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,c Date: October 27,2003 Quarter 3`a Quarter,2003 • ARCO QUARTERLY GROUNDWATER MONITORING REPORT Facility No 0434 Address 501 W Kettleman Lane, Lodi, CA ARCO Environmental Engineer _Paul Supple Consulting Co/Contact Person URS/Vernon Elarth Consultant Project No 38466243 OL058 Primary Agency/Regulatory ID No San Joaquin County Environmental Health Services SJCEHS Assembly Bill 681 Status Property owned by Mark Garibaldi WORK PERFORMED THIS QUARTER (Third 2003): 1 Performed quarterly groundwater monitoring and sampling 2 Prepared and submitted quarterly groundwater monitoring report WORK PROPOSED FOR NEXT QUARTER (Fourth 2003): 1 Quarterly groundwater monitoring and sampling has been scheduled for December 2003 If closure 1s granted, sampling will not be performed and a workplan for monitoring well destruction will be submitted QUARTERLY RESULTS SUMMARY (Third 2003): . Current Phase of Project Monitoring Frequency of Groundwater Sampling W-1 A, W-2, W-2A, W-213, W-3, W-9 sampled quarterly Frequency of Groundwater Monitoring Quarter) Is Free Product (FP) Present on Site No FP Recovered this Quarter NA Cumulative FP Recovered to Date NA Current Remediation Techniques Natural attenuation Approximate Depth to Groundwater 60 49 to 62 42 feet below ground surface Groundwater Gradient Southeast @ 0 0002 ft/ft ANALYTICAL DATA REVIEW: Based on the review of the analytical and hardcopy data (chain-of-custody records, blanks, dilutions,holding times, LCS/LCSD results, MS/MSD results, and surrogate recoveries), the data are acceptable as reported by the laboratory DISCUSSION: Low level concentrations of benzene, total xylenes, and methyl tert-butyl ether (MtBE) were reported in the groundwater sample collected from W-2A this quarter No other analytes were reported above method detection limits in any other groundwater sample collected from site monitoring wells this quarter Groundwater elevations across the site increased relative to the previous reporting period The inferred direction of groundwater flow across the site was toward the southeast at an average hydraulic gradient of 0 0002 ft/ft Wells W-2 and W-2A,clustered 1n the southeast portion of the site have overlapping screen intervals but exhibit significantly different water levels The water level obtained from well W-2A was not used in contouring on Figure 1 because it appears to be anomalous when compared with water levels obtained from the other site wells The water level obtained from well W-2B was not used 1n contouring because the well is screened in a deeper water-bearing zone K XWprocess115 6P ARC01W434VQ--0eT1Y%3 QTR 03W34 GWMR 3003 doe Page 1