Ground gas protection measures verification

Ground gas protection measures verification

Project title:            Local Hospital

Client:                        Multinational Engineer

Location:                  Dumfries and Galloway, Scotland

Start date:                September 2015

End date:                  Ongoing

Services provided:

  • Verification services in line with CIRIA C735 guidance

Key benefits:

  • Meet industry standards
  • Efficient and flexible services
  • Cost-effective services


Ground gas protection measures verification


GGS was commissioned by Laing O’Rourke to perform independent integrity testing of ground gas protection measures at a large development site of a new hospital in Scotland.

img_2388At the point of commission, the hospital development site had already been investigated including ground gas monitoring and risk assessment. Based on the results, the gas regime was considered representative of Characteristic Situation 2. In line with BS8485 guidance, this required ground gas protection measures to be installed. As per CIRIA C735 Guidance, any ground gas protection measures that are installed must be tested by an independent third-party verification engineer.

GGS was therefore appointed to undertake integrity testing of the installed membrane. During verification, one of our qualified engineers performed visual inspections, mechanical point stress testing (or pick testing) and air lance testing. The duration of these tests depends on the number of defects found within the area of inspection. Any defects found require the installer to repair the flaw and the verifier to once again assess the repairs once applied.

img_2394As an additional service, GGS also provided training for workers from Laing O’Rouke that were responsible for the installation of the membrane. This ultimately facilitated a higher class of workmanship going forward and increased the efficiency of the project by reducing the number of non-conformances and re-tests. Ongoing, this higher quality of membrane installation therefore required less retrospective work was, fewer site visits from us and ultimately better quality work.

This commission is ongoing with GGS undertaking further verification work within this large scale development.  To date, the verification of the slab element of the works (membrane laid on a hard, horizontal surface called slab) has been completed, with focus now on membrane installation on the retaining walls. These are structurally designed to resist the lateral pressure of soil when there is a desired change in ground elevation.

So far, each section has successfully passed with only a small number of defects identified, which were rectified during verification works supervised by GGS.

Expect more on this on-going verification case study in the coming months.

To find out more about GGS verification services, click here.