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AL <br /> 4.0 PROPOSED SITE INVESTIGATION PROGRAM <br /> 4.1 Approach <br /> The principal objective of Tetra Tech's proposed work is to determine if petroleum compounds <br /> from the former diesel UST have impacted groundwater. Since local groundwater has been <br /> documented at shallow depths, groundwater quality will be evaluated by hydropunching and <br /> collecting a single water sample at the former tank cavity. <br /> 4.2 Proposed Hydropunch and Sampling Program <br /> The investigation will consist of drilling one soil boring at the midpoint of the former location of <br /> the UST. The boring will be completed until groundwater is encountered (anticipated at 10 to 15 <br /> feet bgs). Drilling will terminate at a maximum depth of 30 feet bgs. A boring location map is <br /> presented in Figure 3. The objective of the soil boring is to to allow for the collection of a grab <br /> groundwater sample. <br /> Drilling and sampling activities will be performed following procedures outlined in Appendix C, <br /> Soil Sampling Procedures. Appendix C also contains detailed protocol for field screening (head <br /> l space analysis), lithological logging, borehole abandonment, and equipment decontamination <br /> [` procedures. Drilling and soil sampling procedures and proposed laboratory analyses are briefly <br /> summarized below. <br /> L <br /> L <br /> L <br /> L <br /> L <br /> L <br /> TETRA TECH:Castle Rock Forest Fire Station,Revised Technical Work Plan Page 6 <br />