I looked at it closely from the river on Saturday.  The waste treatment plant 1st floor is above the river.  It may be on the same level as the ground floor entrance to the elevator.  The elevator does not provide entrance to two levels of Waste treatment plant and there are definitely two levels.  The roof is at level 4 if the river is at 1, waste treatment plant at 2, 3.  I've trying to find schematics for the Wastwater treatment plant which by the way is no longer called a waste treatment plant but a wastewater resource recovery facility (WRRF).  Used to be called a water pollution control plant (WPCP).