(Reuters) - Energy Transfer Partners LP said on Friday sabotage or an accident might have caused diesel to get into drilling fluid that spilled into an Ohio wetland during construction of its Rover natural gas pipeline, but opponents of the project disagreed with the sabotage theory.
U.S. energy regulators banned ETP from new horizontal directional drilling in May until the company explains how diesel, prohibited under its permit, got into 2 million gallons of drilling fluid that spilled into the Tuscarawas River wetland.
Environmental agencies are probing whether ETP's contractor may have used diesel to lubricate the drill to make it easier to cut through rock when crossing large obstacles like highways and rivers.
ETP said it did not believe the contractor used diesel.
"Rover theorizes that these diesel concentrations could have been caused by an inadvertent and unreported spill or leak from equipment operating during the clean-up, or it could have been the deliberate or malicious act of individuals opposed to the project," the company told FERC in a filing Friday, noting the data was inconclusive.
Despite the drilling ban, the company has said it expects to complete the first phase of the project in late summer and the second phase in November.
Once complete, the $4.2 billion Rover will carry gas from the Marcellus and Utica shale fields in Pennsylvania, Ohio and West Virginia to the U.S. Midwest and Ontario in Canada.
Opponents want the federal government to step up its investigation into ETP's construction practices, noting the company has a history of spills in other states.
"Accusations of sabotage are difficult to believe since the Ohio Environmental Protection Agency (EPA) found diesel in multiple locations," said Terry Lodge, a lawyer in Toledo, Ohio, representing groups opposed to the project.
James Lee, a spokesman for the Ohio EPA, could not say how much diesel was in the drilling fluids but noted traces were found in multiple samples from several locations on different days.
After reviewing the Ohio EPA data and conducting extensive sampling of its own, ETP said it was uncertain about the diesel's source but it does not believe its contractors added the fuel into drilling fluids.
ETP "never requested nor approved of the addition of diesel to the drilling fluids" and said if it discovered a contractor intentionally added such materials, it would "take all appropriate action available under the law."
Reporting by Scott DiSavino in New York; Editing by David Gregorio