Closure Report for Corrective Action Unit 356: Mud Pits and Disposal Sites, Nevada Test Site, Nevada with Errata Sheet

This Closure Report (CR) has been prepared for Corrective Action Unit (CAU) 356, Mud Pits and Disposal Sites, in accordance with the Federal Facility Agreement and Consent Order. This CAU is located in Areas 3 and 20 of the Nevada Test Site (NTS) approximately 65 miles northwest of Las Vegas, Nevada. Corrective Action Unit 356 consists of seven Corrective Action Sites (CASs): 03-04-01, Area 3 Change House Septic System; 03-09-01, Mud Pit Spill Over; 03-09-03, Mud Pit; 03-09-04, Mud Pit; 03-09-05, Mud Pit; 20-16-01, Landfill; and 20-22-21, Drums. This CR identifies and rationalizes the U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Operations Office's (NNSA/NV's) recommendation that no further corrective action and closure in place is deemed necessary for CAU 356. This recommendation is based on the results of field investigation/closure activities conducted November 20, 2001, through January 3, 2002, and March 11 to 14, 2002. These activities were conducted in accordance with the Streamlined Approach for Environmental Restoration Plan (SAFER) for CAU 356. For CASs 03-09-01, 03-09-03, 20-16-01, and 22-20-21, analytes detected in soil during the corrective action investigation were evaluated against Preliminary Action Levels (PALs) and it was determined that no Contaminants of Concern (COCs) were present. Therefore, no further action is necessary for the soil at these CASs. For CASs 03-04-01, 03-09-04, and 03-09-05, analytes detected in soil during the corrective action investigation were evaluated against PALs and identifies total petroleum hydrocarbons (TPHs) and radionuclides (i.e., americium-241 and/or plutonium 239/240) as COCs. The nature, extent, and concentration of the TPH and radionuclide COCs were bounded by sampling and shown to be relatively immobile. Therefore, closure in place is recommended for these CASs in CAU 356. Further, use restrictions are not required at this CAU beyond the NTS use restrictions identified in the SAFER Plan. In addition, the septic tank associated with CAU 356 will be closed in accordance with applicable regulations