Mount Soledad landslide devastates area
Nine homes were destroyed and three people were transported to the hospital for medical aid following a devastating landslide which occurred on Wednesday morning, Oct. 3, involving Soledad Mountain Road and Desert View Drive on Mount Soledad in La Jolla.
Maurice Luque, San Diego Fire-Rescue spokesman, said the tragic incident occurred at 8:57 a.m. He said 11 fire engines, two fire trucks, about 90 firefighters and 40 police officers responded to the scene. One-hundred-and-eleven homes in the area were evacuated and are being evaluated for safety.
“Gas mains, water lines and sewer lines were broken,” said Luque. “Nine houses were red-tagged: People can’t live in them anymore. Eight others were yellow-tagged, meaning residents only have temporary access to them during the day, they can’t live in them. Another 44 homes were temporarily yellow-tagged: They’ve got utilities issues - broken gas or sewer lines, no electricity - and they can’t be inhabited until those problems are fixed.”
Council President Scott Peters said, “When something like this happens, our first concern is the effect on the families, the tremendous dislocation for people. It’s more than an inconvenience for people. . . I, my colleagues on city council, the Mayor and the entire city will be fully cognizant of really trying to do all we can to lessen the burden.”
Mayor Jerry Sanders called for a state of emergency, which the City Council ratified, in order for Mount Soledad homewoners to be eligible for state and federal funding.
A shelter was set up with food and water at Kate Sessions Park. Another shelter was made available at La Jolla High School.
Although no one was hurt in the landslide, Luque added two residents in the area with chest pains received medical aid following the incident. There was also a traffic accident which required one victim to be transported to the hospital. SDG&E reported power was cutoff to 2,400 homes in the area immediately following the landslide.
Senior engineering geologist and deputy city engineer Rob Hawk said that the eight houses immediately affected were delivered letters the evening before at 7:30 p.m. recommending that they not sleep in their homes.
The cause of the landslide is under investigation.
There is a history of soil instability in the Mount Soledad area. A landslide that destroyed seven homes under construction occurred in December of 1961. In 1989, a landslide occurred on the 5600 block of Desert View Drive, and in 1994 a landslide affected the canyon below the 5800 block.
Geologist and deputy city engineer Rob Hawk said, “This is a geologically active area. Mt. Soledad is upthrust along a fault. At the time this area was developed in the late 1950’s, most of those features weren’t recognized.
“The grading techniques used at the time we would not allow to be done today. They have created landform geometry that isn’t as stable as we would like it to be. We have had past failures in the area. This one seems to be where we’ve got some geologic conditions that allowed a large block of land to slide off a hill, much like a book off a tilting bookshelf. I have no knowledge of water that was introduced into this that would have triggered the slide.”
The city was informed of pavement cracking by residents of Soledad Mountain Road in July of this year. City geology and field engingeering staff tested the area in mid-July, when water and gas leaks indicated earth movement. In September, after continued cracking began forming a pattern consistent with landsliding, the water line along Soledad Mountain Road was highlined (replaced with an above ground pipeline) to avoid impacts due to earth movement. The speed limit along Soledad Mountain Road was reduced to 25 mph from 35 mph to reduce vibration, and the city hired a geotechnical consultant to evaluate conditions and provide repair design.
“With these types of slides, the worst movement tends to occur in the early hours or days,” said Martin R. Owen, a geotechnical engineer in San Diego who had been retained by two residents whose homes were involved in the landslide to study soil instability in the area. Then it will slow down and come to a creeping stop, sooner or later. How long it will take to stop, at this point, is anyone’s guess.”
Owen said the entire Mount Soledad area is potentially unstable because of geological conditions, because these homes are not far from the Rose Canyon earthquake fault.
But proximity to an earthquake fault is not the only factor contributing to the danger of landslides on Mount Soledad. Said Owen: “The geological formation underlying these homes is Ardath shale, a week sedimentary claystone formation that is susceptible to landslides.”
Owen added groundwater intruding into soils can trigger landslides. He noted there have been recent problems in the area involving water. “There have been a number of water pipe leaks in the street in Mount Soledad Road,” he said. “The city has been out there since August fixing those leaks. The water pipes were raised and put above ground so they wouldn’t have any more leaks.”
Asked whether water was a factor in causing this landslide, Owen replied: “This is a classic chicken and the egg scenario. We don’t know which came first. Was there a weakening in the ground which caused water pipes to rupture? Or did the rupturing of the pipes cause the landslide to occur?”
Owen, however, disagreed with speculation that people watering their yards in the area likely contributed to the cause of the landslide. “That is a possibility,” he said. “Any source of water, if there is enough of it, may trigger a landslide. But there could have been other sources of water.”
Steve Schreiner of the San Diego law firm of Solomon Ward Seidenwurm & Smith, said he litigated a case in the exact same area of La Jolla in 1992-93. He said a homeowner on the western side of Desert Mountain Drive was building a home at that time on the steep slope, and was doing a lot of excavation work and pouring a lot of concrete. “What happened was the excavation along with the natural topography, some fairly heavy soil on top of a clay seam prone to slippage, combined with leakage of water from a city water main to cause the Desert View slope to destabilize,” Schreiner said.
Schreiner said that construction work 15 years ago was alleged to have impacted the adjacent home of Gary and Karen Green, who became his clients. “Their dream home was up there and all of a sudden their walls were cracking, the floors were tilting and the doors were out of kilter,” said Schreiner, who added he filed litigation against both the city and the neighbor following damage to the Green’s home. The end result, Schreiner said, was the city, ultimately, was dropped from the suit, and the Greens were awarded $800,000 for damage to their home.
“This sure sounds similar in a lot of ways to what we were dealing with 15 years ago,” Schreiner said.
Schreiner believes the latest landslide in the area will have an adverse impact on insurance values. He said: “From a homeowner’s insurance standpoint, I just don’t see why any carrier would be willing to write coverage for homes in that area. There’s just an inherent instability on those slopes stemming from heavy soil over clay. They (geologists) call that an ancient landslide. It’s historical. For hundreds, if not thousands, of years there has been slope instability there. There was a slide in 1961 when there were not very many houses there. Certainly, those homes weren’t built out to the edge the way the Desert View and Soledad Mountain houses are now.”
Residents who need to get animals out of Mt. Soledad homes should call (619) 236-2341.
Residents in affected areas should call (619) 570-1070.