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McDowell &Davis Towing Phase U Groundwater Monitoring Well Installation Report -- The filter pack was placed to extend two feet above the perforated casing zone. A Bentonite seal 2- to 3-feet thick was placed in the annular space above the filter pack followed by a cement grout to the surface. Seal and filter pack elevations were determined by the underlying geology and actual elevation at each well location. All well heads were surveyed to within 0.01 feet using an assumed datum of 117 feet as shown on the USGS Escalon Quadrangle topographic map (photo-revised 1981). 2.3 Well Development and Sampling The wells were developed until the well water appeared clear of sediment and allowed to stabilize for twenty-four (24) hours prior to sampling. All soil and groundwater samples were properly labeled with date collected, project number, sample coordinator, and sample identification. Field records document the above information and other significant data, such as names of on- site personnel, sampling methods, date and time of sampling, the number of well volumes removed before sampling, preservatives added, and any filtration performed on samples. The samples were refrigerated immediately for delivery to the laboratory and under no circumstances were opened by anyone other than laboratory personnel. Chain of Custody records were maintained at all times. 2.4 Soil Sampling All soil sampling equipment was thoroughly steam-cleaned before and between sampling to prevent cross contamination. Relatively undisturbed soil samples were taken at intervals of not more than 5 feet in order to evaluate the subsurface materials. Geoprobe' samples were obtained using a Geoprobe® Systems sampler with plastic liners. For augured borings the soil samples were taken using a California Modified Split Spoon sampler with brass liners. A 140 pound hammer repeatedly falling 30 inches drove the sampler. The blow counts necessary to drive the sampler were recorded for each 6-inch interval to help evaluate the consistencies of the materials. The laboratory samples did not have head space and were immediately sealed in their liners using aluminum foil lined plastic caps. The remaining sample was removed from its liner to be used as an aide to the on-site geologist in logging the material at that depth. All soil samples were delivered, under chain of custody, to GeoAnalytical Laboratories, an analytical laboratory licensed by the State of California for hazardous materials work. The samples were analyzed for Total Petroleum Hydrocarbons (gasoline), BTX&E (Benzene, Toluene, Xylene, and Ethyl 5