Here Today, Gone...
A spectrum of degradable EC blankets and tough synthetic TRMs.
Jay Baynes last year rolled out non-synthetic, net-free erosion control blankets for the first time. Now the engineer and owner of Pensacola, FL–based Land Consulting and Improvements LLC is one of the biggest boosters of the “netless” concept.
Baynes turned to biodegradable blankets as his firm installed roadways, sanitary sewers, and a stormwater retention and treatment system to support 200 lots of residential development surrounding a golf course in Pace, FL. The blankets—Curlex NetFree, an erosion control blanket that does not contain any netting—held several attractions for Baynes and his crew.
First, Baynes didn’t worry about animals getting trapped in netting, which is sometimes a concern when contractors use erosion control blankets that feature nylon, plastic, or even jute net. Secondly, he didn’t need to worry that any netting would get caught in mowers once vegetation grew alongside the roadways his crews had installed.
Finally, and most importantly, the blankets, manufactured by American Excelsior Co. in Arlington, TX, worked well with the sod that Baynes and his crew later placed atop them.
“I was really interested in the natural components of the material,” Baynes says. “We had always been planning on coming in after the short term with sod. The sod and the natural blankets complemented each other well during the growing stages. Once we put sod down mixed with a little winter rye, the root system quickly adapted to the natural fabric. The blankets acted as a good long-term as well as a good short-term stabilized base.”
Baynes is far from the only engineer, developer, contractor, or highway department official who has begun using easily biodegradable erosion control blankets. The reasons for these products’ growing popularity? They are the same ones that attracted Baynes to them: Even blankets that do contain netting can be designed to degrade quickly, either photodegradable when exposed to ultraviolet rays in sunlight or degrading relatively quickly through interaction with soil components. Once vegetation grows over these blankets, animals don’t run the risk of getting caught as they can when longer-lasting synthetic netting has worked its way to the surface. Lawnmower blades don’t get caught in the same longer-lasting netting, either.
 |
PHOTO: AMERICAN EXCELSIOR CO |
 |
PHOTO: AMERICAN EXCELSIOR CO |
Most erosion control blankets typically consist of some organic material—straw, wood fiber, rice straw, or other products—sandwiched between two layers of netting. This netting usually is made from nylon or plastic. But, as Baynes and other contractors have discovered, a growing number of companies are creating all-natural blankets, those that don’t use synthetic materials even in their netting.
Highway departments, municipalities, and state parks are three of the biggest drivers of the all-natural blanket industry. Parks, for example, are filled with wildlife. Animals have frequently been seen dragging synthetic netting from their hooves, and snakes get caught in the mesh and die of exposure or deep cuts. Several federal parks, therefore, have prohibited the use of rolled erosion control products that are not completely bio- or photodegradable.
The manufacturers of these products, not surprisingly, expect the demand for non-synthetic blankets to grow as more municipal officials, highway department heads, golf course developers, and others learn their benefits.
“The developers and contractors will buy what is specified for each job. They are only going to bid according to what is specified,” says Jerry Bohannon, director of the earth sciences division of American Excelsior. “They will bid the lowest-common-denominator product that they can get away with because they want to keep their costs as low as possible. It’s the specification work that is so important to getting our natural products out there. If we can get the use of non-synthetic products specified by an engineering company, city, or municipality, then the contractors and developers will have to include them in their plans. The specification community is the real driver of this push toward natural products.”
Net-Free in Florida
The netting that is commonly used on erosion control blankets can present a problem for golf course developers: Landscaping crews need to mow their courses’ grass long before the netting degrades. Typically, engineers working on golf course developments recommend netting that contains UV-degrader additives that cause the netting to photodegrade within about 90 days. The problem is, landscapers can’t wait nearly three months to mow their course’s playing surfaces, so they bring out the lawnmowers before the netting completely disappears. This often results in netting that entangles mower blades.
 |
PHOTO: MAT INC. |
This same challenge faced Baynes while he worked on the infrastructure improvements at Pace’s Stonebrook Village. The village, made up of about 650 home sites, rests on a 185-acre, 18-hole golf course. Baynes and his crew faced the potential for plenty of erosion problems.
