Near Cannon Ball, North Dakota (CNN) The fight against the Dakota Access Pipeline -- the $3.8 billion project expected to move 470,000 barrels of crude oil a day across the Midwest -- lasted long enough for the summer heat to give way to thick, white snow.

For months, Standing Rock Sioux tribe members and their allies battled the energy project they referred to as a "black snake." They stood in the path of the pipeline both during peaceful actions and clashes with authorities that turned violent.

On Sunday afternoon, tribe members and their allies cried tears of joy after the US Army said it would not -- for now -- allow the pipeline to cross under Lake Oahe in North Dakota.

The Army says the plan should be carefully restudied, and alternative routes should be more deeply considered

The Army's statement does not rule out approval for the current plan in the future. And with President Obama leaving office in January, many questions still remain about what's next for the project.

Phil Little Thunder Sr. attends an evening gathering at an encampment of Dakota Access Pipeline protesters on September 3.

Phil Little Thunder Sr. attends an evening gathering at an encampment of Dakota Access Pipeline protesters on September 3.

Flags of Native American tribes from across the United States and Canada line the entrance to a protest encampment on Saturday, September 3.

Flags of Native American tribes from across the United States and Canada line the entrance to a protest encampment on Saturday, September 3.

The Missouri River is seen beyond an encampment near Cannon Ball, where hundreds of people gathered to join the protest on September 4.

The Missouri River is seen beyond an encampment near Cannon Ball, where hundreds of people gathered to join the protest on September 4.

Native Americans ride with raised fists to the sacred burial ground on September 4 to protest the Dakota Access Pipeline.

Native Americans ride with raised fists to the sacred burial ground on September 4 to protest the Dakota Access Pipeline.

Native Americans march to the site of a sacred burial ground on September 4.

Native Americans march to the site of a sacred burial ground on September 4.

Protesters march on September 4 in opposition to the Dakota Access Pipeline.

Protesters march on September 4 in opposition to the Dakota Access Pipeline.

Marlo Langdeau of the Lower Brule Sioux Tribe joins hundreds of Native Americans for a march near Cannon Ball on Sunday, September 4.

Marlo Langdeau of the Lower Brule Sioux Tribe joins hundreds of Native Americans for a march near Cannon Ball on Sunday, September 4.

People hang a sign near what they say was sacred burial ground disturbed by bulldozers in Cannon Ball.

People hang a sign near what they say was sacred burial ground disturbed by bulldozers in Cannon Ball.

Native Americans head to a rally at the state capitol in Denver on Thursday, September 8. They were showing their support for members of the Standing Rock Sioux tribe in North Dakota opposting the Dakota Access Pipeline.

Native Americans head to a rally at the state capitol in Denver on Thursday, September 8. They were showing their support for members of the Standing Rock Sioux tribe in North Dakota opposting the Dakota Access Pipeline.

A protester shows where he was hit by a bean-bag round fired by officers trying to force protesters off the private land.

A protester shows where he was hit by a bean-bag round fired by officers trying to force protesters off the private land.

Tires burn as armed soldiers and law enforcement officers stand in formation to force Dakota Access Pipeline protesters off the private land in Morton County.

Tires burn as armed soldiers and law enforcement officers stand in formation to force Dakota Access Pipeline protesters off the private land in Morton County.

A protester is arrested as law enforcement surrounds the camp on October 27.

A protester is arrested as law enforcement surrounds the camp on October 27.

Pipeline protesters sit in a prayer circle as a line of law enforcement officers make their way across the camp to relocate the protesters a few miles south on Thursday, October 27. Protesters had camped on private property.

Pipeline protesters sit in a prayer circle as a line of law enforcement officers make their way across the camp to relocate the protesters a few miles south on Thursday, October 27. Protesters had camped on private property.

The burned hulks of heavy trucks sit on Highway 1806 on Friday, October 28, near a spot where Dakota Access Pipeline protesters were evicted a day earlier.

