Public officials and riders have talked for years about building a second Transbay Tube — someday. Supervisor Scott Wiener, who is also a member of the regional Metropolitan Transportation Commission, recently said a second tube is needed to provide 24-hour service. [...] at a BART Board of Directors workshop Thursday, Alameda’s public works director said his city is eager to work with the transit agency on a new tube to bring service to his island city. “If anyone wants to know how long it it will take and how complicated it will be, think about the eastern span of the Bay Bridge or high-speed rail or plans to extend runways at SFO,” said Martin Wachs, a retired UC Berkeley planning professor who specialized in transportation and is a senior researcher for Rand Corp.