The subject facility has applied for a renewed NPDES permit which includes modifications that necessitate an antidegradation assessment. New wastewater discharges will be created as the result of the construction and operation of new dry flue gas desulfurization systems (Spray Dryer Absorbers or SDAs) at all three units at the complex. The installation of these systems was required by the terms and conditions of a 2005 Consent Decree between Dynegy, the state of Illinois, USEPA, and the U.S. Department of Justice. Construction of the Unit 3 SDA system and baghouse has been completed and they were put into service prior to December 31, 2010. The Unit 1 SDA system and baghouse were placed into service by December 31, 2011. The Unit 2 SDA system and baghouse were placed into service by December 31, 2012. The new discharges from these systems would consist of sump discharges, air compressor noncontact cooling waters, and miscellaneous floor and storm drainage waters. Dynegy is requesting authorization to discharge these wastewaters to the existing bottom ash pond system and include these discharges as contributory wastewater streams to Outfall 001. Sump discharges are not expected to occur more than once per week with each discharge lasting approximately five minutes. Based on the current operation of the Unit 3 sumps (projected discharge of 0.127 MG/year), it is expected that sump discharges for all units would contribute 0.38 MG/year of flow to the ash pond. Air compressor noncontact cooling waters from the new SDA systems (6.5 MGD) and miscellaneous floor and storm drainage waters would be received by the cooling pond and would be potentially discharged from Outfall 002 during overflow conditions

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• Dynegy

• Fabric Filter

• Spray Dryer Absorber

• Wastewater

• Permit