Start here
0.1 The documents you’ll use
About 45 minutesno prior knowledge needed
Ground investigation in the UK rests on a small set of documents. You do not need to read them cover to cover before you start, but you do need to know what each one is for and where to find it. This lesson introduces each document in plain terms and shows you how to get access to it.
Learning outcomes
- Say what each of the main documents covers and when you would open it.
- Find a legitimate way to read each document: buying it, an employer’s subscription, or a college, university or local library.
Standards, specifications and guidance: what is the difference?
A British Standard (BS) is a document published by BSI, the UK national standards body. A code of practice such as BS 5930 gives recommendations (“should”), based on accepted good practice. Standards are copyright and are sold, not free.
A Eurocode (BS EN) is a European design standard adopted in the UK. Eurocode 7 covers geotechnical design. Each Eurocode comes with a UK National Annex that sets the values the UK has chosen.
A specification is a contract document: it tells a contractor exactly what to do. The UK Specification for Ground Investigation is the standard one for GI in the UK. It is where the questions from your desk study end up, as you will see in lesson 2.3.
Guidance comes from bodies such as the Environment Agency, CIRIA and BRE. Some is free (for example the Environment Agency’s LCRM); some is sold.
The core documents
| Document | What it is, in plain terms | Where it appears in this course |
|---|---|---|
| BS 5930:2015+A1:2020 BSI page | The UK code of practice for ground investigations. Section 2 covers the desk study and field reconnaissance (the site walkover): what to collect, what to interpret and what to report. Later sections cover planning the investigation, exploratory holes, sampling and describing soils and rocks. | Every lesson. It is the backbone of this course. |
| Eurocode 7, BS EN 1997 Part 1 (2004) · Part 1 (2024) | The European standard for geotechnical design. In the first generation, Part 1 gives general rules and Part 2 (BS EN 1997-2:2007) covers ground investigation and testing. A second generation was published in 2024, in which Part 2 is titled Ground properties. BSI will withdraw the first-generation UK Eurocodes on 30 March 2028; until then both are available, so always check which one your project uses. | Lesson 0.2, where the desk study sits in the design process. |
| UK Specification for Ground Investigation, 3rd edition Publisher’s page | Known as the “Yellow Book”. Published by ICE Publishing in 2022 and prepared by an industry working group led by the AGS. It is the standard contract specification and bill structure for UK ground investigation. AGS launch article · free ICE webinar on the changes | Lesson 2.3. The desk study feeds it. |
| BS 10175:2026 | The code of practice for investigating potentially contaminated sites. It replaced BS 10175:2011+A2:2017 in January 2026. It covers how to plan the preliminary and later stages of a contamination investigation. | Lessons 1.3 and 2.2. |
| Land contamination risk management (LCRM) Free on GOV.UK | Environment Agency guidance on assessing and managing risk from land contamination, in England, Wales and Northern Ireland. It replaced CLR11 in 2020. Its first stage, the preliminary risk assessment, is what the contamination part of a desk study delivers. | Lesson 2.2. |
Supporting documents you will meet
BS 8576:2013 guidance on investigating ground gas, and CIRIA C665 on assessing risks from ground gases. Used when the desk study finds a possible gas source such as a landfill, backfilled pit or mine workings.
BRE BR 211, Radon: guidance on protective measures for new buildings (2023 edition). Used to decide whether radon protection is needed in a new building.
CIRIA C681, Unexploded ordnance (UXO): a guide for the construction industry (2009). Used when the desk study shows a risk of wartime bombs.
A free overview of Eurocode 7: presentation by Roger Frank from a European Commission Joint Research Centre training workshop (Brussels, October 2011). It explains the contents of Parts 1 and 2 clearly, but it describes the first generation, so read it as background. The link downloads a PDF.
How to get access without breaking copyright
If you work in industryMany consultancies and contractors subscribe to BSI’s online standards service. Ask your line manager, technical librarian or document controller before you buy anything.
If you are studyingWhether you are at college, on an apprenticeship or at university, ask your library: many give access to British Standards. Search the catalogue for “BS 5930”, or ask a librarian.
If you are learning on your ownBuy the document from BSI or the publisher using the links above, or ask your local library what it can offer. Free sources (LCRM, the map viewers in this course and the webinar) will take you a long way.
Please never share or upload a copy of a standard, including in this course. This course paraphrases and points you to the right clause. It never reproduces the text.
Common mistakes
✗
Citing a standard without its full reference and edition, such as “BS 5930” when the project needs BS 5930:2015+A1:2020.
✗
Using a withdrawn edition because it was the copy you had.
✗
Treating a commercial data report as a desk study. It is one source among several (lesson 0.2).
Try it
Find out how you can read BS 5930. If you are employed, ask who manages standards access. If you are studying, ask your college or university library. If you are learning on your own, decide whether to buy it or start with the free sources. Write down the route in your notes: you will need it in every lesson.
ReferencesBS 5930:2015+A1:2020BS EN 1997-1 and -2UK Specification for GI, 3rd ed.BS 10175:2026LCRM
Start here
0.2 Why a desk study comes first
About 40 minutes
1Desk studythis course
2Site walkoverthis course
3Preliminary ground model and riskthis course
4GI specification and BoQ
5Fieldwork, lab, monitoring
6Factual report
7Interpretation and design
A desk study is the collection and interpretation of everything that is already known about a site and its surroundings, before anyone digs a hole. It is paired with a site walkover (BS 5930 calls it field reconnaissance): a planned visit to confirm and add to what the desk study found. Together they give you a first picture of the ground and its hazards, and that picture decides what the ground investigation needs to do.
