We drove up to see it and when we got to the lagoon we immediately found the scoter swimming around with a gorgeous adult male Redhead. The scoter was life bird 341 for me and it was a new state bird for my friend. This is not the first time I have seen good birds on sewage lagoons. I have seen Barrow's Goldeneye (self found, accidental in Iowa), Snowy Plover, Piping Plover, Least Tern, Ruddy Turnstone and much more at a couple local lagoons by where I live in western Iowa. The lagoons may stink (luckily the one near Yankton didn't) but the birds that you find in them sure don't!
A couple other birds were seen while we were up there including three Western Grebe, some Cackling Geese, and a Bonaparte's Gull.