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1 Weldon Church Site Background Information •' Page 4 of 4 �I in the samples analyzed. ' Seventeen ground water samples were analyzed; TPH-g and BTEX compounds were detected only in the grab ground water samples collected at water-table depth(approximately 10 feet bsg) and at ' total depth of borings B 17 and B 18. The highest concentrations of contaminants were detected in the water table samples at 160,000 µg/1 TPH-g in sample B17-1, and 5,600 µg/1 benzene, 14,000 µg/1 toluene, 3,200 µg/1 ethylbenzene, and 12,000 µg/1 xylenes in sample B 18-1. At total ' depth,maximum TPH-g concentration was 3,900µg/l(B 18-2);however,the BTEX concentrations were considerably lower;benzene was not detected,maximum toluene concentration was 3.8 µg/1 (B18-2), maximum ethylbenzene concentration was 2.2 µg/1 (B17-2), and maximum xylene ' concentration was 16.8µg/l(B 18-2).No other target analytes were detected in the samples analyzed. ' A total of 24 soil borings have been advanced on and off the site, seven of which have been completed as ground water monitoring wells,providing data concerning hydrocarbon impact on soil and ground water, soil composition, and ground water flow direction. Laboratory analysis of soil ' samples collected from monitoring wells and soil probe borings 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 2005, AGE conducted twenty-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 appear impacted bypetroleum hydrocarbons;the fuel components detected have been TPH-g and BTEX, although MTBE and 1,2-DCA have been infrequently detected prior to 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 Ia new fence and guard dog on the site. In 2005,TPH-g and BTEX concentrations in wells MW-1 and MW4 continued to decline from the j Iabrupt increases in 2001.At the time of the fourth quarter monitoring event,petroleum hydrocarbons were not detected in well MW-1, and only benzene in well MW-4, at a concentration of 15 µg/1, exceeded California's Department of Health Services Maximum Contaminant Levels for contaminants in drinking water. I I Advanced GeoEnvironmental,Inc.