United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R04-91/098
June 1991
Superfund
Record of Decision:
Oak Ridge Reservation (USDOE)
(Operable Unit 2), TN
-------
50272-101
REPORT DOCUMENTATION 1'. REPORT NO.'
PAGE EPA/ROD/R04-91/098
l ~
3. ReclpIent'a Acce88lon No.
4. T1Ue md SubtiDe
SUPERFUND RECORD OF DECISION
Oak Ridge Reservation (USDOE) (Operable Unit 2), TN
First Remedial Action
7. Author(a)
5. Report D8te
06/28/91
6.
8. Pertonnlng Organization RepI. No.
II. Pertonnlng Orgllinlzation N8me md Addreu
10. Pl'ojedITa8klWortI UnI1 No.
11. Contr8C1(C) or Gr8J1t{G) No.
(C)
(G)
1 ~ Spon8or1ng Org8lliz8tlon N8me md Addre8a
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report 80 Period Covered
Agency
800/000
14.
15. Supplementary Nole8
16. Ab8tn1ct (Umlt: 200 words)
The Oak Ridge Reservation (ORR) (USDOE) site is an inactive uranium recovery landfill
in Oak Ridge, Anderson County, Tennessee. The United Nuclear Corporation (UNC)
disposal site, which comprises Operable Unit 2 (OU2), is one of several hundred waste
disposal sites or areas of contamination at the ORR site requiring Superfund remedial
action. From 1982 to 1984, the 1.3-acre disposal site received 11,000 55-gallon
drums of cement-fixed sludge, 18,000 drums of contaminated soil, and 288 wooden boxes
of contaminated building and process equipment demolition debris from the
decommissioned UNC uranium recovery facility in Wood River Junction, Rhode Island.
The wastes were placed in 5- to 50-foot deep pits and covered with polyvinyl chloride
sheeting. Although some drums and boxes have deteriorated, rusted, or split open,
investigations show that migration of contaminants to soil and ground water has not
yet occurred. This Record of Decision (ROD) addresses the drummed soil, sludge, and
debris to. prevent future ground water contamination. Subsequent RODs are planned to
fully address the principal threats posed by the ORR site. The primary contaminants
(See Attached Page)
17. Document AnII/ysJs L Descriptors
Record of Decision - Oak Ridge Reservation (USDOE) (Operable Unit 2), TN
First Remedial Action
Contaminated Media: soil, sludge, debris
Key Contaminants: inorganics (nitrite), radioactive materials (strontium-90)
b. identifiers/Open-ended Tem18
c. COSA 11 ReIdIGroup
18. AVllilabiHty Statement
111. Security Cia.. (ThIs Report)
None
20. Security Cia.. (Thla Page)
None
21. No. of Pagea
26
~ Price
{See ANSl-Z3B.18
See IMtruclions on Relfet88
(Fonnerty N11S-35)
D8pu1ment of Commarce
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EPA/ROD/R04-91/098
Oak Ridge Reservation (USDOE) (Operable Unit 2)~ TN
First Remedial Action
Abstract (Continued)
of concern affecting the soil, sludge, and debris are nitrite, an inorganic; and
strontium-90, a radioactive material.
The selected remedial action for this site includes clearing and grubbing sparse
vegetation; placing a multi-layer cover over the drums, soil, sludge, and debris;
revegetating the area and backfilling over the UNC waste with additional soil; and
monitoring ground water. The estimated present worth cost for this remedial action is
$1,467,500, which includes an annual O&M cost of $93,600 for year 0-1 and $69,800 for
years 2-30.
PERFORMANCE STANDARDS OR GOALS: The selected remedy will prevent future contamination
of ground water from landfill wastes. Accordingly, the remedy will meet the SDWA M~L
for nitrate 10 mg/l at downgradient wells and meet a 10-6 risk level for strontium-90.
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... . - i
RECORD QE DECISION
UNITED NUCLEAR CORPORATION DISPOSAL SITE
DECLARATION
SITE NAME AND LOCATION
United Nuclear Corporation (UNC) Disposal Site Y-12 Plant, Oak Ridge, Tennessee
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected action for the UNC Disposal Site'
at the Y-12 Plant in Oak Ridge, Tennessee, which was chosen in accordance with
the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), as amended, and to the extent practicable, the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP). This decision is based
on the Administrative Record for the UNC Site.
The Tennessee Department of Environment and, Conservation (TDEC) and the.
Environmental Protection Agency (EPA) concur with the selected action for the
UNC Disposal Site.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substance from this site, if not
addressed by implementing the response action selected in this Record of Decision
(ROD), may present an imminent and substantial endangerment to the public health,
welfare, or the environment.
DESCRIPTION OF THE SELECTED REMEDY
The major goal of this selected action reduces the mobility of contaminants by
capping and isolating the source from the underlying aquifer system, thereby
minimizing leachate production and potential future contamination of groundwater.
The major component of the action remedy is capping by emplacement of a multi-
layer cover system consisting of the following:
1) a minimum 24-in-thick clay layer over the drummed soil/~ludges and
miscellaneous scrap boxes,
2) a minimum 30-mil synthetic liner,
3) a polyethylene drainage geonet,
4} a polypropylene filter fabric, and
5} a minimum IS-in-thick vegetative layer.
-------
Some variation of thh design may be necessary to accommodate sHe-specif.ic
requirements. The remedial action also includes routine inspection and
maintenance of the cover system and groundwater monitoring. .
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies
with Federal and State requirements that are legally applicable or relevant and
appropriate to the remedial action and is cost effective. This remedy utilizes
containment as the permanent solution" Treatment of the principal threats of
the site was not found to be practicable therefore, this remedy does not satisfy
the statutory preference for treatment as a principal element.
Because this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within five (5) years after
completion of remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment.
~ ~. -=; --~,-,~~t~ -~
gional Administrato , Region IV"""\,.
