Jetty Environmental Standard Chapter 6 - Project Description- Temporary Jetty Development

7/26/2019 Jetty Environmental Standard Chapter 6 - Project Description- Temporary Jetty Development

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Hinkley Point C Preliminary Works Environmental Statement

Temporary Jetty Development 6-1 November 2010

6 PROJECT DESCRIPTION: TEMPORARY JETTY DEVELOPMENT

6.1 Introduction

6.1.1 This Chapter describes the proposed temporary jetty development and includes

descriptions of its on-shore and off-shore infrastructure components (see Section 6.2)

and its phases, as follows:

construction (see Section 6.3);

operation (including maintenance) (see Section 6.4); and

dismantling and restoration (see Section 6.5); or

removal and site reinstatement, following construction, should a DCO for the

Hinkley Point C Project not be granted (see Section 6.6).

6.2 Temporary Jetty Infrastructure

6.2.1 The proposed temporary jetty development would be located within the HEO application

site shown in Figure 1-1, Volume 3 and would include the works shown inFigure 1-2,Volume 3.

6.2.2 The jetty is proposed as a two-staged structure that can be constructed in a manner that

accommodates the emerging transport demands of the Hinkley Point C Project, so that

the first stage could operate alone without the second stage. However, it is expected

that the two stages would in fact be built as one structure under one construction

programme (i.e. stage two would be constructed once stage one is in place without any

interval). This is reflected in the HEO application, which proposes the jetty development

in its entirety. Accordingly, this ES describes the jetty development in its entirety.

a) On-shore Infrastructure

6.2.3 The following paragraphs describe the on-shore infrastructure associated with the jetty

development.

Rock Extraction Area

6.2.4 A rock extraction area (see Figure 1-2, Volume 3 and Section B-B, Figure 6-1,

Volume 3) would be created in the south-east corner of the application site to provide

suitable granular fill material for construction of the development platform for the

aggregates storage area (at a finished level of 20m AOD) and service road.

6.2.5 At present, the land at the rock extraction site varies between approximately 16m and25m AOD. Following extraction, the rock extraction area would have a level of around

14m AOD.

6.2.6 A crushing plant would be used to process the extracted rock to the required

specification. This plant would have tracks, screens, conveyors, a hopper / feeder unit,

a crushing chamber and a power unit.

Service Road

6.2.7 The service road (see Figure 1-2, Volume 3 and Typical Section E-E, Figure 6-1,

Volume 3) would be aligned approximately in an east-west direction between the

aggregates storage area and the existing Hinkley Point Power Station Complex accessroad. The route would follow, in part, an existing farm track and would cross the Hinkley


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Point C Drainage Ditch and a number of existing Public Rights of Way (PRoWs). It

would also branch off to the north to provide a means for limited temporary access to the

foreshore to facilitate construction of the initial jetty bridge spans using land based plant

on the upper foreshore. In addition, the service road would be aligned in a north-south

direction from the existing internal road to provide access to the rock extraction area

(see Figure 1-2,Volume 3).

6.2.8 The service road would be 8m wide to allow two-way vehicular access. Its surface

would comprise 500mm of compacted granular fill. Approximately 5000m3 of

compacted granular fill would be sourced from the rock extraction area and crushed to

the correct size before being used for the service roads construction. Surface water

run-off would fall into a soakaway running along each side the service road.

6.2.9 Where the service road crosses the Hinkley Point C Drainage Ditch, it is proposed to

locally culvert the ditch at the position of an existing crossing using a 1.25m diameter

concrete pipe approximately 16m in length.

6.2.10 Where the service road branches north to the foreshore, it would be constructed usingcompacted granular material, slope at 1 in 10 maximum and be 4.5m wide. It is

anticipated that this would be a short-term, temporary structure, that would be built (c.1

week), operated (c.3 months) and dismantled (c.1 week) within the overall programme

for the jetty developments construction phase.

Aggregates Storage Area

6.2.11 The aggregates storage area (see Figure 1-2,Volume 3and Section A-A, Figure 6-1,

Volume 3) would be positioned close to the landward limit of the jetty in order to

minimise conveyor/pipeline distances required for materials transfer to the stockpiles (for

stone and sand) and silos (for cement), and to facilitate future concreting operations for

the Hinkley Point C Project.

6.2.12 The aggregates storage area would comprise a concrete hardstanding area at a level of

approximately 20m AOD, on which the storage facilities would be laid out. Eight

uncovered aggregate stockpiles (including gravels) and six covered sand stockpiles

(including sand and stone dust) would be situated beneath an inclined conveyor and

tippers (that would extend from the jetty bridge) (see Figure 1-2,Volume 3and Section

A-A, Figure 6-1, Volume 3). An inclined conveyor would rise from the jetty to an

elevated horizontal position above the stockpiles and discharge into the individual

stockpiles. The stockpiles would be separated by low walls / bunds to avoid cross

contamination. The sand stockpiles, as noted above, would be enclosed within a canopy

structure to control fugitive dust emissions.

6.2.13 Cement would be stored in up to eight silos (see Figure 1-2,Volume 3and Section A-

A, Figure 6-1, Volume 3). The silos would have a maximum height of 20m and a

maximum diameter of 12m. The current design seeks to minimise height by assuming

fluidised discharge and indicates that the silos themselves (c.15m) would have flat

bottoms and tops, would be supported on the ground by structural steelwork (c.3m), and

have a dust extractor (2m) on top (i.e. 20m high in total). The design also shows the

silos being c.7m in diameter and closely spaced at 8m intervals (centre to centre). It is

anticipated that the storage would include both ordinary Portland cement and cement

replacement products (e.g. pulverized fuel ash (PFA)).


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6.2.14 It is envisaged that two additional silos would be required to store the volumes of

cement required during the peak concrete production periods during the construction of

Hinkley Point C. These silos are expected to be larger (e.g. c.35m in height and c.12m

in diameter) and would form part of EDF Energys application for a DCO for the Hinkley

Point C Project. They are, therefore, not included in the HEO application and are not

covered by this ES.

6.2.15 The storage area would incorporate a drainage capture system which would comprise

open drainage ditches and underground pipes, and feed into an oil water separator (see

Figure 1-2,Volume 3). This system would discharge into a water management zone

(WMZ; see Figure 1-2,Volume 3), which would regulate the flow into the Hinkley Point

C Drainage Ditch (and, ultimately, Bridgwater Bay) to greenfield rates. The WMZ would

cover an area of approximately 50m by 30m and would be approximately 3m deep.

Contractors Site Compound

6.2.16 To aid construction, a dedicated facility would be established adjacent to the aggregates

storage area (see Figure 1-2,Volume 3). This facility would be sized to accommodateup to 60 construction workers and include temporary offices, mess facilities and a toilet

block. These facilities are expected to take the form of Portakabin type structures.

6.2.17 The facilities would be connected to services such as water supply, electrical power and

sewage facilities, all of which would be temporary services for the duration of the

construction works only. The water supply would comprise a bowser which would be

filled from the existing water supply located in the area of the site entrance. The

electrical supply would be provided by a diesel powered electrical generator. The

generator and its fuel supply would be bunded to prevent the discharge of spillages into

the adjacent watercourse (i.e. the Hinkley Point C Drainage Ditch). The sewage

treatment facility would be an underground cess pool or similar, suitably sized for the

number of staff and duration of the works. This would not be connected and, therefore,

would not discharge into the adjacent watercourse.

Fencing

6.2.18 The aggregates storage area would have its own security fence (see Figure 1-2,

Volume 3). Initially, this fence would comprise a 1.8m tall chain link fence. The line and

level of the fence would follow the existing topography and surround the confines of the

aggregates storage area. The fence would be moveable to allow potential re-positioning

during the works. Once fixed in position, barbed wire protection would be added to the

top of the fence, which would increase its height to approximately 2.14m.

Soil Storage Areas

6.2.19 Two soil storage areas (see Figure 1-2, Volume 3) would be created to store the topsoil

and subsoil arising from the cleared sites for the aggregates storage area and the rock

extraction area. The soil storage areas would be created on land situated to the east of

the aggregates storage area and to the north of the service road.

