EXHIBIT 10.13 FIRST AMENDMENT TO CONTRIBUTION, CONVEYANCE AND ASSUMPTION AGREEMENT THIS FIRST AMENDMENT TO CONTRIBUTION, CONVEYANCE AND ASSUMPTION AGREEMENT (this "Agreement"), dated as of December 15, 1998, is entered into by and among PLAINS RESOURCES INC., a Delaware corporation ("Plains Resources"), PLAINS ALL AMERICAN INC., a Delaware corporation ("PAAI"), PLAINS ALL AMERICAN PIPELINE, L.P., a Delaware limited partnership (the "Partnership"), PLAINS MARKETING, L.P., a Delaware limited partnership ("Plains Marketing"), ALL AMERICAN PIPELINE, L.P., a Texas limited partnership ("All American L.P."), and PAAI LLC, a Delaware limited liability company ("PAAI LLC"). WHEREAS, the parties to this Agreement desire to make certain amendments to the terms of the Contribution, Conveyance and Assumption Agreement (the "Contribution Agreement"), dated as of November 13, 1998, in order to correctly state certain amounts incorrectly recited therein; NOW THEREFORE, in consideration of their mutual undertakings and agreements hereunder and under the Contribution Agreement, the parties to this Agreement agree to amend the Contribution Agreement as follows: 1. The amount of cash distributed by the Partnership to PAAI as a reimbursement for certain capital expenditures as set forth in Section 2.5 of the Contribution Agreement is hereby amended to be $177,589,500. The amount of the cash contributed by the Partnership to Plains Marketing as set forth in Section 2.5(i) of the Contribution Agreement is hereby amended to be $67,100,000. 2. The cash payment made by Plains Marketing to Plains Resources for the sale of the Plain Assets as set forth in Section 2.6(i) of the Contribution Agreement is hereby amended to be $64,100,000. 3. Except as expressly amended herein, the parties to this Agreement confirm all of the terms of the Contribution Agreement. IN WITNESS WHEREOF, this Agreement has been duly executed by the parties hereto as of the date first above written. PLAINS RESOURCES INC., a Delaware corporation By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President PLAINS MARKETING, L.P., a Delaware limited partnership By: Plains All American Inc., a Delaware corporation, as general partner By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President PLAINS ALL AMERICAN PIPELINE, L.P., a Delaware limited partnership By: Plains All American Inc., a Delaware corporation, as general partner By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President 2 ALL AMERICAN PIPELINE, L.P., a Texas limited partnership By: Plains All American Inc., a Delaware corporation, as general partner By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President PLAINS ALL AMERICAN INC., a Delaware corporation By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President PAAI LLC, a Delaware limited liability company By: Plains All American Inc., a Delaware corporation, its sole member By: /s/ Michael R. Patterson ------------------------ Michael R. Patterson, Senior Vice President 3