Experts discuss what they use in the mix and how to apply it

13 Sep Experts discuss what they use in the mix and how to apply it

By Carol Brozowski
Erosion Control Magazine – January/February 2006 Edition pg 60-71.

Jonathan Colbert, owner of Acacia Erosion Control in Santa Barbara, CA, has observed over the past decade that hydroseeding is claiming an increasing market segment in erosion control. Others in his field share his view; Jason Henderson, vice president of Green Thumb in Nehawka, NE, calls himself “a real big believer in hydroseeding.” “With the sod, you are paying for the green color right off the bat – that’s the only good thing I see,” says Henderson. “The problem is it still takes the same amount of water to get it going and to keep it alive. With hydroseeding, you go in, spray it down, and you’re going to get a lot better root system. You’re putting your tackifier on there, so it holds everything together and makes it stick to the ground. With sod, if you get a big rain it could wash out and you’d have to go back in and pull it.”

Colbert cautions that hydroseeding is not a panacea, “but it certainly has a lot of good applications.” His company’s recent jobs illustrate that point. After the January 2005 floods in Ventura County, CA, his company was involved in an emergency erosion control project for the California Department of Transportation.

California Highway 23 between Fillmore and Moorpark “fell apart” after the floods, Colbert recalls. “The Santa Clara River flooded the road in the riverbend. The same road winds up over a small mountain pass and the mountains fell apart, so they had to put the sides of the road back together,” he explains.

Part of the rehabilitation called for hydroseeding and jute blanketing. Colbert could not get jute blankets within the time frame necessary, partly because they had been in high demand following the rains and floods.

“I’m not a fan of jute anyway, so this was an opportunity to sell them on the idea of using bonded fiber matrix instead,” Colbert says. He chose to go with Flexterra, a hydraulically applied product made by Profile. “It’s pretty expensive – top-of-the-line – but still less than jute and much less expensive on labor, because you spray it,” he says. “It’s a better growing medium than any kind of a blanket. You spray it on at 3,500 pounds per acre, a high rate for anything sprayed with a hydroseeding machine – most mulches go on at around 2,000 pounds per acre.”

Colbert got good results. “The cool thing about bonded fiber matrix, as opposed to other hydroseeding, is you don’t have to use binders or tackifiers, because it’s got all that in it,” he says.

The project involved just under 6 acres in a two-month time span in early 2005. What made it different from many other projects for Colbert was its steep slopes. “It was nice to have the spray-on application so I didn’t have to have guys out there doing blanket work,” he says. “I believe in blankets, but I don’t like jute netting. The other challenge is getting stuff to grow in California. I wanted the best growing medium that would retain moisture for the longest amount of time so those plants had a good chance of success.

“Basically, you have to plan around the rain, and you have only about a three-month window of rain from December through February or sometimes January through March. The trickiest thing is whether or not to plant,” he adds. “At the end of the season, it’s almost better not to plant. I have to tell the owners I think we are going to get a false start, so why don’t we just wait until fall. As a contractor, that’s hard to do.”

Testing Products and Techniques

One reason hydroseeding is taking an increasing erosion control market share is the introduction and testing of new products. Through the prompting of the Wilbur-Ellis Co. in Spokane, WA, Tom Mackey, owner of Northwest Tree and Reclamation in Bonners Ferry, ID, received permission from the Idaho Department of Transportation to use HydroStraw from HydroStraw, LLC for a field test in July 2005 before final approval on a new road construction project for US Highway 95. HydroStraw is a composition of annually renewable organic fibers, Silt Stop PAM (polyacrylamide) tackifier, and other additives.

Mackey says that because HydroStraw was a new product to his company as well as to the state, he wanted to do a test run. The project application required 4,000 pounds. “That’s typically double the normal application, but they wanted assurance the soil was stabilized,” he says, adding his company was able to shoot the product at the rate of 2 tons per acre.

Mackey’s company is doing the soil stabilization and post-construction revegetation for the highway. The two-stage project is expected to be completed by October 2007 and includes ongoing erosion control, soil stabilization, and hydromulching before final revegetation.

