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1 of t Canepa's Car Wash 248 East Park Street,Stockton,California Fust Quarter Groundwater Monitoring Report,January 2006 Page 2 of 5 Summary of January 2006 Quarterly Groundwater Monitoring Results Field Activity Number of monitoring wells 7 Number of monitoring wells sampled 7 Dates monitored 1117/06 Site Hydrology Average depth to groundwater below Average increase(+)/decrease(—) in -0 81 foot monitoringwell measuring 26 48 feet depth to groundwater since last g points (MW-3 excluded*) sampling The lowest(deepest) groundwater Approximate groundwater flow direction North elevation has consistently been measured at monitoring well MW-2 Groundwater Contamination Wells containing free product None Wells with petroleum hydrocarbon 4 odor noted Number of wells with benzene Number of wells with benzene concentrations below the benzene MCL 5 concentrations at or above the 2 benzene MCL Range in concentrations Benzene(pg/L) <0 5—7,400 BTEX Toluene(pg/L) <0 5---770 MTBE Ethyl Benzene(pg/L) <0 5—2,200 Nature of contamination TPH-G Total Xylenes(pg/L) <1 0—5,600 MTBE(pg/L) <0 5—2 1 TPH-G(mg/L) <0 05—42 0 • *Depth-to-water measurements for monitor well MW-3 were not used to calculate average change in depth to groundwater because the groundwater elevation measured in the well during the previous monitoring event appears to be anomalous FIELD OBSERVATIONS All monitoring wells were purged using a clean, single-use, polypropylene, disposable bailer Approximately three well casing volumes of water were purged from each well No sheen or separate phase petroleum was noted in the initial groundwater field inspection samples from the wells A strong hydrocarbon odor was noted in monitoring wells MW-2 and MW-5 A slight hydrocarbon odor was noted in monitoring wells MW-3 and MW-6 GROUNDWATER ELEVATIONS AND GRADIENT The static water level in each well was measured to the nearest 0 01 foot with a battery-operated, flat tape, water level indicator The groundwater monitoring field forms and groundwater measurement field form are included m Attachment C The groundwater table has been above the top of all well screens since the August 1996 monitoring event The average groundwater elevation measured during the January 2006 monitoring event was 0 81 foot higher than measured in October 2005 The groundwater elevation measured on October 7, 2005 in monitor well MW-3 appears to be anomalous and may be a result of a potential calculation/equipment error or malfunction, the data point for MW-3 was consequently not used in groundwater elevation change calculation The groundwater elevation contours for the current monitoring event indicate a groundwater gradient variable across the Site, but generally toward the north Ow �� CONDOR