Exhibit 10.1

Cascade Investment, L.L.C.

January 5, 2012

Otter Tail Corporation

4334 18th Avenue South

Suite 200

Fargo, North Dakota 58103

 

  Re: Termination of Standstill Agreement

Ladies and Gentlemen:

Reference is made to that certain Standstill Agreement dated as of July 1, 2009
(the “Standstill Agreement”), by and between Otter Tail Corporation (“Otter
Tail”) and Cascade Investment, L.L.C. (“Cascade”).

By their signatures below, Cascade and Otter Tail hereby agree to terminate the
Standstill Agreement by mutual written agreement pursuant to Section 6(c)(i) of
the Standstill Agreement, the result of which is that the Standstill Agreement
shall terminate on the date first set forth above and be of no further force or
effect.

[signature page follows]

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Letter Terminating Standstill Agreement

January 5, 2012

Page 2 of 2

Please confirm your agreement with the foregoing by executing this letter in the
space provided below.

 

Very truly yours, CASCADE INVESTMENT, L.L.C. By:   /s/ Alan Heuberger  

Name: Alan Heuberger

Title: Authorized Representative

 

Accepted and Agreed: OTTER TAIL CORPORATION By:   /s/ George Koeck  

Name: George Koeck

Title: SVP, General Counsel, Secretary