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<br /> I' <br /> . October 2, 1995 <br /> I File: 520-060-80 <br /> COmL Tl\G E.\GnEEJl:l <br /> " ,q <br /> , ..J <br /> I 1326 Energy Pari Drive Mr. Dwayne Stafford C. <br /> 51. Paul, MN 55108 --) <br /> Public Works Director <br /> I 612-64404389 City of Arden Hills <br /> 1.800.888.2923 1450 West Highway 96 <br /> Fox; 612-644-9446 Arden Hills, MN 55112-5794 <br /> I RE: SANITARY SEWER LIFT STATION REVIEW <br /> I Dear Mr. Stafford: <br /> As requested, we have conducted a brief observation inspection of the majority of the <br /> I sanitary sewer lift stations to evaluate the general condition and make recommendations for <br /> short term improvements. <br /> I C!VIL ENGiNE=.~IN::; Following the site visit and discussions with City operating personnel, we put together the <br /> ENVIRONMENT;'L attached brief discussion on each lift station for your reference. <br /> ..,ClPAl Initially, we would like to commend the operations personnel and the City for the <br /> ~IANNING <br /> SOllDWA$iE maintenance efforts which have been effective in extending the life of the equipment. <br /> . STRUCTURAL Many of the stations were constructed in the 1960's and 1970's, so they are 25 to 35 years <br /> SURVEYING old and still operating well. <br /> "RAFFle <br /> I fRANSPORTAT:ON 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 /> ELECTRIC,;,l/MEC...:;.l\iCAl Number 6. <br /> I :NGINEE?iNG <br /> 'WAC Lift Station Number 6 is a small capacity pneumatic ejector type lift station. It "pumps" <br /> ~OWER DISTRI~U-::"'j the wastewater flow from about 10 homes on the west shore of Lake Johanna. This type <br /> I 5CADA of lift station is very effective for small flows, but it is not commonly used at this time. <br /> SYSTEM C:JNnc~s 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, electric motors, and electrical wiring. <br /> I 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 /> compliance with current safety standards. The vault has limited space for access to the <br /> I equipment and the high humidity in the underground chamber corrodes the equipment and <br /> electrical contacts, and makes electrical work dangerous. When maintenance is required <br /> eICE5IN; on the equipment, extra care is required to ventilate the structure and monitor the repair <br /> . NEAP01l5 operation. <br /> PRIOR LAKE <br /> ST. PAUL <br /> I WA5ECA <br /> 520/OGO-0203.o..:t <br /> An Equal Opportunity Employer <br />