Mary and Tweets,
Another pond not included in your list is the Snohomish WWTP. The previous
years it has played host to a Red Shouldered Hawk through the winter months
if my recollection is correct.
Yesterday, I drove directly up to the ponds and because it was a work day,
the gate was open. I was able to drive up to the main pond. It was loaded
with Northern Shoveler, Scaup, Mew Gull, Gadwall, Glaucous-Winged Gull. There
was a Bald Eagle in a tree at the far end of the WWTP. A Great-Blue Heron in
the pond just on the West side of the road as you drive up along with a
couple Mallards. I heard a Northern Flicker in the distance.
Although, the birds listed are not rare or unusual, they were still nice to
see.

Seven (?) years ago, I went with our master birding class to Marysville WWTP.
As I recall, the ponds were full of a large variety of duck. It has been a
while and I don't know what Marysville's policy is on accessing the treatment
plant currently.

Happily Birding,
Beth Thompson
Arlington, WA