Metropolitan Council Environmental Services, which operates the regional wastewater collection and treatment system, received the Public Works Project of the Year Award on Nov. 19 from the Minnesota Chapter of the American Public Works Association. The award recognizes the successful construction of a project to rehabilitate an aging sewer near Minnehaha Park in south Minneapolis.
The Met Council’s Environmental Services Division faced significant construction challenges when rehabilitating old sewers near Minnehaha Regional Park. Among them:
• Working as much as 75 feet below ground
• Maintaining the flow of millions of gallons of wastewater daily through temporary pumps and pipes throughout the two years of construction
• Avoiding impacts to a rare and protected groundwater resource, Coldwater Spring
• Working with more than 12 unique public stakeholder groups in the center of an urban area and a high-traffic park
“This project presented some unique challenges that our staff met with partnerships, innovation, and excellence,” said Metropolitan Council Member Abdirahman Muse, whose district includes the project area. “We are proud of the work done to plan and execute this project.”
The $20 million project involved rehabilitation of underground wastewater sewers and other structures adjacent to the park that date back to the mid-1930s. A key piece of the project was rebuilding a relief structure designed for a time when a combination of stormwater and wastewater flowed through pipes. The structure diverted higher than normal, rain-induced flows to the Mississippi River when necessary to help prevent upstream wastewater backups, open discharge of wastewater, and damage to downstream sewer facilities.
The combined stormwater and wastewater sewers were separated in the 1990s, and the Met Council has worked with cities since then to reduce the excess inflow and infiltration of clear water into wastewater sewers. As a result, there has not been a wastewater release at this structure in more than 17 years.
However, it is essential to keep this structure in good working order, along with nearby deep tunnels and specially designed shafts that carry wastewater down to these sewers. Because of the age of these facilities and their corrosive environments, we rehabilitated them to provide safe, reliable wastewater service well into the future.
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