11.7 Stormwater ingress

Supporting Information

The volume for the line item is 841 ML.

Quantification Approach

Data Source

Supervisory Control and Data Acquisition (SCADA) data from wastewater treatment plants.

Provided by

Wingecarribee Shire Council.


The value represents the average volume of wastewater measured at the inlet to the wastewater treatment plants on dry days, compared to the average volume on days with rainfall. The difference is assumed to be storm water ingress.

The flow of wastewater from the plants is measured using ABB Magmaster flow meters installed on-site. The data from the flow meters are continually monitored and recorded. External flow verification audits for the flow meters are conducted annually by Hydrometric Consulting Services.

Assumptions, Limitations, Caveats and Approximations

Total wastewater received includes net ingress from stormwater and groundwater. A calculation has been made based on an assumption that the average increase in daily inflow on rainfall days is ingress into the sewerage system.

Uncertainty Information

The volume is based on measured and calculated data. Estimated uncertainty based on meter accuracy and professional judgment is +/– 7%.

Comparative year

The following table compares the value for the 2009–10 year reported in this account with the corresponding value reported in the 2010 Account.


Comparative information from the 2010 Account for line item 11.7

2011 Account line item

2010 Account line item

Value reported in the 2010 Account (ML)

Value reported in the 2011 Account (ML)

Additional information

11.7 Stormwater ingress 

19.6 Water inflow into the urban wastewater system



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