O RENEWABLE ENERGY L - Orkneywind 2888 Chapter 6.pdf · Orkney Renewable Energy Ltd Document...

Registered Office: 8 Albert Street Kirkwall KW15 1HP Registered in Scotland: SC232619

ORKNEY RENEWABLE ENERGY LTD.

Berriedale Wind Energy Project

Road Construction and Transportation

Report ORE/2888 Chapter 6

January 4th 2011

RE LTD.

Orkney Renewable Energy Ltd Document OSE/2888 Chapter 6 05/01/2011

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Summary

1.1 A locally owned wind energy project is proposed for the coastal slope above the farm of

Berriedale in the island of South Ronaldsay in Orkney. The project will consist of three

medium sized wind turbines and a new switchgear building, with existing and new

tracks used for access, all to be owned by a local development company.

1.2 The turbine sites and the route of the access tracks have been subject to assessment,

with ground conditions noted and mapped. The project layout has evolved over the

assessment period, and as the project has been designed to have minimum ecological

impact, care has been taken to avoid areas of sensitive habitat.

1.3 Construction stone, concrete and all turbine components shall be delivered to the site

along public roads. The turbine components shall be delivered by sea from Germany to

Hatston Harbour near Kirkwall then delivered by extended trailer through Hatston

Industrial Estate to the Ayre Mills roundabout and the A963 Pickaquoy Road to The

Crafty roundabout, turning right, along Junction and New Scapa Roads, to Holm

Branch Road Turning right onto the A961 Holm Road through Holm and via the

Churchill Barriers and Burray to a widened site entrance at Berriedale Farm.

1.4 Construction stone and concrete will come from existing Orkney quarries and ready-

mix plant, and transportation will follow a direct route via the A965 and A961.

1.5 Assessment of the volume of materials required, the total weights and traffic numbers

has been calculated, and a method statement for the track, foundation and hardstanding

construction has been completed.

1.6 Carbon balance calculations have been completed, comparing the volume of carbon

emissions from concrete production, against the carbon dioxide emission avoidance of

renewable energy production from the wind turbines.

1.7 This report has been broken down into three parts; track and foundation construction,

analysis of the public road network for delivery and transportation of turbine

components and possible environmental risks are considered for all aspects of the

construction process, with mitigation considered where required.


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2 Track, Foundation and Hardstanding construction

2.1 The proposed site is the coastal slope above Berriedale Farm, South Ronaldsay. The

project will consist of three wind turbines each with a maximum height of 67m, short

lengths of new access track, crane hardstandings and a switchgear building and an

upgraded existing farm track. Turbine locations have been established following

detailed environmental assessment and are within an area of arable fields.

2.2 The small control building is to be located alongside the existing 3 phase 11kV

overhead power line. The existing access track shall be upgraded to accommodate the

large delivery vehicles.

2.3 The hardstanding areas shall have a layered construction. If required, geotextile will be

placed on the excavated surface, with imported crushed rock aggregate placed on top to

form a sub-base layer, followed by a road-base layer. To mitigate any surface run-off

problems the track will only be constructed in dry conditions. Construction of the

hardstandings will follow the general SuDS guidelines published by SEPA, with a

porous construction and a free-draining sub base[1].

2.4 The small quantity of topsoil extracted during excavation work will be used to infill

depressions in existing fields, and to create bunds and soak-away barriers as

recommended in the Hydrology report. Turbine foundations and hardstandings shall be

created, consisting of a layer of free-draining crushed stone 30m x 20m in plan, with a

nominal excavation of 15m diameter for the foundations.

2.5 The total volume of concrete required for the turbine foundations shall be around

525m3. The volume of crushed or excavated rock material for hardstandings shall be

around 720 m3. The requirement for the sections of new and upgraded track will vary

according to ground conditions, however the maximum predicted quantities are as

follows, Table 1. It has been assumed that all rock fill material shall be imported to the

site, however it is likely that rock arising from the foundation excavation shall be used

in the construction, reducing the quantity of imported material significantly.


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Section Sub-base Road – base

Site access tracks 1151m x 4m x 200mm = 921m3 1151m x 4m x 200mm = 921m3

Hardstandings 3x 30m x 20m x 200mm = 360m3 3x 30m x 20m x 200mm = 360m3

Totals 1281m3, or 715T 1281 m3, or 715 T

Table 1; Maximum predicted stone quantities

2.6 It is intended that a local quarry will be used to source the stone. The estimated volume

of stone required from Table 1 is 2562 m3, and although stone will be produced during

the levelling and excavation of the road and foundations, this represents the maximum

volume that could be delivered to site. Allowing for large vehicles with 24 T per load,

approximately 63 loads shall be required for all construction work.

2.7 Concrete will be delivered to site as ‘readymix’. The turbine foundations shall require

around 525 m3 of concrete, with a limit of 8m3 per load. The concrete trucks shall carry

water, with no need for local abstraction. This volume of concrete is equivalent to 66

loads, although in practice it may be more appropriate to deliver larger batches to the

area.

