Researchers at the U.S. Department of Energy’s Pacific Northwest National Library recently released a paper on the Performance Assessment of Pump-and-Treat Systems.
The pump-and-treat (P&T) remediation technology is comprised of three main aspects: groundwater extraction for hydraulic control and contaminant removal, above-ground treatment, and groundwater monitoring to assess performance.
Pump-and-treat (P&T) is a widely applied remedy for groundwater remediation at many types of sites for multiple types of contaminants. Decisions regarding major changes in the remediation approach are an important element of environmental remediation management for a site using P&T. Performance assessment during P&T remedy implementation may be needed because of diminishing returns, the complex nature of the site and contamination, or other factors.
While existing guidance documents for the performance assessment of pump-and-treat systems provide information on design, operation, and optimization for P&T systems, these documents do not provide specific technical guidance to support remedy decisions regarding when to transition to a new remedy or to initiate closure of the P&T remedy.
In the paper, the researchers describe a structured approach for P&T performance assessment that was developed using analysis of three example P&T systems. These examples highlight key aspects of the performance assessment decision logic and represent assessment outcomes associated with optimizing the P&T system, transitioning from P&T to natural attenuation, and supplementing P&T with another technology to hasten transition to natural attenuation.
Decision elements for the P&T performance assessment include:
- Contaminant concentrations and trends
- Contaminant mass discharge from source areas or at selected plume locations
- The attenuation capacity of the aquifer
- Estimated future plume behavior and time to reach remedial action objectives for the site
- P&T system design, operational, and cost information
Categories of decision outcomes for the P&T assessment include:
- Initiate P&T remedy closure
- Continue with existing or optimized P&T
- Transition to Monitored Natural Attenuation
- Supplement P&T with other treatment technologies
- Transition to a new remedy approach