Dune Infiltration Systems for Reducing Stormwater Discharge to Coastal Recreational Beaches

The present issues related to untreated stormwater are significant and must be taken seriously, not only for the sake of aquatic ecosystems where this polluted water is discharged, but also for the sake of human health. After a rainfall, the concentration of fecal bacteria entering coastal waters, as a result of unfiltered discharged runoff, often exceeds the state and federal bacteria limits that are considered safe for human contact; and unfortunately, everyday beach-goers are ignoring the eminent health threats that these waters pose. Direct human contact with the stormwater or the area that receives its discharge can lead to symptoms of gastrointestinal, respiratory, ear, eye, nose and skin infections; yet, contact with discharging stormwater still occurs, despite visible warnings.  Previous studies have shown success capturing bacteria from stormwater using sand filters, so Burchell and his colleagues (2012) arranged the idea of a Dune Infiltration System (DIS) to divert stormwater from existing pipes and into dunes, where the water can be filtered through sand and ground water before it is discharged to the coastal waters. They constructed three DISs in Kure Beach, North Carolina for demonstrational study, and found that the performance of these systems was more successful than expected and that they are a low-cost and low-tech solution for diminishing stormwater discharge and associated fecal bacteria to recreational beaches. –Genevieve Heger
            Burchell, M., Hunt, W., Price, W. D., 2012. Dune Infiltration Systems for Reducing Stormwater Discharge to Coastal Recreational Beaches. Bio&Ag Engineering, 400-412

            Burchell et. al constructed DISs at three distinct sites in Kure Beach, North Carolina—site L, M, and K. Hundreds of samples were collected from each site, in addition to a controlled dune, where no DIS was installed. The fecal bacteria concentrations for each of the samples were measured and compared with the concentrations found in ground water outside the system in order to determine the effects of the DIS. The efficiency of the DISs in North Carolina underwent both short-term and long term monitoring to ensure the stability and reliability of these systems.
            They found that overall, the DISs were a success. The concentration of bacteria was reduced by 98%. Nearly all of the runoff that was generated at the three sites was treated in the DIS before entering the ocean waters. Site L demonstrated 100% stormwater capture, site M demonstrated 96%, and site K demonstrated 80%. The percent captured for site K, although lower than the others, is understandable since it received greater volumes of runoff with higher concentrations of bacteria than the other two sites. The systems appeared to have no negative effects, and the authors believe that the incorporation of these systems may receive positive media coverage and could potentially boost tourism.

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