<PAGE>   1



                           FIRST AMENDMENT TO AMENDED
                         AND RESTATED CREDIT AGREEMENT
                            AND OTHER LOAN DOCUMENTS


         THIS FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT AND
OTHER LOAN DOCUMENTS (the "Amendment"), dated as of May 28, 1997, is among
VERITAS DGC INC., DIGICON GEOPHYSICAL CORP., VERITAS DGC LAND INC., DIGICON
GEOPHYSICAL LIMITED, DIGICON EXPLORATION, LTD. and VERITAS ENERGY SERVICES
PARTNERSHIP, as borrowers (collectively, "Borrowers," and each a "Borrower"),
and WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION, a national banking
association as a bank (in such capacity, a "Bank," and together with each of
the other banks or other lending institutions which is or which may become a
signatory to the Agreement (as hereinafter defined), collectively the "Banks"),
as issuing bank (in such capacity, together with its successors in such
capacity, the "Issuing Bank"), and as agent for itself, the Issuing Bank and
any other Banks (in such capacity, together with its successors in such
capacity, the "Agent").

                                   RECITALS:

         A.      The Borrowers, the Bank, the Issuing Bank and the Agent have
entered into that certain Amended and Restated Credit Agreement (the
"Agreement") dated as of October 21, 1996.

         B.      Pursuant to the Agreement, Digicon (Malaysia) Sdn. Bhd, a
company organized under the laws of the Federation of Malaysia ("Digicon
("Malaysia)") and Euroseis, Inc., a Delaware corporation ("Euroseis," and
together with Digicon (Malaysia), collectively the "Guarantors," and each a
"Guarantor") each executed a Guaranty (each a "Guaranty," and collectively the
"Guaranties") dated as of October 21, 1996 which guaranteed to the Agent the
payment and performance of the Obligations (as defined in the Agreement).

         C.      The Borrowers, the Bank, the Issuing Bank and the Agent now
desire to amend the Agreement as herein set forth.

         D.      Each Guarantor desires to consent to this Amendment.

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

                               ARTICLE ARTICLE I

                                  Definitions

         1       Definitions.   Capitalized terms used in this Amendment, to
the extent not otherwise defined herein, shall have the same meanings as in the
Agreement, as amended hereby.
<PAGE>   2
                               ARTICLE ARTICLE II

                                   Amendments

         1       Amendment to Recitals.  The fifth paragraph of the Recitals to
the Agreement is amended by deleting the reference to "$15,000,000" and
inserting in lieu thereof a reference to "$25,000,000."

         2       Amendment to Definitions.

                 (a)      The following definitions are added, in alphabetical
         order, to the Definitions contained in Appendix A to the Agreement:

                 "Consolidated Net Tangible Assets" has the meaning ascribed to
         such term in the Indenture.

                 "Indenture" means the Indenture dated October 23, 1996 between
         Veritas DGC and Fleet National Bank, a national banking association,
         as such Indenture existed on October 23, 1996, without taking into
         account any amendments, modifications thereof or supplements thereto,
         unless such amendment, modification or supplement has the effect of
         increasing the Maximum Bank Credit Amount, increasing the Permitted
         Subsidiary Indebtedness, or eliminating or reducing the restrictions
         containing in the Indenture with respect to incurring Indebtedness (as
         defined in the Indenture) to the Banks or securing such Indebtedness
         (as defined in the Indenture) to the Banks.

                 "Maximum Bank Credit Amount" has the meaning ascribed to such
         term in the Indenture.

                 "Permitted Subsidiary Indebtedness" has the meaning ascribed
         to such term in the Indenture.

                 "Restricted Subsidiary" has the meaning ascribed to such term
         in the Indenture.

                 "Rights Distribution Plan" means the Shareholder Rights Plan
         being presented to the shareholders of the Borrower at the Annual
         Meeting of Shareholders to be held on Wednesday, May 21, 1997, the
         principal terms, conditions and provisions of which are set out in an
         Executive Summary delivered to the Agent and its counsel on May 19,
         1997 (which Executive Summary contains the terms, conditions and
         provisions to which the Agent and the Banks have consented).

                 "Secured Obligations" means (i) while the Indenture is in
         effect, the Obligations other than that portion of principal amount of
         the Obligations which exceeds, at the time of the determination
         thereof, the greater of (a) the greater of (1) 10% of Veritas DGC's
         Consolidated Net Tangible Assets, or (2) the Maximum Bank Credit
         Amount and (b) any less restrictive prohibition as may be found in the
         Indenture as a result of an amendment that




                                     -2-
<PAGE>   3
         would change the definition of Indenture found in this Agreement and
         (ii) after the termination of the Indenture, or after the elimination
         of the applicable restrictions therein contained regarding the
         granting of Liens by Restricted Subsidiaries to secure Indebtedness
         (as defined in the Indenture) to Banks and the incurrence of
         Indebtedness (as defined in the Indenture) to the Banks, the
         Obligations.

                 (b)      The definition of "Eligible Domestic/Eligible
         Accounts" is amended by adding to the end of clause (s) thereof the
         words:  "to secure the Secured Obligations."

