1.
Introduction
This document is a draft Construction Method Statement (CMS) for the proposed
Mynydd y Gwair Wind Farm.
This draft CMS deals with the construction and post-construction restoration of the
wind farm in compliance with the terms of the planning permission and its attendant
planning conditions.
This document supplements the Environmental Impact Assessment which was carried
out and reported in the Environmental Statement that forms part of the planning
application for the Mynydd y Gwair Wind Farm.
It is good engineering practice for the chosen contractor to decide how best to
undertake each work activity based on their personal experience and the associated
risks. This is in line with the requirements of the Construction (Design and
Management) Regulations 2007 (CDM 2007) to ensure good project planning and
thereby good environmental and health and safety practices. The methods and
processes to avoid or reduce environmental impacts provided in this document are
therefore for guidance only and may be amended prior to construction. However, this
draft CMS will form the basis of the final document which will be agreed with the local
planning authority prior to the commencement of construction activities.
2.
Project Description
The proposed Mynydd y Gwair Wind Farm site lies approximately 15km north of the
centre of Swansea. The site is located on the south facing slopes of Mynydd y Gwair
and Pentwyn Mawr, on common land which rises to 330m above sea level. The
majority of the site is moorland, primarily used for the grazing of sheep, cattle and
horses.
The wind farm is located between the town of Ammanford to the northwest,
Pontardawe to the east, Felindre to the south and Pontarddulais to the west. A
number of dispersed farms and dwellings are located in the vicinity of the wind farm,
outside of the site boundary.
Access to the site will be afforded via the A48 in Pontardulais, from where a track will
be constructed passing across Gopa Hill, Mynydd Pysgodlyn and Mynydd Garn Fach,
before entering the site from the south.
The wind farm will comprise:
16 wind turbines up to 127 metres tip height;
crane hardstanding areas at each turbine;
a single anemometer mast;
an access track from the A48 to site, incorporating improvements to existing
highways;
internal tracks between the turbines;
-
associated cabling between turbines running alongside the path of the access
tracks;
an electrical substation and control building, located to the north west corner
of the site, and associated grid connection; and
an area of 50m x 50m to act as a temporary construction compound and laydown area (to be reinstated after construction).
Construction of the wind farm is expected to take approximately 22 months.
3.
Construction Management – Roles & Responsibilities
Aspects of the construction works that could potentially affect the environment of the
site and for which management practices have been developed are detailed in the
sections below.
Purpose
To establish roles, responsibilities, authorities and accountabilities during the
construction phase.
Procedure
RWE npower renewables (RWE NRL) will nominate a Project Manager for the site
whose responsibilities will include overall environmental management of the site on
behalf of RWE NRL and the land-owners.
All works will be carried out in accordance with the planning consent, planning
conditions attached to the planning consent, and all applicable legislation. The
Contractor will carefully plan the works, and those of his sub-contractors, and provide
details in a Health and Safety Plan (as required under CDM 2007).
All contractors and sub-contractors will be required to adhere to the CMS in its finally
approved form.
Task specific method statements for individual works will be prepared where
necessary and may employ specialist resources to provide advice in preparing and
supervision work methods. This may include ecologists, hydrologists etc.
RWE NRL will appoint a Site Manager who will monitor the day-to-day management of
the site, including legal and environmental responsibilities, site health and safety, and
to ensure adherence to this CMS and all approved method statements and the
planning conditions.
RWE NRL will also appoint a suitably qualified Project Ecologist to assist the Site
Manager, who will identify any sensitivities and set up any monitoring regimes
required. The Project Ecologist will have a visiting role and will be on site during any
particularly environmentally sensitive operations and when monitoring is required.
RWE NRL will appoint a suitably qualified hydrologist to assist the Site Manager in
carrying out further surveys, construction methods, any required mitigations and
monitoring processes. The hydrologist will have a visiting role and will be on site
during any particularly environmentally sensitive operations and when monitoring is
required.
RWE NRL will appoint a suitably qualified Project Archaeologist to undertake
responsibilities associated with an agreed watching brief.
Prior to the commencement of specific construction activities, the Contractor‟s Method
Statements will be reviewed by the Project Manager, the Site Manager and the
Environmental Team (Project Ecologist, Archaeologist and Hydrologist) to ensure that
all operations comply with the best environmental practice and the provisions of the
CMS. Once construction commences the Contractor will have to adhere to these
Method Statements. Should any unexpected environmental issues arise during
construction the Contractor will also be briefed to immediately report them to the Site
Management Team so that suitable measures can be implemented.
4.
Pre-Construction
Prior to the commencement of construction works on site, RWE NRL will liaise with the
local planning authority and any relevant statutory consultees to discharge all precommencement conditions.
Appropriate protected species surveys will be undertaken in accordance with the
recommendations below and any relevant planning conditions or legal requirements.
Where necessary, mitigation measures shall be agreed with the local planning
authority to accommodate any protected species found on site. Detailed site
investigations are also likely to be required in order to complete the design of the
turbine foundations.
Micro-siting of turbine locations and the associated access tracks and infrastructure
(including crane pad locations and temporary working areas including areas for
storage of top soil) will take place, taking into account any protected species
mitigation, ground conditions and localised ecological, topographical and hydrological
considerations, including in particular the objective to avoid peat deposits in excess of
300mm in depth.
The two areas of archaeological interest requiring fencing would be identified and the
fencing erected before construction activities begin on site.
Detailed arrangements for the induction of construction staff will be drawn up in
consultation with the Site Ecologist, Site Hydrologist and Site Archaeologist.
5.
Ecological Sensitivity
Purpose
To ensure the protection of important nature conservation resources, including
protected species and other notable ecological features on the wind farm site.
Specialist environmental support will be sought as required.
