarios should be established before
decisions are made so that exposure scenarios could be determined on the basis of realistic project-
ed land use.
Response: The INEL is in the process of establishing land use scenarios for areas surrounding Site
facilities. Certain areas may be designated for future industrial land use; these scenarios will be used
to form the basis of risk calculations in the future. In the meantime, the agencies have decided to
take the cautious approach to protect workers, the public, and the environment by applying the most
protective land use scenarios in current risk assessments.
15. Comment: One commenter expressed the opinion that results of capping studies from the old
dairy farm and other studies should be used in this evaluation.
Response: INEL-specific research involving capping design Has been included in the preliminary
conceptual designs of the caps evaluated for SL-1 and BORAX-I. The Environmental Science and
Research Foundation is currently conducting cap design experiments at the INEL. These experi-
ments, called the Protective Cap/Biobarrier Experiments, focus on "low-cost, natural systems to
effectively isolate municipal, industrial, and low-level radioactive wastes and contaminated soil sur-
faces from the environment, for centuries." The results obtained thus far in the experiments were
incorporated in the Uranium Mill Tailings Remedial Action type cap design presented in the reme-
dial investigation/feasibility study report. This included a 5-foot (1.6-m) soil layer for water bal-
ance, a 1.5-foot (45-cm) rock/cobble layer in combination with a 1-foot (30-cm) gravel layer for
A-15
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biotic control. During the remedial design phase, such INEL-specific information will be included
in the final cap design.
16. Comment: One commenter demands that Alternative 3 be selected for SL-1 and BORAX-I and
that no further out-of-state shipments of radioactive waste be "allowed to be deposited there".
Response: Alternative 3 is the removal of wastes from the burial ground with disposal at the INEL's
Radioactive Waste Management Complex. Removal and disposal only relocates the contamination
within the ENEL at a high cost and potentially high risk to workers and the public; it does not eliminate
the problem. Alternative 2, covering and controlling the contamination through time while radioactive
decay decreases the risk, is a safer and more cost-effective approach. The SL-1 and BORAX-I sites
have never received waste shipped into the state from other sources. To receive information or ask
questions concerning possible transportation of waste to the INEL from out-of-state, citizens can call
the INEL's toll-free number, 1-800-708-2680, to request additional details and assistance.
17. Comment: One commenter suggested that "debris treatment" should be utilized to reduce volumes
of mixed waste.
Response: Mixed wastes have not been identified at either burial ground. Also see responses 11,
12, and 13.
18. Comment: One commenter asked what considerations to reduce volumes of contaminated soils
were being exercised.
Response: Under the preferred alternative, capping with an engineered barrier, contaminated sur-
face soils will be consolidated at BORAX-I based on field screening and sample data acquired dur-
ing the remedial design phase of the remedial action. No other applicable minimization efforts
have been identified.
A.4 Comment and Response Index
Because comments are summarized in the Responsiveness Summary for response, an index is
included to assist in identifying responses to specific comments. All oral comments, as received at the
public meetings, and all written comments are included verbatim. Each comment is coded with a W,
meaning a written comment, or a T for an oral comment transcribed during the public meetings. Seven
people submitted written comments and three rendered oral comments during the meeting. A total of
19 comments were received.
A-16
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To locate a response to a specific comment, identify the comment on the index, note the associated response number and page num-
ber, and turn to that response in the Summary of Comments and Responses in Section A.3.
Table A-3. Index of comments.
Response
Code Number
W-l 7
W-2 6, 7
W-3 9
W-4 10
W5 8
W-6 8, 16
W-7 14, 17, 18
T-l 2
T-2 2
T-3 1 1
Comment
Alternative 2 is adequate.
Excellent & interesting reports. Cost estimates seem high! I agree with the preferred alternatives. Estimated costs for capping landfills seem very high; if design
is simple and clear, I think competitive bidding (fixed price) should reduce estimated costs shown here in by (25 to 50) %. In particular, const, mg't &
contractor ov'h'd & profit seem very high compared to the direct "Construction of Cap" costs. Possibly this is due to high liability insurance costs, or other job
risk costs that I am not familiar with. At any rate, 1 recommend "working" the cost reduction possibilities very hard.
