Assessment of Surface Water Quality Effects

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Assessment of Surface Water Quality Effects

Project No: 250310 Document Ref:

NCI-3PRE-2ENV-RPT-0039 Revision: 2 2 December 2016

Northern Corridor Improvements

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This report has been prepared for the benefit of the NZ Transport Agency (NZTA). No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person.

This disclaimer shall apply notwithstanding that the report may be made available to other persons for an application for permission or approval or to fulfil a legal requirement.

Quality Assurance Statement

Prepared by: Jennifer Leslie (Pattle Delamore Partners Ltd)

Reviewed by: Hayden Easton and Roger Seyb (Pattle Delamore Partners Ltd)

NZTA Reviewer: David Greig

Approved for issue by Aurecon: Jon Hind Approved for use by NZTA: Deepak Rama

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Document No. NCI-3PRE-2ENV-RPT-0039

Executive summary

Monitoring of six sites within the Oteha Valley, Alexandra Stream and Lucas Creek catchments was carried out on five occasions in May and June 2016 in order to establish a baseline dataset of surface water quality within the area of the Northern Corridor Improvement Project (the Project).

Sites were monitored for a range of field and laboratory parameters. The results were compared with Australian and New Zealand Environment and Conservation Council (ANZECC) (2000) guidelines in order to gain an understanding of the current condition of the Oteha Valley Stream, Alexandra Stream and Lucas Creek. A further aim was to establish whether the nearby Rosedale Landfill was having an influence on surface water quality.

Field and laboratory measurements were compared with those previously collected by Auckland Council at two nearby long-term monitoring sites. The purpose of this comparison was to validate the water quality datasets collected in this study. The water quality results obtained will be used as a baseline to compare with future results in order to establish whether construction and/or operation effects associated with the Project are occurring.

Flow data within each waterway was collected so that it could be determined whether there was a relationship between flow and contaminant loads within the waterway. Overall the study findings were:



Results collected were very similar to the Auckland Council’s long-term monitoring record, with the exception of Total Zinc which was more elevated at Site 1. This may be due to the upstream location of Site 1 being in closer proximity to high-yielding sources of zinc such as industrial roofs and road land uses, while the zinc levels at the Auckland Council monitoring site located

downstream are likely to have been diluted by land uses that discharge lower zinc yields;



In comparison to the ANZECC (2000) guidelines, all physical stressors were within all relevant guideline values. Nutrient concentrations were mostly within guideline values with the exception of one elevated Nitrate-N result. Dissolved metals – Calcium, Magnesium, Potassium and Sodium were all below the ANZECC (2000) 95% environmental protection guideline values, as was Total Lead. However, Total Zinc and Total Copper results exceeded the ANZECC (2000) 95%

environmental protection guideline values. This is likely to be due to the existing industrial and road land uses within the relatively urbanised catchments;



Obtained contaminant concentrations were all well below typical mature landfill leachate values as prescribed by Davis and Cornwell (1991). From the water quality results obtained, it can be concluded that there is no measureable influence of landfill leachate on the surface waters monitored for the events assessed. During the Project construction phase leachate is to be fully contained and discharged to sewer - there is no discharge of land fill associated contaminants therefore expected. Monitoring will be carried out to confirm this containment and discharge is operating as intended – and will be addressed by way of a management plan and the proposed consent conditions;



Based upon the water quality data obtained, it is not possible at this stage to establish whether a relationship exists between flow and contaminant loads due to a lack of variability in the flow conditions assessed. Further monitoring is to be carried out from December 2016 to February 2017 to allow an assessment of seasonal based variability in contaminant concentrations. This

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monitoring will also provide further data to assess the relationship between rainfall, flow and contaminant concentrations;



The effects of sediment discharges from erosion and sediment controls during the construction phase are expected to be no more than minor during typical operation of those controls. There is potential for elevated concentrations of sediment within discharges to the Oteha Stream. Proactive and diligent adaptive monitoring will be required to ensure that the best performance is achieved during the construction phase. The Erosion and Sediment Control Plans will ensure that

compliance is achieved with TP90 and the NZTA Guidelines; and



During the operational phase, the proposed enhanced stormwater quality treatment of existing impervious areas will result in the overall loads of key metals from the Project’s impervious areas being reduced. This means the Project will have a net beneficial effect on stormwater quality and the downstream water quality.

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Total Alkalinity A measure of water’s resistance to change in pH Total Antimony Total antimony including dissolved and particulate forms Total Arsenic The sum of arsenic in both organic and inorganic forms Total Boron Total boron in a solution, including boric acid and borate Total Cadmium Total cadium including dissolved and particulate forms Total

Chromium Total chromium including dissolved and particulate forms Total Copper Total copper including dissolved and particulate forms Total Hardness The concentration of calcium and magnesium ions

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Item Description Total Kjeldahl

Nitrogen The sum of organic nitrogen, ammonia and ammonium Total Lead Total lead including dissolved and particulate forms Total Mercury Total mercury including dissolved and particulate forms Total Nickel Total nickel including dissolved and particulate forms Total

Suspended Solids

The dry weight of particles trapped by a filter

Total Zinc Total zinc including dissolved and particulate forms

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Pattle Delamore Partners (PDP) was engaged by Aurecon on behalf of the NZ Transport Agency to conduct baseline surface water monitoring within the footprint of the Northern Corridor Improvement Project near Albany, Auckland.

The objective of this assessment was to provide baseline stream water quality data for the assessment of effects associated with earthworks during construction (including discharges from works within the Rosedale Landfill) and stormwater discharges during operation. The parameters measured were also chosen to look for existing influences of landfill leachate.

With time, the catchment conditions and environmental standards could change so that the reported assessment and conclusions are no longer valid. Accordingly, the report should not be used to refer to site conditions and environmental standards applying at a later date without first confirming the validity of the report’s information at that time.

The selected baseline monitoring sites are also used as locations for an assessment of the effects of the Project on the freshwater receiving environment.

1 Introduction

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2.1 Project Background

The Northern Corridor Improvements Project (the Project) is an accelerated project. The Project area covers the area of SH18 between Albany Highway and Constellation Drive, and SH1 between Upper Harbour Highway (UHH) interchange to just beyond the Oteha Valley Road Interchange as indicated on Figure 1 below and set out in the suite of plans provided in Volume 5.

