NORWALK, Conn. The flood waters of Hurricane Irene came within 1 foot of topping the dike of Norwalk's wastewater treatment plant Sunday, according to Hal Alvord, director of the Department of Public Works. Some of the plant's effluent was released into Long Island Sound in a chlorinated state after primary treatment only.
On a normal day, the plant runs at 14 million gallons a day. "There were times on Sunday morning when the plant was flowing at a rate of almost 100 million gallons a day," Alvord said. "[That was] only a peak for a short period of time. Consistently we were running at about 40 million gallons a day in the height of the rain, from Saturday night through Sunday. That means we were in storm flow. Of that 40 million gallons, 34 million gallons got full treatment, the other six million got primary treatment."
Primary treatment includes the fluid flowing through a screen to trap grit and other substances. The effluent was heavily chlorinated, Alvord said. "We would normally de-chlorinate before going out into the harbor. It was released fully chlorinated," he said. That gets reported to the Connecticut Department of Environmental Protection.
Storm water also impacted other elements of Norwalk's wastewater treatment system: the 22 pumping stations for neighborhoods that are downhill. Each has a backup generator, but the one on Bell Island was swamped by storm surge and died underwater. Residents were without sewage treatment from 4 a.m. Sunday to early afternoon Tuesday.
Eight other pumping stations lost power and went onto backup generators.
Alvord said his department had plans to button up the treatment plant if it lost power, went to backup generators, and then lost those in a major flood. Fortunately, that did not happen.
"The treatment system worked OK," he said. "I was concerned if that got overflowed and we had to button up the treatment plant the mayor was going to have to tell people, Don't flush your toilets."
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