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Glyn Rhonwy Pumped Storage Development Consent Order · Glyn Rhonwy Pumped Storage Development Consent ... Dylan Huws Senior Engineer ... GLYN RHONWY PUMPED STORAGE DEVELOPMENT CONSENT

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  • Glyn Rhonwy Pumped Storage Development Consent Order

    Deadline 3 Excess Water Management Strategy

    PINS Reference EN010072

    Document Nos. SPH_GREX_DCOD3_04

    Authors SPH/AECOM/GVA/BS

    Revision Date Description

    0 27th April 2016 Issued

  • Prepared by: Walter Robison .......................... Checked by: Dylan Huws Senior Engineer Associate Director

    Approved by: Catherine AndersonAssociate Director

    Glyn Rhonwy Pumped Storage Excess Water Management Strategy

    RevNo

    Comments Checkedby

    Approvedby

    Date

    0 Issued for DCO Deadline 3 DH CA Apr 2016

    1 Tanfield, Edinburgh, EH3 5DATelephone: 0131 301 8600 Website: http://www.aecom.com

    Job No 60484860 m001.004 April 2016

    This document has been prepared by AECOM Limited for the sole use of our client (the Client) and inaccordance with generally accepted consultancy principles, the budget for fees and the terms of referenceagreed between AECOM Limited and the Client. Any information provided by third parties and referred toherein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in thedocument. No third party may rely upon this document without the prior and express written agreement ofAECOM Limited.

  • Glyn Rhonwy PumpedStorage

    Excess Water Management Strategy

    TABLE OF CONTENTS

    1 Introduction .................................................................................................................. 11.1 Introduction............................................................................................................. 11.2 the Development .................................................................................................... 11.3 Basic operation....................................................................................................... 21.4 Discharge locations ................................................................................................ 31.5 Abstraction location ................................................................................................ 4

    2 Excess water management .......................................................................................... 52.1 Excess Water Management ................................................................................... 52.2 release of + excess water ....................................................................................... 52.3 abstraction for - excess water................................................................................. 62.4 Reservoir safety features and incidental release of water ...................................... 62.5 Environmental Management Systems .................................................................... 8

    Appendix A: Drawings & Figures ..................................................................................... 10

  • Glyn Rhonwy PumpedStorage

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    Snowdonia Pumped Hydro Ltd. 1

    1.1 INTRODUCTION

    1.1.1 Optimum operation of the Development requires a constant volume of water within its closed

    reservoir system. Rainfall on the reservoirs can cause additional or excess water within the system.

    Whilst the reservoirs are designed to cope safely with the most severe rainfall that is expected to

    occur, efficient operation of the Development is maintained by the management of excess water.

    1.1.2 This Outline Excess Water Management Strategy is intended to set out the principles by which the

    water within the Development is managed. This document sets out the strategy only; at the time of

    writing the Development has not been subject to detailed design therefore a full operational algorithm

    with precise values of each hydraulic element cannot be given. This strategy therefore cannot go into

    detail on precise water levels, flows rates and volumes involved with specific movement of water

    within the system.

    1.1.3 For the background to the abstraction and discharge rates, together with the environmental and flood

    risk appraisals, reference should be made to the Environmental Permitting applications to Natural

    Resources Wales (NRW) and their supporting documentation.

    1.2 THE DEVELOPMENT

    1.2.1 The Development at Glyn Rhonwy comprises a pumped storage hydro-electric scheme situated

    within a series of disused slate quarries. The quarry system has been numbered from Q1 in the west

    to Q8 in the east, which can be seen in Figure 2 in Appendix A. The quarries used in theDevelopment are:

    Quarry 1 (Q1) Chwarel Fawr; Headpond

    Quarry 6 (Q6) Glyn Rhonwy; Tailpond

    1.2.2 The Development comprises of the following permanent features:

    Headpond reservoir (Q1), its dam, access shaft and spillway infrastructure to the Nant Y Betws;

    Tailpond reservoir (Q6), its dam, access shaft and spillway infrastructure to Llyn Padarn;

    Pumping station in close proximity to Llyn Padarn;

    Power house at Glyn Rhonwy Industrial Estate Platform 5 (south of Q6) with underground

    turbine hall housing pump turbines;

    Penstock (connecting Q1 to the power house); and

    Tailrace (connecting the power house to Q6).

