construction process, dredging and physical processes... · the design of the seawall and the wave...

EJR/EJR/343641/1/UKM/62783439.1 1

CONSTRUCTION PROCESS, DREDGING AND PHYSICAL PROCESSES

Construction Process

3.1 to the Applicant

Table 4.1 of the ES is provided to describe the design options under consideration.

However by comparing the description of the development in Chapter 4 with this

table, not all of the construction options are included in this table.

Please could the applicant provide an updated table, which clearly sets out all of the

options under consideration, including details identifying which of these options

have been assessed in the ES and where applicable, evidence to justify the ‘worst

case’ adopted for the purposes of the assessment?

TLSB's Response

1. An updated version of Table 4.1 is provided at Appendix 3.1.1.

2. Please see also a related note dealing with the comparison of lagoon seawall

construction methodologies of Geotubes® or quarry run at Appendix 3.1.1.

EJR/EJR/343641/1/UKM/62783439.1 2


A number of methods for constructing the sea-wall are described in the ES (Project

Description, paras 4.3.1-4.3.4) and illustrated in Figures 4.4-4.6. It is explained that certain

sections of the sea-wall will require certain construction methods, for example the inclusion

of a rock-armour crest for health and safety reasons.

(a) Please could the applicant provide a figure (drawn to scale), which illustrates

where each of these sections is proposed to be located?

TLSB's Response

1. Drawings 2.2.11, 2.2.12 and 2.2.13 of the Works Plans submitted with the

Application (doc ref 2.2) show 10 cross sections at intervals along the seawall.

Each of these cross sections is designed to the specific criteria in terms of usage,

and to the specific ground and wave conditions for that location. All sections have

a rock armour crest and a concrete wave wall. The rock armour size and height,

and design of the concrete wave wall, increase in size in those locations where the

wave action is more severe (e.g. compare section 2 and 3 to section 1 on drawing

2.2.11).

(b) Paragraph 4.3.1.7 explains that the seawall will be constructed to absorb 60-

70% of wave energy. How will this design requirement be incorporated into

the DCO?

TLSB's Response

2. The energy absorption capability of the seawall depends on the local wave

conditions; on the steepness of the outer armour rock slope; and on the thickness

and porosity of the main rock armour. The design for each of the seawall sections

is shown on Drawing 2.2.11, 2.2.12 and 2.2.13 of the Works Plans (doc ref 2.2).

The wave reflection is calculated for these sections (using the methodology

outlined in the Rock Manual1 which gives a reflection coefficient between 0.2-

0.3, meaning an absorption of the wave height of 70-80% and an absorption of the

wave energy of more than 90% (Note: wave energy is relative to the wave height

squared). The wave reflection was validated and confirmed for the most exposed

section through physical model testing in HR Wallingford.

3. This design requirement (i.e. absorption of 60 to 70 percent of wave energy) is a

natural consequence of using rock as armour for the seawall structure. It is

incorporated into the requirements of the DCO by the inclusion of drawings

2.4.19 to 2.4.21, the designs in which must be implemented in order to comply

with Requirement 5 of Part 3 to Schedule 1 of the draft DCO. If an alternative

design is proposed, it would require the prior approval of the relevant local

planning authority under the terms of requirement 4, a revised version of which is

submitted with these written representations.

1 Chapter 5, CUR/CIRIAC683, 2007

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(c) How has this design been incorporated into the coastal processes modelling?

TLSB's Response

4. In the coastal processes modelling conservative reflection coefficients (0.3) have

been used.

5. In general the reflection from a seawall depends on the wave conditions and

structure parameters. Details on how to calculate the reflection can be found in the

Rock Manual (e.g. equation 5.73).

6. Eastern breakwater: In calculating the reflection for the eastern breakwater (slope

1:2.25) an average reflection of around 0.3 is obtained. This reflection coefficient

was confirmed by HR Wallingford using a physical model where values between

0.2 and 0.4 where found among a range of swell wave conditions.

7. Western breakwater: The western breakwater has a slope of 1:2. With a

computed local wind wave of Hs=1.2 and Tp 3.2s, a reflection of 0.2 is obtained.

No physical modelling was undertaken for the reduced slope of the western

breakwater but, within the modelling to support the EIA, a conservative reflection

coefficient of 0.3 was used.

8. The design of the seawall and the wave reflection has been incorporated into the

coastal process modelling using a 0.3 reflection co-efficient for the seawall, which

is considered a conservative approach.

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Paragraph 4.3.1.11 of the ES (Project Description) states that rock armour will be

placed on the sea-wall, 'at a greater height' to allow for settlement.

(a) What is the maximum extent of the 'greater height'?

TLSB's Response

1. The total settlement was calculated for seven representative sections of the

seawall. The maximum total settlement is calculated at 1.3m for the deeper part of

the western seawall (section 2 on drawing 2.2.11 of the Works Plans - doc ref

2.2). The largest proportion of the calculated settlement will occur during

construction (typically about 80%). A smaller proportion will occur after

completion (i.e. post-construction). During construction, no use will be made of

preloading the bund wall to accelerate settlements. The ‘greater height’ referred to

at paragraph 4.3.1.11 applies to settlement compensation alone.

(b) How much settlement is expected? and;

TLSB's Response

2. The post-construction settlement for the western seawall is 275mm. The average

post-construction settlement for the eastern seawall is 130mm. The final

construction level of the western bund wall will thus be 275mm higher than the

design level to allow these post-construction settlements to take place without

affecting the safety against wave overtopping.

3. These figures are rendered as precise, calculated figures. In fact, the post

construction settlement can be seen to be modest in extent, and will (of course) be

dependent on local conditions so as to vary to some amount within appropriate

engineering tolerances.

(c) Over what timescale is the settlement expected to happen?

TLSB's Response

4. The settlement during construction take place over an average time period of three

years. The post-construction settlement is calculated for a 50 year period. The

general trend is logarithmic, meaning that most of the post-construction

settlement will take place in the first few years after completion. For the

maximum calculated settlement (western seawall) of 275mm after 50 years, about

190mm will take place in the first three years after completions. Ten years after

completion the calculated settlement will be 230mm.

EJR/EJR/343641/1/UKM/62783439.1 5


Paragraph 4.3.1.8 of the ES (Project Description) refers to an 'engineered toe'. No

description of this is provided; it is not known what construction and engineering

requirements will be necessary to provide the 'engineered toe'.

Please can the applicant provide a design drawing showing the engineered toe as

well as a plan showing where it will be required and details explaining how it will be

constructed?

TLSB's Response

1. Drawings 2.2.11, 2.2.12 and 2.2.13 of the Works Plans (doc ref 2.2) show ten

cross sections along the seawall. The engineered toe is shown on each of the

sections, both on the seaward side and on the lagoon side – effectively, the term

refers to the toe structure of the seawall in all locations for this Project. The main

function of the toe structure is to support the armour on the front and rear slopes

of the seawall, and to provide safety against undercutting and localised erosion.

2. In general, the seaward toe structure consists of a 3 to 4 metre horizontal

extension of the primary and secondary rock armour layers, placed on a heavy

(weighted) geotextile. The rock dimensions are determined based on stability

under governing wave attack for each of the sections. For the most exposed

section this has been confirmed in 2D physical modelling. To prevent loss of base

material, a geotexile is placed to prevent sand escaping through the pores of the

rock. The lagoon side toe structure has a reduced width of 2 metres which reflects

the smaller waves inside the lagoon.

3. The toe will be constructed as part of the front and rear armour placement.

Typically, the geotextile under the toe is placed as part of the geotextile placement

on the Geotubes® (as described in paragraph 4.5.3.22 of the ES) and is

subsequently covered by one or multiple rock layers as shown on the works plans

noted at paragraph 1 above. The rock placement will be done by either side stone

dumping or placement by crane, depending on the local depth.

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Paragraph 4.3.3.15 (Project Description) confirms that the gantry crane will sit

above the turbine housing unit, however, it is anticipated that the roof of the unit

will be raised and the crane housed internally. The dimensions of the internal

enclosure are not provided in the ES.

(a) How and where has this part of the construction process been incorporated

into the ES in terms of impacts?

TLSB's Response

1. Paragraph 4.3.3.15 of the ES states: “Figure 4.17 shows an external gantry crane

above the turbine housing structure. However, it is anticipated that the design

will be developed to raise the roof and have an internal crane with much reduced

height.” In this context, it is important to note that the statement "raise the roof" is

not a construction process, but a proposal that the roof height be greater than

shown in the application drawings. Otherwise, the general dimensions of the

structure are unaffected. The revised arrangements of craneage are shown on

drawing TLSB-260614-V0.1 at Appendix 3.5.1 to this response.

2. This is capable of being achieved within the submitted application since the

powers in article 3 and part 2 of Schedule 1 to the draft DCO enable a maximum

height for Work No. 2a of +18.5m CD. The submission of an alternative drawing

is permitted under Requirement 4 in Part 3 of Schedule 1 to the draft DCO. It is

expected that this would result in the substitution of plans bearing application

references 2.2.13 (Works plan) and Planning Drawings 2.4.25-.27. It is intended

that substitute drawings are supplied at ExA deadline 3.

3. The relationship of these proposals to the application and assessments recorded in

the ES is described below.

Main turbine gantry crane and housing

4. The main turbine gantry crane referred to in the Application will now be located

under the roof of the turbine housing which is an integral part of the turbine

housing structure. This will reduce corrosion in the marine environment and allow

some maintenance work inside the turbine housing void, thus improving

operational efficiency. The roof top level above the internal gantry crane is, as

shown in appendix 3.5.1, at +17m CD. This accords with the heights considered

in the visual impact assessment, which is dominated by the size of the offshore

visitor centre (roof top level at +33.5m CD) and which was based on a +16.5m

CD structure with up to 2m upwards deviatoin. As such, the assessment of this

structure is already included in the ES.

Other craneage

5. The turbine tender process and ongoing electrical and mechanical (E&M) design

work for the Project has further updated the craneage requirements since

submission of the Application. This work shows that – while one crane will be

incorporated into the turbine housing structure as described above – other gantry

cranes are still required which must be mobile and external to the turbine housing

EJR/EJR/343641/1/UKM/62783439.1 7

roof. These are required for periodic maintenance purposes: to insert stop logs

(that allow work to occur within a dry turbine chamber); and/or to lift turbines,

start/stop gates, sluice gates or other components requiring servicing. The general

arrangement and top levels of these external cranes is shown on the drawing

attached at Appendix 3.5.1.

6. The top level of these mobile external gantry cranes, as now proposed, varies

from +19.2m CD to +24.2m CD and as such they are smaller than the original

main gantry crane assessed at a height of ~+27.5m CD with a power to deviate

upwards of 2m. The visual impact of these cranes falls within the envelope

considered in the ES supporting the Application, albeit the number of external

cranes has now increased from two to a maximum of four - see appendix 3.5.1.

7. A comparison of the designs from Application to date is shown in the table below:

Lifting

device/purpose

TLSB – submitted design

for Planning Application

(top level)

Present design

(top level)

Turbine

maintenance

Multi-purpose main gantry

crane (+27.5m CD) or;

Internal gantry crane (not

shown)

Internal gantry crane

(+17m CD roof top level)

Turbine

start/stop gates

Not included Internal cylinders for

daily operation (+17m

CD top level).

For maintenance:

External Gantry Crane 1

(+24.2m CD)

Turbine stop

logs

Assumed to be a mobile

crane to be mobilised from

Swansea as and when

needed

External gantry crane 1

(+24.2m CD) – sea side


(+22m CD) – lagoon side

Maintenance

Island - crane

Gantry crane (+27.5m CD) External Gantry crane 4

(+27.5m CD)

Main sluice

gates

A-frame hoist (+16.5m CD,

as per drawing 2.4.26 in

Folder 2, Volume 4).

