<PAGE>   1
                                                                   EXHIBIT 10.15


                              EXCESS BENEFIT PLAN
                                       OF
                       COMMONWEALTH FEDERAL SAVINGS BANK
                     (AS AMENDED EFFECTIVE JANUARY 1, 1998)

         This Commonwealth Bank Excess Benefit Plan (formerly named the
Commonwealth Federal Savings Bank Excess Benefit Plan) (the "Plan") was adopted
by Commonwealth Bank (formerly Commonwealth Federal Savings Bank) (the "Bank")
effective as of January 1, 1994.  The Plan is established and maintained by the
Bank for the purpose of permitting one or more of its officers listed in
Appendix A attached hereto who participate in the Bank's Employee Stock
Ownership Plan ("ESOP"), to receive allocations representing shares of common
stock of the Bank pursuant to this Plan in excess of the number of shares of
common stock of the Bank which are allocable to their accounts within the ESOP
under the limitation imposed by Section 401(a)(17) of the Internal Revenue Code
of 1986, as amended by the Revenue Reconciliation Act of 1993 ("1993 Act").

         The Plan is an unfunded plan maintained for the purpose of providing
deferred compensation for selected officers of the Bank, each of whom is a
member of a select group of management or highly compensated employees for
purposes of Title I of the Employee Retirement Income Security Act of 1974, as
amended.

         The Bank amended the Plan effective January 1, 1998, to reflect the
Bank's current name and to designate an additional participant in the Plan.

         Accordingly, the Bank hereby adopts the amended Plan pursuant to the
terms and provisions set forth below:

                                   ARTICLE I

                                  DEFINITIONS

         Whenever used herein the following terms shall have the meanings 
hereinafter set forth:


         1.1.    "Bank" means Commonwealth Bank, or, to the extent provided in
Section 8.8 below, any successor corporation or other entity resulting from a
merger or consolidation into or with the Bank or a transfer or sale of
substantially all of the assets of the Bank.

         1.2.    "Board" means the Board of Directors of the Bank.

         1.3.    "Code" means the Internal Revenue Code of 1986, as amended
from time to time, and any regulations relating thereto.

         1.4.    "Bank Common Stock" means shares of common stock of the Bank.
<PAGE>   2
         1.5.    "ESOP" means the Commonwealth Bank Employee Stock Ownership
Plan, and each successor or replacement employee stock ownership plan.

         1.6.    "ESOP Allocation" means the number of shares allocable to the
individual account of a participant in the ESOP pursuant to Article IV of the
ESOP.

         1.7.    "Participant" means a salaried employee of the Bank who is a
participant in the ESOP, who is a member of a select group of management or
highly compensated employees within the meaning of section 201 (2) of the
Employee Retirement Income Security Act of 1974, as amended, and who is
selected by the Board of Directors of the Bank to participate in the Plan.

         1.8.    "Plan Year" means the 12-consecutive-month period ending
December 31 of each year.

         1.9.    "Stock Unit" means a bookkeeping unit used for the purpose of
crediting amounts to the account of a Participant, each such Stock Unit being
equivalent to one share of Bank Common Stock.

         1.10.    "Supplemental ESOP Allocation" shall mean the number of Stock
Units allocated to a Participant's account pursuant to Section 3.1 of the Plan.

         1.11.    Words in the masculine gender shall include the feminine and
the singular shall include the plural, and vice versa, unless qualified by the
context.  Any headings used herein are included for ease of reference only, and
are not to be construed so as to alter the terms hereof.


                                   ARTICLE II

                                  ELIGIBILITY

         A salaried employee of the Bank who is eligible to receive the benefit
of an ESOP Allocation, the total amount of which is reduced by reason of the
limitation on compensation which may be taken into account for the purpose of
calculating allocations pursuant to Section 401(a)(17) of the Code, as amended
by the 1993 Act, shall be eligible to be selected by the Board of Directors of
the Bank to participate in the Plan.

                                  ARTICLE III

                           SUPPLEMENTAL CONTRIBUTIONS





                                      -2-
<PAGE>   3
         3.1.    Supplemental ESOP Allocation.

         A Participant in the Plan shall receive a Supplemental ESOP Allocation
of Stock Units each year at the same time that allocations of Bank Common Stock
are made pursuant to the ESOP.  The number of Stock Units allocable to a
Participant for any Plan Year shall be an amount equal to the difference
between (a) and (b) below:

                 (a)      The ESOP Allocation which would have been allocated
                 to the Participant for the Plan Year, as determined by Article
                 IV of the ESOP and the definition of "Compensation" in Section
                 1.10 of the ESOP; provided, however, that (i) a Participant's
                 Compensation shall be deemed to equal $235,840 if the
                 Participant's Compensation, without giving effect to the
                 limitation imposed by section 401 (a)(17) of the Code, equals
                 or exceeds $235,840 both in 1993 and in the year with respect
                 to which the allocation is made, and (ii) the Compensation of
                 a Participant who is not described in (i) shall be determined
                 without giving effect to the limitation imposed by section
                 401(a)(17) of the Code, but. shall not in any event exceed
                 $235,840;

                 LESS

                 (b)      The ESOP Allocation actually allocated to the account
                 of the Participant in the ESOP for the Plan Year.

