1.3 Development of a framework to assess mining impacts on streams
As noted previously, this framework draws upon fundamental research undertaken by the research team, and has been developed in conjunction with end-users including the Department of Conservation (DOC), West Coast Regional Council, Environment Southland, Solid Energy, OceanaGold, Pike River Coal, Francis Mining and consultants. It is intended to be used for internal decision-making by mining companies and to assist with regulatory requirements.
1.3.1 Regulation of the Mining Industry
Mining is a regulated industry primarily governed by requirements under the Crown Minerals Act 1991 and Resource Management Act 1991 (RMA). Three types of regulatory requirements need to be met prior to mining operations proceeding[1]:
- A permit or licence granted under the Crown Minerals Act[2];
- An access arrangement negotiated with all landowners and occupiers; this may include individuals or government departments such as DOC[3]; and
- Resource consents (e.g. use of land and water, discharges to water, air) (district and regional councils).
Permits or licences granted under the Crown Minerals Act are mostly related to the economic aspects of mining, whereas granting of access (in particular that granted by DOC) and resource consents are often concerned with the potential for environmental impacts from proposed operation. The framework is intended to provide a guide to information requirements and interpretation of this information for access arrangements and resource consents. This includes background information that is useful in undertaking assessment of environmental effects (AEEs) required for the development of resources under the RMA or for access arrangements with DOC. The framework is directly applicable for aquatic systems that are managed for aquatic ecosystem purposes (Class AE) according to Schedule 3 of the RMA, although other criteria may need to be taken into account for aquatic systems managed for other purposes. A more detailed overview of the regulatory requirements the framework aims to address is provided in Appendix A.
However, this document does not replace or supersede advice directly from consenting organisations such as regional councils or landholders such as DOC. All potential applicants are advised to liaise closely with regional councils and landholders to discuss any site-specific water quality issues and aquatic biological impacts. Further, the information provided in this document is correct as at June 2010, and users are advised to check with relevant councils and landholders for any updated documentation or requirements.
1.3.2 The Framework
The framework outlines a five-stage process to determine the extent of water quality (pH, metals) impacts on aquatic systems from mining (Figure 3). While elevated suspended-solid loads in mine drainage are a common issue for all mining operations, there is no capability for predicting the likely extent of suspended solid concentrations in mine discharge for a proposed mine site. Thus, proactive management for suspended solids is undertaken and in the framework, discussions on suspended solids and their management are provided separately in Appendix B.
A key aspect of the framework is that explicit ‘acceptable’ water quality criteria are not established, because these are likely to be different at different sites and because social, economic and cultural factors may also influence decision making. Instead the framework provides a robust scientific basis for this decision to be made by end-users during consultation processes.
More detailed technical and background information on all aspects of the framework is provided in the appendices. In addition, a discussion on both natural events (e.g. high rainfall) and mining-related extreme events (e.g. tailings dam failure) that may impact streams downstream of a mine is provided along with options for the minimisation of these impacts.
Each stage of the process is briefly discussed below. Figure 3 outlines the specific steps required for working through each of the five stages. Each step is described in further detail in the following chapters for the different mine types.
Stage 1: Potential for an ecological impact
The potential for ecological impact downstream of a mine is determined by the water quality (pH, metals) that arises from mining operations, which can be predicted from the local and regional geology, geochemical analysis of rocks, and the water quality and quantity of the receiving system. Based on research undertaken by the research team, our framework provides a guide and methodology for the prediction of water quality downstream of mines. General information is provided in Chapters 2 and 3 with specific information in Chapters 4-7. Further detail on geochemical requirements is presented in Appendix C.
Stage 2: Level of potential ecological impact
A combination of biological survey data and toxicity testing using indigenous West Coast macroinvertebrate species has been used to establish the potential level of ecological impact. Our framework identifies several ecological impact thresholds associated with various water qualities. This information is presented in Chapters 4-7. Further detail on the biological effects arising from coal and gold mining and the development of the ecological impact thresholds is provided in Appendix D.
Stage 3 Determining the acceptability of the potential ecological impact
The predicted water quality (Step 1) can then be compared with these ecological impact thresholds to determine the likely ecological impact. This information can be used to determine whether the likely level of impact for the specific operation is acceptable or not. As stated above, the framework does not specify what ‘acceptable’ or ‘unacceptable’ impacts are, but rather provides a robust scientific basis for this decision to be made by end-users during consultation processes.
Stage 4 Options to reduce the potential ecological impact
Where impacts are deemed unacceptable, options for the management of waste rock and tailings (termed operational management) and/or treatment of mine drainage through active or passive treatment systems to mitigate or prevent the formation of poor quality mine water are provided in the framework. This guidance is based on a literature review of operational management and treatment techniques, combined with fundamental research on treatment techniques. This information is presented in chapters 4-7 with further details provided in Appendices E and F.
Stage 5 Developing an ongoing monitoring programme
Guidance is provided on monitoring (geological, treatment systems, water quality and biological), particularly that which should be undertaken on an ongoing basis after mining operations begin. This guidance has been developed from research experience and a literature review. This information is presented in Chapter 8, with further details on biological monitoring provided in Appendix D.
Figure 3. General framework and detailed step-by-step guide for predicting and managing water quality (pH and metal) impacts from mining on streams.
[2] If the minerals are privately owned a permit under the Crown Minerals Act is not needed, but all of the other permits and consents are still required, together with the consent of the mineral owner.
[3] In some cases, a concession from DOC may also be required if a track across DOC land is required to access the land in which the minerals exist; similar access would also be required to be granted by private landholders.
