The District of Columbia has two main strategies for cleaning up its polluted waterways, and, on the face of it, they could not be more different.
The problem is this: Every time there’s a significant rain, Washington’s combined sewer and stormwater systems overflow, sending thousands of gallons of raw sewage and filthy surface runoff into the Potomac and Anacostia rivers.
‘Green’ and ‘Gray’ Strategies
One strategy for addressing this problem, the so-called “gray infrastructure strategy,” was formalized in a consent decree with the EPA in 2005. It calls for spending more than $2.5 billion to construct new massive tunnels that, when completed, would store the excess rainwater runoff until it could be treated. Since July 2013, a gigantic boring machine—longer than a football field and weighing 1,325 tons—has been working on the first of two tunnels, churning out miles of muck from beneath the Anacostia.
The second, “green infrastructure” strategy tries to address the problem in a decentralized manner before the rainwater ever gets to the storm sewer. This method, which the EPA approved in 2014, modifies the original plan to include innovations such as green roofs, municipal planter boxes, permeable pavements that allow rainwater to pass beneath, and rain gardens filled with water-absorbing plants in highly engineered stormwater retention cells.
Does this second approach really work? According to urban planning experts who participated in the inaugural Water and Green Infrastructure Lab held recently at Georgetown University’s School of Continuing Studies (SCS), the answer is a resounding yes. While “gray infrastructure” will always be needed, they say, “green” solutions are rapidly becoming part of an innovative city’s waste management strategy.
“We have to clean it up, but there are more innovative ways of doing it than laying big pipes,” said Martin O’Malley, the former Maryland governor, Baltimore mayor, and Democratic presidential candidate. O’Malley is a Senior Fellow at MetroLab, the national collaborative Georgetown belongs to that brings together cities, counties, and universities to develop solutions for some of today’s most pressing urban challenges.
An Antiquated System
The District’s water pollution problems are common to older cities whose sewer systems are over a century old and ill-equipped to handle the volume of use today. In addition, more than 700 of these cities have sewer pipes that carry stormwater runoff as well as sewage in a combined system. (This includes about a third of the District of Columbia’s network.) When rainfall overloads these systems, the municipalities must release this combined mix of sewage and stormwater into nearby waterways.
The sewage spills may grab headlines, but the stormwater runoff is also toxic.
“The problem is that urban stormwater runoff is a form of metropolitan-wide non-point source pollution,” said Uwe Brandes, Faculty Director of Georgetown’s Urban & Regional Planning master’s degree program. To visualize this pollution, think of what snow looks like after sitting on a city street for a few days.
“The only way to clean it up is to conceptualize how water flows through the metropolitan landscape,” continued Brandes. “This is a public space issue that has many urban planners working on new solutions.”
Other Projects Around the Country
At the start of the national MetroLab meeting at Georgetown, participants heard dozens of presentations on innovative green water projects from cities and universities from around the country. One issue for planners, said Phil Gaebler, Water Resources Specialist for Madison, Wisconsin, is: “How do you implement a [green] program when you have a budget of essentially zero?”
He said that Milwaukee’s sewer district held community-based gatherings to build interest with residents to install rain gardens on their property. This form of community-based engagement mixes policy briefings with the carrots of micro-subsidies for households.
“This represents a new horizon of urban planning practice: data-enabled, community-specific, place-based and performance-driven. This is what smart city planning is all about.” said Brandes.