Utah’s proposed Lake Powell pipeline had been on a fast track for approval, but on Thursday state water officials asked the Interior Department to slow down the controversial billion-dollar project’s review.

The state cited as a reason the 14,000 public comments submitted in response to a draft environmental impact statement (EIS) released in June.

The U.S. Bureau of Reclamation was supposed to have the final EIS out by November, with a final decision in January, but that ambitious time frame is expected to be pushed back while a “supplemental” analysis is conducted, according to Todd Adams, director of the Utah Division of Water Resources.

“The extension will allow more time to consider the comments and complete further analysis, which will contribute to a more comprehensive draft and final EIS,” he said. “When you think about the sheer volume of comments, it’s going to take some time.”

Among those comments was a bombshell request by the six other states that rely on the Colorado River for water to refrain from completing the EIS until the states work out their differences regarding the legality of diverting the water across major drainages.

In the works since at least 2006, the pipeline would move 86,000 acre-feet of Colorado River water 143 miles from Lake Powell to St. George to meet future demand in Utah’s rapidly growing southwest corner, between Las Vegas and Salt Lake City.

Fearing the project would deplete an already over-allocated Colorado River, critics contend Washington County can make do with its existing water resources if it embraces conservation measures that have been successfully implemented by other desert southwest metro areas.

“The Bureau [of Reclamation] comes out with a draft that says, ‘We [in Washington County] need another source of water,’ but they don’t say why. The EIS failed to consider a water conservation alternative,” said Zach Frankel of the Utah Rivers Council

Frankel and other pipeline critics speculated that commenters or higher-ups in the Interior Department had identified “fatal flaws” in the draft study that could render the pipeline’s approval vulnerable to legal challenges that are sure to follow.

“The delay of the environmental review affirms that Nevada and the other Colorado River Basin States are having an impact in this process against Utah,” said Tick Segerblom, who represents Las Vegas suburbs on the Clark County Commission. “With climate change and drought threatening us every day, we must be vigilant until the end. We cannot let our water supply be sucked away for golf courses and green lawns in southern Utah.”

Officials, however, declined to identify any alleged flaws in the draft analysis, but the state’s letter Thursday to the Bureau of Reclamation alluded to the interstate controversy over the project.

“We remain committed to working in good faith with the Colorado River Basin states to resolve legal and operational concerns regarding the Colorado River,” states the letter signed by Adams and Zach Renstrom, general manager of the Washington County Water Conservation District. “We have a history of solving complex challenges associated with the river and will continue to work together.”

That sentiment echoed what Interior Secretary David Bernhardt and Utah Gov. Gary Herbert said on the matter last week when asked at a ceremony they headlined at the Utah Capitol.

“We deal with a lot of complex things and we’ll deal with this one,” Bernhardt said. “The reality, however, is that the basin states have worked cooperatively in a wonderful way for nearly 70 years.”

Marlon Duke, a spokesman in the Bureau of Reclamation’s Utah office, said it was too early to specify a revised time frame for a decision on the pipeline.

“We want to make sure the final is as thorough and robust as possible,” Duke said. “We are looking forward to addressing those comments. We will be working with the state to develop an updated timeline.”