Learning outcomes
- Explain what a desk study is, and why it comes before the ground investigation.
- Tell the difference between the factual part of a desk study and the interpretive part.
- Explain why a commercial data report is useful but is not a desk study on its own.
What the desk study is for
It finds the hazards early. BS 5930 says the desk study should identify the likely ground-related hazards, which then go into the project’s first risk register. It is much cheaper to find an old mine shaft on a map than with a drilling rig.
It makes the ground investigation safe. Buried services, contamination, unexploded ordnance and mine workings are all dangers to the people drilling. The investigation cannot be planned safely without knowing about them.
It shapes the ground investigation. Every hole in a good investigation has a reason. Most of those reasons come from the desk study: “the old pit was here, so we need to know how deep the fill is”.
It starts the ground model. BS 5930 treats the ground model as something you build at the start and keep updating as information arrives. The desk study is version one.
Facts first, then interpretation
BS 5930 describes a desk study as a factual core with interpretive elements added to it. Keep the two apart in your head and in your report.
| Part | What goes in it | Example question it answers |
|---|---|---|
| Factual core | Site details (location, boundaries, current and proposed use, topography, services); site history from maps and photographs; published geology, groundwater and previous investigations nearby. | What was here in 1960? |
| Interpretation | The site constraints that affect the investigation and the development; the ground hazards, ranked; and recommendations for the scope of the ground investigation. | So what does that mean for the new building, and what must the GI find out? |
Where the information comes from
Free public data: geological maps and borehole records, flood maps, heritage and environmental designations, radon maps, coal mining data. You will use each of these in Part 1.
Historical maps and aerial photographs: some free (for example the National Library of Scotland’s online map collection), some through subscriptions such as Digimap, which many universities and colleges provide, or bought in commercial reports.
Commercial data reports: companies sell reports that collect historical maps and environmental records for a site. BS 5930 notes that these are very helpful but are not sufficient on their own: the data can be out of date, incomplete or not site-specific, so you must cross-check it.
Local knowledge: the local authority, previous investigations on or near the site, local libraries and archives. BS 5930 lists these too.
Worked example site
Site D (fictional) is a vacant, fenced plot of about 2.8 hectares on the edge of a town in northern England. A two-storey primary school with a playing field is proposed. You will follow Site D through every lesson. A school is a sensitive end use: children spend years there, and they play on the ground, so contamination and ground gas matter more than they would under a car park.
Example
Before opening a single map for Site D, write down what the development needs from the ground: shallow foundations for a two-storey building if the ground allows; a playing field and soft landscaping where children will touch the soil; drainage, possibly into the ground. Every later finding is judged against these needs.
Common mistakes
✗
Starting the desk study without knowing what is proposed. A hazard for a school may not matter for a car park.
✗
Copying a commercial report’s summary into your own report without checking it against the maps.
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Mixing facts and opinions in the same paragraph, so the reader cannot tell which is which.
Try it
Pick a place you know well, such as a local park or your street. It must not be a site you are working on. Write two sentences on what is proposed there (invent something), then list three things you would want to know about the ground before building it. Keep this “practice site” for the rest of the course.
ReferencesBS 5930:2015+A1:2020, Section 2BS EN 1997-2
Part 1 · Gathering the facts
1.1 Site history
About 1 hour 15 minuteshands-on with free maps
What happened on a site in the past is often the biggest influence on the ground today. A pit that was filled with waste, a tank that leaked, a stream that was piped underground or a mine shaft that was capped: none of these is visible from the road, but all of them show up on old maps. Reviewing the site history is how you find them.
Learning outcomes
- Work through historical maps and aerial photographs in date order and record the changes, on site and off site.
- Explain why each change matters for the development and the ground investigation.
- Recognise the limits of historical maps, so you do not over-read them.
What you are looking for
Past uses that could leave contamination: works, factories, garages, depots, tanks, gasworks, railways, tips, farms with fuel or chemical stores.
Changes in ground level: pits, quarries and ponds that disappear between editions (probably filled), embankments, cuttings and spoil heaps.
Water: streams, springs, wells and ponds, including ones that later vanish because they were culverted or filled.
Buried structures and mining: old buildings and foundations, shafts, adits, “Old Shaft” or “Old Pit” labels, tunnels and culverts.
How to do it
1. Gather the editions. Ordnance Survey maps go back to the mid 1800s. Many older editions are free to view on the National Library of Scotland map website, which covers all of Great Britain for many series. Later editions and aerial photographs usually come from subscriptions (for example Digimap, available through many universities and colleges) or commercial reports.
2. Work in date order, oldest first, and for each edition record what is on the site and what is around it. State the search distance you used around the site and keep to it.
3. Record changes, not everything. After the first edition, note what is new, what has gone and what has changed.
4. Add “why it matters” to every entry. This is the column that turns a list into a desk study.
Limits of old maps
A map is a snapshot. A garage could open and close between two editions and never appear.
Maps show what the surveyor chose to show. Small tanks, spills and dumped waste are rarely drawn.
Aerial photographs have no labels, so you can see that something changed but often not what it was.
“No significant change” between editions means nothing changed on the map. It does not prove nothing happened.
