Assessment of Ecological Effects on the Receiving Environment from the Discharge of Treated Wastewater from an Army Bay WWTP

Assessment of Ecological Effects on the receiving environment from the discharge of treated wastewater from an Army Bay WWTP

(Photo Shane Kelly)

Mark James1, Mike Stewart2, Chris Dada2, Shane Kelly3 and Sara Jamieson4

Prepared for Watercare Services Ltd

November 2018

1Mark James 2 Streamlined Environmental Ltd Aquatic Environmental Sciences Ltd 3 Coast and Catchment Ltd PO Box 328 4 Tracks Ltd Whangamata 3643 Email: [email protected] Cell: 021 0538379

Executive Summary

Watercare is preparing an Assessment of Environmental Effects (AEE) for new consents for the continued operation of a wastewater treatment plant and discharge to service growth in the Hibiscus Coast/ Orewa/Whangaparaoa area. The consent application process requires an assessment of the potential effects on the receiving environments and ecological values.

The report summarises the status of the existing environment in the Whangaparaoa Passage and wider environment based on existing and new information collected as part of the consent application process. The report then provides an assessment of the potential effects of the existing and then the future discharges on the ecological values if a discharge to the existing discharge point (~1.3 km into the Whangaparaoa Passage in 25 m of water) is the final option. Future scenarios considered for modelling were a small increase in population in the “Short- term” through to ~2031 (to 116,000 PE), an increase in population serviced from a combined WWTP to 160,000 PE in the “Medium-term” (~2041) and up to 192,000 PE in the “Long-term” (~2053). Note that slightly lower populations are now being used for each scenario in the final AEE based on updated growth numbers provided and thus the risk assessment is conservative. A number of treatment options were also considered along with timeframes for the infrastructure development of the existing WWTP was at Army Bay and the discharge into the Whangaparaoa Passage.

The existing environment off the Whangaparaoa Peninsula can be summarised as:

 A coastal region that is dynamic and well flushed, supports a diverse and productive intertidal and subtidal ecosystem and is valued for its recreational and cultural values, including kai moana. The region is valued for its terrestrial landforms of cliffs and shore platforms and ecologically for its diversity of biota along the shoreline, inter-tidal and sub-tidal habitats and as feeding grounds for a range of fish and bird species;  Water quality in the current discharge has met the consent conditions over the last 5 years (the period assessed) and between 2012 and 2018 levels of nutrients, biological oxygen demand (BOD) and total suspended solids (TSS) have been decreasing. A UV treatment system was installed in 2006 and has significantly improved the microbial quality of the discharge;  The Whangaparaoa Passage, location of the current discharge point, has relatively high currents with strongest flows around the headlands and tend to be strongest on the ebb tide. Flows are to the north-east into the Hauraki Gulf on the ebb tide and to the south-west on a flood tide;

 Water quality in the Whangaparaoa Passage and nearby sites is high quality and considered to be “excellent” according to the Auckland Council classification. There is no indication that the existing discharge is impacting on water or microbial quality;  Monitoring of microbial indicators in the water and shellfish in the vicinity of the outfall show no effects of the present discharge and are below MFE guidelines for shellfish gathering with at least 92% of the shellfish samples meeting the FSANZ (Australia and New Zealand Food Standards) guideline. Occasionally microbial levels increase during rainfall events but this has not been attributed to the discharge;  There is a relatively diverse benthic community throughout the Whangaparaoa Passage and area around the outer Whangaparaoa Peninsula, diversity and habitat complexity was lower towards the north but increased towards the coastline of the Whangaparaoa Peninsula and Tiritiri Matangi Island. Horse mussels and sponges are abundant and widespread around the margins, scallops are patchily distributed with diverse communities of polychaete worms and crustaceans throughout. The area has high infaunal values but they tend to be lower towards the north where the substrate is muddier and has less shell hash;  Total organic carbon levels were surprisingly high in places but are within levels recorded at other high diversity sites nearby. A microalgae mat well to the north-west of the outfall was found in an earlier survey in the later part of 2017 but was not present when the area was resurveyed in April 2018 and is unlikely to be attributed to the present discharge form the Army Bay WWTP because of the distance from the discharge point;  Overall there is no evidence of effects on water quality or the benthic community from the present WWTP discharge;  The diverse invertebrate biota is reflected in a relatively high valued fisheries and juvenile habitat in the region. The main fish caught is snapper and kahawai. There is likely to be limited fishing in close to shore because of the NZ Defence Force activities in the area. Tiritiri Matangi is highly regarded for its cultural values;  Following creation of a sanctuary and predator control the area around the headland of the Peninsula bird numbers have increased and the area supports at least 14 threatened species; and  A number of mammals are observed in the area including common dolphin and Bryde’s whales and other whale species that are in transit through the area at times.

Effects of future increases to service an increasing population from an Army Bay WWTP

The effects of future growth on a discharge into the Whangaparaoa Passage are as follows:

 Modelling has shown that even when reaching the full population growth predicted for 2053 there will be negligible and undetectable change in the salinity of the receiving waters;  A staged approach to upgrading the plant has been proposed based on the following concept. Following the Stage 1 upgrade 40% of the plant design capacity will be provided using MBR technology which will result in a slight reduction in the discharged concentration for total nitrogen (TN) and TSS. The Stage 2 upgrade will increase the proportion of flow treated using the MBR technology, providing a further reduction in the TSS and further upgrades are proposed which will result in the discharged TN concentration being reduced to 10 mg N/L. Following the Stage 3 upgrade, the full plant will have been converted to MBR technology (or appropriate alternative providing the same effluent quality).  With the proposed staged improved treatment, the annual median discharge for TN (nitrogen is the most important nutrient controlling phytoplankton growth in these environments) is predicted to reduce from the existing 14 mg/L to 12 mg/L and eventually to 10 mg/L over the three proposed upgrade steps and the concentrations for TSS will also improve. The staged reduction reflects continued operation of the existing WWTP alongside new technologies as population growth increases.  Because of the relatively strong currents which will result in rapid dilution (>500x within 100 m of the outfall for over 90% of the time), the water quality of the receiving environment, even when fully developed and with increased nitrogen loads, will not change, will continue to be “excellent” and will not increase the risk of algal blooms;  Even with the minimum dilution factor (70x) at the outfall, levels of metals and emerging contaminants will be reduced to below guidelines and levels known to be of concern;  A quantitative microbial risk assessment (QMRA) has been carried out for enterovirus, adenovirus, and norovirus and shows: o Microbial levels will increase with increasing population and will be higher during winter; o Microbial levels are greatest closest to the discharge point, will rapidly reduce away from the discharge point and decrease significantly by the time the water moves towards Huroa Point and Whangaparaoa Head. Most of the dispersal is likely to be the north-east or south-west;

o For recreational use, modeling has shown the microbial levels would be low and always below a “no observable effects level” of 1% for a 100-fold (2 log) removal efficacy and very low for a 3 log or 1,000x reduction at the WWTP for the three viruses assessed at all sites; o For shellfish gathering microbial levels would be below the “no observable effects level” threshold of 3% for a 100-fold reduction and low and always below thresholds for a 3 log reduction or 1,000x at all sites. Four log reduction would reduce the risk to practically zero; and o It is recommended that at least 1,000-fold (i.e. 3 Log) reduction in viral concentrations at the Army Bay WWTP, prior to discharge, should be sufficient even during the worst-case maximum discharge scenario (192,000 PE), to reduce health risks to an acceptable level for contact recreation and consumption of raw shellfish harvested at all the selected sites in the receiving environment.  There is no evidence that benthic aquatic habitats and communities are adversely affected at present and any effects of the future discharge would only be in the immediate vicinity of the discharge pipe, if they did occur, and would be within the bounds of the natural variability in the area; and  Birds and fish in the coastal environment are highly mobile and would not be adversely affected.

 The overall conclusion is that because of the rapid dilution and dispersion at this site combined with an improved level of treatment there will not be any detectable or ecologically significant change in the receiving environment including trophic state, risk of algal blooms, and there would be no effects on fish resources, mammals or birds. The planned 3 log removal for pathogens will microbial standards for contact recreation and shellfish gathering are met.

Contents

Executive Summary ...... 2 1. INTRODUCTION ...... 8 1.1 Background to Watercare project ...... 8 2. SCOPE OF THIS REPORT ...... 11 3. DESCRIPTION OF THE EXISTING AND FUTURE WWTPS...... 11 3.1 Existing WWTP discharge quality ...... 11 3.1.1 WWTP loads ...... 12 3.1.2 Temporal trend analysis ...... 13 3.1.3 Heavy metals...... 15 3.1.4 Metal/metalloid temporal trends ...... 16 3.1.5 Microbial ...... 16 4. DESCRIPTION OF EXISTING ENVIRONMENT ...... 19 4.1. Physical and ecological setting ...... 19 4.2 Hydrodynamics...... 22 4.2.1 Winds ...... 22 4.2.2 Currents ...... 23 4.3 Water and Sediment Quality ...... 29 4.3.1 Water quality ...... 29 4.3.2 Sediment quality ...... 32 4.4 Microbial characteristics ...... 34 4.5 Contaminants of emerging concern ...... 35 4.6 Benthic habitat and communities ...... 38 4.6.1 Sediments ...... 38 4.6.2 Intertidal habitats ...... 42 4.6.3 Subtidal habitats ...... 43 4.6.4 Shellfish surveys ...... 48 4.7 Birds...... 49 4.8 Fish ...... 50 4.8.1 Commercial fishing ...... 51 4.8.2 Recreational and customary fishing ...... 53 4.9 Mammals ...... 54 5. ASSESSMENT OF EFFECTS ...... 57 5.1 Hydrodynamics...... 59

5.2 Coastal water quality ...... 60 5.2.1. Dilution of nutrients and other contaminants ...... 60 5.2.2 Nutrients and phytoplankton biomass ...... 61 5.2.3 Risk of emerging contaminants in the water column ...... 64 5.3 Effects of microbial contaminants ...... 65 5.3.2 Health risks due to contact recreation at the exposure sites ...... 69 5.3.3 Health risks due to consumption of raw shell fish harvested from exposure sites ...... 70 5.4 Effects on benthic habitats and animal communities ...... 71 5.4.1 Benthic effects of the proposed changes to discharge loads ...... 71 5.5 Effects on fish, mammals and birdlife ...... 75 5.5.1 Effects on fish and mammals...... 75 5.5.2 Bird life ...... 77 5.6 Summary for each increase in population scenario ...... 77 6. ACKNOWLEDGEMENTS ...... 79 7. REFERENCES: ...... 80 Appendix 1. Pivot tables for discharge water quality ...... 89

1. INTRODUCTION

1.1 Background to Watercare project

The Army Bay WWTP is Watercare’s third largest WWTP and services the Hibiscus Coast, Whangaparoa and Orewa areas. The existing connected population of approximately 59,000 is forecast to increase to 97,000 by ~2031, 136,000 by ~2041 and 188,500 by ~2053. Note that the populations used in dilution modelling by DHI were slightly higher than these and are thus conservative.

Army Bay WWTP’s discharge consents (Air 23677 and Water 42146) are due to expire on 31 December 2021. As a result of the Auckland Unitary Plan process, there is significant development anticipated in the Orewa, Silverdale and Dairy Flat area. This area of Auckland is expected to experience significant growth over the next 30 years specifically in Wainui, around the special housing area that was zoned as part of the Unitary Plan process. Significant new wastewater infrastructure will be required to service the planned growth in the area, and various options for the WWTP and discharge are being considered.

The existing Army Bay WWTP batch reactors have a capacity of approximately 60,000 people. The current Council forecast is projecting population growth in the Army Bay catchment to reach the reactor capacity in three years. Expansion of the WWTP is pending the granting of a new discharge consent. Treatment option assessments will be required as part of the consent discharge application.

As the biological capacity is expected to be exceeded in the near future, and some critical process units require replacement due to condition, it has been determined to advance the consenting programme now (rather than in 2021) to ensure any investment in the WWTP is aligned to any future consent conditions.

The current consent allows a daily average discharge of 370L/s but the existing WWTP outfall currently limits the flow through the plant to approximately 300L/s as it is under-sized. Current peak inflows can be as high as 700L/s. The difference is balanced in decant ponds at the WWTP, or preferentially spilt to the environment from the wastewater network. Consent for a larger outfall pipeline and diffuser discharging at the current consented location was granted in 2016. Construction is currently underway and will provide outflow capacity of 1,400L/s allowing the current consent daily average discharge level to be achieved.

As part of this application, an assessment of alternatives has been undertaken to determine the Best Practicable Option (BPO) for wastewater servicing up to a capacity of 1,964 L/s, including the location of the WWTP and discharge method and location. The assessment

included technical, environmental, and financial implications analysis. Following a full BPO assessment the site of the existing Army Bay WWTP is considered to be the preferred option for the treatment but will require significant upgrades over time to accommodate the expected growth levels and to provide an improved discharge quality.

A number of treatment options were considered, including the expansion of the existing sequential batch reactors (SBR); expansion of the SBRs with provision for tertiary filtration using ultrafiltration; and the use of membrane bioreactor technology. Following an assessment of the options, a staged approach to upgrading the plant has been proposed based on the following concept:

 The Stage 1 upgrade will be implemented within five years of the new consent being granted and will increase the design capacity of the plant to 100,000 population equivalents (PE). The additional capacity provided at Stage 1 will be implemented using Membrane Bioreactor (MBR) technology which will operate in parallel with the existing plant. This will result in a slight reduction in the discharged concentration for TN and TSS.  The Stage 2 upgrade will be implemented as the serviced population approaches 100,000, i.e. the design capacity of the Stage 1 upgrade. This upgrade will increase the proportion of flow treated using the MBR technology, providing a further reduction in the TSS concentration discharged. It is also proposed to retrofit the existing SBR reactors to achieve a lower TN concentration. This will result in the TN concentration being reduced to 10 mg N/L.  The Stage 3 upgrade will be implemented as the serviced population approaches 140,000 and will result in the full plant being converted to MBR technology (or appropriate alternative providing the same effluent quality). A concept design outlining the upgraded treatment plant footprint, which identifies the potential land requirements, has been provided by CH2M Beca Ltd and has been considered separately to this report.

The existing (and new consented outfall) is shown in Figure 1-1 and extends 1.3 km into the marine coastal area in approximately 25 m water depth.

Figure 1-1. Map of Whangaparaoa Peninsula showing point of existing and proposed future Army Bay discharge.

As part of the process of developing a new consent application Watercare has to prepare an Assessment of Environmental Effects (AEE). Watercare has carried out strategic reviews of these and associated WWTPs in the sub-region and are considering the best practical option (BPO) to cater for projected growth. A number of discharge options were considered:

1. A discharge through a pipe into the Whangaparaoa Passage at the existing site or alternatively sites to the north of the Whangaparaoa Peninsula; 2. Transfer of treated wastewater through to a discharge pipe out into the Tasman Sea; 3. Reuse for potable water supply and other potential options; 4. Land disposal: and 5. Injection to a deep aquifer.

The final BPO, which will form the consent application, and was the main focus of this report is for a discharge through a pipe at the existing discharge site into the Whangaparaoa Passage.

Some information on hydrodynamics and other features is available from studies for the original outfall and studies focused on a replacement pipeline were carried out as part of the AEE preparation (Tonkin & Taylor 2015, 2016). These studies include:

 Various reports on monitoring the discharge and receiving environment by Allan Aspell & Associates Ltd 1983-1986, and Bioresearches 1988-1999;  A review of ecological effects of the existing discharge (Bioresearches 1999);  Recent monitoring results for receiving waters (e.g. Diffuse Sources 2012);  Hydrodynamics and dispersion modelling for a proposed new pipeline (ASR 2012, Tonkin & Taylor 2013);

 A public health risk assessment in 2011 (Palliser 2011);  Assessments of the effects of a new pipeline on Terrestrial Ecosystems (Tonkin & Taylor 2016), and Marine Ecology (Tonkin & Taylor 2015); and  There is also a large body of information available from more general studies of hydrodynamics, benthic habitat and biota of the wider Hauraki Gulf.

The main ecological values that need to be addressed in the assessment of ecological effects are:

 Hydrodynamics;

 Water quality;

 Microbial Risk Assessment;

 Plankton communities;

 Benthic habitat and communities; and

 Fish, mammal and bird populations.

2. SCOPE OF THIS REPORT

This report provides an overall assessment of the potential ecological effects of the discharge of treated wastewater from the Army Bay WWTP to the Whangaparaoa Passage.

The ecological assessment provides:

 A summary of the WWTP operations and discharge (Section 3);  A summary of the ecological resources of the Whangaparaoa area based on existing information and new work undertaken as part of this project (Section 4); and  A description of the effects of the discharge of treated wastewater on the receiving environments (Section 5).

3. DESCRIPTION OF THE EXISTING WWTP

3.1 Existing WWTP discharge quality

Army Bay WWTP discharge data (discharge volume, biochemical oxygen demand (BOD), enterococci (Ent), faecal coliforms (FC), ammoniacal-nitrogen (NH4-N) and TSS were

compared against relevant consent conditions for the years 2013/14, 2014/15, 2015/16 and 2016/17.1 These years provide a good indication of the existing state of discharge quality.

Compliance limits are set as: maximum over month-to-date values (discharge volume; condition 13); 92nd percentile over 3 months (BOD, Ent, FC, TSS; condition 24); and median over 3 months (NH4-N, BOD, Ent, FC, TSS; condition 24) (Table 3-1).

Between 2013 and 2017, Army Bay WWTP was fully compliant with consent conditions.

Table 3-1. Summary of compliance data for Army Bay WWTP from 2013 to 2017

Maximum annual value Parameter Unit Compliance limit 2013/14 2014/15 2015/16 2016/17

Maximum over MTD values Discharge volume m3 <= 32,147 23,719 20,615 18,622 26,367

92nd Percentile over 3 months BOD mg/L <=35 11.2 4.3 4.1 8.9 Ent cfu/100mL <=1,000 38.1 48.7 14.6 150.0 FC cfu/100mL <=10,000 261 156 96 615 TSS mg/L <=75 31 19 15 21

Median over 3 months

NH4-N mg/L <=15 1.7 1.5 2.4 3.8 BOD mg/L <=20 7.2 3.1 2.6 4.5 Ent cfu/100mL <=100 6.6 1.6 3.3 3.3 FC cfu/100mL <=1,000 50 21 7 20 TSS mg/L <=35 13 10 7 12

3.1.1 WWTP loads

Pivot tables were used to calculate monthly total discharge volume and monthly average concentration. These pivot tables are presented in Appendix 1. Monthly discharge loads for

BOD, TSS, TN, NH4-N, total phosphorus (TP) and dissolved reactive phosphorus (DRP) were calculated by multiplying average concentration (mg/L) for each month by the total monthly discharge (m3) and expressed as Tonnes (t). Annual loads were calculated on a July to June year. The 2017/18 year has only 7 data points (July 2017 to January 2018) and these loads

1 Watercare compliance reports, 2014, 2015, 2016, 2017.

were pro-rata load corrected (multiplying by 12/7) to provide an annual load. Annual loads from July 2012 to January 2018 are summarised in Table 3-2.

