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GREEN LIGHT For Hydro Seeding

By L. Ward Johnson
Copyright 1996. Contact publisher for permission to use.

Summary: Forest Practices Code revegetation requirements have prompted a business boom for hydro-seeding firms like BPL Industries of Salmon Arm.

Few aspects of logging ignite the ire of nature lovers quicker than seeing an ugly washout or a stream running brown with mud. While hiking up a logging road on a sunny summer day, or while standing beside a mountain stream, even the untrained eye recognizes these as indications of poor logging practices.

That’s why, when the BC government introduced its new Forest Practices Code just over a year ago, special emphasis was placed on practices aimed at preventing erosion. Erosion control applies generally to all aspects of logging, but roadbuilding is a primary area of concern. With any new road, even those built strictly to the Code’s tough standards, there is a possibility of cutbank erosion to some degree. In recognition of this potential problem, the Code stipulates that disturbed areas must be revegetated within a year of construction.

One way to green up an area quickly is hydro seeding, a method that has been around since the 1950s but will no doubt see broader use in coming years. In its early years hydro seeding was a two-step process. At the start, a slurry of seed, fertilizer and lime was sprayed on the area, followed by an application of straw mulch. There was no fertilizer and no proper seed protection included in the slurry, and the process was a hit and miss proposition. In the 1960s, the idea took a turn for the better when paper and woodfibre mulches were used. When applied to a seeded area, the mulch stuck in place and held the seed on the slope. Since the mulch formed a mat, it also helped retain moisture in the soil and lessened the effects of wind and water ero-sion.

Application, however, was still a two-step process. In the 1970s seed, fertilizer and mulch were combined into a slurry which enabled one-pass spraying, making the approach more cost-effective. As well, with the use of high-pressure hydraulics, the slurry could be more accurately broadcast over longer distances. From that point, hydro seeding began gaining in both popularity and acceptance as an erosion control and revegetation system. Hydro seeding and erosion control are refined operations today.

Slurry can be sprayed on by truck and pump in the traditional manner, or it can be applied by a helicopter with a drop bucket. Erosion-control contractors are constantly experimenting with various fertilizer and seed mixes, types of mulches and the use of tack-ifiers (vegetable-based glues). When applied, a slurry appears green in colour, but the colour is insignificant, since it i s merely dyed green for aesthetic appearances. Moisture retention agents or MRAs, which are effective for up to two years before biodegradation takes place, can also be part of the slurry. They can retain up to 200 times their weight in water, dramatically reducing the water requirements of the site during the revegetation process.

Slurry can be sprayed on by truck and pump in the traditional manner, or it can be applied by a helicopter with a drop bucket. Erosion-control contractors are constantly experi-menting with various fertilizer and seed mixes, types of mulches and the use of tack-ifiers (vegetable-based glues). When applied, a slurry appears green in colour, but the colour is insignificant, since it i s mere ly dyed green for aesthetic appearances. Moisture retention agents or MRAs, which are effective for up to two years before biodegradation takes place, can also be part of the slurry. They can retain up to 200 times their weight in water, dramatically reducing the water requirements of the site during the revegetation process.

A characteristic of these agents, however, is that they allow water to flow over the top of the mulch, which means there is little natural watering from rain. MRAs are also subject to temperature and moisture limitation dur-ing application, so they are not suitable for every climate or situation in forest industry applications. There is a relatively new product on the market called Soil Guard, a one-step erosion control system made by Weyerhaeuser’s Engineered Fiber Products Division in Snoqualmie, Washington. Soil Guard is a hydraulically applied matt that, when dry, conforms to the soil surface and forms a bonded fibre matrix that holds everything, including moisture, soil and seed, in place.

As the vegetation takes hold, Soil Guard slowly decomposes to enrich the soil. The matrix can be rewet repeatedly and it doesn’t wash away. Final components in the slurry are the appropriate fertilizer and seed. Any fertilizer can be added into the mixture, but knowing which one will do the best job is the key. If experience-based knowledge isn’t available, soil can be tested to determine the most effective fertilizer regime. However, since soils can change frequently along the length of a road or even on a long slope, experience is often the better guide. The same criteria applies to seed.

