New and Improved Innovative Former Landfill Monitoring Services
Periodic ‘spot’ Ground Gas Monitoring
All periodic ‘spot’ landfill gas monitoring is undertaken by a experienced geo-environmental specialist. GGS periodic monitoring includes the measurement of borehole flow rates, bulk gas concentrations (methane, carbon dioxide and oxygen), trace gas compounds (hydrogen sulphide and carbon monoxide) and barometric pressure. A photo ionisation detector (PID) is also used to measure total volatile organic compounds. Groundwater and borehole base depths are measured using a dip meter.
GGS has developed methodologies for recirculation monitoring for the above bulk and trace gases (recommended by BS 8576). This method recirculates the gas sample in the monitoring well leading to a representative sample being measured. For example, gas concentrations can often be stagnant in a well and this may be missed by conventional spot monitoring. Depth profile monitoring can also be undertaken useful again to highlight stagnant gas or establish if gases are particularly concentrated down borehole. Depth profile monitoring and assessment can be a valuable tool for an improved understanding of lateral migration pathways.
Continuous monitoring is invaluable for quantifying the landfill gas regime and identifying offsite migration as part of the environmental permit requirements. It can be used to inform improvements to gas management and collection systems or assist with the surrender of your environmental permit. Continuous monitoring of permanent gases (selected bulk gases, trace gases and total volatile organic compounds) and other environmental parameters provides a wealth of information to identify the dominant processes of gas generation and migration, thus leading to an improved understanding of the landfill gas regime and allowing for a more accurate and truly site specific assessment to be completed. Conventional monitoring programmes can run for several months and can lead to a lack of confidence in results. Continuous monitoring reduces the uncertainty and the monitoring period can be dramatically shortened.
GGS is the UK’s leading environmental consultancy specialising in continuous ground-gas data capture, analysis and interpretation to inform risk assessment and remedial design. All of the staff have experience of correctly utilising and maintaining the full range of gas monitoring equipment including GasClam®, the cutting edge, continuous ground-gas monitoring device.
The collection of continuous time series data allows analysis of variable gas compositions, quality and behaviour. Additional analysis of the datasets can highlight instances where air has entered into the borehole, potentially explosive conditions or where aerobic activity predominates in the well. Below is an example of time series continuous data set from a perimeter monitoring well and further analysis that can be carried out.
Purge and Recovery Tests
The ground-gas purge and recovery test is designed to measure the rate of landfill gas recovery into a monitoring well following inert gas displacement. The landfill gas recovery rate can then be used, in conjunction with well volume, to calculate a ground-gas flux. A ground-gas flux can provide a reliable indication of gas generation rates or stagnant gas and can be used within detailed risk assessments and modelling.
Surface Emission Survey (SES)
Surface Emission Survey can be used to verify cap integrity and to maximise gas collection efficiency or provide a ‘line of evidence’ of potential gas risk to nearby properties. It can also be used to inform the design of an intrusive gas migration investigation. The monitoring of landfill surface methane emissions is an integral part of demonstrating compliance with the landfill directive. This service is undertaken in line with Environment Agency guidance on monitoring landfill gas surface emissions (LFTGN07 v2 2010). Below is an example of a GGS surface emission survey undertaken at a closed landfill site. The high spatial resolution of the survey results in a clear presentation of actual methane emissions from the landfill surface. GGS use Tuneable Diode Laser, FID and GPS technologies for surface emission surveys.
Advanced Flux Box Tests or Survey
This service is undertaken in line with Environment Agency guidance on monitoring landfill gas surface emissions (LFTGN07 v2 2010). GGS use Tuneable Diode Laser technology in conjunction with a GFM gas analyser to measure both methane and carbon dioxide (ppm) being emitted from the landfill surface. Methane and carbon dioxide measurements and flux calculations can provide a valuable insight to methane oxidation occurring through the landfill cap.
Quantitative Surface Emission Survey (Q-SES)
The UK greenhouse gas inventory is collated by Defra for the EU annual report. Defra is likely to be pressing for legislation requiring landfill owners to carry out emissions audits of their closed / non-operational former landfill site. GGS’ innovative Q-SES methodology can provide an accurate and cost effective estimate of methane emissions from an entire site or specific survey area. Below is an example of a Q-SES survey. GGS uses flux calculations developed during the ACUMEN project in conjunction with an improved method of monitoring landfill surface concentrations to estimate total methane emissions from a whole site or specific survey area. The concentration value for each grid square corresponds to a calculated flux value apportioned to each concentration band; extrapolation of the flux values from each grid square will then provide an estimation of total site (or survey area) emissions.
Other specialist Former Landfill Services
GGS offer a range of other services, such as active and passive gas sampling, Tedlar bag gas samples, air quality assessments and gas protection verification. See our ground-gas protection and verification services here.