<PAGE>
 
                                                                  EXHIBIT 10(OO)




                      THE VALLEY NATIONAL BANK OF ARIZONA
                          SUPPLEMENTAL EXCESS BENEFIT
                                RETIREMENT PLAN

<PAGE>
 
                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
 
                                                                                     Page No.   
                                                                                     --------  
<S>                                                                                  <C>       
Article One     Preamble......................................................           1     
                                                                                               
ARTICLE TWO     Construction..................................................           1     
                                                                                               
ARTICLE THREE   Eligibility and Participation.................................           2     
                                                                                               
ARTICLE FOUR    Benefits......................................................           2     
                                                                                               
ARTICLE FIVE    Payment of Benefits...........................................           3     
                                                                                               
ARTICLE SIX     Funding.......................................................           3     
                                                                                               
ARTICLE SEVEN   Administration................................................           3     
                                                                                               
ARTICLE EIGHT   Amendment and Termination of the Plan.........................           3     
                                                                                               
ARTICLE NINE    Assignment....................................................           4     
                                                                                               
ARTICLE TEN     Withholding...................................................           4     
                                                                                               
ARTICLE ELEVEN  Other Benefit Plans of the Bank or Affiliated Companies.......           4     
                                                                                               
ARTICLE TWELVE  Miscellaneous.................................................           4      
</TABLE>
<PAGE>
 
                      THE VALLEY NATIONAL BANK OF ARIZONA
                                        
                  SUPPLEMENTAL EXCESS BENEFIT RETIREMENT PLAN

                                  ARTICLE ONE

                                   PREAMBLE

     The VALLEY NATIONAL BANK OF ARIZONA, a national banking association,
hereinafter referred to as the "Bank," previously adopted THE RETIREMENT PLAN
FOR EMPLOYEES OF THE VALLEY NATIONAL BANK OF ARIZONA, hereinafter referred to as
the "Retirement Plan" and the INVESTMENT INCENTIVE PLAN FOR EMPLOYEES OF THE
VALLEY NATIONAL BANK OF ARIZONA, hereinafter referred to as the "Investment
Incentive Plan".  The Retirement Plan and the Investment Incentive Plan are
subject to the benefit and contribution limitations of Section 415 of the
Internal Revenue Code, hereinafter referred to as the "Code".  By reason of the
limitations of Section 415 of the Code, as incorporated in the Retirement Plan
and Investment Incentive Plan, a Participant's benefits under such Plans may be
reduced from the benefits which would otherwise be payable under such Plans in
the absence of the benefit and contribution limitations of Section 415.  The
Employee Retirement Income Security Act of 1974, hereinafter referred to as the
"Act" authorizes the Bank to establish an "excess benefit plan" for the purpose
of providing retirement benefits to certain employees in excess of the benefits
permitted under the Plans by reason of Section 415 of the Code.  Pursuant to
such authorization, the Bank adopted THE VALLEY NATIONAL BANK OF ARIZONA
SUPPLEMENTAL EXCESS BENEFIT RETIREMENT PLAN, hereinafter referred to as the
"Plan," effective January 1, 1983, to apply to Participants in the Retirement
Plan.  By this amendment and restatement in the entirety, the Bank hereby amends
the Plan to extend coverage to Participants in the Investment Incentive Plan
effective as of January 1, 1983.

                                  ARTICLE TWO

                                 CONSTRUCTION

     Terms capitalized in the Plan shall have the meaning given in Article Two
of the Retirement Plan and Article Two of the Investment Incentive Plan,
whichever is applicable, governing definitions and construction, except where
such terms are otherwise defined in the Plan. If any provision of the Plan is
determined for any reason to be invalid or unenforceable, the remaining
provisions shall continue in full force and effect. All of the provisions of the
Plan shall be construed and enforced according to the laws of the State of
Arizona, and shall be administered according to the laws of such state, except
as otherwise required by the Act, the Code or other applicable Federal law. It
is the intention of the Bank that the Plan, as adopted by the Bank, shall
constitute an "excess benefit plan" as defined in Section 3(36) of the Act.
Benefits under the Plan shall be paid from the general assets of the Bank and/or
Affiliated Companies, and not from any trust fund or other segregated fund. The
Plan shall be construed in a manner consistent with the Bank's intention.
<PAGE>
 
                                 ARTICLE THREE

                         ELIGIBLITY AND PARTICIPATION
                                        
     The Executive Committee of the Board of Directors of the bank shall
designate for participation in the Plan Employees of the Bank and/or Affiliated
Companies who are Participants in the Retirement Plan and/or the Investment
Incentive Plan. Designation of participant's in the Plan may be made
individually or by group designation, or both, as determined by the Executive
Committee. An Employee who is eligible to participate in the Plan shall commence
participation as of the first day of the Plan Year in which the Executive
Committee designates the Employee for participation in the Plan. Such
participation shall continue until the Executive Committee informs the
participant in writing that he is no longer eligible to participate in the Plan.

