<PAGE>   1









                                                                  EXHIBIT 10.33

                       OPERATION AND MAINTENANCE AGREEMENT

            THIS OPERATION AND MAINTENANCE AGREEMENT (this "Agreement") dated as
of June 11, 1999, is entered into by and between Huntley Power LLC, a Delaware
limited liability company (the "Owner"), and NRG Huntley Operations, Inc., a
Delaware corporation (the "Operator").

                                    RECITALS

            1.     The Owner owns an electricity generation facility and
related landfill assets in Tonawanda, New York (the "Facility").

            2.     The Operator has expertise in the operation and maintenance
of electricity generating facilities of the type and character of the Facility
and desires to provide administrative, operating and maintenance services for
the Facility on the terms and conditions set out herein.

            3.     The Owner and the Operator desire to set forth the terms
pursuant to which the Operator shall provide the administrative, operating and
maintenance services for the Facility.

                                    AGREEMENT

In consideration of the premises and the covenants, conditions, and agreements
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledge, the parties hereto agree as
follows:

                                    ARTICLE 1
                                   DEFINITIONS

            Whenever used in this Agreement with initial capitalization, the
following terms shall have the meanings specified or referred to in this Article
1.

            "Affiliate" means, with respect to any person or entity, (i) each
entity that such person or entity Controls, (ii) each person or entity that
Controls such person or entity, and (iii) each entity that is under common
Control with such person or entity.

            "Agreement"  shall have the meaning provided in the introductory
paragraph hereof.

            "Approved Operating Budget" means the Operating Budget as approved
by the Owner, as such Operating Budget may be modified in writing in accordance
with the terms of this Agreement.

            "Calendar Quarter" means the three-month periods commencing January
1, April 1, July 1 and October 1.

            "Calendar Year" means the twelve-month period from January 1 to
December 31 inclusive.

            "Consumables" means water treatment chemicals, reagents and other
chemicals, lubrication fluids and filters, hydraulic fluids and filters, air
filters, ordinary fasteners (nuts, bolts, nails, etc., which are customarily
readily

                                       1
<PAGE>   2


available on normal commercial terms), light bulbs and flourescent tubes,
ordinary gasket materials, gloves, flashlights, batteries, disposable safety
equipment and first aid supplies, replacement hand tools, solder and welding
rods, all supplies for maintenance and plant cleaning materials and supplies,
and all other items commonly considered to be consumables within operations of
similar facilities.

            "Dispatch Schedule" means the schedule that shows the required
generation and fuel for the relevant time period as published by the Owner.

            "Effective Date" means the date of this Agreement.

            "Equipment" means all of the mechanical and electrical equipment,
pumps, piping, Rolling Stock and controls of the Facility owned or controlled by
the Owner and used or intended to be used or useable in the generation of
electric power.

            "Facility" is defined in Recital 1.

            "Five Year Forecast" means a rolling five year operation and
maintenance plan and Operating Budget forecast (including major maintenance and
capital repairs, and recommended improvements and additions) prepared by the
Operator based on the Owner's proposed schedule for dispatch of the Facility for
the same period, submitted to the Owner for approval each July 1.

            "Force Majeure" means an event which (i) is not within the
reasonable control of the Party claiming Force Majeure (the "Claiming Party"),
(ii) was not caused by the acts, omissions or delays of the Claiming Party or
any person over whom the Claiming Party has control, (iii) is not an act event
or condition the risks or consequences of which the Claiming Party has expressly
agreed to assume pursuant to this Agreement, and (iv) by the prompt exercise of
due diligence, the Claiming Party is unable to overcome or avoid or cause to be
avoided. Force Majeure includes, but is not restricted to acts of God, fire,
civil disturbance, labor dispute, labor or material shortage, sabotage, or
action or restraint by court order of any public or governmental authority (so
long as the Claiming Party has not applied for or assisted in the application
for, and has opposed where and to the extent reasonable, such government
action).

            "Hazardous Waste" means waste with inherent properties which make
such waste dangerous to manage by ordinary means, including, but not limited to
chemicals and other wastes defined as hazardous at any time during the term of
this Agreement by the State of [name of state where Facility located] or by any
applicable federal, state or local laws, ordinances, regulations, orders or
other actions promulgated or taken with respect thereto..

            "Independent Public Accountant" means the firm of independent public
accountants of nationally recognized standing selected by the Owner to perform
an annual financial audit pursuant to the terms of this Agreement.

            "In Market Availability ("IMA ")" means a measure of plant
performance for meeting the annual Dispatch Schedule. IMA shall be calculated by
dividing the actual net generation delivered to the grid by the level of
generation prescribed in the Dispatch Schedule, with no value assigned when
dispatch is scheduled at zero. The IMA shall not exceed 100%. The IMA shall be
96% or higher for June, July, August and September. The IMA shall be 95% or
higher for the remaining months. The IMA shall be subject to correction for
significant equipment failures that require an outage or result in unsafe
conditions or violations of Legal Requirements.

            " ISO" means the independent system operator established to sell
Power in the market served by the Facility.



                                       2
<PAGE>   3
            "Labor Agreements" means the collective bargaining agreements
between Operator and local labor unions with respect to the operation of the
Facility or the maintenance thereof.

