The Iowa Utilities Board (IUB) will decide today whether Interstate Power and Light Co. (IPL) can proceed with its proposal to build a $1.8 billion coal-fired generation plant in Marshalltown.

About 150 people filled the IUB’s hearing room at 350 Maple St. this morning. By mid-morning, the three-member board had not yet reached a decision, but seemed to agree their choices are fraught with uncertainties. The board broadly discussed whether the plant would meet the state’s economic development and environmental policies, including whether approving the coal-fired plant would slow down construction of alternative-energy production such as wind turbines in the state.

“We need to balance the risks to the company versus the risks to the ratepayers,” IUB Chairman John Norris said during the discussion, which began at 9 a.m. and is expected to continue until the board reaches a decision. If the demand for additional generating capacity that IPL claims is coming doesn’t materialize over the plant’s decades-long life, utility customers will end up paying more than is necessary, he said. Among the unknowns addressed in the company’s computer modeling of the plant were future costs of carbon capture or sequestration and the future costs of other energy sources.

“For me, that’s the biggest concern,” board member Kristin Tanner of Clive said. “What will IPL’s operating costs for this plant be in a carbon-constrained world?”

Board member Darrell Hanson, a Manchester resident, said the cost of using coal to generate electricity is bound to increase in the future, whether the government mandates more controls on carbon emissions or not. He called IPL’s assumptions “reasonably cautious, given their responsibilities.”

IPL officials have promoted the project as a means for the utility to significantly reduce the amount of electricity it purchases from outside of Iowa. The company currently purchases approximately 30 percent of its energy. The Wisconsin-based company has also formed an alliance to sell about one-third of the plant’s output to four Iowa electric power cooperatives. The plant’s planned operating capacity is 630 megawatts, enough electricity to power 472,500 homes and businesses in the state.

The plant has been opposed by a coalition of environmental groups and the state’s Consumer Advocate, who said building a coal-fired power station is not the most cost-effective option. Opponents say the company should instead increase its energy conservation efforts and build more wind-generation capacity.

Correction: In the original posted story, Interstate Power and Light Co. was incorrectly named.