SAN DIEGO -- The City Council on Monday authorized a mailing to San Diego residents detailing a proposed utility rate hike that officials say is needed to offset an increase in the cost of imported water.

Under the proposal, the average residential water bill in San Diego would rise by about $1.40 a month, beginning in January.

The City Council has set an Oct. 8 hearing to consider the increase.

In advance of that hearing, the city is required to notify residents by mail about the proposed utility rate increase. The mailing will include information on how residents can file a formal protest.

According to Mayor Jerry Sander's office, the increase is needed to counter an 8 percent rise in the rates charged by the San Diego County Water Authority, the agency from which the city buys 90 percent of its water.

The hike would be on top of utility rate increases already approved.

At the mayor's urging, the City Council agreed in February to increase the city's water and sewer fees annually over the next four years to begin to address a $1.4 billion backlog of mandated infrastructure projects.

The notice will also outline a rebate that will temporarily save sewer customers in the city about $3.25 on their monthly bills, starting in November. The savings will be offset by an increase on May 1 of next year.

The rebate stems from the settlement of a lawsuit filed more than two years ago by Michael Shames, executive director of the Utility Consumers' Action Network. Under the terms, San Diego must return $35 million to sewer customers who were incorrectly billed between 1994 and 2004.