Home
Kate McArthur's: Environmental Evidence: Remediation NZ Ltd Water Quality Case
Expert testimony on water quality impacts from a composting facility in the Haehanga Stream catchment, Taranaki Region, New Zealand.
The Expert Witness
Dr. Kathryn Jane McArthur
Independent freshwater specialist with 20 years of post-graduate experience in freshwater resource management. Holds Bachelor of Science with Honours in Ecology and Master of Applied Science with Honours in Natural Resource Management from Massey University.
Former Practice Leader – Water with The Catalyst Group and Senior Scientist – Water Quality with Horizons Regional Council. Member of New Zealand Freshwater Sciences Society (President since 2018) and accredited RMA hearings commissioner.
The Case Overview
Appellant
Remediation (NZ) Ltd operates a composting facility accepting paunch waste, poultry waste, green waste, and drilling waste at Uruti, Taranaki.
Respondent
Taranaki Regional Council declined consent renewal following a hearing in March 2021, leading to this Environment Court appeal.
Section 274 Parties
Te Rūnanga o Ngāti Mutunga and several community health and environmental groups joined as interested parties.
Cultural Significance of the Waterways
The Mimitangiatua River is a tupuna awa (ancestral river) to Ngāti Mutunga, recognized through statutory acknowledgement. The Haehanga Stream, a tributary of the Mimitangiatua, flows through land of considerable cultural significance.
"Waters in the rohe of Ngāti Mutunga are connected, through whakapapa, to their health – if the water is sick then so are they."
The National Policy Statement for Freshwater Management (2020) establishes Te Mana o te Wai as the fundamental concept, requiring freshwater management to prioritize the health and well-being of water bodies and ecosystems first.
Ecological Values at Risk
Threatened Fish Species
Shortjaw kokopu and pīharau (lamprey) - species threatened with extinction and nationally vulnerable. Indigenous fish assemblage includes multiple species of conservation concern.
Kākahi (Freshwater Mussels)
Echyridella menziesii classified as "At Risk - Declining" nationally. These taonga species are highly sensitive to ammonia and require indigenous fish as hosts for their larval stage.
Aquatic Ecosystem
The catchment historically supported diverse indigenous aquatic fauna including giant kokopu, banded kokopu, inanga, tuna (eels), kōura (freshwater crayfish), and abundant invertebrates.
Site Visit Observations - November 2020
During a site inspection on November 18, 2020, significant environmental management concerns were documented during heavy rainfall:
Uncontrolled Stormwater
Significant overland flow throughout the site with stormwater appearing almost completely uncontrolled. Surface water drains connected to the Haehanga Stream were exposed to contaminated runoff.
Inadequate Infrastructure
Composting, paunch waste, truck wash and drilling mud areas were either unlined or inadequately protected. Irrigation ponds were unlined and bunded only by permeable earth material.
Contamination Risk
High potential for contamination of surface and groundwaters observed. Significant volume of water surrounding paunch waste with visible plastic waste including oesophageal clips and stock supplement capsules.
Ammoniacal Nitrogen: The Primary Concern
Ammoniacal nitrogen emerged as the most significant water quality issue, with concentrations far exceeding national standards at multiple monitoring sites.
All sites downstream of operations exceeded national bottom lines for ammoniacal nitrogen toxicity. Very few river sites in New Zealand show concentrations exceeding these thresholds except those impacted by poorly treated point source discharges.
Effects of Ammonia on Aquatic Life
Toxic Impacts
  • Lethal and sub-lethal effects on aquatic organisms
  • Loss of equilibrium and hyperexcitability in fish
  • Increased breathing rate and cardiac stress
  • Reduction in hatching success and growth rates
  • Pathological changes in gill, liver, and kidney tissue

Critical Finding: Ammonia toxicity has no 'safety margin' between concentrations causing lethal versus sub-lethal effects. Concentrations protecting 80% of species may not protect sensitive freshwater mussels or shrimp from lethal effects.
Contamination Beyond Ammonia
Faecal Contamination
E. coli concentrations doubled and enterococci increased 38-fold from upstream to downstream. Extremely high loadings measured in wetland treatment system and irrigation pond discharge.
Treated Sawdust Chemicals
Unauthorized acceptance of LOSP-treated sawdust for ~15 years resulted in detection of propiconazole, tebuconazole, and permethrin. CCA treatment chemicals (copper, chromium, arsenic) also detected.
Dissolved Oxygen Depletion
National bottom line of 4.0 mg/L exceeded at least 16 times across monitoring sites between 2018-2021. Likely underestimates worst-case scenarios as monitoring occurred during daytime.
