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Mr. Jim Barton _RWQCB March 29, 2013 Page 6 Underground Utility Clearance Boring locations will be field located and marked prior to mobilizing drilling and sampling equipment.' An independent utility location contractor will be retained to evaluate subsurface conditions, such as buried metallic objects and underground utilities, at each boring location. The contractor is expected to use metal and magnetic object detectors and radio detection equipment to detect both existing electrical frequencies and contractor induced electrical frequencies, if required. Additionally, the Underground Service Alert will be notified at least 48 hours prior to the commencement of field activities. Prior to any subsurface activities each location will be hand augered to a depth of approximately 3 to 5 feet below ground surface (bgs) for utility clearance. Health and Safety Plan URS's Certified Industrial Hygienist prepared a site-specific Health and Safety Plan (HASP) for the 2012 investigation activities which will be updated prior to field deployment. URS employees and subcontractors will sign a Safety, Compliance Agreement form, which will be included in the HASP. The HASP will be available in the field during drilling activities. Sampling Design and Rationale This follow-up investigation was designed to provide further data along three lines of inquiry. • Shallow soil gas sampling in each of the three investigation areas to assess potential vapor intrusion risks to future building occupants. • Deeper soil gas sampling in each of the three investigation areas to assess potential vapor intrusion risks for future site buildings. • Soil and groundwater sampling to determine the lateral extent of impacts in the boring B-15 area located in the southeastern corner of the site. Soil sampling results will also be used to address potential health threats to construction workers that might work in site.soil(e.g., soil contact in utility trenches). Figure 2 depicts the proposed drilling and sampling locations. Table 1 lists the proposed sampling locations, approximate sample depths, and the rationale for each. General Field Documentation During the drilling and sampling activities,URS field staff will complete appropriate field documentation, including field notes and boring logs at each boring. The field notes will be used to document activities and any other noteworthy site conditions or events. The field notes will be used to prepare the investigation report and will be included as an appendix in the final report. Field information will be entered on appropriate data sheets.