By Carol Brzozowski
Although erosion control is one of the smaller budget items on a construction site, it is nonetheless one of the most critical: Product performance can make or break regulatory compliance. Given the hit that the construction industry has taken in the past several years, erosion control specialists seek to provide clients effective solutions at affordable costs.
Working in the Everglades
In an immense and very environmentally sensitive job in the Florida Everglades early this year, Tom Burst’s company, Twin Oaks Silt Fencing of Apopka, FL, installed 77,000 linear feet of Silt-Saver’s Belted Silt Retention Fence (BSRF) in a saltwater mangrove marsh area. The location is defined as an area of critical environmental concern.
The project is at the site of a road removal project and is long and narrow. It’s so environmentally sensitive that Twin Oaks has installed double rows of the BSRF. On one side of the fence, one can see “very turbid water” and on the other side of the fence, the water is “crystal clear,” notes Burst, a partner with Twin Oaks.
“The double row of fence is there in case one fails,” Burst explains. “It’s just that critical of an area where they don’t want to risk it. Someone is out there every day doing turbidity tests. If it ever gets outside of the second row, they’ll shut the job down. There’s a lot of pressure.”
Imagine Burst’s consternation, then, when the BSRF his company installed was twice compromised.
“One morning, we saw the fence down, so we repaired it,” he says. “The following morning, it was down again.”
The culprit turned out to be an American crocodile. It’s an endangered species that loves the southern tip of Florida, particularly the berms of the cooling canals of the Florida Power and Light (FPL) Turkey Point power generation facility. More sensitive to the cold than alligators, crocodiles like to hang out in coastal mangrove swamps where they are protected from onshore winds.
“This one was a good 12 feet long,” Burst notes. “He had knocked down a section of fence to climb over it. After we fixed it, it was down again, and the environmental guy onsite said, “˜If he wants to go there, he’s going to go there.’
“The crocodile is crossing a section of road that is not coming out between these two canals,” he continues. “We put in floating turbidity barriers, which he seems to have no problem with, so nothing will go out into the waterway on the canal on that side. It’s because of the construction trucks that we use silt fence at all. This crocodile has decided that this is his path, and there’s nothing we’re going to do about it.”
The crocodile is a symbol of the ultimate goal of the project for the area: to restore the marsh area to its original condition of more than 50 years ago, creating more environmentally friendly conditions in which wildlife and aquatic plants and animals can thrive.
The project essentially entails removing roads that serve no purpose.
“These roads really make no sense,” Burst points out. “There are a bunch of little cul-de-sac fingers that were put in the 1950s. This land will never be developed. They are just trying to improve the tidal flow. The salinity levels have gotten so high because these roads keep water from flowing.”
The project is part of a larger effort: FPL’s Everglades Mitigation Bank (EMB) on a 13,249-acre site southwest of the Turkey Point power generation facility near Florida City, FL. According to FPL, the physical and biological characteristics of the site have been greatly altered as a result of the Everglades Drainage District projects in 1907 and the central and south Florida Flood Control Project of 1948. The changes in the regional hydrology and onsite dikes and roads altered the ecosystem’s salinity balance, resulting in hypersaline conditions and a shift of historically freshwater marsh to brackish high marsh flats and tidal marsh.
FPL purchased the site in early 1970 to develop future power generation. Since that time, other options became available to serve the system’s needs. Regional plans emerged to restore and enhance the Everglades system, southeast Florida marshes, and Biscayne Bay.
Following the state’s passage of the Mitigation Banking Rule in 1993 and the Environmental Protection Agency’s adoption of the Mitigation Banking Guidance in 1995, FPL chose to develop the site as a private mitigation bank to align with the public Everglades restoration goals.
The EMB project has two phases-one consisting of 4,223.18 acres and another measuring 9,025.93 acres.
“The area where we are installing the BRSF is actually in the mangroves,” notes Burst. “Unless it rains, it’s typically dry, but very soft, mucky ground. “It’s mostly rainwater that washes through the saltwater marsh area of mangroves, he adds.
