Construction work should begin soon on the Mosaic and Mosaic Uptown, two buildings that will occupy the middle of the block bounded by 10th and 11th Avenues and 51st and 53rd Streets.

The project, which will include 6 condominium loft apartments and more than 620 rental apartments, will be a development of The Dermot Co., and Archstone-Smith, both of which concluded a deal this week with the city for the project.

The development will incorporate facilities for the Intar and Ensemble Studio Theaters and will be integrated with the adjacent Oasis Community Garden. The Mosaic is the south tower of the 24-story complex and it is expected to be ready for occupancy in 2007.

Fox & Fowle is the architect for the $323.5 million project, which includes development over Amtrak rail tracks. Originally the development was known as Clinton Green and The Dermot Co., which had been selected to develop the site by the city in a joint venture with the AFL-CIO Housing and Building Investment Trusts, had commissioned a very bold and colorful design by Gordon Kipping of G Tects and H. Thomas O?Hara.

The original plans called for 142 below-grade parking spaces, 29,000 square feet of publicly accessible open space, 11,600 square feet of retail space, and 2,950 square feet of community facility space in addition to the theatrical and residential spaces. Twenty percent of the rental units will be low-income apartments. The development will have a health club, a tenant lounge, a media room, a library and a full service caf?.

A low-rise building at the southwest corner of Tenth Avenue and 53rd Street that is part of the project will have a dark fa?ade with very tall and narrow windows that are reminiscent of the very impressive fa?ade of the Porter House on the southeast corner of Ninth Avenue and 15th Street. The lower portion of this building will house theater facilities at the corner and its setback top three floors will house the condominium units.