Heading down the rabbit hole into the wonderland of erosion control is a trip to an exotic world where blankets do not cover babies in cribs, mats are not found on tables, and inlets are not narrow blue expanses of water but, in fact, drains. Hills become slopes, rivers and lakes become waterways, and channels are no longer found on the television set. Scouring happens when it rains, not in the sink when the pots are dirty. Flowers and grass vegetate, which in erosion control terms is a good thing and does not mean wasting a Monday morning watching old movies. Runoff has nothing to do with escaping from prison; and rills, while they sound a lot like thrills or trills, are merely gullies. However, the people who speak this language are kind if competitive folk who at the end of the day agree on one thing: Running water is a real problem for dirt.
Public Projects Call for Different Applications
With its tree-lined streets and population of 5,000, the college town of Montevallo, AL, has much to offer those looking for small-town America. It has also become a place for those looking for solace in a war-torn world where young men die way too soon.
A new 479-acre national cemetery north of town was opened June 25, 2009, by the Department of Veterans Affairs. It serves approximately 200,000 veterans in the region, is the third national cemetery in Alabama, and includes extensive and varied internment areas, as well as public and administrative facilities.
Hunter Bruce, vice president of Spreadrite Organics of Chelsea, AL, near Birmingham, was responsible for sediment and erosion control, as well as establishing vegetation on the first phase of developing of the site in mid-2008. “It was interesting to work on,” he says, describing the natural setting, with a large creek, Shoal (a tributary of the Cahaba River) at its edge, and woods and mountains in the background. Manmade additions of Kentucky bluegrass and numerous varieties of wildflowers blowing in the breeze soften the view of simple crosses that mark the memories of those who never made it home to Alabama.
Weather, as always, was a factor in preparing the area for vegetation, Bruce says. “It’s been really wet here. By December 2009, we’d had close to 70 inches of rainfall, well above our annual average. In November, we had two rains of 9 and 7 inches, each within 24 hours.”
More water calls for a different grade of product, and while engineers had specified traditional methods, Bruce says he was able to “value engineer” the product and upgrade the specifications for something “more economical from a time standpoint.”
Bruce says the projects involved some slopes, on which crews used traditional seed and straw followed by a high-end hydromulch and hydroseeding. In the main drainage area behind the property, they used Profile Products’ Enkamat 7010 with Flexterra FGM (flexible growth medium) infill. “This flume drains the site and acts as an overflow from the existing creek,” he explains.
Semi-permanent construction trailers bordered the site for two years, limiting access for erosion control, Bruce says. “It had been rough-graded, but we did the rest of the grading by hand before we laid the blanket. In some cases we had to lay it over the rocks. The crypt area was covered with hydroseeding and rolled Bermuda sod, and it’s manicured like the Augusta National Golf Course.”In addition to thousands of newly planted trees, a major part of the site is covered in wildflowers such as butterfly milkweed, river oats, purple cornflower, and black-eyed Susan. These were provided by Ernst Conservation Seeds of Meadville, PA, Bruce says.
It took an eight-man crew two days to complete the project, according to Bruce, who says wet conditions from rain and an underground spring and limited access made for some challenging hydroseeding, including parking 200 feet away and using hoses. “We used Enkamat 7010 and trenched it in on the edges, preseeding the natural soil. Then we rolled out the mat and stapled it in before hydromulching FGM into it. It’s a porous, high-strength product that nearly fills the voids of the Enkamat TRM [turf reinforcement mat]. When it cures and dries, you have an instant barrier that can be out in the rain.”
Bruce says the total cost of grading and infrastructure for the first phase of the project was $3.5 million.
In the Houston area, where people can enjoy outdoor recreation for most of the year, park development and maintenance is a major industry.
Bob Ferlinski is director of operations for Protective Environmental Strategies in Houston, TX. Last summer he supervised erosion and sediment control at Carl Barton Jr. Park, a 200-acre facility in Conroe, just north of Houston. Conroe’s newest park, in phase one of development, includes 15 athletic fields, a picnic area, and an exercise trail.
“Last summer we had one of the worst droughts on record,” Ferlinski says. “It was a problem growing seed and establishing turf. When the rain came after three months, we received nine inches in two or three hours, and then had two more 6-inch rains. In a couple of channels where we had already seeded, the soil was sloughing off. We installed North American Green’s SC250 and it cleared the problem. These were the only areas that had grown grass during the drought.”
