and in the matter statement of evidence of...

Dr John (Jack) McConchie 1

IN THE MATTER of the Resource Management Act

1991

AND

IN THE MATTER of Greater Wellington Regional

Council’s proposed Natural Resources Plan

STATEMENT OF EVIDENCE OF

JOHN (JACK) ALLEN McCONCHIE

ON BEHALF OF THE

NEW ZEALAND TRANSPORT AGENCY

1. EXECUTIVE SUMMARY

1.1 There is considerable emphasis within the Greater Wellington Regional Council’s

(Council’s) Proposed Natural Resources Plan (pNRP) on improving water quality. I

understand that this is supported by the New Zealand Transport Agency (Transport

Agency), and aligns with its own integrated catchment management approach of

improving stormwater quality over time.

1.2 To achieve the overall improvement objective, the pNRP proposes a quantum shift

towards regulating stormwater discharges based on the origin of the discharge, rather

than on an individual ‘effects based’ approach. In particular, the pNRP imposes stricter

controls on discharges from ‘large sites’; which include the State highway network.

1.3 The grouping of three very different land uses as ‘large sites’ ignores the actual

hydrological and other environmental processes operating. The State highway network

is distinctly different to the other two land uses within the ‘large site’ classification.

1.4 The change in focus represents a paradigm shift from the Regional Freshwater Plan for

the Wellington Region 1999 (Operative Plan), which focused on maintaining water

quality, and regulated stormwater discharges on a case by case basis, based on

compliance with specific measureable standards. The implication of this paradigm shift

is that water quality in the Wellington region has been compromised by past processes

and controls, and particularly, practices related to ‘large sites’.

1.5 An understanding of hydrological processes, and the issues and problems inherent in

water quality monitoring and measurement (discussed in greater detail in my evidence

to follow), highlight a number of potential issues with the pNRP, and its approach to the

management and regulation of stormwater discharges.

1.6 In particular, in my view, the shift towards regulation based on the origin of a discharge


(i.e. from a ‘large site’ as opposed to an ‘individual site’), is not appropriate from the

perspective of managing effects on water quality, because:

a) Rivers and streams have the ability to moderate and attenuate potential

contaminants, and their effect on the environment. This ability is, however, both

catchment and site specific.

b) There is no simple or unique causal relationship between an activity and its

effect. This is because the effect of an activity at a particular location is very site

specific, and reflects the interaction of the activity with both the environment and

any management practices which have been adopted.

c) The grouping of three, very different ‘large sites’ (airports, the State highway

network and Centreport) together ignores the actual hydrological and other

environmental processes operating, and the distinct differences between the

activities (in terms of spatial area and possible effects on individual catchments).

The State highway network is distinctly different to the other two land uses within

the ‘large site’ classification.

d) ‘Individual sites’ in my opinion actually have the potential to have greater effect

of specific catchments, as any development is likely to be focused and localized,

and actually represent a greater proportion of the actual catchment. Any

development is also unlikely to be guided by any ‘management plan’ or ‘industry

best practice’ guidelines.

e) The effects of any discharge on water quality, should be considered on a case-

by-case basis, and regulated according to the actual effects of the discharge, or

the ability of the activity or discharge to comply with specific measurable

standards.

1.7 The particular focus in the pNRP on improving the water quality of stormwater from the

State highway network by stricter regulation through the pNRP provisions, is also not

appropriate for the following reasons:

a) There is a common misconception that roads are a primary source of

contaminants and that targeting roads along with other high contaminate

generating activities, will address water quality issues. The reality is that roads

are only a minor to moderate contributor of contaminants.

b) There is no evidence for the contention that stormwater discharges from the

State highway network have compromised water quality in the Wellington

Region.

c) There is no evidence that large projects (including the State highway network)

have a disproportionate effect on water quality, or that the management of the


effects of these projects could be improved. There is also no evidence that the

water quality of stormwater discharges from these sources is at a level that

requires the number of new specific Objectives and Policies which have been

proposed in the pNRP.

d) The concentration of potential contaminants from the State highway network is

not simple, and the potential effect of any contaminant on the environment will

differ both spatially and temporally. Therefore, in my opinion, any effects are

best addressed through, and managed in accordance with, industry derived Best

Management Practices and/or site specific Stormwater Management Plans.

e) Any adverse effects arising from stormwater discharges from the State

highway network can be managed adequately through permitted activity

conditions in the pNRP (as proposed by Mr Hywel Edwards), and through

the Transport Agency’s existing approach to stormwater management,

which focuses on improving water quality over time through ‘best practice’

and ‘optimising’ the design of stormwater devices to meet specific

environmental outcomes.1

1.8 For reasons which will be expanded upon in my evidence to follow, in my view, the

pNRP should:

a) Provide a clear cascading policy framework which conforms to the Resource

Management Act 1991 (RMA) hierarchy in respect of avoiding, remedying and

mitigating effects; while also recognizing that ‘off-setting’ can be appropriate in

some circumstances. Requiring no net loss, and improved water quality are not

required by the RMA. In the context of linear infrastructure, such a ‘zero bottom

line’ could unduly constrain investment;

b) Provide policy direction on the use of the ‘Best Practicable Option’. For large

infrastructure projects such an approach is critical in considering the benefits,

adverse effects, and financial costs of regionally significant infrastructure;

c) Regulate all stormwater discharges to water, or to land in circumstances where it

may enter water, as a permitted activity, subject to controls in the form of

permitted activity standards. Where the permitted activity standards cannot be

met, then a restricted discretionary activity status should apply. In my opinion, this

should apply in relation to all discharges, including discharges from the State

highway network (including existing, redevelopment of or completely new State

highways); and

1 Through its commitment to managing the environmental effects of its activities under its

Environmental Plan and Stormwater Management Strategy, as mandated under the Land Transport Management Act.


d) Provide clear, specific and measurable water quality standards for stormwater

discharges, and regulate discharges based on compliance with those standards.

