February 20, 1998



          Board of Directors of Dominion Bridge Corporation
          C/o Mr. K. Mitchell Posner
          Managing Director
          Legg Mason Wood Walker, Incorporated
          1735 Market Street, Suite 1100
          Philadelphia, Pennsylvania 19103

          RE:  LETTER OF INTENT
               DOMINION BRIDGE CORPORATION 

          Gentlemen:

                    This letter sets forth the mutual intentions of
          American Eco Corporation, an Ontario, Canada corporation
          ("American Eco"), and Dominion Bridge Corporation, a Delaware
          corporation ("Dominion Bridge"), with respect to (a) the purchase
          of US $5 million of Dominion Bridge common stock by American Eco
          (the "Dominion Bridge Stock Purchase"), (b) a working capital
          loan facility to be provided by American Eco to Dominion Bridge
          (the "Loan Transaction"), (c) the engagement of American Eco to
          provide certain management services to Dominion Bridge ("the
          "Management Arrangement"), and (d) the acquisition by American
          Eco of the business and assets of Dominion Bridge (the
          "Acquisition Transaction" and, collectively, the "Transactions"). 
          The terms and conditions set forth in this letter, in the time
          schedule attached hereto (the "Time Schedule") and in the letter
          agreement, dated February 18, 1998 (the "Letter Agreement"),
          shall supersede the terms and conditions contained in our letters
          of January 15, 1998, January 28, 1998 and February 2, 1998 with
          respect to the proposed Transactions.

                    Upon your execution and return of this letter, the
          parties intend to negotiate in good faith one or more definitive
          agreements reflecting the Transactions, the basic terms of which
          will be as follows:

          1.   The Dominion Bridge Stock Purchase
               ----------------------------------

                    1.01 Purchase of Common Stock.  (a) American Eco will
                         ------------------------
          purchase, in a private placement, 1,923,077 units at a purchase
          price of US $2.60 per unit.  Each unit will consist of (a) one
          share of Dominion Bridge common stock; and (b) 1/10 of a Dominion
          Bridge common stock purchase warrant.  Each whole warrant will
          entitle American Eco to purchase one additional share of Dominion
          Bridge Common Stock at a purchase price of US $3.00 per share
          (subject to customary anti-dilution provisions), exercisable for
          a period of three years following the date of its original
          issuance.  American Eco shall have the right to require Dominion
          Bridge to register the purchased shares of Dominion Bridge common
          stock, as well as the shares of Dominion Bridge common stock
          underlying the warrants under the US Securities Act of 1933, as
          amended (the "Securities Act"); provided, however that Dominion
                                          --------  -------
          Bridge shall not be required to commence such registration
          process unless and until American Eco and Dominion Bridge shall
          terminate their negotiations (or any definitive agreement) with
          respect to the Acquisition Transaction.  Should the $5 million
          gross proceeds from the above-mentioned stock purchase not be
          received by Dominion Bridge in an account designated by it by
          5:00 PM, Montreal time, on February 20, 1998, this letter of
          intent shall be null and void ab initio.

                    (b) Upon consummation of the Dominion Bridge Stock
          Purchase, the Board of Directors of Dominion Bridge shall elect
          Michael E. McGinnis as the representative of American Eco to
          serve on Dominion Bridge's Board of Directors and on the
          Executive Committee thereof.

                    1.02 Documentation.  The specific terms of the Dominion
                         -------------
          Bridge Stock Purchase shall be included in a mutually acceptable
          subscription agreement (and a related warrant agreement) which
          shall contain the provisions outlined above and such other terms,
          conditions and provisions customary for such a stock purchase
          transaction, including representations, warranties and
          affirmative and negative covenants.

