<PAGE>
 
                                                            Exhibit No. 10(a)(2)

                     SECOND AMENDMENT TO CREDIT AGREEMENT


     THIS SECOND AMENDMENT TO CREDIT AGREEMENT,  dated as of May 5, 1997 (this
"Agreement"), is entered into by and among ICF KAISER INTERNATIONAL, INC.
("Borrower"), a Delaware corporation, each of its subsidiaries signatories
hereto (each a "Subsidiary Guarantor" and collectively the "Subsidiary
Guarantors"), the banking institutions signatories hereto (each, a "Bank" and
collectively, the "Banks") and CORESTATES BANK, N.A., as agent for the Banks
under this Agreement (in such capacity, the "Agent").

                                  WITNESSETH
                                  ----------

     WHEREAS, Borrower, each Subsidiary Guarantor, the Banks and the Agent are
parties to a Credit Agreement, dated as of May 6, 1996, as amended as of
December 17, 1996, whereby the Banks have agreed to provide a revolving credit
facility for loans and for letters of credit;

     WHEREAS, the Borrower and the Subsidiary Guarantors have requested, and the
Banks and the Agent have agreed, to further amend the Credit Agreement in
certain respects, as provided herein.

     NOW, THEREFORE, in consideration of the premises and intending to be
legally bound hereby, the parties hereto agree as follows:

1.  AMENDMENT TO CREDIT AGREEMENT.
    ------------------------------

    a.  Clause (1) of Section 2.1(a) is hereby amended to change the Revolver
Termination Date defined therein from June 30, 1998, to December 31, 1998, so
that such clause, as so amended, shall read as follows:

        (1) Subject to the terms and conditions hereof, each Bank agrees,
     severally and not jointly with the other Banks, to make revolving credit
     loans (collectively called the "Revolving Credit Loans" and individually a
     "Revolving Credit Loan") to Borrower from time to time during the period
     commencing the date hereof and ending on December 31, 1998, or on any
     earlier date as provided in Sections 2.7(b) and 10.1 hereof (the "Revolver
     Termination Date"), in principal amounts not to exceed at any time
     outstanding in the aggregate the amount set forth opposite the name of each
     such Bank on Exhibit A hereto under the caption "Revolving Loan Commitment"
     (each such amount being hereinafter called such Bank's "Revolving Loan
     Commitment" and collectively, the Banks' "Aggregate Revolving Loan
     Commitment"). All Loans shall be made by the Banks simultaneously and pro
     rata in accordance with the Revolving Loan Commitments. The failure of any
     one or more of the Banks to make Revolving Credit Loans in accordance with
     its or their obligations shall not relieve the other Banks of their several
     obligations under this subsection, but in no event shall the aggregate
     amount at any one time outstanding which any Bank shall be required to lend
     under this Section 2.1(a), when added to such Bank's Commitment Percentage
     of Letter of Credit Outstandings at such time, exceed the amount of such
     Bank's Revolving Loan Commitment at that time.
<PAGE>
 
        b.     Article VIII is hereby amended in its entirety so that such
Article, as so amended, shall read as follows:

        VIII.  FINANCIAL COVENANTS
               -------------------
 
        Borrower covenants and agrees that, without the prior written consent of
the Required Banks, from and after the date hereof and so long as the Revolving
Loan Commitments are in effect or any Obligations remain unpaid or outstanding,
Borrower will not:

        8.1    Fixed Charge Coverage.
               ----------------------

        (a)    Permit, as of the end of the first fiscal quarter of 1997, the
ratio of (i) EBITDA less Capital Expenditures plus Consolidated Lease Expenses
of Borrower and its Subsidiaries for such quarter, to (ii) Consolidated Fixed
Charges for such quarter to be less than 1.05:1.0.

        (b)    Permit, as of the end of the second fiscal quarter of 1997, the
ratio of (i) EBITDA less Capital Expenditures plus Consolidated Lease Expenses
of Borrower and its Subsidiaries for the six month period ending on June 30,
1997, to (ii) Consolidated Fixed Charges for the six month period ending on June
30, 1997, to be less than 1.05:1.0.

        (c)    Permit, as of the end of the third fiscal quarter of 1997, the
ratio of (i) EBITDA less Capital Expenditures plus Consolidated Lease Expenses
of Borrower and its Subsidiaries for the nine month period ending on September
30, 1997, to (ii) Consolidated Fixed Charges for the nine month period ending on
September 30, 1997, to be less than 1.05:1.0.

        (d)    Permit, as of the end of any fiscal quarter ending in the period
set forth below for the immediately preceding four fiscal quarters, the ratio of
(i) EBITDA less Capital Expenditures plus Consolidated Lease Expenses of
Borrower and its Subsidiaries for such period, to (ii) Consolidated Fixed
Charges for such period to be less than the ratio set forth below:

               Fiscal Quarters Ending
               ----------------------

               October 1, 1997 through December 31,1998    1.20:1.0


        8.2    Interest Coverage.
               ------------------

        (a)    Permit, as of the end of the first fiscal quarter of 1997, the
ratio of (i) EBITDA for such period, to (ii) Consolidated Interest Expense for
such quarter to be less than 1.5:1.0.

