Cost of change against project stage (after ICE 1996)
With profit margins becoming increasingly tight in the construction industry, developers are keen to manage and control risk and uncertainty, whether this be related to the cost and availability of materials, ground contamination, or archaeology. As a site’s archaeological potential is usually unknown, it is a case of moving the site from the unknown, to the known. It will usually be a staged process that is necessary, with each stage of work reducing the level of uncertainty, and therefore the level of risk. The earlier it is considered in a development program the better, as it allows more time to work out projected costs and incorporate any necessary changes to reduce these costs, into a design programme.
Example of Historic Environment Record data
For many projects, most commonly the first step is a desk-based assessment, a non-intrusive survey of known evidence using a range of sources such as historic maps, aerial photos, and the Historic Environment Record, the local authority’s database of sites and findspots. This will determine the likely archaeological potential for a site and is a relatively rapid and cost effective technique. This may not be necessary for small projects however – such as extensions, or one or two dwellings, but developers can seek advice from the local authority archaeologist on this at an early stage.
Deposit model prepared to consider likely depths of archaeological deposits
More and more often however, as a result of NPPF, planners are asking for much more site specific information concerning the likely impact of a development. In these instances the document required is variously called a heritage statement or heritage impact assessment, where a consideration has to be made of the precise nature and extent of the likely impacts of the development upon the identified archaeological resource, as well as putting forward proposals as to how to mitigate the effects of the development upon this archaeology. This relates to both the physical impacts on the below ground archaeology as well as on the setting of monuments in the wider landscape. The issue of setting is a much wider topic, particularly with relevance to wind turbines, which are visible for many miles.
Gathering such information at an early stage in the design programme, through minimal and often non intrusive archaeological intervention can save the time and costs of either redesigning a development plan to avoid the need for further archaeological works, or archaeological excavations further down the line causing added costs and delays. Another thing to consider is engaging an archaeologist to monitor any geotechnical works that are being undertaken, as this will give a good indication of the likely depths of archaeology, made ground or truncation across a site.
More often than not, a DBA may identify an archaeological potential for a site but cannot within certainty determine the precise nature of the archaeological resource that may be present, in which case, intrusive works may be necessary to further characterise the archaeology present within the site – usually, where ground conditions are appropriate, geophysics is a common starting point, followed by trial trenching. As well as providing information on the below ground archaeology, geophysics can help inform and also limit the extent and therefore cost of subsequent targeted trenching.
Evaluation trenching strategy based on geophysical survey results
This level of work should provide a planning authority with sufficient information upon the archaeological resource to allow for the determination of a planning application, and to establish appropriate measures, known as final mitigation, undertaken as a condition of planning. It may be the case that the trial trenching finds little or nothing of interest and that no archaeological condition is imposed. However, where this is not the case, developers will need to consider measures to either preserve the archaeological remains in situ, or to preserve by record, ie. dig it all up.
The concept of preserving the remains in the ground wherever possible, ie preservation in situ, is one of the prime considerations for archaeology and is considered preferable to excavation, ie preservation by record, as this is in itself a physically destructive process. Obviously it also reduces the developer’s bill for archaeology, and in purely financial terms, there is a consideration on such sites as to whether it would be cheaper to use a potentially more costly foundation design (eg piling) that preserves the archaeology, or fund an excavation that records the archaeology to the satisfaction of the planning authority, but allows a more cost effective foundation design to be used. Redesign of the development layout should also be considered, for example, relocating areas of public open space to protect areas of archaeological interest.
So there are ways to manage the archaeological risk, and the thing that we always try to stress to developers is to build in time to consider the likely archaeological issues that may affect a site. Most county councils employ archaeological officers whose role it is to advise planning officers and developers upon the likely implications of a development, and most archaeological contracting companies will also be happy to advise a client. It is sometimes possible to come up with ways to avoid or greatly reduce the need for archaeological investigations, and it is usually possible to manage the risks associated with the possibility of unforeseen costs or delays caused by unexpected findings. Archaeology is inherently unpredictable however, and we never know for certain what we are going to find. I am afraid that we as archaeologists can’t be held responsible for what the Romans did 2,000 years ago!
