Some samples of bottom ash from Metro Vancouver’s garbage incinerator are testing positive for high concentrations of cadmium – sometimes at twice the allowable levels for conventional landfilling in Delta.
A Metro Vancouver staff report shows that so far this year bottom ash loads have failed 19 times out of 479 tests, with eight tests coming back at more than twice the limit.
The test failures are different from the high cadmium levels detected a year ago in some fly ash – taken from scrubbers in the waste-to-energy plant’s stack – that operator Covanta Energy failed to report until those loads were already dumped at the Cache Creek regional landfill.
The bottom ash instead goes to the Vancouver Landfill at Burns Bog in Delta.
Trouble with incoming loads there was first flagged in 2007, when some bottom ash exceeded allowed levels of lead, but Metro’s report says subsequent testing determined it wasn’t hazardous to workers and steps were taken to ensure compliance with the landfill’s operating certificate.
Metro was advised starting in April of this year that some bottom ash was exceeding leachable cadmium levels.
At the request of the B.C. environment ministry, Metro has filed a management plan to address questions about bottom ash.
Meanwhile, bottom ash loads from two weeks in July and one week in August that tested at more than twice the regulatory limit are being stockpiled at the Vancouver Landfill pending further decisions.
Ash that fails the test but is below twice the limit is being landfilled after further tests confirm it’s not hazardous, according to Metro.
Up until April, the ash was being used in road construction and as cover at the landfill.
According to Metro, sources of cadmium in the waste stream are thought to have increased in recent years.
Household batteries are the main source, particularly rechargeables, including electronic device batteries. A much smaller fraction likely comes from plastics.
Metro officials say they intend to further study cadmium sources in the waste stream and to work with Covanta to ensure the treatment of bottom ash to neutralize metals ahead of landfilling is effective.
The region will also push for increased recycling of batteries through product stewardship programs.
The question of what happens to suspect loads of fly ash at the Cache Creek landfill is still unresolved.
Cache Creek Mayor John Ranta said consultants have been hired to try to determine whether it must be landfilled elsewhere instead.
He hopes to learn if the plant’s process for binding bottom ash is effective indefinitely or if it degrades over tiime.
Findings are expected in mid-October.
Fly ash from the incinerator has been trucked to a landfill near Hinton, Alberta instead of Cache Creek, at a cost of about $500,000 more per year, since the test failures came to light.