BISMARCK, N.D. (AP) — The U.S. Army Corps of Engineers on Friday completed more than a year of additional study of the Dakota Access oil pipeline, saying the work substantiated its earlier determination that the pipeline poses no significant environmental threats.

U.S. District Judge James Boasberg in June 2017 ruled that the Corps “largely complied” with environmental law when permitting the $3.8 billion, four-state pipeline built by Texas-based Energy Transfers Partners.

However, the judge also ordered more study because he said the agency didn’t adequately consider how an oil spill under the Missouri River might affect the Standing Rock Sioux tribe’s fishing and hunting rights, or whether it might disproportionately affect the tribal community — a concept known as environmental justice.

It aims to ensure development projects aren’t built in areas where minority populations might not have the resources to defend their rights.

The pipeline has been operating since June 2017, moving oil from North Dakota through South Dakota and Iowa to a distribution point in Patoka, Illinois, from which it can be shipped to the Gulf Coast and potentially lucrative markets abroad.

It has the capacity to move half of the oil produced daily in North Dakota, the nation’s second-leading producer behind Texas.