Sliplining Solves Sewer Leaking Problems

A recent large diameter sewer renewal project in Evansville, IN, solved construction problems using a sliplining installation technique featuring centrifugally cast, fiberglass reinforced, polymer mortar pipe (CCFRPM).

The City of Evansville Interceptor Sewer Rehabilitation, Contract A, involved more than two miles of 90- to 108-inch reinforced concrete pipe (RCP) that was structurally deteriorated and corroded with general leaking and open joints.

A liner was needed to eliminate leakage, stop corrosion, maintain the flow capacity and restore the structural integrity of the sewers which were buried at depths up to 35 feet. Although the normal flow level was only six to 12 inches, by-pass pumping was not an option because of possible rain that would substantially increase the flows. To meet the restriction, a "live" installation was used.

To meet all of these requirements, the specifications of the designer, Rust Environmental and Infrastructure of Indianapolis, allowed only a sliplining installation of CCFRPM pipe with bell-spigot, push-together, gasket-sealed joints. The sewers were sliplined with 78- to 96-inch OD Hobas pipe. Its strength permits it to be manufactured with a very thing wall compared to RCP, so the specified minimum IDs were exceeded by one to five inches. This assured full flow recovery with several instances of increased capacity.

The project included five different diameters, lines on four separate streets, an angle point and a tight curve. Installation contractor Bowen Engineering of Fishers, IN, used seven access shafts for the sliplining. The pipe was pushed into place using an Akkerman pushing machine. This hydraulic-powered, chain drive unit installed the new liners into the host pipes without flow by-pass, plugging or diversion.

There were 13 discrete pushes at rates of 100 to 150 feet per hour. Five pushes were more than 1,000 feet and the longest drive was 1,400 feet. Despite the relatively low flows during installation, the maximum push load was only 110 tons and most runs were completed with 60 to 90 tons. No liner pipes were damaged.

The standard liner sections were 20 feet long with five-foot pieces used in the curve. The radius was so tight that a few joints could not be completed by the push-together method, so they were later sealed in place with permanent, hand-applied fiberglass laminations.

The interceptors included 105 laterals, uncommon in pipes this large. They ranged in size from six to 30 inches. Forty of the 12- to 15-inch laterals were reconnected with an internal lamination of a PVC extension to the liner pipe. A new, shallower collection line was installed to capture the remaining 65 laterals.

Bowen Engineering completed the installation by filling the annular space between the host ID and liner OD with 40 pcf grout in one lift. Once again, no liner damage occurred and no pipes or joints leaked.