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

The MDU Resources Group, Inc. 401(k) Retirement Plan (as restated March 1, 2011)
(the “Plan”), is hereby further amended, effective March 7, 2011, unless
otherwise indicated, as follows:

1.
By replacing the table in Section D-1-2 Eligibility to Share in the Profit
Sharing Feature of Supplement D-1,  Provisions Relating to the Profit Sharing
Feature for Certain Participating Affiliates, in its entirety, with the
following:

Participating Affiliate
Current Effective Date
(Original Effective Date)2
Anchorage Sand & Gravel Company, Inc. (excluding President)
January 1, 1999
Baldwin Contracting Company, Inc.
January 1, 1999
Bell Electrical Contractors, Inc.
January 1, 2002
Bitter Creek Pipelines, LLC1/3
January 1, 2010
(January 1, 2001)
Cascade Natural Gas Corporation
January 1, 2011
July 2, 2007
Concrete, Inc.
January 1, 2001
Connolly-Pacific Co.
January 1, 2007
DSS Company
January 1, 2004
(July 8, 1999)
E.S.I., Inc.
January 1, 2008
(January 1, 2003)
Fairbanks Materials, Inc.
May 1, 2008
Frebco, Inc.
January 1, 2008
(July 1, 2000)
Granite City Ready Mix, Inc.
June 1, 2002

 
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Participating Affiliate
Current Effective Date
(Original Effective Date)2
Great Plains Natural Gas Co.
January 1, 2008
Hawaiian Cement (non-union employees hired after December 31, 2005)
January 1, 2009
Intermountain Gas Company
January 1, 2011
Jebro Incorporated
November 1, 2005
Kent’s Oil Service
January 1, 2007
Knife River Corporation – Northwest (the Central Oregon Division, f/k/a HTS)
January 1, 2010
(January 1, 1999)
Knife River Corporation – Northwest (the Southern Idaho Division)
January 1, 2010
(January 1, 2006)
Knife River Corporation – Northwest (the Spokane Division)
January 1, 2010
(January 1, 2006)
Knife River Corporation - South
(f/k/a Young Contractors, Inc.)
January 1, 2008
(January 1, 2007)
LTM, Incorporated
 
January 1, 2003
 
Montana-Dakota Utilities Co. (including union employees)
January 1, 2008
Oregon Electric Construction, Inc.3
March 7, 2011
Wagner Industrial Electric, Inc.
 
January 1, 2008
 
Wagner Smith Equipment Co.
January 1, 2008
(July 1, 2000)
WBI Holdings, Inc.1/3
 
January 1, 2009
 
WHC, Ltd.
 
September 1, 2001
 

 
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Participating Affiliate
Current Effective Date
(Original Effective Date)2
Williston Basin Interstate Pipeline Company1/3
January 1, 2009
 

1Eligible employees participating in a management incentive compensation plan or
an executive incentive compensation plan are not eligible for a Profit Sharing
Contribution. Employees of the Total Corrosion Solutions division of Bitter
Creek Pipelines, LLC are excluded from this feature.
2In the event a Participating Affiliate adopts a Profit Sharing Feature on a
date other than January 1, effective as of the date of participation in the
Plan, the amount of any such contribution allocated to a Supplement D-1
Participant shall be based upon Compensation, received while in the employ of
the Participating Affiliate after the date of acquisition by the Company or any
Affiliate.
3Requirement to be an Active Employee on the last day of the Plan Year does not
apply.

Explanation: This amendment adds Oregon Electric Construction, Inc. (OEG) as a
Participating Affiliate of Supplement D-1 of the K-Plan as the result of OEG
ceasing participation in a defined contribution multiemployer pension plan.

2.
Effective March 1, 2011, by replacing the second sentence of the second
paragraph of Section D-1-4 Vesting of Supplement D-1 with the following two
sentences:

Service with a Supplement D-1 Company, the Company, and all Affiliates shall be
recognized for purposes of this Paragraph, including, but not limited to,
service that occurred prior to the effective date of Supplement D-1, applying
these rules as if the Supplement D-1 Company (and its affiliates at that time)
were Affiliates under the Plan.  Supplement D-1 Participants who were employed
with Ideal Builders, Inc. on the date of acquisition on August 29, 2008 by Knife
River Corporation – Northwest (the Southern Idaho Division) will have prior
years of service recognized towards Years of Vesting Service.

