<PAGE>

                                                                   Exhibit 10.15

                         AECOM TECHNOLOGY CORPORATION
               MANAGEMENT SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

                            Effective July 1, 1996
<PAGE>

                         AECOM TECHNOLOGY CORPORATION
               MANAGEMENT SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN


I.   Establishment and Purpose

     1.1  Effective July 1, 1996, AECOM Technology Corporation has established
          this Management Supplemental Executive Retirement Plan ("Plan") to
          supplement the retirement benefits payable to certain employees under
          the AECOM Pension Plan. This Plan is intended to be an unfunded plan
          maintained by the Company primarily for the purpose of providing
          deferred compensation for a select group of management or highly
          compensated employees described in Section 201(2) of ERISA.


II.  Definitions

     2.1  Actuarial Equivalent means a benefit of equivalent value, calculated
          --------------------
          using the 1971 GAM Table (75% Male, 25% female) and an 8-1/2% interest
          rate; however, when calculating an Actuarial Equivalent lump sum
          benefit under Section 3.5(b)(1) or 3.6, the guaranteed installment
          options under Section 3.5(b)(2) or the annuity value under Section
          3.1(b)(2), mortality shall be determined using the 1983 GAM Table and
          the interest rate shall be equal to the sum of the rate on 10-year
          U.S. Treasury notes in effect on the first day of the Plan Year
          preceding or coincident with the Retirement Date plus 50 basis points.

     2.2  AECOM Pension Plan means the AECOM Technology Corporation Pension
          ------------------
          Plan, as amended from time to time.

     2.3  Beneficiary means the person(s) designated by the Participant in
          -----------
          writing to receive the remaining installments under the five- or ten-
          year guaranteed installment option if the Participant dies before
          receiving all installments. The Participant may change the Beneficiary
          at any time by submitting a signed written designation to the
          Committee. If the designated Beneficiary fails to survive the
          Participant and the Participant has not designated a successor
          Beneficiary, the remaining installment payments shall be paid to the
          Participant's surviving spouse, or if there is no spouse, his
          surviving descendants by right of representation or if there are none,
          his estate. If the Beneficiary survives the Participant, but dies
          before receiving all remaining installments, the remaining
          installments shall be paid to the Beneficiary's estate.

     2.4  Board of Directors means the Board of Directors of the Company.
          ------------------

                                       2
<PAGE>

     2.5  Change of Control shall be deemed to occur when any person (as defined
          -----------------
          in Section 13(d) of the Securities Exchange Act of 1934), other than
          the Company or any subsidiary or employee benefit plan or trust
          maintained by the Company, shall become the "beneficial owner" (as
          defined in Rule 13d-3 under the Securities Exchange Act of 1934),
          directly or indirectly, of more than 25% of the common stock of the
          Company outstanding at the time, without the prior approval of the
          Board of Directors. A Participant's employment is deemed to have been
          terminated on account of Change of Control if he is involuntarily
          terminated by the Company within 36 months following a Change of
          Control.

     2.6  Code means the Internal Revenue Code of 1986, as amended from time to
          ----
          time.

     2.7  Committee means the Pension Committee or such other committee
          ---------
          designated or appointed by the Board of Directors to administer the
          Plan.

     2.8  Company means AECOM Technology Corporation.
          -------

     2.9  Constructive Termination means a voluntary termination of employment
          ------------------------
          by the Participant within 36 months following a Change of Control if
          (a) the Participant is demoted by a change in his title,
          responsibilities, duties, support services, etc.; (b) the sum of the
          Participant's salary, bonus, and incentive pay is materially reduced;
          or (c) the Participant's aggregate benefits (including retirement,
          welfare and fringe benefits) are materially reduced, other than as a
          result of legislation.

     2.10 Disability has the same meaning as under the AECOM Pension Plan.
          ----------

     2.11 Early Retirement Date means the first date on which a Participant has
          ---------------------
          attained age 55 and has been a Participant for 36 months.

     2.12 Effective Date means July 1, 1996.
          --------------

     2.13 ERISA means the Employee Retirement Income Security Act of 1974, as
          -----
          amended from time to time.

     2.14 Normal Retirement Age means the first date on which a Participant has
          ---------------------
          attained age 62 and has been a Participant for 36 months.

