The Austin City Limits Music Festival will span two weekends next year.

The City Council agreed Thursday to let city staffers negotiate and sign a deal with C3 Presents, the festival's producers, to extend the popular event by an extra weekend, starting in fall 2013.

In exchange, C3 has offered to donate money for improvements to city parks, including Auditorium Shores.

C3 over the past several years has given millions of dollars to the city and the nonprofit Austin Parks Foundation to upgrade Zilker Park's Great Lawn, where the festival is held, and other Austin parks. It has also paid city rental fees required of any groups that hold big events in city parks.

C3 officials have said they don't intend to move the music festival to Auditorium Shores that but they have produced other events there, including the Austin Food & Wine Festival, and have grown concerned about the state of that heavily used park space.

The 2013 ACL Fest will take place Oct. 4-6 and Oct. 11-13.

Mayor Lee Leffingwell removed part of the proposal before Thursday's vote that would have allowed up to five extra days of events at Auditorium Shores once improvements are made. The city's limit is 25 days of events a year at Auditorium Shores.

Neighborhood groups near Auditorium Shores were worried that the idea of extra events hadn't been vetted thoroughly to consider the parking, traffic and parking effects.

Thursday's council vote was unanimous. It's now up to city staffers to negotiate the details of the C3 deal, including how much money the company will donate.

Austin parks Director Sara Hensley has said that her department — which has faced stagnant or reduced budgets over the past few years — does not have the money to overhaul Auditorium Shores. But an infusion from C3 could pay for new sod, a new irrigation system, new restrooms and maybe a food concession space, she has said.

A tally provided to the American-Statesman by C3 in July showed that the company has donated nearly $6 million to the Austin Parks Foundation and paid the city more than $1.1 million in fees and other event expenses since 2006.

Contact Sarah Coppola at 912-2939