RIVERTON — More than a year after the first iteration of the nearly 8,800-unit, 930-acre Olympia Hills development near Herriman shocked and infuriated southwest Salt Lake County residents, a gathering Monday marked a sort of “Kumbaya” moment between city mayors and county officials.

The same people who clashed over Olympia Hills before Salt Lake County Mayor Ben McAdams vetoed the project all met in the same room Monday to begin a new endeavor to plan the future of Salt Lake County’s southwest — owning up to past mistakes that have contributed to messy growth and gridlocked traffic and looking ahead with the goal to do better.

”We could not feel stronger that we have to get this right,” South Jordan Mayor Dawn Ramsey said to a room full of elected officials, regional planners, developers gathered in a conference hall at Intermountain Riverton Hospital.

”This is the last opportunity we have to plan for the building out of Salt Lake County,” she said.

The coalition of southwest mayors — from Riverton, South Jordan, Herriman, West Jordan, Bluffdale and Copperton — and Salt Lake County leaders including Mayor Jenny Wilson came together to launch a roughly yearlong study to guide the future planning of Salt Lake County’s southwest, where the county’s last swath of undeveloped land awaits.

Monday marked the kickoff for the 12- to 13-month effort after both Salt Lake County and southwest cities have contributed to pay for the $250,000 for the study. Consultants from the firm Logan Simpson were hired to help guide the regional plan. Wasatch Front Regional Council is also playing a part.

Logan Simpson has provided “environmental consulting, cultural resources, community planning and landscape architecture design services” in Western states for the past 20 years with a stated goal to “help guide responsible change,” according to its website.

Monday’s meeting came after the dust has somewhat settled over the initial approval of Olympia Hills, which has now morphed into more scaled-down version that’s awaiting consideration once again by county officials.

The controversial project — initially so high-density some said it could have brought more than 30,000 people to 930-acres — sparked concern among the county’s southwest mayors and an eagerness to do more to collaboratively plan the future of the area.

Traditionally, cities have “competed against each other” when it comes to development, said Herriman Mayor Pro Tem Jared Henderson. But decades later, as cities have grown, “we’ve not only reached each other’s borders; we’re overlapping.”

”That’s created a compounding effect on infrastructure,” Henderson said, pointing to worsening east-west traffic gridlock as more and more neighborhoods and multi-family developments crop up in a dwindling amount of open southwest land.

Riverton Mayor Trent Staggs said since the year 2000, more than 160,000 residents have lived in southwest Salt Lake County, representing about 70% of the county’s population growth since that year. As a result, the area has seen a “flurry” of housing development of all types to accommodate the growth, he said.

”The collective impacts of our respective land-use decisions coupled with the lack of coordinated regional planning efforts for the last few decades by state county and city leaders have brought us to a near infrastructure crisis today,” Staggs said. “The impacts of traffic congestion are perhaps the most apparent.”

Meanwhile, “legitimate concerns over the availability of water, stormwater, sewer” and school populations overshadow rapid development, continuing to worry local elected officials when thinking about their communities future, Staggs said.

Their shared goal, Staggs said, is to “think regionally, act locally.”

Wilson — who served on the County Council when Olympia Hills was first approved — attended Monday’s meeting, applauding southwest mayors “who have decided to address growth in a responsible way by joining together.”

”We all know this area has faced significant growth over the past several years, and it is easy to see why,” Wilson said. “One comes to this part of the valley for the beauty, the sense of community and the high quality of life.”

Wilson said county and city officials are “working collaboratively for solutions” through the study. Salt Lake County also hosted a “growth summit” series of public meetings to study the needs of the southwest region.

”All of our answers will not be found within the results of this study, but rather, a collaboration that comes from city, county and state officials working together to put our resources where they are needed,” Wilson said.

Logan Simpson will be launching the study — welcoming one-on-one interviews from all stakeholders — while gathering data to set a “baseline” on the current conditions of the southwest area. Data will guide recommendations after the study’s conclusion, said Bruce Meighen, a principal at Logan Simpson.

”I’ll tell you right now, this is unprecedented,” Meighen told the mayors, adding that the willingness to work together “gives me a lot of faith” in the regional plan.