There are various levels of purity of seed and as many different seed mixtures as there are plants that will grow on the are a Experience-based knowledge can be helpful here as well. Application is also a factor, depending on what is to be achieved with the hydro-seed-ing operation. Erosion control requires a different mixture than simply wanting to grass the area in. The site itself is also a consid-e ration, including soil type, moisture regime, exposure to the sun, elevation and other factors. A hydro-seeding unit consists of a carrier, a tank with agitators to mix the slurry, a pump and a discharge system. Nearly any slurry of any consistency can be discharged from a hydro-seeding unit.

Mixtures can consist of simply water and seed, called wet seeding, a relatively ineffective way of applying seed in most cases, or they can be heavy mixtures of seed, fertilizers, mulches, Soil Guard, and even straw. Most commercial hydro-seeding units are designed to han-dle such mixes without difficulty. BPL Industries Inc., located in Salmon Arm in the BC southern interior, is a hydro-seeding specialist enjoying, like other com-panies in the field, a Code-prompted busi-ness boom. The firm runs two heavy-duty Finn hy d ro-seeding units suitable for forestry applications.

The hydro-seeding units, one mounted on a four-wheel drive, 330-hp Tonka airport scramble vehicle, and one (the newest) mounted on a Peterbilt 26,000 kilogram carrier, are both supplied by Canadian Forestry Equipment (CFE) out of Vernon, BC, the Finn dealer for western Canada. The Tonka carries 1,500 gallons and, with its four-wheel-drive configuration, this unit will out-climb most four-wheel-drive pick-ups. The wheels are mounted close to the vehicle corners, giving it high stability and close-quarter maneuverability. The Peterbilt is a 1,700-gallon unit, and while it is not four-wheel-drive, with its added capacity it is an efficient and cost-effective hydro seeder for extended spraying along roads and on landings. BPL is also a licenced applicator for Soil Guard.

BPL owner Barry Siebenga says there are three ways to seed — dry seeding, wet seed-ing and hydro seeding. He says both dry and wet seeding are often ineffective for forestry applications since neither method ensures the seed will either remain in place until it germinates or can survive the rigours of the weather If it comes to a choice between straight mulch or mulch with tackifier, Siebenga prefers to spend money on the mulch. He says that while mulches by themselves are not as effective in erosion control as mulches with tackifiers, they provide good shade cover for the seed and help hold the soil in place until germination occurs. Sticking with mulch also helps keep costs under control.

According to Siebenga, Soil Guard is an excellent product and is the best you can do in the most sensitive of erosion situations. Siebenga says the most important step when faced with a revegetation project is to discuss the project with the person or com-pany that will be doing the job. “There are lots of options available for revegetating an area, and you should explore what they are and what the cost is for each alternative. Costs can vary considerably, depending on the requirements of the area, type of seed and fertilizer, the makeup of the slurry, when the job can be done, the regime required — all those things figure into the cost and the effectiveness of the application. It’s best to talk about these things first, then get something down on paper before beginning the job. That way there’s no surprises when the job is done and the contractor comes in with his bill.”

Hydro seeding can be a leap of faith, says Siebenga. There is little or no control over what kind of job the contractor will do, and until he develops an understanding of what a good hydro-seeding job is, the purchaser of the service can feel vulnerable. There are a few ways a company can help protect itself from unscrupulous contractors.

“First is to talk to the contractor and get everything on a business-like basis,” Siebenga says. “Any contractor you choose should be knowledgeable, reasonable and competent — that’s just good common sense. Another option is to have the contractor do just a small bit of work and see how that comes out. This approach enables the company to get a handle on the person, the regime and the effectiveness of the operation. I often recommend this approach in areas I haven’t worked before. Forest companies are known to be cautious, but they do build long-term relationships with trusted contractors.” Siebenga says the company can also buy the components and hire the contractor to apply them.

“If you think the contractor might short-change on the components, buy them yourself and just hire the contractor to spread them for you. The only thing about this approach is that you have to know what to use on the area and the most effective application. If you’re not sure, you can try different combinations on different small areas first. That’s helpful in determining different revegetation regimes.” Siebenga believes forestry people and forestry consultants need to become educated in this area.

“Even though hydro seeding seems like a simple concept, it can be complicated and people in the forest industry need to know the most effective way of revegetating an area. That can involve many factors and considerations, and the best way to avoid costly mistakes is to know what you are doing. It looks like erosion control and revegetation will be a major part in timber harvesting in the future, so the best advice I can give at this point is for the industry to get educated. It will definitely save time and money and produce better results.”

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