glyn rhonwy pumped storage development consent...

Glyn Rhonwy Pumped Storage Development Consent Order

Environmental Statement Volume 1: Non Technical Summary

PINS Reference EN010072

Document No. 6.01

Regulation 5(2)(a) and Infrastructure Planning (Environmental ImpactAssessment) Regulations 2009

Author AECOM

Revision Date Description

0 October 2015 Submission Version

Glyn Rhonwy Pumped StorageDevelopment Consent Order

6.01 Non-Technical SummaryVolume 1

October 2015

RevisionNo.

Date ofIssue

Comments Author(s) Checker Approver

0October

2015Final Issued Various CA DR

August /

September

2015

Working Draft Various CA DR



October 2015

ContentsEXECUTIVE SUMMARY

CHAPTER 1 INTRODUCTION

CHAPTER 2 APPROACH TO EIA & CONSULTATION

CHAPTER 3 DESIGN EVOLUTION AND ALTERNATIVES

CHAPTER 4 PROJECT DESCRIPTION

CHAPTER 5 SUMMARY OF ENVIRONMENTAL IMPACT ASSESSMENT

FiguresFIGURE 1.1 SITE LOCATION PLAN

FIGURE 1.2 ORDER LIMITS

FIGURE 3.1 ECOLOGICAL DESIGNATIONS

FIGURE 3.2 LANDSCAPE DESIGNATIONS

FIGURE 3.3 SNOWDONIA NATIONAL PARK AUTHORITY

FIGURE 3.4 SITE DESCRIPTION

FIGURE 3.5 DESIGN REVIEW 1







FIGURE 4.1 DEVELOPMENT OVERVIEW

FIGURE 4.2 INDICATIVE ROUTE OF ELECTRICAL CONNECTION

FIGURE 5.1 ZONE OF THEORETICAL VISIBILITY

FIGURE 5.2 CUMULATIVE DEVELOPMENTS



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Abbreviations & Glossary2012 ES The previously submitted ES

AGL Above Ground Level

AOD Above Ordnance Datum

AQMP Air Quality Management Plan

BOCC Birds of Conservation Concern

BPM Best Practicable Means

BS4142 British Standard – Method for Rating Industrial Noise Affecting Mixed

Residential and Industrial Areas

BS7445 British Standard- Description and Measurement of Environmental Noise

CADW The Welsh Government's Historic Environment Service

CCW Countryside Council for Wales (now NRW)

CEMP Construction Environmental Management Plan

CoCP Code of Construction Practice

CTMP Construction Traffic Management Plan

DCO Development Consent Order

DECC Department of Energy & Climate Change

Development The proposed 99.9MW Glyn Rhonwy Pumped Storage Facility

DMP Dust Management Plan

DNO District Network Operator

EIA Environmental Impact Assessment

EN-1 Overarching National Policy Statement for Energy

EN-3 National Policy Statement for Renewable Energy Infrastructure

EN-5 National Policy Statement for Electricity Networks Infrastructure

EP Environmental Permit

EP Environmental Permit



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ERFMP Emergency Response and Flood Risk Management Plan

ES Environmental Statement

ES The Environmental Statement for the Glyn Rhonwy Pumped Storage

DCO

FCA Flood Consequences Assessment

GAPS Gwynedd Archaeological Planning Service

GC Gwynedd Council

GI Ground Investigation

Ha / ha Hectare

HASP Halth and Safety Plan

HDPE High Density Poly-ethylene

Headpond Upper reservoir

HGV Heavy Goods Vehicle

HMP Habitat Management Plan

HRA Habitat Regulation Assessment

Hz Hertz

ICP Independent Connection Provider

kv Kilovolt – measure of electrical current

LCA Landscape Character Area

LHA Local Highway Authority

LSE Likely Significant Effect

LVIA Landscape & Visual Impact Assessment

LWS Local Wildlife Site

m Metres

m3 Cubic metres

MTAN Minerals Technical Advice Note



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MW Mega Watts – measure of energy, one million watts

MWh Mega Watt Hours – measure of energy generated in hours

NMP Noise Management Plan

NPS National Policy Statement

NRW Natural Resources Wales (formally EAW and CCW)

NSIP Nationally Significant Infrastructure Project

NSR Noise Sensitive Receptor

NTS Non-Technical Summary

NVC National vegetation Classification

PC Principal Contractor

PEIR Preliminary Environmental Information Report

Penstock The pipe connecting the headpond to the power house

PINS Planning Inspectorate

Power House Containing the combined pump/turbines

PPP Pollution Prevention Plan

PPW Planning Policy Wales

PRoW Public Rights of Way

Q1 Quarry 1- Chwarel Fawr

Q2 Quarry 2- Chwarel Cefn Du

Q3 Quarry 3- Cook

Q4 Quarry 4- Ddol

Q5 Quarry 5- unnamed but known locally as Gideon Quarry (previously

known as Glynrhonwy)

Q6 Quarry 6- Glyn Rhonwy (also locally known as Mancer Quarry)

Q7 Quarry 7- Unnamed and is a smaller quarry excavated between and to

the south of Glyn Rhonwy (Q6) and the former munitions store (Q8). It



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has been used to dispose of slate waste and has more established

vegetation colonising its base than other quarries at the site.

Q8 Quarry 8 former WWII munitions store (known locally as the bombstore)

QBC Quarry Battery Company Ltd

SAC Special Area of Conservation

SNP Snowdonia National Park

SNPA Snowdonia National Park Authority

SoCC Statement of Community Consultation

SoS Secretary of State

SP Scottish Power

SPH Snowdonia Pumped Hydro Ltd or “the Applicant”

Spillway Infrastructure A discharge point from the headpond and a joint

discharge/abstraction point from the tailpond

SSSI Site of Special Scientific Interest

SUDS Sustainable Urban Drainage Systems

T&CPA application The planning application submitted under the Town & Country

Planning Act for the 49.9MW scheme as approved by GC

T&CPA Town and Country Planning Act 1990

TA Traffic Assessment

Tailpond Lower reservoir

Tailrace The pipe connecting the power house to the tailpond

TAN Technical Advice Note

TBM Tunnel Boring Machine

The Act The Planning Act 2008

The Applicant Snowdonia Pumped Hydro (SPH) Ltd

The Approved Scheme The approved 49.9MW scheme Glyn Rhonwy Pumped

Storage facility



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TPO Tree Protection Order

TWL Top Water Level

UDP Unitary Development Plan

UXO Unexploded Ordnance

V Volt

WFD Water Framework Directive

WG Welsh Government

WMP Waste Management Plan

WTMP Water Management Plan

ZTV Zone of Theoretical Visibility



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Introduction

This Non-Technical Summary (NTS) accompanies a Development Consent

Order (DCO) application which has been submitted by Snowdonia Pumped

Hydro (SPH – hereafter referred to as “the Applicant”) for the construction

and operation of a pumped storage scheme with an output capacity of 99.9

megawatts (MW) at the Glyn Rhonwy and Chwarel Fawr quarries, near

Llanberis (hereafter referred to as ‘the Development”).

The Development exceeds 50MW installed output capacity, and is therefore

designated as a Nationally Significant Infrastructure Project (NSIP) under

the Planning Act 2008 (“the Act”). The application for the DCO is submitted

to the Planning Inspectorate and will be determined by the Secretary of

State for Energy & Climate Change (SoS).

Environmental Impact Assessment

EIA is the process of identifying, evaluating and, where possible, mitigating

the likely significant environmental effects of a proposed development. It

promotes the early identification and evaluation of the potentially significant

environmental effects of a proposed development and enables appropriate

mitigation (that is measures to avoid, reduce or offset significant adverse

effects) to be identified and incorporated into the design of a development,

or commitments to be made to environmentally sensitive construction

methods and practices.

The Infrastructure Planning (Environmental Impact Assessment)

Regulations 2009 (as amended) (the EIA Regulations) apply in the case of

applications under the Planning Act 2008. The EIA Regulations require an

Environmental Impact Assessment (EIA) to be carried out to determine the

likely significant effects of a proposed development on the environment.

EXECUTIVE SUMMARY



October 2015

The results of the EIA also ensure that decision makers such as the SoS

and statutory consultees such as planning authorities, in this case Gwynedd

Council, as well as other interested parties, including local communities, are

aware of a development’s environmental effects so that these may be

considered before a decision is taken on whether or not the development

should be approved.

An Environmental Statement (ES) reports the findings of the EIA. The ES

which accompanies the application for the DCO has been prepared by

AECOM on behalf of the Applicant.

The methodology section within individual technical chapters of the ES sets

out the criteria used in judging the significance of effects and the process

that has been undertaken to gather baseline information and predict the

likely effects and their magnitude.

Mitigation measures are actions that are implemented to reduce the

significance of an environmental effect. Should a likely significant effect

remain after the implementation of mitigation measures, this is known as a

significant residual effect.

Pre-Application Consultation

Under the Planning Act 2008, the Applicant is required to undertake formal

consultation with the local community and stakeholders to allow them to find

out more about the Development, and give the Applicant their views on the

proposals in line with the requirements of the Act. Formal statutory

consultation was conducted during February and March 2015. Comments

and responses received from the consultation stage were reviewed and

considered in finalising the proposed scheme and the final ES to be

submitted with the DCO application.

Purpose of this NTS

This document provides a Non-Technical Summary (NTS) of the ES

including setting out the evolution of the Development as well as describing

the results of the EIA to allow readers to understand the likely significant

effects of the Development would be, both adverse and beneficial, and the



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proposed mitigation measures to avoid or minimise adverse effects, where

appropriate.

The NTS summarises the ES and is structured as follows:

Chapter 1 – Introduction

Chapter 2 – Approach to EIA & Consultation;

Chapter 3 – Design Evolution & Alternatives

Chapter 4 - Project Description

Chapter 5 – Summary of Environmental Impact Assessment

Chapter 6 - Conclusions

Submission

The SoS will consider the ES and all other relevant technical information, as

part of their responsibilities for determining the application. They will also

take into account any representations made by interested parties during the

examination of the application.

Further Information and Consultation

Additional copies of this NTS can be requested free of charge, and are

available from the project website (www.snowdoniapumpedhydro.com). A

Welsh language version of this NTS is available on the project website and

hard copies are available upon request.

The ES is available on the project website

(www.snowdoniapumpedhydro.com) and can be inspected at several

locations as detailed in Table 1.



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Table 1 Inspection Venue Details

Location & Address Copy available Opening TimesLlyfrgell LlanberisLibrary, Ffordd CapelCoch, Llanberis, LL554SH

One inspection hardcopy and electroniccopies available

Tuesday 1400-1800,Thursday 1000-1200 and1300-1700, Friday 1400-1800.

Gwynedd CouncilHeadquarters, CastleStreet, Caernarfon,LL55 1SE

One inspection hardcopy and electroniccopies available

Monday – Friday 0840-1700

Caernarfon Library,Pavilion Hill,Caernarfon, LL55 1AS

Electronic copiesavailable

Monday and Tuesday 0930– 1900, Wednesday 0930– 1300

Waunfawr Surgery,Liverpool House,Waunfawr, LL55 4AG


Monday, Tuesday &Thursday 0800-1830

Deiniolen Library , TyElidir, High Street,Deiniolen, LL55 3HR


Monday 1500-1800,Wednesday 1400-1700,Friday 1000-1200.

Copies of the ES and DCO submission are available on request and will be

charged at £250 for a printed hard copy (including appendices) and £5 for

an electronic copy on CD/DVD.



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1.1 Introduction

1.1.1 This document is the non-technical summary (NTS) of the Environmental

Statement (ES) for the Glyn Rhonwy Pumped Storage Development

Consent Order (hereafter referred to as the “Development”). The ES has

been submitted in four volumes. This NTS is Volume 1 with the remaining

volumes as follows:

Volume 2 – Main Text (Document Ref: 6.02)

Volume 3 – Appendix (Document Ref: 6.03)

Volume 4 – Figures & Photomontages (Document Ref: 6.04)

1.1.2 The Final ES has been produced to accompany the Development Consent

Order (DCO) Application under the Planning Act 2008 (“the Act”). The

Development exceeds 50 megawatts (MW) capacity and is therefore

classed as a Nationally Significant Infrastructure Project (NSIP) which

requires the consent of the Secretary of State (SoS) through the approval of

a DCO under the Act. The decision of whether or not to grant the DCO will

be made by the Secretary of State for Energy and Climate Change (“SoS”).

If the DCO is granted, the decisions on the detailed approvals under the

conditions in the DCO (known as “Requirements”) will be made by

Gwynedd Council (GC).

1.1.3 The Development will require a number of other consents in addition to the

DCO (for example permission to abstract water from Llyn Padarn to fill the

reservoir) which are not dealt with in this document, but are explained in

Document 5.04 “Details of Other Consents and Licenses” and within the

technical chapters of the ES, as appropriate.

1.1.4 The location of the Development is shown on Figure 1.1.

1 INTRODUCTION



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1.1.5 This NTS gives an overview of the Development, including the need for the

project, the alternatives that have been considered and a description of the

Development itself. This NTS also provides an overview of the conclusions

reached in the ES. Feedback received during the pre-application

consultation process has helped to inform the detail of the Development

and to further refine the EIA. The full and detailed findings of the EIA have

been presented in the ES.

1.1.6 This document is a summary (in non-technical language) of the ES for the

Development. The ES and the accompanying NTS have both been

prepared in accordance with Regulations 2 and 10 of the Infrastructure

Planning (Environmental Impact Assessment) Regulations 2009 (as

amended) (the ‘EIA Regulations’).

1.2 The Applicant

1.2.1 Snowdonia Pumped Hydro Limited (“SPH”) is the applicant for this DCO.

The company is a subsidiary of the Quarry Battery Company Limited

(“QBC”) which seeks to develop disused quarry systems into pumped

storage facilities.



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1.3 Planning History

1.3.1 The Development is located approximately 1.5km north west of Llanberis,

as shown on Figure 1.1.

1.3.2 QBC was granted planning permission (Ref: C12/1451/LL) by GC on the

19th February 2014 for the construction and operation of a 600MWh

(megawatt hours) pumped storage scheme, with an output capacity of

49.9MW, at the Glyn Rhonwy and Chwarel Fawr quarries, near Llanberis.

The permission was granted under the Town & Country Planning Act 1990

(T&CPA). An application (Ref: C15/0308/15/DA) for a non-material

amendment (NMA) (was submitted in March 2015 to correct an inaccuracy

in the plans listed under Condition 2 of the extant permission. The

application was approved on 6th May 2015 and Condition 1 of the NMA

approval lists the approved plans correctly.

1.3.3 An EIA was undertaken of the approved scheme and the T&CPA

application was accompanied by an Environmental Statement.

1.3.4 Subsequent to the grant of planning permission under the T&CPA, SPH has

been established as a subsidiary of QBC to take the Glyn Rhonwy scheme

forward.

1.3.5 Due to changes in the energy market, the decision was taken to increase

the capacity of the approved scheme to 99.9MW. As the capacity of the

scheme is above 50MW, it falls under the definition of a NSIP and therefore

requires a DCO under the Act, rather than Planning Permission under the

T&CPA. The 99.9MW proposal is referred to throughout this document as

‘the Development’.

Terminology

1.3.6 The following terminology is used throughout this NTS (and the ES):

The ‘approved scheme’ refers to the approved 49.9MW Glyn Rhonwy

Pumped Storage facility;

’T&CPA application’ refers to the planning application submitted under

the Town & Country Planning Act for the 49.9MW scheme as approved

by GC;



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The ‘2012 ES’ refers to the previously submitted ES;

‘The Development’ refers to the proposed 99.9MW Glyn Rhonwy

Pumped Storage facility;

‘The Development site’ refers to land within the red line site boundary or

the “Order Limits” shown in Figure 1.2 of the NTS below;

‘Order Limits’ refers to the red line site boundary; and

‘The Applicant’ refers to Snowdonia Pumped Hydro Limited (SPH).

1.3.7 Further details of the Development can be found in Section 4 of this NTS

and in Chapter 4 Project Description of the ES.

1.4 Concept of Pumped Storage

1.4.1 Pumped storage is a method of generating electricity at times of peak

demand at short notice. This is achieved by releasing water from an upper

reservoir, which passes through a turbine, into a lower reservoir. Water is

then pumped back up during periods of low demand. The water is then

stored in the upper reservoir ready for the next time of peak demand. More



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detail is provided in Chapter 4 Project Description of the ES and in section 4

of this NTS.

1.5 Background & Need for the Development

1.5.1 The electricity supply network in the UK relies on the generation of

electricity from several sources, more traditionally through baseload thermal

generation plants such as coal, gas and also nuclear. These generators all

provide power to keep the national grid at a steady 50 Hertz (Hz), essential

to the smooth operation of electrical equipment throughout the UK.

1.5.2 At times of peak demand, pumped storage has the ability to provide

electricity quickly. Pumped Storage systems are able to start extremely

rapidly from cold start and even quicker from standby mode, in some cases

achieving full power within 15 seconds.

1.5.3 Compared to thermal power stations, which can take several hours to reach

full generating capacity, pumped storage has the ability to store and

generate large quantities of energy, making such facilities the most flexible

of all grid-scale electrical generation technologies.

1.5.4 Pumped storage is not a form of renewable energy as it requires energy to

pump the water back up from the lower reservoir to the upper reservoir,

ready for the next supply of energy to the electricity network. This happens

at night when abundant cheaper electricity can be utilised.

1.6 Introduction to the Development

1.6.1 The quarry system has been numbered from Q1 in the west to Q8 in the

east, which can be seen in Figure 1.2:

Quarry 1 (Q1) – Chwarel Fawr;

Quarry 2 (Q2) – Chwarel Cefn Du;

Quarry 3 (Q3) – Cook;

Quarry 4 (Q4) – Ddol;

Quarry 5 (Q5) – unnamed (known locally as ”Film Set Quarry”);

Quarry 6 (Q6) – Glyn Rhonwy;



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Quarry 7 (Q7) – unnamed; and

Quarry 8 (Q8) – former WWII munitions store (known locally as “the

bombstore”).

