Study blames water-saturated soil for San Pedro landslide

A major landslide along a seaside cliff in San Pedro that could cost up to $70 million to repair was triggered last year by soil saturated with groundwater, a new study shows.

A build-up of water was largely blamed for the November collapse of a stretch of Paseo del Mar after a heavy weekend rainstorm, according to an 800-page report from Shannon & Wilson Inc., a geotechnical and environmental consulting firm.

The failure took out 600 feet of the scenic road and carved a gaping chasm into the 120-foot-high coastal bluff, where the ground had been creeping seaward for several months.

“Precipitation, irrigation, and to a lesser extent, coastal bluff erosion may have contributed to the development of the White Point Landslide,” according to the report, which was released Monday.

“Residential development in the area may have also contributed to the landslide because of its influence on groundwater infiltration,” the report noted.

Officials said homes in the area remain safe, although additional measures are needed to further stabilize adjacent land in the White Point Nature Preserve before the next rainy season begins.

There is still some concern because of a continuing buildup of groundwater in the western and northern areas surrounding the slide.

Groundwater levels, however, have leveled off on the east side, which is the closest to homes, and ongoing monitoring has not recorded any significant land movement since Nov. 20.

“It’s very unfortunate. Paseo del Mar is an historic road,” said Los Angeles City Councilman Joe Buscaino, who represents San Pedro. “Our immediate goal is to look for short-term solutions.”

Such measures, which are estimated to cost $6 million to $7 million, include drains to remove water from the landslide area, ways to anchor and brace the ground, detours for motorists and traffic circles at the ends of the collapsed area. About $1.5 million in funding has been identified so far.

The long-term solutions call for grading portions of the slide area and various plans to rebuild and reinforce Paseo del Mar. The most expensive option would require building a new bridge — a project that would cost an estimated $62 million and take up to four years to complete.

Buscaino said the effort to find a long-range solution should involve the community, but building a consensus might be difficult. At a meeting Monday night at White Point Elementary School to discuss the slide, the 70 or so people on hand were divided on the options for Paseo del Mar.

dan.weikel@latimes.com