eds 07-0106 substation flood protection - document … · shall be followed, incorporated and...

Document Number: EDS 07-0106

Version: 3.1

Date: 18/04/2016

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ENGINEERING DESIGN STANDARD

EDS 07-0106

SUBSTATION FLOOD PROTECTION

Network(s): EPN, LPN, SPN

Summary: This design standard outlines the requirements to be followed regarding protecting assets against flood risk when designing a new substation or developing an existing site.

Author: Mark Dunk Date: 18/04/2016

Approver: Paul Elliott Date: 25/05/2016

This document forms part of the Company’s Integrated Business System and its requirements are mandatory throughout UK Power Networks. Departure from these requirements may only be taken with the written approval of the Director of Asset Management. If you have any queries about this document please contact the author or owner of the current issue.

Applicable To

UK Power Networks External

☒ Asset Management ☒ G81 Website

☒ Capital Programme ☒ UK Power Networks Services

☒ Connections ☐ Contractors

☐ Health & Safety ☒ ICPs/IDNOs

☐ Legal ☐ Meter Operators

☒ Network Operations

☐ Procurement

☐ Strategy & Regulation

☐ Technical Training

Substation Flood Protection Document Number: EDS 07-0106

Version: 3.1

Date: 18/04/2016

© UK Power Networks 2017 All rights reserved 2 of 16

Revision Record

Version 3.1 Review Date 25/05/2019

Date 24/07/2017 Author Lee Strachan

Why has the document been updated – Minor version update

What has changed – reference to EDS 07-0108 changed to EDS 07-0003


Date 18/04/2016 Author Mark Dunk

Why has the document been updated – Periodic review

What has changed – Updated document throughout in accordance with timescales and in relation to version 2 of ETR 138.

Document transferred onto a new template and rules applied.



New Section 9 added regarding recording of assets, subsequent sections renumbered. EA Tel Nos updated with Floodline No. Table 2 revised for surface water Section 3 revised to removed repeating phrase

Version 1.0 Review Date


Original


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Contents

1 Introduction ......................................................................................................... 4

2 Scope ................................................................................................................... 4

3 Glossary and Abbreviations ............................................................................... 4

4 Details .................................................................................................................. 5

5 Considering Flood ............................................................................................... 5

6 Site Assessment Process ................................................................................... 6

7 Flood Risk Planning ............................................................................................ 8

8 Designing Out Flood Risk ................................................................................... 9

8.1 Grid and Primary Substation Sites ............................................................................. 9

8.2 Fluvial and Tidal Flooding .......................................................................................... 9

8.3 Surface Water Run-Off Flooding................................................................................ 9

8.4 Plant and Equipment Located Below Ground or Street Level .................................. 10

9 Protecting Existing Substation Sites ............................................................... 11

9.1 On-Site Survey ........................................................................................................ 11

9.2 Standard Outdoor Substations ................................................................................ 11

9.3 Subterranean Substations ....................................................................................... 12

10 Recording Works on the Asset Register.......................................................... 12

11 Flood Protection Systems ................................................................................ 13

11.1 Site Boundary Wall and Flood Gates ....................................................................... 13

11.2 Permanent Protective Walls around Structures (including raising bund walls) ......... 13

11.3 Demountable/Retractable Barriers ........................................................................... 14

11.4 Ancillary Flood Protection ........................................................................................ 15

12 Suppliers ............................................................................................................ 15

13 Reference Documents ....................................................................................... 16

14 Environment Agency Offices ............................................................................ 16


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1 Introduction

Flooding events across England and Wales have highlighted the vulnerability of electricity substations and called into question existing levels of flood protection.

Combined with concerns over climate change and predicted rises in sea level the Minister of Energy, via the Department for Business Enterprise and Regulatory Reform (BERR), called for a review. The resulting review document, The Pitt Review released in June 2009, considered the causes and societal and economic impacts of a major flood event and made a number of recommendations regarding the protection of public and private assets and Critical National Infrastructure.

