Mananui Mineral Sands Project

Project Overview

Client: Westland Mineral Sands Co. Ltd
Location: Mananui, West Coast, NZ
Consent Secured: July 2025, for a 112 ha operation and 16 years mining

Westland Mineral Sands Co. Ltd (WMS) secured resource consent for the Mananui Mineral Sands Project in July 2025, with the hearing decision describing the proposal as “ an exemplar of sustainable mining”. The site covers 112 ha of privately owned farmland adjacent to SH6, with sensitive wetlands and conservation land nearby. Target minerals include ilmenite, garnet, and gold. Heavy mineral concentrate will be exported through Greymouth port.

As the lead hydrology and hydrogeology advisor, Kōmanawa played a pivotal role in the successful consenting of the Mananui Mineral Sands Project. Our advanced technical expertise, robust evidence, and collaborative approach ensured the project satisfied stringent regulatory, environmental, and community expectations.

“Kōmanawa Solutions are a key part of our expert team – providing us with independent expert advice and assessment including as part of resource consent applications, providing evidence at hearings and ongoing compliance and monitoring support.  Zeb, Jens and the team are great to work with, their work is highly credible and sound, and always delivered in a timely, professional manner”

Heather McKay, Group General Manager Environment and Sustainability

1. Rigorous environmental impact assessment

Our comprehensive suite of hydrological and water quality investigations underpinned a scientifically robust assessment of groundwater and surface water systems, potential mining interactions, and the effectiveness of management actions. Key elements included:

  • Baseline investigation and monitoring, including characterisation of dredge pond and tailings seepage water quality
  • Water supply feasibility and impact assessment: leveraging our expertise in groundwater supply development, we identified a target aquifer for water supply and provided well yield estimates for feasibility assessment.
  • Groundwater modelling: We developed a transient groundwater flow and transport model for the mining operation in MODFLOW/MT3D, harnessing the power of FloPy and the broader Python programming environment to deliver rigorous water resource impact analysis at significantly lower cost than our competitors.
  • Integrated analysis: By coupling our deep knowledge of mine operation water management and site hydrology with our research-level modelling capabilities, we quantified potential water quality changes due to mining, simulated potential impacts on sensitive wetlands, and identified water management options to avoid them. Our approach ensured that the final water management solution and associated impact assessment were scientifically validated, and stood up to external scrutiny.
MT3D simulation of travelling dredge pond with infiltration basin at the southern boundary. The simulation shows the percentage of dredge pond water mixing with local groundwater

2. Expert Hearing Evidence

Kōmanawa’s Jens Rekker provided clear explanations of hydrological processes and risks, mitigation strategies, and restoration pathways in his hearing evidence to the independent hearing panel. This was key to addressing council and community concerns, with the hearing decision noting:

Based on WMS’s Offered Conditions and the information supplied, we are
satisfied that the adverse effects on Mahināpua Scenic Reserve, its boundary
wetland and Tūwharewhare will be protected from material harm.

Under the amended conditions negotiated with Poutini Ngāi Tahu, the
current hydrological connection between the farm and Tūwharewhare through
drainage channels will cease. That, in combination with the rehabilitation design
described above using wetlands to polish runoff, we expect will result in a long-term better water quality situation than exists at present.

3. Water management and monitoring solutions to protect local values

Given the site’s proximity to the culturally and ecologically significant Mahināpua lake, Tūwharewhare creek and the bordering wetland, Kōmanawa designed a first-class hydrological monitoring and management system, formalised through enforceable consent conditions:

  • Monitoring Framework:
    Groundwater and water quality monitoring systems to transparently demonstrate environmental protection to regulators, kaitiaki, stakeholders, and the community.
  • Adaptive Management Approach:
    Clear triggers and responsive management procedures for unforeseen impacts, ensuring a high standard of environmental protection.
  • Water Management Plan:
    Practical, verifiable strategies for management, developed in collaboration with key parties.
  • Stakeholder Responsiveness:
    Incorporation of feedback from iwi, DOC, and the community, enhancing robustness and social legitimacy.
  • Transparent Engagement:
    Active outreach and consultation to build stakeholder and community trust in project outcomes.