Baynes has worked with the owner of the Stonebrook Village golf course since 1988, a span that includes 12 different phases of residential development. While drafting erosion control plans for the most recent two phases—phases that included about 200 home sites—Baynes spoke with officials at American Excelsior about Curlex NetFree. He decided to take a chance on the product. Now that infrastructure work on the two phases is complete, and homes are just beginning to go up, Baynes is glad he did.
“It’s worked very well for us,” says Baynes, whose crews installed about half a mile of the blanket. “We put it in during the summer when we were having daily storms here. It protected the areas we needed to protect. It really helped us control the stormwater generated during the rainy season. We had an awful lot of rain during this project, but the blankets held up.”
American Excelsior bills Curlex NetFree as the first erosion control blanket that contains no netting. The product is made up of Great Lakes Aspen curled wood excelsior. A total of 80% of the wood’s fibers are greater than 6 inches in length.
Manufacturers tested the product in 2003 at the ErosionLab in Rice Lake, WI. Tests showed that erosion control blankets without any netting could perform as well as blankets with synthetic or natural netting.
Baynes has since used the blankets on several other smaller erosion control projects, and says he will continue to use the product. “It’s lightweight. It’s easy to install. And it’s all-natural,” he says. “It works well both in the short term and in the long term.”
A Range of Solutions
Mark Myrowich of ErosionControlBlanket.com—a provider of erosion control products based in St. Andrews, MB, Canada—is another supporter of non-synthetic blankets. This isn’t surprising; his company includes several natural, highly biodegradable blankets among the many products it offers. He recognizes, though, that natural blankets still have a way to go if they hope to catch up to the popularity of synthetic alternatives. The reason? Not surprisingly, it’s price.
“A lot of this has to do with cost,” Myrowich says. “The plastic netting is much cheaper than the biodegradable netting. But there is a market niche out there that doesn’t mind the extra cost, that wants to have the biodegradable component to their products.”
Why would any contractor, developer, or municipal official elect to pay more for their blankets? There are circumstances where developers desire a product that degrades quickly.
“Maybe you are working in an area where you have an endangered frog, or some other kind of species,” Myrowich says. “You can’t run the risk of having the frog get stuck in the netting, or having the netting get loose, going into a stream and snaring a frog that way. Some are willing to pay extra for the pure biodegradable product that has a loose weave to it. It is a niche, a very small niche, but it is out there.”
But just because natural products have some clear benefits doesn’t mean that they are the only solution contractors, developers, and engineers should turn to on their projects. There are some cases where synthetic materials, blankets, and turf-reinforcement mats are a better choice.
Synthetic materials, of course, are not new. Engineers, developers, highway department officials, and landscapers have been using them for years to help eliminate erosion, stabilize the earth surrounding their construction projects, or catch large chunks of sediment that might otherwise escape into streams, rivers, and other bodies of water. Such products are stable and hardy, and unlikely to suffer biodegradation or to experience chemical interaction with the soil surrounding them, making them perfect for certain projects.
Other times engineers can get solid results from more traditional erosion control measures—for example, riprap or cement lining in a stormwater channel.
Because there are so many options out there, contractors would be foolish to tag one method as a favorite and then ignore the other solutions. Instead, they look at each project on a case-by-case basis to determine whether natural, synthetic, or other options are the best erosion control measures available.
“One of the biggest mistakes with erosion control is that people think they can use just one product and then cut-and-paste that product for all applications,” Myrowich says. “Even on the same job you might want to use, say, a biodegradable blanket in one section and a photodegradable blanket in another section.”
The key consideration? Contractors should determine how long they want their blankets to last, and then use the appropriate product.
