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                                                                 Exhibit 10.4(a)


                        FIRST AMENDMENT TO LOAN AGREEMENT


                  This First Amendment to Loan Agreement, dated this 20th day of
February, 2002, by and among Michael Baker Corporation, a Pennsylvania
corporation ("MBC"), Michael Baker, Jr., Inc., a Pennsylvania corporation
("Michael Baker Jr."), Baker/MO Services, Inc., a Texas corporation
("Baker/MO"), Baker/OTS, Inc., a Delaware corporation ("Baker/OTS"), Baker
Engineering NY, Inc., a New York corporation ("Baker NY") (each a "Borrower" and
collectively, the "Borrowers"), Citizens Bank of Pennsylvania (assignee of
Mellon Bank, N.A.), a Pennsylvania banking institution ("Citizens"), National
City Bank of Pennsylvania, a national banking association ("NCB"), and Fifth
Third Bank, a national banking association ("Fifth Third") (each a "Bank" and
collectively, the "Banks"), and Citizens Bank of Pennsylvania, as agent for the
Banks (in such capacity, the "Agent") ("First Amendment").

                              W I T N E S S E T H:
                              - - - - - - - - - -

                  WHEREAS, the Borrowers, the Banks and the Agent entered into
that certain Loan Agreement, dated September 5, 2001 (the "Loan Agreement"),
pursuant to which, among other things, the Banks agreed to extend credit to the
Borrowers pursuant to a revolving credit facility in an aggregate principal
amount not to exceed Forty Million and 00/100 Dollars ($40,000,000.00); and

                  WHEREAS, the Borrowers desire to amend certain provisions of
the Loan Agreement and the Banks and the Agent shall permit such amendments
pursuant to the terms and conditions set forth herein.

                  NOW, THEREFORE, in consideration of the premises contained
herein and other valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, and intending to be legally bound hereby, the parties
hereto agree as follows:

                  1. All capitalized terms used herein which are defined in the
Loan Agreement shall have the same meaning herein as in the Loan Agreement
unless the context clearly indicates otherwise.

                  2. Section 6.14 of the Loan Agreement is hereby deleted in its
entirety and in its stead is inserted the following:

                  6.14 Costs in Excess of Billings. Beginning on the Closing
                  Date through the Expiry Date, the Borrowers' Costs in Excess
                  of Billings shall not exceed Thirty Million and 00/100 Dollars
                  ($30,000,000.00) as of any month-ending financial statement
                  date.

                  3. Section 8.17B(i) of the Loan Agreement is hereby deleted in
its entirety and in its stead is inserted the following:

                  (i) Rights Reserved. In the event any Bank shall sell any
                  participation or sub-participation, that Bank shall, as
                  between itself and the purchaser, retain all of its rights
                  (including, without limitation, rights to enforce against the
                  Borrowers the

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                  Loan Documents and any and all other documents in connection
                  therewith) and duties pursuant to the Loan Documents and any
                  and all other documents in connection therewith, including,
                  without limitation, that Bank's right to approve any waiver,
                  consent or amendment pursuant to Section 9.02; provided,
                  however, that (a) any such participation shall be in a minimum
                  amount of Five Million and 00/100 Dollars ($5,000,000.00) and
                  (b) the holder of any such participation shall not be entitled
                  to require such Bank to take any action hereunder except
                  action directly affecting (i) any reduction in the principal
                  amount or an interest rate on any Loan in which such holder
                  participates; (ii) any extension of the Expiry Date or the
                  date fixed for any payment of interest or principal payable
                  with respect to any Loan in which such holder participates;
                  and (iii) any reduction in the amount of any fees payable
                  hereunder with respect to any Loan in which such holder
                  participates. The Borrowers hereby acknowledge and agree that
                  the participant under each participation shall for purposes of
                  Sections 2.11(b), 2.12, 7.03 and 9.16 be considered to be a
                  "Bank"; provided, however, for purposes of Section 2.11(b),
                  the rights of any participant shall not exceed the rights of
                  the participating Bank. Except as otherwise set forth herein,
                  no participant or sub-participant shall have any rights or
                  obligations hereunder, and the Borrowers and the Agent shall
                  continue to deal with the Banks as if no participation or
                  sub-participation had occurred. The Agent shall continue to
                  distribute payments as if no participation or
                  sub-participation had been sold.

                  4. The provisions of Section 2 and 3 of this First Amendment
shall not become effective until the Agent has received this First Amendment,
duly executed by the Borrowers and each Bank.

                  5. Each Borrower hereby reconfirms and reaffirms all
representations and warranties, agreements and covenants made by it pursuant to
the terms and conditions of the Loan Agreement, except as such representations
and warranties, agreements and covenants may have heretofore been amended,
modified or waived in writing in accordance with the Loan Agreement.

