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Dunedin City Council – Kaunihera-a-rohe o Otepoti
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Stormwater monitoring

New 35 year consents were granted by the Otago Regional Council in August 2013 to replace previous consents to discharge Dunedin’s stormwater into the sea.

The consents

We have 10 consents to discharge stormwater from 33 outfalls to Otago Harbour and the coast at St Clair.  The consents relate to the Integrated Catchment Management Plans (ICMP) and are:

  • RM11.313.01 Port Chalmers Catchment (PDF, 576.9 KB, new window)
  • RM11.313.02 Ravensbourne Catchment (PDF, 1.7 MB, new window)
  • RM11.313.03 Halsey Street Catchment (PDF, 1.7 MB, new window)
  • RM11.313.04 Shore Street Catchment (PDF, 1.6 MB, new window)
  • RM11.313.05 Mason Street Catchment (PDF, 1.6 MB, new window)
  • RM11.313.06 Kitchener Street Catchment (PDF, 1.8 MB, new window)
  • RM11.313.07 Portsmouth Drive Catchment (PDF, 1.7 MB, new window)
  • RM11.313.08 Orari Street Catchment (PDF, 1.6 MB, new window)
  • RM11.313.09 South Dunedin Catchment (PDF, 1.6 MB, new window)
  • RM11.313.10 St Clair Catchment (PDF, 1.7 MB, new window)
  • The consent conditions require that we monitor the quality of stormwater, Harbour water, Harbour sediment, and the biological environment (epifauna, infauna and macrofauna sampling and identification, and cockle flesh analysis) so any adverse effects on the receiving environment due to the stormwater discharges can be identified and addressed.

    The sampling includes:

    • stormwater quality sampling at one outfall in each catchment annually
    • automated stormwater quality sampling over the course of three storm events per year, in one priority catchment (rotated between the South Dunedin, Halsey Street, Shore Street, Kitchener Street and Mason Street catchments)
    • dry weather monitoring at each of the 33 outfalls to assist in the detection of cross-connections from the wastewater network (ranging between monthly and annually depending on results)
    • Harbour water quality at six locations twice a year
    • Harbour sediment quality at four locations annually
    • biological monitoring biannually

    Monitoring results

    All stormwater contains contaminants, and monitoring helps identify areas where contaminant levels may be unusually high, and where we may need to investigate further. This monitoring is ongoing.

    Biological monitoring results to date do not show significantly high levels of contaminants in the samples.

    There are no clear trends in Harbour-wide levels of contaminants in sediment, with high variability among contaminant levels and sites.

    The reports in the related information section have more information.

    Stormwater consent sampling locations

    Below are maps of outfall locations covered by consents.

    Central City overview of outfall locations covered by consents
    Central City overview (click the image above for a larger map)

    City overview of outfall locations covered by consents
    City overview (click the image above for a larger map)

    Improving water quality

    Dry weather monitoring at each of the outfalls identifies any cross-connections between the wastewater and stormwater networks so we can remove them.

    The consent has trigger levels for certain contaminants in Harbour water and sediment samples. If these are exceeded due to stormwater discharge, we have to address the issue. The matter is prioritised in the relevant ICMP and stormwater management options to reduce the contaminant concentrations are implemented.

    Other consent conditions include:

    • investigating the need for a Stormwater Bylaw to control discharge of stormwater into the public stormwater system
    • ensuring trade waste discharges to the stormwater system do not occur
    • implementing the ICMP that were developed as part of the Three Waters Strategy
    • ongoing communication with stakeholders
    • reporting to the ORC.

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