Table 3-2. Army Bay WWTP annual loads (t). *7 months of data only. Corrected by multiplying by 12/7

Year range BOD TSS TP DRP TN NH4-N July 2012 to June 2013 10.66 24.00 24.37 21.99 61.98 8.41 July 2013 to June 2014 12.58 29.46 19.87 17.88 51.72 4.51 July 2014 to June 2015 7.09 21.08 19.14 17.43 46.51 5.38 July 2015 to June 2016 6.93 20.14 19.28 17.76 45.99 5.74 July 2016 to June 2017 11.90 30.81 19.65 17.49 52.95 11.57 July 2017 to Jan 2018* 8.65 18.53 20.86 19.37 54.41 4.81

3.1.2 Temporal trend analysis

A temporal trend analysis of all parameters routinely measured from the wastewater discharge was undertaken to provide a longer term view of all potential contaminants discharged, which will assist in informing setting of future consent limits.

Army Bay WWTP discharge data from 5/6/2012 to 20/02/2018 were supplied in Excel format by Watercare Services Ltd. This consisted of weekly nutrient TN, NH4-N, total phosphorus (TP) and DRP, microbial (Ent and FC), and other parameters BOD, TSS ( called NFR in compliance reports), pH, Dissolved Oxygen (DO) and conductivity) data, plus daily discharge flow date.

Trends for all discharge data were established using a Mann-Kendall trend test (Time Trends, NIWA, 2018). A Mann-Kendall trend test was considered more appropriate for most data than using seasonally adjusted data (Seasonal Kendall test), used commonly for river quality trends, as the majority of data did not exhibit obvious seasonal bias. However, where there was apparent seasonal bias to data, a Seasonal Kendall test was also undertaken. Seasons used in this analysis were: Dec – Feb; Mar – May; Jun – Aug; and Sep – Nov.

Non-seasonally adjusted temporal trends are summarised in Table 3-3. Statistically significant trends were determined with p<0.05. The median annual Sen slope is the direction and rate of change. These were were normalised by dividing through by the raw data median to give the relative SKSE (RSKSE). We have followed Scarsbrook (2006) in denoting a ‘meaningful’ trend as one for which the RSKSE is statistically significant (p<0.05) and has an absolute magnitude > 1% per year.

All nutrient (TN, NH4-N, TP, DRP) plus BOD and TSS concentrations in Army Bay WWTP discharge have decreased between 2012 and 2018. However, only TN has a significant and

meaningful decrease (-0.45 mg/L/year). pH, DO, conductivity, Ent and FC have not changed over this time. There has been a significant and meaningful increase in discharge flow (131 m3/d/year) over this time period.

Table 3-3. Non-seasonally adjusted temporal trends (2012-2018) for Army Bay WWTP discharge

Parameter Median P Median annual Sen RSKSE Trend value slope BOD 2.0 0.126 -0.07 -3.45  TSS 5.2 0.083 -0.21 -4.00  TN 14.0 0.000 -0.45 -3.24 

NH4-N 1.3 0.208 -0.02 -1.62  TP 5.8 0.090 -0.17 -2.86  DRP 5.3 0.096 -0.15 -2.83  pH 6.8 0.227 0.00 0.00  DO 3.5 0.747 0.00 0.00  Conductivity 400 0.133 0.00 0.00  Ent 1.6 0.450 0.00 0.00  FC 6.6 0.713 0.00 0.00  Discharge 9291 0.000 131 1.41  volume * Statistically significant trends (p<0.05) are highlighted red (increasing) and blue decreasing. Statistically non- significant trends are not highlighted.  = No trend

Seasonally adjusted temporal trend analysis of selected parameters was consistent with the non-seasonally adjusted trends (Table 3-4), suggesting that seasonal bias has minimal effect on the trend analysis for these data. The possible exception is BOD, for which inclusion of seasonal bias in the trend analysis provide borderline significant (p 0.052) decreasing trends.

Table 3-4. Seasonally adjusted temporal trends (2012-2018) for Army Bay WWTP discharge

Parameter Median value P Median annual Sen slope RSKSE Trend BOD 2.0 0.052 -0.09 -4.35  TSS 5.2 0.114 -0.19 -3.62  TN 14.0 0.000 -0.41 -2.93 

NH4-N 1.3 0.126 -0.02 -1.69 

TP 5.8 0.137 -0.19 -3.21  DRP 5.3 0.178 -0.16 -3.00  DO 3.5 0.826 0.00 0.00  Discharge volume 9291 0.000 172 1.85 

3.1.3 Heavy metals

Heavy metals – cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), nickel (Ni) and zinc (Zn) – plus the metalloid arsenic (As) have been measured in Army Bay WWTP discharge between July 2012 and January 2018 (total 12 samples). Total metals/metalloids and dissolved metals/metalloids have been measured, however we present only the total metal/metalloid data as this is directly comparable to other WWTPs in Auckland, and ANZECC marine trigger values (ANZECC 2000).

Median metal/metalloid concentrations in Army Bay WWTP discharge are presented in Table 3-5, with comparison to Omaha (James et al, 2016a), Clarks Beach and Waiuku WWTP (James et al, 2016b) data (single samples). Army Bay WWTP has similar concentrations of metals/metalloids to the other WWTPs, with notable exceptions being elevated Cr, Pb, and Zn and reduced Ni.

Cu and Zn concentrations consistently exceeded the corresponding ANZECC 95% marine trigger value (Figure 3-1), with median Cu around 2 times the value and Zn around 3 times the value. It should be noted that this is prior to any dilution in the receiving environment and the ANZECC guidelines refer to the receiving environment.

Percentage of ANZECC 95% trigger value

400% As 350% 300% Cd 250% Cr 200% 150% Cu 100% 50% Hg 0% Ni Pb

1/04/2014 1/10/2015 1/10/2012 1/01/2013 1/04/2013 1/07/2013 1/10/2013 1/01/2014 1/07/2014 1/10/2014 1/01/2015 1/04/2015 1/07/2015 1/01/2016 1/04/2016 1/07/2016 1/10/2016 1/01/2017 1/04/2017 1/07/2017 1/10/2017 1/01/2018 1/07/2012

Figure 3-1. Comparison of Army Bay metal/metalloid discharge concentrations with ANZECC 95% marine trigger value

Table 3-5. Comparison of median Army Bay WWTP discharge metal/metalloid concentrations with Omaha, Clarks Beach and Waiuku WWTPs and ANZECC 95% marine trigger value (ANZECC 2000).

Concentration (µg/L)1 ANZECC 95% Total marine metal/metalloid Army Bay Omaha Clarks Beach Waiuku trigger value As2 1.1 2.5 2.3 1.7 4.5 Cd 0.05 <0.05 <0.05 <0.05 5.5 Cr3 1.2 0.41 0.66 <0.5 4.4 Cu 2.4 2.5 6.4 1.6 1.3 Hg4 0.05 Not measured Not measured Not measured 0.1 Pb 1.4 <0.1 0.14 <0.1 70 Ni 0.18 1.5 2.3 0.74 4.4 Zn 40.5 1.1 15 6.1 15 1 Median (n=12) from July 2012 to January 2018 for Army Bay WWTP. Single measurements for Omaha, Clarks Beach and Waiuku WWTPs.

2 Insufficient data to derive a reliable trigger value. An environmental concern level of 2.3 mg/L has been established for As(III) and 4.5 mg/L for As(V) in marine waters. This can be adopted as a low reliability trigger value, to be used only as an indicative working level. Note: As (III) is the more toxic form but is less common in seawater. Therefore the value for As(V) has been used.

3 Based on Cr(VI), the more toxic valency state for chromium.

4 Inorganic Hg.

3.1.4 Metal/metalloid temporal trends

Metal/metalloid temporal trends were assessed using a Mann-Kendall trend test with Time Trends, as for nutrients. Over the time period of 2012-2018 there were no significant increases or decreases in metal/metalloid concentrations (Table 3-6) and levels were below ANZECC guidelines (Table 3-7).

3.1.5 Microbial

Treated wastewater effluent is often associated with pathogens that potentially survive the treatment processes. Because the tests for pathogens are time-consuming and expensive, it is not practical to implement monitoring on a routine basis. Faecal indicator bacteria (FIB) are used instead to assess the quality of treated effluent. Dada (2018) collated existing information

on microbial contaminants in the existing discharge and wider receiving environment and provides a description of the existing environment in terms of microbiological contaminants.

Table 3-6. Non-seasonally adjusted total metal temporal trends (2012-2018) for Army Bay WWTP discharge

Metal/metalloid Median value P Median annual Sen slope RSKSE Trend Total Arsenic 1.09 0.304 -0.05 -4.79  Total Cadmium 0.05 0.203 0.00 0.00  Total Chromium 1.20 0.835 -0.01 -0.67  Total Copper 2.40 0.301 -0.14 -5.83  Total Mercury 0.05 0.203 0.00 0.00  Total Nickel 1.45 0.334 0.07 4.62  Total Lead 0.18 0.071 -0.02 -13.71  Total Zinc 40.50 0.370 -1.73 -4.26 

An analysis of monitoring records from 2013-2018 (Dada 2018) show that the effluent median FC concentration in any 3-month period did not exceed the consent limits of 1,000 CFU/100 mL, neither was the 92%-ile concentration of 10,000 CFU/100 mL exceeded. Similarly, the effluent median Ent concentration in any 12-month period did not exceed 100 CFU/100 mL and neither was the 92%-ile concentration of 1,000 CFU/100 mL exceeded.

Virus concentrations were not required in the consent monitoring schedule for Army Bay WWTP, however additional monitoring of influent and effluent has been undertaken by Watercare as part of the QMRA process.

Based on extensive long-term monitoring data, typical influent viral concentrations in the Auckland region range from 0.04 to 59,000 genomes per litre during non-outbreak periods to as high as 107 genomes per litre of influent during community-wide outbreaks.

Monitoring data based on sampling of untreated influents and treated effluents from the Army Bay WWTP (April 2018 – Table 3-7) indicates that viral concentrations are within the range reported for other WWTPs in the region. Also, up to 2.5 Log reduction in virus concentrations currently occurs following treatment of influent at Army Bay WWTP.

Table 3-7. Virus concentrations of Army Bay WWTP wastewater (April 2018)

Norovirus Sample Norovirus GI GII Adenovirus Enterovirus

Influent 1 7,600 2,800,000 510,000 110,000

Influent 2 7,200 3,600,000 530,000 100,000

Influent 3 5,200 2,800,000 450,000 37,000

Av. Influent Concentration 6,667 3,066,667 496,667 82,333

Effluent 1 125 33,000 500 500

Effluent 2 500 27,000 500 125

Effluent 3 500 30,000 5,300 125

Av. Effluent Concentration 375 30,000 2,100 250

Ave. LogVirus removals 1.2 2.0 2.4 2.5

We note however that the reported reductions following treatment could be much higher than is currently estimated as it is accepted that the polymerase chain reaction (PCR) based approach to molecular marker detection tend to erroneously detect both genomes of live viruses (i.e. virus particles that escape the WWTP treatment process) and dead viruses (i.e. virus particles that are effectively destroyed as a result of WWTP treatment process).

4. DESCRIPTION OF EXISTING ENVIRONMENT

4.1. Physical and ecological setting

The existing Army Bay WWTP is located within the Rodney Ecological District. This Ecological District contains a mixture of low forested ranges, volcanic cones, pasture, alluvial plains, and extensive areas of estuarine and duneland habitats. Coastal habitats such as intertidal flats, mānawa (mangrove; Avicennia marina subsp. australasica) forest, dunelands, salt marshes and terrestrial margins provide extensive and rich feeding grounds for a variety of bird species including oceanic species, waders, marsh birds and forest birds (Budd, 2018).

Wildland Consultants (Budd 2018) provide a summary of the vegetation on the Whangaparaoa Peninsula, which historically would have been dominated by kauri (Agathis australis) and podocarp-broadleaved forest (WF11) with pōhutukawa (Metrosideros excelsa) treeland/flaxland/rockland (CL1) on the coastal fringe (Singers et al. 2017). Areas of gumland (WL1) are also likely to have occurred between Army Bay and Okoromai Bay and around Te Haruhi Bay.

Significant areas reported by Budd (2018) on the outer Whangaparaoa headland (within which the existing WWTP is located) are as follows:

 Remnant coastal forest has been enhanced by restoration plantings within Shakespear Open Sanctuary;  Large scrubland areas provide habitat for ‘At Risk’ lizard species such as moko skink (Oligosoma moco), ornate skink (O. ornata), forest gecko (Mokopirirakau granulatus) and elegant gecko (Naultinus elegans elegans) (Auckland Council 2018) and North Island brown kiwi (Apteryx mantelli; ‘At Risk-Declining’) ;  Much of the vegetation within the Defence Force land on the northern side of the headland comprises mānuka/kānuka scrub in an early successional stage (Benham et al. 1998). Pest plant control is ongoing throughout this area (Wildland Consultants 2017); and  A small patch of high value forest is present near the tip of the Peninsula, featuring kauri, pōhutukawa, pūriri (Vitex lucens), and kowhai (Sophora microphylla) (Benham et al. 1998, Young et al. 1998). The threatened plant species Pimelea orthia (Threatened-Nationally Critical, de Lange et al. 2013) is also present in this area (Wesley & Young 2014).

The coastal section of the existing pipeline extends approximately 1,300 m out into the Whangaparaoa Passage between Huaroa Point and Whangaparaoa Head, with the outfall position in a water depth of approximately 25 m. The land immediately surrounding the existing

outfall is occupied by the New Zealand Defence Force, which restricts public access to the coast. Direct access to the coast on the south-eastern to southern part of the peninsula is also limited due to the presence of Shakespear Regional Park, which limits vehicle access. In addition, an approximately 68 ha “no-fishing or anchoring” area is located off the south-eastern tip the Peninsula. As a result, the tip of Whangaparaoa Peninsula remains largely undeveloped with little coastal modification.

Significant ecological areas

Under the Auckland Unitary Plan (AUP) Operative in part from 15 November 2016, Significant Ecological Areas (SEAs) have been identified for terrestrial areas, and parts of the coastal marine area in the Auckland region. Terrestrial SEAs are defined as “identified areas of significant indigenous vegetation or significant habitats of indigenous fauna located either on land or in freshwater environments”. Marine SEAs are defined as “identified areas of significant indigenous vegetation or significant habitats of indigenous fauna located in the coastal marine area” (Auckland Council 2018).

The cliffs and intertidal platforms of the rocky coastline at the end of the Whangaparaoa Peninsula are made up of sedimentary Waitemata Group rocks that were deposited during the Miocene and this area is classified as a Marine SEA (SEAM1-67) in the AUP (Budd 2018). This SEA includes saltmarsh, intertidal and sub-tidal habitats that provide important feeding, roosting and nesting grounds for birds, and the rocky shores support large populations of reef- fish, kina, other invertebrates and a rich variety of marine-algae. The sediments of the bays on the south of the Peninsula provide habitat for extensive beds of molluscs and in the north- eastern corner of Okoromai Bay grade into a saltmarsh, which is a significant migration pathway for native freshwater fishes. The extensive intertidal feeding habitat for wading birds around the Peninsula, also see it classified as a “significant wading bird area” (SEA-M1w67) (Auckland Council 2018).

In 2010 a predator proof fence was constructed from Army Bay to Okoromai Bay in order to create the publicly accessible Shakespear Open Sanctuary. The remainder of the headland, which is also protected by the predator proof fence, is owned by the New Zealand Defence Force. With the exception of mice, all pest mammals have now been removed from the land area east of the fence. Ongoing trapping and monitoring is carried out to prevent the reinvasion of mammalian pests to the site. All areas of indigenous vegetation within the Sanctuary are designated as Significant Ecological Areas in the AUP (Figure 4-1). These terrestrial SEAs provide habitat for several threatened species and offer important migration pathways for indigenous species (Auckland Council 2018).

Together the cliffs and shore platform in the northern part of the Whangaparaoa Peninsula have been classified as an Outstanding Natural Feature (ONF) in the AUP and are one of several sites on the Whangaparaoa Peninsula that display a regionally important three- dimensional exposure of folds and faults in these rocks. The shore platform is extensive and is considered to be a landform of regional geological importance. Whangaparaoa Head has two significant geological features, a vertically tilted strata and an area of Parnell Grit with huge blocks of displaced basalt forming the point east of Army Bay. The Huaroa Point shore platform in Army Bay is also classified as an ONF due to the extensive intertidal platform cut across dipping Waitemata sandstones and siltstones (Auckland Council 2018).

The area encompassed by Shakespear Open Sanctuary is also considered by the AUP to contain Outstanding Natural Landscapes (ONL) due to the combination of strongly defined patterns of the peninsula headland landform and remnant forest intermixed with pasture, which then descends to wetlands and gently shelving coastal margins. These strongly expressed patterns and interaction between the land and sea have led to the ONL classification. This landscape and the experience for visitors have also resulted in a High Natural Character (HNC) classification under the AUP (Auckland Council 2018).

Watercare has engaged Wildlands to undertake a targeted SEA assessment in the area around the WWTP based on the proposed concept design footprint and as a result, this has not been discussed in further detail here.

(Figure 4-1). Tiritiri Matangi is a predator-free wildlife sanctuary that supports a highly diverse community of indigenous fauna. The island and surrounding coastal area are both classified as SEAs in the AUP (SEA-T-3624 and SEA-M1-94 respectively) (Booth 2018). Figure from Budd (2018).

The Whangaparaoa Headland also provides a valuable ecological linkage between the Auckland mainland and Tiritiri Matangi Island, which lies east of the Whangaparaoa Peninsula.

4.2 Hydrodynamics

Water depths gradually increase towards the east in the Whangaparaoa Passage, reaching around 30 m depth approximately 700 m to 800 m from Tiritiri Matangi, and then rising sharply towards the island (Kelly et al. 2018). The outfall, shown in Figure 4-1, extends some 1,300 m into the marine coastal area east of Huroa Point at a water depth of approximately 25 m. Past modelling indicates that the constrictions created by the Whangaparaoa headland and Tiritiri Matangi Island generate relatively high current flows through the passage, with strongest currents associated with ebb flows (Oldman et al., 2004, Oldman 2018).

