Federal regulators have tentatively approved Utah’s application to build the Lake Powell Pipeline, but they’ve also thrown the state an unexpected curveball.

On Tuesday, the Federal Energy Regulatory Commission (FERC) issued a notice that it had accepted Utah’s application to construct the 140-mile pipeline, intended to pump Colorado River water from Glenn Canyon Dam to St. George and 12 other southern Utah communities. That, FERC said, clears the way for a full study of the project’s environmental impacts.

“This is a major milestone toward meeting Southern Utah’s need to diversify its water supply and develop additional resources to meet anticipated demand,” Eric Millis, director of the state Division of Water Resources, said in a statement. “Permitting a water project is a lengthy process and this is a significant step.”

But FERC also said it was reviewing just how much jurisdiction it actually has over the project — a move that could slow down ultimate approval for the billion-dollar-plus underground pipeline, which is already running behind schedule.

State officials filed the permit application with FERC in 2016 because the Lake Powell Pipeline — at least as currently proposed— is expected to include hydroelectric generating stations along its route through Arizona and Utah. Officials with the Division of Water Resources had long expected that FERC would also be the lead federal agency on the entire project, giving it a key role in obtaining additional permits.

But in its Tuesday notice, FERC said it may only have jurisdiction over the six hydroelectric sites along the route, not the whole pipeline and network of pumping stations and water storage facilities.

If that proves true, it could put Utah more directly in charge of navigating a lengthy review from a host of other federal agencies, forcing additional work on to the Division of Water Resources, which has already spent more than $30 million in taxpayer funds to obtain permits for the pipeline so far.

As proposed, the pipeline would pump water from Lake Powell about 50 miles northwest to a high point within the area of the former Grand Staircase-Escalante National Monument, according to the FERC notice. The water would then flow just under 90 miles downhill through a series of six hydroelectric turbines before arriving at Sand Hollow Reservoir, east of St. George.

Officials with the Division of Water Resources have said they expect the pipeline to cost between $1.1-$1.8 billion.

FERC spokeswoman Celeste Miller said Tuesday the agency had assumed it would not take jurisdiction over the entire water project — just the hydroelectric turbines. She said the commission still planned to produce documentation required by other agencies, such as the National Park Service and the Bureau of Land Management, that have a say in the pipeline’s fate.

A spokesman for the Division of Water Resources said late Tuesday it was unclear exactly what the FERC announcement means, given that state officials had written their application assuming FERC would lead the permitting process,.

While a shift in jurisdiction would not necessarily boost the number of permits Utah officials have to obtain before breaking ground, those permits could be subject to new and different kinds of review if FERC does not play the role state leaders thought, raising the potential for further delays.

Zach Frankel, executive director of the Utah Rivers Council and a long-time opponent of the pipeline, noted that if other agencies play a bigger role in the permitting process, that could subject the pipeline to more in-depth review of whether the project is necessary.

Establishing the purpose and need for a pipeline, said Frankel, will be an important part of the environmental assessment study, which FERC said will be conducted according to the National Environmental Policy Act.

“If it isn’t properly satisfied,” Frankel said, “the courts can rule against an agency” in the event a permitting decision is challenged.

But FERC’s move could also allow the agency to evaluate the pipeline solely with respect to demand for hydroelectricity, and not water — opening the possibility that state officials would not have to prove, as has been asserted, that the pipeline is necessary to prevent southwestern Utah from running out of water.

“By not considering the rest of the project features, it could be easier to approve,” Frankel said in an email. “It’s not a slam dunk for anyone.”