“There is no one blanket type that is better than the others. It all depends on the application,” Myrowich says. “I look at it as insurance. When you get older and you have more things to protect, you buy more insurance. You pay to protect more. On a construction project it can vary. It can be by wetlands where you don’t mind paying higher insurance to make sure the blanket does what you want it to do. Or you can be working on a site where you are far from anything in terms of endangered species or bodies of water. You don’t have to pay for a more expensive product to ensure success in that case.”
Robert Moran, director of marketing with Norcross, GA–based Belton Industries, agrees that the natural-blanket segment of the industry is a niche. But contractors working on projects near golf courses or wetlands—where there are likely to be more concerns about wildlife and the surrounding environment—will always need blankets that degrade quickly.
Belton offers its own natural product. Geojute is made from natural fibers—fibers that are neither dyed nor bleached—and completely biodegradable in two years.
“I think we’ll be seeing more of these kinds of products,” Moran says. “Landscape architects, for one thing, are interested in the biodegradable products. The aesthetics are nicer. It’s never nice when the straw or other materials degrade and the netting is still there, left behind. It doesn’t look so good. Besides, it’s easier to plant through the natural material.”
All-Natural on the Highways
You won’t find construction crews installing any synthetic erosion control blankets along Maine’s highways. The reason? The state’s department of transportation is one of several that use only non-synthetic blankets in their construction projects.
 |
PHOTO: MAT INC. |
This includes all projects going on now, including the $9.7 million worth of improvements to about 15 miles’ worth of US Route 27 as it travels from Eustis to Chain of Ponds, just south of the Canadian border. Because of the project’s length, crews will perform several different tasks. In some sections they’ll be laying new roadbeds, while in others they’ll simply be adding a layer of gravel to an existing stretch of roadway. Crews will also improve the drainage systems along the stretch of road, widen some segments of the roadway, and widen some portions of the route’s shoulders.
The project is due for completion in November 2006. Crews, because of the variety of tasks they face, will use several erosion control blankets. All of them, though, will be non-synthetic.
Peter Newkirk, supervisor of the surface water resources unit for the Maine Department of Transportation, says his department began using only non-synthetic blankets about four years ago. Prior to this period, he says, the department relied, like most agencies, on blankets with polypropylene weave.
Engineers found that such products didn’t work well in Maine, though. “We found through the years—and I don’t know if it’s because we are at a higher altitude or we don’t get enough energy from the sun—that the products, even though the manufacturers said they’d photodegrade, didn’t. That led to some problems. One, we’d get complaints about wildlife snared in the stuff. It doesn’t look good for the traveling public to see a bird stuck in the side of the road trying to get out of some netting. Then there was lawn maintenance. We’d go to mow the lawn the next year and the netting would get snarled in the mowers. Looking at these products, we decided to switch over to the use of biodegradable products.”
Maine now has in its specifications a requirement that all erosion control blankets be biodegradable. The department lays hundreds of miles of erosion control blanket every year, Newkirk says. Maine has a list of erosion control products that are acceptable, and contractors, when bidding for projects in the state, refer to that list.
Of course, blankets are not the only erosion control product that Maine uses. The state often turns to riprap in ditches and channels. Maine requires on its road projects that all slopes of greater than 6% be supported by a stone-lined ditch. For slopes of less than 6%, contractors must use a rolled erosion control product in the ditch’s bottom.
 |
PHOTO: MAT INC. |
These requirements are all part of the department of transportation’s focus on erosion control as opposed to sediment control, Newkirk says. “Instead of putting up all this silt fence and sediment basins, our philosophy has been to prevent a site from eroding in the first place. Then you don’t have to deal with sediment control,” he explains. “The same day contractors cut a ditch, they’ll settle it so there are no exposed slopes for days on end.”