6.2.20 The western topsoil storage area would have an approximate 100m x 110m footprint

and be 2m in height, while the eastern subsoil storage area would have an approximate

100m x 50m footprint and 3m height (sized to accommodate the estimated volumes of

soil to be stored).


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b) Off-shore Infrastructure

6.2.21 Plans and cross-sections of the jettys off-shore infrastructure are shown in Figure 6-2,

Volume 3. Photomontages of the jettys off-shore infrastructure are provided in Figure

6-3,Volume 3.

Stage 1 Summary

6.2.22 Stage 1 of the jettys development includes most of its main elements, including the jetty

bridge, jetty head, berthing pocket, materials handling and conveyance equipment (see

Figure 6-2,Volume 3).

6.2.23 The jetty would extend into the Ministry of Defences (MoD) Lilstock Range Danger Area

(D119), which includes a target area for military helicopter gunnery training. Ongoing

discussions between EDF Energy and the MoD indicate that the target area would be

moved westwards (i.e. away from the jetty) by the repositioning of its marker buoys.

Jetty Bridge

6.2.24 The jetty bridge would extend landwards from the jetty head to the aggregates storage

area (see Figure 1-2, Volume 3). It would be approximately 490m long and 11.5m

wide. Based on a review of maximum wave heights and a 5m wave on mean high water

springs (MHWS), the bridges deck level is positioned so as to provide a minimum 1m

air gap between the wave crest and the underside of deck beams. The deck level at its

seaward end would be +16.5m CD (i.e. 16.5 metres above Chart Datum), which equates

to 10.6m AOD (i.e. 10.6 metres above Ordnance Datum) (see Section C-C,Figure 6-2,

Volume 3). From this point, the bridge would rise on a constant grade to meet the

ground level on land which would be at +25.9m CD (i.e. 20m AOD) (see Section A-A,

Figure 6-1,Volume 3).

6.2.25 The bridge comprises a steel box truss structure supported on concrete cross-heads,

which in turn are supported on raking steel tubular piles driven into the bedrock (see

Section C-C, Figure 6-2, Volume 3). The box truss structure is of consistent form

along the whole bridge up to the last span to the jetty head, where two smaller trusses

accommodate the aggregates conveyor and cement pipeline. A typical crosshead

would have two raking piles but at main bridge joints there would be four raking piles. A

special cross head would be required at the location of the transfer hopper which would

be larger than the other cross heads. The box truss structure provides stability to the

bridge and the opportunity for large spans between the supporting cross heads of

between 25 and 35m, thereby reducing the number of piles and the construction

programme. The number of bridge piles in the arrangement is between 45 and 55depending on the final detailed design of the maximum possible span.

6.2.26 The truss structure would incorporate a pipeline for transporting cement on its western

side, a conveyor for aggregates on its eastern side and service ducts along its internal

western face (see Section C-C,Figure 6-2,Volume 3). These, along with the open

steel mesh flooring, would be supported on longitudinal steel deck beams which, in turn,

would sit on transverse deck beams which are integral with the box truss structure.

6.2.27 Maintenance walkways would be provided on either side of the pipeline and conveyor,

with the primary walkway being centrally located. Hand-railing would be provided on

both sides of the structure for the full length of the bridge. The central walkway, which is

1.5m wide, would be used primarily for pedestrian access to the jetty head, as a central


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maintenance (and emergency) route, and for the transportation of small equipment and

materials by using, for example, a wide wheel based trolley.

6.2.28 Where the jetty bridge connects to the land, it would be necessary to cross over the

coastal footpath and, therefore, minor works may be required to ensure that all health

and safety requirements would be met. For example, the footpath may need to be

lowered slightly to create headroom of some 4m, and a protective cover may need to be

constructed under the approach bridge to ensure that any spillage from above does not

pose a risk to the public using the footpath. Cover could comprise either a self-

supporting structure (e.g. an arch culvert tunnel) or a structure suspended from the

longitudinal beams.

6.2.29 The jetty bridge would not include a dedicated surface water drainage system. Rainfall

run-off would drain directly into the sea.

Jetty Head

6.2.30 The jetty head would comprise a concrete head sized to accommodate 5000 deadweight tonnage (dwt) self-discharging aggregates vessels (e.g. barges) and 2500 to

5000 dwt cement carriers (see Plan, Figure 6-2, Volume 3). This arrangement

assumes that dredgers would discharge from port aft (i.e. from the back of the vessel on

the left-hand side facing the bow).

6.2.31 The size of the main jetty head is expected to be in the order of 60m by 15m, and is

primarily based on providing a suitable berthing face and the requirement to

accommodate cement handling equipment. It is anticipated that the jetty deck would be

a 1.5m thick reinforced concrete slab supported by a combination of both vertical and

raking piles (70-90 in total). Some piles would need to be anchored to withstand the

berthing loads.

6.2.32 The jetty head would have a fendered face to accommodate the berthing energy from

the laden vessels over a range of tides. Emergency access ladders and associated

equipment would be provided on the jetty deck.

6.2.33 It is anticipated that the jetty head would have a mooring dolphin at its eastern and

western ends. The dolphins would consist of a concrete cap supported by raking steel

piles (although, at detailed design stage, consideration could be given to using

monopole construction for the dolphins). The dolphins would be accessed via steel

walkway bridges and would take the vessel mooring ropes.

6.2.34 The berthing face of the jetty head would be parallel to the prevailing dominant east-west tidal current direction and generally parallel to the prevailing west through to south-

west winds. This approach to the berths design should assist vessel manoeuvring

because, for example, berthing with the ship heading into the prevailing conditions is

preferable as it allows greater control of the vessel.

6.2.35 The jetty head would not include a dedicated surface water drainage system. Rainfall

run-off would drain directly into the sea.

6.2.36 Some basic welfare facilities would be accommodated on the jetty head. A welfare

cabin (see Plan, Figure 6-2,Volume 3) would include a self-contained portable toilet

which would be regularly emptied (i.e. it would not discharge to sea or into a foul

drainage connection).


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Berthing Pocket

6.2.37 It is considered necessary for the berth to operate with vessels afloat rather than on the

seabed (i.e. not using a Not Always Afloat But Safely Aground (NAABSA) berth) due to

the exposed nature of the berth. Aggregates vessels would operate within tidal access

windows which are estimated to be 7 hours on spring tides (giving 5.5 hours for off-loading) and 7.5 hours on neap tides (giving 6 hours for off-loading). Cement carriers

would need some 15 hours to off-load and would have to remain at the berth during low

water; hence there would be a preference to deliver cement on neap tides, when there is

least difference between high and low water levels.

6.2.38 In order to increase the tidal window available for off-loading the cement carriers without

going aground, a berthing pocket would be dredged seaward of the jetty heads berthing

face (see Figure 6-2, Volume 3). The berthing pockets dimensions would be

approximately 160m long by 27m wide by up to 3m deep. The sides of the berthing

pocket would have slopes of 1 in 5. An additional depth allowance of up to 0.5m could

be dredged due to over-dredging of the berthing pocket, making a total depth of up to

3.5m. This is because it is assumed that the appointed dredging contractor would over-dredge by up to 0.5m to ensure that the required 3m depth is provided across the

berthing pocket.

6.2.39 Given the berthing pockets dimensions and side slopes, approximately 22,725m3 of

dredged material is expected to arise from the berthing pocket. The maximum potential

for over-dredging (i.e. by 0.5m) would add up to 2,160m3dredged material. Therefore,

the total volume of dredged material that would arise from the berthing pocket would be

approximately 24,885m3.

Disposal of Dredged Material

6.2.40 It is anticipated that the dredged material would be disposed of at an existing off-shore

disposal site known as the Cardiff Grounds (see Plate 6.1and Chapter 7).

6.2.41 The Cardiff Grounds is one of a number of existing off-shore disposal sites located

within the Bristol Channel that are established to receive dredged material. For

example, there are various sites off Cardiff, Swansea Bay Outer and Newport along the

Welsh Coast, off Portishead and Avonmouth along the English coast, and in the middle

of the Bristol Channel at a site known as the Merkur Buoy.

