Note: As a result of changes to the infrastructure in the area, at present it is possible to find only the East coordinates. The South coordinates are S45 51.727. A permanent fix will be made in due course.
The published coordinates should take you to the middle of the footpath beside the bridge.
You need to walk the full length of this footpath across the bridge at least once in each direction, possibly more times depending on your powers of observation.
Look for something unusual/out of place. They are in full view and you do not need to touch or move anything.
These will give you the coordinates for the final cache, which is a Berocca tube, within 200 metres. The cache is hidden above ground level and a tool is attached to it to enable extraction.