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' Rajappan&Meyer • , Date: 1/7/99 <br /> Arch Road/Highway 99 Page: 3 <br /> 2.2 Electromagnetic (EM) and Ground-Penetrating Radar(GPR) Survey <br /> A geophysical survey will be conducted at the site to determine if USTs remain at the site <br /> of the former gas station. The survey will entail an EM and GPR survey and will be <br /> conducted at the location of the former gas station, as determined by an aerial photograph <br /> review. The EM survey measures conductivity values over a specific point to a depth of <br /> ' approximately 18 feet below ground surface (bgs). The GPR survey is a method for <br /> obtaining a continuous reflection profile of shallow subsurface features. The radar signal <br /> is sensitive to differences in electrical conductivity and relative permittivity(the ability of <br /> a material to hold an electrical charge). <br /> If no tanks are detected on site, the geophysical survey may be able to assess the location <br /> ' of the material used to backfill the excavated tanks. If this is the case, soil sampling will <br /> be conducted in the vicinity of the backfill. <br /> 2.3 Soil Borings <br /> This Work Plan details sampling to assess if the USTs leaked when the service station <br /> was in operation. If USTs are determined to be present, they will need to be properly <br /> decommissioned. This will require modification to URSGWC's and the client's <br /> ' (Rajappan & Meyer) statement of work to include tank removal, disposal, and additional <br /> soil sampling. <br /> Ten shallow soil borings will be advanced to a depth of 15 feet bgs. Subsurface soil <br /> samples will be collected utilizing a geoprobe or equivalent direct-push-technology <br /> sampling rig. Two soil samples will be collected from each borehole: one at 10 feet bgs <br /> and one at 15 feet bgs. URSGWC will continuously log each borehole in accordance <br /> with the Unified Soil Classification System. <br /> ' Samples will either be collected in acrylic sleeves or brass sleeves (depending on the type <br /> of drill rig used). The ends of the sleeves will be sealed with TeflonTM tape and <br /> polyethylene end caps, placed in a cooler, and transported under chain-of-custody <br /> ' protocol to a California-certified laboratory. <br /> All down-hole equipment will be decontaminated between sample locations. <br /> ' Each sample will be analyzed for total petroleum hydrocarbons-diesel (TPH-D), TPH- <br /> gasoline, benzene, toluene, ethylbenzene, and xylenes (BTEX), and lead. Samples will <br /> ' not be analyzed for methyl-tertiary-butyl-ether (MTBE), because this additive was not <br /> used in the late 1960s. The proposed borehole locations are presented in Figure 2, and <br /> are subject to change based on geophysical survey results or results of an underground <br /> ' utility survey. <br /> R&M/Arch Rd/43-00066762.00.1000 <br />