SCHENECTADY — Site plan review for Mohawk Harbor, Galesi Group’s $480 million development to revitalize the old Alco site, will start at the end of the month. The city Planning Commission will hold a special meeting March 31 to review the master plan for Mohawk Harbor, which includes housing, a casino and a 50-slip harbor. The meeting is scheduled for 6:30 p.m. in Room 110 of City Hall. The plan includes a 151,000-square-foot casino with an adjacent six-story, 109,000-square-