Install Permeable Reactive Barriers

Permeable reactive barriers (PRBs) can treat groundwater with high levels of nitrogen. They can be installed near the shoreline to intercept groundwater flow before it reaches a bay or cove, or at the edge of a septic system drain field to intercept and treat nitrogen-enriched septic effluent.  In each instance, a trench is dug with a mixture of course sand, wood chips, compost and/or other material, and the carbon source fuels the uptake of nitrogen by microbes in the groundwater.

Nitrogen Removal

  • 70-75%

Cost Efficiency

  • $140 per pound of nitrogen removed

Project Costs

  • Overall Cost Range: $2,500 to $3,000
  • Operations and Maintenance: $220 per year


  • PRBs are less expensive than a full septic upgrade
  • They treat septic effluent or nitrogen-enriched groundwater directly before it enters water body
  • Treats the remaining nitrogen in groundwater from older septic systems
  • PRBS have highly effective (70-75%) nitrogen removal
  • Require little maintenance


  • PRBs are not necessarily under warranty
  • Lifespan of treatment material is still unknown
  • Requires specific lot size and space for construction
  • Correct placement of PRB requires understanding of groundwater flow in the area, etc.
  • Technologies are still in development
  • Unclear requirements for permitting