Mooresville is planning to build two rain gardens at Town Hall to manage stormwater runoff from surrounding parking lots and roads.
Functioning as miniature ecosystems, rain gardens, also known as a bioretention ponds, contain layers of plants and soils that soak up pollutants, such as fertilizers and motor oil, that gets swept up by rainwater. They are meant to minimize their harmful effects on the environment, particularly waterways.
“Those are things you don’t want in your system,” said Jon Young, an engineer for the town.
The size of the gardens planned for the North Main Street municipal building, including one between it and the adjoining post office, will depend on engineering studies that will determine the amount of runoff they would see.
The town has experienced no flooding issues there, and it is not obligated to build them.
But among the largest sources of runoff are places that see much motor vehicle traffic, such as gas stations and parking lots. “It looked like it would be a good place,” Young said.
The project could cost roughly $250,000, he said. To help finance it, the town submitted a preliminary application last month for a $100,000 grant from Duke Energy. The remainder would come from the town’s stormwater utility fund.
The grant is part of a fund managed by Charlotte-based utility, which is expected to announce in June which applicants are eligible to submit another, official application, Young said. To help with the process, the town spent an additional $4,500 to hire W.K. Dickson & Co. Inc., a Charlotte-based engineering design firm.
The fund was set up last year, with $10 million to help preserve waterways in the Carolinas and those downstream from its facilities in surrounding states.
Should the town not receive the grant, it would reconsider whether to move forward with the project, Young said.
Home to four watersheds, Mooresville has had rules to minimize the impact of stormwater runoff on its ecosystems for several years. They are based on guidelines established by the state Department of Environment and Natural Resources.
For example, developers are required to put in place some type of stormwater control based on the extent of impervious surface, such as pavement, that their plans entail.
Rain gardens, for their part, generally filter about an inch of stormwater runoff at a time.
Situated in sunken areas surrounded by impervious surface, they contain layers of material such as mulch and sand. Some are designed to handle large amounts of runoff, draining filtered water into underground storage tanks.
Eventually the layers will be replaced. “You’ll be able to tell when it quits draining as well,” Young said.
While the town has built only one rain garden, as part of a subdivision off Selma Drive in the Cascade community that was built several years ago, it is home to many, particularly in commercial developments.
“You’ve seen them,” Young said. “You just don’t know.”
Retrofitting Town Hall with the rain gardens is not required, as the building was erected before the town adopted its stormwater management rules.
But in addition to controlling runoff, they could serve as a kind of educational tool, with the possibility of the town arranging visits from local schools.
Moreover, it might add some curb appeal. “Everybody comes to Town Hall,” Young said. Referring to the rain gardens, he added, “It’s what they call good housekeeping.”
Jake Flannick is a freelance writer. Have a story for Jake? Email him at firstname.lastname@example.org.