Holding Up Traffic

ISCO Industries Inc.

Many corrugated metal pipe (CMP) culverts across the country will eventually experience rusting, corrosion or some form of deterioration. In the town of Ketchikan, Ala., a 48-in. CMP culvert that ran underneath a busy two-lane road was experiencing extreme deterioration. It was so severe that large holes had opened up in the pipe, causing significant leaks and flooding. These conditions presented major concerns for public safety, as the road was at risk of sinking due to the culvert failure. Hydraulics Engineer Robert Trousil was charged with working as project engineer with the Alaska Department of Transportation and Public Facilities (ADOT & PF) to solve the problem before the roadway above collapsed.

Because the 48-in. culvert was located under a crucial road, the main challenge was finding a way to replace or rehabilitate the pipes without disrupting the traffic pattern on the road above.

The placement of the culvert was not the only challenge faced on the job – Mother Nature played a role as well. Persistent rains before and during the project brought sweeping water flows through the jobsite, disrupting installation. It was imperative to find a solution to repair the crumbling culvert while maintaining a safe work environment.

Solution

NW Relining LLC – an Olympia, Wash.-based company – is a distributor for Snap-Tite products. Sales reps Grey Langemo and Bob Boyes worked with Trousil to find a solution that would save time and money without interrupting traffic. They elected to use 42-in. high-density polyethylene (HDPE) pipe to slip-line and rehabilitate the existing CMP. The 6-in. annular space was filled with grout to hold the liner in place. Although the pipe diameter is decreased, the hydraulic flow capacity is improved when using HDPE.

The Snap-Tite system is durable, is long-lasting and does not rust or corrode. The primary alternative to Snap-Tite – digging up and replacing the pipe – would require the town to close the road, disrupt the flow of traffic and cost the City of Ketchikan large amounts of money and time. Snap-Tite can be installed comparatively easily and inexpensively.

The new Snap-Tite liner will not leak and will outlast the rehabilitated CMP culvert for decades to come. A unique feature of liner is that fusion is not required to join pieces of the HDPE pipe together. The patented male/female machining at either end of the pipe allows the ends to be “snapped” together, piece-by-piece, and pushed into the full length of the existing pipe.

Results

NW Relining LLC trained the ADOT & PF crew both in the classroom and in the field on the proper methods of pipe installation. Now, the ADOT & PF is prepared with a cost-effective, long-lasting solution for future culvert rehabilitation.