Site D · site history
Fictional records for the worked example site. The map dates are invented for teaching.
| Edition | On site | Off site | Why it matters |
|---|---|---|---|
| 1890s map | “Brick Works” in the north-west with two kilns and a chimney. A clay pit of about 0.6 ha in the north. Fields in the south, crossed west to east by a stream. | “Old Shaft (Coal)” about 250 m north. Railway about 150 m east. | The clay pit could later be filled. The shaft shows coal was worked nearby. |
| 1910s map | Pit enlarged to about 1.4 ha. A tramway links the pit to the kilns. | Terraced housing built to the west. | A larger pit means a larger volume of possible fill. |
| 1930s map | Part of the pit shown as a pond. Brickworks still active. | No significant change. | If the pit was filled while holding water, the fill may be soft and contain organic material, which can generate gas. |
| 1960s map | Works marked “disused”. The pit area is labelled “Tip”. Kilns no longer shown. The chimney remains. | No significant change. | “Tip” suggests waste disposal: a possible source of ground gas, leachate and contamination. Kiln foundations may remain as obstructions. |
| 1970s map | Pit area shown level and grassed. A council depot is built on the southern half: a vehicle garage, two tanks and a salt store. The stream is no longer shown across the depot. | Primary school built about 300 m west. | The tip appears to have been filled to ground level. Tanks suggest fuel storage. The stream was probably culverted. |
| 1990s aerial photograph | Depot in use. Uneven, hummocky ground over the former pit. | No significant change. | Hummocky ground is consistent with settlement of fill. |
| 2010s aerial photograph | Depot buildings demolished. Concrete slabs remain. Site fenced. | No significant change. | Demolition may have left rubble and asbestos in the ground. Slabs and bases may be obstructions. |
Schematic plan of Site D. Fictional, not to scale. The dashed outline is the site boundary.
Common mistakes
✗
Describing the surroundings in detail but saying little about the site itself.
✗
Listing features with no “why it matters”, so the reader cannot see the point.
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Reading “major development” into two maps without saying what changed and where.
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Missing a feature that disappears, such as a pond or stream. A disappearance is often the most important entry.
Try it
Open the National Library of Scotland map website and find your practice site on the oldest and the most recent edition you can. Fill in a four-column table like the one above for at least two editions, including one “why it matters” for every row.
ReferencesBS 5930:2015+A1:2020, Section 2 (desk study; earlier uses of site; aerial photographs)
Part 1 · Gathering the facts
1.2 Geology, groundwater and flooding
About 1 hour 15 minuteshands-on with free maps
The published geology tells you what the ground is expected to be. Groundwater and flooding information tells you what water is in and on it. None of this replaces the ground investigation, but it tells you what to expect and what to test.
Learning outcomes
- Read the three layers of a UK geological map (artificial ground, superficial deposits, bedrock) and explain what each means for the site.
- Find aquifer designations, source protection zones and flood zones, and say why each matters.
- Use nearby borehole records with care.
Geology: three layers
Artificial ground is ground changed by people: made ground (material placed by people), worked ground (dug out) and infilled ground (dug out and then filled). The map shows only what the geologists recorded, so no artificial ground on the map does not mean none on site. Your site history is often the better guide.
Superficial deposits are the younger, mostly unconsolidated soils lying on the bedrock, such as glacial till, alluvium (river deposits) and head (material moved downslope). They are often what shallow foundations sit on.
Bedrock is the older rock beneath. Its type matters for deep foundations, excavation, groundwater and some hazards: coal-bearing rocks mean possible mining, chalk and gypsum can dissolve and form cavities.
Where to look: the BGS GeoIndex is free and shows geology, faults and scanned records of past boreholes. The BGS Lexicon describes each named rock unit. Most onshore mapping is at 1:50 000, so treat the boundaries as approximate.
Nearby borehole records
GeoIndex shows the locations of boreholes held by BGS, many with scanned logs. They are free evidence of what was found nearby. Check the date, purpose and quality of each log, and remember that ground can change over short distances. Say how far away each record is and in which direction.
Groundwater
Aquifer designations (Environment Agency, England) describe how important the ground is as a water resource. Principal aquifers are highly permeable and may support water supply or river flow on a strategic scale. Secondary A aquifers can support water supplies at a local scale and may feed rivers. Secondary B are mainly lower permeability layers that store and yield limited groundwater. Unproductive strata have negligible significance for water supply.
Source protection zones (SPZ) are drawn around public water supply abstractions: Zone 1 (inner), Zone 2 (outer) and Zone 3 (total catchment). The closer the zone, the more sensitive the groundwater.
Why it matters: groundwater is a receptor for contamination (lesson 2.2), a constraint on drilling (a borehole must not create a new pathway down into an aquifer) and a practical problem for excavations and soakaways.
Where to look: MAGIC, Defra’s free map, includes groundwater layers.
Flooding
In England, the Flood map for planning shows flood zones from rivers and the sea: Zone 1 (low probability), Zone 2 (medium) and Zone 3 (high). The long term flood risk service adds surface water flooding.
Wales, Scotland and Northern Ireland have their own flood maps, run by their own agencies. Use the one for your site.
Say which map and which flood source you used. “Medium risk” on one map is not the same as Flood Zone 2 on another.
