Sep 06, 2018

Highway Embankment Construction Uses Wrap-Face Vegetated Wall System

Highway Embankment Construction Uses Wrap-Face Vegetated Wall System

Pend Oreille County in New Port, Wash., needed to remove a culvert on Indian Creek that was preventing bull trout from traveling upstream to spawn. The bull trout are a threatened species under the U.S. Endangered Species Act and the stream is considered environmentally sensitive. Additionally, the county needed to address the road’s condition. Its alignment was for a 35 mph road, but the speed limit is 50 mph. It was determined to realign the road and replace the culvert with a 58-ft, single-span bridge to allow the fish to more easily move upstream and to correct the road condition. Limited physical and right-of-way access dictated that the earth-fill embankment approaches required for the new bridge would need steep wing walls.

Highway Embankment Construction Uses Wrap-Face Vegetated Wall System

The owner considered using steel sheet pile walls, but the cost quickly exceeded budget. Vinyl sheet pile walls did not meet the strength criteria. Residents and a local Indian tribe wanted a solution with a natural, vegetated look, rather than a concrete wall along the wetland. Pyrawall was selected because it is an engineered wrap-face, vegetated solution that costs less than a concrete retaining wall. In addition to yielding a natural look, the system’s bracing is all internal, creating a smaller footprint overall. It also can withstand animal loading expected from deer, antelope and moose in the area.

Pyrawall was used to build an east-approach embankment that is 210 ft long and 14 ft tall, and the west-approach embankment that is around 340 ft long and 18 ft tall. Once installed, the system provided immediate erosion control. The constructed wall will be 85% to 90% vegetated in four years and will provide erosion control protection for up to 75 years.

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