<PAGE>   1
                                                                    EXHIBIT 10-C



                                VERITAS DGC INC.

                           THIRD AMENDED AND RESTATED
                  1992 EMPLOYEE NONQUALIFIED STOCK OPTION PLAN
                   (AS AMENDED AND RESTATED DECEMBER 9, 1998)

1.       PURPOSE.

         The purpose of this 1992 Employee Nonqualified Stock Option Plan (the
"Plan") of Veritas DGC Inc. (the "Company") (formerly known as Digicon Inc.) is
to provide officers and other key employees with a continuing proprietary
interest in the Company. The Plan is intended to advance the interests of the
Company by enabling it (i) to increase the interest in the Company's welfare of
those employees who share the primary responsibility for the management, growth,
and protection of the business of the Company, (ii) to furnish an incentive to
such persons to continue their services to the Company, (iii) to provide a means
through which the Company may continue to induce able management and operating
personnel to enter its employ, and (iv) to provide a means through which the
Company may effectively compete with other organizations offering similar
incentive benefits in obtaining and retaining the services of competent
management and operating personnel.

2.       STOCK SUBJECT TO THE PLAN.

         The Company may grant from time to time options to purchase shares of
the Company's authorized but unissued common stock, par value $.01 per share, or
treasury shares of the common stock. Subject to adjustment as provided in
Section 11 hereof, the aggregate number of shares which may be issued or covered
by options pursuant to the Plan is 3,404,550 shares, as adjusted for the one for
three reverse stock split effective January 17, 1995. Shares of common stock
applicable to options which have expired unexercised or terminated for any
reason may again be subject to an option or options under the Plan.



                                     Page 1
<PAGE>   2

3.       ADMINISTRATION.

         (a) The Plan shall be administered by the Compensation Committee of the
Company's board of directors (the "Committee"). The board of directors may, from
time to time, remove members from or add members to the Committee. Vacancies in
the Committee, however caused, shall be filled by the board of directors. No
member of the Committee shall be eligible to receive options under the Plan. The
Committee shall select one of its members chairman and shall hold meetings at
such times and places as it may determine. The Committee may appoint a secretary
and, subject to the provisions of the Plan and to policies determined by the
board of directors, may make such rules and regulations for the conduct of its
business as it shall deem advisable. A majority of the Committee shall
constitute a quorum. All action of the Committee shall be taken by a majority of
its members. Any action may be taken by a written instrument signed by a
majority of the members, and action so taken shall be fully as effective as if
it had been taken by a vote of the majority of the members at a meeting duly
called and held.

         (b) Subject to the express terms and conditions of the Plan, the
Committee shall have full power to construe or interpret the Plan, to prescribe,
amend, and rescind rules and regulations relating to it and to make all other
determinations necessary or advisable for its administration.

         (c) Subject to the provisions of Sections 4 and 5 hereof, the Committee
may, from time to time, determine which employees of the Company or subsidiary
corporations shall be granted options under the Plan, the number of shares
subject to each option, and the time or times at which options shall be granted.

         (d) The Committee shall report to the board of directors the names of
employees granted options, and the number of option shares subject to, and the
terms and conditions of, each option; provided, however that no option may be
granted to an otherwise eligible employee if, after giving effect to the
proposed grant, such employee would then hold options covering more than 500,000
shares of common stock under the Plan.

         (e) No member of the board of directors or of the Committee shall be
liable for any action or determination made in good faith with respect to the
Plan or any option.


                                     Page 2
<PAGE>   3

4.       ELIGIBILITY.

         All full-time salaried employees of the Company and of its
majority-owned subsidiaries shall be eligible to participate in the Plan, and
options may be granted by the Committee to eligible employees designated by the
Committee, either at the Committee's own initiative or upon the recommendation
of management. In determining the employees to whom options shall be granted and
the number of shares to be covered by each option, the Committee may take into
account the nature of the services rendered by the respective employees, their
present and potential contributions to the success of the Company, and such
other factors as the Committee in its discretion shall deem relevant. The
Company shall effect the granting of options under the Plan in accordance with
the determination made by the Committee.

5.       PRICE OF OPTIONS.

         The option price per share shall be not less than the lesser of (i)
fair market value of the common stock on the date the option is granted or (ii)
the average fair market value for the common stock during the thirty trading
days ending on the trading day next preceding the date the option is granted.
Fair market value on any day shall be deemed to be the last reported sale price
of the common stock on the principal stock exchange on which the Company's
common stock is traded on that date. If no trading occurred on such date, or, if
at the time the common stock shall not be listed for trading, fair market value
shall be deemed to be the mean between the quoted bid and asked prices for the
common stock on such exchange or in the over-the-counter market, as the case may
be, on that date.

6.       TERM OF OPTION.

         No option shall be exercisable after the expiration of ten years from
the date the option is granted.