"Legal Requirements" means all laws, statutes, codes, ordinances, Permits,
orders, awards, judgments, decrees, injunctions, rules, regulations,
authorizations, consents, approvals, orders, franchises, licenses, directions
and requirements of all governments or governmental units, courts or
arbitrators, which now or at any time hereafter may be applicable to or affect
the Facility or any part thereof or any streets, alleys, passageways, sidewalks,
curbs, or gutters adjoining the Facility or any part thereof or any use or
condition of the Facility or any part thereof or the acquisition, construction,
ownership, use or operation of the Facility or any part thereof, except those
the non-compliance as to which will not have a material adverse effect on the
acquisition, construction, ownership or operation of the Facility.

            "Margin" means, for the applicable period, the Owner's revenues less
fuel and direct operating and maintenance expenses.

            "Notice" is defined in Section 10.13.

            "Notice of Termination"   means that Notice issued by the Owner or
Operator pursuant to Article 5 of this Agreement which shall terminate this
Agreement.

            "Operating Account" means the account established by and in the name
of the Owner and funded from time to time with sufficient amounts to pay all
Operating Costs as the same accrue and are payable.

            "Operating Budget" means the annual budget to be prepared by the
Operator pursuant to Section 2.2(b).

            "Operating Costs" means the actual costs directly, properly and
reasonably incurred and paid for by the Operator from the Operating Account on
behalf of the Owner in the ordinary course of business solely for the
administration, operation and maintenance of the Facility, including, without
limitation or duplication: (a) wages and overhead costs for employees of the
Operator, including, without limitation, retirement plans, medical and life
insurance, disability and occupational hazard insurance, employee benefits,
employees savings plan, employee taxes and budgeted employee incentive fees; (b)
overtime; (c) employee training including tuition, travel, meals and lodging;
(d) all maintenance costs and expenses, including, without limitation,
scheduled, routine, preventative and unscheduled maintenance; (e) the cost of
Consumables, new and replacement spare parts, and all fuel expenses incurred
under any fuel agreements; (f) Plant Office Expenses; (g) capital expenditures
or replacement of Equipment and Rolling Stock approved in writing in advance by
the Owner; (h) care and handling of any Hazardous Waste; (i) Rolling Stock
Expenses; (j) cost of utility services for the Facility; (k) costs of legal,
accounting and consulting services including labor negotiations; (l) cost of
compliance with the Permits and Legal Requirements; (m) municipal, local and
franchise taxes on the Facility (but excluding any such taxes payable by
Operator as the Operator); (o) lease payments for property or easements and (p)
costs of insurance; provided, however, that no costs incurred or paid by the
Operator to any Affiliate of the Operator shall be treated as an Operating Cost
unless incurred in accordance with Section 4.12(c).

            "Operator Fee" means the fee to be paid by the Owner Entity to Power
Marketing for the services provided pursuant to this Agreement as set forth in
Section 3.1.

            "Performance Incentive" means the payment to the Operator under
Article 9 for achieving certain performance levels of operation.

                                       3
<PAGE>   4






            "Permits" means all of the consents, approvals, authorizations,
directions, licenses and permits issued by any federal, state or local agency
or authority to the Owner or the Operator with respect to the ownership,
construction, operation and maintenance of the Facility in a safe and
commercially sound manner.

            "Person" means any individual or a corporation, partnership, trust,
incorporated or unincorporated association, joint venture, joint stock company,
government (or any agency or political subdivision thereof) or other entity of
any kind.

            "Plant Office Expenses" means costs and expenses associated directly
with and incurred at the administrative offices of the Facility, including but
not limited to telephone and telecopy services, heat, electricity, postage and
overnight mail services, paper, envelopes, file folders, computer paper,
computer software, copy paper, copier and computer supplies, maintenance and
replacement of computer and office equipment, supplies, office cleaning and
maintenance (including light bulbs and fluorescent tubes), miscellaneous office
supplies, internet and cellular telephone services, and any other expenses
related to the Operator's use of the plant office, plant office equipment and
plant office operation.

            "Power Pool" means the New York Power Pool or its successor.

            "Project Agreements" means agreements between the Owner and various
third parties as provided to the Operator by the Owner from time to time,
including, without limitation, those agreements listed on Exhibit A hereto:

            "Prudent Operating Practices" means, at a particular time, those
practices, methods, equipment, and acts then engaged in or approved by a
significant portion of the electric utility industry and commonly used in
utility engineering and operations to operate and maintain equipment equivalent
to the Facility Equipment consistent with good business practices, economy,
reliability, safety, and expedition, having due regard for current editions of
the National Electric Code and other applicable electrical safety and
maintenance codes and standards, manufacturer's warranties and recommendations,
and all Legal Requirements governing the Facility.

            "Rolling Stock" means locomotives, bulldozers, front-end loaders,
forklifts, mobile cranes, person lifts, pickup trucks, tractors, trailers,
automated sweeping equipment and the like, purchased or leased by the Owner for
use at the Facility.

            "Rolling Stock Expenses" means expenses, such as fuels, maintenance
and materials, licenses (if required), lease payments, insurance, and backup
equipment for the Rolling Stock.

            "Scheduling Coordinator" means the Person, designated by the Owner,
that is responsible for (i) developing the Owner's Dispatch Schedule, and (ii)
providing instructions to the Operator regarding the level of generation
required and fuel to be used to meet the Owner's revenue requirements.

