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LAWRENCE & ASSOCIATES <br /> Engineering Geologists • Ground-water 11ydrologists <br /> 170 SOI'TH STRELT,SUITE C <br /> REDDING,CALIFORNIA 96001 <br /> TI:LEPHONE (9161 244-9703 DAVID A. LAWRENCE, C.E.G.618 <br /> C88.02. 04 <br /> February 29, 1988 <br /> DECEIVED <br /> y. (3 1988 <br /> Mr. Dennis Abrahamson <br /> Simpson Paper Company .ENVIRONMENTAL HEALTH <br /> P.O. Box 757 PERWT/SERVICES <br /> Ripon, CA 95366 <br /> Dear Dennis: <br /> SUBJECT: PROPOSAL FOR SERVICES - LEACHFIELD MONITORING <br /> The enclosed SCOPE OF WORK AND PROPOSAL FOR SERVICES addresses <br /> the work and costs to install a monitoring program required by <br /> the State. In addition, the program reflects monitoring and <br /> analysis that could lead to procuring a better-quality water <br /> supply and/or minimize the effects of recycling percolated <br /> effluent . <br /> Following our meeting in Ripon, I reviewed all the data you <br /> provided me, plus several reports I have in my office on ground- <br /> water conditions in the area. As a result, I felt it more <br /> productive to work out a monitoring scheme and costs at this <br /> time. <br /> Three aspects of the ground-water conditions are important to <br /> your site, and should be considered in your future work: <br /> 1 . All evidence indicates a water-table condition that <br /> readily promotes recycling of percolated effluent through the <br /> supply wells. The degree of this recycling is related to <br /> distance between the percolated "mound" and the pumping <br /> wells, any continuous horizontal stratum that may impede <br /> downward movement, formation transmissivity that governs the <br /> radius of influence of the pumping wells, and the location of the <br /> perforated interval in the pumping wells. <br /> 2. The direction of ground-water move:-nent has changed from <br /> a westerly direction to a southerly direction over the last 25 <br /> years. With increased pumpage by the City of Ripon, the movement <br /> of ground water could become more-or-less stagnant at the Simpson <br /> property, compounding the recycling problem. That is, a pumping <br /> depression could develop beneath the City of Ripon wells similar <br /> to that underlying the City of Modesto. Ground-water movement <br />