Poor design doomed composter: study ELISE STOLTE
Engineers find subsequent repairs to roof only made matters worse
Allegations of “flawed” roof repairs and long-standing design issues are the real cause of the sudden closure at Edmonton’s compost facility, according to newly acquired city documents.
City officials initially blamed the high heat and humidity inside the 18-year-old structure that was pulled off-line suddenly last October. But engineering and inspection reports released through a Postmedia freedom of information request suggest corrosion on the central columns was only the first concern.
Corrosion was the reason specialized engineers with ONEC Group were called out in December 2016. But when they climbed into the attic to look for further corrosion, they were instead startled to see the amount of buckled ceiling panels, missing bolts and twisted lateral ties throughout much of the truss system.
They called for a much more extensive investigation.
When a second, independent engineering firm was called in to review, its report found “deflection of the trusses was excessive” and previous efforts to repair it were “flawed.”
Efforts in 2001, 2012 and 2013 to repair and strengthen the roof actually resulted in more stress to the connection plates and panels, “again reducing the load capacity of the system,” stated RND Engineering in a memo to ONEC dated Aug. 15, 2017. It was that report that recommended the city not allow any snow to accumulate on the roof while the composter was operating.
Within a month of receiving RND and ONEC’s report, the city shut operations, sending roughly 50,000 tonnes of otherwise compostable material to the landfill last winter alone.
Edmonton’s $97-million compost facility was once the jewel in a waste management program the city was so proud of it sought to export its expertise around the world. But in the last two years, the illusion of greatness has crumbled.
Now two new high-tech investments using waste to produce energy are behind and over budget, and the city auditor recently questioned the departments’ ability to even report accurately on its targets. The surprise failure of the composter was an additional blow.
But closure was the safe decision to make, said Pascale Ladouceur, the city’s director of facility planning and design, in an interview this week. “We’re not taking any chances.”
Behlen Industries, the company that originally supplied the facility and designed the repair, also did an inspection and said the structure is OK, Ladouceur said.
But the city chose to err on the side of caution. It is planning to shut the facility again this October, before the snow flies, and is working on plans to build a replacement.
Any option so far found for repairing the structure would cost roughly $25 million, more than the building is worth. Those options were presented to council’s utility committee last April, but council members went in private to discuss the history.
When asked if the city is considering legal action, Ladouceur said: “The legal opinion and our opinion on the cause was presented in private and will remain in private.”
Behlen officials could not be reached for comment Thursday.
When the compost facility was built in 2000 by TransAlta it was considered world class, the largest in North America.
TransAlta sold it to the city in 2001. It’s a large, single-storey building measuring 117 metres wide, 200 metres long and about 12 metres high.
According to ONEC research summarized for the city, problems first appeared in 2001 when the ceiling panels buckled on the west side of the building in the middle span, resulting in 45 metres of panels being replaced under warranty.
Eleven years later, officials noticed panels buckled on the east side of the building and Behlen designed a reinforcement system for the roof truss.
In 2013, contractors installed that same reinforcement throughout the middle section.
In a memo dated Feb. 20, 2013, contractor Clark Builders told the city: “This will ensure that we will have no problems going forward.”
But that repair actually made things worse, the RND engineer concluded. Crews should have been required to take the load off the trusses first, then install the reinforcements so they would engage and strengthen the roof immediately.
Instead, the roof trusses need to deflect or slump before the reinforcement catches them. This creates more stress in the system and compromises the roof further.
In addition, RND wrote, the initial design used different kinds of steel in the same structure. That increases the corrosion and stress on the building as it expands and contracts with fluctuating temperature.
Coun. Aaron Paquette, who sits on the utility committee, said it’s frustrating and “a bit of a tragedy.”
“We’re still a bit bewildered why they chose to put a stainless steel roof on a regular steel frame,” he said in an interview last Friday.
But he’s not sure spending more money investigating in the hopes of launching a lawsuit is the right answer. Council needs to move forward and fix this. “Not try to be the world’s leader in composting and just do what works.”
The city did its due diligence, said Coun. Ben Henderson, chairman of the committee.
“I was frustrated by the whole thing and I don’t think there was any culpability on our part . ... It’s battling consultants, quite frankly.”
As for what to do next, city officials are returning to the utility committee on either Oct. 25 or Nov. 9 with a plan. They’re still looking at repair options and designs for rebuilding, Ladouceur said.
But council needs to first decide how strict to make its new green bin and leaf and yard waste pickup programs. Those roll out as a pilot project and a voluntary program this spring. If the leaf and yard waste pickup is successful, it will divert easy-to-compost material and the city can build a smaller, less costly compost facility for the rest.