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ATC <br />ENVIRONMENTAL • GEOTECHNICAL <br />BUILDING SCIENCES • MATERIALS TESTING <br />1117 Lone Palm Avenue, Suite 201B <br />Modesto, CA 95351 <br />Telephone 209-579-2221 <br />Fax 209-579-2225 <br />www.atcgroupservices.com <br />Description of Work <br />Installation of Long Term Soil Vapor Probes <br />The scope of work involving the installation of long term soil vapor probes as described in the January 6, <br />2017 workplan will not be conducted during at this time. This is a result of the non-concurrence of the <br />Regional Water Quality Control Board in correspondence dated February 22, 2017. <br />Advancement of five soil borings <br />Five borings will be advanced using truck mounted Geoprobe® narrow diameter, direct push technology. <br />Drilling will be conducted by a State-licensed (C57) drilling company. Soil samples will be collected in <br />the top five feet, and in the five to ten foot bgs interval in all borings. In a boring located as close to the <br />location of the former waste oil UST as possible (due to age obscuring the precise location) and two <br />additional locations to the west and northwest of the former USTs, samples will be collected at <br />approximately 25 feet bgs beneath the former USTs and in locations not impacted by the leaking former <br />USTs on the site. The depth of sampling for this purpose is based on the reported depth of over-excavation <br />performed at the time of the UST removal (22 feet). <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. <br />CPT and hydropunch borings <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. <br />Three of the borings will be advanced using cone penetrating test (CPT) methods. The CPT borings will <br />be advanced to an estimated depth of 60 ft bgs (or refusal). The borings will be advanced using a direct <br />push CPT rig that will log soil lithology from approximately five feet bgs to the maximum explored depth. <br />Groundwater samples will be collected from separate boreholes advanced adjacent to the CPT boring, <br />and from the additional six locations, using a modified HydroPunch® sampler. The three borings that <br />will be advanced using the CPT logger, upon reaching maximum depth, the CPT logger will be retracted, <br />then drill rods with a disposable drill point will be advance into the same boring to facilitate backfilling <br />with neat cement. Neat cement will be poured slowly through the drill rods until neat cement grout <br />reaches the surface. The drill rods will be retracted from the hole leaving the disposable drill point at the <br />bottom of the bore hole. <br />1 ATC