        (b)    Permit, as of the end of the second fiscal quarter of 1997, the
ratio of (i) EBITDA for the six months ending June 30, 1997, to (ii)
Consolidated Interest Expense for the six months ending June 30, 1997, to be
less than 1.5:1.0.

        (c)    Permit, as of the end of the third fiscal quarter of 1997, the
ratio of (i) EBITDA for the nine months ending September 30, 1997, to (ii)
Consolidated Interest Expense for the nine months ending September 30, 1997, to
be less than 1.5:1.0.

                                       2
<PAGE>
 
        (d)    Permit, as of the end of any fiscal quarter ending in the period
set forth below for the immediately preceding four fiscal quarters, the ratio of
(i) EBITDA for such period, to (ii) Consolidated Interest Expense for such
period to be less than the ratio set forth below:

               Fiscal Quarter Ending
               ---------------------

               October 1, 1997 through December 31,1998    1.75:1.0

        8.3    Senior Funded Indebtedness to EBITDA.
               -------------------------------------

        (a)    Permit, as of the end of the first fiscal quarter of 1997, the
ratio of (i) Senior Funded Indebtedness on the last day of such period, to (ii)
four (4) times EBITDA for such quarter to be greater than 2.5:1.0.

        (b)    Permit, as of the end of the second fiscal quarter of 1997, the
ratio of (i) Senior Funded Indebtedness on the last day of the six months ending
June 30, 1997, to (ii) two (2) times EBITDA for the six months ending June 30,
1997, to be greater than 2.5:1.0.

        (c)    Permit, as of the end of the third fiscal quarter of 1997, the
ratio of (i) Senior Funded Indebtedness on the last day of the nine months
ending September 30, 1997, to (ii) one and one-third (1 1/3) times EBITDA for
the nine months ending September 30, 1997, to be greater than 2.5:1.0.

        (d)    Permit, as of the end of any fiscal quarter ending in the period
set forth below, the ratio of Senior Funded Indebtedness on the last day of any
such fiscal quarter to EBITDA as of such day for the immediately preceding four
fiscal quarters to be greater than the ratio set forth below:

               Fiscal Quarter Ending
               ---------------------

               October 1, 1997 through December 31,1998    2.5:1.0


        8.4    Indebtedness for Borrowed Money to Total Capitalization.  Permit 
               --------------------------------------------------------
the ratio of Indebtedness for Borrowed Money to Total Capitalization on the last
day of any fiscal quarter to be greater than .86:1.0.

        8.5    Indebtedness for Borrowed Money to EBITDA.
               ------------------------------------------

        (a)    Permit, as of the end of the first fiscal quarter of 1997, the
ratio of (i) Indebtedness for Borrowed Money on the last day of such period, to
(ii) four (4) times EBITDA for such quarter to be greater than 6.75:1.0.

        (b)    Permit, as of the end of the second fiscal quarter of 1997, the
ratio of (i) Indebtedness for Borrowed Money on the last day of the six months
ending June 30, 1997, to (ii) two (2) times EBITDA for the six months ending
June 30, 1997, to be greater than 6.75:1.0.

        (c)    Permit, as of the end of the third fiscal quarter of 1997, the
ratio of (i) Indebtedness for Borrowed Money on the last day of the nine months
ending September 30, 1997, to (ii) one and one-third (1 1/3) times EBITDA for
the nine months ending September 30, 1997, to be greater than 6.75:1.0.

                                       3
<PAGE>
 
        (d)    Permit, as of the end of any fiscal quarter ending in the period
set forth below, the ratio of Indebtedness for Borrowed Money on the last day of
any such fiscal quarter to EBITDA as of such day for the immediately preceding
four fiscal quarters to be greater than the ratio set forth below:

               Fiscal Quarter Ending
               ---------------------

               October 1, 1997 through December 31,1997    6.5:1.0
               January 1, 1998 through December 31, 1998   5.75:1.0


2.      CONDITIONS PRECEDENT.  The Amendment to the Credit Agreement contained
        ---------------------
in Section 1 hereof shall be effective upon satisfaction of the following
conditions precedent.

        (a)    Evidence of Authorization. The Banks shall have received copies
certified by the Secretary or Assistant Secretary of Borrower and each
Subsidiary Guarantor of all corporate or other action taken by such party to
authorize its execution and delivery and performance of this Amendment, the
Security Agreement and the Loan Documents as amended hereby together with such
other related papers as the Banks shall reasonably require.

        (b)    Documents. The Agent shall have received all certificates,
instruments and other documents then required to be delivered pursuant to any
Loan Documents, in each instance in form and substance reasonably satisfactory
to the Agent and the Banks.

        (c)    Other Agreements. Borrower and each Subsidiary Guarantor shall
have executed and delivered each other Loan Document required hereunder.

