The University Bridge, shut down when an adjacent water line ruptured Wednesday morning, was re-opened to vehicle traffic at 3 p.m. today today. The bridge...

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The University Bridge, shut down when an adjacent water line ruptured Wednesday morning, was re-opened to vehicle traffic at 3 p.m. today.

The bridge had been closed to vehicles after a 24-inch water main cracked beside it. Pedestrians and bicyclists were allowed to use the bridge earlier in the day.

Metro Transit bus routes 49 and 70 are now crossing the bridge as usual, and four other routes should return to normal by 4:30 p.m., instead of detouring around the bridge., said spokeswoman Linda Thielke.

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Nearby Fuhrman Avenue East remains closed because heavy equipment is there, said Gregg Hirakawa, spokesman for Seattle Department of Transportation.

In an effort to stabilize the area, city crews this morning poured 20 yards of a slurry of concrete and sand to help stabilize the area around the bridge.

Hirakawa had said about 40 yards of the mixture had to be poured before the bridge could reopen. In addition to pouring the slurry, the city is also built a small dam to keep the mixture in place while it hardens, Hirakawa said.

Work crews also have found the pipe crack which is 10 feet long on the underside of the water main. The sinkhole is 20 feet wide 10 feet deep and goes under Eastlake Avenue East.

Hirakawa said the city took measurements and found that there was no movement on the bridge.

In other developments, about 40 homes that lost water Wednesday had it restored and then the homes lost water again Wednesday night from about 7 p.m. to midnight, said Andy Ryan, with the city’s Public Utilities Department.

When the 90-year-old, cast-iron water main ruptured in the shadow of the bridge Wednesday morning, flooding a street and washing two cars into a sinkhole, it also exposed a truth about Seattle’s vast water system: Much of it is wearing out.

Even though Seattle Public Utilities (SPU) replaces two to three miles of drinking-water pipe a year, long stretches of pipe in the 1,800-mile water system are between 50 and 100 years old, approaching the end of their lifespan.

The water main that ruptured Wednesday was laid in 1917. SPU officials reported that workers had fixed leaks in that pipe, in the same vicinity, twice before: in 1986 and 1992. Neither approached the seriousness of Wednesday’s accident.

The city is investigating the accident. There were no injuries.

Water service to the affected areas of Eastlake and Capitol Hill had been restored by Wednesday evening.

The water main gave way just a week after road workers broke a main on Dexter Avenue in the South Lake Union neighborhood; the latest break was not related to construction.

2 vehicles swallowed

The leak had apparently gone unnoticed for a while. Some nearby homes had reported discolored water on Tuesday. Early Wednesday, other neighbors reported that their water pressure dropped significantly. Then at 7:36 a.m., a muddy cascade emerged near the bridge’s southern foundation. The bridge was closed minutes later.

Two cars fell into the 8-foot-deep hole, and one of them came to rest on a natural-gas line. Crews had to remove the vehicles cautiously, delaying the repair to the broken main.

Both cars were owned by employees at the Red Robin restaurant nearby. Jorge Maya, a kitchen manager, said he tried to move his van as the asphalt slumped around it. But he ultimately fled, drenched, and his car was swallowed. “It was scary,” he said.

The owner of the second car, cook Alejandro Medina, never even got a chance to rescue his vehicle before it slipped into the muddy hole.

In the end, the water didn’t damage the bridge itself. Workers will have to pump in sand and concrete to stabilize the abutment, officials said.

More than 31,400 vehicles use that route every day, and the closure snarled the other bridges over the Ship Canal at the Montlake Cut, and in Fremont and Ballard.

Crews remained concerned late Wednesday that the flood could have undermined a block of concrete that supports another water main nearby, said Joe Mickelson, the water-operations director for SPU.

“City’s water is safe”

As spectacular as the break was, only a fraction of the utility’s 1.3 million water customers were affected.

More than 30 customers along Northeast Boat Street used bottled water from the city for most of the day until water was restored in the evening. In other areas along Eastlake Avenue East and on Capitol Hill, water pressure was weak or nonexistent. Some others complained that their water was discolored.

“The city’s water is safe,” Ryan said.

Still, residents with murky or dirty water were advised to let it settle until it clears before drinking it. Officials also suggested that homeowners could clear their lines by running taps for a few minutes and flushing the toilet a few times.

Despite Wednesday’s rupture, water managers said the city’s water system is closely monitored and among the most reliable in the country. Still, the city spends millions every year replacing lines that have outlived their usefulness.

Blame some of the current situation on the changes in pipe materials over the years.

When a glue pot spilled in a cabinet maker’s shop, sparking the Great Seattle Fire of 1889, an inadequate water supply and lousy water pressure allowed the blaze to roar through 29 city blocks, several wharves and the train terminal. When the city began to rebuild, the foundation was laid for today’s water system.

Wooden pipes

The earliest pipes were wooden and mostly lasted for decades until the last sections were replaced in the 1980s. Pipes put in the ground in the early 1900s — like the main that broke Wednesday — were made from thick cast iron, and they were expected to last 100 to 150 years.

Metal shortages during and after World War II resulted in thin, galvanized-steel pipes expected to last 50 to 75 years.

Since the 1960s, the city has used a stronger ductile iron, which is less prone to cracking and breaking.

But now the middle-age pipes are wearing out just as the older mains are also reaching the end of their usefulness.

Eugene Mantchev, the manager responsible for the system’s performance, said most of the really troublesome pipes — the lines from the 1940s and ’50s — are gone. Those steel pipes made up just 20 percent of the system but were responsible for 80 percent of the leaks, he said.

But about 147 miles of cast-iron pipe, some of it laid more than 100 years ago, remains online, Ryan said.

Mantchev said the city has a 20-year plan to replace aging pipes, with the leakiest pipes getting the most attention. Repairing a series of small leaks until the pipe can be replaced is more cost-effective than trying to inspect the pipes already in the ground.

Moreover, Ryan added, some of the old pipe can last 150 to 200 years.

Jon Shimada, the utility’s strategic adviser, said pipe inspections using sonar, X-rays and camera technology cost almost as much as replacement.

“It’s effective, just not cost-effective,” he said.

The utility spent $57.5 million on capital improvements to the water system in 2005 and about $83 million last year, Mantchev said. This year, the city plans to replace nearly 2,300 feet of old steel pipe, and lay 12,700 feet of new pipe, on Queen Anne Hill.

Sara Jean Green: 206-515-5654 or

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