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STA! Cr CALIFORNIA GEORGE DEUKMEJIAN. 601.1 o� <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOAR[ , <br /> CENTRAL VALLEY REGION ''' <br /> 3443 ROUTIER ROAD, SUITE A <br /> SACRAMENTO, CA 95827-3098 <br /> 6 December 1990 <br /> Mr. Paul Levine <br /> Harding Lawson Associates <br /> 10324 Placer Lane <br /> Sacramento, CA 95827 <br /> GROUND WATER MONITORING WORKPLAN APPROVAL, USC STOCKTON, SAN JOAQUIN COUNTY <br /> During the meeting between USC, Harding Lawson Associates, Nolte Associates, <br /> the Department of Health Services (DHS) and the Regional Board we discussed <br /> the waste characterization results, the 26 October 1990 ground water <br /> monitoring workplan and the procedure necessary for DHS concurrence of USC's <br /> non-hazardous self determination. <br /> We have reviewed the waste characterization report and find the report <br /> adequate for our needs to determine potential impacts to ground water quality. <br /> We have also reviewed the ground water monitoring workplan submitted by <br /> Harding Lawson Associates on 26 October 1990. Board staff approves <br /> implementation of the workplan with the following comments: <br /> 1. Since effects of nearby industrial pumping wells on the local ground <br /> water gradient was not investigated, the regional gradient as depicted <br /> in the Fall 1989 report may not reflect the actual seasonal gradient <br /> directly beneath the USC Stockton surface impoundment. The workplan <br /> states that monitoring well locations were selected to "bracket" the <br /> pond in the up and down gradient directions. We note that the proposed <br /> monitoring does not cover the southern or western portion of the ground <br /> water near the surface impoundment. The abandoned roadway directly to <br /> the west of USC's property line and the surface impoundment should be <br /> considered as a location of an additional monitoring well in case the <br /> localized ground water gradient is determined to be tc the west. <br /> 2. A 25 foot screen length appears to be excessive to quantify <br /> horizontal/vertical ground water gradients and chemical characterization <br /> of the ground water in the first water bearing zone. Since drought <br /> conditions and local overdrafting has lowered ground water table levels, <br /> possibly 3 feet per year, setting the screen interval at 15 feet below <br /> the water table and 10 feet above should be considered. <br /> 3. The groundwater chemistry of the CCR Title 22 general minerals would <br /> include a cation/anion balance. <br /> 4. All other well construction aspects are acceptable. <br />