Ashby Pond: Home to Unique Cleanup Project

That curiosity floating on Ashby pond in Fairfax Virginia was well-received by green herons and turtles, which made area residents visiting the Pond very appreciative, too. It turns out it is a manmade island that is designed for water cleanup rather than additional wildlife habitat.

The sign at the Ashby Road Park explains that what appears to be a little island paradise is actually a Floating Treatment Wetland, (FTW) which is specifically designed to “treat urban runoff.”

The basic concept is simple: introduce additional plant life that will “pull nutrients (including pollutants) into plant tissue and also a biofilm that grows on their roots which also consumes nutrients,” said Dr. David Sample, Assistant Professor and Extension Specialist with Virginia Tech.

This means the water will be cleaner, with less nitrogen, phosphorus, and sediment, etc., that will get into the waterways and eventually the Chesapeake Bay.

Having this project in a popular park meant more people got a chance to understand “that their neighborhood is now part of a watershed management plan” that may make their pond cleaner if all goes according to plan.

The floating wetlands had to be protected so geese wouldn’t eat the plants, so there was fencing both above the water and below the surface.  Smaller creatures like tadpoles, arthropods, and turtles that climbed aboard to sun, could still make themselves at home.

Seen as a “really cool, unique initiative,” Sample, who oversaw the project, says that “the Bay program is going to start an expert panel review of this particular project.” It is an innovative approach to pursuing another way to remove pollutants from waterways that build up, especially in the hot summer months. Preliminary research is indeed showing “that there is a noticeable reduction in nitrogen and phosphorus,” said Sample, calling the project a success.

The demonstration project used several full-sized rafts. Five full size rafts were placed in the pond, anchored with poles so the rafts rode up and down the poles with the water level.  

Sample said that many people like the idea of what appears to be a raft garden, for aesthetic reasons, but the potential for removing pollutants is enticing to researchers, particularly since the water surface is not used for anything else.

The plant varieties that are introduced on the rafts are able to grow hydroponically, (take up nutrients directly from the water as opposed to soil) even though that is not their native habitat.  

Once the growing season ends, the plants should to be harvested before the nutrients they have absorbed throughout the growing season leach back into the pond.

Chih-Yu Wang, doctoral student at Virginia Tech assisted on the project, helping set up and monitor the floating wetland. He encountered a lot of curiosity from nearby residents.  “People often asked me what the ‘thing’ in the pond is and what I was doing. After hearing my explanation, their responses generally were ‘this is a great idea,’ and ‘good luck on your study,’” said Wang, who described the project as “well received.”

After one short conversation “a father was so excited he went home and came back with his son and asked me to explain what the FTW is to his kid.”

Adrian Fremont, Special Projects Engineer with Fairfax County at the time, said that “there was a lot of interest in how FTW’s would improve the water quality of Accotink Creek, and an overwhelming response to our efforts to improve the water quality of the pond.”

With funding support from the National Fish and Wildlife Foundation (www.nfwf.org), Fairfax County and  VT researchers were able to join together to make a difference.

Fremont said “the City of Fairfax considers these types of projects to be highly valuable” and called it “a great team effort with Virginia Tech.”

Another resident told Wang he had seen a bevy of turtles-- “Nine snapping turtles at one time,” which is apparently a layman’s take on how to really appreciate the project’s success.