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.� Chevron Products Company Page 3 Chevron Service Station 9-9840,4344 Waterloo Road,Stockton,California September 20,2001 DISCUSSION OF FINDINGS • Based on the data collected during this assessment, low concentrations of petroleum hydrocarbons are present In the soil around CPT-6 and CPT-7, and generally decrease to below laboratory detection limits with depth Vertical definition was achieved in all of the borings except for CPT-7, which had a detection of MtBE (24 mg/kg) In the 60-foot sample Low levels of petroleum hydrocarbons are also present in groundwater beneath the site in the areas between CPT-3 and CPT-7 Groundwater contamination was not defined in the downgradient direction The detections of petroleum hydrocarbons indicate groundwater generally flows towards those boring locations (northwest to northeast) This would be consistent with the groundwater flow direction observed during previous groundwater monitoring episodes performed at the site RECOMMENDATIONS/WORK PLAN FOR FURTHER SITE ASSESSMENT Based on the data collected during this site assessment, SECOR proposes installing three offsite wells In the shoulder of Waterloo Road just north of CPT bonngs CPT-7 and CPT-5, and the Subway building An additional well will be advanced In the vicinity of CPT-2 along the eastern property boundary The proposed well locations are shown on Figure 3 The specific scope of work is as follows • Groundwater Monitoring Wells. Four soil borings will be advanced using an 8-inch diameter hollow-stem auger to an approximate depth of 75 feet bgs Upon completion of drilling, a 2-mch diameter groundwater monitoring well will be installed in each boring The monitoring wells will be screened from approximately 5 feet above to 10 feet below first encountered groundwater • Permitting The applicable permits for the soil borings will be obtained from San Joaquin County, the City of Stockton, and the California Department of Transportation (CalTrans) prior to drilling • Soil Sample Selection and Analysis. Sol] samples will be collected at 5-foot intervals and field screened for petroleum hydrocarbons utilizing a photo ionization detector (PID) or an organic vapor meter(OVM) Selected samples will be sent under chain-of-custody protocol to a California State-certified laboratory Selected soil samples will be analyzed for TPHg, BTEX, and the fuel oxygenates Additionally, the capillary fringe and the bottom sample from each boring will be submitted for chemical analysis • Monitoring Well Development and Sampling. After installation, the monitoring wells will be developed by rigorously surging the wells over the length of the screen interval and by purging approximately 10 casing volumes of water After well development, groundwater samples will be collected from each well and sent under standard chain-of-custody procedures to a • California State-certified laboratory The groundwater samples will be analyzed for TPHg, BTEX, and the fuel oxygenates I 1Chevron1998401REPORTS199840 CPT SA&WPFSA(4 wells)doe