Washington state town wary of slow-moving landslide

UNION GAP, Wash. — A slow-moving landslide in a fertile farming region in Washington state has forced evacuations as officials prepare for what they say is inevitable — the collapse of a ridge that sits above a few dozen homes and a key highway.

People in Washington are especially wary of landslides following one in 2014 north of Seattle that swept through a tiny community and across a state road, killing dozens.

Experts say the slide could happen as soon as late January or early February above Union Gap, a small agricultural town in the rolling brown foothills of the Cascade Range. A chunk of one ridge about the size of 24 football fields is expected to break off, spilling an estimated 4 million cubic yards of rocks and dirt.

Opinions on the impact vary widely, ranging from little damage to widespread flooding, especially in Union Gap. Some worry floodwaters will stretch into Yakima, which has 94,000 residents and sits just a few miles away.

Also nearby are the Yakima River and Interstate 82, which connects Oregon to busy Interstate 90.

I-82 is the main route through central Washington’s Yakima Valley, which produces many of America’s hops, cherries, apples and mint. The state has deemed it safe to remain open but has placed 44 shipping containers — filled with concrete barriers and weighing 9 to 14 tons each — at the bottom of the ridge to keep random rocks from tumbling into traffic.

The hillside has been sliding since at least October, when authorities began monitoring huge cracks in Rattlesnake Ridge’s western slope. At that time, the landslide was moving at less than an inch per day. More recently, it has been measured sliding at 2.5 inches per day.

Looming over all this are memories of a massive March 22, 2014, landslide in the community of Oso. That slide killed 43 people and covered 1 square mile with mud and debris. And more recently this month’s deadly landslide in Southern California.