Roadside Slope Erosion Control

The Department of Transportation (DOT) Maintenance office had the task of trying to stop erosion issues on slopes along the roadside of State Road 70, with the main problem areas at Brandy Branch and Horse Creek. After multiple repairs and maintenance to the problem areas with standard practices, DOT determined it would be best to look for a permanent solution to resolve their erosion issues and reduce the maintenance cost of these problematic slopes along State Road 70.

The DOT reviewed multiple products and ultimately chose the Flexamat® Standard Tied Concrete Mats manufactured by Motz Enterprises. Flexamat Standard consist of concrete blocks embedded into a high strength geogrid. Flexamat® Standard concrete erosion mat includes a backing consisting of wood excelsior erosion control blanket (Curlex II) as the base layer, covered by a leno weave. The concrete mats are used to control erosion in swales, slopes, ditches, channels, shorelines and areas where soil sediment may be lost due to water runoff.

Flexamat® can be fully vegetated giving the system a natural look, while providing hard armor erosion protection, thus creating a Green Hard Armor System. Vegetation establishment within the tied concrete block mats was a key factor in choosing Flexamat® Standard. The DOT has a Wildflower Program with a focus on locating and managing wildflower populations native to the state. Project engineers saw the opportunity to incorporate native wildflower within the tied concrete mats. The DOT Wildflower Program offers a plant range map to help determine the best wildflower species to establish by seed on roadsides. Using the plant range map, it was determined that the best species to plant would be Blanketflower - Gaillardia pulchella. This species has a high aesthetic impact and are self-contained.

Another deciding factor for the Flexamat® Standard system was the speed of installation compared to other hard armor systems, which was an important issue for this project since one lane of traffic would be closed during installation. The awarded contractor had the area for the Flexamat prepared and ready for installation in two days. This included re-grading the eroded slopes and removing one foot of asphalt from behind the guard rails.

Prior to installing Flexamat Standard, the prepared slopes were seeded with a mixture of Blanketflower and Annual Rye Grass. The mats were placed behind the guard rail at the top of the slope, against the asphalt and unrolled parallel with the roadside. Various roll widths of 8’, 10, & 12’ were used to provide erosion protection from the top of the slope. The contractor unloaded six trucks and installed 21,220 FT2 in the first three days, all while having to set up and perform Maintenance of Traffic (MOT) every day during construction. The remaining 3,000 FT2 was finished on the morning of the fourth day. A total of 24,220 FT2 of material was installed in only four days, while having to deal with obstacles and traffic controls. The only piece of heavy equipment that was onsite and used for this project was a Grade-All.

The wildflower and annual rye grass blend established well within the Flexamat concrete erosion mats, providing a pleasant natural look. With the use of wildflower seed, the DOT no longer needs to mow these areas, reducing maintenance cost. Along with the aesthetic benefits and maintenance savings, the Blanketflower within the concrete matting provides important nectar for threatened honey bee populations - All while providing a long-term hard armor erosion protection system.

For more information on this project, please contact us.