     2.15 Participant refers to an employee of the Company who (a) is a member
          -----------
          of a select group of management or highly compensated employees
          (within the meaning of Section 201(2) of ERISA), (b) has completed at
          least 5 Years of Service, (c) is at least 50 years old, (d) has a date
          of hire or adjusted date of hire if later) on or after March 1, 1996,
          and (e) has been selected by the Board of Directors to participate in
          this Plan. The Committee shall maintain a record of Participants.

     2.16 Plan Administrator means the Committee.
          ------------------

                                       3
<PAGE>

     2.17 Plan Year means the twelve-month period ending on September 30, with
          ---------
          the first Plan Year beginning July 1, 1996 and ending September 30,
          1996.

     2.18 Retirement Date means the first day of the month following a
          ---------------
          Participant's termination of employment for any reason, including
          death.

     2.19 Spouse means the person to whom the Participant is married on his
          ------
          Retirement Date or on his date of death, if earlier.

     2.20 Unlimited AECOM Pension Plan Benefit means the annual benefit the
          ------------------------------------
          Participant would have received under the AECOM Pension Plan if:

          (a)  Code Sections 401(a)(17) and 415 did not apply;

          (b)  the benefit was paid as a single life annuity commencing on the
               Participant's Retirement Date;

          (c)  there was no actuarial reduction in the AECOM Pension Plan for
               commencement of benefits at age 62 or later; and

          (d)  the AECOM Pension Plan permitted retirement at any age.

     2.21 Year of Service means a year of Credited Service as defined in the
          ---------------
          AECOM Pension Plan.


III. Retirement and Death Benefits

     3.1  Normal Retirement Benefits
          --------------------------

          A Participant who terminates employment with the Company on or
          after attaining Normal Retirement Age and who executes the agreement
          not to compete described in Section 3.7 shall be entitled to an annual
          benefit which is equal to (a) minus (b):

          (a)  the Participant's Unlimited AECOM Pension Plan Benefit;

          (b)  the sum of (1) and (2)

                    (1)  The annual benefit payable to the Participant under the
                         AECOM Pension Plan determined as though benefits were
                         being paid as a single life annuity commencing on the
                         Participant's Retirement Date.

                                       4
<PAGE>

                    (2)  The Credit from the following table, converted to an
                         Actuarial Equivalent single life annuity commencing on
                         the Participant's Retirement Date.

<TABLE>
<CAPTION>
               For Retirement Date in            ESOP Participation
                Plan Year Ending in:           Commencing in Plan Year
                                                    Beginning in:

                                          1996                   1997
<S>                                    <C>                 <C>

                     1997              $ 8,800                 $    0

                     1998               17,800                  8,800

                     1999               18,700                  9,300

                     2000               19,600                  9,700

                     2001 and later     19,600*                 9,700*

                     *  plus 5% compounded annually
</TABLE>

     3.2  Early Retirement Benefits
          -------------------------

          A Participant who terminates employment on or after his Early
          Retirement Date and before attaining Normal Retirement Age and who
          executes the agreement not to compete described in Section 3.7 shall
          be entitled to an annual benefit equal to (a) minus (b), where (a) is
          an annual benefit equal to the benefit determined under Section
          3.1(a), reduced 1/180th for each month by which the Participant's age
          on his Retirement Date is less than 62, and (b) is the benefit
          determined under Section 3.1(b).

     3.3  Termination of Employment
          -------------------------

          (a)  A Participant who terminates employment with the Company prior to
               his Early Retirement Date (other than on account of Disability,
               Change of Control or Constructive Termination) shall not be
               entitled to any benefits under this Plan.

          (b)  A Participant who terminates employment with the Company prior to
               his Early Retirement Date on account of Disability, Change of
               Control or Constructive Termination is entitled to an annual
               benefit which is equal to (1) minus (2):

               (1)  The Actuarial Equivalent of the Unlimited AECOM Pension Plan
                    Benefit payable at his Early Retirement Date;

               (2)  The sum of (A) and (B):

                                       5
<PAGE>

                    (A)  The Actuarial Equivalent of the annual benefit payable
                         to the Participant under the AECOM Pension Plan as a
                         single life annuity commencing on his Early Retirement
                         Date.

                    (B)  The single life annuity described in Section 3.1(b)(2).

          (c)  A Participant whose employment is terminated for cause shall not
               be entitled to any benefits under the Plan.  A termination is
               "for cause" if the Participant is terminated for reasons related
               to the commission by the Participant in the course of employment
               of any material act of dishonesty, the disclosure by the
               Participant of any confidential information or the commission by
               the Participant of any act of gross carelessness or willful
               misconduct.

