Yellowknife (May 14/04) - Most of the huge pile of dirt excavated for the new federal building is not going anywhere.

"We're trying to keep that material on site as part of a LEED initiative," said John Droog, area manager with PCL Constructors Northern Inc.

LEED stands for Leadership in Energy and Environmental Design, a standard for sustainable buildings which the federal government is following.

Most of the dirt will be used for back fill around the building.

"From a sustainable perspective we don't want soil erosion," said James Dykes, regional manager of architectural and engineering services for Public Works Canada.

The designers considered a steel frame building, but opted for concrete because most of the necessary materials are available in Yellowknife says Dykes.

"We strongly encourage (the contractors) to have (materials) manufactured locally," Dykes said. "There's a lot of greenhouse gases produced in the shipping."

"Another benefit is that during the day, concrete actually absorbs the heat in the building," Dykes said.

The concrete for the building will help reduce greenhouse gas emissions.

Making cement requires high heat and contributes to greenhouse gas emissions, but in the new federal building, Dykes said they plan to mix in fly ash, to reduce the amount of cement used.

PCL plans to replace up to 40 per cent of the cement with fly ash from burned coal. This does not reduce the quality of the concrete.

Vegetation on the "green roof" that will cap the building will also contribute to energy savings.

"A roof of a building becomes very, very hot," said Gino Pin, architect with Pin-Taylor Architects. "The vegetation acts as an insulator and also extends the life of a roof."

A roof in Yellowknife is subject to great changes in temperature throughout the course of a year, says Pin. The expansion and contraction takes its toll. The green roof will help insulate and keep temperature fluctuations to a minimum.

Pin-Taylor Architects designed the Legislative Assembly building. The assembly's service wing has a green roof.