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Roadway Project Presents Steep Challenges

July 12, 2006

The city of Windsor, Ontario, Canada faced challenges of steep proportions in both preventing sediment erosion and establishing turf growth on 11 acres of 2:1 gradient exit ramp embankments. The exit ramps were built to provide motorists with a quicker route into the city, connecting Six Concession Road with Dougall Parkway, a main thoroughfare that turns into Highway 401.

By: Sarah Willnerd

The project's builder had only a small amount of land to work with, due to the private property that was in close proximity to Dougall Parkway, resulting in steep ramp embankments. In addition, the project needed to have topsoil laid over the embankments' 23-ft tall clay soil to establish healthy grass.

Susan St. Louis, the project engineer from Dillon Consulting LTD., turned to John Reynolds of MulchIt, a distributor in Putnam, Ont., for consultation.

"This project was a big challenge," Reynolds said. "Erosion control was obviously necessary to stabilize banks, establish seed growth and prevent erosion of silt and soil into waterways."

Reynolds determined that erosion-control blankets were not appropriate, since stapling them would be dangerous for workers. Furthermore, the embankments' soil was coarse, which could cause the blankets to "tent" and not completely conform to the landscape, thus limiting soil coverage and protection. Reynolds also ruled out bonded fiber matrix (BFM) products, because BFM’s would not efficiently bond to the soil or retain moisture for an extended period of time.

Reynolds recommended using Profile Products' Flexterra Flexible Growth Medium (FGM) . Flexterra is a hydraulically applied FGM made of thermally refined wood fibers, crimped, interlocking fibers and performance-enhancing additives that are engineered to work under extreme conditions. Flexterra also excels at moisture retention, and is the only FGM that does not require cure time to be effective.

"When applied, Flexterra clings to every inch of the ground," Reynolds said. "It helps create a micro-environment for seed growth."

After the exit ramps were built, four inches of topsoil were applied to the native clay soil. Flexterra was then hydraulically applied at a rate of 3,200 to 4,000 lb per acre. Mixed in with the mulch was a combination of grass seed and fertilizer.

The steep embankments proved to be the most challenging places to efficiently apply Flexterra . Reynolds ended up spraying the area from opposite directions to ensure that every square inch would be covered, thus preventing shadowing from occurring on the soil.

Even the presence of rain did not deter the application. Flexterra . is effective immediately upon application and does not need to cure to provide protection. As a result, there was no concern about the mulch washing away, and no downtime waiting for rain to pass.

St. Louis was impressed with the erosion-control results and healthy, consistent grass establishment on the slopes, despite the minimal rainfall the area received over the course of the summer.

"The embankments look great," St. Louis said. "It’s pretty awesome how it filled in. There were no signs of erosion but quite a bit of vegetation."