Document:

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                                                                     Exhibit 4.6

                                   TRANSLATION

                        FEDERAL COMMISSION OF ELECTRICITY

                                                   AGREEMENT NUMBER PIF-005/2003
                                            AMENDMENT AGREEMENT NUMBER 3 (THREE)

AMENDMENT AGREEMENT NUMBER 3 (THREE) TO THE MIXED AGREEMENT OF FINANCED PUBLIC
WORK NUMBER PIF-005/2003, ENTERED INTO BY AND BETWEEN ON THE ONE PART COMISION
FEDERAL DE ELECTRICIDAD (THE FEDERAL COMMISSION OF ELECTRICITY), REPRESENTED BY
ENG. EUGENIO LARIS ALANIS, IN HIS CAPACITY AS DIRECTOR OF FINANCED INVESTMENT
PROJECTS AND ON THE OTHER PART THE COMPANY CONSTRUCTORA INTERNACIONAL DE
INFRAESTRUCTURA, S.A. DE C.V., REPRESENTED BY ENG. LUIS HORCASITAS MANJARREZ, IN
HIS CAPACITY AS LEGAL REPRESENTATIVE, HEREINAFTER REFERRED TO AS THE
"COMMISSION" AND THE "CONTRACTOR", RESPECTIVELY, ACCORDING TO THE FOLLOWING
RECITALS AND CLAUSES:

                                    RECITALS

I. The PARTIES represent:

I.1   That on March 26, 2003, they executed the Mixed Agreement of Financed
      Public Work, recorded with the number PIF - 005/2003, legal instrument
      that shall hereinafter be referred to as the "Agreement", awarded to THE
      CONTRACTOR by means of the International Public Bidding Process,
      established by Articles 27, paragraph I, 28 and 30, paragraph II, 32, 33
      and 45 of the Law of Public Works and Services Related to the Same, which
      purpose consists of: the execution of the Civil Works, Electromechanical
      Works and Associated Works, supply, engineering, manufacturing,
      transportation, installation, testing and start up of two equipped
      turbo-generator Units, of 375 MW of nominal power each, for the fall and
      expense of specified design and that is detailed in Section 8 of the
      Bidding Rules, Works that all together are named the El Cajon
      Hydroelectric Project, and which principal structures are located in the
      Municipalities of La Yesca and Santa Maria del Oro, in the State of
      Nayarit of Mexico.

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      The Works which consist in the Lump-sum Price Activities are described in
      detail in Exhibits OE-3, OE-4 and OE-5 of Section 4 of the Bidding Rules
      and are to be conducted under the lump-sum modality, inasmuch as the
      portion of the Works that correspond to the Lump-sum Activities are
      described in detail in Exhibit OE - 5A of Section 4 of the Bidding Rules
      and shall be executed under the base of unitary prices.

I.2   That the Price of the Agreement that THE COMMISSION agreed to pay to THE
      CONTRACTOR, agreed in Clause 9.1, was agreed to as total payment for the
      execution of the Works that correspond to the Lump-Sum Activities, the
      lump-sum price of US $682,517,584.80 Dollars (Six Hundred and Eighty Two
      Million Five Hundred and Seventeen Thousand Five Hundred and Eighty Four
      Dollars 80/100 Currency of the United States) plus Value Added Tax, and
      for the Unit Price Activities, the price of US $65,773,072.59 Dollars
      (Sixty Five Million Seven Hundred and Seventy Three Thousand Seventy Two
      Dollars 59/100 Currency of the United States) plus the corresponding value
      added tax.

I.3   That the beginning and development of the Works under the Execution
      Schedule, was agreed in Clause 13.1 of the "Agreement" in which THE
      CONTRACTOR was obliged to begin the works subject matter of the Agreement
      on March 26 2003 and to complete them on August 31st 2007, being the term
      for the completion of said works equal to 1620 days.

1.4   That on July 4 2003, THE PARTIES subscribed the Amendment Agreement number
      1 to the Agreement (hereinafter "Amendment Agreement number 1"), pursuant
      to the provisions of Articles 59 of the Law of Public Works and Services
      Related to the same, and 69 and 79 of its Regulations, in order to, (i)
      increase the amount of the Agreement exclusively on the basis of Unitary
      Prices Activities, referred to by clause 9.1 and derived only from various
      extraordinary works and additional works, which were not originally
      contemplated in the scope of the Project nor in the original Execution
      Schedule (hereinafter the "Additional Works"); (ii) agree on the Execution
      Schedule for the Additional Works; (iii) commit to analyze and to
      conciliate the new Execution Schedule

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      and the displacement of Critical Events Dates, for the reasons therein
      established.

