NOT PROTECTIVELY MARKED Page No.: i / iii REDACTED PUBLIC VERSION HPC PCSR3 – Sub-chapter 2.1 – Reference: HPC-NNBOSL-U0-000-RES- Site Description and Data 100006 NNB GENERATION COMPANY LTD REDACTED PUBLIC VERSION HPC PCSR3: CHAPTER 2 – SITE CHARACTERISTICS AND LAYOUT SUB-CHAPTER 2.1 – SITE DESCRIPTION AND DATA { PI Removed } © 2017 Published in the United Kingdom by NNB Generation Company Limited (NNB GenCo), 90 Whitfield Street – London, W1T 4EZ. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording,APPROVED without the written permission of the copyright holder NNB GenCo, application for which should be addressed to the publisher. Such written permission must also be obtained before any part of this publication is stored in a retrieval system of any nature. Requests for copies of this document should be referred to Head of Business Architecture, NNB Generation Company Limited (NNB GenCo), 90 Whitfield Street – London, W1T 4EZ. The electronic copy is the current issue and printing renders this document uncontrolled. NOT PROTECTIVELY MARKED NOT PROTECTIVELY MARKED Page No.: ii / iii REDACTED PUBLIC VERSION HPC PCSR3 – Sub-chapter 2.1 – Reference: Site Description and Data HPC-NNBOSL-U0-000-RES- 100006 APPROVAL SIGN-OFF: { PI Removed } DOCUMENT CONTROL { PI Removed } REVISION HISTORY { PI Removed } Text within this document that is enclosed within brackets {…} is Sensitive Nuclear Information, Sensitive Commercial Information or Personal Information and has been removed. APPROVED NOT PROTECTIVELY MARKED NOT PROTECTIVELY MARKED Page No.: iii / iii REDACTED PUBLIC VERSION HPC PCSR3 – Sub-chapter 2.1 – Reference: Site Description and Data HPC-NNBOSL-U0-000-RES- 100006 TABLE OF CONTENTS 1. INTRODUCTION .................................................................................. 1 1.1. PURPOSE ............................................................................................ 1 1.2. SCOPE ................................................................................................. 1 2. GENERAL SITE DATA ........................................................................ 2 2.1. LOCATION AND PRE DEVELOPMENT LAND USE .......................... 2 2.2. SITE INVESTIGATIONS ...................................................................... 3 2.3. GEOLOGY ........................................................................................... 4 2.4. COASTAL GEOMORPHOLOGY, BATHYMETRY AND SEDIMENTOLOGY .............................................................................. 8 2.5. SURFACE WATERCOURSES .......................................................... 11 2.6. FAUNA AND FLORA ......................................................................... 11 2.7. RADIOLOGICAL ASSESSMENT DATA ........................................... 12 2.8. GRID RELIABILITY ........................................................................... 13 2.9. LOCAL INDUSTRIAL ENVIRONMENT AND TRANSPORTATION .. 13 3. SITE DATA FOR EXTERNAL HAZARDS ......................................... 15 3.1. INTRODUCTION ................................................................................ 15 3.2. EARTHQUAKE .................................................................................. 17 3.3. ACCIDENTAL AIRCRAFT CRASH ................................................... 26 3.4. HAZARDS ASSOCIATED WITH THE INDUSTRIAL ENVIRONMENT28 3.5. EXTERNAL FLOODING .................................................................... 32 3.6. EXTREME CLIMATIC CONDITIONS ................................................ 50 3.7. LIGHTNING AND ELECTRO-MAGNETIC INTERFERENCE (EMI) .. 66 3.8. HEAT SINK SPECIFIC HAZARDS .................................................... 69 4. REFERENCES ................................................................................... 86 APPROVED NOT PROTECTIVELY MARKED NOT PROTECTIVELY MARKED Page No.: 1 / 111 REDACTED PUBLIC VERSION HPC PCSR3 – Sub-chapter 2.1 – Reference: Site Description and Data HPC-NNBOSL-U0-000-RES- 100006 SUB-CHAPTER 2.1 - SITE DESCRIPTION AND DATA 1. INTRODUCTION NNB GenCo (HPC) intends to build a new nuclear power station at Hinkley Point in Somerset in the United Kingdom. The plant, known as Hinkley Point C (HPC), is to be located in close proximity to the existing Hinkley Point Nuclear Power Station Complex, which currently has one operational Nuclear Power Plant (NPP) - Hinkley Point B (HPB) and one plant undergoing decommissioning - Hinkley Point A (HPA). Chapter 2 of the Pre-Construction Safety Report 3 (HPC PCSR3) presents the site characteristics and layout, of which this sub-chapter focuses on the site description and data that is specific for the Hinkley Point site and used to derive or verify the external hazards design basis. 