7.       EXERCISE OF OPTIONS.

         (a) General. Except as provided below, each option may be exercised at
such times and in such amounts as the Committee in its discretion may provide.

         (b) Manner of Exercising Options. Shares of common stock purchased 
under options shall at the time of purchase be paid for in full. To the extent
that the right to purchase shares has accrued hereunder, options may be
exercised from time to time by written notice to the Company stating the full
number of shares with respect to which the option is being exercised, and the
time of delivery thereof, which shall be at least 15 days after the giving of
such notice unless an earlier date shall have been mutually agreed upon. At such
time, the Company shall, without transfer or issue tax to the optionee (or other
person entitled to exercise the option) deliver 


                                     Page 3
<PAGE>   4

to the optionee (or to such other person) at the principal office of the
Company, or such other place as shall be mutually acceptable, a certificate or
certificates for such shares against prior payment of the option price in full
on the date of notice of exercise for the number of shares to be delivered by
certified or official bank check or the equivalent thereof acceptable to the
Company; provided, however, that the time of such issuance and delivery may be
postponed by the Company for such period as may be required for it with
reasonable diligence to comply with any requirements of law, the listing
requirements of the New York Stock Exchange or any other exchange on which the
common stock may then be listed. If the optionee (or other person entitled to
exercise the option) fails to pay for all or any part of the number of shares
specified in such notice or to accept delivery of such shares upon tender of
delivery thereof, the right to exercise the option with respect to such
undelivered shares shall be terminated.



                                     Page 4
<PAGE>   5



8.       NON-ASSIGNABILITY OF OPTION RIGHTS.

         No option granted under the Plan shall be assignable or transferable
otherwise than by will or by the laws of descent and distribution. During the
lifetime of an optionee, the option shall be exercisable only by him.

9.       TERMINATION OF EMPLOYMENT.

         Except as otherwise provided in this paragraph, options shall terminate
90 days following the termination of the optionee's employment with the Company
for any reason, but shall be exercisable following termination only to the
extent that the option had become vested on the termination date. In the event
that the optionee retires from the Company (at or after age 65) the optionee
shall have the right, subject to the provisions of Section 6, to exercise his
option at any time within one year after such termination, to the extent that
such option had become vested on the termination date. If, however, the optionee
shall die in the employment of the Company, then for the lesser of the maximum
period during which such option might have been exercisable or one year after
the date of death, his estate, personal representative, or beneficiary shall
have the same right to exercise the option of such employee as he would have had
if he had survived and remained in the employment of the Company. For purposes
of this Section 9, employment by any majority-owned subsidiary corporation of
the Company shall be deemed employment by the Company.

         In the discretion of the Committee, a leave of absence approved in
writing by the board of directors of the Company shall not be deemed a
termination of employment; however, no option may be exercised during such leave
of absence.

10.      CHANGE OF CONTROL.

         If, at any time, a person, entity or group (including, in each case,
all other persons, entities or groups controlling, controlled by, or under
common control with or acting in concert or concurrently with, such person,
entity or group) shall hold, purchase or acquire beneficial ownership (including
without limitation power to vote) of 50% or more of the then outstanding shares
of the Company's Common Stock, then any portion of the Options which have not
yet become exercisable shall thereupon become immediately exercisable.

11.      ADJUSTMENT OF OPTIONS ON RECAPITALIZATION OR REORGANIZATION.

         The aggregate number of shares of common stock on which options may be
granted to persons participating under the Plan, the aggregate number of shares
of common stock on which options may be granted to any one such person, the
number of shares thereof covered by each outstanding option, and the price per
share thereof in each such option, shall be proportionately adjusted for any
increase or decrease in the number of issued shares of common stock of the
Company resulting from the subdivision or combination of shares or other capital
adjustments, or the payment of a stock dividend 


                                     Page 5

<PAGE>   6


after the effective date of this Plan, or other increase or decrease in such
shares effected without receipt of consideration by the Company; provided,
however, that no adjustment shall be made unless the aggregate effect of all
such increases and decreases occurring in any one fiscal year after the
effective date of this Plan will increase or decrease the number of issued
shares of common stock of the Company by 5% or more; and, provided, further,
that any options to purchase fractional shares resulting from any such
adjustment shall be eliminated.

         Subject to any required action by the stockholders and to Section 10
hereof, if the Company shall be the surviving or resulting corporation in any
merger or consolidation, any option granted hereunder shall pertain to and apply
to the securities to which a holder of the number of shares of common stock
subject to option would have been entitled had such option been exercised
immediately preceding such merger or consolidation; but a dissolution or
liquidation of the Company, or a merger or consolidation in which the Company is
not the surviving or resulting corporation (except for a change in Control as
defined in Section 10 hereof in which case Section 10 shall govern then
outstanding options) shall cause every option outstanding hereunder to
terminate, except that the surviving or resulting corporation may, in its
absolute and uncontrolled discretion, tender an option or options to purchase
its shares on its terms and conditions, both as to the number of shares and
otherwise.

