Pima County writing zoning rules for data centers

For people living near Tucson’s industrial corridors, the rules governing large data centers could soon determine whether facilities are built close to homes, how much water and power they consume, and who gets to approve them. Pima County is drafting new zoning standards after placing a temporary hold on permits for new data centers, while the city of Tucson has already adopted a separate set of restrictions for the largest facilities. Together, the actions reflect growing concern across the region about the effects of an industry expanding alongside Arizona’s demand for electricity and digital infrastructure.

The county’s proposed ordinance would limit data centers to areas zoned for heavy industry. Facilities larger than 25,000 square feet, roughly one fourth the size of a Costco, would require public hearings and approval from both the Pima County Planning and Zoning Commission and the Board of Supervisors. Large data centers would also have to be located at least one half mile from homes. The standards would apply to future projects, but not Project Blue, which already received approval before the county began considering the new rules.

The county’s temporary pause was adopted while officials study where data centers should be allowed and what safeguards are needed. It is scheduled to expire in January, shortly after the county expects to finish its work on the zoning proposal. Planning officials are expected to refine the draft at a meeting in early December before sending it to the supervisors for a final vote later that month. The pause gives the county time to act, but it has also prompted a legal challenge from the Goldwater Institute.

Jon Riches, the institute’s vice president for litigation, argues that the moratorium violates state law. He cited Proposition 207, the Arizona Private Property Rights Protection Act, which can allow property owners to seek compensation when new regulations reduce property values, as well as Title 11, which governs county powers. Riches said a development pause must be tied to proof of an imminent threat, and he questioned whether the county has enough evidence to meet that standard. He said the county’s health study framework acknowledges that clear empirical evidence is still limited regarding exactly how data centers affect public health.

Pima County Supervisor Jennifer Allen disputes that interpretation. She said the county relied on Title 11 and believes it permits a temporary halt when existing zoning does not adequately protect public health. Allen also distinguished the health framework from the evidence supporting the moratorium, saying the framework is a method for evaluating possible impacts, not a report claiming that every data center presents an immediate danger. She pointed to research and observations that data centers can increase surrounding temperatures, a concern she connected to excessive heat warnings and heat related deaths, particularly in rural communities where residents may have fewer options for finding relief.

Water, energy, noise and health concerns have shaped the county’s process. In a survey of nearly 2,000 people, more than 86 percent said they were worried data centers would use too much water. Respondents also expressed similarly high concern about electricity consumption, noise and broader health effects. One county planning commissioner, Bob Cook, voted against the draft ordinance because he believes data centers should be prohibited altogether. He cited the region’s water and energy pressures, housing affordability concerns and the possibility that the industry could affect communities for decades.

Commissioner Valerie Lane supported the county proposal but warned that local rules may not be enough. Data centers can draw on water and power resources across jurisdictional boundaries, she said, so Tucson, Pima County and neighboring counties should coordinate their standards. If one jurisdiction adopts strict rules while another has looser requirements, Lane said, developers may simply shift projects to the easier location. The Goldwater Institute’s legal position also highlights the limits local governments face when they try to restrict property uses that were previously permitted.

Tucson has already taken a more detailed regulatory step. The City Council voted 6 to 1 to adopt one of the city’s strictest zoning frameworks for hyperscale data centers, with Council Member Nikki Lee casting the lone dissenting vote. The ordinance does not automatically allow these facilities in any city zone. A proposed center larger than 25,000 square feet or using more than 20 megawatts of power must seek a Planned Area Development or Planned Community Development rezoning. That process includes a neighborhood meeting, a zoning examiner hearing and a final vote by the mayor and council, a level of review also used for power plants.

The city rules require large facilities to be at least one half mile from homes and schools and 1,000 feet from commercial development. Applicants must complete noise studies and limit generator noise. Backup generators may operate only during power outages or scheduled tests. Drinking water cannot be used for cooling unless a project meets city water requirements and enters into a formal water agreement. Only 40 percent of a site may be developed, with the remaining land preserved as natural space or replaced through payments for conservation elsewhere.

Public testimony before the Tucson council was largely opposed to the ordinance, with many speakers calling for a ban or stricter requirements. Critics said the rules could still leave parts of the city’s south side and areas near the Tohono O’odham Nation’s San Xavier district open to development. Vivek Bharathan of the No Desert Data Centers coalition described that potential siting pattern as environmental racism. Other residents questioned whether companies would follow the requirements and criticized the city’s public engagement process. Council members said several personally oppose hyperscale facilities but considered the ordinance necessary because, without it, a developer could seek approval under existing zoning rules without the new safeguards.

The council also directed city staff to keep studying a legal route toward a complete ban and to return within one year with a review of how the ordinance is working. Staff said adjustments could come sooner if needed. Council members raised additional future issues, including decommissioning and site reclamation, while another suggested that small projects reusing vacant buildings might deserve separate consideration. For now, Tucson has immediate controls in place, while the county is still deciding how far to go. The coming county hearings will determine whether Pima County follows the city’s regulatory model, adds stronger protections or moves closer to the outright ban sought by some residents and officials.