(Reuters) - Ohio regulators have asked the state’s attorney general to pursue civil penalties against Energy Transfer Partners LP for environmental violations during construction of the Rover natural gas pipeline.

The Ohio Environmental Protection Agency said in a filing made available on Monday that ETP violated rules against storm water discharges, industrial waste disposal and the release of bentonite slurry, a clay and water mix, into waterways. One of the spills contained traces of diesel in the slurry, which is not allowed.

“We have been and will continue to discuss these matters with the Ohio EPA in hopes of resolving all outstanding issues,” Alexis Daniel, a spokeswoman at ETP, said in an email.

The $4.2 billion Rover project from Pennsylvania to Ontario is the biggest gas pipeline under construction in the United States.

ETP has long said it expects the first phase of Rover to enter service in late July with the second phase by Nov. 1.

Several energy traders and analysts, however, have said an order by the Federal Energy Regulatory Commission on May 10 banning ETP from new horizontal directional drilling after a spill in Ohio in April could cause delays.

The pipeline will move up to 3.25 billion cubic feet per day of gas from the Marcellus and Utica shale fields in Pennsylvania, Ohio and West Virginia to customers in Ohio, Michigan, Ontario and elsewhere.

One bcf of gas is enough to power about 5 million U.S. homes.

Analysts expect several energy companies to increase gas production once Rover enters service to fill the pipe, including Antero Resources Corp, Eclipse Resources Corp, EQT Corp, Gulfport Energy Corp, Rice Energy Inc, Range Resources Corp and Southwestern Energy Co.