The noise radiated by marine piling for the construction of offshore wind farms

The most commonly used method for the installation of offshore wind turbine foundations in the shallow coastal waters in the UK is pile driving. The construction technique consists of large steel piles being driven up to around 30 m into the seabed using powerful hydraulic hammers, in water depths up to around 25 to 30 m. It is a source of high-amplitude impulsive sound and has the potential for impact on marine life. Methodologies developed for the measurement of underwater sound radiated from marine piling, for the estimation of source level are described in this paper. Data are presented for piles of 5.2 m in diameter driven by hammers with typical strike energies of up to 1350 kJ. Data were recorded as a function of range from the source using vessel-deployed hydrophones, with the data then used to estimate the energy source level. In addition, fixed acoustic buoys were used to record the entire piling sequence, including soft-start period. The dependencies of the radiated noise on the physical parameters of the piling operation are discussed, along with limitations and knowledge gaps

Effectiveness of exclusion zones and soft-starts as mitigation strategies for minimizing acoustic impact from underwater noise sources

Several recent studies have suggested that cumulative Sound Exposure Level (SEL) is an important metric for assessment of the impact of exposure to anthropogenic sound sources by various marine receptors including marine mammals and fish. This metric allows the cumulative exposure of an animal to a sound field for an extended period to be assessed against a predefined impact criteria. Two widely used mitigation strategies used by both industrial and military users to reduce potential impact on marine receptors are exclusions zones (zones from source where received levels exceed a certain threshold), a source is either not started or stopped if receptors are detected within this zone and ‘soft-starts’ or ‘ramp-ups’ (lower energy levels at the commencement of a noise source allowing a receptor to move out of the area). This paper discusses the relative effectiveness of these methodologies in terms of a cumulative exposure impact criteria. Cumulative exposure examples are given including typical marine piling operations for wind-farm construction and sub-surface piling operations for various receptor models, including, static, fleeing and transiting animals

Complexity Bounds for Ordinal-Based Termination

`What more than its truth do we know if we have a proof of a theorem in a given formal system?' We examine Kreisel's question in the particular context of program termination proofs, with an eye to deriving complexity bounds on program running times. Our main tool for this are length function theorems, which provide complexity bounds on the use of well quasi orders. We illustrate how to prove such theorems in the simple yet until now untreated case of ordinals. We show how to apply this new theorem to derive complexity bounds on programs when they are proven to terminate thanks to a ranking function into some ordinal.Comment: Invited talk at the 8th International Workshop on Reachability Problems (RP 2014, 22-24 September 2014, Oxford

Predicting the large-scale consequences of offshore wind turbine array development on a North Sea ecosystem

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Three models were applied to obtaina first assessment of some of the potential impacts of large-scale operational wind turbine arrays on the marine ecosystem in a well-mixed area in a shelf sea: a biogeochemical model,a wave propagation model and an a coustic energy flux model.The results of the models are discussed separately and together to elucidate the combined effects. Overall,all three models suggested relatively weak environmental changes for the mechanisms included in this study, however these are only a subset of all the potential impacts,and a number of assumptions had to be made. Further work is required to address these assumptions and additional mechanisms. All three models suggested most of the changes with in the wind turbine array,and small changes up to several tens of km outside the array. Within the array, the acoustic model indicated the most concentrated, spatially repetitive changes to the environment,followed by the SWAN wave model,and the biogeochemical model being the most diffuse. Because of the different spatial scales of the response of the three models,the combined results suggested a spectrum of combinations of environmental changes with in the wind turbine array that marine organism smight respond to. The SWAN wave model and the acoustic model suggested a reduction in changes with increasing distance between turbines. The SWAN wave model suggested that the biogeochemical model, because of the in ability of its simple wave model to simulate wave propagation,over-estimated the biogeochemical changes by a factor of 2 or more. The biogeochemical model suggested that the benthic system was more sensitive to the environmental changes than the pelagic system. © 2014 Published by Elsevier Ltd.The work was carried out as part of the EBAO project (Optimising Array Form for Energy Extraction and Environmental Benefit, No. NE/J004227/1), and was jointly funded by NERC and Defra (Cefas contract C5325). Sonja van Leeuwen constructed the daily riverine loads database from which the runoff data were used in the GETM-ERSEM model. French water quality data were supplied by the Agence de l’eau Loire-Bretagne, Agence de l’eau Seine-Normandie and IFREMER. UK water quality data were processed from raw data provided by the Environment Agency, the Scottish Environment Protection Agency and the National River Flow Archive. The German river loads are based on data from the ARGE Elbe, the Niedersächsisches Landesamt für Ökologie and the Bundesanstalt für Gewässerkunde. The river load data for the Netherlands were supplied by the DONAR database. The authors gratefully acknowledge the ECMWF (European Centre for Medium Range Weather Forecasting) for allowing the use of the ERA-40 and Operational Hindcast data used as atmospheric forcing for the GETM-ERSEM model

