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I Appendix A I loose fine soil particles on the surface. The sediment in the sample tube will th�n be placed into an appropriate sample container and transported and sealed following the protocols described for soil samples. Samples for VOC analyses will be collected by inserting an Encore''" sampler into the sediment. If the sediment is extremely coarse-grained(e.g.,large gravel) such that the clasts are larger than the diameter of the Encorem samplers,tubes of soil will be submitted in 1 eu of the Encor6l sampler, and recorded in the daily field logbook and the Chain of Custody. A1.2.5 Soil Vapor Sampling Soil vapor data will be collected at 20 locations throughout the site to determine the presence or absence of VOCs and formaldehyde. Soil vapor samples will be collected using guidelines from the advisory on active soil gas investigations prepared by the DTSC and Los Angeles RWQC (DTSC and LARWQCB, January 2003). The collection of soil vapor samples will require the installation of temporary vapor probes using a direct push drill rig. The following describes procedures fors ling soil vapor using soil vapor probes. A1.2.5.1 Temporary Probe Installation • Prior to use at each sampling location, drive rods and any other non-dedic ted,non-disposable equipment that may come into contact with the soil vapor sample will be decontaminated. • Each soil vapor probe will be driven to the target depth and then retracted by 4 to 6 inches to expose the screened sampling tip. • An approximate twelve to fifteen-foot length of disposable %4 to 1/8 inch diameter Tygon or Teflon sampling line will then be inserted into the vapor probe(drive rod)and connected to the screened sampling tip with a threaded connection containing a rubber gasket(post run tubing set-up). • Following installation of the sampling line,the annulus surrounding the p robe rod at ground surface will be sealed with hydrated bentonite. • To allow subsurface conditions to equilibrate,no further procedures shall be conducted for a minimum of 20 minutes following placement of the bentonite. A1.2.5.2 Pre-Sample Purge • While the subsurface is equilibrating,the"dead space volume"will be estimated by calculating the volume occupied by the sample tubing and sampling tip. This value will equal one purge volume. • The low flow pump, flow meter, and"T-valve"are then attached to the end of the sampling line. The"T-valve"is positioned before the pump and flow meter. • After 20 minutes and before starting the pre-sample purge, a rag moist d with the selected leak check compound(butane or isobutene analyzed by ASTM D1945)will a placed on the ground surface around the annulus of the soil vapor probe. At least once a day,it second moistened rag will also be placed near the sampling train to check for possible leaks in the t abing connections. • The"17-valve"will be rotated so that the sampling line is open to the pump. A total of three purge volumes of vapor will then be pumped from the sampling line at a flow rate of approximately 100 to KB61125 APPENDIX A MACTEC Engineering and Consulting, Inc. A5 September 28,2005