Does anyone know what all the dredging in the Harbor is about?

The main thing is to deepen a channel through Boston Harbor to the Conley Terminal in South Boston to allow larger ships to dock there ("Panamax" ships that can fit through the widened Panama Canal).

There was another project to dig a trench from the Reserved Channel to the Deer Island treatment plant for a new electrical conduit to power the plant. The original cable to Deer Island worked fine, but it wasn't dug deep enough to prevent the channel dredging from possibly cutting the line, so the Army Corps of Engineers and Massport sued Eversource and the MWRA; Massport agreed to dig a new, deeper trench for a new cable.