<PAGE>   1
                                                                  Exhibit 10CH





                            CONTRIBUTION AGREEMENT



                                    BETWEEN







                     COLUMBIA GAS TRANSMISSION CORPORATION



                                      AND



                       MILLENNIUM PIPELINE COMPANY, L.P.





                           DATED AS OF JULY 31, 1998
<PAGE>   2
                                     INDEX

<TABLE>
<S>                                                                            <C>
ARTICLE I
DEFINITIONS .............................................................      1

ARTICLE II
CONTRIBUTION OF ASSETS ..................................................      3

ARTICLE III
PROCEEDS, EXPENSES AND TAXES ............................................      4

ARTICLE IV
OPERATIONS AND FACILITIES ...............................................      5

ARTICLE V
DISCLAIMER OF ALL WARRANTIES ............................................      5

ARTICLE VI

ENVIRONMENTAL MATTERS ...................................................      6

ARTICLE VII
REPRESENTATIONS AND WARRANTIES ..........................................      8

ARTICLE VIII
INDEMNIFICATION .........................................................     10

ARTICLE IX
CONDITIONS PRECEDENT AND TERMINATION ....................................     11

ARTICLE X
TRANSFER DATE ...........................................................     13

ARTICLE XI
OBLIGATIONS AFTER THE TRANSFER DATE .....................................     14

ARTICLE XII
DOCUMENTATION ...........................................................     15

ARTICLE XIII
MISCELLANEOUS PROVISIONS ................................................     15
</TABLE>

Schedule I  -     Actions, Suits, Etc.


                                       -i-
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                             CONTRIBUTION AGREEMENT


      THIS CONTRIBUTION AGREEMENT (this "Agreement") dated as of the 31st day of
July, 1998, is by and between COLUMBIA GAS TRANSMISSION CORPORATION, a Delaware
corporation ("Columbia"), and Millennium Pipeline Company, L.P., a Delaware
limited partnership ("Millennium"). Columbia and Millennium may be referred to
herein individually as a "Party" or collectively as the "Parties".

                                    RECITALS:

      A. Columbia owns the Assets located in the State of New York and the
Commonwealth of Pennsylvania.

      B. Columbia is a limited partner in Millennium, and pursuant to the
Agreement of Limited Partnership of Millennium Pipeline Company, L.P. (the "LP
Agreement"), Columbia has the right to contribute the Assets to Millennium as
partial consideration for Columbia's limited partnership interest in Millennium.

      C. The Parties desire to set forth the terms and conditions pursuant to
which the Assets will be contributed by Columbia to Millennium.

      NOW THEREFORE, in consideration of the premises and of the respective
covenants, representations and warranties herein contained, and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Parties hereto, intending to be legally bound, do hereby
covenant and agree as follows:

                                  ARTICLE I.
                                  DEFINITIONS

      1.1 Capitalized terms used in this Agreement shall have the following
meanings:

            "Abandonment Application" shall mean Columbia's application filed
with the FERC in Docket No. CP 98-151-000 for authority, inter alia, to abandon
the Assets.

            "Agreement" shall have the meaning set forth in the introductory
paragraph hereof.

            "AOC" shall mean the Administrative Order on Consent for Removal
Actions, issued by the U.S. Environmental Protection Agency, Regions II, III, IV
and V to Columbia, EPA Docket No. III-94-35-DC, with an effective date of
February 23, 1995, as amended or supplemented.

            "Assessment Report" shall mean the report prepared by Columbia and
approved by EPA regarding the assessment and/or characterization of sites as
required by the AOC, including any remedial recommendations.
<PAGE>   4
            "Assets" shall mean (1) all of the pipeline segments, measuring
stations and compressor stations listed on pages 3, 4 and 5 of Exhibit Z-1 of
the Abandonment Application, as amended or supplemented (the "Facilities"); (2)
all appurtenant structures, facilities, equipment, supplies, machinery, fixtures
and other items of tangible personal property located at or used to operate,
maintain or manage the Facilities, including compression, measuring, regulating,
communications, data, computer, laboratory and other equipment, tools, furniture
and supplies; (3) all improvements to or replacements of the Facilities prior to
the Effective Time, including any overpressure protection facilities constructed
by Columbia at or adjacent to the Facilities pursuant to Section 2.55 of the
FERC's NGA regulations; (4) all of the real estate owned by Columbia on which
any of the Facilities are situated or which is necessary for the operation and
maintenance of the Facilities; (5) all of Columbia's right, title and interest
in any easements, rights-of-way, leases or other interests in real property on
which any Facilities are situated or which are necessary for the operation and
maintenance of the Facilities; (6) any and all assignable rights which Columbia
may have pursuant to any easements, rights-of-way, leases or other interests in
real property to construct, operate and maintain a natural gas pipeline and
related facilities on the route approved in the Certificate Approval, as it may
be amended; (7) all of the real estate owned by Columbia on which any of the
pipeline segments listed on pages 1 and 2 of Exhibit Z-1 of the Abandonment
Application, as amended or supplemented (the "Abandoned Facilities"), are
situated; (8) all of Columbia's right, title and interest in any easements,
rights-of-way, leases or other interests in real property on which any of the
Abandoned Facilities are situated; and (9) all assignable rights which Columbia
may have pursuant to any easements, rights-of-way, leases or other interests in
real property to construct, operate and maintain a natural gas pipeline and
related facilities adjacent to the Abandoned Facilities.

