Casitas Hillside Update
Revised February 2, 2016
A house on Casitas was demolished starting on Friday, January 29th, due to instability of the hillside underneath it. It had separated from the sidewalk by almost a foot, and was in danger of falling on the houses below. The hillside underneath the home appeared to be saturated with water.
The following update is from the San Francisco Department of Building Inspection (DBI) and the San Francisco Public Utilities Commission (SFPUC).
Actions Taken by the SFPUC
Auxiliary Water Supply System Cistern
- DBI received geotechnical reports from the 5 adjacent property owners who received notice last week. Based upon these reports, DBI has concluded there is no imminent hazard to the properties at this time
- Both agencies will continue to work closely with geotechnical experts to monitor and track slope movement of the area.
- Permits will be expedited once slope stabilization is achieved and property owners begin to make repairs.
- The search for a cause of the ground movement is continuing and will take additional time and analyses.
An emergency water system cistern that was constructed at the corner of Landsdale and Casitas was thoroughly investigated. It is highly unlikely that the cistern is a cause of the landslide movement.
- The water levels within the cistern have not decreased
- There are no signs of leaking water around the cistern
- Construction for the cistern was completed in October, and the cistern went through thorough hydrostatic testing for leaks and weaknesses before it was put into service.
- In addition, thorough geotechnical investigations were done as part of the design for the cistern.
- The cistern is a seismically designed structure whose purpose is to survive a major earthquake.
On Saturday, leak detection crews spent hours searching every inch of pipe on the street in search of a leak. After hours of searching, crews identified one leak on the 8 inch main approximately 230 feet, or four houses away, from the demolished home. The leak was repaired that evening.
SFPUC crews will also perform thorough inspections of its sewer lines in the area to ensure their integrity.
The precise cause of the instability of the hillside is under investigation and not known at this time. The SFPUC is working closely with DBI and other City and County agencies to review historical groundwater information and the geology of the hillside.
We will continue to keep the community updated on any developments and next steps.
If you should have any questions, please call 415-554-3289 or contact us via email.