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�..� %./ SPEEDY FOOD MART 8200 HWY 99, Stockton Page 3 been consistently non-detect for MTBE and other hydrocarbon constituents since its installation in December 2000. EHD agrees that a down gradient (east) deep-zone monitoring well is needed, but requests installation of an additional deep-zone monitoring well in the area of the original source of release where the former UST and dispenser were located (near MW1). A continuous core should be obtained from both wells. EHD approves installing a conductor casing for the deep-zone well near the source area to prevent cross-contamination as proposed in the work plan, but a conductor casing is not necessary for the deep-zone well near MW7 since the shallow groundwater there does not appear to be impacted. • Demonstration of the need for an SVE system before installation of an SVE well or performing an SVE pilot test. SVE has limited direct effect on dissolved contamination and is inappropriate as an interim remediation for the purpose of controlling dissolved contaminant migration. Please provide justification for testing SVE as an interim remediation measure—state how SVE is preferable to other methods, the mass to be addressed, the expected results, and what mass will not be addressed at this time. EHD requests that a skimmer be installed in MW-1 by March 1, 2003 to remove the free product and re-initiate sampling MW-1 beginning with the next quarterly monitoring event as long as no measurable free product is found in the well. Groundwater samples have not been collected from MW-1 since August 2001 due to the presence of free product. According to Table 1 of the fourth quarterly sampling report of 2002 (dated January 28, 2003 prepared by GroundZero), the product thickness inside the well before bailing had been measured to be as high as 2.04 feet (August 6,2002) when depth to groundwater had fallen from 61.39 feet bsg Qune 13, 2002) to 65.08 feet bsg. Recently, free product had been measured to be between 0.01 and 0.02 feet (December 30, 2002),when groundwater elevation had risen back to 63.76 feet bsg. A continuous record of contaminant concentrations is needed to help evaluate the effect of the groundwater elevation fluctuation. The detection limit for text-butanol (TBA) should at a minimum,be set at or below the action level of 12 parts per billion (ppb) established by State Department of Health Services (DHS). TBA has been reported as less than the detection limit of 2,000 µg/l for MW4, and less than 20 µg/l for other wells. Since TBA is a suspected candidate in the breakdown product of MTBE with solubility even higher than MTBE,it could potentially migrate as fast as MTBE in dissolved phase. Therefore, the detection limit for TBA should be lowered to at least 12 ppb using EPA Method 8260 analysis. If your laboratory cannot produce these detection limits, EHD recommends you look for a laboratory with that capability. Results of