1.6.2 The Development utilises Q1 and Q6.

The Development

1.6.3 Pumped storage projects comprise of seven main elements:

A headpond - upper reservoir;

A tailpond - lower reservoir;

A power house - containing the combined pump/turbines;

A penstock - the pipe connecting the headpond to the power house;

A tailrace - the pipe connecting the power house to the tailpond;

Pumping station; and

Spillway infrastructure – a discharge point from the headpond and a joint

discharge/abstraction point from the tailpond.

1.6.4 The Development at Glyn Rhonwy comprises of the following permanent

features:

one headpond (Q1), its dam, access shaft and spillway to the Nant Y

Betws;

one tailpond (Q6), its dam, access shaft and spillway to Llyn Padarn;

a pumping station at Llyn Padarn;

a power house at Glyn Rhonwy Industrial Estate Platform 5 (south of Q6)

with an underground turbine hall housing turbines with an electrical

output of up to 99.9MW;

a penstock (connecting Q1 to the power house); and

a tailrace (connecting the power house to Q6).

1.6.5 The Development also incorporates temporary features such as temporary

construction compounds and lay down areas at Q1 and Q6.



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1.6.6 Further details are provided in ES Chapter 4 Project Description and

section 4 of this NTS.

1.7 The Planning Framework

1.7.1 The Department for Energy and Climate Change (DECC) has published a

number of National Policy Statements (NPSs) in relation to energy

infrastructure. These NPSs set out national policy against which proposals

for NSIPs are assessed and determined. The DCO application for the

Development will be determined in accordance with these policies.

1.7.2 The NPS of principal relevance to the proposed Development is the

overarching NPS for Energy (NPS EN-1). This was published in 2011 and

sets out national policy for energy infrastructure as defined by the Act. NPS

EN-1 provides the primary basis for decisions on energy projects by the

SoS. Consideration is also given to the NPS for Renewable Energy

Infrastructure (2011) (NPS EN-3), and the NPS for Electricity Networks

Infrastructure (2011) (NPS EN-5).

1.7.3 NPS EN-1 states that consideration may be given to planning policy outside

the NPSs where it is important and relevant to the SoS's decision. Other

national, regional and local planning policies have therefore been

considered in the preparation of the ES as these may be relevant to the

determination of the proposed DCO Application, including:

• Planning Policy Wales (PPW) (7th Edition, July 2014);

• Technical Advice Notes (TANs);

• Minerals Technical Advice Notes (MTANs) (2009)

• People, Places, Futures: The Wales Spatial Plan Update (July 2008);

• Mon a Menai Strategy Programme (2008)

• Gwynedd Unitary Development Plan (2009)

• Gwynedd Local Planning Authority Supplementary Planning Guidance:

Development Brief Caernarfon Dependency Catchment Area



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• Emerging Anglesey and Gwynedd Joint Local Development Plan

(Deposit Plan, 2014) and

• Glyn Rhonwy Development Plan and Implementation Strategy



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2.1 Introduction

2.1.1 Environmental Impact Assessment (EIA) is the process of compiling,

evaluating and presenting environmental information about the likely

significant environmental effects of a Development. The assessment is

designed to help produce an environmentally informed project. The early

recognition of likely significant adverse environmental effects enables

appropriate mitigation (e.g. measures to avoid, reduce or offset significant

adverse effects) to be identified and incorporated into the design of a

project; or what measures will be taken to protect the environment during

construction and operation.

2.1.2 The EIA provides the decision maker and interested parties with information

about the likely significant environmental effects of the project and

proposed mitigation to assist with the determination of relevant applications.

Scoping

2.1.3 Scoping is a process which seeks to identify a suitable approach to the EIA

based on the best information available at the time that a scoping opinion is

sought.

2.1.4 The scope of the ES submitted with the DCO application has fully

considered the conclusions of the 2012 ES, the conditions attached to the

planning permission for the approved scheme and also the ongoing

discussions with statutory consultees.

2.1.5 During early consultation with the statutory consultees and PINS, the

Applicant sought to agree a scope directly with the statutory consultees,

namely Gwynedd Council (GC), Natural Resources Wales (NRW), Welsh

Government (WG), CADW, Snowdonia National Park Authority (SNPA) and

Gwynedd Archaeological Planning Service (GAPS). Therefore, a letter

setting out the proposed scope of the EIA for the Development was

2 APPROACH TO EIA & CONSULTATION



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submitted to these parties on the 12th November 2015. In response to this

letter, initial comments were provided by SNPA, NRW and GC. Following

this initial dialogue, it was agreed with those parties that a formal request

for a scoping opinion would be made to the SoS.

2.1.6 A request for a Scoping Opinion was submitted to the SoS on 5th January

2015, accompanied by a Scoping Report. The Scoping Report outlined

which environmental topics were to be covered by the EIA and how the

assessments were to be undertaken. The Scoping Opinion from PINS on

the 13th February 2015 and is contained within ES Volume 3, Appendix 2.4.

Draft ES / Preliminary Environmental Information Report (PEIR)

2.1.7 As part of the statutory pre-application consultation for the Development

under s47 of the Act, a Draft ES (February 2015) was prepared as

Preliminary Environmental Information (PEI) and made available to

consultees and the public during formal statutory consultation which

commenced on 12th February 2015. The Draft ES presented the

information gathered to date and provided the draft results of technical

assessments as to the likely significant environmental and social effects,

both positive and negative, of the construction, operation and

decommissioning phases of the Development.

2.1.8 The Draft ES was sent either electronically or in hard copy to all identified

s42 consultees on the 12th February 2015. Consultees were then given a

minimum of 28 days to respond with any comments on the Development

(which finished on the 13 March 2015). It was also available for viewing at a

number of locations in the vicinity of the Development and at the public

exhibitions held on the 27th and 28th February 2015. Full details of the

consultation activities can be found in the Consultation Report (Document

5.01) and in the Summary of Consultation Report (Document 5.01.1).

2.1.9 The Preliminary Environmental Information Report (PEIR) is an

intermediate step in the EIA process as required under the Act, and

provides environmental information compiled by the Applicant at the time of

publication, to enable consultees to develop an informed view of the

Development. The PEIR assesses the likely environmental effects of the



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Development and identifies potential approaches to mitigation based on the

environmental and social data collated at the time of publication, and

outlines whether further assessment needs to be carried out.

2.1.10 Feedback received during the pre-application consultation process has

helped to inform the detail of the Development and to further refine the EIA.

The full results of the technical studies are provided in the Final ES, which

accompanies the DCO application.

EIA

2.1.11 In accordance with EIA regulations, the EIA process for the Development

incorporates the following main steps:

Production of a Scoping Report to identify the likely significant effects

(scoped in) and the proposed methodology for their assessment in line

with relevant legislation, guidance and methods, and justification for any

significant effects that are not likely (scoped out). The Scoping Report

sought agreement of study areas, data sources, survey methodologies

and terminology;

Baseline surveys are undertaken to identify and describe the

environmental character of the area that could potentially be affected by

the Development. Where baseline data indicates major constraints to the

Development, this information is to be provided to the design team

immediately;

Relevant natural and manmade processes that may change the

character of the site are identified;

Consideration is then given to the possible interactions between the

Development and both existing and future site conditions. These

interactions or impacts are assessed using set criteria based on

accepted guidance and good practice;

Using the initial designs of the Development, the likely significant

environmental effects, both direct and indirect, can be established;

Production of a Preliminary Environmental Information report for

consultation purposes:



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Recommendations are made to avoid, minimise or mitigate adverse

effects and enhance positive effects. Alterations to the design will then

be reassessed and the significance of likely residual environmental

impacts ascertained; and

Following statutory consultation, the results of the EIA in combination

with the responses to the Scoping Opinion will be set out in an ES that

will accompany the application for a DCO.

2.1.12 Feedback received during the previous consultation process in connection

with the approved scheme and the ongoing pre-application consultation

through the DCO process has helped to inform the design of the

Development and the findings of and commitments made in the EIA.

2.2 Consultation

2.2.1 Effective pre application consultation is an important requirement of the Act,

which requires applicants to consult with both technical (Section 42) and

community (Section 47) consultees.

2.2.2 The Applicant has engaged in pre-application consultation with a number of

statutory consultees, namely PINS, GC, GAPS, CADW and NRW, prior to

the submission of the DCO. Table 2.1 outlines the meetings which have

been held:

Table 2-1 Record of MeetingsDate Attended by Issues discussed15th October2014

Gwynedd Council Intention to apply for DCO

1st December2014

Gwynedd Council& Cadw

DCO workshop includingdiscussions about the changes inred line boundary

2nd December2014

Gwynedd Council,NRW, PINS

PINS site visit plus follow upmeeting with GC and NRWregarding introduction to theproject and DCO process.Minutes taken.

22nd January2015

NRW To discuss SI works and HRAScreening

9th March 2015 PINS To discuss progress on the DCO26th March 2015 Horizon Nuclear

PowerTo discuss cumulative effects

26th March to 16th NRW, GC & Informal meetings during



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Table 2-1 Record of MeetingsDate Attended by Issues discussedJuly Gwynedd

ArchaeologicalTrust

preliminary GI works.

30th March 2015 NRW & GwyneddCouncil

To discuss s42 responses fromGwynedd Council and NRW.NRW provided a formal responseon the agenda and both partiesalso provided comments on theUXO report. Minutes taken.

15th May 2015 PINS To discuss progress on theproject and draft DCOdocumentation

15th July 2015 NRW andGwynedd Council

To discuss results of the breedingbird and aquatic ecology surveys,UXO and amends to projectdescription. Minutes taken.

16th September2015

PINS To discuss progress on theproject and draft DCOdocumentation

Public Consultation

2.2.3 Consultation with local people, businesses and organisations is also an

essential part of the DCO process and has helped to influence the final

designs of the Development.

2.2.4 Full details of the consultation that has been undertaken by SPH in

connection with the Development are provided in the Consultation Report

(Document 5.01) which records the consultation undertaken and its

conclusions, in particular how it has influenced the Development and the

Application.

2.2.5 Over 200 people attended the public exhibitions held on the 27th February

2015 in Caeathro and 28th February 2015 in Llanberis. Over 640 individual

items of feedback from 639 unique correspondents were received as part of

the s47 consultation.

2.3 Approach to Assessing the Significance of Effects

2.3.1 The following approach provides an overview of the assessment

methodology. However, within individual technical chapters in the ES, the



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approach may differ due to topic-specific guidance, policies and legislation.

Where this occurs, the variation in methodology is explained clearly and

fully.

2.3.2 The determination of the significance of the likely environmental effects

arising from the Development is a key stage in the EIA process. In order to

assess the significance of an impact, it is necessary to establish the

sensitivity or value of the receiving environment or receptor and the

magnitude of the impact occurring, i.e. the scale, duration etc of the change

to the existing conditions as a result of the Development. Assessment of

significance for individual environmental topics will typically combine

professional judgment with consideration of a number of factors:

The sensitivity of the resource or environmental feature (known as 'a

receptor') under consideration;

The magnitude of the impact in relation to the degree of change which

occurs as a result and whether the effect is temporary, permanent,

and/or reversible.

2.3.3 Other factors include the type of effect, i.e. whether it is adverse, beneficial,

neutral or uncertain; and the probability of the effect occurring based on the

scale of certain, likely or unlikely.

2.3.4 The sensitivity of the baseline conditions is assessed according to the

relative importance of existing environmental features on or near to the site,

or by the sensitivity of receptors, which would potentially be affected by the

Development. Table 2-2 lists the criteria for the determination of the

sensitivity or value of receptors are established based on approved

guidance, legislation, statutory designation and/or professional judgment.



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October 2015

Table 2-2: Criteria for determining sensitivity of receptorsSensitivity DefinitionVery High The receptor has little or no ability to absorb change without

fundamentally altering its present character, is of very highenvironmental value, or of international importance.

High The receptor has low ability to absorb change withoutfundamentally altering its present character, is of highenvironmental value, or of national importance.

Medium The receptor has moderate capacity to absorb change withoutsignificantly altering its present character, has someenvironmental value or is of national importance.

Low The receptor is tolerant of change without detriment to itscharacter, is low environmental value, or local importance.

Negligible The receptor is resistant to change and is of little environmentalvalue.

2.3.5 The magnitude of potential effects on environmental baseline conditions is

identified through consideration of the Development taking into account the

scale or degree of change from the existing baseline as a result of the

effect. Consideration is given to the duration and reversibility of the effect as

well as consideration of relevant legislative or policy standards or

guidelines. Table 2-3 provides a general definition for determining the

magnitude of a particular effect.

Table 2-3: Criteria for determining the magnitude of a particular effectMagnitude DefinitionHigh Total loss or major alternation to key elements / features of

the baseline conditions such that post development character/ composition of baseline condition will be fundamentallychanged.

Medium Loss or alteration to one or more key elements / features ofthe baseline conditions such that post development character/ composition of the baseline condition will be materiallychanged.

Low Minor shift away from baseline conditions. Changes arisingfrom the alteration will be detectable but not material; theunderlying character / composition of the baseline conditionwill be similar to the pre-development situation.

Negligible Very little change from baseline conditions. Change is barelydistinguishable, approximating to a “no change” situation.



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October 2015

2.3.6 The general approach adopted in the assessment of significance, as it

relates to sensitivity and magnitude, is outlined in Table 2-4 below. A

combination of the magnitude of the impact under consideration and the

sensitivity of the receiving environment determines the significance of

effect. For some specialist topics, additional categories have been added

where a greater level of definition is required. It should be noted that this

general approach is a framework only, the significance of an effect is

assessed on a case-by-case basis.

Table 2-4 Approach to Assessment of Effects

Magnitude Sensitivity

Very High High Medium Low Negligible

High Major Major Moderate Moderate Minor

Medium Major Moderate Moderate Minor Negligible

Low Moderate Moderate Minor Negligible Negligible

Negligible Minor Minor Negligible Negligible Negligible

2.3.7 The significance of the effects arising from the Development have been

reported using a seven-point scale, as follows:

Major Adverse, Moderate Adverse, Minor Adverse;

Negligible; and

Major Beneficial, Moderate Beneficial, Minor Beneficial.

2.3.8 Effects predicted to be Minor are considered to be manageable and such

effects are considered to be ‘Not Significant’. Effects assessed as

Moderate or Major are considered to be 'Significant'. When the residual

significance of impacts is assessed this takes into account mitigation, i.e.

the assessment applies to the residual effects of the project, which can be

defined as any impact that would remain following the implementation of

proposed mitigation measures.



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October 2015

2.4 Structure of the ES

2.4.1 The ES reports the findings of the EIA and ensures that decision makers

such as the SoS and statutory consultees such as planning authorities, in

this case GC, as well as other interested parties, including local

communities, are aware of a development’s environmental effects so that

these may be considered before a decision is taken on whether or not the

development should be approved.

2.4.2 The ES also contains a series of technical assessments which have

assessed the potential for likely significant effects during the construction,

operation and decommissioning of the Development. The scope of these

technical assessments was presented within the Scoping Report submitted

to PINS on the 5th January 2015 and consultation with interested parties

and statutory consultees has shaped the scope of these assessments.

Further detail on consultation can be found in Chapter 2 Approach to EIA &

Consultation of the ES.

2.4.3 The structure of the ES is as follows:

Introductory chapters including the approach to the EIA and consultation,

the design evolution, the main alternatives considered, the project

description, and planning policy (Chapters 1-5);

Landscape Character and Visual Amenity(Chapter 6);

Ecology (Chapter 7);

Geology & Ground Conditions (Chapter 8);

Water Resources (Chapter 9);

Flood Risk (Chapter 10);

Archaeology & Cultural Heritage (Chapter 11);

Traffic & Transportation (Chapter 12);

Noise and Vibration (Chapter 13);

Air Quality (Chapter 14);

Socio-economics (Chapter 15);



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October 2015

Environmental Management (Chapter 16);

Cumulative Effects (Chapter 17); and

Schedule of Mitigation (Chapter 18).

2.4.4 Additional documentation has been submitted with the ES as follows:

Statement in respect of statutory nuisance (Document 5.02);

European site appropriate assessment report, otherwise known as a

Habitat Regulation Assessment (HRA) (Document 5.03);

Details of other consents and licenses (Document 5.04); and

Code of Construction Practice (CoCP) and associated management

plans (Volume 3, Appendix 16.1).

2.4.5 The CoCP is the document that brings together all the construction phase

mitigation measures proposed for the Development. It covers the

management of a Principal Contractor’s (PCs) activities and those of any

Sub-Contractors, and defines the minimum requirements that have to be

met. It identifies the procedures required to minimise the impact of

construction activities for the Development. It includes details of measures

to be employed to ensure that no pollution incidents occur, that impacts on

protected species / designated sites are minimised as far as possible, that

archaeological features are identified and recorded, and that impacts on

nearby residents are kept to an absolute minimum.

2.5 Cumulative and In-Combination Effects

2.5.1 The effects of the Development have been assessed in combination with

two other developments in the vicinity of the Order Limits (i.e. ‘cumulative

effects’). Consideration has been given to the Wylfa C New Nuclear Power

Station and the Caernarfon to Bontnewydd bypass, but only in relation to

socio-economic and traffic and transportation effects due to the distance

between the Developments.

2.5.2 The effects of the Development on shared receptors have also been

assessed (i.e. ‘combined effects’).



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October 2015

2.5.3 In-combination effects (where two effects which are not significant could

combine to result in a potential cumulative effect which is significant) have

also been considered as part of the EIA and are discussed within each

chapter of the ES (and summarised in Chapter 17 Cumulative Effects) and

in Section 5 of this NTS.


6.01 Non Technical SummaryVolume 1

3-1

October 2015

3.1 Surrounding Environment

3.1.1 The Development is located approximately 1.5km north west of Llanberis

and 11km south east of Caernarfon, as shown in Figure 1.1 of the NTS. It is

located on the slopes of Cefn Du, centred at National Grid reference SH

56268 60660.

