arup may 2020 - lbbd

Dagenham Dock (BRPS and New Market) - ES Volume II Appendix 4-2 : Cooling Water

System – Stage 1 Design Summary

ARUP

May 2020

City of London Corporation

Barking Power Station

Decommissioning

Cooling water system – Stage 1 design summary for Environmental Statement

Issue | 15 May 2020

This report takes into account the particular

instructions and requirements of our client.

It is not intended for and should not be relied

upon by any third party and no responsibility

is undertaken to any third party.

Job number 268591

Ove Arup & Partners Ltd

13 Fitzroy Street

London

W1T 4BQ

United Kingdom

www.arup.com

| Issue | 15 May 2020

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DECOMMISSIONING\EIA APPENDIX REPORT\COOLING WATER SYSTEM S1 DESIGN SUMMARY FINAL.DOCX

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COOLING WATER SYSTEM DECOMMISSIONING\EIA APPENDIX REPORT\COOLING WATER SYSTEM S1 DESIGN SUMMARY FINAL.DOCX

Contents Page

Executive summary 1

1 Scope 2

1.1 Extent of assets assessed 2

1.2 Structure of report 2

2 Desk assessment - the assets 4

2.1 Documents reviewed 4

2.2 Understanding of the assets 4

3 Relevant licences and agreements 20

3.1 Documents reviewed 20

Understanding of key issues 20

4 Decommissioning Scope 28

4.1 Key drivers 28

4.2 Potential solutions 29

Decommissioning methodology 29

5 29

5.1 Buildability and safety 29

6 Hanson Aggregates Consultation 30

7 References 30

Appendices

– Documents reviewed

- Licences and deeds extracts

- Consultation with Regulatory Authorities

- Decommissioning Scope and Methodology


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Executive summary

This report summarises the work carried out by Arup as stage 1 of the barking

power station cooling water system decommissioning. This report is intended to

support the Environmental Statement, and to set out the design development that

is pertinent to the Environmental Impact Assessment (EIA).

The proposed scope of decommissioning has been agreed. It is to completely fill

the intake tunnel but only partially fill the outfall tunnel. The outfall structure will

be demolished but the intake structure left in place.

Pre- application consultation has taken place with the river regulators. The

regulators have raised no objections to the proposed works.

The proposed decommissioning methodology has been agreed for the outfall

structure: underwater cutters will be used which avoids the need for a coffer dam.

If possible, the tunnels will be filled without man entry; but it has not yet been

demonstrated whether this is feasible. Man-entry would require proof that the

water inflow was manageable, and that the tunnel is in safe condition. It might

also require secondary access shafts (s). The feasibility of the two alternative

approaches will be tested in stage 2 by means of a pump test and consultation with

contractors.

The above information has been summarised in briefing notes which have been

provided to other consultants in the project team for an EIA addendum, and for

consultation with planning authorities and affected landowners.

We include a decision matrix which summarises key decisions made and

identifies further decisions required for the next steps in stage 2.


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1 Scope

1.1 Extent of assets assessed

Barking power station is to be decommissioned in order to redevelop the site as a

market place or alternatively for other industrial uses

This report considers the following parts of the cooling water system: See Figure

1:

• Intake and outfall tunnels

• Intake

• Outfall

• Combined shaft

It does not include the cooling recirculation system or the cooling water culverts

within the site. These will be dealt with under other packages.

Figure 1: Plan view of the Cooling Water System that is included in the decommissioning

scope of works (Figure from Ref. 1)

1.2 Structure of report

This initial scoping report includes:

• Section 2: Desk assessment of information provided and gap analysis

• Section 3: Licenses and Agreements

• Section 4: Decommissioning Scope


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• Section 5: Decommissioning Methodology

• Section 6: ECI contractor consultation

• Section 7: EIA Screening

• Section 8: Hanson Aggregates Consultation

• Section 9: Summary of Progress

• Section 10: Residual Risks and Opportunities

• Section 11: Next Steps


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2 Desk assessment - the assets

2.1 Documents reviewed

A schedule of documents reviewed is in Appendix B

The existing structures at the Power Station site were also visually inspected at a

site visit on 13th of June 2019.

