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Project Spotlight: Agassiz NWR Water Control Structures

NCSPA » NCSPA E-News » Project Spotlight: Agassiz NWR Water Control Structures
By: TrueNorth Steel

The U.S. Fish and Wildlife Service was looking to replace various water control structures in north-central Minnesota. The structures were part of a National Wildlife Refuge and were originally installed in the mid-1970s. They reached out to TrueNorth Steel in hopes of identifying a solution to this problem.

The existing concrete water control structures had outlet pipes that were in need of replacement. A couple of structures had been previously restored with steel casing pipe, while others were restored with HDPE pipe. Unfortunately, difficulties were identified in those replacements with adapting the pipe materials to the concrete structures. TrueNorth Steel was able to design a unique, custom-fabricated flange adapter that would be placed on the inside of the concrete wall. This ensured that the adapter would not wash out and that a properly sealed connection would be in place, which would allow for a positive joint connection between the adapter and the remaining footage of the outlet pipe.

After removing the original deteriorated outlet pipes, it was revealed that the openings in the concrete wall wouldn’t quite fit a 42” diameter pipe. Since the hydraulic flow needed to be maximized, TrueNorth Steel was able to provide the customer with a custom 40″ inside diameter pipe, which maximized the waterway area and overall hydraulic performance.

Polymer Coated Spiral Rib was chosen due to its superior service life as well as its hydraulic performance (Manning’s “n” = 0.012). In addition to the CSP, gasketed positive joints with rod and lug band connectors were used. These additions helped limit any leakage into or out of the pipes.

In the end, the customer was pleased with how the adapters and outlet pipes functioned and they incorporated this same flanged adaptor design into various new steel outlet control structures that have since been installed.

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