This cache is placed on one of the many grayness designed to protect Blenheim from a major flood. Groynes work by pushing water away from the edge of the riverbank. I cannot find any information about the groynes built on the Taylor River, but I would guess they were constructed long before the Taylor River Flood Detention Dam was constructed in 1965 as in the 47 years that I have lived in Blenheim the Taylor River I have not seen the river breach its natural banks this far up. Therefore, these groynes appear to be superfluous and the cache should be safe from inundation..
If you have any knowledge about the history of the Taylor River groynes, feel free to let me know in your log.
B.Y.O.P