<PAGE>

                      [CONFIDENTIAL TREATMENT REQUESTED]

INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT 
HAS BEEN REQUESTED. ALL SUCH MATERIAL HAS BEEN FILED WITH THE COMMISSION 
PURSUANT TO RULE 24.



 
                                                                      EXHIBIT 10


                         FIRM PURCHASE/SALE AGREEMENT

Duke Energy Trading and Marketing, L.L.C., a Delaware limited liability company 
("Seller"), and The Providence Gas Company, a Rhode Island corporation 
("Buyer"), each sometimes referred to individually as "Party" and referred to 
collectively as the "Parties" enter into this Firm Purchase/Sale Agreement 
(together with the General Provisions set forth in Appendix "1", collectively, 
this "Agreement"). All capitalized terms not defined in this Firm Purchase/Sale 
Agreement are defined in Appendix 1.


ARTICLE 1. TERM  This Agreement shall be in effect for a term of three (3) years
---------------
from the Effective Date of October 1, 1997. Termination of this Agreement in all
instances shall be subject to Section 9.4.


ARTICLE 2. SCOPE OF AGREEMENT  2.1. Scope of Agreement.  The Parties agree that
-----------------------------       ------------------
this Agreement is a "requirement contract" and that Seller shall be the 
exclusive supplier of Buyer's Requirements Quantity during the term of this 
Agreement. The specific terms and conditions reached between Buyer and Seller 
regarding the purchase of the Requirements Quantity of Gas by Buyer from Seller 
are specified in Exhibit "B" and are herein incorporated by reference. In the 
event of any conflict between the terms of Exhibit B, this Firm Purchase/Sale 
Agreement or Appendix 1, the priority will be that Exhibit B will govern, 
followed by this Firm Purchase/Sale Agreement, followed by Appendix 1.


ARTICLE 3. QUANTITY OBLIGATIONS  3.1. Seller's Obligations.
-------------------------------       --------------------


3.1.1.  Seller's Scheduling and Delivery Obligations and Measurement.  Seller 
        ------------------------------------------------------------
shall Schedule and deliver at the appropriate Delivery Points on a firm basis 
each Gas Day 100% of the total quantity of Gas required by Buyer to meet on such
Gas Day is Requirements Quantity, which includes Gas for Firm Customers on 
Buyer's system and Gas for Interruptible Sales and Gas-Related Transportation 
Requirements as defined in Appendix 1, below. Gas will be measured by Seller's 
Transporter at the Delivery Points.

3.1.2. Interruptible Sales Requirements [CONFIDENTIAL TREATMENT REQUESTED] In
       --------------------------------
the event of unauthorized use of gas by a NFS customer of Buyer, Seller shall
nonetheless be obligated to deliver to Buyer the associated gas quantity, but
Seller shall be entitled to the aggregate amount of any Tariff charges received
by

                                       1
<PAGE>
 
Buyer for such unauthorized usage, net of reimbursement of Buyer's actual LNG
trucking costs or incremental LNG operating costs incurred as a result of such
usage. In order to facilitate Seller's planning processes, [Confidential
Treatment Requested] that were attributable to such customers as soon as
thereafter as practicable. Seller shall notify Buyer promptly (and, where
practicable, on three (3) Business Day's notice) of any condition which, in
Seller's opinion, would make the curtailment or interruption of Buyer's NFS
customers necessary in order to continue to supply the gas requirements of the
Buyer's Firm Customers. Any interruption or curtailment of Buyer's NFS
customers, however, shall be effected by Buyer in its sole discretion in
accordance with the provisions of Buyer's Tariff. Buyer may interrupt its NFS
customers as needed to protect system integrity and operations. Buyer shall give
Seller promptly (and, where practicable, on three (3) Business Day's notice) of
any condition which, in Buyer's opinion would make interruption of NFS customers
necessary.

3.1.3. Seller's Supply Warranty. Seller represents and warrants that it will 
       ------------------------
have and maintain a supply of Gas capable of being delivered to the Delivery 
Points, which will include LNG as described in the Asset Management Agreement, 
sufficient to satisfy Buyer's Requirements Quantity.

3.1.4. Gas- Related Transportation Obligations. As exclusive compensation for 
       ---------------------------------------
servicing Gas-Related Transportation Requirements, Seller shall be entitled to 
receive the net amount of incremental Tariff charges and credits for such 
services received by Buyer, including any associated penalties or charges for 
unauthorized use or daily or monthly imbalances, as calculated in accordance 
with Buyer's Tariff. In the event of unauthorized use of gas or the creation of 
imbalances by a transportation customer of Buyer, Seller shall nonetheless be 
obligated to deliver to Buyer the associated gas quantity, but Seller shall be 
entitled to any charges for such unauthorized usage or imbalance received by 
Buyer, as provided in the preceding sentence. In order to facilitate Seller's 
planning processes, Buyer shall periodically make available to Seller Buyer's 
load data respecting its transportation customers and identify the quantity of 
Buyer's requirements for each Day that were attributable to its transportation 
customers as soon thereafter as practicable.

3.2. Seller's Failure to Deliver. If on any Gas Day Seller fails to deliver 
     ---------------------------
Buyer's Requirements Quantity, then such occurrence shall constitute a "Seller's
Deficiency Default" and "Seller's Deficiency Quantity" shall be the numerical
difference between the actual Buyer's Requirements Quantity and the amount of
Gas actually delivered for such Gas Day. In the event of a Seller's Deficiency
Default where Buyer is able to replace Seller's Deficiency Quantity, Seller
shall pay Buyer as damages an amount equal to the product of the Seller's
Deficiency Quantity multiplied by the Replacement Price Differential. In the
event Buyer is unable to replace Seller's Deficiency Quantity, Buyer's
liquidated damages shall equal the Non-Replacement Price Differential multiplied
by Seller's Deficiency Quantity. Payment to Buyer shall be made on the 25th Day
of the Month in which Seller receives Buyer's statement for same. The
availability of

                                       2



 












<PAGE>
 
this remedy will not relieve Seller of its obligation to stand ready to and 
actually to deliver Buyer's Requirements Quantity during the term of this 
Agreement.

3.3.  Buyer's Notification and Purchase Obligations.  Buyer shall notify Seller 
      ---------------------------------------------
of the quantity of Gas it will require in accordance with the definition of 
Scheduling as it pertains to Buyer as provided in Appendix 1 and in Section 3.1 
with respect to Interruptible Sales and Gas-Related Transportation. Buyer will 
receive at the Deliver Points each Gas Day a quantity of Gas equal to Buyer's 
Requirements Quantity.

