Mark

Many people in the industry are thinking along the  lines you suggest.  We
have been working with others to come up with a robust framework to allow
this approach.  We have also extended it to cover other situations where gas
monitoring should not be necessary as there is negligible gas risk or as you
point out the building construction deals with the gas risk by default (eg
where you need radon protection or already have a void).  At the moment we
have used it on several sites alongside gas monitoring and it gives a
sensible answer.

It is not just brick and inert fill - there are lots of sites with thin
layers of Made Ground that are not producing large volumes of gas that poses
no risk - so why bother installing gas wells and gas monitoring when there
are quicker, more robust and cheaper ways to assess the risk.  On other
sites we also know what the gas protection will be required before we start
- so again do we need wells?

CIRIA are organising a series of seminars that Joanne advertised a few weeks
ago to discuss a simpler approach to gas assessment as a future way forward
by removing the need to install gas wells on many sites.  It is very similar
to the what you have suggested. The link to the seminars is below.  It would
be good if you could come to one to share your experience and discuss your
views:

A simpler approach to ground gas risk assessment 22 June 2011 London and 6
October 2011
http://www.ciria.org/SERVICE/Search2/Core/Events/eventdetails.aspx?iKey=E115
03

http://www.ciria.org/SERVICE/Search2/Core/Events/eventdetails.aspx?iKey=E115
04

If you cannot come give me a call - I would appreciate discussing this with
you.

Don't start me on the radon in all houses issue either!

Steve Wilson, Technical Director
on behalf of EPG 

Tel 07971 277869
www.epg-ltd.co.uk

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-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Marc
Fawcett
Sent: 13 April 2011 13:09
To: [log in to unmask]
Subject: former housing demolition fill - gas assessments

Dear all,

as much I love making money gas monitoring....  I think we are all being
somewhat overly conservative regarding general demolition fill from former
residential properties.

Not intended in anyway meant to be a rant but more of a discussion point to
gather opinions

Over the last 17 years I've collated a lot of gas data to give me confidence
in this and feel that some people (regulators and consultants) are being
grossly conservative regarding general inert brick and concrete demo fill as
typically found on a former housing sites.

We are here to risk assess? in a phased logical approach? - it doesn't have
to be technical all the time... 

So..... the phase 1 identifies historic residential demolition (no other
sources of gas potential identified) and recommends reviewing gas
potential....  what I would suggest is  review and risk assess on additional
information before saying its a must for gas monitoring as a sensible
approach?

If you have undertaken trial pits into the fill and its general demo fill
with no biogenic sources (domestic waste, veg matter, wood, fuel spillage,
ash)  I really do not see why we are defaulting to gas monitoring? other
than to spend clients money and time! (I'd say differently with window
sampling info however due to limited soils profile - as ever its the
accuracy of the data which is key)

Now obviously if there's an additional source from surroundings that needs
considering differently but for purely residential past use I'm talking
about.

Standard house design dictated by NHBC and Building regs generally gives you
2 to 3 points on the British Standard design guide so covers quite a lot of
eventualities - and in my opinion gives the added confidence to these low
risk gas potential sites.  

something else to consider - I think a lot of the perceived residual risk is
from the fact that a lot of consultants aren't stating this fact that
protection measures are being designed into standard construction? the words
'green' and 'no gas protection required' which I see every day in third
party reports is giving the wrong impression of risk mitigation?

I'd be interested to hear your thoughts / discussions on this one.