Two draft data center codes went to the public in the United States this week, one in Pima County, Arizona, the other in Bloomington, Illinois, and both reach past zoning and water into the generator yard. Pima County's planning staff presented their draft in a two-hour video conference on 8 October, reported by KJZZ the next day; Bloomington released its draft text on 9 October, reported by WGLT. Both are writing under their own moratorium: Pima County paused data center development in its unincorporated areas for 120 days on 22 September by a 3-2 vote, Bloomington's six-month pause runs out at the end of November.
Pima County: Certified Engines and Office-Hours Testing
The Arizona draft confines any data center over 25 acres to land zoned CI-2, about 2.3 % of the county, and requires a Type 3 conditional use permit, which means two public hearings and a Board of Supervisors decision. Open-loop cooling is prohibited, adequate water and power supply must be shown, and clean energy is preferred but not required. Diesel backup generators are allowed only if they are newer units certified by the Pima County Department of Environmental Quality. Generator testing, which the staff call the largest noise source of a data center, is limited to weekdays from 8 a.m. to 5 p.m. except in emergencies. The draft sets an absolute noise limit of 75 decibels and a setback of 100 to 200 feet, and the staff invited evidence for a larger distance and other buffers.
Chief zoning inspector Tom Drzazgowski told the meeting that each condition is measurable and enforceable, and that noise, to his surprise, drew more comments than water or energy. The county has received 1,200 to 1,500 comments, most of them against data centers altogether. The Planning and Zoning Commission hears the draft on 28 October; the Board of Supervisors is to vote in December, about a month before the pause lifts.
Bloomington: Thirty Minutes' Notice Before a Start
The Illinois draft sorts data centers into accessory, small-scale commercial (under 10 acres and under 10 MW) and hyperscale, the last needing a special use permit, a general manufacturing district and 1,000 feet from any home, hospital, daycare or school. Adjacent or jointly owned sites count as one, so a project cannot be split to stay below the line. Third-party reports on noise and vibration, water and energy are required before approval and every year after it, together with an emergency response plan, a description of the backup power source and a decommissioning plan under which generators, fuel systems and battery systems are removed when a site stands idle for a year.
The generator clauses are specific. No generators on roofs, vibration isolation required, at least 500 feet from residential, hospital, daycare or education buildings, and use generally prohibited except in emergencies. Developers must warn residents 30 minutes before generators are turned on. Noise is limited to 57 decibels from 7 a.m. to 7 p.m. and 47 decibels overnight, measured at the property line and at the lines of sensitive buildings within 1,000 feet. Planning Commission hearings are on 16 October and 16 November; the council is expected to vote on 23 November.
Reading Both Drafts From the Generator Yard
The 30-minute warning is the clause a commissioning engineer reads twice. An emergency start happens when the mains fail and cannot wait half an hour, so the notice can only apply to scheduled runs; how the final code treats an automatic transfer is the question to put to the city before a set is ordered. Weekday test windows are workable, but the monthly exercise, the annual load bank test and the commissioning programme all have to fit into them. "Newer and certified" in Pima County comes down to which emission certificate the engine carries, so ask the packager for the document, not the brochure.
The setbacks and the roof ban shape the site plan before anything else: a generator plant 500 feet from the nearest house, enclosed or containerised, with its intake and discharge attenuators chosen against a property-line limit measured at night. Those numbers sit in the permit and travel with the site, not with the generator brand. We covered the state-level side of the same movement in the New Jersey air permit item; the county and city codes are now catching up from below.
Sources: KJZZ, WGLT, AZ Luminaria, Coalition for Sonoran Desert Protection