SITE INFORMATION AND CORRESPONDENCE_CASE 2

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Response to Written Comments -13- 24 April 2007 City of Tracy WWTP San Joaquin County infeasible and BMPs and Pollution Prevention requirements are imposed in lieu of a numeric limit as authorized by 40 C.F.R. §122.44(k)(3). RESPONSE: The Delta waterways are listed in accordance with CWA section 303(d) as impaired for mercury, based on bioaccumulation of this pollutant in fish tissue. Regional Water Board staff are developing a draft Methylmercury TMDL for the Delta that proposes methylmercury load reductions for facilities discharging to the South Delta, including Old River. The SIP recommends the Regional Water Board consider whether the mass loading of bioaccumulative pollutants should be limited in the interim to "representative current levels" pending development of applicable water quality standards or TMDL allocation. The intent is, at a minimum, to prevent further impairment while a TMDL for a particular bioaccumulative constituent is being developed. Any increase in loading of mercury to an already impaired water body would further degrade water quality. The tentative Order implements the recommendation from the SIP for bioaccumulative constituents. The interim effluent limitation for mercury was developed based on the current performance of the facility, utilizing the maximum concentration detected in 12 effluent samples collected from August 2004 to July 2005. An annual limit would allow spikes to be averaged out over the year. The development of the interim effluent limitation is reasonable and is in accordance with the SIP. CITY OF TRACY - NPDES COMMENT #21: Provisions IV.B., IV.C., V.B. and VI.C.S, Page E-10, Paragraphs VI, VII, and VIII (relating to groundwater), Page F-67, Paragraphs IV.E. and F, Page F-70, Paragraph V.B., Page F-70 and F-71, Paragraphs VI.D.2. and VLEA., Page F-80, Paragraph VII.B.S., and Page F-81, Paragraph VII.13.7. Unnecessary References and Provisions. These provisions referencing Land Discharge Specifications, Reclamation Specifications, Groundwater Limitations and Monitoring, and Construction, Operation and Maintenance Specifications, and Biosolids Monitoring contain no substantive provisions applicable to this NPDES permit and must be removed. Furthermore, the City objects to references made to the separate WDR Order as someone might claim that this reference incorporates that separate permit into this NPDES permit and, thus, those separate requirements become federally enforceable. Request: Remove Provisions W.B., W.C., V.B and VI.C.S., Paragraphs VI, VII, and V111 in Appendix E, and Paragraphs W.E. and F., V.B., VI.D.2., VI.E.1., VII.B.S., and VII.B.7. in Appendix F as unnecessary. If maintained, all references to the City's WDR Order should indicate that this separate order is not be incorporated by reference into the NPDES permit. Regional Water Quality Control Board, Central Valley Region Board Meeting — 3/4 May 2007 Item#17