Results of Tritium Tracking and Groundwater Monitoring at the Hanford Site 200 Area State-Approved Land Disposal Site-FY1999

The Hanford Site 200 Area Effluent Treatment Facility (ETF) processes contaminated liquids derived from Hanford Site facilities. The clean water generated by these processes is occasionally enriched in tritium and is discharged to the 200 Area State Approved Land Disposal Site (SALDS). Groundwater monitoring for tritium and other constituents is required by the state-issued permit at 21 wells surrounding the facility. During FY 1999, average tritium activities in most wells declined from average activities in 1998. The exception was deep well 69948-77C, where tritium results were at an all-time high (77,000 pCi/L) as a result of the delayed penetration of effluent deeper into the aquifer. Of the 12 constituents with permit enforcement limits, which are monitored in SALDS proximal wells, all were within limits during FY 1999. Water level measurements in nearby wells indicate that a small hydraulic mound exists around the SALDS facility as a result of discharges. This feature is directing groundwater flow radially outward a short distance before the regional northeasterly flow predominates. Evaluation of this condition indicates that the network is currently adequate for tracking potential effects of the SALDS on the groundwater. Recommendations include the discontinuation of ammonia, benzene, tetrahydrofuran, and acetone from the regularmore » groundwater constituent list; designating background well 299-W8-1 as a tritium-tracking well only, and the use of quadruplicate averages of field pH, instead of a single laboratory measurement, as a permit compliance parameter.« less