          2.   The Loan Transaction
               --------------------

                    2.01 Amount. American Eco will provide Dominion Bridge
                         ------
          with a loan facility (the "Loan Facility") of up to US $25
          million.  The specific amount that may be borrowed by Dominion
          Bridge pursuant to the Loan Facility shall be determined by
          American Eco and the Executive Committee of the Dominion Bridge
          Board of Directors based upon their mutual assessment of the
          working capital requirements of Dominion Bridge; provided,
                                                           --------
          however, that a minimum of US $10 million shall be (a) placed in 
          -------
          trust by American Eco by March 5, 1998, and (b) funded by
          American Eco under the Loan Facility by March 23, 1998.

                    2.02 Interest Rate; Term.  Outstanding borrowings under
                         -------------------
          the Loan Facility shall bear interest at the rate of 9% per
          annum, payable monthly in arrears on the last day of each
          calendar month (or on such other day of the month which is
          consistent with Dominion Bridge's payment obligations under its
          existing loan facility with The Bank of New York ("BNY")).  The
          Loan Facility shall terminate, and all borrowings thereunder
          shall be repaid to American Eco, on the first anniversary of
          Dominion Bridge's initial borrowing under the Loan Facility (the
          "Termination Date"); provided, however, that (a) if American Eco
                               --------  -------
          and Dominion Bridge shall terminate their negotiations with
          respect to the Acquisition Transaction, Dominion Bridge shall not
          be permitted to make any additional borrowings under the Loan
          Facility and all outstanding amounts thereunder (together with
          accrued interest thereon) shall be repaid in twelve consecutive
          monthly payments of equal amount, commencing on the last day of
          the month during which such negotiations were terminated, and (b)
          if Dominion Bridge shall consummate a Third-Party Acquisition
          Transaction (as defined in Paragraph 4.07 below) with a third
          party prior to the Termination Date, the Loan Facility shall
          terminate and the outstanding principal amount thereunder,
          together with accrued interest thereon and any fees thereunder,
          shall be repaid on the closing date of such Third-Party
          Acquisition Transaction.

                    2.03 Security.  As security for the loans to be made by
                         --------
          American Eco under the Loan Facility, Dominion Bridge shall grant
          American Eco a pledge and security interest in all of its
          properties and assets, subject only to the prior pledge and
          security interest granted by Dominion Bridge to BNY pursuant to
          Dominion Bridge's existing loan with BNY. 
           
                    2.04 Warrants.  Concurrently with the closing of the
                         --------
          Loan Facility, Dominion Bridge shall authorize the issuance to
          American Eco of warrants (the "Warrants") to purchase up to 10%
          of the outstanding shares of Dominion Bridge Common Stock as of
          the closing date of the Loan Facility.  The number of Warrants to
          be issued will be based, pro rata, upon the maximum amount of
          Dominion Bridge's outstanding borrowings under the Loan Facility
          during the term thereof, less pass-through costs as described in
          Paragraph 2.05 below (the "Peak Borrowing") (e.g., if Dominion
          Bridge's Peak Borrowing is US $25 million, American Eco will
          receive Warrants to purchase 10% of the outstanding Common Stock
          of Dominion Bridge; if Dominion Bridge's Peak Borrowing is US
          $12.5 million, American Eco will receive Warrants to purchase 5%
          of the outstanding Common Stock of Dominion Bridge).  Dominion
          Bridge shall issue such Warrants to American Eco (a) at the time
          of Dominion Bridge's initial borrowing under the Loan Facility,
          and (b) at the time of each subsequent borrowing which results in
          a new Peak Borrowing under the Loan Facility.  The Warrants shall
          be exercisable for a period of two years following the date of
          their original issuance at an exercise price of US $3.00 per
          share, subject to customary anti-dilution provisions.  American
          Eco shall have the right to require Dominion Bridge to register
          the shares of Dominion Bridge common stock underlying the
          Warrants under the US Securities Act of 1933, as amended;
          provided, however that Dominion Bridge shall not be required to
          --------  -------
          commence such registration process unless and until American Eco
          and Dominion Bridge shall terminate their negotiations (or any
          definitive agreement) with respect to the Acquisition
          Transaction.

