"We plan to begin drilling immediately," a spokeswoman for Energy Transfer Partners, the company building the pipeline, told BuzzFeed News.

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The US Army Corps of Engineers has granted an easement to begin construction of the Dakota Access pipeline, a controversial project that was slowed down with court challenges and protests.

The easement was granted Wednesday after the Army Corps told a federal court and members of Congress that it intended to do so, and that it would bypass the customary 14-day waiting period to move quickly on the project.

"We plan to begin drilling immediately," a spokeswoman for Energy Transfer Partners, the company building the pipeline, told BuzzFeed News. The decision came just days after President Trump signed an executive order to continue construction of the pipeline, despite months of tense protests in North Dakota, where the pipeline remains unfinished. "With this action, Dakota Access now has received all federal authorizations necessary to proceed expeditiously to complete construction of the pipeline," Energy Transfer Partners said in a statement.

Thousands of protesters, including members of the Standing Rock Sioux Tribe, have camped at Standing Rock to stop the building of the 30-inch underground pipeline, which will carry light crude oil. Their main dispute involves a portion that is to be placed under Lake Oahe.

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Opponents of the pipeline won a short-lived victory in December when the US Army Corps of Engineers announced it would not grant an easement. The Standing Rock Sioux Tribe said it was "undaunted in its commitment" to challenge the pipeline in a written statement. "We are a sovereign nation and we will fight to protect our water and sacred places from the brazen private interests trying to push this pipeline through to benefit a few wealthy Americans with financial ties to the Trump administration," Dave Archambault II, chairman of the tribe, said in a statement. "The environmental impact statement was wrongfully terminated." When the Army announced it would not grant an easement in December, then-Assistant Army Secretary for Civil Works Jo-Ellen Darcy said the decision was based on a need to look for alternative routes. But in a court filing Tuesday, the US Army Corps of Engineers signaled it was ready to reverse course and get construction of the pipe underway. In a letter to members of Congress delivered Tuesday, the Department of the Army said it was waiving its usual 14-day waiting period from its notice of Congress before issuing the easement. The current acting assistant Army secretary for civil works, Douglas W. Lamont, said in a memorandum attached to the court filing that he determined "there is no cause for completing any additional environmental analysis" of the pipeline. The Army's decision to grant the easement was expected after Trump issued an executive order to continue with construction of the Dakota Access and Keystone pipelines in January. After the executive order was signed, opponents of the pipeline appeared ready for another confrontation.

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In a statement issued Wednesday, the US Army Corps of Engineers said it was "working with the Tribes and local law enforcement to restore the land to its pre-protest state and to mitigate the potential harm of debris, trash and untreated waste in the former protest site as the threat of spring flooding poses a risk to environmental impacts."

Opponents of the pipeline, however, argue an environmental study of the possible impacts of the pipeline is needed before any construction is begun, which is expected to include a section spanning 1.25 miles under the Missouri River. "Trump's reversal of the previous commitments to conduct and [sic] Environmental Impact Statement on the Dakota Access Pipeline is as sickening as it is predictable," Friends of the Earth president Erich Pica said in a statement. The organization said it was ready to help the tribe "put financial pressure on the banks" to stop the construction. Amnesty International also criticized the decision to not seek out an environmental study before issuing the easement. "This is an unlawful and appalling violation of human rights," the organization said in a statement. "The United States is obligated under international law to respect the rights of the Standing Rock Sioux Tribe and all other Indigenous Peoples." Amnesty plans to send human rights observers to the construction site in anticipation of additional protests there. Jan Hasselman, attorney for the Standing Rock Sioux Tribe, suggested it would continue work to stop the pipeline through the courts. "The Obama administration correctly found that the Tribe's treaty rights needed to be respected, and that the easement should not be granted without further review and consideration of alternative crossing locations," Hasselman said in a statement. "Trump's reversal of that decision continues a historic pattern of broken promises to Indian Tribes and violation of Treaty rights. They will be accountable in court." The Standing Rock Tribe is expected to challenge the decision on the grounds that the environmental study was wrongfully terminated, it said. Energy Transfer Partners said it expects the Dakota Access pipeline to be in service by summer of this year.