JR American Horse, left, raised his fist with others while leading a march to the Dakota Access Pipeline site in southern Morton County in North Dakota on Sept. 9. (The Minnesota Star Tribune)

Months before folk singer Joan Baez joined protesters near the Standing Rock Reservation in North Dakota, three influential federal agencies had raised serious concerns about the U.S. Army Corps of Engineers' review of the route proposed for a controversial crude oil pipeline.

Letters were sent to the corps, which is charged with approving the Dakota Access pipeline's underground Missouri River crossing, in March by the U.S. Environmental Protection Agency (EPA), the Department of the Interior and the Advisory Council on Historic Preservation. In them, high-ranking officials raised questions about the project's impact on drinking water supplies and emergency responses to spills or leaks. Doubts also were raised about whether the corps had consulted sufficiently with Standing Rock Sioux Tribe, which considers the reservoir and land around the proposed crossing — much of which were once part of the reservation — to have religious significance.

These agencies are not issuing permits for the pipeline in that area. Nevertheless, it is relatively routine for them to weigh in on projects under evaluation. Minnesotans have seen a parallel process play out positively here with the proposed PolyMet copper mine. Feedback provided by the EPA has substantially strengthened the state-led environmental review. The Obama administration's recent decision to temporarily halt construction of the Dakota Access pipeline near the reservation is both a reasonable response to the concerns raised about the project and a chance to bolster its safety and public support.

The pipeline has faced opposition along its 1,172-mile, underground route through four states. Iowa farmers have sued to block it. But the haunting images of American Indian protesters on sunlit prairies amplified environmental and cultural concerns. Their presence is a welcome example of Indian nations flexing their political muscles.

Still, it's important to note that the delay is not a permanent victory. Pipelines are not risk-free but are generally the safest way to transport explosive crude oil. Without pipelines, it is often moved by riskier rail through cities and over waterways — many of them in Minnesota. The additional scrutiny the project's suspension will bring is welcome but could yield answers protesters don't like, such as reassurances about the pipeline's safety, or that an alternative route isn't feasible given that much of pipeline construction in North Dakota is complete.

A recent ruling by a federal judge, which denied the Standing Rock tribe's request for an injunction, may foreshadow that. A key contention by the tribe is that the Army Corps didn't consult with it about historical areas potentially disturbed by the project. But the judge's opinion methodically details the corps' attempts to do so. It is clear the tribe shares responsibility, through delayed replies or canceled meetings, for the unsuccessful communication.

At the same time, the corps appears alarmingly unprepared to deal with the tribe as a sovereign nation. The agency also appears to lack important context in its dealings with the tribe. Standing Rock land was dubiously seized and flooded decades ago during Missouri River damming, a history fueling distrust today. U.S. Rep. Betty McCollum, D-Minn., is calling for reforms to permanently improve agencies' communication with tribes on big projects, a change that merits support.

The pipeline controversy reinforces the risks with continued fossil-fuel reliance. The push to replace them with renewable energy isn't just an environmental concern, it's about public safety, too.