Two ponds to be created in the Bel Pre and Longmead neighborhoods in Aspen Hill should help support healthier ecosystems, prevent erosion, and mitigate pollution in the Anacostia River watershed.
Montgomery County Department of Environmental Protection staff and contractors explained the $1 million plan to neighbors at a meeting on Thursday night. The plan addresses a 24-acre drainage area in Bel Pre and 19-acre drainage area in Longmead, which staff said have not been updated to modern standards of stormwater management.
Currently there are dry ponds in the drainage areas, which only fill up when it rains. The department will turn these into wet ponds, which will retain water most of the time.
Watershed Planner Jennifer St. John said they aim to address two issues with the ponds: the amount of runoff flowing into streams after storms, and the quality of the water moving downstream.
Ponds help control the quantity of water flowing at one time by retaining it following storm events and releasing it slowly. This prevents the erosion.
Water quality is also improved by allowing the water to settle before entering streams.
“The wet pond helps settle out sediment and nutrient pollution,” said Brett Long, project manager consulting for the department.
A concrete riser in the pond drains water from the middle of the water column to flow downstream, leaving excess sediment and nutrients behind.
“And vegetation uptakes and helps filter out the nutrients,” Long said. Planting will be included in the plan, he said.
This reduces the number of pollutants that enter the stream, run down to the Anacostia River, then the Potomac and the Chesapeake Bay. Nutrient pollution includes nitrates and phosphates from fertilizers that cause harmful algae blooms. Other pollutants are chemicals and heavy metals that run off of impervious - paved - surfaces. Twenty-seven percent of the Bel Pre drainage area is impervious, as is 41 percent of the Longmead area.
Neighbors were mostly supportive of the plans.
“It’s needed. I think it’s really going to improve the look of that area,” said Tim Hummer, who lives near the Bel Pre site.
Two residents who live along a stream in Bel Pre said they hoped that restoration would be a larger part of the plan.
“We’ve seen a dramatic shrinkage from the erosion of the creek,” of the land behind their townhomes, said Lorena Ramirez. She estimated the land has receded about ten feet since she moved in 15 years ago.
St. John said that they likely will do some stream restoration as part of the updates to the drainage area. Planners are still in the design stage. They expect to start construction in December and complete the project in February 2015.