CVRD Inco slag pile reclamation, Sudbury, Ontario, Canada
Mulch-It, Putnam, Ontario, Canada
Profile Products LLC, Buffalo Grove, Ill.
Quality Seeds, Woodbridge, Ontario, Canada
Large slag piles were reclaimed using Terra-Tubes Fiber Filtration Tubes and a custom legume/grass mixture applied in a slurry with Flexterra Flexible Growth Medium.
Grading, slope interruption devices, growth medium, and a custom hydroseed application turn ’mountains’ of slag green.
Over the years, CVRD Inco had produced a "mountain" of slag that was threatening to overrun part of Sudbury, Ontario, Canada. The company’s Sudbury facility is one of the world’s largest fully integrated nickel, copper, and precious metal mining, milling, smelting, and refining operations. The slag, a byproduct of the smelting process, had become both a dominant feature of the landscape and a major challenge to CVRD Inco’s role as a good corporate citizen and environmental steward. As a result, the company decided to study new ways to accelerate its ongoing reclamation of the slag piles and quickly convert them into a green landscape.
A part of the city known as Gatchell had expanded to a point almost adjacent to the slag piles, and in some areas, the two were becoming separated only by a busy roadway. As the slag and the city expanded toward each other, the company recognized a need to change the materials it had been using for slope reclamation.
Mike Peters, CVRD grounds supervisor and greenhouse manager at Sudbury, faced at least two challenges:
- The massive slag accumulation would need to be reshaped, graded, and compacted. Because it was adjacent to a roadway with limited land available, the resulting slopes would be steep (gradient of 3H:1V) and in some cases rise to a height of 100 feet.
- Because of the highly acidic nature of the slag, another growth medium (in this case, clay) would have to be incorporated.
"We had done slope reclamation elsewhere by hydroseeding, using a basic mulch," Peters said. "But this was on more gradual slopes (4H:1V) and we weren’t completely satisfied with the erosion control. So we began looking for something more reliable."
CVRD Inco first targeted a 20-acre section of slag piles adjacent to the roadway. "In some cases, the slag was almost up to the road," said Peters, "so starting there was important not only to mitigate possible problems of blowing dust or erosion onto the roadway, but [also] to make a visible statement to the community that we were working to reduce our environmental footprint."
|CVRD Inco first targeted a 20-acre section of slag piles adjacent to a roadway to make a visible statement to the community that it was working to reduce its environmental footprint..|
Work began in October 2006 and continued through February 2007. The large slag piles were reshaped to create a series of slopes, each 100 feet long and divided from the next by a 20-foot-wide horizontal bench. This required a slope gradient of 3H:1V. As a result, John Reynolds of Mulch-It, Putnam, Ontario, and Cathy Wall of Quality Seeds, Woodbridge, Ontario, were asked to propose a method to establish growth successfully on the steep new slopes.
Following on-site consultation with erosion control expert Dwight Johnson of Profile Products, Reynolds and Wall made their recommendation: Install Terra-Tubes Fiber Filtration Tubes as slope interruption devices, then hydroseed the area using a custom legume/grass mixture applied in a hydraulic slurry with Flexterra Flexible Growth Medium.
CVRD Inco tested this recommendation using a small-scale demonstration area. "In May 2007 we applied the Flexterra/seed mixture on the dam of a nearby tailings pond," Peters said. "The area greened up quickly and became well-established. This confirmed our decision to proceed with these materials on the larger project."
Meanwhile, CVRD began modifying the surface of the slag piles by incorporating an 18-inch layer of clay as a growth medium. An estimated 80,000 cubic yards of the material were trucked in, spread by bulldozers, and then horizontally track-packed to stabilize the surface and aid in erosion control.
Next, more than 1 mile of Terra-Tubes was installed across the graded and packed slag. Well-proven as a slope interruption device, Terra-Tubes are frequently used in conjunction with Flexterra for erosion control on steep, difficult slopes. They were placed at 35-foot intervals across the slopes and, by early August, CVRD Inco was ready to begin hydroseeding. Each hydroseeder load contained 1,000 pounds of Flexterra with 50 pounds of the special legumes/grasses blend plus fertilizer and lime. Profile’s Johnson recommended applying Flexterra at 4,500 pounds per acre—a higher rate than normal. "Because the material had to last over a long winter and because of the length of the slope, we needed a little heavier coverage," he said.
Work began along the top tier of slopes. "We gave this priority," Peters said, "so that by establishing growth we could help minimize erosion on the lower areas until there was time to cover them. We knew we were crowding the end of the season, but our plan was to establish as much growth as possible before the first frost and then continue dormant seeding. In particular, the amount of dormant seeding we’d be doing made it important to have a product that would support the slopes and prevent erosion right through until germination in the spring."
|Each hydroseeder load contained 1,000 pounds of Flexterra Flexible Growth Medium with 50 pounds of the special legumes/grasses blend plus fertilizer and lime.|
"We were confident Flexterra could meet these objectives better than other options," said Mulch-It’s Reynolds. "Compared with other hydraulically applied erosion control materials, it requires no cure time, so you get an immediate protective cover. Also, compared with rolled erosion control blankets, there’s no ’tenting’ that can allow erosion when application has to be made on an irregular surface."
Flexterra’s patented technology combines what the company calls "Thermally Refined" wood fibers with crimped, interlocking, man-made fibers and performance-enhancing additives. This creates an intimate bond with the soil surface, enhances seed germination, and provides immediate erosion protection on steep, difficult slopes.
About 17 acres of the slopes had been covered by mid-October 2007. "We’ve had excellent germination and, as a result, the area where we began in August is now totally green," Peters said. "In fact, we get comments from area residents that, ’It looks like Ireland up there.’ We were able to test the Flexterra early on because we had a heavy rain event not long after our first hydroseeding. It held up well and did a good job of preventing erosion.
"We’re very pleased with the results so far," he added. "You can’t imagine how good it makes you feel when you’re up there working on those slopes and a car drives by, honks, and the driver gives you a ’thumbs-up’ sign. That’s when you’re sure you’re doing the right thing, with the right materials."
Steve Zwilling is Eastern U.S. market development manager for Profile Products LLC. He can be contacted at email@example.com.