Post-Closure Inspection and Monitoring Report for Corrective Action Unit 417: Central Nevada Test Area Surface, Hot Creek Valley, Nevada
Executive Summary This report presents data collected during the annual post-closure site inspection conducted at the Central Nevada Test Area Surface Corrective Action Unit (CAU) 417 in May of 2008. The annual post-closure site inspection included inspections of the UC-1, UC-3, and UC-4 sites in accordance with the Post-Closure Monitoring Plan provided in the CAU 417 Closure Report (NNSA/NV 2001). The annual inspection conducted at the UC-1 Central Mud Pit (CMP) indicated that the site and
... at the site and soil cover were in good condition. Three new cracks or fractures were observed in the soil cover during the annual inspection and were immediately filled with bentonite chips. The vegetation on the soil cover was adequate, but showed signs of the area's ongoing drought. No issues were identified with the CMP fence, gate, or subsidence monuments. No issues were identified with the warning signs and monuments at the other two UC-1 locations. The annual subsidence survey was conducted at UC-1 CMP and UC-4 Mud Pit C in August 2008. The results of the subsidence surveys indicate that the covers are performing as expected, and no unusual subsidence was observed. A vegetation survey of the UC-1 CMP cover and adjacent areas was not performed this year. The next vegetation survey is scheduled for 2009. Precipitation occurring was below average; the total rainfall for this period was 1.52 millimeters (0.06 inches). Soil moisture content data showed that the UC-1 CMP cover is performing as designed, and evapotranspiration is effectively removing water from the cover. The inspection at UC-3 indicated that the site is in good condition. All monuments and signs showed no displacement, damage, or have not been removed. No other issues or concerns were identified.