HDPE pipe battles Mother Nature to rehabilitate weathered pipe in Ketchikan, Alaska

Feb. 2, 2017

Many corrugated metal pipe (CMP) culverts across the country will eventually experience rusting, corrosion or some form of deterioration. In the town of Ketchikan, Alaska, a 48-in. CMP culvert that ran underneath a busy two-lane road was experiencing extreme deterioration 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. diameter 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 to be dealt with during installation. It was imperative to find a solution to repair the crumbling culvert while maintaining a safe work environment.

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 the need to interrupt traffic. They elected to use 42-in. diameter high-density polyethylene (HDPE) pipe to slipline 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, 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 town of Ketchikan large amounts of money and time. Snap-Tite can be installed comparatively easily and inexpensively.

The new liner will not leak and will far outlast the rehabilitated CMP culvert for decades to come. A unique feature of the 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.

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