            "Certificate Approval" shall mean the Final Order by FERC on
Millennium's certificate application pursuant to Section 7(c) of the NGA
granting the application and containing terms acceptable to Millennium.

            "Columbia" shall have the meaning set forth in the introductory
paragraph hereof.

            "Corridor Assets" shall mean the Assets described in subsections
(7), (8) and (9) of the definition of Assets.

            "COWP" shall mean the Work Plan for Construction and Operations at
Work Scope List Facilities, revised March 3, 1995, or the then-current version
of the COWP as approved by EPA.

            "Effective Time" shall mean 11:59 p.m., Eastern Time, on the date
immediately preceding the date on which the Millennium Pipeline System commences
service.

            "Environmental Assessment" shall mean the assessment and/or
characterization of locations as required by the AOC.

            "EPA" shall mean the United States Environmental Protection Agency
and any successor agency.


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<PAGE>   5
            "FERC" shall mean the Federal Energy Regulatory Commission and any
successor agency.

            "Final Order" shall mean any order no longer subject to further
proceedings before the FERC. An order shall be deemed to be a Final Order as of
the date rehearing is denied or the date on which the right to seek rehearing
expires.

            "LP Agreement" shall have the meaning set forth in the recitals
hereof.

            "Millennium" shall have the meaning set forth in the introductory
paragraph hereof.

            "Millennium Pipeline System" shall mean the pipeline system and
facilities authorized in the Certificate Approval.

            "Net Book Value" shall mean with respect to the Assets the net book
value as determined in accordance with FERC accounting standards and
requirements, as the same are modified from time to time.

            "NGA" shall mean the Natural Gas Act, 15 U.S.C.A. Section717, et
seq.

            "Response Action" shall mean any action required by the EPA pursuant
to the AOC.

            "Response Action Completion Final Report" shall mean that document
and/or documents which verify Columbia's performance of Response Actions
required by the AOC and is/are approved by EPA.

            "Response Action Work Plan" shall mean that document and/or
documents that is/are approved by the EPA and which describe(s) the manner in
which Response Actions required by the AOC are to be carried out.

            "Transfer Date" shall have the meaning set forth in Section 10.1
hereof.

            "Work Scope List" or "WSL" shall mean the document titled "Work
Scope List," dated March 23, 1995, submitted by Columbia to EPA pursuant to the
AOC and conditionally approved by EPA on July 12, 1995, as amended or
supplemented.

                                   ARTICLE II.
                             CONTRIBUTION OF ASSETS

      2.1 Upon and subject to the terms, conditions, representations and
warranties set forth in this Agreement, and except as provided in Article VI
hereof, Columbia agrees to assign, transfer and convey the Assets to Millennium
and Millennium agrees to take delivery of and accept the assignment, conveyance
and transfer of the Assets on the Transfer Date but effective for all purposes
as of the Effective Time. Notwithstanding the foregoing, Columbia shall, if
requested by Millennium, assign, transfer and convey certain portions of the
Assets to Millennium prior to the


                                        3
<PAGE>   6
Transfer Date. In the event of an assignment, transfer and conveyance prior to
the Transfer Date, (a) the Net Book Value of that portion of the Assets
assigned, transferred and conveyed shall be determined as of the Effective Time
regardless of the actual date of the assignment, transfer and conveyance, (b)
Columbia shall have until the Transfer Date to be in compliance with
representations contained in Section 7.1(d) hereof, (c) the conditions precedent
set forth in Section 9.1(d) hereof shall have occurred and (d) the indemnities
of the Parties contained in Sections 6.1(b) and (c) and in Article 8 hereof with
respect to such Assets shall commence as of the actual date of the assignment,
conveyance and transfer of such Assets to Millennium.

      2.2 The assignment, transfer and conveyance of the Assets shall be subject
to the limitations and restrictions, if any, contained in such documents of
title, assignment and other similar documents necessary to assign, transfer and
convey the Assets to Millennium. The Assets shall be assigned, transferred and
conveyed to Millennium subject to the representations and warranties set forth
herein. The transfer documents shall reflect Columbia's exceptions to title and
reservation of rights as approved by Millennium.

      2.3 The value of the Assets for purposes of determining the consideration
for Columbia's contribution to Millennium pursuant to the LP Agreement shall be
the Net Book Value of the Assets as of the Effective Time.

      2.4 Anything in this Agreement to the contrary notwithstanding, Millennium
(a) shall, if requested by Columbia, assign, transfer and convey to Columbia the
Corridor Assets, at a mutually agreed value, which Columbia represents are
necessary for Columbia to maintain natural gas transportation services for its
shippers and (b) shall be entitled, at its sole discretion, to assign, transfer
and convey to Columbia at no charge or cost to Columbia at any time within two
years of the Effective Time any of the Corridor Assets which Millennium chooses
not to retain, in which event Columbia agrees to take delivery of and accept
such Corridor Assets.

                                 ARTICLE III.
                         PROCEEDS, EXPENSES AND TAXES

      3.1 Ownership, operation and risk of loss of the Assets shall, except to
the extent that rights have been retained by Columbia pursuant to Section 2.2
herein, pass from Columbia to Millennium as of the Effective Time. If Columbia,
at any time subsequent to the Effective Time, should receive any revenues or
other proceeds attributable to any service provided through or by or related to
the Assets occurring after the Effective Time, Columbia shall promptly remit all
such revenues or proceeds to Millennium. If Millennium at any time subsequent to
the Effective Time should receive any revenues or other proceeds attributable to
any service provided through or by or related to the Assets for periods prior to
the Effective Time, Millennium shall promptly remit all such revenues or
proceeds to Columbia.