Figure 1 Extent of Project area

Source: Base Map from LINZ

The Project proposes to upgrade the existing State highways within the Project area. In summary, the key elements of the Project are as follows:



North and West Motorway Interchange connections – SH1/SH18;



State highway capacity and safety improvements;



Northern busway extension from Constellation Bus Station and connection to Albany Bus Station;



Reconfiguration of Constellation Bus Station converting it from a terminus station to a dual direction station;



Shared Use Path (SUP) provision along existing SH1 and SH18 routes for the full extent of the Project corridor:

2 Background Information

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

Constellation Bus Station to Oteha Valley Road;



Constellation Drive to Albany Highway; and



Intermediate linkages to local network.

A full description of the Project, including its components and construction, is contained in section 5 of the Assessment of Environmental Effects (AEE).

2.2 Purpose of this Report

This report is one of a suite of technical reports that has been prepared to inform the AEE for the Project.

The construction and operation of the Project has the potential to adversely affect water quality in the streams within the Project area. Construction of the Project will involve earthworks, which have the potential to increase sediment runoff into streams. During construction, works will also be required within the Rosedale Landfill. Operation of the Project has the potential to increase contaminant levels in streams associated with stormwater from road surfaces.

The purpose of this report is to outline the results of the baseline water quality and hydrological monitoring and assess the potential effects of construction phase and operational phase stormwater discharges on freshwater quality.

2.3 Catchment Information

The Project area spans three catchments, namely:



Alexandra Stream Catchment to the west,



Oteha Valley Catchment to the east, and



Lucas Creek Catchment to the north.

Table 1 below provides a summary of the characteristics of each catchment.

Table 1 Catchment Information

Name Size and Vegetation Land Use

Alexandra Stream Catchment

270 Hectares (Morphum, 2013)

The catchment is made up of

approximately ¹/3 urban land use, with road and industrial land uses also dominant.

Oteha Valley

Catchment 1311 Hectares (Auckland Council, 2013)

The catchment is approximately ¹/3

pasture and bush, with the remainder made up of urban, industrial, commercial and road land uses.

Lucas Creek

Catchment 626 Hectares (Auckland Council, 2016)

The catchment is predominately

urbanised, with over three quarters made up of urban, industrial, business and road land uses.

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2.4 Surface Water Receiving Environments

The streams within the Project area are shown in Figure 2.

The Project area traverses three streams; Lucas Creek, Oteha Stream and Alexandra Stream. The Alexandra Stream is a sub-catchment of the Oteha Stream. The three streams are referred to separately in this report as they each represent a different local receiving environment for discharges to surface water from the Project area.

The Oteha Valley catchment is located in the centre of the former North Shore City. Oteha Valley Stream is 11.5km long and is joined by the Alexandra Stream approximately halfway along the channel. At 1311ha, the Oteha Valley catchment is the second largest stormwater catchment in the North Shore area, taking up approximately 10% of the city area. The Rosedale Landfill and the Rosedale Wastewater Treatment Plant are within the catchment (Auckland Council, 2013).

The Lucas Creek catchment is located to the north-east of Albany. Lucas Stream is 16.3km long, flowing from the north-east to the south-west and has eight main tributaries feeding into it. Lucas Creek discharges into the Lucas Creek estuary along with eight other streams from other stormwater catchments.

The Alexandra Stream catchment is a sub-catchment of the Oteha Valley catchment. Alexandra Stream is 5km long and flows in a south-north direction from the headwaters in the Unsworth Reserve through to its confluence with Oteha Valley Stream.

Whilst not a ‘stream’ in the traditional sense of the word, the stormwater drainage channels within the Rosedale Wastewater Treatment Plant to the south of Watercare’s Pond 1 fall within the definition of

‘stream’ within the Auckland Unitary Plan Operative in Part (15 November 2016).

The streams all meet near the Albany Village commercial area and flow west to the Lucas Creek estuary. This area is a sheltered depositional environment where most of the contaminants carried by the stream systems will eventually accumulate.

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Figure 2 Map of Sampling Sites

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Auckland Council has two water quality sites downstream of the sites monitored called Lucas @ Gills Rd and Oteha @ Days Bridge. These two monitoring sites are located outside of the Project area and are shown on Figure 2. However, these monitoring sites provide useful information for the Lucas Creek and Oteha Valley Catchments. A summary of data for relevant parameters from January 2014 – June 2016 has been downloaded from the Auckland Council website and is presented in Table 2 below.

Table 2 Auckland Council Data

Parameter Statistic Oteha @ Days Bridge Lucas @ Gills Rd

pH

Mean 7.19 7.23

Standard Deviation 0.29 0.24

Minimum 6.65 6.71

Maximum 7.8 7.95

Dissolved Oxygen

Mean 7.87 8.61

Minimum 4.11 6.23

Maximum 10.55 10.46

Conductivity

Mean 0.23 0.27

Minimum 0.11 0.19

Maximum 0.29 0.35

Total Kjeldahl Nitrogen

Mean 0.34 0.27

Minimum 0.16 0.05

Maximum 1.8 0.65

Dissolved Reactive Phosphorus

Mean 0.016 0.014

Minimum 0.006 0.006

Maximum 0.041 0.026

Total Suspended Solids

Mean 10.99 7.10

Minimum 1.60 1.80

Maximum 77.00 24.00

Total Copper

Mean 0.0022 0.0017

Minimum 0.0011 0.0007

Maximum 0.0055 0.0036

Total Lead

Mean 0.00044 0.00020

Minimum 0.00006 0.00005

Maximum 0.00200 0.00070

Total Zinc

Mean 0.04007 0.00644

Minimum 0.01300 0.00130

3 Summary of Existing Information

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Parameter Statistic Oteha @ Days Bridge Lucas @ Gills Rd

Maximum 0.08500 0.02500

1. All values are in g/m³, except for pH and conductivity.

These results show that pH ranges between 6.65-7.80 with a mean value of 7.19 at Oteha @ Days Bridge, and 6.71-7.95 with a mean of 7.23 at Lucas @ Gills Rd. All of these values are within the ANZECC (2000) guideline values for pH of 6.5-8.5.

Dissolved oxygen mean values are 7.97 g/m³ and 8.61 g/m³for Oteha and Lucas respectively, placing them above the ANZECC (2000) guideline minimum value of 6 g/m³. The minimum value recorded for Oteha is outside of this guideline at 4.11g/m³.

