Noise & Air Quality | Woodbury Data Centers

Overview

Data centers rely on backup generators and cooling chillers that produce continuous noise and air emissions. Woodbury's two IronGate facilities (401 and 500 Bielenberg) are equipped with these systems but have never been required to submit noise studies or air permits to the city.

Key Issue: Eagan required a continuous 24-hour noise study per Minnesota Rules 7030 and found that the same operator's facility exceeded state noise limits. Woodbury has no equivalent requirement on file.

Generator & Chiller Equipment Specifications

401 Bielenberg Drive (MSP 01)

Equipment	Type	Specification	Noise Rating
Generators	Standby diesel/natural gas	Unknown capacity; MPCA construction stormwater permit C00072908 lists "New Generator Bldg" (2025)	Typically 85–95 dBA @ 25 ft
Chillers	Cooling system (closed-loop confirmed per Met Council)	Capacity unknown; multiple units typical at 15 MW facility	Typically 75–85 dBA @ 25 ft
Compressors/HVAC	Air handling units	Large capacity for 15 MW+ load	75–80 dBA @ 25 ft

Source: MPCA Construction Stormwater Permit C00072908 (July 18, 2025) describes "Irongate Remodel & New Generator Bldg" but does not specify generator capacity, fuel type, or noise mitigation.

500 Bielenberg Drive (MSP 02)

Equipment	Type	Specification	Noise Rating
Generators	Standby backup power	Capacity unknown; required for 6 MW operational + 34 MW expansion	85–95 dBA @ 25 ft (estimated)
Chillers	Cooling system	Cooling capacity unknown; closed-loop discharge to sanitary sewer	75–85 dBA @ 25 ft
UPS/Power Systems	Uninterruptible power supply	Multiple units, large capacity	70–80 dBA @ 25 ft

Source: Met Council DPO-000004089 response (401 closed-loop confirmed; 500 has no Met Council facility record despite being 290,000 SF).

Minnesota Rules 7030: Noise Monitoring Standard

Minnesota Rules Chapter 7030 establishes the state standard for noise monitoring. Eagan adopted this standard in their interim ordinance and used it to deny the IronGate facility permit.

7030.0100 — Noise Limit Standards

Time Period	Residential Receiver	Non-Residential Receiver
Day (7 AM – 10 PM)	55 dBA (L50)	65 dBA (L50)
Night (10 PM – 7 AM)	45 dBA (L50)	55 dBA (L50)
Occasional peaks	70 dBA (L10)	75 dBA (L10)

Finding: Sundown neighborhood (186 feet from 401 Bielenberg) is a residential receiver. At night, the state limit is 45 dBA L50 (median sound level over 1-hour period). Combined generator + chiller noise at 85 dBA ÷ distance attenuation ≈ 65–70 dBA at residential property line—well above state limit.

7030.0200 — Monitoring Requirements

The standard requires:

Continuous 24-hour monitoring (not spot tests)
At the nearest residential receiver (not at the facility)
With all equipment at design load (not hypothetical or partial operation)
1/3-octave band analysis (captures low-frequency hum from generators/chillers)
Low-frequency assessment (63 Hz and below, which generators produce)

Eagan Lesson: Eagan Capital's applicant submitted a single 3 a.m. spot test showing 50 dBA compliance. Eagan rejected this as "cherry-picking" and required continuous monitoring. Result: The facility exceeded state limits at night. Permit denied 5-0.

Air Quality & MPCA Requirements

Generator Air Emissions

Stationary diesel and natural gas generators require air emissions registrations with the Minnesota Pollution Control Agency (MPCA).

Generator Size	MPCA Registration Required?	Notes
< 50 kW	No	Exempt from registration
50 kW – 1 MW	Yes (notification)	Stationary engine registration required
> 1 MW	Yes (minor or major permit)	Permit required; NOx and particulate limits apply

Question for City: Does 401 Bielenberg have an MPCA air emissions permit or registration on file? The construction stormwater permit lists "New Generator Bldg" but does not reference an air permit.

Question for City: What is the generator capacity (kW or MW) at each facility, and has it been registered with MPCA?

Current MPCA Registration Status

MPCA Hazardous Waste Generator Status:

401 Bielenberg: Listed as "Medtronic Data Center" — very-small-quantity hazardous waste generator, industrial stormwater permit, aboveground tank TS0124284
500 Bielenberg: No MPCA record found despite being 290,000 SF data center with 6 MW operational

Oddity: 401 is listed under "Medtronic" name in MPCA system, not IronGate or Woodbury Capital LLC. This may indicate third-party facility management or Medtronic as tenant/operator.

Woodbury's Current Requirements

What Exists (as of Sept 2026)

✗ No noise study on file for 401 or 500
✗ No continuous monitoring protocol required
✗ No 1/3-octave analysis required
✗ No reference to Minnesota Rules 7030
✗ No air emissions permit on file for 401 or 500
✗ No setback from residential zones (Eagan required 500 feet)
✗ No sound wall or noise mitigation requirements in permits

Gap: Neither 401 (186 feet from Sundown homes) nor 500 (867 feet from nearest homes) has a formal noise study or air permit. Expansion from 15 MW to 66 MW and 6 MW to 34 MW will increase noise and emissions, but no study is required under current code.

Interim Ordinance Study Recommendation

The city's interim ordinance (approved Sept 23, 2026) authorizes a comprehensive study of data center impacts. The study scope should include:

"The study shall include a noise protocol under Minnesota Rules chapter 7030, with continuous 24-hour monitoring at the nearest residential receiver with all equipment at design load (not spot tests), including 1/3-octave analysis and low-frequency assessment. The 401 and 500 Bielenberg sites shall be mandatory case studies."

What This Means

Real 24-hour data, not single spot tests
Measured at homes, not at the facility
All generators and chillers running at full capacity
Low-frequency noise captured (generators produce 63 Hz hum)
Both facilities studied side-by-side
180-day deadline (completion by ~March 2027)

Key Questions for City Council

1. Noise Monitoring: Why has no continuous noise study per Minnesota Rules 7030 been required at 401 Bielenberg (186 feet from homes) or 500 Bielenberg? Eagan required this and found violations.

2. Air Permits: What MPCA air emissions permits or registrations are on file for generators at 401 and 500? If none, what is the generator capacity and why was MPCA not notified?

3. Setback/Mitigation: What noise mitigation (sound walls, setbacks, hours of operation) is required in current permits for either facility?

4. Expansion Impact: Expansion from 15 MW to 66 MW at 401 and 6 MW to 34 MW at 500 will increase generator/chiller load. Will a new noise study be required before expansion is approved?

5. Study Timeline: The interim ordinance study must include continuous noise monitoring. When will baseline monitoring begin at Sundown neighborhood (nearest residential receiver to 401)?

Sources & References

Minnesota Rules 7030 — State noise standard (https://www.sos.state.mn.us/business-licensing/minnesota-rules/)

MPCA Air Permits & Registrations — Minnesota Pollution Control Agency (https://www.pca.state.mn.us/air-water-land-climate/air-emissions)

MPCA Hazardous Waste Generator Status — 401 Bielenberg listed as "Medtronic Data Center," tank TS0124284

Eagan Capital Permit Denial — City of Eagan Findings of Fact (May 19, 2026); ESI noise study (March–April 2026)

Woodbury Interim Ordinance — Approved September 23, 2026; authorizes comprehensive study including noise protocol

Distance Measurements — OpenStreetMap parcel boundaries; 401 to Sundown homes ~186 feet edge-to-edge