2.2 Understanding of the assets

2.2.1 Intake Shaft & Structure

See Figure 2 to Figure 5. The intake shaft comprises of 65mm thick, 5m internal

diameter steel tube sections 3m long, bolted together at internal flanges. This was

to form a watertight stand-alone caisson, which during construction would

facilitate TBM removal. The caisson is lined with precast concrete segments, with

the annulus between the concrete segments and steel shaft being filled with mass

concrete.

The intake shaft is topped with a reinforced concrete lozenge shaped headwork

structure. The 94 tonnes lozenge-shaped intake headworks are located below the

existing structure of Jetty No 4. The jetty provides protection for the intake head

structure. The intake headwork has 6mm screens to prevent fish getting into the

intake pipes.


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Figure 2: Intake – plan underneath jetty – [Source: CoLC records]

Jetty No.4

supports

Intake structure


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Figure 3: Intake- section [Source: CoLC records]

Jetty No. 4

Intake

structure

Intake shaft


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Figure 4 structure: Intake- isometric view [Figure from Ref. 2]


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Figure 5: Intake shaft [Source: CoLC records]

2.2.2 Outfall shaft & structure

See Figure 6 to Figure 8. Like the intake shaft, the outfall shaft comprises of

65mm thick, 5m internal diameter steel tube sections 3m long, bolted together at

internal flanges to form a watertight stand-alone caisson. The caisson is lined with

precast concrete segments, with the annulus between the concrete segments and

steel shaft being filled with mass concrete


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At the top of the outfall shaft, a 40 tonnes precast concrete, circular headwork is

positioned.

The outfall structure is located within the Thames river about 600m from the north

bank. It consists of a platform supported by 8 piles, which are located on the

vertices of the octagon. The outfall space frame consists of truss panels. The

outfall structure is surrounded by large floating fenders. Its primary function is to

protect the outfall shaft from accidental collision with ships, to support a platform

that facilitates dewatering and filling of tunnels in the permanent case and to

support a temporary platform during construction.


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Figure 6: Outfall structure- plan [Source: CoLC records]

Figure 7: Outfall structure- section [Source: CoLC records]


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Figure 8: Outfall shaft

2.2.3 Dewatering Caps

Within the intake and outfall headworks, there is a steel dewatering cap, which

consists of steel frame and plate. During station operation, the caps are supported

by the upper deck of the headworks. During tunnel dewatering, the caps are

rotated to allow the support brackets to pass through slots in the headwork upper

deck. The cap is then lowered to form a watertight seal (plug) in the shaft. The cap

details are shown in Figure 9.


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Figure 9: Dewatering cap at intake and outfall

2.2.4 Cooling Water Tunnels

See Figure 10 to Figure 12. The intake and outfall tunnels are constructed of pre-

cast concrete segmental linings of 3.35m internal diameter and 3.71m external

diameter, with a 180mm lining thickness. The intake tunnel is 627m length and

the outfall tunnel 1165m. The tunnel linings comprise six trapezoidal segments

with Ethylene Propylene Diene Monomer (EPDM) gaskets installed around their

edges to provide a waterproofing joint. The tunnel lining segments consist of


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reinforced concrete with conventional steel reinforcement cage and concrete grade

C40/50.

We were not able to trace any as built cross section drawings of the tunnels, so the

above description relies on secondary reports.

Figure 10: Plan and long section of tunnels


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Figure 11: Tunnel adjacent to pumping station

Figure 12: Image inside tunnel under construction [Image from Ref. 2]


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2.2.5 Combined Intake/ Outfall Shaft

See Figure 13 to Figure 15. The combined shaft is located on the main station site

and is used to house two 3m internal diameter pipes, which connect the cooling

water tunnels to the pump station. The initial shaft lining was made as a caisson

with precast, reinforced concrete segment rings but due to failure of the temporary

works, it was redesigned as an in situ concrete diaphragm wall shaft, with an

approximate ID of 8m. Steel piles are installed in the shaft and the void between

shaft and pipes is filled with lightweight, foamed concrete.

