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�CAMBRIA with the exception of one sample from boring B-3 where low concentrations of benzene, toluene, xylenes, and MtBE were detected September 2000, Monitoring Well Destruction Wells MW-1 through MW-5, VEW-1 through VEW-3, RW-1 and RW-2 were destroyed by Gregg Drilling, Inc under the direction of Cambria Monitoring well destruction was necessary to allow for redevelopment of the subject property Site Conditions Site Description The subject site, located on the southwest corner of North El Dorado Street and Channel Street in Stockton, California, is being redeveloped as a pedestrian plaza The site was formerly occupied by a Shell service station The Stockton Deep Water Channel runs under a portion of the site Lithology Sediments underlying the site consist of predominantly clay,silt,and sandy silt and clay to a maximum depth explored of 41 5 feet Some sand lenses were also encountered Hydrogeology Depth to groundwater under the site has ranged from 16 to 37 feet below ground surface (bgs) since 1992 In general, the depth to groundwater has decreased over time During the most recent monitoring event in July 2000,the depth to groundwater under the site was approximately 16 feet bgs The groundwater flow direction beneath the site ranges from southeasterly to northeasterly but is predominantly easterly, at a gradient of approximately 0 01 Hydrocarbon Distribution in Sod-There is no longer significant hydrocarbon mass in soil beneath the site In 1996, Enviros drilled eight soil borings adjacent to previously installed wells and borings to assess the effectiveness of remedial actions at the site Benzene, toluene, xylenes, and MtBE were detected in only one of the 29 soil samples collected, and etylbenzene was not detected in any of the samples TPHg was detected m just four of the soil samples at concentrations ranging from 1 4 to 970 ppm The results of these analyses indicate that the bulk of the hydrocarbon mass at the site has been removed by S V E Hydrocarbon Distribution in Groundwater No TPHg was detected in any of the site monitoring wells during the most recent groundwater monitoring event(July 2000) In addition, no BTEX was detected in site wells,with the exception of MW-4,where benzene and toluene were detected at 1 21 ppb and 1 09 ppb, respectively MtBE has been detected at increasing concentrations at the site,predominantly in former upgradient wells The increasing levels of MtBE at the site suggest a recent release,which is not possible from the subject site since the gasoline USTs at the subject site were removed in 1981, prior to widespread use of MtBE in California Graphs of MtBE concentration versus time for Welts MW-5, MW-1, and VEW-4 are presented in Attachment C As noted previously, groundwater flow beneath the site has ranged from northeasterly to southeasterly,with a predominant easterly flow The graphs show MtBE first appears in the most westerly well(MW-5) MtBE was subsequently detected in Well MW-1, to • the center of the site, and then in Well VEW-4, the most easterly well This trend suggests that the MtBE plume originated west of the site,and is migrating across the site,from west to east The MtBE