      3.2 Except for Columbia's environmental obligations contemplated in
Article VI hereof, Millennium shall be responsible for the payment of all costs
and expenses, including expenses for all operating and capital expenses
attributable to the Assets from and after the Effective Time.


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      3.3 Columbia shall be reimbursed by Millennium for any expenses paid by
Columbia with respect to the Assets for non-environmental matters relating to
the period of time on and after the Effective Time.

      3.4 Any and all excise or transfer taxes due and payable as a result of
the assignment, transfer and conveyance of the Assets and all sales taxes
relating to the assignment, transfer and conveyance of Assets and any recording
fees shall be paid by Millennium.

      3.5 All real estate, property and other use or ad valorem taxes assessed
against the Assets for the calendar year in which the Transfer Date occurs shall
be paid by Columbia when due and payable. Millennium shall reimburse Columbia
for Millennium's pro rata share of such taxes for the tax period which includes
the Transfer Date within thirty (30) days after receipt of a request from
Columbia. This provision shall survive the final settlement provisions of
Article XI hereof.

      3.6 For purposes of federal, state and local income and franchise taxes
and other similar taxes, it is the express intent of the Parties that all of
Columbia's right, title and interest in the Assets shall pass to Millennium as
of the Effective Time, that Millennium shall bear all such taxes attributable to
the Assets accruing on and after the Effective Time and that Columbia shall bear
all taxes attributable to the Assets accruing prior to the Effective Time.

                                  ARTICLE IV.
                          OPERATIONS AND FACILITIES

      4.1 Columbia agrees that until the Assets are assigned, transferred and
conveyed to Millennium it shall continue to maintain the Assets in their present
operating condition (reasonable wear and tear excepted) in accordance with
Columbia's standard maintenance practices.

      4.2 Columbia shall keep in full force and effect its existing property and
liability insurance on the Assets, subject to self-retention limits, until the
Transfer Date.

      4.3 Unless (a) this Agreement is terminated pursuant to Section 9.4 hereof
or (b) Millennium elects not to proceed with its proposed project, Columbia
shall not withdraw the Abandonment Application or amend the Abandonment
Application in any manner which could reasonably be expected to have an adverse
effect on Millennium.

                                  ARTICLE V.
                         DISCLAIMER OF ALL WARRANTIES

      SUBJECT TO THE PROVISIONS OF ARTICLE VI HEREOF, THE EXPRESS
REPRESENTATIONS OF COLUMBIA CONTAINED IN ARTICLE VII HEREOF AND IN THE DOCUMENTS
WHICH ASSIGN, TRANSFER AND CONVEY THE ASSETS TO MILLENNIUM ARE EXCLUSIVE, AND
COLUMBIA EXPRESSLY DISCLAIMS AND NEGATES, AND MILLENNIUM HEREBY WAIVES, ALL
OTHER REPRESENTATIONS AND WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, WITH
RESPECT TO ANY ITEMS OF EQUIPMENT, IMPROVEMENTS, FIXTURES AND APPURTENANCES
ASSIGNED, TRANSFERRED AND


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<PAGE>   8
CONVEYED AS PART OF THE ASSETS WHICH ARE ASSIGNED, TRANSFERRED AND CONVEYED, AND
MILLENNIUM ACCEPTS SUCH ITEMS "AS IS, WHERE IS, WITH ALL FAULTS" AND THERE ARE
NO WARRANTIES THAT EXTEND BEYOND THE FACE OF THIS AGREEMENT. MILLENNIUM FURTHER
ACKNOWLEDGES THAT THIS WAIVER IS CONSPICUOUS.

                                  ARTICLE VI.
                             ENVIRONMENTAL MATTERS

      6.1 Columbia shall have the following environmental obligations with
respect to the Assets:

            (a)   Columbia is obligated by the AOC to conduct an Environmental
                  Assessment and, if appropriate, to prepare a Response Action
                  Completion Final Report to address environmental conditions at
                  WSL locations, and Columbia and Millennium agree that such
                  work shall be at Columbia's cost and expense. Columbia's
                  obligations and liabilities under the AOC and this Agreement
                  in regard to the Assets which are at WSL locations shall
                  continue until such Environmental Assessment, as evidenced by
                  an Assessment Report, and, if necessary, a Response Action
                  Completion Final Report, are approved by EPA or until such
                  locations are removed from the WSL by EPA.

            (b)   Columbia shall conduct an Environmental Assessment of the
                  Assets as required by the AOC, the results of which shall be
                  set forth in an Assessment Report. Columbia shall furnish
                  Millennium with a copy of any such Assessment Report upon its
                  approval by EPA. Columbia shall obtain approval of the
                  Response Action Work Plan from EPA and shall furnish evidence
                  of that approval to Millennium. Following the completion of
                  the Response Actions required by EPA, Columbia shall furnish
                  Millennium a copy of the Response Action Completion Final
                  Report approved by EPA, including evidence of such approval.
                  Such approvals by EPA shall be binding on Millennium. Columbia
                  shall be responsible for and shall indemnify and hold
                  Millennium, its partners, employees, officers, agents,
                  representatives and, if applicable, their respective
                  shareholders, harmless from and against any and all losses,
                  liabilities, claims, demands, suits, judgments, fines,
                  penalties and costs of any kind or character with respect to
                  all environmental conditions related to the Assets to the
                  extent that the environmental conditions arose out of
                  Columbia's ownership, control or operation of the Assets prior
                  to the Effective Time.

