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A RESNA Company <br /> Environmental Solutions <br /> Through Applied Science, <br /> 3164 Gold Camp Drive,Suite 200 Engineering A Construction <br /> Rincho Cordova,CA 95670 <br /> Phone(916)852-6690 <br /> FAX f9161852-6688 <br /> November 18, 1991 <br /> Mr. Chuck Carmel <br /> ARCO Products Company s <br /> P.O. Box 5811 <br /> San Mateo, California 94402 <br /> Subject: Addendum to Work Plan for Subsurface Investigation at ARCO Service <br /> Station No. 2130, 7906 North El Dorado Street, Stockton, California. <br /> s <br /> Mr. Carmel: <br /> At the request of ARCO Products Company (ARCO), RESNA Industries (RESNA, <br /> formerly Applied GeoSystems) is submitting this addendum to our previous work plan <br /> (Applied GeoSystems,May 17, 1991, Work Plan No.30003-14). Additional work includes - <br /> a subsurface investigation to evaluate the extent of hydrocarbons in soil and ground water <br /> and a vapor-extraction test to evaluate vapor extraction as a remedial alternative. The <br /> location of the project site is shown on the Site Vicinity Map(Plate 1). The locations of the <br /> proposed monitoring wells are shown on the Generalized Site Plan (Plate 2). <br /> RESNA observed the drilling of one soil boring at the site on June 24, 1991, during a <br /> Preliminary Tank Replacement Assessment investigation. Ground water was encountered <br /> at approximately 68 feet below grade. Laboratory analyses detected residual hydrocarbons <br /> in soil samples collected at 15, 30, 45,55, 60 and 68 feet below grade. Further drilling at r <br /> the site was postponed until the site was added to the San Joaquin County Public Health <br /> Services,Environmental Health Division(SJCPHS-EHD),pilot program. ARCO made this <br /> request in their letter of July 29, 1991, to the SJCPHS-EHD. <br /> On the basis of these data and at the request of ARCO,we will conduct the work outlined <br /> below to evaluate the extent of hydrocarbons in soil and ground water. We understand from ` <br /> personnel with the SJCPHS-EHD that the local groundwater flow direction is to the east <br /> or northeast. <br /> The work will be conducted according to field methods included in our Work PIan dated <br /> May 17, 1991,which describes the site history, local geology,proximity to wells and.utilities, <br /> _soil borings, soil sampling methods, and vapor-well construction. We are modifying our <br /> vapor 61 construction for the screened portion of.the wells to coflsist of factary'perforaied ---- ----------- -- <br /> 3(1D03,4W <br /> NOV 2 0 1991 <br /> ENVIRONMENTAL HEALTH <br /> -V, <br />