SEAVIEW WWTP INTERMITTENT DISCHARGES Resource consent application and Assessment of Environmental Effects October 2017

Resource consent application – October 2017

Document Control Document Information

Document data

Document ID Seaview WWTP Intermittent Discharges Resource Consent and AEE

Document Owner Stewart McKenzie

Issue Date 27 October 2017

Document History

Version Issue Date Changes

1 5/10/17 Internal peer review

2 11/10/17 Client draft for review

3 22/10/17 Revised draft for client review

4 27/10/17 Final for lodgement

Document Sign-Off

Name Role Sign-off Date

Richard Peterson Author 27 October 2017

David Cameron Author 27 October 2017

Stewart McKenzie Approver 27 October 2017

Resource consent application – October 2017

CONTENTS 1. Introduction ...... 1 1.1 Background and Context for the application ...... 1 2. Description of the activity ...... 2 2.1 The proposal ...... 2 2.2 Value of the existing infrastructure ...... 2 2.3 Activities for which resource consent is sought ...... 2 2.3.1 Discharge to the Waiwhetū Stream ...... 3 2.3.2 Discharge to the Hutt River ...... 3 2.3.3 The new discharge structure ...... 4 2.3.4 Deposition of rock rip rap ...... 4 2.3.5 Construction Methodology ...... 5 2.3.6 Disturbance of bed material ...... 5 2.3.7 Diversion of water ...... 6 2.3.8 Occupation and use of the CMA ...... 6 2.3.9 Summary of the Activities ...... 6 2.4 Ancillary activities ...... 7 2.4.1 The outfall pipe extension ...... 7 2.4.2 Disturbance of contaminated soil ...... 7 2.4.3 The storage tank ...... 8 3. Site description ...... 9 3.1 Waiwhetū Stream ...... 9 3.1.1 Location ...... 9 3.1.2 Māori Cultural Landscape ...... 9 3.1.3 Current Natural Character ...... 10 3.1.4 Stream Ecology ...... 10 3.1.5 Hydrology ...... 11 3.1.6 Saltmarsh Habitat ...... 11 3.1.7 Vegetation of Terrestrial Margins ...... 12 3.1.8 Macroalgae ...... 12 3.1.9 Sediments ...... 12 3.1.10 Water Quality ...... 13 3.1.11 Eutrophication ...... 14 3.1.12 Sediment Contamination ...... 14 3.1.13 Shellfish Flesh Toxicity ...... 15 3.1.14 Benthic Invertebrate Community ...... 15 3.1.15 Fish Community ...... 16 3.1.16 Recreation ...... 16 3.1.17 Policy Statement and Plan Schedules applying to the site ...... 16 3.2 Hutt River ...... 17

Resource consent application – October 2017

3.2.1 Location ...... 17 3.2.2 Māori Cultural Landscape ...... 17 3.2.3 Current Natural Character ...... 18 3.2.4 Physical Characteristics ...... 18 3.2.5 Hydrology ...... 18 3.2.6 Ecological Values...... 18 3.2.7 Macroalgae ...... 19 3.2.8 Sediments ...... 20 3.2.9 Water Quality ...... 21 3.2.10 Invertebrates ...... 22 3.2.11 Fish ...... 23 3.2.12 Birds ...... 24 3.2.13 Recreation ...... 24 3.2.14 Hutt River Mouth Sediment Extraction ...... 25 3.2.15 Policy statement and plan schedules applying to the Hutt River site ...... 25 3.3 Wellington Harbour ...... 26 3.3.1 Hydrodynamics ...... 26 3.3.2 Intertidal Ecology ...... 26 3.3.3 Edible Shellfish ...... 26 3.3.4 Subtidal Ecology ...... 26 4. Reasons why resource consent is required ...... 27 4.1 Intermittent discharges to the Waiwhetū Stream ...... 27 4.1.1 Regional Freshwater Plan ...... 27 4.1.2 Proposed Natural Resources Plan ...... 27 4.1.3 Summary ...... 28 4.2 Discharges and physical works in the Hutt River ...... 28 4.2.1 The intermittent discharge of treated wastewater to the Hutt River ...... 28 4.2.2 The new discharge structure in the CMA ...... 28 4.2.3 The deposition of rock rip rap on the bed of the Hutt River ...... 29 4.2.4 The disturbance of seabed ...... 30 4.2.5 The diversion of water during construction ...... 30 4.2.6 Occupation ...... 31 4.2.7 Summary ...... 31 5. Consideration of alternatives ...... 33 5.1 Overview ...... 33 5.2 Possible alternative locations or methods ...... 34 5.3 Selection of the preferred option ...... 37 5.3.1 Options 1 and 2...... 37 5.3.2 Options 3 and 5...... 38 5.3.3 Option 6 ...... 38

Resource consent application – October 2017

5.3.4 Options 8 and 12...... 39 5.3.5 Comparison of options 3 and 12 ...... 39 6. Assessment of Environmental Effects ...... 41 6.1 Introduction ...... 41 6.2 Positive effects ...... 41 6.3 Effects on Māori cultural values ...... 42 6.3.1 Background ...... 42 6.3.2 Seaview Wastewater Treatment Plant and the Temporary Discharge to the Waiwhetū Stream...... 42 6.3.3 The Proposal...... 42 6.3.4 Phase 1 Consent – Māori Cultural Effects ...... 42 6.3.5 Phase 2 Consent – Māori Cultural Effects ...... 43 6.3.6 Conclusions ...... 44 6.4 Water Quality ...... 44 6.4.1 Characterisation of wastewater discharges ...... 44 6.4.2 Plume dilution and dispersion assessment ...... 46 6.4.3 Ammonia water quality criteria ...... 49 6.5 Water quality effects on the Waiwhetū Stream ...... 50 6.5.1 Results of monitoring during repair discharges from the existing Waiwhetū outfall ...... 50 6.5.2 Results of monitoring wet weather overflow discharges from the existing Waiwhetu outfall 51 6.5.3 Assessment of effects of proposed MOP repair discharges to Waiwhetū Stream ...... 51 6.5.4 Assessment of effects of proposed wet weather overflows to Waiwhetū Stream ...... 51 6.6 Water quality effects on the Hutt River ...... 54 6.6.1 Predicted effects of MOP repair discharges to Hutt River ...... 54 6.6.2 Predicted effects of proposed wet weather overflow discharges to Hutt River ...... 58 6.7 Summary of water quality effects of WWTP discharges ...... 59 6.8 Aquatic Ecology ...... 62 6.8.1 Effects of new outfall construction ...... 62 6.8.2 Effects of MOP repair discharges ...... 62 6.8.3 Effects of wet weather overflow discharges on aquatic ecology ...... 64 6.8.4 Summary of effects on aquatic ecology ...... 64 6.9 Effects on natural character ...... 64 6.10 Visual amenity effects ...... 65 6.11 Recreation effects ...... 66 6.12 Flooding effects ...... 67 7. Iwi and stakeholder consultation ...... 68 7.1 Iwi engagement ...... 68 7.2 The Waiwhetū consultation group ...... 69 7.3 Consultation during the options assessment ...... 69 7.3.1 Regional Public Health...... 70 7.3.2 Friends of the Waiwhetū ...... 70

Resource consent application – October 2017

7.3.3 Wellington Recreational Marine Fishers’ Association (Inc) ...... 71 7.3.4 Petone Community Board ...... 71 7.3.5 Seaview Business Association ...... 71 7.3.6 2017 meetings with the Waiwhetū consultation group ...... 71 7.4 Annual Plan Feedback ...... 72 7.5 Market Research Report ...... 72 8. Assessment against relevant provisions ...... 74 8.1 Introduction ...... 74 8.2 Weight to be afforded to the Regional Plans ...... 74 8.3 Planning assessment ...... 75 8.3.1 Protecting and preserving natural character ...... 75 8.3.2 Tangata whenua, kaitiakitanga & cultural relationships ...... 75 8.3.3 Benefits of regionally significant infrastructure ...... 77 8.3.4 Water quality ...... 77 8.3.5 Ecosystems ...... 78 8.3.6 Habitats with significant value ...... 79 8.3.7 Amenity values...... 80 9. Pt II RMA ...... 82 10. Consent conditions ...... 86 10.1 Introduction ...... 86 10.2 Waiwhetū discharge permit conditions ...... 86 10.3 Hutt River coastal permit conditions ...... 87 10.3.1 Discharge to the Hutt River ...... 87 10.3.2 Structure, deposition, disturbance, occupation ...... 87 11. Consent duration ...... 89 11.1 Discharge to the Waiwhetū Stream ...... 89 11.2 Hutt River consents ...... 89 12. Conclusion ...... 91 List of Abbreviations ...... 92 References ...... 94 Appendix A: Application Drawings Appendix B: Application Forms Appendix C: Planning Assessment Appendix D: Water quality guidelines Appendix E: Dye release studies Appendix F: Dilution Assessment – Numerical Model Appendix G: Assessment of Effects on Natural Character and Visual Amenity Appendix H: Recreation Effects Assessment Appendix I: Public Consultation Survey

Resource consent application – October 2017

LIST OF TABLES Table 1 - Summary of activities ...... 6 Table 2: Summary of intertidal substrate classes, 2009 & 2012 (from Stevens & Robertson, 2012) ...... 12 Table 3: Summary of monthly water quality data at RSoE site RS57 (GWRC data) and at Seaview Road Bridge (HCC data) from May 2015 to May 2016 (N=11) ...... 13 Table 4: Summary results for Waiwhetū Stream, 2009 and 2012 (Stevens & Robertson, 2012) ...... 14 Table 5: Nutrient concentrations and loads in the Hutt River at Boulcott (Heath & Greenfield, 2016) ..... 21 Table 6: Summary of water quality results for sites 1, 2 & 3 (HCC monthly samples, June to October 2017, n=5) ...... 22 Table 7: Summary of the NZFFD records for the Hutt River as of June 2015 (n=93)...... 24 Table 8 - Summary of the Hutt River resource consents ...... 31 Table 9: Record of MOP repair discharges from Seaview WWTP to Waiwhetū Stream ...... 44 Table-10: Treated wastewater quality from daily samples collected from MOP repair discharges to Waiwhetū Stream during the 2013/14 and 2014/15 monitoring years ...... 45 Table 11: Record of wet weather overflow discharges from Seaview WWTP to Waiwhetū Stream ...... 45 Table 12: Treated wastewater quality from daily samples collected from wet weather overflow discharges during 2013 to 2017 (n=38) ...... 46 Table 13: Predicted 50th percentile dilution range (x-fold) at eight sensitive sites (from DHI, 2017) ...... 49 Table 14: Trigger values for ammonia toxicity ...... 50 Table 15: Waiwhetū Stream monitoring results during dry weather repair discharges the years to 31 June 2015, 2016 and 2017 (n = 35). Receiving water guidelines are outlined in Appendix D. Exceedances of recommended guidelines are highlighted in red...... 52 Table 16: Waiwhetū Stream monitoring results during wet weather overflow discharges during the year to June 2017 (n=12). Receiving water guidelines are outlined in Appendix D. Exceedances of recommended guidelines are highlighted in red...... 53 Table 17: Predicted contaminant concentrations in the Hutt River and Wellington Harbour during dry weather repair discharges based on 50-percentile treated wastewater concentrations and the lowest 50- percentile dilution value from all dry weather wind and tide scenarios. Exceedances of recommended guidelines are highlighted in red...... 56 Table 18: Predicted worst-case contaminant concentrations in receiving waters during dry weather repair discharges based on 95-percentile wastewater concentrations and the lowest 50-percentile dilution value from all dry weather wind and tide scenarios. Exceedances of guidelines are highlighted in red...... 57 Table 19: Predicted contaminant concentrations in receiving waters during wet weather overflow discharges to the Hutt River based on 50-percentile wastewater concentrations, 0.8 m3/d discharge rate and the lowest 50-percentile dilution value from all wet weather wind and tide scenarios...... 60 Table 20: Predicted contaminant concentrations in receiving waters during wet weather overflow discharges to the Hutt River based on 95-percentile wastewater concentrations, 3 m3/s discharge rate and the lowest 50-percentile dilution value from all wet weather wind and tide scenarios...... 61 Table 21 - Identified Stakeholders ...... 70 Table 22: Part 2 Assessment ...... 82

Resource consent application – October 2017

1. Introduction Resource consents are currently in place for two intermittent discharges of treated wastewater from the Seaview wastewater treatment plant (Seaview WWTP). The discharges are: 1. Discharges during and/or immediately after heavy rain events (WGN120142 [33406]). If as a result of the rainfall events the flow of treated wastewater through the Seaview WWTP exceeds the capacity of the main outfall pipeline (MOP), and the storm tank within the Seaview WWTP is full, treated wastewater is discharged via the outfall to the Waiwhetū Stream. 2. Discharges that occur while repairs are undertaken on the MOP (WGN120142 [33408]). During such works treated wastewater from the Seaview WWTP is diverted from the MOP and discharged via the outfall to the Waiwhetū Stream. Both of these resource consents expire on 1 February 2018. Through this application, Wellington Water seeks to replace these expiring resource consents. The proposal involves the relocation of the discharge point from the Waiwhetū Stream to the Hutt River and the addition of a 10,000 m3 storage tank. To enable the current discharges to continue a number of resource consents are sought as part of this application. These resource consents are described in section 2.2 and more specifically in section 4. Application drawings are included in Appendix A and Application forms are included in Appendix B. 1.1 Background and Context for the application The Seaview WWTP began operating in October 2001 and was formally commissioned in March 2002. The Seaview WWTP provides secondary biological treatment with ultra-violet (UV) disinfection. The 18km long MOP conveys treated and UV disinfected wastewater from the Seaview WWTP to the Pencarrow Outfall at Bluff Point approximately 500m south-east of Pencarrow Head. The pipeline was constructed over the period July 1956 to October 1959 and was commissioned in 1962. The pipeline consists of approximately 4,000 pipe sections of pre-stressed concrete rubber ring jointed construction. Repair work is required on the MOP from time to time, which on occasion requires the operation of the MOP to cease. At such times the treated wastewater from the Seaview WWTP is currently discharged to the Waiwhetū Stream. The frequency, flow rate, volume and quality of these discharges is described in section 6.2. Resource consent was first obtained for these repair related discharges in February 2013. At the same time, resource consent was obtained for wet-weather related discharges that also occur to the Waiwhetū Stream. Compared to the current discharges, the proposal covered by this application makes three key changes to the nature of the discharge:

1. Relocating the discharge point from the Waiwhetū Stream to the Hutt River. 2. Using additional storage at the WWTP to reduce the number of wet weather discharges that would otherwise occur. 3. Using additional storage at the WWTP to enable the repair related discharges to be released on the outgoing tide, which reduces the risk of backflow up the Waiwhetū Stream.

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Resource consentconsent application – October 2017

2. Description of the activity 2.1 The proposal The proposal for which Wellington Water seeks resource consent has two phases.

Phase 1- This involves the continuation of the intermittent discharges to the Waiwhetū Stream for a period of 5 years from the grant of resource consent. The period is required to enable detailed design, tendering, construction and commissioning of the proposed new discharge pipe and structure following grant of this resource consent. The phase 1 discharges will continue to occur from the outfall used for the existing discharges. This outfall is located in the concrete wall that lines the true left bank of the Waiwhetū Stream. The outfall is approximately 120 metres from the mouth of the Waiwhetū Stream. No new infrastructure is proposed as part of phase 1. Phase 2 – This involves the relocation of the discharge point from the Waiwhetū Stream to the Hutt River. The new discharge point is proposed to be located on the true left bank of the Hutt River, approximately 50 metres downstream of the confluence of the Hutt River and Waiwhetū Stream. This phase requires:  the construction of new pipe infrastructure to carry the treated wastewater from the existing discharge point to the proposed discharge point  the construction of a new outfall structure  the construction of a small rock rip rap ‘headland’ in the Hutt River to help mitigate the visual effects of the new outlet,  the construction of additional storage and associated pipework within the Seaview WWTP site. 2.2 Value of the existing infrastructure Clause 3 of Schedule 4 to the Resource Management Act requires –

if the application is affected by section 124 (which relate to existing resource consents), an assessment of the value of the investment of the existing consent holder (for the purposes of section 104(2A)):

To this end it is noted that the optimised replacement cost of the Seaview WWTP is $75.4M. Its depreciated value at 2014 was $43.3M. The Waiwhetū outfall pipe has a replacement cost of $2,300 per metre and depreciated value of $460/m. The existing overflow pipe is approximately 250m long. The MOP has a replacement cost of $55.5M as at 2014 and a depreciated valuation of $20.0M. 2.3 Activities for which resource consent is sought To facilitate the proposal this application seeks resource consent for:  The continuation of the intermittent discharges into the Waiwhetū Stream for a period of 5 years from the grant of resource consent  The discharge of both wet weather and repair related discharges into the Hutt River for a period of 35 years from the grant of resource consent  The construction of a new discharge structure in the Hutt River near its confluence wit h the Waiwhetū Stream  The deposition of rock rip rap on the bed of the Hutt River associated with the construction of the small headland  The disturbance of the Hutt River bed associated with the construction of the discharge structure and the small headland

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Resource consentconsent application – October 2017

 The diversion of water around the proposed headland during construction  The occupation of the CMA.

2.3.1 Discharge to the Waiwhetū Stream This part of the consent application relates to the continuation of the two treated wastewater discharges which are the subject of the current consents. These discharges are: 1. Discharges during and/or immediately after heavy rain events when flows exceed the capacity of the MOP and the existing storage tank is full, treated wastewater is discharged to the Waiwhetū Stream via the existing outfall. 2. Discharges associated with repair works on the MOP which require Seaview WWTP treated wastewater to be diverted and discharged to the Waiwhetū Stream outfall The overflows mentioned in point 1 occur when there is sustained wet weather. Initially in these instances, flows of treated wastewater in excess of the capacity of the MOP are diverted to the existing storage tank. When the storage tank is full, any flow above the capacity of the MOP overflows into the pipeline leading to the Waiwhetū Stream. The discharges mentioned in point 2 occur when the MOP is out of operation for repair. It is proposed that these discharges would operate under the same terms as the existing consent. These are:  Planned repair work shall be carried out between 5 May and 5 July each year, and for a maximum period of 6 weeks; and  Unplanned repair works, which cannot be deferred until the next planned repair period, shall occur for a maximum period of 2 weeks. To allow for the detailed design, construction and commissioning of the proposed alternative discharge outfall the resource consent for discharges to the Waiwhetū Stream is sought for a period of 5 years from grant of this consent (See section 11). 2.3.2 Discharge to the Hutt River Once the necessary infrastructure is in place, it is proposed that the discharge point would be relocated to the Hutt River. The discharge would occur close to the true left bank of the Hutt River, at a point just downstream of the confluence between it and the Waiwhetū Stream (see drawing 80509150-01-001-C001). The discharges would in broad terms be similar to those that currently occur. That is they would involve: 1. The discharge of treated wastewater during and/or immediately after heavy rain events when flows exceed the capacity of the MOP and the storage tanks; and 2. The discharge of treated wastewater while repair work (planned and unplanned) is undertaken on the MOP. In relation to the repair work discharges it is noted that consent is sought based on the same terms included in the current consent. These are:

 Planned repair work shall be carried out between 5 May and 5 July each year, and for a maximum period of 6 weeks; and  Unplanned repair works, which cannot be deferred until the next planned repair period, shall occur for maximum period of 2 weeks.

These terms represent the worst case for the repair work discharges. As is explained in more detail in section 6.2, the actual frequency and duration of repair work discharges has been, and is expected to be, much less than this worst case. The proposal also involves the construction of 10,000 m 3 of additional storage at the Seaview WWTP as a key mitigation measure. This will increase the total storage volume at the WWTP to 15,000 m3. As a result the discharges from the proposed Hutt River discharge point will differ from the existing Waiwhetū Stream discharges in two respects:

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Resource consentconsent application – October 2017

1. The additional storage has been sized to ensure that repair work discharges can be timed to occur on the outgoing tide during dry weather conditions (i.e. the tidal discharge regime). The benefit of the tidal discharge regime is that it significantly reduces the risk of backflow up the Waiwhetū Stream. It does however mean that the volume of discharge on the outgoing tide is doubled. The environmental effect of this is addressed in section 6. 2. The additional storage will reduce the number of wet weather discharges that would otherwise occur. On average over the period of 2003 to 2017 there have been 4-5 wet weather discharges of treated wastewater into the Waiwhetū Stream from the Seaview WWTP per year. Had storage volumes of 15,000 m3 been in operation on the WWTP site during this period, it is expected that the average annual number of discharges would have been 1-2 less. It is noted that the actual number of wet weather discharges that occur in any one year is dependent on rainfall. Therefore, it is not possible to predict the number of wet weather discharges that will occur from the proposed Hutt River discharge point with accuracy. The application therefore does not propose a limit on the timing, duration or number of wet weather discharges. 2.3.3 The new discharge structure To facilitate the proposed discharge into the Hutt River a new discharge structure needs to be constructed. A concept design for the discharge structure is shown on drawings 80509150-01-001-C001 to C102. The main aspect of the structure will be the 1.6m diameter outfall pipe. The concept design shows the outfall pipe extending a lineal distance of 30 metres from the Hutt River bank (measured from the highest astronomical tide mark) and angled downstream so that at its end it is 16 m from the river bank, when measured at right angles from the highest astronomical tide mark. Please note: the exact alignment of the outfall pipe will be confirmed as part of the detailed design process, including responding to the outcome of geotechnical investigations. The confirmation of the outfall pipe alignment will be undertaken under a resource consent condition. The pipe will be encased in concrete, 0.5m thick. The structure and encasing will be secured to the river bed using sheet piles. How deep these piles need to extend below the river bed has not yet been determined. This will require specific geotechnical investigations. These investigation s will be undertaken as part of detailed design. If it is determined that the piles will need to extend to a depth which impacts on the Hutt Aquifer, resource consent will be sought for this at that time. 2.3.4 Deposition of rock rip rap To visually integrate the outlet structure into the Hutt River bank, it is proposed to construct a small ‘landform’ around the pipe using rock rip rap. A concept design for these works is shown on drawing 80509150-01-001-C101. The area of this landform will be approximately 500m2. Its maximum dimension measured at right angles from the Hutt River bank will be approximately 16m from the current highest astronomical tide mark. The rock rip rap will be sized to reduce the risk of erosion during flood events. The rip rap will sit slightly higher than the concrete encasing on the outlet pipe. The top, flat surface of the concrete encasing will not be covered. The rip rap will tie into the existing rip rap that lines the true left bank of the Hutt River at this point. Please note: the exact form of the rock rip rap landform will be confirmed as part of the detailed design process, including responding to the outcome of geotechnical investigations. The confirmation of the landform dimension and shape will be undertaken under a resource consent condition. Should the construction works for either the pipe or the headland require the removal of the existing amenity planting adjoining this part of the river bank this will be replaced, taking account of maintenance requirements of the infrastructure, and in consultation with Hutt City Council Parks and Gardens.

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Resource consentconsent application – October 2017

The construction of the rock rip rap landform will require the re-alignment and replacement of an existing stormwater pipe (see drawing 80509150-01-001-C101 and C102). The replacement pipe will be integrated into the landform. The discharges from this stormwater pipe are covered under the global stormwater consent application (still being processed at time of application). It is considered that this landform does not constitute reclamation of part of the CMA. This is because the land will not become part of the Hutt City district, it will continue to be part of the CMA. 2.3.5 Construction Methodology The construction of the new treated wastewater outfall, replacement stormwater pipe and reclamation is expected to proceed as follows:  Completion of the land based works, not subject to GWRC resource consents (see section 2.4 for details)  Installation of bund/sheet piling around construction site to divert the river  Install erosion and sediment control (as part of the bund)  Remove bed material to required depth, including dewatering  Install foundations of the structure, and bed material  Install pipe, concrete casing and backfill

 Place rock rip rap. Approximate D50 = 800mm to 1000mm. Rip rap to be keyed into river bed  Removal of bund/temporary sheet piling  Soil and planting Re-fuelling and maintenance of all plant will take place away from the river environment. These works are expected to take 3 months, and most likely would occur in summer and early autumn when the weather is more likely to be settled. The works would be programmed to avoid the months of September and October, which is the peak period for upstream migrations of juvenile eels and whitebait. A construction management plan for the works in the bed of the Hutt River will be required by a condition of the resource consent and be prepared by a contractor prior to commencement of construction. This will be submitted to the Greater Wellington Regional Council (GWRC) for certification that it fulfils the condition of the resource consent. 2.3.6 Disturbance of bed material During the construction of the landform and discharge structure, the bed of the Hutt River will be disturbed. This bed disturbance will occur over an area of approximately 500 m2, aligned with the footprint of the proposed landform. The depth of the bed disturbance will be confirmed following geotechnical investigations at the time of detailed design. The bed material removed from the site will most likely be disposed of at Silverstream landfill, either to special cells, or general landfill, depending on the level of contamination. The purpose of the bed disturbance is to provide suitable footing for the outlet structure and rock rip rap. The area around the Waiwhetū Stream mouth and banks is shown on the GWRC SLUR database, and known from previous works in the area (Waiwhetū Stream Clean Up, 2009-10) , as containing contaminated material. The stream clean up works revealed high levels of hydrocarbons, lead, arsenic, cadmium and copper, amongst other contaminants. As part of the geotechnical investigations undertaken for detailed design, samples of the bed material which will be disturbed will be tested for contamination. If these tests indicate contaminant levels above appropriate standards then the material will be disposed of at suitable landfill sites. As with the previous Waiwhetū Stream clean up works, where possible materials will be retained on site. If the soil samples tested in the investigations contain contaminants at concentrations above the guidelines for the protection of excavation workers dealing with this health and safety risk will be dealt with in the Health & Safety Plan. Staff likely to complete the drainage works also regularly

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Resource consentconsent application – October 2017

work with untreated wastewater and are therefore familiar with the precautionary measures that are required to keep them safe. These include:  Avoid contact with fill materials, use disposable gloves and avoid hand-to-face contact.  Treat excavated pits as confined spaces, test and monitor flammable/toxic gas levels (e.g. hydrocarbon vapours, carbon monoxide)  Minimise dust generation by dampening down of soil if necessary  Dust masks to be available on site, to be used during dry/windy conditions as appropriate  Wash hands before eating, drinking or smoking

Please note: the exact location of the bed disturbance will be confirmed as part of the detailed design process, including responding to the outcome of geotechnical investigations. Confirmation of this will be undertaken under a resource consent condition. 2.3.7 Diversion of water The construction works will involve the diversion of water in the Hutt River. Resource consent is sought for this as part of this application. 2.3.8 Occupation and use of the CMA Both the outfall structure and rock rip rap landform require the permanent occupation of part of the CMA. The area of the occupation equates to the foot print of the rock rip rap as shown on drawing 80509150-01-001-C101.

Please note: the exact occupation will be confirmed as part of the detailed design process, including responding to the outcome of geotechnical investigations. Confirmation of this will be undertaken under a resource consent condition.

2.3.9 Summary of the Activities Table 1 summarises the activities for which resource consent is sought from GWRC. The assessment of the activity status is set out in section 4.

Table 1 - Summary of activities

Activity RFP / RCP PNRP consent consent status status Waiwhetū Stream Activities

The intermittent discharge of treated wastewater to the RFP Rule 5 PNRP Rule 61 Waiwhetū Stream Discretionary Discretionary Hutt River Activities

The intermittent discharge of treated wastewater to the Hutt RCP Rule 58 PNRP Rule 61 River Discretionary Discretionary The placement of a new discharge structure in the bed of the RCP Rule 25 PNRP Rule 162 Hutt River Discretionary Non-complying The deposition of rock rip rap on the bed of the Hutt River RCP Rule 48 PNRP Rule 209 Discretionary Non-complying The disturbance of bed material during the construction of RCP Rule 40 PNRP Rule 205 the outfall and landform Discretionary Non-complying

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Resource consentconsent application – October 2017

Activity RFP / RCP PNRP consent consent status status The diversion of water during construction RCP Rule 76 Ancillary activity under rules 162 Discretionary & 209 The occupation of the CMA RCP Rule 16 PNRP Rule 184 Controlled Discretionary

2.4 Ancillary activities To facilitate the proposal described above requires a series of works which do not require resource consents from GWRC. These include:  The extension of the existing outfall pipe leading to the Waiwhetū Stream by approximately 180 m  The excavation of contaminated soil for the outfall pipe extension and the construction of the storage tank and associated pipe work  The construction of the storage tank.

Any dewatering required for these activities will be undertaken in accordance with the global dewatering consent (WGN170366).

The consent requirements for these activities are assessed below. Resource consents that are required will be sought from the Hutt City Council, once this application is lodged with GWRC.

2.4.1 The outfall pipe extension As the outfall pipe is a ‘network utility’ under the Hutt City District Plan, the rules applying to it are contained in Chapter 13. The introduction to Chapter 13 notes that:

The provisions in this Chapter apply to network utilities throughout all zones of the City. The underlying zone objectives, policies and rules do not apply to network utilities, including roads, unless specifically referred to.

The construction, installation and development of underground network utilities is a permitted activity under Rule 13.1.17. However it is expected that the earthworks will exceed the depth and area conditions applying to this rule. It is therefore expected that the installation of this pipe extension will require consent under Rule 13.3.1.15 as a discretionary activity. 2.4.2 Disturbance of contaminated soil Disturbance of contaminated land may be required for the installation of the outfall pipeline extension. The site of this work is located on the GWRC Selected Land Use Register (SLUR). The WWTP site is also shown on the SLUR. Therefore the works associated with the storage tank and its pipework may also disturb contaminated land, however Wellington Water understands that the WWTP site is cleanfill. Earthwork quantities for these works have not yet been estimated, however, if the sites are confirmed to be contaminated land, then the required earthworks may exceed the permitted activity conditions in the National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health. If so resource consent will be required from Hutt City Council for a restricted discretionary activity.

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Resource consentconsent application – October 2017

2.4.3 The storage tank The construction of the new storage tank is likely to be in the south east corner of the WWTP site. The storage tank is proposed to be a coated steel tank with an approximate diameter of 33m and approximately 15 m high. The site proposed for the storage tank and its surrounds are zoned Special Business. While part of this site is designated, this designation does not apply to that portion of the site where the storage tank is likely to be located. As the Seaview wastewater treatment plant is a ‘regionally significant network utility’ under the Hutt City District Plan, the rules applying it are contained in Chapter 13. The introduction to Chapter 13 notes that

The provisions in this Chapter apply to network utilities throughout all zones of the City. The underlying zone objectives, policies and rules do not apply to network utilities, including roads, unless specifically referred to.

It is considered that the tank is a ‘network utility structure’. The tank would not meet the bulk and location conditions for such structures and therefore will require resource consent from the City Council as a restricted discretionary activity under Rule 13.3.1.11 of the District Plan.

