Interim Record of Decision for Oak Ridge National Laboratory Waste Area Grouping 13, Cesium Plots, Oak Ridge, Tennessee

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Interim Record of Decision for Oak Ridge National Laboratory Waste Area Grouping 13 Oak Ridge, Tennessee Office of Environmental Restoration and Waste Management 120 South Jefferson Circle Oak Ridge, Tennessee 37830 under Contract No. DE-AC05-900R2 185 1

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ACRONYMS AND INITIALISMS ................................. iv SITE NAME AND LOCATION ............................ STATEMENT OF BASIS AND PURPOSE ..................... ASSESSMENT OF THE SITE ............................. DESCRIPTION OF SELECTED REMEDY .................... 1-2 PART 2. DECISION SUMMARY ................................ 2-1 SITE NAME. LOCATION. AND DESCRIPTION ................ 2-2 SITE HISTORY AND ENFORCEMENT ACTIVlTIES ............. 2-2 HIGHLIGHTS OF COMMUNITY PARTICIPATION .............. 2-5 SCOPE AND ROLE OF THE RESPONSE ACTION ............... 2-5 SUMMARY OF SITE CHARACTERISTICS .................... 2-6 DESCRIPTION OF ALTERNATIVES ........................ 2-7 Alternative 3-Excavation and Storage at a Currently Operating Alternative 4-Excavation and Disposal at the WAG 6 Low-Level Waste Management Facility ......................... 2-8 Overall Protection of Human Health and the Environment ........ 2-10 Compliance with ARAB ............................. 2-10 Regulatory Agency Acceptance ......................... 2-11 The Selected Remedy .............................. 2-12 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES .... Protection of Human Health and the Environment ............. 2-14

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Use of Permanent Solutions and Alternative Treatment Preference for Treatment ............................ 2-15 EXPLANATION OF SIGNIFICANT CHANGES ................. 2-15 PART 3 . RESPONSIVENESS SUMMARY ........................... 3-1 Background on Community Involvement ................... Summary of Comments Received and Agency Responses .........

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ACRONYMS AND INITIALISMS as low as reasonably achievable applicable or relevant and appropriate requirement Comprehensive Environmental Response, Compensation, and Liability Act Code of Federal Regulations Interim Record of Decision operation and maintenance Oak Ridge National Laboratory Oak Ridge Reservation reasonable maximum exposure Tennessee State Route Tennessee Code Annotated Waste Area Grouping

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SITE NAME AND LOCATION Waste Area Grouping (WAG) 13 Oak Ridge National Laboratory (ORNL) Oak Ridge Reservation (ORR) Oak Ridge, Tennessee STATEMENT OF BASIS AND PURPOSE This decision document presents the selected interim remedial action for the ORNL WAG 13 in Oak Ridge, Tennessee. This action was chosen in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act of 1986, and, to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan. This decision is based on the administrative record file for this site. The state of Tennessee and the U.S.Environmental Protection Agency @PA) concur with this interim action for the WAG 13 remediation. ASSESSMENT OF THE SITE Actual or threatened releases of hazardous substances from this site, if not addressed by implementing the response action selected in this Interim Record of Decision (ROD), may present a current or potential threat to public health, welfare, or the environment. DESCRIPTION OF SELECTED REMEDY The purpose of this interim action is to reduce the risk to human health and the environment resulting from current elevated levels of gamma radiation on the site and at areas accessible to the public and adjacent to the site. To achieve this, only the cesium-contaminated soil within the plot will be addressed. This is not the final action planned for WAG 13. Subsequent actions are planned to fully address the remaining threats posed by the conditions at the site. As mandated in CERCLA, the remaining areas of the site (outside the plot boundaries) will be evaluated during the Remedial Investigation (RI)/Feasibility Study (FS) for the site.

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The major components of the interim action remedy are the following: excavate cesium-contaminated soil until residual contamination is containerize the excavated soil in steel boxes designed for the storage of transport the excavated soil to WAG 6 low-level waste silos by truck; and 0 line each excavated plot with a permeable liner and backfill with a clean compacted fill material and a topsoil layer. Interim remedial action on WAG 13 prior to completion of the RI/FS will provide additional benefits consistent with the goals of CERCLA,including: preventing a known source of cesium-contaminated sediment from producing elevated levels of gamma radiation on WAG 13 and to areas accessible to the reducing further degradation to the environment by eliminating the source of reducing the difficulty and risk associated with future surveillance, maintenance, and remedial activities on WAG 13. This interim action protects human health and the environment, complies with federal and state applicable or relevant and appropriate requirements (ARARs) for this limited-scope action, and is cost-effective. This action is interim and is not intended to use permanent solutions and alternative treatment (or resource recovery) technologies to the maximum extent practicable, given the limited scope of the action. Again, this action is not a final remedy for the WAG. Therefore, the statutory preference for remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element will be addressed at the time of the final response action. Subsequent actions are planned to fully address the remaining threats posed by the site. Because this is an IROD,review of this WAG and of this remedy will be continuing as part of the development of the final remedy for the site.

