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� 1117 Lone Palm Avenue, Suite Modesto, CA 953511 www.atcassociates.com 209-579-2221 .� ASSOCIATES I NC . Fax 209-579-2225 Environmental,Geotechnical and Materials Engineers February 22, 2006 54.28349.0001 Ms. Lori Duncan FEB 2r R L06 San Joaquin County Environmental Health Department ENViRQI' MEN HEALTH 304 E. Weber Street, Third Floor PERMIT/SERVICES Stockton, California 95202 Subject: Fourth Quarter 2005 Monitoring Report, Former Stockton City Taxi Cab Company, 2085 East Fremont Street, Stockton, California Dear Ms. Duncan: This report presents the results of quarterly groundwater monitoring and sampling performed during the fourth quarter of 2005, by ATC Associates Inc. (ATC) at the site located at 2085 East Fremont Street in Stockton, California (Figures 1 and 2). Sampling was performed to monitor the distribution of petroleum hydrocarbons in groundwater. Monitoring was performed to determine the groundwater flow direction and the hydraulic gradient in shallow and deeper groundwater. SITE HISTORY In 1998, two 10,000-gallon gasoline underground storage tanks (USTs) and associated product piping were removed from the site by Advanced GeoEnvironmental. Soil samples were collected from the tank pit and under product piping and analyzed for petroleum hydrocarbons. Analytical testing indicated the samples collected from the tank pit contained detectable concentrations of petroleum hydrocarbon constituents. In February 2000, WHF, Inc. (WHF) advanced two soil borings, B 1 and B2, to depths of approximately 81.5 and 31.5 feet below ground surface (bgs), respectively. Soil and groundwater samples were collected from the borings and submitted for laboratory analyses. These soil.and groundwater samples contained detectable concentrations of petroleum hydrocarbon constituents. In July 2003, WHF advanced six soil borings, four of which were completed as monitoring wells MW 1 through MW4. Soil samples collected from these borings contained detectable concentrations of petroleum hydrocarbon constituents. Petroleum hydrocarbons were detected in groundwater samples collected from MW 1 through MW4. From November 10 to November 12, 2004 and November 15 to November 17, 2004, an ATC geologist supervised the installation of monitoring wells MWS through MW12. Soil samples were i collected from the boreholes of MW5, MW6, MW7, MW8, MW9, MW 10, MW 11, and MW 12 and selected soil samples were submitted for laboratory analyses. Each well was constructed with 2-inch diameter PVC casing, with MW8, MW9, MW10, and MW11 extending to a depth of 65 feet bgs in s:lenviramental1283491reports12005 4QMR.doc I ATC Associates Inc.