Investigation into Fenner windmill collapse focuses on turbine foundations

As experts hone in on what caused a 187-ton windmill to collapse in a Fenner cornfield last year, developers are moving forward with a plan to get the rest of the wind farm’s 19 turbines safely spinning as early as mid-July.

Turbine 18 fell to the ground in the early hours of Dec. 27, shocking neighbors who have lived among the windmills for nearly a decade and industry experts who called the failure unprecedented.

In the weeks after the accident, Enel North America officials launched a comprehensive investigation to determine what led to the collapse: the turbine’s design, construction or conditions over time.

While the final cause has not yet been determined, forensic engineers have been able eliminate the theory that the failure was caused by construction materials or methods.

“We are confident that the foundations were constructed right in the first place,” project manager Steve Pike said Wednesday night during a meeting attended by about two dozen people who packed a small room in Fenner Town Hall.

Teams of experts called in after the incident have spent the past five months analyzing samples from Turbine 18’s 87-ton concrete foundation, reinforced steel beams and soil base.

The consultants also have studied the bases of the wind farm’s other 19 turbines, which were turned off in the aftermath of the collapse.

“We had to assume the worst — that the other turbines were seconds away from having the same problem,” Pike said. “We stopped generating at great expense because public safety and understanding why the turbine failed was the most important thing.”

While the engineers continue to dig into the tower’s design and historic loads, work crews will begin reinforcing the foundations of the remaining 19 windmills, excavating soil in early June and pouring additional concrete that will be tied to the existing foundations with steel dowels.

“While some look the same as the day we put them in, some have degradation that has started,” Pike said of the foundations of the remaining windmills. “The conditions vary. The first step in getting the park back online is to move forward with strengthening the other foundations.”

The turbines are expected to come back online in batches, with the first blades spinning by mid-summer and the park completely operational by early fall.

Pike said the developer is also considering replacing Turbine 18 with a newer model that could possibly tie into efforts to create a solar power farm in Fenner.