Excavation of the Northwest Side Relief Sewer tunnel in northwestern Milwaukee County took more than a year.
Photo: Black and Veatch Excavation of the Northwest Side Relief Sewer tunnel in northwestern Milwaukee County took more than a year.

Homeowners don't like it when their basements repeatedly flood after heavy rains, and they don't want to hear excuses about poor sewer conditions—they just want the problem to go away. The Milwaukee Metropolitan Sewerage District (MMSD) heard these complaints loud and clear, and by 1998, the agency had made the Northwest Side Relief Sewer (NWSRS) project the No. 1 capital improvement project in its 2010 Facilities Plan.

At the plan's inception, sewer flows from the northwest section of Milwaukee County were collected and transported by shallow sewer interceptors, which discharged to the county's Crosstown Tunnel. Rapidly accelerating development and population growth stressed the aging, inadequate infrastructure, causing basement flooding and sewer overflows during wet weather.

“We had two sewers that were like two-lane highways coming together,” said Roger Maurer, MMSD section manager of conveyance. “It created terrible bottlenecks.”

District leaders pinpointed hydraulic bottlenecks in the shallow interceptor system and proposed an intermediate-depth tunnel. The district submitted bids and picked Black & Veatch to steer the project.

Despite setbacks and challenges—regulatory changes, concerns about disrupting thousands of paupers' graves, and potential threats to a rare species of snake—the project worked out well overall. The end result: a 20-foot-diameter tunnel, 7.1 miles long, that has reduced overflows and flooding, and added 88 million gallons of storage to accommodate excess flow. The NWSRS came in on time, under budget, and has been well received by citizens in the seven communities served by the project.

One factor Maurer looks for in an AEC firm—one that can make the difference between success and shortcomings—is a knowledgeable, effective, and communicative project manager.

“They should interact often with the project owner,” he said. Thorough documentation also is key. “When a project is seven years long, like this one, people will start questioning your decisions, and it's important to have the paperwork to back it up.”

David Egger, Black & Veatch water global tunneling practice leader, said his team was mindful of the importance of keeping the MMSD up to speed every step of the way.

“Good communications were based on lots of person-to-person ideas, sharing lessons learned, and creatively forcing dialogue between parties that don't naturally always communicate,” he said.

Milwaukee Northwest Side Relief Sewer

Project completion date: November 2005

Total cost: $132 million

AEC firm: Black & Veatch

Location: Milwaukee County

Neat stat: A total of 525,000 cubic yards of rubble was excavated from the site; the debris was crushed and used in other area projects, including a park and an airport.