6.2.42 It is anticipated that a degree of in-filling of the berth pocket could occur over time and,

hence, maintenance dredging of the pocket could be required over the operational

period for the jetty.

Materials Handling and Conveyance Equipment

6.2.43 The jetty development would incorporate materials handling and conveyance equipment

for imported aggregates and cement.

6.2.44 For importing aggregates, there would be a height adjustable aggregate receiving

hopper to the east of the jetty head, which would be connected to an articulated

conveyor arm (see Plan, Figure 6-2, Volume 3). The supporting structure for the

hopper is provided by the jetty head and the adjacent mooring dolphin. This adjustable

hopper is necessary to allow discharge from a self-discharging dredgers conveyor over

various states of the tide. When not in use, it can be stowed at jetty deck level so as to

prevent damage from wind and waves. Aggregate deposited in the receiving hopper


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would be transported along an articulated conveyor arm and deposited into a transfer

hopper on the jetty bridge and, thereafter, along the jetty bridge via the conveyor to

stockpiles at the aggregates storage area.

Plate 6.1 Location Map of the Cardiff Grounds Off-shore Disposal Site

6.2.45 For importing cement, there would be a loading arm and cement receiver and booster

on the jetty head (see Plan and Section D-D,Figure 6-2,Volume 3). The loading arm

would be used to connect a vessels onboard cement discharge pipe to the jettys

cement receiver and booster for the pipeline to shore.

Aids to Navigation

6.2.46 New navigation aids are proposed to provide safe navigation for vessels using and

passing the jetty (see Plate 6.2; source Eagle Lyon Pope, 2009 (Ref 6.1)).

6.2.47 It is expected that the western end of the jetty head and the eastern mooring dolphin

would be each marked with two fixed green lights in a vertical line with a range of three

nautical miles (nm). Since it is estimated that there could be some 15 days a year with

fog, it is expected that there would be a fog signal to alert any passing small craft of the

jetty position, especially as the jetty is proposed to extend into Bridgwater Bay.

6.2.48 It is also expected that the 2m bathymetric contour is marked by lit green marker buoys

situated to the west and east of the jetty to indicate the limits of the shallow water duringvessels approaching and departing manoeuvres (see Figure 1-2,Volume 3).

Hinkley Point


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Plate 6.2 Indicative Aids to Navigation for the Jetty

Stage 2 Summary

6.2.49 Stage 2 of the jettys development includes provision of a roadway along the jetty bridge

and extension of the jetty head to accommodate a turning circle (for trucks) and

deployment of a mobile crane (see Figure 6-2,Volume 3).

Roadway along the Jetty Bridge

6.2.50 It is anticipated that a roadway would be built along the jetty bridge as an independent

structure adjacent to the truss bridge already in place, but supported by the existing

concrete cross heads and raking piles (see Section C-C,Figure 6-2,Volume 3). The

roads deck arrangement would comprise pre-cast concrete deck units on steel beams

and provide a road that would be 5m wide.

6.2.51 The roadway would not include a dedicated surface water drainage system. Rainfallrun-off would drain directly into the sea.

Jetty Head Extension

6.2.52 It is expected that the jetty head would be extended to accommodate a mobile crane at

the jetty head in order to offload various construction materials and their transportation

to the aggregates storage area (see Plan,Figure 6-2, Volume 3). The jetty head would

be sized to allow vehicles to turn on the deck (and return along the jetty bridges

roadway) and to facilitate the anticipated movement of a mobile crane at this location.

6.2.53 The jetty head extension would not include a dedicated surface water drainage system.

Rainfall run-off would drain directly into the sea.


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d) Lighting Strategy

6.2.54 Appropriate lighting would be installed across the site during the jetty developments

construction. The lighting strategy for the site would:

provide a safe working environment;

avoid over illumination;

minimise upwards lighting;

minimise light spill to neighbouring areas; and

minimise energy consumption.

6.2.55 On-shore lighting has been designed in accordance with British Standard (BS) 12464-2

(2007) and the Bat Conservation Trust Bats and Lighting in the UK version 3 May

2009. Hence temporary works areas, in particular those adjacent to the foreshore and

bat corridors, would be provided with lamps with low UV content such as controllable

LED lighting, metal halide lamps and high pressure sodium (white light) lamps;

minimising the potential for light spill on bat corridors and flora and fauna associated

with foreshore, as well as minimising the UV content.

6.2.56 Off-shore lighting of the jetty needs to meet a number of regulations and standards. For

example, the Docks Regulations 1988, which contain safety requirements for general

dock work applicable to the jetty, require:

average illumination of 20 lux in all working areas;

average illumination of 5 lux in all means of access to working areas;

lighting to be uniform; and

lighting to be suitable for safe working (this may require the lighting to allow

operators to detect spillage / leaks, read labels and correctly distinguish different

colours).

6.2.57 British Standard EN 12464-2 covers shipyards and docks, and would be applicable to

the jetty development. It requires an illumination level of 20 lux and also has

requirements for diversity (uniformity of lighting), glare and colour rendering.

6.2.58 The planned operation of the jetty development would influence the lighting control

scheme and associated light spill. Operation after dark is a certainty, particularly during

the Hinkley Point C Projects peak construction and during shorter winter days, because

delivery to the jetty would be when the tide and weather conditions permit. Providing the

jetty and aggregates storage area can be operated safely, they would be lit so unloading

and other operations can take place. If the jetty and stockpiles are not in use and it is

dark, lighting could be switched off, although some minimal lighting for safe movementaround site might still be necessary.

6.2.59 Navigational lighting would be on all of the time during the jettys operation.

6.3 Jetty Construction

6.3.1 The following paragraphs are intended to provide an indication of the construction

methodology for the proposed temporary jetty development. This description is based

upon the concept design and provides an indicative approach to construction subject to

detailed design and the appointed contractors preferred approach. However,

construction of this type of jetty would be substantially undertaken from sea (e.g. from

jack-up platforms) and, to a lesser extent, from the foreshore (i.e. using land based plantthe first three or four spans). In addition, there would be a construction base located on-


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shore (e.g. for accommodation, concrete casting, advanced fabrication, etc.) and this is

reflected in the text which follows.

a) On-shore Works

6.3.2 The construction methods to be used for the on-shore works would be traditional civil

engineering techniques.

Soil Stripping

6.3.3 Topsoil and subsoil would be stripped from the rock extraction area and the aggregates

storage area and placed at the respective soil storage areas. This activity would leave

the site ready for the works described in the following paragraphs.

Rock Extraction Area

6.3.4 Rock would be excavated from an area of land that is currently at between 16m and

25m AOD. It is envisaged that the appointed contractor would work from the north in asoutherly direction, removing the topsoil, overburden, weathered rock and then fresh

rock, until sufficient material (approximately 107,000m3) is available to use as fill. After

excavation, the rock extraction areas floor would be at a level around 14m AOD and its

sides are likely to be at a slope of 1 in 2. The area would be excavated using tracked

excavators. The resulting materials would be crushed to the size required by a crusher

plant and then distributed around the site by articulated bulk material transport trucks for

use in constructing the service road and platform for the aggregates storage area.

Service Road

6.3.5 Initially, crushed rock would used to create the subgrade of the service road. The

ground would be tested to determine its strength and then, where appropriate, a layer of

woven fabric or plastic ground reinforcement would be laid. The road would then be

made up with a minimum of 500mm of well compacted granular fill. The road would be

laid to shed run-off into soakaways running alongside the road. The service road would

be constructed using traditional earth moving equipment and plant, including tracked

excavators, tracked bulldozers and articulated trucks for the transport of materials on

site. Heavy duty rolling equipment would be used to compact the road and a small

crane used intermittently to offload some bulk materials. Service road construction

could require some excavation works of soft spots along the alignment.

6.3.6 The culvert for the Hinkley Point C Drainage Ditch would be constructed by laying a

1.25m diameter concrete pipe on the bed of the existing channel. Initially, the existingbridge and some vegetation around the ditch would be removed to allow access and

temporary measures made to allow the ditch to flow during the construction of these

works. The bed of the ditch would then be excavated to remove any soft material and

provide a suitable bed for the new pipework. The pipework would be placed at an invert

level that corresponds to the existing ditch and concrete placed up to the mid point of

the pipe. The service road construction would then be made good with well compacted

granular material up to the required level and with a natural slope down into the existing

ditch. The roads top surface would be blinded with fines as necessary and the face of

the slope would be protected using stones of a greater single size grading so as to

protect the face from scour.


