The potential for destructive debris flows in the Station fire burn areas remains high despite forecasts of a dry winter, public officials said this week. The warning came as the first storm of the season dropped more than 1.5 inches of rain in the Foothills through Tuesday night.
"You can get drier than normal throughout the storm season, but if you get a couple of very intense back-to-back storms and still remain below normal for the season, you can have major, major mudflow problems," said Christopher Stone, asst. deputy director for the Los Angeles County Department of Public Works.
The county Flood Control District is wrapping up a $1.2 million project to expand six debris basins in the Foothills, including the Big Briar, Snover and Mullally basins in La Cañada Flintridge.
The capacity of the Big Briar Debris Basin, located at the top of Haskell Street, is being expanded from 2,800 to 4,800 cubic yards. The Snover basin, located off Escalante Drive, is being expanded from 25,000 to 37,000 cubic yards. Both are expected to be complete by Oct. 15, Stone said.
And the Mullally Debris Basin, which crested on Feb. 6, sending mud and debris down Ocean View Boulevard, is being expanded from 9,400 to 17,500 cubic yards and will be completed early next month.
Last winter, which was slightly wetter than average, county workers excavated 407,000 cubic yards of sediment, including burned vegetation, tree branches, rock and sand, from La Cañada basins, Stone said. That translated to approximately 40,700 truckloads of material being transported to three dump sites outside of the city.
"For planning purposes, we are [preparing for] a normal rainfall year," Stone said. "We are [asking] where can we take 407,000 cubic yards of material if we need to. Because of the fire, managing the amount of sediment that is coming off the watersheds into the debris basins and reservoirs is going to be a huge issue for the Department of Public Works."
On Oct. 12, between 9 a.m. and 2 p.m., county workers will reinstall cement barriers known as K-rails across upper Ocean View Boulevard at the entrance to the Paradise Valley neighborhood, Stone said. Additional K-rails will be reinstalled on several other vulnerable streets, including Rock Castle Road and Fairhurst Drive.
The city will host a debris-flow-preparedness workshop on Oct. 19 at 6:30 p.m. in the council chambers at City Hall, Mayor Don Voss said.
"I really encourage people, especially those in the hillsides, to participate in the workshop," Voss said.
The watersheds have began to show early signs of recovery, Stone said, evidenced by grass and shrubbery sprouting up. But it is the roots of larger vegetation that will hold back debris flows and such regeneration will take several years, he said.
"The mudflow situation this year really has not improved a lot," Stone said. "The effects of the Station fire are still going to be [present] for another four or five years."