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Parsons Engineering Science, Inc at any other time in any other wells No BTEX compounds were detected in the most recent groundwater sampling event (September 1996) Re ulatory Assessment This section discusses the existing and potential beneficial uses of groundwater beneath the site, as well as the potential surface water receiving body downgradient of the site This section also summarizes regulatory agency cntena relevant to detected soil and groundwater contamination at the site Beneficial Uses No groundwater use or contact currently occurs on the Greyhound site, and records indicate that no domestic or potable water supply wells are located within I mile of the site Therefore, analytical results from groundwater at the Greyhound site should be interpreted based on potential impacts of contaminated groundwater on Water Quality Objectives (WQOs) for surface water at Mormon Slough, which receives surface water runoff and shallow groundwater through seepage from areas southwest of the site Those WQOs include the California Water Resources Control Board's (WRCB's) policy of non-degradation of beneficial uses of a water body (WRCB 1968) and the maintenance of at least background water quality (Marshack 1995) The listed existing beneficial uses for the Sacramento-San Joaquin Delta include municipal and domestic supply, agricultural irrigation and stock low watering, industrial process and service supply, water contact and non-contact water recreation, cold and warm freshwater habitat, migration of aquatic organisms, wildlife habitat, and navigation (RWQCB 1995) Regulatory Evaluation of Site Soil Contamination In California, impacts of contamination to the environment by TPH-D and BTEX are evaluated on a case-by-case basis No specific site cleanup standards apply to petroleum contamination at the Greyhound site Histoncally, the RWQCB has used 100 mg/kg TPH as a minimum criteria in soil samples for characterization of groundwater in LUFT cases The DHS has used 1,000 mg/kg TPH as a minimum criteria for remediation (considered hazardous by virtue of its ignitability index) Contaminants detected in residual site soil samples at levels of potential concern include TPH-D In 1991, a leaching potential analysis for diesel was performed for the sample collected at B-1 at a depth of 25 0-26 5 feet bgs and the results indicated that the maximum allowable TPH-D levels that may be left in place in the subsurface were 100 mg/kg The general risk assessment criteria analysis indicated that BTEX levels were below acceptable contamination levels (ES 199 11 -2 (520 mg/kg), MW-3 (500 mg/kg), B-1 (6,800 (mg/kg), A total of nine samples�MW SB2-25 (2,900 mg/kg), SB2-30 (1,300 mg/kg), S137-15 (16,000 mg/kg), SB7-25 (9,600 PARESSYR01 VOLIR 1wP1727607 80969127607803 WW6 10