Nespelem School Loop Road Bridge, Confederated Colville Tribes

Akana provided engineering design, permitting, and construction services for approximately ¾ mile of sidewalk, roadside improvements, and a new vehicle and pedestrian bridge between Highway 155 and the Nespelem Grade School.

The existing bridge was a cast-in-place box culvert which carried two lanes of traffic over the Nespelem River. The width of the existing box culvert required a contraction in the roadway, reducing the roadway width to 20’. There were no curbs or sidewalks on either sides of the existing street, but a narrow walkway existed along the north side of the bridge behind the existing guardrail.

The goal for this project was to replace the current bridge with one meeting the minimum maintenance requirements of the Bureau of Indian Affairs (BIA) and to address abutment settlement at the existing bridge. The firm analyzed three alternative structures: a multi-plate corrugated steel pipe arch, a multi-plate corrugated steel bottomless arch, and an aluminum box culvert. A 20-foot precast rectangular aluminum open-bottom culvert structure replacement was recommended as the best option based on cost, fish passage and constructability