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6.3.7 As for the service road, the temporary access to the foreshore would be constructed by

the placement of compacted granular material, but at a slope of 1 in 10 and a width of

4.5m. Its slopes would be graded to allow safe access between the different levels.

Aggregates Storage Area: Platform Construction

6.3.8 The area would be cleared of vegetation, soil stripped (with soil taken to the storage

areas) and excavated as necessary to reach the formation level (i.e. c.20m AOD). Soft

spots would be replaced with well compacted granular material and, where required,

woven or plastic grid soil reinforcement laid onto the formation level. Additional

excavation would take place to accommodate drainage to capture surface water and

discharge it into the existing natural surface water drainage (i.e. the small watercourse

known as the Hinkley Point C Drainage Ditch, which currently discharges onto the

foreshore). The drainage excavation would be backfilled with imported bedding and

granular material up to formation level. Finally, the granular sub-base material would be

sourced from the rock extraction area, crushed, laid and compacted in layers to

complete the formation. These earthworks would be undertaken using traditional earth

moving plant, such as mechanical scrapers, mechanical shovels, excavators andarticulated trucks.

Aggregates Storage Area: Storage Facilities

6.3.9 The stockpile areas would be set out and a layer of plastic damp proof membrane

sheeting would be laid across the formation. Steel reinforcement would be laid onto the

sheeting and then the concrete floor slab would be cast, in bays, and laid to falls for

drainage. The external and intermediate segregation walls would then be installed using

pre-cast concrete.

6.3.10 For the cement silos, appropriately designed foundations would be constructed. This

would involve excavation works, installation of steel reinforcement cages, and casting of

the new concrete foundation. The steel silos are expected to be fabricated off site and

then transported on low loader to the site and erected onto the foundations. The

surrounding area would then be completed, with concrete paving laid to falls to allow

vehicular access to the storage areas.

6.3.11 Minor piping, conveying and offloading equipment would also be erected in place to link

with the main conveyor and pipeline from the jetty bridge.

Contractors Site Compound

6.3.12 To construct the contractors compound, concrete footings would be cast in the groundand then Portakabin type facilities erected and founded on them. The ground area

below these facilities would comprise gravel. The facilities would be connected to

temporary services. Water would be supplied from a bowser, which would require no

construction works. Electricity would be supplied from a diesel powered generator,

which would require the construction of a concrete walled bund around the generator

and its fuel supply. Sewage treatment would be provided by an underground cess pool

or similar, which would require small-scale excavation works to install it.

Fencing

6.3.13 To construct the fence, firstly lines would be established and holes excavated for the

posts and concrete threshold. Vertical plastic coated, galvanised steel posts would then

be erected in place with wire straining posts. Once a number of posts are erected and


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the fence line is fixed, the concrete thresholds would be cast between the straining

posts. The plastic coated chain link fencing would be fixed in place using non-

accessible fittings and the wires tensioned between the straining posts. Barbed wire

protection would then be added to the top of the fence. The security fence would be

constructed using traditional fencing equipment and plant including tracked excavators,

dumper trucks, flatbed delivery vehicles, a small crane for offloading materials, andconcrete delivery lorries.

b) Off-shore Works

Site Demarcation

6.3.14 The appointed contractor would demarcate the main working area for the jetty and the

access routes from the cliff across the foreshore. The actual demarcation method would

be elected by the appointed contractor, however, it is expected that demarcation would

entail the installation of marker posts around the working areas as appropriate. Buoys

could be attached to the marker posts to identify the location when submerged. The

appointed contractor would be required to demarcate the foreshore access routes fromthe cliff to the working area, and this may be undertaken using portable markers

installed during tidal working windows. In addition, the contractor might maintain guards

to ensure that the public are warned and excluded from these areas. It is envisaged that

signage would be installed around the site perimeter.

Jetty Bridge including Materials Handling and Conveyance Equipment

6.3.15 In constructing the jetty bridge, 45 to 55 steel tubular piles in the order of 860mm

diameter would be installed 4m to 5m into the bedrock layer. The depth of pile

penetration could vary since the ground investigation data available to date suggests

that there might be a weathered layer or weaker layer within the rock mass which may

necessitate additional penetration. It might not be feasible to drive the piles directly into

the rock mass; hence the installation method is anticipated to be either by drilling and

driving or by pre-drilling and concreting the pile into the socket, subject to further ground

investigation data.

6.3.16 With the drill and drive method, the pile is seated onto the rock head, a drill is inserted

down the pile shaft and a hole drilled into the rock mass; the pile is then driven into the

hole, the hole is extended and the pile is driven further into the hole until the required

penetration is achieved. This technique would generate a degree of piling noise but is

not anticipated to create much in the way of bed disturbance.

6.3.17 The alternative pile installation method is for the pile to be placed into a concrete filledrock socket. The pile is firstly driven to rock head, a drill is inserted down the pile and

the rock socket is drilled and then enlarged using the under-reaming blades to a

diameter greater than the pile. Concrete is placed into the rock socket and the pile is

driven into the wet concrete. Shear rings on the pile provide a degree of tension

capacity.

6.3.18 Preliminary calculations indicate that the steel piles for the bridge would need to be able

to resist uplifting forces. This could be achieved by using concrete fill within the pile,

anchors or by concreting the pile into a socket.

6.3.19 Once the piles are driven, concrete cross heads would be placed over the pile bents. It

is anticipated that the cross head units would be pre-cast with in situ stitching to the pile,

thus minimising over water concrete works.


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6.3.20 The steel box truss structure units would be prefabricated in lengths that span between

cross head supports. The prefabricated units would incorporate the steel longitudinal

and transverse deck beams. It is also anticipated that the cement pipeline, aggregate

conveyor and open mesh flooring would be installed within the units whilst on-shore.

6.3.21 The inshore end of the jetty bridge, including the first few spans across the upper

foreshore, would be installed using land based plant. For the drilling and placing of the

tubular piles it is anticipated that various plant would be required for the installation of

approximately one pile per day, including a 120t crawler crane, 30t excavator with drill

attachment, piling hammer, 20t excavator to load spoil and 25t dump truck to remove

spoil (4-6 loads per day). It is envisaged that this would result in approximately 10

vehicles per day, including 3-4 concrete deliveries. In addition, piles would be brought

to site by barge and tug, at a rate of one delivery per week.

6.3.22 To place the concrete cross heads and deck steelwork it is anticipated that various plant

would be required on a daily basis, including a 120t crawler crane and a 25t excavator.

Crossheads and truss units would be brought to site by barge and tug at an expected

delivery rate of one delivery per week.

6.3.23 In addition to the above, there would be support plant and equipment such as tractor

and trailer, small dumper trucks, lighting towers, welding sets, etc. required on an ad-

hoc basis. There would also be miscellaneous deliveries each day; these items would

be transported on the tractor and trailer.

6.3.24 All plant would be required to drive on the foreshore via the temporary service road and

move out of the tidal zone at the end of each shift. The typical speed of tracked plant is

5mph over this type of terrain.

6.3.25 The piles beyond the upper foreshore would be installed from sea-based plant in the

form of piling equipment operated from jack-up barges.

6.3.26 These complete units would then be lifted by crane provided off a jack-up barge and

installed over the cross heads.

Jetty Head including Materials Handling and Conveyance Equipment

6.3.27 To support the jetty head, dolphin and fendering, 70-90 steel tubular piles in the order of

910mm diameter would be driven in a similar manner to those installed for the jetty

bridge. Pile installation would be undertaken from a jack-up barge. Tension anchors

would be installed in selective piles or the piles could be concreted into rock sockets.

6.3.28 The jetty head deck and dolphins are anticipated to be cast in situ reinforced concrete,

with construction activities being undertaken from a jack-up barge. The use of pre-cast

concrete elements could be considered during detail design.

