Sound Pipes Are Music to the Ear

SIMI VALLEY —  What with weeks of rain, most Ventura County residents are sick and tired of water. But engineers with the county’s biggest water district know they would get fed up even sooner if their taps ran dry.

So what exactly does it take to ensure that county residents remain flush with water?

Apparently, just a strong swing and a good ear.

Using a technique almost medieval in its simplicity, maintenance and engineering crews from the Calleguas Municipal Water District spent two days last week walking inside the miles of cold, wet water mains beneath the city and banging on the walls with long metal rods.

A ringing vibration in the key of G means everything is fine with the massive concrete pipes, but a dull thud alerts crews to potential problems.

“It’s kind of archaic but it does the trick,” said George Mulligan, maintenance operations manager for Calleguas Municipal Water District.

As part of the district’s Infrastructure Reliability Program, crews wearing hip waders and hard hats descended into these tunnels to check for corrosion caused by Simi Valley’s notoriously acidic soil. They also kept an eye on repairs made after the 1994 Northridge earthquake, which was the last time the pipes were inspected.

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Although this month’s rains have caused problems in sewer lines, they have actually helped these spelunking investigators by allowing them to shut down the water main due to decreased demand among area residents.

They checked the larger of two mains that run through Simi Valley. The mains feed communities in the eastern parts of the county with water imported from rivers in Northern California.

By gauging the sound of metal hammered against concrete, the crews hope to avert the kind of disaster that occurred last March when a line burst. The rupture flooded a quarter-mile stretch of Madera Road and left a soggy crater.

At more than 6 feet high, with walls more than a foot thick, the water mains twist and turn under the streets and subdivisions of Simi Valley to a water district holding station off Olsen Road. Inside, chemicals in the water give the pipes the antiseptic smell of a dentist’s office.

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The 20-foot sections of pipe are fashioned from steel encased in concrete and wrapped in thick wire.

For flexibility in an earthquake, the sections are joined loosely with mortar, forming a line that can pump up to 300 cubic feet of water per second.

“There’s really no problem with these pipes collapsing during an earthquake. . . . They just ride out the waves,” Mulligan said. “But they’re getting a little older, and there have been failures of this kind of pipe popping up all over the country, so we’re just doing this to make sure.”

Preparations for the inspection were made two weeks ago. Valves were closed to drain several miles of the main running from the east end of Simi Valley to the west.

Only one problem was found.

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After descending through a manhole at the edge of a muddy drainage ditch, workers heard the telltale thud in a section of main beneath Arroyo Simi, near Madera Road and Easy Street.

Using a more sophisticated instrument called a Schmidt hammer, which taps the concrete sides with a metal pin, and a computer-operated data collection system, engineers isolated the spot where probable corrosion had softened the concrete.

The section will be replaced within the next month.

“The whole line looks like it’s in pretty good shape, considering its age and what it’s been through, which kind of surprises me,” Mulligan said. “But that’s good. . . . The last thing we want to do is dig up Madera Road.”

If more lines are found with serious problems, the district may resurface the inside of the pipes with a coating of Kevlar--a super-strong material used to make bulletproof vests--or replace them altogether.

The entire program will involve inspections of smaller pipes, pumps, retention basins and everything else in the Calleguas system. It will run at least 10 years, ensuring the system’s efficiency as more people hook onto it.

“It’s a pretty labor-intensive process, but it has to be done,” said district General Manager Donald Kendall. “Since we’re the sole supplier of water for communities in the east county, we’ve got to be sure the lines stay open.”