Mackey says his company obtained favorable results using HydroStraw for soil stabilization. “From typical wood fiber mulch, we are able to go from 1,150 pounds per load to 1,750 pounds, so we are able to do 600 more pounds per load with this product,” he says. “Another reason we like using it is because it mixes very easily, and in application, it falls into place very nicely. Instead of doing two applications, we can do it with one.”

HydroStraw also got field tested in an upscale residential area of California at Norris Canyon, a large canyon in San Ramon, CA. The area has lots of steep slopes and sandy soil. Lucinda Dustin, a senior stormwater management consultant with Stevens, Ferrone & Bailey Engineering Co. in Concord, CA, was approached about trying the product, because essentially it’s an alternative to blowing straw, she says. Dustin says that because California struggles with air-quality issues, she’s not a big fan of blowing straw as a from of erosion control, but indicates HydroStraw is effective in most cases when properly applied.

“It’s a grass straw about the length of wood fiber in a wood fiber mulch, but it comes all in one application, which means when you open the bag and put it in the tank you don’t add anything but what is in the bag,” she says. She cites improved accuracy with the product as opposed to the traditional approach of applying a slurry of seed and mulch, followed by blowing straw and then applying a binder.

“When we have residential pads that are going to stay in final grading over a season or more, we will hydroseed the slopes and stabilize the pads’ surface as well,” Dustin says. “My challenge at Norris Canyon was that we had huge pads, and all the erosion that was going on was almost out of control for us,” Dustin says. “I sat down with the client and our office technician and said, “What do you thing about giving this a try?”

The company tested it on 10 acres in October 2004, and it held through several major storms. “Our big concern was that nobody really had any experience as to how much water the stuff would take, and the application rate we used was 2,500 pounds on the pads,” Dustin says.

She favors the fact that sediments moving through it are captured and held in place. After going through the entire hydroseeding process with no losses during the intense rain events, she says, “I made a decision I was going to be aggressive about having it specified in a place of typical mulch and binder, and a lot of that has to do with the fact it is very accurate.”

She also appreciates the fact that she knows how many bags of material can be used on the project without needing more or wasting extra. “It’s easier for the contractor; the contractor I worked with told me he could get the work done faster because he could do it in one application,” she says. “We had all of the work done in two days with two men. When you look at the bottom line  the dollars  for my client, it is pretty significant.”

Dustin does caution that as HydroStraw, LLC gathers new data to determine HydroStraw’s movement rate, there are concerns in California over any kind of polyacrylamide that could discharge to the waterways, but she has never used the product in such a way to create that potential.

“I am confident we are going to find data that supports that I would be safe to use near a waterway, but until I have that data and can present it, I am very cautious about making sure we don’t run that risk,” she says.

“I stress that anybody who is using HydroStraw needs to educate themselves about it like other products,” Dustin adds. “It’s a new product and people are a little cautious with it because they don’t understand it, but the success I’ve seen with it is pretty phenomenal.”

Seeding From the Air

Perhaps one of the most challenging techniques for hydroseeding is aerial application. Just ask Ted Stallings, president of Aero Tech Inc., an aerial application company headquartered in Clovis, NM, that does aerial application worldwide. While the company’s strength has been in fighting fires and aerial seeding, its foray into erosion control and revegetation followed a fire in the summer of 2000 that destroyed many forest areas in the Los Alamos regions of New Mexico.

Stallings says his company has used fixed-wing aircraft and helicopters for a number of years, but that aerial hydroseeding is a new technique. Although anther company was the first to hydroseed by air using a helicopter, Stallings says his company was the first to apply hydromulch using a fixed-wing aircraft.

In an effort to prevent erosion and other damage, the company used its AT-802 fixed-wing turbine Air Tractors in the Los Alamos case to apply 6.9 million gallons of hydromulch in 25 days. The mixture consisted of fertilizer, seed, and shredded wood bound by a water-based sticky compound to the topsoil and remaining vegetation. Some of the applied seed grew immediately while other seeds sprouted up 36 months later.