6.3.29 Once the jetty head is constructed, the installation of the materials handling and

conveyance equipment (i.e. receiving cement silo and booster, loading arm and crane,

conveyors, pipeline, receiving aggregate hopper, etc.) would take place. It is envisaged

that the equipment to be installed on the jetty head would be delivered by sea and off-

loaded using a crane barge.


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Berthing Pocket and Disposal of Dredged Material

6.3.30 Existing ground investigation information indicates 4m of superficial deposits over rock

head at the proposed position of the berthing pocket. It is proposed to dredge up to

3.5m of this material to create a berth pocket (including up to 0.5m of over-dredge), thus

improving tidal access windows for off-loading of cement. The actual dredging methodwould depend on the dredging equipment available to the contractor appointed to

undertake the works. However, it is expected that dredging would take place using one

of the two dredging methods described below.

6.3.31 One method would be to use a small trailing suction hopper dredger (i.e. hopper

capacity in the range of 2,000m3 to 5,000m3). This type of dredger is a self-propelled

vessel. It has a draghead that extends to the seabed and agitates the sediment as it

moves forward. The agitated sediment along with some of the surrounding water is

sucked into the draghead and up a suction pipe by a centrifugal pump. The mix of

sediment and water is discharged into the dredgers onboard hopper. The hopper filling

process may entail over-flowing (and/or diverting) excess water and some of the finer-

grained sediment overboard. Once the hopper is full, the draghead is retracted and thedredger sails to the disposal ground, releases the dredged material through the hoppers

bottom doors, and returns to the dredging location.

6.3.32 An alternative method would be to use a mechanical dredger, such as a backhoe

dredger. This type of dredger typically works from a jack-up pontoon (i.e. it is a static

piece of equipment) and is supported by a self-propelled transport barge with a built in

hopper (hopper capacity in the range of 1,000m3). This type of dredger is, in essence, a

hydraulic excavator that uses a bucket on the end of a boom and dipper crane arm to

remove the seabed sediment and then bring it above the water surface and place it into

a barge moored alongside. Once the barge is full, it sails to the disposal ground,

releases the dredged material through its bottom doors, and returns to the dredging

location.

Aids to Navigation

6.3.33 The appropriate aids to navigation (e.g. lights) would be attached to the jetty head

and/or its associated structures (e.g. the mooring dolphins) and to marker buoys

deployed at sea at the locations indicated on Plate 6.2. It is anticipated that the marker

buoys (including their lights) and the anchoring system would be pre-fabricated and

brought to site on a barge and deployed by a crane mounted on the barge. The anchors

are likely to take the form of pre-cast concrete blocks, which would be sized to remain in

place given the hydrodynamic regime (e.g. c.5m3). The chains are likely to take the

form of steel link chains. The anchors, chains and buoys are likely to be connected anddeployed by the crane placing the anchor on the seabed.


6.3.34 It is envisaged that the roadway would be constructed from cross-head to cross-head

using a crane on a jack-up barge or land based plant to lift the materials into place. The

pair of steel beams would be placed on bearings and then the pre-cast deck units would

be placed on the steel beams. Pockets within the deck units would be positioned over

shear connectors on the steel beams and the pockets subsequently concreted in situ.

The lighting columns would be supported on the concrete cross heads and installed

from the completed roadway.


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Jetty Head Extension

6.3.35 The jetty head extension would be constructed in a similar manner to the jetty head. It is

anticipated that 25 to 35 steel tubular piles in the order of 910mm diameter would be

driven using a similar methods to that described for the jetty bridge. Pile installation

would be undertaken from a jack-up barge. Tension anchors would be installed inselective piles or the piles could be concreted into rock sockets. The jetty head

extensions deck is expected to comprise in situ cast reinforced concrete, with

construction activities being undertaken from a jack-up barge. The use of pre-cast

concrete elements could be considered during detail design.

6.3.36 It is anticipated that a mobile crane would be transported to site by road, either directly

or on the back of a transporter, and driven along the roadway to the jetty head

extension.

d) Construction Working Hours

On-shore Works

6.3.37 Working hours for construction of the on-shore components of the jetty, including the

initial spans of the jetty bridge and the service road to the foreshore would be:

from 07:00 to 18:00 on weekdays;

from 07:00 to 13:00 on Saturdays; and

no working on Sundays, bank holidays or public holidays.

Off-shore Works

6.3.38 It is anticipated that construction of the jetty would require working hours of 24 hours a

day and seven days a week. Construction would take place with one or two shifts a day

with variable start and finish times as dictated by the state of the tide. These hours are

needed to expedite the jettys construction in relation to the restrictions imposed on

working due to tidal conditions, and relate to both stages of the jetty infrastructure.

e) Construction Programme

6.3.39 An indicative construction programme for the jetty development is provided in Plate 6.3.

6.3.40 Subject to the appropriate consents being granted and other tasks being completed (e.g.

detailed design, contract procurement, etc.), the first stage of the jetty developments

construction is anticipated to take place from Q2 2011. The construction works for stageone is expected to be completed within Q2 2012 and stage two by Q4 2012, assuming

both stages of the jetty are constructed.

f) Construction Personnel

6.3.41 Up to 60 construction workers are estimated to be required during the construction of

the jetty development at any one time.

6.4 Jetty Operation

6.4.1 The jetty would be available to import aggregates (gravel and sand) and cement once

the stage one infrastructure and on-shore works are in place and available to importother construction materials once the stage two infrastructure is in place.


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Plate 6.3 Indicative Construction Programme

Year 2011 2012

Quarter Q2 Q3 Q4 Q1 Q2 Q3 Q4

On-shore Works

Mobilisation and site set upService road / hardstanding / drainage

Stockpiles and silos

Jetty Works Stage 1

Mobilisation and site set up

Install piles for jetty bridge

Cast / install pile caps and crossheads

Install bridge trusses

Install finishing works to jetty bridge

Install piles for jetty head

Cast jetty deck

Install piles for mooring dolphins

Cast dolphin heads

Install linkspans / finishing to jetty head

Install jetty services (lighting, power)

Dredging of berthing pocket

Jetty Works Stage 2

Install piles for jetty head extension

Cast jetty head extension

Install roadway deck on crossheads

a) Jetty Import of Aggregates and Cement

Materials Import: Types and Volumes of Materials

6.4.2 The peak concrete production for the Hinkley Point C Project is anticipated to be in the

region of 30,000m3per month, which would occur during placing of the concrete for the

reactor buildings together with other site works. It is anticipated that there would be two

production peaks each lasting in the region of six months. Concrete production would

require the various imported materials, including cement (or cement replacement

products), sands, stone dust and aggregates.

6.4.3 Under the peak demand scenario, the following volumes of materials would need to beimported via the jetty:

cement: 10,500 tonnes / month;

sand: 21,000 tonnes / month; and

stone: 36,000 tonnes / month.

6.4.4 The normal concrete production for the Hinkley Point C Project is anticipated to be in the

region of 12,000m3 per month. Under the normal demand scenario, the following

volumes of materials would need to be imported via the jetty:

cement: 4,200 tonnes / month;

sand: 8,400 tonnes / month; and stone: 14,400 tonnes / month.


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Materials Import: Vessel Types and Numbers

6.4.5 It is anticipated that vessels would include aggregate barges and cement carriers.

Whilst the selection of operational vessels would be made by the appointed contractor,

indicative vessel dimensions can be determined (see Table 6.1).

Table 6.1 Indicative Vessel Dimensions

Parameter Aggregate Barges Cement Carrier Cement Carrier

Weight (dwt) 5,000 2,500 4,300

Length (m) 100 78 92

Beam (m) Up to 17.5 12 14

Loaded draught (m) 6.0-6.7 5.3 6.3

6.4.6 Based upon the dimensions identified in Table 6.1, the anticipated peak numbers of

vessels visiting the jetty per month would be:

cement carriers: 5 / month (2,500 dwt) or 3 / month (4,300 dwt);

aggregates vessels (sand): 5 / month; and

aggregates vessels (stone): 8 / month.

