Exhibit 10.1

FIRST AMENDMENT TO PROMISSORY NOTE

This FIRST AMENDMENT TO PROMISSORY NOTE (this “Amendment”) is made and entered
into on this 1st day of June 2012 by and between PAA Natural Gas Storage, L.P.,
a Delaware limited partnership (the “Borrower”) and Plains All American
Pipeline, L.P., a Delaware limited partnership (the “Lender”).

WHEREAS, Borrower and Lender executed and delivered a promissory note (the
“Original Note”) in the amount of TWO HUNDRED MILLION AND 00/100 DOLLARS (U.S.
$200,000,000.00) (the “Original Note”) dated as of February 9, 2011; and

WHEREAS, Borrower and Lender wish to amend the Original Note to adjust the
interest rate and Scheduled Maturity Date.

NOW THEREFORE, in consideration of the foregoing, Borrower and Lender hereby
agree as follows:

 

  1. All capitalized terms not otherwise defined herein shall have the
respective meanings ascribed to them in the Original Note.

 

  2. The definition of “Scheduled Maturity Date” in Section 1 of the Original
Note shall be deleted and replaced with the following:

“Scheduled Maturity Date” shall mean June 1, 2015.”

 

  3. Section 2 of the Original Note shall hereby be amended and restated in its
entirety as follows:

“PROMISE TO PAY. Borrower, for value received, absolutely, irrevocably and
unconditionally promises to pay to the order of Lender, in lawful money of the
United States of America and in immediately available funds, the principal sum
of TWO HUNDRED MILLION AND 00/100 DOLLARS (U.S. $200,000,000.00) (the “Borrowed
Amount”), together with simple interest assessed at the fixed rate per annum
equal to (i) five and a quarter percent (5.25%) from February 9, 2011 to May 31,
2012 and (ii) four percent (4.00%) from June 1, 2012 until the Scheduled
Maturity Date, calculated on the basis of a 360 day calendar year (twelve 30 day
months), on the principal balance of this Note as outstanding from time to time,
commencing on the date of this Note and continuing until this Note is paid in
full.”

 

  4. Borrower certifies that the representations and warranties of Borrower
contained in Section 6 of the Original Note are true and correct in all material
respects on and as of the date hereof as though made on and as of the date
hereof.

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  5. Borrower certifies that immediately after giving effect to this Amendment,
no Event of Default under the Original Note has occurred and is continuing.

 

  6. Except as otherwise provided in this Amendment, all of the terms, covenants
and conditions in the Original Note shall remain in full force and effect.

 

  7. This Amendment will be governed by, construed and enforced in accordance
with the laws of the State of Texas without regard to any laws that might result
in the application of the laws of any other jurisdiction.

[THE BALANCE OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

 

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PRIOR TO SIGNING THIS AMENDMENT, BORROWER READ AND UNDERSTOOD ALL OF THE
PROVISIONS OF THIS AMENDMENT.

 

    BORROWER:     PAA NATURAL GAS STORAGE, L.P.     By:  

PNGS GP LLC,

its General Partner

      By:   /s/ Al Swanson       Name:   Al Swanson       Title:  

Executive Vice President and

Chief Financial Officer

   

LENDER:

 

PLAINS ALL AMERICAN PIPELINE, L.P.

    By:  

PAA GP LLC,

its General Partner

    By:  

PLAINS AAP, L.P.,

its Sole Member

    By:  

PLAINS ALL AMERICAN GP LLC,

its General Partner

      By:   /s/ Charles Kingswell-Smith       Name:   Charles Kingswell-Smith  
    Title:   Vice President and Treasurer

 

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