This page contains a Flash digital edition of a book.
Figure 1: John Naylor, GGS Technical
Director, downloads GasClam® data
Figure 2: Continuous ground-gas data and environmental correlations.
F
ollowing a number of disasters in the 1980’s, most and ground water table. Instead of a ‘spot’ reading collected
notably the Abbeystead pumping station explosion once a week, the GasClam® can take over a 1,000 readings
in 1984 and the Loscoe bungalow explosion in 1986, a week.
a considerable amount of guidance has been developed to
Now for the first time high quality ground –gas time-series
measure, monitor and understand ground gas regimes.
data is available. In addition to the wealth of knowledge
However, the conventional hand held monitoring equipment
from the continuous data itself, additional tools can be
has not been able to provide the necessary detail to allow
used to draw out additional information. These include:
ground-gas regimes to be understood with confidence.
Environmental Correlations
The properties of bulk ground-gases are well understood;
the questions to answer have been how much gas is being
Concentration Duration Curves
generated, where is it migrating and what are the risks to Purge and Recovery Tests, and
receptors? To date these questions are addressed by
Differential Pressure Assessment.
periodically sampling gas monitoring wells using handheld
monitoring equipment. These devices monitor the bulk
Now one year on from the end of the DTI research, the
gas concentrations together with the peak and steady
GasClam
®
technology and the GGS data interpretation
state flow rates. The principal limitation with this approach
techniques are rapidly becoming the preferred approach
is that the measurements are taken at a moment in time
by contaminated land professionals. Together, they provide
and may not be representative. Time is the missing
unparalleled information that reduces uncertainty and in-
dimension in these ‘spot’ measurements. Instead of a
creases confidence in the risks associated with problem
single snap shot, what we have needed is a time-series
sites. This innovation is leading to a sea change in the way
that shows the changes over time and how the gas is
ground-gas risks are managed with more sustainable and
affected by other changing parameters.
cost effective solutions being designed on the back of
more robust data, often collected over shorter periods.
Dr Stephen Boult, through both his research at the
University of Manchester and his work with Salamander,
The three research partners are currently writing a best
has been interested in time-series data for many years.
practice guide to the collection and interpretation of
However, it was through his discussions with Simon Talbot,
ground-gas time-series data. This will appear as a CL:AIRE
the then Director of Greater Manchester Geological Unit
Technical Bulletin early in 2010.
(GMGU) which was also based at the University, that The on-going collaborative research has focused on
Steve’s ideas were developed in relation to real world developing and trialling the next generation of VOC
problems. The result was the development of a prototype GasClam
®
s. These contain a broad spectrum PID sensor,
device which was intensively trialled and tested as part of H2S and CO sensor in addition to CO
2
, CH
4
and O
2
bulk
a DTI funded collaborative research project. gas sensors. Ground-Gas Solutions is looking forward to
The outcomes have included successfully bringing the
taking delivery of the first commercially available VOC
GasClam
®
to market and the formation of the specialist
GasClam
®
s early in 2010.
environmental consultancy, Ground-Gas Solutions Ltd (GGS),
About the Authors:
that focuses on providing high quality monitoring and risk Dr Stephen Boult is a senior lecturer in the University of Manchester
assessment services based on GasClam
®
time-series data.
School of Earth, Atmospheric and Environmental Science, and is a
founder and managing director of Salamander. Contact: s.boult@man-
The GasClam
®
is the only ground-gas monitoring device
chester.ac.uk 07913 489 015.
in the world that can sit within a standard monitoring well
Simon Talbot is the Managing Director of Ground-Gas Solutions Ltd and
and continuously sample ground-gas. The standard device
former Director of the Greater Manchester Geological Unit - Contact:
has CH
4
, CO
2
and O
2
sensors and will also record simon.talbot@ground-gassolutions.co.uk 0788 4444 272.
temperature, atmospheric pressure, borehole pressure
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