Impact on groundwater
132The Applicant's ASOFC states the SEOC project fails to address medium to long term risks to landscape functionality, including water quantity, water quality and land quality and is therefore contrary to the precautionary principle and intergenerational equity (ASOFC par 61(a), (b), (c), (d), (h), (i), (j), (l) and (m)):
(a) There is uncertainty about the existing (pre-mining) hydrological and hydrogeological conditions within and also external to the project site;
(b) The project will modify the hydrological and hydrogeological conditions within and also external to the project site;
(c) The extent to which the hydrological and hydrogeological conditions will be modified are predicted by way of mathematical models;
(d) There is uncertainty in the conceptualisation and parameterisation of mathematical models to predict natural systems;
...
(h) The project proposes some monitoring of impacts to alluvium and hard rock aquifers, groundwater, and Glennies Creek surface water and for a period of up to 16 years only after completion of mining;
(i) The potential impact of the mine on groundwater and Glennies Creek is estimated to be approximately 100 years;
(j) Notwithstanding that the impacts on water quality and quantity may last for 100 years, the project approval only requires water quality and quantity to be monitored for a period of up to 16 years after completion of mining;
...
(l) There is uncertainty about the hydrological and hydrogeological conditions (post-mining) within and also external to the project site during and after the proposed rehabilitation; and
(m) The project approval conditions fail to adequately address uncertainty in modelling over the life of the predicted impacts.
133The Minister's ASOFC in reply state that:
In response to paragraph 61 of the SOFC, the Minister:
(a) repeats paragraphs 19-24;
(b) says that:
(i) DGRs for the Project required Ashton to carry out a detailed assessment of the environmental, economic and social impacts of the Project;
(ii) the PAC required further detailed assessment of particular aspects of the environmental impacts of the Project, including impacts on water quantity, water quality and land quality;
(c) contends that Ashton carried out such assessment, in compliance with the requirements of the DGRs and the PAC, and that this assessment includes an adequate assessment of the medium to long-term risks to water quantity, water quality and land quality;
(d) contends that while there are some uncertainties associated with this assessment, as is inherent in all groundwater modelling, these uncertainties have been addressed through the use of detailed sensitivity analysis and conservative assumptions (such as the use of no mitigation measures whatsoever) to produce worst case predictions that are unlikely to eventuate;
(e) says that the assessment concluded that:
(i) the predicted maximum possible, worst-case water quantity impacts scenario (i.e. without mitigation) would result in a reduction in Glennies Creek baseflow of 65 ML/year, which is less than 0.1% of annual average flows, and the inflow of 50 ML/year of alluvial groundwater to the mine;
(ii) these impacts would reduce significantly following the recovery of the groundwater system after mining operations cease, and the predicted worst-case long-term impact on Glennies Creek baseflow is less than 10 ML/year;
(iii) Ashton has access to sufficient water entitlements to cover the predicted maximum possible, worst-case water quantity impacts of the Project;
(iv) the construction of a low permeability barrier between Glennies Creek and the mine would minimise water quantity impacts on Glennies Creek and the connected alluvial groundwater;
(v) the final void in the rehabilitated Project land would create a groundwater sink to ensure that any long-term increase in salinity in the groundwater within the rehabilitated pit area will be contained and will not be able to flow towards Glennies Creek;
(vi) the construction of the low permeability barrier would minimise the potential for saline groundwater discharge toward Glennies Creek and its connected alluvial groundwater post-mining;
(vii) with these mitigation measures, the probable worst-case water quantity impacts of the Project are predicted to result in a reduction in Glennies Creek baseflow of 9.4 ML/year and the inflow of 1.6 ML/year of alluvial groundwater to the mine;
(viii) the Project would result in improvements to the water quality of the alluvial groundwater resource; and
(f) contends that the conditions of the Project contain a comprehensive suite of conditions related to water quantity, water quality and land quality to ensure that the actual impacts of the Project do not exceed the predicted impacts, provide safeguards for surrounding water users, offset any loss of baseflow to Glennies Creek, the alluvial aquifer and the hard-rock Permian aquifer, and ensure that the Project has no long-term impact on water quantity, water quality or land quality, including:
(i) Schedule 3, conditions 29-46, 58-60;
(ii) Schedule 5, conditions 1-4 and 8-9;
(iii) Commitments A1, A2, I1-I7, J1-J8, K1-K12, L1-L5, M1-M3, O1-O8, P1-P2, X1-X6
The Minister contends that the predicted impacts of the Project on water quantity, water quality and land quality:
(a) are not contrary to the precautionary principle as they do not threaten serious or irreversible environmental damage because:
(i) they are confined to the vicinity of the Project;
(ii) they are largely temporary;
(iii) the Minister repeats paragraph 61(d) and (e);
(b) are not contrary to the precautionary principle as there is no scientific uncertainty as to the predicted impacts of the Project on water quantity, water quality and land quality;
(c) are not contrary to the principle of intergenerational equity due to their minimal and temporary nature; and
(d) are not contrary to the public interest in that they have been suitably minimised through the design of the Project and can be appropriately managed and mitigated by conditions of approval.