Total Lead results are all well below the ANZECC (2000) guideline of 0.0034 g/m³ at both sites. Total Zinc results are mostly within the guideline value of 0.008 g/m³at Lucas, however the maximum value recorded exceeds this. The mean value for Oteha exceeds this guideline value, as does the minimum value recorded indicating that Zinc levels within this catchment are quite high. This may be due to the urban, industrial and road land uses within the Oteha Valley catchment.

Table 3 below shows seasonal averages for the two Auckland Council monitoring sites for a selection of parameters.

Table 3 Seasonal Averages

Parameter Season Oteha @ Days Bridge Lucas @ Gills Rd

Conductivity

Summer 0.235 0.277

Autumn 0.218 0.268

Winter 0.231 0.254

Spring 0.230 0.257

Dissolved Oxygen

Summer 6.49 7.22

Autumn 7.65 8.82

Winter 9.86 10.02

Spring 8.27 8.96

Dissolved Reactive Phosphorus

Summer 0.015 0.016

Autumn 0.018 0.014

Winter 0.013 0.013

Spring 0.015 0.014

Total Suspended Solids

Summer 6.07 7.24

Autumn 9.58 5.49

Winter 20.07 9.90

Spring 11.43 6.48

Total Zinc

Summer 0.021 0.004

Autumn 0.041 0.005

Winter 0.071 0.012

Spring 0.037 0.006

1. All values are in g/m³, except for pH.

2. Summer: Jan-Mar, Autumn: Apr-Jun, Winter: Jul-Sept, Spring: Oct-Dec These results show that there is some variation in results across seasons. Dissolved Oxygen and Total Zinc values (at both monitoring sites) and TSS (at the Oteha @ Days Bridge site) are higher during the winter months, and lower during summer. The other parameters show less significant differences between seasons.

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4.1 Field Sampling Locations

Six monitoring sites were selected at four different locations across the three catchments within the footprint of the Project as shown in Figure 2 along with Table A1 in Appendix A which shows the GPS locations. The sites were selected to obtain representative data across the three catchments.

The sampling sites selected and the parameters that were monitored are summarised in Table 4 below.

Table 4 Baseline Monitoring Sites

Name Location Parameters

Site 1 Oteha Stream – South tributary (access from Rosedale Rd)

Full catchment monitoring:

Laboratory analysis, field measurements, flow monitoring Site 2 Oteha Stream – Tawa Reserve (access

from Tawa Drive)

Full catchment monitoring:

Laboratory analysis, field measurements, flow monitoring Site 2A

(2.4mØ Pipe)

Oteha Stream – Greville (access from Tawa Drive) – 2.4m Pipe

Sub-catchment monitoring: field measurements

Site 2B (3.0mØ Pipe)

Oteha Stream – Greville (access from

Tawa Drive) – 3.0m Pipe Sub-catchment monitoring: field measurements

Site 3 Alexandra Stream Peripheral catchment: field

measurements

Site 4 Lucas Creek Peripheral catchment: field

measurements

Sites 1 and 2 cover the majority of discharges from within the Project area. These sites catch flow from the existing SH1 motorway near Spencer Rd, south to the intersection with the Upper Harbour Highway and then west to near Barbados Drive. Outside this area, the Project only includes minor changes to the carriageway. A suite of laboratory water quality testing and in situ parameters were carried out for Sites 1 and 2. These sites were identified for more detailed assessment as they cover the majority of the Project area and receive flows from a significantly larger extent of new high use road than Sites 3 and 4.

Site 3 for the Alexandra Stream and Site 4 for Lucas Creek were assessed using in situ water quality parameters.

Site 1 represents the upper part of the catchment, including stormwater discharges from part of the existing SH1 and SH18, the industrial land east of SH1 and the Rosedale Wastewater Treatment Plant (RWWTP) site which is piped into the Oteha Stream just upstream of the sampling site.

Site 2 is split into three sites; the main Site 2 shows the combined effects of upstream activities, while Sites 2A and 2B immediately downstream of the 2.4m and 3.0m diameter pipe sites represent parts of the Oteha Valley catchment draining on either side of the Rosedale Landfill. Site 2A drains the

northern end of the catchment, which is predominantly residential around Greville Rd, while Site 2B includes the landfill site and drains the southern end around the industrial areas surrounding Triton Drive and Orbit Drive.

4 Baseline Monitoring Methodology

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The Alexandra Stream (Site 3) and Lucas Creek (Site 4) sites represent the peripheral catchments of the same name. These catchments will be influenced by the Project to a lesser extent than the Oteha Valley Catchment, which is why only field measurements were taken rather than full catchment monitoring. The sites were sampled across five monitoring rounds, beginning on 6 May 2016 and ending on the 17 June 2016. Each round was 10 -11 days apart.

The testing parameters were selected on the basis of the expected potential effects to surface water quality in each catchment. Sites 1 and 2 will receive the largest increases in impervious area and therefore metals were assessed so that effects from operational phase stormwater discharges could be assessed if required. Parameters associated with landfill leachate were also assessed at Sites 1 and 2 so that the potential influence of the landfill could be checked. Apart from this, the effects on surface water were considered likely to come from sediment generation during the construction phase – field parameters were considered appropriate to characterise water quality in this respect and have therefore been carried out at all sites.

Sites 2A and 2B were also monitored for field parameters so that any potential sediment discharges could be differentiated to one of these key sub-catchments.

The water quality parameters tested for are listed below.

Laboratory analysis:

Sum of Anions Sum of Cations pH

Total Alkalinity Bicarbonate Total Hardness Electrical Conductivity

Total Suspended Solids (TSS) Total Antimony

Total Boron Dissolved Calcium Dissolved Magnesium Total Mercury

Dissolved Potassium Dissolved Sodium

Chloride Nitrite-N Nitrate-N

Nitrate-N + Nitrite-N Total Kjeldahl Nitrogen

Dissolved Reactive Phosphorus Sulphate

Chemical Oxygen Demand (COD) Total Arsenic

Total Cadmium Total Chromium Total Copper Total Lead Total Nickel Total Zinc Field measurements:

Turbidity pH

Temperature

Electrical Conductivity (EC)

Oxidation Reduction Potential (ORP) Dissolved Oxygen (DO)

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4.2 Chemical Field Sampling Procedures

4.2.1 Order of sampling

The sites were visited in their numbered order, starting with Site 1 at Rosedale Rd. Following this, Site 2 was visited from Tawa Rd, then Site 3 at Alexandra Stream, and finally Site 4 at Lucas Creek.