                  6. Each Borrower hereby represents and warrants to the Banks
and the Agent that (i) such Borrower has the legal power and authority to
execute and deliver this First Amendment, (ii) the officers of such Borrower
executing this First Amendment have been duly authorized to execute and deliver
the same and bind such Borrower with respect to the provisions hereof, (iii) the
execution and delivery hereof by such Borrower and the performance and
observance by such Borrower of the provisions hereof and of the Loan Agreement
and all documents executed or to be executed therewith, do not violate or
conflict with the organizational agreements of such Borrower or any Law
applicable to such Borrower or result in a breach of any provision of or
constitute a default under


                                     - 2 -
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any other agreement, instrument or document binding upon or enforceable against
such Borrower, and (iv) this First Amendment, the Loan Agreement and the
documents executed or to be executed by such Borrower in connection herewith or
therewith constitute valid and binding obligations of such Borrower in every
respect, enforceable in accordance with their respective terms.

                  7. Each Borrower represents and warrants that (i) no Event of
Default exists under the Loan Agreement, nor will any occur as a result of the
execution and delivery of this First Amendment or the performance or observance
of any provision hereof, (ii) the Schedules attached to and made a part of the
Loan Agreement, as amended by this First Amendment, are true and correct in all
material respects as of the date hereof, and (iii) it presently has no known
claims or actions of any kind at Law or in equity against the Banks or the Agent
arising out of or in any way relating to the Loan Documents.

                  8. Each reference to the Loan Agreement that is made in the
Loan Agreement or any other document executed or to be executed in connection
therewith shall hereafter be construed as a reference to the Loan Agreement as
amended hereby.

                  9. The agreements contained in this First Amendment are
limited to the specific agreements made herein. Except as amended hereby, all of
the terms and conditions of the Loan Agreement shall remain in full force and
effect. This First Amendment amends the Loan Agreement and is not a novation
thereof.

                  10. This First Amendment may be executed in any number of
counterparts and by the different parties hereto on separate counterparts each
of which, when so executed, shall be deemed to be an original, but all such
counterparts shall constitute but one and the same instrument.

                  11. This First Amendment shall be governed by, and shall be
construed and enforced in accordance with, the Laws of the Commonwealth of
Pennsylvania without regard to the principles of the conflicts of law thereof.
Each Borrower hereby consents to the jurisdiction and venue of the Court of
Common Pleas of Allegheny County, Pennsylvania and the United States District
Court for the Western District of Pennsylvania with respect to any suit arising
out of or mentioning this First Amendment.



                                     - 3 -

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                  IN WITNESS WHEREOF, and intending to be legally bound, the
parties hereto have caused this First Amendment to be duly executed by their
duly authorized officers as of the date above written.


Attest:                                          Michael Baker Corporation

By:  /s/ H. James McKnight                       By: /s/ William P. Mooney
   -------------------------------------            ---------------------------

Title:  Ex. VP, General Counsel & Sec.           Title:  Executive VP
        --------------------------------                 ----------------------


Attest:                                          Michael Baker, Jr., Inc.

By:  /s/ H. James McKnight                       By: /s/ William P. Mooney
   -------------------------------------            ---------------------------

Title:  Ex. VP, General Counsel & Sec.           Title:  Executive VP
        --------------------------------                 ----------------------


Attest:                                          Baker/MO Services, Inc.

By:  /s/ H. James McKnight                       By:  /s/ William P. Mooney
   -------------------------------------            ---------------------------


Title:  Ex. VP, General Counsel & Sec.           Title:  Executive VP
        --------------------------------                 ----------------------


Attest:                                          Baker/OTS, Inc.

By:  /s/ H. James McKnight                       By: /s/ William P. Mooney
   -------------------------------------            ---------------------------

Title:  Ex. VP, General Counsel & Sec.           Title:  Executive VP
        --------------------------------                 ----------------------


Attest:                                          Baker Engineering NY, Inc.

By:  /s/ H. James McKnight                       By: /s/ William P. Mooney
   -------------------------------------            ---------------------------


Title:  Ex. VP, General Counsel & Sec.           Title:  Executive VP
        --------------------------------                 ----------------------




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                                  Citizens Bank of Pennsylvania, as Agent and
                                  for itself as a Bank

                                  By: /s/ Mark Latterner
                                     ----------------------------------------
                                  Title:  V.P.
                                        -------------------------------------


                                  National City Bank of Pennsylvania

                                  By: /s/ Susan  J. Dimmick
                                     ----------------------------------------
                                  Title:  Vice President
                                        -------------------------------------


                                  Fifth Third Bank

                                  By: /s/ C. S. Helmeci
                                     ----------------------------------------
                                  Title:  Vice President
                                        -------------------------------------