Designing Duluth’s “Grand Finale” lift station
Lift Station No. 8 is the final lift station on Duluth’s Park Point, a 7-mile-long sandspit with residential homes, hotels and marinas stretching outward from the bustling tourist district of Canal Park. Park Point’s single access is across an iconic, 180-foot-tall steel lift bridge which is raised and lowered to accommodate large commercial lake freighters, cruise ships and sail boats.
Lift Station No. 8 has the responsibility of pumping all wastewater from Park Point homes and businesses across the active shipping canal into the main collector system on the mainland. But it does so in quite an unconventional manner: via a force main that extends up and over the top of the bridge itself!
Typically, sewer pipes are buried. But because of the city’s geography and geology, that wasn’t possible. The lift station pumps wastewater through pipes that climb up the sides of the lift bridge and back down the other side, artfully concealed in plain sight to unsuspecting viewers. The lift station’s design addressed several unique challenges and goals set by the City of Duluth. One of the largest challenges was to provide a constructible design while minimizing the risk of failure or overflow. The site was very small and not conducive to construction of a new structure. MSA’s design had to be rebuilt in the same location, while keeping the station operational at all times.
High levels of safety and reliability
Safety related to fall protection and electrical arc flash were also primary objectives. A unique and innovative motor control center connects two electrical sources to the station. The system applied an isolated/separated source transfer control. In conjunction with the manufacturer, MSA designed the dual-feed electrical system that isolated a transfer device. This increases the system’s reliability and safety for operational staff since the lift station can be operated by either power source. It also allows both portions of the station to be completely isolated and de-energized, providing access for maintenance to the electrical power device while the station continues to operate in automatic mode.
The upgraded lift station was built with the latest energy-efficient LED lighting, Clean Power Variable Frequency Drives, energy recovery HVAC system and process equipment to minimize operational costs. The project qualified for multiple energy rebates in almost every category of construction.
The new lift station structure blends into the neighborhood and features grass and plantings. In addition to increased energy efficiency, it also protects Lake Superior, which is a critical concern for the City of Duluth. When the power goes out, the lift station has backup power so sewage can be pumped from Park Point into the gravity system that feeds to the City’s wastewater collection system. Without this backup power, the sewage could be backed up into people’s homes, city streets and the nearby lake.
Now with the reconstructed lift station, the City has the capacity to support additional community development on Park Point, part of the community’s long-term vision of enhancing its close connection with Lake Superior. This project is the recipient of an ACEC-Minnesota Engineering Excellence Honor Award (Waste and Storm Water Category).