134Ashton's ASOFC in reply state that:
In response to the particulars raised in respect of paragraph 61, the Second Respondent says that:
(a) Extensive groundwater and surface water investigations have been undertaken by the Second Respondent to obtain a detailed understanding of the existing (pre-mining) hydrological and hydrogeological conditions within, and also externally, to the Project site;
(b) Based on extremely conservative hydraulic properties/assumptions, the Project is predicted to have a negligible impact on the hydrological and hydrogeological conditions within and also external to the Project site.
(c) While there will always be a degree of uncertainty in predicting natural systems, the Second Respondent has used a highly conservative approach (i.e. assuming extremely conservative hydraulic properties) when predicting potential groundwater and associated surface water impacts and the modelling indicates that there will be negligible impacts from the Project.
(d) In regards to water quantity, the Second Respondent holds adequate regulated river licences to account for and compensate any predicted impacts on Glennies Creek and this is a market mechanism that puts ESD principles into practice.
(e) Under condition 32 of Schedule 3 of the Project Approval the Second Respondent will provide a compensatory water supply to any landowner of privately-owned land whose water supply is adversely and directly impacted (other than an impact that is negligible) as a result of the Project.
(f) The twin mitigation measures of the low permeability barrier (LPB) and final void will be implemented and modelling indicates that either of these measures on their own would be adequate to lead to a net improvement in the salinity of Glennies Creek, and when implemented together, any adverse long-term salinity impact from the Project will be negligible, and certainly very much less than 1%.
(g) The Second Respondent says the comprehensive monitoring regime will be extended for a period of at least five years after completion of site rehabilitation. The monitoring and management plan for the LPB will describe the location and frequency of monitoring to assess the integrity and performance of the LPB including periodic timeframes for further assessments to validate/re-model seepage predictions during and post mining.
(h) In addition, to the LPB and final void, the Second Respondent will undertake strategic planting of deep rooted salt tolerant trees and other vegetation to augment the final void in maintaining permanently depressed groundwater gradients within the rehabilitated landscape and will carry out monitoring biannually for at least five years following establishment of the restoration area. This monitoring will continue until such time that the trees are established within the restoration area and analyses of results following five years of growth are not significantly different from analogue sites.
(i) The strategic use of trees in the rehabilitated landscape and particularly in the area of the final void will assist in lowering water table levels in the post-mine landscape and will assist with maintaining groundwater gradients toward the final void, which will act as a long-term groundwater sink.
135The EA considered the impact on groundwater in appendix 5 (exhibit 1A, vol 2, tab 18). The hydrogeological assessment was undertaken by Aquaterra Pty Ltd dated 2 July 2009. It proposed a buffer of 150m between Glennies Creek and the SEOC pit, restricting the pit to areas outside alluvium and the construction of a low permeability barrier (LPB). Additional modelling was undertaken to address concerns about the permeability between Glennies Creek and the proposed pit, preparing and implementing a groundwater monitoring program (exhibit A, vol 1, tab 7, p 514-515).
