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American Society of Landscape Architects


November 2007 Issue

Nine Mile Rerun
In Pittsburgh, activists bring a biologically dead stream back to life.

By Peter Harnik

Nine Mile Rerun

If Pittsburgh was “Hell with the lid off,” as it was famously called during the worst of its industrial heyday, then its River Styx was surely Nine Mile Run. Polluted into lifelessness, buried in culverts, insulted with trash, gouged by flash floods, and stripped of its floodplain by vast piles of slag, Nine Mile Run was as close to biological death as a stream could get. Today it is the site of the largest urban stream revitalization project ever undertaken by the U.S. Army Corps of Engineers.

It is fitting that Nine Mile Run would be the site of such a grand experiment. For, as Jane Jacobs pointed out in her book The Economy of Cities, it is large urban areas that are always the first to confront mankind’s newest problems, and they are also always the first to be forced to solve them. The very industrial processes that led to Pittsburgh’s once-immense wealth also caused unprecedented problems for Nine Mile Run. Today the city is using some of that old wealth along with the creative energy of its politicians and some of its newest residents to devise solutions. But fixing the environment is harder than damaging it in the first place.

Nine Mile Run was named for the distance from its mouth on the Monongahela River to Pittsburgh’s Point, where the “Mon” meets the Allegheny to form the Ohio River. (Actually, they counted wrong; it should be Seven and a Half Mile Run.) Over the decades Nine Mile Run has been severely modified. The entire lattice of its five-mile-long upper watershed is buried under the streets, yards, and buildings of the eastern edge and suburbs of Pittsburgh. Eventually the westward-flowing waters reach the lush forest of Frick Park and emerge for the first time into the open, 2.2 miles upstream from the Monongahela. Soon after, the run merges with its main tributary, Fern Hollow, coming in from the north through the center of Frick Park. Joined together, the larger stream flows southwest under the massive superstructure of I-376, the Penn Lincoln Highway. The final race to the Monongahela takes it through a narrow channel between two astoundingly steep and high banks of slag that had been dumped for half a century on the former wetlands and wide floodplain of the stream.

In 1998, the last year of its almost two centuries of deterioration, Nine Mile Run was what is called a “flashy”—as in “flash flooding.” It’s a characteristic of most urban streams. Five million dollars of reconstruction later, it is still flashy, but a bit less so. And every succeeding year its ecology functions a bit better. To understand the problem—and the solution—requires getting down into the streambed.

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