CONSTRUCTION GROUTING OF THE BAUMGARTNER TUNNEL

摘要

The Baumgartner tunnel collects sanitary sewage and conveys it to a treatment plant near the mouth of the Meramec River. The nearly 6.2 km (4 mile) long, 3.8 m (12.5 foot) diameter tunnel is 49 to 55 meters (160 to 180 feet) below the Meramec River. During construction, a previously unidentified water-bearing zone containing hydrogen sulfide gas was encountered in the bedrock. The zone, first encountered above the tunnel, eventually intersected the tunnel and was also encountered during the excavation of the screen and lift station shafts. It was necessary to grout the seams within this zone ahead of the tunnel boring machine (TBM) to mitigate water inflow and the risk of encountering dangerous levels of gas.