In order to implement the Pitt Review recommendations, reduce the risk of loss of supply leading to increased Customer Interruptions (CI) and Customer Minutes Lost (CML) and to avoid the costs associated with repairing or replacing plant following a flood event it is essential that UK Power Networks (UKPN) addresses the issue of flooding in its designs for new substations and during modifications/reinforcement of existing substation sites.

This requirement was reinforced by the impacts of storms Desmond, Eva and Frank in December 2015.

2 Scope

This document sets the requirements in relation to protecting Grid and Primary Substation assets from a potential coastal (tidal), fluvial (river) or pluvial (surface water) flood event, which shall be followed, incorporated and enacted into the design process when designing a new Grid or Primary substation or developing an existing site. It also provides guidance and details as to how flood risk is to be assessed and mitigated. Sites considered to be at risk from potential flooding shall be protected to a height in accordance with Table 2.

If there is any uncertainty as to whether a site or asset is at risk or requires protecting from a flood event, the UKPN Asset Management team is to be contacted for further advice.

3 Glossary and Abbreviations

Term Definition

CI – Customer Interruptions

Number of occurrences in which a customer is off supply for more than 3 minutes

CML – Customer Minutes Lost

Number of minutes in which a customer is off supply after the first 3 minutes

UK Power Networks UK Power Networks (Operations) Ltd consists of three electricity distribution networks:

Eastern Power Networks plc (EPN).

London Power Network plc (LPN).

South Eastern Power Networks plc (SPN).


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4 Details

High level surveys and prioritisation assessments have been carried out and a programme of works has been developed in order protect the highest priority sites. On-site surveys of ground level and structures combined with site specific flood level assessments (from the Environment Agency) are necessary to identify vulnerable plant and structures and establish the extent and height of flood defences necessary to mitigate the risk of flood.

The latest Environment Agency flood information is available through the Environment Agency DataShare website www.geostore.com/environment-agency.

5 Considering Flood

When considering the location of a new substation site or developing an existing site it is essential, as well as considering the ecological impact and design suitability, that the risk from flooding is assessed. Flooding can be caused by the rise of watercourses, breaches of coastal defences or from surface water run-off and these factors need to be investigated as part of the design process. Flooding by burst or damaged major water main is another factor to be considered for sites where plant and/or equipment is to be located below ground level.

The design of any substation or development of a substation reinforcement project must ensure that it is safe from flooding and not increase the risk of flooding elsewhere.

If it is found that the proposed or existing site is affected by flooding from any of these potential causes then ideally an alternative site should be sourced. In real terms, however, this cannot always be achieved and it therefore becomes essential that measures are put in place within the design in order to provide mitigation against the effects of flooding.

As part of the design process the flow chart in Section 6 shall be followed and appropriate measures put in place (refer to Section 10 for examples) to ensure that supplies can be maintained or, at the very least, quickly reinstated during or after a flood event.

It is important to prevent the flooding of plant and equipment for the purposes of avoiding asset damage and to reduce the time customers are off supply following a flood event.

The same considerations must also be made when considering reinforcement works on existing substation sites or where the site has already been identified as at risk from a flood event.


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6 Site Assessment Process

When assessing flood risk to a substation and developing substation design the following steps should be taken as a minimum:

Establish location of site and nearest post code

Is there local knowledge or a history of flooding in the

area?

Is the site located within an Environment Agency defined flood area? (Note 1)

Consider designing site such that critical plant,

equipment and buildings are located higher than

surrounding ground levels or are protected from the predicted flood level plus allowance for rising levels and wave action (Note 5)

a) New site: Contact Environment Agency to establish potential flood level. (Note 2)

b) Existing Site: Consult UK Power Networks Asset Management to establish ground and flood levels (Note 3)

Design site such that critical plant, equipment and buildings are located above or are protected from the predicted flood level plus allowance for rising levels and wave action (Note 6)

Identify site / location

Survey/investigate topography and any adjacent hardstanding areas (Note 4)

Yes

No

Yes

No

Is the site located in a dip in the topography?

