A LARGE-SCALE PRESSURE SEWER SYSTEM SOLVES WASTEWATER PROBLEMS ON THE NORTH SHORE OF LAKE SUPERIOR

The Duluth/North Shore Pressure Sewer Collection System (D/NSPSCS) is located on Lake Superior's north shore and extends approximately 14 miles from the City of Duluth to the City of Knife River. The 14.6 million system contains 180,000 feet of piping, 375 grinder pump stations and 2 main pump stations.The project exists to correct the problem of failing individual sewage treatment systems in the project area. The D/NSPSCS serves approximately 405 residential, 18 small commercial, and 2 large commercial connections. The project has been under construction since June 2002 with an anticipated completion date of August 2005.The design phase of this project started in 1999 concurrent with an environmental review process that was completed January 2002. The environmental review detailed the many challenges the project faced with regard to protection of the area's scenic and environmental aspects. The review also contained a unique land use planning process that dealt with the concern for development and growth pressures that could result from the project.The large scale, linear nature of the pressure pipeline network and the terrain along the Lake Superior shoreline created numerous design challenges. These challenges included extensive hydraulic modeling, strategic main pump station placement to avoid empty pipe segments and to limit costs, looped mainline segments, gravity sewer components, odor control for septic conditions, pipeline pigging facilities, trout stream crossings, rock blasting and removal, and unique safeguards to maintain operability during line interruptions. The design also includes a 300,000 gallon detention storage facility to detain wastewater flow from contributing to the sewer overflows during infiltration/inflow related conditions in the receiving sewers.The conclusion and end result of this project is a long-term wastewater solution for the affected north shore of Lake Superior. The use of pressure sewer technology combined with the availability of public funding allowed this much needed project to take place.