4.2.1 Winds

Data from the Whangaparaoa automated weather station from the period between 1 January 1987 and 31 December 2012, shows the dominance of westerly winds around the Whangaparaoa Peninsula (Figure 4-2). The less prevalent easterly winds have the potential to transport surface currents onshore and potentially lead to higher concentrations of FIB along the Whangaparaoa shoreline.

An analysis of the wind record by Oldman (2018) shows that there are very few periods when there are winds from the east for any sustained period and that more typically there will a short period of onshore winds bracketed by more typical westerly-dominated winds. Such a sequence of winds occurred between March and June 1999, during which time there was a period of higher onshore winds in March and April followed by more typical (offshore) wind speeds and directions. This period is used later in the report when undertaking an assessment of the effects of the WWTP on the hydrodynamics.

Figure 4.2. Wind rose for the data from the Whangaparaoa automated wind station for the period January 1st, 1987 through to December 31st, 2012. (Oldman 2018).

4.2.2 Currents

Relatively high current flows occur in the shallower waters around the Whangaparaoa headland and in the Passage between the Whangaparaoa Peninsula and Tiritiri Matangi (Oldman 2018).

The residual currents over the period of the long-term model simulation (March-June 1999) used for the QMRA later in this report are shown in Figure 4-3. The influence of winds on residual currents is evident around the headland of the Whangaparaoa Peninsula, with a net easterly residual to the north and south of the headland and a small offshore directed residual current at the shoreline end of the Army Bay outfall. Relatively complex residual currents occur around Tiritiri Matangi. Residual currents in the Passage between the Whangaparaoa Peninsula and Tiritiri Matangi are very small and show the dominance of the tidal flows. Ebb and flood tide currents are relatively symmetrical within the Whangaparaoa Passage and to the south of the Peninsula (Figures 4-4 and Figure 4-5) (Oldman 2018).

Figure 4-6 shows the predicted ebb and peak flood tide currents within the wider Hauraki Gulf. The flows are relatively high through the Whangaparaoa Passage and flows are to the north- east and out towards the middle of the outer Hauraki Gulf on the ebb tide and on a flood tide are to the south-west i.e towards the coast.

Figure 4-3: Residual currents for the period March-June 1999 (from Oldman, 2018)

Figure 4-4: Peak ebb (outgoing) tidal velocities offshore of the Whangaparaoa Peninsula (from Oldman, 2018).

Figure 4-5. Peak flood (incoming) tidal velocities offshore of the Whangaparaoa Peninsula (from Oldman, 2018).

(A)

(B)

Figure 4-6: Predicted peak ebb (A) and flood tide (B) currents in the wider Hauraki Gulf. (Oldman 2018).

4.3 Water and Sediment Quality

4.3.1 Water quality

Auckland Council carry out monthly marine water quality monitoring of 31 sites in the region, and provide annual reports summarising status and trends of marine water quality at these sites. The reports include a water quality index (WQI) and individual parameters for each site. The most recent report (Vaughan 2017) summarises data for 2016. To provide a 5-year timeframe for longer temporal trend analysis, data from 2012 to 2015 were used (Vaughan & Walker 2015; Walker & Vaughan, 2014, 2013; Williams et al. 2017).

Figure 4-7. Map showing Auckland Council sampling sites (Vaughan & Walker 2015)

Along the East Coast, 6 sites have been monitored since the early 1990s. There are no sites on the Whangaparaoa Peninsula, with the three most proximal being Mahurangi Heads and Orewa to the north and Browns Bay to the south (Figure 4-7).

The current (2016) marine water quality at these three sites is excellent and was for the 3 years prior (Table 4-1). Mahurangi Heads has shown excellent marine water quality over the 5-year period from 2012-2016. Orewa showed good marine water quality in 2012, but has been excellent since. Browns Bay had good marine water quality status in 2012 and 2013 but has been excellent since.

Total inorganic nitrogen (TIN) concentrations at 5 sites north-east of Auckland from 2007-2016 are shown in Figure 4-8 and show that medians are low, less that 0.02 mg/L at all sites, with Orewa and Mahurangi being lowest but not signifcantly so.

Table 4-1. Water Quality Index for proximal East Coast marine water quality sites

Site 2012 WQI 2013 WQI 2014 WQI 2015 WQI 2016 WQI

Mahurangi Heads 93.6 93.6 91.9 100.0 92.8

Orewa 87.2 93.6 92.7 100.0 100.0

Browns Bay 80.7 80.7 92.8 100.0 100.0

Excellent water quality status (>90); Good water quality status (75-90)

Table 4-2. Marine water quality parameters for 2016

Parameter Units Mahurangi Heads Orewa Browns Bay Min Max Median Min Max Median Min Max Median DO % saturation 94.80 102.90 98.85 96.60 104.60 100.40 92.90 108.20 99.10 pH - 7.90 8.13 8.09 7.94 8.16 8.12 7.87 8.16 8.09 Temperature °C 13.12 23.08 17.28 13.03 23.47 16.86 13.34 23.58 16.76 TSS mg/L 2.60 12.00 4.20 0.75 10.00 3.60 1.20 14.00 2.90 Turbidity NTU 0.80 2.20 1.30 0.40 1.70 0.50 0.45 2.10 0.85 Conductivity mS/cm 48.8 54.3 51.8 50.4 54.4 52.1 50.3 54.1 52.0 Salinity ppt 31.8 35.9 33.9 32.8 36.0 34.1 32.2 35.8 34.1

NH4-N mg/L N <0.005 0.029 <0.005 <0.005 0.010 0.005 <0.005 0.013 0.006 TKN mg/L N 0.021 0.095 0.057 0.025 0.092 0.064 0.039 0.13 0.076 TN mg/L N 0.024 0.100 0.059 0.013 0.110 0.067 0.042 0.140 0.087

NO3-N mg/L N 0.002 0.019 0.004 0.002 0.017 0.003 0.002 0.022 0.006

NO2-N mg/L N <0.002 0.002 <0.002 <0.002 0.003 <0.002 <0.002 0.002 <0.002 SRP mg/L P 0.007 0.017 0.010 0.006 0.015 0.011 0.010 0.020 0.014 TP mg/L P 0.008 0.026 0.013 0.009 0.017 0.014 0.012 0.025 0.017 Chlorophyll a mg/L <0.0006 0.002 0.001 0.001 0.002 0.001 <0.0006 0.003 0.001

0.24

0.22

0.20

0.18

0.16

0.14

0.12

TIN (mg/l) TIN 0.10

0.08

0.06

0.04

0.02 Median 0.00 25%-75% Goat Island Mahurangi Heads Browns Bay 10%-90% Ti Point Orewa Outliers Site Extremes Figure 4-8. TIN concentrations at sites on the east coast, north of Auckland 2007-2016.

Table 4-3. Recent water quality measured 1km off Whangaparaoa Head, off the discharge and 1 km off Huaroa Point, and ANZECC guidelines based on SE Australia (ANZECC 2000)

Parameter Amm-N Nitrate-N TN Chl a mg/L 26/4/2018 Whangaparaoa <0.005 <0.002 0.081 0.0009 Head Off discharge <0.005 <0.002 0.080 0.0018 Huaroa Point <0.005 <0.002 0.083 0.0016 16/5/2018 Whangaparaoa 0.021 0.0079 0.10 0.0022 Head Off discharge 0.011 0.0073 0.081 0.0017 Huaroa Point 0.013 0.016 0.083 0.0017 18/9/2018 Whangaparaoa <0.005 0.003 0.068 0.0018 Head Off discharge 0.016 0.0032 0.06 0.0017 Huaroa Point 0.011 <0.002 0.057 0.00078

ANECC 2000 0.015 0.015 0.300 0.004 guideline

There is no monitoring in the Whangaparaoa Passage but monitoring at three sites has now begun and the first set of data is shown in Table 4-3 compared with ANZECC guidelines. Data collected in April and May 2018 show that most water quality at sites 1 km off Whangaparaoa head, the discharge and Huaroa Point are all below the guidelines. In April all were below the guidelines while in May Whangaparaoa Head was above the guideline for amm-N and Huaroa Point was just above the guideline for nitrate. In September all were well below the guidelines except amm-N which was slightly above off the discharge site. Based on the limited data there is no obvious effect from the discharge.

4.3.2 Sediment quality

Surficial sediment samples were collected by Coast and Catchment at 4 sites (5 per site) near the Army Bay WWTP discharge as part of the benthic monitoring programme (Figure 4-9, Kelly et al. 2018). Sediments were measured for total metals (Cd, Cr, Cu, Pb, Hg, Ni and Zn), grain size and total organic carbon. Mean (standard deviation) results of parameters are summarised by each site and metal concentrations compared with applicable guidelines (

Table

Table 4-4).

Figure 4-9. Map showing sites where sediments were sampled (Kelly et al. 2018).

Table 4-4. Mean (Std Dev) sediment metal, mud and total organic carbon (TOC) content of sites sampled as part of the benthic monitoring programme and comparison with applicable guidelines.

Parameter Unit Outfall North South East ERC- ANZECC Green SQGV

Cadmium mg/kg 0.090(0.001) 0.091(0.001) 0.090(0.001) <0.090 1.5

Chromium mg/kg 17.8(5.1) 29.0(0.0) 16.4(2.1) 19.6(5.2) 80 Copper mg/kg 5.3(1.5) 7.9(0.1) 5.2(0.8) 4.6(1.5) 19 65 Lead mg/kg 9.3(2.6) 14.8(0.4) 8.7(0.8) 8.2(2.3) 30 50

Mercury mg/kg 0.054(0.012) 0.078(0.013) 0.047(0.005) 0.050(0.010) 0.15

Nickel mg/kg 6.6(1.9) 11.0(0.0) 6.0(0.7) 6.8(1.8) 21 Zinc mg/kg 41(12) 60(1) 40(5) 39(11) 124 200

Mud % 43(12) 80(2) 38(6) 38(13)

TOC % 4.2(0.7) 4.8(0.2) 3.9(0.3) 4.1(0.7)

Auckland Council Environmental Response Criteria (ERC) (Auckland Regional Council, 2004) were used for Cu, Pb and as they are more conservative (protective) than ANZECC (2000) sediment quality guidelines and provide a traffic light type assessment of water and sediment quality: Green (low risk to the biology so the site is unlikely to be impacted); Amber (medium impacted site, possible impact on biology); Red (high impact site, biology of the site is probably impacted). ANZECC/ARMCANZ recommended Sediment Quality Guideline Values (Simpson et al, 2013)2 were used for Cd, Cr, Hg and Ni.

Sediment metal concentrations were consistently higher at the North sites over Outfall, South and East sites. This was consistent with relatively elevated mud and TOC at the North sites relative to the others. However, all sediment metal concentrations were less than 50% of either ERC-Green or SQGV, suggesting low risk to the biology at all sites.

4.4 Microbial characteristics

Pathogens in the receiving environment

The Army Bay WWTP underwent a significant upgrade in 2006, which included the installation of a new grit removal and handling system along with a new enhanced sequential batch reactor (ESBR) with a new decanted and aeration system. A new ultraviolet light (UV) system was also installed for the final disinfection of the treated effluent. The UV treatment was found to improve the microbiological quality of the discharge, reducing the median Ent from 38 MPN/100 mL before UV to 6 MPN/100 mL post-UV

Historical data (2006-2009) for the receiving marine environment around the WWTP indicate that the Ent concentrations in the receiving water do not exceed the ‘Microbiological Water Quality Guidelines for marine and freshwater recreational areas’ (MfE/MoH, 2003) threshold of 280 CFU/100 mL under dry weather flows and only occasionally under wet weather flows. Above this threshold, water is considered unacceptable for swimming or other forms of contact recreation. For most of the years for which monitoring data was collected for these sites as part of compliance monitoring, median Ent and E. coli concentrations were not more than 10 CFU/100mL (Dada 2018).

Annual monitoring between 2010 and 2017 found that FIB concentrations were generally low (<20 CFU/100 mL) in the receiving environment. On occasion, rainfall of higher than 10mm (in the previous five days) appeared to result in peaks in FIB concentrations; however apart

2 An update of the ANZECC/ARMCANZ (2000) sediment quality guidelines was undertaken by Simpson et al (2013). The previous ISQG-low trigger values have been replaced with Sediment Quality Guideline Values (SQGV). In practice, there has been no change to the values for metals.

from one occasion in May 2015 at Te Haruhi Bay, when E. coli concentration was 600 CFU/100 mL, the concentrations of FIB remained below the MfE/MoH threshold. Overall, the microbiological water quality over the period monitored was considered to be very good and compliant with the MfE/MoH guidelines (2003) for contact recreation.

Receiving environment shellfish microbiological quality

Monitoring data from shellfish tissue collected within the receiving environment between 2009 and 2017 indicate that there has been little or no change of any practical significance in ‘average’ E. coli concentrations in shellfish tissue over time (Dada, 2018). The New Zealand Microbiological Reference Criteria (FSANZ 2002) provides bacteriological guideline values for shellfish gathering, as follows:

 The median FC content of samples taken to meet the guideline standards should not exceed 14 per 100 ml, and not more than 10 percent of samples should exceed 43 per 100 ml.  The E. coli median MPN of the shellfish samples must not exceed 230 E. coli per 100 gm and not more than 10 percent of the samples must exceed an MPN of 700 per 100 gm.

Analysis of the shellfish tissue E. coli concentrations shows that this standard was exceeded only on a few occasions, which as shown for water quality, were usually related to increased rainfall in the days preceding sampling. The only exception to this was at Huaroa Point (the site closest to the discharge) in November 2016, when shellfish tissue E. coli levels were well in exceedance of the FSANZ (2002) guidelines with no obvious correlation to rainfall. The proportion of samples exceeding the FSANZ (2002) guidelines for FC content of shell fish samples collected in the receiving environment was also low. At least 92% of the 150 shell fish samples collected from the receiving environment from 2006 until 2017 complied with the FSANZ (2002) guideline (Dada 2018).

Shellfish samples collected at Huaroa Point and Whangaparaoa Head were also analysed for enteroviruses on 6 occasions. One positive detection was recorded (1 pfu per 100 gm, on 18th December 2007; post UV disinfection) (Dada 2018).

4.5 Contaminants of emerging concern

There are multiple definitions for emerging contaminants (ECs) in the literature, and other inter-changeable terms are used, for example contaminants of emerging concern (CEC), or contaminants of emerging environmental concern (CEEC). Furthermore, definitions of ECs

vary. A commonly accepted definition is provided by the US Geological Survey (USGS) who define an EC as:

"Any synthetic or naturally occurring chemical or any microorganism that is not commonly monitored in the environment but has the potential to enter the environment and cause known or suspected adverse ecological and (or) human health effects”.3

Emerging microorganisms have not been assessed in this study however are extremely unlikely to survive the UV treatment (see microbial section), while chemical ECs are organic rather than inorganic so the term “emerging organic contaminant” (EOC) is used in this report.

As the definition of EOCs covers a wide range of chemicals, they are often grouped into classes depending on their chemical group, their use, or their mode of action. Major EOC classes include industrial chemicals (flame retardants, plasticisers), pesticides, antifouling agents, preservatives, and pharmaceuticals and personal care products (PPCPs).

Treated wastewater discharge is a major source of EOCs to the environment as many show incomplete removal by wastewater treatment processes - even under advanced treatment such as advanced oxidation, activated carbon, nanofiltration, reverse osmosis, and membrane bioreactors. Removal efficiency is related to the physico-chemical properties of the EOC and the treatment process employed (Luo et al., 2014).

Despite this, EOCs are not routinely measured in wastewater effluent in New Zealand. With potentially thousands of EOCs entering the receiving environment through treated wastewater, it is not logistically possible to assess risks from all chemicals. Furthermore, there are many knowledge gaps still surrounding EOC sources, fate and effects.

Previous technical assessments of EOCs in treated wastewater for WWTPs in Auckland to support discharge consent applications (Stewart, 2016a,b,c) have followed a risk-based approach to measure a subset of “indicator” EOCs that are representative of high-use and/or high-risk EOCs. This list of “indicator” EOCs is continually evolving as more information becomes available and analytical methodologies are advanced. For instance, pharmaceuticals now comprise 10 chemicals, whereas previously only 3 were measured.

Sampling of Army Bay WWTP discharge was performed by Watercare staff utilising procedures provided by the analytical laboratory (Grant Northcott, personal communication). Two replicate grab samples (ca. 4 L) were collected.

3 http://toxics.usgs.gov/regional/emc/

Samples were sent to Northcott Research Consultants for analysis by standard tandem mass spectrometry techniques, including appropriate quality assurance and quality control measures. Results are presented in Appendix 2 (Table A1) and compared with Omaha and Waiuku WWTP, New Zealand and international WWTP discharge concentrations of EOCs.

Generally, concentrations of EOCs in Army Bay WWTP discharge were markedly higher than Waiuku and Omaha WWTPs (Stewart, 2016a,b), more in line with concentrations from 13 WWTPs around New Zealand (Northcott et al, 2013), but generally lower than WWTPs worldwide (primarily EU and US). Some EOCs of note include:

 The polycyclic musk galaxolide a synthetic fragrance had an average concentration from Army Bay WWTP discharge (1332 ng/L) well above Waiuku/Omaha (30/60 ng/L), NZ (243 ng/L) and worldwide (850 ng/L). This concentration was approximately half the maximum reported worldwide (2,770 ng/L);  5 of 8 organophosphate flame retardant (TiBP, TBP, TCEP, TCPP, TDCP) average concentrations from Army Bay WWTP discharge were markedly higher than from Waiuku/Omaha and New Zealand WWTPs, with TCPP and TDCP markedly higher than worldwide average concentrations. In contrast 2 (TPP and TBEP) were present at low concentrations in Army Bay WWTP discharge relative to Omaha, New Zealand and worldwide average concentrations;  Aspirin average concentration from Army Bay WWTP discharge (2720 ng/L) was markedly higher than other pharmaceutical concentrations. There was no literature data for comparison with New Zealand or worldwide WWTPs. Salicylic acid (breakdown product of aspirin) was present in low concentrations relative to those reported worldwide, which is possibly a reflection of low WWTP removal efficiency for aspirin from Army Bay WWTP relative to other WWTPs;  Carbamazepine (used for treatment of epilepsy and neuropathic pain) average concentration from Army Bay WWTP discharge (1001 ng/L) was approximately double worldwide average concentration (540 ng/L);  Diclofenac and naproxen (non-steroidal anti-inflammatory drugs) average concentrations from Army Bay WWTP discharge (540 and 240 ng/L, respectively) were around the average worldwide WWTP concentrations (454 and 227 ng/L).