            (c)   Millennium shall be responsible for and indemnify and hold
                  Columbia, its directors, employees, officers, agents,
                  representatives and shareholders harmless from and against any
                  and all losses, liabilities, claims, demands, suits,
                  judgments, fines, penalties and costs of any kind or character
                  with respect to all environmental conditions related to the
                  Assets: (i) caused by the


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<PAGE>   9
                  actions or omissions of Millennium or a third party after the
                  Effective Time, including subsequent transferees, whether or
                  not such conditions are located at WSL locations and (ii) to
                  the extent any environmental conditions arise after the
                  Effective Time. The scope of this indemnification shall
                  include, but not be limited to, claims by any governmental or
                  other third party for damages, study or cleanup of the Assets
                  beyond that required under the AOC, and statutory or common
                  law claims of third parties for bodily injury or property
                  damage based on or relating to environmental conditions at or
                  emanating from the Assets.

      6.2 Columbia represents that it has furnished Millennium with true and
correct copies of the AOC, the WSL and the COWP. Columbia, as soon as
practicable following EPA approval, shall provide Millennium a copy of any
changes to the AOC, WSL and COWP. Millennium hereby (a) acknowledges receipt of
said copies of the AOC, the WSL and the COWP and (b) accepts and acknowledges
that the Assets are subject to regulation under environmental laws of the states
in which they are located and of the United States of America.

      6.3 Millennium agrees (a) not to alter the Assets or to take any action
with regard to the Assets that would impede Columbia's compliance with the AOC
or COWP, and (b) that Millennium's activities and operations of the Assets will
be conducted in compliance with the AOC and the COWP.

      6.4 After the Effective Time, for the period required by Columbia to
discharge its obligations under this Article VI, upon reasonable notice,
Millennium shall provide Columbia, EPA, their employees, agents, representatives
and contractors, the right to enter onto and have access to the Assets in
accordance with Section 12 of the AOC. In providing such access, Millennium
shall not interfere with, delay or prohibit Columbia's compliance with or EPA's
exercise of authority under the AOC. Millennium shall cooperate with Columbia
and use all commercially reasonable means to provide Columbia and EPA access to
the Assets as promptly as possible upon notice.

      6.5 Millennium shall notify Columbia of proposed earth-disturbing
activities as defined in the COWP with respect to Assets which are at WSL
locations at a time and in a manner to be agreed upon by Columbia and
Millennium. Upon such notification, Columbia shall use reasonable efforts to
perform the necessary Environmental Assessment and, if necessary, to obtain a
Response Action Completion Final Report to address any environmental conditions
in accordance with the AOC and COWP prior to Millennium's proposed
earth-disturbing activities.

      6.6 Millennium shall notify Columbia at the earliest possible time of its
intent to transfer ownership or to delegate material or substantial operation of
Assets which are at WSL locations and for which Columbia has not performed an
Environmental Assessment and, if necessary, received a Response Action
Completion Final Report. Upon such notification, Columbia shall use reasonable
efforts to perform Environmental Assessments and remediation, if necessary,
prior to such transfer of ownership or operation by Millennium of such Assets.
Millennium agrees it shall not transfer ownership or delegate material or
substantial operation of Assets which are WSL locations until such time as
Columbia has received EPA approval of an Environmental Assessment and, if
necessary, a


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<PAGE>   10
Response Action Completion Final Report or until such locations are removed from
the WSL. In the event of any such delegation or transfer, Millennium shall
ensure that, as a condition to such transfer or delegation, the transferee or
party to whom the operation of the Assets has been delegated shall agree to be
bound by the obligations of Millennium under this Article VI. Notwithstanding
the preceding sentence, nothing contained herein shall relieve Millennium from
such obligations.

      6.7 In the event of a situation occurring at Assets which are at WSL
locations where immediate action is required for the protection of life, health
or maintenance of physical property, and earth disturbance as defined in the AOC
is required to remedy the situation, Millennium shall perform the
earth-disturbing activity in accordance with the AOC and the emergency
procedures specified in the COWP. Millennium shall immediately notify Columbia
of any such situation and shall cooperate with Columbia in regard to such
actions necessary to ensure compliance with the AOC and COWP.

      6.8 If Columbia, its employees, agents, representatives or contractors
enter upon Millennium's property in order to identify or address any obligations
imposed upon Columbia by this Article VI, Millennium shall indemnify Columbia
and hold Columbia harmless from any and all claims and liabilities resulting
from such claims, asserted by Millennium's employees, representatives,
contractors or agents arising from the presence of Columbia or its employees,
representatives, contractors or agents on the subject property to identify or
address any obligations imposed on Columbia by this Article VI, so long as such
claims do not arise from the gross negligence or willful misconduct of Columbia
and/or Columbia's employees, agents, representatives or contractors.

      6.9 Columbia reserves the right to negotiate such modifications,
amendments or supplements to the AOC, COWP and WSL as it in its sole discretion
deems necessary or advisable; provided, however, that Columbia shall not modify,
amend or supplement the AOC, COWP or WSL without consulting with Millennium if
such modifications, amendments or supplements could reasonably be expected to
have an adverse impact on Millennium or the Millennium Pipeline System. Nothing
in this Agreement shall be construed to impose a separate, contractual
obligation on the part of Columbia to take any action with respect to the Assets
that is not required by the AOC, COWP or WSL. With respect to Assets for which a
Response Action Completion Final Report has been received or which has been
removed from the WSL, nothing in this Agreement shall be construed to impose an
obligation upon Columbia to perform any work to comply with new or more
stringent environmental standards or requirements as may be incorporated into a
subsequent amendment or supplement to the AOC, COWP or WSL.

