Photo Courtesy of Atikokan GS
The contractor at a powerplant in Atikokan, Ontario, is erecting two 5,000-ton concrete silos for storage of white wood pellets, the new fuel source that will replace coal at the plant.

A $170-million retrofit at Atikokan Generating Station in Atikokan, Ontario, is transforming a 28-year- old coal plant to burn 100% biomass and represents a major trend in North American power engineering and construction efforts. "The Ontario Power Authority mandated that this facility be off coal by December 31, 2014," says Brent Boyko, Atikokan station manager. "The biomass fuel source cuts emissions but retains the plant's ability to generate 205 MW of electrical power."

Policy regulations and legal actions are causing similar construction efforts to pick up pace in the U.S. Armed with a $50-million donation from New York City Mayor Michael Bloomberg (R), the Sierra Club said its "Beyond Coal" campaign is more than halfway to its goal of retiring 30% of the U.S. coal fleet by 2020. The Sierra Club, the largest U.S. environmental advocacy group, has filed more than a dozen lawsuits in the past year against coal plants for violating the Environmental Protection Agency's Clean Air Act, first signed by President Richard Nixon (R) in 1970. More than 142 U.S. coal-fired powerplants have closed during its campaign against the fossil fuel, representing 105 GW of electrical capacity, the Sierra Club said.

Construction and engineering firms see environmental policy developments as opportunities and are working hard to provide the expertise and services necessary to help retrofit projects at idled or closed powerplants to start up again. "We pride ourselves on a large workforce with the skill set necessary to perform either new construction or retrofits at powerplants," says Andi Vigue, president of Cianbro Corp. "We are neutral in support of fuel sources for power generation, but biomass technologies are certainly providing an opportunity for idled or closed coal plants to start up again."

Cianbro already has performed several coal-plant conversions, including ReEnergy Holding's Black River Generation facility near Watertown, N.Y., and the Verso paper mill in Bucksport, Maine. The $42-million Verso project included refitting the boiler to burn only wood products and installation of a new 25-MW turbine. Doosan Engineering, Korea, converted Atikokan's lignite boiler to burn biomass.

Converting the 60-MW Black River plant required collaboration between equipment manufacturer, owner and contractor. The major challenge was moving the new equipment into the plant. "We were able to modularize the equipment and assemble it in the plant, rather than bring it in one piece at a time," Vigue says. "With a retrofit, the challenge is to take an existing facility off line and have it back operating within a limited time frame."

ReEnergy's Black River retrofit cost approximately $34 million and provided 178 construction jobs. In Ontario, there are 150 workers currently on-site at Atikokan, and Toronto-based prime contractor Aecon estimated the construction value at $85 million.

Concrete Storage for Wood Pellets

Constructing a new material handling and storage system is key, since coal can be left outside while wood pellets—the new fuel source—cannot. The need to protect the new feedstock from the elements meant the construction of massive silos. "These are 5,000 tons each," Boyko says. "They're 60 feet in diameter and 200 feet tall. They look like missile silos."

FWS Group, Winnipeg, is performing the task in a seven-day continuous pour. "This is when the molds are moved up as the concrete is poured," Boyko says. The 24-hour-per-day job requires 60 workers per shift, 300 truckloads of concrete and 200,000 kilograms of rebar. "At the moment, this has been delayed because we're in the middle of the snowstorm," Boyko says in early April.

Besides the weather, other risks at Atikokan included unknown obstructions. "We had cleared land and laid gravel, thinking the surface was ready to build the foundation. But what we thought was base rock wasn't—it was overburden," Boyko says. "If it's underground, expect the unexpected."