Post-Closure Inspection and Monitoring Report for Corrective Action Unit 110: Area 3 WMD U-3ax/bl Crater, Nevada Test Site, Nevada
This Post-Closure Inspection and Monitoring Report (PCIMR) provides the results of inspections and monitoring for Corrective Action Unit (CAU) 110, Area 3 WMD [Waste Management Division] U-3ax/bl Crater. This PCIMR includes an analysis and summary of the site inspections, repairs and maintenance, meteorological information, and soil moisture monitoring data obtained at CAU 110, for the annual period July 2005 through June 2006. Site inspections of the cover were performed quarterly to identify any significant changes to the site requiring action. The overall condition of the cover, cover vegetation, perimeter fence, and UR warning signs was good. Settling was observed that exceeded the action level as specified in Section VILB.7 of the Hazardous Waste Permit Number NEV HW009 (Nevada Division of Environmental Protection, 2000). This permit states that cracks or settling greater than 15 centimeters (6 inches) deep that extend 1.0 meter (m) (3 feet [ft]) or more on the cover will be evaluated and repaired within 60 days of detection. Along the east edge of the cover (repaired previously in August 2003, December 2003, May 2004, October 2004), an area of settling was observed during the December 2005 inspection to again be above the action level, and required repair. This area and two other areas of settling on the cover that were first observed during the December 2005 inspection were repaired in February 2006. The semiannual subsidence surveys were done in September 2005 and March 2006. No significant subsidence was observed in the survey data. Monument 5 shows the greatest amount of subsidence (-0.015 m [-0.05 ft] compared to the baseline survey of 2000). This amount is negligible and near the resolution of the survey instruments; it does not indicate that subsidence is occurring on the cover. Soil moisture results obtained to date indicate that the CAU 110 cover is performing as expected. Time Domain Reflectometry (TDR) data indicated an increase in soil moisture (1 to 3% VMC change) at a depth of 1.8 m (6 ft.) due to the exceptionally heavy precipitation from the January and February 2005 precipitation events. The moisture profile returned to baseline conditions by October 2005. At 2.4 m (8 ft) below the cover surface, TDR data show soil moisture content remained between 10 and 13 percent VMC. Considering the heavy precipitation experience in this and the previous reporting period, a compliance level will be established when the system reaches a steady state and equilibrium has been established.
- Research Organization:
- National Security Technologies, LLC (NSTec), Mercury, NV (United States)
- Sponsoring Organization:
- USDOE - National Nuclear Security Administration (NNSA)
- DOE Contract Number:
- DE-AC52-06NA25946
- OSTI ID:
- 935208
- Report Number(s):
- DOE/NV-1158; TRN: US0805441
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
COMPLIANCE
DETECTION
ENVIRONMENTAL PROTECTION
MAINTENANCE
MANAGEMENT
METERS
MOISTURE
MONITORING
NEVADA TEST SITE
PLANTS
PRECIPITATION
REPAIR
RESOLUTION
SOILS
WASTES
CAU Post-Closure report
July 2005 - July 2006