Some states — most notably, California, Oregon and Washington — have passed laws and created agencies to assert "siting authority" over proposals for industrial development. It’s relatively simple for those states to turn down power-plant proposals, based on concerns about the full range of socioeconomic and environmental impacts. But Idaho has never established a statewide siting authority.

The Idaho Public Utilities Commission refused to let the Idaho Power Company build a coal plant near Boise in the 1970s, but the PUC has authority only when companies seek Idaho customers. A merchant plant, selling out of state, would escape the PUC’s grasp. Sempra would have only needed a few state permits from other agencies, chiefly for its emissions. And the Legislature has gone out of its way to keep the regulatory leash loose: It passed a "stringency law" in 2005, which discouraged Idaho agencies from getting tougher than federal regulations. Other industries benefited from the law, but in this case it meant that a coal plant’s emissions would only have to pass muster with the federal government — not a great burden under the Bush administration, which has rolled back a suite of Clean Air Act regulations (HCN, 5/2/05: The Winds of Change).

Amazingly, the greatest government hurdle for a merchant coal plant would have been at the local level: the county commissioners who make land-use decisions. That looked easy, too.

The Magic Valley has always been friendly to business; it gained its name from the early white settlers who harnessed the Snake River’s water and made the desert magically bloom with crops. It includes portions of eight counties, most of which welcomed another polluting industry in the 1990s — the giant factory dairies that relocated here because of the state’s lack of regulations (HCN, 4/15/02: Raising a Stink). The valley, home to 160,000 people, sent 77 percent of its votes to Bush in the 2004 presidential elections.

Sempra came in confidently, spreading campaign donations to key politicians, and touting the benefits its plant would bring. The proposed site is in rural Jerome County, which lost 700 jobs in 1986 when a Tupperware factory shut down. Plant construction would bring 1,000 high-paying jobs and $25 million in sales tax revenues, Sempra promised, and long-term operation would create at least 90 permanent jobs and $18 million per year in local and state taxes.

The company bought options on farmland around the butte and 7,600 acre-feet of farmers’ water to cool its turbines. The three Jerome County commissioners seemed agreeable at first: They let Sempra install an air-quality monitoring station on the butte to establish a baseline for its emissions permit.

"We were asleep at the switch in not recognizing that large coal-fired power plants would come (into Idaho)," says Noh, whose living-room windows look out on the Sempra site. "The public, and the political structure, were totally unaware of this possibility. They didn’t have a clue that three county commissioners could (have the authority to) approve something like this."

Everything looked good for Sempra. Or so it seemed.

The campaign against the power plant began with Democrats in the nearby resort towns of Sun Valley and Ketchum in 2005. As usual, the Idaho Democrats got nowhere on their own.

The campaign didn’t really take off until mid-February this year, when the Southern Idaho Home and Garden Show opened in the Magic Valley’s biggest city, Twin Falls. Vendors hawked shiny new rototillers, fancy windows, and other home-improvement products in a crowded dirt-floor rodeo stadium. Next to a booth selling vinyl fences, Carl Nellis, a 66-year-old retiree with a son on military duty in Afghanistan, ran a display for a fledgling group called Citizens for Resource Protection.

It was nothing flashy, just a few colored balloons hovering over a hand-painted sign that said, "Smog Free Idaho," and a picture of a coal-fired power plant with a red slash across it. "I went low-tech," Nellis says, "to promote the David versus Goliath image."

During the three days of the home and garden show, Nellis and a few other volunteers urged people to sign a petition against the coal plant. The response far surpassed their expectations: Magic Valley residents clogged the aisles around the display, and by the show’s end, more than 2,000 had signed the petition. Within a few weeks, more than 8,000 people had signed it.

A tour of Twin Falls, nine miles south of the Sempra site, reveals some of what the company ran into: The small, attractive city prospers through a blend of the Old West and the New. It has a big french-fry plant, a sugar-beet plant, the College of Southern Idaho campus, a new Dell computer service center, shopping centers and hiking trails. New subdivisions along the Snake River Canyon’s rims offer breathtaking views.

Out in the countryside, milking machines pump the udders of 300,000 cows; a Scottish cheese company has recently opened three plants. Springs gush from the canyon walls along the river, feeding the nation’s biggest collection of trout farms. Retirees snap up small acreages and homes for $300,000 or more.

There’s still that Western sense of open space and opportunity. But the locals have learned that their natural resources have limits. Neighbors have battled each other over water shortages, for example, and over ammonia and nitrate pollution from some of the dairy industry’s bad actors.