U. S. Environmental Protection Agency
b.:J.~.Ci/
Date
rt!r ~4.-<-
~ ger, Oak Ridge field Office
U. S. Department of Energy
~ - 2-F-'/
Date
irector, DOE
State of Tennesse ,
Department of Environment and Conservation
~- ~- C\ \
Date
-------
TABLE OF CONTENTS
1.0 Introduction
[[[ .1
2.0 Site Name, Location, and Description ..................................1
3.0 Site History and Enforcement Activities ...............................1
4.0 Highlights of Community Participation .................................2
5.0 Scope and Role of Response Action Within Site Strategy ................2
6.0 Summary of Site Characterizations.....................................3
6.1 Drum and Box Di sposa 1 Area....................................... 3
6.2 Wooden Boxes[[[ 3
6.3 Drummed Soi 1 s/S1 udges ............................................3.
6.4 Adj acent 50; 1 s [[[4
6.5 Groundwater[[[ 4
6.6 Potential Pathways to the Environment ............................4
7 . 0 Summary of Site R is ks ................................................. 5
7.1 Contaminated Media and Contaminants of Concern ...................5
7.2 Exposure Pathways and Populations ................................6
7 . 3 Ri s k As s e s sme n t .................................................. 6.
7.3.1 Ni trate [[[6
7.3.2 Strontium-gO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
7.4 Risk Characterization ............................................7
8.0 Description of Alternatives ...........................................7
8.1 Alternative 1 - No Action ........................................7
8.2 Alternative 2 - Modified RCRA Cap................................8
8.3 Alternative 3 - Treatment and Modified RCRA Cap ..................8
8.4 Alternative 4 - Off-Site Disposal ................................9
9.0 Summary of Comparative Analysis of Alternatives .......................9
9.1 Threshold Criteria .....................~....................... ..9
9.1.1 Overall Protection of Human Health and the Environment ....9
9.1.2 Comp 1 i ance wi th ARARs .................................... 10
9.2 Primary Balancing Criteria..................................... .10
9.2.1 Long-Term Effectiveness and Permanence ...................10
9.2.2 Reduction of Toxicity, Mobility, and Volume Through
Treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.2.3 Short-Term Effectiveness .................................11
9.2.4 Ease of Implementation ...................................11
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11.0 Statutory Determinations................................. ~.......... .12
11.1 Protective of Human Health and the Environment ..................12
11..2 Attainment of the Applicable or Relevant and Appropriate
Requirements (ARAR) ............................................ .12
11.3 Cost Effectiveness............................................. .13
11.4 Utilization of Permanent Solutions and Alternative Treatment
Technology or Resource Recovery Technologies to the Maximum
Extent Practicable .............~...............................13
11.5 Preference for Treatment as a Principal Element .................13
11.6 Documentation of Significant Changes ............................13
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Figure 1
Figure 2
Table 1
Table 2
Table 3
Appendix A
LIST OF FIGURES
Geographic location Map
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-A
Well location and Water Table Map .........................4-A
LIST OF TABLES
Summary of Drum Sampling - RCRA Constituents
........... .3-A
Summary of Drum Sampling - Non-RCRA Constituents ........3-B
Glossary of Evaluation Criteria .........................9-A
LIST OF APPENDICES
Responsiveness Summary
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ARAR
CERClA
Energy
Systems
DOE
EP
EPA
FS
HElP
HQ
MCl
mCi
NCP
NEPA
NPl
NRC
O&M
ORR
pCi
PVC
RCRA
RfD
RI
SARA
SDWA
TDEC
ACRONYMS
applicable or relevant and appropriate requirement
Comprehensive Environmental Response, Compensation, and
liabil ity Act
Martin Marietta Energy Systems, Inc.
u. S. Department of Energy
extraction procedure
U. S. Environmental Protection Agency
Feasibility Study
Hydrologic Evaluation of landfill Performance
Hazardous Quotient
maximum concentration level
mill i curie
National Oil and Hazardous Substances Contingency Plan
National Environmental Policy Act
National Priorities list
National Regulatory Commission
operation and maintenance
Oak Ridge Reservation
pico curie
polyvinyl chloride
Resource Conservation and Recovery Act
reference dose
Remedial Investigation
Superfund Amendments and Reauthorization Act
Safe Drinking Water Act
Tennessee Department of Environment and Conservation
-------
Record of Decision
Remedy Action
The Oecision Summary
United Nuclear Corporation Disposal Site
Y-12 Plant, Oak Ridge, Tennessee
Prepared by:
U. S. Department of Energy
Oak Ridge Operations
-------
RECORD OF DECISION
The Decision Summary
United Nuclear Corporation Disposal Site
Y-12 Plant, Oak Ridge, Tennessee
1.0 Introduction
The Oak Ridge Reservation (ORR) was placed on the National Priorities List
(NPL) on December 21, 1989. The United Nuclear Corporation (UNC) Disposal Site
is one of several hundred waste disposal sites or areas of contamination at the
ORR requiring remedial action under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERClA).
In 1989, the U. S. Department of Energy (DOE) had prepared and submitted to the
U. S. Environmental Protection Agency (EPA) and the State of Tennessee a
closure plan for the UNC Disposal Site. In July 1990, EPA advised DOE that it
should prepare a Feasibility Study (FS) to evaluate several remedial
alternatives, including closure. EPA further advised DOE that a separate
Remedial Investigation (RI) was not necessary and that the report Pathways
Analysis for UNC DisDosa1 Pit. Y-12 Plant could serve as the RI report with
minor supplements, such as Risk Assessment and recent groundwater quality data.
2.0 Site Name, Location, and Description
The UNC Disposal Site is a 1.3-acre landfill located near the crest of Chestnut
Ridge, in the southern portion of the Y-12 'lant, in Oak Ridge, Tennessee
(Fig.1). The excavation for the landfill was cut into the side of Chestnut
Ridge. Pit depths range from 25 to 30 feet on the northern side, to less than
5 feet on the southern side. The UNC Disposal Site contains 11,000 55-gallon
drums of cement-fixed sludge, 18,000 drums of contaminated soil, and 288 wooden
boxes of contaminated building and process equipment demolition debris. The
drums are stacked horizontally, 10 high, in a pyramid shape following the
contour of the excavation. The wooden boxes are on the south side of the
stacked drums, and the entire waste site is covered by polyvinyl chloride (PVC)
sheeting. Observations under the sheeting indicate that many of the drums and
boxes have deteriorated, rusted or split open.
