Rescuers glided through several city neighborhoods in fishing boats and canoes on Tuesday, searching water-logged houses for trapped residents and abandoned belongings, after heavy rains flooded Georgia and other parts of the Southeast. The deluge left eight people dead, dozens stranded and thousands without electricity. As the mucky red-brown waters slowly receded after days of torrential rain, Gov. Sonny Perdue of Georgia declared a state of emergency in 17 counties and pleaded for federal aid. The state insurance commissioner estimated that $250 million worth of damage had been done, mostly to homeowners without insurance. As much as 15 to 20 inches of rain pounded counties around Atlanta for more than 72 hours, and while the rain subsided on Tuesday morning, the authorities were still dealing with dangerous repercussions. A sewage treatment plant northwest of Atlanta flooded late Monday and into Tuesday, spewing sewage into the Chattahoochee River, which had already swollen to at least 12 feet over its minimum flood stage level. City officials said the damage to the plant would amount to tens of millions of dollars. By 5 a.m. Tuesday, 17 bridges across the state were closed, along with sections of major Interstate highways in the Atlanta area, including I-20 and I-285. Several of the deaths occurred on roadways that had suddenly become impassable because of rushing waters. On Tuesday morning, the body of 14-year-old Nicholas Osley was recovered from a cornfield flooded by the nearby Chattooga River in Trion, Ga., according to a spokeswoman for the Chattooga County Emergency Management Agency. On Monday, the teenager and a friend had rushed to an abandoned car to rescue the occupant, not knowing the occupant had already escaped. Nicholas was swept away by the current, while his friend was rescued, the spokeswoman said. Later on Tuesday afternoon, the body of a woman was found in Douglas County, bringing the state