Reducing archaeological risk in residential development: why early assessment matters

Where archaeology can affect a scheme

Foundations, roads, drainage, utilities, landscaping, attenuation features and construction compounds can all remove or truncate buried remains.

Planning policy requires proposals affecting heritage assets to be supported by an assessment of their significance and the potential effect of development. The level of detail should be proportionate to the importance of the assets and no more than is necessary to understand that effect.

The local planning authority will normally seek advice from its archaeological adviser, who will consider the Historic Environment Record and the information submitted with the application. Depending on the site’s archaeological potential and the nature of the proposals, further assessment, geophysical survey or intrusive evaluation may be required.

Where the available information is insufficient, some or all of this work may need to be completed before the application can be determined. Other investigation or mitigation may be secured by condition.

Why early understanding matters

Archaeological requirements can affect:

• land value, viability and abnormal cost allowances
• developable area, density and layout
• drainage, access and engineering design
• the planning application and discharge of conditions
• the start of enabling, infrastructure and construction works

Archaeology should therefore form part of the early review of a site, particularly where assumptions are being made about capacity, layout or viability.

Recorded archaeology nearby does not necessarily mean that remains extend into the site, while an absence of records does not mean that remains are not present. Early assessment can indicate whether archaeology is likely to have a limited effect on the scheme or whether further investigation is needed before key decisions are made.

Assessment and evaluation

Assessment normally begins with a desk-based assessment of Historic Environment Record data, previous archaeological work, historic mapping, aerial photographs, light detection and ranging (LiDAR) and other relevant sources.

Geophysical survey may help identify buried features, although its effectiveness depends on the site conditions and character of the archaeology. Trial trenching may then be required to establish whether remains are present and understand their character, depth, preservation and significance.

The findings can inform the layout and provide a firmer basis for defining mitigation and understanding the likely implications for costs and programme.

Design and mitigation

Where significant remains are identified, the layout may need to be adjusted to avoid or reduce harm. This could involve locating open space over sensitive areas or changing roads, drainage, services and development parcels where practicable.

Preserving remains within a development requires careful consideration. Remains beneath open space may still be affected by landscaping, drainage, tree planting, ground reduction or construction traffic.

Where impacts cannot reasonably be avoided, archaeological investigation, recording and reporting may be required before or during development, with sufficient time allowed for the work and any subsequent analysis.

Managing archaeological risk

Archaeology should be considered before the layout, budget and delivery programme are fixed. Where a site has archaeological potential, the available evidence should be reviewed and a proportionate strategy agreed with the local planning authority’s archaeological adviser.

On most residential sites, archaeological issues can be addressed through assessment, design changes and proportionate mitigation. Identifying potential constraints early makes them easier to incorporate into the planning and delivery strategy.

Further information

Contact Philip Evans