     3.4  Rules Regarding Reductions
          --------------------------

          For purposes of calculating the amounts under paragraph (b) of Section
          3.1, the following rules shall apply:

          (a)  Any portion of the Participant's benefits under the AECOM Pension
               Plan which is payable (or has been paid) to another person
               pursuant to a court order shall be treated as payable to the
               Participant.

          (b)  The Participant's benefit, if any, under the AECOM Pension Plan
               shall be determined without regard to whether benefits have
               commenced, have not commenced, or have been paid in full and
               without regard to the actual form of payment elected by the
               Participant.

     3.5  Form of Benefit
          ---------------

          (a)  Unless a Participant makes an election pursuant to this Section,
               the Participant's benefit under Section 3.1, 3.2 or 3.3, as the
               case may be, shall be paid in equal monthly installments over the
               Participant's life, commencing on his Retirement Date and ending
               with the last payment made before his death.

          (b)  The Participant may elect to receive his benefit in one of the
               following forms:

               (1)  A lump sum paid on his Retirement Date which is the
                    Actuarial Equivalent of the benefit described in paragraph
                    (a).

               (2)  A five- or ten-year term certain, as the Participant elects,
                    which is the Actuarial Equivalent of the benefit described
                    in paragraph (a), paid in equal annual installments
                    commencing on the Retirement Date.  If the Participant dies
                    after installments commence but

                                       6
<PAGE>

                    before receiving all installment payments, the remaining
                    installments will be paid as they come due to the
                    Participant's Beneficiary.

               (3)  A 50% joint and survivor annuity which is the Actuarial
                    Equivalent (calculated using 6% instead of 8-1/2%) of the
                    benefit described in paragraph (a).  Under this form, the
                    Participant receives a reduced monthly payment for life.  On
                    his death, his surviving Spouse will receive a monthly
                    benefit equal to 50% of the benefit the Participant was
                    receiving.  The Participant's benefit will commence on his
                    Retirement Date and end with the last payment made before
                    his death.  The Spouse's survivor annuity will commence on
                    the first day of the month following the Participant's death
                    and end with the last payment made before the Spouse's
                    death.  If the Spouse does not survive the Participant, no
                    survivor benefits will be paid.  If the Participant is not
                    married on his Retirement Date, his election under this
                    subparagraph will be deemed revoked and unless his election
                    specified an alternative default choice, his benefit will be
                    paid pursuant to paragraph (a).

          (c)  The Participant's election must be made in writing within 30 days
               of the date he is notified by the Company of his participation in
               the Plan.  The election is irrevocable.

     3.6  Pre-Retirement Death Benefits
          -----------------------------

          If the Participant dies while employed by the Company (whether or not
          before his Early Retirement Date), his surviving Spouse shall receive
          a monthly benefit for life equal to the amount that the Spouse would
          have received if the Participant's Plan benefits had commenced on his
          date of death paid as an Actuarial Equivalent (using a 6% interest
          rate instead of 8-1/2%) 50% joint and survivor annuity and he had died
          the next day.  The Committee may, in its discretion, pay the Spouse an
          Actuarial Equivalent lump sum in lieu of the monthly benefit for life.

     3.7  Agreement Not To Compete
          ------------------------

          In no event shall any benefit be payable under this Plan without the
          Participant having signed an agreement that, during the five year
          period beginning on the Retirement Date, he shall not, without the
          written consent of the Company, directly or indirectly engage in, or
          become interested in any business which is engaged in the business in
          which the Company has been engaged with any Client (as hereinafter
          defined) or otherwise undertake any employment or competitive activity
          wherein the loyal and complete fulfillment of the duties of the
          employment or activity would call upon the Participant to reveal,
          evaluate, make judgments on, or otherwise use, any confidential
          information or trade secrets of the Company.  As used herein, the term
          "Client" shall mean any customer to

                                       7
<PAGE>

          which the Company has provided its services within the three years
          preceding the Retirement Date. In no event shall the agreement be
          construed to prohibit the acquisition by the Participant of a publicly
          traded security of a corporation engaged in such business so long as
          (a) the Participant has acquired such security for investment
          purposes, and (b) the Participant does not own, directly or
          indirectly, more than 5% of the voting interest of such corporation.
          The agreement shall also provide that the Participant shall not, for
          the five-year period commencing one year before his Retirement Date,
          induce, entice, solicit or influence, directly or indirectly, any
          person who is engaged as an employee, agent or independent contractor
          by the Company to terminate such person's employment or engagement or
          to work with the Participant or with any person or business entity or
          venture with which the Participant becomes affiliated. This Section
          shall not apply if the Participant's Termination of Employment is on
          account of death, Disability, Change of Control or Constructive
          Termination.


