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Based on the above information, T.T. I . recommends the following action <br /> be taken to provide necessary data on which to make further decisions: <br /> I . Prepare a Preliminary Report as directed by the SJLHD and outlined <br /> in the District's document "Leaking Underground Storage Tank <br /> Investigative Formats". <br /> Since this is probably not a tank leak source of contamination, it <br /> is of first importance to determine who is responsible for the <br /> contamination so that the cost of further investigation can be <br /> allocated to the financially responsible party. Obviously, the city <br /> of Tracy does not store, handle, or transport diesel or motor oil <br /> at this site and should not be responsible for the contamination <br /> it found. To continue site investigations, the city should determine <br /> who provided the hydrocarbon contamination; hence, the following <br /> work plan is designed to discover responsibility: <br /> II . Contamination Source Determination. <br /> 1. Dig backhoe pits or make soil borings 500 to 1,000 feet <br /> on each side of the contaminated site. If contamination <br /> is found, continue underground investigations at 1,000 foot <br /> intervals until the boundary of contamination is bracketed, <br /> then investigate within the bracketed area to isolate the <br /> source of contamination and identify the responsible party <br /> or parties. <br /> III . During the work in Item II, the city of Tracy could carry on <br /> the following site specific investigation in accordance with <br /> the lead regulatory agency, (probably the CRWQCB, CVR) <br /> requirements. <br /> Task A: Construct three (3) groundwater monitoring wells in a <br /> triangular configuration to provide the following: <br /> 1. Depth to static groundwater. <br /> 2. Groundwater surface gradient. <br /> 3. Direction of groundwater flow and estimated velocity <br /> of groundwater flow. <br /> 4. Estimated extent of current and future groundwater plume <br /> boundaries. <br /> 5. If hydrocarbon product is found in the groundwater, <br /> initiate groundwater bailing to determine contamination <br /> concentration and feasibility of extraction and <br /> conditioning for disposal . <br /> 2 <br />