The 216-B-3 Pond was a series of ponds used for disposal of liquid effluent from past Hanford production facilities. In operation since 1945, the B Pond System has been a RCRA facility since 1986, with RCRA interim-status groundwater monitoring in place since 1988. In 1994 the expansion ponds of the facility were clean-closed, leaving only the main pond and a portion of the 216-B-3-3 ditch as the currently regulated facility. In 1990, groundwater monitoring at B Pond was elevated from

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... " to assessment status because total organic halides and total organic carbon were found to exceed critical mean values in two wells. Groundwater quality assessment, which ended in 1996, failed to find any specific hazardous waste contaminant that could have accounted for the isolated occurrences of elevated total organic halides and total organic carbon. Hence, the facility was subsequently returned to detection-level monitoring in 1998. Exhaustive groundwater analyses during the assessment period indicated that only two contaminants, tritium and nitrate, could be positively attributed to the B Pond System, with two others (arsenic and iodine-129) possibly originating from B Pond. Chemical and radiological analyses of soil at the main pond and 216-B-3-3 ditch has not revealed significant contamination. Based on the observed, minor contamination in groundwater and in the soil column, three parameters were selected for site-specific, semiannual monitoring; gross alpha, gross beta, and specific conductance. Arsenic, iodine-129, nitrate, and tritium will be monitored under the aegis of Hanford sitewide monitoring to the extent possible. Total and dissolved concentrations of cadmium, lead, mercury, and silver will be analyzed annually for four years. Analysis for these metals will be discontinued after four years if no anomalous concentrations or trends are revealed. Washington State Department of Ecology (Ecology) issued a letter 1 providing guidance for groundwater monitoring at the B Pond system because the standard indicator-parameters evaluation and accompanying interim status statistical approach is inappropriate for detecting potential B-Pond-derived contaminants in groundwater at this facility. Ecology specified in this guidance letter that certain criteria must be met prior to receiving approval of a variance from applying interim status regulations. This plan incorporates the requirements per the variance stated in Ecology's letter 1 , and is in agreement with subsequent proposals with Ecology concerning monitoring network, constituent list, statistical analysis, and reporting procedures.