Geologist Says La Conchita Slide Not Caused by Year’s Heavy Rains

The heavy rains that swept over Southern California in the winter of 1994-95 were not enough to precipitate the massive landslide that inundated the beachside community of La Conchita, a scientist testified Thursday.

David Huntley, a San Diego State University geology professor, told a Ventura County Superior Court judge that irrigation by La Conchita Ranch Co. had filled the underground water basins in the years preceding the collapse of a supersaturated slope.

Huntley is an expert witness for 146 residents who sued the ranch, seeking $24 million in damages.

In 1996, 14 months after the landslide, Huntley visited the ranch to drill 14 holes, take soil samples and measure ground water. He made comparisons between conditions beneath lemon and avocado orchards and places where irrigation never occurred.

There was a dramatic difference in the sites, Huntley told Judge Henry J. Walsh, who is presiding over the nonjury trial.

“The irrigation of the ranch produced approximately an eight-fold increase in ground-water recharge” inside the hill above La Conchita, he said.

The south slope of that hill came crashing down on a rainy afternoon March 4, 1995. In a 40-minute span, 600,000 tons of mud, boulders and trees crashed onto the Vista del Rincon neighborhood. Nine homes were destroyed; the rest of the community was posted as a geologic hazard area and property values plummeted, along with the local economy.

No one was injured in the slide.

Huntley’s testimony is key to the homeowners, who must prove that irrigation practices at the ranch altered the environment and triggered the landslide if they hope to win their case. Their attorneys contend that excessive ground water inside the hill destabilized an ancient landslide that had been secure until the ranch began irrigating in 1975.

But attorneys for the ranch say Huntley’s findings do not adequately account for subsurface water taken up by tree roots. Further, his estimates are based on chemical deposits in ground water, which do not necessarily indicate quantities of irrigation water percolated through soil, defense attorney Frank Sabaitis said.

The ranch’s lawyers will attempt to shoot holes in Huntley’s testimony during cross-examination, expected today.

During his testimony, Huntley said heavy rainfall that winter, including a then-record 16 inches in January a few weeks before the landslide, was not enough to cause the disaster. Using a pointing stick and graphs, he described rainfall patterns at La Conchita over the past 106 years.

For example, Huntley said the hillside withstood many rainy seasons in 1908-15 and 1916-20, periods that produced far more rainfall than the 18 inches that fell at La Conchita in the months preceding the 1995 landslide.

In addition, Huntley said cracks that appeared on the hillside in June 1994, at sites that would later become the origin of the slide, developed after an unusually dry spell.

“From that, I had my first evidence that precipitation by itself did not cause failure of that landslide,” Huntley told the court.

The trial is in its first of possibly two phases, initially focusing on what caused the landslide. If the homeowners prevail, the trial shifts to a damage phase; if they lose, their lawsuit is finished.