The Cache la Poudre River begins in Colorado’s Rocky Mountain National Park, flows through Roosevelt National Forest and then winds its way through the City of Fort Collins. Over its course, the River drops 7,000 feet in elevation, allowing visitors plenty of room along its banks for camping, hiking, fishing and boating.
The City of Fort Collins and Anderson Consulting Engineers identified an area on the left bank of the Cache la Poudre River that could breach if a large flood event occurred. If so, nearly the entire river flow would need to be diverted into a reclaimed pond, part of the City’s Natural Areas Program. These flood flows would pass through the natural area and overtop a major arterial on the east side of Fort Collins, likely resulting in catastrophic failure of the roadway embankment. In order to prevent this from occurring, the L-Path Berm Protection project required the use of hard armor on two controlled spillways along the embankment.
ArmorFlex® articulating concrete block revetment systems were chosen for this project based on the block’s ability to stabilize embankments.
“Previous success with ArmorFlex blocks provided us with a high comfort level,” stated Greg Koch, Vice President with Anderson Consulting Engineers. “Due to rigorous testing procedures to which the blocks have been subjected and the intuitive design methodology, we felt comfortable that the mats would perform as intended. In addition, Contech’s customer service has always added insight and value to our design projects.”
J-2 Contracting installed 28,668 square feet of ArmorFlex Class 40T blocks and 27,146 square feet of ArmorFlex Class 70L blocks. The mats were longer than normally used (45’ in length as opposed to the 40’ maximum standard length) to ensure that the grout seam between mat junctions was below the seasonally variable water surface elevation in the downstream receiving ponds.
ArmorFlex provided a successful solution for the two spillways as they allowed flows to pass safely without compromising the integrity of the embankment. In addition, the project reduced floodplain footprints and minimized the impact of floodwaters in the drainage basin below.