U.S. safety regulators have fined pipeline operator Third Coast $9.6 million for a 2023 oil spill off the coast of Louisiana, marking the agency's largest ever civil penalty.

Third Coast's pipeline leaked 1.1 million gallons of oil into the Gulf of Mexico in November of 2023, as a result of underwater landslides. According to the Associated Press, the U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) determined that Third Coast had failed to address landslide threats prior to the incident, and that the company didn't shut down the leaking pipeline for nearly 13 hours after gauges first indicated that there was an issue.

PHMSA said the civil penalty — which is roughly equal to the combined $8-10 million in fines the agency issues annually on average — reflects both the volume of oil released, and the agency’s findings that the pipeline operator failed to adequately identify and mitigate known geohazard risks. The agency noted that the fine is subject to an administrative process, during which Third Coast can contest the findings or negotiate a settlement before the penalty is finalized.

In a statement to the AP, a Third Coast spokesperson said that the company was "surprised" by the PHMSA's conclusions, and claimed that aspects of the agency's allegations were inaccurate. Conversely, nonprofit watchdog Pipeline Safety Trust labeled the spill a "company-wide systemic failure, indicating the operator's fundamental inability to implement pipeline safety regulations."