SF landslide that threatened homes appears more man-made than natural

SAN FRANCISCO (KTVU) - One house sacrificed, but five others in the Mount Davidson neighborhood of San Francisco, will survive a landslide that appears more man-made than natural.

Over the weekend, public works crews discovered and repaired a rupture in an eight-inch water main under Casitas Avenue.

It may explain why a $2 million dollar home was sliding so perilously it had to be demolished. Now, residents wonder why it took so long for the city to find and fix the leak.

"I was there when they opened it up, and it was like a river under the street," homeowner Ronald Martell told KTVU.

Martell had recently purchased the home, but hadn't yet moved his family in.

Now it's a vacant lot, torn down by emergency order because of the risk it might slip down the hillside onto homes below it.

Martell believes the ongoing water leak caused the landslide.

"We'll let the experts come out with their reports, but to me it's pretty conclusive," he told KTVU Monday afternoon, "and we were the canary in the coal mine."

The pavement on Casitas Avenue shows where holes were bored for water testing, but abandoned without results, after residents complained about spouting and pooling water.

Only after Martell's house was destroyed last Thursday, did the leak detection effort became more determined, resulting in the rupture's discovery.

"We are still under investigation for the cause," Tom Hui, Director of SF. Building Inspection told KTVU, "but if the homeowner wants to rebuild, we will help him to expedite the permits, as soon as we have stabilized the hill, and make sure everything's okay."

Even with the leak capped, the hillside remains saturated, and the soil is still creeping.

One neighbor next door to Martell must make extensive repairs to his foundation. His yard and retaining wall are completely torn up by a bulldozer.

"No, this was not El Nino," project manager Jim Joyce told KTVU, " this is what happens when no one really knows what's going on and water keeps flowing. This is the end effect of too much water."

Martell is resigned to the loss of his family home, and figures financial responsibility will be sorted out in time.
He hopes to rebuild, and feels optimistic now that a root cause is known.

"We were able to save all the homes on the hill," observed Martell, "and that's the silver lining here, we paid the price, but by doing so, saved all the other homes."

There's another twist: several months ago PG&E dug into the street to lay a gas line alongside the water line, raising the possibility utility crews unwittingly damaged the pipe.

San Francisco's Public Utilities Commission plans to test water from the hillside, to see if it is natural groundwater, or contains chemicals common to the public water system.