Port Dinorwic Residential Development, Y Felinheli, Gwynedd

Dinorwic Marina Ltd

Flood Consequences Assessment Report

Drainage Strategy

October 2020

62 Albany Road CARDIFF, CF24 3RR t: 029 2030 2521

Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

Document Control Sheet

Project Number 2037

Project Title Port Dinorwic Residential Development

Client Dinorwic Marina Ltd

Document Title Flood Consequences Assessment Report & Drainage Strategy

Prepared by Checked by Verified by Approved by

Dimitrios Gkraikis Stephen Davis Principal Civil Engineer Director

Revisions

Revision Date Details Authorised by

- 29 Oct 2020 First Issue

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy CONTENTS

1. INTRODUCTION ...... 4 1.1 Background ...... 4 1.2 Existing Site...... 4 1.3 Fluvial Flood and Tide Levels ...... 5 1.4 Development Proposals ...... 5 2. FLOOD CONSEQUENCES ASSESSMENT ...... 5 2.1 Legislation ...... 5 2.2 Flood Zones – NRW Maps ...... 6 2.3 Flood Risk Vulnerability Classification ...... 6 2.4 Flood Risk Vulnerability Classification and Flood Zone Compatibility ...... 6 2.5 Site Specific Sources of Flood Risk ...... 6 2.6 Tide Level Calculations ...... 6 2.7 Proposed Development Finished Floor Levels ...... 8 2.8 Emergency Access/Egress – Flood Hazard Rating ...... 9 3. DRAINAGE STRATEGY ...... 10 3.1 Foul/Surface Water Drainage...... 10 4. CONCLUSIONS ...... 10 4.1 Summary ...... 10 4.2 Conclusion ...... 11

APPENDICES

A SITE SURVEY

B PROPOSED SITE LAYOUT

C NRW FLUVIAL FLOOD/TIDAL FLOOD MAP

D NRW SURFACE WATER FLOOD MAP

E WELSH WATER PLANS

F DRAINAGE STRATEGY

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy 1. INTRODUCTION

1.1 Background 1.1.1 PHG Consulting has been commissioned by Dinorwic Marina Ltd to undertake a flood consequences assessment report for a site located in the Marina area of Y Felinheli (Port Dinorwic), Gwynedd. 1.1.2 This report is to support a planning application for a residential use development. 1.1.3 The site is undeveloped, facing Nant Y Garth, currently used as boatyard. 1.1.4 The report addresses all possible sources of flood risk and demonstrates how the risks are mitigated to make the development safe without increasing flooding elsewhere.

1.2 Existing Site 1.2.1 The site is of rectangular shape with a total area of circa 600m2. It is located at the National Grid Reference SH528679. The site is facing Porth-Y-Llechen to the north boundary and past that is Nant Y Garth. To the east and west the site is bound by neighbouring developed sites. To the back of the site, at the south, there is an existing retaining wall and past that a tarmac road that is about 6m higher. Figure 1 below shows the location plan.

Figure 1: Site location plan

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy 1.2.2 The site topography slopes south east to north west. The site is generally flat with levels between 5.95mAOD to 5.75mAOD at a gradient of circa 1in130. The existing Site Survey is shown in Appendix A. 1.2.3 The site is currently occupied as a boatyard and the whole plan area of the site is impermeable and tarmac paved.

1.3 Fluvial Flood and Tide Levels 1.3.1 The site is within the Marina area and is facing the Nant Y Garth which discharges to the Menai Strait. Due to the proximity of the Marina to the estuary mouth, the flood levels within the vicinity are predominantly affected by the Tide Levels. 1.3.2 According to the available stations for Tide Levels, the closest station is located close to the estuary mouth at Menai Strait. Calculations were undertaken to determine the T200 and the T1000 tide level including climate change using the Menai Strait station tide levels.

1.4 Development Proposals 1.4.1 The proposal comprises the construction of a residential use building with 11 flats within four floors in total. The proposed development Layout is included in Appendix B. 1.4.2 The scheme is also subject to new SAB (SuDS Approval Body) legislation and the proposed scheme will need to adhere to it. In addition to the proposed planning application a pre-SAB and full SAB application and approval process will also run in parallel. The SAB is Gwynedd Council.

