Spectra Scientific | Professional Grade Groundwater Monitoring
What is Low Flow Sampling
Low flow sampling is a groundwater sampling method where water is extracted from a well at a controlled, low rate, ranging between 0.1 to 0.5 liters per minute. This method ensures minimal drawdown in the well, preserving in-situ conditions and providing a more accurate representation of water’s chemical composition. By minimizing agitation, low flow sampling reduces the risk of turbidity and the release of particulates that could skew analytical results.
The Environmental Protection Agency (EPA) highlights low flow sampling as a best practice for collecting groundwater samples, particularly for volatile organic compounds (VOCs), metals, and other sensitive analytes. According to the EPA’s “Low-Flow (minimal drawdown) Ground-Water Sampling Procedures” (EPA/540/S-95/504), the technique ensures sample integrity by maintaining stable water quality parameters.
When to Conduct low flow sampling?
Low flow sampling is typically
conducted in the following scenarios:
- Environmental Remediation
To monitor contaminant levels in groundwater and
assess the effectiveness of remediation efforts.
- Regulatory Compliance
To meet EPA and state-specific monitoring
requirements for groundwater quality.
- Baseline Studies
For collecting initial data on aquifer conditions before any potential impact from construction, industrial activities, or land development.
- Long-Term Monitoring
To track changes in groundwater quality over time while
minimizing the risk of altering aquifer conditions during sample collection.
The method is particularly critical in wells with low recharge rates or where precise
chemical analysis is required, such as detecting trace levels of contaminants or assessing natural attenuation processes.
What Equipment is Used in Low Flow Sampling?
The following equipment is commonly used for low flow sampling:
- 1. Peristaltic Pumps or Bladder Pumps
The Spectra Field Pro III peristaltic
pump or Spectra Bladder Pumps are designed to maintain a consistent, low flow
rate. Spectra Bladder Pumps are often preferred for VOC sampling as they
prevent air contact.
- 2. Flow Controllers and Monitoring Systems
The Spectra Hydro Pro Flow
Controller can be used to regulate and monitor the flow rate to ensure minimal
drawdown and stable pumping conditions.
- 3. Water Quality Meters
Instruments to measure key parameters such as pH,
conductivity, dissolved oxygen, turbidity, and temperature in real-time during
purging to ensure stabilization before sample collection.
- 4. Tubing
PFAS-free or chemically inert tubing to prevent contamination of
samples.
Additionally, field staff should be equipped with protective gear and proper decontamination supplies to prevent cross-contamination between sampling locations. (see figure 1.2 for a comprehensive low flow sampling setup)
Figure 1.2 low flow sampling setup
References
- U.S. Environmental Protection Agency. "Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures." EPA/540/S-95/504. Available at: https://www.epa.gov/
- U.S. Environmental Protection Agency. "Groundwater Sampling Guidelines." Available at: https://www.epa.gov/ground-water-and-drinking-water
By adhering to these guidelines and leveraging the right equipment, low flow sampling can be a reliable method for collecting high-quality, representative groundwater samples for environmental and regulatory purposes.
