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Magnolia Stormwater Management Retrofit

Innovative approach to provide stormwater treatment, infiltration, and conveyance within one system. 
  • Regenerative stormwater conveyance channel and vegetation within six months of project completion-Gannett Fleming

    Existing channel showing extent of ongoing erosion, including vertical bank and exposed root system.

  • Completed channel segment showing weir and step pool system-Gannett Fleming

    Completed channel segment showing weir and step pool system.

  • Existing channel showing extent of ongoing erosion, including vertical bank and exposed root system-Gannett Fleming

    Regenerative stormwater conveyance channel and vegetation within six months of project completion.

Client
Baltimore County Department of Environmental Protection and Sustainability

Location
Baltimore County, Maryland

Our Role
Construction Oversight, Erosion and Sediment Control Plans, Field Assessments and Documentation, Landscaping, Permitting, Regenerative Stormwater Conveyance Design,Total Maximum Daily Load Calculations.

Data
Completed
2014
Type
Rehabilitation
Duration
5 years
Outcomes
  • Innovative approach to provide stormwater treatment, infiltration, and conveyance 
  • Benefits the larger watershed by intercepting storm flow and improving water quality 
  • Use of natural infiltration 
  • Functions well through significant rainfall events.

An innovative approach to provide stormwater treatment, infiltration, and conveyance was the key to repairing eroded storm drain outfall channels and a tributary near Magnolia Avenue in Baltimore County, Maryland. The challenge was to restore and improve the channels to protect against channel and bank erosion and to improve downstream water quality for a suburban neighborhood. Complicating matters, the project location was topographically steep, making it unstable and subject to erosion during storm events. A solution well-suited for this steep terrain was needed. 

Gannett Fleming designed Baltimore County’s first regenerative stormwater conveyance (RSC). 
RSC systems are open-channel, sand seepage filtering systems that use a series of shallow aquatic pools, riffle weir grade controls, native vegetation, and an underlying sand channel to treat and safely detain and convey storm flow and convert stormwater to groundwater through infiltration.  

What We Did

In addition to the RSC design, we performed field assessments and documentation and prepared full bid set plans, including erosion and sediment control plans and landscaping plans with native species and sustainable plantings. We also coordinated with the Baltimore County Soil Conservation District, the Baltimore County Department of Public Works, and other internal agencies to prepare permit applications. Additionally, we performed preliminary calculations for Total Maximum Daily Load (TMDL), a tool for measuring adherence to state water quality standards. 

During the construction oversight, we reviewed contractor requests for information and visited the construction site regularly for oversight. Additionally, during the construction phase, we observed the regenerative stormwater conveyance at work, monitoring its performance to restore and improve the channels and protect against channel and bank erosion.  

Key Features

  • Regenerative Stormwater Conveyance adapted to a piedmont setting
  • Low-impact development, environmental site design, and sustainable green infrastructure
  • Ecosystem restoration
  • Landscaping with native species and sustainable plantings.

Similar Projects: Environmental Management & Remediation: Engineering Design & Construction Management/Inspection, Environmental Management & Remediation, Water/Wastewater: Stormwater, Water/Wastewater