                    2.05 Pass-through of Funding Costs.  All fees and costs
                         -----------------------------
          borne by American Eco in obtaining such funds shall be passed-
          through to Dominion Bridge and shall be included in, and deducted
          from, the amounts to be borrowed by Dominion Bridge under the
          Loan Facility.  Such fees and costs shall be documented to
          Dominion Bridge and shall be based, pro rata, upon Dominion
          Bridge's Peak Borrowing under the Loan Facility (e.g., if
          Dominion Bridge's Peak Borrowing is US $25 million, Dominion
          Bridge shall pay all of such fees and costs; if Dominion Bridge's
          Peak Borrowing is US $12.5 million, Dominion Bridge shall pay 50%
          of such fees and costs); provided, however, that, assuming a Peak
                                   --------  -------
          Borrowing of US $25 million, Dominion Bridge shall not be
          required to pay more than US $1.2 million in fees and costs.

                    2.06 Documentation.  The specific terms of the Loan
                         -------------
          Transaction shall be included in either (a) a mutually acceptable
          direct loan agreement (and related agreements) between American
          Eco and Dominion Bridge, or (b) a mutually acceptable amendment
          to Dominion Bridge's existing loan agreement with BNY pursuant to
          which American Eco will become a subordinated lender thereunder.
          In either case, the loan documentation shall contain the
          provisions outlined above and such other terms, conditions and
          provisions customary for such a Loan Transaction, including
          representations, warranties, affirmative and negative covenants,
          default provisions and remedies.  The obligation of American Eco
          to enter into the Loan Facility shall be subject to the execution
          of a satisfactory subdivision and inter-creditor agreement with
          BNY, and the consents of the third parties, as required by
          Dominion Bridge and American Eco.  Upon the execution and return
          of this letter of intent by Dominion Bridge, American Eco will
          promptly commence discussions with BNY with a view to
          implementation of the Loan Facility as soon as practicable.

          3.   The Management Transaction
               --------------------------

                    3.01 Services to be Provided.  American Eco will
                         -----------------------
          provide Dominion Bridge with management services in connection
          with its ongoing, day-to-day operations.  During the term of
          American Eco's engagement, American Eco shall, subject to the
          general supervision and control of the Executive Committee of the
          Board of Directors of Dominion Bridge, furnish Dominion Bridge
          with the following management services: (i) financing and
          administrative support services, including oversight of
          collection of accounts receivable and payment of accounts
          payable; (ii) marketing administration and support services;
          (iii) human resources management; and (iv) oversight and
          administration of Dominion Bridge's operating units.  In order to
          facilitate the provision of these services, the Chief Executive
          and Chief Financial Officers of American Eco shall be given
          responsibilities within Dominion Bridge's organization which are
          customarily performed by a corporation's Chief Executive and
          Chief Financial Officers, respectively.

                    3.02 Term.   American Eco's engagement to provide
                         ----
          management services for Dominion Bridge shall commence upon the
          execution by the parties of definitive agreements with respect to
          the Transactions and shall terminate upon the later to occur of
          (i) the termination of the Loan Facility and the repayment of all
          outstanding borrowings thereunder, or (ii) the termination by
          American Eco and Dominion Bridge of their discussions (and any
          definitive agreement) with respect to the Acquisition
          Transaction.

                    3.03 Management Fee.  As compensation for the
                         --------------
          management services to be rendered by American Eco to Dominion
          Bridge, Dominion Bridge shall (i) pay to American Eco a
          management fee of US $100,000 per month, and (ii) reimburse
          American Eco for all reasonable out-of-pocket expenses and
          disbursements incurred in rendering such services; provided,
                                                             --------
          however, that (a) such management fee shall be increased to
          -------
          $250,000 if the parties shall terminate their discussions (and
          any definitive agreement) with respect to the Acquisition
          Transaction, and (b) such out-of-pocket expenses and
          disbursements shall not include the hourly costs of American
          Eco's personnel when engaged in performing the management
          services.

