3870 TA RAF Alconbury, Cambridgeshire
Explosive Ordnance Threat Assessment in respect of
RAF Alconbury
For Buro Four
3870TA
19th April 2012
Explosive Ordnance Threat Assessment
in respect of
RAF Alconbury
for
Buro Four
3870TA
19th April 2012
BACTEC International Limited
37 Riverside, Sir Thomas Longley Road, Rochester, Kent ME2 4DP, UK
Tel: +44 (0) 1634 296757
Fax: +44 (0) 1634 296779
Email: bactec.int@
Registered in England No. 2601923. VAT Registration No. GB 573 6627 13
Buro Four
RAF Alconbury
This document was written by, belongs to and is copyright to BACTEC International Limited. It contains valuable BACTEC proprietary and confidential information which is disclosed only for the purposes of the client's assessment and evaluation of the project which is the subject of this report. The contents of this document shall not, in whole or in part (i) be used for any other purposes except such assessment and evaluation of the project; (ii) be relied upon in any way by the person other than the client (iii) be disclosed to any member of the client's organisation who is not required to know such information nor to any third party individual, organisation or government, or (iv) be copied or stored in any retrieval system nor otherwise be reproduced or transmitted in any form by photocopying or any optical, electronic, mechanical or other means, without prior written consent of the Managing Director, BACTEC International Limited, 37 Riverside, Sir Thomas Longley Road, Rochester, Kent, ME2 4DP, United Kingdom to whom all requests should be sent. Accordingly, no responsibility or liability is accepted by BACTEC towards any other person in respect of the use of this document or reliance on the information contained within it, except as may be designated by law for any matter outside the scope of this document.
Distribution
Copy No. 1 2 3
Format Print Copy PDF Copy Print Copy
Date of Issue: 19th April 2012
Originator:
OTB
Recipient Buro Four Buro Four BACTEC International Limited
Copy no. 2
This Report has been produced in compliance with the Construction Industry Research and
Information Association guidelines for the preparation of Detailed Risk Assessments in the management of UXO risks in the construction industry.
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AAA ARP BDO EOD HE HG IB kg LCC LM LSA Luftwaffe m bgl MoD OB PM RAF SI SAA USAAF UXB UXO V-1
V-2 WWI WWII
Glossary of Terms
RAF Alconbury
Anti-Aircraft Artillery Air-raid Precautions Bomb Disposal Officer Explosive Ordnance Disposal (current term for "bomb" disposal) High Explosive Home Guard Incendiary Bomb Kilogram London County Council Land Mine Land Service Ammunition (includes grenades, mortars, etc.) German Air Force Metres Below Ground Level Ministry of Defence Oil Bomb Parachute Mine Royal Air Force Site Investigation Small Arms Ammunition (small calibre cartridges used in rifles & machine guns) United States Army Air Force Unexploded Bomb Unexploded Ordnance "Doodlebug" the first cruise type missile, used against London from June 1944. Also known as `Flying Bomb'. The first ballistic missile, used against London from September 1944 First World War (1914 -1918) Second World War (1939 ? 1945)
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Executive Summary
The Site: The site is located just north and east of the villages of Alconbury, Little Stukeley and Great Stukeley in Cambridgeshire. It is mostly bound by agricultural fields however a railway line is present immediately east and the A1 and B1043 border the site to the south-west. The majority of the study area, centred on the approximate National Grid Reference: 521572, 276540, is currently occupied by RAF Alconbury airbase. The site boundary currently includes runways, taxi ways, dispersal pans, numerous hangars, a WWII-era technical site, a post-WWII bomb dump, many other ancillary buildings and also a large agricultural area to the south-east of the airbase perimeter.
Proposed Works: A large mixed use development is proposed over the entire site. Note however that many parts of the site will not require intrusive work as they will become open spaces or woodland. No precise details regarding the types and depth of the proposed intrusive works were available during the production of this report.
Risk Assessment Methodology: In accordance with CIRIA guidelines this assessment has carried out research, analysed the evidence and considered the risks that the site has been contaminated with unexploded ordnance; that such items remained on site; that they could be encountered during the proposed works and the consequences that could result. Appropriate risk mitigation measures have been proposed.
