AUCKLAND REGIONAL COUNCIL

Commissioners Determination on Consent Review

SUBJECT:

Review of consent conditions under Section 128 of RMA (consent number 12977) of Winstone Aggregates Limited’s consent to take groundwater at 987-1021 Mt. Eden Road, Three Kings.

FROM:

Commissioners Hearing of the Environmental Management Committee held between 21 July 2003 and 4 August 2003 consisting of the following membership:

Mr K Graham (Chair)

DR L Wesley

Mr G Wheeler

FILE: 9798

DATE:

5 SEPTEMBER 2003

 

1. REPORT

INTRODUCTION

The purpose of the hearing was to consider a consent review pursuant to Section 1281(c) of the Resource Management Act 1991. The Auckland Regional Council (ARC) served notice of its intension to review the conditions of Winstone Aggregates’ resource consent to take groundwater at Three Kings Quarry on 4 April 2003.

The service of the Notice of Review and a summary of its contents was notified on 21 May 2003 in accordance with Section 93 of the Resource Management Act 1991 (RMA). Submissions closed on 19 June 2003 with 574 submissions received.

The Auckland Regional Council (ARC) notified a Resource Consent hearing on 10 July 2003 and the Officer’s Report to the Hearing Commissioners was distributed to all submitters that had indicated that they wished to be heard at the hearing. The Hearing commenced on 21 July 2003 and concluded on 4 August 2003 after deliberations.

SITE VISIT

Commissioners Graham, Wesley, Wheeler and Council Officer Smaill visited the site on 18 July 2003.

REPRESENTATION AT THE HEARING

For the Consent Holder:

Christian Whata (Counsel-Russel McVeagh)

Bal Matheson (Counsel-Russel McVeagh)

Chris Ellis (Winstone Aggregates)

Alan Happy (Winstone Aggregates)

Michael Harris (Winstone Aggregates)

Grant Fisher (Industrial Geology)

Alan Pattle (Pattle Delamore)

Peter Millar (Tonkin and Taylor)

Wayne Russell (URS New Zealand Ltd)

Janet Gough (Taylor Baines and Associates)

David Serjeant (Kingett Mitchell)

 

REPORTS RECEIVED BY COMMISSIONERS

The ARC Officer’s Report was circulated to the Applicant, the Submitters that indicated they wished to be heard at the hearing, and the Commissioners prior to the hearing.

In addition, the Commissioners received the following reports prior to the hearing:

Earthtech Consulting Ltd, March 2003. Three Kings Quarry- Peer Review of Dewatering and Settlement Evaluation. Report prepared for ARC.

Fisher, Grant (Industrial Geology), 2003. Geological Update for Three Kings Quarry.

Report for Winstone Aggregates.

Pattle Delamore Partners Ltd, February 2003a. Groundwater Modelling of the Waitematas near Three Kings Quarry. Report prepared for Winstone Aggregates.

Pattle Delamore Partners Ltd, June 2003b. Three Kings Quarry Dewatering:

Assessment of Groundwater. Report for Winstone Aggregates.

Tonkin and Taylor Ltd, February 2003 a. Three Kings Quarry Dewatering. Review of Settlement Predictions. Report for Winstone Aggregates.

Tonkin and Taylor Ltd, June 2003b. Three Kings Quarry Dewatering. Assessment of Supplementary Investigations of April 2003. Report for Winstone Aggregates.

URS New Zealand Limited, March 2003. Review Comment- Three Kings Dewatering and Settlement Predictions. Report for Winstone Aggregates.

EVIDENCE BY ARC STAFF

The Officer’s Report was taken as read and ARC staff presented no additional evidence. The ARC’s consultant Mr Aidan Nelson of Earthtech presented additional information in response to questions from the Commissioners. This related to ground settlement calculations in the Zone IIA area.

 

EVIDENCE BY THE CONSENT HOLDER

(a) Chris Ellis is the General Manager of Winstone. He provided evidence of the company’s key policies and responses as they relate to Three Kings.

(b) Alan Happy is the Resource and Environment Manager with Winstone. He has been responsible for putting in place environmental management and reporting procedures. He described the company’s initiatives relating to the quarry, including the establishment of the community liaison group.

(c) Michael Harris is the Three Kings monitoring manager for Winstone. Mr. Harris outlined monitoring at the quarry and the components of the Monitoring and Contingency Plan.

(d) Peter Millar of Tonkin and Taylor Ltd provided detailed evidence of his assessment of ground settlement and the risks associated with dewatering.

(e) Alan Pattle of Pattle Delamore Partners gave evidence about groundwater modelling, revised predictions for groundwater drawdowns and recommendations for further monitoring and staged dewatering.

(f) Wayne Russel of URS New Zealand Ltd undertook a peer review of the investigations and assessments by Tonkin and Taylor and Pattle Delamore. He provided evidence on this review.

(g) Grant Fisher of Industrial Geology described the geology of the Three Kings Quarry and the surrounding area.

(h) Janet Gough of Taylor Baines and Associates provided evidence about the process of risk assessment undertaken by Tonkin and Taylor and that they conform to accepted standards.

(i) David Serjeant provided a summary of planning and policy issues regarding the dewatering, in particular compliance with regional planning documents.

 

EVIDENCE FROM SUBMITTERS

The following submitters provided evidence which supported continuance of dewatering at the quarry:

(1) Don Tilbrook on behalf of McKenzie and Parma Limited

A number of submitters (26) supported the continuing dewatering of the quarry. These submitters were companies or individuals who used the scoria product from the quarry. They noted that scoria is a valuable product, for several construction purposes, and that it is becoming rare in the Auckland Region. It was also stated that there was an advantage in having this product close to the markets where it was used.

The following submitters provided evidence against further dewatering at the quarry:

(1) ColleenBuist

(2) Corrine McLaren on behalf of Alan Bigelow

(3) Ms Wyn Hoadley provided legal submissions on behalf of Three Kings United Group Inc.

(4) Corrine McLaren on behalf of Three Kings United Group Inc.

(5) Corrine McLaren on her behalf.

(6) Richard Bellamy on behalf of the South Epsom Planning Group Inc.

