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i <br /> thevron <br /> Chevron U.S.A. Products Company . <br /> 2410 Camino Ramon,San Ramon, California'•Phone (510)842-5500 <br /> Mail Address: E0.Box 5004,San Bannon,CA 94583-0804 <br /> August 7, 1992 CEIV8D,r <br /> I <br /> 1$92 <br /> Ms. Mary Meays AW2 1 <br /> ENVI <br /> San Joaquin County Environmental Health R�"MENTAL HEALTH <br /> P.o. Box 2009 PERMIT/SERVICES <br /> Stockton,CA 95201 <br /> Re: Former Chevron Station#9-1918. 45 East Harding Way Stockton CA <br /> Enclosed Groundwater and Vadose Well Installation, Sampling; and Quarterly Monitoring <br /> Report(GTI, 7/22/92) <br /> Enclosed list of environmental-related reports <br /> Dear Ms.Meays: <br /> Enclosed is a report dated July 22, ,1992, which was prepared :by Chevron's consultant, <br /> Groundwater Technology Inc. (GTI), to describe the installation and sampling of two groundwater <br /> monitoring wells and one vadose zone well at the subject site. The completion of the report by <br /> GTI-was delayed in order to have the site resurveyed as requested in your June,l I, 1992 letter. <br /> Also enclosed is a list of all:the environmental;reports which have been generated for this site, as <br /> requested in your March 10, 1992 letter: <br /> Chevron has instructed it's consultant, Geraghty and Miller(GM),to connect the new vadose well, ) <br /> V-6, to the vapor extraction and treatment system(VETS) and recommence the operation of the <br /> system as soon as possible. A copy of each GM monthly VETS compliance sampling report will <br /> be forwarded to you at the same time it is submitted to the San Joaquin Air Pollution Control <br /> District. <br /> A comparison of the recent soil.sampling results from V-6 (May 1992) with those of MW79 (July <br /> 1991)and V-3 (January 1989) indicate that remediation-has been completed to a large degree in the <br /> area around the former underground;tanks where soil had been impacted.by hydrocarbons. In <br /> January 1989, before start-up of the VETS,the benzene concentration in V-3 at 26.feet depth was <br /> 160 parts per million(ppm). In July 1991; after the VETS had been running for several months, <br /> the benzene concentration in MW-9 at,26 feet depth.had decreased to 1.7 ppm. The recent- <br /> sampling of V-3 in May 1992, which.followed more Ihana year of.VETSoperation, showed no <br /> detectable benzene at the 26 feet depth although a trace level (0.12 ppm) was detected at 28 feet. <br /> From the above comparisonit seems that the efficient use of the VETS 'system at this sit e{is <br /> drawing to a close. I would find it very,helpful;to understand your position regarding;the cntena <br /> which should be used to determine when it'may be appropriate to remove the'systetn from the site. <br /> I would like to point out that there is a sharp demand'at other Chevron environmental sites forsoil <br /> vapor remediation equipment such as the VETS which has been employed atahissite... Chevron <br /> hopes to move expensive remediation equipment off of sites which have been largely "cleaned=up" <br /> and which do not any longer allow for efficient remedial efforts and onto sites which have a great 1 <br /> need for and could benefit more from the equipment: <br /> i <br /> Rand latrls - 'r <br />