Gemma Keenan, senior environmental consultant in the renewables and marine development team at Royal HaskoningDHV, considers how tidal stream energy developments can benefit from using the Rochdale Envelope approach.
The Rochdale Envelope approach was developed during onshore planning applications to provide flexibility in design options where details of the whole project are not available when the application is submitted, while ensuring the impacts of the final development are fully assessed during the Environmental Impact Assessment (EIA).
Consents granted on the basis of the Rochdale Envelope are conditional on providing the final details for agreement prior to construction.
The Rochdale Envelope approach has been successfully adopted in the consenting of a number of offshore wind farm projects in the UK and is now being used in the consenting of tidal stream energy developments.
Tidal stream energy consenting
The tidal energy industry is at an early stage of development and there is a wide range of possible technology designs available.
When the project description is highly defined in the Environmental Statement (ES), this can lead to requirements for an addendum to the consent if changes are required. Two examples of developments that have required such an addendum include:
- the original consent for the SeaGen tidal turbine in Strangford Lough, Northern Ireland, required changes to the device foundation from a monopile to pinpiles; and
- an array of Andritz Hammerfest devices in the Sound of Islay by Scottish Power Renewables required adjustments to the device locations within the original boundary.
Importance of flexibility
Addendums are likely to result in delays to the project programme and additional costs to the developer. Lessons learned during consenting show that tidal stream energy sites which have a single technology option require flexibility in the project design envelope, in order to:
- allow variation in device layout pending detailed site investigation surveys to optimise generation efficiency or micro-site around constraints;
- allow for some device and technique advances between submission of the EIA and construction; and
- provide flexibility in some areas of supply chain options which may avoid developers becoming vulnerable to price volatility of a limited supply source, enabling cost reductions for the development.
In addition, some site developers have limited or no affiliation to one technology developer and are therefore keen to maintain flexibility in the device types until further site investigation and technology procurement works are undertaken. Due to the financial constraints on the majority of tidal developments, these works are usually undertaken post-consent when there is greater confidence in the project and financing can be secured.
The Perpetuus Tidal Energy Centre gained consent in April 2016 to demonstrate arrays of a range of tidal technologies. The EIA considers tidal device types that might be installed at the site and undertakes an impact assessment based on realistic worst case scenarios for each receptor impact.
A similar approach has since been proposed by the third sector company Menter Môn, for the development of their proposed Morlais Marine Energy site in north Wales.
Maintaining a high quality EIA
It is important that an ES clearly outlines if the EIA has been undertaken using the Rochdale Envelope principle, including signposting where areas of flexibility are required. Sufficient detail must be provided to allow the impacts to be fully assessed and the parameters used should be transparent. Where there are a range of potential options or parameters the assessment of each impact should outline the relevant realistic worst case scenarios.
It is good practice to discuss and agree the planned approach with the relevant planning authority prior to proceeding with the EIA. Based on experience of using the Rochdale Envelope in offshore renewables, it is clear that stakeholders and regulators are concerned, not only with ensuring that the actual impacts of the development will be equal to or less than those assessed in the EIA, but also that the EIA does not excessively exaggerate the impact by combining multiple worst case scenarios into a development scenario which is highly unrealistic.
Such an exaggerated approach can make it difficult for stakeholders to provide meaningful advice and judgement during the consent determination process.
The Crown Estate report of the Rochdale Envelope workshop for wave and tidal energy developments in the Pentland Firth and Orkney Waters confirms that it is unlikely that developers will be in a position to determine all design parameters prior to submitting an application for consent.
It is therefore important that consent is granted on the basis of conditions which provide the flexibility for detailed design to be finalised post-consent while also protecting the environment.
