WAR Wairarapa Aggregates Ltd

Transcription

1 WAR Wairarapa Aggregates Ltd Supplementary report to Hearing Panel Deirdre Ross

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3 1. Purpose of report The purpose of this report is to provide comments on the briefs of evidence provided by the applicant and distributed by Greater Wellington on 18 May 2010 and any other relevant items since the completion of the section 42A officer s report which was distributed on 26 August The report has been prepared by Deirdre Ross with input from Scott Wilson on hydrogeological matters and Grant Kneebone and Paul Denton on erosion and sediment control measures. 2. Process since initial hearing was postponed The hearing set down for 3 September 2009 was postponed at the request of the applicant following the release of the Greater Wellington (GW) and Carterton District Council (CDC) section 42A officer reports. The applicant requested further time to respond to a number of issues raised in the reports. Since that time the applicant collected further information on groundwater levels and engaged further technical assistance to respond to groundwater related issues. Draft information was provided to GW by the applicant in March 2010, and following an initial response from GW, the applicant and representatives from GW met to discuss the further information and assessment provided. GW identified that the proposal would need additional consents with the information provided as the proposed quarrying operation would dewater groundwater at the site 1. The applicant confirmed that they wished to proceed with a hearing as they believe that additional consents would not be required. GW decided to proceed with the hearing on 1 and 2 June 2010 for the following reasons: The applicant s desires to have the application determined by a hearing The original officer s report outlines conditions to ensure groundwater dewatering would not occur which would negate the need for additional consents, and this position would be maintained at the subsequent hearing. The applicant and submitters were notified of the rescheduled hearing dates on 6 May Key issues This section outlines the key issues that in GW s opinion remain in contention in relation to the application. It is intended to compliment and add to the existing assessment completed in the section 42A officer s report. 3.1 Groundwater levels at the site GW staff have expressed to the applicant since 2008 (prior to the application being lodged) that if extraction at the site was to occur, that it should not encounter or intercept the groundwater table. From this early period, we advised the applicant that 1 The reasons for additional consents is outlined in more detail in section 3.3 of this report. WGN_DOCS-# V2 PAGE 1 OF 10

4 the finished quarry level should not exceed 0.5 metres above the winter groundwater table level. At this point, the applicant was strongly encouraged by GW to excavate test pits/bores to collect information at the site during the winter of 2008 to appropriately determine the winter groundwater table. Unfortunately that did not occur and only limited data from three monitoring bores collected in the winter of 2009 was able to be used in the preparation of our assessment presented in the section 42A report which was finalised in August As internal hydrogeological expertise was unavailable at the time of assessing the application in mid 2009, GW engaged Scott Wilson (Water Matters) to review hydrogeological information presented in the application documents. His review identified that, based on the limited data available, the groundwater levels at the site were higher than those identified in the application. Accordingly precautionary excavation limits were recommended as consent conditions for the three stages of the proposed quarry. Since mid 2009 more groundwater level data has been collected from three monitoring bores which has enabled more robust assessment of the groundwater levels at the site. Scott Wilson has reviewed the evidence of Jack McConchie and presented his findings on the hydrogeology of the site in a Statement of Evidence attached to this supplementary report. In summary this review highlighted the following: The Waingawa wetland was created by, and is sustained by groundwater levels, with additional artificial recharge from the Taratahi water race augmenting the wetland, particularly in summer months. The majority of the proposed quarry floor (124mRL 124.5mRL) will be below the groundwater table, and in the north-east corner of the site the quarry floor will be approximately 2 metres below the groundwater table. The existing groundwater table in the centre of the site has been artificially lowered by existing excavations at the site by approximately 0.8 metres. If groundwater levels were lowered at the site, this would most likely result in the Waingawa wetland relying more heavily on being augmented by the Taratahi water race during summer months. This is because during spring groundwater is likely to be more efficiently drained from its recharge source, leaving lower groundwater levels (and therefore groundwater discharge and wetland recharge) during summer. If cleanfill fills the void created by excavated material, groundwater levels are likely to rise and accordingly any cleanfill would essentially be located directly into groundwater, which presents an unnecessary risk to the environment. To avoid unnecessary risk to the environment (both in terms of changes to the wetland hydrology and locating a cleanfill operation within the groundwater table) it has been recommended to maintain the finished quarry level 0.5 metres above the maximum winter groundwater level. PAGE 2 OF 10 WGN_DOCS-# V2

