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Geosyntec consultants fringe impacts. Therefore, ISCO activities proposed herein are intended to be a follow-up to SVE pending evaluation of SVE effects in the area. ISCO activities contemplated in this Work Plan will follow the same approach as described in the Former Source Area Injection Work Plan(Geosyntec, 2019) including targeted injections in the capillary fringe and groundwater and are anticipated to effectively remediate residual sorbed and dissolved PCE near and below the groundwater table. 3.2 Objectives The objective of the proposed SVE activities is to address elevated soil vapor concentrations of PCE in the shallow vadose zone in the vicinity of SG-100 and to reduce those concentrations to below the commercial CHHSL (603 gg/m3),to the extent reasonably practicable. The objective of proposed ISCO activities is to supplement SVE activities in addressing residual PCE impacts near the capillary fringe and in groundwater near monitoring well MW-007A and MW-009A, to the extent practicable. 3.3 SVE Approach Based on the lateral and vertical extent of the soil vapor impacts determined through additional investigation, Geosyntec proposes to implement a focused SVE effort in the vicinity of SG-100 (Figure 3). The SVE activities will target the shallow vadose zone to a depth of approximately 20 feet bgs. Two SVE wells will be installed near SG-100, one screened between 5 and 10 feet bgs and the other screened between 10 and 20 feet bgs,with the assumption that each will have a radius of influence(ROI)of 50 to 100 feet based on previous SVE data(LFR, 1999).A temporary,mobile trailer mounted SVE system powered by a generator will be utilized to extract soil vapor. Vapor- phase granular activated carbon (VGAC) vessels will be used to treat the extracted soil vapor. Initially, a pilot test will be conducted to assess ROI and to optimize SVE operation.The pilot test will be limited to a five-day period to utilize a pilot testing permit exemption provided by the Central Valley Air Pollution Control District (CVAPCD) and is expected to be sufficient to optimize SVE operation for subsequent efforts, as necessary. Relevant data including VOC concentrations at the SVE influent over time,vacuum,air flow rates, and discharge concentrations will be measured during the pilot test. The pilot test and soil vapor data will be used to confirm the ROI and effectiveness of the SVE wells and assess the need for additional SVE wells. After the initial five-day pilot test, the temporary SVE system will be demobilized, and performance monitoring samples will be collected from SG-100 and the two adjacent SVE wells to evaluate the potential for rebound in PCE soil vapor concentrations.The post-pilot performance monitoring samples are planned to be collected at the 1-, 3-, and 6-month mark following implementation of pilot treatment though, the sample frequency may vary based on sampling results. Additional confirmation samples may also be collected if the data will be valuable in establishing trends and to assess rebound. The rate of rebound in soil vapor concentrations will determine the duration between two sequential performance monitoring events and subsequent SVE activities. If results of the three performance monitoring samples (after 1-, 3- and 6-months) suggest that rapid back-diffusion is occurring (i.e. rebound concentrations substantially exceed the CHHSL and exhibit a rapid and Northern Parking Lot Remedial Plan 4 August 6,2021