4          Outcomes

 

Our study suggested that geotechnical projects could provide a lot of information to archaeologists and could do so in a way which the geotechnical profession might find easy to accept.

 

There was broad agreement, among those interviewed, that geotechnical staff could and would record more archaeologically useful information – but that they would have to be requested, trained and paid to do so.

 

 

Thus we need to persuade those who pay for and commission the recording – the developers and senior engineers – that geotechnical records should be improved to allow basic archaeological interpretation. The local authority archaeological development control staff must also specify that access to enhanced geotechnical records should be required as part of the archaeological brief for a development.

 

We don’t think that geotechnical staff – not specifically trained in archaeology – should try to record or interpret archaeological deposits, because such records won’t be trusted by the archaeologists who need to use them. But we do think that simple matters, crucial to archaeological interpretation, such as the presence of modern contamination, organic matter, soil wetness and the sharpness of boundaries between strata, could be recorded reliably by geotechnical staff without archaeological training. We feel that it was more important that records are consistent and sufficient than comprehensive.

 

There is certainly a strong case for archaeologists and geotechnical staff each to receive some training in the role and methods of the other in order to improve the often poor communication between them.

 

Most of the evidence which archaeologists would like to obtain from geotechnical records is provided for in British Standard BS5930 for geotechnical records and in the recording sheet derived from it.  We think that we are most likely to succeed in encouraging archaeologically useful geotechnical recording through the use of BS5930 rather than  entirely new recording schemes, since this is an existing and comprehensive standard, already accepted by the geotechnical industry.

 

This will require that the standard itself is as widely adhered to as possible – something which archaeologists should therefore aim to encourage in their discussions with developers and engineers.

 

We think that most things which BS5930 does not record, such as the date of pottery fragments, are probably too complex to be recorded by geotechnical staff to a standard which archaeologists would trust.

 

Two additional kinds of data (soil wetness and unit boundaries) not normally included in BS5930, will need to be recorded for archaeologists to make the best use of the records.

 

Any changes in geotechnical recording practice will need to involve several different groups of technical staff. Borehole records are an amalgam of observations made by drillers on site and engineers notes made in the field and the laboratory. Both these groups and the engineers with oversight need to be given the information needed to record with archaeology, as well as geotechnical matters, in mind – as well as being persuaded that it is worthwhile.

 

The density of geotechnical observations within a site, and the distribution of test pits and boreholes, is decided by the engineer responsible, on the basis of the engineering requirements of the project.

 

The locations and numbers of these may not be ideal or sufficient for the archaeologist. There is sometimes scope for negotiation between the engineer and archaeologist so that the pits and boreholes are located to meet the needs of both.

 

Likewise, if a drilling crew or excavating machine is already on site to carry out the geotechnical investigation it can be much cheaper to get any further pits dug and boreholes drilled for the archaeologist at the same time, simply augmenting an already agreed distribution and avoiding the need to get the same crews and equipment back to the site at a later date and at significantly greater cost.

 

Those who use geotechnical records for archaeological interpretation also need to be aware that the classes (such as of particle size or soil colour) defined by BS5930 are not the same as those commonly used on excavations in Britain – though British archaeologists do not work to nationally agreed standards. Geotechnical records are, however, consistent between projects – something that we cannot claim for archaeological records.

 

Engineering geologists have, until now, classified most urban archaeological deposits, along with more modern accumulations, as “Made Ground” – lumping modern refuse and building site levelling dumps with much older strata of key interest to archaeologists. 

 

The geological community is now starting to subdividing made ground and making its definition more precise on the basis of deposit morphology. Parallel efforts are also being made to improve the description of made ground material in geological and geotechnical investigations. Archaeologists could help to define made ground deposits in terms of the nature of the deposits themselves, taking a role in geological mapping of made ground which acknowledges the overlapping interests of the professions.

 

Criteria.  Here is a list of the key things which we think archaeologists want from geotechnical records and which might be reliably recorded by geotechnical staff. Those which we believe could be used in the form defined by BS5930 have been left as such to avoid altering current geotechnical practice.

 

They were chosen because they should be:

 

Easy to record correctly

 

Useful for archaeologists

 

Our aim is to require geotechnical practice to change as little as possible, in improving its value to archaeologists, so that our recommendations are more likely to be accepted. We will therefore keep strictly separate the business of recording properties and interpreting their archaeological origins.

 

For the archaeologist, of course, this interpretation will have to take place since it is the whole point of their investigations. Increasingly, moreover, archaeologists are interested in the origins of the natural deposits around and beneath the archaeological strata since this tells them about the environment in which past communities lived their lives. Thus their interests coincide with those of geologists – and there is real potential for collaboration and shared research which we could do more to explore.

 

 

 

It is unfortunate that the colour and texture of a deposit is described differently by BS5930 and by the standard schemes used by most British archaeologists. Both BS5930 and the normal archaeological schemes are adequate for simple records although the Soil Survey texture scheme and Munsell colour scheme are the more complete Practical experience shows that the BS5930 texture and lithology recording system works well, for geotechnical purposes, and is well established.

