The Bear Creek Valley watershed covers approximately 1,000 acres; about 20% of Bear Creek Valley lands have been used for waste disposal. Figure 4.2 shows an aerial view of the valley. The watershed is bounded on the west by the East Tennessee Technology Park watershed, on the south by the Bethel Valley watershed, to the north by Pine Ridge and the City of Oak Ridge, and on the east by the Upper East Fork Poplar Creek watershed. Water from the waste areas flows into Bear Creek. A groundwater divide exists at the S-3 Ponds, where surface and groundwater flow east into the Upper East Fork Poplar Creek watershed and west into the Bear Creek Valley watershed. The flow of Bear Creek is closely related to groundwater flow, and during rain events groundwater discharges to the creek and its tributaries.

A Remedial Investigation (RI) had been conducted for Bear Creek Valley. One goal for the RI was to understand how contaminants move from waste units into streams. The contaminant sources in Bear Creek Valley are located in the eastern most sector. The main areas of concern in the Bear Creek Valley watershed are discussed below:

The S-3 Ponds were used from the 1950s to 1980s for disposal of more than 2 million gallons of nitric acid solution per year. This solution reacted with the carbonate rock to precipitate uranium and other contaminants under the ponds, which has resulted in a nitrate- and uranium-contaminated groundwater plume that has migrated about 3000 feet from the ponds and impacts Bear Creek. The S-3 Ponds were closed under RCRA.

The Oil Landfarm Area consists of the Oil Landfarm, Sanitary Landfill 1, and the Boneyard/Burnyard, with the Hazardous Chemicals Disposal Area located on top of the Boneyard/Burnyard. The Oil Landfarm was used to dispose of organic wastes; main current contaminants are uranium, beryllium, and PCBs. The RI found virtually no soil contamination around the partially remediated Oil Landfarm. However, groundwater is contaminated with low levels of volatile organic compounds (VOCs).

Little information exists about the types of waste disposed of at the Sanitary Landfill, which has been closed and covered with a clay and soil cap. At the Boneyard/Burnyard, contaminated debris and wastes were buried in trenches. Only the Hazardous Chemicals Disposal Area of the Boneyard/Burnyard has been capped. Contaminants, primarily uranium and to a lesser extent VOCs, flow from the Boneyard/Burnyard into North Tributary 3.

The Bear Creek Burial Grounds were used from the 1950s to the 1980s as the main solid waste disposal area for the Y-12 Plant. Wastes were buried in trenches and covered with dirt. The main contaminants are uranium, thorium, beryllium and VOCs. The Walk-In Pits area was used for disposal of shock-sensitive and pyrophoric materials. Several areas in the Burial Grounds, including the Walk-In Pits, have been closed under RCRA.

Shallow groundwater in the eastern end of Bear Creek Valley is contaminated with uranium and dense non-aqueous phase liquids (DNAPLs). Deep groundwater is also contaminated with DNAPLs. This groundwater contamination impacts surface water in the valley.

Contaminants have also migrated into surface water including:

• nitrates and uranium from the S-3 Ponds area;
• uranium and VOCs from the Oil Landfarm Area; and
• VOCs from the Burial Grounds.

Members noted that almost all contamination within the Bear Creek Valley watershed is concentrated at the valley’s eastern end. Therefore, the Group took the approach that various zones within the watershed should have different end use scenarios.

Since Zone I is uncontaminated, the majority of EUWG members believed it should be designated as unrestricted end use and should be protected from any future contamination posed by disposal sites in other zones in Bear Creek Valley.

Developing an end use recommendation for Zone II was more complicated and generated more discussion. Members generally agreed that Zone II should act as a buffer between the uncontaminated Zone I and contaminated areas in Zone III. An industrial end use for Zone II did not fit some members’ concept of a buffer zone. Since Zone II is heavily forested, it was reasonable to consider a recreational end use to prevent further industrial development even though zoning laws do not typically allow for recreational use in an industrialized area. Most of the Group eventually agreed that Zone II should remain under DOE control as a green space or recreational end use, until groundwater and surface water contaminants can be reduced to acceptable levels for unrestricted use.

End use considerations for Zone III, which contains the S-3 Ponds Area, the Oil Landfarm and the Burial Grounds, ranged from industrial/commercial to restricted access waste disposal. Remediating this area to an industrial/commercial end use is technically possible, but would require excavation of massive amounts of contaminant sources and treatment of secondary contamination. Costs for achieving an industrial/commercial end use range between $1.2 to $7 billion (a cost of at least $6 million per acre). Because of the nature and extent of contamination in this area, worker risks, costs, and uncertainties associated with extensive excavation, transport, and disposal, most members agreed that Zone III should have a restricted waste disposal end use.

• the difficulty of isolating DNAPLs from groundwater;
• the need to allow future generations enough flexibility to decide how they want to use the land.