                                 ARTICLE FOUR

                                   BENEFITS

     Any participant in this Plan who is a Participant of the Retirement Plan
and who receives a benefit under the Retirement Plan (or such participant's
surviving spouse or annuitant in the event of the participant's death) shall be
entitled to a monthly benefit payable hereunder in accordance with ARTICLE FIVE
of the Plan, equal to the excess, if any, of (a) the amount of such
participant's monthly benefit, (or the surviving spouse's or annuitant's monthly
benefit if the participant has died) under the Retirement Plan determined
without regard to the limitations of Section 4.3 of the Retirement Plan and
Section 415 of the Code, over (b) the amount of such participant's monthly
benefit (or the surviving spouse's or annuitant's monthly benefit if the
participant has died) actually payable under the Retirement Plan, as determined
under the provisions of the Retirement Plan, subject to Section 4.3 of the
Retirement Plan and Section 415 of the Code.

     Any participant in this Plan who is a Participant in the Investment
Incentive Plan and who has Accounts under the Investment Incentive Plan (or such
participant's surviving spouse or designated beneficiary in the event of the
participant's death), shall be entitled to a benefit payable hereunder in
accordance with ARTICLE FIVE of the Plan, equal to the excess, if any, of (a)
the total amount which would be allocated to the participant's Accounts under
the Investment Incentive Plan, without regard to the limitations of Section 415
of the Code as incorporated therein, over (b) the amount actually allocated to
the participant's Accounts under the Investment Incentive Plan as a result of
the limitations of Section 415 of the Code as incorporated therein. The
participant shall be credited with interest on the amount so determined at the
currently prevailing rate credited to the Money Market Fund of the Investment
Incentive Plan as of each Accounting Date under the Investment Incentive Plan.

     Benefits payable under this Plan shall be payable to a participant (or the
participant's spouse, beneficiary or other annuitant if the participant has
died) in the same manner and subject to all the same options, conditions,
privileges and restrictions as are applicable to the benefits payable to the
participant (or his spouse, beneficiary or other annuitant) under the Retirement

                                       2
<PAGE>
 
Plan and/or Investment Incentive Plan, as though such benefits were payable
under the Retirement Plan and/or the Investment Incentive Plan, without,
however, taking into account the limitations of Section 415 of the Code as set
forth in the Retirement Plan and the Investment Incentive Plan. An election of
mode of payment under the Retirement Plan and/or the Investment Incentive Plan
shall constitute an election under this Plan.

                                  ARTICLE FIVE

                              PAYMENT OF BENEFITS

     Benefits under the Plan shall become payable when a participant (or his
spouse, beneficiary or annuitant if the participant has died) begins to receive
payments under the Retirement Plan and/or the Investment Incentive Plan, and
shall be payable by the Bank or the Affiliated Company that employed that
participant in the same manner and at the same time as the benefits payable to
the participant (or his spouse, beneficiary or annuitant if the participant has
died) under the Retirement Plan and/or the Investment Incentive Plan, as though
such benefits were payable under the Retirement Plan and/or the Investment
Incentive Plan.

                                  ARTICLE SIX

                                    FUNDING

     Benefits under the Plan shall be paid from the general assets of the Bank
and/or Affiliated Companies, and shall not be segregated in a trust fund or
otherwise funded in any manner prior to the time of payment. The Bank and
Affiliated Companies may, in their sole discretion, accrue and/or accumulate
reserves to fund benefits under the Plan. Such reserves, if any, shall
constitute general assets of the Bank and Affiliated Companies. No participant
shall have any vested rights hereunder nor any right hereunder to any specific
assets of the Bank and/or Affiliated Companies.

                                 ARTICLE SEVEN

                                ADMINISTRATION

     The Plan will be administered by the Committee which administers the
Retirement Plan. With respect to administration of the Plan, the provisions of
Article Eleven of the Retirement Plan, governing the powers of the Committee,
claim procedures and the scope of responsibility of the Committee shall be fully
applicable.

