INSTRUMENT OF AMENDMENT TO THE
MDU RESOURCES GROUP, INC.
401(k) RETIREMENT PLAN

The MDU Resources Group, Inc. 401(k) Retirement Plan (as amended and restated
March 1, 2011) (the “K-Plan”), is hereby further amended, effective July 1,
2011, unless otherwise indicated, as follows:

1.
By replacing Section D-6A-2 Eligibility to Share in the Retirement Contribution
of Supplement D-6A,  Provisions Relating to the Retirement Contribution Feature,
in its entirety, with the following:

 
D-6A-2
Eligibility to Share in the Retirement Contribution.  Participation in the
Retirement Contribution for any Plan Year is limited to individuals who were
active Participants in a Company Pension Plan as of December 31,
2009.  Notwithstanding the foregoing, active Participants in the MDU Resources
Group, Inc. Pension Plan for Collective Bargaining Unit Employees as of June 30,
2011, shall be eligible to participate in this Retirement Contribution Feature,
effective July 1, 2011.

 
          In order to share in the allocation of the Retirement Contribution for
any Plan Year, Eligible Employees must be compensated for 1,000 Hours of Service
in that Plan Year; provided, however, that if the Participant’s failure to be
compensated for 1,000 Hours of Service in the Plan Year is due to the
Participant’s Disability, Death, or Retirement on or after attaining age 60
during such Plan Year, such Participant shall nevertheless be entitled to a
Retirement Contribution for such Plan Year.  Individuals who satisfy the
preceding requirements for Retirement Contributions are referred to herein as
“Supplement D-6A Participants.”

Explanation: This amendment provides for Retirement Contributions to the K-Plan
accounts of those Participants who were Participants in the MDU Resources Group,
Inc. Pension Plan for Collective Bargaining Unit Employees due to freezing
benefit accruals in such plan.

 
2.
By replacing Section D-6A-3 Amount of Retirement Contribution of
Supplement D-6A,  Provisions Relating to the Retirement Contribution Feature, in
its entirety, with the following:

For each Plan Year, Supplement D-6A Participants eligible to participate in this
feature on January 1, 2010 will be credited with the following static
contribution based upon their age as of December 31, 2009, and Supplement D-6A
Participants eligible to participate July 1, 2011, will be credited with the
following static contribution based upon their age as of

 
1

--------------------------------------------------------------------------------

 

 
June 30, 2011, and their eligible Compensation, excluding bonuses for the Plan
Year (paid after initial effective date of the provision).

Age as of
December 31, 2009/
June 30, 2011
Retirement Contribution
Percentage
Less than 30
5.0%
30 but less than 35
7.0%
35 but less than 40
9.0%
40 but less than 45
10.5%
45 and over
11.5%

Notwithstanding the foregoing, if the Retirement Contribution Percentage above
for Participants who are Highly Compensated Employees is more than the amount
permitted under Section 415 of the Code, the Participant’s Retirement
Contributions shall be reduced to the extent necessary to comply with Section
415 of the Code. The Retirement Contribution Percentage above may also be
reduced for Participants who are Highly Compensated Employees, as necessary, to
pass nondiscrimination testing.

Explanation: This amendment provides for Retirement Contributions to the K-Plan
accounts of those Participants who were Participants in the MDU Resources Group,
Inc. Pension Plan for Collective Bargaining Unit Employees due to freezing
benefit accruals in such plan.

IN WITNESS WHEREOF, MDU Resources Group, Inc., as Sponsoring Employer of the
Plan, has caused this amendment to be duly executed by a member of the MDU
Resources Group, Inc. Employee Benefits Committee (“EBC”) on this 30th day of
June, 2011.

 
MDU RESOURCES GROUP, INC.
 
   EMPLOYEE BENEFITS COMMITTEE
             
By:
/s/ Doran N. Schwartz                           
   
Doran N. Schwartz, Chairman

 
2

--------------------------------------------------------------------------------