Philadelphia has announced a $1.6 billion plan to transform the city over the next 20 years by embracing its storm water - instead of hustling it down sewers and into rivers as fast as possible.
The proposal, which several experts called the nation's most ambitious, reimagines the city as an oasis of rain gardens, green roofs, thousands of additional trees, porous pavement, and more.
All would act as sponges to absorb - or at least stall - the billions of gallons of rainwater that overwhelm the city sewer system every year.
The plan's complex funding formula would raise rates somewhat but also attract grants and encourage private investment.
Further, the Water Department says the city's greening would result in more jobs, higher property values, better air quality, less energy use, and even fewer deaths - from excess heat.
The plan is a radical departure from the highly engineered tunnels and sewage plant expansions cities have traditionally opted for.
"This is the most significant use of green infrastructure I've seen in the country, the largest scale I've seen," said Jon Capacasa, regional director of water protection for the Environmental Protection Agency, which has the final say on whether the plan passes muster.
"We commend Philadelphia for breaking the ice," he said.
Whether the plan will work as the department intends is still being analyzed by regulators and environmental experts. (This will take a while. The printed plan is 3,369 pages.)
Theoretically, it's workable, said the Natural Resources Defense Council's water expert, Nancy Stoner. The green techniques "are well-demonstrated," she said. "It's the scaling up that's new. That's what's really exciting."
Others concur - mostly.
"I believe it's the most significant investment in transforming the city that we'll see in our lifetimes," said Patrick Starr, senior vice president of the Pennsylvania Environmental Council. "It will change the way neighborhoods look, the way many streets and blocks look."
Either way, cities big and small are watching to see whether Philadelphia can get the plan approved by the EPA and, if so, deliver on its promise.
"This has national implications," said Christine Knapp, outreach director with the state environmental nonprofit PennFuture.
Here's the trouble with storm water: 60 percent of the city has a combined sewer system, which means both runoff from streets and wastewater from bathrooms and kitchens flow through the same pipes.
In dry weather, the system works pretty well, considering that portions are more than a century old.
But when it rains - even as little as a tenth of an inch - the system overflows.
With no place to go, the water - now laced with road oil, litter, and raw sewage - gushes from 164 pipes directly into the Delaware, the Schuylkill, and Tacony, Pennypack, and Cobbs Creeks. Bacteria levels skyrocket.
Like many cities, Philadelphia is under orders to come up with a plan to reduce the overflows, which amount to 14 billion gallons a year.
About 12 years ago, when officials started devising the plan, they ruled out separating the storm-water and sanitary lines, as is already the case in newer sections of the city.
That would have involved reconfiguring 1,600 miles of pipes and digging up every yard and front walk.
Plus, "it's so expensive nobody even looks at it," said Villanova professor Robert Traver, a storm-water expert.
Two traditional options remained: massively expanding the city's three sewage plants or building gigantic underground tunnels to hold the overflow until it could be pumped back out and treated.
Neither was efficient. On sunny days, the capacity would be wasted. And both options were expensive.
The District of Columbia, for instance, is spending $2.2 billion mostly for three tunnels to handle sewer overflows of three billion gallons a year. The largest will be eight miles long and 23 feet in diameter.
Philadelphia is planning a small expansion of its plants, a minor part of the plan.
But when engineers began to figure what a Philadelphia tunnel would look like (35 feet in diameter) and where it would go (150 feet under the Delaware), they balked.
"Instead of figuring out how to manage this pollution, maybe we should be looking at how to prevent it in the first place," said Howard Neukrug, director of the Office of Watersheds in the Water Department. "Let's break down some of the barriers against nature and deal with rainwater where it lands."
The idea now is to "peel back" the city's concrete and asphalt and replace them with plants - with rain gardens, green roofs, heavily planted curb extensions, vegetated "swales" in parking lots, and mini-wetlands.
Everything from impervious streets to basketball courts would be replaced with paving made out of larger particles that let rainwater flow through and leave no puddles behind.
Where the changes occur on public land, officials hope to leverage other agencies - and share the cost.
Every time a street is dug up for work on utilities, for instance, it can be repaved - at a slightly higher cost - with a porous asphalt.
Or in the case of a playground, like the demonstration project at Second and Reed Streets in South Philadelphia, the Water Department lends its expertise.
The park's rain garden makes it prettier, and the shredded tires on the play surface are not only porous, but also safer for kids since they are soft.
Rina Cutler, deputy mayor for transportation and utilities, said that the effort reflected Mayor Nutter's GreenWorks sustainability road map announced in the spring and that she would do what she could to make this "gutsy" plan work.
As for commercial properties, the city now requires that large developments or redevelopments - ones that disturb 15,000 square feet of land or more - install systems to capture runoff.
For many projects, that means a green roof, which costs more but reduces heating and cooling costs and lasts longer. The one installed on the Philadelphia Museum of Art's parking garage - with one to five feet of soil - supports a sculpture garden.
In July, the Water Department will begin phasing in commercial rates based not on how much water a facility uses, but on how much impervious surface it has.
For a parking lot with, say, three acres of asphalt and two bathrooms, the rates will jump, giving owners incentive to repave.
As for residences, officials are hoping rain barrels on household downspouts become as common as the city's blue recycling buckets.
But even the plan's most ardent supporters see flaws.
For one, it doesn't go far enough. The EPA wants to see overflows reduced by 85 percent; this plan gets the city to just 80 percent.
Cost is also an issue. The department is projecting - with considerable margin for error, given the time frame - that implementing the plan will add $8 to the typical resident's monthly sewer bill over the next two decades, more than the EPA would like.
But this could change. Cutler thinks the plan is ripe for attracting federal funding.
And grants. "There aren't many entities that want to give you money for a tunnel," said Neukrug. "But if the objective is trees, there are a lot of organizations and folks and government agencies that are supportive of that."
Starr, however, is worried the plan depends too heavily on private landowners and an assumption that economic development will not stall.
The city has been shopping its plan to neighborhood groups.
Although there were a few concerns - people who don't like street trees, people worried that letting the rain soak in will make their basements wet - what astounded Water Department officials most was the enthusiasm they found.
Originally hoping to partner with three neighborhoods that would agree to have a few blocks rebuilt, they got such a positive response they upped the ante to 14.
"I love it," said the Rev. Chester Williams, president of the Chew and Bellfield Neighborhood Club. In his view, what's not to like about cleaner air, cooler houses, and prettier streets?
"We're just praying that it moves a little faster," he said.
Ken Kirk, executive director of the National Association of Clean Water Agencies, an industry group, said Philadelphia's plan is "very compelling. It may take a little longer, but at the end of the day, they will be using a lot less energy, they will be using the water resources more efficiently, they will be capturing and recharging groundwater under the city, they'll have less pollution of the rivers.
"So, from a lot of different perspectives, that is the way we want to go," Kirk said. "That is the way we need to go."