By Danna Truslow, P.G., Truslow Resource Consultants LLC
As part of efforts to reduce nitrogen loading to Great Bay, Rockingham County Conservation District and Strafford County Conservation District have collaborated to develop permeable reactive barrier (PRB) demonstration sites at two locations – Durham and Brentwood, NH. The ultimate goal of the project is to test and implement effective nitrogen removal methods in the Great Bay watershed to improve water quality.
A PRB is a passive technology that can be used by private homeowners, communities, and others to reduce inorganic nitrogen discharges from sources such as septic systems. The PRB trench is installed downgradient from a source and is filled with wood chips, exchange media and sand/gravel to transform inorganic nitrogen to nitrogen gas. A PRB can also be adapted for phosphorus removal for freshwater nutrient control applications.
Associated with this project is a groundwater and surface water monitoring network to determine pre- and post- installation water quality at both locations and to document changes after the PRBs are installed. Consequently, this project will not only evaluate the feasibility of this technology for use in the Great Bay – Piscataqua watershed but will also contribute a significant database on actual nitrogen loading from large and small on-site septic systems.
A portion of the work is funded through an NHDES Section 319 grant. In addition to RCCD and SCCD oversight and project participation, the team includes Truslow Resource Consulting – project manager and environmental sampling task manager and Haley & Aldrich (HAI) who is completing the engineering, design and installation of the PRBs along with Lombardo Associates. PRB Installation will be completed with the assistance of the Towns of Durham and Brentwood. Absolute Resource Associates of Portsmouth is the analytical laboratory on the project.
Danna Truslow and project engineer Mark Kelley presented a project update and conceptual PRB designs at the Lamprey River Symposium at UNH on January 9, 2015. You can view the presentation for more background here.
Samantha Wright, Geomorphologist, Truslow Resource Consultants, collects groundwater samples for the permeable reactive barrier project.