Ann: Ohinemuri River Discolouration, page-26

Hello KiwiHawkeye
There is a deposit of tailings further up the river across the road from the pub .
It has been there for years .
It may leach a tiny bit of arsenic.
That's why I suggested test the water further up the river .
I mined the very rich ore full of sulphates and the water as I said ran all the way out to a small sump and pumped back in
The small sump also had yabbies in it .The little buggers could sure bite if you tried to catch them
That's why you need drains the impurities settle as they travel along .