Nov 28 (Reuters) - EQM Midstream Partners LP said on Wednesday it still expected to complete the $4.6 billion Mountain Valley natural gas pipeline from West Virginia to Virginia in the fourth quarter of 2019 despite a legal opinion explaining why an appeals court vacated a water permit for the project.
The U.S. Court of Appeals for the Fourth Circuit issued the opinion late Tuesday explaining why it sided with environmental groups in October and decided to vacate the so-called Nationwide Permit 12 that allows the pipeline to cross rivers in West Virginia.
In the opinion, the court said the project's proposed construction methods violated a special condition put forward by West Virginia, requiring stream crossings to be completed within 72 hours.
The court also pointed to another special condition requiring projects to obtain state water quality certification for pipelines bigger than 36 inches (91.4 centimeters) in diameter. Mountain Valley has a 42-inch pipeline.
West Virginia is in the process of modifying the special conditions to allow Mountain Valley and another gas pipe, Dominion Energy Inc's Atlantic Coast, to move forward.
Analysts at Height Capital Markets in Washington said they expect West Virginia's Department of Environmental Protection to issue the modified special conditions by the end of year, allowing Mountain Valley to seek a new permit from the Army Corps.
"If all agencies move quickly, Mountain Valley could have all permits reinstated by mid-2019, leaving just enough time to finish the project by the end of 2019," analysts at Height Capital Markets said in a report.
Mountain Valley is one of several pipelines under construction to connect growing output in the Marcellus and Utica shale basins in Pennsylvania, West Virginia and Ohio with customers in other parts of the United States and Canada.
When EQM started construction in February, it originally estimated the project would cost about $3.5 billion and be completed by the end of 2018.
The 303-mile (488-kilometer) pipeline is designed to deliver 2 billion cubic feet per day of gas to meet growing demand for the fuel for power generation and other uses in the U.S. Southeast and Mid-Atlantic.
One billion cubic feet is enough gas to supply about 5 million U.S. homes for a day.
Mountain Valley is owned by units of EQM, NextEra Energy Inc , Consolidated Edison Inc, AlatGas Ltd and RGC Resources Inc. EQM will operate the pipeline and owns a significant interest in the venture.
(Reporting by Scott DiSavino; Editing by Richard Chang)