Businesses near the Maine Mall will have to take additional steps to reduce pollution runoff under a federal and state ruling that could have implications for other commercial districts, including the Bangor Mall area.

The U.S. Environmental Protection Agency and the Maine Department of Environmental Protection are requiring the South Portland businesses to apply for permits under the Clean Water Act permits showing they are taking steps to deal with storm water runoff from their parking lots, roofs and sidewalks.

The landmark ruling applies only to Long Creek, a tributary to Fore River that empties into Casco Bay. But depending on the outcome, the approach could be replicated in Bangor where the Penjajawoc Stream near Bangor Mall faces similar – although less severe – pollution problems.

“We’re aware of that as a possibility in the future, but right now our focus is on Long Creek and showing that we can restore an impaired, urban stream,” said DEP commissioner David Littell. “I really want … to show people elsewhere that we can succeed.”

The Conservation Law Foundation, which petitioned for the action in South Portland, says storm water runoff is now the top pollutant of New England rivers, estuaries and oceans.

During storms, water flows off buildings, parking lots and other paved areas picking up toxins and chemicals along the way. The polluted water eventually gets dumped into neighboring rivers and streams from storm drains.

A discharge permit could require Maine Mall-area property owners to make upgrades to their storm water management systems. Those upgrades would range from relatively inexpensive fixes, such as planting trees or diverting runoff to vegetated areas, to retrofitting structures or building costly storm water retention systems.

The city of South Portland has been working with businesses and conservation groups for more than a year on voluntary cleanup measures for Long Creek. In a statement, members of the stakeholder group, known as the Long Creek Restoration Project, said they hope the agencies will allow landowners to continue to work collaboratively rather than requiring individual discharge permits.

Similar collaborative efforts are ongoing in Bangor. Local officials have been working for several years with the Bangor Mall-area businesses on solutions to improve water quality in Penjajawoc Stream and the surrounding watershed.

The city recently submitted a watershed management plan to the DEP that focuses on both improving the stream corridor and wetlands and reducing pollution from existing development. The stream and nearby Meadow Brook eventually flow into the Penobscot River.

Newer projects, such as the Super Wal-Mart under construction, are required to meet strict DEP storm water management regulations that were not in place when much of the area was built out.

Bangor City Manager Ed Barrett said area businesses deserve credit for working with the city and even jointly funding studies of the watershed.

“I think they recognize that there is a problem out there and they want to be part of the solution,” Barrett said.

Steve Hinchman, an attorney at the Conservation Law Foundation in Maine, also credited Bangor and local businesses for working to address the pollution issue in Penjajawoc Stream. And he agreed with Littell that the focus now should be on making this new approach work at Long Creek.

After all, Hinchman said, this is the first time the federal government is requiring storm water discharge permits under the Clean Water Act.

“We have a long way to go with Long Creek,” Hinchman said. “But really the writing is on the wall for other watersheds not only in Maine but throughout New England.”

Another problematic waterway in Bangor is Birch Stream. The city and DEP have worked with Bangor International Airport and the Maine Air National Guard to reduce runoff of toxic deicing chemicals into the stream. But resolving other storm water pollution issues will be challenging because the stream runs underneath the dense commercial district along Union Street.

Last month, the EPA invoked the Clean Water Act to require three Massachusetts towns to control the amount of polluted rainwater running into the Charles River. The Long Creek cleanup is expected to cost at least $2.5 million over 10 years.

James Houle of the University of New Hampshire Stormwater Center said the EPA only now is enforcing a law that has been on the books for decades.

“If you’re a developer, this is a wakeup call that says you’ve got to pay attention to this. You can’t just keep doing the same stuff,” Houle said.

The Associated Press contributed to this report.