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Oak Ridge Field Office Director, DOE Oversight Division Date State of Tennessee Tennessee Department of Environment and Conservation Regional Administrator Date U.S. Environmental Protection Agency, Region IV

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SITE NAME, LOCATION, AND DESCRIPTiON WAG 13 is part of ORNL on the ORR CERCLA Site in Roane County, Tennessee. ORNL is part of the federally owned ORR, managed for DOE by Martin Marietta Energy Systems, Inc. The WAG 13 cesium plots are in an approximately &acre grassy field 330 ft north of the Clinch River at mile 20.5 and 1.3 miles south of the intersection of Bethel Valley Road and Tennessee State Route (SR) 95 (Fig. 1). The WAG 13 cesium plots are enclosed by a perimeter fence approximately lo00 ft by 250 ft. There are eight treatment plots that were used for a simulated nuclear weapons fallout study undertaken by ORNL. Each plot is 33 by 33 ft and is fenced with sheet metal extending 18 in. below the surface and 24 in. above surface. There are no other structures on the site. The elevated gamma radiation levels emitted from these plots pose a potential threat to human health and the environment. In August 1968, t o simulate conditions of a nuclear fallout, four of the treatment plots (Nos. 2, 4, 6, and 7) were contaminated with I3'Cs; the remaining four plots were used as uncontaminated controls (Fig. 2). The seeding was achieved by spreading '37Cs-fused sand particles evenly over the plots at 72 g/m2. Each test plot received 2.2 Ci of I3'Cs, while the control plots received none. A surface radiological investigation was conducted at and around the site between June 1987 and March 1988 by ORNL's Measurement and Development Group (Yalcintas e t al. 1988). Outside the fenced area, radiation levels were measured at 23 locations on the Clinch River and 9 locations along the riverbank. Radiation levels were also measured inside the fenced area. O n December 21,1989, the ORR was placed on CERCLA's National Priorities List, which mandates specific requirements that environmental restoration activities must follow. DOE must also operate in compliance with the National Environmental Policy Act. An Interim Remedial Measures Study (Radian July 1992) for the WAG 13 cesium plots was completed in July 1992 to determine the best alternative for reducing the health threat posed by the gamma radiation in the plots.

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WAQ 13 elto map rhowing tho bution of tho cerium PI&. Environmental Rodordion Program Fig. 2

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HIGHLIGHTS OF COMMUNITY PARTSCIPATXON The Proposed Plan for the ORNL WAG 13 Interim Remedial Action was released to the public in July 1992. The Proposed Plan was made available to the public in the administrative record maintained at the Information Resource Center in Oak Ridge, Tennessee. Notice of availability for the Proposed Plan was published in the Oak Ridger on July 10, 12, and 15, 1992; in the Kizoxville News-Sentinel on July 10, 12, and 15, 1992; and in the Roane County News on July 13, 15, and 17, 1992. A public comment period was held from July 14 to August 12, 1992. Because of the amount of information made available to the public before the Proposed Plan was published, a public meeting was not scheduled, and the public did not request that one be A response to the comments received during the comment period is included in the Responsiveness Summary, which is Part 3 of this IROD. This decision document presents the selected interim remedial action for the ORNL WAG 13 cesium plots. This selection was made in accordance with CERCLA, as amended by the Superfund Amendments and Reauthorization Act of 1986, and to the extent feasible, the National Contingency Plan. SCOPE AND ROLE OF THE RESPONSE ACTION The goal of this response action is to reduce the risk to human health and the environment resulting from the current elevated levels of gamma radiation on WAG 13. During this interim action, only the cesium-contaminated soil within the plots will be addressed. Excavating these soils and placing them in W A G 6 low-level waste silos will prevent a known source of cesiumcontaminated sediment from producing elevated levels of gamma radiation on WAG 13. Subsequent actions under CERCLA are planned to fully address the threats posed by the remaining exposure pathways at the site. These may include, but are not limited to, the soil outside the plot boundaries, groundwater, and surface water. The remaining areas of the site will be evaluated during the RIPS, as mandated in CERCLA. This interim remedial action is consistent with planned future activities at the site. In particular, this interim action will provide a reduction in the difficulty and risk associated with future surveillance, maintenance, and

