Bids for sophisticated tunneling work on two New York City megaprojects will go out later this year. One contract, worth up to $1 billion, is for an extension of an existing subway line under a request-for-proposals process, not a low-bid process, says Philip McGrade, a Metropolitan Transportation Authority program manager. A low-bid contract for work on the first $3.8-billion segment of the planned $16-billion, 8-mile Second Avenue Subway will include a 37-month job to bore 19.5-ft-dia tunnels more than a mile under Manhattan streets, says Mysore Nagaraja, president of the MTA's Capital Construction Co. An RFP for construction management consultant services on that project will also go out.