Dec. 1, 2014 02:47

Site Stabilization

Old, cheesy monster movies can teach us a lot about the work we do. Don’t disturb the soil, as the story goes, or you’ll unearth a monster. Of course, no one ever listens and, like clockwork, someone goes digging where they shouldn’t and out comes an indominable beast. But somehow, in every single movie, humans manage to fight the creature back to its murky depths— usually through a combination of old-fashioned cunning and topsecret technology.

As a soil erosion contractor, you know that it’s a remarkably similar beast. When construction work needs to be done, it’s inevitable that this monster will rear its ugly head. But the good news is, just as in those old movies, numerous technologies exist to help you fight back, allowing you to stabilize your worksite and combat erosion.

The sheer number of erosionfighting products and technologies out there might make you hesitant, however. With so many choices, knowing what to use and when to use it can become almost as frustrating as the erosion itself. Still, even though these tools perform unique functions, they all work toward the same goal: victory over the beast (erosion).

Just as you wouldn’t want to sit around waiting for a monster to attack a major city, it’s best to address soil stabilization early. The sooner you tackle soil issues, the better, especially if you’re in a region with major rainstorms.

And as the old saying goes, controlling erosion is good, but preventing it is even better. If you need to control erosion, you already have an erosion problem. By making prevention your objective, however, you can anticipate erosion conditions before they occur. Then, once you’ve conceptualized the possibilities, you can aim to prevent it, based on your design features.

For that reason, once you’ve cleared a site, it’s essential that your efforts to stabilize the soil begin soon after. Otherwise, the exposed soil stays vulnerable to erosion and water damage. And that’s no way to start a project. So to get you off on the right foot, let’s look at your options.

You’ll find that preferences will shift, depending on your location. In some areas, contractors might prefer chopped straw, mats or sand or gravel bags. In others, they might use gravel barriers or silt fences. The devices you choose will largely depend on the environment you’re dealing with. But, in the end, it won’t matter what you use, as long as you use what works.

When it comes to protecting the soil, geosynthetic mats offer a straightforward, effective solution. You can use mats to cover, stabilize or separate the soil. And if that’s not enough, they’re efficient slope stabilizers and double as drainage aids, too.

Rolled erosion control products, such as erosion-control blankets (ECBs) and turf reinforcement mats (TRMs), come under the geosynthetics umbrella and see frequent use on worksites. And for good reason, too. Often made of biodegradable materials, like coir and straw, ECBs are temporary solutions. TRMs, on the other hand, remain onsite permanently.

“Once a slope is properly prepared, a good turf reinforcement mat or erosion control blanket definitely gets the job done,” says Michael Robeson, technical development manager at Profile Products, LLC in Fort Collins, Colorado.

“For underwater applications, you might need to use a transition mat. After that, it’s a good idea to put down a TRM right at the water line; that way, you can get vegetation and reinforcement when you have flood conditions.”

Whether they’re temporary or permanent, above ground or submerged, geosynthetics offer the versatility necessary for the changing dynamics of a worksite, especially in construction where conditions change day-to-day. With their protection, you won’t wake up to a wet jobsite or slushy soil—and you’ll likely encounter fewer hiccups in general.

Chopped straw is an even more cost-effective erosion control solution, says Mike Allen, owner of Allen Land Services, Inc., in Garden Valley, Indiana. “If you’re anticipating moisture, you can just spread straw around your worksite. It’s a cheap method of controlling erosion. If you have a big rainstorm, the straw stops the larger drops of rain from wiping out your soil.”

For inlet protection, consider gravel or sand bags. These bags function as barriers against runoff and other buildup. They’re also cheap, easy to place and stackable. For that reason, you’ll find that they make highly efficient perimeters, too. And if the border of your worksite shifts, or you need to place a new barrier, they won’t require any lengthy installations, either.

Since the bag fabric can tear, however, it’s important to have other tools at your disposal, says Gil Carrillo, president of Environment Site Maintenance in Simi Valley, California. “We tend to use silt fence in lieu of gravel bags. That’s because sometimes, when the bags get damaged, they end up causing more of a mess. And that’s a mess that you’ll have to later fix or reinstall.”

While silt fencing isn’t necessarily a cure-all for your erosion-control woes, you should ensure its inclusion on your worksite. These barriers are comprised of pieces of permeable, geosynthetic fabric which are trenched and staked into the ground. Once they’re set up, they slow the flow of water and trap sediment, essentially creating a catch basin from which you can later remove the collected sludge.

Mud and runoff can result in drastic damage or severe setbacks, particularly on larger projects or those with tight deadlines. By using silt fencing, you’re taking the first step toward tightening up your site and getting the job done on time.