2.8 Summary construction method statement:

a. Used crushed stone to provide hard standing, graded to match existing slopes.

b. Site office, mess, toilets and any materials storage to be sited on a temporary hardstanding at the turbine site.

c. Topsoil extracted during the construction of the tracks and hard standings should be stored on dry ground prior to distribution around field depressions.

d. The turbine hardstanding is to be constructed with crushed rock from suitable excavated material, with sub-base and road base layers of quarried stone as required.

e. Excavate soil and sub-surface rock till, then cast reinforced concrete foundation in-situ on hard strata and bedrock.

f. Access track and hardstanding are to be unsurfaced and porous with adjacent bunds and filter strips; active drainage is not required.

g. Landscaping of site track; no side slopes, track to be flush with existing ground.

h. Topsoil fill - finished to merge with existing slopes and reseeded to match adjacent land. Use extracted soil to fill land depressions on the adjacent fields.


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3 Access Route

3.1 The route to the site has been considered taking into account the transport requirements

of the Enercon E44 wind turbine, and analysis of the main route between Kirkwall and

the site has been undertaken, Appendix 1.

3.2 The Road Vehicles (Authorisation of Special Types)(General) Order 2003 – STGO.

STGO permits certain types of vehicles to be used on roads notwithstanding that they

do not fully comply with the requirements that generally apply to vehicles permitted on

roads. The Construction and Use Regulations 1986 (C&U) apply to loads which are

wide or long but not heavy. Vehicle and load lengths can be up to 27.4m long and

weigh a maximum of 44T under C&U, up to 30m under STGO and vehicles or loads in

excess of 30m require a Special Order. Widths above 2.9m and less than 4.3m are

permitted under C&U, widths between 4.3m and 5.0m are permitted under STGO and

widths between 5.0m and 6.1m require a Highways Agency Special Order [2].

3.3 The Enercon E44 has a 22m long blade, while the largest tower section would be 22m

long, and no wider than 3.5m, Appendix 2. Maximum weight is 29T for the bottom

tower section, 30T for the nacelle, and the blades weigh a total of 8T. The E44

components are permitted loads under the requirements of the Construction and Use

Regulations, and can be delivered to site over A-class public roads. The police and

Orkney Islands Council Roads section shall be given advance notice. The E44

components are not Abnormal Indivisible Loads as defined under STGO and

accordingly a BE16 permit will not be required.

3.4 The turbine components will be delivered by sea from the German factory to Hatston

Pier in Kirkwall then delivered by extended trailer along the route previously outlined.

Analysis of the transportation route has identified no potentially difficult locations.


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4 Delivery of components

4.1 The transport route has been determined by travelling the roads from Hatston Pier in

Kirkwall to the turbine site. There should be no difficulty in transporting components

of the wind turbines along the public roads.

4.2 There will be five large loads for each turbine: a bottom tower section, approximately

22m by 3.5m diameter, a narrower upper tower section 22m long, a nacelle which

weighs 6.3T, a generator which weighs 24T, a set of 3 blades, each 21.5m long, 2.7m

high and 2.44m wide and a load consisting of the hub and internal fittings. In addition a

crane will be required for the final assembly, which is delivered as a permitted load

under C&U regulations.

4.3 In addition a transformer shall be delivered to site, along with high voltage switchgear

and cabling. The detailed turbine construction programme will be issued at the time of

construction, but can be summarised as follows. Cranes will be needed to offload from

the transporters and to lift and assemble the components, and a large 350T telescopic

crane will be required for assembly:

1 Deliver and install the transformer onto the foundation.

2 Erect the lower tower section directly off the trailer onto the foundation;

3 Deliver the upper tower section and nacelle to the site;

4 Erect the upper tower section and nacelle;

5 Deliver set of blades to the site and assemble on to hub to form rotor;

6 Install the rotor assembly on the turbine nacelle.

4.4 The delivery of long loads through Kirkwall has the greatest potential for disruption,

with traffic management required. Although there are alternative routes for other

vehicles, the most appropriate time to deliver these components is during the daytime

and midweek. Before any components are transported to site, the project owners and

project manager will consult with Orkney Islands Council Roads Section and the Police

to ensure acceptability of the route to site. Existing public road culverts, bridges, verges

and street furniture will be surveyed by the project developers in conjunction with the

Roads Section. A schedule of loads and a timetable will be prepared and circulated

prior to delivery. Road warning signs and lights will be located at all areas of road

works and any items such as fence posts and road signs that have been temporarily

removed will be re-erected following transportation.


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5 Environmental impact and mitigation

5.1 A carbon balance calculation has been completed, based on recommendations from the

Carbon Trust. It should be noted that carbon loss was considered when examining the

soils, and CO2 emissions were considered when examining concrete manufacture.

5.2 The maximum volume of topsoil that could be disturbed is approximately 1387 m3,

consisting of the new access tracks and hard standing area, a total area of 3468 m2 at an

average depth of 0.4m. The carbon content of peaty soils has been discussed by

Chapman et al[3] and for the Berriedale assessment a figure of 0.069 tonnes of carbon

per cubic metre of superficial deposit has been used; the carbon content of the soil is

estimated to be 96 tonnes.