1.1. PURPOSE The purpose of this document is to provide an overview of the HPC site description and data which support the Safety Case and are needed for the detailed plant design and safety analyses. 1.2. SCOPE A number of site investigations and studies have been carried out at the HPC site. This document presents a summary of these studies, highlighting the methodology and presenting the results. Recognising that site data is of particular relevance to the external hazards safety analysis, this sub-chapter is divided into two sections: Section 2 details the General Site Data. This section provides a history of the Site Investigation campaigns and details the general site characteristics which are not directly relevant to external hazards. The site data contained within this section is relevant to a range of topics including civil design, radiological consequence assessment and Probabilistic Safety Assessment (PSA). Section 3 details the Site Data for External Hazards. This section describes and presents the results of the site-specific studies which directly inform the external hazards safety analysis, itself presented in Sub-chapter 13.1. The purpose of this section is to justify the choice of design basis events which are incorporated into the external hazards safety analysis. No detailed safety analysis is included in this sub-chapter, this is provided in later subAPPROVED-chapters. The external hazards list adopted in Sub-chapter 13.1 is justified within Appendix A of this sub-chapter. NOT PROTECTIVELY MARKED NOT PROTECTIVELY MARKED Page No.: 2 / 111 REDACTED PUBLIC VERSION HPC PCSR3 – Sub-chapter 2.1 – Reference: Site Description and Data HPC-NNBOSL-U0-000-RES- 100006 2. GENERAL SITE DATA 2.1. LOCATION AND PRE DEVELOPMENT LAND USE 2.1.1. Location The HPC site is located on the West Somerset coast, 25 km to the east of Minehead and 12 km to the north-west of Bridgwater, in the parish of Stogursey in the District of West Somerset. The permanent development site covers 67.5 hectares (note: 171 hectares including the temporary construction site) and is approximately centred on National Grid reference 320300, 145850. A map showing the location of the site can be seen in Sub-chapter 2.1 - Figure 9. The permanent development site platform is to be set at a nominal height of 14 m above Ordnance Datum (OD), with a small area to the south of the site to be further raised to 20 m OD. The HPC site is located immediately to the west of HPA, which is currently undergoing decommissioning. Immediately east of HPA is HPB, which is currently operational. The hazards posed by both HPA and HPB to HPC are considered in the characterisation of industrial hazards. 2.1.2. Pre Development Land Use The HPC site is generally open countryside, primarily in agricultural use (mixed pasture and arable) with some areas of woodland and minor development associated with the current nuclear installations. The site comprises open, gently rolling mixed lowland farmland with hedgerows of variable quality, small scrubby woodlands and occasional standard trees. Adjacent land use to the south and west is also primarily agricultural. Within the west side, there were three derelict barn buildings (which have now been removed as part of the development), indicating the past agricultural use of the site. Much of the site is under intensive agricultural use, although small areas of species-rich calcareous grassland occur along the cliff edge and in the immediate vicinity of the Hinkley Point Power Station Complex. This area of the site forms part of the Hinkley County Wildlife Site, which includes woodland, scrub and semi-natural grassland. A review of historical maps and plans has identified that both the western and southern areas of the site have remained as green field agricultural land since the earliest available map was published in 1886. Within the west side, Benhole Farm was located on the north-western corner of this land parcel until around 1976 when it was demolished to leave a single remnant outbuilding which is still present on-site, along with two other derelict farm buildings. The east side of the site comprised greenfield, predominantly agricultural land, until 1975 when a small sewage works was constructed at the western boundary. Also, during the construction of the HPB power station an accommodation / construction camp and fabrication area with associated electrical substations were developed on the southern section of the area. By 2005, a visitors centreAPPROVED had also been constructed in this area. 2.1.3. HPC Development Site For the purpose of describing the properties of the HPC Development Site, it is useful to divide the site into three areas, as seen in