2. FLOOD CONSEQUENCES ASSESSMENT

2.1 Legislation 2.1.1 TAN 15 is the planning guidance used in Wales to assess flood risk. A requirement of TAN 15 is that developers making planning applications on sites that are potentially at risk from flooding should consult with Natural Resources Wales and produce a Flood Consequence Assessment (FCA) to support their proposals. This assessment has been conducted in accordance with TAN 15: Development and Flood Risk 2.1.2 Definition of Flood Risk Flood risk is the product of the likelihood or chance of a flood occurring (flood frequency) and the consequence or impact of the flooding (flood consequence). 2.1.3 Flood Frequency 2.1.4 Flood frequency is identified in terms of the return period and annual probability. For example, a 1 in 100-year flood event has a 1% annual probability of occurring. Table 1 below provides a conversion between return periods and annual flood probabilities. Table 1: Flood Probability Conversion Table

Return Period (years) 2 5 10 20 50 100 200 1000 Annual Flood Probability (%) 50 20 10 5 2 1 0.5 0.1

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy 2.2 Flood Zones – NRW Maps 2.2.1 The proposed development area is located outside the flood zones according to the NRW Flood Maps included in Appendix C.

2.3 Flood Risk Vulnerability Classification 2.3.1 The proposed development is residential so is classed as highly vulnerable in TAN 15.

2.4 Flood Risk Vulnerability Classification and Flood Zone Compatibility 2.4.1 The site to be developed according to the maps is outside the floodplain in Flood Zone 1 and the type of development is allowed. 2.4.2 Nonetheless, since the Nant Y Garth is a tide locked watercourse, the Tide Levels, including climate change allowance due to the rising of the sea level, will be taken into consideration.

2.5 Site Specific Sources of Flood Risk 2.5.1 The site is in Flood Zone 1 according to the NRW’s Flood Map, included in Appendix C. The proposed development is facing Nant Y Garth and is circa 300m from the Menai Strait. 2.5.2 Part of the site is at Low Surface Water Flood Risk according to the NRW’s map included in Appendix D. Given the site’s direct proximity to the watercourse, the risk is not taken into consideration as the Tide Level is the predominant source of flood risk. Any surface water will naturally flow from south to north direction towards the watercourse since the site slopes from 5.89mAOD to the south to 5.60mAOD to the north at the watercourse.

2.6 Tide Level Calculations The available data from the UK.GOV web site regarding the Tide Levels are as shown below:

The downloaded “Coastal Design Sea Levels” information was used to obtain the T200 and T1000 with a confidence level of 97.5%. On top of that, the climate change was applied in line with the latest guidance from Welsh Government Document “Adapting to Climate Change: Guidance for Flood and Coastal Erosion Risk”, December 2017.

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

2.6.1 The data “Coastal Design Sea Levels” was analysed to determine the closest tide level station available in relation to the Estuary Mouth of Nant Y Garth in the Menai Strait. The Figure on the next page shows the two available stations. The Station at Chainage _966_2 is selected as it is located close to the Estuary mouth of Nant Y Garth at the Menai Strait

Menai Strait Estuary / Chainage of Station - _966_2 Base Year - 2017

T200 - 4.320 mAOD T1000 - 4.570 mAOD T200 (97.5% confidence level) - 4.500mAOD T1000 (97.5% confidence level) - 4.880mAOD

Climate Change Allowance: THE DESIGN YEAR FOR CLIMATE CHANGE ALLOWANCE IS 2020 + 100 = 2120 SINCE THIS IS A RESIDENTIAL DEVELOPMENT

Period mm increase Cumulative T200 T200 T1000 T1000 Rise mAOD (97.5%) mAOD (97.5%) mAOD mAOD

2017 - 2025 8 x 3.5 28mm 4.4 4.6 4.6 5.0

2026 - 2055 30 x 8.0 240mm 4.6 4.9 4.9 5.2

2056 - 2085 30 x 11.5 345mm 5.0 5.2 5.2 5.5

2086 - 2116 30 x 14.5 435mm 5.4 5.7 5.7 6.0

2117 - 2020 BY INTERPOLATION 5.5 5.7 5.8 6.1

All the above values are rounded up to one decimal place according to the Welsh Government Document Values for 2020 are interpolated using the values for 2085 and 2116 as per the Welsh Government Document

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

2.7 Proposed Development Finished Floor Levels 2.7.1 Given the above Tide Level Calculations, the Design Tide Level T200 is 5.7mAOD, which has resulted by applying the climate change allowance on the 97.5% confidence T200 tide level. 2.7.2 The site, for the Design Tide Level of T200, is not flooding since the tide level is 5.70mAOD and the site boundary to the north has a level ranging between 5.79mAOD to 5.71mAOD. 2.7.3 In the scenario of 1in1000, the Tide Level with a confidence bound of 97.5% and applied climate change is 6.1mAOD. The flood depth on the site ranges from 390mm to 140mm with most of the site close to 270mm. 2.7.4 The proposed development has a FFL on the ground floor of 6.70mAOD, providing a 600mm freeboard from the T1000 level.