6.4.7 Based upon the dimensions identified in Table 6.1, the anticipated normal numbers of

vessels visiting the jetty per month would be:

cement carriers: 1 / month (4300 dwt);

aggregates vessels (sand): 2 / month; and aggregates vessels (stone): 4 / month.

Materials Import: Vessel Manoeuvres

6.4.8 It is assumed that vessels would berth on a rising tide and approach the berth as soon

as there is sufficient depth of water for the required under keel clearance. Vessels

would always try to approach the berth with the bow facing into the wind and / or current

(whichever is the stronger), as this enables greater vessel control and manoeuvrability.

A rising (or flood tide) would mean that the tidal current is flowing from west to east and

would, therefore, require the vessel to head in a westerly direction when berthing and

thus be port side alongside the jetty for unloading materials (hence the jetty head isdesigned for port aft discharge of materials).

6.4.9 It is not envisaged that a pilot would be required to berth vessels but, should one be

required, then the pilot would board a vessel at a designated position (probably between

one to two nautical miles from the jetty) and would steer it to approach the berth at slow

speed from a north-easterly direction. Once the vessel is 10m to 20m off the berth, the

mooring lines would start to be run from the ship to shore. These lines would then be

tensioned and used together with the engines (and bow thruster if fitted) to assist in

bringing the vessel alongside the berth.

6.4.10 Assuming that vessels would not be taking the ground while at the jettys berth, the

vessel would depart the berth during an ebb tide with the current in an east to west

direction from astern. This current direction would not be preferred, but should be


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tolerable for a departure manoeuvre. For departure, a vessel would firstly reduce the

number of mooring lines to the jetty whilst maintaining position alongside the berth. This

would allow the final lines to be released relatively quickly before using the engines to

clear the berth in a north-westerly direction. The pilot would then disembark (if a pilot

has been engaged) before the vessel proceeds on passage to the next port or standing

off waiting for the next tide. There is expected to be some water disturbance due topropeller and thruster wash during these manoeuvres.

Materials Import: Vessel Movements

6.4.11 To supply 30,000m3per month of aggregates and cement to meet the peak periods of

demand for concrete production during the Hinkley Point C Project, 16 to 18 vessels (i.e.

13 aggregates vessels and 3-5 cement carriers) would need to use the jetty. Taking

berthing and departure manoeuvres into account, during peak months there would be 32

to 36 vessel movements.

6.4.12 To supply 12,000m3 per month of sand, aggregates and cement to meet the normal

periods of demand for concrete production during the Hinkley Point C Project, 7 vessels(i.e. 6 aggregate barges and 1 cement carrier) would need to use the jetty. Taking

berthing and departure manoeuvres into account, during normal months there would be

14 vessel movements.

Materials Import: Materials Unloading and Handling

6.4.13 Aggregate vessels would unload via their on-board unloading equipment, which typically

takes the form of a conveyor. Aggregate discharge rates would vary depending on the

vessels onboard unloading equipment. Although self-discharging dredgers have a

quoted discharge rate of some 2,000 tonnes per hour, an average discharge rate of

1,000 tonnes per hour is considered much more achievable and has been

accommodated by the jettys design. From the vessels conveyor, aggregate would be

discharged into the articulated hopper on the jetty head and onto an articulated

conveyor which spans the distance to the transfer hopper on the jetty bridge. The

transfer hopper would discharge aggregate onto the conveyor along the jetty bridge,

which would transport aggregate via a distribution conveyor, feeding the stockpiles at

the aggregates storage area.

6.4.14 The stockpiles would be contained and divided by low bund walls and open on at least

one side so that aggregate can be gained by front loading shovel and transported to a

concrete batching plant during construction of Hinkley Point C. The batching plant does

not form part of the jetty development covered by this ES. It is anticipated that the

stockpiles would contain about one months supply of aggregate to help mitigate berthdowntime due to adverse weather and sea conditions. Surface water run-off due to

rainfall would be managed as part of the aggregates storage areas drainage system

including, as necessary, sand and/or silt separation using catch pits or separators.

6.4.15 The aggregates to be brought to the jetty could be sourced from a number of locations

including quarries on land (e.g. South Wales) and extraction sites in the sea (i.e.

licensed aggregate dredging areas). It is anticipated that on-shore quarries would be

the most likely source because a marine source could necessitate processing (i.e.

washing) to reduce the chloride content of aggregates prior to use. Since no provision is

made for aggregate washing on site, it is not considered in this ES.

6.4.16 Cement carriers discharge using an onboard pneumatic system for blowing the cement

through a pipeline. The cement vessel would discharge to a receiving silo on the jetty


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head. The silo would incorporate a booster pump to pump the cement through the

cement pipeline along the jetty bridge to the silos at the aggregates storage area. The

pipeline joints would be flanged and sealed with gaskets, as appropriate, in order to

mitigate cement dust escaping from the pipeline.

6.4.17 The achievable pumping rates depend on the number of manifolds, diameter of the

pipeline or hose, the distance from the pump to the shore silo, and the difference in

height between the vessel and the silo. In the case of the jetty development, the

distance from the vessel to the silo would be relatively long and it could be necessary to

incorporate a booster pump in the pipeline to increase the discharge rate. For example,

it is most likely that an additional booster pump could be required on-shore to lift the

cement into the silos. This would effectively mean that the vessel would be only

required to pump to the jetty head, because the shore pump would transfer the cement

to the silos on-shore. In these conditions, it is estimated that a discharge rate of some

100 to 250 tonnes per hour could be achieved.

Materials Import: Timing of Materials Unloading

6.4.18 At present, it is assumed that vessels would be able to berth 24 hours a day, subject to

the tide and weather limits.

6.4.19 As identified on Table 6.1, 5,000 dwt aggregates vessels have an indicative loaded draft

of 6.0 to 6.7m. With a tide level of +5.8m CD and seabed level of -2.0mCD, the vessel

would approach the berth with 1.1m to 1.8m under keel clearance. The vessel would

remain at the berth through high water and discharge its cargo. The vessel would then

depart by the time the tide drops to +5.8mCD, although departure could take place on a

slightly lower tidal level if the draft was reduced after off-loading and subsequent

ballasting.

6.4.20 Accordingly, the aggregate unloading is expected to take some 5.5 to 6.0 hours which

would necessitate a discharge rate of some 1,000 tonnes per hour. Therefore, it is

considered that aggregate barges can gain access to the jetty on virtually all tides, using

the upper half of the tidal cycle each time. However, there could be other operational

restrictions, such as weather down time, plant breakdowns, etc. which would need to be

taken into account.

6.4.21 Cement carriers have a lower indicative loaded draft and a slower discharge rate than

aggregate barges, which means they would remain berthed for longer to unload their

contents. Since 2,500dwt vessels would need 15 hours to unload and 4,300dwt vessels

would need 30 hours to unload, cement carriers would remain berthed throughout onefull tidal cycle, including at low tide, and hence the need for the dredged berthing pocket

to provide an additional 2m water depth.

b) Jetty Import of Other Construction Materials

Materials Import: Types and Volumes of Materials

6.4.22 The jettys second stage would be used to import other materials needed for the

construction of Hinkley Point C. It is anticipated that these imported materials would

include unitised and/or pre-fabricated items such as pre-cast concrete pipeline units

(e.g. for the intake and outfall structures), steel reinforcement bars (e.g. for concrete),

brickwork, cabling, piping, ducting, etc.


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6.4.23 The jetty would not be used to offset the import of abnormal indivisible loads (AILs) via

EDF Energys dedicated wharf at Combwich because its design cannot accommodate

the types of vessels used to import AILs and its equipment cannot unload and convey

the AILs.

Materials Import: Vessel Types, Numbers, Manoeuvres and Movements

6.4.24 Since there is no definitive information on the exact types and volumes of materials that

would be imported during its operation, the vessel types, numbers, manoeuvres and

movements associated with the second stage of the jetty development are not known

with precision at the current time. However, some indicative scenarios for the second

stage of the jetty development can be anticipated based on the types of materials likely

to be imported and the availability of the jetty (i.e. the spare tides during which a vessel

could be berthed at the jetty).

