Wellington Water stage two global stormwater discharge consent. Assessment of effects on the environment
- Author
- Cameron D, Liu J
- Year
- 2023
- Journal / Source
- Wellington Water Limited
- Pages
- 204 pp
- Summary
- The stormwater networks owned by Wellington City Council, Porirua City Council, Hutt City Council, and Upper Hutt City Council are administered for the client councils by Wellington Water Ltd. Stormwater is discharged from these networks into freshwater or coastal water environments. The purpose of this Assessment of Environmental Effects (AEE) is to provide technical support for an application for resource consent for the discharge of stormwater from the stormwater networks. This AEE forms part of the consent application documentation that covers all information required under Schedule 4 of the RMA. It should be read in conjunction with the Stormwater Management Strategy (SMS) which also forms part of the consent application. The stormwater networks are located within 35 sub-catchments (or management units) which mostly correspond with stream catchments. The catchments have been modified by varying degrees of urban development, with several having more than 70% of the catchment area serviced by a stormwater network. Descriptions of the existing environment in each of the 35 sub-catchments are provided. The state of the environment is influenced by multiple contaminant sources and stressors, one of which is the discharge of stormwater from local authority stormwater networks. The effects of stormwater discharges from stormwater networks on the receiving environment are assessed. In general, the sub-catchments with the longest stormwater network length and highest proportion of stormwater network area (i.e., Evans Bay, Lambton, Porirua, Waiwhetu) had the highest level of adverse effects. The Owhiro Bay and Houghton Bay catchments showed high levels of adverse effects, but this is attributed, at least partly, to landfills within the catchment boundaries. Locations on the Porirua Coast including Plimmerton South Beach and Titahi Bay South also had elevated levels of effect on aesthetic values and recreational values but in both cases faults with the wastewater network are the dominant source of contamination. The AEE has identified the potential for urban stormwater to cause a ‘more than minor’ level of adverse effect in the receiving environment in 12 of the 35 sub-catchments. Wellington Water proposes to resolve these adverse effects through a Stormwater Management Strategy (SMS), under the governance of a Collaborative Committee.