It is a short easy stroll to GZ, all except the last few yards. When you get close, it's worth taking a few minutes to find an easy route.
The container is a little bigger than a 35mm film canister and is hidden near the old ponds for Retallick Mine (later part of Halamanning Mine).
I assume the structures formed part of the sluice gates - if anyone knows different please let me know.
I hope you enjoy the hunt and find the site interesting.