N° 7 2021 
Dort at Tneste ın Itg 
4.2 Environmental impact 
assessments of underwater noise 
Environmental Impact Assessment (ElA) lies at the heart of licensing 
human activities in Europe. EIA is a consultation process including 
planners, regulators, stakeholders and the public, culminating in an 
Environmental Impact Statement (EIS). The EIS generally involves 
descriptions of the local environment, including an inventory of 
species and other components that could be affected, a description 
af the development, a detailed assessment of its possible effects 
on the local environment, along with what mitigation is proposed. 
Regulators then examine the EIS and decide whether the residual 
effects are permissible. If consent is granted, it may come with 
conditions to ensure mitigation measures are employed. 
As the plans for a Blue Economy have intensified in the past 
decade, so has the development of best practices for marine EISs. 
Noise risk assessments have been carried out for several years in 
association with permit applications for seismic surveys. However, 
the emergence of offshore wind farms has led to improved 
assessments for marine mammals, in particular for harbour 
porpoise. This coincided with the publication of a milestone paper 
on auditory injury thresholds and a disturbance assessment 
“ramework (Southall et al., 2007), updated by Southall et al., 
(2019), which have been used in Europe. Following a risk-based 
approach, the noise EIA should include the characterization of 
che source; the use of numerical sound propagation modelling to 
estimate sound levels at various distances away from the source; 
and some form of exposure assessment using knowledge on 
species' sensitivity to sounds of different frequencies, their risk of 
hearing damage and their distribution and abundance (Faulkner 
et al., 2018). It may also, where data is available, include dose- 
response modelling for the risk of behavioural disturbance and 
sometimes population consequences modelling. A description of 
custom mitigation measures to be implemented and any residual 
risk should also be included. Guidelines* were published by the 
Convention on the Conservation of Migratory Species of Wild 
Animals on EIAs for noise generating activities and some countries 
have their own guidelines or general guidance. There have also 
been several industry-led international initiatives on standards for 
noise impact assessments that promote best practice amongst 
their companies, operating in multiple countries (CEDA, 2011; 
WODA, 2013). Thus, it is expected that the quality of assessments 
should continue to improve. However, it is key that the level of 
detail and complexity of EIAs be proportionate to the risk involved 
and to the level of uncertainty in each stage of the assessment. 
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