<PAGE>
 
                                                                    EXHIBIT 4(g)


     THIS NOTE IS A GLOBAL NOTE WITHIN THE MEANING OF THE INDENTURE HEREINAFTER
REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITORY OR A NOMINEE OF A
DEPOSITORY OR A SUCCESSOR DEPOSITORY.  THIS NOTE IS NOT EXCHANGEABLE FOR NOTES
REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE
EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER
OF THIS NOTE (OTHER THAN A TRANSFER OF THIS NOTE AS A WHOLE BY THE DEPOSITORY TO
A NOMINEE OR THE DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY
OR ANOTHER NOMINEE OF THE DEPOSITORY) MAY BE REGISTERED EXCEPT IN THE LIMITED
CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

     UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS
REQUESED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE
& CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF
DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO
ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS
AN INTEREST HEREIN.


                         ICF KAISER INTERNATIONAL, INC.

                       12% SENIOR NOTE DUE 2003, SERIES B

                                                               CUSIP No.  449244


No. BQ-                                                        $_______________


ICF Kaiser International, Inc., a Delaware corporation (the "Company"), for
value received promises to pay to CEDE & Co., or registered assigns, the
principal sum of _____________________ Dollars on December 31, 2003.

Interest Payment Dates: June 30 and December 31

Record Dates: June 15 and December 15
<PAGE>
 
Reference is made to the further provisions of this Security contained herein,
which will for all purposes have the same effect as if set forth at this place.

IN WITNESS WHEREOF, the Company has caused the Security to be signed manually or
by facsimile by its duly authorized officers.

Dated:

ICF KAISER INTERNATIONAL, INC.

By:_______________________________

By:_______________________________ 
              (SEAL)
<PAGE>
 
                    Trustee's Certificate of Authentication



     This is one of the Series B Notes referred to in the within-mentioned
Indenture.



Dated:                                        THE BANK OF NEW YORK
                                              as Trustee


 
                                              By: _____________________________
                                                      Authorized Signatory
<PAGE>
 
                      12% SENIOR NOTE DUE 2003, SERIES B
                                        

         Certain capitalized terms used but not defined herein shall have the
meanings given to them in the Indenture under which this Note is issued.

          1.     Interest.   ICF Kaiser International, Inc., a Delaware
 corporation (the "Company," which term shall include any Successor under the
 Indenture), promises to pay interest on the principal amount of this Note at
 12% provided that one percent (1%) additional interest (the "Additional
 Interest") is payable on the Notes from the date of, and as provided in, the
 Indenture. The Company files its financial results with the Securities and
 Exchange Commission on quarterly and annual reports, and these reports include
 the Company's earnings after deducting minority interests and before interest,
 taxes, depreciation, and amortization calculated in accordance with generally
 accepted accounting principles ("Earnings"). The Company measures its Earnings
 for trailing twelve month periods, each period to end on the last day of a
 fiscal quarter and extend no further than March 31, 1998 (each a "Quarterly
 Measurement Period"). If the Company's Earnings equal or exceed $36 million for
 two consecutive Quarterly Measurement Periods, then the Company is relieved of
 its obligation to pay any future Additional Interest. However, if the Company's
 Earnings do not equal or exceed $36 million for any subsequent Quarterly
 Measurement Period, up to and including the Quarterly Measurement Period ending
 March 31, 1998, the Company is obligated to commence paying Additional Interest
 until the Company's Earnings again equal or exceed $36 million on a trailing
 twelve month basis calculated quarterly. The Company will pay interest
 semiannually on June 30 and December 31 of each year, or if any such day is not
 a Business Day, on the next succeeding Business Day (each an "Interest Payment
 Date"). Interest on the Notes will accrue from the most recent date on which
 interest has been paid or, if no interest has been paid, from December 31,
 1996; provided, that if there is no existing Default in the payment of
 interest, and if this Note is authenticated between a record date referred to
 on the face hereof and the next succeeding Interest Payment Date, interest
 shall accrue from such next succeeding Interest Payment Date; provided,
 further, that the first Interest Payment Date shall be June 30, 1997. The
 Company shall pay interest on overdue principal from time to time on demand at
 the rate of 1% per annum in excess of the interest rate then in effect; it
 shall pay interest on overdue installments of interest (without regard to any
 applicable grace periods) from time to time on demand at the same rate to the
 extent lawful. Interest will be computed on the basis of a 360-day year of
 twelve 30-day months.

