Mineral company relines damaged culvert under railroad & improves flow

Case Studies September 10, 2015
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Road collapses, road closures and traffic delays are recurring news headlines attributed to failing culverts across the U.S. Many drainage culverts were installed 40 to 50 years ago and are now past their design life.
One such culvert affected a private enterprise in Trona, Calif., Searles Valley Minerals was faced with a failing culvert underneath a railroad that delivers supplies to the company’s plant. The damaged culvert was a 72-in. corrugated metal pipe (CMP) that had a length of 120 ft. A failure of the CMP would compromise the structure of the railway and disrupt service of the rail line going into the plant. The company needed a permanent solution that would not disrupt the railway traffic or compromise the flow of drainage through the pipe.
The solution
Searles Valley Minerals opted to slipline the failing culvert with Snap-Tite. “Six months ago, we were fortunate to run across Snap-Tite’s approach to renovating CMP culverts. We were faced with repairing a CMP culvert that could not be taken out of service for replacement,” said Peter E. Grey, P.E., engineer with Searles Valley Minerals. “The approach made the repair painless.”
The Snap-Tite culvert lining system is made of high-density polyethylene (HDPE) pipe. The patented male/female machining at each end of the HDPE allows the pipe ends to be ‘snapped’ together, piece-by-piece, and pushed into the full length of the existing pipe. The decision was made to slipline the existing CMP with 63-in. outside diam. (OD) pipe. Generally, Snap-Tite pipe liners do not decrease flow even though the diam of the original pipe is decreased with the liner in place. However, the county flood group wanted to make sure that there would be no entrance losses.
In order to increase flow, Snap-Tite provided an inlet control device called a Hydro-Bell. Independent testing conducted by Utah State University found that the Hydro-Bell increases hydraulic flow by approximately 30%, compared to plain end headwalls under inlet control conditions typically found in culvert applications.
Hydraulic flow in short runs of pipe, such as drainage culverts, is often controlled by inlet and/or outlet conditions. It is possible to maximize flow rate by altering the inlet or outlet conditions in the culvert. However, in most cases, the outlet conditions are difficult to alter; but it is possible to modify the inlet condition.
According to the study, as head pressure increases, the Snap-Tite Hydro-Bell system flow rate also increases versus a square end inlet, making it ideal for flood-prone drainage culverts. The Hydro-Bell is designed to “snap” onto the culvert lining system’s machined ends.
The installation
The mineral company’s crew worked quickly to reline the damaged culvert. The Snap-Tite pipe was snapped together and inserted into the damaged CMP. The Hydro-Bell was also snapped on to the end of the pipe, creating a leak-free system. Grout filled in any annular space between the old culvert and the new liner.
The whole time the crew worked, the rail line remained open and in use. As a result, the company continued to use the rail to send and receive materials. The culvert rehabilitation was completed quickly without disruption.
For more information on Snap-Tite or the Hydro-Bell visit www.culvert-rehab.com

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