<PAGE>
                                                                   Exhibit 10.23


                             BAY STATE GAS COMPANY
                     SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

                        (Restated as of January 1, 1992)


                                SECOND AMENDMENT

     WHEREAS Bay State Gas Company (the "Company") adopted the Bay State Gas
Company Supplemental Executive Retirement Plan (the "Plan"), originally
effective July 1, 1986, for the purpose of attracting, retaining and motivating
selected executives; and

     WHEREAS, the Company amended and restated the Plan effective January 1,
1992; and

     WHEREAS, the Company reserves the right to amend the Plan in Section 6.1
thereof; and

     WHEREAS, the Company has most recently amended the Plan effective August 1,
1994 by a First Amendment thereto; and

     WHEREAS, the Company desires further to amend the Plan;

     NOW THEREFORE, the Plan is hereby further amended as follows, effective
January 1, 1997:

     Section 1.7, as heretofore amended by the First Amendment to the Plan, is
     hereby deleted in its entirety and a new Section 1.7 substituted therefor
     to read as follows:

     "1.7 'Participant' means an employee of the Company or an Affiliate who is
          an officer at the vice-president or equivalent level or above who has
          been approved for participation in the Plan by the Compensation
          Committee. An Employee shall become a 'participant' as of the date he
          or she meets the aforementioned eligibility requirements."

     IN WITNESS WHEREOF, Bay State Gas Company has caused this instrument to be
executed by its duly authorized officer.

                                             BAY STATE GAS COMPANY


ATTEST:                                      By:  /s/ Joel Singer
                                                  ------------------------------
/s/ Charles H. Tenney, III                        Its President
-----------------------------
Clerk

<PAGE>
                             BAY STATE GAS COMPANY
                     SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN

                        (Restated as of January 1, 1992)



                                FIRST AMENDMENT



     WHEREAS Bay State Gas Company (the "Company") adopted the Bay State Gas
Company Supplemental Executive Retirement Plan (the "Plan"), originally
effective July 1, 1986, for the purpose of attracting, retaining and motivating
selected executives;

     WHEREAS the Company has most recently amended and restated the Plan
effective January 1, 1992;

     WHEREAS, the Company reserved the right to amend the Plan in Section 6.1
thereof; and

     WHEREAS, the Company desires further to amend the Plan;

     NOW, THEREFORE, the Plan is hereby amended as follows, effective August 1,
1994:

1.   Section 1.6 is hereby amended by adding at the end thereof the following
     sentence:

     "Earnings shall not include any amounts paid by the Company to reimburse a
     Participant for the cost of premiums on any policy of insurance."

2.   Section 1.7 is hereby deleted in its entirety and a new Section 1.7
     substituted therefor to read as follows:

     "1.7    "Participant" means an employee of the Company or an Affiliate who
              is an officer at the vice president or equivalent level or above,
              duly elected by the Board of Directors. An employee shall become a
              "Participant" as of the date he or she meets such eligibility
              requirements."

3.   Section 2.3 is hereby amended by adding at the end thereof the following
     sentence:

     "For purposes of this Section 2.3, "cause" means:

     (a)  Conviction by a court of competent jurisdiction of any criminal
          offense involving dishonesty or breach of trust or any felony or crime
          of moral turpitude which directly and adversely affects the business
          of the Company;

<PAGE>
          (b)  Commission of an act of fraud against the Company; or

          (c)  Willful refusal to perform the duties reasonably assigned by the
               Board of Directors, which refusal continues for more than ten
               days after written notice to the Participant pursuant to a vote
               of two-thirds of the Board of Directors."

4.   Section 3.2(a) is hereby amended by deleting the last sentence thereof and
     substituting therefor the following:

     "For purposes of this Article, the term Early Retirement Equivalent means
     the benefit payable at age 65 reduced by .4% per month for each month or
     part thereof that the Early Retirement Date precedes age 65."

5.   Section 3.2(b) is hereby amended by deleting the first sentence thereof and
     substituting therefor the following:

     "If the Participant's Early Retirement Date is prior to his having attained
     age 60, said gross benefit amount will be reduced by .4% per month for each
     month or part thereof that the Early Retirement Date precedes the last day
     of the month in which the Participant would attain age 60 and that amount
     will be payable from the Early Retirement Date through the month in which
     the Participant attains age 60."