3.4.  Preclusion of Buyer's Purchase of Gas From Others.  If on any Gas Day, 
      -------------------------------------------------
Buyer purchases from a third party any portion of Buyer's Requirements Quantity 
for which delivery is tendered by Seller, then such occurrence shall constitute 
a "Buyer's Deficiency Default" and "Buyer's Deficiency Quantity" shall be the 
quantity of Gas Buyer purchased from third parties on such Gas Day. In the 
event of a Buyer's Deficiency Default, Buyer shall pay Seller an amount equal to
the product of Buyer's Deficiency Quantity multiplied by the Replacement Price 
Differential. Payment to Seller shall be made in accordance with the Financial 
Matters provisions set forth in Appendix "1".

ARTICLE 4.  DEFAULTS AND REMEDIES 4.1.  Early Termination.  If a Triggering 
                                        -----------------
Event (defined in Section 4.2) occurs with respect to either Party at any time 
during the term of this Agreement, the other Party (the "Notifying Party") may 
(i) upon two (2) Business Days written notice to the first Party, which notice 
shall be given no later than Sixty (60) Days after the discovery of the 
occurrence of the Triggering Event, establish a date on which this Agreement 
will terminate ("Early Termination Date") except as provided in Section 9.4, and
(ii) withhold any payments due; provided, upon the occurrence of any Triggering 
Event listed in item (iv) of Section 4.2 as it may apply to any party, a Party 
may at its sole option declare that this Agreement shall terminate, without 
notice, as if an Early Termination Date had been immediately declared except as 
provided in Section 9.4. If an Early Termination Date occurs, the Notifying 
Party shall in good faith calculate its damages, including its associated costs 
and attorneys' fees, resulting from the termination of this Agreement (the 
"Termination Payment"). The Termination Payment will equal (i) the difference 
between the value of (a) the remaining term, quantities and prices under this 
Agreement had it not been terminated and (b) the equivalent quantities and 
relevant market prices for the remaining term either quoted by a bona fide third
party offer or, at Notifying Party's sole option, which are reasonably expected 
to be available in the market under a replacement contract for such Agreement; 
plus (ii) the liquidated value of any hedge positions pursuant to Exhibit B; and
(iii) reasonable transaction associated costs and attorneys' fees. To ascertain 
the market prices of a replacement contract the Notifying Party may consider, 
among other valuations, any or all of the settlement prices of NYMEX Gas futures
contracts, at the applicable delivery point, and/or the Exchange Price, 
quotations from leading dealers in Gas swap contracts and other bona fide third 
party offers, all adjusted for the length of the remaining term and the Basis 
Difference. If the calculation of the Termination Payment does not result in 
damages to the Notifying Party, the Termination Payment shall be zero. The 
Notifying Party shall give the Affected Party (defined in Section 4.2) written 
notice of the amount of the Termination Payment, inclusive of a statement 
showing its determination. The

                                       3
<PAGE>
 
Affected Party shall pay the Termination Payment to the Notifying Party within 
ten (10) Days of receipt of such notice. At the time for payment of any amount 
due under this Article 4, each Party shall pay to the other Party all additional
amounts payable by its pursuant to this Agreement, but all such amounts shall be
netted and aggregated with any Termination Payment payable hereunder.

4.2.  Triggering Event shall mean, with respect to a Party (the "Affected 
      ----------------
Party"):  (i) the failure by the Affected Party to make, when due, any payment 
required under this Agreement if such failure is not remedied within five (5) 
Business Days after written notice of such failure is given to the Affected 
Party; provided, the payment is not the subject of a good faith dispute as 
described in the Billing and Payment provisions in Appendix 1, or (ii) any 
material representation or warranty made by the Affected Party in this Agreement
shall prove to have been false or misleading in any material respect when made 
or deemed to be repeated and such representation or warranty is an essential and
material part of the bargain of the Parties, or (iii) the failure by the 
Affected Party to perform any material obligation set forth in this Agreement 
(other than its obligations to make any payment or obligations which are 
otherwise specifically covered in this Section 4.2. as a separate Triggering 
Event), and such failure is not excused by Force Majeure or cured within five 
(5) Business Days after written notice thereof is given to the Affected Party or
(iv) the Affected Party shall (a) make an assignment or any general arrangement 
for the benefit of creditors, (b) file a petition or otherwise commence, 
authorize or acquiesce in the commencement of a proceeding or cause under any 
bankruptcy or similar law for the protection of creditors, or have such petition
filed against it and such proceeding shall not have been dismissed for thirty 
(30) Days, (c) otherwise become bankrupt or insolvent (however evidenced) or (d)
be unable to pay its debts as they fall due or (v) Seller's unexcused failure to
deliver Buyer's Requirements Quantity for a cumulative period of three (3) or 
more Gas Days in a twelve (12) Month period or a cumulative period of five (5) 
Gas Days during the term of this Agreement, or (vi) Buyer's unexcused failure to
receive its Requirements Quantity, for a cumulative period of three (3) or more 
Gas Days in twelve (12) Month period or a cumulative period of five (5) Gas Days
during the term of this Agreement, (vii) an event of any material default in 
respect of the Asset Management Agreement or (ix) Seller's unexcused failure to 
deliver a sufficient quantity of Gas, which failure directly causes Buyer to be 
unable to serve its Firm Customers on any Gas Day, or (x) the continuance of a 
Force Majeure event rendering the affected Party unable to carry out its 
obligations hereunder in excess of the periods permitted in accordance with 
Article 5, or (xi) the failure to provide additional security in accordance with
the provisions of Section 4.5 or Paragraph 7 of Appendix "1", within two (2) 
Business Days from the date of request.

4.3.  Other Events.  If the Affected Party's activities hereunder are affected 
      ------------
by any law, regulation or governmental action unknown or unplanned to a 
materially greater or different extent than that existing on the Effective Date 
and such event either (i) renders this Agreement illegal or unenforceable or 
(ii) materially adversely effects the application of this Agreement to the 
Affected Party, with respect to its financial position or otherwise, then upon 
request of either Party, the Parties will in good faith attempt to renegotiate 
the terms of the Agreement to respond to such change, but, if they fail to do so
after a period of 30 Days, in the case of (i) above, either 

                                       4
<PAGE>
 
Party, and in the case of (ii) above, only the Affected Party, shall at such
time have the right to declare an Early Termination Date in accordance with the
provisions hereof; provided, notwithstanding the rights of the Parties to
declare an Early Termination Date as above stated, the Affected Party shall be
liable for payment of the Termination Payment calculated by the non-Affected
Party as provided in Section 4.1.
                     -----------

4.4. Offset. Each Party reserves to itself all rights, set-offs, counterclaims 
     ------
and other remedies and defenses consistent with Section 9.3 (to the extent not 
                                                -----------
expressly herein waived or denied) which such Party has or may be entitled to 
arising from or out of this Agreement. The obligations to make payment under 
this Agreement may be offset against each other, set off or recouped therefrom.

