Highway Embankment Construction Using PYRAWALL Wrap-Face Vegetated Wall System

PROBLEM

Pend Oreille County 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. Endanger 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 mile per hour road, but the speed limit is 50 miles per hour. It was determined to realign the road and replace the culvert with a 58-foot, 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.

SOLUTION

The owner considered using steel sheet pile walls, but the cost quickly exceeded budget. Additionally, vinyl sheet pile walls didn’t meet the strength criteria. Also, 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. PYRAWALL can also withstand animal loading expected from deer, antelope and moose in the area.

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