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Before the Hearing Panel – Proposed Natural Resources

Plan for the Wellington Region

Under The Resource Management Act 1991 (the Act)

In the matter of Proposed Natural Resources Plan for the Wellington Region – Hearing Stream Four: Water quality & Stormwater

Between Greater Wellington Regional Council Local Authority

And Masterton District Council Submitter S367 and Further Submitter FS30 South Wairarapa District Council Submitter S366 and Further Submitter FS26

Statement of Evidence of Vaughan Francis Keesing

Dated 26 January 2018

w16025_vk_pnrp_evidence_stormwater_final_20180126.docx 1

Introduction

1. My name is Vaughan Francis Keesing.

2. I am a Senior Ecologist and Associate Partner with the consulting firm of Boffa Miskell

Ltd, Wellington. I hold the qualifications of Doctor of Philosophy (PhD) in Ecology, BSC

(Hons 1st class) zoology, and a Diploma in Research Statistics.

3. My expertise lies in applied ecology under the RMA, and I have specialist skills in the

areas of: limnology, botany, and entomology, with my predominant work experience

being in freshwater ecology.

4. My experience has been gathered over 20 years and includes:

Studies and assessments of seven hydro-generation systems

Large scale irrigation storage schemes (for example, the Waitohi and the Hurunui

schemes)

Six wind farms

Over 20 large-scale subdivisions (e.g. Omaha South (Darby Partners), Long Bay

(Landco) Pegasus Bay (Infinity Co)

Numerous roading projects (such as Transmission Gully Motorway, Mackays to

Peka Peka Expressway), and

Long term aquatic monitoring programs (for example, the KCDC River recharge

baseline monitoring programme, a three-year aquatic data collection process).

5. In addition, I have undertaken assessments for proposals for –

Mining (such as. NZ Gold Mikonui, Roa mines, Dennison and Coal Creek mines)

Quarrying

Water take (Ruataniwha, Hurunui and Waitohi schemes), and

Many other developments involving assessment of values, significance, and effects

related to water use and water discharge.

6. I have been involved in ecological aspects in a number of water related programmes and

projects in Carterton and Masterton, looking at water take and use (for example, Carterton

water races, Henley Lake, Queen Elizabeth Park, and a water take from the Ruamāhanga

River). I am therefore familiar with the ecological aspects of water discharge effects and

water take effects and generally with the towns of the Wairarapa.


7. I confirm that I have read and am familiar with the Environment Court’s Code of Conduct

for Expert Witnesses, contained in the Environment Court Practice Note 2014, and agree

to comply with it. My qualifications are as set out above. I confirm that the issues

addressed in this statement of evidence are within my expertise. I have not omitted to

consider any material facts known to me that might alter or detract from the opinions that

I express.

Scope of Evidence

8. I have been asked to consider the evidence around stormwater effects in the Wairarapa,

how impervious surface levels of townships can be used to predict effects of stormwater,

how this relates to effects on receiving aquatic communities and if there is evidence of

any current stormwater adverse effects in the Wairarapa. I understand my evidence will

inform a revised rule framework relating to local authority stormwater discharges, as

outlined in the evidence of Ms Whitney.

Stormwater

9. Stormwater usually contains a range of contaminants. The range, quantity, and toxicity

of those contaminants depends on the surfaces on which rainfall occurs and the surfaces

over which it then flows. Typically, in human settlements, stormwater is sourced from

roofing, roads, sidewalks and hard surfaces of other sorts, and results in a small suite of

“pollutants” largely composed of heavy metals, polyaromatic hydrocarbons, faecal

material, bacteria (e.g. E. coli), oils and cleaning and pesticide chemical, as well as

sediment.

10. The initial or “first” flush (a debated phenomenon) from impervious surfaces of human

settlements can carry around 50% of the contaminant load present (accumulated over

time since last rainfall) in the first 25% of the total runoff volume (Auckland Council

TP2011/07). This peak flush occurs generally within 30 minutes of rain classified as more

than light rain. If it is not captured and discharged to ground or treated, then it is

discharged to whichever receiving natural water body (a river, lake or the sea) that lies

down gradient.

11. In small settlements (by which I am referring to communities smaller than say Masterton),

there is normally a small array of discharges: some diffuse, some point, some directly to

small streams, drains or to land (for example, soakage pits). The specifics for the

Wairarapa townships are discussed in the evidence of Mr Stephenson and Mr Hopman.