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

2.8 Emergency Access/Egress – Flood Hazard Rating 2.8.1 The proposed development is comprised of the ground, first, second and third floor. The following figure demonstrates the plan layout of the second floor.

2.8.2 There is a retaining wall at the south boundary of the site and past that an existing road, Hen Gei Llechi. The road is circa 6.5m higher than the site, proved to be a safe access and egress point.

2.8.3 A pedestrian access is proposed from the second floor to the road at the south boundary of the building to provide safe access and egress in the scenario of T1000 when the ground floor access to the building is flooded.

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy 3. DRAINAGE STRATEGY

3.1 Foul/Surface Water Drainage 3.1.1 According to the Welsh Water Plans, included in Appendix E, there is a sewage pumping station located circa 40m west of the site on Port Y Llechen. Welsh Water should be advised in relation to the connection arrangements of the development to the pumping station inlet sewer. There is a foul sewer running along the north boundary of the site and connection is proposed via the exiting foul sewer following verification via durvey. 3.1.2 The development is facing Port Y Llechen and is circa 10.5m from Nant Y Garth. Given the location of the site, since the Tide is the dominant source of flooding, providing any attenuation is not beneficial. The runoff from the site will be discharged to the Nant Y Garth via connection to the existing surface water sewer running on the Port Y Llechen, pending verification through survey. 3.1.3 In order to collect the runoff from the downpipes for the proposed building, a Swale/Detention Basin is proposed at the back of the building where an amenity area is proposed in combination of the attenuation of the surface runoff for the low events. The drainage strategy is outlined in Drawing 101 included in Appendix F. 3.1.4 The site is currently used as Boat Perth and its entire area is impermeable. The development provides a betterment to the impermeability since there is a landscaped area at the back of the building and the parking spaces are all proposed to be paved with the Grasscrete system.

4. CONCLUSIONS

4.1 Summary 4.1.1 The proposed development site is located on Flood Zone 1 and is permitted according to the type of the development and its vulnerability. 4.1.2 The proximity of the site to the Nant Y Garth provides protection from any surface water flood issues since the natural drainage path slopes towards the watercourse. 4.1.3 The tide level is considered the predominant source of flood risk to the site 4.1.4 The site is not flooding from the Tide Level with a 0.5% annual exceedance probability, including climate change allowance. 4.1.5 The proposed Finished Floor Levels of the ground floor of the development are set to be 600mm on top of the 97.5% Confidence level of the Tide Level with a 0.1% annual exceedance probability, including climate change allowance. 4.1.6 There is a safe access and egress provided to the proposed building via a bridge towards the high-level road located at the south boundary of the site that is free from flooding.

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

4.2 Conclusion 4.2.1 It is evident from the report that the development is not at risk of flooding, it is not causing any detriment, safe access and egress is provided. 4.2.2 Given the above, it is considered that Planning Consent should not be withheld on flood risk grounds.

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Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

