Groundwater Program

What is Nitrogen?

Nitrogen is an important nutrient that plants need to grow, but when it enters our coastal waters, it can have harmful environmental effects.

How Does Nitrogen Enter our Waterways?

One of the main inputs is through groundwater discharge, which is polluted from outdated septic systems, fertilizers, and atmospheric contributions

Threats of Excess Nitrogen?

• Too much nitrogen causes increased algal growth
• This leads to harmful algal blooms (HABs), poor water clarity, and dead zones
• Marine life is threatened

Why Care?

When marine life is threatened our local fishing economy is threatened

What is a Permeable Reactive Barrier (PRB)?

A trench system, filled with wood chips and installed near the shoreline

Intercepts nitrogen contaminated groundwater before it discharges into coastal waters

DID YOU KNOW?

Wood chips support the growth of beneficial bacteria that convert nitrate (the harmful groundwater nitrate) into gaseous nitrogen (the harmless gas we breathe)

BENEFITS:

• Critical to reduce eutrophication
• Cost-effective
• No above-ground structures, minimal environmental disturbances
• Last decades with little maintenance

NITROGEN POLLUTION THREATS:

• Harmful Algal Blooms (HABs)
• Decreased water clarity
• Dead zones
• Mass mortalities of marine life 

Cornell Cooperative Extension Launches Nitrogen Removal Monitoring at the First Full-Scale Bulkhead Permeable Reactive Barrier (PRB) at Hampton Bays

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

The project builds on past work conducted at a pilot PRB which was installed by the Hampton Hills Association in consultation with the Cornell Cooperative Extension of Suffolk County in 2015. The recent installation was led by the Cornell Cooperative Extension of Suffolk County Marine Program in collaboration with the Center for Clean Water Technology. 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, such as PRBs, will be critical to reduce eutrophication of Long Island’s coastal waters. Even if all onsite septic systems would be replaced with 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 for decades to come due to long groundwater travel times. PRBs are a promising approach to deal with this “legacy nitrogen” and integrating a woodchip-based media behind a perforated vinyl sheeting during marine bulkhead replacement is a cost-effective strategy because heavy machinery is already on site.

Last updated February 8, 2022