Cobb commissioners are expected to take a step next week toward filling two key roles in building the new Atlanta Braves stadium — a construction management firm that will oversee all aspects of the development, and a project manager to represent the county’s interest during construction.

It is unclear if the cost of hiring a project manager will be part of the county’s $300 million commitment toward stadium construction, or if that will be an added expense.

Commissioners on Tuesday will be asked for approval of advertising to solicit companies for both positions on the project, which is estimated to cost $672 million and is scheduled for completion in time for the 2017 season.

The construction manager will be the lead contractor, and will work for both the county and the team. A committee of people from both organizations will make the selection.

Meanwhile, the project manager will work only for the county and will report to commissioners.

Commission Chairman Tim Lee said the development agreement between the county and the team, which is currently being negotiated, will address whether the cost of the project manager is included in the county’s $300 million. Lee said he hopes to have signed contracts with both firms in May.

“Today, I’m including that (project manager) as part of the $300 million, but that is subject to change,” Lee said, adding that the project manager will play a crucial role for taxpayers because the firm will “make sure the money we have invested is (spent) correctly, (and that) we do everything we possibly can to deliver the project on time and on budget.

“We want to make sure our interests … are represented,” Lee said.

Lance Lamberton, president of the Cobb Taxpayers Association, said he thinks the cost of project management, which could be millions of dollars over the three-year construction period, is an obvious part of the county’s investment in the stadium.

“He should know the answer to that question,” Lamberton said of Lee. “The fact that he doesn’t just shows very lackadaisical management.”

In a memo from earlier this month, the county said the project manager’s role is to “protect the county’s interests, to coordinate the review of transactional documents with outside counsel and to provide construction oversight and management services. The project manager will serve as the county’s representative on all matters related to construction of the” stadium.

The memo said the construction manager must be a firm of “nationally or internationally recognized” stature. Its role will be to “build the (project) in accordance with the design criteria, plans and specifications prepared by the” project architect.

Commission members Helen Goreham and JoAnn Birrell did not respond to telephone messages seeking comment.

A Braves spokeswoman said it is unclear who from the Braves organization will help select the construction manager. She referred other questions to a county spokesman.