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Cunninghill Cove Pond Repair and Retrofit

Restored stormwater facility meets state guidelines and improves water quality for the Chesapeake Bay.
  • View of stormwater pond showing new flow control riser structure - Gannett Fleming.

    The Cunninghill Cove Pond retrofit included the design and construction of a new flow control riser structure and principal spillway pipe.

  • Construction of stormwater pond’s earthen embankment - Gannett Fleming.

    Repair work at the facility included grading the earthen embankment to properly manage water volume during heavy rainfalls.

  • Riprap protecting slope around spillway pipe - Gannett Fleming.

    Adequate riprap protection stabilizes embankment slopes and helps prevent erosion.

Client

Baltimore County Department of Environmental Protection and Sustainability


Partner(s)
AB Consultants

Location
Middle River, Maryland

Our Role
Final Design

Data
Size
24,000 cubic feet
Construction Cost
$460,000
Completed
2016
Type
New Construction
Duration
6 months
Outcomes
  • Reduced downstream pollution and improved water quality for the Chesapeake Bay
  • Stormwater pond for 18-acre drainage area restored to fully operational condition
  • Ability to manage more water lessens downstream erosion and mitigates flooding
  • Facility meets current state stormwater management guidelines.

Situated inside the Chesapeake Bay Critical Area, Cunninghill Cove Pond is a stormwater management facility owned by Baltimore County and serves the Cunninghill Cove community. Built in 1989, it was designed to provide 10-year storm peak discharge management, but did not provide water quality treatment volume for the drainage area.

While conducting a routine maintenance inspection, county officials discovered that the piping at the pond’s principal spillway had failed, causing significant embankment erosion and deformation of the outfall, which was lined with a gabion mattress. Because of the damage, the facility no longer functioned in accordance with its original design and required immediate repair. Gannett Fleming developed plans and specifications to repair the pond to a fully operational condition. It also retrofitted the facility as an extended detention basin to provide water quality improvement for total maximum daily load (TMDL) credit as part of the county’s program to meet its municipal separate storm sewer system (MS4) permit requirements. The final design allows the facility to capture and treat approximately 24,000 cubic feet of water from an 18-acre drainage area with nearly 6 acres of impervious surface.

What We Did

Preliminary work included a dam safety inspection, as well as a detailed topographic survey, subsurface investigation to confirm the presence of an impervious core in the existing embankment, drainage area analysis, and hydrologic and hydraulic analyses. The pond’s eroded earthen embankment was repaired and a new flow control riser structure and principal spillway pipe were installed, as was a new endwall and outlet protection.

A shallow wetland treatment system at the bottom of the pond removes sediment and pollutants from runoff, improving water quality. Gannett Fleming also managed the complex process of coordinating the project with multiple regulatory agencies, ensuring that it was completed in accordance with goals set by the Chesapeake Bay Critical Area Commission.

Key Features

  • New reinforced-concrete flow control riser structure, reinforced-concrete principal spillway pipe, and concrete cradle replace failed structures
  • Reinforced-concrete endwall and riprap outlet protection prevent erosion
  • Grading and repair of earthen embankment erosion improve stormwater detention
  • Filter diaphragm and drain remove sediment from runoff.

Similar Projects: Environmental Management & Remediation, Environmental Management & Remediation: Permitting, Water/Wastewater: Stormwater, Stormwater: Stormwater Facilities, Water/Wastewater