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Weldon Church Site Background Information Page 5 of 12 constrain the plume of impacted soil to the immediate vicinity of the former UST excavation. The lateral extent of impacted ground water appears to be delineated in all directions from the former UST excavation. Laboratory analysis of ground water samples collected from well MW-4, north of the former UST excavation, has consistently detected TPH-g and BTEX. Sample analytes have also generally been detected in samples from well MW-1. These detections, however, were not confirmed north of well MW-4 with additional soil borings toward the north, east, and west of MW-4. QUARTERLY GROUND WATER MONITORING EVENTS From July 1996 through December 2007, AGE conducted thirty-eight ground water monitoring events at the Weldon Church site. Of the seven on-site and off-site wells, only wells MW-1 and MW-4 have been impacted by petroleum hydrocarbons. The fuel components detected have been TPH-g and BTEX, although MTBE and 1,2-DCA have been infrequently reported prior to 2005. High concentrations of TPH-g, benzene, toluene, xylenes, and 1,2-DCA had been reported in the ground water samples collected from MW- 1 at high concentrations until 2005. In 2005, AGE conducted three ground water monitoring events at the site. At the time of the third quarter monitoring event, AGE was unable to access monitoring well MW-1 due to the presence of a new fence and guard dog on the site. In 2006, TPH-g and BTEX concentrations in wells MW-1 and MW-4 continued to decline from abrupt increases in 2001. At the time of the fourth quarter monitoring event, only benzene in well MW-4, at a concentration of 13 pg/I, exceeded California's Department of Health Services Maximum Contaminant Levels for contaminants in drinking water. In 2007, with the exception of the March 2007 monitoring event, TPH-g and BTEX concentrations increased in well MW-4. Petroleum hydrocarbons had not been detected in well MW-1 for six consecutive quarters, however in June 2007, TPH-g and BTEX compounds were detected in well MW-1 at a concentration of 600 pg/I (TPH-g), 54 pg/I (benzene), 27 pg/I (toluene), 8.4 pg/I (ethylbenzene), and 94 pg/I (xylenes). During the Octoberand December 2007 monitoring events petroleum hydrocarbons were not detected in well MW-1. Petroleum hydrocarbons had not been detected in well MW-3 since sampling began in July 1996, however during the December 2007 monitoring event TPH-g was detected at a concentration of 100 pg/l. Advanced GeoEnvironmental,lite.