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<br />_ / } ~ ~ ~ 3 J CONSULTING ENGINEERS <br />· ~-"'" Maier Stewart & Associates Inc. <br /> <br />April 7, 1993 <br />File: 23S~OOS~20 <br /> <br />Mr. Bill Birrenkott <br />Elk River Municipal Utilities <br />322 King Street <br />Elk River, MN 55330 <br /> <br />RE: WATER TREATMENT FACILITY <br />BACKWASH WATER POND <br /> <br />Dear Mr. Birrenkott: <br /> <br />In follow-up to the information we faxed to you today, we have prepared this correspondence <br />expanding on the issue of a pond for disposal of the backwash water generated from the water <br />treatment facility. <br /> <br />. Qriginally, the \Vater treatment facility was designed with a concrete basin below the building <br />which has a volume of 108,000 gallons. This will allow for the complete bachvashing of the <br />filter, storage of the 'Miter used, and then a metered discharge to the sanitary sewer system. <br />This design allows for backViashing at any time without overloading the sewer system. The <br />basin is also large enough so that, once the entire water system is chlorinated, the backwash <br />water could be reclaimed through the water treatment facility. <br /> <br />Elk River happens to be one of the few locations in the state which has native soils capable of <br />accepting large volumes of backwash water and percolating them into the ground. The City of <br />Anob has seven water treatment facilities, six of which utilize ponds to dispose of backwash <br />water. <br /> <br />Investigating this option, we have determined that a ponding area would require an area <br />approximately 100 feet by 108 feet. The pond would be eight feet deep but would only fill to <br />a depth of six feet every time the filter is backwashed. This is a volume of approximately <br />100,000 gallons, depending on length of backwash.. According to John Norgren of the City of <br />Anoka, their ponds drain down in about a day. We estinlate Elk River will backwash this filter <br />1~2 times a week, depending on water usage. <br /> <br />We visited one of Anoka's sites at 5th Avenue and East River Road. The backwash water is <br />very turbid, having a brownish iron color. Other than normal grass cutting, John indicated their <br />. maintenance consisted of cleaning the bottom of the pond every 10~12 years. <br /> <br />1959 SLOAN PLACE, SUITE 200, ST. PAUL, MINNESOTA 55117 612-n4-6021 <br />9800 SHELARD PARKWAY, SUITE 102, MINNEAPOLIS, MINNESOTA 55441 612-546-0432 . Equal Opportunity Employer <br /> <br />~.as.lpr <br />