1.9 Consequently, I support the evidence provided by Mr Hywel Edwards, on behalf of the

Transport Agency, with regard to the wording of the policies, objectives and rules in the

pNRP relating to the management of the water quality of stormwater from the State

highway network.

2. INTRODUCTION

Qualifications

2.1 My full name is John (Jack) Allen McConchie. I hold a Bachelor of Science degree with

First Class Honours, and a PhD. I am a member of a number of professional and

relevant associations including the:

a) New Zealand Hydrological Society;

b) American Geophysical Union;

c) New Zealand Geographical Society;

d) Australia-New Zealand Geomorphology Group; and

e) Environment Institute of Australia and New Zealand.

I am a certified Commissioner (2011-present) and an Independent Professional Adviser

to the New Zealand Transport Agency (2011-2018).

Experience

2.2 I am employed by Opus International Consultants Ltd as the Technical Principal

(Hydrology & Geomorphology).

2.3 Prior to the start of 2008, I was an Associate Professor with the School of Earth

Sciences at Victoria University of Wellington. I taught undergraduate courses in

hydrology and geomorphology, and postgraduate courses in hydrology and water

resources.

2.4 For more than 40 years my research and professional experience has focused on

various aspects of hydrology and geomorphology, including; slope and surface water

hydrology (including water quality), groundwater dynamics, landscape evolution, and

natural hazards. Within these fields I have edited one book. I have written, or co-

authored, 10 book chapters and over 40 internationally-refereed scientific publications

including a number of papers focused specifically on water quality, sources of

contaminants, and the natural attenuation of hydrocarbons.

2.5 I have been involved in numerous research projects focusing on erosion and sediment

transport, water quality monitoring, and surface water-groundwater interactions since


completing my PhD on mass movement erosion in the Wairarapa (1986).

2.6 Specific to this evidence, I have investigated leachate quantity and quality (particularly

heavy metals) from the Silverstream and Happy Valley landfills, various sources of

contaminants resulting from land use and other activities in the Kaiwharawhara

catchment, and the natural variability of suspended sediment concentration in the four

major rivers intersected by the Peka Peka to Otaki Expressway. I have also

investigated the use of natural attenuation to remediate BTEX contamination in

unconfined aquifers.

2.7 I have considerable experience working throughout Wairarapa, the Hutt basin,

Wellington City, and on the Kapiti Coast. I worked on the Climate Change Impacts for

Flood Hazard in the Wellington region, the Hutt and Waikanae Rivers Sediment

Transport Studies, the Western Link Road, the Waikanae River Crossing, Transmission

Gully, the Peka Peka to Otaki Expressway, and the Basin Bridge project. As a result of

this experience, I have an in-depth understanding of climate, hydrology, flooding,

sediment transport processes, and water quality issues across the Wellington Region.

3. CODE OF CONDUCT

3.1 Although not necessary in respect of council hearings, I can confirm I have read the

Expert Witness Code of Conduct set out in the Environment Court's Practice Note

2014. I have complied with the Code of Conduct in preparing this evidence, and I

agree to comply with it while giving oral evidence before the hearing committee.

Except where I state that I am relying on the evidence of another person, this written

evidence is within my area of expertise. I have not omitted to consider material facts

known to me that might alter or detract from the opinions expressed in this evidence.

4. SCOPE AND STRUCTURE OF EVIDENCE

4.1 Within the brief of evidence, I have attempted to:

a) Review the documented effects of the State highway network on stormwater

quality;

b) Provide a discussion of the natural variability of one potential contaminant,

suspended sediment, to illustrate the difficulty of measuring and monitoring water

quality;

c) Place the proposed Objectives, Policies and Rules relating to erosion and

sediment control, and stormwater management, in the context of natural

environmental processes, including the inherent spatial and temporal variability;

and

d) Suggest changes to the proposed Rules which will, in my view, improve their


appropriateness, and the guidance they provide to potential land users.

5. CONTAMINANTS IN ROAD RUNOFF

5.1 Studies in New Zealand and overseas have identified urban runoff as a major

contributor to the declining quality of aquatic environments. It is estimated that upwards

of 40% of the contaminant content of this runoff can be attributed to runoff from roads.

Since the 1980's, numerous studies conducted overseas, and in New Zealand, have

tried to characterise the pollutants contained in roadway runoff. The roadways

considered in these studies include rural and urban highways as well as city/town

streets and thoroughfares. The variety of contaminants found in road runoff is

dependent on the type, condition and the purpose of vehicles using the roads, the

roadway materials and condition of the roadway, and the surrounding land use

(Annexure 1).

5.2 The sources of contaminants from roads fall into six main groups: vehicle exhaust

emissions; tyre wear; brake lining wear; transport fuels; lubricant losses; and road

surface wear.

Vehicle exhaust emissions contain a wide range of metals and organic

compounds. It is generally the particulate component of the emissions that is

most important. The particulates from diesel-fueled vehicles are important

contributors of PAHs;

Tyres are an important source of zinc, they also contain a range of organic

compounds;

Brake pads are an important source of copper, lead, and antimony. They also

contain a number of organic compounds;

Vehicle fuels contain a wide range of volatile organic compounds (VOCs), semi-

VOCs and metals. However, fuel losses are probably not a significant contributor

to contamination;

Vehicle lubricants, greases and coolants contain a range of metals, in particular

zinc, and a range of organic compounds. Again, these sources are not likely to be

a significant contributor to contamination; and

Road surface wear is a source of particulate matter and some organic

compounds. Bitumen surfaces contain PAHs in low concentrations.

