RCRA Post-Closure Monitoring and Inspection Report for CAU 91: Area 3 U-3fi Waste Unit, Nevada Test Site, Nevada, for the Period October 1999-October 2000
This annual Neutron Soil Moisture Monitoring report provides an analysis and summary for site inspections, meteorological information, and neutron soil moisture monitoring data obtained at the U-3fi Resource Conservation and Recovery Act Unit, located in Area 3 of the Nevada Test Site, Nye County, Nevada, during the October 1999 to October 2000 period. Inspections of the U-3fi Resource Conservation and Recovery Act Unit are conducted to determine and document the physical condition of the concrete pad, facilities, and any unusual conditions that could impact the proper operation of the waste unit closure. The objective of the neutron-logging program is to monitor the soil moisture conditions along the 128-meter (m) (420-feet [ft]) ER3-3 monitoring well and detect changes that maybe indicative of moisture movement in the regulated interval extending between 73 to 82 m (240 to 270 ft) or to detect changes that maybe indicative of subsidence within the disposal unit itself. Physical inspections of the closure were completed in March and September 2000 and indicated that the site is in good condition with no significant findings noted. The directional survey which is required to be completed every five years was run in the ER3-3 casing to determine if subsidence was occurring in the U-3fi emplacement borehole. Small changes were noted which are attributed to initial settling of the sand pack stemming. No evidence of subsidence within the emplacement borehole was observed. The subsidence survey for the October 1999 to October 2000 monitoring period indicated an increase in elevation of 0.244 centimeters (cm) (0.008 ft) compared to the previous year, July 1999. All changes in subsidence survey data taken to date are so small as to be at the survey instrument resolution level and it is not clear if they represent subsidence or measurement error. There is no clear evidence for any subsidence of the monument. Soil moisture monitoring results indicate dry stable conditions for all quarterly monitoring periods. The Residual Raw Neutron Counts remain below the compliance Action Level of 200 counts within the regulated interval of 73 to 82 m (240 to 270 ft) for the period from October 1999 through October 2000.
- Research Organization:
- Bechtel Nevada Corporation (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC08-96NV11718
- OSTI ID:
- 788769
- Report Number(s):
- DOE/NV-700; TRN: AH200136%%65
- Resource Relation:
- Other Information: PBD: 1 Feb 2001
- Country of Publication:
- United States
- Language:
- English
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