Air Quality Report 6
Withyhedge Landfill Air quality monitoring interim summary report 6
Report number 2423r6v1d0924
Prepared by:
Geotechnology Ltd
Ty Coed
Cefn-yr-Allt
Aberdulais
SA10 8HE
September 2024
Executive summary
This sixth interim report has considered all of the monitoring data gathered since the start of monitoring in February 2024.
It is evident from the frequent and repeated use of the Jerome at monitoring positions in the community around the landfill that concentration levels of Hydrogen Sulphide have fallen from higher levels observed earlier in the year with few occurrences of detectable levels in recent months. At the same time, the incidence of odour considered to be related to landfill gas has declined as has the number of complaints. The concentration of Hydrogen Sulphide and Volatile Organic Compounds detected by diffusion tubes has remained below guidance values for intermediate/lifetime exposure throughout the monitoring to date.
This sixth interim report has provided opportunity for review of all the monitoring data gathered since February 2024 to be considered.
In this context, the community monitoring programme will therefore focus on the measurement of Hydrogen Sulphide using diffusion tubes at D1-D12 along with the data gathered by Pembrokeshire County Council at the fixed position monitor located at Spittal School. This flexible strategy will be subject to continual review.
1. Scope
Over the past nine months, the operator of Withyhedge Landfill has implemented a series of measures agreed with NRW to address odours emanating from the site including re-profiling, capping and additional landfill gas extraction. The site has also not received waste since mid-May 2024. Alongside these measures, the operator is funding a scheme of air quality monitoring in the communities surrounding the site and also within the site.
The monitoring programme is primarily aimed at gathering quantitative data to provide lines of evidence to help assess risks from the exposure to off-site air quality that is impacted by the landfill.
This sixth interim report summarises data gathered from the ongoing monitoring that commenced in February 20024. The monitoring includes diffusion tubes for the assessment of Hydrogen Sulphide and Volatile Organic Compounds (VOCs) that provide averaged concentrations over a defined period, and instantaneous measurements of Hydrogen Sulphide using a Jerome analyser.
As the monitoring programme has now been in place for six months this review considers how the programme will evolve and other aspects related to the odour incident.
2. Monitoring
Landfill gas is typically dominated by methane and carbon dioxide. Numerous other compounds may, however, also be present and some of these can be detected as odour. Such compounds are often sulphur based and can include hydrogen sulphide. As hydrogen sulphide can give rise to odour and can be readily measured, it is being used as a surrogate for the potential presence of landfill gas, whilst recognising that there are a wide range of compounds and sources that can also generate odorous compounds like hydrogen sulphide.
To try and better understand what other compounds may also be present, TENAX diffusion tubes designed to allow the analysis of Volatile Organic Compounds (VOCs) have been used since 8 March 2024 at the same positions as the Hydrogen Sulphide tubes. This data is presented in this report alongside the Hydrogen Sulphide monitoring which has been ongoing since February 2024.