Doing archaeology better

Unearthing and recording our hidden past can be one of the many aspects to be addressed in considering planning applications, but are technological developments not being taken advantage of or even understood? CPRE Kent’s Ashford committee has been investigating.

Our past, it could be argued, is of as much importance as our present and our future. For those of us involved in the conservation of the county’s historical, cultural and natural heritage, it is perhaps ironic that much of the knowledge of our medieval and prehistory is unearthed during development schemes.

While rural campaigners might despair at the loss of yet more countryside, such projects can excite archaeologists, whereas developers often engage with search processes with only limited enthusiasm as they face potential time delays and high survey costs.

Developers’ desk research can be useful but miss areas of archaeological potential – the ‘white space’ on the all-important Kent Historic Environment Record (HER) might simply be the result of a lack of looking.
Taken in its entirety, it’s not a satisfactory situation and CPRE Kent’s Ashford committee has being focusing on the subject, exploring whether contemporary scanning technology could enhance archaeological search without the need for excessive digging.

The committee found that scanning technology is little used by developers’ archaeological consultants – utility companies, on the other hand, have embraced the process more enthusiastically. It’s a surprising conclusion given the amount of time and of course money that could be saved through use of the ‘smarter’ geophysical technology. Indeed, so time-consuming and expensive can the archaeological process be that a development might be shelved altogether.

Even when a scheme is built out, the time lost can be striking. At Appledore, for example, a planning application for four houses was registered in June 2017 and granted permission in May 2019, when an archaeological dig caused a delay of almost 12 months. The land was then sold to another developer, which submitted a further planning application and secured permission for five houses and a revised layout. This was registered in July 2020 and granted permission in December the same year, resulting in another archaeological dig causing more delay – the development is expected to be completed by the middle of this year, while the report and findings of the archaeological consultant have yet to be seen.

If we are to speed things up, one of the most promising forms of new technology is Ground Penetration Radar (GPR) and the Ashford committee learnt about it during a presentation by Matthew Bunting, managing director of Drilline Solutions, the first company in the UK to sell GPR gear commercially. He belongs to the Chartered Institution of Civil Surveying Engineers, which is promoting the use of GPR and trenchless technology.

GPR does not eliminate the need for digging (or ‘trenching’) but reduces how much is necessary and speeds up the development process. Cost ranges from £10,000 to £150,000, but the equipment suitable for archaeological purposes should not exceed £20,000 in price – an outlay that could pay for itself relatively quickly and be useable for at least a decade.

Although the potential for archaeological use is clear, GPR has been used largely for utility mapping, for example at Gatwick airport. In road engineering, it can determine asphalt thickness or degradation, while on the railways it has been used to detect moisture and clay in ballast and whether there is potentially dangerous movement from the washing away of clay.

Various systems are used:

• Entry-level: used on most sites, with a dual-frequency radar that has a low and a high frequency, this can go two or three metres deep. Pushed by hand, it can be connected to GPS and plot where everything is in real time.
• Stream-C: a larger system and single-frequency at 600 MHz. Useful for archaeological digs as it has 32 antennae, giving excellent resolution.
• For small objects in shallow ground: a hand-held device that operates at 2GHz and can pinpoint individual layering of ground. Generally used for concrete but can help analyse the first 80cm of ground.
• Large, vehicle-mounted system: can cover a large area quickly and is dual-frequency, running at 200 MHz and 600 MHz. Recently deployed in the building of a bypass in Staffordshire, where it is being used to locate utilities and archaeological remains. Surveys can be done quickly at speeds up to 50mph

GPR can identify soil disturbance, so if soil is replaced after a hole has been dug that can be detected. Resulting images are called B-scans (‘brightness scans’).

Another advantage of GPR is that it can be used to show where digging should be focused: the ‘test windows’. Although this is rarely done in the UK due to the expense and the fact equipment is often outdated, in truth an outlay of say £15,000 is not overly substantial when the cost of building a housing estate is considered – further, as well as finding archaeological remains, it can help avoid utilities and voids. A lot of money is spent repairing utilities after holes have been dug in the wrong place, while there is also the cost of resultant fines.

If not in the UK, the merits of such geophysical methods are appreciated in Norway, where any development – even a house extension – requires a GPR survey.

Other companies, including for example, GSSI and MALA, sell GPR equipment. GSSI is the preferred option for archaeologists as it goes down to a low frequency, while MALA is a low-cost solution used commonly on construction sites but infrequently in an archaeological or planning context.

Indeed, the archaeological world has been slow to embrace the use of GPR, perhaps because it doesn’t allow any remains found to be dated or have their significance verified. Dating is naturally a critical aspect for archaeologists, so a combination of trenching and geophysical technology is probably the way forward.

It is an issue close to the heart of Wendy Rogers, a senior archaeologist with the county council’s heritage team who acknowledges both the opportunity that development presents and the need to move with the times.

In a separate address to the Ashford committee, Ms Rogers said that, given context, she was keen to see GPR used. In planning, so much is dictated by time and resources, but if there is time on larger sites geophysical surveying can be requested, especially as the process is now becoming markedly cheaper.

