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1 <br /> All the exploratory test holes were installed by hand auger <br /> ' or with a backhoe. The objective was to determine if gross <br /> contamination by gasoline was present . The test holes were not <br /> designed for groundwater monitoring purposes . <br /> ' On March 11, 1988, Tesoro installed two monitoring wells at <br /> the site. The wells were designed to monitor groundwater quality <br /> and to assess the migration of new free floating gasoline contam- <br /> ination onto the site from sources to the north. The monitoring <br /> wells , drilled into the shallow water table aquifer, are 2 inches <br /> ' in diameter and contain 8- to 10-foot sections of slotted PVC <br /> casing . <br /> Exploratory Test Hole Construction <br /> The exploratory test holes were installed by Stockton <br /> ' Service Station Equipment using a hand auger (post hole digger ) <br /> or backhoe. Each test hole was dug to depths ranging between six <br /> and nine feet so that they penetrated the water table. A section <br /> of 6-inch diameter PVC pipe with hand-cut slots every 3 to 6 <br /> inches was installed in 9 of the 11 test holes and then back- <br /> filled with gravel . Two exploratory test holes (TS-7 and TS-11) <br /> were not fitted with PVC pipe because no floating gasoline was <br /> found and were later backfilled with soil. <br /> ' Monitoring Well Installation and Development Protocol <br /> On March 11, 1988, two monitoring wells, MW-1 and MW-2, were <br /> drilled by Datum Exploration using eight-inch hollow-stem <br /> augers . Each well was installed under the direct supervision of <br /> - 5 - <br />