Erosion Control

Silt Stalkings

Many traps are available in the hunt for silt and sediment.

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Credit: ISTOCK/FRANCE68
With construction’s high cost of equipment, fuel, and labor, it’s too bad we can’t harness the power of water. It often seems that nothing can move soil faster than a good rain-unfortunately, not necessarily to the places you want it to go. Therefore, soil and sediment must be captured and kept onsite. Fortunately, there are many products that can get the job done in a cost-effective manner.

Where the Rubber Hits the Road, Sediment Can’t
Highway construction adds “safety” to concerns about silt and sediment. Those items need to be kept not only from storm drains but also off the roadway.

This past fall, Lake City, FL’s Anderson Columbia Construction began work on a 20-mile strip of Interstate 26 near Columbia, SC. The project entailed 10 miles of widening the road, adding one lane in either direction, and 10 miles of rehabbing the asphalt surface. Anderson Columbia took care of the earthmoving and subcontracted the asphalt work to Boggs Paving of Monroe, NC. Boggs’ erosion control manager, Will Auret, was tasked with ensuring sediment stayed out of the storm sewers.

Credit: STORMWATER PROS LLCGator Guards were placed every 50 feet up the hillside. Note the gully produced by the torrential rainfall.
Credit: STORMWATER PROS LLC
Gator Guards were placed every 50 feet up the hillside. Note the gully produced by the torrential rainfall.

“The project started in September 2013, and it’s scheduled to be finished in August 2015,” Auret says. “The new lanes will be built in the existing median. At completion, there will be no grass median-just a permanent barrier wall going down the middle. Although the rehab section gets some too, the majority of the erosion control work is in the widening area.”

The first task: ensuring workers’ safety. “We set up temporary barrier walls, so we could work in the median, as all the work was going on there. The barriers were to protect us from traffic. Then we needed to protect the drop inlets from any sediment. There were drainage grates in the middle of the median, as well as on the road’s shoulders.”

Next on the list: securing inlet protection before any soil was moved. Auret used Grate Pyramids from ACF Environmental in Richmond, VA. A reusable inlet protection device, the Grate Pyramid protects inlet structures from sediment and debris during construction. The heavy-duty frame forms a sturdy barricade over most drop inlets. Because the units attach with hooks, there’s no lifting of heavy grates. The high-flow geotextile filter skirt stops sediment and debris while allowing the filtered water to leave the site. A built-in overflow prevents ponding during major storms. For high visibility and safety, Grate Pyramids are bright orange.

“When we received the project plans, they required a certain type of inlet filter. We could choose one-no particular one was specified-but the chosen product had to meet certain requirements. Grate Pyramids fit what we needed. This is the first time I’ve used them, and I like that they’re reusable. There are hundreds of inlets on this job-150 in each 10-mile strip-and the pyramids were easy for us to attach,” Auret explains. “A three-man crew took just a day to install them all. You don’t need experience to install them. Clean off the inlet, get a smooth surface, drop the Grate Pyramids on, and anchor them with the supplied hooks around the inlet.”

As the Grate Pyramids did their jobs, they needed periodic cleaning. “After a good rain, you’ll see the sediment piled around them. Yet, if you lift them up, the inlet box is clean. The Grate Pyramids worked really well. We have to clean them off once in a while, which is fairly simple. We dust them off, or, if there’s a lot of sediment, shovel dirt off. I don’t know their lifespan yet, so I can’t say how long they’ll last, but it seems the only way to lose one is from construction traffic-even though they’re bright orange,” he chuckles. “Thus far, we’ve only lost one. They will stay onsite during the entire project, then we’ll clean them off and take them back to our shop to reuse someplace else.”

Hilly or sloped areas might need additional protection. “The Grate Pyramids work best when used in conjunction with other erosion control BMPs,” Auret concludes. “For the interchange slopes, we installed check dams made from wattles, to slow the water down before it hits the Grate Pyramids. But all in all, Grate Pyramids are low maintenance, easy to install, and effective.”

Saving Silt, Stopping Accidents
Established in 1971, GCS Erosion Supply of Dallas, GA, has been providing Silt-Saver products for some time. “We started selling the products pretty close to when they came out with the Silt-Saver domes,” says GCS vice president Shawn Whitener. “We do a lot of erosion sales and supplies, as well as performing some projects with Silt-Saver domes. I normally get the standard ones, but they also have a DOT cover with high-flow filters. Mainly, we sell them to customers. However, I’ve used them myself. They’re easy to install, as well as to pop up and reinstall. For example-you’ve already installed them on street drains, but now the concrete curb crew’s coming down the street. If you use filters, concrete crews tear them up. But with a dome, you pop it out, let crews do the curbs, then put the dome back in-it’s fast and efficient.”