These data suggest that Army Bay WWTP generally has a lower efficiency of removal of EOCs than Waiuku or Omaha WWTPs but is similar to others in New Zealand or alternatively input concentrations are higher. The risk of EOCs to the receiving environment is summarised in Section 5.2.4.

4.6 Benthic habitat and communities

Studies of the benthic habitats and communities in the area surrounding the WWTP outfall have been undertaken previously, but this information is considered to be limited in scope or outdated. However, these studies show the coast around the pipeline and existing outfall is considered to contain a complex and diverse mix of intertidal and subtidal habitats (both physical and biogenic).

To ensure that the consent application is supported by the most up-to-date and site-specific information available, Coast and Catchment Ltd have provided a report on the marine ecology of the receiving environment (Kelly et al. 2018). This report includes a review of the currently available information on the benthic habitats and communities in the immediate vicinity of the discharge pipe and wider environment, as well as a survey (undertaken in late 2017) of intertidal and benthic subtidal habitat and communities around the existing discharge point, and mapping of the extent of shellfish beds that may be important to recreational and customary fishers. Findings from this report are summarised in the following sections.

4.6.1 Sediments

Based on the definitions developed in a Technical Publication for the then Auckland Regional Council (Hayward et al., 1999), Sjardin (2015) identified three broad habitat types in the vicinity of the outfall, as follows (generally the mixed kelp assemblage around the sublittoral fringe is used to define the intertidal-subtidal boundary):

 Intertidal sandstone reef (~75% of the Whangaparaoa shoreline) comprising soft fine sandstones and muddy siltstone of the Waitemata geological formation. A key feature of these reefs, is their relatively wide, gently sloping reef platforms adjoining sheer cliff faces;  Subtidal sandstone reef which is an extension of the intertidal habitat, and from aerial photos appear to consist of shallow macroalgae-covered reef flats, dissected by reef gutters largely running perpendicular to the shore. The reef becomes patchier offshore transitioning to isolated rocky outcrops and finally giving way to sediment substrates; and

 Subtidal channel which comprises a mix of sand, shell and mud flats. Sediment depths, texture and softness vary considerably in Whangaparaoa Passage. Broad- scale sediment maps produced by Tuck et al. (2006) show a patch of mixed sediments with muddy-sandy-gravel and high shell content occurs south of the passage, while gravelly-sand with a high shell content occurs through the passage. North of the passage, sediments transition from sandy-mud to mud. Towards the south they transition to gravely-sandy-mud with a high calcium carbon content, to gravelly-mud and on to mud.

Kelly et al. (2018) report that finer scale information on subtidal habitats and sediment characteristics and depth for the area immediately surrounding the existing outfall pipeline was provided by two studies in 2015. Results from these studies indicated that sediments around the outfall were muddy with a high shell content, with reef and sandy sediments being recorded further inshore.

Coast and Catchment undertook a qualitative shoreline survey on 1 March 2018, this survey covered an area within an approximately 2 km radius of the outfall and involved general observations and descriptions of the intertidal habitats present. Kelly et al. (2018) report that the surveyed area was exposed to moderate wind and wave action. Steep, near vertical cliffs were present around the entire surveyed area, with small sandy areas occasionally found between the base of the cliff and the adjoining reef. As has been observed in previous studies, the vast majority of the intertidal zone consisted of low gradient sandstone reef platforms that were strongly ridged in areas. Shallow rock pools were dotted across the mid to lower intertidal area, with scattered small to medium-sized boulders also present in some areas. Reefs were steeper and contained more boulders around Huaroa Point and Whangaparaoa Head. Images from this study can be found in Kelly et al. (2018) and see cover photos.

The survey by Coast and Catchment of subtidal communities used a combination of 100 drop camera images and four video tows along two kilometre transects in northerly, easterly, southerly and north-westerly directions from the existing outfall (Figure 4.10). Detailed results from this sampling can be found in Kelly et al. (2018), but summary results in that report (and Figure 4-11) indicated that while sediments from all sites had relatively high percentages of total organic matter (TOM) and TOC, there were clear differences apparent in the sediment characteristics of the four sampling sites, as follows:  East site contained approximately equal proportions of mud, sand and gravel size fractions and the high percentage of TOC (~ mean 4%).

 North site contained a significantly higher proportion of mud, with a lower percentage of fine sand and minor contributions of other size fractions and a significantly higher percentage (~ mean 4.8%) of TOM than the other three sites.  Outfall and South sites contained similar, high percentages of mud and gravel sized particles, with smaller percentages of sand sized particles, but South site had a significantly higher percentage of TOC (mean 3%) when compared to the outfall site (mean 1.9%).

Kelly et al. (2018) compared TOC concentrations from the Whangaparaoa Passage sites to those obtained from other subtidal sites sampled by Coast and Catchment in the Hauraki Gulf and Kaipara Harbour. The East and South sites from the current survey had the highest mean TOC concentrations in the records, while the Outfall and North sites had concentrations similar to those from beneath mussel farms around Coromandel and from an unfarmed area in the central Firth of Thames (FoT). TOC concentrations at all of the sites were well above those around the Snells-Algies WWTP outfall and at associated reference sites around Martins Bay and Kawau Island, and inside and outside shellfish farms in Tāmaki Strait, north-western FoT, and Kaipara Harbour.

Figure 4-10. Locations of drop camera and grab sample stations, video tracks, and the intertidal area surveyed by Kelly et al. (2018).

Figure 4-11. Substrate types recorded by drop camera and towed video imagery taken by Kelly et al. (2018)

Additional field surveys were carried out in April 2018 to further characterise the microalgae mat observed along the western video transect in the 2017 survey and to obtain total organic carbon (TOC) readings from nearby sites in Kawau Bay with similar habitats to those present in Whangapāraoa Passage.

The results of these recent surveys indicate that:

 The microalgal mat apparent in the initial video footage was a short term, possibly seasonal bloom; and that,  While TOC concentrations obtained from Whangapāroa Passage were high, they are within the range found at a nearby, presumably uncontaminated site.

Kelly et al. (2018) found that there was no significant difference in TN concentrations in the sediments between the four sites sampled around the outfall off Army Bay, and plots of the P data suggested that there was little difference in mean concentrations at the East, Outfall and South sites, however P concentrations at the North site appeared to be higher than those at the other sites. As with P, mean heavy metal concentrations were generally higher at the North site which is likely to reflect the higher proportion of mud at that site. However, all of the

heavy metals analysed were well below threshold effects level (TEL) (MacDonald et al. 1996) and ANZECC (2000) ISQG-L sediment quality guideline values.

4.6.2 Intertidal habitats

Various studies have been carried out previously around the intertidal area of the Whangaparaoa headland; these have included assessments associated with discharges from the Army Bay WWTP, as well as a number of independent research studies. These are summarised in Kelly et al. (2018).

As part of the qualitative shoreline survey undertaken by Coast and Catchment in March 2018 (detailed in the previous section), general observations and descriptions of the species present in the intertidal zone were made. A summary of the findings and observations is provided below, with further results and images provided in Kelly et al. (2018).

 The intertidal community was fairly similar throughout the surveyed area, with the greatest change in species abundance and diversity due to position on the shoreline (tidal zonation);  High shore (splash zone): sandstone surfaces were predominantly bare, with patches of a moss-like algae (Bostrychia arbuscula) present in some place. Brown barnacles (Chaemasipho brunnea), plicate barnacles (Epopella plicata), periwinkles (Austrolittorina antipodum) and black nerita (Nerita melanostragus) were abundantly scattered over the rocks;  Upper shore: patches of coralline turf (Corallina officinalis) covered the depressions where water pools. Rock oysters (Saccostrea glomerata) and black nerita were abundant and common throughout the survey area, while spotted black top shells (Diloma aethiops), snakeshin chitons (Sypharochiron pelliserpentis), limpets (Cellana sp.) and the crab, Cyclograpsus lavauxi, were occasionally present. Dense patches of tube worms (Spirobranchus cariniferus) were occasionally seen;  Mid shore: covered in coralline turf, with patches of Neptune’s necklace (Hormosira banksia) and blue green algae (Lyngbya sp.) present in the depressions where water pools. Rock oysters and plicate barnacles were abundant on the ridges. Tube worm beds were patchily distributed within this zone. Black nerita were abundant over the shore. Snakeskin chitons, spotted top shells, oyster borers (Haustrum scobina), the black sea slug (Onchidella nigricans), horn shells (Zeacumantus subcarinatus), Codium convolutum, and red-mouthed whelks (Cominella virgata virgata) were all occasionally seen in this location;

 Lower shore: almost completely covered in coralline turf and Neptune’s necklace to the south of Whangaparaoa Head and west of Huaroa Point. In the bay closest to the outfall, another brown seaweed, Colpomenia sinuosa, dominated the mid to lower shore, reaching near 100% cover near the existing outfall (as far as we know this species is not associated with enriched environments). In other parts of the outfall bay, C. sinuosa was mixed with coralline turf and Neptune’s necklace. Small clumps of various other seaweeds were occasionally present including Lyngbya sp., Splachnidium rugosum and Scytothamnus australis. Oysters are abundant on the ridges. Black nerita and cat’s eyes (Lunella smaragdus) are also common. Porcelain crabs (Petrolisthes elongatus), red rock crabs (Guinusia chabrus), iron crabs (Ozius deplanatus), blue mussels (Mytilus galloprovincialis), snakeskin chitons, cushion stars (Patiriella regularis), spotted whelks (Cominella maculosa) and dark rock shells (Haustrum haustorium) were occasionally seen; and  Lower shore rock pools: a variety of seaweeds including Codium fragile subsp. novaezelandiae, Jania verrucosa, Ecklonia radiata, Carpophyllum spp., Sargassum sinclairii and Cystophora torulosa. Hermit crabs (Pagurus sp.), glass shrimps (Palaemon affinis), kina (Evechinus chloroticus), cat’s eyes and triplefins (Tripterygiidae) were also present in the rock pools.

Various birds were seen in the intertidal area including red-billed gulls (Larus novaehollandiae), variable oystercatchers (Haematopus unicolor) and shags (Phalacrocorax sp.).

4.6.3 Subtidal habitats

Information from previous studies around the vicinity of the Whangaparaoa Passage is relatively scarce, however it is clear that there are two predominant substrate types in the vicinity of the WWTP outfall. The seafloor habitats associated with the reef and soft sediment substrates are discussed in Kelly et al. (2018), with a brief summary provided below.

Rocky reef

The reef habitats of the Whangaparaoa Passage are characterised by moderate depths, water turbidity and light penetration through the water column (which is a key driver of the depth distributions of habitat forming macroalgae). According to Grace (1983) zonation patterns in this habitat are likely to consist of:

 A shallow mixed weed zone;

 Rock flats that are commonly kept barren by urchin grazing, but may contain kelp forest;  Kelp forest (typically Ecklonia radiata and/or Carpophyllum flexuosum);  A deep zone where kelp plants become more scattered, and the larger sponges start to appear; and  A very deep zone where available light is insufficient to support large brown seaweeds.

Soft sediments

As with the reef habitat, Kelly et al. (2018) found little information was available on the benthic communities associated with subtidal soft sediment habitats in Whangaparaoa Passage. Three studies have been undertaken previously; these are discussed in more detail in Kelly et al. (2018) and summarised below:

 Powell (1937) described the community of Whangaparaoa Passage as a Tawera

(morning star clam)–Glycmeris (probably a dog cockle) formation with Flabellum (a solitary coral)–Notocorbula (basket shell), associated with ‘hard bottom’;  Video recordings of an outfall inspection (White 1999) indicated that the subtidal community was diverse, with species typical of a channel environment with moderate currents. Outfall risers were observed to be heavily encrusted with an assemblage of sponges, ascidians and jewel anemones. Shell debris around the outfall included horse mussel (Atrina zealandica), scallop (Pecten novozealandiae) and dog cockle (Tucetona/Glycmeris sp.) shells;  Sjardin (2015) collected 11 subtidal benthic core samples from a corridor along the outfall pipeline. Composition of the infaunal community varied from inshore to offshore sites along the pipeline, in association with changes in depth and sediment characteristics. A diverse assemblage of taxa was obtained from the cores, including low numbers of the bed forming bivalve species. Polychaete worms were the most numerous taxa, in particular, bamboo worms (Maldanidae) occurring in relatively high numbers in the middle section of the survey area. Three other polychaete worms, Boccardia sp., Cirratulidae and Sphaerosyllis sp. also occurred in reasonable numbers at inshore stations. Tanaid shrimp were found in moderate numbers at one inshore and two offshore stations. The clubbed tunicate, Styela clava was also found at one of the outer stations. This species is classified as “Unwanted Organism”, due to its ability to foul, smoother and outcompete important native species and habitats (e.g. scallops and horse mussels) and is therefore managed under the Biosecurity Act 1993.

2017 survey

As discussed above, in order to update the available information, Coast and Catchment undertook field sampling of subtidal communities in late 2017 within a 2 km radius of the existing outfall using a combination of 100 drop camera images and four video tows along two kilometre transects in northerly, easterly, southerly and north-westerly directions from the existing outfall (Figure 4.10). Detailed results from this sampling can be found in Kelly et al. (2018) and a summary is provided below and examples of the different substrates are shown in Figure 4.11.

In the most recent survey, Kelly et al. (2018) observed that the Whangaparaoa Passage contains a heterogenous mix of subtidal habitats, with considerable variation in substrates and associated biota. The central passage area and north of the outfall contained sediments with little or no visible shell and low habitat complexity. Visible shell content increased, with an associated increase in habitat complexity, towards the shores of Whangaparaoa Head and Huaroa Point west of the outfall, and towards Tiritiri Matangi Island in the east. Sediments towards the south of the outfall were a mix of those with and without low levels of visible shell. The areas of highest habitat complexity were associated with areas of shell gravel/hash containing biogenic species. The only reefs encountered within the survey area were those along the Whangaparaoa shoreline and the habitats here were also considered to be ‘complex’.

Epifauna

Kelly et al. (2018) found that benthic epifauna were recorded in 45% of drop the camera images, including four species, or species groups, that form sensitive biogenic habitats, as follows (see Figure 4-12 for photos of different habitats):

 Macroalgae (10% of images) largely inshore from the outfall either on reef habitat or along reef margins. Video footage showed macroalgae was patchily distributed in other areas, particularly to the south of the outfall and towards the eastern side of the Passage. A dense algal mat was observed to cover a large area of the sediments northwest of the outfall;  Horse mussels (5% of images); a major habitat feature of the Passage, varying in density from scattered individuals to dense beds. These beds were associated with a wide variety and volume of other biota growing on the mussels; and  Various sponges (15% of images); also, a major feature of the Whangaparaoa Passage benthos. Sponges were growing on horse mussels, in shell gravel, in sediments and on reef habitat.

Scallops (possibly or probably live scallops) were recorded in 4% of images, and scallop shell in 7% of images, generally in water depths of around 25-35m along the eastern margin of the Passage, as well as to the south of the survey area and to the west of the outfall.

The marine ecological assessment by Kelly et al. (2018) found little evidence of benthic ecological values being adversely affected by nutrient enrichment around the existing outfall. Having said that, an unusual spring-summer bloom of, what appears to have been, seabed microalgae was recorded north-west of Huaroa Point. The cause of this bloom is difficult to determine, but it was short lived, occurred in relatively deep water, and coincided with a period of high water clarity, clear weather and record high sea temperatures. This combination of unique environmental factors is likely to have heightened the potential for a bloom independent of the operation of the WWTP.

Figure 4.12. Photos of typical benthic habitats recorded from drop camera images: a) sediments, b) sediments - low shell content, c) sediments - high shell content, d) shell gravel/hash, and e) reef. (Kelly et al 2018).

In addition, other notable biota observed during the drop camera and video survey included a dense “worm bed” on the eastern margin of the survey area, the presence of the unwanted Mediterranean fan worm, starfish (particularly within the algal mat blanketing sediments northwest of the outfall) and ray feeding pits, particularly along the eastern video transect.

Infauna

Kelly et al. (2018) sampled infaunal taxa in November 2017 by taking a van Veen grab sample from 10 randomly allocated stations within each of four sampling areas: within a 100 m radius

of the existing outfall, and at 200m diameter reference areas to the north, south and east of the outfall (Figure 4.10).

Infaunal communities were relatively diverse, with a total of 90 taxa (or identified groupings) obtained from the East site, 67 from the South site, and 59 from the Outfall site. The North site was the least diverse, with only 24 taxa being recorded. These findings were supported by statistical analysis which is detailed in Kelly et al. (2018). Multidimensional scaling confirmed that community composition differed among the sites, with stations from the East site clustered towards right of the MDS plot, progressing through the South, Outfall and North sites towards the left.

Polychaetes appear to be the most diverse and abundant phylum, closely followed by crustacean arthropods. Diverse and relatively abundant assemblages of echinoderms (including urchins, sea cucumbers and brittlestars) and molluscs (including bivalves, gastropods, chitons, and sea slugs) were also present. Dominant species varied between the four sites:

 The East site was dominated by bamboo worms (Maldanidae) and amphipods which accounted for >50% of the individual counts;  The North site was dominated by polychaete worms (Myriochele sp., Cossura consimilis, Cirratulidae, Onuphis aucklandensis) and the ostracod crustacean Trachyleberis lytteltonsis, with a number of unidentified brittlestars (Ophiuroidea) also present;  The Outfall site was dominated by polychaete worms (Cossura consimilis, Cirratulidae, Onuphis aucklandensis) and Phoxocephalid crustaceans (amphipods); and  The South site was dominated by Phoxocephalid crustaceans (amphipods) and unidentified amphipods (9%).

4.6.4 Shellfish surveys

Previous studies, summarised by Kelly et al. (2018) have provided some information on potential kaimoana species present in the vicinity of the WWTP outfall, including scallop beds in and around Whangaparaoa Passage and green-lipped mussels, which have historically been collected from the seabed around the outfall and tested for microbial contamination. In 1990 intertidal kaimoana species were the subject of a targeted investigation of the western side of the Whangaparaoa Passage (White 1999). Species reported at that time included:

 Tio repe or New Zealand rock oysters, Saccostrea glomerate; present in harvestable quantities with highest abundances immediately east of Te Haruhi Bay, and large quantities also present at Huaroa Point;  Kūtai or green-lipped mussels, Perna canaliculus; present in patchy beds with low numbers and small sizes, in a band from mid-tide to the low water neap. Occasional

2 densities of 10 per m were found east of Te Haruhi Bay, while “very small numbers” were reported for Whangaparaoa Head and Huaroa Point;  Pūpū or cat’s eyes, Lunella smaragda; present in large numbers of edible size. These were mainly found from mid-tide zone down to the subtidal zone;  Kina or sea urchin, Evechinus chloriticus; present throughout the area from mid-tide pools and crevices through to subtidal depths of at least 15 m; and  Other species which could potentially be consumed included tawari or the white rock shell (Dicathais orbita), ngāeo or dark rock whelk (Haustrum haustorium), māihi or speckled top shell (Diloma aethiops), kākara or Cook’s turban (Cookia sulcata) and two species of ngākihi or limpets (Cellana radians and C. ornata).

