This Corrective Action Investigation Plan contains the U.S. Department of Energy, Nevada Operations Office's (DOE/NV's) approach to collect the data necessary to evaluate corrective action alternatives appropriate for the closure of Corrective Action Unit (CAU) 405, Area 3 Septic Systems, Tonopah Test Range (TTR), under the Federal Facility Agreement and Consent Order. Corrective Action Unit 405 consists of Corrective Action Sites 03-05-002-SW03, 03-05-002-SW04, and 03-05-002-SW07 (also collectively known as: Septic Waste Systems [SWSs] 3, 4, and 7). Located in Area 3 in the northwest section of the TTR, approximately 140 miles northwest of Las Vegas, this location was historically (between 1960 and 1990) used as a research facility with the mission to perform defense-related projects, and whose operations generated sanitary and industrial wastewaters potentially contaminated with COPCs and disposed of in septic tanks and leachfields. Though Septic Waste Systems 3, 4, and 7 were origin ally constructed to receive sanitary sewage, they may have inadvertently received effluent containing potentially hazardous and radiological constituents containing acetone, benzene, ethylbenzene, 4-methyl-2-pentanone, toluene, xylenes, volatile organic compound constituents, phenols, arsenic, barium, lead, mercury, hydrocarbons of oil and grease, and uranium-234, -235, and -238. The Area 3 septic systems were documented in a DOE/NV 1996 report as being included in the septic tank abandonment program conducted by Sandia National Laboratories in 1993; however, this program was not completed and the possibility exists that some of the Area 3 septic tanks may not have been abandoned. Even though all of the SWSs addressed in this CAIP are inactive, geophysical surveys conducted in 1993 were generally inconclusive and did not provide useful data for the purposes of this investigation. The scope of this current investigation, therefore, will be to determine the existence of the identified CO PCs and excavation will be the primary investigation method employed for these leachfield systems, but this effort may be limited by existing facilities and utilities. The results of this field investigation will support a defensible evaluation of corrective action alternatives in the subsequent corrective action decision document.
