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f 1 • • <br /> MWH <br /> January 11, 2008 <br /> Mr. Steve Ross <br /> Department of Toxic Substances Control <br /> 8800 Cal Center Drive <br /> Sacramento, CA 95826-3200 <br /> Re: Response to DTSC Comments and Recommendations dated December 21, 2007 <br /> presented in the DTSC Approval of the Remedial Action Implementation Work Plan <br /> (RAIWP), Marley Cooling Tower Site, Stockton, California <br /> Former Marley Cooling Tower Site,Stockton, California 95215 <br /> Dear Mr. Ross: <br /> On behalf of SPX Corporation, MWH Americas, Inc. (MWH) has prepared this response to <br /> comments and recommendations for the DTSC letter Approval of the Remedial Action <br /> Implementation Work Plan (RAIWP), Marley Cooling Tower Site, Stockton, California. <br /> MWH has provided the DTSC comments and recommendations below followed by the MWH <br /> responses in italics. <br /> Comment 1: Elevated concentrations of chromium have been detected in groundwater samples <br /> from the intermediate zone.Injection is currently not planned for the intermediate zone.Elevated <br /> concentrations for the intermediate zone were detected in samples from monitoring wells MW- <br /> 321,MW-214, and MW-213.It is anticipated that the cleanup of shallower zones will allow for <br /> the intermediate zone concentrations to decrease at a faster rate than would be expected with just <br /> groundwater extraction.Recommend assessment with ongoing groundwater monitoring efforts as <br /> to the effectiveness of the injection to increase the rate of remediation of the intermediate zone. <br /> Response: The current quarterly monitoring and sampling plan will monitor intermediate <br /> wells MW-1,MW-2,MW-213,MW-321,MW-322,MW-323,MW-324,andMW-325for remedial <br /> performance. Dudek will assess the effectiveness of the injection in reducing chromium <br /> concentrations in the intermediate zone in the semi-annual groundwater monitoring reports. <br /> SPX will consider evaluating the monitoring program in the future and incorporate additional <br /> intermediate wells if warranted. <br /> Comment 2: A review of Figure 8 indicates that well screens for the intermediate zone wells <br /> MW-214 and MW-213 are very long.This could allow for dilution of chromium concentrations <br /> if samples are collected utilizing traditional purging methods. Recommend as chromium <br /> concentrations in groundwater samples from long screened wells approach cleanup goals then <br /> 3321 Power Inn Road Tel:916 924 8844 BUILDING A BETTER WORLD <br /> Suite 300 Fax:916 924 9102 <br /> Sacramento,California <br /> 95826 <br />