Surviving Commercial Archaeology 101 – Archaeological mitigation, strip, map and sample or the Open Area Excavation.
So far in our journey through the murky world of commercial archaeology we have looked at:
This time I’m looking at what happens if we have a lot of archaeology, the sort of thing that happens when our geophysical survey looks noisy and our evaluation confirmed the presence of a lot of features. This is when we strip larger areas. These can vary in size from a few square meters to several hectares and are either targeted at specific ‘hot spots’ identified by the geophysical survey and evaluation, or cover the whole site.
These are the sites that I really like doing. We are no longer peeking through the keyhole at the archaeology but exposing the whole area. There is a downside of course, excavation is a destructive process so a full open area excavation like this will leave very little behind. Though the development will remove anything that we do not. Our records will become the only information available on the site, so we have to do a thorough job. Sites can last anything from a few weeks to several months. My last two large-scale sites like this were both in Oxfordshire, one took us 24 weeks the other was 18 weeks. I did the first one nearly 2 years ago now and we are still trying to get the initial write up out, there was that much archaeology! Seriously – so much archaeology, you can see it on Google Maps!
Large scale stripped areas like this give us a lot to look at, we could have a whole settlement with several roundhouses, or we could be looking at ditches as part of a network of fields. We may also come across unknown burial grounds or urn fields all of which can give us a really good idea of what the type of site is that we are looking at, e.g.: domestic, agricultural, ritual etc.
The large open excavations like this are the very last chance that we get to look at the archaeology ahead of any development, in fact it is the last time anyone will be able to see the archaeology in this area as the development will remove almost everything in the area. We must be careful with our records then. Although it may come as a surprise to some that we do not actually excavate everything, instead we ‘sample’ the features. We also remove the topsoil and overburden by machine, although this is often scanned with a metal detector prior to removal, but any features or finds that were contained within this material are generally lost on a commercial site as we simply are not allocated the time available in order to undertake a thorough search of these layers. In such cases, an organised metal detector survey before the archaeological works commence would be useful as they would be able to collect and log any metal finds in the layers that will be stripped away.
It is the same with the archaeology itself. A ditch for instance may cross the site and be 150 meters long and 1.5 meters wide. We will not excavate the whole ditch, rather we usually excavate a 10% sample of the feature. Generally this means excavating slots 1 meter wide at 10-meter intervals along the length of the ditch, although we will be sure to excavate any corners, terminal ends and any place where the ditch crosses another feature as this can tell us which feature is earlier and from that we can extrapolate how the landscape use changed. However, this does mean that 90% of that ditch remains unexcavated when the machines come in to develop the site. It is unfortunate, we could lose a lot in that 90%. Large pits too are generally only excavated as 50% so that we have a section showing us the layers filling the pit, but unless we have a very good reason to excavate the other half then our 50% sample is all we take. Postholes are smaller and are often fully excavated, Likewise, features like burials and cremations are always fully excavated. Special features such as ring ditches are generally excavated to a 50% quota generally as 1-meter slots with 1 meter gaps between. They look very good when they are done.
It would be nice to be able to excavate sites 100%, but unfortunately it looks likely that we may be curbed even more as the government try to cut the ‘red tape’ as part of the shake-up of planning and development. We are already painfully aware of how much we lose under our current conditions, any curtailing to our ability to examine sites prior to development will lead to a huge loss of archaeological information. Many of us are in the process of writing to our MPs in order to ensure that our heritage is protected and point out that developers tend to sit on the sites for 10 years and call us in at the last minute – hence they feel we delay them, but this is another argument for another day, back to today’s discussion, open area excavations.
The main reason I love these sites is that it feels like we can really start to answer the questions about what was happening there in the past, we can start to see different phases of activity. On my last open excavation like this we had Iron Age activity all around the south and central areas of the site, but the Roman material was heavily concentrated to the north showing that people were using the area differently in these periods. We can start considering landscape use and the movement of people through the landscape. These long excavations are fun because we really feel like we are beginning to understand the past use of the site. We generate a lot of paperwork on these projects and it can be tough work, but there always tends to be a good atmosphere and the feeling that these are the jobs that people are really here for. It is these sites where we often find the most interesting archaeology, to name a few: Must Farm, the Viking Mass Grave in Oxfordshire, the Amesbury Archer, the Prittlewell burial and the North Berstead Warrior, but there are also Roman farmsteads, medieval brew houses and many many more.
S. M. Porter
Professional archaeologist and author, S. M. Porter loves history, adventure and digging in the mud. Her career is in ruins - just where she wanted it to be.