5 Based on groundwater monitoring data collected to date, the maximum excavation depths have been assessed to be 1.7 metres for Stage 2, and 2.0 metres for Stages 1 and 3. The draft consent conditions in the section 42A officer s report identified maximum excavation limits. These have been revised following the assessment of data collected by the applicant as outlined in Table 1 below: Table 1: Recommended maximum excavation limits Previous recommended excavation limit (below ground level) Revised recommended excavation limit (below ground level) Stage metres 2 metres* Stage metres 1.7 metres Stage metres 2 metres * This depth is to be determined for the level of the site prior to the existing excavations at the site. GW believes that it is vitally important that maximum excavation limits are set levels which provide protection to the groundwater table for the following reasons: It is not prudent to establish a cleanfill operation in the groundwater table. Unless there are very strict controls over cleanfill management, there are significant environmental risks of non-cleanfill material being directly discharged into the groundwater environment. Whilst dewatering could be managed in a manner which results in clean water being kept separate from sediment laden water, it is highly likely that there will still be additional sediment laden groundwater discharged from the site to the erosion and sediment control measures which may not be able to adequately cope with increased volumes of water. The downstream receiving environment supports a significant wetland. It is likely that there will be a change in the hydraulic regime and deterioration of the quality of recharge water to the wetland if dewatering of the site occurs. It is noted that the Taratahi water race system which currently supplies some water to the wetland is already under considerable pressure to supply enough water for domestic and stock water use during low flow periods when the Taratahi water race is restricted. For the above reasons, GW believes that maintaining appropriate excavation limits will ensure that relevant objectives and policies in the Regional Policy Statement and Regional Freshwater Plan (as listed in the section 42A officers report) are appropriately satisfied. If excavation occurs below the groundwater table we are not convinced that these statutory provisions can be met and that such activity would not represent the sustainable management of the natural and physical resources in this particular environment. It is GW s view also that additional consents (that have not been applied for) are required if the applicant wishes to encounter or intercept the groundwater table, dewater groundwater at the site and place cleanfill within the groundwater table. This is discussed in section 4 of this report. WGN_DOCS-# V2 PAGE 3 OF 10

6 3.2 Erosion and sediment control measures The section 42A officer s report highlighted some concerns around the erosion and sediment control measures presented in the application documents. It was noted that further information would need to be provided at the hearing. The applicant (in Nicolas Keenan s evidence) has provided detailed evidence and justification for the choice of sediment control measures and analyses rainfall patterns to suggest that the measures chosen should in fact provide a conservative level of treatment at this site. If monitoring shows that the devices are not performing to expectations, further modifications can be made to improve performance. Information provided by the applicant suggests that rising groundwater is unlikely to exceed the water depth in the settlement pond and, should a severe event occur, the quarry floor itself will provide storage until water levels recede. It is not clear how this management strategy will keep clean spring-water/groundwater emerging from the existing quarry floor and area of Kiwi Lumber fill from becoming contaminated with sediment in such events. Nor is it clear how effective the treatment mechanisms would be settlement ponds and sumps need to be calm for settlement of sediments to occur. This would be compromised by a combination of the influx of process water, sediment-entrained runoff and groundwater ingress. This could be further compromised by the composition of soil material at the site. GW is not aware of any soil samples being taken by the applicant to check the make up of the material at the site. Soil sampling undertaken by GW at the Waingawa industrial site last year (in the top of the soil profile) showed 9% sand, 45% silt, and 46% clay. Whilst this particular material will be stockpiled, the settling efficiency of this material if required to be processed through the settlement pond is only 11%. The excavation of sumps into the floor of the quarry for settling washwater may not be effective on the current floor as it is already at or below groundwater level as can be seen in the photographs in Figure 1 taken in July The applicant has provided information that the settlement pond will provide 48 hours detention time for washwater. This allows minimal room for stormwater runoff or any groundwater ingress. No test data has been provided to show that 48 hours would be sufficient time for sediment to settle out of the water. Rainwater cannot drain through saturated soils under these circumstances. There will still be considerable run off especially from the active quarry face. Stormwater management could be severely compromised by high groundwater levels in winter, a time when there is unlikely to be much active surveillance on site. PAGE 4 OF 10 WGN_DOCS-# V2

