EXHIBT 3.16

                         CERTIFICATE OF INCORPORATION
                                      OF
                        ENVIRONMENTAL PROCEDURES, INC.


     First:  The name of the Corporation is ENVIRONMENTAL PROCEDURES, INC.
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     Second:  The registered office of the Corporation in the State of Delaware
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is located at the Corporation Trust Center, 1209 Orange Street in the City of
Wilmington, County of New Castle. The name of its registered agent at such
address is The Corporation Trust Company.

     Third:  The nature of the business, objects and purposes to be transacted,
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promoted or carried on by the Corporation are:

          To engage in any lawful act or activity for which corporations may be
     organized under the General Corporation Law of the State of Delaware.

     Fourth:  The Corporation is authorized to issue two classes of capital
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stock, designated Class A Voting Common Stock (hereinafter referred to as
"Voting Common Stock") and Class B Non-Voting Common Stock (hereinafter referred
to as "Non-Voting Common Stock"). The amount of total authorized capital stock
of the Corporation is One Million (1,000,000) shares, divided into Five Hundred
Thousand (500,000) shares of Voting Common Stock, One Dollar ($1.00) par value,
and Five Hundred Thousand (500,000) shares of Non-Voting Common Stock, One
Dollar ($1.00) par value.

     Each share of Voting Common Stock shall entitle the holder thereof to one
vote, in person or by proxy, at any and all meetings of the stockholders of the
Corporation on all propositions before such meetings. No holder of Voting Common
Stock shall have the right to cumulate such holder's votes for the election of
directors, but each holder of Voting Common Stock shall be entitled to one vote
for each share held thereof in the election of each director of the Corporation.

     Except as may be provided in this Certificate of Incorporation, the Voting
Common Stock shall have the exclusive right to vote for the election of
directors of the Corporation and for all other purposes, and holders of the Non-
Voting Common Stock shall not be entitled to receive notice of any meeting of
stockholders at which they are not entitled to vote or consent.

     The holders of the Voting Common Stock and the Non-Voting Common Stock
shall be entitled to receive, when, as and if declared by the Board of Directors
of the Corporation, out of funds legally available therefor, dividends payable
in cash, stock or otherwise.

     Upon any liquidation, dissolution or winding up of the Corporation, whether
voluntary or involuntary, the net assets of the Corporation shall be distributed
pro rata to the holders of the Voting Common Stock and the Non-Voting Common
Stock in accordance with their respective rights and interests.


     Fifth:
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     A.  The name and mailing address of the incorporator is as follows:

         Name                                Mailing Address
         ----                                ---------------
         J. William Wilson                   Nine Greenway Plaza
                                             Suite 3100
                                             Houston, Texas 77046

     B.  The name and mailing address of each person who is to serve as a
director of the Corporation until the first annual meeting of the stockholders
or until a successor is elected and qualified, is as follows:

         Name                                Mailing Address
         ----                                ---------------
         Vincent D. Leone, Sr.               12146 Burgoyne
                                             Houston, Texas 77077

         Charlie V. Danna, Jr.               6887 Oakwood Trail
                                             Houston, Texas 77040

         Charles N. Grichar                  303 Graceland Street
                                             Houston, Texas 77009

         Arthur W. Brown, Jr.                17302 Lazy Hill Lane
                                             Spring, Texas 77379

         Michael S. Winn                     4848 Pin Oak Park
                                             Houston, Texas 77081

     Sixth:  The Corporation is to have perpetual existence.
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     Seventh:  In furtherance and not in limitation of the powers conferred by
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statute, the Board of Directors is expressly authorized:

          (1)  To adopt, amend, or repeal the By-laws of the Corporation.

          (2)  To authorize and cause to be executed mortgages and liens upon
     the real and personal property of the Corporation.

          (3)  To set apart out of any of the funds of the Corporation available
     for dividends a reserve or reserves for any proper purpose and to abolish
     any such reserve in the manner in which it was created.

