3 Inches of Rain Due in Strongest Storm of Winter : Weather: Steady downpour has caused no serious hillside erosion. But officials are concerned about slides in fire-scorched areas if showers intensify.

The most potent storm of the season was expected to drop up to three inches of rain in some areas of the county and blanket mountainous areas above 4,000 feet with up to two feet of snow before skies clear later today.

But the rain, which fell steadily through Sunday night and Monday at a pace of less than a quarter-inch per hour, sank into the ground and did not cause major hillside erosion, officials said.

If the rain continues at the same pace, then subsides for at least three days as expected, county Public Works officials do not anticipate problems.

But if the rainfall intensifies, officials and residents are concerned about potential mud and debris slides in areas where the October fires scorched hillsides above residences.

Barbara Boone, whose Deer Valley Avenue house sits at the foot of a still charred and barren hill in Newbury Park, said she had a foot of mud in her home after rains in December. Now, she said, the back of her house is protected with sandbags as she watches the hillside.

“We haven’t had the slightest bit of a problem so far, but I was up every hour looking at the window,” she said. “We’re still very nervous.”

John Philpott, who lives on Erinlea Avenue in Newbury Park, said he was grateful that the rain has been gentle.

“So far, we’ve been real lucky with the rain being light,” he said. “It’s been quite a year. We’ve gone through the fire, the earthquake and now, here come the rains.”

Locally heavy showers and hail were expected in some areas Monday night, with possible thunderstorms in the mountains. But today, scattered showers in the morning were forecast to give way to clearing skies in the afternoon, said National Weather Service meteorologist Debra Rominger.

Gusty winds up to 30 m.p.h. were expected through the week, but no rain is forecast before Friday, she said.

Sheri Klittich, soil conservationist for the U.S. Soil Conservation Service office in Somis, said the agency has been applying a mixture of mulch, seed and a glue-like substance to the burned hillsides in an attempt to create a ground cover of vegetation to prevent mudslides.

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But up until now, she said, there has not been enough rain for the seeds to take root, and the cover has not returned. But she said the mulch will help slow any runoff.

The areas without vegetation or mulch could be vulnerable to a slide once the ground is saturated.

“With the burn, you get a multiplier effect,” she said. “A storm that might happen only every 10 years would act like a 100-year event and the impacts could increase dramatically.”

Since the October fires, including the Green Meadow fire in Thousand Oaks and the Steckle fire above Santa Paula, the Department of Public Works has begun construction on three catch basins--graded areas with earth dams designed to trap silt and debris and minimize mudslide problems.

Two of the basins built in canyons above Santa Paula are incomplete but are nevertheless expected to operate well enough to contain any mud flow, said Dolores Taylor, division engineer for Ventura County Public Works.

But the third basin being built in Newbury Park got a later start and would probably offer little protection, she said.

“Much of the burn area is underlined by bedrock, so there is just the surface soil that can come off there,” Taylor said. She said other areas of concern are places where the mountains have been graded, and that “compacted soil can get saturated and start moving.”

The city of Thousand Oaks has built up banks of gravel in the canyons above the Deer Ridge area that burned during the fire. The banks are designed to allow the water to go through, while cutting down the flow of silt and mud.

“We haven’t had any problems yet,” said Gil Pableo, city engineer.

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In Simi Valley, rain may have settled into some of the cracks in the earth created by the Jan. 17 earthquake, said Michael Kuhn, senior planner for the city. That could cause additional settling of the ground, he said.

And there is some concern that the earthquake may have left some canyon areas unstable, but those areas are not populated, he said.

Simi’s planned Whiteface development, which would include 1,600 homes between Tapo and Sand canyons, could be an area of concern, so the developer has been instructed to have a geologist investigate the stability of the area, he said.

In Fillmore, rain delayed demolition of the Fillmore Hotel and the city’s Mason’s Building, but demolition was expected to resume as soon as the rain let up. Crews used sandbags to shore up a domed tent that was erected to house displaced merchants after the earthquake.

Public Works crews were out Monday patrolling streets and drainage ditches to make sure that county roads were kept free of rocks and flooding. Road maintenance engineer Loren Blair said the roads were clear.

“We’re keeping an eye on the Yerba Buena area because there is not a lot of vegetation left up there to stop runoff.” But crews were not expected to be needed through the night, he said.

The rain forced crews cleaning up an oil spill in the Santa Clara River east of Piru to postpone much of their work. Only a few hand crews and three vacuum trucks were at work on Monday cleaning up oil that spilled from a ruptured pipeline during the earthquake. More than 400 people were working on the cleanup last week.

Bob Schlichting, a spokesman for the California Department of Fish and Game, now estimates the spill at 193,494 gallons, and said it is about 25% cleaned up.

The rain could spread the remaining oil downstream if river runoff breaches the berms built up to contain the spill, Schlichting said.

“But if we got a really heavy rain, it could actually help wash it down the river and out to sea,” he added.

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Meanwhile, crews finished the cleanup at McGrath Lake, where another ruptured pipeline that was discovered on Christmas Day spilled 84,000 gallons into the lake, the surrounding wetlands and creek.

Heidi Togstad, who supervised the cleanup for Fish and Game’s Office of Oil Spill Prevention and Response, said the official declaration will come after state parks officials sign off on the cleanup.

Test results showed that even less oil than expected remained at the lake bottom, she said.

“It seems like we got the vast majority of that oil,” Togstad said. “But we dug up a lot of earth and we removed a lot of soil.”

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Correspondents Matthew Mosk and Scott Hadly contributed to this story.

* RELATED STORY: Mudslides surge through beachfront houses in Malibu. A1

County Rainfall

Here are rainfall figures from the Ventura County Flood Control District for the 36-hour period ending at 8 p.m. Monday. Oct. 1 marks the beginning of the official rain year. Cumulative totals are preliminary estimates.

Rainfall Rainfall Normal rainfall Location last 36 hours since Oct. 1 to date Camarillo 1.02 4.12 7.87 Casitas Dam 2.24 6.90 13.63 El Rio 1.69 5.17 8.71 Fillmore 0.77 4.22 11.04 Moorpark 0.90 3.95 8.52 Ojai 1.32 5.33 12.20 Upper Ojai 2.15 6.84 13.12 Oxnard 1.05 4.06 8.39 Piru 0.69 3.98 9.93 Santa Paula 1.20 4.98 10.23 Simi Valley 0.73 4.14 8.19 Thousand Oaks 0.74 4.29 8.82 Ventura County Government Center 1.69 5.08 9.28