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Second Quarter,2003 Quarterly Groundwater Monitonng Report Canepa's Car Wash,Pacific Avenue,Stockton CA Page 2 Table 1 �} Summary of April 2003 Quarterly Groundwater Monitoring Results Field Activit Number of oundwater wells 11 Number of groundwater wells sampled 7 Number of groundwater wells 11 Date(s) monitored and sampled 4/1 7-1 8103 monitored Site Hydrology Average depth to groundwater below 35 38 feet Average increase(+)/decrease H in - 1 01 feet monitoring well measuring points depths to groundwater since last sampling (Shallower) Approximate flow direction and Northeast 0 0054 ft/ft as measured between wells groundwater gradient MW-5 and MW-6 Groundwater Contamination Monitor wells containing free product None Monitor wells noted to have hydrocarbon 2 odor Number of monitor wells with 2 Number of monitor wells with 5 concentrations below both the benzene concentrations at or above either or both and MTBE MCLs the benzene and MTBE MCLs Nature of contamination BTEX, Range of analyte concentrations detected TPH-G, in the monitor wells Gasoline Benzene(gg/L) <0 5— 11,000 Oxygenates Toluene (gg/L) <0 5—490 /Additives Ethyl Benzene(pg/L) <0 5— 1,800 Total Xylenes(µglL) <1 0—2,790 TPH-G (mg/L) <0 05—57 MTBE(pg/L) <0 5-630 1,2-DCA(µg/L) <0 5- 120 i TBA(g L) <2 5- <5 0 FIELD OBSERVATIONS On April 17 and 18, 2003, Condor representatives made field observations at the 11 site monitor wells (MW-1 through MW-7, MW-9 through MW-11, and MW-121)), and at one soil vapor extraction (SVE) well (SV-4) Field observations included water level measurement (Table 2, on the following page), appearance of samples (color, clarity, and presence of petroleum product sheen or phase in samples), and collection of water quality field parameters Field observations are included in the field forms, Attachment D No sheen or separate phase petroleum was noted in bailed field inspection samples collected from the wells, however, a sheen was present in the purge water from SV-4, and a broken sheen was present in the purge water from MW-2 A slight and strong sulfurous odor was noted in monitor wells MW-12D and MW-4, respectively, and a strong petroleum odor was noted in monitor wells MW-1, MW-2, and in soil vapor extraction well SV-4 GROUNDWATER ELEVATIONS AND GRADIENT Groundwater elevation contours estimated for the shallow monitor wells (MW-1 through MW-7 and MW-9 through MW-11) on April 17, 2003, indicate that the groundwater gradient is to the northeast and is generally consistent with previously estimated groundwater gradients (Figure 2, attached) Monitor well MW-12D was not used in groundwater elevation contouring due to the well's deep screen interval An estimated groundwater gradient of 0 0054 ft/ft towards the northeast was measured using water level data - — from monitor wells MW-5 and MW-6 The average depth to groundwater measured in the 11 monitor wells at the site decreased by approximately 1 01 feet since January 14, 2003 A hydrograph of historic 4M �1� CONDOR