RECOMMENDATIONS FOR PHASE II VADOSE ZONE CHARACTERIZATION AND MONITORING AT THE E-AREA DISPOSAL SLIT TRENCHES AND MEGA-TRENCH

Technical Report · Tue Feb 01 00:00:00 EST 2000

DOI:https://doi.org/10.2172/1017435· OSTI ID:1017435

Nichols, R; Looney, B; Flach, G; Rossabi, J

A Radiological Performance Assessment Maintenance Plan (SDW, 1997) was prepared in response to Recommendation 94-2 made by the Defense Nuclear Facility Board (DNFSB) and establishes a requirement for preparing and implementing the E-Area Monitoring Program (EMOP). Based on the results of a statistical analysis of the existing groundwater monitoring network at the Burial Ground and a review of alternative monitoring strategies, a vadose zone monitoring system (YZMS) was selected for the EMOP. The EMOP (SWD, 1998) was prepared in 1998 and describes a phased approach for implementation. The YZMS was designed to detect contamination before it reached the water table and includes collection of pore water samples from sediments above the water table and monitoring pore water pressure and water content of the unsaturated sediments that comprise the vadose zone. This information is then used to calculate the flux of contaminants for comparison with the requirements specified in the E-Area Performance Assessment. In 1999, Phase I of the EMOP was implemented by installation of advanced tensiometers, water content sensors, and vertical and angled lysimeters. In addition several cone penetrometer logs of resistivity and stress ratio were collected and shelby tube samples were collected for measurement of hydraulic properties. Results from Phase I of the EMOP show that the general strategy and techniques selected are adequate for monitoring moisture conditions and contaminant migration. Data from Phase I of the EMOP was used to prepare a numerical model of moisture flow beneath a typical disposal trench. The moisture contents, pore pressure, and flow patterns predicted by the model were compared with field data and used to improve the components of Phase II of the EMOP. Based on these data and the numerical analysis of moisture movement at a typical disposal trench, the objectives of the Phase II EMOP characterization and monitoring are: (1) Collect additional data on moisture release properties to minimize uncertainty in flux calculations; (2) Use neutron probe to measure moisture profile and validate water content sensors; (3) Calibrate neutron probe with site specific calibration curve; (4) Locate tensiometers to provide data useful for calculation of hydraulic gradient; and (5) Incorporate new data from EMOP in conceptual of moisture flow at disposal trenches to improve flux calculations. Meeting these objectives will provide the information necessary to determine compliance with the requirements of the E-Area Performance Assessment and protect groundwater resources.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC09-08SR22470
• OSTI ID: 1017435
• Report Number(s): WSRC-TR-2000-00059; TRN: US201113%%725
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CALIBRATION
COMPLIANCE
CONES
CONTAMINATION
HYDRAULICS
GROUND WATER
IMPLEMENTATION
LYSIMETERS
MAINTENANCE
MOISTURE
MONITORING
NEUTRON PROBES
NUMERICAL ANALYSIS
PENETROMETERS
PERFORMANCE
PORE PRESSURE
RECOMMENDATIONS
SEDIMENTS
SENSORS
WATER
WATER TABLES