Idaho Power Company has hired a contractor to shore up two sections of the Snake River Road in Baker County where Brownlee Reservoir has undercut the gravel road as it crosses nearly vertical slopes.
The 41-mile road, which is maintained by the Baker County Road Department, runs between Huntington and Richland, following Brownlee Reservoir for much of that distance.
County Roadmaster Jeff Smith said he asked Idaho Power to work on three sections of the road.
He said officials from the company, which owns and operates Brownlee Dam, agreed that the reservoir was responsible for the road base erosion at two of the three sites.
One is at Canyon Creek near Swede’s Landing, about 12 miles south of Richland, and the other is near Connor Creek, several miles farther south.
Smith said the third site, which is between the other two, will be the county’s responsibility. Stabilization work there won’t happen any sooner than next year, he said.
Brad Bowlin, a spokesman for Idaho Power, said the company hired Knife River Construction to stabilize the two other road sections.
Workers will drill nails into the hillside to hold a reinforced concrete wall in place, Bowlin said.
Work at Canyon Creek started last week and should be finished no later than Halloween, he said.
The road will not be closed during the project, but drivers should expect delays of 20 to 30 minutes and the road has been narrowed to a single lane.
The area near Connor Creek will be done in 2019, “when conditions permit,” Bowlin said.
He declined to say how much the work will cost.
Smith said the erosion is a gradual and ongoing problem.
He said waves, created by wind and by boat wakes, accelerate the erosion. Smith also believes the fluctuating water level — the reservoir in many years drops 40 feet or below full pool during the spring, refills in early summer and then begins to recede again — exacerbates the problem.
A study by the U.S. Army Corps of Engineers found that “rapid reservoir drawdowns coupled with low permeabilities of bank sediments create particularly unstable situations, but slower drawdowns can also lead to failure conditions.”
Fluctuating reservoirs can also affect the height of the water table and increase subsurface erosion from groundwater, according to the study.
See more in the Sept. 24, 2018, issue of the Baker City Herald.