OutdoorNebraska

Floating The Good Life • Nebraska Game and Parks Commission 33 The following are possible material alternatives for constructing the ramp approach pending what specific river characteristics are like and level of construction necessary to sustain the influences of that river. Poured Concrete Pavement: Concrete provides durability and positive traction for traversing when a grooved finish is applied. Clean-out maintenance can be done with mechanical equipment with a low risk of damage to the surface. Forming and pouring concrete below water elevations will require de-watering measures, which increase construction costs. Steel reinforcement within the formed concrete is recommended and should be incorporated as specified by a professional civil engineer. Reinforced Precast Concrete: Reinforced precast concrete slabs or planks allow for forming and finishing the material elsewhere then mechanically placing on site. Traction, clearing sediment and maintenance are similar to poured concrete pavement. This application has advantages over poured concrete in placement below water elevations. A poured concrete solution can be paired with reinforced precast concrete to address below water elevation segments. A precast solution must incorporate some manner of cabling or coupling the individual segments together to form a uniform system with low risk for individual displacement. Articulated Concrete Mats: Articulated concrete mats are precast concrete modular block units that are cast with integral cabled grid. Placement of these articulated mats are typically followed by in filling the void spaces between the block units with aggregate rock or gravel. Similar to reinforced precast concrete, below water installation has advantages over poured concrete. Additionally, articulated mat sections should be cabled or coupled to each other. Note that heavy mechanical equipment is typically required to lift and set the articulated concrete mats in place that may be prohibitive in tight sites to construct within. Traction is good on articulated concrete mats; however, do create some level of slip potential as aggregate within the void spaces are displaced and lie across the top of the concrete block unit. Open Cell Geotextile Mats: Open cell geotextile mats are lightweight synthetic materials that can be stretched out to form a honeycomb pattern in which to infill with other materials. A geotextile fabric or open geotextile grid typically is required as an underlayment to stabilize the mats further. Open cell geotextile mats can be filled with poured concrete, aggregate rock, or a blend of aggregate and soil to grow turfgrass. Mats filled with aggregate or soil is not recommended below high water elevations as flows have the ability to scour the material from the open cells. Clean out of sediment deposited by high water flows is limited to the type of mechanical equipment used without damaging the geotextile material. Mats infilled with poured concrete are better suited for below water flow elevations and provide greater flexibility in clean out and maintenance by mechanical equipment. Traction on geotextile mats are relative to the infill material provided. RAMP APPROACH AT ELKHORN CROSSING RECREATION AREA

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