6.   Article IV is hereby amended by adding at the end thereof a new Section 4.4
     to read in its entirety as follows:

     "4.4      Change of Control. Notwithstanding Section 4.3, if a
               Participant who was a Participant prior to a Change of Control
               terminates employment subsequent to such Change of Control, the
               Participant will be entitled to a benefit, payable as provided in
               Section 3.5, in an amount equal to the benefit determined under
               Section 3.1 or 3.2, whichever is applicable, based on the
               Participant's Earnings and Service as of his termination of
               employment. A Participant to whom this Section 4.4 applies shall
               be deemed to have completed five years of Service (or, if
               greater, the Participant's actual service) for purposes of
               Sections 2.1 and 5.1 and, in the event of the Participant's death
               after his termination of employment but prior to the time
               benefits commence, the Participant shall be deemed to have been
               actively employed at the time of his death for purposes of
               Section 5.1.

               For purposes of this Section 4.4, a "Change of Control" shall be
               considered to have occurred if:

<PAGE>
            (a) Any person, entity or group of persons (other than the Company
                or any wholly-owned subsidiary of the Company), within the
                meaning of sections 13(d) or 14(d) of the Securities Exchange
                Act of 1934 (the "Act"), becomes the beneficial owner, within
                the meaning of Rule 13d-3 promulgated under the Act, directly or
                indirectly, of 25% or more of the Company's then outstanding
                shares of common stock, par value $3.33 1/3 per share ("Common
                Stock");

            (b) Any person, entity or group of persons (other than the Company
                or any wholly-owned subsidiary of the Company), after purchasing
                Common Stock of the Company in a tender or exchange offer,
                becomes the beneficial owner, directly or indirectly, of 25% or
                more of the Common Stock;

            (c) The shareholders of the Company approve (i) a merger or
                consolidation of the Company in which the Company is not the
                continuing or surviving corporation or pursuant to which the
                shares of Common Stock would be converted into cash, securities
                or other property, or (ii) any sale, lease, exchange or other
                transfer of all or substantially all of the Company's assets; or

            (d) There is a change in a majority of the members of the Company's
                Board of Directors within a 25-month period, unless such change
                has been approved by two-thirds of the Directors then still in
                office who were in office at the beginning of the 25-month
                period."


7.  Section 6.1 is hereby amended by adding at the end of the second sentence
    thereof (ending "the needs of the situation") the following clause:

        "provided, that the Participant or, in the case of the Participant's
        death, the Surviving Spouse of the Participant agrees to such
        modification or waiver."

8.  Article VI is hereby amended by adding a new Section 6.1A thereto read in
    its entirety as follows:

    "6.1A  Attorney's Fees.  The Company will pay the costs and expenses
           incurred by a Participant, including without limitation reasonable
           attorney's fees, in an action to obtain or enforce any rights or
           benefits under the Plan in which the Participant





<PAGE>
               is successful."

     IN WITNESS WHEREOF, Bay State Gas Company has caused this instrument to be
executed by its duly authorized officer.


                                   BAY STATE GAS COMPANY


Date:   October 7, 1994            By: /s/ Paul A. Ford
     ----------------------           -----------------------------------
                                      Title -- Senior Vice President, Operations


51634
<PAGE>




                             BAY STATE GAS COMPANY





                     SUPPLEMENTAL EXECUTIVE RETIREMENT PLAN











                                    Restated



                                January 1, 1992
<PAGE>
                                    PREAMBLE


The name of this plan is the "Bay State Gas Company Supplemental Executive
Retirement Plan" (the "Plan"). The Plan has been established by Bay State Gas
Company (the "Company") for the purpose of providing a supplemental amount of
retirement income in order to attract, retain, and motivate selected
executives. The Plan, as originally adopted effective July 1, 1986, and amended
and restated July 1, 1990, shall become effective as further amended and
restated January 1, 1992.

<PAGE>
                                   ARTICLE I

                                  DEFINITIONS

1.1  "Affiliate" means any corporation, partnership, or other organization
     which is designated as an "Affiliate" by the Committee and adopts the Plan.

1.2  "Basic Plan" means the Bay State Gas Company Pension Plan, as amended
     from time to time.

1.3  "Basic Plan Benefit" means the amount of benefit payable from the Basic
     Plan to a Participant (after adjustment for benefits payable for service
     with an Affiliate) in the form of a straight life annuity.

1.4  "Committee" means a committee made up of the Company's Chief Executive
     Officer, Chief Financial Officer, and Senior Vice President of Human
     Resources and Division Management, or such other persons as may be
     designated from time to time by the Board of Directors of the Company.

