A heavily traveled section of Maine Mall Road will be replaced this summer with porous pavement in an unusual effort to stop grease, salt and other pollutants from reaching the Long Creek watershed.

The Maine Department of Transportation plans to replace 1,500 feet of pavement that runs from Philbrook Avenue to Gorham Road with a special mix of road material designed to absorb and filter storm water.

The $2 million project is part of a larger effort by property owners in the Maine Mall area to meet a mandate by state and federal environmental officials to stop polluting the watershed, which flows into Casco Bay.

The effort by area landowners to meet the terms of the federal Clean Water Act also will involve an unrelated project to install a filtration system for cleaning storm water as it runs from business parking lots off Philbrook Avenue, next to the Econo Lodge motel.

Officials say the mitigation work should stop many pollutants from reaching the watershed, where it runs through this highly developed commercial area of South Portland.

Long Creek watershed flows into the Fore River and Casco Bay. It is classified by the state Department of Environmental Protection as one of the most polluted bodies of fresh water in Maine.

Stimulus funds from the American Recovery Reinvestment Act will help cover the costs of repaving the stretch of Maine Mall Road and developing the water treatment system off Philbrook Avenue.

Peter Newkirk, project manager with the state DOT, said rebuilding the stretch of Maine Mall Road should start this summer, with the project completed in October.

Drivers should notice little difference when driving on the porous pavement, which is composed of stones that are larger and coarser than the tightly packed rocks typically mixed with asphalt when paving streets.

“People driving at 25 miles per hour will not notice it. But the surface will look a little like rice crackers,” said Newkirk.

After storm water filters through the porous pavement instead of running off the highway, it will flow through existing drainage pipes to area streams and eventually to the Long Creek watershed.

Although the technology for making porous pavement is more than 20 years old, this will be the first time that porous pavement will be used on a state road in Maine. Examples of porous pavement include the parking lot of the Freeport town offices and a section of Interstate 95 in Massachusetts, at the New Hampshire border, Newkirk said.

Newkirk said porous pavement is more costly than traditional road materials and that replacing the small section of the Maine Mall Road will involve digging up the street entirely and replacing it with layers of new materials.

Crews will remove the existing road and dig down for 30 inches. The new road will include bottom layers of crushed stone and sand that will help to filter water as it seeps through 9 inches of porous pavement above.

Newkirk noted that because water “infiltrates the road,” there should be less splash or spray on vehicles as they drive across it in a rainstorm. “The overall function of it is that you won’t get puddles,” he said.

Maine Mall Road will be repaved on both sides, roughly from Longhorn Steakhouse to On the Border Mexican restaurant. The two-lane road has several travel lanes that exit to businesses. They also will be repaved.

Newkirk said the DOT will have a plan in place for redirecting traffic while the road work is under way to minimize the impact on neighboring businesses. He said the public will be well-informed of the road work to help ease congestion.

South Portland officials are pleased with the mitigation work planned for the Maine Mall area. The Department of Environmental Protection is enforcing a cleanup process for the Long Creek watershed involving older commercial properties that do not meet today’s water pollution standards. New developments already must meet stricter pollution control standards for storm water runoff, developed by the DEP in 2005.

The Long Creek watershed covers Westbrook, Scarborough and Portland. But the largest area is in South Portland, concentrated in the Maine Mall area near Interstate 295.

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