Covering it with concrete sounds excessive and possible not the right solution. What about gas venting?
With respect to the caravans - stick them on a reinforced concrete slab 200mm thick with a good gas membrane below and there will be little risk from gas (I am assuming like most caravans there will not be any need to put services or other penetrations through the slab. They may put a skirt around the caravan but they are usually leaky.
I would be more worried about off site migration if they seal the whole thing.
Steve
-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of David E Jackson
Sent: 21 November 2014 15:17
To: [log in to unmask]
Subject: Risk management in perpetuity
Dear All
I little Friday conundrum for you...
I have a site which is being developed as a caravan site for holiday lets. The site is under single ownership but each of the lots is to be let to tenants under a long lease, the terms of which would allow tenants to use their own caravans and require them to care and manage their lots. Each lot would be connected to full subsurface services managed by the site owner.
Problem... the site is on a former landfill site and testing has revealed soil contaminants above health screening levels for residential land uses. The owner has proposed that the site be entirely covered with concrete with no access to soils. Ground-gas is present at CIRIA C665 (CS2) levels, but as the caravans are off-the-ground and apart from sealing of service conduits, no additional measures are proposed. This all sounds pretty reasonable now but....
How can I approve the development and still ensure that a) there is no soil access and b) the gas protecting void under the caravan, is maintained into the future.
Suggestions so far are, a planning condition requiring annual inspection, a restrictive covenant on the ownership deeds...
Any suggestions?
David E Jackson
Sometime Freelancer