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3. Site description As already described the proposal requires consents for a short term discharge into the Waiwhetū Stream from the existing outfall and consents for a longer term discharge, and associated infrastructure, in the Hutt River near its confluence with the Waiwhetū Stream. The following sections described both of the discharge sites. 3.1 Waiwhetū Stream 3.1.1 Location The discharge to the Waiwhetū Stream will be from the existing outfall. This outfall is an opening in the concrete wall that lines the lower portion of the Waiwhetū Stream. The outfall is located on the true left bank, approximately 120 metres from the mouth of the Stream and is aligned with the end of Gough Street. The outfall is located on the boundary of land parcel Section 2 SO 452270, which is vested in GWRC for river control purposes. The distance of the outfall from the Waiwhetū Stream mouth is greater than 5 times the width of the Stream mouth. The outfall is therefore not considered to be in the CMA.

Figure 1 - Outfall to the Waiwhetū Stream

3.1.2 Māori Cultural Landscape The Māori cultural landscape (pre-colonisation) in this area was vastly different from what exists today. The Māori landscape was part of the estuary area of the Hutt (Te Awakairangi), Te Awamutu, and Waiwhetū Rivers, with the Waiwhetū Pā located on the sand spit at the eastern side of the Hutt River mouth. Māori changed the natural landscape little in establishing Pā and fenced clearings for gardens. There were tauranga waka (canoe landing sites) along the foreshore. The exposed coastal estuarine area quickly gave way to tall indigenous forest as one moved inland along the rivers and streams. The Waiwhetū Pā, like others on the Petone foreshore, was exposed to both weather and possible invaders, and was lightly palisaded. On the opposite side of the Hutt River was another area of sandspit and at the base of the spit was the related Pā of Hikoikoi. The people of Waiwhetū Pā and Hikoikoi were closely related and they moved between each site.

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The existing discharge into the Waiwhetū Stream occurs 100 m downstream of the Owhiti Urupa, which is an historic burial ground associated with the adjacent Waiwhetū Pā. The urupa is in current use and is visited by whānau on a daily basis and burials occur on a regular basis. The whole of the Waiwhetū Stream from the mouth to the headwaters is culturally significant. The Waiwhetū Marae is located just north of White Line East on the banks along with Te Whiti Park. Waiwhetū Pā was occupied by Ngāti Mutunga. They had migrated here in the early 19th century after the musket taua lead by the northern chiefs and were followed by the four large heke from Taranaki along the west coast, the last heke arriving in the 1830s. When Ngāti Mutunga and Ngāti Tama departed for the Chatham Islands in 1835, Te Wharepouri and Te Puni returned from the Wairarapa with their people and occupied these sites including Waiwhetū Pā which became home to Ngāti Haumia/Te Matehou. The fishability of the Waiwhetū Stream has not been a pressing issue for many years now as Māori have ceased to fish the stream, however having water quality that could support a healthy eel population for instance remains a cultural issue. The stream is also largely no longer usable for waka use. 3.1.3 Current Natural Character Today the lower section of the Waiwhetū Stream is completely channelised and contained by vertical concrete walls. However, there is a small area of planting of mixed native coastal species immediately south of the bridge over Waiwhetū Stream where it discharges into the estuary.

Figure 2 - Channelised Waiwhetū Stream

3.1.4 Stream Ecology The Waiwhetū Stream is a small low elevation watercourse which flows from the bush covered Eastern Hutt hills, through urban areas of Naenae, Epuni, Waterloo, Waiwhetū and Gracefield, to its confluence with the Hutt River Estuary at Seaview. It has a total catchment area of about 17.9 km2. The stream has a stony bed in its upper reaches and in part of the estuarine reach, but for most of its length the streambed substrate is soft and muddy. The catchment is heavily urbanised and has a high proportion of impervious surfaces. Consequently stream flows are strongly influenced by stormwater run-off during flood events, resulting in rapid flow fluctuations and highly variable water quality. The estuarine zone extends approximately 2km upstream of the Hutt River confluence, with saline conditions occasionally recorded upstream as far as the Wainui Road Bridge. Over the last 100 years the stream corridor and estuary has been extensively modified by flood protection works, reclamation, and removal of the natural vegetated margin. Over the same period the stream has received an extensive range of contaminant inputs from wastewater overflows, stormwater and in particular from industrial discharges. Surface sediment and water quality investigations (Deely, et al, 1992; Sheppard & Goff, 2001; Sheppard & Goff,

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2002; and Stevens & Robertson, 2009) indicate that the lower reaches of the stream have historically been highly contaminated with heavy metals and organic compounds. Stream sediments in the Gracefield area, downstream of Bell Road, were significantly enriched (up to 10- fold) in metals, particularly lead and zinc, beyond levels found in the headwaters of the stream. The sources of the metals were considered to be either upward re-mobilisation from buried contamination and/or present day stormwater discharges from industries in the Gracefield area. Deely et al (1992) found that in the stretch of the Waiwhetū Stream adjoined by the Seaview industrial area, a considerable proportion of the total heavy metal component was free to move between the sediment, interstitial water and overlying water. An extensive programme of flood control and contaminated sediment remediation was undertaken in the lower reaches of the stream by GWRC and Hutt City Council during 2009 and 2010. Stevens & Robertson (2012), reported in relation to a before/after investigation of the tidal reaches that:

“In conclusion, a range of physical, chemical and biological monitoring indicators of estuary condition in 2009 showed the lower part of the Waiwhetū Stream to be muddy, with organically enriched sediments that contained a range of industrial contaminants. It had poorly oxygenated soft sediment, an “unbalanced” benthic invertebrate community, high nutrient and organic concentrations, and was considered to be in a eutrophic state. Elevated concentrations of some heavy metals and the presence of other metals, pesticides, and industrial chemicals highlighted historical contaminant inputs, while past stream modification had resulted in the loss of most saltmarsh and most of the vegetated terrestrial buffer. Consequently the stream way rated poorly in terms of the key estuary issues of eutrophication, sedimentation, toxicity and sediment loss.

In 2012, reassessment of the same indicators showed significant changes to the lower part of the Waiwhetū Stream following flood control work and sediment remediation. Extensive saltmarsh and terrestrial vegetation plantings have expanded this important habitat, although the total area remains low. Any future expansion is greatly limited by the artificial steep sides of the estuary. In addition much of the densely vegetated margins and many shade trees were lost from the upper estuary during remediation. Along the estuary margins, extensive areas of saltmarsh plantings and bank sediments are being eroded by stream flows.

56,331 tonnes (27,314m3) of contaminated sediments were removed throughout the intertidal and subtidal zones and replaced with clean coarse sands, gravels and cobble. Despite this very significant improvement, sediments retained high nutrient and organic concentrations and were eutrophic, although they supported a slightly improved benthic invertebrate community.”

The authors concluded that “…past stream modification has been significant with the loss of most saltmarsh and the vegetated buffer. While remediation and flood control works have resulted in some improvements to this habitat and a very significant removal of contaminated sediment, overall there has been limited improvement to the ecological quality of the estuary which continues to be rated poorly in terms of eutrophication, sedimentation, toxicity and habitat loss.” 3.1.5 Hydrology Waiwhetū Stream at the Whites Line East flow gauge station has a mean annual low flow of 0.016 m3/s, a mean flow of 0.312 m3/s and a maximum recorded flow of 36.858 m 3/s (GWRC data). The stream is strongly tidal adjacent to the Seaview Outfall, with flows ranging from 9 m 3/s on the outgoing tide to approximately 8 m3/s in an upstream direction on the incoming tide (HCC flow data). The water depth in the lower stream near the outfall varies between approximately 1m at low tide and 2.4m at high tide (spring). The channel width at this location is 15m. Approximately 120m downstream of the Seaview Outfall the Waiwhetū Stream flows into the Hutt River. The estuary is well flushed with a very short residence time. 3.1.6 Saltmarsh Habitat Saltmarsh vegetation is able to tolerate saline conditions where terrestrial plants are unable to survive. Saltmarsh vegetation is important because it is highly productive, naturally filters and

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assimilates sediment and nutrients, acts as a buffer that protects against introduced grasses and weeds, and provides habitat for a variety of species including fish and birds. Stevens and Robertson (2012) observed that while historically the lower Waiwhetū Stream estuary was surrounded by saltmarsh and wetland, in 2009 the stream was confined within narrow banks, often steepened, straightened and reinforced to mitigate flood flows. Due to this modification, combined with extensive historical reclamation and draining of the surrounding land, the only significant saltmarsh habitat remaining in 2009 was a very small remnant (0.06ha, 2.1% of the estuary) downstream of the Seaview Road bridge. Stevens and Robertson gave it a condition rating of “low” based on the low percentage cover within Waiwhetū Estuary. By 2012, restoration planting as part of the stream remediation work had doubled the total area of saltmarsh in the estuary (0.14ha, 4.5% of the estuary). The condition rating remained in the “low” category, however the increase in saltmarsh from 2009 to 2012 was rated “very good”. Another change to the Stream has been a 65% reduction in intertidal flats in the estuary. This has resulted from the channel deepening and bank steepening, including vertical concrete walls, which Stevens and Robertson (2012) consider offer habitat unsuitable for virtually all estuarine species. 3.1.7 Vegetation of Terrestrial Margins A densely vegetated terrestrial margin naturally filters and assimilates sediment and nutrients, is an important habitat for a variety of species, and provides shading to help moderate stream temperature fluctuations. Stevens and Robertson observed that there was very little change in this habitat type from 2009 to 2012. In 2012, 98% of the estuary still lacked a densely vegetated terrestrial margin giving a terrestrial cover ranking of “poor”. There had been a tripling of the cover of native tussock-land from 2009 to 2012 (which included small native trees), but a halving of scrub/forest cover – mainly of established trees downstream of the Bell Road Bridge. The net decrease in densely vegetated terrestrial margin from 2009 to 2012 was rated “poor”. 3.1.8 Macroalgae Macroalgae is an important feature of estuaries, contributing to their high productivity and diversity. However when high nutrient inputs combine with suitable growing conditions, nuisance blooms of rapidly growing algae can occur. Stevens and Robertson (2012) observed that macroalgae was not widespread in the Waiwhetū Estuary in 2009 but in 2012 growths of Ulva intestinalis were more widespread and were present over the vast majority of the intertidal area (84.4% of the intertidal area had greater than 5% cover and 20% of the intertidal area exceeded 50% cover) . The authors noted that despite the relatively high cover, nuisance conditions (e.g. rotting macroalgae and poorly oxygenated and sulphide rich sediments) were not evident in intertidal areas, possibly due to macroalgae being regularly washed out to sea. It was concluded that the extent of macroalgae growth in the Waiwhetū and adjacent Hutt Estuary, while currently below nuisance conditions, indicates an excess of available nutrients. 3.1.9 Sediments In 2012 the un-vegetated intertidal flats of Waiwhetū Stream were dominated by a mix of cobble, gravel and sand, in stark contrast to 2009 where soft muds were the dominant feature (Table 2). Consequently the condition rating provided by Stevens and Robertson (2012) improved from ‘poor’ in 2009 to ‘very good’ in 2012. Table 2: Summary of intertidal substrate classes, 2009 & 2012 (from Stevens & Robertson, 2012) Dominant Feature 2009 Area – Ha (%) 2012 Area – Ha (%) Rock field (man-made) 0.01 (1.2) 0.04 (11.0) Boulder field (man-made) 0.08 (6.7) 0.003 (0.9) Cobble field 0.39 (32.6) 0.07 (16.2) Gravel field 0.11 (9.4) 0.15 (33.6) Firm sand 0.16 (5.2) 0.17 (38.3) Soft mud 0.36 (30.4) 0 (0) Very soft mud 0.17 (14.5) 0 (0) Total 1.28 (100) 0.46 (100)

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3.1.10 Water Quality Surface water quality is routinely monitored by the GWRC in the Waiwhetū Stream at Whites Line East (RSOE site RS57), approximately 3.2 km upstream of the existing Seaview Outfall. Hutt City Council has established an additional monitoring site at Seaview Road Bridge approximately 0.3 km upstream of the existing outfall for the purpose of characterising background conditions near the outfall on the ebb tide. It is noted that the Whites Line East site is above the tidal influence while the Seaview Road Bridge site is strongly affected by tidal inflows. Monthly monitoring results for the period May 2015 to May 2016 is summarised in Table 3. Water quality at Whites Line East is poor; median values for total nitrogen (TN), dissolved reactive phosphorus (DRP), total phosphorus (TP) and E. coli all exceed recommended guideline values (refer to Appendix D for an explanation of guideline values). Further downstream at the Seaview Road Bridge site, median values for DRP, TP and Zn exceed guideline values. Key differences between the two sites are that:  Nitrite-N, nitrate-N, and total-N and E. coli concentrations are higher at the upstream site (and are possibly reduced at the downstream site by tidal inflows of relatively uncontaminated seawater)  DRP and total-P concentrations are higher at the downstream site (indicating a source of phosphorus affecting the lower stream)  pH is higher at the downstream site (due to the influence of tidal inflows). Of the dissolved metals and metalloids tested in stream water at the Seaview Road Bridge site, zinc is significantly elevated and consistently exceeds the guideline trigger value, while copper is occasionally elevated. Concentrations of all other metals were low and below guideline values. Table 3: Summary of monthly water quality data at RSoE site RS57 (GWRC data) and at Seaview Road Bridge (HCC data) from May 2015 to May 2016 (N=11) Waiwhetū Stream at Whites Line Waiwhetū Stream at Seaview Road Guideline Determinant East (GWRC RS57) (HCC) value* median min max median min max Water temp. (oC) 12.3 9.7 20.2 13.9 9.4 21.5 ≤19 Electrical Conductivity 1830 544 4560 DO (mg/L) 8.4 7.2 10.0 pH 6.65 6.30 7.02 7.4 6.8 8.0 6.5-9.0 Turbidity (NTU) 5.1 2.3 50 3.54 1.60 8.80 ≤5.6 Suspended solids (mg/L) 14 3 37 -- Visual clarity (m) 0.945 0.240 2.040 ≥1.6 NNN (mg/L) 0.440 0.003 0.650 0.102 0.005 0.310 ≤0.444 Ammoniacal N (mg/L) 0.066 0.003 0.146 0.070 0.005 0.120 ≤0.900 Total N (mg/L) 0.750 0.250 0.980 0.480 0.290 0.780 ≤0.614 DRP (mg/L) 0.020 0.014 0.035 0.032 0.003 0.065 ≤0.010 Total P (mg/L) 0.046 0.020 0.120 0.068 0.017 0.190 ≤0.033 E. coli (cfu/100ml) 950 220 3600 310 99 1300 ≤540 Dissolved metals:

As (mg/L) <0.001 <0.001 0.003 0.013 Cd (mg/L) <0.0002 <0.0002 <0.0002 0.0002 Cr (mg/L <0.001 <0.001 <0.001 0.001 Cu (mg/L) <0.001 <0.001 0.0023 0.0014 Pb (mg/L) <0.0005 <0.0005 <0.0005 0.0034 Hg (mg/L) <0.0005 <0.0005 <0.0005 0.0006 Ni (mg/L) <0.0005 <0.0005 0.0007 0.011 Zn (mg/L) 0.014 0.003 0.024 0.008 *Refer to Appendix D for an explanation of water quality guideline values

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3.1.11 Eutrophication Excessive organic input is a principal cause of degradation in estuarine benthic environments. In river mouth estuaries like the Waiwhetū, an oversupply of nutrients often promotes nuisance algal growth, and related sediment deoxygenation. As a consequence, the number of suspension-feeders (e.g. bivalves and certain polychaetes) declines, and deposit-feeders (e.g. opportunistic polychaetes) increase in response to increased organic input to the sediment (Pearson & Rosenberg, 1978). Stevens & Robertson (2012) used a number of indicators to assess eutrophication in the Waiwhetū Estuary. These include redox potential discontinuity (RPD), sediment organic matter (total organic carbon, TN and TP), macroalage cover and soft mud. The RPD is the grey layer between the oxygenated yellow-brown sediments near the surface and the deeper anoxic black sediments. It is an effective ecological barrier for most but not all sediment-dwelling species. A rising RPD will force most macrofauna towards the surface to where oxygen is available. The authors concluded that the shallow RPD, elevated organic matter and moderately extensive macroalgae cover indicate eutrophic conditions in key parts of the estuary. They note that the presence of such conditions following site remediation indicates ongoing sources to the estuary are likely, and that estuary condition will continue to decline if they are not managed. As shown in Table 3 water column TP and TN are significantly elevated in the Waiwhetū Stream at Whites Line East, and it is likely that settlement of particulate material further downstream in the estuarine reach will contribute to enrichment of sub-tidal sediments. It is noted that both monitoring sites shown in Table 3 are located upstream the Seaview Outfall and are not greatly affected by intermittent wastewater overflows. 3.1.12 Sediment Contamination Stevens & Robertson (2012) used heavy metals and the metaloid arsenic as indicators of sediment toxicants. The results, summarised in Table 4, show a reduction in metal concentrations in stream sediments at some locations following the remediation work, and increased concentrations at other locations. Lead and zinc in particular remained significantly elevated in the stream adjacent to the Gracefield area. Indeed concentrations were much higher in 2012 after remediation. GWRC staff have advised that these sediments are thought to have originated from a seam of contaminated stream bank material which was capped during completion of the remediation project, and susequently re-exposed by erosion. In 2012, post remediation, stream sediments exceeded ANZECC (2000) ISQG-High trigger values for zinc and lead at two and three sites, respectively, while ISQG-Low trigger values for arsenic, cadmium, copper, mercury and nickel were all exceeded at at least one site. These results indicate on ongoing risk of toxicity for invertebrates living in stream sediments in the lower Waiwhetū Stream. It is noted that sites A, B, and D are all located upstream of the Seaview outfall, but that the discharge plume can move upstream on the incoming tide. Table 4: Summary results for Waiwhetū Stream, 2009 and 2012 (Stevens & Robertson, 2012)

Site RPD TOC TN TP As Cd Cr Cu Hg Ni Pb Zn Waiwhetū cm % Mg/kg (dry weight)

A-01 Subtidal 0.1 4.2 2,600 650 10 1.2 32 65 0.27 15 440 860

2009 A-02 Intertidal 0.1 3.8 2,100 460 10 1.2 42 49 0.56 18 490 660 B-01 Subtidal 0.1 4.8 3,100 730 11 1.3 34 76 0.44 16 1,900 920 B-02 Intertidal 0.1 4.7 3,300 550 11 1.2 34 74 0.34 16 1,200 850 A-01 Subtidal 0 5.9 4,000 720 12.9 0.63 32 66 0.26 19 193 490

A-02 Intertidal >10 0.6 900 420 3.0 0.07 16 8.4 0.11 12 400 89

2012 B-01 Subtidal 0 2.4 1,800 600 6.8 0.41 26 38 0.25 14 1,010 380 B-02 Intertidal >10 2.4 1,900 620 21.0 6.0 63 64 0.53 24 7,900 1,350 D-01 Subtidal 4 2.0 1,800 640 6.3 0.75 47 40 0.11 27 142 290 D-02 Intertidal 4 1.9 1,800 630 8.5 0.18 16 30 0.08 11 99 143

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Site RPD TOC TN TP As Cd Cr Cu Hg Ni Pb Zn Waiwhetū cm % Mg/kg (dry weight) ANZECC ISQG-Low - - - - 20 1.5 80 65 0.15 21 50 200 ANZECC ISQG-High - - - - 70 10 370 270 1 52 220 410

Existing Waiwhetū outfall

Figure 3: Location of monitoring sites in Waiwhetū Stream (from Stevens and Robertson, 2012) 3.1.13 Shellfish Flesh Toxicity Stevens & Robertson (2012) collected blue mussels (Mytilus galloprovincialis) from the mouth of Waiwhetū Stream at Port Road Bridge and had the flesh analysed for metals, organochlorine pesticides (OCP’s) and polycyclic aromatic hydrocarbons (PAH). All results were relatively low, below the Australia New Zealand Food Standards Code (2002). A study of shellfish quality conducted during a 16-day MOP repair discharge to Waiwhetū Stream concluded that shellfish at the Waiwhetū Stream mouth, Petone Beach and Lowry Bay are likely to be unsuitable for human consumption for up to four weeks after a discharge of treated wastewater to Waiwhetū Stream, or after a significant high flow event in the Hutt River, due to the risk of pathogen contamination (MWH, 2013). It was noted that this restriction would rule out most of the year, but would be consistent with the general advice from Regional Public Health, and NZFSA, not to collect shellfish near urban areas because of the ongoing impact of stormwater and wastewater related contamination. On the basis of this information it is concluded that microbiological contaminant (pathogens) are likely to be the primary limiting factor for shellfish consumption by humans, as is generally the case in coastal waters near urban areas. 3.1.14 Benthic Invertebrate Community The benthic invertebrate community living in and on the sediments of the Waiwhetū Estuary during 2012 was dominated by “disturbance tolerant” gastropods, polychaetes and oligochaetes (Stevens

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& Robertson, 2012). Crustacean, nemertean’s, nemotodes and fly larvae were also present but in low numbers. The relatively high diversity was explained by the majority of the animals being juveniles or small immatures, which are mainly recent recruits, bred elsewhere, being washed into the area in low numbers, but not able to survive to adulthood. The results indicate a slight improvement in macroinvertebrate life in 2012 compared with 2009. The results also indicate a dominance of species that tolerate moderate organic enrichment and which live predominantly in a relatively clean layer of oxygenated surface mud that was present above the underlying anoxic sediments. For example, the gastropod Potamopyrgus is intolerant of anoxic surface muds, but its presence in very high number indicates suitable surface conditions. 3.1.15 Fish Community Five species of fish have been identified in Waiwhetū Stream by electro-fishing surveys over the last 10 years (New Zealand Freshwater Fish database: NIWA). The short finned eel (Anguilla australis) was abundant throughout and was the dominant species. Adult inanga (Galaxius maculatus) have been recorded in large shoals in the lower/middle stream and banded kokopu (G. fasciatus) and redfinned bully (Gobiomorphus huttoni) have been locally abundant in the upper stream. Common smelt (Retropinna retropinna), yellow eyed mullet (Aldrichetta forsteri) and estuarine triplefin (Grahamina sp.) have been recorded in the lower stream. Juvenile trout from the Hutt River fishery are known to make occasional use of the lower Waiwhetū Stream, although trout have not been recorded in the electro-fishing surveys. 3.1.16 Recreation In a Recreation Review, undertaken as background information for the Option Assessment Report, Waiwhetū Stream was reported to have little in-water recreation, with some fishing near its mouth, rare waka taua activity, and an occasional small boat. Walking and cycling on the nearby paths were the main reported activity, along with volunteer planting work on its banks. The report notes that whitebait habitat has been identified in the Waiwhetū Stream, but there was no reported fishing activity. 3.1.17 Policy Statement and Plan Schedules applying to the site The following Regional Policy Statement and Regional Plan schedules apply to the Waiwhetū stream site:

Regional Policy Statement  None

Regional Coastal Plan  None

Regional Freshwater Plan  Appendix 7: Rivers with quality needing enhancement for aquatic ecosystem purposes

Proposed Natural Resources Plan  Schedule C: Sites with significant mana whenua values – Waiwhetū Stream – Owhiti pā (Taranaki Whānui ki te Upoko o te Ika a Maui)  Schedule D – Statutory Acknowledgements – Waiwhetū Stream (Taranaki Whānui ki te Upoko o te Ika a Maui) and Hutt River and it’s tributaries (Ngāti Toa RaNgātira)  Schedule F4: Sites with significant indigenous biodiversity values in the coastal marine area – Waiwhetū Estuary  Schedule H2: Priorities for improvement of fresh and coastal water quality for contact recreation and Māori customary use - Waiwhetū Stream - Second priorities for improvement - Fresh water bodies with water quality approaching the NOF bottom line for the health of people and communities from secondary contact with fresh water, identified as those that exceed 1000 cfu/100mL as a 95th percentile

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3.2 Hutt River 3.2.1 Location The proposed discharge location into the Hutt River is located just downstream of the Hutt River’s confluence with the Waiwhetū Stream on the River’s true left bank. Based on the current concept design, the discharge point of the outfall will be approximately 70 m downstream of the Waiwhetū Stream confluence and approximately 16 m from the astronomical low tide mark on the Hutt River bank. The northern extent of the small headland that is proposed around the outfall will be approximately 48 m from the mouth of the Waiwhetū Stream, while the southern extent will be approximately 76 m. These dimension are potentially subject to change during the detailed design process as indicated on drawing 80509150-01-001-C101. On the Hutt River, the CMA ends at the Waione Road Bridge. The proposed discharge point is therefore within the CMA. The site adjoins a small area of vegetation and trees on the verge of Port Road.

Figure 4 - Proposed outfall location to the Hutt River Note: the existing stormwater pipe is just visible above the water in the lower left hand corner of the figure.

3.2.2 Māori Cultural Landscape As noted in section 3.1.2, the Māori cultural landscape (pre-colonisation) in this area was vastly different from what exists today. The Māori landscape was part of the estuary area of the Hutt (Te Awakairangi), Te Awamutu, and Waiwhetū Rivers, with the Waiwhetū Pā located on the sand spit at the eastern side of the Hutt River mouth. There were tauranga waka (canoe landing sites) along the foreshore. The exposed coastal estuarine area quickly gave way to tall indigenous forest as one moved inland along the rivers and streams. On the opposite side of the Hutt River from the proposed discharge site was another area of sandspit and at the base of the spit was the related Pā of Hikoikoi. The people of Waiwhetū Pā and Hikoikoi were closely related and they moved between each site. The proposed discharge site into the Hutt River, near the confluence with the Waiwhetū Stream is still close to the Owhiti urupā in both the cultural and physical sense. This whole area has close cultural connection with the old Waiwhetū Pā and the old Hikoikoi Pā on the opposite river bank.

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The Hutt River estuary was a significant fishery for Māori and is still used by many recreational and customary fishers today. 3.2.3 Current Natural Character The Hutt River mouth, estuary and adjoining shores, are substantially modified compared to their pre-European state. The area is significantly constrained by reclamation and coastal structures and has become a permanent and semi-channelised estuary. Historically, the dynamic river mouth and estuary system would have extended across the area now occupied by the Seaview industrial area. The current position of the river mouth is now fixed by the abutments of the Waione Street bridge. The eastern shoreline of the estuary is dominated by the industrial area, Port Road and the Seaview Marina. A narrow strip of land between Port Road and the estuary provides space for a footpath, a few picnic tables and a row of established pohutukawa trees and other plants immediately adjoining the site of the proposed Hutt River discharge. There is also a small area of planting of mixed native coastal species immediately south of the bridge over Waiwhetū Stream where it discharges into the estuary. Coastal protection along this shore comprises a mix of rocks, broken concrete, bricks and hard fill, creating an unattractive edge. The western shore of the estuary comprises a small embayment, boatsheds, the St James Sea Scouts base and other commercial uses are located along the immediate edge. The GBC Winstones sand extraction plant is located on the south-western point at the river mouth and the eastern extent of the Petone foreshore. There are numerous stormwater outfall structures located in the estuary. The evidence of these is often the presence of a concrete and metal low profile structure visible at low tide. 3.2.4 Physical Characteristics The Hutt Estuary is a moderate sized (3km long) “tidal river mouth” type estuary which drains into Wellington Harbour at Petone. It has been extensively reclaimed and modified, and the banks c lad with large rip-rap boulders (Robertson & Stevens, Kapiti, Southwest, South Coasts and Wellington Harbour. Risk Assessment and Monitoring Recommendations, 2007). Saltwater extends up to 3km, nearly as far as Ewen Bridge (and well upstream of the Estuary Bridge). The estuary is highly modified from its original state. In 1909 it was much larger and included several large lagoon arms and extensive intertidal flats and saltmarsh vegetation. Between 1900 and 1960 most of the intertidal flats and lagoon areas were re-claimed and the estuary was trained to flow in one channel between rock rip-rap lined banks. The terrestrial margin, which was originally vegetated with coastal shrub and forest species, was replaced with urban and industrial land-use (Robertson & Stevens, 2011) 3.2.5 Hydrology The Hutt River at Taita has a catchment area of 556 km2, a median flow 14.243 m3/s and a 7-day mean annual low flow of 3.744 m3/s. The maximum recorded flow of approximately 2000 m 3/s occurred in 1898 (Wellington Regional Council, 1996). 3.2.6 Ecological Values As a result of modifications over the last 100 years, including loss of most of the intertidal flats, lagoon areas and much of its riparian vegetation, the Hutt Estuary now has low habitat diversity. High value habitats such as tidal flats, saltmarsh and sea-grass beds are virtually absent. Instead, the estuary is dominated by lower value, sub-tidal sands and muds and artificial sea walls (Robertson & Steven, 2011). The mid-lower estuary, below the Waione Street Bridge, is dredged to a maximum depth of about 4 meters below the water level by GWRC in order to manage the flooding risk during high flow events in the river. Wear (2011) described the sediments in the extraction zone as essentially anoxic and the benthic biota as “depauperate” and of low ecological value. Nevertheless, parts of the estuary outside of the extraction zone, including the western mudflat embayment and the intertidal flats upstream of the bridge, are considered to be important areas for juvenile flatfish and significant feeding/refuge areas for wading and non-wading birds (Wear, 2011; Stevens & Robertson, 2014; McArthur, Small, & Govella, 2015). Wear (2011) described the intertidal biota

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inhabiting the south-eastern flood protection wall as typical of that occurring elsewhere in Wellington Harbour. 3.2.7 Macroalgae Macroalgal monitoring has been undertaken annually in Hutt Estuary from 2010 to 2016 and is reported most recently by Stevens & Robertson (2015) and Stevens, et al (2016). The authors of both reports note that Ulva intestinalis is the dominant opportunistic macroalgae, growing on almost every area of available habitat from the railway over-bridge to the Hutt River mouth. The red algae Gracilaria and the green alga Ulva were observed as subordinate growths near the estuary mouth. There were no significant intertidal gross eutrophic zones identified (e.g., when there is a combined presence of high macroalgal biomass and cover, soft muds, and poor sediment oxygenation (RPD depth <0.5cm)). Nuisance conditions (rotting macroalgae and poorly oxygenated and sulphide rich sediments) were not widespread in intertidal areas, but were much more readily apparent in sub-tidal areas below the Waione Street Bridge which is currently muddy, poorly oxygenated, and sulphide rich. The primary factor preventing widespread nuisance conditions appears to be the regular flushing of macroalgae from the estuary. This flushing, and particularly flood scouring of the river following rain, is likely to be limiting the length that nuisance macroalgae can grow to along the intertidal main channel margins, while also dislodging and washing macroalgae growing or deposited on the intertidal flats into subtidal zones or out to sea. The results of results of intertidal mapping of opportunistic macroalgal in Hutt Estuary i n January 2016 are summarised in Figure 5.