4.5. Security. In the event either Seller or Buyer fails to maintain a credit 
     --------
rating as published by Standard and Poor's of at least "BBB" or Moody's 
Investors Services, Inc. of "Baa2", then within fifteen (15) days of such 
occurrence, (i) in the case of Seller, Seller shall either (a) cause each of 
Duke Capital Corporation and Mobil Corporation to provide a Guarantee of 
Seller's remaining obligations under this Agreement, or (b) provide a Letter of
Credit satisfactory to Buyer in an amount to be determined at the time of such 
event, and (ii) in the case of Buyer, Buyer shall either (a) maintain a 
prepayment balance with Seller equal to two month's purchase obligation on the 
first business day of each such month in an escrow account established on 
standard commercial terms with a financial institution acceptable to Seller that
will act as escrow agent for the Payment of such balances to satisfy the 
obligations of Buyer arising hereunder for such months, with interest on such 
account balance to accrue and be disbursed monthly to Buyer, unless required to 
make payment to Seller hereunder or to maintain the required monthly escrow 
balance, or (b) provide a Letter of Credit satisfactory to Seller sufficient to 
cover two (2) months worth of purchase obligations.

4.6. Curtailment Priority. In the event Seller fails to deliver all or any part 
     --------------------
of the Requirements Quantity, whether or not such failure is excused under the
terms of this Agreement, Buyer, pursuant to the terms and conditions of its
Tariff, and applicable regulations, shall curtail its Customers pursuant to the
emergency load shedding policies of the Rhode Island Public Utility Commission.

ARTICLE 5. FORCE MAJEURE. Except with respect to payment obligations, in the 
------------------------
event either Party is rendered unable, wholly or in part, by Force Majeure to
carry out its obligations hereunder, it is agreed that upon such Party's giving
notice and full particulars of such Force Majeure to the other Party as soon as
reasonably possible (such notice to be confirmed in writing), the obligations of
the Party giving such notice, to the extent they are affected by such event,
shall be suspended from the inception and during the continuance of the Force
Majeure for a period of up to sixty (60) Days in the aggregate during any twelve
(12) Month period, but for no longer period. Except as provided in Exhibit B,
the Party receiving notice of Force Majeure may immediately take such action as
it deems necessary at its expense for the entire sixty (60) Day period or any
part thereof. The Parties expressly agree that upon the expiration of

                                       5

<PAGE>
 
the sixty (60) Day period Force Majeure shall no longer apply to the obligations
hereunder and both Buyer and Seller shall be obligated to perform. The cause of 
the Force Majeure shall be remedied with all reasonable diligence and dispatch.

ARTICLE 6. TAXES 6.1 Allocation of and Indemnify for Taxes.  The Contract Price
----------------     ------------------------------------- 
includes full reimbursement for, and Seller is liable for and shall pay, or 
cause to be paid, or reimburse Buyer if Buyer has paid, all Taxes applicable to 
the Gas prior to its delivery at the Delivery Points; provided that Buyer will 
be responsible for any inventory tax on Gas held in storage, including LNG 
storage, to the extent the storage service is subject to the Asset Management 
Agreement. In the event Buyer is required to remit such Tax, the amount thereof 
shall be deducted from any sums becoming due to Seller hereunder. Seller shall 
indemnify, defend and hold harmless Buyer from any Claims for such Taxes. The 
Contract Price does not include reimbursement for, and Buyer is liable for and 
shall pay, cause to be paid, or reimburse Seller if Seller has paid, all Taxes 
applicable to the Gas at and after the Delivery Points, including local property
Taxes assessed upon the value of storage Gas held in inventory pursuant to the 
Asset Management Agreement referenced in Article 8 hereof. Buyer shall 
indemnify, defend and hold harmless Seller from any Claims for such Taxes.

6.2  Cooperation.  Upon request, a Party shall provide a certificate of 
     -----------
exemption or other evidence of exemption from any Tax and each Party agrees to 
cooperate with the other in obtaining an exemption and minimizing Taxes payable 
under this Agreement.

ARTICLE 7. TITLE, RISK OF LOSS, INDEMNITY AND BALANCING 7.1 Title, Risk of loss 
-------------------------------------------------------     -------------------
and Indemnity. As between the Parties, Seller shall be deemed to be in exclusive
-------------
control and possession of Gas Schedule hereunder and responsible for any damage
or injury caused thereby prior to the time the same shall have been delivered to
Buyer at the Delivery Points. At and after delivery of Gas to Buyer at the
Delivery Points, Buyer shall be deemed to be in exclusive control and possession
thereof and responsible for any injury or damage caused thereby. Title to Gas
Schedule hereunder shall pass from Seller to Buyer at the Delivery Points.
Seller and Buyer each assumes all liability for and shall indemnify, defend and
hold harmless the other Party from any Claims, including injury to and death of
persons, arising from any act or incident occurring when title to the Gas is
vested in the indemnifying Party. IT IS THE INTENT OF THE PARTIES THAT THIS
INDEMNITY AND THE LIABILITY ASSUMED UNDER THIS SECTION BE WITHOUT REGARD TO THE
CAUSE OR CAUSES THEREOF, INCLUDING, WITHOUT LIMITATION, THE NEGLIGENCE OF ANY
INDEMNIFIED PARTY, WHETHER SUCH NEGLIGENCE BE SOLE, JOINT OR CONCURRENT, OR
ACTIVE OR PASSIVE; PROVIDED, NEITHER PARTY SHALL BE LIABLE IN RESPECT OF ANY
CLAIM TO THE EXTENT SAME RESULTED FROM THE GROSS NEGLIGENCE, WILLFUL MISCONDUCT
OR BAD FAITH OF THE INDEMNIFIED PARTY.

                                       6
<PAGE>
 
7.2. Correction of Imbalances, Cashouts and Penalties.  Seller shall be
     ------------------------------------------------
responsible for any imbalance penalties on any interstate pipeline, unless
caused by Buyer's failure to give proper and/or timely notice in accordance with
Section 3.3 above.
    
