u/RogueShadow95

Context. There's an artificial lake 100+ ft downstream of the opening. Grass is sloped away from the opening like a weir outfall.

Thinking it's an overflow diverter: If HGLs get too high, instead of water coming out of a manhole it comes through the weir opening and sheet flows to the lake... Or maybe it's all they had when constructing and used this inlet as a box?🤣

Edit: Additional Context. Found a sloped headwall closer to the Lake's edge a couple of hundred feet west southwest of this structure.