All site workers will be inducted in relation to the ecological requirements and
sensitivities on the site, including emergency procedures and any exclusion zones,
prior to being permitted to undertake any work on site.
Preliminary vegetation clearance measures to manage the risk to protected species
(nesting birds and reptiles) will be undertaken in consultation with the Site Ecologist
and in accordance with the strategy set out in the ES.
5.1.
Protected Species
5.1.1. Otter & Water Vole
Purpose
To ensure the protection of species of conservation interest on or adjacent to the
Wind Farm.
Procedure
No signs of otter and water voles have been recorded within the Wind Farm study
area. Potential lying up habitat for otters is present along the main (Afon Lliw)
stream corridor but such places tend to be in use by sheep taking water. Water vole
is judged unlikely to use the Wind Farm site on the basis of a lack of suitable habitat
as well as the lack of any signs found during the baseline surveys.
In accordance with best practice, disturbance of otter and water vole sites will be
avoided. This will be achieved through careful design and placement of water course
crossings away from any identified water vole sites identified during the construction
phase. Demarcation within the development boundary will be by the placement of
signage, coloured plastic fencing or tape to mark out areas that are not to be
disturbed during construction should protected species be present.
Any ditches that are to be crossed by access tracks will be surveyed for water voles at
an appropriate time of the year in advance of construction. If any ditches are
identified as supporting water voles, appropriate mitigation will be put into place to
avoid impacts upon active burrows.
An appropriate monitoring programme will be put in place should either species be
confirmed as present on the site during the construction phase.
Site workers will also follow an emergency procedure if Otter or Water Vole are
encountered during the course of the works and work will be stopped where
necessary.
5.1.2. Breeding Birds
Purpose
To ensure the protection of breeding birds on the wind farm site in accordance with
the requirements of the Wildlife and Countryside Act 1981 (as amended).
Procedure
Prior to the commencement of construction, habitat manipulation such as mowing or
surface stripping will be employed in the preceding period to ensure no nests are
present. Alternatively, a survey by an experienced ornithologist will be undertaken.
Contractors will be briefed regarding nesting bird species and if identified, works will
cease until ecological advice can be obtained.
5.1.3. Badgers
Purpose
To ensure the protection of the badgers on the site in accordance with legal
requirements and to have systems in place to be able to react to any changes in
badger activity that affect construction activities.
Procedure
Contractors will be fully briefed and inducted on the legal requirements relating to
badgers and their setts and will be shown the locations of all known badger setts on
the site. They will also be advised of the guidance „stand-off‟ distances to be adopted
when using different types of machinery or where undertaking any other potentially
disturbing activities.
A survey will be carried-out prior to construction to identify the presence of badgers
or badger activity within the development boundary and in particular close to
construction working areas. Relevant licences will be obtained if required. Should any
presence/activity be identified, appropriate mitigation will be implemented such as
fencing and/or demarcation. Micrositing allowances will be utilised to ensure that
infrastructure does not cause unacceptable impacts.
Should workings be required in the vicinity of badgers/badger setts, appropriate
method statements will be developed and implemented, where necessary in
accordance with licenses.
Contractors working on deep excavations will be issued with a standard procedure to
be employed daily for minimising entrapment hazard (e.g. installation of „escape‟
planks in excavations left uncovered overnight).
5.1.4. Reptiles
Purpose
To ensure the protection of reptile species on the wind farm site in accordance with
the requirements of the Wildlife and Countryside Act 1981 (as amended).
Procedure
Prior to commencement of the construction activities the working areas will be subject
to habitat manipulation to discourage their use by reptiles and encourage
displacement. Where this is unavoidable, an inspection by an Ecologist will be
undertaken of the affected area to ascertain its potential to harbour reptiles and
advice on any additional mitigation necessary to ensure legal compliance.
5.2.
Important Habitats
5.2.1. Peat resources and associated vegetation
Purpose
To minimise impacts on any peat resources on the site in order to restrict impacts on
Biodiversity Action Plan habitats, reduce the potential for pollution of hydrological
systems and reduce mobilisation of stored carbon.
Procedure
The objective whenever handling peat or peaty soils will be to minimise handling,
maintain moisture content and prevent contamination with other materials or mixing
of peat with underlying mineral horizons.
The standard protocol for temporarily stored peat will be that it is placed as close to
source as possible, laid on a geotextile membrane or onto heavy duty polythene
sheeting, not stockpiled into mounds any higher than 1.5m and covered with
additional weighted down polythene sheeting to prevent desiccation. Storage areas
will be distributed in flattest areas as far away as possible from watercourses or
drains. Silt traps will be used to capture any suspended solids generated. Storage
areas may first need to be checked for nesting birds or reptiles (see 5.1.2 and 5.1.4
above).
Peat stored for longer than 1 week or during dry conditions will need to be regularly
wetted to maintain near-saturated conditions.
No peat will be exported off-site. If a surplus of arisings occurs, an Ecologist will be
asked to provide advice on suitable locations for on-site deposition (e.g. relict peat
cuttings).
Special construction procedures (floating track) are required where the access track
network (and associated cabling) will cross deep peat deposits. These will be agreed
with the Site Ecologist and the Site Hydrologist prior to implementation.
5.2.2.
Acid grassland and heath-type vegetation
Purpose
To restrict impacts on other Biodiversity Action Plan habitats on site and to promote
their rapid recovery after disturbance.
Procedure
The objective whenever handling mineral soils on the site, including those with a very
thin (e.g. 20mm or less) peaty topsoil layer will be to minimise handling, maintain
moisture content and prevent mixing of horizons.
The standard protocol for storage of non-peat soils will be storage as close to source
as possible onto a geotextile membrane in stockpiles no higher than 1.5m. Darker
(humose) horizons may need to be stripped separately with the surface vegetation
and stored under transparent polythene to maintain wetness and reduce mobilisation
of carbon and other constituents. Storage areas will be distributed in flattest areas as
far away as possible from watercourses or drains. Silt traps will be used to capture
any suspended solids generated. Any soil storage areas may first need to be checked
for nesting birds or reptiles (see 5.1.2 and 5.1.4 above).
