Their presentations were also a reminder that despite the upheavals in the Middle East and the growing efforts to minimize America's carbon footprint, water, not oil, could have a bigger effect on how Philadelphians live.
"We're always arguing about which is more important, carbon or water, water or carbon. It's really a fake choice," said Charles Waldheim, a landscape architecture professor at Harvard University. As he explained, it's impossible to separate rising sea levels from the climatic changes fueled by carbon emissions.
Many expect those changes to lead to increased rainfall in the Northeastern United States, which would make it harder for a city like Philadelphia to deal with the water that surges into its sewers after a heavy storm. More rain could make flash floods more common and increase pollution in the Delaware River, the main source of the city's drinking water.
As in many older cities, Philadelphia's underground sewer pipes collect both waste and rainwater and channel them together to treatment plants. But when it rains hard, facilities can't keep up and have to release untreated sewage into the city's rivers, city Water Commissioner Howard Neukrug told the symposium.
If Philadelphia expects to capture that excess flow, it needs to build a giant collector pipe around its perimeter, from the Betsy Ross Bridge to the Fairmount Dam, at a cost of about $10 billion. That project would gobble up so much revenue, Neukrug argued, it would leave the city with no money for anything else.
Instead, his department is focusing on alternatives, such as conservation. The city is pushing landowners to convert asphalt lots to porous surfaces that can absorb rain and slow the runoff into the city's century-old sewers.
"The goal is to make one-third of the city's land impervious within 25 years," Neukrug said. The city is converting 500 paved acres of its own to parkland.
