Exhibit 2.2


                    FIRST AMENDMENT TO CONTRIBUTION AGREEMENT

         This FIRST AMENDMENT TO CONTRIBUTION AGREEMENT (this "Amendment") is
entered into as of the 6th day of April, 2006 by and among ONEOK, Inc., an
Oklahoma corporation ("ONEOK"), Northern Border Partners, L.P., a Delaware
limited partnership ("Northern Border"), and Northern Border Intermediate
Limited Partnership ("NBILP", and together with Northern Border, the "NBP
Partnerships") (each a "Party" and collectively, the "Parties"). Capitalized
terms used in this Amendment but not defined shall have the respective meanings
given to such terms in the Contribution Agreement.

                                   WITNESSETH

         WHEREAS, the Parties entered into that certain Contribution Agreement
dated as of February 14, 2006 (the "Contribution Agreement"), pursuant to which
ONEOK agreed to contribute to the NBP Partnerships all of the issued and
outstanding Equity Interests in the Companies; and

         WHEREAS, ONEOK Bushton Processing, Inc. ("OBPI") is an indirect wholly
owned subsidiary of ONEOK and is included in the Contribution Agreement as a
Company Subsidiary; and

         WHEREAS, in lieu of contributing OBPI to the NBP Partnerships, the
Parties desire for ONEOK to retain OBPI (through a dividend prior to Closing of
all outstanding Equity Interests in OBPI to ONEOK), and to cause OBPI to enter
into a processing and services agreement with one of the NBP Partnerships or a
Subsidiary thereof that will provide to the NBP Partnerships substantially the
same economic effect as if OBPI had been contributed to the NBP Partnerships;
and

         WHEREAS, the parties also desire for OBPI prior to Closing to dividend
to ONEOK Field Services Company, L.L.C. ("OFS") all OBPI assets that are not
subject to the Bushton Equipment Leases (as defined below) or otherwise used in
the operation of the Bushton plant.

         NOW, THEREFORE, in consideration of the premises and mutual agreements
and covenants herein contained, and intending to be legally bound hereby, the
Parties hereto agree as follows:

         1. The Closing.

            (a) Section 1.3(b)(vi) of the Contribution Agreement is hereby
deleted in its entirety and replaced with the following:

            "(vi) An executed copy of a Processing and Services Agreement (the
            "Processing and Services Agreement") between ONEOK Bushton
            Processing, Inc. ("OBPI") and


            one of the NBP Partnerships or a Subsidiary thereof substantially
            in the form attached hereto as Schedule 1.3(b)(vi)."

            (b) Section 1.3(c)(iii) of the Contribution Agreement is hereby
deleted in its entirety and replaced with the following:

            "(iii) Intentionally Omitted."

            (c) Section 1.3(c)(iv) of the Contribution Agreement is hereby
deleted in its entirety and replaced with the following:

            "(iv) An executed copy of the Processing and Services Agreement."

         2. Definitions. The term "Company Subsidiary" in the Contribution
Agreement and this Amendment shall exclude OBPI. Except as otherwise
specifically provided in this Amendment, the terms "Entity" or "Entities" in the
Contribution Agreement and this Amendment shall include OBPI, including for
purposes of the representations and warranties contained in Section 2 of the
Contribution Agreement.

         3. Representations and Warranties of ONEOK. The following Section 2.24
is added to the Contribution Agreement:

            "2.24 No Transfer to ONEOK. Except in connection with Sections 6.7
            and 6.10 of this Agreement, and except as fully reflected in the
            working capital adjustment described in Section 1.5 of this
            Agreement, from the close of business on March 31, 2006 until
            Closing, no Entity (including OBPI) has distributed, dividended or
            otherwise transferred any cash or assets to ONEOK, any other Entity
            or any other Affiliate of ONEOK, other than as permitted by Section
            4.1 of this Agreement."

         4. Covenants of ONEOK. Section 4.1 is hereby amended by adding the
following language to the end of that Section 4.1:

            "Notwithstanding the foregoing, ONEOK shall have the right, in any
            order, to 1) convert OBPI into a corporation, 2) cause OBPI prior to
            Closing to dividend to ONEOK Field Services Company, L.L.C. ("OFS")
            all property, equipment and other assets of OBPI that are not
            subject to the Bushton Equipment Leases or otherwise used in the
            operation of the Bushton plant, and 3) cause OFS prior to Closing to
            distribute all of the issued and outstanding ownership interests of
            OBPI to ONEOK."