Supplemental ESOP Allocations made for the benefit of a Participant for any
Plan Year shall be credited to an account maintained under the Plan in the name
of each Participant.

                                   ARTICLE IV

                  INVESTMENT OF SUPPLEMENTAL ESOP ALLOCATIONS

         Amounts credited hereunder to the account of a Participant shall be
treated as if they were actually invested in the ESOP account of the
Participant and shall be credited with gains and losses at the same time and in
the same manner as is applicable to amounts invested in the ESOP account of
such Participant. A change by a Participant in the investment election
applicable to amounts in his ESOP account will be effective at the same time
that such change is applicable to his ESOP account.





                                      -3-
<PAGE>   4
                                   ARTICLE V

                             VESTING; DISTRIBUTIONS

         5.1.    VESTING. The vested portion of a Participant's account shall be
a percentage of the total amount credited to the account determined on the
basis of the Participant's number of "Years of Service" (as defined in Section
1.56 (or any successor thereto) of the ESOP) according to the following
schedule:

<TABLE>
<CAPTION>
                 Years of Service                          Percentage
                 ----------------                          ----------

                 <S>                                         <C>
                 Less than 3                                   0%
                           3                                   20%
                           4                                   40%
                           5                                   60%
                           6                                   80%
                           7                                   100%
</TABLE>

         In determining Years of Service for purposes of vesting under the
Plan, Years of Service prior to January 1, 1993 shall be excluded.

         Notwithstanding the above vesting schedule, a Participant shall be
100% vested in his account upon attainment of "Normal Retirement Age" (as
defined in Section 1.36 (or any successor thereto) of the ESOP).

         5.2     DISTRIBUTION. The vested portion of amounts credited to a 
Participant's account shall be distributed to a Participant at the same time,
and (except as provided in Section 8.1) in the same manner, as benefits shall
be distributed from the ESOP pursuant to Article VII of the ESOP.

         If a Participant should die before distribution of the vested portion
of his account pursuant to the Plan has been made to him, any remaining vested
amounts shall be distributed to his beneficiary in the method designated by the
Participant in a writing delivered to the Bank prior to his death. If a
Participant has not designated a beneficiary, or method of distribution, or if
no designated beneficiary is living on the date of distribution, such vested
amounts shall be distributed to those persons entitled to receive distributions
of the Participant's account under the ESOP and in the same method as
distribution is made under the ESOP.





                                      -4-
<PAGE>   5
                                   ARTICLE VI

                           ADMINISTRATION OF THE PLAN

         6.1.    Administration by the Bank. The Bank shall be responsible for
the general operation and administration of the Plan and for carrying out the
provisions thereof.

         6.2     General Powers of Administration. All provisions set forth in
the ESOP with respect to the administrative powers and duties of the Bank,
expenses of administration, and procedures for filing claims shall also be
applicable with respect to the Plan. The Bank shall be entitled to rely
conclusively upon all tables, valuations, certificates, opinions and reports
tarnished by any actuary, accountant, controller, counsel or other person
employed or engaged by the Bank with respect to the Plan.

                                  ARTICLE VII

                            AMENDMENT OR TERMINATION

         7.1.    Amendment or Termination. The Bank intends the Plan to be
permanent but reserves the right to amend or terminate the Plan when, in the
sole opinion of the Bank, such amendment or termination is advisable. Any such
amendment or termination shall be made pursuant to a resolution of the Board
and shall be effective as of the date of such resolution.

         7.2     Effect of Amendment or Termination. No amendment or
termination of the Plan shall directly or indirectly reduce the vested portion
of any account held hereunder as of the effective date of such amendment or
termination.  Upon termination of the Plan, distribution of vested amounts
credited to the account of a Participant shall be made to the Participant or
his beneficiary in the manner and at the time described in Section 5.2 of the
Plan.  No additional credits of ESOP Allocations shall be made to the account
of a Participant and no additional Years of Service (within the "meaning of
Section 5.1) shall be credited after termination of the Plan, but the Bank
shall continue to credit gains and losses pursuant to Article IV until the
vested balance of his account has been fully distributed to the Participant or
his beneficiary.

