Quake Study Rates Dam Safe

Looming high above one of this city’s swankiest neighborhoods, Bard Reservoir has long been the source of much speculation and worry.

What if--residents of Wood Ranch have been known to ask--that earthen dam fails? Will it unleash a torrent of water over our posh homes, beloved families and graceful landscaping? Is it vulnerable to the Big One?

In a word: No.

So says the most recent study about the seismic stability of Bard Reservoir--Calleguas Municipal Water District’s artificial lake, which can store more than 3 billion gallons of water for local use.

The upshot of the report: The reservoir--with a 10,000 acre-foot capacity--can withstand a 7.0 earthquake along the nearby Simi-Springville fault without swamping its downhill neighbors. It would take a small explosive device or an improbable mega-quake to rupture the massive earthen dam built three decades ago.

Calleguas Municipal Water District, the county’s biggest water supplier, paid about $144,000 to fund the voluntary report. General Manager Don Kendall is hoping that this most recent study, which will be forwarded to the state Division of Safety of Dams for certification, will allay any concerns that Wood Ranch neighbors may have. The study’s results will be presented at Calleguas’ meeting next week.

“For the community’s sake, we wanted to make sure, because we know there will be more earthquakes,” Kendall said. “We wanted to leave as little to chance as possible.”

To that end, engineers from Harza Engineering Co. of Los Angeles sampled the soil from the earthen dam that forms Bard Reservoir. They then plugged into a computer program the soil information, the shape of the reservoir and the 3-mile distance to the nearest fault. From there, they modeled some heavy shaking, with both horizontal and vertical movement.

The dam held firm during a 7.0 earthquake, said Paul Burridge, Harza project manager. Seismologists don’t believe that the nearby Simi-Springville fault--also called the Simi-Santa Rosa fault--is capable of a larger quake.

“We don’t think that the people downstream need to feel concerned about the dam,” Burridge said.

What might get soggy is the golf course, which was deliberately placed in the reservoir’s flood plain. Original Wood Ranch plans had called for homes to be built in the flats beneath the reservoir--an idea the City Council nixed.

“That’s why the golf course is where it is,” said Mayor Greg Stratton, a Wood Ranch resident. “Your homes are safe, but you don’t particularly want to be at the third tee during the Big One.”

The report’s findings are a relief to some Wood Ranch neighbors, even those who have never looked warily at the big oval artificial lake above their posh homes.

Snug in her hillside home above the Wood Ranch Golf Course, retiree Sybil Duhig is sanguine about living so close to the reservoir.

“From what I’ve seen, I don’t feel my house is in any danger,” she said. “Now there are houses below me, 40 or 50 feet down the hill, maybe they should worry.”

Nearby sits the home of Anita Fee, an 11-year resident of Wood Ranch.

When she entertains on her patio, which looks out on the Bard Reservoir hill, Fee’s friends sometimes cast a suspicious eye upward.

Fee said she didn’t even notice the reservoir until after she moved in. Nor did she give much thought to living next to Westlake Lake in her previous home.

With a true Californian’s optimism, she says the study is peachy, but it won’t change her life.

“I don’t worry about it,” said the retired Fee. “I just love living here.”

City officials were a bit more enthusiastic.

Even though they have long believed the reservoir to be a benign neighbor, bureaucrats want a copy of the study to add to their collection, Senior Planner Michael Kuhn said.

“We get a lot of interest from people looking to buy homes in Wood Ranch,” Kuhn said. “They look up, see the dam and get concerned. So we keep a compendium of the reports here and ask them to take a look.”