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9.1.2 Step 1: Collate background and baseline information
Chapter 2 provides an overview of the information required to support decisions made when predicting mine drainage.
Things to consider:
What background information is useful to assist in determining water quality impacts from the mine operation?
Historical data as outlined in Section 2.2 include:
- Background geological data including map and bore log data;
- Stream flow (there are often gauging points on streams);
- Stream ecology; and
- Mining history (MED has many of the old NZ Mines Department reports; old mine plans are also held at various locations).
Where might this information be obtained? (Section 2.2)
- Mineral exploration reports (MED has reports available electronically on their website. These have location maps, drill-hole data, geological summaries, cross sections, historical mine sites);
- Geological maps and reports (university theses, NZJGG publications, consent applications, MED reports and drill-hole database also have geological summaries, cross sections and maps);
- River flow and climate data (regional councils, NIWA, regional reports, consent applications within the area);
- DAME database (this will be held by the regional councils); and
- Regional council database and reports (database containing flow data, water quality, consent applications, regional science reports).
A checklist outlining information types and sources is provided in section 2.4.
What factors are important to consider in the design of baseline surveys? (Section 2.3)
- Biological sampling includes sampling invertebrates, noting the habitat and environment (Section 2.3.3).
- Physical factors (Section 2.3.1) including flow volumes and flow variability (from gauging). All flow >5% of flow volumes require measurements.
- Water quality (section 2.3.2) data including natural sources of acid rock drainage (ARD), background or baseline physiochemical properties (pH, electrical conductivity (EC), dissolved oxygen, etc.) and concentrations of sulphate, dissolved Fe and Al, and other dissolved trace elements such as As and Zn and existing sources of mine drainage.
- A BACI (before after control impact) design (Figure 6) is the optimal design for biological sampling. Two ‘types’ of control: one upstream of impact, while a likely unimpacted stream provides additional baseline information.
- Note: flow gauging, collection of water samples and biological sampling are best to be completed at the same time and location.
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