by Brett Hanavan
La Jolla's GDC Construction says there are ways homeowners can help prevent landslide damage.
The Oct. 3, 2007 landslide along Soledad Mountain Road came quickly. A massive wall of earth moved down the hillside toward homes below, forcing the closure of Soledad Mountain Road between Desert View Drive and Palomino Circle.
About 180 homes were affected. Two homes were initially destroyed. On Jan. 17 of this year, the earth moved again in the same area.
With recent rainstorms and the possibility of more wet weather looming, the conditions for more erosion exist. So what can a homeowner do?
GDC Construction of La Jolla believes that a proactive approach for property owners is important.
"People can learn to prepare their land and surroundings to help in the prevention of landslides," said GDC Construction.
GDC says that protecting the land for property owners is the first step of eight that GDC recommends to get moving in this direction. They are:
Hire a general contractor as your construction manager to coordinate all necessary consultants and manage your budget.
- Have a civil engineer survey the property. Have a geotechnical engineer test the soil conditions and write a report.
- Have a structural engineer design a foundation shoring system.
- Have a landscape architect design a drainage and grading plan.
- Have a permit expeditor package the drawings and submit to the City for permit.
- Assemble construction costs.
- Pull the building permit and begin construction.
GDC said there are several causes of landslides.
"The most prevalent cause is water intrusion into unstable soils causing movement and the soil can liquefy," GDC said. "Loose and not compacted soils that are saturated can cause ground movement or sinkholes."
A number of other factors generally contribute to landslides, such as gravity, steepness of the slope and the geological strength of the soil and rock in the area.
The 800-foot, television transmitter-covered Mount Soledad was created about 45 million years ago, when the ancient sea floor was thrust upward by seismic movement within the Rose Canyon fault.
The subdivision along the east side of Soledad Mountain Road and Desert View Drive was graded for construction in the early 1960s. In December 1961, a landslide in the same general region destroyed seven homes under construction. Then, in 1990, new home construction caused a landslide on Desert View Drive. A third slide happened again in 1994 at the same site.
Today, hiring a firm to make assessments is the logical step for homeowners. It seems expensive at first, but GDC said that for the average property owner, the assessments are affordable and a worthy investment.
"It is a good investment to help protect your home," GDC said. "Some of these defenses are drought-resistant plants, subterranean and area drains, gutters, proper deck slopes and sloping the finish grade away from the home."
These are all logical steps when homes in much of Southern California are in designated landslide zones.
"When we build custom homes or do major remodels, we always incorporate proper drainage and make sure the soil is sloping away from the home," GDC said.
Homeowner insurance policies typically do not cover landslides.
"With proper drainage, you minimize that risk," GDC said. "We recommend you review your lot with a licensed soil engineer, especially if you are on a sloped lot or if you're near a cliff or an embankment."
GDC recommends all purchasers of new or existing dwellings hire a licensed soil engineer to come in and evaluate the condition and drainage of the property.
"Proper sloping of the property and good drainage are essential elements to managing a property," GDC said. "The emphasis now has been on drought-resistant vegetation. Overwatering your yard is the worst offender and causes major problems. With drought-resistant plants, this substantially reduces overwatering and will help to mitigate soil or drainage concerns."
"We are a general contractor specializing in custom homes and remodeling," GDC said. "We provide our customers with superior service and craftsmanship of uncompromising quality."
Additionally, GDC offers structural consulting, proper drainage, landscaping and plumbing work to help improve La Jolla properties, he added.
For more information go to www.gdconstruction.com.
Residents can also access more information about the geologic quality of land in San Diego by visiting the San Diego Geographic Information Source service at www.sangis.org.
According to mapping provided by SANGIS, the Mount Soledad landslide area is in a zone rated at the highest risk level, a 4.2.