Post-Closure Inspection Report for Corrective Action Unit 404: Roller Coaster Lagoons and Trench Tonopah Test Range, Nevada, Calendar Year 2001

Abstract

Post-closure monitoring requirements for the Roller Coaster Lagoons and Trench (Corrective Action Unit [CAU] 404) (Figure 1) are described in Closure Report for Corrective Action Unit 404. Roller Coaster Sewage Lagoons and North Disposal Trench. Tonopah Test Range. Nevada, report number DOE/NV--187, September 1998. The Closure Report (CR) was submitted to the Nevada Division of Environmental Protection (NDEP) on September 11, 1998. Permeability results of soils adjacent to the engineered cover and a request for closure of CAU 404 were transmitted to the NDEP on April 29, 1999. The CR (containing the Post-Closure Monitoring Plan) was approved by the NDEP on May 18, 1999. As stated in Section 5.0 of the NDEP-approved CRY post-closure monitoring at CAU 404 consists of the following: (1) Visual site inspections done twice a year to evaluate the condition of the cover and plant development. (2) Verification that the site is secure and condition of the fence and posted warning signs. (3) Notice of any subsidence, erosion, unauthorized excavation, etc., deficiencies that may compromise the integrity of the unit. (4) Remedy of any deficiencies within 90 days of discovery. (5) Preparation and submittal of an annual report. In addition to the above activities, vegetative monitoring of the cover (a plant census) will be done in the first, third and fifth year following revegetation. (Vegetative monitoring will done in fiscal year 2001, and the results reported in the 2002 Post-Closure Inspection Report.) Site inspections were conducted on May 16, 2001, and November 6, 2001. The site inspections were conducted after completion of the revegetation activities (October 30, 1997) and NDEP approval of the CR (May 18, 1999). All site inspections were conducted in accordance with the Post-Closure Monitoring Plan in the NDEP-approved CR. This report includes copies of inspection checklists, photographs, recommendations, and conclusions. The Post-Closure Inspection Checklists are found in Attachment A, a copy of the field notes is found in Attachment B, and copies of the inspection photographs are found in Attachment C.