Abstract
Since 2003, the European Marine Energy Centre Ltd (EMEC) has provided purpose-built, accredited open-sea testing facilities for wave and tidal energy converters across four test sites in the Orkney Islands. Fall of Warness, established in 2005, is the full-scale, grid connected tidal energy test site.
EMEC has identified a requirement for a Navigation Risk Assessment (NRA) compliant to the Maritime and Coastguard Agency MGN 543 in order to update the previous NRA, including impact on navigational safety and identification of revised recommendations as required.
This NRA is device neutral, not assessing any particular device or type of device, but instead assumes a range of possible devices located within the test site.
Vessel traffic analysis was undertaken on data from the Automatic Identification System, visual observations from a shore-based survey conducted over a number of years and a variety of secondary sources.
The Fall of Warness test site is not within port limits. Orkney Islands Council Marine Services has Vessel Traffic Services (VTS) with full radar coverage of the Fall of Warness test site, but they do not actively monitor or direct traffic outside the Statutory Harbour Authority (SHA) limits.
The site is within an IMO-adopted ATBA, which was established following the Braer oil spill. All vessels over 5,000 GT carrying oil or other hazardous cargoes should avoid this area.
The greatest density of traffic is to the south of the development to and from Eday and the mainland. A lesser number of vessels transit through the Fall of Warness in a southerly or northerly direction, though these tend to avoid the existing test devices by keeping to the west. There are also a number of ferry transits from the south passing west of Muckle Green Holm then turning back south towards Eday Pier during strong south easterly winds and flood tides. The density of traffic close inshore is not significant, although these areas are used by fishing vessels “potting”.
As part of this assessment, consultation was undertaken with a number of local stakeholders and statutory regulators to better understand the baseline conditions and possible impacts to their activities. No consultees raised any significant concerns regarding the test site. In addition, a review of incident data from the Marine Accident Investigation Branch identified only one incident in the vicinity of the site which involved a service vessel while at anchor and resulted in no damage to the vessel, serious injury or loss of life.
A number of impacts on navigation were identified and individually assessed, these are as follows:
- No significant impact on vessel traffic routeing was identified, with the route through the Fall of Warness remaining open for transiting vessels;
- Any devices positioned in the site posed a low risk of contact from passing vessels;
- An assessment of under keel clearance requirements was undertaken. The results show that the risk of subsurface contact could be reduced significantly if devices were greater than 10m below the surface at Lowest Astronomical Tide; however each device would need to be assessed individually;
- No impact on collision risk or visual navigation was identified given the physical size of the devices anticipated to be deployed. Similarly, no impact on communications, radar or positioning systems is anticipated;
- The failure of device moorings was considered at the site. However, it was determined that this should be assessed on a device by device basis;
- No significant impacts on recreational or fishing activity were identified as a result of the continued operation of the test site;
- The presence of underwater cables was not assessed to pose a significant hazard to fishing or anchoring operations;
- No impact on Search and Rescue capability was anticipated; and
- Whilst there are no other renewable developments currently in close proximity to Fall of Warness, future exploitation of existing and planned lease areas may result in cumulative and in-combination effects.
A navigation risk assessment was conducted that identified 11 hazards relevant to this site. The likelihood and consequence of each were scored based on the results of this assessment and all hazards were deemed to be low risk.
A number of site-wide risk controls were identified which are currently in place to manage any risks to navigating vessels. In addition to this, a list of possible risk controls which could be considered for future devices were identified.
Finally, guidance is provided for developers conducting device-specific NRA addendums and the considerations which should be made in each case. This assessment has provided the baseline information for developers to consider during their device-specific assessment but as this assessment is device neutral, any deviations as a result of the specific characteristics of a device should be taken into account.
In summary, the NRA has not identified any significant hazards that relate to the current Fall of Warness Site. This document should be reviewed and updated at regular intervals to provide developers with an up-to-date and relevant site-wide assessment of the risks associated with the continued operation of the Fall of Warness test site.