6.4.25 As for the import of aggregates, it is anticipated that the jetty would receive vessels of

sizes up to 5,000dwt due to the limitations of the berth (e.g. the water depth available at

the berth).

6.4.26 It is anticipated that vessels would make best use of the tidal windows available to them.

Therefore, the potential operational capacity of the jetty (i.e. the number of vessels

potentially using the jetty) would depend on the availability of jettys berth over spare

tides. Spare tides are those tides when the berth is not occupied by a vessel delivering

aggregate or cement for concrete production during the construction of Hinkley Point C,

or when the berth cannot be occupied due to adverse weather.

6.4.27 Assuming an average of 60 tides per month, a preliminary analysis of spare tides has

been made (see Table 6.2). This analysis identifies the indicative number of tides

available per month, over winter and summer, during periods of peak and normal

concrete demand, and both including and excluding tides in between aggregate and

cement deliveries. As would be expected, there would be more opportunity to import

materials during normal concrete production compared to peak concrete production.

Table 6.2 Indicative Available Tides

Available Tides (including tides in betweenaggregate and cement deliveries)

Available Tides (excluding tides inbetween aggregate and cement deliveries)

Peak ConcreteProduction

Normal ConcreteProduction

Peak ConcreteProduction

Normal ConcreteProduction

Winter Summer Winter Summer Winter Summer Winter Summer

26 32 38 (25*) 44 4 11 29 (2*) 36

Note: * if aggregates supplied by smaller vessels of 1,200dwt

6.4.28 The tides available when aggregate and cement deliveries are excluded represent the

most realistic scenario of spare tides for the jetty. Under this scenario, there would be

between 4 and 29 spare tides during winter months and between 11 and 36 spare tides

per month during summer months.

6.4.29 During the months of peak demand for aggregates and cement for concrete production

during construction of Hinkley Point C, there would be between 4 and 11 spare tides permonth. Assuming one vessel per every spare tide and taking berthing and departure


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manoeuvres into account, there would be a monthly maximum of between 8 and 22

vessel movements to add to the 32 to 36 vessel movements associated with the import

of aggregates and cement.

6.4.30 During the months of normal demand for aggregates and cement for concrete

production during construction of Hinkley Point C, there would be between 29 and 36

spare tides per month. Assuming one vessel per every spare tide and taking berthing

and departure manoeuvres into account, there would be a monthly maximum of

between 58 and 72 vessel movements to add to the 14 vessel movements associated

with the import of aggregates and cement.

6.4.31 It is anticipated that vessels would access and depart the jetty with similar manoeuvres

to those described for aggregate dredgers and cement vessels.

Materials Import: Materials Unloading and Handling

6.4.32 Although precise information is not currently available on all the types and volumes of

materials that would be imported at stage two, it is assumed that vessels would beunloaded using the mobile crane situated on the extended jetty head. The crane would

load materials onto trucks, which would then transport the materials along the jetty

bridge and on-shore to the construction site for Hinkley Point C.

6.4.33 The timing of unloading operations would have to fit around the times when the jetty is

not being used for importing aggregates and cement, and around the tidal cycle as

relevant to the vessel (e.g. in terms of draught available across the tidal cycle).

c) Jetty Maintenance

Maintenance of Handling and Conveyance Equipment

6.4.34 During the operational life of the jetty, a degree of maintenance would be required.

Given that the import of aggregates and cement would be within discrete timeframes

related to demand and tides, and that EDF Energy might want to import other materials

via the jetty, it is important that downtime due to equipment failure is limited as far as

reasonably practicable.

6.4.35 It is considered that the main area of maintenance would be mechanical and electrical

maintenance associated with the receiving aggregates hopper and articulated conveyor

and the cement booster pumps and pipeline. Maintenance and minor replacement of

items would be undertaken locally unless significant replacement of equipment is

required. Maintenance walkways are to be provided along the jetty bridge on eithersides of the aggregates conveyor and cement pipeline via the 1.5m wide central

walkway.

6.4.36 Should it be necessary to replace significant pieces of equipment, which would be very

unlikely, delivery could be achieved by a vessel berthing at the jetty and using its

onboard unloading equipment to unload items. Alternatively, if the stage two jetty

infrastructure is in place, delivery could be achieved either by a vessel berthing at the

jetty and using the crane on the jetty head, or by truck driving along the jettys roadway

with items being off-loaded and craned into position.

6.4.37 During routine maintenance operations, regular inspection of hydraulic equipment would

be undertaken in order to ensure that pollution associated with hydraulic oils is avoided.It is expected that this would include inspection of the crane located on the jetty head.


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Maintenance of the Berthing Pocket

6.4.38 It is anticipated that a degree of sediment infilling would occur over time and, hence,

maintenance dredging of the berthing pocket might be required to ensure sufficient

water depth for vessel berthing and unloading operations. A maintenance dredging

regime has not been determined for the berthing pocket, but it is anticipated that themethod for maintenance dredging and the dredged material disposal site would be

similar to capital dredging.

6.4.39 Accordingly, it is anticipated that a small trailer hopper suction dredger or a backhoe on

a jack-up platform would be used to carry out the dredge, and that the dredged material

would be disposed of at the Cardiff Grounds.

Maintenance of Aids to Navigation

6.4.40 It is expected that the aids to navigation would be inspected every 6 or 12 months to

ensure that the lights and systems are working correctly and the marker buoys are in the

correct position (i.e. that they have not been dragged out of position by currents).

d) Aggregates Storage Area

6.4.41 The aggregates storage area would receive and store the imported aggregates and

cement in the stockpiles and silos. The area provides storage for approximately one

months typical demand for materials in the eight aggregate stockpiles, four sand

stockpiles, two stone dust stockpiles and up to eight cement silos. This level of storage

would provide contingency against disruption to supply via the jetty primarily due to

weather downtime, but also from other supply issues.

6.4.42 Given the aggregate storage areas arrangement (see Figure 1-2, Volume 3), it has

been considered that transfer of aggregates and cement to the concrete batching plant

would be by trucks or tankers, respectively. However, it is conceivable that, depending

on the location of the batching plant, transfer of aggregates and cement could be made

by an arrangement of conveyors and pipelines, respectively.

e) Lighting

6.4.43 The jetty and the on-shore area would be designed to operate in periods 24 hours a day,

7 days a week. These areas would need to be lit at relevant times to provide a safe

working environment. The jetty developments lighting strategy is described in Section

6.2. The following paragraphs describe operations for which lighting might be required.

Jetty Operations

6.4.44 When unloading aggregates, the vessel would discharge during a specific tidal window

on the upper half of the tidal cycle and if this occurs during dusk / darkness, operational

lighting would be required during the unloading period and for a short time either side of

the window. When unloading cement the vessel would remain at the berth for up to 30

hours and the operational lighting would be required throughout this time during periods

of dusk / darkness. In addition, operational lighting would be required during any

maintenance work on the jetty.


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On-shore Operations

6.4.45 The on-shore area may be lit for longer periods than the jetty, as on-shore distribution of

aggregates and cement may occur a 24 hours a day, 7 days a week at periods of peak

concrete production during the construction of Hinkley Point C. During non-operational

periods, a lower level of lighting would be maintained throughout the facility for securityand safety reasons.

f) Working Hours

6.4.46 It is anticipated that operation of the jetty and the aggregates storage area would require

working over 24 hours a day, 7 days a week. Operation would take place with one or

two shifts a day with variable start and finish times as dictated by the state of the tide.

These hours are needed to operate the jetty development in relation to the restrictions

imposed on operations (e.g. berthing and unloading of vessels) due to tidal conditions,

and relate to both stages of the jetty infrastructure.

g) Operation Programme

6.4.47 The jetty development is proposed as a temporary feature to facilitate construction of the

Hinkley Point C Project and, therefore, it is expected to be operational for up to eight

years.

6.4.48 Use of the jetty would be related to the demand for aggregates and cement for concrete

production during the construction of Hinkley Point C. It is anticipated that there would

be two periods, each of six months, during which the jetty would be operating at its

maximum potential in terms of berth occupancy by aggregate barges (over high tides on

all tidal ranges) and cement carriers (over all states of the tide during neap tidal ranges).

