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kn KLEINFELDER <br /> 3 FIELD ACTIVITIES <br /> This work plan presents a scope of work to conduct a soil-gas survey around the tank <br /> excavation, collect soil samples from three radial borings, and install and sample three <br /> onsite ground water monitoring wells. Soil and water samples from the borings and wells <br /> +- will be analyzed to assess petroleum hydrocarbon contamination. <br /> Based on observations made during excavation and on the regional ground water elevation <br /> contour maps published by the San Joaquin FIood Control and Water Conservation <br /> District, it appears that ground water is very shallow under the site (approximately 10 to 12 <br /> feet below ground surface) and is flowing east-northeast. Because ground water appears to <br /> be only 4 to 6 feet below the removed tank, Kleinfelder recommends that the possible <br /> presence and extent of ground water contamination be investigated. <br /> To guide the placement of ground water sampling wells, Kleinfelder recommends first <br /> performing a soil-gas survey to assess possible the presence of volatile hydrocarbon <br /> ,. contaminates in the ground water. The soil-gas survey will be followed by a limited soil <br /> sampling and monitoring well installation, development, and sampling. The individual <br /> tasks are described in more detail below. <br /> 3.1 SOIL-GAS SURVEY <br /> Kleinfelder will perform an active soil-gas survey around the tank excavation. Mobile <br /> laboratory services will be supplied by Tracer Research. Initially, approximately eight <br /> locations will be sampled. These "first-stage" station locations are shown on Plate 2. <br /> �- Additional soil-gas sample locations will then be chosen, based on initial results, to further <br /> assess the lateral extent of contamination. The estimated second stage station locations are <br /> also shown on Plate 2, but may be revised based on the initial results. <br /> During the soil-gas survey, a 3/4-inch steel probe will be driven approximately 5 to 10 feet <br /> into the ground at each station. The probes will be decontaminated prior to use and a <br /> probe-blank will be analyzed. After installation, approximately 3 probe-volumes of air <br /> 4W <br /> (--10 liters) will be excavated from the probes. Soil-gas samples will then be collected <br /> from the probes using a 10-cc gas syringe. The air samples will be analyzed onsite for <br /> �- 181-89-719 3 <br />