Mundy Road sentinel site, 13 Feb 2014 (Sunbury locality)

Issue

Sentinel sites are routinely sampled weekly to ascertain any early indications of water quality changes. A routine sample at the Mundy Road sentinel site resulted in a positive
detection for E.coli (1org/100ml).

Actions

he system was immediately flushed extensively to pull fresh water through to the extremity. Resampling was then conducted for three consecutive days with each sampling effort requiring the collection of a set of three samples, five minutes apart. The first resample returned a further positive result for faecal streptococci (2orgs/100ml) indicating that system ingress had occurred. All follow up results were clear.

These detections were immediately preceded by a major bushfire in the Sunbury/Riddells Creek water quality localities. The CFA were drawing on the drinking water system in the immediate vicinity of the sample point with two trucks reporting that they were experiencing low water
pressure at the time. This indicates a high likelihood that backflow may have occurred from either one or both trucks.

The key learnings from this issue were that the reticulation system is vulnerable when under significant pressure due to bushfire.