6.
Construction Methods
6.1.
Site Construction Compound
Purpose
To identify the most suitable methods for installation of the site construction
compound, storage, plant re-fuelling and maintenance areas.
Procedure
The intended location of the temporary construction compound is shown on layout
drawing Figure 1.2 within the Environmental Statement. The construction compound
will occupy an area of approximately 50m x 50m and is to be located to the south of
turbine number 7. The compound will comprise:




A laydown area for materials and turbine components;
Temporary portacabin type structures, for site offices and welfare facilities
including toilets (with provision for sealed waste storage and removal);
Parking for cars and construction vehicles; and
Hardstandings to be used for material storage.
Following on from any works required in respect of nesting birds and/or reptiles, a
temporary fence will be erected around the construction compound (approximately 2
metres in height).
The construction compound area will be identified by surveyors and clearly pegged.
Surface soils will be excavated and set aside in storage bunds for reinstatement on
completion of the project. These soils will be separated and stored for re-use
following best practice guidelines as discussed above. Any existing drainage lines or
paths will be diverted around the extent of the compound, if necessary. Unsuitable
soils will be excavated and stockpiled until a suitable formation is reached. The
proposed construction compound area is situated on a shallow slope, such that cutand-fill techniques can simply be employed to facilitate a level surface to the
compound. As with the access tracks, a geotextile will be placed over the area and
crushed stone will be laid and compacted in layers to provide an adequate smooth
surface. Geogrids may be required to ensure optimal weight distribution and the area
will be graded to provide drainage falls to adjacent ditches.
Welfare facilities will be provided in accordance with the Construction (Design and
Management) Regulations 2007. Facilities for waste management, refuelling, power,
water supply and chemical storage will be provided. All welfare facilities will be
provided for the duration of the contract and until the permanent facilities are
completed within the substation compound.
Welfare units will be self contained, typically housing its own under unit storage tank.
The tanks will be regularly emptied by a registered waste disposal contractor.
Fuels delivered to site will be stored within a bowser bunded to 110% capacity
strategically located within the construction compound. Wherever practical, all
refuelling of plant will be undertaken within a designated location in the compound by
trained operatives. The operatives will be trained on the safe procedure for refuelling
including emergency procedures for dealing with spillages. Emergency equipment
such as spill kits will be readily available.
Site security will be on site 24 hours a day to protect the works from theft or
vandalism. Lighting will be used around the compound to assist with the overall
security of the facilities.
Reinstatement
Following completion of the works and commissioning of the turbines, the site
compound will be removed and the land returned to its original condition. Material
used to construct the compound will be excavated and used within the site track
network to make good any potholes. Stockpiled subsoil and topsoil will then be
replaced to replicate the original ground conditions and contours. An appropriate
grass seed mix may be applied to quickly restore exposed areas and thereby prevent
erosion of the topsoil.
6.2.
Electrical Substation and Control Building
Purpose
The proposed electrical substation and control building will occupy an area of
approximately 60m by 60m in the north west corner of the site (outwith the existing
common land). Construction needs to be undertaken so as to minimise the impact on
the ecology in the area.
Procedure
The access track will be constructed across the site and down to the substation area
to provide access to the substation construction area. All significant deliveries made
from the south will be brought across the site rather than using the local roads.
The works will include:
-
Strip area of topsoil and subsoil, including break-through of relict field
boundary
Earthworks to provide level substation area and landscaping bund
Groundworks to transformer and switchgear plinths
Control building construction
Modifications to existing 132kV pylon
Installation of palisade fencing and gates
Installation of switchgear and transformer including cabling
Commissioning of substation and connection to the grid
Landscaping and restoration works
As with the site construction compound, the area will be surveyed and pegged out.
The topsoil and subsoil will then be stripped and separately stockpiled adjacent to the
works for later reinstatement. The subsoils will be used to create the level area
required for the electrical switchgear and the control building.
It is likely that a separate but smaller set of cabins will be required at the substation
for the electrical contractors. This will involve the same procedures as set out under
Section 6.1 of this document, but on a much smaller scale. All materials and
equipment will be stored in secure cabins within this area.
The electrical switchgear and transformer will be anchored on a number of concrete
plinths within the substation compound. These plinths will be constructed by
excavating the required area, installing the steel reinforcement and then pouring the
ready mix concrete, in a similar manner to the turbine foundations. Concrete may
also be used to construct the substation roads with intermediate areas then covered
with a layer of graded aggregate laid over a geotextile layer.
The control building will be founded on a reinforced concrete foundation and
constructed from blockwork with a pitched roof.
To ensure health and safety requirements the whole compound will be fenced on
completion of the earthworks with a 2.4m high palisade fence with high security
gates.
The connection to the grid will be undertaken by Western Power Distribution and will
be subject to a separate construction method statement. However, it is anticipated
that the methodologies employed will be similar to those included within this
document.
Reinstatement
A detailed reinstatement plan will be produced and agreed for the substation area
prior to the commencement of these works. Earthworks and landscaping will be used
to minimise the visual impact of the substation.
Stripped topsoil will be spread over exposed areas adjacent to the substation on
completion of the earthworks. Planting in accordance with the approved plan will be
undertaken during the earliest planting season to provide screening as soon as
possible.
6.3.
Site Track Design & Construction
Purpose
To construct the site tracks with minimal visual impact or disturbance to vegetation.
