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. 3.0 PROPOSED SITE INVESTIGATION PROGRAM <br /> 3.1 Approach <br /> The principal objective-of-Tetra-Tech's proposed-soil=invesfigafon-is-to-assess-theextent`o.f <br /> etroleum.contaminat o rn elated`_to t4kff3and-the associated piping.' Data acquired during the <br /> investigation will serve to derive an appropriate strategy for remedial and/or other.measures. <br /> 3.2 Proposed Soil Investigation Program_ <br /> The soil investigation will consist of a minimum of 6 soil.borings around Tank#3 and borings at <br /> �20-foot.piping.run intervals (estimated at four to five borings, assuming 90 feet of piping). <br /> Boring B- ' a slant boring designed to collect a 20=foot sample to identify the vertical extent of <br /> identified petroleum hydrocarbons. ..Each boring placed around the tank body will be extended to <br /> a minimum depth of 20 feet below ground•surface (bgs). Deeper samples will be collected in the <br /> event that contamination is detected (by visual`observation or field screening).at the 20-foot <br /> depth interval of any borings: A minimum of five borings will'be placed around the perimeter of <br /> the tank to assess the lateral extent of hydrocarbons in the soil. The proposed soil boring <br /> ` locations are presented on Figure 3. Based on..data collected through on-site field screening, a. <br /> decision will be made to drill additional step-Out soil borings, if considered necessary. <br /> Approximately four to five borings will be .drilled.along-the piping to the boiler room. These <br /> borings will be extended to a minimum depth of 10 feet bgs to evaluate the extent of potential <br /> hydrocarbon contamination associated with the piping. Deeper samples may be collected and/or <br /> additional step-out borings may be conducted to completely delineate any hydrocarbon <br /> contamination. Approximate boring locations are presented in Figure 3. <br /> Drilling and soil sampling activities will be performed following procedures outlined in <br /> Appendix C, Soil Sampling Procedures. Appendix C also contains protocols for site clearance, <br /> sample handling, field screening (head space 'analysis), lithoiogicallogging, equipment <br /> decontamination procedures and borehole abandonment. Drilling and soil sampling procedures <br /> and proposed laboratory analyses are briefly summarized below. <br /> fiTETRA TECH:Stockton Developmental Center,Revised Site Investigation Work Plan Page 6 <br /> kr` <br />