County uses new technology in N.W. Thompson Road slide repair

Multnomah County Transportation used an innovative new product made by a local firm to repair a landslide that closed N.W. Thompson Road in early 2011.

The landslide on the downhill side of the road threatened to erode the shoulder and the eastbound traffic lane. The county has a small budget for emergency road repairs like the Thompson Road slide. Last winter’s heavier rainfall led to more landslides than in a typical year. Because the county lacked funds to repair all the slides, staff researched several options looking for a repair that would be effective and affordable. Eventually, project leaders chose a product made by Maverick Solutions of Lake Oswego to repair the Thompson Road slide. It’s the first time the product has been used on a county road.

After excavating the slide, crews installed layers of plastic netting which were then covered with gravel and lined with bags of earth. The system is all tied together by strong plastic connectors. The end result provides the stability of a conventional slide repair and allows the hillside edge to be re-planted, adding strength and environmental benefits.

The technology developed by Maverick Solutions has been used locally to stabilize banks of rivers as a flood control measure and is increasingly being used to repair landslides.

“We decided to try this product due to the number of small slope failures we routinely see over the winters,” said County Engineer Brian Vincent. “The technique has really proven effective. It gives us another tool in our box. Other benefits include free drainage and the ability to either hydroseed the wall face or plant other native plants directly in the face, resulting in a more ‘natural’ looking finished product.”

“I can't say enough about the hard work and commitment from the county crews – especially the District 1 team – who completed this repair. This project was bigger than we intended, but it has come together very well.”

The damaged section of N.W. Thompson Road is in a rural area between NW Cornell Road and NW Skyline Blvd. County engineers are considering using the new technology to repair other landslides threatening county roads.

The heavy rains during the middle of January caused further damage to Thompson Road before the road could be opened, however. Multnomah County spokesman Mike Pullen explains, “The county had hoped to reopen Thompson Road by the end of January. However, the severe storms in January created new urgent tasks for our road crews that will impact the reopening schedule for Thompson Road.

“Several culverts under Thompson Road a half-mile east of the slide were damaged and are being dug out and replaced. And crews have needed to respond to storm damage elsewhere on our road system, including downed trees, landslides, and washouts.”

A few tasks remain to be completed around the landslide repair, as well. These include replanting the slope on the downhill side of the road to add stability and return it to its natural state; rebuilding the drainage ditch on the uphill side of the road; placing protective concrete barriers on the outside shoulder; and putting down temporary lane striping.

Pullen continues, “Thompson Road is expected to reopen in the next one to two months. The main factor impacting the schedule will be weather conditions. Good weather will allow our crews to catch up on storm repairs and complete the Thompson work.”

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