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f 1� Applicable Regulations and Guidelines � . PP g Soils No standards have been promulgated for petroleum hydrocarbons in soil; levels in soil E required to protect groundwater may vary with local climate and geologic conditions. The California Regional Water Quality Control Board LUFT Field Manual includes a leaching potential analysis for estimating concentrations of BTEX and TPH-Gas that may be left in place without threat to groundwater (Appendix G). For the conditions present at the Del Monte Disco location, the target level. of benzene, toluene, ethylbenzene, and xylenes is nondetectable: and the target level for TPH-Gas is 10 mg/kg. Based on -the results of this investigation and the leaching potential of petroleum hydrocarbons into the shallow groundwater, benzene will be the primary focus of soil remedial action. Groundwater 11 Quantitative action and cleanup levels of BTEX in groundwater have been established by both the State of California and U.S. Environmental Protection Agency (EPA). There are no regulations or guidelines quantitatively addressing concentrations of TPH. The State of California 'EPA Maximum Contaminant Levels (MCLS) for BTEX and lead are shown in Table 3-5. The most stringent regulatory action or cleanup levels of ` dissolved BTEX constituents is for benzene. The California MCL for benzene is 1 ug/1. Lower quantitative limits of 0.66 ug/l benzene in potable water have been set by the U.S. EPA as part of the national ambient water quality criteria. Benzene was found to exceed the hazardous waste Toxicity Characteristic Leaching Procedure (TCLP) level of 0.5 mg/l in Monitoring Wells MW-DIS-1 and.-2. Benzene ' levels exceed the California MCL of 0.001 mg/I in Monitoring Wells MW-DIS-1, -2, -3, and -7D. iBased on these results and regulations, benzene will be the primary focus of groundwater remedial action. Concentrations of ethylbenzene, toluene, and xylenes found above established groundwater regulatory levels in the vicinity of the former Disco tanks will also be addressed in the Feasibility Study (Section 4). Groundwater Use Water supply wells located within 1 mile of Plant 33 are shown an Figure 3-8 and described in Table 3-7 (Del Monte Plant 33 wells are not included). The majority of these wells are reportedly domestic supply located to the south and southwest of { Plant 33. These wells are screened at various intervals between 140 feet and 435 feet bgs. l sF0316041RP1006.51 3-17 1