At each site, the laboratory water samples were collected first to ensure that there was no disturbance of the water quality in the stream. Following this, the field measurements were taken, and lastly, the flow gauging was carried out.

4.3 Water Grab Samples Collection Procedures

A Mighty Gripper was used to collect water samples, so that water from the centre of the stream could be collected, without having to enter the stream potentially disturbing sediments and contaminating the sample.

Samples were collected directly into the appropriate sample bottles which had been supplied and certified clean by the analysing laboratory. The exception to this was the sample bottles containing digests, which were filled from the bulk bottle so that they were not over-filled. Each sample bottle was uniquely identified in accordance with the PDP chain of custody and sampling labelling procedure.

After collection, the water samples were kept chilled, and sent under standard PDP chain of custody documentation to the appropriate laboratories within 24 hours of sampling. This was to ensure the laboratories received the samples within the required hold times and to ensure sample integrity was maintained.

4.3.1 Field Measurements

Three pieces of equipment were used to measure the field parameters. A Hach 2100Q Turbidimeter was used to measure field turbidity. A YSI Multi Meter was used to measure temperature, pH, Electrical Conductivity and Oxidation Reduction Potential, while a YSI Dissolved Oxygen meter was used to measure Dissolved Oxygen.

4.4 Flow Monitoring Procedures

Flow monitoring was carried out using a SonTek FlowTracker Handheld-ADV® (Acoustic Doppler Velocimeter). On the first visit to Sites 1 and 2, the cross-sections to measure were selected. Cross- sections were chosen in a straight reach of the channel with uniform streamlines and relatively free of slack water, eddies and turbulence. Sections with abrupt changes in bed topography due to large rocks and cobbles were avoided. At Site 1 there was a lot of weed present, so this was removed from upstream and downstream of the chosen cross-section to eliminate effects on flow.

Once the cross-sections were selected, landmarks defining the locations were recorded in the field notes so that the same cross-section would be measured in the following monitoring rounds.

To undertake the gauging, a measuring tape was secured across the section, and a minimum of 20 stations across the stream were measured, at a depth of 0.6 of the water depth at each station. Upon returning to the office, the flow data was downloaded onto the computer and saved.

The FlowTracker was calibrated in the field, prior to measurements being undertaken. PDP owned handheld water quality meters were calibrated in the field prior to use following relevant calibration procedures supplied in the instrument user manuals. Rented handheld water quality meters were calibrated by the rental suppliers.

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5.1 Flow Results

The results of the flow gaugings are shown below in Figure 3 for the five monitoring rounds for Sites 1 and 2. The daily rainfall totals recorded at the nearby Oteha @ Rosedale Ponds Auckland Council rain gauge are also shown, to show the antecedent conditions for each event. Figure 3 shows that the stream discharge recorded was similar for four of the five events, with an elevated discharge recorded on the 27 May 2016 gauging. This was due to the 10 days of rainfall that were recorded prior to this gauging, which would have increased the amount of stormwater and groundwater reaching the stream system.

Flow gauging was carried out in order to establish whether there was a relationship between the amount of flow and the concentration of contaminants. Due to the lack of variation in flow data, it is not possible to draw a conclusion regarding this relationship from the results obtained. Low flow data would be required, which is most likely to be present throughout the summer months. Further flow monitoring will be undertaken from December 2016 to February 2017 in order to supplement the data collected to date. The data collected to date is considered sufficient for this phase of the assessment and with the additional data to be collected will form a robust baseline dataset.

Measured flow for events 1, 4 and 5 is considered not affected by rainfall. Flows were between 6.5 and 7.2 L/s for Site 1 and 9.1 and 14.8 L/s for Site 2.

Figure 3 Discharge and Rainfall

0 0.01 0.02 0.03 0.04 0.05 0.06

0 5 10 15 20 25 30 35 40 45 50

Discharge (m3/s)

Daily Rainfall Total (mm)

Discharge (m ³ /s) and Daily Rainfall Totals

Daily Rainfall Total Site 1 Site 2

5 Results

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5.2 Water Quality Evaluation Criteria

The ANZECC (2000) guidelines have been used as the primary water quality guidelines to assess the current health of surface water within the area of the Project. These guidelines have been derived using data from single species toxicity tests on a range of test species. High-reliability trigger values were calculated from ‘chronic no observable effect concentrations’ (NOEC) data. A statistical distribution method has been used to calculate four different protection levels (99%, 95%, 90% and 80% ecosystem protection) for high-reliability trigger values. In this assessment the 95% protection trigger values have been used as the default values.

5.3 Water Quality Monitoring Results

5.3.1 Physical Stressors

The pH results and the ANZECC (2000) guideline values of 6.5-8.5 are shown below in Figure 4. The results are consistent with those collected by Auckland Council at the Oteha @ Days Bridge and Lucas @ Gills Road monitoring sites which range from 6.65-7.80 and 6.71-7.95 respectively.

Figure 4 pH measured in the field compared with ANZECC (2000) guidelines

The majority of Dissolved Oxygen results recorded were above the ANZECC (2000) guideline value, as shown in Figure 5. The results are consistent with those collected by Auckland Council at the Oteha @ Days Bridge and Lucas @ Gills Road monitoring sites which range from 4.11-10.55 and 6.23-10.46 respectively.

0 1 2 3 4 5 6 7 8 9

6-May 17-May 27-May 7-Jun 17-Jun

pH

Site 1 Site 2 Site 2A Site 2B Site 3 Site 4

ANZECC (2000) Guideline

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Figure 5 Dissolved Oxygen measured in the field compared with ANZECC (2000) 95% guidelines

No guidelines are available for Turbidity, but the values recorded were all relatively low, indicative of clear water (Figure 6).

Figure 6 Turbidity measured in the field

Temperature recorded in the field decreased with each monitoring round as shown in Figure 7 below.

This is likely due to seasonal changes in weather conditions, as it moved into winter. Overall, the water temperatures are considered consistent with an urban stream catchment and the riparian conditions present.

