Fairfax Water Annual Water Quality Report

Every year public water suppliers are required to issue an annual drinking water quality report to their customers before July first of the following year. In June Fairfax Water released their report which can be found in its entirety at this link. Fairfax Water owns and operates the James J. Corbalis Jr. and the Frederick P. Griffith Jr. treatment plants. These plants are the primary source of water for most of Fairfax County and portions of Loudoun county and Prince William County. Fairfax Water acquired the City of Falls Church water distribution system (the green areas) as well as a tiny area (orange area) that serve approximately 120,000 people and obtain their water from the Dalecarlia and McMillan treatment plants, part of the Washington Aqueduct which is owned and operated by the U.S. Army Corps of Engineers.

The result is that now Fairfax Water provides water to county residents from their two water treatment plants and buy water from the Washington Aqueduct to supply residents in and around the City of Falls Church. These were historic systems that were once town owned. The newer developments around Merrifield and the Dunn Loring Metro Station are supplied water from the Fairfax Water owned plants. Thus, they are required to report on the water quality of all these sources. 

Both the Washington Aqueduct and Fairfax Water run excellent water treatment plants. All four plants use advanced technologies and practices in drinking-water treatment, which is the process of cleaning raw water to make it safe to drink. Fairfax Water reports that their water consistently surpasses all federal (US EPA Safe Drinking Water Act) and state standards. Of the 182 compounds that are required to be tested for, very few were found in the finished drinking water. Those found were in concentrations well below the EPA’s maximum contaminant levels under the Safe Drinking Water Act. Fairfax Water’s state-certified Water Quality Laboratory performs or manages the testing required by federal and state regulations. The Washington Aqueduct does the testing for the water they supply. 

Over the years as the county grew Fairfax Water expanded its infrastructure. They built the Frederick P. Griffith Jr. Treatment Plant first and then the James J. Corbalis Jr. plant and expanded their distribution system which today serves over 1.7 million people with the lowest water rates in the region.

In order to ensure that tap water is safe to drink, the EPA limits the amount of certain contaminants (a list of more than 90 contaminants) that can be in the water provided by public water systems under the Safe Drinking Water Act. When untreated water enters the treatment plants, coagulants are added to cause small particles to adhere to one another and settle in a sedimentation basin. The water is then filtered through activated carbon and sand to remove remaining fine particles. This produces water with extremely low turbidity and provides excellent barrier against pathogens such as Cryptosporidium and Giardia. 

Next, the water is disinfected with chlorine to kill harmful bacteria and viruses. A corrosion inhibitor is added to help prevent leaching of lead and copper that might be in household plumbing (Fairfax Water reports that all lead containing service laterals were removed from the system). Fluoride is added to protect teeth. Powdered activated carbon and potassium permanganate may also be added to the treatment process to remove taste or odor-causing compounds. In addition to these treatment steps, the Corbalis and Griffith plants use ozone to further reduce odors and organic material. Fairfax Water’s state-certified Water Quality Laboratory performs or manages the testing required by federal and state regulations. The Washington Aqueduct does the testing for the water they supply.

Fairfax Water and the Washington Aqueduct continually monitor and test the water during the treatment process and the finished drinking water as it leaves the plant and in customer homes a part of the Lead and Copper Rule testing. The Virginia Department of Health performs, source-water assessments for the watersheds. The assessment consists of maps of the evaluated watershed area, an inventory of known land-use activities, and documentation of any known source-water contamination within the last five years. Based on the criteria developed by the VDH, the Potomac River and the Occoquan Reservoir were determined to be of high susceptibility to contamination.

Nonetheless, the quality of the finished drinking water being produced at Washington Aqueduct and Fairfax Water is excellent. It meets or exceeds all United States Environmental Protection Agency (US EPA) standards and requirements. The water quality report released in June covers the sampling done during calendar year 2019. There were no violations of the U.S. EPA’s Safe Drinking Water Act. The full report is at this link.