Flagstaff planning commission weighs rules for data centers, asks staff for stricter standards and a prohibition alternative

FLAGSTAFF, Ariz. — The Flagstaff Planning & Zoning Commission on March 11 reviewed a staff proposal to add a formal definition of "data center" to the zoning code and to require conditional‑use permits and specific design and impact studies for any such facility.

"We probably had a bigger hole in our code than we wanted to leave open," Tiffany Antel, the city's zoning code manager, told the commission as she outlined the draft definition, an exception for small, ancillary server rooms, and new site‑specific standards. Antel also told commissioners that, under current practice, data centers could be treated as a heavy general industrial use unless the code is clarified.

Under the draft, data centers would be allowed only by conditional use permit in the heavy industrial and heavy industrial‑open zones and would not be permitted by right in light industrial areas. The proposal would add site design and architectural standards, require mechanical and cooling equipment to be screened, prohibit outdoor storage except during construction, and require perimeter fencing integrated with landscaping.

The draft sets maximum noise levels at 72 dBA during daytime and 65 dBA at night measured at the property line, restricts the use of backup generators to Tier 4 equipment for emergency and testing purposes only, and requires a baseline noise study and a noise‑contour exhibit as part of any CUP. Applicants would also submit an energy assessment with projected peak demand and the percentage of carbon‑free energy, and a water‑sewer impact analysis showing anticipated daily and annual water use and wastewater constituents.

"Data centers are currently allowed," Antel said during the presentation, explaining that the change would make the city’s regulation more specific rather than banning the use outright.

Commissioners and members of the public pressed staff on multiple fronts. Commissioner Norton questioned whether data centers belong in the city’s general and regional plans and said the proposal felt "incompatible with our city" unless the code gave clearer grounds to deny a permit. Norton and others said the conditional‑use process can be difficult to use defensively, because CUP entitlement analysis can favor applicants once a use is allowed by the code.

Several commissioners urged caution about state preemption — if the city tries to ban data centers, Norton said, it could face legal challenges or a state law requiring localities to permit them. Staff said adopting clear local standards could place the city in a better position if state legislation arrives.

Noise, especially so‑called infrasound (very low‑frequency vibration below 20 hertz), drew sustained attention. Commissioner Luki and multiple public speakers said existing acoustic limits may not capture low‑frequency effects that residents have reported around other facilities, and requested that infrasound monitoring be added to the baseline study requirement.

Public commenters raised related concerns. Kyro Russo, a local political scientist, told commissioners federal policy has moved to fast‑track some large AI/data‑center projects and said, based on his research, that "a small data center" can consume "about 360,000 gallons of water per day," a figure he urged the commission to consider when weighing water contracts and reclaimed‑water availability. Residents also asked about potential indirect effects on utility rates and long‑term decommissioning plans for facilities that later shut down.

Commissioner Shehi cited examples from other Arizona cities (including Chandler) that limit data centers to heavy industrial zones and add requirements such as mandatory sound‑attenuating walls, large setbacks, closed‑loop cooling, and decommissioning language. Several commissioners asked staff to research those options before the public hearing.

Staff told the commission it prefers strong CUP standards rather than an outright prohibition because prohibiting the use, they said, could increase the risk of state preemption. Commissioners were split: some asked staff to prepare a stricter CUP draft, while others asked for an additional draft that would prohibit data centers entirely so the council could consider both approaches.

Antel confirmed the timeline: the commission will hold a public hearing in two weeks, with a City Council public hearing on April 7 (first reading) and a potential second‑reading/adoption on April 21. The commission also asked staff to return with more technical detail from water services, sustainability and utility staff, stronger language on baseline and infrasound monitoring, and examples of mandatory setbacks and decommissioning clauses used elsewhere.

The work session did not include a vote. Commissioners directed staff to prepare both a strengthened conditional‑use draft and an alternate prohibition for the public hearing and council review.