Aging Infrastructure: Sliplining Helps Restore Failing Clay Tile Sewer
The City of Lima, OH, was faced with a failing 78-inch diameter clay tile-lined sewer ranging in depth from 25 to 31 feet. Several remediation options were reviewed to restore the structural integrity to the existing sewer before sliplining was selected as the most cost effective solution.
|66-inch diameter segmental pipes were placed one at a time into the existing 78-inch diameter clay tile lined sewer.|
Lima, a city with a population of roughly 40,000 in Northwestern Ohio between Dayton and Toledo, boasts a rich manufacturing background. Lima is notably the home of the Lima Army Tank Plant, built in 1941, which is the sole producer of the M1 Abrams, the principle battle tank of the U.S. Army and the Marine Corps, as well as of the armies of Egypt, Kuwait, Saudi Arabia, Australia, and Iraq.
Ford Motor Company also calls Lima home with a 2,400,000 sq. ft. facility, which has about 1,600 total employees making its new all-aluminum, 3.5-liter Duratec 35 V6 engine. The plant was originally built in 1957 to manufacture V-8 engines for the Edsel.
Predating these manufacturing facilities are portions of the city's infrastructure. Constructed in 1921, a failing 78-inch diameter clay tile-lined sewer ranges in depth from 25 to 31 feet.
"The condition assessment was performed and found a deteriorating structural condition," said Jack Huber, Utilities Department Field Service Division, City of Lima. "To assist in determining a solution to rehabilitate the sewer both a conventional CCTV and a digital laser survey was performed."
"The proposed rehabilitation system must restore structural integrity, be corrosion resistant and, as an annulus grouted composite, be sufficiently robust to deal with frequent surcharge as well as being back grouted to deal with possible voids immediately outside the sewer," said Ray Hutchinson, Vice President / Principal Engineer, MWH Atlanta, GA.
The survey revealed many obstacles that would need to be overcome. The max ovality of the existing sewer was 10.5 percent with the max deflection of 7 percent; several major encrustations existed as well as debris such as loose tiles. It was determined that a nominal 66-inch diameter Hobas pipe with an outside diameter of 69.2 inches could be successfully installed within the deteriorating line.
"Several remediation options were reviewed to restore the structural integrity to the existing sewer, however sliplining appeared to offer the ideal cost effective solution," said Gary Sheely, Director of Utilities, City of Lima.
Hobas supplied 1,140 feet of centrifugally-cast, fiberglass-reinforced, polymer mortar (CCFRPM) pipe with a flush joint. Advantages of sliplining with CCFRPM included an optimization of capacity, a continuous smooth pipeline and a structural solution, and an increase in chemical resistance; it is also cost effective.
Midwest Mole, headquartered in Greenfield, Ind., was awarded the project and began work in May 2012. Before installation began, one of the 20-foot long pipes delivered to the project was used as a mandrel. The success of the mandrel test led to the pipe installation from one shaft location. The downstream push of roughly 1,060 feet occurred over the course of five days. The upstream push and the pipes in the pit were subsequently installed.
"The liner was plugged at the downstream end and allowed to fill to counteract buoyancy while grouting the annular space between the host and the liner," Huber said.
Cellular grout was placed in the annular space, and flowable fill was placed in the pit area.
"The sewer is fully commissioned at this stage and the final inspection has been completed," concluded Ray Hutchinson, Vice President/Principal Engineer, MWH Global, Inc.
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