            "Subcontractor" means any person, firm or corporation which performs
work for the Operator or the Owner at the request and direction of the Operator
pursuant to the terms of this Agreement and, subject to the provisions of
Section 4.2(c), may include Affiliates of the Owner or the Operator. Such
Subcontractors shall be qualified by the Operator's evaluation of credentials
and qualifications in accordance with a qualification program approved by the
Owner.

                                    ARTICLE 2
                               OPERATOR WORK SCOPE

            2.1         Operator Work Scope:

                                       4
<PAGE>   5
                        (a)   Subject to the provisions of Section 3.1, the
            Operator agrees to administer, operate and maintain the Facility in
            accordance with the terms and conditions of this Agreement.

                        (b)   Subject to the terms of this Agreement and so
            long as it remains in effect, the Owner hereby grants the Operator
            the non-exclusive right (which shall not constitute an easement or
            other restriction on the Facility) to enter on the premises on
            which the Facility is located and to occupy and have free access to
            use the same for solely the purposes set forth in this Agreement.
            The Operator agrees that in its capacity as the Operator it does
            not and shall not claim at any time any interest or estate of any
            kind or extent whatsoever in the Facility by virtue of this
            Agreement or the Operator's occupancy or use of the Facility
            hereunder.

                        (c)   Operator covenants that it will not cause or
            permit any waste or destruction of, or damage to, the Facility,
            ordinary wear and tear excepted, and shall not use or permit the
            use of the Facility other than as described in this Agreement, and
            that it will not suffer to be maintained any nuisance or unlawful
            or improper use of occupation of the Facility; provided, however,
            that noise from equipment shall be referred to the Owner for
            correction as a maintenance or capital budget item.

                        (d)   The Operator agrees that all programs, procedures
            and other intellectual property developed by the Operator for use
            on or at the Facility shall remain the property of the Owner.

            2.2         General Duties: The Operator shall, in consideration
for the Operator Fee and Performance Incentive, administer, operate and
maintain of the Facility in accordance with the Approved Operating Budget, the
Dispatch Schedule, Prudent Operating Practices and all Legal Requirements. It
is understood and agreed that the Operator shall incur Operating Costs in the
Owner's name and such Operating Costs shall be payable from funds on deposit in
the Operating Account. The Owner shall manage the Operating Account, writing
checks, drafts, and making wire transfers, in paying Operating Costs. Without
limiting the generality of the first sentence of this Section 2.2, of the
Operator shall perform the following tasks:

                        (a)        Perform all administrative work of the
                        Facility including:

                                    (i)    Plan, schedule and conduct all
                        business related to the operation and maintenance of
                        the Facility.

                                    (ii)   Coordinate the fuel supply including
                        delivery, unloading and inventory as required by the
                        Dispatch Schedule, on a day to day basis.

                                    (iii)  Develop a spare parts and inventory
                        program and submit the same to the Owner for approval,
                        such program being intended to minimize carrying costs
                        of the Owner and risks of shortages of inventory.

                                    (iv)   Based on the approved spare parts
                        and inventory program, and as provided for in the
                        Approved Operating Budget, purchase and inventory spare
                        parts, materials, and supplies (including Consumables
                        and items covered by Plant Office Expenses and Rolling
                        Stock Expenses), and review and approve invoices for
                        same.

                                    (v)    Based on the Dispatch Schedule, ISO
                        and Power Pool rules (A) maintain the required IMA and
                        (B) advise the Owner of risks associated with fuel and
                        dispatch issues, including any recommended
                        curtailments.

                                    (vi)   Provide such operating and
                        maintenance consulting services to the Owner as it may
                        deem necessary or desirable.


                                       5
<PAGE>   6
                                    (vii)  Respond in a timely manner to
                        written requests for Facility information from the
                        Owner.

                                    (viii) Develop a qualification program for
                        evaluating the qualifications and credentials of
                        Subcontractors, and maintain the existing R Stamp
                        program for boiler and pressure vessel repair.

                                    (ix)   Cooperate with and assist the Owner
                        in performing the Owner's obligations, and the
                        obligations of any party acting for or as the assignee
                        of the Owner, under the Project Agreements.

                                    (x)    Obtain and maintain such workers'
                        compensation, unemployment and other employee-related
                        insurance as is required under applicable state law.

                                    (xi)   Negotiate and administer the Labor
                        Agreements to achieve continuity of labor forces, labor
                        harmony and efficient use of labor forces in accordance
                        with the Approved Operating Budget.

                                    (xii)  Maintain necessary administrative
                        office facilities.

                                    (xiii) Jointly with the Owner, provide for
                        good community relations.

                                    (xiv)  Prepare and provide periodic reports
                        on behalf of and at the request of the Owner.

                                    (xv)   Provide recommendations to the Owner
                        to increase reliability and reduce expenses.

                                    (xvi)  Obtain and maintain required and
appropriate levels of insurance with respect to its activities hereunder.

                                    (xvii)  Provide assistance to the Owner in
tracking purchase and sales of emissions credits.

                        (b)         Perform all work associated with the Annual
                        Operating Budgets including:

                                    (i)    Provide accounting for any monthly,
                        quarterly, year end or other reports.

