From the May-2017 issue
Case Studies in Tube-Based Sediment Control
With traditional sediment control devices like straw wattles and silt fence, a drop-and-go installation style could be disastrous. Proper trenching, staking, and preparation of the BMP-soil interface means the difference between success and failure, which has led many manufacturers of sediment control products to design the next generation of more robust and installation-ready devices based on more sophisticated technology.
The resulting variety of devices can be overwhelming, particularly within the available selection of wattles and filter socks: weighted or non-weighted, natural or synthetic fillers, mesh or geotextile casing, and so on. Peter Tonn, president of Silt Sock Erosion Control Products in Portage, WI, advises folks who are considering these types of sediment control to select environmentally sound filler material, properly sized for the desired outcome. “The possibilities and applications for tube-based erosion control is limited only by the design objectives and project budget,” says Tonn. “The different combinations of materials put a lot of options in the tool box.”
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Tonn also notes that wattles and filter socks can serve one of several temporal roles on a project site:
- Temporary sediment control that will be removed after site revegetation
- Permanent installation of a durable fully or partially synthetic device that becomes part of the long-term structure
- Permanent installation of a pre- or post-vegetated device (i.e., seed injected, plugs, hydroseeding)
- Semi-permanent with biodegradable exterior fabric or mesh but with the filler material remaining
Deciding the role of the sediment control device should be the first step to narrow down appropriate products. The duration and role a product serves also influences the installation process. While installation demands of newer tube-based sediment control products have eased, the trickiest part of evaluating the appropriateness of these products for a project might be pricing.
Because each product has a different design, obtaining a cost estimate for one or two products doesn’t necessarily give a good picture of the larger market. Accurate pricing of materials and shipping costs can be obtained from each manufacturer using a project’s unique attributes, but they are easily more expensive than traditional straw wattles or silt fence. For that reason, users may opt to use traditional BMPs where possible and deploy a more robust, next-generation product in demanding site areas or for particularly sensitive projects.
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California Fire Remediation
As a waste management engineer for the California Department of Resources Recycling and Recovery (CalRecycle), Todd Thalhamer occasionally serves as operations chief for large-scale fire remediation projects throughout California. Recently, he directed structural debris cleanup operations for the massive Valley Fire. Covering 76,000 acres in Lake County and minor portions in adjacent Napa and Sonoma Counties, the fire consumed nearly 2,000 structures containing potentially hazardous asbestos and heavy metals.
Under the leadership of CalRecycle and Thalhamer, cleanup of commercial and home sites begins with appropriate hazardous and non-hazardous debris disposal. Cleanup readies the disaster areas to be reinhabited and rebuilt; making them safe for the public is the primary motivation. “In prepping these sites for rebuild, we scrape them down to bare earth, which turns them into very small erosion control projects within a larger disaster zone,” says Thalhamer. “We only put erosion and sediment control down on the areas we disturb, which means the structural ash footprint only.”
Thalhamer describes the overall fire remediation process as a triage situation. When tasked with such a project, CalRecycle’s first step involves assessing the disaster area for threatening conditions such as drifting airborne contaminants or hazardous materials located near public areas. With safety properly assessed and hazardous materials secured, widespread cleanup begins by stripping debris from individual sites. “It’s triage beyond triage,” says Thalhamer. “In the Valley Fire, 1,400 homes burned down, so we’re doing erosion control 50, 60, or 70 lots at a time.” Even in smaller incidents like the 3,900-acre Clayton Fire that destroyed 300 structures in 2016, crews tackle remediation whole blocks at a time.
Using products that install rapidly and easily with minimal crew training makes Thalhamer’s job easier. He and his contractors often form crews from within the communities affected by the fires and train them in safety protocols and basic fire remediation techniques, including the application of erosion and sediment control. “You can’t just say ‘I need 200 guys to start tomorrow,’ and then in three days you have no more work,” says Thalhamer. “Plus the products aren’t just sitting on a shelf somewhere. They must be produced. There is a limit to what you can and cannot do.”
