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BLIC hEALTH SERVICES PpUtN <br /> PU o.. <br /> SAN JOAQUIN COUNTY a -51 <br /> ENVIRONMENTAL HEALTH DIVISION y: <br /> Ernest M. Fujimoto, M. D., M.P.H., Acting Health Officer <br /> 304 E. Weber Ave., Third Floor • P. O. Box 388 Stockton, CA 95201 <br /> L . <br /> 209/468-3420 (7(0 <br /> BRETT HUNTER DEC 0 j 19vab <br /> ENVIRONMENTAL ENGINEER <br /> CHEVRON USA <br /> P O BOX 5004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Lincoln Village Chevron Station #9-4275 SITE CODE: 1952 <br /> 2905 West Benjamin Holt <br /> Stockton CA 95207 <br /> San Joaquin County Public Health Service, Environmental Health Division (PHS/EHD) has reviewed <br /> the faxed information regarding the evidenced soil contamination beneath the former underground <br /> storage tank piping and the proposed location of an additional vapor extraction well. The additional <br /> well will be located, along with the final vapor extraction well originally proposed, in the areas that <br /> are anticipated to encompass this shallower contamination within their radius of influence. <br /> To evaluate the site, given the currently available information, PHS/EHD has requested by telephone <br /> the following conditions, prior to the installation of new product piping: <br /> 1. The design of the remaining two vapor extraction wells should provide sufficient <br /> vacuum influence to efficiently remediate the shallower soil contamination. As <br /> PHS/EHD has stated, the currently installed vapor extraction wells are screened <br /> between 17 and 10 feet below ground surface (bgs). <br /> 2. The evaluation of the affect that the proposed piping trench fabric liner may have on <br /> the ability of the vapor extraction wells to remediate the shallower soil <br /> contamination. <br /> 3. A soil boring through the former tank pit. This boring will provide vertical definition <br /> of the secondary source at the former tanks location. The proposed vapor <br /> extraction's manifolded system will be able to estimate the recovery of petroleum <br /> hydrocarbons in specific areas. <br /> Better definition of the former tanks contamination will allow for better evaluation of <br /> secondary source recoveries, so that if recoveries in the former piping area are less <br /> than anticipated, it would suggest that the soil contamination evidenced was limited. <br /> This will provide an additional line of evidence supporting your request to postpone <br /> trench sampling, which would have provided the vertical definition and mass of <br /> contamination potentially impacting groundwater. If however, recoveries are greater <br /> than anticipated in the former piping area, it would suggest more extensive soil <br /> contamination that may warrant further investigative or remedial efforts. <br /> Also, it is PHS/EHD's understanding that the reason that the proposed vapor extraction system has <br /> not yet been completely installed nor started, is that there were some problems with obtaining PGE <br /> approval. Evidently, it is anticipated that the system will be operational within two weeks and that <br /> this delay will not affect the ability of Chevron to comply with the October 28, 1996 compliance <br /> proposal Chevron put forth following the October 24, 1996 administrative hearing. <br /> A Division of San Joaquin County Health Care Services <br />