UXO Desk Study Report

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Glyn Rhonwy Pumped Storage Development Consent Order

Appendix 8.5 Zetica (2015) UXO Desk Study Report

Project No. P3300-12

Project Title SITESAFE UXO DESK STUDY Project Location Glyn Rhonwy, Llanberis, Gwynedd

Client Quarry Battery Report Ref. P3300-12-R1-C

Report Date 12th May 2015

Prepared by Clark Friend Checked by Stefan Lang

Authorised by Mike Sainsbury

CONTENTS Page Executive Summary 1 INTRODUCTION 14 1.1 Project Outline 14 1.2 Report Structure 15 2 THE SITE 16 3 SOURCES OF INFORMATION 18 3.1 Historical Information 18 3.2 Zetica Ltd Defence Related Site Records 18 3.3 Zetica Ltd Bombing Density Records and Maps 18 3.4 Ministry of Defence and Government Records 18 3.5 Other Historical Records, Maps and Drawings 19 3.6 Local Authority Records 19 3.7 Local Record Offices and Libraries 19 3.8 Local Historical and Other Groups 19 3.9 Data Confidence Level 19 4 SITE HISTORY 20 4.1 General History 20 5 SITE OPERATIONS 31 5.1 RAF Llanberis Ordnance Depot 31 5.2 Ordnance Disposal at RAF Llanberis 35 5.3 Other Sources of UXO 39 6 EXPLOSIVE ORDNANCE CLEARANCE ACTIVITIES 41 6.1 No. 71 MU EOD Operation, 1969-1975 41 6.2 Post-1975 UXO Discoveries 56 6.3 Residual UXO Hazard 57 6.4 Radioactive Contamination 57 7 ANTICIPATED ORDNANCE TYPES 58 8 UXO HAZARD ASSESSMENT 64 8.1 UXO Hazard Level 64 9 UXO RISK ASSESSMENT 69 9.1 UXO Risk Register 69

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9.2 Risk Management Recommendations – Ground Investigation 71 9.3 Risk Management Recommendations – Future Works 72

Appendices Appendix 1 Overall Clearance Summary Appendix 2 Abbreviations Appendix 3 Glossary & Definitions Appendix 4 Bibliography Appendix 5 General Notes

Figures, Plates & Tables Figure 1 Site location map Figure 2 Historical map, 1889 Figure 3 Historical map, 1914 Figure 4 Historical map, 1920 (with MoD annotations) Figure 5 Historical map showing land requisitioned for RAF Llanberis, 1938 Figure 6 Historical map, 1953 Figure 7 Historical map, 1972 Figure 8 Plan of RAF Llanberis, 1946 Figure 9 Plan of bomb stores at RAF Llanberis, post-1942 Figure 10 Plan showing ordnance disposal pits at RAF Llanberis, WWII Figure 11 Plan showing post-WWII disposal areas and pits at RAF Llanberis Figure 12 Plan of disposal pits and connecting tunnels at RAF Llanberis, 1969 Figure 13 Ordnance recovered from Disposal Area No. 1 Figure 14 Clearance Certificate for Disposal Area No. 1 Figure 15 Ordnance recovered from Disposal Area No. 4 Figure 16 Clearance Certificate for Disposal Area No. 4 Figure 17 UXO hazard zone plan of the Site Figure 18 UXO hazard zone plan of the Site (with GI locations) Figure 19 Plan of fixed EOD facility

Plate 1 Recent aerial photograph of the Site

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Plate 2 Aerial photograph, 10th May 1946 Plate 3 Aerial photograph, 1954 Plate 4 Aerial photograph, 1962 Plate 5 Aerial photograph, 1973 Plate 6 Aerial photograph, 1986

Plate 7 Aerial photograph of RAF Llanberis, 10th May 1946 Plate 8 Aerial photograph of Disposal Area No. 2, 1962 Plate 9 Oblique aerial photograph showing former disposal pits at RAF Llanberis Plate 10 Photograph of ramp from Pit 2A into Pit 2C, RAF Llanberis Plate 11 Photograph of ordnance clearance Pit 2C, RAF Llanberis Plate 12 Photograph of the Bomb Pile in Pit 2C, RAF Llanberis Plate 13 Photograph of stacked 25lb IBs in Pit 2C, RAF Llanberis Plate 14 Photograph showing steaming plant at RAF Llanberis Plate 15 Photograph of typical WWII RAF SAA Plate 16 Photographs of a typical and an excavated WWII Mills No. 36 hand grenade Plate 18 Photograph of American Navy 100lb bombs at RAF Llanberis Plate 18 Illustrations of 25lb incendiary bombs Plate 19 Photograph of new and degraded 4lb incendiary bomb Plate 20 Illustrations of AAD bombs Plate 21 Photograph of an M103 fuze

Table 1 EOD designation of numbered disposal pits, WWII Table 2 Bombing statistics Table 3 Live items found Pit 2C, 1st January 1973 – 31st March 1973 Table 4 Live items found Pit 3C, 1st January 1973 – 31st March 1973 Table 5 UXO hazard assessment for preliminary ground investigation Table 6 UXO risk assessment for the Site

Accompanying Drawings P3300-12-DWG01-C Unexploded Ordnance Hazard Zone Plan P3300-12-DWG02-B UXO Hazard Zone Plan (with GI Locations)

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UXO DESK STUDY & RISK ASSESSMENT

Glyn Rhonwy, Llanberis, Gwynedd

Executive Summary

Zetica Ltd was commissioned by Quarry Battery to carry out an Unexploded Ordnance (UXO) Desk Study and Risk Assessment for an approximate 27 hectare (ha) area of former Royal Air Force (RAF) land at the Glyn Rhonwy Slate Quarry, Llanberis, Gwynedd (the ‘Site’). The aim of this report is to gain a fair and representative view of the UXO hazard for the Site and its immediate surrounding area in accordance with the Construction Industry Research and Information Association (CIRIA) ‘Unexploded Ordnance (UXO), a Guide for the Construction Industry’. Initial works on the Site comprise a preliminary ground investigation, including boreholes, trial pits and sample pits. It is understood that further ground investigations will take place prior to the development of a Pumped Storage Facility. Works for the Pumped Storage Facility may include excavations, tunnelling, trenching and Horizontal Directional Drilling (HDD) associated with the development of a dam, a turbine house, a pipeline and related infrastructure.

UXO Hazard Assessment

Quarry Pits During and post-WWII, the quarry pits at the former Glyn Rhonwy Slate Quarry were used to dispose of large quantities of ordnance. These were divided into 4No. separate disposal areas. The entire Disposal Area No. 2 was located on the Site and comprised 3No. separate quarry pits. These were designated as Pits 2A, 2B and 2C. Additionally, Pit 1B and a small section of Pit 3A were located within the Site boundary. During the 1970s, an Explosive Ordnance Disposal (EOD) operation was undertaken at the former quarry pits and large quantities of ordnance were cleared. Despite this, areas have been identified where a potential UXO hazard may remain:- On the south-eastern side of Pit 2C, a large Bomb Pile had built up, comprising a mixture of live and inert ordnance. During the EOD operation in the 1970s, this Bomb Pile was not completely cleared. It was only partially removed until the frequency of encounter of live bombs was determined to be 0.5%. The remaining part of the Bomb Pile was buried under slate waste. Given that there is positive evidence that live ordnance remains at this location, this part of the Site is assigned a high UXO hazard level.

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The quarry floor of Pit 2C was used to dispose of thousands of tons of ordnance with items ranging from cartridges, fuzes and grenades to Incendiary Bombs (IBs), Anti-Aircraft Devices (AADs) and American High Explosive (HE) bombs. This was cleared by the EOD operation in the 1970s. However, it is known that the floor of the pit (which is currently flooded) has numerous crevices. Despite the thorough clearance efforts, it is probable that ordnance remains within the crevices on the quarry floor. As such, this part of the Site is considered to have a moderate UXO hazard level. Pit 2B was used as a dump for ordnance-related scrap arising from the EOD operation in the 1970s. Given the vast quantities of ordnance being disposed of, and the less rigorous working standards of the period, it is possible that live items of ordnance remain within the scrap. At the end of the EOD operation, Pit 2B is recorded as having been completely infilled with slate debris. This infill is recorded as being sterile and is assigned a low UXO hazard level. Beneath the infill, it is considered that the UXO hazard level is moderate to account for the possibility of live explosives being present within the designated ordnance scrap. Pits 1B and 3A are recorded as having been used for the disposal of ordnance both during and after WWII, particularly 25lb IBs and various fuzes. Many of the items discovered in the pits during the post-WWII EOD operation were disposed of in situ, with the ordnance scrap being channelled into crevices. As with Pit 2C, there is a potential for UXO to remain within the crevices in these quarry pits, either due to it being incorporated into designated ordnance scrap or missed during the clearance operation. These areas of the Site are considered to have a moderate UXO hazard level. Pit 2A is not recorded as having been used for the disposal of ordnance. However, records indicate that crevices within the pit floor were used for the disposal of ordnance scrap, some of which may contain explosive material. As such, this part of the Site is considered to have a moderate UXO hazard level. Slate Piles (within quarry pits) The slate piles within the quarry pits (including the current access paths) were all modified or moved about as part of the EOD operation in the 1970s. The clearance was progressive and, to maximise efficiency, cleared slate was used to backfill the pits after the completion of the EOD operation. Because of the large volume of ordnance disposed of within the quarry pits, and the very difficult working conditions during the EOD operation, there is a possibility that some ordnance-related items remain within the slate piles. This is proved by the discovery of 2No. items of UXO in quarry Pit 3A (part of which is on the Site) during the 1980s. As such, the slate piles within the quarry pits are assigned a moderate UXO hazard level. This also applies to the slate backfill on the floor of the lagoon in Pit 2C. Slate Piles (at surface) The slate piles at the surface, surrounding the quarry pits, do not appear to have been modified since prior to WWII. There is no evidence to suggest that any live ordnance or ordnance scrap was dumped in these areas. The slate piles at the surface are considered to have a low UXO hazard level.

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Open Ground The open ground at the surface of the quarry pits was used for open-air ordnance storage during WWII. At the end of WWII all the stores were cleared. The materials were either sent to other depots, sea-dumped or, together with imported materials, disposed of in the quarry pits. There is no evidence of ordnance disposal taking place at the surface of the quarry pits. In order to provide a safe working environment for the personnel, the open ground and surrounding areas were the first to be cleared during the EOD operation in the 1970s. Further, without major earth movements the ground conditions were not suitable for disposal by burial. The areas of open ground at the surface of the quarry pits are considered to have a low UXO hazard level. The Figure below, reproduced as Figure 17 in the main report, is a UXO hazard zone plan of the Site. A more detailed plan is provided in Zetica Drawing P3300-12-DWG01-C.

Figure UXO hazard zone plan of the Site

Source: Client Not to Scale

Very Low Low Moderate

Legend Site High Very High boundary

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The main findings of the report are summarised below.

 There are no records of bombing or significant military activity on the Site during World War One (WWI) or the Inter-War years.