12. Such flushed stormwater typically contains a range of metals related mostly to vehicles

(mainly zinc, but also copper, cadmium, lead, chromium, and nickel), as well as

polyaromatic hydrocarbons (a wide range of substances loosely related to automobile


fuels) and smaller quantities of nutrients (P, N, K), oils, sediments (total suspended solids

‘TSS’), “rubbish” and products used in cleaning or pest management (organochlorine

pesticides), and on occasion faecal coliforms (birds, dog, etc) and bacterium (e.g. E. coli.)

13. The “damage” of these contaminants to receiving aquatic habitat depends on the total

quantity of contaminants released to the “natural” waterway, the concentrations, the

frequency of such releases, the position of deposition zones, and the tolerance of the

receiving environments animal and plant assemblages.

Wairarapa Stormwater Consenting Framework

14. The MDC and SWDC, in response to the local authority stormwater network rules

proposed in the PNRP, seek to make discharge of stormwater within the Ruamahanga

and Wairarapa Coast Whatua, a permitted activity through a new rule R50A. It does so

under a number of permitted activity conditions, with item (b) being a provision that such

a discharge does not significantly or accumulatively adversely affect the life supporting

capacity of the receiving water body.

15. The District Council’s approach presupposes that industry, which has potential pollutants

which could be discharged to the community stormwater system, has separate controls

that govern the level and type of allowed pollutants to be discharged to the communities’

stormwater systems. Mr Stephenson’s evidence articulates that this is the case for the

South Wairarapa main towns.

16. The proposed rule (R50A) is based on addressing the level of urban development within

the catchment of the discharges (and thus potential for damage causing pollution) by

using the proxy of total impervious cover / surface as a proportion of the contributing

water catchment. Impervious surface refers to any surface on which rain falls that does

not absorb the water but causes it to run directly off and into the stormwater system (e.g.

building roofs, sidewalks, roading, parking lots in hard stand, tennis courts etc).

17. Toxic effects of stormwater pollution is complex and suspended input quantity by itself

does not reflect bioavailability, uptake by organisms, or the level of damage. Toxic effects

are more often acute not chronic and occur from long term periodic small-scale events

which carry no alert but accumulate over a long period.

18. The influence of total impervious land cover has long been recognised as a critical and

overarching factor indicating the level of development at which there are measurable

long-term effects on the quality of stormwater (for reviews see: Brabec et al 20021,

1 Brabec, E; Schlte, S; Richards, P. Impervious surfaces and water quality: A review of current literature

and its implications for watershed planning. Journal of planning literature 2002: vol 16: pg 499.


Schueler et al 20092). There are over 250 scientific papers now outlining research that

illustrates the fact that, as impervious cover in a catchment increases, the quality of

discharging stormwater water decreases and a change in the species present occurs to

reflect the persistence of the more tolerant species.

19. While there is an array of responses to stormwater contamination, the research

acknowledges clear trends which show that at a level of 10% total impervious cover there

are significant and predictable decreases in the quality of the receiving water which gets

progressively worse with increasing imperviousness (e.g. Wang et al 20013, Schiff &

Benoit 20074, Miller et al 20145). Several research papers (e.g. Walsh et al 2005a6, Morse

et. al 20037) further reflect that from about 5-6% imperviousness, measurable declines

and adverse changes in terms of the macroinvertebrate communities and algae

communities are typically evident. A generalised model is shown in Figure 1.

20. For these reasons, and to prove that these effects in the natural system by biological

monitoring can take many years of intensive sampling at a large cost, the proposed new

rule (R50A) that identifies a permitted activity status, regarding stormwater networks and

discharge, should be restricted to those townships or settlements which have an

impermeable surface cover of 5% or less of the local water catchment. This is a

precautionary level as the research suggest that a 10% level is the more certain level at

which aquatic adverse effects become measurable.

21. I have, through the assistance of BML GIS expert (Ms Hume-Merry) undertaken to

establish some of the Wairarapa Total Impermeable Areas (TIA) measures (Table 1). The

method of estimation for the impermeable surface and relevant catchment8 is given in

Annexure 1, along with maps of the mapped areas. I note that in calculating the

impermeable surface cover as the predictor for effects, the estimate does not consider

the fate of the water. Where stormwater is directed to soak pits and not directed to the

town stormwater network, then that water has little ability to pollute receiving aquatic

2 Schueler, T; Fraley-McNeal, L’ Cappiella, K. 2009. Is impervious cover still important? Review of recent

research. Journal of hydrologic engineering April 2009 / 309. 3 Wang, L; Lyons, J; Kanehl, P. 2001. Impacts on stream habitat and fish across multiple spatial scales.

