On a day that many in the Bay Area felt a magnitude 3.9 temblor, work continued last Thursday to re-pipe, rebuild, and earthquake-proof the infrastructure of the Crystal Springs Reservoir.
Crystal Springs serves primarily as a backup water source for the northern portion of San Mateo County and for the City of San Francisco. In a typical year, 15 percent of its water is used by residents; 85 percent is left in storage. The water held in the reservoir comes from the Hetch Hetchy valley near Yosemite, and from local watersheds.
The work that began in early April has a two-fold purpose. The first is to protect this primary source of backup water that would be needed in case any of the unsteady faults in the Bay Area rupture enough to create a crippling earthquake.
Piplines that would ultimately take the emergency water from the reservoir to our taps are old.
"Some of our pipelines and other facilities are aging and need to be addressed," says Maureen Barry, communications manager for the San Francisco Public Utilities Commission. "Many of them were built early in the 20th century and have reached the end of their useful life."
Ironically, the reservoir lays virtually on top of the notorious San Andreas fault.
The second purpose is to add nine feet of height to the dam in Lower Crystal Springs. Doing so will restore the capacity of the reservoir to its “historic levels”, enabling the capture of more summer Sierra runoff in years of abundant snowpack, and conversely, helping to better cope with anticipated drought conditions in dry years.
The San Francisco Public Utilities Commission, which manages Crystal Springs, has employed contractors on the $320 million project through the summer, work that in some cases will continue until 2013.
"Some of these facilities we haven't been able to take out and maintain because we have such a demand for water," says Barry. "Redundancy is now being built in so we can do a better job when something breaks down and still deliver water."
The project work on Crystal Springs is being built to withstand an earthquake of magnitude 7.8, the largest ever recorded on the San Andreas fault.
For hikers, Sawyer Camp Trail - adjacent to the reservoir - has been closed several times during the summer because of the project. Barry says there may be more trail closures coming, as work crews hustle to beat the rainy season.