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Figure 5: Map of intertidal opportunistic macroalgae biomass (g/m 2) (from Steven’s et al, 2016) 3.2.8 Sediments The results of annual sediment monitoring in the Hutt Estuary from 2010 to 2016 are reported by Stevens, et al, (2016). Measurement of depths to four concrete plates buried in intertidal sediment in 2010 was undertaken to assess the sedimentation rate. Redox potential discontinuity (RPD) depth and sediment grain size were assessed to indicate sediment condition. The results show that soft mud habitat is not a significant intertidal feature in the Hutt Estuary, and that there has been no net vertical build-up of sediment on the intertidal flats since 2010. Further, the results show no increase in sediment muddiness since measures were established in 2014. Grain size analyses show that sediments on the intertidal flats (where sediment accumulation commonly occurs in estuaries) were sand-dominated with relatively low mud content. Stevens, et al, (2016) assessed the overall risk of detrimental impacts to intertidal estuarine biota from muds as “Very Low” based on the small area of intertidal soft mud, low rates of sediment build-up and relatively low mud contents within sediments on intertidal flats.

Stevens, et al, (2016) observed that the most extensive remaining habitat within Hutt Estuary is now its sub-tidal component, and that these areas may be at risk from adverse eutrophication symptoms. In order to assess this they conducted a synoptic fine scale sediment and water quality survey in the mid- lower Hutt Estuary (Figure 6) in conjunction with broad scale habitat mapping. Sites A-C were located in the basin downstream of Waione Street Bridge, and site D was located upstream of the bridge, in shallow well flushed gravels. Sediment mud content The mid-lower section of the Hutt Estuary forms a shallow basin approximately 1.2 to 3m deep, which is regularly dredged by GWRC to manage the flooding risk. Sites A-C in the deeper lower estuary were characterised by a thick anaerobic, organically enriched and muddy layer overlying relatively clean sediments. By contrast, site D in the shallow upstream river gravels, had a low mud content. The authors considered that the elevated mud contents at the majority of the sites is likely indicative of relatively poor sediment oxygenation, and a high stress risk to mud and organic enrichment sensitive benthic biota. Figure 6: Hutt Estuary sediment sampling locations Redox Potential Discontinuity (RPD) The depth of the RPD boundary indicates the extent of oxygenation within sediments. Stevens et al, (2016) reported that the RPD depth was at the surface at most sub-tidal sites in the lower estuary (below the bridge) indicating a high risk of ecological impacts and poor conditions for sediment macrofauna in that area. Within the gravels and cobble dominated substrate at upstream site D, sediment oxygenation is good. Total Organic Carbon (TOC) and Nutrients For most lower estuary sites, both TOC and TN were at high levels indicating, like the RPD results, a high risk of ecological impacts and poor conditions for sediment macrofauna in that area. TP concentrations were also measured and, like TN, showed high concentrations at the lower estuary sites, but unlike TN showed high concentrations at Site D as well.

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Sediment Toxicity Indicators Stevens et al, (2016) found that, at all sites, the heavy metals Cd, Cr, Cu, Hg, Pb, Zn, and arsenic were present at “VERY LOW” to “MODERATE” concentrations, with all non-normalised values below the ANZECC (2000) ISQG-Low trigger values (and therefore unlikely to pose a toxicity threat to aquatic life). However, the heavy metal nickel exceeded the ISQG-Low trigger values at the majority of lower estuary sites, but not the ISQG-High values. The area around the Waiwhetū Stream mouth and banks is shown on the GWRC SLUR database, and known from previous works in the area (Waiwhetū Stream Clean Up, 2009-10) , as containing contaminated material. The stream clean up works revealed high levels of hydrocarbons, lead, arsenic, cadmium and copper, amongst other contaminants. 3.2.9 Water Quality Nutrients Surface water quality monitoring is routinely monitored by GWRC at three RSoE sites in the main stem of the Hutt River. The most downstream of which is site RS22 at Boulcott, which is located upstream of the estuarine reach and approximately 3.2 km upstream of the Waiwhetū Stream mouth. Monthly monitoring results from this site show that the lower reaches of the Hutt River retains moderately high water quality and mostly achieve recommended guideline values. In terms of nutrient concentrations Heath & Greenfield (2016) reported nutrient concentrations and loads for the Hutt River at Boulcott. Table 5: Nutrient concentrations and loads in the Hutt River at Boulcott (Heath & Greenfield, 2016) DIN TN DRP TP Concentrations (mg/L) 0.178 0.32 0.005 0.010 (0.085-0.39) (0.15-1.83) (<0.004-0.008) (<0.004-0.39) Annual load (tonnes/yr) 214 313 3.99 18.6

Recreational water quality GWRC monitors 13 coastal sites in Wellington harbour for recreational water quality, including sites at Petone Beach, Sorrento Bay, Lowry Bay, York Bay Days Bay and Eastbourne. The results from this monitoring are compared to national guidelines and used to calculate an overall grade for the beach. The coastal sites at Petone and the eastern bays are either graded C (moderate risk of illness) or B (low risk of illness) as shown in Figure 7.

Figure 7: GWRC beach grades for the 2016/17 summer (GWRC, 2017)

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The results of additional surface water quality monitoring conducted by HCC at three locations in the Hutt River mouth (Figure 8) are summarised in Table 6. Hutt River sites 1 and 2 are clearly estuarine and are affected by a variety of influences while site 3, within the harbour, has a consistently higher salinity and lower indicator bacteria concentrations than the river sites. The highest indicator bacteria concentration are recorded at site 2, which may be a localised effect of the Waiwhetū Stream inflow to the Hutt River. The mid-lower section of the Hutt Estuary, below the Waione Street Bridge, forms a shallow basin approximately 1.2 to 3m deep, which is regularly dredged by GWRC to manage the flooding risk. Steven’s et al, (2016) conducted a synoptic water quality assessment in this reach on 24 January 2016. The results indicated a salinity stratified water column with lighter, low salinity water on the surface (<0.5m) and denser, high salinity water below. The data also showed some elevated chlorophyll a concentrations in the bottom water at the deeper and lower sites, but water column dissolved oxygen concentrations were all well above saturation. Table 6: Summary of water quality results for sites 1, 2 & 3 (HCC monthly samples, June to October 2017, n=5) Hutt River (1) Hutt River (2) Wellington Harbour (3) Determinant Guideline value* median min max median min max median min max Salinity (ppt) 4.6 2.6 19 10.0 6.9 23 32 29 32 - Turbidity (NTU) 2.24 0.79 3.49 3.44 1.56 8.79 1.43 0.72 6.05 - Shellfish gathering: Faecal coliforms 92 16 420 150 20 300 52 8 230 median <14 & (cfu/100ml) 90% <43 Enterococci Bathing, single 56 16 240 300 36 2,300 38 4 160 (cfu/100ml) sample ≤280

1

2

3

Figure 8: Location of HCC water quality monitoring sites at Hutt River mouth 3.2.10 Invertebrates Fine scale monitoring reported by Robertson & Stevens (2012) includes survey of infauna from sediment core samples collected at two Hutt Estuary sites (A & B) in 2010, 2011 and 2012. In all three years the macroinvertebrate community was found to have low-moderate numbers of species at both sites. In terms of abundance, the results show a large reduction at both sites between

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2010 and 2012. Compared with other tidal river estuaries in New Zealand the abundances were relatively low. The mud tolerance of the Hutt Estuary macroinvertebrate community was in the “moderate-high” category in 2012, a slight improvement from the previous two years (Figure 9). The results show that the community was dominated by species that prefer mud rather than those that prefer sand.

Figure 9: Mud tolerance macroinvertebrate rating, sites A and B, 2010-2012 Overall, the sediment results indicate that macroinvertebrate diversity and abundance is likely to be adversely affected by the sediment mud content, and that fine sediments have reached levels where both sites and nearly all sensitive species are affected. However, there is evidence that some improvement occurred between 2010 and 2012. Wear (2010) noted that the river mouth downstream of the Waione Street Bridge is regularly dredged to maintain flood capacity and that the “extraction zone” benthos is sparsely distributed in that area. Wear also observed that the south-western seawall consists of man-made materials positioned along the true left bank as protection from flooding and erosion, which forms intertidal habitat dominated by green algae (Ulva) and Enteromorpha intestinalis and the blue mussels Mytilus galloprovincialis, with patches of necklace seaweed (Hormosira banksii). 3.2.11 Fish Migratory freshwater fish species recorded in the Hutt River including the majority of fish species listed in Table 7 rely on the estuary zone to provide unimpeded access from the open harbour waters to the upper reaches of the river (or vice versa) for the purposes of spawning. Additionally a number of marine species venture into the estuarine area to breed or feed, including yellow-eyed mullet (Aldrichetta forsteri), sand flounder (Rhombosolea plebia) and kahawai (Arripis trutta), and in particular the estuary is considered to be an important nursery area for juvenile sand flounder (Wear & Haddon, 1992; Wear, 2010). Despite the general unsuitability of the main-stem for inanga spawning, there are records of inanga spawning in areas in the tidal reach where bank armouring is absent. These include observations near the Sladden Park boat ramp in Petone, at Te Mome Stream and Opahu Stream (Taylor & Kelly, 2001).

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Table 7: Summary of the NZFFD records for the Hutt River as of June 2015 (n=93). Scientific name Common name Migratory species Threat status (Goodman et al 2014)

Anguilla australis Shortfin eel yes Not threatened Anguilla dieffenbachii Longfin eel yes At risk (declining) Galaxias argenteus Giant kokopu yes At risk (declining) Galaxias brevipinnis Koaro yes At risk (declining) Galaxias divergens Dwarf galaxias no At risk (declining) Galaxias maculatus Inanga yes At risk (declining) Galaxias fasciatus Banded kokopu yes Not threatened Geotria australis Lamprey yes Threatened (Nationally Vulnerable) Gobiomorphus basalis Crans bully No Not threatened Gobiomorphus cotidianus Common bully yes Not threatened Gobiomorphus gobioides Giant bully yes Not threatened Gobiomorphus hubbsi Bluegill bully yes At risk (declining) Gobiomorphus huttoni Redfin bully yes At risk (declining) Retropinna retropinna Common smelt yes Not threatened Salmo trutta Brown trout yes Introduced/naturalised *Not listed in the NZFFD but recorded by Perrie (2013)

3.2.12 Birds The western arm tidal flat of the Hutt Estuary is an important roosting, wading and feeding area for a number of birds, including the variable oystercatcher, black shag, little black shag, royal spoonbill, reef heron, mallards and grey ducks, red-billed gulls, and terns (Wear & Haddon, 1992; McArthur, Robertson, Adams, & Small, 2015). In the Proposed Natural Resources Plan, GWRC has identified the Hutt River reach from the river mouth to 1.3 km upstream of the mouth as a site of significance for indigenous birds (McArthur and Lawson, 2013). The ecological context is that “this site provides seasonal or core habitat for black shag, little black shag, royal spoonbill, variable oyster catcher and red-billed gull”. Present threats identified in McArthur and Lawson 2013, include disturbance caused by recreational users, dogs and vehicles, disturbance and habitat modification caused by flood protection activities. 3.2.13 Recreation A variety of recreation activities are undertaken near the mouth of the Hutt River. It is likely to be one of busier recreation settings in Wellington Harbour after the Lambton Harbour area and Oriental Bay, although it is very unlikely to compete as a swimming site with the bays south of Lowry Bay and east and south of Oriental Bay. The Estuary Bridge and the western area of the Hutt River mouth are main locations for fishing, particularly for netting, in the wider area. Small boats frequent the Hutt River mouth area, and include waka ama (competitive outrigger canoes), waka taua (large ceremonial or war canoes), rowers, sailing dinghies, kayakers, rafters (mostly Sea Scouts), sea kayakers and SUP (stand-up paddle boarding). The Sea Scouts and Cadets activities result in many instances of water contact recreation in the area. Whitebaiting occurs during the season on both banks of the Hutt River near the mouth. Almost all the coastal margin is publicly accessible from adjacent land, and is bordered by walking and cycle opportunities, both on and off-road. The Hutt River to its mouth is identified as a primary water contact site for recreation, a trout fishery and a first order priority area for improvement for contact recreation and Māori customary use in the Proposed Natural Resources Plan for the Wellington Region,. Summer is the busiest season. Weather is the key limiting factor for participation.

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3.2.14 Hutt River Mouth Sediment Extraction GWRC, Flood Protection, holds consent to extract an average of 50,000 m3 of sand and shingle annually from the bed of the Hutt River downstream of the Waione Street bridge for the purpose of flood mitigation. Extraction of sediment is by way of a mobile hydraulic excavator mounted on a barge and positioned by tugboat. The extraction digs the seabed to a maximum depth of about 4 m below the water level. When the barge has a full load of about 60 m3 it is pushed to shore where the sediment is unloaded for processing. The by-product is barged to a designated 6 ha disposal area located about 700 m south of the Hutt River mouth. Exclusion zones, where no dredging is undertaken, are located at the mouth of the Waiwhetū Stream (including the site of the proposed discharge structure), at Waione Street Bridge, adjacent to Hikoikoi Pa and in the western mudflat embayment.

3.2.15 Policy statement and plan schedules applying to the Hutt River site Regional Policy Statement  Appendix 1: Rivers and lakes with significant amenity and recreational values (relates to policies 19, 43 and 53) – Hutt River  Appendix 1: Rivers and lakes with significant indigenous ecosystems (relates to policies 19 and 43) – Hutt River - Habitat for threatened indigenous fish species, Habitat for six or more migratory indigenous fish species & Inanga spawning habitat (reach of tidal influence)

Regional Coastal Plan  Planning Map 5 – Hutt Valley Aquifer Zone  Planning Map 8D – Water managed for contact recreation

Regional Freshwater Plan  Appendix 5: Water bodies with Regionally important amenity and recreational values – water to be managed for contact recreation purposes

Proposed Natural Resources Plan  Schedule B: Ngā Taonga Nui a Kiwa - Te Awa Kairangi/Hutt River (Ngāti Toa RaNgātira & Taranaki Whānui ki te Upoko o te Ika a Maui)  Schedule C: Sites with significant mana whenua values - (Taranaki Whānui ki te Upoko o te Ika a Maui)  Schedule D: Statutory Acknowledgements – Hutt River (Taranaki Whānui ki te Upoko o te Ika a Maui & Ngāti Toa RaNgātira)  Schedule F1: Ecosystem and habitats with significant biodiversity values: Habitat for six or more migratory indigenous fish species– Te Awa Kairangi/Hutt River  Schedule F1b: Ecosystem and habitats with significant biodiversity values: Inanga Spawning Habitat – Te Awa Kairangi/Hutt River  Schedule F2: Habitats for indigenous birds – Hutt River Estuary  Schedule F4: Sites with significant indigenous biodiversity values in the coastal marine area – Hutt River Mouth Estuary  Schedule F5: Habitats with significant indigenous biodiversity values in the coastal marine area - Te Awa Kairangi/Hutt River  Schedule H1: Regionally significant primary contact recreation water bodies - Te Awa Kairangi/Hutt River  Schedule H2: Priorities for improvement of fresh and coastal water quality for contact recreation and Māori customary use - Te Awa Kairangi/Hutt River - Regionally significant primary contact recreation rivers at or below the NOF minimum acceptable state for primary contact with freshwater at flows below 3x median flows, and at one or more sites  Schedule I: Important trout fishery rivers - Te Awa Kairangi/Hutt River

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3.3 Wellington Harbour 3.3.1 Hydrodynamics Wellington Harbour has a maximum tidal range of 1.5m and an average tidal range of 0.75m. The tidal zone can be classified as low, mid and high tide and is a significant factor in the determination of biological communities inhabiting intertidal habitats. The Harbour is well flushed with a flushing time of approximately 10 days (Heath, 1977). During flood events the discharge from the Hutt River causes harbour waters to become more fresh and turbid, however at most times there is little if any influence of freshwater on harbour salinities. Tidal flow is generally in a clockwise direction on the flood tide and in an anticlockwise direction on the ebb tide (Brodie, 1958). 3.3.2 Intertidal Ecology Intertidal habitats along the eastern side of Wellington Harbour include estuary, sandy beaches and rocky shores. Moderately sheltered and sheltered rocky reef habitat is found on outcrops between Pt Howard and Eastbourne, with firm sandy beaches and gravel field at Lowry Bay, York Bay, Mahina Bay, Days Bay and Eastbourne. South of Eastbourne, the rocky reef is moderately exposed, becoming very exposed south of Inconstant Point (EHEA 1998). A broad scale habitat assessment conducted by McMertrie & Brennan (2016) found broadly similar habitat types to those described by EHEA (1998), albeit at a finer scale. McMertrie & Brennan (2016) observed that the community composition of the Eastern Bays was as expected for this general location (lower North Island) and rocky shore habitat, and is similar to the rocky shore communities found elsewhere in Wellington Harbour. No taxa that are indicative of significant nutrient enrichment or fine sediment input were present in any great abundance, with exposure and substrate seeming to be the main factors influencing the communities of this area. 3.3.3 Edible Shellfish A survey of edible shellfish beds in Wellington Harbour coastline indicates that the green lipped mussel (Perna canaliculus) and the blue mussel (Mytilus edulis) are found on many of the rocky outcrops between Pencarrow Head and Point Arthur (EHEA 1997). Paua (Haliotis iris), kina (Evechinus chloroticus) and rock lobster (Jasus edwardsii) are found along the Pencarrow coast south of Eastbourne. Pipi (Phaphies australis) are found at Days Bay and Petone Beach (Stevens, B, & Robertson, 2004), while the cockle (Austrovenus stutchbury) is found at York Bay, Lowry Bay, Sorrento Bay and Point Howard. Scallops are found further offshore in waters of 5 to 15m depth between Point Howard and Eastbourne. The open scallop season for Wellington runs from 15 July to 14 February. 3.3.4 Subtidal Ecology Oliver (2013) described the benthic community health at 16 subtidal sites in Wellington Harbour, including two sites offshore from Petone Beach, one site seaward of the Hutt River mouth and one site offshore from Lowry Bay. A total of 124 invertebrate taxa were identified in the 2011 survey. The most abundant species within the community were polychaete worms, crustaceans, sipunculids and bivalves. The heart urchin, Echinocardium cordatum, was the dominant member of the biomass, along with the bivalve Dosina zelandica, and the brittle star Amphiura rosea. Overall, the invertebrate community composition was broadly similar across surveys conducted in 2006 and 2011, despite some differences in the relative abundance of most dominant species at some sites.

Subtidal sites WH15 and HW18 are closest to the Hutt River mouth, and both have ‘sandy mud’ sediments, and relatively low concentration of metals and other contaminants compared with sites closer to Wellington City (Oliver 2013). The subtidal benthos were dominated numerically by preditors/scavengers at site WH15 and by subsurface deposit feeders at WH18. The heart urchin Echinocardium and the bivalve mollusc Dosina were the dominant members of the biomass at both locations.

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4. Reasons why resource consent is required Several aspects of the proposal trigger the need for resource consents from GWRC. The reasons for these consent requirements and the overall consent status is set out below. Resource consents may also be required from the Hutt City Council. These are described in section 2.4. 4.1 Intermittent discharges to the Waiwhetū Stream To determine the resource consent requirement of the intermittent discharges the first decision that must be made is whether the discharges occur into the coastal marine area or to freshwater. The coastal marine area boundary, as it relates to the Waiwhetū Stream is not mapped in either the Regional Coastal Plan or the Proposed Natural Resources Plan. Section 2 of the RMA defines the inner boundary of the CMA, where that line crosses a river, as the lesser of: • one kilometre upstream from the mouth of the river; or • the point upstream that is calculated by multiplying the width of the river mouth by 5. The mouth of the Waiwhetū Stream is approximately 20m wide. Therefore the line of the CMA is 100 m upstream from the mouth of the Stream. The existing outfall is located approximately 120 m upstream of the mouth of the Waiwhetū. The discharge to the Waiwhetū Stream is therefore considered to be to freshwater. 4.1.1 Regional Freshwater Plan The discharge of treated wastewater to the Waiwhetū Stream does not fall under the specific discharge rules in the Regional Freshwater Plan. It therefore is a discretionary activity under Rule 5 – All remaining discharges to freshwater. 4.1.2 Proposed Natural Resources Plan Under the Proposed Natural Resources Plan, where it is existing, the discharge of wastewater into freshwater is a discretionary activity under Rule 61. The Plan defines an existing discharge as:

In the context of wastewater discharged into fresh water from a wastewater treatment plant or a wastewater network means a discharge already authorised by resource consent at the time of application for a new resource consent relating to the same activity.

It is considered that the proposed discharge to the Waiwhetū Stream would fall under the definition of an existing discharge and therefore Rule 61 applies. It is noted that while the lower portion of the Waiwhetū Stream is identified in Schedule F4 (sites with significant indigenous biodiversity in the coastal marine area) it is considered that Rule 67 of the Proposed Natural Resources Plan does not apply to the proposed discharge into the Waiwhetū Stream. The reasons for this conclusion are:  Rule 67 is general in nature.  The structure of the Proposed Natural Resources Plan deals with specific types of discharge and then has a heading “all other discharges” under which rule 67 is located  Rule 67 is therefore considered to apply to all discharges other than those specifically addressed in the immediately preceding rules.  Rules 61 is a specific rule relating to wastewater discharges.  Rule 61 is therefore more specific than rule 67 and should prevail.

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4.1.3 Summary Based on the assessment above, the proposed discharge of treated wastewater to the Waiwhetū Stream is a discretionary activity. 4.2 Discharges and physical works in the Hutt River There are several elements of the proposed long term solution for the intermittent discharges which require assessment against regional plan rules. These are:

 The intermittent discharge of treated wastewater to the Hutt River  The placement of a new discharge structure in the bed of the Hutt River  The deposition of rock rip rap on the bed of the Hutt River to create the new ‘landform’  The disturbance of bed material during the construction of the outfall and landform  The diversion of water during construction  The occupation of the CMA

The activity status of each of these elements is assessed in turn below: These activities are downstream of the Waione Street Bridge, therefore are within the coastal marine area.

4.2.1 The intermittent discharge of treated wastewater to the Hutt River The Regional Coastal Plan

The discharge of treated wastewater in the coastal marine area is included in Rule 58 of the Regional Coastal Plan. This rule provides that: Except within an Area of Significant Conservation Value, any discharge of human sewage to the coastal marine area (except from vessels) which has not passed through soil or wetland is a Discretionary Activity.

The site of the proposed discharge is not within an Area of Significant Conservation Value. The discharge will not first pass through soil or a wetland.

Proposed Natural Resources Plan

Under the Proposed Natural Resources Plan all discharges of wastewater into coastal water are a discretionary activity under Rule 61. It is noted that while the site of the proposed Hutt River discharge is identified in Schedule F1b (Known rivers and parts of the coastal marine area with Inanga spawning habitat) and Schedule F4 (sites with significant indigenous biodiversity in the coastal marine area) it is considered that Rule 67 of the Proposed Natural Resources Plan does not apply to the proposed discharge. The reasons for this conclusion are as set out in 4.1.2. 4.2.2 The new discharge structure in the CMA The Regional Coastal Plan

Under the Regional Coastal Plan there are no specific rules applying to the proposed structure. It is therefore considered that the structure falls under Rule 25 All remaining activities involving the use and development of structures outside any Area of Significant Conservation value. This rule provides that

Any activity involving the use or development of any structure or any part of a structure fixed in, on, under or over foreshore or seabed outside an Area of Significant Conservation

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Value that is not specifically provided for in Rules 6 to 24 or Rules 26 or 27 or which cannot meet the requirements of those Rules is a Discretionary Activity.

Proposed Natural Resources Plan Under the Proposed Natural Resources Plan, the site of the proposed Hutt River discharge structure is identified in:

 Schedule C4 (Sites of significance to Taranaki Whānui kit e Upoko o te Ika a Maui)  Schedule F4 (Sites with significant indigenous biodiversity in the coastal marine area)  Schedule F5 (Habitats with significant indigenous biodiversity values in the coastal marine area) – Inanga Spawning Habitat.

Consequently the new structure, including any associated:

a) occupation of space in the common marine and coastal area, and b) disturbance of the foreshore or seabed, and c) deposition in, on or under the foreshore or seabed, and d) discharge of contaminants, and e) diversion of open coastal water is a non-complying activity under Rule 162.

4.2.3 The deposition of rock rip rap on the bed of the Hutt River The Regional Coastal Plan Under the Regional Coastal Plan there are no specific rules applying to the proposed deposition of rock rip rap. It is therefore considered that the deposition falls under Rule 48. This rule provides for: Any activity involving the deposition of sand, shingle, shell or other natural material on any foreshore or seabed:

(1) that is not specifically provided for in Rules 44-47 or any other rules in this Plan; or (2) which cannot meet the requirements of those rules;

is a Discretionary Activity and shall comply with the terms below.

Terms (1) The Hydrographer of the Royal New Zealand Navy shall be notified at the time permission is given and at commencement of the work, and which the deposition is complete.

Proposed Natural Resources Plan

Under the Proposed Natural Resources Plan, the site of the proposed deposition is identified in:

 Schedule C4 (Sites of significance to Taranaki Whānui kit e Upoko o te Ika a Maui)  Schedule F4 (Sites with significant indigenous biodiversity in the coastal marine area)  Schedule F5 (Habitats with significant indigenous biodiversity values in the coastal marine area) – Inanga Spawning Habitat.

Consequently the deposition falls under Rule R209:

Deposition inside sites and habitats identified in Schedule C (mana whenua), Schedule E4 (archaeological sites), Schedule F4 (coastal sites), Schedule F5 (coastal habitats) or Schedule J (geological features) in, on or under the coastal marine area, including any associated:

(a) disturbance of the foreshore or seabed, and (b) discharge of contaminants

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that is not a permitted activity under Rule R206 or a controlled activity under Rule R207 or a discretionary activity under Rule R208, is a non-complying activity.

4.2.4 The disturbance of seabed The Regional Coastal Plan Under the Regional Coastal Plan there no specific rules applying to the proposed bed disturbance. It is therefore considered that the disturbance falls under Rule 40. This rule provides for:

Any activity involving the destruction, damage, or disturbance of any foreshore or seabed:

(1) that is not specifically provided for in Rules 28 – 39 or Rule 43 or any other rules in this Plan; or (2) which cannot meet the requirements of those rules;

is a Discretionary Activity and shall comply with the terms below.

Terms (1) The Hydrographer of the Royal New Zealand Navy shall be notified at the time permission is given and at commencement of the work, and which the deposition is complete.

Proposed Natural Resources Plan

Under the Proposed Natural Resources Plan, the site of the proposed disturbance of the seabed is identified in:

 Schedule C4 (Sites of significance to Taranaki Whānui kit e Upoko o te Ika a Maui)  Schedule F4 (Sites with significant indigenous biodiversity in the coastal marine area)  Schedule F5 (Habitats with significant indigenous biodiversity values in the coastal marine area) – Inanga Spawning Habitat.

Consequently the disturbance falls under Rule R205:

Destruction, damage or disturbance inside a site and habitat identified in Schedule C (mana whenua), Schedule E4 (archaeological sites), Schedule F4 (coastal sites), Schedule F5 (coastal habitats) or Schedule J (geological features) in the coastal marine area, including any associated:

(a) deposition in, on or under the foreshore or seabed, and (b) discharge of contaminants, and (c) diversion of open coastal water

that is not permitted, controlled, restricted discretionary, discretionary or prohibited, is a non-complying activity.

4.2.5 The diversion of water during construction The Regional Coastal Plan Under the Regional Coastal Plan there no specific rules applying to the proposed diversion. It is therefore considered that the diversion falls under Rule 76. This rule provides for: Any activity involving the taking, use, damming, or diversion of water from the coastal marine area, other than open coastal water, outside any Areas of Significant Conservation Value: (1) which is not specifically provided for in Rules 73-75 or 77 or any other rules in this Plan; or (2) which cannot meet the requirements of those rules; is a Discretionary Activity.

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Proposed Natural Resources Plan Under the Proposed Natural Resources Plan the proposed diversion of water is ancillary to the construction of the structure and the deposition of the rock rip rap. A separate consent for the diversion is not required.

4.2.6 Occupation The Regional Coastal Plan Under the Regional Coastal Plan Rule 16 provides for: The occupation by any lawful structure of any land of the Crown or any related part of the coastal marine area, is a Controlled Activity provided that activity complies with the terms listed below. Terms (1) The person responsible for the structure shall at all times throughout the period when the structure occupies land of the Crown or any related part of the coastal marine area, pay to the consent authority, on behalf of the Crown, any sum of money required to be paid by regulations made under section 360(1)(c) of the Act; (2) The activity shall comply with the general terms listed in section 14.2.

Control The matters over which the Wellington Regional Council shall exercise its control are: (1) the duration of the consent; and (2) the information and monitoring requirements; and (3) the administrative charges payable; and (4) the degree of exclusivity of the occupation; and (5) any maintenance requirements. The proposed occupation of the CMA would fall under this controlled activity rule.

Proposed Natural Resources Plan Under the Proposed Natural Resources Plan the proposed occupation falls under rule R184, which provides for:

The occupation of space in the common marine and coastal area that is not permitted, controlled, restricted discretionary, non-complying or prohibited is a discretionary activity.

4.2.7 Summary Table 8 - Summary of the Hutt River resource consents

Activity RFP / RCP PNRP consent consent status status The intermittent discharge of treated wastewater to the Hutt RCP Rule 58 PNRP Rule 61 River Discretionary Discretionary The placement of a new discharge structure in the bed of the RCP Rule 25 PNRP Rule 162 Hutt River Discretionary Non-complying The deposition of rock rip rap on the bed of the Hutt River RCP Rule 48 PNRP Rule 209 Discretionary Non-complying The disturbance of bed material during the construction of RCP Rule 40 PNRP Rule 205 the outfall and rock rip rap landform Discretionary Non-complying

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Activity RFP / RCP PNRP consent consent status status The diversion of water during construction RCP Rule 76 Ancillary activity under rules 162 Discretionary & 209 The occupation of the CMA RCP Rule 16 PNRP Rule 184 Controlled Discretionary

Given the co-dependence of the discharge and the physical works in the Hutt River, and the overlap of the effects of these activities, it is considered that the principle of ‘bundling’ should be applied to the various resource consent applications. Consequently, the proposed activities in the Hutt River are non-complying activities, based on the status of the resource consent applications for the proposed structure, deposition of rock rip rap and bed disturbance under the Proposed Natural Resources Plan.

All activities are discretionary or controlled activities under the Regional Coastal Plan.

