<PAGE>

                                             Exhibit 10.17.1

                              May 26, 1995

Mr. King Oberg
Vice President - Gas Supply
Cascade Natural Gas Corporation
PO Box 24464
Seattle, WA 98124

     RE:  Continuation of Water Power's Jackson Prairie
          Storage Release to Cascade

Dear King:

     In anticipation of FERC's approval of the certificated release of Jackson
Prairie storage capacity to Cascade later this fall, I would propose the
following procedures with respect to the ongoing payment of charges:

     (1)  As for the monthly payments identified in Section 3.1 of the Storage
Release Agreement, I propose that Cascade would continue to remit payment to
Water Power;

     (2)  If FERC does not grant certificate authority to continue the 
release or does so upon terms which are unacceptable to the parties, or if 
FERC does not otherwise finally act on the application by November 1, 1995, 
then Water Power will take title to Cascade's working natural gas inventory 
presently in storage at Jackson Prairie (480,000 Dth) and would provide 
"peaking gas supplies" to Cascade of up to 15,000 Dth per day of firm 
deliverability and 5,533 Dth per day of best-efforts deliverability for the 
period May 1, 1995 through April 30, 1996, subject to the terms and 
conditions of the Gas Storage Project Agreement dated September 25, 1989, and 
such regulatory approvals as may be required. As additional compensation for 
making these peaking gas supplies available, Water Power shall charge, and 
Cascade shall pay, $54,120.50 per calendar month for the one year term of 
this arrangement, and any payments previously received in accordance with 
paragraph 1 above shall be credited against Cascade's monthly payment 
obligation. It is also understood and agreed that Cascade will purchase 
480,000 Dth of peaking gas supplies from Water Power prior to May 1, 1996, 
under this agreement.

<PAGE>

Mr. King Oberg
Page - 2

     If the foregoing terms and conditions are acceptable to you, please sign 
where indicated and return a copy of this letter to me at your earliest 
convenience.

                                Very truly yours,
                                /s/
                                Patricia A. Grable
                                Manager, Pipeline & Regulatory Affairs
                                The Washington Water Power Company



ACKNOWLEDGED AND AGREED
TO THIS  28   OF   May   , 1995
       ------    -------



 /s/
----
King Oberg

Vice President - Gas Supply

Cascade Natural Gas Corporation

<PAGE>

                       FIRST AMENDMENT TO THE AGREEMENT FOR THE RELEASE

                             OF JACKSON PRAIRIE STORAGE CAPACITY

     On this 28th day of  April  , 1995, The Washington Water Power Company
             ------      -------
("Water Power") and Cascade Natural Gas Corporation ("Cascade") (hereinafter
collectively referred to as the "Parties") have entered into this Agreement
("First Amendment") for the purpose of amending the Agreement for the Release of
Jackson Prairie Storage Capacity ("Release Agreement") previously executed by
the Parties on July 23, 1990.

                                    WITNESSETH:

     WHEREAS, Water Power and Cascade are parties to a Release Agreement,
whereby Water Power will release a portion of its capacity and deliverability in
the Jackson Prairie Storage Project to Cascade, for a primary term ending April
30, 1995; and

     WHEREAS, Water Power and Cascade desire to extend the primary term of the
aforementioned Release Agreement to April 30, 1998, subject to the receipt of
necessary regulatory approvals;

     NOW, THEREFORE, in consideration of their mutual covenants, the Parties
hereby agree to amend the Release Agreement in the following respects:

<PAGE>

     1.   Section 4.1 of the Release Agreement is hereby deleted and replaced
with a new Section 4.1 which reads, in its entirety, as follows:

               4.1 Subject to the satisfaction of all conditions precedent,
          including the receipt of necessary regulatory approvals, the primary
          term of this Agreement shall continue until April 30, 1998, and
          thereafter, on a year-to-year basis unless terminated by either Party
          upon twelve (12) months' written notice of termination received prior
          to April 30, 1998, or any anniversary thereafter.

