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Scientific tests are being carried out along the Kakanui River to find the reasons behind a sustained period of elevated E. coli levels.
Weekly water-quality tests conducted by the Otago Regional Council (ORC) at Clifton Falls, near Five Forks, have breached health guidelines four times since December 12, and peaked at 2400 parts per 100ml on January 3.
Although ORC resource science manager Matt Hickey said the high reading recorded in January was in part down to a high river flow, the E. coli levels had still been higher than expected in the preceding weeks.
''It looks like we had about 60cu-mecs in that river around the time of sampling, but to be fair, those levels leading up to that sample were high as well - higher than we would expect or want. So we are still taking weekly samples and I have got a staff member doing sampling further upstream trying to track that source of possible E. coli contamination.''
The council aimed to keep E. coli levels at under 300 parts per 100ml, but sampling had indicated that levels had fluctuated between 500 and 1000 in the three tests before January, Mr Hickey said.
Although the levels of E. coli were not dangerous, people could have a ''crook tummy'' if they ingested contaminated water.