Site D · geology and water
Fictional findings for the worked example site.
| Item | Finding | Why it matters |
|---|---|---|
| Artificial ground | Infilled ground mapped over the former pit. None mapped under the former depot. | The site history shows a depot with tanks and demolition, so made ground is likely there too. The map is incomplete. |
| Superficial deposits | Glacial till: clay with sand, gravel and cobbles. | Often suitable for shallow foundations, but variable. Cobbles can obstruct drilling. |
| Bedrock | Coal-bearing mudstone, siltstone and sandstone. A coal seam outcrop is mapped crossing the north of the site. | Possible shallow coal and old workings under the building (lesson 1.3). Mudstones can contain pyrite, which can produce sulfate. |
| Borehole records | Two logs about 200 m west, drilled in the 1970s for housing: 4 to 6 m of till over weathered mudstone; water struck at 3 m in one. | Useful for expected thickness of till. Too far away to say anything about the pit fill. |
| Aquifers and SPZ | Bedrock: Secondary A aquifer. Till: secondary (undifferentiated). Not in a source protection zone. | Groundwater is a receptor to protect, but not the most sensitive category. |
| Flooding | A strip along the culvert line is in Flood Zone 2, with surface water flood risk along the same line. | Affects the site layout, drainage design and access for the investigation in wet weather. |
Common mistakes
✗
Pasting the BGS description of a rock unit without saying what it means for the site.
✗
Reading “Principal aquifer” as “there is a lake of water under the site”. It describes permeability and water resource value.
✗
Concluding there is no made ground because none is mapped, when the site history says otherwise.
✗
Quoting a flood “risk” without naming the map, the source of flooding or the date you checked.
Try it
For your practice site, use GeoIndex to record the artificial ground, superficial deposits and bedrock, and the nearest borehole record (distance and direction). Then check the flood zone. Add a “why it matters” to each.
ReferencesBS 5930:2015+A1:2020, Section 2BGS GeoIndex and LexiconEnvironment Agency aquifer designations
Part 1 · Gathering the facts
1.3 Site constraints and hazards
About 1 hour 15 minuteshands-on with free maps
Now check the things that are not geology but still shape the project: protected buildings and wildlife, radon, mining, wartime bombs, old landfills and buried services. For each one the question is the same: is it here, and if so, what does it mean for the development and for the ground investigation?
Learning outcomes
- Tell a site constraint from a ground hazard.
- Check heritage, ecology, radon, mining, unexploded ordnance, landfill and services using free UK sources.
- Write a “so what” for each finding, including what it means for the ground investigation.
Constraint or hazard?
A constraint limits what you can do, or how: a listed building next door, protected trees, a buried gas main, a narrow gate.
A hazard is something in or of the ground that could cause harm or cost: soft or variable fill, mine workings, contamination, ground gas, dissolution cavities, high groundwater, aggressive chemistry, obstructions.
BS 5930 asks for both: a catalogue of the site constraints, and a prioritised list of ground hazards with proposals for further investigation.
The checks, and where to make them
| Check | Free source | Why it matters |
|---|---|---|
| Listed buildings, scheduled monuments, registered parks and battlefields | Historic England, Search the List (England). Wales, Scotland and Northern Ireland have their own lists. | Vibration and settlement limits; consents may be needed for works to them; archaeology may need investigating. |
| Conservation areas and protected trees | The local planning authority. | Consents, and limits on tree removal and access. |
| Protected sites for wildlife and landscape | MAGIC | Designated sites nearby may limit working methods. Protected species and invasive plants (such as Japanese knotweed) need an ecologist’s advice. |
| Radon | UKradon maps (UK Health Security Agency) | In a Radon Affected Area (1% or more of homes estimated above the Action Level), new buildings may need protection. BRE BR 211 is the guide. |
| Coal mining | Mining Remediation Authority map viewer (formerly the Coal Authority) | In a Development High Risk Area, a planning application needs a Coal Mining Risk Assessment. Drilling into coal seams or workings needs the Authority’s permission. |
| Unexploded ordnance | Zetica UXO risk maps | A regional first look only. Where the risk may be significant, a specialist UXO risk assessment follows (CIRIA C681). |
| Landfill and waste sites | Environment Agency historic landfill records (open data), and the site history. | Sources of ground gas and leachate, on site or nearby. |
| Buried and overhead services | Records from the utility companies. | A struck gas main or power cable can kill. Needed before any digging. |
Site D · constraints and hazards
Fictional findings for the worked example site.
| Finding | So what |
|---|---|
| The brickworks chimney on site is a Grade II listed building. | It must be protected. Vibration from piling or drilling near it needs limits, and works to it need consent. Record its condition before any work. |
| No statutory wildlife sites within 1 km (MAGIC). | Low constraint, but an ecologist should still check for protected species and invasive plants. |
| Radon Affected Area (UKradon). | Radon protection is likely to be needed in the school. Check against BR 211. |
| Within a Development High Risk Area. Recorded mine entry about 250 m north. Coal seam outcrop mapped across the north of the site. | A Coal Mining Risk Assessment is needed. The GI must find out whether there is shallow coal or old workings under the building, and needs the Mining Remediation Authority’s permission to drill into them. |
| Low UXO risk on the regional map. | No specialist assessment needed at this stage. Keep it in the register. |
| A historic landfill record matches the former clay pit. | Confirms the “Tip” on the 1960s map. Ground gas and leachate are likely. A gas investigation will be needed (BS 8576). |
| Utility records show a gas main along the eastern boundary. The culvert crosses the south. | No-dig zones for the GI. The culvert’s route, depth and condition are unknown. |
Common mistakes
✗
Listing every designation within 1 km with no “so what”.
