Following the news last week about a $2+ million house that had to be demolished immediately, by order of the city, because the hill it was sitting on in SF's Sherwood Forest neighborhood was rapidly on the move and threatening other homes, further investigation has shown that a broken water main, and not our recent rainstorms, may be the blame. As CBS 5 reports, neighbors shot cell phone video and photos of a broken, eight-inch water main just up the hill that has been leaking water into the soil for an unknown length of time.

Says Ronald Martell, the homeowner who just purchased the now demolished home in October and whose family had still not moved in, "This isn't El Nino. There's a significant source of water that saturated the entire hill and up behind our hill."

Another neighbor emailed SFist last week with hints about a possible problem that may be linked to this water main. Resident Frank Gibbs explains:

Since being built 40-60 years ago, the homes on Casitas Avenue have stood strong through many greater deluges than this year's El Niño. But that was before the city dug a four-story deep hole on the same street (just 40 yards uphill from the endangered homes) to install a new underground cistern — done just last year in their zeal to spend federal TARP funds and give the Fire Department a juicy slice of the pork.

The city has about 200 underground cisterns that supplement the firefighting capacity of trucks and hydrants, and this topic came up two years ago following that big fire in Mission Bay and the difficulties putting it out.

The cistern expansion project Gibbs mentioned involves 30 new cisterns, of which this one may have been part of Phase 1 described here by the SF Public Utilities Commission. This also involves the installation of new pipes to access the water in the cisterns, and "the current system includes over 135 miles of underground pipelines and tunnels dedicated to emergency firefighting throughout the City."

Gibbs adds, "This needs to come to light fast. If the effect of the new underground equipment on local rainwater drainage is not reassessed competently, we will not know when the next series of homes is going to be threatened."

Mr. Randall's house at 256 Casitas Avenue was demolished on Thursday and Friday after neighbors observed it appearing to crack away from its hillside foundation and begin moving significantly away from the street.

The silver lining for him, now, is that it may be the city's and the PUC's insurance that will have to cover this, and not his own. The investigation is, obviously, ongoing.

Previously: House In Sherwood Forest Gets Demolished As Sliding Hillside Threatens Several Homes