Desk studies

The first step in any site investigation is the desk study. Since 1950 this has changed out of all recognition with the advent of information technology (IT) associated with the internet and electronic publications that provide immediate access to enormous quantities of data. This represents an incredible step forward from the old approach, which required physical visits to libraries, newspaper archives, museums, etc. There can be no excuses these days for not carrying out a comprehensive desk study that brings together all relevant information about a site of interest. However, based on some of the observed practice it is necessary to issue some words of warning that that are particularly relevant in the context of the EGGS Cambridge Conference.

• It is necessary to ensure any literature searches differentiate between fact and fiction. There are millions of websites that contain information of relevance to environmental and engineering geology; however, not all can be trusted to provide accurate data. For example, there are websites that attempt to give credence to Bishop Ussher's view that the Earth was created on 23 October 4004 BC, or that the Earth is flat. Accessing sites that can be trusted is vital and the most suitable are listed below.

  • National, regional and local government and government departments. All aspects of development planning stem from government decisions and the documentation will be available on government websites. There will also be departments or offices within the government that have special responsibilities, such as the Department for Environment, Food and Rural Affairs (DEFRA) in the UK.

  • Government support agencies. In all countries there are government agencies that are nominally independent of the government and some may also undertake commercial work. These agencies set guidelines, prepare codes of practice and lay down standards that will be referred to in contracts for mining, environmental or construction work. In the USA an example is the Environmental Protection Agency (EPA) and in the UK the equivalent would be the Environment Agency, which is sponsored by DEFRA.

  • Standards organizations. A key element in environmental and engineering geology is the adoption of ‘standards’ that define the methods for carrying out work. These standards are often internationally recognized and form a key component of commercial contracts to ensure work is carried out in a way that is fully compliant with a specification. BSI Group (the British Standards Institution) is the national standards body for the UK, although it also operates internationally. There is also the International Organization for Standardization (ISO), and the geotechnical standards relevant to the UK carry both a BS and an ISO kitemark. A full discussion on these UK and European standards has been given by Norbury (2017). In the USA there is ASTM International (formerly the American Society for Testing and Materials), which has over 12 000 standards that are used globally. The military may also be a source of standards; for example, the US Army Corps of Engineers produces documents on codes of practice to be used in areas of contaminated land and for geotechnical investigations. Many of the standards developed by these various groups fall within the field of environmental and engineering geology, and failure to use the standards correctly can have legal implications.

  • National and regional geological surveys, soil surveys and conservation services. These surveys can be found in countries throughout the world. For example, the United States Geological Survey (USGS) provides a vast amount of free information and high-quality data not just for the USA but globally. The British Geological Survey (BGS) takes a similar role in the UK. In the USA each of the states also has its own geological survey. National and regional geological survey websites should be the first call in any desk studies.

  • National, regional and local museums, and local libraries. In the UK, the British Museum and the Natural History Museum hold a wealth of data, although in common with most museums not all the information is available through the websites, and site visits and often special permissions are required to access it. Local museums, and local libraries, can be particularly useful sources for information about prior use of brownfield sites in their region.

  • National libraries and institutions. There are many examples of these types of institution. In the USA the Smithsonian Institution, which was established in 1846, is the world's largest complex of museums and research centres and is administered by the US Government. In the UK, the British Library in London describes itself as the largest library in the world in terms of the number of items catalogued. In Australia CSIRO (formerly the Commonwealth Scientific and Industry Research Organisation) is a more active research institution and is Australia's largest patent holder. In Hong Kong the Geotechnical Engineering Office (GEO) is a government-based organization that has led and sponsored extensive research into ground conditions within the area and provides comprehensive and freely available reports. NASA would fall under this category and provides an enormous amount of free remote sensing data. These types of institutions can be relied on to provide access to accurate and up-to-date information, as well as holding long data archives.

  • National parks, geoparks, World Heritage Sites, etc. This is a broad category as every country has its own designation for locations that have been identified as having special scientific merit. However, these all have websites that are excellent sources of information and often hold spectacular images. The US National Parks Service deserves special mention in this respect.

  • International bodies. United Nations based bodies such as UNESCO, UNISDR, FAO, UNEP and WHO are important sources of both data and long-term plans for improving global conditions (e.g. issues of sustainability, climate change, human rights, etc). The UN supports groups such as the Intergovernmental Panel on Climate Change (IPCC), which is an international group set up by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to advise on and monitor the latest research pertaining to global climate change. The European Commission has also supported many research programmes that have provided substantial funding to member countries, much of which has been geared towards societal improvement. Reports from these European Union projects are readily available.

