Cities may store water in aquifir

San Francisco and Daly City are moving toward reaching a formal agreement on the cooperative use of an underground aquifer to store water for use during a drought or an emergency, officials announced Friday.

The groundwater basin, which runs beneath San Francisco, Daly City, Colma, South San Francisco and San Bruno, stores enough water for 150,000 households for a year. It has historically been used by San Mateo consumers as a regular source of their drinking water supply.

Two years ago, a pilot program was launched in which the San Francisco public utilities agency, which runs the regional Hetch Hetchy water system, allowed Daly City, San Bruno and South San Francisco to use its surface water rather than pump water from the basin. That provided extra water storage capacity in the aquifer, which can be tapped when times get tough.

Now, plans are in the works to expand the program. The City Council in Daly City gave the go-ahead this week to enter into negotiations with San Francisco to formalize the agreement. Next, San Francisco hopes to win approvals from South San Francisco and San Bruno.