          (4)  By a majority of the whole Board of Directors, to designate one
     or more committees, each committee to consist of two or more of the
     directors of the Corporation. The Board of Directors may designate one or
     more directors as alternate members of any committee, who may replace any
     absent or disqualified member at any meeting of the committee. Any such
     committee, to the extent

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     provided in the resolution or in the By-laws of the Corporation, shall have
     and may exercise the powers of the Board of Directors in the management of
     the business and affairs of the Corporation and may authorize the seal of
     the Corporation to be affixed to all papers which may require it; provided,
     however, that the By-laws may provide that in the absence or
     disqualification of any member of such committee or committees, the member
     or members thereof present at any meeting and not disqualified from voting,
     whether or not he or they constitute a quorum, may unanimously appoint
     another member of the Board of Directors to act at the meeting in place of
     any such absent or disqualified member.

          (5)  When and as authorized by the affirmative vote of the holders of
     a majority of the stock issued and outstanding having voting power given at
     a stockholders' meeting duly called upon such notice as is required by
     applicable law, or when authorized by the written consent of the holders of
     a majority of the voting stock issued and outstanding, to sell, lease or
     exchange all or substantially all of the property and assets of the
     Corporation, including its goodwill and its corporate franchises, upon such
     terms and conditions and for such consideration, which may consist in whole
     or in part of money or property including securities of any other
     corporation or corporations, as the Board of Directors shall deem expedient
     and for the best interests of the Corporation.

     The Corporation may in its By-laws confer powers upon its Board of
Directors in addition to the foregoing and in addition to the power and
authority expressly conferred upon the Board of Directors by applicable law.

     Eighth:
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          (a)  Limitation of Liability. To the fullest extent permitted by the
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     General Corporation Law of the State of Delaware, as the same exists or may
     hereafter be amended, a director of the Corporation shall not be liable to
     the Corporation or the stockholders for monetary damages for breach of
     fiduciary duty as a director.

          (b)  Indemnification and Insurance.
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               (i)   The Corporation shall indemnify any person who was or is a
     party or is threatened to be made a party to any threatened, pending or
     completed action, suit or proceeding, whether civil, criminal,
     administrative or investigative (other than an action by or in the right of
     the Corporation) by reason of the fact that he is or was a director,
     officer, employee or agent of the Corporation, or is or was serving at the
     request of the Corporation as a director, officer, employee or agent of
     another corporation, partnership, joint venture, trust or other enterprise,
     against expenses (including attorneys' fees), judgments, fines and amounts
     paid in settlement actually and reasonably incurred by him in connection
     with such action, suit or, proceeding if he acted in good faith and in a
     manner he reasonably believed to be in or not opposed to the best interests
     of the Corporation, and, with respect to any criminal action or proceeding,
     had no reasonable cause to believe his conduct was unlawful. The
     termination of any

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     action, suit or proceeding by judgment, order, settlement, conviction, or
     upon a plea of nolo contendere or its equivalent, shall not, of itself,
     create a presumption that the person did not act in good faith and in a
     manner which he reasonably believed to be in or not opposed to the best
     interests of the Corporation, and with respect to any criminal action or
     proceeding, had reasonable cause to believe that his conduct was unlawful.

               (ii)   The Corporation shall indemnify any person who was or is a
     party or is threatened to be made a party to any threatened, pending or
     completed action or suit by or in the right of the Corporation to procure a
     judgment in its favor by reason of the fact that he is or was a director,
     officer, employee or agent of the Corporation, or is or was serving at the
     request of the Corporation as a director, officer, employee or agent of
     another corporation, partnership, joint venture, trust or other enterprise
     against expenses (including attorneys' fees) actually and reasonably
     incurred by him m connection with the defense or settlement of such action
     or suit if he acted in good faith and in a manner he reasonably believed to
     be in or not opposed to the best interests of the Corporation and except
     that no indemnification shall be made in respect of any claim, issue or
     matter as to which such person shall have been adjudged to be liable to the
     Corporation unless and only to the extent that the Court of Chancery or the
     court in which such action or suit was brought shall determine upon
     application that, despite the adjudication of liability but in view of all
     of the circumstances of the case, such person is fairly and reasonably
     entitled to indemnity for such expenses which the Court of Chancery or such
     other court shall deem proper.

