SAN DIEGO -- The U.S. Environmental Protection Agency tentatively granted San Diego a third waiver from a federal law requiring secondary treatment for sewage discharged into the ocean from the Point Loma Wastewater Treatment Plant, the mayor announced Thursday.

The Point Loma plant operates on a waiver to the Clean Water Act from the EPA to treat sewage at what's known as an "advanced primary" level. That process removes fewer solids and other pollutants from wastewater than a "secondary" treatment level.

Upgrading the Point Loma plant to bring the level of wastewater treatment up to the higher standard would cost the city more than $1 billion, a cost that would be passed on to ratepayers, Mayor Jerry Sanders said.

"The waiver will save the ratepayers up to $1.5 billion," he said. "That would have caused our sewer bills to skyrocket unnecessarily."

The five-year waiver -- the third granted the city -- is tentative pending a Jan. 28 hearing by the EPA and San Diego Regional Water Quality Board.

The City Council authorized officials to seek another sewage discharge waiver from the EPA in November to avoid having to pay to upgrade the Point Loma plant.

Sanders sought the waiver after a scientific panel concluded that treated water from the plant, which is discharged more than four miles out into the Pacific Ocean, does not harm the environment.

He was backed by a coalition of business and government officials from around San Diego County.

Local environmentalists, led by San Diego Coastkeeper, have been opposed to the waiver and instead want the city to advance the level of treatment at the Point Loma plant.

Sanders said he is open to working with the environmental community to develop a long-term plan for wastewater, rather than taking up the issue every five years.

"I think we need to plan much further out than a five-year horizon on issues as large as wastewater and water," Sanders said, "so, I would hope that we could come together and decide some type of way to do that so we can benefit the region."