AMENDMENT NO. 4 TO THE THIRD AMENDED AND RESTATED AGREEMENT OF LIMITED PARTNERSHIP OF PLAINS ALL AMERICAN PIPELINE, L.P.

EXHIBIT 3.1

AMENDMENT NO. 4 TO THE THIRD AMENDED AND RESTATED
AGREEMENT OF LIMITED PARTNERSHIP
OF
PLAINS ALL AMERICAN PIPELINE, L.P.

     This Amendment No. 4 (this “Amendment No. 4”) to the Third Amended and Restated Agreement of Limited Partnership (as amended, the “Partnership Agreement”) of Plains All American Pipeline, L.P. (the “Partnership”) is hereby adopted by PAA GP LLC, a Delaware limited liability company (the “General Partner”), as general partner of the Partnership. Capitalized terms used but not defined herein are used as defined in the Partnership Agreement.

     WHEREAS, the General Partner desires to amend the Partnership Agreement to make certain adjustments to certain allocation provisions and the definitions related thereto, which adjustments shall be effective in accordance with Section 761(c) of the Code as of January 1, 2007; and

     WHEREAS, acting pursuant to the power and authority granted to it under Section 13.1(d) of the Partnership Agreement, the General Partner has determined that the following amendment to the Partnership Agreement does not adversely affect the Limited Partners in any material respect and does not require the approval of any Partner.

     NOW THEREFORE, the General Partner does hereby amend the Partnership Agreement as follows:

     Section 1. Amendment.

     (a) Section 1.1 is hereby amended to add or amend and restate the following definitions:

     (i) “Disposed of Adjusted Property” has the meaning assigned to such term in Section 6.1(d)(xii)(B).

     (ii) “Net Termination Gain” means, for any taxable year, the sum, if positive, of all items of income, gain, loss or deduction recognized by the Partnership (a) after the Liquidation Date or (b) upon the sale, exchange or other disposition of all or substantially all of the assets of the Partnership Group, taken as a whole, in a single transaction or a series of related transactions (excluding any disposition to a member of the Partnership Group). The items included in the determination of Net Termination Gain shall be determined in accordance with Section 5.5(b) and shall not include any items of income, gain or loss specially allocated under Section 6.1(d).

     (iii) “Net Termination Loss” means, for any taxable year, the sum, if negative, of all items of income, gain, loss or deduction recognized by the Partnership (a) after the Liquidation Date or (b) upon the sale, exchange or other disposition of all or substantially all of the assets of the Partnership Group, taken as a whole, in a single transaction or a series of related transactions (excluding any disposition to a member of the Partnership Group). The items included in the

determination of Net Termination Loss shall be determined in accordance with Section 5.5(b) and shall not include any items of income, gain or loss specially allocated under Section 6.1(d).

     (b) Section 5.5(d) is hereby amended and restated in its entirety as follows:

     (i) In accordance with Treasury Regulation Section 1.704-1(b)(2)(iv)(f), on an issuance of additional Partnership Interests for cash or Contributed Property or the conversion of the General Partner’s Combined Interest to Common Units pursuant to Section 11.3(b), the Capital Accounts of all Partners and the Carrying Value of each Partnership property immediately prior to such issuance shall be adjusted upward or downward to reflect any Unrealized Gain or Unrealized Loss attributable to such Partnership property, as if such Unrealized Gain or Unrealized Loss had been recognized on an actual sale of each such property for an amount equal to its fair market value immediately prior to such issuance and had been allocated to the Partners at such time pursuant to Section 6.1(c) in the same manner as any item of gain or loss actually recognized following an event giving rise to the dissolution of the Partnership would have been allocated. In determining such Unrealized Gain or Unrealized Loss, the aggregate cash amount and fair market value of all Partnership assets (including, without limitation, cash or cash equivalents) immediately prior to the issuance of additional Partnership Interests shall be determined by the General Partner using such reasonable method of valuation as it may adopt; provided, however, that the General Partner, in arriving at such valuation, must take fully into account the fair market value of the Partnership Interests of all Partners at such time. The General Partner shall allocate such aggregate value among the assets of the Partnership (in such manner as it determines in its discretion to be reasonable) to arrive at a fair market value for individual properties.