1.5  "Compensation Committee" means the committee of the Board of Directors
     charged with the responsibility for compensation and employee benefit
     matters.

1.6  "Earnings" means a Participant's average annual total cash compensation
     for his highest 36 months during his final ten years of employment with
     the Company and its Affiliates, which compensation shall include any
     contributions through a salary reduction agreement to a cash or deferred
     plan under IRC Section 401(k) and shall include any incentive compensation
     awards under the Company's Key Employee Incentive Compensation Plan.
     Incentive Compensation awards shall be included in earnings for the period
     in which the award was earned, regardless of when the award was paid. The
     incentive compensation awards included shall not exceed three annual
     awards, whether or not such incentive compensation was deferred under the
     Company's Key Officer Deferred Compensation Plan, and shall exclude any
     other incentive compensation

                                                                             I-1

<PAGE>
     In the case of a Participant having less than 36 months of employment with
     the Company and its Affiliates, "Earnings" means his average annual total
     compensation for his or her total final continuous period of employment
     with the Company and its Affiliates.

1.7  "Participant" means an employee of the Company or an Affiliate who is an
     officer at the vice president or equivalent level or above who has been
     approved for participation in the Plan by the Compensation Committee. An
     Employee shall become a "Participant" as of the date he or she meets the
     aforementioned eligibility requirements.

1.8  "Retirement" means the termination of a Participant's employment with the
     Company and its Affiliates on one of the retirement dates specified in
     Section 2.1.

1.9  "Service" means a Participant's years of service for vesting purposes
     under the terms of the Basic Plan and, if approved by the Compensation
     Committee, years of service with another organization(s) prior to Service
     with the Company.

1.10 "Surviving Spouse" means the spouse of a deceased Participant.

                                                                             I-2
<PAGE>
                                   ARTICLE II

                            ELIGIBILITY FOR BENEFITS

2.1  Retirement Dates.   Each Participant is eligible to retire and receive a
     benefit under the Plan beginning on one of the following dates:

          (a)  "Normal Retirement Date," which is the first day of the month in
               which the Participant reaches age 65 and has 5 years of Service.

          (b)  "Early Retirement Date," which is the first day of any month
               after the Participant reaches age 55 and has 5 years of Service.

          (c)  "Postponed Retirement Date," which is the first day of any month
               following the Participant's Normal Retirement Date in which the
               Participant terminates employment with the Company.

2.2  Disability.    If, prior to his Retirement Date, a Participant sustains a
     total disability as determined by the Committee, he shall be entitled to
     receive a benefit hereunder beginning on any Early Retirement Date or on
     his Normal Retirement Date at the Participant's election.

2.3  Non-Competition or Discharge For Cause. If any Participant entitled to a
     benefit under the Plan is discharged for cause, or enters into competition
     with the Company, or interferes with the relations between the Company and
     any customer, or engages in any activity that would result in any decrease
     in or loss of revenues by the Company, the rights of such Participant to a
     benefit under the Plan, including the rights of a Surviving Spouse to a
     benefit, will be forfeited, unless the Committee determines that such
     activity is not detrimental to the best interests of the Company. However,
     if the individual ceases such activity and notifies the Committee in
     writing of this action, then the Participant's right to receive a benefit,
     and any right of a Surviving Spouse to a benefit, may be restored within 60
     days of said notification, unless the Committee in its sole discretion
     determines that the prior activity has caused serious injury to the
     Company, which determination will be final and conclusive.

                                                                            II-1




<PAGE>
                                  ARTICLE III

                     AMOUNT AND FORM OF RETIREMENT BENEFIT

3.1   Benefit at Normal Retirement.  The annual retirement benefit payable at a
      Participant's Normal Retirement Date as a single life annuity under the
      Plan will equal 4% of Earnings times completed years and full months of
      his Service, up to 15 years of Service, less the sum of the Benefit
      Offsets defined below calculated as benefits payable at age 65. The
      maximum annual benefit hereunder, payable as a single life annuity, shall
      be an amount equal to 60% of the Participant's Earnings, less the sum of
      the Benefit Offsets.

      For purposes of this Article, the term Benefit Offsets means the sum of
      the following annual amounts to which the Participant may be entitled,
      payable in the form of a single life annuity: (i) the amount of any Basic
      Plan retirement benefit excluding any Early Retirement Supplement payments
      made prior to age 62, (ii) the amount of any retirement benefit payable
      from a defined benefit plan of any prior employer of the Participant, and
      (iii) the amount of any retirement benefit payable from a defined benefit
      plan of any company affiliated with the Company.

