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February 11, 2019
(Milwaukee, WI) – Aging and failing equipment for the Deep Tunnel is slated for replacement in early 2019 after a unanimous vote today by Commissioners of the Milwaukee Metropolitan Sewerage District (MMSD).
“We have to be rain ready all year long with the crazy, unpredictable weather patterns we’re seeing,” said MMSD Commission Chair Kris Martinsek. “Asset management is crucial when it comes to optimizing reliability and performance when it counts. It’s a $1.4 billion investment (including financing) we’re making over the next six years.”
Regional treatment plants and sewers will see the bulk of MMSD’s $92.9 million capital project/program spending in 2019.
With today’s Commission action, work will be performed within two dropshafts to the Deep Tunnel. There are 24 dropshafts that control wastewater and stormwater flow into the Deep Tunnel, which is about 300 feet below ground. Each dropshaft site contains flow control gates that open and close with hydraulic cylinders, similar to the back gate of a garbage truck. Hydraulic cylinders are broken at two dropshaft sites.
There are backup (redundant) gates and cylinders at both dropshafts. However, a failure of the backup equipment could result in sewer overflows. Work on the equipment is expected to start near the end of February.
This is a dramatically oversimplified graphic showing various segments of the sewers underground and the Deep Tunnel. Work taking place for the project mentioned above will occur in the chamber marked “Flow Control Gate W/Hydraulic Cylinders. The gates in these structures control whether flow is allowed into a dropshaft to the Deep Tunnel. When the gates are open wastewater and stormwater are allowed into the tunnel. When the gates close during severe storms to reduce the risk of basement backups, excess water in the sewer system is channeled to an overflow pipe (relief valve) that goes to the nearest river.