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California Regional Water QualityControl Board
<br /> Central Valley Region
<br /> Robert Schneider,Chair
<br /> Winston H.Hickox O Gray Davis
<br /> Secretaryfor Sacramento Main Office IV Governor
<br /> Environmental Internet Address: http://w .swrcb,ca.gov/mgcb5 C
<br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 r
<br /> Phone(916)255-3000•FAX(916)255.3015
<br /> C71
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<br /> 11 July 2002 = lc
<br /> Cn
<br /> Mr. David Lieb
<br /> Marley Cooling Tower Company
<br /> 150 N. Sinclair Avenue
<br /> Stockton, CA 95215
<br /> PROPOSED REVISIONS TO GROUNDWATER MONITORING PROGRAM FOR MARLEY
<br /> COOLING TOWER COMPANY FACILITY, STOCKTON, SANJOAQUIN COUNTY
<br /> The Regional Water Quality Control Board(Board) has the reviewed the proposal dated June 11, 2002,
<br /> prepared by Dudek&Associates on behalf of Marley Cooling Tower Company. The letter requests a
<br /> reduction in the sampling frequency of several groundwater monitoring wells and lysimeters based on
<br /> historical concentrations of dissolved total chromium.
<br /> We generally concur with the approach to reduce the sampling frequency as indicated in Table 1 of the
<br /> proposal, starting with the next groundwater event, with exceptions as indicated.
<br /> We suggest continuing or revising the proposed schedule to annual sampling for the following wells for
<br /> total chromium:
<br /> • Upgradient wells MW-209, MW-210, and MW-441.
<br /> • Farthest downgradient and plume definition wells for the different water bearing zones (MW-
<br /> 300,MW-304, MW-400, MW-303, MW-410, MW-411, MW-310, MW-325, MW-327, MW-
<br /> 433,MW-446, MW-462, MW-463, MW-364, MW-465.
<br /> We suggest revising the proposed schedule to semiannual sampling for the following wells, at this time,
<br /> for total chromium, and hexavalent chromium:
<br /> • Irrigation, domestic, and production wells (5166I, Columbini wells 1,2, and 3, Cuneo, Solari,
<br /> MSI, CWS-20, CWS-35, CWS-52, and CWS-62). The EPA IRIS Reference Dose as drinking
<br /> water for hexavalent chromium is 21 parts per billion (ppb). Hexavalent chromium (upto 15
<br /> parts per billion)has been detected in these wells since October 2000.
<br /> hi addition,we suggest Marley develop and submit for our review, a process and a decision tree to refine
<br /> the groundwater sampling program for the Marley facility. The factors for development should consider
<br /> (a)purpose and use of data collected, (b) site conditions (hydrogeology including fate and transport), (c)
<br /> location of wells (plume definition wells, in plume wells,up gradient wells, down gradient wells, cross
<br /> gradient wells, sentry wells etc.), and(d) sensitive receptors. Periodic evaluation of collected data could
<br /> be used to further refine the process flow chart that may translate to potential cost savings due to a
<br /> decrease in the number of wells for sampling or a decrease in sampling frequency. Upon request,we can
<br /> California Environmental Protection Agency
<br /> 0d Recycled Paper
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