Generally take the points being raised but care over establishment of
preferential pathways when backfilling service trenches?
Also not convinced why the magic 1.0m figure is being quoted, the whole
scientific robustness of that assumption is debatable - if clay permeability
is the answer and Darcy's law is deemed applicable as if relating to clean
water flowing through such materials then "breakthrough times" can be
calculated.
As an Industry of "Regulators, Developers, Contractors and Consultants" (and
Government / DEFRA advisors?) we really do need to bottom out this debate
and move forwards by combining well established geotechnical principles with
environmental science and toxicology. The current debates on this list make
me realise that we all really do have to pull together and move things along
- even more than I thought was required than before!
I only hope we do not lose sight of the need for good quality
investigations, sampling, storage and testing protocols before we arrive at
our 95th percentile values to compare against the limited number of
published SGV's we have at our disposal.
Dr. Paul H. McMahon
Director of Earth Sciences
On behalf of RoC Consulting
81-83 Chapel Street
Manchester
M3 5DF
Tel: 0161 839 2233
Fax: 0161 839 2244
Mob: 0781 252 1819
[log in to unmask]
http://www.rocconsulting.com
-----Original Message-----
From: Ivens, Rob [mailto:[log in to unmask]]
Sent: 19 November 2003 14:37
To: Dr. Paul H. McMahon
Subject: Re: Vapour proof membranes
Services may or not may not need protecting depending on depth of clean fill
etc..
but I would agree it could be something that would easily get neglected
especailly in a commercial situation.
re residential properties we normally require 1.0m of clean if the
conditions are horrible.... isnt this normally deep enough to protect the
services.?
The idea of the clay is to reduce the level of vapour migration.... I liked
the idea any way. Though I know clay is not totally impermeable. Confronted
with a dirty site under commercial buildings I thought it had some merrit to
helping protect the building footprint rather than relying on just a
membrane... which we have allowed in the past.
a thought any way.
but for the membrane we would still require a QA'd/QC'd guarranteed
installer to be used on a contract basis rather than leaving the site
workers to do it.
-----Original Message-----
From: Adam Czarnecki [mailto:[log in to unmask]]
Sent: 19 November 2003 14:29
To: [log in to unmask]
Subject: Re: Vapour proof membranes
And what do you do with services?
Do you protect the membrane?
What exactly is the function of the clay?
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