Western North Carolina Landslides
Thursday, January 1, 2009
Sprinkler Systems Should be Banned on Mountain Slopes
October 8, 2008 photo of the Portland West Hills neighborhood landslide-The Oregonian
Authorities cannot control rainfall, a natural occurrence and the most frequent cause of slope failures, but they can provide a measure of protection by outlawing the use of sprinkler systems on steep slopes.
These are the lessons that North Carolina regulators can learn from a recent landslide in Portland, Oregon. Although not conclusive, numerous investigations indicate that this multi-property financially-devastating tragedy was precipitated by the use or perhaps overuse of a sprinkler system on the part of an uninformed homeowner.
The mountain counties of North Carolina are geologically hazardous: lives and property are under the ever-present threat of an unstable land environment. Rain was the trigger for the disastrous Western North Carolina landslide events of September 2004. These slope failures killed five people and cost millions of dollars in uninsurable real estate losses. Another Western North Carolina landslide fatality occurred in December 2003. The cause: a leaking water pipe.
It is time for North Carolina lawmakers to recognize that sprinkler systems pose a significant threat to public safety. Current permit holders should be warned of the risks and all new permits should be denied. The following article details the history of the Portland landslide.
Portland Officials Believe Sprinkler System Responsible for West Hills Landslide
In the early morning hours on October 8, 2008, an unimaginable event transformed the landscape of a well-established Portland West Hills neighborhood. When the slope collapsed under the home on 6438 S. W. Burlingame Place, it became a swift-moving mass destroying two homes and significantly damaging several others. The companies providing insurance for the injured parties have so far declined coverage for the landslide property losses. (Homeowners policies do not cover this peril).
Portland officials have ruled out rain and leaking city water and sewer lines as possible causes of the slide. The Oregonian reported on November 21, 2008 that the primary suspect appears to be a sprinkler system that was installed on the back yard slope where the landslide occurred.
Portland Commissioner, Randy Leonard, told the press, “What has changed to cause the soil conditions to become so malleable that what had held for 75 years broke loose? What’s different is the installation of an irrigation system combined with an unusually high use of water.” Records show that the property owners, Kathei and David Hendrickson, received a city permit to install the system in March 2005. The City of Portland Natural Resources website shows that the Burlingame property was located on a slope greater than 25% and subject to landslides and soil erosion.
Bill Burns, an engineering geologist for the state, said he believed the slide was likely caused by several factors: water in the soil, unstable ground and the steep slope the house was erected upon.
The Portland metropolitan area experienced catastrophic landslides in February 1996. Geologists found that the West Hills Soil Province suffered hundreds of slope failures during this wet-winter period. Soil sediments, which cover the area, are suitable building sites when dry but are dangerous when water-laden.
The Hendricksons are facing numerous lawsuits. The city has denied all responsibility for the slope failure and resultant property damage. It should be noted that if the sprinkler system is found to be the cause of the landslide the city granted the permit.