Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 5 Assessment of Potential Impacts and Control Measures
5.4. WIDER DEVELOPMENT CONCERNS
The wider development concerns were identified as: accidental spills, potential for causing offences
to European Protected Species and impacts to Protected Areas.
5.4.1. ACCIDENTAL SPILLS
Uncontrolled hydrocarbon spills following an uncontrolled blowout at both the Flyndre and Cawdor
wells are modelled and discussed in Section 6. This section also models the fate of the loss of the
diesel inventory from the drilling rig, and discusses the tiered response strategy of Maersk Oil to
combat and mitigate such spills.
5.4.2. PROTECTED AREAS AND SPECIES
The closest protected area is the Dogger Bank pSAC which is situated 120 km to the south of the
development. No significant impacts on any forms of marine or coastal protected areas have been
identified.
There are two forms of offences that can be caused to European Protected Species (EPS), the ‘injury
offence’ and the ‘disturbance offence’, the control of potential offences to EPS is controlled by the
issuing of licences, in the case of oil and gas activities this is by DECC. The EPS licence assessment for
the activities associated with the Flyndre and Cawdor development are discussed below.
INJURY EPS ASSESSMENT
The loudest sounds generated from the Flyndre and Cawdor development will be during the
installation of the 0.6 m diameter piles. If the activity was to proceed without any form of mitigation
measures in place, there could be a very small risk of exposing cetaceans in the immediate vicinity of
piling operations to sound levels that could cause a Temporary Threshold Shift, although the cetacean
would have to be in such close proximity, 1m from the pile driver, this is considered unrealistic. A TTS
is not a hearing injury, but a temporary reduced hearing sensitivity that is recoverable with time.
Sound modelling illustrated that the received noise levels decrease very rapidly with increasing
distance from the source, it is only in the immediate piling area, within the first few metres, that there
is any risk of causing a temporary threshold shift in cetaceans. The modelling suggests the zone of
injury was not exceeded. Providing the mitigation measures for piling are in place there will be a
negligible risk of causing injury, and no requirement to apply for an EPS licence for the injury offence.
DISTURBANCE EPS ASSESSMENT
The modelling predicts that noise levels from piling may not fall below background levels out to a
distance of 25 km. The piling sounds are likely to be audible (dependent upon prevailing ambient
sound levels) to marine mammals out to this extent. It is possible that upon receiving these sound
signals marine mammals could exhibit behavioural reactions and move away from the wider area of
piling operations, as has been demonstrated from research studies into piling undertaken by the wind
farm industry (Carstensen et al., 2006; Tougaard et al. 2009). In order to ascertain how many marine
mammals could potentially be exposed to the sound levels, abundance and density estimates were
calculated for the area affected using the SCANS‐II survey information, (this is currently the best
available abundance and density estimates for the species likely to be present in the development
area).
A conservative estimate of the number of marine mammals that could be exposed to levels of sound
above ambient levels within an area of 25 km 2 (derived from π * radius 2 ) i.e. area around each
manifold is shown in (Table 5‐13).
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