PROVO — A group hoping to tackle pollution at Utah Lake envisions building an island city there that could house up to 500,000 people.

Todd Parker, project director with Arches Utah Lake, says the idea isn't far-fetched.

The proposed islands would mirror Utah's iconic Delicate Arch in Arches National Park to offer a place for floating ice to pile up without damaging the shore and surrounding area, Parker said.

The plan could also help guard against potentially toxic algal blooms and E. coli that have plagued the lake in recent years, he said, and remove invasive grasses and nonnative carp.

The group would first seek to rehabilitate the water that has had a difficult history before building 10 to 15 years later, Parker said.

His proposal comes almost a year after lawmakers approved a symbolic resolution, HCR26, to encourage aggressive treatment for Utah's largest freshwater lake.

When the Provo River was diverted to water orchards in Orem decades ago, thousands of June sucker fish there died, he said. Nonnative European carp were brought in, but they uprooted plants on the lake floor. High levels of phosphorous and nitrogen have made it difficult to restore the lake to balance.

"You get these issues that happen year after year for 100 years, and the lake becomes impacted," Parker said.

Arches Utah Lake wants to dredge the lake and use its own sand to build the city, but would first need approval from Utah lawmakers. And Parker says he's confident the $6.4 billion price tag would be covered by private funding.

The project would include 76 miles of restored shoreline, plus 190 miles of new shoreline and nine marinas, he said.

For the early phases, Parker said he hopes schools, families and communities will have a hand in tackling pollution.

"I hope that there's excitement about participating in the restoration of the lake," he said. "That's what it's going to take."

Contributing: Annie Knox, Andrew Adams