“Silt fencing is a great choice for a perimeter. It’s a sturdy border and allows you to save money during construction—and it’s portable,” says Robeson. “While your service contours are changing over the course of a project, you can reinstall silt fencing and periodically maintain it, rather than implementing finalized erosion control products. It really helps minimize your costs from a construction standpoint.”

Along with the other products that you’re using, hydroseeding is also worth looking into, especially if you’re working with slopes. Hydroseeders—or hydraulic mulch seeders, as they’re sometimes called—use a slurry of seed, fertilizer and mulch. These machines spray that mixture over a prepared site in a uniform layer. A tackifier is also used to keep the seed stuck to the soil. Then, the fertilizer within the blend encourages rapid growth.

The best part is, since it’s sprayed on the surface, a slope’s gradient is less of a concern. You could be facing a 90-degree angle and still get the job done. It’s essentially a spray-on blanket, and for slope protection, it’s an excellent choice.

In an area with flow problems, however, you might consider other options. Runoff and unexpected water require immediate attention and a careful approach, says Christine Williams, environmental coordinator at CC Myers, Inc., Anaheim, California.

“We use pipes or barriers to push the water to a less vital location. We also document. That’s definitely the biggest BMP. That way, if there’s any failure to our BMPs, we have documentation that it didn’t come from our work area. It covers our end on liability.”

But it’s not just runoff you should be worried about, says Williams. “We also have a lot of ‘run-on’ issues. Whether it’s the neighbors, an irrigating farmer or a flow left by a prior contractor, it’s always a shock. We work with the owner to try to divert the water, move it around, or get it through the project. If that doesn’t work, we have to deal with the water as it comes in.”

If pipes and barriers don’t remove all of the water, consider installing sediment traps. These small ponds trap excess water in specific locations, preventing overflow and runoff while, at the same time, capturing run-on. And, as their name suggests, they’re also excellent at controlling sediment. You’ll want to install permanent stormwater ponds after the project’s completion, however, since sediment traps are only temporary.

Once the job is completed, or at least nearing conclusion, choose groundcover, such as trees, grass or shrubs, to provide a more lasting erosion-control solution. Groundcover provides permanent soil stabilization and also beautifies the site. Native plants work particularly well since they’re durable and rapidly acclimate themselves to the surrounding environment.

“After the job’s done, any sort of ground cover is best for permanent stabilization. Not only does groundcover present numerous options, particularly from an aesthetic standpoint, it also acts as a filter as well as stabilizing slopes. So, essentially, you’re able to give the site a facelift while simultaneously creating stabilization,” says Carrillo.

But it’s important to remember that technology, products and techniques are only half the battle. Vigilance, claims Carrillo, is the real key to winning the war. “A few of our clients make sure there’s a set amount of hours that we’ll be at the location every week, to continually assess the site. Once we’re there, we can repair or replace any BMPs that are broken or damaged. It helps keep things from building up and becoming major issues.”

“If you’re there on a weekly basis, you can stay on top of it,” adds Carrillo. “Whereas, if you’re not there for a month, and then all of a sudden, a client calls with an emergency, you might not be ready to handle it. With only twenty-four hours notice from the builder, what are you supposed to do, throw ten guys out there? That’s not possible if you’re already booked up.”

Another thing to look out for, says Carrillo, are any subcontractors on a jobsite. After you’ve finished the project, encourage the location’s owner to teach proper site management. That way, you know that your work won’t be undone by anyone in or around the area.

“We’re out there to assess the site for them and work for the supervisor, to let them know where issues might exist,” says Carrillo. “If certain people are running over rock bags or parking on the wrong lots, we let them know. It’s preventative, especially when it means you won’t have to repair or replace as much if the damage doesn’t happen in the first place.”

And if you haven’t already joined one, consider looking into professional organizations and associations, like the IECA. These associations usually offer classes, seminars and certifications, and they also help you connect with other professionals in the field.

“Numerous construction organizations, stormwater associations and building groups exist to help contractors, and depending on the kind of work that they do, they’ll generally provide specific assistance. And usually the state water boards themselves have things available for contractors,” says Williams.

So pay attention the next time you watch an old monster movie. You’ll notice that, time and again, the filmmaker waits before exposing the creature — a convention that plays on our fear of the unknown. Once the monster is finally exposed, the characters toil over their options, desperately searching for a solution until… Eureka! They have their answer: a way to defeat the monster.

Luckily, unlike those hapless characters, you won’t have to rack your brain for that elusive secret. These technologies already exist for erosion control and site stabilization. All you have to do is use them. What’s to be afraid of?

Also in Featured Articles

In many ways, we are fortunate that, in our chosen profession, we are able to help people when certain disasters occur: the tornadoes in Missouri, Oklahoma, Louisiana and Georgia, the flooding in Louisiana, the snows in the northeastern part of the country, the rain in California, and the snow in Colorado....

Do not miss another issue.
Read the new issue of Soil Erosion Magazine online