3.1.2 The site is located within, and in close proximity to, environmentally

designated sites; Llyn Padarn to the east is a Site of Special Scientific

Interest (SSSI), as shown in Figure 3.1.

3.1.3 The Development site itself is within a Landscape Character Area (LCA)

(designated for its historical landscape) and also within Dinorwig Landscape

of Outstanding Historical Interest, as shown in Figure 3.2.

3 DESIGN EVOLUTION AND ALTERNATIVES



3-2

October 2015

3.1.4 The site is located approximately 1km outside of Snowdonia National Park

(SNP), this is shown in Figure 3.3.



3-3

October 2015

3.1.5 The Development site encompasses a series of disused quarries, the Glyn

Rhonwy Industrial Estate platforms and an area adjacent to Llyn Padarn, all

within the boundary of GC. This is shown in Figure 3.4.

3.1.6 The Development covers an area of approximately 91.24ha.

3.1.7 The site’s physical characteristics include a number of quarry pits, slate

tips, a mature plantation woodland, rough grazing land and road network

leading to Glyn Rhonwy Industrial Estate platform in the south and off the

A4085 in the north. Ffordd Clegir separates two of the lower quarries and

also forms the western boundary of the Glyn Rhonwy Industrial Estate. This

is shown in Figure 3.4.

3.1.8 Water has collected in two of the quarries. Bathymetric surveys undertaken

in Q6 have recorded the depth at approximately 17m. Q1 is estimated to be

approximately 7m deep.

3.1.9 The slopes around the quarries are built up with slate waste and

interspersed with the remains of outhouses and quarry workings, scattered

over grazing land. The neighbouring land is mainly agricultural, although



3-4

October 2015

there is an industrial estate between Glyn Rhonwy and Llyn Padarn, an

area of commercial forestry to the south west, and a large industrial

complex to the south of the site towards Llanberis.

3.1.10 A former World War II munitions store (Q8) is not included within the Order

Limits but is within close proximity to the Development.

3.1.11 Several Public Rights of Way (PRoW) cross the Order Limits in addition to

Ffordd Clegir (translated as Clegir Road) which bisects the quarry system.

Several individual properties are located on Ffordd Clegir with the nearest

properties approximately 400m away in Clegyr and Pen-draw. Additional

dwellings and properties are located approximately 1-2 km to the north west

of the Order Limits in Gallt-y-Celyn, Pen-y-Bwlch and Bwlch. The settlement

of Waunfawr is located approximately 2 km to the west of Q1 and the main

centre of Llanberis located approximately 1.5km from Q6. Further detailed

information is provided in Chapter 4 Project Description of the ES.

3.1.12 Although development of the Glyn Rhonwy industrial site has provided

improved access – including public access – access to the site is restricted

by locked gates and the quarries themselves are fenced off. The site is

used for informal (unauthorised) leisure activities and there is evidence that

forced access has been gained. Some quarries and buildings including the

Industrial Estate itself have been known to suffer vandalism in the form of

tipping, graffiti and damage to the fencing, which has facilitated

(unauthorised) access.

3.2 Design Evolution

3.2.1 The Development has evolved in two principal stages. The first design

evolution related to the approved scheme, with the second evolution taking

place following the grant of permission for the approved scheme in advance

of the submission of the DCO. This was in response to the Electricity

Market Reform which meant that the approved scheme was unlikely to be

deliverable with an output capacity of 49.9MW and that an increased

capacity would be required.



3-5

October 2015

Approved Scheme - Review 1: Initial Design prepared for report to

accompany formal Scoping Request to Gwynedd Council (November 2011)

3.2.2 The initial design was based upon technical requirements of the pumped

storage scheme together with development constraints including proximity

to residential dwellings and designated sites, and incorporated three dams

at Q1, Q2 and Q6 with heights of 12m, 26m and 17m above ground level

(AGL) respectively. An alternative option was considered which comprised

an increase in the height of the dam at Q1 to 15m AGL, thereby avoiding

the need for a dam at Q2, and a reduced dam height at Q6 of 8m AGL.

3.2.3 The overland penstock route was to be routed on the northern side of the

Cook (Q3) and Dhol (Q4) quarries to avoid protected birds. The penstock

would be up to 2000m long with two 2.5m diameter pipes.

3.2.4 The power house was to be located on the western side of Ffordd Clegir in

Q5. The location of site compounds and access tracks was undetermined.

3.2.5 The use of Llyn Padarn as a tailpond was considered but was discounted

on the basis that it is designated as a SSSI and is a popular recreational

destination. The scheme at Design Review 1 is shown in Figure 3.5 below



3-6

October 2015

Approved Scheme Review 2: Engineering review following survey works

(April 2012)

3.2.6 The principal change as part of Design Review 2 was the removal of the

dam at Q2. The engineering review identified the potential to provide

approximately 1,100,000m3 of storage in Q1 meaning that the three dams

initially proposed were not required. In addition, the engineering review also

identified that significant engineering and geotechnical stabilisation works

would be required at Q2 and Q5, in addition to the ecological constraints

identified in Q5. As a result, dams were only required at Q1 (headpond) and

Q6 (tailpond) which would be 25m above ordnance datum (AOD) and 15m

AOD high respectively.

3.2.7 The proposed location of the power house was moved (from the munitions

store) to Platform 5 of the Glyn Rhonwy Industrial Estate.

3.2.8 Two penstock / tailrace construction methods to transfer water from Q1 to

Q6 were still being considered at this stage – one above ground and one

below ground. Design Review 2 is shown in Figure 3.6 below.



3-7

October 2015

Approved Scheme - Review 3: Review following stakeholder consultation

(July 2012)

3.2.9 It was determined that the penstock for the approved scheme should be

constructed by underground tunnel excavation. The route, established at

Design Review 2, would be used, albeit along a more direct underground

route between Q1 and Q6. The open cut construction option was

discounted following consultation with regulators.

3.2.10 The location of the spillway pipe from Q6 to Llyn Padarn was still subject to

landownership discussions, specifically related to the bombstore (Q8). A

location for the pumping station was identified at a small inlet adjacent to

the public car park.

3.2.11 It was agreed that the excess material excavated from Q1 and Q6 would

stay onsite and be landscaped into the existing spoil mounds at Q1, to

avoid any adverse effects from transportation offsite through Waunfawr.

3.2.12 The scheme at Design Review 3 is shown in Figure 3.7 below.



3-8

October 2015

Approved Scheme - Review 4: Final design for planning approval (August

2012)

3.2.13 The construction method for the penstock was confirmed as underground

tunnel excavation, removing the need for any above ground excavation.

3.2.14 Two dams were proposed; one at Q1, approximately 25m above existing

ground levels and 510m long (at the longest point), and a second at Q6,

approximately 15m above existing ground levels and 215m long (at the

longest point). The power house for the approved scheme was located on

Platform 5 of the Glyn Rhonwy Industrial Estate.

3.2.15 The location of the pumping station was confirmed as being at National Grid

ref SH 57250 61192 on the banks of Llyn Padarn due to the deeper water

and minimal effect on the car parking areas in this location.

3.2.16 The location of the spillway was confirmed as being to the south and south

east of Q8, outside of the bombstore, and therefore reducing the impact on

the former munitions store. The scheme at Design Review 4 (the approved

scheme) is shown in Figure 3.8 below



3-9

October 2015

DCO Development - Review 5: Engineering Review to increase output

capacity to 99.9MW (December 2014)

3.2.17 It was confirmed that the output capacity of the Development could be

increased to 99.9MW without any substantial changes being made to the

principal elements of the approved scheme. The main changes included:

More powerful turbines with a combined output capacity of 99.9MW

located within the underground turbine hall. The turbine hall remained

the same size as the approved scheme;

If required, additional noise attenuation for the turbines was proposed to

comply with any limits set by a DCO Requirement (as per planning

conditions for the approved scheme); and

A minor increase in the number of construction based deliveries to bring

the larger turbines and associated infrastructure on to site. As the

additional deliveries would have been to Q6, it was predicted that the

A4086 road infrastructure would accommodate the slight increase in

construction delivery traffic (particularly as the planning conditions

relating to traffic mitigation and management for the approved scheme

were to be reflected in DCO Requirements).

3.2.18 The Order Limits proposed for the Development at this stage comprised an

area of 59.3ha which reflected the size of the redline boundary for the

approved scheme, as shown in Figure 3.8 in this NTS.

DCO Development: Review 6: Design Review for report to accompany

formal Scoping Request to SoS (January 2015)

3.2.19 The Order Limits around Q1 were increased to allow for construction

activities around the new excess slate mounds to the south and an area to

the north to accommodate potential quarry wall re-profiling.

3.2.20 The area around and including Q1 is registered as Common Land, so an

application will be made to deregister the parts which will be permanently

affected and fenced off. The land north and south of the penstock corridor

and west of the Q1 construction compounds was identified as replacement

land in terms of being a similar quality, size and access. The land was



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October 2015

included in the Order Limits as land negotiations had not been concluded at

the time; this was to ensure that powers could be sought under the DCO to

compulsorily acquire rights over / ownership of this land if required. An

additional area was also included for a potential replacement road to the

power house.

3.2.21 The Order Limits around the penstock were widened to 114m to allow for

flexibility in the underground penstock route due to the potential for dolerite

intrusions which may be present.

3.2.22 The Order Limits were also extended to allow for flexibility in the location of

the pumping station and its working area. The pumping station was still

proposed to be constructed in the manner outlined in the 2012 ES (i.e.

sunken design with a control box / kiosk above ground). The depth of the

spillway infrastructure into Llyn Padarn remains 5m beneath the water level

– this depth was previously agreed with the Countryside Council for Wales

(CCW) (now NRW) as it would avoid any potential effects to Arctic Char by

being above the thermocline, and also to recreational users.

3.2.23 As a result of the design review, the Order Limits increased from 59.3ha to

91.73ha. This was included within the Draft ES and is shown in Figure 3.9.



3-11

October 2015

DCO Development - Review 7: Engineering Review (February – March

2015)

3.2.24 Subsequent to the issue of the Draft ES (February 2015) as part of the

consultation period, the Applicant undertook a final review of the temporary

and permanent PRoW diversions required in connection with the DCO. This

identified a need to extend the Order Limits by approximately 6ha to a total

of 97.77ha, this is shown in Figure 3.10.

3.2.25 During the formal consultation period, the Applicant continued to carry out

survey work of the land within the Order Limits. This included a full

topographical survey of the access route to Q1 (Green Road) and the laser

mapping of the Q1 and Q6 voids to prepare a more extensive and accurate

picture of the site’s topography. Localised topographical surveys around the

quarries were also completed to supplement the digital terrain and LiDAR

mapping previously undertaken for the entire site.

3.2.26 In addition, the preliminary GI works were also being undertaken at this

time. However the results of these investigations did not affect the Order

Limits.



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October 2015

DCO Development - Review 8: Final Design for DCO Application (August

2015)

3.2.27 Since the issue of the Draft ES in February 2015, a final series of further

changes have been made to the Development design and the Order Limits.

These have been made in response to comments received through the

formal consultation process, and to also reflect a reduction in the extent of

land take required for the DCO. Changes to the Development design have

also occurred as a result of the extensive mapping and data collection

exercise. The overall land area within the Order Limits was reduced to

91.24ha. Further details of the amendments made at this design review

stage are provided below.

Increase in Storage Capacity

3.2.28 Since the submission of the Draft ES, the mapping of the quarry voids has

identified the potential to increase the storage capacity from 1,100,000m3 to

up to 1,300,000m3. This increase in potential storage capacity does not

materially change the Development as consulted on in February 2015. Both

GC and NRW were informed of this capacity change in a meeting held on

the 15th July 2015.

3.2.29 The increase in reservoir capacity will deliver an increase in energy

generating capacity from 600MWh to up to approximately 800MWh. The

overall output capacity of the Development remains at up to 99.9MW (as

the increased storage capacity will allow the facility to operate for a longer

time period).

3.2.30 It must be noted that the increased storage capacity has not been achieved

through any changes to the overall size of the dams or the above ground

buildings (such as the power house). It is purely a result of the greater

volume of the reservoirs being confirmed which increases the length of time

the scheme can operate at its maximum output of 99.9MW.

Changes to Material Volumes

3.2.31 The detailed topographic and digital mapping survey also identified that

whilst the void at Q1 is larger than previously estimated, Q6 is smaller than



3-13

October 2015

originally estimated. At Q6, this is due to the presence of a number of

geological intrusions below the surface of the water identified through the

bathymetric survey - these intrusions will need to be removed to create the

reservoir at Q6. In order to provide the equivalent storage capacity in Q6 as

Q1, up to approximately 650,000m3 of screened unsuitable material will

need to be moved from Q6; all suitable virgin material will be used for the

construction of the Q6 dam.

3.2.32 SPH therefore undertook a design review, under which alternative storage

areas for spoil material were considered. It was considered that any

potential storage would potentially have an adverse visual effect and be in

closer proximity to residential dwellings and private water supplies. In

addition, the lack of available space to store the excess material

permanently in the vicinity of Q6 rendered this option unviable.

3.2.33 In full recognition of the previous commitment not to transport excess

material through Waunfawr, it is therefore proposed that the excess

material not utilised in the construction of the Q6 dam will be transported

through the penstock with a conveyor. Excavation of the penstock utilises a

conveyor for removal of excavated material, and this conveyor will be

connected to run the full penstock length between Q6 and Q1 to carry

material. This material will then be deposited within the proposed slate

mounds at Q1.

3.2.34 The material excavated from Q6 will result in an increase in the volume of

the slate mounds at Q1 from up to approximately 690,000m3 to up to

approximately up to 935,000m3. However, the slate mounds still remain in

the same orientation as approved previously and as per the photomontage

of Viewpoint 2 Moel Eilio (see Volume 4 Figure 6.4b). The excess slate

mounds will occupy a slightly larger footprint than previously proposed, but

will remain 4m away from the nearest public right of way (and their

associated permanent diversions), 10m away from the Nant Y Betws and

2m away from the Order Limits boundary in any other non-constrained

areas. The use of detailed terrain data has confirmed that there is sufficient

space to accommodate this increase and the landscape and visual impact

assessment has confirmed that there are no additional effects.



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October 2015

Changes at Q6 and Pumping Station

3.2.35 To enable the construction of the potential bifurcation valve, a secondary

temporary access shaft and access tunnel will be sunk to enable

excavation. This will be in addition to the main turbine shaft and tailrace but

will not be used during operation and so will be removed after construction.

3.2.36 Whilst there was no change in the Order Limits, the location of the pumping

station was moved further back from Llyn Padarn to an area of vegetation

adjacent to the main car park. A secondary alternative location is also being

investigated and is subject to ongoing discussions with utility companies

regarding easements. This alternative location is immediately adjacent to

the toilet block in front of the access to the bombstore. The DCO Work

Plans have accounted for this flexibility should the secondary option be

feasible from an easement and engineering perspective.

3.2.37 The scheme at Design Review 8 (the Development subject to the DCO

application) is shown in Figure 3.11 below.



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October 2015

3.3 Rochdale Envelope

3.3.1 As the Development has evolved since the grant of planning permission for

the approved scheme, further investigation into the proposed engineering

design has been undertaken. In light of this, sufficient flexibility has been

built into the DCO to allow for the final design to reflect the most appropriate

construction techniques identified for the delivery of the Development. This

flexibility may be required to address unexpected constraints, such as

ground conditions and alternative construction methods.

3.3.2 As certain aspects of the Development still require design flexibility, the

DCO application, and therefore the EIA, is based on the application of

maximum and, where relevant, minimum parameters or limits of deviation.

These include the tunnelling method, the height of dams, the location of the

pumping station, the horizontal and vertical alignment of the penstock, and

the internal configuration of the power house. In light of this, it was

necessary for the technical assessments to assess an ‘envelope’ within

which the works will take place.

3.3.3 To remain in accordance with the EIA regulations it is essential that the

parameters are as ‘“limited” as possible to ensure that the ‘likely significant

effects’ are identified, rather than unrealistically amplified effects, which

could be deemed to be unlikely. It was proposed to use maximum and

minimum parameters for the Development in each relevant technical

assessment.

3.3.4 The final Rochdale envelope parameters are provided in Table 4-1:



3-1

October 2015

Table 4.1 – Rochdale Envelope Parameters

Area Description

Q1

Maximum elevation of dam of 395m AOD to crestPlan width 150m and length 371mMax volume of 1,300,000m3

Max water level 392m AOD

Excess SpoilsMounds Max combined volume of 935,000m3

Penstock

To be tunnelled within 114m buffer and between a maximumelevation of 330m AOD to a minimum depth of 55m AODUp to 1600m long within Order Limits (plan length) but potentiallyup to 1800m to allow for any underground deviations, and 4.5minternal diameter

Tailrace Up to 160m long Tailrace, 4.5m internal diameter

Q6

Maximum elevation of 156m AODPlan width 95m and length 210mMax volume of 1,300,000m3

Max water level 154m AOD

Power House 15m high to apex x 27m wide x 60m long

Turbine HallTwo underground turbines with maximum electrical output of up to99.9MWVolume of excavation approximately 100,000m3

Switchgear 10m high to apex x 18m wide x 30m long

Transformer 7m wide x 7m long x Assumed to be 10m high

GIS Substation12m high to apex x 12m wide x 30m longGas Insulated

PumpingStation 1.6m high x 2m long x up to 0.8m deep



3-2

October 2015

3.4 Alternatives

Engineering Alternatives

3.4.1 Throughout the design evolution, alternatives have been considered. These

are outlined in detail in Sections 3.6 – 3.7 of the Final ES and are

summarised below:

The use of Llyn Padarn as the tailpond – whilst the potential optimal

solution in terms of engineering, this was discounted early in the scheme

development due to its highly sensitive, environmental, ecological and

social importance;

An alternative to the movement of material offsite through Waunfawr

resulted in the creation of the excess slate mounds and internal

conveyor from Q6;

The underground excavation of the penstock was confirmed on the basis

of significantly adverse visual, environmental and archaeological effects

from an open cut alternative;

Routing of the underground penstock to avoid any potential geotechnical

instability issues from drilling under existing slate mounds and close to

quarries contained highly sensitive and protected ecological features;

and

Placement of the discharge outlet into Llyn Padarn above the

thermocline to avoid any potential effects on the Arctic Char.

