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Lab error may be behind failed incinerator ash tests: Metro
Metro Vancouver now suspects lab errors may be to blame for the recent failed tests of fly ash from its Burnaby garbage incinerator and that the material may not be hazardous after all.
The regional district and the provincial environment ministry have been weighing whether to dig up and remove ash buried at the Cache Creek regional landfill after failed tests in July and August found leachable cadmium levels above the permitted limit for disposal there.
More frequent testing had been underway since the summer failures came to light in late September and had not turned up any more exceedances – until last Friday, when Metro was informed another fly ash sample taken last week also failed.
Metro solid waste manager Paul Henderson said the sample was retested and passed the second time, leading him to doubt the accuracy of the lab's so-called TCLP test for leachability.
"The lab confirmed there'd been an error in that sample that previously showed as failed," he said. "It showed us absolutely there's a possibility of failure of the TCLP test."
Henderson said there's now a "strong possibility" lab testing error was the cause of all the failures.
"We think it's important information that really leads us to further investigation before any conclusion that the material is hazardous and needs to be removed."
He's recommending re-testing of older failed samples by a new lab to help determine if lab error was to blame in those cases as well.
Testing error had been considered one possible cause of the failures, as well as a possible problem with the ash treatment process that left too much leachable cadmium behind.
Treatment is supposed to render toxic metals in the ash inert so they can't leach into the environment around Cache Creek, if the landfill's liner were to fail.
Since Sept. 27 – when incinerator operator Covanta belatedly informed the Cache Creek landfill operators of the failed summer tests – the fly ash has been shipped to a landfill near Hinton, Alberta.
Ash deposited at Cache Creek landfill since mid-2010 is in a dedicated cell with its own liner and a separate leachate collection system.
TCLP testing so far on the 1,800 tonnes of ash sent there in July and August had found a five per cent failure rate and plans are underway to begin testing older ash dumped there over the past two years.
A separate pH test of each load of ash leaving the incinerator to flag high levels of metals – done as a surrogate for the main TCLP test – has consistently come back within limits.
Cadmium is a carcinogenic metal found in batteries and some plastics.
Cache Creek Mayor John Ranta said he wants to get to the bottom of the testing concerns, adding he hasn't yet seen compelling evidence that's to blame.
"If the lab results are that inconclusive that we can do a test, find it exceeds the limit and do another test and find it passes, then what about all the other tests that have been done from 2000 to the present day saying it passed?" he asked.
"Should we be re-testing that and maybe find that some would fail?"
He also wonders if the samples to be re-tested are different in any way from the originals that failed.
The environment ministry has so far taken the position that no ash needs to be removed from Cache Creek.
Shipping ash to the Hinton-area landfill is costing Metro an extra $50 per tonne, potentially adding up to an extra $500,000 per year if it continues indefinitely.
Henderson said Metro wants Covanta to pay for the extra costs.
The toxic ash tests had prompted fresh criticism in recent weeks from Fraser Valley politicians, who oppose Metro plans to build a new waste-to-energy plant burning 370,000 tonnes of waste per year – 30 per cent more than the Burnaby incinerator.
Covanta is one of the expected bidders in the procurement process that got underway this fall.