ESI Ltd - Environment Specialists

Hydrogeological risk assessment for a landfill PPC application


Courtesy of Courtesy of ESI Ltd - Environment Specialists

Client: Waste Management Industry

Location: Co-disposal landfill site for non-hazardous and hazardous waste,  Worcestershire.

Services: Hydrogeological risk assessment, landfill monitoring support, Environmental permit application support ,

Issues: Potential risk to groundwater,  Environmental Permit determination

Summary: ESI provided Hydrogeological Risk Assessment, data collection, reporting and landfill monitoring support services to facilitate the application for a PPC permit (now Environmental Permit) for the site. A new Hydrogeological Risk Assessment (HRA) and Environmental Setting and Installation Design (ESID) report were prepared and submitted with the application.  The client benefited from ESI’s experience in regulatory negotiation and risk assessment and a permit was subsequently issued for the site.

ESI was commissioned to review a PPC permit application for a co-disposal landfill site for non-hazardous and hazardous waste in Worcestershire. The previous application has been refused by the Environment Agency and following a thorough review of the Hydrogeological Risk Assessment (HRA) provided with the previous application ESI undertook further data collection and prepared a revised (HRA). ESI also prepared an Environmental Setting and Installation Design (ESID) report for a new PPC permit application.

The Agency has been processing PPC permit applications for hazardous and non-hazardous landfills since June 2003. It is using the pollution prevention and control (PPC) regime to bring landfills up to the standards required by the EU Directives on landfill and groundwater. ENDS reported (May 2005) that more than a quarter of the first landfill permit applications for non-hazardous waste sites have been refused, with groundwater risks posing the principal problems.

ESI undertook a comprehensive review of the initial Hydrogeological Risk Assessment (HRA) for the landfill, consulted the client and liaised with the Environment Agency on their behalf, prepared a new (HRA) and prepared an Environmental Setting and Installation Design (ESID) report required for a new PPC application.

The landfill has seven chambers (referred to as phases) that are filled or to be filled in the future and it is proposed for the landfill to be in operation until 2027. Because of uncertainty over the depth of the Mudstone/Sandstone interface underneath the site, a new >100m deep borehole was drilled in 2005. ESI’s commercially available Risk Assessment Software (RAM) was customised to undertake a risk assessment and derive concentrations at various compliance points throughout the landfill’s lifecycle and to derive site specific control and trigger levels. The source term was taken as the volume of waste after completion of the landfilling operation. Pathways considered were infiltration through the composite liner, the underdrain, the geological barrier, the Mercia Mudstone and the Sherwood Sandstone. The choice of leachate determinants for inclusion in the HRA was based on the need to characterize the performance of the containment system for a broad range of List 1 and List 2 substances. The risk assessment considered the current operational phase in which groundwater is actively managed through dewatering of the active phases, the post-operational managed phase (60 year) in which groundwater levels will be controlled to remain below the external groundwater level and the post-managed phase (until 5000 years from now). A number of failure scenarios of the membrane cap and the composite liner have been addressed by explicit modelling. Based on the results of the HRA, ESI developed a groundwater risk based monitoring scheme for the site.

In response to ESI’s HRA the Environment Agency stated that although there were issues that needed to be resolved these would not prevent a PPC permit being issued. These issues were addressed in a revised HRA which was supplied to the client together with the ESID report for a new PPC permit application and a permit was subsequently issued.

ESI is recognized as a UK centre of excellence for the assessment and management of groundwater risks and has a proven track record in successful completions of PPC permit applications.

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