<PAGE>
                                                         Exhibit 10.6


                             FIRST AMENDMENT TO
                 SECOND AMENDED AND RESTATED CREDIT AGREEMENT

          This First Amendment to Second Amended and Restated Credit Agreement,
dated as of March 22, 1996 (this "Amendment"), is made by and between Michael
Baker Corporation (the "Company"), Michael Baker Jr., Inc., Baker Engineering
NY, Inc., Baker Engineering, Inc., Baker Environmental, Inc., Baker/MO 
Services, Inc., Baker Support Services, Inc., Baker/Mellon Stuart Construction,
Inc., Baker Heavy & Highway, Inc., Mellon Stuart Building Services, Inc.,
Mellon Stuart Construction International, Inc., Baker/OTS, Inc., Baker 
Construction, Inc. (a/k/a Michael Baker Construction, Inc.) and Vermont General
Insurance Company (collectively, the "Borrowers"), and Mellon Bank, N.A. (the 
"Bank").  Capitalized terms used in this Amendment and not otherwise defined
have the meanings assigned to such terms in the Credit Agreement (as defined
below).

                           PRELIMINARY STATEMENTS:
                           -----------------------

     1. The Borrowers and the Bank are parties to the Second Amended and 
Restated Credit Agreement dated as of April 13, 1995 (as amended, modified, 
restated or supplemented from time to time, the "Credit Agreement"), under
which the Bank provided the Company with a $17,500,000 revolving credit 
facility.

     2.  The Bank has extended credit under the Credit Agreement evidenced by
the Revolving Credit Note dated as of April 13, 1995 (the "Existing Note")
made by the Borrowers in favor of the Bank in the original principal amount of
$17,500,000.

     3.  The Borrowers and the Bank desire to amend and restate the Existing
Note to, among other things, (i) increase the maximum commitment to $25,000,000
and (ii) extend the maturity date to May 31, 1998.

      4.  The Borrowers and the Bank desire to amend the Credit Agreement to,
among other things, (i) reflect the amendments to the Existing Note, (ii) 
increase the maximum facility to $25,000,000, (iii) modify the interest rates
and fees applicable under the Credit Agreement, (iv) continue to provide
Michael Baker Jr., Inc. with a corporate credit card line and (v) modify 
certain financial covenants, on the terms and subject to the conditions of this
Amendment.

                           AGREEMENT:
                           ----------

      The Borrowers and the Bank agree that the following terms and conditions
apply to this Amendment:

      1.  AMENDMENTS TO CREDIT AGREEMENT
          ------------------------------

      On the date this Amendment becomes effective, after satisfaction by the
Company of each of the conditions set forth in Section 4 of this Amendment (the
"Closing Date"), the Credit Agreement is amended as follows:

      1.1  Section 1.01 of the Credit Agreement is amended by adding the 
definitions of "Credit Card Line" and "Credit Card Line Amount" after the 
definition of "Corresponding Source of Funds" as follows:
           
            "Credit Card Line" shall have the meaning assigned to 
       such term in Section 2.01 of this Agreement.

            "Credit Card Line Amount" shall have the meaning      
        assigned to such term in Section 2.01 of this Agreement.

       1.2  Section 1.01 of the Credit Agreement is amended by deleting the
definition of "Maturity Date" and replacing it as follows:

            "Maturity Date" shall mean May 31, 1998.

       1.3  Section 1.01 of the Credit Agreement is amended by adding the
definition of "Sale/Lease-Back Arrangements" after the definition of "Rollover
Loan" as follows:

            "Sale/Lease-Back Arrangements" shall mean those certain 
       sale and lease-back arrangements with respect to certain of the
       Borrowers' computer and related equipment purchased throughout 
       any fiscal year and sold to a financial institution to create 
       an operating lease.

