A discussion of current practices

By Carol Brzozowski

Hunter Bruce, vice president and technical engineer for SpreadRite Organics in Birmingham, AL, points out that in the Southeast, the erosion control practice is to set up perimeter protection before clearing begins on a construction site.

“People will have to be more involved and do the erosion control measures throughout the site, not just at the beginning,” Bruce asserts.

He’s heartened by some trends he notes. He says his company is starting to see more post-construction measures instituted at new developments, including many larger commercial developments that may institute a “trickle-down” effect.

“We are seeing bioswales, sediment ponds being turned into either dry or wet ponds, and we are starting to see a little bit of a movement of potential green roofs on a smaller scale, but I think that is going to be a bigger deal in the metro area,” he says.

Photo: Landscape Development Inc.

A concrete washout station

Many erosion control contractors are deviating from the way they’ve always done business to try new products and practices. But the process of getting an erosion control product approved by the United States Environmental Protection Agency can be challenging.

Just ask Rod Tyler, CEO of Filtrexx. His compost-based products include FilterSoxx, erosion control tubes used for sediment and erosion control; berms, used for similar practices in more naturalized areas; and compost blankets, used for slopes.

FilterSoxx was recently approved by the EPA after a somewhat lengthy run. The process for approval began several years ago through the EPA’s Environmental Technology Verification program. Filtrexx became one of the first companies to sign up. After a few snags, the product went through testing and became approved after a yearlong process.

FilterSoxx can be used in both construction and post-construction phases, Tyler says. During construction, it’s used as an alternative to silt fences for perimeter control. “Our joke at the company is, ‘Our socks don’t fall down,’” in contrast to silt fences that can fail, says Tyler. FilterSoxx also can be used for inlet protection around drains and for concrete washouts. The product is formed as a ring, with the water flowing through and leaving the concrete washout material behind. It can also be used in ditches in places of straw bales. “Those applications are very effective because they are usually better at filtering and are something that can be left there long-term,” Tyler says.

Photo: Landscape Development Inc.

Slope protection during large-scale grading

“There is a lot of frustration on the enforcement side of the EPA in the field when people go to the job site and see BMPs [best management practices] like silt fence and there are problems. Then there are our FilterSoxx that have been installed properly, so the natural progression is to like the new tool that doesn’t have a problem with it,” Tyler says. “We get a lot of default business because of that.”

Tyler points out another consideration in the marketplace is the life cycle of products and their associated costs. “That’s where the compost-based tools really have an edge,” he points out. Costs to consider include installation, maintenance, removal, disposal, and repair.

With the compost-based socks, all that’s needed for disposal is to slice the netting, empty out the contents, grade it out, and grow grass on top, he says.

Disposing of a silt fence is a soil-disturbing activity, Tyler points out. “When it’s pulled up, usually there’s a trench, and you have to smooth it out before it rains, because then you can have erosion,” he says.

Photo: Landscape Development Inc.

Earthen berms and sandbag check dams

In the case of berms and blankets, there are instances where seed is injected into the berm and it’s left to vegetate, and in that case, there is no removal cost. “That type of application for socks and berms has been popular in instances where people may have steep, unmowed rural ditch areas, such as in a DOT [department of transportation] application where they have no intention of growing anything there,” Tyler says. “They want something to slow down the water and offer a permanent speed bump.”

The compost blanket has become advantageous for its ability to establish vegetation, in contrast to some geotextile products, which Tyler says is effective in slowing down water or reducing raindrop impact, but because they have no soil mending properties, there is no vegetation establishment. The compost blankets can achieve 100% ground contact, so there is no water running underneath and they have more moisture retention and less phosphorous discharge, he says.

A common challenge when introducing a new product into a market is that when it’s first presented to a contractor, the contractor may like it but want an engineer to sign off on it, Tyler says. The engineer doesn’t want to put his reputation on the line, so he indicates it needs to be approved by the state regulatory agency. The government agency, though, might say an engineer needs to sign off on it as a test project.