     2.   Section 5.3 of the Release Agreement is hereby deleted and replaced
with a new Section 5.3 which reads, in its entirety, as follows:

               5.3 If all conditions precedent are not satisfied in time to
          allow for Cascade's use of the released Deliverability and Capacity by
          November 1, 1995, either Party may, upon fifteen (15) day's written
          notice, cancel this Agreement.

     3.   The Parties agree to substitute revised versions of the following
Exhibits, which were previously attached to the Release Agreement:

          Exhibit A: Substitution of First Revised Appendix A to Jackson Prairie
          Storage Project Agreement, as amended and currently in effect.

          Exhibit B: consent of Northwest Pipeline and Washington Natural Gas
          Company to the Release.

          Exhibit C: Transportation Service Agreement entered into between
          Cascade and Northwest Pipeline is deleted in its entirety.]

<PAGE>

     IN WITNESS WHEREOF each Party has caused this First Amendment to be
executed under the hands of its duly authorized representative.

THE WASHINGTON WATER POWER         CASCADE NATURAL GAS
     COMPANY                            CORPORATION



By:    /s/ Gary G. Ely             By:  /s/ King Oberg
   ------------------------           -----------------------
     Gary G. Ely                        King Oberg
     Vice President, Natural Gas        Vice President, Gas 
Supply

<PAGE>



                                 Exhibit A

Revised Appendix to Gas Storage Project Agreement



<PAGE>

                           FIRST REVISED APPENDIX A
                                     TO
                         GAS STORAGE PROJECT AGREEMENT

     A.   Characteristics and Capabilities of the Jackson Prairie Storage
Project for the 1989/1990 Storage Cycle and thereafter:

     Cushion Gas:
       Zone 2              Sot less than 16.8 Bcf
       Zone 9              Not less than 2.0 Bcf
     Working Gas
       Capacity            Not more than 15.1 Bcf
     Zone 2 Storage Gas    Not more than 34.4 Bcf
     Deliverability:       
       Firm                Not more than 450,000 Mcf Daily
       Best Efforts        Up to 71,800 Mcf daily

     B.   Unless the Management Committee approves an alternate method, the
Seasonal Working Gas Quantity available for withdrawal during any Storage Cycle
is determined by the lessor of;

       (1)     The quantity of Working Gas in storage at the beginning of the
       Storage Cycle; or
       
       (2)     The least quantity of Working Gas in storage at any time between
       August 31st and September 30th of the preceding Storage Cycle divided by
       0.80; or
       
       (3)     The least quantity of Working Gas in storage at any time between
       June 30th and September 30th of the preceding Storage Cycle divided by
       0.35.
       
     The maximum amount of Seasonal Working Gas Quantity is equivalent to the
Working Gas Capacity and shall not exceed 15.l Bcf, as stated above in Section
A.

     C.   During any Storage Cycle, the project Operator shall be required to
withdraw from the Storage Project, upon demand by Northwest Pipeline Corporation
pursuant to Section 6.3 of ARTICLE VI of the Gas Storage Project Agreement, a
daily quantity of natural gas determined as follows:

<PAGE>

        (1)    Subject to the limitations on the replacement of Working Gas as
        stated in Paragraph D of this Appendix, when the Working Gas in the
        Storage Reservoir exceeds 45 percent of the Working Gas Capacity, the
        dally withdrawal quantity shall be 100 percent of the Firm
        Deliverability (defined above as not more than: 450,000 Mcf). For
        withdrawals below 45 percent of the working Gas Capacity, the daily
        withdrawal quantity shall be reduced one percent of Firm Deliverability
        for each additional one percent of the working Gas withdrawn below 45
        percent of the Working Gas Capacity. For calculation purposes, this
        percent of Working Gas withdrawn shall be based on the percent
        withdrawn at the beginning of the given day; and
        
        (2)    The dally Best Efforts Deliverability quantity as that quantity
        is stated in Section A above.