                                 ARTICLE EIGHT

                     AMENDMENT AND TERMINATION OF THE PLAN

     The Plan may be amended in whole or in part, prospectively or
retroactively, by action of the Bank's Board of Directors, and may be terminated
at any time by action of the Bank's Board of Directors; provided, however, that
no such amendment or termination shall reduce any 

                                       3
<PAGE>
 
amount payable hereunder to the extent such amount accrued prior to the date of
amendment or termination.

                                 ARTICLE NINE

                                  ASSIGNMENT

     No participant or beneficiary of a participant shall have any right to
assign, pledge, hypothecate, anticipate or any way create a lien on any amounts
payable hereunder. No amounts payable hereunder shall be subject to assignment
or transfer or otherwise be alienable, either by voluntary or involuntary act,
or by operation of law, or subject to attachment, execution, garnishment,
sequestration or other seizure under any legal, equitable or other process, or
be liable in any way for the debts or defaults of participants and their
beneficiaries.

                                  ARTICLE TEN

                                  WITHHOLDING

     Any taxes required to be withheld from payments to participants hereunder
shall be deducted and withheld by the Bank or the Affiliated Company making such
payments.

                                ARTICLE ELEVEN

            OTHER BENEFIT PLANS OF THE BANK OR AFFILIATED COMPANIES

     Nothing contained in the Plan shall prevent a participant (or his spouse,
beneficiary or annuitant if the participant has died), from receiving, in
addition to any payments provided for under the Plan, any payments provided for
under the Retirement Plan and/or the Investment Incentive Plan, or which would
otherwise be payable or distributable to the participant (or to his spouse,
beneficiary or annuitant if he has died) under any plan, policy or arrangement
of the Bank or an Affiliated Company. Nothing in the Plan shall be construed as
preventing the Bank or an Affiliated Company from establishing any other or
different plans providing for current or deferred compensation for employees.

                                ARTICLE TWELVE

                                 MISCELLANEOUS

     Nothing contained in the Plan shall be construed as a contract of
employment between the Bank or an Affiliated Company and an employee, as a right
of any employee to be continued in the employment of the Bank or an Affiliated
Company, or as a limitation of the right of the Bank or an Affiliated Company to
discharge any of its employees, with or without cause.

     All of the provisions of the Plan shall be binding upon all persons who
shall be entitled to any benefit hereunder, their heirs and personal
representatives.

                                       4
<PAGE>
 
     IN WITNESS WHEREOF, THE VALLEY NATIONAL BANK OF ARIZONA has signed this
instrument the 27th day of November, 1985.

                                   THE VALLEY NATIONAL BANK OF
                                   ARIZONA



                                   By:  /s/  Leonard W. Huck
                                      ----------------------------
                                        Its President & CAO



                                      ----------------------------  
                                                 "Bank"

Attest:

By:  /s/  G.E. Wright
   ------------------------------
   Its Cashier

          _______________________

                                       5
<PAGE>
 
                              FIRST AMENDMENT TO

                      THE VALLEY NATIONAL BANK OF ARIZONA

                  SUPPLEMENTAL EXCESS BENEFIT RETIREMENT PLAN

     Effective in 1983, THE VALLEY NATIONAL BANK OF ARIZONA, a national banking
association (hereinafter referred to as the "Bank") adopted THE VALLEY NATIONAL
BANK OF ARIZONA SUPPLEMENTAL EXCESS BENEFIT RETIREMENT PLAN (hereinafter
referred to as the "Plan") to benefit certain participants in the Retirement
Plan for Employees of The Valley National Bank of Arizona and the Investment
Incentive Plan for Employees of The Valley National Bank of Arizona (hereinafter
respectively referred to as the "Retirement Plan" and the "Investment Incentive
Plan."  Effective January 1, 1987, certain provisions of the Internal Revenue
Code enacted under the Tax Reform Act of 1986 will restrict contributions on
behalf of certain executives and key employees of the Bank under the Investment
Incentive Plan.  By this Amendment the Bank desires to amend the Plan for the
purpose of supplementing contributions that may no longer be made under the
Investment Incentive Plan with benefits under this Plan.  By this instrument,
the Bank accomplishes such amendment.

     1.   This Amendment shall be effective January 1, 1987. Except as amended
by this First Amendment, the Bank hereby ratifies the Plan as most recently
restated November 27, 1985. Except as amended herein, the Plan shall remain in
full force and effect.