“There is a circle of being bounced around like a ping pong ball, and the reason is there is no formal process for new products to be accepted, welcomed, and celebrated in this industry, and it’s a crying shame,” says Tyler, calling for IECA or an equivalent association to create a performance-based program that assesses product using the same peer view processes.

Photo: Landscape Development Inc.

This site employs several measures, including hydraulically applied protection.

Spread Rite Organics uses Filtrexx products in nearly every facet of its business, including streambank stabilization, sediment control, perimeter protection, curb inlet protection, residential construction, and back-of-curb applications. “We’ve been instrumental in trying new things—different diameters, sizes, and colors,” Bruce says. He notes that the company has been using the Filtrexx FilterSoxx for more than a year and has not encountered a client who does not like it—compared to other methods—after it’s installed.

“From my standpoint as an engineer, this is a new technology, and a lot of guys are so used to the old school that it’s tough to change,” he says. “I think the movement is starting to happen, not only with Filtrexx FilterSoxx but also with wattles. We don’t even bat an eye now when it comes to a rain event.”

With it being a newly approved technology, FilterSoxx has a learning curve, Bruce says. Filtrexx offers an annual certification course, taken by Spread Rite employees.
“The process of putting it down requires a large machine as far as getting the area prepped,” says Bruce. “Once it’s prepped, it’s pretty easy to put down. Every job is challenging and different, but it’s less invasive than any other method of trenching or silt fencing. We can go into an existing area of woods and run hose all the way through those woods, and when we pull the hose back out, we leave the sock in place. So we can leave nature where it needs to be, and a lot of developers really like the ability to save as much green space as possible.”

Installation entails ensuring the sock has good ground contact and eyeballing potential problems. At swales and corners, the socks need to be beefed up by using a double row or larger diameter.

“It’s a filter, not a ban,” Bruce says of the socks. “A silt fence should never be put into a concentrated flow area. We see a lot of silt fence failures where they just totally lay over because of the intensity of rains we get. The FilterSoxx allows water to permeate through it and captures the sediment on the upstream side.

“If sediment fills the sock up, you can easily replace another sock right on top without having a major failure.”

Removal can be a challenge for some products.

Photo: Landscape Development Inc.

Interior sediment control during the grading phase

“There are so many projects where you go back and there are metal posts and metal wire, and the fabric has degenerated over time,” Bruce says. “Odds are that wire and posts will stay there until the homeowner or someone gets out there to remove it, and there’s a big cost associated with that.

 “A lot of the post, wires, and big rolls you have when you are picking up silt fence doesn’t need to go into a landfill,” he says.

Bruce says while the Filtrexx FilterSoxx may cost slightly more at the front end, the approach is more cost-effective in the long run, considering the cost of removing other products.

“And from the standpoint of it being EPA-approved, the counties and cities in our locale like to see it more because they know it works better,” he says. “They know the ultimate failure of a perimeter protection silt fence is not going to happen.

“A silt fence may work great two and a half months and then all of the sediment builds up behind it and you get one big rain and it lays over and everything behind it you have captured for two months potentially can get loose.”

Photo: Landscape Development Inc.

Wattles used as a defensive barrier at the front of a residential lot during construction

Curt Millward, environmental compliance officer for Centex Homes in Dallas, TX, says since the erosion and sediment control industry involves a host of new products on the market, his company is doing a lot of experimentation to determine what will work. For instance, the company will use a particular product at one of its developments and another product at a different development to compare how they work. In evaluating the products, Centex considers upfront as well as long-term costs.

Millward points out what initially turns off builders to some erosion and sediment control products is cost, “but if they look at it long-term, there may be less maintenance on it and [it may] be more cost-effective in the long run.”