Access tracks are required throughout the site for the movement of materials
including the delivery of the turbine components to their proposed locations, and for
maintenance and operation of the wind farm. Excavation, construction and
maintenance of access tracks to the wind turbines (WTGs) will be undertaken to
minimise disturbance to vegetation and hydrology at the site. The tracks need to be
sufficient to allow the delivery of large and heavy turbine components and
transformers.
Procedure
The tracks have undergone a preliminary 3D design iteration to ensure the track
geometry can be achieved within the works boundary. The computer aided design
also ensured that the design could be achieved whilst balancing the cut and fill of the
earthworks where required.
The tracks within the wind farm site will take the routes set out in the Environmental
Statement, subject to any local variations in response to local ecological or
hydrological sensitivities. The tracks will be surfaced and designed to standards that
ensure control of water and integrity of the track surface.
The design requirements for the tracks will depend on the chosen turbine type but are
likely to require a track capable of carrying vehicles of up to 145t and up to 55m long
with axle weights of up to 20t. Geometric parameters for the site tracks are based:


maximum gradient of 10%;
minimum running surface width of approximately 5m on straight sections with
widening on curves; and
minimum inside radius on bends 20m.
The track width will be increased proportionately at bends and junctions. Passing
places have been limited to the hardstanding areas and at strategic points along the
initial access track on to site.
a) “Cut” Type Design
“Cut” type track design will be used where geographical / topographical conditions
require. The circumstances where “Cut” type design will be used will be determined
by the Project Manager and such operations will be designed to achieve a good
balance where possible and to cause the minimum amount of impact to the area.
Following on from any works required under sections 5.1.2 and 5.1.4 above in respect
of nesting birds and/or reptiles, the track area will be surveyed and pegged out prior
to being cleared of all vegetation. The track width will be stripped of topsoil and
subsoils and these will be separately stockpiled in the vicinity for eventual
reinstatement in accordance with the best practice methods set out at section 5.2
above. Material removed from small cuttings will be hauled to fill areas where
suitable to balance the cut and fill. The track will be constructed with crushed graded
rock with chemical composition appropriate to the site conditions, laid and compacted
in layers to form the required profile. Selected smaller graded rock will be imported
to finish off the tracks to the required profiles and to provide a smooth, bound and
impermeable running surface. The stripped topsoil will be re-used to dress the slopes
and verges of the track.
The depth of stone will be determined during the detailed design and will depend on
the underlying ground conditions. Typically the track depth will be between 300 and
500mm deep laid on a geo-textile membrane.
Sections of track identified through softer or peaty ground may be moved to drier,
firmer ground, within the 30m micro-siting allowance. Alternatively, trial pitting may
be used to establish the depth to suitable formation. If this is not possible a “floating
road” design may be used.
b) “Floating Road” Type Design
A “floating road” design will be required where the track crosses peaty or softer
ground conditions. Depending on the strength and depth of the soft material it may
be preferable to build a floating road rather than the cut type track previously
described.
The track may consist of a 500mm to 700mm layer of aggregate constructed on a
geotextile or geogrid placed directly onto the existing ground level, i.e. no topsoil strip
will be undertaken. Additionally in particularly soft ground, a second geogrid will be
incorporated to strengthen the formation.
Construction of the floating tracks will allow for continued drainage perpendicular to
the track, either through constructing the sub-base with coarse granular material or
by constructing drains through the peat at regular points under the length of the
track.
Drainage
Trackside drains, if required, shall have a depth of not less than 250 mm below the
formation edge and a longitudinal gradient of not less than 2%. Catchpits, settlement
ponds and filters will be provided in and adjacent to the drains to avoid pollution and
sedimentation of watercourses. Trackside drains will not be led directly into
watercourses. Further description of track drainage appears in Section 6.9.
Wherever possible, turfs will be stripped where drains are required and the turfs
reinstated within the invert of the drain to facilitate rapid re-establishment of
vegetation and thereby minimise scour.
Flow in the trackside ditch will be minimised by removing water through regular cross
culverts sited to suit the landform and located at regular intervals. They will
discharge into silt traps excavated on the downhill side. Water from these will either
soak away or discharge over surface vegetation. Downhill of each culvert mouth a
small rock dam will be constructed in the ditch to minimise the possibility of flow
passing the culvert in extreme weather events.
The tracks are generally located on the ridges around the site and are therefore fairly
level without prolonged steep sections, thereby reducing the likelihood of rapid flows
along the track edges. Furthermore, as they are located on the ridges any surface
flows will be lower than those experienced on the lower slopes. However, there may
be short sections which experience higher flow rates. The principal means of
minimising scour and silt run-off from steep tracks lies in ensuring a well bound
surface through well graded material and the track crossfall. Within the track ditches,
small rock “arrester” dams will be placed at regular intervals to slow down flow and
retain granular material (sediment).
The location of cables, tracks and crossings will be considered and sections of ditch
piped where required. During the construction period, the track drainage will be
planned in such a way so as to minimize the production of silty run-off water. Check
dams and/or filtration fences will be erected as and when required.
Reinstatement
Following the completion of the construction and erection phase, the edge of the
access track will be topsoiled to permit the invasion of vegetation along the side of
the track. The vegetation will start to green the edges of the tracks, reducing future
scour whilst still permitting the passage of wide vehicles if necessary during the
operation phase.
As the track will incur limited disturbance during the operational phase, a partial
covering of grass, moss and lichen will form reducing the visual effect of the track.
Depending upon the level of usage following construction, after 2 to 3 growing
seasons the tracks will have developed a reasonable vegetation cover concentrated at
the edges and centre of the track.
Safety considerations during operation of the wind farm mean that it is not feasible to
develop full vegetation cover over the width of the track.
6.4.
Crane Hardstandings
Description
Crane hardstandings are required to provide a suitably robust and level area, upon
which cranes are used to lift turbine components into place.