      That according to the provisions of Clause Third of the Amendment
      Agreement Number 1 THE COMMISSION and THE CONTRACTOR agreed to extend the
      original amount of the Unitary Prices Activities of the Agreement in the
      amount of $5,801,271.26 U.S. Dollars (Five million Eight Hundred and One
      Thousand Two hundred and seventy one Dollars 26/100 Currency of the United
      States), plus value added tax, which represented an increase of 8.82%
      (eight point eighty two per cent ) in connection with that originally
      agreed, resulting in an aggregate amount of the Agreement based on Unitary
      Prices of $71,574,343.85 U.S. Dollars (Seventy One Million Five Hundred
      and Seventy Four Thousand three hundred and forty three Dollars and
      85/100) plus the corresponding value added tax, according to the budget of
      the Additional Works.

1.5   That on September 10, 2003, the PARTIES executed the Amendment Agreement
      Number 2 to the Agreement (hereinafter the "Amendment Agreement Number 2")
      in accordance with that established in Articles 59 of the Law of Public
      Works and Services Related to the Same, and 69 and 79 of its Regulations,
      in order to: (i) under the Sixth Clause of the Amendment Agreement Number
      1, modify the original Execution Schedule due to the new date for the
      commencement of the Works that is April 24, 2003; (ii) agree to the
      displacement of the Critical Events Dates 1.1, 1.2, 1.3 and 1.4
      established in Exhibit Number 3 of the Agreement, derived from the
      modifications to the contractual conditions that have ruled up to this
      date according to Clause 13.1 of the Agreement; (iii) recognize and pay,
      if applicable, under the modality of unit prices the Additional Costs
      related to the modifications of the original Execution Schedule, as a
      consequence of the late delivery and under different conditions to those
      established in the Bidding Rules and in the Agreement, of the portals of
      the diversion tunnels and the access road to the Site, for causes not
      imputable to THE CONTRACTOR and adjust the Lump-sum Activities because of
      the diminution to the length of the diversion tunnels and the reduction of
      the volume of the cofferdam in the upstream waters; (iv) approval in the
      event THE COMMISSION decides their completion, of the payment of the
      Associated

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      Additional Costs that derive from the Additional Works of Diversion under
      the modality of unitary prices for the building of the diversion tunnels
      and the pre- diversion tunnels by the left or right margins; (v) ratify in
      accordance with the Seventh Clause of the Amendment Agreement Number 1
      that the Critical Event 1.4 of Exhibit 3 of the Agreement ceased to be a
      Punishable Critical Event.

In accordance with that established in the Sixth Clause of the Amendment
Agreement Number 2 THE COMMISSION and THE CONTRACTOR agreed to increase the
original amount of the Lump-sum Activities of the Agreement, due to the
Additional Works of Diversion hereinafter described, subject to the condition
that THE COMMISSION decides their execution:

      -     The increase of resources and extension of the crossing tunnel
            equals the amount of US $ 1,810,899.51 Dollars (One Million Eight
            Hundred and Ten Thousand Eight Hundred and Ninety Nine Dollars
            51/100 Currency of the United States; plus VAT;

      -     Pre-diversion by the left bank equals the amount of US $
            2,969,437.75 Dollars (Two Million Nine Hundred and Sixty Nine
            Thousand Four Hundred and Thirty Seven Dollars 75/100 Currency of
            the United States) plus VAT;

      -     In the event THE COMMISSION decides not to execute the pre-diversion
            by the left bank, this shall pay for the endoorment of said tunnel
            the amount of $ 338,578.50 Dollars (Three Hundred and Thirty Eight
            Thousand Five Hundred and Seventy Eight Dollars 50/100 Currency of
            the United States) plus VAT;

      -     Pre-diversion by the right bank equals the amount of US $
            3,533,182.44 Dollars (Three Million Five Hundred and Thirty Three
            Thousand One Hundred and Eighty Two Dollars 44/100 Currency of the
            United States), plus VAT;

      -     In the event THE COMMISSION decides not to execute the pre-diversion
            by the right bank, THE COMMISSION shall pay for the construction of
            the access road, the ramp and the endoorment of said tunnel the
            amount of US $ 1,662,411.00 Dollars (One Million Six Hundred and
            Sixty Two Thousand

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            Four Hundred and Eleven Dollars 00/100 Currency of the United
            States) plus VAT.

