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SECTION III- FIELD INVESTIGATION A. GENERAL 1. Monitoring Well Locations and Rationale Placement of the proposed monitoring wells is predicated on the findings from the two previous PEI subsurface investigations that included grab groundwater samples from borings and four temporary monitoring wells. Factored into the consideration of placement is the acquisition of sufficient data to assess groundwater gradient across the site, to generate geologic cross-sections (from the borehole logs) to depict the subsurface lithologic characteristics, and to generate groundwater contaminant plume maps. The proposed well locations are shown on Figure 7. Enlargements of the areas of concern are included as Appendix A. No wells are planned to be constructed in the warehouse interior, and groundwater will not be sampled from the interior borings unless soil impact is documented at depth. Soil sampling is discussed below in Section III.E. 2. Survey Details Well and site surveying will be performed by a California licensed professional land surveyor (PLS) experienced with the GeoTrackerTM specifications, and all work will conform to the California State Water Resources Control Board's "GeoTrackerTM Survey_XYZ Guidelines & Restrictions" (Rev. 6, June 3, 2004). That document is incorporated herein by reference. 3. Equipment Decontamination Procedures All sampling equipment will be thoroughly decontaminated between sampling locations (including sample depths if new or pre-cleaned tooling is unavailable) using either steam cleaning or non-phosphate detergent wash with double tap water rinse and a final deionized water rinse. Equipment field blanks will be obtained by passing distilled or deionized water, as appropriate, through the decontaminated sampling equipment. 4. Health and Safety Plan The Health and Safety Plan for the site field work is included in Appendix B. B. DRILLING AND LOGGING METHODS In the previous subsurface investigations conducted by PEI in 2012, a direct- push rig(Geoprobe®6600)was successfully used to advance the borings and to collect soil matrix and groundwater samples. As recorded on the borehole log (Figure 5), the subsurface earth materials consist predominantly of silt, with the two-foot-thick water- bearing horizon of clayey sand. No lenses of gravels, cobbles, or highly consolidated soils were encountered.