Project at a Glance:
Potash Brook lies primarily in South Burlington, VT and is classified as stormwater impaired. The City of South Burlington contracted Watershed Consulting Associates and Hoyle, Tanner & Associates, Inc. to complete a watershed-wide retrofit assessment and modeling study for flow restoration of Potash Brook as part of the implementation of the watershed-wide Total Maximum Daily Load (TMDL) plan.
Client: City of South Burlington
Partners: Hoyle, Tanner & Associates, Inc.
Location: South Burlington, VT
WCA, in partnership with Hoyle, Tanner & Associates, Inc., was contracted by the City of South Burlington to complete a flow restoration plan (FRP) of the stormwater impaired Potash Brook. The Potash Brook FRP will act as a guidance document for the five Municipal Separate Storm Sewer System (MS4) entities in the watershed as they implement the stormwater Best Management Practices (BMPs) necessary to attain the flow restoration targets established by the Potash Brook Total Maximum Daily Load (TMDL). The TMDL requires a 16.5% reduction in stream high flow.
Existing BMPs that did not meet current stormwater management standards were field evaluated to determine if they could be retrofitted to provide improved treatment and detention of stormwater runoff. These new BMPs were then incorporated into the Best Management Practice Decision Support System (BMPDSS) model. Additionally, new BMPs were identified throughout the watershed. The team determined optimal locations for proposed BMPs, completed BMP designs, and assessed the watershed-wide impact of the proposed retrofits. These BMPs were added to the model until the required stream flow reduction target of 16.5% established in the TMDL was achieved. The final model run included 107 sites; forty (40) retrofits to existing BMPs, forty-one (41) new detention systems, eighteen (18) new infiltration systems, five (5) new gravel wetlands, two (2) new bioretention systems, and one (1) new median filter system.
Once the final list of required BMPs was determined, these projects were ranked using a comprehensive matrix and scheduled for construction over a 17-year period. A final FRP was developed including a financial and implementation plan.