Laserfiche WebLink
Response to Written Comments -29- 24 April 2007 <br /> City of Tracy WWTP <br /> San Joaquin County <br /> salinity problems in the southern Delta. Even if the Tracy discharge were <br /> removed it would not solve the salinity problems in the area. The proposed <br /> Order provides reasonable salinity controls that put the Discharger on the path to <br /> reducing its salt loading to the Delta. <br /> The proposed Order includes an interim annual mass-based effluent limitation for <br /> total dissolved solids (TDS) (see Section IV.A.5.f.). TDS is a measure of salinity, <br /> similar to electrical conductivity (EC), and was used for the interim limit because <br /> it can be converted to a mass loading using a conversion factor and the effluent <br /> flow rate. EC cannot be converted to a mass loading. The interim effluent <br /> limitation for TDS is based on current treatment plant performance and will <br /> ensure that the mass loading of salinity does not increase as the effluent flow <br /> rate increases. Holding the discharge's mass loading will result in lower <br /> concentrations of EC as the City expands its discharge. The modeling shows <br /> that the increases in salinity concentrations caused by the Tracy discharge in the <br /> south Delta are reduced as the effluent flow rate is increased to its permitted <br /> capacity of 16 mgd. Furthermore, the proposed Order requires the Discharger to <br /> implement measures to reduce the salinity in its discharge to Old River and <br /> requires the Discharger implement best practicable treatment or control (BPTC) <br /> of its discharge and develop and implement a pollution prevention plan for <br /> salinity in accordance with CWC section 13263.3. <br /> SDWA — NPDES COMMENT #2: The proposed Order references the 1995 Water <br /> Quality Control Plan, but fails to mention the 2006 Bay-Delta Water Quality Control Plan <br /> adopted on 13 December 2006. <br /> RESPONSE: This was an inadvertent omission. The proposed Order has been <br /> updated to mention the latest update of the Bay-Delta Water Quality Control <br /> Plan. <br /> SDWA — NPDES COMMENT #3: The proposed Order represents that the permit will <br /> result in the degradation of the waters of the south Delta, but finds that such <br /> degradation is "consistent with the maximum benefit to the people of the state." This <br /> conclusion lacks any basis in the documents and needs to be explained. <br /> RESPONSE: The Fact Sheet contains a detailed Antidegradation analysis. See <br /> response to ELF — NPDES COMMENT #1, below. <br /> SDWA — NPDES COMMENT #4: On page F-8 of the proposed Order it states that <br /> there is a mass loading limit of salt based on current loading. This was not found in the <br /> proposed Order. Why is the permittee allowed to maintain current mass loading rather <br /> than be required to make incremental, enforceable decreases in the loading? <br /> RESPONSE: See response to SDWA — NPDES COMMENT #1. <br /> Regional Water Quality Control Board, Central Valley Region <br /> Board Meeting — 3/4 May 2007 <br /> Item#17 <br />