Design of the Fort Wayne CSO Tunnel Through Complex/Wet Rock

摘要

The Three Rivers Protection and Overflow Reduction Tunnel (3RPORT) is a critical component of Fort Wayne's Long Term Control Plan to reduce the volume of combined sewer overflow (CSO) entering the waterways of Fort Wayne, Indiana. The project consists of 24,580 ft (7,500 m) of 16 ft (4.9 m) finished diameter deep rock tunnel, 9 drop structures, Tunnel Boring Machine (TBM) launch and retrieval shafts, a 30 MGD (113,500 m~3/day) deep dewatering pump station (DDPS), and associated deaeration chambers, adits, and near surface infrastructure. The local geology consists of horizontally bedded dolomite interbedded with chert and fractured dolomitic bank reef formations with artesian groundwater. Key considerations in the tunnel design will be presented including planned groundwater mitigation strategies for construction, which is scheduled to start in early 2017.