With one side refusing to show up, opponents of copper-nickel mining on the edge of Minnesota's pristine wilderness packed a hearing Tuesday in the Twin Cities.

A group of 17 organizations that support the mining proposal boycotted the event, while speakers from a crowd of about 1,000 were unanimous in opposing copper-nickel mining in a watershed on the edge of the Boundary Waters Canoe Area Wilderness and Voyageurs National Park.

It became their night to talk about the beauty and solitude of a wilderness that not only has become a tradition in some families for generations but supports thriving recreational and tourist businesses. One by one, speakers lined up in the event hall at St. Paul RiverCentre, urging federal officials to ban copper-nickel mining, which they say would threaten the northern forests and lakes.

The listening session was the second of three set up to gather public comment. The first hearing in Duluth in March also drew about 1,000, but they included both mine supporters and opponents.

The hearings are part of what may be a three-year study that will determine whether the federal government will ban copper-nickel mining for two decades in the Superior National Forest.

In December, during the waning days of President Barack Obama's administration, the federal government decided not to renew long-standing leases for mineral exploration on federally owned lands in the watershed and opened the longer-term review of whether to allow mining there.

In seeking public opinion, federal officials were inundated with 20,000 comments via e-mail, mail and phone calls during the first 30 days, prompting them to extend the usual 90-day comment period by another 120 days. Since then, federal officials have received "many tens of thousands more," said Jason Kirchner, a spokesman for the U.S. Forest Service.

"The volume of comments tells how important this is to people everywhere," he said.

Those boycotting Tuesday's event say they'll continue to make their case for mining "loud and clear" at a hearing next week in Virginia, Minn.

"Why must the people with the greatest stake, whose jobs and regional economic viability are at risk, have to keep turning out for these charades?" the group said in a statement. "When was the last time federal agencies held a hearing Up North on projects in the Twin Cities, such as the Green Line or St. Croix River Crossing?"

Organizers of the listening session said they were disappointed by the boycott.

"We want to hear from everyone," Kirchner said.

Even proponents of the ban said they were disappointed the other side didn't show up, arguing it perpetuates divisive rhetoric.

"People who support the Boundary Waters are not anti-mining," said Adam Fetcher, a board member for the Save the Boundary Waters campaign. "I recognize that a lot of people are hurting on the Iron Range because of the economic changes. There are a lot of places to mine, just not near the Boundary Waters."

Bob Tammen of Soudan, who spent years working in the mining industry, spoke Tuesday against copper-nickel mining on the edge of the wilderness.

"It's just not worth destroying wetlands, because we don't have a good enough reputation restoring them when things go wrong," he said.

Mining as a method of economic development fails, Tammen said.

"I go back to all the places where I earned a decent paycheck in the mining industry and I don't see towns that are thriving," he said. Instead, automation has slashed mining jobs and towns have suffered as schools close and city parks are overgrown with weeds.

"Mining has failed to create healthy communities," Tammen said.

While mining proponents say the area is in desperate need of more jobs, those in favor of the ban are making a jobs argument as well. Some 200 outdoor businesses, from California-based Patagonia to Ely-based Piragis Northwoods Co., have formed a coalition to argue that northern Minnesota's pristine lakes and forests are an economic engine that deserve protection. Altogether in Minnesota, outdoor recreation generates $11.6 billion in consumer spending and 116,000 jobs, according to data from the national Outdoor Industry Association.

For now, only one company β€” Twin Metals Minnesota, a subsidiary of Chilean mining giant Antofagasta β€” is affected by the ban. It was actively exploring federal lands for copper-nickel as it developed a plan for a $2.8 billion underground mine and waste-storage facilities on the Kawishiwi River just outside the BWCA. Last fall, Twin Metals sued the federal agencies, claiming they had no right to deny the company's renewal of two mineral leases it's held for decades.