Internal cylinders for

daily operation (+16.5m

CD top level).

EJR/EJR/343641/1/UKM/62783439.1 8

For maintenance: assumed

to be a mobile crane to be

mobilised from Swansea as

and when needed

For maintenance:


(+19.2m CD)

Sluice gate stop

logs

Assumed to be a mobile

crane to be mobilised from

Swansea as and when

needed


(+19.2m CD)

8. The table above shows the worst case. If possible, the additional, specialised

cranes 1 to 4 described above will be combined into fewer general-purpose

crane(s), which will remain within the required parameters. When not in use, the

crane(s) will be stored on the turbine and sluice gate dividing structure

(maintenance island).

9. Although there may be more cranes than originally anticipated, these will all be

located together in the same general area. In terms of heights, as identified in the

table above, the cranes are all considerably lower than the original proposed

gantry crane, ranging from around 4.5m to 11.7m above the seawall (17m –

24.2m above CD). The cranes would be black/grey in colour (as stated in the ES),

slender, and can be stored together, thereby minimising potential effects.

Notwithstanding this, a further review of the potential effects from relevant

viewpoints has been undertaken and is provided below.

Verification of assessment

10. The SLVIA allowed for an assessment of a turbine and sluice gate dividing

structure that included an external semi-goliath gantry crane. The worst case now

proposes to include the following cranes: 1no. internal gantry crane; and up to

4no. mobile external gantry cranes.

11. Within the ES, a Zone of Theoretical Visibility (ZTV) was undertaken

incorporating the largest block structures of the Project. For the offshore area this

was the Offshore Building. Within the ZTV the following heights as described in

Chapter 4 of the ES (para 4.3.5.9 and para 4.3.5.22) were assumed:

Offshore Building - 25.5m above the Lagoon seawall; and

Western Landfall Building - 13.5m above the Lagoon seawall.

12. As identified in Chapter 4 at paragraph 4.3.1.11, the permanent level of the top of

the rock armour along the most exposed sections is +13.5mCD (Chart Datum), as

shown on Figure 4.4, falling to +13mCD for a section adjacent to the Neath

Channel and will be +12.5mCD for the sections of the seawall approaching

landfall on both sides, shown on Figure 4.5.

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13. The actual height of the offshore building will be 33.5m above CD, as such the

ZTV was based on a larger “envelope” than that actually proposed for the

offshore Project structures (namely 36m above OD, see Figure 13.05 of the ES)

and a worst case ZTV has been prepared and used for the SLVIA. As the cranes

would be slender plant items, which could be moved around, they were not

included in the ZTV block, but reference was made to them in consideration of

effects upon relevant viewpoints throughout the discussion within the SLVIA

chapter of the ES (Chapter 13).

14. The SLVIA (Chapter 13 of the ES) identifies that, from the 22no. viewpoints

assessed, the turbine and sluice gate dividing structure and semi-goliath gantry

crane would potentially be a feature of views from the following locations:

Viewpoint 1 - Aberavon Sands, South

Viewpoint 2 - Aberavon Sands, North

Viewpoint 4 - Headland Road, St. Thomas, Swansea

Viewpoint 5 - The Knab, Adjacent to Mumbles Pier

Viewpoint 6 - Mumbles Hill Nature Reserve

Viewpoint 7 - Swansea Promenade, near Lido

Viewpoint 8 - Clyne Golf Course, Swansea

Viewpoint 9 - Nicander Parade, Townhill, Swansea

Viewpoint 10 - Meridian Quay, Swansea

Viewpoint 11 - Swansea Promenade

Viewpoint 13 - Kilvey Hill, Swansea

Viewpoint 16 - Swansea University Science and Innovation Campus

Viewpoint 18 - PRoW on Mynydd Brombil

Viewpoint 19 - Swansea Bay

Viewpoint 21 - Pant y Celyn Road, Townhill, Swansea

Viewpoint 22 - Clyne Gardens, Swansea

15. Following the introduction of further, mobile gantry cranes to be located mainly

on the dividing structure, it is predicted that they will be viewed as an additional

element, most noticeably from close distance views including locations within

Swansea Bay (Vp19), on Swansea Promenade (including VP7 and VP11), The

Mumbles (VP5) and Meridian Quay (VP10). They may also be noticeable from

elevated locations including Kilvey Hill (VP13) and the areas of St. Thomas

(VP4) and Townhill (VP9 and VP21), both within Swansea. However, they are

predicted to be viewed in conjunction with the Offshore Building as opposed to as

isolated features.

16. From other, more distant locations, the additional cranes will be minor elements

of the view. It is concluded that, although visible, the introduction of further

cranes and any subsequent additional effects on visual amenity as a result of their

introduction into the landscape/seascape, beyond those currently identified within

the SLVIA within the ES, will not be to an extent that will affect the conclusions

of that assessment, which still stand.

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(b) Please could the applicant explain how this design aspect will be secured in

the DCO?

TLSB's Response

17. The form of the turbine house, including craneage is secured by Requirement 5 of

the DCO, which requires construction of the Project in accordance with the plans

that it lists. These include the drawings with reference 5118483-ATK-02-ZZ-DR-

C-1110, 1208, 1209 and 1213.

18. If and to the extent that it is proposed to construct the Project other than in

accordance with the above drawings, the details of any alternate design must be

approved in advance of construction by the relevant local planning authority. The

mechanism for this is secured by requirement 4, for the revised wording of which

please refer to the Response to Written Question 3.2b.

EJR/EJR/343641/1/UKM/62783439.1 11

3.6 to the Applicant, MMO and NE

The ES includes a description of temporary work required to facilitate the construction

of the development (Section 4.5 (of the Project Description onwards)). The draft DCO

does not appear to refer to some of the aspects of the temporary construction works, (for

example, lay-down areas, material handling facilities, demolition of sea walls and

existing development and concrete crushing etc.)

(a) Please can the applicant provide a list of work processes and areas that will

be included in the 'temporary works' and confirm (by cross referencing the

work processes and areas to the relevant sections of the ES) that all aspects

have been assessed in the ES.

TLSB's Response

1. Section 4.7.7 in Chapter 4 of the ES describes the temporary elements associated

with construction of the Project, and identifies a number of potential construction

site locations for possible use (Figure 4.56 of the ES and re-produced below.) The

areas shown in the figure allow maximum appropriate flexibility for siting of

facilities for the construction phase. The boxed areas illustrate the sizes required,

although only one compound of each type of area would be required.

2. The construction masterplan at Appendix 3.9.1 shows the areas that are being

considered for the activities described below.

3. The areas are as follows and are described further in the relevant paragraph in

Chapter 4:

i. Area A - offices, stores, car parking, site access control and plant yard.

Requires an area of approximately 26,000 m2 (260m x 100m or equivalent)

(paragraphs 4.7.7.5 – 4.7.7.7, Figure 4.57)

ii. Area B - concrete batching plant, stockpiling area and pre-casting yard.

Requires an area of around 17,000m2. Two possible locations have been

identified. (paragraphs 4.7.7.8 – 4.7.7.10, Figure 4.58)

iii. Area C - steelwork fabrication yard. Requires an area of approximately

22,500m2. Two possible locations have been identified. (paragraph 4.7.7.11,

Figure 4.59)

iv. Area D - storage yard. Requires an area of approximately 62500m2 (625m x

100m or equivalent). Two possible locations identified. (paragraph

4.7.7.12).

EJR/EJR/343641/1/UKM/62783439.1 12

3. This temporary land requirement for construction has been included in the

assessment on terrestrial ecology presented in Chapter 12 of the ES, at sections

12.5.3 “Potential construction impacts, mitigation and residual impacts” and

12.5.4 “Potential construction impacts on key ecological receptors”. The

assessment has been informed by site-specific surveys undertaken for the Project.

Further information on this survey work is provided in the Technical Appendix to

Chapter 12 of the ES, sections 12.2 – 12.8. The area surveyed cover the areas

being considered for use during the temporary construction phase.

4. Lay down areas would be provided on an ad hoc basis where and when required

within these compounds or elsewhere in the Order limits. Activities in such areas

would include: loading and unloading of vehicles; storage of materials; vehicles

and plant parking; storage of small plant and containers for small tools; and are

not predicted to be environmentally intrusive.

Rock storage

4. Rock storage areas for rock armour delivered by sea will be required to allow

flexibility in the work programme, and to make allowance for varied weather

conditions. This approach means that a buffer of rock supplies can be established

so that construction may continue even if access to the Project or from the

quarries is precluded for reasons such as adverse weather conditions. Further

information is provided in TLSB's Response to Written Question 3.18. See

drawing at Appendix 3.9.1 where these areas are shown on an OS based map.

5. Chapter 4 of the ES, paragraph 4.5.3.24, states that “The stockpiles would be

located near the landfalls at both sides of the Lagoon. The stockpile adjacent to

EJR/EJR/343641/1/UKM/62783439.1 13

the western seawall would be approximately 400m by 400m and piled up to 3m

high. The stockpile adjacent to the eastern seawall within the lagoon would be

approximately 250m by 250m in area and piled up to 3m high”.

6. These stockpiles will be located in the intertidal area adjacent to the area of the

construction works at the Western landfall and Eastern landfall, within the

Lagoon footprint. This is shown on Plan 1117:WMp:001 at Appendix 3.9.1. The

rock will be stockpiled to a height of 3m above Chart Datum.

7. The loss of this habitat is included in Table 4.4a of Chapter 4, which shows that

the loss of intertidal area as a result of these rock stockpiles between year 1 and 3

of construction will be approximately 22.25 ha. The positioning of the western

rock storage area would fall within the area used for the western landfall

facilities/boating centre, thereby minimising impacts. For the eastern landfall

rock storage area, once operational this intertidal area is predicted to re-colonise.

Onshore construction access and routeing

8. Road access to the Project for construction traffic will be via Fabian Way from

the traffic light controlled junction opposite the Park and Ride shown on plan

2.4.38 and then through the Port. For the western landfall, the access route will

follow the permanent proposed Project access road. It is expected that deliveries

will use the M4 and followed by the A483 (Fabian Way) to reach the Project site.

This is as assessed as part of the study area set out in paragraph 15.4.1.2 of the

ES.

9. For the eastern landfall, the road access will follow the same route; however, once

at the existing shoreline in the vicinity of the existing Swansea Port security gate,

a temporary track will be constructed across brownfield land (a former BP tank

farm), seaward of the existing sea wall, and across intertidal land to the south of

SUBC. This construction access to the eastern landfall will run along the

southern strip of the old tank farm behind the existing rock armour and concrete

retaining wall.

10. Construction Phase Travel Management Plan ("CTMP") (a draft of which is

included at Appendix 15.12 of the ES and also annexed to the draft CEMP) will

govern deliveries to the site. The final version of the CTMP will be approved by

the relevant local planning authorities under the terms of Requirement 6 annexed

to the DCO.

11. The on-site construction access routes are shown in Figure 4.60 below.

EJR/EJR/343641/1/UKM/62783439.1 14

12. For routine site deliveries all delivery wagons will access the site as indicated

above. Abnormal deliveries will be planned to ensure the Baldwins Bridge access

is clear, if necessary a holding location will be agreed where the delivery vehicles

will wait until they are required. If a large amount of deliveries are expected over

a short period (e.g. turbine elements) these will be planned to ensure that only a

certain amount arrive at site at any one time, again the holding location can be

used to control this.