Though Maine requires non-synthetic blankets, the option might not be right for other departments of transportation or agencies, Newkirk points out. “We’ve received a lot of inquiries from other states about using the natural products,” he says. “I always tell people that the products work well in the proper applications. I do think, though, that the uses of these products are site-specific. If you are a developer working in an urban setting, you’re not concerned about wildlife and you’re not going to have to mow the site after you’re done, so certainly a synthetic weave product would work just as well.”
Not all highway departments rely solely on natural blankets. Some, like the Minnesota Department of Transportation, use a mix of blankets—both natural and synthetic—depending on the project.
Minnesota has experience using all kinds of erosion control blankets. The state’s department of transportation began using them way back in 1967, says Leo Holm, section director in the erosion control and forestry group with the department. Holm estimates that today 95% of the erosion control blankets his department uses are biodegradable, usually made of straw or wood excelsior.
Contractors will be rolling out biodegradable blankets during several ongoing road projects. Crews for the last four years have been installing a new bridge just south of St. Paul, a project that has involved many rolls of blankets. Crews are also using blankets during the Highway 494 reconstruction project now underway in Minneapolis.
“Back when we started using the blankets, we were building the interstate highway system,” Holm says. “We had a lot of exposed soils and a lot of big slopes to deal with. There were areas where we could not blow traditional mulch on the slope. The slopes were just too large. So we started using the erosion control blankets as an alternative. You could seed the slope by hand or by hydroseeding. You could carry the blankets up the slope and roll them out.”
Today, Minnesota uses erosion control blankets on nearly every road project, Holm says. The Department of Transportation even uses the product after installing some of its signal lights. Holm says his department will continue to use a mix of blankets—some with no nets, most biodegradable, and a small amount synthetic. The department, which is in charge of 12,600 miles of roadway, lays about 1 million square yards of erosion control blankets every year.
Holm says he’s especially pleased with some of the improvements manufacturers have added, including, but not limited to, the creation of net-free blankets. For instance, Holm is happy that blankets now come in wider varieties, including those that are 8 feet or 16 feet wide.
“The quality of blankets has certainly improved over the years,” Holm says. “For instance, the wider blankets are very helpful. If you are using blanket in a ditch bottom, you don’t want a bunch of seams exposed. The less seams you have, the better off you are. Going with an 8-foot or 16-foot blanket in that case is a good idea.”
Saving the Monkey
Mat Inc., based in Floodwood, MN, offers more evidence that engineers and contractors can turn to a wide variety of blanket products. The company offers, for instance, Grass-Mat, a blanket created from wood and corn fiber. These blankets are designed to help vegetate soils on slopes and flat areas.
The product’s greatest benefit? It can be created in netted or non-netted varieties. The product biodegrades in six to eight months, depending on the area’s weather conditions.
Mat, though, is more widely known for its Soil Guard, another product that speaks to the great variety of solutions now available to anyone dealing with erosion issues. Soil Guard is hydraulically applied but, once on the ground, dries to form a bonded fiber matrix. Once dry, the matrix can be wet repeatedly and still hold soil and seed without washing away. As vegetation takes hold, Soil Guard slowly decomposes into the soil.
“Many of our products allow contractors to go netless,” says Tom Rich of Mat Inc. “That is an obvious benefit.”
Advertisement
Soil Guard played a major role in 2001 in saving the Green Monkey Golf Course in the Sandy Lane complex at Holetown in Barbados, West Indies. Soil on the course’s island is made of rough sand that constantly shifts. Winds and unpredictable hard rains made the soil even more difficult to handle. The course’s owner, then, had struggled during the grow-in period to establish vegetation.
The contractors on the project turned to Soil Guard to hold the sands stable in all areas except for the course’s greens. Crews used Soil Guard with seed in rough areas and without seed in tee boxes and non-bunker faces. The product worked well, saving several hours of labor. Native grass began showing on the fourth day after application, and vegetation has now taken hold at the course.
