The cache isn't at the posted coordinates, it is a short distance downstream along the bikepath.
At the posted coordinates, you will find a nice art piece embedded in the wall. It consists of 6 rows and 6 columns.
Beginning in the upper left (R1C1), number the columns 1 - 6 left to right. Number the rows 1 – 6 top to bottom. Lower right is R6C6.
To determine the cache coords, count the letters of the word formed at the following intersections:
A = _____ = R2C4 – R3C5
B = _____ = R6C2
C = _____ = R4C4
D = _____ = R1C4 X R5C1
E = _____ = R6C3 – R6C4
F = _____ = R4C2
G = _____ = R5C1
H = _____ = R4C5 – R3C3
J = _____ = R1C4 X 2
Checksum: A thru J should add up to 39.
IMPORTANT NOTE:
In addition to finding and signing the log, to properly log this cache as "FOUND", you MUST also create and post in your log a meaningful phrase using at least 4 words taken from the art piece. (10 extra points if you use the "?".) LOGS NOT INCLUDING A PHRASE WILL BE DELETED.
The coords of the final are:
40 A.BCD -105 EF.GHJ
The cache container (micro, magnetic, log only, no pen) is located a short distance downstream along the bikepath.