                                  ARTICLE VIII

                               GENERAL PROVISIONS

         8.1.    Participant's Rights Unsecured. To fund its obligations under
the Plan, the Bank may elect to form a trust, or to utilize a pre-existing
trust, to purchase and hold the alternative forms of assets which are permitted
under the ESOP, including shares of Bank Common Stock, subject to compliance
with all applicable securities laws. If the Bank elects to use a trust to fund
its obligations under the Plan, a Participant shall have no right to demand the
transfer to him of stock or other assets from the Bank, or from such a trust
formed, or utilized by the Bank. Any





                                      -5-
<PAGE>   6
assets held in a trust, including shares of Bank Common Stock, may be
distributed to a Participant in payment of part or all of the Bank's
obligations under the Plan. The right of a Participant or his designated
beneficiary to receive a distribution hereunder shall be an unsecured claim
against the general assets of the Bank, and neither the Participant nor a
designated beneficiary shall have any rights in or against any specific assets
of the Bank.

         8.2.    General Conditions. Except as otherwise expressly provided
herein, all terms and conditions of the ESOP applicable to an ESOP Allocation
will also be applicable to an allocation of Stock Units pursuant to this Plan.
Nothing in this Plan shall operate or be construed in any way to modify, amend
or affect the terms and provisions of the ESOP.

         8.3.    No Guarantee of Benefits. Nothing contained in the Plan shall
constitute a guaranty by the Bank or any other person or entity that the assets
of the Bank will be sufficient to pay any benefit hereunder.

         8.4.    No Enlargement of Employee Rights. No Participant shall have
any right to receive a distribution of contributions made under the Plan except
in accordance with the terms of the Plan.  Establishment of the Plan shall not
be construed to give any Participant the right to be retained in the service of
the Bank.

         8.5.    Spendthrift Provision. No interest of any person or entity in,
or right to receive a distribution under, the Plan shall be subject in any
manner to sale, transfer, assignment, pledge, attachment, garnishment, or other
alienation or encumbrance of, any kind; nor may such interest or right to
receive a distribution be taken, either voluntarily or involuntarily for the
satisfaction of the debts of, or other obligations or claims against, such
person or entity, including claims for alimony, support, separate maintenance
and claims in bankruptcy proceedings.

         8.6.    Applicable Law. The Plan shall be construed and administered
under the laws of the Commonwealth of Pennsylvania to the extent such laws are
not superseded by federal law.

         8.7.    Incapacity of Recipient. If any person entitled to a
distribution under the Plan is deemed by the Bank to be incapable of personally
receiving and giving a valid receipt for such payment, then, unless and until
claim therefor shall have been made by a duly appointed guardian or other legal
representative of such person, the Bank may provide for such payment or any
part thereof to be made to any other person or institution then contributing
toward or providing for the care and maintenance of such person.  Any such
payment shall be a payment for the account of such person and a complete
discharge of any liability of the Bank and the Plan therefor.

         8.8.    Corporate Successors. The Plan shall not be automatically
terminated by a transfer or sale of assets of the Bank or by the merger of
consolidation of the Bank into or with any other corporation or other entity,
but the Plan shall be continued after such sale, merger or consolidation only
if and to the extent that the transferee, purchaser or successor entity agrees
to





                                      -6-
<PAGE>   7
continue the Plan.  In the event that the Plan is not continued by the
transferee, purchaser or successor entity, then the Plan shall terminate
subject to the provisions of Section 7.2.

         8.9.    Unclaimed Benefit. Each Participant shall keep the Bank
informed of his current address and the current address of his designated
beneficiary.  The Bank shall not be obligated to search for the whereabouts of
any person.  If the location of a Participant is not made known to the Bank
within three (3) years after the date on which payment of the Participant's
account may first be made, payment may be made as though the Participant had
died at the end of the three-year period.  If, within one additional year after
such three year period has elapsed, or, within three years after the actual
death of a Participant, the Bank is unable to locate any designated beneficiary
of the Participant, then the Bank shall have no further obligation to pay any
benefit hereunder to such Participant or designated beneficiary and such
benefit shall be irrevocably forfeited.

         8.10.    Limitations on Liability. Notwithstanding any of the
preceding provisions of the Plan, neither the Bank nor any individual acting as
employee or agent of the Bank shall be liable to any Participant, former
Participant or other person for any claim, loss, liability or expense incurred
in connection with the Plan.

         IN WITNESS WHEREOF, Commonwealth Bank has caused these presents to be
duly executed as of the 9th day of December, 1997.


                                           COMMONWEALTH BANK


Attest:


[SIG]                                      By: /s/ PATRICK J. WARD
----------------------------                   --------------------------





                                      -7-
<PAGE>   8
                                   APPENDIX A

         The Bank has designated the following persons as Participants in its
Excess Benefit Plan:

1.       Charles H. Meacham, Chairman and Chief Executive Officer, effective
         January 1, 1994.

2.       Patrick J. Ward, President and Chief Operating Officer, effective
         January 1, 1998.





                                      -8-