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On the recommendation of PHS/EHD one new monitoring well is proposed adjacent to Wright <br /> boring B-5 (see Figure 2). The shallow aquifer observed :in the previous borings occurs between <br /> about 10 to 25 feet below the surface. Wright assumes that this aquifer is hydrostratigraphically <br /> the same as that penetrated by the C.H2M Hill wells. On that basis the new well screen interval <br /> will be placed from depths of about 10 to 25 feet. Groundwater level monitoring will measure <br /> water levels in existing wells MW-HP-7 and MW-HP-8 together with the new well for plotting <br /> the groundwater flow direction. Quarterly monitoring will only sample the new monitoring well <br /> for TPHD to assess groundwater chemical quality at the project site. <br /> 3.0 Field Methods—Drilling and Sampling Exploratory Borings <br /> One exploratory boring will be drilled at the location shown on Figure 1. Drilling and well <br /> installation permits will be secured from the SJC/EHD. A site safety plan and underground <br /> utility clearance with WWCF staff will be performed prior to doing the fieldwork. The well will <br /> be advanced to depths of about 25 feet. <br /> The borehole will be drilled with a truck-mounted hollow-stem auger rig. All drilling equipment <br /> and sampling tools will be cleaned prior to arriving, and before leaving the site. The <br /> decontamination rocess will use a tri-phosphate soap to wash the soil sampler between each <br /> sam le run a each borehole Augers and drill rods will be decontaminated in similar fas ion <br /> between each bore o using a pressure washer to clean and remove soil/sediment adhering to <br /> the augers, rods and drill bits. The hollow-stem augers will be advanced and discrete soil <br /> samples will be collected for logging at five-foot depth intervals from each borehole. The augers <br /> and drill rod will be advanced to the desired sampling depth interval, and a drive split spoon <br /> sampler was driven ahead of the drill bit. If any soil samples are retained for analysis, they will <br /> be sealed with Teflon paper and plastic endcaps, labeled, logged onto chain-of-custody forms <br /> and placed in a chilled ice chest on crushed ice for transport. <br /> The borehole will be logged under the supervision of a professional geologist using the Unified <br /> Soil Classification System together with additional lith.ologic information to describe the <br /> subsurface geology. The soil samples will be collected at five-foot intervals, at intervals of <br /> obvious contamination and at stratigraphic features of interest if encountered. Soil samples will <br /> be field screened with a portable photoloivzation detector(PID) for fuel hydrocarbons vapor and <br /> staining. Upon completion of the borehole drilling and collection of soil samples, the borehole <br /> wi11 be converted to a groundwater monitoring well using the procedures discussed below. <br /> Borehole drill cuttings, decontamination water, cement mixing and cleanup water will be placed <br /> into closed top drums, labeled and left at the City of Tracy specified location onsite. <br /> 4.0 Groundwater Monitoring Well Installation and Sampling <br /> 4.1 Monitoring Well.Design and Tnstallation <br /> One monitoring well will be constructed using threaded Sch. 40 PVC casing; glues will not be <br /> used. Final well design will be modified to the site-specific conditions encountered in the <br /> borehole during drilling. Once the aquifer strata are defined, the casing will be lowered to the <br /> Page 3 of 5 <br />