Spectra Scientific | Professional Grade Groundwater Monitoring
Well purging is a critical step in groundwater sampling, ensuring that collected water samples accurately represent the aquifer’s water quality. This guide explains what well purging is, when it should be performed, and the equipment typically used, referencing EPA guidelines for proper execution.
What is Well Purging?
Well purging is the process of removing stagnant water from a monitoring well to collect groundwater samples that accurately represent the aquifer’s natural conditions. This ensures that the sample is free from contaminants or altered chemistry caused by stagnant water in the casing.
During purging, field professionals monitor key stabilization parameters to determine when the water being purged is representative of the aquifer. These parameters include:
- pH: Indicates the acidity or alkalinity of the water.
- Temperature: Reflects ambient aquifer conditions.
- Dissolved Oxygen (DO): Essential for assessing redox conditions.
- Oxidation-Reduction Potential (ORP): Measures the water's redox state.
- Specific Conductance (Conductivity): Reflects the ionic strength of the water.
- Turbidity: Measures water clarity and the presence of suspended particles.
When Do You Perform Well Purging?
Well purging is performed in various scenarios, such as:
- 1. Before Groundwater Sampling
- 2. During Environmental Site Investigations
- 3. Compliance Monitoring
- 4. Post-Remediation Sampling
- 5. Routine Monitoring Programs
What Equipment is Used in Well Purging?
The following equipment is commonly used for effective well purging:
- Pumps
- Bladder Pumps: Ideal for low-flow purging, minimizing aquifer disturbance.
- Peristaltic Pumps: Used for shallow wells.
- Submersible Pumps: Designed for deep well applications.
- Water Level Meters
- Turbidity Meters
- Flow Controllers
- Multi-Parameter Meters
Measure key stabilization parameters like pH, conductivity, DO, and ORP
in real time.
Regulatory Guidelines and References
- EPA Groundwater Sampling Guidance (EPA/540/S-95/504)
- ASTM D6771 – Standard Practice for Low-Flow Purging and Sampling
