They could do White Rivers at Icy Creek in the Green and perhaps Palmer. Nice cold water. They used to do Springs (WR) at Hupp Springs (on Minter) so that is another option. There are lots of options.

Springers seem to show the best results on yearlings, so you are going to need a water supply that is very strong in the summer in terms of both flow and low temperatures. Springs were also done at Hood Canal. I don't think it was a big program and I don't know just how successful it was but you could reduce the chum program to do Springs.