     (ii) In accordance with Treasury Regulation Section 1.704-1(b)(2)(iv)(f), immediately prior to any actual or deemed distribution to a Partner of any Partnership property (other than a distribution of cash that is not in redemption or retirement of a Partnership Interest), the Capital Accounts of all Partners and the Carrying Value of all Partnership property shall be adjusted upward or downward to reflect any Unrealized Gain or Unrealized Loss attributable to such Partnership property, as if such Unrealized Gain or Unrealized Loss had been recognized on an actual sale of each such property immediately prior to such distribution for an amount equal to its fair market value, and had been allocated to the Partners, at such time, pursuant to Section 6.1(c) in the same manner as any item of gain or loss actually recognized following an event giving rise to the dissolution of the Partnership would have been allocated. In determining such Unrealized Gain or Unrealized Loss the aggregate cash amount and fair market value of all Partnership assets (including, without limitation, cash or cash equivalents) immediately prior to a distribution shall (A) in the case of an actual distribution which is not made pursuant to Section 12.4 or in the case of a deemed contribution and/or distribution occurring as a result of a termination of the Partnership pursuant to Section 708 of the Code, be determined and allocated

in the same manner as that provided in Section 5.5(d)(i) or (B) in the case of a liquidating distribution pursuant to Section 12.4, be determined and allocated by the Liquidator using such reasonable method of valuation as it may adopt.

     (c) Section 6.1(d)(xii) is hereby amended and restated in its entirety as follows:

     Corrective and Other Allocations. In the event of any allocation of Additional Book Basis Derivative Items or any Book-Down Event or any recognition of a Net Termination Loss, the following rules shall apply:

     (A) Except as provided in Section 6.1(d)(xii)(B), in the case of any allocation of Additional Book Basis Derivative Items (other than an allocation of Unrealized Gain or Unrealized Loss under Section 5.5(d) hereof) with respect to any Partnership property, the General Partner shall allocate such Additional Book Basis Derivative Items (1) to (aa) the holders of Incentive Distribution Rights and (bb) the General Partner in the same manner that the Unrealized Gain or Unrealized Loss attributable to such property is allocated pursuant to Section 5.5(d)(i) or Section 5.5(d)(ii) and (2) to all Unitholders, Pro Rata, to the extent that the Unrealized Gain or Unrealized Loss attributable to such property is allocated to any Unitholders pursuant to Section 5.5(d)(i) or Section 5.5(d)(ii).

     (B) In the case of any allocation of Additional Book Basis Derivative Items (other than an allocation of Unrealized Gain or Unrealized Loss under Section 5.5(d) hereof or an allocation of Net Termination Gain or Net Termination Loss pursuant to Section 6.1(c) hereof) as a result of a sale or other taxable disposition of any Partnership asset that is an Adjusted Property (“Disposed of Adjusted Property”), the General Partner shall allocate (1) additional items of gross income and gain away from the holders of Incentive Distribution Rights to the Unitholders and the General Partner, or (2) additional items of deduction and loss away from the Unitholders and the General Partner to the holders of Incentive Distribution Rights, to the extent that the Additional Book Basis Derivative Items allocated to the Unitholders or the General Partner exceed their Share of Additional Book Basis Derivative Items with respect to such Disposed of Adjusted Property. For this purpose, the Unitholders and the General Partner shall be treated as being allocated Additional Book Basis Derivative Items to the extent that such Additional Book Basis Derivative Items have reduced the amount of income that would otherwise have been allocated to the Unitholders or the General Partner under this Agreement (e.g., Additional Book Basis Derivative Items taken into account in computing cost of goods sold would reduce the amount of book income otherwise available for allocation among the Partners). Any allocation made pursuant to this Section 6.1(d)(xii)(B) shall be made after all of the other Agreed Allocations have been made as if this Section 6.1(d)(xii) were not in this Agreement and, to the extent necessary, shall

require the reallocation of items that have been allocated pursuant to such other Agreed Allocations.

     (C) In the case of any negative adjustments to the Capital Accounts of the Partners resulting from a Book-Down Event or from the recognition of a Net Termination Loss, such negative adjustment (1) shall first be allocated, to the extent of the Aggregate Remaining Net Positive Adjustments, in such a manner, as reasonably determined by the General Partner, that to the extent possible the aggregate Capital Accounts of the Partners will equal the amount which would have been the Capital Account balance of the Partners if no prior Book-Up Events had occurred, and (2) any negative adjustment in excess of the Aggregate Remaining Net Positive Adjustments shall be allocated pursuant to Section 6.1(c) hereof.

     (D) In making the allocations required under this Section 6.1(d)(xii), the General Partner, in its sole discretion, may apply whatever conventions or other methodology it deems reasonable to satisfy the purpose of this Section 6.1(d)(xii).

     Section 2. General Authority. The appropriate officers of the General Partner are hereby authorized to make such further clarifying and conforming changes to the Partnership Agreement as they deem necessary or appropriate, and to interpret the Partnership Agreement, to give effect to the intent and purpose of this Amendment No. 4.

     Section 3. Ratification of Partnership Agreement. Except as expressly modified and amended herein, all of the terms and conditions of the Partnership Agreement shall remain in full force and effect.

     Section 4. Governing Law. This Amendment No. 4 will be governed by and construed in accordance with the laws of the State of Delaware.

     IN WITNESS WHEREOF, the General Partner has executed this Amendment No. 4 on April 14, 2008, to be effective as of January 1, 2007.