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ATC <br />ENVIRONMENTAL • GEOTECHNICAL <br />BUILDING SCIENCES • MATERIALS TESTING <br />/ Lone Palm Avenue, Suite 201B <br />Modesto, CA 95351 <br />Telephone 209-579-2221 <br />Fax 209-579-2225 <br />www.atcgroupservices.com <br />will be present to log all soil samples. Descriptions of soil types encountered and sample collection <br />intervals will be recorded on boring logs. Soil samples will be collected at five-foot intervals, field <br />screened with a Photo-Ionization Detection (PID) meter, and an estimated two or three soil samples from <br />each of the borings will be submitted for laboratory analysis. Soil sample selection will be based on the <br />need for shallow soil direct contact risk assessment in each of these borings and from the samples <br />collected during other segments of the scope as discussed above, as well as the request for metal data at <br />three of the direct push boring locations. Soil samples will be collected in the top five feet, and in the <br />five to ten foot bgs interval in all borings. In a boring located as close to the location of the former waste <br />oil UST as possible (due to age obscuring the precise location) and two additional locations to the west <br />and northwest of the former USTs, samples will be collected at approximately 25 feet bgs to provide data <br />on the metals content in the soil beneath the former USTs and in locations not impacted by the leaking <br />former USTs on the site. The depth of sampling for this purpose is based on the reported depth of over- <br />excavation performed at the time of the UST removal (22 feet). The two baseline samples will be <br />collected at the same depth for consistency. <br />The two remaining locations will be advanced to ten feet bgs, as their sole purpose is evaluation of the <br />shallow soil direct contact risk. <br />Following soil sample collection, the borings will be backfilled with neat cement grout to the ground <br />surface. All drill cuttings, if any, will be stored on-site in a 55-gallon drum or other appropriately sized <br />container pending laboratory results. <br />Sample Analysis <br />The soil samples from the Geoprobe soil borings and other borings will be immediately placed in a cooler <br />with ice and delivered under chain-of-custody documentation to a State-certified analytical laboratory. <br />Soil and groundwater samples will be analyzed for TPHg by EPA method 8015; BTEX by EPA method <br />8020; naphthalene by EPA method 8270; and MTBE by EPA method 8260. <br />The samples collected in connection with the former waste oil UST will be analyzed for the above list, as <br />well as volatile organic compounds (VOCs) including trichloroethylene (TCE) and tetrachloroethylene <br />(PCE), semi-volatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), and Title 22 <br />metals. <br />CHARACTERIZATION OF GROUNDWATER <br />In correspondence dated November 18, 2016, the RWQCB requested additional evaluation of the lateral <br />and vertical extent of the groundwater plume in deeper groundwater. ATC proposes to advance nine soil <br />borings for the purpose of collecting groundwater samples. Soil samples will also be collected during the <br />clearance stage of each boring and submitted for analysis as described in the previous section. <br />Boring Advancement <br />ATC will contract with a C-57 licensed drilling company to advance nine hydropunch borings to <br />approximately 60 feet bgs to collect groundwater samples between 40 and 60 feet bgs. The borings will <br />S:\62596\reports\SVIS_WP ADD-201adoc <br /> 4 ATC