Passing through new construction, you may have noticed an odd greenish-grey-coloured coating, alongside the road.
What is that weird-looking stuff? And why is it there?
The answer is – hydroseeding – a mix of grass seed, mulch, fertilizer, water and a few ingredients to make all that stick together. (The mulch is coloured with a natural and biodegradable green dye to help see where the product has been applied.) This concoction is sprayed on newly excavated or filled slopes to give them a head start to re-vegetation.
The special slurry forms a blanket on bare soil, protecting the soil from erosion and runoff, and holding the seed in place until it gets growing. The seed is a specially designed mix that is unappetizing to wildlife (animals grazing roadside can mean danger for both them and vehicles), grows quickly and forms a healthy root mass. Hydroseeding is a preferable to other erosion control techniques like traditional broadcasting or sowing of dry seed, because the mulch and tackifier (binding ingredient) hold the soil together while the seed is growing.
It’s important to keep sediment and debris from running into streams, creeks, lakes and the ocean. Vegetation beside highways is also critical to absorb some of the moisture from rain, snow and ice, which could undermine and damage the road base.
Another method we use to prevent erosion and revegetate bare earth are erosion control blankets. Seed is first distributed on the soil, and then the long fibre mats are manually rolled out on top, and staked to the ground. This method is used in areas prone to slope erosion, or when there are environmental concerns that heavy rains could transport sediment into sensitive areas.
Each year, we cover more than a thousand hectares with hydroseeding, as part of our construction and maintenance projects. For example, hydroseeding was sprayed on about 20 hectares alongside the Malahat Highway, on southern Vancouver Island, in spring and fall 2017, and fall 2018.
In 2018, we also invested in hydroseeding on roadsides in the Southern Interior that were impacted by wildfires, to help prevent erosion and stop invasive plants from taking root. Across BC, hydroseeding is part of protecting water quality and sensitive ecosystems next to our highways, as well as halting the spread of invasive plants.
So, the next time that you see slopes looking like they’ve been slathered with off-putting hospital-green colour paint, know that the area will soon transform to good-looking ground cover. As the grass grows, weird green will give way to verdant natural beauty that protects ecosystems and highways.
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