ANGELES NATIONAL FOREST -- After years of discussion about cleaning out the tons of boulders filling Rubio Canyon, Mother Nature has apparently solved the problem herself.

Last week's heavy rains blasted out the debris generated in 1998 by a water pipeline replacement project gone awry. The storm dropped 10.5 inches of rain at the nearby home of Heinz Ellersieck. The downpour apparently turned the 80-foot rock pile into a giant dam that broke during the storm. Rushing water tossed thousands of granites rocks from the narrow gorge and distributed them across the canyon floor.

Five waterfalls and a portion of the historic Mount Lowe Railway that had been covered by the rock pile are now visible. A lower waterfall that was previously exposed is now buried in debris.

Inside the canyon, an area of 20 feet across and at least half a mile long has become a deep wash of bare stone, from pulverized sand to boulders the size of furniture. Uprooted trees, mangled pipes and scars on the canyon walls bear witness to the violence of the deluge.

"It must have been an amazing event when it happened," said Paul Ayers, a Glendale lawyer who has spent years advocating for the rocks to be cleaned up. "Happily, no one was there when it happened or we'd probably find them next spring."

The rock pile was created by contractors working for the Rubio Canyon Land and Water Co. The nonprofit water company provides drinking to parts of Altadena. Between 10 percent and 15 percent of that water comes from the creek in Rubio Canyon, company officials said.

Workers stabilizing a water company pipeline blasted 35,000 cubic yards of rock from the canyon wall and left it in a pile on top of the waterfalls. The project cost $485,000, financed principally by Federal Emergency Management Agency fund, and left an environmental mess.

Ever since, the contractors, Forest Service officials, the water company, FEMA officials and environmentalists have wrangled about how to clean up the mess. It has been the subject of public debate, lawsuits, studies and planning documents for six years.

The proposal backed by the Forest Service called for a temporary road to be build. Using dynamite, helicopters and 7,000 truck trips, the rocks would be moved away.

Those plans were rendered suddenly obsolete by the rainstorm Oct. 20.

Ellersieck, a retired Caltech professor whose land would have been crossed by the road, said he was very pleased the road would no longer be needed.

"If (the project) had been done this summer, we would have had a real environmental disaster with the road washing out" in the heavy rains, he said.

Ayers said he hopes the blowout of the rocks will result in public discussions about the use of the canyon. Ultimately, he said, he hopes the water company will be confined to taking water from a well at the mouth of the canyon instead of maintaining the network of pipes that collect water high up the mountain.

Any plan to fix the pipes or remove rocks will be subject to guidelines in the National Environmental Policy Act, which calls for public input, said Don Cosby, district ranger for the Los Angeles River Ranger District of the Angeles National Forest.

Jan Fahey, president of the water company board, said she did not know yet what they will do with the pipes. "The canyon is unstable and we want to protect it," she said. "We'll wait out (this week's) storm and take inventory of the situation."

Meanwhile, water company officials can take comfort in being able to say we told you so. They had appealed the Forest Service's plans for a road. Their alternative suggestion for the cleanup: Let nature take its course.