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t3.0 FIELD PROGRAM <br /> ' The field activities were performed from August 2 through the 9th, 1993. One 5-inch diameter <br /> pilot boring was drilled to a total depth of 140 feet. The drilling was performed with a Failing <br /> 1500 mud rotary rig, using a 94mm wireline sampler, by Exploration Drilling Services of <br /> Redwood City, California. A mud rotary rig continuously pumps a bentonite drilling fluid (mud) <br /> down the hole to lubricate the drill bit. A de-sander was placed in a lined 20-yard roll off <br /> garbage bin to collect sediment strained from the drilling mud. A continuous coring device <br /> allowed for retrieval of a continuous sample of the subsurface sediments. These soils were <br /> ' logged by the onsite geologist, according to the Unified Soil Classification System (USCS), and <br /> Munsell color standards. The pilot boring was then geophysically logged by Colog, Inc. of <br /> Petaluma, California. The geophysical logs included electric logs with gamma ray for aquifer <br /> thickness and aquitard verification. An organic vapor meter (OVM) was used to take readings <br /> on selected soil samples, and borehole and breathing zone conditions during drilling. No <br /> ' elevated OVM readings were identified on this project. After completion of geophysical logging, <br /> a 1-inch diameter PVC pipe was placed to the bottom of the borehole, and a 5% bentonite <br /> ' grout mixture was pumped into the boring until the grout reached the surface. The displaced <br /> drilling mud was released into the large storm water containment pond (dry) adjacent to the <br /> drilling site. <br /> ' The drill rig was moved 10 feet away from the pilot boring and drilling for the monitoring well <br /> ' installation was begun. A 5-inch diameter boring was drilled to 83 feet below ground surface <br /> (ft bgs). The soils at this depth are stiff clays. The boring was then reamed out with a 16-inch <br /> diameter bit to 83 ft bgs. Four 20-foot lengths and one 10-foot length of 10 3/4 inch o.d. steel <br /> pipe (conductor casing) were welded together with an electric arc welder and lowered into the <br /> borehole. The conductor casing was then pressed into the intact clay soil 1.5-feet, using the <br /> t force of the drill rig. The bottom of the conductor casing was located at 84.5 ft bgs, and the <br /> top was cut off 1.5 feet above ground surface. A 1-inch diameter PVC pipe was placed to the <br /> bottom of the borehole, within the annular space, and a 5% bentonite grout mixture was <br /> ' pumped between the exterior of the conductor casing and the side of the borehole. The drilling <br /> mud inside the conductor casing was then flushed out using 1000 gallons of fresh water, and <br /> ' released into the large storm water containment pond (dry) adjacent to the drilling site. The <br /> following day, after the annular seal had hardened, the drilling continued inside the conductor <br /> casing using a 9 7/8 inch diameter drill bit. The boring was drilled to a total depth of 117.5 ft <br /> ' bgs. The drilling mud was then flushed out of the borehole using 800 gallons of fresh water, <br /> and released into the large storm water containment pond (dry) adjacent to the drilling site. <br /> ' 14744003.013 2 <br /> TRC <br />