MountainOne Financial Partners in North Adams plans to unite its banking operations under a single charter next year. 

Following the combination of Hoosac Bank and Williamstown Savings Bank operations earlier this year, the company is bringing its South Coastal Bank unit into a common MountainOne Bank charter for all three banks. 

The banks will retain their current identities and independent community focus while operating as divisions of MountainOne Bank, the bank said in a statement. The integration is subject to regulatory approval and is targeted for completion in the third quarter of 2013.

"We will preserve the heritage of three fine institutions," Thomas S. Leavitt, president and chief executive officer, said in a statement. "We are fulfilling a commitment to a common platform that will drive efficiency and allow us to focus our programs on outstanding customer care." Leavitt will serve as CEO of the unified bank and South Coastal Bank CEO Robert Fraser will become chief operating officer.

The action to consolidate Hoosac Bank, Williamstown Savings Bank – a division of Hoosac Bank – and South Coastal Bank under one bank charter was approved by the board of directors of each of the banks and by MountainOne Financial Partners. Formal applications will be filed with the Massachusetts Division of Banks and the Federal Deposit Insurance Corp.