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PUBLIC HEALTH SEItTICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H.,Health Officer <br /> ��ir <br /> 304 East Weber Avenue,Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> KAREN PETRYNA FEB 0 4 2002 <br /> EQUIVA SERVICES LLC <br /> PO BOX 7869 <br /> BURBANK CA 91510-7869 <br /> RE: Equilon (former Shell#204-7524-4) Site Code:1883 <br /> 3011 W. Ben Holt Dr. ROM 0000486 <br /> Stockton, CA. 95207 <br /> San Joaquin County Environmental Health Department(EHD)has reviewed the"Site <br /> Investigation Report and Work Plan"dated January 11, 2002 submitted by Cambria on January <br /> 14, 2002 and has the following comments. <br /> This report of findings covered the installation of soil borings"SB-13"through "SB-17" during <br /> December 2001. Additionally,this report contains a proposal to install one (1)deep monitoring <br /> well in the area of existing, shallow monitoring well "MW-2". <br /> EHD concurs with your consultant's conclusion that the soil contamination has been vertically and <br /> laterally defined for TPH as gasoline, BTEX, lead scavengers, and the oxygenates. The grab <br /> groundwater sample results confirm that the low levels of Lead contamination detected in the soil <br /> samples may not have impacted the groundwater to any great extent. Additional groundwater <br /> sampling events from existing and new monitoring wells should include Lead analysis to confirm <br /> these findings. <br /> In reviewing this site's soil and groundwater data from 1994 to date, EHD has been unable to rule <br /> out whether the Total Extractable Petroleum Hydrocarbons (TEPH)range C9 to C24 previously <br /> reported as Diesel (TPH-d) is still present in the groundwater. Neither soil nor groundwater <br /> samples were analyzed for this constituent in this last phase of investigation. Quarterly <br /> monitoring events that included TPH-d analysis were last conducted on May 14, 2001. Current <br /> TEPH (TPH-d)data is to be included in the Problem Assessment Report due at the end of this <br /> investigative phase. <br /> Recommendations included within this report dealt only with the MtBE that was detected in the <br /> groundwater samples from "SB-13", even though the majority of the samples from"SB-14, 15, & <br /> 17"had detectable concentrations of MtBE. <br /> The highest level of MtBE detected in the groundwater samples during this phase was in "SB-13" <br /> (all three samples),with the highest concentration, 210 ug/l, from the deepest sample at 119 feet <br /> below ground surface(' bgs). With the highest concentrations of MtBE detected in the deepest <br /> sample collected, the vertical extent of the contamination cannot be considered delineated. <br /> Soil borings"SB-11"and"SB-12"were placed in this same area on different dates and at different <br /> depths. MtBE was detected in the groundwater grab sample from SBA 1 at 15.5' bgs at 26,000 <br /> ug/I in August 1998. MtBE was detected at 6.9 ug/I at 26.5' bgs which was the only other <br /> groundwater grab sample from this boring. The highest MtBE groundwater concentration <br /> detected in Soil boring"SB-12"drilled in July 2001 was 120 ug/I,which was from the sample <br /> collected at 77' bgs. A quarterly groundwater-sampling event held on December 7, 2001, showed <br /> that MW-2, located in this same area and screened from T to 22' bgs, detected MtBE at 2,600 <br /> ug/I. <br /> A Division of San Joaquin County Health Care Services <br />