There are two approaches when talking to a developer or contractor: one is when there is already an idea of what might be found, while the other is going in ‘blind’ to see what might be discovered.

Roman building material might be evident on a site, so a team will study aerial photographs to see if there are signs of a Roman building. There could be a recommendation for a geophysical survey, while there might possibly also be metal-detecting finds.

Other resources include old Ordnance Survey maps and knowledge of geology and land use. An analysis of what is known about the site both in terms of archaeology and the type of proposed development will help guide what work, if any, is necessary if it is believed something of interest is present.

The National Planning Policy Framework stresses the word ‘potential’ in relation to archaeological remains, so that can be enough to trigger a search.

GPR is useful, said Ms Rogers, but it is unable to date finds or verify significance. It might highlight an anomaly, but it cannot tell if it is Roman or recent.

If the process were free and without time restraints, her team would ask for GPR on all relevant greenfield sites, but as this is not the case the easiest method to find anything of archaeological significance on a greenfield or industrial site is trenching.

Trenches measure 20 x 1.5 metres and are dug over 5 per cent of a development site, giving enough evidence of remains of significance. If a geophysical survey is carried out, trenches will be targeted on any anomalies. Trenching will always be necessary to clarify date, function and significance, which is what is wanted in the NPPF, said Ms Rogers. GPR is rarely able to determine the significance of archaeological discoveries.

Developers tend to be highly restrictive with archaeological costs that are not part of their scheme and are obviously keen to ensure profit margins make it viable. With the need for other work such as ecological surveys, they are not inclined to fund archaeological work before planning consent has been granted, so the minimum spend, in the form of trenching, will be assigned. Once consent has been granted, however, developers are often happier to allow the necessary time and funds.

While some might lament a perceived reluctance to adopt new technology, there is nevertheless regular updating of techniques among archaeological contractors.

Drones are increasingly used to take aerial shots for excavations and Light Detection and Ranging (LiDAR). The Environment Agency’s LiDAR is accessible on its website but not of high enough resolution for archaeological assessment of landscape issues – it is, though, sometimes used for larger Heritage Lottery Fund projects.

Happily, some techniques are becoming substantially cheaper, while their variety is increasing: aside from GPR, we have the magnetometer, resistivity (which can detect stone walls) and magnetic susceptivity, which can highlight clusters of activity.

In short, an open mind and willingness to adopt an attitude of trial and error have never offered so much potential.

While it is clearly right and proper to know what has happened in the past, some in the Ashford committee question whether present archaeological practices are out of balance and slightly indulgent or indeed if the cost and delays are affordable and justified.

Like it or not, we have to accept change and in a sense perhaps the best way we can do that is to look back. Archaeology helps us in that regard – we just need to do it better.

Friday, June 3, 2022

• A number of important documents have yet to emerge. For example, a rigorous transport plan and a finalised air-quality assessment. The latter is critical given that allocations at Teynham will feed extra traffic into AQMAs.
• There seems to be no coherent plan for infrastructure delivery – a key component of the plan given the allocations being proposed near the already crowded Junction 7.
• There seems to have been little or no cooperation with neighbouring boroughs or even parish councils within Swale itself.

The removal of a second consultation might have been understandable if this final version of the plan were similar to that being talked about at the beginning of the consultation process. It is, however, radically different in the following ways:

• There has been a major shift in the balance of housing allocations, away from the west of the borough over to the east, especially around the historic town of Faversham. This is a move that raises many concerns.
• A new large allocation, with accompanying A2 bypass, has appeared around Teynham and Lynsted, to which we are objecting.
• Housing allocations in the AONB around Neames Forstal that were judged “unsuitable” by the council’s own officers have now appeared as part of the housing numbers.
• Most of the housing allocations being proposed are on greenfield sites, many of them on Grade 1 agricultural land – a point to which we are strongly objecting.

Concerns about the rush to submit the plan

The haste with which the plan is being prepared is especially worrying given the concentration of housing in Faversham. If the town is to take a large amount of new housing, it is imperative that the policies concerning the area are carefully worked out to preserve, as far as possible, the unique nature of the town. The rush to submit the plan is likely to prove detrimental.

As Swale does not have a five-year land housing supply, it is open to speculative development proposals, many of which would run counter to the ideas contained in the current plan. Some are already appearing. This is a common situation, and one that, doubtless, is a reason behind Swale’s haste.

Our overriding fear, however, is that this emphasis on haste is ultimately going to prove counterproductive. This is because it is our view that the plan, in its current form, is unlikely to pass independent examination. We are urging Swale to listen to and act upon the comments being made about the plan and to return the plan to the council with appropriate modifications before submitting it to the Secretary of State.

Essentially, this means treating the current consultation not as the final one but as the ‘lost’ second consultation.

The consultation ends on Friday 30 April and we strongly urge residents to make their opinions known if they have not already done so.

Further information

• Read more on the Swale Local Plan
• Read CPRE Kent’s detailed comments on the plan
• View the council’s consultation document