WASTEWATER/City uses sliplining to rehab interceptor sewer

Evansville, Ind ., recently rehabilitated more than two miles of an interceptor sewer using polymer mortar pipe and sliplining. The $8 million project involved four streets, an angle point and a tight curve, and it incorporated multiple pipe sizes.

Buried at depths as great as 35 feet, the interceptor lines were originally constructed of 90- and 108-inch reinforced concrete pipe. However, during the 20 years since their installation, the pipes had deteriorated, producing open joints and leaks, and affecting flow capacity.

In 1998, when Evansville officials decided to repair the concrete pipe, they faced an immediate problem: Although the normal flow level was only six to 12 inches, rain could increase that level significantly, making bypass pumping infeasible. Because of that, the city opted for “live” installation of a liner.

The project got under way in spring 1999. Rust Environmental and Infrastructure, based in Indianapolis, performed the sliplining using 78-inch and 96-inch pipe from Houston-based Hobas Pipe. Reinforced with fiberglass, the po-lymer mortar pipe was installed with bell-spigot, push-together, gasket-sealed joints.

During the project, seven access shafts accommodated a hydraulic chain drive unit that pushed the liners into the host pipes without the necessity for bypassing or diverting flow, and without plugging the lines. The installation contractor, Bowen Engineering of Fishers, Ind., made 13 discrete pushes at rates of 100 to 150 feet per hour. Five pushes exceeded 1,000 feet, and the longest drive was 1,400 feet. The liner pipe was supplied in standard 20-foot-long sections, and five-foot pieces were used in the curve.

The interceptors included 105 laterals, ranging in size from six to 30 inches. Forty of the 12- to 15-inch laterals were reconnected by internally laminating a PVC extension to the liner pipe. A collection line was installed to capture the remaining laterals. The contractor finished the installation by filling the annular space between the host and the liner with grout. The underground work was completed last December, and surface restoration – including some street and sidewalk rehabilitation – continued until fall 2000.