The stages for good ground gas protection
For anyone looking to work within the ground gas industry or for any construction/building professionals looking to employ someone from the sector, there are multiple stages you need to consider before proposing any form of ground gas protection. They include site investigations, system design, considerations and detailing, communication, system delivery & installation and finally verification.
To find out more, click on the expandable text sections below.
The process of conducting ground gas investigations and establishing the presence of and likely risks from harmful ground gas should be a task performed by a suitably trained and competent geotechnical engineer. This should include as deemed appropriate:
- Preliminary investigation: using historical maps, geographical maps, regulation data, research on landfill sites and memories
- Ground investigation: including the use of ‘trial pits’
- Laboratory testing: with consideration of the use of WAC (Waste Acceptance Criteria) testing on soil samples
The processes of site evaluation and risk assessment are set out in ‘BS8485:2005’ (design of protective measures for ground gases for new buildings). To gain a better overview of the site investigation process, click on the button below to view a flow chart that illustrates the process.
Site investigation and site classification services are not provided by PCA members and should be provided by a suitably trained and competent geotechnical engineer.
Site Investigation Flow Chart >>
Many failures with ground gas protection are attributable to insufficient consideration of the relevant factors, leading to poor or inappropriate ground gas design.
It is the role of a ground gas designer to configure products and systems within that structure in order to afford the required levels of ground gas protection. The goal of this is to ensure 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.
No two ground gas projects will look the same. However, as with all protection design solutions for ground gas, the primary considerations should be:
- What are the underlying ground conditions?
- What is the risk of harmful gas?
- What is the potential of contamination that may release harmful gases?
- What is being built and what are the buildings going to be used for?
Ground gas design must consider the structure as well as the soil and ground conditions together with the gas hazards that have been identified. Any proposed ground gas protection system must deliver a solution that can be installed successfully to eliminate risk as far as is practicable and assure a built environment that is safe for occupation.
It is important to note that if a ground gas designer is not up to speed with the knowledge contained within BS8485:2005 (and the soon to be launched PCA Code of Practice) then that designer is failing the client/customer.
If you are a ground gas designer and you are not up to speed, we strongly suggest you read the appropriate documentation within the buttons below
The methods commonly adopted in to deliver ground gas protection are typically based around:
- Structural design and detailing
- Ventilation
- Gas protection barries/membranes
Depending on the ground gas risk, the type of construction and property type; these measures may be used individually or in combination.
The need for ground gas protection will be identified by the geotechnical engineers as part of any site investigation. The findings of the geotechnical engineers will be used to inform a conceptual site model that in turn will determine the risk and subsequent levels of ground gas mitigation that will be needed for any development. The detail of this process can be found in BS8485:2005 Code of Practice for the ‘Protective Measures for methane and Carbon Dioxide Ground Gasses for New Buildings’.
It is also possible that contamination and ground gas hazards are found to be a risk in existing buildings. In such situations, a geotechnical engineer will be required to conduct evaluations, evaluate the hazards present and conduct the necessary risk assessment. These can then be used to inform the subsequent ground gas protection strategies.
It is important that during all stages of the design process that the geotechnical engineer, system designer, the specialist installer and any verification consultant establish robust channels of communication that are maintained throughout the build process.
Good communication prevents misunderstanding, allows problems to be solved and prevents damage to systems that are being installed. Openness and problem sharing allows problems and obstacles to be overcome in a collaborative way saving time and money AND delivering a better job!
Ground gas protection systems should always be detailed and installed by specialists that are properly trained and competent. Specialists who have detailed knowledge, experience and an understanding of the implications of defects will ensure safety-critical designs are delivered and executed properly!
Ground gas specialists, must be skilled, knowledgeable and experienced. Technicians, supervisors designers and verifiers should have attended appropriate training and have gained the appropriate qualifications.
When selecting a ground gas protection specialist, look for the following
- The company can demonstrate experience in the successful delivery of similar ground gas protection systems and on projects of a similar scale and complexity.
- Installer that can demonstrate relevant qualifications
- Detailed product knowledge and training commensurate with the application, jointing and handling of the product types that are to be used.
- Access to technical back up and support and detailed knowledge of the relevant codes of practice and technical guidance
To find a PCA approved ground gas specialist who has been assessed and that meets the criteria set out above, click on the button below.
Find a PCA ground gas specialist >>