A sewer pipe burst under the pressure of a huge downpour Monday morning creating a sinkhole that swallowed a costly home in San Francisco’s swank Sea Cliff district.
Two other houses, a three-story home and an old wooden classic townhouse that once belonged to photographer Ansel Adams, teetered on the brink of destruction Monday.
Ten other houses and a dozen families were evacuated, and all power and utility service to the neighborhood was cut off.
The area is one of San Francisco’s best, and includes both Sea Cliff and West Clay Park. The wrecked house, on the edge of the Presidio, was described as a “grand secluded mansion” when it was offered for sale two years ago for $2.6 million.
The sewer that caused the accident was a 100-year-old brick storm and sewage tunnel that runs under 24th Avenue.
The tunnel was being connected to a new sewer project - and some neighbors claimed Monday that the city project had contributed to the collapse.
The problem began at about 3:30 in the morning, during an intense downpour that dumped more than 1 and 1/2 inches of water on the city. The sewer tunnel, which is 6 feet in diameter, gave way at the dead end of 24th Avenue near West Clay Street.
The water suddenly began pouring down the slope, which is largely sand, undermining the houses. Authorities were alerted and immediately began calling people.
Not long after dawn, the 80-year-old house began tilting, the timbers creaking and snapping.