ARTICLE 8. ASSET MANAGEMENT AGREEMENT.  In connection with this Agreement, Buyer
-------------------------------------
will release or assign to Seller by mutually agreeable instrument of transfer
and Seller will take responsibility for all Gas supply and transportation assets
of Buyer that are currently used by Buyer to serve Buyer's Requirements
Quantity, including, without limitation, Buyer's interstate pipeline
transportation and storage contracts, Buyer's contracts for the purchase of Gas,
and Buyer's LNG storage and purchase contracts, all of which collectively are
referred to as the "Gas Assets," with the mutually agreeable instrument of
transfer referred to as the "Asset Management Agreement." The Asset Management
Agreement will include, among others, provisions regarding the following
matters: (i) the release or assignment by Buyer to Seller of Buyer's Gas Assets;
(ii) the agreement by Buyer and Seller to execute any necessary consent, release
or assignment document needed by either Party to effectuate the transfer of the
Gas Assets as contemplated by the Parties; (iii) the agreement by Seller to take
full responsibility for the burdens and management of all the Gas Assets and
associated contracts transferred by the Asset Management Agreement, including
payment of all charges, penalties or fees associated with such Gas Assets and
assumption of all liability arising from such Gas Assets or their associated
contracts from the date of transfer; (iv) the corresponding agreement of Buyer
to permit Seller to obtain the full value of any benefits associated with the
Gas Assets and associated contracts from the date of transfer; (v) the agreement
by Buyer to permit Seller to manage the Gas Assets on a daily basis as Seller
determines in its sole discretion; (vi) the corresponding agreement by Seller to
refrain from taking any action that would modify beyond the term of this
Agreement the provisions of a contract related to a Gas Asset or impair the
value of any of the Gas Assets without Buyer's written consent; (vii) the
agreement by Seller to transfer the Gas Assets back to Buyer upon termination of
this Agreement or for other specified reasons of default; (viii) the agreement
by Seller to provide Buyer with specific information concerning management of
the Gas Assets to permit Buyer to be assured that Seller will be capable of
satisfying its obligation under Article 3 of this Agreement, including in
particular, information concerning LNG storage and use; (ix) the agreement that
notwithstanding such arrangements, Buyer shall retain the exclusive possession
and control of all its physical operating facilities; (x) the agreement that the
amount payable to Seller shall be subject to adjustment from time to time
pursuant to a "Tracker Agreement" to reflect changes in the demand charges
payable by Seller pursuant to pipeline transportation or storage contracts
assigned thereunder and changes in the economic value of gas assets attributable
to interim modifications thereto effected by Buyer; and (xi) the agreement by
the Parties to permit a Party to use injunctive or other equitable relief to
enforce the provisions of the Asset Management Agreement.

ARTICLE 9. MISCELLANEOUS 9.1. Notices.  All notices, including, without 
------------------------      -------
limitation, consents, and communications made pursuant to this Agreement shall 
be made as specified in Exhibit "A." Notices required to be in writing shall be 
delivered in written form by letter,

                                       7

<PAGE>
 
facsimile or other documentary form. Notice by facsimile or hand delivery shall 
be deemed to have been received by the close of the Business Day on which it was
transmitted or hand delivered (unless transmitted or hand delivered after close 
in which case it shall be deemed received at the close of the next Business Day)
or such earlier time confirmed by the receiving Party. Notice by overnight mail 
or courier shall be deemed to have been received two Business Days after it was 
sent or such earlier time confirmed by the receiving Party. Notices by US Mail 
shall be deemed received by the recipient four (4) days after being sent. Any 
Party may change its addresses by providing notice of same in accordance 
herewith.

9.2.  Transfer.  This Agreement, including, without limitation, each 
      --------
indemnification, shall inure to and bind the permitted successors and assigns of
the Parties; provided, neither Party shall transfer this Agreement without the 
prior written approval of the other Party which may not be unreasonably 
withheld; provided further, either Party may transfer its interest to any parent
or affiliate by assignment, merger or otherwise without the prior approval of 
the other Party; provided that no such transfer will materially impair 
performance under this Agreement and provided further that no such transfer 
shall operate to relieve the transferor Party of its obligations hereunder. Any 
Party's transfer in violation of this Section 9.2 shall be void.

9.3.  Limitation of Remedies. Liability and Damages and Mitigation.  THE PARTIES
      ------------------------------------------------------------
DO HEREBY CONFIRM THAT THE EXPRESS REMEDIES AND MEASURES OF DAMAGES PROVIDED IN
THIS AGREEMENT SATISFY THE ESSENTIAL PURPOSES HEREOF. FOR BREACH OF ANY 
PROVISION FOR WHICH AN EXPRESS REMEDY OR MEASURE OF DAMAGES IS HEREIN PROVIDED, 
SUCH EXPRESS REMEDY OR MEASURE OF DAMAGES SHALL BE THE SOLE AND EXCLUSIVE REMEDY
HEREUNDER, THE OBLIGOR'S LIABILITY SHALL BE LIMITED AS SET FORTH IN SUCH 
PROVISION AND ALL OTHER REMEDIES OR DAMAGES AT LAW OR IN EQUITY ARE WAIVED. IF 
NO REMEDY OR MEASURE OF DAMAGES IS EXPRESSLY HEREIN PROVIDED, THE OBLIGOR'S 
LIABILITY SHALL BE LIMITED TO DIRECT ACTUAL DAMAGES ONLY, SUCH DIRECT ACTUAL 
DAMAGES SHALL BE THE SOLE AND EXCLUSIVE REMEDY HEREUNDER AND ALL OTHER REMEDIES 
OR DAMAGES AT LAW OR IN EQUITY ARE WAIVED. UNLESS EXPRESSLY HEREIN PROVIDED, 
NEITHER PARTY SHALL BE LIABLE FOR CONSEQUENTIAL, INCIDENTAL, PUNITIVE, EXEMPLARY
OR INDIRECT DAMAGES, LOST PROFITS OR OTHER BUSINESS INTERRUPTION DAMAGES, IN 
TORT, CONTRACT, UNDER ANY INDEMNITY PROVISION OR OTHERWISE. IT IS THE INTENT OF 
THE PARTIES THAT THE LIMITATIONS HEREIN IMPOSED ON REMEDIES AND THE MEASURE OF 
DAMAGES BE WITHOUT REGARD TO THE CAUSE OR CAUSES RELATED THERETO, INCLUDING, 
WITHOUT LIMITATION, THE NEGLIGENCE OF ANY PARTY, WHETHER SUCH NEGLIGENCE BE 
SOLE, JOINT OR CONCURRENT, OR ACTIVE OR PASSIVE. TO THE EXTENT ANY DAMAGES 
REQUIRED TO BE PAID HEREUNDER ARE LIQUIDATED, THE PARTIES ACKNOWLEDGE THAT THE 
DAMAGES ARE DIFFICULT OR IMPOSSIBLE TO DETERMINE, OTHERWISE OBTAINING AN 
ADEQUATE REMEDY IS INCONVENIENT AND THE LIQUIDATED DAMAGES CONSTITUTE A 
REASONABLE APPROXIMATION OF THE HARM OR LOSS. The Parties acknowledge the duty 
to mitigate damages hereunder. 

                                       8
<PAGE>
 
Each Party may utilize its discretion, with commercially reasonable foresight,
to adjust the timing and staggering of the purchases or sales of Gas quantities
in its efforts to mitigate damages. No claim that a Party failed to mitigate
damages shall be grounded solely on the basis of counter Gas market movement.

9.4.  Winding Up Arrangements. Upon the expiration of the Parties' sale and 
      -----------------------     
purchase obligations under this Agreement, any monies, penalties or other
charges due and owing Seller shall be paid, any corrections or adjustments to
payments previously made shall be determined, and any refunds due Buyer made,
within 60 Days. Any imbalances in receipts or deliveries shall be corrected to
zero balance within 60 Days. All indemnity and confidentiality obligations and
audit rights shall survive the termination of this Agreement. The Parties'
obligations provided in this Agreement shall remain in effect after such
expiration solely for the purpose of complying with this winding-up Section 9.4.