 During WWII, the Site was in the Rural District (RD) of Gwyrfai, which officially recorded a very low regional bombing density. No records of German bombs falling on the Site have been found.

 During WWII the Site was within the boundary of Royal Air Force (RAF) Llanberis, a major ordnance depot. The quarry pits on the Site were subsequently used by the RAF Explosives School for the demolition and burial of surplus and defective munitions.

 During WWII an approximate total of 173,000No. 25-pound (lb) IBs and 81,000No. 4lb IBs were disposed of in the quarry pits. Between the end of WWII and 1955 a considerable variety of RAF ordnance, together with other munitions, were disposed of in the pits.

 RAF Llanberis was closed in 1956 and retained in Ministry of Defence (MoD) ownership.

 A major EOD operation was undertaken between 1969 and 1975 with the aim of rendering safe the quarry pits. During this time a total of 121,420No. explosive items (352 tons) and 213,881No. items of ordnance scrap were cleared.

 Clearance certificates were issued for Disposal Areas No. 1 and No. 4 during this period with a final summary of the ordnance removed being issued in November 1975.

UXO Hazard Assessment for Preliminary Ground Investigation

The Table below, reproduced as Table 5 in the main report, provides a UXO hazard assessment for each of the proposed preliminary ground investigation locations.

Table UXO hazard assessment for preliminary ground investigation UXO Hazard GI Location Potential UXO Hazard Assessment BH1 Open ground Low BH2 Open ground Low BH3 Open ground Low BH4 Open ground Low BH5 Open ground Low BH6 Open ground Low BH7 Open ground Low BH8 Open ground Low BH9 Slate piles (within quarry pit) Moderate BH10 Slate piles (quarry surface) Low BH11 Open ground Low BH12 Open ground Low BH13 Open ground Low BH14 Open ground Low BH15 Open ground Low

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BH16 Open ground Low BH17 Open ground Low SP1 Slate piles (quarry surface) Low SP2 Open ground Low SP3 Slate piles (within quarry pit) Moderate SP4 Slate piles (within quarry pit) Moderate SP5 Slate piles (within quarry pit) Moderate TP1 Open ground Low TP2 Open ground Low TP3 Open ground Low TP4 Open ground Low TP5 Open ground Low

The Figure below, reproduced as Figure 18 in the main report, is a UXO hazard zone plan of the Site showing the proposed ground investigation locations. A more detailed plan is provided in Zetica Drawing P3300-12-DWG02-B.

Figure UXO hazard zone plan of the Site (with GI Locations)

Source: Client Not to Scale

Very Low Low Moderate

Legend Site High Very High boundary

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Risk Assessment

The Table below, reproduced as Table 6 in the main report, provides a UXO risk assessment for potential works on the Site. Further details on the methodology for the risk assessment, and the ratings given, are provided in Section 9.1 of the main report.

Table UXO risk assessment for the Site

Potential UXO

Potential Works PE UXO Risk

PD PD

Hazard Risk

Rating

P = PE xP = PE

Severity

Likelihood

Shallow Excavations 2 2 4 2 4 8 Moderate Deep Excavations 5 3 15 4 5 20 Very High Bomb Pile Boreholes 4 4 16 4 5 20 Very High Tunnelling/HDD 5 4 20 5 5 25 Very High Shallow Excavations 1 2 2 1 4 4 Low Deep Excavations 2 2 4 2 4 8 Moderate UXO in Pit 2B Boreholes 2 3 6 3 4 12 Moderate Tunnelling/HDD 3 3 9 3 4 12 Moderate Shallow Excavations 1 2 2 1 4 4 Low UXO in Quarry Deep Excavations 2 2 4 2 4 8 Moderate Floors (crevices) Boreholes 2 3 6 3 4 12 Moderate Tunnelling/HDD 3 3 9 3 4 12 Moderate Shallow Excavations 1 2 2 1 4 4 Low UXO in Quarry Slate Deep Excavations 2 2 4 2 4 8 Moderate Piles Boreholes 2 3 6 3 4 12 Moderate UXO in Surface Slate Excavations 1 1 1 1 4 4 Low Piles Boreholes 1 1 1 1 4 4 Low Excavations 1 1 1 1 4 4 Low UXO at Surface Boreholes 1 1 1 1 4 4 Low PE (Probability of Encounter), PD (Probability of Detonation), P (Overall Probability) Shallow Excavations defined as <1.0m. It should be noted that there will no UXO risk to any tunnelling activities within the existing bedrock.

Risk Management Recommendations – Ground Investigation

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Typically, no other measures are considered essential in areas with an identified low UXO hazard level. If UXO is discovered in an area with an identified low UXO hazard level, a re-assessment of the hazard level for that area would be recommended. Moderate Hazard Areas The raising of awareness for site staff (as per the low hazard areas) is considered essential. For the excavating of the sample pits with a moderate UXO hazard level, Explosive Ordnance Clearance (EOC) Engineer supervision is recommended. The EOC Engineer will carry out a visual assessment on any suspect items uncovered during the excavation task and classify them as potential UXO or other material. It is recommended that any drilling into areas of waste slate/materials is avoided and that non- intrusive techniques are used where practical. If drilling in these areas cannot be avoided, then consideration should be given to remote-controlled drilling techniques to ensure the safety of the operative in the unlikely event that an item of UXO is encountered and detonated. Alternatively, the slate waste at any borehole locations can be removed under EOC Engineer supervision before drilling. Once undisturbed bedrock is penetrated there is no UXO risk. Further risk mitigation measures are available if a zero tolerance to risk is adopted. Zero tolerance is typically adopted for sites that have safety critical infrastructure, such as nuclear establishments and oil refineries.

Risk Management Recommendations – Future Works

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By using a competent commercial EOD company, EOD operations are not only undertaken using health and safety best practice, but also with due cognisance to commercial and public relation issues that focus on minimising disruption to all those on site and the surrounding areas. With the flexibility to use more extensive and commercial blast mitigation techniques, the planning of a commercial EOD operation is less involved due to the ability to reduce the impact and extent of an evacuation zone (if any). For dealing with the Bomb Pile, a fixed EOD facility would be established on a remote part of the Site. The construction would typically involve a 2m deep trench, stepped at 1m, lined with 1 tonne sandbags to prevent the walls of the trench collapsing. ISO shipping containers are typically used around the outside of the trench. These containers would be covered with 1 tonne sandbags to form a protective wall around the trench. The Figure below, reproduced as Figure 19 in the main report, is a plan of a typical fixed EOD facility.

Figure Plan of fixed EOD facility

Source: Sitesafe Alliance

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The Bomb Pile would be investigated using a combination of manual and mechanical excavation, with an EOC Engineer present to perform a visual inspection of all items uncovered. Any UXO (if safe to move) would be transported from the Bomb Pile to the fixed disposal site where further layers of protection would be added, using 1 tonne sandbags placed above the UXO. The quantity of 1 tonne sandbags would be sufficient to reduce the effects of blast and fragmentation from the UXO detonation. UXO in Quarry Pits (Crevices) Whilst there are records of crevices in the floors of the quarries on the Site, their exact locations are unknown. Records indicate that these crevices were used for disposal of ordnance and ordnance scrap. It is not known whether all the crevices within the pits were cleared of live ordnance. For any excavations around identified crevices, EOC Engineer supervision is recommended. It is recommended that any drilling into areas of waste slate/materials is avoided and that non- intrusive techniques are used where practical. If drilling in these areas cannot be avoided, then consideration should be given to remote-controlled drilling techniques to ensure the safety of the operative in the unlikely event that an item of UXO is encountered and detonated. Alternatively, the slate waste at any drilling locations can be removed under EOC supervision before drilling. Once undisturbed bedrock is penetrated there is no UXO risk. UXO in Quarry Pits (Slate piles) For excavations within the slate piles in the quarry pits, EOC Engineer supervision is recommended. If significant quantities of UXO are found at a location then an EOD operation may be necessary to fully mitigate the risk. For any boreholes, a remote-controlled drilling technique is recommended as outlined above. Reusing Slate Waste from Quarry Pits It is understood that waste from the quarry pits will be used in the construction of the Glyn Rhonwy dam. Given that the slate piles in the quarry pits may contain ordnance, any slate waste removed from the pits for use in the dam construction should be subject to visual inspection by an EOC Engineer. Alternatively, waste from the slate piles at the quarry surface (which have a low UXO risk) could be used.

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Potential UXO in Pit 2B This pit has been completely infilled. If more information on its extent is required, we would recommend that non-intrusive geophysical techniques are first considered in preference to drilling. Techniques such as electromagnetic profiling alongside electrical resistivity imaging or seismic refraction, may provide information on the lateral extent and depth of waste. Records indicate that the base of the pit is filled with ordnance scrap, above which is a layer of slate fill. Above this is a layer of domestic waste, with the remainder of the pit backfilled with slate, meaning that the more significant risk will be at depth. The risk to those undertaking shallow excavations or similar work can be mitigated through UXO awareness briefings to site staff. Other risk mitigation methods are required for materials at depth that may contain UXO. This may just entail supervision by an EOC Engineer depending on the proposed works. For any boreholes, a remote-controlled drilling technique is recommended as outlined above.

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UXO DESK STUDY & RISK ASSESSMENT

Glyn Rhonwy, Llanberis, Gwynedd

Note: To aid the reader of this report, Zetica has colour coded each paragraph. Paragraphs with black text on a white background are paragraphs that provide site-specific information or information specifically researched as part of this project.

Paragraphs in a dark blue text with a grey background are paragraphs containing background information or explanations which may appear as standard text in all similar reports.

1 INTRODUCTION

1.1 Project Outline

The aim of this report is to gain a fair and representative view of the UXO hazard for the Site and its immediate surrounding area in accordance with the Construction Industry Research and Information Association (CIRIA) ‘Unexploded Ordnance (UXO), a Guide for the Construction Industry’. This hazard assessment includes:

 Likelihood of ordnance being present.  Type of ordnance (size, filling, fuze mechanisms).  Quantity of ordnance.  Potential for live ordnance (UXO).  Probable location.  Ordnance condition. It is essential to note that the effects of military activity will often extend beyond the source of the activity. For example, a base for armed forces may use surrounding areas of open land outside the official or recorded military boundaries for practice and military related activities. In addition, World War One (WWI) and World War Two (WWII) aerial bombardment was not discrete. ‘Pinpoint’ targeting did not exist in WWI or WWII. The effects of bombardment would be apparent in areas around the intended target. It is for these reasons that it is important to address military activity both on the Site and in the relevant surrounding areas. It should be noted that some military activity providing a source of UXO hazard may not be readily identifiable and therefore there cannot be any guarantee that all UXO hazards on the Site have been identified in this report.

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1.2 Report Structure

Section 2 of this report gives a brief description of the Site and its location. Section 3 outlines the sources of information that have been used in compiling the report. Section 4 provides a general history of the Site, from its establishment as a slate quarry until the present day. Section 5 details the operational history of the Site, including its use for both ordnance storage and disposal. Section 6 describes the nature of the Explosive Ordnance Disposal (EOD) operation that took place on the Site during the 1970s. It details the extent to which the operation has mitigated the UXO risk on the Site and highlights areas where a residual risk may remain. Section 7 describes the ordnance types most likely to remain on the Site. Section 8 provides a UXO hazard assessment for the Site. Section 9 provides a UXO risk assessment for the Site and outlines the recommended risk mitigation options.

