Is Dominion underestimating the toxic air pollution from its proposed NC gas storage site?

From Helena Moriah Road, the planned site of the Moriah Energy Center disappears up a dirt driveway and behind a large dirt mound.

Nearby residents and environmental groups are worried about the air pollution that will float over that dirt and into homes along the rural Person County roads if Dominion Energy is allowed to move forward with a planned liquefied natural gas storage facility on the site, near Rougemont.

Dominion plans to build the facility in two phases, with a pair of towering tanks capable of holding up to 25 million gallons of liquefied natural gas, or gas that is cooled down to extremely low temperatures in order to be shrunk and stored more easily. When the gas is needed, Dominion would heat it back up and inject it into a nearby pipeline, with the gas in each tank expanding to as much as two billion cubic feet.

The company is seeking a minor air permit from the N.C. Department of Air Quality, the final approval Dominion needs before it can start construction on the Moriah Energy Center. Emissions come when the facility is heating and cooling gas, but also when it burns off the non-methane chemicals that are removed before the gas is cooled.

Dominion’s calculations of its air pollution likely underestimate how much formaldehyde, acrolein and other toxins will be emitted from the natural gas facility, a coalition of more than a dozen environmental groups told DAQ in a comment letter. Some of those undercounts could be so significant, they said, that Dominion should be required to seek a more stringent major air permit and conduct constant monitoring around the plant.

During a public hearing in early August, dozens of residents from Person County and nearby Durham urged the Department of Air Quality to reject Dominion’s permit. If nothing else, they said, the company should be monitoring the air.

“I was shocked to learn that regular air quality monitoring is not a requirement for this facility. People just assume that air pollution monitoring will be in place to ensure compliance with standards,” Julie Nye, who lives a mile from the site, said at the hearing before asking for “robust, ongoing” monitoring if the permit is not denied.

Questions about formaldehyde levels

Formaldehyde is one of the chemicals environmental groups are particularly concerned about. It was one of four air pollutants for which DAQ required Dominion to model concentrations, along with acrolein, benzene and hexane. All four are toxic.

Dominion had to show its emissions would keep air concentrations in surrounding communities below levels considered dangerous. For formaldehyde, that ambient air level is 150 parts per million averaged over a one-hour period. Dominion’s modeling showed its emissions will peak at 116 ppm over that time frame.

But environmental groups say modeling frequently underestimates toxic air pollutants. If trends hold at the Moriah Energy Center, they told DAQ, formaldehyde and other chemicals could actually be at unsafe concentrations around the Dominion facility.

There are two air monitors that measure formaldehyde from North Carolina industrial facilities, representatives from groups like Appalachian Voices, the Blue Ridge Environmental Defense League, the Environmental Defense Fund and the Person County Community Action Network noted in a comment letter.

Those monitors have measured formaldehyde concentrations that are 1.4 and 1.8 times higher than the maximum shown in the model for nearby facilities, while national data indicates that formaldehyde emissions are usually twice as high as models show.

If Dominion’s formaldehyde emissions are higher by the same proportion as the two other North Carolina facilities, the Moriah Energy Center would cause concentrations in nearby air to be out of compliance with federal standards.

Formaldehyde is a probable human carcinogen , according to the U.S. Environmental Protection Agency, with exposure linked to lung and nasopharyngeal cancer. Exposure to high levels of the chemical can cause coughing, wheezing and irritations of the eyes and throat.

To ensure that ambient air levels remain within acceptable ranges and protect neighboring communities, the environmental groups asked DAQ to require that Dominion pay for third-party monitoring for acrolein and formaldehyde specifically at the facility’s border and in the surrounding community.

“We recommend air monitoring be used as a way to ground truth modeling data,” the groups wrote in a joint public comment letter. “We understand that this is typically required in response to violations of a facility’s permit, but waiting until the community has already been polluted and exposed is unacceptable in our view.”

Dominion insists that its models are based on technical data required by North Carolina air quality officials who then signed off on the company’s estimates.

“Dominion Energy is confident in its air dispersion modeling, which was conducted in accordance with NCDEQ regulations and was submitted to the agency for verification. The modeling demonstrates that the Moriah Energy Center would operate below acceptable ambient levels (AAL), which have been established to be protective of human health,” Persida Montanez, a Dominion Energy spokeswoman, wrote in an email.

In August, researchers from Cornell University, the Environmental Defense Fund and the University of Oklahoma published a peer-reviewed study that found measured benzene levels near refineries were between three and 95 times higher than model predictions based on self-reported emissions during unplanned releases at 14 Texas refineries between 2019 and 2022.

When there are discrepancies between measured and modeled concentrations, that means either the models themselves are flawed or information such as emissions that is being put into the model is inaccurate, Libby Mohr, the Environmental Defense Fund’s petrochemicals team senior data analyst and one of the study’s authors, told The News & Observer. The latter could stem from using flawed methodologies to estimate emissions of a given chemical from a given activity.

“While models are never perfect, we continue to find more and more evidence that emissions are being underestimated in many cases, and that this plays a substantial role in observed discrepancies between measured and modeled pollution levels” Mohr said in an email.

New gas in Person County

The Moriah Energy Center is one of several new natural gas facilities planned for Person County. Dominion is also proposing crossing the county with a new pipeline, although Montanez has consistently said that the new pipeline would not connect with the gas storage facility.

Dominion’s pipeline would include a leg running north to the shore of Hyco Lake , where Duke Energy is proposing closing a coal-fired power plant and replacing it with a pair of gas-fired plants.

Environmental groups have expressed concerns about all of the projects. They note that methane, the primary component of natural gas, is a potent greenhouse gas even if it doesn’t last as long in the atmosphere as carbon dioxide.

Sierra Club estimates found that the use of natural gas from the Moriah Energy Center could cause greenhouse gas emissions equivalent to 1.3 million tons of carbon dioxide, or the annual emissions of about 264,000 gas-powered cars.

“At a time when we need to quickly transition away from fossil fuels, the (Moriah Energy Center) and related gas projects put us further down the road to climate hell,” the environmental groups wrote in their public comment letter.

Effectiveness of flares

Another comment focused on the flare Dominion is proposing to use to burn off chemicals that are removed from the gas before it is cooled.

Ron Sahu, an environmental engineering consultant working for the Environmental Integrity Project, told DAQ that Dominion’s application says the flares will be 98% efficient at burning those chemicals off. But that can change quickly based on winds and chemicals in the so-called waste gas, which can impact a flare’s speed and temperature.

Increasing emissions from the flares could quickly result in the facility having more emissions than allowed under the permit, including of carbon monoxide. Dominion’s draft permit says the facility is capable of 95.76 tons of carbon monoxide emissions annually. At 100 tons, Dominion would need to seek a major permit.

“We note that small changes in control efficiency have a dramatic effect on the emissions. For example, a drop from 98% to 97% in the control efficiency results in a 50% increase in the calculated emissions — this is simply how the math works,” Sahu wrote.

Only by constantly monitoring, Sahu argued, will DAQ be able to ensure that Dominion is remaining within the bounds of its requested permit.

The public comment period has closed, and DAQ is now considering the application.

NC Reality Check is an N&O series holding those in power accountable and shining a light on public issues that affect the Triangle or North Carolina. Have a suggestion for a future story? Email realitycheck@newsobserver.com

This story was produced with financial support from the Hartfield Foundation and Green South Foundation, in partnership with Journalism Funding Partners, as part of an independent journalism fellowship program. The N&O maintains full editorial control of the work. If you would like to help support local journalism, please consider signing up for a digital subscription, which you can do here .