0 2 4 6 8 10 12 14

DO (mg/L)

Dissolved Oxygen (DO) mg/L

ANZECC (2000) 95% Guideline

0 5 10 15 20 25 30

Turbidity (NTU)

Turbidity (NTU)

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Figure 7 Temperature measured in the field

Total Suspended Solids (TSS) results are shown in Figure 8 below. The results for Site 1 were consistent across the five monitoring rounds, while Site 2 was more varied. The higher TSS results recorded on 27 May and 7 June were following several days of rainfall, which is likely to transport higher sediment loads into the waterways. Overall, the TSS levels measured are considered to be relatively low.

Figure 8 Total Suspended Solids results for Site 1 and 2

Chemical Oxygen Demand results are shown in Figure 9 below. No guidelines are available for Chemical Oxygen Demand, however, the range of COD values measured within this study are within the range observed in stormwater runoff. Elevated COD concentrations up to 100 mg/kg can be

0 2 4 6 8 10 12 14 16 18 20

Temperature (°C)

Temperature (°C)

0 2 4 6 8 10 12 14 16 18

Total Suspended Solids (g/m3)

Total Suspended Solids (g/m ³ )

Site 1 Site 2

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observed during first flush events as a result of petroleum residues being mobilised from carparks and road surfaces.

Figure 9 Chemical Oxygen Demand (COD) results for Site 1 and 2

5.3.2 Metals

5.3.2.1 Total Metals

Total Lead results are shown in Figure 10 below. The result for Site 2 on 17 June 2016 was below laboratory detection limits. All results are well below the ANZECC (2000) 95% guideline value of 0.0034 g/m³. (This limit is not shown on the figure below as it is tenfold greater than the results and would not allow the differences between sites to be shown.)

Figure 10 Total Lead results for Site 1 and 2 0

5 10 15 20 25 30

Chemical Oxygen Demand gO2/m3)

Chemical Oxygen Demand (gO ₂ /m ³ )

Site 1 Site 2

0 0.00005 0.0001 0.00015 0.0002 0.00025 0.0003 0.00035 0.0004 0.00045

6-May 17-May 27-May 7-Jun 17-Jun Total Lead (g/m3)

Total Lead (g/m ³ )

Site 1 Site 2

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Total Zinc results all exceed the ANZECC (2000) 95% guideline value of 0.008 g/m3 as shown in Figure 11 below.

Figure 11 Total Zinc results for Site 1 and 2

.

Total Copper results all exceed the ANZECC (2000) 95% guideline value of 0.0014 g/m3 as shown in Figure 12 below. There is a spike in results on 27 May 2016. This aligns with the heavy rainfall in the days preceeding sampling which increased flows to the river, likely causing the increase in copper levels.

Figure 12 Total Copper results for Site 1 and 2 0

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

6-May 17-May 27-May 7-Jun 17-Jun Total Zinc g/m3)

Total Zinc (g/m ³ )

Site 1

Site 2

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045

6-May 17-May 27-May 7-Jun 17-Jun TotalCopper g/m3)

Total Copper (g/m ³ )

Site 1

Site 2

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5.3.2.2 Dissolved Metals

Dissolved Calcium results are shown in Figure 13 below. Dissolved calcium is within the range typically found within urban stormwater.

Figure 13 Dissolved Calcium results for Site 1 and 2

Dissolved Magnesium results are shown in Figure 14 below. Dissolved magnesium is within the range typically found within urban stormwater.

Figure 14 Dissolved Magnesium results for Site 1 and 2 0

5 10 15 20 25

Dissolved Calcium g/m3)

Dissolved Calcium (g/m ³ )

Site 1 Site 2

0 1 2 3 4 5 6 7 8

Dissolved Magnesium g/m3)

Dissolved Magnesium (g/m ³ )

Site 1 Site 2

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Dissolved Potassium results are shown in Figure 15 below. Dissolved potassium is within the range typically found within urban stormwater.

Figure 15 Dissolved Potassium results for Site 1 and 2

Dissolved Sodium results are shown in Figure 16 below. Dissolved sodium is within the range typically found within urban stormwater.

Figure 16 Dissolved Sodium results for Site 1 and 2 0

0.5 1 1.5 2 2.5 3 3.5 4

6-May 17-May 27-May 7-Jun 17-Jun Dissolved Potassium g/m3)

Dissolved Potassium (g/m ³ )

Site 1 Site 2

0 5 10 15 20 25 30 35 40

Dissolved Sodium g/m3)

Dissolved Sodium (g/m ³ )

Site 1 Site 2

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5.3.3 Nutrients

Nitrate-N results and the ANZECC (2000) 95% guideline value of 0.7 g/m³ are shown in Figure 17 below. The results are within the guideline value with the exception of one result recorded at Site 1 on 27 May 2016 which slightly exceeded this value.

Figure 17 Nitrate-N results for Site 1 and 2

Total Kjeldahl Nitrogen results are shown in Figure 18 below. The TKN concentration measured at Site 2 on 27 May 2016 is elevated compared to the other results. This sample was collected following rainfall and elevated TKN concentrations are typically recorded during first flush events due to the runoff of petroleum compounds (which contain urea), animal excrement and fertilisers from

landscaping areas. Slightly elevated levels were also seen in other parameters such as Total Copper and Nitrate-N on this sampling date.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

6-May 17-May 27-May 7-Jun 17-Jun Nitrate-N g/m3)

Nitrate-N (g/m ³ )

Site 1

Site 2

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Figure 18 Total Kjeldahl Nitrogen results for Site 1 and 2

Dissolved Reactive Phosphorus results are shown below in Figure 19. There is an elevated concentration measured for Site 2 on 27 May 2016. As discussed previously, this aligns with increased rainfall and is consistent with trends seen in other parameters.

Figure 19 Dissolved Reactive Phosphorus results for Site 1 and 2

5.4 Comparison with Existing Data

Auckland Council has water quality monitoring sites on both Oteha Stream and Lucas Creek that are monitored monthly. When comparing this data with that collected during the baseline monitoring rounds conducted by PDP, it can be seen that results for physical stressors such as pH, Dissolved Oxygen and Total Suspended Solids are very similar.