Alternatives to the site at Glyn Rhonwy

3.4.2 As required by the Overarching National Policy Statement for Energy (EN-

1) and as advised by the SoS in Section 2.56 of his Scoping Opinion

(February 2015) consideration has been given to alternatives to the

Development as proposed in the DCO application. The following section

details why SPH selected the Glyn Rhonwy site for the Development over

other potential locations.

3.4.3 The technologies, plant and construction methodologies to be used, where

definable at this stage of the development process, are detailed within the

following section in this NTS and ES Chapter 4 Project Description.



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October 2015

Alternative construction methods and technologies to those assessed in the

ES were considered; however, they have not been carried forward or

selected for the final design for various reasons, typically due to their

engineering inefficiency and non-compliance with best practice guidelines.

3.4.4 Sites suitable for pumped storage are limited by the need for specific

physical characteristics. Importantly, pumped storage requires at least two

or more quarries or reservoirs where water can be released from a high to a

low elevation. An initial source of water is also required and sites need to be

reasonably close to existing electrical connections.

3.4.5 The feasibility study work undertaken by the Applicant for the development

of pumped storage included a detailed mapping exercise undertaken to

examine the feasibility of pumped storage throughout Great Britain, against

key indicators including:

the geology, ground conditions and terrain;

accessibility;

safety and feasibility of construction;

the physical shape and sizes of the reservoirs and requirements for

dams;

the distance between the reservoirs and the distance to the transmission

grid;

the environmental sensitivity of the site; and

whether any impacts of the development could feasibly be designed out

or mitigated.

3.4.6 This exercise identified a number of locations where pumped storage is

considered feasible, including Glyn Rhonwy. However, Glyn Rhonwy was

identified as a highly suitable location for pumped storage for several

reasons:

There are two quarries separated by a large height difference but

geographically close to each other;



3-4

October 2015

The local geology of the Llanberis Welsh Slates formation is a

reasonably impermeable seam, the use of which has already been

proven by the Dinorwig Pumped Storage facility; and

The site is only 7km from a connection point to the electricity network,

which, given the other critical criteria, is considered to be relatively close.

3.4.7 The Gwynedd Unitary Development Plan (UDP) (2001 - 2016) specifically

identifies pumped storage (Policy C27) as a suitable use on the previously

developed land at Glyn Rhonwy Redevelopment Site (Policy C6).

Do Nothing Scenario

3.4.8 Pumped storage provides fast response energy in times of peak demand.

Without this ability to rapidly respond to peak demand the UK would rely

increasingly on baseload thermal power stations and inflexible forms of

renewable energy, such as wind, to provide energy whether it is required or

not. This would lead to significant inefficiencies and unnecessary green

house gas emissions through unnecessary burning of fossil fuels.

3.4.9 NPS EN-1 supports the use of technologies such as pumped storage under

the classification of “electricity storage” to provide back up to an energy

market increasingly supplied by less predictable renewable energy sources.

Section 3.3.12 of NPS EN-1 states

‘There are a number of other technologies which can be used to

compensate for the intermittency of renewable generation, such as

electricity storage, interconnection and demand-side response, without

building additional generation capacity. Although Government believes

these technologies will play important roles in low carbon electricity system,

the development and deployment of these technologies at the necessary

scale has yet to be achieved. The Government does not therefore consider

it prudent to solely rely on these technologies to meet demand without the

additional back-up capacity. It is therefore more likely that increasing

reliance on renewable will mean that we need more total electricity capacity

than we have now, with a larger proportion being built only or mainly to

perform back-up functions.’



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October 2015

3.4.10 There are limited sites across the UK which are deemed suitable for

pumped storage. Making use of the Glyn Rhonwy site to provide electricity

storage capacity will make an important contribution to the delivery of a low

carbon electricity system in the UK, as outlined in NPS EN-1. In a ‘Do

Nothing Scenario’, this contribution would not be made.

Project Optimisation

3.4.11 This EIA assesses the worst case scenario by making reasonable

assumptions based on current knowledge and engineering design. The

engineering design has been undertaken and refined where possible based

on the information gained to date and there will be elements which will be

subject to detailed design and further site investigation works.

3.4.12 However there is also the potential for opportunities within the design for

engineering improvements and optimisation. These are indentified as

follows:

Turbine Shaft - The turbine shaft as shown in ES Volume 4, Figure 4.11

is considered the maximum extent of excavation. However the turbine

shaft can be optimised by excavating two smaller individual shafts or a

thinner single shaft opening into a larger underground turbine hall.

Therefore the assessment has been made on the worst case

engineering option.

Material to be excavated - The volume of material to be excavated has

been derived using a bulking factor of 1.6. This is considered to be a

conservative assumption and any lesser value would be considered an

improvement.



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October 2015

4.1 Development Overview

4.1.1 The Development will cover an area of 91.24ha. The Development consists

of the following components:

one headpond (Q1), its dam, access shaft and spillway infrastructure to

the Nant Y Betws;

one tailpond (Q6), its dam, access shaft and spillway infrastructure to

Llyn Padarn;

a pumping station at Llyn Padarn;

a power house at Glyn Rhonwy Industrial Estate Platform 5 (south of

Q6);

a penstock (connecting Q1 to the power house); and

a tailrace (connecting the power house to Q6).

4.1.2 Q8 does not form part of the Development but will be in close proximity to

the Order Limits. This is shown in Figure 4.1 of this NTS.

4.1.3 Q7 is included within the Order Limits due to some localised reprofiling

which may be needed around Q7 for the construction of the Q6 dam and

continuation of the existing access road to the upper platforms. A retaining

wall will be built to maintain structural integrity for the road. It is proposed

not to infill or enter Q7 other than to seal connecting tunnels.

4.1.4 The following sections provide a description of the key components of the

Development, construction methods and programme. These sections also

highlight the status and progress of certain elements of the design including

those that are subject to detailed design or those that have a lesser degree

of flexibility. Working areas are allocated as per the submitted Works Plans

(Document 2.04).

4.1.5 The Development is illustrated in Figures 4.1 to 4.16 within Volume 4 of the

Final ES, and on the indicative plans, elevations and sections submitted as

4 PROJECT DESCRIPTION



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October 2015

Documents 2.05 and 2.06. These drawings provide an indication of the

Development proposed based on the parameters assessed within this ES.

Headpond – Q1

4.1.6 The headpond will be formed at Q1 by the construction of a dam across the

south western side of the quarry. The headpond will have an approximate

volume of 1,300,000m3 of water. The dam will have a maximum elevation of

395m AOD. The normal maximum operational water level is 392m AOD.

The overflow level is 393m AOD which provides up to 1m of freeboard for

operating water level fluctuations before any overflow (spilling) would occur.

A further 2m of freeboard above the overflow is provided, primarily for wave

action.

4.1.7 Externally, the dam will be landscaped using slate and profiled so as to

appear similar to the slate mounds which surround the existing quarries. It

is likely to have a slope of between 1:1 and 1:2 although this is subject to

detailed design and agreement from the Construction Engineer appointed

under the Reservoirs Act.

4.1.8 To make the quarry safe and operable as a reservoir, stabilisation and

lining of the quarry may be required, once access has been made by

battening platforms into the quarry sides.

4.1.9 Stabilisation works will include the remodelling and reprofiling of the current

quarry edges to remove the fractured rock face and provide a smoother

operational surface. The use of rock anchors in appropriate locations to

stabilise the quarry sides will be undertaken as required. The quarry may

also need to be lined to reduce or prevent water loss through natural

seepage.

4.1.10 A freestanding combined overflow and relief valve outlet structure (or draw-

off tower) will be constructed adjacent to the Q1 dam and within the

reservoir. The overflow is provided in case of failure of the pump system or

cessation of generation which would result in natural filling of the reservoir.

The relief valve outlet (also commonly known as the 'scour' and shown on

drawings as such) provides a means of draining the reservoir to the level of

the base of the dam if required in an emergency situation.



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October 2015

4.1.11 The spillway infrastructure to the Nant Y Betws will consist of two pipes –

one 800mm diameter drainage pipe and a 400mm diameter scour pipe

which will be within an enclosed spillway infrastructure channel.

Tailpond – Q6

4.1.12 The tailpond at Q6 will be formed by the construction of a dam across the

north eastern end of the quarry following stabilisation and access works to

make the quarry operationally safe and functional. The dam will have a

maximum elevation of 156m AOD. Q6 would also hold a maximum volume

of up to 1,300,000m3 of water. The maximum normal operational water level

is 154m AOD. The overflow level is 154.5m which provides up to 0.5m of

freeboard for operating water level fluctuations before any overflow (spilling)

would occur. A further 1.5m of freeboard (above the overflow) is provided,

primarily for wave action.

4.1.13 In a similar construction method to Q1, the dam at Q6 may potentially be

lined and stabilised. The extent of the stabilisation works at Q6 may affect

the existing slate mound to the north of Q6, hence why this precautionary

approach to the extent of the Order Limits.

4.1.14 A freestanding combined overflow and relief valve outlet structure (or draw-

off tower) will be provided within the Q6 reservoir. This would generally

operate as per the overflow and relief valve (or ‘scour’) tower in Q1. The

relief valve outlet or scour pipe also acts as a rising main for water

abstraction from Llyn Padarn to Q6.

Removal of Water within the Quarries

4.1.15 Both Q1 and Q6 hold water within the existing quarry voids. Bathymetry

surveys estimate a depth of 7m in Q1 and 17m in Q6. Water sampling for

determining water quality has been undertaken within the quarries and

more details are provided in ES Chapter 9 Water Resources.

4.1.16 Water in Q1 will be pumped out and discharged to Nant Y Betws. If

required, the water will be passed through settlement lagoons and / or a

‘Siltbuster’ (or similar) to minimise the discharge of suspended solids. There

is up to approximately 100,000m3 of water within Q6 which will be pumped



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October 2015

out to the adjacent Llyn Padarn via a temporary pumping main. The rate

and volume of any discharges will be undertaken in line with the required

Environmental Permit.

Excavation of the Quarries

4.1.17 Approximately 550,000m3 will be excavated from Q1, most of which is

expected to be utilised within the dam construction. Approximately

360,000m3 will be excavated from Q6, with approximately 90,000m3 to be

utilised in the dam construction.

Stabilisation Works

4.1.18 The sides of the existing quarries Q1 and Q6 are potentially unstable and

require stabilisation to allow the safe construction and operation of the

reservoirs. Where rock excavation is required then stable slopes will be

formed using controlled blasting, with localised remedial works as required.

In other areas, stabilisation works will include the remodelling and

reprofiling of the current quarry sides to form stable rock faces, excavation

will either be by machinery or by controlled blasting or by a combination of

these two methods.

4.1.19 Due to a combination of geological variations and previous quarry workings,

Q1 will be stabilised by reprofiling. The south eastern side is to be retained

as far as possible with any loose material removed.

4.1.20 Stabilisation works on the northern side of Q6 may have the potential to

infringe on the existing slate mound further to the north of Q6. Detailed site

investigation works will confirm if this existing mound is stable and also if

any stabilisation works have the potential to affect it. Should stabilisation be

required this would be achieved by removing the spoil mound area which

could be at risk and temporarily relocating this to another area within the

existing slate mound. Once stabilisation works are complete the area will be

regraded and landscaped.

4.1.21 Other methods of stabilisation potentially include the following:

Removal – removal or scaling of individual features;



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October 2015

Containment – localised containment using rock netting or rock traps

(these can be permanent or temporary fences, ditches or stand-offs);

Strengthening – localised reinforcement using rock anchors, bolts or

dowels; and

Support or protection – localised support using retaining walls,

buttresses, sprayed concrete or anchored beams.

Unexploded Ordnance (UXO) & Sediment Remedial Works

4.1.22 There is documented evidence of the lower quarries being used historically

for military bomb storage and disposal. The bombstore (Q8) was

abandoned after the roof collapsed during World War II, but has been

subsequently remediated by the former Welsh Development Agency. There

are records of ordnance being disposed of in Q6 and also of a later

remediation operation in the 1970s by the Ministry of Defence. However,

there is the potential for unexploded ordnance (and also spent ordnance

scrap) to be present in and around Q6. As part of the development, a

recorded Ordnance Management Strategy will be undertaken in full

consultation with the appropriate authorities in relation to any potential

unexploded ordnance (UXO).

4.1.23 A UXO report is contained within ES Volume 3, Appendices 8.5 and 8.6

which provides further details, with an assessment contained within ES

Chapter 8 Geology & Ground Conditions.

4.1.24 Sediment collection from Q1 and Q6 was attempted in May 2015, however,

no discernible samples were collected due to the absence of any significant

depths of sediment. Once drained, should there be any sediment at the

base of the quarries, this will be tested and investigated for UXO and

contamination. Depending on the level of potential contamination present or

ordnance found, this will be remediated as, and if, required. It is not

proposed to remove any contaminated sediments from the Development.

Quarry Lining Works

4.1.25 For the base of the quarries, one of the following two methods is intended

to be employed (to be confirmed at detailed design):



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October 2015

1. An impermeable High Density Poly-ethylene (HDPE) liner will be

constructed in the base of the quarry. A sub-lining drainage system

would be required to collect and discharge any leakage and

groundwater. This will comprise of the following elements:

Landforming of the base;

A sub-lining drainage system;

Underlying and overlying regulating layers;

Impermeable liner;

Overlying protection geotextile fleece; and

Cover or protection layers.

This would prevent uplift pressures occurring during drawdown of the

pond in generation and would allow the detection of leakage through

the base; or

2. Pressure grouting of the base will be undertaken through boreholes in

the base of the quarry. The grout would fill in any fractures within the

rock mass and therefore reduce permeability.

4.1.26 It is likely that pressure grouting using cementitous grout will be the most

appropriate method for the quarry side slopes. The requirement for side

slope grouting will be confirmed by permeability testing following detailed

site investigation works as part of the enabling stage.

Dam Footprints

4.1.27 The dams will be founded on sound bedrock. This requires any superficial

deposits and existing quarry spoil to be removed prior to dam construction.

The elevation of the bedrock profile is likely to be variable and will only be

confirmed following stripping of the existing quarry spoil. Because of the

difference between existing ground level and bedrock level, the roots of the

dam will extend underground until they meet bedrock. Ground levels will be

restored to at or about the existing ground levels (or as otherwise agreed)

around the edges of the dams.



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October 2015

Wave Action and Protection

4.1.28 The dams will have a concrete wave wall running along the crest that the

upstream impermeable membrane will be tied into. Depending on the type

of impermeable membrane used (i.e. if an HDPE geo-membrane is used),

surface protection to the upstream face of the dam may be required through

the placement of a layer of selected rock, able to resist wave action. This

will be underlain by protective and regulating layers between the membrane

and a gradation of materials comprising sand through to crushed rock.

Penstock & Tailrace

4.1.29 The penstock is a pipe which will convey the flow of water between the

headpond and power house (and vice versa). The tailrace (or 'draft tube') is

a pipe which will convey water from the power house to Q6 (and vice

versa). The penstock will include a bifurcation in the approach to the power

house, this is shown in Figure 4.1 of the NTS. These will both be tunnelled.

4.1.30 The penstock will be approximately 1600m long, stretching from Q1 to Q6

(as shown on Figure 4.1) and have an approximate internal diameter of

4.5m. The length may deviate to a total length of 1800m dependent on

ground conditions.

4.1.31 The proposed excavation method is to use either a Tunnel Boring Machine

(TBM) or drill and blast. However due to the presence of potentially doleritic

intrusions within the bedrock, drill and blast may be used, or a combination

of the two approaches. This will be confirmed upon instruction of a Principal

Contractor (PC).

4.1.32 The outlet from Q1 is at an elevation of approximately 335m AOD

(approximately 50m below current ground levels). Where the penstock

enters the shaft for the turbine hall at the power house it is at an elevation

of approximately 60m AOD (approximately 90m below current ground level)

It should be noted that the elevation of the penstock may change

underground during detailed design of the scheme dependent on the

ground conditions and particular technical requirements, including the

pump-turbines selected. Construction of the penstock is likely to take up to

12 months.



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October 2015

Power House

4.1.33 The power house is an above ground building with offices, plant hall,

crane(s), workshop, welfare facilities and a control room. This building is

approximately 15m high to its apex, 60m long and 27m wide. The power

house straddles the shaft that contains the turbine hall which houses the

turbine-pumps and generators.

4.1.34 It is likely to be faced and roofed in slate but the final external design and

appearance will be subject to a DCO Requirement. It is expected that the

power house will be manned by up to approximately 35 people during

normal operation. The turbine hall will house turbines with a combined net

output capacity of 99.9MW. Due to the depth of the turbine hall, specialist

heavy equipment will be needed to lift the turbine and associated

infrastructure into position at depth.

4.1.35 The power house is also likely to contain the switchgear equipment which is

required to connect the Development to the electricity network.

Pumping Station

4.1.36 The pumping station is required so that water may be abstracted from Llyn

Padarn into Q6 in order to fill up the Development as part of the

commissioning process and also to 'top up' levels, or discharge any excess

water, during operation. The pumping station will only be operational when

water is required to be pumped from Llyn Padarn into the Development and

will not be operational when water is discharged to Llyn Padarn.

4.1.37 In response to consultation responses, the location of the pumping station

has been located away from the edge of Llyn Padarn, within an area of

vegetation adjacent to the car park. A secondary location is being

investigated further back towards the existing toilet block and is subject to

ongoing discussions with utility providers.

4.1.38 The pumping station will comprise of a below ground wet well, valve

chamber and cable pit, and above ground control box / kiosk. The majority

of the structure is below ground and can be located so as to avoid any

areas normally used by users of the car park and lagoon area.



