Halting Slides: A Big Price and a Big If : Peninsula: The Corps of Engineers says it could cost $60 million to stop the movement--if it can be done at all.

Although the city of Rancho Palos Verdes has succeeded in the Herculean task of slowing massive landslides in the Portuguese Bend-Abalone Cove areas, federal experts say efforts to stop the slides completely could cost up to $60 million.

Even then, the experts add, the efforts might not be successful.

That assessment was made by the U.S. Army Corps of Engineers in a preliminary study that will help decide whether the federal agency joins the costly, long-running battle against the geologic forces that are driving mountains of earth seaward.

Even with $10 million in bond money that a Superior Court recently ordered Los Angeles County to pay toward slide abatement efforts in Abalone Cove, Rancho Palos Verdes doesn’t have anywhere near the kind of money needed to fund the total project, officials said. So the city has asked the Corps of Engineers for help.

More than 200 homes have been damaged or destroyed by the slow-moving slides over the last 35 years, reports show. Nearly $7 million has been spent by property owners and the city in desperate efforts to stop the creeping earth that has moved houses and roads hundreds of feet seaward.

“The city has shown it can slow (the slides) down . . . but we don’t know where a landslide has ever been stabilized,” said Steve Fine, chief of the Corps of Engineers’ Southern California coastal resources branch.

As a result, before the corps can decide its response to the city’s aid request, he said, more studies are needed to determine if these slides can be stopped and, if so, at what cost.

“There is still a high degree of uncertainty” in the minds of the experts who have spent three years investigating the slide areas and monitoring abatement efforts, Fine said. Their report is being reviewed by top federal officials and will be released in September, he added.

The causes of the earth movement on the south-facing bluffs and headlands along the Palos Verdes Peninsula are a complex mix of unstable geologic conditions, the impact of urban development and heavy shoreline erosion caused by wave action, according to the experts.

Deep below the peninsula’s surface, a layer of waxy mineral called bentonite underlies the rugged dirt and rock slopes and canyons. When water in underground aquifers wets the bentonite, it becomes slippery, and the crushing weight of the layers of rock and earth above it send the slow-moving slides inching downhill.

Rains, street drainage and septic tanks all add water to the aquifers, lubricating slide zones and making them more unstable, experts say.

Technically, there are four slide areas along the coast near Portuguese Bend and Abalone Cove. Although experts argue whether these are part of a larger, single slide area, lawyers for the county, the city and homeowners have been battling for years to see who is liable for damages.

The first and largest of these slow-moving slides started above Portuguese Bend in June, 1956. Lawsuits by homeowners established that the 270-acre Portuguese Bend slide was triggered by county road-building crews who were moving and dumping tons of earth as they extended Crenshaw Boulevard. Parts of the slide are still moving, and damages for the 145 homeowners involved were set at more than $7 million.

The county was also held liable for a smaller slide in nearby Abalone Cove that first became noticeable in late 1977 that damaged or destroyed 48 homes. After years of litigation, the county settled the Abalone Cove case in 1987, paying nearly $5 million in damages and agreeing to underwrite a $10-million bond issue to help the city’s Redevelopment Agency stop the slides.

Rancho Palos Verdes recently received the bond money and is convening a panel of experts to determine how best to use it.

Priorities are a sewer system to replace the area’s septic tanks and a storm drain system to channel and control surface runoff. Also, a large block of the money will probably be used to stop wave erosion on the bluffs and for other shoreline protection.

The slide abatement efforts in Abalone Cove were begun not long after the slide began moving, and these efforts have become a kind of proving ground for abatement efforts at Portuguese Bend and elsewhere.

Early on, Abalone Cove homeowners formed an improvement district and joined in the city’s effort to “dewater” the slippery underground layers of bentonite. Pumping millions of gallons of water out of the aquifers was the first step.

In addition to drilling these wells, slide-fighters moved great quantities of earth from the upper slopes, placing millions of tons further down slope to redistribute the massive weight that was pushing the slide.

The success of these early efforts raised officials’ hopes, and similar work was begun in the larger Portuguese Bend slide area.

Before these abatement efforts were started, the earth was moving seaward by as much as 40 feet a year. Over the last three decades, a mile-long section of Palos Verdes Drive South was pushed 300 feet down slope. The city recently spent $900,000 rebuilding the vital arterial road and budgets $300,000 a year to keep the route open, officials reported.

These days in Abalone Cove and on the upper slopes of Portuguese Bend, movement has slowed measurably and is creeping along at only a few inches a year. But along the bluffs in lower Portuguese Bend, the land is still moving six to seven feet a year, city officials report.

Officials blame this movement on wave action that is rapidly eroding the cliffs. They say that as the bluffs fall into the ocean, the earth above moves and slips more rapidly downhill.

The worry is that as the bluffs and headlands below Palos Verdes Drive South erode, the whole slide area may once again begin to move more rapidly, causing more damage to homes, roads and utilities.

“We don’t have control down close to the bluffs because of the wave action,” city Public Works Director Charles Abbott said. “What we need to do is stop the waves.”

The city hopes that the Army Corps of Engineers can justify coming into the project to do just that. But federal experts are leery of unexpected engineering problems they might encounter, he said.

There is no question about the corps’ ability to build seawalls and breakwaters, but the problem in Rancho Palos Verdes is complicated by such large-scale earth movement that may prove unstoppable, Abbott said.

“The corps won’t do (the project) if they determine the slide is just going to undo all of their work,” Abbott said. “So we are trying to prove we can stabilize the slide.”

Because of the cost, federal involvement is essential. Abbott estimated that major projects such as seawalls can cost $20 million or more.

Estimates by corps’ officials of the overall cost range from $15 million to $60 million, according to Fine.

If the corps joins the battle and gets funding from Congress, Fine said tentative plans call for some kind of seawall or breakwater just offshore. In addition, the toe of the cliffs would have to be buttressed with some kind of stone revetments, he said.

The work would radically alter marine and coastal environments along the south-facing coastline and would probably raise environmental questions.

Fine contended such a project would produce major environmental benefits. He said the slides and the bluff erosion have dumped tons of rock debris on tidal pools, destroying marine life and turning the sea muddy brown.

“If the slides are stabilized, this marine life will be restored,” he said.

He cautioned, however, that the federal government may decide not to get involved because experts are not certain the slides can be stopped.

Even if the corps gets the green light, it would be at least eight to 10 years before construction could start, officials acknowledged.

In the meantime, anxious residents of the Abalone Cove area hope that the $10 million from the county will fund enough abatement work to once and for all stop the slide that continues to plague them.

BACKGROUND

In 1956, road construction crews working in the hills of the Palos Verdes Peninsula triggered the Portuguese Bend landslide that damaged or destroyed 145 homes in the wealthy, gated subdivision above the Pacific Ocean. In the 35 years since, three other massive, slow-moving slides have plagued Rancho Palos Verdes. The city and landowners have spent millions of dollars trying to halt the slides that once were moving at 40 feet per year but have slowed in recent years.