5.3 In addition to the routine contaminants found in road runoff, there is potential for the

stormwater quality to be impacted by accidental spills or discharges of contaminants.

For example, the accidental release of fuel to the road from a ruptured fuel tank after a

vehicle collision.


5.4 It is primarily the suspended solids that absorb and transport many of the contaminants

present in stormwater. Consequently, removing the suspended solids achieves a

significant reduction in the potential contaminant load of road runoff. Stormwater

treatment methods generally remove more than 75% of the suspended solids from new

impervious areas. Since the metal ions are bound to the suspended sediment,

treatment also removes that major component of these from affecting the environment

and downstream receiving waters.

5.5 The concentrations of contaminants contained in the road runoff can be affected by

variables of the storm, such as duration, volume and intensity of the storm; as well as

the antecedent dry periods. In addition, the volume of traffic during the antecedent dry

period as well as traffic during the storm can also affect the contaminant loading in the

stormwater generated from the roadways. The concentration of potential contaminants

in stormwater runoff from the State highway network are therefore spatially and

temporally variable.

5.6 Despite the above, there is to the best of my knowledge, no evidence for the contention

that stormwater discharges from the State highway network have compromised water

quality in the Wellington Region, or that water quality from stormwater discharged from

these sources is at a level that requires the number of new specific Objectives and

Policies which have been proposed through the pNRP provisions.

5.7 It is a common misconception that roads are a primary source of contaminants, and that

targeting roads (along with other high contaminate generating activities), will address

water quality issues. The reality is that roads are only a minor to moderate contributor of

contaminants. I discuss the reasons for this in greater detail below.

6. CONCEPTUAL FRAMEWORK

6.1 Any discussion of the status and management of water quality is problematic because of

the high level of inherent natural variability (caused by changes in the source, transport

and deposition of contaminants), which is compounded by issues relating to sampling,

measurement and monitoring.

6.2 The popular perception of water in its natural state in rivers, lakes and groundwater is

that it is ‘pure’. However, in the scientific sense this is not the case. One of the reasons

water is so important to the environment, and to living things, is that it is an excellent

solvent. As such water almost always contains dissolved impurities. These impurities

i.e. potential ‘contaminants’, provide nutrients to plants, and supply some vital trace

elements to animals and people.

6.3 Quality is a very difficult concept to define, even though most people have some idea of

what it means. Water quality usually comes to our attention when the level of impurities

becomes too high to use the water for a particular purpose i.e. a restriction on


recreational contact or prohibition on water use for potable purposes.

6.4 The ionic concentrations of stream water under baseflow conditions have a wide range;

with high values at least 10 times, and sometimes 50 times, greater than low values.

The upper and lower quartiles usually differ by a factor of about three. The

concentrations are approximately log-normally distributed i.e. there are a number of

extremely high or low values which lie well outside of the ‘average’. This needs to be

recognised and taken into account when sampling, and using statistical tests to

compare the concentrations of samples at different sites. This is particularly problematic

when setting ‘background levels’ as required under the pNRP.

6.5 The above relate to baseflow samples i.e. those not affected by direct rainfall runoff.

The total variability of ‘contaminants’ within any river is actually several orders of

magnitude greater than indicated above when the effects of flood events are

considered.

6.6 There are a wide range of potential contaminants which can affect water quality. This

evidence, however, will focus on suspended solids, and their effect on turbidity, which is

generally considered one of the easier parameters to measure. Other water quality

determinants are even more problematic with respect to sampling, measurement and

monitoring.

HYDROLOGICAL PROCESSES

6.7 Many of the potential environmental effects of any State highway network project on

water quality relate to its interaction with the rainfall-runoff relationships which exist

within the project area. It is the hydrological processes which occur between

precipitation within the catchment, and runoff into the respective harbours, which affect

the water quality of any stormwater.

6.8 The paths taken by water as it moves through a catchment are important because they

determine many of the characteristics of a landscape, the nature and generation of

storm runoff, the magnitude of any erosion and sediment transport processes, the

potential to mobilise or trap any contaminants, and the strategies required to mitigate

any potential adverse environmental effects (Figure 1).


Figure 1: The hydrological cycle, showing the continuous movement of water through

various phases, numerous stores, and diverse pathways (McConchie, 2001).

6.9 Streamflow at a point within a drainage basin fluctuates temporally. As a result, the

concentration of potential contaminants, and water quality, also vary both temporally

and spatially.

6.10 Rivers within the Wellington Region have highly variable discharges because of limited

storage capacity within their catchments. High discharges are experienced following

heavy rainfall, with a number of flood events occurring each year. These floods are

separated by sustained periods of relatively low flows. As a result, mean discharges or

contaminant concentrations, for any river or stream can be quite misleading. In Porirua

Stream for example the mean flow (i.e. 0.74m³/s) is almost twice the median flow (i.e.

0.38m³/s).

6.11 The construction of major infrastructure projects has the potential to affect the rainfall-

runoff relationships of any catchments intersected. It should be recognised, however,

that the percentage of a catchment affected, even by large infrastructure projects, is

extremely small. For example, the Peka Peka to Otaki (PP20) Expressway is

approximately 12.7km long, and traverses a catchment area of 447km². Assuming that

the Expressway is 30m wide (which is conservative), this means that the Expressway

actually effects only 0.09% of the total catchments intersected; a very small amount.