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October 2015

4.1.39 The pumping station size will depend on the final location but will be

completely underground and located at depth. A small above ground

control box would be present and this is likely to be approximately 2m long

by 1.6m high by up to 0.8m deep and would resemble a communications

control box, most likely covered in British Standard 14-C-39 Green (subject

to DCO Requirement). A manhole cover and grid plate is also required to

gain access to the pumping station for maintenance purposes.

4.1.40 There would be no operational requirement for fencing around the control

box and no operational lighting. The underground pumping station will be

equipped with sufficient acoustic attenuation to minimise any disturbance

above ground.

Spillway Infrastructure

4.1.41 The spillway infrastructure contains an overflow from Q6 which will be

connected to Llyn Padarn directly with an approximately 800mm diameter

pipe. The spillway infrastructure also contains a combined scour and rising

main as a separate pipe approximately 450mm in diameter.

4.1.42 The spillway infrastructure will be culverted under the Q6 dam and will be

buried in an opencut trench for the full route to the pumping station and

then to Llyn Padarn. The indicative route around the south side of the

bombstore, and across the A4086, to the pumping station (which is

bypassed by the overflow and relief or scour outlet) and then to Llyn Padarn

is shown in Figure 4.1 of the NTS.

4.1.43 Valving will allow the relief or scour to discharge direct to Llyn Padarn

(bypassing the pumping station). The purpose of the overflow is to

discharge excess water collected within the reservoir(s) during operation.

The purpose of the scour is to allow drawing-down of the water level in the

reservoir to the base of the dam, including in an emergency situation. Any

relief or overflow discharges will be gravity fed.

4.1.44 As part of the 2012 ES, it was agreed that spillway infrastructure would be

screened to avoid any impacts to fish, be located above the thermocline,

approximately 5m below the minimum recorded water survey level to avoid

impacts to protected fish species, Arctic Charr, and impacts to recreational



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October 2015

users. Surface buoys would mark the location of the pipe terminals. There

will be a fine mesh screen on the pipes to prevent any wildlife, detritus or

material from entering the pipe.

4.1.45 As it will be at depth, the working environment will be sheet piled to ensure

a safe, water tight environment for the installation of the spillway

infrastructure. This will be approximately 5m x 20m.

4.1.46 Where the spillway infrastructure enters Llyn Padarn through the tree line,

the working width will be minimised as much as possible to minimise any

impacts to tree root systems. A tree survey will be undertaken prior to

construction commencing to microsite the pipe through this area. Any trees

that are removed will be subject to mitigation measures outlined in the

Habitat Management Plan (HMP).

4.1.47 Where construction enters Llyn Padarn, access around this immediate area

will be temporarily restricted to maintain a safe environment to the users of

Llyn Padarn. This is expected to last up to 12 weeks.

4.1.48 There are potentially two options for the construction of the spillway

infrastructure into Llyn Padarn, as follows:

Option 1

4.1.49 Using the coffer dam area, as outlined above, the pipes will be “strung out”

and sunk in place with pre-cast concrete weights.

4.1.50 Once the pipe is laid and the dry area reflooded, reinstated and coffer dam

removed, access will be allowed. It is expected that this element of the

construction of the pumping station and spillway infrastructure will be short

and temporary in nature. It is paramount that the health of safety of the

construction is managed correctly due to the nature of the works.

Option 2

4.1.51 A smaller coffer dam would be used but a small boat or barge would then

be used to string out the pipes and then connect to the onshore pipework

once the pipe is sunk using pre-cast concrete weights. Access to this area

would again be temporarily restricted whilst these works are ongoing to

maintain the health and safety of users and construction workers.



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October 2015

4.1.52 Detailed information on the construction method is contained with section

4.6 of Chapter 4 Project Description of the ES.

Commissioning

4.1.53 Once the pumping station and spillway infrastructure is in place, pressure

testing will be undertaken. This will be a temporary occurrence and last a

few weeks. Once the Q6 reservoir is ready to receive water, the abstraction

from Llyn Padarn will commence.

4.1.54 On the basis of 1,300,000m3 required, this will take 394 days on the basis

of 3300m3 per day. An abstraction license has been granted on the basis of

1,100,000m3 and a variation to this license will be submitted to NRW prior

to the start of the Examination in relation to the1,300,000m3 volume.

Programme

4.1.55 It is proposed not to work within the summer school holidays to minimise

any significant adverse effects to users of Llyn Padarn and the lagoons.

Outside summer school holidays, it is proposed to construct the overflow

and pumping station sequentially to minimise any disturbance to users of

Llyn Padarn and the lagoons. A small construction compound may be

required but access for cycle and vehicle users on the shore will not be

impeded, where necessary diversions will be implemented. It is not

proposed to block off or sever any existing routes for Llyn Padarn users but

some traffic management will be in place during critical activities.

4.1.56 There is no requirement for night time lighting during construction outside

working hours other than for security purposes.

Electrical Connection

4.1.57 The Development will be connected to the electricity distribution system

network via a new electrical connection. This will be exported from an

onsite substation to an offsite connection terminating at Pentir. This is

shown on Figure 4.2 of the NTS

4.1.58 This is likely to be a 132kV connection, which as associated development in

Wales, will not be consented under the Act. It may be possible to complete

the works under SP Manweb’s permitted development rights, or through the



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October 2015

formal grant of planning permission under the Town and Country Planning

Act 1990. Any application for the appropriate consents will be made by

SPH, an Independent Connection Provider (ICP) or SP Manweb as

appropriate. A high level cumulative assessment has been undertaken on

the indicative route and this is assessed in ES Chapter 17 Cumulative

Effects. This assessment is based on the current grid connection

agreement which was applicable at the time of submission.



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October 2015

4.1.59 SPH has committed to this connection being provided underground and the

current grid connection offer being discussed with SP Manweb seeks an

underground connection.

4.1.60 The switchgear building is adjacent to the power house and is also likely to

be faced and roofed in slate. The final building materials and finishes will be

subject to a DCO Requirement. The substation will contain 11kV and 400V

electrical distribution equipment and will measure approximately 10m high,

18m wide and 30m long.

4.1.61 The external transformer compound will have provision for a single

11kV/400V transformer and two 11kV/132kV transformers for the 132kV

electrical connection. Only the building required to house the substation

equipment will be included within and authorised by the DCO.

Permanent Excess Slate Mounds

4.1.62 Up to two excess slate mounds will be created south of Q1 with a volume of

up to 935,000m3. This will consist of a new slate tip to the south of the

existing mound, and an extension to the existing mound.

4.1.63 Material will be generated from the excavation of the Q1 and Q6 quarries to

form the headpond and tailpond reservoirs. This material will be crushed

and graded with only suitable material utilised in the construction of the

dam(s), with less suitable material used for landscaping purposes or

incorporated into the new excess slate mounds south west of Q1.

4.1.64 Excess material generated at Q6 will be transported by a conveyor within

the completed penstock for placement within the excess slate mounds.

Access

4.1.65 Access to Q1 will be via the existing unclassified road (known as the Green

Road) from the A4086 and through Waunfawr. Upgrades will be made from

the A4086 to the Q1 site compound with temporary access tracks from the

compound to the quarry. These upgrades are classed as associated

development and so will be subject to a planning application to Gwynedd

Council. Based on dialogue with the Council to date, the road will retain its

single track status with several passing places being constructed for vehicle



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October 2015

movements. The improvements to Green Road will be undertaken before

construction and then fully reinstated to adoptable road standards once

construction is complete. Further detail can be found in ES Chapter 12

Traffic and Transportation.

4.1.66 Access to Q6 will be through the existing road network off the A4085 to

within the existing Glyn Rhonwy Industrial Estate. Minor amendments may

be made to the A4085 and Industrial Estate junction for delivery of plant

and materials during construction although these will be reinstated post-

construction, unless their retention is agreed with the Highways Authority.

4.1.67 Ffordd Clegir, which runs between Q5 and Q6, will not be used for any

construction or operational traffic, although it may be subject to a temporary

closure for health and safety reasons on critical activities. Advance notice

will be given to the local residents, appropriate signage provided on the

road, and approval of GC as Highways Authority will be gained prior to any

works commencing.

4.2 Construction Phase

4.2.1 The construction phase is expected to last approximately 4 years from

commencement of works. Table 4-1 outlines an indicative simplified

programme of the Development. Please note that several activities have

been incorporated together which in reality will be distinctly separate in the

programme. A PC has not yet been appointed, and so it is envisaged that

the following indicative construction sequence will be followed.

Glyn Rhonwy Pumped Storage Development ConsentOrder


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October 2015

Table 4-1 Indicative Construction ProgrammePhase Location Activity Year 1 Year 2 Year 3 Year 4

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4Enabling Works Q1 & Q6 Offsite access road improvements, creation of replacement temporary car park

Establish construction compounds including fencing and security.Onsite general Mobilisation (and potential GI works) and site clearance

Dewatering Q1 & Q6 Dewatering of quarriesReservoir Works Q1 Access made to quarry floor and reprofiling including blasting, drilling, lining,

excavation and rock bolting and grout curtain constructionPartial removal of existing spoil mounds and crushing of excavated materialsConstruction of damConstruction of scour tower, overflow / relief valves and spill, inlet / outlet worksand chambersPlacement of excess material in new slate moundsConstruction of spillway infrastructure to Nant Y Betws

Q6 Access made to quarry floor and reprofiling including blasting, drilling, lining,excavation and rock bolting and grout curtain constructionPartial removal of existing spoil mounds and crushing of excavated materialsUXO Remedial worksConstruction of dam and placement of excess materialConstruction of scour tower, overflow / relief valves and associated pipework, inlet/ outlet works and chambersFill reservoir from abstraction and rainfall

Pumping Station Llyn Padarn Construction of spillway infrastructure to Llyn Padarn and pumping stationPenstockConstruction

Penstock Sink launch shaft from platform 5Excavation of penstock, bifurcation value and chambersLine tunnel

Conveyor Setup and movement of material from Q6 to Q1Power House Platform 5/6

Glyn RhonwyIndustrialEstate

Sink turbine shaft and construction of tailraceLining works and fit out shaft infrastructureConstruct power house superstructure, including crane and fit out power houseInstall turbines and electrical infrastructure below ground and above ground.Test and commission

De-mobilisation Q1 & Q6 Removal of site compounds and equipment from site. Reinstatement of accessroad improvement works.



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October 2015

4.2.2 Site preparation and enabling works will be required prior to

commencement of the main construction phase. These include:

Highway improvements to be completed;

PRoW diversions to be implemented;

Potential secondary ground investigation (GI) works; and

Mobilisation to site and establishment of temporary compounds.

4.2.3 Temporary construction buildings and laydown areas will be required.

These will be located within the Order Limits and consist of offices, meeting

rooms, a car park, storage and laydown areas for construction equipment

and vehicles, and welfare facilities for workers. The indicative location of

these temporary features is shown in Figure 4.1 of the NTS.

4.2.4 A variety of standard construction plant and equipment will be required as

part of the construction activities and these include (but are not limited to):

Low loaders – for delivery of plant and equipment;

Moxy – dumper trucks for transportation of materials internally in

quarries and externally to storage areas;

Wheeled and tracked 360 Excavators - for excavations works;

Mobile crushing and screening plant;

Bulldozers;

Graders;

Compaction plant; and

Cranes.

4.2.5 Other machinery and equipment may include, but not be limited to::

Concrete batching plant;

Welfare units and portacabins;

Pipework (in sections);

Temporary fencing;

Generators (at Q1 for electrical supply unless locally available); and



4-17

October 2015

Bowsers.

4.2.6 Should TBM be used as the penstock excavation method, this will be

brought to site in a modular fashion on the back of a low loader.

4.2.7 The 2012 ES proposed a Construction Environmental Management Plan

(CEMP) which the PC will be required to operate under. This has evolved

into a CoCP submitted in support of the DCO Application. It will implement

the mitigation measures identified within the 2012 ES, the planning

conditions attached to the T&CPA permission for the approved scheme,

and any additional measures identified in the ES. Further details are found

in Chapter 16 Environmental Management of the ES.

4.2.8 Construction working hours will be 07:00 – 19:00 Monday to Friday and

07:00 – 13:00 Saturday. Where construction activities are required outside

these hours, then this will be undertaken only with the prior approval of GC.

4.2.9 The number of construction staff on site will vary according to the

construction phase and activities being undertaken, and will be confirmed

by the PC upon instruction. However it is expected that up to 250 people

will be employed during the construction phase at its peak, after which it will

then generally decrease as construction is progressed through to the

commissioning phase. However, this will be subject to the requirements of

the PC and therefore could change.

4.2.10 Security lighting will be required within the Development during

construction, especially on the temporary compounds and storage areas.

This lighting will have due regard to nearby residential properties and

sensitive habitats and species. Workplace lighting at the onsite temporary

compounds will have due regard to UK guidelines on construction lighting,

namely Health and Safety Executive guidance HSG38 Lighting at Work and

also Bat Conservation Trust Statement on the Impact and Design of

Artificial Light on Bats (May 2011).

4.2.11 Access around the two working areas and the existing and diverted PRoWs

will be maintained during construction wherever possible to recreational and

common land users. The car park at Q1 will be temporarily relocated near

the temporary PRoW diversion so that these links can still be used.



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October 2015

4.2.12 Temporary closures of the PRoWs may occur and access to land may be

controlled during certain times in the construction phase for critical path

activities such as blasting or drilling. This is due to health and safety for

users, residents and the onsite workers. Appropriate signage will be

deployed on all PRoW diversions and the appropriate notice provided for

any closures.

4.2.13 In addition, the two working areas around Q1 and Q6 will have 24 hour

security to prevent public access with appropriate fencing, signage, lighting

and CCTV installed. There will no workers villages or overnight

accommodation at either temporary compound during construction. The

only 24 hour attendance will be security.

4.3 Operational Phase

4.3.1 The indicative operational lifespan of the Development is 125 years. The

Development will have continuous operation throughout its lifecycle except

for planned maintenance.

4.3.2 SPH estimate that approximately up to 35 people will be employed during

the operational lifetime of the Development to perform operational and

maintenance tasks. Therefore, operational traffic is limited to staff travel and

delivery of ancillary materials and plant during the Development lifespan.

4.3.3 As per the construction phase, the operational lighting strategy will have

due regard for residents, ecology and health and safety. It is proposed that

this is agreed as part of a DCO Requirement.

4.3.4 Once the Development is fully commissioned with 1,300,000m3 of water,

this will pass between Q1 and Q6 in order to provide the battery storage

and generate electricity at peak times.

4.3.5 Operational discharges will be intermittent and dependant on rainfall and

operational requirements. An essential component of any raised reservoir is

the ability to lower the water level behind the dam (draw-down); emptying

the reservoir to the point where there is no hydraulic load on the structure.

For the purpose of reservoir safety this facility must be available at all times.



4-19

October 2015

4.3.6 At times of normal operation, the main and primary mechanism for draw

down for the Q1 reservoir is through the penstock to Q6. The penstock pipe

has the capacity to provide draw-down of the reservoir in approximately 7

hours at a rate in the order of 46 m3/s. This is more than adequate to serve

the draw-down need for the Q1 reservoir.

4.3.7 At times of normal operation, the main and primary mechanism for draw

down for the Q6 reservoir is through the penstock to Q1, using the turbines

in the turbine house in pumping mode. However, because of the variables

in operation and maintenance of the scheme, and the need to have a draw-

down capacity at all times; it is considered prudent to include a facility to

lower the reservoir independent of the penstock and powerhouse.

4.3.8 Therefore both dams provide a secondary method for draw down, with

water being discharged to the Nant y Betws at Q1 and to Llyn Padarn at

Q6. This will only occur if the penstock is unavailable. The relief valves are

sized to allow the reservoir(s) to be drawn down to 50% of the volume

impounded by the dam(s) within 7 days. These discharges would be

controlled through the required discharge consent.

4.3.9 The relief valves are manually activated i.e. they will only be opened when

the operator intervenes. Such intervention will only take place in one of two

scenarios as follows:

a) when the there is a need to lower the water level behind the dam and

the water cannot, for whatever reason, be drawn down through the

penstock i.e. it would only be in an unusual situation when drawdown of

the reservoir is required and this cannot be achieved through the

penstock.

b) for maintenance; to ensure the valves are operational as part of the dam

safety regime, it will be necessary from time to time to briefly operate the

valves.

4.3.10 In short, emergency valve operation is considered an extremely unlikely

situation and, other than infrequent small amounts for valve testing, are not

part of the normal operation of the scheme and would be very unlikely,

possibly never, in an unplanned situation.



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October 2015

4.3.11 In the maintenance scenario (b above) the discharge would be managed as

per the requirements of the discharge consent. In this scenario, the valve

can be used in a controlled manner, when the flows in Nant-y-Betws and

the Afon Gwyrfai are low enough to accept the flows from the reservoir

without causing an increased risk of flooding from the watercourses.

4.3.12 No water is directly discharged into Llyn Padarn from the turbines.

4.4 Decommissioning

4.4.1 For the purposes of the EIA, it is assumed that decommissioning may occur

after an indicative 125 year operational lifespan. The implications of

decommissioning will be reviewed once it is evident the plant is

approaching the end of its working life.

4.4.2 At the end of the 125 year operational life, the Development will be

decommissioned:

Assessment of any buildings that are to be removed, including ecology;

Removal of all above ground structures, notably the power house;

Water will be drained from Q1 to Q6 and released at an agreed rate and

timescale through the appropriate licensing regime into Llyn Padarn;

Pumping station will be removed, although the overflow pipework at Q6

will remain in situ after being sealed;

Dams and access tracks to remain in situ;

Security fences will remain although access through the dam structures

will be secured;

Penstock pipework between Q1 and Q6 will remain in situ and sealed;

and

Overflow pipework at Q1

4.4.3 It is proposed that due to the anticipated lifespan of the Development, a

Decommissioning Plan will be required by the relevant authorities at the

point of decommissioning this Development. This will therefore be a

Requirement of the DCO.



