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Soil-Vapor Sampling and Analysis Work Plan Former Shell Central Valley Crude-Oil Pipelines August 15,2007 Machado Property(Neighborhood B)Parcel 209-060-08 Page 3 of 4 Area of Excavation Sample Depth Excavation Depth (feet bgs) (feet bgs) B2 13 14 B3 24 25 B6 9.5 10.5 B8 10 11 B9 30 31 B 12 17 18 For each area where soil gas is sampled,an additional sample location is planned immediately adjacent to the above-listed excavation areas(to the northeast,in the inferred down-gradient groundwater flow direction),from which vertical profile samples will be collected at 5, 10,and 15 feet bgs. In the event that a soil-vapor sample is unattainable as a result of high moisture content(due to proximity of the water table to the sample point)or due to difficulty penetrating the subsurface to the targeted depth,the location will be abandoned. A total of 24 soil-vapor samples from six excavation areas will be collected through temporary soil-vapor probes with the use of a Geoprobe®rig. The remaining six areas(131, B4,B5, B7, 1310,and B11)will not be sampled due to the shallow depths of impacted soil and/or low to non-detectable concentrations of the constituents of concern in these areas. Soil-Vapor Sampling Procedures Soil-vapor sampling will be performed in accordance with procedures outlined in two guidance documents issued by the California Environmental Protection Agency(Cal/EPA). These documents are titled Advisory—Active Soil Gas Investigations published January 28,2003,and Guidance for the Evaluation and Mitigation of Subsurface vapor Intrusion to Indoor Air published December 15,2004, and revised February 7,2005. The procedures are outlined below. • Soil-vapor samples will be collected through temporary probes advanced using a Geoprobe®rig. • Prior to soil-vapor sample collection at least 30 minutes should elapse following retraction of the probe tip to allow the subsurface soil-vapor conditions to equilibrate. • The soil-vapor probe will be constructed such that it consists of one continuous run of tubing from the base of the vapor-probe borehole to the ground surface,with a check valve at the ground surface. • A flow regulator will be placed between the probe and the SummaTm canister to ensure that the canister is filled at the appropriate flow rate. Flow rates should not exceed 200 milliliters per minute(ml/min).