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This will allow Wildish Construction, working under contract to the Metropolitan Wastewater Management <br />Commission, to build a new, 96-inch outfall pipe from the treatment plant to the west side of the river. This pipe <br />will discharge peak flows of treated wastewater from the treatment plant. <br /> <br />The dam will be constructed using bulk bags, each filled with 3,000 <br />pounds of washed round river rock, stacked pyramid style. The <br />river side of the structure will be lined with plastic, held in place by <br />sandbags, to help seal off water. Once the dam is in place, the <br />work area will be dewatered using four 30-horsepower pumps. In <br />accordance with permits required by state and federal agencies, a <br />fisheries biologist will be present during dewatering to safely <br />capture all protected marine species and release them <br />downstream. Construction of the cofferdam should take about a <br />week, and it will be in use for approximately six weeks. <br /> <br />In another major modification at the treatment plant, a change is <br />being made to the deign of large mixing units that will save <br />220,065 kilowatt hours of electricity per year under expected <br />operating conditions, a reduction <br />valued at $12,104 at today’s power <br />rates. During the initial review of <br />improvement modifications to <br />comply with new regulations and <br />meet projected service demands for <br /> <br />Large sacks of rock are carefully loweredinto the river. <br />the next 20 years, engineers <br />identified an opportunity to change the mixers to energy-efficient variable-speed <br />units from the traditionally used fixed-speed design. The mixers are large-bladed <br />propeller devices that mix primary effluent so it can be aerated in a process that <br />reduces the organic load and the ammonia concentrations. The variable-speed <br />feature allows for slower start-ups and better control of mixer speeds to reduce the <br />power consumption. In addition to the long-term savings, an incentive check of <br />$33,010 was received from EWEB for the project after the mixers were installed and <br />their efficient operation was proven and documented. This energy-saving measure <br />will return its investment to the wastewater rate payers in less than 2.5 years. <br /> <br />Mixer unit exposed in drained aeration <br />chamber. <br />For more information about improvements at the treatment plant, contact <br />Wastewater Division Director Peter Ruffier at 682-8606. <br /> <br /> <br />EUGENE CITY COUNCIL NEWSLETTER PAGE 3 <br />July 16, 2009 <br />