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MPCA. Because the Minnesota River, which flows into the Mississippi River, already contains <br /> approximately 0.2 mg/I phosphorus, the Mississippi River will likely continue to fail to meet <br /> standards unless the Minnesota River quality improves significantly. As a regulatory <br /> consequence, wastewater treatment discharge could be required to meet the water quality <br /> standard as a discharge limit. <br /> Achieving compliance with a 0.3 mg/I phosphorus limit requires additional facilities for chemical <br /> addition, pumping, filtration, and solids processing facilities. Estimated capital cost (current <br /> prices) for the Council's wastewater treatment plants is $400 million. Estimated annual <br /> operation and maintenance cost is an additional $15 million. <br /> Achieving compliance with a 0.1 mg/I phosphorus limit requires investments for chemical <br /> addition, tertiary clarifiers, pumping, membrane filtration, and solids processing facilities. <br /> Estimated capital costs (current prices)for the Council's wastewater treatment plants are <br /> approximately $2 billion. Estimated annual operation and maintenance costs are approximately <br /> an additional $30 million. <br /> Total annual operation and maintenance costs, plus annual debt service on the capital, are <br /> estimated at approximately$45 million for 0.3 mg/I phosphorus limit and $180 million for 0.1 <br /> mg/I phosphorus limit. These potential costs would raise regional wastewater rates by 40% to <br /> 100%. <br /> Nitrogen. The Minnesota Pollution Control Agency is considering a water quality standard for <br /> nitrate nitrogen based on levels considered toxic for aquatic life. The Minnesota Pollution <br /> Control Agency with assistance and guidance from the U.S. Environmental Protection Agency <br /> recently developed a nutrient reduction strategy for the Mississippi River watershed to protect <br /> the Gulf of Mexico. Nitrate is a nutrient necessary for aquatic growth, but excessive amounts <br /> can lead to problems such as algae blooms, decreased oxygen levels, and fish kills. <br /> Currently, the Council's wastewater treatment plants meet seasonal effluent limits for ammonia <br /> nitrogen, to meet a water quality standard for ammonia nitrogen based on toxicity for aquatic <br /> life. The wastewater treatment plants use biological treatment to convert ammonia to nitrate <br /> nitrogen, with average nitrate discharge of 15 to 20 mg/I. <br /> If the Minnesota Pollution Control Agency adopts a nitrate nitrogen standard, the Mississippi <br /> River will likely continue to fail to meet standards because the Minnesota River contributes most <br /> of the nitrate nitrogen loading to the Mississippi River. As a regulatory consequence, <br /> wastewater treatment plant discharges could be required to meet the water quality standard as <br /> a discharge limit. Meeting this standard would require major capital improvements to remove <br /> nitrate by a biological denitrification process. A small change in specific concentration limits of <br /> nitrate nitrogen and total nitrogen would result in a correspondingly large change in costs. <br /> Changes to the biological treatment process would also affect the performance of treatment <br /> plants to remove phosphorus. Estimated capital costs are approximately$1.0 billion to meet a <br /> 10 mg/I total nitrogen limit and approximately $1.5 billion to meet a 5 mg/I total nitrogen limit. <br /> Substantial Impacts and Substantial Departures from the Metropolitan <br /> Wastewater System Plan <br /> Thrive MSP 2040 and the regional system plans comprise the Council's Metropolitan <br /> Development Guide, which is the region's plan to ensure orderly and economical development <br /> 44 <br />