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October 2015

5.1 Introduction

5.1.1 The ES identifies the key environmental topics that have been assessed as

part of the formal EIA process. These are as detailed in Section 2.3 of this

NTS.

5.1.2 For each assessment topic, the ES describes the proposed approach to

assessment, provides existing information on the local environment (the

environmental ‘baseline’ of the surrounding area), and describes the

potential effects on that environment during construction, operation and

decommissioning.

5.1.3 The environmental topic areas reported on in the ES are summarised

below.

5.2 Landscape Character and Visual Amenity

5.2.1 Chapter 6 of the ES contains an assessment of the landscape and visual

effects of the Development. The LVIA has been informed by the production

of a Zone Theoretical Visibility (ZTV) map for the quarry dams and slate

tips, which was undertaken for the 2012 ES.

5.2.2 Based on the ZTV, 12 representative viewpoints were agreed with

Gwynedd Council (GC), Environment Agency Wales (now NRW) and

Snowdonia National Park Authority (SNPA) as part of the 2012 ES. These

12 viewpoints have been used in the ES for the DCO, in order to present

views of the Development in the landscape. The ‘worse case scenario’ is

defined as the views from the most sensitive landscape and visual

receptors with the highest visibility of the Development. The ZTV and

locations of the 12 viewpoints can be seen in Figure 5.1 of the NTS. A

number of photomontages were produced for these viewpoints, showing the

Development as it will look when operational. These are shown in Volume

4, Figures 6.4a to 6.4l of Volume 4 of the ES.

5 SUMMARY OF ENVIRONMENTAL IMPACT

ASSESSMENT



5-2

October 2015

5.2.3 The landscape and visual effects have been assessed during the

construction, operation and decommissioning stages with respect to:

Landscape elements within the Development;

Landscape designations and the Snowdonia National Park;

LANDMAP aspects areas (geological, habitats, visual and sensory,

historic and cultural);

Views (visual amenity).

Effects during Construction

5.2.4 Construction elements and activities will have an adverse effect on the

landscape around Llanberis and the Snowdonia National Park. This effect is

however limited by the screening of the surrounding hills. Construction will

affect views from Moel Eilio, the Llanberis Lake Railway, Cefn Du and

Dinorwig. Screening by vegetation and the limited disruption on the

underlying character or focus of the view mean these effects of the

Development are limited.



5-3

October 2015

Effects during Operation

5.2.5 The visual amenity of walkers using Cefn Du will be moderately adversely

affected by the permanent dam at Q1.

5.2.6 Mitigation measures have been integrated into the design as far as

reasonably possible through excavation of the penstock rather than open

trench pipe route; layouts to minimise the effects on vegetation; the

reinstatement of landforms and vegetation and the use of natural screening

to avoid direct views from sensitive viewpoints onto material storage and

the power house. Permanent features and structures such as the power

house will be clad with local materials, and dams and excess spoil mounds

will use slate waste excavated on site to soften their features. Stone walls

will be reinstated wherever necessary and fencing at Q1 and Q6 will be

chosen to reflect existing fencing types.

Effects during Decommissioning

5.2.7 Decommissioning effects will be temporary and of a short duration. The

elements of the Development to be removed at the decommissioning stage

are described within ES Chapter 4 Project Description. The lifespan of the

development is such that the landscape will have evolved during the 125

years and an appropriate restoration strategy will need to be developed

reflecting the future character and visual amenity of the landscape. It is not

considered that the landscape and visual effects during decommissioning

would be greater than the residual effects assessed (in the LVIA) during

summer year 15.

Conclusions

5.2.8 There will be No Permanent Significant effects on the LANDMAP

Aspects, LCAs or landscape designations within the study area.

5.2.9 There will be a permanent Significant adverse residual effect on receptors

at Viewpoint 7 (Cefn Du) due to the close proximity of the viewpoint to the

dam and reservoir at Q1.

5.2.10 No Significant residual visual effects have been identified for the remaining

viewpoints. This is due in part to the limited visibility of the components of



5-4

October 2015

the Development in the wider study area, with much screening provided by

the topography of the study area and wooded nature of the area

immediately surrounding the site. The mitigation measures proposed as an

inherent part of the Development, notably the use of existing slate, will

successfully integrate the development into the landscape context, further

reducing its potential visual prominence.

5.3 Ecology

5.3.1 Chapter 7 of the ES contains an assessment of the effects of the

construction, operation and decommissioning of the Development on

sensitive ecological receptors.

5.3.2 To assess the current ecological conditions at the Development site, the

following surveys and assessments have been undertaken:

Consultation with the County Ecologist and NRW;

Desk based study to identify sites of nature conservation and protected

and priority species in the surrounding area;

Extended Phase I Habitat Survey (which is a habitat classification study)

for the majority of the Order Limits;

Assessment of Bat Potential;

Winter/Hibernation and Summer Bat surveys;

Reptile Surveys;

Amphibian survey;

Great Crested Newts Habitat Suitability Assessment;

Breeding Bird Habitat Suitability Assessment;

Breeding bid surveys;

Winter bird surveys;

Badger surveys;

Otter surveys;

Invertebrate Habitat Suitability Assessment;



5-5

October 2015

Habitat Regulations Assessment – Stage One: Screening;

Freshwater surveys in Q1 and Q6 for diatoms, phytoplankton,

invertebrates, fish and aquatic plants;

Aquatic plant surveys for floating water plantain, spring quillwort and

Canadian/Nuttall’s pondweed;

National Vegetation Classification (NVC) Survey;

Fungi and lichen surveys; and

Arboricultural Assessment.

5.3.3 Further details are provided in the ES Chapter 7 Ecology and its

accompanying appendices in Volume 3 of the ES.


5.3.4 The Development will have a permanent residual minor adverse effect on

Llyn Padarn SSSI through the potential very small loss of lake bed habitat

due to the pipe line connection to the lake bed. The effect on Llyn Padarn

SSSI is deemed to be Not Significant.


Bwlch-y-Groed Quarry Local Wildlife Site (LWS) through the loss of 9.0ha

(21.9%) low value habitat due to the construction of the spoil heaps and Q1

dam. The effect on Bwlch-y-Groed Quarry LWS is deemed to be NotSignificant.


Coed Donen Las LWS and Llwyn Coed Heath LWS through the loss of

10.7ha (16.1%) and <0.001ha (0.001%) respectively of low value habitat

due to the construction of the Q6 dam. The effect on both the LWS’s is

deemed to be Not Significant.


Pen Gilfach LWS through the loss of low value habitat to facilitate access

for the construction of the pumping house and outlet pipes. The effect on

Pen Gilfach LWS is deemed to be Not Significant.



5-6

October 2015


Cefn Du LWS through the loss of 1.0ha (0.3%) low value habitat to facilitate

the construction of a section of the Q1 dam. The effect on Cefn Du LWS is



broadleaved semi-natural woodland through the loss of 0.5 ha (10.7%) of

habitat due to the enabling works for the provision of access to facilitate the

construction of the pumping house and lake bed outfall, the construction of

the pumping house, and a section of the Q1 dam. Due to the small loss of

overall habitat and implementation of a CoCP, the effect on broadleaved

semi-natural woodland is deemed to be Not Significant.


coniferous woodland through loss of 8.0ha (72.7%) of negligible value

habitat due to the creation of the permanent slate mounds. However, this

area is managed plantation and has been subject to recent felling. The

effect is therefore considered to be Not Significant.


semi natural mixed woodland through the loss of habitat due to the enabling

works for the provision of access to facilitate the construction of the

pumping house and lake bed outfall. The effect on semi-natural mixed

woodland is deemed to be Not Significant.


dry heath / acid grassland through the loss of low value habitat due to the

construction of the Q1 dam. The effect on dry heath / acid grassland is



standing water (oligotrophic water) through the loss of habitat due to the

infilling with water of Q1 and Q6. The effect on standing water (oligotrophic

water) is deemed to be Not Significant.


the quarry habitat through the loss of habitat due to the infilling with water of



5-7

October 2015

Q1 and Q6. The effect on the quarry habitat is deemed to be NotSignificant.


the spoil habitat through the loss of negligible value habitat due to the

creation of the two dams. The effect on the spoil habitat is deemed to be

Not Significant.

5.3.16 The Development will have a permanent residual minor beneficial effect on

the spoil habitat through the creation of approximately 8.85ha of spoil

habitat. The effect on the spoil habitat is deemed to be Not Significant.


the stone wall habitat through the loss of habitat. The effect on the spoil

habitat is deemed to be Not Significant.


the Tree Protection Order (TPO) designated area A5 through the loss of

habitat. The effect on the TPO area A5 is deemed to be Not Significant.


Arctic Charr through vibration. The effect on the Arctic Charr is deemed to

be Not Significant.


reptiles through the loss of habitat (removal of quarries, spoil, grassland,

scrub and woodland). The effect on the reptiles is deemed to be NotSignificant.


the Schedule 1 of the Wildlife and Countryside Act bird species, and Birds

of Conservation Concern (BOCC) Red and Amber List bird species through

the loss of habitat (removal of potential nesting habitat through removal of

quarries and woody habitats). Due to the availability of alternative habitat,

and the timing and proximity of the construction activities of the

Development. The effect on the Schedule 1 bird species, and BOCC Red

and Amber List bird species is deemed to be Not Significant.



5-8

October 2015

5.3.22 Development will have a permanent residual minor adverse effect on bats

from construction vibration, roost modification, loss of roosts in tunnels,

isolation and fragmentation and operational lighting. The effect on the bats

is deemed to be Not Significant. Development will have a permanent

residual moderate adverse effect on bats from loss of tree roosts. The effect

on the bats is deemed to be Significant.

5.3.23 Ecological mitigation measures are to include:

enhancement of the existing tunnels and bat habitat to mitigate those

lost as part of the Development,

pre-construction surveys,

the employment of an Environmental Clerk of Works,

implementation of a Habitat Management Plan, and

engineering solutions (such as the placement of the outlet into Llyn

Padarn above the thermocline (which is a transition temperature layer

between the mixed layer at the surface and a deep water layer within

a water body) to avoid any adverse effects to fish, namely Arctic Charr

proposed mitigation for bats is outlined the Bat Licence Application

Method Statement.


5.3.24 Once operational, there will be a permanent loss of the quarry habitats in

Q1 and Q6 but no other effects from day to day operation.

5.3.25 The Development will have a residual minor adverse effect on Afon Gwyrfai

a Llyn Cwellyn Special Area of Conservation (SAC) through the alteration of

the flow regime, alteration of temperature during the routine discharges,

nutrient enrichment, and introduction of invasive species. The effect on

Afon Gwyrfai a Llyn Cwellyn SAC is deemed to be Not Significant.

5.3.26 The Development will have a residual minor adverse effect on Llyn Padarn

SSSI through the alteration of the hydrological regime, alteration of

temperature during the routine discharges, nutrient enrichment, light spill,



5-9

October 2015

and pollution during routine maintenance. The effect on Llyn Padarn SSSI

is deemed to be Not Significant.

5.3.27 Precautionary measures will ensure that no invasive species are transferred

from Q6 into Llyn Padarn. In addition, should the water within Q6 be found

to be contaminated, prior to discharge to Llyn Padarn, an Environmental

Permit (EP) will be applied for and the appropriate treatment measures

undertaken.

5.3.28 The Development is not expected to influence algal bloom in Llyn Padarn.

Scour and wave action will be minimised by the design and siting of the

outlet pipes


5.3.29 The residual effects during decommissioning are likely to be similar to those

identified during construction. However, due to the lifespan of the project

(125 years) it is not currently possible to predict potential and residual

effects on designated sites, habitats and species, as the baseline is likely to

change over this period.

Conclusions

5.3.30 Implementation of the mitigation measures outlined will avoid or minimise

the potential effects on the majority of the ecological receptors. The overall

residual effect is assessed as minor adverse (excluding effects on bat tree

roosts). Therefore the effects are considered to be Not Significant. The

overall residual effect assessment on bat tree roosts only is assessed as

moderate adverse. Therefore the effects are considered to be Significant

in EIA terms. Mitigation measures have been incorporated in the design to

minimise impacts on bats; these are outlined in the bat licence application.

Other European Protected Species Licences will be applied for if required.

5.3.31 A No Significant Effects study (HRA screening assessment) was

undertaken to identify what effects the Development could have on Natura

2000 sites in the surrounding area. This HRA Screening concluded that with

the implementation of mitigation measures the Development will not haveany Likely Significant Effects (LSE’s) on the integrity of Natura 2000



5-10

October 2015

Sites. Therefore, an Appropriate Assessment – Stage Two of the HRA

process – was not required.

5.4 Geology

5.4.1 Chapter 8 of the ES contains an assessment on the geo-environmental

characteristics within the Order Limits. It provides an assessment of the

impacts of the Development on these characteristics during the

construction, operational and decommissioning phases.

5.4.2 The study area has been set to incorporate all potential receptors that could

be impacted (i.e. sensitive environments) and historical land uses that may

have an impact on the Development (i.e. historical development in

surrounding area, potentially contaminative permitted activities, etc).


5.4.3 The Development is not expected to adversely affect local geology or soils.

5.4.4 Slate waste, which is excavated, will be recycled into the dams at Q1 and

Q6, however there will be an excess of slate waste from the Development

of up to approximately 810,000m3. Approximately 650,000m3 will be derived

from works at Q6 and will be incorporated into permanent slate mounds at

Q1. Quarry reprofiling and general landscaping will disturb ground and

there is the potential for the discovery of unidentified contaminated land or

unexploded ordnance (UXO) (from previous use of part of the site as a

munitions store).

5.4.5 If any residual ground contamination is discovered, this will be managed

through appropriate remedial strategies developed with NRW and GC

secured through a DCO Requirement.

5.4.6 An Ordnance Management Strategy will outline what happens if any

unexpected ordnance or munitions are found.


5.4.7 The Development is unlikely to adversely affect local geology or soils during

operation.



5-11

October 2015


5.4.8 The Development is not expected to adversely affect local geology or soils

during decommissioning as the dams will remain in situ.

Conclusions

5.4.9 The Development comprises the utilisation of former slate quarries

excavated mainly into the Llanberis Slates Formation. Slate waste created

from the works will be re-used on site as aggregate for the dams at Q1 and

Q6 and in the stabilisation of slate mounds to the south of Q1.

5.4.10 The only nationally important geological feature in the area is part of the

Afon Gwyfrai a Llyn Cwellyn SSSI, located to the west of the Order Limits.

This includes a small exposure of a fluorite mineral working. As the location

of the SSSI is upstream of the Development, this would not be affected by

the Development.

5.4.11 Overall, it is concluded that effects of the Development on soils and geology

will be Not Significant.

5.5 Water Resources

5.5.1 Chapter 9 of the ES contains an assessment of the potential effects of the

Development on the surface water environment and water resources in the

vicinity of the Development.


5.5.2 Private water supplies were identified and consulted upon as part of the

2012 ES. Due to the increase in the Order Limits, this consultation was

repeated to identify any further private water supplies. The Development,

however, is not expected to affect any private water supplies or water

quality of the designated water bodies connected to the Development.

5.5.3 The construction phase of the Development presents a potential risk to

water resources largely through the generation of runoff with high sediment

loads. Pollution prevention measures would be implemented around all

construction areas to prevent the direct discharge of silt laden runoff to

surface watercourses. All site runoff would be directed through appropriate

treatment systems before being discharged, potentially under consent from



5-12

October 2015

NRW. With mitigation measures being implemented impacts are predicted

to be minor adverse with regards to Llyn Padarn and negligible for all other

water bodies. Therefore this is considered to be Not Significant.

5.5.4 Good construction site management would be implemented through the

CoCP to control potentially contaminative activities associated with the

construction site operations. There is the potential for the accidental

spillage or release of construction materials (such as cement, concrete,

diesel or hydraulic fluid) directly into surface water drains and into the

quarries in the vicinity of construction activities. Such materials may also

become mobilised by surface runoff and eventually enter watercourses,

drainage systems or groundwater and may result in a deterioration in water

quality and pose a temporary minor adverse effect with regards to

groundwater and all surface waters except Llyn Padarn, where a temporary

localised moderate adverse effect is predicted due to its position

downstream of the works and the need for works directly in the lake.

5.5.5 Water would be discharged to Llyn Padarn during the construction phase in

Q6. Although there is no evidence that this water poses a risk to the lake, a

programme of water quality monitoring would be implemented to determine

any variations in the quality of the water discharged, and if necessary,

treatment would be undertaken under an Environmental Permit and the

discharge made under consent from NRW.

5.5.6 Following the completion of the works on Q6, water would be abstracted

from Llyn Padarn to assist in the initial filling of the reservoir. The reservoir

also would be filled through the storage of rainfall incident to the quarry and

the surrounding area. A daily abstraction of 3300 m3 equates to

approximately 0.00022% of the total lake volume per day or approximately

a 3.4mm drawdown per day across the entire lake surface. It is considered

that there would be no significant adverse effect of the abstraction on lake

levels in Llyn Padarn. This is due to the hands off flow condition on the

abstraction license, linked to levels in the downstream Afon Seiont.

Consequently, it is considered that there would be no effect on aquatic

receptors in the lake (including at its margins). Overall, the abstraction

regime is not considered to have any significant impact on lake water levels



5-13

October 2015

(and therefore littoral habitat quality and extents) and/or water quality (as it

is affected by changing water levels). Therefore, a negligible impact is

predicted on Llyn Padarn from the short term abstraction of commissioning

water and any future ‘top-up’ abstractions.

5.5.7 Precautionary monitoring at Llyn Padarn and post-construction consents

and licenses regarding Llyn Padarn will be agreed in consultation with

NRW. A Water Management Plan has been included within the CoCP

which is found in Appendix 16.1 in Volume 3 of the ES.

5.5.8 It is concluded that with the implementation of the mitigation measures, the

residual effects of the Development on water resources during the

construction phase would be minor to negligible adverse and thus NotSignificant.


