Instead of a simple grab-and-go, I thought I'd create this easy multi-cache with a twist that should take about 20 minutes to complete. Let's see if I can trick you up a bit with some simple logarithmic calculations! Make sure to Bring Your Own Pen! You do NOT need to go onto private property to get the coordinates or to retrieve the cache.
Congratulations to Kirkgirls for the FTF!
There is nothing at the posted coordinates; they are merely how you get to the cache page.
Waypoint 1: Distance to Redmond West Wetlands: 0."AB"
Waypoint 2: Distance to Downtown: "C.D"
Waypoint 3: The last number of the fourth mailbox from the right will be "E". The last number of the third mailbox from the left will be "F".
FINAL: Calculate the following to create the coordinates for the final; geochecker below.
G = A + log5(25)
H = B + log3(19683)
I = C + log25(625)
J = D + log2(512)
K = (E + log3(81))-log2(64)
L = F + log5(3125)
Implement the numbers like so: N 47 39.GHI W 122 07.JKL
If you can't remember how to do logarithmic calculations, here's a simple calculator: Logarithm Calculator

You can validate your puzzle solution with certitude.