Alan Trick
It looks like it's actually a drainage going over another stream. This drainage was built a while back to divert water from the Quinsam River into Campbell lake, in order to reduce the amount of toxic effluent comming from the Quinsam Coal Mines (http://www.env.gov.bc.ca/wat/wq/objectives/quinsam/quinsam.html)

I added a culvert because that makes the most sense, but it would be good to confirm that it's actually there.