Ferlinski gives credit to theVmax3 SC250, a permanent, high-strength, three-dimensional matting that incorporates a straw and coconut-fiber matrix. “In our climate, coconut works best for erosion control and seed germination. The problem is that engineers often specify ordinary tight-woven poly products; these control normal erosion. But with excessive amounts of rain and heat, where it rains one day and gets up to 100 degrees the next day, that product is poor for seed germination. Therefore, for primary stabilization of turf, we try to get a high-performance coconut product.”
Ferlinski says coconut breathes, allowing oxygen in to facilitate seeding, and it also does a good job of containing moisture. “North American Green makes a unique matrix. Most materials are flat, but this has a double polymer, which encases the coconut. It is not just monofilm net; it allows for extension. Because it is three-dimensional, it allows water to disperse.”
He says he tries to get coconut fiber, or coir, specified in a project where vegetation is important. “The coconut remains in the soil and provides a longer-lasting solution.” And the challenges on this project were twofold: drought, followed by torrential rains. “In the fall we might get three inches in a day; in the summer we can get three inches in one to one-and-a-half hours. If the mat gets undercut, you get rills and washouts and you lose your seed base, especially in the summer.”
Vmax3’s ease of application also appeals to Ferlinski. “The system is nice on large projects because there is a dot matrix on the mat, with painted dots that tell you where to put each anchor. It helps with overrun on staples.”
Ferlinski says the cost on this relatively small, six-month project was $10,000 to $15,000. “A lot of products [from] overseas save on materials, but they don’t have the same quality. This one [the SC250] has double the netting.”
Terraced Building Complex Presents ChallengesMatt Edgemon is vice president of Southwest Erosion Control Inc. in Prosper, TX. In 2009, he spent a week and a half on a $32,000 erosion control project at Collin County Youth Detention Facility. His job was to divert water from areas around the multi-building complex to keep water flow from cutting into the structures’ foundations. “These buildings were built on a fairly steep slope,” he explains. “They drop to cascading retaining walls, which support the pods where the youths are housed. It is a three-tiered series of buildings, stair-stepped with retaining walls of eight to 12 feet. There are 15- to- 20-foot slopes between the buildings and stepped retaining walls, which are 100 to 150 feet apart from each other.
“We altered the grading and diverted the water to new riprap and erosion mat-lined channels. We seeded, installed rock check dams, and put in straw wattles to reduce the water velocity in areas where riprap was not installed. We used Western Excelsior’s biodegradable R-1 because the county wanted to be able to mow and maintain the area with tractors after vegetation was established.”
Edgemon says that Western Excelsior is just one of his suppliers, but he has been impressed by the company. “The product has consistent quality and a heavier amount of fiber per square yard. The material is ground aspen with green dye.”
The county imposed no product restrictions on the project, Edgemon says, although it did specify biodegradable material on the edges where the soil meets the riprap. “The mat will hold a year before it degrades,” Edgemon says. “Vegetation was established within 30 days, mostly rye grass.”
He notes that Western Excelsior’s mat comes in bundled rolls, which are easy to handle and install. “The quality is consistent; sometimes there can be voids in the fiber of mats. You need the fiber to hold the soil and stimulate seed germination uniformly when installed correctly. A few years ago, we had some problems with quality control in the mats we were purchasing, and this led us to change to a product that was more dependable.”
Subdivisions Require Remediation Over Time
Glenn Stewart is the president of Duck Hawk Environmental Contractors in the metroplex that is Dallas-Fort Worth. Over time, in the city of Garland, TX, the Universal Channel banks had eroded in one of the older subdivisions. “As Garland built up, the watershed went from wooded areas to asphalt and concrete,” Stewart says. “So the creek was now carrying more runoff, and as it tried to find a level of stabilization, it was straightening out its banks and deepening its channel.”
The result for homeowners was literally a loss of property. Because the creek extends to the edges of the subdivision, its overflow was taking out carports, swimming pools, and walls. “The creek forms a boundary on both sides of the subdivision,” Stewart explains. “Some homeowners gain access to their land by a bridge, so in some cases people were losing both property and access.”
The city of Garland employed the US Army Corps of Engineers to widen and deepen the channel and to encase it in precast, 1,500-pound concrete blocks textured for appearance. “Then we went in and did the mitigation, planting natural grasses, plants, and trees,” Stewart says.