7 Figure 1: Existing quarry floor with groundwater ingress WGN_DOCS-# V2 PAGE 5 OF 10

8 Overall, whilst GW believes there are particular difficulties for managing sediment at the proposed quarry site, we are satisfied with the information provided by the applicant to address key concerns highlighted in the section 42A officer s report. There are robust draft consent conditions that will ensure that any effects of the discharge are avoided, remedied, or mitigated including: Requirements for ensuring that an appropriate Quarry Management and Operations Plan is submitted and approved prior to commencement of each stage of works. Making adjustments to erosion and sediment control measures as required e.g. requiring use of flocculent. Setting appropriate discharge standards to be met on the receiving environment. Monitoring discharge standards through water quality monitoring, particularly during the start up phase of each stage of works. Accordingly I am satisfied that the relevant statutory provisions in the Resource Management Act 1991, Regional Policy Statement, and Regional Freshwater Plan are satisfied subject to the draft consent conditions being adopted Updated Quarry Management Plan The applicant has submitted a revised Quarry Management Plan (QMP). The previous revision had removed all reference to cleanfill. This replacement document now includes management of cleanfill in sections 2.2.6, and 3.5. The applicant now states that cleanfill will be inspected and managed such that only materials that comply with Ministry of Environment guidelines for cleanfill will be accepted onto the site, stockpiled and progressively used as fill and which will be compacted by the quarry s earthmoving equipment before being overlain by a layer of soil. The QMP also states that records will be kept of fill accepted onto the site and that the site will be secured to prevent illegal dumping of wastes. I consider that the management of any cleanfill to be incorporated into the quarry site as rehabilitation is extremely important in this sensitive environment. There is already a history at this site of inappropriate materials, particularly timber by-products, being dumped, although it is clearly noted that this is not related to the applicant. Hence the applicant may wish to consider for their own protection to take a photographic record at appropriate intervals of material being accepted at the site. 4. Reasons for additional consents 4.1 Background GW advised the applicant when the application was originally lodged in 2008 that additional consents may be required based on the proposed quarry floor level and the very limited groundwater information that was available for the site, but that our preference was for excavation to be undertaken above the winter groundwater table plus an appropriate buffer zone. PAGE 6 OF 10 WGN_DOCS-# V2

9 The section 42A officer s report was then prepared with the understanding that the applicant was to constrain the quarry operations so that groundwater would not be intercepted. There are several statements (including the quoted agreement with the landowner) contained in the Quarry Management Plan and other documents which formed part of the application to the effect that no material would be excavated within 0.5m of the water table. From the initial review undertaken by Scott Wilson for GW and then subsequent work by Jack McConchie for the applicant, it became clear to GW that additional consents would be required if the applicant wished to continue with the proposed quarry floor of 124mRL for stages 1 and 2, and 124.5mRL for stage 3. As noted earlier rather than place the application on hold under section 91 of the Resource Management Act 1991 (for further consent applications) which would have likely resulted in the application being re-notified, the applicant informed GW that they wished for the hearing to proceed as they did not believe that additional consents were required. As GW s position has always been that our preference is for excavation activities to not intercept groundwater (and therefore not require a separate resource consent for this activity) the hearing has proceeded. 4.2 Land use consent and water permit for excavation into groundwater table The Regional Freshwater Plan (RFP) defines a bore in the interpretation section as: any hole regardless of the method of formation that has been constructed to provide access to groundwater or which intercepts groundwater in an aquifer, excluding geotechnical investigation bores An aquifer is defined as a geological formation through which water moves under natural conditions and is capable of yielding water at a sufficient rate to be a practical source of water. A water table is generally an unconfined aquifer. Rule 15 of the RFP states: The construction of any bore is a discretionary activity. As the proposed quarry floor will intercept groundwater for a large proportion of the site (and by up to 2 metres in the north-east corner of the site adjacent to BH1), a land use consent is required. Rule 9B of the RFP states: The diversion of groundwater is a permitted activity, provided that it complies with the conditions specified below: (1) There shall be no adverse effects on water supply other than for a temporary period during construction of no more than 24 hours. (2) There shall be no flooding of land on any neighbouring property. WGN_DOCS-# V2 PAGE 7 OF 10

