Page 246 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
run ashore on the south-east coast of Alderney. Additionally, it is assumed that the construction
of an onshore substation will be necessary infrastructure for the project, although the exact
location of this is currently unconfirmed. It is presumed that a 200m x 120m substation will be
constructed (based on the London Array offshore windfarm for AC cables) within Mannez
Quarry to the east of the island (AEA, 2007). A larger substation may, however, be necessary
which would require additional space, particularly if a DC-AC convertor is required.
7.4.2 Impact Assessment
The Draft Plan has the potential to affect the infrastructure of the study area through a number
of impact pathways which are assessed in the following sections:
ƒ Cable Crossing Requirements with Existing Marine and/or Terrestrial Infrastructure
(Section 7.4.2.1);
ƒ Direct Damage to Existing Terrestrial Infrastructure (Section 7.4.2.2); and
ƒ Reduced Access to Existing Infrastructure for Maintenance or Repair Activity Collision
Risk (Section 7.4.2.3).
The importance of infrastructure is considered moderate based on the use and implication of
any loss of infrastructure. No highly sensitive infrastructure is identified and all infrastructure is
considered built to a suitable standard following best practice measures. Sensitivity is therefore
considered to be moderate throughout this assessment.
7.4.2.1 Cable crossing requirements with existing marine and/or terrestrial infrastructure
Cable crossing requirements with existing marine and/or terrestrial infrastructure may be
required during the operation of cable routeing. Cable crossing agreements may therefore
require or the removal and replacement of infrastructure if no alternative cable route is
available.
As discussed in Section 7.1.2.1, Alderney has an onshore network of buried electricity cables
(some sections above ground) (Figure 24) that may intersect with the offshore power cable.
This is generally controlled and regulated by the organisation that is responsible for the existing
network, and any connection requirements would therefore need to be negotiated with AEL
(ARE, 2011).
It is recommended that cable routeing follows already existing road and cable routes to
minimise disturbance, and impacts to terrestrial infrastructure are likely to be minimal.
Additionally considering the onshore substation for a single tidal array is expected to be
developed within the Mannez Quarry site, the exposure to change to other terrestrial
infrastructure on the island is considered negligible resulting in an insignificant impact.
Additional onshore substations may be required for the full build out of the Draft Plan (a
minimum of four onshore substations/converter stations, see Section 2.2.2), which would result
in a large area of land required, particularly if an HVDC converter station is required. Given the
limited infrastructure on Alderney, the exposure to change if all these onshore substations are
required is considered to be low resulting in a minor adverse impact.
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