(7) Marcia Fullam on behalf of herself and Alan Jamieson.

(8) Austen Bell

(9) Paul Smith on behalf of himself and Melita Smith.

(10) Veronica Friedlander

(11) Peter Friedlander

(12) Andrew Carline

(13) John Oliver

(14) Malcolm Metcalfe, also on behalf of Hazel Metcalf and George Bernard Shaw

(15) Michael Jamieson

(16) Margret Moore

(17) Jim Walsh

(18) Paul Casey

(19) Elizabeth Lamb on behalf of herself and John Lamb.

(20) Julie Hunt on behalf of herself and Stan Hunte

(21) Gary Bryant

(22) Nicole Bremner, also on behalf of Iain and Joanne Bremner, Craig Turner, Richard and Elizabeth Graham, Malcolm and Heather Beehre.

(23) Patricia Sim.

(24) Wayne Oakely

(25) Othmar Lichtnecker

(26) Rob Anderson

(27) Adrienne Millar

(28) lain Whittet

(29) Gary Preston

(30) Stuart Bracey and Ann Williams for Housing New Zealand.

(31) Shaylene Roberts

(32) John Laur

(33) Jen Vella for the Epsom Environmental Effects Society Inc.

(34) Jenny Miller

(35) Mike MeQuillan for the Auckland City Council

(36) Maree Faid for Transit New Zealand.

(37) Jan Bassett on behalf of himself and Sharon Bassett.

(38) Alan Kirk.

(39) Ben Hamid on behalf of himself and Kate Edenborough.

(40) David Bennett.

(41) Mary-Ann White

(42) John White.

(43) Alastair Page.

(44) Philip Lowe on behalf of himself and Peggy Lowe

(45) Joanne Pilgrim.

(46) Nigel Cartmell.

(47) Paul Cavanagh and Philip Wood for the Trustees of the Goldwood Trust.

(48) Pete France

(49) Catherine MeArdle.

 

The following written submissions were tabled:

(1) Dr and L H Rendel

(2) Bryan Cameron, Jane Cameron, Frazer Cameron, Max Cameron, Patricia Sigley, Amjad Raza and family.

(3) Aoteroa Waka Party

(4) Jim Lello

(5) A further submission from Austin Bell.

 

Issues raised by the submitters in their written submissions are summarised in the Officer’s Report. No new issues were raised at the hearing. However, submitters provided considerably more detail at the hearing, expanding on their written submissions. The main issues raised are summarised as follows:

(i) Increased Zone of Dewatering and Settlement

A large number of submitters were concerned that the zone of dewatering is now predicted to be significantly larger than that predicted in the original application, and that ground settlement is occurring and is predicted to occur in areas where it was not identified previously.

(ii) Cancellation of Consent

The majority of submitters asked for the consent to be cancelled and/or for the taking of water to cease. Several wanted groundwater to return to its natural levels. Many stated that they wanted the consent cancelled due to inaccuracies in the original application, and that new conditions will not provide enough certainty for landowners.

 

(iii) Dewatering to Cease

As an alternative many submitters asked that dewatering (further lowering of the water table) should cease and/or the groundwater level should be maintained where it is now and no lower. Some submitters asked that the take quantity on the consent be reduced.

(iv) Damage to Property

The major concern of submitters is damage to their property, houses, services, and public buildings from subsidence/settlement. One submitter was worried about the stability of Big King. Several submitters were concerned that lives may be endangered. Comparisons were made by some submitters with Waihi and Huntly. Some submitters were worried about the effect on gardens and trees. Several submitters was concerned about effects on historic buildings and stonewalls.

(v) Reported Damage

A small number of submitters reported potential damage to their property that could be related to ground or foundation movement. The submitters attributed this to ground settlement caused by the dewatering.

(vi) Loss of Value

A major concern of submitters is the potential loss of property value. A number were concerned that Auckland City Council (ACC) would place comments regarding settlement on LIM reports and this would further add to loss of value.

(vii) Insurance

Many submitters are concerned that their house insurance and the Earthquake and War Damages Commission does not cover damage to their properties from ground settlement caused by dewatering. Many asked who was responsible, and that there was a lack of an accountable agency. Others stated that Winstones and the ARC should be made more accountable. There was a general lack of confidence in the present Winstones insurance scheme. Some stated that Winstones should make good any damage or loss of value to property. It was suggested a fund should be set up to pay for any damage or other financial assurances should be put in place.

(viii) Standard of Investigations

There was considerable concern about the standard and completeness of investigations undertaken on behalf of the Consent Holder. It was stated that the geological investigations were not complete or comprehensive enough. In particular, there is poor understanding of the Tauranga Group sediments. Many submitters stated that they had little confidence in the latest investigations, based on inaccuracies in the original application. Some submitters noted that groundwater drawdown and ground settlement calculations are not an exact science. Others stated that no further dewatering should occur until further, more comprehensive investigations, are undertaken. One submitter stated that there were two few ground settlement monitoring sites and that there were flaws in the statistical methodology in the analysis of such data. Several submitters noted that no baseline survey of all properties, in terms of a detailed structural analysis, has been undertaken. One submitter added that the walk-by survey’s undertaken to date were inadequate. Another submitter stated that the added effects of seismic activity had not been taken into account.

 

CONSENT HOLDER IN REPLY

Mr Whata provided submissions in reply to the submitters. In particular, Mr. Whata provided a set of suggested conditions, which included a regime in which dewatering could continue in a staged manner. Mr. Whata suggested that the recommendations in the Officer’s Report were too conservative and that any adverse effects from dewatering could be avoided, remedied or mitigated by a staged dewatering approach as outlined in the conditions he tabled.

Mr Peter Millar and Mr Alan Pattle provided evidence in reply to technical issues raised by the submitters.

 

 

2. COMMISSIONERS’ DETERMINATION

2.1 DECISION

After considering the Officer’s Report, written submissions and the evidence presented by the Consent Holder and Submitters at the Hearing, the Commissioners' decision is that the consent can continue to be exercised, with changes to conditions and additional new conditions as stated on the consent document appended to this determination. In particular, dewatering may continue in a strictly controlled way in a slow stepwise fashion, provided increased monitoring supports further dewatering.

