This paper reports the experiences of SLP Energy as a project developer in planning, procuring and managing the environmental, geophysical and geotechnical site investigations for Sheringham Shoal offshore wind farm. The paper examines the lessons that have been learned by SLP and suggests areas in which the current Society of Underwater Technology (SUT) guidance document, "Site Investigation for Offshore Renewable Energy Projects"1, can be developed to improve the guidance available to developers of marine renewable energy projects, especially offshore wind
The development of an offshore wind farm is a complex process, bringing together a diverse range of considerations including environmental, economic and technological issues. Understanding the parameters of an offshore wind farm site is fundamental to its development, and therefore the correct choice of survey methods and equipment is a key factor in the success of such projects.
The offshore renewables industry is relatively new and brings with it new challenges and perspectives. Unlike other sectors of the energy industry, the economic benefits of offshore wind projects are marginal and carry a high level of uncertainty; this is demonstrated by the fact that only around 20% of planned Round 1 capacity has so far been installed2. With the UK government setting the aim of 20% of the UK electricity supply to come from renewables by 20203, there are also significant time pressures placed on projects to drive them forward.
Comprehensive guidance is required for the offshore renewables industry to help developers specify surveys that will inform environment impact assessments (EIAs), facilitate front-end engineering design (FEED) studies and yield sufficient levels of information to satisfy marine contractors, investors and stakeholders. This must be done whilst keeping costs proportionate to the maturity of the project at each development stage and meeting project timescales. Guidance is required that will focus surveys on the key uncertainties affecting future development decisions.
This paper has been written as a follow-up to the article entitled ‘The Importance of Careful Site Selection and a Systematic Approach to Site Investigation for Offshore Windfarms’ by Fish in 20034. The article discusses the site investigation experiences from a typical Round 1 offshore windfarm project at Kentish Flats in the Thames Estuary.
To achieve consent to build an offshore wind farm, an EIA must be completed. A range of seabed environmental surveys have to be undertaken to inform the EIA process. The topics of interest normally include, but are not limited to,
Biogenic reefs (e.g. Sabellaria spinulosa)
Seabed sediments (with respect to plumes, scour and cable burial methods)
Seabed mobility (e.g. sand waves and shoals)
Marine archaeology (e.g. wrecks and buried evidence of paleolithic communities)
Unexploded explosive ordnance (UXO).
Both geophysical and shallow geotechnical surveys are required to provide the relevant data to investigate these topics:
Biogenic reefs - swathe bathymetry, side-scan sonar
Seabed mobility - swathe bathymetry
Seabed sediments - vibrocores and cone penetration testing (CPT)
Benthic communities - grab samples
Marine archaeology - vibrocores
Unexploded ordnance (UXO) -magnetometer.