[en] The U.S. Department of Energy (DOE) is conducting cleanup activities at the Weldon Spring site, which is located in St. Charles County, Missouri, about 48 km (30 mi) west of St. Louis (Figure 1.1). Cleanup of the Weldon Spring site consists of several integrated components. The quarry residuals operable unit (QROU) is one of four operable units being evaluated. In accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended, a remedial investigation/feasibility study (RI/FS) is being conducted to evaluate conditions and potential responses for the following areas and/or media that constitute the QROU: (1) the residual material (soil and sediment) remaining at the Weldon Spring quarry after removal of the bulk waste (about 11 million L [3 million gal] of uranium-contaminated ponded water was also addressed previous to bulk waste removal); (2) other media located in the surrounding vicinity of the quarry, including adjacent soil, surface water, and sediment in Femme Osage Slough and several creeks; and (3) quarry groundwater located primarily north of Femme Osage Slough. Potential impacts to the St. Charles County well field downgradient of the quarry area are also being addressed as part of QROU RI/FS evaluations. For remedial action sites, it is DOE policy to integrate values associated with the National Environmental Policy Act (NEPA) into the CERCLA decision-making process. The analyses contained herein address NEPA values as appropriate to the actions being considered for the QROU. A work plan summarizing initial site conditions and providing conceptual site hydrogeological and exposure models was published in January 1994. The RI and baseline risk assessment (BRA) reports have been completed. The RI discusses in detail the nature and extent and the fate and transport of contamination at the quarry area