Looking forward to the end of the Aurora Avenue North construction? Not so fast.
For a second time, utility crews in the boomingest part of Seattle have found concrete in the sewage pipes while performing emergency repairs.
This time, the site is Aurora Avenue North — where Seattle Public Utilities closed one general-traffic lane in each direction this week, in response to a sewage overflow. Traffic jams in the morning extended back from Queen Anne Hill to Woodland Park or beyond.
Previously, a concrete blockage was found in an SPU pipe below Fairview Avenue North, causing lane closures, emergency pumping, and now an 86-foot pipe replacement expected to take four weeks and cost $350,000.
Crews tried to drill through the Aurora clog to restore the flow, but that strategy failed when they found about 40 feet of collapsed pipe, officials say.
Work on Aurora was supposed to be finished Friday, until crews found the blocked and collapsed segment of pipe. That will send the job into overtime — up to two weeks longer, said SPU spokesman Andy Ryan.
The one bit of good news for commuters is that both general lanes and the bus lane will be open southbound, until 7 p.m.
But northbound, one general lane will continue to be blocked around the clock.
The area north of downtown Seattle is among the nation’s fastest growing places, where development appears out of control to many residents. Mercer Street and its feeders have been gridlocked for nearly two years, a side effect of a good economy, a resurgence in urban living, and the rise of Amazon’s high-tech campus.
For both Aurora and Fairview, SPU has yet to prove where the concrete came from, but the agency has collected samples that can be compared in a laboratory to materials at nearby construction projects. The city could seek to recover repair costs from builders if a clear trail is shown.
A number of possiblities exist — ranging from intentional dumping, to a spill on the jobsite, to punctures by diagonal “tiebacks” where steel tendons support a building foundation. In the latter case, horizontal drilling might puncture a nearby pipe. Concrete grout is often injected into the soil to strengthen big structures, and could seep into previous or new pipe cracks. In the past, there have been a few incidents a year citywide where concrete winds up in a sewer line, Ryan said.
Grout and sludge have been obstructing the pipe in the center of Aurora between Comstock and Ward streets, officials said.
“I certainly understand the frustration of motorists trying to get through the area. We are working to clear the blockage and repair the pipe as soon as possible. The last thing we want is for sewage to start backing up into homes,” said Jeff Fowler, SPU construction management director.
This stretch of Aurora carries 74,400 vehicles a day, including well over 20,000 transit riders. Despite construction closures, the Seattle Department of Transportation has been maintaining its Aurora bus lanes for transit only, said SDOT spokeswoman Marybeth Turner.
The lower segment near Mercer Street has already been reduced from three lanes to two each way, so Seattle DOT can build its $95 million Mercer West project beneath Aurora. That project will be done next year — but Aurora will continue to be crimped there until the Highway 99 tunnel portal nears completion, in late 2016 at best. So the current stall of tunnel machine Bertha at Pioneer Square is prolonging the congestion north of downtown.