Procedure
The location of the crane hardstandings has been designed to make best use of the
existing topography (minimising cut and fill requirements), prevailing wind conditions
(to enable safe lifting) and likely erection procedure. As with access tracks, topsoil
(including peaty horizons) and subsoil will be excavated and stored in separate bunds
for later reinstatement.
The area adjacent to each turbine will be surveyed and set out to the required
dimensions (typically a single rectangular pad up to 50m by 25m) and excavated to a
suitable formation. Plate bearing tests will be conducted at regular intervals across
the excavation to prove the bearing capacity of the underlying strata. If unsuitable,
geogrids may be used to facilitate better distribution of weight. A geotextile will be
laid and coarse rock fill will then be placed and compacted in layers. The final surface
will be formed from selected smaller granular material and trimmed to allow surface
water run-off, to either drainage ditches or soakaways. The fill materials will be of a
type consistent with ensuring there is no scope for significant changes in soil and
water chemistry in the locality of the construction areas.
Crane hardstandings will be formed as the construction of site tracks progress.
However the pads may be formed initially to provide lay-down areas for materials
associated with WTG foundation materials and finalised closer to the lifting operations,
once the foundation has been cast. Where relevant, the active top layer of peat will be
carefully removed and stacked close to the excavation for re-use in restoration.
Excess peat will be used to form track-side batters.
Where turbine bases and associated hardstandings are located on shallow (<300mm)
peat this will be followed by excavation of the peat/underlying mineral soils to
formation depth. The peat turf and underlying peat will be stored in low (max 1.5m)
mounds outwith the working area. Where glacial till is excavated, material excess to
backfilling requirements may be utilised for crane hard standing at the wind turbine
location or in the access track construction programme. These materials will be
temporarily stored within the working area.
Reinstatement
On completion of the lifting operations and following successful commissioning of the
turbine, the crane hardstandings will be left in situ for future turbine maintenance.
However, the topsoil will be spread over the hardstandings and the areas left to
revegetate. If necessary, the areas will be seeded to prevent the erosion of the
topsoil layer.
6.5.
Turbine Foundations
Description
Reinforced concrete foundations are required to support the large turbine structures.
The bases need to be constructed with minimal disturbance to the vegetation and
surrounding hydrology.
Procedure
The position of each WTG will be surveyed and set out to the agreed co-ordinates
(subject to 30m micrositing allowance). The extent of the foundation will be marked
on the ground and an allowance made for working space and shuttering. Any
evidence of surface water flows which would convey surface water towards the area
will be diverted in advance of any excavations. The required area will be stripped of
topsoil and subsoil and these stockpiled separately for reinstatement. The area will
be excavated to a suitable formation and cleared of all loose, fractured rock.
Drainage ditches will be excavated around the perimeter to keep the excavation dry.
An outfall ditch will be created where possible or a sump formed for pumping out of
the excavations. Batters will be formed on all sides where appropriate and in cases
where these are adjacent to site tracks, bunds will be formed along the top edge. In
some instances, it may be the case that site tracks need to be widened to allow safe
passage of construction plant and vehicles. Alternatively, the Contractor may decide
to provide temporary support to the excavated face.
A plate bearing test will be carried out to prove the bearing capacity of the strata
below and work only allowed to continue on a successful result. Failure of the test will
result in either further excavation or placement of rock fill and retesting of the bearing
capacity.
Blinding concrete will be placed and levelled to the required dimensions and level and
finished with a vibrating power screed. The base will be set out to the required
dimensions and offered for inspection prior to steel fixing.
Reinforcing steel bars will be delivered to site and stored adjacent to the excavation.
A telehandler will deposit the largest bundles of bars onto the blinding concrete to cut
down on manual handling. Steel fixers form the reinforcement cage to the required
dimensions and levels as indicated on the design drawings and schedules. All steel
will be adequately supported on chairs, cover blocks and tied securely. The area will
be cleared of all debris prior to edge formwork being erected and secured.
All ducts, earth connectors, drainage pipes and bolt assemblies will be inserted in
accordance with the drawings.
Edge formwork will be pre-fabricated and be sufficiently robust for repeated use
across the site. The formwork will be positioned to the required dimensions and
adequately shored. Height checks will be set where necessary and on completion the
base will be offered for inspection in advance of the concrete pour.
Prior to the concrete pour, accurate local weather forecasts will be obtained and
checked for temperature, wind speed and general outlook. The decision to pour will be
based on this information. This data will also be used to determine the curing agents
and protection measured required for the pour.
The concrete will be delivered to the turbine locations in truck mounted mixers and
discharged through a mobile concrete pump into the formwork until the required
profile and level is achieved. Vibrating pokers will be used to ensure the concrete is
adequately compacted. Concrete deliveries will be slump tested and cubes taken at
the required frequency for later testing. The exposed faces will be finished and an
appropriate curing agent applied in accordance with the manufacturers
recommendations. Covers will be applied when necessary to protect from hot or cold
weather.
Formwork will be carefully removed on satisfactory curing (no earlier than 24 hours)
and care taken so as not damage any ducts or inserts.
Reinstatement
Voids around the turbine foundations will be backfilled as required to facilitate cabling
and earthing works and completed on successful testing. Subsoil excavated from the
existing location will be used and topsoil, including any peaty horizons, spread to tie
to existing ground levels. The area will then be turfed or seeded in consultation with
the Site Ecologist.
6.6.
Installation of Wind Turbine Generators
Purpose
To install the components of the wind turbine with no significant adverse ecological
effects.
Procedure
The components of the wind turbine (towers, nacelles and blades) will be delivered
directly from the highway network via the access tracks to the working areas at the
prepared wind turbine bases.