9.5.  Applicable Law. THIS AGREEMENT AND THE RIGHTS AND DUTIES OF THE PARTIES 
      --------------
ARISING OUT OF THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED, ENFORCED AND 
PERFORMED IN ACCORDANCE WITH THE LAWS OF THE STATE OF RHODE ISLAND, WITHOUT 
REGARD TO PRINCIPLES OF CONFLICTS OF LAW, AND ANY PROCEEDING BROUGHT TO ENFORCE 
ANY PROVISION OF THIS AGREEMENT WILL BE BROUGHT IN A COURT IN THE STATE OF RHODE
ISLAND.

9.6.  Entire Agreement Evidence of Agreement, Modification, No Third Party 
      -------------------------------------------------------------------
Beneficiary, Severability, Headings and Incorporation by Reference. This 
------------------------------------------------------------------
Agreement, the Exhibits and Appendices hereto, if any, constitute the entire 
agreement between the Parties relating to the subject matter contemplated by 
this Agreement. There are no prior or contemporaneous agreements or 
representations (whether oral or written) affecting the subject matter other
than those herein expressed. No amendment or modification to this Agreement
shall be enforceable, unless reduced to writing and executed by both Parties.
The provisions of this Agreement shall not impart rights enforceable by any
person, firm or organization not a Party or not bound as a Party, or not a
permitted successor or assignee of a Party bound to this Agreement. Except as
otherwise herein stated, any provision, article or section declared or rendered
unlawful by a court of law or regulatory agency with jurisdiction over the
Parties or deemed unlawful because of a statutory change will not otherwise
affect the lawful obligations that arise under this Agreement. The headings used
for the Articles herein are for convenience and reference purposes only. All
Exhibits and Appendices references in this Agreement, if any, are incorporated.

9.7.  Confidentiality. Each Party will not disclose the terms of this Agreement 
      ---------------
to a third party (other than the Party's and its affiliates' employees, lenders,
counsel, accountants or prospective purchasers of any rights who have agreed to 
keep such terms confidential) except in order to comply with any applicable law,
order, regulation or exchange rule; provided, each Party shall notify the other 
Party of any proceeding of which it is aware which may result in disclosure and 
use reasonable efforts to prevent or limit the disclosure. Seller further agrees
not to disclose or utilize for its competitive benefit information gained 
hereunder respecting Buyer's operations that is not readily or generally known 
to other gas marketers doing business in Rhode Island,

                                       9
<PAGE>
 
including customer lists and customer specific usage information The Parties
shall be entitled to all remedies available at law or in equity to enforce, or
seek relief in connection with, this confidentiality obligation; provided, all
monetary damages shall be limited in accordance with Section 9.3; and provided
further, that each Party will only be required with respect to the obligations
regarding confidentiality to exercise such care in maintaining the
confidentiality of this Agreement as it normally exercises in preserving the
confidentiality of its other commercially sensitive documents. If a Party (the
"Receiving Party") is requested or required to make a disclosure of such
information pursuant to law, legal process or a regulatory request or
requirement, the Receiving Party will notify the other Party (the "Disclosing
Party") of such request or requirement as soon as reasonably possible so that
the Disclosing Party may pursue all available remedies to prevent such
disclosure including, but not limited to, a protective order. The Receiving
Party shall cooperate with the Disclosing Party in any attempt by the Disclosing
Party to prevent such a disclosure and, if required to disclose any of the
confidential information despite attempts by the Disclosing Party to prevent
same, will disclose only that part that it is required to disclose.
Notwithstanding the above, Buyer may, under appropriate requests for
confidentiality protections from a regulatory body with jurisdiction over Buyer,
which may or may not be granted, disclose and discuss this Agreement with any
such regulatory body, and either Party may disclose the existence of this
Agreement, but not the specific pricing terms, to a pipeline if required to
effectuate this Agreement or the Asset Management Agreement, provided that a
confidentiality agreement has been executed with such pipeline.

9.8 Counterparts.  The Parties have executed this Agreement in multiple 
----------------
counterparts to be construed as one effective as of the Effective Date;


DUKE ENERGY TRADING AND MARKETING, L.L.C.

Name /s/ Donald Sinclair 
     -----------------------------------------
 
Title ________________________________________



THE PROVIDENCE GAS COMPANY


Name /s/ James Demetro 
     -----------------------------------------
 
Title Senior Vice President
      ----------------------------------------

                                      10

<PAGE>
 
                                 APPENDIX "1"
                              GENERAL PROVISIONS

Paragraph 1.  USAGE AND DEFINITIONS: All references to Articles and Sections are
              --------------------- 
to those set forth in this Agreement. Reference to any document means such 
document as amended from time-to-time and reference to any Party includes any 
permitted successor or assignee thereof. The following definitions and any terms
defined internally in this Agreement shall apply to this Agreement and all 
notices and communications made pursuant to this Agreement.

     "Asset Management Agreement" means the agreement so titled between Buyer 
      --------------------------    
     and Seller dated as of the date hereof.

     "Asset Management Contracts" shall mean those transportation, storage, or
      --------------------------    
     supply agreements identified in the Asset Management Agreement that are
     either assigned to Seller or managed by Seller on Buyer's behalf.

     "Basis Difference" shall mean the difference that may exist for any period 
      ----------------    
     between the Exchange Price and the Spot Price at the Delivery Point.

     "Btu" means the amount of energy required to raise the temperature of one 
      ---
     pound of pure water one degree Fahrenheit from 59 degrees Fahrenheit to 60
     degrees Fahrenheit.

     "Business Day" means a Day on which Federal Reserve member banks in New 
      ------------
     York City are open for business and a Business Day shall open at 8:00 a.m.
     and close of 6:00 p.m. local time.

     "C.T." means prevailing Central Time.
      ----

     "Claims" means all claims or actions, threatened or filed and whether
      ------
     groundless, false or fraudulent, that directly or indirectly relate to the
     subject matters of the indemnity, and the resulting losses, damages,
     expenses, attorneys' fees and court costs, whether incurred by settlement
     or otherwise, and whether such claims or actions are threatened or filed
     prior to or after the termination of this Agreement.

     "Contract Price" means the price for the purchase or sale of Gas pursuant 
      --------------
     to this Agreement.

     "Day" means a period of 24 consecutive hours, beginning at midnight C.T. on
      ---
     any calendar Day.

     "Delivery Point(s)" means the appropriate points of delivery into Buyer's 
      -----------------
     System.

     "Exchange Price" means the price for any specified delivery months as 
      --------------
     established by trading natural gas futures on the New York Mercantile
     Exchange covering such delivery

                                       1
<PAGE>
 
     months for Henry Hub.