3.0 Site History and Enforcement Activities
The UNC Disposal Site was established to receive waste from the decommissioning
of the UNC uranium recovery facility in Wood River Junction, Rhode Island.
Following shutdown of the recovery operations in 1980, UNC was required to
decontaminate its facilities, excavate contaminated soil and sludge from the
associated ponds and trenches, and remove the resultant low-level radioactive
waste from the State of Rhode Island. Once. the pit was excavated and prepared
for receipt of waste, disposal operations commenced. The UNC Disposal Site
operated between June 1982 and November 1984. At present the UNC site is
inactive and has not received additional waste since 1984.
Information available at the time the waste was accepted for disposal indicated
that it was not a hazardous waste as defined by Resource Conservation and
Recovery Act (RCRA) regulations. Extraction procedure (EP) toxicity testing in
1
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Y-12 PLANT SITE
MARTIN MARIETTA ENERGY SYSTEMS, INC.
Fig. 1. Location of UNC Disposal Site
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1985 on the drummed sludge and soil confirmed the waste to be nonhazardous
under RCRA. Additional testing of soil and groundwater in the immediate
vicinity of the disposal site indicates that migration of contaminants had not
occurred. However, based on the deteriorated condition of the drums and the
estimated source inventory and mobility of waste constituents present, the UNC
Disposal Site was deemed a potential risk to human health and the environment.
In December 1989, EPA and Tennessee approved the Energy Systems plan for
closure of the UNC Disposal Site. However, before this plan could be
implemented, the ORR was placed on the NPL, which consequently required DOE to
follow CERCLA Response Action Program requirements for remedial action
selection and implementation.
4.0 Highlights of Community Participation
The UNC Disposal Site FS and Proposed Remedial Action Plan were released to the
public on March 18, 1991. These two documents were made available at the DOE
Information Repository located in the former Ridge Theater building, 105
Broadway, Oak Ridge, Tennessee, 37831. The notice of availability was
published in The Oak Ridger, Knoxville News-Sentinel, and the Knoxville,Journal
on March 31, April 1, 2, 14, 15, 16, and 28, 1991. Notices were also pUblished
in The Roane County News on April 1, 3, 5, 15, 17, and 19, 1991. A public
comment period was held from March 18, 1991, through April 30, 1991. In
addition to public comment and the accessibility of the information, a public
meeting was held on April 16, 1991. At this meeting representatives of DOE and'
Energy Systems answered questions and addressed community concerns. A response
to comments received during this period is included in the Responsiveness
Summary, Appendix A of the Record of Decision.
This decision document presents the selected remedy for the UNC Disposal Site
chosen in accordance with CERCLA, as amended, and to the extent practicable.
the National Contingency Plan. The decision is based on the administrative
record. .
5.0 Scope and Role of Response Action Within Site Strategy
The major goal of this response action is to prevent or minimize the
contamination of shallow groundwater beneath and down gradient of the UNC
Disposal Site. This action is considered a final action with respect to the
UNC Disposal Site only. Subsequent actions are planned to address fully the
principal threats posed by the ORR.
Groundwater at the Y-12 Plant 1s not presently used as a source of drinking
water and, as stated previously, there is no indication at present that
groundwater under the UNC Disposal Site has been contaminated. However,
shallow groundwater at the Y-12 Plant is a potential source of drinking water
and its future use as a potable water supply cannot be ruled out. In
evaluating future use scenarios, it was determined that source control action
was necessary to prevent future exposure to contaminants in groundwater at
levels that would pose an unacceptable health risk. Specifically, this action
is being taken to ensure that mobile contaminants in the UNC waste, principally
nitrate and strontium-90, are not leached to groundwater at a rate that would
2
-------
result in concentrations of these contaminants above safe drinking water
standards. . .
6.0 Summary of Site Characteristics
6.1 Drum and Box Disposal Area
The UNC Disposal Site, in general, represents a safety hazard to workers. The
29,000 drums are stacked 10 high, and some have rusted and split open, thereby
exposing their contents. A high risk for industrial accidents exists at the
site because of the potential of shifting and falling drums and exposed rusty,
sharp metal. Therefore, in their present condition, the drums and boxes, even
though nonhazardous, could adversely affect workers entering the site.
6.2 Wooden Boxes
There are 288 plywood boxes located at the site. They are located in front of
the stacked drums and many have split open, spilling their contents. Contents
of the boxes vary from miscellaneous industrial scrap material (piping,
conveyors, industrial scrap, etc.) to sand in plastic bags. A walk-over
radiological survey of the drums and boxes was conducted in August 1990.
6.3 Drummed Soils/Sludges
During 1985, 82 samples, based on a statistical program, from 76 randomly
selected drums at the UNC Disposal Site were analyzed by the RCRA extraction
procedure (EP) toxicity leach test for hazardous waste characterization. Half
of the samples were from drums containing soil and half of the samples were
from drums containing sludges mixed with cement.
The EP toxicity extract was analyzed for a wide range of constituents in
addition to the metals, herbicides, and pesticides typically required in
accordance with RCRA. Based on process knowledge of the UNC Disposal Site, the
wastes were also tested for corrosivity, nitrates, moisture content, and
radionuc1ides. A summary of the results, is presented in Tables 1 and 2,
respectively.
