The Baumgartner Tunnel in St. Louis was constructed to carry wastewater from the Baumgartner Lagoon Pump Station to the newly constructed Lower Meramec Wastewater Treatment Plant. The tunnel, which was excavated in shale and limestone formations utilizing a 12.5-foot diameter hard rock TBM, is 21,000 feet in length. The tunnel is approximately 200 feet below grade. The sewer delivers wastewater from a substantial portion of southwest St. Louis County to a very large lift station; that then conveys wastewater into a new wastewater treatment plant, located at the confluence of the Meramec and Mississippi Rivers.
This project involved the construction of three shafts using diaphragm walls for excavation support. The total 69,104 square feet of diaphragm wall was constructed using hydraulic clamshells. The three shafts ranged from 34 to 100 feet in diameter at depths of 200 to 230 feet. The diaphragm wall excavations were keyed into claystone and limestone at depths ranging from 114 to 130 feet, followed by rock excavation utilizing drill and blast methods.
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