Because fire remediation involves dealing with hundreds or thousands of burned and exposed acres with limited personnel and materials, small crews of six to eight move quickly to install a variety of erosion and sediment control products. “We use erosion control mats, hydroseeding, and straw fiber rolls on many property boundaries,” says Thalhamer. But SiltSoxx, made by Filtrexx International from Filtrexx Mesh and composted FilterMedia, became his preferred product for certain applications because of its superior performance and rapid installation. “On a project like the Valley Fire, I’m probably using two truckloads in addition to multiple other erosion control strategies,” says Thalhamer.
Primarily, he calls for SiltSoxx along the lowest stretch of a property boundary, where sheet flow attempts to leave the lot. “We’ve found that [SiltSoxx] works extraordinarily well in preventing sheet flow erosion as long as the surface is relatively level,” says Thalhamer. Justin Hill, foreman for Pacific States Environmental Contractors, agrees. “We also drop [SiltSoxx] where we can’t really anchor it well, like across concrete driveways,” says Hill. Working regularly with CalRecycle as a fire remediation contractor, Pacific States installs its share of erosion and sediment control products. “I think SiltSoxx does a good job. It’s easy to lay down, you don’t have to trench it, and it’s heavy enough to settle in once it gets wet.”
Pricing considerations aside, Hill prefers working with SiltSoxx because of its simple installation, which is why Thalhamer also specifies the product for occasional pre-cleanup applications, such as around particularly sensitive environmental areas with rainy weather predicted. “For example, if there’s a lot of ash close to a creek, we drop SiltSoxx to prevent sheet flow and hold the ash until we can return and clean it up,” says Thalhamer. Even in drop-and-go conditions, Thalhamer and Hill testify to the product’s performance. “Recently we cleaned up a hilltop site with a long, steep driveway,” says Hill. “The silt was running right down, but we put the SiltSoxx across the driveway and it wasn’t a problem anymore. It took care of the silt and you could still use the driveway.”
Having worked on many fire remediation projects, Thalhamer claims he’s tried every erosion and sediment control product on the market but now has no plans of using anything but SiltSoxx for critical applications. “With some other products, there’s more of a quality control and quality assurance problem and they’re not as durable,” he says. Thalhamer even worked with Filtrexx to tweak the original SiltSoxx design because he liked the performance tremendously but found they were too heavy at their originally designed diameter. “[Filtrexx] actually shrank them down to five inches in diameter after I explained the crews couldn’t carry these rolls down slopes to put them in. They were just too heavy.”
After cleanup, the erosion and sediment control products are left in place as homeowners return and rebuild. As blocks of sites are cleaned up and released back to homeowners, cleanup continues elsewhere in the area. During this period, Thalhamer observes how the products endure time and abuse. Although Filtrexx doesn’t recommend driving over the SiltSoxx, he’s seen plenty of folks do so and the product handles it well. “They tend to hold up to a significant amount of abuse. Homeowners’ contractors will sometimes move them around. The straw rolls sometimes get in the way, and they don’t hold up when you drive over them.”
Hill also recognizes that sediment control products generally shouldn’t be driven over, but he has seen it happen occasionally to SiltSoxx. “It leaves tread marks in it a little bit, but it doesn’t just flatten out,” he says. Both Thalhamer and Hill have seen them continue performing even after being dented a bit.
When it comes to eventual disposal, SiltSoxx continues to be low maintenance thanks to the organic composted filling that can be spread onsite. “You can just cut them open and dump the compost on the ground,” says Thalhamer. “The only downside is they’re not 100% biodegradable; you have to throw the outer sock away.” Compared to the 225,000 tons of debris removed over four months from the areas impacted by the Valley Fire, the outer sock is a drop in the bucket.
