Groundwater Purging

Posted on 15 Apr 2020

Groundwater monitoring forms part of an effective Environmental Compliance Monitoring Programme which enables proactive quality and quantity assessment, identification of impacts and rectification planning. Purging of groundwater monitoring localities is generally required to comply with sampling quality assurance plans and procedures which is conducted prior to obtaining a representative sample from the groundwater aquifer by displacing the stagnant water.

Purging of boreholes involves the removal of sufficient water until the general water quality is stable, through:

  • Pumping the borehole until in-situ measured parameters stabilize. Traditionally, purging entails the removal of sufficient water until the field chemistry parameters such as pH, Electrical Conductivity (EC), Dissolved Oxygen (DO), Oxidation-Reduction Potential (ORP), temperature, and turbidity remain stable (U.S. Geological Survey 1980); or
  • The removal of three (3) to five (5) times the volume of the standing water in the borehole (calculated according to the Groundwater Sampling Manual, WRC Report Number TT 733/17.

Guidelines on borehole purging procedures, techniques. equipment and device requirements are extensively described in a number of studies (e.g. Barcelona et al. 1984; Barcelona et al. 1985; Barcelona and Helfrich, 1986; and Weaver et al. 2007), while techniques have evolved considerably over recent years. To date gentle pumping is preferred which minimises turbulence and aeration within the monitoring boreholes, which in return reduces suspended solid and volatile compound erroneous results. Gentle pumping or low flow purging is thus considered to present an accurate water quality profile.

ENVASS has an automated purging unit specifically designed for purging of related boreholes. If you may require a proposal for these services please do not hesitate to contact our highly qualified and experienced specialists at ENVASS on 012 460 9768 or info@envass.co.za