Subsoil and ground of Paris’s 4th arrondissement
No quarry recorded Paris 75004
The 4th arrondissement (Hôtel-de-Ville, Marais, Île de la Cité, Île Saint-Louis) is historically marked by a former filled-in branch of the Seine (the « marsh » proper) and by alluvial islands. Infill and modern alluvial deposits may be significant at depth. No known quarry is recorded by the IGC (Paris quarry inspectorate) for this area.
What the public data say about the 4th
| Underground quarries recorded by the IGC (Paris quarry inspectorate) | None |
|---|---|
| Nature of the ground | Former oxbow lake of the Seine (Marais, Îles) |
| Foundation issue | Historically wet and backfilled ground: risk of differential settlement on heterogeneous backfill. A G1 followed by a G2 geotechnical study is recommended before any project, with particular attention to the depth of sound load-bearing ground. |
Ground, fill and clay shrink-swell
The 4th arrondissement (Hôtel-de-Ville, Marais, Île de la Cité, Île Saint-Louis) is historically marked by a former filled-in branch of the Seine (the « marsh » proper) and by alluvial islands. Infill and modern alluvial deposits may be significant at depth. No known quarry is recorded by the IGC (Paris quarry inspectorate) for this area.
Historically wet and backfilled ground: risk of differential settlement on heterogeneous backfill. A G1 followed by a G2 geotechnical study is recommended before any project, with particular attention to the depth of sound load-bearing ground.
Unlike almost all French municipalities, inner Paris has no official mapping of the clay shrink-swell hazard (RGA). The BRGM explains this explicitly: the Paris subsoil is largely made up of reworked and artificial materials (backfill, infilled former quarries), which does not correspond to the standard methodology for this mapping — centred on detached houses, which are in the minority in Paris. This does not mean that there is no risk of differential settlement, but that no official area-by-area study exists for the capital: a ground investigation remains the only reliable way to assess a specific plot before purchase or construction.
Your steps to take in the 4th before a purchase or works
- IGC (Paris quarry inspectorate) information sheet — the authoritative source on the condition of the parcel’s subsoil: €10, issued within 8 days, via the City of Paris online service.
- Statutory risk statement (ERP) — mandatory for sale and letting, generated from Errial; note, it does not return cavity data in Paris.
- geotechnical survey — G1 mission before purchasing a building plot, G2 AVP before a construction or underpinning project.
- Referral to the IGC (Paris quarry inspectorate) for planning — prefectoral orders require it to be consulted for any planning permission in a quarry-risk area.
Frequently asked questions
Are there underground quarries beneath Paris’s 4th arrondissement?
No former underground quarry is recorded by the IGC (Paris quarry inspectorate) for the 4th arrondissement. The areas of former quarries in inner Paris are concentrated in the south (5th, 6th, 12th, 13th, 14th, 15th, 16th, in Lutetian coarse limestone) and in the north-east (10th, 18th, 19th, 20th, in gypsum). This does not mean that there are no ground-related issues: the 4th is covered by the « ground and foundations » section.
Is a ground study still needed in the 4th?
Yes, whenever there is a construction, extension or underpinning project. Historically wet and backfilled ground: risk of differential settlement on heterogeneous backfill. A G1 followed by a G2 geotechnical study is recommended before any project, with particular attention to the depth of sound load-bearing ground.
Why does cavity data for the 4th not appear on Géorisques?
Because for départements 75, 78, 91, 92, 93, 94 and 95, cavity data are not published on the Géorisques portal: they can be consulted with the IGC (Paris quarry inspectorate) for Paris and the inner suburbs, or with the relevant interdepartmental service. This is why a standard statutory risk statement (ERP) remains silent on Paris quarries and gypsum.
Is the 4th’s quarry risk covered by insurance?
Disorders linked to former quarries do not fall under the « natural disaster » scheme. In the event of collapse, infill works, estimated at 40 000 to 200 000 €, remain the responsibility of the owners. This is what makes checking before purchase essential.
Other arrondissements
- Subsoil of the 3rd arrondissement
- Subsurface of the 5th arrondissement
- Subsoil of the 2nd arrondissement
- Subsoil of the 6th arrondissement
- See the 20 arrondissements
Sources
- City of Paris — PLU explanatory report (geological context)
- Wikipedia — Paris, Geology section
- Annales des Mines — Beneath the streets of Paris (urban geology)
- BRGM — Why is there no map of the clay shrink-swell hazard for Paris?
- Géorisques — Clay shrink-swell, 2026 version (data)
- Géorisques — Underground cavities (data)
- City of Paris — the IGC (Paris quarry inspectorate) location
- City of Paris — Known areas of former quarries (IGC)
Page updated on 11 September 2026.