6.12 Therefore, while a State highway project has the potential to affect a number of

variables, it generally affects only a small percentage of the overall catchment as:

Any infrastructure project will have no effect on the storm characteristics;

Interception and detention: While there may be a small reduction in interception

losses until a vegetation cover is re-established, there is likely to be an increase in

detention storage as a result of erosion and sediment control measures (during

construction) and stormwater management devices (following construction);

Any changes in evaporation or moisture losses are likely to be negligible;

Infiltration rates are likely to be reduced where the soil surface is disturbed,


compacted, and sealed. Again, while the area affected in this manner may be

greater during construction, it will still affect only a small percentage of any

catchment;

Any effects on the subsurface moisture storage capacity are likely to be small

because of the generally thin (i.e. <1m) soils and regolith and steep slopes; and

While there may be a significant change in land use on the road alignment, the

land use is likely to have already undergone significant changes in the past. For

example, the removal of a forest cover, and its replacement with pasture, would

have generally resulted in a significantly greater degree of change than the

formation of any subsequent infrastructure project.

6.13 Overall therefore, any changes to the catchment runoff parameters are likely to be small,

and their effects extremely localised. Any effects will be moderated and attenuated

rapidly either downslope or downstream as the upstream catchment becomes larger.

The inclusion of appropriate erosion and sediment control (during construction) and

stormwater management devices (following construction) mitigates any effects even

further.

6.14 Larger rivers and streams, those most likely to be impacted by the State highway

network, because of their larger catchment areas and greater flows, have a greater

capacity to attenuate and moderate the discharge of any potential contaminants. This

can be illustrated with respect to both the Ruamahanga and Hutt Rivers were flow is

monitored at various locations down the catchment (Table 1).

Table 1: Hydrometric stations on the Ruamahanga and Hutt Rivers.

Site Parameters Start Date End Date Duration (years)

Catchment Area (km²)

Ruamahanga River

Ruamahanga River at Mt Bruce

Water Level

Flow 1-Jan-1975 13-Dec-2017 42 78.6

Ruamahanga River at Wardells

Water Level

Flow 10-Nov-1954 13-Dec-2017 63 660

Ruamahanga River at Gladstone Bridge

Water Level

Flow 6-Jun-1992 13-Dec-2017 25 1337

Ruamahanga River at Waihenga Bridge

Water Level

Flow 31-Dec-1956 13-Dec-2017 61 2361

Hutt River

Hutt River at Kaitoke Weir Water Level

Flow 3-Feb-2004 15-Dec-2017 13 87

Hutt River at Te Marua Water Level

Flow

5-Mar-1984

6-Aug-1991

15-Dec-2017

15-Dec-2017

33

26 189

Hutt River at Birchville Water Level

Flow 7-Sep-1970 15-Dec-2017 47 426

Hutt River at Taita Gorge Water Level

Flow 16-Mar-1979 15-Dec-2017 38 559

Hutt River at Estuary Bridge Water Level 28-Sep-1976 15-Dec-2017 35 614

Akatarawa at Cemetery Water Level

Flow 19-Feb-1979 15-Dec-2017 38 117


Mangaroa at Te Marua Water Level

Flow 20-May-1977 15-Dec-2017 34 103

6.15 For the period of concurrent record, it is apparent that while the discharge increases,

largely as a function of the increasing catchment area, the coefficient of variation actually

decreases (Table 2). The coefficient of variation is a measure of the relative flow

variability and is the ratio of the standard deviation to the mean. The higher the

coefficient of variation, the higher the variability, or ‘volatility’, of river.

Table 2: Summary statistics for flows recorded at various locations along the Ruamahanga River.

Site Max Mean Median U.Q. L.Q. Quartile Range

Std. dev.

C.O.V

Ruamahanga River at Mt Bruce 446 9.9 4.5 9.04 2.6 6.44 18.5 1.874

Ruamahanga River at Wardells 844 23.9 12.5 25.5 6.6 18.9 37.6 1.571

Ruamahanga River at Gladstone Bridge

1255 40.0 19.1 41.1 9.3 31.8 69.9 1.747

Ruamahanga River at Waihenga Bridge

1165 80.9 47.9 91.9 25.2 66.7 107.2 1.325

6.16 The effect of increasing catchment size on flow attenuation and moderation is illustrated

with respect to a major flood event passing down the Ruamahanga catchment (Figure

2).

Figure 2: Flood hydrographs at various locations in the Ruamahanga catchment as a

large event passes downstream.

6.17 The same patterns of response as catchment size increases are also apparent within the

Hutt River. As the flood passes down a catchment, the peak discharge is prolonged,

attenuated, and moderated.

6.18 Consequently, it is not appropriate to treat all rivers and streams in the same

manner. While the pNRP proposes to classify ‘Surface water bodies’ into two

classes, these classes appear to take no account of the hydrology and hydrological

dynamics of the actual water bodies. The water bodies are classified largely in

terms of what the water is used for, rather than the physical processes and

dynamics of the hydrological system. It is these physical processes which are


critical when assessing the potential for changes to the contaminant concentrations

and their effect on the environment.

6.19 The management of rivers and streams would be better served by also recognising

the scale of the river, the potential for it to be affected by anthropogenic activities,

and its ability to assimilate, moderate and attenuate any effects of changes to the

hydrological processes operating within the catchment. In the Wellington Region, it

might be appropriate to classify stream, and part of streams, in terms of their ‘stream

order’. For example, ‘zero order catchments’, and then orders 1-2, 3-4, 5-7.

VARIABILITY OF ‘CONTAMINANTS’

6.20 Issues associated with the monitoring and measurement of potential ‘contaminants’ in a

river can be illustrated with reference to a detailed study of turbidity undertaken as part

of the ‘pre-conditions’ for the Peka Peka to Otaki Expressway (PP2O) i.e. conditions in

an effectively ‘natural’ catchment, and not one in which construction activities are being

undertaken.

