Friday, May 3, 2019

Travel reduced to one lane on SR 20 near Loup Loup Summit

Load restrictions and signal-controlled traffic are currently in place

By Lauren Loebsack

UPDATE - Friday, May 31
At 9 p.m. on Tuesday, June 4, SR 20 will reopen to one lane of signal-controlled traffic near Loup Loup Summit at the site of a washout in early May. The highway had been fully closed for about a week as repairs continued on the hillside. Repair work is ongoing for what is estimated to be a few more weeks so drivers should expect some delays through the work zone and be alert and safe around road workers.

UPDATE - May Thursday, May 23
The emergency repair happening on SR 20 east of Loup Loup Pass following a washout earlier this month will require a full closure of the highway. From 6 a.m. Tuesday, May 28 until 9 p.m. Tuesday, June 4, the highway will be fully closed at milepost 222.4. The contractor has reached a point in their work that will require them to excavate very soft fill material under the roadway, which could compromise the stability of the lane that is still open to traffic. For the safety of drivers, it will be necessary to restrict all travel through that area until that work is complete. Westbound traffic from Okanogan toward Twisp will be detoured south along US 97 and eastbound traffic from Twisp toward Okanogan will be detoured south along SR 153.

UPDATE - Monday, May 20
Work continues on the emergency repairs to SR 20 near the summit of Loup Loup between Twisp and Okanogan following a washout earlier this month. The contractor completed an access road from the roadside down to the bottom of the washout. Next they'll haul rip rap and fill down the road to rebuild the slope from the bottom up. One lane, signal-controlled traffic is still in place though it's possible some full closures may be necessary as the repair continues.

UPDATE - Tuesday, May 7
An emergency contractor has been named to rebuild the hillside under the eastbound lane of SR 20 between Loup Loup summit and Okanogan that washed out on Wednesday, May 1. Our geotechnical engineers have designed a repair plan and Hurst Construction of East Wenatchee will begin mobilizing and could begin staging equipment as soon as this weekend.

For now, as the hillside under the westbound lane remains stable and single-lane alternating traffic will continue, as will oversize load restrictions with no vehicles wider than 12 feet being permitted. As the repair work proceeds, some full closures and a detour are likely to be necessary. An estimated 15-20,000 cubic yards of rocks and mud slid toward Loup Loup Creek hundreds of feet below the highway. Our geotechnical engineers determined ground water saturated the soils and caused the washout below the road seven miles east of Loup Loup Pass at milepost 222.4.

There is no estimate for how long the repairs will take. The initial hurdle to overcome is locating and transporting 2,000 dump truck loads of boulders, rock and gravel to rebuild the hillside.

The current slide area is about a mile further east from where a series of slides closed 16 miles of SR 20 in April, 2017, requiring almost four months to repair.

Original Post
We've seen some beautiful weather lately and with that comes plenty of people out exploring our state. But if you're planning a trip on SR 20 between Twisp and Okanogan, be prepared for some delays. A mudslide earlier this week has left just one lane open about seven miles east of Loup Loup Pass at milepost 222.4. Our geotechnical crews have been on scene since the incident and have determined that ground water eroded the bank below the road. An emergency repair plan is being developed, but for now, we've installed a traffic signal as well as barriers and cones to help guide traffic through the one open lane. Additionally, no vehicles wider than 12 feet are permitted.

There is no estimate yet on when the roadway will be restored to normal.

The current slide area is less than a mile east of the location where a series of slides closed SR 20 in April 2017. At that time, nine distinct slide areas from milepost 207 to milepost 222 closed SR 20 and required almost four months of repair work.
A look at the location of the mudslide that has a lane closed on SR 20. (Picture courtesy of Okanogan County EMS).

A traffic signal will direct traffic through the open lane at the site of the SR 20 mudslide east of Loup Loup Pass summit.

Repairing the roadway will be no easy task. The height and slope of the roadway and hillside present very challenging conditions. It's not known yet if making repairs from below the roadway is feasible, and at best, the work will be very difficult. If it's not possible to make repairs from below, we'd need to work from above the washout. Repairs could require a full closure of the roadway.

If you must drive through the area, please be prepared for potential delays and be alert for road workers. Watch your speed and abide by the traffic signals. We will provide updates as a plan is developed.
A mudslide took down guardrail and some of the shoulder of SR 20 east of Loup Loup Pass summit earlier this week.

The steepness of the slope and height of the road will make emergency repairs a significant challenge.