The term of the consent cannot be changed, and it is not recommended that the consent be cancelled.

It is recommended that the quantity of water allocated does not change.

Condition 1, the review condition is changed to allow for annual reviews.

Conditions 2, 3, 4, 5, 6, 8, 9, and 10 are not part of the review and cannot change (the numbers in the attached conditions remain the same).

Condition 7 is changed to reflect additional groundwater level monitoring sites. These include monitoring bores drilled since the original consent was granted, six bores requested by Transit NZ in the Carr Road area and a new bore at the intersection of Mt Eden and Landscape Roads.

Conditions 11 and 12 regarding the Monitoring and Contingency Plan are replaced with new conditions 14 and 15.

Condition 13 is maintained as it is (attached as condition 16).

New conditions requiring a bond are added (conditions 17, 18, 19, 20).

New conditions are added for ground settlement monitoring (condition 12), making good damage (condition 11), and settlement limits (condition 13), protection of historic buildings, and an assessment panel with relevant expertise to carry out inspections on potentially damaged structures (condition 21).

 

Condition 13 contains a differential settlement limit of 1:1,000. The consent holder is required to cease taking water if differential settlement reaches this level.

Condition 12 allows for increased monitoring of ground settlement in the form of more monitoring locations, particularly in zones IIA, IIB, IIIA, IIIB. Monitoring is also extended to the full extent of the assumed dewatering zone. In addition, the monitoring frequency is increased from six monthly to three monthly while dewatering is taking place.

Conditions 21A and 21B allows for the establishment of an Assessment Panel and a process for the assessment of claims for damage, which is breach of the conditions.

It is determined that water levels can be lowered below 34mRL in the quarry, if strict criteria are met. These criteria will substantially reduce the level of uncertainty in predicting potential ground settlements so that adverse effects on the environment in the form of damage to structures and services will be avoided, remedied or mitigated (conditions 22, 22A, 22B, 22C, 22D). Dewatering is limited to 34mRL in the quarry until at least 31 December 2004 (condition 22). Dewatering below this level is only permitted if the criteria in new Condition 22B, 22C and 22D are complied with. Condition 22A requires any further dewatering to be undertaken in 5m steps with a minimum 2 year hold period between drawdown steps. Dewatering shall cease if differential settlement reaches 1:2,000, total settlement is greater than 100mm (or 75mm in monitoring points established after 30 September 2002), the settlement rate is greater than 10mm per year and if there is drawdown in bores Tl to T4.

New conditions (conditions 23 and 24) are added to the consent to carry out building surveys, with owners permission in areas of greatest risk to ground settlement, particularly zone IIA.

A new condition (condition 25) is added to protect Historic buildings, particularly those historic buildings that are not protected by condition 10.

A new condition (condition 26) is added to allow the consent holder to apply for a

change in conditions for any reason in accordance with the Resource Management

Act 1991.

2.2 REASONS FOR THE DECISION

This process is a review of consent conditions. It is not an application for a resource consent. The decisions that the commissioners can make in this review are outlined in Section 132 of RMA. They are limited to changing the conditions that are under review and adding appropriate new conditions that will avoid, remedy or mitigate any actual or potential adverse effects. The commissioners are unable to change the duration of the consent, but in this case are able to cancel the consent in accordance with Section 132 (4) of RMA.

The matters to be considered in a review are set out in Section 131 of RMA. In this case Section 131 (1) is relevant. The commissioners:

(a) Shall have regard to the matters in section 104 and to whether the activity allowed by the consent will continue to be viable after the change; and

(b) May have regard to the manner in which the consent has been used.

 

 

2.2.1 CONSIDERATION OF CANCELLATION

 

Section 132 of RMA sets out what a consent authority may do in regard to decisions on a review of consent conditions. Section 132(4) allows a consent authority to cancel a consent in certain circumstances.

Section 132 (4) states:

Notwithstanding sections 128 to 131 and subsections (1) to (3), where-

(a) A consent authority reviews a resource consent under section 128 1c; and

(b) The application contained inaccuracies which the consent authority considers materially influenced the decision made on the application; and

(c) There are significant adverse effects on the environment resulting from the exercise of the consent-

The consent authority may cancel the resource consent.

 

 

All three must apply:

(a) Where a consent authority reviews a resource consent under section 128 (1) (c) of RMA. This is the case in this review, as outlined in the Notice of Review to the consent holder.

(b) Where the application contained inaccuracies which the consent authority considers materially influenced the decision made on the application. This is the case here. In particular, monitoring has indicated that dewatering is occurring as a result of the exercise of the consent in additional geological formations and over a greater area than was indicated in information supplied with the consent application. Ground settlement has also occurred in areas that were not predicted in the application. If this was known at the time, then the outcome may have been different. At the very least the monitoring conditions would have been substantially different and covered a much wider area. All parties, including Winstone, agree that there were inaccuracies in the model predictions and that these materially influenced the decision.

(c) Where there are significant adverse effects on the environment resulting from the exercise of the consent. It should be noted in this case the adverse effects must be significant.

The meaning of effect is set out in section 3 of RMA and includes:

(a) Any positive or adverse effect; and

(b) Any temporaiy or permanent effect; and

(c) Any past, present, or future effect; and

(d) Any cumulative effect which arises over time or in combination with other effects-regardless of the scale, intensity, duration, or frequency of the effect, and also includes

(e) Any potential effect of high probability; and

(f) Any potential effect of low probability which has a high potential impact.

 

A number of submitters have suggested that adverse effects are occurring at present, in the form of damage to property. The Officers’ report concludes that it is unlikely that the exercise of the consent has caused this reported damage, as measured differential settlements are at a level that damage is unlikely. No submitter could substantiate their claims that this damage was caused by quarry dewatering. To cancel the consent on the basis of present adverse effects the commissioners would require more proof that the "damage" reported was caused by the exercise of the consent, and the adverse effects were significant. This would be difficult based on the low measured differential settlements.

