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Chevron Products Company Page 3 Chevron Station #9-3232 9660 Lower Sacramento Road Stockton, California October 23. 2001 Twelve wells were identified within the one-mile radius of the subject site. The closest well, a City of Stockton municipal supply well , is located approximately 1 ,690 feet south of the site. DWR well data is summarized in Table 2. A site map with permitted water well locations is included as Figure 3 . Neighborhood Well Survey In order to determine the location of undocumented wells, a SECOR representative conducted a door-to-door survey of the area. On July 18 , 2001 SECOR' s representative went to businesses , commercial buildings, and personal residences within a 2,000-foot radius of the site to interview property owners or residents about possible wells on their property. If the property owner or resident was not present at the time of the survey, a well survey form, along with a self-addressed envelope was left in their mailbox. No well surveys were returned from the survey area. WORK PLAN FOR FURTHER SITE ASSESSMENT Concentrations of TPHg, TBA, and 1 -2 DCA were detected in groundwater samples collected from CPT- 1 through CPT-4. SECOR proposes installing three nested pairs of groundwater monitoring wells (1 shallow and 1 deep) in the area between CPT- 1 and CPT-2, the area between CPT-3 and CPT-4, and downgradient of CPT-3 and CPT-4 to confirm and monitor these chemicals. TPHg was also detected in the groundwater sample collected at CPT-6. SECOR proposes installing a single shallow well near this location. The specific scope of work is discussed below: • Groundwater Monitoring Wells. The groundwater monitoring wells will be advanced using 8-inch diameter hollow-stem augers in the general locations shown in Figure 2. The shallow wells will be advanced to a depth of approximately 50 feet below ground surface (bgs). The deeper wells will be advanced to a depth of not more than 70 feet bgs. Upon completion of drilling, a 2-inch diameter groundwater monitoring well will be installed in each of the borings. The shallow wells will be screened from approximately 10 feet above to 10 feet below first encountered groundwater and the deeper wells will be screened across the bottom 5 to 10 feet of the borehole, depending on soil stratigraphy. Soil samples will be collected continuously in the deeper of the nested wells and every five feet in the single shallow well. No soil samples will be collected from the shallow nested wells due to their close proximity to the deeper continuously cored wells. • Permitting. The applicable permits for groundwater monitoring wells will be obtained from the City of Stockton and San Joaquin County prior to drilling. An access agreement will also be obtained for the offsite wells . • Soil Selection and Analysis. Soil samples collected at 5-foot intervals will be sent under chain-of-custody procedures to a California State-certified laboratory for analysis of TPHg and methanol using modified EPA Method 8015, BTEX by EPA IAChevron\93232\REP0RTS\93232 CPT SA 2001 Am