10 (3) There shall be no lowering of water levels in any river, lake, or wetland. (4) There shall be no lowering of groundwater levels on any neighbouring property. This rule is applicable as the proposed activity (if the excavation is completed to a depth of 124mRL to 124.5mRL) will result in groundwater being diverted into a watercourse connected to the Waingawa wetland. Greater Wellington is not satisfied that condition (3) and (4) are satisfied in order for the activity to be considered a permitted activity for the following reasons: The quarry is sited immediately adjacent to neighbouring properties. Dewatering and diverting groundwater will result in the lowering of groundwater levels on these properties, particularly at the north-eastern corner of the site where the groundwater table could potentially be dewatered by 2 metres. It is noted that there are several domestic bores to the east of the proposed quarry site which access this unconfined groundwater table aquifer that could be potentially affected by dewatering of the unconfined aquifer to the scale proposed. The Waingawa wetland is maintained by groundwater flows which are augmented by the Taratahi water race. As noted in Scott Wilson s evidence, the dewatering of the groundwater table will potentially lower the supply of groundwater to the wetland, particularly in summer months. Rule 16 of the RFP states: That the diversion of water which cannot meet the requirements of those (permitted) rules is a discretionary activity Accordingly Greater Wellington believes that a water permit is required for the proposed activity as presented in the application documents. 4.3 Discharge permit to place cleanfill directly into groundwater It has come to our attention in the preparation of this supplementary report that the act of placing cleanfill within the groundwater table may require a resource consent under Rule 5 of the Regional Freshwater Plan as a discretionary activity, as contaminants are likely to be discharged to water. Contaminants as defined in the RFP and RMA are considered to be any substance (including solids) which changes or is likely to change the physical, chemical or biological condition of water or land to which it is discharged. Water in the RFP and RMA means water in all its physical forms whether flowing or not and whether over or under the ground. 5. Changes to draft consent conditions GW has reviewed the draft consent conditions presented in the section 42A officer s report and the suggested changes provided by the applicant. A revised set of consent conditions has been completed and is attached with this report. PAGE 8 OF 10 WGN_DOCS-# V2

11 A number of changes as recommended by the applicant have been adopted. The key areas where changes put forward by the applicant have not been accepted by GW are identified in Table 2 below: Table 2: Key areas of difference in draft consent conditions Condition Review condition discharge permit Monitoring frequency of discharge Excavation limits Monitoring groundwater levels Review condition water take Ceasing abstraction during minimum flow Reason The frequency recommended is considered important given the uncertainties presented in the assessment of the application. The applicant requested monitoring after storm events only. GW originally requested monthly monitoring. This has been revised to require two monthly monitoring during the first year (start up phase) of each stage. The applicant proposes that no excavation takes place below groundwater, however GW believes that the proposed quarry floor will result in that occurring. GW has reviewed the excavation limits and revised the depth of extraction based on data collected since August The applicant proposes to monitor only BH1 on a monthly basis. Given the sensitive nature of the site, GW believes that it is still important to monitor groundwater levels automatically in all three monitoring bores. The applicant believes this is not necessary. It is generally standard practice for GW to place review conditions on water take consents and sees no reason why this water take is different. Based on observed non-compliance with the operation of maximum water take limits by CDC for the Taratahi water race, GW believes that it is important to the applicant to monitor river flows in the Waingawa and take appropriate action during low flows to ensure compliance with minimum flows in the RFP. Other water users taking water directly or indirectly from the Waingawa River are subject to similar conditions of consent. It is noted that the recommended consent term of GW is 10 years, whilst the applicant requests 15 years. GW believes further justification is required from the applicant for a 15 year term given that a maximum operating life of the quarry of 7 years was identified. 6. Summary and conclusion In summary, GW has provided a revised set of draft consent conditions to ensure that the potential effects of the proposed activity are avoided, remedied or mitigated. Whilst the site is difficult to manage in terms of erosion and sediment control, we are satisfied that the further information provided addresses concerns raised in the section 42A officer s report, and that there are adequate conditions to ensure the receiving environment is appropriately protected. WGN_DOCS-# V2 PAGE 9 OF 10

12 The key issue of contention remaining revolves around the depth of the proposed quarry and the associated effects on the receiving ground and surface water environment. GW s position from the outset of this process has been that it is our preference that effects on the groundwater table are avoided and that excavation limits are established with a buffer zone above the high groundwater table level. The reasons for this are: The potential adverse effects of changing the hydrogeology of the Waingawa wetland by lowering the groundwater table and re-routing groundwater. The potential effects of managing larger volumes of sediment laden water that is likely to be generated from the site as a result of dewatering the groundwater table. The potential effects on neighbouring properties that may arise from dewatering groundwater at the site. The potential effects of establishing a cleanfill operation that is likely to directly discharge contaminants into the groundwater environment which is connected to the Waingawa wetland. Due to these reasons and in the absence of resource consent applications that are required for both intercepting and dewatering groundwater, we strongly recommend that the maximum excavation limits are adopted. The applicant s position initially started with a similar goal to protect the groundwater environment. This applicant s position now appears to have changed, as whilst information that has been gained in recent times which clearly demonstrated that the proposed floor quarry will intercept groundwater, no adjustments have been made by the applicant to avoid potential effects of the activity on the receiving ground and surface water environment. Report prepared by: Peer reviewed by: Deirdre Ross Resource Advisor Stephen Thawley Team Leader, Environmental Regulation Approved for submission by: Al Cross Manager, Environmental Regulation PAGE 10 OF 10 WGN_DOCS-# V2