       1.4  Section 2.01 of the Credit Agreement is amended by deleting the
first paragraph of such section and replacing it as follows:

       The Bank hereby establishes a credit (the "Commitment") in
       favor of the Borrowers equal to a Commitment of $25,000,000. 
       Subject to the terms and conditions hereof, the Bank agrees
       to make loans (the "Revolving Credit Loans") to the Borrowers
       on any Business Day, at any time or from time to time prior
       to the Maturity Date in an aggregate principal amount not
       exceeding the Commitment; provided, however, that the sum of all
       Loans outstanding at any one time, including any reimbursement
       obligations arising from draws on Letters of Credit, plus the
       aggregate undrawn amount of all outstanding Letters of Credit at
       such time, plus the Credit Card Line Amount shall not exceed the
       Commitment at such time.  If, at any time, an excess shall for
       any reason exist, the Borrowers shall forthwith repay to the
       Bank, in funds immediately available, the amount of such excess,
       together with all interest accrued on the amount so repaid.

      1.5   Section 2.01 of the Credit Agreement is further amended by adding
the following paragraph to the end of such section as follows:

            Subject to the terms and conditions of this Agreement,
       the Bank agrees to make available for the account of Michael
       Baker Jr., Inc. a corporate credit card line (the "Credit
       Card Line"), up to a maximum outstanding amount of $4,000 (as the
       same may be reduced as described below, the "Credit Card Line
       Amount"); provided, however, that on any date on which Michael
       Baker Jr., Inc. utilizes the Credit Card Line, and after giving
       effect to such extension of credit by the Bank, the sum of all
       Loans outstanding at any such time (including any reimbursement
       obligations arising from draws on Letters of Credit, plus the
       aggregate undrawn amount of all outstanding Letters of Credit at
       such time), plus the Credit Card Line Amount shall not exceed the
       Commitment at such time.  If, at any time, an excess shall for
       any reason exist, the Borrowers shall forthwith repay to the
       Bank, in funds immediately available, the amount of such excess,
       together with all interest accrued on the amount so repaid.  The
       Credit Card Line shall be governed by, and shall be subject to
       the terms and conditions of, the Bank's Master Card and Business
       Card Agreement, a copy of which has been provided by the Bank to
       Michael Baker Jr., Inc.  At the written request of Michael Baker
       Jr., Inc., the Credit Card Line Amount shall be permanently
       reduced in increments of $1,000; provided, however, that in no
       event shall the Credit Card Line Amount be reduced to an amount
       less than the outstanding principal balance of the Credit Card
       Line at such time.

       1.6  Section 2.02(a) of the Credit Agreement is amended by deleting the
first sentence of such section and replacing it as follows:

       At the request of any Borrower (which shall be made at least
       five (5) Business Days prior to the date, which shall be
       a Business Day, on which such Letter of Credit is proposed to be
       issued), and pursuant to an Application duly executed by the
       applicable Borrower, one or more Standby Letters of Credit will
       be issued by the Bank for the account of the Borrowers in an
       aggregate face amount not exceeding an amount equal to the Bank's
       Commitment at such time minus the aggregate principal amount of
       all then outstanding Loans (including any reimbursement
       obligations arising from draws on the Letters of Credit plus the
       aggregate amount of all outstanding Letters of Credit, as the
       same may be changed from time to time by amendment or otherwise
       pursuant to the terms thereof) and minus the Credit Card Line
       Amount (the "Standby Letter of Credit Limit").  The aggregate
       undrawn amount of all outstanding Standby Letters of Credit, as
       the same may be changed from time to time by amendment or
       otherwise pursuant to the terms thereof, shall be charged against
       the Standby Letter of Credit Limit and against the Bank's
       Commitment.

       1.7  Section 2.02(b) of the Credit Agreement is amended by deleting the
third sentence of such section and replacing it as follows:

       The Borrowers agree that upon the issuance of a Standby Letter
       of Credit, the Bank shall be paid a fee equal to 1.00% per
       annum based upon the amount of the Standby Letter of Credit
       issued; provided, however, that the Borrowers shall pay an
       annual minimum fee of $250 per annum if the fee of 1.00% per
       annum would result in an annual fee of less than $250.

