High Performance Turf Reinforced Matting and Hard Armor Erosion Systems Used for Culvert Rehabilitation on Auburn's Storm Water Facility Grounds

Attendees may come to learn the story of how a team of volunteers rehabilitated a stormwater culvert outlet while battling time and weather in preparation for the annually hosted Field Day at Auburn University. The University's has an impressive and innovative Storm Water research facility where they help determine best practices for DOT’s and project managers. At this event, which is hosted along with IECA's Southeastern Chapter, attendees get hands on experience to learn about best practices for erosion control and stormwater management. By way of performing many different erosion related tests, the facility experiences its own erosion and sediment control problems when simulating water flow. In the spring of 2024, in preparation for the upcoming field day event, a large culvert outlet needed rehabilitation in time for the demonstrations that would be taking place where large amounts of water would artificially be pumped into a retention area. The solution provided was not only to serve the purpose of improved erosion control protection, but also required simple and quick installation for inexperienced volunteers to install the materials properly and on time.

Full Abstract: At Auburn University's Stormwater research facility, there are multiple retention pond areas used to store and move water through various testing apparatus. By performing this work, they experience their own erosion issues as water flows from area to area. An access road conflicts with a natural flow path where water accumulates in a retention area lowest in the watershed for the facility grounds. This conflict was corrected by installing a 36” pipe culvert underneath the road to let the water flow freely. Downstream, at the culvert outlet, the sloped channel leading to the retention area was originally protected by rip rap and natural vegetation. For the flows experienced in the area, these means served as sufficient protection for many years with the aid of a sandbag weir installed approximately 35ft downstream from the pipe outlet. On top of the erosion caused by the work the testing facility does, the facility in itself is a large watershed area that experiences erosion issues when significant storms pass through the area. Auburn University being located north of the Gulf Shore area of Alabama experiences significant thunderstorms annually. This unique combination of watershed events left the culvert outlet overpowered over time as slopes started to erode and sediment buildup started to accumulate in the channel bed. While the current circumstances were not causing issues as of 2024, over time if left as is, the slopes supporting the road and channel at the outlet site could eventually have become unstable. Large equipment regularly uses the road and access could become jeopardized if the slopes around the area are not permanently protected. A solution was proposed using a system comprised of different elements to create an outlet channel that was permanently protected from further erosion and still maintained a natural look with stone and vegetation. Aside from further erosion on the slope, another concern to be addressed was the structural integrity of the road. The solution proposed included gabion basket walls and reno mattresses in lieu of the rip rap as a hard armor to permanently protect the outlet from erosion as well as retain soil behind the slope supporting the road. In addition, high performance turf reinforced matting was installed to protect the slope channel downstream and support the establishment of vegetation. The materials selected and installation procedures implemented were designed to achieve a system that was in the end monolithic and performed as a singular unit for durability. Efficiency of material and ease of installation were critical as the project was to be performed by volunteers over a short period of time with donated materials. Through the process of design and installation for such a project, many lessons were learned regarding the best installation practices, creative problem solving in the field, and bridging the gap between theory and practicality. The purpose of the presentation will not only be to share the story of the lessons learned and the overall process of completing the culvert outlet protection, but also to educate attendees on the solutions used and their purposes for consideration when designing or constructing similar projects.