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2 THE SITE

The Site is centred on Ordnance Survey National Grid Reference (OSNGR) SH 566608, approximately 1.2km northwest of Llanberis. The Site comprises part of the disused Glyn Rhonwy slate quarries, with associated slate waste tips, access roads and hardstanding. The eastern end of the Site comprises a track leading to Llyn Padarn. Figure 1 is a Site location map and Plate 1 is a recent aerial photograph of the Site.

Figure 1 Site location map

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Plate 1 Recent aerial photograph of the Site

Source: Bing Maps Not to Scale Legend Site boundary

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3 SOURCES OF INFORMATION

3.1 Historical Information

With most locations, the potential presence of UXO as a result of enemy action, unauthorised disposal or unrecorded military activity can never be totally discounted. Detailed records of military activity are rarely released into the public domain. Even when military information is made public there may be gaps in the records because files have been lost or destroyed. Records for periods such as WWII are only as detailed and accurate as the resources and working conditions would allow at the time. Densely populated areas tend to have a greater number of records than rural areas. Such records may be inaccurate due to the confusion surrounding continuous air raids. Press records can supplement local information, although this source of information must be treated with caution, as inaccuracies do exist, either inadvertently or intentionally in order to confuse enemy intelligence. Classified official records can sometimes be considered inaccurate for the same reason. Recent research indicates that England alone had 17,434No. recorded defence sites, of which 12,464No. were classified as defensive anti-invasion sites. The precise locations of many of these sites are still to be identified, illustrating the scale of the problem when establishing potential risks from limited historical data.

Zetica Ltd researched the military history of the Site and its surrounding area utilising a range of information sources. The main sources of information are detailed in the following sections and referenced at the end of this report.

3.2 Zetica Ltd Defence Related Site Records

Zetica Ltd’s in-house records were consulted, including reference books and archived materials from past work in the region. Relevant documents have been cited within the bibliography of this report.

3.3 Zetica Ltd Bombing Density Records and Maps

Reference has been made to the Zetica Ltd bomb risk maps located on Zetica Ltd’s website (http://www.zetica.com/uxb_downloads.htm).

3.4 Ministry of Defence and Government Records

Recently-released Ministry of Defence (MoD) records relating to the EOD operation at the former RAF Llanberis were consulted.

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3.5 Other Historical Records, Maps and Drawings

Numerous reference documents including historical maps, aerial photographs and drawings have been consulted from sources such as the National Archives, the Royal Commission on the Ancient & Historical Monuments of Wales (RCAMW), the Central Register of Air Photography in Wales and the Defence of Britain Project. The British Geological Survey (BGS) was consulted for borehole information.

3.6 Local Authority Records

Information has been sought from Gwynedd Council.

3.7 Local Record Offices and Libraries

Information was obtained from Caernarfon Record Office.

3.8 Local Historical and Other Groups

Local history groups and archaeological bodies, including the Gwynedd Archaeological Trust, were consulted.

3.9 Data Confidence Level

In general, there is a high level of confidence in the researched information sources used for this report. Exceptions to this are specifically detailed in the text of the report.

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4 SITE HISTORY

4.1 General History

Glyn Rhonwy Slate Quarry opened in the 1840s and by the end of the 19th century several large pits had been excavated on the Site, connected to each other by a series of tunnels. This is shown on the historical map of 1889 (Figure 2). The London & North Western Railway (LNWR) ran across the eastern part of the Site and this had narrow gauge rail links to the quarry.

Figure 2 Historical map, 1889

The slate quarrying resulted in the accumulation of large slate tips on the Site, as shown on the historical map of 1914 (Figure 3).

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Figure 3 Historical map, 1914

Legend Site boundary

Figure 4 is an historical map dating from 1920. It includes annotations by the MoD outlining the areas of land to be purchased and requisitioned for use as an ordnance depot. Boundaries of extant mineral workings are also included, the main Glyn Rhonwy Slate Quarry having closed in 1930.

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Figure 4 Historical map, 1920 (with MoD annotations)

Source: National Archives Not to Scale

Site boundary MoD purchased MoD requisitioned Legend Mineral workings

Figure 5 is an Air Ministry plan, dated 25th November 1938, highlighting the land finally acquired for the ordnance depot, which became known as RAF Llanberis (see Section 5.1).

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Figure 5 Historical map showing land requisitioned for RAF Llanberis, 1938

Source: National Archives Not to Scale

Legend Site boundary MoD land

The easternmost quarry at Glyn Rhonwy, adjacent to the Site, was converted into an underground ordnance depot and backfilled with slate. Part of this collapsed in 1942, resulting in the whole area being cleared of ordnance and debris.

Plate 2 is an aerial photograph dated the 10th May 1946. It shows the extent of RAF Llanberis, with a number of dispersed ordnance stores on either side of the Glyn Rhonwy Slate Quarry.

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Plate 2 Aerial photograph, 10th May 1946

Source: RCAHMW Not to Scale

Legend Site boundary

The historical map of 1953 (Figure 6) shows the change in layout to the easternmost quarry. The other pits remained unchanged and were used during this period for disposing of surplus ordnance (see Section 5.2).

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Figure 6 Historical map, 1953

Legend Site boundary

Plate 3 is an aerial photograph dating from 1954, shortly before the closure of RAF Llanberis. The majority of the WWII storage facilities had been removed, with only few ancillary buildings remaining. A small amount of ammunition remained stacked in the open area of the easternmost quarry.

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Plate 3 Aerial photograph, 1954

Source: RCAHMW Not to Scale

Legend Site boundary

RAF Llanberis closed in 1956. Thousands of tons of live and scrap ordnance was left in the quarries and the whole area was fenced off, with warning signs erected. The fence line surrounding the quarry pits can be seen in Plate 4, an aerial photograph dating from 1962.

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Plate 4 Aerial photograph, 1962

Source: RCAHMW Not to Scale

Legend Site boundary

During the 1960s, the security at the quarry was breached and illegal dumping took place. Additionally, ordnance was stolen from the quarry pits and removed offsite. This led to an incident where several people in Anglesey were injured when an item stolen from the former RAF Llanberis detonated. In the late 1960s, it was decided to attempt an EOD operation at the former RAF Llanberis, including the destruction and removal of all remnant ordnance in the quarry pits. This task began in 1969 and was completed in October 1975 by No. 71 Maintenance Unit (MU) Bomb Disposal Flight (see Section 6.1). Figure 7 is the historical map for 1972, made during the EOD clearance period.

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Figure 7 Historical map, 1972

Plate 5, an aerial photograph dating from 1973, shows the main quarry on the Site now emptied of water (note the ‘tide mark’) as part of the EOD operation. The shadow of the cliff on the southern side of the quarry also gives an indication of its height.

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Plate 5 Aerial photograph, 1973

Source: RCAHMW Not to Scale

Legend Site boundary

Plate 6 is an aerial photograph showing the Site after the completion of the EOD task. Note the landscaping of the area and the fact that the main quarry on the Site is now filling with water.

Plate 6 Aerial photograph, 1986

Source: RCAHMW Not to Scale

Legend Site boundary

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Since 1986, several of the slate tips on the quarry surfaces have been removed and large parts of the Site were landscaped for a proposed industrial development. This included the construction of new access roads around the quarries.

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5 SITE OPERATIONS

5.1 RAF Llanberis Ordnance Depot

The former Glyn Rhonwy slate quarries were acquired by the Air Ministry in 1939 for the storage of 18,000 tons of bombs, in addition to a range of other ordnance for the RAF. RAF Llanberis opened in May 1941 under the control of No. 31 MU. The easternmost slate quarry at Glyn Rhonwy, located adjacent to the Site boundary, was chosen as the original storage location. Ordnance was stored in two-storey concrete bays within a network of tunnels. The storage area was backfilled with 40 feet of slate to reach the surface of the quarry pit. Stores were brought in through a narrow-gauge railway, connected to the mainline by a tunnel. Whilst RAF Llanberis was an operating bomb store it would have been established with the facilities for the disposal of unserviceable explosive items. Given the amount of ordnance at the store it is likely that disposals would have taken place. These would have occurred in the existing quarry pits (see Section 5.2 below). The first consignment of ordnance arrived at RAF Llanberis in June 1941.

On the 25th January 1942, two-thirds of the depot collapsed under the weight of the slate backfill, burying approximately 14,000 tons of ordnance, comprising 14% of RAF stock at the time. The entire area was subsequently cleared by the 22nd October 1942 and most of the ordnance was salvaged for future use (only 19No. bombs out of approximately 75,000No. were damaged beyond repair). After this, ordnance storage was moved out of the tunnels and into the open, either in the area of the collapse or on the surface around the perimeters of the quarries. This covered a large area, as shown in Plate 7. Stacks of Small Arms Ammunition (SAA) are evident in the area of the collapse.

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Plate 7 Aerial photograph of RAF Llanberis, 10th May 1946

Source: RCAHMW Not to Scale Legend Site boundary Original bomb store

Figure 8 is a plan dating from 1946 further demonstrating the extent of the ordnance storage on the Site and in the surrounding area.

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Figure 8 Plan of RAF Llanberis, 1946

Source: RAF Museum Not to Scale Legend Site boundary Outdoor Bomb Store Areas

Figure 9 is a plan and section dating from post-1942 showing the reduced extent of the underground bomb store adjacent to the Site.

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Figure 9 Plan of bomb stores at RAF Llanberis, post-1942

Source: RAF Not to Scale

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RAF Llanberis continued to store and issue ordnance throughout the remainder of WWII. Immediately after the war, because of its secure storage and rail connections, it was temporarily used as a storage facility for 14,000 tons of bombs filled with tabun (a toxic nerve gas) which had been seized from German ammunition depots. These were transferred to RAF Llandwrog between August 1946 and July 1947. Conventional ordnance continued to be stored at the depot post-WWII, although in smaller quantities. During this time, surplus and faulty ordnance was disposed of in the adjacent quarry pits (see Sections 5.2 and 6). In 1955, No. 31 MU moved to RAF Llandwrog and the remaining ordnance at RAF Llanberis was moved to other depots, disposed of in the quarry pits or stockpiled for deep sea dumping. By 1955 the remaining stores mainly consisted of SAA, detonators, fuzes and other components. The majority of the former storage areas were subsequently demolished and access to the underground bomb store was blocked. None of the ordnance storage areas at RAF Llanberis are considered to provide a source of UXO hazard to the Site. Associated disposal activities are detailed in the Section below.