After the general contractor had backfilled the area behind the wall, Duck Hawk leveled and graded the soil before putting down a synthetic mat, Stewart says. The city had specified Western Excelsior’s Excel PP5-8 TRM, consisting of a matrix of ultraviolet-stabilized, synthetic fibers stitched between two ultraviolet-stabilized, heavy-duty synthetic nets. With its target weight of 8 ounces per square yard. Stewart says it was ideal for the situation at hand. “The synthetic fabric has the strength and weight for the shear force. It never degrades if properly installed. No mat can compensate for improper installation.”
Getting a smooth grade is also important, according to Stewart, who says grading was a challenge in wet conditions. “We leveled and graded before placing the mat. You can’t have any lumps or let air get in. If the mat doesn’t touch every bit of the surface, you get rills.”
Crews soil-filled the mat in order to seal it and subgraded it to aid germination and develop a root zone. The soil-loam and clay-tended to form clods, and although it was easy to break up and till when dry, there was significant rain during the project. “We got 15-and-a-half inches of rain in October; that’s a third of Garland’s annual rainfall,” Stewart says. “It increased the time it took to lay the subgrade.”The project began in June 2009 and was ongoing in December. “The creek is 1,500 feet long, and we’re working on both sides,” Stewart says, adding that his crew followed behind the general contractor.
Because this was a mitigation project, native grasses were mandated, he notes. The crews used bluestem, side-oats grama, and Eastern grama grass, all of which are drought-resistant. “If they get a good start, they will hold and produce a root system that creates a barrier and increases the rate of water flow that the mat can take.” Crews also used a Grasslander seeder designed to sow native grasses.
Stewart said he is a fan of synthetic mats. “They can be expensive, but their long-term advantages outweigh any disadvantages.”
Joel Seawell, CPESC, is owner of Erosion Pros LLC in Auburn, AL. Recently he dealt with erosion from stormwater runoff on a county right of way in Auburn. “The subdivision was on a ridge, and the water was bypassing the detention pond due to the intensity of rainfall in southern Alabama,” Seawell says. “The subdivision was built in a previously forested area, and the paving operation and increased impervious surface created an increased velocity and volume of runoff.”
Seawell says the channels were discharging into Parkerson Mill Creek, “a valued waterway of the state” that had problems over the years. “It was not originally on the 303(d) list, but it has since been added,” he says, referring to the state’s list of impaired waters. “It’s a sensitive-water stream.”
Due to the high visibility of the creek water, the local regulatory authorities mandated that the subdivision’s owner perform remediation. “We first looked at the flood characteristics of the channel in order to determine what type of blanket was needed,” Seawell says. “American Excelsior’s Recyclex was a cost-efficient solution because the city preferred a green look to concrete. It’s a synthetic mat made of recycled soda bottles. I like it; it is a permanent TRM. Vegetation grows through the matting, which has a permissible shear stress for the flow of the channel.”
To repair the 4- to 5-foot channels, workers first repaired the gullied areas, then hydroseeded the channels. “We put the mat on top of the seed; it’s cheaper that way,” Seawell says. “We used American Excelsior wattles on top of the matting to slow the velocity of the water. These were removed once the vegetation was fully established.”
Workers applied a mixture of perennial vegetation that included quick-germinating rye grass, unhulled and hulled Bermuda grass, fescue, reseeding Crimson Clover, and Bahiagrass.
The challenges on this approximately $8,000 project involved traffic along the road and the degraded condition of the channels themselves. “It took us a while to prepare the site,” Seawell notes. “There was trash everywhere; it was a wreck.”
Cleaning Up Ohio River Is an Ongoing Task
Gulf Oil owned and operated a refinery in Whitewater Township near Cincinnati, OH, from 1931 to 1986. The facility was taken over by Chevron, which closed it in May 1986, after a hydrocarbon sheen was observed the previous year to be leaking into the Miami River. In 1993, Chevron entered into an agreement with the EPA to remediate the site.
Tony Blatnik is branch manager for JMD Co. in Macedonia, OH. The company specializes in mine and construction products, and Blatnik, who has a construction background, was requested to assist in some of the geotechnical and erosion control aspects on a project on the banks of the Little Miami River in December 2008.
Blatnik worked on an 8.5-acre site along the river where sheet-pile barriers were already in place to stabilize the riverbank.
“The shear stresses above that elevation exceeded 13 pounds PSF,” he says, pointing out that the shear stress of Niagara Falls is 20 by comparison. “I’ve seen cars from the salvage yard up the river go over the top of this flood plain during the spring floods. Ice backs up, and huge six- to eight-foot blocks of ice come down as well.”
