Muttakir,
What you propose is not a "break layer" as described in CIRIA and other guidance (see also CIRIA SP106) - simply a physical barrier to soil disturbance.
A "break layer" prevents upward migration of moisture (and dissolved contaminants) due to capillary action and typically consists of coarse granular material. Such a granular layer will require protection to prevent infiltration of fine soil - typically a geotextile would be used for this both below and above the coarse material.
Geotextiles will not impede upward (or downward) migration of moisture. When the surface of unsaturated soil is moistened by rain, water is drawn downwards into the dryer underlying soil by capillary action.
A near-surface break layer can cause flooding because downward flow is inhibited.
A break layer can probably be formed by a plastic egg-box structure sandwiched geotextile layers.
Regards,
Mike Smith
+++++++++++++++++++++++++
Mike Smith
M A Smith Environmental Consultancy
Farthing Hill
Browns Springs
Potten End
BERKHAMSTED
HP4 2SQ
01442-872968
07961-312790
[log in to unmask]
www.michael.a.smith.btinternet.co.uk
-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Muttakir Mohammed
Sent: 26 July 2012 12:15
To: [log in to unmask]
Subject: Re: Help with Geotextile Membrane guidance
Hi All,
In my email I meant to say the membrane will be used as a break layer between an inert cover and underlying contamination. Sorry for the confusion and also sorry for double posting, I didn't realise I posted the same email twice.
Muttakir Mohammed
Pollution Control Technician
Neath Port Talbot County Borough Council
|