5.2 Ordnance Disposal at RAF Llanberis

The first records of authorised disposal at RAF Llanberis date from June 1943 when the RAF School of Explosives was transferred to No. 31 MU. Part of the instruction for the School was the disposal of IBs in the western quarry pits at Glyn Rhonwy. This included the Site. In November 1943, for instance, 571 tons of 4lb and 25lb IBs were disposed of by burning in the pits. Between December 1943 and September 1944, 173,000No. 25lb IBs and 81,000No. 4lb IBs were disposed of at RAF Llanberis. From 1944, more formalised disposal of conventional weapons took place at RAF Llanberis with surplus and unserviceable ordnance brought to the depot for destruction in the pits. This included HE bombs, IBs, fuzes and detonators. Figure 10 shows the location of the WWII disposal pits at RAF Llanberis. They were numbered from 1 to 8, with disposal Pits 1, 2, 3 and 4 on the Site, in addition to a small section of Pit 5.

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Figure 10 Plan showing ordnance disposal pits at RAF Llanberis, WWII

Source: National Archives Not to Scale Legend Site boundary

It is clear from Figure 10 that the identified burning pit was not assigned a number at this time and that subsequently it became Pit 3B after WWII. This un-numbered disposal pit was clearly separate from the slag pile that is recorded to have accumulated in Pit 3C (see below). On the basis of Figure 10, Pit 3C appears not to have been used for disposal during WWII. During WWII the pits were designated for the destruction of particular types of explosive materials, as listed in Table 1.

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Table 1 EOD designation of numbered disposal pits, WWII Pit No Use Pit 1 (on the Site) Demolition of 25lb IBs Pit 2 (on the Site) Used as a rubbish pit with no demolition or disposals Pit 3 (on the Site) Used as a rubbish pit with no demolition or disposals Pit 4 (on the Site) Demolition of target indicators Pit 5 Demolition of IBs and fuzes Pit 6 Demolition of detonators Pit 7 Demolition of signal cartridges Pit 8 Demolition of detonators

The evidence provided by the records of later recoveries and consequent disposals indicate that this designation was not fully adhered to. It is presumed that after WWII, when the area was used for the wholesale destruction of surplus stock, the sheer volumes of ordnance caused problems and new orders were issued for the use of particular pits. Between 1946 and 1955, large amounts of ordnance continued to be disposed of at the quarry pits at RAF Llanberis. The pits in use during WWII were retained, with more added to the west. Figure 11 is a post-WWII plan, dated the 31st March 1970, showing 4No. separate disposal areas, each comprising of lettered pits. Bomb Disposal Area No. 2, comprising 3No. pits, was on the Site, in addition to Pit 1B and a small part of Pit 3A.

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Figure 11 Plan showing post-WWII disposal areas and pits at RAF Llanberis

Source: National Archives Not to Scale Legend Site boundary

The typical method of disposal was to start a large fire at the base of the quarry before tipping ordnance down chutes at the surface into the burning pit. If the fire became extinguished, it was re-ignited by dropping a cluster of IBs into the pit. Records indicate that this disposal was not always successful. Firstly, ordnance would often get lodged on rock shelves, in slate piles or within crevices when tipped into the quarry, never making it into the burning pit. Secondly, when the ordnance was being destroyed in the pit there would occasionally be minor explosions which resulted in UXO being discharged into crevices or onto land surrounding the quarries. There are also records stating that some of the ordnance dropped into the pits was not completely destroyed and remained live, mixed in with the burnt debris. In March 1955, No. 31 MU was transferred to RAF Llandwrog and RAF Llanberis became a maintenance sub-unit.

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Between 1955 and 1956, ‘Operation Sandcastle’ took place. This involved the dumping in the Irish Sea of the 14,000 tons of 250kg tabun bombs that had once been stored at RAF Llanberis. Due to the need for extra disposal capacity, Llanberis remained open until 1956. Records indicate that during this period ordnance disposed of mainly consisted of IBs, fuzes, detonators and cartridges. During the late-1960s, a former Chief Technician from RAF Valley made a formal statement indicating that Phosgene-filled bombs had been dumped in the disposal pits at RAF Llanberis in the period 1953/4.

A Board of Inquiry was set up between the 29th October and the 26th November 1969 to verify the statement and reported on the 30th January 1970. The Board concluded that the Chief Technician was mistaken and that at no time had Phosgene bombs or any other chemical weapons been disposed of at RAF Llanberis. The Board of Inquiry also found that all German chemical weapons appeared to have been successfully removed from RAF Llanberis to RAF Llandwrog before being sea dumped. Ordnance disposal ceased at RAF Llanberis in 1956, the site was closed and the quarries secured with high wire fencing. Disposal activities at RAF Llanberis are considered to provide a source of UXO hazard within the quarry pits on the Site (see Sections 6 and 8 for further details).

5.3 Other Sources of UXO

5.3.1 Small Arms Ranges

Small arms ranges (such as rifle ranges) and close combat ranges (such as mortar and grenade ranges) are likely to provide a significant source of UXO. It should be noted that even on small arms ranges, larger munitions such as mortars or grenades cannot be discounted.

There was a miniature rifle range at RAF Llanberis during WWII, located approximately 0.2km southeast of the Site. This indoor location is likely to have been used for small-bore rifles, and perhaps pistols, only. There was also a miniature indoor range at Llanberis Drill Hall, approximately 1.4km southeast of the Site. These ranges are not considered to provide a source of UXO hazard to the Site.

5.3.2 WWII Bombing

Table 2 gives details of the overall bombing statistics recorded for the Local Authority Districts of the Site and surrounding districts. During WWII, the Site was located in the Rural District (RD) of Gwyfrai. The figures for West Ham CB, generally considered to represent a high regional bombing density, are included for comparison.

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Table 2 Bombing Statistics Bombs Recorded

Area High Parachute Bombs per 405ha Other Total Explosive Mines (1000 acres)

Gwyrfai RD 26 1 0 27 0.3 Caernarvon MB 0 0 0 0 0.0 West Ham CB 1,498 45 47 1,590 334.0

No records have been found indicating that bombs fell on or in the vicinity of the Site during WWII. WWII bombing is not considered to provide a source of UXO hazard to the Site.

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6 EXPLOSIVE ORDNANCE CLEARANCE ACTIVITIES

6.1 No. 71 MU EOD Operation, 1969-1975

After the closure of RAF Llanberis in 1956, the former quarry pits used for ordnance disposal were fenced off to prevent public access. Plate 8, an aerial photograph dating from 1962, shows Disposal Area No. 2 and Pit B of Disposal Area No. 1, on the Site. Some of the remnant RAF buildings are still extant. For example, the Nissen huts in the centre of the Site. The pits on the Site have been labelled with their final designations. Pits 2A and 2C were always connected and 2B was always separate. The positioning of Pit 2B is important as this has been completely infilled and is no longer visible on the ground.

Plate 8 Aerial photograph of Disposal Area No. 2, 1962

2A 2C

Source: RCAHMW Not to Scale

Legend Site boundary Pit numbers: 2A

At the end of 1969, after the recommendation of a Board of Inquiry, it was decided that the security of the site was not guaranteed and consequently a working party was set up to formulate a plan. This followed several break-ins at the quarry pits, including one in which an item of UXO was stolen and taken to Anglesey where it later detonated, injuring several people.

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Flight 5131 (BD) from No. 71 MU at RAF Bicester was formed to carry out an EOD operation, task commitment No. MC/BD/12080/69, to render safe and clear the remaining ordnance from the quarries. The individual quarries were given letters and placed into numbered Disposal Areas, as shown in Plate 9.

Plate 9 Oblique aerial photograph showing former disposal pits at RAF Llanberis

Source: After the Battle Not to Scale

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Note that Pit 2B, shown on the Site in Plate 8, appears to have been mostly infilled and covered, with just a wall still apparent. A working party initially carried out a reconnaissance of the pits and found that explosive materials were scattered around their surfaces, as well as on the floors of those that were accessible. It was concluded that some of the explosive materials had probably been thrown back out of the pits during demolition operations and not cleared. It was also concluded that no clearance operations had been carried out when RAF Llanberis finally closed in 1956. During the reconnaissance operation some limited clearance of some of the quarry ledges, where considerable quantities of UXO had become lodged during routine disposal operations, took place. Figure 12 is a plan of the disposal pits on the Site and the tunnels connecting the individual pits together.

Figure 12 Plan of disposal pits and connecting tunnels at RAF Llanberis, 1969

Source: Caernarfon Record Office Not to Scale Legend Site boundary

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The clearance plan was designed to take place in 6No. phases, allowing access through the connecting tunnels and therefore confining all operations to the former quarry pit floors. Phase I lasted from July 1969 – May 1970. Phase II lasted from June 1970 – December 1970. Phase III lasted from January 1971 – June 1972. Phase IV lasted from July 1973 – March 1975. Phase V lasted from July 1973 – February 1975. Phase VI lasted from March 1973 – March 1975. Due to operational difficulties, some of these phases overlapped. To allow access to the various parts of the quarry pits a ramp was constructed into Pit 2A and from there workers could use the tunnels that originally connected the different pits together (see Figure 12 above). A series of water tests were carried out assessing the amount of heavy metals (Sn, Cu, Pb, Zn and Ba) present together with any organo-phosphorus compounds. Whilst the inventory of metals sought was small, the documentary evidence found shows that these tests were all negative. An additional set of chemical tests was carried out regarding the reactions between the chemicals in smoke floats: zinc oxide (ZnO), calcium silicide (CaSi2) and possibly the frequently found additive, hexachloroethane (C2Cl6), with water. A series of experiments were designed to look at the toxicity of the chemicals and their reaction products to fish, particularly species of trout. Whilst all of the dilutions used in several experiments caused death to the fish, there was no evidence that this had happened within the environment of the Site. In March 1970, the clearance of the quarry pits began. Phase I comprised the establishment of the operational facilities and an initial surface clearance of all of the quarry areas in order to allow for safe working conditions. Any live explosives were destroyed, either by burning or detonation, with the residues and any inert ordnance scrap either channelled into crevices or deposited in Pit 2B for final burial. The main items encountered were IBs, detonators for HE bombs and various fuzes, much of which was in a hazardous condition. Other ordnance included British and American HE bombs. Standing Orders for RAF Llanberis from the start of the clearance in 1969 set limits on the amount of ordnance that could be stockpiled and the quantities of explosive and incendiary materials that could be disposed of at any one time. The limits for demolitions were 10lb of HE in Pit 3B, and 500lbs of incendiary material to be burnt in Pit 3A. The following sections describe the clearance operations undertaken in each designated disposal area.

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6.2.1 Disposal Area 2

Disposal Area No. 2 was entirely within the Site boundary (see Figure 12). Its clearance was a very complex task which was recognised early. The floors of both Pits 2A and 2C were not directly accessible and were partly flooded. Pit 2C had been allowed to flood after closure so that it formed a large lake, recorded by the EOD team as being up to 55 feet (17m) deep, therefore securing the ordnance below.

The initial work to clear Disposal Area No. 2 commenced on the 5th September 1969 and by the 1st October 1969 Pits 2A and 2B were deemed to be clear of explosives. Pit 2A Once the surface areas of Pit 2A were cleared, Royal Engineers (RE) personnel commenced construction of an entry ramp into the floor area of Pit 2A from which Pit 2C could be reached. The area of Pit 2A is recorded as containing no explosives, only inert material. All dumped inert scrap was removed and the next steps to reach the floor could be taken. It is also recorded that the floor of Pit 2A had a large crevice in it which could be used for the burial of ordnance scrap. It was agreed that this could then be buried under slate waste that could be moved or blasted off the sides of the pit. The construction of the ramp into Pit 2A, shown in Plate 10, was accomplished by using tracked vehicles. Specialist mechanical diggers were also employed which could be operated from ledges on the sides of the quarry in order to remove ordnance-related materials.

