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3.3 LABORATORY ANALYSIS AND RESULTS Fourteen groundwater samples were submitted for analyses to Centrum Analytical of Redlands, California, a State of California-certified hazardous waste analytical laboratory. ._� The samples were analyzed for the following: EPA 8015 modified -Total petroleum hydrocarbons as Gasoline (TPH-G); ; 1 • EPA 8015 modified - Total Petroleum Hydrocarbons as Diesel (TPH-D); • EPA 8020 — Benzene, Toluene, Ethylbenzene, Total Xylenes (BTEX), and Methyl Teri Butyl Ether (MTBE); • EPA 8260 —Volatile Organic Compounds (VOCs); Additionally, Tertiary Butyl Alcohol (TBA), Di-Isopropyl Ether (DIPE), Ethyl Tertiary Butyl Ether (ETBE), and Tertiary Methyl Ether (TAME) were analyzed. EPA Method 8260 detected none of these compounds. =� A summary of the laboratory results for groundwater samples is presented in Table 1. A copy of the laboratory reports and chain-of-custody records are presented in Appendix B. The following are the results of the groundwater sampling: TPH-D concentrations were detected in groundwater samples from two wells, MW-6 1=- (970 pg/1) and VW-2 (2,900 pg/1). -=---:, • TPH-G concentrations were detected in groundwater samples from two wells, (1,500 pg/1) and VW-2 (7,800 pg/l). • Benzene concentrations were detected in groundwater samples from four wells, MW-1 (5.0 pg/1), MW-2 (1.0 pgll), MW-6 (12 pg/1), VW-1 (30 pg/1), and VW-2 (1,100 pg/1). E-s These concentrations equal or exceed the Maximum Contaminant Leel MCL or benzene in drinking water(1.0 pg/1). • Concentrations of toluene, ethylbenzene, and xylenes were detected in site wells by EPA method 8020. Toluene concentrations were detected in Wells MW-1 (4 pg/I) and =i VW-2 (360 pg/1). Ethylbenzene concentrations were detected in Wells MW-1 (3.0 pg/1), MW-6 (12 pg/1), VW-1 (3.0 pgll), and VW-2 (290 pgll). Xylenes were detected in Wells MW-1 (14 pg/1), VW-1 (0.4 pg11), and VW-2 (1,100 pg/I). • MTBE concentrations were detected in Wells MW-6 (7.6 pg/1) and VW-2 (54 pg/1). } • A trace concentration of chloroform was detected in the groundwater sample from Well VW-1 (0.9 pg/1). = 1 Concentrations of 1,2-Dichloroethane (1,2-DCA) were detected in Wells MW-6 (53 pg/1), MW-11 (14 pg/I), MW-12 (11 pg/1), and VW-2 (19 pg/1). These concentrations exceed the MCL for 1,2-DCA for drinking water (0.5 pg/i). . �. F:Transfer\Report\CALTRANS\Cally097 571917\STOCKTON1gm498rin 3