TasWater boil alert triggered after “reasonably high” levels of E. coli discovered

Pot with water

UPDATE (3 November 2017):
 Risdon Vale boil water alert has been lifted

The temporary boil water alert issued for residents of Risdon Vale has been lifted.

Test results indicate the water being supplied to TasWater customers meets the standards of both the Tasmanian Drinking Water Quality Guidelines (TDWQG) and the Australian Drinking Water Guidelines (ADWG). This means Risdon Vale residents are able to consume water from their household taps without having to boil it first. TasWater will continue to provide ongoing monitoring and testing to demonstrate water quality meets the drinking water guidelines.

Posted 2 November 2017:

The boil water alert was put in place on 31 October. About 600 households were affected by the alert.

TasWater Systems Performance Department Manager Lance Stapleton said the level of E. coli contamination was “reasonably high for an urban reticulation system”. Initial tests showed a level of 51 colony-forming units/mL, when a level of one is enough to cause some concern.

Since the announcement, the utility has set up an incident room to investigate the outbreak and isolate the source, which could be due to a number of culprits. Stapleton said it could have been caused by a backwash from firefighting trucks pulling water out near the testing site. It could also be from human sources or animal faecal contamination. However, the latest laboratory test results show no repeat of irregularities in the water supply.

“While the latest results are encouraging, further results will be needed before the Department of Health and Human Services can again give the Risdon Vale system the all clear,” Stapleton said. 

The bulk of water supplied to Risdon Vale comes from the Bryn Estyn water treatment plant, which continues to operate normally. Additional water supplies come from Risdon Brook Dam, which likewise continues to meet Australian Drinking Water Guidelines.

“We have cleared out the Risdon Vale Reservoir, with a diver carrying out a full inspection, but there were no irregularities in the infrastructure that might have led to the outbreak,” Stapleton said. 

“On that basis we suspect the contamination is likely to be very localised and might even be the result of some back flow from last weekend when fire trucks were refilling from a fire hydrant close to the testing site that returned the E. coli reading.”

TasWater will continue to carry out widespread flushing of water mains in the area until tests come back clean. 

The alert comes in the midst of a heated back-and-forth between TasWater and the State Government over a proposed government takeover of the utility. It’s as yet unclear how this latest development will affect the proposed takeover and council vote.

Information on the boil water alert is available on the TasWater website or call 136 992.