**Abstract Text**
The subsurface (also known as submerged) gravel wetland is an emerging stormwater control measure in North Carolina. While subsurface gravel wetlands were developed in the 1990s as a technology for treating wastewater, their use as a stormwater management device did not emerge until the late 2000s in New Hampshire. Since then, their acceptance as an approved SCM has expanded across the eastern U.S. to include Maryland, New Jersey, Tennessee, West Virginia, and Georgia. At this time, only a few subsurface gravel wetlands have been implemented in North Carolina, but there is growing interest in their use as well as in monitoring their performance to evaluate their potential for inclusion in a future iteration of the North Carolina Stormwater Design Manual.
Tetra Tech assisted The North Carolina Department of Transportation Hydraulics Unit to provide design and construction support for the state’s third subsurface gravel wetland as part of the Unit’s NPDES Retrofit Program. The wetland is designed to intercept, treat, and store stormwater runoff from the interchange on I-85 and Gate 1 Road prior to discharge into Falls Lake. Falls Lake is classified as WS-IV and NSW; therefore, nutrient reduction was a particular emphasis of the design. Our presentation will highlight some unique considerations for the highway environment, construction challenges, and lessons learned that can be applied for future implementation as subsurface gravel wetlands gain popularity as a suitable practice for meeting stormwater regulatory requirements in North Carolina.



**Abstract Text**
**The subsurface (also known as submerged) gravel wetland is an emerging stormwater control measure in North Carolina. While subsurface gravel wetlands were developed in the 1990s as a technology for treating wastewater, their use as a stormwater management device did not emerge until the late 2000s in New Hampshire. Since then, their acceptance as an approved SCM has expanded across the eastern U.S. to include Maryland, New Jersey, Tennessee, West Virginia, and Georgia. At this time, only a few subsurface gravel wetlands have been implemented in North Carolina, but there is growing interest in their use as well as in monitoring their performance to evaluate their potential for inclusion in a future iteration of the North Carolina Stormwater Design Manual.**
**Tetra Tech assisted The North Carolina Department of Transportation Hydraulics Unit to provide design and construction support for the state’s third subsurface gravel wetland as part of the Unit’s NPDES Retrofit Program. The wetland is designed to intercept, treat, and store stormwater runoff from the interchange on I-85 and Gate 1 Road prior to discharge into Falls Lake. Falls Lake is classified as WS-IV and NSW; therefore, nutrient reduction was a particular emphasis of the design. Our presentation will highlight some unique considerations for the highway environment, construction challenges, and lessons learned that can be applied for future implementation as subsurface gravel wetlands gain popularity as a suitable practice for meeting stormwater regulatory requirements in North Carolina.**



Design and Construction of a Subsurface Gravel Wetland in the North Carolina Highway Environment (Room 301 B, Wednesday 9th, 10:30am-12:00pm)

The International Low Impact Development Conference highlights interdisciplinary practice, research, and implementation of Low Impact Development (LID), Green Infrastructure (GI), Sustainable Urban Drainage Systems (SUDS) and Water Sensitive Urban Designs (WSUD). The focus will be on using our past and present understanding of LID to tune management programs, design practice, and operation and maintenance into the future.