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rS r <br /> Tosco Marketing Company 3 <br /> Tosco Service Station 8671,8606 Thornton Road,Stockton,CA March 16 1999 <br /> concentrations of 3 06 ppb and 74 8 ppb, respectively TBA, TAME, <br /> DIPE, and EtBE were reported as nondetect in all wells <br /> Groundwater analytical data is presented in Table 2 and is shown on <br /> Figure 2 Field and laboratory procedures are presented as <br /> Attachment B Groundwater sampling parameters are included on the <br /> field sheets in Attachment D <br /> The wells were surveyed to mean sea level by Morrow Surveying, a <br /> licensed surveyor Attachment E contains the surveyor's site plan <br /> showing the locations and elevations of the wells <br /> • Groundwater Flow Direction. Depth to groundwater at the site <br /> ranged from 27 88 feet bgs to 29 32 feet bgs Based on monitonng <br /> data collected on January 15, 1999, groundwater flow was to the <br /> east-northeast at 0 0013 ft/ft and is shown on Figure 3 <br /> • Stockpiled Sail. Approximately three cubic yards of soil generated <br /> during the installation of the four wells was stockpiled onsite One <br /> composite sample (4 sleeves to 1 sample) was collected from the <br /> stockpiled soil and analyzed for TPH-g, BTEX, MtBE and total lead <br /> All analytes were reported as nondetectable Stockpiled soil analytical <br /> data is presented in Table 3 <br />• <br /> SUMMARY OF FINDINGS <br /> o TPH-g, BTEX compounds, and MtBE were reported as nondetect in <br /> all soil samples analyzed <br /> • TPH-g was reported in one groundwater sample (well MW-2) at a <br /> concentration of 100 ppb Benzene was reported in all four <br /> groundwater samples at a maximum concentration of 3 56 ppb MtBE <br /> was reported in groundwater samples collected from monitoring wells <br /> MW-1 and MW-4 at concentrations of 3 06 ppb and 74 8 ppb, <br /> respectively <br /> • February 15, 1998 groundwater monitoring data indicated that the <br /> depth to water was 27 88 feet bgs to 29 32 feet bgs and groundwater <br /> flow was to the east-northeast at 0 0013 ft/ft <br /> CONCLUSIONS <br /> Based on the data collected during this assessment, groundwater beneath the site has <br /> been impacted by relatively low levels of gasoline hydrocarbons <br /> Prior to further assessment activities, additional monitoring and sampling will be <br /> performed to confirm the direction of groundwater flow beneath the site, evaluate <br /> 7G888-010-03/well install doc <br />