SUNDRIDGE – How do you build a four-lane highway through miles of rock and swamp? The same way one eats an elephant — a bite at a time.
Trucks and excavators are working like ants west of South River and Sundridge, taking load after load of rock from the hills, and laying a road bed through the swamp.
“You don’t really get a feel for how much is being accomplished unless you come back on a weekly basis,” said John Garrett.
Garrett is a senior contract control officer with the Ministry of Transportation (MTO). His job is to oversee construction of the highway on the ministry’s behalf.
“I’m basically the ministry’s front-line representative between the field and the office,” he said.
Garrett took the Almaguin News on a guided tour of the Sundridge and South River bypass recently, offering a look at some of the progress happening in places that are not easily visible to the public.
The bypass is made up of two separate projects — the $65-million South River project, and the $60-million Sundridge project, which began in the fall. Both are contracted to BOT Construction.
The first stop on the tour was at Hwy. 11 and Hwy. 124, south of Sundridge, where preliminary work is underway to construct a road base through one of the swampier sections of the bypass.
“The soil here is deep and it’s wet, and it doesn’t have very high load-bearing capacity,” said Garrett.
Much of the Sundridge bypass will be constructed over muskeg, a boggy mixture of wet soil and decaying vegetation. Ideally, the muskeg is excavated down to bedrock and replaced with rock, but sometimes it’s just too deep to make that practical. Such is the case at the Hwy. 124 interchange. Here, they are partially excavating the muskeg, and using the weight of the fill to squeeze the water out of what remains. As the soil compresses, rock is added in five-foot layers. Wick drains accelerate the process.
The Rock is blasted from a nearby cut, which will make way for the rerouted Hwy. 124. As it is removed, it is loaded into dumptrucks and taken a short distance to where the road base is gradually making its way through the muskeg.
“It’s a very efficient process,” said Garrett.
As the fill makes its way north, a similar operation is moving southward from Boundary Road. This is the most efficient way to lay a driveable road through the miles of muskeg in between, allowing equipment to move more easily.
Working in the winter is something of a mixed blessing.
“You’re definitely restricted in what you can do,” said Garrett. “One thing you have to avoid is building on frozen ground, because it can cause issues down the road.”
However, the frozen ground can be an advantage for swamp excavation, allowing equipment access to places not easily reached in the summer.
One of the challenges of excavating a swamp is disposing of the material. Rock and gravel are used in construction, but some material is essentially useless.
“Muskeg isn’t a very friendly material to get rid of, “ said Garrett. “Good soil or sand is fairly desirable for people.”
Since they can’t unload it on anyone else, muskeg, along with clay, silt and other undesirable materials, is managed on the MTO’s own rights of way.
The base for what will be the southbound lanes of Hwy. 11 is now reaching about 1.5 km south of Boundary Road. This is just the first 1.5-metre layer of rock. More will be added to build the embankments to the desired height, but the first order of business is to extend the road as far as possible.
“Once they get down the first layer, then they’re not working in a swamp anymore,” said Garrett.
The first layer of the Boundary Road extension is also making significant progress, stretching to a rock excavation just a few hundred metres of the existing highway.
To the north, the base of the southbound lanes provides a driveable road through Machar Township, reaching almost to Eagle Lake Road, while construction has gotten underway on the base of the northbound lanes. Heading north, the tour passed a gravel extraction. Granular B gravel is used in the construction of the road base, with granular A finishing off the top. A gravel deposit is conveniently located next to the new highway, providing a ready supply of granular B.
“We’re fortunate to have access to this quality of material this close to the road,” said Garrett.
Just short of Eagle Lake Road, the future highway is making its way through a large swamp. On the other side, another crew is working toward them.
“They’re very close to joining up,” said Garrett. “They’re within sight of each other.”
Digging out the swamp are the aptly-named long stick backhoes. These excavators are so named for the long, skinny boom arm that allows them a longer reach into the swamp while remaining on terra firma.
“They’re specially designed for this kind of excavation,” said Garrett.
Once this swamp is crossed, trucks can move fill from blasting sites north of South River to where it will be used.
Across the swamp, the highway crosses Black Creek. Preparations are underway to install a culvert in the new year, at a time when it will least affect fish spawning. The MTO has worked closely with the Ministry of Natural Resources, as well as Fisheries and Oceans, to plan the crossing of the creek, which involves diverting it and replacing lost fish habitat.
“All efforts are made to minimize the impact on the natural environment,” said Garrett.
After crossing Eagle Lake Road, the highway reaches the South River, where cranes have recently been installing bridge girders. Beyond that are stockpiles of fill and a temporary bridge installed to facilitate the movement of rock across the existing highway. Across that bridge, embankments for the South River interchange have been built up considerably, while a little further down the road, work is still underway on the largest rock cuts of the project.
Rock blasting for highway construction is done in two stages. In order to get the sort of nice, clean cut we see in the Trout Creek area, a technique called pre-shear blasting is used. Small, closely spaced holes are drilled through the rock along the line of the cut. They are filled with a fast explosive that gives, as Garrett puts it, “a sharp, hard crack.” This splits the rock neatly along the line, allowing the excess rock to be blasted apart the old-fashioned way, leaving a flat rock face behind.
The second part of the blasting uses ANFO, a common ammonium nitrate and fuel oil explosive, similar to the infamous “fertilizer bomb,” but made specifically for blasting.
“It’s got an incredible amount of energy, but instead of a hard crack, it’s like a slow push,” said Garrett.
Holes for this explosive are larger, and capped to direct the blast down, into the rock. The resulting concussion shatters the rock into surprisingly small pieces. Detonation of the charges is precisely timed, and follows a sequence that starts at the outermost charges and works toward the centre. This happens in a fraction of a second, and the result is that the majority of rubble ends up piled in one place.
“If you started blasting from the centre out, the rock would be all over the bush,” said Garrett.
In some cases, the rock is covered with blast mats, made from recycled truck tires. This helps to contain flying debris when necessary. However, the highlight of the tour was an unmatted blast using 37 tonnes of ANFO. Video of the explosion, which pulverized a rock face and threw chunks of granite high in the air, can be found on the web at www.almaguinregion.com.
Overall, this part of the Hwy. 11 four-laning is moving forward without any serious problems, which is to the credit of the men and women doing the work. Garrett pointed out that some of the workers are far from home, and might not see their families for weeks at a time.
“Sometimes, it’s long weekend to long weekend in the summer,” he said. “And especially at this time of year, the evenings in the motel room can seem pretty long.”
This will continue until the South River and Sundridge projects are completed, and a final contract is awarded to tie the pieces together, pave and tie in to the existing highways. A significant amount of planning goes into building a major highway around existing roads with as little disruption as possible.
“It’s kind of a chess game,” said Garrett. “It’s all designed to minimize the effect on traffic.”
Editorial
