Sept/Oct 2009

Engineering Exchange

A multi-disciplinary design: Creating a long-term, sustainable lake from scratch takes good communication and a multi-teamed approach

By M. Eisner

 

Aerial view of the compensation lake project site — the Phase 1 drainage network drains west to the Muskeg River.


Environmental sustainability is perhaps one of the most important, and most challenging, aspects of the mining industry. From water conservation and innovations in tailings management to the reclamation of land, the goal is to meet the present needs of society without compromising the capacity of future generations to meet their needs.

When Norwest Corporation was hired by Shell Canada to develop and create a lake able to support year-round fish habitat for the Athabasca Oil Sands Project, Norwest knew it was being presented with a unique and exciting challenge. The lake, to be built directly east of the Muskeg River at the confluence of the Muskeg Creek and Muskeg River, will utilize the Muskeg Creek as its primary inlet.  Once the lake is constructed and filled, it will begin to balance the habitat lost during mining in portions of the Khahago, Shelley, Pemmican, Blackfly and Green Stockings watersheds.

Compensating for lost fish habitat was an essential requirement in the authorization for Shell’s Jackpine Mine – Phase 1 project, located about 75 kilometres northwest of Fort McMurray, Alberta. The lake needed to be a sustainable feature of the area and maintain fish passage from the Muskeg River through the lake and upstream along the Muskeg Creek for a minimum of 100 days of the year.

Designing ways

“It [the design] certainly was a unique, multi-disciplinary project,” says Adam Bedard, vice-president of water resource engineering at Norwest. “It required civil and mining engineers, hydrologists, geotechnical engineers, fisheries biologists, hydrogeologists and Shell’s environmental group. There were a lot of aspects that had to be evaluated, so there was a long design process.”

There were regulatory components to consider as well with agencies such as the Department of Fisheries and Oceans, Alberta Environment, Alberta Sustainable Resources Development and the Energy Resources and Conservation Board. “It was a fairly cutting-edge design — a very customized solution for a very unique set of challenges,” says Bedard.

Essential features

The lake is designed to be comprised of three main sections — a northern basin, a shallow interconnecting narrow section and a larger deep southern basin. The total surface area is expected to be 47.3 hectares and an erosion control berm has been designed along the lake’s west shoreline to manage interaction between the lake and the Muskeg River. The lake will have a primary inlet as well as a secondary inlet to handle high flood flows. Both inlets will use existing Muskeg Creek channels, which will flow into the northeast portion of the lake. In the south, a primary outlet will connect the lake to Muskeg River. Within the erosion control berm, secondary outlets have been designed at specific elevations to correspond to various flood frequency levels and allow for uninterrupted flow between the lake and river during flood events.

The design of the lake also includes habitat complexing to accommodate various types of fish habitats. Reclamation will be adaptively managed, with natural vegetation monitored to determine further reclamation needs.

Location, location, location

“The biggest challenge to the project as a whole was the location,” explains Twyla Hutchison, water resource engineer and engineering design team member on the project.

The lake is situated immediately upstream of the confluence of the Muskeg River and Muskeg Creek. Once the lake is in place, the Muskeg Creek will be its primary inlet and will connect back to the Muskeg River by the primary lake outlet. “The lake is in a naturally existing flood plain of the Muskeg River,” says Hutchison. “Being in the flood plain, it’s a very wet area, and there were a lot of challenges with managing the water during our first phase of construction.”

The first phase was to pre-drain the project site for lake construction purposes, prepare the foundation for the spoil piles and to divert natural waters away from construction activities. The surface drainage system, which was constructed between January and March of this year, is a network consisting of a series of ditches that lead to two sedimentation ponds that discharge into the Muskeg River.

Timing is everything

Phase 2 of lake construction began the week of August 19, 2009. “It’s been draining since March,” says hydrogeologist and project manager Sara McCartney.  “Construction will start in the highland areas and move towards the Muskeg River. It will get more and more saturated, so we’ll stay in dry areas until winter will improve construction conditions.”

Probably the biggest challenge now is the completion of the lake in time for spring. The Muskeg Creek has quite high flows in the spring, and routing it into the lake is the very last step of construction. Timing is essential, since once the creek is flowing into the lake it could fill in as little as one week. Construction must be completed by mid-March 2010 to ensure everything is in place prior to spring flows.

Current priorities surrounding construction include the handling of all the materials that are being excavated. “There are numerous materials that are being managed during construction,” explains McCartney. “The first step involves stripping suitable reclamation material and stockpiling it for use when the lake is completed. It’s going to be a staged approach,” she says. “As they enter into a new area, they’ll strip reclamation material prior to excavation and then segregate remaining materials depending on characteristics such as construction suitability.”  A total of five distinct on-site stockpiles will be utilized.

Having the bulk of the lake construction take place during the fall and winter months was done purposely to give the project a positive edge in meeting the spring deadline.  “It does get quite cold in the winter, but that facilitates the construction,” explains Keith Wilson, Norwest vice-president of mining and mine development.

“That’s the intention of starting now [August 19],” agrees Tim Fitzgerald, vice-president of oil sands and a lead player on the project’s construction. “Basically, it gives us the required amount of time between now and March to get the lake built.”

Communication is key

The design of the lake has involved many elements, from water resources, environmental, civil, geotechnical and mining engineering, to fisheries and geology, which has led to an iterative approach for the successful management of the project. It was essential to have a team that worked closely together, with consistent, ongoing communication, in order for everyone to understand how their portion of the design affected the other design components.

“The key word is communication,” says Fitzgerald. “From Norwest’s point of view, there is the recognition that a lot of this work is a joint effort between Norwest and Shell. It’s just good project planning that the consultants and the client communicate. The interaction between Shell, Norwest, and North American Construction Group is literally a daily thing.”

A rewarding experience

With the project well into the final phase, a lot of excitement is building up to see the end result. Although it has been a long process — it will be three years from the initial work on site to the completion in March — and a technically challenging one at that, Bedard says the experience has been especially rewarding.

“We’ve learned a lot and developed significant experience with regard to habitat construction,” he says. “It’s an integrated project and will leave a lasting legacy for Shell and the surrounding community. It’s very rewarding and exciting and we’re looking forward to building it and getting to see it happen in real time.”

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