               (iii)  To the extent that a director, officer, employee or agent
     of the Corporation has been successful on the merits or otherwise in
     defense of any action, suit or proceeding referred to in Sections Eighth
     (b)(i) and (b)(ii) of this Certificate of Incorporation, or in defense of
     any claim, issue or matter therein, he shall be indemnified against
     expenses (including attorneys' fees) actually and reasonably incurred by
     such person in connection therewith.

               (iv)   The determination that an officer, director, employee or
     agent has met the applicable standard of conduct set forth in Sections
     Eighth (b)(i) and (b)(ii) of this Certificate of Incorporation (unless
     indemnification is ordered by a court) shall be made (i) by the Board of
     Directors by a majority vote of a quorum consisting of directors who were
     not parties to such action, suit or proceeding, or (ii) if such quorum is
     not obtainable, or even if obtainable a quorum of disinterested directors
     so directs, by independent legal counsel in a written opinion, or (iii) by
     the stockholders.

               (v)    Expenses incurred by an officer or director in defending a
     civil or criminal action, suit or proceeding shall be paid by the
     Corporation in advance of the final disposition of such action, suit or
     proceeding upon receipt of an undertaking by or on behalf of the director
     or officer to repay such amount if it shall ultimately be determined that
     he is not entitled to be indemnified by the Corporation as authorized in
     this Section Eighth (b). Such expenses incurred by

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     other employees and agents may be so paid upon such terms and conditions,
     if any, as the Board of Directors deems appropriate.

               (vi)   The indemnification and advancement of expenses provided
     hereunder or granted pursuant to the other subsections of this Section
     Eighth (b) shall not be deemed exclusive of any other rights to which those
     seeking indemnification or advancement of expenses may be entitled under
     any By-law, agreement, vote of stockholders or disinterested directors or
     otherwise, both as to action in his official capacity and as to action in
     another capacity while holding such office. The Board of Directors shall
     also have the authority to authorize the Corporation to make advances with
     respect to and to indemnify any person named in Sections Eighth (b)(i) and
     (b)(ii) of this Certificate of Incorporation against, or to make payments
     on behalf of or to reimburse such person for, any costs or expenses
     (including attorneys' fees), judgments or fines or amounts paid in
     settlement in connection with any threatened, pending or completed action,
     suit or proceeding, whether civil, criminal, administrative or
     investigative to the extent not inconsistent with law as evidenced by an
     opinion of counsel.

               (vii)  The Corporation may purchase and maintain insurance on
     behalf of any person who is or was a director, officer, employee or agent
     of the Corporation, or is or was serving at the request of the Corporation
     as a director, officer, employee or agent of another corporation,
     partnership, joint venture, trust or other enterprise against any liability
     asserted against him and incurred by him in any such capacity, or arising
     out of his status as such, whether or not the Corporation would have the
     power to indemnify him against such liability under the provisions of this
     Section Eighth (b).

               (viii) For purposes of this Section Eighth (b), reference to the
     "Corporation" shall include, in addition to the resulting corporation, any
     constituent corporation (including any constituent of a constituent)
     absorbed in a consolidation or merger which, if its separate existence had
     continued, would have had power and authority to indemnify its directors,
     officers, employees or agents so that any person who is or was a director,
     officer, employee or agent of such constituent corporation, or is or was
     serving at the request of such constituent corporation as a director,
     officer, employee or agent of another corporation, partnership, joint
     venture, trust or other enterprise, shall stand in the same position under
     the provisions of this Section Eighth (b) with respect to such constituent
     corporation if its separate existence had continued.

               (ix)   For purposes of this Section Eighth (b), references to
     "other enterprises" shall include employee benefit plans; references to
     "fines" shall include any excise taxes assessed on a person with respect to
     an employee benefit plan; and references to "serving at the request of the
     Corporation" shall include any service as a director, officer, employee or
     agent of the Corporation which imposes duties on, or involves services by,
     such director, officer, employee, or agent with respect to an employee
     benefit plan, its participants, or beneficiaries; and a person who acted in
     good faith and in a manner he reasonably believed to

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     be in the interest of the participants and beneficiaries of an employee
     benefit plan shall be deemed to have acted in a manner "not opposed to the
     best interests of the Corporation" as referred to in this Section Eighth
     (b).