         5. Books and Records. Section 5.1(a) is hereby deleted in its entirety
and replaced with the following:

            "(a) No later than ten (10) days after Closing, ONEOK will make
            available to the NBP Partnerships or their designee, at ONEOK's sole
            cost and expense, originals of all files, records, information and
            data (in all formats) owned by or primarily relating to the Entities
            that are in the possession or control of ONEOK or its Affiliates,
            except that ONEOK will retain all such originals items with respect
            to OBPI and instead provide copies thereof, at ONEOK's sole cost and
            expense, to the NBP Partnerships. In addition, with respect to the
            Entities other than OBPI, ONEOK will make available to the NBP
            Partnerships all ONEOK's and its Affiliate's contractual rights to
            request other such files, records, information and data from any
            third party."

         6. Intercompany Accounts. Section 6.7 is hereby deleted in its entirety
and replaced with the following:

            "6.7 Intercompany Accounts. Except for amounts related to normal
            operational sales and cost of sales and fuel, prior to Closing, but
            effective as of the close of business on the last day of the month
            immediately preceding the Closing Date, ONEOK will settle all
            Intercompany Accounts and intercompany arrangements between any
            Entity, on the one hand, and ONEOK and its Affiliates (other than an
            Entity), on the other hand, and the Entities will not have any
            Liability whatsoever with respect to such settled intercompany
            arrangements and Intercompany Accounts. ONEOK shall be solely liable
            for any contractual or other Liabilities, express or implied,
            arising out of the termination, cancellation and elimination of any
            of the foregoing."

         7. Indebtedness for Borrowed Money. Section 6.10 is hereby deleted in
its entirety and replaced with the following:

            "6.10 Indebtedness for Borrowed Money. Prior to the Closing, but
            effective as of the close of business on the last day of the month
            immediately preceding the Closing Date, (i) ONEOK shall repay or
            otherwise settle any Indebtedness due to the Entities from ONEOK or
            its Affiliates (other than the Entities) and (ii) ONEOK shall cause
            the repayment or settlement of any Indebtedness due

            from the Entities to ONEOK or its Affiliates (other than the
            Entities), in each case, including interest and other amounts
            accrued thereon or due in respect thereof, other than any
            Indebtedness fully reflected in the Closing Working Capital. The
            Parties acknowledge and agree that ONEOK has loaned certain amounts
            to the Entities after the close of business on March 31, 2006 to
            fund working capital requirements of the Entities after such date
            and that such amounts will be repaid by the NBP Partnerships to
            ONEOK in the ordinary course of business or through the working
            capital adjustment described in Section 1.5 of this Agreement."

         8. ONEOK Marks. The second sentence of Section 6.9 is hereby amended by
adding the following language to the beginning of that sentence:

            "Except with respect to OBPI, "

         9. Dividend of Certain OBPI Assets to OFS. The following Section 6.15
is added to the Contribution Agreement:

            "6.15 Dividend of Certain OBPI Assets to OFS. Prior to Closing,
            ONEOK shall cause OBPI to dividend to OFS all property, equipment
            and other assets of OBPI that are not subject to the Bushton
            Equipment Leases or otherwise used in the operation of the Bushton
            plant. The term "Bushton Equipment Leases" means those certain
            leases dated November 26, 1991 entitled: "Equipment Lease --
            Undivided Interest (Bushton Equipment Trust 1991-A)", "Equipment
            Lease -- Undivided Interest (Bushton Equipment Trust 1991-B)",
            "Equipment Lease -- Undivided Interest (Bushton Equipment Trust
            1991-C)", "Equipment Lease -- Undivided Interest (Bushton Equipment
            Trust 1991-D)", and "Equipment Lease -- Undivided Interest (Bushton
            Equipment Trust 1991-E)", originally by and between The First
            National Bank of Chicago, not in its individual capacity, but solely
            as trustee under the Trust Agreements that create the trusts
            described above, as Lessor, and Enron Gas Processing Company (now
            known as ONEOK Bushton Processing, Inc.) as Lessee."

        10. Conditions to Closing. Section 7.1(k) and Section 7.2(m) of the
Contribution Agreement (regarding Bushton Consents) are hereby deleted from the
Contribution Agreement in their entirety.



        11. Indemnification. Section 9.2(c) is hereby deleted in its entirety
and replaced with the following:

            "(c) To the extent that ONEOK or its Affiliates (other than the
            Entities, but including OBPI) has the right to seek indemnification
            from third parties for the benefit of the Entities (other than OBPI)
            or their assets, and the Entities (other than OBPI) are not entitled
            to seek such indemnification on their own accord, ONEOK, upon
            Northern Border's written request, shall assign such indemnification
            rights to Northern Border or, if such rights cannot be assigned,
            assert (at Northern Border's cost) a claim relating to such matter
            against such third party on behalf of the applicable Entities (other
            than OBPI), and provide to Northern Border all benefits of such
            indemnification as, when and if provided by such third party.
            Notwithstanding the foregoing, neither ONEOK nor its Affiliates
            shall be obligated to make any additional payments or to take any
            action that would cause them to incur or be subject to any
            additional liabilities or costs with respect to any actions taken
            under this Section 9.2(c)."

