Exciting and unexpected archaeological discoveries show how no evaluation process for sites is fool proof. What happens next shows how important cooperation and communication is, particularly for the County Archaeology Service, who are tasked with supporting development AND safeguarding heritage. The critical concept is “significance” – how important are the remains; what is their potential to inform us about the past? Rachel Foster, Assistant County Archaeologist reports:
In 2017 Wessex Archaeology excavated a new housing development north of Bitham Park in Westbury. I had requested this work as a condition of planning permission, based on limited evaluation results. Unexpected discoveries demonstrated the challenges faced by Planning Archaeologists in understanding the significance of archaeological sites based on the results of trial trench evaluation.
The 2018 National Planning Policy Framework states that local planning authorities should identify and assess the particular significance of any “heritage asset” that may be affected by a proposal. In line with this advice, we often ask for sites to be investigated before the determination of a planning application, so that we have that information. Evaluation usually this consists of geophysical survey followed by trial trench evaluation. The Wiltshire and Swindon Historic Environment Record which contains detail on archaeological sites, buildings and finds, informs our decision making.
Archaeological evaluation can feel like a game of battleships. When geophysical survey goes well, and reveals features that look like potential archaeology, we ask for trenches to be dug and the features investigated by commercial archaeologists. The aim is to understand the significance of the site by investigating features within the trenches, which is not always so easy: if geophysical survey has not been carried out or is unsuccessful, then trenches are placed either systematically or randomly across a site and there is potential to miss remains. Today, the trenching is usually a 3-5% sample of the development site but in exceptional circumstances, up to 10% may be carried out. That sample of trenching should find archaeological remains within a site and provide enough information to understand the importance, extent and significance of any remains. Results of evaluation will then inform our advice to the planning officer on the impact of the development on archaeological remains. Remains considered to be of national significance are likely to be preserved in situ and not developed, but other remains are likely to be investigate. Early knowledge about archaeology and its potential effect helps the developers manage their risk and adequately budget for excavation costs, as well as post-excavation work and publication.
The geophysical survey results at Bitham Park didn’t show much other than a few lines representing ridge and furrow remains across parts of the site and a few other possible linear features. This image gives an example of the greyscale plot of the geophysical survey results (magnetromotry).
Geophysical survey isn’t always reliable, so I asked for trial trench evaluation prior to determination of the planning application: in some cases, later ridge and furrow can hide earlier remains. As the geophysical survey indicated, there were remains of medieval/post-medieval ridge and furrow cultivation; however, my assessment that there might be more archaeology was correct. Archaeological features were discovered across several trenches, mostly concentrated in the western part of the site. They included ditches, gullies and pits containing small, worn pottery fragments from the early/middle Iron Age and Romano-British periods (150BC onwards). Nevertheless, the significance and extent of the remains could not be fully understood, so I asked for a second stage of evaluation to provide more data. The extra information would help me define an area for archaeological mitigation – the full excavation of important features. The results confirmed prolonged and intensive agricultural use from the medieval period (1066- 1540). This had truncated and displaced features and artefacts from the earlier Iron Age and Romano-British periods; however, theses features included and arrangement of post holes representing a possible structure (see trench locations of two evaluation stages below).
On the basis of the two evaluations I asked for an area of excavation within the vicinty of where the most significant archaeological features were recorded, in the western part of the site and along a north-south trajectory.
In advance of the housing development an initial area was stripped with contingency and here’s an aerial view of the site below, can you spot anything interesting?
At the end of August I celebrated five years with the archaeology team here at the History Centre in Chippenham. I thought this a suitable milestone in which to reflect on some of the most exciting discoveries in the central part of Wiltshire (the area I cover), discovered through the advice we give on planning applications.