Both Whitener and his customers appreciate Silt-Saver’s sturdy construction. “The domes are reusable-you can use them over and over. After some time, the fabric covers have to be replaced, but the plastic domes last and last. Yes, the units are pricey at first, but because they can be reused, they become more cost-effective. I probably sell hundreds of them in the Atlanta area, and with the unusual weather we had this past winter, the domes held up really well. There are domes to fit 48-inch round or square manholes. They arrive 20 dome frames to a pallet and store atop each other very well.”

In addition to sediment control, the Silt-Saver domes contribute to site safety. “One good thing about these, not only do they help keep silt out of manholes, but they also keep people from falling into manholes, which are extremely deep. These add safety for animals and kids,” Whitener explains. “At the end of the project, the domes are removed, concrete throats are usually poured around the manhole, then it’s complete.”

In-the-field experience has caused a few changes to Silt-Savers over the years.

“They’ve made little changes on the covers, because they get feedback from customers. Some dome filters would invert, drooping down into the manhole when there was lots of sediment, so they changed the fabric so it wouldn’t do that,” Whitener concludes. “I wish I could’ve come up with the idea. Roger [Singleton, Silt-Saver’s president] is a smart guy.”

Gators Protect Desert Homes
Those who don’t live in desert areas think of them as rainless. For the most part, that’s true, but when the rain comes, it can come in torrents, quickly causing floods. In 2013, a Phoenix, AZ, neighborhood experienced such conditions and hired Stormwater Pros LLC to help solve the problem.

“This project was for the Mountain Park Ranch homeowners association, a fairly large association with thousands of houses in a hilly desert area,” explains Stormwater Pros’ owner Brig Christensen, EIT. “There had been erosion control problems during storms-soil washed down hills and into the homeowners’ yards. One home’s 8-foot-deep swimming pool was filled halfway with sediment.”

To prevent such problems in the future, Christensen used products from Gator Guard Environmental Products Inc. in Boise, ID. “We used a series of Gator Guard sediment control wattles up the hillside, like a check dam, to slow water down, control its flow, and slow its velocity. The Gator Guards are also sediment traps. These were installed permanently, a cost-effective solution that wasn’t labor intensive.”

The homeowners association, which owns the hillside, had a limited budget, as well as concerns about other sediment-trapping products. “We could’ve brought in rocks, but those would have been more expensive and labor intensive. The association didn’t want to do straw wattles, as local wildlife would have eaten them, and they wanted a long-lasting solution. As Gator Guard has a five-year lifespan, and doesn’t include straw, we thought that was the best bet. We worked in conjunction with a landscaper. We suggested riprap stabilization with filter fabric at the base of the hill, along with the Gator Guard. No plantings were put in to stop or slow the erosion.”

The problem area, which affected about 50 houses, required 5,000 linear feet of Gator Guard. “We put a line of the 6-inch-diameter wattles along the bottom of the hill, a couple of thousand feet each. Then we staggered them 400 feet up the hillside, every 50 feet, making a 20-foot-wide barrier of Gator Guard. For these check dams, we used the 9-inch-diameter products. We used Gator Guard’s standard black, the new woven product that lasts the longest. Unfortunately, the supplied Gator Guard stakes didn’t work here; for this rocky area, we had to purchase larger stakes to secure them into the ground. The project took about four or five days to complete, because we had to haul all these items in, and there wasn’t any easy access for getting the products where they had to be. The landscaper had a tractor, and we brought them into the area as far as we could; the rest of the way, the items were carried.”

When the project was completed, the homeowners’ association was very happy, and so was Christensen. “We will use Gator Guard again.”

Don’t Take a Lightweight to a Sediment Fight

Credit: STORMWATER PROS LLCRiprap was also added to the site.
Credit: STORMWATER PROS LLC
Riprap was also added to the site.

Justin Quiggle, CPESC, now works for Roseville, CA’s Jacobson James & Associates, an environmental consulting firm specializing in stormwater and soil remediation, but at a previous job had more experience with trapping silt and sediment. His choice for many applications was World Textile and Bag (WTB) of Sacramento, CA.

“I’ve used World Textile and Bag’s Heavyweight wattle a little bit in my current position, but more in the previous company I worked for,” Quiggle reports. “I’m still doing a lot of sediment control; Jacobson, James has used it in a few areas.”

