Exhibit 10.22.4 TWENTY-NINTH AGREEMENT AMENDING NEW ENGLAND POWER POOL AGREEMENT THIS AGREEMENT, dated as of the 1st day of May, 1993 is entered into by the signatories hereto for the amendment by them of the New England Power Pool Agreement dated as of September 1, 1971 (the "NEPOOL Agreement"), as previously amended by twenty-eight (28) amendments, the most recent of which was dated as of September 15, 1992. WHEREAS, Participant generation resources, other than hydroelectric units, whose annual hours of operation are restricted by regulatory requirements, contract terms or engineering or operating constraints, may require treatment different from that otherwise provided in the NEPOOL Agreement for Capability Responsibility and energy billing purposes; and WHEREAS, the signatory Participants have determined to amend the NEPOOL Agreement in the manner specified below in order to provide for a modified Capability Responsibility and energy billing treatment for restricted generation resources. NOW THEREFORE, the signatories hereby agree as follows: SECTION I TEXT OF AMENDMENTS A. Amendment of Section 9.2(b)(2) Section 9.2(b)(2) of the NEPOOL Agreement is amended by inserting the following additional provisions immediately following the present final paragraph of Section 9.2(b)(2): The New Unit Adjustment Factor for any Restricted Unit for which proposed plans were submitted subsequent to November 1, 1990 for review pursuant to Section 10.4 (or, in the case of a unit with a rated capacity of less than 5MW, for which notification was first given to NEPOOL subsequent to November 1, 1990) and for the Peabody Municipal Light Plant's Waters River #2 unit shall be determined in accordance with the formula previously specified in this Section 9.2(b)(2), modified as follows: n = K1(c-C) + K2(f-F) + K3(m-M) + K4(d-D) + K5(f-F)c2 + K6(2500-a) The symbols used in the above formula, as modified, shall have the meanings previously specified, except that the symbols "K6" and "a" shall have the following meanings: K6 is a scaling factor of 0.0001. a is as follows: for units with more than 2500 annual hours available for operation, "a" = 2500, for units with annual hours available for operation between 500 and 2500, inclusive, "a" = annual hours available for operation, and for units with annual hours available for operation less than 500 hours, "a" = - 7500; provided, however, that a Participant may elect to avoid, in whole or part, the effect on its Capability Responsibility of a Restricted Unit's availability being limited to 2500 hours or less a year by agreeing to leave unfilled a portion of its dispatchable load allocation in accordance with rules to be adopted by the Operations Committee. B. Amendment of Section 12.6 The first two sentences of Section 12.6 of the NEPOOL Agreement are amended to read as follows: If pursuant to Section 12.5A, a Participant is deemed to have received energy service in any hour when the Participant (i) had Entitlements in one or more generating units which were available for service but were not scheduled for operation by NEPEX at their full available Reserve Capability (or, to the extent applicable, at their full available Temporary Reserve Capability) and which, in the case of any Restricted Unit, had an unused portion of an available Restricted Unit Operational Allowance and/or (ii) had Scheduled Outage Service Entitlements, the Participant shall be deemed to have received Economy Flow Service and/or Scheduled Outage Service in an amount equal to the lesser of: (a) the amount of energy service the Participant is deemed to have received pursuant to Section 12.5A, or (b) the amount of energy service which could have been provided from its share of (1) the unused portion of the available Reserve or Temporary Reserve Capabilities of the units described in (i) above, as limited in the case of any Restricted Unit by the unused portion of its available Restricted Unit Operational Allowance, plus (2) its Scheduled Outage Service Entitlements. Economy Flow Service is service which a Participant is deemed to receive at any time to replace service which it could have provided at the time from units described in (i) above, and the amount of Economy Flow Service which it is deemed to receive at the time shall not exceed the amount of energy service which could have been provided from its share of the unused portions of the available Reserve Capabilities (or, to the extent applicable, the unused portion of the available Temporary Reserve Capabilities or the unused portion of the available Restricted Unit Operational Allowances, whichever is controlling) of such units. C. Addition of Definitions of "Restricted Unit" and "Restricted Unit Operational Allowance". The NEPOOL Agreement is amended by adding the following definitions following the definition of "Reserve Savings Shares" in Section 15.37A: 15.37B. Restricted Unit is a generating unit, other than a hydroelectric unit, that is restricted in annual hours available for operation by regulatory requirements, contract terms or actual engineering or operating constraints. Planned or forced outages due to maintenance requirements are not considered restrictions in annual hours available for operation. 