Ruddlesden geotechnical

Ground Gas Assessments

Ruddlesden geotechnical has considerable expertise in undertaking ground gas assessments, in accordance with BS 8485: 2015 'Code of Practice for the Design of Protective Measures for Methane and Carbon Dioxide Ground Gases for New Buildings' and NHBC Report 'Guidance on Evaluation of Development Proposals on Sites where Methane and Carbon Dioxide are Present'.

The breakdown of organic material in made ground can produce ground gas, though it may also be produced by other, natural, sources (e.g. coal, peat). The principal components of ground gas are methane (potentially explosive) and carbon dioxide (potential asphyxiant).

If desk study information and/ or initial intrusive investigation indicates there to be a potential risk from ground gas, a detailed  assessment of ground gas regime should be carried out using the recorded levels of methane and carbon dioxide combined with gas flow rates, to produce gas screening values (GSVs), so that the site's BS 8485 Characteristic Situation (CS) or NHBC Traffic Light classification can be ascertained.

Depending on the site's CS/ classification and the proposed development, gas protection measures are recommended, which might include a combination of floor slab construction, gas resistant membrane and/ or subfloor ventilation.

Case Study

Ground Gas Assessment for Large Residential Development Site

After completing a Phase 1 contamination assessment, Ruddlesden were instructed to undertake a ground gas risk assessment for a proposed residential development near Rugby.

Case Study

Cliff Stability Assessment, Dorset

There was a stability risk at a cliff-top site on the Isle of Portland, as indicated by a Phase 1 Geotechnical Assessment, previously undertaken by Ruddlesden geotechnical.