TriHydro Engineers of Laramie, WY, engineered the project, and the company’s original design intent, according to Blatnik, was to line the riverbank with rock and a simple erosion blanket. “With the kind of velocity and shear stress we had, I convinced them to tweak the plan and use Profile’s Green Armor system,” he says. “It’s a neat system, and we needed that hydraulically applied growth medium within the TRM, given the time period. It was December, and we needed to hold the soils in place all winter. With ordinary mats, the water runs through and under the TRM. With Green Armor, the seed is shot into the 3-D matrix and becomes part of the mat, while the flexible growth medium will hold long enough to establish vegetative growth. It’s one of the few that would meet this shear stress requirement before the vegetation can become established. It has the necessary tensile strength in the mat itself, which provides support for the root system and stem of the plant, because it grows within the three-dimensional matrix of the TRM. The seed germinates in the blanket, not above or below the TRM.”
Blatnik says that engineers, wanting to ensure the system would hold, designed 3-foot by 3-foot anchor trenches perpendicular to the river’s flow every 50 feet along the bank and drove in live stake anchors between the trenches. “We dumped rocks into the anchor trenches to tension the Enkamat TRM while maintaining intimate contact with the underlying sandy, loamy soil.”
For vegetation, Blatnik says, they came up with an endophyte-free seed plan to make the grass insect-proof. “These were cool-season grasses such as pasture bluegrass with rhysomic characteristics, fawn fescue with a horizontal root structure, and perennial rye grass for quick germination. Every couple of feet we put in live stakes, like willows and butterfly brush-natives that would hold and trap the natives.”
The challenges on this job were nasty weather and a significant time constraint. “It was terrible weather, freezing conditions and snow,” Blatnik recalls. “Chevron gave us three weeks before we had to be out of there, and I was leery to spray a hydraulically applied product onto a mat. Most products need cure time. But I told the engineers that if any product would work, it would be this one.”
Chevron was pleased with the result, Blatnik says. “We went back there once four weeks after we finished, and the lower portions of the TRM areas were under 10 feet of water. I was nervous. But when we could get access to get back there in April, we had not lost one inch of matting or underlying soil. Nothing had moved. The live stakes were in underwater, and sand and leaves from upriver were deposited everywhere. But nothing had moved. We got germination by early spring. It was a big success.”The cost of installation for the project, excluding the cost of live stakes, was $12 per square yard, Blatnik says. “Ecology and safety were Chevron’s main concerns. It was not necessarily a cost issue; they just wanted the best solution out there that would hold up. Green Armor was a new product, but I had faith in it, so I went out on a limb. It was a huge success.”
Testing New Products Is All Part of the Fun
In Minnesota, more than 200,000 drivers daily ply their way over the Twin Cities’s Highway 62, which has always joined and interweaved with Interstate Highway 35W in a mile-long stretch known as the Crosstown Commons. After years of delays, construction to improve the area began in May 2007. The new interchange features three through-lanes for I-35W (including one HOV lane) in each direction and two separate through-lanes for Highway 62 in each direction, eliminating the need to weave across traffic. The project is scheduled to be completed in 2010 with a final cost of over $300,000.
Dwayne Stenlund is a certified erosion and sediment control officer for the state of Minnesota. In this capacity, he is responsible for overseeing demonstrations of various installations before they are approved for the official state list of practices.
The challenge in this particular project, according to Stenlund, was that the design did not address getting the water to flow down a retaining wall. “It’s a steep slope, at least two-to-one, and drainage was needed to stabilize it,” he says. “The wall stops at the noise wall and drainage plunges 15 feet down to the road.”
In addition, a drainage ditch extends back 1,000 feet from the roadway, and this also needed to be stabilized. “We put a turf mat-Multimat 100-down and injected vegetation into it,” Stenlund says. “Together they offered a synergy, blending to solve the problem.”
Stenlund says that environmental regulations require contractors to stabilize exposed soil within 14 days of its being disturbed and before permanent erosion control is in place. “Our goal is to get green spaces in an ultra-urban environment,” he says.
In this project, the first job was to “rip” the soil, tilling to break up the hardpan and let water infiltrate the soil. “We tilled, then fertilized and seeded, modifying the SWPPPs [stormwater pollution prevention plans] to see what this particular product would do, in lieu of what was shown in the plan,” Stenlund explains. “The plan called for straw mulch to be crimped in, but that wouldn’t work well with these installation logistics: a 40-foot-high wall with a terrace halfway down. It would be very difficult to install straw.”
