WK Dickson has received an Engineering Excellence Grand Award from the American Council of Engineering Companies of North Carolina for our work on the Caswell Beach Dune Infiltration Project in Caswell Beach, North Carolina. Only the second of its kind in North Carolina, the project features a dune infiltration system (DIS) that will accept and infiltrate stormwater runoff that ponds on the primary road serving the town.
Over the past few decades, portions of Caswell Beach Road in Caswell Beach, NC, had become impassible to passenger vehicles from moderate rainfall events. The road is the only ingress/egress for approximately 240 residents, the Duke Energy Progress Nuclear Pumping Station, the United States Coast Guard Station on Oak Island, and the North Carolina Baptist Assembly grounds at Fort Caswell. This new system allows the town to pump out the low points along Caswell Beach Road into a series of infiltration chambers embedded within the dunes that utilize the in-situ sand as infiltration media. The DIS system is optimized to reduce street flooding to a level safe for vehicular traffic within two to four hours.
In addition to providing water quantity benefits, the DIS also provides a secondary water quality benefit. When it rains, water flows across the ground and picks up pollutants. Elevated bacterial levels in these pollutants can lead to beach closings or swimming advisories. However, a DIS uses the sand’s natural filtering ability to remove rainfall runoff pollutants. Studies show these systems remove between 75% and 95% of pollutants, including pathogens, hydrocarbons, and excess nutrients.
Mayor Deborah Ahlers adds, “Being prepared for flooding and the safety of our citizens is a primary concern for the town. The recently completed dune infiltration system will help and provide a water quality benefit – an essential component for coastal communities like Caswell Beach. With this project being only the second one of its kind in the state, we are proud to lead the way in how our neighboring communities can deal with coastal flooding.”
Want to know more? Check out this short video that explains how the dune infiltration system works.