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PUBLIC HEALTH StRVICE' S <br /> SAN JOAQUIN COUNTY : <br /> ENVIRONMENTAL HEALTH DIVISION Ur <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor• Stockton, CA 95202 <br /> 209/468-3420 <br /> WILLIAM J HUNTER DEC 2 2 5997 <br /> 2220 LOMA VISTA DRIVE <br /> SACRAMENTO CA 95825 <br /> RE: Letter Dated November 6, 1997, On Investigation Required At 1876 <br /> Country Club Blvd., Stockton <br /> San Joaquin County Public Health Services, Environmental Health Division <br /> (PHS/EHD) has reviewed your letter dated November 6, 1997, regarding <br /> PHS/EHD directives for 1876 Country Club Blvd., Stockton and provides the <br /> following comments. <br /> At the above referenced site, monitoring well 3 (MW3), which is located closest <br /> to the former tank pit, evidenced soil contamination at 23 feet below grade (fbg). <br /> Soil samples from beneath 23 feet in MW3 were not analyzed. Lab analysis of <br /> soil from soil probe E, which was completed in the former tank pit evidenced soil <br /> contamination to a depth of 21 fbg. The boring log for this probe indicates a <br /> possible petroleum odor at 26 fbg. Therefore, the vertical extent of soil <br /> contamination has not been defined. <br /> Until the vertical extent of soil and groundwater contamination have been <br /> defined, it cannot be stated that the lateral extent has been defined. It is not <br /> known if the existing wells are constructed deep enough to intercept the deepest <br /> contamination. <br /> Due to the dramatic change in groundwater levels in some areas of San Joaquin <br /> County and the fact that at most sites we do not know when the petroleum <br /> release occurred, we have directed investigation of soil at historical low depth to <br /> water levels. These investigations have shown that soil contamination exists <br /> below current groundwater levels and that groundwater contamination exists <br /> below screened intervals of existing monitoring wells. <br /> At the above referenced site, current groundwater level is above the top of the <br /> screened interval of the existing monitoring wells. When the water level was <br /> within the screened interval, benzene levels in the water samples collected from <br /> monitoring well 1, which is down gradient of the former tank pit, averaged about <br /> 10,000 parts per billion. The continuing source of this contamination must be <br /> determined. <br /> A Division of San Joaquin Counry Health Care Services <br />