In considering potential adverse effects, the Commissioners have taken into account; the full meaning of effect, the fact that the consent presently allows drawdown to sea level, and whether any potential effect can be avoided, remedied or mitigated. If the potential effects can be avoided, remedied or mitigated by changing, or adding, conditions then there is no case for cancellation.

The Officers’ report concludes that there is a likelihood of adverse effects if dewatering continues to a depth of 0mRL. The Officer’s report concludes that differential settlement in zone IIA may be approaching levels where damage to structures may occur at present. On this basis the probability of damage with lower dewatering could be considered high. The impact of such damage would be considerable, particularly on land values, to the individual land owners and the neighbouring community. The psychological impact on the community of settlement related damage actually occurring could be high. The high impact of these potential adverse could be considered significant. Therefore, cancellation on this basis could be justified.

However, the Officers report concludes that potential adverse effects can be avoided, remedied or mitigated by limiting the drawdown in the quany to 34mRL and providing tighter controls by the addition of new conditions. The Commissioners agree with this assessment, therefore cancellation is not justified. Furthermore, the Commissioners consider that effects on the environment can be avoided by staging dewatering in a controlled way. The proposed conditions will allow such dewatering if strict criteria are met. If they are not met, dewatering will cease and groundwater level will remain static. Under such circumstances cancellation of the consent is not justified.

Cancellation of the consent would cause the water level to raise in the quarry until it had reached it original level. This would not allow the removal of all quarryable rock that could be extracted without causing environmental effects. The value of the scoria resource to the Region is acknowledged. The maximum quantity of rock should be able to be removed without causing adverse effects on the environment. Cancellation of the consent would not allow this.

If it is considered that there could be adverse effects by continuing to pump water then it would need to shown that the adverse effects were "significant", in order to be able to cancel the consent.

There is a continuum of adverse effects from minor to significant. A significant adverse effect is at the high end of the scale. Importantly, it is much greater than "more than minor. Dictionary meanings of "significant" include "of a noticeably or measurably large amount". . In this context the risk of significant adverse effects from continuing to dewater with the regime proposed is low and cancellation is not justified.

 

 

 

 

2.2.2 INFLUENCE OF DE-WATERING ON SURROUNDING PROPERTY, BUILDINGS AND UTILITIES

2.2.2.1 General

The unusual background to this hearing has created some problems for the Commissioner’s in evaluating the evidence presented to them. The expected outcome from the drawdown of groundwater presented at the original application by the applicant’s technical experts has turned out to be seriously flawed, and the explanation offered by the consent holder’s advisers, as to why this was the case is not convincing. Very simplistic assumptions were adopted at the time of the original hearing regarding the expected groundwater behaviour, and confident predictions made of negligible ground settlement away from the immediate vicinity of the quarry. This was despite the fact that the intended water table lowering of over 50m was very large, and could

hardly help but have a very significant impact on the groundwater behaviour in the vicinity of the quarry. Unless very complete and accurate information was available on geological conditions, it seems unreasonable to assume that the material immediately adjacent to the volcanic crater would not be affected by the formation of the crater. It would also seem unreasonable to assume that there would be a complete absence of compressible materials in the zone likely to be affected by de-watering at the quarry. The compressible soils in the Hillsborough Road area are little more than 200m from the edge of the volcanic cone, and no allowance appears to have been made at the time for the possible presence of such deposits, or the likelihood that they would be affected by groundwater lowering. Never the less, the Commissioners in the original hearing did recognise the need for a comprehensive monitoring programme for both groundwater levels and ground settlement. The existing monitoring programme has been successful in determining that groundwater drawdowns and ground settlements have occurred outside those anticipated in the original application. This has lead to ARC undertaking this review.

 

2.2.2.2 The Groundwater Model

Computer groundwater models have a place in groundwater studies and predicting future groundwater behaviour, but they can seldom be more than rather crude aids, especially in areas of mixed uncertain geology, as is the case at Three Kings. Such modelling invariably involves simplified (or idealised) assumptions, and cannot hope to cover all the factors involved in any particular situation. Anne Williams, providing evidence on behalf of Housing New Zealand, gives an overview of what she sees to be the weaknesses and defects of the groundwater model, and highlights its many uncertainties. The points she raises seem valid and it appears to the Commissioners that a rather."optimistic" view has been taken by the consent holder’s advisers, of the reliability of the model, and of the likely extent and effects of the de-watering.

Areas of optimism in the model appear to be the adoption of a coefficient of permeability in the undisturbed (normal) Waitemata materials, 100 times lower than conventional, (ie normally accepted) values, and the adoption of a radius of influence of the dewatering of 1.5km. Adoption of both these values will tend to limit the zone of influence of the dewatering, and create a marked difference in behaviour between the "high permeability" zone adjacent to the crater and the material further out. It is noted that while groundwater levels may provide some support for this "model" the settlement measurements do not appear to do so. Figure 1 of T&T Report on Investigations of April 2003, shows a rather random pattern of settlement, with measurable settlement occurring to the north northwest and to the south-east of the quarry up to the maximum distance of almost 1,000m from the quarry centre. This is well beyond the limit of the high permeability zone, which the model limits to about 750m from the centre of the quarry. It is noted also that in the Hillsborough Road area the settlements are large and may still be increasing with distance from the quarry. The contours in T&T Figure 1 (April, 2003) are not sufficiently complete to show whether this is the case or not.

The Commissioners consider that the groundwater model is at, or beyond, its predictive limits. This is not unusual for models in such complex situations. Total reliance on the predictive capability of the model is not good management. It is just one tool which should be used. The Commissioners agree with the Consent Holder that it is vital to monitor the changes in the groundwater regime while pumping and modify models with time. This is normal practice. The fact that the model has changed, and will change further in the future, is not surprising and is considered good management practice.

2.2.2.3 Settlement Measurements and Estimates

Interpretation of water level drawdown and settlement monitoring records at Three Kings Quarry, and its usefulness for making future projections, is still very much a developing process. This is not surprising, as de-watering has only been in operation since 1999. This is a relatively short period in view of the low permeability materials encountered over much of the site. The Consent Holder’s own evidence illustrates and concedes that this is the case. Quite significant changes in their evaluation of the situation have occurred over the 6 months prior to the hearing.