        12. No Contribution. Section 9.5 is hereby deleted in its entirety and
replaced with the following:

            "9.5 No Contribution. ONEOK shall not have and shall not exercise or
            assert (or attempt to exercise or assert), any right of
            contribution, right of indemnity or other right or remedy against
            any Entity (other than OBPI) in connection with any indemnification
            obligation or any other Liability to which it may become subject
            under or in connection with this Agreement."

        13. Tax Matters. For purposes of Section 10 (Tax Matters) of the
Contribution Agreement, and the corresponding definitions to the extent used in
such Section 10, the term "Entities" shall be deemed to exclude OBPI.

        14. Certain Definitions.

            (a) Section 11.18 of the Contribution Agreement is hereby amended to
replace each of the following definitions:

            " "Converting Companies" means each of ONEOK Sayre Storage Company,
            OkTex Pipeline Company, ONEOK Field Services Company and Mid
            Continent Market Center, Inc."

            " "Northern Border Indemnitees" means the NBP Partnerships and their
            respective Affiliates (including, without limitation, the Entities,
            but excluding OBPI) and their respective Representatives."

            (b) Section 11.19 of the Contribution Agreement is amended to add
the following defined terms in the appropriate alphabetical order:

            "Bushton Equipment Leases                  6.15
             OFS                                        4.1
             OBPI                                       1.3(b)(vi)
             Processing and Services Agreement          1.3(b)(vi)"

         15. Exhibits and Schedules.

             (a) Exhibit A to the Contribution Agreement is hereby replaced in
its entirety by Exhibit A to this Amendment.

             (b) Schedule 1.3(b)(vi) to the Contribution Agreement is hereby
replaced in its entirety by Schedule 1.3(b)(vi) to this Amendment.

             (c) The first page to Schedule 1.5 to the Contribution Agreement is
hereby replaced in its entirety by Schedule 1.5 to this Amendment.

             (d) Schedule 2.1(e)(iii) to the Contribution Agreement is hereby
amended in its entirety to read as follows:

             "Software vendor/licensor consents as may be necessary."

             (e) Schedule 2.4(b) is hereby amended by adding the following
language to the end of that Schedule:

             OFS will distribute to ONEOK, prior to Closing of the Agreement,
             all of the outstanding equity interests of OBPI."

         16. Further Assurances. The Parties agree to make such additional
amendments or modifications to the Contribution Agreement, and to execute and
deliver such additional documents and take such other and further action, as may
reasonably be necessary to effect the restructuring of the Contribution
Agreement as described in this Amendment.

         17. Ratification. Except as expressly set forth herein, all other terms
and conditions of the Contribution Agreement shall remain unmodified and in full
force and effect, and the Parties hereby confirm and ratify such terms and
conditions and agree to perform and comply with the same.


         18. Severability. If any provision of this Amendment is invalid or
unenforceable, the balance of this Amendment shall remain in effect.

         19. Counterparts. This Amendment may be executed in any number of
counterparts, each of which will be deemed an original, but all of which
together will constitute one and the same instrument.

         20. Governing Law. This Amendment shall be construed under and governed
by the internal laws of the State of Delaware without regard to its conflict of
laws provisions.

         IN WITNESS WHEREOF the parties hereto have caused this Amendment to be
executed as of the date set forth above by their duly authorized
representatives.

                                    ONEOK, INC.


                                    By:  /s/ David L. Kyle
                                         ---------------------------------------
                                    Name:  David L. Kyle
                                    Title:  Chairman of the Board, President and
                                    Chief Executive Officer



                                    NORTHERN BORDER PARTNERS, L.P.


                                    By:  /s/ William R. Cordes
                                         ---------------------------------------
                                    Name:  William R. Cordes
                                    Title:  Chief Executive Officer



                                    NORTHERN BORDER INTERMEDIATE
                                    LIMITED PARTNERSHIP


                                    By:  /s/ William R. Cordes
                                         ---------------------------------------
                                    Name:  William R. Cordes
                                    Title:  Chief Executive Officer





                       EXHIBIT A TO CONTRIBUTION AGREEMENT
                        (COMPANIES/COMPANY SUBSIDIARIES)


COMPANIES:

