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Weston Solutions, Inc. <br /> Remedial Action Work Plan for the San Joaquin County Human Services Agency Site—Stockton, California <br /> PROPOSED IMPLEMENTATION PLAN <br /> minimum of three tubing volumes will be purged prior to sampling. The temperature, pH, <br /> electrical conductivity,dissolved oxygen(DO),and oxidation-reduction potential(ORP)of the <br /> purge water will be measured using a flow-through cell during the well purging and will be <br /> recorded for each tubing volume on a sampling data sheet. Stabilization will be determined <br /> after two successive readings for all parameters (except ORP) are within 10 percent. <br /> Groundwater samples will be collected from the tubing discharge after disconnecting from the <br /> flow-through cell. The flow rate will be reduced to less than 200 mL for samples collected for <br /> volatile analysis. <br /> Groundwater samples will be collected and preserved in appropriate containers based on the <br /> standard analytical methods. Samples will be labeled, sealed in a plastic bag, and placed on <br /> ice in an insulated cooler. The samples will then be submitted to the laboratory under chain- <br /> of-custody control for analysis using methods presented in the Monitoring and Reporting <br /> Program presented in Appendix A. <br /> 6.8 CONTINGENCY ACTIONS <br /> Central Valley Water Board Order No. R5-2015-0012 requires a contingency plan to be <br /> implemented to correct unacceptable water quality effects in case violations are found at the <br /> point of compliance wells. Unacceptable water quality effects will be assessed based on <br /> comparison of concentrations of dissolved metals, nitrate, and sulfate with their baseline <br /> concentrations established prior to injection of treatment amendments(see Appendix A for the <br /> plan to establish background concentrations)and/or comparison with established water quality <br /> objectives. <br /> If the concentrations of dissolved metals, nitrate, or sulfate exceed their background levels by <br /> more than 20 percent, or exceed water quality limits in compliance wells, a confirmation <br /> sample will be collected within four weeks of learning of the exceedance. If the exceedance is <br /> confirmed, the Central Valley Water Board will be notified in writing within 10 days. <br /> Following notification, a Corrective Action Work Plan will be submitted to the Central Valley <br /> Water Board within 30 days and will include one or more of the following actions: <br /> 6-5 Febraary 2021 <br />