Acknowledging that the effectiveness of some BMPs is still in the research stage, in order to select the most appropriate method, Millward does his own research. “I look at case studies, and a lot of times, I’ll talk to my contractors,” he says. “The good thing about working at Centex is we have a lot of divisions nationwide, so usually I can call a contractor at another division to find out how a product worked or did not work and get an unbiased opinion on it, because they work for Centex, not the product’s company.”

Photo: Landscape Development Inc.

Curb inlet protection

Millward faces the challenge that a particular BMP might be effective in one region of the country and not so in another. “And a lot of local regulations won’t allow you to do anything different,” he points out, adding that in one city in his state, the regulations allow nothing other than a silt fence.

Another consideration is the topography and soil type. “Right now, we have two projects that have a huge amount of topography, so we are doing a lot of experimenting on those,” he says. “We’re doing more erosion control than we are sedimentation control.”

Centex trains its employees to choose and install appropriate BMPs on construction sites. “Each of our field guys has a minimum of 10 hours’ stormwater training,” Millward says. “That way they know the different technologies, laws, and rules,” he adds. The company’s subcontractors are trained onsite with superintendents.

The company also uses a DVD program that is trade-specific. For example, the concrete contractor watches the brief video to learn about the interaction between stormwater and that particular segment of the construction process. “We’re looking at new kinds of training techniques out there, too,” Millward says.

Millward also works with various cities on their differing and evolving NPDES requirements. “The biggest difficulty is that you have three levels of regulatory requirements—the federal EPA, the state department of environmental quality, and local requirements,” he says. “Each of them has to adopt a minimum requirement, but then they can adopt additional requirements.” Arlington, TX, for example, has added numerous requirements on top of existing regulations.

One of the issues centers on inlet covers—at what stage during construction they are allowed. “That’s one of those BMPs that if not properly used or maintained do more damage than they do good,” Millward says, adding that there was a case in his region where the inlet covers flooded some of the streets after a 9-inch rain hit the area.

Photo: Landscape Development Inc.

Reinforced silt fence, sandbags, and hydraulically applied BFM

For erosion control, Millward prefers erosion control blankets and finds them aesthetically pleasing. “When you drive by, you see a nice green mat along the front, nothing obstructive like a silt fence, and there’s not a wall to get over,” he says. He also likes the fact that if someone runs over it, it’s still somewhat effective. “A lot of BMPs, if damaged or run over, actually do more harm than good,” Millward says. “A good example of that is a damaged silt fence that creates a funnel, channeling everything to one area with increased velocity.”

Millward also likes hydraulically applied blankets based on bonded fiber matrix and including tackifiers. “With a lot of them, you can add seed to it, so not only are you getting the initial blanket control over it, but eventually it grows vegetation, which is the best long-term erosion control device,” he says.

The company also uses sedimentation ponds on many sites to allow more water to infiltrate.

In its development design, Centex considers post-construction measures that will result in long-term effectiveness. “We are trying to steer completely away from concrete-lined channels, and instead of using as much rock riprap, we’ll use something natural like permanent geotextile practices or American Excelsior Company’s Recyclex, an erosion control mat made from recycled green soda bottles,” he says.

Photo: Landscape Development Inc.

Inlet protection at a large stage of construction

One practice many municipalities are still becoming familiar with and trying to implement is low-impact development, which emphasizes infiltration and keeping runoff on the site rather than relying on curb-and-gutter arrangements to carry most of the water to a storm sewer system.

“We are on the educational process on that, and eventually when the engineers and the cities learn more about it, it will be a good thing and result in fewer impervious areas, such as pavement,” Millward says, predicting the practice will take root in more areas in a few years.

Eric Woodhouse is division president of Earth Services for Landscape Development, a commercial landscape and erosion control contractor in Valencia, CA. His company is involved in about 80 projects, ranging from 5 to 1,400 acres. “On the larger projects, often we sit down with the developer, civil engineers, and landscape architects when they are in the initial pre-planning stage to develop plans based on the different phases of the project: the grading, the infrastructure installation, and then the home construction,” he says.

