Auckland  Regional  Council    -    Officers  Report    -    Review of the Dewatering at Three Kings Quarry


Section 6 of the Officers Report






Issues raised by submitters will be discussed in the order that they are listed in section 4 above.


1.         Increased zone of dewatering. This is one of the main reasons that residents in the area made submissions. This is also the main reason that this review has been initiated under section 128 of RMA as discussed in section 3 above.


2.         Cancellation of consent. Where a consent review is undertaken under section 128 1(c) it is possible for the consent authority to cancel the consent in some circumstances. It is recommended that the consent continue, with changes to conditions and not be cancelled. The issue of cancellation is covered in section 5 in the discussion on section 132 of RMA. It is recommended that adverse effects on the environment can be avoided, remedied or mitigated by restricting the drawdown in the quarry to 34mRL and making appropriate changes to the conditions.


3.         Dewatering to cease. Many submitters suggested an alternative to cancellation of the consent of holding the groundwater level in the quarry at its present level and no lower. This course of action is recommended in this report.


4.         Damage to property. The major concern of most submitters is damage to property, houses, services, and public buildings from subsidence/ settlement. The aim of this review is to make appropriate changes to the consent conditions to avoid damage. The recommendations in this report will do this. There appears to some misconceptions in many submissions on how settlement may manifest itself. In this case compressible materials between the volcanic rocks and the Waitemata sandstones have the potential to settle. At the ground surface there is a lowering of the surface level. Generally this can only be detected in survey monitoring and cannot be seen by the naked eye. Damage to buildings only occurs where there is excessive differential settlement and shows itself initially as cracking. Holes do not appear in the ground as in the case in Waihi or Huntly. There is no danger to life. One submitter was concerned about effects on historic buildings. This is a very valid concern as such buildings were not built to modern building codes, but must be protected. An additional condition is recommended to cover such buildings. Some submitters were worried about effects on trees and gardens. Gardens and trees rely on soil water processes and will not be affected by the lowering of the groundwater. Water will continue to drain at the same rate from the base of the soil horizon.


5.         Reported Damage. A number of submitters reported potential damage to their property that could be related to ground or foundation movement. It is very unlikely that this has been caused by dewatering at the quarry. The levels of settlement recorded in the monitoring are considerably less than that that would cause damage. At present differential settlements across the area that has been affected by dewatering are generally about 1:20,000 to 1:30,000 with maximum differentials of 1:4,500 between measured settlement points about the point of maximum settlement on Hillsborough Road. Damage to structures can start to occur at 1:500.


6.         Loss of value. A major concern of submitters is the potential loss of property value. This issue is discussed in detail in section 5.3.


7.         Insurance. The lack of suitable insurance cover or financial assurances is a concern. A bond is recommended to be added to the consent conditions. This is discussed in more detail in section 7.11.


8.         Standard of investigations. The ARC’s peer reviewers have concluded that sufficient investigations have been carried out in terms of the general description of site geology and the geological model on which the Pattle Delamore groundwater model is based. The extent of the detailed Hillsborough and Shackleton Road investigations is considered to be acceptable for the preparation of the settlement models, but borehole and settlement monitoring data is deficient along the edges of the basalt flows located in the buried valleys. Similar investigations may be required in other areas within the zone of dewatering to assess potential differential settlement. It is highly likely that further buried valleys exist particularly to the north and east of the Hillsborough Road valley. The geology is well known close to the quarry, but is much less known in the outer areas of the dewatering zone. The extent and number of buried valleys has only been defined in very broad terms. This creates a high level of uncertainty. In terms of predictions, the high variable ground conditions restrict the ability to interpolate between boreholes and/or settlement points and to make reliable settlement predictions.


