The Sunset Reservoir South Basin which delivers drinking water to 43 percent of The City, is empty for the first time since 2016.
But not to worry.
The 33-foot-deep, 270 acre-feet reservoir has been drained for the past two months as part of a maintenance and inspection operation by the San Francisco Public Utilities Commision and will be operational again by around mid-August.
The reservoir is “periodically cleaned every few years,” in an operation that involves around five SFPUC employees, according to Steve Ritchie, 64, Assistant General Manager for water at SFPUC.
“The work is about checking on sampling points, inspect the structure, and clean up the valves where the water is coming from,” said Bill Teahan, SFPUC’s Operational Manager.
An empty reservoir is an unusual sight, but Teahan has become accustomed to it.
“I think I’ve seen every one of these over the 40 years I’ve been working here,” he chuckled.
The Sunset Reservoir South Basin contains 87.3 million gallons of water pumped from the Hetch Hetchy Reservoir and the San Andreas and Crystal Springs reservoirs in San Mateo County, and delivers potable water to 43 percent of San Franciscans.
The reservoir takes about a week to fill but can take in up to 50 million gallons a day in the case of an emergency. It is normally filled only up to 27 feet, but can go up to a maximum of 31 feet.
While two recent earthquakes in Southern California — a 6.4 magnitude and a 7.1 magnitude near Ridgecrest on last Thursday and Friday — generated concern in San Francisco, Ritchie said he is confident in the City’s ability to handle incoming earthquakes or fires while the reservoir is shut down.
The City has multiple backups for water including fire hydrants, 229 cisterns and two other reservoirs within city limits in the case of a fire or earthquake.
“We have many programs to respond to any given emergencies and disasters,” said Lt. Jonathan Baxter, a spokesman for the San Francisco Fire Department.
The next reservoirs to be cleaned will be Summit Reservoir followed by Merced Manor.