With stricter regulations under the National Pollutant Discharge Elimination System requirements and tougher mandates from local governments, contractors everywhere are looking for effective and economical ways to control erosion and establish vegetation. A plethora of choices is available, but for many projects, hydroseeding is the way to go. The mixture of mulch, tackifier, seed, and soil amendments sprayed onto slopes is often more economical than applying blankets and, under many circumstances, is as effective.
Here are some criteria for choosing hydroseeding over other techniques:
- Slopes steeper than 2.5:1 or along a waterway
- Rough or inaccessible areas
- Require stabilization even before vegetation can sprout
- Need quick establishment of vegetation, but not enough budget for sod
- Not enough budget for blankets
- Need soil stabilization during a rainy season or winter, before vegetation can be established
- Require moisture retention without having to resort to heavy irrigation
As the hydroseeding industry has matured, companies are offering more choices of mulch types. The most common applications are wood and paper, with newcomers also in the mix. However, the basic wood and paper mulches mixed with guar tackifier have evolved into cross-linked applications. Cross-linking fibers provide more strength and stability to the mulch. Many of the manufacturers of hydraulically applied materials claim that their products rival blankets for stability and growth of vegetation.
Soft Wood Mulches
The Seattle-Tacoma International Airport’s third runway project, a massive billion-dollar earthmoving project, required erosion control measures that could withstand jet blast even on stockpiles of dirt and steep slopes. EcoAegis II was applied, including seed, and has held up well for 18 months.
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Photo: Dietz |
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Photo: Dietz |
The product is one of three classes of wood mulch developed by Canfor (Canadian Forest Products Ltd.) of British Columbia. Each product can be applied with a conventional hydroseeding machine with as little as 10 minutes’ mix time.
The first, EcoFibre, is a mulch appropriate for general seeding purposes. With added tackifier, it can be used for slopes as steep as 2.5:1. It can hold 10 times its weight in water. For moderate to severe slopes, EcoMatrix is stabilized fiber matrix (SFM). It is recommended for slopes from 4:1 to 2:1 and lasts three to six months. The third class of mulch is EcoAegis, a bonded fiber matrix (BFM). Wood fibers of varying lengths cross-link into a mat that will retain water, prevent erosion and rilling, and hasten seed germination. After curing, the mulch forms a “hydromat” that absorbs rainfall but still allows penetration of moisture and air.
Each of these products is made from soft wood. Joe Hargitt of Canfor explains that the tubular cell structure holds moisture better than hardwood mulches. These preparations need water for about 10 minutes, three times a day. The mulch is prepared with a thermomechanical process, rendering the mixture sterile and taking away the threat of disease or weed seed. The wood used is waste from wood mills, not reclaimed wood that might be contaminated.
Steve Jones of Fiber Marketing Inc. in Renton, WA, a distributor for Canfor, notes that in many instances, EgoAegis performed as well as erosion control blankets but at a cheaper cost. In a test plot, EgoAegis was put down at a rate of 3,000 pounds per acre on a 1:1 slope. Dry weather lasted during application, but within three or four hours, torrential rain fell. The slope held even though no vegetation was started.
The Washington Department of Transportation has approved Canfor products for use on state projects. According to the testing, the products met all requirements for stability and for nontoxicity to aquatic life.
Jones notes that one advantage of hydroseeding is that the mixture has closer contact with the soil than erosion control blankets. Labor cost with hydroseeding is lower than that of installing blankets. Another option, blowing straw to be used in place of mulch, can come up against dust control regulations in some locations.
Lucinda Dustin, senior stormwater management consultant for Stevens, Ferrone & Bailey of Concord, CA, specifies wood mulch products for many projects. For large projects where huge plots of land are opened up for development, hydroseeding is the most economical application. Many projects are using BFM materials alone without seeding. Dustin says that areas where EcoMatrix has been used in this way have been stabilized without seed growth for up to a year.
One challenge Dustin has seen with BFMs is that they form such a heavy crust that germination and plant breakthrough is hampered, especially in dry weather. If the products can be applied just before the rainy season, better vegetation is the result.
One large project for which Dustin specified materials is the Diablo Grande development in the central valley of California. The 3,000-acre development is a combination of residential areas, golf courses, hotels, and commercial plots, and the project will take several years to build. In 2002, 30 truckloads of EcoMatrix were put down to stabilize acres of disturbed land. Hydroseeding techniques were the most economical choice for the soil stabilization. Even areas that were not seeded held for more than two years.
In California, many projects are requesting native seeds, so Dustin usually applies custom mixes, including grasses and wildflowers. For high-profile areas to look their best, more wildflowers are added to the mix.