  • University repositories. Increasingly universities around the world have digital repositories where publications by staff can be accessed.

  • Learned and professional bodies. Around the world there are institutions such as the International Society for Engineering Geology and the Environment (IAEG), Geological Society of London (GSL), Institution of Civil Engineers (ICE), Institute of Materials Minerals and Mining (IOM3), the Geological Society of America (GSA), the American Institute of Professional Geologists (AIPG), the Australian Geomechanics Society (AGS), the Canadian Geotechnical Society, etc. All such institutions have their own codes of ethics that ensure material they and their members publish is of the highest scientific standard. In addition, many such bodies have their own publishing houses, which can be relied upon for providing state-of-the-art and peer-reviewed work.

  • Company websites. Company websites can usually be trusted to provide accurate and up-to-date information in countries where laws against incorrect and inappropriate advertising are enforced. Civil engineering construction companies are a particularly useful source of case studies, as indeed are local museums and libraries.

  • National and regional newspaper archives. Although newspapers tend to hold their own political views and the standard of scientific writing is often disappointing, they do record the occurrence of natural and human-made disasters fairly accurately. These reports can be invaluable when trying to establish the regularity of occurrence of geohazards and provide useful information on the effectiveness of disaster planning and recovery plans.

• It should be remembered that the internet will remain only a partial source of information until comprehensive archives of data from all previous site investigations are available. Many of these ‘grey’ data are locked away in client files and remain inaccessible, some because they are available only as hard copy and are not readily recoverable or transferable but others because of issues surrounding copyright and client confidentiality.

• Publications that are more than 10 years old do have legitimacy and should not be ignored. Some older guidance documents (although current) have been removed from government websites but many are located on the CL:AIRE (2019) website.

The scope of a desk study was described by Clayton & Smith (2013), who quoted AGS (2006) that a desk study ‘is often considered to be the most cost-effective element of the investigation’. It is axiomatic that as much prior information as possible about a site is collected beforehand, so any ground investigations can be focused on priority areas, such as those lacking data or that are particularly problematic.

Remote sensing

Another element of desk studies that has developed beyond all recognition since the Berkey Volume is the nature, availability and scope of remote sensing. Remote sensing for engineering projects in 1950 involved using stereographic pairs of black and white aerial photographs. Interpretation (API) was carried out manually on overlays that were then transferred to spatially correct maps and plans. The advent of satellite imagery from the 1970s onwards has transformed the amount and quality of data that can be obtained from remote sensing. Multispectral (MSS) and hyperspectral scanners (HSS) mounted on satellite platforms allowed the collection of data over a much larger part of the electromagnetic spectrum and at high resolutions.

The most recent relatively cheap high-resolution remote sensing technique is the use of airborne drones. With the capability of carrying digital cameras providing data that can be geo-referenced and enhanced using a range of easily obtainable software systems, these are capable of collecting large-scale images of sites that are of direct value to engineering, environmental and mining projects. As an example, Figure 2 shows a drone image of a landslide in SE Spain that lies on the outside of a meander bend. This image provides data that allow an interpretation of the nature and cause of the landslide to be undertaken.

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Fig. 2.

Maleguica landslide in SE Spain. Image created by taking overlapping vertical images using a DJI Phantom 3 Professional drone. The images have been stitched together using AGISsoft Photoscan. Resolution is c. 20 cm (image produced by M. Stokes, SoGEES, University of Plymouth and used with permission).

It is not just the passive satellite receivers that have changed; a range of active scanning systems mounted on satellites and aircraft have emerged. LiDAR (light detection and ranging) is one of the most important as it can provide spatially corrected high-resolution ground images for interpretation even if the terrain is covered in dense forest. Increasingly, countries are providing LiDAR data as an open access resource and Figure 3 shows a LiDAR image of the same landslide as shown in Figure 2. Using contour colouring highlights the shape of the landslide with the backscar and accumulation debris being clearly delineated. Combining the LiDAR and drone data allows digital elevation models (DEMs) to be constructed over which a range of Earth science data can be draped to produce digital terrain models (DTMs).

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Fig. 3.