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5. Consideration of alternatives 5.1 Overview The existing resource consents1 require that an analysis of various options is undertaken prior to lodgement of the current application. In addition to this requirement  Schedule 4 to the RMA requires, if it is likely that the activity will result in any significant adverse effect on the environment, a description of any possible alternative locations or methods for undertaking the activity  Section 105 of the RMA requires that, in relation to discharge permits consent authorities must have regard to any possible alternative methods of discharge, including discharge into any other receiving environment  The Proposed Natural Resources Plan includes policies which promote the discharge of contaminants to land over direct discharge to water, and which requires that adverse environmental effects be minimised and which define ‘minimise’ to include the consideration of alternative locations and methods for undertaking the activity.

To respond to these drivers Wellington Water and Hutt City Council undertook a detailed assessment of alternatives. The process undertaken, the range of options assessed and the information which informed the selection of the shortlist and preferred option are set out in detail in the Option Assessment Report provided to the Regional Council in August 2017. This report summarises over four years of investigation work. A summary of the alternatives assessment process followed is set out in Figure 10.

Timing Project Phase Inputs  Existing consent conditions Sept 2016 Identification of the long list of  Seaview WWTP Alternative Outfall and Storage Options options Study  Seaview WWTP Temporary Outfall Options: An assessment of effects on the aquatic ecology

 Seaview WWTP Alternative Outfall and Storage Options Study  Seaview WWTP Temporary Outfall Options: An assessment of effects on the aquatic ecology October 2016 Long list assessment  Land Disposal Memo  A preliminary assessment of treatment options  MOP Issues and Options Report  Inputs from project team  Engagement with key stakeholders Nov - Dec 2016 Stakeholder engagement

 Initial multi-criteria analysis of environmental issues  Seaview WWTP Temporary Outfall Options: An assessment of effects on the aquatic ecology  Rodamine dye test results  Preliminary assessment of the effects of options on Māori Assessment of the short list cultural values (culminating in the draft Alternatives  Preliminary Assessment of options on natural character, January 2017 Assessment report, dated February visual amenity and recreation 2017)  Stakeholder feedback  Seaview WWTP Alternative Outfall and Storage Options Study  Evaluation of flood management implications of the options  Report on Treatment Upgrade for Ammonical Nitrogen Concentrations  Update of estimated capital cost of the options

1 Condition 26 of resource consent 33406 and condition 34 of resource consent 33408.

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Timing Project Phase Inputs  Evaluation of the options against statutory instruments  Preliminary assessment of the effects of options on Māori February 2017 Detailed RMA policy and consent cultural values risk analysis  Preliminary Assessment of options on natural character, visual amenity and recreation  Seaview WWTP Temporary Outfall Options: An assessment of effects on the aquatic ecology

April - May 2017 Annual Plan consultation and detailed survey of residents’ views on options

May - June 2017 Further analysis of natural character and visual amenity, recreation use and Māori Cultural Values

June-Aug 2017 Finalise Alternatives Assessment Further analysis undertaken over February to June Report

August/September HCC/UHCC adoption of the Inputs as described in the ‘Options Assessment Report’ 2017 preferred option

Figure 10 - Options Assessment Process

5.2 Possible alternative locations or methods As indicated above the first steps in the process were to identify and assess a long list of options. The long list was selected based on the direction contained in the existing consent conditions. This direction was considered to represent an appropriate range of options and included the following broad level options and combinations of them:  The status quo  Discharge location alternatives (Waiwhetū Stream, Hutt River & Wellington Harbour)  Storage capacity upgrade  Treatment plant upgrade  Major upgrade or replacement of the Main Outfall Pipeline.

It was also decided that land disposal should be included in the long list. While land disposal is not referred to in the conditions of the existing consent, it is promoted in the Proposed Natural Resources Plan.2

The long list of options was therefore: 1. The status quo 2. Hutt River (near mouth of Waiwhetū Stream); 3. Hutt River (100m off-shore of Barnes Street); 4. Wellington Harbour (2km south of Matiu-Somes Island); and 5. Wellington Harbour (at Hutt River mouth 100m off-shore of Port Road corner). 6. Wellington Harbour (at Hutt River mouth 600m off-shore of Port Road corner). 7. Option 1 plus treatment upgrade 8. Option 2 plus treatment upgrade 9. Option 3 plus treatment upgrade 10. Option 5 plus treatment upgrade 11. Option 1 plus storage upgrade 12. Option 2 plus storage upgrade 13. Option 3 plus storage upgrade 14. Option 5 plus storage upgrade

2 Policy 62

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15. Option 2 plus storage and treatment upgrade 16. Land disposal 17. Replace and upsize Main Outfall Pipeline 18. Renovate the Main Outfall Pipeline.

The long list was assessed though a ‘fatal flaw’ analysis and mini-MCA (multi criteria analysis) as described in Options Assessment Report. The outcome of this analysis was that:  There was only a small range in the scores (i.e. the range is 2.5-3.3 across the 14 options which passed the fatal flaw analysis)  Multiple options had the same score, e.g. four options scored 3.0  The closeness of the scores is in part a reflection of the fact that the options that scored better on environmental, social and cultural criteria, generally scored worse on affordability (and vice versa)

As a result it was concluded that while the mini-MCA provides some guidance on the options that should be selected for the shortlist it did not on its own provide a clear short list of options. The project team therefore decided to apply a broader ‘rationale’ based approach to the selection of the short list. The following rationale was applied: 1. The outcomes of the mini-MCA should be taken as a starting point for the selection of the shortlist. Specifically the top four scoring options would be carried through to the short list. These were: o Option 2 Hutt Confluence o Option 3 Barnes Street o Option 6 600 m off Port Road o Option 12 Hutt Confluence discharge plus storage 2. The short list should contain a range of options, including a range consistent with previously expressed stakeholder preferences and the conditions of the existing consent. Based on this the project team decided to include another harbour option to balance the two Hutt River options, Therefore Option 5 (100m off Port Road) was added to the short list. The project team also considered that to reflect the existing consent conditions a treatment option should be included in short list. Option 8 (Hutt confluence plus treatment) was therefore included in the short list. It is noted that Option 8 and Option 9 (Barnes Street plus treatment) scored the same in the mini-MCA. Option 8 was selected as the additional cost of treatment was considered to add more benefit to the Hutt confluence option than it adds to the Barnes Street option or to the status quo. 3. The project team decided that the short list should include the status quo. This was decided because it is the existing situation and therefore offers a base for comparison with the other options, and given the importance of affordability (cost) from HCC perspective.

Based on this process the following short list of options was identified: 1. The status quo 2. Hutt River (20m into Hutt River near mouth of Waiwhetū Stream) 3. Hutt River (100m off-shore of Barnes Street) 5. Wellington Harbour (at Hutt River mouth 100m off-shore of Port Road corner) 6. Wellington Harbour (at Hutt River mouth 600m off-shore of Port Road corner) 8. Option 2 plus treatment upgrade 12. Option 2 plus storage upgrade The location of these options is shown on Figure 11.

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Figure 11: Location of shortlist options

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5.3 Selection of the preferred option Wellington Water adopted a ‘Best Practicable Option’ (BPO) approach to determine its preferred option. The RMA definition of BPO is as follows: … the best method for preventing or minimising the adverse effects on the environment having regard, among other things, to — (a) The nature of the discharge or emission and the sensitivity of the receiving environment to adverse effects; and (b) The financial implications, and the effects on the environment, of that option when compared with other options; and (c) The current state of technical knowledge and the likelihood that the option can be successfully applied: Application of a BPO approach is considered appropriate as the activity in question is a discharge and because it provides a structured and transparent process for the consideration of range of factors relevant to option selection. A BPO approach has in recent years been used by a number of local authorities in assessing options and working with their communities, other key stakeholders and tāngata whenua in determining the most appropriate solution for community infrastructure, particularly for water, wastewater, stormwater and solid waste.

Such an approach is particularly relevant to this Project as it brings in the sensitivity of the receiving environment and the relative financial implications of the options (among other things). These key components are all well embodied in the RMA’s interpretation of the BPO as set out above.

Therefore to assess the short list options in relation to the BPO definition, a structured decision making framework using the following headings was applied:

 The nature of the discharge or emission  The sensitivity of the receiving environment to adverse effects  The financial implications of each option when compared with other options  The effects on the environment of each option when compared with other options  The current state of technical knowledge  The likelihood that each option can be successfully applied

The information that was considered in relation to these headings is based on the detailed information in the Appendices to Option Assessment Report submitted to GWRC in August 2017. This includes a detailed MCA on environmental values which is described in Appendix I of the Options Assessment Report, and an engineering and cost assessment. The approach was to first compare the options in ‘like’ pairs, and from this determine if either of the pair had the potential to be the BPO for the project. It is noted that because the shortlist is an odd number this comparison of pairs could not be applied to all options. For this reason, and because it is does not have a readily comparable option on the shortlist, option 6 was assessed on its own. 5.3.1 Options 1 and 2 There has been a record of continuous improvement in the management of wastewater from the Seaview WWTP. This history of improvement has reflected the needs and wishes of the Hutt communities (and is reflected in the conditions of the existing consent). In this context, it was concluded that Options 1 and 2 would fail to make sufficient environmental improvement. This is reflected in the low environmental MCA score given to each option (3.08 and 3.31 out of 5 respectively). Both options will not alter the nature of the discharge and both discharge into relatively less dynamic (therefore lower dilution potential) and more sensitive receiving environments.

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The outcomes of the environmental MCA indicates that both options will have significant adverse effects on Māori cultural values and that option 1 will also have significant adverse effects on freshwater and marine ecology. Given the potential for these significant adverse effects, notwithstanding that these options have the lowest estimated capital costs, it was considered that neither option could represent the BPO for this project. 5.3.2 Options 3 and 5 As with options 1 and 2, options 3 and 5 would not alter the nature of the discharge, however, the receiving environment would change substantially for both. Option 3 is at the mouth of the Hutt River 100m off-shore from the end of Barnes Street. The outfall would be located at a water depth varying between 2 m and 3.5 m, depending on the tide, and would be in the middle of the river’s flow, which would aid dilution of the discharge. The distance of the discharge point from the Waiwhetū Stream means that the discharge plume is unlikely to be pushed back into the Stream. Option 5 is into the harbour 100m off-shore from the Port Road corner. The outfall would be located at a water depth varying between approximately 2 and 4m depending on the tide. Dilution for this option is lower than option 3 due to a combination of the shallow water and low water velocities. Again given the distance of this option from the mouth of the Waiwhetū Stream, impacts on the Stream are very unlikely. The overall environmental impact of these options (as indicated by the environmental MCA scores) is similar, and both would result in a meaningful improvement on the status quo. Neither option has been identified as having any significant adverse environmental impacts. The slightly higher MCA outcome for option 3 arises from better scores in relation to freshwater and marine ecology and human health, which reflects the improved dilution efficiency at option 3. It was noted that GWRC flood protection staff have raised concerns about the potential adverse impact of option 3 in relation to navigation, dredging, safety of the structure, effect on the aquifer, flooding effects and GWRC responsibility. These issues were carefully considered and it was considered that each of the issues could be satisfactorily addressed by appropriate design or construction responses. Based on the current concept design, the capital cost of option 5 is estimated to be approximately $6M more than option 3. Costs at this level would have significant impact on Hutt Valley ratepayers, and/or would constrain Council’s ability to fund other infrastructure improvements such as improvements to resilience of the untreated wastewater delivery pipelines, network renewals including critical rising mains, or planned improvements to partially treated wastewater overflows. Taking account of the higher estimated capital cost for option 5, and noting that the MCA score for option 3 is slightly better than for option 5, it was that concluded that option 5 could not be the BPO for this project. Option 3 was considered to represent a potential BPO and should be considered against other potential BPO options. 5.3.3 Option 6 Option 6 would not alter the nature of the discharge, however the receiving environment would change substantially. Option 6 is into the harbour 600m off-shore from the Port Road corner. The outfall would be located at a water depth of 10m, approximately 1,600m south of the Waiwhetū Stream mouth, 400m west of the entrance to the Seaview Marina and 330m north-west of the Point Howard Wharf. The discharge plume would be unlikely to have any material influence on the water quality or aquatic ecology of Waiwhetū Stream. The water depth and velocity at this location are expected to provide the highest dilution potential of any of the options. This factor combined with the less sensitive harbour receiving environment is a key factor in the option receiving the highest environmental MCA score of all of the options. The environmental MCA identified that this option would not have any moderate or greater adverse effects on any of the factors considered.

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Option 6 is estimated to have the highest capital cost, at $34m. Costs at this level would have very significant impact on Hutt Valley ratepayers, and would constrain Hutt City Council’s ability to fund other infrastructure improvements which might provide greater environmental benefit. Overall it was considered that while this option has the best MCA score, its very high capital cost, rules it out as a ‘best practicable’ option. This is because there are considered to be other environmentally appropriate options available at significantly less cost. 5.3.4 Options 8 and 12 Options 8 and 12 are the only two options to change the nature of the discharge. Option 8 does this by adding further treatment at the WWTP. The further treatment would remove ammonaical nitrogen from the discharge. Option 12 changes the discharge by providing greater storage at the WWTP. This would achieve two outcomes. First this option would reduce the number of wet weather related discharges by approximately 1-2 per year3. Second it would enable dry weather discharges to be held back until the next outgoing tide. This would substantially reduce the risk of the discharge plume flowing back up the Waiwhetū Stream. The sensitivity of the receiving environment is the same as for option 2, although as noted the receiving environment for option 12 is less likely to include the Waiwhetū Stream. The two options may become operationally less effective in the event of sea level rise. However this is not considered to be a significant issue on the basis that expert advice suggests that this is unlikely to occur within the next 50 years. By this time it can be expected that a more significant upgrade of the MOP will have been undertaken. Both options are expected to have similar overall adverse environmental effects. The options’ overall adverse effects are considered to be identifiably better than those of options 1 and 2, i.e. they would represent an improvement on the status quo and continue the record of continuous improvement. It is recognized that options 8 and 12 were assessed in the environmental MCA as achieving less environmental benefit than options 3, 5 and 6. None of the individual adverse environmental effects of options 8 and12 were identified as being significant in the environmental MCA. The worst potential adverse effects of these options were identified in the environmental MCA as being ‘moderate’ and related to:  the ‘Relationship of Māori, their culture and taonga’ for both options  ‘freshwater and marine ecology’ for option 12. All other adverse environmental effects were assessed in the MCA as being moderate-minor, minor or less than minor. The estimated capital costs of options 8 and 12 are approximately $21M and $12M (respectively). These represent a substantial cost increase relative to the status quo (and option 2). The capital cost of option 8 is on a par with that for option 3 but does not offer the same environmental benefit. The capital cost of option 8 is $9M more than option 12 and provides limited additional environmental benefit (mitigation) relative to that option. It was therefore concluded that option 8 could not be the BPO for this project. Option 12 is considered to have the potential to be the BPO. It was therefore carried forward to be considered against option 3. 5.3.5 Comparison of options 3 and 12 The MCA scores for these two options are 3.59 for Option 12 and 4.19 for Option 3. This indicates that option 3 would provide a better environmental outcome (greater mitigation). The differences in adverse environmental effects identified through the MCA process relate to:  Freshwater and marine ecology (minor adverse effect for option 3 and moderate adverse effect for option 12)  Human Health (minor adverse effect for option 3 and moderate-minor for option 12)

3 There are currently 4-5 wet weather discharges on average per year.

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 Water colour, clarity and odour (minor adverse effect for option 3 and moderate-minor for option 12)  Relationship of Māori, their culture and taonga (moderate-minor adverse effect for option 3 and moderate for option 12)  Amenity values & recreation activities and opportunities (very minor for option 3 and moderate-minor for option 12) It is of note that option 12 would reduce the number of overflow events per annum which is consistent with the direction in Policy 81 of the PNRP to reduce the frequency and volume of wastewater discharges that occur following rainfall events. As noted GWRC flood protection staff have raised concerns about this option. However it is considered that these can be resolved through careful design. Given the forces generated by flood flows in the Hutt River, option 3 will require piling into the aquiclude of the Waiwhetū aquifer. While this presents a potential risk to the aquifer it is not an uncommon practice and the risks can be managed through standard construction methodologies. In relation to the relative capital cost of the two options, the capital cost of option 3 is approximately $8m higher than option 12. The additional $8m cost of option 3 would mean less money available to Hutt City Council for other infrastructural works which might provide greater environmental benefit. This potentially includes the reduction of untreated wastewater overflows entering freshwater upstream of the treatment plant. In the next 10 years there is currently a focus on improving the resilience of the wastewater network through duplication or renewal of critical rising mains and some planned works on wet weather wastewater overflows in the network, including additional storage and/or partial treatment. The issue of whether either option would have additional costs in the future has also been considered. It is considered probable that option 12 would not be a suitable outfall during future major repairs or replacement of the MOP, which could take several months. It is therefore appropriate to consider the cost of additional works to construct a suitable outfall during these major repairs as part of option 12. To do so a Net Present Value (NPV) assessment was undertaken. The NPV assessment indicated that taking a longer term perspective on the financial costs and benefits of options 3 and 12 does not substantially change the cost difference between them. Public consultation, as part of the Hutt City Council annual plan process, and a survey of Hutt residents showed that overall the Hutt community is likely to prefer option 12 over option 3. The reason for this appears to be that the public has assessed capital costs against the environmental benefits delivered by each of the options and determined that Option 12 represents the best balance. Having considered the differences between option 3 and 12, it was clear that in determining which option represented the BPO the key question was whether the additional environmental benefit (illustrated by the MCA score for option 3) is sufficient to warrant the $8m additional capital cost. In this respect, the difference in overall environmental adverse effects is a movement from effects expected to be moderate-minor for option 12 to those which are minor for option 3. Neither option has adverse effects in relation to the individual criteria assessed that are identified as being significant4. Both options would result in a significant improvement over the current situation. Based on this, it was concluded that the environmental outcomes expected from both option 3 and 12 are acceptable and that the environmental outcome from option 3 is not significantly better. In contrast, the difference in capital cost between the options is significant. Therefore it was concluded that option 12 is the BPO for this project.

4 It is noted that since the option assessment process was completed in August 2017, more detailed assessment of the effects of option 12 has been undertaken. This has provided greater confidence that the adverse effects of this option will not be significant and that, at worst, they are minor- moderate.

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6. Assessment of Environmental Effects 6.1 Introduction In scoping the proposal’s potential environmental effects the following matters have been considered:  Part II and Schedule 4 of the Resource Management Act  The Regional Policy Statement  The Regional Coastal Plan  The Proposed Natural Resources Plan  Water quality guidelines: ANZECC (2000), the NPS-FM National Objectives Framework and the Aquatic Life Ambient Water Quality Criteria for Ammonia – Freshwater (USEPA, 2013).  The views of iwi  Feedback received from the Consultation Group and from other community engagement  Specialist opinion.

Based on these matters it is considered relevant to assess the following environmental effects:  Positive effects  Effects on Māori cultural values  Water quality  Ecological effects, including construction effects  Effects on natural character  Visual amenity effects  Recreation effects  Flooding effects.

6.2 Positive effects The intermittent discharge of treated wastewater from the Seaview WWTP is an important part of the overall Hutt Valley wastewater network. The wastewater network enables essential public health protection by providing for the safe conveyance, treatment and disposal of the community’s wastewater.

The discharges of treated wastewater into the Waiwhetū/Hutt River enables repair to occur on the MOP. If the discharges could not occur one of two scenarios would result. Either leaks would occur along the MOP at uncontrolled locations with resulting discharges of treated wastewater into the eastern bays of the Wellington Harbour, or the community of the Hutt Valley would be forced to invest in the replacement of the MOP. This is a very significant investment, currently estimated to be between $100-200 million. It is recognised that, without significant technological/construction advances, an investment of this scale will be required in the future. However based on the most recent investigations of the structural condition of the MOP, this investment is not expected to be necessary within a 20 year term and possibly longer. Therefore not being able to complete repair works, because of the lack of an alternative discharge location, would impose significant financial cost on the Hutt Valley community. This financial cost would undoubtedly come with significant opportunity costs in terms of other Hutt City and Upper Hutt City Council projects that would need to be deferred.

It is not practical for a wastewater conveyance and treatment network to be sized so that it has capacity to carry all wastewater (either treated or untreated) in all situations. Being able to discharge wet weather overflows of treated wastewater to the Waiwhetū Stream (initially) and Hutt River enables wastewater to be secondary treated and UV disinfected at the Seaview treatment

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facility even when the flow exceeds the capacity of the MOP to convey it to Bluff Point, at Pencarrow Head. If there was no ability to discharge the overflow of treated wastewater to the Waiwhetū/Hutt River then it would not be possible to treat as much wastewater in wet weather conditions. This would lead to increased overflow of untreated wastewater upstream of the treatment plant. 6.3 Effects on Māori cultural values This assessment of effects on Māori cultural values was completed by Raukura Consultants. 6.3.1 Background The Seaview Wastewater Treatment Plant is located in the vicinity of the old Waiwhetū Pa and adjacent to the Owhiti Urupā or burial ground. The Waiwhetū Stream links the Urupā and the old Pa to the more modern Waiwhetū Marae and papakainga. The Owhiti area including the Pa and Urupā were once on an island in the estuary of the confluence of the mouths of the Waiwhetū, Te Awa Mutu streams and Te Awa Kairangi (Hutt River). This was an area of high cultural significance to the Te Ātiawa people of the old Waiwhetū and Hikoikoi Pā. The ancestors’ descendants are now a part of Waiwhetū Marae and papakainga. The Hutt River estuary which is much smaller than it was in 1840 was a rich source of kaimoana/seafood as well as providing waka access into the hinterland via Te Awa Kairangi and the streams of Te Awa Mutu and Waiwhetū. The whole estuary area uplifted in 1855 and the estuary became smaller. From the early times of colonisation the area, now known as Seaview, became the subject of extensive reclamation providing for the industrial area we know today. Māori eventually abandoned the Waiwhetū Pa and eventually moved upstream to what is now Waiwhetū Marae and Te Whiti Park onto the approximately 100 acre block known as Hutt Section 19. 6.3.2 Seaview Wastewater Treatment Plant and the Temporary Discharge to the Waiwhetū Stream. The Seaview WWTP was constructed to treat the wastewater from Hutt and Upper Hutt Cities and their suburbs. The main outfall pipeline (MOP) takes the treated wastewater out to the ocean discharge point at Pencarrow Head, most of the time. From time to time the MOP is not available due to maintenance requirements and the temporary outfall is currently into the Waiwhetū Stream just downstream of the Owhiti Urupā. These discharges can usually be anticipated and these planned discharges occur during a set time in winter. Unplanned repair related discharges may occur outside winter, but for a shorter duration (2 weeks). This outfall is also used in times when the total discharge volume exceeds the capacity of the MOP when there is high rainfall in the catchment. 6.3.3 The Proposal The proposal for resource consent being sought has two phases.

Phase 1 is the continuation of intermittent discharges to the W aiwhetū Stream for a period of 5 years from the grant of consent from the existing outfall just downstream of the Owhiti Urupā.

Phase 2 involves the relocation of the discharge point from the Waiwhetū Stream to the Hutt River. This will be via a new pipeline and with the construction of the new outfall structure projecting into the Hutt River. This will also include the construction of and additional treated wastewater tank at the Seaview Plant site. The consent for this phase would be for a period of 35 years.

The Māori cultural effects of both phases are outlined below. 6.3.4 Phase 1 Consent – Māori Cultural Effects The phase 1 consent in essence is simply a continuation of the expiring consent for the period required to consent, design, construct and commission the new outfall and the new storage tank. The cultural effects of this continuing discharge on the tangata whenua remain significant. It goes without saying that the temporary consent for Phase 1 must not allow any delay in the construction of the new outfall. It has been clear for some time that the status quo is not acceptable to Māori

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particularly the elements where the discharge point is close to the Owhiti Urupā and the discharge is into the Waiwhetū Stream. It is noted that there has been considerable effort by Central and Local Government to clean up this part of the Waiwhetū Stream in large part driven by Māori cultural effects.

For many tangata whenua even a 5 year consent is much longer than they would desire however, if they are aware of the planned upgrade of the outfall and the storage tank and various milestone achievements in the project, they would be tolerant of the continuing cultural offense. There is a strong desire to minimise this phase and to move as quickly as practicable to Phase 2.

The on-going effects of a large discharge of treated wastewater on the native fish population in the Waiwhetū Stream is well known. Anecdotal evidence has shown the possible return of the whitebait species into the stream, however the inanga and the banded kokopu juveniles are quite sensitive to the discharges particularly when they are coming into the stream in spring along with the glass eel/elvers. These species are all indicators of the cultural health of the stream. Care taken in selecting the times of year the discharges occur, where that can be managed, will help mitigate these effects. The proposal for management of the discharges acknowledges these matters will ensure the effects are avoided.

In this phase there is an issue of ammonia in the discharge which at times provides some aroma at the outfall and may have some effects for the native fish. This is also the case in Phase 2. 6.3.5 Phase 2 Consent – Māori Cultural Effects This is not just the construction phase but it also becomes the long term implementation phase for the discharges. The consent and its implementation provide a long term solution at least in part to the key Māori cultural effects. The discharge of treated wastewater adjacent to an operational urupā or even one that is no longer in current use is an offence to all Māori and especially for those whose tupuna are interred nearby. Although the Waiwhetū Stream is no longer fished culturally it flows past a very active Marae and papakainga and the people there are highly aware of its ‘cultural health’ or mouri/mauri. They can see the streams health particularly in the fish life in the stream.

The proposed new outfall into the Hutt River with detention that will enable discharges to largely be achieved on the outgoing tide, will mean the discharge would be unlikely to enter the stream. There will however remain effects on the inward migrating juvenile fish if discharges of treated wastewater occur into the main river in the spring period as they tend to use the margins of the Hutt River. With the discharge point out into the main flow of the river and management of the times of discharge these effects can be largely avoided or mitigated

The issue of the use of the estuary, river and harbour areas by waka of all types including waka ama (outrigger canoes), waka taua (war canoes) and waka hourua (voyaging waka) is to a degree a cultural effect and it is more difficult to avoid with a relocated outfall. However the discharge into the much larger volume of the Hutt River does help mitigate matters. Notification by text or email when discharges are about to occur will provide a useful form of mitigation. In that way the area can be avoided during the period of discharge.

The cultural effects of treated wastewater discharges on the Owhiti Urupā are avoided when the Hutt River discharge point is brought into operation and discharge is made on the outgoing tide.

The design of the outfall to integrate into the true left bank of the Hutt River is going from a man - made bank which was a part of the reclamation process for Seaview. This is different from the right bank or Hikoikoi side which has a more natural character. The discharge pipe should go out into the main flow of the river clear of the slower waters of the river margins used by native fish. This would be enhanced by having the water flow at the margins of the river around the pipe able to allow fish passage into the Waiwhetū Stream. The rock riprap around the pipe may provide the necessary slower flow to enable fish passage around the pipe.

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6.3.6 Conclusions From the cultural perspective the shorter Phase 1 lasts the better, as that is largely the continuance of the status quo, which has been tolerated but is not acceptable. The better solution from Phase 2 needs to be steadily progressed.

The cultural effects of Phase 2 are significantly reduced when compared with the status quo. With the discharge going into the main flow of the Hutt River, along with the proposed storage tank and good operational procedures, should ensure that the discharge will not flow back up the culturally significant Waiwhetū Stream, and certainly not back to the vicinity of the Owhiti Urupā.

Careful design of the outfall will be necessary to help native fish to move back into the Waiwhetū Stream and ensure effective outflows to the River and ultimately into the Harbour.

Conditions that provide for notification of repair and wet weather discharges to the likes of the waka ama clubs and other water users will help mitigate adverse effects. This also applies for the discharges during storm events or other non-scheduled events.

6.4 Water Quality 6.4.1 Characterisation of wastewater discharges As background to the assessment of water quality effects it is necessary to characterise the nature of the discharges. The history of the existing discharges helps to do this and is set out below.

Rate and duration of MOP repair discharges

MOP repair discharges to Waiwhetū Stream have occurred on 8 of the last 14 years, at an average frequency of 0.9 discharge events per year. The discharges had an average flow rate of 416 L/s and a peak flow rate was 2,640 L/s. The volume of wastewater discharged averaged 374,971 m3 per year while the duration averaged 146 hours (or 6 days) per year (Table 9). Table 9: Record of MOP repair discharges from Seaview WWTP to Waiwhetū Stream Year Discharge events Mean discharge Peak discharge Total overflow Total duration (1 Apr – 31 Mar) per year flow (L/s) flow (L/s) Volume (m3/yr) (hours/yr) 2003-04 1 Not recorded Not recorded 1,801,200 528 2004-05 0 0 0 0 0 2005-06 0 0 0 0 0 2006-07 2 431 1,336 16,994 7 2007-08 1 301 1,068 21,100 20 2008-09 1 469 520 1,068* 1* 2009-10 2 523 1,368 394,028* 166* 2010-11 0 0 0 0 0 2011-12 3 440 1,352 757,056 331 2012-13 0 0 0 0 0 2013-14 1 546 1,758 483,577 246 2014-15 2 625 2,640 1,774,575 748 2015-16 0 0 0 0 0 2016-17 0 0 0 0 0 Average 0.9 416 1,255 374,971 146 Note * - major outages 26 March to 13 May and 22 May to 25 July 2009 excluded from table as an outlier. Approximately 7,000,000m3 of treated effluent was discharged to the Waiwhetū Stream during this period.

