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Launching Nitrogen Removal Monitoring at the First Full-Scale Bulkhead Permeable Reactive Barrier at Hampton Bays

Funded by the Community Preservation Fund and the Town of Southampton the first full-scale bulkhead Permeable Reactive Barrier (PRB) was installed in 2020 in Hampton Bays. The 100 feet wide and 10 feet deep woodchip-based subsurface barrier intercepts nitrogen polluted groundwater flowing towards Shinnecock Bay and provides conditions conducive to microbial mediated denitrification.

The project is a collaborative effort between the Cornell Cooperative Extension Marine Program (CCE) and the Center for Clean Water Technology. The project builds on past work conducted at a PRB test cell which was installed by the Hampton Hills Association in consultation with the CCE in 2015, and since 2016 researchers from the Center have been actively involved in this project. Based on preliminary field and laboratory work (Graffam et al. 2020) the PRB is expected to remove more than 1.5 metric tons of nitrogen over the next 20 years.

Different PRB configurations were established at the site, including PRBs of different thicknesses, a PRB column array configuration, and control units without woodchip media. Sampling ports upstream, within, and downstream of the PRB in the replicated PRB units will allow for detailed analyses of nitrogen removal performance of different PRB configurations, providing invaluable data to inform and optimize future PRB installations on Long Island.

Groundwater nitrogen removing technologies will be critical to reduce eutrophication of Long Island’s coastal waters, because even if all septic systems on Long Island would be replaced innovative/alternative onsite wastewater treatment systems within the next few years, nitrogen that has accumulated in Long Island’s aquifer over the past decades will continue to seep into our coastal bays in coming decades. Permeable Reactive Barriers that are a promising approach to deal with this “legacy nitrogen” and integrating a woodchip-based matrix behind a perforated vinyl sheeting during marine bulkhead replacement is a cost-effective strategy because heavy machinery is already on site.

PRB Column Array PRB Installation PRB Sampling Perforated Bulkhead Vinyl Sheeting Sampling Ports

Graffam M., Paulsen R., Volkenborn N. (2020) Hydro-biogeochemical processes and nitrogen removal potential of a tidally influenced permeable reactive barrier behind a perforated marine bulkhead. Ecological Engineering 155: 105933 (