    1INTRODUCTION

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    1.2.3 A schematic representation of the scheme is presented on Drawing SHT-10-ZN00-Z-001 inAppendix A showing the hydraulic connections between the system components and theenvironment.

    1.3 BASIC OPERATION

    1.3.1 A pumped-storage system essentially consists of two reservoirs, upper and lower (Headpond and

    Tailpond). Inputs are the natural hydrology of the area; watercourses that flow into the reservoirs and

    direct rainfall. Outputs (losses) are evaporation, controlled release (e.g. compensation flow),

    uncontrolled release (e.g. flow over a spillway) and infiltration/seepage losses from the reservoirs;

    infiltration and seepage are usually negligible relative to any incoming watercourse. Water flowing

    from the upper reservoir drives turbines to generate power. The water is collected in the lower

    reservoir and is later pumped back to the upper reservoir.

    1.3.2 If there is more water in the reservoir system than required there is said to be positive excess water.If there is less water in the reservoir system than required then there is said to be negative excess

    water.

    If over time Rainfall > Losses (evaporation / infiltration): Positive (+) Excess Water is to be

    released to Llyn Padarn

    If over time Rainfall < Losses (evaporation / infiltration): the scheme will be in a state of

    Negative (-) Excess Water, and the closed system will require to be topped-up.

    1.3.3 Both positive and negative excess water can have an impact on the optimum operation of the

    Development, therefore a means and strategy for managing excess water on a day to day, week to

    week basis is required.

    1.3.4 The water input and outputs applicable to the scheme are summarised in Table 1 below:

    Table 1 Glyn Rhonwy Pumped Storage Scheme, excess water factors

    Input (incoming water) Applicability to scheme

    Watercourse None

    Rainfall Direct rainfall on reservoir surfaces

    Output (water losses) Applicability to scheme

    Evaporation Evaporation from open water bodies (reservoirs)

    Controlled release (e.g. compensationflow) No compensation flow or other required outflow

    Uncontrolled release (e.g. flow over aspillway) None planned

    Infiltration/seepage losses Unknown at this stage; reservoirs will be designed tominimise these losses.

    1.3.5 In a pure pumped-storage scheme, isolated from the wider environment, the total volume of water inthe reservoir system; i.e. headpond, tailpond, shafts and tunnels remains constant. This constant

  • Glyn Rhonwy PumpedStorage

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    Snowdonia Pumped Hydro Ltd. 3

    volume of water is simply moved between the upper and lower reservoirs during the

    generating/pumping cycle.

    1.3.6 The Development is essentially a pure pumped storage system. Figure 1 below shows the inputsand outputs to the closed reservoir system.

    Figure 1: Glyn Rhonwy Pumped Storage Scheme input / output schematic

    1.3.7 Overall water management within the reservoirs, including draw-down, release and abstraction of

    excess water is summarised in Table 5 below and is shown on the Water Management Schematicsin Appendix A.

    1.4 DISCHARGE LOCATIONS

    1.4.1 When it is necessary to release water from the system, the primary mechanism to discharge water

    will be from Q6 to Llyn Padarn. Water in Q1 can be released to the Nant y Betws, although this is not

    done in the normal operation of the scheme. Release of excess water from Q1 would be to Llyn

    Padarn via the penstock and Q6. Discharge locations, for both the reservoir spillway and the relief

    valve outlets, are shown in Table 2 below:

    Table 2 Glyn Rhonwy Pumped Storage Scheme, discharge locations

    Reservoir Discharge Location Waterbody / Watercourse Discharge Location Grid Ref

    Q1 Headpond Nant y Betws SH 55110 59660

    Q6 Tailpond Llyn Padarn SH 57290 61190

    1.4.2 These locations are indicated as outlet to Nant y Betws (Q1) and intake/outlet (Q6) on DrawingSHT-10-ZN00-G-001 in Appendix A.

    House

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    1.5 ABSTRACTION LOCATION

    1.5.1 If it is necessary to abstract water to top up the closed reservoir system; water would be abstracted

    from Llyn Padarn to the Tailpond (Q6). The abstraction location is the same as for the discharge

    outlet to Llyn Padarn:

    Table 3 Glyn Rhonwy Pumped Storage Scheme, abstraction location

    Reservoir Discharge Location Waterbody / Watercourse Discharge Location Grid Ref

    Q6 Tailpond Llyn Padarn SH 57290 61190

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    Snowdonia Pumped Hydro Ltd. 5

    2.1 EXCESS WATER MANAGEMENT

    2.1.1 The hierarchy and logic diagram for operational discharges contained within Appendix A.

    2.1.2 Positive + excess water is expected if over time rainfall exceeds evaporation and

    infiltration/seepage from the reservoirs. During normal operation + Excess Water is to be

    released to Llyn Padarn from the tailpond Q6.

