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MW-6 has intermittently had low levels of toluene (12 to 38 µg19) since it was installed. Ethylbenzene and ' xylenes were detected during the March 1994 sampling event at 8.8 and 33 µg19 respectively. SECOR conducted a Phase I Environmental Site Assessment of the site in July 1995. At the time of the initial ' inspection,there were seven USTs (two gasoline,five septic)on the King Island property. Based on previous investigations,SECOR recommended that a soil and groundwater investigation be conducted ' on both the King Island and Holiday Harbor portions of the site. This report outlines the details of the investigation. ' 1.3 REGIONAL GEOLOGIC AND HYDROGEOLOGIC CONDITIONS - The site is located on King Island, within the Sacramento River Delta. The primary structural features in this region are the Midland Fault Zone located 10 miles west of the site and the Stockton Fault located approximately 15 miles to the south. The Midland Fault Zone trends northwest/southeast and the Stockton Fault trends northeast/southwest. Based on information obtained from the United States Geological Survey's Geology of the Fresh Groundwater Basin of the Central Valley, the site lies on Holocene flood basin deposits. ' Soil in the area includes mud, peat, muck, loam, and lesser amounts of silt and sand. Groundwater in the vicinity of the site flows in a general northeast direction from Honker Cut towards Lodi. ' Regionally, groundwater typically flows away from the levees towards the lower lying areas and is also influenced by tidal fluctuations. A primary use of surface water in the Delta region is irrigation of agricultural land, and is controlled by irrigation ditches found throughout the region. Local variations in groundwater flow ' exist which are related to topography and the geometry of local aquifers. Depth to groundwater in the area ranges from 2 to 12 feet below ground surface(bgs). 1 ' Soi7�-oofm