✗
Dismissing a hazard only because it is some distance away, without thinking about how it could reach the site.
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Treating “not recorded” as “not present”. Many old shafts and tips were never recorded.
✗
Writing “a specialist is needed” without saying what for and at which stage.
Try it
For your practice site, check the heritage list within 250 m, the radon map, the mining map and the UXO risk map. Write one “so what” per check, even if the answer is “nothing found, so no action at this stage”.
ReferencesBS 5930:2015+A1:2020, Section 2BRE BR 211 (2023)CIRIA C681BS 8576:2013
Knowledge check
Check your understanding: Part 1
10 minutesanswers explained when you check
- Which part of a desk study answers the question “what was on this site in 1960?”
Site history is part of the factual core. Interpretation comes after: what that past use means for the project.
- You have bought a commercial environmental data report for a site. What should you do with it?
BS 5930 notes these reports are helpful but not sufficient on their own: data can be out of date, incomplete or not site-specific.
- A 1960s map labels a former clay pit “Tip”. What is the most important thing it tells you?
“Tip” suggests waste disposal. Check landfill records and plan for ground gas and contamination.
- The 1930s and 1960s editions show no change on a site. What can you conclude?
Maps are snapshots. Uses can start and stop between editions without being drawn.
- The geology map shows no artificial ground on a site that was a depot for 40 years. What should you assume?
Artificial ground is only shown where it was recorded. The site history is often the better guide.
- A site is in a coal mining Development High Risk Area. What does the planning application need?
Development in a Development High Risk Area needs a Coal Mining Risk Assessment to show it will be safe and stable.
- Which statement about a Principal aquifer is correct?
The designation describes permeability and water resource value, not a body of open water.
Part 2 · Making sense of it
2.1 The site walkover
About 1 hour
The walkover is where the desk study meets the real site. BS 5930 calls it field reconnaissance and describes it as a thorough visual examination to confirm, add to and fill gaps in the desk study. It is not a stroll. You go with a plan, a list of questions from the desk study, and a way of recording what you find.
Learning outcomes
- Plan a safe walkover, including permission and a risk assessment.
- Know what to look for, on and around the site.
- Record observations separately from interpretations, with photographs you can locate.
Before you go
Do it after the desk study. BS 5930 recommends the walkover once the factual information has been compiled, so you know what to look for.
Take the right papers: a site plan, maps, the geology map and aerial photographs, and your list of questions.
Get permission from both the owner and the occupier where needed.
Write a health and safety risk assessment based on the desk study (for example possible contamination, open water, unstable ground, livestock, lone working), and update it on site if you find something new. Brief everyone who goes.
If you see an immediate danger to people or the environment, report it to whoever controls the site.
What to look for
| Look at | Clues |
|---|---|
| Ground surface and levels | Hummocks, hollows, steps, embankments, cuttings; brick, ash, clinker or waste at the surface (signs of fill). |
| Water | Streams, springs, wet ground, standing water, culvert inlets and outlets, drains. |
| Vegetation | Dead or stressed plants in patches (possible contamination or gas), plants that like wet ground, invasive species, protected trees. |
| Signs of past use | Old slabs, foundations, tanks, pipes, staining, drums, odours. |
| Services | Manhole and valve covers, marker posts, overhead lines, substations. |
| Structures on and near the site | Cracks, tilting, settlement: clues to the ground and to what is sensitive to your works. |
| Exposures nearby | Cuttings, quarries and banks that show the soils and rocks. |
| Access for the investigation | Gate widths, slopes, soft ground, overhead lines, where a rig could work. |
Recording: observation, then inference
Write down what you see in one column and what you think it means in another. The observation is a fact anyone could check. The inference is your judgement, and it may be wrong. Number every photograph and note its location and the direction you were facing.
Site D · walkover record
Fictional walkover notes for the worked example site.
| Photo | Observation | Inference and action |
|---|---|---|
| P1, north area, facing north | Uneven, hummocky ground. Brick fragments, clinker and ash at the surface. | Consistent with the filled pit. Supports the need to find the depth and nature of the fill. |
| P2, south-east, facing east | Two concrete plinths. Dark staining and bare soil around them. | Likely the former tank bases. Possible fuel spill. Target this area in the GI. |
| P3, east boundary, facing south | Dense stand of tall plants with hollow, bamboo-like stems near the culvert outfall. | Possibly Japanese knotweed. Needs confirming by a specialist. Do not disturb. |
| P4, chimney base, facing west | A vertical crack in the brickwork at the base of the listed chimney. | Condition unknown. Recommend a structural condition survey before any work nearby. |
| P5, east boundary, facing north | Covers marked “Gas” and marker posts along the fence. | Confirms the gas main in the utility records. No-dig zone for the GI. |
| P6, gate, facing south | Gate about 3.5 m wide. Firm ground in the south. Soft, waterlogged ground in the north after rain. | Rig access is possible from the south. Plan the northern holes for drier weather or use ground protection. |
| P7, off site, railway cutting 150 m east | Brown clay with stones over grey, layered rock in the cutting face (viewed from a public footpath). | Consistent with till over mudstone, as mapped. |
Common mistakes
✗
Concluding that water is contaminated because few fish or birds were seen. That is not evidence; only testing can tell you.
✗
Calling features the wrong thing, such as a stream a lake, which confuses everyone who reads the report later.
✗
Photographs with no location, direction or number.
