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Your GPW Editor-on-Occasion is Petra Fried in the City.
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stories along The Way

Thursday, January 14, 2010

Learning to love hydromulch the hard way

...and Tom LaBonge told anyone who would listen that  hydromulch doesn't work.
Silly man. From yesterday's Daily Journal of Commerce (Oregon) with a wicked-cool photo:

Burn recovery: Griffith Park gains hope for future

POSTED: Wednesday, January 13, 2010 at 05:03 PM PT
BY: DJC Staff

(Wind cowls mounted atop Shiley Hall, shown in this early design, use wind pressure to pull air out of the building with no energy consumption. Interface Engineering used complex models to prove their effectiveness. (Photo courtesy Interface Engineering) Sky Cranes applied hydromulch at a rate of 3,000 to 4,000 pounds per acre to mitigate the destruction of 840 acres of vegetation by a May 2007 fire in Griffith Park in Los Angeles. (Courtesy of Kleinfelder Erickson)

In May 2007, fire raged through Griffith Park in Los Angeles, destroying more than 840 acres of vegetation and leaving behind large stretches of exposed, charred soil. As the rainy season neared, residents began to worry the bare areas, when hit by heavy rains, would give rise to dangerous landslides and mudflows that would spill into residential areas. City officials were worried, too. They knew that burned soil areas often have high rates of runoff in the first seasons following wildfires. The burned areas in Griffith Park were ripe for such a situation.

The city turned to Kleinfelder for help. Working in a consultant capacity, Kleinfelder was handed the task of not only assessing the potential for erosion in burn areas, but also of coming up with ideas to secure and mitigate the burn sites. Kleinfelder began by conducting a site assessment of the often steep terrain of the park. Then the firm’s scientists began collecting data, taking soil and topographic samples that allowed them to evaluate the potential for erosion of the area that had been burned in the wildfires. Working on an aggressive schedule, Kleinfelder combined erosion modeling results with infrastructure assessments. By adding information about topographical features, Kleinfelder and a city team developed a plan for applying hydromulch to the burned areas to secure the soil. The extreme hill slopes in some areas required two different hydromulch formulations. Depth of the applications also varied based on topography. The affected areas survived the rainy season without significant soil movement, but Kleinfelder’s work also had long-term impacts. The accuracy of the hydromulch applications created positive conditions that attributed to the long-term recovery of native plants in the park. In addition, the techniques Kleinfelder developed while working on the Griffith Park burn sites not only prevented soil from washing away during winter rains, but also are expected to be able to benefit other communities trying to reduce or prevent areas damaged by wildfires.