6.21 One of the outcomes of the Board of Inquiry decision on the PP2O Expressway was a

requirement to conduct environmental baseline monitoring of turbidity in four rivers and

streams which may be affected by construction activities.

6.22 Despite being ‘industry standard’ turbidity sensors, the resulting data are still prone to

interference from debris, biofouling, and drift over time.

6.23 As expected, data collected in each of the four rivers demonstrate a general relationship

between flow and turbidity, with elevated flows/levels coinciding with an increase in

turbidity (Figure 3). All four sites experienced turbidity maxima of between 600-1200

NTU, that correlate with each river’s mean flow i.e. the higher the mean flow the higher

the turbidity maxima.

Figure 3: Flow and turbidity for Otaki River at Pukehinau.

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6.24 The turbidity and flow data presented in Figure 3 reflect the actual variability of flow and

turbidity measured in the Otaki River over only an 8-month period. It should therefore be

recognised that the sensors were in a major ‘natural’ water course, and installed

immediately downstream of the Tararua Forest Park. The data therefore reflect natural

variability only, and variability over a relatively short time period.

6.25 While any obviously anomalous data were removed, the remaining data are those

actually measured using ‘best practice’ and ‘industry standard’ sensors. Consequently,

these data are likely to reflect ‘natural’ conditions upstream of the construction of the

PP2O Expressway.

6.26 Turbidity and flow data recorded at a 10-minute resolution in the Otaki River at

Pukehinau were correlated (Figure 4). Despite this being a log-log plot, the relationship

between flow and turbidity is still weak. For example, at a flow of 100m³/s, turbidity

varies over two orders of magnitude or 100 times.

Figure 4: Log-log plot and correlation between flow and turbidity in the Otaki River.

6.27 On 19 September 2016, a major turbidity event occurred, the largest recorded over the

8-months of monitoring, even though river flow was receding (Figure 5). A detailed

review of this ‘peak in turbidity’ suggests that the data are correct, and that turbidity did

actually increase significantly over this period. This event was therefore likely entirely

‘natural’ and reflects the variability in turbidity within a natural, largely unmodified

catchment.


Figure 5: A peak in turbidity during recession of flow in the Otaki River at Pukehinau.

6.28 Therefore, despite some initial problems relating to the installation of the four turbidity

sensors, they functioned well; providing approximately 8-months of data, at 10-minute

intervals. The turbidity data support the following conclusions:

Measuring turbidity on a continuous basis is problematic, and issues around

obtaining a reliable turbidity record are well known. Despite the use of ‘industry

standard’ sensors, which included automatic wipers and anti-fouling mechanisms,

a range of environmental factors such as debris and variable water levels, and

instrumental issues including calibration, drift, the growth of algae on the lens, and

electronic ‘glitches’ still affected the turbidity records;

The relationship between flow and turbidity was different for each river, and likely

between different locations on the same river;

In each river there was also a high degree of variability in the relationship between

flow and turbidity during each flood event;

There is no unique turbidity value, at any particular time and place, as the actual

measurement depends to a degree on the instrumentation used. Different

turbidity sensors may output different turbidity values for the same sample. The

use of the same type of sensor (i.e. same model from the same manufacturer)

may help to overcome this issue. Best practice is to use the same turbidity sensor

unit in either before and after, or upstream-downstream applications; and

Relative measures of the difference in turbidity between two sites on the same

watercourse, using the same meter, are more reliable and accurate for identifying

‘change’ than the actual measurements themselves;

6.29 The measurement of water quality parameters, even relatively simple measures, is

problematic. This leads to considerable uncertainty regarding environmental

indicators, the establishment of particular triggers or thresholds, and ultimately

compliance with conditions of resource consents.

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7. BASIS FOR CHANGES TO THE WATER QUALITY MANAGEMENT APPROACH

7.1 The focus of the pNRP has shifted from ‘maintaining water quality’ to ‘improving water

quality’, and regulating discharges on the basis of their origin, rather than compliance

with specific water quality standards. The implication of this paradigm shift, is that water

quality has been compromised by past processes and practices and, because of the

proposed shift in ‘activity status’, that these adverse effects are related specifically to

‘large sites’; namely airports, the State highway network and Centreport.

7.2 The presumption of the pNRP rules in relation to the State highway network specifically,

appears to be that the State highway network is currently having an adverse effect on

water quality.

7.3 To the best of my knowledge, there is no evidence to support the contention that water

quality as a result of stormwater discharges, particularly from the State highway

network, has been, and is being, compromised in the Wellington Region. Further, there

is no evidence that large projects (including the State highway network) have a

disproportionate effect on water quality, or that the management of the effects of these

projects could be improved. Finally, there is no evidence that the water quality from

these sources is at a level that requires the number of new specific Objectives and

Policies which have been proposed through the pNRP.

7.4 The Council’s “River and stream water quality and ecology in the Wellington Region –

state and trends”2 report makes no mention of the State highway network as being a

critical, or even major, control on degrading water quality within the Wellington Region.

In fact, there are no references to the State highway network at all in the report.

7.5 The report states that “The majority of SoE (State of the Environment) sites exhibited

stable water quality and ecological health over the time periods examined (2006 to 2011

and 2004 to 2011 respectively). Generally speaking, the majority of statistically

significant trends tended to be indicative of improving water quality (predominantly

declining nutrient concentrations) but deteriorating ecological condition (increasing

periphyton cover/biomass and declining macroinvertebrate community health). In most

cases the reasons for the observed trends were unclear.”

