Water in Washington, Arlington County Confirmed Safe to Drink as Boil Advisory Lifted

A glass of water is filled at a kitchen tap in this undated file photograph. Cate Gillon/Getty Images

Water in Washington and Arlington County was confirmed safe to drink again on July 4, just one day after precautionary boil water advisories were issued because of increased algal blooms.

The District of Columbia Water and Sewer Authority (DC Water) announced in a press release that all DC Water customers who had been under the precautionary boil water advisory may now use tap water for all purposes.

Officials confirmed that the drinking water provided by the Washington Aqueduct, which is sourced from the Potomac River, had “never deviated from U.S. EPA [Environmental Protection Agency] established water quality standards as had been anticipated.”

The boil notice was lifted as of 7:30 a.m. on Independence Day, according to the press release.

Just one day earlier, as the nation’s capital readied for the Fourth of July celebrations, DC Water advised all of its customers in the district, as well as the Pentagon, Arlington National Cemetery, and Reagan National Airport, to boil drinking water as a “conservative measure” to protect public health because of “unknown quality.”

Algae Blooms in Potomac River

The Baltimore District of Army Corps of Engineers runs the Washington Aqueduct, which produces an average of 135 million gallons of water per day for approximately 1 million people in Washington, Arlington County, Virginia, and other areas in northern Virginia, including portions of Fairfax County, according to its website.

In the initial advisory, DC Water said it had been notified by the Army Corps of Engineers that Dalecarlia Water Treatment Plant was reducing operations due to turbidity—or elevated cloudiness or haziness—in the water supply, and moving operations to the McMillan Treatment Plant.

Officials said the turbidity was linked to an increase in algal blooms in the reservoirs of the Potomac River, triggered by high temperatures.

“Algae blooms generally occur during high temperatures, causing conditions in water where nutrient levels are high,” the Army Corps of Engineers said in a July 4 press release.

The Army Corps noted that turbidity is an important factor in water quality because it can interfere with the effectiveness of water treatment processes and impact the color, taste, and smell of drinking water.

No Threat to Public Health

While turbidity has no known health impacts, it can indicate the presence of various disease-causing organisms such as bacteria, viruses, and parasites that can cause nausea, cramps, diarrhea, and headaches.

Those organisms pose a greater health risk to infants, young children, older adults, and individuals with compromised immune systems.

Washington Aqueduct employees worked throughout the night to ensure the water supply met water quality standards established by the EPA, according to a recent update from the Army Corps of Engineers.

“Staff closely monitored water levels, implemented additional mechanical and chemical treatment solutions, washed filters to increase production, made necessary chemical adjustments, and brought alternate filters online for additional treatment capacity,” the Army Corps of Engineers said.

“After determining the water replenishing process was successful with levels within normal ranges, and no threat to public health, the Washington Aqueduct recommended lifting the boil water advisory,” it said.

Caden Pearson contributed to this report.