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. • a URS Ms.Margaret Lagorio Page 4 San Joaquin County Environmental Health Department January 13,2004 lead scavengers (1,2-DCA and EDB)by EPA Method 8260B(preparation EPA Method 5030). Analytical data will be uploaded into Geotracker. Attachment C presents detailed soil and groundwater sampling and analysis procedures. PHASE II — GROUNDWATER MONITORING WELL INSTALLATION URS proposes to install one deep groundwater monitoring well to assess the vertical extent of 1,2-DCA contamination. In addition,if necessary up to four shallow monitoring wells will be installed to monitor the lateral extent of contamination. The boring locations will be selected based on receipt and evaluation of data from the soil and groundwater grab sampling analytical results. Drilling and Soil Sample Collection Each of the borings will be drilled using a 8.25-inch diameter HSA equipped drill rig. The deep boring will be advanced vertically to approximately 100 feet bgs for the purpose of constructing a 2-inch diameter groundwater monitoring well. Four additional borings (if necessary)will be advanced vertically to approximately 10 feet below first encountered groundwater to construct four 2-inch diameter monitoring wells. Groundwater at the site is expected between approximately 56 to 65 feet bgs. The deep well will be placed on-site in the area reporting the highest 1,2-DCA concentrations. The shallow wells (if necessary)will be installed in locations to monitor the lateral extent 1,2-DCA. wtt(s/LV'/ " 5 q,,f Sh•wk Ix S,4 P A URS geologist will collect samples of the subsurface soils at 10-foot intervals beginning at 10 feet bgs during the drilling of each boring. A portion of each sample will be used for headspace screening with a PID and for lithologic logging. A portion of each sample will also be retained and be submitted to the laboratory for possible analysis. The borings will be logged using the samples collected from 10-foot e"1if sp w„� cws S-ISN intervals (and from drill cuttings)by the URS geologist according to the Unified Soil Classification Sh,y,"eJ- System. 8 Each soil sample retained for possible chemical analysis will be collected in brass liners,capped with Teflon®tape and plastic end caps,labeled, and placed in a cooler on ice for delivery to Sequoia in Petaluma,California under chain of custody. Soil samples showing visible staining or elevated PID readings will be analyzed by the laboratory. If staining or elevated PID readings are not encountered the sample collected in the capillary fringe just above first water will be analyzed. At least one soil sample from each boring will be analyzed for GRO by EPA Method 8015B (preparation EPA Method 5030), BTEX,MtBE,TBA,DIPE,ETBE,TAME, 1,2-DCA, and EDB,by EPA Method 8260B (preparation EPA Method 5030). Deep Monitoring Well Installation A groundwater monitoring well will be constructed in the deep borehole using 2-inch-inside-diameter, Schedule 40,flush-threaded polyvinyl chloride(PVC)well casing. Five feet of 0.020-inch machine- K:\WprocessV5 BP ARCO\00760\2004 Assessment\760 GW Workplan 04.doc