None of the samples exceeded the pH regulatory limit for corrosivity of < 2.0
or > 12.5. Similarly, none of the extracts contained contaminant
concentrations exceeding the regulatory limits set forth under RCRA. Most
contaminant concentrations were below the detection limits or levels measured
in blanks. With the exception of strontium-90 and nitrate, all other ana1ytes
were below the SDWA maximum contaminant level (MCl) regulatory criteria. The
concentrations of nitrates in the EP toxicity leachate ranged from < 0.5 mg/L
to 8880 mg/l. The highest concentrations of nitrates were found in extracts
obtained from the sludges that were mixed with cement. A total nitrate (as
nitrogen) inventory for the site was estimated by assuming that the extraction
fluid used in the EP test effectively dissolved all of the leachable nitrate in
a specified mass of the sample. A nitrate inventory of approximately
53 tons was calculated using the available data and the referenced assumptions.
The inventory of strontium-90 was estimated by assuming the same average weight
3
-------
iV
Table I. Summary of drum sampling • EP toilclty testing for
RCRA hazardous waste conilllueoU
Constituent
Hg
Ag
Ba
Cd
Cr
Pb
As
So
2,4-D
Undane
Endrine
Toxaphene
2,4,5 TP-Silvex
Melhoxyctilor
Average
concentration
<0.001
0.0062
0.6200
0.0072
0.0123
0.05
0.0055
0.0060
2.05
0.021
0.01
2
0.2
0.092
Units
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
|ig/L
0g/L
1-g/L
i-g/L
*g/L
-g/L
Standard
deviation
.
0.0013
1.26
0.012
0.0054
0.05
0.0017
0.0033
0.44
0.0067
-
-
-
0.11
Minimum
concentration
<0.001
<0.006
<0.001
<0.003
<0.004
<0.05
<0.005
<0.004
<2
<0.02
<0.1
<2
<0.2
<0.08
Maximum
concentration
<0.001
0.01
93
0.1
0.03
0.05
0.01
0.02
4
0.07
0.1
2
0.2
1.08
No. of
analyses
82
82
82
82
82
82
82
82
82
81
81
81
81
81
Regulatory
criteria*
02
5
100
1
5
5
5
1
10,000
400
20
500
1,000
10,000
No. above
criteria
0
0
0
0
0
0
0
0
0
0
0
0
0
•o
•Regulatory criteria consist of levels 100 limes drinking water standards
Table generated from analytical data reported by Kirkpatrick and McCall 1986
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Table 2. Summary of drum sampling - EP toxlcliy testing for
aon-RCRA waste consllluents
U)
CD
Average
Constituent concentration
Al
Ni
P
Zr
Gross alpha
Gross beta
Gross gamma
""Np
Strontium
"Sr
""Cs
»Tc
"*Pu
"•Pu
Uranium
F
Moisture
NO, -N (soils)
NO, -N (sludge)
PH
SrKd
12300
0.043
0.27
0.017
0.47
0.92
<20
0.0092
6.2
0.18
<20
188
0.006
0.006
0.0101
188
19.6
17
3252
43.1
Units
mg/L
mg/L
mg/L
mg/L
dpm/mL
dpm/mL
dpm/mL
dpm/mL
dpm/g
dpm/mL
dpm/mL
dpm/mL
dpm/mL
dpm/mL
Pg/mL
mg/mL
wt%
mg/L
mg/L
mL/g
Standard
deviation
177
0.075
0.29
0.047
112
1J2
0.026
5.65
02
1.91
0.027
2.87
118
34
2488
293
Minimum
concentration
<0.02
<0.01
<0.2
<0.005
<0.002
0.01
<20
<0.006
0.56
<0.01
<20
<2
<0.006
< 0.006
<0.001
0.06
0.4
<03
35
3.7
3.29
Maximum
concentration
12.0
0.48
2.4
0.4
183
534
20.0
0.24
19.0
1.23
20
113
0.006
0.006
0.17
113
49J
152
8880
113
139
No. of
analyses
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
39
43
82
82
Regulatory
criteria"
20
3
2
0.2
0.4
20
12
8
6
10
10
No. above
criteria
0
0
0
0
3
0
0
0
0
18
0*
a
0
0
0
0
0
5
43
0
0
"Regulatory criteria for NO,' based on the Safe Drinking Water Act MCL. Other regulatory criteria consist of levels 100 limes drinking water standards obtained from
the following sources: Ni • Tennessee Superfund Guidelines; Gross Alpha - Safe Drinking Water Act MCL;
"No, ?Sr, '"Cs, **Tc. "Pu, **Pu, and uranium based on concentration representing an equivalent dose rate of 4 mrem/year.
*AU values below detection limit.
Table generated from analytical data reported by Kitkpalrick and McCall 1986.
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and number of drums and using the average of 6.2 dpm/g of strontium-90 in the
solids. An estimated inventory of 25 mCi of strontium-90 was calculated.
6.4 Adjacent Soils
In 1986, several soil samples were obtained from the vicinity of the UNC
Disposal Site and analyzed for heavy metals and nitrates. Two holes were
augured within the excavated pit immediately downgradient of the stacked drums
and samples were obtained from various intervals over the 20-ft core depths.
Data for background soil concentrations were obtained from the upper 3 feet of
soil at two locations east and west of the disposal site and from the archived
cores taken during installation of a nearby groundwater monitoring well.
The analytical results indicated that heavy metal concentrations were higher
than background levels typical of soils derived from limestones and dolomites.
However, all of the samples exhibited similar metal concentrations, and the
higher concentrations were not limited to the shallow soil depths. Some of the
greatest concentrations were observed in soil samples taken at a depth of 25 ft
during drilling of well GW-173. Well GU-173 is a background well located
approximately 1 mile from the UNC Disposal Site. The low levels of nitrates
observed in the samples appear to indicate that the wastes at the site have not
leached into the vadose zone.
6.5 Groundwater
Groundwater monitoring of the UNC Disposal Site has been conducted since 1986.
Previous sampling reports concluded that there was no evidence of migration
from the Site. During calendar years 1987 and 1988, a more restricted suite of
groundwater chemical analyses was performed with an overall goal of detecting
the initiation of contaminant migration. Subsequent evaluations of these
results performed in 1989 concluded that there was no indication of leakage
from the site. Seven groundwater monitoring wells at the UNC Disposal Site
(Fig.2) are now sampled quarterly and analyzed for metals, various radioactive
species, nitrates, and other conventional water quality parameters. The depth
to groundwater, in the area, is typically 40 - 60 feet, below the base of the
UNC Disposal Site.
