2013 December – Gisborne Road Tank, Western Water (Victoria). Streptococci

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Incidents reported under section 22 Safe Drinking Water Act 2003

Gisborne Road Tank, 2 Dec 2013 (Lerderderg locality)

Routine sampling at the tank resulted in detection of 1 org/100ml of faecal streptococci in the presence of 0.01mg/L free chlorine and 0.06mg/L of total chlorine.

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The tank was isolated from supply and spot dosed. While the tank was isolated, freshly chlorinated water was pumped into the reticulation system via a local chlorine
booster station.

Flushing was also conducted at the extremities of the system in order to ensure increases in chlorine residuals were met.

Operational site visits to the tank were increased along with spot dosing and works to increase water turnover in the tank.

Resampling was conducted for three consecutive days with all results clear for the tank.

However, one reticulation site downstream of the tank returned positive results for faecal
streptoccoci despite increases in chlorine across the system.

The reticulation site in question was inspected. The sample tap was an old garden-style tap fitting which brought into question the integrity of the sample collected. A new clickin
fitting was installed and the reticulation site resampled for three further days with all results remaining clear.