What's New in Wattles
Does the word Wattle instantly conjure up the fleshy, wrinkled, brightly colored orangish-red skin hanging from the throat of a turkey? or a long, flexible, netted tube of straw used for erosion control on hillsides and ditches? If you chose the second answer you’re reading the right magazine, as the wattles we’re going to talk about are not a part of your Thanksgiving turkey.
Commonly referred to as sediment retention wattles (SRWs), slope interruption devices (SIDs) or sediment retention fiber rolls (SRFRs), these snake-like tubes offer perimeter protection along the bases of slopes, contours, inlets and roadways. Their main purpose is to reduce and re-direct water runoff and retain sediment. Using wattles is the most cost-effective method of reducing soil erosion and helping to stabilize stream banks, slopes, wetlands, and hillside soils.
With outer shells made of 100 percent biodegradable and photodegradable material, burlap netting or coir twine (coir is the husk fiber extracted from coconuts), wattles can be filled with various types of materials. The most common material used is compacted straw, but other stuffings include wood shavings, coir fibers, aspen fibers, rice straw, recycled tires and sometimes, stones.
Wattles come in various lengths, from 10- to 30-feet long, and are available in 6, 9, 12, 18, and 20- inch diameters. They can be used individually or tied together to achieve any desired length, and are installed by staking in place or weighted to sit in place. Think of wattles as the last line of defense against erosion.
Now that we’ve gotten the conventional uses noted, let’s talk turkey. . . .
Water runoff control
Stormwater runoff is generated when precipitation from rain and snowmelt flows over land and impervious surfaces and does not percolate into the ground. Instead, it accumulates debris, chemicals, sediment and other pollutants that can adversely affect water quality if the runoff is not contained.
When water continually runs down a slope or hillside, you’re asking for a slope failure. To avoid the situation, consider implementing wattles; think of them as slope interruption devices. The wattles stabilize the slope by shortening the slope’s length, spreading and filtering the water flow and slowing the velocity of water runoff.
They are designed to absorb excess water and filter sediment, which can quickly remedy the negative effects of slope steepness.
When properly installed, wattles will prevent sheet erosion in rill and gully development. A rill is a natural fluvial topographic feature that forms as a shallow waterway on an exposed slope, and is an initial sign of erosion. Both a rill and a gully will occur when a runoff flow is uninterrupted down a slope.
For flat ground areas, wattles can be staked down or just be put into place; to do so you must use wattles that are constructed with heavy stabilizing materials, such as metal bars. Wrap them around an inlet or storm drain or other water collection areas, to prevent stormwater pollution from getting in. They are also extremely effective in reducing pooling of water and flow velocities across channel bottoms.
Wattles will also stabilize stream banks, as will filter socks. Both of these are manufactured mesh containment products, filled with a variety of organic materials; some biodegrade, some don’t. Most can be left onsite to become part of the area habitat.
Filtrexx International, LLC, in Grafton, Ohio, makes a number of different types of filter socks. GroSoxx is a heavy-duty tubular mesh netting filled with compostgrowing media. If desired, a custom seed mix can be injected into the compost during manufacturing. A series of these types of wattles create natural anchors that stabilizes waterway banks and prevents future erosion of riparian areas.
These products were utilized recently in North Carolina, where a stream bank restoration project in a residential area of Charlotte had issues with stormwater runoff due to excessive rains. The client’s house was located on a lot that backed up against a stream, and the backyard was being washed away. To solve the problem, a Filtrexx bank stabilization system was installed.
“Due to recent construction upstream, an increasing amount of water was being distributed into the stream,” explained J.R. Stewart, a Filtrexx representative who helped oversee the installation. “Houses nearby were built close together and that, in combination with a narrow driveway and excessive grades into the backyard, made the area inaccessible for heavy equipment. The stabilization system allowed for the bank to remain secure while germination was achieved.”
To control sediment, silt and sand around construction sites, storm drains, and even in low-flow channels, wattles provide the most effective erosion control. When soil is eroding, loose sediment will wash away, often finding its way to the closest water source. Wattles stop this sediment from getting into the water and polluting it.
By staking wattles along the contours of newly constructed or disturbed slopes, you can capture and hold sediment in place. This will also create reliable filtration boundaries around your jobsites that do not require removal at the completion of the jobs.