The measurement of the underwater radiated noise from a marine piling operation

Assessment of the underwater acoustic radiated noise during a marine piling operation was carried out in UK coastal waters in April 2006. A 2 m diameter, 65 m long test pile was driven into a "hard chalk‟ sediment. The pile was placed in an area of average water depth of 10-15 m approximately 3 km offshore

Up and down the number line: modelling collaboration in contrasting school and home environments

This paper is concerned with user modelling issues such as adaptive educational environments, adaptive information retrieval, and support for collaboration. The HomeWork project is examining the use of learner modelling strategies within both school and home environments for young children aged 5 – 7 years. The learning experience within the home context can vary considerably from school especially for very young learners, and this project focuses on the use of modelling which can take into account the informality and potentially contrasting learning styles experienced within the home and school

Theoretical comparison of cumulative sound exposure estimates from jacket and tripod foundation construction

Foundation pile driving during offshore construction has led to increasing concerns regarding radiated noise and its effects on the marine fauna (receptors). In the case of many static offshore developments two commonly used foundation techniques are tripod-constructions involving installation of a series of smaller diameter piles surrounding a central structure and mono-piles using a single larger diameter pile. Pile installation itself may involve sequences of percussive piling at different hammer energies, vibro-piling (more rapid, lower level vibrations) and drilling. In some cases all three techniques are used on a single pile installation. The spectral characteristics, as well as duration and level of the total radiated energy from these techniques can vary significantly and may result in different Sound Exposure Levels (SEL) experienced by marine fauna. This paper theoretically explores the potential difference in total SEL for various receptor scenarios for each of these techniques using available source characteristics data. The total sound SEL’s for each scenario are compared and model sensitivities identified

Generating socially appropriate tutorial dialog

Analysis of student-tutor coaching dialogs suggest that good human tutors attend to and attempt to influence the motivational state of learners. Moreover, they are sensitive to the social face of the learner, and seek to mitigate the potential face threat of their comments. This paper describes a dialog generator for pedagogical agents that takes motivation and face threat factors into account. This enables the agent to interact with learners in a socially appropriate fashion, and foster intrinsic motivation on the part of the learner, which in turn may lead to more positive learner affective states

What is the source level of pile-driving noise in water?

To meet the growing demand for carbon-free energy sources, the European Union (EU) has ambitious plans to increase its capacity for generation of offshore wind power. The United Kingdom and The Netherlands, for example, plan to increase their offshore power-generating capacity to 33 and 6 GW, respectively, by the year 2020. Assuming that this power is generated entirely by wind and that a single wind turbine can generate up to 10 MW, at least 3,900 offshore turbines would be required by these two states alone to achieve this goal. A popular turbine construction method known as “pile driving” involves the use of hammering a steel cylinder (a “monopile”) into the seabed. A concern has arisen for the possible effect on mammals (Southall et al. 2007) and fish (Popper and Hastings 2009) of the sound produced by the succession of hammer impacts required to sink the pile to its required depth (tens of meters)