136The PAC considered that the additional modelling undertaken by Ashton and Dr Frans Kalf, consulting hydrogeologist and principal of Kalf and Associates Pty Ltd engaged by the Department, provided an adequate basis for evaluating the extent of the likely risk (exhibit A, vol 3, tab 30, p 2725). It would be possible to establish an adequate monitoring regime. PAC considered that the monitoring regime proposed by Ashton must be endorsed by the NSW Office of Water (NOW) before its lodgement with the Director-General and that the plan be approved and implemented prior to the commencement of mining (exhibit A, vol 3, tab 30, p 2725). The PAC highlighted the following changes, relevant to the question of water impacts: extension of the LPB, improvements to design and long-term maintenance, increased setback distance from Glennies Creek (to 200m); and location and shape of the final void. It would be possible to use the data from the improved monitoring system to produce updated modelling predictions throughout the mining period and shorter term adaptive management responses (exhibit A, vol 3, tab 30, p 2725). The PAC considered that the requirements to collect improved data, utilise that to produce revised modelling predictions and to assess whether these predictions require adjustment to mining operations should be independently reviewed, with the results provided to the NOW and the Department. Appropriate conditions had been drafted to reflect this (exhibit A, vol 3, tab 30, p 2726).
137The PAC considered that there should be a condition imposed that there be negligible inflow of water to the pit from Glennies Creek and/or its associated alluvial aquifers. The PAC noted that there were backup provisions if water moves into the pit from Glennies Creek and its associated alluvial aquifer for which Ashton should be held to account via penalty provisions if it fails to deliver on its assurances (exhibit A, vol 3, tab 30, p 2728).
138The PAC accepted on the basis of the proposed revised monitoring program that it should be possible to detect leakage into the pit through or around the LPB and that the period of monitoring proposed is adequate for this.
139The PAC considered that the risk of saline water migrating from the SEOC project site to Glennies Creek post mine closure was adequately addressed (exhibit A, vol 3, tab 30, p 2732). The PAC also considered that the risks of flooding were adequately addressed and the commitment to incorporate the levee into the final landform should minimise any longer term risks (exhibit A, vol 3, tab 30, p 2732).
140Conditions before the Court include Sch 3 condition 30 which requires Ashton to ensure that there is no more than negligible inflow of water into the pit from Glennies Creek and its associated alluvium and colluvium, and no more than negligible outflow of water from the pit to Glennies Creek or its associated alluvium and colluvium. Condition 31 requires Ashton to ensure that it has sufficient water for all stages of the SEOC project and if necessary adjust the scale of mining operations on site to match its available water supply to the satisfaction of the Director-General. Condition 32 requires Ashton to provide a compensatory water supply to any landowner of privately-owned land whose water supply is adversely and directly impacted as a result of the SEOC project in consultation with the NOW to the satisfaction of the Director-General. If Ashton and the landowner cannot agree on the measures to be implemented or there is a dispute about the implementation of these measures, either party may refer the matter to the Director-General for resolution. Condition 33 requires Ashton to ensure that all surface water discharges from the SEOC project site comply with the discharge limits set in any environment protection licence or relevant provisions of the Protection of the Environment Operations Act 1997 or Protection of the Environment Operations (Hunter River Salinity Trading Scheme) Regulation 2002.
141Condition 34 requires Ashton to prepare and implement a groundwater verification and monitoring program to the satisfaction of the NOW and the Director-General. Condition 35 requires Ashton to design the LPB to the satisfaction of the NOW and the Director-General and includes design specifications. Condition 36 requires Ashton to install the LPB prior to undertaking any mining operations within 40m of the Glennies Creek alluvium and colluvium, include quality assurance and testing and submit a report concerning LPB construction to the Director-General and the NOW. Condition 37 requires Ashton to prepare and implement a LPB monitoring and management plan to the satisfaction of the NOW and Director-General. Condition 38 requires Ashton to prepare and implement a water management plan for the Ashton mine complex to the satisfaction of the Director-General to manage potential impacts of the SEOC project. This plan must be prepared in consultation with the OEH, the Environment Protection Authority (EPA), the DRE within the Department of Trade and Investment, Regional Infrastructure and Services and Singleton Shire Council, endorsed by the NOW and then submitted to the Director-General for approval prior to carrying out any development on the SEOC project site. The plan must include a site water balance, sediment control plan, a surface water management plan, a groundwater management plan and a surface and groundwater response plan. In condition 58 one of the rehabilitation objectives which Ashton must comply with is no more than negligible environmental consequences to Glennies Creek and its alluvial aquifer, including negligible leakage through the LPB, negligible adverse impact on surface water and groundwater quality, and negligible impact to other surface water and groundwater users.