Dear all,
I am dealing with a particularly awkward part of a gas works (are there any
simple ones!) site with the Environment Agency. There are a number of issues
and the site is split into different plots - some developed, some not. All
of which are a potential problem. However, I need advise on one plot in
particular. I will attempt to give a verbal conceptual model.
The site has planning permission for residential development. The original
permission was subject to a contamination planning condition and groundwater
monitoring. The site was investigated and remediated with a very detailed
validation statement produced.The remediation removed all sources to
specified depths. Engineered barriers where then put in place. These where
placed above the most contaminated areas. The horizontal and vertical clay
barriers did not cover the entire extent of the site. They where intended to
prevent any contamination migrating upwards from the unsaturated layer into
the remediated layer. When the validation statement was submitted the
contamination planning condition was removed. However, the additional
groundwater monitoring revealed a series of very nasty organics residing in
the unsaturated layer but below the remediated layer. Following onto this
the boreholes were sealed (potential pathway upwards) and we requested
shallow boreholes upto 2metres to test the remediated layers. No issues of
concern where identified in the remediated layer.
However, the Environment Agency are still unhappy with the soil/unsaturated
layer quality beneath the remediated layer based on what was found in the
deep boreholes. I wouldn't disagree with this as the substance remaining is
almost pure tar (very nasty). The Agency also believe there is a risk to the
remediated layer from the substances below due to the incomplete nature of
the capping layer. The geology of the remediated layer is sand and clay
(consultants claiming it to be not very permeable).
Anybody dealing with a similar situation?!
My question(s) are:
What is the best piece of legislation to use to deal with this matter?Should
it be dealt with or is it ready for development?
I had considered two possibilities;
push the agency to use the water resources act or
use Part IIA legislation under pollution of controlled waters for the risk
to the aquifer i.e. likely to enter controlled waters and significant
possibility of significant harm for the risk to the remedaited layer. This
is almost a reversal of the a standard contaminated land problem because the
risk of contamination to the remedaited layer is from below 2 metres with
the pathway being migration upwards due the rsising water table in wet
periods.
I prefer option 1, water resources act, for various reasons, one of the
being that the original polluter will be prosecuted not the developer who
have been as co-operative as they could have been. I appreciate this may not
be a consideration.
Confused yet? If anybody has any advice on the above please be in touch.I
know there are too many issues for a simple answer. It is likely that we
need to get an independent party to review the evidence. Nethertheless any
opinouns,experience or advice on the matter would be greatly appreciated.
Thanks,
Michael Williams
Technical Officer
Health and Housing
Pollution Team
Breckland Council
Elizabeth House
Walpole Loke
Dereham
Norfolk
NR19 1EE
Tel: 01362 656334
Fax: 01362 656266
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