Scottish Government: Business, Enterprise & Energy Directorate

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Scottish Government: Business, Enterprise & Energy Directorate
Appraisal of the Implications of the proposed Beauly to Denny transmission line development on the River Moriston Special Area of
Conservation (SAC)
2009
The following appraisal has been prepared by the Scottish Ministers as the Competent Authority for the above proposal.
1
Project and site description
Brief description of the project
Scottish and Southern Energy (SSE) and Scottish Power (SP) submitted applications to
Scottish Ministers (under section 37 of the Electricity Act 1989) proposing an upgrade of
the main electricity transmission line from the Highlands to the Central Belt. The proposal
is to replace the existing 132kV line from the Beauly substation near Inverness to
Bonnybridge in Stirlingshire with a 400kV line from Beauly to Denny, near Falkirk.
The proposal includes the following:
220km of new double circuit 400kV overhead transmission line on steel lattice
towers from Beauly substation to a new substation near Denny via Fasnakyle.

Development of new or existing substations at Beauly, Fasnakyle, Fort Augustus,
Tummel and Braco substations.

Removal of all the existing 132kV overhead transmission line.
The purpose of the project is to provide the transmission infrastructure to enable new
generators in the north and west of Scotland, to link to centres of demand further south.
2
Brief description of the designated Natura The River Moriston is approximately 27km in length and flows from the eastern end of the
site
Loch Cluanie reservoir and enters Loch Ness at its northern side, 1km southeast of
Invermoriston. The site, which is 195 hectares in extent, comprises inland water bodies
(standing water as well as running water), bogs and marshes, heath and scrub and broadleaved and coniferous woodland.
The River Moriston is a SAC for the following qualifying species:
 Freshwater pearl mussel
 Atlantic salmon
3
Conservation objectives for the designated Conservation objectives of the River Moriston SAC species interests are:
Natura site
To avoid deterioration of the habitats of the qualifying species (listed above) or significant
disturbance to the qualifying species, thus ensuring that the integrity of the site is
maintained and the site makes an appropriate contribution to achieving favourable
conservation status for each of the qualifying features; and
To ensure for the qualifying species that the following are maintained in the long term:







4
population of the species, including range of genetic types for salmon, as a viable
component of the site
distribution of the species within site
distribution and extent of habitats supporting the species
structure, function and supporting processes of habitats supporting the species
no significant disturbance of the species
distribution and viability of freshwater pearl mussel host species
structure, function and supporting processes of habitats supporting freshwater pearl
mussel host species
Screening
Is the proposal directly connected with, or The proposal is not directly connected with, or necessary to, the conservation management
necessary to, conservation management of the of the River Moriston SAC and therefore further consideration is needed.
designated Natura site?
5
Consider whether there are any likely direct, The proposed 400kV overhead transmission line route crosses 40m of the SAC
indirect or secondary impacts of the project approximately 150m upstream of the existing 132kV overhead transmission line crossing
on the designated Natura site
point.
The potential impacts of the proposal include:
6

Potential for increased watercourse sedimentation within SAC during construction
phase. This could have a significant impact upon salmon spawning beds and/or the
gills of salmon juvenile being smothered and/or also their movements impeded.
Sedimentation could also have a significant impact upon freshwater pearl mussels
which could be smothered, it could interfere with their filter feeding and also
prevent the establishment of juvenile pearl mussels.

There is also a possible risk of contamination of the watercourse from the fuel and
chemical spillages/leaks. Any loss of water quality could adversely affect the
salmon and freshwater pearl mussel interests.