3.2   Benefit at Early Retirement.  The annual benefit payable at a
      Participant's Early Retirement Date will equal the gross benefit
      determined in Paragraph 3.1 before reduction for the Benefit Offsets,
      based upon his Earnings and Service at his Early Retirement Date, subject
      to the following adjustments:

            (a)  If the Participant's Early Retirement Date is on or after his
            having attained age 60, said gross benefit amount will be reduced by
            the sum of the Benefit Offsets calculated as immediate benefits
            payable at the Early Retirement Date under the terms of the
            respective plans, or if such Benefit Offset amounts are either not
            immediately payable at the Early Retirement Date under the terms


                                                                           III-1
<PAGE>
          of such plans or are not readily determinable based on the information
          available to the Company, then such Benefit Offset amounts shall be
          equal to the Early Retirement Equivalent of the Benefit Offset amounts
          payable at age 65. For purposes of this Article, the term Early
          Retirement Equivalent means the benefit payable at age 65 reduced by
          4.8% per year for each year or part thereof that the early retirement
          data precedes age 65.

     (b)  If the Participant's Early Retirement Date is prior to his having
          attained age 60, said gross benefit amount will be reduced by 4.8% per
          year for each year or part thereof that the Early Retirement Date
          precedes the last day of the month in which the Participant would
          attain age 60 and that amount will be payable from the Early
          Retirement Date through the month in which the Participant attains age
          60. Commencing the first day of the next month, that amount will be
          further reduced by the sum of the Benefit Offsets calculated as
          immediate benefits payable at the Early Retirement Date under the
          terms of the respective plans, or if such amounts are either not
          immediately payable at age 60 or are not readily determinable based
          upon information available to the Company, then such amounts shall be
          equal to the Early Retirement Equivalent of the Benefit Offset amounts
          payable at age 65.

3.3  Benefit at Postponed Retirement.  The annual benefit payable at a
     Participant's Postponed Retirement Date will be equal to the benefit
     determined in accordance with Section 3.1 but based upon his or her
     Service and Earnings up to his or her Postponed Retirement Date.

3.4  Disability Benefit. A Participant who sustains a total and permanent
     disability pursuant to Section 2.2 may elect to begin to receive benefits
     on the date elected pursuant to Section 2.2. The amount of his benefit
     shall be determined as provided above for a benefit at his Normal
     Retirement Date or Early Retirement Date, but based upon the


                                                                           III-2
<PAGE>
          Service he would have accrued had he continued as an employee of the
          Company until the date benefits began hereunder, and based upon his
          Earnings had his rate of base pay (as in effect immediately prior to
          such disability) continued until the date on which benefit payments
          begin hereunder, plus his highest three consecutive incentive
          compensation awards.

     3.5  Form of Benefit. The benefit determined under the Plan will be
          payable in an annuity or lump sum form, as elected by the Participant.
          If payment in the form of an annuity is elected, the annuity type
          shall be the same as that elected by the Participant with respect to
          his benefit, if any, payable under the Basic Plan. If benefits
          hereunder are paid in an annuity form other than a straight life
          annuity, the amount of the benefit from this Plan shall be reduced by
          the Basic Plan's factors for payment in a form other than a straight
          life annuity. If payment in the form of a lump sum is elected, the
          lump sum amount payable will be calculated in the same manner and
          according to the same interest rates and mortality tables as under the
          Basic Plan.

                                                                           III-3
<PAGE>
                                   ARTICLE IV

                         PAYMENT OF RETIREMENT BENEFITS

4.1  Time of Payment.    Annuity benefits payable in accordance with Article III
     will commence on the Participant's date of Retirement as the Participant
     may elect. Benefits will continue to be paid on the first day of each
     succeeding month. The last payment will be made on the first day of the
     month in which the retired Participant dies unless otherwise elected in
     accordance with Section 3.5. Lump sum benefits payable in accordance with
     Article III will be payable as soon as practicable after the Participant's
     date of Retirement.

4.2  Coordination With Basic Plan. In the case of a Participant who is eligible
     to receive a normal or early retirement benefit under the Basic Plan, his
     benefit under the Plan shall be paid beginning at the same time as such
     Basic Plan benefit except in the case of a Participant whose Early
     Retirement Date occurs prior to age 60.

4.3  Pre-Retirement Termination.   No benefits are payable under the Plan if a
     Participant terminates employment for any reason, other than death, prior
     to his or her Retirement date, except as explicitly provided in this Plan.