Explosive Ordnance Risk Assessment: BACTEC concludes that there are areas of Low/Medium, Medium/High and High risk at the site of the proposed development. This is based on the following factors:
Allied Unexploded Ordnance Risk
o The site is partially situated within the historic perimeter of RAF Alconbury, a WWII-era/Cold War-era airbase. Experience has shown that the `housekeeping' at historic RAF/USAAF stations was often poor with unwanted or unused ordnance sometimes buried, burnt, lost or otherwise discarded within or in close proximity to the airfield perimeter. Furthermore, the requirement for a swift post-WWII USAAF exit from England meant that some American military equipment was simply abandoned, poorly disposed of or buried within or close to their bases.
o Previous BACTEC work on several former RAF stations has shown that the former bomb stores and dispersal pans/aircraft armament areas (where aircraft were loaded with weapons), have a higher risk of UXO contamination. As these features were/are located within the study area, the risk of encountering such munitions is elevated. BACTEC also recently exhumed WWII British HE bombs buried outside the perimeter of RAF Oakington, a WWII RAF Bomber Command base.
o 1946 RAF Alconbury site plans show that several defence huts, pyrotechnics stores, armouries and gunnery ranges were positioned around the airfield, away from the bomb dump. The locations of these features will also have a slightly heightened risk of UXO associated with them.
o Home Guard units and possibly regular army units are likely to have carried out guard duties and training within and in close proximity to the base. During such activities small arms ammunition and land service ammunition (grenades, mortars, etc) would have been issued to personnel, increasing the chance of UXO contamination.
o If UXO remains at RAF Alconbury it is more likely to be of WWII-era because the frequency and intensity of operations during this period, coupled with a generally more relaxed attitude towards health and safety meant that items of UXO were more likely to be misplaced or buried. Although RAF/USAF rules and regulations regarding handling and storage of munitions have become increasingly more stringent in the post-WWII period, the possibility cannot be discounted that American UXO from the period 1953 ? 1995 could be encountered on site, particularly in the current bomb dump facility, to the north.
German Unexploded Ordnance Risk
o Due to its rural nature, Alconbury was situated in an area of low bombing density throughout WWII. The only viable Luftwaffe targets in the region were several RAF airfields including that which occupied the site. The presence of this facility did locally raise the bombing density however. Records indicate that three small scale air raids were made on the airbase between 1940 and 1941. These attacks resulted in 46 HE bombs recorded on and close to the airfield.
o Levels of access will have been variable across different parts of the site. Generally the main airfield site and communal area to the west would have been regularly frequented during the war. Furthermore, the buildings are likely to have been subject to checks for evidence of UXO, that would have been fairly obvious, following the air raids. During the raids it is considered highly likely that AA defences at the airfield would have engaged the attackers. This coupled with the small number of aircraft involved suggests it is likely that a UXB strike would have been observed.
o The airfield peripheries and the agricultural area to the south-east will have been accessed to a much lesser degree. Therefore it is conceivable that a UXB strike could have gone unobserved and an entry hole would have been easily obscured; note that the entry hole of an SC 50 HE UXB, the most commonly deployed HE bomb, may have been as small as 20cm in diameter and therefore easily obscured by dense crops or soil debris (ploughed field).
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o Immediate post-WWII RAF aerial photography of the site does not exhibit any large scale damage or bomb craters within the study area. An anecdotal account also describes only minor damage to two aircraft during the three air raids.
For the large part there has not been any significant redevelopment of the airfield since it became a nonoperational base in 1995. There has however been some development within the airfield in the post-WWII period and therefore the risk of encountering shallow buried UXO (such as SAA, 1kg German incendiaries, AAA shells and USAAF munitions) in these areas will have been partly mitigated since any such items may have been discovered during excavations. However the risk from deep-buried German HE UXBs will only have been mitigated at the precise locations of and down to the depths of any post-war deep excavations or pile foundations. Note that the risk posed by these munitions is considered to be relatively low.