Plate 10 Photograph of ramp from Pit 2A into Pit 2C, RAF Llanberis

Source: National Archives

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Pit 2B Pit 2B was assessed to contain only non-explosive scrap and clearance was completed on the 1st October 1969. The pit was then designated as the destination for most of the inert ordnance scrap produced by the EOD operation. For instance, 161No. 4lb smoke bombs, 172No. 10lb practice bombs and 20,000lb of IB and pyrotechnic scrap (all deemed inert) are recorded as having been dumped in Pit 2B. The methods for determining what ordnance scrap was, and whether any live explosives remained within such scrap, were not as rigorous as the standard practices of today. Given the volume of ordnance that required clearance, and the working practices of the period, it is possible that some explosive items were inadvertently disposed of in Pit 2B and residues may have remained within some of the casings. Once the EOD operation had finished in 1975 the pit floor was covered with 1m of quarry waste. For a short while the pit was used for domestic waste disposal and it was then completely backfilled with slate debris and covered. Pit 2C The clearance of Pit 2C was in Phase IV of the overall clearance plan and commenced on the 23rd January 1973. In order to assess the problem in the Pit 2C lake, Royal Navy (RN) Bomb Disposal divers carried out a topographic survey of the floor of the lake and confirmed the presence of thousands of tons of ordnance within it, including large numbers of Anti-Aircraft Device (AAD) Bombs. During this operation the RN divers specifically identified 1No. 1,000lb HE bomb in the centre of the quarry, 1No. leaking 150lb HE bomb on a ledge and a pile of No. 36 hand grenades. To provide access to the ordnance, the lake was drained of approximately 20 million gallons of water. The lake was emptied by April 1973 and the remnant ordnance, which included the live HE bombs, was progressively cleared over the next two years until the operation concluded in October 1975. The approximate 3,000No. tons of ordnance identified as being present was recovered at a rate of 10 tons per day. Plate 11 shows the state of the bottom of Pit 2C as the water levels fell. Ordnance can be seen scattered in haphazard heaps across the floor.

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Plate 11 Photograph of ordnance clearance Pit 2C, RAF Llanberis

Source: After the Battle Plate 12 is a photograph of part of the base of the Bomb Pile encountered on the southeast side of Pit 2C once the water had been drained. This photograph gives an impression of what was encountered prior to the clearance and the enormity of the task.

Plate 12 Photograph of the Bomb Pile in Pit 2C, RAF Llanberis

Source: National Archives

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Smaller ordnance items were destroyed in situ and a burning license was obtained for Pit 2C for the trepanning and steaming out of larger bombs, including 100lb American HE bombs. Some of the ordnance (notably 25lb IBs) discovered in Pit 2C was initially planned to be stockpiled under guard until February 1974 for disposal by sea dumping. Plate 13 demonstrates this. However, no records have been found confirming that stockpiled items were sea-dumped and they may have ultimately been destroyed in situ.

Plate 13 Photograph of stacked 25lb IBs in Pit 2C, RAF Llanberis

Source: National Archives Table 3 illustrates some of the ordnance types cleared from Pit 2C during the first three-month period of the clearance operation.

Table 3 Live items found Pit 2C, 1st January 1973 – 31st March 1973 Item Number Bombs AAD 475 Exploders 3 Grenades No.36 82 Primers 1oz 4 These items are all indicated to have been destroyed in situ. A wide variety of other ordnance types were eventually recovered from Pit 2C. These included smoke and flame floats, a number of different flare types (ranging from 4.5” to marine markers), a variety of fuzes, booster charges and detonators. A number of different types of radio destructors were also recovered.

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The Bomb Pile on the southeast side of Pit 2C was progressively cleared from the top. Live IBs were taken to Pit 3B for burning. It proved a difficult and time-consuming task and at some point a decision was made to halt the process when the frequency of live encounter reached 0.5%. It is not evident why this figure was accepted and how it was determined to have been reached. Once this level of encounter was deemed to have been reached, the operation was halted and the remaining parts of the Bomb Pile were covered with slate waste. This means that there are still live ordnance items within the remainder of the pile, constituting a significant source of UXO hazard. The remaining inert items and scrap were pushed into crevices and the quarry floor was covered with approximately 2m of sterile slate scree and flattened. The lake was allowed to reform, with the water soon returning to its natural level.

6.2.2 Disposal Area 1

Pit B of Disposal Area No. 1 was located on the Site (see Plate 8). Pit A, which comprised the old underground bomb store of RAF Llanberis, was located immediately adjacent to the Site boundary. Pit A had been cleared of ordnance after the 1942 collapse and was again cleared as part of the post-WWII EOD operation, forming a major part of Phase I. The clearance comprised both a visual and instrument search and the open section of the old bomb stores was one of the first areas to be addressed. Pit B, which contained explosive material scattered across the floor, was cleared subsequently. This involved the destruction of some items of UXO in situ, with the resulting ordnance scrap either channelled into crevices within the quarry pit or removed for dumping in Pit 2B. Figure 13 details the ordnance recovered from Disposal Area No. 1.

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Figure 13 Ordnance recovered from Disposal Area No. 1

Source: Caernarfon Record Office Disposal Area No. 1 was declared safe in May 1970 and a clearance certificate was issued on the 6th July 1970, as shown in Figure 14.

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Figure 14 Clearance Certificate for Disposal Area No. 1

Source: Caernarfon Record Office

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6.2.3 Disposal Area 3

The majority of Disposal Area No. 3, which comprised of 3No. pits, was located to the west of the Site (see Figure 12). A small part of Pit 3A encroached upon the Site. Pits 3A and 3B Pits 3A and 3B were partly filled with rock debris. Pit 3A was considered the major problem because of the extent of ordnance scattered across the floor. Pit 3B was used as a demolition area for any live items discovered in either of the pits and from Pit 2C. Large quantities of incendiary material were also subjected to disposal by burning in Pit 3A.

On the 1st January 1971 work started on the entrance tunnel to Pit 3A, which connected to Pit 2C.

On the 12th May 1971 work began at the western wall of Pit 3A to locate the connecting tunnel to Pit 3B. By April 1972 the clearance of Pit 3A was almost complete and the pit was in use for the demolition of small stores. Initially it was planned that ordnance scrap produced in these pits would be pushed into crevices in the floor of the quarry in Pit 3A and then buried. Other evidence suggests that the ordnance scrap was taken to Pit 2B.

On the 2nd November 1972 clearance of Pits 3A and 3B was declared complete. The quarry floors were covered with approximately 1m of sterile slate scree and flattened. Pit 3C

On the 25th October 1971 the tunnel between Pit 3B and 3C was located, enabling clearance of the quarry floor. In April 1972 it was reported that surface clearances had produced approximately 2 tons of live ordnance which were stacked in the pit to await destruction. The majority of ordnance comprised incendiary materials, in addition to large quantities of American fuzes. Pit 3C was the location of a pile of magnesium slag produced during the burning of IBs and other incendiary materials. During clearance of the slag heap it was discovered that the previous disposal process had been inefficient and was incomplete, with live and semi- destroyed material still in place. Unburnt magnesium powder was interspersed with live detonators and other explosives. Table 4 illustrates some of the ordnance types cleared from Pit 3C during a three-month period.

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Table 4 Live items found Pit 3C, 1st January 1973 – 31st March 1973 Item Number Bombs Incendiary 4lb 9,850 Bombs Incendiary 4lb X-type 107 Bombs Practice 10lb 96 Detonators Aircraft bomb 35 Fuzes AN-M100 925 Fuzes AN-M103 100 Fuzes AN-M120 760 Fuzes M111 230 Fuzes VT90 90 Projectiles Cluster No. 6 9

The clearance of Pit 3C was completed in February 1975. The quarry floor was reportedly covered with approximately 1m of sterile slate scree and flattened.

6.2.4 Disposal Area 4

Disposal Area No. 4 comprised 2No. pits located approximately 0.3km southeast of the Site. A wide variety of ordnance was discovered scattered over the floor of Pit 4A, with only a small amount of explosive material in Pit 4B. The two pits were connected by a tunnel that was partly blocked by ordnance.

Clearance commenced on the 3rd May 1970 and was completed by the 12th July 1971. Figure 15 details the ordnance recovered from Disposal Area No. 4. It consisted mainly of 4lb smoke bombs and detonators, in addition to radio destructors and 4lb IBs containing powdered magnesium.

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Figure 15 Ordnance recovered from Disposal Area No. 4

Source: Caernarfon Record Office

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This inventory demonstrates that all of the ordnance scrap produced during the clearances was dumped in Pit 2B, on the Site.

A clearance certificate for Disposal Area No. 4 was issued on the 26th April 1972, as shown in Figure 16.

Figure 16 Clearance Certificate for Disposal Area No. 4

Source: Caernarfon Record Office Disposal Area No. 4 subsequently became the location of plant for trepanning and then steaming out explosives from HE bombs.

This plant commenced operations on the 12th July 1971. It was used to dispose of the 1No. 1,000lb MC bomb, and the 250lb MC and 100lb DC bombs found. Plate 14 shows the steam generator plant for this operation.

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Plate 14 Photograph showing steaming plant at RAF Llanberis

Source: National Archives Once the pits were cleared the floors were covered with approximately 3m of compacted slate waste and the tunnels blocked off. Approximately 121,420No. items of explosives (352 tons) and 213,881No. items of ordnance debris had been cleared by the end of the EOD operation (see summary in Appendix 1). It should be noted that the RAF was unwilling to certify the quarries completely free of explosives, despite rendering safe each disposal area.

6.2 Post-1975 UXO Discoveries

1982 In 1982, during filming for the movie ‘The Keep’, 2No. items of UXO were found within the slate scree in Pit 3A. These comprised 1No. practice bomb and 1No. UXB. 2015 During recent Site walkovers, the Client has encountered potential items of UXO on the access path to Pit 2A. These have included 30mm shells which have shown evidence of burning. These discoveries indicate that, despite the extensive EOD operation undertaken, not all items of ordnance within the quarry pits were accounted for.

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6.3 Residual UXO Hazard

It is important to note that despite the extensive EOD operation undertaken in the 1970s, potential sources of UXO hazard remain within the quarry pits on the Site. For most of the Site, it is considered unlikely that significant quantities of ordnance remain. The most significant hazard is the remnants of the Bomb Pile in Pit 2C, which documentary evidence indicates was not fully cleared. Indeed, the RAF accepted after their clearance operation that the Bomb Pile still contained live ordnance. It is also recorded that some ordnance scrap produced during the operation was pushed into crevices on the floor of the quarries. Some of this scrap, whilst theoretically inert, may still contain explosives residues given the less rigorous practices of the time and the sheer quantity of ordnance that required destruction. Additionally, given the large quantities of ordnance thrown into the quarry pits, it is possible that some ordnance already lodged in crevices in the floor of the pits was missed during the EOD operation. The post-1975 discovery of UXO in Pit 3A (part of which is on the Site) demonstrates that ordnance was missed in the slate scree, deemed sterile at the time, used to cover the pit floors after the EOD operation. It is therefore possible that small numbers of both inert and live ordnance remain buried in the slate piles on the pit floors.