The water quality analyses of samples collected from the seven UNC Disposal
Site assessment wells during 1989 and the first quarter of 1990 show no
indication of leakage from the site. Detectable concentrations of metals
during 1989 and 1990 were commonly below applicable federal drinking water MCLs
or within ranges observed in background wells located on Chestnut Ridge. The
detected metal concentrations are supported by historical groundwater data at
the site and are representative of the groundwater chemistry of Chestnut Ridge.
6.6 Potential Pathways to the Environment
The results of sampling and analysis programs conducted on the UNC wastes
indicated nitrate and strontium-90 to be the only contaminants of concern.
Migration pathways considered to have potential impact and requiring evaluation
are surface water and groundwater routes.
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E 53.000
E 54.000
N 29.000
N 28,000
N 27.000
E 53.000
29,000
28.000
N 27.000
E 54.000
E 55.000
REFERENCES:
Eiwv Sytwm. Inc F«M DflB
»
Scale: 1:4«00
C.L.5(Mt
Ground*a«»r tmbto «*^mnoo»
Grid ComdinatM Bawd on Y-12
Ptant Adminirtratiy* Grid Syctrnn
MARTIN MARIETTA ENERGY SYSTEMS, INC.
Fig. 2. Well locations and water table map for the
UNO Disposal Site, second quarter, 1990
4-A
-------
Migration of nitrates and strontium-90 from the UNC Dispo,sa1 Site via
groundwater and recharge to surface water pathways was evaluated using a water
balance computation and two-dimensional groundwater contaminant transport
simulation. The water balance was estimated using EPA's Hydrologic Evaluation
of landfill Performance, or HELP model. The results of the HELP simulations
were adjusted to support the data input requirements of the WMPlUME model used
to simulate contaminant transport through groundwater. The simulations,
performed in 1985, were based on the existing conditions at the site, which
represented an .uncapped, exposed. excavation.
Required input variables included waste characteristics and soil, geological,
and climatological data. In the absence of specific data, conservative
assumptions were made based on characteristics of the site and boundary
conditions of the model.
Based on the waste analysis, available site-specific data, and relevant
conservative assumptions, the simulations predicted the following:
1. Strontium-90 and nitrate-contaminated leachate would reach the
groundwater table in approximately 10 years.
2. Approximately 3 years beyond the time at which the leachate reaches
the groundwater system, the plume of contamination would have reached
steady-state conditions. A maximum concentration of 193 mg/l (as
nitrogen) for nitrate, and 50 pCi/l for strontium-90 was predicted.
3. The average contribution of nitrate (as nitrogen) to the nearest
surface tributary would range from 10 to 30 mg/l, depending on the
extent of groundwater discharge to the stream (basef10w).
Since these estimates are conservative, potential contaminant concentrations in
groundwater at the site may be lower.
7.0 Summary of Site Risks
CERClA directs that human health and the environment must be protected from
current and potential exposure to hazardous substances. In order to assess the
current and potential risks for the UNC Disposal Site, a baseline risk
assessment was performed by the Risk Analysis Section, Health and Safety
Research Division, at the Oak Ridge National laboratory (ORNl), and is included
in the Feasibility Study.
7.1 Contaminated Media and Contaminants of Concern
Soil and groundwater analysis has not identified any migration of contamination
from the UNC waste. The only contaminated media at the UNC Disposal 'Site are
the drummed soils/sludges and miscellaneous scrap (source media). The
contaminants of concern in the source material are nitrate and strontium-gO.
No migration to the soil or groundwater of these constituents has occurred.
Waste characterizations have indicated both these constituents are in high
concentration and have the greatest potential to leach from the drummed wastes.
Based on their source inventory concentration and on their toxicological,
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physical, chemical, and environmental fate characteristics, these constituents
were deemed most likely to contribute to potential human risk.
7.2 Exposure Pathways and Populations
The UNC Disposal Site is situated within the limited access area of the Oak
Ridge Y-12 Plant. Direct access by the general public is unlikely now, or at
any time within the foreseeable future due to the location of the site on the
Oak Ridge Reservation (ORR). Employees of the DOE facilities are the most
likely exposed population, and only a small percentage of these employees are
expected to access the UNC Disposal Site. After remedial action, groundwater
is the only potential exposure pathway for contaminants in the UNC waste.
Modeling was used to conservatively predict the effect nitrates and strontium-
gO could have on various environmental media, if the site was left in its
present condition. Modeling identified a potential impact to both groundwater
and surface water through groundwater releases. Groundwater is the only
exposure pathway for contaminants in the UNC waste.
7.3 Risk Assessment
Quantification of risk for the UNC waste is limited to the adverse health
effects of the two contaminants of concern, nitrate and strontium-gO. To
provide perspective on the potential for nitrate and strontium-gO to affect
human health adversely, hazard quotients and cancer risks were determined for
present conditions and each remedial alternative. The residual risk associated
with the UNC waste, if left as is, provides a baseline to judge the remedial
alternatives.
The pathways analysis indicates no current human exposure to contaminants at
the UNC Disposal Site. Nevertheless, as a conservative means of evaluating the
effectiveness of the remedial alternatives, human exposure was assumed to occur
through ingestion of contaminated groundwater. .
7.3.1 Nitrate
Nitrate is not listed as a hazardous constituent by EPA under RCRA. However,
the federal drinking water standard for nitrate is 10 mg/L (as nitrogen).
Chronic exposure to nitrates results in methemoglobemia in infants less than 3
or 4 months old due to conversion of nitrates to nitrites in the
gastrointestinal tract. Nitrate has a Group D cancer classification, meaning
there is no evidence of carcinogenicity in humans or animals. There has been
no evidence of mutagenicity related to nitrate exposures.
