Monday, December 14, 2009

Landslide Hazards for Tiger and The Cliffs

—The Buncombe County Soil Hazards Map has not been released—

Location of The Cliffs at High Carolina
Subdivision and Tiger Woods Golf Course
on Buncombe County Hazardous-Land Map— NCGS.

Slope Movements and Slope
Movement Deposits Map—NCGS

Stability Index Map—NCGS

Map of Known and Potential Debris
Flow Pathways—NCGS

No one has asked Jim Anthony, developer of The Cliffs at High Carolina, or Tiger Woods his partner whether they have considered the consequences of building a golf course on landslide-hazardous ground.

Mr. Anthony cannot avoid the fact that his subdivision and the Tiger Woods Golf Course have geologic conditions which predispose the development site to landslide events. In addition to the North Carolina Geological Survey Buncombe County landslide hazard maps, the U.S. Army Corps of Engineers issued a Public Notice on July 3, 2008 identifying the predominant soils found throughout The Cliffs at High Carolina subdivision. Western North Carolina Soil Surveys state that these soil compositions are highly erodible and are not suitable for residential development.

So the question is, does Mr. Anthony know what impact the golf course and its irrigation system might have on the mountain’s defined unstable base?

Mr. Anthony may not know the answer but geologists do.

Golf course construction alters the landscape. These expansively remodeled sites are cleared of native vegetation and are replaced with turf grass which requires irrigation. When golf courses are built in stable environments their location and maintenance requirements are not an issue, but when they are placed in geologically hazardous locations they are a matter of concern as demonstrated in the following histories.

Landslides Linked to Golf Course Construction and Irrigation

View of Ocean Trails
Golf Course Landslide—
Ninyo & Moore

Ocean Trails Golf Course Landslide—Rancho Palos Verdes, CA— 1999 (Trump National Golf Club)

Ninyo & Moore, a geotechnical and environment sciences firm, was hired to provide a forensic evaluation for the Ocean Trails Golf Course Landslide. A summary of its findings:
On June 2, 1999, an approximately 16-acre ancient landslide on the coastal bluff was reactivated, sliding approximately 50 feet toward the ocean. The ancient landslide destroyed much of the 18th fairway and green along with adjacent improvements, including an active County sewer line. The geologic setting included gently to moderately tilted beds of the Monterey Formation. The Monterey Formation at this locality included interbedded sequences of fine silty sandstone, siltstones, shales, dolomitic shales, siliceous zones, and bentonitic ash beds. The basal rupture surface was formed along a relatively continuous bentonite layer at a depth of approximately 90 feet. The geologic evaluation included detailed geologic mapping, 26 large-diameter borings, two rotary wash continuous core borings, 12 inclinometers, and the excavation and evaluation of buried sewer lines and artificial lakes. The analysis included preparation of multiple geologic cross sections, slope stability analysis, and evaluation of potential reactivation causes including seismic activity, precipitation, wave erosion, irrigation, construction activities, lake leakage, and sewer line leakage.
Donald Trump purchased the bankrupt Ocean Trails Golf Course in 2002 and he has spent $55 million to restore and stabilize the property.

In addition to the presently contained landslide located underneath the Trump National Golf Club Course, three others are located on the peninsula according to the Rancho Palos Verdes Chamber of Commerce. The largest, the Portuguese Bend landslide, was reactivated in 1956 and moves about a foot a year, depending on rainfall. This underground landslide tract covers 260 acres and has an average depth of 135 feet. Geologists attribute the onset of movement to irrigation, installation of pools and septic tanks that increased ground water levels.

South Golf Course Landslide—Colorado Springs, C0— 1993

Engineers investigating the site determined that irrigation was the cause of the reactivation of the ancient landslide underneath the South Golf Course. Their findings:
The construction of the golf course modified the site hydrology by adding irrigation water inflows and by changing the vegetation from native grass and scrub oak to turf grass over 55 percent of the total area. An analysis of the irrigation and precipitation rates and the turf grass water consumption rates showed a relatively high infiltration rate in the turf grass areas compared to the unirrigated native areas.

Proposals for Slowing the Landslide:

(1) ground water dewatering systems, (2) surface water control systems, (3) collection of flow from horizontal drains, and (4) control of irrigation.
1) Tetra Tech, Inc., USA
2) Colorado State University, USA

Arcadia Bluffs Golf Club Landslide—Manistee, Michigan— 1998

Massive landslides damaged this golf course during a September storm event. Improperly designed drainage inlets were the cause.

Reference: “Arcadia Bluffs sage continues”— Andrew Overbeck Golf Course News—November 2001.

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