       1.8  Section 2.05(a)(i) of the Credit Agreement is amended by deleting
the first paragraph of such section and replacing it as follows:

       Interest shall accrue on Prime Rate Loans at a rate per annum
       for each day equal to the Prime Rate plus 0.25%.

       1.9  Section 2.05(a)(ii) of the Credit Agreement is amended by deleting
the first paragraph of such section and replacing it as follows:

       Interest shall accrue on CD Rate Loans at a rate per
       annum (based on a year of 360 days and actual days elapsed) for
       each day equal to the CD Rate plus 2.50%.

        1.10  Section 2.05(a)(iii) of the Credit Agreement is amended by
deleting the first paragraph of such section and replacing it as follows:

        Interest shall accrue on Euro-Rate Loans at a rate
        per annum (based on a year of 360 days and actual days elapsed)
        for each day at a rate equal to the Euro-Rate plus 2.50%.

        1.11  Section 2.05(a)(iv) of the Credit Agreement is amended by 
deleting the first paragraph of such section and replacing it as follows:

        Interest shall accrue on As-Offered Rate Loans at 
        a rate per annum for each day equal to the As-Offered
        Rate plus 2.50%.

        1.12  Section 5.02(a) of the Credit Agreement is amended by deleting
subsection (2) of such section in its entirety and replacing it as follows:

              (2) Liens arising as a result of the Sale/Lease-Back
        Arrangements.

        1.13  Section 5.02(d) of the Credit Agreement is amended by adding the
following subsection (v) of such section as follows:

         and (v) sales of assets under the Sale/Lease-Back
         Arrangements.

        1.14  Section 5.02(e) of the Credit Agreement is amended by adding the
following subsection (7) of such section as follows:

              (7) Investments with a cash purchase price of not more
        than $2,000,000 and a total purchase price (cash plus stock) of
        not more than $4,000,000 during the period from March 22, 1996
        through May 31, 1998.

        1.15  Section 5.02(f) of the Credit Agreement is amended by adding the
following subsection (i)(C) of such section as follows:

        and (C) may make aggregate dividends, distributions, or
        stock purchase of not more than $2,000,000 during the period from
        March 22, 1996 through May 31, 1998,

        1.16  Section 5.02(j) of the Credit Agreement is amended by deleting
such section in its entirety and replacing it as follows:

              (j)  Maintenance of Minimum Consolidated Cash Flow
        Coverage Ratio.  Permit as of the last day of any fiscal quarter
        of the Borrowers the Consolidated Cash Flow Coverage Ratio for
        the immediately preceding four fiscal quarters to be less than
        1.2:1.

       1.17  Section 5.02(k) of the Credit Agreement is amended by deleting
such section in its entirety and replacing it as follows:

            (k)  Maintenance of Minimum Ratio of Consolidated Income
       From Operations to Consolidated Interest Expense.  Permit as of
       the last day of any fiscal quarter of the Borrowers the ratio of
       Consolidated Income from Operations to Consolidated Interest
       Expense for the immediately preceding four fiscal quarters to be
       less than 5:1. 

       1.18  Section 5.02(l) of the Credit Agreement is amended by deleting
such section in its entirety and replacing it as follows:

             (l) Maintenance of Maximum Ratio of Consolidated Total
       Liabilities to Consolidated Tangible Net Worth.  Permit the
       ratio of Consolidated Total Liabilities to Consolidated Tangible
       Net Worth to exceed 2.1:1 at any time.

       1.19  Section 5.02(m) of the Credit Agreement is amended by deleting
such section in its entirety and replacing it as follows:

             (m)  Consolidated Capital Expenditures.  Permit Consolidated
       Capital Expenditures to exceed $4,500,000 in any fiscal year.

       1.20 Section 5.02(o) of the Credit Agreement is amended by deleting
subsection (3) of such section in its entirety and replacing it as follows:

            (3) purchase money Indebtedness not in excess of $500,000 in
       the aggregate during the term of this Agreement incurred in
       connection with the purchase of property other than inventory,
       recourse for which is limited solely to the assets financed
       thereby;

       1.21  Section 5.02(o) of the Credit Agreement is further amended by
adding the following subsection (6) to such section:

             (6) Indebtedness arising from the Sale/Lease-Back
        Arrangements.