         3       Amendment to Article IV.

         (a)     The following is added to Section 4.10 prior to subsection (a)
         thereof:

                 Subject to the limitations set forth at Section 4.11, the
         Borrowers agree as follows:

         (b)     The following new Sections 4.11 and 4.12 are added to the
                 Agreement:

                 Section 4.11     Limitations on Joint and Several Liability
                 for the Obligations.  No Borrower other than Veritas DGC shall
                 be liable for any Obligations in excess of the sum of (a) the
                 Secured Obligations plus (b) the Permitted Subsidiary
                 Indebtedness.

                 Section 4.12     Application of Payments.  All principal
                 payments shall first be applied to that principal portion of
                 the Obligations that does not constitute Secured Obligations,
                 but neither the Agent nor any Bank shall be required to keep
                 any separate records in respect thereof, such agreement about
                 application to apply automatically.

         4       Amendment to Section 6.1.  Section 6.1 is hereby amended by
deleting the reference therein to "Obligations" and by inserting a reference to
"Secured Obligations" in lieu thereof.

         5       Amendment to Section 10.4.  Section 10.4 is amended by adding
at the end of the introductory clause thereof the words:  "and except for the
Rights Distribution Plan".

         6       Increase of Revolving Credit Commitment.  The reference to
"Revolving Credit Commitment:  $15,000,000" opposite the signature line of the
Bank in the Agreement is deleted and a reference to "Revolving Credit
Commitment: $25,000,000" is inserted in lieu thereof.

         7       Amendment to Exhibits.  Exhibit "A" and "D" to the Agreement
are deleted and Exhibits "A" and "D" attached hereto are substituted therefor,
respectively.





                                      -3-
<PAGE>   4
         8       Amendment to Other Loan Documents.

                 (a)      Each reference in the Loan Documents (other than the
         Agreement and the Guaranties) to "Obligations" is deleted and a
         reference to "Secured Obligations" is inserted in lieu thereof.

                 (b)      Paragraph 1.(a) in each Guaranty is amended by adding
         the following after the first sentence thereof:

                 ; provided, however, that the Guaranteed Indebtedness shall
                 not exceed the sum of the "Secured Obligations," as defined in
                 the Credit Agreement, plus the "Permitted Subsidiary
                 Indebtedness," as defined in the Credit Agreement.

                              ARTICLE ARTICLE III

                              Conditions Precedent

         1       Conditions.  The effectiveness of this Amendment is subject to
the satisfaction of the following conditions precedent:

                 (a)      The Agent and the Bank shall have received all of the
         following, each dated (unless otherwise indicated) the date of this
         Amendment, in form and substance satisfactory to Agent and the Bank:

                          (1)     Amendment Fee.  An amendment fee of $36,000;

                          (2)     Amendment.  This Amendment executed by all
                 parties and consented to in writing by each Guarantor;

                          (3)     Note.  A new Note reflecting the increase
                 Commitment executed by the Borrowers and payable to the order
                 of the Bank;

                          (4)     Resolutions.  Resolutions of the Board of
                 Directors of each Borrower (or each corporate partner of such
                 Borrower if such Borrower is a partnership) certified by such
                 Person's Secretary or an Assistant Secretary which authorize
                 the execution, delivery, and performance by such Borrower of
                 this Amendment and the other Loan Documents to which such
                 Borrower is or is to be a party hereunder;

                          (5)     Incumbency Certificate.  A certificate of
                 incumbency certified by the Secretary or an Assistant
                 Secretary of each Borrower (or each corporate partner of such
                 Borrower if such Borrower is a partnership) certifying the
                 names of the officers of such Borrower (or each corporate
                 partner of such Borrower if Borrower is a partnership)
                 authorized to sign this Amendment and each of the other Loan
                 Documents to which such Borrower is or is to be a party
                 hereunder (including the certificates contemplated herein)
                 together with specimen signatures of such officers





                                      -4-
<PAGE>   5
                 and certifying that such articles of incorporation, articles
                 of association, partnership agreement, bylaws or memorandum of
                 association, as applicable, of such Borrower, in the
                 respective forms delivered to the Agent in connection with the
                 October 21, 1996 closing of the Agreement, have not been
                 amended or modified and remain in full force and effect;

                          (6)     Governmental Certificates.  Certificates of
                 the appropriate government officials of the state or country
                 of incorporation or organization of each Borrower (other than
                 Veritas Energy Services Partnership) as to the existence and
                 good standing, as applicable, of each Borrower, each dated
                 within 10 days prior to the date of this Amendment;

                          (7)     Opinion of Counsel.  A favorable opinion of
                 Porter & Hedges confirming that this Amendment and the Note
                 are the legal, valid and binding obligations of the Borrowers
                 and the Guarantors, as applicable, and otherwise satisfactory
                 to Agent;

                          (8)     Additional Information.  The Agent and the
                 Bank shall have received such additional documents,
                 instruments and information as they or their legal counsel,
                 Winstead Sechrest & Minick P.C., may request; and

                 (b)      The representations and warranties contained herein
         and in all other Loan Documents, as amended hereby, shall be true and
         correct as of the date hereof as if made on the date hereof;

                 (c)      No Event of Default shall have occurred and be
         continuing and no event or condition shall have occurred that with the
         giving of notice or lapse of time or both would be an Event of
         Default.

                 (d)      All corporate proceedings taken in connection with
         the transactions contemplated by this Amendment and all documents,
         instruments, and other legal matters incident thereto shall be
         satisfactory to Agent and Bank and their legal counsel, Winstead
         Sechrest & Minick P.C.

