Braidwood residents are still being advised to boil their drinking water for at least three minutes due to possible E coli contamination. A report to Council in Thursday evening's Council Business Paper sets out the detail of events leading to Braidwood's Boil Water Alert being issued.
Weekly samples are sent off to DAL (the Division of Analytical Laboratories) in Lidcombe, Sydney. DAL conducts microbiological analysis on the water for the bacteria E. coli (Escherichia coli) and total coliform bacteria numbers.
The report says that "testing water for specific coliforms or pathogens is impractical, unrealistic and unreliable. For this reason tests are carried out for bacteria which will indicate the presence of faecal contamination. Testing for E. coli is the most common, specific and reliable indicator for recent faecal contamination. It is not necessarily the E. coli itself that is the problem. Given that E. coli is present in the digestive tract of all warm blooded animals, its presence thus proves faecal contamination and therefore undoubtedly means the presence of pathogenic faecal coliforms."
From the end of October 2007 to present, samples taken from the Braidwood reticulated town water supply has on four occasions (but not date sequentially) failed on E. coli counts. Total coliform counts have failed on six occasions for the same period.
According to the report on the morning of Monday 7 January, the NSW Department of Health contacted councils EHO's to inform of a failure due to E. coli and total coliforms from a sample taken from on 2 January, and council was on stand-by for a "Boil Water Alert" for Braidwood pending action by council to dose the town's water with chlorine.
The report continues that "Council EHO's took sample water chlorine readings between 10:30 am and 11:30am from the three outlets in Braidwood - Bicentennial Park; Uniting Church Monkittee Street; and the Council Depot off Ryrie Street. The chlorine levels were low. Council's water operator had made an adjustment at the plant and it was decided by council engineers to flush the system. By late afternoon the chlorine level taken by the water operator was satisfactory enough for the NSW Department of Health not to issue a "Boil Water Alert".
Over the next two days the chlorine readings were inconsistent to the point where the Engineering Department informed the EHO's that there had been an air lock in the chlorine feed pipe over night, Tuesday 8 January, resulting in very low chlorine levels. The NSW Department of Health concluded that a "Boil Water Alert" be issued.
With the airlock in the chlorine delivery line repaired, the water quality appears to be returning to normal. The report concludes that "it will be necessary that the results continue to be clear and daily testing for residual chlorine demonstrates consistent adequate levels before NSW Health will allow the Boil Water notice to be lifted.
Last Monday and Tuesday's samples were clear, but Wednesday's failed. Council Director Bill Ellison said that this was due to repairs being carried out and interrupting the dosing. Mr Ellison expects to get three clear samples in a row this week and to lift the Boil Water Notice next week.
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