The agency alleged that from 1996 through 2000, Shell modified the plant, significantly increasing SO₂ emissions, without getting a permit requiring emission controls to prevent deterioration of air quality. The agency also alleged that an SO₂ impact analysis was not completed before the plant was modified.

“EPA's mission is to protect public health and the environment,” said Regional Administrator Thomas V. Skinner. “We will take whatever steps are needed to ensure compliance with the Clean Air Act.”

These are preliminary findings of violations. To resolve them, the EPA may issue a compliance order, assess an administrative penalty or bring suit against the company. Merit and Shell had 30 days from receipt of the notice to meet with the EPA to discuss resolving the allegations.

Sour gas is natural gas containing H₂S. Removal of the H₂S produces SO₂ as a byproduct. Exposure to SO₂ can impair breathing, aggravate existing respiratory diseases like bronchitis and reduce the ability of the lungs to clear foreign particles. SO₂ can also contribute to acid rain and fine particle pollution. Children, the elderly and people with existing heart and lung conditions are the most sensitive to the chemical.