An advantage of these types of products, according to Dustin, is the all-in-one-bag mix. “I want consistency,” she says. If a contractor has to mix the product, there is an opportunity for inconsistency in the mix and the application. She doesn’t want to have to walk several acres to see if the product is applied evenly. With premixed products, labor costs are decreased because she can do a bag count at the end of the day and know that the proper amount of product was applied.
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Photo: Dietz |
Dustin, who has been in the industry for about 11 years, believes the only place for sod is in a high-profile area that must be green “right now.” In most other areas, she prefers hydroseeding, but “everything, each technique, has its place,” she notes. She will specify blankets in waterways where the measures have to hold up to water velocity or be standing in water.
All in the Timing in Ohio
When a motel in Fort Smith, OH, needed erosion control measures along banks with slopes of more than 2:1, Tim Luers’s company Henderson Turf Farms of Franklin, OH, applied interlocking-fiber mulch with heavy amounts of tackifier and crown vetch seed for fast germination. Using Finn HydroSeeders, Luers has undertaken a number of projects using different hydromulches and seed mixes. “Sod,” he says, “is mostly used for aesthetic purposes—the front of a building or along ditch lines that are highly erosive.”
He has used similar techniques for projects near a Wal-Mart store building, parks, and schools. Athletic fields, he says, require a careful consideration of the timing. If the field will be in use quickly, more expensive sod will be needed. If a few months are available before games begin, hydroseeding will give good coverage at a lower cost.
A park in Cincinnati was one of Luers’s larger projects. The park covers 180 acres, and about 120 of those were hydroseeded with mulch and a grass/wildflower mix. Most of the land is fairly flat. Some areas, about 50 acres, were seeded, fertilized, and covered with straw.
Fire Emergency
After a fire destroyed vegetation along California’s Highway 18 near Big Bear Mountain in 2005, Hydrosprout of Escondido, CA, was called in by the California Department of Transportation. The fear was that heavy rains on the slopes laid bare by fire would undercut the highway. Hydrosprout was able to get rolling in 24 hours and began spraying the 100 acres of slope with Canfor’s EcoFibre wood mulch at 3,000 pounds per acre and Terra Novo’s EarthGuard at 10 gallons per acre. An extra challenge was the crust and ash left by the fire. Included in the mixture was a native seed mix. About a month later, the vegetation had not quite started when heavy rains struck the area. The rains caused flash flooding in some areas, but the area treated by Hydrosprout held.
Originally, BFM had been specified for this emergency highway project, according to Leo Brindis of Hydrosprout. He recommended a change to EarthGuard SFM, a fiber matrix soil stabilizer. In tests by San Diego State University, application of EarthGuard reduced sediment runoff by 95% over bare soil. The stabilizer is designed to be used in combination with mulch, seed, and fertilizers. Brindis says that although the BFM generally encapsulates the soil particles, with fire damage, this would not be possible. EarthGuard actually treats the soil, giving it an electrical charge, and it would still be effective on fire-damaged soil.
Brindis and his wife Suzanne, owners of Hydrosprout, work on state and federal contracts, including highways, parks, schools, prisons, and landfills. They have also contracted for some large developments. He says that the options just a few years ago were mulch and tackifier or BFM, with nothing in between. The problem with BFM products, he says, was that they sometimes formed such a hard crust that plants had problems breaking through. Although the BFMs have improved, he often favors SFM products.
The EarthGuard mix can be adjusted according to local conditions. Brindis says that when the company is contracted to hydromulch a development, for example, the area may include flat pads and slopes up to 2:1. He varies the amount of EarthGuard in the hydromix to fit the situation, which is easier than using two or three different products for different slopes. The concentration can vary from 6 to 8 gallons per acre along with 2,000 pounds of EcoFibre and provide protection for up to three months. This application also costs less than using BFM at the recommended rate.
Hot and Dry in Texas
The summer of 2006 was especially hot and dry in Texas. Many days of triple-digit temperatures and lack of rainfall forced changes in hydroseeding techniques. Robert Forsyth and Rich Hazlewood, partners and owners of Outdoor Illusions Landscape Management Inc. of Krum, TX, have altered their mixture to handle the dry conditions. Forsyth, with a background in horticulture and ag management, and Hazlewood, an arborist and irrigator, teamed up to develop methods to handle the difficult summer.
One big difference is adding a hydrogel to the hydroseeding mixture. Forsyth says the mixture they have been using is EarthGuard SFM, wood mulch, hydrogel, triple 20 fertilizer, and native seed such as Bermuda. The hydrogel increases the moisture level and dissipates moisture over time to be available to the seed. EarthGuard seals the mixture in so that the seed is insulated from the sun and dry air and has time to germinate.
