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Ground Gas Investigation & Design Considerations

In recent years, the importance of ground gas protection on sites where hazards have been identified through investigations has become a critical element of the success of many projects. High profile failures have highlighted the real risk to life and health that inadequate, or ill-conceived ground gas protection measures have failed to eliminate.

Where a need for ground gas protection has been identified by the site investigation report, it is advised that a specialist in ground gas investigation, design & protection should be engaged at the earliest design stage of the building. Early involvement of a specialist will maximise the chances of a successful development/project/scheme, while reducing costs and the likelihood of defects and failure.

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When / How is the need for a ground gas investigation identified?

Ground investigations are carried out as part of the pre planning stage of most new build projects. If there is any perception of risk from ground gasses then the site will be subject to a full investigation by qualified geotechnical engineers. 

What a typical ground gas investigation is made up of

The task of the ground gas site investigation is typically led by suitably trained and competent geotechnical engineers. This should include as deemed appropriate:

  1. Preliminary investigation: using historical maps, geographical maps, regulation data, research on landfill sites and memories
  2. Ground investigation: including the use of ‘trial pits’
  3. Laboratory testing: with consideration of the use of WAC (Waste Acceptance Criteria) testing on soil samples

This processes of site investigation & evaluation and risk assessment are set out in ‘BS8485:2005’ (design of protective measures for ground gases for new buildings). 

Download: Site investigation flow chart >>

Site investigation, Hazards & Risks Considerations

The investigation, hazards & design requirements for any ground gas protection system will be dictated by a number of variable factors including the use and design of the structure. However, the underlying ground conditions, the presence of harmful ground gas or contamination that has the potential to release harmful gases are primary considerations.

As mentioned above, the processes of site evaluation and risk assessment for carbon dioxide and methane are set out in BS8485:2015+A1:2019. This process of conducting ground investigations and establishing the presence of and likely risks from a wide range of harmful ground gas is a task performed by a suitably trained and competent geotechnical engineer.  

The designer of the gas protection system must rely on the information provided from the investigation and by the geotechnical engineers.

The CS requirement is a classification derived by taking a combination with the building type and site characteristics that is used to direct the levels of protection that must be delivered when designing  of the ground gas protection system. 

After the ground gas investigation - Design & Protection

Once the site investigation, conditions and the proposed building are fully understood; objectives and instructions are typically defined. It is then the role of the ground gas design protection specialist to configure products and systems within that structure in order to afford the required levels of ground gas protection.

Options for protection will be dependent on many factors including, previous land use, intended use of the type and size of the building, site conditions, type of gases present and the hazards associated with them.

The ground gas designer must also consider the appropriate factors detailed within this Code of Practice so that the objectives of the proposed ground gas protection system are successfully met, and structures and occupants are protected from the risk of harmful ground gas in the long term.

Ground gas investigation, design & installation is a specialist area!

Ground gas protection systems should always be applied and installed by those who are properly trained and competent. Installers should be experienced in using the products and methods that are specified and must be fully aware of the implications of any defects or issues that lead to a lack of continuity.

Individual technicians should be skilled, knowledgeable and experienced. Where appropriate and available they should have attained a relevant qualification.  

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Ground gas training courses >>

Free training - Ground gas related CPD videos

Want to learn more about the Ground Gas Protection Group?

For those interested in learning more about Ground Gas Protection Group, there is a variety of PCA training options for surveying professionals as well as technical/trade professionals. 

Use the search tool below to find available Ground Gas Protection Group related training courses or simply go to our training & qualifications section.  Alternatively, if you want to chat to someone, contract our training team on 01480 400 000 or contact them online.

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Ground Investigation & Design

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