7.3.2 Strontium-gO
EPA classifies strontium-gO as a Group A carcinogen because ionizing radiation
is known to be carcinogenic in humans and animals. Strontium is acquired by
humans primarily through ingesting strontium-gO contaminated food. It is
retained by the body largely in bone and may inhibit bone calcification.
Absorption of strontium-gO by the body is relatively high, and it has a long
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biological retention time. Animal studies have also shown acute effects to
strontium exposure, Including respiratory failures In rats.
7.4 Risk Characterization
To evaluate the noncarcinogenic effects of nitrate, a measure of the potential
health risk Is obtained by comparing exposure levels to the Reference Dose
(RfD). Potential nitrate exposure levels, calculated for Ingestion of
groundwater, are Identified as milligrams per kilogram of body weight per day
(mg/kg/d). For the current conditions representing an exposed excavation,
modeling predicted 10 years for the nitrates to reach the groundwater system.
After 13 years, a maximum nitrate concentration of 193 mg/L was predicted. The
Hazard Quotient (HQ) for the groundwater nitrate concentration of 193 mg/L is
3.4. This HQ is greater than 1.0, indicating that the no-action alternative may
result in nitrate concentrations that may cause adverse noncarcinogenic health
effects. As previously stated, human exposure is not occurring and was only
assumed as a means of evaluating the effectiveness of the treatment
alternatives.
Potential strontium-90 exposure levels are identified as picocuries (pCi). For
the no-action alternative, modeling predicted 10 years for stront1um-90 to
reach the groundwater system. The maximum concentration predicted by the model
for the defined conditions was 50 pCi/L. Risk was then calculated to determine
the probability of an individual developing cancer over a lifetime as a result
of exposure to the potential carcinogen. The risk for the no-action
alternative is 8.3 x 10"5, which is within EPA's range of concern (10"4 to
10'6).
8.0 Description of Remedial Action Alternatives
8.1 Alternative 1: No Action
The NCP requires the no-action alternative be considered through the detailed
alternatives analysis. It provided a baseline for comparison of other
alternatives. Under this alternative, no source control remedial measures
would be undertaken at the site. However, groundwater monitoring, site
monitoring and maintenance, and drainage maintenance and erosion control would
be continued for 30 years. Appropriate warning signs also would be posted.
Construction Cost: $240
Annual Operation and Maintenance Costs (O&M)
0-1 years: $68,000
2-30 years: $44,000
Present Worth (30 yr) $483,000
Months to Implement 3-4
The no-action alternative would not eliminate any exposure pathways or reduce
the level of risks.
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8.2 Alternative 2: Multi-Layer Cover
Alternative 2 involves covering the drummed sOils/sludges and miscellaneous
scrap (boxes) with a multi-layer cover for long-term minimization of
infiltration. Little site preparation is required to construct the cover.
Some movement of barrels and boxes may be necessary to facilitate grading.
Additional site preparation with this design includes only minor grading and
negligible clearing and grubbing because the "land surface at the UNC Disposal
Site has only sparse vegetation. A multi-layer cover is composed of a minimum
24-in-thick clay layer over the drummed soil/sludges and miscellaneous scrap
boxes, overlain by a minimum 30-mi1 synthetic liner, overlain by a polyethylene
drainage geonet, overlain by a polypropylene filter fabric, overlain by a
minimum 18-in-thick vegetative layer. Additional soil will be backfilled over
UNC waste prior to installation of the cover. Some variations of this design
may be necessary to accommodate site-specific requirements.
Construction Cost:...........................~...S780,500
Annual O&M:
1 year:........................................ $93,600
2-30 years:................................... .$69,800
Present Worth (30 yr)..........................SI,467,500
Months to Implement.....................................8
The time frame in which a cover could be placed is relatively shorter than
alternatives that use treatment as the principal element. Treatment rates,
disposal distances, and imposed limitations are negligible or not applicable to
the alternative.
8.3 Alternative 3: Treatment and Multi-Layer Cover
This alternative treats only the 11,000 drums containing sludges mixed with
cement. The 18,000 drums of soil are not treated because they account for only
1 percent of the nitrate at the site. Miscellaneous demolition materials are
not treated due to compositional variations and negligible nitrate content.
The alternative involves four main processing steps: (I) solid waste
processing of the drummed sludge, (2) leaching of the nitrate from the sludge,
(3) treatment of the nitrate-bearing leachate; and, (4) containment of the
leached sludge, drummed soil, and miscellaneous boxed scrap.
Solid waste processing involves identifying the drummed sludges from the soils,
removing the waste from the barrel, reducing the particle size of the solid
waste by primary and secondary crushing, shredding empty barrels, and leaching
nitrates from the crushed solid waste. Deheading of the drums and identifying
the "contents would be performed manually. Drums containing soil would be
emptied and their contents covered with PVC sheeting and isolated until
completion of the treatment process. A concrete pulverizer would remove the
drums surrounding the concrete and reduce the concrete fragments to less than
9 inch diameter and then a secondary crusher would crush the material to the
optimum particle size for nitrate leaching. A soil washing system would be
used to leach nitrate from the crushed material. Wastewater generated from the
solid waste leaching would require treatment by neutralization/pH adjustment,
anaerobic fixed film treatment, and sedimentation. The leached crushed sludge,
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soil emptied from the drums, and miscellaneous scrap would be placed back in .
the existing excavation and capped with a multi-layer cover as outlined in
Alternative 2. The miscellaneous scrap would be removed from the wooden boxes
to prevent void spaces during filling. All barrels would be shredded. Soil
would be removed from the drums and placed in the excavation, and the drums
would be shredded.
Construction Cost:.......................... $2,353,100
Annual O&M:
1 year:...................................... 593,600
2-30 years:.................................. 569,800
Present Worth (30 yr)........................ $3,033,000
Months to Implement:................................. 25
8.4 Alternative 4: Off-Site Disposal
Shipment and disposal of UNC wastes off Y-12 Plant grounds is considered to
provide an alternative involving minimal long-term oversight or maintenance.