13. As stated in paragraph 12.5.3.8 “Other construction activities, for example,

development of the seafront beside the Queens Dock for an access road, would

result in disturbance of coastal grassland and scrub communities, whilst

potentially enhancing the ecological value of land currently largely devoid of

interest (with the exception of localised populations of species such as Golden-

samphire) due to the presence of rock armouring and concrete. In addition, a

haul road aligned along the existing coastal edge will be constructed between the

docks and eastern landfall. Ultimately, the haul road will be become enveloped

within an artificial dune front although part of it will be re-used as a cycleway.”

Demolition of the seawall

14. Demolition of the existing port sea walls is a work, shown in the Planning

Drawings at 2.4.41 – 2.4.44, which comprise demolition plans.

EJR/EJR/343641/1/UKM/62783439.1 15

15. As identified in paragraph 4.3.7.8 of the ES “The proposed Project road will

extend along the south side of the Queen’s Dock and utilise the alignment of the

existing Port road. The majority of the existing 2m high concrete flood wall will

be removed to open up views to the Lagoon, this is shown in Figure 4.37 below.

Where there are existing World War II features, such as pill boxes, these

structures will be retained, along with a 3m section of wall either side, shown on

Figure 4.38 below. More information on these features can be found in Chapter

21, Cultural Heritage: Terrestrial Archaeology and Historic Landscape.”

16. As identified above, these works would be adjacent to the Project road works and,

as such, the extent of impacts will be minimised. Further information on

additional plant such as crushing plant is provided in TLSB's Response to Written

Questions 3.17, 10.14 and 10.15. The timing of the removal of the seawall would

be programmed such that coastal protection within the Port is maintained.

(b) Does the DCO require amendment to refer to these temporary works?

TLSB's Response

17. It is suggested that the draft DCO does not refer to all aspects of the temporary

construction works for the Project. In particular, this includes lay-down areas,

material handling facilities, demolition of sea walls and existing development and

concrete crushing.

18. Some of the items listed are not themselves works, being demolition. That would

apply to demolition of existing sea walls and "existing development." These are

provided for in article 3(2) which includes "decommissioning and demolition of

any buildings or other structures within the order limits to the extent they relate to

are required by or are incidental to the carrying out of the authorised

development." Further, such works are controlled by Requirement 5 and plans

2.4.41-2.4.44.

19. In respect of the other items it would be possible to include a list of temporary

works expanding schedule 1 to the development consent order to include those

identified in the ES, should this assist the Examining Authority. However, the

extent of the works in question does not require them to be identified as scheduled

works.

EJR/EJR/343641/1/UKM/62783439.1 16


The ES Chapter 4 (Project Description) identifies that piling is likely to take place

offshore during the construction of the cofferdam that is required for the turbine

and sluice-gate housing, as well as to create the dolphin piles that are proposed to

surround the outer edge of the lagoon in the vicinity of the turbine and sluice gates.

(a) Is piling proposed to take place in any other location?

TLSB's Response

1. As stated in the submission in respect of the construction of the temporary

cofferdam, submitted to the Examining Authority in June 2014, TLSB now

intends only to pursue seawall construction techniques using a sediment-based

berm with Geotubes® as a method of constructing the cofferdam. It no longer

proposes construction of a twin wall sheet piled cofferdam. Therefore, piling of a

cofferdam structure as described in the ES will no longer be required for this part

of construction, with a commensurate and material reduction in piling activity.

See paragraphs 4.5.3.35 - 4.5.3.38 of the ES for more detail on the preferred

method.

2. Nevertheless, a slurry wall will still need to be piled into the temporary bund for

the now-proposed method of construction. This wall will be installed from and

through the top of the temporary bund by vibrating a H-beam into the ground and

pulling it back while jetting grout into the structure. This creates an impermeable

cut-off within the temporary bund wall. In contrast to the piling required for the

sheet pile cofferdam, this piling will require vibration piling only, and, although

offshore, will be undertaken using land based equipment in the dry of the

temporary cofferdam. It will be a 24/7 activity, although the duration will be 6

weeks, rather than 6 months needed for the other (piled) method of construction.

3. Piling is required for the dolphin piles forming the turbine exclusion zone (Work

No.2c). There will be 10 dolphin piles, with piling required for 10-15 days during

daytime hours only. Vibration piling will be used as far as possible, although

there is a small likelihood of percussion piling.

4. A cut off sheetpile will be required at the toe of the turbine house (Work No 2a).

This piling will take place in the dry within the temporary cofferdam. It will take

4 weeks of vibration piling, during daytime hours only.

5. The quay wall of the boating area (Works No. 6a and 6b) will require 1 month of

vibration piling, but percussive piling will be required if hard layers are

encountered. This will be daytime piling only.

6. The boating centre building and hatchery, and the offshore building will both

require 2 weeks of percussion piling using land based equipment. This will be

daytime piling only.

7. A small amount of piling will also be needed for the water shuttle pontoon and the

floating jetty boating are Works No. 9a and 9b. These will both require 2-3 days

of vibration piling, daytime only.

EJR/EJR/343641/1/UKM/62783439.1 17

8. Please see the plan given at Appendix 3.7.1 for further details and locations of all

proposed piling activity.

9. Noise and vibration impacts have been assessed from percussive piling at the

turbine and sluice gate housing structure for both daytime and night-time periods

for onshore receptors and have been shown to have no significant impact. All

land-based piling is proposed to take place during the daytime only, and will use

vibro-piling. In the case of the quay wall boating and boating centre building and

hatchery area, percussion piling may have to be used for the last few metres of the

piles, dependent upon ground conditions. However, an evaluation of potential

noise levels has been undertaken and assessed. Noise from piling will be audible

at some receivers; however, when assessed using BS5228-1, levels at all receivers

would be below the fixed noise limit criterion.

(b) If so, please could the location be shown on an OS based plan, together with

the provision of details of the likely duration of the piling, the type of piling

proposed and whether the piling will be undertaken 24/7?

TLSB's Response

10. Please see the plan at Appendix 3.7.1.

EJR/EJR/343641/1/UKM/62783439.1 18


The ES Chapter 4 (Project Description) identifies that both percussion piling and

vibration piling/piling by jack-up barge using a piling rig are likely to be required,

with percussive methods necessary when harder base rock materials are

encountered.

Have the noise and vibration calculations given in ES Chapter 19 assumed that

piling would be carried out by vibration piling alone?

TLSB's Response

1. Chapter 19 of the ES submitted with the Application assesses both vibration

piling and impact (percussion) piling methods. It is not assumed that vibration

piling alone will be deployed.

2. The assessment for air borne noise and the effects on the terrestrial environment

as a result of piling is provided at paragraphs 19.5.2.12 – 19.5.2.20 of the ES.

Tables 19.19 and 19.20 show predicted day-time and night-time noise levels

arising from impact (percussion) piling activities, and tables 19.21 and 19.22

show predicted day-time and night-time noise levels arising from vibro-piling

(vibration piling) activities.

3. The assessment for underwater noise is provided at paragraphs 19.5.2.27 -

19.5.2.34. Table 19.27 shows source underwater noise levels for both impact and

vibration piling, and Table 19.28 shows predicted underwater noise levels for

impact and vibration piling at a range of distances.

4. The effects on the ecological receptors are discussed in the relevant chapters of

the ES, namely Chapter 9, Fish, including commercial and recreational fisheries;

Chapter 10, Marine Mammals and Turtles; Chapter 11 Coastal Birds; and Chapter

12 Terrestrial Ecology. The chapters use the assessment from Chapter 19, for both

impact and vibration piling, but take into consideration that impact piling will

only be used when necessary.

5. The vibration effects as a result of piling, which takes into account both impact

and vibration piling, are considered at paragraphs 19.5.4.3 and 19.5.4.4.

6. As discussed in response to the previous question the 24/7 piling over 6 months

associated with a sheet-piled cofferdam is no longer proposed to form part of the

Project. The assessment of these impacts, as presented in the ES, was considered

as a worst case. Based on the assessment undertaken, vibro-piling would be

within acceptable levels to fish and marine mammals and no mitigation would be

required. For percussive piling, JNCC standard mitigation measures would be

implemented.

7. As identified in response to Written Question 3.7 above, other offshore piling

activity is proposed, namely the dolphin piles associated with the navigation

safety zone. Ten dolphin piles will be installed over a 10 to 15 day period. The

intention will be to use vibro-piling but there would be a small possibility of

impact piling if necessary. An assessment of the effect of this piling has been

undertaken for fish and marine mammals, as described below.

EJR/EJR/343641/1/UKM/62783439.1 19

Fish

8. Noise calculations have been undertaken for vibro- and impact-piling respectively

for 2 m diameter dolphin piles. In the absence of precise information on piling

locations, the plots have been calculated centring on the turbine housing, but they

could be expected to shift south-westerly by some tens of metres, depending on

final locations. Source levels are as follows:

i. Vibropiling (2m diameter dolphin piles) 205 dB@1m (peak), 190 dB@1m

(rms)

ii. Impact piling (2m diameter dolphin piles) 235 dB@1m (peak), 220

dB@1m (rms)

9. Peak values have been used as worst case, as shown in the table below.

10. Predicted avoidance zones associated with vibro-piling are confined to ranges of a

few tens of metres for salmon, sea trout, eels and epibenthic hearing generalists

(dab and other flatfish, elasmobranchs, gobies etc.). Vibro-piling avoidance

ranges (>75dB) for cod and herring are slightly larger at around 355m and 630m

respectively. Impact piling potential avoidance ranges increase to around 1 km for

less sensitive species and 10km for cod, 17 km for herring.

11. For both vibro-piling and impact piling soft-start procedures will be used for the

first 20 minutes to enable fish to move away before full piling energy levels are

reached. In this way the impact of this piling activity will be minimised.

Marine mammals

12. The following sections address piling impacts relating to marine mammals as set

out in the ES.

13. For the Project, piling activities will generate the greatest levels of underwater

noise. A temporary cofferdam and associated sheet piling is no longer required for

the construction of the turbine and sluice gate housing structure. Instead, ten

tubular dolphin piles of 1.8m diameter will be used to delineate part of the

perimeter of the turbine and sluice gate structure which are estimated to take

approximately 10 days to install.

14. The ground investigation results (provided in Chapter 6 of the ES) suggest that

the most appropriate piling method would be vibratory, but there may be times

when harder material is encountered and in these circumstances percussive

methods may need to be adopted. Percussive piling (which is also referred to as

impact/hammer piling), will generate the highest noise Source Levels (SLs) and,

EJR/EJR/343641/1/UKM/62783439.1 20

therefore, the assessment has focussed on the potential noise effects of this type of

approach in the first instance, on a worst-case basis.

15. Based on these requirements, an underwater noise assessment of the construction

components of the Project was carried out to assess the impacts on grey seal and

harbour porpoise. The un-weighted peak and Root Mean Squared (RMS) SLs

from vibro-piling and impact piling measurements of 2m tubular piles, which is

the approximate diameter of the tubular dolphin piles proposed, were derived

from a review undertaken by the California Department of Transport.

i. Vibropiling (2m diameter dolphin piles) 205 dB@1m (peak), 190 dB@1m

(rms).

ii. Impact piling (2m diameter dolphin piles) 235 dB@1m (peak), 220

dB@1m (rms).

16. By comparing the received sound levels derived from the logarithmic noise

propagation model with the criteria proposed by Southall et al. (2007). Permanent

Threshold Shift (PTS) will occur in grey seals within 8m from the source of

impact piling and Temporary Threshold Shift (TTS) will occur within 14m. In

harbour porpoise, PTS will occur within 1-2m from the source of impact piling

and TTS will occur within 3-4m. Neither PTS nor TTS will occur in grey seal or

harbour porpoise even at the source of vibro-piling noise.

