Corrosive Soil Threatens Pipes Carrying Water
Corrosive soil is slowly gnawing away at underground steel pipelines here, posing a threat to Ventura County’s water lifelines.
Those supply lines--fat steel and concrete pipes built for Calleguas Municipal Water District--carry cool, clean imported water to about three-quarters of the county’s residents.
Officials with the county’s biggest water supplier have hired experts to assess the extent of pipeline damage. Within a few months, they could embark on a multimillion-dollar project to shore up--or replace--the vulnerable lines a few feet beneath Simi Valley’s streets.
The hope is that any weakened segments of pipeline can be reinforced or replaced before an earthquake--or other calamity--could cause them to burst.
Because Calleguas’ water lines branch out from two trunks in Simi Valley, the fate of the pipes could also affect Thousand Oaks, Moorpark, Camarillo, Oxnard and Port Hueneme, which receive some or all of their water from Calleguas.
Were the pipes in Simi Valley to burst, cities to the west would only be able to get their imported water--piped from Northern California--from plentiful reserves in the Bard Reservoir and Las Posas Basin Aquifer.
“To me, those lines are accidents waiting to happen,” said Calleguas’ general manager, Donald R. Kendall. “If there was a surge for any reason--such as an earthquake--it could be bad. It could throw a spray of water and chunks of asphalt into the air.”
Corroded pipelines are believed to have contributed to a water main break in Simi Valley that occurred in March when an apparent power failure knocked out pumping stations along a line that was partially closed for repairs. Those factors created a powerful “water hammer” that burst the pipeline, flooded Madera Road and left a gaping sinkhole.
Fixing the imperiled pipes won’t be cheap, though.
The tab for what Calleguas is calling its “infrastructure reliability program” depends on how much damage has been inflicted on the pipes beneath Madera, Cochran Street and Fitzgerald Road.
If testing shows that every segment of pipeline has been weakened--and must be replaced with stronger pipes--it could cost as much as $100 million over a decade. By way of comparison, the water district’s annual budget is about $40 million.
Just building a surge tank--a 10- by 20-foot aboveground receptacle that could catch the occasional gush of water--for the short Madera Road segment is expected to cost about $2.2 million, Kendall estimates.
His board is poised to approve design and construction of a surge protector within the next month. The decisions will only get tougher from there.
Corrosive soil is “very serious,” said Frederick J. Gientke, general manager of the United Water Conservation District, whose pipelines are not affected by corrosive soil.
“It’s something that will start attacking the pipelines immediately,” he said. “But it could take 10 years or 20 years for a problem to happen. It’s a cumulative thing.”
That cumulative gnawing at the pipelines weakens the steel within them.
Known as prestressed concrete pipelines, the tubes beneath Simi Valley are essentially big straws made of mortar, surrounded by a thin layer of steel, encased in a few inches of concrete. Steel tension wires encircle the pipes to add strength. Some pipes in Simi Valley are 4 feet in diameter; others have diameters stretching 5 1/2 and 6 1/2 feet.
The soil in western Simi Valley--with its high ground-water levels and metallic content--apparently wreaks havoc on prestressed lines. It is not clear whether the soil closer to Los Angeles County is as corrosive.
The problem of corrosive soil damaging prestressed lines is hardly exclusive to Simi Valley. The prestressed lines--touted as cheaper and stronger than pipes with a thicker layer of steel--were all the rage among water agencies 20 to 30 years ago. Now they are being replaced or reinforced across the country.
“It happens all over the place because there is corrosive soil everywhere--in Utah, Arizona, everywhere,” said John List, a consultant with Flow Science Inc. in Pasadena. “It’s a problem any time you put anything into the ground.”
To combat the corrosion, Kendall said, Calleguas is considering a variety of solutions:
* Tearing out the prestressed lines and replacing them with new pipes that have a thicker inner layer of steel.
* Lining the existing pipelines with an additional layer of steel.
* Installing surge protectors at vulnerable segments of the pipelines.
* Working with water purveyors to keep water demand flat throughout the day, thus lessening the chance of surges.
“The best solution is to get rid of the present lines altogether,” Kendall said. “That’s our ultimate solution. Just rip them out and replace them. But I don’t have the $100 million to do it.”
Although she has just learned of Calleguas’ corrosion problem, environmental activist Carla Bard said she is impressed with Calleguas’ approach.
“It sounds like they’re being very foresightful to me,” she said.
Jeff Borenstein, treasurer of Calleguas’ board of directors, wants to see the results of soil and pipeline testing before making any costly decisions.
“My opinion is, based on what has happened thus far and what is likely to happen, I wouldn’t rush into replacing the entire pipeline,” he said. “That could be overkill.”
Both Borenstein and board President Pat Miller say Calleguas would likely float bonds to pay for a massive pipeline-repair project rather than passing costs on to customers.
“You hear the talk going on about the price of water,” Miller said. “I don’t think we’d be inclined to raise rates.”
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Corrosivee soil threatens the underground pipes though Simi Valley that carry water to residents in Thousand Oaks, Simi Valley, Moorpark, Camarillo, Oxnard and Port Hueneme. Repairs could cost up to $100 million in the next decade to ensure water supplies to the county.
Source: Calleguas Municipal Water District