APPENDIX A – SITE TOPOGRAPHICAL SURVEY

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5.51

5.55

5.54 SV

5.55 NRG1 IC CL = 5.86 TARMAC

5.90

5.61

5.62 RL = 13.66 5.91

5.88 SV 6.13 5.65 SV

6.13 5.63 5.92 5.65 5.59 IC CL = 6.02

11.25

5.89 G 5.60 Building

10.04 6.12 Block Paving

EL = 10.95

5.68 5.72

11.41

5.68

5.93 Tarmac Footpath 5.85 5.71

5.76 Palisade H=1.8m Palisade

11.64 EL = 10.92 5.96 5.70

Palisade H=1.8m

5.72 TARMAC

5.94 5.77

5.77 5.88

11.78 5.84

10.54 5.82 5.83 Hardcore

5.84 5.87 5.85 Container 5.79 5.78 5.76 NRG3 5.83 5.84 5.83

11.97 NRG4 5.80

5.84 5.84 Retaining Wall

5.84 5.71

5.83

12.05 Hardcore 5.71 5.89

IC CL = 5.75 5.71 5.89

5.71 5.89 IC CL = 5.74

5.79 5.76

5.70 5.79 5.85

10.94 G

5.70 5.88 LP 12.33

5.75 Tarmac Footpath 5.90 5.77 5.92 5.78

5.88 TARMAC

5.75

11.15 5.88

5.97 5.76 12.45 Hardcore 5.75 11.19

5.74 5.93

5.76 5.91 Retaining Wall Hardcore 5.84 NRG5 5.96 5.90

5.91 12.64

5.70 5.67

NRG2 5.70

11.49 5.69 12.82 5.84 IC CL = 5.86

IC CL = 6.01 5.99

IC CL = 5.83 Palisade H=1.8m Palisade 6.00

11.60

12.87 5.97 EL = 11.15 Tarmac Footpath

11.74 5.97 RL = 14.06 5.66

IC CL = 5.78

6.44 5.97

EL = 11.046.03

IC CL = 5.93 5.98 5.96

IC CL = 5.98

5.65 13.15 6.25

11.93 5.96 5.90

6.24 TARMAC

5.60 12.05

6.21

5.61

Block Paving

12.24 13.48 Building

5.57

5.51 G TARMAC

5.51

5.52

5.52 DRAWING REFERENCE # PROJECT CLIENT SURVEYED BY SCALE TITLE www.nrgsurveys.co.uk email: [email protected] Tel: 01248 681240 LL33 OAN Conwy Llanfairfechan Station Road Castle View Notes Building And Floorplan Features Additional Notes For Fencing Point/Line Features (Where Applicable) 1:200 @ A3 1373/TP/01 : 01 SR Sill Level Threshold Level Ridge Level Eaves Level Soffit Level Damp Proof Course Level Floor Level Safety Fence Concrete Panel Close Boarded Palisade Chainlink Post and Rail Post and Wire Port Dinorwic Marina Port Dinorwic Marina Stay Topographic Survey IC CL = IC CL = IC CL = BT CL = MP Cabinet AV Gas SV Rod RE FH G Meter Bin LP TP EP IC CL = Pylon IC CL = Litter Bin Lamp Post Stay Wire Anchor Overhead Cable Telegraph Pole Electricity Pole Pylon Inspection Cover (Triangular) Inspection Cover (Rectangular) Inspection Cover (Square) Inspection Cover (Circular) Electric Cover Telecom Cover Underground Service Marker Post Electricity Cabinet Air Valve Gas Valve Stop Valve Earth Rod Rodding Eye Fire Hydrant Gully Water Meter DRAWN BY DATUM Services Ltd NRG Engineering Newlyn SR SL THL RL EL SOF DPC FL S/F C/P C/B PAL C/L P/R P/W RS WL = IL = 999.99m TL RP Post PO Box BM = Bollard Water Level Invert Level Spot Height Permanent Benchmark Permanent Ground Marker Hedge Undergrowth Tree Canopy Tree Bole Tree Stile Gate Wall Safety Fence Fences Telephone Kiosk Traffic Light Reflective Hazard Post Post Box Road Sign Post Seat Bollard DATE GRID 19/12/2018 OSGB36(15) ISSUE 01 Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

APPENDIX B – PROPOSED SITE LAYOUT

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PRELIMINARY PDA Job No: This drawing must not be scaled. Rev: Chk'd: 18131 Figured dimensions and levels to be used. Any inaccuracies must be notified to the SITE ORG. DRG NO. DIS. REV architect. PLANNING Detail drawings and large scale drawings take PDA ZA 00 SK A (21)200 precedence over smaller drawings. Cardiff . Swansea . London t +44 (0)33 33 201 001 www.powelldobson.com @PDArchitects VOLUME LEVEL DR TYPE NUMBER A1 DESIGN Contract: Port Dinorwic Residential Development Scale: 1 : 100 TENDER Date: 20/07/20 Drawn: ML Title: THIS DRAWINGS IS COPYRIGHT © CONSTRUCTION Ground Floor Plan Checked: DR

Registered Office: Powell Dobson, Suite 1F, Building One, Eastern Business Park, Wern Fawr Lane, Old St Mellons, Cardiff CF3 5EA. Powell Dobson is a trading name of Powell Dobson Ltd a company registered in England and Wales No 3873802. \\global\cardiff\General\Union Square Projects\18131 Port Dinorwic Residential Development\0 - PDA Drawings\4 - Model\3 - REVIT\Port Dinorwic_CENTRAL v19. MLC.rvt PRELIMINARY PDA Job No: This drawing must not be scaled. Rev: Chk'd: 18131 Figured dimensions and levels to be used. Any inaccuracies must be notified to the SITE ORG. DRG NO. DIS. REV architect. PLANNING Detail drawings and large scale drawings take PDA ZA 00 SK A (21)201 precedence over smaller drawings. Cardiff . Swansea . London t +44 (0)33 33 201 001 www.powelldobson.com @PDArchitects VOLUME LEVEL DR TYPE NUMBER A1 DESIGN Contract: Port Dinorwic Residential Development Scale: 1 : 100 TENDER Date: 20/07/20 Drawn: ML Title: THIS DRAWINGS IS COPYRIGHT © CONSTRUCTION First Floor Plan Checked: DR

