Pond Renovation at Mason District Park
(Conservation Currents, Northern Virginia Soil and Water Conservation District)
The old farm pond at Mason District Park on Columbia Pike has gotten a major facelift. Construction began in January 2003. The new pond design helps control stormwater runoff from the 56 acres of drainage area above it, resulting in reduced pollution and downstream erosion.
Stormwater management ponds reduce the peak volume of runoff by releasing it over time, typically 2-3 hours, to prevent flooding.
Some stormwater management ponds control not only the quantity of runoff but also the quality of runoff. In such cases, the stormwater ponds are called BMP ponds. BMPs, or best management practices, are techniques to manage runoff in ways that reduce water pollution. In a BMP pond, a flow regulator reduces the size of the outlet, forcing the pond to hold the water for a longer period. This allows more time for the sediment and attached nutrients to settle out.
In 1998 the voters of Fairfax County approved a Park Authority Bond Referendum that included a pond renovation project for the Mason District Park. The goals of this project were to replace the existing pond outlet structure and construct amenities to compliment the pond, making it more of a focal point for the park. Further scrutiny of the pond by the Park Authority found that the dam and outlet structure needed significant structural repairs beyond those originally anticipated. When funds originally allocated for an erosion control project became available, there was a sufficient amount to reconstruct the dam and outlet structure, convert the pond into a BMP facility, and still beautify the pond area.
“Rarely do we find a project that is a win/win/win all around,” said Mason District Supervisor Penny Gross. “The pond renovation at Mason District Park addresses management of stormwater, improves water quality, AND provides a beautiful new water feature at the park entrance — a winning combination for everyone!”
This project is a partnership among the Park Authority, Department of Public Works and Environmental Services (DPWES), and the Northern Virginia Soil and Water Conservation District. DPWES monitored the existing stream conditions, and the conservation district helped document the evolution of the project for others who may be interested in retrofitting an existing pond to reduce water pollution and downstream erosion.
At one end of the new pond is a forebay to trap litter and sediments. The other end has a constant pool of water. Connecting the forebay and permanent pool is a meandering baseflow channel through wetland plantings. The created wetlands have several zones in which various types of wetland communities are established. Although the wetland is saturated at all times, it is submerged only during storm events.
Part of the landscape around the pond addresses the overpopulation of geese at the park. A vegetative barrier between the pond and athletic fields makes it more difficult for the geese to enter and exit the water. If geese do not have access to water, they leave the area.
The project leaves the playground equipment behind the dam embankment undisturbed and includes an ADA trail to enhance the site.