“There are a lot of crabs when we do have water on the ground, but it’s too salty for other creatures,” he says. “The removal of these roads will help fix that problem.”
Despite the ground conditions, the BSRF can be installed with stakes that are placed into the ground, creating a suction effect. “We have to shove the flap in with a spade that actually pushes it down 12 inches into the muck,” says Burst. “It’s been working out just fine.”
The BSRF was specified because of its ability to filter water quickly, allowing flow, says Burst.
“If you hold the four corners of a 3-foot piece of typical black silt fence, it will puddle and drip underneath, whereas water goes right through a BSRF and takes more of the sediment out as it does that,” he says.
Because the Everglades site is an area of critical environmental concern, the regulations protecting it “are way beyond anything the Florida Department of Environmental Protection is specifying,” notes Burst. “Our rules are much tighter. We have to be careful where we step. We are having to put everything in by hand, not using machinery, because we’d be running over mangroves.
“The soil conditions are extremely soft and silty; basically, it’s a mud flat. It’s been an absolutely brutal job. We’ve been proud to do it. We bid it properly and we knew what we were getting into, so it’s not like there were any surprises. But it has been extremely labor-intensive.”
As a contractor, Burst would like to see more government agencies that specify erosion control materials consider the BSRF for restoration projects.
“I don’t think they’ve educated themselves as to the value of this product,” he says. “They’re used to the “˜same old.’ They don’t understand that there’s something better.”
Indeed, that “something better” is where the industry is endeavoring to head with respect to runoff protection and sediment control.
Working on a Brownfield Site
After a delay to reconsider its previous numeric effluent limits for construction sites for its construction general permit (CGP), the EPA earlier this year requested additional information and feedback on sample collection, the ability of smaller sites to meet numeric limits, cold-weather considerations, and applicability of the numeric limit to certain types of construction, among other issues.
In 2009, EPA published effluent limitation guidelines calling for a limit of 280 nephelometric turbidity units (NTUs) from most construction sites 10 acres or larger. The guidelines also called for other erosion and sediment control measures, such as using perimeter controls and minimizing the amount of land disturbed at one time.
However, many believed the numeric limit to be unrealistic or unaffordable. Following the issuance of the guidelines, the Small Business Administration and the National Association of Home Builders petitioned for EPA to reconsider the numeric limit based on a potential error in the way that number had been calculated.
The EPA reexamined the data and stayed the limit in January 2011 and is reexamining the issue. In the meantime, the agency has outlined a definition of “passive treatment” and is addressing the limitations of sampling equipment and practices as well as comments it received regarding the potential toxicity of chemicals used in treatment systems to reduce turbidity.
Doug Stein is president of Stein Construction Co. and Earthscapes Solutions in Chattanooga, TN. Earthscapes encompasses the erosion control and water-quality sector of his business.
Stein had testified before EPA in 2008 on the potential impact of the EPA’s construction general permit as part of the agency’s effort to hear input from construction industry small businesses.
“I was relieved to see that they did make some changes they were considering,” Stein says. “They were contemplating water-quality standards that were essentially unattainable. It involved the use of large detention ponds being then water pumped into what I call frac tanks.”
Stein was able to share from personal experience with a job on a brownfield reclamation site that failed to meet the standards.
“I think a lot of the EPA’s calculations early on were done on spreadsheets and not in the field. Their initial calculations were done on paper, and we work in dirt,” says Stein. “For example, it calculated the amount of water or runoff that would come from a site being disturbed. They had neglected to take into consideration that all sites on the earth are connected to other sites on the earth, so if it rains, it doesn’t just rain on the 20 acres that you happen to be disturbing. It rains upstream from that and downstream from that. Their calculations didn’t give that enough weight.”
EPA had asked Stein to estimate what the cost of the regulations, in terms of cost per acre, would be on local development. Stein’s estimate: $50,000 per acre.
