<PAGE>   1
                                                                   Exhibit 10.23


                               RELEASE AGREEMENT


     This Release Agreement is made this 8th day of December, 1999 by and
between Equitable Resources, Inc., a Pennsylvania corporation having a business
address at One Oxford Centre, Suite 3300, Pittsburgh, Pennsylvania 15219 (the
"Company") and John C. Gongas, Jr. ("the Employee").

                                   WITNESSETH

     WHEREAS, the Company and the Employee are parties to a Non-Competition
Agreement under which execution of this Release Agreement by Employee is a
condition to and consideration for payment by the Company of the amounts
referenced in Paragraph 2 of the Non-Competition Agreement; and

     WHEREAS, the parties desire to settle any and all matters relating to
Employee's employment and the termination thereof;

     NOW, THEREFORE, the Company and Employee, in consideration of the
premises, covenants and agreements contained herein and each intending to be
legally bound, agree as follows:

     1.   The employment of the Employee will be terminated as set forth in the
Employment Agreement ("termination date").

     2.   This Release Agreement is not, and should not be construed as, an
allegation or admission on the part of either Employee or the Company that
either of them has acted unlawfully or has violated any federal, state or local
law, rule or regulation.

     3.   Except as otherwise provided in Paragraph 6 hereof, in return for the
consideration described in the preamble hereto, Employee, on behalf of himself
and his heirs, executors, representatives, estates and assigns, voluntarily and
irrevocably releases the Company, is subsidiaries, predecessors, affiliates,
shareholders, and their respective officers, directors, employees, agents,
attorneys, successors and assigns (severally and collectively called
"Releasees") from any and all claims (known and unknown) which Employee has or
might have against any of the Releasees arising in any manner at any time up to
the effective date of this Release Agreement. This release includes, without
limitation, claims which Employee has or might have involving his employment
with any of the Releasees, the termination of that employment or its timing or
the terms and conditions of that employment. This includes, without limitation,
any claim arising under any constitution, law, statute, ordinance, regulation,
rule, guideline, or common-law theory, and specifically all claims arising
under all state, federal or local employment discrimination or wrongful
discharge laws, regulations or common-law theories, including, but not limited
to, Title VII of the Civil Rights Act of 1964, the Employee Retirement Income
Security Act of 1974, the Americans With Disabilities Act of 1990, the Age
Discrimination in Employment Act of 1967, the Older Workers Benefit Protection
Act, and the Pennsylvania Human Relations Act, as well as any claim for breach
of contract or wrongful


                                       1
<PAGE>   2


discharge or otherwise for any reason arising prior to the effective date of
this Agreement. Employee also releases all Releasees from any and all claims
for the fees, costs and expenses of any attorneys who have at any time
represented Employee (or are now representing Employee) in connection with this
Agreement or in connection with any matter released in this Agreement.

     4.   Employee agrees not to file a lawsuit against any of the Releasees in
any court of the United States or any State thereof concerning any matter
released in this Release Agreement. Notwithstanding any other language in this
Release Agreement, the parties understand that this Release Agreement does not
prohibit Employee from filing an administrative charge of alleged employment
discrimination under Title VII of the Civil Rights Act of 1964, the Age
Discrimination in Employment Act of 1967, the Americans with Disabilities Act
of 1990 or the Equal Pay Act of 1963. Employee, however, waives his right to
monetary or other recovery should any federal, state or local administrative
agency pursue any claims on his behalf arising out of or relating to his
employment with and/or separation from employment with any of the Releasees.
THIS MEANS THAT BY SIGNING THIS RELEASE AGREEMENT, EMPLOYEE WILL HAVE WAIVED
ANY RIGHT HE HAD TO BRING A LAWSUIT OR OBTAIN A RECOVERY IF AN ADMINISTRATIVE
AGENCY PURSUES A CLAIM AGAINST ANY OF THE RELEASEES BASED ON ANY ACTIONS TAKEN
BY ANY OF THE RELEASEES UP TO THE DATE OF THE SIGNING OF THIS RELEASE
AGREEMENT, AND THAT EMPLOYEE WILL HAVE RELEASED THE RELEASEES OF ANY AND ALL
CLAIMS OF ANY NATURE ARISING UP TO THE DATE OF THE SIGNING OF THIS AGREEMENT.

     5.   If Employee files suit against any of the Releasees in breach of the
release and covenant not to sue, then Employee shall pay to the Company all
attorneys' fees and expenses incurred by the Company in connection therewith
plus interest at the legal rate. This provision is not intended to limit
Employee's liability to the Company if the actual damages to the Company exceed
these costs.

     6.   Notwithstanding the foregoing release and covenant not to sue,
Employee shall be entitled to receive those payments and benefits as described
in Paragraphs 3 through 6 of the Employment Agreement.

     7.   Employee acknowledges that Employee has been advised to consult with
an attorney about this Agreement prior to signing it and that Employee has had
a full and fair opportunity to consult with an attorney if Employee desired to
do so. Employee further acknowledges that Employee had been given at least 21
calendar days in which to consider this Agreement and to make a decision as to
whether to accept it.

     8.   Within seven (7) calendar days after signing this Release Agreement,
Employee may change his mind and revoke his acceptance by delivering a
revocation in writing to Equitable Resources, Inc., 420 Boulevard of the
Allies, Pittsburgh, Pennsylvania 15219, Attention: Gene D. Musial -- Director,
Human resources. This Release Agreement shall not become effective or
enforceable until that seven-day revocation period has expired.

     9.   except for the Non-Competition Agreement and the Employment
Agreement, this Release Agreement contains the entire agreement of the parties
relating to Employee's employment and termination of employment. There are no
representations or terms relating thereto other than those set forth in this
written Release Agreement. This Release Agreement



                                       2
<PAGE>   3

and the rights of the parties relating to the subject matter hereof shall be
governed by and construed in accordance with the laws of the Commonwealth of
Pennsylvania.

         10.      If any of the provisions of this Release Agreement are
declared or determined by any court to be invalid or unenforceable for any
reason, the remaining provisions and portions of this Release Agreement -- at
the company's sole option -- shall be unaffected thereby and shall remain in
full force to the fullest extent permitted by law.

         11.      EMPLOYEE ACKNOWLEDGES THAT EMPLOYEE HAS CAREFULLY READ AND
FULLY UNDERSTANDS ALL OF THE PROVISIONS OF THIS RELEASE AGREEMENT, AND THAT
EMPLOYEE IS VOLUNTARILY EXECUTING AND ENTERING INTO THIS RELEASE AGREEMENT,
WITH FULL KNOWLEDGE OF ITS SIGNIFICANCE AND INTENDING TO BE LEGALLY BOUND BY IT.

         IN WITNESS WHEREOF, the Company has caused this Release Agreement to
be executed by its officers thereunto duly authorized, and the Employee has
hereunto set his hand, all as of the day and year first above written.


ATTEST:                             EQUITABLE RESOURCES, INC.


/s/ Vanessa J. Lombardo             /s/ Gregory R. Spencer
-------------------------           --------------------------
Vanessa J. Lombardo                 Gregory R. Spencer
                                    Senior Vice President and
                                    Chief Administrative Officer



WITNESS:                            EMPLOYEE:


/s/ Deborah Patterson               /s/ John C. Gongas, Jr.
-------------------------           --------------------------
Deborah Patterson                   John C. Gongas, Jr.


                                       3