Figure 13: Combined shaft at Pump Station – plan at base of pump station

[Source: CoLC records]


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Figure 14: Combined shaft at pump station section through shaft [Source: CoLC records]


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Figure 15: Combined shaft- elevation [Source: CoLC records]

2.2.6 Combined Pump Station & Seal Pit

The pump station includes a circular reinforced concrete wall with internal walls

and other features. See Figure 16 and Figure 17. The circular diaphragm caisson

excavation support consists of a 1.02m thick reinforced concrete wall. The

internal diameter of the caisson wall is 44.3m. It is formed of 24 interlocking

panels. The general toe level of the wall is at -18m OD but this extends down to -

21m OD adjacent to the combined shaft. On the inside of the diaphragm wall, a

500mm thickness inner lining wall has been placed. The inner lining wall is fixed

to the diaphragm wall with drill-in anchors. Most of the internal elements (walls,

slabs, beams and plant support or housings) are in-situ concrete. Some elements

have been constructed with pre-cast concrete and structural steelwork.


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Figure 16: Pump station – plan [Source: CoLC records]

Figure 17: Pump station- section [Source: CoLC records]


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2.2.7 Condition of the Assets

2.2.7.1 Intake/Outfall Tunnels

Two condition surveys of the water tunnels were conducted back in 2000 and

2010, in accordance with the ten-year inspection period for the cooling water

system, as identified by Balfour Beatty. The year 2000 survey inspected the first

100m of the outfall tunnel and the chainages between 450m-600m in the intake

tunnel. The survey revealed evidence of marine growth in the tunnels and layers

of silt with a thickness of 10mm. Possible deflections in the tunnel lining could

not be picked up by the survey. The 2010 survey also identified marine growth

and silt in the tunnels. Holes in the tunnel lining were also identified, which could

indicate a deterioration in the tunnel condition. After the cessation of the pump

station operation back in 2014, a dewatering cap was installed on the outfall shaft,

sealing the tunnels from the river and isolating the water within. Dewatering tests

showed that the tunnels get recharged after the water is fully pumped out.

Inspection of the cap revealed no obvious signs of damage that could justify water

ingress through the cap. Therefore, it is likely that water ingress could occur

through the tunnel lining itself or through the outfall shaft.

2.2.7.2 Above Ground Structures

A walk-over survey dated back in 2015 by Atkins found that the above ground

assets are in generally good condition, with no obvious signs of structural

deterioration. The key areas of consideration, taking account of decommissioning

options, are:

• Outfall shaft marine structure: the eight concrete filled steel piles,

which form part of the outfall structure will not be able to be removed in a

single lift due to their large size and weight. Therefore, they will need to

be cut into pieces and then removed

• Intake Shaft & Jetty No 4: the intake shaft is located under the Jetty No

4, which is owned by Hanson Aggregates. The jetty can be accessed by a

bridge from the adjacent Hanson Aggregates site. This jetty is a Grade II

listed structure and load restrictions of 3tonnes and 10tonnes have been

imposed on the access bridge and jetty respectively. This might have

implications on the decommissioning works on the intake shaft.

• Cooling Water Pump Station: there is no direct ground level access to

the combined intake/outfall shaft in the cooling water pump station.

Modification to the existing water retention tanks may be required if

decommissioning works are to be serviced from this area.


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3 Relevant licences and agreements

3.1 Documents reviewed

The consents and licenses that have been reviewed are presented in the Appendix

A.

Understanding of key issues

There are at least 14 stakeholders that will require an agreement or license for

works to the cooling water system. There are at least 15 existing licenses to be re-

negotiated.

There are still some gaps in information: 1) Planning Consents (?), 2) 4 land

owners’ Deeds of Grant 3) Water discharge license 4) plans shown land

ownership of PLA, Crown Estates and National Power Plc

There appears to be a conflict of interpretation between PLA and Crown Estates

regarding the decommissioning of the river works- PLA wrote informally “Works

that are held on a RWL need to be removed in their entirety otherwise any works

that remain need to be retained on a license-any of the tunnels/shafts/piles

extending over MHW and are not removed will need to be retained on a River

works license” They also indicated informally that demolition to 1m below river

bed level may be acceptable. Conversely, Crown Estates reportedly want the

outfall structure and tunnel underneath their property to be removed.