         2.  Method of Payment.    The Company will pay interest on the Notes
(except defaulted interest) to the Persons who are registered Holders of Notes
at the close of business on the record date next preceding the Interest Payment
Date, even if such Notes are cancelled after such record date and on or before
such Interest Payment Date.  Holders must surrender Notes to a Paying Agent to
collect principal Payments.  The Company will pay the principal of, premium, if
any, and interest on the Notes in money of the United States of America that at
the time of payment is legal tender for payment of public and private debts
("U.S. Legal Tender").  The Company, however, may pay such amounts by check
payable in such U.S. Legal Tender.  It may mail an interest check to a Holder's
registered address.
<PAGE>
 
         3.  Paying Agent and Registrar.   Initially, The Bank of New York (the
"Trustee") will act as Paying Agent and Registrar.  The Company may change any
Paying Agent, Registrar or co-registrar without notice to any Holder.  The
Company may act in any such capacity.

         4.  Indenture and Guarantees.   The Company issued the Notes under an
Indenture dated as of December 23, 1996 (the "Indenture") between the Company
and the Trustee.  The terms of the Notes include those stated in the Indenture
and those made part of the Indenture by reference to the Trust Indenture Act of
1939, as amended (15 U.S. Code (S)(S) 77aaa-77bbbb), as in effect on the date of
execution of the Indenture until such time as the Indenture is qualified under
the TIA, and thereafter as in effect on the date on which the Indenture is
qualified under the TIA.  The Notes are subject to all such terms, and Holders
are referred to the Indenture and such Act for a statement of such terms.
Capitalized and certain other terms used herein and not otherwise defused have
the meanings set forth in the Indenture.  The Notes are unsecured general
obligations of the Company limited to $15,000,000 in aggregate principal amount.
Payment on each Note is guaranteed, jointly and severally, by the Guarantors
pursuant to Section 5.11 of the Indenture.

         5.  Optional Redemption.   The Notes may not be redeemed prior to
December 31, 1998, but will be redeemable at the option of the Company, in whole
or in part, at any time on or after December 31, 1998, at the following
redemption prices (expressed as percentages of principal amount), together with
accrued and unpaid interest, if any, thereon to the redemption date, if redeemed
during the 12month period beginning December 31:


<TABLE>
<S>                                     <C>                    
                                               Optional        
                Year                       Redemption Price    
            -------------               ---------------------- 
                                                               
                1998                           108.0%           
                1999                           106.4%           
                2000                           104.8%           
                2001                           103.2%           
                2002                           101.6%            
</TABLE>


         If fewer than all of the Notes are to be redeemed at any time,
selection of the Notes to be redeemed will be made by the Trustee from among the
outstanding Notes on a pro rata basis, by lot or by any other method permitted
in the Indenture.  Notice of redemption will be mailed at least 30 days but not
more than 60 days before the redemption date to each Holder whose Notes are to
be redeemed at the registered address of such Holder.  On and after the
redemption date, interest shall cease to accrue on the Notes or portions thereof
called for redemption.
<PAGE>
 
         6.  Offers to Repurchase.

          (a) Change of Control Offer.  In accordance with the terms of the
Indenture, upon the occurrence of a Change of Control, the Company will be
required to offer (a "Change of Control Offer") to purchase all outstanding
Notes at a purchase price equal to 101% of the aggregate principal amount of the
Notes, plus accrued and unpaid interest to the date of purchase.

