Fixed Volume Groundwater Purge and Sample
Typically 3 or more times the volume of water in the well lining is pumped from the monitoring borehole or well prior to sampling using relatively
high pumping rates. Purge volumes can be reduced by monitoring for chemical stability during pumping (usually by measuring temperature, pH and EC - sometimes extended to include DO
and redox if a flow cell is used).This is currently the default guidance when sampling boreholes and wells in the UK and Ireland.
Good for:
Inducing inflow from a larger volume of aquifer Routine monitoring programmes Non specialistsIssues:
Generates relatively large purge volume for disposal High pumping rates can create large drawdown in water level High pumping rates can produce non laminar turbid flow, which can impact on some chemical
constituents - particularly volatile organic carbons (VOCs) Time and labour intensiveSuitable equipment from Waterra: Bailers, Inertial pumps, Suction pumps, Submersible pumps.
See Also:
Groundwater Sampling Methods
Low Flow Groundwater Purging and Sampling
Zero Purge/Passive Groundwater Sampling
Research and Development in Groundwater Sampling Methods
Borehole Purge Volumes
Waterra Tubing Diameters and Volumes