I did. Goatface
the wise nailed it. It was a manual storm surge valve. Apparently all the people in the neighbourhood had them at one point, many still work. It's in a flood plane, and when the houses were built the builders thought it prudent to put these in. A neighbour 2 houses over still shuts hers when there is a major storm coming. My friend's house was no longer functional. In the early 2000s the plumbing from the street to the house was full of roots, and was replaced and bypassed this with more modern check valves and the like. I'm going to end up cutting the whole thing out and overlay with cement. They want to make a family room in there, and that thing would just be a pain in the ass.