The Utah Department of Transportation has made a final decision to convert U.S. 89 into a full freeway in Davis and Weber counties to connect Interstates 15 and 84 — but an upset grass-roots group says it is planning to sue to block it.

UDOT approved and released late Tuesday a final state environmental study, making its decision for the new freeway final. On Wednesday, a group named Residents’ Voice United on 89 (ReVU89) said it plans legal action against that.

UDOT says detailed design and property acquisitions for the project now will proceed. Construction is expected to begin next year and be completed by 2021. It is estimated to cost $275 million.

While the decision is now final, “We’ll continue working closely with the cities and other stakeholder groups, as more detailed design takes place and throughout construction,” said UDOT Project Director Mike Romero.

UDOT plans to widen U.S. 89 from four to six lanes and convert it into a freeway between Shepard Lane in Farmington and I-84 in South Weber. U.S. 89 already essentially is a freeway between Shepard Lane and I-15.

All traffic-signal intersections will be converted into either freeway interchanges or grade-separated crossings.

(Chris Detrick | The Salt Lake Tribune) Traffic on U.S. 89 in Davis County near Cherry Lane Thursday, Aug. 24, 2017.

Existing highway access from some driveways and parking lots will be eliminated, but access in some locations will be preserved via new frontage roads.

Final plans call for the relocation of 22 structures — 20 residences, one business and one municipal water tank.

ReVU89 fought the proposal over the past year, saying that placing a freeway in what is now almost an entirely residential area will ruin communities by attracting a swarm of businesses to interchanges.

It also argues that Kaysville soon will have three parallel freeways — I-15, U.S. 89 and the new West Davis Corridor — separated by only about 4.5 miles. They argued that is poor planning, and it would be wiser to simply widen nearby I-15 instead.

Greg Ferguson, a ReVU89 board member, said his group has retained an attorney and plans legal action to try to stop the freeway. “It’s the only way to get UDOT’s attention about problems, which are numerous.”

He said while UDOT held hearings and accepted comments on the proposal, “nothing really changed.” He said six lanes of freeway plus four lanes of frontage road in some areas “will have 10 lanes carving through the foothills,” increasing air pollution problems.

UDOT said it evaluated alternatives, including those suggested by ReVU89, but concluded that converting U.S. 89 into a freeway “will best meet the purpose and need of the project while minimizing environmental impacts.”

(Chris Detrick | The Salt Lake Tribune) Traffic on U.S. 89 in Davis County near 1400 North, Thursday, Aug. 24, 2017.

UDOT spokesman Vic Saunders said his agency changed plans a bit at residents’ request during the environmental review process.

For example, it will use “noise-dampening pavements to try and reduce highway noise,” Saunders said. Also, “The citizens have asked for us to look into greater landscaping options to provide for a better buffer between the vehicles and the residences.”

UDOT has said that without the project, congestion would increase by 20 percent to 35 percent on the corridor by 2040 — creating peak travel times of one hour from Shepard Lane to I-84. With planned improvements, that same trip in 2040 is projected to take nine to 10 minutes.

The study and an interactive map of the project are available online at