Manganese is a natural element picked up by water as it travels through gravel.
The Cromwell Community Board yesterday resolved to spend about $95,000 test-drilling and installing a new water bore, which was deemed the fastest way to provide residents with clearer water. All going well, the town could have a new water supply in late October.
Central Otago District Council utility services manager Peter Greenwood provided a report on the issue to the board, in which he recommended a new bore be installed in preference to four other options which included filtering manganese or using water from Lake Dunstan.
Mr Greenwood said the level of manganese in Cromwell's water was not harmful to health, but did not look good and could stain clothes and other surfaces.
As part of the construction of Cromwell's two existing bores, test-drilling was done around the town, the results of which will be reviewed to determine whether any previous test sites are suitable for a new bore.
Mr Greenwood said it was a risky option, as a new bore could supply water with the same level of manganese, or much cleaner water, as found in one of the existing bores.
Alternatives were either more costly or involved larger risks, he said.
If water was sourced from Lake Dunstan, the council would have to advise residents to boil it, and it was a costly option at between $3 million and $5 million.
Using Cromwell's clean bore would diminish supplies needed during summer months, and filtering manganese would involve high levels of chlorine.
Total costs depend on how many exploratory bores are required. The project will be funded from water supply capital budgets.