Kelly et al. (2018) identified five potential kaimoana species during their recent intertidal survey (but noted that there is a warning sign near the outfall advising against the collecting of shellfish from the area because of potential health risks):

 Rock oysters (tio)—small oysters were abundant on the ridges throughout the survey area;  Sea urchin (kina)—occasionally present in deeper rock pools;  Blue mussels (kūtai or kuku)—uncommon, a few single juvenile mussels were seen;  Cat’s eyes (pupu)—common on the lower intertidal area, small in size; and  Black nerita (makerekere), abundant across the whole intertidal area.

4.7 Birds

A desktop assessment of the information available on bird life around the Whangaparaoa Peninsula was undertaken by Wildland Consultants Ltd. A summary of the findings from this report is provided below, with a detailed species list, and associated threat classification, provided in the Wildland Consultants report (Budd 2018).

The establishment of the Shakespear Open Sanctuary, and the resultant removal of mammalian predators (with the exception of mice) from the area, has resulted in a significant increase in bird numbers, with birds from neighbouring Tiritiri Matangi becoming established on the mainland. A total of 72 indigenous bird species have been recorded in the outer

Whangaparaoa Peninsula and Whangaparaoa Passage (refer Budd 2018). The area supports at least 14 ‘Threatened’ species, 31 ‘At Risk’ species, and four migratory species.

Indigenous forest bird species known to be dispersing from Tiritiri Matangi include bellbird (Anthornis melanura), kaka (Nestor meridionalis), kakariki (Cyanoramphus novaezelandiae novaezelandiae), and occasionally hihi (Notiomystis cincta) (SOSSI 2016, Auckland Council 2018). Twenty little spotted kiwi (Apteryx owenii) were released into the park in May 2017. Common forest bird species such as fantail and grey warbler are also thriving in the predator- free environment.

The wetlands of the Whangaparaoa headland provide habitat for threatened indigenous birds, including spotless crake (Porzana tabuensis tabuensis), fernbird (Bowdleria punctata vealeae), banded rail (Gallirallus philippensis assimilis), New Zealand dotterel (Charadrius obscurus), and Australasian bittern (Botaurus poiciloptilus).

The coastline also provides extensive intertidal feeding habitat for wading birds such as pied stilt (Himantopus himantopus leucocephalus) and oystercatchers (Haematopus spp.). While seabirds such as the grey-faced petrel (Pterodroma macroptera gouldi), Cook’s petrel (Pterodroma cookii), and sooty shearwater (Puffinus griseus) are frequently seen foraging in the waters of the Whangaparaoa Passage.

Outside of the protected area, Whangaparaoa Peninsula is heavily impacted by urbanization and birds outside the protected Open Sanctuary area are threatened by a mix of direct disturbance, habitat loss, and mammalian predators such as mustelids (Mustela spp.), rats (Rattus spp.), hedgehogs (Erinaceus europaeus), and domestic cats (Felis catus) and dogs (Canis lupus) (Budd, 2018).

4.8 Fish

A desktop assessment of the information available on fish and fishing around the Whangaparaoa Peninsula was undertaken for Watercare by Coast and Catchment Ltd. A summary of the findings from this report is provided below, with further detail, including species lists and figures showing distribution, can be found in the Coast and Catchment report (Sim- Smith & Kelly 2018).

There is not a lot of specific information available on the fish assemblages around the Whangaparaoa Peninsula, however they are considered to be similar to those that occur in the inner Hauraki Gulf. Sim-Smith & Kelly (2018) analysed data from trawl catches around the inner Hauraki Gulf (including the Peninsula) and found the ten most abundant species in shallow waters over muddy substrate were, in decreasing order: yellow-eyed mullet

(Aldrichetta forsteri), kahawai (Arripis trutta), yellow-belly flounder (Rhombosolea leporina), spotty (Notolabrus celidotus), snapper (Chrysophrys auratus), rig (Mustelus lenticulatus), sand flounder (Rhombosolea plebeia), eagle ray (Myliobatis tenuicaudatus), trevally (Pseudocaranx dentex) and spotted stargazer (Genyagnus monopterygius) (Kendrick & Francis 2002).

As discussed in previous sections, the tip of Whangaparaoa Peninsula and Tiritiri Matangi Island are fringed with shallow rocky reefs, and these areas have a moderately high species richness of reef fishes (Figure 4-13). The most common fish seen in these habitats are variable triplefins (Forsterygion varium), spectacled triplefins (Ruanoho whero), parore (Girella tricuspidata), leatherjackets (Parika scaber), sweep (Scorpis lineolata), jack mackerel (Trachurus novaezelandiae) and goatfish (Upeneichthys lineatus) (Smith et al., 2013).

Demersal fish values are relatively high around the Peninsula and Whangaparaoa Passage, most likely reflecting the diversity of benthic habitats in the area. Sim-Smith & Kelly (2018) observed that this region contains areas that are in the top 10% of the most important areas for demersal fish in the Hauraki Gulf, with values declining towards the eastern side of the passage (Leathwick et al., 2006). The most prevalent demersal fish species caught in trawls around the Whangaparaoa Peninsula were snapper, red gurnard (Chelidonichthys kumu) and John dory (Zeus faber) (Kendrick & Francis 2002). Whangaparaoa Passage also appears to be a moderately important area for snapper reproduction, with a moderate abundance of snapper eggs collected from the passage during egg surveys. The abundance of biogenic habitats in and around the Passage suggest that this area is also likely to be attractive to juvenile snapper.

4.8.1 Commercial fishing

The area around Whangaparaoa Peninsula is of low importance to commercial fishing, with trawling and Danish seining being prohibited around this area (Figure 4-14). Very low levels of commercial longlining do occur around the peninsula, with less than 10 longline sets/3 km2 conducted between 2014 and 2016. Commercial fishers are likely to be mainly targeting snapper, which is the primary fish caught in the inner Hauraki Gulf.

Figure 4-13. Reef fish species richness around the Whangaparaoa Peninsula based on dive survey data (from Sim-Smith & Kelly, 2018).

Figure 4-14. Areas where trawling and Danish seining are either prohibited or restrictions apply to the vessel size or times when trawling and Danish seining can occur. (Figure reproduced from Hauraki Gulf Forum (2017)).

4.8.2 Recreational and customary fishing

The Hauraki Gulf is one of the most intensively fished areas in New Zealand. Aerial surveys indicate that the area around Whangaparaoa Peninsula is subject to relatively low recreational boat fishing pressure, but the area west of Tiritiri Matangi Island is subject to high fishing pressure. The main forms of recreational fishing in the vicinity of the outfall are likely to be line fishing from boats, however anchoring is prohibited along the coast from Army Bay to the southern tip of Whangaparaoa Peninsula, which is likely to deter recreational boat fishing in the area. Public access to the New Zealand Defence Force land on the tip of Whangaparaoa Peninsula is prohibited, and thus, there is unlikely to be any shore-based fishing near the

outfall. Some shore-based fishing may occur along the Peninsula west of Army Bay and south of Whangaparaoa Head.

The main fish species likely to be targeted by recreational fishers in the vicinity of the outfall are snapper and kahawai. Species such as kingfish (Seriola lalandi), John dory, parore, gurnard, trevally, blue moki (Latridopsis ciliaris), porae (Nemadactylus douglasii) and various sharks and rays will potentially be caught by line fishers, but in lower numbers. Reef species, such as red moki, butterfish and silver drummer may also be targeted by fishers and divers using set nets or spears.

There are no rohe moana areas, mātaitai reserves or areas of significant cultural value identified in the operative Auckland Unitary Plan – Coastal Section around the Whangaparaoa Peninsula. Tiritiri Matangi Island is, however, of cultural important to iwi, and Te Kawerau a Maki and Ngāti Paoa, have traditional guardianship (mana whenua) over the island (Dodd 2008; Anon no date).

4.9 Mammals

A desktop assessment of the information available on marine mammal species observed around the Whangaparaoa Peninsula has been undertaken for Watercare by Coast and Catchment Ltd. A summary of the findings from this report is provided below, with further detail, including species lists and figures showing distribution, to be found in the Coast and Catchment report (Sim-Smith & Kelly 2018).

The most commonly seen marine mammals in the vicinity of Whangaparaoa Peninsula are common dolphins (Delphinus delphis) and Bryde’s whales (Balaenoptera edeni brydei). However, southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), sei whales (Balaenoptera borealis), blue whales (Balenoptera musculus), beaked whales (unspecified), bottlenose dolphins (Tursiops truncates) and killer whales (Orcinus orca) have also been recorded around the Whangaparaoa region.

Common dolphins are widely distributed, both within New Zealand and internationally, and are thought to live to at least 25 years old (du Fresne 2008). They are present in the Hauraki Gulf year-round, moving closer inshore during winter and spring, and further offshore in summer and autumn (Dwyer et al., 2016). In the Hauraki Gulf, pods typically comprise less than 50 individuals, but can reach over 500 dolphins (Stockin et al., 2008, Dwyer 2014; Dwyer et al., 2016). Common dolphins are opportunistic feeders, feeding on a range of species including arrow squid (Nototodarus spp.), jack mackerel, kahawai, yellow-eyed mullet (Aldrichetta

forsteri), flying fish (Cheilopogon pinnatibarbatus pinnatibarbatus), parore and garfish (Hyporhamphus ihi) (Neumann & Orams 2003; Stockin 2008).

Bryde’s whales occur along the entire north-eastern coast of New Zealand from Hauraki Gulf to North Cape but are most common in the Hauraki Gulf where there are about 50–200 resident/semi-resident individuals. They are listed as ‘Nationally Critical’ because of their limited distribution and small population size. Bryde’s whales feed by gulping up large volumes of water along with their prey, which is then filtered through their baleen combs. In New Zealand, potential prey items include krill (Euphausia superba), saury (Scomberesox saurus saurus), anchovy (Engraulis australis), garfish, jack mackerel, pilchard (Sardinops sagax) and sprat (Sprattus antipodum) (Behrens 2009).

4.10 Summary of existing environment

The Whangaparaoa Passage is a dynamic and well flushed region with relatively high currents that support a diverse and productive intertidal and subtidal ecosystem and is valued for its recreational and cultural values, including kai moana. Water quality is also high quality.

The existing discharge and receiving environment have relatively low levels of FC and Ent. Monitoring of microbial indicators in the water and shellfish in the vicinity of the outfall show no effects of the present discharge and are below MFE guidelines for shellfish gathering. Occasionally microbial levels increase during rainfall events but this has not been attributed to the discharge and there is no evidence that the existing outfall is affecting contact recreation or shellfish gathering.

There is a relatively diverse benthic community throughout the Whangaparaoa Passage and area around the outer Whangaparaoa Peninsula, with a muddier habitat to the north. Horse mussels and sponges are abundant and widespread around the margins, scallops are patchily distributed with diverse communities of polychaete worms and crustaceans are common throughout. Overall there is no evidence of effects on water quality or the benthic community from the present WWTP discharge.

There is likely to be limited fishing in close to shore because of the NZ Defence Force activities in the area and Danish seining and trawling is banned in the area. The area is important for recreational fishing and Tiritiri Matangi is highly regarded for its cultural values.

The terrestrial and marine area around the outer Whangaparaoa Peninsula is recognised for its birdlife and the area supports a number of threatened species. A number of mammals are

observed in the area including common dolphin and Bryde’s whales and other whale species that are in transit through the area at times. There is no evidence that fish resources, birds or marine mammals are impacted by the existing discharge from the WWTP.

Watercare has engaged Wildlands to undertake a targeted SEA assessment in the area around the WWTP based on the proposed concept design footprint and this will be reported separately.

5. ASSESSMENT OF EFFECTS

The effects of the discharge of treated wastewater to aquatic environments will depend on the level of treatment, type and location of discharge and the sensitivity of the receiving environment. Most discharges of treated wastewaters to rivers, estuaries and coastal waters are through point source discharges, such as the existing discharge into the Whangaparaoa Passage.

In the following sections we assess the potential effects of the discharge of treated wastewater on the water quality and biota in the receiving environments for the future scenarios. The status of the existing environment with the existing discharge is discussed in Section 4. This assessment is based on descriptions of the receiving environments of the Whangaparaoa Passage and nearby sites, various guidelines and trigger levels, and published and unpublished information on the sensitivities of various habitats and biological communities to contaminants, such as those that may be released with treated wastewater under future scenarios.

The key areas of concern with treated wastewater reaching the coastal waters in the area are:

 Deteriorating water quality and general health (through increases in nutrients, microbial contaminants, heavy metals);  Changes to the water balance, including increased freshwater discharge;  Potential for nuisance plant growths, mainly phytoplankton in this case although there will be macroalgae inshore;  Changes to benthic fauna either directly through toxicity or indirectly the through the food web leading to fish and birds;  Development of anoxic conditions through oxygen depletion, sulphide-rich sediments and poor health of the benthic habitat which have flow-on effects to higher levels in the food web; and  Increased risk of microbial contamination of shellfish (including aquaculture) and for recreational activities.

The potential for these adverse effects as a result of the discharge of treated wastewater on the receiving environments and their physical, chemical and biological features is discussed below.

The average daily flows and peak weather flows under various population increases (Scenarios) as used in the assessment of effects are summarized in Table 5-1 and the resulting loads are provided in Table 5-2. Note that the median concentrations used for these

estimates are relatively conservative in terms of what we would expect as the staged development takes place except perhaps TN which may be slightly higher for Scenario 1 and TSS which will be higher until Scenario 2.

Also note that the population estimates used for staging treatment were 97,000 for Stage 1, 136,000 for Stage 2 and 188,500 for Stage 3.

Table 5-1. Parameters for scenarios considered and assessed. ADF = Average daily flow, PWWF = Peak wet weather flow.

2018 ~2031 ~2041 ~2053

Existing Scenario 1 Scenario 2 Scenario 3 Average Dry Weather Flow 12,960 21,600 30,240 42,336 (ADWF) m3/d Peak Dry Weather Flow 39,825 65,475 91,800 127,238 (PDWF) m3/d Peak Wet Weather Flow 53,100 87,300 122,400 169,650 (PWWF) L/s 615 1,010 1,417 1,964

Table 5-2. Predicted loads for population scenarios considered and used in the assessment of effects. Note that the 2018 loads are actual measured loads.

~2018 ~2031 ~2041 ~2053

Existing Scenario 1 Scenario 2 Scenario 3 Median

Concentration cBOD5 (t/yr) 5 12 40 56 77 TSS (t/y) 5 31 40 56 77 Ammoniacal 5 12 40 56 77 Nitrogen (t/yr) Total Nitrogen (t/yr) 10 53 96 112 155

Water quality parameters in the discharge will improve once new treatment is fully commissioned to the meet the proposed limits in Table 5-3. Limits for the current WWTP are also given for comparison. Note that the new level of treatment will take some time to develop with annual median TN reducing from the present 14 mg/L to 12 mg/L by 2024 (Stage 1

upgrade) and then 10 mg/L by ~2031 (Stage 2 upgrade). The annual median TSS will reduce from the present level of just over 5 mg/L to 4 mg/L through until around 2041 when there will be a further reduction following the Stage 3 upgrade. This is because the existing WWTP plant will continue to operate alongside the new staged development until the final upgrade has occurred.

Table 5-3. Proposed treated wastewater quality standards for the new WWTP and current limits at different stages of treatment upgrade. (na = no current limit or non-applicable)

Parameter Units Existing Stage 1 - 5 Stage 2 - When Stage 3 - When Consent Years from Serviced PE Serviced PE Consent reaches 97,000 reaches 136,000

Median 92 Median 92 Median 92 %ile Median 92 %ile %ile %ile

cBOD5 g O2/m3 20 35 5 20 5 20 5 20 TSS g/m3 35 75 15 30 15 30 5 20

NH4-N g N/m3 15 N/A 5 15 5 15 5 15 Total N g N/m3 N/A N/A 15 30 10 20 10 20 E. Coli cfu/100 N/A N/A 10 150 10 150 10 150 mL Enterococci cfu/100 100 1000 10 150 10 150 10 150 mL

5.1 Hydrodynamics

The main concern with effects on the hydrodynamics of receiving waters is the impact on salinity with most biota having a salinity tolerance range, and the effect on dilution and mixing processes. The intrusion of freshwater can also form a layer of lower salinity water over seawater which can result in stratification of the water column.

There is no indication that the present discharge off the Peninsula into the Whangaparaoa Passage is resulting in any impacts on the receiving environment. Modelling by DHI (Oldman 2018) shows that, as expected, the maximum change in salinity of 0.24 PSU, will occur directly over the outfall. The mean change in salinity (i.e. averaged over all states of tide and wind conditions modelled) over the outfall even with the future discharge under Scenario 3 (2053) is less than 0.02 PSU. The area where the average change in salinity is more than 0.01 PSU would extend some 2km south of the outfall and 3km to the north of the outfall.

In summary the predicted levels will not cause any change in the salinity of the receiving environment, which has a salinity of 32-26 PSU (Table 4-2). The environment in the Whangaparaoa Passage has strong currents, is dynamic and highly dispersive with rapid dilution at the site of the proposed discharge.

5.2 Coastal water quality

5.2.1. Dilution of nutrients and other contaminants

Dilution and mixing effects are critical to dispersion and level of contaminants that can affect the receiving environment. The levels of dilution predicted by DHI (Oldman 2018) are shown in Table 5-4 at the outfall and at 50 and 100 m for Scenario 3. Scenario 3 is the worst case as with the higher flows there will be slightly less dilution near the discharge pipe compared with lower flows (Existing, Scenario 1 and 2). The implications of this dilution for the distribution of contaminants is discussed under each section below.

Table 5-4. Percentile dilution estimates over the outfall and at 50 and 100 m from it for the Scenario 3.

