Stormwater Subsurface Gravel Wetlands in Vermont
February 1, 2020 to January 31, 2022
Subsurface gravel wetlands (SGW) are stormwater treatment practices that use a saturated bed of gravel and sometimes wetland vegetation to filter incoming water and remove pollutants, such as phosphorus. Water level is controlled by an outlet structure to retain a permanent subsurface pool, providing retention of stormwater volume in addition to pollutant removal. SGW are becoming increasingly popular tools for stormwater treatment in Vermont and are recommended by the 2017 Vermont Stormwater Management Manual.
Because of recent questions surrounding the performance of SGW to mitigate the impacts of urban stormwater pollution on Lake Champlain and its subwatersheds, researchers will investigate the field performance of two permitted and installed subsurface gravel wetlands of similar age and drainage area characteristics over two growth seasons. Researchers will use both field monitoring and sampling and laboratory experiments to measure phosphorus capture in comparison to state standards and measure road salt chloride impacts on the performance of the SGW.
Findings will directly inform the Vermont regulatory community as they make decisions about SGW use and recommendation. Outcomes can be incorporated into community outreach on Green Stormwater Infrastructure in underserved areas in collaboration with Lake Champlain Sea Grant staff.