       1.22  Section 5.02 of the Credit Agreement is amended by adding the
following Section 5.02(p) to such section:

             (p) Minimum Consolidated Tangible Net Worth.  Permit
       Consolidated Tangible Net Worth to be less than $38,000,000 at
       any time during the period from December 31, 1995 through
       December 30, 1996, and to be less than $40,000,000 at any time
       thereafter.

       1.23  Section 5.03(a) of the Credit Agreement is amended by deleting
subsection (ii) of such section in its entirety and replacing it as follows:

             (ii)  Additional Reports.  The Borrowers shall also furnish:

                 (1) within 90 days after the end of each fiscal year,
              consolidating financial statements prepared on a legal entity
              basis, including balance sheets, income statements and cash flow
              statements for the Company and each Subsidiary for such year;

                 (2) within 30 days after the end of each month, unaudited
              consolidated and consolidating financial statements prepared on
              an operating unit basis, including balance sheets, income
              statements and cash flow statements for the Company and each
              operating unit, for such month; 

                 (3) within 20 days after the end of each month, a report
              containing an aged accounts receivable analysis and an aged
              accounts payable analysis for such months for each legal entity
              as of the end of such month; and  

                 (4) within 30 days after the end of each month, a project
              status report and a backlog report for such month for the Company
              and each of its Subsidiaries as of the end of such month.

       2.  AMENDMENTS TO EXHIBITS AND OTHER LOAN DOCUMENTS
           -----------------------------------------------

       2.1  Amendments to Revolving Credit Note.  On the Closing Date, the
Existing Note is amended, restated and replaced in its entirety by the First 
Amended and Restated Revolving Credit Note dated as of the Closing Date (the 
"Amended Note") made by the Borrowers in favor of the Bank substantially in
the form of Exhibit A to this Amendment, and Exhibit A to the Credit
Agreement is replaced by Exhibit A to this Amendment.  

      2.2  Amendments to Mortgages.  On the Closing Date, each Open-End 
Mortgage and Security Agreement dated as of April 13, 1995 (collectively, the
"Existing Mortgages"), made by the Company or Baker/Mellon Stuart Construction,
Inc., as applicable, in favor of the Bank and relating to the Real Property is
amended by a First Amendment to Open-End Mortgage and Security Agreement dated 
as of the Closing Date (each, a "Mortgage Amendment") made between the Company
or Baker/Mellon Stuart Construction, Inc., as applicable, and the Bank 
substantially in the form of Exhibit B to this Amendment.

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

        To induce the Bank to enter into this Amendment and to extend future
credit under the Credit Agreement, as amended by this Amendment, each Borrower
represents and warrants to the Bank that:

       3.1  Due Authorization; No Conflicts; Valid and Binding.  The execution,
delivery and performance of this Amendment, the Amended Note and the Mortgage
Amendments, as applicable, are within its corporate powers, have been duly
authorized by all necessary corporate action, have received all necessary
governmental, regulatory or other approvals (if any are required), and do not
and will not contravene or conflict with any provision of (i) any law, (ii) any
judgment, decree or order, or (iii) its certificate of incorporation or 
by-laws, and do not and will not contravene or conflict with, or cause any lien
to arise under any provision of any agreement or instrument binding upon the
Company or upon any of its property.  This Amendment, the Amended Note, the 
Mortgage Amendments, as applicable, and the Credit Agreement, as amended by 
this  Amendment, are the legal, valid and binding obligations of each Borrower,
enforceable against such Borrower in accordance with their respective terms.

        3.2  No Default; Representations and Warranties.  As of the Closing
Date, (i) no Event of Default or Potential Event of Default under the Credit
Agreement, as amended by this Amendment, has occurred and is continuing or will
result from the amendments set forth in this Amendment and (ii) the 
representations and warranties contained in the Credit Agreement are true and
correct.