Percentile Dilution over the outfall Dilution 50 m from the Dilution 100 m from the outfall outfall 5 71 164 363 10 98 207 506 20 153 292 689 30 210 378 847 40 261 462 1030 50 314 549 1262 60 366 643 1580 70 419 766 2439 80 479 975 4887 90 556 1275 7896

For all of the proposed flow volumes in Table 5-1, the hydrodynamic study carried out by DHI (Oldman 2018) showed that N and P concentrations in the receiving waters from a discharge off Whangaparoa would be rapidly diluted to background levels beyond the near-field of several meters from the discharge point. Dilutions at the outfall itself will be rapid and diluted by at least 70x for over 95% of the time and 360x at 100 m away.

With a final discharge median of <10 mg TN/L (same as recently consented for Snells Beach WWTP) this would need to be diluted by 1000x to reduce to background median levels of

<0.010 mg/L (Browns Bay and Orewa). This level of dilution would occur at the 40th %ile within 100 m of the discharge.

5.2.2 Nutrients and phytoplankton biomass

The following assessment is based on descriptions of the receiving environments of the Whangaparaoa area, various guidelines and trigger levels and a recent assessment of the sensitivity of estuary and coastal waters that was carried out for Clarks Beach WWTP (James et al. 2016).

Effects on water quality and comparison with standards and guidelines

Coastal waters such as those off Army Bay have relatively low levels of nutrients and good or excellent water quality (see Table 4-1 to Table 4-3, Figure 4-8). As discussed above, there will be rapid dilution away from the outfall and it is not expected to see any increase in nutrient concentrations or change in the overall classification of waters downstream, beyond 100 m from the discharge location. This is supported by the limited data to date for the Whangaparaoa Passage which didn’t show any consistent trend at the three different sites.

Various thresholds have been applied in New Zealand and overseas with the most applicable ones for New Zealand coastal waters considered to be the ANZECC (2000) guidelines and the pilot Estuary National Objectives Framework (NOF) thresholds which have recently been developed, but not yet published. The ANZECC (2000) guidelines tend to be applied by default in New Zealand and have a number of limitations and are generally considered to be too conservative for New Zealand (Dudley et al. 2017).

Assessments against the commonly used thresholds are discussed below, along with the Auckland Council objectives.

The index which the Auckland Council uses represents the deviation from “natural” conditions in the Auckland Region. As discussed earlier the level of nutrients measured over the last three years off Orewa and Browns Bay would be classified as “Excellent”. With the proposed improvement in concentrations of most parameters of the discharge at Army Bay the water quality at these sites would remain as excellent. The concentrations of nutrients in the discharge will reduce and the discharge water is rapidly diluted by water passing through the Passage. Thus levels would be maintained or in the case of TSS and TN be reduced on a concentration basis and the downstream water would be indistinguishable from background levels for all Scenarios. The reduced concentrations, particularly for TN, are an important

aspect of the proposal as the discharge quality would improve, even if the effects on the receiving environment were indistinguishable.

Recent data off Orewa and Browns Bay for NH4-N , nitrate-N and TN are below the ANZECC (2000) guidelines for inshore coastal waters (0.015 mg/L, 0.005 mg/L, 0.120 mg/L respectively) while the DRP levels are slightly over the guideline of 0.010 mg/L. However, the relevance of P trigger values in particular is questionable in New Zealand because our coastal waters have higher levels than those in SE Australia where the guidelines were developed. As stated above, under the future scenarios, the TN values would be expected to reduce even further, will not change the present “excellent” rating and we would not expect any change to the risk of phytoplankton blooms.

Modelling by DHI (Oldman 2018) has shown that in the immediate dilution at the outfall would be at least 500x for 90% of the time within 100 m. This would reduce median TN (after Stage

2 upgrade commissioned) to below <0.02 mg/L and 92nd %ile levels to below 0.04 mg/L. NH4- N levels would be reduced to <0.01 mg/L and <0.03 mg/L respectively, well below the level identified by the USEPA (1999) for chronic effects on aquatic biota and the ANZECC (2000) trigger levels for 95% protection (0.66-2.3 mg/L depending on the pH and temperature).

The recommended median level of BOD in the discharge is <5 mg/L, with a 92nd percentile limit of 20 mg/L (Table 5-3). Mixing will quickly reduce BOD concentrations, with the 50th percentile dilution prediction for Scenario 3 exceeding 1000x within 100 m of the discharge point. Consequently, under the 50th percentile dilution prediction and the 92nd percentile limit, BOD would be < 0.02 mg/L 100 m from the outfall. This compares with average reported minimum and maximum DO concentrations at Auckland Council’s east coast monitoring sites between Mahurangi Heads and Browns Bay of around 6.8 to 8.7 respectively4. Discharge- related BOD demand 100 m from the outfall under the 92nd percentile limit would therefore represent around 0.2% to 0.3% of DO concentrations recorded from East Coast monitoring sites. This is likely to be within the range of natural daily variability. The median BOD limit is more protective.

Loads

Nutrient loads are unlikely to result in increased risk of a deterioration in water quality under all future scenarios as the water will be rapidly dispersed and diluted downstream through tidal

4 Williams, P., Vaughan, M., Walker, J. (2017) Marine water quality annual report 2015. Technical Report 2017/015, Auckland Council, Auckland. 48 pp.

and wind driven currents and mixing with coastal waters. Any accumulations, if they were to occur, would be very transient and short-term.

The proposed new limits for each stage of the upgrades will mean a reduction in TN concentrations (Table 5-3) (median discharge at present is 14 mg/L, is predicted to be 12 mg/L until ~2031 and then will meet the proposed long term limit of 10 mg/L) which will mean the quality of the discharge will improve. Whether the projected increase in loadings for the future scenarios will result in adverse effects on the coastal environment off Whangaparaoa, and in particular stimulate nuisance blooms of phytoplankton downstream, is very difficult to determine because of the range of factors and complex processes outlined above (effects of currents, light, nutrients, grazing pressure).

Proposed nutrient loads were provided by CH2M Beca Ltd and Watercare and as expected show that while the median concentration is an improvement on the existing discharge for most water quality parameters, the loads will gradually increase over time. It is estimated that the load of TN in 2016/17 from the Army Bay WWTP was 53 t (Table 5-2). The load is predicted to increase under Scenario 1 to 96 t TN/y (~2031, population 116,000), to 112 t TN/y under Scenario 2 (~2041, 160,000) and to 155 t TN/y under Scenario 3 (~2053, population 192,500).

To put this into context is very difficult without having run complex linked physical-biological models for the region. However, Zeldis (2006) assessed potential N loadings to the Firth of Thames (FoT) and Hauraki Gulf and concluded that the total catchment load (total organic and inorganic N) at that time was 4,550 t N/y to the Hauraki Gulf (including the FoT) while exhange with the open ocean introduced 8,800 t N/y. Thus the load introduced from the WWTP at the end of the consent in 2053 (Scenario 3) would be ~1% of the total load to the Hauraki Gulf annually. The region is a highly dynamic one so even with the loadings from an Army Bay WWTP, Snells Beach WWTP (20t/y under future scenarios - James et al. 2016c) and Rosedale combined, we would not expect to see a change in the water quality status or risk of algal blooms increase. However it is important to continue to assess cumulative loads as Auckland’s population continues to grow across the region.

Effects of nutrients on phytoplankton

A number of factors will control phytoplankton (microscopic plants in the water column) and macroalgal growth (larger plants mostly routed in the substrate), including light availability, flushing rate, supply of macronutrients (N and P), supply of micronutrients such as silica and iron, and grazing pressure by benthic and pelagic animals (see James et al. 2016 for further background on the drivers of nuisance plant growth). However, nutrient availability is

considered a major factor leading to enrichment and increased growth of nuisance macroalgae and phytoplankton in estuaries and coastal systems in areas such as off Whangaparaoa Peninsula.

Small increases in nutrients can lead to increased diversity and productivity, but excessive nutrient concentrations are particularly detrimental and can potentially lead to nuisance phytoplankton blooms, reduced water and sediment quality, and increased risk of toxic effects. These in turn can impact on the productivity and diversity of higher trophic levels.

The supply of N is considered to be the most important limiting nutrient in New Zealand coastal waters because P concentrations are often high relative to the needs of plants and are generally of minor concern in New Zealand’s coastal ecosystems.

The response of marine plants to increased nutrients in coastal waters varies seasonally with generally less risk of adverse effects during autumn and winter, and greater risk because of warmer temperatures and light levels in spring and summer.

As previously stated in Section 4 based on monitoring of the receiving environment off Orewa and Browns Bay the existing environment is considered to be of “Excellent” quality including for phytoplankton biomass and is expected to be similar in the Whangaparaoa Passage. The nutrient levels and phytoplankton biomass are expected to stay that way under the future scenarios including Scenario 3 in 2053 and there will actually be an improvement in the quality of the discharge from the Army Bay WWTP in terms of concentrations for all scenarios. With the coastal tidal and wind driven currents in the area it is not expected that there would be any discernible change in nutrient concentrations, even though loads will increase in time.

5.2.3 Risk of emerging contaminants in the water column

Average concentrations of EOCs from measurements in the Army Bay WWTP discharge were compared against applicable ecological guidelines (see Appendix 2: Table A2). It is expected the concentrations in the future discharge will be the same as now and there will be corresponding increase in flows. Twenty-two (22) EOCs were present in Army Bay WWTP discharge at less than 10% of the applicable guideline, six (6) were present at between 10- 99%, seven (7) were present at or above the applicable guideline, while three (3) EOCs had no guidelines from which to compare.

Those above applicable guidelines ranged from 100% of the guideline (triclosan) to 1158% (β-estradiol, suggesting the minimum dilution necessary to reduce discharge EOC concentrations to below applicable guidelines is around 12x). Even with the minimum (5th

percentile) dilution over the outfall of 71x and under Scenario 3, this will be achieved. In practice a median (50th percentile) dilution over the outfall of 314x would be achieved most of the time, suggesting risks from EOCs is very low.

5.2.4 Water Quality Summary

In summary the concentrations of TN and TSS in the discharge will decrease with the proposed level of treatment and NH4-N will not change under all three growth scenarios. Therefore there would be no increased risk of eutrophication or nuisance phytoplankton or macroalgal blooms as a result of this proposal.

The levels of NH4-N and nitrate-N are well below levels that would cause toxicity to marine biota and emerging contaminants and metals would be rapidly diluted to levels below accepted guidelines.

There will be a small improvement in the quality of the discharge for TN and TSS at each of the short to medium upgrade steps and then a significant improvement when the population reaches 100,000 and 140,000 respectively.

The high quality of the water and levels of phytoplankton biomass below the ANZECC guidelines would be expected to be maintained even though TN and TP loads will increase over time under all scenarios (up to 3x under Scenario 3 in 2053) as it is a very dynamic and dispersive environment. Even under Scenario 3 the inputs are negligible compared with inputs of N from other sources including natural processes associated with offshore exchange and catchment inputs from the FoT and wider Hauraki Gulf.

The commentary on effects in the following subsections take into account the staged nature of the treatment upgrades and the subsequent staged implementation of the discharge quality improvements.

5.3 Effects of microbial contaminants

The majority of pathogens in wastewater influents include protozoans, viruses and bacteria which affect the digestive system, and can present a serious health risk if ingested, particularly through consumption of shellfish. After significant upgrade in 2006, the existing Army Bay WWTP, comprises an improved UV system and the discharge has low levels of Ent and FC microbial contaminants and viral concentrations are in the range reported for other WWTPs.

Despite expected low levels of microbial population after treatment, some pathogens associated with treated wastewater effluent potentially survive the treatment processes and thus present a risk for recreation and shellfish consumption.

5.3.1 Methodology of assessment

The approach taken for the QMRA (Dada, 2018) for Army Bay was to obtain a typical range of influent values of pathogens of interest (from other NZ studies and a limited amount of sampling and analysis at Army Bay WWTPs), and calculate the likely treated wastewater effluent concentrations as a consequence of different levels of wastewater treatment or scenarios:

i. No treatment, or complete failure of the entire WWTP,

ii. Two log reduction, i.e. 100-fold removal,

iii. Three log reduction, i.e. 1000-fold removal, and

iv. Four log reduction, i.e. 10,000-fold removal.

Median dilutions (including virus inactivation) were predicted at each of the recreational and shellfish gathering sites identified in the hydrodynamic studies (see Figure 5-1 for an example), dose-response relationships were incorporated, and finally the risk of illness from either respiratory diseases (recreation) or gastrointestinal diseases (recreation or consuming raw shellfish harvested from the site) were calculated using Monte Carlo methods to generate a most probable number.

Figure 5-1. Scenario 3 (2053) 95th percentile concentration of viruses in the surface layer of the model with summer inactivation. Treated wastewater is assigned a value of 100. A value of 0.2 represents 500-fold dilution, 0.1 represents 1000-fold dilution and 0.01 represents 10000-fold dilution. (From Oldman 2018)

Figure 5-2. Map showing Army Bay WWTP outfall location, REMP monitoring sites (Diffuse Sources 2009) and selected assessment sites for the QMRA (Sites 1,2, 5, 6 and 7) as informed by DHI’s three-dimensional ocean model.

Sites selected for the assessment of the microbial risk on swimming and shellfish gathering were informed by the dispersion modelling carried out by DHI. These exposure sites are Huroa Point, Whangaparaoa Head, Bollons Rock-Tiritiri Matangi, Army Bay, and Te Haruhi Bay (Figure 5-2).

Reference pathogens used in the QMRA were derived from international literature and other New Zealand studies. These pathogens were:

1. Adenovirus (linked with respiratory diseases via inhalation of aerosols from contaminated water during swimming, water-skiing or other water related recreational activity) – Chosen for contact recreation (swimming) only. Adenovirus is very infective and may be present in treated wastewater. Compared to other viruses, adenovirus has been reported to have prolonged survival time and increased resistance to disinfection, e.g. UV treatments (Albinana-Gimenez et al. 2009; Wyer et al. 2012; Kundu, McBride, and Wuertz 2013; Hewitt et al. 2013).

2. Enteroviruses (related to enteric infections) – Chosen for swimming and shellfish consumption. Enteroviruses are less infective, but health consequences can be more severe than adenovirus. Although human enterovirus outbreaks can occur throughout the year in temperate climates, infections are most prevalent during summer months (Sedmak, Bina, and MacDonald 2003; Costan‐Longares et al. 2008; PHAC 2015).

3. Norovirus – Chosen for swimming and shellfish consumption. Norovirus are unquestionably the most common viral cause of gastroenteritis for which dose- response data are available (Mara and Sleigh, 2010; Teunis et al., 2008). Norovirus outbreaks can occur throughout the year but have been reported to occur more frequently during the colder winter seasons in temperate climates (Lofranco 2017; CDC 2014; Maunula, Miettinen, and Von Bonsdorff 2005; Ahmed, Lopman, and Levy 2013).

Typically, no bacteria and protozoa are included as reference pathogens in the QMRA because being larger microbes, they are effectively eliminated during the WWTP treatment process. Conversely, viruses are comparatively less susceptible to advanced wastewater treatment systems. The greatest public health risk linked with the discharge of treated wastewater therefore relates mainly to viruses (Courault et al. 2017; Prevost et al. 2015). This explains their wide-scale use as reference pathogens for treated wastewater discharge QMRAs (McBride 2013, 2016a,b).

Exposure was calculated for all five recreational and shellfish harvesting sites at five different continuous discharge flow scenarios:

a) A baseline case, i.e. no expansion in current discharge levels and the existing (2018) population (64,000 population equivalents [PE] is discharged from the outfall);

b) Short term (2031), i.e. a future population of 116,000 PE;

c) Medium term, i.e. a future population of 160,000 PE;

d) Long term, i.e. a future population of 192,000 PE; and

e) Extreme long term i.e. a future population of 192,000 PE during extreme conditions of peak wet weather flow.

Note that the PEs stated here are higher than they are now predicted to be but were what was used in the earlier modelling and are thus conservative.

Different risks (based on exposure times) were calculated for children (enterovirus and norovirus) and adults.

Dose-response relationships were derived mainly from microbial challenge studies (though some “outbreak” data were also considered). In these studies, adult volunteers are each challenged with a dose of a pathogen and their infection and illness states are monitored for a few days thereafter.

Risk represents the quantitative part of the QMRA using Monte Carlo statistical modelling. The Excel add-on “@Risk” was used to make the calculations from 1,000 iterations for each virus for each site and for each scenario. On each iteration 100 individuals were ‘exposed’. This repetitive sampling from distributions and ranges of key variables produces a more robust and realistic risk rather than just using average values.

Dada (2018) presents risk in terms of illness for enterovirus and assumed that all individuals who become infected with enterovirus also become ill. For the other pathogens (adenovirus and norovirus), risk was presented in terms of documented probabilities of illness, given that infection has occurred. The resulting output in terms of an individual’s illness risks facilitates were thereafter compared with relevant guidelines.

5.3.2 Health risks due to contact recreation at the exposure sites

Regardless of the QMRA reference pathogen used, some conclusions were the same in the Dada (2018) QMRA report. For instance, among all the assessment sites considered in this study, greatest risks were associated with Huroa Point and Army Bay sites following discharge of untreated wastewater (no virus load reduction) from the existing outfall site. Also, risk associated with illness is generally higher among children than adults. This is generally understandable given that children tend to ingest a higher volume of water during recreation.

QMRA results also generally indicate that risks increase with increasing wastewater flows based on population estimates, i.e., 2018 <2031<2041<2053. Also, risks during winter are generally higher than risks during summer for all simulated scenarios of varied future discharges based on population estimates. This is typically due to increased potentials for UV- based inactivation associable in summer months. In terms of the extent of impact of the discharge on the assessment sites, risks due to swimming in waters potentially contaminated with viruses are in increasing order (site numbers from Figure 5-2): Bollons Rock-Tiritiri Matangi (5)

At all the five sites (i.e. Huaroa Point (1 on Figure , Whangaparaoa Head (2), Bollons Rock- Tiritiri Matangi, Army Bay, and Te Haruhi Bay), the predicted recreational health risks (IIR) were:

 No treatment scenario - High and often exceeded the “no observable effects level” of 1% for enterovirus, adenovirus and norovirus;  Two log treatment scenario - Low and always fell below a “no observable effects level” of 1% when there was a 100-fold removal of enterovirus, adenovirus and norovirus at the Army Bay WWTP prior to discharge;  Three log treatment scenario - Very low and always fell below a “no observable effects level” of 1% when there was 1,000-fold removal of enterovirus, adenovirus and norovirus at the Army Bay WWTP prior to discharge; and  Four log treatment scenario - Practically zero and always fell below a “no observable effects level” of 1% when there was 10,000-fold removal of enterovirus, adenovirus and norovirus at the Army Bay WWTP prior to discharge.

