|
A range of materials, styles, and longevities for any application
By Carol Brzozowski
The St. Charles Park District in St. Charles, IL, has had some challenges over the years when it comes to erosion control along streambanks.
In one case five years ago, district officials found they had to stabilize Otter Creek after streambank construction had taken place, with construction machines having torn up the area. The district’s goal was to re-create the streambank with attractive vegetation without harming wildlife in the process.
The district turned to rolled erosion control blankets to do the job.
Rolled erosion control products include erosion control blankets, turf reinforcement mats, and associated products such as wattles, coir logs, and staples and fasteners.
Erosion control blankets tend to be lighter in weight and lighter in expense. They’re typically meant to last for one season until vegetation grows. The blankets are often constructed of straw, excelsior, or some other lightweight fiber sandwiched between two layers of netting, which is sometimes biodegradable or photodegradable.
Some are made without nets. Those types of blankets are chosen for use in areas where there are concerns about wildlife getting caught in the nets (snakes and other animals’ hooves can sometimes get caught) or about the net getting caught in mower blades if the vegetation needs to be mowed prior to the blanket completely degrading.
Pre-seeded blankets are available; sometimes blankets are laid atop seed to prevent erosion and hold in moisture to assist the germination process.
In contrast, TRMs (turf reinforcement mats) are heavier, can last several seasons, and are often made with UV-resistant synthetic nets. They are often made with heavier material such as coir and are sometimes constructed in multiple layers. They can be used for channel protection where high water velocities or shear stresses might occur.
In the case of the St. Charles Park District, officials chose Nedia Enterprises Inc.’s woven coir fabric products for two streambank restoration projects—one conducted five years ago and one less than a year ago.
Nedia Enterprises Inc. is based in Ashburn, VA. In addition to the woven coir products, the company offers a selection of erosion control blankets, coconut fiber logs, and composite TRM among its many products.
“We used the woven coir specifically because it is a natural fabric,” says Mary Ochsenschlager, assistant superintendent of parks/natural resources and interpretive service for the St. Charles Park District.
“When you use an artificial fabric, it is often hard on wildlife, especially when snakes get caught in it,” she adds. “We’re working in a natural area, and we definitely want to be wildlife friendly.”
 |
Photo: Reed & Graham |
| Rolled erosion control products on a hillside |
Park officials favored the all-coconut fiber construction of the rolled erosion control products for the streambank restoration projects. “We use a heavy blanket because the stream has a fairly good flow,” Ochsenschlager says. “We use one of the heaviest of Nedia Enterprises’ products. It’s like rope, but it’s woven.”
Park officials did a lot of research on the stream before embarking on the streambank restoration projects. “We knew a lot about what its flows were and a lot about its dynamics and how heavy a product we needed,” says Ochsenschlager of the stream. “Our consultant told us how to explore different products that were out there. I got different samples from all of the companies, read up on them, and talked to them about how I could get the heaviest fabric I could get with the flow of the stream.”
After choosing a product, it was time to do the math. In calculating the amount of rolled erosion control blanket product needed for the project, park district officials figured out how much streambank area needed to be addressed for the project. “The consultant was helpful. We knew what it would take, but we added a little extra so we wouldn’t run out,” Ochsenschlager says.
Everyone joined in on the installation: the consultant and a construction contractor (both of whom had previous experience with such projects) and employees of the park district.
Ochsenschlager compares the installation pattern the group designed to crossing one hand over another in crisscross fashion. “When we put the fabric down, we cut measured strips lengthwise so half hung in the water and the other half was at a right angle to the bank,” she says. “Then we put another one next to that, overlapping downstream to upstream, so when water comes, the overlap is going the right way.
“The overlap fabric part goes on the upstream side. If we had it on the downstream side, water would get underneath. We just kept laying those strips until we had all of the bank covered that we wanted as far along as wanted.”
The group would put soil on top of one strip of erosion control fabric, seed it, and flip the other strip of fabric hanging down on the bank over it to make a wrap. The installation was conducted in a lengthwise fashion.
“We were just trying to be careful that we didn’t let any soil slide in,” says Ochsenschlager. “Water flow is a big issue as far as how these are installed, so we did it so the water wouldn’t get underneath.”
 |
Photo: Reed & Graham |
| Ease of installation allows for a quick learning curve when it comes to placing erosion control fabric. |
 |
Photo: Reed & Graham |
After the fabric strip that was hanging in the water was brought over the other strip, it was staked down to what was already installed on the bank and also covered with soil before additional seed was applied. “We were very anxious to get plants going. But we didn’t use a lot, because it would have washed over,” Ochsenschlager notes. The project covered an area from 8 to 12 feet upwards of the bank.