URS in their letter to Russel McVeagh dated 19 March, 2003, state that "full calibration of the model has been restricted by the limited data set from the low permeability Waitemata Group rocks, as monitoring wells have not been in existence for sufficient time to develop reliable trends of water level change. At this early stage of model development, the focus has been on determining the extent of water level change"

As one of the submitters, Mr Philip Wood, (giving evidence for the Goldwood Trust) points out, Pattle Delemore in their February 2003 report, recommend that "active dewatering of the quarry should be reinstated quickly to allow a simpler de-watering model for transient calibration of the groundwater analysis" and "that water level monitoring should continue as it is" and "no further well installations are required". Five months later they recommend (PDP Report of July, 2003) that de-watering be held at its current level, and that "a further technical review of ongoing monitoring data should be undertaken within the framework of the Monitoring and Contingency Plan before any further lowering of quarry water levels occurs". The July 2003 report reflects a more conservative approach to further dewatering by the consent holder’s advisers.

To date, the measured settlements are quite small and very unlikely to have a noticeable effect on buildings. They are well within criteria that are commonly used in such situations to assess risk of building damage. The consent holder’s interpretation and projection of current trends generally shows that this ought to remain the case when the water level is further lowered, except possibly for certain "risk" areas where unfavourable geological conditions exist. The site of the least favourable conditions known to be affected by de-watering to date is the Hillsborough Road area. The geological conditions here are complex. There is uncertainty as to the actual thickness of the various layers and the shape of boundaries between them, as well as to the extent of future water table lowering (or "depressurisation"). The consent holder’s estimate (T&T report of June, 2003, and evidence statement of Mr Millar), is about 100mm of settlement and a differential of 1:700 when dewatering at the quarry reaches R.L.Om. However, the ARC’s review consultant, Earthtech Ltd, estimates settlement of 140mm and a differential of 1:316 for a "best estimate" and 188mm and a differential of 1:240, for a "worst case" situation (given in ARC Officer’s report). On this basis dewatering should not be allowed to continue to that level. There will however, be a point between the present situation and a point where acceptable (the consent holder recommends that this is at 1:2,000 differential settlement) differential settlement limits are reached. The Commissioners agree that 1:2,000 is an acceptable conservative limit. Differential settlements will not reach the predicted levels because the consent conditions will limit them to 1:2,000. Dewatering can continue in a controlled way until further monitoring indicates that the point is reached.

Apart from the generally tentative nature and uncertainties in current predictions, there are some aspects of the interpretation of the data, and future predictions that appear to be rather optimistic, and some issues which are ignored. These include the following:

1) The spacing between settlement markers is quite wide, and the settlement pattern recorded to date is very irregular (see Figure 1 of T&T Report on Investigations of April , 2003). This means that the measured differential settlements may not represent the worst values. There could be worse situations between markers not identified. There are areas where settlement to date is not known because of the absence of markers, and the installation of additional markers for future monitoring will be a sensible move, but cannot capture the settlement which has already occurred. More settlement points and more frequent monitoring are required by the conditions

2) There is an assumption made by the consent holder’s expert witnesses that once the water table drops below the level of the base of the compressible layers (particularly the Tauranga Group deposits) and enters the underlying Waitemata layers, no further compression will occur in these upper compressible layers. The T&T report of Feb.2003, section 5.2.1, (last paragraph) states that "We would further note that once groundwater level drops below the base of the Tauranga Group soils, no further settlement should occur as a result of dewatering". The URS letter of 19th March, 2003, to Russel McVeagh (5th bullet point of conclusions), appears to be making a similar assumption. The PDP Report of July, 2003, in discussing the Hillsborough area makes the statement that piezometric levels "will drop below the paleo valley floor in response to a further 5m reduction in groundwater level, and therefore any Waitemata underdrainage effects will have reached their peak well before the pumping level of RL Om is reached".

This is not a safe assumption. It is not the case that once the water table level drops below a particular layer further drops will not affect that layer. As the water table sinks deeper into the Waitemata layers, it will induce progressively lower (ie more negative) pore pressures in the layers above it, and the effective stress will rise causing further consolidation to occur. In other words, depressurisation continues throughout the soil profile, and not just below the water table. This point is of considerable significance as it means that the "worst case" scenario in the Hillsborough Rd area would be worse than that postulated by Earthtech Ltd. For this reason, dewatering should cease well before the settlement monitoring is at a level where damage may occur. The conditions therefore require dewatering (lowering of the water table) to cease at a measured differential settlement of 1:2,000 (new condition 22D attached) and for water pumping to cease (causing the water table to rise) at a differential settlement of 1:1,000 (new condition 13 attached). This is considered by the Commissioners to be a conservative course of action.

No explanation is offered for the apparent levelling off of settlement at the Hillsborough Road area, many years ahead of the predicted time for settlement of the Tauranga sediments present in this locality. Rafting by the overlying ash materials is offered as one possible explanation for actual settlements to date being less than predicted. The Commissioners are not convinced that rafting is likely to account for this difference, having regard to the aerial extent of the soft materials. Further monitoring will provide insight into this. In the meantime, monitoring and operation within strict limits will provide protection to the community.

3) The possible effect of lowering the groundwater on seasonal movement at the ground surface has not been considered. The Commissioners are unclear as to whether this is an important issue or not, but believe it ought to be addressed, and has not been. It is possible that lowering the ground water level could result in greater drying of the soil at the surface during summer, and consequent greater shrinkage than has previously occurred. If this were the case it would probably only become apparent during an unusually dry summer - a 10 year or 25 year drought. It would then be difficult to determine whether any damage to houses resulting from such soil shrinkage was due to the unusually dry summer alone or to an added component coming from the de-watering. The Commissioners consider the effects of dewatering on seasonal ground movement at the ground surface can only exacerbate the situation ie. the effects will not be less than the case of no dewatering even though the adverse effects may well be no more than minor.

