Atlanta will get a 13-year extension on sewer system upgrades required by federal regulators, according to a proposed agreement between the city, Georgia officials and federal regulators.

Top city officials said the long-sought extension will provide relief to Atlanta residents by allowing the city to complete the remaining work more frugally. The targeted completion date would be pushed out to the summer of 2027, instead of the summer of 2014.

"Very, very exciting news for the city," said Natalyn Archibong, chair of the City Council's utilities committee.

A landmark 1999 consent decree required Atlanta to eliminate sewage overflows into rivers and streams. The city says it has already spent $1.5 billion and plans to spend another $445 million to make up for decades of neglect that allowed Atlanta's streams and rivers to be fouled with sewage.

It is unclear how much money the proposed agreement will save Atlanta residents. Atlanta's water and sewer rates are slated to hold steady for the next four years after repeated increases.

Atlanta residents shoulder some of the heaviest water and sewer bills in the country.

"The consent decree extension will allow the city to continue vital infrastructure repairs that reduce sewage overflows and protect our natural resources and drinking water," Mayor Kasim Reed said in a statement. It "enables the city to complete its work without putting any further burden on ratepayers."

Sally Bethea, founding director of the Upper Chattahoochee Riverkeeper, said the watchdog group is supportive of Atlanta's request for extra time. The Riverkeeper sued Atlanta in the mid-1990s over rampant sewage spills, spurring the federal government to step in and push Atlanta to clean up its waterways.

"The city has done a very good job in meeting the requirements of the consent decrees," Bethea said Monday. She noted that the city has a plan to reduce the volume of sewage spills by 99 percent, compared to when the consent decree took affect, by the original 2014 deadline.

"We feel comfortable with an extension, should it be approved," Bethea said. "The city has been under an aggressive schedule to meet the 2014 deadline, and they've exhibited good faith throughout the process. They've shown measurable results."

A spokesman for Georgia's Environmental Protection Division declined to comment, deferring to the U.S. Environmental Protection Agency. An EPA spokeswoman said in an email that the agency expects to reach an outcome "that is fair and reasonable to the people of Atlanta, and that will continue to benefit human health and the environment."

History: By the time the city reached an agreement in 1999 to repair decrepit sewers and clean up its waterways, accumulated fines and penalties from state and federal regulators had reached a combined $20 million, according to a Georgia State University case study. In 2010, Atlanta applied for an extension to make the remaining repairs ordered by regulators.

What happens next: The agreement is subject to approval of Atlanta's City Council. If the Council and all the parties approve it, the documents will be filed in U.S. District Court. A public comment period will follow. After gathering and evaluating the public comments, federal regulators will determine whether to seek court approval.