Drinking water protection during the harmful algal bloom

Fri, 08/06/2021 - 21:30

The City of Winchester is monitoring the drinking water for potential effects.

The City of Winchester and the Virginia Department of Health (VDH) are monitoring the harmful algal bloom (HAB) currently affecting the North Fork Shenandoah River where the City obtains its water supply. The City is taking every precaution to prevent impacts to drinking water. At this time, the City’s water is safe to drink and there are no restrictions on drinking water use while monitoring continues.

Harmful algal blooms are caused by cyanobacteria, which can produce a variety of toxins known as cyanotoxins. Cyanotoxins can affect human health if consumed in excessive quantities over an extended period of time.

HAB impacts were first observed 1.5 miles upstream of the City’s raw water intake on July 27. Since then, the City optimized its treatment process for the removal of cyanotoxins. Enhanced water monitoring and optimized treatment activities will continue for the duration of the algae bloom, which could continue through October or longer.

Anatoxin-a is a neurotoxin produced by the HAB that can impact health. There is not a federally established health advisory level for anatoxin-a. VDH has established a level of 0.4 micrograms per liter as a very conservative level. If anatoxin-a is measured to exceed this threshold for ten or more days, then additional action will be necessary. 

Drinking water samples collected today by the City indicated the possible presence of anatoxin-a, however, these initial samples could not determine the exact concentration of anatoxin-a. The City is working with a certified laboratory to determine the exact concentration of anatoxin-a in the finished drinking water.

The City and VDH are actively monitoring the situation. The City will continue to monitor for cyanobacteria for the duration of the algae bloom and will advise the public if any protective action is warranted.

Customers with questions should contact Perry Eisenach, Public Services Director at the City of Winchester at (540) 667-1815, extension 1407.