Environmental management Vol 28, No.2, pp 255-266. 4 Schiff, R; Benoit, G. 2007. Effects of impervious cover, at multiple, spatial scales on coastal watershed

streams. Journal of American water resources association, vol 43, No.3. 5 Miller, J’ Kim, H; Kjeldsen, T; Packman, J; Grebby, S’ Dearden, R. 2014. Assessing the impact of

urbanization on storm runoff in a peri-urban catchment using historical change in impervious cover. 2014. Journal of hydrology vol. 515, pp 59-70. 6Walsh, C.J., T.M. Fletcher, and A.R. Ladson, 2005a. Stream Restoration in Urban Watersheds Through

re-Designing Stormwater Systems: A Hypothetical Framework for Experimental Watershed Manipulation. Journal of the North American Benthological Society 24(3):690-705 7 Morse, C; Huryn, A; Cronan, C. 2003. Impervious surface area as a predictor of the effects of

urbanization on stream insect communities in Maine, USA. Environmental Monitoring and Assessment vol 89, No. 1, pp: 95-127. 8 There is an accepted convention for GIS operators as to the extent of the wider catchment to allocate or use in relation to the proportion of permeability of the “township”.


systems. The cover estimate does not take this into consideration. I note, from Mr

Stephenson’s evidence (paragraph 21) that the proportion of rain water falling on the

townships and ending in the stormwater network is relatively small; therefore, the

impermeable cover estimate is super precautious as a predictor of adverse aquatic

effects.

Figure 1 - Generalised Model of Relationship between Stream Quality and Watershed Impervious Cover [Diagram from Center for Watershed Protection (CWP). (1998). Rapid watershed planning handbook, CWP, Ellicott City, Md.]

Table 1 - TIA Estimates

Township / settlement Impermeable Surface (%of catchment) SW effect issue

Masterton 6.36% Potentially

Carterton 4.16% No

Featherston 3.75% No

Greytown 3.24% No

Ngawi 2.18% No

Martinborough 2.15% No

Lake Ferry 0.51% No

Mangatoetoe 0.07% No

Castlepoint 0.05% No


22. Table 1 above shows the final calculated impermeable surface cover as a percentage of

the total stormwater catchment area for each township. The far right column shows the

predicted effect level of that cover on receiving aquatic environments.

23. Even the largest township with the largest population in the Wairarapa has only 6.4%

impermeable surfaces, meaning the stormwater runoff is likely to be at the stage of some

measurable adverse effect.

24. The additional townships modelled are all smaller than Masterton, which generally have

very small proportions of their local catchments as impermeable surfaces, and have only

small areas of that surface with surface stormwater systems, and there is little chance of

typical residential stormwater having more than temporary and very minor adverse

effects, even accumulatively over time.

25. The very small “townships” (clusters of houses in some cases) will have no measurable

effect.

Alternative Approaches

26. As an alternative to the suggested impervious cover system put forward in my evidence

(and new rule R50A), I have considered the monitoring approach promoted in the PNRP.

27. In my experience, attempting to determine an adverse effect of a broad infrastructure

delivery system (such as SW) that is:

highly variable over time in its delivery of water to systems, and affected by many

additional (e.g. rural up stream) inputs, and whose input types and concentrations

change seasonally, as well as in relation to weather, and

which has aggregated (non-random positioned) species taxa (the metric being

measured), that also change spatially and in composition with flow conditions,

and season, at small spatial scales,

is incredibly problematic. It requires substantive sampling effort, with lots of replication

over a large area and over a large amount of time, at some cost.

28. For example, I have been monitoring fish and macroinvertebrate communities and

sediment accrual in six major streams for the Transmission Gully Motorway project over

the last five years, monitoring two times a year at six locations with 30 samples per

sampling effort per site (3 sets of 10 pooled kick net samples). As a result of large

sediment discharges, and substantive bed deposition, there is clear visual habitat

degradation; but the sampling (i.e. 900 individual processed samples) is still insufficient


to show a statistical difference in the quality of the macroinvertebrate metrics (e.g. QMCI),

and variations occur apparently randomly in the data.

