Why Ad-Blue is Not Green

By Paul Stapleton, Director Geo2

Ad Blue has been regarded in the past as a ‘green’ product.
Investigations by Geo2 as part of a forecourt redevelopment suggested
A major UK fuel producer and retailer commissioned Geo2, a land
remediation specialist, to manage environmental matters during the
redevelopment and expansion of one of their flagship sites, including
a full knockdown and rebuild, replacement of all tanks and
underground infrastructure, and a doubling of the site’s footprint
through the addition of a new HGV forecourt area.
During underground tank removal, strong ammonia odours were
coming from the ground. The odours were so strong that the
contractor could not safely work, especially as the source of the
release, and the nature of the contaminant, was unclear.
The situation was very serious for the client:
• The site had an unknown contaminant, with a business adjoining
the site which may be impacted by vapour, and watercourses on
two sides of the property which included protected species
• The contractor on site could not proceed with the development until
the source and type of contaminant were established so that
PPE and breathing apparatus used by Geo2 engineers
during delineation trial pitting works.
With personal ‘ammonia in air’ monitors
32 APEA tel: 0345 603 5507


Articles appropriate H&S measures could be put in place
• The contamination needed to be managed in line
with environmental responsibilities, UK law and
redevelopment planning conditions
• The delays with redevelopment were causing
significant knock-on impacts for the programme,
increasing contractor costs and delaying the
opening of the store, with commercial
Investigations by Geo2 concluded that the source
was likely to be Ad-Blue, a diesel supplement used in
HGVs and other diesel vehicles to reduce emissions.
The product is based on industrial urea, breaking
down into ammonia. Investigation by the client
discovered that there had been an incident with an
Ad-Blue above-ground tank, underground line and
pump fitted at the HGV filling area, prior to the
redevelopment. It appeared likely that the losses
associated with this leak had been vastly under-
estimated by the third-party operator of the system
at the time.
To confirm the source, Geo2 undertook soil and
water sampling using full respiratory equipment.
Samples were submitted for a range of contaminants,
including urea. Urea sampling is not a common test,
so specialist laboratories had to be found for these
works, although the turn-around time for the
specialist analysis was protracted. This confirmed the
source to be urea, and its breakdown products.
Contamination was noted around the HGV filling area
(the likely source area) but also in water and sediments in an adjacent
watercourse. The ground at the site consists of a stiff clay, with little
groundwater, and flooded during heavy rain. Soils between the source
and the watercourse were unimpacted, so it was considered that the likely
transmission route was via high-permeability pathways during heavy
rainfall events, such as pea-gravel beds, located around drainage services,
which ran to an interceptor, that discharged to the watercourse.
Investigation by Geo2 could find no record of a similar significant Ad-Blue
release. There was no UK precedent, so rapid action on determining safe
site-specific target values was required, establishing a remediation
working plan and engaging and agreeing the methods with the client,
contractor and regulators in order to progress the works safely, quickly,
efficiently and legally.
Remediation was undertaken in the source area by mass excavation and
disposal. As validation sampling turn-around times for urea were too long
to be pragmatic, excavation was undertaken using hand-held vapour
meters to field screen material. Careful screening of material was required,
as the high organic content meant that significant disposal costs would
otherwise be incurred. In addition, works were undertaken in the adjacent
watercourse to carefully remove impacted sediments from the sides and
base, preventing environmental harm and averting risk to human health.
Final validation of the works was undertaken by a programme of water
monitoring in adjacent watercourses, with regulatory sign-off being

For more information:
Susan Fairley, Marketing Manager: susan.fairley@geo2.co.uk

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