Kevin,
In my experience, where cuts have been infilled there is usually gas. We have investigated many inert fills and while there is very little methane, 0 to <1% where there is very little or no visible organic material CO2 can be 1 to 15%. This is usually when the material is unconsolidated and there is varying degrees of void space in the fill. Flows vary from hole to hole as does the concentrations accross sites. Needless to say there are exeptions when there is no visible organic material identified and thre are high levels of methane 1 to as much as 10%. As Judith pointed out, what is shown on a map is not always acurate and the extent of the area can be 2 to 4 times the area of the former surveyed area, meaning it was mapped, extended and then filled. The one question I would as is would gas reach the receptor in concentrations that is likely to cause risk? These are observations I have made but there are a few experts who can hopefuly shed some light on the great gas conundrum within the group.
Regards,
Robin Mackenzie
Contaminated Land Co-ordinator
Perth and Kinross Council
Tel 01738 476443
Mob: 07810057566
[log in to unmask]
----- Original Message -----
From: Contaminated Land Management Discussion List <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Wed May 20 10:52:36 2009
Subject: Re: Landfill Gas
Dear Kevin
I can't comment on the landfill gas, but I can tell you that the extent of the chalk pit shown on the map may not be correct.
A while ago, I investigated an infilled chalk pit expected to be a certain size and likely to be investigateable with a JCB (so maximum 3-4m deep). Trenching to locate the edges of the pit, revealed an old topsoil and a much larger pit which had been infilled at intervals with a variety of rubbish. I can't remember how far the actual edges of the pit were compared to what was shown on the map but it could have been 50m or more.
In the end we had to get a Himac in - the pit ended up being 7m+ deep and we unearthed a car.
So whatever they "officially" filled the pit with, there could have been some unofficial filling prior to that.
Judith
________________________________
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of L.Warhurst
Sent: 20 May 2009 10:21
To: [log in to unmask]
Subject: Re: Landfill Gas
Hi Kevin,
We have an infilled railway cutting (in limestone, probably fissured)
where a Waste Disposal Licence was granted to the site operators in 1977
giving permission to deposit building rubble and excavation material not
containing any combustible or putrescible material or any other waste
likely to cause a nuisance or pollution.
However, intrusive investigations carried out during the past 5 years
have revealed areas containing ash, clinker, plastic, wood, paper,
clothing and other non-inert waste. Gas monitoring has recorded
localised pockets of methane over 50% and carbon dioxide up to 20%.
Regards,
Leigh Warhurst
Environmental Protection Technician - Land
Ashfield District Council
Urban Road
Kirkby in Ashfield
NG17 8DA
Direct line 01623 457477
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Kevin
Beer
Sent: 18 May 2009 14:30
To: [log in to unmask]
Subject: Landfill Gas
Hi all,
I have a site that has come through the planning process where the
applicant wants to build a new property approx 100m from an infilled
chalk pit. The applicant states the pit was infilled with inert clay
material, however we have no way of knowing this for sure.
In order to give us more weight in our argument I was just wondering if
anyone has any examples of where someone has said a pit or quarry has
been infilled with apparently inert material only for a site
investigation to show that it is giving off elevated gas concentrations?
I have a feeling there was a part IIA site from a couple of years ago
where there was a similar situation??
Many thanks
Kevin
Kevin Beer
Contaminated Land Officer
Community Protection
Basingstoke & Deane Borough Council
Civic Offices, London Road, Basingstoke, Hants, RG21 4AH
Tel: 01256 845520
Fax: 01256 845200
email: [log in to unmask]
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