Wood Fibre And Floating Access Roads Reduce Ground Disturbance

By Graham Chandler

[Figure 1]

It looks like scrap, but the proper name is drivable wood fibre. Last fall, Devon Canada constructed an access road to a lease just south of Grande Prairie, Alta., using wood chips instead of gravel or access matting. Its contractor was Triple G Construction Ltd., a firm from northwestern Alberta. Another innovative road-making strategy is based on floating mats made from cutting-edge composite materials, developed by Edmonton's ATR Manufacturing Inc. Each access technology has unique advantages, depending on loads and terrain type.

"We like doing things with the least amount of impact," says Mike Head, Devon's lease construction consultant and supervisor. "We always try to find ways to reduce our footprint." The Canadian Association of Petroleum Producers, recognizing the company's commitment to minimizing surface disturbance, presented Devon with the 2009 President's Award from its Steward of Excellence Program.

Triple G, based in Grande Prairie and Grande Cache, has handled wood harvesting and small oilfield contracting for almost 30 years. In the spring of 2008, Gervin Antypowich, its owner and CEO, recognized an opportunity to combine those two operations into a new service-building drivable wood fibre roads. The diversification didn't even require new equipment. "We could do the mulching and everything-a one-solution company," Antypowich says.

Drivable wood fibre surfaces are just what the name implies. Surplus natural wood products ideally from locally cleared rights-of-way are mulched into mixed chip sizes and spread over a separation material to create a road surface, staging area, or work site. They're also called engineered wood fibre, wood residue, or wood mulch surfaces.

Size mix is important: when they are compacted, the fibres mesh with each other and bind together for strength while allowing water to drain through. Antypowich says the necessary compacting or water drainage characteristics won't be there with, for example, just sawdust. "You need the bigger chips and longer strands," he says. "We don't use the screens in our mulchers. Then we get pieces a foot, six inches, or two inches, along with slivers." In fact, the roads eliminate the need for drainage ditching because they are built above ground level.

In order that the mulch doesn't simply get mixed and mushed into the mud or whatever is under it, the technique is to first lay down a separation layer. Normally, that is GeoTech, a type of cloth used for separating layers on crossings, says Antypowich, to ensure no mixing of soils. Alternatively, GeoGrid-a snow fence-like plastic-can be used. "It's a grid, with half-, one-, or two-inch holes," he explains. "That helps spread the load." He adds that it doesn't spread loads as effectively as conventional matting, "but each has its application. If you're dealing with a lot of water, matting will spread the load a little better."

A major advantage of wood fibre roads over matting is cost, according to Triple G. "We can build you a chip road that costs the same or less than a dirt road," Antypowich says. "And reclamation costs are down to 10 per cent [of a dirt road]. It can be picked up easily because of the separation layer. And the mulch can be reused." Where locally cleared wood can be used for the mulch, further trucking costs are saved.

[Figure 2]

Wood fibre roads are best for shorter term access-up to five years. But Head says some of Devon's routes will hopefully become permanent. "If we have to add some wood to it once in a while to keep it in shape, we're going into this with the intention of trying to make a road that will last," he says.

Especially in certain conditions, Devon plans to continue with the technique. "I find that where this stuff works best is if you have a little ground base with lots of stumps and you don't have to disturb the dirt," Head says. "You basically take that and shave those stumps down flush with the surface and don't disturb the roots."

Triple G's Antypowich says mulching machines can process 200 tons per hour, enough to normally accommodate 100 to 150 metres of road. Beyond roads, he tells of a 700 foot by 900 foot work site pad that the firm built for Devon's Jackfish 2 site near Fort McMurray. "We gave them a 30-inch pad and they topped it with dirt," he says. "It took 380 truckloads of wood."

Head brought the concept to the attention of the Alberta government. "They're open to be shown new ideas and to go on field tours and look at some of the things that we've got going on," he says. "I showed them all of our good stuff and all of our bad stuff." Alberta Sustainable Resource Development subsequently issued Information Letter 2008-06 last September, announcing it was receiving applications for dispositions to use the technique for a five-year trial period, testing for adverse environmental effects like leachate and frost retention.

[Figure 3]

Wood fibre roads aren't as effective over ground with high water content. "A wood mulch road generally in muskeg conditions doesn't work very well because there isn't that support," says Craig Wronko, president of Edmonton-based ATR Manufacturing. "That's important because in muskeg you want to avoid shearing it. As soon as that happens, you destroy the foundation and it just gets worse."

ATR's solution is the all-terrain road-mats with a polypropylene honeycomb core bounded by layers of woven fibreglass-reinforced epoxy resin. Traditional wood, steel, or plastic matting all have drawbacks in muskeg-water retention, load distribution, or deforming. "It [All-Terrain Road] was designed specifically for access to muskeg areas," says Wronko. The secret? "We're using aerospace technology. We use a technique that allows us to bond materials that can't be bonded together. Others have tried, but can't get the chemical bonding."

The result is a mat that's lightweight, easy to install, and can float, Wronko says. Moreover, ATR mats remain compliant to shear forces: bending rather than failing, yet rigid enough to support heavy equipment. It's the product's first year on the market. To help with application, a computer model is offered that can predict response to specific load conditions and ground properties. Based on independent compression, shear, and bend tests, the computer model enables the user to estimate maximum allowable loads under various ground conditions.

[Figure 4]

"The ground conditions [input] range from wetlands to muskeg, sand, and then to a clay or firmer surface," explains Wronko. "It will tell you exactly how the mat system will perform or deflect in each particular case. You can give yourself a range, and it's also dependent upon what's going onto the mats." For example, in muskeg under a central load of 22,500 pounds, the model predicts vertical mat deflection is 1.65 inches along 14 feet.

"Even over a time period in certain muskeg conditions, it will always come back and retain its shape," says Wronko. "The mats never take a set, never deform. Even with the suction that happens between the ground and the mat, there's enough force on that system that over time even if it's compressed or sucked down into the ground, it will always come back."

For tracking purposes, each ATR mat has its own passive RFID (radio frequency identification) tag for the client to identify his mats, says Wronko. "And secondly, we attach all our information in them-all parts and quality control, etc." Installation is relatively quick. The Edmontonian says that by using two skid-steers, "we can connect and lay a mat every 45 seconds." So he reckons a truckload, which consists of 92 to 104 mats, can be laid in around two hours.

"There are applications where people want to cross an open body of water, let's say a pond-not a lake or moving water and not so large you'll get wave action," says Wronko. ATR recently tested a new fitment system for its floating mats in wetlands. "It was unsupported on water," the company president says. "We wanted to put a lot of stress onto the joints, so we drove a truck, and I drove my car, out to the end of the mat system, which was just supported on water like a floating dock. The mats didn't even get water on them. That was with a 7,000 pound load."