Riverbank Filtration Tunnel and Pump Station

Completed in 2011 by Mole Constructors, the Riverbank Filtration Tunnel and Pump Station project included a work shaft, 7,763 linear feet of 12-foot diameter tunnel for water conveyance, four collector well systems, and a 65 MGD pump station. The work shaft was supported by a 41-foot diameter slurry wall through saturated soft ground, followed by conventional blasting methods to a depth of 187 feet.
The four collector wells were constructed using 13-foot diameter concrete caissons installed along the bank of the Ohio River, with horizontal wells placed at the bottom of the caissons. These wells were connected to the tunnel below by a drilled drop shaft. Blasting methods were used to excavate the starter tunnel, while the remainder of the tunnel was excavated using a 12-foot diameter Robbins Main Beam Tunnel Boring Machine (TBM) through limestone and shale at depths ranging from 150 to 155 feet. Initial support for the tunnel consisted of rock dowels and channels, and the final lining was a 10-foot diameter monolithic unreinforced, cast-in-place concrete. Additionally, a 65 MGD pumping station was constructed above the work shaft.