May 10 (Reuters) - U.S. natural gas pipeline venture

Mountain Valley Pipeline said on Friday it repaired a segment of

pipe that failed a water test earlier in the month and will

continue to prepare the long-delayed West Virginia-Virginia pipe

for service.

The venture was on track to complete the $7.85 billion

project by the end of May, U.S. energy firm Equitrans Midstream ( ETRN )

, the lead partner in the Mountain Valley venture, said

in late April.

Mountain Valley made its latest comments about the pipe

repair in a filing with the U.S. Federal Energy Regulatory

Commission (FERC) on Friday.

Mountain Valley said that as of April 30, it had

successfully completed hydrostatic testing for 269 miles of the

project's 303-mile route.

Hydrostatic testing involves the use of water to pressure

test the pipe for a specified time period, exposing all pipeline

components to a pressure that exceeds the maximum allowable

operating pressure to ensure all components will operate safely

prior to the introduction of gas into the pipe, Mountain Valley

said in the FERC filing.

Mountain Valley said it notified federal and state agencies

on May 1 of a hydrostatic testing failure at milepost 245.95.

Since then, the company said it "has successfully performed

hydrostatic testing on additional segments, including the

repaired segment where the disruption occurred, without

incident."

Mountain Valley is the only big gas pipeline under

construction in the U.S. Northeast. It has encountered numerous

regulatory and court fights that have stopped work several times

since construction began in 2018.

The pipe, which is key to unlocking gas supplies from

Appalachia, the nation's biggest shale gas-producing region,

needed a bill from the U.S. Congress that was signed into law by

the president and help from the Supreme Court before it could

restart construction.

Environmentalists have said that the project would harm soil

and water quality in the forest, increase the use of natural

gas, a leading fossil fuel and greenhouse gas emitter, and

stymie efforts to address climate change threats.

When Mountain Valley started construction in February 2018,

Equitrans estimated the 2.0-billion cubic feet per day project

would cost about $3.5 billion and enter service by late 2018.

The 303-mile (488-kilometre) Mountain Valley project is

owned by units of Equitrans, the lead partner building the pipe

with a roughly 49% interest, NextEra Energy,

Consolidated Edison ( ED ), AltaGas ( ATGFF ) and RGC Resources ( RGCO )

. Equitrans will operate the pipeline.