Wescom Credit Union said Wednesday that San Diego-based Great American Credit Union will merge into it.

The move will nearly double Wescom’s presence in the San Diego region.

As part of the agreement, Wescom of Pasadena said it will maintain and operate all four Great American branches in the San Diego area and will offer employment to all existing Great American employees.

The merger is expected to be completed by Dec. 1 if it is approved by Great American’s members.

Wescom operates more than 50 branches in the Southern California region.