Value Propositions

HDL’s core value proposition is to redirect government funding allocated to managing acid mine drainage (AMD) into a lasting solution: the Stockton Plateau Hydro Scheme.

Continuation of existing AMD treatments yield no economic impact or significant environmental improvements. Commissioning of the Stockton Plateau Hydro Scheme will secure long-term management of AMD liabilities for over a century, while generating significant renewable energy and delivering broad economic, social, and environmental benefits to the region and beyond.

Ideally construction will take place while export mining is taking place. It will provide employment for staff and contractors as Bathurst’s plans for continuation are advanced. Most components of the Scheme can be built by local businesses employing plant and skills used in the mining industry.

The Scheme would divert all tributary catchments affected by historic, current and future coal mining into the 2 reservoirs where dilution with less acidic surface runoff from high intensity rainfall would take place. The Scheme can collect all mine water from new mining prospects in the adjoining Waimangaroa catchment.
Acid mine drainage would not flow into the Ngākawau River other than in extreme events when spill from the reservoirs occurred. Mine water would not flow into the Waimangaroa River from future mining prospects.

Economic and social benefits

The Scheme will put $300M+ through the West Coast economy over an extended construction period; min 6 years.
Ideally construction would take place during the last years of export mining and provide a transitional employment for staff and contractors. Most components could be built by local businesses employing plant and skills used in the mining industry.
Staging can be aligned to optimise mining opportunities, rehabilitation and regeneration plans which will follow expiry and probable extension of the mining licences, due before 2026/27.
The Scheme’s infrastructure and administration will be established for the long-term to operate a hydro scheme within a regulated environment.
Local govt and Iwi participation in the governance of the Scheme would be encouraged to ensure locally directed regeneration of Stockton Plateau.

Renewable Energy Benefits

Renewable energy from Stockton would be injected into the northern end of West Coast’s national grid at Waimangaroa.
The 2024 peak West Coast demand is 91MW. The 2024 peak West Coast generation is 35MW. The difference of c56MW between generation and demand is imported from the national grid mainly from the 220kV supply at Kikiwa.
Stockton Plateau Hydro Scheme’s peak output of 60MW would cover the difference in peaks if the West Coast was isolated from the grid. Storage at Stockton may be sufficient to cover 5-6 days of West Coast demand.
Running Stockton at peak output could be used to reduce demand on the national grid to avert voltage collapse elsewhere.
Stockton generation injected at Waimangaroa would reduce the scale of upgrades required to the West Coast grid to meet Transpower’s forecast demand growth (155MW by 2038).
Stockton storage would support new renewable intermittent generation (solar, wind, run of river) connected to the grid throughout the Coast and connected regions.
Stockton generation would be complementary to the planned Waitaha 20MW generation injected into the southern end of the grid.

Water quality benefits

The Scheme would divert all tributary catchments affected by historic, current and future coal mining into the 2 reservoirs where dilution with less acidic surface runoff from high intensity rainfall would take place.
Water quality modelling using existing data indicates that, most of the time, the quality of diluted water in Weka Reservoir would meet the conditions of consent that discharges into Buller Bay must not affect ambient conditions in the Bay. There would be times when treatment of Weka Reservoir may be required before discharge to Buller Bay (after prolonged dry spell)
Central tendencies derived from current data indicate that infrequent dosing of Weka Reservoir (managing AMD collected from the entire Plateau) may be ~14% of the dosing currently required in Mangatini Stream managing AMD from the smaller coal mining licence area.
Acid mine drainage would not flow into the Ngākawau River other than in extreme events when spill from the reservoirs occurred.

Aspirational design and consenting

The value of the aspirational design and consenting of the Stockton Plateau Hydro Scheme should be significant for energy investors, developers, government, iwi and the community:

HDL’s consents for the Stockton Plateau Hydro Scheme are aspirational providing the best possible renewable generation and environmental outcomes. Over the long-term, the Scheme will manage AMD from the risks of disturbance of waste dumps by weathering and natural hazards. The scheme will meet financial and environmental objectives which cannot be met by other solutions.

HDL's consents for the Stockton Plateau Hydro Scheme set upper limits. The scheme may be configured within the limits in response to a investment partner's investment objectives. With the imminent wind-down of mining possibly making a 250+ work force redundant, the highest value proposition may be to provide dedicated green energy to a high energy-use industry looking for green power security, a skilled workforce and green credits for resolving the government’s environmental liabilities.

Underlying HDL’s value proposition is the holistic environmental baseline set by the conditions of consents for the Stockton Plateau Hydro Scheme. It creates the opportunity for an energy investor, government, Iwi and the community to work together to optimise the generation profile of the scheme and agree the standards of environmental outcomes appropriate for the long-term regeneration of the Buller Coal Field

Value Propositions

Economic and social benefits

Renewable Energy Benefits

Water quality benefits

Aspirational design and consenting

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