Each of those phases requires a different approach to soil stabilization and other erosion concerns under National Pollutant Discharge Elimination System standards. “During the grading phase, we do a lot of interior sediment control,” Woodhouse says. “We check structures and the basin for water retention, and as the slopes become certified by the engineer, then we put temporary hydraulic applications on.”

Another approach is to tie an erosion control blanket into the permanent landscape theme, as opposed to using temporary measures, to help defray the developer’s costs.
During the time the pads are getting paved and underground utilities are being installed, Landscape Development starts stabilizing lot fronts, giving each its own retention barrier to hold back silt and slow the water down coming off each lot.

“We will also in many cases spray the lots with a stabilizer,” Woodhouse says. “Not all developers are up to that speed. We talk to them about the calculations based on the rain flow in this area—when you get an inch an hour of rain, for example, you can usually count on 20,000 to 30,000 gallons of water per acre running off, whether it is a slope or a flat area. Our silt loads are based on the different cover factors, steepness, and soil types.”

He also talks with developers about handling dirt twice. “It’s better to keep it in place rather than work on a sediment control basis,” he says. “Over the 14 years I have been doing this, we’ve seen a 30% to 40% decrease in the cost for these larger projects where the companies have a more comprehensive stabilization or erosion control program combined with silt management during the grading period.”

During the home construction phase, the lots are built up with a system that helps hold as much water and silt on the lots as possible, especially during the rainy season. Landscape Development develops a defensive barrier at the front of each lot with modified silt fences, wattles, a gravel bag retention lining at the back of the curb, or other measures.

Photo: Landscape Development Inc.

Lot stabilization on a large-scale project

“We will also introduce rock aprons at each lot or every two or three lots so there is stabilized access for forklifts to get in and out without tracking dirt out into the streets,” Woodhouse says. “Of course, concrete washouts become a very important factor, as well as routine maintenance and monitoring.”

Woodhouse says a company cannot favor just one BMP, but it’s prudent to use a combination because of the rapidly changing technology. “Some of the old standbys are antiquated in some of the applications they used to be so commonly used for,” he says.
For example, during the past year, his company has manufactured and placed 2.2 million sandbags, gravel bags, and rock bags and installed about 48 million square feet of slope stabilization either as a spray-on or blanket. “Sandbags have a great use during the mass grading, where we are trying to retain soils and flow of water, but once we get into the construction phase, we’ve got hard surfaces where we’ve got paving and we’ve got a better area where we can drop the water where we are not going to get scouring and erosion,” Woodhouse says. “So we’ve got to employ different things.”

A modified silt fence has an 8- to 12-inch toe in the ground and sits up about 12 inches; it can protect an area during framing, plastering, roofing, and drywalling, he says. “It allows us to control the water coming off, and it also prevents people from driving in and out, whereas if I put a wattle or sandbag out in that same place, the forklift can drive right over it and not think twice about it,” he says. “They’re a little less prone to drive over a silt fence sticking up.”

Woodhouse’s company is seeing more catch basin inserts and Continuous Deflective Separation (CDS) units being deployed in new projects, especially those close to coastal areas. “Out in the high desert, where the water goes nowhere but into the aquifer, we see a whole different concept of water management,” he says.

John Gentillon, president of San Diego Erosion Control in San Marcos, CA, also favors site-based erosion control methods during construction. His company considers each lot as a “postage stamp” piece of property and establishes controls for it onsite.

“California lots are now between 7,000 and 10,000 square feet or less, and we are handling the drainage off that lot onto the street,” he says. “We try to get down to the minutia, even though one lot is amongst a large development. Each individual lot is a job, because that is really the source of sedimentation; it is source control.”