5.5.9 During the operation of the Development, potential impacts on water

resources would largely be restricted to the management of excess water

from within the Development.

5.5.10 The spillway from Q6 initially would form the spillway infrastructure from

Llyn Padarn to assist in the filling of Q6. The outfall will be fitted with a

diffuser head to help disperse flows and avoid scour of the lake bed

immediately in front of the outfall. The intake and outfall will be positioned at

least 5 m below the average minimum annual water level so as to avoid

impacts on lake users, and above the thermocline. Although the loss of lake

bed to new structures has been minimised, in accordance with the

assessment criteria a permanent moderate adverse effect is predicted.

There would also be a residual effect of moderate adverse effect on the

Nant-y-Betws stream due to the potential culverting of two short sections of

this watercourse to provide access for the PRoW diversions.

5.5.11 The spillway infrastructure will be constructed from both Q1 and Q6 to

provide a controlled discharge from the two quarries to manage excess

water. It is proposed that under normal operation excess water would

discharge from Q6 to Llyn Padarn, rather than from Q1 to the Afon Gwyrfai



5-14

October 2015

via the Nant-y-Betws, although the facility at Q1 would be utilised should it

not be possible to use the Q6 spillway or transfer water from Q1 to Q6.

5.5.12 It is considered that a negligible effect would occur from discharges to Llyn

Padarn (including bathing waters) and the Afon Gwyrfai. However, due to

the smaller size of the Nant-y-Betws stream and its lower dilution potential,

a minor adverse effect is predicted, despite the extremely low frequency of

discharges to this watercourse - although this is unlikely due to the

preference during operation to discharge from Q6 to Llyn Padarn. However,

a review of available water quality data and the proposed operation of the

Development does not give rise to any concerns and No Significantadverse impacts are predicted.

5.5.13 Sealing of Q6 potentially may block existing drainage pathways between

the quarries. This could cause flooding in Q5, which could have adverse

ecological impacts. Subject to further detailed investigations, it may be

necessary to provide a water management scheme in Q5, potentially

involving dewatering, to maintain an acceptable water level in Q5.

Maintenance of an appropriate water level in Q5 will minimise ecological

impacts and have an adverse minor residual impact on surface water flow.


5.5.14 The Development is not expected to affect private water supplies or water

quality of the designated water bodies connected to the Development

during decommissioning. The draining of Q6 will be undertaken via the

Decommissioning Plan agreed with the appropriate regulators at that time

and water will be gradually released into Llyn Padarn so as not to cause

any adverse effects.

Conclusions

5.5.15 As a result of the geological conditions of the area, it is considered that

groundwater does not form an important contribution to regional or local

water resources.

5.5.16 There are a number of private water supplies in the vicinity of the

Development. As the Development will have no impact on groundwater



5-15

October 2015

flow, and the fact that Q2 and the adjacent area of the slate spoil heap will

not be disturbed by the Development, it is concluded that the existing

private supplies will not be affected.

5.5.17 The construction phase of the Development presents a potential risk to

water resources largely through the generation of runoff with high sediment

loading (potentially containing elevated levels of aluminium), the risk from

chemical spillages, and in the short term from the discharge of dewaters

from Q1 and Q6. Mitigation measures would be implemented around all

construction areas to prevent the direct discharge of contaminated runoff to

surface watercourses.

5.5.18 It is concluded that with the implementation of the mitigation measures, the

impacts of the Development on water resources during the construction

phase would be minor to negligible adverse and are therefore NotSignificant.

5.5.19 Following the completion of construction, impacts on water resources would

be limited to those associated with the effective management of excess

water in the system. Excess water would be discharged from Q6 to Llyn

Padarn replicating the current flows. No Significant adverse impacts are

predicted.

5.5.20 New crossings for the PRoW diversions over the Nant-y-Betws and two of

its tributaries, together with the diversion of one tributary would result in a

permanent effect of moderate adverse significance, which is considered

Significant. However these are short crossings and any effects will be

temporary in nature during the short construction of the culverts.

5.5.21 The results of an assessment under the WFD have shown that the

Development is compliant with the objectives of the WFD and associated

proposed mitigation measures for Llyn Padarn, Afon Seiont and the Afon

Gwyrfai.

5.5.22 Other than the possible need to include a water management system in Q5

and the short crossings on the Nant-y-Betws, it is concluded that the

operation of the Development would have negligible impacts to water



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October 2015

resources receptors other than a minor effect on the Afon Gwyrfai via the

Nant-y-Betws. No Significant effects on water resources are predicted.

5.6 Flood Risk

5.6.1 Chapter 10 of the ES contains an assessment of the flood risk presented by

the Development.


5.6.2 The Development will not increase the risk of local flooding resulting from

construction activities. Activities and events that have been assessed as

part of the Flood Consequences Assessment (FCA) include working within

the floodplain, restriction of flow by mud or debris, a temporary increase in

impermeable areas, fluvial flooding and flooding from overland flow and

groundwater. Implementation of an Emergency Response and Flood

Management Plan, incorporated into the CoCP, and the installation of

temporary Sustainable Drainage Systems (SuDS) will result in negligible

effects on receptors from these construction activities and events. Upon the

implementation of mitigation measures, the risk of flooding is reduced to a

negligible effect, and therefore Not Significant.


5.6.3 The Development will not increase the chance of local flooding. Reservoir

safety design and construction standards, in line with the Reservoirs Act

1975, will ensure that dam breach risks are minimised to acceptable levels.

5.6.4 In addition to compliance with legislation relevant for the construction

maintenance and monitoring of dams and reservoirs, in the unlikely event of

a breach, the topography and large areas of land surrounding the site will

limit flow reducing negative effects. The Emergency Response and Flood

Risk Management Plan, which will be developed in conjunction with NRW

and GC, will ensure that an effective and coordinated response to any

emergency can be implemented to further mitigate the potential

consequences of such an event.

5.6.5 Overall, it is considered that the residual effects during operation of the

Development, assuming appropriate design and management, including



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October 2015

implementation of the mitigation measures, will result in No Significanteffects.


5.6.6 During decommissioning the dams will be slowly drained into Llyn Padarn in

agreement with NRW. The emptying of the dams will be managed by

agreement with NRW through discharge consent.

5.6.7 Once the dams have been emptied, there will be no risk of a breach of the

dams or a flooding event.

Conclusions

5.6.8 There are potential risks during construction and operation from

groundwater flooding, pluvial flooding and flooding from existing drainage

which require consideration within the detailed design of the site, the

buildings, the surface water drainage systems and the reservoirs.

5.6.9 The assessment demonstrates that it is possible to mitigate the identified

risks through the application of appropriate site management at the

construction stage, appropriate design principles at the detailed design

stage, and appropriate system management principles in operation. The

mitigation measures outlined in the CoCP are designed to protect the users

of the development, the development itself, and off-site properties from the

effects of flooding.

5.6.10 The FCA has set out the guiding principles by which the design will be

undertaken to ensure that there is no unacceptable increase in flood risk

from the Development. It is therefore considered that effects during

construction, operation and decommissioning will be Not Significant.

5.7 Cultural Heritage and Archaeology

5.7.1 Chapter 11 of the ES contains an assessment which identifies the potential

effects that the Development may have on archaeological and cultural

heritage resources.

5.7.2 The assessment has collated data from online sources and databases,

historic mapping and other documentary sources. A site visit was also

undertaken in October 2014, as well as extensive consultation under with



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October 2015

GAPS and CADW. The assessment of the archaeological and cultural

heritage sites within a 1km study area identified a total of 329 recorded

assets.


5.7.3 It is anticipated that all effects on heritage assets will be restricted to the

construction phase with 24 assets or groups of assets likely to be wholly or

partially affected by the Development. The majority of these assets are

associated with the slate extraction industry in the area, and the

construction of the reservoirs and associated dams will result in the total

loss of a number of assets. The re-modelling of spoil heaps and

construction of new spoil heaps will also result in the loss or partial loss of

further assets, as will the construction of access tracks, work compounds,

and associated infrastructure.

5.7.4 There is potential for previously unrecorded archaeological features to be

present within the Order Limits, although this is considered to be limited to

areas currently occupied by spoil heaps. Following consultation with the

Senior Planning Archaeologist at GAPS and archaeological advisor for GC,

further archaeological investigation will be required within the Order Limits.

This will inform the requirement for additional archaeological mitigation.

5.7.5 Mitigation is likely to comprise building recording, landscape survey,

archaeological excavation and recording, and archaeological monitoring.

This work will be agreed with the Senior Planning Archaeologist at GAPS

and will provide a record of the affected assets. The Development will have

a permanent residual moderate adverse effect and will therefore have a

Significant effect on archaeology and cultural heritage.

Effects during Operation and Decommissioning

5.7.6 There are not expected to be any adverse effects on remaining

archaeological features and cultural heritage assets during operation or

decommissioning. Should any additional heritage assets be identified as

part of any new amended Development, proposed extensions or

remodelling after the proposed site becomes operational, they would be

subject to an additional planning application.



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October 2015

Conclusions

5.7.7 Effects on heritage assets are expected to be restricted to the construction

phase of the Development, however they will have a Significant adverse

effect on heritage assets. Mitigation works will be agreed with GC to provide

a record of the affected assets.

5.8 Traffic and Transportation

5.8.1 Chapter 12 of the ES considers the traffic impact of the Development during

the construction, operation and decommissioning phases. The scope of

assessment was discussed and agreed with GC (as Local Highway

Authority (LHA)) as part of the 2012 ES. Further discussions have taken

place with the LHA during the preparation of the DCO application in relation

to the upgrade to the Green Road to Q1.

5.8.2 A baseline of existing conditions has been established which analyses

traffic flow data and accessibility for all modes of transport in order to

accurately assess the effects of the Development on the local transport

network.


5.8.3 During the construction phase, access will be required to both sides of the

quarry system, Q1 on the Waunfawr side (west) and Q6 on the Llanberis

side (east) of the site.

5.8.4 Traffic movements during construction include additional vehicle

movements from workforce, deliveries and abnormal loads. Traffic

requirements during operation of the facility will be restricted to staff

commuting and site maintenance, and therefore will be concentrated at the

Glyn Rhonwy (Q6) end of the Development.

5.8.5 A Construction Traffic Management Plan (CTMP) will schedule heavy

goods vehicle (HGV) movements and abnormal loads to minimise delays

for other road users; detailing how traffic will be managed and how

pedestrian and cyclist movements will be safely managed in the event of

closures and/or diversions to routes during construction. The CTMP will be

part of the CoCP.



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October 2015

5.8.6 The number of HGVs associated with construction traffic is likely to have an

adverse, but temporary, effect on the local highway network, and therefore

the programming of such movements will be subject to restricted periods of

the day and working week.

5.8.7 A community liaison group will be formed to facilitate communication

between the PC and local residents.

5.8.8 The CTMP will also promote sustainable travel to the site and detail

measures to control traffic to site and minimise effects to the surrounding

communities.

5.8.9 The CoCP also contains both an Air Quality Management Plan and a Dust

Management Plan which will be implemented to reduce dust emissions

from construction traffic locally.

5.8.10 Slate waste will be re-used on site wherever possible minimising movement

of material off site and reducing the need to import materials for dam and

track construction.

5.8.11 The Development is predicted to have No Significant adverse effectsduring construction.

5.8.12 Minor highway improvements will be carried out on Green Road from

Waunfawr to Q1. As associated development, these improvements do not

form part of the DCO application but will be subject to a planning application

under the T&CPA.


5.8.13 During operation, it is not expected that there will be significant vehicle trips

required to and from the Development on a daily basis. Only those needing

to operate the facility or perform routine maintenance are expected to

require travel to the site. Therefore there are no adverse effects predicted,

which is considered to be Not Significant.


5.8.14 During decommissioning it is not expected that there will be significant

vehicle trips required to and from the Development on a daily basis and

therefore there are no adverse effects expected.



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October 2015

Conclusions

5.8.15 The findings of the traffic assessment demonstrate that all traffic can be

accommodated on the local road network without compromising existing

traffic levels.

5.8.16 The Traffic and Transport chapter within the ES outlines that the

Development will result in a temporary increase in traffic volume on the

surrounding network. However mitigation measures have been identified to

reduce the potential traffic effect – this includes improvement to the road

network to Q1 and implementation of a CTMP.

5.8.17 The Development therefore accords with the relevant local, regional and

national planning policy guidance in that it is accessible by a range of

modes other than the private car. The CTMP will also assist in complying

with the relevant guidance by encouraging use of alternative modes to

minimise single occupancy car trips to the site.

5.8.18 The internal site layout provides for pedestrian movement both within the

Development and through the site to the surrounding area, where

achievable.

5.8.19 It is concluded that traffic effects from the construction, operation and

decommissioning of the Development are Not Significant.

5.9 Noise

5.9.1 Chapter 13 of the ES contains an assessment of the noise and vibration

impacts of the Development. The assessment provides an update to that

carried out on the approved scheme in the 2012 ES.

5.9.2 The study area for noise and vibration has been defined as the distance

around the site where potential effects of noise from construction and

operation phases may be expected. In consultation with GC, agreement

was made on six residential receptor locations for the monitoring of existing

ambient and background noise levels. Noise monitoring has been repeated

at the six monitoring locations from the 2012 survey and at two additional

locations, a caravan park which is currently under construction and Surf

Lines (commercial/leisure premises). For the April 2015 surveys, 24-hour



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October 2015

unattended noise surveys were carried out at locations surrounding the

Development site. Supplementary attended noise monitoring was

conducted during daytime, evening and night-time periods. Survey locations

are presented in Figure 13.1 in Volume 4 of the ES.

5.9.3 Baseline noise monitoring was conducted at these locations to establish the

existing noise environment and determine representative background noise

levels at the surrounding Noise Sensitive Receptors (NSRs) near to the

Development site.

5.9.4 Measurements have been conducted in accordance with the principles of

BS 7445-1:2003 'Description and Measurement of Environmental Noise

Part 1: Guide to Quantities and Procedures' and BS 4142:2014.


5.9.5 Noise and vibration limits are predicted to be temporarily exceeded during

construction in some locations because of activities including surface plant,

tunnel drilling and blasting, and traffic, giving rise to potential temporary

significant effects to localised properties. However, levels of vibration

generated are unlikely to cause cosmetic damage to structures. Based

upon a preliminary assessment of potential noise from surface plant during

the construction phase, it is considered that effects of up to major adverse

could arise without mitigation. Such effects should be minimised where

possible by adopting Best Practicable Means, a CoCP and a Noise

Management Plan (NMP), and the setup of a local liaison group, to

specifically identify potential effects and appropriate mitigation based upon

site specific information as the project progresses. Once specific and exact

construction methods are known by a contractor, an assessment should be

undertaken to determine a more accurate noise assessment.

5.9.6 Significance of construction traffic noise and vibration effects has been

considered for representative NSRs. Construction traffic effects can be

mitigated through management methods, road maintenance and ongoing

monitoring and would be anticipated to result in short term effects (less than

5 years). This would result in effects that are no greater than minor adverse

at the worst affected NSRs and therefore are considered Not Significant



5-23

October 2015


5.9.7 During operation, noise and vibration effects potentially result from turbines

and generators; transformers and switchgear; the workshop and pumping

station. However due to the underground or enclosed nature of these

components combined with appropriate building design and materials, the

Development is predicted to result in negligible effects on NSRs, and

therefore is considered Not Significant. Noise control and mitigation

measures will be finalised during detailed design in order to ensure that

airborne noise emissions from operational plant will achieve suitable

operational limits following guidance from BS 4142.


5.9.8 As the quarries and dams will remain in situ, no blasting or crushing will be

required and it is considered that the effects will be negligible and therefore

Not Significant.

Conclusions

5.9.9 Based upon a preliminary assessment of potential noise from surface plant

during the construction phase, it is considered that effects of up to major

adverse could arise without mitigation. Such effects should be minimised

where possible by adopting Best Practicable Means (BPM), a CoCP and a

NMP, and the setup of a local liaison group, to specifically identify potential

effects and appropriate mitigation based upon site specific information as

the project progresses. Once specific and exact construction methods are

known by a contractor, an assessment should be undertaken to determine

a more accurate noise assessment.

5.9.10 Construction traffic effects can be mitigated through management methods

and therefore are considered Not Significant.

5.9.11 Effects during operation and decommissioning will be Not Significant.

5.10 Air Quality

5.10.1 A qualitative assessment was conducted to determine the potential dust

effects during the construction phase of the Development, with reference to



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October 2015

proposed activities, duration of works, baseline conditions and proximity of

potential sensitive locations.


5.10.2 Dust emissions are likely to be caused by construction activities including

drilling, blasting, rock bolting, bulk excavation, crushing of excavated

material and partial removal of existing spoil heaps.

5.10.3 The effect of construction dust will be mitigated through the methods

outlined in both the Air Quality Management Plan (AQMP) and Dust

Management Plan (DMP) within the CoCP, which are based on best

practice guidelines. Before starting work, potential dust generating activities

will be identified and good site planning and management will prevent

unnecessary dust generation, for example through the use of wheel wash

facilities, road sweepers and speed restrictions.

5.10.4 Where appropriate, dust generating activities will be undertaken off-site,

however, where this is not possible these activities will be located away

from residential properties.

5.10.5 The Llyn Padarn SSSI is located adjacent to where the outlet and pumping

station will be constructed, but is over 100m from other construction

activities. However, this is a wet environment, and so the risk of effects due

to dust were considered to be negligible and not significant (no other

designated ecological sites are located with 100m of the Development site).

5.10.6 Based on the proximity of the nearest sensitive receptor and potential dust

emission class, the risk of effects during the earthworks, construction works

and track-out was considered to be a likely, major, adverse effect, if no

mitigation measures are adopted.

5.10.7 General mitigation measures are recommended to be used in conjunction

with more detailed, activity specific measures. Mitigation measures include

the preparation and implementation of a Dust Management Plan which will

be used in conjunction with more detailed, activity specific measures such

as onsite monitoring. The overall significance of the residual effects are

determined to be a likely, minor, adverse effect for both human and



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October 2015

ecological exposure. Overall the Development effects will be NotSignificant, with regard to air quality.