                                    (ii)   Provide monthly and quarterly
                        detailed financial and operating reports with Approved
                        Operating Budget comparison.

                                    (iii)  Review and approve all invoices.

                                    (iv)   Maintain true, complete and accurate
                        cost ledgers and accounting records in accordance with
                        generally accepted accounting principles
                        ("GAAP")utilized by the Owner regarding the services
                        provided and expenses paid or incurred by it pursuant
                        to this Agreement.

                                    (v)    Cooperate with the Independent
                        Public Accountant authorized by the Owner to perform
                        annual financial audits.

                                    (vi)   Provide a proposed Operating Budget
                        on or before July 1 of each year for the



                                       6
<PAGE>   7

                        next eighteen (18) month period for approval in advance
                        by the Owner, based on the Owner's inputs. The Operator
                        shall take into account the Dispatch Schedule, fuel and
                        other contracts, and other relevant matters, in the
                        preparation of the proposed Operating Budget. The
                        Operator shall list all assumptions, including
                        emissions data, and provide adequate information to
                        identify risks. For any partial Calendar Year, the
                        Operator shall submit a proposed Operating Budget to
                        the Owner for the balance of the first partial Calendar
                        Year plus the following Calendar Year for the Owner's
                        approval.

                                    (vii)    Provide a proposed Five Year
                        Forecast on or before July 1 each year for the next
                        five years for approval by the Owner, based on the
                        Owner's inputs.

                                    (viii)   Provide Notice to the Owner
                        promptly if Operating Expenses exceed or are expected
                        to exceed the Approved Operating Budget by the lesser
                        of $50,000 or 10% of any individual line item in the
                        Approved Operating Budget, including detailed
                        information impacting specific line items. Provide
                        proposed revisions to the Operating Budget based on
                        changes in the Owner's expected Dispatch Schedule for
                        the relevant period, and fuel and/or other contracts.

                                    (ix)     Identify and determine the
                        necessity and cost of capital improvements and annually
                        recommend a capital budget to the Owner.

                        (c) Perform operation and maintenance services at the
                        Facility including:

                                    (i)      Maintain an effective and
                        sufficient operating work force through appropriate
                        on-going hiring, training, administration and
                        compensation and coordination with the Owner's
                        management personnel.

                                    (ii)     Develop and maintain safety
                        procedures, a safety manual, an employee job-site
                        conduct handbook and an effective safety program,
                        including, without limitation, fire and explosion
                        safety measures.

                                    (iii)    Operate and maintain the Facility
                        in a clean, safe and efficient manner in accordance
                        with the Approved Operating Budget, Dispatch Schedule,
                        Prudent Operating Practices, the Project Agreements,
                        equipment manufacturers specifications and warranty
                        terms, and all Legal Requirements, including developing
                        and maintaining an environmental program. Such
                        operation shall economically limit the use of emission
                        allowances.

                                    (iv)     Maintain true, complete and
                        accurate operating logs, records and reports necessary
                        or beneficial for proper operation and maintenance of
                        the Facility.

                                    (v)      Maintain drawings, instruction
                        books and operating and maintenance manuals and
                        procedures and revise drawings and manuals as
                        modifications are made. All such material, including
                        all revisions and updates, regardless of medium used,
                        shall remain the Owner's property.

                                    (vi)     Maintain all tools and instruments
                        necessary to operate and maintain the Facility.

                                    (vii)    Develop, implement and regularly
                        update a maintenance program that is intended to
                        minimize maintenance costs, maximize intervals between
                        major maintenance outages, and does not invalidate
                        equipment manufacturers' warranties, specifications and
                        recommendations or Prudent Operating Practices and
                        meets the requirements of the authorized insurance
                        inspector.

                                    (viii)   Schedule and perform or cause to
                        be performed the work specified in the



                                       7
<PAGE>   8

                        maintenance program in accordance with the Dispatch
                        Schedule, the Approved Operating Budget, Prudent
                        Operating Practice, and all Legal Requirements.

                                    (ix)     Schedule, perform and record
                        periodic operational checks and tests of equipment in
                        accordance with the equipment manufacturers'
                        specifications and recommendations Prudent Operating
                        Practices and all Legal Requirements, and arrange for
                        required environmental or other required specialized
                        equipment tests to be performed.

                                    (x)      Evaluate the nature and impact of
                        any equipment failure and if the failure is major or
                        material, promptly provide Notice to the Owner and
                        review the situation with the Owner and mutually agree
                        on a reasonable remedy of the matter.

                                    (xi)     Cooperate with and assist the
                        Owner's personnel in obtaining and maintaining required
                        Legal Requirements.

                                    (xii)    Operate the Facility in accordance
                        with the Approved Operating Budget for such items, and
                        if a new operating budget is not timely approved by the
                        Owner, operate in accordance with the preceding
                        Approved Operating Budget until a new Operating Budget
                        is approved by the Owner, and approval shall be subject
                        to dispute resolution in a timely manner.

                                    (xiii)   Provide for necessary and
                        desirable security services for the Facility.

                                    (xiv)    Provide for building, structural
                        and yard maintenance services.

                                    (xv)     Order, receive and maintain
                        adequate inventories and supplies.

