Unfortunately in the 1890's Pittsburgh city engineers decided it would be more economical to combine sewer and stormwater pipes. After the population mushroomed, the rivers became so full of waste they became stagnant. The current system handles the waste water during dry weather but when it rains (as little as one tenth of an inch) raw sewage dumps out of the 19th century outfalls directly into the rivers.
Gardez L'eau is one of many potential alternatives to the resource heavy waste infrastructure. Other options including storm water management are located in the back of the accompanying magazine.
below image is from the book Humanure Handbook by Joseph Jenkins