5.3.3 Health risks due to consumption of raw shell fish harvested from exposure sites

At all five sites, the predicted health risks (IIR) due to consumption of raw shell fish harvested from the exposure sites were:

 No treatment scenario - High and often exceeded the “no observable effects level” of 3% for enterovirus and norovirus;  Two log treatment scenario - Reasonably high, i.e. >2.0, although IIR was still below the 3% threshold when there was a 100-fold removal of enterovirus and norovirus at the Army Bay WWTP prior to discharge;  Three log treatment scenario - Low, and always fell below a “no observable effects level” of 3% when there was a 1,000-fold removal of enterovirus and norovirus at the Army Bay WWTP prior to discharge; and  Four log treatment scenario - Practically zero and always fell below a “no observable effects level” of 3% when there was a 1000-fold removal of enterovirus and norovirus at the Army Bay WWTP prior to discharge.

Further analyses for high levels of consumption of shellfish (up to 800 gm/d) showed that at this level and with peak flows log 3 reductions would be required for Scenario 3 to reduce risks to an acceptable levels (Dada 2018).

5.3.4 Summary of microbial effects and recommendations

In summary because of the very high dilution levels available at the discharge site, 2 Log viral removal (100 fold) is sufficient to reduce the risk of illness to swimmers to negligible levels. The discharge of highly-treated wastewater (at least 1000-fold reduction in viral concentrations) from the Army Bay WWTP under current and possible future wastewater discharge rate scenarios will reduce the risk of illness to individuals who consume raw shellfish harvested from the selected exposure sites to negligible and acceptable levels.

From a conservative perspective, Dada (2018) recommended at least 1,000-fold (i.e. 3 Log) reduction in viral concentrations at the Army Bay WWTP prior to discharge. Even during the worst-case maximum discharge scenario (192,000 PE), this level of treatment is sufficient to reduce health risks to acceptable levels associated with contact recreation and even high consumption of raw shellfish harvested at all the selected sites in the receiving environment. This treatment will be present through each of the upgrade stages.

5.4 Effects on benthic habitats and animal communities

The benthic ecology in the Whangaparaoa Passage, and the effects of the existing discharges from the Army Bay WWTP are assessed in the benthic ecological assessment (Kelly et al. 2018). Benthic values and the effects of the existing discharges on those areas are summarised in Section 4.6 above. The conclusion was that the existing discharge has no observable or ecologically meaningful effects on benthic habitat and communities for the existing discharge off Army Bay.

5.4.1 Benthic effects of the proposed changes to discharge loads

The proposed discharge from the Army Bay WWTP as a result of servicing a larger population could affect benthic sediments and biological communities by potentially increasing the risk of:

 Toxic effects;  Organic enrichment of sediments caused by increasing organic matter loads in the discharge; and/or,  Eutrophication caused by increasing nutrient loads.

Toxicity

Heavy metals and other toxic contaminants from the discharged wastewater may directly affect benthic species. The key heavy metals (and metalloids) with the potential to adversely affect them are considered to be As, Cd, Cr, Cu, Hg, Pb, Ni and Zn.

The only heavy metals that exceed the ANZECC 95% marine trigger values in the current discharge are Cu and Zn. Existing Cu concentrations in the discharge require around 2-fold dilution, and existing Zn concentrations require around 3-fold dilution to fall below their respective ANZECC guidelines (2000). This dilution is predicted to be easily achieved in the immediate vicinity of the outfall even under Scenario 3. Thus, the effects of discharged metals on benthic species are considered to be negligible and little change in these concentrations and effects is anticipated with the proposed scenarios.

Organic enrichment of sediments

In extreme cases, increases in organic matter can result in deoxygenation of sediments and hydrogen sulphide buildup. However, this outcome appears highly unlikely under any of the scenarios, because:

. sediments around the existing discharge were found to have similar TOM concentrations to the three reference sites sampled by Coast and Catchment, and lower total organic carbon concentrations than two of the three reference sites; and . improvements to the treatment process are expected to reduce loads of TSS and particulate organic matter.

Nutrient enrichment effects on benthic environment

A major concern with the discharge of treated wastewaters into marine environments is nutrient enrichment and the direct and indirect effects on benthic communities. The effects of nutrient enrichment are reasonably well understood. Those impacts manifest themselves through increases in algal productivity, which if significant can decrease water clarity, affect dissolve oxygen concentrations, enrich sediments (by increasing organic loads) and change biochemical processes, leading to alterations in the structure and functioning of benthic communities and habitats.

Associated benthic effects can include:

. the promotion of nuisance macroalgal blooms,

. effects on subtidal seagrass and macroalgal beds if an increase in phytoplankton productivity reduces water clarity, with an associated reduction in light levels on the seabed (note that seagrass is not present in Whangaparaoa Passage). . the alteration of benthic infaunal communities due to nutrient-driven organic enrichment, including reductions in species richness and diversity, that typically involves an increase in the abundance of small, opportunistic species such as polychaete worms and, the loss of large, long-lived invertebrates.

Nutrient loads will increase under all growth scenarios, but nutrient concentrations in the highly dynamic environment off Army Bay are unlikely to change to the point where a measurable effect in phytoplankton productivity occurs. Pooled 2009 to 2016 summer results from Auckland Council’s East Coast monitoring sites (Goat Island, Ti Point, Mahurangi Heads, Orewa and Browns Bay) show there is no relationship between instantaneous measures of TN and TIN concentrations up to approximately 0.16 mg/L and 0.12 mg/L respectively, and chlorophyll a concentrations (a proxy for phytoplankton productivity) (Figure 5-3). Accordingly, a measurable increase in phytoplankton productivity is not expected to occur, provided concentrations in Whangaparaoa Passage are maintained below these levels. This is expected to be achieved at the actual discharge point. It also follows that adverse effects caused by nutrient-driven organic enrichment would also be avoided.

a. -2.0

-2.2

-2.4

-2.6

-2.8

-3.0

Chlorophyll a (mg/L) -3.2

log -3.4

-3.6

-3.8 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 Total nitrogen (mg/L) b. -1.0 -1.2 -1.4 -1.6 -1.8 -2.0 -2.2 -2.4 -2.6 -2.8

Chlorophyll a (mg/L)

10 -3.0

log -3.2 -3.4 -3.6 -3.8 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 Total inorganic nitrogen (mg/L)

Figure 5-3. Relationships between a) total nitrogen and b) total inorganic nitrogen and log10 chlorophyll a concentrations from Auckland Council’s East Coast monitoring sites (data provided by the Research, Investigation and Monitoring Unit (RIMU)).

5.5 Effects on fish, mammals and birdlife

The discharge of treated wastewater is unlikely to have any effect on fish resources, mammals or bird in the region. Wastewater discharges can directly affect fish by:

 Reducing DO concentrations through the effects of oxygen demanding substances and eutrophication;  Reducing water clarity by promoting phytoplankton productivity and increasing suspended solids concentrations; and  Introducing toxic contaminants into the receiving environment.

Indirect effects on fish can occur through changes in the availability of prey or habitat.

Marine mammals are also susceptible to effects caused by the discharge of toxic contaminants, but neither fish nor marine mammals are likely to be affected by human pathogens.

5.5.1 Effects on fish and mammals

The potential for the proposed Army Bay discharge to cause adverse effects on fish resources and mammals is considered below, using information provided on discharge quality, predictions of dilution around the outfall, and ambient water quality, together with water quality guidelines and available information on species sensitivities to some environmental stressors.

Dissolved oxygen

Median DO levels in the discharges are predicted to be similar under all scenarios to those at present (median 3.5 mg/L). Mixing will quickly increase DO concentrations in the discharge plume, with the 50th percentile dilution prediction for Scenario 3 exceeding 1000x within 100 m of the discharge point. Using this dilution and the average minimum concentration reported at Auckland Council’s east coast monitoring sites between Mahurangi Heads and Browns Bay in 20155 (6.8 mg/L), DO concentrations beyond the mixing zone would be at least 6.8 mg/L for all scenarios. This is considered to be ecologically indistinguishable from ambient concentrations.

5 Williams, P., Vaughan, M., Walker, J. (2017) Marine water quality annual report 2015. Technical Report 2017/015, Auckland Council, Auckland. 48 pp.

Recommended BOD limits for the treated discharge are lower than the current limits and BOD effects are likely to be within the range of natural daily variability. Consequently, any DO effects are not expected to extend beyond the mixing zone.

Effects from changes in water clarity and suspended solids

Information on the effects of suspended solids on New Zealand marine fish species is limited to snapper (Chrysophrys auratus). Snapper are visual feeders and larvae and small juveniles require good water clarity to feed on pelagic prey. TSS concentrations of 32 mg/L were found to cause ≤20% mortality in snapper larvae after 12 hours, and concentrations of 157 mg/L were found to cause 50% mortality (Partridge & Michael 2010). In juvenile snapper, TSS concentrations of >23 mg/L were found to be correlated to higher levels of gill deformation (Lowe et al. 2015). Turbidity was also found to affect the feeding choices of snapper with fish primarily consuming pelagic prey in clear estuaries, but primarily consuming benthic prey in estuaries with TSS concentrations of more than 23 mg/L (Lowe et al. 2015).

While New Zealand effects data are limited, the findings from snapper studies suggest the impacts of TSS concentrations in the discharge, even right at the discharge point (<0.1 mg/L), on fish are likely to be negligible.

Toxicity

Heavy metals, NH4-N , and other toxic contaminants (including contaminants of emerging concern) from the discharged wastewater may directly affect fish and marine mammals, or in some cases, indirectly affect them through biomagnification up the food chain (e.g. mercury). The key heavy metals with the potential to adversely affect fish and marine mammals are considered to be As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn.

The only heavy metals that exceed the ANZECC (2000) 95% marine trigger values in the current discharge are Cu and Zn. These two metals are essential for fish and mammals, but are toxic at high concentrations. Zn and Cu have been shown to accumulate in marine mammals, with concentrations increasing with age. However, there is no evidence that these two metals biomagnify up the food chain (Marcovecchio et al. 1994). Existing copper concentrations in the discharge require around 2-fold dilution, and existing zinc concentrations require around 3-fold dilution to fall below their respective ANZECC (2000) guidelines. This dilution is predicted to be easily achieved in the immediate vicinity of the outfall with levels for 95% of the time being at least 70x right at the discharge point (Table 5-4). Thus, the effects of discharged metals on fish and mammals are considered to be negligible.

The ANZECC (2000) 95% toxicity guideline for Amm-N in slightly to moderately disturbed systems is 0.91 mg/L total NH4-N , which is well above concentrations in the proposed discharge in the near-field after immediate dilution (as is the 99% guideline value of 0.5 mg/L).

The effects of NH4-N will therefore be negligible.

In summary, given the relatively low concentration of nutrients and contaminants in the treated wastewater, and the rapid dilution of the discharge, the effects of the discharge on fish and marine mammals are considered to be negligible.

5.5.2 Bird life

The values associated with shore and estuarine birds and estuarine fish are intrinsically linked to water quality. However, impacts of the discharge of treated wastewater to estuaries and coastal environments on bird and fish populations are highly unlikely unless there are substantial releases of organic matter and changes to the benthic invertebrate and macroalgal community. Increases in organic matter could result in smothering of juvenile fish, fish eggs and benthic invertebrates but as the discharge is unlikely to cause changes in these communities and habitats, and water quality will be improved, at least in terms of concentrations in the discharge, then we would not expect such effects from the future discharges, if the treatment is to the proposed level.

Shellfish and animals that feed on benthic invertebrates, such as oystercatchers and some fish species can be impacted through bioaccumulation of contaminants, including pathogens and heavy metals. Heavy metals would be rapidly diluted to well below ANZECC (2000) guidelines beyond the near-field and FC levels in the discharge water are very low and often below detection limit. Thus, the future discharge would not be expected to cause any effects on these communities.

In summary changes to the benthic fauna that provides the food resource for fish and bird life are also not predicted to occur and thus flow on effects would not be expected.

5.6 Summary for each increase in population scenario

Scenario 1 effects – 2031 (116,000 PE)

Under Scenario 1 by ~2031 flow will increase, water quality will either be maintained or in the case of TN will be a slightly improved in terms of concentrations. Because of the rapid dilution of at least 70x for at least 95% of the time then concentrations will be rapidly diluted to be indistinguishable from background. Loads (flow x concentrations) of constituents being

discharged will increase approximately 2 fold over the existing situation for the likes of BOD and amm-N,up to 1.8 fold for TN and around 1.3 fold for TSS. Again because of the high level of dilution and dispersal we would not expect to see any increased risk or change to the level of trophic state or nuisance algae. Only a 1 log reduction in microbial contaminants is required to meet standards in the receiving environment for recreation or shellfish gathering except for high shellfish consumption that would require 2 log reduction. Watercare are planning on providing a 3 log reduction. Any effects on the benthic habitat and biota, if they occurred would be acceptable, if they did occur, even at the discharge point itself. There would be no effects on fish resources, mammals or birds.

Scenario 2 effects – 2041 (160,000 PE)

Under Scenario 2 there would be slightly less dilution compared with Scenario 1 due to higher flows but again concentrations of nutrients and other contaminants would be maintained or slightly improved improved. Loads for BOD and amm-N would increase 2.3 fold and TSS and TN would increase 1.8 and 2.1 fold compared with the existing situation. Because of maintenance or improvement in concentrations and the strong currents and rapid dilution and dispersal any changes in trophic state or risk of nuisance blooms would be indistinguishable from background. As for Scenario 1 only a 1 log reductions in pathogens would be required to meet standards in the receiving environment for recreation or shellfish gathering except for high levels of shellfish consumption which would require 2 log reduction and Watercare are planning on a 3 log reduction As for Scenario 1 there would be no impacts on fish resources, mammals or birds.

Scenario 3 effects – 2053 (192,500 PE)

Scenario 3 would result in further improvements in water quality however the higher flow rates would mean less dilution but as discussed earlier there would still be more than 70x dilution for 95% of the time at the pipe itself, and considerably higher dilution as one moves away from the discharge point. Annual loads for the TN would increase 2.9 fold, TSS by 2.5 fold and BOD and NH4-N by 3.2 fold. While these levels would potentially result in greater risk to nutrient status and nuisance algal blooms, the rapid dilution and dispersal would not be expected to result in changes that would be detectable, taking into account the discharge will have improved quality and the negligible contribution compared with the amount of TN (the major nutrient driver of phytoplankton growth) that comes from the ocean each year and from rest of the catchments in the FoT and Hauraki Gulf. As for Scenario 1 and 2 only a 1 log reductions in pathogens would be required to meet standards in the receiving environment for recreation or shellfish gathering except for high levels of shellfish consumption which would require 2 log reduction and at peak wet weather flow would require 3 log reduction. Watercare are planning

on a reduction of 3 log. As for Scenario 1 and 2 there would be no impacts on fish resources, mammals or birds.

The overall conclusion is that because of the rapid dilution and dispersion at this site combined with an improved level of treatment there will not be any detectable or ecologically significant change in the receiving environment including trophic state, risk of algal blooms, and there would be no effects on fish resources, mammals or birds. The planned 3 log removal for pathogens will microbial standards for contact recreation and shellfish gathering are met.

6. ACKNOWLEDGEMENTS

To John Oldman for input on hydrodynamics, Carina Sim-Smith for input on mammals and fish, Sarah Budd Goldwater for input on birds and Luke Faithfull for reviewing the draft report.

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Appendix 1. Pivot tables for discharge water quality

Wastewater parameters

Jun 3.0 6.6 1.6 3.2 5.9 6.1 21.0 1.4

Jul 1.5 5.8 1921.9 2201.6 6.5 6.2 13.0 0.8 Aug 3.0 8.1 2.3 6.6 4.9 4.9 14.5 1.6 6.8 14.6 3.4 403 Sep 4.3 9.5 9.7 25.0 4.3 4.0 18.0 2.0 6.8 15.8 3.3 401 Oct 4.1 6.9 1.6 57.3 6.2 5.5 19.2 2.1 6.8 18.4 3.3 399 Nov 5.9 9.0 2.4 22.0 8.0 6.8 18.0 6.4 6.8 19.5 3.3 398 Dec 2.9 6.0 3.7 53.7 7.5 6.8 12.5 4.6 6.8 20.5 3.3 400 2013 3.8 8.9 11.2 33.7 6.5 5.7 17.8 1.7 6.8 19.3 3.5 400 Jan 1.9 7.4 1.6 2.9 4.4 4.0 13.0 1.6 6.8 21.0 3.4 398 Feb 1.7 5.1 4.5 13.7 9.3 8.6 17.8 2.0 6.8 22.3 3.4 396 Mar 1.2 2.7 1.6 3.3 7.2 6.6 17.5 1.6 6.8 23.0 3.5 394 Apr 1.4 2.0 2.6 8.2 6.6 6.1 15.2 1.4 6.8 22.1 3.4 401 May 2.3 3.6 3.7 28.3 5.8 5.7 17.5 1.4 6.9 16.8 3.3 398 Jun 2.7 7.4 19.4 46.2 6.6 4.7 17.3 1.5 6.8 15.6 3.5 400 Jul 2.9 9.1 3.2 15.0 4.4 4.4 19.6 1.2 6.8 16.4 3.5 395 Aug 4.2 9.4 7.0 9.4 6.4 5.9 16.3 1.3 6.8 17.1 3.8 394