                                    (xvi)    Provide the Owner and the Owner's
                        designees with unrestricted access to the Facility and
                        cooperate with the Owner and its representatives and
                        designees in all Owner inspections of the Facility.
                        Such inspections may occur without Notice at any time
                        and shall not unreasonably interfere with personnel
                        safety or the operation and maintenance of the
                        Facility.

                                    (xvii)   Operate and maintain the Facility
                        in such a way as to satisfy all Legal Requirements,
                        taking such samples and performing and reporting such
                        tests as are required by all Legal Requirements, and
                        promptly provide Notice to the Owner of any areas of
                        Legal Requirements conflicts or violations or
                        unsatisfactory conditions or test results, including
                        performing all necessary testing and reporting in
                        accordance with Legal Requirements.

                                    (xviii)  Dispose of all waste materials,
                        including ash, in accordance with Legal Requirements
                        and the Owner's waste disposal agreements, if any.

                                    ARTICLE 3
                          RESPONSIBILITIES OF THE OWNER

            3.1         Owner Responsibilities. The Owner shall have exclusive
operational control and decision making authority with respect to the overall
operation of the Facility. In addition, the Owner shall be responsible for the
following:

                        (a)         Operator Fee. The Owner shall pay to the
            Operator the base Operator Fee of $400,000 per calendar year, in
            equal quarterly installments in arrears (prorated for any partial
            quarterly period between the Effective Date and the first day of
            the next full Calendar Quarter), due and payable on the first day
            of the following Calendar Quarter until such time as this Agreement
            is terminated as provided for in

                                       8
<PAGE>   9

            Article 5 or 6. Such fee is not subject to escalation.

                        (b)   Fund Operating Account. The Owner shall promptly
            fund and replenish the Operating Account upon request of the
            Operator in the amounts specified by the Operator as necessary to
            pay all current Operating Costs and all other Operating Costs
            reasonably projected by the Operator to become due and payable
            during the next thirty (30) days.

                        (c)   Accounting Guidelines. The Owner shall provide
            the Operator with accounting policies, directives and procedures so
            that the Operator can perform its responsibilities in Article 2.

                        (d)   Approval of Submittals. The Owner shall promptly
            review the proposed maintenance program, the five year forecast,
            and the proposed operating budget. The Owner shall meet with the
            Operator to discuss the same and, if the Owner determines that any
            item proposed should be changed and if the parties are unable to
            resolve a dispute in good faith with respect to the submittals, the
            same shall be submitted to dispute resolution.

                        (e)   Remedy of Major Equipment Failures. The Owner
            shall promptly meet with the Operator to determine the course of
            action to be taken to remedy or repair major equipment failures;
            provided, however, that the Operator shall take such action as it
            deems prudent to protect life or property in the event of an
            emergency involving failure of equipment.

                        (f)   Preparation of Dispatch Schedules. The Owner
            shall be responsible to provide to the Operator by June 1 each year
            a proposed Dispatch Schedule for the next five (5) years. The
            Dispatch Schedule shall show all anticipated fuel requirements, as
            well as periods of time and corresponding generation levels
            required for the Owner's revenues.

                        (g)   Approval of Capital Budget. The Owner shall
            promptly review any capital additions or replacements recommended
            by the Operator, and shall approve such capital additions or
            replacements as the Owner deems necessary or desirable. The Owner
            shall separately contract for any major maintenance replacements or
            capital improvements that are outside of the capacity of the
            Operator's resources.

                        (h)   Provide copies of Legal Requirements and Project
            Agreements. The Owner shall provide to the Operator copies of all
            Legal Requirements and Project Agreements.

                        (i)   Safety: The Owner shall be responsible to ensure
            that there is adequate funding available for safety related capital
            expenditures, and to ensure that the Operator implements an
            effective safety program.

            3.2         Owner's Representative.  The Owner's Commercial Asset
Manager shall be the Owner's site representative and shall be responsible for
the following:

                        (a)   Work with the Operator to ensure that the Owner's
            obligations under the Project Agreements are performed.

                        (b)   Work with the Operator to ensure that Legal
            Requirements are maintained.

                        (c)   Ensure that the Power Pool, bilateral and income
            statement accounting (including but not limited to closing the
            books monthly, quarterly and annually) is performed and required
            reports are issued, including the Independent Public Accountant's
            annual report.

                        (d)   Ensure that invoices are properly cost coded and
            timely reviewed and approved.


                                       9
<PAGE>   10


                        (e)   Represent the Owner's interests with respect to
            local community relations, including property tax issues.

                                    ARTICLE 4
                      REPRESENTATIONS, WARRANTIES AND COVENANTS

            4.1         Representations and Warranties. The Owner and the
Operator each hereby represents and warrants to the other that the following
statements are true and correct as of the date hereof and shall be true and
correct at all times that it is a party hereto:

                        (a)   It is duly formed, validly existing, and in good
            standing under the laws of the jurisdiction of its incorporation or
            formation; to the extent required by applicable law, it is duly
            qualified and in good standing in the jurisdiction of its principal
            place of business, if different from its jurisdiction of
            incorporation or formation; and that it has full power and
            authority to execute and deliver this Agreement and to perform its
            obligations hereunder, and all necessary actions by the officers,
            managers, members or other applicable persons necessary for the due
            authorization, execution, delivery, and performance of this
            Agreement by it have been duly taken.

