Archaeological Desk Based Assessment
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National Grid Grain LNG Limited Grain LNG Phase 3B APPENDIX 1.3: ARCHAEOLOGICAL DESK BASED ASSESSMENT ES Volume 2: Technical Appendices GRAIN LNG PHASE 3B Isle of Grain Hoo Peninsula County of Kent Archaeological desk based assessment November 2020 © Museum of London Archaeology 2020 Museum of London Archaeology Mortimer Wheeler House 46 Eagle Wharf Road, London N1 7ED tel 020 7410 2200 | fax 020 410 2201 https://www.mola.org.uk general enquiries: [email protected] GRAIN LNG PHASE 3B Isle of Grain Hoo Peninsula Kent Archaeological Desk Based Assessment NGR 587080 175798 Historic Environment Record search reference: Isle of Grain, Medway Sign-off history issue Issue date Prepared by Reviewed by Project Manager Notes no. 1 03/11/2020 Melissa Cutting Rupert Featherby Philip Stastney First issue (Archaeology) Lead Consultant Archaeology 2 06/11/2020 Melissa Cutting - Philip Stastney Second issue (Archaeology) Ashley Blair (Graphics)- 3 10/11/2020 Melissa Cutting Project name revised (Archaeology)) 4 27/11/2020 Philip Stastney Philip Stastney Minor revisions, and updated site outline 5 09/12/2020 Philip Stastney Minor revision. MOLA code: P20-345 www.mola.org.uk © MOLA Mortimer Wheeler House, 46 Eagle Wharf Road, London N1 7ED tel 0207 410 2200 email: [email protected] Museum of London Archaeology is a company limited by guarantee Registered in England and Wales Company registration number 07751831 Charity registration number 1143574 Registered office Mortimer Wheeler House, 46 Eagle Wharf Road, London N1 7ED Contents Executive summary 1 1 Introduction 2 1.1 Origin and scope of the report 2 1.2 Designated heritage assets 2 1.3 Aims and objectives 3 2 Methodology and sources consulted 4 2.1 Sources 4 2.2 Methodology 4 3 The site: topography and geology 6 3.1 Site location 6 3.2 Topography and geology 6 4 Archaeological and historical background 8 4.1 Overview of past investigations 8 4.2 Chronological summary 8 5 Statement of significance 14 5.1 Introduction 14 5.2 Factors affecting archaeological survival 14 5.3 Archaeological potential, and significance of likely remains 17 6 Impact of proposals 19 6.1 Proposals 19 6.2 Implications 19 7 Conclusion and recommendations 21 8 Gazetteer of known historic environment assets 22 9 Planning framework 27 9.1 National Planning Policy Framework 27 9.2 Local planning policy 29 10 Determining significance 31 11 Non-archaeological constraints 32 12 Glossary 33 13 Bibliography 35 13.1 Published and documentary sources 35 13.2 Other Sources 36 13.3 Cartographic sources 36 13.4 Available site survey information checklist 36 Archaeological Desk Based Assessment © MOLA 2020 i Grain LNG Phase 3B3B 09/12/2020 Figures Cover: Grain Parish Tithe Map of 1839 Fig 1 Site location Fig 2 Historic environment features map Fig 3 Geological features, geotechnical survey data (Soil Mechanics 2010) and historic borehole data (BGS 2020) map Fig 4 Grain Parish Tithe Map of 1839 Fig 5 Ordnance Survey 1st edition 5”: mile map of 1863 Fig 6 Ordnance Survey 1:2,500 scale map of 1967 Fig 7 Ordnance Survey 1:10,000 scale map of 1993 Fig 8 Site Layout, showing existing site and surrounding area layout and proposed new T355 Tank location (National Grid 2020) Fig 9 Tank Layout Plan showing existing and proposed Phase 3B construction (National Grid, PL3/PLA/108, Rev A1, 31/08/2007) Fig 10 LNG Storage Tank Section and Plan View (National Grid, Figure 3.3, June 2006) Note: site outlines may appear differently on some figures owing to distortions in historic maps. North is approximate on early maps. Archaeological Desk Based Assessment © MOLA 2020 ii Grain LNG Phase 3B3B 09/12/2020 Executive summary National Grid Grain LNG Limited has commissioned MOLA to carry out an Archaeological Desk Based Assessment in advance of development at the Grain LNG Importation Facility, Isle of Grain in the County of Kent in support of the discharge of planning conditions for Phase 3B. The scheme comprises the construction of a LNG storage tank, installation of three submerged combustion vaporisers and provision of related infrastructure, including a temporary laydown area for the construction phase of the LNG storage tank and associated plant, referred to as “Phase 3B”. Grain LNG Phase 3B received permission under wider proposals which also included the construction of a jetty, internal access roads and other infrastructure. These components and the first LNG storage tank have already been built (i.e. Phase 3A). This assessment will focus on the site of the second permitted LNG storage tank and associated laydown area south and east of the tank location which are proposed and have not yet been constructed. This desk-based study assesses the impact of the scheme on archaeological remains (buried heritage assets). Above ground heritage assets (historic structures) are not discussed in detail, but they have been noted where they assist in the archaeological interpretation of the site. Archaeological remains that may be affected by the proposals comprise: • Palaeoenvironmental evidence. The geology of the