    2.1.3 Negative - excess water may occur if over time losses from the system (evaporation,

    infiltration/seepage) exceed the incoming rainfall falling on the surface of the reservoirs. In this

    circumstance, the Development will require abstraction of water from Llyn Padarn to top up to

    the required volume.

    2.2 RELEASE OF + EXCESS WATER

    2.2.1 The surface area of the reservoirs are approximately 54,000 m2 and 34,000 m2 for Q1 and Q6

    respectively. Average annual rainfall is around 1850 mm, average annual evaporation is

    expected to be around 450 mm. Ignoring other losses there may be up to 123,000 m3 of net

    volume increase from rainfall. It is intended to release this volume from Q6 to Llyn Padarn; this

    will be done on an irregular basis (rainfall dependant) and at a rate not exceeding the draw-

    down capacity of the Q6 reservoir (see Section 2.4 below).

    2.2.2 The maximum allowable rate of water release is to be addressed together with the discharge

    consent and any other conditions to be agreed with NRW. These conditions will be

    incorporated into the final Excess Water Management Strategy for as required by

    Requirement 20 of the DCO.

    Table 4 Reservoirs data

    Reservoir: Headpond Reservoir (Q1) Tailpond Reservoir (Q6)

    Surface Area 54,000 m3 34,000 m3

    Top Water Level (TWL)[level of reservoir spillway]

    393.0 mAOD 154.5 mAOD

    Maximum OperationalWater Level (Max OWL)

    392.0 mAOD 154.0 mAOD

    Minimum Operational WaterLevel (Min OWL)

    340.0 mAOD 90.0 mAOD

    2 EXCESS WATER MANAGEMENT

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    2.2.3 Under normal operation the water level in Q1 will not exceed the Maximum Operational Water

    Level (Max OWL) of 392.0 mAOD, 1.0 m below the Top Water Level (TWL) of 393.0 m AOD,

    and the Max OWL of 154 mAOD in Q6, 0.5 m below the Q6 TWL of 154.5 m AOD. Top Water

    Level is the level of the reservoir spillway above which water will spill out of the reservoir.

    2.2.4 Under normal operation of the scheme all release of excess water will be from Q6 to Llyn

    Padarn under controlled circumstances; there is no anticipated need to allow the reservoirs to

    spill or to release water to the Nant y Betws.

    2.2.5 Excess water from direct rainfall on both Q1 and Q6 will be managed within the freeboard of

    the reservoirs, the available capacity between Max OWL and TWL, and then released from the

    system via Q6 to Llyn Padarn.

    2.2.6 With positive excess water within the system, transfer of water from Q1 to Q6 will cause the

    level in the tailpond (Q6) to rise above the Max OWL. Positive excess water is to be released

    from Q6 to Llyn Padarn to maintain the optimum volume within the system.

    2.2.7 For a release of + excess water to take place:

    System Volume > Optimum (e.g. Max OWL in Q1 & Min OWL in Q6)

    AND Llyn Padarn level < a level specified by Natural Resources Wales

    2.2.8 In the event of an extreme rainfall event, the available storage between Max OWL and the

    reservoir spillway allows + excess water to be held safely within the system, and subsequently

    released days after the event. Depending on the position in the generation cycle, the system

    will have varying capacity to accept incoming water without spill. In the worst case position (Q6

    at Max OWL) the system has capacity to accommodate 0.5 m depth of rainfall without spill.

    2.3 ABSTRACTION FOR - EXCESS WATER

    2.3.1 All water within the Development, with the exception of the contribution of direct rainfall, will

    have been abstracted from Llyn Padarn to Q6. Top up abstraction in the event of negative

    excess water is also from Llyn Padarn as circumstances require.

    2.3.2 For an abstraction of top up - excess water to take place:

    System Volume < Optimum

    AND Llyn Padarn level > a level specified by Natural Resources Wales

    2.4 RESERVOIR SAFETY FEATURES AND INCIDENTAL RELEASE OF WATER

    Relief Valve at Q1

    2.4.1 The Development includes a relief valve from Q1 to Nant y Betws; this is a reservoir safety

    feature and is not for use in regulating excess water. The Q1 relief valve provides a secondary

    method for the reservoir water level to be lowered, if required; the primary means is by transfer

    of water to Q6 via the penstock.

