Project Name: Cedar Valley Reservoir Auxiliary Spillway Repairs
Location: Garnett, Kansas
Date of Installation: July-October 2023
Contractor: Rodriguez Mechanical Contractor Inc.
Owner: City of Garnett, KS
Application/Solutions: Flexamat® used on spillway repair project as a permanent erosion control solution.
The dam and spillway at the Cedar Valley Reservoir were damaged by heavy flooding in 2019. The City of Garnett, KS, then had to find a solution to repair this damage and erosion. They needed a solution that would provide protection against future floods and prevent the possibility of erosion. The city also wanted a product that could be mowed and maintained with a controlled burn in early spring.
Another challenge to navigate was that the only access to the spillway to work on repairs was by crossing the dam. The dam holds back the town’s drinking water and is a vital part of the city’s infrastructure. If they used rip-rap, it would have required over 2,300 loads to complete the project. Engineers believed this would damage the dam, requiring a rebuild and costing the city millions.
Flexamat Plus FR was selected as the solution. Flexamat is a tied-concrete block mat secured with cross plate percussion anchors and used for permanent erosion control. The ‘Plus FR’ version of Flexamat has 5,000 PSI concrete blocks connected by a bi-axial geogrid with a flame-resistant coating.
A hard armor solution that could also be vegetated was the preferred solution. Flexamat allows for vegetation growth in the 1-inch gaps between the concrete blocks. Once fully vegetated, the installed Flexamat will blend into the natural vegetation. To control vegetation on the spillway, the city can maintain it by mowing over the Flexamat or by a controlled burn. The flame-resistant grid of the Flexamat Plus FR will remain unharmed during necessary controlled burns. To complete the project, 72 truckloads of Flexamat were hauled across the dam. This was a significant reduction of loads passing over the dam compared to the 2,300+ loads of rip rap the project would’ve required.
A tied-concrete block mat with flame resistant grid and cross plate percussion anchors.
This project had a material coverage area of 8 acres and utilized 9,000 cross-plate percussion anchors with 6-foot cables. The final result will be a hard armor system that uses both mechanical anchoring and natural vegetation to protect the spillway from future flood erosion. The City of Garnett is pleased with the results and now has a permanent solution with minimal maintenance for this formerly erosion-prone area.
Vegetation started growing through the 1-inch gaps between the concrete blocks in the Flexamat before the installation was completed. Two years later, the Flexamat is fully vegetated, blending into the surrounding environment and providing resilient erosion protection.
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