0 1 2 3 4 5

Total Kjeldahl Nitrogen g/m3)

Total Kjeldahl Nitrogen TKN (g/m ³ )

Site 1 Site 2

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

Dissolved Reactive Phosphrous g/m3)

Dissolved Reactive Phosphorus (g/m ³ )

Site 1 Site 2

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Total Kjeldahl Nitrogen results in the baseline monitoring rounds were also similar to the Council record, with the exception of the spike recorded on 27 May 2016. Dissolved Reactive Phosphorus results were very similar to the Council record and were within the range of minimum and maximum results recorded.

In general the Auckland Council data for metals (Total Copper, Zinc and Lead) is consistent with the results from the baseline monitoring results with the exception of Total Zinc at Site 1, where results were more elevated. This is likely due to Site 1 being further upstream in the catchment, closer to the sources of Zinc and before dilution and mixing has occurred. As all results were collected during Autumn (based on the hydrological year), it is not possible to draw conclusions regarding the effects of seasonality on the results collected. However, the results are consistent with the Autumn averages calculated for the Auckland Council dataset (see Table 4 in Section 4 above).

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6.1 Physical Stressors

The majority of physical stressors were within guideline values.

pH values recorded were all close to or within ANZECC (2000) guideline values of 6.5-8.5, while the majority of Dissolved Oxygen results recorded were above the recommended minimum value of 6 mg/L. There were some differences in pH results recorded in the field and those from the laboratory, which is being investigated further.

Temperature recorded in the field decreased with each monitoring round, likely due to seasonal changes in weather conditions, as it moved into winter.

No guidelines are available for Turbidity, but the values recorded were all relatively low, indicative of clear water. An increase in Turbidity values was recorded on 27 May 2016, likely due to the increased flows during this period following 10 days of rainfall. This would mean more runoff would reach the stream system, increasing turbidity.

Chemical Oxygen Demand results showed no sign of influence from landfill leachate. Mature landfill leachate typically has COD results of 100-500 gO2/m³(Davis and Cornwell, 1991) which is 10 fold greater than results recorded for Sites 1 and 2.

6.2 Metals

Total Zinc and Copper results all exceed the 95% ANZECC (2000) guideline value of 0.008 g/m³ 0.0014 g/m³ respectively. This is to be expected due to the existing industrial and road land uses in the catchment.

Total Lead results were well below the 95% ANZECC (2000) guideline of 0.0034 g/m³. There was a spike in lead concentrations on 27 May 2016 which aligns with the increased flow recorded on this date as discussed previously.

Dissolved metals results for Calcium, Magnesium, Potassium and Sodium were all low; at least four to tenfold less than the typical landfill leachate values.

6.3 Nutrients

Nitrate-N results were mostly below the ANZECC (2000) guideline value of 0.7 g/m³, with the

exception of one result recorded at Site 1 on 27 May 2016 which slightly exceeded this value. Typical landfill leachate values of 5-10 g/m³are 10 fold greater than this.

Dissolved Reactive Phosphorus results are over 20 fold less than the typical values in mature landfill leachate of 4-8 g/m³. There is an elevated value for Site 2 on 27 May 2016 that is over ten times greater than other results recorded.

There was also an elevated value for Total Kjeldahl Nitrogen of over 4 times greater than the other results recorded at Site 2 on 27 May 2016. The elevated value in both TKN and Dissolved Reactive Phosphorus (DRP) on this date suggests there was a source of contamination related to these higher nutrient values, such as bird excrement washing into the stream system during the period of elevated flow.

6 Summary of Baseline Results

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7.1 Construction phase - sediment

Sediment is the key contaminant expected to be discharged to surface water during the construction phase of the Project. Other potential contaminants during the construction phase, such as landfill leachate, hydrocarbons from asphalt and refuelling operations and pH from concrete works are expected to be fully contained and management procedures will be in place to avoid discharges occurring. Details of the proposed management approaches are set out in the Assessment of

Construction Water Management (Volume 3 – Technical Assessment 4) and the Landfill (Volume 3 – Technical Assessment 7).

The assessment of, and proposed management approach for, construction phase sediment

discharges is set out in Sections 1.3, 4 (Sediment Control Design Philosophy) and 5.2 (Monitoring) of the Assessment of Construction Water Management.

The proposed management approach follows a Best Practical Option approach and is summarised as follows:



Detailed erosion and sediment control plans (which will include a range of erosion and sediment control measures) are proposed to be developed, certified by Auckland Council and implemented to manage the amount of sediment discharged;



The erosion and sediment control measures are to be designed and implemented in accordance with best practice as outlined in relevant erosion and sediment control guidelines (including Auckland Council’s TP90 and NZ Transport Agency’s Erosion and Sediment Control Guidelines for State Highway Infrastructure, Construction Stormwater Management (dated September 2014)).

Where there is a difference between these documents the more stringent approach is to be adopted;



“Adaptive monitoring” of the discharges from representative devices will be carried out to confirm the sediment retention ponds and controls are performing as intended and any trends indicating a deterioration in device performance are identified as soon as practicable; and



Various assessment responses and actions result from these triggers to proactively check and improve the device performance and discharge quality.

The Project has some 61 hectares of areas that will be “worked” at some point. However much of this area is pavement regrading where the surface exposed will be aggregate and therefore it will be inherently resistant to erosion and low loads of sediment are expected to be generated. The larger, more “traditional”, bulk earthworks surfaces and the use of chemical treatment sediment retention ponds is focussed in the south around State Highway 1 and the Constellation Drive interchange.

The proposed earthworks management approach is therefore expected to manage and treat the concentrations of sediment in discharges to a high standard. Flocculation is to be used on all sediment treatment devices. Use of organic flocculants is to be considered provided that the most effective flocculant in terms of sediment removal will be selected. As an indication of the discharge quality expected from chemically flocculated ponds, Auckland Regional Council testing recorded a median sediment concentration discharge of 118 g/m³ (Performance of a Sediment Retention Pond Receiving Chemical Treatment, AC TR 2008/021). Note it is not possible to state that such a quality will actually be achieved in any given event (as rainfall is a key input to any stormwater treatment system and is inherently variable with no practical upper limit). Notwithstanding this point, the performance of flocculation treatment for sediment retention ponds is the best available technology

7 Characterisation of the discharges

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and provides significantly better performance than untreated ponds. On an operational basis the detention volume component of sediment retention devices typically provides enough storage to contain runoff from a 2 year rainfall event. Events larger than this will overtop the service spillway and are likely to discharge higher concentrations of sediment.

