City officials will spend $15,000 retesting the Spokane trash incinerator for dioxin emissions after getting some unusually high readings last fall.
Data in a Feb. 25 report recently submitted to clean air officials show the plant slightly exceeded its permit limit for the first time in a smokestack test last September.
The violation was so small local air quality officials now say the plant is in compliance - but “at the regulatory limit” - for dioxin emissions.
In very small amounts, dioxin can cause immune system disorders, liver damage and reproductive problems, as well as some cancers.
Trash incinerators are one of the primary sources of dioxin nationwide. It’s formed by burning the polyvinyl chloride found in plastic.
The dioxin numbers “are significantly above the results from previous testing,” the Spokane County Air Pollution Control Authority said in a March 13 letter to the city.
SCACPA wants to know whether:
“Non-typical wastes,” including industrial wastes brought in from Canada, were burned during the test.
The plant was operating abnormally at the time.
Any maintenance activities during the tests could have influenced the emissions.
The city’s decision to retest for dioxin emissions came at a Friday meeting of trash plant supervisors and operators, and clean air officials.
“We have offered to do a retest, and SCAPCA felt that would be a good idea,” said Damon Taam, the city’s solid waste director.
Garbage ratepayers will pay for the new tests. They will be conducted at the end of March in three runs of 240 minutes each.
The results will be available 60 days later, Taam said.
The plant’s permit limit is .50 nanograms of dioxin per cubic meter of air. A nanogram is a billionth of a gram.
Dioxin levels at Unit 1 of the plant’s two smokestacks showed an average .506 nanograms in the 1997 tests. The highest reading was .685 nanograms, the lowest .299.
The other smokestack was far lower, an average of .014 nanograms, the report says.
Plant supervisors think the higher-than-normal emissions could have come from a faulty test, Taam said.
“It’s a number that we feel is an anomaly. But we need to prove that,” Taam said. “The last six years of plant data says this is very uncharacteristic.”