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Chevron Products Company �� Page 3 Chevron Station##9-1452 334 East N n Street Ripon,California —Now October 29 2001 fi The groundwater sample collected from Geoprobe boring GP-3 at 39 ft bgs contained benzene, xylenes, MtBE, and TAME at concentrations of 0.51 pg/l, 0.91 µg11, 76 µg/l, and 5.3 µg/l, respectively. No other target analytes were detected above the method reporting limits in the three water samples analyzed by the laboratory. Stockpiled Soil. Less than 1 cubic yard of soil, generated while drilling GP-1 through GP-3, was placed on plastic sheeting and covered. Four soil samples from the stockpile were collected and submitted to the laboratory. The soil samples were composited to one soil sample and analyzed for TPHg, BTEX, and lead. Toluene was detected in the sample at 0.058 mg/kg. Stockpiled soil analytical data is presented in Table 1. CONCLUSIONS MtBE was detected in soil and groundwater samples from Geoprobe boring GP-2 and in groundwater samples from Geoprobe borings GP-1 and GP-3. TAME was also detected in groundwater samples from all three borings. Benzene and xylenes were detected in groundwater from Geoprobe borings GP-2 and GP-3. MtBE concentrations in all Geoprobe borings exceed California primary and secondary drinking water quality goals of 13 and 5 µg11, respectively. Based on the results of the water samples from the Geoprobe borings, SECOR recommends that the four current wells and the five wells proposed in the following section be placed on a quarterly monitoring and sampling program. This program will be initiated during the fourth quarter 2001. PROPOSED SCOPE OF WORK Based on the data collected during this site assessment, SECOR proposes installing two additional shallow groundwater monitoring wells and three deeper groundwater monitoring wells along the southern property boundary (Figure 2). The specific scope of work is discussed below: + Groundwater Monitoring Wells. The soil borings for the wells will be advanced adjacent to the Geoprobe boring locations as shown in Figure 2, using 8-inch diameter hollow-stem augers, to a depth of approximately 40 feet bgs for the two shallow wells and to approximately 60 feet bgs for the three deeper wells. The deeper borings will be continuously cored below 40 feet bgs to log soil stratigraphy. Soil samples will be collected at 5-foot intervals below 40 feet bgs in the deeper borings for chemical analysis. Upon completion of drilling, a 2-inch diameter groundwater monitoring well will be installed in each of the borings. The wells will be screened from approximately 5 feet above to 10 feet I\Chevron1914521REPORTS12001 Geoprobe SA&well wp_Rev B.doc