Re the gas works have you looked at the old planning fiches. I have found
that if you go back to the 1960's even for things like signs, toilet blocks
or a bike shed you often get accurate maps of the site. In our case it shows
that the town gas works is about 6 times bigger than the maps would suggest.
RE the origine of the PAH have a similar problem to this on an old highways
depot whic is being developed for housing.Strangely the first report circa
1995 had PAH levels of around 1000mg. The second and 3rd reports circa 2002
had consistent PAH levels of ~ 300.
We have needed a second oppinion.. not because of the developent but because
the residents are objecting to the removal of the material!
We are advised the fragments of scalpings should not get analysed as they
will be sieved out. So it begs the question where is the PAH coming from?
how risky are the actual fragments?
and what is actually being analysed.
I wonder if the difference in PAH levels between 1995 aand 2002 reports is
sampling error or it just shows a difference in the lab tests.
If anyone can shed any light it would be much appreciated.
-----Original Message-----
From: Philip Wright [mailto:[log in to unmask]]
Sent: 26 May 2004 10:25
To: [log in to unmask]
Subject: Re: Risk Assessment of PAH's
Thanks Mike,
The samples were taken at two depths per borehole, 0.1-0.3m and again at
0.6-0.8m with natural clay at about a meter, no conclusive picture as to
higher concentrations at the surface or at depth.
Age of the gasworks pre-dates O/S mapping in the area but the age of some of
the buildings and road boundaries would appear to contain it in most
directions.
Metals aren't generally a problem and ash/clinker seems in general to be
confined to the production area of the old gas site where PAH levels are
significantly higher than the rest of the site. The coal fragments away from
the footprint of the site appear in many cases to be unburnt material, we
haven't confirmed the source of B(a)P to be coal yet, its an avenue we think
may be worth considering given the likely problems further sampling in the
urban area will bring.
Regards
Phil Wright
-----Original Message-----
From: Williams, Mike [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: Wednesday, May 26, 2004 9:07 AM
To: Phil Wright
Cc: [log in to unmask]
Subject: RE: Risk Assessment of PAH's
Phil,
Don't have any information in terms of risks that coal (is it coal or
coal residue - clinker and ash?) actually poses and was unaware that
coal waste would reveal elevated levels of B(a)P. Generally speaking
when I have dealt with clinker contaminated sites the main problem has
been elevated metals
I've dealt with town gas works previously. Although I didn't have the
problem that you are describing.
I did however, discover, that the gas works covered a much larger site
and was a lot older than originally thought. Maybe the site did once
include or dispose of its waste on the neighbouring land, hence, your
elevated contaminants? However, if your info is accurate i.e. the houses
were there before the gas works this seems unlikely.
I suppose other possibilities would include that the surrounding houses
had used the clinker waste from the gas works as a garden material or
the B(a)P being associated with lateral migration of the coal tar off
the gas works site and into the surrounding houses. What depths were the
samples taken from? Is the B(a)P definitely from the coal material?
Just a few ideas - hope this helps,
Kind regards,
Mike Williams
Salford City Council
Environmental Services
Scientific Officer
0161 793 2139
-----Original Message-----
From: Phil Wright [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: 25 May 2004 17:02
To: [log in to unmask]
Subject: Risk Assessment of PAH's
Hi there,
We are currently investigating a small former town gas plant that now
has
residential housing on it, unfortunately no contaminated land planning
conditions were applied to the developments.
The investigation so far has revealed an almost universal problem across
the site, elevated PAH's, in particular B(a)P, no surprises there!
However the investigation has now progressed a significant distance from
the footprint of the old gasworks and again elevated levels of B(a)P are
still being discovered, there does not appear to be an obvious reason
for
this such as an engineering works or the likes as the PAH values are
random
in concentration, no declining trend from the source.
One common property of all the samples taken to date is the occurance of
coal fragments, which may be the source of the elevated PAH's, coal
fragements have been found in areas where there is no evidence to
suggest
the gas site existed, infact many of the areas surrounding the gas site
are
older properties constructed before the turn of the last century.
I suspect that the coal fragments in these areas may be due to the
historic
activities of former owners spreading ash from domestic fires grates in
the
past and as a result of coal storage at the properties.
Is there anyone out there who has done or knows of a source of
information
that may be of help in determining what risks coal actually poses, I
guess
there are two issues here, the first in seperating the coal fragments
for
analysis and then determining the actual risk this poses in a robust
quantitive way as it will need to be a supporting document in a
determination. I feel that at present further sampling will only reveal
more of the same if the radius of sampling is increased to include more
similar properties of a historic nature.
Regards
Phil Wright
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