Water Officials Make Sure Tanks Will Hold Their Fill

Water officials aren’t taking any chances with two storage tanks in Santa Ana that are designed much like the Westminster tank that burst two months ago, sending a wall of water through a subdivision.

The two tanks, one owned by Santa Ana and the other by the Orange County Water District, have been empty since before the Sept. 21 Westminster disaster and will not be filled until they are examined, officials said Wednesday.

The tanks are near one another on Bear Street in Santa Ana.

The city and the water district are confident that the above-ground tanks are secure, and city officials met last week with residents living near the structures to calm their fears.

“I’m concerned,” said Richard Baskerville, 54, who bought his home 24 years ago. “Were these structures constructed per the drawings? And I’m even more concerned with their condition. . . . Will they burst in the middle of the night? Would we be safe?”

Kelly Walter, 39, said she isn’t losing any sleep over the possibility of a water tank bursting and flooding her neighborhood.

“If it bursts, we wouldn’t have a home,” said Walter, who has lived in the neighborhood nine years. “But I think they’re taking the necessary precautions. You just have to hope and pray that you don’t have to deal with” a rupture.

Early Sept. 21, the Westminster tank burst, sending 5 million gallons of water cascading into the adjacent neighborhood. The flood injured six people, displaced more than 30 families and caused $30 million in damage.

Westminster officials said Tuesday that an investigation revealed that design and construction flaws caused the rupture. An identical tank in the city also was drained for inspection.

Critical steel reinforcements, called hairpins, in the outer foundation were missing and a steel cable reinforcing an inner section was misplaced during construction, engineers discovered. The concrete cracked, and water seeping in over the years corroded the steel, which snapped.

“I don’t think that would happen here,” said Santa Ana Water Manager Thom Coughran. “But we’ve hired a structural engineer to examine the tank before we put it back into full operation.”

Santa Ana drained its 5-million-gallon tank, built in 1965, last July to replace pumps and some piping.

The tank is 16 feet high, compared to the 25-foot-high facility in Westminster, and also is built seven feet below ground level. Coughran said these two features create less pressure on the walls. In addition, the city has wrapped three cables around the outside “like a belt on a pair of pants.”

Santa Ana sold the nearby tank, which holds 6 million gallons of water, to the county water district in 1984. The district has never filled the tank. After seeing the report from Westminster this week, officials said they will have a structural engineer inspect it for any defects.

“It certainly is a wake-up call,” said Bill Mills, the water district’s general manager. “This is our first experience having a large tank and we will, of course, be cognizant of what happened in Westminster. We think that the hairpins are there, but we want some assurance from our engineers that they are.”

Last week, Coughran met with neighborhood associations in the area to try to calm nerves.

“People saw the newspaper reports and they called,” Coughran said. “I was happy to go down and talk to them and informed them that we had hired a structural engineer to help assess the structural integrity of the tank.”

Still, neighbors remain nervous.

When Rita and Dante Allegrini bought their home 20 years ago, they called city officials and asked if the tanks were safe.

“They told me everything was safe. . . . I took their word,” said Rita Allegrini, 78. “We’ve always felt safe, but now we’re a little apprehensive.”

Dante Allegrini, 85, said after reading news reports about the tank rupture in Westminster, he got scared.

“We’re only 100 feet from the tank,” he said.

In reporting the cause of the rupture, Westminster officials had said that two similarly designed tanks built by the same company, now defunct, are in Santa Ana and one is in San Clemente.

But in San Clemente, officials said Wednesday the city’s tank simply isn’t like the ones in Westminster. “We’re a bit chagrined that it was gratuitously offered up [Tuesday] that we have a similar tank, because we do not,” said David Lund, public works director for San Clemente.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

Why the Tank Burst

Two structural problems were central factors causing Westminster’s concrete water storage tank to burst in September:

Chain of Events

1. Without steel reinforcement “hairpins” in place, concrete sections are not tied together.

2. Foundation cracks when tank is first filled, separating inner foundation from outer ring curb.

3. Over time, water leaks into crack, and steel reinforcements (rebar) tying inner foundation and outer ring curb begin to corrode.

4. Rebar snaps, placing all tank’s water pressure on outer ring curb; it pops away and lower portion of wall bursts.

Two Key Problems

A. Hairpins not in place, water pressure transferred to outer ring curb instead of down to inner ring foundation

B. Because steel cable placed in inner foundation instead of outer ring curb, cable not able to exert inward pressure when rebars snapped

Source: Montgomery Watson

Graphics reporting by TOM REINKEN