Description
There are a series of seven stormwater ponds that manage runoff generated by Kennedy Drive. The City worked with an engineer to design improvements to these ponds, so that they can treat additional runoff that currently bypasses the ponds untreated, as well as upgrading select ponds to subsurface gravel wetlands to enhance the phosphorous removal of the treatment system. Kennedy Drive Pond 3 was selected for both expansion and retrofit to a subsurface gravel wetland.
Problem
Pond 3 previously managed approximately 2.86 acres of Kennedy Drive impervious area and was originally designed to meet the WQv and overbank protection design standards. However, the existing pond was only
designed to treat the additional impervious acreage associated with the Kennedy Drive road expansion, thereby not meeting the treatment standards for the entire contributing drainage area.
Additionally, there is currently untreated stormwater runoff generated from a 4.26 acre drainage area that bypasses the pond by way of a culvert that passes under Pond 3’s access drive. This project captured the additional area, as well as expanded and retrofit the pond into a subsurface gravel wetland to provide Water Quality and Channel Protection treatment for the existing and expanded drainage area.
This project was identified as part of the Potash Brook Flow Restoration Plan (FRP), prepared by the City of South Burlington, in an effort to reduce flows to the impaired Potash Brook and improve water quality in the Lake Champlain drainage area.
Benefit
Based on HydroCAD modeling conducted by the consultant, the project could reduce the peak flow of the 1-year, 24-hour storm event by 50%, from 2.75 cubic feet per second (cfs) to 1.37 cfs.
Funding
On November 6, 2018 voters approved a ballot item related to reconstruction of the Kennedy Drive Stormwater Detention Pond 3. All construction costs were provided by the State of Vermont under the Green Stormwater Sponsorship Pilot Program.
The State of Vermont’s Green Stormwater Sponsorship Pilot Program provides principal loan forgiveness to incentivize green stormwater projects. Under this pilot program, an applicant pairs a traditional treatment works project (e.g. a wastewater treatment facility upgrade or pump station upgrade) with a green stormwater project. Upon final completion of the projects, the green stormwater project debt is then forgiven in its entirety. The City paired the Kennedy Drive pond 3 reconstruction with the Hadley Road Pump Station project. This pairing allows the City to access full loan forgiveness for the Kennedy Drive pond 3 project.
Timeline
The project was constructed in the 2019.
This page was last updated on 12/6/2019