When scientists announced this summer that the Chesapeake Bay had seen “significant” improvements in water quality and aquatic life, some of the success was attributed to cleanup strategies throughout the region.

Twenty percent of pollution in the bay is from contaminants in stormwater — everything from fertilizer to animal waste that flows into creeks and rivers that feed the bay.

As a way to combat pollution from runoff, more than 1,000 bioretention sites, commonly known as rain gardens, have been built throughout Howard County, to catch and filter stormwater before it reaches streams.

This summer, the Trinity School in Ellicott City is installing a 9,903-square-foot bioretention site on its grounds.

The project is led by a partnership between the Office of Community Sustainability and the Ellicott City-based Center for Watershed Protection.

The center and the Office of Community Sustainability worked together to apply for a grant from the Maryland Department of Natural Resources Chesapeake and Atlantic Coastal Bays Trust Fund for the project, which cost $220,000, according to sustainability project and stormwater manager Lindsay DeMarzo.

A bioretention site is a garden that catches and soaks up rainwater and runoff from nearby lawns and impervious surfaces, including parking lots, patios and roofs.

Rain gardens look similar to typical gardens, but are dug deeper and include a mixture of soil, sand and compost.

Rain gardens slow down water as it flows to nearby streams and help filter out the three biggest pollutants to the bay, phosphorous, nitrogen and sediment, according to program director at the Center for Watershed Protection Greg Hoffmann.

At the Trinity School, the bioretention site will be designed to capture just over an inch of rainfall per storm, Hoffmann said. The school is considered a good choice for the bioretention site because of its available space near the discharge from the campus’ main water runoff pipes, meaning that the rain garden will easily catch stormwater runoff.

The school was approached by the county and the center about the project. Trinity is one of 203 nonprofits in a partnership with the county to allow it to assess the property for potential stormwater projects.

In exchange for the partnership, nonprofits can opt out of the county’s watershed protection fee, which costs commercial properties, including nonprofits, $15 per every 500 square feet of impervious surface.

The project fit well with the school’s envronmental philosophy, said Tom Pilon, a parent and volunteer member of the school’s Facilities Committee that approved the project.

Trinity is a certified “Green School” by the Maryland Association for Environmental and Outdoor Education, meaning it provides significant opportunities for environmental sustainability.

“We don’t believe we own the planet,” Pilon said. “We believe we’re stewards.”

Howard County is also trying to bring more residents into the watershed protection effort.

An increasing number of residents, who pay between $45 and $90 per property for the watershed protection fee, have opted to join the county’s homeowners’ rain garden programs.

The Office of Community Sustainability created two incentive programs for homeowners to construct rain gardens.

Since 2012, Cleanscapes has offered reimbursements up to $1,200 for homeowners to install a rain garden. Rain Gardens for Clean Water, established in 2016, brings in contractor Village Gardeners to build a rain garden on residential properties and the county pays 75 percent of the average $3,738 bill.

Residents have built 241 rain gardens through the Cleanscapes program and 40 rain gardens through Rain Gardens for Clean Water, according to DeMarzo. The Rain Gardens program has grown so popular that there is a 121-property waiting list.

The county’s Rain Gardens for Clean Water budget is $60,000 this year, which DeMarzo anticipates will pay for 15 to 18 sites. Each rain garden catches roughly a quarter to half of the water from impervious surfaces at a property.

While each of the gardens on their own may not save the bay, DeMarzo said that at the local level, it’s more important to get people involved in stormwater management efforts and keep their surrounding streams clean.

“If someone has a garden in their yard, while it might not be a huge amount, it’ll have a decent impact on the stream in their backyard or the nearest stream in their area,” she said.

“And if we clean up the streams in our backyard, the bay will most likely be able to heal — because our water is what’s filling the bay.”