Author's Bio: Dan Rafter is a technical writer based in Illinois.
November-December 2005
Here Today, Gone...
A spectrum of degradable EC blankets and tough synthetic TRMs.
Jay Baynes last year rolled out non-synthetic, net-free erosion control blankets for the first time. Now the engineer and owner of Pensacola, FL–based Land Consulting and Improvements LLC is one of the biggest boosters of the “netless” concept.Baynes turned to biodegradable blankets as his firm installed roadways, sanitary sewers, and a stormwater retention and treatment system to support 200 lots of residential development surrounding a golf course in Pace, FL. The blankets—Curlex NetFree, an erosion control blanket that does not contain any netting—held several attractions for Baynes and his crew.
First, Baynes didn’t worry about animals getting trapped in netting, which is sometimes a concern when contractors use erosion control blankets that feature nylon, plastic, or even jute net. Secondly, he didn’t need to worry that any netting would get caught in mowers once vegetation grew alongside the roadways his crews had installed.
Finally, and most importantly, the blankets, manufactured by American Excelsior Co. in Arlington, TX, worked well with the sod that Baynes and his crew later placed atop them.
“I was really interested in the natural components of the material,” Baynes says. “We had always been planning on coming in after the short term with sod. The sod and the natural blankets complemented each other well during the growing stages. Once we put sod down mixed with a little winter rye, the root system quickly adapted to the natural fabric. The blankets acted as a good long-term as well as a good short-term stabilized base.”
Baynes is far from the only engineer, developer, contractor, or highway department official who has begun using easily biodegradable erosion control blankets. The reasons for these products’ growing popularity? They are the same ones that attracted Baynes to them: Even blankets that do contain netting can be designed to degrade quickly, either photodegradable when exposed to ultraviolet rays in sunlight or degrading relatively quickly through interaction with soil components. Once vegetation grows over these blankets, animals don’t run the risk of getting caught as they can when longer-lasting synthetic netting has worked its way to the surface. Lawnmower blades don’t get caught in the same longer-lasting netting, either.
|
PHOTO: AMERICAN EXCELSIOR CO |
|
PHOTO: AMERICAN EXCELSIOR CO |
Most erosion control blankets typically consist of some organic material—straw, wood fiber, rice straw, or other products—sandwiched between two layers of netting. This netting usually is made from nylon or plastic. But, as Baynes and other contractors have discovered, a growing number of companies are creating all-natural blankets, those that don’t use synthetic materials even in their netting.
Highway departments, municipalities, and state parks are three of the biggest drivers of the all-natural blanket industry. Parks, for example, are filled with wildlife. Animals have frequently been seen dragging synthetic netting from their hooves, and snakes get caught in the mesh and die of exposure or deep cuts. Several federal parks, therefore, have prohibited the use of rolled erosion control products that are not completely bio- or photodegradable.
The manufacturers of these products, not surprisingly, expect the demand for non-synthetic blankets to grow as more municipal officials, highway department heads, golf course developers, and others learn their benefits.
“The developers and contractors will buy what is specified for each job. They are only going to bid according to what is specified,” says Jerry Bohannon, director of the earth sciences division of American Excelsior. “They will bid the lowest-common-denominator product that they can get away with because they want to keep their costs as low as possible. It’s the specification work that is so important to getting our natural products out there. If we can get the use of non-synthetic products specified by an engineering company, city, or municipality, then the contractors and developers will have to include them in their plans. The specification community is the real driver of this push toward natural products.”
Net-Free in Florida
The netting that is commonly used on erosion control blankets can present a problem for golf course developers: Landscaping crews need to mow their courses’ grass long before the netting degrades. Typically, engineers working on golf course developments recommend netting that contains UV-degrader additives that cause the netting to photodegrade within about 90 days. The problem is, landscapers can’t wait nearly three months to mow their course’s playing surfaces, so they bring out the lawnmowers before the netting completely disappears. This often results in netting that entangles mower blades.
|
PHOTO: MAT INC. |
This same challenge faced Baynes while he worked on the infrastructure improvements at Pace’s Stonebrook Village. The village, made up of about 650 home sites, rests on a 185-acre, 18-hole golf course. Baynes and his crew faced the potential for plenty of erosion problems.
