REPORT Waikato River Water Take and Discharge Proposal - Board of Inquiry River Ecology Assessment Prepared for Watercare Services Limited Prepared by Tonkin & Taylor Ltd Date December 2020 Job Number 1014753.100 Tonkin & Taylor Ltd December 2020 Waikato River Water Take and Discharge Proposal - Board of Inquiry - River Ecology Assessment Job No: 1014753.100 Watercare Services Limited Document Control Title: Waikato River Water Take and Discharge Proposal - Board of Inquiry Date Version Description Prepared by: Reviewed Authorised by: by: 11/12/2020 1.0 Final Liza Kabrle Dean Miller Peter Roan Distribution: Watercare Services Limited 1 electronic copy Tonkin & Taylor Ltd (FILE) 1 electronic copy Table of contents 1 Introduction 1 2 Project background 4 2.1 Description of the consent application 4 2.2 Proposed abstraction rate and intake design 5 2.3 Indicative construction methodology 6 3 Waikato Regional Plan 8 3.1 Planning limitations 8 3.2 Information requirements 8 3.3 Waikato Regional Plan Change 1 (Healthy Rivers) 9 3.4 National Policy Statement – Freshwater Management 9 4 Assessment methodology 11 4.1 Step one: Assigning ecological value 11 4.2 Step two: Assess magnitude of effect 11 4.3 Step three: Assessment of the level of effects 12 4.4 Assigning an RMA interpretation to level of effect 12 5 Ecology of the Waikato River 13 5.1 Waikato River water quality 13 5.1.1 WRC water quality records 13 5.1.2 Watercare Waikato River water quality records 14 5.2 River freshwater biota 15 5.2.1 Macroinvertebrates 15 5.2.2 Fisheries 16 5.3 Riparian and wetland values 19 6 Existing intake structure 21 6.1 Existing intake design 21 6.2 Intake impingement and entrainment records 21 6.3 Impingement and entrainment monitoring results 22 7 Existing WTP discharges 25 7.1 Quantity of the existing WTP discharges 25 7.2 Quality of the existing WTP discharges 26 7.2.1 Dimensions of the mixing zone 28 8 Assessment of ecological effects 30 8.1 Assigning ecological value 30 8.2 Construction effects 31 8.2.1 Effects on river water quality 31 8.2.2 Effects on the river bed 32 8.2.3 Effects on river freshwater biota 32 8.3 Operational effects 33 8.3.1 Effects on river temperature and dissolved oxygen due to reduced flow in the Waikato River 33 8.3.2 Effects on river water quality through routine cleaning of the screens 38 8.3.3 Effect of the WTP discharge on water quality and the ecology of the lower Waikato River 39 8.3.4 Effects on river freshwater biota through the abstraction of water and operation of the intake screens 44 8.4 Summary of effects 49 Tonkin & Taylor Ltd Waikato River Water Take and Discharge Proposal – Board of Inquiry River Ecology Assessment Watercare Services Ltd 9 Reference list 54 10 Applicability 57 Appendix A : Waikato River Take - Wetland Classification for Waikato Intake Structure (Beca, 2020) Appendix B : EcIA Guidelines Tables Appendix C : Waikato Raw Water - Watercare 2016 – 2020 Appendix D : Effect of the proposed discharge on Waikato River FAC concentrations at Q5 low flow (185.9 m3/s) Appendix E : Bench testing of free available chlorine (Source: Watercare 2017) Tonkin & Taylor Ltd Waikato River Water Take and Discharge Proposal – Board of Inquiry River Ecology Assessment Watercare Services Ltd Executive summary Introduction Watercare Services Limited (Watercare) is seeking consent through the Board of Inquiry process to abstract a further 150,000 m3/day net from the Waikato River, year round, as well as consents for the construction and operation of a new water intake and the discharge of process water and off- spec water. This report provides an assessment of the river ecological effects prepared to inform the application to be considered by the Board of Inquiry. This report provides an assessment of the ecological values of the lower Waikato River, downstream of the Waikato Intake. An assessment is made of the effects associated with the construction and operation of the intake structure, the proposed water take and any associated changes in water levels and flow and proposed Water Treatment Plant discharges on these values. Specifically, the report: · Describes freshwater values within the lower Waikato River based on a desktop review and monitoring information from the existing Waikato Water Treatment plant. · Provides an assessment of effects on ecological values in general accordance with Ecological Institute of New Zealand (EIANZ) guidelines. · Describes measures to avoid, remedy, mitigate the potential adverse effects, where necessary. Freshwater values The Waikato River provides for a diverse range of native fish species, as well as a pathway for various species to migrate upstream and downstream to complete their lifecycles. Of the nineteen native fish species recorded in the lower Waikato River, two are considered to be ‘Threatened’ and eight are considered to be ‘At risk’ (Dunn et al., 2018). However, when assigning an overall ecological value to the lower Waikato River, a number of other factors have also been taken into consideration. For example: · Macroinvertebrate