15.37C. Restricted Unit Operational Allowance "Allowance") for a Participant's Entitlement in a Restricted Unit for any calendar year (or for the term of the Entitlement in any year, if such term is for a shorter period than the year) is the number of hours for which the Restricted Unit is available for operation during the year or such shorter period, whichever is applicable. The Allowance for a Participant's Entitlement in a Restricted Unit for any year or shorter period shall be deemed to be exhausted when (i) the number of hours that the Operations Committee determines the Participant would have used its Restricted Unit Entitlement to minimize the Participant's overall energy costs in the absence of NEPEX dispatch, plus (ii) the number of hours that the Participant is deemed to receive Scheduled Outage Service with respect to its Entitlement in the Restricted Unit during the year or such shorter period pursuant to Section 12.6, equals the Allowance. D. Modification of Definition of "Scheduled Outage Service Entitlement". The definition of "Scheduled Outage Service Entitlement" in Section 15.38B of the NEPOOL Agreement is amended to read as follows: 15.38B Scheduled Outage Service Entitlement of a Participant is the amount of Scheduled Outage Service which the Participant is entitled to receive in any hour with respect to a generating unit which is scheduled by the Operations Committee to be out of service, in whole or in part, for maintenance during a period approved for it by the Operations Committee for Scheduled Outage Service and is in fact out of service, in whole or in part, for any reason during the approved period. Such amount is equal to the lesser of (i) the portion of the Participant's share of the Reserve Capability of such unit which is unavailable for service times an estimated average availability of such unit between its periodic scheduled outages or (ii) in the case of any generating unit with a currently applicable Temporary Reserve Capability, the portion of the Participant's share of the Temporary Reserve Capability which is unavailable for service; provided, however, that (a) in the case of any Limited Fuel Unit, the amount of a Participant's Scheduled Outage Service Entitlement shall be reduced, if appropriate, to take account of any limit on the availability of stream flow or fuel to operate the unit during the outage period, and (b) in the case of any Restricted Unit, the Participant's Scheduled Outage Service Entitlement shall be limited to the unused portion, if any, of its currently available Restricted Unit Operational Allowance for the unit. The Operations Committee shall develop rules for establishing the estimated average availability of each unit between scheduled outages. Such rules shall become effective upon approval by the Management Committee. SECTION II EFFECTIVENESS OF AGREEMENT Following its execution by the requisite number of Participants, this Agreement, and the amendments provided for above, shall become effective on August 1, 1993, or on such later date as the Federal Energy Regulatory Commission shall provide that such amendment shall become effective. SECTION III USAGE OF DEFINED TERMS The usage in this Agreement of terms which are defined in the NEPOOL Agreement shall be deemed to be in accordance with the definitions thereof in the NEPOOL Agreement. SECTION IV COUNTERPARTS This Agreement may be executed in any number of counterparts and each executed counterpart shall have the same force and effect as an original instrument and as if all the parties to all the counterparts had signed the same instrument. Any signature page of this Agreement may be detached from any counterpart of this Agreement without impairing the legal effect of any signatures thereof, and may be attached to another counterpart of this Agreement identical in form hereto but having attached to it one or more signature pages. IN WITNESS WHEREOF, each of the signatories has caused a counterpart signature page to be executed by its duly authorized representative, as of the 1st day of May, 1993. COUNTERPART SIGNATURE PAGE TO TWENTY-NINTH AGREEMENT AMENDING NEW ENGLAND POWER POOL AGREEMENT DATED AS OF MAY 1, 1993 The NEPOOL Agreement, being dated as of September 1, 1971, and being previously amended by twenty-eight (28) amendments, the most recent prior amendment being an amendment dated as of September 15, 1992. By: /s/ Name: Title: Address: