Murky, foul-smelling water could flow through millions of Bay Area faucets until the middle of next week because a major water agency continued to draw from an algae-tainted reservoir for a week after the bloom was detected.
The San Francisco Public Utilities Commission says the blue-green algae growing at its Calaveras Reservoir near Fremont, the largest drinking water reservoir in the Bay Area, does not pose any health hazards, but it decided on Tuesday to shut off the spigots Wednesday following a slew of complaints.
“It smelled and tasted like potting soil,” said San Francisco resident Jesse Taggert, who said the problem has come and gone in recent days. “I thought it was that my Brita filter was old, but then I was in the shower and I got a whiff of it.”
Taggert is one of roughly 2.5 million customers in San Francisco, the Peninsula and the southern stretches of the East Bay who use water sold by the SFPUC.
The SFPUC detected the algae bloom a week ago, according to the agency's water quality manager, Andrew DeGraca, but continued pumping water from the reservoir to help run down the water level to prepare for construction of a new dam wall slated to begin in the winter. The reservoir has been operating at reduced capacity since the state deemed the dam seismically unsafe in 2001.
“Normally, if we see a small bloom at a reservoir we will take it out of service,” DeGraca said, but “we have to reduce the level.”
The algae-laden water has been snaking through a labyrinth of pipes, first drawing complaints from East Bay and Peninsula residents before reaching San Francisco faucets in recent days.
The SFPUC discovered early Tuesday afternoon that the bloom had continued to grow. That finding, coupled with the continued complaints, prompted the agency to announce that it would take the reservoir offline Wednesday. The water will be treated with the chemical sodium percarbonate, which will kill the algae and improve the water's smell and taste, according to SFPUC spokesman Tyrone Jue. The treatment is expected to take a day or two, he said.
Blue-green algae often blooms in warm conditions, generally fed by nutrients that run into water from farms and sewers.
Jue said such blooms "are sort of routine" in the SFPUC's reservoirs. "The only complicating factor is the Calaveras Dam project," he said.
Calaveras Reservoir is one of six major reservoirs that the SFPUC owns and operates. While it is offline, Jue said the agency will use the San Antonio Reservoir as a backup and does not expect water shortages.
Water drawn from the Calaveras Reservoir prior to Wednesday’s shutdown will continue to flow through the SFPUC's pipes for up to a week, according to Jue. “There is no public health issue with the quality of our drinking water,” he said.
Customers can remove traces of the algae by filtering their water. Refrigerating the water could help improve its flavor.
Federal law requires most water agencies to filter their water before selling it, but the SFPUC obtained a waiver because 85 percent of its water is drawn from Yosemite National Park's Hetch Hetchy Reservoir, which is fed by pristine snowmelt.
Instead of filtering its water, the SFPUC uses an array of ultraviolet lights that kill germs responsible for stomach bugs.