The Government set out its requirements for the planning system in the National Planning Policy Framework in 2012. Section 12 deals with conserving and enhancing the historic environment. The advice we give on planning applications follows this guidance which needs to be relevant, proportionate and necessary. It is important to understand the significance of heritage assets impacted by development, which is why we ask for a proportionate level of investigation to be undertaken prior to determining applications. Various stages of investigation are carried out. To begin with an archaeological Desk Based Assessment (DBA) pulls together existing information, using as a baseline the Historic Environment Record and other sources where available such as historic maps, aerial photographs, field surveys and site assessment. The DBA helps to establish the potential for archaeological remains to be present within a development site. Sometimes, there is little existing information available because there have been few investigations within the area. In such cases geophysical survey is a useful method for revealing unknown archaeological remains within a site. We get greyscale plots and interpretation plans to help understand what potentially is of archaeological origin. In most cases we ask for trial trench evaluation following geophysical survey. Trial trenching enables us to understand the significance of the archaeological remains which will be impacted by development. Depending on the heritage asset’s significance (to use NPPF terminology) we may ask for a site to be preserved in situ i.e. not impacted by development, or preserved by record i.e. it gets excavated, the remains assessed and then reported and/or published. The following examples show previously unknown settlements which have been found through such methods.
Westbury Trial trench evaluation followed a geophysical survey in 2015 which discovered a number of features dating to the Romano-British period including a number of trackways and ditches. The site has yet to be developed.
Melksham Trial trench evaluation followed a geophysical survey in 2014 which confirmed the presence of a Romano-British settlement. The site is currently being excavated, more detail to follow.
At another site in Melksham, a geophysical survey identified a number of features and the trial trench evaluation confirmed remains dating to the prehistoric, Roman, medieval and post-medieval periods. The site has yet to be developed.
Trowbridge Geophysical survey across a large proposed development site highlighted two sites of particular interest. Trial trench evaluation confirmed a concentration of early Romano-British ditched enclosures associated with trackways and pits and posthole features which appear to represent settlement remains. The relationship between the two sites is of interest. More ephemeral prehistoric activity was represented in other parts of the site which the geophysical survey did not pick up.
In the archaeology service most new archaeological discoveries tend to be through our advice on planning applications. If a proposed development has the potential to impact heritage assets and in particular those with archaeological interest (as referred to in the National Planning Policy Framework), then we advise planning officers that a programme of archaeological investigation needs to be carried out in order to determine the significance of heritage assets affected by the proposals. Since I joined the archaeology service in August 2012 there have been some really exciting discoveries through development management, an overwhelming amount dating to the Romano British period. To name some of the top sites over the last few years that date to this period, we've had a Roman villa in Devizes, a roadside settlement near Beanacre, a high status farmstead outside Chippenham, two farmsteads on the outskirts of Trowbridge...the list goes on. In fact I have been surprised at just the amount of activity going on during this period in our county. Maybe it's not surprising considering we have some major Roman roads running through (see map below) including the main routes from London to Bath; from Silchester to Dorchester (Port Way); from Lincoln to Exeter (Fosse Way) and from Winchester to Charterhouse (Mendips). The two towns of Cunetio (Mildenhall) and Sorviodunum (Salisbury) lay at important junctions of the strategic road network and other towns of Durocornovium (Wanborough) and Verlucio (Calne) are also known to lie along the road network.
Many of you no doubt have read recently in the newspapers or heard on the radio that there has been a major new Roman discovery in the Deverills. We got a call from Luke Irwin who explained that whilst constructing an electricity cable to one of his outbuildings his workmen stumbled upon some kind of tiled floor surface and the tiles appeared to be quite small and colourful. He ordered the workmen to stop digging and that is when he contacted us. Of course my initial reaction was that of incredible excitement tempered by the realism, "what are the chances", people often tend to over exaggerate the significance of archaeological discoveries in their gardens. Despite my cynicism I quickly arranged to visit the site the following day with the County Archaeologist, Melanie Pomeroy-Kellinger. Upon our arrival Luke explained that one of his workmen was interested in archaeology so had meticulously cleaned the floor. When we peered down the cable trench both our mouths must have dropped open and I think we both said at the same time "I don't believe it, you have got a Roman mosaic!!!” There was no arguing with the clearly distinctive Roman mosaic pattern, a common geometric border pattern known as guilloche.