Execution Copy

by Smith
October 7th, 1996
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                                                                  EXECUTION COPY

                  FOURTH AMENDMENT made as of September 27, 1996 (the
"Amendment") to FORBEARANCE AGREEMENT made as of June 7, 1996, as amended by the
First Amendment thereto, dated as of June 28, 1996 (the "First Amendment), the
Second Amendment thereto, dated as of August 13, 1996 (the "Second Amendment")
and the Third Amendment thereto, dated as of September 3, 1996 (the "Third
Amendment")(as so amended and as amended through the date hereof, the
"Forbearance Agreement") among SMITH ENVIRONMENTAL TECHNOLOGIES CORPORATION, BCM
ENGINEERS INC., a Pennsylvania corporation, BCM ENGINEERS INC., an Alabama
corporation, RIEDEL ENVIRONMENTAL SERVICES INC., each of the Lenders which are
parties to the Loan Agreement, and CHEMICAL BANK, as Agent for the Lenders.
Terms which are capitalized herein and not otherwise defined shall have the
meanings ascribed to them in the Forbearance Agreement.

                  WHEREAS, pursuant to the Third Amendment, the Current
Forbearance Period automatically terminates on September 30, 1996; and

                  WHEREAS, the Borrowers have requested the Lenders to consider
extending the Current Forbearance Period to October 31, 1996 and the Lenders
have so agreed, on the terms and subject to the fulfillment of the conditions
contained in this Amendment.

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

SECTION 1. EXTENSION OF CURRENT FORBEARANCE PERIOD. The Current Forbearance
Period is hereby extended to October 31, 1996. Accordingly, the First Amendment
is hereby modified by deleting the third sentence of Section 2 thereof and by
substituting the following in lieu thereof:

                  "However, for the period commencing on the date hereof and
                  terminating on October 31, 1996 (the "Current Forbearance
                  Period"), so long as none of the events described in the
                  following clauses (a), (b) or (c) shall have occurred during
                  the Current Forbearance Period, the Lenders shall not demand
                  payment of the Liabilities, nor shall the Lenders otherwise
                  seek to exercise any of their rights or remedies under the
                  Loan Agreement, any of the Other Agreements or applicable law
                  with respect to the Designated Default (and the Forbearance
                  Agreement is hereby amended to so provide): (a) any Event of
                  Default (other than the Designated Default) shall have
                  occurred or other event which, with the giving of notice or
                  passage of time would constitute an Event of Default shall
                  have arisen, (b) the Gould Award shall have been paid by any
                  Borrower in whole or in part or shall have been entered as a
                  judgment in any court of competent jurisdiction and the
                  enforcement of such judgment shall not have been stayed or (c)

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                  any default by any Borrower in the performance of the terms of
                  this Agreement shall have occurred."


SECTION 2. CONDITIONS PRECEDENT TO EFFECTIVENESS OF AMENDMENT. This Amendment
shall not be effective unless and until each of the following conditions shall
have been satisfied in the sole discretion of the Lenders or waived by the
Lenders, for whose sole benefit such conditions exist:

                           (a) The Agent and each of the Lenders shall have
received a fully executed counterpart or original of this Amendment.

                           (b) Upon the effectiveness of this Amendment, all
representations and warranties set forth in the Loan Agreement shall be true and
correct in all material respects on and as of the effective date hereof, except
for (x) such inducing representations and warranties that were only required to
be true and correct as of a prior date, (y) such representations and warranties
as relate to the defaults described in clause (ii) hereof and (z) such
representations and warranties as relate to the occurrence of an event which has
had or is reasonably likely to have a Material Adverse Effect, but only to the
extent that such event constitutes the Gould Event, and no Default or Event of
Default shall have occurred and be continuing, other than (i) the Designated
Default and (ii) defaults under agreements made in the ordinary course of
business between or among any of the Borrowers and Persons other than the Agent,
the Lenders, or any Affiliate of the Borrowers, such as lease agreements, none
of which agreements is material to the business of such Borrower and none of
which defaults, singly or in the aggregate, has had or is reasonably likely to
have, a Material Adverse Effect.

                           (c) Except for the collectibility of the Referenced
Account and the occurrence of the Gould Event, no event or development shall
have occurred since the date of delivery to the Lenders of the Borrowers' most
recent financial statements which event or development has had or is reasonably
likely to have a Material Adverse Effect.

                           (d) All corporate and legal proceedings and all
documents and instruments executed or delivered in connection with this
Amendment shall be satisfactory in form and substance satisfactory to the
Lenders and their counsel, and the Lenders and their counsel shall have received
all information and copies of all documents which the Lenders and their counsel
may have requested in connection herewith and the matters contemplated
hereunder, such documents, when requested by them, to be certified by
appropriate corporate authorities.

                           (e) The Lenders shall have received such further
agreements, consents, instruments and documents as may be necessary or proper in
the reasonable opinion of the Lenders, the Agent and their counsel to carry out
the provisions and purposes of this Amendment.

SECTION 3.                 GENERAL PROVISIONS.


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                           (a) Nothing contained in this Amendment shall be
deemed to be a waiver of any Defaults or Events of Default, whether or not the
Agent or any of the Lenders shall have any knowledge thereof, nor shall anything
contained in this Amendment be deemed to be a waiver of any future Default or
Event of Default whatsoever.

                           (b) Except as herein expressly amended, the
Forbearance Agreement, the First Amendment thereto, the Second Amendment
thereto, the Third Amendment thereto and the Loan Agreement and all other
agreements, documents, instruments and certificates executed in connection
therewith, are ratified and confirmed in all respects and shall remain in full
force and effect in accordance with their respective terms.

                           (c) All references in any document or agreement to
the Forbearance Agreement shall mean the Forbearance Agreement as amended as of
the effective date hereof.

                           (d) This Amendment may be executed by the parties
hereto individually or in combination, in one or more counterparts, each of
which shall be an original and all which shall constitute one and the same
agreement.

                           (e) The Third Amendment, Waiver and Consent dated as
of May 15, 1996 is hereby modified by deleting the date "September 30, 1996" set
forth in Section 7(a) thereof and by substituting in lieu thereof the date
"October 31, 1996".

                           (f) This Amendment shall be governed and controlled
by the laws of the State of New York without reference to its choice of law
principles.

                  IN WITNESS WHEREOF, each of the Borrowers, BCM-Alabama, the
Lenders and the Agent have caused this Amendment to be duly executed by their
respective officers thereunto duly authorized as of the day and year first above
written.

SMITH ENVIRONMENTAL TECHNOLOGIES            RIEDEL ENVIRONMENTAL SERVICES INC.
CORPORATION

By: /s/ John W. Poling                      By: /s/ John W. Poling
    -------------------------------             ---------------------------
    Vice President                              Vice President

BCM ENGINEERS INC.,                         CHEMICAL BANK, as a Lender and as
a Pennsylvania corporation                     Agent

By: /s/ John W. Poling                      By: /s/ E.J. Hess
    -------------------------------             ---------------------------
    Vice President                              Vice President

BCM ENGINEERS INC.,                         BTM CAPITAL CORPORATION, formerly
Alabama corporation                          known as BOT Financial Corporation

By: /s/ John W. Poling                      By: /s/ David A. Meehan
    -------------------------------             ---------------------------
    Vice President                              Senior Vice President