MARBLEHEAD – The Planning Board has unanimously approved developer Heidi Wattendorf?s downtown YMCA project, the town?s first Smart Growth development.The approval comes after months of meetings.The building will contain 17 condominiums and a commercial space on the first floor.Board members allowed Wattendorf to include a commercial space that is smaller than the law requires, 9.2 percent of the first floor rather than 25 percent of the first floor.Wattendorf and her lawyer, Attorney Paul Lynch, originally wanted to build without any retail space, but struck a compromise with the planners when neighbors protested the developer?s proposal for underground parking, which could require blasting.So now the first floor will contain indoor parking and a commercial space that faces Pleasant Street.