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A S S O C I A T E S one boring, SB-1, contained detectable concentrations of toluene, ethylbenzene, and xylenes. A grab groundwater sample was also collected .from boring SB-1 and contained detectable concentrations of TPHg and toluene, ethylbenzene, and xylenes. The samples from perimeter borings SB-2, SB-3, and SB4 did not- contain detectable concentrations of petroleum hydrocarbons. No groundwater samples were collected from the perimeter borings (SB-2, SB-3, and SB4) to evaluate the lateral extent of dissolved hydrocarbon constituents. The results of the analysis are presented in Attachment 1. After presenting the results of the soils investigation to PHS/EHD in a report prepared by Helmick and Lerner Inc. titled Preliminary Site Assessment- Stagg High School dated September 23, 1997, PHS/EHD requested additional work at the site. Helmick and Lerner Inc. subsequently submitted a workplan titled Work Plan for Installation of Monitoring Well, Stagg High School- Stockton Unified School District dated February 6, 1998. The workplan purposed methods and procedures evaluate groundwater for the presence of petroleum hydrocarbons with the installation of a single monitoring well. This workplan was approved by PHS/EHD, in correspondence dated March 25, 1998. On February 25, 1999, ATC supervised the advancement of soil boring MW-1 to a total depth of 24.5 feet bgs. This soil boring was subsequently converted into a 2-inch diameter PVC monitoring well which was completed at a depth of 23 feet bgs. Soil samples collected from boring MWl at 10.5 feet bgs and 23.5 feet bgs contained concentrations of for total petroleum hydrocarbons as gasoline (TPHg) at 1,900 part per million (ppm) and 2.5 ppm, respectively. The initial groundwater collected from well MWl contained concentrations of TPHg (3,900 part per billion (ppb)), toluene (86 ppb), ethylbenezne (100 ppb), total xylenes (530 ppb), and methyl tertiary butyl ether (MTBE) (12.5 ppb). Subsequent quarterly sampling events have shown decreasing concentrations of dissolved petroleum hydrocarbon constituents over time. Analytical results of soil samples are summarized in Table 1. Analytical results of groundwater samples are summarized in Table 2. SCOPE OF WORK Plannine and Permits ATC has completed the soil boring permit application for the proposed subsurface investigation. The permit application and associated fees (check no. 384) are attached to this workplan (Attachment 2). Following,the approval of this workplan and soil boring permit approval, ATC will schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform any other necessary field preparation and job start- up activities. A private underground utility locating service may be warranted due to the proximity of nearby underground sewer, gas, and electrical lines. w:117292.0002Vq)ortslwkp.d00 2