Nov 22 (Reuters) - For months, North Dakota's Standing Rock Sioux tribe has been protesting the Dakota Access Pipeline's planned crossing under the Missouri River, adjacent to their lands, in part due to worries about contamination of their primary water source.
As of early next year, however, the Native American tribe will be gathering their water 70 miles (113 km) downstream of the oil pipeline's location, thanks to a long-awaited water treatment plant.
The reservation, which spans North and South Dakota, currently gets water 20 miles away from the pipeline's planned location.
While the scope of contamination of a future oil leak is difficult to predict, the distance from the pipeline to the new intake could reduce widespread contamination risks, regulators and environmental analysts said.
The Standing Rock Sioux say the new supply point is not enough to ease their concerns over the pipeline. The developer behind the pipeline, Energy Transfer Partners LP, has vowed not to reroute the line.
"Just because the new intake is 70 miles away doesn't mean our water is still not threatened," said David Archambault, chairman of the Standing Rock Sioux tribe.
The project, which has received little attention in the months-long fight over the Dakota Access pipeline, has been a goal for the Sioux for more than a decade. It was first funded in 2009.
The $3.7 billion Dakota Access pipeline is intended to carry oil from North Dakota to Illinois en route to the Gulf of Mexico. The tribe and climate activists have been protesting for months; a final decision has yet to be reached.
The Sioux received about $30 million from the 2009 American Recovery and Reinvestment Act to build a new water treatment plant, pump station, 5 million-gallon storage tank and several pipelines to feed fresh water to roughly 10,000 reservation residents.
The project has taken years to complete, but federal officials say the timeline was not affected by the Dakota Access controversy.
The existing intake valve is located in a shallow part of the Missouri River near Fort Yates, North Dakota, roughly 20 miles from the planned pipeline river crossing.
The new valve in Mobridge, South Dakota, 70 miles from the pipeline route, came online earlier this year. Once the pipeline system is completed, it will service the entire reservation, according to the U.S. Department of the Interior's Bureau of Reclamation.
The Missouri River typically moves at about 5 to 8 miles per hour in the upper Midwest, meaning it would take nine to 14 hours for oil to reach the tribe's new intake valve.
"The new intake really does effectively reduce the concerns that this oil pipeline could impact the tribe's water supply," said Julie Fedorchak, head of North Dakota's Public Service Commission, which gave state approval to the pipeline.
The U.S. Environmental Protection Agency would not speculate on how a leak could affect the new water system. "Circumstances related to oil releases can vary significantly," said EPA spokesman Richard Mylott.
State officials have repeatedly said they believe the pipeline poses few safety risks.
Regional and federal regulators look to a recent spill as instructive for Standing Rock. In January 2015, an oil pipeline leaked more than 1,000 barrels into the Yellowstone River near Glendive, Montana, forcing officials to flush the city's water treatment pipes after tests revealed hydrocarbons in the water supply.
That would be ominous for the tribe were the Fort Yates intake value to remain, even though Fedorchak and other regulators note the Dakota line is to be buried 92 feet (28 m) below the riverbed in hard clay.
Following the Montana leak, water quality tests in Williston, N.D., roughly 80 miles downstream, showed its water supply was not polluted, as it was able to close intake valves quickly.
Tribal officials said the danger remains. They also say the project's construction has already damaged historical sites with religious significance to the tribe, and further construction could cause more destruction.
"If this pipeline breaks, it's not only going to pollute our drinking water, but destroy the environment," Archambault said. (Reporting by Ernest Scheyder; Editing by Marguerita Choy)