Blacklick Creek Sanitary Sewer Tunneling

Michels Trenchless, Inc. was the managing partner in a joint venture that used an earth pressure balance tunnel boring machine to construct a 22,620-foot sanitary sewer interceptor tunnel. The 12-foot outer diameter fiber-reinforced concrete tunnel liner was installed in a single pass. Prior to installation, the precast liner was corrosion protected, bolted, and gasketed.

The project included construction of 10 shafts and corresponding manholes, with excavation dimensions up to 68 feet wide and as deep as 140 feet, excavated through soft ground with cobbles and boulders and into sedimentary bedrock. Also included in the scope was a short section of open cut installation, hydraulic drop structures, a passive odor control vault, and appurtenances.

The tunnel follows Blacklick Creek and environmentally sensitive areas draining into the creek, follows and crosses a major county road, one railroad track and seven jurisdictions. The tunnel has 12 curves, nine with a 1,300-foot radius, one with a 3,000-foot radius, and two with 3,600-foot radii. The tunnel was excavated in highly permeable geologies, including soil with silts, sands, gravels, cobbles, boulders, and rock. The tunnel alignment and shafts reach up to 120 feet below the groundwater table and were designed to accommodate up to 4.5 bar of pressure. The alignment encompasses gassy sections with high methane concentrations, carbon monoxide, and hydrogen sulfide.