Agenda Packets - 1993/11/09 - Laserfiche WebLink

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and construct a backwash reclaim tank outside the existing build- ing. This would be a 14 foot high, 30 foot diameter circular steel tank. The estimate of cost for such a tank is $150,000 at each plant. In addition there would be costs for piping and automating the control system. The existing equipment at the filter plants occasionally exceed the state guideline of 0.05 mg/litre for manganese, iron levels are well below the 0. 3 mg/litre guideline and normally below the specification requirement of 0.15 mg/litre. In remodeling filter plants 2 and 3 there were 3 priorities discussed with the Council. The first was to substantially reduce iron -and manganese levels in the filtered water to reduce and eventually eliminate the "dirty water" complaints. The second priority was to reclaim the backwash water from the filters. The Minnesota Pollution Control Agency has instituted strict standards and discharges from water treatment plants to the state's waters (such as Rice Creek, the receiving water from our filter plants) . Discharges must be dechlorinated or held for 24 hours prior to reaching public waters. Permits are $1 ,230 annually and subject to changing requirements. As previously noted, constructing backwash reclaim tanks for our existing equipment is as costly as new equipment. The third priority for remodeling was to automate the filter plants. The existing equipment must be manually backwashed and requires 3 to 4 hours of labor for each backwash. The filters are back washed at least once a week in the summer and at least once a month the balance of the year. When filters need to be back- washed on weekends, the operators are on overtime pay. Each backwash of the existing filters requires 125,000 to 150 ,000 gallons of water. Automating the filter equipment and reclaiming the backwash water saves approximately 300 hours of labor annual- ly and over 5 million gallons of water. Additionally sanitary sewer charges for the 2 plants would exceed $6 ,000 annually if backwash water is not reclaimed. Additional information will be presented at the Council meeting. Ric Mi for City Engineer/Director of Public Works