The cranes will be brought to the site in a disassembled condition. The main crane
body is expected to be a self propelled wheeled unit which can drive to site. All
counterweights and boom sections will be delivered by articulated lorries. An
additional tail crane may be required which is a smaller hydraulic telescopic rough
terrain crane. Before moving on the site the main cranes will require disassembling to
reduce the overall weight and the axle loading to a maximum of 15 tonnes. The tail
crane may in some instances move with the counterweights fitted if it is safe to do so.
The towers will be erected from the delivery trailer onto the foundation bolts. The
HGVs and cranes will operate from the track and the hard standing at each base
location.
The nacelle will be unloaded from its trailer and laid adjacent to the base within the
base working area prior to erection on the tower using the crane. Some minor work
on the nacelle will be required on the ground prior to the lift. Upon delivery, the
blades will be fitted onto the rotor. The rotor assembly will then be lifted onto the
previously erected nacelle by crane. Alternatively the hub may be lifted and attached
to the nacelle followed by a one-to-one installation of the blades.
It is anticipated that the installation of each turbine will take 2 lifting days in good
weather, however, the construction programme allows for an element of weather
downtime.
6.7.
Cable Installation
Description
Cables are required between each of the turbines and the substation compound
at the northwest corner of the wind farm site (on land outside of the common)
and will be located alongside the access tracks. The cables will be laid with
minimal disturbance to vegetation and hydrology at the site.
Procedure
The position of trenches will be surveyed and marked out and the line stripped of
turfs and topsoil and set aside for reinstatement. The trench will be excavated to
the required dimensions and the spoil set aside for backfill, if suitable. Where
depth allows, further segregation of the vegetation layer and topsoil will be
undertaken to prevent burying of the upper vegetation layers in deeper soil upon
replacement. Excavators on open ground will be fitted with low ground pressure
bog tracks if necessary. Extreme care will be taken to minimise damage to areas
of significant peat during cable trenching. Trenches will be excavated to follow
the profile of the existing ground where practical. Typically, sand bedding will be
placed and levelled following insertion of earth conductors (if required). The
cables will be laid onto the sand bedding and a further layer of sand installed to
provide suitable protection above the cable. Following testing by the electrical
works contractor, the trench will be backfilled and compacted in layers with
suitable material and reinstated with previously excavated topsoil and turfs.
Cable ducts will be used where the cables pass under sections of track or
hardstandings.
To minimise exposed ground and the potential for surface run-off, cable trenches
will be excavated and backfilled on a rolling basis in short sections. Where
trenches may become conduits for rainfall, clay bunds will be installed at regular
intervals to prevent sub-surface flows.
Reinstatement
Cable trenches will be constructed at the track edges and will therefore be
incorporated into the restoration of the batters. For any small sections of cable to
be installed away from the tracks, the trench construction and backfilling method
employed on site will entail the re-use of topsoil and turfs without the
requirement for additional treatment.
6.8.
Anemometry Masts
The single anemometry mast will be constructed in the position shown on Figure 1.2
in the Environmental Statement. Construction of the anemometry mast base will be
similar in style to that of the turbine bases, but reduced in size to suit the reduced
loads. The mast will be delivered to site in sections and assembled on the ground
prior to the erection using a suitable crane.
6.9.
Control of Water
Description
Control of surface and ground water is of great importance during construction to
prevent exposed soils eroding and silting up surrounding watercourses and to
protect habitats reliant on specific hydrological regimes. It is essential that the
works have little or no impact on the existing hydrology due to the sensitive
ecology of the surrounding countryside and the presence of public and private
potable water supplies.
Procedure
During the construction phase of the wind farm, measures will be adopted by the
Contractor in order to prevent silt from being washed into existing watercourses.
These measures will be based on construction best practice and guidance
provided by the Environment Agency and CIRIA. Areas exposed due to the
removal of vegetation are more susceptible to erosion during heavy rainfall or
through rapid surface run-off so areas will be reinstated as soon as possible to
minimise this effect.
Surface water flows will be captured through a series of drainage ditches to
prevent water entering excavations or eroding exposed surfaces. The flows will
be controlled through the use of settlement ponds, small dams, sediment traps
and other hydraulic features to reduce water velocity (thereby reducing erosive
power), maximise infiltration and evaporation and to remove as much sediment
as possible. Surface water flows will then be discharged across open areas
adjacent to the works to allow further reduction in sediment transfer and
increased infiltration of flows.
Where areas are disturbed, the following measures may be implemented to
minimise these effects:
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Ditches shall be provided adjacent to tracks and other operational areas,
where practicable, and will primarily be used to hold water temporarily and
to encourage infiltration/discharge into the ground locally to where the
rainfall hits the ground. This can be achieved through the provision of
small check dams at regular intervals within the ditches. The stone used
for the construction of the check dams will typically be 20mm „clean‟
graded stone of a type appropriate to the site conditions in order to ensure
that no changes to the base chemical status of surface and groundwaters
arise. On steeper slopes the check dams may be reinforced using larger
stone placed on the downhill side of the dam to prevent washing away of
the smaller stones. The check dams will serve dual functions, both
removing and settling out silts and reducing flow velocities, therefore
mitigating against the effects of erosion within the ditch.
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Under track drainage/pipes will be provided with associated sumps and
check dams. The under track drainage provides a means for flows to pass
from a ditch on the uphill side of the slope to the downhill side of the
slope.
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The level of silt in run-off during construction shall be regularly monitored
and if it is excessive in any area this can be managed by providing straw
bales locally around the problem areas. These will filter the run-off and
trap silt.
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During construction of the turbine bases, hardstandings, and inter-turbine
tracks drainage will be effected by ditches draining either to mini
settlement ponds (where practicable) or to infiltration trenches. These will
either infiltrate the water to the ground or discharge over open vegetated
areas across the site. Any watercourses at risk of being contaminated by
silty run-off water can be protected by slit fences as a precautionary
measure.