The SPERT 1 reactor program was also concluded with a destruct test which occurred in the early to mid 1960s, similar to the BORAX-I destruct test.
The SPERT 1 destruct test must have resulted in contaminated debris and soil. Why is SPERT I not included in any proposed clean-up plan?
Why do you continue to waste taxpayers $. Your publications plus the expenditures directed towards low risk projects are a total waste. You guys are out-of-control.
1 favor Alternative 3 as the only permanent solution for decontamination of the SL-1 and BORAX-I sites. 1 fear that Alternative 2 would leave us vulnerable
to natural disasters, vandalism, or cutbacks in monitoring in the long run.
The IN EL. being situated above the Snake River Aquifer and in an earthquake sensitive area, is a disaster awaiting its own fulfillment. I demand that
Alternative 3 be instated and that no further out-of-state shipments of radioactive waste be allowed to be deposited there.
• Utilize "debris treatment" for reducing vol. of mixed waste
• Closure goals must be established considering future "land use" criteria
• DOE must establish "land use" criteria for the INEL
• What considerations are being exercised to minimize volume of contaminated soils to be disposed.
There's been a lot of discussion on these plumes, and what might reach the groundwater. Of course, that's one of the major things that the citizens of the
State of Idaho are concerned about. 1 heard tonight that it was going to be 10,000 years before the heavy metals, U-235 would reach the groundwater by
modeling by a code named G '/SCREEN. My understanding is there's been very little benchmarking of these codes done. Last summer there was what
was called the aquifer stress lest to try and do some benchmarking. There's been considerable work to validate codes - we've heard about the NRC -
to validate computer codes to make sure that they predict what's right. The codes that are being used at the INEL are not benchmarked. They are not
validated. And 1 think we're getting the cart before the horse on this and going out and taking actions before we really know what we've got as far as
contaminants. Let's get some good computer codes. Let's gel some good modeling. 1 see fate and transport modeling in here. And again, it's the old adage
of "garbage in, garbage out." And I think (hat's what we've got here. We don't know the ion exchange of these metals between the soil. Conservative values
most largely are being used, but there's a lot of unknowns, and there needs to be some overall benchmarking of those computer codes that are being used similar
to what the NRC has done with the RELAP models, the Skadat (sic) (TRAC?) models. We talk about us spending huge sums of money on reactor safety, and
we're talking about risk here supposedly, according to the EPA of 5 in 10,000. This is much greater than what the NRC is saying you're going to have from
some of these spare reactor accidents. So let's get some codes validated and benchmarked, and then let's proceed with what we have - either a No Action or
Alternative Actions.
I heartily agree with what's just been said when it comes to the need for the improvements that he's (Robert Wadkins, comment T- 1 ). There's certainly a
real need there.
According to DOE's reports regarding remediation of these sites, considerable uranium-235 remains unrecovered - about two pounds at the SL-1 site and
about eight pounds at the BORAX-I site. Because of U-235's very long half-life, as a practical matter it will never decay away, and there is enough there to
make one or more nuclear weapons. With today's improved equipment, scraping an inch or two of topsoil from the ground surface and passing the scrapings
and any other appropriate excavated soil through soil decontamination equipment and a heavy metal particle separation device could probably recover a
considerable amount of the uranium and other radionuclides for disposition elsewhere. And before replacing more cover material, it appears that this should
be tried on a limited scale and used more extensively if the trials prove successful. Removal of uranium-235 will not only restore this uranium to secure
storage, it will also decrease these sites' long-term impacts that will not be reduced appreciably during the limited lifetime of an engineering barrier.