  • Glyn Rhonwy PumpedStorage

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    Snowdonia Pumped Hydro Ltd. 7

    2.4.2 The relief valve (a reservoir safety feature) is to allow, in the event of an emergency, the

    reservoir to be drawn down to 50% of the volume impounded by the dam within 7 days. This

    equates to a flow of approximately 0.60 m3/s.

    2.4.3 For a release of water to the Nant y Betws to take place, the following conditions are required:

    When the there is a need to lower the water level behind the dam,

    AND water cannot, for whatever reason, be drawn down through the penstock to Q6.

    2.4.4 These conditions determine when water (not excess water) would be released from Q1 to the

    environment.

    2.4.5 For maintenance; to ensure the valve is operational as part of the dam safety regime, it will be

    necessary from time to time to briefly operate the valve. The volume and rate of water released

    in this circumstance is considered negligible in regard to the management of excess water and

    is ignored in this strategy.

    Q1 Spillway

    2.4.6 There is the possibility of discharge to the Nant y Betws watercourse from the Q1 dam spillway

    (also known as the overflow). The spillway is an essential reservoir safety feature, the operation

    of which is likely to be extremely rare.

    2.4.7 For a release of excess water via the spillway to the Nant y Betws to take place, the following

    conditions are required:

    Prolonged period of the system being out-of-operation; i.e. the reservoir remaining full for

    a significant period of time.

    AND a build up of excess water (likely several months required) eventually causing the

    level in Q1 to increase above the spillway level.

    2.4.8 The reservoir has more than sufficient capacity to accommodate the direct rainfall from the

    Probable Maximum Precipitation (extreme rainfall event for reservoir safety design) above the

    Maximum OWL without spilling.

    Relief Valve at Q6

    2.4.9 The Development includes a relief valve from Q6 to Llyn Padarn; this is a reservoir safety

    feature and also the means by which excess water is released from the system.

    2.4.10 The relief valve arrangement of the Q6 reservoir is expected to have a minimum draw-down

    capacity of 0.3 m3/s (draw-down of 50% of the volume impounded by the dam within 7 days). It

    is considered that the design draw-down rate for Q6 could be increased to in the region of

    between 0.6 1.0 m3/s with negligible increase in flood risk within the downstream catchment

    as a result of the released flow.

  • Glyn Rhonwy PumpedStorage

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    2.4.11 Release of excess water is as described in the preceding section. For the release of water to

    take place, over and above the normal release of excess water, the following conditions are

    required:

    When there is a need to lower the water level behind the dam,

    AND water cannot, for whatever reason, be transferred by pumping to Q1.

    2.4.12 These conditions determine when water (not excess water) would be released, e.g. for dam

    safety purposes, from Q6 to the environment.

    2.4.13 For maintenance; to ensure the valve is operational as part of the dam safety regime, it will be

    necessary from time to time to briefly operate the valve. The volume and rate of water released

    in this circumstance is considered negligible in regard to the management of excess water and

    is ignored in this strategy.

    Q6 Spillway

    2.4.14 There is the possibility of discharge to Llyn Padarn from the Q6 dam spillway (also known as

    the overflow). The spillway is an essential reservoir safety feature, the operation of which is

    likely to be extremely rare.

    2.4.15 For a release of excess water via the spillway to Llyn Padarn to take place, the following

    conditions are required:

    Prolonged period of the system being out-of-operation; i.e. the reservoir remaining full for

    a significant period of time.

    AND a build up of excess water (likely several months required) eventually causing the

    level in Q6 to increase above the spillway level.

    2.4.16 The reservoir has more than sufficient capacity to accommodate the direct rainfall from the

    Probable Maximum Precipitation (extreme rainfall event for reservoir safety design) above the

    Maximum Operational Water Level without spilling.

    2.5 ENVIRONMENTAL MANAGEMENT SYSTEMS

    2.5.1 The type of environmental management system (EMS) that will be implemented is to be

    determined at a later date by the scheme operator.