Ploughing and re-working of farmland has been known to exhume shallow buried items of UXO, however purposely buried UXO has also been encountered at depths below that of normal ploughing methods. Therefore the risk of encountering UXO at any depth within the south-eastern part of the study area will not have been fully mitigated.
Bomb Penetration Assessment: It has been assessed that a 500kg bomb would have had a maximum bomb penetration depth of up to 12m below WWII ground level. Penetration depth could potentially have been greater if the UXB was larger (though only 4% of German bombs used in WWII over Britain were of that size). Note that UXBs may be found at any depth between just below the WWII ground level and the maximum penetration depth.
Risk Mitigation Measures: Due to the large scale and complexity of the RAF Alconbury redevelopment BACTEC suggests that a meeting be held with Buro Four in order to create a bespoke risk mitigation strategy for the site, prior to intrusive works. This is likely to include the following mitigation measures:
All Risk Zones
o Explosive Ordnance Safety and Awareness Briefings to all personnel conducting intrusive works.
o The provision of Unexploded Ordnance Site Safety Instructions.
Medium/High and High Risk Zones only
o On greenfield areas only: Non-Intrusive Magnetometer Survey and target investigation ahead of any intrusive works.
In developed areas, including areas of hard-standing, roads, made ground, buildings, etc a Non-Intrusive Magnetometer Survey is inappropriate due to high levels of background `noise'. In these areas the following is recommended:
o Explosive Ordnance Disposal (EOD) Engineer presence on site to support shallow intrusive works.
In making this assessment and recommending these risk mitigation measures, the proposed works outlined in the `Scope of the Proposed Works' section were considered. Should the planned works be modified or additional intrusive engineering works be considered, BACTEC should be consulted to see if a re-assessment of the risk or mitigation recommendations is necessary.
Risk Map
High Risk Zone
Medium/High Risk Zone
Low/Medium Risk Zone
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Contents
Distribution ...........................................................................................................................ii
Glossary of Terms ................................................................................................................iii
Executive Summary.............................................................................................................. iv
Contents ............................................................................................................................... vi
Annexes ............................................................................................................................. viii
1. Introduction .................................................................................................................. 1
1.1.
Background ........................................................................................................................... 1
2. Construction Industry Duties and Responsibilities.........................................................2
2.1.
The UK Regulatory Environment ..............................................................................................2
2.2.
The Health and Safety at Work Act, 1974 .................................................................................2
2.3.
Construction (Design and Management) Regulations 2007 ..........................................................2
2.4.
Other Legislation ...................................................................................................................2
3. The Role of the Authorities and Commercial Contractors ...............................................2
3.1.
The Authorities ......................................................................................................................2
3.2.
Commercial Contractors .........................................................................................................3
4. This Report ....................................................................................................................3
4.1.
Aims and Objectives...............................................................................................................3
4.2.
Risk Assessment Methodology .................................................................................................3
4.3.
Approach ..............................................................................................................................3
4.4.
Sources of Information ...........................................................................................................3
4.5.
Reliability of Historical Records ................................................................................................4
4.5.1.
General Considerations...........................................................................................................4
4.5.2.
Bombing Records...................................................................................................................4
5. The Site .........................................................................................................................4
5.1.
Site Location .........................................................................................................................4
5.2.
Site Description .....................................................................................................................4
6. Scope of the Proposed Works ........................................................................................ 4
7. Ground Conditions ......................................................................................................... 5
8. Site History ....................................................................................................................5
8.1.
Mapping ...............................................................................................................................5
8.2.
History of RAF Alconbury ........................................................................................................5
8.2.1.
RAF Use 1938 - 1942 .............................................................................................................5
8.2.2.
USAAF WWII Use 1942 - 1945 ................................................................................................6
8.2.3.
USAF Cold War Use 1953 ? Present..........................................................................................6
9. The Threat from Allied Military Ordnance.......................................................................7
9.1.
RAF Station Contamination .....................................................................................................7
9.2.
General ................................................................................................................................7
9.3.
Ground Defensive Positions .....................................................................................................7
9.3.1.
Anti-Aircraft Artillery Gun Emplacements ..................................................................................7
9.4.
Home Guard Training .............................................................................................................8
9.5.