Page
Number
A-ll
A-10
A-ll
A-12
A-ll
A-ll
A-15
A-14
A-15
A-6
A-6
A-12
T-4
What water transport time (from the surface to the aquifer) and what flow rate in the aquifer were used in the evaluation? Since these are uncertain, what
extremes were considered in the uncertainty analyses? What kind of uncertainty analyses were done, and what were the resultant extremes of dosage
imposed by the more significant radionuclides in the aquifer plumes from SL-1 and BORAX-I?
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Table A-3. (continued)
Code
Response
Number Comment
Page
Number
T-S 4 Will the SL-1 contaminant plume in the aquifer overlap the plume from BORAX-I? Will these plumes overlap the plume from the previously evaluated
RWMC Pad A? (Pad A is downstream from BORAX-I and SL-1. And for Pad A. DOE previously concluded that a cap will be installed over about
18,000 55-gallon drums and 2,000 4x4x7 foot boxes of alpha-contaminated Rocky Flats waste that is to be left buried there.) My concern is the combined
impact of these on a future member of the public since it is the combined impact on the maximally exposed individual that counts. And this combined
impact is what should be considered in deciding what to do about the waste at each disposal site. In addition, the following locations emit plumes that may
overlap the plumes from SL-I and BORAX-I and Pad A: waste buried from 1984 through the end of RWMC waste disposal operation, the Test Reactor
Area, the Idaho Chemical Processing Plant, and the portion of the RWMC that was used for rad waste disposal from 1952 to 1984. The impact of all of the
plumes that overlap should be considered in reaching a conclusion regarding the appropriate remediation action for waste at any one of the locations.
Moreover, the extent of time in the future that should be addressed should not be restricted to a relatively short time period like 100 years or 1,000 years but
should extend much further to at least 10,000. A-9
T-6 5 These sites are essentially inactive disposal sites for spent fuel, transuranic waste, greater than Class C waste, and low level waste. There are laws against disposal
of such waste - that is, 40 CFR 193 and the Low Level Waste Policy Act of 1985 - unless the waste can be shown to be adequately confined for at least 10,000
years. How are these require nents accounted for? A-9
T-7 I Considering the Nuclear Regulatory Commission scenarios regarding a future inadvertent intruder onto an in-future abandoned waste disposal site - that is, the
well drilling scenario, basement excavation and home construction, farming and excavation and discovery of buried articles - what would be the maximum
dosage to such and intruder at the times of maximum dosage regardless of how far these are in the future? Or at least to 10,000 years? How do these dosages
compare with DOE and NRC dosage limits for a future inadvertent intruder onto an unrecognized abandoned rad waste facility? A 6
T-8 12 The planned cleanup of Pit 9 could provide experience-derived information on which to base cost estimates for cleaning up the SL-1 and BORAX-I sites.
And changes to their cost estimates could influence the decision regarding which remediation alternative to pursue. Consideration should be given to deferring
the final decision regarding these issues until Pit 9 cleanup has progressed sufficiently to permit better assessment of the methods and costs that should be
involved in their cleanup. Also possibly some of the waste generated in these cleanups could best be prepared for disposal by processing them through the Pit 9
treatment facilities. A-14
T-9 13 The Site Disposition Alternatives considered apparently only one involving waste removal - removal of all contaminated materials, the most expensive of all.
Partial cleanup involving the above mentioned ground scraping plus removal of materials contaminated beyond 10 CFR 61 Class A limits deserves consideration
as an alternative. Such a partial cleanup could substantially reduce the very long half-lived portion of these sites' radioactivity plumes in the aquifer and their
impacts on future inadvertent intruders, and the cost should be substantially less than that of total cleanup. A-14
T-10 14 I still have a question on the land use and the industrial scenario, and I think that any further action or closing out or accepting of any alternatives be delayed until
we get a land use plan for the INEL so we know where we're going and what we're going to do with it. The one in ten scenario - again I believe on the industrial,
the risk scenario, I believe there's a direct exposure driving that, and it's a direct exposure to an individual with no capping, no asphalt, or something like that.