                               ARTICLE ARTICLE IV

                 Ratifications, Representations and Warranties

         1       Ratifications.  The terms and provisions set forth in this
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Agreement (and, as applicable, the Loan Documents) and except as
expressly modified and superseded by this Amendment, the terms and provisions
of the Agreement and the Loan Documents are ratified and confirmed and shall
continue in full force and effect.  The Borrowers, the Agent and the Bank agree
that the Agreement (and, as applicable, the Loan Documents) as amended hereby
shall continue to be legal, valid, binding and enforceable in accordance with
its (their) terms.





                                      -5-
<PAGE>   6
         2       Representations and Warranties.  Each Borrower hereby
represents and warrants to the Agent and the Bank that (i) the execution,
delivery and performance of this Amendment and any and all other Loan Documents
executed or delivered, or both, in connection herewith have been authorized by
all requisite corporate or partnership, as applicable, action on the part of
each Borrower and will not violate, as applicable, the articles of
incorporation, articles of association, memorandum of association, partnership
agreement, or bylaws of such Borrower, (ii) the representations and warranties
contained in the Agreement, as amended hereby, and any other Loan Document are
true and correct on and as of the date hereof as though made on and as of the
date hereof, (iii) no Event of Default has occurred and is continuing and no
event or condition has occurred that with the giving of notice or lapse of time
or both would be an Event of Default, and (iv) such Borrower is in full
compliance with all covenants and agreements contained in the Agreement as
amended hereby.

                               ARTICLE ARTICLE V

                                 Miscellaneous

         1       Survival of Representations and Warranties.  All
representations and warranties made in this Amendment or any other Loan
Document including any Loan Document furnished in connection with this
Amendment shall survive the execution and delivery of this Amendment and the
other Loan Documents, and no investigation by the Agent, the Bank or the
Issuing Bank or any closing shall affect the representations and warranties or
the right of any such Person to rely upon them.

         2       Reference to Agreement.  Each of the Loan Documents, including
the Agreement and any and all other agreements, documents, or instruments now
or hereafter executed and delivered pursuant to the terms hereof or pursuant to
the terms of the Agreement as amended hereby, are hereby amended so that any
reference in such Loan Documents to the Agreement shall mean a reference to the
Agreement as amended hereby.

         3       Expenses.  As provided in the Agreement, each Borrower jointly
and severally agrees to pay on demand all reasonable costs and expenses
incurred by the Agent or the Bank, or both, in connection with the preparation,
negotiation, and execution of this Amendment and the other Loan Documents
executed pursuant hereto and any and all amendments, modifications, and
supplements thereto, including without limitation the costs and fees of the
Agent's and the Bank's legal counsel, and all costs and expenses incurred by
the Agent or the Bank, or both, in connection with the enforcement or
preservation of any rights under the Agreement, as amended hereby, or any other
Loan Document, including without limitation the reasonable costs and fees of
the Agent's or the Bank's legal counsel or legal counsel for both.

         4       Severability.  Any provision of this Amendment held by a court
of competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.





                                      -6-
<PAGE>   7
         5       GOVERNING LAW; VENUE; SERVICE OF PROCESS.  THIS AMENDMENT
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
TEXAS AND THE APPLICABLE LAWS OF THE UNITED STATES OF AMERICA.  THIS AMENDMENT
HAS BEEN ENTERED INTO IN HARRIS COUNTY, TEXAS, AND IT SHALL BE PERFORMABLE FOR
ALL PURPOSES IN HARRIS COUNTY, TEXAS.  SUBJECT TO THE ARBITRATION PROVISIONS
FOUND IN THE LOAN DOCUMENTS, WHICH REMAIN IN FULL FORCE AND EFFECT, ANY ACTION
OR PROCEEDING AGAINST ANY BORROWER UNDER OR IN CONNECTION WITH ANY OF THE LOAN
DOCUMENTS MAY BE BROUGHT IN ANY STATE OR FEDERAL COURT IN HARRIS COUNTY, TEXAS.
EACH BORROWER HEREBY IRREVOCABLY (A) SUBMITS TO THE NONEXCLUSIVE JURISDICTION
OF SUCH COURTS, AND (B) WAIVES ANY OBJECTION IT MAY NOW OR HEREAFTER HAVE AS TO
THE VENUE OF ANY SUCH ACTION OR PROCEEDING BROUGHT IN ANY SUCH COURT OR THAT
ANY SUCH COURT IS AN INCONVENIENT FORUM.  EACH BORROWER AGREES THAT SERVICE OF
PROCESS UPON IT MAY BE MADE BY CERTIFIED OR REGISTERED MAIL, RETURN RECEIPT
REQUESTED, AT ITS ADDRESS SPECIFIED OR DETERMINED IN ACCORDANCE WITH THE
PROVISIONS OF SECTION 14.12 OF THE AGREEMENT.  NOTHING HEREIN OR IN ANY OF THE
OTHER LOAN DOCUMENTS SHALL AFFECT THE RIGHT OF THE AGENT, THE ISSUING BANK OR
THE BANKS TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR, SUBJECT TO
THE ARBITRATION PROVISIONS FOUND IN THE LOAN DOCUMENTS, WHICH REMAIN IN FULL
FORCE AND EFFECT, SHALL LIMIT THE RIGHT OF SUCH PERSONS TO BRING ANY ACTION OR
PROCEEDING AGAINST A BORROWER OR WITH RESPECT TO ANY OF ITS PROPERTY IN COURTS
IN OTHER JURISDICTIONS.  SUBJECT TO SECTION 15.20 OF THE AGREEMENT, ANY ACTION
OR PROCEEDING BY THE BORROWERS AGAINST ANY OF THE AGENT, THE ISSUING BANK OR
THE BANKS SHALL BE BROUGHT ONLY IN A COURT LOCATED IN HARRIS COUNTY, TEXAS.