29. I use this experience to explain that standard common biological sampling procedures

are affected by a range of variables which one cannot often adequately control for, and

that it takes many samples over extensive time, even with a relatively obvious causation,

to achieve a conclusive result. It is rare (if ever) that conditions of consent set sufficient

and well targeted data collection that could isolate the activity effects, and with sufficient

replication to actually conclude (with statistical rigour) an effect. To do so would be

incredibly costly and often impractical. As such, in my opinion, for most activities that

have unclear effects (such as stormwater) trying to measure an effect to a

macroinvertebrate community and ascribe it to stormwater discharge in small rural

affected stream will be a significant challenge; and given the scale of sampling which is

acceptable, not be possible.

30. The impermeable surface indices approach proposed in R50A, on the other hand, builds

on substantial science to allow a precautionary predictor as a consent trigger, avoiding

the issue of small scale data collection which is not conclusive. In my opinion, R50A is a

more pragmatic, and considered approach to a low risk situation, which gives greater

certainty to the Councils at far less cost than the approach proposed in the PNRP.

Monitoring for the sake of collecting some data, but not data that can answer the question

properly, is not an approach I, as a professional ecologist, support.

Is there currently evidence of effects in the Wairarapa?

31. There are no State of the Environment (SOE)monitoring sites related to any of the smaller

townships which can be used to indicate existing water quality issues specific to

stormwater. Most of the Wairarapa plains has a mix of rural and urban runoff (but

predominantly rural) and various specific industry or infrastructure (e.g. wastewater

treatment discharges, NZTA State Highway road discharges, industry discharges (e.g.

saw mills)) which make any investigation into stormwater effects by themselves very

difficult. This difficulty arises because separating out the various other upstream

influences is virtually impossible, and because the toxicity to instream life is acute (non-

lethal) and determined by the bioavailability, which involves aspects such temperature,

water hardness, types of organisms present, and the places of pollutant accumulation).

Also, as I mentioned above (Para 30), measuring an effect is difficult when considering

fish or macroinvertebrate communities, because of the natural variation in those

communities related to season, flow, spatial distribution, resource clustering and

sampling efficiencies, mean many samples (replication) over long time periods are

required to develop sufficient data to develop valid conclusions as to effects.


32. There are a few studies in the Wairarapa that I have been able to locate which illustrate

water and habitat quality in relation to discharges.

33. There is a study, and an array of data, for the Papawai stream (and Tilsons Creek) which

“drain” the Greytown urban area but includes discharge from the wastewater treatment

system as well as rural land uses and a water race (GWRC (Keenan 20099)). There are

also several studies on Donaldson’s Creek and Abbott’s Creek around Featherston

(Coffey 201010, River lake 201611). These are also related to wastewater discharge

effects. None of the studies provide water quality data relating to stormwater (i.e. metals,

hydrocarbons), but both have macroinvertebrate quality data downstream of the towns.

Both the Coffey’s and RiverLink study areas include rural land use effects, town

stormwater and wastewater effects, and these different drivers of water quality, in the

data, are inseparable. To that end (so as to have an upstream (above stormwater input)

comparison), I requested South Wairarapa District Council sample for macroinvertebrate

communities in Donaldson’s Creeks above stormwater entry points to compare with the

downstream samples in the literature (refer to Table 2 below). While sampled at different

times, and with a limited effort (i.e. one sample), and reflecting variance in weather

condition, the comparison suggest that the macroinvertebrate communities are very

similar and suggests that there is no obvious evidence of stormwater pollution.

Table 2 - Various Donald’s Creek macroinvertebrate summary quality metrics (SDC 2017, RiverLink 2016, Coffey 2010 data)

Donald's Creek (above town)

SDC

Donald Creek (below town) (Riverlake)

Donald Creek (below town) (Riverlake)

Donald's Creek up stream of WWP (Coffey)

Date Nov 2017 Oct 2016 Nov 2016 April 2010

Taxa Richness 26 21 25 16.6

MCI-hb 93.8 92.5 90.5 90

EPT Richness 8 6 8 9

QMCI-hb 4.5 3.8 4.3 4.3

Total abundance 226 595 2216 115

Numerically dominant EPT taxa Deleatidium Deleatidium Deleatidium Deleatidium

Hydrobiosis Hydrobiosis Hydrobiosis Aoteapsyche

Oxyethira Pycnocentrodes Pycnocentrodes

Oxytheria

9 Keenan, L. 2009. Instream flow assessment for Papawai Stream. Greater Wellington internal publication,

GW/EMI-T09/332 10 Coffey, B.T. 2010. Ecological survey of Donald (Boar) Creek to meet conditions 21 to 24 of consent WAR 970080 that permit the discharge of contaminants to water from the Featherston Wastewater Treatment Plat. Report prepared for SWDC. 11 River lake Ltd (Hamill. K.) 2016. Ecological survey of Donald Creek and Otauira Stream, 2016. A report prepared for SWDC.


