Mill Creek Tunnel, Contract 2

OWNER: Northeast Ohio Regional Sewer District

SOUTHLAND HOLDINGS TEAM:  Mole Constructors, Inc.


This project included the excavation of 13,200 lf of 23-ft, 8-in diameter tunnel for a sanitary sewer through shale and 2,015 lf of 10-ft diameter exploratory tunnel through shale including shaft excavations to depths of 200 vertical feet. Tunnel excavation performed via a Robbins TBM for the 23-ft, 8-in diameter tunnel and via a Lovat TBM for the 10-ft tunnel. The initial tunnel support consisted of steel ribs and wood lagging for larger tunnel and fiberglass rock dowels for the smaller tunnel. The final lining consists of 20-ft diameter reinforced, cast-in-place concrete for the larger tunnel. The shafts were supported via ground freezing or liner plates within the soft ground, and rock dowels, welded wire fabric, and shotcrete within rock. Tangential approach flow, baffle-type flow, and standard drop structures were constructed within the shafts.