Lilburn will need extra innings to complete a deal with a California-based operator of large softball facilities.

The Lilburn City Council approved Monday a six-month extension to reach an agreement with Big League Dreams. The move gives city officials and Big League Dreams until September to hash out details on a plan to finance, develop and construct a massive complex near the intersection of U.S. 29 and Indian Trail Road.

Big League Dreams "has a track record and they've been mostly successful," said Lilburn council member Tim Dunn. "I think it's important for the city. Nobody else has brought anything else to the table to attract other businesses here."

The extension also disallows Big League Dreams from entertaining any other proposals or entering into negotiations with another city or area within a 20-mile radius of Lilburn and all of Cobb County.

Last month, the Gwinnett County Board of Commissioners agreed to sell a 38-acre property -- a former water treatment facility -- to the Lilburn Downtown Development Authority for $1.31 million, its appraised value. The property is slated to become the site of the Big League Dreams facility.

Lilburn Mayor Johnny Crist has said the athletic complex could open by June 2013. City officials are working with Big League Dreams to develop the project with private money.

In 2010 Lilburn announced plans for a baseball, softball and soccer venue on the property. It would host Little League baseball, adult softball tournaments, athletic camps, concerts and weddings.

City officials believe the nearly $20 million park could make Lilburn a destination for visitors and be a catalyst for economic growth. Currently, the city of 11,500 has no hotels, movie theaters or fine dining restaurants and struggles with an aging infrastructure and transient population.

"What the [Big League Dreams facility] does is attract other things," Dunn said. "People will need places to eat, to stay, to gas up their car."

An appraisal done by real estate consultant Carr, Lawson, Cantrell & Associates valued the property at $1.31 million in its current condition. If Gwinnett demolished the treatment plant and performed a needed environmental cleanup -- work estimated to cost $690,000 -- the firm concluded it would be worth $2 million.

The Lilburn Downtown Development Authority offered to pay $1.31 million for the property as is. Crist has said the city will recoup the purchase price from the private developer.

Lilburn council member Thomas Wight was skeptical of the assessment and the city's claim that the project will be privately financed.

"I have been opposed to this from the get-go," said Wight, who nonetheless cast a vote approving the extension Monday. "You try and buy [38] acres of prime industrial land for [$1.3 million]. Someone cooked the books to let a private developer have it for that much."

Wight said his research of property values shows the land was worth significantly more, without going into specifics.