Registered Office: Powell Dobson, Suite 1F, Building One, Eastern Business Park, Wern Fawr Lane, Old St Mellons, Cardiff CF3 5EA. Powell Dobson is a trading name of Powell Dobson Ltd a company registered in England and Wales No 3873802. \\global\cardiff\General\Union Square Projects\18131 Port Dinorwic Residential Development\0 - PDA Drawings\4 - Model\3 - REVIT\Port Dinorwic_CENTRAL v19. MLC.rvt PRELIMINARY PDA Job No: This drawing must not be scaled. Rev: Chk'd: 18131 Figured dimensions and levels to be used. Any inaccuracies must be notified to the SITE ORG. DRG NO. DIS. REV architect. PLANNING Detail drawings and large scale drawings take PDA ZA 00 SK A (21)202 precedence over smaller drawings. Cardiff . Swansea . London t +44 (0)33 33 201 001 www.powelldobson.com @PDArchitects VOLUME LEVEL DR TYPE NUMBER A1 DESIGN Contract: Port Dinorwic Residential Development Scale: 1 : 100 TENDER Date: 20/07/20 Drawn: ML Title: THIS DRAWINGS IS COPYRIGHT © CONSTRUCTION Second Floor Plan Checked: DR

Registered Office: Powell Dobson, Suite 1F, Building One, Eastern Business Park, Wern Fawr Lane, Old St Mellons, Cardiff CF3 5EA. Powell Dobson is a trading name of Powell Dobson Ltd a company registered in England and Wales No 3873802. \\global\cardiff\General\Union Square Projects\18131 Port Dinorwic Residential Development\0 - PDA Drawings\4 - Model\3 - REVIT\Port Dinorwic_CENTRAL v19. MLC.rvt PRELIMINARY PDA Job No: This drawing must not be scaled. Rev: Chk'd: 18131 Figured dimensions and levels to be used. Any inaccuracies must be notified to the SITE ORG. DRG NO. DIS. REV architect. PLANNING Detail drawings and large scale drawings take PDA ZA 00 SK A (21)203 precedence over smaller drawings. Cardiff . Swansea . London t +44 (0)33 33 201 001 www.powelldobson.com @PDArchitects VOLUME LEVEL DR TYPE NUMBER A1 DESIGN Contract: Port Dinorwic Residential Development Scale: 1 : 100 TENDER Date: 20/07/20 Drawn: ML Title: THIS DRAWINGS IS COPYRIGHT © CONSTRUCTION Third Floor Plan Checked: DR

Section through Hen Gei Llechi 1 : 200

Rear Elevation 1 : 200

PRELIMINARY PDA Job No: This drawing must not be scaled. Rev: Chk'd: 18131 Figured dimensions and levels to be used. Any inaccuracies must be notified to the SITE ORG. DRG NO. DIS. REV architect. PLANNING Detail drawings and large scale drawings take PDA ZA 00 SK A (21)402 precedence over smaller drawings. Cardiff . Swansea . London t +44 (0)33 33 201 001 www.powelldobson.com @PDArchitects VOLUME LEVEL DR TYPE NUMBER A1 DESIGN Contract: Port Dinorwic Residential Development Scale: 1 : 200 TENDER Date: 20/07/20 Drawn: ML Title: THIS DRAWINGS IS COPYRIGHT © CONSTRUCTION Initial Massing in Context Checked: DR

APPENDIX C – NRW FLUVIAL/TIDAL FLOOD MAP

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Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key Main Rivers Flood Defences Areas Benefiting from Flood Defences Flood Storage Areas Floodmap Flood Zone 3 Floodmap Flood Zone 2