As well as any impacts upon salmon, similar effects are also possible on resident
trout populations. This could also indirectly affect the freshwater pearl mussel
interest which relies on juvenile salmon and trout to complete its lifecycle.
Consider the key phases of development and During all phases of the development, but particularly during the construction and
the risk of effects associated with each.
dismantling phases, a key consideration is pollution which may have a direct toxic effect
on the aquatic protected species, as well as a degradation of their habitats. Pollution can
also take the form of silt laden run-off. This may also have direct effects on species, such
as inhibiting of respiration through affecting gill function or interfering with filter feeding.
Silt also affects the habitats of aquatic protected species, such as the infill of salmon redds,
smothering of mussels or interfering with the establishment of juvenile mussels. Siltation
may also result in increased nutrient status, leading to the eutrophication of the aquatic
protected species’ habitat.
During the operation phase, risks are fewer because there will be less activity on site, but
accidental spillages from vehicles or storage areas are still possible and could affect the
SAC as described above.
Construction
Construction activities give rise to the risk of direct loss or and/or disturbance of habitats,
disruption to otter travelling routes, pollution and sedimentation of watercourses and
impacts upon channel management.
Operation
The operation phase of the development carries less risk of effects on the specified interests
than the construction phase, due largely to routine maintenance activities.
Dismantling
Dismantling of the existing 132 kV line gives rise to the risk of effects similar to those
associated with the construction of the proposed line, including direct loss and/or
disturbance to habitats, pollution, increased sedimentation etc.
Dismantling of the proposed 400 kV line gives rise to the risk of impacts which are
currently hard to assess given the expected ‘lifespan’ of the line being c. 80 years. Any
risks associated with this dismantling process are likely to be similar to those associated
with the construction phase of the development, and mitigation measures would be
required to ensure any impact on the SAC is minimised.
7
Appraise which individual elements of the
overall project would give rise to the greatest
risk of effects. State any element of the
project where the scale or magnitude of effect
is not known
The elements of the proposal which will give rise to the greatest risk of effects are the
construction phase, the operational phase and the dismantling and removal of the 132kV
line.
Construction phase
Construction of transmission line tower bases and towers – The proposed 400kV
transmission line route would cross the site for 40m, and cross the wider catchment area.
Construction sites for tower bases and towers of varying distances from the River Moriston
and associated tributaries would, therefore, be required through this area.
Construction of borrow pits – Construction of borrow pits may be required in the River
Moriston catchment area.
Access track construction – Track upgrades and construction would be undertaken both to
the north and south of where the proposed 400kV overhead transmission line would cross
the SAC.
Crossing of waterbodies/watercourses – Fording of waterbodies/watercourses by vehicles
and plant will not be permitted through the entire working corridor of the proposed 400kV
line. Where the crossing of a waterbody/watercourse associated with the River Moriston
catchment is unavoidable, bridges will be used in preference to culverts.
Tree felling – Tree felling would be required on the southern valley side to provide an
overhead corridor and access tracks for the proposed transmission line. In addition, tree
felling would also be required where the proposed transmission line would cross the A887
Trunk Road to allow for scaffold erection.
Operational phase
Routine maintenance would involve inspection of each tower and conductors
approximately every 5-6 years to asses the requirement for remedial works. Maintenance
could result in general pollution and siltation.
Dismantling 132kV line
Removal of transmission line tower bases and towers – One of the two closest towers to the
SAC to be removed would be approximately 20m from the River Moriston’s southern
bank; the other would be approximately 180m from the river’s northern bank.
De-stringing of transmission lines – the technique of de-stringing lines uses a method
called Catenary Support System (CSS) which would ensure that conductors are not pulled
through waterbodies/watercourses.
Borrow pits – potential impacts associated with the construction of borrow pits in the
dismantling phase would be consistent with those associated with the construction phase.
Access track construction – Similarly, the construction of access tracks required for the
dismantling phase would have potential impacts like those associated with the construction
phase.
Crossing of waterbodies/watercourses – Same as in construction phase.
Tree felling – the potential impacts associated with tree felling on aquatic protected
species, namely increased flows, siltation and acidification.
8
9
Is the plan/project likely to have a significant
effect on the River Moriston Special Area of
Conservation, either alone or in combination,
with other plans or projects?