Phase 3B area is comprised of thick alluvial deposits with lenses of peat and organic material. There is high potential for encountering remains of likely geoarchaeological interest which can be utilised to reconstruct past local environments, indirect evidence of local human activity and useful data to assist our understanding of past sea level changes. Minerogenic deposits such as alluvial silts and clays have the potential for preservation of diatoms that can provide information on the salinity status of the depositional environments that would enhance interpretation of the sedimentary sequence. These remains would be of low or medium significance, depending on the presence of datable material and their historic and evidential value. • Prehistoric remains. The Phase 3B area is located within the intertidal marshland area. There is low potential for remains of associated structures such as platforms, bridge piers, jetties, and fish traps which may have been constructed. The ephemeral nature of these activities suggests that little tangible and/or visible evidence may remain. There is moderate potential for undisturbed alluvial deposits within the site which could contain evidence of successive episodes of prehistoric activity. The significance of the any prehistoric remains would depend on their nature and extent. Extensive and well preserved features may be of low to medium significance, depending on their evidential and historical value. Isolated and/or residual artefacts would likely be of low significance. There is low potential for remains from all other periods as the Phase 3B area was located in low-lying marshland prone to flooding and then existed as pastoral agricultural land during the later medieval and post-medieval periods. The Phase 3B area and surrounding area have been extensively developed and levelled since the mid-1950s during industrial expansion. The main impact from the scheme will be the piled foundation of the LNG storage tank base, which would remove archaeological/palaeoenvironmental remains within the footprint of each pile. Other site works, including obstruction removal, below ground vaporisers and other minor foundations, may also impact the upper levels of surviving alluvium deposits. The Phase 3B area is not located in an Archaeological Priority Area. Although the proposed development has high potential to contain palaeoenvironmental evidence of low to medium significance and low to moderate potential to contain prehistoric remains of low to medium significance, in light of the localised area of the proposed impact, it is unlikely that the local authority would require further preliminary site-specific archaeological evaluation. It is likely, however, that given the uncertainty of site-specific geological remains archaeological monitoring of intrusive works (below ground) would be requested in order to confirm the precise level of natural deposits along with presence and depth of any archaeological remains. The previously proposed mitigation of a watching brief, as recommended during the 2006 and 2007 assessments, remains appropriate. Any archaeological work would need to be undertaken in accordance with an approved Written Scheme of Investigation (WSI) and be carried out under the terms of Discharge of Condition 27 as set out in decision notice MC/07/1683. Archaeological Desk Based Assessment © MOLA 2020 1 Grain LNG Phase 3B3B 09/12/2020 1 Introduction 1.1 Origin and scope of the report 1.1.1 National Grid Grain LNG Limited has commissioned MOLA (Museum of London Archaeology) to prepare an Archaeological Desk Based Assessment in advance of development at the Grain LNG Importation Facility, Isle of Grain in the County of Kent; National Grid Reference (NGR) 587080 175798: Fig 1. It has been prepared in support of the discharge of planning conditions (Planning Ref: MC2007/1683, amendment of MC2006/1428) for the construction of Phase 3B at the Grain LNG Importation Facility on the Isle of Grain, Kent. 1.1.2 The scheme comprises the construction of a LNG storage tank, the installation of three submerged combustion vaporisers and the provision of related infrastructure, including a temporary laydown area for the construction phase of the LNG storage tank and associated plant. Grain LNG Phase 3B (sitting within an area formerly known as Phase 3 Northern Zone) received permission under wider proposals which also included the construction of a jetty, internal access roads and other infrastructure. These components and the first LNG storage tank have already been built. This assessment will focus on the site of the second permitted LNG storage tank and associated laydown area south and east of the tank location. 1.1.3 This desk-based study assesses the impact of the scheme on archaeological remains (buried heritage assets). It forms an initial stage of investigation of the area of development (hereafter referred to as ‘Phase 3B area’) and may be required in relation to the planning process in order that the local planning authority (LPA) can formulate an appropriate response in the light of the impact on any known or possible heritage assets.