                                  ARTICLE VII.
                         REPRESENTATIONS AND WARRANTIES

      7.1 As of the Transfer Date, Columbia represents and warrants to
Millennium as follows:

            (a)   Columbia is a duly organized, validly existing corporation in
                  good standing under the laws of the State of Delaware, with
                  full corporate power and authority to engage in the business
                  in which it is now engaged.


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<PAGE>   11
            (b)   Columbia has the corporate authority to execute, deliver and
                  perform this Agreement. The execution, delivery and
                  performance of this Agreement by Columbia has been duly
                  authorized by all necessary corporate action and no additional
                  corporate or FERC approvals or authorizations are required in
                  connection with Columbia's execution, delivery and performance
                  of this Agreement. Neither the execution and delivery of this
                  Agreement nor the consummation of the transactions herein
                  contemplated will violate the articles of incorporation or
                  other governing documents of Columbia or will result in any
                  breach or default under any agreement or other instrument to
                  which Columbia is a party;

            (c)   Neither the execution and delivery of this Agreement nor
                  (assuming receipt of a Final Order approving the Abandonment
                  Application) the consummation of the transactions contemplated
                  by this Agreement will violate any statute or regulation
                  applicable to Columbia in any material respect, or any order
                  or decree of any court or governmental authority applicable to
                  Columbia;

            (d)   Other than as provided for in Schedule I attached hereto and
                  made a part hereof, as supplemented on the Transfer Date,
                  Columbia (i) has no actual knowledge of any actions, suits or
                  administrative proceedings or investigations pending or
                  threatened against Columbia that relate in any respect to the
                  Assets and is not in default with respect to any order,
                  injunction or decree of any court or governmental department,
                  commission, board or agency relating to the Assets; (ii) has
                  no actual knowledge of any outstanding claims or demands
                  relating to damage to property arising out of Columbia's
                  ownership, operation or maintenance of the Assets; and (iii)
                  has no actual knowledge of and has not received any notice
                  from any governmental body or official thereof of any material
                  violation of any law, order or regulation relating to the
                  ownership, maintenance and operation of the Assets;

            (e)   The Assets are owned by Columbia and are being assigned,
                  transferred and conveyed to Millennium free and clear of all
                  claims, mortgages, liens and encumbrances arising by, through
                  or under Columbia, but not further;

            (f)   That portion of the Assets consisting of tangible property has
                  been maintained in good repair and working condition, subject
                  to reasonable wear and tear;

            (g)   The financial statements used to determine the Net Book Value
                  are complete, true and correct in all material respects;

            (h)   That there have not been, except as may have been disclosed to
                  Millennium, any material adverse changes in the condition of
                  Assets between the effective date of this Agreement and the
                  Transfer Date; and


                                        9
<PAGE>   12
            (i)   Columbia has not made any regulatory applications, other than
                  the Abandonment Application, relating to the Assets.

      7.2 As of the Transfer Date, Millennium represents and warrants to
Columbia as follows:

            (a)   Millennium is a duly organized, validly existing limited
                  partnership in good standing under the laws of the State of
                  Delaware, with full partnership power and authority to engage
                  in the business in which it is now engaged.

            (b)   Millennium has the partnership authority to execute, deliver
                  and perform this Agreement. The execution, delivery and
                  performance of this Agreement by Millennium has been duly
                  authorized by all necessary partnership action and no
                  additional partnership or FERC approvals or authorizations are
                  required in connection with Millennium's execution, delivery
                  and performance of this Agreement. Neither the execution and
                  delivery of this Agreement nor the consummation of the
                  transactions herein contemplated will violate the LP Agreement
                  or other governing documents of Millennium or will result in
                  any breach or default under any agreement or other instrument
                  to which Millennium is a party.

            (c)   There are no pending or threatened legal actions or suits with
                  respect to Millennium or its properties and assets which in
                  any way affect consummation of the transactions contemplated
                  hereby and Millennium is not subject to any judgment, order,
                  decree, seizure or lien which would adversely affect the
                  transactions contemplated hereby.

            (d)   Except for the Abandonment Application, Millennium has
                  obtained or will be solely responsible for obtaining any
                  permits, licenses or consents required by any governmental
                  authority or other entity in connection with the use and
                  occupancy of the Assets, whether necessary due to the
                  non-transferability of any permit, license or consent
                  comprising the Assets or for any other reason.

            (e)   Neither the execution and delivery of this Agreement, nor the
                  consummation of the transactions herein contemplated, will
                  violate any statute or regulation applicable to Millennium, or
                  any order or decree of any court or governmental authority
                  applicable to Millennium.

                                 ARTICLE VIII.
                                INDEMNIFICATION

      8.1 Millennium shall indemnify, defend and hold Columbia, its employees,
directors, officers, agents and its shareholders harmless from and against any
and all losses, liabilities, claims, demands, suits, judgments, fines, penalties
and costs of any kind or character, whether groundless or not, (a) that accrue
or relate to any period of time after the Effective Time with respect to the
Assets, (b) that arise from Millennium's failure to comply with Millennium's
obligations as set forth


                                       10
<PAGE>   13
herein in Article VI hereof or (c) that result from any material breach by
Millennium of any representations, warranties, covenants or agreements which
survive the assignment, transfer and conveyance of the Assets to Millennium
pursuant to this Agreement. If a claim involves a claim by a third party against
Columbia for which Millennium has an indemnification obligation, Millennium may,
at its sole discretion and expense, assume the defense of such claim.

