How to find a Manhole Cover – Russell, Bay of Islands.
Had a call from Gary – He’d lost a manhole cover!
A big, heavy, cast iron manhole cover… put down over a water bore in the early 1990’s.
Now normally a manhole is an easy target, except this one wasn’t where it was supposed to be.
Going off the 30 year old recollections of the previous caretaker who was present at the installation showed that memory can be a fickle thing especially with the passage of time.
As more memories came in, the story about the location became confused and strewn with ‘red herrings’. Was the manhole even still there, or had it been replaced with wood, or had the plastic bore casing and alkathene been sealed and backfilled with no metallic targets to find?
Consulting old aerial photos online , and even the Regional Council borehole database didn’t help improve the odds of refining the actual, or even general location given the database showed it was out in the adjacent estuary.
With the bore stated as being « 60cm below surface », the orchard started to show the effect of false, but promising targets.
An old fencing stake buried vertically below the surface was chased downwards in the hope it was marking the bore (that was a big hole!), and even a spoon made an appearance in another hole as I hunted for a potential deep brass, copper or galvanised fitting.
As the final remaining pockets of grass among the trees were cleared, the detector – set for maximum sensitivity for a deep target, suddenly overloaded the headphones – and there, just under the grass was the edge of a manhole cover.
Fortunately only 6cm down, and not 60…
A significant expense to drill a new bore had been avoided.
