<PAGE>   1

                                                                   EXHIBIT 10.23

                                                                  EXECUTION COPY




         SECOND AMENDMENT AND WAIVER dated as of February 1, 1996,
("Amendment") to LOAN AND SECURITY AGREEMENT dated as of October 18, 1995 (as
amended through the date hereof, the "Loan 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 or which may become 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 Loan Agreement.

         WHEREAS, Smith Environmental has advised the Agent, pursuant to a
letter dated January 5, 1996, a copy of which is annexed hereto, that Smith
Environmental and its Subsidiaries have failed to maintain a consolidated ratio
of current assets to current liabilities of at least 1.50 to 1.00 for the
fiscal quarter ending in December, 1995, as required under paragraph 14(o)(iv)
of the Loan Agreement; and

         WHEREAS, Smith Environmental has requested that the Agent and the
Lenders (i) waive as an Event of Default such failure to maintain such ratio
and (ii) amend the Loan Agreement so as to revise the minimum consolidated
ratio of current assets to current liabilities to be maintained by Smith
Environmental and its Subsidiaries for the first three fiscal quarters of 1996,
and the Agent and each of the Lenders have so agreed, upon the terms and
subject to the conditions set forth in this Amendment;

         NOW, THEREFORE, in consideration of the mutual promises contained
herein, the amendment of Paragraph 6(e) of the Loan Agreement, as described in
Section 2(a) hereof and the payment of the fee described in Section 4(g)
hereof, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Borrowers, the Lenders and
the Agent hereby agree as follows:

         1.      Waiver of Failure to Maintain Current Ratio.  Upon the
fulfillment of the conditions set forth in Section 4 hereof, effective as of
the date hereof, each of the Lenders and the Agent waive as an Event of Default
the failure of Smith Environmental and its Subsidiaries to maintain a
consolidated ratio of current assets to current liabilities of at least 1.50 to
1.00 for the fiscal quarter ending in December, 1995, provided that the actual
consolidated ratio of current assets to current liabilities maintained by Smith
Environmental and its Subsidiaries for such fiscal quarter is not less than
1.44 to 1.00.
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         2.      Amendment.  Upon the fulfillment of the conditions set forth
in Section 4 hereof, effective as of the date hereof, the Loan Agreement is
hereby amended as follows:

                 (a)      Paragraph 6(e) of the Loan Agreement is amended by
deleting such paragraph in its entirety and by substituting the following in
lieu thereof:

                 "Limitation on Eurodollar Loans.  Notwithstanding any thing to
                 the contrary contained herein, during the period from the
                 Closing Date until the date upon which the Agent shall have
                 notified Smith Environmental that each Lender shall have
                 completed the primary syndication of its Commitment, (x) each
                 Eurodollar Loan made during such period shall be for an
                 Interest Period consisting of one month only and (y) the
                 Interest Period with respect to all outstanding Eurodollar
                 Loans, as of any date of determination, shall end on the same
                 day."

                 (b)      Paragraph 14(o) of the Loan Agreement is amended by
deleting subparagraph (iv) thereof in its entirety and by substituting the
following in lieu thereof:

                 "(iv) Consolidated Current Ratio.  Smith Environmental and its
                 Subsidiaries, on a consolidated basis, shall maintain as of
                 the end of each period set forth below a ratio of (A)
                 consolidated current assets to (B) consolidated current
                 liabilities of not less than the ratio set forth below
                 opposite each such period, provided, however, that solely for
                 purposes of determining the Borrowers' compliance with this
                 covenant, (x) consolidated current assets shall exclude any
                 cash or its equivalent then on hand in excess of the aggregate
                 amount of $1,800,000 and (y) consolidated current liabilities
                 shall not include the outstanding principal balance of the
                 Revolving Loans:





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<TABLE>
<CAPTION>
                                                                      Minimum Consolidated
                                   Measuring Period                        Current Ratio    
                                   ----------------                   --------------------   
                          <S>      <C>                                    <C>
                          (A)      fiscal quarter ending in               1.50 to 1.00
                                   December, 1995

                          (B)      fiscal quarter ending in               1.25 to 1.00
                                   March, 1996

                          (C)      fiscal quarter ending in               1.25 to 1.00
                                   June, 1996

                          (D)      fiscal quarter ending in               1.25 to 1.00
                                   September, 1996

                          (E)      fiscal quarter ending in               1.50 to 1.00
                                   December, 1996 and each
                                   fiscal quarter thereafter
</TABLE>

                 3.       Representations and Warranties.  In order to induce
the Lenders and the Agent to enter into this Amendment, Smith Environmental and
each other Borrower makes the following representations and warranties in favor
of each of the Lenders and the Agent (which representations and warranties
shall survive the execution and delivery of this Amendment) as of the date
hereof:

                          (a)     Smith Environmental and each other Borrower
has the corporate power, authority and legal right to execute, deliver and
perform this Amendment, and the instruments, agreements, documents and
transactions contemplated hereby, and has taken all actions necessary to
authorize the execution, delivery and performance of this Amendment, and the
instruments, agreements, documents and transactions contemplated hereby;

