Des Moines County supervisors debate setbacks, wildlife buffers and safety rules in draft wind-energy ordinance

Des Moines County supervisors spent the bulk of their Oct. 7 meeting reviewing a draft wind-energy ordinance that would set siting and design standards for turbines, including setback distances, wildlife protections, equipment standards and operational safeguards.

The board reviewed a draft Article 3 that would require nonparticipating occupied dwellings to be set back from turbines by the greater of three times turbine height or 1,800 feet, with participating-property setbacks generally set at two times turbine height. Supervisor Tom Brooker said he favors the proportional setback and a minimum of 1,800 feet, a figure he tied to local incident reports and county measurements of debris from previous turbine failures in other counties. “Three times the turbine height or the greater of three times turbine height or 1,800 feet,” Brooker said as the board discussed a cap and how the rule would scale with taller turbines.

Conservation staff and board members pushed for much larger wildlife buffers around sensitive ecological areas. Chris Lee, Conservation Director, and Terry Davis of the Conservation Board presented a memo recommending science-based buffers: a five-mile buffer along the Mississippi River corridor for active bald-eagle foraging areas, three miles for properties with documented threatened or endangered bat species, and a one-quarter-mile buffer for forested riparian corridors. The conservation presenters cited US Fish and Wildlife Service, Iowa DNR guidance and local acoustic survey data that identify the county’s parks and riparian corridors as important habitat for multiple bat species, including species listed by state and federal agencies.

Safety and equipment standards drew sustained attention. Board members discussed two widely noted incidents — a multi-turbine event in Mechanicsville and a turbine failure in another county — in which fragmented composite debris reportedly scattered hundreds to more than a thousand feet. Supervisors emphasized decommissioning and emergency removal timelines. The ordinance would require turbines to be removable and to include bonds or indemnification to cover cleanup and property damage; the draft also calls for turbine materials and designs that have been proven in at least two comparable regional projects for five years.

Fire suppression and lightning protection were added to the draft following public and staff comments. The draft requires each turbine be equipped with lightning protection and an on-site fire suppression system that is capable of detecting and extinguishing fires and preventing their spread to surrounding property; the board directed staff to clarify language on detection and worker safety procedures. The draft also proposes aircraft-detection lighting systems where approved by the FAA and a shadow-flicker limit — not more than 30 hours per year on the external wall of the nearest occupied dwelling on a nonparticipating property — with permit-stage studies required to forecast impacts and mitigation plans.

Other technical issues under debate included undergrounding of electrical collection lines, noise limits (a 50 A-weighted decibel limit at occupied dwellings or civic buildings, with exceptions during severe storms or outages), blade-ice mitigation and manufacturer-specific anti-icing or operational controls, and measures to avoid interference with communication links and radar. The draft would require applicants to provide NTIA/communications studies and, where relevant, mitigation plans for Doppler-radar or microwave-path interference.

Conservation board members acknowledged a late submission of technical recommendations and asked the board to incorporate them into the wildlife section or to apply them as siting constraints. “We have data showing federally and state-listed species and high-value corridors here,” Terry Davis said, urging the supervisors to consider the conservation recommendations despite their late delivery. Supervisors said they will review the materials and revisit specific setback distances and wildlife buffers.

Next steps: staff will circulate the conservation board’s mapping and technical memo to supervisors and the public. The board did not adopt Article 3 at this meeting; supervisors said they will continue refining setback distances, wildlife protections, and technical requirements (including complaint-resolution and enforcement language) before a future vote.

(Reporting note: the transcript contained multiple spellings of the county name (e.g., "De Mo County"); this article uses the standardized form "Des Moines County." All direct quotes are attributed to speakers identified in the meeting record.)