         Adjustments under this Section shall be made by the Committee, whose
determination as to what adjustments shall be made, and the extent thereof,
shall be final, binding and conclusive.

12.      AGREEMENTS BY OPTIONEE.

         Each individual optionee shall agree:

                  (a) If requested by the Company, at the time of exercise of
         any option, to execute an agreement stating that he is purchasing the
         shares subject to option for investment purposes and not with a view to
         the resale or distribution thereof;

                  (b) To authorize the Company to withhold from his gross pay 
          any tax which it believes is required to be withheld with respect to
          any benefit under the Plan, and to hold as security for the amount to
          be withheld any property otherwise distributable to the optionee under
          the Plan until the amounts required to be withheld have been so
          withheld.



                                     Page 6
<PAGE>   7

13.      RIGHTS AS A SHAREHOLDER.

         The optionee shall have no rights as a stockholder with respect to any
shares of common stock of the Company held under option until the date of
issuance of the stock certificates to him for such shares.

14.      EFFECTIVE DATE.

         The Plan was effective as of September 1, 1992, upon approval by the
holders of a majority of the shares of outstanding capital stock present at the
December 17, 1992 annual meeting of the Company's stockholders. The Plan was
amended by the board of directors on August 29, 1997, and amended and restated
by the board of directors on March 10, 1997, and December 9, 1998.

15.      AMENDMENTS.

         (a) The board of directors may, from time to time, alter, suspend or
terminate the Plan, or alter or amend any and all option agreements granted
thereunder but only for one or more of the following purposes:

             (1) To modify the administrative provisions of the Plan or options;

             (2) To make any other amendment which does not materially alter the
         intent or benefits of the Plan; or

             (3) Increase the maximum number of shares as to which options
         may be granted under the Plan either to all persons participating in
         the Plan or to any one such person.

         (b) It is expressly provided that no such action of the board of
directors may, without the approval of the stockholders, alter the provisions of
the Plan or option agreements granted thereunder so as to:

             (1) Decrease the option price applicable to any options granted 
             under the Plan, provided, however, that the provisions of this
             clause (1) shall not prevent the granting, to any person holding an
             option under the Plan, of additional options under the Plan
             exercisable at a lower option price; or

             (2) alter any outstanding option agreement to the detriment of the 
             optionee, without his consent.



                                     Page 7
<PAGE>   8

16.      EMPLOYMENT OBLIGATION.

         The granting of any option under this Plan shall not impose upon the
Company any obligation whatsoever to employ or to continue to employ any
optionee, and the right of the Company to terminate the employment of any
officer or other employee shall not be diminished or affected by reason of the
fact that an option has been granted to him under the Plan.

17.      VES OPTIONS.

         In order to carry out the terms of (i) the Combination Agreement dated
May 10, 1996, between the Company and Veritas Energy Services Inc. ("VES") which
was approved by the Company's stockholders at a special meeting held on August
20, 1996 and (ii) the Plan of Arrangement under Part 15 of the Business
Corporations Act (Alberta) relating to the combination of the Company and VES
which, pursuant to an interim order of the Court of Queen's Bench of Alberta
date July 18, 1996, was approved at special meetings of VES optionholders and
shareholders held August 20, 1996, this Plan shall include under its terms each
of the options (the "VES Options") outstanding on the Effective Date (as defined
in the Combination Agreement) (which includes all outstanding options granted
under VES' Stock Option Plan for Directors, Officers and Key Employees (the "VES
Option Plan")) without any further action on the part of any holder thereof
(each a "VES Optionholder"). Effective as of the Effective Time, each VES Option
will be exercisable to purchase that number of shares of the Company's common
stock determined by multiplying the number of VES common shares (the "VES Common
Shares") subject to such VES Option at the Effective Time by the Exchange Ratio
(as defined in the Combination Agreement), at an exercise price per share of
such VES Option immediately prior to the Effective Time, divided by the Exchange
Ratio. On the Effective Date (as defined in the Combination Agreement), such
option price shall be converted into a United States dollar equivalent based on
the noon spot rate of exchange of the Bank of Canada on such date. If the
foregoing calculation results in an exchanged VES Option being exercisable for a
fractional share of the Company's common stock, then the number of shares of the
Company's common stock subject to such option will be rounded down to the
nearest whole number of shares and the total exercise price for the option will
be reduced by the exercise price of the fractional share. The term,
exercisability, vesting schedule and all other terms and conditions of the VES
Options will otherwise be unchanged and shall operate in accordance with their
terms, notwithstanding anything to the contrary contained herein.



                                     Page 8