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3.0 SOIL VAPOR SAMPLING AND HUMAN HEALTH RISK ASSESSMENT <br /> L& The soil vapor sampling and human health risk assessment were completed according to <br /> Ramage Environmental's Work Plan, Soil Vapor Sampling and Analysis, dated December 7, <br /> 2007, as approved by EHD on December 24, 2007. A copy of the regulatory approval letter is <br /> LW included in Appendix C. <br /> �.. 3.1 Project Planning and Permitting <br /> To execute the proposed scope of work, Ramage Environmental obtained a drilling permit <br /> (SR#53973) from EHD. The contractor listed on the permit is Western Resource Management <br /> (WRM), a subcontractor to Ramage Environmental. A copy of the approved permit is included in <br /> �., Appendix C. <br /> Since all of the drilling was conducted on-site, neither off-site access agreements nor <br /> encroachment permits were required. At least two working days prior to field work, WRM <br /> notified EHD and Underground Service Alert so that regulatory and underground utility <br /> a. inspections could be scheduled. <br /> On April 25, 2008, under the supervision of WRM, SubDynamic Locating Services, Inc. <br /> (SubDynamic) surveyed the drilling locations with hand-held radio detection conductance and <br /> electromagnetic inductance equipment. SubDynamic identified any subsurface anomalies, and <br /> �.. minor adjustments to the drilling locations were made as necessary. <br /> 3.2 Soil Vapor Sampling and Analysis <br /> �L. <br /> On April 30, 2008, under the supervision of WRM and inspection of EHD, Environmental Control <br /> w. Associates (ECA), a state of California licensed drilling subcontractor (C-57 License#695970), <br /> collected soil vapor samples from five on-site locations (SV-1, SV-2, SV-3, SV-4, and SV-5). <br /> Due to low flow conditions, soil vapor was not sampled from the sixth proposed location. The <br /> 6.0 soil vapor sample locations are shown on Figure 2. <br /> L,, ECA collected the soil vapor samples according to the California Department of Toxic <br /> Substances Control Interim Final Guidance for the Evaluation and Mitigation of Subsurface <br /> Vapor Intrusion to Indoor Air, dated December 14, 2004 and revised February 7, 2005. To <br /> collect the soil vapor samples, ECA advanced each of the shallow borings to approximately five <br /> feet bgs using portable direct-push sampling equipment. A retractable vapor sampling probe tip <br /> W connected to '/8-inch diameter Teflono tubing was threaded through the center section of the <br /> 1.0 8 <br />