Exactly one year ago, Washington County Land Use and Transportation made the decision to close Timber Road indefinitely due to a slow-moving landslide collapsing the roadway between Glenwood and Timber.
The area had seen three previous landslides in the immediate 12 months prior.
This one was more serious, owing to it being under the roadway, resulting in the pavement slowly collapsing under the county road and sliding down a steep cliff.
So now, 12 months after, where do repair plans stand? There’s not much to report since our last major update in December, but today Washington County said that the design process for landslide repairs was about 30% complete and shared the design plans.
This first set of plans define “the project area, depth of excavation and the general design,” the county said, and give county staff a chance to provide feedback on the plans to the design engineers working for their consultants.
Here’s a graphic the county shared, along with their explanation of what it means.
“This preliminary cross-section taken from the 30% design plans shows what the repair could look look like. It illustrates how we will stabilize the landslide by excavating down to stable ground and rebuilding the slope with stronger materials.
The bottom layer is drainage rock to allow water to filter into an underground drain. Above the drain rock will be several layers of gravel wrapped in plastic geogrids, providing a stable road base.
We will then build the road on top. A stone embankment on the downslope side will provide additional support for the reconstructed slope.
We expect design work will continue through the spring. The next milestone will be “90% design,” which includes specific plans for the entire work area, the road, excavation, erosion control and more.”
According to the current timeline found on the webpage dedicated to the Timber Road landslide, the project is in the “consultant is designing the project” phase until late spring, when the county will begin the process of acquiring right-of-way. After that, bids will go out for the project in the summer, construction is planned for late summer, and the plan right now is to see the road reopened by the end of this year.
According to the county, the “Shear Key at Roadway and Embankment Reconstruction” method outlined in documents obtained earlier by the Banks Post was selected after the costs and benefits of a number of options were developed by Tigard-based Cornforth Consultants and reviewed by county staff.
With funds expected to be drawn from the county Road Fund, repairing the road will come in at an estimated $3 to $5 million.
“We will be excavating the soft earth under the road and in the downhill embankment down to stable ground and replacing it with a stronger rockfill to improve stability,” said Washington County Land Use and Transportation spokesperson Chris Lueneburg in an email.
Chas Hundley is the editor of the Banks Post and sister news publications the Gales Creek Journal and the Salmonberry Magazine. He grew up in Gales Creek and has a cat.
