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                                                             EXHIBIT 5.1 AND 8.1
 
                      OPINION OF THELEN REID & PRIEST LLP
 
                                                              New York, New York
                                                           July 2, 1998
 
American Eco Corporation
11011 Jones Road
Houston, Texas 77070
 
Ladies and Gentlemen:
 
     We have acted as counsel for American Eco Corporation, an Ontario, Canada
corporation (the "Company"), and the Guarantors (defined below), in connection
with the proposed issuance by the Company of up to $120 million in aggregate
principal amount of its 9 5/8% Series B Senior Notes due 2008 (the "Series B
Notes"), in exchange for an equivalent amount of its outstanding 9 5/8% Series A
Senior Notes due 2008 (the "Series A Notes"). The terms of the offer to exchange
the Series B Notes for the Series A Notes (the "Exchange Offer") are described
in a Registration Statement on Form S-4 to be filed by the Company with the
Securities and Exchange Commission (the "Registration Statement"), for the
registration of the Series B Notes under the Securities Act of 1933, as amended
(the "1933 Act"). The Series A Notes have been, and the Series B Notes will be,
(a) guaranteed (the "Subsidiary Guarantees") by certain subsidiaries of the
Company (the "Guarantors"), and (b) issued pursuant to an Indenture, dated as of
May 21, 1998 (the "Indenture"), among the Company, the Guarantors and State
Street Bank and Trust Company, as Trustee.
 
     In rendering this opinion, we have assumed the genuineness of all
signatures, the legal capacity of natural persons, the authenticity of all
documents submitted to us as originals and the conformity with original
documents of all documents submitted to us as certified or photostatic copies.
We have also assumed the truth, accuracy and completeness of all
representations, warranties and certifications made by the Company and the
Guarantors.
 
     With respect to the opinion expressed below as to the due authorization by
the Company of the Series B Notes, we have relied solely upon the opinion of
even date hereof of Cassels Brock & Blackwell, Ontario counsel to the Company,
which is being filed as an exhibit to the Registration Statement.
 
     With respect to the opinion expressed below as to the due authorization by
the Guarantors (other than the Guarantors incorporated in the State of Delaware)
of the Subsidiary Guarantees, we have assumed for purposes of rendering such
opinion that the laws of their respective jurisdictions of incorporation or
organization are identical in all respects to the laws of the State of New York.
 
     Based upon the foregoing and subject to the qualifications hereinafter set
forth, we are of the opinion that the Series B Notes and the Subsidiary
Guarantees have been duly authorized for issuance and, when the Registration
Statement has become effective under the 1933 Act, and the Series B Notes and
the Subsidiary Guarantees have been duly executed, issued and authenticated in
accordance with the Indenture and issued and sold in exchange for the Series A
Notes as contemplated by the Registration Statement and in accordance with the
Exchange Offer, (a) the Series B Notes will constitute valid and legally binding
obligations of the Company, and (b) each Subsidiary Guaranty will constitute a
valid and legally binding obligation of its respective Guarantor, in each case,
subject to (i) bankruptcy, insolvency, reorganization, moratorium, liquidation,
rearrangement, fraudulent transfer, fraudulent conveyance and other similar laws
(including court decisions) now or hereafter in effect and affecting the rights
and remedies of creditors generally or providing for the relief of debtors, (ii)
the refusal of a particular court to grant equitable remedies, including,
without limitation, specific performance and injunctive relief, and (iii)
general principles of equity (regardless of whether such remedies are sought in
a proceeding in equity or at law).
 
     We are further of the opinion that the statements contained in the
prospectus constituting a part of the Registration Statement under the caption
"CERTAIN TAX CONSEQUENCES -- United States Taxa-
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tion," as qualified therein, constitute an accurate description, in general
terms, of the indicated United States tax consequences of the purchase,
ownership and disposition of the Series B Notes.
 
     The opinions expressed herein are limited exclusively to the federal laws
of the United States of America, the laws of the State of New York and the
General Corporation Law of the State of Delaware, and we are expressing no
opinion as to the effect of the laws of any other jurisdiction, domestic or
foreign.
 
     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the statements made with respect to us under the
caption "Legal Matters" in the Prospectus included as part of the Registration
Statement.
 
                                            Very truly yours,
 
                                            THELEN REID & PRIEST LLP