The burned hulks of heavy trucks sit on Highway 1806 on Friday, October 28, near a spot where Dakota Access Pipeline protesters were evicted a day earlier.

Cousins Jessica and Michelle Decoteau take part in a protest outside the North Dakota state capitol in Bismarck on October 29.

Cousins Jessica and Michelle Decoteau take part in a protest outside the North Dakota state capitol in Bismarck on October 29.

Tribe members make their way back to their camp on Saturday, October 29.

Tribe members make their way back to their camp on Saturday, October 29.

Dozens of protesters wade in cold creek waters as they confront local police on November 2.

Dozens of protesters wade in cold creek waters as they confront local police on November 2.

Tonya Stands recovers after being pepper-sprayed by police on Wednesday, November 2. Stands was pepper-sprayed after swimming across a creek with other protesters hoping to build a new camp to block construction of the Dakota Access Pipeline.

Tonya Stands recovers after being pepper-sprayed by police on Wednesday, November 2. Stands was pepper-sprayed after swimming across a creek with other protesters hoping to build a new camp to block construction of the Dakota Access Pipeline.

In this image provided by the Morton County Sheriff's Department, law enforcement and protesters clash near the pipeline site on Sunday, November 20.

In this image provided by the Morton County Sheriff's Department, law enforcement and protesters clash near the pipeline site on Sunday, November 20.

People protest along Highway 1806 as they walk past a sprawling encampment on Thursday, November 24.

People protest along Highway 1806 as they walk past a sprawling encampment on Thursday, November 24.

A sculpture stands at an encampment where protesters of the pipeline have been gathered for months.

A sculpture stands at an encampment where protesters of the pipeline have been gathered for months.

People against the construction of the Dakota Access Pipeline speak at a news conference near Cannon Ball on Saturday, November 26.

People against the construction of the Dakota Access Pipeline speak at a news conference near Cannon Ball on Saturday, November 26.

A procession makes its way down to the Cannonball River to take part in a Native American water ceremony on December 1.

A procession makes its way down to the Cannonball River to take part in a Native American water ceremony on December 1.

Dan Nanamkin of the Colville Nez Perce tribe drums a traditional song by the Cannonball River in Cannon Ball, North Dakota, on Thursday, December 1.

Dan Nanamkin of the Colville Nez Perce tribe drums a traditional song by the Cannonball River in Cannon Ball, North Dakota, on Thursday, December 1.

Activists celebrate at Oceti Sakowin Camp on December 4. An executive order by President Donald Trump in January allows work to resume on the Dakota Access Pipeline, which the activists oppose.

Activists celebrate at Oceti Sakowin Camp on December 4. An executive order by President Donald Trump in January allows work to resume on the Dakota Access Pipeline, which the activists oppose.

An activist rides down from a ridge on the edge of the Standing Rock Sioux Reservation on December 4.

An activist rides down from a ridge on the edge of the Standing Rock Sioux Reservation on December 4.

Activists embrace after the December halt of the Dakota Access Pipeline route. The $3.7 billion project that would cross four states and change the landscape of the US crude oil supply. The Standing Rock Sioux tribe says the pipeline would affect its drinking-water supply and destroy its sacred sites.

Fireworks lit the sky at the Oceti Sakowin Camp near Cannon Ball, North Dakota on December 4, 2016, after the Army Corps of Engineers halted the Dakota Access Pipeline route. An executive order by President Donald Trump in January allowed work to resume.

Fireworks lit the sky at the Oceti Sakowin Camp near Cannon Ball, North Dakota on December 4, 2016, after the Army Corps of Engineers halted the Dakota Access Pipeline route. An executive order by President Donald Trump in January allowed work to resume.

Why are Native American leaders celebrating?

Tribe members say that an oil spill at the lake would contaminate their water supply. The tribe's reservation lies a half-mile south of the proposed crossing location.

They also say that the construction would cut through sacred land and destroy burial sites.

The Army's announcement Sunday afternoon came one day before a looming deadline for protesters. North Dakota's governor had ordered protesters to leave their campsite by Monday, citing harsh weather conditions.

