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.


Andres Torizzo
Principal, Watershed Consulting Associates, LLC
andres [at]

Eric Roy
Assistant Professor, University of Vermont
eric.roy.1 [at]

Donna Rizzo
Professor, University of Vermont
drizzo [at]

Resulting Publications

Research Webinar: Stormwater Subsurface Gravel Wetlands in Vermont

Published 2020
In this video, as part of the Lake Champlain Sea Grant Research Webinar Series, Andres Torizzo, Principal Hydrologist at Watershed Consulting, and Eric Roy, professor at the University of Vermont, give a presentation on ongoing research on the effectiveness of subsurface gravel wetlands on flow attenuation and phosphorus capture, and how chloride impacts performance.