CORRECTIVE ACTION DECISION DOCUMENT FOR THE AREA 3 LANDFILL COMPLEX, TONOPAH TEST RANGE, CAU 424, REVISION 0, MARCH 1998

This Corrective Action Decision Document (CADD) has been prepared for the Area 3 Landfill Complex (Corrective Action Unit [CAU] 424) in accordance with the Federal Facility Agreement and Consent Order (FFACO) of 1996. Corrective Action Unit 424 is located at the Tonopah Test Range (TTR) and is comprised of the following Corrective Action Sites (CASs), each an individual landfill located around and within the perimeter of the Area 3 Compound (DOE/NV, 1996a): (1) Landfill A3-1 is CAS No. 03-08-001-A301. (2) Landfill A3-2 is CAS No. 03-08-002-A302. (3) Landfill A3-3 is CAS No. 03-08-002-A303. (4) Landfill A3-4 is CAS No. 03-08-002-A304. (5) Landfill A3-5 is CAS No. 03-08-002-A305. (6) Landfill A3-6 is CAS No. 03-08-002-A306. (7) Landfill A3-7 is CAS No. 03-08-002-A307. (8) Landfill A3-8 is CAS No. 03-08-002-A308. The purpose of this CADD is to identify and provide a rationale for the selection of a recommended corrective action alternative for each CAS. The scope of this CADD consists of the following: (1) Develop corrective action objectives. (2) Identify corrective action alternative screening criteria. (3) Develop corrective action alternatives. (4) Perform detailed and comparative evaluations of the corrective action alternatives in relation to the corrective action objectives and screening criteria. (6) Recommend and justify a preferred corrective action alternative for each CAS. In June and July 1997, a corrective action investigation was performed as set forth in the Corrective Action Investigation Plan (CAIP) for CAU No. 424: Area 3 Landfill Complex, Tonopah Test Range, Nevada (DOE/NV, 1997). Details can be found in Appendix A of this document. The results indicated four groupings of site characteristics as shown in Table ES-1. Based on the potential exposure pathways, the following corrective action objectives have been identified for CAU No. 424: (1) Prevent or mitigate human exposure to subsurface soils containing waste. (2) Remediate the site per applicable state and federal regulations (NAC, 1996c). (3) Prevent adverse impacts to groundwater quality. Based on the review of existing data, future land use, and current operations at the TTR, the following alternatives were developed for consideration at the Area 3 Landfill Complex CAU: Alternative 1 - No Action; Alternative 2 - Administrative Closure; Alternative 3 - Partial Excavation, Backfill, and Recontouring The corrective action alternatives were evaluated based on four general corrective action standards and five remedy-selection decision factors. Based on the results of this evaluation, preferred alternatives were selected for each CAS as indicated in Table ES-2. The preferred corrective action alternatives were evaluated on their technical merits, focusing on performance, reliability, feasibility, and safety. The alternatives were judged to meet all requirements for the technical components evaluated. These alternatives meet all applicable state and federal regulations for closure of the site and will reduce potential future exposure pathways to the contents of the landfills. During corrective action implementation, these alternatives will present minimal potential threat to site workers who come in contact with the waste. However, procedures will be developed and implemented to ensure worker health and safety