                        (b)   It has duly executed and delivered this Agreement
            and the other documents contemplated herein, and they constitute
            its legal, valid and binding obligations enforceable against it in
            accordance with their terms (except as may be limited by
            bankruptcy, insolvency or similar laws of general application and
            by the effect of general principles of equity, regardless of
            whether considered at law or in equity).

                        (c)   Its authorization, execution, delivery, and
            performance of this Agreement does not and will not (i) conflict
            with, or result in a breach, default or violation of, (A) its
            organizational documents, (B) any contract or agreement to which it
            is a party or is otherwise subject, or (C) any law, order,
            judgment, decree, writ, injunction or arbitral award to which it is
            subject; or (ii) require any consent, approval or authorization
            from, filing or registration with, or notice to, any governmental
            authority (including any approvals required by the Federal Energy
            Regulatory Commission) or other person, unless such requirement has
            already been satisfied.

                        (d)   It is not a party to any litigation the outcome
            of which could reasonably be expected to adversely affect its
            ability to perform its obligations hereunder or to have a material
            adverse effect on its properties, business or financial condition.

                        (e)   The Owner does not warrant or represent that the
            Facility's premises are safe, healthful, or suitable for the
            performance of the Operator's obligations hereunder.

                        (f)   The Owner is an exempt wholesale generator
("EWG") as defined in the regulations of the Federal Energy Regulatory
Commission.

            4.2         Covenants. The Owner and the Operator hereby covenant
            and agree as follows:

                        (a)   Each will timely acquire and maintain all
            permits, licenses, waivers and approvals (including, if required,
            approval to operate as an EWG) required by any state or federal
            regulatory authority in order for it to perform its obligations
            hereunder.

                                      10
<PAGE>   11

                        (b)   Each will at all times abide by all laws, rules
            and regulations of any state or federal governmental authority
            applicable to the conduct of the Parties or the performance of
            their obligations hereunder.

                        (c)   The Operator will not acquire any assets or
            services from or to any Affiliate except in the ordinary course of
            the Operator's business upon terms no less favorable to the
            Operator than would be obtained in a comparable arms length
            transaction with a Person not an Affiliate and then only with the
            written consent of the Owner after receiving a reasonable
            description in writing of each of the terms thereof. Affiliate
            services shall also be subject to the Operator's Subcontractor
            qualification program.

                                    ARTICLE 5
                              TERM AND TERMINATION

            5.1         Term. This Agreement shall be effective on the
Effective Date and remain in effect until the fifth anniversary of the
Effective Date. This Agreement shall automatically be renewed for successive
five-year periods subject to Notice of Termination of both Parties one hundred
eighty (180) days prior to the end of the Term. The Operator shall be
reimbursed for usual and customary demobilization costs and employee severance
costs, if any, if the Owner elects to not renew this Agreement.

            5.2         Termination for Convenience. Notwithstanding the
foregoing the Owner may at any time and in its sole discretion terminate this
Agreement upon at least six (6) months prior Notice of Termination to the
Operator. This Agreement shall thereupon terminate on the date set forth in
such Notice of Termination. In the event of such termination, the Owner shall
pay the present value of the Operator Fees for the remaining period of the
Term, discounted at prime plus 6%, plus usual and customary demobilization
costs and employee severance costs, if any.

            5.3         Termination for Cause. The Owner may terminate the
Operator for failure to remedy an Event of Default, such termination to be
effective on the date specified in the Notice of Termination, and the Operator
shall forfeit any Operator Fee not yet paid or owing for the remainder of the
Term.

            5.4         Affiliate Termination. The Owner may terminate this
Agreement with at least six (6) months prior Notice if NRG Energy, Inc. or one
of its Affiliates ceases to maintain an ownership interest in the Owner of at
least 25%. In the event of such termination, the Operator shall be reimbursed
for usual and customary demobilization costs and employee severance costs, if
any, but shall not be paid any amount in respect of the Operating Fee scheduled
to accrue during the period after the date of such termination.

                                    ARTICLE 6
                    EVENTS OF DEFAULT AND DISPUTE RESOLUTION

            6.1         Events of Default.

                        (a)   The Owner shall be in default under this
            Agreement if the Owner fails to pay when due any amount payable by
            the Owner hereunder not being disputed by the Owner in good faith
            in writing, and fifteen (15) days have elapsed after such due date.

                        (b)   The Operator shall be in default if the Operator
            commits a material breach of its obligations under this Agreement,
            or if its breach under this Agreement causes a material default in
            any Project Agreement or a material adverse variance in the
            Approved Operating Budget and the Operator shall fail to promptly
            cure such failure within forty-five (45) days after Notice thereof,
            or if the failure is capable of being cured but is not resolved
            within forty-five (45) days after Notice thereof, and the Operator
            has

                                      11
<PAGE>   12

            commenced and is diligently pursuing a cure to such default, such
            default is not cured within one hundred eighty (180) days after
            Notice thereof. Failure to meet the required IMA for two
            consecutive Calendar Quarters is an Event of Default.

