Havre de Grace is beginning the final phase of a three-phase project to naturally treat stormwater before it goes into the Chesapeake Bay and the Susquehanna River.
“The ultimate goal is to take the project all the way around Concord Point and to Water Street,” Havre de Grace Public Works Director Tim Whittie said.
The third phase, which is being paid for with a $400,000 grant from Maryland Department of Natural Resources, will treat stormwater runoff from rooftops and streets in a system in the open space between the Havre de Grace Maritime Museum and Decoy Museum.
“Before, the water rushed right into the river,” Stephanie Noys, the municipal separate storm sewer system (MS4) permit coordinator for the city. “This will take it offline instead.”
Rather than travel down a pipe, the water will infiltrate through a regenerative stormwater conveyance system and be treated along the path, Noys said.
One form of pollution is thermal pollution, Whittie said. When it rains on the hot asphalt, the rainwater is warmed and goes into the storm drain, without allowing the water to cool, and into the drains and subsequently the river.
Higher water temperatures promote algae and bacteria growth, which both thrive in hotter temperatures.
In the regenerative stormwater conveyance system, the water travels mostly underground, similar to a spring, and is cooled off before it goes into the river.
“This will give the rainwater more of a chance to infiltrate and be treated by native plants that will do a lot of work,” Noye said. “The root systems are larger and take up a lot of pollutants.”
“When the stormwater comes out, it’s a cooler temperature, better for aquatic life,” Whittie said.
The engineering work has been completed and the number of pools determined; the city is working with the Decoy Museum and Maritime Museum to finalize their alignment, Whittie said.
Construction, expected to take about six weeks, is set to begin the first week of December and, if the weather cooperates, should be completed by the end of January, he said.
It will be difficult for the general public to see the system, other than a natural area with native plants and materials, including gravel walkways. The slopes will be gently rolling.
“They won’t see it as something treating the stormwater,” Noye said.
The property will still be able to be used for activities it’s used for now, especially parking, she said.
The first phase of the project was to build an RSC step pool system into the area behind the Maritime Museum and creating a living shoreline inside the promenade, Noye said.
“It’s meant to be enjoyed by everyone and it also serves as a soft launch for kayaks, et cetera, so we have access to the river that way," she said.
Behind the beach is a wetlands area the promotes healthy amphibians and other habitats.
The second phase was a dry stream channel to take stormwater runoff from the parking lot in front of the Decoy Museum and collect it in a bio-retention pond. The pond includes soils and native plants to absorb stormwater and pollutants.
“It also slows down the velocity of the rain coming off the parking lot so it has time to infiltrate and move underground,” Noye said.
The cost for the second and third phases was $300,000 to $400,000.