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Mr. Harlin Knoll July 31,2002 San Joaquin County Public Health Services Project No. 2007-0065-01 Page 2 On May 4 and 5, 2000, Stratus installed two groundwater monitoring wells (MW-9 and MW-10) to assess the lateral extent of petroleum hydrocarbon impact southwest of the site. Stratus also installed one air sparge well (AS-1) in the vicinity of the active pump islands. Monitoring well MW-5, located in the shoulder of Lower Sacramento Road, was destroyed on May 5, 2000. The City of Lodi requested the abandonment of well MW-5 due to a proposed street widening project. All existing monitoring wells (with the exception of MW-7) and the newly installed MW-9 and MW-10 were surveyed on August 4, 2000 by Morrow Surveying, Inc. The location of the wells is shown on Figure 2. During the resurvey MW-7 was not located. Stratus installed a soil vapor extraction system (SVES) in July and August 2000. A system startup and source test was conducted on August 15, 2000. The results of the startup and source test were reported to San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) on October 19, 2000. . Stratus installed one vapor extraction well (VW-1) on May 2, 2001. Stratus connected well VW-1 to the SVES on May 3, 2001. GROUNDWATER GRADIENT AND DIRECTION The second quarter 2002 groundwater monitoring event was conducted on May 2, 2002. The activities consisted of measuring groundwater levels, purging the groundwater monitoring wells, and collecting groundwater samples for chemical analysis. Groundwater levels were measured using an electronic sounding device and recorded on the field data form presented in Appendix A. Table 1 presents the historical and second quarter 2002 groundwater elevation data. Field sampling procedures are presented in Appendix B. At the time of the second quarter monitoring event, groundwater was encountered at depths ranging from 41.65 to 43.62 feet below ground surface (bgs). The measured water levels were corrected to mean sea level (MSL) and used to plot a groundwater elevation contour map. Figure 2 presents groundwater elevations and contours for the second quarter 2002 monitoring event. The groundwater flow direction was calculated to be towards the south-southeast at an _ average gradient of 0.001 ft/ft. A south-southeast groundwater flow direction is consistent with previous monitoring events (before the SVES was operational). PAUSA Gasoline100651Qtrly120021USA_65_2Q02.doc 5T'RArU5