In recent years, many homes in Southern California have been subjected to an elevated threat of damage and destruction - not from terrorism, but from the ground upon which they were built.

The rains that have pummeled Southern California in recent years have had a devastating effect upon many hillside communities. For example, scores of homes have literally crumbled to pieces in locations such as Laguna Beach, La Conchita, the Anaheim Hills and Studio City, to name but a few.

Forensic investigations upon the soils where such homes once stood will undoubtedly reveal one or more of the three most common conditions associated with soils failures. One, ancient landslides; two, impermeable layers of clay; or three, improperly compacted fill material.

Unfortunately, the ramifications of such soils conditions beneath a home are devastating. Some residents with homes erected upon or around ancient landslides have been made brutally aware that the designation “ancient” does not mean static and secure. Geologists and soils engineers will tell you that the vast majority of ancient landslides are quite dynamic. When an already dynamic soils condition becomes saturated from the types of downpours Southern California experiences from time to time, the natural result is slippage.

Residents of homes built upon soils containing layers of impermeable clay found when water is introduced, the ability of the water to dissipate can be impeded by the clay. This results in an accumulation of moisture between the clay and the other layers of soils above it. The trapped moisture essentially acts as a lubricant allowing the soils above the clay to slide.

Many homes are constructed upon “fill” material. Simply stated, fill consists of soils obtained from other locations and introduced to sites which were not level or needed to be elevated. The fill material is placed where required and compacted to create level building pads. Fortunately for most of the owners of homes built on fill, the builder removed all the foreign materials such as roots, branches, leaves, rocks and trash from the fill before compacting it to the density level required by the local building code.

When fill material is not properly compacted, the likely result is soil subsidence. Assuming the distance traveled is minimal, subsidence in and of itself may not prove to be a significant problem, provided that all the soils beneath the entirety of the home move uniformly, i.e., at the same time and the same distance. On the other hand, when only a portion of a home is setting upon improper fill, subsidence generally is not uniform. This causes “differential settlement.”

Differential settlement is problematic because as different sections of the ground beneath the home move different distances and/or in different directions, the home can literally be torn apart. Moreover, when rainfall is introduced to inadequately compacted soils, the resulting subsidence is accelerated and multiplied.

One glaring example of the subsidence potential from insufficiently compacted fill was exposed during a lawsuit conducted in the late 1980s involving the development of a condominium complex located just northeast of the Los Angeles Civic Center, in the Monterey Hills. In the case of Eaton Crest vs. The California Redevelopment Agency, et. al., soils testing revealed that a canyon, one hundred feet deep, had been filled to create a level surface upon which to build the complex. Soils experts determined that the fill material had not been properly compacted. Based upon the depth of the fill and the lack of proper compaction, the experts predicted that the soils introduced into the canyon could subside as much as 14 inches.

With the prediction of additional rainfall for Southern California due to the climactic condition known as “El Nino,” what can you do to protect your home from such dangers and damages?

Make sure that your existing drainage systems, including the area drains in your yard and your roof gutter system, are functioning properly. Proper drainage should divert excess water away from the foundation of your home and out of your yard. If necessary, additional drainage should be installed.

Plant ground cover on hillsides. The roots of the plants will help to hold the soils in place during the rains.

Install retaining walls to secure the soils. Also, install drainage on the uphill side of the wall to limit the accumulation of water behind the wall. This is essential to relieve the forces, known as hydrostatic pressure, exerted by water when trapped behind retaining walls.

Unfortunately, the rains in recent years have produced far too many soils failures for people to feel completely comfortable with the earth beneath their homes. Therefore, it is important to recognize conditions that constitute the early signs of soils movement beneath a home.

Conditions which most people simply consider annoying, may actually be signs of underlying soils movement. For example, soils movement can manifest itself by rotating interior and/or exterior door sills. Only a slight change of position to a door sill will cause the door to bind and no longer open and close properly. Similarly, window frames can shift causing the windows to bind and stick when opened and closed.

Soils movement can manifest itself by rendering floors uneven. If the house sets on a concrete slab, soils movement can literally crack the slab to pieces. Generally, the widths of the cracks increase as the movement of the soils increase. Cracks may also appear in the seams of interior drywall panels and exterior stucco material.

Indications of soils migration are not limited to areas within one’s home. Exterior walls, planters, driveways, curbs and patio slabs will also crack when soils shift.

Another potential manifestation associated with soils movement can be detected when structures such as walls and street curbs, which had been completely painted, begin to expose unpainted areas which were previously below the soils line.

If signs of soils movement continue, notwithstanding the existence of a properly functioning drainage system, complete vegetation cover on slopes and/or the installation of retaining walls, then an engineered remedy may need to be employed.

There are many engineering methods available to secure migrating soils. Just to list a few, sinking pilings into the ground down to the bedrock, injecting cement into the soils or shoring sections of soil. In any event, if it is necessary to employ an engineered fix, a soils engineer should be consulted.

If your home has already suffered some type of damage due to land movement, there are things you should do. First, you should review your insurance policy and consult your insurance carrier. Unfortunately, most standard homeowner policies exclude coverage for soils-related damages; however, one should still check. If it appears from the language of the policy that such damages are covered and the carrier denies coverage, you should obtain an independent second opinion.

Notwithstanding the presence or absence of insurance coverage, one may look to the design, development and construction professionals involved in the building of the residence for a remedy.

The average homeowner does not have the capacity to determine the stability of the soils under his or her home. On the other hand, homeowners should be able to rely upon the integrity of the soils beneath their homes. The professionals who develop residential housing are required to investigate the conditions of the soils prior to erecting structures. If the conditions are too unstable, construction should not take place and the city or county should not grant the developer authority to build there.