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<br />. <br /> <br />. <br /> <br />. <br /> <br />Mr. Pat Klaers <br />February 3, 1993 <br />Page Two <br /> <br />The proposed design flow (3.00 MGD) would be about 4.5 times the existing sewage flow <br />(0.67 MGD). <br /> <br />In regard to the wastewater treatment plant effluent discharge standards, we have been advised <br />by the Minnesota Pollution Control Agency (MPCA) that the plant's effluent is currently <br />discharged to the Mississippi River, which is classified as "Outstanding National Resource <br />Water"; therefore, the Nondegradation Regulation applies. Under this regulation, the total <br />mass loadings of Carbonaceous Biochemical Oxygen Demand (CBOD) and Total Suspended <br />Solids (TSS) from the treatment plant to the receiving water should not exceed the loading <br />rates stipulated in the current permit. As the wastewater flow increases, additional treatment <br />is required to further lower the effluent CBOD and TSS concentration. The existing plant is <br />permitted 1.04 MGD with 25 mg/l CBOD (mass loading 98.3 kg/day) and 30 mg/l TSS (mass <br />loading 118 kg/day). When the sewage flow is increased to 3.00 MGD, the effluent CBOD <br />and TSS must be reduced to 8.67 mg/l and 10.40 mg/l respectively in order to comply with <br />the mass loadings requirement. To achieve such an effluent quality, it will cost more to treat <br />every gallon of wastewater than it does now. <br /> <br />For the City of Otsego, MPCA indicated verbally that 25 mg/l CBOD and 30 mg/l TSS may <br />be their effluent limits if they construct their own wastewater treatment plant. When this issue <br />is discussed, the City of Otsego should be made aware of the more stringent treatment and <br />higher treatment cost at the Elk River Plant. Whether it would be economical to deliver <br />sewage to Elk River for more extensive treatment or to build their own treatment plant to meet <br />a probably less stringent effluent limit should be reassessed. <br /> <br />We would like to continue the discussion with the City Council relative to design flow as soon <br />as possible so we can proceed with the process design. If you have any questions or <br />comments, please feel free to call. <br /> <br />Yours truly, <br /> <br />MAIER STEWART & ASSOCIATES, INC. <br /> <br />~~~(itU <br />T;;;;;.~~~r, P.E. <br /> <br />bO;M/f/ <br /> <br />Bill Chang, P .E. <br /> <br />BC:tp <br /> <br />151-0304.fOO <br />