Ocean Winds has published a report demonstrating how the “low-order deflagration” method for disposal of unexploded ordnance (UXO) creates predictable low levels of underwater noise in the marine environment after using the technique at its 882MW Moray West offshore wind farm.
The report has been compiled following the first large scale use of the method during UXO clearance prior to offshore construction of the array in the Moray Firth, Scotland.
As noted by lead author Nuria Abad Oliva, offshore consents manager for the project, the technique had previously only been used for military purposes.
This was the first successful use of low-order deflagration to support offshore renewable developments, with underwater noise measurements made by Seiche Ltd during disposal operations.
All 82 UXOs identified for disposal were safely eliminated using the technique with the works undertaken by Scottish-based EODEX.
Mines, bombs, torpedoes and naval shells with explosive content varying in size from 6kg to 700 kg were successfully neutralised. Underwater noise was limited to the small disposal tool charge, avoiding large underwater explosions from traditional UXO disposal techniques.
The report identifies a key advantage of the technique as being the accuracy of underwater noise modelling and impact assessment compared to less certain and potentially large estimates of noise from traditional disposal techniques. Traditional techniques can cause significant environmental damage and harm marine mammals.
By publishing the outcomes of this study, Ocean Winds hopes regulators and the offshore wind sector will benefit from these findings about the environmental benefits of low-order deflagration, it said.
“The challenge of disposal of over 80 UXOs using traditional techniques was daunting,” said Ocean Winds head of permitting and environment Catarina Rei.
She added: “Working with EODEX to deploy low-order deflagration for the first time on an offshore wind farm has been fantastic achievement.
“The disposal resulted in negligible underwater noise and ensured the protection of the prized marine mammal populations in the waters around the project.
“We hope this report will lead to informed guidance from regulators and appropriate adoption of the technique by developers where environmental sensitivities indicate it would be a useful tool.”
University of Aberdeen professor Paul Thomson said: “Our previous measurements of noise from UXO disposal at other offshore windfarms have highlighted how conventional high order techniques may impact protected marine mammals.
“This work represents an important proof of concept that will help reduce risks both to wildlife populations and to the delivery of the offshore wind projects being developed to meet climate targets.”