7.6 Further “The RSoE (Regional State of the Environment) sites in poorest condition – in

particular those with small catchments dominated by urban or intensive agricultural land

uses – share in common one or more of the following ‘stressors’: nutrient enrichment,

poor water clarity, nitrate or heavy metal toxicity, microbiological contamination, and

instream habitat degradation. Management of these stressors requires a whole of

catchment approach that addresses municipal wastewater discharges to water (in the

2 River and stream water quality and ecology in the Wellington region. State and trends. Report

prepared by A. Perrie, S. Morar, J.R. Milne & S.Greenfield. ISBN: 978-1-927217-13-9 June 2012.


Wairarapa Valley in particular), nutrient loss (from both overland runoff and leaching via

shallow groundwater) in intensively farmed rural catchments, sediment runoff associated

with erosion-prone farmland, exotic forestry and urban development, sewer

infrastructure leaks/faults, urban stormwater discharges, water abstraction, and direct

stock access to streams and riparian margins.”

7.7 Consequently, Council’s Environmental Monitoring and Investigations Department do

not appear to have any data to support the contention that the State highway network is

a major contributor of either contaminants or to declining water quality.

7.8 In recommending the pNRP’s proposed provisions for managing stormwater discharges

be adopted in the s42A Reports, the Council Officers appear to have relied on the

primary evidence of Ms Claire Conwell3 for guidance regarding the distinction between

the water quality emanating from ‘large sites’ and ‘individual sites’. Consequently, it is

critical that Ms Conwell’s evidence is placed in context, and areas of uncertainty

clarified.

7.9 Ms Conwell’s principal argument in support of maintaining the distinction appears to be

that proposed Rule 52 is necessary since ‘large sites’ “may contain both a wide range of

contaminants and relatively high concentrations and/or loads of contaminants compared

to individual sites, it should be managed differently to stormwater discharges from

individual sites.”

7.10 Furthermore, Ms Conwell appears to suggest that because the types of activities and

the scale of activities are different, ‘large sites’ should be managed in a different manner

to ‘individual sites’.

7.11 With respect, I disagree with Ms Conwell’s conclusions. In my view, it is not the

activities which should be regulated but their effects on the environment. There is no

simple or unique causal relationship between an activity and its effect. This is because

the effect of an activity at a particular location is very site specific, and reflects the

interaction of the activity with both the environment and any management practices

which have been adopted. There are a wide range of controls on the activities for all

three ‘large sites’ identified in the pNRP, and these have a significant effect on any

potential risk from contaminants in stormwater to the environment.

7.12 While recognising that ‘large sites’ are different, and “As such, it is expected and

common for contaminant discharges from large sites to be managed in accordance with

industry derived Best Management Practices and/or site specific Stormwater

Management Plans” Ms Conwell’s opinion is that Rule 52 is still necessary.

3 Statement of primary evidence of Claire Conwell on behalf of Wellington Regional Council.

Technical – Large site stormwater quality in regards to Rule 52 Stormwater from large sites 12 January 2017.


7.13 Airports, the State highway network, and Centreport are all classified as ‘large sites’.

The State highway network, however, is distinctly different to the other two land uses in

that it is linear infrastructure as opposed to a concentrated focus of activity.

7.14 For example, the estimated surface area of the State highway network is 44ha;

however, this is spread as linear infrastructure across the entire region. Consequently,

the 44ha is actually spread over a large number, and wide range, of catchments. The

effect of the State highway network in any particular catchment is actually very small.

7.15 This can be illustrated with reference to three elements of the State highway network

(Figure 6).

Figure 6: Three components of the State highway network.

7.16 As already discussed, the PP2O Expressway directly affects stormwater from less than

0.09% of the catchments which it intersects. On the same assumption as used for the

PP2O Expressway for the other elements of the State highway network (which would be

extremely conservative since these are generally two lane highways as opposed to four)

then SH2, with a length of 67.2km, interacts with 0.06% of the Ruamahanga catchment

(i.e. 3188km²). SH2 through the Hutt catchment has a length of 40.52km and has the

potential to affect 0.19% of the runoff throughout the catchment.

7.17 The airports on the other hand affect a total area of ~280ha, of which about 82ha is

impervious. Any environmental effect is concentrated within only a very few, and

generally small, catchments. The effect within these catchments is potentially


significantly greater than that of the more dispersed State highway network.

7.18 Likewise, CentrePort covers approximately 28.3ha and essentially drains a single

catchment; draining directly into Wellington Harbour. This situation is also very different

to the State highway network, and would potentially have different catchment-scale

effects.

7.19 The grouping of these three very different land uses as ‘large sites’ therefore ignores the

actual hydrological and other environmental processes operating. The State highway

network is distinctly different to the other two land uses within the ‘large site’

classification.

7.20 It should also be noted that ‘individual sites’ actually have the potential to have a greater

effect on the specific catchments, as any development is likely to affect a greater

proportion of the actual catchment. Any development is also unlikely to be guided by

any ‘management plan’ or potentially even ‘industry best practice’. The pNRP would

result in the management of such areas being less restrictive than the State highway

network.

7.21 I would agree with Ms Conwell that “the stormwater from the State Highway Network is

well defined, described in detail, and is supported by a track record of pro-active and

targeted investigations.”

7.22 The effect of the State highway network can also be positive as shown with the Mackays

to Peka Peka Expressway. Comparing the modified/constructed wetlands and other

stormwater management and control structures with the pre-existing condition highlights

the positive outcomes for the environment from the Expressway.

7.23 I would also agree with Ms Conwell that “copper and zinc represent contaminants in

stormwater that are ubiquitous in road runoff, present in concentrations that are of

potential environmental concern, are reliably measured in the laboratory, and are

routinely measured in targeted investigations.”