      8.2 Columbia shall indemnify, defend, and hold Millennium, its partners,
employees, officers, agents, representatives, and, if applicable, their
respective shareholders, harmless from and against any and all losses,
liabilities, claims, demands, suits, judgments, fines, penalties and costs of
any kind or character, whether groundless or not, (a) that accrue or relate to
any period of time prior to the Effective Time, (b) that arise from Columbia's
failure to comply with Columbia's obligations as set forth in Article VI hereof
or (c) that result from any material breach by Columbia of any representations,
warranties, covenants or agreements which survive the assignment, transfer and
conveyance of the Assets to Millennium pursuant to this Agreement. If a claim
involves a claim by a third party against Millennium for which Columbia has an
indemnification obligation, Columbia may, at its sole discretion and expense,
assume the defense of such claim. Columbia's obligations under this Section 8.2
shall terminate on the date that is two (2) years after the Effective Time,
except with respect to its obligations relating to matters arising under Article
VI hereof, if any, which shall terminate in accordance with the terms of that
section, and provided that Columbia's obligations, if any, under this Section
8.2 shall continue after the expiration of such two (2) year period with respect
to claims that were asserted during such two (2) year period and as to which
Millennium made a proper claim for indemnification by Columbia under this
Section 8.2 during such two (2) year period.

      8.3 The provisions of this Article VIII shall survive the Transfer Date.

      8.4 Nothing contained in this Article VIII is intended to limit the
indemnification obligations of the Parties pursuant to Section 6.1(b) and (c)
hereof which shall survive indefinitely.

                                  ARTICLE IX.
                     CONDITIONS PRECEDENT AND TERMINATION

      9.1 All obligations of Columbia under this Agreement are subject to
fulfillment of each of the following conditions precedent:

            (a)   All of the representations and warranties made by Millennium
                  under Section 7.2 hereof shall be true and correct as of the
                  Transfer Date;

            (b)   Millennium shall have performed and complied in all material
                  respects with all agreements, provisions and conditions
                  required by this Agreement to be performed or complied with by
                  Millennium prior to or at the Transfer Date;

            (c) The Certificate Approval shall have occurred;


                                       11
<PAGE>   14
            (d)   Prior to or on the Transfer Date, Columbia shall have: (i)
                  received a Final Order approving the Abandonment Application
                  on terms which are not materially different than those set
                  forth in the Abandonment Application and (ii) received all
                  other necessary regulatory approvals that are required in
                  order for Columbia to consummate the transactions contemplated
                  by this Agreement; and

            (e)   Subject to Section 9.3 hereof, there shall be no bona fide
                  suit, action or other proceeding or investigation before any
                  court or before any governmental agency or submission by any
                  governmental agency of information relating to the subject
                  matter of the transactions contemplated by this Agreement nor
                  any other bona fide material claim or demand pending in which
                  the consummation of this Agreement or the transactions
                  contemplated hereby may be restrained, prohibited,
                  invalidated, set aside or delayed in whole or in part.

      9.2 All obligations of Millennium under this Agreement are subject to
fulfillment of each of the following conditions precedent:

            (a)   All of the representations and warranties made by Columbia
                  under Section 7.1 hereof shall be true and correct as of the
                  Transfer Date;

            (b)   Columbia shall have performed and complied in all material
                  respects with all agreements, provisions and conditions
                  required by this Agreement to be performed or complied with by
                  Columbia prior to or on the Transfer Date;

            (c)   Prior to or on the Transfer Date, Columbia shall have received
                  (i) a Final Order approving the Abandonment Application and
                  (ii) all other necessary regulatory approvals that are
                  required in order for Columbia to consummate the transactions
                  contemplated by this Agreement;

            (d)   Prior to or on the Transfer Date, Columbia shall have obtained
                  a release of the Assets from Columbia's Wilmington Trust
                  Company mortgage;

            (e)   If necessary, Columbia shall have notified the EPA of the
                  transfer contemplated herein thirty (30) days prior to the
                  Transfer Date;

            (f)   There shall be no bona fide suit, action or other proceeding
                  or investigation before any court or governmental agency nor
                  any other bona fide material claim or demand, pending in which
                  the consummation of this Agreement or the transactions
                  contemplated hereby may be restrained, prohibited,
                  invalidated, set aside or delayed in whole or in part;

            (g)   Millennium has obtained satisfactory financing for the
                  construction of the Millennium Pipeline System; and


                                       12
<PAGE>   15
            (h)   Millennium has constructed all or substantially all of the
                  Millennium Pipeline System.