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Quality of MOP repair discharges

The results of treated wastewater quality monitoring during repair discharges to Waiwhetū Stream in May 2013, and June, July and August 2014 are summarised in Table-10. Table-10: Treated wastewater quality from daily samples collected from MOP repair discharges to Waiwhetū Stream during the 2013/14 and 2014/15 monitoring years Constituent units n. samples Treated wastewater quality minimum median 95-percentile maximum pH pH 51 7.0 7.40 7.59 7.60 Temperature °C 15 14.6 17.2 18.1 18.3

Dissolved O2 mg/L 15 2.2 3.2 5.6 6.3

cBOD5 mg/L 51 3.0 6.0 13.9 19.0 Turbidity mg/L 51 0.62 4.08 13.8 16.5 Faecal coliforms /100ml 51 <4 100 4,895 10,800 E. coli /100ml 51 <4 88 3,991 4,300 Enterococci /100ml 51 <1 110 2,530 3,400 DRP mg/L 51 0.865 2.070 2.737 2.990 Nitrite-N mg/L 51 <0.01 <0.01 0.348 0.400 Nitrate-N mg/L 51 <0.005 <0.005 0.119 0.320 Ammonia-N mg/L 51 14.1 23.7 29.7 31.7 Copper (dissolved) mg/L 51 <0.004 0.006 0.010 0.056 Zinc (dissolved) mg/L 51 0.012 0.022 0.027 0.029

Rate and duration of wet weather overflow discharges

Wet weather treated wastewater discharges have occurred on average 4.3 times each year with an average duration of 13 hours per event and 58 hours per year (2.4 days). Wet weather discharges occur at an average flow rate of 339 L/s up to a maximum recorded rate of 2,895 L/s. The total discharge volume has averaged 79,406 m3 per year (Table 11). Table 11: Record of wet weather overflow discharges from Seaview WWTP to Waiwhetū Stream Year Discharge Average Maximum Average Maximum Overflow Duration/ Duration/ (1 Apr – 31 events per volume volume flow Flow volume year Event Mar) year (m3) (m3) (L/s) (L/s) (m3/yr) (hours) (hours) 2003-04 6 11,017 19,900 317 840 66,103 65 11 2004-05 4 29,830 91,545 424 1080 119,318 53 13 2005-06 1 8,649 8,649 353 360 8,649 7 7 2006-07 9 46,601 150,600 453 1364 419,412 230 26 2007-08 1 44,100 44,100 670 821 44,100 16 16 2008-09 7 6,773 16,474 317 900 47,414 57 8 2009-10 4 6,183 12,254 255 786 24,732 36 9 2010-11 2 25,119 37,926 388 700 50,238 29 15 2011-12 3 10,200 22,464 227 832 3,060 11 34 2012-13 3 4,330 7,560 248 600 12,990 13 4 2013-14 7 12,618 37,740 297 2600 88,328 106 15 2014-15 1 1,500 1,500 200 686 1,500 2 2 2015-16 2 7,449 14,223 282 2895 14,898 11 5 2016-17 10 21,094 59,670 309 2882 210,938 169 17 Average 4.3 16,819 37,472 339 1,239 79,406 57.5 13

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Quality of wet weather overflow discharges

The results of treated wastewater quality monitoring during wet weather overflow discharges to Waiwhetū Stream during the period 2013 to 2017 (38 days in total) are summarised in Table 12. During wet weather overflows the treated wastewater typically has lower concentrations of nutrients but higher concentrations of indicator bacteria compared with dry weather discharges. Table 12: Treated wastewater quality from daily samples collected from wet weather overflow discharges during 2013 to 2017 (n=38) Treated wastewater quality Constituent units n. samples minimum median 95-percentile maximum

cBOD5 mg/L 38 <1 4.5 23 25 Faecal coliforms /100ml 38 <1 345 22,320 45,000 E. coli /100ml 38 <2 269 21,720 36,000 Enterococci /100ml 38 <1 335 16,800 22,000 DRP mg/L 38 0.220 0.610 1.52 2.19 Nitrite-N mg/L 38 <0.01 0.180 0.640 0.660 Nitrate-N mg/L 38 <0.01 0.670 3.14 6.04 Ammonia-N mg/L 38 2.24 8.93 19.52 22.9 Copper (dissolved) mg/L 1 <0.005 - - - Zinc (dissolved) mg/L 1 0.030 - - -

6.4.2 Plume dilution and dispersion assessment Investigations

Hutt City Council commissioned a series of investigations in order to determine the dilution and dispersion characteristics of the discharge plume from the existing outfall and for five alternative outfall options that have been considered as part of the project. The dispersion investigations referenced in this assessment include:  Dye dilution and dispersion from a planned repair wastewater discharge into Waiwhetū Stream (Barter, 2013);  HCC Plume Dispersal Data Report (Stevens, Brewer, Elliot, Grant, & Rickard, 2013); and  HCC Plume Dispersion of the preferred option (Tuckey, 2017)

Dye dispersion study

In 2013 a dye dilution and dispersion study was undertaken to collect field data that could be used to validate and verify the three-dimensional numerical model. The dye release occurred from the existing outfall in the Waiwhetū Stream.

Data was collected during a neap ebb tide during a period of fine weather and light northerly winds. During the dye release the discharge flow from the Seaview WWTP varied between 570 L/s and 1,250 L/s, averaging around 944 L/s. During this study a portion of the wastewater volume was stored in the storm tank and later released from the existing Seaview outfall on the outgoing tide, in accordance with consent conditions.

The effluent formed an elongated plume that hugged the eastern bank of the Hutt River as it made its way out into Wellington Harbour. Dilution within the Hutt River was relatively low, with less than 5:1 dilution achieved 150m downstream of the Waiwhetū Stream mouth and subsequent dilutions of 10:1 and 25:1 taking place as far as 350 m and 1000 m downstream, respectively.

Dye was never detected on the western side of the Hutt River, and never crossed the midline of the river channel. When the ebb tide finished and the tide turned, dye (hence treated wastewater) was no longer detected at the mouth of the Waiwhetū Stream. All dye (hence wastewater) was

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observed flowing upstream from the Waiwhetū Stream outfall, under the influence of the flood tide (Barter, 2013).

Figure 12: Wastewater dilution contours in the Hutt River downstream of the Waiwhetū Stream (from Barter, 2013)

Additional dye releases were conducted in November 2017 and October 2017 (see Appendix E) to confirm the direction of surface water flow in the Hutt River and Waiwhetū Stream on the incoming tide. These studies indicate that surface water continues to move downstream in the Hutt River during the incoming tide, except perhaps when driven by south or south-westerly winds. Some of the surface water flowing downstream in the Hutt River during the incoming tide enters the Waiwhetu Stream and is then carried upstream with the tide.

Hydrographical data collection NIWA conducted field observations of the hydrography in Hutt River and Wellington Harbour as the first phase of the plume dispersion study. The observations included three instrumented moorings that measured water column velocity structure, near bed temperature and salinity. These moorings were located (a) in the Hutt River up-stream of the Waiwhetū Stream, (b) in the Hutt River mouth, and (c) in Wellington Harbour south of Matiu/Somes Island. These three moorings were augmented by nine profiling transects designed to capture the spatial evolution of the river plume in the harbour.

The field observations show that flow speeds in the Hutt River were around 0.01 m/s except during storm-driven rain when the river flowed into the harbour at a rate of over 0.4 m/s for a period of up to three days. The data show upstream flow in the Hutt River both at depth and at the surface for some of the tidal cycle, but not at the same time (Figure 13). This curious behaviour may be either a local effect based on the river shape where the current profiler was located or it could be a stratified adjustment where the tides drive not only a change in water elevation but also an internal change (Craig Stevens, pers. comm.).

Salinity at the river mouth is bimodal, switching from coastal ocean to near-fresh over very short periods of time. The harbour mooring indicates that the tides are only a modest component of flow (<0.005 m/s) and that the currents are multi-directional.

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Figure 13: North-south flow velocities in surface water (blue) and deep water (black) at the Hutt River mooring. Negative values show flows south, out into the harbour (from Stevens et al 2013). Near field mixing The numerical modelling comprises two components, the first looking at the near-field dispersal, the second extrapolating and integrating the near-field solution into the wider flow field (far-field) in order to estimate the large scale plume dispersal characteristics.

A near field mixing assessment was conducted using the CORMIX modelling system to provide predictions 100m downstream of the proposed discharge point below the Hutt/Waiwhetū confluence. The predicted plume behaviour, as described by DHI (DHI, 2017) is as follows:  Salinity stratification for the full tidal cycle significantly decreases the dilution of wastewater, since the wastewater plume will be very positively buoyant compared with the receiving water which inhibits the mixing of wastewater. The wastewater will remain within the overlying freshwater layer where it fully mixes vertically.  For the dry weather condition with a 1.1 m 3/s discharge on outgoing tide, dilutions range from 3.6 fold to 6.0 fold at a distance of 100 m from outfall and 3.1 to 8.8 fold at end of near-field mixing zone, with a range of 12 to 350 m from the outfall.  For the wet weather conditions with a constant 0.8 m 3/s discharge, a dilution of 3.3 fold is achieved at a distance of 100 m from the outfall location and 1.8 fold at end of near-field mixing zone 2 m downstream of the outfall.  For the wet weather conditions with a constant 3.0 m 3/s discharge, a dilution of 2.4 fold is achieved at a distance of 100 m from the outfall location and 2.3 fold at end of near-field mixing zone 19 m downstream of the outfall.

Far field dilution Following the initial dilution phase, a reasonably coherent surface plume moves away from the discharge site under the impetus of the coastal or tidal current. As it moves it continues to spread and dilute, but at a slower pace than in the initial dilution phase. The far-field assessment involved the use of DHI’s fully dynamic 3-dimensional flow and transport modelling system MIKE 3 FM, which is suitable for use where three dimensional density stratified flows are important as is the case for this study where the mixing behaviour of a buoyant plume and saline intrusion within the lower Hutt River must be generally reproduced. The flexible mesh allows for a varying resolution computational grid so that a finer resolution can be used for areas of interest (i.e. Hutt River and outfall locations) and a lower resolution can be used for other areas. The results of modelling the three discharge conditions are described in detail in DHI (2017). For the purpose of this assessment we have considered the 50th percentile dilution range for various wind and

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tide scenarios at each of eight predetermined sensitive sites, and selected the minimum dilution in each range (bold) for input into mass balance calculations (Table 13). Table 13: Predicted 50th percentile dilution range (x-fold) at eight sensitive sites (from DHI, 2017)

Repair discharge, Wet weather Repair + wet Repair discharge at Discharge regime 1.1 m3/s on ebb discharge at 0.8 weather at 3 m3/s, 1.1 m3/s on ebb tide, 5 days m3/s, 1 day one day tide, 30 days

Petone Beach W (1) 381 – >1000 776 - >1000 205 - >1000 199 - >1000

Petone Beach E(2) 264 – >1000 934 - >1000 248 - >1000 237 - >1000

Waione St. Br. (3) >1000 >1000 >1000 >1000

100m D/S of 6 - >1000 54 - >1000 18 - >1000 4 - 31 confluence (4)

Lowry Bay (5) 118 – >1000 201 - >1000 54 - >1000 134 - >1000

Sensitive sites Days Bay (6) 152 – >1000 416 - >1000 109- >1000 99 - 398

Port Rd beach (7) 106 - 704 210 - >1000 55 - >1000 43 - 249

Seaview Marina (8) 124 - 626 235- >1000 63 - >1000 37 - 97

6.4.3 Ammonia water quality criteria Because of the complexities of both the proposed discharge regime and the proposed receiving environment there is no single ammonia toxicity guideline that could be applied across the board. Instead, three water quality guidelines have been considered to cover the various scenarios included in the consent application. As summarised in Table 14, these are ANZECC (2000) Freshwater and Marine, the NPS-FM (2014) National Objectives Framework and the Aquatic Life Ambient Water Quality Criteria for Ammonia – Freshwater (USEPA, 2013). The guideline value applied in this AEE for each receiving water type is shown in bold in Table 14.

The Hutt River in the vicinity of the Waiwhetū Stream mouth is estuarine, consisting of freshwater at the surface and saline water at depth. The wastewater discharge has a similar density to freshwater and consequently mixes mostly with the surface layer, with little penetration to depth except during storm conditions. On that basis freshwater quality guidelines are applied at Hutt River locations upstream of Port Road corner; downstream of that point marine water quality guidelines would apply.

At most times the tidal discharge regime will produce a discharge plume at the lower reach of the Hutt River on a 6-hours on / 6-hours off cycle, for the duration of the discharge. The Aquatic Life Ambient Water Quality Criteria for Ammonia – Freshwater (US EPA, 2013) provide guidance for short duration discharges (which is not available in ANZECC 2000 or NPS-FM 2014). US EPA (2013) recommend a chronic criteria concentration (CCC) as a 30-day rolling average (not to exceed 2.5 times the CCC as a four day average within the 30 days, more than once in three years on average).

Table 14 includes ANZECC (2000) freshwater guidelines which could be applied if a continuous discharge were to occur to the Hutt River. Given the high degree of modification to the Hutt River near the Waiwhetū confluence, and the disturbance of benthic habitats caused by intermittent flood flows, sediment deposition and regular dredging, this habitat is described as being highly disturbed and having low ecological value (see Section 3.2.6). Accordingly either the 80% or 90% level of

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protection would be appropriate. The NPS-FM ‘National Bottom Line’ total ammonia-N criteria are also included in the table. While the proposed discharge location is in the CMA, and therefore outside of the jurisdiction of the NPS-FM, this guideline could be used as an alternative to ANZECC (2000) for continuous discharges.

Finally, locations in Wellington Harbour beyond the Hutt River mouth are sufficiently removed from the outfall that the tidal discharge regime will result in a more or less continuous plume, albeit highly dilute. Habitats in Wellington Harbour beyond the Hutt River mouth, while modified, have generally retained significant ecological value. On that basis the ANZECC (2000) 95% protection trigger values for marine water would be appropriate (see Table 14). Table 14: Trigger values for ammonia toxicity Receiving Discharge Level of Trigger value Reference environment type modification USEPA, 2013 Hutt River near 6 hours on; ≤ 2.7 mg/L (30-day average)1, Highly disturbed Freshwater Waiwhetū mouth 6 hours off ≤ 6.8 mg/L (4-day average) (at pH 8 & 20oC) ≤ 0.32 mg/L (99% protection) ANZECC (2000) – ≤ 0.90 mg/L (95% protection) Freshwater ≤ 1.43 mg/L (90% protection) (at pH 8 & 20oC) Hutt River near ≤ 2.30 mg/L (80% protection) Continuous Highly disturbed Waiwhetū mouth ≤ 0.05 mg/L (99% protection) >0.05 and ≤ 0.4 mg/L (95% protection) NPS-FM (2014) Freshwater >0.4 and ≤ 2.2 mg/L (80% protection) (at pH 8 & 20oC) 2.2 mg/L (National Bottom Line) Slightly to ANZECC (2000) Wellington Continuous moderately Marine Harbour ≤ 0.91 mg/L (95% protection) disturbed (at pH 8 & 20oC) Notes: 1US EPA Freshwater CCC criteria: freshwater mussels absent; protection required for early life stage fish. 6.5 Water quality effects on the Waiwhetū Stream To assess the effects of the proposed 5 year discharge to the Waiwhetū Stream, results from previous discharges to the Stream have been reviewed. 6.5.1 Results of monitoring during repair discharges from the existing Waiwhetū outfall The results of water quality monitoring conducted during temporary discharges of treated wastewater from the Seaview WWTP to the Waiwhetū Stream, for the years to 30 June 2015 (two discharge events), 2016 (no discharge events) and 2017 (one discharge event) are summarised in Table 15.

Treated wastewater discharge concentrations of turbidity, E. coli, enterococci, nitrate nitrogen and dissolved zinc were lower than in the receiving waters of Waiwhetū Stream, while pH and dissolved copper were in a similar range. There was no evidence that wastewater discharges caused any adverse effects in respect of those parameters in receiving waters.

Conversely, treated wastewater concentrations of BOD, dissolved reactive phosphorus and ammonia nitrogen were elevated in the discharge and caused a measurable increase of those contaminants in the Waiwhetū Stream, and in the Hutt River 50m downstream of the Waiwhetū Stream mouth. Dissolved oxygen minima were lowest at the three sites influenced by the discharge plume (refer Table 15).

Total ammonia nitrogen levels at the Port Road Bridge had median and maximum concentrations of 3.82 mg/L and 11.30 mg/L, respectively, well in excess of the both the ANZECC (2000) 80% protection level of 2.3 mg/L and the NPS-FW National Bottom Line of 2.2 mg/L. It probably would also have exceeded the US EPA (2013) CCC criteria which specify a 30-day average of 2.7 mg/L and a 4-day average of 6.8 mg/L. Based on that information there is a relatively high risk that ammonia toxicity has had adverse effects on benthic biota in the reach of the Waiwhetū Estuary extending 120m downstream of Seaview WWTP outfall, and upstream at least as far as the Owhiti urupā, a distance of approximately 200m.

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Although the ecological values of the Waiwhetū Estuary are relatively low, the existing wastewater discharge is one of a number of factors that contribute to its poor state. It is concluded that the adverse effects of the existing discharges on the water quality and aquatic ecology of the Waiwhetū Estuary are significant. 6.5.2 Results of monitoring wet weather overflow discharges from the existing Waiwhetu outfall The results of water quality monitoring conducted during wet weather overflow discharges of treated wastewater from the Seaview WWTP to the Waiwhetū Stream for the year to 30 June 2017 (12 monitoring days) are summarised in Table 16.

General water quality characteristics such as pH, temperature, dissolved oxygen and BOD 5 were similar both upstream and downstream of the outfall, and were not influenced by the discharge. Concentrations of nitrate nitrogen, ammonia nitrogen and dissolved reactive phosphorus (DRP) were clearly higher in the discharge than in the Stream but, again, the discharge has had little influence on stream concentrations. Faecal coliforms, E. coli and enterococci were lower in the treated wastewater discharge than in the receiving water on all but one monitoring occasion. The highest indicator bacteria concentrations were mostly recorded at Bell Road Bridge, which is upstream of the tidal zone and not affected by the Seaview WWTP overflow, but can be affected by other wastewater overflows higher in the catchment.

Wet weather wastewater overflow events from the Seaview WWTP to Waiwhetū Stream occurred on nine separate occasions during the year to 30 June 2017, for an average duration of 22 hours. During such occurrences the background conditions were invariably poor, especially in terms of microbiological quality, due to rainfall run-off from the Waiwhetū catchment. Consequently the impact of overflow discharges on the water quality of Waiwhetū Stream has been minor and, considered over the course of the year, represents minimal disturbance to the stream ecology or to recreational activities within the local area. 6.5.3 Assessment of effects of proposed MOP repair discharges to Waiwhetū Stream Wellington Water is seeking consent for a continuation of the existing discharge to the Waiwhetū Stream for a period of 5 years to allow for the detailed design, construction and commissioning of a new Hutt River outfall and a new wastewater storage facility. It is anticipated that the effects of the proposed MOP repair discharge to the Waiwhetū Stream will be similar to those described in section 6.5.1, and are therefore not sustainable beyond the short term. 6.5.4 Assessment of effects of proposed wet weather overflows to Waiwhetū Stream Wellington Water is seeking consent for a continuation of the existing discharge of wet weather overflows to the Waiwhetū Stream for a period of 5 years to allow for the detailed design, construction and commissioning of a new Hutt River outfall and a new wastewater storage facility.

It is anticipated that the adverse effects of wet weather discharges to the Waiwhetū Stream will be similar to those described in section 6.5.2, and are unlikely to cause any more than a minor change in water quality or disturbance to the aquatic ecology.

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Table 15: Waiwhetū Stream monitoring results during dry weather repair discharges the years to 31 June 2015, 2016 and 2017 (n = 35). Receiving water guidelines are outlined in Appendix D. Exceedances of recommended guidelines are highlighted in red. Wastewater discharge Waiwhetū Stream Waiwhetū Stream Waiwhetū Stream Hutt River @ 50m u/s Hutt River @ 50m d/s Waiwhetū mouth units @Bell Road Bridge @ Urupa @ Port Road Waiwhetū mouth Guidelines median 95%ile max median max median max median max median max median 95%ile max

pH pH 7.20 7.40 7.40 7.10 7.60 7.20 7.70 7.30 7.70 7.40 7.80 7.35 7.60 7.70 6.5 - 9.0

Temperature °C No data No data No data 11.8 16.8 11.3 16.7 11.1 16.8 10.75 14.3 12.0 16.40 16.60 < 19.0

1 1 1 1 1 o 2 Dissolved O2 mg/L No data No data No data 9.10 8.10 10.0 7.7 9.50 7.50 11.1 8.5 9.95 11.80 6.9 > 8 @ 15 C

cBOD5 mg/L 3.0 10.5 11.0 <3 <3 <3 7 <3 6 No data No data No data No data No data < 2.0

Salinity ppt <2 <2 <2 <1 5.7 2.1 9.2 2.5 7.3 2.90 10.0 3.55 10.5 11.0 -

Turbidity NTU 1.9 12 14 6.1 30.3 6.3 36 4.27 40.3 8.80 161.0 7.39 41.6 42.6 < 5.6 Faecal coliforms /100ml 28 4,605 8,600 890 9,200 300 5,200 240 7,400 135 3,600 220 9,250 11,000 ≤ 43 (shellfish)

E. coli /100ml 14 2,034 3,500 831 8,400 254 4,500 196 6,800 no data no data no data no data no data < 260 (bathing)

Enterococci /100ml 47 2,440 4,400 700 10,000 410 8,800 370 6,900 120 3,400 320 6,700 9,000 < 280 (bathing)

DRP mg/L 1.42 2.15 2.19 0.04 0.46 0.11 0.44 0.26 0.94 0.02 0.46 0.07 0.51 0.57 < 0.010 ANZECC 80% ≤ 2.3 Ammonia-N mg/L 20.3 25.0 25.5 0.38 6.48 1.30 5.70 3.82 11.30 <0.01 0.75 1.05 6.08 6.29 NPS-FM ≤ 2.2 USEPA (2013) < 6.83

Nitrate-N mg/L <0.01 0.89 1.54 0.45 1.13 0.31 1.03 0.25 1.46 0.23 0.94 0.28 0.48 0.49 < 1.7

Nitrite-N mg/L <0.01 0.15 0.22 <0.01 <0.01 <0.01 <0.01 <0.01 0.19 <0.01 <0.01 <0.03 - <0.03 -

Copper (dis.) mg/L <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.01 <0.01 <0.01 <0.01 <0.01 <0.01 - <0.01 0.0014

Zinc (dis.) mg/L 0.02 0.03 0.03 0.04 0.09 <0.01 0.08 <0.01 0.05 <0.01 <0.01 <0.01 - <0.01 0.008 Notes: 1Dissolved oxygen minimum concentration 2 0 Based on 80% of O2 saturation concentration in water at 15 C (80% of 10 mg/L) 3Four-day average value at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013)

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Table 16: Waiwhetū Stream monitoring results during wet weather overflow discharges during the year to June 2017 (n=12). Receiving water guideli nes are outlined in Appendix D. Exceedances of recommended guidelines are highlighted in red. Waiwhetū Stream Waiwhetū Stream Wastewater discharge Waiwhetū Stream @Bell Road Bridge units @ Urupa @ Port Road Guidelines median 95%ile max median 95%ile max median 95%ile max median 95%ile max pH pH no data no data no data 7.00 7.29 7.30 6.95 7.20 7.20 7.00 7.39 7.40 6.5 - 9.0

Temperature °C no data no data no data 13.9 17.5 17.6 13.8 16.63 16.70 13.9 16.5 16.5 < 19.0

1 1 1 o 2 Dissolved O2 mg/L no data no data no data 8.80 10.61 7.90 9.60 10.60 7.70 9.55 9.55 8.40 > 8 @ 15 C cBOD5 mg/L 4.0 25 25 1.5 <3.0 <3.0 1.5 <3.0 <3.0 1.5 <3.0 <3.0 < 2.0

Salinity ppt no data no data no data <1.0 2.26 2.40 <1.0 2.44 2.60 <1 2.26 2.40 -

Faecal coliforms /100ml 220 20,190 28,000 7,150 13,590 13,600 6,450 11,930 12,000 6,750 13,000 13,200 ≤ 43 (shellfish)

E. coli /100ml 208 19,740 27,000 4,650 11,722 12,100 4,100 11,727 12,000 4,000 11,020 11,200 < 260 (bathing)

Enterococci /100ml 310 16,500 22,000 9,350 39,300 41,000 7,650 44,100 47,000 7,350 28,300 29,000 < 280 (bathing)

DRP mg/L 0.52 1.75 2.19 0.04 0.25 0.27 0.04 0.30 0.32 0.03 0.74 0.81 < 0.010 ANZECC 80% ≤ 2.3 Ammonia-N mg/L 8.75 20.15 22.90 0.05 2.51 2.76 0.05 2.96 3.22 0.04 9.31 10.30 NPS-FM ≤ 2.2 USEPA (2013) < 6.83

Nitrate + nitrite N mg/L 0.67 2.94 3.65 0.45 1.16 1.20 0.45 1.16 1.20 0.34 0.73 0.77 < 0.444 Notes: 1Dissolved oxygen minimum concentration 2 0 Based on 80% of O2 saturation concentration in water at 15 C (80% of 10 mg/L) 3Four-day average value at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013)

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6.6 Water quality effects on the Hutt River 6.6.1 Predicted effects of MOP repair discharges to Hutt River Overview The proposal to re-locate the Seaview Outfall from the Waiwhetū Stream to the Hutt River would have the obvious benefit of eliminating the direct discharge of treated wastewater to the Waiwhetū Stream. Furthermore, the possibility of the discharge plume being carried upstream from the Hutt River into the Waiwhetū Stream is minimised by the proposed tidal discharge regime which, during dry weather, would store incoming wastewater on the flood tide and discharge on the ebb tide (i.e., approximately six hours on, six hours off). The net result would be a reduced duration of discharge but increased rate of discharge on the ebb tide.

On rare occasions, when the available storage is utilised to manage peak wet weather flows, the tidal discharge option might not be available. At such times, surface water flows in the Hutt River consistently move in a downstream direction throughout the tidal cycle, preventing upstream movement of the discharge plume. Dye dispersion studies indicate that while the discharge plume could potentially enter Waiwhetū Stream when driven by south-westerly winds, the likelihood of such an event under the proposed discharge regime is very low (refer Appendix E).

The proposed Hutt River outfall would extend approximately 16m into the River beyond the intertidal zone, discharging via a single port at a water depth of 1 to 3 m. In terms of duration, the worst case would be a discharge of six weeks duration in the period 5 May to 5 July, and/or a discharge of up to 2 weeks at any other time. In practice a discharge of more than six weeks duration has occurred only once, in 2009, when a malfunction at the main pump station resulted in excessive pressure in the pipeline and consequent damage to multiple pipeline joints. HCC records show that discharge durations are typically far less, averaging one event per year with a duration of six or seven days (Table 9).

Dispersion studies indicate that the discharge would form an elongated surface plume that hugged the eastern bank of the Hutt River as it dispersed out into Wellington Harbour. Due to the tidal discharge regime, in most instances the plume would occur intermittently, 6 hours on, 6 hours off, for the duration of the overflow event. Predicted receiving water concentrations, based on 50-percentile wastewater quality are summarised in Table 17, while ‘worst case’ predictions using 95-percentile wastewater concentrations are summarised in Table 18. These two sets of predictions indicate the likely range of water quality effects. Ammonia toxicity Total ammonia concentrations resulting from the proposed dry weather MOP repair discharge are predicted have a median value of 3.4 mg/L in the Hutt River, near the true left bank, 100m downstream of the outfall, and predicted worst case value less than 5 mg/L. The ebb tide discharge plume will hug the true left bank and probably not extend beyond the centre line of the river. By comparison the observed ammonia concentrations in the Hutt River resulting from discharges to the Waiwhetū Stream have median and 95-percentile values of 1.05 mg/L and 6.08 mg/L, respectively (Table 15). Although elevated ammonia concentrations are predicted near the true left bank, toxic effects on benthic biota or fish are unlikely within the Hutt River provided the 4- day average concentration does not exceed 6.8 mg/L. Nutrient enrichment Predicted and observed concentrations of dissolved inorganic nitrogen (nitrate + nitrite + ammonia) and dissolved reactive phosphorus (DRP) are locally elevated in the Hutt River downstream of the discharge (see tables 17-20). Elevated nutrient levels have the potential to stimulate macroalgae growth in intertidal habitats along the south-eastern rock wall between the Waiwhetū Stream mouth and the Port Road corner if sustained over an extended period, especially during the summer/autumn growth season. In practice, however, repair discharges have occurred on average once each year for a duration of six days, which would generally not be long enough to noticeably increase algae production. Longer duration discharge events of up to six weeks are occasionally scheduled during the winter ‘repair window’, when low temperatures, low sunlight hours and more frequent flood flows minimise the risk of nuisance algae growth.

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The nutrient load delivered to the Hutt Estuary and Wellington Harbour is dominated by inputs from the Hutt River which is estimated to contribute 214 tonnes of DIN and 4 tonnes of DRP per annum (Heath & Greenfield, 2016). By comparison the combined discharges from the Seaview WWTP are estimated to contribute 0.015 tonnes of DIN and 0.001 tonnes DRP per annum, just a fraction of one percent of the total load.

The overall assessment is that the risk of significant adverse effects associated with nutrient enrichment is low.

Oxygen demand and depletion Five day biochemical oxygen demand (BOD5) concentrations in receiving waters are predicted to remain less than 2 mg/L at most times, but may exceed 2 mg/L for brief periods. BOD5 values greater than 2 mg/L raise the possibility of dissolved oxygen (DO) depletion in the receiving water of the Hutt River from time to time. The monitoring results summarised in Table 15 show a number of DO results less than 8 mg/L in the Waiwhetū Stream and a single result less than 8 mg/L in the Hutt River during discharges to the Waiwhetū Stream. Based on these results it is anticipated that some localized and temporary oxygen depletion may occur in Hutt River from time to time as a result of the proposed discharge, however, given the large size of the River and the beneficial effects of tidal flushing, it is anticipated that any depletion below 80% saturation would be rare, isolated events with negligible effect on aquatic biota.

Microbiology Concentrations of indicator bacteria (faecal coliforms, E. coli and enterococci) are typically low in the wastewater discharge because of the high level of treatment provided at Seaview WWTP. Monitoring results show that on most occasions the concentration of indicator bacteria is lower in the discharge than in the receiving waters of the Hutt River (Table 15). The quality of treated wastewater is variable however, and, in the worst case the discharge may cause a measurable increase in indicator bacteria concentrations in the Hutt Estuary, potentially exceeding recreational bathing water quality criteria (refer Table 18).

The microbiological effects of a treated wastewater discharge to Waiwhetū Stream were assessed during a structural condition survey of the main outfall pipeline in May 2013 (MWH, 2013). The study focused on Escherichia coli, Enterococci and Norovirus concentrations in water and edible shellfish (mussels, pipi and cockles) in the Hutt Estuary, Petone Beach and Sorrento/Lowry Bay. The results indicate that all sites were exposed to the discharge plume. Both indicator bacteria and norovirus loads were elevated in water and shellfish at Waiwhetū Stream mouth and were an order of magnitude lower at the more distant locations of West Petone Beach and Lowry Bay. The authors recommended that shellfish should not be collected for human consumption at locations between Petone Beach west and Lowry Bay less than four weeks after a discharge of treated wastewater to Waiwhetū Stream, or less than four weeks after a significant high flow event in the Hutt River or Waiwhetū Stream, which may result in the discharge of contaminated stormwater or an overflow of wastewater into these water bodies. It was noted that this restriction would likely rule out much of the year, but would be consistent with the general advice previously provided by Regional Public Health, and by NZFSA, not to collect shellfish near urban areas because of the on- going impact of stormwater and wastewater related contamination.

The risk to contact recreation uses of the Hutt Estuary can be adequately managed by development and implementation of a public communication strategy that will advise against contact recreation activities during and after a discharge event.

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Table 17: Predicted contaminant concentrations in the Hutt River and Wellington Harbour during dry weather repair discharges based on 50-percentile treated wastewater concentrations and the lowest 50-percentile dilution value from all dry weather wind and tide scenarios. Exceedances of recommended guidelines are highlighted in red.

