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January 11, 2000

Hey jute, bring that Dirtbag over here

  • 'Geosynthetic' products are environmentally friendly
  • By JON SAVELLE
    Journal Environment Editor

    In the world of geosynthetics, a lot of the fun is in the vocabulary. There are geonets and geocomposites, Eco-Stakes and coconut blankets. There are coir logs and Geo-Jute; strip drains, Petrogrid, wire gabions and biobags. And, of course, there are floating turbidity curtains, straw wattles, Siltsacks and Dirtbags.

    What are they?

    Pat Gowan is glad you asked. He sells them all from the ACF West office and warehouse in Woodinville, where bulky rolls of the stuff are stacked to the roof.

    The products are designed to aid erosion control, drainage, soil stabilization, landscaping and paving. They are made by a variety of manufacturers in an assortment of materials, ranging from biodegradable jute and coconut to eternal polypropylene.

    As Gowan explained, the uses of geosynthetics are limited only by the imagination. Many are familiar: silt fences and straw matting for erosion prevention, landscape fabric for weed control. Others are equally useful but less well known.

    Petromat, for example, is an Amoco fabric overlay that seals and stabilizes old pavement while providing a substrate for new asphalt. A related product is Petrotrac, a "peel and stick" waterproofing membrane for repair of pavement cracks and joints, and for sealing bridge decks.

    Underneath pavement, Gowan said geotextiles are useful for maintaining separation between the soil and the gravel roadway base. This maintains the thickness and drainage characteristics of the gravel, he said, which reduces maintenance costs and extends the life of the road.

    Other applications are even less obvious. Retaining walls and embankments, for example, can be built up from pancake-like layers of soil separated by layers of fabric; their exposed faces can be planted or covered with masonry or shotcrete. Fabrics also are used for streambank stabilization and scour-protection layers, and for waste containment.

    geosynthetics in action
    Some uses of geosynthetics.
    These uses have made the materials popular. Gowan said that, statewide, about 20 million square yards of them are sold every year. But he thinks they would be much more popular if more people knew about them. Architects and engineers in particular.

    "It's a mixed bag," Gowan said. "For all the years these products have been out there, there are still a lot of applications where they could be used -- but are not."

    Part of the problem is that few university training programs offer courses on geosynthetics, as opposed to concrete and steel. But some training is available elsewhere. For example, North American Green of Evansville, Ind., a maker of jute matting (used for jobsite erosion control, often in conjunction with hydroseeding), offers a design program for engineers.

    And Gowan himself often presents talks and seminars on geosynthetics. He describes the materials as a way to build a better project at a better price, but he cautions that price needs to be calculated over a long period, and should include the savings resulting from less maintenance and rework. The prices for materials vary widely, depending on the product and quantity: The range is 50 cents to $10 per square yard.

    The materials themselves are just as diverse. Geosynthetic clay liners, for example, sandwich bentonite clay between layers of fabric. Gowan explained that the clay swells when wet, forming a nearly impermeable layer that can seal itself when punctured.

    Another example is "permanent turf reinforcement matting," made of plastic mesh, which is buried in the soil to hold it in place -- especially in areas subject to heavy runoff.

    Coconut mats are often used to start vegetated walls; once those are established, the mat decomposes. Coconut also is used in coir logs, which look like big jute sausages. They can be used like a silt fence, to control erosion and runoff along streams or drainage channels. (The materials come from India and Sri Lanka, but Gowan didn't know whether they are fumigated to eliminate any pests that might be hitching a ride.)

    Then there's "cellular confinement material," such as TerraCell, a kind of deep plastic mesh that holds soil or gravel while providing structural support. Wire gabions are mesh cubes, filled with rock, which are placed like building blocks along roadways, banks and slide areas to stabilize them; Eco-Stakes are biodegradable anchors for fabrics.

    If all of those products are inadequate to keep soil from running off of the site, there are always Drain Diapers, Siltsacks and Dirtbags. A Drain Diaper is what it sounds like: a permeable fabric bag that is suspended in a catchment basin under a drain. Like the Siltsack, it is used to catch sediment, oil and grease that finds its way to the drain.

    And for catching and storing larger volumes of sediment-laden water, there's the Dirtbag -- which looks like the world's largest water bed.

    "It's really kind of fun," Gowan says. "There's good reasons for using the materials we sell. You're solving a problem with some of these materials.

    "We're just having a blast out here."

    Gowan has been in the business for 16 years, and he says it is finally beginning to take off. ACF plans to expand in the Northwest (its headquarters is in Portland) to try to capture some of that growing market. And although he'll be contending with half a dozen competitors, Gowan said the market has room for companies that offer good products, knowledge and service.

    Not to mention Dirtbags.



    
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