17. In terms of the dBht (Species) scale, the model predicts that grey seal will exhibit

a strong behavioural response at 90dBht within 1.3km from the source of

percussive piling and 40m if a vibratory hammer is used. Harbour porpoise is

predicted to show a strong behavioural response at 90dBhtht within over 5km

from the source during percussive piling and 1km from the source during vibro-

piling.

18. The effects of piling noise on marine mammals also needs to be considered in

relation to the duration of exposure. It is proposed that the piling work will take

approximately 10 days to complete, with vibratory piling thought to be the most

appropriate piling method based on the preliminary ground investigation results.

However, there may be times when harder material is encountered and in these

circumstances percussive methods may need to be adopted. Therefore any marine

mammals in Swansea Bay would only be exposed for a maximum of around 3

weeks (10 – 15 days, daytime only) and, taking a precautionary approach, it is

assumed that only a maximum 50% of that time would involve impact piling

19. It is also important to consider that the area in which the construction will take

place already experiences shipping, as well as maintenance dredging and,

therefore, marine mammals are likely to be habituated to a certain level of

anthropogenic background noise for periods of time.

20. Applying the standard impact assessment criteria, the sensitivity of harbour

porpoise and grey seal is considered to be moderate to underwater noise

generally. The probability of occurrence is high as is the importance of harbour

porpoise and grey seal, given their level of protection. Given that any effects

during vibro-piling, which is the preferred construction method, are limited to

EJR/EJR/343641/1/UKM/62783439.1 21

behavioural responses within 1km to the construction site, the magnitude of the

effects is considered to be medium. With respect to percussive piling which will

be used during construction on an ‘as required basis only’ (see above),

physiological effects (PTS or TTS) are predicted to occur within close proximity

to the construction site (14m) and a strong behavioural response will occur over a

larger area in the context of the 4155ha of subtidal habitat comprising Swansea

Bay (approximately 12% and 100% for grey seal and harbour porpoise

respectively) and therefore the magnitude of the effect is considered to be large.

The overall exposure and vulnerability of marine mammals to adverse noise

during impact piling is therefore considered to be high. Despite the temporary and

short term duration of the piling, given the level of exposure and sensitivity and

importance of marine mammals, the overall impact is assessed as a moderate

adverse impact during vibro-piling and a major adverse impact during impact

piling.

21. In order to reduce the significance of the impact during vibro and percussive

piling, several mitigation measures are proposed which are below. These include

following JNCC “Statutory nature conservation agency protocol for minimising

the risk of injury to marine mammals during piling” (JNCC, 2010) and also using

soft-start procedures for any vibro or percussive piling. With these measures in

place, residual impacts on marine mammals from construction noise are assessed

as being of minor adverse significance.

22. Confidence in this assessment is considered to be medium, given that the

underwater noise model is based on theoretical parameters and there is limited

empirical evidence of the behavioural effects of noise on marine mammals.

23. The following mitigation measures and monitoring will be implemented during

the installation of the dolphin piles:

i. Monitoring and mitigation would be undertaken during any vibro-piling or

impact piling following the guidelines highlighted in the JNCC “Statutory

nature conservation agency protocol for minimising the risk of injury to

marine mammals during piling” (JNCC, 2010);

ii. Installation of dolphin piles would be during daylight hours only;

iii. For vibro and percussive piling for dolphin piles, establishment of a

‘mitigation zone’ of radius 500m around the piling site, prior to any piling;

iv. Within this mitigation zone, detection would be undertaken by a Marine

Mammal Observer (MMO) and acoustically using appropriate Passive

Acoustic Monitoring (PAM) equipment;

v. Both the observers and equipment will be deployed at least 20 minutes

before any piling is due to commence;

vi. Any piling will not commence if marine mammals are detected within the

mitigation zone or until 20 minutes after the last visual or acoustic

detection;

EJR/EJR/343641/1/UKM/62783439.1 22

vii. The MMO/PAM operative should track any marine mammals detected and

ensure that they are satisfied that the animals have left the mitigation zone

before they advise the crew to commence percussive piling activities.

viii. Piling will commence using an agreed soft start procedure for at least 20

minutes (the gradual increase of piling power, incrementally, until full

operational power is achieved). The soft-start procedure will vary according

to hammer and pile design and other factors.

EJR/EJR/343641/1/UKM/62783439.1 23


Please can the applicant provide an OS based plan (or set of plans), showing both

the locational context and the layout of the following construction areas (drawn at a

standard scale and with a north point):

(a) The concrete batching plant and associated yard and storage bin areas;

TLSB's Response

1. The information is provided on the plan attached at Appendix 3.9.1.

(b) The areas of sea wall and breakwater that are to be demolished;

TLSB's Response

2. Drawings 2.4.41, 2.4.42, 2.4.43 and 2.4.44 of the Planning Drawings submitted

with the Application (doc ref 2.4) show details of the demolition works. The

seawall is to be retained at the location of the pill boxes and 3m on either side (see

also paragraph 4.3.7.8 of Chapter 4 of the ES).

(c) Locations for storage of rock armour and other construction aggregate

supplies brought to site by sea; and

TLSB's Response

3. The information is provided on the plan attached at Appendix 3.9.1.

(d) The turbine fabrication yard area including the turbine fabrication building.

TLSB's Response

4. It is no-longer proposed to incorporate a turbine fabrication yard or turbine

fabrication building within the development to be authorised by the DCO.

Instead, the turbine manufacturing and assembly facility will be promoted by a

separate planning application under the Town and Country Planning Act 1990.

EJR/EJR/343641/1/UKM/62783439.1 24

3.10 to the Applicant. Part (a) of the question is aimed at all interested parties including (but not

restricted to Dŵr Cymru (Welsh Water) (DCWW) and NRW)

The sediment analysis chart in ES Chapter 4 (Project Description, Table 4.2) gives

the results of the analysis for a suite of metals taken from various samples within the

proposed lagoon area, at various depths. The analysis results are compared with

CEFAS thresholds, which consider their suitability for sea disposal. The

contaminants have not been considered against Dutch Standards, which are

environmental pollutant reference values used in environmental remediation,

investigation and clean up. The 0.7m depth sample from VC206 shows arsenic

values of 48.3mg/kg, which is close to the threshold for the Dutch intervention

threshold (55mg/kg)2. The copper, lead, nickel and zinc levels from this sample are

above the Dutch intervention levels. Samples from VC202, 204 and 208 also have

metal contents above the Dutch target value3 but below the intervention value. All of

the contaminated samples were located along the western and southern areas within

the lagoon footprint.

(a) Are the Dutch standards relevant to marine sediments? If not, are there any

other standards that are commonly used in the UK, which give thresholds

relating to metal contamination in sediments, in terms of their potential for

ecological harm in the marine environment?

TLSB's Response

1. The Dutch standards (and also Canadian Standards) were commonly used in the

UK before CEFAS developed its own standards which are now the accepted 'UK

Standards'. Effectively, the results derived for the Project can be compared against

any of the standards, but the CEFAS ones are the recognised UK standards and

hence the most appropriate standards to employ. As CEFAS will be advising

NRW (MLT) on the dredging aspect based on these standards, its standards have

been used in the assessment.

2. It is also worth noting that the standards are not 'pass' or 'fail' levels. They set

guidance levels against which each application can be assessed on a case-by-case

basis. In determining the standards, CEFAS have based the levels on a number of

factors – one of which is the potential ecological effect to the environment.

3. Therefore, Dutch standards remain relevant to marine sediments, but CEFAS

action levels are 'more' relevant since they are the accepted UK standards that

CEFAS will be looking to see used (since the development will be within UK

territorial waters). The CEFAS action levels are the recognised UK standards for

consideration of metal contamination in sediments, in terms of their potential

effect (including that on ecology) within the marine environment.

2 The soil remediation intervention values indicate when the functional properties of soils for humans, plants and animals

is seriously impaired or threatened. They are representative of the level of contamination above which a serious case of

soil contamination is deemed to exist.

3 The target value is related to Dutch national background concentrations.

EJR/EJR/343641/1/UKM/62783439.1 25

(b) What additional sampling and analysis of sediment samples within the

lagoon area is proposed, in order to identify whether there are any more

contaminated areas?

TLSB's Response

4. CEFAS has noted the higher levels of contaminants at VC206 and requested

additional sampling to check if the levels of contaminants were an anomaly or if

this location constituted a "hot spot". However it also confirmed that, as they are

below CEFAS Action Level 2, they are acceptable for disposal to sea.

5. In addition to this CEFAS has requested further sampling to characterise the

sediments within the proposed boating area (near to Work No. 6a and 6b) and to

meet the requirements of the potential maximum volume of material to be

disturbed/disposed. This is because when the initial sampling was undertaken a

smaller volume was estimated. However, based on the results of the preliminary

Geotech survey sediment results, which are provided Table 4.2, Chapter 4,

additional material will need to be disturbed/disposed, and hence further sample

analysis is required.

6. CEFAS has confirmed that based upon a 8.1 million m3 dredged volume

additional samples are required, further samples should be collected and analysed

for metals, organotins, Polyaromatic Hydrocarbons, Polychlorinated Biphenyls

(PCBs) and particle size analysis. Samples would be taken from four sites within

the secondary dredge area in the middle of the lagoon (see Appendix 3.10.1) and

from two sites within the dredging area for leisure access (the boating area as

discussed at paragraph 5 above). At every sampling site, samples will be taken at

every metre down to the proposed dredge depth.

7. As clarified with CEFAS, the secondary dredge area is unlikely to be dredged

and, as such, sampling in this area would not be required. However, should it

become apparent that the secondary dredge area needs to be dredged this area

would also need to be sampled and the analysis approved by the MLT prior to the

commencement of any undertaken of dredging within this area. As such, to

ensure that the construction programme is not restricted, sampling will be

undertaken in the secondary dredged area as well, such that the data is available if

need be.

8. Finally it is proposed to collect a vibro core sample from two additional locations:

the proposed outfall extension corridor (although not essential, as the material is

not to be disposed of, samples will be collected to provide information on ground

conditions); and the small triangle area adjacent to the Neath channel which will

be dredged to widen the entrance to the channel; identified under works to Neath

Harbour Channel including the widening of the entrance to the channel and

replacement of its training wall.4 The samples from both these sites will include

samples for the CEFAS chemical suite at 1m depth intervals.

4 Work 4 – Draft DCO

EJR/EJR/343641/1/UKM/62783439.1 26

(c) What measures will be taken to minimize the risk of mobilizing the metals

within these contaminated areas during dredging and avoiding their use in

the lagoon walls?

TLSB's Response

9. As identified by the results of the ground investigation, all samples are acceptable

for use and disposal where necessary and in fact 73.5% of samples were below

CEFAS action level 1. In terms of metal uptake, the fine grained fraction of

sediment, namely the silt to clay fraction, facilitates the uptake of metals more

than any other grain size. As such, these would tend to have the higher metal

levels. In terms of engineering properties for use in the Geotubes®, coarse

sediments and gravel are required for use in the Geotubes® and the smaller

fractions are not appropriate. Consequently, the objectives of engineering

structural stability and avoidance of contaminated areas are intrinsically linked.

10. Based on the results of the geophysical survey and the geotechnical surveys, the

most appropriate sediments in the lagoon footprint for use in the lagoon wall will

be targeted. As such, by nature of design, the sediments with the highest potential

for contamination (e.g. silts) will be avoided. In areas where material is

unsuitable either from an engineering or chemical point of view, as identified in

Chapter 4, 4.5.3.14 "Any of these areas would be entered into the onboard

computers of the dredger to ensure they are avoided."

