That wall on Grand Street in Williamsburg that was being held up by an intricate bracing system after it threatened to come crashing down during demolition has been safely taken down. The wall started to collapse, possibly because of vibrations, during the takedown of the Gandar’s Building at Grand and Driggs and neighboring structures. Developers plan a 14-story “Monster Tower” on the site, which brings us to the next topic: downzoning. Community Board 1 is voting tonight on a rezoning proposal that would limit building height to 50 feet on Grand Street and 70 feet elsewhere. If the rezoning goes forward, the tall buildings could only rise if work is far enough advanced when the rezoning takes effect. The CB1 meeting will take place at 6:30 PM at 211 Ainslie Street.