    2.5.2 Chapter 4 Project Description in the Environmental Statement states that an Environmental

    Management System (EMS) will be in place for the operational hydro-scheme. Snowdonia

    Pumped Hydro do commit to having an environmental policy and management system in place,

    but this is subject to confirmation at a later date as to which specific EMS the scheme will

    implement.

    2.5.3 It is envisaged that the electricity generation company operating the developed scheme will

    establish an appropriate system.

  • Glyn Rhonwy PumpedStorage

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    Table 5 Glyn Rhonwy Pumped Storage Scheme, water management & operation

    Reservoir Operation Management and Release of Water

    Q1 Headpond

    NormalOperation

    Inflow from Direct Rainfall.

    All direct rainfallaccommodated within the1.0m between Max OWL andTWL.

    Water transferred from Q1 to Q6 andreturned by pumping to Max OWL. i.e.excess water remains within Q6.

    Drawdown ConditionWater transferred to Q6.

    i.e. no release of water to the environment.

    UnusualCircumstance

    Prolonged inflow over timefrom Direct Rainfall, with notransfer of water to Q6.

    i.e. WL allowed to build up toTWL.

    Direct Rainfall may discharge to Nant yBetws via overflow if Q1 exceeds TWL.

    Drawdown Condition, withoutmeans to transfer water fromQ1 to Q6.

    Water discharged from Q1 to Nant y Betws;water released via Relief Valve at anappropriate rate (in consideration of floodrisk downstream) until WL below the damlevel.

    Q6 Tailpond

    NormalOperation

    Direct Rainfall and excesswater from Q1.

    All direct rainfall istemporarily accommodatedwithin the 1.0m between MaxOWL and TWL.

    Excess water released to Llyn Padarn.

    Drawdown Condition

    Water transferred to Q1, and/or waterreleased to Llyn Padarn.

    Preference would be to transfer water to Q1for future use rather than release to LlynPadarn.

    UnusualCircumstance

    Prolonged inflow over timefrom Direct Rainfall, with notransfer of water to Q1.

    i.e. WL allowed to build up toTWL.

    Direct Rainfall may discharge to Llyn Padarnif Q6 exceeds TWL.

    Drawdown Condition, withoutmeans to transfer water fromQ1 to Q6.

    Water discharged from Q6 to Llyn Padarn viaRelief Valve at an appropriate rate (inconsideration of flood risk downstream) untilWL below the dam level.

  • Glyn Rhonwy PumpedStorage

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    Drawing 4.1 of the ES Development Overview

    Drawing 2.05 of the DCO Scheme Layout Plan

    Drawing SHT-10-ZN00-G-0001 Scheme Schematic Diagram

    Water Management Schematic, 1 of 5 Water Management at Glyn Rhonwy

    Water Management Schematic, 2 of 5 Release of +Excess Water

    Water Management Schematic, 3 of 5 Abstraction of -Excess Water

    Water Management Schematic, 4 of 5 Spill of +Excess Water

    Water Management Schematic, 5 of 5 Reservoir Draw-down

    Appendix A:Drawings & Figures

  • __

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    _Q8

    Q7Q6

    Q5Q4

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    Crown copyright, All rights reserved. 2012 Licence number 0100031673

    This document has been prepared by AECOM for the sole use of our Client (the "Client") and in accordance with generally accepted consultancy principles, the budget for fees and terms of reference agreed between AECOM and the Client.

    Verified:Date:

    Checked:Approved:Scale at A3:

    Drawing Number:

    Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM.

    0 500 MetresDrawn:

    A3

    LCSC

    LCCA

    OCTOBER 2015GR_151001_4.1_v8

    KEY:Order Limits

    _ Quarry Location_ Proposed Pumping Station_ Alternative Pumping Station

    Spillway InfrastructurePenstockTemporary Tunnel and Access ShaftTailraceTemporary Construction CompoundDam FootprintReservoir EdgeExcess Slate MoundQ1 Permanent Public Car ParkQ1 Temporary Public Car ParkPower HousePower House Compound

    1:10,000Title:

    Project:Client: GLYN RHONWY PUMPED STORAGE DEVELOPMENT CONSENT ORDERFIGURE 4.1 - DEVELOPMENT OVERVIEW 1 Callaghan SquareCardiffCF10 5BT