Design site in accordance with UK Power Networks Standards


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Note 1: The Environment Agency provides high level details of potential 1:100 and 1:1000 flood areas on the Flood Map section of its internet site (www.environment-agency.gov.uk) and through its ‘DataShare’ site (www.geostore.com/environment-agency). This can be used to establish whether a substation site is within a flood plain by typing in the post code of an existing or potential site or nearby road and will help in identifying the source of potential flood.

Note 2: Information regarding potential new sites can be obtained from the Environment Agency which can be contacted on 03708 506506 or [email protected] for all UK Power Networks licensed areas. Alternatively the appropriate Environment Agency local office can be contacted directly; details in Section 14. It should be borne in mind that there is a 20 working day reply period for information from the Environment Agency and this should be factored into the project design programme.

Note 3: Existing UK Power Networks sites at risk from flooding have been identified, surveyed and the flood risk and depth of flood water calculated and information can be obtained from the UKPN Asset Management. If the individual site under assessment is not listed it will be necessary to consult with the Environment Agency to obtain flood level information and conduct a topographical survey of the site in order to establish ground levels which will enable the flood depth affecting the site to be determined.

Note 4: Hardstanding/hard landscaping in place of grassed/soft landscaped areas will reduce the time in which surface water reaches the site and is also likely to increase the volume of run-off affecting the site.

Note 5: Locating critical plant or equipment in land lower than the surrounding topography increases the risk of flooding from surface water run-off. In order to mitigate this risk it may be necessary to elevate the plant or equipment above the predicted potential flood level or the surrounding ground level in order to protect in the same way as for fluvial or coastal flooding.

Note 6: Possible mitigation solutions include raising equipment and plant above the predicted flood level, protecting/bunding critical equipment and plant or protecting/bunding the site; refer to Section 8.

http://www.environment-agency.gov.uk/


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7 Flood Risk Planning

The National Planning Policy Framework (NPPF) and ENA ETR 138 Resilience to Flooding of Grid and Primary Substations should be consulted for guidance on the rules governing the installation/construction of permanent protection of sites. In some cases a requirement to provide external storage of the displaced flood water may be required. In addition, as part of the planning process, it is likely that it will be necessary for an independent Flood Risk Assessment (FRA) to be carried out in order to assess the impact that the substation development or flood protection measures will have on the flood plain and the flood level.

There are three levels of FRA as described in the Table 1 below:

FRA Level Description

Level 1 Screening study: Used to identify whether there are any flooding issues related to the site or development that will warrant further consideration.

Level 2

Scoping Study: Undertaken if the Level 1 FRA indicates that the site/development is in a flood risk area. The Level 2 study should include:

An appraisal of the availability and adequacy of the existing information.

An appraisal of the flood risk posed to the site (e.g. 1:100, 1:200, 1:1000),

and potential impact of the site flood defence development on flood risk

elsewhere.

An appraisal of the possible measures available to mitigate the flood risk to

an acceptable level.

Level 3

Detailed Study: Undertaken if the Level 2 FRA indicates that further quantitative analysis is required to assess the flood risk issues related to the site and should include:

A quantitative appraisal of the flood risk posed to the site (i.e. the potential

maximum depth of flood water).

A quantitative appraisal of the potential impact of the site flood defence

development on flood risk elsewhere.

A measurable demonstration of the effectiveness of the proposed mitigation

measures.

Table 1 – Levels of Flood Risk Assessment

By following the processes laid out in this document Level 1 and Level 2 FRAs will have effectively been carried out. A partial Level 3 FRA has been carried out in order to ascertain baseline risk for UKPN Grid and Primary substations (available from the Asset Management Civils Standards Manager). Specialist advice will be required to calculate the upstream impact of any flood mitigation measures at the substation.


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8 Designing Out Flood Risk

8.1 Grid and Primary Substation Sites

The most effective way of ensuring a substation is not affected by fluvial or tidal flooding is to avoid building it on a flood plain in the first instance. This should always be the first response to any internal or external proposal that suggests otherwise. It is accepted, however, that there will be times where construction and placement of assets on an area at risk from flooding is unavoidable as demonstrated by the fact that over 250 existing Grid and Primary substation sites across the three licensed areas have been built in flood risk areas.

