SSO 700 is an unremarkable spot. Just a pipe, hidden by trees and brush, emptying into Mill Creek near downtown Cincinnati. ''It just gushes, even in dry weather,'' says Mike Fremont, president of the Ohio environmental group Rivers Unlimited. ''If you know what it is, you keep your distance.'' What it is, is human waste -- hundreds of gallons of it at a time flowing untreated from toilets into the creek. Sanitary Sewer Overflow 700 is not only disgusting, it is illegal. But the city won't shut it off because plugging SSO 700 and more than 100 pipes like it all over Cincinnati would require raising sewer rates about 1,500%.