City Unveils Plan to Stabilize the Asilomar Bluffs

By Sarah Stockman
Staff Writer

The Asilomar Bluffs have presented a challenging problem since 1958, when two landslides extending from the street to the ocean, at 60 and 85 feet deep, were identified.

The Northridge earthquake in 1994, and major flooding in 2005, helped create an increase in slide movement below Asilomar Boulevard (between El Medio and Almar).

Residents along Asilomar and in Tahitian Terrace and Palisades Bowl (two mobile home parks located below the bluffs) listened to a presentation on July 12 by the City of Los Angeles Bureau of Engineering at the Palisades Library to discuss the Asilomar Boulevard Street Stabilization plan.

The city proposes to stabilize the top of Asilomar Bluffs with a dirt and concrete mix- ture. The middle and bottom of the hill belong to different property owners.
The city proposes to stabilize the top of Asilomar Bluffs with a dirt and concrete mix- ture. The middle and bottom of the hill belong to different property owners.

A major problem in dealing with the hill and landslide is the fact that the property has three owners: L.A. City, Eddie Biggs (owner of Palisades Bowl) and John McDonald (owner of Tahitian Terrace).

The city owns the top section—Asilomar Boulevard and the Bluffs Park. The remaining hillside, including the now-in-ruins Puerto Del Mar access road, is privately owned.

Three de-watering wells are currently being installed 140 feet under Asilomar, between Wynola and Almar. The goal is to pump groundwater to the sewer system, thus reducing the potential for more slide movement. This part of the project should be completed by October.

But that is only a Band-Aid for a broad hillside that needs more drastic intervention. At a meeting hosted by the city a year ago, several proposed methods were introduced to stabilize Asilomar: a wall with tiebacks; a two-tiered wall with tiebacks; large 10-ft. diameter concrete poles; a soil-nail wall and deep-soil cement-mixed columns.

At the July 12 meeting, a city official announced that the city has decided on deep-soil mixing (DSM). This method involves digging holes that are three feet wide, but do not remove the dirt. Rather, the soil is loosened and then concrete is added. The soil and concrete are mixed, creating a solid column. The process is then repeated along the area of the slide.

Richard Louie, the project manager for the Department of Engineering, explained the choice.

“The DSM method provides some great benefits, including reducing the amount of export and import of soil required,” Louie said. “[This] is anticipated to be more environmentally friendly . . . and will reduce the amount of truck traffic required, which is a benefit to the neighborhood and community.”

Louie also noted that the slope would maintain its current aesthetic, which was cited as important to residents at the August 2016 meeting.

“Additionally, DSM will be completed within the ground, beneath Asilomar Boul- evard and will create a minimal, if any, change to the existing appearance of the hillside,” Louie said.

DSM has not previously been used by the City of Los Angeles and so the City wants to do some experimentation before implementing it on Asilomar.

“We are planning to do a pilot study project…[to] help us refine our design,”Louie said, noting the study will begin in summer 2018 and last two weeks. Work will be on Asilomar between Wynola and Arbramar, a block south of the slide.

“[We are] going to install several improvement zones 5-feet wide, 11-feet long and 120-feet deep,” he said.

In each zone, a different type of soil mixing will take place to see which will work best for the Asilomar slide. After a month, which is the amount of time it takes for the concrete to solidify, the team will take samples and determine the best method.

“[This pilot study will] allow the city to collect data to refine and expand our knowledge for future City of Los Angeles projects,” Louie said.

During the study, the city will work on getting permits for slide stabilization. The goal is to start construction in early 2020 and complete it within about 18 months, during the summer 2021.

After the city’s presentation, the meeting was opened for questions.

“I don’t like being part of an experiment,”one resident said. “Is there a way you can make us feel like we’re not just a bunch of guinea pigs?”

Farid Motamed, a consultant for Fugro Consultants Inc., a geotechnical agency working with the city, said: “The objective is to make sure we can get some data to design our final project. We want to make sure we do a test section to get additional data to optimize how this cement gets mixed into the soil.”

Essentially, this is less of an experiment as to whether or not the project will work, but rather what is the best mix of soil and concrete to stabilize the slide.

“The final design will determine how many holes, which pattern and how to inject the cement,” Motamed said. “The pilot study will help us design better.”

A big concern for mobile park residents was that this stabilization might not help them. “It seems the only people getting the benefit are the ones at the top of the bluff,” one resident said.

“[This project] is intended to stabilize the city’s street and public right-of-way,” Louie said. “The project will provide some benefit to the overall stability of the slope, but is not intended to stabilize the entire hillside.”

He said the DSM method would force the landslide to a lower depth, which should stabilize the landslide overall. “It will help to provide some benefit to the overall stability of the landslide which will actually decrease risk to the people in the mobile home parks.”

The estimated cost is between $15 and $30 million, but “The city has not found those funds to date,” Louie said, noting that design plans were previously funded, so his team will continue applying for permits.

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