If there is no other option other than to build the substation in a flood risk area then the most effective way of protecting critical plant and equipment is to elevate it above the level of the flood and ensure that all duct entries are designed to be sealed against water ingress. Basements shall be designed to be water resisting structures except on sites where ground water uplift is considered an issue.

Where the elevation of transformers would make installation and/or operation impractical the transformer compound bund wall should be raised above the flood level and removable stop planks installed in areas where the bund wall is lowered in order to facilitate delivery or removal of the plant.

It should be noted that consideration must be given to the prevention of possible overhead busbar clearance infringement by personnel walking along the top of an elevated bund wall.

In order to prevent ingress through building services route non-return valves shall be installed in storm and foul water drainage systems and, where required, air bricks shall be installed above the flood level.

As well as approaching the Environment Agency in order to obtain information regarding flood risk and levels, it would also be useful to enquire about existing or proposed flood defences works in the area. This may alter the site specific flood protection works requirement although reliance on third parties to provide and maintain flood defences to protect UK Power Networks assets should be avoided.

8.2 Fluvial and Tidal Flooding

The design height at which plant is to be protected to or located above ground level is to be determined by the calculated flood depth (Flood Level – Ground Level) plus factors of safety taking into account predicted rises due to climate change and freeboard to accommodate wave action and inaccuracies in flood data and modelling in accordance with ENA document ETR (Engineering Technical Report) 138 and as detailed in Table 2.

8.3 Surface Water Run-Off Flooding

For sites potentially affected by surface water run-off flooding, the protection options are either to raise the design height of the plant, equipment and buildings such that they will be above any predicted flood level or by designing a catchment ditch or drainage system around the perimeter of the site in order to divert the run-off before it reaches any critical equipment.


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Flood Type

Protection Level Grid Substation

Protection Level Primary

Substation

Allowance for climate change

level rises Freeboard

Fluvial 1:1000 Flood

Level 1:100 Flood Level

Flood Depth x 20% or use of EA CC factored levels

300mm

Tidal 1:200 Flood Level 1:200 Flood Level 105mm or use of EA CC factored levels

300mm

Surface Predicted flood

level Predicted flood

level Flood Depth x 20% 300mm

Table 2

8.4 Plant and Equipment Located Below Ground or Street Level

It has been shown that sites with equipment located below ground or street level are vulnerable to water inundation following a mains failure in addition to possible fluvial or tidal flood risk. As with sites vulnerable to fluvial or tidal flooding the most effective way to avoid flooding by failed water main is to avoid locating plant or equipment below ground or street level. The decision process detailed in EDS 07-0003 ‘Enclosed Major Substation Civil Engineering Standard’ shall be referred to prior to agreeing a subterranean location for any substation.

Given the reduced availability of above ground space in many major towns and cities it is accepted building substations entirely at or above ground level may not always be possible. In these cases local water main service records shall be checked and the risk of water inundation following a mains failure assessed and measures put in place to mitigate.

Where the installation of plant and equipment below ground or street level is not possible the provision of stop planks, water tight doors and/or internal dwarf walls shall be considered as well as ensuring that all duct entries are designed to be completely sealed against water ingress.


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9 Protecting Existing Substation Sites

The flood protection of existing substations shall be carried out following an internal assessment and prioritisation of the most ‘at risk’ sites. A high level survey and flood mapping exercise has been carried out across the three UK Power Networks licensed areas (refer to Section 6 (Note 3)) in order to provide details of predicted flood depths and to prioritise the flood protection work programme. Works planned at any sites highlighted as ‘at risk’ from flooding should consider mitigating flood effects during the design stage.

9.1 On-Site Survey

Due to the individual nature of the existing substations the solution to flood protection will have to be developed on a site by site basis; it is important that each site at risk is visited and surveyed to establish what plant, equipment and structures are at risk.