Background water quality Predicted receiving water concentrations at the following locations: Treated Hutt River wastewater Petone Petone Units Wellington 100m Port Road Seaview concentration Hutt River Beach west Beach east Lowry Bay Days Bay Guidelines Harbour downstream Corner Beach Marina (50th percentile) (site 1) (site 2) of outfall 50 %ile dilution - - - 6 106 124 390 264 118 152 cBOD5 mg/L 3 0.5 0.5 0.9 0.52 0.52 0.51 0.51 0.52 0.52 < 2.0

Turbidity NTU 1.9 2.2 1.5 2.2 2.2 1.50 1.5 1.5 1.50 1.50 < 5.6

Faecal coliforms cfu/100ml 28 135 10 117 134 10 10 10 10 10 ≤ 43 (shellfish)

E. coli cfu/100ml 14 130 8 111 129 8 8 8 8 8 < 260 (bathing)

Enterococci cfu/100ml 47 120 4 108 119 4 4 4 4 4 < 280 (bathing)

DRP mg/L 1.42 0.005 0.005 0.241 0.018 0.016 0.009 0.010 0.017 0.014 < 0.010

Nitrate + nitrite N mg/L 0.015 0.16 0.005 0.136 0.159 0.005 0.005 0.005 0.005 0.005 < 0.444 ANZECC 95% ≤ 0.91 Ammonia-N mg/L 20.3 0.01 0.01 3.392 0.201 0.174 0.062 0.087 0.182 0.14 USEPA (2013) < 6.81

Arsenic mg/L 0.003 0.0005 0.0015 0.001 0.0005 0.0015 0.002 0.0015 0.0015 0.0015 ≤ 0.013

Cadmium mg/L 0.001 0.00025 0.00005 0.0004 0.0003 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0007

Chromium mg/L 0.01 0.00025 0.0005 0.0019 0.0003 0.0006 0.0005 0.0005 0.0006 0.0006 ≤ 0.0044

Copper mg/L 0.0060 0.0011 0.00005 0.0019 0.0011 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0014

Lead mg/L 0.0120 0.00005 0.00005 0.0020 0.0002 0.0001 0.0001 0.0001 0.0002 0.0001 ≤ 0.0044

Mercury mg/L 0.0007 0.0001 0.0000006 0.0002 0.0001 0.00001 0.000002 0.000003 0.000007 0.00001 ≤ 0.0004

Nickel mg/L 0.010 0.00025 0.0033 0.0019 0.0003 0.0034 0.0033 0.0033 0.0034 0.0033 ≤ 0.007

Zinc mg/L 0.0220 0.0018 0.000078 0.0052 0.0020 0.0003 0.0001 0.0002 0.0003 0.0002 ≤ 0.015 Notes: 1Four-day average total ammonia-N limit at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013)

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Table 18: Predicted worst-case contaminant concentrations in receiving waters during dry weather repair discharges based on 95-percentile wastewater concentrations and the lowest 50-percentile dilution value from all dry weather wind and tide scenarios. Exceedances of guidelines are highlighted in red.

Background water quality Predicted receiving water concentrations at the following locations: Treated Hutt River wastewater Petone Petone Units Wellington 100m Port Road Seaview concentration Hutt River Beach west Beach east Lowry Bay Days Bay Guidelines Harbour downstream Corner Beach Marina (95th percentile) (site 1) (site 2) of outfall

50t%ile dilution - - - 6 106 124 390 264 118 152 cBOD5 mg/L 11 0.5 0.5 2.3 0.60 0.58 0.53 0.54 0.59 0.57 < 2.0

Turbidity NTU 12 2.2 1.5 3.8 2.3 1.58 1.5 1.5 1.59 1.57 < 5.6

Faecal coliforms cfu/100ml 4605 135 10 880 177 47 22 27 49 40 ≤ 43 (shellfish)

E. coli cfu/100ml 2034 130 8 448 148 24 13 16 25 21 < 260 (bathing)

Enterococci cfu/100ml 2440 120 4 507 142 24 10 13 25 20 < 280 (bathing)

DRP mg/L 2.15 0.005 0.005 0.363 0.025 0.022 0.011 0.013 0.023 0.019 < 0.010

Nitrate + nitrite N mg/L 1.04 0.160 0.005 0.307 0.168 0.013 0.008 0.009 0.014 0.012 < 0.444 ANZECC 95% ≤ 0.91 Ammonia-N mg/L 25 0.01 0.01 4.175 0.246 0.212 0.074 0.105 0.222 0.17 USEPA (2013) < 6.81

Arsenic mg/L 0.003 0.0005 0.0015 0.001 0.0005 0.0015 0.002 0.0015 0.0015 0.0015 ≤ 0.013

Cadmium mg/L <0.001 0.00025 0.00005 0.0004 0.0003 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0007

Chromium mg/L 0.01 0.00025 0.0005 0.0019 0.0003 0.0006 0.0005 0.0005 0.0006 0.0006 ≤ 0.0044

Copper mg/L 0.01 0.0011 0.00005 0.0026 0.0012 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0014

Lead mg/L 0.012 0.00005 0.00005 0.0020 0.0002 0.0001 0.0001 0.0001 0.0002 0.0001 ≤ 0.0044

Mercury mg/L 0.0007 0.0001 0.0000006 0.0002 0.0001 0.00001 0.000002 0.000003 0.000007 0.00001 ≤ 0.0004

Nickel mg/L 0.01 0.00025 0.0033 0.0019 0.0003 0.0034 0.0033 0.0033 0.0034 0.0033 ≤ 0.007

Zinc mg/L 0.027 0.0018 0.000078 0.0060 0.0020 0.0003 0.0001 0.0002 0.0003 0.0003 ≤ 0.015 Notes: 1Four-day average value at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013)

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6.6.2 Predicted effects of proposed wet weather overflow discharges to Hutt River Overview The proposal to re-locate the Seaview Outfall from the Waiwhetū Stream to the Hutt River has the obvious benefit of eliminating the direct discharge of treated wastewater to the Waiwhetū Stream. In addition, the construction of 10,000 m 3 of additional storage is expected to reduce the average number of wet weather discharges by 1 to 2 events per year.

Ammonia toxicity As a result of the discharge, receiving water concentrations of ammonia are predicted to increase slightly in the Hutt River downstream of the outfall, but are not expected to exceed ANZECC (2000) guidelines (Table 19). The predicted worst case ammonia concentration in the Hutt River 100m downstream of the Waiwhetū Stream mouth is 1.1 mg/L compared with the ANZECC (2000) 80% protection TV of 2.3 mg/L (Table 20). No toxic effects on benthic biota or fish are not expected as a result of wet weather overflow discharges.

Nutrient enrichment Background concentrations of dissolved inorganic nitrogen (nitrate + nitrite + ammonia) and dissolved reactive phosphorus (DRP) are typically elevated in the Hutt River during rainfall events due to runoff from agricultural and urban catchments. Wet weather overflow discharges provide additional nutrient inputs, potentially contributing to a temporary exceedance of guideline values at the river mouth (Table 18 & Table 20).

Elevated nutrient levels, if sustained over a period of many days or weeks, would have the potential to stimulate macroalgae growth in intertidal habitats along the south-eastern rock wall between the Waiwhetū Stream mouth and the Port Road corner. However, in the case of the proposed wet weather overflow discharges from the Seaview WWTP, the average duration of 13 hours is not sufficient to materially increase macroalgae production. Indeed these discharges are often associated with high flows in the Hutt River which are capable of scouring away macroalgae biomass from intertidal areas. The overall assessment is that the risk of significant adverse effects associated with nutrient enrichment is very low.

Oxygen demand and depletion Five day biochemical oxygen demand (BOD5) concentrations in receiving waters are predicted to remain less than 2 mg/L during wet weather overflow discharges except in the worst case when concentrations up to 3 mg/L are predicted 100m downstream of the outfall. The relatively low oxygen demand of the discharge, in combination with high river flows, high water velocities and increased turbulence, ensure the there is little risk of the discharges causing a significant depletion of dissolved oxygen in the receiving waters (Table 18 & Table 20).

Microbiology Concentrations of indicator bacteria (faecal coliforms, E. coli and enterococci) are normally low in Resource consent application – October 2017 Seaview treated wastewater. However, the performance of the UV irradiation plant can be reduced at times of peak flow through the plant, resulting in wet weather overflow discharges tending to have a higher microbiological content than average (Table 18 & Table 20).

The reduced treatment efficiency during peak flows is offset to some extent by the poor background quality of the receiving waters and higher rates of dilution available within the initial mixing zone at such times. The net result is a moderate increase in indicator bacteria in the Hutt River downstream of the discharge, with smaller but still measurable increases further afield in Wellington Harbour at Petone Beach, Lowry Bay and Days Bay. During extreme rainfall events the microbiological quality of the Hutt River and Wellington Harbour is predicted to be poor and would not be suitable for contact recreation activities during or immediately after the event.

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6.7 Summary of water quality effects of WWTP discharges MOP repair and wet weather discharges to Waiwhetu Stream Overall, the principal water quality issue associated with existing WWTP discharges to the Waiwhetu Stream is the risk of ammonia toxicity to aquatic biota. Although the occurrence of elevated ammonia concentrations is intermittent and temporary, it can affect almost all of what remains of the Waiwhetu Estuary and is one of a number of factors that contribute to the poor current state of the estuary. For that reason the combined adverse effects of MOP repair discharges and wet weather overflow discharges to the Waiwhetu Stream are significant. Proposed MOP repair discharges to the Hutt River The principal water quality effect of the proposed MOP repair discharge is that it is predicted to cause a marked increase in ammonia concentrations in the Hutt River on the ebb tide. The discharge plume will occur intermittently, 6 hours on, 6 hours off, hugging the true left bank and probably not extending beyond the centre-line of the river. The potential adverse effects of ammonia toxicity are avoided or mitigated by the following: a) a discharge regime that prevents inflows of treated wastewater to the Waiwhetū b) increased dilution available in the Hutt River (compared to the Waiwhetū Stream) c) the intermittent character and short duration of the discharge and d) the relatively localised extend of the discharge plume. A secondary effect of the proposed discharge is that it will increase dissolved nutrient concentrations (DIN and DRP) in the river downstream of the outfall. The potential adverse effects of elevated nutrient concentrations are mitigated by the following: Limiting planned repair discharges to the winter period when low temperatures, low sunlight hours and more frequent flood flows minimise the risk of nuisance algae growth. Proposed wet weather overflow discharges to the Hutt River At those times when wet weather overflow discharges occur, wastewater inflows to the Seaview WWTP are considerably diluted by stormwater inflows or infiltration to the wastewater network , and the receiving waters of the Hutt River are typically at high flow or in flood. These factors tend to moderate the potential adverse effects of these discharges. It is relevant also that these events have historically occurred on average four or five time each year, with an average duration of 13 hours per event. The net result is that wet weather overflow discharges cause a slight to moderate increase in Hutt River concentrations of total ammonia-N, dissolved nutrients and in microbiological content, but that the adverse effects associated with these events are minor. Resource consent application – October 2017

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Table 19: Predicted contaminant concentrations in receiving waters during wet weather overflow discharges to the Hutt River based on 50-percentile wastewater concentrations, 0.8 m3/d discharge rate and the lowest 50-percentile dilution value from all wet weather wind and tide scenarios.

Background water quality Predicted receiving water concentrations at the following locations: Treated Hutt River wastewater Petone Petone Units Wellington 100m Port Road Seaview concentration Hutt River2 Beach west Beach east Lowry Bay Days Bay Guidelines Harbour downstream Corner Beach Marina (50th percentile) (site 1) (site 2) of outfall

50th %ile dilution - - - 55 210 235 776 934 201 416 cBOD5 mg/L 4 1 0.5 1.1 1.06 0.52 0.50 0.50 0.50 0.51 < 2.0

Turbidity NTU 10 7 4 7.1 7.06 4.03 4.01 4.00 4.01 4.01 < 5.6

Faecal coliforms cfu/100ml 220 240 50 239 240 51 50 50 50 50 ≤ 43 (shellfish)

E. coli cfu/100ml 208 200 40 200 200 41 40 40 40 40 < 260 (bathing)

Enterococci cfu/100ml 310 120 20 126 124 21 20 20 20 20 < 280 (bathing)

DRP mg/L 0.52 0.01 0.008 0.025 0.0202 0.0106 0.0085 0.0084 0.0087 0.0088 < 0.010

Nitrate + nitrite N mg/L 0.67 0.27 0.01 0.282 0.2780 0.0133 0.0106 0.0105 0.0109 0.0111 < 0.444 ANZECC 95% ≤ 0.91 ANZECC 80% ≤ 2.3 Ammonia-N mg/L 8.75 0.01 0.01 0.275 0.1848 0.0537 0.0186 0.0163 0.0216 0.0244 NPS-FM ≤ 2.2 USEPA (2013) < 6.81

Arsenic mg/L 0.003 0.0005 0.0015 0.0006 0.0006 0.0015 0.0015 0.0015 0.0015 0.0015 ≤ 0.013

Cadmium mg/L <0.001 0.00025 0.00005 0.0003 0.0003 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0007

Chromium mg/L 0.01 0.00025 0.0005 0.0005 0.0004 0.0005 0.0005 0.0005 0.0005 0.0005 ≤ 0.0044

Copper mg/L 0.01 0.0011 0.00005 0.0012 0.0012 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0014

Lead mg/L 0.012 0.00005 0.00005 0.0004 0.0003 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0044

Mercury mg/L 0.0007 0.0001 0.0000006 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 ≤ 0.0004

Nickel mg/L 0.01 0.00025 0.0033 0.0005 0.0004 0.0033 0.0033 0.0033 0.0033 0.0033 ≤ 0.007

Zinc mg/L 0.027 0.0018 0.000078 0.0024 0.0022 0.0002 0.0001 0.0001 0.0001 0.0001 ≤ 0.015 Notes: 1Four-day average value at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013) 2Seventy-five percentile values from monthly SOE monitoring at Hutt River - Boulcott (GWRC data)

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Table 20: Predicted contaminant concentrations in receiving waters during wet weather overflow discharges to the Hutt River based on 95-percentile wastewater concentrations, 3 m3/s discharge rate and the lowest 50-percentile dilution value from all wet weather wind and tide scenarios.

Background water quality Predicted receiving water concentrations at the following locations: Treated Hutt River wastewater Petone Petone Units Wellington 100m Port Road Seaview concentration Hutt River2 Beach west Beach east Lowry Bay Days Bay Guidelines Harbour2 downstream Corner Beach Marina (95th percentile) (site 1) (site 2) of outfall

50th %ile dilution - - - 18 55 62 205 248 54 109 cBOD5 mg/L 23 1 1 2.2 1.4 1.35 1.11 1.09 1.41 1.20 < 2.0

Turbidity NTU 20 30 20 29.4 20.0 20.00 20.00 20.00 20.00 20.00 < 5.6

Faecal coliforms cfu/100ml 22,300 1000 300 2183 700 655 407 389 707 502 ≤ 43 (shellfish)

E. coli cfu/100ml 21720 800 280 1962 670 626 385 366 677 477 < 260 (bathing)

Enterococci cfu/100ml 16800 600 300 1500 600 566 380 367 606 451 < 280 (bathing)

DRP mg/L 1.52 0.03 0.01 0.1128 0.0375 0.0344 0.0174 0.0161 0.0380 0.0239 < 0.010

Nitrate + nitrite N mg/L 3.78 0.60 0.03 0.7767 0.0982 0.0905 0.0483 0.0451 0.0994 0.0644 < 0.444 ANZECC 95% ≤ 0.91 ANZECC 80% ≤ 2.3 Ammonia-N mg/L 19.52 0.02 0.05 1.1033 0.4040 0.3640 0.1450 0.1285 0.4106 0.2286 NPS-FM ≤ 2.2 USEPA (2013) < 6.81

Arsenic mg/L 0.003 0.0005 0.0015 0.0006 0.0015 0.0015 0.0015 0.0015 0.0015 0.0015 ≤ 0.013

Cadmium mg/L 0.001 0.00025 0.00005 0.0003 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 ≤ 0.0007

Chromium mg/L 0.01 0.00025 0.0005 0.0008 0.0007 0.0007 0.0005 0.0005 0.0007 0.0006 ≤ 0.0044

Copper mg/L 0.006 0.0011 0.00005 0.0014 0.0002 0.0001 0.0001 0.0001 0.0002 0.0001 ≤ 0.0014

Lead mg/L 0.012 0.00005 0.00005 0.0007 0.0003 0.0002 0.0001 0.0001 0.0003 0.0002 ≤ 0.0044

Mercury mg/L 0.0007 0.0001 0.0000006 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 ≤ 0.0004

Nickel mg/L 0.01 0.00025 0.0033 0.0008 0.0034 0.0034 0.0033 0.0033 0.0034 0.0034 ≤ 0.007

Zinc mg/L 0.022 0.0018 0.000078 0.0029 0.0005 0.0004 0.0002 0.0002 0.0005 0.0003 ≤ 0.015 Notes: 1Four-day average value at pH8, temperature 20oC, assuming freshwater mussels absent but protection required for early life stage fish (from USEPA 2013) 2Estimated values during high flow events in the Hutt River

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6.8 Aquatic Ecology 6.8.1 Effects of new outfall construction The proposed new discharge structure on the true left bank of the Hutt River, immediately downstream of the Waiwhetū Stream mouth, as described in Section 2.3.3, includes an 1.6 metre diameter outfall pipe that will be angled downstream. The pipe will be encased in concrete and, in order to visually integrate the structure, a small headland will be constructed around the pipe using suitable sized rock rip-rap (see drawings in Appendix A). The total area of the construction footprint will be approximately 500 m2. The structure will be secured to the riverbed using sheet piles. The final alignment of the outfall pipe and rock rip rap landform will be confirmed during detailed design.

These works are expected to take 3 months to complete, including up to 1 week to establish bunds (or sheet piles) to divert the river flow around the works site, so that the majority of construction activities can be conducted in the dry. These construction activities would be programmed to avoid the months of September and October, so as to minimise the risk of disrupting the upstream migration of juvenile eel, flounder and galaxiid fish.

These works will disturb the banks and bed of the Hutt River within the footprint of the outfall pipeline. As part of this work an area of contaminated bed material at the mouth of the Waiwhetū Stream may be disturbed. GWRC records indicate that this material contains heavy metal and hydrocarbon contamination. The quality of bed sediments in this area will be tested as part of the geotechnical investigations. Should these tests indicate contaminant levels in excess of ANZECC (2000) ISQG-High values, then the material will be removed and disposed of at suitable landfill sites.

The potential adverse effects of these construction activities include the following:  Disruption to a stand of bankside vegetation on the pipeline alignment which includes several semi-mature pohutukawa as well as ngaio and karo;  Excavation of river bed material within the footprint of the proposed outfall structure and rock rip rap landform. The existing ecological values associated with these intertidal and sub-tidal habitats are low.  Work in the wetted channel of the Hutt River days during construction of bunds and/or installation of sheet piles. The construction area enclosed within the bunds would occupy no more than 20% of the river width. Within the context of the wider area of the Hutt River mouth, which is routinely dredged by GWRC to maintain its capacity to contain flood flows, the proposed works are minor in terms both their physical extent and duration. Consequently the potential for adverse effects on the aquatic Resource consent application – October 2017 ecology is low.

The most significant effects may be those associated with the loss of trees on the terrestrial margin. 6.8.2 Effects of MOP repair discharges Macroalgae As described in Section 3.2, Ulva is the dominant opportunistic macroalgae, growing on almost every area of available habitat in the estuary. Nevertheless no significant intertidal gross eutrophic zones have been identified, and nuisance conditions (rotting algae and poorly oxygenated, sulphide rich sediments) are not widespread in intertidal areas, but were much more readily apparent in sub-tidal areas below the Waione Street Bridge

Repair discharges have occurred on average once each year for a duration of six days, which would generally not be long enough to noticeably increase macroalgae production in intertidal areas, or decaying algae in sub-tidal areas. Longer duration discharge events of up to six weeks are occasionally scheduled during the winter ‘repair window’, when low temperatures, low sunlight

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hours and more frequent flood flows minimise the risk of nuisance algae growth. The overall assessment is that the risk of significant adverse effects associated with excessive macroalgae growth is low.

Seagrass and saltmarsh The Hutt estuary below Waione Street Bridge has relatively low habitat diversity. High value habitats such as seagrass and saltmarsh are virtually absent. The proposed discharge will therefore have no effect on these habitat types.

Benthic invertebrates The discharge plume is expected to hang close to the true left (east) bank as it moves out into the harbour, probably coming into contact with the intertidal benthos along the sea wall between the Waiwhetū Stream mouth and the Port Road corner. The invertebrate community in this area, which is typical of that occurring elsewhere in Wellington Harbour, is potentially susceptible to the effects of both nutrient enrichment and ammonia toxicity. However, the risk of nuisance algae growth is at least partially mitigated by scheduling planned discharges during the winter period when algae production is low and riverbed scouring events occur more frequently.

There is some risk of toxicity to intertidal benthos along the sea wall immediately downstream of the proposed outfall, where an undiluted discharge plume first contacts the shore. That might result in a localised change in the relative abundance of some taxa (compared to an un-impacted community), with sensitive taxa giving way to those that are more tolerant. However, the risk of toxicity after reasonable mixing, assumed to be a distance of 100m from the outfall, is low provided the 4-day average total ammonia concentration does not exceed 6.8 mg/L.

The proposed discharge is not expected to mix with the deeper saline water in this area and is unlikely have any effect sub-tidal habitats. In any case, sub-tidal biota in the Hutt Estuary in the vicinity of the proposed outfall are sparsely distributed and of low ecological value. The substrate consists of an aneorobic, organically enriched and muddy layer overlying relatively clean sediments. This appears to be the result of fine sediment deposition in the shallow ‘basin’ below the Waione Street Bridge, as well as ongoing dredging activity.

Mahanga kai species Mahanga kai species are sparsely distributed in the Hutt Estuary and are not suitable f or human consumption due to the presence of microbiological and other contaminants. The proposed repair discharge may contribute to this contamination, however due to the very limited abundance of mahanga kai species in the area, the effect of occasional repair discharges will not be significant.

Fish The reach of the Hutt Estuary potentially affected by the proposed discharge, that is the true left side of the river between the Waiwhetū Stream mouth and Port Road corner, is important for fish passage between the harbour and river, and for upstream access into Waiwhetū Stream. The proposed discharge regime, where planned discharges are limited to the winter months from mid- Resource consent application – October 2017 May to mid-July, would avoid the periods of peak fish migration and so minimise the risk of disruption to migrations. While some unplanned discharges are expected to occur outside of that winter window from time to time, the proposed tidal discharge provides frequent opportunities for migrating fish to move upstream past the outfall. It is noted also that the plume is unlikely to occupy the full width of the river or contact the true right bank. The overall assessment is that the proposed discharge is not likely to have any material effect on fish migration.

Sedimentation rate The mid-lower section of the Hutt Estuary is a natural depositional zone, however the rate of deposition is balanced by ongoing dredging activity in the area which has resulted in no net vertical build-up of sediment on the Te Mome intertidal flats since 2010.

The treated wastewater discharge normally has lower turbidity levels than the receiving waters of the Hutt River, indicating that the discharge does not noticeably increase the sediment load of the river, or cause an increased rate of sediment deposition on the riverbed. On that basis it is concluded that while the Hutt Estuary sedimentation rate may be above that expected under

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natural conditions, the proposed repair discharge will not cause a measurable increase in the rate of sediment deposition.

Mud content The mid-lower section of the Hutt Estuary is a natural depositional zone, which is regularly dredged by GWRC to manage the flooding risk. A survey conducted in 2016 showed that monitoring sites located in the deeper lower estuary had relatively high (25-50%) sediment mud content. Stevens, et al, (2016) considered this is likely indicative of relatively poor sediment oxygenation, and had a high stress risk to mud sensitive benthic biota.

As discussed above, the proposed discharge is not likely to cause a measurable increase in the sediment rate of the River, and will not cause a significant increase in mud content of riverbed sediments. 6.8.3 Effects of wet weather overflow discharges on aquatic ecology The potential or actual effects of wet weather overflow discharges on the aquatic ecology of the Hutt Estuary consistently are less than described above for MOP repair discharges, and overall are expected to be negligible. 6.8.4 Summary of effects on aquatic ecology Taken as a whole the potential adverse effects of planned and unplanned MOP repair discharges, which typically occur around once each year, and intermittent wet weather discharges, which are predicted to occur on average 3 or 4 times each year, with the additional storage, are summarised as follows:  Potential excess growth of macroalgae associated with an abundant supply of nutrients in the Hutt Estuary are mitigated by the timing of planned discharges during the winter and the generally short duration of discharges that may occur at other times.  High value habitats such as seagrass and saltmarsh are virtually absent from the Estuary and will not be affected by the proposed discharges.  The benthic invertebrate community of intertidal habitats within the Hutt River seawall on the true left bank will be influenced by the discharge plume in the reach between the Waiwhetū Stream mouth and the Port Road corner and, within the first 100m length of this reach, ammonia concentrations might result in a change in the relatively abundance of some taxa. This effect, if it occurred, would be highly localised and reversible, and would not affect the higher value habitats such as the western mudflat embayment or the intertidal flat upstream of the Waione Street Bridge.  Mahanga kai species are sparsely distributed in the Hutt Estuary and are not suitable for human consumption due to the presence of microbiological and other contaminants, regardless of the Resource consent application – October 2017 operation of the Seaview WWTP intermittent overflow.

 Where practicable the proposed discharges will be limited to the winter period when the upstream migration of juvenile fish is at a minimum. Furthermore the discharge plume would occupy only the true left side of the Hutt River (east side) and will mostly be limited to the outgoing tide. These factors, together with the infrequent occurrence of discharge events, will ensure that the activity does not interfere with fish movement between marine and freshwater habitats.  The proposed discharges do not contribute significantly to the suspended solids load of the Hutt River and will have no material effect on sedimentation rates or mud content of the estuary. 6.9 Effects on natural character Boffa Miskell undertook an assessment of Effects on Natural Character and Visual Amenity of the proposal on the surrounding environment (see Appendix G). As identified in the table below, taken from the Natural Character and Visual Amenity Report, it was concluded that that the existing level of natural character in the estuary is low, as:

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“this area has been significantly transformed and the level of modification of natural character is extreme. The area has become industrialised and totally utilitarian; the functioning as an estuary has been compromised. Apart from the presence of water, wave action and tidal movements, the perceptual and experiential aspects normally associated with an estuary are either not present or severely compromised”.

Hutt River Estuary (Including Waiwhetū Stream)

Existing Proposed Works Level of natural Level of natural character character Physical Low Low Terrestrial Biological Low Low Physical Moderate Moderate Marine Biological Moderate Low Moderate low

Experiential Low Low

Overall Low Low

Through the assessment, the report identified that the effects on the natural character of the terrestrial biota will be limited to the removal of vegetation. Although the proposed riprap ‘peninsula’ will be a larger structure than a pipe outlet structure, its natural rock cladding and organic shore line configuration will reduce potential effects on that natural character. The report also determined that effects on the aquatic ecology are not considered to be significant.

With regards to natural character, the report concluded that:

“The Hutt River estuary is currently considered to have a low level of natural character. The already low levels of natural character reduce the coastal environment’s sensitivity to cha nge, in particular further reduction in condition. The proposal will not significantly change the overall level of natural character in the estuary and therefore the effects on natural character are neutral”.

6.10 Visual amenity effects

As stated above, the landscape has been significantly modified. The report Natural Character and Resource consent application – October 2017 Visual Amenity Report undertaken by Boffa Miskell determined that the visual amenity aspects have already been compromised, and that the landscape has a low level of visual amenity.

With regards to visual amenity, the report concluded that:

“The outfall structure will be a new and additional feature on the shoreline. However, the proposed design avoids the introduction of a simple pipe structure with an obvious utility purpose, i n favour of extending the coastal protection to create small riprap’ peninsula’. The natural rock finish will be in keeping with coastal environment location, and the small protrusion of the coastal edge will break the monotony of the linear coastal edge.

…..

The proposed outfall, designed to be integrated into an extension of the shoreline protection riprap, will not adversely affect the visual amenity of the area which already has a low level of visual amenity”.

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The report made a number of recommendations to further ensure effects on the visual amenity of the area is minimised. The recommendations from the report that have been adopted by Wellington Water are:

 Removal of trees should be kept to a minimum with those retained must be protected from damage during works.  Final design to ensure that appropriate vegetation can be established in the vicinity of the works once construction is complete.  Ensure that the rock riprap for the outfall structure is the same as the riprap to be used on the upgraded riverbank.  The final design of the riprap ‘peninsula’ should seek to achieve as natural a form as possible, avoiding straight line and planar surfaces as practicable, such as sinuous curves at the waterlines.  The final design of the surge chamber ventilation pipe will need careful consideration of its aesthetic quality in relation to people using the road and footpath.

6.11 Recreation effects This section is based on the Recreation Effects Assessment prepared by Rob Greenaway and Associates (see Appendix H).

A dye and dispersion study shows that the Hutt River discharge would remain on the eastern side of the Hutt River (true left) and would not cross the midline of the river channel. Recreation activities in the plume area potentially affected include whitebaiting on the true left of the Hutt River mouth, and beach activities west of the Seaview marina. Fish other than whitebait taken recreationally in the mouth area may also pass through the plume, and some line-fishing occurs at the Waiwhetū Stream mouth. Walkers and cyclists pass nearby on Port Road.

Water quality effects have been assessed (see above) under two scenarios: programmed maintenance discharges and wet weather overflow discharges. The scale of effect of these discharges on human health and biota are summarised in the Assessment of Environmental Effects report.

During wet weather overflows, and periods when rain events overcome storage during maintenance discharges, the levels of background contamination in the Hutt River and Waiwhetū Stream mask that of the discharge and result in no additional requirements to avoid contact recreation or the consumption of shellfish in the affected area (Petone Beach west to Lowry Bay south).

Wet weather and high flow periods have low recreation amenity generally. Standard and existing recreational warnings about avoiding water contact and the taking of shellfish during and after high Resource consent application – October 2017 river flow periods will remain necessary with the proposed outfall in place, and during significant rain events there is unlikely to be any additional restriction on recreation in the study area as a result of the proposal.

Planned maintenance discharges are programmed for winter when recreation use is low, and outside the whitebait season. There are unlikely to be any changes to winter recreation patterns as a result.

Unplanned maintenance discharges can occur at any time, but are for shorter periods of two weeks. The worse-case scenario for recreation would be an unplanned discharge occurring during the whitebait season, although whitebaiting occurs on incoming tides, with repair discharges timed for ebb tides. The aquatic ecology assessment indicates that the discharge will not have any effect on fish migration. High southerly wind events could drive surface water back up the Hutt River mouth, but the level of dilution would be extremely high upstream of the discharge and on the true right (David Cameron, Stantec, pers comm).