34. While data is sparse in terms of stormwater quality (be it from SDC, MDC or GWRC), I

am confident (based on my own experience) that stormwater related water quality effects

of a measurable quantity are not of issue in the Wairarapa, and habitat quality effects are

most pronounced in relation to rural and specific industry outputs.

35. The Keenan report (Papawai Stream) supports my contention. That study was done to

set minimum flows, but includes some water quality data (from consent monitoring). The

issues found there were: rural runoff and stock access, a high macrophyte growth

lowering dissolved oxygen, waste water discharge from oxidation ponds (high E. coli and

nutrient issues) and (mentioned but never addressed) Greytown stormwater.

Wairarapa Town Local Authority Stormwater Networks

36. The existing local stormwater networks of the three larger townships in the SWD are well

described in Mr Stephenson’s evidence. A very important fact is that the proportion of

each township that is served by a classic stormwater network is very limited. Most of the

stormwater discharge in the South Wairarapa is on-site discharge (to soak pits). A policy

in the Combined Wairarapa District Plan requires all new development to manage its

stormwater on-site (discharge to land) meaning the discharge of stormwater to

waterbodies via the local authority stormwater networks cannot grow into the future. On

this basis, I do not anticipate any adverse effects of SW discharge to increase beyond

those effects which are current and which, in my opinion, are minor.

Measured Stormwater Quality

37. I accept there is limited data available on stormwater quality in the Wairarapa townships.

The SWDC undertook some sampling in 2016 in Martinborough, Greytown and further

sampling was done in 2017 in Featherston. MDC produced a small study of two

catchments in 2014 specifically around Stormwater discharge quality.

38. The SWDC work showed that the majority of measures (metals and hydrocarbons) were

low, below detection or well below ANZEEC (2000) guidance levels for toxicants.

39. Zinc, however, was different. Table 3 below summarises the zinc data for each site and

provides the ANZEEC guidance value for the protection of aquatic systems with different

tolerances.

40. Two caveats for the above results are that no water hardness correction has been

undertaken (this can raise the level at which toxicity occurs), and one sample is

insufficient to assume a wide level of toxicity persists.


Table 3 - Table 3 A2: Summary of Zinc Data for main towns in stormwater discharge collected by South Wairarapa District Council

Protection level

ANZEEC (g/m3)

Martinborough (upstream)

Featherston (upstream)

Featherston (downstream)

Greytown (upstream)

Greytown (downstream)

99% 0.0024 0.281 0.017 0.063 0.128 0.333

95% 0.008 - - - - -

90% 0.015 - - - - -

80% 0.031 - - - -

41. The results show that most sample data have zinc levels in the stormwater that are much

higher than even the lowest level of protection suggested by ANZEEC. These values are

incongruous with expectation given the level of impervious cover. There are no industries

that could/should be contributing. Only the impacts of the State Highways with multiple

untreated discharges offer a plausible explanation.

42. It needs to be kept in mind that these zinc levels are not being discharged directly into

sensitive aquatic habitats, and in most towns not even into aquatic habitats at all.

Featherston is sometimes the exception.

43. Some zinc is essential for aquatic life and good growth. There is a gradient of zinc within

the environment from deficient, to optimal, to toxic to lethal. Publication on general

dissolved zinc effects on aquatic systems is limited. Research focuses generally on

particular species (fish and marine invertebrates) (e.g. Stringer et al 201512).

44. Effects are less related to dissolved metals and more to the accumulated metals in the

sediments. Very quickly dissolved metals adhere /absorb to suspended particles,

especially sediment fines, and are taken out of suspension and sequestered in the

organic matter and sediments in the benthos.

45. In freshwater systems dissolved zinc is only readily available to filter feeding species

(such as freshwater mussel). It is my understanding that species are limited in the

Wairarapa streams about the towns.

46. Fish toxicity research in America suggests a level of 0.8 g/m3 zinc is a threshold for the

protection of fish in Illinois (Reed et al 198013). This is a much higher threshold than the

ANZEEC guide.