Ochsenschlager says she and other park district officials have been happy with the results. “It looks great,” she says. “In the latest project we did, you can still see some fabric in some places, but we staked it down really well and it’s holding up just fine. Everything’s growing and we’ve been happy. We believe it did what we needed it to do.”
Saving Slopes in Pennsylvania
Mary Lou Burke, president of Valley Seeding Co. in Sugarloaf, PA, says it seems like more government entities such as the Pennsylvania Department of Transportation (PennDOT) and private industries are favoring erosion control blankets because of their ability to hold the topsoil.
Initially, Burke had been skeptical of the products. But once she started using the erosion control blankets, she and her installers were hooked. “They are a great product,” she says. “Everybody likes them.”
 |
Photo: St. Charles Park District |
| Stapled fabric along a streambank |
Valley Seeding Co., which does mostly highway and commercial landscaping, uses products from East Coast Erosion Control Blankets in Bernville, PA. The company makes a straw single-net blanket, a straw biodegradable single-net blanket, an excelsior single-net blanket, a straw double-net blanket, a straw biodegradable-net blanket, and a straw/coconut double-net blanket.
For one project on which Valley Seeding worked, an original seeding job didn’t set well as there had been a great deal of slope failure due to the fine nature of the soil. The seed didn’t have sufficient time to germinate, and the slopes were being lost to spring rains.
“They decided to try the blankets to see how that worked, and the blankets worked well,” Burke says.
While highway work erosion control products are already specified, Burke says her company is allowed to use another product that meets or exceeds the state’s specifications.
In order to determine how much of the product her company will use, Burke relies on information about how much coverage is needed from contractors. Her company stocks the rolls so that when they are needed they are ready to go.
Burke says it doesn’t take workers long to learn how to install erosion control blankets. Generally, her company installs them from the top to the bottom of a slope.
Another Pennsylvania company that uses East Coast Erosion Blankets, as well as those of American Excelsior and Hanes Geo Components, is RAM-T in Westchester, PA. RAM-T provides services—including erosion control—to contractors, land developers, and builders. The company does highway work for PennDOT and the Delaware Department of Transportation.
American Excelsior of Lake Wylie, SC, offers erosion control blankets made of excelsior fibers (Curlex), TRM made of recycled bottles (Recyclex), sediment logs made of excelsior, straw erosion control blankets, coconut-fiber erosion control blankets, and straw/coconut erosion control blankets.
Hanes Geo Components of Charlotte, NC, offers ExcelHigh jute matting, coconut fiber biologs, and coir matting; Applied Polymer Systems’ Floc Log, a semi-hydrated polyacrylamide blended block; and rolled erosion control products from Western Excelsior Corp.
RAM-T favors high-performance products, says the company’s Dave Klonicke. “We’ve done very well with TRMs. We believe they hold the seed in place, especially over winter.
“When you are talking about a developer stabilizing a large area of slope and you see one of the heavier products in there, as an installer, we like to see that. We’ve had good success with TRMs.”
 |
Photo: St. Charles Park District |
| Stapling (top) and laying (bottom) woven coir, a natural and thus wildlife-friendly fabric |
 |
Photo: St. Charles Park District |
When calculating how much to order, accounting for overlapping, RAM-T bills by the square footage in place, including the overlap, rather than billing by the roll.
It doesn’t take long to learn how to install erosion control blankets, Klonicke says. “It takes a couple of days on the job to learn how to do the trenching on the sides of the check slots.”
RAM-T installs from top to bottom of a slope. Klonicke says the most challenging jobs are those that involve steep slopes that are 2:1 or steeper. “The moisture runs off so quickly that it’s hard to keep enough moisture in the soil for the seed to germinate, so seed tends to germinate slower and there also is the associated erosion control potential,” he says.
Another challenging issue is installation timing, Klonicke notes. “You can give us any site condition and if we can address it in the correct seeding season—namely in the fall or early spring—it’s like night and day compared to doing it out of season. Timing of the installation is just as important as the type of product.