IV.  Amendment and Termination

     4.1  Amendment
          ---------

          The Board of Directors reserves the right in its discretion to amend
          this Plan at any time in whole or in part, provided, however, that no
          amendment shall result in the forfeiture of any Participant's Plan
          benefits earned prior to the date the Board adopts the amendment.  The
          Company shall notify Participants (and the Spouses of deceased
          Participants) of any amendments which affect the amount or timing of
          benefits within 90 days of the effective date of such amendments.

     4.2  Termination
          -----------

          The Board of Directors may terminate the Plan at any time.
          Termination shall not result in the forfeiture of any Participant's
          benefits earned prior to the date the Board adopts a resolution
          terminating the Plan.


V.   Administration

     5.1  This Plan shall be adopted by the Company and shall be administered by
          the Committee.

     5.2  The Committee shall have the sole authority, in its discretion, to
          adopt, amend and rescind such rules and regulations as it deems
          advisable in the administration of the Plan, to construe and interpret
          the Plan, and the rules and regulations, and to make all other
          determinations and interpretations of the Plan.  All decisions,
          determinations, and interpretations of the Committee shall be final
          and binding on all persons, except as otherwise provided by law.
          Committee members who are

                                       8
<PAGE>

          Participants shall abstain from voting on any Plan matters that would
          cause them to be in constructive receipt of benefits under the Plan.
          The Committee may delegate its responsibilities as it sees fit.

     5.3  If a Participant or Spouse believes benefits have been incorrectly
          calculated or denied, such person may file a claim with the Committee.
          The Committee shall follow the claims procedures in the AECOM Pension
          Plan.

     5.4  All Plan administrative expenses shall be paid by the Company.

     5.5  The Company shall indemnify the Committee and each Committee member
          against any and all claims, losses, damages, expenses (including
          reasonable counsel fees), and liability arising from any action,
          failure to act, or other conduct in the member's official capacity,
          except when due to the individual's own gross negligence or willful
          misconduct.


VI.  General Provisions

     6.1  No Funding Obligation. The amounts accrued by a Participant hereunder
          ---------------------
          are not held in a trust or escrow account and are not secured by any
          specific assets of the Company or in which the Company has an
          interest. This Plan shall not be construed to require the Company to
          fund any of the benefits provided hereunder nor to establish a trust
          for such purpose. The Company may make such arrangements as it desires
          to provide for the payment of benefits. Neither the Participant, the
          Spouse nor the Participant's estate shall have any rights against the
          Company with respect to any portion of the Participant's benefits
          except as a general unsecured creditor of the Company. No Participant
          has an interest in his benefits until the Participant actually
          receives payment.

     6.2  Non-alienation of Benefits.  No benefit under this Plan may be sold,
          --------------------------
          assigned, transferred, conveyed, hypothecated, encumbered,
          anticipated, or otherwise disposed of, and any attempt to do so shall
          be void.  No such benefit shall, prior to receipt thereof by a
          Participant or Spouse, be in any manner subject to the debts,
          contracts, liabilities, engagements, or torts of such Participant.

     6.3  Limitation of Rights.  Nothing in this Plan shall be construed to
          --------------------
          limit in any way the right of the Company to terminate a Participant's
          employment at any time for any reason whatsoever with or without
          cause; nor shall it be evidence of any agreement or understanding,
          express or implied, that the Company (a) will employ a Participant in
          any particular position, (b) will ensure participation in any
          incentive programs, or (c) will grant any awards from such programs.

                                       9
<PAGE>

     6.4  Applicable Law.  This Plan shall be construed and its provisions
          --------------
          enforced and administered in accordance with the laws of the State of
          California except as otherwise provided in ERISA.

This Plan is hereby adopted by the Company on this _________ day of _________,
1997.


                                AECOM TECHNOLOGY CORPORATION

                                By____________________________________________

                                Its___________________________________________

                                       10