Hydroseeding for Mining Sites

Sept. 18, 2016

Mining: Overcoming Soil Hurdles
Normand Cossette, president of Irrigation NORCO Inc. based in Quebec, says his company has been working since 1996 on a variety of mining sites located in Fermont (in Quebec) and Wabush and Labrador City (in the province of Newfoundland and Labrador). Each of these mining regions has similar challenges in terms of revegetation.

“The extremely low fertility level of the medium of growth [results from] metalliferous mill tailings, from local iron ore bodies with high silica content,” says Cossette. This means the area is “usually totally sterile and solely mineral, with 0% organic matter. Some microelements are too abundant, namely manganese and iron, and we must discard plant species that do not tolerate high manganese and iron content in the soil.”

Climate also poses a challenge in these regions. “One must select species with outstanding winter hardiness, species able to survive minus 45 degrees Celsius,” says Cossette, adding that the hardiness zone for this area’s landscaping purposes is 0 to 1a or 1b.

Revegetation goals for these sites are straightforward, he says: “To grow permanent, perennial, self-sustaining herbaceous vegetation, and to turn the sterile and solely mineral media of growth into a fertile soil, into a genuine living soil.”

Accomplishing this goal has meant embracing various hydroseeding techniques at the sites.

“To grow successfully herbaceous vegetation upon mining wastes, overburden material, and tailings sand, we use three different techniques, depending on the slope and surface conditions—for example, a smooth, cultivable surface versus a rocky or gravelly surface, or a gentle slope versus a steep slope. One is broadcast spreading of seeds plus harrowing plus fertilizer. The second is to spread hay mulch plus ‘crimp’ hay mulch plus direct, precision drill-seeding plus fertilizer(s), broadcast spread. The third, wherever a farm tractor cannot travel safely, is hydroseeding.” Of these three techniques, he says, hydroseeding is the most expensive one, and the per-hectare or per-acre cost is adjusted according to the number of “coats” of hydroseeding slurry sprayed upon the surface.

The company owns five trailer-mounted hydroseeding machines in the 1,050- to 1,250-gallon range and one larger 3,300-gallon machine Cossette refers to as “our Hulk.” He describes the Epic Mfg. Easy Lawn units, dating from 2004 and 2006, in particular as “highly reliable and versatile.” The all-hydraulic operation, paddle wheel agitator, and slurry pump—hence no clutch to operate—means they are safer for workers to operate, he says, and the stainless steel tank and agitator rotor makes them rust and corrosion free. He also has found the hose reel located at the back of the trailer appealing.

In the fall of 2014, Mountain Hydroseeding began an ongoing battle with erosion on a very steep slope near strip mines in Berry County, KY.

“There was some erosion happening, and they decided to fix it with a bulldozer and seed it,” says Boyd Brock, owner of Mountain Hydroseeding based in Pineville, KY. With a revegetation goal of 95% grass for the 2-acre site, the company used a Caudill Seed mix that included red clover, white clover, Kentucky 31 fescue, and Korean lespedeza on the site.

“They always give us a good product, and if we need any other kind of support from them it’s always there,” says Brock. “We got a really good grass blend.”

The selection of grass seed mix for a site like this requires careful consideration. “It depends on the permit package and the post-mining land use,” explains Kevin Howard, environmental quality control manager at Caudill Seed’s Allen, KY, branch. “When they get issued a permit, they receive a permit package. It lets you pick out of several species what you will use on the site.

“These are grasses that are approved by the Division of Mining Permits. They allow alternatives if you can’t get [the ones on the list]. You can get those approved, too. There are many steps in a revegetation plan.”

Orchard grass, timothy grass, clovers, and fescues are commonly used for revegetating mining sites in the region, as is winter rye. Howard says an annual grass is added to hold the soil in place.

Although Brock says the area didn’t experience considerable rain at the time of application, a variety of erosion control methods were employed.

“For erosion control we used runoff ponds, we used all-weather mulch in our seeding, and we use rock ditches,” he says. “Everything was put back on the slope, and it worked out.”

About the Author

Tara Beecham

Based in Morgantown, PA, Tara Beecham is a frequent contributor to Forester publications.