The cost for Gwinnett County’s taxpayer-funded minor league Braves stadium started to exceed the county’s $40 million estimate as early as March — less than two months after the project was announced — and reached as high as $62.4 million at one point, according to internal budget documents obtained Friday under Georgia’s Open Records Act.

A small group of Gwinnett Convention and Visitors Bureau and county officials ultimately decided to make $19 million in changes and upgrades, much of which aren’t required for the Braves to play ball.

By March 31, the Triple-A ballpark had grown to 196,370 square feet, with a $45 million price tag, the records show. A month later, it grew by more than 14,000 square feet and its cost ballooned to $55.1 million.

Gwinnett convention officials, who are building the project for the county, did not announce a final budget of $59 million until Aug. 29, with the stadium construction well under way. The county Board of Commissioners approved the increase Tuesday, with some saying they had little choice because the work was already under way.

Asked why they did not disclose the rising figures earlier, GCVB officials said the price was changing up until late last month. That’s when they said they settled on a figure to put in their contract with their construction management company, Barton Malow Co. of Southfield, Mich.

The numbers went up and down as officials toured minor league baseball stadiums in other states, added features, cut others and consulted the Dallas-based architectural firm of HKS Inc., Barton Malow and the Braves, while rushing to get the stadium open by the team’s baseball season in the spring.

“Anything we let out would have been a hypothetical number,” GCVB Chairman Richard Tucker said. “You wouldn’t call a press conference or issue a press release to say, ‘We have some preliminary bids in and it is tracking higher’ because all the time we were still looking at, ‘What can we eliminate that is in the design?’ And, in fact, all of the design had not even been done. It just doesn’t work that way.”

GCVB and county officials say some of the additional expenses are unavoidable, such as $1 million in increased costs for materials. Others will help save money in the future, including the $1.5 million plan to use highly treated wastewater to irrigate fields and flush toilets, which could save up to 7 million gallons of drinking water a year, GCVB officials said.

But GCVB officials concede the stadium could be built without many of the additions, including the $7.5 million plan to build a concourse surrounding the stadium, erect canopies over some of the seating and the entrance and upgrade finishes. The GCVB is also considering spending more for a high-definition scoreboard, though that amount is not finalized, a convention and visitors bureau official said.

County Commissioner Bert Nasuti said he was “stunned” when he first learned of the additional $19 million cost from GCVB officials last month. Still, Nasuti, who also serves on the GCVB board, said he voted along with fellow Gwinnett commissioners last week to cover that amount with county reserve funds so the ballpark would be “first class.”

“We set a standard here of doing things correctly, doing things upscale, nice, family-friendly, user-friendly, good fan experience,” Nasuti said, adding county officials decided to “stick with that philosophy and build a first-class, state-of-the-art baseball stadium.”

None of the other four county commissioners responded to a message left at their office Friday.

GCVB officials have downplayed the role the Braves played in making changes, saying the team had a seat at the table in discussions but did not have final say on them. Budget documents and e-mails, however, show the Braves communicated directly with the construction management company and proposed numerous specific changes, including substituting a certain type of Bermuda grass for another in the infield.

In a July 7 e-mail from the Braves director of engineering to a Barton Malow official, the team weighed in on many parts of the stadium, ranging from the parking lot lights to the bar and restaurant.

A Braves spokeswoman declined to comment Friday.

Nasuti said the stadium must adhere to certain minor league baseball standards, so it makes sense for the Braves to be directly involved, even if county taxpayers are footing the bill for much of the ballpark.

“If a landlord is building a facility for a specific tenant… I don’t think it is unusual at all for the tenant to have some input in how it is being built,” Nasuti said.

Barton Malow will be paid about 5 percent of the “hard” costs for the stadium, said Preston Williams, the GCVB’s point man for the construction project. Williams said last week that he could not immediately say precisely how much more Barton Malow will be paid based on the increased cost of the stadium. The AJC requested a copy of Barton Malow’s contract last week.

Also among the correspondence the AJC obtained under the Open Records Act was an Aug. 30 e-mail a public relations firm sent Nasuti. In the e-mail, the Hayslett Group, which has been hired by the GCVB, offers a statement Nasuti could use to respond to questions from the public about the stadium cost increases.

“Throughout the design process, very deliberate decisions were made that are impacting the scope of the project and, in turn, the final budget,” the statement reads in part. “Those decisions have focused on creating a world class facility with a greater attention to the overall fan experience and improved environmental standards and practices.”

Meanwhile, the stadium’s foundations are complete and construction is slightly ahead of schedule, according to the GCVB, and the ballpark is expected to open by April.