Organic engineering

On a cool December day at the Beaver Lake Sanctuary, you can hear sparrows skittering amongst the leaves in the thickets. You’ll spy them, too, hopping amongst the still-green leaves of swamp marigold in the mud flats. A bright red cardinal chirps and hops across the boardwalk. A chipmunk tries to slink away, unnoticed, when you approach the water’s edge. An elderly woman walks briskly around the meandering loop the boardwalk makes through the marshy sanctuary. Cattails sway in the breeze.

And, over near the parking lot, a new pond greets visitors. Just within view of motorists whisking by on Merrimon Avenue, the pond represents the next step in developing the Sanctuary. The Elisha Mitchell Audubon Society, which owns half of the 8-acre park, won a state grant to create this eco-filter — an artificial wetland that will deal with the polluted, sediment-laden runoff from Merrimon Avenue and the developed properties along it, which winds up in the stream that feeds Beaver Lake.

“There are a lot of problems with streams in urban areas,” says Audubon Society board member Marilyn Westphal, who has a degree in environmental sciences and specializes in water-pollution analysis. “Every time there’s a rain, pollutants wash off the roads and parking lots — and [they] end up in the stream,” she emphasizes. Westphal is director of the Volunteer Water Information Network, which monitors water quality at 170 stream sites in seven Western North Carolina counties. VWIN, a joint project of RiverLink and UNCA’s Environmental Quality Institute, has reams of data showing that the stormwater draining into the lake contains heavy metals like zinc and copper, and hydrocarbons from gasoline and other sources.

“Most of these pollutants are attached to the sediment in stormwater runoff,” Westphal explains. Hydrocarbons, however, tend to float on the water’s surface — those pockets of bluish film evident near the drain pipe that feeds into the lake.

“It’s pretty dirty,” said Sanctuary Coordinator Len Pardue when he surveyed the wetlands work in early December. He pointed to a large pipe that workers had exposed: 250 feet long and 54 inches in diameter, it has captured runoff from Merrimon and fed it directly into Beaver Lake. for the past three decades. Audubon members realized that the 30-year-old pipe hadn’t been maintained; it was leaky and rusty — and did nothing to keep pollutants out of the lake, Pardue recounted. “If it were to become blocked by debris or flooded, [the Society] would be responsible. So we considered plans to remove it and create a wetlands area,” he continued.

The Society received a $139,700 grant from the North Carolina Clean Water Management Trust Fund — to remove the old pipe, create a pond, rebuild the earthen berm above the stream that feeds the lake, and plant native species of trees, shrubs and other vegetation that will filter out sediment and pollutants. The grant also includes an endowment that will fund annual maintenance costs for years to come. “The result will be that the water that enters the lake will be significantly cleaner than it was,” Pardue observed.

That’s what attracted the attention of trust-fund officials. “We were interested in the project because it’s an innovative approach,” said Field Representative Tom Massie in Sylva. Partly financed by fines levied against industrial users, the fund supports projects that protect and restore water quality in streams, creeks, waterways and estuaries all over North Carolina, he explained. Since its creation in 1996, the agency has awarded $162 million to nonprofit organizations, local governments, utilities and others undertaking water-quality projects, Massie noted. To date, however, few grant recipients have involved the use of eco-filters — which let nature do the work of dealing with sediment and pollutants, he remarked. “This is a method we’d like more and more [people and agencies] to consider,” noted Massie.

“It’s a well-designed project,” observed Asheville Engineer Trainee Maria Keranis, who reviewed and approved the Society’s initial plans. Most of the erosion-control plans Keranis deals with are for temporary installations of riprap, rock dams and holding ponds, to help contain pollutants and sediment at construction sites, she explained.

But the Society’s eco-filter will be a permanent one, and it will help Asheville get the jump on tighter regulation of storm-runoff drainage systems, Keranis emphasized. City ordinances in effect since 1994, she explained, require developers and property owners to address only the quantity of runoff, not the quality of the water that eventually enters local streams and rivers. But stricter state and federal mandates will take effect in 2002, requiring municipalities to consider water-quality issues, too, Keranis reported.

In that light, the wetland project puts the Society a little ahead of its time, some observe. “We thought this would be a good demonstration project,” reflected Westphal. Runoff from Merrimon will drain into the pond; as the water circulates, the sediment will settle to the bottom. That’s good for the lake in several ways: Even unpolluted sediment accumulates over time, and the artificial lake must be dredged periodically to keep it from filling in, said Westphal, adding, “We want to keep Beaver Lake a lake, and it’s cheaper to dredge the new pond.”

The project also entails planting native species that will help filter out contaminants in stormwater runoff. Those native species, reports environmental biologist Dr. Ed Hauser, will include trees such as white oak, sour gum, sugar maple and green ash; and shrubs such as button bush, red-stemmed dogwood and wild raisin. Closer to spring, native perennials will also be planted around the pond, he added. Hauser, who also serves on the Audubon Society board, says the wetland project will include educational displays along the sanctuary’s boardwalks, to help visitors learn about native plant and animal species. “This is a unique opportunity to indicate the functional values of a wetland in an urban area, which is rare. Wetlands are disappearing,” said Hauser.

Beside preserving the Beaver Lake wetland, Audubon Society members are also trying to protect native species such as touch-me-not and swamp marigold, Hauser continued. And, come spring, the pond will be dotted with lily pads and yellow pond weed, in an effort to root out such invaders as Japanese honeysuckle. “That’ll be the next major focus, in the next five years,” said Hauser.

For his part, Pardue believes it’s well worth the effort. A dozen years ago, the Sanctuary property was slated for commercial development, like the rest of Merrimon Avenue. “But lo and behold, [the Audubon Society] raised $400,000 and bought it,” he observed. The Society hosts monthly bird walks, giving participants a chance to view warblers, vireos, sparrows, orioles, kingfishers, the occasional hawk and a host of other birds. For the past few summers, some diligent bird watchers have caught sight of the warbling vireo — “not found in many places in North Carolina,” Pardue noted. Then, gazing into the thickets and stands of cattails, he remarked: “It’s good to enjoy a little area of quiet in an urban neighborhood. We need more places like this.”