Actually their 100% green renewables number has a bit of fudging done to it. And some of the hydro power that their coop eletric company buys is from a hydro electric dam near me. One that I visited for work. I think I posted some photos of it here.
http://www.pbs.org/newshour/bb/vermont-city-come-rely-100-percent-renewable-energy/
A lot of the hydro dams have been removed in Maine. We used to be a leader in hydro generation capacity. But I guess as the dams aged, they were too expensive to maintain. Florida Power and Light used to own a few dozen up here. It was always strange seeing FPL trucks running around up here.