San Francisco supervisors approved an immediate, 45-day citywide halt to new data-center construction on Oct. 6, opening a review of the facilities’ potential environmental effects and putting planned projects on hold. The measure, introduced by District 10 Supervisor Shamann Walton and co-sponsored by Supervisors Connie Chan, Jackie Fielder and Cheyenne Chen, directs city planners to study data centers’ effects on water use, energy, air quality, land use and surrounding communities. The Planning Commission is expected to hold a hearing on the findings at the end of the pause. If the review identifies significant environmental impacts, the city could extend the moratorium for as long as 22 months or adopt permanent controls or restrictions. Walton has said he wants the temporary pause to lead to a permanent ban. “We need to know what these impacts are,” he said when announcing the proposal. “Until we know what that is, it needs to stop.” The freeze affects projects in several parts of the city, including a planned expansion of NOVVA, a 7.6-acre data center at 400 Paul Ave. in Bayview. The company had planned to raise the facility’s capacity from 9 to 36 megawatts by 2028. A separate proposal for a 160,000-square-foot data center at 1215 Michigan St. in Dogpatch has permits filed, but construction has not begun. The review comes as concerns grow about the resource demands and neighborhood effects of data centers. District 10, which includes Bayview-Hunters Point, already hosts two of the city’s largest facilities and has endured decades of disproportionate air pollution, including pollution linked to truck traffic and a now-closed PG&E power plant. The city’s study will examine what additional effects data centers may have. The legislation defines a data center broadly as a facility that houses computing equipment—such as servers, storage and networking systems—and associated power and cooling infrastructure, primarily to process, store or distribute electronic data. The pause also lands amid a District 10 supervisor race. Walton’s term ends in January 2027, and the leading candidates—Theo Ellington, J.R. Eppler and Dion-Jay Brookter—have supported a moratorium. At a recent candidate forum, all three said they would support a permanent ban, according to the report.