Storm water is nasty and dirty and can cause flooding. So the sooner it gets off a property, the better.
But it's about to become valuable stuff in Philadelphia. Businesses can make money by embracing it. Or face losing money if they let it go.
This week, the Water Department is sending notices to 79,000 commercial customers about a new billing structure for storm water that will begin in July.
As always, there will be winners and losers.
By the end of a four-year phase-in period, at least 1,500 customers could see an increase of $500 or more a month in their bills, said Joanne Dahme, public affairs manager for the department's Office of Watersheds.
About three dozen unlucky customers could see hikes of more than $10,000 a month.
But the program isn't just a stick. As a carrot, it's offering discounts for those who reduce runoff.
The program will not affect residential customers.
Currently, storm-water charges are embedded in sewer bills, which are based on water use.
But everyone knew this wasn't fair. It didn't account for storm water's gushing from a site into the sanitary-sewer system - which costs the city more than $100 million a year to maintain.
Plus, 40,000 city properties that have no water meter - vacant lots, parking lots, and utility rights-of-way - get sewer service for their storm-water runoff for free.
Now the city is factoring in storm water not only as a way to make billing fair, but also to encourage ways to reduce the flow every time it rains.
It's separating out the storm-water charge and basing it on the size of the property plus the amount of "impervious" surface, which prevents the absorption of rain into the ground.
The potential losers are those with low water use, and thus low bills now, but big roofs or parking lots.
Philadelphia International Airport - at nearly 700 acres, more than half sealed off by runways, parking lots, and roofs - tops the list.
Its monthly bill could triple from $53,000 to nearly $180,000 by the end of the phase-in, the city estimates.
Customers with smaller sites and large water use - hospitals, high-rises, and chemical companies, for instance - could see their bills decrease.
According to initial calculations, the Hospital of the University of Pennsylvania tops that list, with its monthly bill set to shrink from nearly $14,000 to less than $2,500.
But all this can change, Dahme said. Businesses can reduce their bills by installing retention basins, green roofs, and porous pavement.
So while airport chief executive officer Mark Gale said he was "very concerned about the financial impact," changes are already in the works.
The new employee parking lot has a "bioswale" to absorb runoff, and a recent environmental plan outlines other steps that could reduce the bill "substantially," he said.
The new effort comes five months after the city announced a 20-year $1.6 billion storm-water plan that experts have called innovative.
The problem is that more than half the city has "combined" sewers - pipes that carry both storm water and sewage. When it rains, the system fills quickly. The surplus, which includes raw sewage and road oil, backs up into basements and gushes untreated into rivers through 164 overflow pipes.
Other major cities have opted to build miles-long, multibillion-dollar tunnels to hold storm-water overflows, pumping it back into the system when the rain stops.
Philadelphia's plan envisions transforming the city into an oasis of rain gardens, green roofs, treescapes, and porous pavements.
Advocates say it's cheaper than the tunnel and has many other benefits, including a prettier city, which leads to higher property values.
The new storm-water rates help bring the vision closer, said environmental lawyer Joseph M. Manko, chair of the Pennsylvania Infrastructure Investment Authority, which has approved a $30 million low-interest loan for the Water Department's greening.
"If you tell people whose bills that may go up, 'You have the right to reduce them, and four years to phase it in,' I think there's going to be a real impetus" to change, he said.
There are, of course, concerns about the impact on business revenue.
Many properties with large buildings and parking lots "are also places of employment," said Patrick Starr, a vice president of the Pennsylvania Environmental Council.
They include factories and retail spaces like Franklin Mills Mall, where the monthly bill could rise from $8,000 to $52,000.
But Starr also called the plan "a great model." He said many companies would likely look at the long-term economics and offset as much as they could. "This stuff is really doable," Starr said.
Manko and others do not fear creating another Board of Revision of Taxes, faulted for wildly divergent assessments and undue political influence. The storm-water plan "is equitable. It's rational," Manko said.
While real estate assessments can be squishy, storm water is science, said Shandor Szalay, senior technical director for AKRF Inc. in Marlton. The city hired the environmental planning and design firm to work with the hardest-hit customers.
"These are established practices with established design standards," Szalay said. A set amount of rainfall creates a specific volume of storm water at a certain size facility.
What made the new storm-water-rate system possible was new, sophisticated mapping techniques that allowed the city to delineate how much impervious surface each parcel has, Dahme said.
The billing formula, however, has meant that a property's sheer size can drive up rates. This has led to some surprises, bumping absorbent parcels that nevertheless have large footprints - like golf courses and cemeteries - toward bigger bills.
The Schuylkill Center for Environmental Education, a 250-acre island of green in Upper Roxborough, wound up No. 31 on the list of potential losers, with the possibility its bill would rise from $118 a month to $11,270.
"That's more than some people make around here," said executive director Dennis Burton, once he got his breath back.
But he's confident the center's new storm-water plan - a green roof and two rainwater cisterns - will be enough to negate the increase.
"Maybe we'll even get a rebate," he added. "We're a nonprofit. We could use it."
Indeed, Dahme cautioned that the new mapping did not take into account storm-water facilities currently in place.
So for those alarmed by their notices, she advised: "Don't have a nervous breakdown." Instead, take stock of the property. "We need to hear about your trees, your woods, your meadows," she said. "What is your property already doing?"
Steven Cupps, development manager for Realen Properties, a Philadelphia developer and property manager whose real estate fleet includes a parking garage, called the plan "capitalism at its best."
"What's really exciting is they've figured out a way to make it economically expedient to get on board," he said. "To put on green roofs . . . to get the credits so you don't have to pay the monthly fee."
It's already happening, Szalay said. Franklin Mills is looking into how an existing retention basin can be modified to capture more storm water.
Cardone Industries, a Northeast Philadelphia company that makes auto parts, plans to construct a naturalized retention basin that would manage 20 acres of runoff.
Contact staff writer Sandy Bauers at 215-854-5147 or email@example.com.