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In the proposed investigation, it is planned to drill the boreholes for soil sampling and for monitoring well installation with a hollow-stem auger. Continuous cores will be collected for lithologic (soils) identification. The project geologist or engineer will log the cores from the liners of the sampling system, and remove the sections selected for soil laboratory analyses. (See Section E. below for the description of soil sampling protocol.) Logging descriptions will conform to the Unified Soil Classification System (USCS). If, from four locations across the site, the project geologist/engineer concludes that the subsurface materials are relatively consistent and continuous across the site to characterize site stratigraphy, subsequent boreholes will be sampled at 5-ft discrete-depth intervals. C. MONITORING WELL DESIGN The design, as well as the placement, of the proposed monitoring wells is predicated on the findings from the two previous PEI subsurface investigations conducted at the site in 2012. The target zone for the monitoring wells is the clayey- silty sand (SC) stratum identified, typically, at the 26-to-28-foot-depth interval. The 2-inch(ID)PVC wells will be installed within the 8.25-inch borehole drilled by the hollow-stem auger (HSA). The HSA will penetrate the silt stratum to 5 ft below the bottom of the water-bearing zone to collect a sample for chemical analysis. The silt stratum will be backfilled (plugged) by emplacing bentonite almost to the permeable zone, then inserting the capped screen section (with a short sump/sediment trap) in the borehole. The screened section will be 15 ft in length-as directed by the CVRWQCB-of 0.020-inch slot-size screen, joined to blank casing rising to the finished top-of-casing elevation near ground surface. A filter pack of #2/16 (or equivalent) sand will be tremied into the annular space around the well screen to a maximum of 2 ft above the screened interval. The well will be pre-developed before placement of the transition seal to promote settlement of the filter pack and remove bridging that may have occurred. Additional sand may be added after predevelopment. A 2-ft-thick transition seal of bentonite chips or pellets will be tremied or poured into the annular space above the filter pack, and hydrated. Above the transition seal, the annular space will be pumped or tremied with neat cement to approximately a foot below the finished top of casing. A monitoring well construction detail sample form is presented in Figure 8. The well will be capped with a locking cap and be protected in a surface completion consisting of a well box with traffic-rated cover. Both cap and cover will be marked with the well identification number. Well construction will be documented on the boring/well construction log. Top of casing will be surveyed post completion per Section III. A. The top of casing will be marked on the north side to indicate the reference point for the survey and for measuring water levels.