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12/28/08 I is for ICE THROW: Part Nine in our look at the history and contents of the Town of Union's Large Wind Ordinance

I is for ICE THROW

click on the images below to watch video shot by two different residents of the same wind farm in Fond du Lac County, Wisconsin and hear what they have to say about ice and snow build up on turbine blades:

Why does the town of Union's large wind ordinance have a 2640 foot setback?

Noise and shadow flicker aren't the only problems to be considered when siting industrial wind turbines near homes.

Dangers from ice throw and blade throw must be considered as well.

Here's what the Union ordinance says about ice throw and blade throw. (Download the entire ordinance by clicking here)

"Wind turbines have been known to throw ice and debris from the turbine blades. According to Professor Teny Matilsky from the Department of Physics and Astronomy at Rutgers University, ice throws from large wind turbines can reach up to a distance of 1750 feet and blade throws can reach 2500 feet."

Some residents of Rock County still bristle when they recall the wind developer who denied there was any danger of ice throw from turbines. "He talked to us like we were stupid," remembers one resident, "He said, 'You country people don't understand how ice falls. In Chicago, people live with ice falling from buildings all the time."

Though wind developers continue to insist that ice throw isn't a problem, people who live near wind turbines are beginning to tell a different story.

A December 4th, 2008 news story began like this: "Residents complained when the 260ft wind generator began hurling shards of ice, some measuring two feet long, after the cold snap over the weekend."

The headline?

"Wind turbine closed after showering homes with blocks of ice"

(Click here to read it at its source):

A December 2nd article about the same incident began like this:

"Wind Turbine's Deadly Ice Shower"

"Residents were left fearing for their safety after shards of melting ice fell on homes and gardens from the blades of a giant wind turbine."

(click here for source)

Here are some quotes from those who witnessed it:

"Somebody is going to get killed. There was huge lumps of ice shooting off and landing everywhere."

"No one wants to leave the house because they are frightened and worried about the ice falling."

"The ice makes such a loud noise when it shatters we thought a bomb had gone off in the yard."

"We were assured that ice could only cause a problem in severe weather conditions... and two days later we got javelins thrown at us.

"I am worried about the safety of my family and everyone in the area, we should not have to put up with this."

"It's worrying. Ice froze on the blades and, when it started moving, it started throwing it all over."

And this from a New York Times article that ran on December 26, 2008

(Click here to entire article at the source)

"Winter may pose even bigger safety hazards in the vicinity of wind turbines. Some observers say the machines can hurl chunks of ice as they rotate.

'It’s like you throw a plate out there and that plate breaks,' said Ralph Brokaw, a cattle rancher in southeast Wyoming who has 69 wind turbines on his property. When his turbines ice up, he stays out of the way.'

What do the experts say?

This email was sent from John Zimmerman, the president of VERA to some members of the American Wind Energy Association.

VERA provides and manages tasks and technical issues considered in commercial scale wind project development. Mr. Zimmerman’s experience is in performing technical due diligence and risk assessment across a variety of technologies.

Because of what he has witnessed in regard to ice throw from wind turbines, Mr. Zimmerman seems to suggest the same setback as that in the Union Ordinance of .5 miles or 2640 feet.

The following email was written in January of 2000

Subject: Ice Shedding from Turbines and Public Safety

Dear [AWEA member names]

I’ve watched over the wind turbines GMP has had installed in Vermont over the last 10 years and I have several thoughts that [may] be useful to this discussion

Here in Vermont, and elsewhere in the northeastern US, the winds blow strongest at the mountain tops, where it is also the most icy.

A common first question to wind developers in this region is ‘why don’t you put the wind turbines at the ski areas (where there is human development)’?

The answer is because of the danger to public safety due to ice throws.

Ski areas are not a good place for wind turbines.

Back in the mid 1980s one of the windy areas that was being considered for wind development was near to ski trails. Boeing and/or Hamilton Standard did some work to determine how far we must stay away from the ski trails to be safe from ice being thrown from their turbines (the MOD 5b was the [B]oeing machine at the time). Without going back to dig up those papers, and if I remember correctly, the distance was between .25 and .5 miles away, down wind. It’s a function of blade tip speed, so applicable to present day turbines too.

While the Boeing study was academic
, the danger from ice being release[d] from rotor blades overhead is real—and a hard hat is not going to provide you with much comfort.

I have stood near the turbines GMP had on Mt. Equinox in the early 1990’s and more recently the Zond 500 KW turbines in Searsberg VT during and after icing events.

When there is heavy rime ice build up on the blades and the machines are running you instinctually want to stay away. They roar loudly and sound scarey. (sic) Probably you would feel safe within the .5 danger zone however.

One time we found a piece of ice near the base of the turbine that was pretty impressive. Three adults jumping on it couldn’t break [it] It looked to be 5 or 6 inches thick, 3 feet wide and about 5 feet long. Probably weighed several hundred pounds. We couldn’t lift it. There were a couple of other pieces nearby but we wondered where the rest of the pieces went.

In the winter, icing is a real danger and GMP therefore restricts public access to the site(s). Maintenance workers have developed protocol for working on turbines during icing conditions, though I am not familiar with the details. I’ll ‘dig into it’ if you want.


John Zimmerman,

Without an ordinance, wind developers can site 400 foot tall turbines 1000 feet from homes in your township. And until someone is seriously injured, they will continue to deny there are problems with ice throw. Unfortunately, the drive for profit among wind developers is so strong that even death or serious injury may not stop them from continuing to making the claim that there is no danger from turbine ice throw.

Wondering how to help your township work on an ordinance? Contact us by clicking here.

Posted on Sunday, December 28, 2008 at 10:53AM by Registered CommenterThe BPRC Research Nerd | Comments Off

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