               (x)    The indemnification and advancement of expenses provided
     by, or granted pursuant to, this Section Eighth (b) shall, unless otherwise
     provided when authorized or ratified, continue as to a person who has
     ceased to be a director, officer, employee or agent and shall inure to the
     benefit of the heirs, executors and administrators of such a person.

               (xi)   Notwithstanding anything contained in this Certificate of
     Incorporation or the By-laws of the Corporation (and notwithstanding that a
     lesser percentage may be specified by law, this Certificate of
     Incorporation or the By-laws of the Corporation) to the contrary, the
     alteration, change, amendment, repeal or adoption of any provisions
     inconsistent with this Section Eighth shall require the affirmative vote of
     the holders of at least 80% of the voting power (after giving effect to the
     provisions of Section Tenth) of the outstanding shares of capital stock of
     the Corporation entitled to vote generally in the election of directors of
     the Corporation, voting together as a single class.

     Ninth:  Meetings of stockholders and the Board of Directors may be held
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within or without the State of Delaware, as the By-laws may provide. The books
of the Corporation may be kept (subject to any applicable law) outside of the
State of Delaware at such place or places as may be designated from time to time
by the Board of Directors or in the By-laws of the Corporation. Elections of
directors need not be by written ballot unless the By-laws of the Corporation
shall so provide.

     Tenth:  The Corporation reserves the right to amend, alter, change or
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repeal any provision contained in this Certificate of Incorporation in the
manner now or hereafter prescribed by applicable law and this Certificate of
Incorporation, and all rights conferred upon stockholders herein are granted
subject to this reservation.

     IN WITNESS WHEREOF, I the undersigned, being the incorporator hereinabove
named, do hereby execute this Certificate of Incorporation this 29th day of
September, 1992.


                                        /s/ J. William Wilson
                                        --------------------------------
                                        J. William Wilson

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                           CERTIFICATE OF OWNERSHIP

                                    MERGING

                        ENVIRONMENTAL PROCEDURES, INC.

                                     INTO

                        ENVIRONMENTAL PROCEDURES, INC.

                    (PURSUANT TO SECTION 253 OF THE GENERAL
                         CORPORATION LAW OF DELAWARE)

     Environmental Procedures, Inc., a corporation incorporated on the 30th day
of September, 1992, pursuant to the provisions of the General Corporation Law of
the State of Delaware does hereby ratify that this corporation owns all the
capital stock of Environmental Procedures, Inc., a corporation incorporated
under the laws of the State of Texas, and that this corporation, by a resolution
of its board of directors duly adopted at a meeting held on the 23 day of
December, 1996, determined to and did merge into itself said Environmental
Procedures, Inc. which resolution is in the following words to wit:

          RESOLVED:  That Environmental Procedures, Inc. be merged into this
     Corporation, and that all of the estate, property, rights, privileges,
     powers and franchises of Environmental Procedures, Inc. be vested in and
     held and enjoyed by this Corporation as fully and entirely and without
     change or diminution as the same were before held and enjoyed by
     Environmental Procedures, Inc. in its name; and

          FURTHER RESOLVED:  That Corporation assume all of said subsidiary's
     liabilities and obligations; and

          FURTHER RESOLVED:  That the President and the Secretary of this
     Corporation be and they hereby are directed to make, execute and
     acknowledge a Certificate of Ownership and Merger and Articles of Merger
     setting forth a copy of the resolution to merge said Environmental
     Procedures, Inc. into this Corporation and to assume said subsidiary's
     liabilities and obligations and the data of adoption thereof and to file
     the same in the office of the Secretary of State of Delaware and a
     certified copy thereof in the Office of the Recorder of Deeds of New
     Castle; and

          FURTHER RESOLVED:  That the effective time of the Certificate of
     Ownership and Merger setting forth a copy of these resolutions, and the
     time when the merger therein provided for, shall become effective shall be
     December 31, 1996.




     IN WITNESS WHEREOF, the directors of this Corporation have caused this
Certificate to be signed by its authorized officer, the 23rd day of December,
1996.

                                   ENVIRONMENTAL PROCEDURES, INC.


                                   By:  /s/ John F. Lauletta
                                        -----------------------------------
                                        John F. Lauletta, President

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