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Silt run-off from stockpiles and excavated spoil heaps can be contained
through the placement of geotextile silt fences, mats or straw bales on the
downhill side of the stockpile. Stockpiles will be covered with plastic
sheeting or geotextile materials to prevent erosion through heavy rainfall.
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Any check dams and mini-settlement ponds will be regularly inspected and
maintained to ensure their effectiveness. All excess silts will be removed
and disposed of within site earthworks. Where check dams have become
fully blocked with silt, they shall be replaced in accordance with the
following procedure:
1. Silt deposits to be removed from the upstream side of check dams.
2. Removed silt to be disposed of by spreading in an area of the site
where surface run-off will not convey silt deposits back to a
watercourse.
3. The existing stone check dams are to be removed and disposed of
in the general fill. Stone materials removed from the check dams
should not be disposed of over vegetated areas of the site.
4. Replacement check dam to be installed using fresh stone.
5. Where there is a regular incidence of check dam blockage further
check dams can be installed within the ditches together with
alternative solutions previously described.
Reinstatement
Ditches will remain in place to convey surface water flows during the operational
life of the wind farm. The ditches will therefore be seeded or turfed as soon as
they have been formed to ensure their maximum effectiveness. Check dams and
any settlement pools may also be retained to remove silt and reduce the velocity
of surface water flows.
7.
Prevention of Peat Instability
An investigation into peat instability has been undertaken which has shown the site is
generally safe to develop (See Appendix 11.4 of the Environmental Statement).
However, appropriate construction practices for peatland areas will be implemented at
the Mynydd y Gwair site to ensure that all reasonable measures are taken to prevent
the possible occurrence of peat failure.
A number of recommendations for construction and design practices that would limit
the possibility of peat failure were made following the site investigations and these
are listed below:
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Avoid placing arisings from excavations on slopes covered with significant
(i.e.>300mm) peat.
All water discharged from excavations will be directed into suitably designed
channels in line with previous statements on water control.
Excavations in peat areas will be carefully designed to ensure ground stability and
avoid collapse.
Placing fill and excavations in the vicinity of steeper peat slopes will be avoided.
All infrastructure and access tracks will be located away from the crest of such
slopes unless the ground has previously been assessed as being adequate.
If required, geotechnical supervision of excavations will be provided.
On-going assessment and inspection of ground conditions shall be carried out as
construction progresses.
If poorer ground is encountered, micrositing will be utilised. If this is not
possible, installation and monitoring of geotechnical instrumentation may be
carried out.
Site reporting procedures will ensure that working practices are changed to
reflect changes in ground conditions. Contingency plans may be developed,
detailing suitable responses.
These recommendations will be taken into account when detailed construction method
statements are developed for the Mynydd y Gwair site.
8.
Pollution Prevention Measures
Fuel and Oils
All construction plant will be in good condition with no excessive emissions of
exhaust, oil, fuel or coolants. Plant operators will be required to check machines
daily for oil/fuel leaks and take appropriate action. All re-fuelling will be
undertaken within the designated bunded area of the construction compound.
Absorbent material (spill kits) will be available at all times at both the
construction compound and at all active working areas and will be deployed to
contain drips and small spillages. All other fuels, oils and potential contaminants
will be stored within the construction compound in secure, fit for purpose
containers within bunded containment as appropriate and in accordance with
Environment Agency guidance.
Concrete
All concrete used in connection with the construction of the Wind Farm will be
sulphate resistant. Concrete deliveries will be delivered at the location of the
foundation and transferred to the formwork by truck mounted concrete pump or
by crane and skip method. Optionally direct discharge from the delivery truck
into the formwork may be used as appropriate.
Formwork will be constructed and secured to ensure that no concrete loss occurs
at joints. Any concrete loss will be either removed or contained.
All vehicles, tools and buckets will only be cleaned within a designated area
adjacent to the excavation and the cementitious wash water discharged into a
specially prepared catchpit lined with a geomembrane. This area will then be
excavated and the spoil removed from site by a licensed waste company. The
catchpit will then be backfilled with spare materials from the foundation
excavation.
If a concrete spillage occurs during transfer it will be cleared immediately in
accordance with the requirements detailed in the Emergency Response Plan.
Silt
A number of silt and sediment specific measures are detailed above in the
respective sections, particularly where they refer to tracks or control of water.
There will be no discharge or disposal of any material directly into any river,
stream or drainage ditch. All discharges will be via a settlement tank or lagoon
prior to discharge over ground, thereby allowing percolation or evaporation prior
to entering the nearest watercourse. Where silty water is to be pumped out of
excavations, the water will be pumped out from a sump within the excavation in
order to avoid disturbance to sediments.
Settling lagoons will typically be made from straw bales lined with a suitable
textile membrane or follow other best practise guidance (such as CIRIA Control of
Water Pollution from Linear Construction Projects). The settling lagoons will be
constructed to an appropriate size to suit local requirements. Where necessary a
series of settling lagoons will be used to ensure that no silty water is discharged.
Pumps will be small-bore and will operate continually to prevent large volumes of
silty water building up in the excavation.
Water will be prevented from entering excavations by the use of cut-off ditches
where appropriate.
All site tracks will be kept free of soil and mud deposits, weather permitting.
Small dams will be placed in trackside ditches to aid silt retention. Fording of
rivers and streams will not be permitted.
Temporary topsoil, peat and subsoil mounds will be sited away from watercourses
and drains. Surface water will directed away from construction activity to avoid
silty run-off entering watercourses or ecologically sensitive areas. Where there is
a high risk of fines or silt washing off stockpiles their size and the duration for
which they will be in such a location will be minimised as far as is reasonably
practicable.
Waste and Litter
Contractors will be required to provide a Site Waste Management plan which will
include details on waste minimisation, recycling and disposal of all waste streams.
The requirements of this plan will be implemented on site as required.
