The Pennsylvania Department of Transportation (PennDOT) planned to rehabilitate a section of Interstate 99 which included the replacement of nearly 25,000 feet of deteriorated storm drainage system. The PennDOT District 9-0 engineers traveled to the project location of Bedford and Blair counties to perform a field inspection of the project; they soon discovered this was a complex situation that would require a unique solution. Most of the original culvert had deteriorated and was in need of replacement. Some of the pipes were almost 60 feet beneath the roadway surface of Interstate 99. Traditional open cut replacement and pipe jacking were investigated and found to be to cost prohibitive. PennDOT looked into a Snap-Tite slip line system, and the discovery of almost $9 million in savings blew them away.
Snap-Tite officials were required by PennDOT’s Bureau of Design to submit engineering computations that demonstrated that the polyethylene pipe would withstand soil pressure from the deepest depths (60 feet) as a stand-alone pipe. The pipe proved it could withstand height of cover exceeding the 60-foot fill depth. Snap-Tite also demonstrated to the Department additional environmental benefits, including minimizing road work, stream diversions, and earth disturbances. This would eliminate queuing of traffic and its release of harmful emissions since the traffic would be maintained using the existing roadway. No special traffic control, such as crossovers or single lanes, would be required in order to install the slip-line. Polyethylene is also fully recyclable and has a virtually unlimited life expectancy.
Almost 24,600 linear feet of Snap-Tite was delivered to the PennDOT contractor along with site evaluations, full technical support and training. The sections of Snap-Tite were shipped to the jobsite with machined ends already completed. They were then placed horizontally to the roadway at each culvert. Once the host pipe was ready to be lined, a section of Snap-Tite was aligned with the pipe and partially inserted into the pipe. The next section of pipe was then aligned with the pipe, a lubricant was sprayed on the ends of the pipe and a rubber gasket was added. The pipes were then simply snapped together with a come-along. The result is a watertight joint with inside and outside diameters that are the same as those of the pipe, providing a consistent I.D. throughout the entire pipe.
The pipe was then pushed or pulled through the deteriorated host pipe. This procedure was repeated until the entire pipe was lined. Bulkheads were then constructed at each end of the pipe. Then a flowable fill grout was then pumped around the HDPE pipe and the host pipe. Enough grout was pumped into the annular space to fill all the voids that had been created by the water escaping from the host pipe. Savings for the project compared to traditional open cut methods amounted to almost $9 million. These savings took into consideration expenses needed for pipe installation, traffic control and user delay costs.
One of the largest savings for the Snap-Tite system comes from the machined ends of the pipe. Traditionally, polyethylene requires a specialized fusion machine with trained fusion operators to heat fuse the pipe together. With the Snap-Tite system, no fusion machine or trained technicians are needed. Poor weather does not pose a problem. This allows contractors, municipalities, and Departments of Transportation the ability to use the product without any highly trained personnel or expensive equipment.
“A 30 percent savings on a $6 million project is something that will get you noticed,” said David Hundley of Snap-Tite. “But I think that the environmental benefits of the entire Snap-Tite process are what will make this method of culvert rehabilitation are also substantial. Issues like sustainability are becoming the focus for state funded infrastructure projects and there’s nothing out there that can compete with the Snap-Tite process. Snap-Tite is truly the permanent solution.”