6.4 Radioactive Contamination

No records have been found indicating that any items providing a potential source of radioactive contamination were disposed of on the Site.

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7 ANTICIPATED ORDNANCE TYPES

When assessing the risk from UXO, it is important to be aware of ordnance type and function. The following Section briefly describes and illustrates some of the main ordnance types that have been recovered from, and may still be present on, the Site.

7.1.1 Small Arms Ammunition

Small Arms Ammunition (SAA) is one of the more recognisable categories of ordnance which is primarily designed for anti-personnel use. SAA include rounds generally up to a calibre (diameter) of 20mm. During WWII the RAF primarily used .303” and .5” machine gun rounds together with some aircraft equipped with 20mm cannon shells. Larger calibre small arms munitions (generally 20mm and greater) can contain fuze mechanisms and high explosives or pyrotechnic fillings and may have been used for anti- aircraft or anti-vehicle purposes. Some of the 20mm HE rounds had a No. 253 fuze which contained copper azide which was too unstable and so proved unsuitable. These rounds were discovered at RAF Llanberis and were considered to be very dangerous. Generally SAA has a relatively low risk as UXO, although the larger calibre categories may have the same detonation risk as larger high explosive ordnance. SAA is often associated with discarded ammunition boxes around firing practice ranges. On the Site it is likely to come from spillages that occurred during the destruction process. Plate 15 illustrates typical SAA: top is a .303” round, centre is a .5” round, and bottom is a 20mm round.

Plate 15 Photograph of typical WWII RAF SAA

Source: http://www.quarryhs.co.uk/

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These SAA rounds could be ball, tracer, incendiary or, in the case of the 20mm round, fuzed high explosive.

7.1.2 Hand Grenades

Mills No. 36 hand grenades have been recovered from Pit 2C. They can be filled with explosives or chemicals and have 3No. main parts; a body, a fuze with a pull ring, and a safety-clip assembly. Fragmentation grenades are the most common and have a metal or plastic body filled with explosive. Most use a burning delay fuze that functions for 3 to 5 seconds after the safety lever is released. Some, such as smoke grenades, are activated instantly when the lever is released. Plate 16 illustrates the typical character and condition of No. 36 hand grenades that have been excavated from a site.

Plate 16 Photographs of a typical and an excavated WWII Mills No. 36 hand grenade

Source: Google Images Source: Zetica Ltd 7.1.3 High Explosive (HE) Bombs

Both British and American HE bombs have been recovered from the Site. The most frequently encountered HE bomb was the American Navy 100lb Light Case HE bomb, together with associated fuzes and detonators. Some of those bombs recovered were still crated and in their original packaging, indicating that they had simply been dumped. The aircraft in which they were to be used can be identified by the number of suspension lugs, 1No. centrally mounted lug for British aircraft, 2No. lugs, one either end of the bomb, for American aircraft. Plate 17 illustrates American 100lb HE bombs recovered from the Site.

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Plate 17 Photograph of American Navy 100lb bombs at RAF Llanberis

Source: After the Battle Disposal methods for these LC bombs were sought from US authorities. The instructions were for them to be split with a 1oz burster charge on a weld join and the explosive then burned out. 1No. British 1,000lb MC HE bomb and 1No. 250 lb MC HE bomb were also found on the Site.

7.1.4 Incendiary Bombs

British Incendiary Bombs (IBs) ranged from small 4lb magnesium powder-filled bombs to a 25lb IBs. Larger versions were available but do not appear to have been taken to RAF Llanberis for disposal. In some cases, particularly the larger bombs, the IBs were fitted with a small HE bursting charge. This exploded after the bomb had been alight for a few minutes causing burning debris to be scattered over a greater area. Plate 18 shows a cross-sectional diagram and a restored version of a British 25lb IB.

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Plate 18 Illustrations of 25lb incendiary bombs

Source: IWM

Plate 19 is a photograph of British 4lb IBs showing their original and degraded states. This type contained compressed thermite pellets typically comprising magnesium, and sometimes aluminium powder. Those bombs found at RAF Llanberis appear to have been magnesium- filled.

Plate 19 Photograph of new and degraded 4lb incendiary bomb

Source: IWM

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Because both magnesium and phosphorus were common components in IBs, some localised chemical contamination may occur where the contents of live or partially destroyed ordnance have leached out of the IB into the surrounding soil. No evidence of such contamination on the Site has been found and the watercourses in the quarry pits were found to be free of significant contamination.

7.1.5 Anti-Aircraft Devices (AAD Bombs)

Large quantities of AAD bombs were disposed of in the pits. These were intended to be used on aerial ropes, for example from barrage balloons and on parachute-borne wires, designed to obstruct enemy aircraft and then explode. These weapons were concluded not to be very effective and were also difficult to handle. Their disposal appears to have commenced during WWII. Plate 20 shows a sectional and display version of an AAD bomb.

Plate 20 Illustrations of AAD bombs

Source: RAF Source: Inert Ordnance 7.1.6 Fuzes

Large quantities of bomb and other types of fuzes were disposed of at RAF Llanberis. These comprised both British and American varieties and included both nose (e.g. AN-M103, AN- M120) and tail (e.g. M100, M102) fuzes. Some fuzes disposed of were for target indicators and flares. For example, the M111 fuze was commonly used with 4.5” flares.

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One group of fuzes was for cannon shells which contained copper azide. These were rejected and sent for destruction as the azide became very unstable, particularly in damp conditions. Plate 21 shows a front view of a recovered, rusty M103 fuze.

Plate 21 Photograph of an M103 fuze

Source: Inert Ordnance 7.1.7 Explosive Residue Hazards

The WWII and post-WWII EOD operations provide the potential for sources of explosive chemical residues and contamination. Items such as fuzes and detonators may include the use of mercury fulminate and various azides including copper and lead, all highly sensitive initiating substances. The initiating substances such as mercury fulminate, lead azide and lead styphnate are unstable, and are unlikely to have survived in these forms over a long period of time. However, the decomposition products of these materials, especially mercury and lead, can be highly toxic. Records also show that 1,000lbs of trinital was disposed of at RAF Llanberis and not all of this may have been recovered. Explosive materials and residues can also be released to the wider environment during disposals as well as accidental explosions.

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8 UXO HAZARD ASSESSMENT

Initial works on the Site comprise a preliminary ground investigation, including boreholes, trial pits and sample pits. It is understood that further ground investigations will take place prior to the development of a Pumped Storage Facility. Works for the Pumped Storage Facility may include excavations, tunnelling, trenching and Horizontal Directional Drilling (HDD) associated with the development of a dam, a turbine house, a pipeline and related infrastructure.

8.1 UXO Hazard Level

The definitions for the levels of UXO hazard are provided below.

Hazard Level Definition

There is positive evidence that UXO is not present, e.g. through physical Very Low constraints or removal.

There is no positive evidence that UXO is present, but its occurrence Low cannot be totally discounted.

There is positive evidence that ordnance was present and that other Moderate uncharted ordnance may be present as UXO.

High There is positive evidence that UXO is present.

As high, but requires immediate or special attention due to the potential Very High hazard.

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Open Ground The open ground at the surface of the quarry pits was used for open-air ordnance storage during WWII. At the end of WWII all the stores were cleared. The materials were either sent to other depots, sea-dumped or, together with imported materials, disposed of in the quarry pits. There is no evidence of ordnance disposal taking place at the surface of the quarry pits. In order to provide a safe working environment for the personnel, the open ground and surrounding areas were the first to be cleared during the EOD operation in the 1970s. Further, without major earth movements the ground conditions were not suitable for disposal by burial. The areas of open ground at the surface of the quarry pits are considered to have a low UXO hazard level. Figure 17 is a UXO hazard zone plan of the Site. A more detailed plan is provided in Zetica Drawing P3300-12-DWG01-C.

Figure 17 UXO hazard zone plan of the Site

Source: Client Not to Scale

Very Low Low Moderate

Legend Site High Very High boundary

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UXO Hazard Assessment for Preliminary Ground Investigation

Table 5 provides a UXO hazard assessment for each of the proposed preliminary ground investigation locations.

Table 5 UXO hazard assessment for preliminary ground investigation UXO Hazard GI Location Potential UXO Hazard Assessment BH1 Open ground Low BH2 Open ground Low BH3 Open ground Low BH4 Open ground Low BH5 Open ground Low BH6 Open ground Low BH7 Open ground Low BH8 Open ground Low BH9 Slate piles (within quarry pit) Moderate BH10 Slate piles (quarry surface) Low BH11 Open ground Low BH12 Open ground Low BH13 Open ground Low BH14 Open ground Low BH15 Open ground Low BH16 Open ground Low BH17 Open ground Low SP1 Slate piles (quarry surface) Low SP2 Open ground Low SP3 Slate piles (within quarry pit) Moderate SP4 Slate piles (within quarry pit) Moderate SP5 Slate piles (within quarry pit) Moderate TP1 Open ground Low TP2 Open ground Low TP3 Open ground Low TP4 Open ground Low TP5 Open ground Low

Figure 18 is a UXO hazard zone plan of the Site showing the proposed ground investigation locations. A more detailed plan is provided in Zetica Drawing P3300-12-DWG02-B.

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Figure 18 UXO hazard zone plan of the Site (with GI locations)

Source: Client Not to Scale

Very Low Low Moderate

Legend Site High Very High boundary

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9 UXO RISK ASSESSMENT

9.1 UXO Risk Register

A UXO risk assessment has been undertaken for potential future works, taking into consideration the identified UXO hazard. Firstly, the probability of encountering UXO (PE) has been considered and rated for the different construction techniques, as detailed below.

Probability of Encounter (PE) Rating Frequent, highly likely, almost certain. 5 Probable, more likely to happen than not. 4 Occasional, increased chance or probability. 3 Remote, unlikely to happen but could. 2 Improbable, highly unlikely. 1 Impossible 0

Secondly, the probability of detonating a UXO (PD) has been considered and rated for the different construction techniques, as detailed below.

Probability of Detonation (PD) Rating Frequent, highly likely, almost certain. 5 Probable, more likely to happen than not. 4 Occasional, increased chance or probability. 3 Remote, unlikely to happen but could. 2 Improbable, highly unlikely. 1 Impossible 0

Next, the probability of encountering and detonating the UXO (PE x PD) have been used to generate an overall likelihood rating (P).

P = PE x PD LIKELIHOOD of Encounter and Detonation Rating

20 to 25 Frequent, highly likely, almost certain. 5 13 to 19 Probable, more likely to happen than not. 4 6 to 12 Occasional, increased chance or probability. 3 2 to 5 Remote, unlikely to happen but could. 2 0 to 1 Improbable, highly unlikely. 1 0 Impossible 0 P ranges from 25, a certainty of UXO being encountered & detonated on the Site by engineering activity, to 0, a certainty that UXO does not occur on the Site & will not be detonated by engineering activity.