Baynes has worked with the owner of the Stonebrook Village golf course since 1988, a span that includes 12 different phases of residential development. While drafting erosion control plans for the most recent two phases—phases that included about 200 home sites—Baynes spoke with officials at American Excelsior about Curlex NetFree. He decided to take a chance on the product. Now that infrastructure work on the two phases is complete, and homes are just beginning to go up, Baynes is glad he did.
“It’s worked very well for us,” says Baynes, whose crews installed about half a mile of the blanket. “We put it in during the summer when we were having daily storms here. It protected the areas we needed to protect. It really helped us control the stormwater generated during the rainy season. We had an awful lot of rain during this project, but the blankets held up.”
American Excelsior bills Curlex NetFree as the first erosion control blanket that contains no netting. The product is made up of Great Lakes Aspen curled wood excelsior. A total of 80% of the wood’s fibers are greater than 6 inches in length.
Manufacturers tested the product in 2003 at the ErosionLab in Rice Lake, WI. Tests showed that erosion control blankets without any netting could perform as well as blankets with synthetic or natural netting.
Baynes has since used the blankets on several other smaller erosion control projects, and says he will continue to use the product. “It’s lightweight. It’s easy to install. And it’s all-natural,” he says. “It works well both in the short term and in the long term.”
A Range of Solutions
Mark Myrowich of ErosionControlBlanket.com—a provider of erosion control products based in St. Andrews, MB, Canada—is another supporter of non-synthetic blankets. This isn’t surprising; his company includes several natural, highly biodegradable blankets among the many products it offers. He recognizes, though, that natural blankets still have a way to go if they hope to catch up to the popularity of synthetic alternatives. The reason? Not surprisingly, it’s price.
“A lot of this has to do with cost,” Myrowich says. “The plastic netting is much cheaper than the biodegradable netting. But there is a market niche out there that doesn’t mind the extra cost, that wants to have the biodegradable component to their products.”
Why would any contractor, developer, or municipal official elect to pay more for their blankets? There are circumstances where developers desire a product that degrades quickly.
“Maybe you are working in an area where you have an endangered frog, or some other kind of species,” Myrowich says. “You can’t run the risk of having the frog get stuck in the netting, or having the netting get loose, going into a stream and snaring a frog that way. Some are willing to pay extra for the pure biodegradable product that has a loose weave to it. It is a niche, a very small niche, but it is out there.”
But just because natural products have some clear benefits doesn’t mean that they are the only solution contractors, developers, and engineers should turn to on their projects. There are some cases where synthetic materials, blankets, and turf-reinforcement mats are a better choice.
Synthetic materials, of course, are not new. Engineers, developers, highway department officials, and landscapers have been using them for years to help eliminate erosion, stabilize the earth surrounding their construction projects, or catch large chunks of sediment that might otherwise escape into streams, rivers, and other bodies of water. Such products are stable and hardy, and unlikely to suffer biodegradation or to experience chemical interaction with the soil surrounding them, making them perfect for certain projects.
Other times engineers can get solid results from more traditional erosion control measures—for example, riprap or cement lining in a stormwater channel.
Because there are so many options out there, contractors would be foolish to tag one method as a favorite and then ignore the other solutions. Instead, they look at each project on a case-by-case basis to determine whether natural, synthetic, or other options are the best erosion control measures available.
“One of the biggest mistakes with erosion control is that people think they can use just one product and then cut-and-paste that product for all applications,” Myrowich says. “Even on the same job you might want to use, say, a biodegradable blanket in one section and a photodegradable blanket in another section.”