 

2.2.2.4 Risk of Building or Amenities Damage.

The consent holder’s experts, in their reports prior to the hearing, and in evidence at the hearing, have adopted a criteria of differential settlement in order to assess the likelihood of damage to buildings from the de-watering operation. A table is provided in the Tonkin and Taylor report of Feb, 2003 relating expected categories of building damage to differential settlement (listed as ground slope). This is not an unreasonable approach, and is probably the only approach available to the consent holder. However, the Commissioners believe it is a crude measure and not very reliable, and is not really intended for use in situations such as the present one. The table provided is taken from a Building Industry Authority document and is headed "Design criteria for Civil and Building Works". It is primarily intended to enable building designers to ensure that differential foundation settlement caused by the building loads, or other expected foundation movement, does not exceed limits that might damage the structure. (1:250 for a "typical" building, during its life) In some cases, where foundation conditions are critical, this allowance could have been "used up" by the designer. For residential dwellings or low rise buildings of the type predominantly present at the Three Kings area, this would not normally be the case.

The evidence presented by Tonkin &Taylor at the hearing appears to imply that there is a large safety margin against damage because the known maximum differential settlement to date is well below the value of 1:500 (the differential which could result in minor damage)or even 1:1,000. The written evidence does not specifically discuss the fact that some structures could be close to the limit in their present state. It is likely that some houses in the area already have suffered damage from seasonal ground movement or for other reasons. It is possible that a very limited number of other buildings may be at the point where any further movement will cause damage. Under questioning Mr Millar agreed that this could be the case and for this reason he recommends a "trigger" value of 1:2,000 and a maximum acceptable limit of 1:1,000 between survey marks. This appears to be a reasonable approach. It should make the possibility of damage very small, but may not necessarily prevent it entirely. The Commissioners have therefore placed limits for differential settlement in the conditions (new conditions 13 and 22D).

The Tonkin and Taylor report of February 2003, quite rightly discusses the difficulty of distinguishing between damage caused by seasonal movement from that caused by dewatering effects, and states that "hence the importance of maintaining tight controls to monitor actual differentials is emphasised." This appears to imply that provided the measured differentials are less than some specified value (such as the recommended 1:2,000) then damage could not be attributed to de-watering effects. The consent conditions proposed by the consent holder appear to provide a reasonable procedure for determining whether the quarry de-watering is responsible for damage in any particular case. As a result the Commissioners have added additional conditions requiring an Assessment Panel and a procedure for assessment of claims of damage to property (conditions 21A and 21B on the conditions attached to this decision). These conditions are similar to those proposed by the consent holder.

 

2.2.2.5 Monitoring and a Staged Dewatering Approach

The Commissioner's view is that the predictive capacity of the groundwater modelling is still quite limited, and that the water level and settlement measurements are the best information currently available from which to estimate future behaviour and that this will always take preference over the model projections. However, the trends apparent from these measurements are still somewhat tentative and that considerably more time is needed to be sure that current interpretations by the applicant are justified. An expanded ground settlement monitoring network and more frequent monitoring is provided in the conditions. Additional groundwater monitoring is required at the intersection of Landscape and Mt. Eden Roads. Further groundwater monitoring is also required in the Carr Road area, as agreed between Transit and the consent holder (revised condition 7). A limit of no drawdown in these bores has been placed on some of the "Transit" bores (new condition 22D). This is likely to further restrict the level of drawdown in the quarry.

It appears prudent therefore to hold the water level at its current position for a longer period than that currently envisaged by the consent holder, and to allow a "hold" period for any further stages of dewatering, on a very conservative basis which will ensure that the risk of damage to surrounding properties is negligible .The new consent conditions set out criteria for this staged approach (new conditions 22, 22A, 22B,22C and 22D). The Commissioners are of the opinion that holding the water level at its current level for a longer period, until at least 31 December 2004 (new condition 22), and then lowering it and holding it at RL 29m (5m below present level) for the stipulated time (at least two years), will allow the groundwater "model" and settlement trends to be established on a much more reliable base than is currently the case. It is possible that further dewatering below this level can be undertaken if strict criteria are met (new condition 22B and 22C). These include limits on measured differential settlement of 1:2,000, limits on total settlement of 100mm (or 75mm on new settlement monitoring points), a maximum ground settlement rate of 10mm per year, dewatering in 5m steps with a minimum two year hold in dewatering between drawdown steps. The Commissioners consider that setting a differential settlement limit at 1:2,000 is conservative, but necessary to protect the interests of the community. The Commissioners consider it vital that any chance of damage to property is avoided. The slow and measured, staged drawdown regime allowed by the revised conditions is a suitably conservative approach. The limits set in the conditions may well be reached before dewatering reaches 0mRL. However, the Consent Holder should not be limited in its ability to extract rock in circumstances that are not causing adverse environmental effects as demonstrated by further monitoring. In this regard the Commissioners consider that the recommendations in the Officer’s Report are too conservative.

 

2.2.3 PROPERTY VALUES

Concern was raised by many submitters, both in written submissions and in evidence, about the effect of the dewatering on the value of their properties. The Commissioners agree with the analysis in the Officer’s Report. This is largely repeated here for completeness.

The issue of effect on property values is complex, and the case law from the Environment Court is somewhat contradictory. In Giles v Christchurch City Council (A92/2000) the court held:

A consent authority and this Court on appeal, is required to have regard directly to the likely effects on the environment of allowing the activity. A valuer's appraisal of the way those effects might impact on market value would duplicate the consent authority's function in an indirect way. We prefer to rely on the evidence of qualfied resource management planners about the effects themselves.

In Land Air Water Association and Ors v Waikato RC, Waikato DC, Envirowaste and Anor (Al 10/0 1) the court considered whether the effect on value is an "effect" within the meaning and context of the RMA. The Court noted:

Section 104 (1) requires us to have regard to "effects on the environment. Effect" is defined in section 3 and includes "any temporaiy or permanent effect".............The operative word is "economic" in sub-paragraph (d). In our view the effect on values is an economic condition which affects "people and communities" and "natural and physical resources"..........The weight we should give to such evidence depends on the facts and circumstances of each case.

However, the court also noted:

We agree with the Environment Court in Giles to the extent that it is preferable for the Court to rely on the evidence of experts in determining the adverse effects that will be generated by the proposal.

