EPG has recently advised a Local Authority in Scotland on the removal of gas monitors from houses affected by landfill gas migration. The monitors had been installed in over 30 houses in response to landfill gas migration. The migration had been dealt with by installing a gas extraction system and vent trenches and there was an extensive in ground gas monitoring network around the site.
The cost of annual calibration and servicing was a significant on-going cost for the council, which EPG has helped to reduce considerably. This was achieved by a rigorous assessment of the geology and identification that gas migration was occurring along a preferential pathway. Natural levels of background carbon dioxide were identified so that differentiation between natural sources and landfill gas could be made in the monitoring wells in the migration zone. Gas modelling was used to confirm the extent of gas migration and the assessment also showed a reduction in migration over time. This allowed the majority of the internal systems to be safely removed, except for a few houses located very close to the landfill.
As part of the review EPG also identified adjustments to be made to the gas extraction and flare systems to ensure that they continued to work effectively to limit gas migration from the landfill site.