That effort led to other jobs, such as a rehabilitative hydroseeding project after the June 2005 Coal Seam Fire in Glenwood Springs, CO. The fire had destroyed more than 12,000 acres, including 29 homes, and required a massive firefighting effort costing several million dollars. In its aftermath, the Bureau of Land Management awarded the contract to Aero Tech to revegetate 500 acres of the burned area. Western States Reclamation was also involved in the project, using four T330 Finn Hydroseeders and crew.

The approach involved 200,000 pounds of Biosol Mix organic fertilizer, 30,000 pounds of Rantec Corp.’s Super Tack – a guar-gum based tackifier – and 46,000 pounds of American Excelsior’s Excel FiberMulch II. Each HydroSeeder’s load contained 2,800 gallons of water, 2,400 pounds of wood mulch, 960 pounds of Biosol, 180 pounds of seed, and 144 pounds of Rantec Super Tack.

Using a global navigations system to download and print GIS maps, Aero Tech’s four AT-802 turbine Air Tractors flew to Colorado to execute the work. Each aircraft hopper was filled with the slurry, with one load covering half an acre. In seven days, the aircraft applied more than 1,000 loads throughout the treatment area, located along both sides of Interstate Highway 70.

The work took two days more the planned because high winds and rain. The mountains terrain reached 10,000 feet and features 80-degree slopes. In the end, the Bureau of Land Management pronounced the project – which cost more than $1 million – very successful.

Aero Tech uses its expertise through its air tanker resources, akin to fighting fires by air. “When you fight fires, you drop a lot of retardant in a short amount of time and you need to be very precise,” Stallings says. “We are using the aerial guidance system to guide the airplane and keep track of when the doors open and close, and we regulate how much goes out of the doors so we’ll know how much we have on an exact spot. With our guidance system and air tanker technology, we can cover an area evenly and get the right amount of product out.”

Stallings says the aircraft carries 800 gallons, and some contracts can call for up to 3,500 gallons per acre. “Your mulch can be 3 inches thick on the side of mountain, but it’s got to be even, so when we dump a load, our footprint is 27 feet wide and about 1,200 feet long,” he says. “If you take that area by 800 gallons, it’s not going to be enough product.

“To make the calibrations come out right, even though the footprint is 27 feet wide, you may only move over about 7 or 8 feet each pass, and that’s the width of the cockpit, so you have a tendency to want to move over too far because you look at it and the whole ground is covered. But we’ve got this guidance system we follow precisely which tells us how much we need to move over to be sure we get the right calibration on the right number of acres.”

There are times when Aero Tech uses hydroseeding in conjunction with other erosion control methods, working with other contractors who may be laying blankets. Aero Tech doesn’t favor any particular seed mix other than native grass seeds or what the US Forest Service or Fish and Wildlife agency requires. “Whatever was there before is what we’re going back and seeding with,” Stalling says.

Stopping erosion is the primary reason Aero Tech hydroseeds. “When you have a fire on a mountain above a town’s historic site or above one of the nation’s top security areas above a nuclear reactor, a 2-inch rainstorm could be a catastrophic disaster. So it’s important to get mulch on the mountainside quickly and evenly,” Stallings says. “Sometimes, you might have a fire today and five days later we will be applying mulch on an emergency mulch program, because they know erosion after fire will wipe out valuable resources they don’t want taken out.”

Specialized Sites: Airports and Gold Courses

In August 2005, Henderson of Green Thumb in Nebraska tackled one of his biggest jobs ever. His company is hydroseeding a 60-acre airport in Tulsa, OK, after a general contractor lays new sewer lines for an American Airlines hub. The project is expected to be completed by next April.

Following specifications for either Bermuda grass or K-31, Green Thumb used a mix of 3 pounds of Bermuda and 8 pounds of Kentucky 31 from Pennington Seed in Madison, GA, applying 11 pounds per acre but taking into account seasonal variations. At the end of the summer, the company started applying the K-31 only for cool seasons.

