The run of stellar weather in Hokitika on the West Coast has had an unpleasant side effect - stinking sewage ponds at the northern entrance to town.

A number of complaints about the Two Mile oxidation ponds have been lodged with the Westland District Council after the smell started getting worse about a week ago.

The Hokitika Guardian has also fielded calls about the stench from locals, who say it is the worst they can remember.

Council team leader of operations Peter Anderson said the weather, high waste loading from some local industries and a previous pipe blockage had affected the oxygen levels in the ponds.


Cooler temperatures during winter and spring slowed down the bacteria in the ponds. But as they warmed, the bottom layer mixed with other layers and produced both gases and solids on the surface of the ponds.

"Fortunately for those of us on holiday, but unfortunately for those living near the ponds, the run of very warm weather and little wind is continuing," Mr Anderson said.

The council and Westroads staff were doing as much as possible to help the process, including trialing an additive from Westland Milk Products which helped improve pH levels, and, if resources allowed, arranging a "sucker truck" to remove the scum layer around the outlet pipe.

Westroads staff were currently looking for a dinghy with an outboard to use to help aerate the ponds as well, he said.

"We are having trouble locating one so if anyone can lend us one that would be great. It won't correct things but it will aid it by helping us get oxygen into the ponds."

He said the odour was fluctuating throughout the day and was slowly improving.

"Nature has to run its course. Unfortunately, it's not an overnight fix and it may be a day or two until normal conditions resume and odours disappear."