There is a monument here which tells you about some interesting things that happened at this site at a time when there was a building here named Solano House. You will need to obtain some data off the monument; be sure to look at both sides of it. The back is nearly as interesting as the front:
A = the number of letters in Captain Poole's first name.
B = in the triangle.
C = (A - B) - B
D = the month when the monument was dedicated. (Jan = 1, Feb =2, ...)
E = the last digit of the year when the monument was dedicated.
F = D - B
You should be able to find the cache at:
N 38° 31.EFC W 121° 45.DCD
You may wonder if the nearby walls are foundations of the original Solano house. That is not the case. Those wall remnants are form a later period and were probably used to hold water.
Caution: there are lots of little critters around (you will be able to hear them whistle at you). They have dug lots of holes; so be careful where you step: tread lightly. Also at the cache location you may encounter vermin; so be careful where you stick your hands.
This is a reincarnation of the Solano House cache originally placed by Nylimb, and adopted by me. For the current version a different container was hidden at a different location in a different manner.