     D.   After the commencement of an annual Storage Cycle, withdrawals from
the Seasonal Working Gas Quantity may be replaced both to maintain the
Deliverability of the Storage Project and to restore the quantity available for
withdrawal; provided, however, that Working Gas injected above the level of the
Seasonal Working Gas Quantity established at the beginning of an annual Storage
Cycle shall be considered as applicable to the Seasonal Working Gas Quantity of
the next succeeding Storage Cycle and shall not increase the Seasonal Working
Gas Quantity of the current Storage Cycle.

     The Project Operator shall transfer up to 500,000 Mcf of Cushion Gas from
Zone 9 to Zone 2 of the Storage Project during the period from October 1 through
April 30 of any Storage Cycle to maintain the Deliverability as stated above and
shall replace said Cushion Gas prior to the commencement of this next storage
Cycle by retransfer from Zone 2 to Zone 9.

     This Appendix A shall become effective on the date designated by the
Federal Energy Regulatory Commission and on such date shall supersede any
previously effective Appendix A establishing the Characteristics and
Capabilities of the Jackson Prairie Storage project.

<PAGE>

Attest:                              THE WASHINGTON WATER POWER COMPANY


/s/  Merilee Fulton                  By:  /s/ Gary E. Ely
                                     Vice President


Attest:                              WASHINGTON NATURAL GAS COMPANY
                                     In Its Individual Capacity and
                                     as Project Operator

/s/ Paul A. Hoglund                  By /s/ Robert R. Golliver
                                     President

Attest:                              NORTHWEST PIPELINE CORPORATION



/s/ Karen B. Martinez                By  /s/ Tim J. Hausler
                                     Vice President


<PAGE>



                              Exhibit B

                          Consent to Release



<PAGE>

                           February 2, 1995


Mr. James Gustafson
Senior Vice President
Washington Natural Gas Corporation
815 Mercer Street
Seattle, WA 98111

Mr. Matt J. Gillis
Vice President of Operations
Northwest Pipeline Corporation
295 Chipeta Way
PO Box 58900
Salt Lake City, UT 84158-0900

RE:  Waiver/Consent of Jackson Prairie Management Committee
     Concerning Release of Capacity and Deliverability by Washington
     Water Power to Cascade

Gentlemen:

     The Washington Water Power Company (WWP) and Cascade Natural Gas 
(Cascade) intend to amend their existing agreement (hereinafter "Release 
Agreement"), whereby WWP would continue to release a share of its capacity 
and deliverability in the Jackson Prairie Storage Project (Project) to 
Cascade. In order to effectuate this continued release, the following waivers 
and consents must be obtained from the Management Committee of the Project.

     In accordance with Article 5.3 of the Gas Storage Project Agreement, 
dated September 25, 1989, the Management Committee, comprised of the 
undersigned, hereby consents to the release by WWP to Cascade of 150,000 
therms of firm deliverability, 55,328 therms of best efforts deliverability, 
and 4,800,000 therms of seasonal capacity in the Project, for an additional 
period extending from May 1, 1995 to April 30, 1998. Moreover, to the extent 
that this release is, or may be, construed as an assignment of a portion of 
WWP's interest in the Project, the undersigned, as representative of each 
owner of the Project, expressly waive any rights of first refusal arising 
under Article 13.1 of the Gas Storage Project Agreement.

<PAGE>

     If you are in agreement with the foregoing, please sign in the space 
provided below and return the original to my office. An original signed by 
all parties will be returned to you. Thank you for your attention to this 
matter.

                           Very truly yours,

                           THE WASHINGTON WATER POWER COMPANY


                           /s/ Gary G. Ely
                           Gary G. Ely


ACKNOWLEDGED AND AGREED TO
THIS  27th  DAY OF FEBRUARY, 1995.
     ------


/s/ James Gustafson
Mr. James Gustafson
ON BEHALF OF WASHINGTON NATURAL 
GAS COMPANY





ACKNOWLEDGED AND AGREED TO
THIS  12th  DAY OF MARCH, 1995.
     ------


/s/ Matt J. Gillis
By  Mr. Matt J. Gillis
ON BEHALF OF NORTHWEST PIPELINE
CORPORATION