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SUMMARY OF SITE CHARACTERISTICS Contamination on WAG 13 has resulted solely from the intentional deposition of '"Cs for the purpose of gaining knowledge of the effects of nuclear fallout. A total of 8.8 Ci was spread over the four test plots and has decayed to 5.1 Ci as of June 1992. The surface radiological investigation conducted at the site concluded that the maximum exposure to the public would be approximately 19 pR/h along the shoreline closest to the I3'Cs plots and up to 150 pR/h at the perimeter fence. Gamma ray exposure rates measured at plot boundaries within the fenced area ranged from 1.3 to 35 mRh (Yalcintas et al. 1988). Soil samples taken within the plots indicate that the '"Cs has been detected above 1 pCi/g (detection limit) at depths up to 3 ft. SUMMARY OF SITE RISKS A preliminary health risk assessment study was conducted for WAG 13 and the only contaminant of concern was determined to be 137Cs(Radian July 1992). Cesium-137 is a beta emitter (512 KeV) that also releases gamma at 661 KeV and has a 30-year half-life. Although 1987 soil samples from two locations between the contaminated plots and the nearby creek bed show that '"Cs contamination has migrated (ORNL 1988), the scope of this action is limited to contamination in the test plots. Therefore, the risk analysis does not consider possible contributions from 137Csthat may have migrated beyond the test plots. External exposure to ionizing radiation poses the majority of risk to the exposed populations and was determined to be the dominant pathway of concern for all three scenarios. The exposure scenarios examined in the preliminary health risk assessment were: a worker who mows the area, * a fishermadboater on the Clinch River who comes within 150 ft of the cesium a future on-site homesteader who lives inside the area that is currently fenced. Lifetime cancer risks associated with the WAG 13 cesium plots were calculated assuming reasonable maximum occupational exposure for the worker mowing the area, reasonable maximum exposure (RME)for a fishermanhater on the Clinch River, and RME for an on-site homesteader. RME assumptions for the preliminary health risk assessment were adopted from

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The RME scenario for the worker assumes that an individual spends 25 h/year on-site for 25 years and is exposed to an average gamma rate of 150 p R h measured on-site. The RME scenario for the fishermadboater assumes that an individual spends 52 h/year (1 h/week) on the Clinch River near the WAG 13 cesium plots for 30 years and is exposed to a maximum gamma rate of 19 p w h measured on the Clinch River. The Rh4E scenario for the future on-site homesteader assumes that an individual spends 5600 h/year (16h/d for 350 d) for 30 years inside the fence and is exposed to an average gamma rate of 4 mwh. The risk to the worker was estimated to be 1 x la’ (1 in lo00 chances of developing cancer). The risk to the fishermanhater on the Clinch River was estimated to be 2 x loJ,and risk to the on-site homesteader was calculated to be 3 X 10’. Calculated risks from lifetime exposure to radionuclides and chemicals were compared to the EPA’s target risk range of 1 X 106 to 1 X lo-‘. Any risk values greater than 1 x 1V (1 in 10,OOO chances of developing cancer) are unacceptable, and any risk values less than 1 X lod (1 in l,OOO,OOO chances of developing cancer) are acceptable by EPA. Acceptance of risks between 1 x lod and 1 x 104 depends on site-specific conditions (Le., population exposure). The risk to the fishermanhater falls within EPA’s acceptable risk range. Although exposure to the worker is within DOE guidelines (DOE- Order 5480.1l), risks to the worker mowing around the cesium plots and to the on-site homesteader exceed EPA’s target risk range. Ecological risk to plants and animals has not been quantitatively analyzed, but removal or shielding of the contaminated soil will have a positive benefit for all risk scenarios. The WAG 13 area will need further evaluation for the CERCLA Ecological Risk Assessment and Natural Resource Damage Assessment during the RI. If no interim remedial action is taken, actual or threatened releases of hazardous substances from the WAG 13 cesium plots may present a current or potential threat to public health, welfare, or the environment. DESCRWTION OF ALTERNATIVES This section provides a description of how each alternative would address the contamination found at WAG 13. Four alternatives are presented. These alternatives are not intended to remediate the entire WAG 13 site. Rather, they are intended to reduce the threat to human health, and to reduce further degradation of the environment resulting from elevated gamma radiation exposures. Remediation of the entire site will be addressed in future CERCLA

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CERCLA requires that the no-action alternative be evaluated to serve as a baseline for comparison at each site. Under this alternative, no further action would be taken to reduce the risk to human receptors from the current elevated levels of gamma radiation. Implementing this alternative would involve no additional costs. Shielding involves placing reinforced concrete boxes over each cesium plot. m e boxes will deflect and contain the gamma radiation within the box. After shield installation, gamma radiation exposure rates will be reduced to 9 plUh at the perimeter fence, thus reducing risk to the general public on or near the Clinch River. Besides reducing the level of gamma radiation to 9 p …