Tui Mine Water Quality & Ecological Monitoring

Client: Waikato Regional Council
Date: Ongoing

We were first engaged in 2009 as environmental consultants for the Waikato Regional Council to undertake water quality and ecological monitoring in the Tui and Tunakohoia Streams in the vicinity of Tui Mine, Mt Te Aroha.  The monitoring is associated with remedial works carried out at the mine site to improve stream water quality.

Key Aspects:

  • Stream flow monitoring
  • Water quality monitoring
  • Assessment of mass load of contaminants
  • Stream macroinvertebrate monitoring
  • Stream habitat assessment

Client: Waikato Regional Council
Date: Ongoing

Ecological Monitoring

Ecological monitoring was undertaken at the site in 2009 prior to the rehabilitation of Tui Mine, in 2013 following mine rehabilitation and following in 2015. Monitoring was undertaken within the Tunakohoia and Tui streams at four sampling locations: un-impacted Tui Stream (upstream of tailings discharge), impacted Tui Stream (downstream of tailings discharge), un-impacted Tunakohoia Stream (south branch above north branch confluence) and impacted Tunakohoia Stream (north branch below discharge).

Macroinvertebrates were collected semi-quantitatively using a kick net in a 3m² area of stream bed. Four replicates were collected at each site. Macroinvertebrate samples were preserved in the field for later processing and analysis. At each site, habitat and periphyton cover was assessed. Water quality parameters (temperature, conductivity, dissolved oxygen and pH) were also taken.

Results from ecological monitoring at the site have found an increase in macroinvertebrate index scores and taxonomic richness with caddisflies and stoneflies now present at impact sites in the Tui and Tunakohoia streams compared to baseline (pre-remediation) monitoring in 2010.

Water Quality Monitoring

Baseline water quality monitoring was undertaken at the site in 2010 prior to the rehabilitation of Tui Mine in 2011. Water quality monitoring has since been undertaken on an annual basis since the mine remediation in 2012, 2013, 2014 and 2015. Three monitoring rounds are undertaken each year in September, October and November.

Water quality samples are collected under low or moderate flow conditions at nine of the ten sites in the catchment area and are tested for a range of parameters including pH, electrical conductivity, total suspended solids (TSS), total and dissolved metals, cation anion profile, total dissolved silica and total cyanide. Stream flow monitoring is assessed at nine of the ten sites via a mixture of flow gauging, volumetric methods and a v-notch weir.

The water quality results to date have shown that there has been a significant overall decrease in the mass loads of cadmium, copper and zinc being discharged into the Tui and Tunakohoia streams compared to the baseline (pre-remediation) monitoring in 2010.

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