In late 2021, Supreme Court judges unanimously rejected the seabed mining over lack of environmental caution, sending it back to the EPA with a direction to decline the mining bid if consent conditions could not prevent pollution.
Trans-Tasman’s lawyer, Morgan Slyfield, told the new EPA hearing that started in Hāwera this week the operational sediment plume model (OSPM) would be part of an early warning system, and a critical tool to manage mining discharge.
“The OSPM is a tool that enables TTR to glance into a crystal ball for the short-term future and say: ‘This is where the sediment is going’.”
Slyfield said the miners would know about sediment movement using forecasts of currents, weather and tides, and would change their work to make sure they did not breach their consented sediment limits.
“While the OSPM is running, TTR will have the ability to ask ‘is there something about the material we are discharging now that in three days’ time, or seven days’ time, or 10 days’ time will put us over [the limit]’?”
All sounded rosy until Slyfield delivered the bombshell.
“Now the point about the OSPM is that it doesn’t exist yet — it hasn’t been developed.”
Slyfield insisted that during a two-year “pre-commencement period” before mining, a numerical model could be built and tested against pre-mining data.
“Reality-checked is how I talk about it, against what is actually observed in the environment.”
The EPA’s decision-making committee (DMC) chairman, the retired appeal court judge Lyn Stevens, said they needed to be convinced the OSPM would be fit for purpose.
“Intent is one thing: the DMC is interested in reality and actuality.”
He pressed the company’s expert witness on sedimentation, Michael Dearnaley, to report back on whether the OSPM and the consent conditions as they stand would be enough to effectively limit pollution.
“It’s inevitable that there will be findings in this case of material harm in various respects and that’s been admitted.
“Our job will be to assess how significant such material harm is and, given those findings, how might conditions mitigate those. Or can they?”
Dearnaley said it would be impossible to be certain how operations would affect the environment until TTR designed, built and put to work its processing vessel.
But he said the OSPM could provide useful data on sediment flow and storm impacts.
“In a two-year period, sufficient data will be collected to ensure that there’s data to have an improved and operationally useful sediment transport plume model that will be able to be used to inform these things.”
“That two-year period of collecting the data and putting the model together is, I think, certainly adequate … [to] create an acceptable and valuable tool.”
Dearnaley said many factors needed to be measured.
“If you know what conditions of the flows and waves are, and what a snapshot of suspended sediments concentrations in the water column at a particular time are, and where sediment is on the bed, you might have a reasonable stab at making your forecast of here’s what we expect the flows and waves to be over the next three, five, 10 days — how’s that going to influence that distribution of sediment?”
Stevens encouraged Trans-Tasman to get on with it.
“We are troubled by this concept of pre-commencement monitoring because it can be done pre-commencement, why hasn’t it been done already?
“It may be that work could be done. Start now, just get on with it, don’t wait.”
A year ago the National Institute of Water and Atmospheric Research (Niwa) found an unexpected bounty of reefs teeming with life alongside the mining area.
Sonar found the Pātea Banks studded with 14 rocky reefs in a “Goldilocks zone” for sea life, with shallow waters admitting sunlight, but the offshore reefs avoiding sediment pollution from distant rivers and erosion.
The reefs are covered in kelp forests, macroalgal meadows and sponge gardens, with blue cod (including four nurseries), scarlet wrasse, butterfly perch, leatherjackets and tarakihi the dominant fish, and snapper, trevally, kingfish, and kahawai also present.
LDR is local body journalism co-funded by RNZ and NZ On Air.
