Aurora committee approves Butterfield data center final plan with stringent noise, testing conditions

The Building, Zoning and Economic Development Committee approved revisions to plats and the final plan for the Butterfield Phase 2 Unit 5A data center campus in Aurora on Sept. 24, authorizing consolidation of lots and the construction of a single larger data center building while attaching a set of staff‑recommended conditions focused on noise control, stormwater and site access.

The committee voted 4‑0 to approve three related actions: vacation of a water‑main and cross‑access easement, a final plat revision consolidating two lots, and the final plan revision for the Butterfield Phase 2 Unit 5A complex. The final plan approval includes conditions requiring third‑party sound verification before occupancy, full‑height walls around generator yards and closed‑loop, low‑water chillers.

Why it matters: nearby residents and aldermen raised concerns about noise from other data centers in the area. Committee members and city staff negotiated conditions intended to produce enforceable checks — including field sound testing at worst‑case operating conditions and a provision allowing the city to require additional third‑party testing if complaints continue.

City planning staff introduced the item. “The petitioner is requesting a final plan revision on Butterfield Phase 2 Unit 5A … in the form of a data center,” Jill Morgan, senior planner, told the committee, explaining that the revised proposal replaces previously planned smaller buildings with one larger building and includes associated easement vacations and landscape buffering.

The developer, Seafreed Properties, and the proposed operator, Edge, described technical and community mitigation measures. Doug Houser of Seafreed Properties said Edge is pursuing sustainable designs and that the project will use closed‑loop cooling and “integrated electric vehicle charging” that will be available to the public, beginning with eight chargers at the site’s north corner. Patrick Rice of Edge described the operational focus on low power usage effectiveness (PUE) and said proprietary Maglev chillers and other systems improve efficiency and reduce noise.

Noise and testing commitments were central to debate. Alderman Will White pressed whether testing would include nighttime measurements; Houser and the developer team said tests would be conducted at night if the issue arises, and that occupancy would not be granted until field testing confirmed compliance. The committee’s final written conditions require a third‑party acoustical engineer to confirm that the modeled sound emissions match field measurements at building commissioning and again prior to issuance of any certificate of occupancy.

Acoustical consultant Joe Keefe of Ostergard Acoustical Associates summarized the firm’s modeling and testing: the firm measured chillers and generators in controlled settings and incorporated those measurements into a conservative model accounting for terrain, reflections and wind effects. “Garbage in equals garbage out,” Keefe said, describing why vetted source measurements are necessary to produce reliable predictions.

Other conditions adopted by the committee require: updated fire access plans; architectural drawings showing vibration isolation mounts and sound‑attenuating screens or parapet walls around chillers; full‑height walls enclosing generator yards; manufacturer‑rated, low‑noise fan and condenser options; a plan to install aftermarket baffles if field testing shows noncompliance; and records retention and disclosure of test results to the city upon request. The staff memo also notes the project’s stormwater detention exceeds site requirements and that the project owner is working with ComEd on a substation to serve the campus.

Developers and the committee also discussed timing and city process. Developers said the site was rezoned in April 2023 to allow data‑center use and the first building is already constructed and operating. The applicant said it hopes to begin construction on the new building before winter and to complete the broader campus by the end of 2026, but that construction phasing and final tenant commitments remain subject to market conditions. The committee and staff noted a pending city council discussion of a proposed temporary moratorium on new data‑center applications; staff said projects that filed applications before any moratorium trigger would be processed under existing rules, and the draft moratorium includes hardship and “proceed at your own risk” provisions that would allow limited paths forward for projects already in process.

The committee recorded projected economic impacts presented by the developer: about $800,000 per year in property taxes and approximately $3.5 million per year in utility tax revenue, along with an estimate of 40–60 full‑time operations jobs per building and roughly 2,000 construction jobs over a multi‑year buildout. The developer said no municipal economic incentives were requested.

The committee approved the final plan and plat with the conditions read into the record by staff; staff noted the final plan and plat approvals are subject to the city’s standard five‑day appeal period for committee decisions and that the easement vacation will proceed to city council. Committee members asked staff to ensure aldermen in the affected area are notified during the appeal period.

The meeting concluded without public comments on the item. The committee’s vote attaches enforceable conditions intended to require field verification and ongoing responsiveness should neighborhood noise complaints continue.

The final plan and plat decisions will proceed through the city’s appeal and council processes as specified in staff materials; the city will not issue certificates of occupancy for any phase of the data‑center buildings until the required third‑party acoustical verification and other conditions are satisfied.