 

Inclusions are recorded with other Minor Constituents on a BS5930 recording form. While archaeologists would find it very useful for geotechnical staff to record precisely the nature of any inclusions – such as Roman pottery – there is too great a risk of misidentification. There are, however, certain artefacts which can only be modern – such as plastic bags, ring-pulls and concrete reinforcing bars – which can and should be recognised and recorded as such. In archaeological terms the important distinction is, in any case, between modern materials, which do not warrant more detailed study, and non-modern materials, which do. Other artefacts should be simply recorded as present as minor constituents of the deposit they are found in.

 

The amount of organic matter in a deposit is often crucial in interpreting the kind of archaeological evidence which may be found in it. BS5930 includes quite a full description of the organic matter content of deposits and, if followed carefully, would be sufficient for most archaeological purposes.

 

We recommend that, for clarity, only soils and deposits which are formed predominantly of organic matter are described as such and that, where a deposit contains organic matter but is predominantly mineral this is explicitly recorded.

 

Deposit moisture is not included in the BS5930 criteria, although geotechnical records contain relevant information about water ingress into pits and boreholes since this is an important geotechnical consideration. Archaeologists want to know if deposits are wet because this may mean that organic evidence (from leather shoes to pollen grains) is well protected from bacterial decay and may survive intact. If a deposit is dry this survival is very unlikely.

 

Archaeologists are also, of course, interested in the logistics required of excavation – which can be a lot more complicated in wet deposits than dry.

 

Packing density (along with compactness and strength) is described in detail in BS5930 because of its obvious relation to the bearing properties of the ground. The same criteria are relevant to archaeologists who, with experience, can distinguish certain kinds of strata (such as a common kind of dark, highly granular and relatively loose urban Medieval deposit) by their density, among other properties.

 

Stoniness can be described fully using BS5930.

 

The nature of boundaries is a key consideration in archaeological, as well as pedological and geological interpretation but does not appear on the BS5930 description form. We propose a very limited classification between Diffuse (grading over more than 15cm), Gradual (grading over 6cm to 15cm), Abrupt (grading over 1-6cm) and Sharp (grading over less than 1cm) to keep the recording scheme simple for field use.

 

To sum up – to improve the archaeological information which can be extracted from geotechnical records we propose that geotechnical staff, in the field and laboratory, routinely apply BS5930 paying particular attention to colour, inclusions, organic matter, packing density and stoniness and noting deposit moisture and the nature of boundaries between deposits in addition. It is also important that the location and height of the pit or borehole is recorded.

 

Training and dissemination. Site staff will need to receive some simple training in recording these new criteria and the means by which this training can be achieved must be agreed with the professional bodies (Institution of Civil Engineers, British Drillers Association, Association of Geotechnical and Geoenvironmental Specialists, British Geological Survey, Geological Society and others). Supervising engineers are likely to need access to some, slightly different, training to explain the reasons behind these proposed initiatives and the way that they are intended to be applied.

 

 

We think  that a combination of on-site training and supporting materials (such as video and leaflets) will be useful. 

 

Developers and senior engineers need to be persuaded of the value of this additional recording if it is ever to be widely applied. We think that a few pilot projects should be set up to explore the practicalities of such application and the experience of those who already, routinely combine geotechnical and archaeological recording should be collated.

 

Locating pits and boreholes. Input from archaeologists may lead to better site investigation design since boreholes or trial pits could, as noted above, be situated to meet both archaeological and geotechnical site investigation needs – making a saving to the client.

 

We think that the single most useful way in which the use of BS5930 could be improved is for the location of pits and boreholes and, most importantly, their height to be recorded precisely in all cases.

 

The archaeologist finds such position control invaluable because it allows them to model the distribution and volume of archaeological deposits, relate them to others on adjacent sites and, in some of our most important historic cities (such as London, Bristol and York) relate buried remains to sea level – a key influence on the way such remains have formed and been preserved.

 

Local variations. It is likely that some local variations will need to be developed in the way geotechnical recording criteria are adapted to help archaeologists because the nature of archaeological deposits and key archaeological questions vary from region to region and town to town.

 

Here the skills of local geotechnical crews, many of whom have vast experience of the deposits of their area, might be of particular value and the training of such staff in simple recording, largely within BS5930, may produce particularly valuable archaeological records without much additional expense.

 

The early involvement of local archaeological curators and archaeological consultants (and perhaps geoarchaeologists who have specific skills in deposit interpretation) in development project planning will help to clarify the key things that need to be recorded on a specific site. Some archaeological briefing of geotechnical site staff and project engineers might also be very helpful at this stage and may save cost and avoid problems later in the project. Perhaps the archaeological community might provide a series of local advice notes stating the things of particular interest and concern in each historic town, where the need for guidance may be greatest.

 

Communication. We think that geotechnical engineers, drillers and archaeologists need to coordinate their work more effectively.  Some of this can be achieved through training and practice but it may be useful to reinforce the role that planners should play in encouraging this.

 

Some larger projects already incorporate close coordination between the archaeological and geotechnical teams with information being fed between the engineers, archaeologists and planners. There are few reasons why this should not happen on smaller projects as well – there seems much to gain and little to loose.