McComas-Lacina Construction, based in Iowa City, Iowa, employed this technique when they were contracted to build a new 14-story dormitory space for students at the University of Iowa in Iowa City, Iowa. Sediment loss was a concern, because existing buildings and structures surrounding the site sat on a 3:1 slope.
Workers used more than 990 linear feet of Grimes, Iowa-based Soil- Tek’s e-tube biodegradable filter sock, which was filled with a blend of compost and mulch. Water filters through it, while sediment is trapped before it’s lost. The product’s flexibility allowed it to protect the soil as it wrapped around the structures on the 1.5-acre site.
The e-tube’s durability was tested during a rainstorm that produced three-quarters of an inch of rain per hour, with zero site loss, notes Brian Denham, Soil-Tek’s general manager. Mobility also was a concern at the site, where there were many different contractors located within a single confined space. The e-tubes can be moved and then “put back in place before they leave the site and before another rainfall,” said Denham.
Sediment control in urban areas brings its own unique challenges. In Newark, Delaware, the site of a former Chrysler plant is being redesigned by a local university. After the plant had been torn down, the school contracted Lindstrom Excavation Contractors, Inc., in Worton, Maryland, to begin installing a 4,000-foot gas line. Runoff at the site, which has approximately 60 acres of blacktop, had been an initial concern during construction, in terms of sediment control.
“The original design for the project included silt fencing,” said Duane Lindstrom, president of the company. But he suggested using Erosion Eels, from Friendly Environment in Shelbyville, Tennessee, instead. Erosion Eels are sediment tubes filled with an effective filter ballast material consisting of 100% shredded, recycled tire rubber.
“Since you have a hard surface, it’s beneficial to use Erosion Eels, so you don’t disturb anything,” Lindstrom said. In the end, it’s less expensive than putting silt fence in and pulling silt fence out. Another advantage, he said, was that the Eels would not destroy the existing blacktop.
Erosion Eels were placed around the area where the gas line was being installed; they require no staking into the ground. The ease of moving them was also appealing. One unique aspect of using the product is that when a project is completed, they can be reused after they have been cleaned.
Fires create yet a different kind of sediment issue that requires another type of wattle attack plan. After the fires in San Diego, California, Jason Locklin was contacted to help with damaged land near reservoirs in Fallbrook, California. Locklin is president of Sierra Construction Services, Inc., in Aliso Viejo, California.
The vegetation surrounding four of the reservoirs had been burned by the wildfires, endangering the town’s water supply. The soil at these sites did not have the crust that sometimes is present after a wildfire. Instead, the soil was silty and soft, with a lot of ash. Locklin and his company created a plan to mitigate erosion and sedimentation at the sites. The plan called for a combination of silt fence, fiber rolls and hydroseeding.
In both water runoff and sediment control applications, wattles are more effective when used in combination with other soil erosion techniques such as revegetation, surface roughening, mulching, erosion control blankets and soil stabilizers.
Straw wattles from Earth Savers in Woodland, California, were installed around the reservoirs and every 10 feet on the 2:1 slopes; the wattles were filled with weed-free California rice straw. According to Locklin, the wattles protected the reservoirs from both erosion and sediment loss. They reduced the velocity of runoff down the slopes near the reservoirs, turning it into sheet flow rather than direct flow, and trapping suspended sediment.
Once the wattles were down, Sierra Construction Services hydroseeded the areas with wood fiber tackifiers, and a specified seed mix native to San Diego County.
The combined methods dramatically decreased the amount of erosion. The wattles reduced the runoff by absorbing much of the water and filtering the rest, while the captured sediment provided a good seed bed for vegetation.
Locklin says that the area has since experienced heavy rains, but all the wattles are holding, so the water supply for Fallbrook is safe.
Sediment control is a common problem in neighborhoods. A new housing development in Roanoke County, Virginia, was suffering significant sediment problems. The area of rolling hills was primed for erosion with 2:1 and 3:1 slopes. Silt fences and straw bales were installed and the roadside swales had been seeded.
However, during heavy rains, both the fences and the bales failed to keep the sediment onsite. In some places, they acted as barriers to the water rather than letting it filter through while capturing sediment. In other areas, sediment flowed under the fences and bales. The sediment load was migrating to nearby waterways and gullies and cutting through seeded areas, causing an eyesore for potential home buyers.
A plan was developed using a variety of products from North American Green of Poseyville, Indiana. SedimentSTOP, a 70% straw and 30% coconut-fiber matrix encased in multiple layers of netting, was chosen for sediment control. Turf reinforcement mats (TRMs) and erosion control blankets completed the products used for the project.
