What a washout

IT’S known to hikers and road maintenance officials as “the slide,” which doesn’t really do it justice. Avalanche is more like it, a swath of mountain innards 1,000 feet high and 300 to 400 feet wide that tore off the side of a ridge last February and buried the Henninger Flats Trail above Altadena.

The giant dirt pile, plus two other slides and a washed-out access road, put a trail that attracts 25,000 people a year on the disabled list, where it’s remained ever since -- and the hikers are getting restless.

Web pages on Henninger Flats buzz with postings about the status of the slide. Mickey Long, regional park superintendent at nearby Eaton Canyon Nature Center, where some Henninger hikers have relocated, says he gets quizzed every day: “When are they going to fix the slide?”

“We knew [the trail] was popular, but when it closed, we found out how popular it was,” says Long.

“There is frustration,” notes Mike Regan, a local resident who used to trek up the three-mile route with 1,400 feet of gain every morning. “What’s happening is you’re seeing people starting to cross that lower slide on foot.”

Last year’s storms put a lot of trails out of commission, but few for as long or as dramatically as Henninger Flats, also known as the Mt. Wilson Toll Road, which leads to campgrounds, a forest nursery and Mt. Wilson. The scale of the damage is extensive enough that Pasadena, which has jurisdiction over the lower portion of the trail, where the major slide is located, turned to the Federal Emergency Management Agency for funding. The city has received approval from FEMA for $860,000 to help cover repairs. But before any work can begin, officials are awaiting a geological report assessing the stability and depth of the slide, due by the end of December.

“The big issue is the instability of the material that’s hanging off the side of the mountain,” says David Leininger, chief of the forestry division for the L.A. County Fire Department. “There’s a lot of material up above. It’s not a simple process of just putting a ‘dozer on the road and start pushing the slide, because we’ve got all that material hanging above.”

Officials say the scale of the damage and a long list of storm-ravaged roads that had to be repaired first have kept the trail out of action for 2005. The closure has sidelined nature lovers as well as fitness enthusiasts, who train on the steep grade to Henninger Flats.

“It’s a great place to run because they have running water at Henninger,” says Regan. “You can get refreshed and hydrated, then cruise back home.”

The roadblocks have also shut down visits to the campsites and conservation center at Henninger, set up in 1928 as a high-elevation forest nursery. The site farms conifers, replanting some 15,000 around the county each year, and offers educational programs for the public. With work crews unable to get up the road, a skeletal staff is tending the nursery -- and getting plenty of exercise. Deputy forester Jose Martinez hikes up to the center every day on a route around the slides cut through brush.

Landslides are no news bulletin in this part of the San Gabriel Mountains. Two fault zones in the area have spawned steep, unstable slopes over the centuries. Henninger Flats itself was formed when it became the receiving end of a massive slide 12,000 years ago.

Al Fortune, supervisor of firefighting and construction equipment operations for the L. A. County Fire Department, has been tangling with shaky hillsides here since the 1970s. He’s seen two big slides in the same spot as the current one, but they weren’t as large. A decade ago crews dynamited a slide in this spot to bring down the loose material. He remembers saying back then, “If it ever gets bigger than this, it’s going to be a real problem.”

Leininger doesn’t know if crews can use the same approach this time. “It’s so high I don’t know how we’re going to get any equipment in there to drill the holes to set up the charges,” he says.

Getting to the site may be one of the trickiest issues. Because the paved entrance road has been undermined and a good chunk of it washed away by an altered streambed -- rerouted by the landslide -- Fortune thinks the only feasible approach is to bring equipment down to the slide from the top of Mt. Wilson.

In the meantime, those needing their regular fix have found a way to the unblocked portions of the trail. Some are taking a path through Walnut Canyon, a.k.a. “the switchbacks” or “horse trail,” from Eaton Canyon Nature Center, which emerges onto Mt. Wilson Toll Road above the first slide (about a quarter mile in) and a couple of miles below the second.

A few, feeling lucky, have taken to scrambling across the slides. Since Fortune thinks it will be another year before the road is opened, the odds of scramblers taking a slide themselves during the interim may be about to increase. “It’s really quite a Pandora’s box,” he says.

Joe Robinson can be reached at joe.robinson@latimes.com.