         6       Successors and Assigns.  This Amendment is binding upon and
shall inure to the benefit of the Agent, the Bank, the Issuing Bank and each
Borrower and their respective successors and assigns, except no Borrower may
assign or transfer any of its rights or obligations hereunder without the prior
written consent of the Agent, the Bank and the Issuing Bank.

         7       Counterparts.  This Amendment and the Joinder and Consent of
the Guarantors may be executed in one or more counterparts, each of which when
so executed shall be deemed to be an original, but all of which when taken
together shall constitute one and the same instrument.

         8       Effect of Waiver.  No consent or waiver, express or implied,
by the Agent, the Bank or the Issuing Bank to or for any breach of or deviation
from any covenant, condition or duty by any Borrower or any Guarantor shall be
deemed a consent or waiver to or of any other breach of the same or any other
covenant, condition or duty.





                                      -7-
<PAGE>   8
         9       Headings.  The headings, captions, and arrangements used in
this Amendment are for convenience only and shall not affect the interpretation
of this Amendment.

         10      Non-Application of Chapter 15 of Texas Credit Code.  The
provisions of Chapter 15 of the Texas Credit Code (Vernon's Annotated Texas
Statutes, Article 5069-15) are specifically declared by the parties not to be
applicable to this Amendment or any of the Loan Documents or the transactions
contemplated hereby.

         11      ENTIRE AGREEMENT.  THIS AMENDMENT AND ALL OTHER INSTRUMENTS,
DOCUMENTS AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH THIS
AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES HERETO AND
SUPERSEDE ANY AND ALL PRIOR COMMITMENTS, AGREEMENTS, REPRESENTATIONS AND
UNDERSTANDINGS, WHETHER WRITTEN OR ORAL, RELATING TO THIS AMENDMENT, AND MAY
NOT BE CONTRADICTED OR VARIED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR
SUBSEQUENT ORAL AGREEMENTS OR DISCUSSIONS OF THE PARTIES HERETO.  THERE ARE NO
ORAL AGREEMENTS AMONG THE PARTIES HERETO.

         Executed and delivered as of the date first written above.


BORROWERS:

                                        VERITAS DGC INC., a Delaware corporation



                                        By: /s/ Anthony Tripodo              
                                           -------------------------------------
                                            Anthony Tripodo                  
                                            Executive Vice President and     
                                            Chief Financial Officer          
                                                                             
                                        Address for Notices:                 
                                        3701 Kirby Drive, Suite 112          
                                        Houston, Texas  77098                
                                        Fax No.:  (713) 512-8701             
                                        Telephone No.:  (713) 512-8820       
                                        Attention:  Chief Financial Officer  





                                      -8-
<PAGE>   9
                                        DIGICON GEOPHYSICAL CORP., a Delaware   
                                        corporation                             
                                                                                
                                                                                
                                                                                
                                        By: /s/ Anthony Tripodo                 
                                            ------------------------------------
                                            Anthony Tripodo                     
                                            Executive Vice President and        
                                            Chief Financial Officer             
                                                                                
                                        Address for Notices:                    
                                        3701 Kirby Drive, Suite 112             
                                        Houston, Texas  77098                   
                                        Fax No.:  (713) 512-8701                
                                        Telephone No.:  (713) 512-8820          
                                        Attention:  Chief Financial Officer     


                                        VERITAS DGC LAND INC., a Mississippi
                                        corporation                         
                                                                            
                                                                            
                                                                            
                                        By: /s/ Anthony Tripodo             
                                            ------------------------------------
                                            Anthony Tripodo                 
                                            Executive Vice President and    
                                            Chief Financial Officer         
                                                                            
                                        Address for Notices:                
                                        3701 Kirby Drive, Suite 112         
                                        Houston, Texas  77098               
                                        Fax No.:  (713) 512-8701            
                                        Telephone No.:  (713) 512-8820      
                                        Attention:  Chief Financial Officer 





                                      -9-
<PAGE>   10
                                        DIGICON GEOPHYSICAL LIMITED, a company
                                        organized under the laws of England   
                                        and Wales                             
                                                                              
                                                                              
                                                                              
                                        By: /s/ Allan C. Pogach               
                                            ------------------------------------
                                            Allan C. Pogach, Director         
                                                                              
                                                                              
                                        Address for Notices:                  
                                        3701 Kirby Drive, Suite 112           
                                        Houston, Texas  77098                 
                                        Fax No.:  (713) 512-8701              
                                        Telephone No.:  (713) 512-8820        
                                        Attention:  Chief Financial Officer   
                                                                              
                                                                              
                                        DIGICON EXPLORATION, LTD., a Delaware 
                                        corporation                           
                                                                              
                                                                              
                                        By: /s/ Anthony Tripodo               
                                            ------------------------------------
                                            Anthony Tripodo                   
                                            Executive Vice President and      
                                            Chief Financial Officer           
                                                                              