Atlantic salmon: Likely significant effect – The proposed overhead line runs over
40m of the SAC giving rise to potential impacts upon salmon from pollution,
sedimentation, disturbance and habitat loss.
Freshwater pearl mussel: Likely significant effect – As above, the proposed
overhead line runs over 40m of the SAC giving rise to potential impacts upon pearl
mussels from pollution, sedimentation, disturbance and habitat loss. Any impact
upon the presence of salmon or trout will have an indirect impact upon pearl
mussels due to their key role in the early stages of pearl mussels’ life cycle.
Appraisal of Impacts on Site Integrity
Identify the relevant conservation objectives The conservation objectives to consider are those that relate to the qualifying species and
to consider for the designated Natura site.
habitat which may be affected by the proposal, these are to avoid deterioration of the
habitats of the qualifying species (listed above) or significant disturbance to the qualifying
species, thus ensuring that the integrity of the site is maintained and the site makes an
appropriate contribution to achieving favourable conservation status for each of the
qualifying features; and
To ensure for the qualifying species (Atlantic salmon, freshwater pearl mussel) that the
following are maintained in the long term:







population of the species, including range of genetic types for salmon and lamprey,
as a viable component of the site
distribution of the species within site
distribution and extent of habitats supporting the species
structure, function and supporting processes of habitats supporting the species
no significant disturbance of the species
distribution and viability of freshwater pearl mussel host species, and
structure, function and supporting processes of habitats supporting freshwater pearl
mussel host species.
10 Can it be ascertained that the proposal/plan Atlantic Salmon
will not adversely affect the integrity of the
River Moriston SAC?
 To avoid deterioration of the habitats of the qualifying species (listed above) or
significant disturbance to the qualifying species, thus ensuring that the integrity of
the site is maintained and the site makes an appropriate contribution to achieving
favourable conservation status for each of the qualifying features - as described
below, the proposed development could result in the deterioration of the river
habitat as the line would pass over 40m of the SAC including the river itself.

population of the species, including range of genetic types for salmon, as a viable
component of the site - The salmon population and its genetic component could be
affected by juvenile salmon gills being smothered by siltation or pollution during
construction or dismantling activities. Siltation can also smother salmon eggs by
clogging the spaces between the gravel and preventing oxygenated water reaching
the incubating eggs.

distribution of the species within site – The loss of Atlantic salmon connected to the
SAC by contamination of watercourses during construction may reduce the
occupation of the SAC, and hence the distribution within the SAC.

distribution and extent of habitats supporting the species – The proposal crosses the
SAC and runs alongside it at other points, and pollution may affect the quality of
the water and consequently the habitats of the SAC.

structure, function and supporting processes of habitats supporting the species –
Atlantic salmon require well oxygenated water, low sediment loads and overall
excellent water quality to survive. These features could be compromised by the
proposal.

no significant disturbance of the species –. A significant pollution event or noise
and vibration from construction and dismantling activities could constitute
significant disturbance to Atlantic salmon within the SAC. If the disturbance
resulted in salmon becoming absent from sections of the SAC, this would constitute
significant disturbance.
Freshwater pearl mussel
 To avoid deterioration of the habitats of the qualifying species (listed below) or
significant disturbance to the qualifying species, thus ensuring that the integrity of
the site is maintained and the site makes an appropriate contribution to achieving
favourable conservation status for each of the qualifying features - as described
below, the proposed development could result in the deterioration of the river
habitat as the line would pass over 40m of the SAC including the river itself.

population of the species as a viable component of the site - The River Moriston
supports a functional freshwater pearl mussel population. Pearl mussels are present
from downstream of a hydro electric dam to the confluence with Loch Ness. Like
Atlantic salmon, freshwater pearl mussels require well oxygenated water, low
sediment loads and overall excellent water quality to survive. This makes the
mussels sensitive to pollution, including increased sedimentation and siltation.

distribution of the species within site – Pearl mussels are extremely sensitive to
pollution and sedimentation. Sedimentation could smother pearl mussels living on
or in the riverbed. Should this happen then their distribution within the SAC would
become restricted.