I believe it needs to be a realistic scenario on the industrial scenario, and that factors again into this land use. I think that we're just sitting here spinning our wheels
and perhaps spending a lot of money along with the wheel spinning if we proceed with some of these alternatives before we've got a land use plan in place for
these areas that we're considering tonight, and perhaps even the total INEL. The soil consolidation variables that were mentioned, I think that if you're picking
up any contamination out there under the EPA criteria, if you're going to say that it's going to be exposed and there's no cover on it, you're going to have to
consolidate the soil. I don't think you've got any choice with the cesium-137 out there. A-14
T-11 15 The other question I have, is there's a number of studies going on various capping things on what was called the old dairy farm out there. I don't know what those
studies are called, but they've done a number of studies and looking at animals burrowing into the soil and things like that. I think those should be factored in.
Here there's a lot of research going on out there, and I keep seeing these things and none of it factored in here. Here we're proposing some things, that of capping
and that - let's use what work we've done and what research we've done out there. A-15
T-12 7 Looking at and having read this and having a pretty good grasp about the natural sciences, having degrees in it, 1 think the Containment Number 2 would be in my
opinion the Preferred Alternative in this situation. I think that No Action is -1 think that we created this mess in our lifetime, we need to clean up this mess in our
lifetime. I don't think we need to leave it for future generations. Plus I think that there is a good possibility that we could have airborne paniculate activity with
this thing as far as with wind erosion, and that is really what I'm mostly concerned.about in this situation, in all of these sites, really, is the possibility of having
wind erosion take place. I think that in any of these sites I would prefer that nothing that is contaminated is ever touched again and everything is left in place.
I you're going to mound on top of it sufficient weight where the shaking of the earthquake - I mean, there is a fault line that is running through this area - you
wouldn't worry about it sloughing off and creating even a larger problem than is already there. I think it'll indicate to whoever happens upon it in the future
generations, it will indicate to them that this wouldn't be a proper place to put a foundation for a home or put a garden in. Whether we are able to communicate
to those future generations or not, in 400 years Lord knows where we'll be as far as the human race, we all know that, so that's about all I have to say about that. A-11
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Appendix B
Administrative Record File Index
B-1
-------
B-2
-------
Idaho National Engineering Laboratory
Administrative Record File Index for the Track 2 Scoping of the
ARA-II SL-1 Burial Ground OU 5-05 and 6-01
6/26/95
File Number
AR1.1 Background
Document #: EGG-GEO-10068
Title: A Modeling Study of Water Flow in the Vadose Zone beneath the RWMC
Author: Baca, R.G.
Recipient: N/A
Date: 01/01/92
*Note: This Document is filed in the Pad A Administrative Record Binder
Operable Unit 7-12 Volume I
Document #: EGG-BG-9175
Title: Independent Verification and Benchmark Testing of the Porflo-3 Computer
Code, Version 1.0
Author: Baca, R.G.
Recipient: N/A
Date: 08/01/90
Document #: KJH-09-94
Title: Interviews with Darrell Hanni Regarding the SL-1 Burial Ground
Author: Holdren, K.J.
Recipient: Halford, V.E.
Date: 07/06/94
• Document #: 10022
Title: Record of Meeting with Roger G. Jensen, U.S.G.S., Regarding Depth to Aquifer
nearBORAX-I/SL-1
Author: VanDerpoel, G.
Recipient: N/A
Date: 02/17/94
Document*: 10023
Title: Record of Meeting with Dick Meservey, EG&G Idaho, Regarding BORAX-I
Author: Tucker, J.
Recipient: N/A
Date: 02/17/94
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File Number
AR1.1
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ARA-fl SL-1 Burial Ground OU 5-05 and 6-01
6/26/95
Background (continued)
10024
Record of Meeting with Roger Wilhelmson, EG&G Idaho, Regarding Pipes in
SL-1 Burial Ground
Meadows, G.
N/A
04/15/94
10025
Record of Meeting with Eddy Chew, DOE-Idaho Regarding SL-1 Burial Ground
Pipes
Meadows, D.
