Teamwork needed to fix broken water main
Minutes after a 30-inch water main fractured in Northeast Portland on the morning of March 17, the first four Portland Water Bureau employees already were rushing to the area to begin the complex and dangerous task of shutting off the gushing water.
They were alerted to the break by 911 dispatchers fielding calls from neighbors and alarms going off at the storage facilities at both ends of the 100-year-old pipe. The break near Northeast 23rd and Skidmore had ruptured the pavement above it, releasing 40,000 gallons of water a minute into the neighborhood. The alarms were triggered by the sudden drop in water levels at the Kelly Butte Reservoir in Southeast Portland and the Vernon Tanks at Northeast 19th and Skidmore.
It took more than two dozen bureau employees about 38 hours to fix the pipe. None of the work was easy. And only a few of the managers were required to be there.
"The break happened on a Saturday and our (union) contract doesn't require employees to work weekends. They'll get paid overtime, but they didn't have to respond. Our workers are dedicated to their jobs," said bureau Maintenance and Construction Director Ty Kovatch, who was one of the first four employees on the scene.
Shutting off the water was not as simple as twisting a single handle at the reservoir that was feeding the main. The pipe was connected to other, smaller mains in the area. A total of 12 valves had to be identified, located and turned off by forcing internal metal or hardened rubber plates across the full diameters of the pipes.
Water was surging through all of the mains under tremendous pressure. A mistake could cause one or more of the valves to fail, creating additional problems that had to be fixed. Even worse, the force of the water was strong enough to kill anyone near such a failure.
"The pressure against the largest valves is enough to lift a front loader, which weighs 50,000 pounds," Kovatch said. "The pressure against the smaller ones can still lift a car."
Working in the mud
All of the valves were located in concrete vaults beneath the streets between the Vernon Tanks and Northeast 60th and Holladay. The largest ones were reached through manhole covers, the others through smaller plates in the street. The four employees started turning the first of them off by hand using specialized gate keys; an exhausting task because some required up to 250 turns to completely shut off. Fortunately for them, other bureau employees soon began arriving in trucks with machines to finish the work.
One valve could not be closed, however. Doing so also would have shut off all water to a large part of Northeast Portland. That meant water had to still be flowing though the broken main while it was repaired, adding mud to the already dirty job.
When the first workers arrived at the scene of the break, the broken pipe was visible through the water in the ground. The pavement and dirt above it had been blown out by the force of the water that still looked like a fountain in the middle of the street. They closed the streets between Northeast 21st Avenue and 30th Avenues, helped evacuate residents in 12 homes and worked with Pacific Power to cut the electricity to as many as 14,155 customers in the area as a precaution.
As the valves were being shut off, five gas-powered pumps were brought to the site to drain as much water as possible out of the crater before it was further dug out with a large excavator so the walls could be shored up.
With the still-flowing water reduced to manageable levels, workers then had to enter the crater and excavate under the pipe about 16 inches. This allowed a specially-designed saw powered by compressed air to be fastened to the pipe to cut through it. The saw circled the pipe on a chain, guided by a worker who made sure the it stayed on track and the cut ended exactly where it began.
The first cut took around two hours. The second went a little faster, about an hour-and-a-half. When it was finished, the broken section was lifted out by a large excavator.
As all this was happening, a replacement pipe was located at the bureau's warehouse at 664 N. Tillamook St. and loaded onto a flatbed truck, along with two 30-inch diameter sleeves to be used to connect both ends of the main that were still in the ground. A decision was made that one of the sleeves would have a valve that cut shut the water off at that location for future projects in the area.
When the replacement pipe arrived at the scene, the "air saw" was used again to cut it to the right replacement length. It was then lowered into the crater and secured into place with the sleeves, all while water continued running through it.
With that work complete, the process of reopening the closed valves began — once again, in the proper sequence. At the same time, water was flushed out of the main through a manhole west of the site of the break to remove sediment in the water stirred up by the rupture and work.
"This was the largest main break we've dealt with and it was repaired in 38 hours. That phenomenal outcome was the result of our committed crews and support staff," said Portland Water Bureau Director Michael Stuhr.
No cause has been found
Because so much pavement was blasted away and damaged, bureau workers are upgrading other pipes under the street there before the Portland Bureau of Transportation fills the crater and repaves it. When all the work is completed, the only reminder will be the new surface.
Kovatch said that, despite the age of the main that broke, no cause for the rupture has been found. That section has been inspected and it is still in good shape with no significant corrosion. That means there is no reason to replace the rest of it any time soon.
Bureau officials estimate the cost of the repair at about $152,000, including approximately $98,000 is in direct labor, materials and equipment cost. These figures do not include restoring the street.
"We get about 200 main breaks a year, although nothing this large in a long time. Most don't get any news coverage. Factor can include age or nearby construction projects, but they're impossible to predict and the reasons aren't ever known in most cases," Kovatch said.
The 12 valves that were shut off are part of the approximately 60,000 total in the bureau's transmission and distribution system. Of those, 1,200 in the transmission system — which includes the mains — are considered critical and tested every two year. Others are tested less frequently. They are rarely fully closed, however, because that would disrupt water supplies. All of the valves that needed to be closed for the March 17 break worked.
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