FOUR CORNERS PROJECT OPERATING AGREEMENT AMENDMENT NO. 13

The parties to this Amendment No. 13 (this “Amendment”) to the Four Corners Project Operating Agreement (the “Operating Agreement”) are: ARIZONA PUBLIC SERVICE COMPANY, an Arizona corporation; EL PASO ELECTRIC COMPANY, a Texas corporation; PUBLIC SERVICE COMPANY OF NEW MEXICO, a New Mexico corporation; SALT RIVER PROJECT AGRICULTURAL IMPROVEMENT AND POWER DISTRICT, an agricultural improvement district, organized and existing under the laws of the State of Arizona; SOUTHERN CALIFORNIA EDISON COMPANY, a California corporation; and TUCSON ELECTRIC POWER COMPANY, an Arizona corporation, formerly known as Tucson Gas & Electric Company (collectively, hereinafter referred to as the “Participants”).

This Amendment is made with reference to the following facts, among others:

Amendment No. 11, dated May 23, 1997; and Amendment No. 12, dated February 3, 2000.

For and in consideration of the premises and the mutual obligations of, and undertakings by, the Participants, as hereinafter provided in this Amendment, the Participants agree as follows:

The term “Switchyard Facilities” shall have the meaning given to it in Section 5.72 of the Operating Agreement. Exhibit 1 of this Amendment, however, is included as a reference with respect to the ownership percentages of the Switchyard Facilities.

Section 8 of the Operating Agreement is hereby amended by adding the following to the end of Section 8.1:

The Engineering and Operating Committee’s functions and responsibilities set forth in this Operating Agreement shall no longer apply to the Switchyard Facilities, to the extent the continued application of such functions and responsibilities to the Switchyard Facilities after the effectiveness of this Amendment would be duplicative of, or inconsistent with, the functions and responsibilities of the Switchyard Engineering and Operating Committee for the Switchyard Facilities under this Operating Agreement or assigned to the Switchyard Engineering and Operating Committee by the Coordination Committee.

8A.1. The Switchyard Engineering and Operating Committee is hereby established. It shall consist of not more than two representatives designated by each of the Participants. Each such representative shall be authorized by the Participant by whom he or she is designated to act on its behalf, with respect to those matters that are the responsibilities of the Switchyard Engineering and Operating Committee.

8A.2. The Switchyard Engineering and Operating Committee shall be and remain in existence during the term of the Operating Agreement; provided, however, that any action or determination of the Switchyard Engineering and Operating Committee shall require an affirmative vote of all Participants, acting through

their respective representatives, that have an ownership interest in that portion of the Four Corners Project that is the subject matter of the action or determination. Only those Participants having an ownership interest in that portion of the Four Corners Project that is the subject matter of an action or determination may participate in the discussions relating to such action or determination; provided, however, that this restriction shall apply only when required by a regulatory authority with jurisdiction over the Participants(s), an applicable code of conduct, or a Participant’s reasonable competitive concerns.

8A.7. The Switchyard Engineering and Operating Committee shall direct that, pursuant to FERC requirements, an ad hoc committee be formed to review all Participant and third party requests to add facilities or interconnect to the Switchyard Facilities.

8A.8. The Switchyard Engineering and Operating Committee shall have the authority to review and approve requests from any Participant to affix its name to Switchyard Facilities capital items, the granting of such approval only being subject to guidelines to be established by the Switchyard Engineering and Operating Committee as to the manner and location on which the name shall be affixed.

This Amendment may be executed in any number of counterparts, and upon execution by all of the Participants, the counterparts shall have the same force and effect as an original instrument and as if all of the Participants had signed the same instrument. Any signature page of this Amendment may be detached from any counterpart of this Amendment without impairing the legal effect of any signature thereon, and may be attached to another counterpart of this Amendment identical in form hereto but having attached to it one or more signature pages.

Except as specifically amended or otherwise modified herein, the Operating Agreement, as previously amended, shall remain in full force and effect.

This Amendment shall be effective upon the date when executed by all of the Participants.

[Remainder of page intentionally left blank; signature page follows]

The signatories hereto represent that they have been appropriately authorized to enter into this Amendment on behalf of the party for whom they sign. This Amendment is hereby executed as of the 1st day of December, 2010.