     2.   ARTICLE FOUR of the Plan is hereby deleted in its entirety, and the
following ARTICLE FOUR is inserted in lieu thereof:

                                 ARTICLE FOUR

                                   BENEFITS

     Any participant in this Plan who is a Participant in the Retirement Plan
and who receives a benefit under the Retirement Plan (or such participant's
surviving spouse or annuitant in the event of the participant's death) shall be
entitled to a monthly benefit payable hereunder in accordance with ARTICLE FIVE
of the Plan, equal to the excess, if any, of (a) the amount of such
participant's monthly benefit (or the surviving spouse's or annuitant's monthly
benefit if the participant has died) under the Retirement Plan determined
without regard to the limitations of Section 4.3 of the Retirement Plan and
Section 415 of the Code, over (b) the amount of such participant's monthly
benefit (or the surviving spouse's or annuitant's monthly benefit if the
participant has died) actually payable under the Retirement Plan, subject to
Section 4.3 of the Retirement Plan and Section 415 of the Retirement Plan and
Section 415 of the Code.

     Any participant in this Plan who is a Participant in the Investment
Incentive Plan and who has Accounts under the Investment Incentive Plan (or such
participant's surviving spouse or designated beneficiary in the event of the
participant's death) shall be entitled to a benefit payable hereunder in
accordance with ARTICLE FIVE of the Plan, equal to the excess, if any, of 

                                       6
<PAGE>
 
(a) the total amount which would be allocated to the participant's Accounts
under the Investment Incentive Plan, without regard to the limitations of
Section 415 of the Code as incorporated therein. The participant shall be
credited with interest on the amount so determined at the currently prevailing
rate credited to the Money Market Fund of the Investment Incentive Plan as of
each Accounting Date under the Investment Incentive Plan.

     Any participant (or such participant's surviving spouse or designated
beneficiary in the event of the participant's death) in this Plan who is a
Participant in the Investment Incentive Plan and who is unable to direct (or is
subject to a refund of directed amounts) Pre-Tax Required Contributions (as
defined in the Investment Incentive Plan) under the Investment Incentive Plan in
the amount of six percent (6%) of Earnings (as defined in the Investment
Incentive Plan) by reason of the Seven Thousand Dollar ($7,000) limitation on
such contributions under Section 402(g) of the Code and the corresponding
provisions of the Investment Incentive Plan, or the "anti-discrimination"
requirements of Section 401(k)(3) of the Code and the corresponding provisions
of the Investment Incentive Plan, shall be entitled to a benefit hereunder in
accordance with ARTICLE FIVE of the Plan equal to the amount of Employer
Contributions (as defined in the Investment Incentive Plan) that would have been
credited to such participant's Employer Contributions Account (as defined in the
Investment Incentive Plan) as a matching contribution based on the Pre-Tax
Required Contributions the participant could have made in the absence of such
limitations, together with interest credited on such Employer Contributions as
though such Employer Contributions had been credited to the Money Market Fund of
the Investment Incentive Plan (and not withdrawn) and adjusted as of each
Accounting Date under the Investment Incentive Plan.

     Benefits payable under this Plan shall be payable to a participant (or the
participant's spouse, beneficiary or other annuitant if the participant has
died) in the same manner and subject to all the same options, doncitions,
privileges and restrictions as are applicable to the benefits payable to the
participant (or his spouse, beneficiary or other annuitant) under the Retirement
Incentive Plan and/or the Investment Incentive Plan, without, however, taking
into account the limitations of Section 415 of the Code as set forth in the
Retirement Plan and the Investment Incentive Plan.  An election of mode of
payment under the Retirement Plan and/or the Investment Incentive Plan shall
constitute an election under this Plan.

     IN WITNESS WHEREOF, THE VALLEY NATIONAL BANK OF ARIZONA, has signed this
instrument this 31st day of December, 1986.


                                   THE VALLEY NATIONAL BANK OF
                                   ARIZONA
                                   By: /s/
                                      -----------------------------------
                                      Its Chairman of the Board

ATTEST:

By:  /s/  G. E. Wright
   -----------------------------
   Its Cashier                 

                                       2
<PAGE>
 
                                  RESOLUTION

     WHEREAS, Section 415 of the Internal Revenue Code imposed certain
limitations on pension payments from the Retirement Plan for Employees of The
Valley National Bank of Arizona;

     WHEREAS, The Board of Directors deems it to be in the best interest of the
Association to provide supplemental payments to certain executives of the
Association and its corporate affiliates, to be designated by the Executive
Committee of the Board of Directors;

     NOW, THEREFORE, BE IT RESOLVED, That The Valley National Bank of Arizona
Supplemental Benefit Plan presented to this meeting be, and the same hereby is,
approved and adopted;