Working in conjunction, the logs and mats trapped sediment and provided a growth environment for vegetation. Two months later, a heavy rainfall event of 11 inches proved the success of the project. The SedimentSTOP slowed the water enough to prevent sediment from flowing to the runoff.
Wattles are flexible enough to conform to most applications. They are easy to transport, and a single person can usually install as many as six a day. For a relatively low cost, they deliver a lot of bang for your buck.
Those made out of straw are sterile and seedless, eliminating the introduction of non-native vegetation. Wattles help establish and store moisture for native vegetation that is already in place. When using netting that is photodegradable, the wattle’s “stuffing” will become incorporated into the soil as the netting dissolves. They’ll remain in place until fully established vegetation and root systems are present and can survive on their own.
Many varieties are available to use in areas where aesthetics are a concern; their compact structure makes them difficult to see from a distance. They’ll often blend right into the soil, buried in the vegetation, which acts as an added camouflage.
Gabe Ramirez of Inland Erosion Control in Riverside County, California, uses wattles in numerous projects, both residential and commercial. Ramirez says his standard use of wattles includes behind curbs, on the lengths of slopes, and as sediment control in burned areas.
He notes that a three- or six-person crew can easily install the wattles. “A crew of six can put down as much as 3,000 feet per day,” said Ramirez. Silt fences cannot be used on steep slopes or uneven ground, so wattles are the better choice for these situations. In addition, he points out, they can be left in place, alleviating the extra cost of removing silt fences.
But wait, there’s more
Say you’re working on a large construction site, where there’s always a heavy amount of traffic constantly through the area. In their haste, workers fail to notice a row of wattles and drive right over them. These products will then need to be replaced. This means buying more materials and paying for more labor for installation.
There are manufacturers out there who recognize this dilemma. World Textile & Bag, Inc., in Roseville, California, for example, offers a flexible sediment control barrier which they call the Heavyweight Wattle. This device is designed to rebound back into its original shape every time it compresses, so you can drive over it repeatedly.
“Construction people don’t always know or care where the sediment barriers are; they need to get to work,” says Richard Quinley, management and product development for the company. This is very helpful in terms of accessibility, because drivers don’t have to worry about finding a way around the wattles.
Envirotech Biosolutions in Honolulu, Hawaii, has developed a similar product, the BioSock. This device is made up of a tube which is filled with compost. Weighing in at 10 pounds per foot, it too can be run over repeatedly.
In addition, the BioSock will not only filter stormwater as it passes through, but the microorganisms living inside its compost will break down pollutants such as heavy metals, pesticides, petroleum and microscopic bacteria. “Ninety-nine percent of the time on these construction sites, you’re dealing with situations where you’re going to have very fine particulates passing through your sediment control barriers,” said Alan Joaquin, president of Envirotech. “Traditional wattles can absorb fine sediment, but can’t destroy it. This product does just that.”
When dealing with sediment containment, another option to consider is Gator Guards. Manufactured by Gator Guard Environmental Products Inc., of Boise, Idaho, they are fabric sleeves filled with recycled scrap foam. “We’ve been using Gator Guards in place of straw wattle or fiber rolls,” says Todd Hudson, project engineer for Storm Water Inspection and Maintenance Services Inc., in Discovery Bay, California. “I had seen it at trade shows, but I first used it in quantity at a William Lyons Homes residential project.”
“On this project, the lots are fairly flat, they’ve already been graded, and the streets are in,” said Hudson. “We placed the Gator Guards behind sidewalks, curbs, and gutters as a sediment protection for the 100 existing graded lots. I like Gator Guard because it can be reused.” For future projects, Hudson will use Gator Guard where it ‘fits.’ A new trend in wattles is the continuous wattle. Companies like Filtrexx and Soil-Tek now manufacture and produce wattles that are put on a pallet system. The continuous run can come in various sizes and lengths, up to 180 feet. This gives the installer ease and efficiency of application, as they can be pulled or peeled off the pallet. This trend is growing, as more and more companies set up national manufacturing and distribution centers, making this type of product more readily available.
Let’s face it, all soil—whether on hillsides or flat ground—is subject to erosion and stormwater runoff. With the proper selection and implementation of wattles, you can slow down, block or filter sediment particulates and polutants. And for that, we can all give thanks.