Historic Catholic Church Cemetery Employs Green Infrastructure to Address Stormwater Pollution
It’s not every day that I attend a conservation event in a cemetery. Then again, the Mount Olivet Cemetery rain garden project is no ordinary project. New nature-based infrastructure at the cemetery is the result of a dynamic collaboration between The Nature Conservancy, impact investors, asset managers, engineers, and a new partner—the Catholic Church.
In 2015, Pope Francis released his encyclical on the environment, stating that Catholics have a “duty to protect the earth and to ensure its fruitfulness for coming generations.” The Archdiocese of Washington heeded the call and was inspired to tackle an environmental challenge in their own backyard: stormwater runoff at Mount Olivet Cemetery in Washington, D.C.
Tackling a Growing Source of Pollution
Washington, D.C. has a stormwater problem. When it rains, water rushes over impermeable surfaces like roads and sidewalks, and picks up pollutants like trash, oil and pesticides. These pollutants end up in storm drain systems and eventually make their way into local rivers, such as the Anacostia and Potomac. More than 3 billion gallons of stormwater runoff and raw sewage flow into D.C.’s rivers each year, making it the fastest growing source of water pollution both in the Chesapeake Bay and freshwater bodies worldwide.
At Mount Olivet, stormwater was flowing off paved surfaces in the cemetery and draining directly into Hickey Run, one of the Anacostia River’s tributaries. The Archdiocese knew something had to be done.
There are a few ways to address the pollution problem from stormwater runoff. One approach is to build underground tunnels and vats to collect pooled water and route it to water treatment plants. In the conservation world, we refer to this as “gray infrastructure.”
Another solution is “green infrastructure”—think of it as strategically engineering nature back into cities. These innovations do it all: capture the stormwater, slow down runoff, clean it up, cool it down, and slowly release it back into the river over time, mimicking natural processes. The result is cleaner rivers all around us. What’s more, green infrastructure typically costs less than gray infrastructure and provides a host of immediate co-benefits for free, like greening a neighborhood, reducing urban heat islands, cleaning the air, restoring nutrients to the soil, and creating local green jobs.
What does green infrastructure look like? At Mount Olivet, it means removing and replacing unused access roads with bioretention rain gardens. The gardens collect water and filter it through layers of mulch, soil, plants, and gravel—a process that has been proven to slow the speed of stormwater runoff and treat pollutants before they reach the river. Native vegetation also provides habitat for urban wildlife and pollinators, such as bees and birds.
Smart Policy Lays the Groundwork for Creative Solutions
Like many cities, DC has a mandate to address stormwater runoff. But the District has a unique advantage: innovative regulations on new construction that allow for cash flow generation.
There are two important components to these regulations. First, developers are required to address the stormwater runoff caused by their new construction and renovation projects—but they can take care of half of these abatement requirements by purchasing Stormwater Retention Credits (SRCs) from offsite green infrastructure projects. That’s where we get demand for the projects.
Second, properties throughout D.C.—both new and old construction—can install green infrastructure projects that generate credits. They can sell these credits back to developers to generate revenue and recoup their costs. There’s your supply.
The result is a market for SRCs that benefits nature, communities, and the economy. You can think of it as a triple win.
- Nature is protected when polluted runoff is captured before reaching local waterways. These projects also encourage the restoration of wildlife habitat and can improve air quality.
- Communities benefit from more green space and a reduction in localized flooding. Instead of building a green roof on a new hotel, developers can purchase credits from projects that bring nature to areas of the city that need it most.
- The economy gets a boost. Developers save money they would typically spend on solutions like green roofs and cisterns. Organizations like the Archdiocese can generate revenue and recoup the costs of green infrastructure projects through the sale of retention credits. And we can attract big investors who expect a return on their investment.
Diverse Groups Rally Around Common Goal to Protect Nature
Washington’s progressive regulations also facilitate partnerships with diverse organizations that can make big conservation gains. In this case, a religious organization, a conservation group, civil engineers, construction contractors, scientists, asset managers, and impact investors all came together to address the common goal of reducing stormwater runoff.
The project at Mount Olivet Cemetery is TNC’s first collaboration with the Catholic Church—and it turns out we have a lot in common. As the spiritual home to more than one billion people around the world, the Catholic Church is an ideal ally for conservation projects that will benefit nature and people in cities around the world. Cardinal Wuerl, the Archbishop of Washington, said it best during his remarks at the dedication event: “Pope Francis reminds us of the need for such cooperative efforts to care for our environment: ‘We need a conversation which includes everyone, since the environmental challenge we are undergoing, and its human roots, concern and affect us all.’”
Mount Olivet Cemetery itself is a noteworthy place for residents to visit. It’s the largest Catholic burial ground in DC and the first to be racially integrated. The Church is in the process of dedicating a memorial and is working with TNC to build a commemorative garden to honor the many people buried there who were enslaved. The garden’s design will provide reflective spaces for people and habitat for pollinators, using the power of nature to connect people with history. The garden will also host community educational events to share the story of those who were enslaved, disenfranchised, and denied the opportunity to have grave markers.
Our financial partners on this project didn’t just make this work possible—they also helped to show the world a new way to lever up investor capital to drive conservation. Because of DC’s progressive regulations and the potential to generate cash flow, we were able to raise 100% of the capital for the project from institutional impact investors: Prudential Financial provided the capital, Encourage Capital brokered the deal and helped to found District Stormwater, LLC in conjunction with TNC’s impact investing unit.
As the conservation partner on this project, TNC led the charge on developing nature-based solutions that both addressed the sacred functions of the cemetery and ensured maximum conservation benefit for nature. We conducted studies of the cemetery’s topography and soil composition to identify the most optimal locations for rain gardens. And we employed ground-penetrating radar to ensure that construction plans would maintain the sanctity of the grounds. All work was done in concert with the Church, who lived up to the Pope’s encyclical every step of the way.
Next Steps: Replicate and Scale
At TNC, we are replicating this model of