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UXO Risk Matrix

SEVERITY (S)

5 4 3 2 1 0 5 25 20 15 10 5 0 4 20 16 12 8 4 0 3 15 12 9 6 3 0 2 10 8 6 4 2 0 1 5 4 3 2 1 0 LIKELIHOOD (P) 0 0 0 0 0 0 0

The final risk assessment for the Site is given in Table 6.

Table 6 UXO risk assessment for the Site

Potential UXO

Potential Works PE UXO Risk

PD PD

Hazard Risk

Rating

P = PE xP = PE

Severity

Likelihood

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Matrix UXO Risk Definition Rating

0-1 Little action is required by the client provided that suitable Very Low records and procedures are in place to ensure appropriate action is undertaken should the UXO risk level change. 2-5 Tolerable to the client as engineering activity need not alter if Low UXO related procedures and controls are strictly adhered to. 6-12 May be tolerable for the client, but it is prudent to reduce the risk Moderate where cost effective and reasonably practicable. 13-19 Tolerable to the client only where further risk reduction is High impracticable or disproportionate to the risk involved. Essential that all practicable measures are taken to reduce the level of risk. 20-25 Unacceptable to the client except in extraordinary circumstances. Very High Imperative that all control measures are taken.

9.2 Risk Management Recommendations – Ground Investigation

Low Hazard Areas For works in areas with a low UXO hazard level, industry good practice is simply to raise the awareness of those involved in excavation so that in the unlikely event that a suspect item is discovered, appropriate action is taken. This can be achieved through UXO awareness briefings to site staff. Typically, no other measures are considered essential in areas with an identified low UXO hazard level. If UXO is discovered in an area with an identified low UXO hazard level, a re-assessment of the hazard level for that area would be recommended. Moderate Hazard Areas The raising of awareness for site staff (as per the low hazard areas) is considered essential. For the excavating of the sample pits with a moderate UXO hazard level, EOC Engineer supervision is recommended. The EOC Engineer will carry out a visual assessment on any suspect items uncovered during the excavation task and classify them as potential UXO or other material. It is recommended that any drilling into areas of waste slate/materials is avoided and that non-intrusive techniques are used where practical. If drilling in these areas cannot be avoided, then consideration should be given to remote-controlled drilling techniques to ensure the safety of the operative in the unlikely event that an item of UXO is encountered and detonated. Alternatively, the slate waste at any borehole locations can be removed under EOC Engineer supervision before drilling. Once undisturbed bedrock is penetrated there is no UXO risk.

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Further risk mitigation measures are available if a zero tolerance to risk is adopted. Zero tolerance is typically adopted for sites that have safety critical infrastructure, such as nuclear establishments and oil refineries.

9.3 Risk Management Recommendations – Future Works

For all areas of the Site, it is considered essential to raise the awareness of those involved in excavation so that in the event that a suspect item is discovered, appropriate action is taken. This can be achieved through UXO awareness briefings to site staff. The areas with a moderate to very high UXO risk can be mitigated in a practical and routine manner. To reduce the risk in these areas to As Low As Reasonably Practicable (ALARP) the following mitigation is recommended:- Bomb Pile in Pit 2C It is considered essential that the remnants of the Bomb Pile are cleared through an EOD operation. This should be undertaken before any intrusive works or rock blasting occurs in the area. With increasing strain on military EOD units through commitments abroad and at home, it is now routine for commercial organisations to undertake EOD operations in the UK. Where there is a realistic expectation of encountering ordnance during a commercial operation or private working (as there is on the Site), a competent commercial contractor can be employed to undertake EOD. By using a competent commercial EOD company, EOD operations are not only undertaken using health and safety best practice, but also with due cognisance to commercial and public relation issues that focus on minimising disruption to all those on site and the surrounding areas. With the flexibility to use more extensive and commercial blast mitigation techniques, the planning of a commercial EOD operation is less involved due to the ability to reduce the impact and extent of an evacuation zone (if any). For dealing with the Bomb Pile, a fixed EOD facility would be established on a remote part of the Site. The construction would typically involve a 2m deep trench, stepped at 1m, lined with 1 tonne sandbags to prevent the walls of the trench collapsing. ISO shipping containers are typically used around the outside of the trench. These containers would be covered with 1 tonne sandbags to form a protective wall around the trench. Figure 19 is a plan of a typical fixed EOD facility.

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Figure 19 Plan of fixed EOD facility

Source: Sitesafe Alliance

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It is recommended that any drilling into areas of waste slate/materials is avoided and that non- intrusive techniques are used where practical. If drilling in these areas cannot be avoided, then consideration should be given to remote-controlled drilling techniques to ensure the safety of the operative in the unlikely event that an item of UXO is encountered and detonated. Alternatively, the slate waste at any drilling locations can be removed under EOC supervision before drilling. Once undisturbed bedrock is penetrated there is no UXO risk. UXO in Quarry Pits (Slate piles) For excavations within the slate piles in the quarry pits, EOC Engineer supervision is recommended. If significant quantities of UXO are found at a location then an EOD operation may be necessary to fully mitigate the risk. For any boreholes, a remote-controlled drilling technique is recommended as outlined above. Reusing Slate Waste from Quarry Pits It is understood that waste from the quarry pits will be used in the construction of the Glyn Rhonwy dam. Given that the slate piles in the quarry pits may contain ordnance, any slate waste removed from the pits for use in the dam construction should be subject to visual inspection by an EOC Engineer. Alternatively, waste from the slate piles at the quarry surface (which have a low UXO risk) could be used. Potential UXO in Pit 2B This pit has been completely infilled. If more information on its extent is required, we would recommend that non-intrusive geophysical techniques are first considered in preference to drilling. Techniques such as electromagnetic profiling, alongside electrical resistivity imaging or seismic refraction, may provide information on the lateral extent and depth of waste. Records indicate that the base of the pit is filled with ordnance scrap, above which is a layer of slate fill. Above this is a layer of domestic waste, with the remainder of the pit backfilled with slate, meaning that the more significant risk will be at depth. The risk to those undertaking shallow excavations or similar work can be mitigated through UXO awareness briefings to site staff. Other risk mitigation methods are required for materials at depth that may contain UXO. This may just entail supervision by an EOC Engineer depending on the proposed works. For any boreholes, a remote-controlled drilling technique is recommended as outlined above.

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Appendices

Appendix 1 – Overall Clearance Summary

Below is a reproduction of the final clearance summary issued in November 1975 for the all the Glyn Rhonwy quarry pits. Area Standard of Clearance Pit 1 (A + B) Thorough visual search Pit 2 (A) Thorough visual search Pit 2 (B) Thorough visual search and backfilled with inert scrap and 1m of slate scree Pit 2 (C) Lake drained, area subjected to thorough visual search and lake refilled to natural level Pit 3 (A) Thorough visual search and backfilled with inert scrap and 1m of slate scree Pit 3 (B) Thorough visual search Pit 3 (C) Slag heap broken down and subjected to thorough visual search and backfilled with 1m of slate scree Pit 4 (A + B) Thorough visual search

Dates: 21st July 1969 to 31st October 1975 (13,047No. man days).

Live Recoveries

Type No. Bomb HE 250lb MC 1 Bomb HE 100lb LC 286 Bomb HE 100lb LC (Nose) 4 Bomb HE 100lb LC (Tail) 3 Bomb HE 40lb GP 2 Bomb HE 23lb Frag. 6 Bomb HE 20lb GP 2 Bomb Incendiary 30lb 5 Bomb Incendiary 25lb 13,474 Bomb Incendiary 25lb (Pots) 510 Bomb Incendiary 4lb 45,277 Bomb Incendiary 4lb ‘X’ Head 3,828 Bomb Practice 25lb 147 Bomb Practice 10lb (Tail) 203 Bomb Mortar 3” 37 Bomb Smoke 4lb 1,850 Bomb AAD 4,599 Bomb AW 2 Bomb SD2 1 Cluster Projectile No. 6 26

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Depth Charge 250lb 1 Cartridges SAA 10,431 Cartridges .50 Ball 1 Cartridges 20mm Ball 50 Cartridges 20mm HE/1 190 Cartridges 30mm Ball 2 Cartridges Engine Starter 50 Cartridges Cable Cutter 1 Cartridges Signal 1.5” 2,250 Cartridges 12 Bore 430 Capsules Type C 6,682 Charges Propellant 3” Shell 50 Container Y3 6 Container G2 7 Detonators Bomb 7,541 Detonators Electric (USA) 1,600 Detonators No. 116 104 Detonators Grenade 47 Destructors Radio Flat 32 Destructors Radio Tubular 566 Exploders Bomb 58 Fuze No. 286 35 Fuze No. 35 2 Fuze No. 42 90 Fuze VT 90 351 Fuze No. 848 22 Fuze No. 860 37 Fuze No. 893 1 Fuze No. 896 330 Fuze No. AN-M5 3 Fuze No. AN-M100 3,517 Fuze No. AN-M101 9 Fuze No. AN-M102 24 Fuze No. AN-M103 7,100 Fuze No. AN-M111 1,604 Fuze No. AN-M114a 1 Fuze No. AN-M120 4,154 Fuze No. AN-M155 8 Fuze No. AN-M166 1 Fuze Magazines 10 Flare Ground Indicating 1 Flare 4” Training 3 Flame Floats 31 Floats Smoke 120lb 416 Grenades No. 36 115

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Grenades Phosphorus 1 Generators Smoke 2 Igniters Incendiary Cluster 2 Markers Marine 6 Photoflash 4” 4 Projectiles Signal Mortar 32 Signals Distress 2 Star Red 1,736 Smoke Floats 142 Shell 2” 3 Shell 3” 5 Shell Smiths Gun 48 Sea Markers 2 Pellets CE 1 Primers 10oz 1 IB Scrap 10,939lb Tritonal 1,000lb This list does not include 1No. 1,000lb MC bomb found in Pit 2C that is documented elsewhere.

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Appendix 2 Abbreviations

AAD Anti-Aircraft Device

ACPO Association of Chief Police Officers

ALARP As Low As Reasonably Practicable

AXO Abandoned Explosive Ordnance

CMD Conventional Munitions Disposal

DCLG Department of Communities and Local Government

EO Explosive Ordnance

EOC Explosive Ordnance Clearance

EOD Explosive Ordnance Disposal

EOR Explosive Ordnance Reconnaissance

ERW Explosive Remnants of War

ESA Explosive Substances and Articles

FFE Free From Explosives

HE High Explosive

HSE Health and Safety Executive

JSEODOC Joint Services EOD Operations Centre

IB Incendiary Bomb

IED Improvised Explosive Device

IEDD Improvised Explosive Device Disposal

MoD Ministry of Defence

MMU Mobile Meteorological Unit

MU Maintenance Unit

PUCA Pick Up and Carry Away

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RAF Royal Air Force

RAOC Royal Army Ordnance Corps

RE Royal Engineers

TEP Time Expired Pyrotechnics

UXB Unexploded Bomb

UXO Unexploded Ordnance

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Appendix 3 Glossary & Definitions

Abandoned Abandoned Explosive Ordnance is explosive ordnance that has not Explosive been used during an armed conflict, that has been left behind or Ordnance disposed of by a party to an armed conflict, and which is no longer (AXO) under control of that party. Abandoned explosive ordnance may or may not have been primed, fuzed, armed or otherwise prepared for use.