12 Stringer, T; Glover, C; Keesing, V; Northcott, G; Tremblay, L. (2012). Development of a harpacticod

copepod bioassay: selection of species and relative sensitivity to zinc, atrizine and phenanthrene. Ecotoxicology and Environmental Safety 80 (2012) 363–371.

13 Reed, P; Richey, D; Roseboom, D. 1980. Acute toxicity of zinc to some fishes in high alkalinity water.

Illinois State Water Survey, Urbana. ISWS/CIR-142/80.


47. A watercress study (Edmonds 200114) looking at levels of contaminant in water cress

surveyed the Papawai, Parkvale stream, Opaki and Manaia streams (in the Wairarapa)

found accumulated zinc levels between 2.88 and 6.5 gm3. This shows accumulation of

zinc in organisms which reflect environmental metal levels. The watercress levels were

10 times and more than that of stormwater (as measured by SWDC) but are still well

within NZ food guidelines (40 g/m3 zinc).

48. It is recognised that measures of total zinc in freshwater are highly variable and have a

seasonal component (as has rainfall). An Auckland Council study (Shedden 2014 15)

showed that measures taken since 1995 in over 15 Auckland urban streams (e.g. Lucus

Creek, Oakley Creek, Oteha Stream and Puhinui Stream), all very developed

catchments, had averaged total zinc levels between 0.2 and 0.44 g/m3. Large proportions

of these areas’ catchments are impermeable

49. The records returned by SWDC are incongruous with the ability of roofs and vehicle

discharges to produce such levels. The only other source I can think off is the State

Highways and their separate discharges to the same streams. That said as shown in

Table 2 there is no evidence of an adverse effect of this zinc.

50. GWRC SOE 2015-2016 monitoring of total recoverable zinc did not include measures in

the Wairarapa but did have some measures in western catchments (as shown below in

Table 4).

Table 4 - Summary of Total Recoverable Zinc (mg/L) concentrations measured at six RSoE sites between July 2015 and June 2016

Note 1 mg/L = 1 g/m3

14 Edmonds, C. 2001. Microbiological and Heavy metal contamination of watercress in the Wellington

Region. Victoria University, Wellington, Thesis for Diploma of Applied Science in Hydrology. 15 Shedden, B.A. 2014. Critical review of zinc trends in Auckland streams, estuaries and harbours. -https://12240-console.memberconnex.com/Folder?Action=View%20File&Folder

https://12240-console.memberconnex.com/Folder?Action=View%20File&Folder_id=390&File=b_shedden.pdf


51. Levels here are generally lower than those the Wairarapa stormwater measure, although

the Porirua has concentrations of similar level. These measures do not reflect stormwater

but rather ambient in-stream levels. A GWRC study of stormwater (Milne & Watts 200816)

included samples of first flush in Porirua (Table 3.2 of Milne & Watts). These data showed

that first flush measures varied from between 0.06 g/m3 to 1.17 g/m3 and where typically

around 0.2 g/m3. The SOE averaged measure of 0.02 (at Glenside) is around 10 times

less than the first flush measures (some also at Glenside).

52. It does appear as an anomaly that Porirua should have similar levels to Martinborough,

a much smaller, less intensely developed, town versus a city. However, in regard to the

Donald’s Creek discharges (Featherston) (based on the GWRC research) we can expect

that the zinc measures, for example at the drain outflow, are only a tenth of that which

will be measurable after the zone of reasonable mixing in Donald’s Creek downstream.

Impermeable Surface Cover and Effects

53. As supporting evidence of the efficacy (and conservativeness) of impervious cover

indices, I make reference to a paper prepared by Ms Jaquiery (Senior Environmental

Health Officer for MDC) in 2014 (report entitled: Preliminary Investigations into

Stormwater Derived Chemical Contaminants at Selected Urban Stream and Rivers in

Masterton). In that work, she sampled nine rain events upstream and downstream of two

main urban catchments in Masterton – Lansdowne and Waipoua for stormwater quality.

The results show that downstream (stormwater influence) in Lansdowne (a more

residential catchment) there was raised zinc and copper levels (breaching ANZECC 2000

95% protection levels17) but not so in the Waipoua catchment (a rural catchment). She

found that both up and downstream sites had raised DRP, nitrogen products and

ammonia (most likely rural in source).

54. I suggest this study helps supports the contention some urban catchments have

increased copper and zinc at levels at which long term damage may start to be

measurable, and that this shows, I suggest, that the imperviousness cover estimate is

relatively accurate and close to prediction (section 20 of my evidence) – which is that

Masterton is of a size where by stormwater pollution is beginning to be of a concentration

and frequency that long-term instream effects could be accumulating. However, this is

the level below which effects will not be conclusively measurable instream.

