I believe they go to porto potties after October. Although sometime the handicapped bathrooms at the top of the stairs are open even when the others are closed (at the far west beach.) There are usually people there throughout the year bike riding and walking and dog walking. They also work on the place after the official season ends. I think the nature center may stay open after the "beach season" as well. It's a geat hangout for older folks after school starts up.
2018 season runs until October 8th for Hammonasset Beach State Park, from their website.
Check on the website but i think most of the place is locked up then
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