Major challenges were apparent from the start. First, the water elevation had to be lowered to permit construction of the littoral shelf. The construction of the shelf had to be precise to accommodate suitable conditions that would foster healthy growth of select marsh grasses. Because the slope down to the water elevation is subject to maintenance equipment and soil movement, a material with adequate strength and integrity was required to withstand forces that might otherwise damage the root reinforced vegetated system, leading to the potential of compromised protection of the lagoon bank.
THE ENKA SOLUTION
On the banks of The Landings’ Oakridge No. 5 Lagoon, the grade was established, including construction of the littoral shelf, and the area then compacted and smoothed.
The best fit for both the engineer and the owner: Particularly attractive to the H & K Engineering Group was the openness of the entangled filament mat, which clearly permits uninhibited vegetative growth, while the high modulus, high strength of the integrated geogrid provides the means for exceptionally long-term durability — always a consideration in the design of permanent erosion control systems. From a budgetary and an aesthetic perspective, reinforced vegetation was a welcome alternative for installing costly concrete or unsightly hard armor solutions, commonly the method used for the stabilization of lake banks and slopes.
Next, anchor trenches were excavated at the top and toe of the slope. EnkaMat R was laid perpendicular to the shore line, eliminating breaks in the runs from top of slope to toe, just below water elevation. A lightweight nonwoven geotextile was used below the water elevation to capture fines and minimize soil movement, while percussive-driven earth anchors (PDEAs) were installed to mechanically attach the EnkaMat firm against the soil while creating tension on the soon to be submerged turf mat.
INSTALLATION BENEFITS & RESULTS
EnkaMat is easy to handle, remains flexible and conforms extremely well to the soil surface, making it popular with installers. By tensioning the EnkaMat and the underlying geotextile layer firm against the soil, there was less risk for soil movement in the submerged zone, providing the best opportunity for hearty plant and root development of the marsh grasses – key to the success of this soft armored solution. Going beyond a conventional, stabilized shoreline solution
allowed elimination of hard surfaces.
The owner saved money with a more aesthetically pleasing, naturally vegetated lake bank which provides an enhanced ecosystem, improving the quality of the lake. The use of reinforced vegetation also improves fish and wildlife habitat, as well as for the humans that encounter the lake and its beautiful shorelines.