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The 2016 Sydney Drinking Water Catchment Audit

22 September, 2017Posted in: Other

  • The Sydney Drinking Water Catchment Audit is undertaken every three years on behalf of the NSW Minister for Energy and Utilities.
  • Council participates in the audit process and provides data on key indicators and actions.
  • The audit provides the Minister with scientific recommendations to mitigate risks to the catchment and assist in focusing State resources and monies to controlling key threats to the catchment.
  • The 2016 Audit of the Sydney Drinking Water Catchment was tabled in Parliament on Tuesday 8 August 2017.
  • The document is available at
  • The report refers to raw water quality and not drinking water. Raw water storage and supply is managed by WaterNSW.
  • Raw water is subsequently treated by Council to meet the Drinking Water Guidelines as approved by NSW Health.
  • These practices meet the Australian Drinking Water Guidelines for potable water supply.
  • Council continues to work with WaterNSW in improving the water quality in the Wingecarribee Catchment.
  • As noted in the Audit report, the increase in the phosphorus load at the Moss Vale Sewage Treatment (STP) is attributed to the town’s population grown.
  • The capacity of the Moss Vale STP is being addressed through planned upgrades, most particularly a planned $25.5 million upgrade over the next three years.
  • Despite the increase the Moss Vale STP continues to comply with EPA licence requirements.
  • Conversely Mittagong, Bowral and Bundanoon STP’s have experienced decreases in phosphorus loads.
  • Council has allocated $63,249,000 to our Shire’s sewerage network over the next four years including major upgrades to the Moss Vale STP.
  • Council monitors water quality upstream and downstream of all our sewage treatment plants in line with licence requirements.
  • Operation of all our STP’s is in-line with licence requirements.
  • One of the major improvements since the last audit in 2013 audit has been the completion of the $33.6 million Robertson Sewerage Scheme.
  • The audit notes multiple ongoing stressors in the Wingecarribee Catchment including soil erosion and gullying, sewerage treatment plants reaching capacity, development pressure, nutrient loads from dairy effluent and adverse impacts from the 1998 peat island separation.
  • There are numerous catchment stakeholders that have roles in improving catchment conditions including WaterNSW and South East Local Land Services who have also been delivering programs targeting the grazing and intensive livestock industries in the catchment area.
  • Overflows predominantly occur as a result of wet weather events where high levels of unwanted flows of diluted stormwater and groundwater enter into the sewerage system.
  • Stormwater effluent is comprised almost entirely of rainwater.
  • Under current EPA licences, Council has approval to discharge diluted sewage at designated points at our Treatment Plants.
  • Controlled discharges protect the treatment process, prevent system backup and protect public and private amenity.
  • All discharges at Council’s STP’s are monitored, analysed and reported accordingly as per the licence conditions.
  • Council recognises the issues regarding wet weather impacts and continues to work closely with the EPA to develop ongoing assessments and programs to reduce the impact of wet weather events on its treatment plants.
  • Council also has an ongoing program of sewerage maintenance which assists in reducing stormwater inflow and infiltration. This includes annual sewer main and manhole renewals, smoke testing and house-to-house inspections, condition assessments of sewer mains and manholes, sewer flow gauging, sewer modelling and containment assessment.
  • Council also undertakes upgrades of pipes, pumps and other structures to increase capacity and reduce the occurrence of wet weather overflows.
  • The audit also notes activities to improve wetlands by community groups in the Wingecarribee Shire and riparian management activities are likely to have had beneficial impact on the catchment.
  • Council continues to support the Mittagong Creek Rivercare group as part of our Bushcare activities.