Archaeology has become an increasingly common statutory component of construction and refurbishment projects since PPG16 (Planning Policy Guidance16: Archaeology and Planning) applied the 'polluter pays' principle to disturbance of archaeological remains in 1990. Twenty years on, every local planning authority (LPA) has incorporated PPG16 into its local plan, the number of archaeological investigations has increased dramatically, the Institution of Civil Engineers has published a standard form contract for archaeological investigations (Thomas Telford 2004) and now the new PPS5: Planning for the Historic Environment has broadened its scope and applicability. Most projects proceed satisfactorily, mainly because archaeology is still relatively inexpensive, but inexperienced clients and their advisors are still tripping up over the legislation, to their cost and embarrassment. This short article summarises the statutory basis of archaeology in the planning system and explains how designers and contract administrators can anticipate and minimise their clients' 'heritage' liabilities.

PPG16 was brutally simple and poorly explained: Disturbance of archaeological remains is an economic 'externality' – i.e. unintended consequence – of development projects, the cost of which is to be borne by the developer. The cost is the price archaeological organisations charge for the excavation, analysis and academic publication of those remains, there being no State funding for development-lead archaeology in Britain. This created, overnight, a market for archaeological contractors and professionals that had not existed before. There are now several hundred commercial archaeological contractors in Britain, ranging from sole traders to multi-nationals and a smaller number of consultancies, and most of the larger multi-disciplinary consultancies employ at least one archaeologist. In 1994, PPG15: Planning and the Historic Environment applied the same principle to development and refurbishment projects affecting historic buildings – Listed or not – and PPS5 (2010) has amalgamated both into a single statutory instrument. It is important that construction professionals appreciate that the Law now regards historic buildings – Listed or not – in the same light as archaeological sites: it is not merely their appearance that is important, but the archaeological details of their construction as well.

The protocols through which this statutory obligation is effected are now well established, if poorly explained to construction professionals. Nearly all LPAs employ the services of a 'curatorial archaeologist' to vet planning applications for those that potentially affect archaeological remains, by reference to a 'sites and monuments record'. The 'sites and monuments record' – sometimes known as a 'historic environment record' – is a database of all known archaeological sites and finds within an LPA's area, which is publically accessible, many via the internet. The curatorial archaeologist will identify those application sites where there is a possible archaeological constraint and request one or more of several sequential forms of work to inform and support the planning application, or as a condition of consent. It is not a 'box-ticking' exercise, but one designed to reduce ambiguity in what is an inherently unpredictable undertaking and one that can be managed in the clients' interests, but the cheapest option will not always prove the least expensive or quickest in the long run.

The process moves from the 'general' to the 'specific' through a series of stages analogous to the investigation and remediation of contaminated sites. It usually starts with some form of 'desk-based' study followed by, or in conjunction with, site investigation that 'evaluates' the archaeological potential of a site or historic building. Only then is the LPA archaeological officer able to recommend to the planning officers whether the project should continue with or without further 'mitigation' works – i.e. archaeological excavation, or record survey in the case of historic buildings. Where such 'mitigation' works are conditioned, discharge of the condition will require academic publication of the results: i.e. not in Current Archaeology or similar magazines, but in peer-reviewed scientific journals or monographs.

The requirements of each stage of work are set in advance by an LPA 'Brief', that archaeological contractors and consultants have little opportunity to influence, and specified in a 'written scheme of investigations' usually prepared by the contractor. It is one of the idiosyncrasies of commercial archaeology that contractors usually write their own specifications. The likelihood of this process being applied to a project can be assessed in advance by pre-application consultation with the LPA's archaeological officer or an archaeological consultant, NOT the planning officer. Furthermore, most local plans identify areas of 'Higher Archaeological Potential' and many LPAs have published supplementary planning guides explaining exactly how and where the process will be applied. The process and its terminology is also explained in detail in the recent CIRIA guide to archaeology so there is no shortage of guidance. Critically, all this has to be paid for by the applicant, be they a commercial developer or a disabled householder, with a substantial proportion of the costs being incurred before planning permission has been secured.

Mistakes to avoid

Most projects now run smoothly, but mistakes are still made. Projects falling foul of the 'heritage' issue do so usually for one of six reasons:

1. Avoiding pre-application consultation in the belief that it will elicit archaeological works that wouldn't otherwise have been asked for, resulting in a last minute scramble to get the 'evaluation' done within the six week determination period. It won't: LPA archaeological officers will ask for such work only where they have good reason to believe it is justified, currently less than 25% of all applications, of which only a fraction get beyond the 'evaluation' stage.

2. Commissioning a 'desk study' on the advice of a planning officer, in the belief that it will secure planning permission or, even less likely, satisfy a condition of permission: it won't, except in the rare instance where it can demonstrate conclusively that the site has been completely quarried away. In most cases, formal 'stand alone' desk studies are a waste of time and money, except when used explicitly to inform the design of subsequent site investigations.

3. Believing that submission of a 'written scheme of archaeological investigations' satisfies the LPA's requirements: it does not. It is the works described in the 'WSI' that have to be completed. Furthermore, the term, 'archaeological investigations' is intentionally non-specific about the type of works required: that is left to the LPA officer's discretion.

4. Failing to ensure that the 'evaluation' site investigations answer the applicant's needs as well as the LPA's. The LPA simply needs to know whether there are any archaeological remains within the site: the applicant also needs to know how much it will cost to fully excavate and analyse those remains BEFORE detailed design and cost planning commences. This is particularly important in urban sites such as London or Bristol, where the thickness and quality of the remains is the critical determining factor in the cost of their excavation and analysis. An 'evaluation' that identifies only the upper level of those remains is of little use to foundation designers.

5. Proceeding with 'mitigation' works such as archaeological excavation on the basis of simple lump sum contracts and inadequate 'evaluations', rather than comprehensive Bills of Quantities. The archaeological contractor will either make a disproportionate profit, or will face a loss. The latter is more problematic because it can lead to expensive claims and disputes or the work not being completed, resulting in the planning condition not being discharged. Bankruptcy is still rare in commercial archaeology, but it does happen.

6. Opting for 'watching brief' conditions in the belief they will be carried out by the LPA's archaeological officer – they won't – or be less onerous and expensive than a pre-determination 'evaluation' site investigation. On domestic scale projects this can be the case, but construction on commercial or constrained urban sites will be complicated by the presence of a team of archaeologists trying to investigate sensitive remains whilst the civils are trying to dig them out. It can also be highly dangerous. Watching briefs are also costed on a day rate basis with only the vaguest of estimates for off-site analyses and report preparation: the scope for claims and disputes is enormous.

Properly anticipated and managed, archaeology will not inconvenience a development project nor add substantially to costs: ignored or badly managed, it can derail the most ambitious of projects at any stage and affect the reputation of the professionals involved.

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