                                                                            IV-1
<PAGE>
                                   ARTICLE V

                             DEATH BENEFITS PAYABLE

5.1  Surviving Spouse Benefit.  If a Participant dies while still actively
     employed and either after 5 years of Service or after age 65, but prior to
     Retirement, the Surviving Spouse will receive a benefit from the Plan. The
     benefit payable under this Article V shall be determined as follows:

     (a)  If the Participant dies after attaining eligibility for Early or
          Normal Retirement, but prior to Retirement, the Surviving Spouse will
          receive a benefit equal to 50% of the amount of the Participant's
          benefit determined and paid in the same manner as provided in Article
          III, calculated as if the Participant had retired and commenced
          receiving a benefit on the first day of the month following the date
          of his death in the form of a 50% Joint and Survivor Annuity with his
          Surviving Spouse as beneficiary. The benefit will be payable monthly
          for the life of the Surviving Spouse and will commence on the first
          day of the month following the month in which the Participant dies.

     (b)  Effective June 1, 1990, if the Participant dies after 5 years of
          Service, but prior to his Early Retirement Date, the Surviving Spouse
          will receive a benefit equal to 50% of the gross amount of the
          Participant's benefit determined and paid in the same manner as
          provided in Article III, Paragraph 3.2, calculated based on Earnings
          and Service at date of death and as if the Participant had retired at
          age 55 and commenced receiving a benefit in the form of a 50% Joint
          and Survivor Annuity with his Surviving Spouse as beneficiary. The
          benefit is payable monthly for the life of the Surviving Spouse and
          will commence on the first day of the month following the month in
          which the Participant attains age 55.


                                                                             V-1
<PAGE>
                                   ARTICLE VI
                                 MISCELLANEOUS

     6.1  Termination, Amendment, Suspension.     The Board of Directors of the
          Company may, in its sole discretion, terminate, suspend, or amend the
          Plan at any time or from time to time, in whole or in part. The
          Compensation Committee may in its sole discretion in special cases
          such as Participant illness, extraordinary service, etc., modify or
          waive ancillary Plan provisions to meet the needs of the situation.
          However, no termination, amendment, suspension or modification of the
          Plan will affect a retired Participant's right or the right of a
          Surviving Spouse to continue to receive a benefit in accordance with
          the Plan as in effect on the date such Participant or Surviving Spouse
          commenced to receive a benefit hereunder, nor will any such
          termination, amendment, suspension or modification result in a
          reduction of Participant's accrued benefit based on the Participant's
          Earnings and Service to the date of such change in the Plan.

     6.2  No Guarantee of Employment. Nothing contained herein will confer upon
          any Participant the right to be retained in the employ of the Company
          or any Affiliate, nor will it interfere with the right of the Company
          or an Affiliate to discharge or otherwise deal with a Participant
          without regard to the existence of the Plan.

     6.3  Funding. The Plan is unfunded and the Company will make Plan benefit
          payments solely on a current disbursement basis out of the general
          assets of the Company.

     6.4  No Alienation or Assignment of Benefit. To the maximum extent
          permitted by law, no benefit under the Plan shall be assignable or
          subject in any manner to alienation, sale, transfer, claims of
          creditors, pledge, attachment, or encumbrance of any kind.



                                                                            VI-1


<PAGE>
6.5  Administration.  The Committee may adopt rules and regulations to assist it
     in the administration of the Plan. The Committee shall have the sole
     authority to interpret the Plan based on its intent, and any decision by
     the Committee with regard to any Participant's or Surviving Spouse's
     benefit hereunder shall be conclusive and binding.

6.6  Participant's Access to Documents.  Each Participant will receive a copy of
     the Plan.

6.7  Governing Law.  The Plan is established under and will be construed in
     accordance with the laws of the Commonwealth of Massachusetts.

6.8  Gender and Number.  The masculine gender, where appearing in the Plan, will
     be deemed to include the feminine gender, and the singular may include the
     plural, unless the context clearly indicates otherwise.

6.9  Headings.  Headings are included for convenience of reference only and are
     not to be used in interpreting the Plan.


EXECUTED this 28th day of April, 1992.


BAY STATE GAS COMPANY

By:  /s/ Paul A. Ford
   ------------------------------------

Title:  Senior Vice President
      ---------------------------------

ASSET:

By:  /s/ Charles H. Tenney, III
   ------------------------------------

Title:  Clerk
      ---------------------------------


                                                                            VI-2