                          (b)     No consent of any Person (including, without
limitation, shareholders or creditors of Smith Environmental, as the case may
be) other than the Lenders, and no consent, permit, approval or authorization
of, exemption by, notice or report to, or registration, filing or declaration
with, any governmental authority, is required in connection with the execution,
delivery, performance, validity or enforceability of this Amendment, and the
instruments, agreements, documents and transactions contemplated hereby;

                          (c)     This Amendment has been duly executed and
delivered on behalf of Smith Environmental and each other Borrower by its duly
authorized officer, and constitutes the legal, valid and binding obligation of
Smith Environmental and each such Borrower, enforceable in accordance with its
terms;





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                          (d)     Neither Smith Environmental nor any other
Borrower is in default under any indenture, mortgage, deed of trust, agreement
or other instrument to which it is a party or by which it may be bound.
Neither the execution and delivery of this Amendment, nor the consummation of
the transactions herein contemplated, nor compliance with the provisions hereof
or thereof will (i) violate any law or regulation, (ii) result in or cause a
violation by Smith Environmental or by any other Borrower of any order or
decree of any court or government instrumentality, (iii) conflict with, or
result in the breach of, or constitute a default under, any indenture,
mortgage, deed of trust, agreement or other instrument to which Smith
Environmental or any other Borrower is a party or by which it may be bound,
(iv) result in the creation or imposition of any lien, charge, or encumbrance
upon any of the property of Smith Environmental or of any other Borrower,
except in favor of the Agent for the benefit of the Lenders, to secure the
Liabilities, or (v) violate any provision of the Articles or Certificate of
Incorporation, By-Laws or any capital stock provisions of Smith Environmental
or of any other Borrower;

                          (e)     No Default or Event of Default has occurred
and is continuing, except for such Default and Event of Default as have been
waived pursuant to this Amendment;

                          (f)     Since the date of the Agent's receipt of
Smith Environmental's consolidated and consolidating financial statements for
the period ended November 30, 1995, no change or event has occurred which has
had or is reasonably likely to have a Material Adverse Effect; and

                          (g)     The recitals contained in this Amendment are
true and correct in all respects.

                 4.       Conditions Precedent.  This Amendment shall not
become effective until all of the following conditions, the fulfillment of each
of which is a condition precedent to the effectiveness of this Amendment, shall
have occurred or shall have been waived in writing by the Agent and the
Lenders.

                          (a)     The Agent and each of the Lenders shall have
received a fully executed counterpart or original of this Amendment, together
with all schedules and exhibits hereto appropriately completed to the extent
required.

                          (b)     Upon the effectiveness of this Amendment, all
representations and warranties set forth in the Loan Agreement (except for such
inducing representations and warranties that were only required to be true and
correct as of a prior date) shall be true and correct in all material respects
on and as of the effective date hereof, and no Default or Event of Default
shall have occurred and be continuing.





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                          (c)     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)     The Agent shall have received a certificate
from Smith Environmental, executed by its Chief Executive Officer or other
authorized officer, as to the accuracy and completeness of the representations
and warranties contained in Section 3 hereof.

                          (e)     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.

                          (f)     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.

                          (g)     The Agent shall have received from Smith
Environmental, for the pro rata benefit of the Lenders, a non-refundable fee,
in cash, in the amount of $2,000, which fee shall be paid by the Agent's debit
of the loan account of Smith Environmental, effective as of the opening of
business on the date of execution of this Amendment.

                 5.       General Provisions.

                          (a)     Except as herein expressly amended, 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.

                          (b)     All references in the Other Agreements to the
Loan Agreement shall mean the Loan Agreement as waived and amended as of the
effective date hereof, and as waived and amended hereby and as hereafter
amended, supplemented or modified from time to time.  From and after the date
hereof, all references in the Loan Agreement to "this Agreement," "hereof,"
"herein," or similar terms, shall mean and refer to the Loan Agreement as
waived and amended by this Amendment.

                          (c)     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.





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                          (d)     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.


<TABLE>
<S>                                               <C>
SMITH ENVIRONMENTAL TECHNOLOGIES                  RIEDEL ENVIRONMENTAL SERVICES INC.
CORPORATION

By: /s/ J. POLING                                 By: /s/ J. POLING                               
   --------------------------------                  --------------------------------
   V.P. TREASURER                                    EXECUTIVE V.P.

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

By: /s/ J. POLING                                 By: /s/ E. JOSEPH HESS
   --------------------------------                  --------------------------------
   V.P.                                              V.P.

BCM ENGINEERS INC.,                               BOT FINANCIAL CORPORATION
an Alabama corporation

By: /s/ J. POLING                                 By: /s/ WILLIAM R. YORK, JR.                                
   --------------------------------                  -------------------------------
   V.P.                                              SENIOR V.P.   
</TABLE>





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