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California Regional Water Quality Control Board ' <br /> �■/ Central Valley Region <br /> Winston H.Hickox Steven T. Butler, Chair <br /> Gray Davis <br /> Srrrrrartfor Sacramento Main Office r* IuL .,11 Q�J Governor <br /> Environmental rtion Intemet Address: http://www.swrcb.ca.gov/lrwq b5 y p i �, <br /> Prntertinn 3443 Routier Road,Suite A,Sacmmento,Califomia 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 30 June 2000 <br /> Mr. David R. Lieb <br /> Marley Cooling Tower Company <br /> 150 North Sinclair Avenue <br /> Stockton, CA 95215 <br /> PROPOSED REVISIONS TO GROUNDWATER MONITORING PROGRAM FOR <br /> MARLEY COOLING TOWER COMPANY(MCTC) FACILITY, SAN JOAQUIN COUNTY, <br /> Case No. 2971 <br /> The Board and the Department of Toxic Substances Control (DTSC) have reviewed the <br /> Proposed Revisions to Groundwater Monitoring Program for Marley Cooling Tower Company <br /> Facility, dated 2 December 1999, as prepared by Dudek & Associates, Inc. (Dudek). Based on <br /> Dudek's review of cumulative total chromium concentration trends observed in the monitoring, <br /> extraction, and reclamation wells, and the hydrogeological data including groundwater elevation <br /> maps and groundwater quality hydrographs, it is their opinion that reduction in the frequency of <br /> groundwater monitoring at the facility is warranted. As discussed in our meeting at MCTC on <br /> 12 June 2000. the Cal/EPA Office of Environmental Health Hazard Assessment (OEHHA) <br /> established a Public Health Goal (PHG) for hexavalent chromium in drinking water(February <br /> 1999). The PHG is based on a health protective criterion of 0.2 ppb (0.0002 ppm) for hexavalent <br /> chromium. Based on this new information, we regretfully cannot accept your proposal to reduce <br /> the frequency of monitoring until we have gathered additional information. <br /> In this regard, MCTC should collect a minimum of 4 quarters of groundwater and lysimeter <br /> samples from all sampling points in order to; (1) determine background concentrations for <br /> hexavalent chromium, (2) determine whether domestic, agricultural, and production wells are <br /> impacted, (3) determine the vertical and horizontal extent of the hexavalent chromium plume in <br /> all water bearing zones, and(4) determine the quality of water extracted from the soil flushing <br /> project at the retort pit. Those sampling points that have detected total chromium greater than <br /> 0.01 µg/L may be excluded at this time. Additional wells may be required to be monitored for <br /> hexavalent chromium as the plume decreases in size over time, as appropriate. <br /> Dudek's proposed reduced frequency of monitoring points is based upon several years of data <br /> showing ND where the total chromium detection limit was 10 mg/L (0.01 µg/L) using EPA <br /> Method 6010. MCTC should use EPA Method 7199, Determination of Hexavalent Chromium in <br /> Drinking Water, Groundwater, and Industrial Wastewater Effluents by Ion Chromatography. <br /> • The Method Detection Limit should be 0.5 ppb (µg/L). <br /> California Environmental Protection Agency <br /> Qa Rervrled Paper <br />