Above-ground storage facilities and underground tunnels are important parts of MSD Project Clear’s efforts improve water quality and alleviate many wastewater concerns in the St. Louis region over the next generation.

The links below will provide specific information about each project as design moves closer to construction.


As part of MSD Project Clear, eight significant underground construction projects will begin over the next dozen years. These projects will use different types of construction to build underground wastewater storage facilities. These storage facilities are needed: during heavy rains or significant snow melt, too much stormwater enters the wastewater system. When too much stormwater enters the system, it may exceed the capacity of the sewer system and MSD’s treatment plants. To prevent overflows, MSD will construct above-ground storage tanks to store wastewater, or deep underground tunnels to both store and transport wastewater during these heavy rains or significant snow melt until capacity is available at MSD treatment plants.

The majority of the deep tunnel projects will be built in the limestone rock layer by a specialized piece of equipment called a Tunnel Boring Machine (TBM). A lining is then installed that will keep groundwater out and keep wastewater in the tunnel. The benefit of this deep tunnel boring technology is minimal surface disturbance to neighborhoods and properties in proximity to the project. Working at up to 230 feet below the surface, the TBM will bore the tunnel totally out of the sight of the public. Very little will be felt or heard, resulting in little disturbance to properties above the surface.

For smaller storage facilities that are too short to use a TBM, controlled blasting will be used deep underground. This blasting is done by experienced contractors in small increments; just like TBM construction, there will be minimal disturbance on the surface.

MSD Project Clear reached a milestone in 2014 with the completion of the first phase of the 3,200-foot-long x 9-foot-diameter tunnel, dug by TBM Chelsea the Chomper, as part of the Lemay Redundant Force Main project. The second construction project of Project Clear is scheduled to begin in 2016. The Maline Creek Storage Facility project is in the final design phase and the work will go to bid next year.

This timeline roughly estimates the progress of a MSD Project Clear tunnel over the life of the initiative.


Stormwater disconnections

When stormwater enters the wastewater system, it is considered wastewater by MSD’s regulators. In the combined sewer system, this occurs by design. The system carries both wastewater and stormwater in the same pipe. In heavy rains, the system can be overloaded by too much stormwater. In the separate sewer system, this can occur due to incorrect connections of stormwater to the wastewater system. MSD is working to remove these connections through stormwater disconnections.