2021 March: Sawmill Settlement (Victoria) – E.coli

March 24/27 2021: Sawmill Settlement (Vic) – E.coli.
E.coli was detected in the Sawmill Settlement Rosella St Clearwater Storage (CWS) and
reticulation system (retic) after routine monitoring.
490org/100mL (max). 2 Non-complying samples. 1 detection and investigation conducted (s.22), 2 samples where the Standard was not met (s.18)
GVW undertook an immediate check of water treatment plant (WTP) operations, no
operational issues of the WTP were found that would cause such an issue.
There were no Critical Control Point (CCP) failures and all other WTP processes and parameters
had been operating within normal operating ranges. Inspection of the CWS by drone and internal
observation found light penetration from a previous repair to the roof. Suggesting possible ingress
from recent rain as the most likely cause of the E.coli detections.
GVW declared a Level 2 Incident and formed an Incident Control Centre (ICC). GVW issued a Boiled
Water Advisory (BWA) in consultation with the Department of Health (DH) to our customers in the
water sampling locality. Repairs to the roof of the CWS where the suspected ingress occurred were
undertaken on the 24 March 2021. Chlorine levels in both CWS were increased to 1.5mg/L.
Resampling occurred after flushing and then a second round of sampling occurred late on the
afternoon/evening of the 25 March 2021. All resampling results complied with the SDWA 2015.
Customers were advised of the BWA via SMS, Website, social media and media release, variable
message boards, specific information to critical customers who were all personally and directly
contacted. Bottled water and water tanker was provided to customers from a pickup point in the
town as an alternative source of drinking water. Temporary supply was established for key sites
(school and accommodation facilities) for the duration of the event.
The BWA was lifted on the 27 March 2021 in consultation with DH

“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.

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 2011