9.         Support for dewatering. Twenty six submitters supported the continued dewatering at Three Kings Quarry. These submissions dominantly came from the construction and contracting industry, that uses the scoria quarried at Three Kings. These submitters made the point that scoria is a valuable resource, in particular, that it is used extensively in drainage works. Three Kings is one of two main quarries producing scoria in the Region. It is also close to markets, reducing transport costs. A discussion of positive effects of dewatering is provided in section 5.4.


10.       The ARC is looking after its ratepayers by instigating this review under section 128 of RMA.


11.       Ground settlement should be within the bounds of seasonal soil movement. This is an unreasonable expectation. Ground settlement often occurs where there is the taking of groundwater. In almost all instances it goes unnoticed. Ground settlement caused by dewatering is only an adverse effect when it becomes excessive to the point that it is noticeable and has the potential to cause changes to the ground surface and structures on the surface.


12.       A number of residents were concerned that they did not know about the dewatering when they bought their property. A lot of information about an area is not listed on the LIM reports. Resource consents, such as this one, and provisions Regional and District Plans should be researched before a property is bought. This information is readily available at City and Regional Councils.


13.       Submitters are correct that the consent could be cancelled in this case and this was not clear on the notice of review. However, the duration of the consent cannot be altered.


14.       It is recommended that the ARC assess damage to property if it occurs, using an independent consultant. The consultant would assess the damage and the monitoring data in the surrounding area including groundwater level and ground level surveys, and then make a judgement on whether or not the exercise of the consent has caused the damage. If it has then the consent holder must make good the damage. If the consent holder is unable or unwilling to do so the ARC may draw on the bond and repair the damage. A condition requiring such a consultant is recommended.


15.       The concerns of Transit NZ will be met by the changes to the consent that have been recommended.


16.       Several submitters asked for a extension of the submission period. Over 9000 persons were notified. 574 submissions were received, which is a very good response. It is considered that everybody who wanted to make a submission had adequate time to make one. Several submitters suggested that the ARC use Section 92 of RMA to require the consent holder to gather more data. Section 92 cannot be used in a review under Section 128. The consent authority is undertaking the review. It is not a consent application. Obviously it is in the consent holders interest to provide enough information to facilitate a positive review. The consent authority must use what information is available and make a decision accordingly.


17.       One submitter did not want any reduction in groundwater level beneath their property at all. This is an unreasonable expectation. A property owner does not own the water beneath their property. The RMA allows groundwater to be taken and used as long as any adverse effects are avoided, remedied or mitigated. It is common for groundwater to be drawn from beneath other properties.


18.       Winstones is doing a “pump and hope” experiment. This is a reasonable concern. A potentially affected party should be able to have the expectation that the effects on them have been identified, and that any adverse effects are able to be, avoided, remedied or mitigated, and know how this will be achieved. There is a concern by ARC officers that all potentially adverse effects have not been identified. Hence the main recommendation in this report is to maintain groundwater levels in the quarry at present levels.


19.       New conditions should not be able to be changed without a public resource consent review. This in fact the case. Changes to conditions can only be changed by an RMA process.


20.       The original decision did have regard to Part II and section 104 of RMA and was made on the information that was available at the time.


21.       The groundwater in the volcanic aquifer in particular feeds streams and springs. The drawdowns in the volcanics have been assessed to be the same as in the original application. Effects on streams and springs were assessed in the original decision which concluded that there would not be any adverse effects. Drawdown in the Waitemata sandstones will not affect springs and streams.


22.       A condition has been recommended to cover effects on historic buildings.


23.       The ARC should take a conservative view. This is correct, but is often termed a precautionary approach.


24.       Continued dewatering may be contrary to the Proposed Air, Land, and Water Regional Plan. This is discussed in section 5 above.


25.       Settlement could possibly affect the water tightness of homes if differential settlements are great enough to cause cracking in areas critical to water tightness. However, the level of differential settlement would need to be large.


26.       There have been some questions on how some of the survey data is reported and analysed. The ARC will take further expert advice on interpretation of survey data. The advice at present is that the differences in interpretation do not significantly alter differential settlements presently encountered.