55. However, I would note that there is no instream flora and fauna evidence to currently

support an adverse effect related to stormwater.

16 Milne, J; Watts, L. 2008. Stormwater contaminants in urban streams in the Wellington region.

Environmental monitoring and investigation department, GWRC. GW/EMI-T-08/82. 17 Several upstream samples also had raised levels on occasions, as well as occasional cadmium and lead


56. Several of the small townships assessed for impervious cover are coastal (Mangatoetoe

and Castlepoint and Ngawi) and these stormwater systems discharge to a stream which

discharges to a very active coast and there is no doubt in my mind that such low

concentrations of stormwater would be rendered unmeasurable within 10m of being

discharged.

Conclusion

57. In my opinion, the townships of the Wairarapa, other than Masterton, are too small (and

with very low proportions of their catchment in a network) to have stormwater inputs that

would (under normal circumstances) have measurable adverse effects in freshwater

receiving systems. Few have anything but a rudimentary collection and focusing system

of stormwater that has a point discharge. The level of impermeability is too low by world

research standards to suggest the potential for adverse effects. That is coupled with the

instream biota typically being of a tolerant nature, developed under the influences of many

years with rural inputs.

58. What data we have on instream biota does not suggest stormwater pollution. Indeed, the

research illustrates nutrient and rural effects, as well as wastewater effects, but no

stormwater effects. While zinc levels are higher than expected, this does not suggest SW

pollution is in effect.

59. In my opinion, no amount of macroinvertebrate and fish monitoring in the short to middle

term, given the array of other potential causational factors (especially rural runoff) and

the minor levels of contamination, will successfully determine a pollution cause-and-

effect. Considerable cost and sampling would be involved at the worst potential

contamination sites and would still not provide a robust measure of a stormwater pollution

effect. In my experience, measurement of stormwater chemistry alone does not provide

sufficient evidence of an adverse environmental effect.

60. The impermeable surface cover indices proposed in my evidence are conservative and

a reliable tool, with enough caution in it that for these small towns it makes a sensible and

efficient tool to trigger resource consent needs for South Wairarapa. Where the threshold

is not breached then a resource consent should not be required. Some confidence can

be had that there are no adverse instream effects of the existing network stormwater.

Further provisions are included in the sought permitted activity rule to further ensure the

discharge does not adversely affect the life supporting capacity of the receiving aquatic

habitat.

Dr Vaughan Keesing 26 January 2018


Annexure 1 Imperviousness calculations and resultant maps.

GIS Methods to Determine Impervious Surfaces

1. Areas of Interest

Representative areas of interest from the Wairarapa Region were chosen for this study. This included urban areas from both significant rural towns, such as Masterton, and coastal settlements such as Mangatoetoe. In total, 11 areas of interest were chosen - Carterton, Castlepoint, Featherston, Greytown, Lake Ferry, Mangatoetoe, Martinborough, Masterton, Ngawi, Riversdale and Whangaimoana.

2. Catchment Selection

A catchment selection process was used to determine which catchments may be affected by storm water processes occurring within the urban environment. An intersection was calculated between NZ River Environment Classification 2 (REC2) catchments and the urban environments as zoned by the relevant district plan. 33 catchments were selected in total covering the 11 areas of interest – Carterton (3), Castlepoint (1), Featherston (4), Greytown (3), Lake Ferry (4), Mangatoetoe (2), Martinborough (3), Masterton (6), Ngawi (2), Riversdale (5) and Whangaimoana (1).

3. Percent Total Impervious Area (PTIA)

A PTIA value was calculated separately for each of the 11 areas of interest. Using aerial imagery of 0.3m pixel size, bands 4, 3 and 1 (alpha, blue and red respectively) were extracted to better distinguish urban features from natural features. The imagery was processed using a supervised classification technique which required creating training samples to aid the classification algorithm. To select training samples, polygon areas were manually selected and classified as one of the following surface types: Impervious (Developed) or Pervious (Forest, Barren/Dry Paddock, Paddock, Water). To ensure a representative cover, each surface type included >10 training samples for small catchments and >20 samples for larger catchments. The Support Vector Machine Classifier tool was then run using the training sample file and major classification errors were reconciled with the manual reclassify tool. The impervious area percentage was then calculated using the following formula:

PTIA = TIA/TCA * 100

TIA = Total Impervious Area as derived from the aerial classification TCA = Total Catchment Area (including ALL catchments intersecting the urban settlement)

LIMITATIONS AND ASSUMPTIONS

- Image classification is a technique used to provide estimates for surface area; as

the process was made to fit a diverse range of towns, the accuracy of classification

may be reduced.

