Help close 3D shape

Hi guys,
i m drawing this part of a skatepark, and somehow i can t figure out how to close the model.
I m usually using curviloft for that.

waterfall part1.skp (129.5 KB)

any idea why i can t close it?


There’s a small edge in the lower corner that you may be missing during selection.
Curviloft will work however.

And the arc on the left doesn*t end at the endpoint of the “ground level” arc

thank you so much guys