The deeds of grant of 6 land Owners mention “safe” or “harmless” regarding the

state of tunnels after cease of operation of the Power Station- This poses a risk of

interpretation: “In the event that the power station shall cease to be operational

for a continuous period of 4 years at the end of such 4 year period to render the

Authorised Tunnel harmless in accordance with the then current safety

standards”

“In the event the Power Station ceases to operate for a continuous period of 4

years, at the end of such period, BPL shall clean out the Authorised Tunnel Cap

and fill the same with materials which will Render the Authorised Tunnel safe,

such materials to accord with the then current safety standards”

Jetty No 4 is a listed structure. Listed Building Consent will be required for any

significant works to the intake structure

Key Opportunities

PLA and EA both have indicated informally that it may be acceptable to them to

grout up the shafts (only) and not the tunnels

Key Risks to programme

The volume of agreements/licences suggests a high programme risk.


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A dredging licence will may be required for removal of intake or outfall structure.

This would add considerably to the consents process duration

The duration of There is risk of anan EIA

3.1.1 PLA

PLA are landowners of north bank and are responsible for navigation on the river

Existing Licences/Agreements:

There is an existing licence combined with The Crown Estates (see extracts on

Error! Reference source not found.). A river works licence for any changes and

for any residual assets in the river will be required. Important information relevant

to the river works license is listed below:

• River work license with PLA and the Crown estate to construct and retain

two tunnels/intakes/outfalls is for 30 years (starting from 1992)-It expires

in 2022.

• River Works License is owned only by BPL and cannot be assigned to a

3rd party

• On expiry or sooner termination of the license, BPL must remove the

River Works and make good the airspace above and the river bed to the

reasonable satisfaction of PLA- If BPL does not comply, PLA will carry

out the necessary works and charge BLP

• Hogen Lovells note that in the deed there is no option to make safe or

leave the River Works in Situ.

Consultation:

In 2015 Atkins consulted with the PLA on decommissioning the cooling water

system. Arup and CoLC re- consulted with PLA on 5th of August 2019. See

Appendix C for the PLA Meeting of Minutes.

Key Issues:

• Structures are to be cut down to approximately one metre below existing

river bed level; however, the exact depth needs to be confirmed by the

PLA consents manager, depending on the riverbed condition.

• PLA are comfortable in principle to retain the existing intake structure

• A River Works License will be required for retained structures under the

river

• A new licence would still be a combined PLA and Crown Estates licence.

PLA will take the lead, as PLA own more of the affected land in the tidal

Thames. The new licence will cover the financial aspects for both PLA

and Crown Estates.

• In addition, a Marine Licence will be required from the MMO


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• The PLA/MMO Concordat is under renewal. PLA will take the lead, but

CoLC/Arup should consult with MMO in parallel. PLA are happy to

support the process. Arup should be consistent and apply the same

information to PLA and MMO

• Although it is a matter for the PLA’s Estates Team (and the Crown Estate)

it is likely that the existing annual licence fee would be reduced to reflect

less infrastructure after decommissioning and non-usage of the

infrastructure.

• PLA have 3 months to reach a decision from the date of receipt of the

applications for a licence, otherwise application is deemed refused. There

is a potential for delay in finding agreement from all parties

• Works on the Intake Shaft must be organised in a way so as to protect the

Jetty No.4 structure, which is listed as a safeguarded wharf by PLA

• Outfall shaft must be removed to at least 1m below construction river bed

level, which is approximately 2.5-3m below current river bed level

• Works that are held on a RWL need to be removed in their entirety

otherwise any works that remain need to be retained on a license-any of

the tunnels/shafts/piles extending over MHW and are not removed will

need to be retained on a River works license. (Appendix J-correspondence

Atkins-PLA)

• PLA recognise the benefits from complete removal of the outfall structure

but would not require its removal

• Dredging- would need a separate approval from PLA

• Scour protection- this would need to be recorded for navigation purposes if

it remains on the river bed

• PLA do not have any special requirements regarding the infill material of

the tunnels and shafts.

3.1.2 The Crown Estates –

The Crown Estates Commissioners are landowners of south bank of the river (See

Figure 18)

Existing licences/Agreements.

There is a joint River Works License with PLA (see Section 3.1.1 above). A new

licence will be required for the residual assets retained on their land

Consultation:

CoLC reported verbally on previous communication between the City of London

and the Crown Estate Commissioners


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Key Issues:

• As reported by CoLC, the Commissioners are expecting CoLC to fully

remove all the assets in The Crown Estates land, including removing the

shaft to full depth and the outfall tunnel. However, this will be impractical

to achieve.

