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Deoxygenated gas occurrences in the Lambeth Group of central London, UK

T. G. Newman, R. C. Ghail and J. A. Skipper
Deoxygenated gas occurrences in the Lambeth Group of central London, UK
Quarterly Journal of Engineering Geology and Hydrogeology (May 2013) 46 (2): 167-177


Deoxygenated air poses a serious, life-threatening hazard (confined space hypoxia) for engineering projects in London, particularly within the Upnor Formation of the Lambeth Group. This paper reviews its causes and postulates that it was induced by regional-scale dewatering and drawdown of the Lower Aquifer during the industrial growth of London, bringing air into contact with these sediments, which became oxidized. Ensuing post-industrial recharge and resaturation resulted in accumulations of often compressed deoxygenated air, trapped beneath overlying impermeable clay strata. Historically, glauconite has been considered to be the mineral most likely to remove oxygen from the trapped air, but it lacks potency as a reducing agent and remains unaltered in many oxidized sediments. Pyrite and organic carbon are both plausible, but rare. Green rust, a mixed Fe(II) and Fe(III) layered double hydroxide, is more likely, as it rapidly oxidizes on contact with air and is only briefly observed in fresh core samples. Two key ground engineering hazards are, therefore, identified: the misidentification of risk by reliance on observations of glauconite; and the likelihood of encountering pressurized deoxygenated air within Lambeth Group sediments in underground projects following short- or long-term changes in the groundwater level.

ISSN: 1470-9236
EISSN: 2041-4803
Serial Title: Quarterly Journal of Engineering Geology and Hydrogeology
Serial Volume: 46
Serial Issue: 2
Title: Deoxygenated gas occurrences in the Lambeth Group of central London, UK
Affiliation: Imperial College, Department of Civil and Environmental Engineering, London, United Kingdom
Pages: 167-177
Published: 201305
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 36
Accession Number: 2013-046171
Categories: Engineering geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects.
N51°30'00" - N51°30'00", W00°10'00" - W00°10'00"
Secondary Affiliation: Geotechnical Consulting Group, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201329
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