Groundwater inflow problems in tunneling at west leg interceptor contract 3, Cleveland, Ohio

West Leg Interceptor Contract 3 is part of a new sanitary sewer system in the southwest suburbs of Cleveland. The mainline tunnel was excavated through sandstones and shales by a shielded TBM equipped with disc cutters and grippers. Groundwater inflows in three tunnel reaches caused major concerns and resulted in claims for differing site conditions. At Stations 202+50 to 200+50, the tunnel crossing of the Rocky River had special challenges during both design and construction. An anchored concrete cap and a grout curtain were placed prior to tunneling. Gasketed liner plate was used as the tunnel support. At Stations 197+90 to 183 + 00, seepage from the overlying sandstone aquifer and into weathered shale resulted in bearing failures at the TBM grippers. A change in support from rock bolts to ribs & lagging was required at three locations to allow continued advance of the TBM. At Stations 212+00 to 278 + 00, high water inflows from open fractures and bedding planes in hard, massive sandstone washed cuttings from the face. Silt and fine sand accumulated on the TBM trailing gear and on the track. Hand mucking and additional pumping effort were necessary to avoid damage to the electric motors and to allow passage of muck trains.