“I told them at that time that we were selling industrial real estate here in Chattanooga for about $35,000 per acre, so that would essentially shut the market down,” he says.
Chattanooga is ahead of the curve in terms of compliance, Stein says. “We are the closest municipality with more than 100,000 to EPA District 4 in the Atlanta area. In Chattanooga, environmental quality and intelligence has been a big part of the renaissance here. Not just water, but air as well. We’ve done some green roofs, and there’s a lot of understanding of the value of low-impact development.”
Stein serves on a technical advisory group that is helping the city rewrite its stormwater regulations. He’s served on the city’s stormwater regulations board over the past decade and was the first to write erosion control regulations for the city in the 1980s.
“We’re in front, but we’re still struggling with understanding across the board, coordinating among the agencies so they all understand what methods work best,” he says, adding that it isn’t a statewide initiative.
In addition, what happens in Georgia and Alabama in terms of which best management practices (BMPs) are being used influences Tennessee, he points out.
“The regulations now control the first inch to fall, and that’s going to require different management practices,” Stein says. “It’s been slow to dawn on everybody that that’s the case.”
Although his company deals with silt fence, Stein favors “socks,” particularly those manufactured by Filtrexx International.
“We’ve been using hay bales, rock check dams, and brush barriers,” he says. “Those are filters. A silt fence is a screen. They’re making new products that go by the name of silt fence, but the most commonly used silt fence is impervious material with holes in it like a screen.
Filtrexx systems are effective for breaking up the flow anywhere within the site perimeters.
“When the flows are low, the small particles that are dislodged pass through the holes and some of the large ones get knocked out,” he adds. “You see a little silt pile at the bottom of the fence and they say it’s working, but it’s not. It’s passing the small pieces, but not the big pieces. So it’s screening. When the flows get heavy, the big particles are dislodged, they clog the holes, and the silt fence becomes a dam. When it attains a critical volume, which is usually under a very heavy flow, the silt fence fails and releases all of the sediment right there at the point of high flow.”
Stein uses Filtrexx socks because they are filled with graded, composted mulch and weigh 50 pounds per foot. “The organic matter in there binds a lot of the material,” he says. “It has a sufficient flow-through that it doesn’t become a dam. If it’s improperly blown, which is how it’s manufactured, it can become a dam.
“I’ve discovered ways that it won’t work by making those mistakes myself,” he adds. “You can’t just reconstitute a log. You have to have the openings in it, which means the mulch has to be graded. When it passes through, it has sufficient weight that it will stay in place and sufficient density and material inside the sock that can serve as a filter, unlike some other products that have started to hit the market that look the same but are straw wattles, coir logs, and things like that that are so open that they don’t function well either-although they’re still better than silt fence.”
When Stein uses Filtrexx Filtersoxx, he doesn’t use them just as perimeter control, but also places them around the site in places where they can break up the flow and perform as they were designed to do. “You can get excellent results with it,” he says.
In 2007 in Chattanooga, a Walmart store was being constructed on a brownfield site that had previously been a coal tipple, auto junkyard, and landfill.
“Walmart was under a national edict from the EPA to tighten up their erosion control standards on all of their sites,” Stein says. Walmart had specified silt fence at the site, which was adjacent to a significant stream, Mountain Creek. The creek had existing environmental problems that were being cleaned up.
“They didn’t want any negative impact to that, so we were able to convince Walmart to substitute the Filtrexx product,” says Stein. “There was zero impact to the stream as a result. You could see where the silt runoff was coming down to the socks. You could see the water on one side of the sock was muddy and filled with the sediment of the site and the other side of the creek was clear as a bell.”
Stein says the filtration socks are not prone to damage as are other erosion control methods. “If a tree falls on a sock, it doesn’t do anything,” he says. “The first thing you have to do when you install silt fence is disturb the ground, which is another thing that always bothered me about it. Here you are, trying to mitigate the effects of ground disturbance, and the first thing you do is go in and disturb the ground.
