Date: 2/04/2013
Estimated duration of incident: Isolated incident
Location of incident: Picola
Nature of incident: E.coli exceedance in the reticulation (7 MPN/100mL) at Picola. Also E.coli detected in the Clear Water Storage (3 MPN/100mL) in routine weekly testing.
Drinking water supplies potentially affected: Picola
Action taken in response: Checked chlorine residuals at time of sampling, within limits. Investigation into incident revealed that there had been no water treatment process issues over the previous days, no CCP breaches had occurred. Storage checked for signs of ingress points, none found. Reticulation system flushed and response samples taken. All samples were clear of E. coli.
Communication with customers: nil
DH notification: A Section 22 notification was sent to the Department of Health on 4/04/2013.

Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG