Cliff collapse in North Pacific Beach may be a harbinger
by DAVE SCHWAB
Published - 09/24/15 - 02:35 PM | 1 1 comments | 33 33 recommendations | email to a friend | print
On Friday, Sept. 11, approximately two tons of dirt and rocks tumbled down the cliff face below 417 Sea Ridge Drive at Tourmaline Beach. / Photo by Dave Schwab
On Friday, Sept. 11, approximately two tons of dirt and rocks tumbled down the cliff face below 417 Sea Ridge Drive at Tourmaline Beach. / Photo by Dave Schwab
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The foundation of a house overlooking Tourmaline Beach is exposed after the cliff crumbled last week. / Photo by Dave Schwab
The foundation of a house overlooking Tourmaline Beach is exposed after the cliff crumbled last week. / Photo by Dave Schwab
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The city has told the owner of a vacation rental house, which is perched on a bluff that partially collapsed near Tourmaline Surf Park in North Pacific Beach, that they must hire a private consultant to research the cause and find a remedy to the situation.

On Friday, Sept. 11, approximately two tons of dirt and rocks tumbled down the cliff face below 417 Sea Ridge Drive about 1:30 p.m. The collapse caused no injuries, no apparent damage to residences on the bluff top and resulted in no evacuations. The incident prompted lifeguards to close a stretch of beach.

However, with reports of a building El Niño condition with warmer-than-normal ocean temperatures possibly leading to an extremely wet rainy season this winter, the incident has raised concerns about the potential for further cliff collapse there and elsewhere along the coast in Pacific Beach and La Jolla.

City spokeswoman Lynda Pfeifer said a call came in Sept. 11 of a minor coastal bluff failure, which she said prompted the city to send geologists out to assess the situation.

“They (geologists) did a quick triage, then they yellow-tagged the house,” Pfeifer said. “This was on private property, and the responsibility (for remediation) is up to the (property) owner.”

A yellow tag indicates the home is still habitable but urges residents to enter/exit with caution.

Pfeifer added lifeguards below the bluff put cautionary tape around the fallen debris.

“What happened was residents left the pool water running, and it topped the pool running over the pool deck and flowed over the coastal bluff face,” Pfeifer said.

The property owner could not be reached for comment by Beach & Bay Press.

Pfeifer said the property owner has subsequently hired a private consultant, a geotechnical consultant and an architect to evaluate the site of the collapse, study the prevailing geological conditions and “determine appropriate measures to stabilize the situation.”

The city’s supervising public information officer added that the incident has raised concerns about how future rains might impact eroding bluffs along Sea Ridge Drive in Bird Rock.

Michael Pallamary, a La Jolla land-use consultant, has been involved in researching numerous landslides, including one on Mount Soledad a few years back that completely split a road and destroyed four homes. He said many blufftop areas in La Jolla and Pacific Beach are at risk due to prevailing geological conditions.

“A lot of homes are on hillsides with soils that could wash away,” Pallamary said, adding there exist detailed maps of soil conditions in problematic areas with images that “scare you to death.”

Noting coastal bluffs in the area are “constantly eroding” from the effects of wind, waves and storm runoff, Pallamary pointed out geological faults criss-crossing the area, as well as poorly compacted soils, are two factors increasing the likelihood of landslides occurring.

“The neighborhoods have different soil characters as you head from Pacific Beach into La Jolla,” Pallamary said, noting some areas, like La Jolla Cove, are composed of very hard cemented sandstone. But in other areas, like north PB, Pallamary noted prevailing soil conditions are of “a much different composition.”

“A lot of the soil there is unconsolidated rock and cobble left from an ancient river,” he said. “It’s not native material. It’s not cohesive.”

After World War II in the '50s, Pallamary noted there was a housing boom that led to increased land development involving lots of infill being brought and used, which continues to be problematic.

“A lot of infill and grading was done with unsophisticated skill before they had contemporary engineering science to really guide them,” Pallamary said. “I predict there’s going to be a heck of a lot more of these (landslides) going on.”

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mpallamary
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September 25, 2015
It is to be noted that contemporary engineering by qualified soils engineers and geologists will stabilize these sites. Get a good engineer!
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