“Unfortunately, we don’t determine the schedule, so we’re held by our customer’s schedule and we install the material and stabilize the slopes whenever they are prepared,” he adds. “But it’s challenging when somebody asks you to come out in the beginning of June and stabilize a 1:1 slope with crown vetch, which takes two years to totally fill in anyway.”
 |
Photo: Reed & Graham |
| Installation timing is as critical to a project’s succes as what type of product you choose. |
 |
Photo: Reed & Graham |
Klonicke sees a lot of potential for bonded fiber matrix material, which his company has used with good success. “Price point is such an important issue when it comes to erosion control,” he notes. “The nice thing with hydraulically applied blankets is that it’s cost-effective to do it.”
Securing the Southwest
Sunbelt Reclamation in Mesa, AZ, is an erosion control and hydroseeding contractor that installs a number of best management practices, including riprap, TRMs, and erosion control blankets.
Sunbelt Reclamation services the residential, commercial, and municipal sectors. In 2006, blankets and mats comprised about 12% of the company’s overall erosion control efforts.
Among the products that Sunbelt Reclamation uses are those produced by Propex Geosynthetics, which produces geosynthetic, furnishing, and industrial fabrics and fiber, including erosion control blankets and turf reinforcement mats. Sunbelt uses Landlok erosion control blankets and TRMs and Pyramat high-performance TRMs.
Landlok erosion control blankets are made of straw, coconut fiber, or a mix of both or of polypropylene yarns and fibers and are reinforced on one or both sides by a polypropylene netting.
Landlok TRMs are made of 100% synthetic, UV-stabilized components and are nondegradable. Pyramat HPTRMs (high-performance TRMs) have a three-dimensional construction of polypropylene yarns.
“Pyramat and Landlok are a good share of all of the RECPs we use,” says Rich Shelton, general manager for Sunbelt Reclamation. “We consider them by far the leader.”
In measuring for the product to account for overlap, Sunbelt Reclamation calculates by the square yard. “We’ll take a look at the plans, take our measurements, and figure out what the overlap is in account for whatever the square yardage is,” says Shelton. “That’s how we’ve quoted to our customers and invoice it.”
 |
Photo: Reed & Graham |
| The most efficient approach to RECP installation depends on the site, as no two are the same. |
 |
Photo: Reed & Graham |
Sunbelt Reclamation may retain some products onsite, but the company generally tends to order only that which is needed, Shelton says.
He says most workers learn to install the products fairly quickly. “If someone is new to the industry, it may take several days to a week to figure it out, depending on the individual learning curve. If they have some experience in erosion control, it doesn’t take them very long. Our superintendents are right there to teach them every step of the way in the installation.”
As for the installation itself, Shelton says he believes the most efficient approach depends on the site, although the company prefers to install the products from the top down. “Each site—and the conditions on that site—is different,” he points out. “On some sites, we started from the bottom and have gone up, and on others, we started at the top and had gone down.”
Factors that would necessitate installing erosion control blankets and mats from the bottom up include steepness of slope and the turndown ratio. “We bring it up from the bottom to a certain point to the top to tie it in,” Shelton explains.
Sunbelt Reclamation has addressed a number of erosion control challenges with blankets and mats. One project in Maricopa County, AZ, involved “some rather large turn-downs, some slopes, and some compaction issues in which we had some transition between two different products,” says Shelton. “We had three different directional flows to contend with while we were installing.”
In addition to those influencing factors, there was water running at the site, scour, and another slope that was funneling water.
“We were trying to figure out how to put that in with the engineering design, and in talking with the engineer about the field conditions and the challenges, when the final installation came in, it was right,” says Shelton. “The product held up just fine.”
Similar products are offered by the following companies:
- Excelfibre, a division of Excelhigh, in New York, NY, offers woven coir fiber geotextiles, stitched erosion control blankets, coir logs/tubes, and coco gabions.
- ErosionControlBlanket.com of St. Andrews, MB, Canada, offers rolled erosion control blankets made of straw, coconut, a straw/coconut mix, and TRMs, as well as straw wattles.
- Earth Saver in Yolo, CA, offers rice straw wattles, hay bales, TRMs, and rolled erosion control products made of straw, coconut fiber, and straw/coconut fiber.
- North American Green of Evansville, IN, offers a variety of short-, extended-, and long-term erosion control blankets in both standard and biodegradable versions, as well as heavy-duty TRMs and Guardian Seed Protection Mulch Mat.
- RoLanka International of Stockbridge, GA, offers temporary mats designed to last six to nine months, made of straw, jute, and excelsior, as well as more durable temporary mats and semi-permanent and permanent mats made of coir. It also offers products for use in bioengineering projects, such as coir rolls and blocks.
Carol Brzozowski is a journalist in Coral Springs, FL.
EC - PSD 2008 |
