Discovery CE often carry out Gas and Groundwater Monitoring during our ground investigations, utilising a dip meter and GFM430 Gas Monitor. A gas monitor records different concentrations of gases such as Oxygen, Carbon Dioxide, Methane, Hydrogen Sulphide and Carbon Monoxide, also recording flow rate and differential pressure. Brownfield sites require routine gas and groundwater monitoring events due to the potential build-up of gases within buildings. Methane and Carbon dioxide being the most notable gases, these building up to dangerous levels in confined spaces. Gas and Groundwater Monitoring is the last fieldwork event before the final interpretative report can be written. If gas is recorded in excessive quantities or flows, then further visits may be required. The usual monitoring period is three months, six visits every two week, however further monitoring visits of three to four weeks may be possible.
Usually, after ground investigations are completed, gas and groundwater wells are installed within the boreholes. Each well has a gas tap bung fitted on top of the pipework within the borehole, allowing for gas reading to be taken from the sealed environment.
Groundwater can be recorded using a dip meter and groundwater samples are often taken with a bailer or water pump. These samples are sent off for laboratory analysis in order to determine the level of contamination in the Source, Pathway, Receptor model. The result of the groundwater risk assessment will determine whether further remediation measures are needed for COCs (Contaminants of Concern).