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Community threatened by sliding hillside
A community in Marin City is on edge because a hillside above them is starting to give way. A co-op has been protected by a retaining wall for years, but the barrier has seen some damage.
MARIN CITY, Calif. - NASA and US Geological Survey researchers have documented a "growing landslide crisis" in California. Climate extremes have accelerated the occurrence of slides even though there were landslides even before humans came here, largely due to steep terrain and more recent geological formation.
A national model
Marin City may actually be a national model for dealing with climate change because it has two major threats: sea level rise and landslides. During the pandemic, a series of atmospheric rivers caused a 70-year-old wooden retaining wall to fail in two spots: a total of some 40 feet.
Fortunately, it did not slide into the 48-unit Oak Knolls Cooperative.
"Our soil is not alluvial mud. Our soil is rocky clay and that's been a bit of our advantage. These trees, they help hold; the roots are holding the soil," said Curtis Finley, Oak Knolls Co-op VP.
Absent a permanent solution, tarp coverings have kept them stable. But last Christmas, another section fell away, indicating the entire wall might fail soon.
Water is relentless
The land above the slide is owned by a county agency, the Marin City Community Services Division.
"We're trying to come to a solution with the county, with the CSD and with Oak Knolls so we can have the wall repaired," said Finley.
The residents and the district note that the wooden wall stood 70 years without incident, but the climate has changed significantly.
"It's pretty new and with the atmospheric river storms we've been having and stuff lately, it's just a lot of water for the hillsides to absorb at one time," said Donald Parker of the Marin City Community Services District.
"Under complete, catastrophic situation, where you have five days of torrential rain, then all bets are off," said Finley.
Water is relentless. "It will go down in the ground, and it will start digging, and it will come out at the place of least resistance and all that hydrostatic pressure; it starts to create underground streams. And, when it does that, all of a sudden, it will just let that whole hillside slides out," said Parker.
Potential loss of homes
Then the wall and the homes could be lost in seconds. This one needs a permanent fix. They're gonna have to come up with a fix that won't slide or blow out any time soon," said Parker. "Can we work and make something reasonable that we can all afford?" said Finley,
It's likely a permanent repair could overwhelm the residents and the district. So, the hunt is on. "But there are grants and stuff out there, state, local and Federal and that's what they're gonna need to get this thing dealt with," said Parker.
But the clock is not ticking just here. Any community with this topography is vulnerable.
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