Multnomah County, OR Noise from Specific Sources: Generator Noise (2026)
Key Facts
- Noise limit
- 5 dBA above ambient or 55 dBA
- Testing hours
- 8 a.m. to 8 p.m. only
- Power-outage use
- Exempt at any hour
- Applies to
- Wireless-facility back-up generators, unincorporated county
- Citation
- MCC § 39.7740(A)(3)
Summary
Multnomah County limits backup generator noise at wireless facilities to 5 dBA above ambient or 55 dBA, whichever is greater; testing is barred from 8 p.m. to 8 a.m., though outage-driven generator use is always exempt.
Noise. Noise levels shall not exceed 5 dBA above ambient levels or 55 dBA Sound Pressure Level (SPL), whichever is greater, on adjacent properties. Operation of a back-up generator in the event of power failure or the testing of a back-up generator between 8 AM and 8 PM are exempt from this standard. No testing of back-up power generators shall occur between the hours of 8 PM and 8 AM.
(4) Environmental Resource Protection. All wireless communication facilities shall be sited so as to minimize the effect on environmental resources. To that end, the following measures shall be implemented for all WCFs:
(a) The facility shall comply with Significant Environmental Concern regulations when applicable, including the conditions of an SEC permit for any excavation or removal of materials of archaeological, historical, precontact or anthropological nature;
(S-1 2022)
7-42
Full Breakdown
Multnomah County's zoning code caps noise from a wireless communications facility's ancillary equipment, including its back-up power generator, at 5 dBA above ambient sound or 55 dBA SPL at the property line, whichever is higher (MCC § 39.7740(A)(3)). Generator testing may only run between 8 a.m. and 8 p.m.; testing between 8 p.m. and 8 a.m. is barred outright, though running the generator during an actual power failure is exempt at any hour. This rule sits in the zoning code's cell-tower approval criteria -- it governs unincorporated county land only, not Portland, and doesn't set hours for ordinary household or construction generators, which fall instead under the county's separate Sound Control Law (MCC §§ 15.265-15.274).
Violations & Fines
Operating or testing a wireless facility's back-up generator outside the 8 a.m.-8 p.m. testing window, or exceeding the 5 dBA/55 dBA property-line limit, violates the facility's zoning approval and can trigger code enforcement action.
Frequently Asked Questions
Can I run my home generator at night in unincorporated Multnomah County?
Does this rule apply inside Portland?
Sources & Official References
Other rules in Multnomah County
Compare Multnomah County to another location·View the Oregon noise from specific sources overview
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