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I _ Quarterly Report - Third Quarter 2004 • PACIFIC CAR WASH I4405 Pacific Avenue, Stockton, California 1.0. INTRODUCTION Advanced GeoEnvironmental,Inc (AGE)has prepared this quarterly report for 4405 Pacific Avenue I (the site), Stockton, California The scope of work included the performance of a quarterly ground water monitoring event and preparation of this report The objectives were to characterize, assess, and monitor concentrations of petroleum hydrocarbons in ground water and to characterize ground water flow direction and gradient at the site The site setting is illustrated on Figure 1 Site structures and monitoring well locations are depicted on Figure 2 This report is prepared in accordance with guidelines issued by the California Regional Water Quality Control Board - Central Valley Region (CRWQCB) for the investigation of underground storage tank(UST)sites A summary of previous investigations at the site was included in the AGE- prepared Feasibility Studies Work Plan, dated 15 February 2002 , ground water monitoring data acquired to date is included in the tables of this report Previous soil characteristics data obtained by Cone Penetrometer Testing (CPT) and during soil . boring/well drilling enabled AGE to define five informal hydrogeologic units (Multi-Level I Monitoring Well Installation Report - Fourth Quarter 2003, dated 10 May 2004) The informal hydrogeologic units were defined as First Water Zone(15 to 45 feet bsg),First Confining Unit(45 to 70 feet bsg), Second Water Zone (70-95 feet bsg), Second Confining Unit (95-115 feet bsg), and Third Water Zone (115 to at least 125 feet bsg) ' 2.0. PROCEDURES On 29 September 2004, a ground water monitoring event was performed at the site on ground water ' monitoring wells MW-1 through MW-19, construction details for each monitoring well are summarized in Table 1 Groundwater monitoring procedures for the site were outlined in WorkPlan Addendum, dated 11 April 2003, prepared by AGE and approved by San Joaquin County Environmental Health Department (SJCEHD) by letter dated 07 May 2003 2 i GDvv1 rL `TVATED iiivi'4.LX u�ivG PROCEDTTO wC On 29 September 2004, depth to ground water was measured in each well from the top of the well casing to the nearest 0 01-foot utilizing a Solinst water level meter The ground water elevation in each well was calculated by subtracting the measured depth to ground water from the surveyed casing elevations(Table 2) Ground water elevations were plotted and contoured on a scaled site map • (Figure 3) Advanced GeoEnvironmental,Inc I