Verdugo Debris Basin above Oakmont Country Club, in Glendale, seen from the Glendale Police Department helicopter on Monday. Air patrols keep an eye on debris basins and river beds after major storms for dangerous changes that could threaten residential areas.

Verdugo Debris Basin above Oakmont Country Club, in Glendale, seen from the Glendale Police Department helicopter on Monday. Air patrols keep an eye on debris basins and river beds after major storms for dangerous changes that could threaten residential areas. (Tim Berger)

The facades of local hillsides went mostly unscathed last week, but the risk of movement will remain for at least a few weeks until the heavily saturated layers of soil dry out, officials said.

That means even a relatively minor storm forecast for Wednesday night could cause significant damage, or at least push back the drying out period.

Last week's torrential rains caused street flooding and some rock and mudslides on mountain roads, but didn't overflow local foothill-area debris basins with dirt and natural material, said Bob Spencer, a spokesman for Los Angeles County Department of Public Works. Foothill-area debris basins reached just 20% of their capacity during the storm.

"But that doesn't mean we are out of the woods," he said. "It will be several weeks before the hillsides dry out."

Meanwhile, Spencer said county officials are hoping for more mild winter weather conditions so the massive amount of loosened material stays in the hillsides and not in the local debris basins.

Glendale officials have used the Glendale police helicopter to monitor hillsides and note any damage or changes, said Public Works Director Steve Zurn.

"Overall, the northern burn areas did very well, however, we took a lot of rain and we remain vigilant in our preparation and response efforts," he said in an e-mail.

As part of their daily air patrols, helicopter pilot Sgt. Steve Robertson and his crew have been looking for any fractures or fissures that may signal a dangerously weak hillside.

The pilots also photograph the hillsides above Deukmejian Wilderness Park and nearby water tanks and report back to city engineers and public works officials.

County crews on Monday began clearing mud and rocks from the Mullally Debris Basin, which overflowed during a February rainstorm, destroying several homes along Ocean View Boulevard in La Cañada Flintridge.

Large dump trucks have been scheduled to haul the debris to the controversial Dunsmuir Sediment Placement Site. The cleanout could take up to a week, county officials said.

County officials assured residents on Dec. 14 that several measures had been taken to ensure the sediment site was stable enough to handle the additional deposits.

Residents have expressed concern that the packed site could give way during a major rainstorm and have also been troubled by the high volume of dump-truck traffic on residential streets that lead to the site.

County officials have been working with Glendale officials to address neighborhood concerns regarding the site, said Dave Ahern, capital project administrator for the Community Services & Parks Department.

If all goes well, the city may reopen a soaked Deukmejian Wilderness Park later this week, he added.

The park was closed to the public during the rainstorm after some small runoffs were discovered, but the newly reconstructed park trails held up well during last week's storms, Ahern said.

"The park held up remarkably well," he said.