                    3.04 Documentation.  The specific terms of the
                         -------------
          Management Arrangement shall be included in a mutually acceptable
          management services agreement which shall contain the provisions
          outlined above and such other terms, conditions and provisions
          customary for such a management relationship, including
          representations, warranties, affirmative and negative covenants
          and indemnification provisions.

          4.   The Acquisition Transaction
               ---------------------------

                    4.01 Form of Transaction.  American Eco (or a wholly-
                         -------------------
          owned subsidiary) and Dominion Bridge will enter into a merger or
          other mutually acceptable transaction providing for the
          acquisition by American Eco of the business and assets of
          Dominion Bridge.

                    4.02 Purchase Price.  As consideration for the
                         --------------
          Acquisition Transaction, American Eco will issue to the
          stockholders of Dominion Bridge convertible notes (the
          "Convertible Notes") in the principal amount of US $3.00 for each
          outstanding share of Dominion Bridge common stock as of the
          closing.  The parties intend to investigate the possibility of
          restructuring the consideration so that the transaction will be
          tax-free to the holders of Dominion Bridge common stock.

                    4.03 Terms of Convertible Notes.  (a) The Convertible
                         --------------------------
          Notes will bear interest at the rate of 7-1/2% per annum (payable
          quarterly in arrears) and the Convertible Notes will be payable
          three years after the closing date of the Acquisition
          Transaction.

                    (b) The Convertible Notes will, at the option of the
          holder, be convertible into American Eco common stock at a
          conversion rate of US $15 per share, subject to standard anti-
          dilution provisions, as follows: (i) commencing 180 days
          following the issuance date, one-third of each holder's
          Convertible Notes will be convertible, (ii) commencing 360 days
          following the issuance date, two-thirds of each holder's
          Convertible Notes will be convertible, and (iii) commencing 540
          days following the issuance date, all of the Convertible Notes
          will be convertible.  American Eco will have the right to force
          conversion at a rate of US $15 per share of American Eco common
          stock if the average closing price of American Eco common stock
          on the Nasdaq National Market shall equal or exceed US $16.00 per
          share for any twenty consecutive-day trading period, and the
          Convertible Notes are in good standing and not in arrears.

                    (c) Upon 60 days prior written notice to the holders,
          American Eco will have the right to redeem the outstanding
          Convertible Notes, at US$3.00, plus accrued and unpaid interest;
          provided, however, that, following the receipt of such notice and
          --------  -------
          prior to the date set for redemption, the holders shall have the
          right to convert all or a portion of their Convertible Notes into
          American Eco common stock at a rate of US $15 per share of
          American Eco common stock.

                    (d)  Both the Convertible Notes and the underlying
          shares of American Eco common stock will be registered under the
          Securities Act and will be listed on the Nasdaq National Market
          or such national securities exchange or market system as such
          shares are then listed or traded, prior to the closing of the
          Acquisition Transaction.    

                    4.04 Due Diligence. We are confident that the results
                         -------------
          of our due diligence, thus far, have provided us with the
          necessary comfort to move forward with this transaction. 
          However, American Eco will continue with its due diligence
          investigation of Dominion Bridge promptly following Dominion
          Bridge's execution and delivery of this letter of intent in
          accordance with the letter, dated November 29, 1997, from Legg,
          Mason, Wood Walker, Incorporated to American Eco, the terms of
          which letter are incorporated herein.

                    Subject to the execution by Dominion Bridge of a
          satisfactory confidentiality agreement, American Eco shall make
          available to Dominion Bridge and its representatives, at
          reasonable times, all information relating to its business which
          Dominion Bridge or its representatives may reasonably request in
          order to evaluate the Acquisition Transaction.

                    4.05 Conduct of Business.  Dominion Bridge will, from
                         -------------------
          and after the date it accepts and agrees to the terms herein,
          conduct its business in the ordinary course and in substantially
          the same manner as previously conducted, including not making any
          changes in its capital stock.  Dominion Bridge shall keep
          American Eco advised of any and all material developments in its
          business in addition to any information employees of American Eco
          may learn by reason of the management arrangement.  Dominion
          Bridge shall use its reasonable best efforts to preserve in full
          force and effect its franchises, licenses, permits, contracts,
          and the goodwill of its suppliers, employees, customers and
          others having business relationships with Dominion Bridge.