I.6   That the concept of Additional Costs agreed in the Amendment Agreement
      number 2 shall further include and without including any limitation
      whatsoever those derived from the following events:

      a)    The change of the trace of the baseboard, stated in official
            communication number LECAJ 1502/AGN/523/2004 of THE COMMISSION and
            the note to the Binnacle 438 of Contention Works, which defined the
            design of the foundation of the baseboard and its geometry between
            points 9 and 11 due to the geological conditions found in the river
            bed, after the Competitive Bidding and the execution of the
            Agreement as it appears in section 8.2.1.3 of the Bidding Rules and
            to the questions and answers of the bidders in the clarifications
            meetings, specifically to question number 47 made at such meeting.

      b)    The late commencement of the construction of the concrete face of
            the curtain for the reasons explained in the precedent paragraph.

1.7   That the Agreement and this Agreement are regulated by the Law of Public
      Works and Services Related to the same, its Regulations and other federal
      laws that result applicable, in accordance with Clause 31.1 of the
      Agreement.

1.8   That this instrument complies with the provisions of articles 59 of the
      Law of Public Works and Services Related to the Same, 69 and 79 of its
      Regulations where it stated that the Entities within their authorized
      investment plan, under their responsibility and due to express reasons
      duly grounded, may modify the mixed public works Agreements in those
      portions corresponding to the unitary prices by means of amendment
      agreements, provided that these, considered jointly or severally, do not
      surpass twenty five per cent of the amount or term agreed in the
      Agreement, do not imply essential variations to the original project, or
      they are entered to avoid in any manner the fulfillment of the Law or
      Treaties.

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II.   THE COMMISSION represents that:

      It determined that it is necessary to amend the Agreement, therefore the
      execution of an Amendment Agreement (hereinafter the "Amendment
      Agreement") is necessary by virtue of the following:

II.1  To define and comply with the agreement provided in the First Clause
      paragraph (iv) of the Sixth Clause of the Amendment Agreement number 2 and
      set forth in section 1.5 of the Representations of this Agreement, and to
      the petition of THE COMMISSION and THE CONTRACTOR by means official
      communication no. FSC-1083/03 dated October 29 2003, and to begin the
      construction of the pre-diversion tunnel of the right bank, being the same
      completed and diverting the river on December 29 2003, which allowed the
      conclusion of the cofferdam waters upstream before the beginning of the
      raining season of 2004, preventing therefore that the Date for the
      Completion of the Project is deferred for one year.

II.2  It has considered to recognize to THE CONTRACTOR the affectations to the
      Execution Schedule approved in the Amendment Agreement number 2, and the
      in last paragraph of the Fourth Clause, inasmuch as THE COMMISSION ordered
      THE CONTRACTOR the construction of the pre-diversion by the right bank by
      means of the official communication FSC-1083/03 of October 29 2003, which
      determined the completion of the cofferdam waters upstream before the
      beginning of the raining season 2004.

II.3  The geological conditions foreseen for the construction of diversion
      tunnel no.1 aggravated by the intersection with the crossing tunnel,
      affected the advance in the excavation of tunnel 1 itself, provided THE
      CONTRACTOR, first had to incorporate resources and thereafter extend the
      crossing until tunnel 2 in order to be able to comply with the conclusion
      before July 10 2004, and to open fronts by this second tunnel.

II.4  In the river bed, in the zone of the displacement of the baseboard,
      between points 9 and 11, geological conditions different to those informed
      in the

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      Bidding Rules, arose due to the presence of a fault-dam that was
      identified during the excavation of the river bed. This fault has been
      called "Calypso", and the solution by THE COMMISSION required a change of
      the project, in the structural trace and design of the baseboard.

      The foregoing is grounded in official communication number
      LECAJ1502/AGN/523/2004 of THE COMMISSION and the note of binnacle 438 of
      Contention Works, which define the structural trace and design of the
      foundation of the Baseboard.