“Bermuda is a hot-climate grass, and the ground temperatures need to be pretty high to get Bermuda to grow to the end of September here,” says Henderson, who adds his company stops planting it during the second week of August.

The project has involved many 2:1 and 3:1 slopes, on which he applied Pennington’s Penn-Tac tackifier. He also uses a soil cover mulch blend from Profile. “I’ve probably been putting on 3,000 pounds of mulch per acre on the 2:1 with the tackifier, and that’s been doing really well so far,” he says.

Henderson says the airport job is different from anything else he’s done because it is large and spread out, requiring more travel time, and because it features the steepest slopes he’s ever hydroseeded.

When it comes to slopes, golf courses can also offer hydroseeding challenges. The Aspen Corp. in Daniels, WV, does golf course construction and renovation. The company recently worked on hydroseeding projects for two newly constructed golf courses in West Virginia and Ohio. Both projects had different slopes, ranging from 2:1 to 5:1.

“The challenges with those were tying to get the right mixture of the Finn product to stabilize those slopes,” says Project Manager Richard Hagy, adding his company must use different types of tackifiers at different rates to address the slopes. Hagy used HydroMax to stimulate early germination and root development; HydroGel, a moisture retention polymer; and HydroStik, a tackifier.

“Whereas our fairways are fairly flat, the amount of mulch we put in remained the same, which was 1,500 pounds per acre,” he says. “The tackifiers were about 40 pounds per acre. We did add more of the tackifiers to our native areas; instead of using 40 pounds to the acre, we used 60 to 80 pounds of the tackifiers to help on the slopes. The HydroMax and HydroGel all increased based on the slope  the HydroMax was usually 5 gallons per acre and, depending on the slope, we went to 15 or 10 gallons per acre.”

Because the company works on golf courses, it must work with special seed requirements. The fairways, greens, and tees were seeded with L-93 bentgrass. The roughs were done in a blend of three different types of grasses: a regular bluegrass, a bluegrass with fescue, and a native mix for out-of-the-way areas where there wouldn’t be a lot of play.

Choosing the Right Seed Mix

Cathy Powell and her husband Michael own Pro Seeding in Conyers, GA. The Powells’ company, which uses Bowie equipment, has had such notable hydroseeding contracts as the Wolf Creek Olympic Shooting Complex, where the 1996 Summer Olympics skeet shooting took place. Other major clients include Georgia Power. Powell says seedmixes for each job are dependent upon the soil into which they will be placed, but she favors lespedeza for deep root systems. She also points out that it puts nitrogen back into the soil. Powell credits it in one case for enabling a dam to remain stable while parts of the dam where the seed was not planted did not.

When Hurricane Opal came through the Albany, GA, area in 1995, there had been a dam break. “The engineer felt the only place the dam broke was where he did not have a full stand of lespedeza. He felt the lespedeza held the remainder of the dam, so after they got the dam put back in place and everything fixed, he gave us the seed mix he wanted – which was primarily lespedeza – to get that good root system to hold that soil in place – so hopefully they would never have another dam break there,” Powell says.

She adds that the state’s power company strongly encourages the use of lespedeza on its sites as well. “Usually we will plant lespedeza and love grass together for areas designed to be mowed and maintained,” Powell says.

Seasonal variations are always considered in the hydroseeding mix Powell uses. “In the fall, we have to plant unscarified lespedeza and mix it with a nurse grass and, usually, fescue,” says Powell. “The theory is that in the spring and summer of the following year, the hull on the seed will deteriorate and allow that seed to germinate and grow.”

She says unhulled Bermuda does not fare well. “Bermuda is what we use primarily for mowable areas, and the theory is to plant unhulled Bermuda with either ryegrass or fescue as a nurse grass. Then, in the following spring or summer, the hulls will have deteriorated and Bermuda grass will germinate and grow, but that just doesn’t work that well,” Powell says. “You have to usually go back in there and scout what other nurse grass is there to allow the sunlight and everything to get down to the native seeds.”

