Water and Wastewater Treatment Capacity FAQ

Data center developers and operators use different cooling technology – water cooled or air cooled – based on several proprietary factors. The decision about which cooling technology is used is owner-determined and project-specific. 

The drinking water provided by Prince William Water to serve new development in the western service area comes from public sources in the Potomac River and Lake Manassas, not from groundwater wells. Hence, public water supply does not affect ground water supply for private wells. 

Data centers do not decrease water supply availability to Prince William County. Prince William Water’s system has eastern and western components, with drinking water supplied primarily by Fairfax Water. See graphic below.

• Western Prince William County: Data centers are primarily located in the western areas of Prince William County. Western Prince William County drinking water is supplied by Fairfax Water’s Corbalis Water Treatment Plant, which draws from the Potomac River. Once used by data centers in western Prince William County, the wastewater is treated at the Upper Occoquan Service Authority Water Reclamation Plant and released as reclaimed water to the Occoquan Reservoir. In this water cycle, water used from the Potomac is reclaimed and released into the Occoquan Reservoir, adding volume.

   

• Eastern Prince William County: Drinking water for the east system is supplied by Fairfax Water’s Griffith Water Treatment Plant, which draws water from the Occoquan Reservoir. The eastern system does not supply data centers or other developments in western Prince William County and as a result development in western Prince William County effectively increases the water supply available to meet eastern Prince William County water demands.

As part of the Master Plan Addendum, Prince William Water explored the feasibility of a water re-use program for the Digital Gateway. While the study did not indicate that water re-use is viable for the Digital Gateway, this does not preclude considering water re-use for other projects.

No, Prince William Water has a strong and efficient planning process to monitor water capacity, use and timing of future demand to plan for purchasing additional water capacity. Prince William Water’s planning aligns with the Prince William County Comprehensive Plan and relevant land use policies. Additional purchased capacity must be timed in coordination with required infrastructure improvements for both Prince William Water and Fairfax Water, since purchasing additional capacity and delivering more drinking water may require infrastructure improvements.

Yes. Prince William Water can support development activity as envisioned in the Prince William County Comprehensive Plan, including the latest Comprehensive Plan update which included the Digital Gateway, with capacity currently owned by Prince William Water supplemented with the purchase of additional capacity when needed from Fairfax Water.  

As specific land use applications are submitted with the related water requirements, Prince William Water will continuously monitor and assess the availability of existing water supply and, if necessary, the required timing to purchase additional capacity from Fairfax Water. Any additional capacity from Fairfax Water would be withdrawn from the Potomac River. 

Prince William Water continually plans for water and sewer infrastructure improvements that are needed to support development activity. 

In December 2022, the Prince William Board of County Supervisors approved a revised Comprehensive Plan that removed public sewer restrictions in the Rural Area. Prince William Water conducted a Master Plan Addendum, which indicated that demands required by the updated Comprehensive Plan, including the Digital Gateway, may require additional water supply capacity to be purchased in the future. As noted, Prince William Water has the ability to purchase additional capacity from Fairfax Water when needed.  

However, the absence of water and sewer infrastructure in any given part of Prince William County is not an impediment to development under Prince William Water’s “growth pays for growth” policy, which requires that infrastructure extensions be designed, constructed and paid for by development applicants to serve their development.  

Prince William Water annually assesses water needs against the Prince William County Comprehensive Plan, ensuring supply meets demand through the Washington Metropolitan Council of Governments (MWCOG) planning timeline (currently 2045). Prince William Water closely monitors new demand requirements and regularly discusses demands and timing with project applicants. Prince William Water staff reviews various development scenarios and requirements to assess the timing of necessary water supply capacity increases and any required infrastructure improvements. 

No, existing customers do not subsidize new customers and growth. Additionally, Prince William Water does not receive Prince William County tax dollars. Prince William Water policy requires that “growth pays for growth,” meaning that developers pay the cost for new water and wastewater capacity and the infrastructure needed to support new development. This is detailed in the Prince William Water Service Connection Policy and the Development Review Process and System Improvement Policy.  
 

Data center water consumption depends on factors such as facility size, cooling type (water intensive or air cooled) and outdoor temperature. Prince William County had 34 data centers in 2023. Seasonal weather affects data center water use; facility water use is lower in winter and higher in summer. In 2023, data centers in Prince William County consumed approximately 1.4% of Prince William Water's average daily water demands and 6% of its maximum daily water demands.