Maleguica landslide in SE Spain produced from publicly available Spanish Instituto Geografico Nacional LiDAR data; resolution for 1 pixel is 1 m horizontal (image produced by M. Stokes, SoGEES, University of Plymouth and used with permission).

Another useful active scanning satellite system is InSAR (interferometric synthetic aperture radar). This scanner can map and monitor surface deformation and is capable of detecting deformation of the ground surface to millimetre accuracy. Repeated measurements over days or even decades mean it is now possible to monitor landslide or subsidence movements from space.

The wealth of remote sensing techniques and readily available data has led to an increase in their use in the initial stages of a site investigation. However, information derived by remote sensing still needs to be checked by the process known as ‘ground truthing’. This can be achieved only by field mapping.

Field mapping

Back in the 1970s famous practising engineering geologists such as Dearman & Fookes (1974) and Clark & Johnson (1975) emphasized the importance of engineering geological and geotechnical mapping to provide a spatial framework for designing and interpreting ground investigations. Brunsden et al. (1975) showed how mapping the geomorphology could provide information on natural hazards, present-day processes and relict landforms that was directly relevant to interpreting the ground conditions for engineering projects. The value of mapping in engineering practice was summarized by Dearman (1991) and Griffiths (2002). All this mapping was based on fieldwork, although it drew heavily on the interpretation of remote sensing data. However, looking at the last decade of the UK literature in engineering geology there are fewer examples of actual field mapping as a component of site investigation, and that is concerning. The UK led the world in field mapping for engineering projects and the fear is that the skill is being lost (Griffiths 2014; Privett 2019).

Figure 4a is an example of some large-scale geomorphological mapping on part of the Undercliff landslide complex on the Isle of Wight from Griffiths et al. (2015). There were no subsurface data available at the time of the mapping but there was literature on other parts of the Undercliff that was used in conjunction with field mapping to allow a cross-section of the landslide complex to be compiled (Fig. 4b). This took two person-days on-site and one person-day for writing up the report. The report was used as the basis for designing a ground investigation to stabilize the coastal road. By any measure this was a very cost-effective exercise.

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Fig. 4.

(a) Geomorphological map and (b) cross-section of the Binnel Bay landslide (reproduced from Griffiths et al. 2015, with permission from the Geological Society of London).

As one of the leading exponents of the art Hearn (2017) demonstrated the continuing importance of maintaining these field mapping skills, but the list of UK practitioners who are still doing work of this type is disappointingly short and the names on the active list are getting worryingly ‘mature’. This is one example of a sub-discipline of engineering geology that did advance significantly but now appears to be regressing.

Usefulness of various in situ tests

According to Simons et al. (2002, p. 246), in the presentation of his paper at an international conference Mayne (2001) asked the question: ‘Is it time to retire the SPT?’ It was Terzaghi at the 1947 Texas Soil Mechanics Conference who first recognized that the blow count of an SPT could be used to obtain soil consistency or density data (Fletcher 1965). But 66 years later in the July 2013 edition of the on-line journal Geotechnica there was a report of a recent geotechnical meeting where it was stated: ‘Discussion moved on to consider the use of SPT for design. It would seem that this is now the most commonly used test to determine ground strength and hence bearing pressure’ (Anonymous 2013). It is doubtful that Terzaghi would have been impressed by the continued use of the SPT for design work given the developments in CPT technology since 1947. Table 2 is based on Robertson & Cabal (2015) and compares the value of the data obtained from a range of in situ tests including SPT and various types of CPT including the piezocone (CPTu) and the seismic cone (SCPTu). There are also data on the flat plate dilatometer (DMT) and the seismic dilatometer (SDMT). Comparing the CPT with the SPT shows that the CPT provides high-quality data for a much wider range of ground conditions.

The difference between CPT and SPT data was highlighted in a paper by a Japanese team working in the Mekong River Delta in Vietnam (Hoang et al. 2016) (Fig. 5). They showed the results from different techniques in an investigation of the geotechnical properties of a late Pleistocene to Holocene deltaic sediment sequence. In Figure 5 the geological log on the left in column (a) was compiled using continuous sampling with a hydraulic thin-walled sampler. The soil-behavior-type classification in column (b) is an interpretation of the piezocone results shown in columns (c)–(h) using charts such as those of Robertson & Cabal (2015). Column (i) on the right gives the SPT results. Figure 5 shows that if a simplified interpretation of ground conditions is all that is wanted then an SPT will suffice, but if an accurate record of the actual soil types and their geotechnical properties is needed the CPT piezocone provides much better results.

