Guidance for large schemes
Cultural Heritage should be ‘scoped in’ and appropriate assessments included as part of the Environmental Statement. The Infrastructure Planning (Environmental Impact Assessment) Regulations 2017 states "The EIA must identify, describe and assess in an appropriate manner…the direct and indirect significant impacts of the proposed development on…material assets, cultural heritage and the landscape." (Regulation 5 (2d)).
Potential for impact on archaeology
Developmental impact for solar farms includes tens of thousands of piles, cable trenching, associated infrastructure and mitigation measures such as scrapes and wildlife ponds, all of which could disturb and destroy surviving archaeology. There is potential for compaction during construction and decommissioning while through the lifetime of the scheme there will be refits which involve ripping out the old infrastructure and putting in new. In archaeological terms we as a profession are coming to realise that solar schemes are at least as damaging to archaeology as housing developments.
Full impact zone
The full extent of the proposed development area, including the connector route corridors, will need to undertake sufficient evaluation to allow for a programme of suitable mitigation. Archaeological impacts and subsequent mitigation have the potential for significant financial and scheduling impacts. Sufficient evaluation is therefore essential in informing the selection process and in ensuring the subsequent design and work programme is devised with an understanding of the level of archaeological work which may be required before and during the construction phase.
Search requirements
Archaeological evaluation will be undertaken as part of the assessment process, details and intended scheduling should be provided at the earliest opportunity and more specific information will be required going forward.
HER data for a 2 kilometre radius is required from the redline boundary and including any proposed options. Until they are descoped all cable route options need to be properly assessed as part of the development and as part of the Environmental Statement (ES).
All designated assets (for example, Scheduled Monuments and Listed Buildings) within a 5 kilometre radius should be taken into account for setting assessments. The significance of each asset must be assessed prior to scoping which assets would be affected. Modelling should particularly include any identified assets which have the potential to be visible or have their setting affected by the taller elements of the development.
Requirements for sufficient evaluation
It’s vital that a competent full desk based assessment (DBA) be completed at the earliest opportunity as desk based work provides the basis for initial understanding. This is informed by and built upon by a full air photo, LiDAR assessment and geophysical survey which in turn assists in the development of the trial trenching programme. The results of all the evaluation phases are required to form the baseline evidence and allow for sufficient understanding of the archaeological potential across the scheme. The evaluation work must be completed in time to inform the mitigation strategy which will lay out how the developmental impact on archaeology will be dealt with, therefore this will need to be submitted as part of the EIA.
Desk based assessment (DBA)
A desk based assessment must be submitted prior to the trenching WSI as it is required to inform an effective evaluation strategy. The DBA should include all reasonably available desk based information for the full extent of all proposed impact areas including any cable or connector routes.
Desk based sources should include full LiDAR and air photo coverage and assessment (details below); archaeological reports; Portable Antiquities Scheme (PAS) data and local sources and archives.
Map regression should include all available maps to provide a reasonable understanding of the development and time depth of the sites.
LiDAR and air photo assessment
A full competent LiDAR and air photo analysis, interpretation and assessment is required with full aerial photo coverage using all available oblique and vertical air photos including the Historic England Archive and Cambridge University Collection of Air Photos as well as RAF and Ordnance Survey photos including those held by Lincolnshire County Council.
Geophysical survey
A geophysical survey must be undertaken of the main development site and all potential cable connector routes until they have been selected or descoped.
The results are required to identify site-specific archaeological potential and to inform a programme of archaeological trial trenching and subsequent mitigation. Pre-determination evaluation of the cable connection corridors can be very useful with informing a decision on the most cost effective and viable route.
Regarding the geophysical survey a single Written Scheme of Investigation should be prepared that all contractors adhere to. This must include appropriate quality and control measures to ensure consistency of data recovery across the site.
In the event of multiple contractors separate reports for each contractor should be supplied in full and the consultant will supply a comprehensive and robust overarching report presenting the combined results as this will inform the subsequent evaluation trenching.
Trial trenching
Trial trenching is required as trenching results are essential for effective risk management, project management, programme scheduling and budget management. Failing to do so could lead to unnecessary destruction of heritage assets, potential programme delays and excessive cost increases that could otherwise be avoided.
Curators across the country are on a steep learning curve regarding the extent of the impact across these schemes as the specific impacts across the redline boundary are not included in the submission documents. It’s clear to us now that 1% or 2% trenching isn’t sufficient to undertake an adequate assessment and this has informed the emerging regional guidance requiring 3 – 5% trenching while understanding that this percentage will mean that significant archaeology is lost.
As well as targeting known and potential archaeology the trenching strategy will need to target those areas where earlier evaluation phases have not been successful in locating archaeology. Targeting blank areas is an essential part of determining the archaeological potential across a proposed development as different types of archaeology and geology may limit or mask the effectiveness of non-intrusive evaluation techniques.
Sufficient trenching will be required across the full impact zone to determine the presence, absence, significance, the depth and extent of any archaeological remains which could be impacted by the development.
The results of trial trenching will inform a robust mitigation strategy which will need to be agreed by the time the Environmental Statement is produced and submitted with the Development Consent Order (DCO) application.
Settings assessment
Regarding a competent settings assessment, the application site may affect the setting of several scheduled monuments as well as a large number of designated and non-designated heritage assets. The settings assessment or heritage impact assessment needs to begin from an understanding of the significance of each of those assets in order to assess the potential impact of the development on them and put forward any potential benefit or mitigation of proposed negative impact.
Environmental impact assessment (EIA)
The EIA will require the full suite of comprehensive desk-based research, non-intrusive surveys, and intrusive field evaluation for the full extent of proposed impact. The results should be used to minimise the impact on the historic environment through informing the project design and an appropriate programme of archaeological mitigation. The provision of sufficient baseline information to identify and assess the impact on known and potential heritage assets is required by Infrastructure Planning (Environmental Impact Assessment) Regulations 2017 (Regulation 5 (2d)), National Planning Statement Policy EN1 (Section 5.8), and the National Planning Policy Framework.
Sufficient information on the archaeological potential must include evidential information on the depth, extent and significance of the archaeological deposits which will be impacted by the development. The results will inform a fit for purpose mitigation strategy which will identify what measures are to be taken to minimise or adequately record the impact of the proposal on archaeological remains which must be submitted with the EIA.
This is in accordance with The Infrastructure Planning (Environmental Impact Assessment) Regulations 2017 which states "The EIA must identify, describe and assess in an appropriate manner…the direct and indirect significant impacts of the proposed development on…material assets, cultural heritage and the landscape." (Regulation 5 (2d)).
Please note that the Historic England Regional Science Advisor should be consulted on the project as well as providing advice on geoarchaeological assessment.