      9.3 Notwithstanding the provisions of Section 9.1(e) above, the resolution
of proceedings before the United States Court of Appeals with respect to one or
more petitions for review of a Final Order granting the Certificate Approval and
approving the Abandonment Application shall not constitute a condition precedent
of Columbia's obligations under this Agreement if Millennium (a) notifies
Columbia that all of the conditions precedent set forth in Section 9.2 hereof
have been satisfied or waived, (b) indemnifies and holds Columbia, its
directors, employees, officers, agents, representatives and shareholders
harmless from and against any and all losses, claims, demands, suits, judgments,
fines, penalties and costs of any kind or character arising from or relating to
the fact that Columbia transferred, conveyed and assigned the Assets to
Millennium while any such suit, action or proceeding was pending and (c)
provides Columbia with a guaranty or guarantees of the indemnification
obligations of Millennium pursuant to this Section 9.3 or other form of credit
support from an entity or entities with a rating of BBB or better by Standard &
Poor's (or an equivalent rating by another rating agency) acceptable to
Columbia.

      9.4 This Agreement may be terminated on the following terms and
conditions:

            (a)   By mutual agreement of the Parties;

            (b)   By either Party if the conditions set forth in Sections 9.1
                  and 9.2 hereof are not met or waived by December 31, 2000;

            (c)   By Millennium if Millennium elects not to proceed with the
                  construction of the proposed project; and

            (d)   By Columbia if Columbia receives a notice from Millennium that
                  Millennium has elected not to proceed with the construction of
                  the proposed project.

                                  ARTICLE X.
                                 TRANSFER DATE

      10.1 The assignment, transfer and conveyance of the Assets shall take
place on a date which is not more than ten (10) days after date on which
Millennium places the Millennium Pipeline System in service and shall take place
at a time and place to be mutually agreed upon between the Parties (the
"Transfer Date").

      10.2 On the Transfer Date the following events shall occur, each being a
condition precedent to the others and each being deemed to have occurred
simultaneously with the others:

            (a)   Columbia shall execute, acknowledge and deliver to Millennium
                  assignment, transfer and conveyance documents and such other
                  instruments as may be


                                       13
<PAGE>   16
                  necessary to assign, transfer and convey to Millennium the
                  Assets in the manner contemplated by this Agreement;

            (b)   Columbia shall deliver to Millennium possession of the Assets
                  and Millennium shall take possession of the Assets as of the
                  Effective Time; and

            (c)   Columbia and Millennium shall prepare a preliminary settlement
                  statement showing all known costs and expenses owed or due at
                  the Transfer Date, subject to the preparation of a final
                  settlement statement to be prepared in accordance with Section
                  11.2 hereof.

                                  ARTICLE XI.
                      OBLIGATIONS AFTER THE TRANSFER DATE

      11.1 Except for the Abandonment Application and as otherwise provided in
this Agreement, Millennium shall obtain any permits, licenses or consents
required by any governmental authority or other entity in connection with the
use and occupancy of the Assets, whether necessary due to the
non-transferability of any such permit, license or consent, or for any other
reason. The obtaining of any such permits, licenses or consents shall be the
sole responsibility and liability of Millennium.

      11.2 Within one hundred eighty (180) days after the Transfer Date, a final
settlement statement shall be prepared by Millennium and shall be agreed upon by
Millennium and Columbia.

      11.3 If the assignment, transfer and conveyance of the Assets occurs,
Millennium and Columbia shall be deemed to have waived, to the fullest extent
permitted under applicable law, any right to contribution, set-off or recoupment
against each other and any and all rights, claims and causes of action they may
have against each other arising under or based on any federal, state or local
statute, law, ordinance, rule or regulation or common law or otherwise;
provided, however, that nothing contained herein shall be deemed to constitute a
waiver of any rights, claims or causes of action that either Party may have
against the other Party for a breach of any of the covenants to be performed by
such other Party at any time after the Effective Time or any other provisions of
this Agreement that survive the Transfer Date in accordance with Article VIII
hereof.

      11.4 If the assignment, transfer and conveyance of the Assets occurs, the
sole and exclusive remedy of the Parties with respect to any claim arising out
of the assignment, transfer and conveyance of the Assets shall be pursuant to
the express provisions of this Agreement. Columbia and Millennium acknowledge
that the payment of money, as limited by the terms of this Agreement, shall be
adequate compensation for breach of any covenant or agreement contained herein
or for any other claim arising in connection with or with respect to the
transactions contemplated in this Agreement. As the payment of money shall be
adequate compensation, Millennium and Columbia waive any right to rescind this
Agreement or any of the transactions contemplated hereby. The Parties
acknowledge that prior to the Transfer Date there will be no adequate remedy at
law for Millennium for a breach of the covenants and agreements of Columbia
contained herein. It is accordingly agreed that, in addition to any other
remedies that may be available to Millennium upon


                                      14
<PAGE>   17
the breach by Columbia of such covenants and agreements, Millennium shall have
the right to obtain injunctive relief to restrain any breach or threatened
breach of the covenants or agreements or to otherwise obtain specific
performance of any such covenants and agreements.

                                 ARTICLE XII.
                                 DOCUMENTATION

      12.1 Prior to or on the Transfer Date, Columbia, at Millennium's request
and expense, shall furnish or make available for inspection and copying to
Millennium, its affiliates, partners and their representatives, the following
materials:

            (a)   Copies of all deeds, leases, easements, rights-of-way,
                  licenses, permits and other grants of rights or authority
                  utilized by Columbia in connection with the construction,
                  operation, repair and maintenance of the Assets;

            (b)   Copies of all maps and construction, design, engineering and
                  other data pertinent to the construction, operation, repair
                  and maintenance of the Assets. Such information shall include
                  any U.S. Department of Transportation, Office of Pipeline
                  Safety records and reports, all available records relating to
                  materials, supplies and maintenance work performed and all
                  reports relating to inspection of the Assets;

            (c)   All available records relating to assessment, appraisal, entry
                  and payment of taxes relating to the Assets;

            (d)   All notices, certificates, orders, fines and other
                  communications from any pertinent government regulatory
                  authority relating to construction, maintenance, repair or
                  operation of the Assets and to compliance with applicable law
                  or regulations; and

            (e)   All notices, claims or demands from any person, legal entity,
                  government authority or subdivision relating to the validity
                  of any easement, right-of-way, privilege, license or permit of
                  Columbia in connection with the Assets.