11. These measures are expected to be secured by conditions to be attached to the

marine licence to be issued by NRW.

(d) Para 4.3.1.27 of ES Chapter 4 (Project Description) states that the 'final

location of the dredged areas will be dictated by the location of the most

suitable material from an engineering property and quality perspective'.

TLSB's Response

12. Yes. As discussed in response to Question 3.10 above there is a positive link

between the two characteristics and this will be to the benefit of the project

twofold: first, in terms of engineering properties; and secondly, in terms of

reduced potential contamination.

(e) Does 'quality' include consideration of contamination levels?

TLSB's Response

13. Yes. If an area has been identified as inappropriate (eg above action level 2), then

the area would be avoided. The results of the sediment analyses from the ground

investigation are all below Action Level 2 and therefore are fit for use, although

additional sampling is to be undertaken (see response to 3.9(b) above).

EJR/EJR/343641/1/UKM/62783439.1 27


Figure 4.35 of ES Chapter 4 shows the location of the proposed access road and the

text in Paragraph 4.3.7.6 in this document states that the access track will be

constructed in the same method as the seawall, including rock-armour and then the

proposed dune-scape built up either side.

(a) Is it proposed to surface the access track, in order to reduce noise and dust

emissions from dump trucks and the lorries moving construction materials

including concrete around the site?

TLSB's Response

1. It is not proposed to surface this track during the construction phase. The track

will be used predominantly for access for earthworks plant engaged in the

construction of the eastern breakwater. The construction of the track will be

sufficiently robust to take this plant, as shown in Figure 4.36 of the ES. The

control of dust will be by water bowser, as and when required. The track will be

maintained regularly to retain a flat surface during construction, and this will

reduce vehicle noise. Noise will be monitored at the agreed receptors, and should

levels exceed the agreed allowable levels, control measures will be implemented

to rectify the situation.

(b) Is there any difference in construction methods/surfacing between the 'Port

Road' and the 'Project Road' identified in Para 4.3.7.9 and shown on Figure

4.37 and 4.38?

TLSB's Response

2. The construction of the two roads will be more-or-less the same. Where the roads

fall in plan over the existing internal port road (e.g. as shown in Figure 4.38 the

project road falls over the existing road) the construction of the existing road will

be assessed and retained if it meets design criteria. In this case the existing road

would be resurfaced.

(c) Please could the applicant show on a OS based plan the proposed access and

egress points into the construction areas for all HGV delivery lorries, as well

as details of lorry routing around the construction areas?

TLSB's Response

3. The Construction Masterplan (Ref. Plan No: 1117: WMP: 001, Appendix 3.9.1)

shows the access routes from the road network, and the internal site routes that

will be used for HGVs.

4. HGVs will generally leave Fabian Way at the Park and Ride junction (next to

McDonalds) and proceed to the site support area in which the materials are going

to be used. For example, the materials for concrete will go to the batcher (Area

B), where they will be mixed and loaded into ready mix trucks for onward

transmission to the temporary bund via the haul road shown over the broad

seaward park on the plan.

EJR/EJR/343641/1/UKM/62783439.1 28

5. Some materials, for example some of the steel reinforcement bars for the

concrete, will be delivered directly to the bunded site. In these instances, the

materials will drive to the site access control area (Area A on the Plan), where

they will be directed to the particular work-front inside the bunded construction

site.

EJR/EJR/343641/1/UKM/62783439.1 29


ES Chapter 4 (Project Description) paragraph 4.5.2.5 describes the working hours

for the project.

(a) Will HGV movements to and from the construction site be restricted to

normal working hours (eg 0800-1800 Monday to Friday and 0800-1300

Saturday)?

TLSB's Response

1. It is not proposed to restrict movements to and from the Project to normal

working hours as this may affect the programme for delivery of the Project.

Nevertheless, it is desirable to limit movements of HGV’s at peak times, to

minimize disruption to the road network. Therefore, the approach is to balance

the needs of the project with the sensitivity (or otherwise) of receptors. It is

important to bear in mind that the vast bulk of material required for the Project

will be sourced from or delivered by sea.

2. As stated at paragraph 15.5.2.2 of the ES “Working hours during the construction

phase have not yet been finalised”. However, it is likely that there will be

continuous working during some phases of construction such as sea wall

construction or concrete pours for the turbine housing. As such, it is not proposed

to restrict HGV movements to normal working hours as this could considerably

constrain the overall Project programme. The onshore import of some materials

will be closely linked to the offshore works and those within the offshore

cofferdam. These works will be 24/7 and, as such, any restriction in deliveries

would affect the offshore programme. In addition to this, in terms of disturbance

to receptors, the proposed access would be off Fabian Way into/via an active Port,

which is not itself constrained by hours of operation.

3. Overall, Fabian Way is a busy dual carriageway with over 34,000 two-way traffic

movements per day during the week falling to around 19,500 on a Sunday (Table

15.3, Chapter 15 – ATC data near Baldwins Bridge). Although overnight these

levels are considerably lower, there are still on average over 3000 two way

movements between 2000hrs and 0600hrs during the week and on a Saturday, and

around 2600 two way movements on a Sunday. Table 15.5 in the ES provides

information on the proportion of HGV traffic and for Fabian Way this varies from

around 3% to 6% along the main dual carriageway. As such, potential

disturbance to receptors through additional 24/7 traffic during the temporary

construction phase as a whole is anticipated to be limited.

4. In terms of impact on other traffic using the local highway network, the key

busiest periods are the AM and PM commuter peaks, typically 08:00-09:00 and

17:00-18:00. When work is carried out in shifts, the start and finish times

generally do not coincide with the regular commuter peaks. For clarity, impacts

on vehicle movement, etc. are considered to be greatest during the day when more

traffic is on the road. As shown in Chapter 15 of the ES the assessment of traffic

has been undertaken during daytime hours, which is considered the worst case

assessment.

EJR/EJR/343641/1/UKM/62783439.1 30

5. It is considered that the effect on Fabian Way can best be managed by use of a

Construction Phase Travel Management Plan. This is annexed to the CEMP, and

must be approved by the relevant local planning authority under requirement 6.

(b) Will the concrete batching plant work 24/7?

TLSB's Response

6. The concrete batching plant will work 7 days a week during the construction of

the structures that form the generating station. It will work for 24 hours a day at

certain times where so needed. Such times are anticipated to be April 2016 to

September 2017.

EJR/EJR/343641/1/UKM/62783439.1 31

3.13 to the Applicant - Cornwall Council is requested to respond to part (c) in particular

Chapter 4, Para 4.6.2.1 and Table 4.6 identify that 1.92mt of rock armour and

0.87mt of rock underlayer will be supplied from Dean Quarry in Cornwall by 10,000

tonne capacity barge. As construction is anticipated to take place over 3 years, a rate

of rock supply/importation of circa 930,000 tonnes of rock is assumed necessary.

(a) Dean Quarry has recently been marketed for sale with the sales particulars

identifying that it operated up to 2005 with an annual output of

approximately 200,000 tpa. The loading jetty is included in the sale, although

the conveyor system installed on the jetty deck has been removed. In view of

the dormant nature of the quarry, and the previous output levels of circa

20% of the required output level to supply the TLSB project:-Is there a

supply agreement in place between the quarry owners and the applicant to

deliver circa 930,000 tpa of rock and rock armour over a 3 year period?

TLSB's Response

1. The production capability for Dean Quarry is described below. However, it is

important to identify a number of matters. First, the operation of Dean Quarry

previously undertaken was different in character and output to that proposed for

the Project. The grade of aggregate produced by the quarry was much finer and

necessitated different handling facilities to those now required to produce rock

armour. As such, it is not necessary to replicate removed machinery for the

Project.

2. Second, a supply agreement is not required. This is because the ownership of the

quarry is to be secured by a company associated with TLSB, meaning that supply

arrangements are not dependent solely on a contractual supply relationship – the

resource is available to the Project.

3. Rock armour production will be achieved through a specifically procured fleet of

robust earth moving equipment, and a suitable blasting schedule, with skilled

operators. Production estimates are generally provided in terms of normal quarry

operations. Therefore, generous efficiency factors are used to arrive at realistic

outputs. In normal quarry work the operating efficiency is a standard of 90

percent; with face loading equipment rated at 400 tonnes per hour (tph). In rock

armour work the operating efficiency is generally 60 percent of actual output.

4. The following calculation depicts how extraction of the required volume of rock

can be achieved, noting that the quarry will continue to operate outside the

shipping season (i.e. quarrying can continue even when seasonal restrictions

preclude the construction works in Swansea Bay from proceeding):

400 (tph) x 60% = 240 (tph) per machine x (2 machines) x (65 hrs/week) =

31,200 tonnes per week

31,200 tonnes/week x 48 weeks per year = 1,497,600 tonnes per annum

(tpa) capacity

EJR/EJR/343641/1/UKM/62783439.1 32

5. The annual capacity given above is approximately 20 percent in excess of the

total annual output required for the Project from the quarry (being some 1,200,000

tonnes).

(b) Will it be possible to re-establish the quarry infrastructure necessary in

order to deliver a major increase in rock outputs level within the required

timeframe?

6. Dean Quarry has the benefit of an existing planning permission, recently reviewed

under ROMP provisions allowing it to be worked until 2035. A copy of that

planning permission is attached at Appendix 3.13.1. In addition, the quarry

contains sufficient quantities of rock to supply construction of the Project. The

application to discharge conditions attached to the planning permission has been

submitted, which will enable the extraction of rock to commence by Q4 of 2014.

Subsequently, an appropriate marine licence application to ensure marine access

for Dean Quarry will be submitted in early Q4 of 2014.

7. Following the granting of planning permission the infrastructure will be updated

in accordance with the consent. As part of the proposed works, a new loading area

and breakwater will be constructed with the physical capacity to meet the loading

and shipping requirements of the proposed extraction programme, as detailed

above. Due to the size of rock required for the lagoon seawall, rock will be loaded

directly onto a rock barge by specialised plant. This supports TLSB’s confidence

that the required infrastructure can readily be put in place, with the means to

supply the volume of rock required, within the necessary timeframe.

8. Even if it were the case that Dean Quarry was not available at the very outset of

construction, which is considered unlikely, it would be possible to source rock

armour from other sources on an interim basis. Suitable alternative locations

from which armour could be sourced are:

a. “West of England” quarry in Cornwall

b. Quarry in Scotland

c. Quarry in Norway

(c) Are there any planning permission restrictions on outputs or schemes

required pursuant to conditions that have to be satisfied before rock

extraction can re-commence at Dean Quarry?

9. There are no restrictions on output from the quarry and an application has been

submitted to discharge the outstanding conditions to enable the rock extraction to

recommence. A copy of the planning permission is at Appendix 3.13.1.

(d) How realistic is it to expect deliveries of rock and rock armour from Dean

Quarry to take place at the rate of 3 x 10,000 tonne barges per week, all year

round?

10. The proposed works programme for Dean Quarry is to extract rock on a year

round basis, in accordance with the conditions of the minerals consent. Excess

rock, which is ready for delivery outside the construction seasons in Swansea Bay,

EJR/EJR/343641/1/UKM/62783439.1 33

will be stored in a designated rock storage and grading area, within the quarry

area.

11. The loading of rock from Dean Quarry and transport to Swansea Bay will only be

performed during a 30 week period per year (avoiding winter phases), ensuring

that the delivery of rock will be carried out in the optimal seafaring months. The

allocated sub-contractor will be required to have sufficient equipment and

expertise to load 30,000 tonnes per week and load vessels at a rate of at least 300

tonnes per hour. At this rate, a 10,000 tonne barge van be filled in 33 hours.

