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' REQUEST FOR SITE CLOSURE <br /> General MWs Facihty <br /> 2000 West Turner Road <br /> Lod:, Cahfornta <br /> Delta Project No 40-92-708 <br /> Page 3 <br />' construct the water table contour snap shown m Figure 5 The direction of ground water flow has been <br /> consistently toward the southwest at an approximate hydraulic gradient of 0 003 to 0 005 <br /> Ground water samples were collected from each monitoring well during tour quarterly sampling events <br /> and submitted to a certified laboratory for analyses of BTEX and TPH as diesel No 6 BTEX or TPH <br />' as diesel No 6 were not detected in any of she ground water samples collected The ground water <br /> sample results are presented in Table 4 The laboratory data sheers are presented in Delta's reports dated <br /> June 9 and October 16, 1992, and January 21 and May 28, 1993 <br />' 2.6 Communications with San Joaquin County <br /> In a letter dated February 17, 1993, San Joaquin County Public Health Services, Environmental Health <br />' Division (County) presented a review of the site conditions and, based on their review, requested <br /> additional site assessment work. Apparently, the County performed a Leaching Potential Analysis <br /> described in the Leaking Underground Fuel Tank (LUF1) Manual and, based on that analysis, determined <br /> that number 6 heating oil detected in the tank basin floor in October 1991 had the potential to migrate <br />' to ground water <br />' In a letter dated March 18, 1993, Delta presented a Leaching Potential Analysis, based on information <br /> collected during the hydrogeologic investigation conducted at the site Presented in Table 5 is Delta's <br />' analysis. Our analysis indicates that the maximum allowable TPH as diesel No 6 concentrations should <br /> be 1,000 ppm <br /> On April 15, 1993, representatives of the County, Delta, and General Mills met to discuss appropriate <br /> actions at the site It was determined that the difference between the County's and Delta's Leaching <br /> Potential Analyses was the assumed depth to ground water- the County assumed a minimum depth to <br />' ground water from the soil samples containing fuel oil #6 was Iess than 25 feet and Delta assumed that <br /> it was greater than 25 feet (see Table 5) Using the County's assumption, the maximum allowable <br />' concentration of TPH as diesel No 6 should be 100 ppm, using Delta's assumption, the maximum <br /> allowable concentration should be 1,000 ppm <br /> RYTO76 TA <br /> 1 <br />