                    4.06 Conditions to Acquisition.  The consummation of
                         -------------------------
          the Acquisition Transaction will be subject, among other things,
          to (a) the approval of the acquisition by the Board of Directors
          and shareholders of Dominion Bridge; (b) the agreement of
          beneficial owners of more than 5% of the outstanding Dominion
          Bridge common stock to vote their shares for approval of the
          Acquisition Transaction, (c) the approval of the acquisition by
          the Board of Directors and, if required, shareholders of American
          Eco; and (d) the receipt of all consents, approvals, clearances
          and other authorizations necessary to consummate the acquisition,
          including (i) compliance with the Hart-Scott-Rodino Antitrust
          Improvements Act and the Australian Corporations Law; (ii) the
          consent of the Province of Quebec Finance Administration; and
          (iii) clearance by the U.S. Securities and Exchange Commission
          and any required Canadian authorities of definitive proxy
          material for the Dominion Bridge stockholders meeting and of the
          registration statement for the Convertible Notes (including
          receipt of any required valuation or fairness opinion); and (iv)
          the consent of the respective lenders of American Eco and
          Dominion Bridge.  Upon the execution by the parties of a
          definitive acquisition agreement, American Eco will promptly
          apply to the Australian Securities Commission for relief from the
          requirements of the Australian Corporations Law.

                    4.07 Exclusive Dealing.  (a) In order to induce
                         -----------------
          American Eco to expend the out-of-pocket expenses necessary for
          its due diligence investigation of Dominion Bridge and the
          drafting of definitive agreements reflecting the Transactions,
          Dominion Bridge agrees that (a) Dominion Bridge and its officers,
          directors, employees, representatives and agents shall
          immediately cease any discussions or negotiations with any
          parties conducted heretofore with respect to any Third-Party
          Acquisition Transaction (as defined below) and cause any such
          party in possession of confidential information about Dominion
          Bridge that was furnished by or on behalf of Dominion Bridge or
          its agents with respect to a possible Third-Party Acquisition
          Transaction to return or destroy all such information in the
          possession of any such party or in the possession of any agent or
          adviser of any such party; and (b) Dominion Bridge and its
          subsidiaries, and their respective officers, directors,
          employees, representatives and agents, will not solicit,
          initiate, encourage, continue or enter into negotiations or
          discussions of any type, directly or indirectly, with, or furnish
          any information or data to, any person, firm or corporation
          relating to a Third-Party Acquisition Transaction; provided,
                                                             --------
          however, that if Dominion Bridge receives an unsolicited written
          -------
          bona fide proposal for a Third-Party Acquisition Transaction,
          Dominion Bridge may participate in discussions or negotiations
          with, or furnish information to, such third party pursuant to an
          appropriate confidentiality agreement if the Board of Directors
          of Dominion Bridge concludes in good faith, based upon written
          advice of outside counsel, that the failure to provide such
          information or participate in such discussions or negotiations
          would cause the members of the Board of Directors to breach their
          fiduciary duties to Dominion Bridge's stockholders.  Dominion
          Bridge shall promptly provide American Eco with a copy of any
          written proposal with respect to a Third-Party Acquisition
          Transaction received and inform American Eco of the status and
          content of any discussion with such third party.  Representatives
          of American Eco, as part of the management services they are to
          render to Dominion Bridge pursuant to Paragraph 3.01 herein,
          will, at the request of Dominion Bridge s Board of Directors,
          cooperate in the due diligence requests of any such third party
          for information which is part of the records of Dominion Bridge.

