It’s not every day that someone in America goes to jail for an environmental crime. But yesterday, Mark Easter, the operations manager of the Fishers Island (N.Y.) Ferry District got hit with 30 days, for dumping raw sewage into Long Island Sound and the Thames River, in New London, Connecticut. And the federal magistrate in Hartford who is overseeing the case hit him with a $10,000 fine for good measure.

It’s hard for me to say whether the punishment fits the crime here. But I have a feeling that someone is being let off the hook, politically if not legally — and I’m not saying it’s Mark Easter.

Easter was charged and pleaded guilty after federal investigators determined that the two ferries that connect Fishers Island to the mainland were dumping pretty much all their sewage into local waters. From January 1999 until July 2004, a period during which the boats’ sewage holding tanks should have been pumped out twice a week, or about 570 times, they in fact were pumped out only seven times.

How could that be? Simple. Easter ordered that the pipes be left open, to empty directly into the Sound and the Thames (which, by the way, is pronounced Thaymes in these parts, not Tems). Pursued and caught by the Coast Guard and the U.S Attorney, Easter pleaded guilty in September. And so, off to jail he’ll go.

But Easter wasn’t a free agent. He was a municipal employee (Fishers Island is just off the coast of Connecticut, but it’s part of Southold, a town on Long Island). And the Fishers Island Ferry District is overseen by a board of directors that consists of Fishers Island residents.

So shouldn’t someone from the island or the town have been aware that for five and a half years they were paying virtually nothing for sewage disposal? That instead of 570 pump-outs, they had just seven? Did town and ferry-district officials not notice? Did no one audit the books or the operation?

The residents of Fishers Island probably prefer it when Southold officials keep their noses out of the island’s business. And because Fishers Island is physically isolated from the rest of the town, it would be easy for officials to ignore the goings on there — easy, but not acceptable.

Island residents may be physically removed but they are not bumpkins. In addition to the 250 people who live there year-round, there’s a large and very wealthy seasonal population. A couple of summers ago they invited me out to give a talk as part of a week-long environmental awareness week. It’s a beautiful place, a 7-mile-long strip of glacial sand at the border of the Sound and the Atlantic. One of our hosts was a DuPont. The chatter at the post-talk cocktail party was about how one of their golfing buddies, a fellow named Porter Goss, had just been named head of the CIA. When I got home, I ran into a Roosevelt, who told me he was sorry that he happened to have been off-island at the time, otherwise he would have come to the talk.

All the island residents I talked to that day consider themselves environmentalists (in some cases appropriately), and I’d be surprised if you’d find more than a handful of people on such a beautiful place who don’t. All of them take the ferry.

But for five and a half years none of their neighbors on the ferry district’s board, and none of their municipal officials, noticed that the sewage disposal costs were so low.

I don’t feel bad for Mark Easter. But shouldn’t someone else at least admit they should have asked to see the bills?