communities recorded at WRC sites closest to the intake do not appear to contain taxa that are particularly sensitive to changes in water quality or habitat disturbance; · Riparian vegetation is largely dominated by exotic species including willows and alder; and · Water quality is noted as “Unsatisfactory” for some key parameters such as total phosphorus and turbidity. When taking all these factors into consideration, for the purpose of this assessment we have considered the lower Waikato River as being of High ecological value. However, the Nationally and Regionally significant wetlands approximately 13 km downstream have specifically been given an ecological value of Very High. Freshwater effects The potential effects on freshwater values can be broken down into short term effects associated with the construction and long term effects relating to the operation of the intake and operational discharges. Potential effects related to the construction phase include effects on river water quality, the river bed and river freshwater biota associated with the piling activities and construction of a coffer dam. For the operational phase this effects assessment focuses on potential effects on water quality and river biota as a result of changes to water levels and flow due to the abstraction, changes to water quality associated with operational discharges into the Waikato River and the potential effects associated with the intake structure and screens on river biota. Tonkin & Taylor Ltd Waikato River Water Take and Discharge Proposal – Board of Inquiry River Ecology Assessment Watercare Services Ltd Potential effects during the construction period have been minimised as far as practicable by minimising the footprint of temporary and permanent structures on the river bed, disposing any spoil from the pilling away from the river, ensuring water contaminated with cement is not discharged directly into the river and having appropriate emergency spill kits are held on site. Potential for longer term effects on native fish will be minimised or mitigated through locating the screens in fast flowing water away from the bank but not in the centre of the river, installing screens with a 1.5 mm slot widths on the wedge wire screen and “approach” velocities of less than 0.15 metres per second. To maximise the protection it is also proposed that water velocities parallel with the screen (i.e. the sweep velocity) would be at least twice the approach velocity. Water quality effects due to discharges will be managed by including limits for key contaminants in the consent, de-chlorination is proposed where necessary and high dosage glycerine removed from site rather than discharging into the river. Conclusion Overall, the level of effects on river ecological values associated with the construction and operation of the Waikato Intake structure, abstraction of the water from the Waikato River and operational discharges will be between Low and Very Low. Therefore, the proposal’s overall level of effect on river ecological values is Low. There can be a high level of confidence in our predictions of effects due to the existing monitoring that has occurred for a similar intake structure and WTP discharge regime operating immediately adjacent to the location proposed under this application. Given the proposed works and design, and overall effect on ecological values as determined through this assessment, no further mitigation measures beyond those identified in this report, and included as part of the proposal, are considered to be required. Tonkin & Taylor Ltd Waikato River Water Take and Discharge Proposal – Board of Inquiry River Ecology Assessment Watercare Services Ltd 1 Introduction Watercare Services Limited (Watercare) is a lifeline utility providing water and wastewater services to a population of 1.7 million people in Auckland. Its services are vital for life, keep people safe and help communities to flourish. More specifically, Watercare is the council-controlled organisation of Auckland Council responsible for municipal water supply within Auckland, and the provider of bulk water supply services to Pokeno and Tuakau in the Waikato District1. Watercare supplies approximately 440,000 cubic metres of water per day (m3/day) on average across the year, derived from a range of sources and treated to the Ministry of Health Drinking Water Standards for New Zealand 2005 (revised 2018). Watercare’s three main water supply sources are:2 · Water storage lakes in the Hūnua and Waitākere ranges; · A groundwater aquifer in Onehunga; and · The Waikato River. The exact proportion supplied from each source varies daily, depending on a range of factors including the levels in the storage lakes, forecast rainfall, treatment plant capacity, and maintenance requirements. In December 2013, Watercare applied to the Waikato Regional Council (“WRC”) for resource consents to authorise abstracting an additional 200,000 m3/day (net) of water from the Waikato River, a new water intake structure and discharges from a new water treatment plant.