                    (b) If, (i) during the period commencing on the date
          hereof and ending on the Termination Date (as defined in
          Paragraph 5.04 below) (the  Exclusivity Period ), Dominion Bridge
          or its directors, officers or employees shall (a) breach their
          obligations in Paragraph 4.07(a) above, or (b) participate in
          discussions or negotiations with, or furnish information to, a
          third party in accordance with the proviso in Paragraph 4.07(a)
          above, and (ii) within one year after the Termination Date
                 ---
          Dominion Bridge's Board of Directors shall authorize entry into
          an agreement with any person or entity with which it had such
          discussions or negotiations during the Exclusivity Period, or
          shall recommend acceptance of, or shall fail to recommend
          rejection of, a tender offer or exchange offer that, if
          successful, would result in a Third-Party Acquisition
          Transaction, or a Third-Party Acquisition Transaction otherwise
          shall have been consummated (each, a "Payment Event"), then
          Dominion Bridge shall pay to American Eco a fee of US $3,500,000
          (such fee to be payable by wire transfer of immediately available
          funds upon the closing of any such Payment Event.)  Nothing
          contained in this Paragraph 4.07 shall constitute or shall be
          deemed to constitute liquidated damages.

                    (c)  For purposes of this Paragraph 4.07, "Third-Party
          Acquisition Transaction" shall mean any bona fide proposal made
          by a third party to acquire (i) beneficial ownership (as defined
          under Rule 13(d) of the Securities Exchange Act of 1934, as
          amended) of a majority or greater equity interest in Dominion
          Bridge pursuant to a merger, consolidation or other business
          combination, sale of shares of capital stock, tender offer,
          exchange offer or similar transaction involving Dominion Bridge
          including, without limitation, any single or multi-step
          transaction which is structured in good faith to permit such
          third party to acquire beneficial ownership of a majority or
          greater equity interest in Dominion Bridge, or (ii) 50% or more
          of Dominion Bridge's business (measured by revenues for the
          preceding fiscal year or the current fiscal year through the last
          complete fiscal quarter preceding such proposal) or consolidated
          assets of Dominion Bridge.

                    4.08 Documentation.  The specific terms of the
                         -------------
          Acquisition Transaction between Dominion Bridge and American Eco
          shall be included in a mutually acceptable acquisition agreement
          which shall contain the provisions outlined above and such other
          terms, conditions and provisions customary for such a
          transaction, including (i) representations and warranties as to
          the business, operations and historical financial position and
          results of operations of the parties; (ii) compliance with all
          applicable laws and regulations by the parties; (iii) the
          obtaining of all necessary consents and approvals by the parties
          for the Acquisition Transaction; (iv) the absence of any adverse
          material change in the financial condition, operations or
          prospects of each party from that represented to the other party;
          (v) the compliance by the parties with all contracts, licenses
          and real property leases and the enforceability thereof against
          each other party thereto; (vi) the absence of regulatory
          problems; and (vii) such other representations and warranties,
          conditions precedent and opinions of legal counsel customary to a
          transaction of this kind.  The acquisition agreement shall
          contain a termination provision which shall state, among other
          things, that the acquisition agreement (and the parties'
          obligation to consummate the Acquisition Transaction) shall
          terminate six months after the execution date of the acquisition
          agreement, subject to extension by the mutual agreement of the
          parties.

          5.   General
               -------

                    5.01 Expenses.  Each party hereto shall bear its own
                         --------
          costs and expenses including, without limitation, costs and
          expenses with respect to legal, accounting, investment banking
          and due diligence, in connection with the investigation,
          negotiation and consummation of the Transactions.

                    5.02 Disclosure.  Except as and to the extent required
                         ----------
          by law, without the prior written consent of the other party
          hereto, neither American Eco nor Dominion Bridge shall make,
          directly or indirectly, any public comment, statement, or
          communication with respect to, or otherwise to disclose or permit
          the disclosure of the existence of discussions regarding any of
          the terms, conditions or other aspects of the Transactions
          proposed in this letter of intent, in the Time Schedule attached
          hereto or in Letter Agreement.  If either party is required by
          law to make any such disclosure, not less than 24 hours prior to
          the release of such disclosure (or such shorter period as may be
          required by law upon the advice of counsel) it shall provide to
          the other party hereto the content of the proposed disclosure,
          the reasons that such disclosure is required to be made publicly
          by law, and the time and place that such disclosure will be made. 