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Fig. 5.

Comparison of logs obtained from various in situ tests obtained for a site in the Mekong Delta, Vietnam (from Hoang et al. 2016; open access paper and reproduced under creative commons license CC BY-NC-ND-4.0).

Geophysics for construction engineering

In 1950 geophysics in ground investigation was in its infancy, although it was probably first developed in the early 1920s (McDowell et al. 2002). Most developments of the techniques have been within other industrial sectors, notably in petroleum exploration and mining. The offshore hydrocarbons industry, having experience in geophysical applications for exploration during the 1950s and 1960s, readily made widespread use of geophysical techniques in the investigation of seabed and shallow subsurface conditions for offshore structures such as oil platforms and submarine pipelines. However, the onshore ground investigation industry has been more reluctant to embrace the techniques (Griffiths & Culshaw 2004) and has preferred to concentrate on the use of exploratory holes. This may be partially explained by the comment of Clayton & Smith (2013, p. 27): ‘Geophysical investigations have a high failure rate under unfavorable circumstances’. Nevertheless, Gunn (2017) reviewed some 140 papers from the 50 years of the QJEGH (and its forerunner the QJEG) that illustrated the development and use of geophysical techniques for ground investigation over the previous 50 years. Sixty per cent of the contributions involved seismic, electrical resistivity and thermal methods. The EGGS Working Party report by McDowell et al. (2002) reviewed the full range of geophysical techniques that can be applied in engineering practice and a summary of the methods has been provided by Tuckwell (2018). Geophysical techniques have advanced significantly since the Berkey Volume and it remains a mystery to this author why too many engineering geologists are willing to ignore techniques that are perfect for filling in the gaps in subsurface information between exploratory holes as well as identifying anomalies requiring further investigation. Hopefully, as the large number of positive examples make their way into the scientific literature, geophysical techniques will become increasingly accepted as a key onshore ground investigation tool.

Communications

Early images of field geologists show, predominantly, men out in the wilds and a long way from their head office. In the world of engineering geology, until the widespread availability of mobile phones in the late 1990s, any engineering geologist who was on-site in the UK was essentially on their own, apart from the odd phone call from a public phone booth or hotel (if they were lucky enough to be staying in one) to their line manager. The engineering geologist on-site kept a detailed hardcopy site diary and if problems arose had to deal with them by themselves, learning from the experience. Thus, from the time of the Berkey Volume until the late 1990s the site experience of engineering geologists in the UK was very similar. The advent of mobile and satellite phones, laptop computers and emails has changed this image beyond recognition. Now if problems arise phone calls can be made to line managers straightaway. At least one UK company is also offering an app for smartphone or tablet that allows the user to interact with desk study information and add geo-referenced notes, photos, etc. that can be viewed by a manager back in the office in real time (Envirocheck 2019). One concern is that this immediate access can lead to the temptation to micro-manage the engineering geologists who are on-site. There will be many early career engineering geologists who have thought, ‘I wish my line manager would stop phoning and let me get on with the job!’ Although the opportunity provided by mobile phones may have resulted in some deterioration in the learning experience for early career engineering geologists, rapid communications will almost certainly have led to better ground investigations with fewer delays. Although more mature engineering geologists may reflect on some of the ‘white-knuckle rides’ during their early career experiences on-site with a degree of rose-tinted hindsight, better ground investigations, effective risk assessment and improved standards of health and safety resulting from modern communications must be lauded.

Data management

Extensive site investigations generate vast amounts of data, and in common with all facets of geology, these data are spatially related (‘geolocated’). From the time of the Berkey Volume until the early 1970s these data will have been collated, compiled and analysed by teams of engineering geologists who would produce hardcopy reports where interpretations and data were typed up with graphs, maps and diagrams drawn by specialist cartographers from hand-drawn originals. This changed once readily accessible computing power became available. Reports were word-processed, data were loaded into databases and spreadsheets to be analysed, and maps, plans and diagrams could be produced using computer-aided drafting (CAD) systems. Initially, this still tended to result in hardcopy reports where data were not fully integrated, but this changed with the development of geographical information systems (GIS), specialist borehole data handling software (e.g. AGS 2012) and a preference for electronic reports that could be made available to all users. Komac (2018) wrote that the term GIS describes ‘any information system that integrates, stores, edits, analyses, shares, and displays geographically defined information’. Although Turner (2003) advocated the use of the term GeoScientific Information Systems (GSIS) for GIS that involved geoscience data interpolation and extrapolation procedures and interactive data manipulation, the term GIS has now been accepted to describe the spatial database systems that are one of the most widely adopted approaches in engineering geological data management on large complex construction projects. However, looking to the future, a critical aspect of any GIS for use by engineering geologists is the need to ensure it is able to integrate data from other systems, notably some of the industrial standards for recording borehole data such as the AGS data format (Bland et al. 2014).

