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Odic Environmental <br /> Page 2 of 4 <br /> Since the gasoline station has operated onsite since 1974 and no information related to the installation dates <br /> of the USTs removed in 1998 was provided, additional investigation related to potential orphan USTs is <br /> warranted. <br /> Scope of Work <br /> In accordance with the requirements of Wells Fargo Bank(WFB),Odic proposes the following scope of <br /> work: <br /> Geophysical Survey: <br /> To address the possibility of unknown or orphan tanks, a Geophysical Survey including at a minimum a <br /> grid survey using Ground Penetrating Radar (GPR) will be completed in the three (3) identified <br /> open/undeveloped areas shown on Figure 2. A qualified geophysical contractor will be employed to <br /> complete the survey. The survey will be performed on a minimum 2-foot grid spacing across the areas of <br /> interest, and will identify any subsurface velocity anomalies (i.e. excavation backfill or void spaces) that <br /> may represent former UST locations. Odic notes that the soil at the Site is composed primarily of a Silty <br /> Sand (SM)material. While the radar signal can typically penetrate deeper into coarser grained soils, it is <br /> also likely that any backfill materials will have a similar seismic velocity to native soils, and it may not be <br /> possible to show the subtle differences in velocity between backfill and native soils. As such, the GPR <br /> survey may not conclusively identify the location of former or orphan tanks, if the tanks have been <br /> removed and backfilled with native soils or imported sandy materials of similar velocity. Electromagnetic <br /> methods will also be employed to identify any metallic signatures. Any orphan USTs encountered onsite <br /> will be further investigated,registered,and removed in accordance with current and applicable regulations, <br /> and closure documentation will be provided to WFB(additional scope and cost). <br /> Soil Sampling: <br /> The following soil boring are proposed: <br /> -3 borings to 20 feet at USTs <br /> -8 borings to 10 feet at fuel dispensers <br /> -2 borings to 5 feet at product line runs <br /> In additional the following is recommended: <br /> -2 borings to 15 feet at suspected former fuel dispensers <br /> -1 boring to 20 feet at possible former UST location <br /> -1 boring to 20 feet at former waste oil UST <br /> Soil samples will be collected at 5-foot intervals, except for the 5-foot borings where samples will be <br /> collected at depths of 3 and 5 feet. Soil samples will be screened for volatile organic compounds using a <br /> Photo-ionization Detector (PID) and logged in accordance with the Unified Soil Classification System <br /> (USCS)by a qualified field representative. If field evidence of contamination is encountered,borings may <br /> be advanced below the proposed target depths until the vertical extent of impact has been determined, <br /> refusal is encountered, or until groundwater is encountered. If groundwater is encountered (expected at <br /> approximately 80 feet bgs), groundwater grab samples will be collected. If contamination is encountered, <br /> additional borings may be advanced in a radial pattern to identify the lateral extent of impact(additional <br /> scope and cost). <br /> Immediately upon collection, soil samples will be packaged for laboratory analysis, labeled, placed into a <br /> ziploc bag, and stored in an ice-chilled cooler. One sample from each soil boring will be submitted to a <br /> State of California certified laboratory for analysis of: <br />