On March 1, 1872, 2.2 million acres of majestic, seemingly boundless wilderness was "dedicated and set apart as a public park or pleasuring ground for the benefit and enjoyment of the people" and "for the preservation, from injury or spoliation, of all timber, mineral deposits, natural curiosities, or wonders, and their retention in their natural condition." It was with this Act of Congress that the diverse wildlife, abundant geysers and hot springs of the world's first and oldest national park were forever protected. This land, located near Cody, Wyoming, was embossed with the name Yellowstone.

Presently, 370 miles of paved roads thread like thick veins through the park, twisting through the narrow valleys and steep slopes in the heart of the Rockies. Being largely devoid of vegetation due to construction activities, the flanking slopes along a few sections of these roads are exposed to severe wind and water erosion. Moreover, because excessive sediment deposition in waterways would endanger the area's abundant fresh water fish population and degrade the area's aesthetic qualities, a comprehensive erosion control plan was mandated. As part of the U.S. Forest Service erosion control plan, only 100% biodegradable erosion control products are allowed for use inside or near the park's boundary. A rich wildlife population is one preeminent reason for specifying only biodegradable products near the park. The area's abundant wildlife population is second to none in the contiguous United States, and history has shown that animals of all sizes are prone to entanglement in the plastic net structures found with some erosion control products. For the benefit of wildlife in and around the park, the reconstruction plans for Highway 14 exclude the use of all plastic netting materials.

Identifying the Problem and Finding a Solution

Some of the most popular features at Yellowstone National Park are geological in nature, including the geothermal phenomena (there are more geysers and hot springs here than in the rest of the world combined), the colorful Grand Canyon of the Yellowstone River, fossil forests, and the size and elevation of Yellowstone Lake. Approximately 5% of the park is covered by water, 15% is grassland and 80% is forested.

Highway 14 travels adjacent to the North Fork Shoshone River and forms the east entrance to Yellowstone National Park near Cody Peak. Reconstruction specific to 16.50 km (10.25 miles) of Highway 14 just outside the park's boundary, in Shoshone National Forest, left a significant amount of the area's characteristically dry, rocky volcanic soils unvegetated. It was desirable to quickly re-vegetate these bare roadside slopes and channels before any serious soil erosion took place. Not an easy task considering the relatively infertile soil and the fact that the area only receives 38 cm (15 in) of rain per year. Thus, any erosion control/revegetation product used must do much more than provide excellent erosion control and be 100% biodegradable. It was imperative for the material to possess excellent mulching capabilities which would regulate soil surface temperatures and effectively retain moisture at the seed bed in order to quickly promote seed germination and early plant growth.

After reviewing several proposals and various products, the Wyoming Department of Transportation (WYDOT) elected to use North American Green's BioNet™ products to fulfill their erosion control and revegetation needs. At the time, WYDOT agronomist John Samson noted that it was a revegetation job to meet the U.S. Forest Service and National Park Service criteria, along with Environmental Impact Statement Requirements (EIS). With these requirements in mind the Wyoming DOT specified North American Green's SC150BN for use on the roadside slopes, and for the drainage swales alongside the road, the C125BN was specified. Because the matrix of the SC150BN features a mixture of 70% straw and 30% coconut fiber, the blanket has a significantly greater functional longevity (approximately 18 months) than most 100% straw blankets - an increase in functionality desperately needed in this dry western climate where vegetation often requires two growing seasons to achieve full maturity. The C125BN, with its dense 100% coconut fiber matrix, provided increased shear stress resistance and a functional longevity of 24 months for the small drainage swales alongside the roadway. This increased ability to resist shear stress would be very important when spring snow melt from the high mountain slopes concentrates in the narrow roadside channels.

Yellowstone National Park is the first and oldest national park in the world, with 96% of the land located in the state of Wyoming, while the remaining 4% is located in Montana and Idaho. Approximately 99% of the park's more than 3,400 square miles (2.2 million acres) remains undeveloped, providing a wide range of habitat types that support one of the continent's largest and most varied large mammal populations.

"Persistence of biodegradable nets under the large game populations that occur along this highway corridor was originally a concern", says Samson. The BioNet blanket easily held up to this hoof action and persisted into the next Fall and beyond." He explains, "time has proven that hoof damage from moose, big horn sheep, elk and bison are limited to a localized hole in the nets. [The holes] appear much like a paper punch effect, leaving the surrounding blanket undisturbed. In comparison, the plastic nets tend to catch more on the animal's hock and large areas are dragged and destroyed."

Both the SC150BN and C125BN employ two woven jute nettings which are 100% biodegradable. This netting material, when compared to polypropylene nettings, proves very effective in retaining moisture and contouring to the soil surface, providing a higher level of erosion protection. In addition, the jute netting on the BioNet products is constructed with a "Leno" weave which allows the strands of the netting to move independently of each other yet still maintain the structural integrity of the net. A net configuration such as this minimizes the risk of wildlife entanglement without compromising erosion control performance.

Successful Results

Aside from an occasional curious bison or bull elk, installation of the erosion control blankets went smoothly; no animals were harmed by the area's human activities, thanks in part to the BioNet's unique construction. Altogether over 146,400 m2 (175,093 yd2) of erosion control blankets were installed along Highway 14 to re-establish vegetation and prevent soil from washing into Shoshone River. Observing the site just one year after seeding and blanket installation, it is indisputable how well the blankets performed in controlling erosion and enhancing seed germination. Native seed planted under the blankets has sprouted and matured (in one growing season) into a thick mat of brown, green, and red grasses, further exemplifying the moisture retention abilities of the erosion control blankets. Moreover, there are no visible signs of erosion occurring on the site.

The established vegetation will now provide the primary means of erosion control and the annual production of seeds from this native vegetation will ensure a thick vegetative stand in the future. During the course of the next 12-18 months the BioNet blanket's biodegradation will be nearly complete, with the only indication its installation ever took place being the thick layer of vegetation now growing along Highway 14. Mr. Samson concluded that “the original EIS preparation found much more concern over project impact on wildlife and sedimentation of the Shoshone river. North American Green and others have proven the doomsayers wrong.”