Annual Post Closure Inspection And Monitoring Report For Corrective Action Unit 329 PDF Download

This report presents the data collected during field activities and quarterly soil-gas sampling activities conducted from May 9, 2005, through May 20, 2006, at Corrective Action Unit (CAU) 329, Area 22 Desert Rock Airstrip (DRA) Fuel Spill; Corrective Action Site (CAS) 22-44-01, Fuel Spill. The CAU is located at the DRA, which is located approximately two miles southwest of Mercury, Nevada, as shown in Figure 1-1. Field activities were conducted in accordance with the revised sampling approach outlined in the Addendum to the Closure Report (CR) for CAU 329 (NNSA/NSO, 2005) to support data collection requirements. The previous annual monitoring program for CAU 329 was initiated in August 2000 using soil-gas samples collected from three specific intervals at the DRA-0 and DRA-3 monitoring wells. Results of four sampling events from 2000 through 2003 indicated there is uncertainty in the approach to establish a rate of natural attenuation as specified in ''Streamlined Approach for Environmental Restoration (SAFER) Work Plan for Corrective Action Unit 329: Area 22 Desert Rock Airstrip Fuel Spill, Nevada Test Site, Nevada'' (DOE/NV, 1999). As a result, the Addendum to the CR (NNSA/NSO, 2005) was completed to address this uncertainty by modifying the previous approach. A risk evaluation was added to the scope of the project to determine if the residual concentration of the hazardous constituents of JP4 pose an unacceptable risk to human health or the environment and if a corrective action was required at the site, because the current quarterly monitoring program is not expected to yield a rate constant that could be used effectively to determine a biodegradation rate for total petroleum hydrocarbons (TPH) in less than the initial five years outlined in the CR. Additionally, remediation to the Tier 1 action level for TPH is not practical or technically feasible due to the depth of contamination.