Cracked beam delays Park & Ride
November 24, 2008 · Updated 4:00 PM
Yet another delay has stretched the schedule for the completion of the Mercer Island Park and Ride lot on the North end of the Island. It is the fourth time the project has been delayed since work began.
Construction managers from Sound Transit said last week that re-designing a defective support structure in the two-story garage has been difficult and is the reason for delaying the opening. The first attempt by engineers to eradicate problems associated with a cracked concrete support beam discovered in early October 2006, failed, and plans for the second try are currently being reviewed by the city’s planning department.
“The proposed repair was just not compatible with the beam design,” said Christine Post, a construction manager in Sound Transit’s capital projects department. “Since most of the building is already constructed the designer is faced with an existing structure and existing support that makes it more like a retrofit. It’s not a blank slate anymore and we did not get the best understanding of the cracked beam and found out the repair just couldn’t work.”
The first re-design required the removal of two of the 450 planned parking spaces. Linda Robson, a spokesperson with Sound Transit, said that the new re-design has 447 parking spots. The initial cost for the fix has also gone up about 15 percent, from $2 to $2.3 million.
Originally scheduled to open last March, the project completion date is now up in the air pending on the success and approval of the current re-designs.
“It’s subject to a number of steps and we are not able to predict a positive result so we have to take it one step at a time,” Post said.
There is the possibility the redesign woulf fail to secure the problem, in which engineers would have to take another crack at fixing the defective beam.
“It is a possibility that it may go back to the engineers,” Post said. “We are hoping the repair is going to work and proceed to the final step, which is a load test on the beam. If we find out the repair has been effective, then the repair will be done in December — depending on the permits.”
A load test will follow the repair work if the re-design is approved. That may take place in January if the current fix works, Post said.
Robson said the organization can’t promise an opening date at this time because officials have to be sure of the garage’s safety before moving on.
The need to redesign the garage’s support structure is the result of errors and omissions in the design which caused the concrete beam to crack, according to Sound Transit officials. The transit agency is currently in litigation with the contracted engineering firm, arguing over who is accountable for the mishap. Sound Transit stated that an independent, third-party inspection determined the cracks resulted from design flaws and wants to recoup the costs of the fix from the design firm.
After inspecting the cracks for a couple of months, engineers found flaws in the design that caused them. Too much pressure was being exerted on the beam because other support structures, called shear walls, were not providing enough support.
Last spring, Sound Transit officials also stated that the damaged, 100-foot-long beam would not be replaced or removed to get fixed. Instead, the cracks will be injected on-site with a high-pressure concrete grout mixture and sealed with a high-pressure epoxy.
While the cracked beam has caused the most significant delays in the project, there have been other times when work ceased, threatening to postpone the project schedule.
Actual demolition of the old parking lot began in April 2006. However, the demolition was initially planned to begin on Feb. 13, 2006. Sound Transit officials had said the demolition delay wouldn’t postpone the construction schedule, and the start date was pushed back so Puget Sound Energy could install a new transformer. Before construction fencing could be put up, the energy company needed to install some equipment.
Then a red Jeep Liberty abandoned in the old parking lot pushed the demolition back even further. Attempts to contact the Jeep’s owner were unsuccessful, and a note left on the front seat indicated it was in the process of being repossessed and was abandoned.
The Jeep had Pennsylvania license plates. Although police issued a warning that it would be towed on March 27, it remained the last vehicle in the lot before construction began in April.
Later that summer, a strike by concrete workers required construction crews to work on other parts of the project while mix was unavailable around the entire region. The strike, which nearly lasted the entire month of August, did not result in a large delay at the Island’s Park and Ride, but Sound Transit officials conceded the finish date could be postponed from the backlog of orders.
That didn’t seem to matter about a month later, though, when a series of cracks was found in a concrete support beam on Oct. 4, 2006. In response to the startling discovery, crews were evacuated and police shut down three blocks on North Mercer Way for half a day. After an emergency procedure to secure the beam took place, a steel plate was set up to prevent the spread of lateral debris should the structure collapse.
A year later, the project was scheduled to be opened by December 2007 until news that the second proposed fix wouldn’t get approved in time. Since the lot was closed in April, several interim park and ride lots were opened around the Island, and Metro instituted some shuttle service. Those will continue to be available for residents while the new garage remains closed, Robson said.