        3.3  Litigation.  As of the Closing Date, except as previously 
disclosed to the Bank in writing, there is no litigation or governmental 
proceeding by or against any of the Borrowers or any Subsidiary that is pending
or, to the knowledge of any of the Borrowers, threatened which, in the opinion
of any of the Borrowers, involves any substantial risk of any material adverse
effect on the financial condition or business of the total enterprise 
represented by the Borrowers or any Subsidiary on a consolidated basis.  In
addition, there are no inquiries, formal or informal, which might give rise to
such actions, proceedings or investigations.  

         4.  CONDITIONS TO EFFECTIVENESS
             ---------------------------

         The obligation of the Bank to make the amendments contemplated by this
Amendment, and the effectiveness of such amendments, are subject to the 
following:

          4.1  Representations and Warranties.  The representations and
warranties contained in this Amendment are true and correct as of the Closing
Date.

          4.2  Documents.  The Bank must have received all of the following,
each duly executed and dated as of the Closing Date (or such other date as is
satisfactory to the Bank) in form and substance satisfactory to the Bank:

          (A) Amendment to Credit Agreement.  This Amendment.

          (B) Amended Note.  The Amended Note, substantially in the form of
      Exhibit A to this Amendment.

          (C) Mortgage Amendments.  The Mortgage Amendments, each substantially
      in the form of Exhibit B to this Amendment.

          (D) Title Company Documents.  Date-down endorsements from the Title
      Company with respect to the Real Property covered by the Existing
      Mortgages, each adding the Amended Note to the Title Policy with
      only those exceptions permitted by the Bank. 

          (E) Opinion of Counsel.  An opinion of the Borrowers' legal counsel
      covering such matters as are satisfactory to the Bank and its
      counsel.

          (F) Secretary's Certificates.  A certificate from the Secretary of
      each Borrower regarding (i) the incumbency of officers, (ii)
      resolutions authorizing this Amendment, the Amended Note and the
      Mortgage Amendments, as applicable, and (iii) no change in such
      Borrower's certificate of incorporation or by-laws since April 13, 1995.

          (G) Consents, Etc.  Certified copies of all documents evidencing any
      necessary corporate action, consents and governmental approvals,
      if any, with respect to this Amendment, the Amended Note, the
      Mortgage Amendments or any other document provided for under this
      Amendment.
 
          (H) Other.  Such other documents as the Bank may reasonably request.

           4.3  Facility Fee.  The Bank must have received a one-time facility
fee of $31,250 from the Borrowers on the Closing Date.

           5.  MISCELLANEOUS
               -------------
         
           5.1  Captions.  The preliminary statements to this Amendment (except
for definitions) and the section captions used in this Amendment are for 
convenience only, and do not affect the construction of this Amendment.
 
           5.2  Governing Law; Severability.  THIS AMENDMENT IS A CONTRACT MADE
UNDER AND GOVERNED BY THE LAWS OF THE COMMONWEALTH OF PENNSYLVANIA, WITHOUT 
REGARD TO CONFLICT OF LAWS PRINCIPLES.  Wherever possible, each provision of 
this Amendment must be interpreted in such manner as to be effective and valid
under applicable law, but if any provision of this Amendment is prohibited by
or invalid under such law, such provision is ineffective to the extent of such
prohibition or invalidity, without invalidating the remainder of such provision
or the remaining provisions of this Amendment.

           5.3  Counterparts.  This Amendment may be executed in any number of
counterparts and by the different parties on separate counterparts, and each
such counterpart is deemed to be an original, but all such counterparts 
together constitute but one and the same Amendment.

          5.4  Successors and Assigns.  This Amendment is binding upon each
Borrower and the Bank and their respective successors and assigns, and inures
to the sole benefit of each Borrower and the Bank and their successors and
assigns.  No Borrower has the right to assign its rights or delegate its 
duties under this Amendment.

