Crazy thing.. and I can't say this for sure because I wasn't there.. but the caddis hatch on the Columbia in Castlegar during the summer (August-ish) is even thicker than that I believe.
I was standing there trying to fish and was all 'wigged out' by the hundreds of caddis crawling all over me and any given time. I kept doing the 'heebee jeebee's dance'!