✗
Going without the desk study, so the walkover cannot confirm or correct it.
✗
Entering pits, confined spaces or water, or lifting covers without authority.
Try it
Write a one-page walkover plan for your practice site: what you will check (from your desk study notes), the hazards to you and how you will control them, and what you will bring. If you visit, stay on public land and record at least three observations with inferences.
ReferencesBS 5930:2015+A1:2020, Section 2 (field reconnaissance)
Part 2 · Making sense of it
2.2 Preliminary conceptual site model
About 1 hour 15 minutes
A conceptual site model (CSM) is your best current picture of the site: what is in the ground, how it could move, and who or what it could harm. BS 5930 notes that it is the contamination equivalent of the geotechnical ground model, and both are updated as the investigation goes on. At desk study stage it is preliminary: built from existing information and your walkover, and waiting for the ground investigation to confirm it.
Learning outcomes
- Explain a pollutant linkage: source, pathway and receptor.
- Define your likelihood, consequence and risk categories before you rank anything.
- Build a linkage table and a geotechnical hazard register for a site.
Source, pathway, receptor
Source: a contaminant or hazard, such as asbestos in fill, fuel from an old tank, or gas from buried waste.
Pathway: a route from the source to the receptor, such as swallowing soil, breathing dust, gas moving through permeable ground, or leaching into groundwater.
Receptor: who or what could be harmed: future users, construction workers, neighbours, groundwater, surface water, buildings, buried concrete and water supply pipes.
A pollutant linkage exists only when all three are present and connected. A source with no pathway to a receptor is not a risk, which is why the model matters: it lets you say where risk is and is not.
Define before you rank
A risk ranking means nothing unless the reader knows what “high” means. Define likelihood, consequence and the resulting risk in your report, then use only those terms. Many organisations adapt the approach in CIRIA’s guide to contaminated land risk assessment (C552). Use your organisation’s matrix if it has one. The matrix below is a simple example used in this course.
| Consequence ↓ / Likelihood → | Unlikely | Possible | Likely |
|---|---|---|---|
| Severe | Moderate | High | High |
| Moderate | Low | Moderate | High |
| Minor | Low | Low | Moderate |
Likely: the linkage is present and harm is probable over the life of the development. Possible: the linkage could be present, but the evidence is uncertain. Unlikely: the linkage is doubtful or harm is improbable.
Severe: serious harm to people, or major pollution or damage. Moderate: harm or damage that needs remediation or repair. Minor: limited harm or damage that is easily put right.
Site D · preliminary pollutant linkages
Proposed use: primary school with playing field.
| Source | Pathway | Receptor | Likelihood × consequence | Risk |
|---|---|---|---|---|
| Ground gas (methane, carbon dioxide) from the filled pit | Migration through fill and into buildings | Pupils and staff | Likely × severe | High |
| Asbestos, metals and tar compounds in made ground | Swallowing soil, breathing dust, skin contact in the playing field and planting | Pupils and staff | Possible × severe | High |
| As above | Dust and contact during earthworks | Construction workers | Possible × moderate | Moderate |
| Fuel from former tanks | Leaching and migration through the ground | Secondary A aquifer; culverted stream | Possible × moderate | Moderate |
| Fuel from former tanks | Permeation through plastic pipe walls | Water supply pipes | Possible × moderate | Moderate |
| Sulfate in fill and mudstone | Direct contact | Buried concrete | Possible × moderate | Moderate |
| Mine gas from possible workings | Migration through fractured rock and fill | Buildings and their users | Unlikely × severe | Moderate |
Geotechnical hazard register
Alongside the CSM, list the ground hazards that affect design and construction, with the same honesty about what is known and unknown.
| Hazard | Evidence | Why it matters | Risk |
|---|---|---|---|
| Variable, compressible fill in the former pit | 1960s “Tip”; landfill record; hummocky ground (P1) | Large and uneven settlement under buildings and pavements | High |
| Shallow coal or old workings | Development High Risk Area; seam outcrop; shaft 250 m north | Collapse of workings under the building | High |
| Buried obstructions | Kiln and depot foundations, slabs (P2) | Delays to drilling, piling and excavation | Moderate |
| Culvert of unknown route and condition | Stream lost from 1970s map; utility records | Collapse, flooding and a no-dig zone | Moderate |
| Listed chimney | Heritage list; crack at base (P4) | Damage from vibration or ground movement | Moderate |
Common mistakes
✗
Ranking risks without defining the categories, or using a category (“very low”) that was never defined.
✗
Listing a receptor with no realistic pathway, or a source with no receptor.
✗
Forgetting buried concrete, water pipes and construction workers as receptors.
✗
Ranking a risk “low” because the site “has had no construction”, when the site history says otherwise.
✗
Naming the geology differently in different sections of the same report.
Try it
For your practice site, write three pollutant linkages (source, pathway, receptor) and rank each using the matrix above. For each, write one sentence saying what evidence would change the ranking.
ReferencesBS 5930:2015+A1:2020, Section 2BS 10175:2026LCRMCIRIA C552
Part 2 · Making sense of it
2.3 From desk study to ground investigation
About 1 hour
The last job of the desk study is the most useful one: turning every hazard and every unknown into a question the ground investigation must answer. BS 5930 lists recommendations for the scope of the investigation as one of the interpretive elements of a desk study. A good question is specific enough that you can tell, afterwards, whether it was answered.