           5.5  References.  From and after the Closing Date, each reference in
the Credit Agreement, the Existing Note or the Existing Mortgages to "this 
Agreement," "this Note," "this Mortgage," "hereunder," "hereof," "herein," or
words of like import, and each reference in any other Loan Document to the 
Credit Agreement, the Existing Note, the Existing Mortgages or to any term, 
condition or provision contained "thereunder," "thereof," "therein," or words
of like import, mean, and are a reference to, the Credit Agreement, the 
Existing Note or the Existing Mortgages (or such term, condition or provision,
as applicable) as amended, supplemented or otherwise modified by this 
Amendment, the Amended Note or the Mortgage Amendments, as applicable.

            5.6  Continued Effectiveness.  Notwithstanding anything contained 
in this Amendment, the terms of this Amendment, the Amended Note or the 
Mortgage Amendments are not intended to, and do not serve to, effect a novation
as to the Credit Agreement, the Existing Note or the Existing Mortgages.  Each 
Borrower and the Bank expressly do not intend to extinguish the Credit
Agreement, the Existing Note or the Existing Mortgages.  Instead, it is the
express intention of each Borrower and the Bank to reaffirm the indebtedness
created under the Credit Agreement, which is evidenced by the Existing Note
and secured in part by the Existing Mortgages.  The Credit Agreement, as 
amended by this Amendment, the Existing Note, as amended and restated by the
Amended Note, and the Existing Mortgages, each as amended by the Mortgage 
Amendments, remain in full force and effect, and their terms and provisions
are ratified and confirmed by the Borrowers.

            5.7  Costs, Expenses and Taxes.  Each Borrower affirms and 
acknowledges that Section 7.02 of the Credit Agreement applies to this
Amendment and the transactions, agreements and documents contemplated under
this Amendment.

                               *   *   *<PAGE>

       Delivered at Pittsburgh, Pennsylvania, as of the day and year
first above written.

<TABLE>
<CAPTION>
<S>                                <C>
ATTEST                             MICHAEL BAKER CORPORATION


/s/ H. James McKnight                   /s/ J. Robert White
--------------------------         By: --------------------------- 

Title:  Secretary                  Title:  Chief Financial Officer
--------------------------         -------------------------------- 


                                   MICHAEL BAKER JR., INC.


                                   By: /s/ J. Robert White
                                   -------------------------------   
                                   Title:  Chief Financial Officer
                                   --------------------------------



                                   BAKER ENGINEERING NY, INC.


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------



                                   BAKER ENGINEERING, INC.


                                   By: /s/ J. Robert White
                                   ------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------


                                   BAKER ENVIRONMENTAL, INC.


                                   By: /s/ J. Robert White
                                   -------------------------------
                                   Title:  Chief Financial Officer
                                   --------------------------------
<PAGE>

                                   BAKER/MO SERVICES, INC.
                                     

                                   By: /s/ J. Robert White
                                   --------------------------------

                                   Title:  Chief Financial Officer
                                   --------------------------------



                                   BAKER SUPPORT SERVICES, INC.


                                   By: /s/ J. Robert White
                                   ------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------


                                   BAKER/MELLON STUART 
                                    CONSTRUCTION, INC.


                                   By: /s/ J. Robert White
                                   --------------------------------

                                   Title:   Chief Financial Officer
                                   --------------------------------  


                                   BAKER HEAVY & HIGHWAY, INC.


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   ------------------------------- 



                                   MELLON STUART BUILDING
                                    SERVICES, INC.

                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   ------------------------------- 

<PAGE>
                                   MELLON STUART CONSTRUCTION 
                                    INTERNATIONAL, INC.


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------


                                   BAKER/OTS, INC.


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title: Chief Financial Officer
                                   -------------------------------


                                   BAKER CONSTRUCTION, INC. 


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------


                                   VERMONT GENERAL INSURANCE
                                     COMPANY


                                   By: /s/ J. Robert White
                                   -------------------------------

                                   Title:  Chief Financial Officer
                                   -------------------------------


                                   MELLON BANK, N.A.


                                   By: /s/ Gary A. Saul
                                   ------------------------------

                                   Title:  Vice President
                                   -----------------------------
</TABLE>
<PAGE>