            6.2         Rights Upon Default.

                        (a)   Right of Operator. Upon the occurrence and
            continuance of a default described in 6.01(a), the Operator may, at
            its option, terminate this Agreement by delivering written Notice
            of termination to the Owner, which Notice of termination shall be
            effective forty-five (45) days after the date it is received by the
            Owner; provided, however, that if the Owner has cured or undertaken
            to cure such default within thirty (30) days of actual delivery of
            such Notice of termination to the Owner, such Notice of termination
            shall be deemed to have been canceled and shall be null and void.
            In the event of such termination, the Owner shall pay all amounts
            due the Operator, including the Operator Fee, Incentive Fee (if
            any, for the current period), and any unreimbursed costs advanced
            by the Operator for Operating Costs then due. In such event,
            Operator shall take all necessary steps to shut down and protect
            the Facility, leaving the same in an orderly and safe condition,
            prior to leaving the premises. The rights and remedies of the
            Operator (and of any Person acting on behalf of or claiming through
            the Operator) under this Section 6.2(a) shall be the Operator's
            (and any such Person's) sole right and remedy for any breach of or
            default under the terms of this Agreement.

                        (b)   Right of the Owner. Upon the occurrence and
            continuance of an Event of Default described in Section 6.1, the
            Owner may, at its option, terminate this Agreement, in accordance
            with Section 5.3, by delivering written Notice of termination to
            the Operator, which Notice of termination shall be effective
            immediately. In such event, Operator shall take all necessary steps
            to protect the Facility, leaving the same in an orderly and safe
            condition, prior to leaving the premises. The rights and remedies
            of the Owner (and of any Person acting on behalf of or claiming
            through the Owner) under this Section 6.2(b) shall be the Owner's
            (and any such Person's) sole right and remedy for any breach of or
            default under the terms of this Agreement.

            6.3         Dispute Resolution. In the event the parties are unable
to resolve a dispute in good faith within thirty days, the aggrieved party
shall Notice the other party and the matter shall be referred to a senior
officer of each party, who shall have thirty (30) days to resolve the matter,
after which either party may pursue any and all other remedies available at law
or in equity.

                                    ARTICLE 7
                    INDEMNIFICATION; LIMITATIONS OF LIABILITY

            7.1         Indemnifications. To the extent not otherwise covered
by Facility insurance, each party hereto will indemnify and hold harmless the
other and each director, officer, employee and Affiliate thereof, from and
against all losses, claims, damages, expenses or liabilities to which the such
indemnified party or such director, officer, employee or affiliated Person may
become subject, insofar as such losses, claims, damages, expenses or
liabilities (or actions, suits or proceedings including any inquiry or
investigation or claims in respect thereof) arise out of, in any way relate to,
or result from a breach of this Agreement by the indemnifying party; provided
however, that such party shall not have the right to be so indemnified for its
own gross negligence or willful misconduct as finally determined by a court of
competent jurisdiction after all appeals and time for appeals have expired. If
any action, suit or proceeding arising from any of the foregoing is brought
against a party or any other Person indemnified or intended to be indemnified
pursuant to this Section 7.1, the indemnifying party will, if required by the
indemnified party or any such indemnified Person, resist and defend such
action, suit or proceeding or cause the same to be resisted and defended by
counsel reasonably satisfactory to the Person or Persons indemnified or


                                      12
<PAGE>   13


intended to be indemnified. Each indemnified Person shall, unless the
indemnified party or such indemnified Person has made the request described in
the preceding sentence and such request has been complied with, have the right
to employ its own counsel (including staff counsel) to investigate and control
the defense of any matter covered by such indemnity and the reasonable fees and
expenses of such counsel shall be at the expense of the indemnifying party.
Notwithstanding anything contained in this Section 7.1 to the contrary, each of
the Owner and the Operator shall be named insured on the insurance covering the
Facility's property and business, and no party shall be required to indemnify
the other for any loss for which such insurance shall provide a recovery.

            7.2         Limitation of Liability. The liability of either party
to the other on all claims of any kind (excluding death or bodily injury),
whether based on contract, indemnity, warranty, tort (including, as the case
may be, a party's own negligence), strict liability or otherwise, for all
losses or damages arising out of, connected with, or resulting from this
Agreement or from the performance or breach thereof, or from any services
covered by or furnished during the term of this Agreement, shall in no case
exceed five times the annual Operator Fee.

            7.3         Waiver of Consequential Damages. In no event, whether
based on contract, indemnity, warranty, tort (including, as the case may be, a
party's own negligence) or otherwise, shall the Operator or its Subcontractors
and suppliers be liable to the Owner, or the Owner, its Subcontractors and
suppliers be liable to the Operator, for special, incidental, exemplary,
indirect or consequential damages including, but not limited to, loss of
profits or revenue, loss of use of the equipment or any associated equipment,
cost of capital, cost of purchased power, cost of substitute equipment,
facilities or services, downtime costs, or claims of customers of the Owner or
the Operator for such damages, and each party shall indemnify the other, its
Subcontractors and suppliers against any such claims from the other's suppliers
or customers.