Disposal of the UNC wastes off-site involves handling and preparing the waste
for shipping transportation, and disposal at an appropriate facility. Waste
preparation is assumed to consist of handling, overpacking drummed soil and
sludges, and containing miscellaneous wastes. Transportation would be via
truck. Potential low-level radioactive contamination greatly reduces the
number of disposal facilities that will accept the wastes. For this analysis
it is assumed the wastes would be transported to u.s. Pollution Control's land
disposal facility in Beatty, Nevada. Once waste is removed, the site will be
backfilled with clean soil and returned to a natural state.
Capital Cost:................................ SI3,954,000
Annual O&M:
1 year:....................................... $63,000
2-3 years:................................~... $39,000
Present Worth (4 yr)......................... SI4,073,000
Months to Implement:.................................. 12
9.0 Summary of Comparative Analysis of Alternatives
This section provides the basis for determining which alternative: (i) meets
the threshold criteria of overall protection of human health and the
environment and compliance with ARARS, (ii) provides the "best balance" between
effectiveness and reduction of toxicity, mobility, or volume through treatment,
implementability, and cost; and, (iii) state and community acceptance. A
glossary of the evaluation criteria is provided in Table 3.
9.1
Threshold Criteria
9.1.1 Overall Protection of Human Health and the Environment
Alternative 1, No Action, is not protective of human health and environment
because it would not eliminate the direct contact/external radiation exposure
pathway posed by the boxed materials and would likely result in contamination
of groundwater above safe drinking water standards. Alternative 2, capping
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TABLE 3
GLOSSARY OF EVALUATION CRITERIA
Overall Protection of Human Health and Environment - addresses whether or not
a remedy provides adequate protection and describes how risks posed through
each pathway are eliminated, reduced, or controlled through treatment
engineering controls or institutional controls.
ComDliance with ARARs - addresses whether or not a remedy will meet all the
applicable or relevant and appropriate requirements of other Federal and State
environment statutes and/or provides grounds for invoking a waiver.
Lona-term Effectiveness and Permanence - refers to the magnitude of residual
risk and the ability of a remedy to maintain reliable protection of human
health and the environment over time once cleanup goals have been met.
Reduction of Toxicity. Mobility. or Volume Throuah Treatment - is the
anticipated performance of the treatment technologies that may be employed in
a remedy. .
Short-Tenn Effectiveness - refers to the speed with which the remedy achieves
protection. as well as the remedy's potential to create adverse impacts on
human health and the environment that may result during the construction and
implementation period.
ImDlementabilfty - is the technical and administrative feasibility of a
remedy. including the availability of materials and services needed to
implement the chosen solution.
Cost - includes capital and operation and maintenance costs.
State AcceDtance - indicates whether the State concurs with. opposes, or has
no comment on the Proposed Plan.
Community AcceDtance - the Responsiveness Summary in the appendix of the
Record of Decision reviews the public comments received from the Proposed Plan
public meeting.
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with a multi-layer cover, offers the highest degree of protection of human
health and ~nvironment because it requires minimal worker exposure to wastes
and disruption of the site, eliminates the direct contact exposure pathway, and
ensures the future maximum nitrate concentration in groundwater does not exceed
the safe drinking water standard. Alternative 3, treatment and capping with a
multi-layer cover, and Alternative 4, off-site disposal, each provide less
overall protection of human health and environment than Alternative 2 due to
significant handling and processing of the waste and potential exposure to the
environment.
9.1.2 Compliance with ARARs
Although there is no evidence of contaminated groundwater or soil, the
potential exists (based on modeling) for groundwater contamination. Therefore,
the Safe Drinking Water Act (SDWA) maximum contaminant levels (MCls) for
nitrate (10 mg/l) and strontium-90 (8 pCi/l) have been identified as a
chemical-specific ARAR's for the UNC 5ite. The no-action alternative would not
comply with SDWA MCls. The other three alternatives would minimize the
potential leaching of contaminants into the groundwater, thus ensuring
compliance with the MCls. There are no federally listed endangered or
threatened plants or animals at the site.
9.2
Primary Balancing Criteria
9.2.1 long-Term Effectiveness and Permanence
Human health risks after remediation give an indication of the long-term
effectiveness of an alternative. Alternative 1, no action, has a low long-term
'effectiveness because of the post-implementation residual risks are equal to
the long-term risks at the site. Capping with a multi-layer cover, as provided
in Alternative 2, reduces the mobility of contaminants but its long-term
effectiveness and permanence requires a commitment of long-term maintenance to
ensure cap integrity. Alternative 3, treatment and capping with a multi-layer
cover, offers a high degree of long-term effectiveness and permanence. The
toxicity and volume of the main constituent of concern, nitrate, is reduced 70
percent, and migration of residual material is reduced by the multi-layer
cover. Alternative 4, off-site disposal, offers the highest degree of
long-term effectiveness. The UNC waste would be transported off-site to a
treatment and disposal facility. No source material remains at the s1te.
9.2.2 Reduction of Toxicity, Mobility, and Volume Through
Treatment
Of the four alternatives considered, only Alternative 3, treatment of the
drummed sludge and capping with a multi-layer cover, reduces the toxicity and
volume of the nitrate in the source material. It is predicted that the
treatment alternative would reduce the potential nitrate groundwater
concentration to 2 mg/l.
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9.2.3 Short-Term Effectiveness
For a given set of.alternatives, short-term effectiveness typically decreases
as the complexity of the alternatives increase because of handling and
processing considerations. The no-action alternative, Alternative 1 provides
the greatest degree of protection to workers, the public, and the environment
because the drummed soil/sludges and miscellaneous scrap are left undisturbed.
