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Tapping Green Infrastructure to Curb Sewer Overflows

Utilizing EPA research and guidance, Cleveland and Cincinnati plan to reduce sewage overflows with the help of sustainable, green practices.

Illustration of sewer system in dry and wet weather.

Illustration: Combined sewer overflows during dry and wet weather (note: "POTW" means "publicly owned treatment works").

Imagine running your shower for three thousand years or filling a swimming pool twice the size of Massachusetts. This is the rough equivalent of five billion gallons of water. The sewers of Cleveland, OH dump nearly five billion gallons of untreated sewage into Lake Erie every year. Even more impressive: the sewers of another Ohio city, Cincinnati, discharge 14 billion gallons of wastewater annually into the urban stream Mill Creek.

Like many cities across the country, Cleveland and Cincinnati suffer from aging wastewater systems that cannot properly handle the large amount of stormwater runoff that occurs during severe downpours. These cities have what is called a combined sewer system where sewage and stormwater merge into one series of pipes.

During heavy rainstorms, so much water runs off of common urban surfaces such as pavement and roofs that the system overflows. Combined sewer overflows (CSOs) discharge raw sewage and untreated runoff straight into nearby lakes and rivers, polluting valuable water resources and threatening public health and the environment.

Both Cleveland and Cincinnati have recently negotiated federal consent decrees (legally binding agreements between city, state, and federal agencies) that set CSO pollution reduction goals. The goals are ambitious, but both cities are up for the challenge, formulating plans for new installations and upgrades to existing sewer systems.

With support from EPA, these cities also plan to implement more environmentally-friendly and sustainable stormwater management projects, commonly referred to as green infrastructure.

"In the context of stormwater management, green infrastructure represents a set of practices that can rely on plants and soils to infiltrate, store, and transpire rainfall and excess runoff, or practices that catch rain before it turns into runoff," explains Dr. Bill Shuster, a research hydrologist at EPA.

Examples of green infrastructure include cisterns, green roofs, permeable pavement, wetland-like retention basins, and rain gardens. The goal of green infrastructure is to retain or redirect excess water runoff into the ground where plants and soil will naturally detain and filter the water—and keep it out of the sewers.

Following EPA's guidance and research, Cincinnati and Cleveland are on the leading edge of green infrastructure implementation.

Cleveland Turns Vacancies into Economic, Social, Environmental Assets

Based on technical guidance from EPA experts, part of Cleveland's consent decree Exit EPA Disclaimer calls for an innovative green infrastructure pilot program estimated to remove 44 million gallons of stormwater from the Northeast Ohio Regional Sewer District's (NEORSD's) combined sewer system. This green infrastructure program is intended not only to reduce stormwater runoff, but also to turn urban eyesores into community assets.

Two photographs of the same yard and house, displaying improvements in the more recent photo.

Before and after: Cleveland vacant lot before and after extensive post-demolition debris removal, soil management, and plantings. The once-vacant lot is now an attractive and functional part of the neighborhood.

"Back in June of 2009 I was in a meeting with the sewer district and other departments within Cleveland," recalls Shuster, who is technical advisor to the federal consent decree enforcement team for Cleveland. "It occurred to me that we have this surfeit of vacant land, and that this land could be used to sop up the excess stormwater runoff volume that otherwise goes into these combined systems and causes overflows."

The transformation of urban vacant lots into park-like gardens that catch stormwater runoff would not only help remedy the CSO problem, but also improve the social and economic fabric of neighborhoods historically lacking green space.

Shuster, along with regional EPA employees Brooke Furio and Bob Newport, became known as "The Green Team." Working closely with NEORSD, the Green Team used their research and knowledge to help formulate a plan for turning vacant land into green infrastructure systems.

Urban Soil Assessment

Before Cleveland's vacant lots could be converted to green, water-absorbing areas, researchers began an extensive survey of vacant lot soils to determine which soils would best retain stormwater runoff.

Led by EPA's Dr. Bill Shuster, researchers noted physical characteristics of soil core samples, measured nutrient composition and surveyed the natural vegetation of vacant lots.

These measurements help identify how excess stormwater will (or will not) move through surface and deeper soils.

Since little is known about urban soils, the results from this research will give guidance on where to locate green infrastructure so it can be most effective at taking in stormwater runoff.

This type of guidance should be of particular value to urban planners, land managers, and sewer districts.

"We were able to come in and put together what we know about vacant land, what we know about stormwater and wastewater, what we know about enforcement, and what we know about the cities that have to mediate and handle these enforcement orders and put together this project," explains Shuster.

In theory, many vacant lots, especially those in low income residential areas, will help to revitalize their neighborhoods once concrete and debris are removed and ponds, gardens, or other green systems are built in their place. This first-of-its-kind green project will also further EPA's work to advance environmental justice.

"We believe that it's a good way of comprehensively addressing social equity, economic stabilization, and environmental quality simultaneously," says Shuster. "I think our work has shown that proactively getting out there and making a national demonstration of this work in Cleveland, that hey, we can do this, we can work together, we can share risk, we can collaborate and adaptively manage towards optimal sustainable solutions. This is good stuff as far as environmental management is concerned."

Green Demos Foster Research in Cincinnati

The current draft of Cincinnati's consent decree Exit EPA Disclaimer calls for a 2 billion gallon reduction of CSO discharge by 2018. That's roughly the equivalent to 570 million toilet flushes.

Like Cleveland, Cincinnati's consent decree is destined to have a green infrastructure component.

Two photographs of the same yard and house, displaying improvements in the more recent photo.

Soaking it in: "It's like a mini research facility," remarks Alfaqih of the newly installed rain gardens at St. Francis Court Apartments Exit EPA Disclaimer in Cincinnati. Once the site of unused parking lots, the demonstration rain gardens host specialized monitoring and measuring equipment from EPA and the US Geological Survey.

Throughout the city, EPA scientists monitor green infrastructure demonstration projects to further increase understanding of how these systems work, and especially how reliable and effective they are for reducing CSO.

Along with similar monitoring efforts at Cincinnati State Technical and Community College, EPA installed sensors beneath porous pavement—pavement designed to soak in rainwater instead of diverting it to sewer drains. Elsewhere, EPA scientists are doing collaborative research with the University of Cincinnati to study rain gardens and porous pavement in terms of water infiltration and the effectiveness of these green systems.

"The science community needs this [research]," says Laith Alfaqih, of The Metropolitan Sewer District of Greater Cincinnati (MSD). "Green systems are in their infancy. How they work, the maintenance, the design of it, all these things are new, but with the help of the US EPA, the research, the implementation of these systems, and showcasing how they work…it's very important and helps a lot for the public and the science community."

EPA has partnered with the Cincinnati MSD and other local groups to study these demonstration sites, called "early success" projects.

This work in Ohio exemplifies how EPA and other organizations have come together to study and support green infrastructure as part of a successful wastewater management program.

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