Plans for a five-story mixed-use apartment building on the corner of West Main Street and Sweezy Avenue were presented for the first time to the Riverhead Town Board yesterday. Georgica Green Ventures of Jericho, the developers of Riverview Lofts on East Main Street and one of two developers designated to do the transit-oriented development across from the Long Island Rail Road station, and the Kulka Group of Hauppauge are proposing the construction of a 58-foot 7-inch tall b