7.24 With respect, the data presented in Table 3 of Ms Conwell’s evidence, while reflecting

information held in the URQIS database, need to be interpreted with caution. For

example, with respect to any potential environmental effect it is the bioavailability which

is critical, and not the total concentration. The difference between the ‘Dissolved’ and

‘Total’ concentrations is likely to reflect the concentration of metals bound to sediment.

This material is not generally bioavailable.

7.25 Considering the ‘Dissolved’ concentrations of both Cu and Zn, even for roads with a vpd

>20,000, these are less than those from Low-density residential; dramatically so for Zn.

Yet it is proposed, through the pNRP provisions, to control activities relating to the State

highway network to a greater degree than Low-density residential development.


7.26 To understand the actual potential effects of these discharges, it is also important that

these ‘point measurements’ of concentration are placed within a wider environmental

context. For example, if these contaminated discharges represent a large proportion of

the flow within a catchment, they have the potential to have a greater adverse effect on

the environment than if the discharge is to a larger water body. The potential for dilution

is therefore a critical control on the ‘effective concentration’ and the potential effects on

the receiving environment. It should be noted that the State highway network generally

passes through larger catchments, with larger discharges and therefore with a greater

dilution potential, than other components of the roading network.

7.27 Even considering the total concentrations, which I would argue is not appropriate for the

reasons given above, the differences between Low-density residential and Roads

>20,000vpd are small, and the potential effect of dilution and any management

interventions still need to be considered.

7.28 In addition to the above considerations, the limits and assumptions provided by Ms

Conwell must also be considered when placing these data in the context of the State

highway network.

7.29 The concentration of potential contaminants from the State highway network is therefore

not simple, and the potential effect of any contaminant on the environment is even less

certain. Any effect will differ both spatially and temporally, and in my opinion are best

addressed through, and managed in accordance with, industry derived Best

Management Practices and/or site specific Stormwater Management Plans.

7.30 As mentioned previously, it is my understanding that the Transport Agency supports,

and actively promotes, efforts to improve water quality. For example, it has developed,

produced and regularly updates a range of guidance and ‘best practice’ documents and

manuals. These include:

NZTA Environmental and Social Responsibility Policy

https://www.nzta.govt.nz/assets/resources/environmental-and-social-responsibility-

manual/docs/environmental-and-social-responsibility-policy.pdf

NZTA Environment Plan

https://nzta.govt.nz/assets/resources/environmental-plan/docs/environmental-plan.pdf

NZTA Stormwater and Treatment Standard for State Highway Infrastructure

https://www.nzta.govt.nz/assets/resources/stormwater-management/docs/201005-nzta-

stormwater-standard.pdf

NZTA Project Management Manual - Part 4 Guidelines

Project Management Manual guidelines outlines minimum standards for social and

environmental management


- includes MS Z/4 - Contractor's social and environmental management plan; and

SM032 (State Highway maintenance contract pro forma manual) - Contractor's quality

plan - environmental management.

7.31 These documents illustrate an ongoing and pro-active commitment by the Transport

Agency to the continual improvement of the water quality of stormwater emanating from

the State highway network. I also understand that the Transport Agency uses best

practice environmental management strategies to mitigate the effects of discharges

when undertaking new roading projects. On the existing network, the Transport Agency

is progressively improving effects by identifying sensitive receiving environments that

are being adversely affected by State highway runoff, and treating the identified sites as

appropriate, based on a pragmatic, prioritisation approach.

8. DISCUSSION OF THE PROPOSED PLANNING FRAMEWORK

8.1 Based on Mr Hywel Edwards’ evidence, I understand that under the pNRP all existing

and new stormwater discharges from the State highway network:

a) Onto land are permitted;

b) Into or onto water or onto land in circumstances where they may enter water

require consent as a Restricted Discretionary activity;

c) Into or onto water or onto land in circumstances where they may enter water in

sites of significance require consent or as a Non-Complying activity.

8.2 However, the matters over which the Council has retained its discretion are ambiguous,

and would require a high degree of background research to be able to demonstrate

compliance. The matters over which they have retained their discretion are also not

necessarily well understood (for example, mahinga kai), and no clear guidelines or

standards are provided. Without clear standards it is not possible to assess the level of

effect which is permitted before ‘adverse effects’ result.

8.3 Consequently, the proposed ‘process’ will be ambiguous, potentially time consuming

and costly. This will, in my opinion, lead to inefficiencies and uncertainty, with no

guarantee of a better outcome than achieved at present.

8.4 The pNRP fails to recognize the inherently high degree of variability in water quality, in

both natural and modified watercourses. It also fails to recognise the difficulty in

quantifying various water quality parameters in absolute terms.

8.5 There also appears to be the perception that activities can be undertaken in such a way

that there will be no effects. Large infrastructure projects will invariably have an effect

on water quality and hydrological processes. Whether these effects are measurable

and quantifiable is less well defined. These effects, however, can be reduced and


mitigated by applying best practicable options.

8.6 For the various reasons outlined in my evidence, it is inappropriate and in my opinion,

not effective or efficient from a water quality perspective, to regulate activities based on

the size or type of the activity rather than the effect.

8.7 To the best of my knowledge, there is no evidential basis, or effects based reason for

imposing a stricter activity status on discharges from the State highway network.

