It turns out the hazardous material that left about 100 dead fish floating in Piney Branch near Center Street North was ordinary tap water.
On Aug. 16, Greg Brown, regional biologist for the Virginia Department of Environmental Quality (DEQ) went out to Piney Branch to investigate calls from the hazardous materials team at the Fairfax County Fire Marshal's office, as well as from four local residents, describing the localized marine carnage.
One concerned resident was Bob McCahill, whose son, Colin, found the dead fish the day before. McCahill was concerned that something could be "terribly wrong" in the stream.
However, in a memo, Brown concluded that the kill had resulted from a water main break, which had occurred in town on Aug. 14 and spilled drinking water into Piney Branch. He estimated about 100 fish killed.
Lt. Terry Jenkins, at the Fire Marshal's office, said fish kills from tap water are not uncommon, resulting from the water's chlorine levels and from the sudden change in temperature. "We run into the same problem after there's a big fire, and there's been a lot of water flowed" in fighting it, Jenkins said.
Ed Stuart at DEQ added tap water also contains little to no oxygen for fish to breathe. He said recent weather was also a factor. High temperatures and lack of rainfall in early August had lowered water levels and already placed fish at risk. "Certainly, any aquatic life was under stress," said Stuart. When the cold, treated water rushed into the dehydrated waterway, it was "essentially replacing what's in the stream with water that has no oxygen," he said.
The Town of Vienna has estimated that about 2,000 gallons were spilled, which Stuart said is "not a lot, but it's enough when it's a small stream."
A support block under the water main had been washed away by erosion, and the pipe had burst while town employees were performing repairs, said Holly Chu, engineer with the Department of Public Works.
The tap water having passed through, the stream is again safe, she said. "Chlorine is a pollutant that evaporates, so there are no residual or lasting side effects and not much cleanup, either," said Chu.
She said the Department of Public Works had not reported the incident to DEQ quite as soon as it could have because some employees had been unaware that drinking water constituted a pollutant.
Once the main was broken, little could have been done to save the fish, anyway. However, Chu said a memo has been sent around the department in case of future incidents.