The Likely Scenario

It's likely that this dam cannot be modified to become compliant with the 1,000-year storm event, and that's why the conversation should shift to,  "What would we like to see there?"

In 2023, Ramboll, Inc. prepared a report for the City about the Woolen Mill dam. They calculated the current spillway capacity at 2,750 cubic feet per second (cfs) which is well short of meeting even the 100-year storm event. 

Now, if the dam is to remain, it needs to somehow be modified or completely rebuilt to handle the 1,000-year event which would require more than tripling the current spillway capacity to handle about 8,300 cfs. There isn't space to build a new dam there that large, even if money is not an object. Lowering the crest enough to become compliant would create a low-head dam, also known as a "drowning machine" because of the hydraulic situation they create, and there's no reason to create that kind of danger. 

This dam is not historic, nor original. Talking about spending millions to keep it in the name of preserving history already doesn't make sense, and makes even less sense if keeping it means building a whole new, very large dam - which is probably not possible. Why do we need a dam there in the first place?