Lepper, P A; Robinson, S P; Cheong, S-H; Wang, L; Tougaard, J; Griffiths, E T; Hartley, J (2024) Deflagration: A Method For Lowering Noise From Underwater Unexploded Ordnance (UXO) Clearance Operations. In: The Effects of Noise on Aquatic Life. Springer. ISBN 9783031104176

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Abstract

Significant amounts of historic WWI and WWII Unexploded Ordnance (UXO) are still located in our seas and waterways with an estimated 300,000 to 500,000 pieces in UK waters alone [DEFRA, 2022]. These weapons have individual historic explosive charge sizes ranging from a few tens of grammes to greater than 500 kg of TNT equivalence explosive charge mass. These have been largely left undisturbed in-situ in the post-war periods, however, in recent years there has been a significant increase in the number of required controlled Explosive Ordnance Disposal (EOD) operations required due to offshore activities such as offshore wind energy developments, ground fishing and others, to make the areas of these operations safe.

A commonly used method of UXO clearance (EOD) involves a Blow- or Blast-in-Place (BiP) operation carried out by co-location of a modern explosive ‘donor’ charge, typically around 5-10 kg of TNT equivalence and initiating a simultaneous ‘high-order’ detonation of both the primary donor charge and the secondary often-larger historic charge of the UXO. This process has the potential for generation of very large underwater explosive events with associated high acoustic and vibrational energy levels in both the water column and the seabed. This has led to a growing concern of potential negative impacts on aquatic fauna and their environments related to these detonations. Potential impacts include the generated high levels of acoustic noise and seabed vibration, [Yelverton et al, 1973; Ketten et al, 1993; NOAA, 2016; Dahl et al, 2020; Todd et al, 1996; Finneran et al, 2000; Danil & St. Leger, 2011; Sundermeyer et al, 2012; von Benda-Beckmann et al, 2015; Parsons et al, 2000; Salomons et al, 2021, Cottrell & Dupuy, 2021; Siebert et al, 2022, Robinson et al, 2022, Jenkins et al, 2022, Smith et al, 2022, Favretto-Cristini et al, 2022a,b], seabed damage [Garlan et al., 2018], chemical toxicity [Strehse et al, 2017; Appel et al, 2018; Maser & Strehse, 2020, Schuster et al, 2021, den Otter et al, 2023; Maser et al 2023], and others.

In 2019 the underwater acoustic characteristics of both traditional high-order methodologies and an alternative low-order EOD methodology known as deflagration were investigated in trials in a flooded quarry in the UK [Robinsons et al 2020]. The low-order deflagration process investigated used a small shaped explosive charge to penetrate the outer typically metallic shell on a munition and then to initiate a ‘low-order’ burning process of the historic explosive material. In this paper, data from acoustic measurements of both ‘high-order’ and ‘low-order’ methodologies used on of like-for-like surrogate munition shells are presented. These data show a significant reduction in the acoustic levels associated with the low-order methodology of around 20 dB for a 10 kg historic charge disposal. Following on from the quarry experiments, provisional results data are presented for open water trials that took place in the Little Baelt, Denmark in January 2022 of both high and low-order methodologies used on actual historic (WWII) UXO’s of charge sizes in the range 200-430 kg. As with the quarry test, significantly lower acoustic noise outputs were observed using a deflagration process on these UXO’s compared to the high-order detonation. Potential noise impacts and relative noise levels of both high and low-order methodologies are discussed as well as other factors such as seabed damage and chemical toxicity in the context of current EOD operations and potential impacts on underwater environments.

Item Type:	Book Chapter/Section
Keywords:	UXO, explosive ordnance disposal, deflagration
Subjects:	Acoustics > Underwater Acoustics
Divisions:	Medical, Marine & Nuclear
Publisher:	Springer
Identification number/DOI:	10.1007/978-3-031-10417-6_91-1
Last Modified:	13 Nov 2024 15:41
URI:	https://eprintspublications.npl.co.uk/id/eprint/10097