He gives an example of the product’s use. “I was working as the environmental compliance manager for a large homebuilder and had problems with straw wattles being damaged during the construction process. Too much traffic over a straw wattle, and that’s it-it has to be replaced. I was on a national stormwater committee, which did a project on wattle efficiency; I did a cost study on how much it cost to keep replacing straw rolls. By comparison, WTB held up to the traffic and could be reused. The Heavyweight’s initial cost was higher, but in the long run, we could reuse them and save the company money.”

Credit: STORMWATER PROS LLCA wattle stands ready to slow the runoff onsite.
Credit: STORMWATER PROS LLC
A wattle stands ready to slow the runoff onsite.

Quiggle first discovered WTB products about a decade ago. “Since we were having trouble with standard fiber rolls, I tried the Heavyweight product. At that time, several items were available from many manufacturers, but we found Heavyweights were easy to install, they offered reusability, and stood up to traffic. Heavyweights saved the company a lot of money, eliminated waste, and we could store and reuse them. They’re easy to store. Although they’re shipped compressed, once used, Heavyweights are laid out lengthwise. Some went into a steel conex box, and you can store it outside. I’d guess you can fit about three times the length into the bed of a truck as you can a standard straw wattle.”

Reusable, easy to store-but do they stop sediment? “Heavyweights worked really well-better, I thought, than regular wattle. They’ve been tested; sediment is significantly reduced over a regular wattle.” (According to WTB’s website, Heavyweights filter 96.6% of sediment and have been ASTM D7351 field tested.) “I saw Heavyweights in action. It’s pretty impressive how much they stood up. They contain foam, so the wattles want to float up, but because they’re anchored down, the sediment has to go through and be captured. As for straw wattles, they become waterlogged, and sediment escapes.”

He continues, “On my former job, work on a couple thousand home lots was stopped due to a Sacramento building moratorium. After Hurricane Katrina, when the New Orleans levee didn’t hold, the federal government required study of the levees around the Sacramento and American rivers. It turned out the FEMA mapping was inaccurate; all those houses being built were in a flood zone! The current sediment control was fading, so we put in 20,000 or 30,000 linear feet of Heavyweight wattle. This was done in 2007, and the Heavyweight wattles are still there, doing their job. They don’t break down in sunlight, from traffic-they’re robust.”

His current employer has also used WTB products. “We have used the weighted wattle in a couple of locations, like for a check dam or around a stockpile on asphalt. However, now we do much work for a utility company, which requires the use of biodegradable BMPs that can be left in place. But if I was working on a construction site with traffic, I’d use World Textile and Bag’s Heavyweight wattle at the stabilized construction entrance.”

Pase Contracting has been using the WTB Heavyweight wattle for years. “We do sediment and erosion control land reclamation,” Curt Pase reports. “Right now, we’re using Heavyweight wattles on Shea Homes’ Stepping Stone development, which encompasses 1,500 homes at least, perhaps a couple thousand. This is an ongoing project that started in spring 2013. We use the Heavyweights for sediment control during construction. After the curbing and gutters go in, the Heavyweights go behind the curb. We used 160,000 feet of it last year alone.”

Pase has been using the product for most of the past decade. “A Heavyweight is a 4.5- by 4.5-inch square of foam, 12 feet long, with geotextile around it, and a 12- or 18-inch skirt that gets buried in the dirt and anchors it down. They’re easier to transport than a wattle; they arrive at the job site compressed, easy to put on the truck and take out. Once you cut the shipping binders, the wattle balloons up with air.”

The Heavyweights take the abuse, but are still of use. “They’re pricier than straw, but a week or two later, straw wattles will be torn up and have to be replaced. Heavyweights will take a lot of abuse on the job site. Once homebuilding starts on a big land development, so many people need to access the lot-drywallers, framers, brickworkers-and they all have vehicles, and sometimes heavy loads. Forklifts, appliance trucks, even big concrete trucks can run over them at the washouts. Straw wattles just rip apart if you drive over them too many times. In some instances WTB Heavyweight wattles last the life of the home’s construction. Plus, they’re reusable-up to a point, of course. As far as keeping sediment contained, nothing can compete with WTB’s product right now.”

Cutting costs is always desirable, if one’s careful to not let “initial cost” blind one to the “eventual cost.” “Builders and developers are finding value with Heavyweights,” Pase says. “At first they thought “˜silt fence, straw wattles,’ but they found the products just don’t last. Some builders will want silt fence or straw wattles during the initial earthmoving, but once they start building homes they want Heavyweight, because it will last.

“We reclaim them whenever the project superintendent tells us to, usually once the landscaping is finished. Our customers are happy with Heavyweights, and so are we,” he concludes. SW_bug_web

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