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U i l impact. - Soil samples will be collected from the boring for lithologic logging and field screening. The samples will be collected in a 5-footer-1�5--inch O.D._core sampler equipped with an acetate liner. Soil samples will be collected at approximate five-foot intervals ani a f fervais where staining or color or texture changes are noted.The field staff will examine representative portions of the soil samples and prepare soil boring logs that describe the encountered soil in general accordance with the American Standards for Testing Materials(ASTM) 2488-06 and the Unified Soil Classification System (USCS). The soil boring logs will indicate the depth of the various strata, and record other pertinent information regarding the advancement and sampling of each borehole. Each soil sample will be field screened for volatile.organic vapor's with a photoionization detector(PID)or similar instrument. The field screening readings will be recorded on the soil boring log. A portion of each soil sample will be.retained for.potential laboratory analysis. The samples will be collected in an acetate liner and the liners will be cut at the desiredm saple interval and sealed with Teflon®tape and plastic caps 4 at each end. All samples will be stored in an ice chest cooled to approximately 4 degrees Celsius(°C)with ice. Upon completion of the soil boring,the monitoring well (proposed well,MW-11)will be constructed with no more than 5 feet of 0,_010 inch slotted Schedule 40(Sch-40)2-inch diameter polyvinyl chloride(PVC). The well screen will be located from approximately 20 to 25 feet bgs. Approximately 20 feet of blank Sch-40, 2-inch diameter-P_VC.casing will be located from 20 feet bgs to approximately 6-inches below grade. The north side of the casing will be notched to facilitate consistent groundwater monitoring data acquisition. The boring annular space will be filled with appropriate filter sand extending from the maximum explored da th t depo approximately four feet bgs. The annular space will e i led with bentonite pellets or chip frs om approximately four to three feet bgs. Above the bentonite seal the annular space will be filled with Portland type II ceme gro)or grout/bentonite slurry to approximately 6-inches below grade. The surface completion will consist of a traffic rated well box set in concrete with a 2-inch diameter locking well cap. Drill cuttings will be stored on-site in 55-gallon drums pending laboratory results. Soil cuttings will be profiled and disposed of at an appropriate facility within 90 days: At least 72 hours after the installation of the monitoring well, the newly installed monitoring well will be surged with a 2-inch nominal diameter surge block-to_remove fines from the filter pack. Subsequent to surging, the well will be developed using centrifugal pump until`the produced water is relatively sediment free or until a volume equivalent to at least 10 well casings of water have been removed, which ever occurs first. All purge water will be stored in 55-gallon drums and staged on-site pending laboratory analysis for disposal. The development of the well will be performed a minimum of 72 hours after installation. F At least 72 hours after completion of the monitoring well surging and development,ATC will return to the Site to collect groundwater samples. The newly installed well will be sampled along with the other mandated wells as part of the semi-annual monitoring program. Prior to collection of groundwater I samples, dedicated polyethylene sample tubing will be inserted to the depth equivalent to midway down ` the screened interval so as not to disturb the standing water column above the screened interval and not ll! to stir up colloidal particles or sediment. The tubing will then be connectedlo a peristaltic pump and a Horiba Water Quality Monitor Model U-22XD meter(or equivalent) with a flow-through cell. Groundwaterwill be slowly pumped while simultaneously monitoring the DTW and adjusting the pump rate until no or minimal drawdown is observed. Drawdown greater than 0.33 ft results in a reduction of pumping rate or a temporary shut down. Once the pumping rate is stabilized at a rate not exceeding 0.54'=A' f J� L/min, temperature, pH, specific conductance;dissolved oxygen, and turbidity will be measured. When U � Additional Investigation Workplan Addendum Quik Stop No. 132,Stockton,CA I ...<. ..<. ,.<. July 28,2009 t