         A Holder of Notes may tender or refrain from tendering all or any
portion of his Notes at his discretion by completing the form entitled "OPTION
OF HOLDER TO ELECT PURCHASE" appearing below on this Note.  Any portion of Notes
tendered must be in integral multiples of $1,000.

          (b) Asset Sale Offer.  In accordance with the terms of the Indenture,
if the Company or any Restricted Subsidiary consummates an Asset Sale, the
Company will, under certain circumstances, be required to utilize a portion of
the net proceeds received from such Asset Sale to offer to purchase Notes at a
purchase price equal to 100% of the aggregate principal amount of the Notes plus
accrued interest to the date fixed for the purchase.

         A Holder of Notes may tender or refrain from tendering all or any
portion of his Notes at his discretion by completing the form entitled "OPTION
OF HOLDER TO ELECT PURCHASE" appearing below this Note.  Any portion of Notes
tendered must be in integral multiples of $1,000.

         Subject to the provisions described above and compliance with Article 6
of the Indenture, the Company may sell or otherwise dispose of all or
substantially all of its assets to a Successor that assumes all of the Company's
obligations under the Notes and Indenture, and thereafter be discharged from
such obligations.

          7.    Denominations, Transfer, Exchange.   The Notes are in registered
form without coupons in denominations of $1,000 and integral multiples of
$1,000.  The transfer of Notes may be registered and Notes may be exchanged as
provided in the Indenture.  The Registrar and the Trustee may require a Holder,
among other things, to furnish appropriate endorsements and transfer documents
and to pay any taxes and fees required by law or permitted by the Indenture.

          8. Persons Deemed Owners. The registered Holder of a Note may be
treated as its owner for all purposes.

          9.  Unclaimed Funds.    If funds for the payment of principal or
interest remain unclaimed for two years, the Trustee and the Paying Agent will
repay the funds to the Company at its request.  After that, all liability of the
Trustee and Paying Agent with respect to such funds shall cease.
<PAGE>
 
          10. Discharge.   The Company may be discharged from its
obligations under the Indenture and the Notes, except for certain provisions
thereof, upon satisfaction of certain conditions specified in the Indenture.

          11. Amendments and Waivers.   Subject to certain exceptions, the
Indenture or the Notes may be amended or supplemented with the consent (which
may include consents obtained in connection with a tender offer or exchange
offer for Notes) of the Holders of at least a majority in principal amount of
the Notes then outstanding, and any existing Default under, or compliance with
any provision of, the Indenture may be waived (other than any continuing Default
or Event of Default in the payment of interest on or the principal of the Notes,
or any failure to comply with the provisions of the Indenture relating to a
Change of Control Offer (as defined in the Indenture)) with the consent (which
may include consents obtained in connection with a tender offer or exchange
offer for Notes) of the Holders of a majority in principal amount of the Notes
then outstanding.  Without the consent of any Holder, the Company and the
Trustee may amend or supplement the Indenture or the Notes to cure any
ambiguity, defect or inconsistency; to provide for the assumption of the
Company's obligations to Holders in the case of a merger or acquisition; to
provide for uncertificated Notes in addition to or in place of certificated
Notes; to make any change that does not adversely affect the legal rights of any
Holder; to surrender any right or power conferred upon the Company in the
Indenture or the Notes; or to modify, eliminate or add to the provisions of the
Indenture or the Notes to such extent as shall be necessary to effect the
qualification of the Indenture under the TIA or under any similar federal
statute hereafter enacted.

        The right of any Holder to participate in any consent required or sought
Pursuant to any provision of the Indenture (and the obligation of the Company to
obtain any such consent otherwise required from such Holder) may be subject to
the requirement that such Holder shall have been the Holder of record of any
Notes with respect to which such consent is required or sought as of a date
identified by the Trustee or the Company in a notice furnished to Holder in
accordance with the terms of the Indenture.

