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Wright Environmental t cf�T�",i tf�1�f_off Services, Inc. F' f'i 411T. s�_,) 1(,i_ October 14,2003 Construction ♦ Engineering • Remediation 03 OCT 6 QM 1 4a Project No 4090-P Ms Janice Brown c/o Cox&Cox 1593 Arrowhead Drive St Helena,California 94574 Re: Cox&Cox,Quarterly Monitoring Well Sampling Report Site at 595 East 11th Street,Tracy,CA Dear Ms Brown, Wright Environmental Services, Inc (Wright) has prepared this quarterly monitoring well sampling report for the above referenced site As you know, several phases of work have been performed at this site This quarterly groundwater monitoring work is in response to a request from the San Joaquin County Public Health Services (PHS EHD)for site quarterly groundwater monitoring for the dissolved plume Monitoring Well Sampling Methods The site was sampled on August 25, 2003 Well MW-6 was not sampled due an automobile parked over that wellhead The attached table(s) lists the wells historic and current groundwater level data (see Table 1) The contract sampler proceeded to purge well volumes of groundwater using a submersible electric purging pump or bailer (a volume calculation was done for each well following sounding measurements) Conductivity, pH, and water temperature measurements were obtained between each well volume purge, and these were noted on the attachedgroundwater sampling information sheets Once these readings stabilized after two consecutive purge volumes, aquifer water was assumed to be entering the well When the well recovered to about 80% of the initial water level, the sample was collected Purge water was stored on-site in drums The well sampling information sheets are attached Each groundwater sample was collected with a new disposable bailer The groundwater sample was then poured with minimum cavitation into the appropriate, laboratory prepared sample containers leaving minimum headspace The sample container was then immediately capped, labeled under chain-of-custody documentation and placed in a chilled ice chest for shipment to STL/Chromalab, Inc in Pleasanton, California(a State Certified Testing Lab) Groundwater Contour Map and Flow Gradient A groundwater contour map to a known datum was prepared for the data listed in Table 1 (see Figure 1) The groundwater flow direction was northerly under a calculated gradient of 0 003, which is consistent with historic observed trends Overall groundwater levels appear to have declined roughly 0 75 feet from the previous quarter Chemical Analytical Methods and Resuits Eight groundwater samples were analyzed using EPA Methods 5030/8015 602 and 8260 for Total Petroleum Hydrocarbons as Gasoline (TPHG), Benzene, Toluene, Ethvlbenzene and Xylene (BTEX) and tuel oxygenates including Methyl-tert-butyl-ether (MTBE), Tert-Butyl Alcohol (TBA), Di-isopropyl Ether (DIPE), Ethyl tert-butyl ether(ETBE),Tert-Amyl Methyl Ether TAME) The analytical results of the groundwater samples for this sampling event are attached and listed below in Table 1 (and Figures 2, 3 and 4) and historic data is presented in attached historic sampling data spreadsheet Table 2) i 67 E 10th Street . Tracy, CA 95376 209 833 0758 e Fax 209 832 5152 wright@inreach com Lic ;6SLi01 rt-B HacMat Page 1 �4M. websit hup 11home inreach com/wright 1