Some major dredge work in the harbor

If you haven't seen the dredging going on off Castle Island, don't worry about rushing down in today's heat to see it - a contractor will be dredging a channel through Boston Harbor for the next three years, so you have some time.

The point of the work is to make a channel deep enough for so-called Panamax ships - big enough to just barely squeeze through the newly enlarged Panama Canal - to get to and from the Conley Terminal next to Castle Island.

The Army Corps of Engineers signed a $122.2-million contract with a contracting group headed by Cashman/Dutra of Quincy earlier this year for the work, which will involve removing "11.7 million cubic yards of silt, blue clay, till and weathered rock" to create a channel at least 47 deep from the Reserved Channel out to President Roads - which is basically the entrance to Boston Harbor from Massachusetts Bay (more detailed map - from the last major dredging project, in 1986, which included deepening a channel all the way to Chelsea Creek).

Most of the dredged stuff will be hauled out to a point about 20 miles offshore and dumped there.

Before the work could begin, the Army Corps of Engineers and Massport, which owns the Conley Terminal, first had to deal with an Eversource power cable out to Deer Island that might have been sliced by the dredging.

The two agencies sued Eversource and the MWRA because the then Boston Edison didn't bury the cable deep enough when it installed it in 1990. Eversource last year agreed to lay a new cable - away from the Reserved Channel and the deeper channel the contractors are now creating.