Nicely done! I tried doing that as well, but putting more of West Valley in the map than East Valley.
Which brings me to one thing I didn't see on the map; Where is the Yakima river? Or the Naches River? I think thats one of the things I don't like about the water tables in SC4. You should be able to have lakes, streams and rivers at any altitude.
But, I can't really complain for the fact you can use the US Geological maps to create any map for SC4.
Thanks for a great map.
Cheester