On April 12, 2017, the Public Utility Commission ordered noise monitoring for the Bent Tree Wind Project after numerous complaints pressured for action on those complaints.  Bent Tree is located in Freeborn County just north east of Albert Lea, Minnesota, north of Interstate 90, and on the  west side of Interstate 35, opposite where they now want to put up the Freeborn Wind Farm, south of I-90 and east of I-35.  They put up monitors at a few locations near the homes of those who filed complaints, and then, for some reason the turbines near those homes are off (Curtailment? Why am I suspicious? Apparently they’ve never been off at other times.).  Then they took the monitors away.

But the study is “complete?”  Here it is.

Bent Tree_Report_Noise Monitoring_20179-135856-01

On page one, the cover letter, they admit there are times of non-compliance. What’s important in this is that the problematic “noise” is the infrasound, which is found in “C weighted” scales, and not the “A weighted” scale that is the subject of Minn. R. 7030.  Further, the Minnesota Rules Ch. 7030 does not address impulsive sounds, such as sounds from a gun range, or some sound from wind turbines.

7030.0020 DEFINITIONS.
7030.0080 VARIANCE.

MPCA’s Commissioner, John Linc Stein, agrees that the Minnesota Rules do NOT cover infrasound, and there are no rules covering infrasound, but yet will not initiate rulemaking:


Back to the studies.  the protocol for the “study” is taken from the Minn. R. Ch. 7030, Measurement Methodology.   Monitoring data was excluded if the wind speed was over 11 mph, but for the Langrud monitor, the report says that wind speed was not over 11 mph.  Is that reasonable?  Look at average wind speeds generally, considering that higher wind speed is desirable for generating electricity (click for larger version):

When wind speeds are high, that is when the noise from the turbines is most unbearable, and under the report protocol, when wind speeds are high, were excluded. Average wind speed n the Bent Tree area is 15.7 – 16.8.  So in the chart above, it says 0% were excluded due to high wind. Does that mean there were no times that the wind was over 11 mph?  That’s doubtful, although spring and fall are times with higher wind, typically, but, color me skeptical.

But yet Table 4-1 says wind speed did not go over 11 mph during the monitoring, and so no data where wind was over 11 mph was excluded.  Curtailment is also unclear, because we do not know what turbines were curtailed, if it was only ones near the monitors, or the entire project (usually is is some but not all).  It also says results were skewed by bird chirping and insect noise, which would not have been present in early spring or fall.  WHAT?!?!  And early spring is planting time so lots of farm equipment out, and fall is harvest. Makes no sense.

So how is the report valid?

Dave Langrud, a landowner in the Bent Tree footprint, has tracked when the turbines were off and on, and we’re working on comparing those times to the times in the report — they do have some info in this report for comparison showing time they admit the turbines were off:

And there were C weighted measurements, note how high these go:

We’ve submitted a Data Practices Act Request for more data:

Miltich – Dept of Commerce_Data Practices Act Request

Nothing has showed up yet.

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