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1444 MARIPOSA ROAD <br /> WKA No 2938 05 <br /> August 26, 1999 <br /> ' Page 9 <br /> Quarterly Sampling <br /> Groundwater beneath the site has been monitored from October 1993 to June 1999 Though <br /> initially reported below detection levels,petroleum hydrocarbons have been present in groundwater <br /> samples obtained from wells MW1 and MW2 during several of the quarterly sampling events In <br /> general terms, concentrations of petroleum hydrocarbons and BTEX fuel constituents reached <br /> ' their highest concentrations in April of 1994 These constituents, however, appear to have <br /> significantly decreased with time <br /> It should be noted that a tremendous fluctuation in groundwater elevation has occurred during <br /> this time frame and is likely the result of rebounding aquifers following drought conditions <br /> prevalent during the early 1990's The measured depth to static groundwater in wells ranged <br /> from 47 10 to 48 02 feet below top of well casing on June 16, 1999, up from a historic low of <br /> approximately 69 feet below site grade recorded in April of 1994 A summary of depth-to- <br /> groundwater measurements, groundwater elevations and analytical results are included in Tables <br /> 3 and 4,respectively <br /> Field Investigation <br /> Sensitive Receptor Survey <br /> As part of our site investigation, we performed a sensitive receptor survey for the surrounding <br /> area within a 2,000 foot radius of the property boundary. The primary potential pathway <br /> concerns are surface water bodies or groundwater wells near the site Our surface water body <br /> survey consisted of a windshield survey and a review of the USGS 7 5 Minute Topographic Map <br /> of the Stockton East Quadrangle, California Based on this survey, surface water located within <br /> a 2,000 foot radius is Mormon Slough which is located approximately 500 feet north of the site <br /> ' In addition to the above windshield survey, our water well survey included a review of California <br /> Department of Water Resources (CDWR) well construction records These confidential records <br /> were obtained with the help of staff from CDWR <br /> 1 WALLACE KUHL <br /> Rec cledpaW &ASSOCIATES INC. <br />