GRANITE FALLS -- An Upper Minnesota River Valley citizens group asked the Minnesota Public Utilities Commission to unplug plans for a 630-megawatt, coal-fired power plant by denying requests to build the power lines to transmit that power to Minnesota customers.

Clean Up the River Environment, known as CURE, challenged the proposed Big Stone II power plant on both environmental and economic grounds in testimony offered Friday in Granite Falls.

The plant could stifle the development of community-owned wind power in western Minnesota, and burden rural consumers in the region with electric costs much higher than projected if the nation adopts a carbon tax as many expect, warned Patrick Moore, executive director of the organization.

He called the plant a "direct threat" to the organization's goals of promoting the area and protecting its natural resources.

Moore and others offered testimony to Administrative Law Judge Barbara Neilson. It will be used by the utilities commission in deciding whether to approve the certificate of need that Otter Tail Power and six other owners for the proposed plant are seeking in order to upgrade transmission lines.

The plant would be built adjacent to the 450-megawatt Big Stone I plant near Milbank, S.D., but provide the majority of its power to Minnesota utilities and customers.

Environmental issues posed by the plant include the 189 pounds of mercury the combined Big Stone I and II plants could emit annually. The plants will also emit 4.7 million tons of carbon dioxide, a greenhouse gas, each year, according to testimony offered on Friday.

Hannah Hankins, a high school senior at Lac qui Parle Valley High School in rural Madison, asked company officials to consider wind and other energy sources that did not emit greenhouse gases in place of coal. "Is this too much to ask for my generation?" she asked.

Casey Wojtalewicz, a Lac qui Parle Valley High School senior, called it "immoral" to emit mercury, which he called a known poison. He challenged plant officials on the permit issued in South Dakota for the plant: It would allow the plant to emit as much as 399 pounds of mercury in each of its first three years.

Even at 189 pounds a year, the plants would produce 7,560 pounds of mercury that will bio-accumulate in the region over the course of the Big Stone plants' expected life span, according to Frances Moore, a Montevideo High School graduate.

The company has pledged to keep the combined mercury emissions from Big Stone I and II to 189 pounds per year, or equal to what Big Stone I now produces. Mark Rolfes, project manager, said the company will be acquiring the very best possible technology for mercury emission reductions. He said the company intends to keep emissions under the 189-pound level.

Rolfes said Big Stone will also seek to meet federal requirements that will allow no more than 54 pounds of mercury to be emitted by all sources in South Dakota by 2018.

Along with emission concerns, Patrick Moore said CURE is concerned about the permit for the plant issued by the state of South Dakota. It allows the plant to withdraw 10,000 acre feet, or more than 3.2 billion gallons, of water from Big Stone Lake. The permit was issued without any input or consultation with Minnesota, he charged.

Duane Ninneman, CURE development director, and Andrew Falk, a Murdock wind developer, also testified that the project will harm the development of wind power in the region.

Company officials said they are committed to spending additional monies -- in the millions of dollars -- to upgrade power lines beyond what is needed to carry the plant's power. They emphasized that the lines would have 800 to 1,000 megawatts of additional capacity that could carry wind power.

But Ninneman and Falk said that there is more than 6,000 megawatts of new energy being proposed for the region. That power is already in the Midwest Independent System Operator's queue system and seeking an allocation of transmission capacity. Smaller, community-owned projects face formidable challenges getting on the grid as a result, they argued.

Eric Laverty, manager for transmission service planning with MISO, said MISO and utilities are looking at a variety of projects to increase transmission capacity to handle the more than 6,000 megawatts of power projects being proposed. They include both coal, natural gas and wind projects. The owners of the proposed Big Stone II power plant have some 850 megawatts of wind power in the drawing boards to satisfy the Minnesota Renewable Energy objective for 2015.