Louise
Get the developers/consults to provide a detailed conceptual model before you start.
In Gloucester there are rarely groundwater issues (Lias Clay) so any risk assessment and remediation invariably focuses of human health. The main potential pathways are vapour phase exposures (mainly indoor, but potentially outdoor) and drinking water services infiltration. Generally redevelopment proposals have not included gardens or soft landscaping, but if they did then there would be other possible linkages as well. Its also important to consider possible off-site impacts.
We also ask for a degree of risk assessment - but do balance off the level of detail required against remedial proposals. If the developer is intending to use suspended slabs, ventilated voidspace and a hydrocarbon resistant barrier membrane then generally I'd accept more contamination or 'uncertainty' remaining in the ground.
In general:
I'd always expect speciated hydrocarbon analysis - to include BTEX and usually MTBE (though this has never been a problem).
I always request justification for whatever clean-up levels are proposed.
Usually I'd expect soils removal and validation sampling to be carried out concurrently with any UST removal.
Usually I'd want removal of any gross free-phase product.
I'd typically expect vapour protection measures (as outlined above) to be incorporated into the foundations.
I'd require copies of the necessary documentation from the Petroleum Officer and Water Services Provider.
The Water Services Provider should be provided with copies of all relevant SI reports and will typically specify the use of barrier pipe on former service stations. Where conditions are really poor they may require over excavated trenches backfilled with clean material, or even lined. Clay 'stanks' can be used to prevent lateral migration of contaminated groundwater along service trenches. They often use an assessment system known as CLIPS - details of which are on the WRAS website.
http://www.wras.co.uk/publications/default.htm
Regards
Steve Moreby
Environmental Health Department
Gloucester City Council T 01452 396 312
Herbert Warehouse F 01452 396 340
The Docks stephen.moreby@gloucester.gov.uk
Gloucester, GL1 2EQ www.gloucester.gov.uk
-----Original Message-----
From: Louise Halloran [SMTP:[log in to unmask]]
Sent: 23 June 2004 10:17
To: [log in to unmask]
Subject: A Query
Within our Borough we are experiencing a lot of redevelopment of petrol
stations to create flats, in the main. The main issues are TPH and PAH.
Given that there are no specific levels set other than EA level of 1000mg/KG
there can still be issues with odour below this threshold as well as issues
of attack on services etc. I was wondering what approach other authorities
took, in particular with regards to design solutions and how effective these
have been?
Thanks very much for your time
regards
Louise Halloran
^**********************************************************************^
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.
[log in to unmask]
http://www.merton.gov.uk
**********************************************************************
^**********************************************************************^
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.
[log in to unmask]
http://www.merton.gov.uk
**********************************************************************
=========================================================================
DISCLAIMER
This message is intended for the recipient only and may contain privileged information.
If you are not the addressee, or you have received it in error, you may not copy, disclose, print, or deliver this message to anyone. Should this be the case, please delete this message, and inform the sender of your action by reply e-mail.
Gloucester City Council does not guarantee the accuracy or reliability of information in this message, and any views expressed are not necessarily the views of Gloucester City Council.
Gloucester City Council does not accept any responsibility for any disruption or loss to your data or computer systems that may occur whilst using any program or document attached to this message.
You are advised not to send confidential or sensitive information by e-mail, as the security of the site cannot be guaranteed.