6.4.49 The jettys usage would reduce as Hinkley Point Cs first reactor unit becomes

operational and would cease in advance of Hinkley Point Cs second reactor unit

becoming operational. It is expected at this point, the jetty would be no longer required

and dismantling would be initiated (see Section 6.5).

h) Operation Personnel

6.4.50 Up to 10 operation workers are estimated to be required during the operation of the jetty

development at any one time. It is estimated that four to six linesmen would be required

for berthing the vessels and a further two to four workers would be required for the

unloading operation (this would depend on the shore discharging arrangement).

6.5 Jetty Dismantling and Restoration

6.5.1 The temporary jetty would be dismantled at the end of its operational life. It is

anticipated that reuse of materials handling equipment would be feasible along with

reuse and/or recycling of some of the jettys structural items.

6.5.2 Once the jettys infrastructure has been dismantled and taken off-site, the land affected

by the platform for the aggregates storage area would be restored to its former use for

agriculture.


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a) On-shore Works Dismantling

6.5.3 The hardstanding platform area created for the aggregates stockpiles and cement silos

would be broken out. The resulting rubble would be crushed for on- or off-site re-use.

b) Off-shore Works Dismantling

6.5.4 The following paragraphs set out the dismantling and restoration activities for the jetty in

the order that they are expected to take place and assuming that both stages of the jetty

development would be in place.

Materials Handling and Conveyance Equipment at the Jetty Head

6.5.5 The materials unloading and handling equipment at the jetty head (e.g. articulated

conveyor, silo, booster, hoppers and crane) would be dismantled and shipped away

from the jetty. It is anticipated that many of these items could be reused by EDF Energy

or sold on for use by others.

Materials Handling and Conveyance Equipment along the Jetty Bridge

6.5.6 It is anticipated that following some local dismantling work the steel truss inclusive of the

cement pipeline and aggregate conveyor would be removed in units in a similar manner

to that in which it was installed. This would require a crane barge to transport the units.


6.5.7 The roadway deck would be systematically dismantled in a linear manner. Firstly, the

pre-cast concrete deck sections would be removed from the steel beams. This would

involve local breaking out of the in situ concrete surrounding the shear studs; hydro-

demolition could be used in order to minimise damage to reinforcement. The steel

beams would then be disconnected from the cross heads and removed. It should be

feasible to re-use the steel beams and pre-cast concrete deck sections at another

location.

Jetty Bridge

6.5.8 The concrete cross heads would be dismantled from the piles by cutting of the piles

immediately below the cross head. The concrete could be recycled, subject to the

degree of reinforcement.

6.5.9 It is not considered feasible to pull out the steel tubular piles, hence cutting of the pilesat rock head / seabed level would be used to remove the main section of pile shaft. On

the foreshore, where the pile locations could pose a risk to people walking and falling

into holes, the remaining section of pile and internal void would be in-filled with grout. At

locations on the foreshore where the holes / restoration are visible, a natural stone slab

would be placed into the concrete plug. The voids left within the seabed beyond the

foreshore would not be plugged with concrete but allowed to infill naturally with seabed

deposits.

6.5.10 A barge with craneage would be necessary to support, dismantle and transport these

units for recycling as reuse is considered impractical. If tension anchors are used in

place of concrete infill, the piles could be re-used.


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Jetty Head

6.5.11 The dismantling of the jetty head structure and dolphin caps (including an extended jetty

head) would involve demolition of the in situ reinforced concrete into sections, which

would then be cut from the pile heads and lifted onto a barge for subsequent removal

from the site. The dismantling of the tubular piles would be undertaken in a similarmanner to those of the jetty bridge.

6.5.12 The voids left within the seabed would not be plugged with concrete but allowed to infill

naturally with seabed deposits.

Aids to Navigation

6.5.13 Dismantling of the marker buoys would entail the recovery of the anchors, chains and

buoys by crane. They are expected to be placed on a barge and taken off-site for re-

use, recycling and, if necessary, disposal.

c) Restoration

6.5.14 Following infrastructure dismantling, the western area affected by the jetty

developments on-shore works (e.g. the aggregates storage area, WMZ) would be

restored. The eastern area of the jetty developments on-shore works (e.g. service road,

rock extraction area) would become part of the Hinkley Point C Projects permanent

works (e.g. the nuclear power station) and, therefore, would not be restored.

6.5.15 Restoration would seek to restore and enhance the landscape character, improve

biodiversity, and provide improved public access. The western part of the site would be

restored for predominantly agriculture use, with some woodland and hedgerow planting.

All proposed planting is to be of native species of local provenance where possible,

selected to fit with existing local landscape character and to suit site conditions. The

stripped topsoil and subsoil to be retained and stored on site would be used for the

restoration works.

6.5.16 In addition, the existing PRoWs would be reinstated and Green Lane upgraded to a

bridleway. Footpaths and bridleways would be clearly defined and signposted, and

maintained to a high standard. Access would take into account the needs of less able

people. For example, self-closing bridle gates would be proposed, rather than stiles, to

avoid creating barriers to the less able.

6.5.17 The restoration strategy for the jetty development would form part of the overall land

restoration strategy associated with the completion of construction of Hinkley Point C,and is described in more detail in Section 21.6and shown in Figure 21-27,Volume 3.

d) Working Hours

6.5.18 Dismantling and restoration of all components of the jetty development is anticipated to

require the following working hours:





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e) Dismantling and Restoration Programme

6.5.19 It is expected that dismantling and restoration would take approximately two years,

including dismantling of the jetty, earthworks to reprofile the site and planting.

f) Dismantling and Restoration Personnel

6.5.20 Up to 25 workers are estimated to be required for dismantling and restoration of the jetty

development at any one time.

6.6 Jetty Removal and Reinstatement

6.6.1 The jetty development would be removed and the site reinstated if it is not required

because the Hinkley Point C Project is not granted its consent. This would comprise two

key activities: infrastructure removal and site reinstatement.

a) Infrastructure Removal

6.6.2 To physically remove the jetty developments on-shore and off-shore infrastructure, the

same process would be adopted as that described for dismantling in Section 6.5.

b) Site Reinstatement

6.6.3 Following removal, the on-shore area affected by the jetty development would be

reinstated to the extent that is practical and practicable.

6.6.4 Reinstatement would seek to reinstate and enhance the landscape character (including

the landform and the coastal cliff), improve biodiversity, and provide improved public

access. The majority of the area affected by the jetty development would be returned to

agriculture use. All proposed planting is to be of native species of local provenancewhere possible, selected to fit with existing local landscape character and to suit site

conditions. The stripped topsoil and subsoil to be retained and stored on-site is

expected to be used for the landscape reinstatement. The reinstated landform, soil

structure and hedgerow framework would support the agricultural end use.

6.6.5 In addition, as for site restoration, existing PRoWs would be reinstated across the entire

application site and Green Lane would be upgraded to a bridleway. Footpaths and

bridleways would be clearly defined and signposted, and maintained to a high standard.

Access would take into account the needs of less able people. For example, self-

closing bridle gates would be proposed, rather than stiles, to avoid creating barriers to

the less able.

6.6.6 The reinstatement strategy for the jetty development is described in Section 21.6and

shown in Figure 21-26, Volume 3.

c) Working Hours

6.6.7 Removal and reinstatement of the jetty and the on-shore components of the jetty

development is anticipated to require the following working hours:





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d) Removal and Reinstatement Programme

6.6.8 No programme is set for removal and reinstatement because this component of the jetty

development may not be required, unless circumstances dictate otherwise. However,

the timescales for infrastructure removal would be similar to that described for

dismantling (see Section 6.5) and the timescales for removal and reinstatement areestimated to be up to one year for removal and two years for reinstatement.

e) Removal and Reinstatement Personnel

6.6.9 It is estimated that up to 25 construction workers would be required, at any one time,

during the removal of the jetty and reinstatement of the site in the development area.

6.7 References

6.1 Eagle Lyon Pope (2009). Combwich Marine Impact Assessment. Eagle Lyon Pope.


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Jetty Environmental Standard Chapter 6 - Project Description- Temporary Jetty Development

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