If a site is within an area of potential archaeological interest the applicant may need to provide the Planning Authority with information of the likely impact of the scheme on any buried remains. This is estimated from existing records, including historical accounts, and reports of archaeological work in the vicinity, in conjunction with a number of sources which suggest the nature of deposits on the site, like bore-hole logs and cellar surveys. This is presented in a standard format, known as a Desk Top Assessment.
Written Scheme of Investigation
A Written Scheme of Investigation is a detailed document which sets out the precise work required, covering the area to be excavated, the volume of deposits to be recorded, the methodology employed, the degree of expertise required, the amount of analysis and research required, finds collection policies, conservation of perishable artifacts, the deposition of finds and archives and the eventual publication of the results. Such programmes are expensive and time-consuming, and represent to the developer a construction cost against which to balance the real benefits of locating in the chosen area.
In many cases the small scale of the disturbance associated with a development, or the low probability that archaeological remains will have once existed, or survived on the site, will mean that a much lower level of observation and recording is required. Known as a Watching Brief, this is the time-tabled attendance of a suitably qualified archaeologist employed by the developer at the point when digging is underway. Any archaeological deposits encountered will be quickly recorded and any finds collected, without undue disruption to the construction work. Again, the County Archaeologist will provide the specification for the Watching Brief.
On the basis of the information provided in the Desktop Assessment, the Planning Authority will determine the need for further work to test whether deposits predicted in the Assessment have survived on this plot. This is usually achieved by trial excavation and is known as a Field Evaluation. This programme will also be defined by the County or Industrial Archaeologist, and may employ a range of survey and analytic techniques besides excavation (such as field walking or geophysical survey). Should important remains be brought to light, the preferred option would be avoidance of disturbance for example by the use of building techniques that ensure minimal disturbance of the buried remains on the site.
With the benefit of the Assessment and Evaluation reports, the Planning Authority can make the appropriate decision (in the context of the Policies set out in the Local Development Plan) on whether to give consent to the scheme or not, and, if so, what further steps need to be taken to mitigate the destructive effects of the development on the archaeological remains. This will ensure that any remains that will be unavoidably destroyed are archaeologically excavated, analysed and published, so that the site is 'preserved by record' if not in fact. The requirements for further work will normally be attached to the Planning Consent as a condition.
Where standing buildings form a component of the archaeological resource, there may be a need to undertake Building Recording in advance of demolition or renovation. This will not be restricted to Listed Buildings, which are selected mainly on an architectural criteria. Many outwardly unprepossessing structures are important in forming a link with past communities and industries, and which will merit recording by qualified archaeologists or building historians to an agreed specification which will reflect the importance of the structure and detail the most suitable recording methodology (eg photographic survey, elevation recording etc).
Evaluation by exploratory fieldwork usually takes three forms; field walking of agricultural land earmarked for development, geophysical survey, and test trenching across fields to be build-over. It is not uncommon that a combination of all three are requested by the Planning Authority to inform the Planning Decision Process. To mitigate the damaging effects on the archaeological heritage of green-field development, where previously unknown archaeological sites may await discovery, it is becoming common practice for Local Planning Authorities to ask developers to undertake such fieldwork on green-field sites to be destroyed by substantial developments.
Geophysical survey is a non-intrusive technique used to identify buried features, which are then further investigated by excavation to determine whether or not they are archaeological in origin.
There are several main methods:
- Electromagnetic surveying measures changes in the magnetic field. The fill of a pit or ditch for example, will produce an anomaly because of the contrast in the strength of the magnetic field between the magnetically enhanced topsoil used to fill the feature and the surrounding subsoil. Palaeochannels and other geological features, hearths, ovens, burnt material and metal objects will also create anomalies. When these anomalies are mapped using an instrument called a magnetometer, the geophysicist can deduce whether these features are likely to be of archaeological origin.
- Resistivity passes an electric current into the ground through a line of probes and measures the resistance to the current at set points across the site, which depends on the conducting abilities of the soil and any features within it. Ditches or pits for example give a low resistance. Features such as wall foundations, rubble, yards, roads and cobbled trackways give a high resistivity. Again, the features can be mapped allowing a preliminary assessment of the site's likely archaeological potential to be drawn up.
- Ground Penetrating Radar emits a pulse of energy into the ground and measures the time it takes for its echoed return. Travel times are recorded and converted into depth measurements. Thus interfaces between different strata and features can be detected. The advantage of this technique is that it can provide a 3D view of a buried site. Unlike electromagnetic surveying and resistivity which work best on undisturbed green-field sites, GPR works well on deeply stratified urban sites.
(Source: 'The use of Geophysical Techniques in Archaeological Evaluations' IFA Paper No. 6 and 'Geophysical survey in archaeological field evaluation', Research and Professional Services Guideline No 1, English Heritage).
Technique used on arable land to collect surface artifacts which have been turned up by the plough. The site is divided up into a grid of squares, each grid square is then systematically walked across in turn by the archaeologists and any small finds such as pottery shards, flint tools, clay tobacco pipes, coins etc are collected and bagged. The finds are analysed and the number of each type and date of find from each square is recorded onto a site plan. Concentrations of particular types or ages of find may indicate that different parts of the site were used for different activities or at different periods in the past. Such areas may then be targeted by trial trenching to determine whether or not the finds are associated with a structure or feature of some sort. Field walking will be requested by the Planning Authority on proposed development sites on arable land, often in conjunction with a geophysical survey.
Maritime archaeology has become an increasingly popular subject, which has not, in the past, received the attention it deserves. With recent changes at national level in the way the coastal heritage is cared-for, Local Authorities have been given a wider role, particularly as holders of information on the archaeology of coastal waters.
The Tyne & Wear Historic Environment Record is currently being expanded to include maritime sites, and the County Archaeologist, as a member of an active underwater archaeology group, the Maritime Archaeology Project, is involved in a number of local projects, including a survey of an iron-hulled sailing ship, the Inga, which was built in Sunderland and wrecked off Cullercoats in the Great Storm of 1901.
Marine and inter-coastal sites are known from the earliest times, as evidenced by scatters of flint tools, until the Second World War, when a large number of vessels were sunk by enemy action off the coast of Tyne & Wear.
Further information about the maritime archaeology being undertaken at the moment can be obtained by contacting the County Archaeologist.
In extremely rare circumstances, exceptional and unpredicted remains are encountered while development is in progress. There are powers at the discretion of both the Secretary of State, and the Planning Authority to intervene to ensure that nationally important remains are protected. The developer can insure against any resultant loss, and would, if all appropriate steps have been taken, be entitled to compensation. In most cases, it has proved possible to achieve a satisfactory conclusion through voluntary negotiation. The best insurance is to take the appropriate steps (Assessment, Evaluation etc) at the right time.
Early consultation with the County Archaeologist and the Industrial Archaeologist is of enormous importance. They can provide an initial appraisal of the likelihood that archaeologically sensitive deposits need to be considered for any specific planning application, and give advice on the steps that may need to be taken at each stage of the process.
Where standing buildings form a component of the archaeological resource, there may be a need to undertake Building Recording in advance of demolition or renovation. This will not be restricted to Listed Buildings, which are selected mainly on an architectural criteria. Many outwardly unprepossessing structures are important in forming a link with past communities and industries, and which will merit recording by qualified archaeologists or building historians to an agreed specification which will reflect the importance of the structure and detail the most suitable recording methodology ( e.g. photographic survey, elevation recording etc).