<Table>
<Caption>
                                                                                STATE OF
                                                                              INCORPORATION          OWNERSHIP
                      NAME                             TYPE OF ENTITY         OR FORMATION           PERCENTAGE
- -------------------------------------------------- ----------------------- -------------------- --------------------
                                                                                       
Mid Continent Market Center, Inc.                  Corporation                   Kansas                100%
- -------------------------------------------------- ----------------------- -------------------- --------------------
OkTex Pipeline Company                             Corporation                  Delaware               100%
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Field Services Company                       Corporation                  Oklahoma               100%
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Gas Gathering, L.L.C.                        Limited Liability            Oklahoma               100%
                                                   Company
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Gas Storage, L.L.C.                          Limited Liability            Oklahoma               100%
                                                   Company
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Gas Storage Holdings, L.L.C.                 Limited Liability            Delaware               100%
                                                   Company
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Gas Transportation, L.L.C.                   Limited Liability            Oklahoma               100%
                                                   Company
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Midstream Gas Supply, L.L.C.                 Limited Liability            Oklahoma               100%
                                                   Company
- -------------------------------------------------- ----------------------- -------------------- --------------------
ONEOK Sayre Storage Company                        Corporation                  Delaware               100%
- -------------------------------------------------- ----------------------- -------------------- --------------------
</Table>


COMPANY SUBSIDIARIES:

<Table>
<Caption>
                                                                                 STATE OF
                                                                              INCORPORATION          OWNERSHIP
                      NAME                             TYPE OF ENTITY          OR FORMATION          PERCENTAGE
- -------------------------------------------------- ----------------------- --------------------- -------------------
                                                                                        
ONEOK WesTex Transmission, L.P.                    Limited Partnership           Delaware               100%
- -------------------------------------------------- ----------------------- --------------------- -------------------
Potato Hills Gas Gathering System                  Joint Venture                 Oklahoma               51%
- -------------------------------------------------- ----------------------- --------------------- -------------------
Sycamore Gas System                                General Partnership           Oklahoma             48.445%
- -------------------------------------------------- ----------------------- --------------------- -------------------
ONEOK VESCO Holdings, L.L.C.                       Limited Liability             Delaware               100%
                                                   Company
- -------------------------------------------------- ----------------------- --------------------- -------------------
</Table>


     
Notes:

        1. The outstanding membership interests in ONEOK Field Services Holdings, L.L.C. were transferred by
        ONEOK Field Services Company to ONEOK, Inc. prior to execution of the Contribution Agreement.




     
        2. ONEOK Field Services Company (one of the Companies listed above) owns 50% of the outstanding equity
        interests in Fox Plant, L.L.C., a Delaware limited liability company. However, since ONEOK does not
        control Fox Plant, L.L.C., the ownership interest for that company is listed on Schedule 2.4(b),
        rather than on this exhibit.

        3. ONEOK VESCO Holdings, L.L.C. (one of the Company Subsidiaries listed above) owns 10.1765% of the
        outstanding interests in Venice Energy Services Company, L.L.C., a Delaware limited liability company.
        However, since ONEOK does not control Venice Energy Services Company, L.L.C., the ownership interest
        for that company is listed on Schedule 2.4(b), rather than on this exhibit.

        4. ONEOK Field Services Company, L.L.C. will distribute to ONEOK, Inc. prior to the Closing of the
        Contribution Agreement all of the outstanding stock of ONEOK Bushton Processing, Inc.





                               Schedule 1.3(b)(vi)

                        Processing and Services Agreement




                                  SCHEDULE 1.5

                                AGREED PRINCIPLES

For purposes of determining Net Working Capital, the following principles shall
be used:

         o   GAAP: Net Working Capital shall be determined in accordance with
             GAAP, except as set forth below.

         o   Reference Statement: The accounts listed on Exhibit D (the
             "Reference Statement") shall be used in determining Net Working
             Capital, except for those adjustments shown on the Reference
             Statement.

         o   Gas in Storage and Commodity Exchange: The value of the accounts
             entitled "Gas in Storage" and "Commodity Exchange" on the Reference
             Statement shall be determined at market as set forth in Annex 1.5.

         o   Closing Working Capital and Effective Time. The same principles
             used to calculate Target Working Capital (including those set forth
             in this Schedule 1.5 and Annex 1.5 and as reflected in the
             Reference Statement) shall be used to calculate Closing Working
             Capital, except that the "Effective Time" for purposes of
             calculating Target Working Capital shall be close of business on
             the date of the Reference Statement and the "Effective Time" for
             purposes of calculating Closing Working Capital shall be close of
             business on the last day of the month immediately preceding the
             Closing Date; provided that natural gas and natural gas liquids
             shall be measured and valued as of 7:00 a.m. on each of such dates,
             rather than as of the close of business.