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- <br /> Mr. Tim Gill Page 2 <br /> Hydrocarbons at a concentration of 5.8 ppm. Using data from November 19, 1993 and May 31, <br /> 1988 PHS/EHD`1.concludes that contamination is present from 8 feet to 13 feet 4 inches. ; <br /> PHS/EHD has determined that the vertical extent of contamination has been defined as <br /> previously stated. The lateral extent of the contamination has not been defined at this time. Both <br /> the vertical and lateral extent of contamination must be defined in order to perform a risk <br /> appraisal for any site. <br /> In the section entitled "Review of Soil Sample Results" the letter states the leaching potential <br /> rating for this site outlined in the LUFT Manual is 44. Based on this rating a "General Risk <br /> Appraisal" needs to be performed. Under the general risk appraisal the level of contamination <br /> at this site may be left in place. <br /> PHS/EHD has determined that the leaching potential rating for this site is 38 using a depth to <br /> seasonal high groundwater from the 1986 San Joaquin County Flood Control Map of 25 feet and <br /> a sample depth of 8 feet. The maximum allowable BTXE levels for a site with this rating is <br /> below .005 ppm:' The maximum allowable levels for TPH as Gas is 10 ppm and for Diesel is <br /> 100 ppm. <br /> PHS/EHD has determined that the level of contamination confirmed by laboratory analysis at <br /> this former underground storage tank location exceeds the maximum allowable level of <br /> contamination to Heave in place. The lateral extent of the existing contamination has not been <br /> adequately characterized to appraise the risk to groundwater of leaving the existing <br /> contamination in'place. <br /> PHS/EHD recommends that remediation of the existing contamination or additional subsurface <br /> investigation to define the lateral extent of the existing contamination proceed by May 15, 1995. <br /> If you have any questions please contact Steven Sasson, REHS at (209) 468-3459. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Steve asson, �qrHS Diane Hinson, RE S <br /> Site Mitigation Unit Supervisor <br /> SS <br /> cc: CVRWQCB - Elizabeth Thayer <br /> cc: Ann Farr Ph.D. <br />