Prior to installation of the erosion control products, to ensure uniformity and integrity of the subgrade, the contractor proof rolled the slopes.
At the crest of the spillway, approximately 6,000m2 of topsoil, seed and mulch was placed followed by a blanket of P42, a turf reinforcement mat fabricated from 100% polypropylene fibres. With vegetation, the maximum permissible flow velocity is 4.9m/s.
On the slope, ranging from 6:1 to 9:1, Armorflex was installed with an underlying layer of 50mm dia. Clear limestone and 400R non-woven geotextile. Design flow velocities were calculated by the engineers with the U.S Army Corps of Engineers HEC-RAS model. Utilizing Armortec’s software, which calculates the class of block required based on the hydraulic design parameters, the engineers’ specification of class 40T tapered block was confirmed. The maximum permissible flow velocity (vegetated) was determined to be 7.5m/s. A standard mat dimension for this class is 2.4m x 6.1m x 0.12m thick, weighing approximately 2,600 kg. Due to the geometry of the slope, custom dimensions of mats were also fabricated. The contractor then placed 100mm of topsoil with seed over the mats. In approximately 4weeks, 6,000m2 of Armorflex was installed using an excavator and spreader bar.
The undisturbed, existing embankment of the river was protected by two rows of A-Jacks installed at the toe of the spillway slope approximately 2m behind the river bank. A-Jacks are high stability concrete armour units designed to dissipate energy and resist erosive forces of flowing water. Each unit (model AJ-24) weighs approximately 36 kg.
Otherwise known as Armorflex, these interlocking matrix concrete blocks are connected by a series of cables to form an articulated mat that has excellent performance in erosion control. Armourflex mats have proven to be an aesthetic and functional alternative to dumped stone, rip rap. This is a permanent system that allows for vegetation, is easy to install and virtually no maintenance. Extensive research and testing of performance with wave and open channel flow conditions makes this product a proven system.
Slope stabilization and erosion protection for an existing earthen emergency spillway on the Binbrook Dam connecting Lake Niapenco and the Welland River was required for passage of the Inflow Design Flood of approximately 215 m3/s, in accordance with Ministry of Natural Resources criteria.
Devron worked in conjunction with CRL Campbell providing detailed installation and onsite support. A combination of P42 (turf-reinforcement mats), Armorflex (articulated concrete block revetment) and A-Jacks was installed to form the slope stabilization and erosion protection lining for the emergency spillway.
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