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.
Project and site description
1 Brief description of the project
Scottish and Southern Energy (SSE) and Scottish Power (SP) submitted applications to
2 Brief description of the designated Natura site
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.
The River Moriston is approximately 27km in length and flows from the eastern end of the
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

3 Conservation objectives for the designated
Natura site
Screening
4 Is the proposal directly connected with, or necessary to, conservation management of the designated Natura site?
(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
Conservation objectives of the River Moriston SAC species interests 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 that the following are maintained in the long term:
 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
The proposal is not directly connected with, or necessary to, the conservation management of the River Moriston SAC and therefore further consideration is needed.

5 Consider whether there are any likely direct, indirect or secondary impacts of the project on the designated Natura site
6 Consider the key phases of development and the risk of effects associated with each.
The proposed 400kV overhead transmission line route crosses 40m of the SAC approximately 150m upstream of the existing 132kV overhead transmission line crossing point.
The potential impacts of the proposal include:

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.
During all phases of the development, but particularly during the construction and 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

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 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.
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.

8 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?
Appraisal of Impacts on Site Integrity
9 Identify the relevant conservation objectives to consider for the designated Natura site.
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.

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.
The conservation objectives to consider are those that relate to the qualifying species and 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:

10 Can it be ascertained that the proposal/plan will not adversely affect the integrity of the
River Moriston SAC?
 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.
Atlantic Salmon

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

11 Consider whether mitigation measures can be adopted to avoid impacts on site integrity 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.
The Environmental Statement proposes mitigation to address the impacts of the proposed 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;

Conclusion of Appraisal
12 Can it be ascertained that the proposal will not adversely affect the integrity of the
River Moriston SAC?
• 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.
Provided that the mitigation measures outlined in the relevant sections 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
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.