The beaver utilized a substantial causeway that crosses the wide Means Brook swamp behind Huntington Street. The causeway has a 10 ft gap which the river flows through (it's a good 5 feet deep), and there was once a bridge over the gap that has washed out. The vast majority of the "beaver dam" was actually this causeway. The causeway is accessible from the Rec Path at a sharp bend in the Land Trust meadow off of Lane Street (look into the woods a bit and you will see beaver-cut trees). The causeway is normally overgrown with vegetation and parts are wet, which why winter is the best time to check it out. Here's a video of the causeway where the beaver were, clearly showing they are gone.