With respect to the control of „litter‟ on site, all such waste will be collected and
stored within sealed containers within the site compound and serviced by a
registered waste carrier. No disposal of litter will be permitted at other locations.
Site Induction and Training
The contractor‟s Detailed Construction Method Statement will contain details of
their Site Induction process. All employees and sub-contractors will undergo a
site induction to ensure that they are familiar with the site rules prior to any work
commencing on site. In addition, the contractor will ensure that all operatives and
sub-contractors responsible for handling fuel, oil, concrete or other potential
pollutants undergo a thorough induction programme with respect to the proposed
pollution control measures.
Site inductions will include, as an example, the following:
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Protected species mitigation measures;
Details of exclusion zones;
Habitat protection measures;
Potential sources of pollution and their effects on the environment;
Requirements of the contract and legislation with respect to pollution;
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9.
The contractor‟s pollution avoidance plan;
Traffic management and routing;
The Emergency Spill Procedure;
Emergency Environmental Procedures; and
Training in the use of pollution control equipment.
Emergency Spill Procedure
The appointed contractors will implement an Emergency Spill Response Plan for use in
the event of a pollution incident. The plan will be formulated based on construction
best practise, CIRIA publications and Environment Agency guidelines guidelines.
The contractor will provide and maintain on site, suitable oil spill response kits to deal
with pollution emergencies. In addition, individual items of plant including mobile fuel
bowsers will carry oil spill kits. The contractor will replenish materials which are
removed or expended as soon as possible.
In the event that a spill occurs on site, actions will be taken to limit the amount of
spill by isolating and controlling/stopping the source. The spill will be contained by
applying absorbent material and, in the case of spillage to a watercourse, by the use
of booms. Action will be taken to ensure that no ecologically sensitive area can be
contaminated.
Clean-up operations can proceed by excavation and removal of contaminated ground
and/or mop-up material and removal from the site in a skip, for controlled disposal of
hazardous waste. Consultation with the Environment Agency for further instructions
would follow. A spill/incident report will be produced for any environmental incident.
Near miss reporting will also be undertaken on site to ensure that lessons are learnt
from near miss incidents to prevent more serious re-occurrences.
10.
Private Water Supplies
A number of properties have been identified which utilise private water supplies
sourced from a spring, borehole or well, which are potentially at very low, but nonnegligible, risk of contamination during construction. Water quality monitoring may
be undertaken throughout the works to ensure no negative impacts occur.
Environmental controls will be put in place as discussed in previous sections to
construction best practises and the Environment Agency pollution control guidelines.
An Emergency Plan shall be put in place to ensure prompt response to any complaint
of perceived impact on private water supplies, including monitoring of the water
supply in question and the immediate cessation of associated water-sensitive
construction activities.
11.
Prohibited Activities
Description
The works contractors will be expected to have due consideration for the
environment in which the works are located. The contractor will therefore ensure
the sympathetic development of the site and restrict practices which could have a
negative effect on the ecology of the site following construction.
Procedure
The following activities will be prohibited:
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Work on site by any personnel who have not completed the site induction
process, including health and safety and environmental management
training.
Entry of plant or personnel to any areas outside of designated working
areas;
Unauthorised construction work near protected species sites;
Disposal of waste materials on site;
Use of seed mixes that haven‟t been authorised by the Project Ecologist;
Lighting of fires;
The presence of pets;
Vehicles parking and operating outside of designated parking areas;
Fuelling outside of designated areas;
Direct discharge to waterlogged areas, flushes, streams or other surface
waters.
In addition to the above, a set of site rules will be developed based on previous
experience and introduced to all authorised persons working on the site. Visitors
will be escorted. A suitable site passport carrying the site rules and authorising
the person carrying the passport will be available.
12.
Environmental Monitoring
Description
The Site Management team will call on specialist consultants (i.e. ecologists,
hydrologists, ornithologists etc) as required to ensure that construction is being
carried out in accordance with the requirements set out in the Environmental
Statement, the conditions attached to the planning permission, environmental
best practise and the approved Method Statements.
Procedure
A series of site visits will be completed by the consultants throughout the relevant
periods of construction, particularly when new activities commence on site. The
appointed consultants will confirm that the planned arrangements are being
followed and if any non-compliance is identified, these will be discussed with the
site management team and remedial measures identified and implemented. A
short site visit report will be produced identifying good practices and potential
improvements.
13.
Working Hours
The construction programme will be based on a working week of 5.5 days, 07:00 to
19:00 on weekdays and 07:00 to 12:00 on Saturdays (subject to planning).
Generally, night time or Sunday work will not be permitted. However, working at
night, outside daylight hours and on Sundays may be required to disassemble, move
and re-assemble the main cranes if, for any reason, this work is not completed within
normal working hours. It is essential that the crane movement takes place as
programmed in order not to slow down turbine erection work. Furthermore, critical
operations, (eg a foundation concrete pour that cannot be stopped before completion
or the lifting of turbine parts where the work has to continue to a safe condition) may
require working outside of standard hours.
If work is undertaken outside of normal working hours it is likely to involve operation
of generators, machines and cranes.
No blasting operations are proposed under the works.
Floodlighting may be provided during extended working hours or periods of early
darkness to ensure safe working conditions. The floodlights will be positioned in such
a way as to limit light pollution in the direction of local residents or ecologically
sensitive receptors. Lighting will be powered by mobile generators which will have
drip traps and will be re-fuelled by an approved mobile fuel bowser using a suitable
pump and hose.
14.
Staff Movements
It is generally necessary for security to be present on site outside of work hours.
Other than security, there will be no overnight presence on the construction site. All
personnel will meet in the morning and depart after completing their work. It is
assumed that most workers will use minibuses or vans to travel to the site, although
there may be a number of private cars used along with various contractors‟ fourwheel-drive vehicles.