The National Park Service wants further review of an oil refinery proposed near North Dakota's Theodore Roosevelt National Park to see how emergency flaring could affect air quality.
The Park Service's request is among about 11,000 emails received by the North Dakota Department of Public Health during a comment period for the refinery's air quality permit, which ended last week.
Meridian Energy Group wants to build the Davis Refinery near Belfield, which is about 5km from the park. The health department is reviewing a permit for a refinery capable of processing 55,000 barrels of oil per day.
An analysis by the National Park Service's Air Resources Division found that the refinery wouldn't significantly impact the park under normal operations, the Bismarck Tribune reported . But the Park Service said more evaluation is needed on the impact of flaring, which could significantly increase emissions.
"Based on our analysis, emissions from the refinery could cause visibility impairment at Theodore Roosevelt NP under upset conditions when blowdown emissions are exhausted through the flares," the Park Service wrote in a letter.
Wendy Ross, the park's superintendent, said the Park Service is also concerned about future impact if Meridian wants to expand.
Meridian Energy Group has said it would be the "cleanest refinery on the planet".
The Environmental Protection Agency has also been involved in the refinery's permit review process. The federal agency submitted technical comments and recommended that the health department analyse air quality impact from phase one of the refinery, which will process 27,500 barrels of oil per day.
Terry O'Clair, director of the health department's air quality division, said reviewing and responding to comments and making a final recommendation will take about two months.
Health officials said that the project's review process has been more rigorous than required because of public interest.