“With this filter sock, you lay it on the ground without disturbing it. And you don’t have to disturb the ground when you take it back up. You just go in there when everything is vegetated, slit the sock, and spread out the mulch, and everything is good to go.”
The soil conditions on the Walmart site encompassed “a lot of dirt and a bunch of rocks,” says Stein. “We laid the filter sock in a boggy area, so putting the silt sock in there did not disturb the water.”
Stein says another aspect he likes about the Filtrexx product is that he can place it around trees and it doesn’t hurt them. “It doesn’t slice up the roots when you put it in. Another thing that’s nice is if you’ve got an area that’s got a bit of pavement, like an existing road, you can lay [the sock] on the pavement. It works beautifully on hard surfaces as a filter, too.”
“After heavy rains, you inspect it like you do silt fence. The sediment doesn’t pile up like it does against the silt fence. It gets into the sock. It is bound by the organic material except under pretty heavy flows, and you may have to go back and remove the sediment from the sock.”
The socks are more expensive than silt fence, Stein says. “It depends on how large a sock you’re blowing and the cost of your mulch,” he says. “I have started manufacturing my own mulch because I do my own clearing. That helps with the cost. In this part of the country, people who are putting in the silt fence are putting it in awfully cheap, and the filter sock is about double for us. It’s 50% to 100% more expensive, but it’s still a small item in the context of the whole site.” Stein says his company has found it can use fewer linear feet to mitigate the costs.
“We do still put in silt fence, because we have had a very difficult time with some customers [comparing] the silt fence we’ve put in for $1.75 a foot and putting in something like filter socks that costs $3.50 a foot,” he says.
“If I’ve got a land owner who insists on silt fence because he says that is what he designed, I try to talk them into doing something else, but I fail frequently. We recently did a job that was $27,000 worth of silt fence, and it would have been $36,000 worth of SiltSoxx. They have had a lot more problems and extra costs having to repair silt fence than they would have had using the socks, in my opinion.”
Calculating Runoff
Adam Lyman, engineering manager for the Syman Company in Nampa, ID, says his company has written a few stormwater plans since the EPA’s new construction general permit came out and uses the Natural Resources Conservation Service RUSELE2 software to do runoff calculations. The RUSELE2 software is a tool for conservation planning, inventory of erosion rates, and estimation of sediment delivery.
“If we’re within 50 feet of a waterway and showing our planned BMPs will equal a 50-foot buffer with whatever buffer we can preserve, that’s what we have been using,” he says.
The Syman Co. is a design/build erosion control company that writes stormwater plans and helps implement BMPs; the company also sells erosion control materials from its warehouse.
Some of the Syman Company’s clients have a hard time with the CGP guidelines, Lyman notes. “In southern Idaho, rainfall is so light, it’s pretty easy to contain our runoff,” he says. “We don’t have a lot of problems with sediment basins and runoff from our construction sites that way. We’re in a semi-arid climate.
“There are several jobs we work on in the mountains above here that have real issues. The rule is so specific that many of our clients have a hard time swallowing that pill. It’s very costly. We find most of our clients are trying to compromise: We’ll put in a sediment basin but we’re only going to put in this much or this big. I’m always trying to tell them that in order to follow this rule, we need to be doing this. It usually gets comprised down. It’s a tough one.”
Idaho is a non-primacy state, making EPA the National Pollutant Discharge Elimination System (NPDES) permit authority. “We have to follow the 2012 Construction General Permit,” Lyman says, adding that his company, like others, looks to EPA for guidelines on what it needs to do for treating stormwater and the documentation of those procedures.
“It used to be in Idaho, they didn’t let us use polymers and we’ve been trying to get more official in working with the EPA when we need to use polymers for dewatering,” Lyman says. “We have used flocculants. We could never use them in the past if the water went to the waters of the United States, so we were limited to where we could use them.”