II.5  Derived from the aforementioned representations, the Critical Events
      stated below were affected in the following manner:

      (i)   Critical Event 1.3 "Beginning of the construction of the tunnel of
            access to the enginehouse" due to the impossibility of beginning the
            construction of the cofferdam downstream, that is integrated to the
            curtain and is made a part of the critical event.

      (ii)  The critical event 1.5 "Beginning of the first stage of the pouring
            of the slabs of the concrete face of the curtain to an elevation of
            296", due to the execution of the pre-diversion tunnel by the right
            bank and the geological conditions located in the river bed, at the
            zone of excavation of the baseboard, between points 9 and 11;

      (iii) Critical Event 1.6 "Conclusion of the second stage of the pouring of
            the slabs of the concrete face of the curtain to an elevation of
            373.00", due to the reasons stated in the precedent paragraph.

      (iv)  Critical Event 1.12 "Beginning of the first pouring at the
            enginehouse for the electromechanical mounting" for the reasons
            stated in paragraph (i).

II.6  Notwithstanding the rights and obligations of the parties derived from the
      Agreement to this date, the Critical Events 1.2, 1.3, 1.4, and 1.10 of
      Exhibit 3 of the Agreement have been fulfilled under the binnacle note no.
      407 dated March 30 2004, set forth in commercial folio number 6 of book 6
      of the diversion works; the Binnacle note no. 53 dated January 15 2004,
      stated in folio number 26 of book 1 of the generation works; the Binnacle
      note no. 414 dated July 15

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      2004, set forth in folio no. 27 of book 4 of the contention works and the
      Binnacle note number 10 dated August 23 2004, set forth in folio number 5
      of book 1 of the pressure tubing, respectively.

II.7  The execution of this Agreement is justified by the reasons stated in the
      precedent representations, and other considerations contained in the
      technical opinion which is made a part of this Agreement as Exhibit 1.

III.  THE CONTRACTOR represents that:

III.1 It agrees and acknowledges the extent of the amendments and clarifications
      subject matter of this Agreement, that it has legal capacity and it has
      the necessary organization and elements to comply with the same.

III.2 For the amendment of the Execution Schedule, which is attached hereto as
      Exhibit 5, THE CONTRACTOR has considered the actual advance to this date
      in the tunnel of access to the enginehouse, pressure tubing, relief tunnel
      and oscillation drift, as well as the change of the foundation of the
      baseboard and its geometry between the points 9 and 11, therefore it shall
      apply all its expertise, capabilities, skills and resources to maintain as
      the date for the conclusion of the Project foreseen on August 31 2007 the
      start up of Units 1 and 2 on February 28 and May 31st, respectively.

Thereafter THE PARTIES hereto agree to the execution of this Agreement under the
provisions of Article 59 of the Law of Public Works and Services Related to the
same, 69 and 79 of its Regulations and any other applicable rules and legal
provisions, and for such purposes they grant and submit to the following:

                                     CLAUSES

FIRST. - THE PARTIES agree that the subject matter of this Agreement is:

(i)   To modify the Execution Schedule of the Amendment Agreement number 2,
      under the provisions of Second and Third Clauses and in the last paragraph

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      of the Fourth Clause of the Amendment Agreement number 2, as well as that
      stated in Recital number 1.6 and II of this Agreement and after having
      analyzed such geological conditions in the diversion tunnel no. 1, at the
      intersection with the crossing tunnel, the activities carried out for the
      execution of the pre-diversion by the left bank and the effect on the
      construction of the baseboard due to the Calypso fault, THE PARTIES agree
      to a new Execution Schedule for the Works attached hereto as Exhibit 5.

(ii)  To recognize the actual amount of the Additional Related Costs, derived
      from the execution of the Additional Diversion Works, ordered by THE
      COMMISSION under the modality of unitary prices, for the execution of the
      diversion tunnels and the pre-diversion tunnel by the right bank, as well
      as the works ordered by THE COMMISSION, for the possible pre-diversion by
      the left bank.

(iii) To cancel the amounts of the Additional Diversion Works indicated in the
      Sixth Clause of the Amendment Agreement number 2, which execution was not
      necessary.

(iv)  To recognize and pay, as the case may be, under the modality of unitary
      prices, the affectations of time and cost for the recovering of the
      schedule derived from that which has been stated in Representation number
      1.6 and the Representations of point II of this Agreement.

