The U.S. Federal Energy Regulatory Commission (FERC) on Dec. 16 ordered Energy Transfer Partners LP and its Rover Pipeline LLC unit to explain why the company should not pay a $40 million civil penalty for alleged violations during construction of a 711 mile-long interstate natural gas pipeline in Ohio.

An investigation by FERC’s Office of Enforcement concluded that Rover Pipeline included diesel fuel and other toxic substances and unapproved additives in the drilling mud during its horizontal directional drilling (HDD) operation under the Tuscarawas River in Stark County, Ohio.

In April 2017, shortly after Rover began its HDD operation, a large inadvertent release of 2 million gallons of drilling mud reached the ground surface and flowed into a nearby protected wetland, FERC said.

Testing conducted by the Ohio EPA found petroleum hydrocarbons consistent with diesel fuel, it said.

Energy Transfer Partners and Rover have 30 days to respond to the Commission’s show cause order.

The companies were not immediately available for comment.

Onshore