        Without the consent of each Holder affected, the Company may not take
certain actions, including: (i) reduce the amount of Notes whose Holders must
Consent to an amendment, supplement or waiver; (ii) reduce the rate of or change
the time for payment of interest, including default interest, on any Note; (iii)
reduce the Principal of or change the fixed maturity of any Note or alter the
provisions with respect to optional redemption or mandatory repurchase of the
Notes under the Indenture; (iv) make any Note payable in money other than that
stated in this Note; (v) make any change in certain provisions of the Indenture
regarding a Change of Control, a waiver of past Defaults and the rights of
Holders to receive payment; or (vi) waive a continuing Default or Event of
Default in the payment of principal of or interest on the Notes or that resulted
from a failure to comply with the Change of Control provisions of the Indenture.

         12.  Restrictive Covenants.   The Indenture contains certain covenants
which, among other things, limit: (i) the incurrence of additional Indebtedness
by the Company and Restricted Subsidiaries; (ii) the payment of dividends; (iii)
the repurchase of capital stock or subordinated indebtedness; (iv) the making of
certain other distributions, loans and investments; 
<PAGE>
 
(v) the sale of assets and the sale of the stock of Restricted Subsidiaries;
(vi) the creation of restrictions on the ability of Restricted Subsidiaries, to
pay dividends or make other payments to the Company; and (vii) the ability of
the Company and Restricted Subsidiaries to enter into certain transactions with
Affiliates or to merge, consolidate or transfer substantially all assets. These
restrictions are subject to important qualifications and exceptions. The Company
must report to the Trustee on compliance with such limitations.

         13.  Defaults and Remedies.   Events of Default include: default in
payment of interest on the Notes for 30 days; default in payment of principal on
the Notes; failure by the Company for 60 days after notice to it to comply with
any of its other agreements in the Indenture or the Notes; certain defaults
under other Indebtedness; certain final judgements that remain undercharged; and
certain events of bankruptcy or insolvency.  If an Event of Default occurs and
is continuing, the Trustee or the Holders of at least 25% in principal amount of
the then outstanding Notes may declare all the Notes to be immediately due and
payable for an amount equal to 100% of the principal amount of the Notes plus
accrued interest to the date of payment, except that in the case of an Event of
Default arising from certain events of bankruptcy or insolvency, all outstanding
Notes become due and payable immediately without further action or notice.
Holders may not enforce the Indenture or the Notes except as provided in the
Indenture.  The Trustee may require indemnity satisfactory to it before it
enforces the Indenture or the Notes.  Subject to certain limitations, Holders of
a majority in principal amount of the then outstanding Notes may direct the
Trustee in its exercise of any trust or power.  The Trustee may withhold from
Holders notice of any continuing default (except a default in payment of
principal or interest) if it determines that withholding notice is in their
interests.  The Company must furnish an annual compliance certificate to the
Trustee.

          14. Trustee Dealing with Company.   The Trustee, in its individual
or any other capacity, may make loans to, accept deposits from, and perform
services for the Company or its Affiliates, and may otherwise deal with the
Company or its Affiliates, as if it were not Trustee.

         15.  No Records Against Others.    A director, officer, employee or
stockholder, as such, of the Company shall not have any liability for any
obligations of the Company under the Notes or the Indenture or for any claim
                                                                       -----
based on, in respect of or by reason of such obligations or their creation.
Each Holder by accepting a Note waives and releases all such liability.  The
waiver and release are part of the consideration for the issuance of the Notes.

          16. Authentication.   This Note shall not be valid until
authenticated by the manual signature of the Trustee or an authenticating agent.

         17.  Abbreviations.   Customary abbreviations may be used in the name
of a Holder or an assignee, such as: TEN COM (-- tenants in common), TEN ENT (--
tenants by the entireties), JT TEN (-- joint tenants with right of survivorship
and not as tenants in common), CUST (--Custodian), and U/G/WA (-- Uniform Gifts
to Minors Act).

