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} <br /> n � <br /> Work Plan for Additional Subsurface Assessment and Feasibility Study—Former Unocal Station#0187 <br /> September 14,2000 <br /> wells will be installed in six sets consisting of two wells each Each set of wells will consist of one well <br /> installed to a depth of approximately 75 feet bgs and the other well to a depth of approximately 120 feet <br /> bgs Because the two wells in each set will be installed 5 feet apart, soil samples for description and <br /> possible chemical analysts will only be obtained from the 120 foot well boring at five-foot intervals, as a <br /> minimum A GR geologist will monitor the drilling activities and prepare a log of the deepest bonng <br /> only Soil samples collected at 30 feet bgs, and every 10 feet in depth thereafter will be submitted for <br /> chemical analysis as described in Task 5 <br /> Soil from each sampled interval will be screened in the field for the presence of volatile organic <br /> compounds using a photoionization detector (PID) These data will be collected for reconnaissance <br /> purposes only, and will not be used as verification of the presence or absence of petroleum hydrocarbons <br /> Screening data will be recorded on the boring logs <br /> The groundwater monitoring wells will be constructed with 2-inch diameter Schedule 40 polyvinyl <br /> chloride (PVC) well casing and 0 02-inch machine slotted well screen One well in each set will be <br /> constructed with a screened interval of between approximately 65 and 75 feet bgs, and the other well will <br /> be screened from approximately 110 to 120 feet bgs The actual screen interval will depend on the <br /> groundwater depth and lithologic conditions encountered during drilling Proposed well construction <br /> details are presented in Figures 4 and 5 <br /> Drill cuttings will be stored at the site pending receipt of chemical analytical data for disposal The drill <br /> cuttings will be stockpiled on and covered with plastic sheeting Four discrete soil samples will be <br /> collected from the drill cuttings for disposal characterization These samples will be submitted to the <br /> laboratory for compositing and analysis, and will be collected as described in Task 5 Stockpiled soil and <br /> steam cleaning rinsate will be transported for disposal at an appropriately licensed facility <br /> Task 3. Well Development and Sampling <br /> The newly installed groundwater monitoring wells will be developed after being allowed to stand a <br /> minimum of 72 hours following completion During development, the clarity of the discharged well <br /> water and selected groundwater parameters (pH, temperature, and conductivity) will be monitored When <br /> the discharge water runs clear and the groundwater parameters have stabilized, a groundwater sample will <br /> be collected Groundwater removed from the well during development and sampling will be transported <br /> to an appropriately licensed facility for disposal The groundwater samples will be analyzed as described <br /> in Task 5 The newly installed wells will be included in the quarterly monitoring program beginning with <br /> the quarter following installation <br /> Task 4. Wellhead Surveying <br /> Following installation,the elevation of the top of well casings for all the wells at the site will be surveyed <br /> to mean sea level by a California licensed surveyor Horizontal coordinates of the wells will also be <br /> obtained <br /> I <br /> 240042 08 5 <br /> I <br />