BISMARCK — In a victory for the Standing Rock Sioux Tribe, a federal judge has decided the U.S. Army Corps of Engineers must perform an environmental review of the controversial Dakota Access Pipeline.

The U.S. District Court for the District of Columbia ruled Wednesday, March 25, that the federal agency's previous analysis did not adequately assess the impact of the pipeline on the tribe and others in its path. Judge James E. Boasberg wrote in his decision that too many questions remain about leak detection, the operator's safety record and the possibility of a worst-case spill.

The agency must now do a full "environmental impact statement" on the pipeline. Tribal Chairman Mike Faith said Wednesday's ruling is a "significant legal win" after four years of court battles between the tribe and the agency. A spokesperson from the agency did not immediately respond to a request for comment.

It remains unclear whether the pipeline will be allowed to continue operating while the agency conducts the review, but Boasberg will likely consider briefs submitted by the parties to answer that question.

The original $3.8 billion pipeline project, which crosses under the Missouri River near the tribe's reservation, prompted protests from tribal members and climate activists in 2016 and 2017. The 1,172-mile underground pipeline transports crude oil from the Bakken formation in western North Dakota to central Illinois, from which it is shipped to Midwest and Gulf Coast refineries.

The tribe also announced in a press release Wednesday, March 25, it will not appeal a North Dakota Public Service Commission order that allows pipeline operator Energy Transfer Partners to build a pump station in Emmons County, N.D. The all-Republican commission unanimously approved last month a siting permit for the $40 million pump station that would make it possible to increase the capacity of the pipeline from 570,000 to 1.1 million barrels of oil (23.9 million to 46.2 million gallons) per day.

The tribe intervened in the case last year and wanted the commission to ask the company to hand over documents relating to the risk of an oil spill. The company and tribe butted heads over the proposed expansion at a 15-hour November hearing in Linton. The tribe's witnesses said adding capacity to the pipeline could increase the risk and severity of potential leaks. The company maintained throughout the application process that expansion would help meet consumer demand for North Dakota crude oil without posing any greater risk to the environment or people living along the pipeline.

Commission Chairman Brian Kroshus said last month the board's review of the application was "exhaustive," and in the end, the application met state and federal guidelines.

The tribe said in the release it is not in its own best interest to appeal the state's order, even though it maintains the three-member commission failed to conduct a rigorous review.