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® Concentrations of the gasoline related compounds sec-butylbenzene tert- !-E butylbenzene, isopropylbenzene, napthalene, 1,2,4 trimethyl benzene, and 1,3,5 trim ethyl benzene were detected in samples of site groundwater this quarter. "J 4.0 SUMMARY AND CONCLUSIONS W Based on the December 2, 1998 groundwater data the groundwater flow direction is to the east with a hydraulic gradient of 0.001 meter per meter (0.001 foot per foot). • Average groundwater elevations are 0.57 meters (1.86 feet) higher than the average groundwater elevation measured for the Third Quarter 1998 monitoring event. • TPH-D concentrations were detected in Wells MW-6 and VW-2 ranging from 970 to -'' 2,900 pgll . TPH-G concentrations were detected in Wells MW-6 and VW-2 ranging from 1,500 to 7,800 pgll. Benzene concentrations were detected in Wells MW-1, MW-2, MW-6, VW-1, and VW- 2 ranging from 1 to 1,100 pg/l. These concentrations equal or exceed the MCL for E -- benzene in drinking water. • Concentrations of toluene, ethylbenzene, and xylenes were detected in site wells by EPA method 8020. Toluene concentrations were detected in Wells MW-1 and VW-2 and ranged from 4 to 360 pg/l. Ethylbenzene concentrations were detected in Wells MW-1, MW-6, VW-1, and VW-2 and ranged from 3 to 290 pg/l. Xylenes were detected in Wells MW-1, VW-1, and VW-2 and ranged from 0.4 to 1,100 11. 9 pg • MTBE concentrations were detected in Wells MW-6 and VW-2 by EPA method 8260 i � and ranged from 7.6 to 54 pg/l. • A trace concentration of chloroform was detected in Well VW-1 (0.9 pg/1). Concentrations of 1,2-DCA were detected in Wells MW-6, MW-11, MWA2, and VW-2 ; the concentrations ranged from 11 to 53 pg/l. These concentrations exceed the MCL >j for 1,2-DCA in drinking water. __ • The oxygenates TBA, DIPS, ETRE, and TAME were not detected in the EPA Method 8260 analyses this quarter. F:TransierlReport%CALTRANS4Caliya9717lO1 A.STOCKTONlgm4981in 4