Demil Derived from the term ‘Demilitarisation’, it refers to the break down and the recycling or disposal of ordnance components.

Detonation The high-speed chemical breakdown of an energetic material producing heat, pressure, flame and a shock wave.

Device This term is used for any component, sub-assembly or completed ordnance, which may or may not have an explosive risk. It can apply to detonators, primers, gaines, fuzes, shells or bombs.

Explosive The term explosive refers to compounds forming energetic materials that under certain conditions chemically react, rapidly producing gas,

heat and pressure. Obviously, these are extremely dangerous and should only be handled by qualified professionals.

Explosive Explosive Ordnance is all munitions containing explosives, nuclear Ordnance (EO) fission or fusion materials and biological and chemical agents. This includes bombs and warheads, guided and ballistic missiles, artillery, mortar, rocket, small arms ammunition, mines, torpedoes, depth charges, pyrotechnics, cluster bombs & dispensers, cartridge & propellant actuated devices, electro-explosive devices, clandestine & improvised explosive devices, and all similar or related items or components explosive in nature.

Explosive Explosive Ordnance Clearance is a term used to describe the operation Ordnance of ordnance detection, investigation, identification and removal, with Clearance EOD being a separate operation. (EOC)

Explosive Explosive Ordnance Disposal is the detection, identification, on-site Ordnance evaluation, rendering safe, recovery and final disposal of unexploded Disposal (EOD) explosive ordnance.

Explosive Explosive Ordnance Reconnaissance is the detection, identification and Ordnance on-site evaluation of unexploded explosive ordnance before Explosive Reconnaissance Ordnance Disposal. (EOR)

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Explosive Explosive Remnants of War are Unexploded Ordnance (UXO) and Remnants of Abandoned Explosive Ordnance (AXO), excluding landmines. War (ERW)

Explosive substance are solid or liquid substance (or a mixture of Explosive substances), which is either: Substances and Articles (ESA) • capable by chemical reaction in itself of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings. • designed to produce an effect by heat, light, sound, gas or smoke, or a combination of these as a result of a non-detonative, self- sustaining, exothermic reaction. Explosive article is an article containing one or more explosive substances.

Fuze A fuze is the part of an explosive device that initiates the main explosive charge to function. In common usage, the word fuze is used indiscriminately, but when being specific (and in particular in a military context), fuze is used to mean a more complicated device, such as a device within military ordnance.

Gaine Small explosive charge that is sometimes placed between the detonator and the main charge to ensure ignition.

Geophysical A geophysical survey is essentially a range of methods that can be used survey to detect objects or identify ground conditions without the need for intrusive methods (such as excavation or drilling). This is particularly

suited to ordnance as disturbance of ordnance items is to be avoided where ever possible.

High Explosive Secondary explosives (commonly known as High Explosives (HE)) make up the main charge or filling of an ordnance device. They are usually less sensitive than primary explosives. Examples of secondary explosives are: Nitro glycerine (NG), Trinitrotoluene (TNT), AMATOL (Ammonia nitrate + TNT), Gunpowder (GP), and Cyclotrimethylenetrinitramine (RDX).

MagCone MagCone is a method by which ordnance (or other similar metallic items) can be detected at significant depths. This is conducted by the

use of a specialised probe. The probe contains a sensitive magnetometer that is pushed into the ground. The magnetometer is able to detect items such as buried ordnance and thus advise on clear routes for drilling, piles, deep excavation or alike.

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MagDrill Similar technique to MagCone, but utilises an augering or drilling (rather than probing) technique to advance the magnetometer into the soil. Munition is the complete device charged with explosives, propellants, Munition pyrotechnics, initiating composition, or nuclear, biological or chemical material for use in military operations, including demolitions. This includes those munitions that have been suitably modified for use in training, ceremonial or non-operational purposes. These fall into three distinct categories:-

• inert - contain no explosives whatsoever. • live - contain explosives and have not been fired. • blind - have fired but failed to function as intended.

Primary Primary explosives are usually extremely sensitive to friction, heat, and Explosive pressure. These are used to initiate less sensitive explosives. Examples of primary explosives are: Lead Azide, Lead Styphnate, and Mercury Fulminate. Primary explosive are commonly found in detonators.

Propellants Propellants provide ordnance with the ability to travel in a controlled manner and deliver the ordnance to a predetermined target. Propellants

burn rapidly producing gas, pressure and flame. Although usually in solid form they can be produced in liquid form. Examples of propellants are: Ballistite often found in a flake form and Cordite used in small arm ammunition.

Pyrotechnic A pyrotechnic is an explosive article or substance designed to produce an effect by heat, light, sound, gas or smoke, or a combination of any of

these, as a result of non-detonative, self-sustaining, exothermic chemical reactions.

Unexploded UXO is explosive ordnance that has been either primed, fuzed, armed Ordnance or prepared for use and has been subsequently fired, dropped, (UXO) launched, projected or placed in such a manner as to present a hazard to operations, persons or objects and remains unexploded either by

malfunction or design.

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Appendix 4 Bibliography

Airfield Research Group, Munitions 1915 – 1919, Airfield Research Publishing, June 1996 Anon, Royal Air Force Bomb Disposal, After the Battle 68, pp. 34-47, 1990 Bulloch G, Steeds J E, Green K, Sainsbury M G, Brockwell J S & Slade N J, Land Contamination: Technical Guidance on Special Sites: MoD Land Bulloch G, Steeds J E, Green K, Sainsbury M G, Brockwell J S, & Slade N J, R&D Technical Report P5-042/TR/03, Land Contamination: Technical Guidance on Special Sites: Explosives Manufacturing & Processing Sites Burls N, RAF Bombs and bombing, 1939-1945, Royal Air Force Journal 47, 25-36, 2009 CIRIA, Unexploded Ordnance (UXO), a Guide for the Construction Industry, 2009 Department of the Environment, Sampling Strategies for Contaminated Land, Department of the Environment: Contaminated Land Research Report, CLR Report No. 4, 1994. Jones I, Airfields and Landing Grounds of Wales: North, 2008 McCamley N J, Disaster Underground, 2003 Ministry of Defence JSP 364, Joint Service EOD Manual Ramsey W, The Blitz Then and Now, Vol 1, 1987 Ramsey W, The Blitz Then and Now, Vol 2, 1988 Ramsey W, The Blitz Then and Now, Vol 3, 1990 Wooldridge M, Explosives, Royal Air Force Journal 35, 41-53, 2005 Sloan R, The Tale of Tabun: Nazi Chemical Weapons in North Wales, 1998 Soilleux R, Steeds J E & Slade NJ, R&D Technical Report P5-042/TR/02, Land Contamination: Technical Guidance on Special Sites: Chemical Weapons Sites, 2001 US Naval Ordnance Systems, British Explosive Ordnance, NAVORD OP 1665, 1946

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Appendix 5 General Notes

1. This report has been prepared in relation to the specific requirement of the contract or commission. The report should not be used by third parties without prior consultation with Zetica Ltd. 2. The copyright for this report remains with Zetica Ltd. No part of this report may be reproduced, published or amended without prior written consent from Zetica Ltd. 3. The report refers to the conditions of the Site at the time of investigation/ reporting. Zetica Ltd cannot accept liability for subsequent changes of Site conditions. 4. Zetica Ltd may have relied on externally provided information. Zetica Ltd cannot be held responsible for the accuracy of such information or data supplied. 5. The report has been written utilising relevant guidance and legislation in use at the time of report compilation. Subsequent improvement in techniques, changes in legislation or in Site conditions may render parts of this report obsolete. If the report is utilised after such changes have occurred or at a time in excess of 1 year of the issue date, it would be prudent to contact Zetica Ltd to reassess the report under a new contract.

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Established for over 20 years, Zetica’s services include

Desk studies

Unexploded ordnance risk assessments and risk mitigation

Topographic surveys

Utility services detection

Environmental and engineering geophysical surveys

Transport infrastructure surveys

Pipeline & cable route surveys

Intrusive ground investigations

More details are available at

www.zetica.com

Zetica Ltd – Report No. P3300-12-R1-C 85

Notes: A Base map detail is based on drawings provided by the Client B Zetica does not accept responsibility for the accuracy of information provided by third parties

Legend

High UXO Hazard Level

Moderate UXO Hazard Level

Low UXO Hazard Level

Site Boundary

Pit 1A Original ordnance storage area

Pit 2A Potential for UXO within slate scree/crevices

Pit 2C

Bomb Pile Potential for UXO within slate scree/crevices Pit 1B Potential for UXO within slate scree/crevices Pit 2B (Approx) Ordnance scrap below slate fill

Pit 3A

Pit 3B

Pit 3C

Pit 4A

Client Quarry Battery

Location

Pit 4B Glyn Rhonwy, Llanberis, Gwynedd Project UXO Desk Study

Title Unexploded Ordnance Hazard Zone Plan Drawn by Checked by

S Lang M Sainsbury

Horizontal Scale Date of Survey Issue Date

NTS N/A 12.05.2015

Zetica Ltd. Units 15/16 Hanborough Business Park Long Hanborough Oxfordshire zetica OX29 8LH Tel: +44 (0) 1993 886682 Fax: +44 (0) 1993 886683

Project Code Drawing No. Sheet Rev. P3300-12 DWG-01 - C Notes: A Base map detail is based on drawings provided by the Client B Zetica does not accept responsibility for the accuracy of information provided by third parties

Legend

High UXO Hazard Level

Moderate UXO Hazard Level

Low UXO Hazard Level

Site Boundary

Borehole

TP001

Borehole

Pit 1A TP002 Original Ordnance Storage Area Borehole TP003

BH001 Sample Pit

BH003 Trial Pit SP01 BH010

Pit 2A BH007 TP005 Potential for UXO within slate scree/crevices BH006 BH004 SP03 Pit 2C BH013 TP004 SP05 Bomb Pile BH002 Potential for UXO within slate scree/crevices SP04 BH005 Pit 1B Potential for UXO within slate scree/crevices Pit 2B (Approx) Ordnance scrap below slate fill

Pit 3A BH008 SP02

Pit 3B BH015

BH014 Pit 3C

BH011

BH012

BH016

Pit 4A BH017

Client Quarry Battery

Location

Pit 4B Glyn Rhonwy, Llanberis, Gwynedd Project UXO Desk Study

Title UXO Hazard Zone Plan (with GI Locations) Drawn by Checked by

S Lang M Sainsbury

Horizontal Scale Date of Survey Issue Date

NTS N/A 12.05.2015

Zetica Ltd. Units 15/16 Hanborough Business Park Long Hanborough Oxfordshire zetica OX29 8LH Tel: +44 (0) 1993 886682 Fax: +44 (0) 1993 886683

Project Code Drawing No. Sheet Rev. P3300-12 DWG-02 - B