Learning outcomes
- Write specific questions for the ground investigation, each linked to a hazard.
- Outline how each question could be answered, ready to be written into a ground investigation specification.
- Structure a desk study report so a reader can find the facts, the judgements and the recommendations.
From hazard to question to method
Site D · questions for the GI
The methods are outlines. A ground investigation specification turns them into detailed instructions for the contractor.
| Question | Why we need the answer | How the GI could answer it |
|---|---|---|
| Where are the edges of the former pit, how deep is the fill and what is it made of? | Decides where shallow foundations can go and where they cannot. | Trial pits across the expected edges; boreholes through the fill into natural ground; possibly a geophysical survey to map the edges. |
| Is there shallow coal or old workings under the building footprint? | Collapse risk; needed for the Coal Mining Risk Assessment. | Rotary probe holes to a depth set by the mining assessment, with the Mining Remediation Authority’s permission. |
| What gas is produced by the fill, and at what flow? | Decides the gas protection needed in the school. | Gas monitoring wells in the fill, monitored over time, designed to BS 8576. Results used with BS 8485. |
| Is the soil contaminated where children will play? | Protects future users; decides any clean cover or removal. | Soil sampling across the playing field and planting areas, with targeted samples at the former tanks, to BS 10175. |
| Has fuel reached groundwater or the culvert? | Protects the aquifer and stream; affects remediation. | Groundwater monitoring wells near the former tanks, with sampling. |
| How aggressive is the ground to concrete? | Sets the concrete specification for foundations. | Sulfate and related chemical tests on soil and groundwater samples. |
| Where is the culvert, how deep is it, and what condition is it in? | Safety of the GI and design of the layout. | Utility survey and a camera survey of the culvert. |
| What are the strength and stiffness of the till away from the pit? | Foundation design. | Boreholes with in situ testing and samples for laboratory testing. |
Structuring the desk study report
1. Introduction: purpose, the proposed development, sources used, and limitations (for example “based on records available on the date of the search; the site was viewed from within the boundary only”).
2. The site: location, boundaries, current use, topography, services.
3. Site history: the table from lesson 1.1, with a plan.
4. Geology, groundwater and flooding: lesson 1.2.
5. Constraints and hazards: lesson 1.3.
6. Walkover: observations, inferences and photographs (lesson 2.1).
7. Preliminary ground model and conceptual site model: with your defined risk categories (lesson 2.2).
8. Recommendations for ground investigation: the questions above.
References and appendices: every source with the date you accessed it; maps, plans and the photo log.
Common mistakes
✗
Vague recommendations such as “a GI should be carried out”, with no questions to answer.
✗
A recommendation that does not follow from any hazard in the report, or a hazard with no recommendation.
✗
No limitations section, so the reader thinks the desk study is more certain than it is.
✗
Drifting into detailed design (for example sizing a retaining wall) before the ground has been investigated.
Try it
For your practice site, write three questions for a ground investigation in the three-column format above. Check that each one traces back to something in your desk study notes.
ReferencesBS 5930:2015+A1:2020, Sections 2 and 3BS 8576:2013BS 8485:2015+A1:2019BS 10175:2026
Knowledge check
Check your understanding: Part 2
10 minutesanswers explained when you check
- According to BS 5930, when should the site walkover normally take place?
The walkover confirms and adds to the desk study, so you need the desk study first to know what to look for.
- A walkover note says: “Very few birds seen, so the stream is contaminated.” What is wrong?
Record the observation. Contamination can only be established by sampling and testing.
- When does a pollutant linkage exist?
All three elements must be present and linked. Remove any one and there is no risk from that linkage.
- A report defines risk as High, Moderate or Low, then ranks two linkages “Very low”. What should be fixed?
Every ranking must use a category the reader can look up in the report.
- Which is the most useful recommendation for a ground investigation?
A good recommendation is a specific question with a reason, so you can later check it was answered.
- Which of these receptors is most often forgotten in a preliminary CSM?
Materials are receptors too: sulfate attacks concrete, and some hydrocarbons can permeate plastic pipes.
Capstone
Capstone project: desk study for Site E
About 5 hoursoptional paid marking
Your task. Write a desk study report for Site E, a fictional site, using only the data pack below. You cannot visit Site E, so the walkover notes are provided: your job is to interpret them. Please do not look up real places, and do not use documents from a real project.
The brief
A developer proposes 40 two-storey houses with gardens, an estate road and soakaways to drain surface water into the ground, on a site of about 3.4 hectares on the edge of a village in southern England. You have been asked for a desk study and site walkover report to inform the planning application and the ground investigation.
Schematic plan of Site E. Fictional, not to scale. The ground falls about 8 m towards the south-east.
A. Site details
Disused farmyard in the north (steel-framed barns, a brick workshop, a concrete yard). Pasture in the south. Access from a lane on the west boundary. A public footpath crosses the south of the site. Hedges with mature trees on the western boundary.
B. Historical maps and aerial photographs
| Edition | On site | Off site |
|---|---|---|
| 1870s map | Fields. Farm buildings in the north. “Chalk Pit” of about 0.2 ha in the north-east corner. | “Tumulus” about 80 m north-east. Lane to the west. |
| 1900s map | The pit is labelled “Old Chalk Pit”. | No significant change. |
| 1930s map | The chalk pit is no longer shown; the area is shown as field. Two new barns in the farmyard. | No significant change. |
| 1946 aerial photograph | Farm and fields. No other features identifiable. | An airfield with runways about 2 km south. |
| 1960s map | “Sheep Dip” beside the barns. “Tank” beside the workshop. | Pond about 150 m south. |
| 1980s map | Two large barns replace the older ones. “Slurry Lagoon” east of the yard. | No significant change. |
| 2000s aerial photograph | The lagoon is no longer visible; the area is grassed. | No significant change. |
| 2020s aerial photograph | Barns with damaged roofs. Farm disused. | No significant change. |
C. Geology
Artificial ground: none mapped.