7.2 Operational phase - metals

Metals are expected to be the key contaminant to be discharged with stormwater from the Project area during the operational phase. Other potential contaminants such as from the landfill drainage system are considered to be fully contained in the long term and assumed to not affect surface water quality.

Zinc and copper are identified as key metals for consideration.

The assessment of, and proposed management approach for, operational phase stormwater discharges is set out in the Assessment of Stormwater Management (Volume 3 – Technical Assessment 11). Sections 4 (Project Design) and 9 (Summary and Conclusions) are of particular note.

Stormwater quality acute effects on the local freshwater environment are typically transitory as runoff moves through the catchment following a storm. Longer term chronic effects require more consistent water quality concentrations; or for metals to settle out, adsorb to sediment particles and accumulate within streams. Sediment within streams is usually moving through the catchment to some extent and therefore long term effects associated with stormwater quality are considered in the estuarine

environment where sediment and metals have longer retention times which allow settlement and much lower energy hydrodynamic processes which allow accumulation.

The Assessment of Stormwater Management report has followed a Best Practical Option approach and has carried out a detailed options assessment to arrive at the stormwater management approach, which includes:



A treatment train series of controls;



Extensive retrofitting of stormwater treatment to existing high use roads;



Treating all new high use roads to design guidelines set out in relevant Auckland Council and NZTA documents; and



The use of wetlands as the primary means of stormwater treatment – which targets metals for treatment.

The baseline monitoring sites have been adopted as locations to assess the effects of Project

discharges on the freshwater receiving environment. As all the streams discharge to the downstream Lucas Creek Estuary and contaminants will accumulate there, the estuary is identified as the

representative downstream marine receiving environment.

The extent of impervious area within the Project area and the extent of treatment provided to that impervious area provides a useful means of assessing the potential for effects in terms of operational stormwater discharges. Treatment is currently provided for 10.97 ha of the 21.07 ha of existing high use roads (HUR) within the Project area. Following construction, 28.94 ha of the 29.36 ha of high use road will be treated.

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Table 5 Stormwater catchments

Monitoring Site / Receiving environment

Catchment

Motorway sub catchment

Motorway HUR Impervious

Area (existing

and proposed)

Motorway Impervious

Area

Motorway Pervious

Area

Monitoring Site Catchment

Area

1 Oteha –

south trib M2S 1.59 2.21 0.27 212

S2R 9.42 12.13 4.65

2

Oteha – Tawa Reserve

R2C 6.54 8.43 4.62 252

C2PM 3.79 3.79 2.59

3 Alexandra PM2AH 4.57 4.89 1.73 179

4 Lucas Creek OV2M 3.45 4.44 1.21 306

All 29.36 35.89 15.07

Lucas Creek

Estuary 2500 approx

Notes:

1. All areas in ha

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8.1 Freshwater

A range of fresh water aquatic values are identified in the Assessment of Freshwater Ecological Effects (Volume 3 – Technical Assessment 5). Table 5 of that report summarises the sites assessed and their ecological values and identifies that they range from moderate to very low.

Moderate values are identified at Lucas Creek, a tributary on the northern side of the Oteha stream and the Alexandra Stream. Baseline water quality monitoring Site 1 is assumed to have a low value – although no assessment was carried out it is similar in appearance (a straight engineered channel with sections of armoured bed and banks and limited riparian vegetation) to some upstream sites assessed within the Project area as having low to very low values.

Table 6 Ecological Values

Baseline Water Quality

Monitoring Site Freshwater Ecological Site

Catchment Area to Monitoring Site

Ecological Value Oteha – south tributary

(Site 1) None 212 Assumed Low

Oteha – Tawa (Site 2) Tawa Reserve 252 Low

Alexandra (Site 3) Alexandra Stream – North 179 Moderate

Lucas (Site 4) Lucas Creek 306 Moderate

Note:

1. All areas in hectares.

2. Refer to the Assessment of Freshwater Ecological Effects for more detailed assessments of the ecological assessments undertaken near Sites 2, 3, 4

8.2 Marine

All of the freshwater streams eventually join and discharge to the Lucas Creek estuary to the west of Albany. The catchment to the estuary is approximately 2500ha with an estuary size of 178ha (ARC, Regional Maps of Settling and Outer Zones, TP170, 2002). Lucas Creek estuary is identified in the Auckland Unitary Plan as a Significant Ecological Area (SEA): Marine 1.

8 Receiving Environment Characteristics

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9.1 Construction phase

The Assessment of Construction Water Management identifies the maximum extents of earthworks areas in Table 3. These have been reviewed and approximately divided into the relevant surface water catchments so that effects on each catchment can be assessed – refer Table 7.

Table 7 Project Zone Earthwork Areas

Construction Zone

Monitoring Site 1 (Oteha Stream –South

trib)

Monitoring Site 2 (Oteha Stream- Tawa

Reserve)

Monitoring Site 3 (Alexandra

Stream)

Monitoring Site 4 (Lucas)

Total Area (ha)

Zone 1 – SH1/SH18

Interchange 10.5 10.5

Zone 2 – SH18 to

Constellation Drive 5.3 5.3 10.5

Zone 3 – SH1 Northbound 3.5 7.0 3.5 13.9

Zone 4 – SH1 Southbound 3.9 6.7 0.5 11.2

Zone 5 – SH1 Median 0.7 1.3 0.1 2.1

Zone 6 – Albany Park and

Ride 0.9 0.9

Zone 7 – Busway Albany

to Greville 2.9 1.4 4.3

Zone 8 – Busway Greville

to Constellation 5.5 1.8 7.3

Totals 29.4 19.7 5.3 6.4

Notes:

1. Construction zone areas are taken from the Assessment of Construction Water Management and broadly split into the relevant catchments.

2. All areas are in hectares and have been rounded to 1 dp.

A qualitative assessment of factors relating to sediment loads from the Project construction zone areas has been carried out (refer Table 8). The assessment broadly splits the construction zone areas into bulk earthworks areas treated by sediment retention ponds, earthworks areas treated by other erosion and sediment controls (such as check dams and silt fences) and the remaining working area. The assessment shows that both the absolute extent of earthworks area and the ratio of earthworks areas to upstream catchment area will be smaller at Alexandra Stream and Lucas Creek than those to the Oteha Stream via Tawa Reserve and the Oteha southern tributary.

