A mobile lab detected a plume with elevated levels of mercury in the air downwind of the Noranda Alumina plant in St. James Parish last month, according to a state Department of Environmental Quality report.
The Mississippi River complex, which converts bauxite ore into alumina, a precursor for aluminum, has been under scrutiny since revelations earlier this year that the facility may have been releasing minute amounts of mercury into the air unexpectedly for decades without a permit.
“The results seemed to indicate a plume of elevated levels the night of March 16 into the early morning of March 17,” the DEQ report says.
The DEQ Mobile Air Monitoring Lab found that mercury in the air east of the Noranda complex was two-and-a-half times higher than the worldwide ambient average, though that’s still 230 times below the state’s safe level, the report says.
The state standard is for an eight-hour rolling average.
The sampling also detected one-hour and five-minute peaks in the air with mercury concentrations that were 7.5 and 19 times greater than the worldwide background average, respectively, but still well below the level the state has deemed as safe.
Mercury is a heavy metal that in higher concentrations can harm the human nervous system, heart, kidney, brain and lungs. Even in small amounts, mercury is a worry because it doesn’t break down but accumulates in fish and shellfish that people eat.
DEQ officials cautioned this week, however, that the results at this point are not over a long enough sample period to be generalized.
“It’s really too small to draw any decent conclusions,” said Greg Langley, DEQ spokesman.
The lab, which is a recreational vehicle stocked with monitors, had to cut short its planned monitoring after collecting 27 hours of samples.
The visit had been planned for 48 hours, but the mobile lab’s generator ran into problems after the RV moved to account for shifting winds, the DEQ report says. The report appeared on the agency’s online database earlier this month.
Langley said the agency plans to return for another unannounced visit.
Location maps and data provided in the DEQ report show samples were taken at two points nearly two and nearly three miles to the east of the Noranda complex in St. John the Baptist Parish near the Garyville and Mount Airy communities.
The Noranda facility is on the St. James-St. John parish line. Gramercy and the Veterans Memorial Bridge lie in St. James Parish to the complex’s west.
Noranda’s own maintenance work uncovered the problem last year, and Noranda reported it to DEQ. Noranda is under a DEQ compliance order to conduct its own testing to get a better handle on the emissions.
Noranda and DEQ officials have said they believe the amounts are too small to pose a risk to the public or the environment. After requesting an air permit change last year that would have allowed Noranda to emit up to 250 pounds of mercury per year, the second-largest emission in Louisiana in 2013, company officials now say they believe the annual mercury emissions levels will be less than the state minimum standard of 25 pounds per year.
Below that rate, state law views the emissions as insignificant and, on a case-by-case basis, DEQ can choose not to require a permit.
Still, the revelations have sparked concern among residents and business owners and calls for testing independent of DEQ and Noranda. Parish officials in St. James and St. John the Baptist parishes have agreed to share in the cost of testing that a St. James consultant recommends, parish officials have said.
John Parker, Noranda spokesman, said this week that the company believes DEQ is the regulator “best suited to evaluate the extent of mercury air emissions, if any.”
Langley said DEQ is still reviewing Noranda’s testing plans. He said the company submitted additional information last week that DEQ had requested.
Follow David J. Mitchell on Twitter, @NewsieDave.