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F I L L <br /> PUBLIC HEALTH SERVICTS <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <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 /> JOE KIRIM SEP 1 5 2000 <br /> UNIVERSITY OF THE PACIFIC <br /> 3601 PACIFIC AVE <br /> STOCKTON CA 95211 <br /> RE: UNIVERSITY OF THE PACIFIC Site Code: 000732 <br /> 1081 W MENDOCINO <br /> STOCKTON CA 94204 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has reviewed the Subsurface Soil and Groundwater Assessment Report (report) dated <br /> August 25, 2000, prepared by Environmental Science Associates for the above referenced <br /> site. Soil and groundwater samples collected at this site evidence petroleum <br /> contamination. Further evaluation and definition of the contaminated groundwater at this <br /> site is necessary. <br /> Methyl-tert-butyl ether (MTBE)was evidenced in a groundwater sample collected at 25 <br /> feet below surface grade (bsg) at concentrations as high as 1300 parts per billion (ppb). <br /> The maximum contaminant level for MTBE is currently 13 ppb. Concentrations of <br /> MTBE in the groundwater must be confirmed by utilizing repeatable sampling points to <br /> obtain representative groundwater samples. <br /> Monitoring wells (MWs) should be constructed at the site to evaluate the groundwater <br /> conditions and to establish the groundwater gradient. MWs should be screened at an <br /> interval that is representative of the affected groundwater. Groundwater samples should <br /> be analyzed quarterly for Total Petroleum Hydrocarbons as gasoline by EPA Method <br /> 8015; Benzene, Toluene, Ethylbenzene and Xylene by EPA Method 8020; and for <br /> Oxygenates, 1,2 Dichloroethane, Ethylene dibromide,methanol and ethanol by EPA <br /> Method 8260. <br /> The soil boring logs presented in the report indicate silty sand at 20 feet below surface <br /> grade. Although MTBE was not detected in the 20-foot soil sample collected in boring <br /> TP-4, the potential for contaminant migration below this lithology exists. A site <br /> investigation must be conducted below this interval to the historic low groundwater level <br /> in order to confirm the vertical extent of groundwater contamination. MTBE plumes <br /> can be long, narrow and erratic (meandering). Therefore, the lateral extent of <br /> groundwater contamination must be determined as well. Because of possible pumping <br /> influence from wells located north of this site, as shown in the Groundwater Well <br /> Location Map (Figure 3) in the report, investigation of soil and groundwater to the north <br /> of the TP-4 location must be conducted. <br /> A Division of San Joaquin County Health Care Services <br />