         18.  CUSIP Numbers.   Pursuant to a recommendation promulgated by the
Commission on Uniform Security Identification Procedures, the Company has caused
CUSIP 
<PAGE>
 
Numbers to be printed on the Notes as a convenience to the Holders of the
Notes.  No representation is made to the accuracy of such numbers as provided on
the Notes, and reliance may be placed only on the other identification numbers
printed thereon.

         19.  Governing Law.  THIS NOTE AND THE INDENTURE SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT
REGARD TO PRINCIPLES OF CONFLICTS OF LAW.

         The Company will furnish to any Holder upon written request and without
charge a copy of the Indenture.  Request may be made to:

              ICF Kaiser International, Inc.
              9300 Lee Highway
              Fairfax, Virginia 22031-1207
              Attention:  Executive Vice President and
                          Chief Financial Officer
 
<PAGE>
 
                                   GUARANTEE
                                        
    The Guarantors (as defined in the Indenture referred to in the Note upon
which this notation is endorsed and each hereinafter referred to as a
"Guarantor," which term includes any successor to a Guarantor) have
unconditionally guaranteed (such guarantee by each Guarantor being referred to
herein as the "Guarantee") (a) the full and prompt payment of the principal of
and premium, if any, on any Note when and as the same shall come due and
payable, whether at the stated maturity thereof, by acceleration, redemption or
otherwise and (b) the full and prompt payment of any interest on any Note when
and as the same shall become due, according to the terms of such Note and the
Indenture.

    No stockholder, officer, director or incorporator, as such, past, present or
future, of any Guarantor shall have any liability under this Guarantee by reason
of his or its status as such stockholder, officer, director or incorporator.

    The Guarantees shall not be valid or obligatory for any purpose until the
certificate of authentication on the Notes upon which the guarantees are noted
shall have been executed by the Trustee under the indenture by the manual
signature of its authorized officers.

                         GUARANTORS:

                         CYGNA CONSULTING ENGINEERS AND
                         PROJECTS MANAGEMENT, INC.

     Attest:             BY:
                            ------------------------------------     
                         Name:              
                         Title:

                         ICF KAISER GOVERNMENT PROGRAMS, INC.

     Attest:             BY:
                            ------------------------------------     
                         Name:
                         Title:

                         PCI OPERATING COMPANY, INC.

     Attest:             BY:
                            ------------------------------------ 
                         Name:
                         Title:

                         SYSTEMS APPLICATIONS INTERNATIONAL, INC.
 
     Attest:             BY:
                            ------------------------------------     
                         Name:
                         Title:
<PAGE>
 
                                ASSIGNMENT FORM


     To assign this Note, fill in the form below: (I) or (we) assign and
transfer this Note to

------------------------------------------------------------------------ 
(Insert assignee's Soc. Sec. or tax I.D. No.)

------------------------------------------------------------------------  

------------------------------------------------------------------------ 

------------------------------------------------------------------------ 

------------------------------------------------------------------------ 
(Print or type assignee's name, address and zip code)

and irrevocably appoint___________________________to transfer this Note on the
books of the Company.  The agent may substitute another to act for him.



Date:___________________

                                Your Signature: ______________________________
                                (Sign exactly as your name appears on the face
                                of this Note)


Signature Guarantee:
<PAGE>
 
                      OPTION OF HOLDER TO ELECT PURCHASE
                                        


         If you want to elect to have this Note purchased by the Company
pursuant to an Asset Sale Offer or a Change in Control Offer, please execute and
return this form to the Company.

         If you want to elect to have only part of the Note purchased by the
Company pursuant to the Indenture, state the amount you elect to have purchased:
$______________________




Date: ______________________

                                Your Signature: ______________________________
                                (Sign exactly as your name appears on the face
                                of this Note)



Signature Guarantee: