FIELD DOCUMENTS_2000-2003 - Laserfiche WebLink

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STAFF REPORT • • 2 SPX CORPORATION MARLEY COOLING TOWER COMPANY GROUNDWATER EXTRACTION AND TREATME-NT SYSTEM SAN JOAQUIN COUNTY new effluent limitation, the Discharger has not had an opportunity to conduct additional studies, undertake a Basin Plan amendment study, or pro«de a cost estimate for additional treatment or alternative disposal methods which may be necessary to comply with this limitation. A time schedule for compliance with this new TDS effluent limitation is provided in a Provision of this Order. In the interim, this Order retains the average monthly limitation for TDS in the previous Order of 1000 mg/L (ppm). Consideration of Agricultural Supply (AGR) Beneficial Use The new final effluent limitation for TDS may not be fully protective of the SDC for unlimited AGR use under all conditions. The TDS water quality criteria concentration for unrestricted AGR use, considering application of water to the most sensitive crops, is lower than the MUN water quality protective criteria(450 mg/L,ppm). This TDS concentration also corresponds to the SWRCB's Salinity Plan's promulgated standards of 700 umhos/cm EC during summer months (April through August) and 1000 umhos/cm EC during the remainder of the year. As noted previously, the summer months coincide with the lowest reported flows in the SDC, when limited or no water is available due to the diversion for AGR use upstream of the SDC. The appropriate TDS water quality criteria concentration for AGR in the SDC downstream of the discharge may be influenced by other conditions including site specific soil types, irrigation practices, and precipitation patterns. Evaluation of these factors may result in the protective water quality criteria for the AGR beneficial use remaining below, or adjusted above the criteria concentration protective of the MUN beneficial use. At this time it is not known whether the criteria for MUN or AGR is controlling. Provisions of this Order allow the Discharger time to; study the hydrologic characteristics of the SDC, consider the Basin Plan amendment process and de-designation of beneficial uses, study site specific conditions that affect the AGR water quality criteria concentration, and/or, evaluate alternative treatment or disposal options. Without new information concerning site specific conditions and water quality criteria concentrations protective of the AGR beneficial use, it may be necessary to reduce the current final effluent limitation from 500 mg/L to 450 mg/L during the summer months. Upon conclusion of the studies.this Order may be reopened to consider any new information and modification of the effluent limitation. The Discharger commented in part that MUN is not an existing beneficial use of the SDC, that limits should be based on dilution during the period when water from the Calaveras River is diverted through the SDC, and that the naturally occurring concentrations of TDS in groundwater exceed 500 mg/L. Deltakeeper commented that the time schedule provided for compliance with the new limitation was too lengthy. Staff applied the beneficial uses and associated limitations considering the best available information and in accordance with the Basin Plan. This proposed Order allows the Discharge time to pursue a variety of compliance alternatives. The Discharger has historically utilized reverse osmosis as a part of the designed treatment process to remove groundwater contaminants of concern, discharging brine with the treated water. The review of alternatives and implementation of a compliance alternative will likely take substantial time and effort.