9 Effects Assessment

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Table 8 Construction phase sediment load risks

Monitoring

site Catchment Catchment area

Catchment pervious

area

Working zone area

Working zone area / catchment area, %

Earth- works

area

Earthworks area / Catchment

Area, %

Ecological value

1 Oteha –

South trib 212 58 29.4 13.9% 10.9 5.1% Assumed

low

2

Oteha – Tawa Reserve

252 87 19.7 7.8% 6.4 2.5% Low

3 Alexandra 179 66.7 5.3 3.0% 1.0 0.5% Moderate

4 Lucas 306 122 6.4 2.1% 1.2 0.4% Moderate

Notes:

1. All areas are in hectares

2. Catchment pervious area is for the maximum development of land use under the Auckland Unitary Plan (AUP).

3. Earthworks areas are broadly estimated from the Assessment of Construction Water Management Erosion and Sediment Control drawings and assume all identified earthworks areas are open simultaneously.

The assessment indicates that there is the most potential for increases in the instream sediment concentration at Site 1 and the least potential at Sites 3 and 4.

It will be important that the erosion and sediment controls, including progressive stabilisation, for the Project are managed and monitored proactively and diligently so that the best practice performance can be achieved, discharge concentrations are minimised and the potential for adverse effects is minimised.

The instream TSS concentration measured during the baseline monitoring round on 27 May is the only baseline event that was carried out following several days of rainfall - instream TSS concentrations of 5 and 12 g/m³ of sediment were recorded at Sites 1 and 2 respectively. The Auckland Council monitoring site Oteha @ Gills recorded seasonal TSS averages between 6 and 20 g/m³. However, there could be a wide variation between the baseline value used and the actual instream

concentration in response to rainfall and upstream earthworks and stream erosion. More baseline monitoring is required to address this potential variation and establish the likely instream sediment concentrations at the baseline monitoring sites. This monitoring is planned for December 2016 to February 2017.

Effects from the construction phase sediment discharges have considered the above factors and the Resource Management Act (RMA) section 107 matters. Overall the effects on the receiving

environment are assessed as follows:



Within the Alexandra and Lucas catchments, the extent of the work is predominately pavement regrading with limited bulk earthworking of soils. Treatment will be provided mainly by silt fences and checks dams. Earthworks areas are small compared to the upstream catchments and therefore significant dilution is available. Therefore, the effects from potential sediment discharges from the site are expected to be no more than minor;



In the centre of the Project area, discharges from the causeway will be directed to the Watercare ponds and therefore the earthworks will not cause any effects on freshwater quality; and



Much of the works on SH1 that will drain to the Oteha Stream via Tawa Reserve or the Oteha southern tributary is also pavement regrading, and therefore the extent of bulk earthworks is

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significantly smaller than the actual area of the Project’s physical works. However, the bulk earthworks areas are larger than those in Lucas and Alexandra catchments and constitute a slightly greater proportion of the receiving environment’s upstream catchment area. Treatment will be provided by a combination of flocculation treated sediment retention ponds and other methods such as silt fences and check dams. Management by progressive stablilisation will prevent the release of sediment. The treatment and management methods proposed are considered best practice. It is expected that there will be no more than minor effects as a result of the site’s sediment discharges on the receiving environment.

It is recommended that water quality monitoring is undertaken at the baseline monitoring sites during the construction phase to check the actual level of receiving environment effects due to sediment discharges and ensure that the best practicable performance is achieved by the erosion and sediment controls. This will be developed as part of the erosion and sediment control plans.

9.2 Stormwater quality long term

The annual stormwater loads have been estimated for the current level of development within the Project area and compared to the proposed development plus treatment. This clearly shows the effect of the stormwater management approach whereby untreated existing high use roads are now to be treated. Annual loads of TSS, zinc and copper from the Project area all decrease. It is, therefore, expected that overall quality of stormwater discharged from the Project area will improve following development. However, given the larger existing loads of contaminants from the wider catchments, any net positive change in water quality at the baseline monitoring sites is likely to be minor.

Table 9 Assessment of Proposed Stormwater Treatment Scenario Impervious

Area

Pervious Area

Untreated HUR Area

Treated HUR Area

TSS, t/annum

Zn, kg/annum

Cu, kg/annum

Existing 21.08 29.90 10.09 10.97 48 162 47

Proposed Project : operational phase

35.89 15.07 0.42 28.94 28 152 35

Notes:

1. All areas are in hectares.

2. All HUR roads are assumed to have 20,000 to 50,000 vpd.

3. In post Project scenario other impervious areas are assumed equivalent to roads with up to 5000 vpd.

4. Loads have been estimated using the ARC’s 2006 Contaminant Load Model.

5. Treatment is assumed to occur by a wetland in all cases.

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Additional monitoring is to undertaken for all three catchments over the months of December 2016 to February 2017, consisting of:



Lucas Creek and Alexandra Stream catchments



Targeted at baseline monitoring for sediment effects during construction; and



Includes field measurements only.



Oteha Stream catchments



Targeted at baseline monitoring for sediment effects during construction;



Includes field measurements;



Laboratory analysis; and



Flow monitoring to understand the seasonal variation in flow and contaminant concentrations.

The additional baseline monitoring will be carried out to:



Provide more data for instream sediment concentrations in response to rainfall events and thereby provide the baseline for understanding potential effects from sediment discharges during

construction.



Understand the seasonal variations in baseflow and contaminant concentrations that will be used to check for changes in landfill related contaminants during the construction phase.

10 Additional Baseline Monitoring

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The baseline sediment, contaminant and flow monitoring will be used to inform the development of the Erosion and Sediment Control Plans (ESCP).

During the construction phase, monitoring for the management of surface water discharges and freshwater quality will include:

1. “Adaptive monitoring” of the erosion and sediment controls and discharges from sediment retention ponds to confirm they are performing as intended and any trends indicating a deterioration in performance are identified as soon as practicable;

2. Water quality monitoring at baseline Sites 1, 2, 3 and 4 to check for effects related to site discharges. This monitoring and response and action criteria for these results should be included in the ESCPs.

Assessment of Surface Water Quality Effects