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                                                                     EXHIBIT 3.1



                          CERTIFICATE OF INCORPORATION
                                       OF
                           BLACKHAWK ACQUISITION CORP.

                                    ARTICLE I

         The name of the Corporation is Blackhawk Acquisition Corp. (the
"Corporation").

                                   ARTICLE II

         The name of the Corporation's registered agent and the address of its
registered office in the State of Delaware is Corporation Service Company, 2711
Centerville Road, Suite 400, Wilmington, New Castle County, Delaware 19808.

                                   ARTICLE III

         The purpose of the Corporation is to engage in any lawful act or
activity for which corporations may be organized under the General Corporation
Law of the State of Delaware ("Delaware General Corporation Law").

                                   ARTICLE IV

         The total number of shares of capital stock which the Corporation shall
have the authority to issue is one thousand (1,000) shares of Common Stock, $.01
par value.

                                    ARTICLE V

         In furtherance of and not limiting the powers conferred by the laws of
the State of Delaware, the Board of Directors are expressly authorized to alter,
amend or repeal the bylaws of the Corporation or to adopt new bylaws.

                                   ARTICLE VI

         The incorporator is Albert R. Fox, Jr., whose mailing address is 1717
Main Street, Suite 2800, Dallas, Texas 75201.

                                   ARTICLE VII

         The number of directors constituting the initial Board of Directors is
one (1), and the name and address of the person who is to serve as director
until the first annual meeting of the stockholders or until her successor is
elected and qualified is:


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<Table>
<Caption>

       Name                                             Address
<S>                                         <C>
Michelle P. Goolsby                         2515 McKinney Avenue, Suite 1200
                                                  Dallas, Texas 75201
</Table>

                                  ARTICLE VIII

         A director of the Corporation shall not be personally liable to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director, except for liability (i) for any breach of the director's
duty of loyalty to the Corporation or its stockholders, (ii) for acts or
omissions not in good faith or which involve intentional misconduct or a knowing
violation of law, (iii) under Section 174 of the Delaware General Corporation
Law, or (iv) for any transaction from which the director derived any improper
personal benefit. If the Delaware General Corporation Law is amended after the
filing of this Articles of Incorporation to authorize corporate action further
eliminating or limiting the personal liability of directors, then the liability
of a director of the Corporation shall be eliminated or limited to the fullest
extent permitted by the Delaware General Corporation Law, as so amended.

         Any repeal or modification of the foregoing paragraph by the
stockholders of the Corporation shall not adversely affect any right or
protection of a director of the Corporation existing at the time of such repeal
or modification.

                                   ARTICLE IX

         A. Right to Indemnification. Each person who was or is made a party or
is threatened to be made a party to or is otherwise involved in any action, suit
or proceeding, whether civil, criminal, administrative or investigative
(hereinafter a "proceeding"), by reason of the fact that he or she, or a person
of whom he or she is the legal representative, is or was a director or officer
of the Corporation or is or was serving at the request of the Corporation as a
director or officer of another corporation or of a partnership, joint venture,
trust or other enterprise, including service with respect to an employee benefit
plan (hereinafter an "indemnitee"), whether the basis of such proceeding is
alleged action in an official capacity as a director or officer or in any other
capacity while serving as a director or officer, shall be indemnified and held
harmless by the Corporation to the fullest extent authorized by the Delaware
General Corporation Law, as the same exists or may hereafter be amended (but, in
the case of any such amendment, only to the extent that such amendment permits
the Corporation to provide broader indemnification rights than permitted prior
thereto), against all expense, liability and loss (including, without
limitation, attorneys' fees, judgments, fines, excise taxes or penalties and
amounts paid or to be paid in settlement) incurred or suffered by such
indemnitee in connection therewith and such indemnification shall continue with
respect to an indemnitee who has ceased to be a director or officer and shall
inure to the benefit of the indemnitee's heirs, executors and administrators;
provided, however, that, except as provided in paragraph (B) hereof with respect
to proceedings to enforce rights to indemnification, the Corporation shall
indemnify any such indemnitee in connection with a proceeding initiated by such
indemnitee only if such proceeding was authorized by the Board of Directors of
the Corporation. The right to indemnification conferred in this Article IX shall
be a contract right and shall include the right to be paid by the Corporation
the expenses incurred in


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defending any such proceeding in advance of its final disposition (hereinafter
an "advancement of expenses"); provided, however, that, if the Delaware General
Corporation Law requires, an advancement of expenses incurred by an indemnitee
shall be made only upon delivery to the Corporation of an undertaking
(hereinafter an "undertaking"), by or on behalf of such indemnitee, to repay all
amounts so advanced if it shall ultimately be determined by final judicial
decision from which there is no further right to appeal (hereinafter a "final
adjudication") that such indemnitee is not entitled to be indemnified for such
expenses under this Article or otherwise.

