When the Board of Supervisors tasked the Park Authority with finding sites for demonstration rain gardens to absorb stormwater, the site-seekers used two main criteria: need and visibility, according to Park Authority naturalist Charles Smith. The Mount Vernon RECenter on the corner of Belle View Boulevard and Fort Hunt Road met both criteria. Runoff from the RECenter’s multi-tiered parking lots and the recycling center area above them streams quickly down the asphalt, usually into storm sewers but occasionally into the front lobby. And anyone driving down Belle View or using those lots will pass signs for the rain garden and be enticed into checking out the environmentally-friendly landscaping more closely, perhaps becoming inspired to do their own.
But now that the project has gone from planning and design to the initial stages of construction, the site’s visibility has drawn unintended attention, and some negative assumptions. Patricia Tyson has worked out regularly at the RECenter for years. After a week-long vacation, she returned to the center at the beginning of last week and discovered that about six trees, some of them mature crabapples, had been cut down. “I was surprised and shocked,” she said.
Tyson, a landscape architect, said she had admired the trees for years, and was anticipating their response to the changing season. She said she knew the landscape architect who planted the trees almost 30 years ago, and that ornamental crabapples of that age were a precious resource. “They were just about to have a great fall color, then drop their leaves and show their berries.”
She explained that the berries “usually will persist on the tree until they’ve gone through the winter, freezing and thawing, freezing and thawing. Then, when the birds come back after the winter they are there for the birds as food, so they have habitat value, and that is important to me, and should be important to the county.”
SMITH SAID THE ORNAMENTAL TREES had not been getting the care they needed, and would be replaced by native trees with even more habitat value, probably sometime in March, when the transplanted saplings will be dormant. The bulk of the county project will be completed within the next few weeks. Smith said workers will take out two 50-foot sections of the curb that runs beside the driveway to the parking lot. Water from the hill will flow into the grassy swale, where most of it will collect in a rain garden that will slowly absorb the water and return it to the soil.
When the county built its stormwater management infrastructure in the 1950s, the intent was to get rid of water as quickly as possible, routing it to storm sewer vents beside roads which drained directly into pipes that dumped water into the nearest naturally flowing stream. In the past 50 years, planners have realized this technique is good at clearing streets, but devastating to the area’s watersheds, which are persistently eroded by the collective water of entire storms slamming into them at once and degraded by the chemicals and trash that washes out with the rainwater.
Rain gardens are designed to absorb and clean water runoff, filtering it through vegetation and soil and releasing it gradually into the earth when possible or into collection drains. Smith said the Board of Supervisors assigned discretionary money from their carry-over funds to publicize Low Impact Development projects and encourage land-owners, residential and commercial, to install the “series of techniques to improve water quality by imitating nature.” The five LID projects in the county, of which Mount Vernon’s is one, will cost a total of $150,000.
The county wants people to know that rain gardens can be built cheaply and relatively easily. Their most important component parts are a hole several feet deep and heavy gravel to fill it, Smith said. Water drains through a layer of soil, then a piece of fabric, and finally into the gravel, which may slow it for hours or even days. “You try to hold your water as long as possible,” Smith said, “and infiltrate it back into the ground as groundwater, which is what natural systems would do.”
In soil with poor absorption, such as clay, a storm drain beneath the gravel may be required. But Smith said the Mount Vernon site is particularly attractive because unlike almost any other place in the county, its ground is composed of sand and gravel from an ancient seashore, which drains water very effectively. Smith said that after a journey of years, the rainwater will eventually drain through the earth and into the Potomac, but not before much of it has fed into the roots of trees and other plants above.
MOUNT VERNON RECENTER’S site manager, Trina Taylor, said Tyson has been the only person to complain to her personally about the felled trees. Taylor acknowledged that stormwater is not an obvious problem for the center. Although water from the hill above has occasionally come pouring into the foyer, this happens rarely. After hearing Tyson’s complaint, Taylor posted a diagram of the project and a description of its intent on the RECenter bulletin board.
In an e-smail response to that description, Tyson suggested that the 30-year old recreation center, which houses a swimming pool and ice skating rink but must cram its aerobic machines into the front of the lobby, has more pressing issues than stormwater management. But Smith said funding for any renovation projects within the center was unrelated to funding for the environmental demonstration project. The purpose of the tree-cutting and the construction that will follow is broader than renovations to a single center. He said the site provided an opportunity to show people how to modify existing resources on their property, like a grassy swale beside a driveway, to benefit the environment and the property’s appearance.
Smith said the county will plant native “showy plants” that should flourish in the well-watered soil, and will replace the trees it cut with eight native trees that will provide better habitat benefits for animals. The county also plans to convert two acres of mown grass near the recycling center to one acre of forest and another of meadow with paths winding through them. “Mount Vernon ended up being a great site because of the need, the visibility and because of those great soils,” Smith said.