Row Average Average Average of Average Average Average Average Average Average Average Average Average of Labels of BOD of NFR Enteroccoci of Faecal of TP of DRP of TN of NH3 of pH of Temp of DO Conductivity Coliform Sep 7.1 17.3 6.9 16.5 5.0 4.4 17.5 1.6 6.8 17.3 3.6 400 Oct 7.6 18.2 67.3 158.1 4.1 3.6 19.4 1.7 6.8 18.3 3.7 399 Nov 10.1 13.3 4.5 52.8 9.8 8.0 25.5 3.3 6.8 20.0 3.5 403 Dec 3.5 10.9 4.5 38.3 7.8 6.6 18.3 1.5 6.7 21.3 3.9 424 2014 1.9 5.3 10.1 116.9 5.2 4.8 12.0 1.5 6.7 19.8 3.5 399 Jan 1.9 5.5 15.0 138.7 5.1 4.7 14.8 1.3 6.8 22.0 3.4 396 Feb 1.2 2.9 4.0 51.8 3.7 3.4 11.5 0.8 6.8 23.0 3.7 400 Mar 0.7 2.8 14.1 76.5 7.3 7.1 10.6 0.8 6.7 21.7 3.7 405 Apr 1.8 4.1 3.4 684.2 5.8 5.6 10.0 0.9 6.8 21.4 3.5 399 May 1.6 5.0 6.2 46.4 7.5 6.7 11.3 1.0 6.8 19.5 3.5 395 Jun 1.3 3.1 17.4 39.0 6.5 5.6 11.3 1.1 6.7 19.3 3.3 398 Jul 1.6 3.7 48.6 171.4 5.6 5.7 10.8 1.0 6.7 18.2 3.4 399 Aug 1.1 3.7 1.6 2.4 4.7 4.4 12.0 1.1 6.7 17.5 3.7 395 Sep 2.1 5.0 1.6 11.4 3.0 2.6 11.4 1.2 6.7 16.9 3.4 396 Oct 2.1 4.8 1.6 6.1 5.2 4.5 10.3 3.4 6.8 19.0 3.4 401 Nov 3.1 8.7 1.6 47.7 1.6 1.3 14.1 4.0 6.7 19.5 3.4 400 Dec 3.8 13.0 1.6 17.0 6.7 5.6 15.6 1.3 6.7 20.4 3.4 401 2015 2.0 6.2 10.2 44.6 6.2 5.7 13.7 1.2 6.8 19.9 3.6 398 Jan 2.9 8.9 2.9 18.9 9.1 7.4 20.0 1.1 6.8 21.5 3.6 393 Feb 1.4 4.3 18.2 15.9 6.3 6.1 17.0 0.9 6.7 21.3 3.6 400

Row Average Average Average of Average Average Average Average Average Average Average Average Average of Labels of BOD of NFR Enteroccoci of Faecal of TP of DRP of TN of NH3 of pH of Temp of DO Conductivity Coliform Mar 1.3 7.0 6.9 54.1 6.5 6.4 12.8 0.6 6.8 20.7 3.7 397 Apr 2.4 8.5 4.5 27.9 6.6 6.4 15.3 1.4 6.8 20.0 3.6 395 May 2.2 4.2 2.9 5.2 7.4 6.6 14.8 2.3 6.8 19.2 3.4 398 Jun 1.0 3.9 5.3 21.4 5.4 5.0 11.9 0.7 6.8 19.0 3.8 397 Jul 1.1 3.3 4.9 40.3 5.1 3.8 9.9 0.7 6.7 18.0 3.4 405 Aug 1.2 3.3 3.3 2.4 6.1 5.1 10.1 1.2 6.8 19.0 3.4 405 Sep 2.0 5.0 4.2 11.1 2.7 2.4 9.3 1.3 6.8 19.4 3.5 400 Oct 2.6 9.2 3.2 24.8 5.3 5.1 13.0 1.3 6.7 20.0 3.6 395 Nov 3.5 11.5 58.3 273.8 8.4 8.5 16.5 1.8 6.7 20.5 3.4 399 Dec 2.2 5.8 1.6 4.1 5.6 5.2 15.0 1.4 6.7 20.4 3.6 398 2016 2.9 8.3 22.0 99.7 5.6 5.1 14.1 3.0 6.8 19.3 3.4 403 Jan 2.4 6.0 5.8 3.3 5.7 4.7 18.3 1.5 6.8 21.0 3.4 399 Feb 2.0 5.3 2.4 6.4 4.8 4.5 15.8 1.5 6.7 21.7 3.6 403 Mar 2.0 4.9 1.6 28.3 2.7 2.3 13.0 2.0 6.8 22.0 3.4 401 Apr 1.6 3.0 2.8 5.7 7.7 7.8 14.5 3.1 6.8 21.0 3.5 400 May 1.8 4.7 1.6 12.1 6.5 6.7 15.4 2.8 6.8 19.5 3.5 403 Jun 2.4 9.5 1.6 2.0 7.5 6.9 13.0 1.8 6.8 17.3 3.4 405 Jul 2.3 8.1 1.6 1.6 5.5 5.6 11.5 1.6 6.8 17.1 3.4 400 Aug 4.1 12.3 2.3 7.9 5.9 4.9 13.2 2.2 6.8 17.3 3.4 406 Sep 5.1 13.0 8.5 23.7 4.3 4.1 12.7 6.2 6.9 17.8 3.4 420

Row Average Average Average of Average Average Average Average Average Average Average Average Average of Labels of BOD of NFR Enteroccoci of Faecal of TP of DRP of TN of NH3 of pH of Temp of DO Conductivity Coliform Oct 4.2 10.4 221.6 1048.7 3.6 2.8 16.0 10.6 6.8 17.4 3.4 400 Nov 3.9 10.0 26.6 106.1 5.5 4.7 13.6 2.4 6.8 19.5 3.4 399 Dec 3.6 12.7 2.0 11.5 7.1 6.2 13.0 1.5 6.8 20.7 3.5 403 2017 2.3 4.6 9.6 46.2 5.5 5.0 13.1 1.5 7.1 22.3 3.5 401 Jan 6.2 6.2 5.5 28.5 9.3 8.4 15.2 4.7 6.8 24.2 3.4 405 Feb 1.7 5.2 8.8 50.0 6.7 6.5 14.0 1.4 6.8 25.5 3.5 399 Mar 2.0 4.1 1.6 5.6 3.7 3.0 13.0 1.4 6.8 25.2 3.4 403 Apr 1.4 4.5 1.6 2.4 3.7 3.3 12.0 0.8 6.8 24.6 3.4 400 May 1.0 3.2 3.6 3.3 4.0 3.5 12.0 0.9 6.8 21.6 3.4 399 Jun 1.1 2.6 1.6 4.1 1.3 1.1 11.8 1.1 6.8 20.3 3.3 387 Jul 2.3 2.9 41.7 246.6 3.9 3.7 10.1 0.9 6.8 20.2 3.5 393 Aug 2.1 5.1 35.5 110.1 5.1 5.1 13.2 1.4 7.0 19.5 3.8 412 Sep 2.1 2.6 1.6 4.3 4.8 4.5 12.3 1.2 6.8 20.2 3.6 413 Oct 2.1 3.3 1.6 4.2 5.6 4.9 13.2 1.1 6.8 20.6 3.5 403 Nov 2.3 6.8 1.6 14.1 6.9 6.4 14.0 1.4 10.6 21.8 3.4 399 Dec 2.2 7.5 1.9 60.2 5.8 5.2 16.0 1.3 6.8 22.3 3.4 396 2018 2.1 5.6 2.0 7.3 4.8 4.5 16.9 1.1 6.8 23.5 3.2 393 Jan 2.1 5.6 1.6 6.2 5.2 4.8 18.6 1.2 6.8 23.5 3.2 393

Feb 2.0 5.5 2.7 9.3 4.1 4.0 14.0 0.9

Wastewater discharge flow

Row Sum of Discharge Max of Discharge Labels Vol Vol2 2012 2273898 19935.83 Jun 285182 11549.26 Jul 342006 19935.83 Aug 384819 18948.93 Sep 352018 19331.82 Oct 309441 10894.35 Nov 290397 11310.80 Dec 310033 11236.69 2013 3704727 23719.48 Jan 285577 9761.17 Feb 251062 9564.53 Mar 268524 9250.98 Apr 282179 12208.06 May 371181 17795.84 Jun 400079 20366.77 Jul 324094 12358.10 Aug 383624 21550.04 Sep 390856 23719.48 Oct 253066 9813.66 Nov 234471 9234.89 Dec 260016 16351.69 2014 3292219 20614.84 Jan 239466 8373.67 Feb 217069 9154.88 Mar 227911 9131.52 Apr 226544 11496.69 May 242112 8645.99 Jun 285528 16340.11 Jul 340554 19450.64 Aug 303300 16571.54 Sep 368595 20614.84 Oct 291178 14436.42

Nov 253403 11550.09 Dec 296558 18976.09 2015 3310314 19322.46 Jan 246443 9268.29 Feb 233056 10943.61 Mar 256166 10379.49 Apr 242227 9725.67 May 304170 19322.46 Jun 291372 13775.84 Jul 296619 15649.78 Aug 337140 17141.21 Sep 318885 18621.87 Oct 259677 9390.73 Nov 264223 12345.42 Dec 260336 10887.20 2016 3700925 21929.18 Jan 283375 15022.68 Feb 259537 17341.51 Mar 277576 14862.29 Apr 263725 14964.90 May 282358 11442.07 Jun 309733 17782.71 Jul 365445 16784.28 Aug 391549 21929.18 Sep 343898 18819.44 Oct 351928 20681.54 Nov 291829 14665.62 Dec 279971 13422.37 2017 4040582 26367.43 Jan 264280 10582.28 Feb 255578 16359.02 Mar 377167 20955.73 Apr 408960 25625.12 May 362369 21205.13 Jun 359330 26367.43

Jul 418822 18816.25 Aug 346416 18435.01 Sep 360417 15768.39 Oct 320029 15035.17 Nov 284961 10939.65 Dec 282253 12512.32 2018 665076 23579.95 Jan 309684 14648.05 Feb 355392 23579.95 Grand 20987741 26367.43 Total

Appendix 2. Technical data for EOC risk analyses. Table A1. EOC concentrations from Army Bay WWTP discharge and comparison with typical WWTP discharge concentrations in Auckland, New Zealand and worldwide

Army Bay WWTP Auckland WWTPs1 NZ WWTPs2 International EOC/Class CAS# Average SD %CV Waiuku Omaha Average Average3 Range4 Antimicrobials and parabens Chloroxylenol 88-04-0 167 6 4 7.0 18.6 322 300 No data Methylparaben 99-76-3 2.7 0.7 25 <0.1 3.9 82 19 No data Ethylparaben 120-47-8 <0.1 NA NA <0.1 <0.1 4.1 2.5 No data Butylparaben 94-26-8 <0.1 NA NA <0.1 <0.1 2.7 No data No data Methyl triclosan 4640-01-1 15 1 5 3.0 <0.1 1.4 No data No data Triclosan 3380-34-5 20 1 4 8.4 4.5 38 200 10-6,880 Alkylphenols Total Tech NP 84852-15-3 152 6 4 52 283 No data No data <30-7,800 Steroid hormones Estrone 53-16-7 27 1 3 <0.1 20 No data 81 <1-80 17β-estradiol 50-28-2 4.6 0.2 4 <0.1 <0.1 No data 2.8 <1-7 Estriol 50-27-1 <0.1 NA NA NT NT No data 1.0 No data 17α-ethinyl estradiol 57-63-6 <0.2 NA NA <0.5 <0.5 No data 1.5 <1-2 Plasticisers dimethylphthalate (DMP) 131-11-3 7.8 1.0 12 1.5 <0.5 No data 340 ND-1,520

Army Bay WWTP Auckland WWTPs1 NZ WWTPs2 International EOC/Class CAS# Average SD %CV Waiuku Omaha Average Average3 Range4 diethylphthalate (DEP) 84-66-2 85 10 12 11 6.7 No data 800 No data dibutylphthalate (DBP) 84-74-2 56 1 2 24 10.9 No data 570 ND-4,130 butylbenzylphthalate (BBP) 85-68-7 6.9 0.4 5 <1.0 <1.0 No data 180 No data diethylhexylphthalate (DEHP) 117-81-7 70 8 11 10 <50 No data 2400 0.1-54,000 Bisphenol A 80-05-7 4.8 0.5 11 5.1 3.6 17 200 <30-1,100 Polycyclic musks Galaxolide 1222-05-5 1332 105 8 30 60 243 850 <60-2,770 Tonalide 21145-77-7 27 4 14 2.0 1.4 61 250 <50-320 Organophosphate flame retardants Tri-isobutyl-phosphate (TiBP) 126-71-6 49 2 4 <0.2 27.6 29 160 No data Tri-n-butyl-phosphate (TBP) 126-73-8 70 9 13 23 39 128 300 No data Tris(2-chloroethyl) phosphate (TCEP) 115-96-8 331 1 0 96 167 108 350 60-2,400 Tris (1-chloro-2-propyl) phosphate (TCPP) 13674-84-5 2772 33 1 513 1064 321 1500 100-21,000 Tris(2-chloro-1-(chloromethyl)ethyl)phosphate (TDCP) 13674-87-8 410 4 1 35 85 222 150 No data Triphenylphosphate (TPP) 115-86-6 6.7 0.4 5 <0.5 165 301 50 No data Tris-(2-butoxyethyl)-phosphate (TBEP) 78-51-3 49 2 3 69 110 783 440 No data Tris(2-ethylhexyl) phosphate (TEHP) 78-42-2 <0.2 NA NA <0.2 <0.2 No data No data No data Insect repellent Diethyltoluamide (DEET) 134-62-3 269 4 1 NT NT 220 700 610-15,800

Army Bay WWTP Auckland WWTPs1 NZ WWTPs2 International EOC/Class CAS# Average SD %CV Waiuku Omaha Average Average3 Range4 Pharmaceuticals Acetaminophen 103-90-2 5.1 1.0 19 NT 6.0 No data 88 ND-30 Aspirin (acetylsalicylic acid) 50-78-2 2720 29 1 NT NT No data No data No data Salicylic acid 69-72-7 18 1 3 NT NT No data 78 ND-500 Carbamazepine 298-46-4 1001 12 1 NT NT No data 546 5-4,600 Clofibric acid 882-09-7 <0.5 NA NA NT NT No data No data ND-330 Diclofenac 15307-86-5 540 1 0 NT 51 No data 454 1-690 Ibuprofen 15687-27-1 234 3 1 NT 145 No data 277 ND-55,000 Ketoprofen 22071-15-4 <0.1 NA NA NT NT No data 138 3-3,920

Meclofenamic acid 644-62-2 <0.5 NA NA NT NT No data No data Naproxen 22204-53-1 240 2 1 NT NT No data 227 <2-5,090 1 Waiuku (Stewart 2016b); Omaha (Stewart, 2016a). 2 From 13 WWTPS around New Zealand (Northcott et al,2013). 3 From Margot et al. (2015) where available. Review of studies on a wide range of WWTPs in Europe or in the United States 4 From Luo et al. (2014). Review of WWTPs worldwide Risk Assessment

It has to be noted that few EOCs have established national water quality guidelines (ANZECC, 2000a) and those that do exist are generally low reliability (ANZECC, 2000b). Therefore, to assess ecological risk, discharge concentrations were compared against the lowest relevant water quality guidelines (WQGs) available in the international literature or, if none available, predicted no effects concentrations (PNECs) or lowest effects concentrations (LOECs). ANZECC (marine) trigger levels (95% protection) were used in preference to international WQGs, when they exist, and PNECs were used in preference to LOECs.

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To provide the most conservative assessment of risk, concentrations below detection limits were set at the detection limit for comparison with ecological guidelines.

Table A2. Comparison of Army Bay WWTP discharge concentrations with water quality guidelines or predicted no effects concentrations1

Army Bay WWTP Lowest WQG WQG Lowest % of WQG or EOC/Class2 discharge PNEC reference (ng/L) reference4 PNEC PNEC concentration (ng/L)3 Antimicrobials and parabens Chloroxylenol 167 266 Margot (2015) 640 Methylparaben 2.7 4000 Margot (2015) 0.07 Ethylparaben <0.1 21000 Margot (2015) 0.0005 Butylparaben <0.1 2000007 Dobbins (2009) 0.0001 Methyl triclosan 15 ND5 ND5 ND5 Triclosan 20 20 EQS (EU) 100 Alkylphenol Total Tech NP 152 10008 ANZECC 15 Steroid hormones Estrone 27 3.6 EQS (EU) 751 17β-estradiol 4.6 0.4 EQS (EU) 1158 Estriol <0.1 67 Margot (2015) 0.1 17α-ethinyl estradiol <0.2 0.037 EQS (EU) 541 Plasticisers DMP 7.8 3700000 ANZECC 0.0002

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Army Bay WWTP Lowest WQG WQG Lowest % of WQG or EOC/Class2 discharge PNEC reference (ng/L) reference4 PNEC PNEC concentration (ng/L)3 DEP 85 900000 ANZECC 0.01 DBP 56 25000 ANZECC 0.2 BBP 6.9 20000 EQS (EU) 0.03 DEHP 70 10009 ANZECC 7 Bisphenol A 4.8 1500 EQS (EU) 0.3 Polycyclic musks Galaxolide 1332 6800 Margot (2015) 20 Tonalide 27 3920 Margot (2015) 1 Organophosphate flame retardants TiBP 49 110 NC 44 TBP 70 660 NC 11 TCEP 331 1440000 Margot (2015) 0.02 TCPP 2772 120000 Margot (2015) 2 TDCP 410 10000 Margot (2015) 4 TPP 6.7 140 Margot (2015) 5 TBEP 49 76000 Margot (2015) 0.1 TEHP <0.2 ND5 ND5 ND5 Insect repellent DEET 269 41000 0.7 Pharmaceuticals Acetaminophen 5.1 500 Margot (2015) 1 Stuer-Lauridsen Aspirin 2720 61000 4 (2000) Salicylic acid 18 3200 Margot (2015) 1 Carbamazepine 1001 500 EQS (EU) 200

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Army Bay WWTP Lowest WQG WQG Lowest % of WQG or EOC/Class2 discharge PNEC reference (ng/L) reference4 PNEC PNEC concentration (ng/L)3 Clofibric acid <0.5 492010 Ferrari (2004) 0.01 Diclofenac 540 50 EQS (EU) 1080 Ibuprofen 234 300 EQS (EU) 78 Ketoprofen <0.1 132411 Minguez (2016) 0.01 Meclofenamic acid <0.5 ND5 ND5 ND5 Naproxen 240 1700 EQS (EU) 14 1 Colour coding. Green = negligible ecological risk (< 10% of WQG/PNEC); Orange = minor ecological risk (10-99% of WQG/PNEC); Red potential ecological risk (>100% WQG/PNEC); Grey = insufficient data to assess. 2 For acronym definitions see Table A1. 3 Calculated from 2 consecutive grab samples. 4 EQS are the chronic environmental quality standards for inland surface waters (annual average value) under European Union Water Framework Directive (reviewed in Margot et al., 2015); NCs are concentrations causing negligible effects to ecosystems (Verbruggen et al., 2006); ANZECC are marine trigger values for protection of 95% of species (ANZECC, 2000a) 5 Not able to be derived 6 Low reliability PNEC 7 LOEC value 8 Low reliability ANZECC trigger value for 4-nonylphenol supported by USEPA chronic saltwater guideline of 1700 ng/L 9 Low reliability ANZECC trigger value for DEHP supported by EQS (EU) value of EU EQS of 1300 ng/L 10 Chronic against Rotifer species 11 Artemia salina - Marine water

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