                    5.03 Notices.  All notices, requests, claims, demands
                         -------
          or other communications hereunder shall be in writing and shall
          be deemed to have been duly given (i) when delivered in person,
          by courier or by fax; and (ii) upon receipt if sent by express
          mail, or by registered or certified mail (postage prepaid, return
          receipt requested) to the respective parties as follows:

                    If to American Eco then to:

                    American Eco Corporation 
                    11011 Jones Road
                    Houston, Texas 77070

                    Attention:  Michael E. McGinnis, President

                    with a copy to:

                    Bruce A. Rich, Esq.
                    Reid & Priest LLP
                    40 West 57th Street
                    New York, New York 10019

                    If to Dominion Bridge then to:

                    Michel L. Marengere
                    Chairman of the Board of Directors of Dominion Bridge
                      Corporation
                    500 Notre Dame Street
                    Lachine, Quebec

                    with copies to:

                    Mr. K. Mitchell Posner
                    Managing Director
                    Legg Mason Wood Walker, Incorporated
                    1735 Market Street, Suite 1100
                    Philadelphia, Pennsylvania 19103

                    and

                    Joseph P. Galda, Esq.
                    Buchanan Ingersoll
                    1835 Market Street
                    Philadelphia, Pennsylvania 19103

          or to such other address as the person to whom such notice is
          given may have previously furnished to the other party in writing
          in the manner set forth above; provided, however, that any notice
                                         --------  -------
          of a change of address shall be effective only upon receipt
          thereof.

                    5.04 Legal Effect.  This letter of intent does not
                         ------------
          create any legally binding obligations, except with respect to
          the matters set forth in Paragraphs 4.04, 4.05, 4.06, 4.07, 5.01
          and 5.02 hereof.  The purpose of this letter of intent is to set
          forth the basis upon which the parties shall enter into good
          faith negotiations to conclude definitive agreements with respect
          to the Transactions.  Drafts of such agreements shall be prepared
          by counsel to American Eco upon the execution and return of this
          letter of intent by Dominion Bridge.  The parties will commence
          the negotiations of the definitive agreements immediately, with a
          view to their execution as soon as practicable.  If (a) any of
          the events set forth in the Time Schedule attached hereto are not
          completed by the deadlines provided for therein, (b) definitive
          agreements with respect to the Loan Transaction and the
          Management Arrangement are not executed on or prior to March 23,
          1998, or (c) a definitive agreement with respect to the
          Acquisition Transaction is not executed on or prior to April 6,
          1998, or, in each case, by such later date or dates as shall be
          mutually agreed to by the parties (the "Termination Date"), this
          letter of intent shall be of no further force or effect and
          American Eco and Dominion Bridge shall not have any liability to
          each other, except, if applicable, with respect to the matters
          set forth in Paragraphs 4.07(b) and (c), 5.01 and 5.02 hereof.

                    5.05 Entire Agreement.  This letter of intent and the
                         ----------------
          attached addendum constitute the entire agreement between
          Dominion Bridge and American Eco as to the subject matter herein,
          and supersede all prior oral and written agreements except the
          letter referred to in Paragraph 4.04 herein.  This letter of
          intent and the attached addendum cannot be amended, modified or
          terminated except by a writing executed by the parties hereto.

                    5.06 Governing Law.  This letter of intent shall be
                         -------------
          governed by, and construed in accordance with, the laws of the
          State of Delaware.

                             *           *             *

                    If the foregoing accurately summarizes our
          understanding, please so indicate by having a duly authorized
          officer of Dominion Bridge execute and date both copies of this
          letter in the space provided below and return one copy to the
          undersigned.  If this letter is not executed and returned by 3:00
          PM, Montreal time, on the date hereof, the proposed Transactions
          shall be null and void and this letter shall be without any legal
          force or effect.