It appears from this that an effect on property value is an "effect on the environment" that may be taken into account. However, it is very difficult to quantify the actual effect as evidence on value is often contradictory. It is fair to say in this case, that if there is a physical adverse effect on a property from ground settlement caused by dewatering, then there may well be an adverse effect on the value of the property. The Commissioners consider that if there is no physical effect on a property from dewatering then any change in property values is not an effect caused by the exercise of this consent.

 

2.2.4 POSITIVE EFFECTS OF CONTINUED DEWATERING

A number of submitters (26), who support the continued dewatering at the quarry, were concerned about the potential loss of the valuable scoria and rock resource. The value of the rock resource is an issue that must be taken into consideration as outlined in the Regional Policy Statement.

The quarry is presently quarrying beneath the original groundwater level. The present groundwater level is at 34mRL (approximately 22m below pre-pumping levels) and the existing consent allows for dewatering, and hence quarrying down to 0mRL. Therefore there is a considerable amount of rock resource still in the ground. There may be at least 30 years of quarrying still available, depending on the rate of extraction, which can be variable. Limiting further dewatering would have a considerable effect on the amount of rock that could be removed and the future economic viability of the quarry. The Commissioners understand that it is not economically viable at present to quarry the rock beneath the groundwater without first dewatering.

The main material extracted is scoria which is highly valued particularly as a drainage material, due to is its high surface area and light weight, and also as a decorative and lightweight aggregate. Three Kings Quarry is one of only two major scoria quarries left in the Auckland region. A number of submitters pointed out that the quarry is close to markets, making the resource more valuable, as transport is a major cost of aggregate. The aggregate from this quarry provide important social and economic benefits to the community.

Chapter 2 Of the Regional Policy Statement states:

The need to accommodate an expanding urban population has placed pressures on mineral resources in the Region, namely sand and aggregates. The demand for these continues, yet the resource is limited. If Auckland is not to face the high costs and accompanying adverse impacts on the environment of transporting heavy aggregates from elsewhere in New Zealand, then the existing resources must be carefully managed. This is of strategic importance because not all mineral resources in the region are available for extraction because of the heritage values associated with their particular location and/or landform.

It is clear to the Commissioners that aggregate resources are of strategic importance to the region. The continued viability of the quarry, even if quarrying is more limited than the present consent allows, will ensure that this resource is exploited for the benefit of the whole Region.

 

 

2.2.5 THE QUANTITY OF WATER ALLOCATED

The quantity of water presently allocated is a maximum of 7,750 cubic metres per day and 2,737,500 cubic metres per year. The quantity of water allocated is one variable that controls the area or radius of the dewatered zone. The quantity is being reviewed so that the extent of the dewatering could be modified if this was thought to desirable. The extent of dewatering can also be regulated by limiting the level of drawdown in the pumped well. It is determined that the quantity allocated shall remain the same, and the extent of the dewatering zone be controlled by regulating groundwater levels in the quarry.

 

2.2.6 REVIEW CONDITION

The present review condition (condition 1 as modified by Consent Order) allows for a review of the conditions of the consent by the consent authority at five yearly intervals. A review is required for the purpose of dealing with adverse effects on the environment which may arise from the exercise of the consent. The length of time between potential reviews depends on the level of certainty in the assessment of effects. Previously this was set at five years. The level of uncertainty (discussed in section 2.2.2 above) at present is such that the ability to be able to review the conditions on an annual basis is required. The amended condition (as condition 1) is included in the conditions attached to this decision.

 

2.2.7 GROUNDWATER LEVEL MONITORING

Groundwater monitoring is set out in the present consent in condition 7. The condition requires the bores listed in the condition to be monitored monthly, and the water level recorded. It also requires the water level records to be submitted to the ARC quarterly. As pointed out in the Officer’s Report the list of bores in the condition is out of date. In fact many more bores are presently being monitored. It is recommended that the bore list is updated, and the monitoring and reporting frequency be maintained as per the existing consent. Additional bores are added in the Carr Road area, at the request of Winstone as a result of discussions with of Transit NZ. The Commissioners believe that there are significant gaps in groundwater monitoring network. These gaps are, in the area of the Landscape Road and Mt Eden Road intersection, the intersection of Landscape Road and St Andrews Road, McCullough and Duke Streets and in Zone IIIB to the south of BH 27. Settlement is occurring in some of these areas and there are gaps in the groundwater monitoring network.

 

2.2.8 GROUND SETTLEMENT MONITORING

Ground settlement monitoring requirements in the original consent are set out in the Monitoring and Contingency Plan. The Officer’s Report recommends that these requirements are set out in a new condition and that the Plan contains details of the monitoring locations, circumstances where additional monitoring should be undertaken, record keeping and surveying methods. The Commissioners agree with this recommendation

The existing Plan requires ground level surveys to be completed once for every 5m of drawdown in the quarry, or every six months, whichever comes first. The Officer’s Report recommends that the six monthly frequency be maintained. In addition, the Commissioners require monitoring to be at three monthly intervals during drawdown periods. This will allow the identification of accelerated ground settlement particular in areas of higher risk.

The Commissioners determine that the existing network as shown on Figure 8 (drawing no. 18670-02) in Tonkin and Taylor (2003a) be maintained and that the monitoring network be extended as shown on the same figure. The Commissioners consider that the survey marks shall be not greater than 100m apart, and that in areas of higher potential settlement the recommendations in Tonkin and Taylor (2003 a) be implemented. That is, in those areas of expected or measured differential settlement steeper than 1:10,000, survey marks should be spaced at no more than 50m centres. This includes zones IIA, IIB, IIIA, and IIIB shown on figure 7 of Tonkin and Taylor (2003a). In addition, settlement points shall not be at a greater spacing than 25m along roads in zone IIA. These areas have been identified as areas of higher risk by the consent holder. It follows that the level of monitoring should be higher in these areas. New condition 12 is included in the reviewed consent to require this monitoring.