Macroinvertebrate Community Health
Macroinvertebrate communities serve as biological indicators of stream health, integrating water quality conditions over time. The evidence revealed pervasive impacts throughout the Haehanga catchment.
100%
Sites Below National Bottom Lines
All monitoring sites in the Haehanga Stream recorded MCI, SQMCI, and ASPM scores below national bottom lines for macroinvertebrate health.
20%
SQMCI Decline
More than 20% reduction in Semi-Quantitative Macroinvertebrate Community Index between upstream and downstream sites of wetland discharge.
Poor
Overall Stream Health
Macroinvertebrate communities dominated by pollution-tolerant taxa, indicating organic pollution and nutrient enrichment throughout the catchment.
Impacts on the Mimitangiatua River
Despite the Haehanga Stream comprising only 0.4% of the Mimitangiatua catchment area, monitoring revealed disproportionately large effects downstream of the confluence.
Measured Increases Downstream
  • Conductivity consistently higher
  • Ammoniacal nitrogen elevated on all occasions
  • E. coli greater on 4 out of 6 sampling dates
  • Dissolved reactive phosphorus elevated on 3 out of 5 occasions
June 2021 Incident
Ammoniacal nitrogen in the Mimitangiatua River exceeded the national bottom line (0.51 mg/L equivalent toxicity) following contamination from the Haehanga Stream (8.85 mg/L - more than twice the bottom line).
With short travel time to the Mimitangiatua Estuary, microbial pathogen die-off is unlikely before water reaches coastal areas used for cultural practices and recreation.
Incident History: Ongoing Compliance Issues
1
February 2018
Rupture in drilling mud pad bunding. Elevated ammonia, chloride and BOD reported. Infringement fine issued as company already under abatement notice.
2
February-March 2019
Elevated contaminants from suspected Pad 3 leachate break-out. Abatement notice issued requiring investigation and remedial work.
3
June 2021
Foamy discharge to Mimitangiatua River. Free ammonia at toxic levels, ammoniacal nitrogen exceeded national bottom lines. Overflow from irrigation field L1 identified as source. Abatement and infringement notices issued.
4
March 2022
Substantial leakage of contaminated groundwater. Ammoniacal nitrogen 10 times greater than national bottom line at site HHG000106. Further investigation ongoing.
National Policy Statement Framework
The National Policy Statement for Freshwater Management (NPS FM 2020) establishes a comprehensive framework for protecting ecosystem health through five biophysical components.
Water Quality
Physical and chemical measures including temperature, dissolved oxygen, pH, nutrients and toxicants.
Water Quantity
Extent and variability in level or flow of water.
Habitat
Physical form, structure, riparian vegetation and connections to floodplain and groundwater.
Aquatic Life
Abundance and diversity of biota including microbes, invertebrates, plants, fish and birds.
Ecological Processes
Interactions among biota and their environment including nutrient cycling and trophic connectivity.
"In a healthy freshwater ecosystem, all 5 biophysical components are suitable to sustain the indigenous aquatic life expected in the absence of human disturbance."
Expert Conclusions and Recommendations
Dr. McArthur's evidence concluded that ongoing persistent effects from RNZ operations significantly impact the Haehanga Stream and Mimitangiatua River, with multiple lines of evidence supporting this assessment.
1
Pervasive Water Quality Impacts
Cumulative inflow of pollutants along the Haehanga Stream from contaminated groundwater, diffuse surface runoff, stormwater contamination, and leachate from composting and vermiculture operations.
2
National Bottom Lines Exceeded
All sites except upstream controls exceeded national bottom lines for ammoniacal nitrogen toxicity. Concentrations far exceed typical New Zealand waterways.
3
Ecosystem Health Compromised
Macroinvertebrate communities in poor health throughout catchment. Multiple stressors including ammonia, low dissolved oxygen, faecal contamination, and toxic chemicals.
4
Downstream Effects Confirmed
Disproportionate impacts on Mimitangiatua River despite small catchment contribution. Effects on tupuna awa inconsistent with Te Mana o te Wai principles.
Te Mana o te Wai: Prioritizing Water Health
The Fundamental Principle
Under Te Mana o te Wai, the health and well-being of waterbodies and freshwater ecosystems must be prioritized first. This requires managing discharges to avoid exceeding national bottom lines and protecting compulsory values including mahinga kai, ecosystem health, human contact, and Māori freshwater values.
The evidence demonstrates that current operations result in water quality exceeding national bottom lines and significant impacts on freshwater values, making it difficult to reconcile with the requirement to prioritize the health and well-being of water and ecosystems.
"It is difficult to reconcile water quality that exceeds national bottom lines and impacts on freshwater values as being consistent with prioritising the health and well-being of water and ecosystems."
Evidence presented to the Environment Court of New Zealand, April 14, 2022