SALEM — A garden at Winter Island is full of rocks. It has a trap for things like cigarette butts and oil dripping from cars.
It won't grow tomatoes, but officials say it will help save the whales as more like it are built around the state.
Officials with the state's Office of Coastal Zone Management were in Salem Tuesday afternoon to visit the rain garden that was recently built on the northeast corner of the main parking area outside the Winter Island Park hangar.
The garden is no more than 33 feet long and measures roughly 57 feet at its widest point, according to satellite data from Google. But it's positioned downslope from the parking lot, so gallons of stormwater runoff have to pass through it before reaching Salem Harbor.
On Tuesday, Salem Sound Coastwatch director Barbara Warren stood at one of two stormwater runoff channels in the rain garden. Beyond it, a field of stones led to a mulched area in the middle. The rocks were recently cleared of sand and sediment, but a half-dozen cigarette butts still remained from the last rainfall.
"These are the pretreatment bays," Warren said, pointing out where the stormwater flows. "As the water runs off the pavement, it runs into here — and the rocks collect the sediment, all the trash. You can see all the cigarette butts."
Underneath the mulch, Warren said, sits "18 inches of a special media that absorbs all the pollutants, and we also have plant roots which are absorbing it."
"The goal is to keep that first inch of rain that's washing the parking lot to get treated here and sifted out before it goes out to the ocean," Warren said, then pointing to a small wetland area behind the garden. "If we get a huge rainstorm, this will overflow and go into the overflow dome in there."
The garden was designed in 2018 and built in 2019, in part with a $128,650 grant from the state's Coastal Pollutant Remediation Grant Program and a $42,883 match. At the time, the garden was described as cutting down on "decreased water quality" at Salem Harbor "from sediment, bacteria, metals, oils and grease."
"What's running off here is suspended sediment, so you're adding lots of sediment that isn't clean into the water (in Salem Harbor)," Warren said. "People are pretty good about picking up after dogs, but you can get dog waste, which adds bacteria. ... We could also have nitrogen and phosphorous, which are nutrients that increase the amount of invasive species of seaweed we have."
On Tuesday, Coastal Zone Management officials were in Salem to announce another round of coastal pollutant remediation grants available "for communities to address stormwater issues," said Adrienne Pappal, a coastal habitat and water quality manager for the state office.
"There's a total of $500,000 that's available, and a maximum of $175,000 for each project," Pappal said. "That's available for communities within the coastal watershed. That's about 220 municipalities in Massachusetts."
The Winter Park garden is one of about a half-dozen rain gardens around the city. And Coastwatch is in the process of using $45,100 awarded by Coastal Zone Management last year to create a "series of training videos which demonstrate the correct operation and maintenance of stormwater green infrastructure."
Warren said without the grant, "it's really hard for municipalities — especially when you've got something new like this, something that people are just starting to learn about in New England."