Baumgartner Tunnel Project Sanitary Sewer

The Baumgartner Tunnel Project is part of the MSD’s approximately $220 Million Lower Meramec River System Improvements.  Located in St. Louis and Jefferson Counties near the confluence of the Meramec and Mississippi Rivers, the system improvements included construction of a new wastewater treatment plant, the Baumgartner Tunnel, sewer connections via drop shafts on the new tunnel, and closure of the Meramec and Baumgartner Lagoons.

The Baumgartner Tunnel is approximately 20,200 feet long and conveys wastewater by gravity from MSD’s Meramec Lagoon and Baumgartner Lagoon service areas to the new wastewater treatment plant. The deep tunnel is approximately 12.5 foot in diameter with a 96-inch diameter, reinforced concrete pipe installed in the tunnel. The tunnel was bored at depths of about 160 to 180 feet below the ground surface through the underlying bedrock. 

DMA structural engineers provided design and planning for a 100 foot diameter lift station shaft.  This shaft extended 223 feet below the ground surface and was constructed with 16 slurry wall panel supports 108 feet in depth.  A Tamrock Tiger hydraulic track drill was utilized to excavate the remaining 115 feet of rock.

Our civil engineers provided design and planning for vortex drop shafts to convey wastewater from existing tributary sewers into the deep tunnel.  These special structures included a spiral intake chamber and de-aeration chamber to dissipate energy, reduce air entrapment, and minimize the release of odors and corrosive gases.

Our surveyors provided topographic and property surveys along the tunnel alignment.