Becher Street Tunnel Project
This project involved the installation of 5,041 lineal feet of 130" bore, 108" inside diameter, single pass segment lined tunnel, and three shafts. As part of the project, we also installed 500 lineal feet of 12x8’ box culvert via open cut approximately 25’ deep. The Becher Street project was very unique as it had virtually every ground condition present in the tunnel profile. Given the difficult site conditions, the City of Milwaukee opted to go with the Segment Lined Tunnel versus pipe jacking. Based on that decision we constructed the tunnel using a LOVAT 129SE EPB TBM equipped with a screw conveyor disposal system, and a ground stabilization system. While tunneling we employed the full EPB mode due to difficult soils and very urban setting. The tunnel began in heavy/sticky clays, then transitioned into mixed face of clay and limestone, and finally into very wet sandy silts over limestone. Numerous adjustments to cutting tools and ground conditioning methods we implemented to address the varying ground conditions.