                                        Very truly yours,

                                        AMERICAN ECO CORPORATION



                                        By: /s/ Michael E. McGinnis
                                           ---------------------------------
                                             Name: Michael E. McGinnis
                                             Title: Chairman, President,
                                                    and CEO

          ACCEPTED AND AGREED TO THIS
          20th DAY OF FEBRUARY, 1998


          DOMINION BRIDGE CORPORATION



          By: /s/ Michel L. Marengere
             -------------------------------
              Name: Michel L. Marengere
              Title:Chairman and CEO
              


PRIVATE AND CONFIDENTIAL

          LETTER AGREEMENT, DATED AS OF FEBRUARY 18, 1998, BETWEEN AND
AMONG AMERICAN ECO CORPORATION, MICHEL L. MARENGERE, NICOLAS MATOSSIAN
AND RENE AMYOT.

          This Letter Agreement forms an integral component of the
Letter of Intent (the "Letter of Intent") between American Eco
Corporation and Dominion Bridge Corporation.

PART 1
- ------

(1)     Services Agreements:
        Michel L. Marengere February 28, 1998
        (base salary US $360,000 + minimum guaranty bonus US $180,000) x 5 years
        = US $2,700,000

        Nicolas V. Matossian January 31, 1998
        (base salary US $240,000 + minimum surplus bonus US $96,000) x 6 years 
        = US $2,106,000

        Rene Amyot one time payment of US $250,000

(2)     Non-compete signing bonus for Michel L. Marengere to equal
        250,000 free trading shares of American Eco Corporation.

(3)     Cause the Dominion Bridge Corporation to:

        (i)     Write-off or cancel the US $1,850,000 subscription
                receivable.

        (ii)    Cancel the Roger Miller/Fidutech International
                guaranty for Edinov Corporation transaction. The total
                amount was written off as of September 30, 1997 fiscal
                year end.

(4)     Waiver and indemnification letters from each party for past up
        to closing of AEC/DBC Acquisition Transaction.

(5)     Satisfactory release of Michel L. Marengere, Nicholas
        Matossian and Rene Amyot from personal liabilities relating to
        Dominion Bridge's outstanding fiduciary deductions of
        approximately Can $14,500,000.

PART 2
- ------
MICHEL L. MARENGERE
- -------------------
(1)     Co-Chairman of combined entity for 3 years at US $250,000 per
        year plus related expenses (resignation side letter post dated
        6 months from close of Acquisition Transaction).

(2)     Remain chairman of McConnell Dowell Corporation until the next
        annual meeting.

(3)     Commission plan on a case-by-case basis for each transaction
        that Michel L. Marengere is involved with and accepted by
        American Eco Corporation.

(4)     Services of Rosa Nespeca as Executive Secretary to Michel L.
        Marengere paid by American Eco Corporation up to one year.

(5)     Office space for Michel L. Marengere and Rosa Nespeca for one
        year.

NICHOLAS V. MATOSSIAN
- ---------------------
Consulting Agreement for 3 years at US $150,000 per year plus related
expenses.

RENE AMYOT
- ----------
Board of combined entity or a consulting agreement for 3 years at US
$120,000 per year plus Board fees of McConnell Dowell Corporation.

GENERAL
- -------
Part 1 and 2 of this Letter Agreement dated 02/18/98 to the Letter of
Intent Agreement 02/20/98 shall become effective and be in full force
and payable at the Closing upon the successful completion of all Phase
3 events as outlined in the Time Schedule attached to the Letter of
Intent.



                                             American Eco Corporation




                                             By: /s/ Michael E. McGinnis
                                                --------------------------


                                                /s/ Michel L. Marengere
                                                --------------------------
                                                 Michel L. Marengere


                                                /s/ Nicolas V. Matossian
                                                --------------------------
                                                 Nicolas V. Matossian


                                                /s/ Rene Amyot
                                                --------------------------
                                                 Rene Amyot