Aerial photo of the Newport Marina and the gravel treatment wetland near Prouty Bay on October 4, 2023.

The Memphremagog Watershed Association recently completed a stormwater improvement project on Farrant and Lake Streets in Newport City. The improvements now collect and treat stormwater runoff from nearly 125 acres uphill of Prouty Bay and the Newport Marina. The project will prevent 22,000 pounds of sediment and 19.8 pounds of phosphorus from entering Lake Memphremagog each year.  
Newly installed stormwater infrastructure includes nearly 750 feet of storm drain, 2 catch basins, 3 manholes, a hydrodynamic separator, and a 4,500 square foot gravel treatment wetland. The underground drainage infrastructure conveys storm runoff to the separator unit where oil, grease, sand, and other particulate pollutants are removed from the water. Stormwater then discharges from the separator unit to an inlet control structure, which regulates inputs to the subsurface-flow gravel treatment wetland. Once in the constructed wetland, a host of physical, chemical, and biological processes common to natural wetlands work to remove dissolved pollutants and further cleanse the water.

The gravel treatment wetland is sized to handle all runoff from at least a 1-inch rainstorm. In heavier rainstorms, the wetland will swell, allowing for brief periods of ponding, before discharging water through an underdrain outlet structure and into Prouty Bay. For those truly historic rains – like the ones we experienced this past July – a bypass pipe will safely discharge excess stormwater to the lake while still treating those ‘first flushes’ at the beginning of the storm.

MWA contracted Dale E Percy, Inc. of Stowe to construct the project. The Percy crew worked speedily while diligently navigating numerous unanticipated challenges. Unanticipated challenges included multiple buried water mains, several design modifications, and handling and disposal of approximately 1,250 cubic yards of urban fill. The urban fill was uncovered during construction of the gravel wetland and consisted of the remains of a woodworking shop that burned down decades ago and was buried on-site. To assist with handling this difficulty, MWA contracted Waite-Heindel Environmental Management to perform soils characterization and advise on disposal requirements. Before completing the project, a polyethylene liner was installed to isolate the gravel wetland from potential residual soils.

The project is an excellent example of a private, public, State, and non-profit partnership. The Spates Family, LLC donated a permanent easement to the City of Newport for the project. The City – who will own and maintain the project after completion – covered the cost of the easement, provided technical support through the Department of Public Works, hauled urban fill away from the project for proper disposal, and covered the cost to repair a failing culvert at the top of the project. The Newport Marina Condo Association donated $10,000 toward construction of the project. Casella NEWSVT has pledged at least $10,000 to offset some of the disposal costs for the urban fill.

The project, in planning for 5 years, was funded through Vermont’s Water Investment Division through a Design & Implementation Block Grant managed by Watersheds United Vermont.