(v)   To define the new Dates for the Critical Events number 1.3, 1.5, 1.6 and
      1.12, provided in Exhibit number 3 of the Agreement, derived form the
      amendments to the contractual conditions that have applied until this
      date, according to Clauses 13.3 and 27.3 of the Second paragraph of the
      Agreement being attached hereto as Exhibit 4, replacing those indicated in
      Exhibit 3 of the Agreement.

(vi)  To determine the average daily proceeds that THE CONTRACTOR, under the
      Execution Schedule, shall execute for each one of the materials that form
      the enrockment dam in each one of the stages of its construction process,
      in

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      order to comply with Critical Event 1.9 related to the "final closing of
      the diversion tunnels for the beginning of the filling of the impounding",
      which date is July 1st 2006, attached hereto as Exhibit 6.

SECOND. The new Execution Schedule of the Works, attached hereto as Exhibit 5 of
this Agreement, includes the formats OE10, OE11, OE11A and OE13 (Calendarized
activities net and critical route, Monthly Amount Schedule for the lump-sum
portion and Unitary Prices and Calendarized Disbursement Schedule of the
lump-sum portion of the monthly utilization of the materials and permanent
installation equipment) and OT-7 (General Project Plan) which replace formats
OE10, OE11, OE11A, OE13 and OT-7 of Exhibit 5 of the Amendment Agreement number
2, this adjustment is the result of the amendment of the Works Execution
Schedule and is essential for the fulfillment of the other terms and conditions
of the Agreement.

THE COMMISSION agrees, with the purpose of complying the aforementioned
Schedules, that the construction of the concrete face of the curtain be carried
out in three stages, in lieu of the two stages contemplated in the original
planning, according to that established in the format OE10, attached to this
document and according to this, the wording of Critical Events 1.5 and 1.6
changes in the following manner:

      1.5 Beginning of the first stage of the pouring of the slabs for the
      concrete face of the curtain to an elevation of 280.

      1.6 Termination of the third stage of the pouring of the slabs for the
      concrete face of the curtain to an elevation of 388.

THIRD. - According to Clause Sixth of the Amendment Agreement number 2 THE
PARTIES acknowledge to increase the original amount of the unitary prices
portion of the Agreement for the Additional Related Costs derived from the
execution of the following Additional Diversion Works ordered by THE COMMISSION
and that were actually completed:

(i)   Extension of the crossing tunnel from the connection of the tunnel 1 to
      the tunnel 2 the amount of this Additional work equals $261,145.08 U.S.
      Dollars

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      (Two Hundred and Sixty One Thousand One Hundred and Forty Five Dollars
      08/100), plus VAT, according to the budget described in Exhibit 2 of this
      Agreement.

(ii)  The execution of the pre-diversion by the right bank, the amount of this
      Additional Work equals $1,457,047.88 U.S. Dollars (One Million Four
      Hundred and Fifty Seven Thousand Forty Seven Dollars 88/100), plus VAT,
      according to the budget specified in Exhibit 3 of this Agreement.

According to the above, there is an increase with respect to the original amount
of the Agreement Price in the portion related to the Unitary Prices Catalogue,
in the amount of $1,718,192.96 U.S. Dollars (One Million Seven Hundred and
Eighteen Thousand one Hundred and Ninety Two Dollars 96/100), which represents
2.6% (two point six percent) in increase with respect to the original amount of
the Agreement Price in the portion related to Unitary Prices and a 11.43 %
(eleven point forty three percent) accumulated with respect to the original
amount of the Agreement Price in the portion regarding the Unitary Prices,
resulting therefore an aggregate amount of the Unitary Prices Portion of the
Agreement, the amount of $73,292,536.81 U.S. Dollars (Seventy Three Million Two
Hundred and Ninety Two Thousand Five Hundred and Thirty Six Dollars 81/100) plus
VAT.

THE PARTIES acknowledge that the aforementioned amounts in paragraphs (i) and
(ii) replace and cancel all the amounts provided in the Sixth Clause of the
Amendment Agreement number 2, pending the conciliation, to be incorporated in
another agreement, of the additional resources of the pre-diversion by the left
and right banks.

FOURTH. - Notwithstanding the rights and obligations of the parties, derived
form the Agreement THE COMMISSION acknowledges that the critical events 1.2,
1.3, 1.4, and 1.10 of Exhibit 3 of the Agreement have already been fulfilled.

