Go to the published coordinates and you will find a plaque on a stone.
This stone is from the foundations of the original Berrima bridge.
On the plaque there are three dates, use these to calculate the location of the cache.
"Berrima bridge opened in ABCD"
"The stones dated EFGH and JKLM"
S34 (L-M)(F+E).(L-G)(D+C)(A+C+F-G)
E150 (L-E-D)(L-H-F-A).(L-B)(B-M)(A+E+J+D)