N/A
04/14/94
10026
Record of Meeting with Glenn Briscoe, Regarding SL-1 Burial Ground
Meadows, D.
N/A
01/25/94
10027
Record of Meeting with Craig Kwamme, LITCO, Regarding Basis for RWMC
Disposal Costs
Vetter, D.
N/A
12/02/94
10028
Memo of Conversation with Richard Green, Regarding Pipes in the SL-1 Burial
Ground
Holdren, K.J.
N/A
04/14/94
10133
Support Documentation: Estimation of Uranium-235 Surface Soil Concentrations Based
on Mass Unrecovered at the BORAX-I Ruria' Ground
R. Filemyr
J. Holdren
08/30/95
10134
Errata for the Remedial Investigation/Feasibility Study Report for Operable Units 5-05
and 6-01 (SL-1 and BORAX-I Burial Grounds)
R. Filemyr
N/A
08/30/95
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Document #: 10135
Title: Support Documentation: Annual Dose Calculation for Selected Scenarios at the SL-1
and BORAX-I Burial Grounds
Author: R. Filemyr
Recipient: J. Holdren
Date: 08/30/95
Document*: 10136
Title: SL-1/BORAX-I Class C Waste Equivalency Determination
Author: R. Filemyr
Recipient: J. Holdren
Date: 08/30/95
ARA-II SL-1 Burial Ground OU 5-05 and 6-01
6/26/95
File Number
AR1.7 Initial Assessments
Document #: 2984
Title: ARA-06, ARA H SL-1 Burial Ground
Author: N/A.
Recipient: N/A
Date: 09/15/86
• Document #: 2629
Title: BORAX-02, BORAX-I Burial Site
Author: N/A
Recipient: N/A
Date: 10/03/86
AR3.8 Risk Assessment
Document #: MISC-94001
Title: Preliminary Baseline Risk Assessment for the OU-5-05 and 6-01, SL-1 and
BORAX-I Burial Grounds RI/FS
Author: N/A
Recipient: N/A
Date: 10/01/93
• Document #: 5662
Title: Overview of Exposure Scenarios for the Baseline Risk Assessment for the
OU 5-05 and 6-01, SL-1 and BORAX-I Burial Grounds RI
Author: N/A
Recipient: N/A
Date: 10/01/93
Document*: INEL-95/103 Rev 2
Title: ARA Windblown Area Risk Evaluation
Author: D. Jorgensen
Recipient: N/A
Date: 09/07/95
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Document*: 10137
Title: Assessment of Surface Soils Surrounding the SL-1 Burial Grounds
Author: K. J. Holdren
Recipient: N/A
Date: October, 1995
ARA-II SL-1 Burial Ground OU 5-05 and 6-01
6/26/95
File Number
AR3.10
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Scope of Work
EGG-ER-10998
Scope of Work for Operable Units 5-05 and 6-01 (SL-1 and BORAX-I Burial
Grounds) Remedial Investigation Feasibility Study (RI/FS)
Halford, V.E.
N/A
03/01/94
AR3.12
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Remedial Investigation/Feasibility Study
OPE-ER-157-94
Transmittal of the Draft Remedial Investigation/Feasibility Study Report for
Operable Units 5-05 and 6-01 (SL-1 and BORAX-I Burial Grounds RI/FS);
Volume 1 of 2
Lyle, J.L.
Pierre, W.; Nygard, D.
06/15/94
INEL-95/0027
Remedial Investigation/Feasibility Study Report for Operable Units 5-05 and
6-01 (SL-1 and BORAX Burial Grounds)
Holdren, K.J.; Filemyr, R.G.; Vetter D.W.
N/A
03/01/95
AR4.3 Proposed Plan
• Document #: 10011
Title: Proposed plan for Operable Units 5-05 and 6-01 Stationary Low-Power
Reactor-1 and the Boiling Water Experiment-I Burial Grounds
Author: DOE, EPA, IDHW
Recipient: N/A
Date: 05701/95
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