FIFTH. - THE PARTIES agree that the new dates for the Critical Events 1.3, 1.5,
1.6, and 1.12 of Exhibit 3 of the Agreement, derived form the amendments to the
covenants in effect to this date under Clause 13.1 of the Agreement, and that
are

<PAGE>

attached hereto as Exhibit 4, replacing those indicated in Exhibit 3 of the
Agreement.

SIXTH. - THE CONTRACTOR according to the Execution Schedule shall place the
average volumes provided in Exhibit 6 of this Agreement of each of the materials
that form the enrockment dam in each one of the stages of its construction
process.

SEVENTH. - Due to the delay that suffered the construction of tunnel 1, as
consequence of the geological fault located at the intersection with the
crossing tunnel and to the geological fault (Calypso) found in the river bed
between points P9 and P11 of the baseboard, the beginning of the construction of
the baseboard in the river bed was delayed, due to causes not imputable to THE
CONTRACTOR.

THE PARTIES, agree to analyze also, the problems caused by the excavation of the
channel of the so called outlet work, which product used to spill over the right
bank and to review and authorize in due course, as the case may be, within sixty
days of the filing of the petition by THE CONTRACTOR, the affectations that may
arise, to comply with the date stated in critical event no. 1.9 on July 1st
2006. It is made clear that for the preparation of the Execution Schedule the
days of the delay derived from these unforeseeable events were not take into
account.

EIGHTH. The monthly advances of the concepts covered by this Agreement that
correspond to works to be executed, including the Additional Costs mentioned in
the First Clause Paragraph (ii) of this Agreement and the Additional Related
Costs defined in the Amendment Agreement number 2, shall have the same treatment
of recognition and form of payment as those set forth by the Agreement for the
Unitary Prices Activities according to clauses 9.2, 10.1 and 13.4, THE
COMMISSION will recognize them in an independent manner according to Exhibit 14
of the Agreement and to the First and Second Memorandum of Clarifications to the
Agreement, that is to say, as if they were an event of recognition of advances
in the construction provided in the economic format OE-11B.

<PAGE>

NINTH. For every Additional Costs, Additional Related Costs as they were defined
in the Amendment Agreement number 2 and those additional costs derived from this
Agreement, under section 1.6 of the Recitals and the First Clause paragraph (ii)
of this Agreement, THE PARTIES commit to conciliate them within a term no longer
than 60 days as of their submission by THE CONTRACTOR, who will include them in
the Report of the Monthly Advance of the month following to that such
conciliation is made.

TENTH.- According to the provisions of Representation III.1 of this Agreement,
in the event that due to an Act of God or Force Majeur event or to a
Governmental Force Majeur event or to an event of default by THE COMMISSION, the
additional or outstanding works ordered by THE COMMISSION, Real Estate Rights,
Site Conditions differing from the ones provided for the project in terms of
section 8 of the Bidding Rules, prevent the obtaining of the results of the new
Execution Schedule and this prevents the conclusion of the Critical Event 1.9 of
Exhibit 3 of the Agreement "Final Closing of the diversion tunnels for the
beginning of the filing of the impounding", no later than on July 1st 2006, both
Parties, according to that indicated in Clauses 26.5, 27.3 and other applicable
of the Contract, shall analyze, conciliate and formalize a new Execution
Schedule, including Exhibit 3 of the Agreement, within a term of thirty (30)
days counted as of the date on which the termination of the Critical Event 1.9
of Exhibit 3 of the Agreement called "Final Closing of the diversion tunnels for
the beginning of the filling of the impounding" should have taken place, for
such purpose the possible limitations to the financing of THE CONTRACTOR should
be taken into account, and that THE COMMISSION shall absorb, abiding to the
Agreement, in the event that what is foreseen by this Clause arises, the
financial costs of an extension to the Execution Schedule, considering the
provisions of said Clause 26.5 of the Agreement and as of the expiration of the
60 days term provided for in the same and up to a term of the extension of the
Execution Schedule agreed. In this case, the application of the penalties for
THE CONTRACTOR foreseen in Clauses 13.6 and 26.1 of the Agreement shall not
apply nor those of the Law of Public Works and Services Related to the same and
its Regulations shall apply during the extension term agreed by THE PARTIES.