                                        Address for Notices:                  
                                        3701 Kirby Drive, Suite 112           
                                        Houston, Texas  77098                 
                                        Fax No.:  (713) 512-8701              
                                        Telephone No.:  (713) 512-8820        
                                        Attention:  Chief Financial Officer   
                                                                              
                                                                              
                                        VERITAS ENERGY SERVICES PARTNERSHIP   
                                        a Partnership by its duly authorized  
                                        Partner                               
                                                                              
                                        By: VERITAS GEOPHYSICAL LTD.         
                                                                             
                                                                             
                                                                             
                                            Per: /s/ Lawrence C. Fichtner    
                                                 -------------------------------
                                                 Lawrence C. Fichtner, 
                                                 Director  
                                            




                                      -10-
<PAGE>   11
                                                        -and-                  
                                                                               
                                       By:      VERITAS SEISMIC (1987) LTD.    
                                                                               
                                                                               
                                                                               
                                                Per:/s/ Lawrence C. Fichtner   
                                                    ---------------------------
                                                        Lawrence C. Fichtner,  
                                                        Director               
                                                                               
                                                        -and                   
                                                                               
                                       By:      CANEX INFORMATION SERVICES LTD.
                                                                               
                                                                               
                                                                               
                                                Per:/s/ Lawrence C. Fichtner   
                                                    ---------------------------
                                                        Lawrence C. Fichtner,  
                                                        Director               
                                                                               
                                       Address for Notices:                    
                                       Suite 300                               
                                       615-3 Avenue S.W.                       
                                       Calgary, Alberta T2P 0G6, CANADA        
                                       Fax No.:  (402) 266-9359                
                                       Telephone No.:  (403) 266-9350          
                                                                               
                                                                               
                                       AGENT:                                  
                                                                               
                                       WELLS FARGO BANK (TEXAS), NATIONAL 
                                       ASSOCIATION          
                                                                               
                                                                               
                                       By: /s/ J. Alan Alexander               
                                           -------------------------------------
                                                J. Alan Alexander              
                                                Vice President                 
                                                                               
                                       Address for Notices                     
                                       1000 Louisiana, Third Floor 
                                       MAC 5002-031                
                                       Houston, Texas  77002                   
                                       Fax No.:  (713) 520-7912                
                                       Telephone No.:  (713) 250-1651          
                                       Attention:  J. Alan Alexander           
<PAGE>   12

                                       ISSUING BANK:    

                                       WELLS FARGO BANK (TEXAS), NATIONAL 
                                       ASSOCIATION            
                                                                               
                                                                               
                                       By: /s/ J. Alan Alexander               
                                           ------------------------------------
                                                J. Alan Alexander              
                                                Vice President                 
                                                                               
                                       Address for Notices                     
                                       1000 Louisiana, Third Floor 
                                       MAC 5002-031                  
                                       Houston, Texas  77002                   
                                       Fax No.:  (713) 520-7912                
                                       Telephone No.:  (713) 250-1651          
                                       Attention:  J. Alan Alexander           
                                                                               
                                                                               
                                       BANKS:                                  
                                                                               
                                       WELLS FARGO BANK (TEXAS), NATIONAL 
                                       ASSOCIATION            
                                                                               
                                                                               
                                       By: /s/ J. Alan Alexander               
                                           ------------------------------------
                                                J. Alan Alexander              
                                                Vice President                 
                                                                               
                                       Address for Notices                     
                                       1000 Louisiana, Third Floor 
                                       MAC 5002-031                  
                                       Houston, Texas  77002                   
                                       Fax No.:  (713) 520-7912                
                                       Telephone No.:  (713) 250-1651          
                                       Attention:  J. Alan Alexander           





                                      -12-
<PAGE>   13
                              JOINDER AND CONSENT


         Each Guarantor hereby consents and agrees to the foregoing Amendment,
consents, in particular, to the provisions of Section 2.6(b) of the Amendment
and agrees that its Guaranty and all other Loan Documents to which it is a
party shall remain in full force and effect as amended by the Amendment and
shall continue to be the legal, valid and binding obligation of such Guarantor
enforceable against such Guarantor in accordance with its terms as amended by
the Amendment.


                                       GUARANTORS:

The common seal of DIGICON      )
(MALAYSIA) SDN. BHD. was        )
hereto affixed in the presence  )
of _______________________      )


                                       DIGICON (MALAYSIA) SDN. BHD.      


                                       By:                                    
                                           ------------------------------------
                                           Director

                                       By:                                    
                                           ------------------------------------
                                           Director/Secretary


                                       EUROSEIS, INC.


                                       By:
                                           ------------------------------------
                                           Anthony Tripodo, Executive Vice 
                                           President and Chief Financial Officer





                                      -13-
<PAGE>   14
                               INDEX TO EXHIBITS


<TABLE>
 <S>                     <C>                                        <C>
 Exhibit                 Description of Exhibit                     Section
 -------                 ----------------------                     -------

 Exhibit "A"             Form of Revolving Credit Note              2.3 of Amendment;
                                                                    2.2 of Agreement
 Exhibit "D"             Revolving Credit Advance Request Form      2.3 of Amendment;
                                                                    7.2(a) of Agreement
</TABLE>





                                      -14-
<PAGE>   15
                                  EXHIBIT "A"

