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railroad ballast and pea gravel will be encountered. The ballast/gravel will be monitored for volatile organic vapors with a photoionization detector (PID). If ballast/gravel is encountered with HD readings above 250 parts per million (ppm), the ballast/gravel will be stockpiled on plastic for subsequent profiling and disposal. If soil is encountered in a spot excavation, a soil sample will be collected from each excavation and analyzed for the following: TPHg, in accordance with Modified EPA Method 8015 and Method 5035 preservation; TPHd and TPHo, in accordance with Modified EPA Method 8015B; and VOCs, in accordance with EPA Method 8260B and Method 5035 preservation. Liquid should not be encountered since the spot excavations will not breach/penetrate the drain. Imported gravel will be used to fill the spot excavations for safety purposes. The location of the drain and soil samples will be recorded with GPS or by survey. 2.6 SOIL GAS SURVEY The passive soil gas sampling technique is a near-surface screening method that can identify a large range of VOCs migrating to the surface from soil and groundwater. This system provides rapid screening of soils and groundwater, and data from the soil gas survey can be used to estimate the extent of contamination at a site and guide soil borehole and well placement.5 A passive soil gas survey using GORE-SORBER technology will be performed at 35 selected locations as shown in Figure 4. Samples from 28 locations will be collected in Parcel 24, and seven (7) in Parcel 4. Soil gas sampling will not be performed in Parcel 3 due to recent remedial actions performed (Wallace Kuhl, 2005) and subsequent site development. In Parcel 24, the 28 soil gas sample points are located in areas of (1) the former Union Pacific railroad track spurs, (2) the northern and western property boundaries, (3) in the vicinity of possible storage areas, and (4) to provide background or inter-parcel conditions. In Parcel 4, the (7) seven soil gas sample points are located in areas of the former Union Pacific railroad track spur, areas of previous structures and/or along property boundaries. Prior to commencement of the soil gas survey, a GPS grid will be established over the project area similar to that indicated in Table 3 and Figure 4. Each soil gas sample point will be located on the ground surface with a flag or survey lath. The sample point will be labeled with the grid identification number that corresponds to the location indicated on the map, and will be used as the sample identification number with the depth of the sample also indicated. Implementation of the passive soil gas survey using GORE-SORBER technology will be accomplished by the installation of GORE-SORBER modules into pilot holes. The pilot holes will be advanced to a depth of between two (2) and three (3) feet bgs6 using either a slam bar or electric rotary hammer-drill. The diameter of the pilot hole is typically 0.5-inch to 0.75-inch. 5 Validation of the GORE-SORBER technology as an effective soil gas-screening tool is discussed in US EPA Environmental Technology Verification Report EPA/600/R-98/095, dated August 1998. 6 The GORE-SORBER modules may be installed at depth greater than three feet. Golden State Environmental, Inc. - 16 - Los Angeles, San Diego and Houston Revised Work Plan — Soil and GW Characterization July 2006