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Mr. Henderson - 2 - February 23, 2012 Following underground utility clearance, ENVIRON will direct the drilling subcontractor to advance four soil borings at the site. The locations of the borings are intended to be located in the area of former fuel dispensers and USTs; as such, ENVIRON is currently reviewing historical aerial photographs to determine specific locations, and the figure included with this work plan merely identifies the general area of the investigation. The borings are anticipated to be outside of existing building footprints and accessible with standard truck-mounted drilling equipment. At SJCEHD request, an updated figure may be provided showing final proposed boring locations. Soil cores will be logged for lithology by an ENVIRON geologist and soil headspace readings will be collected using a photoionization detector (PID) to screen for the presence of VOCs. Two soil borings will be advanced to a depth of approximately 10 feet bgs in the area of the former fuel dispenser pumps. Soil samples will be collected from these borings from depths of five feet and 10 feet bgs. Two soil borings will be advanced to a depth of approximately 15 feet bgs in the area of the former fuel USTs. Soil samples will be collected from these borings from depths of 12 feet and 15 feet bgs. The number and depth of soil samples may be adjusted in the field based on observations and field soil screening results. It is not anticipated that groundwater will be encountered. Soil samples will be sealed in glass jars or in sections of the acetate drilling liner, labeled, placed on ice in an insulated container, and transported to the analytical laboratory under chain- of-custody documentation. The soil samples will be requested to be analyzed for total petroleum hydrocarbons as gasoline, diesel, and motor oil (TPHg, TPHd, and TPHmo) by EPA Method 8015M and VOCs (including fuel oxygenates) by EPA Method 8260B. From each soil boring, the deeper samples will be placed on hold at the analytical laboratory pending the results of the shallower samples. Sample data will be compared to the San Francisco Bay Regional Water Quality Control Board (RWQCB) Environmental Screening Levels (ESLs) for commercial/industrial land use for shallow soil where ground water is a current or potential source of drinking water. The San Francisco RWQCB ESLs are conservative screening criteria for the evaluation of potential human and ecological health and other environmental concerns under a variety of land use scenarios, including residential and commercial development. Under most circumstances, the presence of a chemical in soil, soil gas, or groundwater at concentrations below the corresponding ESL can be assumed to not pose a significant, long-term (chronic) threat to human health and the environment. The presence of a chemical at concentrations in excess of an ESL does not necessarily indicate that adverse impacts to human health or the environment are occurring; this simply indicates that a potential for adverse risk may exist and that additional evaluation may be warranted. Therefore, although not directly applicable due to the site's location outside the jurisdiction of the San Francisco RWQCB (and in the Central Valley RWQCB's area), the ESLs are presented for reference purposes in comparison to the data obtained for this investigation. If analytes are detected above applicable ESLs in a given sample, the deeper contingent sample will be released for analysis. Following sample collection, the borings will be backfilled with Portland cement in accordance with SJCEHD guidelines. Soil cuttings and decontamination fluids generated during drilling and sampling will be contained in 5-gallon buckets or a single 55-gallon drum for appropriate disposal at a later date, pending analytical results. HAPW\Projects\Extra Space Storage\Stockton Phase ffermitting\Work PIan.Docx