(As of 8/11/20 the locks are opened after a summer long closure due to the North Washington Street Bridge demolition.) This dam consists of 3 sets of parallel locks. 2 sets are roughly 20'x100' and the third is about twice as big. The lock master monitors ch 16 and 13. To request passage sound two long followed by two short horn blasts. I'm not sure what the hours of operation are but I have been through the locks at 4 am and at midnight.
The North Washington Street bridge is has been demolished and will be under construction until 2023. Adjacent to the old pilings is a temporary bridge with a height of 28 feet (not verified) at high tide. For now navigation from the Charles river locks to the harbor is narrow and crowded with work barges but it is navigable for most recreational boaters that can traverse the river. Check online or call the Mass State Police Marine unit for more info.