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rONMENTAL HEALIr DEPARTMENT <br /> ` <br /> ENV IR <br /> O.PQu'1N'.0 <br /> s <br /> SAN JOAQUIN COUNTY Unit Supervisors <br /> i' <br /> Donna K.�Ieran,R.E.H.S. . 171Td FIOOI Carl Borgman,R.E.H.S. <br /> 304 East Weber"Avenue, Mike Huggins,R.E.H.S.,R.D.I. <br /> Director <br /> Al Olsen,R.E.H.S. S[OCktOn, California 95202-2108 Douglas W.Wilson,R.E:H.S. <br /> • �. _. . a p,ogr�rn,Manage, Telephone:.(209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> gCi'Fo'tia Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Progrnn2 Manager Fax: (269) 464-0138 Mark Sarcellos,R.E.H.S. <br /> PAUL SUPPLE DEC 0 .1 2003 <br /> ARCO PRODUCTS COMPANY <br /> P O BOX 6549 <br /> MORAGA CA., 94570 <br /> RE: ARCO #5469 SITE CODE: 0710 <br /> 130 S. Wilson Way <br /> Stockton, California <br /> San Joaquin` County Environmental Health :,Department (EHD) has received and <br /> reviewed Quarterly Groundwater Monitoring Report dated 31 October 2003, prepared for <br /> the above-referenced site by Delta Environmental Consultants, Inc. (Delta) and <br /> discussed the site with Delta on 22 October 2003. <br /> As noted in,jhe quarterly report, during the 22 October discussion with Delta, EHD <br /> requested that a site conceptual model (SCM) for the site that includes data from the <br /> 101 S. Wilson Way and 102 S. Wilson Way sites be. prepared by Delta to better <br /> understand the distribution and migration of contaminants on the three sites. An SCM is <br /> a valuable tool for properly investigating and managing a'release of contaminants to the <br /> subsurface, as will be noted below, but the current impetus for preparation of an SCM <br /> arises as a result of a request from the consultant for the E102 S. Wilson Way site to Have <br /> a meeting toIresolve potential commingled plume issues. involving the three sites. EHD <br /> believes such:a meeting could be useful if all participants are familiar with all the data <br /> and have interpreted and modeled the data. A productive meeting will be the .result of <br /> carefully analyzing, testing and evaluating the models and cooperatively determining the <br /> course of future actions. <br /> Please prepare an SCM to prepare for this meeting and:to use as a tool for future work <br /> r an SCM ares to demonstrate where the contaminants <br /> on. your site. The purposes fo <br /> came from, where they are at the present time, how they move through the subsurface, <br /> how they will respond to changes in the groundwater flow characteristics or to potential <br /> remediation efforts, what the. contaminants ultimate environmental fate will be, and to <br /> help evaluate the risk posed by the contaminants to groundwater supplies and sensitive' <br /> receptors. In addition, the SCM -may demonstrate data gaps, thereby illustrating where <br /> additional investigation is needed.-To be sure;that the SCM will adequately address the <br /> assessment remediation and, ultimately, final closure requirements for this site, please <br /> include the following, as appropriate, in the SCM: <br /> Local and regional plan view maps with sources, boring and monitoring well <br /> c locations, lines of cross section, extent of contaminants in each media, direction <br /> and�l rate of ground water flow, and receptor locations, including water supply <br /> wells within 2,000 feet of the site.. <br /> i <br />