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9-09-1997 3:36PM FROM P. 2 <br /> en vi os,,, <br /> September 9, 1997 <br /> Ms_ Mary Meays <br /> San Joaquin County Public Health Services <br /> Environmental Health Divirion <br /> Site Mitigation Unit <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> RE: REVISED SITE ASSESSMENT WORK PLAN <br /> Shell Service Station <br /> 2575 Country Club Boulevard <br /> Stockton,California <br /> WIC 204-7524-3505 <br /> Dear Ms.Meays: <br /> Enviros, Inc. (Enviros) has prepared this Revised Site Assessment Work Plan on behalf of <br /> Shell Oil Products Company to address issues raised in San Joaquin County Public Health <br /> Service(SJCPHS)correspondence dated August 27, 1997 and subsequent telephone <br /> conversations with SJCPHS personnel. These issues refer to the August 13, 1997 Work <br /> Plan Addendum prepared on behalf of Shell by Enviros. <br /> In the August 13, 1997 Addendum,two soil borings were proposed to demonstrate that the <br /> clay layer observed in Boring RW-IA from depths of approximately 25 to 45 fbg extended <br /> across the site to act as a barrier to vertical migration of contaminants. It was our opinion <br /> that the presence of this layer,combined with the chemical properties of the contaminants <br /> of concern would retard the vertical migration of contaminants. SJCPHS subsequently <br /> indicated that they did not concur with this opinion. Because methyl tertiary butyl ether <br /> (MTBE) was detected in a domestic well located at 2468 Country Club Boulevard, but has <br /> not been detected in site investigation well MW-3, SJCPHS believes that migration of <br /> contaminants to the domestic well is occurring through a deeper water bearing zone. It is <br /> also SJCPHS's opinion that BTEX levels of less than 1 ppm detected from soil boring <br /> RW-B 1 at a depth of 46.5 feet resulted from vertical migration and warrant installation of <br /> deeper wells. <br /> A revised scope of work is presented to respond to SJCPHS's requests regarding the <br /> investigation. This proposed scope is presented in lieu of and supersedes the scope <br /> proposed in the August 13, 1997 addendum. <br /> Task One - Installation of Three Additional Shallow Ground Water <br /> Monitoring Wells <br /> A total of three shallow ground water monitoring wells are proposed in the locations shown <br /> on Plate 2. One of these wells, located within the Caltrans right of way was previously <br /> approved by SJCPHS and has been permitted with SJCPHS and Caltrans. Two additional <br /> wells are proposed on the south side of Country Club Boulevard, southeast of Shell's <br /> source area The purpose of these wells is to provide further data for evaluation of <br /> Env,rns. Inc 370 vvh"s shrrl ,,ra'H"ra r I70 7 - .SJ <br /> P 0 80.E"2 95'o�,0.59 01, '0' <br />