Powell says one contractor told her he planted unhulled Bermuda with ryegrass and set the field on fire. “That broke the hull on the unhulled Bermuda, and it germinated and grew just as if they had planed hulled Bermuda grass,” Powell says. “Unfortunately, in most situations you can’t set a field on fire.”

Steep slopes can make hydroseeding a challenge, and for these Powell uses Flexterra. “It’s basically an erosion control blanket we use extensively and it’s a considerable savings to the contractor or developer in lieu of conventional matting, because it is four to five cents a square foot cheaper than conventional matting. I think it works better because it adheres to the soil,” she says.

“Conventional or jute or straw matting is laid on top of the soil, so water has a chance to get underneath it and undermine the dirt. With Flexterra, you are applying it hydraulically and it follows the contour of the soil, so you don’t have that risk for water to get up underneath and wash out the dirt.”

Comparing and Combining Erosion Control Techniques

Stevens, Ferrone & Bailey used straw rolls in conjunction with HydroStraw on the two major steep slopes on the Norris Canyon project. “There is no guarantee Mother Nature’s not gong to slam us, so it’s an added protection,” Dustin says.

On steep slopes, Aero Tech uses Rantec’s Super Tack tackifier. “The products you use through a truck with hoses might be totally opposite of something you use in the air, because you’ve got to have a product that will fly right and not clump up.” Stallings points out. “You want a material that, when you open it, is going to fly right through the air and lay evenly.”

Effectiveness is a key factor for those who do hydroseeding. Hydroseeding operators say that while the practice can be more costly at the front end, in the long run, it’s more cost-effective: It requires one machine instead of several, it normally doesn’t have to be redone, and it can be applied quickly.

That latter point is especially important to Dustin. “Two or three people can handle it, as opposed to blankets, where you have to have an improved surface, it takes a lot of people to apply them, and, like all products, it has to be applied properly,” she says.

She also sees hydroseeding as a more cost-effective method, citing one case in which she’s dealing with a slope that’s 320 feet long and is 2:1 and 1-1/2:1 in some areas. “It would take forever to get that blanketed, whereas it could probably take a day to get it done with a good hydroseeding machine,” she says. “Up front, material costs for the higher-end hydroseeding products are equivalent to blanket cost. But in the end, there’s a lot less labor, and I have a comfort level with the material. I specify blankets when it is necessary.”

Henderson agrees blankets have their place, “but now with hydroseeding, you’ve got different products you can use to replace the blankets so it’s not as labor-intensive and does the same job – if not a little bit better – than your old-fashioned straw blanket.”

Dustin believed the key to deriving effectiveness and efficiency from hydraulically applied materials is a well-informed hydroseeding professional. “There’s a huge difference between hydroseeding and stabilization,” she says. “The higher-end products – like the and HydroStraw require training and knowledge to apply. “Hydroseeding is doing a slurry of 500 pounds of mulch and seed and the mulch is in there as a tracer so you can see where you’ve sprayed. That’s hydroseeding. Hydroseeding in combination with stabilization is when you are adding the seed to a stabilization and applying it.”

She cites one project in which she had to do a 5,000-pound application in four passes to make it work. “I didn’t want the material so heavy that it flew off the slope,” she says. “We went through the entire season with out any failure. When you get to rates that are 3,000 pounds and higher, the applicator needs to understand this is a multiple task, because these products aren’t just spraying on; they actually seal the surface. That means every inch of it needs to have the material applied.”

The more specialized the techniques of hydroseeding, such as aerial applications, can be expensive. Stallings says. But he points out that in some cases – such as the Coal Seam Fire in Colorado – it’s the only alternative.

“We’re talking about doing a whole mountainside, and some of the mountainsides are at 60- to 70-degree slopes and the mountainside can be 1,800 to 2,500 vertical feet,” he says. “Doing it from a truck on a 70-degree slope is just not possible. Your only access may be from the bottom. You can’t get the hoses and mulch on the sides of the mountain, so by air is the only way to do it.”