                                 ARTICLE XIII.
                           MISCELLANEOUS PROVISIONS

      13.1 It is the intent of Millennium to acquire and of Columbia to assign,
transfer and convey all of Columbia's interest in the Assets except as provided
in Article II hereof. In the event that any interest owned by Columbia in the
Assets are omitted or incorrectly described herein, the Parties agree to execute
the documents necessary to effect the intent stated herein.

      13.2 Except to the extent otherwise provided herein, each Party hereto
shall pay its own expenses incidental to the preparation of this Agreement, the
carrying out of the provisions of this Agreement and the consummation of the
transactions contemplated hereby.


                                       15
<PAGE>   18
      13.3 Each Party shall cooperate with the other Party in its efforts to
obtain any regulatory authorization necessary to consummate the transactions
contemplated under this Agreement.

      13.4 All notices, requests, demands, consents, waivers or other
communications hereunder shall be in writing and shall be deemed given when
delivered personally or upon receipt by the addressee if deposited in the United
States first-class mail or United States registered or certified mail, return
receipt requested, postage prepaid, as follows:

            If to Millennium to:

                  Millennium Pipeline Company, L.P.
                  c/o Millennium Pipeline Management Company, L.L.C.,
                        General Partner
                  12801 Fair Lakes Parkway
                  P. O. Box 10146
                  Fairfax, VA  22030-0146
                  Attn: Mr. David C. Pentzien
                  Telephone:  (703) 337-3200
                  Telecopy:   (703) 227-3225


            If to Columbia, to:

                  Columbia Gas Transmission Corporation
                  12801 Fair Lakes Parkway
                  Fairfax, VA  22030
                  Telephone:  (703) 227-3200
                  Telecopy:   (703) 227-3225

or to such other address or party at that address as may be designated by prior
written notice by the Party entitled to receive such written notice.

      13.5 All section headings are for convenience only and shall in no way
modify or restrict any of the provisions thereof.

      13.6 This Agreement shall be governed by and interpreted in accordance
with the laws of the State of New York (without reference to its conflict of
laws provisions).

      13.7 This Agreement shall be binding upon and inure to the benefit of and
be enforceable by the respective successors by law of the Parties; provided,
however, that no assignment shall be made without prior written consent of the
other Party which consent shall not be unreasonably withheld. This Agreement may
not be amended or terminated except by written instrument signed by the Parties
or as provided herein.


                                       16
<PAGE>   19
      13.8 This Agreement was drafted by the joint effort of the Parties and
neither Party shall be deemed to have predominated in or controlled the
drafting.

      13.9 Nothing in this Agreement shall entitle any person other than the
Parties or their respective successors and assigns permitted hereby to any
claim, cause of action, remedy or right of any kind. There are no intended
third-party beneficiaries to this Agreement.

      13.10 This Agreement and the exhibits and schedules hereto collectively
constitute the entire agreement between the Parties pertaining to the subject
matter hereof and supersede all prior agreements, understandings, negotiations
and discussions, whether oral or written, of the Parties relating to the subject
matter hereof except as specifically set forth in this Agreement, and neither of
the Parties shall be bound by or liable for any alleged representation, promise,
inducement or statements of intention not so set forth.

      13.11 This Agreement may be executed in several counterparts, each of
which shall be an original. This Agreement and any counterparts so executed
shall be deemed to be one and the same instrument. It shall not be necessary in
making proof of this Agreement or any counterpart hereof to produce or account
for any of the other counterparts.

      13.12 If any section or provision of this Agreement shall be held by any
court of competent jurisdiction to be illegal, void or unenforceable, such
section or provision shall survive to the extent enforceable as allowed by law,
but the illegality or unenforceability of any such section or provision shall
have no effect upon and shall not impair the enforceability of any other section
or provision of this Agreement.

      13.13 The obligations of Columbia under this Agreement shall remain in
full force and effect if Columbia becomes a "Withdrawing Limited Partner" as
that term is defined in the LP Agreement.





               [THE REMAINDER OF THIS PAGE INTENTIONALLY BLANK]


                                       17
<PAGE>   20
      IN WITNESS WHEREOF, Columbia and Millennium have caused this Agreement to
be executed as of July 31, 1998.

                             COLUMBIA GAS TRANSMISSION
                             CORPORATION

                             By:_________________________________________
                             Printed Name: ______________________________
                             Title: _____________________________________



                             MILLENNIUM PIPELINE COMPANY, L.P.,
                             a Delaware limited partnership

                             By:   Millennium Pipeline Management Company,
                                   L.L.C., a Delaware limited liability company,
                                   its General Partner


                             By: ________________________________________
                                 David C. Pentzien, Chairman




                                SIGNATURE PAGE TO
                             CONTRIBUTION AGREEMENT




                                       18
<PAGE>   21
                       SCHEDULE I - ACTIONS, SUITS, ETC.


1.    AOC
2.    Mortgage in favor of Wilmington Trust Company