        (d)    Change. No material adverse change shall have occurred in the
financial condition or prospects of Borrower since December 31, 1996.

3.      REPRESENTATIONS AND WARRANTIES.
        -------------------------------

        The Borrower confirms the accuracy of the representations and warranties
made in Article 3 of the Credit Agreement as of the date originally given and
restates to the Banks such representations and warranties, as previously
amended, on and as of the date hereof as if originally given on such date.

4.      COVENANTS.
        ----------

        (a)    The Borrower warrants to the Banks that the Borrower is in
compliance and has complied with all covenants, agreements and conditions in
each Loan Document on and as of the date hereof, that no Potential Default or
Event of Default has occurred and is continuing on the date hereof and that,
upon the consummation of the transactions contemplated hereby, no Potential
Default or Event of Default shall have occurred and be continuing.

        (b)    The Borrowers shall provide to the Agent and its representatives
all requested access and assistance as shall be reasonably necessary for such
due diligence review as the Agent shall determine is necessary or advisable,
including without limitation a collateral audit.

                                       4
<PAGE>
 
5.      EFFECT OF AGREEMENT.
        --------------------

        This Agreement amends the Loan Documents only to the extent and in the
manner herein set forth, and in all other respects the Loan Documents are
ratified and confirmed.

6.      COUNTERPARTS.
        -------------

        This Agreement may be signed in any number of counterparts, each of
which shall be an original, with the same effect as if the signatures hereto
were upon the same instrument.

7.      GOVERNING LAW.
        --------------

        This Agreement and all rights and obligations of the parties hereunder
shall be governed by and be construed and enforced in accordance with the laws
of Pennsylvania without regard to principles of conflict of law.

        IN WITNESS WHEREOF, Borrower and the Banks have caused this Agreement to
be executed by their proper corporate officers thereunto duly authorized as of
the day and year first above written.
 
CORESTATES BANK, N.A.                          ICF KAISER INTERNATIONAL, INC.

 
By:    /s/ John D. Brady                       By:    /s/ Michael K. Goldman
Name:  John D. Brady                           Name:  Michael K. Goldman
Title: Assistant Vice President                Title: Executive Vice President

BHF-BANK AKTIENGESELLSCHAFT                    SIGNET BANK

 
By:    /s/ John Sykes                          By:    /s/ Brian M. Haggerty
Name:  John Sykes                              Name:  Brian M. Haggerty
Title: Assistant Vice President                Title: Vice President

By:    /s/ Tony Heyman
Name:  Tony Heyman
Title: Assistant Treasurer
 
 

                                       5
<PAGE>
 
The Subsidiary Guarantors:
<TABLE> 
<CAPTION> 

<S>                                 <C>                                 <C>        
CLEMENT INTERNATIONAL               CYGNA GROUP, INC.                   HENRY J. KAISER 
CORPORATION.                                                            COMPANY


By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         
    -----------------------             -----------------------             -----------------------
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor                      
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

EXCELL DEVELOPMENT                  ICF INFORMATION                     ICF INCORPORATED
CONSTRUCTION, INC.                  TECHNOLOGY, INC.

 
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

ICF KAISER ENGINEERS                ICF KAISER ENGINEERS                ICF KAISER ENGINEERS
CORPORATION                         (CALIFORNIA)                        MASSACHUSETTS, INC.
                                    CORPORATION

     
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor  
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer 

ICF KAISER ENGINEERS                ICF KAISER GOVERNMENT               ICF KAISER ENGINEERS,
GROUP, INC.                         PROGRAMS, INC.                      INC.

 
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

ICF KAISER HOLDINGS                 ICF KAISER HANFORD                  ICF RESOURCES
UNLIMITED, INC.                     COMPANY                             INCORPORATED
 

By: /s/ Timothy P. O'Connor         By: /s/ Paul Weeks, II              By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Paul Weeks, II                Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Secretary          Title: Assistant Treasurer             
</TABLE> 

                                       6
<PAGE>
 
<TABLE> 
<CAPTION> 
<S>                                 <C>                                 <C> 
ICF LEASING                         KE SERVICES                         KE LIVERMORE, INC.
CORPORATION, INC.                   CORPORATION

 
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

KAISER ENGINEERS AND                KAISER ENGINEERS                    CYGNA CONSULTING
CONSTRUCTORS, INC.                  INTERNATIONAL, INC.                 ENGINEERS & PROJECT
                                                                        MANAGEMENT, INC.
 
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor 
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

TUDOR ENGINEERING                   PCI OPERATING COMPANY,              SYSTEMS APPLICATIONS
COMPANY                             INC.                                INTERNATIONAL, INC.

 
By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor         By: /s/ Timothy P. O'Connor
    -----------------------             -----------------------             -----------------------         
Name: Timothy P. O'Connor           Name: Timothy P. O'Connor           Name: Timothy P. O'Connor              
Title: Assistant Treasurer          Title: Assistant Treasurer          Title: Assistant Treasurer             

</TABLE>

                                       7