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Report: Groundwater-quality Monitoring January 20, 2003: 7500 West Eleventh Street, Tracy, CA. Page i <br /> Table of Contents <br /> PROFESSIONAL CERTIFICATION AND LIMITATIONS..................................iii <br /> 1.0 INTRODUCTION...................................... ................................................................ 1 <br /> 1.1 Site Location............................................................................................................ I <br /> 1.2 Site Codes ................................................................................................................ I <br /> 1.3 Background.............................................................................................................. I <br /> 1.4 Geology and Hydrogeology..................................................................................... 3 <br /> 1.5 Distribution of Hydrocarbons in the Subsurface ..................................................... 4 <br /> 2.0 JANUARY 20, 2003 GROUNDWATER SAMPLING AND ANALYSIS................ 6 <br /> 2.1 Groundwater Elevations and Flow Direction .......................................................... 6 <br /> 2.2 -Purgin g of Monitoring Wells................................................................................... 8 <br /> 2.2.1 Disposal of Purge Water................................................................................... 9 <br /> 2.3 Recovery of Groundwater Samples from Monitoring Wells................................... 9 <br /> 2.4 Analyses of Groundwater Samples.......................................................................... 9 <br /> 2.4.1 Groundwater Quality in the Near-Surface Unconfined Aquifer..................... 10 <br /> 2.4.2 Groundwater Quality in the Deeper Confined Aquifers...................... .......... 12 <br /> 3.0 RECOMMENDATIONS........................................................................................... 14 <br /> 3.1 Close Wells Penetrating Protective Aquitards....................................................... 14 <br /> 3,2 Close Redundant Well MW-8................................................................................ 15 <br /> 3.3 Reduce Monitoring Frequency to Twice per Year .........i...................................... 15 <br /> 3.4 Remediate Area of Floating Product Across West Eleventh Street....................... 15 <br /> 3.4.1 Recommended Remediation Process.............................................................. 15 <br /> 3.4.2 Preparation for Remediation Work................................................................. 16 <br /> 3.5 Sample Down-gradient Potable Water-supply Wells............................................ 16 <br /> 3.6 Requirement for a Letter of Direction Before Work Can Proceed........................ 16 <br /> 4.0 FUTURE ROUNDS OF GROUNDWATER SAMPLING AND ANALYSIS ........ 18 <br /> 5.0 REFERENCES .......................................................................................................... 19 <br /> TABLES <br /> Table 1: Depths to Groundwater <br /> Table 2: Results of Analyses of Samples of Groundwater <br /> sic <br />