The EPA fined Enterprise Crude Pipeline $5,000 for a 100-barrel spill into Bull Creek, a tributary of the Colorado River.
The river is a key waterway for the U.S. south. Texas, and much of the United States, is struggling with lingering drought. Parts of the United States haven't had significant rainfall in more than a month.
The fine was imposed for violations of the Clean Water Act, which prohibits the discharge of oil or other potentially hazardous substances into U.S. waterways or adjoining shorelines.
Enterprise operates more than 5,000 pipelines in the United States.
"As part of an expedited settlement with the EPA, the company has certified it has investigated the cause of the oil spill, cleaned up the oil spill and has taken corrective actions that will prevent future spills," the environmental agency stated.