Comments on Specific pNRP Provisions

8.8 I support the intent of Objective 48, which encourages any adverse effects on the quality

and quantity of water in stormwater networks be reduced over time. This objective

aligns with the concept of integrated catchment management to improve stormwater

quality over time. However, as noted by Mr Edwards, the RMA is not a ‘zero effects’

piece of legislation. It is therefore anticipated that effects may be ‘remedied’ or

‘mitigated’, and this assumes that any effects are of sufficient impact that they need to

be addressed. Furthermore, water quality is spatially and temporally variable and it is

difficult to envisage a situation where the adverse effects of stormwater no longer

require improvement i.e. that stormwater is ‘pure’. I therefore agree with the proposed

changes to Objective 48 made by Mr Edwards, to refocus the objective on improving

water quality where the existing quality is degraded, and maintaining water quality where

the existing quality is acceptable.

8.9 The intent of Policy 62 is supported as it promotes the discharge of contaminants to land

rather than directly to water. This allows for moderation, attenuation and ‘treatment’ of

many potential contaminants by various processes within the soil before they enter a

waterbody.

8.10 Policy 67 sets a very high standard which ignores the natural variability which exists

within the environment, and the moderating and attenuating effects of rivers and

streams. While the concept is fully endorsed, the goal should be to ‘minimise’ rather

than the higher standard of ‘avoiding’. Many activities would have great difficulty in

‘avoiding’ the production of contaminants. Whether a potential contaminant actually has

an adverse effect is often both site and catchment specific.

8.11 Policy 71 is endorsed as it takes a pragmatic approach to the variability of water quality

and potential discharges. It also recognises that the quality of any discharge should be

directly related to the quality of the receiving water. The upstream/downstream

comparison allows for natural variability, while at the same time quantifying the nature of

the potential impact of any discharge.

8.12 As shown above, there would appear to be no reason, given the underlying aim of Rule

48, to exclude Local Authority stormwater networks, ports, airports or State highway


network from this rule. Since the rule is to allow discharges as a Permitted activity,

assuming that it meets certain standards, it should apply equally to all parties. The rule

applies to the quality of the discharge, as it should, and therefore it should not be

applied differently to different land uses or the size of the property parcel.

8.13 There appears to be little justification, and no quantitative data, to support Rule 52. In

addition, Rule 52 appears to focus on activities rather than on effects. Finally, the

inclusion of the State highway network with ports and airports ignores the distinct

differences between these three activities, particularly with respect to the potential of

runoff from these land use to have adverse effects on the environment.

8.14 Rule 52 is problematic in that makes the discharge of stormwater from the State

highway network (including the existing State highway network) a Restricted

Discretionary activity, and requires consent to be applied for in relation to the entirety of

the existing State highway network within the Wellington region.

8.15 Consequently, I support the evidence provided by Mr Hywel Edwards, on behalf of the

Transport Agency, with regard to the wording of the policies, objectives and rules

relating to the management of the water quality of stormwater from the State highway

network.

9. SUMMARY AND CONCLUSIONS

9.1 There is considerable emphasis within the pNRP on improving water quality. I

understand that this is supported by the Transport Agency, and aligns with its own

integrated catchment management approach of improving stormwater quality over time.

It therefore appears to me that the Transport Agency and the Council have the same

goals about what should be achieved, albeit a difference of opinion on how to achieve

this in terms of managing discharges from the State highway network.

9.2 I support the overall direction towards improving water quality in the Wellington region.

However, for the reasons outlined in this evidence, I do not consider that the provisions

currently proposed in the pNRP are the most effective way to achieve this. In my view:

a) The shift towards regulation based on the origin of a discharge (i.e. from a ‘large

site’ as opposed to an ‘individual site’), rather than either the effect of the

discharge or the ability of the activity or discharge to comply with specific

measureable standards, is not appropriate. Rivers and streams have the ability to

moderate and attenuate potential contaminants, and their effect on the

environment. This ability is, however, both catchment and site specific.

Therefore, effects of stormwater discharges on water quality need to be assessed

on a case-by-case basis.

b) There is a common misconception that roads are a primary source of


contaminants and that targeting roads along with other high contaminate

generating activities, will address water quality issues. The reality is that roads

are only a minor to moderate contributor of contaminants. There is no evidence

for the contention that stormwater discharges from the State highway network

have compromised water quality in the Wellington Region.

c) The focus in the pNRP on improving the water quality of stormwater from the

State highway network by stricter regulation is, in my view, not appropriate given

the nature of the stormwater, the level of any measured effects, and the existing

focus of the Transport Agency on ‘best practice’ and ‘optimising’ the design of

stormwater devices to meet specific environmental outcomes.

d) Any adverse effects arising from discharges from the State highway network are

managed adequately through the permitted activity conditions as proposed by Mr

Hywel Edwards, and through the Transport Agency’s approach to stormwater

management (through its commitment to managing the environmental effects of

its activities under its Environmental Plan and Stormwater Management Strategy,

as mandated under the Land Transport Management Act). In addition,

improvements to existing stormwater systems are most efficiently undertaken in

conjunction with road upgrades. I would also argue that the environmental

outcomes from such an approach are greater than having to retrospectively apply

for consent for all existing State highways.

e) In my opinion, stormwater discharges from the State highway network to water, or

to land in circumstances where it may enter water, should be regulated as a

permitted activity, subject to controls in the form of permitted activity standards.

This is the situation under the Operative Plan. Where the permitted activity

standards cannot be met, then a restricted discretionary activity status should

apply. This applies in relation to all discharges, whether from existing,

redevelopment of, or completely new State highways.

9.3 Consequently, I would support the evidence provided by Mr Hywel Edwards, on behalf

of the Transport Agency, with regard to the wording of the policies, objectives and rules

relating to the management of the water quality of stormwater from the State highway

network.

John (Jack) Allen McConchie

30 January 2018


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and in the matter statement of evidence of...

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