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Work Plan,Decommissioning Monitoring Wells MW-3,MW4,and MW-7 <br /> 2130 West Washington Street <br /> Stockton,California <br /> Sierra-Pacific Project No.92-033.04 <br /> i.3 <br /> Elevated Total Dissolved Solids (TDS) concentrations, including chlorides, detected in ground-water <br /> samples from MW-3, MW-4, and MW-7 indicate that brackish(connate) ground water pervades near- <br /> surface deltaic sediments of the Port of Stockton. The seasonal infiltration of relatively fresh storm <br /> water flushes saline components from near-surface sediments, most notably in areas where storm <br /> L' water ponds at the surface. Soil borings advanced in the western part of the site routinely intercepted <br /> olive-green silty-sand formations which contained elevated concentrations of dissolved salts. Several <br /> years of laboratory testing indicate that molasses feed product constituents which are present in the <br /> subsurface beneath the Washington Street facility have little or no deleterious effect on shallow <br /> ground-water resources. <br /> The California Regional Water Quality Control Board (RWQCB) notified Unocal in writing on <br /> September 2, 1998 that with no significant change in ground-water conditions at the site, no further <br /> investigative work or other actions would be required by the RWQCB. Decommissioning shallow <br /> monitoring wells MW-3, MW-4, and MW-7 will close Unocal's involvement with the site. <br /> G <br /> 2.0 PURPOSE OF MONITORING WELL DECOMMISSIONING <br /> L <br /> Monitoring wells MW-3, MW-4, and MW-7 will be properly sealed and decommissioned to preclude <br /> the introduction of contaminants into the abandoned wells and to reduce the vertical movement of <br /> shallow ground water through the well packs. <br /> G <br /> Sierra-Pacific Groundwater Consultants,Inc. 2 <br /> c <br />