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t.i 1 <br /> r <br /> ENVIRONMENTAL HEALTH DEPARTMENT <br /> °PaU N SAN JOAQUIN COUNTY <br /> c i Donna K Heran,R E H S Unit Supervisors <br /> h Director 304_East Weber Avenue, Tlurd Floor Carl Borgman,R E H S <br /> Al Olsen,R E H S Stockton, California 95202-2705 Mike Huggins,R E els,R D I <br /> cQti�aa��P Program Manager Telephone (209) 4683420 Douglas W Wilson,R E H S <br /> R - <br /> Laurie A Cotulla, <br /> E H S Margaret Lagorio,R E H S <br /> Program Manager Fax (209) 464-0138 ���� <br /> MARt McClelion,R E H S <br /> MAR 1`110fts'REHS <br /> PAUL SUPPLE KITTY WALKER <br /> ATLANTIC RICHFIELD COMPANY COS REDEVELOPMENT AGENCY <br /> PO BOX 6549 305 N EL DORADO STREET <br /> MORAGA Ck- --94590 - -- STOC:`KTON - CA 95202 <br /> RE ARCO Station #4493 <br /> 205 N Center Street <br /> Stockton CA 95202 <br /> San Joaquin County Environmental Health Department(SJC/EHD)has received the"Monitoring Well <br /> Installation Report"dated February 4, 2003 and the `Quarterly Groundwater Monitoring Report'(QMR) <br /> dated February 5, 2003 that were submitted on your behalf by URS Group, Inc (URS)and has the <br /> following comments <br /> A work plan prepared by URS to install two dual-completion, down-gradient groundwater monitoring <br /> • wells at this site was conditionally approved by SJC/EHD in correspondence dated October 23, 2002 <br /> The installation of two wells had been agreed upon at a site meeting in June 2002 During fieldwork to <br /> install these wells in November 2002, extensive underground utilities at one selected location <br /> prevented the installation of one of the wells at that time However, it was always the understanding of <br /> SJC/EHD that an alternative location would be selected and the well would be installed at a later date <br /> The Monitoring Well Installation Report documents the installation of one dual-completed groundwater <br /> monitoring well(MW-11-MID) located to investigate the lateral and vertical extent of the plume in the <br /> down gradient direction As the gradient at this site has historically shifted east to northeast, two dual- <br /> completed wells were to have been installed to cover this area The report states that MW-1I-MID <br /> was sampled on December 5, 2002 However, Table 2-Fuel Oxygenates Analytical Data MW-11-M/D <br /> reports two sample dates and analytical results for this well One of these sample dates is listed at <br /> September 16, 2002, which is before the wells were installed Please have URS explain this <br /> discrepancy and/or correct the data table in this and all future reports <br /> SJC/EHD will evaluate URS's conclusion that the vertical extent of impacted groundwater has been <br /> delineated in the area of MW-11-M/D after additional monitoring events However,both the lateral <br /> extent of impacted groundwater and the vertical extent in the areas of MW-8-M/D and MW-9-M/D still <br /> need to be delineated Please submit a work plan to continue the investigation at this site and to <br /> install the additional dual-completed well The work plan is due May 16, 2003 <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> b--Ll I", tititir� <br /> • Lori Duncan, Senior REHS Nuel C Henderson, Jr, RG <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc James L L Barton, CVRWQCB <br /> Brown, Daley&Heft <br /> ernon Elarth, URS <br /> i <br />