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Photo: Dietz |
Forsyth says EarthGuard mixes easily in the hydroseeding machine and decreases clogging. As a usual technique, he runs water through the hose before spraying to slicken it up before the mixture is run through it. Often, he reduces the amount of mulch in the mixture to reduce clogging and then caps off a section with the tower, giving it another layer.
In the Timberland development, the company was contracted to hydroseed a detention pond. Forsyth says the company used tough, native buffalo grass as the seed. It has deep roots, providing good stabilization of slopes, and grows well in drought conditions. He avoids millet grass because it grows tall enough to require mowing; buffalo grass requires less maintenance.
A new subdivision in the area needed soil stabilization during construction. The area included a detention pond and 6.5 acres of 3:1 to 1:1 slopes up to 40 feet tall. With the mix of EarthGuard, wood mulch, hydrogel, seed, and fertilizer, a good stand of vegetation grew under the severe weather conditions.
Forsyth says the company will often put down extra mulch mixture to guarantee good seed growth. “I believe in doing it right the first time,” he adds.
Paper Covers It
Jack Eaton, general manager of Landscape Support Services from Goffstown, NH, has contracted for a variety of small jobs, such as residential landscaping. He uses mulch from Phoenix Paper of Lostant, IL. One of his favorites is EZ Spray, a 50/50 mix of corn fiber and paper. For residential projects, the land is usually flat or slightly sloped, and Eaton applies at a rate of 1,000 to 1,500 pounds of mulch per acre. He also uses a variety of tackifiers, including Dirt Glue, an acrylic latex polymer manufactured by DirtGlue Enterprises of Amesbury, MA. DirtGlue is formulated to dry to a flexible crust that locks in moisture and nutrients and still allows seed penetration.
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Photo: Dietz |
The landscaping projects that Landscape Support Services accomplished last spring withstood torrential rains in the area. In late May, 13 inches of rain fell in 72 hours, and 4 to 5 inches fell over each of the next two weekends. Eaton says very little respraying was required, even on projects where vegetation was not yet established.
For residential hydroseeding, Eaton mixes mulch, tackifier, seed, and a fertilizer. The most requested seed mix is 50% ryegrass, 25% creeping fescue, and 25% bluegrass. Sometimes he uses tall fescue in low-maintenance–low-mowing areas: “We’ve had a lot of success with this particular mix.”
One reason that Eaton prefers paper mulches over wood is the lack of machine clogging. He said that material costs may be higher with the corn/paper mulches, but the application rate is less, so there is a savings in labor costs and wear and tear on equipment.
Eaton decides the proper mix and type of mulch and tackifier on a case-by-case basis, which he says separates his company from some of the larger hydroseeding practitioners. For each project, he uses the manufacturer’s recommendations and his own experience to choose the proper mix.
A Mulch Newcomer
Paper and wood mulches have been around for years, but there is a newcomer to the mulch industry, recently approved by the Georgia Department of Transportation. GeoSkin Cotton Hydromulch is made from waste cotton. The cotton-straw mulch forms a matrix that retains moisture and can be added to mixtures of seed, fertilizer, and tackifiers similarly to other mulches. One difference is that the cotton adds nutrients such as nitrogen. Wae Ellis of Mulch and Seed Innovations LLC in Centre, AL, which has been selling the product since April 2006, explains that the carbon-to-nitrogen ratio with wood mulches is about 400:1, but with the cotton, it’s 40:1. “The more nitrogen you have, the better,” he says. The nitrogen bound in the cotton is released gradually, giving soils continual feeding.
Cotton Inc., a cotton marketing group from Cary, NC, approached Andy Ellis of Mulch and Seed Innovations with the idea of creating a cotton mulch. The Ellises worked for three years to develop the product. Their plant had to be rebuilt to improve the pumpability of the product and decrease the fines.
The recommended application rate of the new mulch is 2,000 pounds per acre. Wae Ellis notes that mixing in one-third more product results in thicker paste slurry and decreases the amount of water used. The product still sprays and cleans up easily. Mixing more in a tank can save labor and fuel costs, as the truck can spray more with each load.
The dye in most mulches is the familiar aqua green, but Mulch and Seed Innovations uses a dark green dye. Homeowners like it because it has the look of grass before any seed has sprouted. The cotton-straw mulch is mixed and applied with normal hydroseeding equipment. Wae Ellis says that it hits the soil with a splat and contours easily to the ground, providing good soil contact. The mulch will last from six to 12 months, depending on weather. Vegetation has a good amount of time to become established. The cotton mulch has great water retention power, making seed growth easier.
As the mulch industry evolves, more products will be introduced, as will variations on the tried and true. The industry people interviewed for this article agree that hydroseeding and hydromulching is a growing segment of the erosion control industry. Hargitt believes that the green industry and federal regulations are forcing growth in hydroseeding as one of the most economical methods for erosion control and vegetation growth.