Lake Casitas Overflow Signals End of Drought : Weather: A mudslide on California 150 forces traffic to the shoulder. Officials worry about Piru Creek flooding.

Water tumbled over the dam of Ventura County’s largest reservoir early Tuesday for the first time in six years, signaling that the season’s extraordinary rainfall has restored water supplies to pre-drought levels.

The overflow from Lake Casitas began splashing down its long spillway at 1:30 a.m. Tuesday, dam tender Dwight Clements said.

By Tuesday afternoon, the dam was spilling 30 cubic feet of water per second, marking the only time the huge reservoir has filled since 1986.

“It signaled the end of the drought that started after the rains of 1986,” said Dick Barnett, engineering manager at the reservoir. “The drought is not officially over until the reservoir spills.” The reservoir holds 254,000 acre-feet. One acre-foot is enough to supply a family of four for a year.

“We’re totally out of trouble,” agreed Lowell Preston, the county’s water resources manager.

But Tuesday’s storm didn’t make everyone happy.

The downpour, which dropped about 1 inch in the coastal areas and up to 4 inches in the mountains, caused a large mudslide on a two-lane highway west of Santa Paula and left residents along Piru Creek worrying if they would have any back yards left today.

County flood-control officials said they were bracing for another storm that is expected to sweep through the area late Thursday or Friday.

“We’re very concerned about what may happen” in that storm, county hydrologist John Weikel said. “There’s a possibility for flooding just about everywhere.”

Although the Ventura and Santa Clara rivers remained at levels well below the February, 1992, floods, Santa Paula Creek is the highest it has been in 24 years, he said.

But “the real critical point is Piru Creek,” Weikel said.

Residents along Piru Creek in central Piru kept watch late Tuesday to see how far the stream would rise and how much more of their yards it may wash away.

Although the downpour stopped by Tuesday afternoon, the volume of water rushing down Piru Creek is expected to double by later today as Los Angeles County officials increase the outflow from Pyramid Lake reservoir, Weikel said.

Pyramid Dam spills over into Piru Creek, which carries the overflow to Lake Piru and, ultimately, to the Santa Clara River and out to the ocean.

Since late last week, Piru Creek has already eaten away large parts of three house lots along its east banks.

“We lost about 30 feet of property,” said Pablo Ramirez, 31, whose family owns all three houses. “That’s a lot of land.”

Since Thursday, county and water district workers have piled hundreds of tons of rocks along the creek’s banks and dug a channel down the middle of the stream bed to divert the water away from the houses.

Weikel and members of the Ramirez family now said they’ll just watch and hope the reinforcements hold.

Elsewhere in the county, Tuesday’s storm caused a 5- to 7-foot mudslide onto California 150 seven miles west of Santa Paula.

Motorists were forced to drive along the shoulder of the narrow two-lane mountain highway as Caltrans workers cleared away 100 cubic yards of dirt, state transportation department officials said.

Both lanes of California 150 were reopened by Tuesday afternoon, but a section of California 33 about 30 miles north of Ojai will remain closed for about three weeks because of a rockslide earlier this week, Caltrans officials said.

Recent rains also contributed to a 26-barrel oil spill on Unocal Corp. property at the north end of Wheeler Canyon Road north of Santa Paula.

The spill occurred earlier this week when debris from the rains clogged an old pipe that siphons oil from a natural reserve in a mountain cave, causing a storage tank to overflow, a Unocal spokesman said.

The fluid, which was more than 90% water, was ultimately washed into the Santa Clara River, the spokesman said.

Officials for the state Department of Fish and Game described the spill as small to medium.

Despite oil spills, mudslides and threats of flooding, Tuesday’s downpour continued a series of storms that ultimately will benefit county residents, local water officials said Tuesday.

“Back in 1983 was probably the last time it was so good,” said Fred Gientke, manager of the United Water Conservation District, which oversees the county’s underground water basins.

“All the ground-water basins have come up significantly,” he said.

Since the height of the drought in January, 1991, the county’s largest underground aquifer--the Piru basin--has risen 90 feet to about 600 feet, he said.

Ground-water basins supply water for about 300,000 people in the west county. Residents of Simi Valley, Thousand Oaks, Moorpark and parts of Camarillo and Oxnard depend on state water that runs down from the Sierra.

Recent storms have brought the snowpack in the Sierra to 150% of normal levels, said Don Kendall, general manager of the Calleguas Municipal Water District, which manages state water locally.

State reservoirs that are fed by the snowpack are almost at pre-drought levels, he said.

“After six years of dryness, it’s very difficult to get that back in one year,” he said. “But if you could do that, this would be the year to do it.”

Times staff writer Peggy Y. Lee contributed to this story.

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