The Army Corps of Engineers also had warned that activists could be arrested if they hadn't left by Monday, but the agency later said it had no plans to forcibly remove those who stayed.

As the deadline approached, protesters prepared to stand their ground in the face of a potential forced removal. After hundreds had camped out at Standing Rock for months, thousands of reinforcements -- including US military veterans -- had flocked to area over the past week in a show of solidarity.

A protester demonstrates in solidarity with the Standing Rock Sioux tribe in North Dakota over the construction of the Dakota Access oil pipeline in Philadelphia.

"People have said that this is a make it or a break it, and I guess we made it," Chief Arvol Looking Horse, Keeper of the White Buffalo Calf Pipe.

Is this the end of Dakota Access Pipeline?

Far from it. For now, Jo-Ellen Darcy, the Army's assistant secretary for civil works, said in her letter to the Corps that the proposed crossing at Lake Oahe requires more analysis, including a deeper consideration of alternative routes.

"A more robust analysis of alternatives can be done and should be done ... before an easement is granted for the Dakota Access Pipeline to cross the Missouri River on Corps land," Darcy wrote.

The US Energy Information Administration shows the network of existing crude oil pipelines across the country.

Darcy called for the creation of an official environmental impact statement , a months-long process that would allow the public to weigh in.

She did not announce a timetable.

Where might the pipeline go instead?

It's not exactly clear. Darcy did not propose alternate routes.

Her letter noted that one previously proposed alternative -- having the pipeline cross the Missouri River about 10 miles north of Bismarck, the state capital which itself is well north of Lake Oahe -- was eliminated early in the planning phase.

The current proposed route would stretch 1,172 miles from North Dakota into South Dakota, slithered through Iowa and ended in southern Illinois.

JUST WATCHED Officials: Pipeline will be re-routed Replay More Videos ... MUST WATCH Officials: Pipeline will be re-routed 01:29

Energy Transfer Partners and Sunoco Logistics Partners, the corporations behind the Dakota Access Pipeline, said in a statement Sunday night they "fully expect to complete construction of the pipeline without any additional rerouting in and around Lake Oahe."

"Nothing this Administration has done today changes that in any way," the company said in a statement.

Is the fight over at Standing Rock?

While Sioux supporters may have celebrated a huge victory Sunday, they're already looking ahead toward potential fights ahead over the pipeline.

"So it feels good I'm really happy that I'm here to witness it and celebrate with a lot of my elders and the youth, but I think that we also need to keep in mind that we need to be ready to keep going," protester Morning Star Angeline Chippewa-Freeland said.

Iktce Wichasa Oyate, a small group that has provided security for protesters, called the decision Sunday nothing more than a "delay tactic" designed to "diffuse the power of the camp." They now hope the project gets stopped entirely before a new plan under a new administration gains traction.

"The snake is trying to move from the open field, to the tall grass," the group said in a Facebook post. Watch it carefully, there will be a new snake handler soon."

JUST WATCHED Protester: 'It will be a battle' Replay More Videos ... MUST WATCH Protester: 'It will be a battle' 02:16

President Obama is about to leave office. What happens with Trump?

Tribal leaders worry the Army's current openness to alternate routes could end with the incoming Trump administration.

"More threats are likely in the year to come, and we cannot stop until this pipeline is completely and utterly defeated, and our water and climate are safe," Dallas Goldtooth, lead organizer for the Indigenous Environmental Network, said in a statement.

Likewise, May Boeve, executive director of the environmental group 350.org, warned pipeline opponents.

"If Trump tries to go up against the leaders at Standing Rock he'll just end up looking petty and small," she said. "The fight against Dakota Access has fired up a resistance movement that is ready to take on any fossil fuel project the Trump administration tries to approve. On Dakota Access and every other pipeline: If he tries to build it, we will come."

Jason Miller, spokesman for the transition team of President-elect Donald Trump, said Monday that the pipeline is generally "something that we support construction of." The Trump administration will review the matter after the inauguration, Miller said.