<PAGE>

ELEVENTH. - The PARTIES agree that the amount of the Compliance Guarantee
granted by THE CONTRACTOR for an amount equivalent to ten percent (10 %) of he
amount of the authorized investment for the second fiscal year, is sufficient to
guarantee the due, proper and absolute fulfillment by THE CONTRACTOR of all its
obligations derived from the Agreement and this Amendment Agreement for the
current fiscal year, inasmuch as the Works Execution Schedule originally agreed
was adjusted as consequence of that agreed in the Amendment Agreement.

TWELFTH. - The execution of this Agreement does not represent a waiver to the
rights available to THE CONTRACTOR, derived from the execution of the works in
the terms established in the Bidding Rules, in the Agreement, and in the
Amendment Agreements numbers 1 and 2 nor of any other situation prior to the
execution of this Amendment Agreement.

THIRTEENTH. - THE PARTIES agree that, except for that expressly provided for in
this Amendment Agreement, the rest of the Clauses that are made a part of the
Agreement and its Amendment Agreements are mandatory, and they shall rule in
full force and effect.

The terms used with capital letters in this document shall have the same meaning
as the one given to them in Clause 1.1 of the Agreement and in the First, Second
and Third Amendment Agreements, except as otherwise expressly specified in this
Amendment Agreement.

IN WITNESS OF THE ABOVE, THE PARTIES execute and deliver, through their legally
authorized representatives, this Amendment Agreement, in six counterparts
equally valid, in Mexico City, Federal District, on the 30th day of September
two thousand and four.

By the "COMMISSION"                                 By the "CONTRACTOR"

(An illegible signature)                   (An illegible signature)
-------------------------------------      -------------------------------------

<PAGE>

MR. EUGENIO LARIS ALANIS                   MR. LUIS HORCASITAS MANJARREZ
MANAGER OF PROJECTS OF                     LEGAL REPRESENTATIVE
FINANCED INVESTMENTS

LIST OF EXHIBITS:

EXHIBIT Num. 1- Technical Report
EXHIBIT Num. 2- Extension of the crossing tunnel (catalogue)
EXHIBIT Num. 3- Pre-diversion by the right bank (Catalogue)
EXHIBIT Num. 4- Dates of Critical Events
EXHIBIT Num. 5- Works Schedule Amendment Agreement num. 3
EXHIBIT Num. 6- Results of collocation of materials in the curtain, to comply
                   with Critical Event 1.9<PAGE>
                                                                     Exhibit 4.7

                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

AMENDMENT AGREEMENT NUMBER 4 (FOUR) TO THE MIXED AGREEMENT OF FINANCED PUBLIC
WORK NUMBER PIF-005/2003, FOR THE RECOGNITION AND PAYMENT OF THE INCREASE IN THE
COST OF STEEL ENTERED INTO BY AND BETWEEN ON THE ONE PART COMISION FEDERAL DE
ELECTRICIDAD (THE FEDERAL COMMISSION OF ELECTRICITY), REPRESENTED BY ENG.
EUGENIO LARIS ALANIS, IN HIS CAPACITY AS DIRECTOR OF FINANCED INVESTMENT
PROJECTS AND ON THE OTHER PART THE COMPANY CONSTRUCTORA INTERNACIONAL DE
INFRAESTRUCTURA, S.A. DE C.V., REPRESENTED BY ENG. LUIS HORCASITAS MANJARREZ, IN
HIS CAPACITY AS LEGAL REPRESENTATIVE, HEREINAFTER REFERRED TO AS THE
"COMMISSION" AND THE "CONTRACTOR", RESPECTIVELY, ACCORDING TO THE FOLLOWING
RECITALS AND CLAUSES:

                                    RECITALS

I. The PARTIES represent:

I.1      That on March 26, 2003, they executed the Mixed Agreement of Financed
         Public Work, recorded with the number PIF - 005/2003, legal instrument
         that shall hereinafter be referred to as the "Agreement", awarded to
         the CONTRACTOR by means of the International Public Bidding Process,
         established by Articles 27, paragraph I, 28 and 30, paragraph II, 32,
         33 and 45 of the Law of Public Works and Services Related to the Same,
         which purpose consists of: the execution of the Civil Works,
         Electromechanical Works and Associated Works, supply, engineering,
         manufacturing, transportation, installation, testing and start up of
         two equipped turbo-generating Units, of 375 MW of nominal power each,
         for the fall and expense of specified design and that is detailed in
         Section 8 of the Bidding Rules, Works that all together are named
         Hydroelectric Project El Cajon, and which principal structures are
         located in the Municipalities of La Yesca and Santa Maria del Oro, in
         the State of Nayarit of Mexico.