Explanation: This amendment clarifies the current practice that Hours of Service
with any Affiliate are included for the purpose of determining vesting years of
service for Profit Sharing Contributions, and that years of vesting service with
Ideal Builders, Inc. will be included for Supplement D-1 Participants employed
as a result of the acquisition.

3.
By replacing the table in Section D-2-2 Eligibility to Share in the Retirement
Contribution of Supplement D-2,  Provisions Relating to the Retirement
Contribution Feature for Certain Participating Affiliates, in its entirety, with
the following:

 
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Participating Affiliate
 
Current Effective Date (Original Effective Date)
Special Contribution Amount – Percentage of Compensation
Bitter Creek Pipelines, LLC1
January 1, 2006
(January 1, 2001)
5%
Cascade Natural Gas Corporation (non-bargaining)
January 1, 2011
(July 2, 2007)
5%
Cascade Natural Gas Corporation (Field Operations Bargaining Unit employees
hired on or after 1/1/2007)
July 2, 2007
 
4%
Fidelity Exploration & Production Company2
January 1, 2006  
(July 2, 2001)
5%
Great Plains Natural Gas Co.
January 1, 2003
5%
Hamlin Electric Company
January 1, 2005
5%
Intermountain Gas Company
January 1, 2011
(October 12, 2008)
5%
Oregon Electric Construction, Inc.
March 7, 2011
6%
Rocky Mountain Contractors, Inc. (Union)3
January 1, 2008
3%
Rocky Mountain Contractors, Inc.
January 1, 2005
5%

1The following participants of Bitter Creek Pipelines, LLC are excluded: Brien
Beadle, Grady Breipohl, Jon Forbes, Richard Guderjahn, Steven Haag, Raymond
Harms, Wade Hasler, Douglas Henry, Pamela Lynn, Todd Mandeville, Marlin Mogan,
Dale Sudbrack, and Barbara Sunford due to participation in the appropriate
pension plan replacement contribution.
2The following participants of Fidelity Exploration & Production Company are
excluded: Harlan R. Jirges, Timothy M. Ree, Marvin E. Rygh, Judy A. Schmitt, and
Dennis M. Zander due to participation in the appropriate pension plan
replacement contribution.
3Requirement to be compensated for 1,000 hours of service does not apply to
Rocky Mountain Contractors, Inc. (Union).

Explanation: This amendment adds OEG as a Participating Affiliate of Supplement
D-2 of the K-Plan as the result of OEG ceasing participation in a defined
contribution multiemployer pension plan.

4.
Effective March 1, 2011, by replacing the second sentence of the second
paragraph of Section D-4 Vesting in each of Supplements D-2 through Supplement
D-7 with the following:

 
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Service with a Supplement D-[applicable supplement number] Company, the Company,
and all Affiliates shall be recognized for purposes of this Paragraph,
including, but not limited to, service that occurred prior to the effective date
of Supplement D-[applicable supplement number], applying these rules as if the
Supplement D-[applicable supplement number] Company (and its affiliates at that
time) were Affiliates under the Plan.

Explanation: This amendment clarifies the current practice that Hours of Service
with any Affiliate are included for the purpose of determining vesting years of
service for Profit Sharing and Retirement Contributions.

5.
By replacing the following entry to Schedule A of the Plan for Oregon Electric
Construction, Inc.:

Oregon Electric Construction, Inc. (“OEG”) shall make a matching contribution
equal to one hundred percent (100%) of each OEG employee’s participating savings
contribution, up to the maximum savings contribution of two (2%) of compensation
for each pay period.  Prior to March 7, 2011, OEG did not make matching
contributions for OEG employees.

Effective March 7, 2011.

Explanation: This change updates Schedule A to add matching contributions for
eligible employees of OEG as a result of OEG ceasing participation in a defined
contribution multiemployer pension 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 29th day of
March, 2011.

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

 
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