                                      13

<PAGE>   14



                                    ARTICLE 8
                                   ASSIGNMENT

            8.1         Assignment. Neither Party shall assign this Agreement
or its rights hereunder without the prior written consent of the other Party,
provided, however, either Party may, without the consent of the other Party
(and without relieving itself from liability hereunder), (i) transfer, sell,
pledge, encumber or assign this Agreement or the accounts, revenues or proceeds
hereof in connection with any financing or other financial arrangements by or
for the benefit of the Owner Entity or NRG Northeast Generating LLC, (ii)
transfer or assign this Agreement to an Affiliate of such Party if such
Affiliate's creditworthiness and technical ability to perform hereunder is not
materially different than that of such Party, (iii) transfer or assign this
Agreement to any person or entity succeeding to all or substantially all of the
assets of such Party, or (iv) in the case of the Owner Entity, transfer or
assign this Agreement to any person or entity acquiring the Station; provided,
however, that in each such case, any such assignee (other than an assignee in a
transaction referred to in clause (i) above) shall agree in writing to be bound
by the terms and conditions hereof and such assignee's creditworthiness and
technical ability to perform hereunder shall not be materially different than
that of such Party.

                                    ARTICLE 9
                             PERFORMANCE INCENTIVES

            9.1         Performance Incentives.

                        (a)   The Operator may be entitled to receive an
            Incentive Fee or obligated to pay a Penalty, as specified in
            Appendix A.

                        (b)   The Incentive Fee or Penalty will be due each
            August 1, and will be based on the preceding twelve month period
            ending July 1. Penalties, if any, may be recouped or set-off
            against the next due and payable Operator Fee or Incentive Fee and
            adjusted for any partial operating year following the date of this
            Agreement.

                                   ARTICLE 10
                                  MISCELLANEOUS

            10.1        Independent Contractor. Except as otherwise expressly
stated in this Agreement, the Operator shall at all times be deemed an
independent contractor and not by reason of this Agreement a joint venturer,
agent or principal of the Owner and none of the Operator's officers, directors,
partners, employees, agents or representatives or the officers, directors,
partners, employees, agents or representatives of its Subcontractors shall be
considered officers, directors, partners, employees, agents or representatives
of the Owner.

            10.2        Severability.  The invalidity, in whole or in part, of
any of the provisions of this Agreement will not affect the validity of the
remaining provisions hereof.

            10.3        Entire Agreement. This Agreement and all amendments
thereto contain the complete agreement between the Owner and the Operator with
respect to the matters contained herein and supersede all other agreements,
whether written or oral, with respect to the matters contained herein between
the Owner and the Operator.

            10.4        Amendment. No modification amendment, or other change
to this Agreement will be effective unless consented to in writing by each of
the parties hereto.

                                      14
<PAGE>   15

            10.5        Waiver. Failure or forbearance by a party to exercise
any of its rights or remedies under this Agreement shall not constitute a
waiver of such rights or remedies. No party shall be deemed to have waived or
forborne any right or remedy resulting from such failure to perform unless it
has made such wavier specifically in writing.

            10.7        Counterparts. This Agreement may be executed in one or
more counterparts each of which shall be deemed an original and all of which
shall be deemed one and the same Agreement.

            10.8        Choice of law.  This Agreement shall be governed by the
laws of the State of New York.

            10.9        Title Passage. Title to all materials and services
provided under this Agreement shall pass to the Owner upon performance of the
work or upon the Owner becoming obligated to make payment therefor. It is
expressly understood and agreed, however, that the passage of title shall not
release the Operator from its responsibility to fully carry out its obligations
under this Agreement. The Operator shall issue purchase orders in the name of
the Owner as the Owner's agent.

            10.10       Effect of Force Majeure. If either party is rendered
unable by an event of Force Majeure to carry out, in whole or part, its
obligations under this Agreement, then, for only the pendency of such Force
Majeure, the party affected by the event (other than the obligation to make
payments then due or becoming due with respect to performance which occurred
prior to the event) shall be temporarily relieved of its obligations hereunder
insofar as they are affected by Force Majeure but for no longer period. The
party affected by an event of Force Majeure shall provide the other party with
written notice setting forth the full details thereof within two (2) Business
Days after the occurrence of such event and shall take all reasonable measures
to mitigate or minimize the effects of such event of Force Majeure.

            10.11       Interest on Amounts due. Any amounts owing fifteen (15)
days after the due date thereof shall bear interest at the prime rate of
interest as reported from time to time in the Wall Street Journal plus 2%.

            10.12       Continuous Operation. During the pendency of any
dispute arising under this Agreement, unless otherwise agreed between the
parties the Operator shall continue to operate the Facility without default or
interruption in service.

                                      15

<PAGE>   16


            10.13       Notice:  A Notice, consent, approval, or other
communication (each a "Notice") shall be delivered in writing via mail or
facsimile, and if meant for

            Owner delivered to:                  Operator delivered to:

            Commercial Asset Manager             President
            Huntley Power LLC                    NRG Huntley Operations, Inc.
            1221 Nicollet Mall, Suite 700        1221 Nicollet Mall, Suite 700
            Minneapolis, MN 55403                Minneapolis, MN 55403
            612-373-5350 (phone)                 612-373-8668 (phone)
            612-373-5346 (fax)                   612-373-5346 (fax)

            IN WITNESS WHEREOF the parties have executed this Agreement as of
the date first set forth above.

                                                 HUNTLEY POWER LLC

                                                 By: /s/ Craig A. Mataczynski
                                                    ----------------------------
                                                 Title: President
                                                       -------------------------


                                                 NRG HUNTLEY OPERATIONS INC.

                                                 By: /s/ Louis P. Matis
                                                    ----------------------------
                                                 Title: President
                                                      --------------------------
                                      16