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Geosyntec D consultants 4. SCOPE OF WORK 4.1 Rationale and Approach To address the data gaps presented above, temporary soil vapor probes will be installed to collect soil vapor samples from up to three depths per location. Temporary soil vapor probes will be initially installed approximately 15 feet to the north, south, east and west of SG-100, pending access and field conditions, to evaluate the lateral extent of elevated PCE concentrations. Temporary soil vapor probes will also be installed along the sanitary sewer line servicing the former Lincoln Village Cleaners suite to assess whether there are remaining vadose zone impacts along the utility corridor(Figure 3). The temporary soil vapor probes will initially be installed at approximately 6.5 and 13 feet bgs, pending subsurface conditions, consistent with the depths of SG-100 where elevated concentrations of PCE were reported. If elevated impacts are observed in the 15-foot soil vapor probe, a third depth(approximately 25 feet bgs)may be sampled. If elevated impacts are not observed in the initial 13-foot probes, additional probes may only be installed at 6.5 feet bgs. Deeper samples may not be warranted if shallow soil vapor is not impacted because impacts observed in deeper soil vapor but not shallow soil vapor would indicate a groundwater source rather than vadose zone source and is outside the scope of this investigation. Following the construction of the initial temporary soil vapor probes, a HAPSITE® portable gas chromatograph will be used to screen soil vapor samples and obtain real-time quantitative data with a reporting limit of 1.4 gg/m3 for PCE.The results from the HAPSITE®will be used to select step-out locations for additional temporary soil vapor probes as necessary, to evaluate the extent of elevated PCE concentrations in shallow soil vapor in the vicinity of SG-100 and along the sanitary sewer lateral. Step-out locations,both vertically and laterally,will be based on an exceedance of the commercial CHHSL of 603 gg/m3. Active remediation in the area was performed until PCE concentrations reached the CHHSL of 603 µg/m3 in 2013.Potential for VI into nearby buildings is currently being evaluated as part of the on-going VI investigation activities at the Site as detailed in the Pilot Study Work Plan. If the HAPSITE® results have a reported concentration of PCE greater than the CHHSL (603 gg/m3), which was the criteria used for closure in 2013, a step out location will be selected approximately 10 to 20 feet in the same cardinal direction, pending access limitations and underground utility conflicts. Distance, depths and location of additional step-out locations may be altered in the field based on professional judgement and results of the initial HAPSITE® samples. If PCE concentrations exceed 603 µg/m3 in continual step-out locations, step-outs will cease once an adjacent building/suite is reached. Once impacts have been evaluated using the HAPSITE®, confirmation soil vapor samples will be collected from the outermost soil vapor probes using one-liter(1L) summa canisters and submitted to the laboratory for analysis of VOCs by EPA method TO-15. Samples submitted to the laboratory for analysis will primarily be collected from the furthest step-out locations to confirm the lateral extent and evaluate the potential for vapor intrusion in nearby buildings. 202012 Lincoln Center Soil Vapor Assessment Work Plan 6 December 2020