Arlington Board Approves the Connection to Fairfax Water

At last week’s Arlington Board of Supervisors meeting the under the consent agenda the Board authorized the County Manager to execute the Agreement for Construction of Water Facilities and Emergency Use of Water with Fairfax County Water Authority, subject to legal review by the County Attorney.

Arlington obtains their water from the Washington Aqueduct, a federally owned and operated by the Army Corp of Engineers and dates back to 1853. The Aqueduct produces an average of 155 million gallons of water per day and sells that water to the District of Columbia (about 75% of the finished water), Arlington County, Virginia (about 15%), and the City of Falls Church, Virginia (10%). The Washington Aqueduct consists of the Dalecarlia Reservoir and Water Treatment Plant, the Georgetown Reservoir, and the McMillan Reservoir and Water Treatment Plant. The Washington Aqueduct draws water from the Potomac River and treats it to provide finished drinking water to the water distribution companies that buy water from them.

The maximum capacity of the Aqueduct is 320 million gallons of water per day much more than even the peak demand for drinking water and fire fighting for their customers. Water use peaked at an average of 180 million of gallons a day nearly 20 years ago, the system was expanded in the 1950’s anticipating serving Montgomery and Prince George counties, but the Washington Suburban Sanitary Commission (WSSC) instead built what is today the WSSC's principal water supply facility, the Potomac River Filtration Plant in western Montgomery County to supply their needs. Despite the excess capacity, the water supply remains vulnerable to a chemical spill or other disruption in the Potomac River upstream from the Aqueduct’s intake.

This deal with Fairfax Water is an insurance policy. Fairfax Water has two water treatment plants. The Corbalis Water Treatment Plant, the newer of the two also draw water from the Potomac River. However, the older Griffith plant draws from the Occoquan Reservoir. Fairfax Water produces 160 million gallons of water per day from both the Corbalis plant and the Griffith plant, but the combined total capacity of both plants is 345 million gallons/day. In an emergency when intake from the Potomac River is not possible for an extended period of time this water main could supply water to Arlington and Falls Church balancing the use of the regions Reservoirs and water supply by the ICPRB.

There is already a half mile water main connecting Falls Church to the Fairfax Water system. This project would extend that by another three quarters of a mile to Arlington along North Powhatan Street for emergency use purposes. This project provides redundancy for Arlington County’s water supply in case of an emergency. Currently, its sole water supply is from the Washington Aqueduct. Fairfax Water estimates that the Powhatan Street Main Cost will equal $2,875,000. The Arlington County portion is 70%, currently estimated at $2,012,500. Fairfax Water will build, maintain and operate the water main.

The quality of the 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 release at the end of 2019 covers the sampling done during calendar year 2018. There were no violations of the U.S. EPA’s Safe Drinking Water Act and you can view the report here. The Aqueduct report can be viewed here.