Officials: Cheyenne’s data‑center water use currently small; city requires water‑efficient cooling

Cheyenne Board of Public Utilities (BOPU) engineering manager Frank Strong said the city’s data centers used about 93 million gallons of water last year — roughly 2% of local water sales — and that approved and under‑construction projects could add an estimated 120 million gallons annually under older (evaporative) cooling assumptions. Strong said a transition to closed‑loop cooling greatly reduces ongoing water demand.

"The data centers used around 93 million gallons of water... that's about 2% of our water sales," Strong told the panel, adding that with closed‑loop conversions the typical large building’s annual water use falls from an estimated 3–5 million gallons to about 400,000 gallons.

Jonathan Noble, who leads state and local government affairs for Microsoft’s cloud operations, described company commitments to design facilities that minimize water use and to move toward closed‑loop and air‑chilled systems. Noble said Microsoft will continue to coordinate with utilities and invest in local infrastructure and workforce programs.

Mayor Patrick Collins said the city requires water‑efficient cooling technology: "we do require technology to pool. ... It's got to be a technology that's water efficient." He and others explained that a closed‑loop system typically requires an initial fill (panelists discussed an example of about two acre‑feet, roughly 651,702 gallons) to charge the loop; after that the system recirculates water for years and uses only domestic water for toilets and sinks. Panelists noted maintenance flush cycles discussed in industry practice range from roughly three to six years depending on design, and said the city and utilities use conservative assumptions (three years) when modeling future demand.

On wastewater, BOPU and engineering staff said they meter every connection into a data center, have an industrial pre‑treatment and sampling program and have implemented attenuation requirements so large evaporative discharges do not overwhelm sewer capacity. The utility also reported a new local limits study reduced allowable dissolved copper from treatment plants; panelists said this prompted closer work with operators that used copper‑based piping in evaporative systems and required segregating cooling loop drains from sanitary sewer feeds or routing them for specialized treatment.

Panelists emphasized curtailment equity: if regional water allocations require reductions, data centers will be subject to the same staged conservation actions as other customers, starting with outdoor irrigation limits and moving to additional cuts as required.