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' Well Installation and Quarterly Groundwater Monitoring Report <br /> Second Quarter 2008 <br /> 1950 West Fremont Street, Stockton, California <br /> found to exceed regulatory criteria (as identified in the Final PEA Report and DTSC's October 2007 <br /> review letter): nickel,NDMA, and MTBE. This reduction in analyses would remain consistent with the <br /> ' purpose of the groundwater monitoring, which is to determine whether groundwater is migrating off-site <br /> with concentrations of chemicals of potential concern exceeding regulatory criteria. For future <br /> ' monitoring events, the trend of nickel, NDMA and MTBE concentrations in groundwater will be <br /> evaluated to assist with site closure decisions. <br /> Based on the direction of groundwater flow (to the north), as determined by the Second Quarter 2008 <br /> groundwater monitoring event, the monitoring wells (MW-2 and MW-3) are appropriately located <br /> ' immediately down-gradient of the prior detections of nickel, NDMA and MTBE in groundwater. <br /> Groundwater from MW-3 has nickel at a concentration (0.11 mg/L) slightly exceeding its MCL (0.1 <br /> mg/L), indicating that the well locations are appropriate for monitoring the leading edge of the impacted <br /> groundwater. At this time, the installation of an additional monitoring well is not recommended; <br /> ' however, the potential need for an additional well will continue to be evaluated based on the additional <br /> data that will be collected during the next quarterly monitoring events. <br /> 5.0 REFERENCES <br /> ' Bouwer, H. 1989. The Bouwer and Rice Slug Test An Update. Ground Water 27(3): 304-309. May- <br /> June. <br /> Bouwer, H. and R.C. Rice, 1976. A Slug Test Method for Determining Hydraulic Conductivity of <br /> Unconfined Aquifers with Completely or Partially Penetrating Wells; Water Resources Research, <br /> vol. 12,no. 3,pp.423-428. <br /> Cooper, H.H., J.D. Bredehoeft and S.S. Papadopulos, 1967. Response of a Finite-diameter Well to An <br /> Instantaneous Charge of Water,Water Resources Research,vol. 3,no. 1,pp. 263-269. <br /> ' Earth Tech,Inc., 2007. Final Preliminary Endangerment Assessment Report for Tyco Electronics <br /> Facility at 1950 West Fremont Street, Stockton, California.August. <br /> Department of Toxic Substances Control (DTSC), 2007. Review of Final Preliminary Endangerment <br /> Assessment Report, Tyco Electronics Corporation, Stockton, California. October 4. <br /> Project 102790 12 July 2008 <br />