CREDIT: MAREK LANDSCAPING
Streetscape Directional Drilling
Based in Boise, ID, Earth Energy provides drilling and specialty excavation services to diverse utility and energy clients in the Northwest region, including Suez Water, Tesoro, Level 3 Communications, and Syringa Network. Recently hired by Idaho Power, Earth Energy employed directional drilling in the streets of Boise to complete a right-of-way cable replacement project for the electrical power utility. By guiding a drill under streets, sidewalks, or even rivers from a single location, utility pipe and conduit can be laid underground without excavating or trenching.
A directional drill can be precisely guided on an exact direction and elevation, avoiding existing infrastructure and utilities, which can be quite a feat in an urban or suburban right of way where utilities compete for limited space. “The utilities come out and mark the lines, then we can assess and pick our path through the right of way,” says Erv Hoge, co-owner of Earth Energy. “There’s a lot more to it than what people think. It’s complicated, and room is running out within the right of way. We’re having to install more in the street now and deal more with asphalt.”
Although direction drilling disturbs a much smaller surface area than trenching or excavating to achieve the same results, soil erosion can still occur at localized spots along the project length. “Every so often we come to a transformer or other obstacle and we have to cut a hole in the street and leave material there,” says Hoge. “That’s when we use wattles to contain the work area where the drill is set up. We use them to contain excavated soil and drilling fluids.” Also based in Boise, Gator Guard Environmental Products has been Earth Energy’s supplier of sediment control products for over a decade and, with the debut of Gator Guard’s weighted wattle, will likely maintain the relationship for years to come. Earth Energy recently used the Extreme version of Gator Guard’s weighted wattle on the Idaho Power directional drilling project.
At 12 feet long and 6 inches in diameter, the Extreme wattle’s geotextile tube contains an inner geotextile bag of sand wrapped on the sides and top with closed-cell polyethylene foam. A 12-foot length folds down into a 4-foot-long, 50-pound bundle for easy shipping and handling. “One person can lift and handle a single section, and they connect together,” says Randy Prindle, utility construction supervisor at Earth Energy. Each length has a sleeve on one end to facilitate connecting multiple lengths together. “They can be as long as you want and are really easy, user-friendly, and tough,” says Prindle.
The weighted wattle has a soft, nonwoven geotextile bottom that conforms to surfaces. “They conform to the ground so they’ll settle in place,” says Prindle. “No need to stake or anchor them. Just lay them in place and get to work.” Hoge and Prindle appreciate both the efficiency and durability of the weighted wattle version. “You can actually run them over and it doesn’t seem to damage them, plus you can reuse them time and time again,” says Hoge. He adds that the woven geotextile shell helps dirt and mud slough off easily as it dries.
Although Gator Guard doesn’t recommend driving over the wattles, it does state that they hold their shape well on such occasions. In addition to the Extreme wattle, Gator Guard offers a shorter weighted Gutter Wattle. At 3 feet long, its slightly modified design allows it to bend easily across a street gutter while conforming to the surface. Gator Guard states that both products are intended for roughly five years of reuse and were designed for simpler, lighter installation.
Hawaiian Tropical Storm Emergency
“The situation could have been really, really bad, but within twenty-four hours, it was made right,” says Alan Joaquin, president of Honolulu’s EnviroTech BioSolutions, referring to an exposed 2-acre residential property confronted with torrential Hawaiian tropical storm conditions. “The traditional BMPs like silt fence were failing, and the client reached out for help. The contractor, BioSocks Hawaii based in Waimanalo, HI, provided an emergency service to help repair and restore the perimeter and stabilize all the open areas.”
BioSock Compost Filter Socks were installed as slope interruption devices and for perimeter control, while all exposed surfaces were stabilized with hydromulch. Joaquin estimates some project slopes at roughly 4:1. “Then the site had a week of pounding rain, but the project was secure,” says Joaquin. “Runoff and offsite sediment was eliminated and the project stayed in compliance.” Joaquin has found that silt fence installed as traditional perimeter control typically doesn’t function well in Hawaii because of the islands’ propensity for high winds and rain. Failures and required repairs commonly needed during the most inconvenient weather conditions can make contractors anxious, or lead to project failures. “For Hawaii’s unique environment with frequent flash floods, the filter sock is really the only viable option to install protective measures during a storm event, being able to fix a problem while it’s happening. Can you imagine trying to trench in a silt fence in a storm with mud everywhere? It’s impossible.”