Superficial deposits: head (clay, silt and gravel with flints) along a shallow dry valley in the south-east. None mapped elsewhere.
Bedrock: chalk.
Dissolution features: two natural cavity records within 250 m. One, about 120 m west, is recorded as a “swallow hole” on a survey from the 1950s.
Borehole records: one water well about 400 m north, drilled in the 1950s: chalk to 60 m; water struck at 35 m.
D. Groundwater and flooding
Chalk: Principal aquifer. Head: secondary (undifferentiated).
The site is in Source Protection Zone 2 for a public water supply borehole about 1.5 km south-east.
Flood Zone 1. A surface water flow path follows the dry valley, with low to medium surface water flood risk along it.
E. Constraints and other records
Heritage: the tumulus is a Scheduled Monument (a round barrow) about 80 m north-east. No listed buildings within 250 m.
Trees: the hedgerow trees on the western boundary are covered by a Tree Preservation Order.
Ecology: no statutory wildlife sites within 1 km. Pond about 150 m south.
Radon: less than 1% band; not a Radon Affected Area.
Mining: outside the coal mining reporting area. Small historic chalk workings, including some underground, are known in the wider district.
Unexploded ordnance: moderate on the regional risk map.
Landfill: no historic landfill records within 500 m.
Services: an 11 kV overhead line crosses the north-west corner. Water main in the lane. No gas supply.
F. Walkover notes (provided)
| Photo | Observation |
|---|---|
| E1, north-east corner, facing north | A shallow, roughly circular depression about 6 m across and 0.5 m deep, with a hawthorn in the centre. |
| E2, workshop, facing east | A rusted above-ground steel tank on a brick plinth. Dark staining on the soil beneath. |
| E3, barns, facing north | Corrugated roof sheets, several broken, with fragments on the ground. |
| E4, beside barns, facing west | A concrete trough with an outlet pipe leading to a grated pit in the ground next to it. |
| E5, east of yard, facing south | A level grassed area about 0.5 m higher than the field around it, with dense nettles. |
| E6, near field gate, facing west | Blackened ground with ash, glass and scraps of metal. |
| E7, south-east, facing north-east | A gentle grassy hollow along the dry valley. No water at the time of the visit. |
| E8, west boundary, facing north | Gate about 4 m wide onto the lane. Overhead line crossing the north-west corner. Footpath signs at both ends of the path. |
Deliverables
A desk study and site walkover report of no more than 4,000 words (tables, figures and appendices extra), structured as in lesson 2.3.
A site history table with “why it matters” for every row.
An interpretation of every walkover note, as an observation and an inference.
A preliminary conceptual site model with your defined likelihood, consequence and risk categories, and a geotechnical hazard register.
At least six questions for the ground investigation, each with a reason and an outline method.
A limitations section and a reference list.
Marking guide
25%Factual core complete, organised and interpreted: every item has a “why it matters”.
30%Hazards and conceptual site model: defined categories, justified linkages, nothing important missed.
25%Ground investigation questions follow logically from the hazards and are specific.
20%Clarity, structure, limitations and references, written in your own words.
Want expert feedback on your desk study? Submit your report for detailed marking against the guide above: £80, with feedback within 10 working days and one half-price resubmission (£40) within 30 days. Please use only the Site E data pack, never documents from a real project. I do not accept work that is, or forms part of, a university assignment. How capstone marking works
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Reference library
Documents and data sources
Editions checked in September 2026. Always confirm the current edition before you rely on a document.
BS 5930:2015+A1:2020Code of practice for ground investigations. Section 2: desk study and field reconnaissance.
BS EN 1997-1 and -2 (Eurocode 7)First generation (2004+A1:2013; Part 2: 2007) and second generation (2024). First-generation UK adoptions withdrawn by BSI on 30 March 2028.
UK Specification for Ground Investigation, 3rd editionICE Publishing, 2022. The standard contract specification for UK ground investigation.
BS 10175:2026Investigation of potentially contaminated sites. Code of practice.
Land contamination risk management (LCRM)Environment Agency guidance, free on GOV.UK.
BS 8576:2013; BS 8485:2015+A1:2019; CIRIA C665Ground gas: investigation, protective measures and risk assessment.
CIRIA C552Contaminated land risk assessment: a guide to good practice.
BRE BR 211 (2023 edition)Radon: guidance on protective measures for new buildings.
CIRIA C681Unexploded ordnance (UXO): a guide for the construction industry.
BGS GeoIndex and BGS LexiconFree geology maps, borehole records and rock unit descriptions.
MAGIC; Flood map for planning; long term flood riskFree environmental designations, groundwater layers and flood maps (England).
Historic England, Search the List; UKradon; Mining Remediation Authority map viewer; Zetica UXO risk maps; National Library of Scotland mapsFree heritage, radon, mining, UXO and historical map checks.
This course reflects my own experience and general UK practice. It is independent of any employer or client, and all examples are fictional.