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Board debates noise, height and testing standards for energy systems
Summary
Members debated lowering the draft 55 dBA limit, whether noise should be measured at dwellings or property lines, and whether height exceptions are needed to allow agrivoltaic systems; staff said they will consult Henry County noise language and experts.
The board examined technical performance standards in the draft ordinance, including maximum structure heights, noise limits measured in weighted decibels (dBA) and prohibitions on experimental materials.
On height, the draft sets a 15‑foot cap for most solar arrays with an exception that increases height by 1 foot for every 2 feet of additional setback; several participants said the exception could produce very tall panels near distant dwellings and recommended a hard maximum for agrivoltaic uses. “We’re testing between 20 and 25 feet” for agrivoltaics at Iowa State, one participant said; planners suggested a capped upper limit (for example, 30 feet) and a targeted agrivoltaics clause to accommodate crop or livestock operations.
Noise limits generated a lengthy debate. The draft used a 55 dBA weighted standard; several speakers urged a lower limit (45–50 dBA) to preserve rural character while others said 45 dBA is unusually restrictive for industry practice. Planners clarified the metric is A‑weighted decibels (dBA) and noted enforcement will measure at occupied dwellings in normal operating conditions, with narrow exceptions for rare short‑term events such as storms. “Decibels are logarithmic…55 decibels is about twice as loud as 45 decibels,” Kenny Olson warned, underscoring trade‑offs in numeric choices.
Planners said they will import Henry County’s more detailed noise language for review and consult acoustical experts to recommend a specification that is enforceable, separates day/night conditions, and addresses infrasound and measurement protocols.
The board did not adopt numeric thresholds at the meeting and asked staff to return with draft language informed by county comparisons and expert guidance.