(e) What contingency arrangements would there be for rock supply at times

when the transport of the rock by sea cannot be achieved, due to unsuitable

sea conditions?

12. As stated previously, transhipment of rock will only be conducted in the best

seafaring conditions (being 30 weeks per year) per annum. TLSB will ensure

allocation of a leading marine contractor, familiar with working limitations of

their specialised fleet. There are two stockpile areas provided for in the

construction laydown areas of the Project, which allow for further contingency

should bad weather disrupt delivery. These are shown on the drawing at

Appendix 3.9.1.

13. On the basis of the above, TLSB does not consider that a contingency is required.

TLSB is confident that the delivery programme for the Project can be achieved.

EJR/EJR/343641/1/UKM/62783439.1 34

3.14 to the Applicant and Swansea Port Operator (ABP)

The possibility of bringing the raw materials for concrete by rail is identified in ES

Chapter 4, paragraph 4.6.3.2. The site of a potential rail-head for

cement/PFA/GGBFS/other is also identified on drawing 4.58 (this shows the

Indicative batching plant layout). The quantities of each type of building material

required and the number of HGV movements that these would generate are given in

Table 4.6.

(a) In view of the applicant's stated intention to include principles and elements

of sustainable development in the project design, if the raw materials for the

concrete were imported by rail, it would reduce the number of HGVs visiting

the site by an average of 400 HGV movements per week over the

construction phase. In order to establish whether these materials can be

delivered in a sustainable manner, by rail, it is important to establish

whether the adjacent rail head could be adapted for the importation of

construction materials:-Please could the applicant describe the technical and

financial feasibility (or otherwise) of using the adjacent port rail-head for the

importation of construction materials, including cement, cement replacement

materials and the construction aggregates necessary to produce 220,000 m3

of concrete over three years? The statement should address matters

including (i) the infrastructure improvements necessary to accommodate the

types and sizes of freight wagons required for the various types of

construction materials; (ii) the availability of rolling stock for delivering

materials by rail; (iii) the availability of time-slots on the rail network to

enable a reliable supply to construction aggregates, cement and cement

substitutes to be delivered to the project by rail. These details could be

addressed through a Statement of Common Ground.

TLSB's Response

1. TLSB's potential concrete suppliers have proposed differing sources of materials

for the concrete, with varying options for moving materials to the site, including

by rail.

Infrastructure Improvements

2. The railhead shown on Figure 4.58 accompanying the ES was an indicative

representation of the principle that, for delivery of cement and cement

replacement materials direct to the batching plant from rail, the batching plant

would have to be adjacent to rail provision. This is because cement and cement

replacement materials are pumped through flexible hoses from tankers (either

road or rail mounted) into the silos that are part of the batching plant. This is

theoretically possible for the northernmost of the two potential sites shown, using

existing rails. However, the existing rail connection into Swansea docks have

been out of use for some time, and would require extensive maintenance and

repair work to bring back into use. There are tight radii on these rails that would

mean that rolling stock would have to be moved by shunter rather than mainline

freight locomotives. Theoretically, this railhead could also be used for delivery of

aggregates used in the concrete.

EJR/EJR/343641/1/UKM/62783439.1 35

3. The existing rail infrastructure does not extend onto the potential construction

compound site shown on the peninsula between docks, nor the potential sites for

Permanent Works footprints, referred to in paragraph 4.7.7.3 of the ES. As such,

double handling would be required.

4. There is a working railhead to the north of Fabian Way which could be used to

offload materials for the concrete. This railhead has been offered by one of the

suppliers who has tendered to TLSB. This railhead would require the onward

transmition of materials using road wagons or dump trucks for aggregates and

road tankers for cementitious materials from the railhead to the batching plant and

adjacent storage areas.

5. There will be a premium to pay for delivery of materials by rail, based on the

quotation received from suppliers. The exact amount of this premium will depend

on cost of bringing the Port of Swansea railway lines back into use, and transfer

costs for materials from rail to the batcher.

The availability of rolling stock and capacity on the rail network

6. Rolling stock owned by prospective suppliers is available. Time slots are

currently available on the local rail network to allow delivery of these materials.

Arrangements for delivery of materials by rail have been discussed with the

landowner, ABP. The financial feasibility of delivery of concrete component

materials by rail can only be fully determined when the location for the batcher is

determined and the concrete supply for the project is chosen.

(b) In ES Chapter 4 (Project Description), Table 4.6, the last column is entitled,

'Movements per Week' and the number of HGV movements is given for the

various types of construction materials required by the project. In this table,

is a HGV movement equivalent to 1 HGV bringing materials to the site (in

which case there are also an equivalent number of empty HGVs leaving the

site), or do these HGV movements reflect the fact that for every delivery,

there is also an empty HGV leaving the site (in which case the number of

HGVs delivering material to the site are half of the stated numbers within

this table)?

TLSB's Response:

7. An HGV movement in the table represents 1 HGV bringing materials to the site,

with an equivalent number of empty HGVs leaving the site.

(c) Are the vehicle movements per week the average number of vehicles per

week over the project construction phase, or the maximum number of

vehicles per week? If they are average numbers, please could maximum and

minimum numbers of HGVs be provided, as well as the average and

maximum number of HGV movements on a daily basis during the various

stages of construction?

TLSB's Response:

8. The vehicle movements per week are quantities averaged over the period during

which the particular operation is programmed to happen. Where the delivery rate

EJR/EJR/343641/1/UKM/62783439.1 36

of an item is constant, this is maximum. For completeness, the maximum,

minimum and daily numbers are shown on the table attached to these Responses

at Appendix 3.14.1.

EJR/EJR/343641/1/UKM/62783439.1 37


Two options are identified for dealing with the DCWW (DCC) water outfall pipe;

they are (i) leave it where it is and provide additional treatment processes to reduce

the risk of microbial contamination of the lagoon water or (ii) extend the outfall pipe

by 1.5km so that it discharges outside the southern edge of the lagoon.

DCC's view is that the only viable option in respect of the current outfall is extension

beyond the sea wall. This will provide a consistent solution which is resilient to

future potential population growth and the effects of climate change. DCC stated in

their RR that they, "therefore supports the extension of the outfall in accordance

with Work no. 3, Part 1, Schedule 1 of the draft DCO and is carrying out detailed

design and costings analysis to inform TLSB".

The Non –Technical Summary states in the introduction that, 'An integral part of

the Project is the provision of an enclosed water sports venue capable of providing a

safe body of water for local, regional, national and international events'. In view of

this aspiration and DCC's view:

(a) Would option (ii) provide a more robust solution for ensuring that the

microbial levels within the lagoon are kept at levels which facilitate water

sports activities all year round?

(b) If the outfall is left where it is, what is the risk and likelihood of unexpected

heavy rainfall events causing storm water flows to discharge into the lagoon

which give rise to elevated microbial levels and thus water sports would not

be safe?

(c) Please could the applicant identify on a plan the location, size (including

height) and layout of the proposed UV treatment plant, if it is to be

incorporated into the design?

(d) Is there an agreement in place between the applicant and DCWW for the

operation of the UV plant after it has been constructed?

(e) Is the applicant prepared to agree with DCC that the foul water outlet will

need to be extended outside the lagoon as part of the DCO?

TLSB's Response

1. Following submission of the Application, further discussions have been

undertaken with Dwr Cymru Welsh Water ("DCWW") to develop proposed water

quality enhancement options. Although detailed modelling has confirmed that,

UV disinfection, combined with a water quality management plan, would permit

large parts of the lagoon area to be used for all year round water sport activities,

in DCWW's view there was scope for longer term water quality management

issues and DCWW's duties.

2. The alternative option of extending the existing outfall by some 1.5km would

provide Excellent (rBWD) bathing water and improved shellfish water quality

throughout the lagoon, provided that the engineering consequences of taking the

outfall beyond the lagoon structure, ie the seawalls, are able to be resolved. These

EJR/EJR/343641/1/UKM/62783439.1 38

technical challenges have been progressed by the parties and an acceptable design

concept has been agreed in principle.

3. A number of other stakeholders, including Natural Resources Wales, the City and

County of Swansea and Port Health Authority, have noted the location of the

outfall within the lagoon. Each has indicated that an extension of the existing

outfall would be their preferred engineering solution in respect of long term use of

the lagoon for water contact sports or for the presence of shellfish beds.

4. On the basis of the above, based on DCWW's concerns about future

responsibility, on other representations raised, and having regard to the relative

neutrality of environmental impacts between the two options for water quality

enhancement, TLSB has proposed the exclusion of Work No. 8 (UV treatment

works) from further consideration as part of the authorised development

comprising the Project. As such, it is not necessary to address items a-d above

and item e is self-evidently considered in this response.

EJR/EJR/343641/1/UKM/62783439.1 39

Physical/Coastal Processes


(a) Potential impact on water chemistry from impoundment resulting from sea

walls is described on page 51 of the Water Framework Directive (WFD)

Report. Is this impact considered acceptable under the terms of the WFD?

TLSB's Response

1. Yes. So far as TLSB understands, the impact on water chemistry from the

impoundment of the seawalls is acceptable in terms of the WFD objectives. The

conclusions drawn in the WFD report submitted with the Application (doc ref 8.3)

are currently being updated in line with discussions with NRW and an updated

report will be supported by the more detailed assessment of the individual

chemical components in Chapter 7 of the ES, at section 7.7.7.

2. The assessment referred to above demonstrates that the water impounded within

the seawalls constructed as part of the Project will not be subject to chemical

change simply as a result of impoundment. If, as is now proposed, the DCWW

long sea outfall is extended beyond the impounded area of the lagoon, the water

quality within the area of the lagoon itself will be improved above its quality as at

the present day.

3. Furthermore, the status of the waters in water bodies considered under Article 4.8

of the WFD is not predicted to deteriorate as a result of the Project in relation to

water chemistry see ES Chapter 7, 7.8.3.

(b) Given the need for there to be certainty over what is to be consented would

there be any negative consequences upon the removal of provisions from the

DCO to remove the option of retaining the outfall outlet pipe in its current

position (thus by default requiring the outfall to be relocated out with the

proposed lagoon)?

TLSB's Response

4. It is now proposed to remove Work No 8, comprising a UV treatment facility,

from the authorised development comprised in the draft DCO (doc ref 3.1). This

means that the approach to water quality within the lagoon can be addressed in

one of two ways. First, the use of the lagoon for water contact activities can be

regulated if the long sea outfall remains within the impounded area. TLSB is

confident that this would not unduly restrict the use of the lagoon, but does accept

that less weight could be afforded to the use of the lagoon for water-based leisure

activities in identifying the benefits of the Project. Secondly, the DCWW long

sea outfall could be extended beyond the seawall of the lagoon, with beneficial

consequences for water quality as described above.

5. A summary of the potential effects on water quality of impoundment is provided

below. Overall there would be an increase in disturbance during construction, but,

in the context of the wider extent of works associated with the Project as a whole,

and the long term benefit and security afforded by the outfall extension, these

could be perceived as minimal.

EJR/EJR/343641/1/UKM/62783439.1 40

6. As identified in the updated Table 4.1 the combination of Position A with the

outfall extension and variable speed turbines, with pumping at the end of the tidal

cycle, would still maintain excellent water quality in the lagoon.

1. Table 1 Summary of issues considered in option elimination process5

Outfall extension

Bathing water quality

in lagoon in operation

“Excellent” under the revised bathing water quality directive. No specific bathing

management plan required within lagoon. No adverse effect on other bathing

waters.

