Dune Filters After Installation (image) North Carolina State University Share Print E-Mail Caption The dune filtration systems are built under dunes that are covered with vegetation, making it difficult or impossible to tell that the dunes have been disturbed. A three-year study found that the dune systems reduced the concentration of bacteria in stormwater runoff by 96 percent. Credit Michael Burchell, North Carolina State University Usage Restrictions Photo credit must be given. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.