     "Firm Customers" means all customers of Buyer receiving services under firm
      --------------
     sales rate schedule.

     "Force Majeure" means an event not anticipated as of the Effective Date,
      -------------    
     which is not within the reasonable control of the Party, or in the case of
     third party obligations of facilities, the third party claiming suspension
     and which by the exercise of due diligence such Party, or third party, is
     unable to overcome or obtain or cause to be obtained a commercially
     reasonable substitute performance therefor; provided neither (i) the loss
     of Buyer's markets nor Buyer's inability economically to use or resell Gas
     purchased hereunder nor (ii) the loss or failure of Seller's Gas supply
     including, without limitation, depletion of reserves or other failure of
     production except as provided in the Asset Management Contracts, nor
     Seller's ability to sell Gas to a market at a more advantageous price,
     shall constitute an event of Force Majeure, "Force Majeure" shall include
     an event of Force Majeure occurring with respect to the facilities or
     services of the Buyer's or Seller's Transporter and incorporates by
     reference Force Majeure as defined by the Asset Management Contracts.

     "GAAP" means generally accepted accounting principles, consistently 
      ----
     applied.

     "Gas" means methane and other gaseous hydrocarbons or liquefied natural gas
      ---     
     ("LNG") meeting, with respect to non-LNG, the quality standards and
     specifications of the Transporter used to deliver the Gas at the Delivery
     Points or with respect to LNG, of such quality that it does not impair the
     proper operation of the storage facility or vaporization equipment used for
     such LNG.

     "Gas Day" means a period of twenty-four (24) consecutive hours beginning at
      -------
     the time of the applicable Transporter's gas Day.

     "Gas-Related Transportation Requirements" means the delivery and
      ---------------------------------------
     availability to Buyer of the full quantity of gas and capacity resources
     required to meet Buyer's gas-related obligations under its transportation
     rate schedules or the successors thereto, including obligations as to daily
     and monthly balancing (including "cash-outs"), pool balancing services,
     assignment to and utilization by FT-2 transportation customers of storage
     resources, and the assignment and release of designated pipeline capacity
     to transportation customers, all in accordance with the provisions of the
     Tariff as in effect from time to time.

     "Indemnified Party" and "Indemnifying Party" means the Party receiving and 
      -----------------       ------------------
     providing an Indemnity, respectively.

     "Interest Rate" means, for any date, two percent over the per annum rate of
      -------------
     interest announced as the "Prime Rate" from time-to-time for commercial
     loans by Citibank,

                                       2
<PAGE>
 
N.A. as established by the administrative body of such bank charged with the 
responsibility of establishing such rate, as same may change from time-to-time;
provided, the Interest Rate shall never exceed the maximum lawful rate permitted
by applicable law.

"Interruptible Sales Requirements" means the delivery to Buyer of the full 
 --------------------------------
quantity of gas required to meet Buyer's obligations to its interruptible 
customers under its Non-Firm Sales Service rate schedule, Rate-60 ("NFS") or its
less than 365 Day Cogeneration Services rate schedule, Rate 50 (S)2, or the 
successors thereto, or pursuant to its November 1993 Contract with the
(Confidential Treatment Requested)

"Letter of Credit" means an irrevocable letter of credit, issued by a financial 
 ----------------
institution who holds a minimum credit rating as published by Standard and 
Poor's of "BBB-" or Moody's Investors Services, Inc. of "Baal", and acceptable 
to the party whose favor the letter of credit is issued, such acceptance not to 
be unreasonably or arbitrarily withheld.

"MMBtu" means one million Btus.
 -----

"Month" means a period of time beginning at midnight C.T. on the first Day of 
 -----
any calender Month and ending at midnight C.T. on the first Day of the following
calender Month.

"Non-Replacement Price Differential" means the positive difference, if any, 
 ----------------------------------
obtained by subtracting the Contract Price from the greater of (i) 110% of 
                                           ----     -------
the average Spot Price for that Gas Day for any location in the United States 
east of Rocky Mountains, or (ii) the actual pipeline penalty charge for 
unauthorized takes or overruns incurred by Buyer as a result of Seller's 
failure.

"Operational Needs" means the Gas needed by Buyer to satisfy all system 
 -----------------
integrity, balancing and physical operational requirements, plus any Gas 
required to satisfy the Gas-Related Transportation Requirements and 
Interruptible Sales Requirements.

"Period of Delivery" means the period from the date Scheduling obligations are 
 ------------------
to commence to the date same are to terminate.

"Pipeline" means a company authorizes to ship Gas on behalf of itself or others 
 --------
on physical Gas transmission facilities.

"Replacement Price Differential" means (i) in the event of a Seller's Deficiency
 ------------------------------
Default, the positive difference, if any, obtained by subtracting the Contract
Price from the sum of (a) the cost to Buyer, including incremental 
transportation costs and other basis adjustments, or penalty charges incurred, 
to replace Seller's Deficiency Quantity for such Gas Day plus (b) 25% of that 
total delivered cost as an administrative charge representing liquidated damages
to cover Buyer's costs in arranging for such replacement supply; and

                                       3


<PAGE>
 
(ii) in the event of a Buyer's Deficiency Default the sum of (a) the positive 
difference between the Contract Price and the price to Seller, subtracting all 
incremental costs incurred by Seller, received in reselling the Gas to a third
party; and (b) twenty-five percent (25%) of that total delivered cost as an 
administrative charge representing liquidated damages to cover Seller's costs in
arranging such sales.

"Requirements Quantity" means the quantity of Gas on any Gas Day that is needed 
 --------------------    
to serve the full requirements of Buyer on that Gas Day, which includes Gas 
required by Buyer for its Firm Customers and Gas required by Buyer to serve its 
Operational Needs; provided that in no event will the Requirements Quantity on 
any Gas Day be greater than the sum of Buyer's maximum daily transportation 
quantities (excluding transportation of storage withdrawal quantities), plus 
Buyer's maximum daily storage withdrawals, plus Buyer's maximum daily LNG 
withdrawals, all as provided in the Asset Management Agreement.

"Scheduling" or "Schedule" means that (i) with respect to Seller, Seller shall 
 ----------      -------- 
arrange for the delivery of the quantity of gas required to meet Buyer's system
demand at each Delivery Point during the Gas Day, as provided in the Asset
Management Agreement. In connection with this obligation, Seller shall utilize
the no-notice and intra-day capabilities embedded in the supply resources
detailed in the Asset Management Agreement to provide for unanticipated changes
in Buyer's projected requirements; and (ii) with respect to Buyer, Buyer will
cooperate with Seller in the development of seasonal, monthly and daily
operational plans to assist in the determination of Buyer's Requirements
Quantity and will provide Seller with (a) a preliminary Requirements Quantity on
the Day prior to gas flow, (b) information on gas scheduled for delivery to
serve Buyer's transportation service customers, (c) updates of the projected
Requirements Quantity as weather and Buyer's operating conditions change, (d)
notification regarding specific operational needs of Buyer at specific Delivery
Points and (e) other information as specified in the Asset Management Agreement.