                         Form of Revolving Credit Note





                                      
<PAGE>   16
                             REVOLVING CREDIT NOTE


$25,000,000.00                 Houston, Texas                   May 28, 1997


         FOR VALUE RECEIVED, the undersigned, VERITAS DGC INC., a Delaware
corporation, formerly known as Digicon Inc., DIGICON GEOPHYSICAL CORP., a
Delaware corporation, VERITAS DGC LAND INC., a Mississippi corporation,
formerly known as Digicon/GFS, Inc., DIGICON GEOPHYSICAL LIMITED, a company
organized under the laws of England and Wales, DIGICON EXPLORATION, LTD., a
Delaware company and VERITAS ENERGY SERVICES PARTNERSHIP, a partnership
organized under the laws of Alberta, Canada (collectively the "Borrowers," and
individually each a "Borrower"), hereby jointly and severally promise to pay to
the order of WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION (the "Bank"), at
the Agent's office located at 1000 Louisiana, Houston, Texas 77002 for the
account of the Applicable Lending Office of the Bank, in lawful money of the
United States of America and in immediately available funds, the principal
amount of Twenty-Five Million and No/100 Dollars ($25,000,000.00) or such
lesser amount as shall equal the aggregate unpaid principal amount of the
Revolving Credit Advances made by the Bank to the Borrowers under the Credit
Agreement referred to below, on the dates and in the principal amounts provided
in the Credit Agreement, and to pay interest on the amount of each such
Revolving Credit Advance, at such office, in like money and funds, for the
period commencing on the date of such Revolving Credit Advance until such
Revolving Credit Advance shall be paid in full, at the rates per annum and on
the dates provided in the Credit Agreement.

         The Borrowers hereby authorize the Bank to endorse on the Schedule
annexed to this Note the amount of Revolving Credit Advances made to the
Borrowers by the Bank and payments of principal in respect of such Revolving
Credit Advances, which endorsements shall, in the absence of manifest error, be
conclusive as to the outstanding principal amount of all such Revolving Credit
Advances; provided, however, that the failure to make such notation with
respect to any such Revolving Credit Advance or payment shall not limit or
otherwise affect the obligations of the Borrowers under the Credit Agreement or
this Note.

         This Note is one of the Revolving Credit Notes refereed to in the
Amended and Restated Credit Agreement dated as of even date herewith, among the
Borrowers, the Bank and certain other banks parties thereto and Wells Fargo
Bank (Texas), National Association, as Agent for the Bank and certain other
banks (such Amended and Restated Credit Agreement, as amended by that certain
First Amendment to Credit Agreement dated of even date herewith, as the same
may be amended, modified, or supplemented from time to time, being referred to
herein as the "Credit Agreement"), and evidences Revolving Credit Advances made
by the Bank thereunder.  The Credit Agreement, among other things, contains
provisions for acceleration of the maturity of this Note upon the happening of
certain stated events and also for prepayments of Revolving Credit Advances
prior to the maturity of this Note upon the terms and conditions specified in
the Credit Agreement.





REVOLVING CREDIT NOTE - Page 1
<PAGE>   17
Capitalized terms used in this Note have the respective meanings assigned to
them in the Credit Agreement.

         Notwithstanding anything to the contrary contained herein, no
provision of this Note shall require the payment or permit the collection of
interest in excess of the Maximum Rate.  If any excess of interest in such
respect is herein provided for, or shall be adjudicated to be so provided, in
this Note or otherwise in connection with this loan transaction, the provisions
of this paragraph shall govern and prevail, and neither the Borrowers nor the
sureties, guarantors, successors or assigns of the Borrowers shall be obligated
to pay the excess amount of such interest, or any other excess sum paid for the
use, forbearance or detention of sums loaned pursuant hereto.  If for any
reason interest in excess of the Maximum Rate shall be deemed charged, required
or permitted by any court of competent jurisdiction, any such excess shall be
applied as a payment and reduction of the principal of indebtedness evidenced
by this Note; and, if the principal amount hereof has been paid in full, any
remaining excess shall forthwith be paid to the Borrowers.  In determining
whether or not the interest paid or payable exceeds the Maximum Rate, the
Borrowers and the Bank shall, to the extent permitted by applicable law, (i)
characterize any non-principal payment as an expense, fee, or premium rather
than as interest, (ii) exclude voluntary prepayments and the effects thereof,
and (iii) amortize, prorate, allocate, and spread in equal or unequal parts the
total amount of interest throughout the entire contemplated term of the
indebtedness evidenced by this Note so that the interest for the entire term
does not exceed the Maximum Rate.

         THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE
LAWS OF THE STATE OF TEXAS AND THE APPLICABLE LAWS OF THE UNITED STATES OF
AMERICA.  THIS NOTE IS PERFORMABLE IN HARRIS COUNTY, TEXAS.

         The Borrowers and each surety, guarantor, endorser, and other party
ever liable for payment of any sums of money payable on this Note jointly and
severally waive notice, presentment, demand for payment, protest, notice of
protest and non-payment or dishonor, notice of acceleration, notice of intent
to accelerate, notice of intent to demand, diligence in collecting, and all
other formalities of any kind, and consent to all extensions without notice for
any period or periods of time and partial payments, before or after maturity,
and any impairment of any collateral securing this Note, all without prejudice
to the holder.  The holder shall similarly have the right to deal in any way,
at any time, with one or more of the foregoing parties without notice to any
other party, and to grant any such party any extensions of time for payment of
any of said indebtedness, or to release or substitute part or all of the
collateral securing this Note, or to grant any other indulgences or
forbearances whatsoever, without notice to any other party and without in any
way affecting the personal liability of any party hereunder.

