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" . _ r <br /> ;� -__.�� a r- <br /> � o�W°..� a =u � ,�,,L'rg;*•WW &`rs, �.n � ww. .,, a *' ,,cJ'. 5 .rr-., _ '.ss�..,esn1` " . t r .�- - ,_. '�+'+.'x,�.- ' <br /> F��'�,�"�' � ,.'��F <br /> Brown and Caldwell <br /> Consuitants <br /> 72355;,cct JUL5 771 <br /> Ca;dcrrn <br /> a55e1a•?flop <br /> '&fefm916) a017.3 l: VIR )NNIENTALHEALN <br /> FW 19161 4ae.3.137 PER, 11T/SERVICES <br /> July 11, 1991 <br /> Mr. Chuck Carmel <br /> ARCO Products Company <br /> Post Office Box 5811 <br /> San Mateo, California 94402 017-5690-2411 <br /> Subject. Draft Final Remediation Plan for ARCO Station 2133, Stockton, California <br /> Dear Mr. Carmel: <br /> This report is the Final Groundwater Remediation Plan (Plan) for ARCO .Products Company <br /> (ARCO)Station 2133(site)located at 2908 Benjamin Holt Drive,Stockton California. Figure 1 <br /> shows the location of the site. The Plan is organized so that it basically follows the outline <br /> presented in the final.Remediation Plan section of Appendix A of the Tri-Regional Board Staff <br /> e Recommendations for Preliminary Evaluation and Investigation of Underground Tank Sites. The <br /> J preparation of the Platt was required by the San Joaquin County Public Health Services, <br /> Environmental Health Division (County). <br /> Presently, groundwater remediation is underway at this site. This remediation consists of a <br /> groundwater extraction system which discharges directly to the sanitary sewer under a City of <br /> Stockton Wastewater Discharge Permit. This permit expires on December 31, 1992,and will be <br /> renewed at that time. The extraction system will be explained in detail in the appropriate section <br /> of the Plan. <br /> Hydrogeologic Measurements and Predictions <br /> On August 31, I990.a step-drawdown pumping test was performed on the groundwater recovery <br /> well (.R-13) at the site (Figure 2). In addition, well logs, water-level data, and groundwater <br /> sample data generated during previous investigations of the site were reviewed. These data <br /> formed the basis for a modeling analysis that was used to estimate a pumping rate which should <br /> be sufficient to continue to control the hydrocarbon plume found beneath the site. <br /> Water-Level and Pumping Data. A water-level database was created using data collected by <br /> Brown and Caldwell for the period January 1989 to the time of the pumping test in August 1990. <br /> f The analytical data is presented in tabular form in Appendix A. Hydrographs for wells for which <br /> data are available were prepared and are presented in Appendix B. The time between the dates <br /> E shown on the hydrographs is 100 days. During this time, the recovery system was undergoing <br /> modifications to comply with regulations imposed by the City of Stockton. The pun►, located <br />