The Syman Co. had some projects in which water would drain to a private stormwater swale. To avoid plugging up the sand and soil, the company would treat the water with flocculent so it could be infiltrated into the ground.
“With the new CGP, we can get permission from the EPA to use flocculants to discharge to the waters of the US,” Lyman says. “We’re in the process of finding out what the EPA wants to see on our plans. It’s going to open up some opportunities.”
The Syman Co. uses Gator Guard drainage and sediment control wattles on projects, such as Terrace Lakes in Garden Valley, ID. A golf course and water infrastructure has been constructed there, and a residential area is now being developed.
“We did all of the stabilization to prepare for the winter rains and used a lot of Gator Guard for keeping water from running over slopes,” says Lyman. “It works so well.”
The project was at a high elevation, and water is diverted to sediment traps and check dams as opposed to merely running over slopes. “We used a lot of Gator Guard up there for that,” Lyman says, adding that when it snowed, the project had to be put on hold. “They still have to put in power, so we’ll be helping them as they put in power utilities and finish the paving of all of the roads.”
The Gator Guard was used in conjunction with straw-bale-reinforced silt fence, straw bale check dams, sediment basins, and rock riprap.
“We used the Gator Guard to filter close to riprap, which channeled the water down the slope drain to a sediment pond and to the outlet,” Lyman says.
Creating Native Habitat at a Golf Course
At the site of the construction of the Edgefield Golf Course in Troutdale, OR, storm events sent water flowing through storm drains from a subdivision that had been constructed in 1997 on a hill above the golf course into a channel that was more like a gully in the hill.
“Whenever there was a storm, it would go down there fairly flashy and it eroded all the way down to bedrock,” says Robin Cook, general manager for Sunmark Environmental Services in Portland, OR. The company sells native seeds for reclamation, stormwater filters, and soil conditioners and also installs Agrecol’s Envirolok Vegetated Environmental Solutions, such as vegetated slope-protection walls.
The severe erosion was not evident until after non-native plants that heavily covered the area were removed to make way for a new golf course hole, only to unearth evidence of channel erosion so severe that in some places it had eroded more than 4 feet, all the way down to the hard clay bottom, exposing old clay drain tile. The situation created a sediment problem, with even the smallest rain events creating a torrent that deposited large amounts of sediment in the watercourse. The watercourse discharges into wetlands, which filters out much of the sediment and serves to improve the wetlands’ water quality.
To mitigate the erosion, Sunmark in August 2007 installed an Envirolok Vegetated Retaining Wall system, which consists of soil-encapsulating bags, on the bottom and sides of the ditch. Geogrid reinforced the structure so that it could withstand the force of the water.
“What was nice was that the geosynthetic bags are able to contain the soil media that we use to grow our plants. All of the roots grow right through that material in the bag,” says Cook.
The use of foundation bags in the bottom of the channel provided an anchor to hold all of the bags together. The system was hydroseeded with native plants.
“The ecosystem is growing desirable native species that added new habitat to the golf course,” says Rob Llewellyn, Envirolok’s director of business development.
The ability of the Envirolok Vegetated Retaining Wall System to withstand flashy storm events solved a persistent and costly erosion control issue, says Llewellyn. “Storm event erosion is absolutely zero since the installation.”
Five years after the project was completed, Cook was pleased to discover how well the solution worked. “It’s still a flashy system in that every time it rains, there’s a pretty good torrent that comes down there, but all of the soil is held in place and the vegetation continues to grow,” he says.
A year after the system was installed, the grasses started to grow. By the third year, the area was converting to a woody plant community, and by the fourth year, there was a prevalence of woody plants and willows on the site, Cook notes. The new ecosystem is growing desirable native species that provide habitat for birds, butterflies and other species. The native vegetation also improved the aesthetics of the golf course.
“The benefits of the system to provide erosion control and a secure place for native vegetation to anchor to are both ecological and financial,” says Llewellyn.
