The U.S. Federal Energy Regulatory Commission (FERC) halted new drilling Wednesday on the Rover Pipeline until it addresses its 2 million gallon spill of drilling fluids into Ohio wetlands.

The decision was made just days after the Ohio Environmental Protection Agency (EPA) slapped parent company Energy Transfer Partners (ETP) with a $431,000 fine over numerous water and air pollution violations along the route of the $4.2 billion project. ETP is the same company behind the controversial Dakota Access Pipeline, which also happened to leak 84 gallons of oil in South Dakota early last month.

Terry Turpin, director of FERC's Office of Energy Projects, said in a Wednesday letter to the developer that FERC staff has "serious concerns" about the sizable spill, its environmental impacts and the "lack of clarity regarding the underlying reasons for its occurrence, and the possibility of future problems."



The two spills of betonite mud were discovered April 13 and 14 in Stark and Richland County wetlands and was caused by pressure during drilling that allowed mud to rise to the surface, the Ohio EPA said.



Although the mud is nontoxic, officials worry that it could smother wildlife, plants and affect the wetlands' water chemistry.

ETP cannot conduct any new horizontal directional drilling activities until it complies with certain measures to help prevent spills, the FERC letter said.

"The action taken Wednesday by FERC is a step in the right direction," Ohio EPA spokesman James Lee told NBC News.



According to S&P Global Platts, FERC's order affects horizontal directional drilling in eight out of 30 drilling areas associated with the project. The regulators have also required Rover to obtain independent third-party consultants to study the company's drilling plans.

The drilling ban will remain in place until FERC authorizes it to start again. The company can still finish drilling activities it already started or other non-drilling construction work.

"We have received the letter from the FERC. We continue to work with them and the [Ohio Environmental Protection Agency] on a resolution to this matter," Alexis Daniel, Energy Transfer Partners spokeswoman, told Platts.

But Ohio EPA Director Craig Butler told acting FERC chairman Cheryl LaFleur that Rover has "taken the position that Ohio has no authority to enforce violations of its federally delegated state water pollution control statutes, water quality standards or air pollution control statutes ... Ohio EPA strongly disagrees with Rover's position."

The finished 713-mile Rover Pipeline will carry fracked gas across Pennsylvania, West Virginia, Ohio, Michigan and Canada, and crosses three major rivers, the Maumee, Sandusky and Portage, all of which feed into Lake Erie. The pipeline is designed to transport 3.25 billion cubic feet of domestically produced natural gas per day.

ETP said the pipeline will enter service in two phases in July and November.