27.       Fearon Park. The park and the surrounding area is at the edge of a lava flow to the west of Three Kings. The submitter has indicated that there are also areas of fill. The area has had settlement problems in the past. The submitter has also suggested that site specific investigations should be undertaken in this area. This area hasn’t been thoroughly investigated. It is agreed that further investigations would be needed in this area if dewatering were to continue.


28.       The original consent was applied for during a period of water shortage in Auckland. Submitters have suggested that because of the drought the ARC was pressured into granting the original consent. While the potential use of the water for municipal supply was considered as a positive effect to be taken into consideration, the decision on the application was made after the drought, and the ARC was not pressured into making a decision in this regard.


A number of submissions are considered to be not relevant to this review. This will be discussed in the order they are listed in section 4.


1.         The issue of use of the water for drinking water is a matter for Auckland City Council. The present consent allows for this to occur if Auckland City Council want to use it in this way. This is not under review.


2.         The issue of the discharge of water into the stormwater system is a matter for the owners of the stormwater system, Auckland City Council. The discharge from the stormwater system is presently authorised, and is being considered in a separate process where Auckland City Council have applied to renew all their stormwater discharge consents.


3.         Issues relating to dust and blasting arc not covered by the consent to take groundwater.


4.         Issues relating to trucks are relevant to the District Plan, not the consent to take groundwater.


5.         The right of the quarry to exist where it does is dealt with in the District Plan. The quarry is in a zone which allows quarrying specifically. This is not a relevant issue for this review. Auckland City Council is the regulatory authority responsible for the District Plan.


6.         Issues regarding end use options are again addressed in the District Plan.


7.         Winstones did not leave Lunn Avenue Quarry because of residents concerns, they ran out of rock.


8.         The ARC, or any other public body, is not being paid for the rock removed at Three Kings.


9.         The resource consents for the water treatment plant are Auckland City Council land use consents. The ARC has no jurisdiction over these and cannot review them.


10.       The 1915 Auckland City volcano legislation has nothing to do with the taking of groundwater and so is not relevant to this review.


Submitters have also suggested changes to conditions as well as additional conditions. These are discussed in the order they are listed in section 4.


1.         Additional survey monitoring points are recommended, particularly in the Hillsborough Road area.


2.         A bond condition has been recommended.


3.         Holding the water level in the quarry at 34mRL is recommended in this report.


4.         An annual review of the consent conditions is included in suggested conditions.


5.         Monthly reporting of data is appropriate in some cases and has been included for survey data that is collected at a monthly or lesser frequency.


6.         The formation of an independent disputes tribunal is not appropriate. The ARC is the regulatory authority in this case, and the higher authority is the Environment Court, should any disputes arise. The ARC will however, use an independent consultant to assess any damage to structures.


7.         It is recommended that properties in higher risk areas be surveyed. A condition requiring this has been recommended. A structural survey of the whole area is not practical.


8.         A requirement for Winstones to purchase properties of those who do not wish to stay in the area is not appropriate. Winstones must however make good any damage.


9.         The ARC will have monitoring data peer reviewed at intervals of less than one year, particularly is areas where it does not have expertise. It is not appropriate to place a condition on Winstones to do this as it will be done by the ARC.


10.       Staged dewatering has been recommended by Tonkin and Taylor (2003 a). The recommendation of this report is to halt dewatering, making this suggestion redundant.


11.       A condition requiring an update of the existing Monitoring and Contingency Plan is included.


12.       Recommendations in the Tonkin and Taylor, and Earthtech reports have been included where these are consistent with a halt in dewatering.


13.       Peer Review of monitoring data is covered in 9 above.


14.       A bond condition has been recommended and is discussed in detail in the following section.


15.       It is not recommended that the rate of groundwater take be reduced. It is recommended that a better mitigation of potential effects is a limit on the pumping level. This is included in the recommended conditions.


16.       A condition requiring Winstones to make good any damage is included.



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