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There is unlikely to be an increased risk of illness resulting from contact recreation during maintenance discharges; a result of the high level of treatment at the Seaview WWTP. However, treatment occasionally – albeit rarely – does not fully remove all pathogens and so it cannot be guaranteed that there will be no increase in risk (David Cameron, Stantec, pers comm). The Assessment of Environmental Effects report does not characterise the change in risk due to its small scale, but, as a precaution, health warning signs will be required to advise and exclude whitebaiters on the true left of the Hutt River mouth, and beach users west of Seaview marina, during discharge periods, and for both winter and summer for beach use to include general coastal activities such as swimming a dog.

The frequency of these events is such that the effect on recreation values will be minor. The outfall will most likely create a focal point for whitebaiting where the fish are forced around the structure and be more easily targeted upstream of it 6.12 Flooding effects The current GWRC Hutt River flood model, developed and provided by DHI, was used to assess the impacts on flood levels of the proposed outfall.

The above ground structure was put into the model, stretching out a horizontal distance of 20m perpendicular from the bank. In reality the proposed structure would be on an angle from the bank causing less of an obstruction, however the model currently only allows modifications across the cross section.

Modelling the effect of this modification showed a maximum increase in sea level of approximately 12mm in a 1 in 440 year average recurrent interval storm event at the peak of the storm, just upstream of the outfall, with this rise tapering off upstream. This maximum change occurs at CH49705, and at this location the water level is contained within the left and right banks of the Hutt River. This is a very small impact. Within a kilometer upstream of proposed outfall site the water level rise has reduced to negligible.

There is the potential for a small increase in flood risk outside Hutt River. During this large storm, the hydraulic model does show there are some areas where the flood waters escape from the main river during the base case (that is, without the option present). At this point of the assessment with such as small increase in water level due to the option, the potential for changes in extent of water inundated has not been calculated. With a ground slope of 2% toward the river, a 12 mm increase will extend the area flooded by 0.6 m horizontally, which is considered to be negligible.

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7. Iwi and stakeholder consultation This section sets out the consultation activities undertaken with iwi and stakeholders as part of the exercise of the current resource consent and in the preparation of this application.

A key aim of the consultation was to engage with iwi and stakeholders as part of the process to identify the preferred option.

The engagement objectives were:

 To provide the opportunity for stakeholders and the community to input into the options and consent renewals, feel they have been listened to and feedback has been taken on board during the options development  To generate meaningful feedback that can be used in the development of the preferred option  To gain feedback through engagement activities that provides WWL and Hutt City Council with a robust consenting process and a strong platform for preparing resource consent applications. 7.1 Iwi engagement Throughout the alternatives assessment process the project team has engaged with:  Ngāti Toa RaNgātira  Port Nicholson Block Settlement Trust  Te Runanganui o Taranaki Whānui ki Te Upoko o Te Ika a Maui Inc

No formal response was received from these groups during stage 1 of the consultation on the future options, undertaken from September 2016 to January 2017 (see section 7.3).

Morrie Love of Raukura Consulting was consequently appointed to assist the project team to engage with iwi. A hui with representatives of all three groups was held on 28 March 2017 at which the project team presented the project and the options on the shortlist. Views expressed at the hui indicated a preference for harbour options and for options with the least environmental impact. It was agreed at the hui that a single assessment of effects on Māori cultural values would be prepared by Raukura Consultants, which would incorporate the perspectives of all three groups.

A second hui was held on 28 June 2017. At this hui the project team’s preliminary conclusion from the assessment of the shortlist was presented. This was that Option 12 should be recommended to the Hutt City Council because this option offers:  Improved environmental and cultural outcomes relative to existing situation Resource consent application – October 2017  A discharge which is not into the Waiwhetū Stream  Storage which will minimise the risk of back flow up the Waiwhetū Stream on incoming tides  Reduced number of wet weather discharges  Lower capital cost.

Feedback received at the hui was:  There is a concern that the project team and Hutt City Council do not understand and will not adequately acknowledge the impacts of the options on Māori cultural values  The discharge of wastewater, no matter how well treated, is offensive to Māori values  There are measures that can be taken to make matters which are tapu become noa  The list of parties who are notified during discharges needs to include Taranaki Whānui and the waka ama club  Some meeting attendees wish to observe the dye test to be undertaken following the hui  Addressing the discharges of untreated wastewater up-pipe of the Seaview Treatment Plant is a higher priority

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 There is some level of acceptance that community affordability needs to be taken into account in decision making, particularly in light of the need to address the untreated wastewater discharges up-pipe of the WWTP  Is it possible that storage could be increased in the future to reduce overflows further, both at Seaview and up the network?

Attendees of the second hui were invited to a further hui in mid-October. The purpose of the October hui was to provide a briefing on the decision to seek resource consent for Option 12, and to explain the nature of the resource consent application. The hui was also intended to discuss possible resource consent conditions. Attendees were project team members and Kara Dentice and Morrie Love (project team members and iwi representatives). There was good discussion and the results of the dye tests were positively received. It was agreed that engagement with iwi should continue following lodgement of the application. 7.2 The Waiwhetū consultation group Conditions of the existing consents required that a consultation group – Waiwhetū Consultation Group (WCG) be established. The individuals and community groups included in the WCG Group are:  East Harbour Environmental Association Inc  Wellington Recreational Marine Fishers’ Association (Inc)  Friends of the Waiwhetū  Regional Public Health (RPH)  Te Runanganui o Taranaki Whanui ki te Upoko o te Ika a Maui Inc.

These parties submitted on the original consent application and were active during the pre-hearing meetings. They indicated that they wished to participate in the WCG and have been actively involved in the implementation of the consents.

The functions of the WCG, as noted in the conditions on the existing consent, has been to provide:

1. Comment on the Public Notification Strategy. The Strategy includes methods for warning the general public, and targeted groups within the community of the risks associated with water contact recreational activities and seafood (including shellfish) gathering during the discharges, and notification requirements following water quality monitoring. 2. Comment on the Overflow Contingency Plan (OCP). The OCP outlines procedures adopted during an overflow discharge event. 3. Comment on the option assessment report directly to GWRC. 4. Be a line of communication between the consent holder, the submitters and the wider community for the duration of the consents.

Resource consent application – October 2017 7.3 Consultation during the options assessment From September 2016 to January 2017 stage 1 of the consultation on the future options was undertaken. Two briefing papers were sent to the stakeholders identified in Table 21.

 Issue 1 (early October 2016) – introducing the project  Issue 2 (late October 2016) – setting out the short list of options and inviting comments.

A project website was set up, with link available here: https://wellingtonwater.co.nz/work-in-your- area/seaview-outfall/. The briefing papers were made available on the website. The following technical information was also uploaded to provide background information:

 Seaview WWTP Outfall Options – An Assessment of Effects on the Aquatic Ecology of the Waiwhetū Stream, Hutt Estuary and Wellington Harbour (MWH, October 2016)  Seaview WWTP Alternative Outfall and Storage Options Study (MWH, June 2016)  Main Outfall Pipeline Conditions Report (MWH, August 2016).  Results of Hutt River Dye Test (MWH, November 2016).

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Table 21 - Identified Stakeholders Stakeholder East Harbour Environmental Te Runanganui o Taranaki Whanui kit e Upoko o te Association Inc Ika a Maui Inc Wellington Recreational Marine Ngai Toa RaNgātira Fishers’ Association (Inc) Friends of the Waiwhetū Port Nicholson Block Settlement Trust Regional Public Health Harbour Master (GWRC) Eastbourne Community Board Regulatory Services (GWRC) Petone Community Board Flood Protection (GWRC) Friends of the Hutt River Seaview Marina Forest and Bird (Lower Hutt) Centreport

Lowry Bay Yacht Club Hutt Valley Chamber of Commerce

Wind Surfers Association Seaview Business Association

A meeting was held at the Seaview WWTP on 8 November 2016 with the WCG and other interested parties. The short list of options was outlined and feedback was sought on the options. Feedback was received from the following stakeholder groups and is summarised below:  Regional Public Health  Friends of the Waiwhetū  Wellington Recreational Marine Fishers’ Association (Inc)  Petone Community Board  Seaview Business Association.

7.3.1 Regional Public Health In its response Regional Public Health (RPH) noted that the public health risk from direct physical health harm is adequately managed by all options, including status quo. However, RPH also noted, some options are more likely to address indirect health effects, for example, the impact on the mauri of the water for iwi with discharge of treated wastewater into the Waiwhetū Stream.

RPH recognised that the decision around the preferred option will involve balancing a number of competing impacts including, addressing iwi spiritual concerns, affordability, ecological impacts or Resource consent application – October 2017 potential health risks from recreational activities (for example, the site of discharge relative t o water sports and fishing activities). In this regard they prepared a matrix of their assessment of each option’s impact on the important aspects that they consider need to be balanced. RPH states that it is important that any option chosen has the ability to:  Be compatible with any potential future works to the main outfall system  To be responsive to community and regulatory expectations of recreational water quality  Is sensitive to ongoing iwi concepts of the mauri of the waterways  Is affordable to rate payers  Is considered as part of an overall plan to reduce the need for emergency overflows including ongoing work with infiltration and inflow. 7.3.2 Friends of the Waiwhetū From the Friends of the Waiwhetū (FOW) perspective as an environmental care group, it concluded that Options 3, 5 and 6 all seem to offer a substantial improvement over the current arrangement for the intermittent discharge of WWTP treated wastewater when the existing main outfall pipeline has insufficient capacity or is undergoing repairs. Each of these options would

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ameliorate their concerns about the impact of the intermittent WWTP discharge on Waiwhetū Stream from the other short‐listed options (Options 1, 2, 8 and 12). 7.3.3 Wellington Recreational Marine Fishers’ Association (Inc) Jim Mikoz representing the Wellington Recreational Marine Fishers’ Association only supports Option 4 (which was not the short listed). He has submitted a detailed submission with supporting information and an assessment of each option presented in the short list.

His conclusion states that “Adopt Option 4 and move the discharge point closer to Somes Island. While this option is the most expensive there is no point in constructing a storage tank. The cost of laying the long pipe and building a large pumping station will be minor compared the cost involved in repairing the damage to both humans and the environment caused by any of the other options. Option 4 is the only option that can be seen as planning for the future in the event of a major earth quake. Any other option will prove to be an environmental disaster as the storage tank will still be used to dump waste water close to shore.”

7.3.4 Petone Community Board The Petone Community Board (PCB) supported option 6 because:  Option 3 could still have some limited plume effect on the Waiwhetū Stream  Option 5 could have an effect on the marina and beach area  Option 6 has better dilution than option 5 and seems less likely to have effects on the marina and beach areas 7.3.5 Seaview Business Association The Seaview Business Association (SBA) stated that it would like to see Hutt City Council spend the money on fixing the problem so the overflow is not needed. They believe that resources should be put into tracking every business and residents stormwater to see where the water is getting into the system. The SBA believes that it is time to give the system an overhaul.

If this is not possible then the SBA supports the option with the pipe located further out into the harbour away from the stream and to have the nitrogen removed from the wastewater before being released.

7.3.6 2017 meetings with the Waiwhetū consultation group Two meetings were held with the WCG in 2017. Resource consent application – October 2017 The first occurred on the 4th of July 2017. The purpose of this meeting was to brief the WCG on the outcomes of the options assessment, including on the recommendation that the project team’s would be making to Hutt and Upper Hutt City Councils. The briefing set out the stages in the options assessment process.

Questions, comments and discussion points during the briefing included:  What were the recreation results? The questions did not seem to take into account marine knowledge. o The area has been identified as a recreation hot spot and it is widely used by a number of different activities. o While the surveyor does have marine knowledge the requirement for this survey was to look at recreational use.  Concern that a discharge 300m from the Seaview marina would allow the wastewater to be pushed into the marina.  Close to the 100m off Port Road option there is a very popular little beach.  At 600m off Port Road the wastewater would be pushed into Lowry Bay

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 The confluence of Waiwhetū and Hutt River with storage will allow the discharge to occur on the outgoing tide  It was acknowledged that all the options have an impact somewhere.

The group was informed that further work would be undertaken, including dye tests to determine if option 12 (the project team’s recommended option) would result in treated wastewater flowing back up the Waiwhetū Stream in any conditions.

The representative from the Wellington Recreational Marine Fishers’ Association strongly opposed option 12 as they considered that strong South West winds will blow the wastewater up the Waiwhetū Stream.

A representative of the Friends of the Waiwhetū asked how the tide affected the Hutt River given its greater flow and would there be sufficient storage for the rain events. It was noted that storage would not be sufficient to hold all wastewater until the outgoing tide in wet weather. However at these times the increased flow is very likely to mean that the treated wastewater would not go up the Waiwhetū Stream.

A further meeting of the consultation group was held on 17 October 2017. The purpose of the meeting was to provide a briefing to the group on the content of the final application and to seek any further feedback. Key agenda items were:

1. Any questions Options Assessment Report sent to the group on 31 August 2017 2. The results of the dispersion modelling and dye tests 3. Proposed consent conditions 4. Consent duration being sought 5. Physical form of the outlet

The discussion at the meeting focussed particularly on the results of the dye test and dispersion modelling, and also the design of the outlet and rock riprap peninsula. Feedback re-iterated the consultation group’s desire to minimise the risk on the Waiwhetū Stream. The representative of the Wellington Recreational Marine Fishers’ Association also raised concerns regarding the engineering design of the outlet, including the need for piling, risk to the aquifer from piling and the need for a surge chamber. 7.4 Annual Plan Feedback Feedback on the project was sought as part of Hutt City Council 2017 Annual Plan consultation. For the Annual Plan consultation only 4 options were put forward public consideration. That was in recognition of the fact that this is a complex issue, and expert advice was that the seven options on the short list were too many for the community to sensibly appraise. In making a decision to limit the number of options consulted on, Council was seeking an indication of the community’s Resource consent application – October 2017 preference in terms of a balance between environmental outcomes and cost, rather than an absolute option selection.

In summary, the result of the consultation showed that when Hutt City residents are asked to rate the options “not acceptable”, “could live with it”, or “acceptable”, option 12 received the highest “acceptable” rating. When asked to select a number one preference, option 12 had the highest rating. 7.5 Market Research Report Given the complexity of this issue, a more detailed and targeted survey was also commissioned by Hutt City Council during the Annual Plan consultation period (see Appendix I). In this survey, 300 respondents (selected to cover a spread of geography, age, gender and ethnicity) were pre- selected and sent an “information pack” to read and understand before undertaking the phone survey.

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The consultants undertaking the survey commented on the excellent level of engagement produced by the approach, to the extent that many of the respondents visited the sites of the proposed discharge to enhance their understanding.

The results of this survey indicate that option 12 may be the most acceptable option overall. Sixty one percent (61%) of respondents ranked it either first or second in their selection and very few (6%) ranked it as their least preferred option.

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8. Assessment against relevant provisions 8.1 Introduction Schedule 4 (2) to the RMA requires that an application for a resource consent must include an assessment of the activity against any relevant provisions of a national environmental standard, other regulations, a national policy statement, a New Zealand coastal policy statement, a regional policy statement, a plan or proposed plan.

To comply with this requirement an analysis against the relevant objectives and policies of the following documents has been undertaken. The relevant provisions of these documents are included in Appendix C:

 The New Zealand Coastal Policy Statement (NZCPS)  The National Policy Statement for Freshwater Management (NPS-FM)  The Regional Policy Statement (RPS)  The Regional Freshwater Plan (RFP)  The Regional Coastal Plan (RCP)  The Proposed Natural Resources Plan (PNRP).

In addition it is noted that:  an assessment of the proposal against the rules in the RFP, RCP and PNRP is included in section 4  a preliminary assessment of the proposal against the National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health and the rules of the Hutt City District Plan is included in section 2.4  an assessment of the proposal in relation to relevant parts of ANZECC (2000) Freshwater and Marine, the NPS-FM National Objectives Framework (2014) and the Aquatic Life Ambient Water Quality Criteria for Ammonia – Freshwater (USEPA, 2013) is included in sections 6.4 to 6.7.

8.2 Weight to be afforded to the Regional Plans There are currently multiple regional plans which apply to the application, being the operative RCP and RFP, and the PNRP. Resource consent application – October 2017

The PNRP was notified in 2015, and is the subject of various submissions. Several of the submissions specifically address the provisions of the PNRP which are relevant to this application and seek substantive changes to them. The hearing on these provisions is now not scheduled until 2018 and the decisions are scheduled to be released in November 2018. How the provisions of the PNRP may change in response to submissions is uncertain.

Based on this, and notwithstanding that the PNRP has been included in the following planning assessment, it is considered that currently little weight should be given to the objectives and policies of the PNRP in considering this application.

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8.3 Planning assessment Based on a review of the objectives and policies 5 relevant to this application, it is considered that the key policy directions relevant to this application relate to:

 natural character  the role of local iwi as tangata whenua and kaitiaki, and their cultural relationships with the receiving environments  the benefits that arise from the use and development of Regionally Significant Infrastructure  water quality  the integrity and functioning of ecosystems, and indigenous biological diversity  ecosystems and habitats with significant biodiversity values  amenity, including public access and recreation opportunities.

The focus of the following sections is on how the proposed long term discharges to the Hutt River, and the associated physical works, relate to these policy directions.

With respect the proposed discharges to the Waiwhetū Stream it is acknowledged that these do not protect the strong cultural relationship of iwi to the Stream. Further the discharges to the Stream will have adverse effects on water quality and aquatic ecology which are unlikely to be appropriate in the long term. The decision to select an alternative to the Waiwhetū discharge is in part a recognition that this discharge is not consistent with the relevant provisions of various statutory documents. However, a short term consent is required for the discharge to the Waiwhetū Stream to enable the construction and commissioning of the infrastructure necessary to facilitate the Hutt River discharge.

8.3.1 Protecting and preserving natural character All of the policy statements and plans reviewed contain provisions relating to natural character which are relevant to the proposal. General policy which is common to these documents include the direction to preserve and / or protect natural character, avoid significant adverse effects on natural character and avoid, remedy or mitigate other effects. The plans and policy statements also direct that in determining what may be an appropriate or inappropriate activity with respect to natural character the factors that should be considered include:  The degree of modification to the natural character of the area  The nature, scale or extent of the activity  The existence of other structures.

An assessment of the natural character of the area has been completed (see Appendix G) as part of this application. This concludes that the overall natural character of the wider estuary area (Hutt Resource consent application – October 2017 River and Waiwhetū Stream estuary) is low, with a high degree of modification. The report assesses the proposal to have a neutral effect on natural character in the area.

Based on this, it is considered that the proposal will preserve the existing level of natural character and avoids significant and other adverse effects on it. The proposal is therefore consistent with the natural character objectives and policies in the various policy statements and plans , including, but not limited to, Objective 2 of the NZCPS, Objective 4 of the RPS, Objective 4.1.4 of the RFP, Objective 4.1.5 of the RCP and Objective O17 of the PNRP. 8.3.2 Tangata whenua, kaitiakitanga & cultural relationships Throughout the policy statements and plans there are a significant number of objectives and policies which address the resource management issues of relevance to tangata whenua, their role as kaitiaki and their cultural relationships to the environment.

5 These are set out in full in Appendix C.

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Directions common to the policy statements and plans, and relevant to this proposal, include the need to:  take into account the principles of the Treaty of Waitangi  recognise the role of tangata whenua as kaitiaki  recognise and protect the cultural relationships of tangata whenua to water, sites of significance  sustain the mauri of water  maintain water quality consistent with tangata whenua values  consult with tangata whenua.

The Regional Coastal Plan recognises (within Objectives 4.1.3, 4.1.14 and 4.1.16) the particular relationship of tangata whenua to the coastal marine area, and requires that particular regard be given to adverse effects on areas of the coastal marine area with significant cultural value.

It is considered that the options assessment process undertaken for this project and the proposal are consistent with this direction. The particularly significant value placed by local iwi on the Waiwhetū Stream has been recognised through the decision to select an alternative discharge site.

Throughout the life of the current consent and during the options assessment process Hutt City Council and Wellington Water have consulted with local iwi on their option preferences and their values. The strong preference to relocate the discharge from the Waiwhetū Stream has been consistently signalled throughout this consultation.

It is also of note that at the hui in March 2017, Wellington Water sought agreement from iwi on who is appropriate to prepare the cultural impact assessment for this project. This was done in recognition of the status of local iwi as tangata whenua.

From the engagement with iwi it is understood that their preference would be for the discharge not to go into the Hutt River estuary. However it is understood that there is a degree of pragmatism about this outcome given the financial implications for the community of alternatives which would remove the discharge from the Estuary, higher priorities for this investment (particularly the untreated wastewater overflows elsewhere in the catchment), and also given the mitigation measures proposed (tidal discharge regime and notification when discharges occur).

There are provisions in the PNRP which the proposal is not consistent with, specifically Policy 45 and by association Objective 35.

Policy 45 directs that:

In the first instance, activities in sites with significant mana whenua values identified in Schedule C (mana whenua) shall be avoided. Resource consent application – October 2017 If the site cannot be avoided, more than minor adverse effects on the significant mana whenua values must be evaluated through a cultural impact assessment undertaken by the relevant iwi authority or iwi authorities. The adverse effects of activities shall be managed in accordance with tikanga and kaupapa Māori as recommended in the cultural impact assessment by: a) Avoiding more than minor adverse effects, and b) Where more than minor adverse effects cannot be avoided, remedying them, and c) Where more than minor adverse effects cannot be remedied, mitigating them, and d) Receiving written consent of the iwi authority.

Where more than minor adverse effects on significant mana whenua values identified in Schedule C (mana whenua) cannot be avoided, remedied or mitigated, the activity is inappropriate. Offsetting of effects in sites with significant mana whenua values is inappropriate.

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The Hutt River estuary is a Schedule C site. The proposed activity will not avoid it. While it is not considered practicable to do so because of the additional financial cost, the activity can avoid it if an additional $13-14 million were invested in the project. It is noted that this proposed policy is subject to submissions and the decision on those submissions will not be released until late 2018.

There are similar policies in the PNRP relating to structures and deposition in Schedule C sites. These policies seek that such activities avoid these areas. However there is an exemption for regionally significant infrastructure (which the Hutt Valley wastewater network is) provided that there are no practicable alternatives. It is considered that, because of the additional financial cost, the alternatives in this case are not practicable.

8.3.3 Benefits of regionally significant infrastructure The policy statements and plans include objectives and policies which recognise the benefits of use and development of resources generally, or infrastructure in particular. The RCP contains the most explicit provision which requires consideration of the development of structures for network utility operations as appropriate in the coastal marine area (Policy 6.2.1). However this direction needs to be considered in the context of numerous other provisions in the RCP which direct the protection of key values or avoidance of adverse effects.

In relation to these ‘benefit’ objectives and policies it is relevant to note that the Hutt Valley wastewater system is regionally significant infrastructure as defined in the Regional Policy Statement. The intermittent discharges and associated infrastructure, which are the subject of this application, are integral to the wastewater system.

The provision for the intermittent discharges means that the MOP is able to be effectively maintained, extending its functional life. If the MOP could not be maintained in this way the community would need to invest in its replacement much sooner than otherwise, with a very significant financial cost.

In addition it is not practical to size the main outfall pipeline so that it can carry all possible wastewater flows. A key benefit therefore arising from these intermittent discharges is that they allow more wastewater to be treated in wet weather conditions than is able to be conveyed by the MOP.

8.3.4 Water quality The common directions in the objectives and policies relating to water quality are:  maintain water quality and enhance where it is degraded  avoid significant adverse water quality effects on ecosystems and habitats  safeguard life-supporting capacity  maintain aquatic ecosystem health. Resource consent application – October 2017

Based on the water quality assessments in sections 6.4 to 6.7 it is considered that this proposal is consistent with these objectives and policies.

The RCP and PNRP (in particular) contain specific direction to meet numerical or qualitative water quality standards. These are associated with:  contact recreation (policies 10.2.2 and 10.2.3 of the RCP and O24 and P63 of the PNRP)  Māori customary use (O24 and P63 of the PNRP)  Aquatic ecosystem health and mahinga kai (O25 and P70 of the PNRP).

The numerical and qualitative standards covered in these provisions are addressed in sections 6.6 and 6.8 of the assessment of environmental effects. Based on these assessments it is expected that the objectives and policies will be met by both the wet weather and repair discharges.

The PNRP also includes policies specific to wastewater discharges. Policy 80 relates to the replacement of existing consents. It requires that:

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Applicants replacing existing resource consents to discharge wastewater to fresh water and coastal water shall identify: a) The objectives, limits, targets, discharge standards or other requirements set out in the plan relevant to wastewater discharges to water, and b) The results of consultation with the community and mana whenua on their values and interests in relation to discharges and receiving waters, including adverse effects on māori customary use and mahinga kai, and c) In response to consultation with the community and mana whenua, the short-term and long-term goals for wastewater discharges to water, where short-term goals are within the lifetime of the plan and long-term goals are beyond the lifetime of the plan, and d) How the short- and long-term goals for wastewater discharges to water will satisfy provisions of the plan, and

Infrastructure changes needed to meet long-term goals for wastewater discharges to water, including key milestones and dates.

In relation to this policy, it is noted that the relevant provisions referenced in clause (a) are set out above and in Appendix C. The results of community consultation is set out in section 7 of this application. The short term goal that has been identified is to relocate the discharge from the Waiwhetū Stream. This goal can be achieved within 5 years of granting of the consent, i.e. within the lifetime of the PNRP. This goal reflects the strong preference signalled by mana whenua. The selection of the discharge to the Hutt River, with additional storage is consistent with the indicated community preference in recent consultation by Hutt City Council.

Policy 81 of the PNRP also specifically addressed wastewater discharges. This policy requires that: The adverse effects of existing discharges of wastewater to fresh water and coastal water shall be minimised, and: a) In the case of existing discharges to fresh water from wastewater treatment plants, the quality of discharges shall be progressively improved and the quantity of discharges shall be progressively reduced, and b) In the case of existing discharges to fresh water or coastal water from wastewater networks during or following rainfall events, the frequency and/or volume of discharges shall be progressively reduced.

It is considered that the proposal is consistent with this policy in that it removes the discharge from the Waiwhetū Stream, and seeks to reduce the frequency of wet weather events through the construction of additional storage.

NZCPS Policy 23 (2) also directly addresses wastewater discharges. This directs that: Resource consent application – October 2017

In managing discharge of human sewage, do not allow: a. discharge of human sewage directly to water in the coastal environment without treatment; and b. the discharge of treated human sewage to water in the coastal environment, unless: i. there has been adequate consideration of alternative methods, sites and routes for undertaking the discharge; and ii. informed by an understanding of tangata whenua values and the effects on them.

The proposed discharge is treated, an extensive assessment of alternatives has been completed and this has been informed by an understanding of tangata whenua values and effects on them.

8.3.5 Ecosystems The common directions in the objectives and policies relating to general ecosystem health and biodiversity are to:

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 Maintain and enhance biological and physical processes  Safeguard aquatic ecosystem health  Protect the integrity and functioning of ecosystem processes  Safeguard life supporting capacity  Maintain fish passage  Avoid significant adverse effects, and avoid remedy or mitigate other adverse effects.

Based on the assessment of effects in sections 6.4 to 6.8 it is considered that the proposal is consistent with the direction in the objectives and policies.

The PNRP includes a specific objective (O18) and policy (P22) which recognise the particular values of estuaries, including their sensitivity as low energy receiving environments, and directs that significant adverse effects on their ecosystem values shall be avoided. The assessment in section 6.8 shows that the proposal is consistent with this direction. 8.3.6 Habitats with significant value The common direction in the objectives and policies relating to habitats of significant value includes the requirement to protect, maintain and restore these areas.

The Hutt River estuary is identified in the PNRP as an ecosystem and habitat with significant biodiversity values. Based on the assessment in sections 6.4 to 6.8 it is considered that the effects of the proposal on the estuary are consistent with the relevant objectives and policy. In this regard it is noted that section 6.8.4 of this assessment summarises the effects of the proposal as follows:  Potential excess growth of macroalgae is mitigated by the timing of planned discharges during the winter and the generally short duration of discharges that may occur at other times.  High value habitats will not be affected by the proposed discharges.  The benthic invertebrate community of intertidal habitats within the Hutt River may be subject to highly localised and reversible effects on the relative abundance of some taxa  Such impacts would not affect higher value habitats  The combination of various factors in the proposed discharge regime will ensure that the activity does not interfere with fish movement between marine and freshwater habitats.  The proposed discharges do not contribute significantly to the suspended solids load of the Hutt River and will have no material effect on sedimentation rates or mud content of the estuary.

Policy 11 of the NZCPS provides particularly strong direction in relation to valued habitats and species. It requires: To protect indigenous biological diversity in the coastal environment: a) Avoid adverse effects of activities on: i) Indigenous taxa4 that are listed as threatened5 or at risk in the New Zealand Threat Resource consent application – October 2017 Classification System lists; ii) Taxa that are listed by the International Union for Conservation of Nature and Natural Resources as threatened; iii) Indigenous ecosystems and vegetation types that are threatened in the coastal environment, or are naturally rare6; iv) Habitats of indigenous species where the species are at the limit of their natural range, or are naturally rare; v) Areas containing nationally significant examples of indigenous community types; and vi) Areas set aside for full or partial protection of indigenous biological diversity under other legislation; and b) Avoid significant adverse effects and avoid, remedy or mitigate other adverse effects of activities on: i) Areas of predominantly indigenous vegetation in the coastal environment; ii) Habitats in the coastal environment that are important during the vulnerable life stages of indigenous species;

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iii) Indigenous ecosystems and habitats that are only found in the coastal environment and are particularly vulnerable to modification, including estuaries, lagoons, coastal wetlands, dunelands, intertidal zones, rocky reef systems, eelgrass and saltmarsh; iv) Habitats of indigenous species in the coastal environment that are important for recreational, commercial, traditional or cultural purposes; v) Habitats, including areas and routes, important to migratory species; and vi) Ecological corridors, and areas important for linking or maintaining biological values identified under this policy.

In relation to clause (a) most of the values listed in the sub-clauses are not present in the Hutt River estuary. However indigenous taxa that are listed as threatened or at risk in the New Zealand Threat Classification System lists are present from time to time (refer clause (a) (i)). These are the seven indigenous fish species listed in Table 7 above as “at risk” or “threatened”, and “migratory”. These species need to pass through the Hutt Estuary on upstream migrations as juveniles. However, it is not considered that the proposal will have adverse effects on these species.

