Arlington Activates Two New Safeguards in Fight Against Flooding

Published on September 26, 2023

ballston wetland ribbon cutting.jpg

Arlington is celebrating two significant safeguards in its pursuit of flood resilience—Ballston Wetland Park and the Cardinal Elementary School Stormwater Vault.

The new Ballston Wetland Park expands control systems and capacity for what is now Ballston Pond, originally built in 1980 to hold storm runoff from I-66 just to the north.

Cleared of sediment and now capable of taking excess rainwater from 450 surrounding acres, the retrofitted wetland system improves stormwater flow and filtering – plus capture of trash – while also serving as a wildlife refuge and pastoral commons within its “urban village” setting.

Lubber Run flows through the wetland on its way to Four Mile Run. The park expands the ability to meet state Chesapeake Bay Watershed regulations while cultivating native plants that replaced invasives and provides new boardwalk areas and fresh interpretive signs.

The $4 million project, with construction from late 2021 to August 2023, was celebrated with a public ribbon-cutting on Tuesday, Sept. 26.


Less than two miles away, below ground in the Westover neighborhood, lies the Cardinal Elementary School Stormwater Vault. Sitting under restored playing fields, the 47,000 square-foot vault is capable of temporarily storing over 4 million gallons of water (equal to six Olympic swimming pools), offering a unique Arlington solution to limited public space.

Westover homes, businesses and roadways suffered heavy damage in a torrential July 2019 flash flood emergency that saw three to four inches of rain dumped on Arlington within an hour.

In the aftermath, the County launched its Flood Resilient Arlington effort and developed the Cardinal vault, one of the largest structures of its kind on the East Coast. Construction lasted from late 2021 to summer 2023 at a cost of $18 million.

A ribbon cutting—above ground—is slated for Westover Day, a community celebration of the newly completed Cardinal Elementary campus on Saturday, Sept. 30.

Flood Resilient Arlington

Climate change has made sudden, intense rainstorms more likely and more powerful. Flood Resilient Arlington is developing a monitoring network to better understand the factors that affect and contribute to flooding.

The Cardinal Elementary vault includes six sensors that measure flow velocity, two sensors that measure water depth, and one rain gauge. The flow data will be made publicly available. The monitoring system collected its first storm data in late June of this year. As of early September, it has collected data for 15 events. The heaviest rainfall was 1.2 inches in 45 minutes on Aug. 8, when the level of water inside the vault increased to 30 inches. 

The County has significantly increased funding for stormwater management in its FY 2023-32 Capital Improvement Plan.

Additional photos of both projects can be found on the Department of Environmental Services' Flickr page: Ballston Wetland ParkCardinal Elementary School Stormwater Vault.

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