PITTSBURGH — For more than a century, the Allegheny, Monongahela and Ohio rivers were the cradle of Pittsburgh industry and, in many ways, the American economy. Long before railroads, they were the only continental highway to the interior of the country.
As cities industrialized in the late 19th and early 20th centuries, enterprising engineers laid out combined sewer systems that funneled household and industrial waste straight to neighboring rivers. It was a novel if naive design later reinforced by mid‑century faith that bigger pipes and pumps could manage whatever cities sent their way.
“The thought was dilution was the solution,” said Douglas Jackson, director of maintenance and operations at regional sewer and wastewater treatment authority ALCOSAN. “And the rivers and the streams and nature can handle the rest.”…