By Janet Raloff
New studies in California and Wisconsin reveal a dirty little secret: Out of sight, many urban sewer pipes are failing and germ-ridden filth is bleeding out.
The studies tracked material hemorrhaging into storm drains. These pipes, which channel their contents into streams and coastal waters, are designed to collect fairly clean rainwater and runoff from watered lawns. Yet raw sewage at times constituted nearly 20 percent of one local storm drain’s flow, reports Patricia Ann Holden of the University of California, Santa Barbara and her colleagues.
“We found the same thing,” says Sandra McLellan of the University of Wisconsin–Milwaukee. In the August Water Research, her group reports finding a bacterial indicator of human feces — Bacteroides — in samples from all 45 storm water outflows in the Milwaukee area that it monitored over four years. The data show that sewage contamination “is nearly ubiquitous in the urban environment,” McLellan says.