5.10.8 The potential effects due to road vehicle emissions during the construction

phase were also assessed and deemed to be Not Significant.

Environmental Effects during Operation

5.10.9 The Development will produce negligible emissions to air during operation

and will therefore be Not Significant.

Environmental Effects during Decommissioning

5.10.10 The Development will produce negligible emissions to air during

decommissioning and will therefore be Not Significant.

Conclusions

5.10.11 Overall the Development effects will be Not Significant, with regard to air

quality.

5.11 Socio-Economics

5.11.1 Chapter 15 of the ES contains an assessment of the potential socio-

economic, access, and amenity effects of the Development on:

Socio-economics: the local communities and associated economies in

the vicinity of the Development; and

Tourism and Recreation: Tourist/visitor attractions as well as recreational

land uses such as visitor centres and walking or cycling routes.

5.11.2 The study area defined takes into account potential receptors of effects

such as local communities that could be affected by the scheme, local

tourism operators and recreational users (such as users of Public Rights of

Way (PRoW), cycleways and areas of high public amenity value).


5.11.3 At the peak of construction there will be approximately 250 construction

staff onsite, although on average there will be about up to 100 construction

staff at any one time and dependant on the build programme.



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October 2015

5.11.4 There will be direct and indirect positive effects to the local economy during

the construction phase from increased employment activities and indirect

benefits through increased use of facilities in the area, such as

accommodation and restaurants. There will be direct inward investment due

to use of local services and employment. SPH, or the PC as appropriate,

will hold "meet the buyer" events to encourage local businesses to engage

with the construction tender process. It is considered that employment

opportunities will have a temporary regional minor beneficial impact. The

Development is likely to have a temporary local, minor, beneficial impact on

the local economy.

5.11.5 During the construction phase, tourism facilities located alongside the

A4086, A4085 and the minor road leading to Q1 are likely to be temporarily

affected by construction traffic during the construction period. Recreational

activities involving public access in the immediate vicinity of the site will

experience a temporary, local, minor adverse impact during this phase of

development.

5.11.6 Any decrease in tourist visitor numbers due to the construction activities will

only be temporary in nature.

5.11.7 A CTMP will be produced to ensure there is minimal disruption to

community and tourist traffic during the construction phase. SPH will work

with the local communities and businesses within villages such as

Waunfawr, Croesywaun and Groeslon to ensure the phasing of the

construction works minimises any negative effects on the local

communities.

5.11.8 Mitigation measures will include temporary closures and diversions of

PRoWs, permissive routes and open access land within the Order Limits to

ensure safety to recreational users during the construction period. These

temporary and permanent diversions will be secured through the DCO

process. There is likely to be a temporary, local minor adverse impact

during construction on the Green Road affecting villages such as

Waunfawr, Croesywaun and Groeslon due to upgrading the access road.



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October 2015


5.11.9 During the operational phase, 20-35 jobs will be created and the

Development will have a number of net benefits on the local and regional

economy.

5.11.10 There will be negligible effects to socio-economic receptors during

Operation, effects are therefore Not Significant.

Environmental Effects during Decommissioning

5.11.11 There will be negligible effects to socio-economic receptors during

decommissioning, effects are therefore Not Significant.

Conclusions

5.11.12 There are no Significant adverse effects on socio-economic receptors

expected throughout the life cycle of the Development. There will be some

likely localised temporary minor beneficial effects on receptors due to

increased expenditure in the region during construction and potential

localised temporary minor adverse effects on tourism routes and points of

interest.

5.12 Environmental Management

5.12.1 Chapter 16 of the ES describes the Applicant's proposals for the

environmental and waste management strategy. This strategy has been

developed into an outline CoCP which will be developed further at the

detailed design stage, subject to written approval from GC and NRW. The

CoCP provides a framework to ensure that the appropriate environmental

management practices are adopted during construction of the

Development. This will ensure that environmental effects are minimised and

mitigation measures, as described in the ES, are implemented.

Construction

5.12.2 The aim of the CoCP is to provide a framework of minimum standards to

ensure:



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October 2015

Mitigation measures identified in the ES are implemented and that there

is an agreed approach to identifying mitigation for any unexpected

environmental effects that occur during construction;

The adoption of good construction practices;

That the PC and other subcontractors are complying with environmental

legislation and statutory consents; and

That the PC and other subcontractors comply with auditing,

environmental monitoring, environmental inspections and reporting

requirements.

5.12.3 The CoCP sets out a variety of control measures for managing the potential

environmental effects of construction works including control and

management of noise, dust, surface water runoff, waste and pollution

control.

5.12.4 The CoCP includes the following topic specific environmental management

plans:

Water Management Plan (WTMP) – provided as outline in the CoCP;

Pollution Prevention Plan (PPP) – provided as outline in the CoCP; and

Construction Traffic Management Plan (CTMP) - provided as outline in

the CoCP.

5.12.5 These plans will be finalised and agreed with GC and NRW through the

submission of the finalised CoCP which will be submitted and agreed prior

to construction commencing in accordance with a DCO Requirement.

5.12.6 Further plans which will be written under the CoCP in conjunction with the

PC in line with DCO Requirement 6 include:

Dust Management Plan (DMP)

Waste Management Plan (WMP)

Reinstatement/Landscape Plan;

Noise Management Plan (NMP);

Waste Management Plan (WMP);



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October 2015

Emergency Response and Flood Risk Management Plan (ERFRMP);

Habitat Management Plan (HMP);

Breeding Bird Method Statement; and

Silt Management Plan;

5.12.7 Other plans required as per Requirement 7 are as follows:

Air Quality Baseline Monitoring Plan;

Materials Management Plan;

Ordnance Management Strategy;

Archaeological Compensation and Enhancement Strategy;

Land Discovery Strategy;

Health & Safety Plan (HASP); and

Bio Security Plan.

5.12.8 Some construction activities may be noisy, such as blasting and ground

preparation works. Due consideration will be given to the timings of such

works and also the methods to mitigate any potential noise impacts.

Operation

5.12.9 The site will be subject to the operators’ Environmental Policy and subject

to regular monitoring and auditing. The Development will also have a

health, safety and environmental integrated management system assured

under relevant standards. The management system will incorporate

environmental control procedures, which will be regularly independently

audited and certified.

5.12.10 Waste generation during the operational phase will be minimal, resulting

mainly from maintenance activities and will either be recycled using the

onsite recycling facilities or, where this is not possible, be disposed offsite.

Decommissioning

5.12.11 At the time of decommissioning, a Decommissioning Plan will be developed

in consultation with the necessary bodies to ensure that works are

undertaken in compliance with all relevant legislation and regulations.



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October 2015

Conclusions

5.12.12 All mitigation measures outlined in the ES will be developed into a full

CoCP, which will be subject to detailed design and then agreed and

finalised with GC, NRW, CADW and GAPS. These will include several other

management plans to cover water, waste, transport, noise, dust, flood risk

and waste which will be finalised with the PC is instructed and prior to

construction works starting.

5.13 Cumulative Effects

5.13.1 Chapter 17 of the ES identifies and outlines the cumulative effects

associated with the Development, both for intra-project (in-combination) and

inter-project effects.

5.13.2 Cumulative effects can be defined as the effects on the environment that

result from incremental changes caused by the combination of the

Development together with other reasonably foreseeable future actions.

Intra-project (In-combination) effects

5.13.3 For the purpose of this assessment, consideration has been given to “in-

combination effects” between environmental topics and also the potential

for ‘shared receptors’ that may be affected by the different components of

the Development, such as a local resident that could be affected by dust,

noise and traffic disruption during the construction of a scheme, with the

result being a greater nuisance than each individual effect alone.

5.13.4 In-combination effects were considered in relation to how effects may

interact and whether combining individual effects may enhance the overall

effect on a receptor.

5.13.5 There are unlikely to be any intra-project effects from the operation and

decommissioning phases of the Development and so these are not

considered further.

5.13.6 For the construction period, shared receptors identified included local

communities, ecological features and water bodies. The cumulative effects

of traffic and construction works on noise levels and air quality were

considered. Through the application of mitigation measures, which will be



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October 2015

secured in the CoCP and its various management plans, it is considered

that the intra-project combined effects are negligible and minor.

5.13.7 These are therefore unlikely to add to the overall significance of proposed

effects of the Development and therefore are considered to be NotSignificant.

Inter-project effects

5.13.8 A review of the planning applications and proposed developments within

the area around the Development was undertaken to scope in the

developments that were considered to constitute ‘major development’

schemes. Cumulative developments are shown in Figure 5.2 of the NTS.

5.13.9 The sources of potential cumulative effects in the vicinity of Glyn Rhonwy

have been identified as:

The electrical connection and the switchgear station to connect the

Development to the electricity distribution system (to be developed and

owned by SP Manweb);



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October 2015

The construction of Wylfa Newydd Nuclear Power Station and its

associated infrastructure and developments; and

The construction of the Caernarfon to Bontnewydd bypass.

5.13.10 The main source of potential cumulative effects in the vicinity of the site was

identified as Wylfa C New Nuclear Power Station. Traffic and Transport,

and socio-economic effects were considered.

5.13.11 However, due to the distance between the two developments, the

staggered timing of enabling and peak construction periods of both

developments, plus the potential alternative means for Wlyfa Newydd to

reduce traffic volumes if required, there are also no cumulative effects

anticipated on local road networks including the A5.

5.13.12 Cumulative effects may arise through the upskilling of businesses in the

region to work in the construction of low carbon energy developments such

as Wylfa Nuclear Power Station. Therefore this is anticipated to be a minor

beneficial cumulative effect.

5.13.13 Due to the substantial distance between Wylfa Newydd Nuclear Power

Station and the Development, there are no cumulative effects anticipated

on tourism or recreational receptors.

5.13.14 Presuming appropriate mitigation is adopted during the construction of the

Caernarfon to Bontnewydd Bypass, such as diversions and warnings to

road users, and the scale of construction activities, these potential effects

will be minimised. As the works will also be temporary, in-combination

effects on the local highway network are likely to be minor adverse.

However, the local investments resulting from these developments are

likely to have minor beneficial effects.

5.13.15 The electrical connection was also considered. Through early pre-

application discussion and at the request of GC and NRW, a high level

assessment on the current known details and route of the electrical

connection has been undertaken.



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October 2015

Electrical Connection

5.13.16 As the electrical connection will be underground, it is unlikely that there will

be any significant adverse effects on the surrounding landscape. In

addition, due to the size, location, scale and nature of the Development and

the electrical connection, it is likely that these will be viewed as a single

construction project.

5.13.17 It is considered that due to these elements, the construction of the electrical

connection would not be seen from the wider landscape, nearby

settlements or indeed by the majority of the visual receptors. In addition, the

excavation for the electrical connection would only require a shallow trench

and therefore it is unlikely that there would be any need for any tree

removal. Therefore in combination with the power house, this is considered

a negligible effect.

5.13.18 The narrow trench and confined working area will minimise the production

of dust during the installation. Dust is therefore considered to have no

potential for cumulative effects.

5.13.19 However, it is recognised that there may be some adverse effects to the

local communities on the A4244 whilst the connection is being installed into

the highway verge from disruption and disturbance from the works. It is

recognised that there may be a perception that these construction works

will be of the same magnitude of the repair works to the 400kv connection

to the Pentir substation for the Dinorwig scheme. It is not possible to

provide details at this stage about the duration of construction works or the

method of installation. An initial grid connection offer statement prepared by

SP Manweb considers disruption to have a temporary minor adverse effect.

This is considered Not Significant.

5.13.20 It is considered that No Significant effects resulting from the Development

and the electrical connection for the Development, the Wylfa Newydd

Nuclear Power Station or the Caernarfon to Bontnewydd Bypass will occur.



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October 2015

5.14 Summary

5.14.1 This NTS outlines the findings and conclusions of the EIA for the

Development which were reported in the ES which accompanied the DCO

application. Sensitive receptors have been identified and potential

environmental effects of the Development assessed by competent

professionals in line with best practice for their specific technical topic.

5.14.2 Where necessary and reasonably practical, mitigation measures (detailed in

full in ES Chapter 18, Schedule of Mitigation) have been committed to

reduce the significance of the effects of the Development.

5.14.3 Following the implementation of the identified mitigation measures during

the construction, operation and decommissioning of the Development,

residual effects have been assessed and are summarised in Table 5-1

below.

5.14.4 In addition to stand-alone technical assessments, inter and intra project

cumulative effects of the Development have been assessed, however none

were found to be significant.



October 2015

Table 5-1. Summary of ES Significance of Effects

Topic Significance of Effects within the ES for the Development

LandscapeCharacter andVisual Amenity

There are no fundamental changes to the above ground structures or features of the Development incomparison to the approved scheme and therefore the number of receptors has not changed. There will beNo Permanent Significance effects on the LANDMAP Aspects, LCAs or landscape designation in the studyarea. There will be a Significant adverse residual effect on the receptors at Viewpoint 7.These findings are consistent with the effects identified in the 2012 ES.

Ecology The overall residual effect ecological impact assessment is assessed as minor adverse (excluding effects onbat tree roosts). Therefore the effects are considered to be Not Significant in EIA terms.

The overall residual effect assessment on bat tree roosts only is assessed as moderate adverse. Thereforethe effects are considered to be Significant in EIA terms. Mitigation measures have been incorporated inthe design to minimise impacts on bats; these are outlined in the bat licence application.Although the Final ES conclusions have been supplemented with additional survey data, these findings areconsistent with the effects identified in the 2012 ES.A No Significant Effects Report has been prepared (Document 5.04) and this has concluded that there areNo Significant Effects to any Natura 2000 sites

Geology andGround Conditions

It is considered unlikely that any major sources of ground contamination would be identified. Overall it isconcluded that the Development would have No Significant impacts on soil and geology duringconstruction, operation or decommissioning. The management of any UXO will be dealt with as per DCORequirement 7 for the Ordnance Management Strategy.This is consistent with the findings of the 2012 ES

Water Resources Appropriate mitigation measures will be implemented through the abstraction license and the updated WFDassessment and water balance model has concluded that the impacts of the Development on waterresources during the construction phase would be negligible, and therefore Not Significant.Sealing of Q6 may potentially block existing drainage pathways which may result in flooding in Q5.



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Therefore, subject to further detailed investigations a water management system may need to be included.Other than this it is concluded that the operation of the Development would have negligible effects (NotSignificant) on water resources receptors

With the exception of the Q5 drainage, this is consistent with the findings of the 2012 ES

Flood Risk There are potential flooding risks during construction and operation from groundwater flooding, pluvialflooding and flooding from existing drainage. Overall it is considered that, if appropriate mitigation measuresare implemented, the residual impacts will be of negligible effect and Not Significant.The reservoirs will be designed in line with the requirements of the Reservoir Act and therefore the potentialfor breach will be minimised. Therefore there is no change to the operational effects and these are stillconsidered to be Not Significant.This is consistent with the conclusions of the 2012 ES.

Archaeology andCultural Heritage

This assessment has been updated to incorporate changes including amendments in the Order Limits. Whilethe impacts on the archaeology and cultural heritage of the site are of the same nature, the wider area of theOrder Limits has resulted in a larger number of sites that potentially could be impacted by the Development.As a result the Development will have a significance of effect of moderate adverse on archaeology andcultural heritage and will therefore be Significant.DCO Requirement 7 outlines the requirement to implement an archaeological enhancement andcompensation scheme. However the overall conclusion is still consistent with the 2012 ES.

Traffic &Transportation

The Development will result in an increase in traffic volume on the surrounding network and the mainconstruction access points have not changed since the approved scheme. However mitigation measures,such as the CTMP, have been identified to reduce the potential traffic effect. Therefore it is concluded thattraffic effects from the construction and operation of the Development are Not Significant.This is consistent with the conclusions of the 212 ES.



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Noise Residual effects during construction are still expected to range from negligible (Not Significant) to moderateadverse (Significant) during construction and it has been concluded that once specific and exactconstruction methods are known by a contractor, an assessment should be undertaken to determine a moreaccurate noise assessment. A NMP will be implemented during construction.It is still expected that potential effects during operation will be negligible and therefore Not Significant.This is consistent with the conclusions of the 2012 ES.

Air Quality Due to changes in assessment procedures, significance criteria and mitigation controls have been updated.However the overall Development effects are still considered to be Not Significant with regards to airquality.It is still expected that potential effects during operation will be negligible and therefore Not Significant.This is consistent with the conclusions of the 2012 ES.

Socio-Economics There will be direct and indirect beneficial effects to the local economy during the construction phase fromincreased employment activities and indirect benefits through increased use of facilities in the area.The construction phase is likely to cause an increase in traffic along the A4086 and A4085. A CTMP willmitigate as far as is reasonably practicable any disruption caused by traffic generated during theconstruction phase and therefore the impact will be Not Significant.Other management plans will be implemented such as the NMP and DMP. In addition the EnvironmentalClerk of Works will maintain a communication programme to inform local residents of the main constructionactivities such as blasting and abnormal loads.Works at Llyn Padarn will be timed to avoid summer school holidays to minimise any disruption to users.Health and Safety will be paramount during the main spillway infrastructure and pumping station works.Minor diversions may be in place but access will not be impeded. The car park area will still be in use byusers.



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The pumping station will not have any operational lighting or fencing, and only an above ground kiosk /control box will be visible. Through the consultation period. The location of the pumping station has beenrelocated further back from Llyn Padarn. Therefore it is considered that effects during operation areconsidered to be Not SignificantThis is consistent with the conclusions of the 2012 ES.

Cumulative and In-combination Effects

The Development has been cumulatively assessed against Wylfa C New Nuclear Power Station for trafficand socio-economic effects. There are expected to be No Significant cumulative effects should theconstruction of both projects coincide. The inter-project effects were also considered for the construction ofthe electrical connection and the Caernarfon to Bontnewydd Bypass. No Significant effects were noted.There are expected to be No Significant in-combination effects for the Development.