The cliff that collapsed onto Interstate 90 near Snoqualmie Pass early Sunday, killing three women, was considered so low-risk by the state Department of Transportation that preventive measures weren't likely to be undertaken there for years, if ever.

"We had really no warning here," Tom Badger, the agency's assistant chief engineering geologist, said yesterday.

Added DOT Secretary Doug MacDonald, "It's more art than science trying to figure out when a piece of a mountain is going to fall."

The three victims were identified yesterday as Janet J. Ichikawa of Lynnwood, Janel A. Lindsey of Bothell and Heather E. Rider of Castle Rock, Cowlitz County, all 28. They were returning from a country-music concert at The Gorge Amphitheatre in Grant County about 1 a.m. Sunday when a falling boulder crushed Ichikawa's Volvo.

The DOT rated 2,500 unstable slopes along state highways in the 1990s when it began a program to identify and address slopes before they caused problems, rather than simply responding to landslides and rockslides.

The cliff that fell Sunday, labeled Slope 604 in the DOT's database, scored just 273 on a scale ranging from 33 to 891 — the greatest possible risk. The agency's preventive-maintenance program for unstable slopes for the next few years addresses only slopes with scores of 350 or higher, said Steve Lowell, DOT's chief engineering geologist. There are hundreds of those projects, with a total price tag approaching $100 million.

The DOT's budget for unstable-slope work for 2005-07 is less than $13 million, agency officials said.

"This one is way down the list," Lowell said. "We have limited dollars."

Another boulder tumbled onto the roadway yesterday, just a few feet west of Sunday's collapse.

Nobody was hurt when the boulder, about the size of a large pickup, fell onto the westbound lanes at 5:17 p.m., DOT spokesman Mike Westbay said.

Slope 604, nearly vertical, was created when road builders blasted a new route for I-90's westbound lanes in the 1970s. Its risk-rating sheet is dated August 2000, but Lowell said that's a mistake, and that it probably was prepared in the mid-1990s by an engineer at the department's Yakima regional office.

That engineer indicated that falling rocks from Slope 604 were likely to be less than 1 foot in diameter and total less than 3 cubic yards — about 30 percent of a dump-truck load. Rocks were unlikely to reach the freeway's travel lanes, the engineer wrote.

Before the slide early Sunday morning, DOT officials say, they had no reason to question that assessment.

"We hadn't had a history of significant failures in this area," Badger said.

"No one has touched that slope since it was constructed in the 1970s," Lowell said.

Badger spent eight hours Sunday at the scene, about two miles west of Snoqualmie Summit. Here's what he says happened:

The collapse began about 5 or 10 feet up the cliff, above a 30-foot-wide ditch designed to catch falling rock. A chunk of granite about 60 feet high, 20 feet wide and 10 feet thick shattered, sending about 300 cubic yards of rock — the equivalent of 30 dump-truck loads — into the ditch and onto the shoulder and all three westbound lanes, a distance of about 70 feet.

Debris covered 50 to 100 feet of freeway, Badger said. Some rocks were 6 to 10 feet in diameter.

A boulder 5 feet in diameter landed on Ichikawa's car, he said, crushing it.

According to family members of the victims, the three women were friends who had driven to the Gorge on Saturday to see country-music star Keith Urban.

Sandra Lindsey, of Marysville, said her daughter and Ichikawa had been friends since they were at Snohomish High School together. When Ichikawa lost her parents to disease, it was Lindsey who stayed with her friend and nursed her through her grief, Sandra Lindsey said.

"She was the kind of person who took care of everyone. She always cared for people," Lindsey's mother said.

Ichikawa and Rider met while the two were students at Washington State University, according to a Rider family member.

DOT geologists will try to learn why the cliff collapsed, Badger said. Initially he suspected that heavy rain Saturday might have played a part, but now he considers that less likely.

The DOT says it was among the first transportation agencies to adopt a "proactive" approach to landslides, rockslides, erosion, settling and other geological problems, beginning in 1993. Lowell called it a national model.

All slopes were prioritized using a system that included such factors as the likely magnitude of a slide, its impact on the highway, traffic volumes, slide and accident history, and annual maintenance costs. Each slope was rated in 11 categories and given a score in each category of 3, 9, 27 or 81.

The system helps the DOT weigh costs and benefits for each project.

In a paper presented at a landslide-risk-management conference last May in Vancouver, B.C., Lowell, Badger and L.J. Moses of the DOT said projects had been completed on more than 100 slopes between 1993 and 2003.

To address potential landslides, the department has removed loose rock, scaled back slopes, inserted huge bolts in rock faces to stabilize them, built protective walls along highways and installed cable nets to keep boulders from crashing onto highways.

In their paper, Lowell, Badger and Moses pointed to Tumwater Canyon, along Highway 2 near Leavenworth, Chelan County, as a success story. Between 1995 and 2002, they wrote, projects were completed on most of the known unstable slopes in the 10-mile corridor.

The DOT's budget for unstable-slope work this biennium is less than half what it was during the two preceding two-year budget cycles, officials said. Multiple projects are scheduled on Highway 2 near Stevens Pass and Highway 12 near White Pass.

MacDonald, the DOT secretary, said he'd like more money but, despite Sunday's fatalities, he still has higher safety priorities: seismic projects on highways to reduce damage in the event of an earthquake, and installation of cable barriers in the median of stretches of Interstate 5.

"I don't think we'd respond to an accident like this — horrific as it is — with a huge reshaping of our programs," he said. "... It truly has the nature of a freak accident about it."

Seattle Times staff reporters Christine Clarridge, Jennifer Sullivan and Peyton Whitely contributed to this report.

Eric Pryne: 206-464-2231 or epryne@seattletimes.com