    T +44 (0)29 2067 4600F +44 (0)29 2067 4699www.aecom.com

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    INTAKE/OUTLET

    TEMPORARY

    TUNNEL

    ACCESS

    SHAFT

    POWER

    HOUSE

    COMPOUND

    PUMPING STATION LOCATION

    SPILLWAY

    INFRASTRUCTURE

    PENSTOCK

    INLET/OUTLET

    SHAFT

    RISING

    MAIN

    INLET

    COMBINED OVERFLOW/

    SCOUR/RISING MAIN TOWER

    TEMPORARY

    ACCESS

    TUNNEL

    RETAINING

    WALL

    NEW

    SPOIL

    MOUND

    HEAD POND

    TAIL POND

    DAM

    DAM

    SPILLWAY INFRASTRUCTURE

    TO NANT Y BETWS

    COMBINED RELIEF

    VALVE/ OVERFLOW

    TOWER

    HEAD POND

    NEW

    SPOIL

    MOUND

    1 Callaghan Square

    Cardiff

    CF105BT

    T +44 (0)29 2067 4600

    F +44 (0)29 2067 4699

    www.aecom.com

    Drawn:

    Verified:

    Date:

    Drawing Number:

    Checked:

    Approved:

    Scale at A1:

    Project:Client:

    This document has been prepared by AECOM for the sole use of our Client (the "Client") and in accordance with generally accepted consultancy principles, the budget for fees and terms of reference agreed between AECOM and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the document. No third party may rely upon this document without the prior and express written agreement of AECOM.

    A1

    GLYN RHONWY PUMPED STORAGE DEVELOPMENT CONSENT ORDER

    2.05 Indicative Layout Plan

    2.05

    JJA AH

    CA CA

    07.08.15 1:5000

    ORDER LIMITS

    EXTENTS OF EARTHWORKS

    MAX. OPERATIONAL WATER LEVEL

    EXTENTS OF RE-PROFILING

    PERMANENT DIVERSION

    NEW DAM OPERATIONAL ACCESS

    TRACK

    PERMANENT REPLACEMENT PUBLIC

    CARPARK

    1. ALL DIMENSIONS IN METERS UNLESS

    OTHERWISE NOTED. DO NOT SCALE.

    2. ALL LEVELS IN METRES AND REDUCED TO

    ORDNANCE DATUM UNLESS OTHERWISE

    NOTED.

    LEGEND

    NOTES

    0 125 250

    1:5000

    m

  • MAX OWL 392 mAOD

    Q1

    HEADPOND

    RESERVOIR

    RELIEF

    OUTLET

    OVERFLOW

    SPILLWAY

    STILLING BASIN

    TURBINE/PUMP

    LLYN PADARN

    PUMP

    OVERFLOW

    SPILLWAY

    OUTFALL WITH

    COARSE SCREEN

    ABSTRACTION

    INTAKE WITH

    FINE SCREEN.

    FLOW

    MONITORING

    WATER LEVEL

    MONITORING

    NANT Y BETWS

    FLOW MONITORING:

    1. ABSTRACTION FLOW AT PUMP

    STATION.

    WATER LEVEL MONITORING:

    1. HEADWATER RESERVOIR LEVEL.

    2. TAILWATER RESERVOIR LEVEL.

    3. STILLING BASIN ON HEADWATER

    RESERVOIR OUTLET.

    4. DOWNSTREAM WATER LEVEL IN

    NANT Y BETWS.

    5. LLYN PADARN (PUMPING STATION).

    OUTFALL

    TO NANT Y

    BETWS

    PUMPED ABSTRACTION

    FOR INITIAL FILLING AND

    LATER TOP UP.

