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Hi Russell,
CO sensors typically see interference from hydrogen.
Kind regards
John
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]]
On Behalf Of Steve Wilson
Sent: 31 March 2017 09:54
To: [log in to unmask]
Subject: Re: Non-coal Mine Gas
Russell
Sorry – should have read more carefully – I misread CO as CO2 – 2000ppm CO is high!
Have you taken lab samples for analysis – There can be interference between CO and another gas (cannot remember which off top of my head).
Steve Wilson, Technical Director
The Environmental Protection Group Ltd
Tel 07971 277869
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From: Russell Bowman [mailto:[log in to unmask]]
Sent: 31 March 2017 09:02
To: Steve Wilson <[log in to unmask]>;
[log in to unmask]
Subject: RE: Non-coal Mine Gas
Steve,
Thanks for your comments.
In general, I’m interested by the gases themselves but also whether or not they’re indicators of mine workings in close proximity to the wells. Going back to my earlier question (back in 2013), the CO and H2S were detected in bedrock deposits within close proximity (~50m) of extensive sandstone workings (Yorkshire Stone).
In response to your first question, they were monitored for completeness – we were dipping the wells and so monitored on the first rounds (before groundwater levels were dipped). Bungs were left open over the duration of the monitoring visits and monitored once again at the end with only moderate reductions in concentrations of both gases. Densities of both gases would suggest this is to be expected – atmospheric pressure was steady, falling very slightly perhaps.
Yes, the fact the wells are flooded is key here as far as the direct source is concerned, what the original sources are is less clear to me.
The Till deposits are negligible on one of the sites where this phenomena is noted and whilst end use risk will quite likely be low I’m minded to consider it further with respect to construction worker safety (service excavations) as GW appears to be shallow on this site. I understand that at 0.2% (2000ppm), Carbon Monoxide can be fatal (in a confined atmospheres).
As far as sources are concerned, the hydrogen sulphide is likely natural (perhaps augmented by human activity, e.g. mining) but I’m less certain about the presence of the carbon monoxide in the wells. Given they’re both mine gases I was thinking of this as a potential source.
Regards,
Russell Bowman
Curtins
T.
0113 274 8509 |
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0113 274 8496 |
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]]
On Behalf Of Steve Wilson
Sent: 31 March 2017 08:17
To: [log in to unmask]
Subject: Re: Non-coal Mine Gas
Russell
Jenny is spot on with groundwater. Why were you monitoring wells designed for groundwater sampling for gas? Gas monitoring should only be carried out in wells designed for that purpose with response zones preferably above the groundwater table. Deep groundwater wells simply create an artificial chimney for gas to accumulate in as it partitions out of the groundwater and is not representative of gas migration to the surface through the Till, nor of the likely risk.
Gas in groundwater is not normally a high risk unless you are pumping the groundwater from depth (as happened at Abbeystead – but that incident has very little relevance to the situation on most contaminated land sites) or leachate from MSW landfills.
Methane can also be present as trapped gas in all Coal Measures rocks – it has been there for a very long time so it is not mobile. It can be trapped in pores or adsorbed onto carbonaceous surfaces in the rocks.
The hydrogen sulphide may also be present because of reduction of sulphates by bacteria.
2000ppm carbon dioxide in the ground is not particularly high (0.2% v/v).
Steve
Steve Wilson, Technical Director
The Environmental Protection Group Ltd
Tel 07971 277869
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]]
On Behalf Of Jenny Lightfoot
Sent: 29 March 2017 09:34
To: [log in to unmask]
Subject: Re: Non-coal Mine Gas
Hi Russell
Have you considered natural groundwater as a possible gas source? Experience from industrial groundwater abstraction boreholes has shown dissolved gas concentrations in Coal Measures groundwater can be problematic (particularly methane and nuisance levels of hydrogen sulphide). Explosions have occurred at groundwater abstraction boreholes in Yorkshire over the last century, one resulting in a fatality at a brewery abstraction.
Jenny Lightfoot
Arup North West and Yorkshire
Sent from my iPhone
On 29 Mar 2017, at 08:25, Russell Bowman <[log in to unmask]> wrote:
Good morning all,
Bumping this thread along with some recent experience and a couple of questions.
We’ve monitored (GFM portable) two sites in the last twelve months (centre of Leeds and Huddersfield respectively) where the overall gas risk situation has been low (shallow demo fill, Till, no landfills etc) but boreholes installed deep into the bedrock (installed for groundwater studies) have recorded high CO and H2S concentrations (up to 2000ppm CO and 160 H2S). Both sites have no known coal mining locally and no evidence on the sites themselves although there is reason to suspect unrecorded workings locally to both (I understand it wasn’t uncommon for large industrial sites back in the day to dig their own pits) and so it appears to be leaning towards a mine gas source. Worth noting that the sewers have not been surveyed and are present within 50m of installs.
