Rockslide traps tiny town of Diablo; officials warily watching mountainside

NEWHALEM, Whatcom County — Geologically speaking, it was the twitch of an eyebrow — Ma Nature adjusting her granite girdle.

But in human terms, 3 million cubic yards of rock — the amount that cut loose from a mountainside a mile east of here Sunday — is almost impossible to fathom.

You have to see the mammoth rock slide to get a sense of how easily it wiped out a section of Highway 20, which has been closed indefinitely at Newhalem, well ahead of the normal snow-closure schedule.

You have to get close to the slide — and the house-sized boulders it tossed about like popcorn in a wind tunnel — to understand why state and federal officials hovering in helicopters yesterday are worried.

They don't know what it will cost to clear and rebuild the highway. Nor do they know if more of the mountain is poised to fall, posing a risk to repair crews and leaving the tiny town of Diablo, above the slide, isolated.

For the near future, at least, you can't see this spectacle. Nobody, save a few brave rock climbers, geologists, engineers and highway workers, is being allowed up Highway 20 beyond Newhalem, so precarious is the fractured mountainside that gave way after a record deluge dumped seven inches of rain here several weeks ago.

But if you could take it all in, this would be the picture: About a mile up the road in the narrow canyon leading east out of tiny Newhalem, a large field of debris is found near the Falls Creek Bridge. Until recently, that debris included a massive, road-blocking boulder, as big around as a double-wide trailer and half as long, and weighing about 50 tons.

	GREG GILBERT / THE SEATTLE TIMES About 3 million cubic yards of rock broke loose Sunday morning. Climbers placed Global Positioning System sensors on the mountainside yesterday to help geologists predict when the next slide will occur.

The boulder was blasted to bits Wednesday and hauled off by workers who opened a single-lane emergency road — all the while keeping a wary eye on the crumbling mountainside directly over their heads.

To see where the behemoth rock came from, you have to crane your neck all the way back, peering straight into the sky, more than 2,000 vertical feet above. If you could see that far — the equivalent of 3½ Space Needles stacked end to end — you would see a jagged, raw scar where an entire portion of this unnamed mountain gave way around 6 a.m. Sunday, plunging into the narrow Skagit River canyon below.

The bulk of the slide — described by geologists as a rock mass roughly 1,000 feet wide, 1,000 feet long and about 100 feet thick — swept down the east side of the ridge, filling the Afternoon Creek drainage with rubble up to 100 feet deep.

Most of this rock stopped short of the highway. Today, it hangs above it, precariously, absorbing water from the creek that goes into the pile but does not visibly come out.

Some of the largest chunks, however, plummeted straight down the west side of the divide, in the Falls Creek drainage, smashing portions of the highway and damaging a bridge. There were no vehicles on the road at the time. Seismic sensors monitored at the University of Washington recorded the event.

At the top of the slide, visible from downtown Newhalem, looms another 1 million to 2 million cubic yards of rock, old and newer cracks visible across its face. A rainstorm predicted for the coming two days is likely to work its magic on this area, as well, filling the cracks with water, which later will freeze and expand — the likely cause of the first landslide.

"The incoming weather is a major concern," said Doug Anderson, a state Department of Transportation (DOT) engineering geologist who calls the Falls Creek slide "huge — the biggest I've seen in my career."

Winthrop-bound Seattleites won't notice much disruption from the closure of Highway 20, which typically is closed for the winter at Newhalem about this time of year.

But the slide creates urgent problems for highway repair crews, state budgets and Seattle's power supply.

Several other washouts farther up the highway need to be repaired, and threaten to get far worse if they're not.

And the slide has isolated the Seattle City Light company town of Diablo, home to about 70 utility employees and their families and a few road-work contractors.

Because earlier washouts on Highway 20 above Diablo already had closed the road to the east, escape via that route through Winthrop is impossible until more road repairs are made. Those repairs have been delayed by the blockage near Newhalem.

By the time they are complete, snow may well have blocked the road, making an eastbound exit impossible until next spring.

Children who bus to school in nearby Concrete were ushered out of Diablo and likely will stay with friends until the road home is safer, said Tom Purcell, City Light Utility Manager. Work crews and supplies are being ferried into town by helicopter.

Diablo residents are accustomed to being isolated from civilization by washouts and snow storms.

"They've been cut off from the world before," Purcell said as he loaded cases of fresh carrots and bread onto a small helicopter bound for the little company town.

	GREG GILBERT / THE SEATTLE TIMES A giant rock slide Sunday just east of Newhalem, Whatcom County, left a white scar on the mountainside and blocked the North Cascades Highway, seen at left along the Skagit River. Concerned highway crews are keeping an eye on the splintering rock still hanging above.

But any long-term road closure west of Diablo would be a problem for City Light, which relies on the highway to get heavy construction equipment and maintenance materials to powerhouses at Ross, Diablo and Gorge dams.

"Public power in the city of Seattle is sold as dependable energy," he said. "When you turn on the lights, it's there. We'll do whatever we have to do to make sure that continues to happen."

A large portion of the city's power has been generated on the Upper Skagit River since turbines spun into motion at Gorge Creek Dam in 1924. Diablo and Ross dams followed, holding the upper Skagit behind concrete walls that to this day are engineering marvels, particularly given the harsh, isolated environs in which they were built.

That same terrain is hostile to roadbuilders. This paved path through jagged, glaciated peaks often described as "America's Alps" was the first highway route surveyed through Washington's Cascades — and the last to be built.

Now a national scenic route known as the North Cascades Highway, Highway 20 was surveyed in 1895 but not completed until 1971. Heavy snows close the road annually, usually between late November and April, between Newhalem and Mazama.

The new slide could put a crimp in that schedule. Transportation officials don't know how to proceed with road repairs because the slope above appears very unstable, said Anderson, the DOT engineering geologist.

Rock-climbing subcontractors, racing an approaching storm, worked yesterday to place a string of electronic reflectors and highly sensitive Global Positioning System sensors across the fractured slope. With bitter winds whipping through the canyon, the work — conducted by climbing up the face from below to gear caches dropped by a helicopter — was precarious.

The sensors should allow the slide area to be monitored for movement beginning today, Anderson said. Some of the gear, on loan from the Cascade Volcano Observatory in Southwest Washington, can monitor earth movements as subtle as one centimeter or less, he said.

	Seattle City Light employees Arturo Espinoza, left, and Tom Purcell load a helicopter yesterday with supplies for the residents of Diablo, which now is accessible only by air or emergency route.

In the meantime, the slide has been monitored the old-fashioned way — by people, watching with binoculars from Newhalem and from a perch across the narrow valley.

"Visually, we are seeing more strain" in the rock face, including some 10-foot-wide cracks that appear to be getting wider, Anderson said.

The goal is to have a monitoring system in place by week's end to establish a computer "baseline" of slope movement, giving geologists a sense of the danger of making road repairs — and, much further down the line, allowing general automobile traffic to use the highway again.

DOT officials will begin crafting a long-term solution early next week.

They don't know how much the high-tech slope monitoring and repairs will cost. A federal disaster-relief official has flown over the site, and North Cascades National Park officials are being briefed.

Anderson, staring up at the sheer walls through which the highway passes, said it's amazing a highway was built here in the first place.

"I'm absolutely surprised," he said, "that we aren't up here more often."

Ron C. Judd: 206-464-8280 or rjudd@seattletimes.com.