Big boulder falls from coulee wall, blocks highway

A big boulder fell from the wall of the Grand Coulee during the night, blocking most of two lanes on SR-155 along Banks Lake.

Drivers could still drive around it where it was coned off at a wide spot in the shoulder of the road on an area of light traffic. But drivers Saturday morning found one-lane (mostly on a pull-out) traffic on the highway just south of the entrance to Steamboat Rock State Park.

The Washington State Department of Transportation sent out an alert on its mobile app about 3 a.m. Saturday warning of a "rockslide."

WSDOT workers were on it and had the road partially open in the early morning with the big rock coned off and drivers able to make their way around it at the wide spot in the road as two "automated flagger" units allowed traffic only one way at a time.

By 12:15 p.m. Saturday, a man could be seen from a distance gingerly making his way across the top of boulder, carrying something carefully.

Surmising action was coming soon, a reporter headed from the old highway that crosses the road that enters the state park toward the now one-lane highway at a time of light traffic. What looked like an orange fuse led away from the rock. The man was on the ground by then. When asked if they were preparing to "blow it up," he responded, "We're going to turn it into smaller pieces."

The big piece of basalt, perhaps a third the size of a small house and 1,000 times its weight, apparently fell from far up the coulee wall, where a fresher patch of disturbed rock can be spotted.

The impact at the bottom created a hole several feet deep through the pavement.

The event turning it into smaller pieces, and the big boom that echoed up and down the Grand Coulee, was caught on video by several onlookers from different angles and posted to social media for sharing. We link to and embed one such video in this story at grandcoulee.com.

As of Monday evening, the highway was open and paved.

Abelow for online: Embed of closeup video of blast: