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<br /> . c---- <br /> I .1 M~AI October 2, 1995 <br /> File: 520-060-80 <br /> . COlSlL TING ENGI,\EEIt~ <br /> , .4 - <br /> "J <br /> I 1326 Energy Park Drive Mr. Dwayne Stafford ( <br /> St. Paul, MN 55108 -_\ <br /> Public Works Director <br /> I 612-644-4389 City of Arden Hills <br /> 1-800,888,2923 1450 West Highway 96 <br /> fax: 612-644-9446 Arden Hills, MN 55112-5794 <br /> . RE: SANITARY SEWER LIFT STATION REVIEW <br /> I Dear Mr. Stafford: <br /> As requested, we have condueted a brief observation inspection of the majority of the <br /> . sanitary sewer lift stations tD evaluate the general condition and make recommendations for <br /> short term improvements. <br /> I CNll ENGINEERING Following the site visit and discussions with City operating personnel, we put together the <br /> ENVIRO~MEN;AL attached brief diseussion on each lift station for your reference. <br /> .e :~~~,:~ Initially, we would like to commend the operations personnel and the City for the <br /> SOUDWASTE maintenance effDrts which have been effective in extending the life of the equipment. <br /> . snU(TURAL Many of the stations were constructed in the 1960's and 1970's, so they are 25 to 35 years <br /> SURVEV;NG old and still operating well. <br /> ~RAf;IC <br /> . -~ANSPCRTATiON The attached discussion sheets provide some site specific recommendations, but the <br /> majority of the issues are routine maintenance type efforts. The exception is at Lift Station <br /> :~ECR.iCALi MEC-iANICAL Number 6. <br /> . :\iGr-.;E.:;t.\iG <br /> '-N.i.,( Lift Station Number 6 is a small capacity pneumatic ejector type lift station, It .pumps" <br /> :;OWER. Dlsrn;UTiO', the wastewater flow from about 10 homes on the west shore of Lake Johanna. This type <br /> I SCAD,'. of lift station is very effective for small flows, but it is not commonly used at this time. <br /> SYSEM cONTRees Wastewater flows by gravity into a pressure chamber or "pot". When it reaches a preset <br /> . level, a valve is automatically opened to direct compressed air into the pot and "force" the <br /> collected wastewater up to the higher elevation gravity sewer. The "pumping" operation <br /> involves sensors, automatic valves, air compressors, electrie motors, and electrical wiring. <br /> . All of this equipment is contained inside an underground concrete vault in Lift Station <br /> Number 6. The structure and equipment is approximately 34 years old, and is not in <br /> eompliance with current safety standards. The vault has limited space for aecess to the <br /> . equipment and the high humidity in the underground chamber corrodes the equipment and <br /> OfFICES IN; electrieal contacts, and makes electrical work dangerous. When maintenance is required <br /> on the equipment, extra care is required to ventilate the structure and mDnitor the repair <br /> .e MINNEAPOLIS operation. <br /> PRIOR LAKE <br /> ST. PAUL <br /> . W ASECA <br /> 520i060.0103.0d <br /> An Equal Opportunity Employer <br />