The key consideration? Contractors should determine how long they want their blankets to last, and then use the appropriate product.
“There is no one blanket type that is better than the others. It all depends on the application,” Myrowich says. “I look at it as insurance. When you get older and you have more things to protect, you buy more insurance. You pay to protect more. On a construction project it can vary. It can be by wetlands where you don’t mind paying higher insurance to make sure the blanket does what you want it to do. Or you can be working on a site where you are far from anything in terms of endangered species or bodies of water. You don’t have to pay for a more expensive product to ensure success in that case.”
Robert Moran, director of marketing with Norcross, GA–based Belton Industries, agrees that the natural-blanket segment of the industry is a niche. But contractors working on projects near golf courses or wetlands—where there are likely to be more concerns about wildlife and the surrounding environment—will always need blankets that degrade quickly.
Belton offers its own natural product. Geojute is made from natural fibers—fibers that are neither dyed nor bleached—and completely biodegradable in two years.
“I think we’ll be seeing more of these kinds of products,” Moran says. “Landscape architects, for one thing, are interested in the biodegradable products. The aesthetics are nicer. It’s never nice when the straw or other materials degrade and the netting is still there, left behind. It doesn’t look so good. Besides, it’s easier to plant through the natural material.”
All-Natural on the Highways
You won’t find construction crews installing any synthetic erosion control blankets along Maine’s highways. The reason? The state’s department of transportation is one of several that use only non-synthetic blankets in their construction projects.
|
PHOTO: MAT INC. |
This includes all projects going on now, including the $9.7 million worth of improvements to about 15 miles’ worth of US Route 27 as it travels from Eustis to Chain of Ponds, just south of the Canadian border. Because of the project’s length, crews will perform several different tasks. In some sections they’ll be laying new roadbeds, while in others they’ll simply be adding a layer of gravel to an existing stretch of roadway. Crews will also improve the drainage systems along the stretch of road, widen some segments of the roadway, and widen some portions of the route’s shoulders.
The project is due for completion in November 2006. Crews, because of the variety of tasks they face, will use several erosion control blankets. All of them, though, will be non-synthetic.
Peter Newkirk, supervisor of the surface water resources unit for the Maine Department of Transportation, says his department began using only non-synthetic blankets about four years ago. Prior to this period, he says, the department relied, like most agencies, on blankets with polypropylene weave.
Engineers found that such products didn’t work well in Maine, though. “We found through the years—and I don’t know if it’s because we are at a higher altitude or we don’t get enough energy from the sun—that the products, even though the manufacturers said they’d photodegrade, didn’t. That led to some problems. One, we’d get complaints about wildlife snared in the stuff. It doesn’t look good for the traveling public to see a bird stuck in the side of the road trying to get out of some netting. Then there was lawn maintenance. We’d go to mow the lawn the next year and the netting would get snarled in the mowers. Looking at these products, we decided to switch over to the use of biodegradable products.”
Maine now has in its specifications a requirement that all erosion control blankets be biodegradable. The department lays hundreds of miles of erosion control blanket every year, Newkirk says. Maine has a list of erosion control products that are acceptable, and contractors, when bidding for projects in the state, refer to that list.
Of course, blankets are not the only erosion control product that Maine uses. The state often turns to riprap in ditches and channels. Maine requires on its road projects that all slopes of greater than 6% be supported by a stone-lined ditch. For slopes of less than 6%, contractors must use a rolled erosion control product in the ditch’s bottom.
|
PHOTO: MAT INC. |
These requirements are all part of the department of transportation’s focus on erosion control as opposed to sediment control, Newkirk says. “Instead of putting up all this silt fence and sediment basins, our philosophy has been to prevent a site from eroding in the first place. Then you don’t have to deal with sediment control,” he explains. “The same day contractors cut a ditch, they’ll settle it so there are no exposed slopes for days on end.”
