I did not know about that amazings eletricity rates, my first tough was: "if it's real, google must have a datacenter there". And yes, the have one. Amazing. How do you have your gpu mining farm hosted here, may I ask? I hadn't found any private datacenter with a fast search on datacentermap.
Actually Google does not have one in Douglas County, WA. You are probably confusing with the one they have in Douglas County, GA. However, Douglas County, WA is the location of multiple other datacenters: Sabey's Intergate.columbia (where colo is possible), VMware, and T-Mobile. And Google does have a datacenter 130 miles south in The Dalles, where power is still relatively inexpensive at $0.05/kWh from the local provider Northern Wasco PUD.
There is more than just the price of electricity that determines where to host a datacenter: local job market, distance to large cities, etc. I am sure Google had valid reasons for deciding against hosting in Douglas County.
Personally, I just rented office space for my GPU farm. Colocation always adds too much overhead costs over the raw cost of electricity. Some colos may say they "sell electricity at cost", but they always force you to pay additional fixed monthly recurring charges (eg. a fixed price per rack cabinet), so at the bottom line, you are paying a lot more than "at-cost" electricity.