No end is in sight yet for Alexandra's water quality woes.
Two trials to reduce lime scale have failed to impress users, and a recent report has recommended against further development of the borefield.
The Central Otago District Council has been investigating options for improving the water quality for more than four years.
The domestic water-supply system, which has been in place for more than 35 years, caters for about 5000 people. It is sourced from six bores on the true left bank of the Clutha River, near Eclipse St.
"The supply has an E grading and has problems with hardness, scaling and taste and odour issues that give rise to user dissatisfaction," council development engineer Peter Morton said in a report to be tabled at the Vincent Community Board meeting on Monday.
"The borefield is also adjacent to a closed landfill and whilst there is no evidence of this causing problems, there is a perception that contamination of the supply may be a risk, under some circumstances," he said.
An investigation in 2007 into water supply alternatives identified solutions ranging in cost from $1.77 million to $13.62 million. The board was told in May this year that removing the hardness from the water and meeting drinking-water standards could cost residents an extra $420 a year on their rates bills.
A report by URS Consultants, of Christchurch, said redevelopment of the borefield was not recommended and re-engineering the borefield was unlikely to remove the scaling problem.
The report recommended a site on the riverbank north of the town be investigated to see whether it could provide a better water supply.
Mr Morton outlined the results of four-month trials in two parts of the town, involving two different processes aimed at reducing the lime scale.
One unit was placed in Molyneux Estate, covering 47 households, and the other unit was in the O'Neill Cres area and involved 49 households.
Only 11% of the people involved thought the water quality had improved.
He has recommended the board look at a new water source site on the riverbank north of the town, rather than developing or improving the present borefield site.