Where it is safe to do so surveys shall commence with establishing the actual ground level above ordnance datum (mAOD) in order to confirm the accuracy of the LiDAR ground level data. On sloping or terraced sites this may require several points being established. Once ground level is established the actual on-site flood depth from the data included in this document can be confirmed and the height of essential plant and equipment above ground level measured; assume control equipment etc. will be effected by flood if it reaches the underside of the kiosk. The survey and any consequent flood protection should only look to protect plant and equipment essential to the safe, continued supply of electricity.

The survey should also record door threshold heights, building construction materials and building condition and foul and surface water drainage services. Comment on the flood protection (if any) of buildings beyond the boundary of the site, existing flood defences and the surrounding topography should also be recorded. The survey report shall consider how particular flood protection options may affect the accessibility and operation of the plant and equipment.

Flood protection levels for existing above ground/outdoor sites should be designed in accordance with Table 2. Below are some suggestions of flood protection solutions that may be considered, although not exclusively, during the development of a substation flood protection design. Examples of the suggestions are shown in Section 10.

9.2 Standard Outdoor Substations

Reinforced concrete retaining/flood walls around entire substation sites or individual structures combined with flood gates and flood planks (left in place).

Raising plant/equipment above the level of flood.

Sealing door or site entries with flood gates or removable flood planks.

Ensure all ducts are sealed from water ingress using RISE, ISP or other proprietary approved duct sealing system with a water pressure head rating.

Sealing low level air brick vents.

Installing non-return valves on storm and foul water drainage systems in order to prevent backflow into the substation building services.

Dry ditches/moats (possibly combined with earth bunds constructed from the arisings) around the perimeter of the substation creating a storage capacity external to the site. This could be combined with a weir or pump system with an outlet to a watercourse or to an area beyond the substation boundary.

Temporary flood barriers.


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In order to reduce incidents of the flood gates being left open when operatives leave the site it is recommended that flood gates be provided with “gate open” alarms connected to control.

LV supply to pumps:

At Grid sites. LV supply to be taken from existing Auxiliary transformer.

At Primary sites. The secondary substation supplying LV may have to be flood resilient to the same level of the substation (1:200 or 1:100). Where this is considered technically unfeasible an alternative option is to introduce an RMU inside the flood protected area of the substation where the LV supply can be safely taken from during the flood event.

9.3 Subterranean Substations

Sealing door or site entries with flood gates or removable flood planks.

Construct a bund wall system around low level ventilation inlets and outlets.

Ensure all ducts are sealed from water ingress using RISE or other proprietary approved duct sealing system with a water pressure head rating.

Temporary flood barriers.

10 Recording Works on the Asset Register

Upon completion the details of all flood protection works are to be recorded on UK Power Networks’ Asset Register database.

Details are to include the flood risk level to which the site is protected (e.g. 1:100, 1:200, 1:1000 or other design level), the type of flood defence and construction material and, where standard ETR 138 flood protection levels have not been met, a short explanation in the text field explaining the reasoning behind the decision to protect to a lower level (e.g. not technically or financially viable).

This information will help UK Power Networks operate and maintain the flood defences around the vulnerable sites as well as being able to justify the flood protection level decision process.


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11 Flood Protection Systems

The following sub-sections gives examples of possible flood mitigation solutions that could be used solely or in a combined system to protect existing vulnerable substations. New build sites in flood risk areas should be designed as described in Section 8 in order to be able to mitigate the effects of flooding without additional flood protection measures.

11.1 Site Boundary Wall and Flood Gates

Shown below are typical examples and products used to create a permanent flood protection bund wall around a site in its entirety. Typically this approach utilises a reinforced concrete boundary wall with flood gates at points of vehicular and pedestrian access. It should be noted that while this offers the most effective form of flood defence it is also the most expensive scheme of those suggested in this document and is likely to have local planning implications.