Having been in the erosion and sediment control industry for 20 years, including time spent in commercial landscape construction, Joaquin has plenty of experience. Years ago he began brainstorming a filter sock design in partnership with Tonn. “I’m always looking at it from a contractor’s perspective,” says Joaquin. “What would I want as a contractor that’s going to work, be rapid to deploy, and be reliable?”
The BioSock evolved from their collaboration. An outer mesh, sourced from Tonn and Silt Sock, encloses locally sourced inner netting, which in turn contains compost filter media. Joaquin attributes the effectiveness and durability of the BioSock to this two-layer system, and estimates the product is used by 90% of the Hawaiian compost sock market, installed by BioSocks Hawaii.
The 9-inch-diameter BioSock comes in 20-foot lengths, which Joaquin estimates to weigh approximately 140 pounds each. “It’s able to be installed by hand and moved around and adjusted as needed,” he says. The socks’ substantial design makes trenching unnecessary, and staking becomes important only if they are installed on a slope. “We have a staking diagram that shows the protocols. If it’s a 2:1 slope versus a 4:1 slope, there’s different staking methods and spacing to use.”
Joaquin and BioSocks also use a lighter-duty version of the filter sock that can be left in situ to fully biodegrade, natural wood fiber mesh included. “But for heavy-duty use and high-traffic areas, we have not been able to find anything that can compare to a predominantly plastic-based outer mesh,” he says. Although a plastic mesh must be disposed of when a BioSock reaches its life expectancy, as with similar products, the organic inner media can be spread onsite.
Joaquin estimates average life expectancy to be roughly two years, but he notes many contractors reuse the filter socks on multiple projects because they hold up well. Some contractors keep pallets of the Compost Filter Sock on hand and use as needed for small containments like delivery of a soil stockpile. “The biggest obstacle [to life expectancy] would be the media breaking down, depending on rainfall and microbial activity and other environmental factors,” he says.
Due Diligence in an Evolving Market
“Every time you use a product, there’s a pro and a con,” reminds Thalhamer. “That’s why there are multiple products out there.” Over his long career, Thalhamer has tried every roll and fiber mat available to find what works best for his projects. “I’m constantly seeing different products and new methodologies coming up, because there’s always a better way to do something.” As technology continues advancing and manufacturers evolve to meet customer needs, more products and improved designs will continue to become available.
That’s exactly what happened to Bob Hanson, owner of Gator Guard Environmental Products. “I had received requests for a weighted wattle several times over the last eleven years but had no product to offer until a potential customer told me I just needed to make them,” he says. His contractor customers knew the importance of a durable, high-performance product with rapid installation. That’s also how BioSocks Hawaii came to be called upon to solve erosion during tropical storm conditions. “You don’t have to wait until after the storm to clean up and install BMPs,” says Joaquin.
This ability to act rapidly with assurance can also help a contractor’s or project’s bottom line during challenging weather and degrading site conditions. “If a contractor is out there hustling, making every effort to fix problems, make repairs, and clean the site as much as possible in the rain, then inspectors are going to look at that as good faith,” he says.
During his time in the erosion and sediment control business, Joaquin has interacted considerably with enforcement agencies and observed plenty of contractors receive notice of violations. “For a lot of projects with NPDES [National Pollutant Discharge Elimination System] violations for sediment going offsite, attitude and approach is a huge part,” he says. “If a contractor’s intent is to do the right thing, and if they’re out during a storm trying to make things right, that shows they’re coming with the right attitude. No one wants a notice of violation, because that has a major impact on insurance rates, bonding rates, and reputation.”
Across the nation, the latest tube-based sediment control products have established themselves as reliable tools for demanding situations. If a project’s priorities include rapid and simple installation, durable construction, and high-quality performance, these products may save time and headaches in the long run.