Policy 41 of the PNRP directs that: In order to protect the ecosystems and habitats with significant indigenous biodiversity values identified in Policy P40, in the first instance activities, other than activities carried out in accordance with a restoration management plan, shall avoid these ecosystems and habitats. If the ecosystem or habitat cannot be avoided, the adverse effects of activities shall be managed by: a) Avoiding more than minor adverse effects, and b) Where more than minor adverse effects cannot be avoided, remedying them, and c) Where more than minor adverse effects cannot be remedied, mitigating them, and d) Where residual adverse effects remain it is appropriate to consider the use of biodiversity offsets.

Proposals for mitigation and biodiversity offsets will be assessed against the principles listed in Schedule G (biodiversity offsetting). A precautionary approach shall be used when assessing the potential for adverse effects on ecosystems and habitats with significant indigenous biodiversity values. Where more than minor adverse effects on ecosystems and habitats with significant indigenous biodiversity values identified in Policy P40 cannot be avoided, remedied, mitigated or redressed through biodiversity offsets, the activity is inappropriate. The Hutt River estuary is a habitat with significant indigenous biodiversity values identified in Policy P40. The proposal obviously will not avoid this area. Avoidance can only be achieved with an additional investment of approximately $13-14 million. It is not considered that this is the best practicable option for the project. In this respect it is noted that the assessment of ecological effects has identified that the effects will be low. This is in part due to the mitigation measures Resource consent application – October 2017 incorporated into the proposal including the tidal discharge regime for dry weather discharges and the reduction frequency of wet weather discharges due to storage.

There are similar policies in the PNRP relating to structures and deposition in scheduled sites with indigenous biodiversity values. These policies seek that activities avoid these areas. However there is an exemption for regionally significant infrastructure (which the Hutt Valley wastewater network is) provided that there are no practicable alternatives. It is considered that, because of the additional financial cost, the alternatives in this case are not practicable.

8.3.7 Amenity values The provisions relating to amenity values address visual amenity, recreation and public access. Common general directions relate to:  Maintaining and enhancing public open space quality and recreation opportunities  Maintaining and enhancing public walking access to and along the coast  Maintaining and enhancing amenity

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 Minimising significant adverse effects on the use and enjoyment of the coast  Protecting recreation resources from adverse effects where practicable and mitigating effects where it is not  Enhancing access to and along areas of significant biodiversity value and Wellington harbour  Minimising adverse effects on visual amenity.

An assessment of effects on visual amenity was prepared as part of this application (see Appendix G). This identifies that the landscape context for the proposal is significantly modified and that the visual amenity of the area is compromised. Without mitigation the outfall is assessed to have moderate adverse effects on the visual amenity of the area. These potential adverse effects will be mitigated by incorporating the structure into a rock rip rap ‘landform’ which will integrate with the appearance of the river bank. Wellington Water proposes that vegetation near the Port Road footpath which will need to be removed during construction will be replaced. In summary, it is considered that the proposal will be general accordance with the relevant objectives and policies relating to amenity values, including Objective 4.1.9 and 12.1.1 of the RCP, and Objective O18 of the PNRP.

With respect to recreation, there are two aspects relevant to the proposal. These are walking access and water based recreation. Walking access along the coast line will be maintained and once construction is completed the top of the concrete encased outlet will offer a potential viewing platform for the public. As such, it is considered that the proposal will be consistent with the relevant objectives and policies relating to public access, including Objective 4 and Policy 19 of the NZCPS, Objective 8 and Policy 53 of the RPS, Objective 4.1.8 of the RCP and Objective O10 and Policy P9 of the PNRP.

With respect to water based recreation, the recreation assessment prepared for this application (see Appendix H) identified potential effects on whitebaiting downstream of the outfall if unplanned repair events occurred during the whitebaiting season. However due to the infrequency of such discharge events it is consider that any effects will be small and can be further mitigated through signage. As such, the proposal is considered to be consistent with the relevant objectives and policies relating to recreation, including Objective 4 and Policy 18 of the NZCPS, and Objective O9 and Policy 133 of the PNRP.

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9. Pt II RMA Schedule 4 (2) to the RMA requires that an application an assessment of the activity against the matters set out in Part 2 of the RMA.

Within Part 2, Section 5 outlines the Act’s purpose. Section 6 sets out matters of national importance, section 7 outlines ‘other’ matters and section 8 requires those exercising functions and powers under the RMA to take into account the principles of the Treaty of Waitangi.

To meet the requirements of Schedule 4, the table below provides an assessment of the activity against the requirements of Part 2 of the RMA.

Table 22: Part 2 Assessment Provision Assessment

Section 5 The Hutt Valley wastewater system is an important physical In this Act, sustainable resource, which contributes to the social and economic management means managing wellbeing, and health of the Hutt Valley community. The the use, development and intermittent discharges and associated infrastructure, which protection of natural and physical are the subject of this application, are integral to the resources in a way or at a rate wastewater system. that allows people and

communities to provide for their social, economic and cultural wellbeing and for their health and safety, while… Section 5(2)(a) It is considered that the assessment of effects shows that the Sustaining the potential of natural water resources will be sustained by the proposal. and physical resources (excluding minerals) to meet the reasonably foreseeable needs of future generations Section 5(2)(b) It is considered that the assessment of effects shows that the Safeguarding the life-supporting life-supporting capacity of affected water resources will be capacity of air, water, soil, and safeguarded. Resource consent application – October 2017 ecosystems Section 5(2)(c) The proposal has been designed to avoid effects (through Avoiding, remedying or mitigating relocation of the outfall and additional storage) where possible any adverse and to otherwise mitigate these effects (through tidal effects of activities on the discharge regime, signage and integration of the outfall environment structure into the river bank).

Section 6(a) As assessment of the natural character of the area has been The preservation of the natural completed as part of this application. This concludes that the character of…rivers and their overall natural character of the wider estuary area (Hutt River margins, and the protection of and Waiwhetū Stream estuary) is low, with a high degree of them from inappropriate modification. The report assesses the proposal to have a subdivision, use and neutral effect on natural character in the area. development

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Provision Assessment

Based on this, it is considered that the proposal will preserve the existing level of natural character and protects its from inappropriate use and development.

Section 6(c) Based on the assessment in sections 6.4 to 6.8 of this The protection of areas of application ecological values of the Hutt River estuary will be significant indigenous vegetation protected. In this regard it is noted that section 6.8.4 of this and significant habitats of assessment summarises the effects of the proposal as indigenous fauna. follows:  Potential excess growth of macroalgae is mitigated by the timing of planned discharges during the winter and the generally short duration of discharges that may occur at other times.  High value habitats will not be affected by the proposed discharges.  The benthic invertebrate community of intertidal habitats within the Hutt River may be subject to highly localised and reversible effects on the relative abundance of some taxa  Such impacts would not affect higher value habitats  The combination of various factors in the proposed discharge regime will ensure that the activity does not interfere with fish movement between marine and freshwater habitats.  The proposed discharges do not contribute significantly to the suspended solids load of the Hutt River and will have no material effect on sedimentation rates or mud content of the estuary.

Section 6(e) and Section 7(a) Iwi representatives have advocated strongly to relocate the The relationship of Maori and discharge from the Waiwhetū Stream to protect the cultural their culture and values associated with the Stream. This will be achieved by traditions with their ancestral this proposal. lands, water, sites, waahi tapu, and other taonga. From the engagement with iwi it is understood that their

preference would be for the discharge not to go into the Hutt Resource consent application – October 2017 Kaitiakitanga River estuary. However it is understood that there is a degree

of pragmatism about this outcome given the financial implications for the community of alternatives which would remove the discharge from the Estuary, higher priorities for this investment (particularly the untreated wastewater overflows elsewhere in the catchment), and also given the mitigation measures proposed (tidal discharge regime and notification when discharges occur).

Section 7 (b) The MOP is considered to be an existing and significant asset The efficient use and (physical resource) that still has a significant lifespan. WWL development of natural and and HCC therefore have responsibility to maximize the use of physical resources this asset, consistent with sound asset management. Enabling the continuation of the intermittent discharges will facility the on-going efficient use of this resource, by allowing

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Provision Assessment maintenance activities to be planned and undertaken as required.

Section 7(c) An assessment of effects on visual amenity identifies that the The maintenance and landscape context for the proposal is significantly modified enhancement of amenity and that the visual amenity of the area is compromised. values Without mitigation the outfall is assessed to have moderate adverse effects on the visual amenity of the area. However it is proposed to mitigate these effects by incorporating the structure into a rock rip rap ‘landform’ which will integrate with the appearance of the river bank.

With respect to recreation it is considered that there will be no adverse effects on walking access and some small benefits. While with respect to water based recreation, there is the potential for adverse effects on whitebaiting downstream of the outfall if unplanned repair events occurred during the whitebaiting season. However due to the infrequency of such discharge events it is consider that any effects will be small and can be further mitigated through signage.

Overall it is considered that amenity values will be maintained.

Section 7(d) The intrinsic values of ecosystems have been given particular Intrinsic values of ecosystems regard in the preparation of this application and in the assessment of environmental effects. The assessment has concluded that:  Potential excess growth of macroalgae is mitigated by the timing of planned discharges during the winter and the generally short duration of discharges that may occur at other times.  High value habitats will not be affected by the proposed discharges.  The benthic invertebrate community of intertidal habitats within the Hutt River may be subject to highly localised and reversible effects on the relative abundance of some taxa  Such impacts would not affect higher value habitats Resource consent application – October 2017  The combination of various factors in the proposed discharge regime will ensure that the activity does not interfere with fish movement between marine and freshwater habitats.  The proposed discharges do not contribute significantly to the suspended solids load of the Hutt River and will have no material effect on sedimentation rates or mud content of the estuary.

Section 7(f) The assessment of effects shows that the environment quality Maintenance and enhancement of the Hutt River estuary will in many respects be maintained. of the quality of There will be some adverse effects on water quality, however the environment

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Provision Assessment these are expected to be moderate at worst and only temporary.

Section 7(h) It is not considered that trout or salmon habitat will be The protection of the habitat of adversely impacted by this proposal. trout and salmon Section 8 In relation to Section 8, it is noted that consultation with iwi In achieving the purpose of this has been undertaken in the preparation of this application. Act, all persons The strong preference of iwi that the discharge be relocated exercising functions and powers from the Waiwhetū Stream has been consistently signalled under it, in throughout this consultation and is a key matter addressed in relation to managing the use, this proposal. development, and protection of natural and physical It is also of note that at the hui in March 2017, Wellington resources, shall take into account Water sought agreement from iwi on who is appropriate to the principles of the Treaty of prepare the cultural impact assessment for this project. This Waitangi. was done in recognition of the status of local iwi as tangata whenua.

From the engagement with iwi it is understood that their preference would be for the discharge not to go into the Hutt River estuary. However it is understood that there is a degree of pragmatism about this outcome given the financial implications for the community of alternatives which would remove the discharge from the Estuary, higher priorities for this investment (particularly the untreated wastewater overflows elsewhere in the catchment), and also given the mitigation measures proposed (tidal discharge regime and notification when discharges occur).

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10. Consent conditions 10.1 Introduction This section sets out the nature of the resource consent conditions proposed by Wellington Water. These conditions reflect key mitigation measures associated with the proposal including  the operation of the discharges and increased storage  notification of stakeholders and potentially affected recreation groups at the time of discharges  public signage  the design of the outfall structure and rock rip rap  construction methodology and construction management for the outfall structure and rock rip rap.

In addition, conditions are proposed in relation to the consultation group, monitoring and reporting. 10.2 Waiwhetū discharge permit conditions The resource consent application for the intermittent discharges of treated wastewater to the Waiwhetū Stream is sought based on generally the same terms and conditions as the existing consent. It is therefore proposed that the resource consent(s) be granted with conditions relating to:  The operation of the discharge including the requirement that: o the wastewater which is discharged via the outfall is secondary treated and UV disinfected o wet weather related discharges are limited to occasions when the flow exceeds the capacity of the MOP and the existing storm tank is full o planned repair related discharges only occur between 5 May and 5 July each year and for a maximum period of 6 weeks o unplanned repair related discharges only occur when the repair works cannot be delayed until the next planned repair window, and for a maximum period of two weeks per event o repair related discharges are discharged on the ebb tide as far as practicable  The ongoing operation of the consultation group established under the existing resource consent  The ongoing implementation of the Public Notification Strategy  The ongoing operation of warning signage  The continued notification of GWRC and RPH in advance of planned repair discharges and within 8 hours of the commencement of unplanned repair discharges and wet weather Resource consent application – October 2017 discharges  The continued submission of detailed information on the discharges to GWRC and RPH within two days of a discharge stopping  The addition of iwi and the consultation group to the list of those notified of discharges and who receive details on the discharge once the discharge has stopped  Detailed monitoring and reporting conditions (including monitoring of discharge and receiving water quality for both discharge types)  The continued maintenance of a complaints register  The continued implementation of the Overflow Contingency Plan  The preparation of an Annual Report and submission to GWRC, RPH, iwi and the consultation group.

It is not proposed that conditions relating to option investigations and reporting be included on the resource consent for discharges to the Waiwhetū Stream. These conditions are no longer necessary as Wellington Water has now identified the best practicable option for the foreseeable future.

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It is also not proposed to include conditions relating to the tangata whenua values monitoring, as are included on the existing consent. It is noted that in consultation with GWRC these conditions were not implemented. This was because GWRC determined that the intention of the conditions would be better achieved through a co-ordinated approach to cultural values monitoring rather than through ad hoc conditions on resource consents. We understand that this continues to be GWRC’s preference.

An additional condition proposed for the Waiwhetū Stream consent is the placement of a requirement for the consent holder to include a section in the Annual Report on progress of construction and commissioning of the Hutt River outfall. 10.3 Hutt River coastal permit conditions 10.3.1 Discharge to the Hutt River The conditions proposed for the Hutt River discharge are similar to those proposed for the Waiwhetū Stream discharge. However key differences or additional conditions are:  Wellington Water proposes that the consent be subject to a condition requiring that prior to any discharge occurring into the Hutt River from the proposed outfall that an additional 10,000 m3 of storage for treated wastewater be constructed and operational  The wet weather discharges should not operate unless the total storm tank capacity is utilised  The discharge regime for repair related discharges shall require that, as far as practicable, discharges occur only on the ebb tide. Implementing the following regime would be considered to be compliance with this objective: o Treated wastewater shall be diverted into the storm tanks during each flood tide; o If the capacity of the storm tanks is not reached prior, then stored wastewater shall be released over a five hour period during the ebb tide beginning approximately 30 minutes after the high tide as measured at the Hutt River outfall o If the capacity of the storm tanks is reached prior to the high tide then additional treated wastewater can be discharged via the Hutt River outfall during the flood tide  As above, iwi and the consultation group will be added to the list of those notified of discharges and who receive details on the discharge once the discharge has stopped  Hikoikoi Waka Ama shall also be added to the groups that receive notification at the commencement of discharges  The existing Public Notification Strategy and Overflow Contingency Plan shall be combined into a single document and implemented  The signage by the Seaview Road bridge shall not be required  Detailed monitoring and reporting conditions (including monitoring of discharge and receiving water quality, and a one-off shellfish quality survey once the proposed Hutt River Resource consent application – October 2017 outfall is in operation).

10.3.2 Structure, deposition, disturbance, occupation There will be various resource consents associated with the construction of the new outfall structure and rock rip rap landform. It is anticipated that these consents will contain similar conditions. Wellington Water proposes that these conditions should address:

 The requirement for the location, dimensions and design of the structure, reclamation, deposition of rock and disturbance of the river bed to be general accordance with the information in the application, including drawings.  Confirmation of the final dimensions and extent of the physical works following completion of detailed design  Maintenance of public access during construction and after construction  Maintenance of a complaints register during construction  The requirement for a construction management plan (CMP) to be prepared and implemented

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 The CMP shall be submitted to GWRC for certification that it covers the content identified in the conditions  The objective of the CMP shall be to ensure that the construction related adverse environmental effects are mitigated and that all practicable steps are taken to minimise increased sedimentation and turbidity and to ensure contaminants (oil, petrol, diesel and hydraulic fluid) are not released into water  The CMP shall include: o Roles and responsibilities of key site personnel o Identification of experienced person(s) to manage the environmental issues on site o Details of any public access restrictions and what measures will be in place to minimise disruption of public access o Proposed hours of operation o Details of processes/measures to be put in place to prevent the discharge/spillage of oil, grout, cement and other contaminants to the coastal marine area; and o Procedures to be undertaken in the event of a discharge/spillage of oil, grout, cement and other contaminants to the coastal marine area o Details of processes/measures to be put in place to mitigate adverse effects arising from the disturbance of the river bed o Details of processes/measures to be put in place to manage the risk associated with the potentially contaminated bed material which may be disturbed at the mouth of the Waiwhetū Stream o Details of proposed planting to be undertaken to replace trees or plants removed during construction works  Requirement for Wellington Water to maintain the structure and reclamation so that any erosion that is attributable to the structure and reclamation is repaired, the integrity of the structure is maintained, public access is maintained and rock rip rap replaced as necessary  Exclusion period for construction to avoid the spring fish migration period.

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11. Consent duration 11.1 Discharge to the Waiwhetū Stream For the discharge permit for the discharged of treated wastewater to the Waiwhetū Stream a consent duration 5 years is sought. This period is required to provide sufficient time for the following activities which cannot occur until resource consent is granted and the terms and conditions of that consent are confirmed:  Detailed design of the infrastructure and outfall pipe, including geotechnical and soil contamination investigations  Property negotiations  Obtaining building consents and resource consent which may arise due to detailed design changes  Contract tendering  Construction and commissioning of the new infrastructure.

The period is considered to appropriately balance the time reasonably needed to undertake these activities, while recognising the significance of the effects of this discharge and therefore attempting to keep the duration of the on-going discharge to the Waiwhetū Stream as short as possible. 11.2 Hutt River consents The following resource consents are required in the relation to the proposed discharge to the Hutt River:

1. A coastal permit for the discharge of treated wastewater to the Hutt River estuary 2. A coastal permit for the erection of the outfall structure and deposition of rock material, and associated disturbance of seabed, occupation of part of the coastal marine area and diversion of coastal water

Section 123 of the RMA sets out the requirements with respect to resource consent duration. In relation to the resource consents outlined above this section states that:

…The period for which any other coastal permit, or any other land use consent to do something that would otherwise contravene section 13, is granted is such period, not exceeding 35 years, as is specified in the consent and if no such period is specified, is 5 years from the date of commencement of the consent under section 116… Resource consent application – October 2017

The duration sought for all of the Hutt River consents is 35 years. This duration is considered appropriate for the following reasons:

 The proposal is a significant capital investment (estimated at approximately $12 million) and the infrastructure being constructed will have a functional lifespan of approximately 80 years. Therefore a resource consent duration of less than 35 years will not provide Wellington Water and Hutt City Council with sufficient return on this to warrant the investment.  Since the existing consents were granted in 2013 Hutt City Council initially and more recently Wellington Water have undertaken a very thorough assessment of alternatives. This assessment is detailed in the Options Assessment Report provided to the GWRC in August 2017. The conclusion of this assessment is that the proposed option is the ‘Best Practicable Option’ for this intermittent discharge of treated wastewater.  As part of the alternatives assessment there has been a very thorough assessment of environmental effects. The outcome is that there is a high level of confidence and certainty

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about the adverse environmental effects that are expected from the discharge and associated infrastructure.  The adverse effects arising from the discharge are not anticipated to be significant, and although they may include intermittent and localised water quality fluctuations, they will not result in noticeable sustained deterioration of the water quality or ecology of the Hutt River. They will also not prevent improvement in both the water quality and ecology of the Hutt River being made by addressing the key contributors to the current state of the River (e.g. stormwater and the overflow of untreated wastewater).  The proposal is consistent with the objectives and policies of the Regional Coastal Plan. It is not considered that weight should be given to the proposed Natural Resource Plan in determining the duration of the resource consent. This is because at this time the relevant hearings on Proposed Natural Resources Plan submissions have yet to be held and it is noted that significant changes are sought to the Proposed Natural Resources Plan in the submissions.  The proposal is a significant capital investment (estimated at approximately $12 million) and the infrastructure being constructed will have a functional lifespan of approximately 80 years. Therefore a resource consent duration of less than 35 years will not provide Wellington Water and Hutt City Council with sufficient return on this to warrant the investment.  There is insufficient data to be able to put a set timeframe on the remaining life of the MOP. However the most recent assessment, completed in 2013, showed the reinforcing steel of the pipeline was in relatively good order. Condition assessments of the pipeline, with targeted maintenance through replacing weakened sections of the pipeline, will allow WWL to continue to use this asset for a number of years. This maintenance programme is considered to represent efficient use of the existing physical resource, consistent with s7 (b) of the RMA.

As well as improvements to the level of treatment since construction, in recent years there have been changes in the operating procedure to minimise the stress on the pipeline, and prolong the life. Due to the age and material of the pipeline it is always at risk of failure from natural hazards, particularly seismic events. After each reasonable seismic event the pipeline route is driven and monitored to see if there are any visible leaks at the ground surface. It is currently believed the MOP is in good working order, and under existing conditions will remain so for the foreseeable future.

In general terms the MOP is considered to be an existing and significant asset that still has a significant lifespan. Wellington Water therefore have responsibility to maximize the use of this asset, consistent with sound asset management. To enable this, and to assist Wellington Water with its long term planning the certainty of a long term consent is required.

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12. Conclusion Wellington Water is seeking to replace the resource consents currently in place for two intermittent discharges of treated wastewater from the Seaview WWTP, as both of these resource consents expire on the 1 February 2018. The proposal also involves the relocation of the discharge point from the Waiwhetū Stream to the Hutt River and the addition of a 10,000 m3 storage tank. The Seaview WWTP provides secondary biological treatment with ultra-violet (UV) disinfection. The 18km long MOP conveys treated and UV disinfected wastewater from the Seaview WWTP to the Pencarrow Outfall at Bluff Point approximately 500m south-east of Pencarrow Head. Repair work is required on the MOP from time to time, which on occasions requires the operation of the MOP to cease. At such times the treated wastewater from the Seaview WWTP is currently discharged to the Waiwhetū Stream. In addition, due to extreme wet weather the flow of treated wastewater from the WWTP exceeds the capacity of the MOP and storage on occasions and any excess flow is discharged to the Waiwhetū Steam. The proposal covered by this application represents a significant improvement on the current situation by making three key changes to the nature of the discharge:

1. Relocating the discharge point from the Waiwhetū Stream to the Hutt River. 2. Using additional storage at the WWTP to reduce the number of wet weather discharges that would otherwise occur. 3. Using additional storage at the WWTP to enable the repair related discharges to be released on the outgoing tide, which minimises the risk of backflow up the Waiwhetū Stream.

Reducing the impacts on the Waiwhetū Stream is therefore a key goal of the proposed works.

The proposal has been identified following significant consultation with iwi and key stakeholder groups, and following a thorough options assessment process.

The environmental effects of the proposal have been assessed. In relation to effects on Māori cultural values it is considered that these will be significantly reduced when compared with the status quo. Water quality and ecological effects are expected to be minor to moderate, while natural character and visual amenity effects are neutral.

Overall it is considered that the proposal is consistent with the direction of the various relevant policy statements and plans, and with Part 2 of the RMA. It is therefore considered that resource consent should be granted to the application, subject to the conditions recommended in section 10.

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List of Abbreviations

AEE Assessment of Environmental Effects

BOD Biochemical Oxygen Demand

BOD5 Five Day Biochemical Oxygen Demand

BPO Best Practicable Option

CCC Chronic Criteria Concentration

Cd Cadmium

Cm Centimetres

CMA Coastal Marine Area

CMP Construction Management Plan

Cr Chromium

Cu Copper

DIN Dissolved Inorganic Nitrogen

DO Dissolved Oxygen

DRP Dissolved Reactive Phosphorus

FOW Friends Of The Waiwhetū

GWRC Greater Wellington Regional Council

GWRC (SLUR) Selected Land Use Register

Ha Hectare

HCC Hutt City Council

Hg Mercury

ISQG Interim Sediment Quality Guideline

Km Kilometres

Km2 Kilometres Squared

l/s Litres Per Second

m3/s Cubic Meters Per Second

MCA Multi Criteria Analysis

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MOP Main Outfall Pipeline

NOF National Objectives Framework

NPS-FM The National Policy Statement For Freshwater Management

NPV Net Present Value

NZCPS The New Zealand Coastal Policy Statement

NZFSA New Zealand Foo Safety Authority

OCP Organchlorine Pesticides

OCP Overflow Contingency Plan

Pb Lead

PCB Petone Community Board

PNRP The Proposed Natural Resources Plan

RCP The Regional Coastal Plan

RFP The Regional Freshwater Plan

RPD Redox Potential Discontinuity

RPH Regional Public Health

RPS The Regional Policy Statement

SUP Stand-Up Paddle Boarding

TN Total Nitrogen

TOC Total Organic Carbon

TP Total Phosphorus

TV Trigger Value

UV Ultra-Violet

WCG Waiwhetū Consultation Group

WWL Wellington Water

WWTP Wastewater Treatment Plan

Zn Zinc

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References Barter, P. (2013). Dye dilution and dispersion from a wastewater maintenance bypass discharge into Waiwhetu Stream: Lower Hutt. Report prepared by Cawhron Institute for Hutt City Council. Brodie, J. D. (1958). A note on tidal circulation in Port Nicholson, New Zealand. NZ Journal of Geology and Geophysics 1: 685-702. DHI. (2017). Waiwhetu Outfall Options - Dilution Assessment. Numerical Modelling. Report prepared for Wellington Water by Ben Tuckey. Greater Wellington Regional Council. (2017). Is it safe to swim in the Hutt Valley - recreational water quality monitoring results for the 2016/17 summer. Greater Wellington Regional Council. Heath. (1977). Circulation and hydrology of Welliington Harbour. NZOI Oceanographic Summary. Heath, M., & Greenfield, S. (2016). Benthic cyanobacteria blooms in rivers in the Wellington Region. MWH. (2013). Main Outfall Pipeline Condition Assessment - Shellfish Quality Monitoring Report. Report prepared for Hutt City Council. Robertson, B., & Stevens, L. (2007). Kapiti, Southwest, South Coasts and Wellington Harbour. Risk Assessment and Monitoring Recommendations. Prepared for Greater Wellington Regional Council. Robertson, B., & Stevens, L. (2011). Hutt Estuary: Fine Scale Monitoring 2010/11. Report prepared for Greater Wellington Regional Council. Stevens, C., Brewer, M., Elliot, F., Grant, B., & Rickard, G. (2013). HCC Plume Dispersal Data Report. Prepared by NIWA for Hutt City Council. Stevens, L., & Robertson, B. (2012). Waiwhetu Stream 2012. Broad and Fine Scale Baseline Monitoring in the Tidal Reaches. Prepared for Greater Wellington Regional Council. Stevens, L., & Robertson, B. (2015). Hutt Estuary - Intertidal Macroalgae Monitoring 2- 14/15. Wellington: Report prepared by Wriggle Ltd for Greater Wellington Regional Council. Stevens, L., B, R., & Robertson, B. (2004). Broad scale habitat mapping of sandy beaches and river estuaries - Wellington Harbour and South Coast. Nelson: Report prepared for Greater wellington Regional Council by Cawthron Institute. Stevens, L., Robertson, B., & Robertson, B. (2016). Hutt Estuary 2016: Broad scale habitat mapping. Nelson: Report prepared by Wriggle Ltd for Greater Wellington Regional Council. Taylor, & Kelly. (2001). Inanga spawning habitats in the greater Wellington Region. Report prepared for Greater Wellington Regional Council. Wellington Regional Council. (1996). Living with the river. Hutt River floodplain Management Plan: Phase One Summary Report. Wellington Regional Council.

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Appendix A: Application Drawings

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Appendix B: Application Forms

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Appendix C: Planning Assessment

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Appendix D: Water quality guidelines The water quality guideline values used in this report (Table D-1) generally follow the approach outlined by Milne & Morar (2017). In most instances the guideline values used are the ANZECC (2000) ‘default’ trigger values for lowland aquatic ecosystems or (chronic) toxicity. The trigger values for lowland aquatic ecosystems are intended to be compared against the median values from independent samples at a site. Table D-1: Water quality guideline values

Variable Guideline value Reference Water temperature (oC) <19 Quinn and Hickey (1990) & Hay et al (2007) Dissolved oxygen (%sat) >80 RMA 1991 Third Schedule pH 6.5-9.0 ANZECC (1992) Visual clarity (m) >1.6 MfE (1994) – guideline for recreation Turbidity (NTU) annual median <5.6 ANZECC (2000) lowland TV Nitrate-nitrogen (mg/L) annual median <0.444 ANZECC (2000) lowland TV Nitrate-nitrogen (mg/L) annual median <6.9 NPS-FM national bottom line ≤ 0.05 mg/L (99% protection) >0.05 and ≤ 0.4 mg/L (95% protection) >0.4 and ≤ 2.2 mg/L NPS-Freshwater management (2014) (80% protection) 2.2 mg/L (National Bottom Line) Ammoniacal nitrogen max ≤ 0.90 (mg/L) (95% protection) max ≤ 1.43 (90% protection) ANZECC (2000) freshwater toxicity TV max ≤ 2.3 (80% protection) 30-day average < 2.7 US EPA (2013) - Freshwater 4-day average ≤ 6.8 Dissolved inorganic annual median <0.465 ANZECC (2000) by addition of the nitrate, nitrite & ammonia TVs nitrogen (mg/L) Total nitrogen (mg/L) annual median <0.614 ANZECC (2000) lowland TV Dissolved reactive annual median <0.010 ANZECC (2000) lowland TV phosphorus (mg/L) Total phosphorus (mg/L) annual median <0.033 ANZECC (2000) lowland TV E. coli. (cfu/100 ml) 95th percentile <540 PNRP Primary contact recreation (rivers and estuaries) E. coli. (cfu/100 ml) annual median <1000 PNRP secondary contact recreation (rivers and estuaries) Enterococci (cfu/100ml) 95Th percentile ≤ 500 PNRP Primary contact recreation (coastal waters) Dissolved arsenic (mg/L) annual median <0.0013 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved boron (mg/L) annual median <0.37 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved cadmium (mg/L) annual median <0.0002 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved copper (mg/L) annual median <0.0014 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved chromium (mg/L) annual median< 0.001 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved lead (mg/L) annual median <0.0034 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved nickel (mg/L) annual median <0.011 ANZECC (2000) freshwater toxicity TV (95% protection level) Dissolved zinc (mg/L) annual median <0.008 ANZECC (2000) freshwater toxicity TV (95% protection level)

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Appendix E: Dye release studies

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Appendix F: Dilution Assessment – Numerical Model

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Appendix G: Assessment of Effects on Natural Character and Visual Amenity

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Appendix H: Recreation Effects Assessment

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Appendix I: Public Consultation Survey

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