Bag samples seems to be the way to go again but I was wondering if anyone else had experienced this and also, what the residence times of these gases are in the ground – could this be Victorian mine gas trapped in fissures? On the latter, I could imagine the CO remaining trapped (unreactive) and that the H2S could be produced by more recent phenomena.
Thanks in advance for your thoughts.
Russell
Russell Bowman
Curtins
T. 0113 274 8509 | F. 0113 274 8496 | [log in to unmask]">[log in to unmask]
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Michael Smith
Sent: 06 February 2013 10:53
To: [log in to unmask]
Subject: Re: Non-coal Mine Gas
Dear All,
Steve’s comment may be a little misleading.
The reaction that produces foaming in concrete and other cementitious materials is between metallic aluminium (added as powder) and the alkali in the cement. This reaction is used in the production of aerated concrete blocks such as Celcon & Thermalite. It can also be a problem when ash derived from burning refuse is used with cement because this ash will usually contain some aluminium.
The aluminium in pulverised fuel ash (PFA) and cement is bound in crystalline aluminates, aluminosilicates and ferroaluminosilicates or in aluminosilicate glass and is therefore not free to react with alkali to yield hydrogen.
PFA and cement clinker are formed under highly oxidising conditions so sulfide concentrations are either zero or very low (I don’t have any analyses to hand).
Rusting of iron and steel also produces hydrogen and is thus another possible (more likely?) source.
Incidentally, it is believed that it was the ignition of hydrogen due to reaction between aluminium and alkali that caused a major explosion in a waste disposal shaft at Dounreay a few decades ago.
Regards,
Mike Smith
+++++++++++++++++++++++++
Mike Smith
M A Smith Environmental Consultancy
Farthing Hill
Browns Springs
Potten End
BERKHAMSTED
HP4 2SQ
01442-872968
07961-312790
www.masmithenvironmental.co.uk
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Steve Wilson
Sent: 05 February 2013 14:03
To: [log in to unmask]
Subject: Re: Non-coal Mine Gas
Russell
Lime in the cement could react with aluminium in the PFA and generate hydrogen. Hydrogen was also the gas generated in some foamed concrete grouts to act as the foaming agent. I think from memory that hydrogen can cause interference on the CO channel of the monitor. I would check with the manufacturer and also take samples for lab testing.
The H2S could be from sulphides in the sandstone reacting with acid water.
You need to understand the chemistry of the ground and groundwater. However in both cases the gas release is probably a short term effect due to installation of the monitoring well.
Steve Wilson,
UK Registered Ground Engineering Adviser
Technical Director
on behalf of EPG
Tel 07971 277869
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Information contained in this e-mail is intended for the use of the addressee only, and is confidential and may contain commercially sensitive material. Any dissemination, distribution, copying or other use of this communication, other than for which it is explicitly intended, without the permission of the sender is strictly prohibited. If you have received this e-mail in error, please advise the sender immediately and delete it from your system. Whilst all e-mails are screened for known viruses, the company cannot accept responsibility for any which have been transmitted.
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Russell Bowman
Sent: 05 February 2013 11:26
To: [log in to unmask]
Subject: Non-coal Mine Gas
Dear all,
Quick query regarding non-coal mine gas.
I’m currently looking at a site upon which hydrogen sulphide and carbon monoxide have been recorded within a borehole whose response zone bridges a historic shallow (3m to 7m bgl) sandstone mine. The mine is believed to have been grouted and the borehole logs appear to reflect this (possible PFA:Cement grout) however void spaces are present within which these gases are believed to have accumulated.
First round of monitoring record; 90ppm CO and 30ppm H2S within 1 of 3 boreholes advanced through the relic seam. No H2S and CO were recorded on a subsequent visit at comparable environmental conditions.
First gas generation scenario is a historic mine fire (mine shut in 1950s) leading to the generation of CO and then subsequent generation of H2S from limited sulphates (~1%) present in the mine grout (PFA). The non-detection on the second visit suggests the well and possibly the void has been purged of these gasses.
A side-line question from this is whether anyone has known mine grout (PFA type) to generate H2S?
The alternative gas generation scenario is sewerage leaking into surrounding soils from a sewer recorded in relatively close proximity to the ‘gassing’ borehole. The localized nature of the gasses leans towards this conclusion.
Any comments/thoughts the group has would be appreciated.
Russell
Russell Bowman Senior Environmental Engineer
Curtins Consulting
T. 0113 274 8509 | [log in to unmask]">[log in to unmask]
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