distribution and extent of habitats supporting the species –. Mussels require very
good water quality and a riverbed with areas of clean gravel and sand. Pollution
could cause such habitat to become unsuitable, thereby reducing the distribution
and extent of habitat supporting pearl mussels.

structure, function and supporting processes of habitats supporting the species –
Adult pearl mussels are able to tolerate some silt for unknown lengths of time, but
juveniles are never found in this silty habitat. Juvenile pearl mussels tend to live
entirely buried within the river substrate and are therefore much more vulnerable to
any increases in silt or suspended solids which can smother the gravel bed,
preventing the supply of oxygen and organic food particles to the mussels. The
River Moriston supports a pearl mussel population that is, in places, showing signs
of active recruitment.

no significant disturbance of the species – As the proposal will cross the SAC for
40m there is a risk of disturbance of the pearl mussel population due to noise and
vibrations from construction traffic and human activity. During the operation phase,
no impact is predicted apart from effects similar to those for construction that may
occur due to maintenance work.

distribution and viability of freshwater pearl mussel host species – As described for
Atlantic salmon, but also applies to trout populations.

structure, function and supporting processes of habitats supporting freshwater
pearl mussel host species – As described for Atlantic salmon habitats, but also
applies to habitat supporting trout populations.
11 Consider whether mitigation measures can be The Environmental Statement proposes mitigation to address the impacts of the proposed
adopted to avoid impacts on site integrity
development. The proposed mitigation addresses the requirements as detailed in the
previous section for maintaining the habitats/qualifying species. Additionally, the
contractor would follow best construction site practices at all times and during all stages of
construction, including SEPA’s Best Management Practices, Pollution Prevention
Guidelines, and statutory conditions applied through General Binding Rules or higher CAR
authorisations. In addition, the following mitigation measures are proposed to further
address the impacts of the proposed development:
(a) In respect of the River Moriston Special Area of Conservation (SAC) and the River
Moriston Catchment Area as defined by SNH:
• the outside edge of each tower base shall be a minimum of 50m from all water
courses and water bodies within the SAC and a minimum of 50m therefrom within
the River Moriston Catchment Area unless other mitigation measures proposed are
implemented to permit reductions in the distance specified;
• the outside edge of all borrow pits, quarries, etc. shall be a minimum of 50m from
all water courses and water bodies within the SAC;
• the outside edge of all permanent non mobile storage facilities for oil, fuel etc.
shall be a minimum of 100m from all water courses and water bodies within the
River Moriston Catchment Area;
• no re-fuelling shall take place within 30m of watercourses and water bodies within
the River Moriston Catchment Area;
• no generators or similar plant and machinery shall be used within 30m of
watercourses and water bodies within the SAC nor within 10m from watercourses
and 30m of water bodies within the River Moriston Catchment Area;
• no spoil heaps shall be constructed within 30m of watercourses and water bodies
within the River Moriston Catchment Area unless other mitigation measures
proposed are implemented to permit reductions in this distance specified;
• no operations involving concrete transfer between vehicles or into vehicles shall
take place within 30m of watercourses and water bodies within the River Moriston
Catchment Area.
(b) The transmission line shall not be commissioned, i.e. transmit electricity between
Beauly and Denny, until a plan for emergency repair/maintenance works within the SAC
has been submitted to and approved in writing by Scottish Ministers in consultation with
SNH and the relevant planning authority. Any emergency repair/maintenance works shall
be carried out in accordance with the approved plan.
Conclusion of Appraisal
12 Can it be ascertained that the proposal will Provided that the mitigation measures outlined in the relevant sections of the
not adversely affect the integrity of the Environmental Statement and in section 11 are adopted and implemented on-the-ground by
means of enforceable conditions attached to any consent (through either the Electricity
River Moriston SAC?
Act/Town and Country Planning Act or through CAR regulatory procedures) then the
Beauly Denny proposal will not adversely affect the integrity of the River Moriston SAC.
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