Someone forwarded me a notice. (I also found the DOB work permit, which was issued Tuesday, so presumably it could have been announced earlier.)
This morning, I asked Empire State Development why it hadn't produced a Supplemental Construction Alert. This afternoon they circulated a notice:
B14- 535 Carlton Avenue:The notice in full
During the next two Saturdays, March 7, 2015 and March 14, 2015, excavation and foundation work will be taking place on the project site. Work will include the drilling of 24” solder piles in the northeast corner of the site ( Pacific Street), installation of tie backs along the South wall (Dean Street) and stressing of ties backs along the west wall (Carlton Avenue) of the project site. Work will be taking place during the hours 9 AM to 6 PM pursuant to the Department of Buildings weekend work permit.