(Updated at 4 p.m.) People and pets should avoid Four Mile Run downstream of Mount Vernon Avenue, Arlington County says.
The advisory follows a reported fish kill.
“County environmental staff are investigating a fish kill along Four Mile Run between Mount Vernon Avenue and Route 1,” the county said in an Arlington Alert message Wednesday morning. “Avoid contact with the water for at least the next 48 hours. Updates will be posted.”
A tipster told ARLnow that numerous dead fish could be seen downstream of Arlington’s sewage plant, near Potomac Yard.
“I would like to report seeing all of these dead fish in [Four Mile Run] just downstream from the wastewater treatment plant [at] 7:30 a.m.
today,” the tipster wrote.
On Wednesday afternoon, the county said its investigation found that an error at the sewage plant caused the fish kill.
From an Arlington County press release:
Water quality levels in Four Mile Run are returning to normal near Route 1 in Arlington after a fish kill – a sudden, unexpected death of a number of fish over a short period of time – occurred overnight.
An investigation found a manual operation error at the County’s Water Pollution Control Plant released higher-than-usual levels of sodium hypochlorite into the waterway late on March 12, 2024, as part of the regular wastewater treatment process. A correction was made in less than 90 minutes.
There is no ongoing threat to Four Mile Run.
Officials at the plant will review and refine procedures working with the Virginia Department of Environmental Quality.
County environmental staff are investigating a fish kill along Four Mile Run between Mount Vernon Avenue and Route 1. Avoid contact with the water for at least the next 48 hours. Updates will be posted. https://t.co/p4B3tho8rg pic.twitter.com/LLsE1XZpqq
— Arlington Department of Environmental Services (@ArlingtonDES) March 13, 2024