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|  ARTICLE I DEFINITIONS  |  1 |
|-----------------------------------|---------|
|                              |    |

|  ARTICLE II AGREEMENT TO SELL AND PURCHASE  | 4 |
|-------------------------------------------------------|---|

|   | 2.1 | Sale      and Purchase  | 4 |
|--------|-----|------------------------------|---|

|   | 2.2 | Closing  | 5 |
|--------|-----|---------------|---|

|   | 2.3 | Effective      Date; Development Costs  | 5 |
|--------|-----|----------------------------------------------|---|

|   | 2.4 | Conditions      to Obligations of Purchaser  | 5 |
|--------|-----|---------------------------------------------------|---|

|   | 2.5 | Conditions      to Obligations of Seller  | 6 |
|--------|-----|------------------------------------------------|---|

|   | 2.6 | Purchase      Price Allocation for Tax Purposes  | 6 |
|--------|-----|-------------------------------------------------------|---|

|  ARTICLE III REPRESENTATIONS AND WARRANTIES OF      SELLER  |  6 |
|-----------------------------------------------------------------------|---------|

|   | 3.1 | Organization  | 6 |
|--------|-----|--------------------|---|

|   | 3.2 | Organization      and Qualification of Bison  | 6 |
|--------|-----|----------------------------------------------------|---|

|   | 3.3 | Authority  | 7 |
|--------|-----|-----------------|---|

|   | 3.4 | Ownership  | 7 |
|--------|-----|-----------------|---|

|   | 3.5 | No      Conflicts or Violations; Consents  | 7 |
|--------|-----|-------------------------------------------------|---|

|   | 3.6 | Certain      Proceedings  | 8 |
|--------|-----|--------------------------------|---|

|   | 3.7 | Brokers      or Finders  | 8 |
|--------|-----|-------------------------------|---|

|   | 3.8 | Taxes  | 8 |
|--------|-----|-------------|---|

|  ARTICLE IV REPRESENTATIONS AND WARRANTIES OF      PURCHASER  |  8 |
|-------------------------------------------------------------------------|---------|

|   | 4.1 | Organization  | 8 |
|--------|-----|--------------------|---|

|   | 4.2 | Authority  | 8 |
|--------|-----|-----------------|---|

|   | 4.3 | No      Conflicts or Violations; Consents  | 8 |
|--------|-----|-------------------------------------------------|---|

|   | 4.4 | Certain      Proceedings  | 9 |
|--------|-----|--------------------------------|---|

|   | 4.5 | Brokers      or Finders  | 9 |
|--------|-----|-------------------------------|---|

|   | 4.6 | Investment      Intent; Access  | 9 |
|--------|-----|--------------------------------------|---|

|  ARTICLE V COVENANTS OF THE PARTIES  | 9 |
|------------------------------------------------|---|

|   | 5.1 | Expenses  | 9 |
|--------|-----|----------------|---|

|   | 5.2 | Pathfinder      Project  | 10 |
|--------|-----|-------------------------------|----|

|   | 5.3 | Northern      Border Pipeline Company Capacity  | 10 |
|--------|-----|------------------------------------------------------|----|

|   | 5.4 | Discussions      with Shippers  | 10 |
|--------|-----|--------------------------------------|----|

|   | 5.5 | Further      Assurances  | 10 |
|--------|-----|-------------------------------|----|

|   | 5.6 | Tax      Matters  | 10 |
|--------|-----|------------------------|----|

|  ARTICLE VI INDEMNIFICATION; REMEDIES  | 12 |
|--------------------------------------------------|----|

|   | 6.1 | Survival      of Representations, Warranties and Covenants  | 12 |
|--------|-----|------------------------------------------------------------------|----|

|   | 6.2 | Indemnification      and Payment of Damages by Seller  | 13 |
|--------|-----|-------------------------------------------------------------|----|

|   | 6.3 | Indemnification      and Payment of Damages by Purchaser  | 13 |
|--------|-----|----------------------------------------------------------------|----|

|   | 6.4 | Limitations      on Indemnification  | 13 |
|--------|-----|-------------------------------------------|----|

|   | 6.5 | No      Security Holder Liability  | 13 |
|--------|-----|-----------------------------------------|----|

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|  ARTICLE VII GENERAL PROVISIONS |  14 |
|--------------------------------------|----------|

|   | 7.1 | Public      Announcements  | 14 |
|--------|-----|---------------------------------|----|

|   | 7.2 | Confidentiality  | 14 |
|--------|-----|-----------------------|----|

|   | 7.3 | Notices  | 14 |
|--------|-----|---------------|----|

|   | 7.4 | Waiver  | 15 |
|--------|-----|--------------|----|

|   | 7.5 | Entire      Agreement and Modification  | 15 |
|--------|-----|----------------------------------------------|----|

|   | 7.6 | Assignments;      Successors; No Third-Party Rights  | 15 |
|--------|-----|-----------------------------------------------------------|----|

|   | 7.7 | Severability  | 16 |
|--------|-----|--------------------|----|

|   | 7.8 | Article      and Section Headings; Construction  | 16 |
|--------|-----|-------------------------------------------------------|----|

|   | 7.9 | Time      of Essence  | 16 |
|--------|-----|----------------------------|----|

|   | 7.10 | Enforcement  | 16 |
|--------|------|-------------------|----|

|   | 7.11 | Governing      Law  | 16 |
|--------|------|--------------------------|----|

|   | 7.12 | Counterparts  | 17 |
|--------|------|--------------------|----|

|   | 7.13 | No      Other Representations; Disclaimers  | 17 |
|--------|------|--------------------------------------------------|----|

|   | 7.14 | Waiver      of Certain Damages  | 17 |
|--------|------|--------------------------------------|----|

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|   | (a)       | nation,      state, county, city, town, district or other jurisdiction of any      nature;                                                                                                |
|--------|-----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |      |                                                                                                                                                                                      |
|   | (b)  | federal,      state, local, municipal, foreign or other government;                                                                                                                       |
|   |      |                                                                                                                                                                                      |
|   | (c)       | governmental      or quasi-governmental authority of any nature (including any governmental      agency, branch, department, official or entity and any court or other      tribunal); or |

|   | (d) | body      exercising, or entitled to exercise, any administrative, executive,      judicial, legislative, police, regulatory or taxing authority or power of      any nature. |
|--------|-----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

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|   |  SELLER:                               |
|--------|---------------------------------------------|
|   |                                        |
|   |  Northern Border Pipeline      Company |
|   |                                        |
|   | By:                                         | TransCanada Northern Border      Inc., |
|   |                                        | its      Operator  |

|   |                        |
|--------|-----------------------------|
|   | By:                         | /s/      Paul      F.      Miller |
|   | Name:             | Paul      F. Miller  |
|   | Title:            | Vice      President and General Manager  |
|   |                        |   |
|   | By:     | /s/      Patricia M. Wiederholt  |
|   | Name:                       | Patricia      M. Wiederholt  |
|   | Title:                      | Principal      Financial Officer andController  |

|   |  PURCHASER:                   |
|--------|------------------------------------|
|   |                               |
|   | TransCanada      PipeLine USA Ltd. |
|   |                               |
|   | By:                           | /s/      Donald R. Marchand |
|   | Name:                              | Donald      R. Marchand  |
|   | Title:                             | Treasurer  |
|   |                               |   |
|   | By:       | /s/      Donald J.DeGrandis  |
|   |                               | Assistant Secretary  |
|   |                               |   |