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Page 13 <br /> three-dimensional block model will be updated/augmented with data collected from this proposed <br /> HRSC investigation. <br /> TASK 3: SUPPLEMENTAL WELL INSTALLATION AND ONE-TIME GROUNDWATER <br /> MONITORING <br /> No monitoring wells currently characterize perched or deeper water table groundwater conditions <br /> within the inferred hot spot of contamination near the historic (pre-1988) Shell fueling infrastructure <br /> near eastern Property margins. EES therefore proposes to install two new groundwater monitoring wells <br /> to better characterize these identified impacts (one well in the perched water zone and one in the <br /> deeper water table zone). <br /> These wells may be re-sampled for future use in remedy planning, but will be developed, surveyed, and <br /> sampled only initially under this current work plan." <br /> TASK 3A: GROUNDWATER MONITORING WELL INSTALLATION <br /> Installation of two monitoring wells is planned under Task 3A.The proposed locations for MW-11 and <br /> PMW-12 are included on Figure 3. EES will develop these monitoring wells in accordance with Ecology <br /> and EPA guidelines prior to sampling. <br /> ■ One water table monitoring well (MW-11) is proposed in the eastern portion of the Property, as <br /> impacts to the deeper water table zone have not been characterized in this area. The targeted <br /> screened interval for MW-11 is approximately 60 to 70 feet bgs but will be dependent on <br /> material/water level encountered during boring installation. <br /> ■ One shallow perched zone monitoring well (PMW-12) is proposed along the eastern Property <br /> boundary near the location of HRSC boring MIPB, where significant petroleum impacts were <br /> identified.The targeted screened interval for this monitoring well is approximately 5 to 10 feet <br /> bgs.This interval was selected to evaluate perched water conditions that could be encountered <br /> by excavation/utility workers in this inferred contaminated area.17 <br /> ■ To the extent that substantial contamination is observed while drilling these two wells, <br /> particularly in the uppermost 15-foot perched zone, supplemental soil sampling/testing will be <br /> considered as described under Task 2B. <br /> TASK 3113: LIMITED GROUNDWATER MONITORING <br /> Following development and surveying of the two new wells (Task 3A), perched zone (SGW-1, SGW-2, <br /> SVE-4, SVE-8, SVE-10, SVE-13, SVE-14, SVE-15, and PMW-12) and water table monitoring wells (MW-2 <br /> through MW-11, plus SVE-6 and SVE-11) will be sampled (anticipated May-June 2024) and analyzed for <br /> the following chemical indicators: <br /> ■ Gasoline-range hydrocarbons <br /> ■ Gasoline-related volatile constituents (BTEXN, EDC, MTBE) <br /> 16 Only a single groundwater monitoring event is included in this work scope. <br /> 17 The sanitary sewer line is located approximately 8-10 feet bgs in the sidewalk adjacent to the this proposed well <br /> location. <br /> EES ENVIRONMENTAL CONSULTING,INC. 2120-02 2024 SOW 20240408f <br />