Shellfish water quality

in lagoon

WQ within the lagoon would meet excellent quality and therefore should meet

future shellfish standard.

WFD (Biological and

supporting elements)

No effect

WFD (Chemical) No effect

HRA No effect

Recreational and

commercial fishermen

The existing outfall provides localised habitat diversity (sand/gravel with rocky

outcrop) through the presence of the diffuser section and the increased nutrients

during significant wet weather. If the outfall is relocated to outside the lagoon this

will allow mobile species to colonise the new habitat and therefore remain as a

focal point for fishermen. The outfall extension will be 1.5km in a straight line

continuing the alignment of the existing outfall, which will take it approximately

750m outside the lagoon. This position will be approximately 3km from the start of

the Neath channel training walls and as such not in the direct line of shipping

access the area. The Neath Pilot boarding station will also be relocated further

south thereby moving waiting ships further away from the lagoon seawalls and

new outfall location (para 14.6.1.22). As such, it is anticipated that current whelk

fishing/potting activities as well as other recreational fishing activities should be

able to continue if the outfall were extended.

Construction

considerations

As discussed at paras 4.3.9.9 – 4.3.9.11 the new outfall section would be laid on the

seabed or buried at a similar depth (1-2m) as the existing outfall. The works would

be undertaken by marine plant which would already be on site for the construction

of the lagoon walls. In this way potential impacts are reduced and potential issues

relating to bio-security of invasive non native species (INNS) are not worsened.

The timing of construction of the outfall extension would be during the main

lagoon wall construction, and it would be completed before the final section of the

lagoon wall is put in place. To put the construction of the outfall in the wider

lagoon construction context, sediment disturbance from excavation of a narrow

trench will be minor compared to the worst case assessment undertaken within the

EIA for the lagoon wall. The impacts of the construction of the lagoon walls as a

whole have been assessed as minor adverse to neutral (locally) and neutral across

the wider Swansea Bay (Table 6.20). As the outfall construction works are

considered “minimal” in comparison to the wider lagoon wall construction, their

impacts are considered to be neutral.

In terms of water quality the extension of the outfall will involve the removal of the

diffuser section. During this period the initial dilution of the effluent will be

reduced and the outfall shortened by some 80-100m. Although this will not affect

compliance of the bathing waters during dry weather, if a significant storm event

were to occur during the construction phase and the outfall were to spill, bathing

water quality could be affected. As such the timing of these works would be

discussed and agreed with NRW with respect to bathing water compliance and the

potential need for “discounting” of routine beach sampling.

5 All paragraph and table references herein refer to the ES submitted with the Application.

EJR/EJR/343641/1/UKM/62783439.1 41


Para 4.7.7.10 of Chapter 4 (Project Description) states that there may be a need to

bring a mobile crushing plant to site at times to re-process temporary slabs and

hard-standing as well as crushing of the concrete that is produced from the

demolition of the sea wall. It is important to understand whether the concrete

derived from the demolition of the sea walls and other concrete structures will be

crushed on site or whether these materials will be removed off site for recycling.

(a) How much concrete will be derived from the sea wall demolition, when will it

be produced within the construction phase and over what timescale?

TLSB's Response

1. TLSB estimates that there is 4000 cubic meters of concrete to be broken out of the

seawall. The initial demolition of parts of the seawall will take place at the start of

the construction phase, to allow access to the construction of the landfall and from

any adjacent areas to the breakwaters. It is currently anticipated that other sections

of the seawall will be demolished in the final year of construction, when the

public realm finishes are being constructed and when sea defence benefits of the

Project to the Swansea Port area have been realised.

(b) If it is not crushed on site, where will it go for recycling or disposal?

TLSB's Response

2. If there is concrete to be crushed, it this will take place on site. Concrete arising

from the works will be reused in the works. It will either be crushed and reused as

a fill or sub-base to roads, or it will be broken up and reused as fill.

(c) What is the likelihood of the concrete being crushed on site?

TLSB's Response

3. It is likely that some concrete will be crushed on site. This is likely to occur in the

site support areas.

(d) What mitigation will be used during the use of the crushing plant in terms of

noise and dust control and how will these measures be incorporated into the

DCO?

TLSB's Response

4. The use of water mist sprays at the point of dust release, or other appropriate best

practice methods will be used to suppress dust when dust is being released.

Adequate noise damping and shielding will be provided to ensure that noise levels

at receptors is within acceptable levels. A method statement which includes best

practice for dust suppression will be included in the CEMP, and use of a crusher

would be conditional on meeting these requirements.

EJR/EJR/343641/1/UKM/62783439.1 42

5. Allowable Noise levels at receptors will be included in the CEMP, and

monitoring of noise levels included establishing that these conditions are being

complied with.

6. The mobile crushing plant would be located in the Port near to the area of

proposed works, as such it will be in a dock/port environment. Notwithstanding

this, standard mitigation measures will be employed if needed (see Chapter 23,

19.1 of the ES), these would include:

Implementation of best practice for haulage contractors as per BS5228;

Screening of potentially noisy construction works (therefore acoustic

screening around the crushing plant);

Regulation of working hours;

regular maintenance of construction equipment; and

Soft start procedures for percussive piling.

7. In terms of dust, mitigation measures are summarised in chapter 23, 16.3. These

include:

No bonfires.

Site layout will be planned; machinery and dust- causing activities will be

located away from sensitive receptors, where possible.

Reduce speeds of vehicles tracking across un-made surfaces.

Use of water as a dust suppressant, where appropriate during dry weather.

Minimise drop heights for a delivery of aggregates · Regular vehicle

cleaning and covered loads.

Cleaning of mud tracked onto main highways if necessary.

8. As noted above, appropriate mitigation measures associated with noise and dust

would be secured in the CEMP through the DCO process.

EJR/EJR/343641/1/UKM/62783439.1 43


Paragraph 4.7.7.15 of the Project Description states that rock will be stored in an

area of 400m by 400m at the western landfall and 250m by 250m at the eastern

landfall. It is unclear whether these areas will be located onshore or offshore. If they

are to be located offshore, how will the storage areas be constructed and where in

the ES has this operation been considered in terms of impacts on the environment?

TLSB's Response

1. Chapter 4 of the ES, paragraph 4.5.3.24, states that “The stockpiles would be

located near the landfalls at both sides of the Lagoon. The stockpile adjacent to

the western seawall would be approximately 400m by 400m and piled up to 3m

high. The stockpile adjacent to the eastern seawall within the lagoon would be

approximately 250m by 250m in area and piled up to 3m high”.

2. These stockpiles will be located in the intertidal area adjacent to the area of the

construction works at the western landfall and eastern landfall, within the Order

limits. See drawing at Appendix 3.9.1 where these areas are shown on an OS

based map.

3. The loss of this habitat is included in Table 4.4a, Chapter 4, which shows that the

loss of intertidal area as a result of these rock stockpiles between year 1 and 3 of

construction will be approximately 22.25 ha. The positioning of the western rock

storage area has been chosen to fall within the area used for the western landfall

facilities/boating centre. In this way the area affected is potentially reduced and

impacts are minimised. The long-term direct loss of these intertidal habitats as a

result of the Lagoon itself has been assessed specifically in Sections 8.5.8 and

8.5.9 of the ES. In terms of the eastern rock area, once operational this intertidal

area will re-colonise.

4. The rock stockpile areas are temporary facilities needed during construction only.

Once construction of the seawalls is completed, these stockpile areas are no

longer needed and will be removed. They will then be allowed to revert to their

original status. Monitoring of this process can be undertaken, and, if required,

would take the form of low level surveys.

5. The construction methodology for the stockpile areas is not specialised. It

involves first, Sabellaria translocation works and possibly removal of some of the

stones/cobbles to be used as herring spawning media. Thereafter, establishment

simply requires placing the stockpiled rock at this location. There will be

different stockpiles for each of the different rock size fractions, and rock will be

placed up to 3m high. There will be sufficient space in between the various rock

stockpiles to allow easy access by trucks and loading equipment. The stockpiled

rock will then later be used for the construction of the seawalls. No specific

preparation of the stockpile area will be required.

EJR/EJR/343641/1/UKM/62783439.1 44


In view of the proposed location of the Project walls adjacent to the channels of the

River Tawe and River Neath:

(a) Will the presence of the lagoon walls adjacent to the river channels give rise

to a reduction in velocity of the river water entering the bay?

TLSB's Response

1. The situation post-construction remains similar to that of the baseline for the

River Neath Estuary (with training walls aligning the river flow), and there

will be no blockage to river flow from the Tawe (the existing breakwater

arrangement at the mouth of the Tawe is also maintained). Consequently,

there is not predicted to be any reduction in velocity of river waters entering

the Bay.

(b) Will there be an increase in sediment deposition either side of the lagoon,

caused by changes in river velocity and/or turbidity?

TLSB's Response

2. The coastal processes assessment contained in Chapter 6, summarised at Table

6.22 as it relates to Monkstone, predicts increases in sediment deposition, but not

as a result of changes in river velocity or turbidity. For the River Tawe, the

increases are likely to be as a result of reductions to flow and waves resulting in a

lower energy environment, meaning deposition is more favourable than in the

baseline case. For the River Neath, the potential for deposition is primarily

associated with the short-lived deposition during the construction phase.

EJR/EJR/343641/1/UKM/62783439.1 45

Statement to frame following questions

Chapter 6 of the ES is entitled Coastal Processes, Sediment Transport and

Contamination. In paragraph 6.5.1.41, baseline conditions for flood and ebb tidal

currents are described as follows:

The characteristics of the baseline flood and ebb tidal currents within Swansea Bay

lead to a clear tidal residual pattern (see Figure 6.40, Volume 2), which includes:

i. an anticlockwise circulation eddy to the west of Swansea Channel, extending

from the shoreline to the 10m below CD contour;

ii. shoreline parallel residuals across the Swansea Bay intertidal areas in a

westerly direction between Mumbles Head and Port Talbot; and

iii. north-east tidal residuals in the eastern region of the bay, between 0m CD

and the 10m below CD contour, orientated towards Aberafan Sands and

Port Talbot.

The long term effect of creation of a lagoon is described in paragraph 6.5.2.59 of

Chapter 6 of the ES Coastal Processes in the following terms:

It is considered that the completed Project will modify and redefine the

existing residual circulation within the western region of Swansea Bay by

effectively splitting the bay into two smaller embayment cells whereby the

Lagoon structure essentially becomes a headland, thus restricting exchanges

between either sides of the Lagoon; and

… the western region of the bay is expected to experience an increased

'trapping' potential of sediments (predominantly mud) in the future

compared to existing conditions, particularly across the shallow subtidal

areas adjacent to the Blackpill SSSI and within the Swansea Approach

Channel.

EJR/EJR/343641/1/UKM/62783439.1 46

3.20 to NRW and Applicant

Are the dominant forces affecting sediment transportation and coastal morphology

in and around Swansea Bay sufficiently understood to enable reliable assessments to

be made of the broad consequences for patterns of erosion and deposition in and

around the Bay from the introduction of a coastal lagoon between the mouths of the

Rivers Tawe and Neath?

TLSB's Response

1. The assessment of potential effects of the Project on coastal processes, sediment

transport and contamination (as reported in Chapter 6 of the ES), has followed an

appropriate baseline understanding and technical approach as used for a wide

number of other EIA studies on other Nationally Significant Infrastructure

Projects (including port developments (such as the ABLE Marine Energy Park

EIA and a number of Round 3 offshore wind farm projects). The approach taken

involves an initial data collation stage, whereby previous studies of relevance and

existing and newly-collected survey data have been assessed to provide a suitably

comprehensive description of the baseline environment (termed ‘evidence base’).

