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Wright Environmental Services, Inc. Construction • Engineering • Remediation December 31, 2003 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 for October 30,2003 Site at 595 East 11th Street, Tracy,CA Dear Ms Brown, Wight 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 Environmental Health (EHD)for site quarterly groundwater monitoring for the dissolved plume • Momtoring Well Sampling Methods The site was sampled on October 30, 2003 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 attached groundwater 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 uvtial 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 mtmmum headspace The sample container was then immediately rapped, 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 depth to groundwater was corrected for the separate phase product layer The groundwater flow direction was northerly under a calculated gradient of 0 0025, which is consistent with histone observed trends Overall groundwater levels appear to have declined roughly 0 75 feet from the previous quarter This decline in groundwater levels is attributed to the draining of the 48" diameter irrigation pipeline that bisects the site running north to south westerly of MW-3 and MW-9 67 E 10th Street . Tracy, CA 95376 209 833 0758 . Fax 209 832 5152 wright@utreach corn Lic x#651501 4-B HazMat C21 Page 1 websit hap 11wnghtenvtronmentalsemces corn