This post is stimulated from none other than fan and friend Patricia Herron!
Patricia: So they’re building a housing development near me. My daughter noticed that on the hills they have placed rolls of something that look like hay. They’re also spraying the hillside with some sort of greenish blue stuff. We couldn’t figure out why. I said to her it’s probably stuff to stop weeds or some kind of grass seeding system. Then I told her I’ll just ask my friend Celebrity Landscaper Ahmed Hassan. So… am I right?
Ahmed: You’re right, the greenish spray is what’s known as hydroseed. I would love to credit Ahmad Hassan Landscape Services as the inventor, but that simply is not the case. Yet I do know what the product is used for, and can give a little insight for you and your daughter to satisfy curiosities sake. Hydroseed is a slurry of grass seed that’s sprayed with a greenish paper pulp mulch, or sometimes, a finely ground wood of sorts. The mulch helps keep the seed moist until it germinates.
The rolls of straw or hay are called “wattles” and they’re used for erosion control to keep run off, soil, and dirty water from going into gutters and storm drain systems; as well as protect clean water ways like streams, creeks, and brooks. Whenever there’s new development and we get into the rainy season, you’ll see these tools and practices used.
Construction and development requires excavation of soil. This bare, exposed soil doesn’t drain very fast. Instead, it washes away down hill. Both hydroseeding and straw wattles are used to limit this run off and keep it from contaminating drainage systems. The cleaner a drainage system is, the better it functions. The problem with run off is twofold. First, you have to deal with small landslides and/or erosion of a hillside sliding away and sloughing off which would cause a construction clean-up nightmare.
The second, and more severe problem runoff creates, is of primary concern though. If you’ve ever washed soil down your driveway and had it end up in the gutter, then you have met this unassuming beast. The last of the super fine remains of soil are heavy, and require a lot of time, water, and broom work to push. This thick sludge like stuff is known as silt. By definition Silt is literally the last remains of soil. It is the smallest, sand like, particulate matter and it’s extremely difficult to manage and wash away.
Because this material is difficult to move, municipalities do everything possible to avoid ever getting it in their drainage ways. I know my city of Sacramento is more than diligent about it. The reason? Silt collects more of itself. So not only is silt heavy and hard to move; it builds up on itself, and like a magnet, attracts more silt. This heavy silt begins clogging up pipes and drain lines with a type of sludge (bust out your smart phone and look up “silt trap”). Here in California we use the date of October 15th as the official rainy season date. Other states may have different different deadlines. This is the date you’d better have erosion and soil water runoff control measures in place, or pay fines upwards of $30k if a municipality shows up and your construction site isn’t properly managed.
One other thing I wanna mention is what’s known as a “silt sock”.
If you walk down to the storm drain that your gutters empty into, you’ll likely see what looks like landscape fabric underneath the gutter drain grate. This is the final means of control before dirty, silty water enters the main, piped underground system.
So to recap:
1. Hydroseed is a method of applying and starting grass from seed. This grass grows roots that are used to take up water and stabilize hillsides by aggregating soil and holding it together. The foliage intercepts rain water so that it doesn’t compact soil, but instead hits the grass blades and runs down slowly into the soil, preventing erosion during construction and development.
2. Straw wattles are a second line of defense to slow and dam up silty water that’s running down hill. The water passes through the straw and the silt is caught there. This lessens the impact and the momentum of erosion while allowing water to do what it does and travel downhill.
3.Silt socks and catch apparatuses are used directly under and around storm drains.
All of these practices are mandated and enforced by local governments to keep our waterways clean and our drain ways flowing. They help avoid avoid floods and back ups. It’s a group effort to prevent floods and keep our reservoirs clean. The more you know, the more you can help do your own part.