The cache is not at the posted coordinates.
Solve the Dance and Do the Puzzle.
Least significant digit of the year.
N 38° 48.ABC' W 121° 16.DEF'
A = Delft Explosion
B = Hurricane San Calixto II, the deadliest Atlantic hurricane on record
C = St. Elizabeth's Flood
D = Black Monday Hail Storm
E = Death of Paul Revere
F = Amelia Earhart takes first flying lesson

You can validate your puzzle solution with certitude.