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SSGWs and ABSs
Gravel Rain Gardens
Mitigating Compaction

Storm Water Nutrient Management

Barnegat Bay, like many coastal areas in the country, is undergoing water quality problems that affect both its use and ecology (Driscoll et al. 2003).  The most pressing issue to affect the Bay is over-enrichment by nutrients, primarily nitrogen, from surface runoff, although phosphorus is also a problem in many streams that drain to the Bay.  It is estimated that approximately half (~50%) of the nitrogen loads to Barnegat Bay originate from surface runoff (Kennish et al. 2007).  Increased nitrogen can lead to a variety of water quality problems: eutrophication and hypoxia (lowered dissolved oxygen), increased harmful algal blooms, loss of submerged aquatic habitat, altered benthic communities, and loss of fisheries (Driscoll et al. 2003; Kennish et al. 2007).  Recreational activities, ecological functions and environmental services are negatively impacted due to excessive nitrogen entering the Bay.  The immediate need for improving the quality of Barnegat Bay is to reduce these nitrogen inputs.

Of these three sources of nitrogen entering the Bay (aerial deposition, runoff and groundwater), the most potential for success lies in controlling runoff loads.  To accomplish this, best management practices (BMPs) can be established.  BMPs are behaviors or structures implemented to mitigate the release of nutrients and other pollutants carried via surface runoff.  Structural BMPs act by intercepting contaminated runoff and treating it before it has the opportunity to reach receiving waters.  

Georgian Court is conducting research on the effectiveness of some of these structural BMPs in two key areas

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Subsurface Gravel Wetlands (SSGW) and Advanced Bioretentention Systems (ABS): SSGWs are designed to efficiently remove nutrients and other pollutants from stormwater runoff The design includes the typical dense vegetation of all stormwater basins, in which nutrients are removed from the water by the plantsí root systems.  However, the more important source of nutrient removal comes from thick layers of crushed stone lying in an impervious liner below ground.  This water retention creates an anaerobic environment to promote microbial growth, and in particular the growth of the denitrifying microbes which convert nitrogen fertilizer chemicals (nitrate, ammonium) to harmless N2 gas.  As anoxic reduced systems (meaning no air, so redox potential is low), SSGW systems provide ideal conditions for denitrification. However, they donít do as well in providing conditions conducive to nitrifying ammonia and organic nitrogen, or for removing P.  The ABS is a vertical flow wetland, where runoff passes vertically through an oxidized zone which effectively nitrifies ammonia and organic nitrogen. Proponents for this kind of system claim superior performance of this system in both N and P removal.

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 Gravel Rain Gardens (scaled down versions of subsurface gravel wetlands designed for homeowner or small scale community use)