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UST Closure Work Plan October 6,2000 6425 Pacific Avenue Project No.3944 Stockton,California Page 2 beneath the three existing 10,000-gallon USTs; • Collect one soil sample per temporary boring two feet below the pea-gravel/native soil interface; • Analyze soil samples for TPH-g by EPA Method 8015 (modified); benzene,toluene, ethylbenzene and xylenes(BTEX)by EPA Method 8020; and methyl tert-butyl ether (MTBE) and other fuel oxygenates and lead scavengers using EPA Method 8260b; and • Prepare a soil a UST Closure report. 3.0 BOREHOLE DRILLING AND SAMPLING Borings for soil sampling will be situated in the approximate locations shown on Figure 2. Six borings will be advanced to approximately 2 feet below the first encountered native soil. We anticipate native soil will be encountered at a depth of approximately 25 feet below grade (fbg). 3.1 Drilling Procedures At present, there are three 10,000-gallon USTs in a common excavation. These USTs will be removed and will be disposed of in accordance with local, state and federal regulations and guidelines. After the USTs are removed, the excavation will be filled with pea-gravel to replace the volume displaced by the USTs. A Geoprobe drilling rig will then be used to collect soil samples in the locations shown on Figure 2. It is probable that plywood will need to be placed over the pea-gravel to prevent the Geoprobe rig from sinking into the pea-gravel during the investigation. The Geo-probe rig uses a hydraulic ram to push a steel probe into the soil for the purpose of collecting soil samples. A geologist, under the direct supervision of a California Registered Geologist, will log the borings. The geologist will observe significant changes in material penetrated, changes in drilling conditions, hydraulic pressure, and drilling action. The geologist will observe and record changes by time and depth. He will also observe and record the relative moisture content of the samples, soil or rock type, color, grain-size, texture, hardness, presence of hydrocarbons, and most importantly the depth of the pea-gravel/native soil interface. This record will be used later to prepare a detailed lithologic log for each boring. The lithologic log will be included in the UST Closure Report. 3.2 Soil Sampling One soil sample will be collected from each boring two feet below the pea-gravel/native soil interface. Based on our present knowledge of Site conditions this interface is at approximately 25 fbg. Soil samples will be collected using a Geo-probe sampling core tube with a clear acetate sampling liner. The sampling liner will be cut with a hacksaw to collect a soil sample from the appropriate depth. Immediately after cutting the sampler, the ends will be completely covered with Teflon sheets and end caps will be placed will be placed such that an airtight seal is \\Tom\d\Centm1 Project File\3944 Stockton\Workplan.dcc