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STAFF REPORT • 4 SPX CORPORATION MARLEY COOLING TOWER COMPANY GROUNDWATER EXTRACTION AND TREATMENT SYSTEM SAN JOAQUIN COUNTY Concerning the Discharger's comments, although the discharge supports the aquatic environment, aquatic life beneficial uses apply to the SDC from the point of discharge to the confluence with the Calaveras River and must be protected. Available information suggests that the SDC is at times dry, absent the discharge, and may be dry for extended periods. EPA ambient water quality criteria for copper and hexavalent chromium are composed of one hour(acute), and four day(chronic) criterion values. The new limits were developed to protect aquatic life during these periods of limited or no dilution. With regard to Deltakeeper's comment on the compliance schedule justification,prior to issuance of the Tentative Order, the Discharger was unaware of the outcome of the reasonable potential analysis, and establishment of new effluent limitations. The Discharger did not have an opportunity to comment on Findings in the permit prior to issuance of the Tentative Order, and has not had an opportunity to contest items of the proposed Order with which they do not agree. The Discharger has made diligent efforts to quantify pollutant levels and their sources. Source control and/or pollutant minimization measures are not relevant to this groundwater remedial action. Text in the proposed Order has been revised to read that if a compliance schedule justification is not submitted within 80 days of permit adoption, the final effluent limitations will become effective on that date. Whole Effluent Toxicity (WET) Testing This proposed Order includes requirements for continued chronic WET Testing. The Discharger commented that historical aquatic testing has shown that the discharge meets criteria, and that the results of a Toxicity Identification Evaluation(TIE) conducted in 1995 in response to sub lethal toxic effects was inconclusive. Sporadic instances of unknown toxicity have been reported in WET testing accomplished by the Discharger in the past. Staff does not agree that continued toxicity testing is unnecessary based on the fact that results of the 1995 TIE were inconclusive. TIE test methods have improved since that time, and short-term WET tests are a necessary part of the weight of evidence approach to assessing toxics control and toxicity. In the Technical Support Document for Water Quality-based Toxics Control (TSD,March 1991), USEPA recommends an integrated chemical-specific,whole effluent and bioassessment approach to fully protect aquatic habitats. This proposed Order requires chronic toxicity testing in accordance with the latest USEPA test methods which were revised in December 2002. September 2002 Release, Fish Kill Incident The September 2002 release that resulted in a fish kill was caused by a pH meter malfunction. The false pH signal in tum caused the caustic pH adjustment pump to continuously operate. Because the meter signal was frozen and sending a false low pH signal, the system shut-down feature did not activate as it was designed to do. The malfunction resulted in a discharge of approximately 2160 gallons of 50%by weight sodium hydroxide into the SDC and a fish kill of approximately 4,500 fish in the SDC. The Discharger has installed some additional pH control measures to prevent such an event in the future. l