A nor'easter finds Salem from the south, coming up the Merrimack Valley with the wind behind it, and the plows start rolling while the interstate is still nothing but headlights and spray. Irriscape Landscaping runs snow work through those nights — driveways and lots plowed, entrances and walkways shoveled, salt and sand laid down where traffic would otherwise pack the snow to glass. It is steady, unglamorous work at strange hours in a truck that smells like coffee. The route covers Salem and reaches out to Windham, Pelham and Derry. What you get for it is a lot cleared to its corners at six in the morning and a town that can go about its day.