Ordnance/Explosives Storage and Disposal ...............................................................................8
9.6.
Practice Bombing ...................................................................................................................8
9.7.
Aircraft Weapons Testing ........................................................................................................9
9.8.
Pipe Mines/Demolition Charges................................................................................................9
10. Threat Posed By Allied Explosive Ordnance ...................................................................9
10.1.
General ................................................................................................................................9
10.2.
Small Arms Ammunition (SAA) ................................................................................................9
10.3.
Land Service Ammunition (LSA) ..............................................................................................9
10.3.1.
General ................................................................................................................................9
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10.3.2. 10.3.3. 10.4. 10.5. 10.6. 10.6.1. 10.6.2. 10.6.3. 10.7.
Mortars .............................................................................................................................. 10 Grenades ............................................................................................................................ 10 Miscellaneous ...................................................................................................................... 10 Anti-Aircraft Artillery Shells ................................................................................................... 10 Practice Bombs.................................................................................................................... 10 Bomb Characteristics ........................................................................................................... 10 Explosive Content ................................................................................................................ 11 Hazards .............................................................................................................................. 11 Allied High Explosive and Incendiary Ordnance ........................................................................ 11
11. The Threat from Aerial Bombing .................................................................................. 12
11.1.
General Bombing History of Huntingdonshire........................................................................... 12
11.1.1.
First World War ................................................................................................................... 12
11.1.2.
Second World War ............................................................................................................... 12
11.2.
Aerial Delivered Ordnance in the Second World War ................................................................. 12
11.2.1.
Generic Types of WWII German Air-delivered Ordnance ........................................................... 12
11.2.2.
German Air-delivered Ordnance Failure Rate ........................................................................... 13
11.2.3.
UXB Ground Penetration ....................................................................................................... 13
11.2.3.1.
General Considerations......................................................................................................... 13
11.2.3.2.
The "j" Curve Effect ............................................................................................................. 13
11.2.3.3.
Second World War Bomb Penetration Studies .......................................................................... 14
11.2.4.
Initiation of Unexploded Bombs ............................................................................................. 14
11.3.
Bombing of Alconbury .......................................................................................................... 14
11.3.1.
Second World War Overview ................................................................................................. 14
11.3.2.
Second World War Bombing Statistics .................................................................................... 15
11.3.3.
Site Specific Bombing ........................................................................................................... 15
11.3.4.
Second World War Era Aerial Photographs .............................................................................. 15
11.3.5.
Abandoned Bombs ............................................................................................................... 15
11.3.6.
Site Specific Bomb Penetration Considerations ........................................................................ 16
11.4.
Deductions.......................................................................................................................... 16
11.4.1.
Density of Bombing.............................................................................................................. 16
11.4.2.
Frequency of Access............................................................................................................. 16
11.4.3.
Ground Cover ...................................................................................................................... 17
11.4.4.
Damage.............................................................................................................................. 17
11.4.5.
Bomb Failure Rate ............................................................................................................... 17
12. Ordnance Clearance and Post-WWII Ground Works .................................................... 17
12.1.
General .............................................................................................................................. 17
12.1.1.
EOD Bomb Disposal and Clearance Tasks................................................................................ 17
12.2.
Post-War Redevelopment...................................................................................................... 17
13. The Overall Explosive Ordnance Threat Assessment .................................................... 18
13.1.
General Considerations......................................................................................................... 18
13.2.
The Risk that the Site was Contaminated with Unexploded Ordnance ......................................... 18
13.3.
The Risk that Unexploded Ordnance Remains on Site ............................................................... 19
13.4.
The Risk that Ordnance may be Encountered during the Works ................................................. 19
13.5.
The Risk that Ordnance may be Initiated ................................................................................ 19
13.6.
The Consequences of Encountering or Initiating Ordnance ........................................................ 19
13.7.
BACTEC's Assessment .......................................................................................................... 20
14. Proposed Risk Mitigation Strategy ............................................................................... 21
14.1.
General .............................................................................................................................. 21
14.2.
Recommended Risk Mitigation Measures ................................................................................. 21
Bibliography ........................................................................................................................23
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