         This Note is executed in renewal, extension and increase of, but not
in novation or discharge of, that certain Revolving Credit Note dated October
21, 1996, executed by the Borrowers and payable to the order of the Bank in the
original principal amount of $15,000,000, which Revolving Credit Note was
executed in renewal and extension of, but not in novation or discharge of, that
certain Revolving Credit Note dated July 18, 1996, executed by the Borrowers
(other than Veritas





REVOLVING CREDIT NOTE - Page 2
<PAGE>   18
Energy Services Partnership) and payable to the order of the Bank in the
original principal amount of $15,000,000.

         This Note is secured as provided in the Credit Agreement and is
entitled to all the benefits of the Credit Agreement and all other Loan
Documents.

                                       VERITAS DGC INC.                        
                                                                               
                                                                               
                                       By:                                     
                                          ------------------------------------ 
                                            Anthony Tripodo                    
                                            Executive Vice President and       
                                            Chief Financial Officer            
                                                                               
                                       DIGICON GEOPHYSICAL CORP.               
                                                                               
                                                                               
                                       By:                                     
                                          ------------------------------------ 
                                            Anthony Tripodo                    
                                            Executive Vice President and       
                                            Chief Financial Officer            
                                                                               
                                       VERITAS DGC LAND INC.                   
                                                                               
                                                                               
                                       By:                                     
                                          ------------------------------------ 
                                            Anthony Tripodo                    
                                            Executive Vice President and       
                                            Chief Financial Officer            
                                                                               
                                       DIGICON GEOPHYSICAL LIMITED             
                                                                               
                                                                               
                                       By:                                     
                                          ------------------------------------ 
                                            Allan C. Pogach,                   
                                            Director                           
                                                                               
                                       DIGICON EXPLORATION, LTD.               
                                                                               
                                                                               
                                       By:                                     
                                          ------------------------------------ 
                                            Anthony Tripodo                    
                                            Executive Vice President and       
                                            Chief Financial Officer            





REVOLVING CREDIT NOTE - Page 3
<PAGE>   19

                                       VERITAS ENERGY SERVICES                 
                                       PARTNERSHIP, a Partnership by           
                                       a duly authorized Partner               
                                                                               
                                       By:  VERITAS GEOPHYSICAL LIMITED        
                                                                               
                                                                               
                                            Per:                               
                                                ------------------------------ 
                                                 Lawrence C. Fichtner,         
                                                 Director                      
                                                                               
                                                                      - and -  
                                                                               
                                       By:  VERITAS SEISMIC (1987) LTD.        
                                                                               
                                                                               
                                            Per:                               
                                                ------------------------------ 
                                                 Lawrence C. Fichtner,         
                                                 Director                      
                                                                               
                                                                      - and -  
                                                                               
                                       By:  CANEX INFORMATION SERVICES LTD.    
                                                                               
                                                                               
                                            Per:                               
                                                ------------------------------ 
                                                 Lawrence C. Fichtner,         
                                                 Director                      
                                                                               
                                                                 - BORROWERS - 
                                                                               
                                                                               



REVOLVING CREDIT NOTE - Page 4
<PAGE>   20
                                    Schedule



<TABLE>
<CAPTION>  
                                                                                            Unpaid   
                                                                 Amount of                 Principal
          Date Made                  Amount of                   Principal                  Balance  
           or Paid                   Advance                     Page                       of Note  
         ----------------------------------------------------------------------------------------------
          <S>                        <C>                         <C>                        <C>

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

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

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

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

</TABLE>


REVOLVING CREDIT NOTE - Page 5
<PAGE>   21
                                  EXHIBIT "D"

                     Revolving Credit Advance Request Form
<PAGE>   22
                     REVOLVING CREDIT ADVANCE REQUEST FORM

                                                   Date: ________________, 199__

TO:      WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION

Ladies and Gentlemen:

         The undersigned Borrowers hereby refer to the Amended and Restated
Credit Agreement dated as of October 21, 1996 among the borrowers listed on the
signature line hereof (the "Borrowers"), Wells Fargo Bank (Texas), National
Association, as agent (the "Agent"), and the Banks and the Issuing Bank
signatories thereto, as the same may be amended, modified, supplemented or
restated from time to time (the "Credit Agreement") and gives you irrevocable
notice pursuant to Section 4.1 of the Credit Agreement, of the Revolving Credit
Advance specified below:


<TABLE>
         <S>                                                                      <C>
         A.      REVOLVING CREDIT ADVANCE REQUEST INFORMATION:

                 1.       Revolving Credit Commitment                              $25,000,000.00

                 2.       Borrowing Base breakdown by company calculated as of
                          the last month end:

                          (a)     Veritas DGC Inc.

                                  (i)      Eligible Domestic/Domestic Accounts     $______________________________

                                  (ii)     Eligible Domestic/Foreign Accounts      $______________________________

                          (b)     Digicon Geophysical Corp.

                                  (i)      Eligible Domestic/Domestic Accounts     $______________________________

                                  (ii)     Eligible Domestic/Foreign Accounts      $______________________________

                          (c)     Veritas DGC Land Inc.

