Noranda Alumina officials say they believe their nearly 55-year-old refinery in St. James Parish has been releasing mercury into the air without a permit, possibly since operations began in 1959.

The Tennessee-based owners of the once-bankrupt Kaiser Aluminum complex on the Mississippi River are asking state regulators for permission to release up to 250 pounds of mercury per year. That would make the plant one of the largest mercury polluters of Louisiana’s air while Noranda officials figure out what is causing the air releases, state and federal records show.

Noranda officials told the state Department of Environmental Quality in April and May that they believe the mercury is rising from steam vents tied to plant heat exchangers, although DEQ has not permitted the release of mercury into the air from anywhere at the plant.

“If so, the facility has probably always emitted these small amounts of mercury to the atmosphere, and the emissions can be expected to continue into the future,” Noranda Alumina President David P. Hamling wrote to DEQ on May 28.

John Parker, Noranda vice president of communications, said the emissions are not a risk to the public. Company officials have since “been working with DEQ at DEQ’s pace to set up monitoring protocols for this,” he said.

Bryan Johnston, senior environmental scientist in DEQ’s Air Permits Division, said “there is no indication at this point that there is anything to be concerned about.”

But the air permit that Noranda is asking for would make the plant Louisiana’s second largest air emitter of mercury or mercury compounds, according to U.S. Environmental Protection Agency Toxic Release Inventory data. In 2013, the latest year for which data has been reported, only NRG’s Big Cajun II coal-fired plant in New Roads, which released 486 pounds, would have surpassed the 250-pound limit Noranda is now seeking.

“Two-hundred-fifty pounds of mercury per year is not an insignificant amount because mercury is so highly toxic at very low concentrations,” said John Walke, director of the clean air program for the Natural Resources Defense Council, a national environmental group.

The Noranda plant, near the foot of the Veterans Memorial Bridge and across La. 3213 from Gramercy, makes alumina, which feeds the company’s aluminum smelter near New Madrid, Missouri. The alumina also is sold and can be used in industrial catalysts and abrasives, as well as deodorant.

Noranda officials suspect the mercury is coming from bauxite ore, which stains the facility a rust color, and is the source rock from which the plant extracts up to 1.3 million tons of alumina annually. The ore is mined in Jamaica and shipped up the Mississippi River to Gramercy.

Eight months after the company’s first reports of air emissions outside its permit, DEQ officials have not yet issued a compliance order nor a notice of potential penalties. Enforcement officials said they are waiting on information from Noranda, in particular air modeling and information on how long emissions have occurred, and cannot say whether the facility will be fined.

“It is under environmental review and an appropriate order will be issued, I can say, in the very near future,” Celena Cage, DEQ Enforcement Division administrator, said.

She said that in cases like this one, DEQ often starts with putting the company on notice for potential penalties. If DEQ does not issue fines, it will say why in later documents, she said.

Marylee Orr, Louisiana Environmental Action Network executive director, called for the company to be fined if the mercury releases have occurred as Noranda suspects. She said enforcement of environmental laws is vital for public safety, adding that Louisiana has a history of not enforcing regulations.

“Responsible self-reporting should be commended but cannot be a get-out-of-jail-free card,” Orr said in an email.

Mercury is a heavy metal that has been found to be harmful to people and the environment . Some environmentalists say mercury should raise particular concerns, even in small amounts, because it doesn’t break down and accumulates in animals that people eat.

Methylmercury accumulations in fish and shellfish can impair the neurological growth of fetuses, infants and children, the U.S. Environmental Protection Agency website says. According to DEQ reports, one of the sources of mercury in fish in the state comes through airborne deposits in the water.

The Blind River, which runs through St. James Parish, northwest of Gramercy and into Lake Maurepas, and the Petit Amite and Amite River Diversion Canal, which feed into the Blind, are among the bayous, rivers and lakes in Louisiana that DEQ has declared to be impaired due to fish with high concentrations of mercury.

All three have had mercury consumption advisories for choupique or grinnel at least since 2003 or 2004, the state Department of Health and Hospitals says.

DEQ and EPA have been on a decades-long drive to reduce mercury air emissions, primarily from power plants and the chemical industry. Louisiana has seen sizeable decreases, federal pollution reporting data show.

DEQ’s Johnston said that the interim limit Noranda is seeking would be “somewhat significant” for mercury air releases, though likely a sign the company is playing it safe with limits on a future permit.

He said knowing how far mercury releases might travel in the air depends on modeling. Noranda still has to find an appropriate way to measure the mercury emissions.

“That’s ongoing at the plant,” Johnston said.

He said a variety of factors greatly affect the distance of travel, such as stack height and stack temperatures.

At the Gramercy plant, Noranda has long been permitted to release mercury from the ore processing through water or mixed and diluted in massive, leveed-off piles of waste “red mud” on the company’s site in between Airline Highway and River Road, permit records show.

With just those discharges, the Noranda complex is regularly one of the largest emitters of mercury or mercury compounds in Louisiana, federal self-reporting data say.

In 2013, Noranda released 1,803 pounds of mercury, tops in the state. The next highest overall source for mercury or mercury compounds was Mosaic’s Uncle Sam fertilizer plant in St. James at 764 pounds, TRI data say.

Noranda officials told DEQ they had believed all the mercury from the bauxite ore was bound to other chemicals used in its process, and could not escape into the air.

But workers ran across specks of elemental mercury on March 26 in scale that had built up in tubing being replaced for one of the plant’s heaters. Small liquid drops of mercury were also on concrete below the heater.

Parker said company officials quickly shut down maintenance so the mercury could be cleaned up.

Noranda’s Hamling told DEQ that tubing for the heater where the mercury was found had not been replaced since the heater was built 14 years ago. That’s before Noranda obtained a 50-percent stake in the plant in 2004. Noranda now owns it outright.

Past heater tubing replacements have not turned up mercury, Hamling wrote.

He added that testing of steam vents appeared to show mercury concentrations of 0.5 parts per billion.

Though minute — 1 part per billion is equivalent to one drop of water in a swimming pool — even 0.5 ppb would be more than three times the safe eight-hour background level for air, which is 0.145 ppb, DEQ rules say.

DEQ does not enforce that standard, however, until the emissions leave the plant site and would likely be more diffuse, agency officials said.

Hamling also told DEQ that sampling in the steam vents was done with monitors sensitive to heat and moisture, so he counted those results as unreliable.

Follow David J. Mitchell on Twitter, @NewsieDave.