Low levels of E.coli were found in the Amberley Beach water supply on December 6.
However results came back clear for all other test points in the Amberley area. As a precautionary measure, the Hurunui District Council decided to implement a boil water notice at the Amberley beach community at that time.
Eight days later, on December 14, low levels of E.coli were found in the water supply feeding into Amberley Beach, so a boil water notice was initiated for properties on the pipelines leading to Amberley Beach.
At this time Amberley and other areas still showed no presence of E.coli
Late on December 15, test results showed a low level of E.coli at one of the main reservoirs in the Amberley scheme. Although the levels were not high enough to automatically trigger a boil water notice, the council decided that given the bigger picture and that the contamination source was unknown, the risk was high enough to immediately introduce chlorine to the water supply to disinfect it.
Further investigations and test results have shown the likely contamination point is before the main reservoir. However the introduction of chlorine has removed any trace of E.coli, so ascertaining the cause is much more difficult.
The council says to further complicate matters, the demand on the supply has increased dramatically with the recent hot, dry weather. When the demand gets this high we introduce another water source into the mix. Under usual circumstances reservoirs can be isolated easily to test for contamination but with the increased demand we can’t maintain this single source. For this reason, the scheme will continue to be chlorinated until early January when the council intends return the water supply to normal.
The additional source being re-introduced has slightly elevated hardness and iron levels compared with the current sources and therefore it is only used when absolutely necessary. This supply will be mixed with the current sources to minimize the impacts of hardness and iron. The entire system will continue to be monitored and flushed regularly.
The council is working with Canterbury District Health Board, to systematically process each possible contamination point. The Amberley scheme is fed from multiple sources of water, making it a very complex process to prove all contamination is removed. Once areas have been isolated and the results show no traces of E.coli, chlorine will be switched off.