The aggregate, a granular base material made up of gravel, sand and other particles, contained too much fine material or “fines” — more than double the amount specifications allow. Burbach Aquatics, Inc., the architectural firm …
City approves eight-week completion extensionFlawed aggregate material used in the construction of the Powell Aquatic Center will delay the pool's completion by up to two months, but the problem can be solved and the structure's integrity will not be compromised, according to project leaders.The project was originally scheduled to open in January 2010. During a special Powell City Council meeting Tuesday, the council approved an eight-week extension for the completion date. The delay is a direct result of the defective aggregate, and the facility is now slated to open by Feb. 28, 2010.
The aggregate, a granular base material made up of gravel, sand and other particles, contained too much fine material or “fines” — more than double the amount specifications allow. Burbach Aquatics, Inc., the architectural firm hired for the pool, worried that rising and draining groundwater would drag the fines out and eventually clog the pool's drain system.
The fine material resembles flour in consistency, said Project Engineer David Burbach.
“We were concerned the excessive amount of that would get in the underdrains and block the system,” Burbach said.
The problem, which was discovered in February, delayed construction until a solution was determined and successfully tested. Some of the aggregate is still exposed and two sections — the diving hopper floor and a second portion of the pool — are covered with concrete.
To remedy the problem, the fines will be flushed from the aggregate, beginning this week. Burbach and Sletten project leaders performed experiments in a test-cube that mimicked the pool site and showed how material would respond to flushing.
Crews will “irrigate” the site, flushing it with water and the downward movement will take the fine material out, leaving the aggregate intact.
Taxpayers will not be responsible for any of the costs related to fixing the aggregate mishap.
On Tuesday, Burbach assured the mayor and council that the flushing system will solve the problem.
“I am 100 percent convinced that this irrigation system will work and that the project will meet specifications,” Burbach said.
When the fines are flushed from the aggregate, their absence shouldn't result in voids underneath the foundation, said Casey Waltari, project manager with Sletten Construction, the general contractor.
“It's really fine material, like powder coating the rocks,” Waltari said. “We don't anticipate that there will be any voids.”
Waltari added that crews will make sure it settles before they pour concrete over it.
For the aggregate under the concrete, fines will be flushed using the pool's pump system. The sump pumps — located deep in manholes — will be turned off, allowing the groundwater to rise. The pumps will then be turned back on, and as the water is drawn down, it will take the fines with it.
The concrete will be sound-tested to make sure there are no voids beneath the surface.
As part of the agreement approved Tuesday, Sletten will install clean-outs in the underdrain system, so that all underdrain lines can be accessed and cleaned as necessary. Crews will be able to put cameras into the clean-outs and see the underdrains and monitor any build-up that accumulates.
“It's very important to be able to televise the lines and confirm if they're clean,” Burbach said.
The clean-outs weren't part of the pool's original design, but with the concern of excess fines blocking the drains, project engineers wanted to be able to closely monitor the underdrains. Sletten will pay for the clean-outs and taxpayers won't be charged for the additional cost, Waltari said.
Burbach added that he anticipates some residual material to end up in the underdrains even after it's flushed, but the clean-outs will allow crews to catch the problem and clean it out.
Councilman Jim Hillberry asked Burbach if the aquatic center's structural integrity will be affected by the aggregate issue.
“Absolutely not,” Burbach replied. “I'm very confident that this will be very successful.”
Hillberry abstained from voting on the approval, citing a possible conflict of interest with subcontractors. He declined to specify which one, though his daughter is married to one of the owners of Capstone Construction, a subcontractor on the project.
Hillberry said he believes the solution is the right one, even if it delays the project.
“I think it was good, even though we had to extend the final completion date,” he said. “We will get a good product —the one that we envisioned from the very beginning.”
Councilman Josh Shorb said he isn't happy about the eight-week extension.
“Eight weeks on what we've already lost is a lot of revenue for the city,” he said.
He added that it will also cost the school district to continue using and maintaining the old pool.
Shorb said he understands why the extension is necessary, but told Burbach he won't be as apt to approve additional delays that may surface later.
Shawn Warner, president of Sletten Construction, said he understands that time is money.
“We're very sensitive of the time issue,” he said.
He told the council the construction may only take an additional four weeks rather than the approved eight, which was recommended by Burbach.
Powell Aquatics Superintendent Carrie Parmer said everyone on the project is working toward a common goal —a quality facility for the community.
“We're happy to be moving forward, and we just want it to be top-quality,” she said.