Wednesday 17 March 2021
The Otago Regional Council (ORC) has received two independent reports into fish deaths in the lower Kaikorai Lagoon, which followed the mechanical opening of the coastal mouth by ORC contractors as a flood mitigation.
ORC commissioned the two reports because of its dual role as operator and regulator, in order to keep those powers separate: one on the cause of the fish deaths for the engineering team by Ryder Environmental, and one by Wynn Williams reviewing the compliance investigation.
The independent expert review by Ryder Environmental could not establish a factual cause and effect relationship associated with the deaths, but makes recommendations to minimise environmental risks from the activity.
ORC engineering mechanically opened the Kaikorai coastal mouth as a flood mitigation before the deaths were reported.
The review by Ryder Environmental found that this timing suggested the opening may have played a role in the fish deaths, but there was no strong evidence to support a cause and effect relationship.
General Manager Operations Gavin Palmer said the engineering team will take the suggestions for minimising any environmental risk associated with this activity on board.
“While it is impossible to establish a concrete scientific link between opening the coastal mouth and the fish deaths in the Kaikorai, it is always a concern when a significant fish kill occurs, hence our commitment to determining whether our works may or may not have contributed.
“The independent report suggests a series of considerations for future coastal mouth openings, particularly around the timing of these activities. These include monitoring dissolved oxygen and water temperature levels, coinciding openings with incoming tides and rainfall, and aiming to open coastal mouths on windy days and in cooler conditions. We are incorporating these considerations into our future flood mitigation activities,” Dr Palmer said.
As the relevant regulatory body, ORC’s compliance team also commissioned an independent review of the compliance investigation by Wynn Williams, to determine in particular whether the engineering team’s conduct was a permitted activity under the Regional Plan: Coast, or if it may have constituted an RMA offence.
Chief Executive Sarah Gardner said the independent review backed up the findings of ORC’s compliance team.
“The findings of the Wynn Williams review largely align with the assessment by compliance staff, that the opening of the coastal mouth was a permitted activity and that the opening of the coastal mouth was a likely contributing factor to the fish deaths.
“The review notes that ORC’s investigation into the fish deaths was ‘thorough, timely and sound’, and backs up the conclusions of that investigation,” Mrs Gardner said.
The Wynn Williams review offers further recommendations for ORC to consider, including consultation with Fish and Game when works are to be undertaken to open coastal mouths.