- Lack of high-resolution multispectral imagery meant that we had to use 4-band

imagery to run analysis. This can reduce accuracy of the classification

- The rec2 catchment boundaries do not always extend to have complete coverage

of coastal towns and come with their own set of limitations and assumptions as

provided by NIWA and in the Ministry for the Environment User Guide.

https://www.niwa.co.nz/freshwater-and-estuaries/management-tools/river-environment-classification-0

https://www.mfe.govt.nz/sites/default/files/environmental-reporting/about-environmental-reporting/classification-systems/rec-user-guide-2010.pdf


Appendix 2. TIA catchment maps

Greytown

Carterton

PTIA: 4.16%

W16025

Surface Classification: CartertonDate: 17 January 2018 | Revision: 1

Plan prepared for SWDC by Boffa Miskell LimitedProject Manager: [email protected] | Drawn: HHu | Checked: VKewww.boffamiskell.co.nz

DRA

FT

File Ref: W16025_SurfaceClassification_A3P

0 1,200 m

Projection: NZGD 2000 New Zealand Transverse Mercator

Data Sources: Greater Wellington Regional Council, BoffaMiskell

°

This plan has been prepared by Boffa Miskell Limited on thespecific instructions of our Client. It is solely for our Clients usein accordance with the agreed scope of work. Any use orreliance by a third party is at that partys own risk. Whereinformation has been supplied by the Client or obtained fromother external sources, it has been assumed that it is accurate.No liability or responsibility is accepted by Boffa MiskellLimited for any errors or omissions to the extent that theyarise from inaccurate information provided by the Client orany external source.

Legend

Town CatchmentsTown ExtentPermeableImpermeable

1:60,000 @ A3

Castlepoint

PTIA: 0.5%

W16025

Surface Classification: CastlepointDate: 17 January 2018 | Revision: 1


DRA

FT


0 400 m



°


Legend


1:20,000 @ A3

Featherston

PTIA: 3.75%

W16025

Surface Classification: FeatherstonDate: 17 January 2018 | Revision: 1


DRA

FT


0 600 m



°


Legend


1:30,000 @ A3

Greytown

Carterton

PTIA: 3.24%

W16025

Surface Classification: GreytownDate: 17 January 2018 | Revision: 1


DRA

FT


0 1,000 m



°


Legend


1:50,000 @ A3

Whangaimoana

LakeFerry

PTIA: 0.51%

W16025

Surface Classification: Lake FerryDate: 17 January 2018 | Revision: 1


DRA

FT


0 1,600 m



°


Legend


1:80,000 @ A3

Mangatoetoe

PTIA: 0.08%

W16025

Surface Classification: MangatoetoeDate: 17 January 2018 | Revision: 1


DRA

FT


0 400 m



°


Legend


1:20,000 @ A3

MartinboroughFeatherston

Greytown

Carterton

PTIA: 2.15%

W16025

Surface Classification: MartinboroughDate: 17 January 2018 | Revision: 1


DRA

FT


0 2,800 m



°


Legend


1:140,000 @ A3

Carterton

Masterton

PTIA: 6.36%

W16025

Surface Classification: MastertonDate: 17 January 2018 | Revision: 1


DRA

FT


0 2,000 m



°


Legend


1:100,000 @ A3

Mangatoetoe

Ngawi

PTIA: 2.56%

W16025

Surface Classification: NgwaiDate: 17 January 2018 | Revision: 1


DRA

FT


0 200 m



°


Legend


1:10,000 @ A3

Riversdale

PTIA: 1.14%

W16025

Surface Classification: RiversdaleDate: 17 January 2018 | Revision: 1


DRA

FT


0 400 m



°


Legend


1:20,000 @ A3

Whangaimoana

PTIA: 0.54%

W16025

Surface Classification: WhangaimoanaDate: 17 January 2018 | Revision: 1


DRA

FT


0 400 m



°


Legend


1:20,000 @ A3

Documents

Before the Hearing Panel Proposed Natural Resources Plan ...pnrp.gw.govt.nz/assets/Uploads/HS4-S367-Masterton-District-Counci… · urbanization on storm runoff in a peri-urban catchment