Instead, Stenlund took advantage of industry’s continuous desire to have new products tested and approved by departments of transportation. In this case, the company was Mat Inc., which wanted to test Flex Guard, a hydromulch, in combination with Tenax Multimat 100. “This was not a formal test,” Stenlund says. “I just like to see how many ways I can do it wrong on any project and it will still work.”
Stenlund believes the future of the industry lies in hydraulically applied mulches. “Hydraulic “˜glues’ cost more but they save on labor; this was a challenging site.”
In conveyance systems such as ditches, Stenlund says, he ordinarily prefers to use a blanket, but he acknowledges that this manufacturer had come up with a system that works there also. “In this case, we had a defined watershed confined by a wall in addition to a steep slope design error. We applied the Flex Guard into the ditch and onto the slopes. This was a conveyance ditch that discharges down a steep slope into the gutter line of the main line. During construction that part always eroded. Previously the contractor had always used a backhoe, rolled out the mat, shot fiber into it, seeded, fertilized, and prepared the area. Not here.”
On the Pipeline in Mississippi
Bobby Thomas is president and co-owner of Reel Neet Erosion Control in Olive Branch, MS. He recently supervised the restoration, erosion control, and “re-revegetation” on 12 miles of newly installed 36-inch natural gas pipeline for Midcontinent Express, a 500-mile system that extends from the southeast corner of Oklahoma across northeast Texas, northern Louisiana, central Mississippi, and into Alabama and interconnects with numerous major pipeline systems in the chain that extends from newly developed areas in Oklahoma and Texas into high-demand Eastern US markets.
The site, in the Vicksburg, MS, area, was completely wooded and involved clearing 100 to 140 feet of right of way in “sandy, loamy soil,” Thomas says. These are loess soils, highly erosive and almost like talcum powder. The project began with hot, dry weather in June 2009. Then, about 30 inches of rain fell in one month, according to Thomas. From that point, dealing with high-velocity water and holding the soil in place became the project’s main challenges.
“One company on an adjacent line had used seed and straw, and they had problems, so we went with Flexterra FGM [Profile Product’s flexible growth medium],” Thomas says. “We used GreenArmor on some of the slopes and in the water bodies. We installed an Enkamat 7020 TRM and sprayed Flexterra into it. These mats will last indefinitely because they are not exposed, and they hold the roots in situations where there is a high velocity of water. I’ve used them all, and this is the best so far.”
The project, which took about a year to complete, involved a variety of techniques, according to Thomas. “We had to put riprap in two ditches where the groundwater leaches into the banks. We had to bore under rivers and streams.”
Workers also had to deal with some steep slopes and used several different pieces of equipment for access. “Once we had installed the pipe and covered it, we put the dirt back to its natural state and put vegetation up and down the hills, with many near 1:1. Then we applied the GreenArmor and Flexterra with one Finn HydroSeeder mounted on a decommissioned six-wheel-drive US Army truck, and another HydroSeeder on a skid pulled behind a D-5 dozer. In one case, we used a D6T wide-track dozer to pull the seeder over the hill. We used six 330-trackhoes, seven D-6 trackhoes, and two D-5s. We used compactors on the soil and sprayed it with Flexterra. I like to use a roller compactor because it helps with erosion. I do that on all of my jobs if possible. If we couldn’t get in on steep areas, we used a Bobcat with a compactor. We shot the Flexterra at 3,500 pounds per acre, and 4,000 pounds on the steeper areas. It held up real well, especially considering the amount of rain we had. On the most critical slopes, we just covered the entire slope with the GreenArmor.
Thomas says Profile’s GreenArmor system is superior to ordinary matting. “It sticks like paint. A regular mat pulls up and you get rills. Regular mats lay on top of the soil and you get water underneath. Eventually conventional matting will be a dinosaur because of the technology of hydraulic mulch. Other products are close, but they are not quite there yet. When there is high velocity of water, FlexTerra alone may not be enough, but if you add GreenArmor, it will hold.”
Thomas says that the Federal Energy Regulatory Commission prohibited using fertilizer near the water bodies and specified that no soil enter the streams. “We used water bars to divert the runoff and silt fences at the creek banks. We sprayed the rights of way with FlexTerra and laid Enkamat. Then we mixed the seed and sprayed into it. It germinated even with the rain we had.”
