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S <br /> O <br /> t <br /> ADDENDUM TO FINAL REMEDIAL PLAN <br /> I MANTECA BEAN FACILITY <br /> c 229 MOFFAT BOULEVARD <br /> MANTECA, CALIFORNIA <br /> sa <br /> February B, 1991 <br /> k7 <br /> i.0 INTRODUCTION <br /> This report is presented as an addendum to the Final Remedial Plan(FRP)submitted by The Golden Grain <br /> Company or,September 17,1990 to San Joaquin County Public Health Services. The site history,geology, <br /> hydrogeology and the design of the proposed remediation system are presented In the FRP. This <br /> addendum documents the recovery well installation at the Manteca site, and Includes the results of an <br /> aquifer pump test and an evaluation of the design of the water treatment system presented In the FRP based <br /> on the new data. <br /> 2.0 RECOVERY WELL INSTALLATION <br /> z <br /> On November 8, 1990, a Groundwater Technology registered geologist supervised the installation of a <br /> groundwater recovery well. Air Rotary drilling techniques were utilized to drill a twelve-inch diameter <br /> - borehole to fifty-one feet below ground surface(BGS). Casing was driven during drilling to prevent caving <br /> of the hole, and to eliminate any cross contamination from the upper to the lower aquifer. Because the <br /> subsurface in the vicinity of the recovery well has been well characterized,soil samples were only collected <br /> with a split-spoon sampler from the clay layer separating the two aquifers at 25 feet SGS. Knowledge of <br /> the exact depth of this clay layer was important to determine the required depth of the sanitary seal to avoid <br /> communication between the upper and lower aquifer. The rest of the boring was logged from the drill <br /> cuttings (Appendix A). <br /> The recovery well consists of 8 inch diameter 0.05rj-slot low carbon steel screen from 50 feet BGS to 30 feet <br /> BGS, and low carbon steel casing to grade. A Monterey 8-12 sand was used as a filter pack.--The screen - -- - - - <br /> t <br /> size and filter pack were determined prior to ins.ailation from grain size analyses. The filter pack was <br /> compacted by pumping from the well prior to installation of the sanitary seal. The sanitary seal consists of <br /> neat cement from 31 feet BGS to nt;ar gradeAlnstallation of the sanitary seal was ob,3erved by a representative <br /> OROUND"ATEK <br /> TECHNOLOGY,INC. <br /> Qom® <br />