     RESOLVED FURTHER, That the Chairman of the Board or the President of this
Association be, and he hereby is, authorized, empowered and directed, for and on
behalf of this Association, and in its corporate name, and as its corporate act
and deed, to execute the Supplemental Benefit Plan with such changes, deletions
or additions therein as he may approve, his execution thereof to conclusively
evidence his approval of such changes, deletions or additions;

     RESOLVED FURTHER, That the Executive Committee of the Board of Directors of
this Association shall designate for participation in  said Supplemental Benefit
Plan such officers and other employees of this Association and affiliated
corporations as said Executive Committee shall determine, in its sole and
absolute discretion.

     RESOLVED FURTHER, That the acts and deeds of the officers of this
Association and the Executive Committee necessary to carry out the intent and
purpose of these resolutions be, and the same hereby are, ratified, confirmed,
approved and adopted as the acts and deeds of this Association.

     I, G. E. Wright, Vice President and Cashier of The Valley National Bank of
Arizona, hereby certify that the above is a true copy of a resolution adopted by
the Board of Directors of  The Valley National Bank of Arizona at a meeting held
July 20, 1983.

     IN WITNESS WHEREOF, I have hereunto set my hand and affixed the seal of
said Bank this 25th day of August, 1983.


                                    /s/ G. E. Wright
                                  ----------------------------------
                                  Vice President and Cashier
<PAGE>
 
                                  RESOLUTION
                                        
     WHEREAS, Section 415 of the Internal Revenue Code of 1954 (the "Code")
imposes certain limitations on benefits payable from qualified employee pension
and profit sharing plans;

     WHEREAS, The limitations of Section 415 of the Code will reduce the
benefits payable to certain executives and key employees of The Valley National
Bank of Arizona (the "Corporation") and its corporate affiliates under the
Retirement Plan for Employees of The Valley National Bank of Arizona (the
"Retirement Plan") and the Investment Incentive Plan for Employees of The Valley
National Bank of Arizona (the "Investment Incentive Plan");

     WHEREAS, The Board of Directors of the Corporation deems it to be in the
best interest of the Corporation and its corporate affiliates to establish an
"excess benefit plan" as defined in Section 3(36) if the Employee Retirement
Income Security Act of 1974 under which certain executives and key employees of
the Corporation and its corporate affiliates designated by the Executive
Committee of the Board of Directors will have their benefit payments under the
Retirement Plan and its Investment Incentive Plan supplemented by payments
designed to ensure that the total benefits received by such executives and key
employees under the Retirement Plan and the Investment Incentive Plan and under
the "excess benefit plan" will equal the benefits to which the executives or key
employees would have been entitled under the Retirement Plan and the Investment
Incentive Plan in the absence of the limitations of Section 415 of the Code;

     WHEREAS, As a Supplemental Excess Benefit Retirement Plan was adopted at a
meeting on July 20, 1983;

     WHEREAS, The Board of Directors now desires to amend the Plan to extend its
coverage to executives and key employees whose benefits under the Investment
Incentive Plan will be reduced by the limitations of Section 415 of the Code;

     NOW THEREFORE BE IT RESOLVED, That the Plan be amended to extend its
coverage to certain executives and key employees designated by the Executive
Committee of the Board of Directors of the Corporation, whose company
contribution allocations under the Investment Incentive Plan will be reduced as
a result of the limitations of Section 415 of the Code; and

     RESOLVED FURTHER, That said amendment shall be effective as of January 1,
1983; and

     RESOLVED FURTHER, That the President or a Vice President be and hereby is
authorized to execute such amendments or revised plan documents as in his
opinion will carry out the objectives of these resolutions; and

     RESOLVED FURTHER, That the acts and deeds of the officers of the
Corporation necessary to carry out the intent and purpose of these resolutions
be, and the same hereby are, ratified, confirmed and adopted as the acts and
deeds of the Corporation.
<PAGE>
 
     I, G. E. Wright, Senior Vice President and Cashier of The Valley National
Bank of Arizona, do hereby certify that the foregoing is a copy of a Resolution
adopted by the Board of Directors of The Valley National Bank of Arizona at a
meeting held November 20, 1985, and entered on the minutes of the Bank.

     IN WITNESS WHEREOF, I have hereunto set my hand and affixed the seal of
said Bank this 19th day of December, 1985.


                                   /s/  G. E. Wright
                                   ------------------------------------
                                   Senior Vice President & Cashier

                                       2