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Alex
Hydrogen or ethane in the well can be recorded as carbon monoxide.
Have you carried out lab testing on gas samples to confirm it is CO?
Then look at conceptual model – is there a source of CO? Low levels can be produced by nacent hydrogen reacting with metals in the soil. In this case – probably low risk, but you can check by looking at the chemical equations and working out how much is likely to be produced.
Is there a higher risk source – smouldering underground fire in a landfill?
Finally use the data you have to model migration into the proposed development and compare against the values quoted by Adam. You can then modify the analysis to show the benefit of any gas protection (eg a ventilated void)
You should be able to demonstrate whether it is an unacceptable risk or not.
Steve Wilson, Technical Director
on behalf of EPG
Tel 07971 277869
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Adam Czarnecki
Sent: 31 March 2011 16:06
To: [log in to unmask]
Subject: Re: Carbon Monoxide
Wikipedia has this;
Concentration | Symptoms |
35 ppm (0.0035%) | Headache and dizziness within six to eight hours of constant exposure |
100 ppm (0.01%) | Slight headache in two to three hours |
200 ppm (0.02%) | Slight headache within two to three hours; loss of judgment |
400 ppm (0.04%) | Frontal headache within one to two hours |
800 ppm (0.08%) | Dizziness, nausea, and convulsions within 45 min; insensible within 2 hours |
1,600 ppm (0.16%) | Headache, tachycardia, dizziness, and nausea within 20 min; death in less than 2 hours |
3,200 ppm (0.32%) | Headache, dizziness and nausea in five to ten minutes. Death within 30 minutes. |
6,400 ppm (0.64%) | Headache and dizziness in one to two minutes. Convulsions, respiratory arrest, and death in less than 20 minutes. |
12,800 ppm (1.28%) | Unconsciousness after 2-3 breaths. Death in less than three minutes. |
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Alex Smiles
Sent: 31 March 2011 15:56
To: [log in to unmask]
Subject: Carbon Monoxide
Just a quick one, have been attempting to locate some guidance re: assessment of risk posed by elevated concentrations of Carbon Monoxide ground gas.
We have a site which has been reporting levels ranging between 200 and 400ppm and I have turned up a blank in the usual places (CIRIA 665 etc) regarding the assessment of risk posed. Gas flow rates have been reported around 2l/hr during varying atmospheric conditions including falling.
Would be interesting to know if anyone has dealt with CO and what guidance is available to evaluate risks.
Thanks
Alex
Alex Smiles
Senior Geo-environmental Engineer,
On Behalf of RoC Consulting
T: 0161 833 9737
F: 0161 834 5619
M: 07790 548596
RoC Consulting Ltd, Studio B Commerical Wharf, 6 Commercial St, Manchester, M15 4 PZ
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