South Taranaki Bight
The South Taranaki Bight Project proposes to excavate up to 50 million tonnes of sand each year, separating iron ore from the sediment and returning 90 per cent of the sand to the sea bed in a controlled manner.
The project area is off the coast of Kakaramea and Manutahi in water depths of 20 to 42m. It is within New Zealand's Exclusive Economic Zone (EEZ). Decisions about the EEZ area are governed by the Continental Shelf (Environmental Effects) Act 2012, also known as the EEZ Act. Applications for marine consent are considered by the Environmental Protection Agency (EPA).
On gaining our marine consent, it will take about two years to finance, build and commission the operation with first export production targeted for mid-2018.
The Southern Taranaki Bight mining operation
We will commission an entirely new integrated mining vessel (IMV). This will be designed to operate through almost all weather conditions in the area and to be surveyed and maintained entirely at sea. To extract the sand we will build two seabed crawlers. Only one crawler will be in operation at a time. It will be tethered to the IMV and controlled remotely from it, and move along the deposits, transferring iron sand to the IMV.
Onboard, magnetic separators will remove the titano-magnetite ore without using heat or chemicals. Once ore has been extracted, the remaining 90 per cent of the sands extracted will be returned to the previously mined area in a controlled process just 4m above the seabed, restoring the area from which sand has been removed. Ore will be transferred to a trans-shipment vessel to be dewatered and stored before being transferred to export vessels.
Safeguarding the environment
Over the past six years, we have undertaken a detailed baseline study programme and modelling to assess potential environmental effects of the project. We have commissioned more than 35 expert reports and incorporated New Zealand's National Institute of Water and Atmospheric Research (NIWA) research as well as evidence gathered from overseas seabed mining into our planning. This body of New Zealand specific and international evidence has guided the refinement of our extraction and processing methodology to minimise any potential environmental effects.
How the mining process works
We will commission an entirely new integrated mining vessel (IMV) based on mature technologies developed for successful offshore seabed mining operations internationally. This vessel will be 335m long and 60m wide and designed to operate through all expected weather conditions in the area and to be surveyed and maintained entirely while at sea. The IMV will include a processing plant, desalination plant and power generation, as well as house the two seabed crawlers which operate on a rotation basis to dredge sediment from the seabed.
Additionally, we will commission a trans-shipment vessel to store iron ore and transfer it from the IMV to bulk export vessels.
The seabed crawlers
Each crawler is 8m high and moves at 0.04km per hour. Only one crawler will be in operation at a time. When a crawler is not in use it will be winched aboard the IMV for maintenance. The operating crawler will be tethered to the IMV and controlled remotely from it, dredging the sediment from the featureless, naturally shifting sands in the project area. The crawler has onboard sensors to assist with navigation.
Mining will be carried out in blocks with a 900m x 600m area mined every 30 days. The IMV will be stationed over this block, tethered to the seabed by four anchors which will be moved into place by an anchor-handling tug.
The crawler will be winched into a position which allows the IMV to follow the crawler as it mines. The crawler will move along the deposits using a suction head which rotates at a 120⁰ angle to extract sediment. The crawler is designed to dredge to the full depth of ore-rich sediment deposit creating a 22m wide lane between 2m and 11m deep. Sediment will be transferred to the IMV via a pipe. The crawler will only ever need to make one sweep over any section of seabed.
Reinstating the seabed
While the crawler is transferring iron-rich sediment to the IMV, a deposition pipe at the bow of the IMV will return sand from which ore has previously been removed in a controlled process just 4m above the seabed - backfilling as we go so that the seabed is reinstated almost immediately.
Processing the iron ore
Onboard the IMV the processing plant will use magnetic separation and for a portion of the seperated sediment a grinding mill is required to lightly grind the sediment to separate the iron ore concentrate. This process will be completed wet using seawater. No heat, chemicals or additives will be used in the process. The iron ore concentrate makes up about 10 per cent of the iron sand and the remaining sediment is returned to the seafloor.
The iron ore concentrate will be stored temporarily in the IMV before being transferred as slurry to the trans-shipment vessel. Fresh water from the desalination plant will be used to rinse salt from the iron ore. The concentrate will be dewatered on the trans-shipment vessel then loaded into an export vessel using dry bulk ship-to-ship loading systems. This entire process will take place at sea and the ore will then be shipped directly to world markets.
What it will mean for Taranaki?
In terms of physical impact, most people in Taranaki will not be aware of the project. Operations will be carried out entirely at sea, from specially designed vessels and will not be visible from the shore. The major impact will be largely beneficial to the local economy including the direct and indirect creation of new jobs and tens of millions in operational spending flowing into the region each year. A summary of economic benefits can be found here.