Another facet of data management that has emerged is building information modelling (BIM). This is the process of creating and managing data on a construction project across the whole project lifecycle (Kensec 2014). Through BIM, the construction industry is undergoing its very own digital revolution. BIM is a way of working and creates value from the combined efforts of people, process and technology. The key output is the building information model, the digital description of every aspect of the built asset. Creating a digital building information model allows those who interact with the infrastructure to optimize their actions, resulting in a greater whole-life value for the asset. However, there continues to be a need to ensure all the data held in these various digital systems are integrated with other ground investigation data.

Ground model

A key element of data management for engineering geologists is the construction of a ground model (Fookes 1997), which is now regarded as a fundamental component of a site investigation. Although the basic idea has been around since the Berkey Volume, as can be seen in the examples of cross-sections for dam sites given by Burwell & Moneymaker (1950), carrying out this process has been revolutionized by the computing power now available. Parry et al. (2014) defined three types of ground model.

Status recognition of the profession

In 1950 both in the USA, based on the Berkey Volume, and in UK the concept of an ‘engineering geologist’ requiring a ‘professional’ qualification does not appear to have been a high priority. Suitably experienced geologists would be used on civil engineering projects as required, working alongside civil and geotechnical engineers. However, in the UK over the following 30 years the concept of ‘chartered status’ became an increasing requirement, notably when the Engineering Council was established in 1981 with the responsibility of licensing member organizations, including the Institution of Civil Engineers (ICE) and IMM (as it was then), to be able to award professional titles such as CEng. Just after this the Institution of Geologists (IG, originally part of the Geological Society of London (GSL)) sought to establish the title Chartered Geologist (CGeol) as the geologist's professional equivalent of CEng. With the reunification of the IG and the GSL at the start of the 1990s the title CGeol became a core award the GSL could confer on appropriately qualified geologists under its own Royal Charter. Since then, work by Ground Forum (GF), GSL, ICE, IOM3 and the British Geotechnical Association (BGA) facilitated the establishment of the register of ground engineering professionals (RoGEP) that, in 2011, finally put CGeol and CEng on an equivalent status for appropriately qualified individuals working in the civil engineering industry. For engineering geologists, it is only chartered geologists who can submit a peer-reviewed application to be placed on the register and their status continues to be recognized only by the production of a recorded programme of continuing professional development (CPD). However, as of September 2018 there are still fewer than 1000 people listed on the RoGEP in the UK. Part of the problem is that clients for ground engineering projects have still not fully embraced the need to appoint a RoGEP listed professional to manage activities such as ground investigations, and this may also be a product of the preference for some clients to always choose the cheapest option (see above discussion).

Status recognition remains a work in progress in the UK, a theme that is also encountered in the USA (Tepel 2004). All the elements are in place but there remains a great deal to do to promote the importance of appointing professionally qualified staff to undertake projects in engineering geology.

International standards for site investigation

Norbury (2017), in his 17th Glossop lecture, provided a summary of the development and importance of national and international standards to define best practice in site investigations, including accepted methods for describing soils and rocks for engineering purposes. Without doubt the development of such standards by internationally recognized bodies is one of the most important features of the modern practice of engineering geology. By 1952 in the USA, just after the Berkey Volume was published, the main system for classifying soils was accepted as the Unified Soil Classification System. In the UK the first publication that defined the standards of a site investigation, and included information on soil and rock description, was BS CP 2001:1957 (BSI 1957). The latest standards for the UK are described in a series of publications by the BSI (Norbury 2015, 2017) that meet the requirements of the ISO based in Geneva. These standards define best practice for all aspects of a site investigation and ensure all such work is carried out to a common level of quality using terminology that is accepted and recognized by all engineering geologists. The importance of these standards cannot be overstated.