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%Roof DRAFT <br /> With regard to the water quality objectives for organic chemicals, the State <br /> Department of Health Services (DHS) has set MCLS for benzene, toluene, ethylbenzene, <br /> and xylene (BTEX) in drinking water of I ppb, 100 ppb, 680 ppb, and 1,750 ppb, <br /> respectively. (Cal. Code of Regs., tit. 22, § 64444). Although DHS has not yet set an <br /> MCL for methyl-tertiary-butyl-ether(MTBE), DHS has set an interim action level of <br /> 35 ppb (DHS Memorandum from Joseph P. Brown, Ph.D., Acting Chief, Water <br /> Toxicology Unit to Alexis M. Milea, P.E., Acting Supervisor, Standards and Technology <br /> Unit, Office of Drinking Water(February 19,.1991) at p. 2). DHS has adopted a 5 ppb <br /> MTBE concentration as a secondary drinking water standard for taste and odor. The <br /> threshold odor concentration of commercial gasoline (measured as total petroleum <br /> hydrocarbon gasoline, or TPH-g) in water is commonly accepted to be 5 ppb, with 10 ppb <br /> giving a strong odor. <br /> The following is a brief historical summary of petitioner's site at 1665 Pacific <br /> Avenue in the City of Stockton. The site is located in a commercial/residential area of <br /> the city and was an operating service station from about 1947 to 1988; gasoline was <br /> dispensed from two 10,000 gallon capacity USTs. Since demolition of the station and <br /> removal of the USTs in 1988, the site has remained vacant. <br /> The site is underlain by flood plain sediments (clay, silt and sand) of the <br /> Pliestocene Victor Formation. In the vicinity of the site, groundwater in the more <br /> permeable strata of Victor Formation is generally of inferior quality (concentrations of <br /> nitrate greater than 45,000 ppb, chloride greater than 300,000 ppb, and TDS greater than <br /> 1,000,000 ppb) and is not viewed by local water purveyors as a source of drinking water. <br /> Underlying the Victor Formation are the alluvial sediments (clay, silt, sand, and gravel) <br /> of the Plio-Pliestocene Laguna Formation. Groundwater in the Laguna Formation is used <br /> extensively throughout the area for municipal, industrial, and agricultural supply. There <br /> are no water supply wells within 800 feet of the site and those municipal wells located in <br /> the general area are routinely constructed with annular seals which extend to depths of <br /> 150 to 200 feet so as to exclude the shallower poor quality groundwater in the Victor <br /> Fnrrnatinn. The nearest surface water_ a canal which extends easterly from the Port of <br />