Algae investigation complete

An investigation into the presence of algae in Lake Wanaka has been completed with recommendations due to go before the Wanaka Community Board next week, QLDC capital works manager Ken Gousmett said.

The Council engaged MWH Limited to investigate and report on the growth and the implications for the Wanaka water supply. MWH worked together with a University of Otago research team. Algae has caused problems to some homeowners by blocking filters on home appliances, although the number of complaints had reduced in 2011, with eight received in January, one in February and none since. The reason for the decline in complaints is not clear.

“The most significant finding supports the Council’s own research that the algae pose no health risk,” Mr Gousmett said.

Despite a downturn in reported issues the algae were not forecast to improve however and mitigation of clogging needed to be addressed.

The report found the cost of constructing a treatment system that would eliminate the problem was prohibitive.

“It has identified that the preferred approach is a number of low cost measures designed to reduce the presence of the algae in the supply,” Mr Gousmett said.

It would also be important to continue to closely monitor the situation.

Recommended next steps included:

• Clean both intake screens and inspect on a regular basis
• Increase the pump cycle at both pump stations.
• Investigate a new method of backwash to help minimise algae build up on the screens.
• Investigate ‘light shields’ for both intakes (algae growth being light sensitive).

The Wanaka Community Board would be asked to receive the report on Tuesday.