Land, Noise, Diesel Generators, Light and Traffic

Big campuses take big land. The Gemstone Technology Park near Kuna, Idaho covers about 620 acres, and Meta's nearby site about 485, according to a February 2026 guest column in the Idaho Capital Sun by Adam Young, a Bingham County farmer. The Idaho Conservation League puts Gemstone at 600 to 800 MW. Tucson's Project Blue sat on 290 acres with up to 10 buildings and about two million square feet planned, according to Data Center Dynamics. Most buildings are one or two stories, so a campus spreads out more than it rises.

At a hearing, size matters less than zoning. Ask what zone the parcel is in, what the zone allows, what it sits next to, and whether the county is being asked to change any of that.

Zoning and land use

Many county codes written before 2020 do not mention data centers at all. Planners then slot them into "warehouse," "light industrial" or "utility," each of which may carry different setbacks and noise rules. Watch for these moves at a hearing:

• Rezone from agricultural or rural residential to industrial.
• Conditional use permit where the zone allows the use only with conditions.
• Text amendment that adds "data center" as a permitted use, sometimes countywide.
• Annexation into a city to get city water and sewer, the step that sank Project Blue in Tucson.
• Development agreement, a contract spelling out roads, utilities and payments.

A text amendment deserves the most attention. It applies to every parcel in the zone, including ones nobody at the hearing is thinking about.

Noise

The sound comes mostly from rooftop and yard cooling equipment: fans, chillers, dry coolers, transformers. It runs day and night. Virginia's JLARC concluded in 2024 that data center noise is low-frequency and generally not loud enough to damage hearing or break noise ordinances, but that some nearby residents say the constant hum affects their well-being. JLARC also found that most data centers generate no noise complaints at all.

Most limits use dBA, which discounts low frequencies, so a hum can annoy people while the meter stays under the limit. Ask whether the ordinance or the developer's study includes a C-weighted or octave-band measure. Distance also matters. Sound from a single point source drops about 6 dB each time distance doubles. A unit measured at 70 dBA at 50 feet is about 64 at 100 feet, 58 at 200 and 52 at 400, before walls and berms. A yard of 40 units is not one point source, so a developer's model matters more than this rule of thumb.

Backup diesel generators and air permits

Nearly every data center keeps diesel generators to ride through outages. JLARC found almost all Virginia sites used them, mostly EPA Tier 2 units permitted for emergencies and maintenance testing only.

The federal rule at 40 CFR 60.4211(f) caps maintenance and readiness testing at 100 hours a year per emergency engine, of which up to 50 may be used for limited non-emergency purposes. It bars using emergency engines for routine peak shaving. Emergency hours are unlimited. State permits often set tighter limits.

JLARC found Northern Virginia's data center generators produced less than 4 percent of regional nitrogen oxide emissions and 0.1 percent or less of carbon monoxide and particulates. Regional shares can still hide local exposure next to a yard of 100 engines on a test day, which is why Virginia DEQ was studying local effects.

A generator fleet that size usually needs a state air permit before construction. In Idaho, the Department of Environmental Quality applies the Rules for the Control of Air Pollution in Idaho, IDAPA 58.01.01, with permit-to-construct requirements in sections 200 to 228 and exemption categories in sections 220 to 223. The application lists every engine, its tier, its hours and modeled emissions at the fence line. Ask DEQ whether the permit will go out for public comment, and when and where the notice will be posted.

What to find in the air permit file	Why
Number, size and EPA tier of engines	Tier 4 units emit far less than Tier 2
Hour limits per engine and fleet-wide	Caps on testing and non-emergency use
Testing schedule (one engine at a time or many)	Simultaneous tests create local peaks
Modeled concentrations at the property line	Shows nearest-neighbor exposure
Fuel storage volume	Spill planning and fire code
Reporting and recordkeeping	What logs you can request later

Light and traffic

Security lighting runs all night. Ask whether the county has a dark-sky or shielded-fixture standard and whether it is written into the conditions.

Traffic is mostly a construction problem. JLARC reported that each building takes 12 to 18 months with up to about 1,500 workers at peak. Add concrete trucks, steel and transformers on oversize loads. Once open, a typical 250,000-square-foot building has about 50 workers, so daily traffic drops sharply. The county road department or state transportation agency will have the haul route and any road use agreement.