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Weston Solutions, Inc. Remedial Action Work Plan for the San Joaquin County Human Services Agency Site—Stockton, California PROPOSED IMPLEMENTATION PLAN A variable speed injection (positive displacement) pump is typically used for injection. The injection subcontractor and oversight engineer will record the injection depth intervals, injection pressures, and flow rates and volumes of injection materials for each injection point. After injection of BOS 200 is completed in all borings,wells MW-2 will be surged and pumped with well redevelopment equipment to clear out treatment reagent(if any). Once the injection of BOS 200 reagent is completed, each boring will be backfilled with hydrated bentonite and the surface paving will be restored. 6.7 GROUNDWATER PERFORMANCE MONITORING AND REPORTING Groundwater monitoring will be conducted as a component of the corrective action to evaluate the effectiveness of the BOS 200 injections in treating the petroleum hydrocarbons at the Site. This groundwater monitoring and reporting will be conducted in accordance with the proposed Monitoring and Reporting Program presented in Appendix A. This Monitoring and Reporting Program will be finalized following review and approval by the Central Valley Water Board as part of coverage under Order No. R5-2015-0012. Table 6-2 presents a summary of the proposed monitoring program. Per the requirements of the Central Valley Water Board, the monitoring wells are characterized as treatment zone, compliance zone, and background wells. Treatment zone wells will be monitored to assess the remediation progress in the vicinity of remediation zone. Compliance zone wells will be monitored to evaluate compliance with groundwater concentration limitations. Background wells will be used to establish background reference values for the assessment of unacceptable water quality effects at the point of compliance wells. Groundwater samples will be collected using low-flow micropurge sampling methods consistent with routine semi-annual monitoring conducted at the site. The low-flow micropurge method of sampling will be completed using a decontaminated submersible pump attached to tubing dedicated to each well. The pump will be placed within the lower 5 feet of the screened interval of the well. The well will be purged at a flow rate ranging from 200 to 500 milliliters (mL) per minute while monitoring the depth to groundwater to ensure that no drawdown of the water level occurs. The tubing volume will be calculated for each well; a 6-4 February 2021