Graddfa / Scale 1: 4,999

Dyddiad / Date 23/06/2020

Ceir rhestr lawn o delerau ac amondau yn https://naturalresources.wales/rhybuddsafonol neu drwy gysylltu ag 0.3 0 0.13 0.3 [email protected]. A full list of terms and condiitions is available from the https://naturalresources.wales/StandardNotice or by contacting [email protected] © Crown copyright and British_National_Grid Kilometers database rights 2017 Ordnance Survey 100019741. Geological Mapping: British Geological Survey ©NERC. Centre for Ecology & Hydrology © NERC (CEH). Defra and Met Office © Crown copyright. © Cranfield University. © James Hutton Institute. Land & Property Services © Crown copyright and database right. Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key Flood Defences Risk of Flooding from Rivers & Sea High

Medium

Low

Very Low Risk of Flooding from Reservoirs - Extent Low Surface Water Flood Risk - Extent

Graddfa / Scale 1: 4,999

Dyddiad / Date

Ceir rhestr lawn o delerau ac amondau yn https://naturalresources.wales/rhybuddsafonol neu drwy gysylltu ag [email protected]. A full list of terms and condiitions is available from the https://naturalresources.wales/StandardNotice or by contacting [email protected] © Crown copyright and database rights 2017 Ordnance Survey 100019741. Geological Mapping: British Geological Survey ©NERC. Centre for Ecology & Hydrology © NERC (CEH). Defra and Met Office © Crown copyright. © Cranfield University. © James Hutton Institute. Land & Property Services © Crown copyright and database right. Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

APPENDIX D – NRW SURFACE WATER FLOOD MAP

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Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key Low Surface Water Flood Risk - Extent

Graddfa / Scale 1: 4,999

Dyddiad / Date 23/06/2020

APPENDIX E – WELSH WATER PLANS

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09/04/2020

Scale: 1: 621

252824,367896

Dwr Cymru Cyfyngedig (‘the Company’) gives this information as to the position of its underground apparatus by way of general guidance only and on the Reproduced from the Ordnance Survey’s Whilst every reasonable effort has been taken to strict understanding that it is based on the best information available and no warranty as to its correctness is relied upon In the event of excavations or EXACT LOCATION OF maps with the permission of the correctly record the pipe material of DCWW assets, other works made in the vicinity of the company’s apparatus and any onus of locating the apparatus before carrying out any excavations rests entirely on Controller of Her Majesty’s Stationary there is a possibility that in some cases pipe material you. The information which is supplied hereby the company, is done so in accordance with statutory requirements of sections 198 and 199 f the water ALL APPARATUS TO Office. Crown Copyright. Licence No: (other than Asbestos Cement or Pitch Fibre) may be industry Act 1991 based upon the best Information available and in particular, but without prejudice to the generality of the foregoing, it should be noted that BE DETERMINED ON WU298565. found to be Asbestos Cement (AC) or Pitch Fibre (PF). the records that are available to the Company may not disclosure the existence of a drain sewer or disposal main laid before 1 September 1989, or if they It is therefore advisable that the possible presence of do, the particulars thereof including their position underground may not be accurate. It must be understood that the furnishing of this information us entirely SITE AC or PF pipes be anticipated and considered as part without prejudice to the provision of the New Roads and Street Works Act 1991 and the company’s right to be compensated for any damage to its of any risk assessment prior to excavation apparatus. Dinorwic Marina Ltd, Port Dinorwic Residential Development Y Felinheli, Gwynendd Flood Consequences Assessment Report & Drainage Strategy

APPENDIX F – DRAINAGE STRATEGY

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Grasscrete Parking

Dock Existing Foul Sewer Bollards Proposed Surface Water Sewer ASSUMED EXISTING OUTFALL to be verified Existing Surface Water Sewer

Site Planting

Landscaped Area

EXISTING SURFACE WATER SEWER (IL 3.67m)

assumed existing foul sewer location to be verified

Proposed Grasscrete Parking Spaces 13

DN 15 - 27.10.20 First issue KF DG Rev: Date Details By. Chk. Amendments Port Dinorwic Client: Proposed Swale/Basin Dinorwic Marina Ltd

Consulting Engineers

PHG Consulting Ltd 62A Albany Road Orifice Plate to ensure maximum Cardiff CF24 3RR T : +44(0)29 2030 2521 utilisation of the available storage E : [email protected] W : www.phg-consulting.co.uk

@PHG_consulting in the Swale and ensure www.linkedin.com/company/ appropriate detention times phg-consulting-engineers PORTH Y LLECHEN Project:

Port Dinorwic Residential Development

Drawing title:

Drainage Strategy

Drawn: Chk: Status: Scale: KF DG Approval 1:250 @ A1

Date: Job no. Drg. no. Rev. 29.10.20 2037 101 -