St. Louis MSD Completes First of Nine Tunnel Projects

Lemay Redundant Force Main

Crews move the final connection piece of the Lemay Redundant Force Main into place.

The Metropolitan St. Louis Sewer District (MSD) recently cleared a major milestone this month when crews connected the new Lemay Redundant Force Main to existing lines at the Lemay Wastewater Treatment Plant. The Lemay Redundant Force Main is the first of nine tunnel projects to be completed in MSD’s Project Clear, the District’s capital improvement program to improve water quality and alleviate many wastewater concerns in the St. Louis region.

Construction on this first tunnel began in February of 2014 when Chelsea, a 300,000-llb, 250-ft long tunnel boring machine (TMB), began chomping her way through nearly 3,000 ft of limestone under the River Des Peres.

The new force main allows the treatment plant to accept a higher volume of wastewater and allows MSD to inspect the original force main for the first time since its construction in the 1960s. Because of topographic barriers that prevent the flow of wastewater by gravity alone, force mains use pressure to propel wastewater to treatment plants. The original force main has been in constant use since its construction, pumping wastewater to the Lemay Wastewater Treatment Plant, meaning that the 50-plus-year-old pipe has not seen inspection since it went into service.

“We are continuing efforts through MSD Project Clear to keep the rain out of our system through rainscaping and stormwater disconnections and by an ambitious program of maintenance and repair. However, much of our system is aging and needs improvement,” stated MSD Executive Director Brian Hoelscher. “New construction based on topography, watershed, and wastewater needs may include new sewer lines to convey additional wastewater, above-ground storage tanks or deep underground tunnels like the Lemay Redundant Force Main.”

Tunnels will be an important part of MSD Project Clear’s efforts to handle the wastewater needs of MSD’s service area by reducing pollution to our waterways and improving the water quality in our communities and neighborhoods. These tunnels will store and convey additional flow during heavy rain events until capacity is available at the respective treatment plants. Eight additional tunnels are scheduled under MSD Project Clear and listed below.

Lemay Redundant Force Main

The final piece of the Lemay Redundant Force Main is secured.

About MSD Project Clear

MSD’s Project Clear is the Metropolitan St. Louis Sewer District’s initiative to improve water quality and alleviate many wastewater concerns in the St. Louis region. MSD Project Clear will invest billions of dollars over a generation in planning, designing and building community rainscaping and system improvements, along with an ambitious program of maintenance and repair and the disconnection of some residential downspouts in parts of St. Louis County’s separate sewer area from the wastewater sewer line. This work is part of an agreement between MSD and the U.S. EPA. The St. Louis region’s success with MSD Project Clear will only be possible through strong partnerships and clear communications with the public.

To learn more about the MSD agreement with EPA, please visit:

For more information on MSD Project Clear, visit or follow on Twitter @ProjectClearSTL.

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