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HARGIS+ASSOCIATES, INC. i <br /> Consultants in Hydrogeology <br /> 2223 Ave- cc De lc Po,- 5 �•e 30J . <br /> Lc J,-Ac. C- 92037 <br /> (619) 4540165 <br /> May 6, 1988 <br /> VIA FEDERAL EXPRESS <br /> Mr. David Bates <br /> Chief Production Engineer <br /> MARLEY COOLING TOWER COMPANY <br /> 5800 Foxridge Drive <br /> Mission, KS 66202 <br /> RE: Modifications by the California Department of Health <br /> Services to the Work Plan for Mitigation Activities, <br /> Marley Cooling Tower Company, Stockton. California <br /> Dear Mr. Dave: <br /> Pursuant to your request we have reviewed the letter of April 29, 1988 <br /> sent to you by James T. Allen of the California Department of Health <br /> Services (DHS) . This letter conveys our preliminary comments and concerns <br /> regarding the modifications made by DHS to the Phase IV Groundwater <br /> Assessment Work Plan. We are concerned by: 1) the DHS addition of nests of <br /> monitor wells at each proposed well location, 2) the arbitrary insistence on <br /> maximum 10-foot screen intervals in all monitor wells, and 3) the addition <br /> of arsenic, copper, and general minerals as analytes for all monitor wells <br /> for routine monitoring. <br /> DHS has mandated nests of monitor wells at nine locations. The <br /> rationale for the construction of shallow and deep zone monitor wells at <br /> these nine locations is not provided. Four of the mandated shallow monitor <br /> wells appear to be designed to determine the extent of groundwater <br /> containing no detectable concentrations of chromium. The other five shallow <br /> wells will be unnecessary if the upgradient shallow monitor wells contain no <br /> detectable concentrations of chromium. <br /> The appropriateness of the placement of deep zone monitor wells at each <br /> of these locations is also uncertain at this time. The approach described <br /> in the Phase IV Groundwater Assessment Work Plan is to first determine the <br /> zones of the aquifer that are contributing chromium to California Water <br /> Service Well 20 (CWS-20) by means of nested monitor wells. The groundwater <br /> assessment would then be conducted both upgradient and downgradient of well <br /> CWS-20 in the zones identified as contributing chromium to well CWS-20. <br /> DHS has mandated that all monitor wells be completed with a maximum 10- <br /> foot screened interval with the exception of monitor wells completed at the <br /> water table. While 10-foot screened intervals may be appropriate in some <br /> Phoenix office. Tucson office. <br /> 2222 Souih Dobson Rood Suue 401 3385 Norih Campbell Avenue Swie 12`. <br /> Mesa, Arizono 85202 Tucson, Arizona 85719 <br /> (6n?) 145 0888 (602) 8817300 <br />