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i <br /> P _ <br /> BLIC HEALTH SERVIC S ,oP � <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION N ` <br /> Karen Furst, M.D., M.P.H., Health Officerq <br /> �/FOR <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> JERRY MOORE <br /> MOORE PETROLEUM <br /> P O BOX 67 OCT 12 2000 <br /> BANTA CA 95304 <br /> RE: Moore Petroleum <br /> 5491"F" Street <br /> Banta,CA 95304 <br /> San Joaquin County Public Health Services,Environmental Health Division(PHS/EHD)has reviewed the <br /> "Results Report for Limited Subsurface Investigation and Third Quarter 2000 Groundwater Monitoring <br /> Report"(report),dated August 29,2000. The report included a history of the site and a report on the results <br /> of the installation of three monitoring wells(MW-10,MW-11,and MW-12),as well as one deep soil boring <br /> (SB-Deep). <br /> Methyl tertiary butyl ether(MTBE)has been detected at 110µg/1 just 15 feet from the domestic well east of <br /> the site. Potentially,MTBE may have already reached the domestic well and is merely being diluted to <br /> non-detect levels by a larger screened interval in the well. Additional data will be required to evaluate the <br /> potential for contamination to the domestic well. PHS/EHD hereby directs you to conduct the following <br /> data-collecting procedures: <br /> • Begin monthly monitoring of the domestic well. Install a sample.tap between the wellhead and <br /> check valve to enable water samples to be retrieved directly from the domestic well. <br /> • Determine groundwater velocity. Perform aquifer analysis tests to determine the distribution of <br /> hydraulic conductivity. Collect soil samples for porosity analysis. Use the measured hydraulic <br /> conductivity,hydraulic gradient,and aquifer porosity data to determine the velocity of <br /> groundwater flow using the seepage velocity equation. <br />� • Determine vertical gradient. Existing well logss may provide enough <br /> information to calculate this <br /> information. <br /> • Submit a well log for the domestic well. If a well log is not available,determine the depth of the <br /> well during the installation of the sample tap. <br /> • Define the vertical and lateral extent of the MTBE plume at the site using depth discrete grab <br /> groundwater samples. PHS/EHD does not agree with the statement in the report that the vertical <br /> extent of MTBE can be defined by a single boring. <br /> • Complete the dual phase pilot test by November 15,2000. In the Conclusions and <br /> Recommendations section of the report,Apex states that the dual phase pilot test at the facility and <br /> the results of the pilot test will be completed by November. The dual phase pilot test should in fact <br /> already have been completed. <br /> • Conduct a physical search of the area for wells and receptors within a 2,000-foot radius of the site, <br /> as directed by PHS/EHD in our letter dated.March 9,2000. Additional analysis of the well survey <br /> A Division of San Joaquin County Health Care Services <br />