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Drill cuttings were distributed on the ground surface near each drilling site as allowed in the EMP Workplan. Temporary wells were constructed within each borehole using one- inch diameter, Schedule 40 PVC casing and screen with flush-threaded joints to permit hand assembly. The temporary screen extended 10 to 20 feet upward from the bottom of each borehole, and the screen zone was backfilled with No. 2/12 sand. The filter pack sand extended at least one foot above the top of the screen, and a two-to three-foot thick medium chip bentonite seal was constructed above the filter pack. The temporary wells permitted collection of groundwater samples to determine the adequacy of the locations for construction of permanent monitoring wells. 4.3 PHASE I EMP FIELD WORK During the first phase of work, three temporary wells (MW-9, MW-10, and MW-11) were permitted, drilled, logged, constructed and sampled as described in the preceding sections. Logs for these temporary wells are provided in Appendix B. The presence of VOCs at estimated trace and low, but measurable concentrations in the temporary well samples suggested that the plume extent could not be accurately assessed, requiring a second phase of investigative drilling. After the boreholes were drilled, temporary wells were constructed, sampled, and abandoned as described in the following sections. 4.3.1 Phase I Temporary Well Construction In accordance with the EMP workplan, the County's drilling contractor, Gregg Drilling, Inc., drilled three temporary boreholes (MW-9, MW-10, and MW-11; Figure 3) between October 11 and 13, 2011. Boreholes were drilled using eight-inch diameter hollow stem auger techniques under the direct field supervision of a State of California Certified Engineering Geologist and Certified Hydrogeologist. Lithologic samples were collected at five-foot intervals and logged by the field geologist to ensure proper stratigraphic correlation with existing site monitoring wells. Boreholes were advanced through the Holocene alluvium and into the Pleistocene Corcoran Clay. Once the Corcoran Clay was reached, the driller was directed to advance the borehole into the Corcoran Clay until water was encountered. A one-inch diameter Schedule 40 PVC casing with 0.010-inch slots was installed at this depth, and the borehole was backfilled with No. 2/12 sand until the perforated section of the casing was surrounded by the sand pack. The temporary wells were secured at the ground surface using plywood weighted down with sand bags. Temporary well construction information is summarized on the following table. EMP Report—Phase IIGeo-Loic Page ■ 7 1 Corral Hollow Sanitary Landfill ASS O C I AT E Sg August 21,2012