    MIN OWL 340 mAOD

    TWL 393 mAOD

    MIN OWL 90.0 mAOD

    TWL 154.5 mAOD

    DAM

    MAIN INLET

    VALE

    PENSTOCK

    NORMALLY OPEN FOR

    RELIEF, WILL BE

    CLOSED FOR

    ABSTRACTION

    PUMPING

    NORMALLY CLOSED

    VALVE, WILL BE OPEN

    FOR ABSTRACTION

    PUMPING

    Q6

    TAILPOND

    RESERVOIR

    RELIEF

    OUTLET

    MAX OWL 154.0 mAOD

    DAM

    RELIEF VALVE

    RELIEF

    VALVE

    TWL TOP WATER LEVEL

    OWL OPERATING WATER LEVEL

    I/R DATE DESCRIPTION

    ISSUE/REVISION

    A 17.02.15 DRAFT ISSUE

    B 06.07.15 ISSUED FOR REVIEW

    1 10.07.15 FINAL ISSUE

    Filenam

    e: F

    :\P

    RO

    JE

    CT

    S\E

    NE

    RG

    Y - G

    LY

    N R

    HO

    NW

    Y E

    NG

    IN

    EE

    RIN

    G\03 E

    XE

    CU

    TIO

    N\04-C

    AD

    \20-S

    HE

    ET

    S\60332577-S

    HT

    -10-Z

    N00-Z

    -0001.D

    WG

    PROJECT

    GLYN RHONWY PSH

    PROJECT NUMBER

    60332577

    SHEET TITLE

    GLYN RHONWY

    SCHEME SCHEMATIC DIAGRAM

    SHEET NUMBER

    60332577-SHT-10-ZN00-Z-0001

    CONSULTANT

    AECOM

    1 Tanfield

    Edinburgh, EH3 5DA

    +44 (0) 131 301 8600 tel 8699 fax

    www.AECOM.com

    LEGEND

    NOTES

    1. DRAWING IS A SCHEMATIC: THIS IS NOT

    INDICATIVE OF SIZE OR SCALE, AND DOES

    NOT INCLUDE DETAIL.

    Snowdonia Pumped Hydroc/o Quarry Battery Company

    CB1 Business Centre, 20 Station Road

    Cambridge, CB1 2JD

    +44 (0) 1223 65 3026 tel.www.snowdoniapumpedhydro.com

    I/R DRAWN BY CHECKED

    APPROVED FOR ISSUE

    APPROVED

    A LGB WHR JIG

    CLIENT

  • Water Management at Glyn Rhonwy: Scheme Schematic

    Water Management Schematic - Page 1 of 5

    Rainfall

    Q1Headpond

    PowerHouse

    Infiltration / Seepage

    Evaporation

    Rainfall

    Infiltration / Seepage

    Evaporation

    Max OWL

    Min OWL

    Q6Tailpond Llyn Padarn

    Release of+ Excess Water

    Initial Fill &Top-up ( - Excess

    Water)

    If over time Rainfall > Losses (evaporation / infiltration):Positive Excess Water is to be released to the Llyn Padarn

    If over time Rainfall < Losses (evaporation / infiltration):Negative Excess Water will require the closed scheme to betoped-up

  • Q1 HEADPOND

    Q6 TAILPONDLLYN PADARN

    Excess Water: Release of +Excess Water

    Rainfall > LossesExcess Water released to Llyn Padarn

    Excess water within systemmanaged within freeboard ofreservoir; i.e. without spill.Excess water is later released toLlyn Padarn via the relief valve.

    Water Management Schematic - Page 2 of 5

  • Q1 HEADPOND

    Q6 TAILPONDLLYN PADARN

    Water Shortage: Abstraction of Excess Water

    Rainfall < LossesTop-up abstraction from Llyn Padarn

    Lack of waterwithin system

    Top-upabstraction

    Water Management Schematic - Page 3 of 5

  • Q1 HEADPOND

    Q6 TAILPONDLLYN PADARN

    Spill of +Excess Water

    Rainfall > Losses =Build-up of + Excess Water

    Excess waterwithin system

    Only after a prolonged period of no operational activity would thebuild-up of excess water reach the spill.

    Each reservoir would eventually spill only incoming rainfall

    Water Management Schematic - Page 4 of 5

  • Reservoir Draw-down

    Q1 HEADPOND

    Q6 TAILPONDLLYN PADARN

    Use of Penstockunavailable

    Note:Only water impounded by damreleased under draw-down

    Water Management Schematic - Page 5 of 5

    Under Normal Circumstances: Drawdown of Q1 is by transfer of water from Q1 to Q6 Drawdown of Q6 is by transfer of water from Q6 to Q1

    Only Under Abnormal Circumstances; would drawdownof Q1 or Q6 required release of water from the system.

    COVER Excess Water Management StrategyExcess Water Managementr Strategy_Rev0_finalVol4A Fig 4.1 Development OverviewDCO Figure 2.052.05_Indicative_Site_Layout_Plan_ISSUED2.05

    04_60332577-SHT-10-ZN00-Z-000105_Glyn Rhonwy Discharges 1 of 506_Glyn Rhonwy Discharges 2 of 507_Glyn Rhonwy Discharges 3 of 508_Glyn Rhonwy Discharges 4 of 509_Glyn Rhonwy Discharges 5 of 5