The short-term effectiveness decreases in the alternative in the following
order:. 2, 4, and 3. Alternative 2, capping with a multi-layer cover, will
require little handling or movement of the drums or boxes. Once initial layer
of fill material is deposited, the source material will be isolated from the
workers. Alternative 4, off-site disposal, has a lower degree of short-term
effectiveness than Alternative 1 or 2 because it requires handling of the drums
and miscellaneous scrap. However, once a drum is overpacked, it is isolated
from the worker. Alternative 3, treatment and capping with a multi-layer
cover, has the highest degree of short-term risk. Extensive handling and
movement of the drums is required. Dust produced from the crushing activities
may have high concentrations of nitrate and radioactive contaminants. It also
requires the longest time to complete.
9.2.4 Ease of Implementation
Materials required for the no-action alternative are readily available and
essentially negligible. The remaining alternatives are all technically and
administratively feasible. The cover design of Alternative 2 is easily
implemented. Alternative 3 is the most difficult remedy to implement because
of engineering, design, and administrative requirements. Alternative 3
combines tested and available technologies to achieve the treatment, but their
combination has high engineering demands. Alternative 4 has high
administrative requirements because of the large volume of material to be
transported off-site.
9.2.5 Costs
The comparative analysis of costs incorporates only differences in capital.
operation and maintenance, and present worth values. Costs for each
alternative have been provided in Sections 8.1 through 8.4. The costs increase
with the complexity of the alternative and the volume of waste to be managed.
The no-action alternative has the lowest costs, with a 30-year present worth of
$483,000. Alternative 2, emplacement of a multi-layer cover, has a 30-year
present worth of $1,467,500. Alternative 3, treatment and emplacement of a
multi-layer cover, has a 30-year present worth of $3,033,000. Alternative 4,
off-site disposal is the highest cost alternative. It has a 4-year present
worth of $14,073,000.
9.2.6 State Acceptance
The State of Tennessee, as represented by the Tennessee Department of
Environment and Conservation, concurs with the selected alternative,
emplacement of a multi-layer cover on the UNC Disposal Site.
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9.2.7 Community Acceptance
Based on comments made by citizens at the public meeting held on April 16,
1991, DOE perceives that the community believes the selected action will
effectively protect human health and the environment.
10.0 The Selected Remedy
Based upon consideration of the requirements of CERCLA, the detailed analysis
of the alternatives, and public comments, DOE has determined that the capping
with a multi-layer cover alternative is an appropriate remedial action for the
UNC Disposal Site.
I .
The goal of the selected remedy is not to clean up groundwater, because
groundwater is not contaminated, but to prevent future groundwater
contamination beyond a level deemed safe for drinking ~ater. Accordingly, the
remedy will meet the SDWA MCl for nitrate of 10 mg/l at the down gradient
perimeter monitoring wells. The carcinogen risk level associated with
ingestion of groundwater containing strontium-90 could reach a level of
8.3 x 10-5 if no action was taken. The selected remedy should achieve a
carcinogen risk level of 3.3 x 10-6, assuming groundwater at the UNC Disposal
Site is used for drinking water in the future. The remediation goals as
described herein will be met at the down gradient boundary of the UNC Disposal
Site.
11.0 Statutory Requirements
DOE, EPA, and TDEC believe that the multi-layer cover will satisfy the
statutory requirements of providing protection of human health and the
environment, attain applicable or relevant and appropriate requirements
directly associated with this action, and will be cost-effective. Sections
11.1 through 11.6 below summarize the statutory requirements for this Site.
11.1 Protection of Human Health and the Environment
The selected remedy, capping with a multi-layer cover, provides long-term
protection of human health and environment because it reduces the potential
(future) risk of exposure to contaminated groundwater by minimizing the
leaching of contaminants to groundwater. While the remedy does not eliminate
entirely the possibility of future groundwater degradation, the concentration
is not expected to exceed 8 mg/l for nitrate and 2 pCi/l for strontium-90.
Based on potential ingestion of strontium-90 contaminated groundwater, the
conservative estimations of carcinogenic risk is within EPA's range of concern
(10"4 to 10"6). The remedy also eliminates direct exposure to the waste and
will not cause unacceptable short term risks or cross medial impacts.
11.2
Attainment of the Applicable or Relevant and Appropriate
Requirements (ARARs)
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,
j
The only ARAR identified for this action is the SDWA MCLs for nitrate and
strontium-go. The selected remedy will comply with this appropriate and
relevant requirement. .
11.3 Cost Effectiveness
The 30-year present worth cost of capping and associated ma1ntenance and
. monttoring is Sl,46;,500. Treatment and capping residuals would cost twice as
much and provide a comparable level of protection. Off-site disposal would
cost ten times the cost of the selected remedy. .
The selected remedy utilizes a design similar to caps previously installed at
the Y-12 Plant. This technology has proven effective for reducing.the
migration of various contaminants at the Y-12 Plant. With proper maintenance,
the selected remedy is cost-effective.
1 L 4 Utili zat i on of Permanent Sol ut ions and A 1 ternat he
Treatment Technology or Resource Recovery Technologies to
the Maximum Extent Practicable.
The selected remedy does not utilize treatment or resource recovery
technologies. It is a.containmeni technology that, when applied, will minimize
the potential for contaminant leaching to groundwater. The capping remedy was
chosen over the alternative that featured treatment because it will achieve a
comparable level of protection at a considerable cost savings. Although
considered to offer less permanence than the off-site disposal alternative, the
capping remedy does not transfer the problem to. another locale and is
substantially lower in cost.
11.5 Preference for Treatment as a Principal Element
This remedy does not satisfy the statutory preference for treatment as a
. principal element. Instead, this remedy utilizes containment as the permanent
solution. Treatment of the principal threats. of the site was not found to be
practicable based on consideration of cost versus level of protection provided
as compared to the se 1 eded remedy. . .
11.6 Documentation of Significant Changes
The Proposed Plan for the UNCDisposal Site was released for public comment on
March 18, 1991. The Proposed Plan identified the multi~layer cover-p as the
preferred action remedy for the constituents of concern. DOE reviewed all
written and verbal comments submitted during the public comment period. Upon
review of these comments, it was determined that no significant changes to the
remedy, as it was originally identified in the Proposed Plan, were ne~essary.
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t" I
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