Three Rivers Protection and Overflow Reduction Tunnel

The Three Rivers Protection & Overflow Reduction Tunnel (3RPORT) project in Fort Wayne, Indiana involves the construction of a new tunnel to reduce combined sewage overflows (CSO) along the St. Joesephs, St. Marys, and Maumee Rivers. The project includes three shafts varying from 25 to 68 feet in diameter and depths up to 230 feet, installed through soft ground with slurry walls and supported in rock with rock bolts and shotcrete. The tunnel will have a finished inside diameter of 16 feet and will be 24,500 feet in length. The tunnel will be mined with a slurry TBM through water bearing rock.

Schnabel assisted the successful bidder by preparing a pre-bid geotechnical and hydrological analysis of the contract documents, evaluating geotechnical parameters, specified tunnel ground support systems, and construction aspects of the water-bearing, highly porous bedrock. In addition, Schnabel prepared preliminary designs for the large shafts to assist the contractor in bidding. After award, Schnabel, in conjunction with our JV partner, SWS, designed the precast concrete segmental tunnel lining. Schnabel designed the initial rock support the shafts and starter and tail tunnels, designed support of excavation for near surface diversion structures, designed the TBM launch frame and concrete crane pads, developed testing and QC procedures, performed review of subcontractor designs for the slurry walls, and performed review of production records for the initial support and segment manufacture. Schnabel also provided consulting regarding installation and testing of initial support and developed alternative designs based on changes in subsurface conditions or tunnel configurations.