A geosynthetics provider and a local distributor provided assistance with materials and expertise for temporary housing and landfill expansion in the aftermath of northern Alberta wildfires
By Don Talend
Wildfires fanned by rare southeasterly winds up to 100km (62mi) per hour destroyed several hundred homes, businesses, and municipal buildings in the town of 7,000 in May 2011. Heavy rains in July caused further damage to remaining foundations and infrastructure. Just two of many organizations that have assisted recovery efforts, Layfield and Apex have provided geosynthetic materials and expertise for construction of a temporary trailer park for residents displaced from their homes, plus an expansion of a local landfill in the wake of the fire.
At more than $700 million in damage, the Slave Lake wildfires are the second-costliest insured disaster in Canadian history, according to the Insurance Bureau of Canada. An ice storm that hit Quebec and Ontario in 1998 cost more than $1.8 billion, adjusted for inflation. The Slave Lake fires—about 150 miles north of Edmonton— were significant enough that Great Britain’s Duke and Duchess of Cambridge, William and Catherine, made an impromptu stop during their summer 2011 North American visit to raise morale amid recovery efforts.
Apex’s Slave Lake facility is a supplier of industrial and oilfield products and services, one of the first branches to open when the company began operations in 1999. Ken Hedin, the Apex branch manager, pointed out that the LP6 nonwoven, needle-punched geotextile material is often used to stabilize road subbases in remote oil-production areas with muskeg (i.e., marshy) soils.
The soil where one of two temporary trailer parks is located particularly required the geotextile stabilization. The landfill required proper separation of waste from soil and the groundwater protection that geotextiles also provide. The town also needed the dedication and expertise of suppliers such as Hedin and the resources of the local construction industry.
Hedin, a former firefighter, helped several extended family members and others evacuate and he was one of the few local people allowed back into town as firefighters battled the fires. The distributor provided parts to keep the firefighting equipment operating. In the fire’s aftermath, the company has donated equipment from fencing to cordon off the smoldering residential areas to shelving for the local curling rink, where the Canadian Red Cross has stored relief supplies.
Soil stabilization for temporary housing
One of the critical tasks in the recovery has been establishing long-term shelter for several hundred families who lost their homes in the fire and who might have to wait a few years for their homes to be rebuilt. News reports said that about 700 families were displaced and many temporarily moved in with relatives or were living at campgrounds as the weather turned colder in fall 2011; others opted for public housing or permanently relocated out of town.
Since mid-August 2011, Slave Lake-based Seguin Construction has been building slabs, driveways, and roadways for the trailer park. By early October, about 30 trailers were occupied, with full occupation by mid-October.
“This is something that we have all lived through as a community,” said Dave Redgate, manager at Seguin who lost his home in Widewater, a small community located west of Slave Lake. “Some of our company contractors, suppliers, and employees are moving into the facility that we have built; we all know someone who has been directly affected by this tragedy.”
Seguin specializes in earth-moving projects primarily for the oilfield industry but has been diversifying into more civil work in recent years, Redgate reported. The fire recovery effort is expediting the diversification process, he said.
Each of five sections of the trailer park consists of 30 slabs for individual trailers. Each of the slabs measures 12m x 32m (40ft x 106ft). The trailers are constructed in two rows of 15 per section with utility corridors running the full length of the slabs behind the trailers.
To stabilize the muskeg soils for the slabs, driveways, and roadways, Seguin initially installed 7,031m2 (75,654ft2) of LP200 woven, slit-film, polypropylene geotextile over a temporary working pad. This pad was built on undisturbed parent ground, was filled and compacted with clay to a depth of 600mm (about 2ft). The same process was employed throughout the 81,500m2 development. However, weather conditions and timelines dictated a departure from the plan.
The rush for temporary housing with cold weather looming necessitated a three-week construction window. Heavy rains in July, which forced short-term closures of the roads surrounding Slave Lake, saturated the soil even more. Rather than use clay fill, Alberta Infrastructure and Seguin thought that a sandy-pit run material would enable sustained operations during wet weather and make adherence to the three-week timeline realistic.
The subsequent engineering decision was to shift from LP200 to a heavier-duty LP315 geotextile product. The total amount of LP315 installed under the pads, driveways, and roadways throughout the development was 117,057m2 (1.26 million ft2).
The project engineer, Focus Corp. from Edmonton, installed the LP315 directly on the undisturbed parent soil before fill was placed. Imported sandy-pit run fill was hauled, placed, and compacted to a depth of 800mm (about 2½ft); more than 112,000m3 (nearly 4 million ft3) of fill was imported for the project. Additional aggregate material was imported for individual trailer pads, roadways, and driveways.
Installing geotextile material in the region’s muskeg soil is challenging under normal circumstances; the heavy rains made the task even more difficult. The site was deforested and crews entered the site to install the geotextile materials.
“It was essentially a crew of laborers rolling out each roll individually, sometimes in [marsh] up to their armpits, to get the proper overlaps and weighing the rolls down with available rocks or whatever they could until the fill could be applied on top of it,” said Redgate, the Seguin manager. “My hat’s off to the laborers.”
Redgate reported that the LP315 was holding up well on the muskeg soil following construction. “The weight loads that are on top of that product and evenly distributed across the entire 9 hectares (about 22 acres) are phenomenal,” he said. “But the product is holding up very well. [At] two months, there was no settlement or degradation of the pad integrity at all.”
An environmentally safe landfill
A disaster such as this generated plenty of unexpected consequences. In Slave Lake, one such consequence was that the Lesser Slave Lake Regional Landfill in Widewater was overwhelmed with about 3,500 fire-damaged refrigerators in three days, according to the Edmonton Journal. The newspaper reported that the existing landfill would have had enough capacity for three more years but, due to the fires, had to be expanded immediately.
The expansion from two cells to three began in early September 2011 and was completed by mid-October. Each of the two existing cells covered about 2.2 hectares (about 5.5 acres) and the third covers the same area. Overseen by the project engineer, Associated Engineering of Edmonton, in adherence with Alberta Environment guidelines and regulations, such expansion of Class II waste landfills incorporate geosynthetic materials.
LP200 geotextile was used to line collection trenches at the bottom of the landfill cell. A 600-mm (2-ft) clay liner was placed over the collection system and a leachate collection pipe was covered with an impermeable clay liner 600mm (2ft) thick. Over the clay liner, A 300mm (about 1ft) -thick layer of tire shred was placed that served as another filtration system to ensure that minimal solids and suspended fines do not clog up the collection systems. All told, the landfill expansion used 7,525m2 (81,000ft2 ) of geotextile material.
A local effort
Redgate looked back with pride and admiration on the efforts of numerous local contributors in the rebuilding efforts. “Because the temporary subdivision development was a local project, we can all feel that, as a community, we banded together to provide for those who have lost everything,” Redgate continued. “I am so proud, at this moment, to be a Slave Laker,” he said. “This tragedy has and will reshape us as individuals and as a community; let’s hope that it is for the better.”