         B. Right of Indemnitee to Bring Suit. If a claim under paragraph (A) of
this Article is not paid in full by the Corporation within sixty days after a
written claim has been received by the Corporation (except in the case of a
claim for an advancement of expenses, in which case the applicable period shall
be twenty days), the indemnitee may at any time thereafter bring suit against
the Corporation to recover the unpaid amount of the claim. If successful in
whole or in part in any such suit, the indemnitee shall also be entitled to be
paid the expense of prosecuting or defending such suit. In (i) any suit brought
by the indemnitee to enforce a right to indemnification hereunder (but not in a
suit brought by the indemnitee to enforce a right to an advancement of expenses)
it shall be a defense that, and (ii) in any suit by the Corporation to recover
an advancement of expenses pursuant to the terms of an undertaking, the
Corporation shall be entitled to recover such expenses upon a final adjudication
that, the indemnitee has not met the applicable standard of conduct set forth in
the Delaware General Corporation Law. Neither the failure of the Corporation
(including its Board of Directors, independent legal counsel or its
stockholders) to have made a determination prior to the commencement of such
suit that indemnification of the indemnitee is proper in the circumstances
because the indemnitee has met the applicable standard of conduct set forth in
the Delaware General Corporation Law, nor an actual determination by the
Corporation (including its Board of Directors, independent legal counsel, or its
stockholders) that the indemnitee has not met such applicable standard of
conduct, shall create a presumption that the indemnitee has not met the
applicable standard of conduct or, in the case of such a suit brought by the
indemnitee, be a defense to such suit. In any suit brought by the indemnitee to
enforce a right to indemnification or to an advancement of expenses hereunder or
by the Corporation to recover an advancement of expenses pursuant to the terms
of an undertaking, the burden of proving that the indemnitee is not entitled
under this Article or otherwise to be indemnified, or to such advancement of
expenses, shall be on the Corporation.

         C. Non-Exclusivity of Rights. The rights to indemnification and to the
advancement of expenses conferred in this Article IX shall not be exclusive of
any other right which any person may have or hereafter acquire under this
Certificate of Incorporation or any bylaw, agreement, vote of stockholders or
disinterested directors or otherwise.

         D. Insurance. The Corporation may maintain insurance, at its expense,
to protect itself and any indemnitee against any expense, liability or loss,
whether or not the Corporation would have the power to indemnify such person
against such expense, liability or loss under the Delaware General Corporation
Law.

         E. Indemnity of Employees and Agents of the Corporation. The
Corporation may, to the extent authorized from time to time by the Board of
Directors, grant rights to indemnification and to the advancement of expenses to
any employee or agent of the Corporation to the fullest extent of the

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provisions of this Article IX or as otherwise permitted under the Delaware
General Corporation Law with respect to the indemnification and advancement of
expenses of directors and officers of the Corporation.

                                    ARTICLE X

         No stockholder of the Corporation shall by reason of his holding shares
of any class of its capital stock have any preemptive or preferential right to
purchase or subscribe for any shares of any class of the Corporation, now or
hereafter to be authorized, or any notes, debentures, bonds or other securities
convertible into or carrying warrants, rights or options to purchase shares of
any class or any other security, now or hereafter to be authorized, whether or
not the issuance of any such shares or such notes, debentures, bonds or other
securities would adversely affect the dividend, voting or any other rights of
such stockholder; and the Board of Directors may issue shares of any class of
the Corporation, or any notes, debentures, bonds or other securities convertible
into or carrying warrants, rights or options to purchase shares of any class,
without offering any such shares of any class, either in whole or in part, to
the existing holders of any class of stock of the Corporation.

                                   ARTICLE XI

         Cumulative voting for the election of Directors shall not be permitted.

         IN WITNESS WHEREOF, the undersigned incorporator of the Corporation
hereby certifies that the facts herein stated are true, and accordingly has
signed this instrument this 3rd day of April, 2001.


                                                    /s/ Albert R. Fox, Jr.
                                              ----------------------------------
                                                   Albert R. Fox, Jr.,
                                                   Incorporator


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