This cache can help with several challenges. Rhyme Time Challenge, California Multi Cache Challenge, and maybe more.
This is a simple 2 stage multi. GZ should take you to a city street lamp with an alphanumeric designation. Convert the letter to its numeric value, add the four digits together to get a 2 digit sum, then square that sum (X). Add X to 617 to get your North coords (N38 00.N). Subtract X from 841 to get your West coords (W122 17.W).
Final coords check sum for ALL digits: 51