Though the 89-year-old Prospect Street Bridge itself will stay in service until the summer, some preparation for its $3.5 million replacement has already begun. Work began Monday with the closure of Canal Street between Lock and Prospect Street as the contractor, C.J. Fucci, began working on the utilities and pilings. The Prospect Street Bridge proper, which spans the Farmington Canal, will close in July or August and is scheduled to reopen in June 2010. The project follows the replacement of two sister bridges over the canal trail on Hillhouse Avenue and Temple Street. The replacement of all three bridges was part of a $10 million development agreement signed in October 2006 between the city and the University.