La Plata County is growing. So is the Southern Ute Indian Tribe community.

That realization led officials with the tribe, Colorado Department of Transportation, La Plata County and Ignacio to spend nearly six years working on a joint planning effort addressing the impacts of current and future growth on Colorado Highway 172.

The effort, initiated by the tribe, came to a close Wednesday with the ceremonial signing of an intergovernmental agreement that pulls together each of the four entities in a plan that addresses future access and management on the highway corridor, county documents said.

Local and tribal officials have called the arrangement a “landmark” project, as it is the first time those agencies all have come together for such an “extensive transportation planning project,” county documents said.

The study looked at parts of Highway 172, County Road 517 and Colorado Highway 151.

About a dozen needed improvements along or near Highway 172 have been identified, said Jim Davis, director of La Plata County public works.

The agencies shared the $300,000 cost of the planning, and the cost-sharing arrangement for future improvement and construction efforts along the corridor will be determined as needs and grant opportunities arise, Davis said.