"Spot Price" means the price set forth in Gas Daily(R) (Pasha Publications, 
 ----------
Inc.), or successor publication, in the column "Daily Price Survey" under the 
listing applicable to the geographic location agreed for the relevant Gas Day.
If there is no single price published for that particular Gas Day, but there is 
published a range of prices under the above column and listing, then the Spot 
Price shall be the average of such high and low prices.  In the event that no 
price or range of prices is published for that particular Gas Day, then the Spot
Price shall be the average of the following: the price (determined as stated 
above) for each of the first Gas Day immediately preceding and following the Gas
Day in which the default occurred for which a Spot Price can be determined.

"Tariff" means the tariff of the Providence Gas Company on file with the Rhode 
 ------
Island Public Utilities Commission, RI-PUC-PGC-NO.100, to the successor thereto.

"Taxes" means any or all ad valorem, property, occupation, severance, 
 -----
production,

                                       4





<PAGE>
 
     extraction, first use, conservation, Btu or energy, gathering, transport,
     Pipeline, utility, gross receipts, gas or oil revenue, gas or oil import,
     privilege, sales, use, consumption, excise, lease, transaction, and other
     or new taxes, governmental charges, licenses, fees, permits and
     assessments, or increases therein, other than taxes based on net income or
     net worth.

     "Transporter" means either the Pipeline delivering or receiving Gas at a 
      -----------
     Delivery Point.

Paragraph 2. Representations and Warranties. As a material inducement to 
             ------------------------------
entering into this Agreement, each Party, with respect to itself, hereby 
represents and warrants to the other Party continuing throughout the term of 
this Agreement as follows: (i) there are no suits, proceedings, judgments, 
rulings or orders by or before any court or any governmental authority that 
materially adversely affect its ability to perform this Agreement or the rights 
of the other Party under this Agreement, (ii) it is duly organized, validly 
existing and in good standing under the laws of the jurisdiction of its 
formation, and it has the corporate right, power and authority and is qualified 
to conduct its business, and to execute and deliver this Agreement and perform 
its obligations under the same, and all regulatory authorizations have been 
maintained as necessary for it to legally perform its obligations hereunder, 
(iii) the making and performance by it of this Agreement is within its powers, 
has been duly authorized by all necessary action on its part.

Paragraph 3. Transportation. Seller shall obtain, or cause to be obtained, 
             --------------
transportation to the Delivery Point, and Buyer shall obtain, or cause to be 
obtained, transportation from the Delivery Point.

Paragraph 4. Gas Specifications. Seller represents that all Gas delivered 
             ------------------
hereunder shall meet or exceed the specifications required above.

Paragraph 5. Operational Flow Orders. Should either party receive an operational
             -----------------------
flow order or other order or notice from a Transporter requiring action to be 
taken in connection with this Agreement or Gas flowing under this Agreement 
("OFO"), such Party shall immediately notify the other Party of the OFO and 
  ---
provide the other Party a copy of same by facsimile. Each Party shall indemnify,
defend and hold harmless the other Party from any Claims, including, without 
limitation, all non-compliance penalties and attorneys' fees, associated with an
OFO of which the Indemnifying Party failed to give the Indemnified Party the 
notice required hereunder.

Paragraph 6. Financial Matters: Billing Invoice Date Charges and Payment. Buyer 
             -----------------  -------------------- -------------------
agrees to pay Seller for all gas delivered at the price(s) provided for in 
Article 3 and Exhibit B of this Agreement. By the 10th Day of each calendar 
Month following the Month in which Gas was Scheduled under this Agreement,
Seller shall provide Buyer with a written statement setting forth Gas Scheduled
during the preceding Month, and other charges due Seller, including, without
limitation, deficiency charges under Article 3. Billing and payment will be
based on Scheduled quantities. Within five Business Days of the request of
either Party, the other Party shall provide, to the extent it has a legal right
of access thereto and/or such statement is then available, a copy of the
Transporter's allocation or imbalance statement applicable to Gas sold

                                       5

<PAGE>
 
hereunder for the requested period. The difference, if any, between Scheduled 
and actual quantities delivered or accepted shall be treated as imbalances under
Article 7. Buyer shall remit any amounts due on the 25th Day of the Month by 
electronic funds in which Seller's statement was received. If the due date for 
any payment to be made under this Agreement is not a Business Day, the due date 
for such payment shall be the following Business Day. Payment of all funds shall
be made in U.S currency and as indicated in Exhibit "A" in such manner that 
funds are immediately available to the payee on the applicable due date. Each 
Party shall take all actions necessary to effect payments in accordance with the
process stated in Exhibit "A". If Buyer or Seller should fail to remit any 
amounts in full when due hereunder, interest on the unpaid portion shall accrue 
from the date due at a rate equal to the Interest Rate. Billings, payments and 
statements shall be made to the accounts or the address/facsimiles specified in 
Exhibit "A".

Paragraph 7. Failure to Pay. If either Party fails to make a timely payment and 
             --------------
such failure is not remedied within ten (10) Business Days after such Party 
receives written notice of default, the nondefaulting Party may require 
additional security until such default is cured; provided, if the defaulting 
Party, in good faith, shall dispute the amount of any such billing or part 
thereof and shall pay such amounts as it concedes to be correct, no such 
security requirement shall be permitted.

Paragraph 8. Audit Rights. During the term of this Agreement and for a period of
             ------------
two years from the last day of the Month in which Gas was delivered. Buyer or
Seller or any third party representative thereof shall have the right, upon
reasonable notice and at reasonable times to examine the books and records of
the other to the extent reasonably necessary to verify the accuracy of any
billing statement, payment demand, charge, payment or computation made under
this Agreement. The records of the Parties shall be retained in accordance with
Section 9.6 of the Firm Purchase/Sale Agreement for a like period to facilitate
the audit rights of the Parties.

Paragraph 9. Financial Information. If requested by Buyer, Seller shall deliver 
             ----------------------
(i) within 120 Days following the end of each fiscal year, a copy of the
combined audited financial statements of Duke Energy Trading and Market
Services, L.L.C. and Duke Energy Marketing, L.P. for such fiscal year and (ii)
within 60 Days after the end of each of its first three (3) fiscal quarters of
each fiscal year, a copy of the quarterly report containing unaudited combined
financial statements of Duke Energy Trading and Marketing, L.L.C and Duke Energy
Marketing, L.P. for such fiscal quarter. In addition, Duke Energy Trading and
Marketing, L.L.C. will notify The Providence Gas Company within five (5)
Business Days in the event there is any material adverse change in the financial
condition of Duke Energy Trading and Marketing, L.L.C and Duke Energy Marketing,
L.P. If requested by Seller, Buyer shall deliver (i) within 120 Days following
the end of each fiscal year, a copy of its annual report containing consolidated
financial statements for such fiscal year certified by Independent certified
public accountants and (ii) within 60 Days after the end of each of its first
three fiscal quarters of each fiscal year, a copy of its quarterly report
containing unaudited consolidated financial statements for such fiscal quarter.
In all cases the statements shall be for the most recent accounting period and
prepared in accordance with GAPP; provided, should any such statements not be
timely due to a delay in preparation or certification, such delay shall not be
considered a default so long as such Party diligently pursues

                                       6
<PAGE>
 
the preparation, certification and delivery of the statements.

