Id think they are living on the upsteam side as well, most times they are but not always. If not, they should have a nice trail going over the dam, great place there for a set. Being summer id set a foot trap on the upside of the crawl over on a drowner, set it deep for a backfoot catch so you can avoid the million turtles, 'rats, otters, etc. also using it.
Id scout the area out first before doing anything, any channel they are using to get to feed, grooming area's or whatever id set up blind.
Basically blind set everything and maybe toss a castor mound set in and get as many as you can to begin with. Then after that is done if any are still left id take them out with the dam break set.
With all of that said, more times than not I don't have any sets to make so have to start out with a dam break set OR two. But I hate having to do that from the get go if I can avoid it.
If you have to order lure, get a jar of Woodchipper
from paul also, gives you one more option to use if all else fails.