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Unocal Station No. 5325 <br /> r.r' August 29, 1994 <br /> TieId Screening of Soil Samples <br /> A PID is used to perform head-space analysis in the field for the presence of organic vapors <br /> from the soil sample. This test procedure involves removing soil from the tip of the <br /> sampling device or sample liner into a clean glass jar, and immediately covering the jar with . <br /> aluminum foil secured under a ring-type threaded lid. After approximately twenty minutes, <br /> the foil is pierced and the atmosphere within the jar tested using a PID. Head-space <br /> screening results are recorded on the boring log. Head-space screening procedures are <br /> performed and results recorded as reconnaissance data. GSI does not consider field <br /> screening techniques to be verification of the presence or absence of hydrocarbons. <br /> Construction of N4011iforina Wells <br /> Monitoring wells are constructed in the exploratory soil borings with Schedule 40 polyvinyl <br /> chloride (PVC) casing. All joints are thread joined; no glues, cements, or solventsare used <br /> in well. construction. The screened interval is constructed of machine-slotted PVC well <br /> screen which extends from the total well depth to a point above the groundwater. An <br /> appropriately-sized sorted sand is placed in the annular adjacent to the entire screened <br /> interval. A bentonite seal is placed in the annular space above the sand, and,the remaining <br /> annular space is sealed with heat cement or cement grout. <br /> Wellheads are protected-with water-resistant traffic-rated vault boxes placed flush with the <br /> ground surface. The top of the well casing is'sealed with a locking waterproof cap. A lock <br /> is placed on the well cap to prevent vandalism and unintentional introduction of materials <br /> into the well. <br /> Meastirement of Water Levels <br /> The top of the newly-installed well casing is surveyed by a California-licensed Land. <br /> Surveyor to mean sea level (MSL). Depth-to-groundwater in the well is measured from the <br /> top of the well casing with an electronic water-level indicator. Depth-to-groundwater is <br /> measured to the nearest 0.01-foot, and referenced to MSL. <br /> 4814702-18 <br /> GeoStrategies Inc. <br />