Paragraph 10. Warranty of Title to Gas. Seller warrants that title to Gas to be 
              ------------------------
Scheduled by Seller is free from all production burdens, liens and adverse 
claims and warrants its right to sell the same. Seller agrees to indemnify, 
defend and hold harmless Buyer against all Claims to or against the title of 
said Gas. In the event any Claim is asserted to said Gas, Buyer, in addition to 
other remedies, may suspend its obligation to pay for said Gas up to the amount 
of such Claim.

Paragraph 11. Alternate Price Redetermination. If any or all of the indices used
              ------------------------------- 
to determine the Spot Price are not available in the future, the Parties agree 
to promptly negotiate a mutually satisfactory alternate index for the Spot 
Price.

Paragraph 12. Effect of Waiver or Consent. No waiver or consent by either Party,
              ---------------------------
express or implied, of any one or more defaults by the other Party in the 
performance of any provision of this Agreement shall operate or be construed as 
a waiver or consent of any other default or defaults whether of a like or 
different nature. Failure by a Party to complain of any act of the other Party 
or to declare the other Party in default with respect to this Agreement, 
regardless of how long that failure continues, shall not constitute a waiver by 
that Party of its rights with respect to that default until the applicable 
statue of limitations period has run.

Paragraph 13. Indemnification. With respect to each indemnification included in 
              ---------------
this Agreement the indemnity is given to the extent authorized by law and the 
following provisions shall be considered applicable. The Indemnified Party shall
promptly notify the Indemnifying Party in writing of any Claim and the 
Indemnifying Party shall have the right to assume the investigation and defense 
thereof, including the employment of counsel, and shall be obligated to pay 
reasonable related attorneys' fees; provided, the Indemnified Party shall have 
the right to employ separate counsel and participate in the defense of any 
Claim, but, the attorney's fees of such counsel shall be paid by the Indemnified
Party unless the employment of such counsel has been consented to in writing by 
the Indemnifying Party or the Indemnifying Party has failed to assume the 
defense and employ counsel in a timely manner; provided further, if the named 
parties to any Claim includes both Parties, and the Indemnified Party shall have
been advised by counsel that there may be a legal defense available to it which 
is different from those available to the Indemnifying Party, the Indemnified 
Party may elect to employ separate counsel at the expense of the Indemnifying 
Party, in which case the Indemnifying Party shall pay the defense of the Claim 
on behalf of the Indemnified Party. The Parties shall use reasonable efforts to 
cooperate in the defense of any Claim. The Indemnifying Party shall not be 
liable for any settlement of a Claim without its express written consent 
thereto. The Indemnifying Party shall reimburse the Indemnifying Party for 
payments made or costs incurred in respect of an indemnity with the proceeds of 
any judgment, insurance, bond, surety or other recovery made with respect to an 
event covered by the indemnity.

                                       7

<PAGE>
 
                                  EXHIBIT "A"
                         FIRM PURCHASE/SALE AGREEMENT

                       NOTICE / COMMUNICATION / PAYMENT



TO SELLER:                             10777 Westheimer, Suite 650
                                       Houston, Texas 77042
Notices/Correspondence:                Attention: Contract Administration
                                       Phone:         (713) 260-1800
                                       Facsimile No:  (713) 260-1825
Invoices:                              Attention: Gas Accounting
                                       Phone:         (713) 260-1800
                                       Facsimile No.  (713) 260-1825
Payments by Wire Transfer:             Duke Energy Trading and Marketing, L.L.C.
                                       Chase Manhattan Bank
                                       New York, NY
                                       [CONFIDENTIAL TREATMENT REQUESTED]

Nominations:                           Attention: Gas Control
                                       Facsimile No.: (713) 260-1850
TO BUYER:                              100 Weybosset Street
                                       Providence, Rhode Island 02903
Notices/Correspondence:                Attention:
                                       Phone:    
                                       Facsimile: 
Invoices:                              Attention:
                                       Phone:
                                       Facsimile:
Payments:
Nominations:

                                       1

<PAGE>
 
                                  EXHIBIT "B"
                         FIRM PURCHASE/SALE AGREEMENT


The Exhibit "B" outlines the Agreement between Buyer and Seller regarding the 
firm purchase and sale of Gas under the following terms and conditions.


CONTRACT QUANTITY:       Requirements Quantity

DELIVERY POINTS:              The appropriate points of delivery into Buyer's 
                         System.

CONTRACT PRICE:          [CONFIDENTIAL TREATMENT REQUESTED]

PERIOD OF DELIVERY:      October 1, 1997 to September 30, 2000

     *The parties acknowledge that the Contract Price for Firm customers as
provided herein is the result of Buyer's and Seller's Agreement to fix an
Exchange Price and Basis difference for the Term of this Agreement ("Trigger
Price")

     The parties acknowledge that a hedge position is a financial transaction
which requires liquidation if physical delivery or receipt of fixed price Gas or
Trigger Price Gas is interrupted for any reason (except a force majeure event
declared by Seller or interruption caused by Seller's breach). Such interruption
may require liquidation of the entire position, which may not be partially
liquidated to accommodate only the duration, or anticipated duration, of the
interruption. In the event any hedge position is undertaken by Seller in order
to meet its obligations hereunder, and the delivery of the fixed price or
Trigger Price Gas is interrupted for any reason, except force majeure declared
by Seller or interruption caused by Seller's breach, then the Buyer shall be
liable to Seller for any loss incurred by Seller in liquidating such hedge
position in a commercially reasonable manner, which shall include reasonable
efforts to mitigate any such loss and to limit any liquidation to the term of
actual interruption. A loss is incurred when all costs of undertaking the
position exceed the net liquidation proceeds. In the event such liquidation
yields a profit (i.e. net liquidation proceeds exceed all costs of undertaking
the position), then the Buyer shall be paid or credited with such profit.
Seller, in the exercise of its reasonable commercial discretion, shall
determine: (i) whether the anticipated or estimated duration of the interruption
justifies liquidation of the entire position, and (ii) whether the affected
hedge position may be feasibly or economically liquidated in part only. For
purposes of this Exhibit "B," a force majeure event declared by Seller shall not
include any event declared by a third party (neither Buyer nor Seller) which
prevents Seller form carrying out its obligations hereunder.