by Tom Wedegaertner
Last year, Chicago's O'Hare International Airport moved 76 million people through its doors and was host to more than 925,000 flights, so it's no wonder that the airport has long seen a need for expansion and revitalization. The vision eventually came to life as what is now known as the O'Hare Modernization Program (OMP), managed by the City of Chicago. Part of the ongoing program's goals included runway modifications designed to reduce aircraft delays in inclement weather and increase capacity on the airfield. O'Hare previously housed seven runways, which all intersected except for one. The OMP planned to reconfigure the airfield into a more efficient and modern parallel configuration, similar to other large airports, allowing for additional arrival streams.
As the development plans took shape, engineers needed to address the grassy buffer strips that outlined the runway and determine the best way to seed the area, promote quick growth and protect it from erosion during the growing period. Aside from the goals of remaining on schedule and under budget, O'Hare planned to host a 5K race on its tarmac to commemorate opening the new runway and promote the City's bid to host the 2016 Olympic games, and needed the area vegetated in time for the festivities — only 9 weeks away.
Specification
The challenge was to determine the erosion control method best suited for the airport's unique needs. Historically, O'Hare's buffer strips were covered by sod for instant vegetation, but the existing budget could not accommodate the costs of purchasing and watering sod. Additionally, there was a rising concern of importing foreign diseases along with the sod patches. Erosion control blankets with nets would not work due to the risk of jet engines sucking up the nets during take–off and landing procedures; and traditional hydromulch was excluded because engineers felt confident that it would not be able to handle the amount of stormwater runoff that would certainly accumulate from the runway.
The local Soil and Water Conservation District was also concerned about the environmental ramifications of construction to the airfield. Countryside Industries, the local landscape contractor hired to seed the site, selected North American Green's HydraCX2™ Extreme Slope Matrix™ to aid the district's objective of preventing dirty water from entering into receiving waters.
Developed by Mulch & Seed Innovations LLC (Centre, AL), along with Cotton Inc. and the USDA, HydraCX2 is a high–performance hydraulic erosion control product made with mechanically processed straw fibers, reclaimed cotton plant material, and proprietary performance–enhancing tackifiers.
Installation
Specification for the site was modeled around a 0.5 inch storm event, which was predicted by the average rainfall that could be expected during the late summer grow–in time. As a result, it was determined that the buffer strip would need to be 10–feet wide along each side of the runway to successfully guard against erosion and standing water on the runway. Beyond the first 10 feet, a 50/50 paper and wood mulch was used as a cost–saving approach in areas where the ground cover was less threatened by stormwater runoff and engine thrust.
Mixed with Dry Spell, a grass seed that repels an airplane's general enemy — birds, the product was applied in late July 2008 from two opposing directions at a rate of 2500 lbs/acre to ensure optimum coverage.
“The mixing and application were not labor intensive,” said Lee Keenan, vice president of production for Countryside Industries, “and it didn't require us to put forth a lot of clean–up effort on the hydroseeders when it was time to switch projects and go back to using the 50/50 blend of mulch.”
How it Works
The product forms to the rocks and uneven surfaces of the earth. Its combination of straw, reclaimed cotton plant material and a blend of performance enhancing tackifiers and additives form a protective web that holds soil in place on slopes as steep as 1:1.
“HydraCX2 contains beneficial nitrogen, phosphorus and potassium nutrients that, when made available to the soil, are important for plant growth,” said Wae Ellis, vice president of sales and marketing for Mulch & Seed Innovations. “It's an absorbent material with water holding capacity, which assists germination and encourages the establishment of vegetation. Meanwhile, its crosshatching matrix provides air space and porosity for seedlings to push through with little resistance.”
Results
Crews quickly began regularly watering the site with water tankers to accelerate growth, but within three days of the application, the site was drenched by a late summer rain event. “There was zero evidence of wash out and no standing water. The product protected, insulated and provided moisture protection for the seed. It did precisely what it was designed to do,” said Keenan.
Within two weeks, germination was evident throughout the areas and engineers were pleased with the solid binding of soil and grass.
Weeks later, thousands of runners converged on Runway 9 Left/27 Right for the “5K on the Runway” and celebrated the first new runway at O'Hare Airport since 1971. In hindsight, Keenan reiterated the importance of proper product selection to successfully face the unique challenges O'Hare Airport presented.
“In one of the busiest airports in the country, there's no time to close a runway for repairs. We had one chance to get it right and we wanted to use a product we knew would do the job right the first time.”
About the Author
Tom Wedegaertner is director of cottonseed research and marketing for Cotton Incorporated. He can be reached at 919–678–2369 or via e–mail at [email protected].