11.2 Permanent Protective Walls around Structures (including raising bund walls)

The examples below demonstrate a more selective option by locally protecting the critical assets within a substation as opposed to the whole substation site. This option utilises a waterproof membrane and wall around the switchouse and is normally combined with an extension of the height of the transformer bund walls. This is a more cost effective solution than the complete bund wall option and is unlikely to be affected by planning requirements to make space for water although non-critical plant or equipment will not be protected.


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11.3 Demountable/Retractable Barriers

Shown below are typical examples of demountable flood protection systems. These demountable flood protection systems are site specific and designed to be used where the warning period of a flood event given by the Environment Agency is adequate to allow their erection. Alternatively they can be used where periodic inspection of plant is required and the construction of a permanent protective barrier would interfere with access. These barriers can also be used across doorways of ancillary buildings not included in the main flood protection scheme or across vehicle entrances in whole site bunded schemes where a high volume of vehicle movement could render a standard flood gate inappropriate.


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11.4 Ancillary Flood Protection

As part of any major flood protection scheme it is essential that all flood entry routes are addressed. Measures must be put into place in order to prevent water ingress via storm or foul sewers or through ventilation air bricks. Below are examples of an air brick sealing flap which only operates during flood conditions allowing the air brick to function normally at all other times, a non-return valve and ducts sealed with the RISE duct dealing system.

12 Suppliers

Below is listed a selection of suppliers, manufacturers and consultants that can supply, design and install and advise on flood protection products and solutions. This list is not exclusive or exhaustive nor does the inclusion of a particular company imply UK Power Networks approval.

Caro Flood Defence Systems (Tel: 01763 244446)

Flood Ark Limited (Tel: 01603 879977)

Flood Control Limited (Tel: 01822 832385)

Floodguards System Limited (Tel: 0845 500 0077)

IBS Engineered Products Limited (Tel: 01925 428940)

Total Flood Solutions (Tel: 0845 4567175)

UK Flood Barriers Limited (Tel: 01905 773282)


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13 Reference Documents

The documents listed below have either been referred to in this document or should be referred to during the process of designing and implementing the flood protection measures.

BS 8102: 2009 Code of Practice for Protection of Below Ground Structures against Water from the Ground

EDS 07-0003 Enclosed Major Substation Civil Engineering Standards

ENA ETR 138 Energy Networks Association: Resilience to Flooding of Grid and Primary Substations

Environment Protection Act 1990

NPPF National Planning Policy Framework 2012

The Pitt Review: Learning Lessons from the 2007 Floods

Water Resources Act 1991

14 Environment Agency Offices

General Enquires

National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY

Southern Region

Office Type Address

Regional Southern Regional Office, Guildbourne House, Chatsworth Road, Worthing, West Sussex, BN11 1LD

Area Sussex Area Office, Saxon House, Little High Street, Worthing, West Sussex, BN11 1DH

Area Kent Area Office, Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent ME19 5SH

Area Hampshire and Isle of Wight Area Office, Colvedene Court, Colden Common, Hampshire, SO21 1WP

Thames Region

Regional Thames regional Office, Kings Meadow House, Kings Meadow Road, Reading, Berkshire, RG1 8DQ

Area West Area Office, Red Kite House, Howbery Park, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BD

Area South East Area Office, Swift House, Frimley Business Park, Camberley, Surrey, GU16 7SQ

Area North East Area Office, Apollo Court, 2 Bishops Square Business Park, St Albans Road West, Hatfield, Hertfordshire, AL10 9EX

Anglian Region

Regional Anglian Regional Office, Kingfisher House, Goldhay Way, Orton Goldhay, Peterborough, Cambridgeshire, PE2 5ZR

Area Northern Area Office, Waterside House, Waterside North, Lincoln, Lincolnshire, LN2 5HA

Area Eastern Area Office, Iceni House Cobham Road, Ipswich, Suffolk, IP3 9JD

Area Central Area Office, Bromholme Lane, Brampton, Huntingdon, Cambridgeshire, PE28 4NE

Flood information for individual sites can be obtained from the Environment Agency – Floodline Tel: 0345 988 1188.