5.3 The carbon emission factor of grid electricity is 0.117 T/MWh [4] and assuming a mean

windspeed of 8m/s, three 900kW wind turbines in this area will produce an annual

energy yield of around 10500 MWh at a capacity factor of 45%. An average production

of 28.8 MWh per day, giving a positive carbon balance of 3.37 T per day; 28 days of

generation are required to compensate for the potential carbon released from the topsoil.

It should be noted that the construction process will retain the integrity of the soil

systems, and all topsoil will be reused in other parts of the farm to avoid the release of

carbon.

5.4 It is recognised that concrete production results in the emission of CO2 from both the

energy required during manufacture and from the calcining of limestone when

producing cement. A cubic metre of concrete is made from 2T of aggregate and 450kg

of cement and the project will require approximately 525 m3 of concrete. 525 m3 of

concrete requires 210 T of cement, and assuming 0.75T of CO2 per tonne for the energy

requirement, and 0.5T of CO2 per tonne from the calcining of limestone[5], , the total

CO2 emissions during concrete manufacture for the project is 263 T. Using a CO2

avoidance factor of 0.49T CO2/MWh from an average daily production of 28.8 MWh,

the wind turbines provide a positive CO2 balance of 14 T per day; 19 days of generation

are required to compensate for the carbon dioxide released during concrete

manufacture.

5.5 The construction activities during mobilisation and installation of the turbines represent

a pollution risk. This may be through operational discharges or as the result of an

unplanned or accidental event. Measures will be taken to protect against the release of

any material with the potential to leach into the soil or water courses.


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5.6 The construction of the access track and the areas of hardstanding have a potential

pollution risk, and SEPA’s Pollution Prevention Guidelines PPG2, PPG4, PPG5, PPG6,

PPG8 and PPG21 have been adopted by the project[6]. To combat the potential risk of

run-off from these areas, it is proposed that some of the mechanisms used to construct

Sustainable Urban Drainage systems be adopted, using methodologies recommended in

the Control of Water Pollution guidelines CIRIA C532, C649, C648 and CIRIA C697

the SuDS Manual; a permeable surface on the upper access track will allow water to

pass through the upper layer, along with filter strips and bunds of vegetated soil to

providing filtering and flow attenuation of water run-off.

5.7 The construction of the wind turbine foundations involves pouring fresh concrete, and

has the greatest risk of pollution impact. The nearest watercourse is around 50m from

the nearest turbine location, reducing the risk of pollution run-off and it is proposed that

all concrete be brought onto site in ready mix trucks to minimise the risk of spills.

Cleaning of formwork and the washing of equipment will only be done away from site.

To minimise risk of pollution from oils and fuels during project construction, all work

will be to COSHH regulations[7] and any machinery, equipment or construction material

will be located on the area of hardstanding clear of water courses. Any waste will be

transported away from the work area and disposed of using standard waste handling

procedures.

5.8 Silt run-off, both direct and indirect to watercourses, can cause problems to burns and

rivers. Silt can access watercourses both by uncontrolled overland flow and directly by

percolation into field drains and rock fractures. At Berriedale the existing site access

track drains to the adjacent ground.

5.9 Fuel or oil pollution from the construction vehicles would have a serious affect on water

quality should it enter any water courses, and accordingly fuels will be managed in a

bunded storage area, well away from any water courses, and good site management will

be established. Refuelling activities for construction vehicles and equipment will be

restricted to contained areas of hardstanding at the fuel storage area, and to minimise

the potential for contamination of land, any spills would be contained during fuel

transfer, and a store of absorbent material will be provided on site.


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References, web links and bibliography

1 SEPA recommendations on drainage systems in Scotland - Sustainable Urban Drainage

Systems (SUDS). http://www.sepa.org.uk/publications/leaflets/suds/?lang=_e

2 The Road Vehicles (Authorisation of Special Types)(General) Order 2003.

http://www.dft.gov.uk/stellent/groups/dft_rdsafety/documents/page/dft_rdsafety_023695-

01.hcsp

3 Chapman, S.J., Towers, W., Williams, B.L., Coull, M.C., Paterson, E. (2001) Review of the

Contribution to Climate Change of Organic Soils Under Different Land Uses. Scottish

Executive Central Research Unit.

4 The Carbon Trust. Guidelines on measuring carbon and CO2 emissions from electricity.

http://www.thecarbontrust.co.uk/carbontrust/low_carbon_tech/dlct2_1_6.html

5 Boden, T.A., G. Marland, R.J. Andres, (1995). Estimates of global, regional, and national

annual CO2 emissions from fossil-fuel burning, hydraulic cement production, and gas flaring:

1950-1992, Oak Ridge National Laboratory. Report ORNL/CDIAC-90, NDP-030/R6.

6 SEPA pollution prevention guidelines http://www.sepa.org.uk/guidance/ppg/

7 Control of Substances Hazardous to Health COSHH Regulations http://www.hse.gov.uk/coshh/


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Figure 1: Route from Hatston Harbour to Berriedale

Appendix 1

Transport Route


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Figure 2: First stage of route from Hatston Harbour

Figure 3: Route through Kirkwall


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Appendix 2

Turbine weights and dimensions

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