Consultation has now closed

Consultation on the Pūharakekenui Styx draft Stormwater Management Plan has now closed. People were able to provide feedback from 25 July - 4 September 2023.

During this time, we heard from eight individuals and groups. You can read their feedback and find out how this influenced the Council decision. You can also read the updated Pūharakekenui Styx Stormwater Management Plan.

This plan will come into effect once provided to Environment Canterbury.

Stormwater Management Plans (SMPs) contribute to reducing contamination and demonstrating the ways stormwater discharges will be progressively improved.

This Stormwater Management Plan is one of seven plans being prepared over the period 2020 to 2024 for the Ōpāwaho-Heathcote, Huritini-Halswell, Ihutai-Estuary and Coastal and Ōtūkaikino catchments and Settlements of Te Pātaka-o-Rākaihautū-Banks Peninsula, and Ōtākaro-Avon and Pūharakekenui-Styx catchments.

The Pūharakekenui-Styx Catchment encompasses an area of approximately 7,000 hectares situated on the northern urban periphery of Christchurch. This spring-fed river system, stretches for 22km from its headwaters in the Harewood area to the sea. It meanders in a north-easterly direction, passing through reserves, pastures, horticultural areas, and residential developments before reaching the sea via Te Riu o Te Aika Kawa-Brooklands Lagoon and the Waimakariri River.

The Pūharakekenui-Styx Stormwater Management Plan has three key purposes:

  1. To propose targets for lowering stormwater contaminants.
  2. To describe the ways stormwater discharges will be improved over time to meet environmental objectives.
  3. To discuss how flooding risks will be dealt with, if there are any.

Map of stormwater catchments

Pūharakekenui Styx outlined in orange

Pūharakekenui Styx outlined in orange

Our goals

Our goals are:

1.1. Ensure the quality of stormwater from all new development sites or re-development sites is treated to best practice.

1.2. 100 per cent of stormwater treatment facilities contributing to contaminated load reduction targets for the Pūharakekenui-Styx catchment (consent condition 6b) are constructed and conform to WWDG standards.

1.3. Sediment from 95 per cent of consented construction activities on the flat is treated to best practice by 2025.

1.4. Analyse options for carrying out street sweeping, sump cleaning, and diversion to wastewater trials in 2020/21 (Schedule 4b & d).

Recommended for further consideration

1.5. Road sediment is reduced by a best practicable option determined by the results of street sweeping, sump cleaning and alternative treatment trials (Schedule 4c, f, g & h.).

Our goals are:

2.1 [repeats Goal 1.2] All the facilities required to meet the zinc targets in the SMP are constructed.

2.2 By 2025 the Council will have investigated zinc mitigation measures and carried out cost/benefit analyses toward identifying their effectiveness as best practicable options.

2.3 By 2025 the Council has consulted with key stakeholders and identified a long-term zinc strategy consistent with current technologies.

2.4 The Council collaborates with local and regional government in a joint submission to central government seeking national measures and industry standards to reduce the discharge of building and vehicle contaminants.

Recommended for further consideration

2.5 The Council engages in research and trials into means of trapping roof-sourced zinc on site.

2.6 The Council adopts a zinc limitation strategy based on identified best practicable options.

Our goals are:

3.1 The Council consults with the government, through the Ministry for the Environment, about legislation to limit the copper content in vehicle brake pads.

3.2 The Council does not permit stormwater discharges into the network from unprotected copper cladding, spouting or downpipes.

3.3 The Council will investigate the feasibility of a district plan rule to discourage the use of copper claddings.

Our goals are:

4.1 A database of industrial sites considered to be medium or high risk is compiled, based on the best available information, by 2025.

4.2 High risk industrial sites are audited by the approved procedure under the CSNDC.

Our goals are:

5.1 By 2025 the Council will be working with community groups to engage with the public to educate participants about current stormwater practice and enable the public to take action to stop contaminants at source.

5.2 By 2025 the Council will be engaging regularly with the Ministry for the Environment to collaborate on contaminant reduction initiatives.

Our goals are:

6.1 The quantity of stormwater from all new development sites or re-development sites will be attenuated to at least the minimum standard in the SMP.

6.2 Protection for property will continue to be achieved through controls on development and controls on new floor levels.

What we're going to do

Stormwater from new development is usually managed in detention basins which both limit discharge increases and serve as treatment facilities. Based on modelling, environmental drivers and tangata whenua values, and considering best practicable options, the first eight contaminant load reduction actions below will be implemented in this catchment:
  • Action 1 - Residential roofs - All new residential roofs are expected to be coated (i.e. painted) or non-steel (normal practice).
  • Action 2 - New developments - Stormwater from the new developments in Styx Drain, Highfield, Oakbridge, Middle Styx and Kā Pūtahi sub-catchments will be treated through first-flush basins and wetlands.
  • Action 3 - Sub-catchment treatments - Stormwater from fully developed Kruses Drain and Prestons Creek sub-catchments will be treated in first-flush basins and wetlands between Prestons Road and Queen Elizabeth II Drive.
  • Action 4 - Hardstanding areas - Stormwater generated from hardstanding areas within each industrial allotment to be pre-treated using an approved gross pollutant trap (GPT), vegetated swale or other proprietary pre-treatment device.
  • Action 5 - Industrial roof coating - All new industrial roofs are required to be coated (painted).
  • Action 6 - Erosion and sediment control - Erosion and sediment control on development and construction sites, (Section 12 Goal 1.3).
  • Action 7 - Auditing high-risk industrial sites - Auditing high-risk industrial sites and working with occupiers to remediate contaminated stormwater discharges, (Section 12 Goal 4.2 to 4.4).
  • Action 8 - Working with community groups - Working with community groups and the public to educate the community about the effects of and mitigation of stormwater contaminants, (Section 12 Goal 5.1).

These actions can be implemented by the Council using its powers under the Local Government Act.

Source control options such as roof painting could be desirable but at present are not within the Council’s powers under the Local Government Act.