Figure 18: Land Ownership Plan – Yellow: Crown Estates & Red: Unregistered Land

claimed by PLA (Source: received by PLA on 05/08/2019)

Deloitte, which is the CoLC planning consultant is responsible for the

consultation with The Crown Estate Commissioners. At the moment of writing

this report, we are not aware of the status of this consultation.

3.1.3 Environment Agency

The Environment Agency (EA) is responsible for all works in river, intake and

extraction and contamination risks everywhere (river and on land). The EA was

formerly the National River Authority (NRA).

Existing Licenses/Agreements:

Existing flood defence licences with the NRA, which is now the EA, are listed

below:

• Abstraction licence with NRA (original in 1992 and later in 2001) we

understand that this also includes licence to discharge.

• Consent to construct an outfall marine structure at River Thames (Consent

to Works)

• Consent to construct an intake structure at River Thames


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• Consent to construct an Outfall Tunnel under the flood defence river wall

• Consent to construct an Intake Tunnel under the flood defence river wall

• Environmental Permit for prevention of Pollution (EA)

(non-relevant: Existing Consent to discharge Trade Effluent into the sewers to

the Dagenham Breach with Thames Water Utilities)

Consultation:

Atkins consulted informally with the EA in 2015 to discuss decommissioning

options. Arup and CoLC consulted with EA on 12th September 2019, see EA

Minutes of Meeting and briefing note in Appendix C

Key Issues:

• The decommissioning proposals are considered low risk for EA statutory

comments. Flood risk level is not expected to be an issue

• The EA indicated no issues of principle to the outline proposals in Atkins

assessment.

• The EA is interested in knowing the construction methodology that will be

followed for the outfall structure demolition (underwater operations,

cofferdam)

• The EA may be concerned about groundwater or river water

contamination from any grouting operation. The fill material of the tunnels

and shafts should ensure that no water migration occurs between the river

and the chalk aquifer

• The EA would not object to small rock scour protection being left at the

river bed, if it is small rocks. However, if there is a gabion or other form of

mattress, EA would need to investigate this matter further

• The EA referred to the local planning authorities for EIA consultation

• If a Marine License is obtained, there is no requirement for EA flood

activity environmental permit for works below MHWS, as the MMO

Marine License addresses the EA requirements

• Environmental Permit will be required for the landward works that are

located within 16m distance in plan from the flood defences.

• An Environmental Permit might be required if new discharges or

connections through the flood defences are constructed.

• An Environmental Permit will be needed for any decommissioning option

The EA stated that a licensing application might be required if:

• temporary works structures are required over the river walls


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• for river works access for transporting material (e.g. conveyor belts, jetty

use)

3.1.4 Marine Management Organisation (MMO)

The MMO is responsible for granting a Marine Licence for any works below tidal

waters.

Existing Licenses/Agreements:

There are no existing licenses/agreements; the MMO didn’t exist back in 1992.

Consultation: Arup and CoLC consulted with the MMO on 10th September

2019.- see MMO Minutes of Meeting and briefing note in Appendix C.

Key Issues:

• Marine Licence is required for any works below the MHWS (mean high

water springs) under the Marine and Coastal Access Act 2009

• Any marine license application must include a detailed methodology of the

demolition/removal of structures and any mitigations proposed. MMO

expressed concern about environmental impacts of the construction works

(migratory fish, birds, designated areas nearby, navigational issues,

pollution on Thames)

• Potential requirement for an EIA under the Marine and Coastal Act 2009

• Timescales for MMO licences are very uncertain. The timescale will

extend substantially if a dredging licence or EIA is required MMO

MMO said a dredging licence might be required if:

• scour protection is removed. MMO clarified that this might not

specifically be a marine license for dredging activities, but it would be a

licensable marine activity under MCCA, 2009 (e.g. Removal activities)

• It is impossible to extract the outfall structure piles from the river bed and

excavation is required-This depends on the volumes of excavated

material. MMO clarified that there are certain exemptions that apply for

low dredge volumes, but these have specific criteria

3.1.5 Local Planning Authorities

Barking and Dagenham is the local planning authority for north bank up to mid-

river, where the intake structure is located.

The outfall is in Bexley borough council jurisdiction (see