Though Maine requires non-synthetic blankets, the option might not be right for other departments of transportation or agencies, Newkirk points out. “We’ve received a lot of inquiries from other states about using the natural products,” he says. “I always tell people that the products work well in the proper applications. I do think, though, that the uses of these products are site-specific. If you are a developer working in an urban setting, you’re not concerned about wildlife and you’re not going to have to mow the site after you’re done, so certainly a synthetic weave product would work just as well.”
Not all highway departments rely solely on natural blankets. Some, like the Minnesota Department of Transportation, use a mix of blankets—both natural and synthetic—depending on the project.
Minnesota has experience using all kinds of erosion control blankets. The state’s department of transportation began using them way back in 1967, says Leo Holm, section director in the erosion control and forestry group with the department. Holm estimates that today 95% of the erosion control blankets his department uses are biodegradable, usually made of straw or wood excelsior.
Contractors will be rolling out biodegradable blankets during several ongoing road projects. Crews for the last four years have been installing a new bridge just south of St. Paul, a project that has involved many rolls of blankets. Crews are also using blankets during the Highway 494 reconstruction project now underway in Minneapolis.
“Back when we started using the blankets, we were building the interstate highway system,” Holm says. “We had a lot of exposed soils and a lot of big slopes to deal with. There were areas where we could not blow traditional mulch on the slope. The slopes were just too large. So we started using the erosion control blankets as an alternative. You could seed the slope by hand or by hydroseeding. You could carry the blankets up the slope and roll them out.”
Today, Minnesota uses erosion control blankets on nearly every road project, Holm says. The Department of Transportation even uses the product after installing some of its signal lights. Holm says his department will continue to use a mix of blankets—some with no nets, most biodegradable, and a small amount synthetic. The department, which is in charge of 12,600 miles of roadway, lays about 1 million square yards of erosion control blankets every year.
Holm says he’s especially pleased with some of the improvements manufacturers have added, including, but not limited to, the creation of net-free blankets. For instance, Holm is happy that blankets now come in wider varieties, including those that are 8 feet or 16 feet wide.
“The quality of blankets has certainly improved over the years,” Holm says. “For instance, the wider blankets are very helpful. If you are using blanket in a ditch bottom, you don’t want a bunch of seams exposed. The less seams you have, the better off you are. Going with an 8-foot or 16-foot blanket in that case is a good idea.”
Saving the Monkey
Mat Inc., based in Floodwood, MN, offers more evidence that engineers and contractors can turn to a wide variety of blanket products. The company offers, for instance, Grass-Mat, a blanket created from wood and corn fiber. These blankets are designed to help vegetate soils on slopes and flat areas.
The product’s greatest benefit? It can be created in netted or non-netted varieties. The product biodegrades in six to eight months, depending on the area’s weather conditions.
Mat, though, is more widely known for its Soil Guard, another product that speaks to the great variety of solutions now available to anyone dealing with erosion issues. Soil Guard is hydraulically applied but, once on the ground, dries to form a bonded fiber matrix. Once dry, the matrix can be wet repeatedly and still hold soil and seed without washing away. As vegetation takes hold, Soil Guard slowly decomposes into the soil.
“Many of our products allow contractors to go netless,” says Tom Rich of Mat Inc. “That is an obvious benefit.”
Soil Guard played a major role in 2001 in saving the Green Monkey Golf Course in the Sandy Lane complex at Holetown in Barbados, West Indies. Soil on the course’s island is made of rough sand that constantly shifts. Winds and unpredictable hard rains made the soil even more difficult to handle. The course’s owner, then, had struggled during the grow-in period to establish vegetation.
The contractors on the project turned to Soil Guard to hold the sands stable in all areas except for the course’s greens. Crews used Soil Guard with seed in rough areas and without seed in tee boxes and non-bunker faces. The product worked well, saving several hours of labor. Native grass began showing on the fourth day after application, and vegetation has now taken hold at the course.