Lime spill kills life in stream
By Margot-Jane Smith
A toxic spill from Dunedin's Mount Grand water treatment
station has killed all aquatic life in the Kaikorai Stream for about 10km.
About two tonnes of lime was accidentally discharged from a storage area
at the Dunedin City Council plant into a tributary of the stream on Wednesday
As well as almost 1000 trout, the spill killed eels, crayfish, insects,
algae and even worms on the stream's banks. "It's not a minor spill,
it's a major, major spill," Fish and Game officer Monty Wright said.
"I've worked on fish kills in other places and they generally take
out [kill aquatic life for] around 1km. This has taken out kilometres
and kilometres of water, so it's a disaster."
There was no risk to humans, he said. It would take two or three years
for the stream to return to normal. Dunedin City Council water manager
Nigel Harwood said plant staff were unaware of the spill until contacted
by the Otago Regional Council. "Once the ORC said `Is there anything
that might have affected the stream' people went out and checked everything
and said `Hell, looks like it happened here'," Mr Harwood said.
A formal investigation into the accident would be held this morning. However,
initial thoughts were that a slurry, including 25% lime, had been put
into a storage area with an open valve, which discharged into the creek.
Mr Harwood said it was not easy to tell whether the valve was open or
not. "It appears at this stage to be one of those human errors,"
he said. Water was diverted from the treatment plant to help flush any
residual lime out of the stream.
Lime was used at the plant to help improve the taste and reduce the corrosive
nature of treated water. Mr Wright said the deaths occurred because lime
removed oxygen from water.
Some trout and eels had tried to leap out of the poisoned water, and worms
had crawled out of the soil and up the bank.
The lime was diluted as it travelled downstream until bigger fish could
survive."The last dead fish we saw was
at Harroway mill [at Green Island] and the first live one was at the Green
Island rugby grounds," Mr Wright said. Ducks appeared to have been
Friday 27 October 2000
This information obtained from and with the
permission of the Otago Daily Times.