The source of it has not definitely been discovered. Possible sources of the chlorine, officials said yesterday, include homeowners dumping old pool chemicals or a resident's leaking backyard pool. A similar kill occurred last year in Rockland County, when Clarkstown municipal workers used powdered chlorine to neutralize a sewer main break and ended up killing several hundred fish in a nearby brook. Stoutenburgh said the DEC could assess penalties, depending on its findings. Since Sunday, county and Yorktown officials have discovered several catch basins containing chlorine residue upstream of the pool.
Chlorine is used to disinfect drinking water supplies, pool water and sewage treatment effluent.
New York City adds chlorine to its drinking water but not until the water is in the pipes and ready for distribution. The chemical breaks down in water by reacting with other dissolved materials or sunlight. That's why Ryan and other officials aren't overly concerned about the spill's effect on the water supply and aquatic life downstream. The original shock, though, was enough to kill the trout, which are susceptible to low levels of the chemical. No dead fish were visible yesterday in the Amawalk River along Wood Street, about 500 yards south of Route 35.