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PUBLIC tEALTH SERVICES = aP �oz <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer • �4t;Foii`'�p <br /> 445 N. San Joaquin Street • P.O. Box 388 • Stockton, CA 95201-0388 <br /> (209) 468-3420 <br /> BOB BOUST <br /> UNOCAL <br /> 2000 CROW CANYON PL STE 400 ru J v G 4 X994 <br /> SAN RAMON CA 94583 <br /> Re: 437 East Miner Ave Site Code: 1181 <br /> Stockton CA 95202 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has <br /> completed review of the "Quarterly Data Report" dated September 13, 1994 which was prepared <br /> by MPDS Services and the "Well Installation and Exploratory Soil Boring Report" dated <br /> September 21, 1994 which was prepared by GeoStrategies. PHS/EHD has the following <br /> comments for your consideration. <br /> Three on site monitoring wells (Ul - U3) and five soil borings (UI - UM) were drilled and <br /> sampled between July 6 and July 8, 1994. Soil contamination was encountered during the <br /> sampling of U2, U3, UJ, UK, UL, and UM. Based on the location of the soil borings and the <br /> concentrations of contamination which were evidenced, the possibility exists that soil <br /> contamination may have migrated off site, particularly to the east and to the south of the site. <br /> Groundwater samples were collected from the monitoring wells on August 19, 1994 and <br /> evidenced significant groundwater contamination in all samples collected up to 510 ppm TPH-gas <br /> and 9,700 ppb benzene. The groundwater gradient direction determined from the first round of <br /> groundwater monitoring was to the west. <br /> Additional soil and groundwater investigation will be necessary to determine the full extent of <br /> the petroleum hydrocarbon contamination. Once the results of the next sampling and monitoring <br /> event are available, PHS/EHD will require that a work plan be submitted to continue the soil <br /> and groundwater investigation. <br /> Please submit the next quarterly monitoring report by December 30, 1994. Please be informed <br /> that PHS/EHD inspections of sampling events are an important aspect of local regulatory <br /> oversight. The next quarterly sampling event should be scheduled by November 19, 1994. <br /> PHS/EHD should be provided with at least 48 hours notice prior to sampling events. <br /> A Division nr San Joaquin Counts Health Care Services <br />