His company establishes special drainage details to handle water ponding on the lot and then slowly drain it off onto the streets like a miniature sedimentation trap. A variety of techniques and products is employed, including empty and filled poly and burlap gravel bags, Amoco woven and non-woven filter fabrics, coir and straw fiber rolls, Greenfix America straw and coir blankets, Enkamat Type C and 7000 Series blankets and liners, jute netting and visqueen fabric, ACF Environmental Siltsack and Dirtbag, Triangular Silt Dike, and Enviroberm.

Through his other company, Stormwater Compliance Specialists, Gentillon helps clients design post-construction measures to avoid problems down the road. He notes that enforcement of water-quality regulations has ramped up in the area.

“A number of different developers have been cited for improper management of their job site,” he says.

Sometimes erosion control to protect water quality takes place right on the water. This is often the situation for Tom Silva, president of Sterling Building Specialists in Destin, FL, a company with a focus to work on coastal soil erosion issues in places such as northwest Florida. The company favors the HESCO Bastion Concertainer for its work.

One job in which the company was involved featured 340 feet of beach that had sustained erosion from 80 feet to 16 feet since 2004, when a series of hurricanes passed through the area.

“The serious problem was the scouring of the waves as they were coming in from a southeasterly direction,” Silva points out.

What made the erosion particularly disconcerting was that on the other side of the 16 feet was a 6-foot deck and a 20-foot by 40-foot swimming pool, and 25 feet away from that was a building on spread footings; if the remaining 16 feet would have been lost and there was consistent wave action during a storm, the possibility of the pool moving northward through the building was very real.

A number of options were considered, including a solid wall construction, geotubes, and the HESCO Bastion system. The Concertainer is a prefabricated, multicell system constructed of galvanized steel Weldmesh and lined with nonwoven polypropylene geotextile.

The project engineer turned down the wall idea because of the fill that would be needed to add weight and the possibility of it coming into contact with the swimming pool; in addition, a large wave hitting the wall would take sand back with it into the water. The tubes were turned down out of concern they could tear.

While the HESCO Bastion system was more expensive from the outside, it was believed that it would have more staying power in the long run and be the best choice for this particular application, Silva says.

The HESCO Bastion system was chosen because it could be installed in a row-like, step-down fashion and tied together by rods through each corner and on the bottom, forming a cohesive unit.

Silva explains that each basket holds from 3,800 to 4,000 pounds of sand and, constructed in such a fashion, should not move. The baskets are drilled through in each corner and every 6 feet all the way through the back to accommodate water overflow. The project was completed in about 13 days.

Silva says the system is also aesthetically pleasing as the units are covered by sand and have the natural appearance of a dune. Even though that cover layer of sand might be lost in a storm, some 45% of it—the sand in the baskets—would still be retained.
“Since these are individual baskets, if a large piece of wood or something else were to hit an individual basket, you pull out four rods, replace the basket, fill it full of sand, and you are back in business,” he says.

There’s an added environmental benefit, Silva points out. The area has been a nesting place for animals and their habitat had been destroyed. “When you do something of this nature, you are trying to recreate this nesting place for these small creatures,” he says.
Some area residents, in reacting to beach erosion, have put up wood or concrete, something Silva notes is “not going to fly” with state environmental officials.
As for NPDES permit authority inspections, some erosion control specialists are seeing an increase, while others do not.

Bruce says permit authorities do not conduct inspections frequently enough.
“In our locale, they are ramping up, trying to get funding to do a better job,” he says. “It’s not that they are not doing a good job—they’re understaffed and there are too many projects.”

Millward indicates more cities are starting to conduct inspections relating to NPDES. “Before, you saw very little enforcement, but now you are starting to see a lot more by the cities,” he says. “A couple of years ago, they might have done some enforcement if there was dirt in the streets. Now they are doing more enforcement before dirt gets into the street. It used to be less stringent; now they are issuing citations and fines, and you are finding a lot more cities getting involved in it,” he says.

“I think they are getting educated and find out the benefits of it, and they know what to do.”

Carol Brzozowski is a journalist in Coral Springs, FL.

EC - September/October 2006