As part of a due diligence programme ahead of leasing a large existing warehouse, our client wanted assurance that the gas protection system identified in the building was working efficiently and did not exceed criteria beneath the warehouse slab. GGS was commissioned to investigate and report on the condition of these gas protection measures.
Following a review of existing ‘as-built’ drawings and original site investigation data, discussions with our client and other stakeholders were held and a scope of works developed to provide information on several raised ground gas and vapour concerns.
Our initial investigations, including visual inspection and internal emissions surveys, identified the expected gas protection system elements, however it was discovered that the ventilation system and gas membrane were not installed correctly.
Further to our initial findings, GGS drilled and installed a series of VaporPin® units into the slab. The sub-slab locations were monitored to collect time series data for a range of gases, trace gas and vapour components.
Additional tracer gas zone of influence testing was carried out under GGS supervision to enable the design of retrofit gas protection if required.
Upon completion of the investigation, reinstatement works were completed, including resealing of any investigation damage to the gas membrane. The ensuing report and expert guidance provided by GGS allowed the client to proceeded with leasing the property with confidence, knowing due diligence and all lines of enquiry had been followed.
This complex project involved demolishing house extensions, construction of a gas-barrier, rebuilding the extensions, and retesting for gas.
GGS produced a ground gas management plan for a wastewater treatment works to effectively manage the risk from and migration of ground gases.