Another key factor in efficiency and effectiveness is knowing how much seed to use: Too much results in waste, while too little necessitates a job having to be redone. Dustin will sometimes require contractors to do a bag count at the end of each day.

To strike a balance between applying too little or too much seed, Henderson says he and his employees try not to carry all of the seed bags on the machine to avoid spillage. Additionally, they measure the seeds into 5-gallon buckets. “Some guys dump it in and guess, but the way everything cost – including fuel – you’ve got to be more careful,” he says. “We take the steps to weigh it all out and make sure we’re getting the right amount in there.”

Powell says her vendor seed companies tell her she uses too much. “I’d rather put out a little extra seed in the initial seeding than have to touch up or redo it,” she says. “We get a lot of stats on different jobs and they don’t require as much as we know it will take to get the desired results, so I always plant what we know works. They may call for 15 pounds of one type of seed per acre when I know it’s going to take 50 pounds to get the desired results they want. As long as we’re going by the specs – they are giving the minimum amount, and we increase it – then I’m fine. If we are going to change something, I go to the engineer or owner and make a suggestion.”

While many who do hydroseeding see it claiming a greater market share, they add there are caveats. Dustin, who’s been in the business for more than a decade, says although she doesn’t work much with the turf market, California’s residential growth, coupled with laws that owners can’t take occupancy until the front yard is landscaped, means that turf or sod could become the way to go. “You can roll it out and move in tomorrow,” she says. “Hydroseeding yards is not as prevalent here as in other states.”

But when it comes to revegetation and habitat work, hydroseeding is the better option. It all comes down to how it’s applied, she emphasizes. There’s one project in which the application rate is 4,000 pounds per acre and Dustin’s specifications to the contractors are to apply the seed in a minimum of two steps. “They will do a 2,500-pound application with the seed and slurry directly to the slope, then come back with the remainder of the application,” she says. “I do that because I want the seed exposed to the surface of the soil, and when you do higher application rates, you run the risk of getting the seed bound up in the material, away from the surface, and you don’t get the germination rate you should have.

“I work very closely with a couple of seed companies in the West, so I’ve been getting an education about the success of germination, which is the key to the revegetation issue.”

Powell believes hydroseeding is taking an increasing market segment of erosion control, spawning a cottage industry, but she favors licensing to weed out “fly by night” companies. “We’ve been in the hydroseeding business 32 years, and when the economy gets good, everybody buys these little machines. But the regulations are hard, because we have to be able to tap into water sources, so we have to have water permits from every county we work in. Most of them require anywhere from $500 to a $2,000 deposit,” she adds.

“I’m not knocking little companies, because we started out with an 800-gallon machine, but most of these companies don’t have the financial resources to have $12,000 worth of water deposits all over metro Atlanta,” she says. Then too: “Some of these companies do a poor job, and then the developer or contractor gets a bad taste in his mouth about hydroseeding. He paid somebody and he expected vegetation and got nothing, and [the company might be] either gone or not willing to make it good.”

Hagy says new tackifiers are underscoring the increasing market share being claimed by hydroseeding. He has seen hydromulch hold up well after rains. Yet, he notes, “I would still prefer to see sod on steep bunkers.” He regularly utilizes traditional erosion control methods, such as sod and blankets, with hydroseeding

Stallings says his company has not yet had to redo any of the areas I hydroseeded by air. He recalls one job where his company had hydroseeded after a fire and the mulch held after a rainstorm that brought 4 inches in one afternoon. “That’s petty phenomenal that it held,” he notes.

Henderson hasn’t had to redo any hydroseeding jobs, either. “You are putting your seed in water so it helps that germination process, but moisture is critical, whether you use conventional or hydroseeding methods,” he says. “In hydroseeding, you are putting everything – the seed, fertilizer, mulch, and tackifier – in one application compared to a couple of different steps in conventional seeding, where you have to go back in and blow your straw on and try to get that held down. For the money, hydroseeding is the way to go. It’s a lot less labor-intensive.”

22 Dec 2009