While zone IIA has a closer spacing along streets than other areas, the monitoring points are generally parallel to the groundwater drawdown. It would be preferable to have more points at right angles to the drawdown. The Commissioners determine that two transects of monitoring points be placed at right angles to Hillsborough Road. It recognised that these may have to be placed on private property and may cause some problems. For this reason the location of these points should be identified as part of the preparation process for the Monitoring and Contingency Plan.

 

2.2.9 MONITORING AND CONTINGENCY PLAN

Condition 11 of the consent requires the consent holder to prepare a Monitoring and Contingency Plan for ground subsidence. The original condition requires the Plan to contain; details of groundwater monitoring, trigger levels for groundwater levels, details of surface ground level monitoring, trigger levels for ground settlement, and details of all contingency measures to be undertaken.

The role of a Plan is to describe "how" monitoring is to be undertaken not "what" is to be monitored. It is a manual for those individuals who are responsible for the compliance of the consent conditions to assist them in carrying out there role efficiently. The description of contingency measures in the Plan allows those individuals to act quickly and efficiently when things go wrong. It is appropriate for the Plan to contain details which expand on the conditions themselves that assist in the compliance of the conditions. For example it is appropriate to include trigger levels for ground settlement in the Plan. Such triggers will assist in ensuring that limits for ground settlement set in the conditions are not exceeded. The Commissioners determine that monitoring requirements, standards and limits be set in the conditions and, that a new condition 14 is drafted to replace condition 11. The condition is attached.

The present condition 12 of the consent requires the Monitoring and Contingency Plan to be approved by the ARC and a peer reviewer. It is considered that the requirement for a peer reviewer is unnecessary. The present practice at the ARC is for the ARC to engage expert consultants for advice, in areas where there is a lack of expertise within the ARC, with the final approval being in the hands of a Council officer. The Plan shall be submitted to the ARC within three months of the decision on the review. Condition 12 is replaced with a reworded condition (now as condition 14 in the attached conditions).

Condition 13 requiring the compliance with the Monitoring and Contingency Plan remains the same (now as condition 15 in the attached conditions)

 

2.2.10 REPAIR OF DAMAGE

During the exercise of the consent the consent holder is responsible for ensuring that the conditions of the resource consent are met, including any monitoring or remedial measures as may be required to ensure the prevention of adverse effects on the environment including damage to buildings, services and other property. It follows that the consent holder is responsible for repairing any damage caused by the exercise of the consent. A new condition to this effect is recommended (No. 11 in the conditions attached). The Commissioners consider that this is necessary to make it clear where responsibility lies for the repair of any damage caused by the exercise of the consent.

 

2.2.11 FINANCIAL ASSURANCES (BOND)

The Consent Holder is responsible for ensuring that the conditions imposed in the Resource Consents are met, including standards, limits and any monitoring or remedial measures as may be required. However, problems may occur if the permits are terminated or if the Consent Holder, for whatever reason, is unable to carry out its obligations or, any adverse effect becomes apparent after the expiry of the permits. It is important to note that a resource consent is a right not an obligation. It is common practice that bonds held by the ARC for large projects have a term equal to the term of the consent plus five years.

To ensure that monitoring continues and to cover termination of the permits or the inability of the Consent Holder to carry out its obligations, a bond is placed on the Consent Holder. The purpose of the bond is for the Consent Holder to make a long term commitment to the continued monitoring and to the remediation of any problems that may result from exercising consents that are granted for activities related to the taking of groundwater at the quarry.

Resource consents are issued on the understanding that a thorough evaluation of the environmental effects has been completed and that the exercise of the consent will be undertaken by a competent operator in accordance with best practice. Monitoring conditions should ensure that early warnings are obtained of any potential adverse or unexpected effects, allowing appropriate mitigation measures to be put in place.

In spite of the best intentions and precautions, quarrying activities cannot be completed without some risk. Deep excavations where dewatering is involved carry a risk which cannot be completely avoided or addressed in conditions. In these cases, the ARC requires a financial bond to be used for remedial works in the event of noncompliance or non-performance by the consent holder.

Section 108 of the RMA allows for bonds to be placed on the holder of Resource Consent. A condition imposing a bond pursuant to this section is contained in the conditions appended to this decision.

Bonds are routinely placed on Resource Consents within the Auckland Region. They are routinely placed on earthworks consents and are on all the operative landfill and wastewater treatment plants consents in the region.

Bonds may be secured in a number of forms. They are usually either cash or a bank guarantee (letter of credit). Other forms of guarantee are possible.

 

The quantum of the bond should reflect the risk of damage and the potential cost involved in repairs. Damage caused by ground settlement as a result of dewatering manifests itself slowly and in isolated areas. Damage is caused by differential settlement, not total settlement. Differential settlement that causes damage will only occur in relatively small areas. Damage, if it occurs, is likely to be confined to a small number of buildings at any one time. Bonds are set up so that they are "topped up" after a payout. So as long as the remedial works bill at any one time is not greater than the quantum of the bond, there will be enough money to pay for ongoing or future problems.

Winstones presently have an insurance policy to cover damage to property, for $5 million. This is not a requirement of any resource consent. There is considerable lack of confidence in the community of this insurance arrangement. Submitters may be happier if the assurance was a bond actionable through the resource consent. The Commissioners consider that a bond at the same level as the present insurance policy ie $5 million is adequate. The sort of damage that would need to be repaired would involve plastering and painting, and at the worst remedial works on foundations. $5 million is more than sufficient to cover this. Many submitters expressed the view that $5 million was inadequate. The Commissioners do not agree. If damage was to occur, it would likely be isolated and occur slowly. A $5 million bond that is able to be

topped up is more than adequate.

 

3. CONCLUSION

The Commissioners consider that this consent can continue to be exercised with changes to conditions, and new conditions, stated on the consent document appended to this report. Subject to compliance with the conditions of consent, the adverse effects of dewatering in the quarry on the environment will be avoided, remedied or mitigated so as to be consistent with Part II of the Resource Management Act (1991) and the relevant policies of the Auckland Regional Policy Statement and the Proposed Regional Plan Air, Land and Water.

 

Ken Graham

Chairperson (signature) Date: 5 . 9 . 03




horizontal line
Back to the home page























horizontal line