From this baseline description (provided in Section 6.4 of the ES), a conceptual

understanding of the dominant controls on coastal processes across the study area

has been derived. The EIA studies have been carried out using the ‘Source >

Pathway > Receptor’ model, to assess how a predicted effect on any one part of

the system potentially results in a direct (or indirect) effect on the identified

receptor.

2. Within the baseline description and conceptual understanding, consideration has

also been given to the various sources and sinks of sediment across the study area.

These sources and sinks differ in regard to the different material types, with

coarser material (sands and gravels) being controlled by different pathways to

those controlling finer (mud) material. These sediment transport processes

ultimately control the coastal morphology across the study area. With specific

regard to coastal processes, the assessed controls on the sediment regime and

morphology are primarily the hydrodynamic and wave environments, which act to

control the various aspects of sediment transport across both Swansea Bay and the

wider area.

3. The relative importance of the controls on sediment transport varies depending on

the type of sediment under consideration (mud, sand, gravel) and on the transport

pathway. Generally, sand material is transported under predominantly tidal

conditions in the outer part of the bay and along the Bristol Channel, with large

swell and storm waves (in particular) playing a more dominant role in the

shallower parts of the Bay where littoral transport processes may occur. With

regard to mud material, the transport pathway is almost entirely tidal, with waves

only acting to stir up the bed in shallower regions (or in deeper water under larger

storm conditions) and entrain more material into suspension, for onward transport

by the tide. Section 6.4.3 of the ES provides a detailed description of the

conceptual understanding of the sediment regime (sources, pathways, sinks), and

morphology across the study area.

EJR/EJR/343641/1/UKM/62783439.1 47

4. An enhanced description of the baseline environment (including associated

process controls) has been prepared for Kenfig SAC (Appendix 1.15.1), and

Crymlyn Burrows SSSI and Blackpill SSSI (Appendix 1.15.1) in response to

ongoing discussions between TLSB and NRW in respect of the negotiation of

appropriate Statements of Common Ground.

5. Assessment of the identified controls has been informed through the description

of the baseline environment and conceptual understanding of it. In addition,

numerical modelling software has also been used to support and enhance the

baseline description and conceptual understanding of the coastal processes, and to

subsequently inform the assessment of potential effects from the Project. The

baseline hydrodynamic and wave models have been calibrated and validated

against a range of field observations, to ensure they are providing an adequate

description of representative ‘real-world’ conditions (as described in Appendix

6.1, Volume 3). Furthermore, the results of sediment transport modelling for

muds have been verified against known annual dredging (and, hence, inferred

deposition) rates within the Port Talbot and Swansea approach channels. The

modelling software applied within the Project is commonly used to assess the

potential EIA effects of proposed developments. The software is considered state

of the art and fit for purpose in describing the relevant physical processes across

the study area.

6. The calibration and validation stage of the modelling approach provides a

measure of the ability of the model to adequately replicate the baseline conditions

observed across the study area. The performance of the model has been tested

against a defined set of calibration guidelines, and has been shown to perform

well within the defined limits (see Appendix 6.1 to the ES - doc ref 6.3). The

successful calibration and validation of the baseline models helps to limit the

uncertainty within the assessment and provides confidence that the tools being

used to inform the EIA are wholly suitable and fit for purpose.

7. As a result of the approach taken (combined with the existing understanding and

the breadth of available studies within the wider Swansea Bay/Bristol Channel

region), it is considered that the dominant forces affecting sediment transportation

and coastal morphology in and around Swansea Bay are sufficiently understood.

This has enabled assessments to be made of the likely broad consequences of the

Project for patterns of erosion and deposition in and around the Bay, the results of

which are considered reliable, sensible and justified. These assessments, and the

conclusions drawn from them are recorded in Chapter 6 of the ES.

EJR/EJR/343641/1/UKM/62783439.1 48


Have the consequences of changes in the processes and patterns of erosion and

deposition on the shoreline east and west of the proposed lagoon been appropriately

examined and assessed for:

1 Features of interest of:

(a) the Kenfig SAC

(b) the Crymlyn Burrows SSSI; and

(c) the Blackpill SSI.

2 The sandy beaches and amenity value of:

(a) Swansea Town Beach; and

(b) Aberavon Town Beach (Aberafan Beach).

TLSB's Response

1. Prior to the EIA studies undertaken for the Project, an initial feasibility study6 was

carried out to assess and confirm the extent of the study area and the likely broad-

scale effects of a lagoon scheme (provided at Appendix 3.21.1). The scoping

phase of the EIA studies identified (through consultation with stakeholders) the

coastal processes receptors that required consideration with the detailed

assessment. Following this, the detailed EIA studies looked to provide predicted

effects for each of the identified receptors (a list which included each of the

features included in 1 & 2, above, along with a number of other receptors, as

presented in Table 6.22, in Chapter 6 of the ES).

2. As described above, the approach taken within the assessment has been to

describe the baseline conditions and develop a well-established conceptual

understanding of the processes across the study area. The assessment of potential

effects for each receptor (including each of those listed above) has subsequently

been informed by this conceptual understanding in order to provide context to any

predicted change.

3. The assessment of potential effects for each receptor has been carried out for each

project stage (construction, operation and decommissioning), and for a range of

representative conditions (calm, typical, storm conditions, sea-level rise as a result

of projected climate change etc.). Furthermore, the detailed assessment has

considered the short, medium and long-term effects on each receptor, using a

realistic worst case scenario approach (see Section 6.5 of the ES for the

assessment of effects for each project phase, along with descriptions of the

realistic worst case scenarios, where appropriate).

6 R.1956TN, May 2012, Swansea Bay Tidal Lagoon Feasibility Modelling

EJR/EJR/343641/1/UKM/62783439.1 49

4. As discussed above, the assessment used the ‘Source > Pathway > Receptor’

approach, quantifying any changes by comparing the baseline scenario (existing

situation) to the scheme scenario (with inclusion of relevant Project components).

When considered against the conceptual understanding of process controls across

the study area, this approach enables the identification of both direct and indirect

effects on the listed receptors. In this way, in addition to any direct effects that

might be predicted, an effect on a specific pathway that is linked to a receptor (for

example, the sediment transport pathways feeding sediment to Kenfig SAC) is

also considered with due regard to any potential knock-on effect.

5. Furthermore, the coastal processes assessment has also considered potential

cumulative and in-combination effects arising from the Project and others that are

located across the wider study area. The scoping phase also identified the full list

of activities (as agreed with stakeholders) that was subsequently included in the

cumulative / in-combination assessment, and Section 6.6 of the ES details the

results of this phase of the EIA studies.

6. A paper specifically addressing effects upon Kenfig SAC, Crymlyn Burrows SSSI

(which is largely related to nitrogen deposition, rather than sediment transport)

and Blackpill SSSI is attached at Appendix 1.15.1.

7. As such, it is considered that the consequences of changes in the processes and

patterns of erosion and deposition on the shoreline east and west of the proposed

lagoon have been appropriately examined and assessed for the receptors listed in

Written Question 3.21. A summary of the receptors and the impacts is provided

in Table 6.22 (Chapter 6); specifically, Swansea Town Beach is termed “Swansea

designated bathing beach” and additional assessment is also provided for “Wider

bay Swansea sandy beach areas and effect on lower shore”. Please note also that

Aberavon Town Beach (Aberafan Beach) is referred to as Aberafan Sands in

Table 6.22.

EJR/EJR/343641/1/UKM/62783439.1 50


Are there other features of Swansea Bay that are considered particularly sensitive to

changes in patterns of erosion and deposition that have not been appropriately

examined and assessed

TLSB's Response

1. As discussed in the Response to Written Question 3.21, the scoping phase of the

EIA studies identified the coastal processes receptors that required consideration

within the detailed assessment. The scoping phase for the coastal processes

assessment identified a number of receptors across the study area. These included

the features of interest listed at Written Question 3.21 (e.g. Kenfig SAC, both

Crymlyn and Blackpill SSSIs; amenity beaches), along with other receptors (such

as the Swansea, Neath and Port Talbot approach channels). Aspects of the EIA

that were identified as having a coastal processes component, along with the

identified receptors, are provided in Section 6.5.0.5 and Table 6.22 of the ES.

2. Similar scoping phases were carried out for each EIA topic and any reliance or

dependence between different EIA topics has been included within the ES. As

such, the assessments of potential effects on other topic receptors, which might be

directly or indirectly influenced by coastal processes (e.g. benthic ecology, marine

mammals, birds, fish, navigation, recreation etc.), include consideration of such

within the relevant ES chapter. A description of the interrelationships between

EIA topics is provided in Chapter 24 of the ES.

3. As a result of the approach to the EIA studies (including the scoping phase and

the inclusion of interrelationships between topics and associated

interdependencies between topic receptors), it is considered that there are no other

features of Swansea Bay that are particularly sensitive to changes in patterns of

erosion and deposition, that have not been appropriately examined and assessed

and reported in the ES.

EJR/EJR/343641/1/UKM/62783439.1 51


Would further hydrological modelling significantly assist in predicting the impact on

coastal processes of the existence of the proposed lagoon?

TLSB's Response

1. The numerical modelling carried out as part of the detailed EIA studies into

potential effects on coastal processes has followed widely accepted methods used

for this type of assessment. A number of representative scenarios have been

assessed across and within each process control. These scenarios provide an

assessment that includes consideration of a number of:

i. Tidal conditions – spring tide / neap tide / surge tide / sea-level rise as a

result of projected climate change;

ii. Wave conditions – various return period events from each of two dominant

wave approach directions;

iii. Sediment grain sizes – ranging from sand to mud, with relative proportions

of each informed by targeted project surveys; and

iv. River flow scenarios – typical and high discharge rates (associated with

high precipitation conditions).

2. Where considered relevant and representative, these assessment scenarios have

not only been considered in isolation but also in combination. For example, the

assessment of potential changes to wave conditions has been assessed for each of

‘spring tide’, ‘spring tide + surge tide’ and ‘spring tide + sea-level rise’ tidal

scenarios; whilst the assessment of potential changes to sediment transport

pathways has been assessed for each of ‘tide only’, ‘tide + typical wave’ and ‘tide

+ extreme wave’ scenarios.

3. The approaches taken, and the respective scenarios assessed, are considered

appropriate and representative to inform the likely effects on coastal processes for

the purposes of EIA. As such, whilst further modelling could be undertaken, it is

considered that this would be of limited value. Such additional modelling would

be likely only to reinforce the findings of the present assessment, rather than

producing materially different outcomes. The conservative nature of the

assessment (primarily achieved through the use of the realistic worst case scenario

approach) acts to manage, wherever possible, the uncertainties that exist within

both the Project description and the approach to assessment. The approach taken

by TLSB in respect of "uncertainty" in the assessment approach for coastal

processes is provided at Section 6.3.5 of the ES, whilst Chapter 4 of the ES

provides a description of the Project options which have been included within the

EIA.

4. It should noted here that the Adaptive Environmental Monitoring Plan (which is

in development through consultation with NRW will look to ensure predicted

changes are confirmed (or otherwise) and quantified (where appropriate), likely

over the lifetime of the Project. Additional modelling at this stage is unlikely to

change these monitoring requirements, which are likely to be extensive (both

spatially and temporally) – at least over the short-term – as a result of this Project

being a ‘first-of-its-kind’ development.

EJR/EJR/343641/1/UKM/62783439.1 52

5. Consequently, it is considered that further hydrological modelling would not

significantly assist in further predicting the impact on coastal processes of the

existence of the proposed lagoon.

construction process, dredging and physical processes... · the design of the seawall and the wave...

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