                                  (i)      Eligible Domestic/Domestic Accounts     $______________________________


</TABLE>




REVOLVING CREDIT ADVANCE REQUEST FORM -  Page 1
<PAGE>   23

<TABLE>
                 <S>                                                                <C>
                                  (ii)     Eligible Domestic/Foreign Accounts       $______________________________

                          (d)     Digicon Exploration, Ltd.

                                  (i)      Eligible Domestic/Domestic Accounts      $______________________________

                                  (ii)     Eligible Domestic/Foreign Accounts       $______________________________

                                  (iii)    Eligible Foreign/Foreign Accounts        $______________________________

                          (e)     Digicon Geophysical Limited

                                  (i)      Eligible Foreign/Foreign Accounts        $______________________________

                          (f)     Digicon (Malaysia) Sdn. Bhd.

                                  (i)      Eligible Foreign/Foreign Accounts        $______________________________

                          (g)     Veritas Energy Services Partnership

                                  (i)      Eligible Foreign/Foreign Accounts        $______________________________

                 3.       Borrowing Base calculation                                $______________________________

                          (a)     Eligible Domestic/Domestic Accounts

                                  (i)      Sum of 2(a)(i), 2(b)(i), 2(c)(i) and
                                           2(d)(i)                                  $______________________________

                                  (ii)     80% of 3(a)(i) above                     $______________________________

                          (b)     Eligible Domestic/Foreign Accounts

                                  (i)      Sum of 2(a)(ii), 2(b)(ii), 2(c)(ii)
                                           and 2(d)(ii)                             $______________________________

                                  (ii)     70% of 3(b)(i) above                     $______________________________
</TABLE>




REVOLVING CREDIT ADVANCE REQUEST FORM -  Page 2
<PAGE>   24

<TABLE>
                 <S>                                                                <C>
                          (c)     Eligible Foreign/Foreign Accounts

                                  (i)      Sum of 2(d)(iii), 2(e)(i), 2(f)(i)
                                           and 2(g)(i)                              $______________________________

                                  (ii)     50% of 3(c)(i) above                     $______________________________

                          (d)     Aggregate Borrowing Base (sum of 3(a)(ii),
                                  3(b)(ii) and 3(c)(ii) above)                      $______________________________

                 4.       Principal amount outstanding under the Revolving
                          Credit Note prior to Requested Revolving Credit
                          Advance                                                   $______________________________

                 5.       Total amount of Requested Revolving Credit Advance        $______________________________

                 6.       Remaining Availability under Revolving Credit
                          Commitment after Requested Revolving Credit Advance       $______________________________

                 7.       Amount of Prime Rate Advance . . . $________ requested on __________, 199___.

                 8.       Amount of Eurodollar Rate Advance with Interest
                          Period of:

                          (i)     one month of $____ requested to be made on _____________, 199___.  
                          (ii)    two months of $____ requested to be made on _____________, 199___.  
                          (iii)   three months of $____ requested to be made on _____________, 199___.

                 9.       Amount of Secured Obligations

                          (i)     Maximum Bank Credit Amount                        $______________________________

                          (ii)    Amount equal to 10% of Consolidated Net           
                                  Tangible Assets                                   $______________________________

                          (iii)   Greater of (i) or (ii)                            $______________________________

                          (iv)    Permitted Subsidiary Indebtedness                 $______________________________
</TABLE>



REVOLVING CREDIT ADVANCE REQUEST FORM -  Page 3
<PAGE>   25

<TABLE>

                          <S>                                                       <C>
                          (v)     Sum of (iii) and (iv)                             $______________________________

</TABLE>

         The Borrowers confirm that they have granted a Lien to the Agent
pursuant to the Loan Documents to secure the Secured Obligations and that no
Borrower has taken any action to cause such Lien to become unperfected.

         The Borrowers hereby represent, warrant and agree, pursuant to the
Credit Agreement, that the delivery of this Revolving Credit Advance Request
Form and the acceptance by the Borrowers of the proceeds of the Revolving
Credit Advance constitutes a representation and warranty by the Borrowers that,
on the date of such Revolving Credit Advance, and before and after giving
effect thereto and to the application of proceeds therefrom, all conditions
precedent set forth in Article VII of the Credit Agreement have been satisfied
and that all the representations and warranties of the Borrowers set forth in
Article VIII of the Credit Agreement remain true and correct on and as of the
date of such Revolving Credit Advance with the same force and effect as if such
representations and warranties had been made on and as of such date.

         Immediately after the Revolving Credit Advance to which this Revolving
Credit Advance Request Form relates, no Default or Event of Default shall have
occurred and be continuing.

         The proceeds of Revolving Credit Advances which are the subject of
this Revolving Credit Advance Request Form will be used for the purposes
permitted under the Credit Agreement.

         All capitalized terms not otherwise defined herein shall have the
respective meanings ascribed to them in Appendix A to the Credit Agreement.

                                       VERITAS DGC INC.                       
                                       DIGICON GEOPHYSICAL CORP.              
                                       VERITAS DGC LAND INC.                  
                                       DIGICON GEOPHYSICAL LIMITED            
                                       DIGICON EXPLORATION, LTD.              
                                       VERITAS ENERGY SERVICES PARTNERSHIP    
                                                                             
                                                                             
                                       By:____________________________________ 
                                          Authorized Signatory for and on      
                                          behalf of each of the Borrowers      
                                                                               




REVOLVING CREDIT ADVANCE REQUEST FORM -  Page 4