May 7 (Reuters) - Environmental regulators in West Virginia said Energy Transfer Partners LP could restart work on its $4.2 billion Rover natural gas pipeline after ordering the company to stop some work in the state due to permit violations:
* The West Virginia Department of Environmental Protection (DEP) said last week it lifted the March 7 cease and desist order on the Rover Sherwood Lateral on May 2.
* Rover is the biggest gas pipe under construction in the United States. It is designed to carry up to 3.25 billion cubic feet per day (bcfd) of gas from the Marcellus and Utica shale fields in Pennsylvania, Ohio and West Virginia to the U.S. Midwest and Canada's Ontario province.
* One billion cubic feet of gas is enough to fuel about 5 million U.S. homes for a day.
* The latest cease and desist order was not the first time West Virginia stopped ETP from work on Rover. The DEP also ordered the company to halt some work from July 17 to Aug. 9 due to violations of storm water rules.
* In addition, the U.S. Federal Energy Regulatory Commission (FERC) stopped ETP from horizontal drilling in Ohio from May 10 to Sept. 18 after an estimated 2 million gallons of drilling fluid spilled into a wetland near the Tuscarawas River.
* Energy companies use horizontal drilling to cross under obstacles such as rivers and highways.
* Before those stop work orders, ETP expected to finish Rover in November. ETP said it still expects to complete the project by the end of the second quarter of 2018. Rover has been partially in service since August and is now able to transport up to 1.7 bcfd.
* Major producers signed up to use Rover include units of privately held Ascent Resources, Antero Resources Corp, Range Resources Corp, Southwestern Energy Co, Eclipse Resources Corp and EQT Corp.
Reporting by Scott DiSavino Editing by Marguerita Choy