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Chevron Products Company 3 Chevron Station#9-4275.2905 $e4.0.Holt Drive,Stockton.California February 23,2001 46 penetrometer tests (CPTs), installation of one sentry well, and the collection of soil and groundwater samples. A groundwater extraction system, including three groundwater extraction wells, conveyance piping and treatment facilities may be constructed contingent on the results from the assessment. The specific scope of work is discussed below: • Direct Push Borings. Approximately ten direct push soil borings will be advanced at the general locations shown on Figure 2. Each CPT will be performed to obtain lithologic and hydrogeologic information. Based on the lithologic information and pore pressure dissipation test results collected during each CPT, three to four depth discrete groundwater samples will be collected to evaluate the presence of chemicals of concern in groundwater at specific depths. The locations of depth discrete samples will be determined in the field. The CPTs will be advanced to approximately 100 feet bgs. • Sentry Well. One sentry well will be completed into the groundwater system hydraulically connected to Municipal Well No. 10. The well will be drilled at the location shown on Figure 2- Site Plan using 8-inch diameter hollow-stem augers to approximately 90 feet bgs. Upon completion of drilling, a 2-inch diameter groundwater monitoring well will be installed in the boring. The well will be screened from approximately 85 feet bgs to 90 feet bgs and sealed from surface to the bottom of the clay confining layer at approximately 72 feet bgs. • Soil and Groundwater Analysis. Depth discrete samples collected from the CPTs will be submitted to a California State-certified laboratory and analyzed for the presence of TPHg, benzene, toluene, ethylbenzene, and xylenes (BTEX), and MtBE by EPA Method 8250. A groundwater sample from the sentry well boring will also be submitted for analysis. • Report. A report will be prepared after completion of necessary fieldwork and upon receipt of laboratory analytical results. A conceptual site model will be developed using this physical and chemical information. Calculations will be provided for mass flux and mass discharge. Data analysis, CPT logs, boring logs, well construction details, site map, as well as soil and groundwater analytical reports, and chain-of-custody records will be provided. Findings and recommendations that support the need for further work, including groundwater extraction wells will be presented, if needed. • Groundwater Extraction Wells. If needed, approximately three groundwater extraction wells will be drilled at the general locations shown on Figure 2-Site Plan. Each well will be constructed to a depth to IAChevron1942751REP0RTS12001 Assessment_RevB.doe