         The Works which consist of the Lump-sum Price Activities are described
         in detail in Exhibits OE-3, OE-4 and OE-5 of Section 4 of the Bidding
         Rules and are to be
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         conducted under the modality of lump-sum, because the portion of the
         Works that correspond to the Lump-sum Activities are depicted in detail
         in Exhibit OE - 5A of Section 4 of the Bidding Rules and shall be
         executed under the base of lump-sum.

I.2      That on July 04, 2003, the PARTIES executed the Amendment Agreement
         Number 1 to the Agreement (hereinafter "Amendment Agreement Number 1").

I.3      That the Price of the Agreement that the COMMISSION agreed to pay to
         the CONTRACTOR, agreed in Clause 9.1, was agreed to as total payment
         for the execution of the Works that correspond to the Lump-Sum
         Activities, the lump-sum price of US $ 682,517,584.80 Dollars (Six
         Hundred and Eighty Two Million Five Hundred and Seventeen Thousand Five
         Hundred and Eighty Four Dollars 80/100 Currency of the United States),
         and for the Unit Price Activities, the price of US $ 65,773,072.59
         Dollars (Sixty Five Million Seven Hundred and Seventy Three Thousand
         Seventy Two Dollars 59/100 Currency of the United States) plus the
         corresponding value added tax.

         According to that established in the Third Clause of the Amendment
         Agreement Number 1 the COMMISSION and the CONTRACTOR agreed to increase
         the amount of the Unit Price Activities of the Agreement in the amount
         of US $ 5,801,271.26 Dollars (Five Million Eight Hundred and One
         Thousand Two Hundred and Seventy One Dollars 26/100 Currency of the
         United States) plus the Value Added tax, which represented an increase
         of 8.82 % (eight point eighty two per cent) relative to that originally
         contracted, thus remaining an accumulated aggregate amount of the
         Agreement based in unit prices of US $ 71,574,343.85 Dollars (Seventy
         One Million Five Hundred and Seventy Four Thousand Three Hundred and
         Forty Three Dollars 85/100 Currency of the United States) plus the
         corresponding value added tax, in accordance with the budget of
         Additional Works.

                                                                               2
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

I.4      That on September 10, 2003, the PARTIES executed the Amendment
         Agreement Number 2 to the Agreement (hereinafter the "Amendment
         Agreement Number 2") in accordance with that established in Articles 59
         of the Law of Public Works and Services Related to the Same, and 69 and
         79 of its Regulations, in order to: (i) under the Sixth Clause of the
         Amendment Agreement Number 1, modify the original Execution Schedule
         due to the new date for the commencement of the Works that is April 24,
         2003; (ii) agree to the disarrangement of the Critical Events Dates
         1.1, 1.2, 1.3 and 1.4 established in Exhibit Number 3 of the Agreement,
         derived from the modifications to the contractual conditions that have
         ruled up to this date according to Clause 13.1 of the Agreement; (iii)
         recognize and pay, if applicable, under the modality of unit prices the
         Additional Costs related to the modifications of the original Execution
         Schedule, as a consequence of the late delivery and under different
         conditions to those established in the Bidding Rules and in the
         Agreement, of the portals of the deviation tunnels and the access road
         to the Site, for causes not imputable to the CONTRACTOR and adjust the
         Lump-sum Activities because of the modification to the length of the
         deviation tunnels and the reduction of the volume of the cofferdam in
         the upstream waters; (iv) approval in the event the COMMISSION decides
         their completion, of the payment of the Associated Additional Costs
         that derive from the Additional Works of Deviation under the modality
         of unitary prices for the building of the deviation tunnels and the
         pre-deviation tunnels by the left or right margins; (v) ratify in
         accordance with the Seventh Clause of the Amendment Agreement Number 1
         that the Critical Event 1.4 of Exhibit 3 of the Agreement ceased to be
         a Punishable Critical Event.

         In accordance with that established in the Sixth Clause of the
         Amendment Agreement Number 2 the COMMISSION and the CONTRACTOR agreed
         to increase the original amount of the Lump-sum Activities of the
         Agreement, due to the Additional Works of Deviation hereinafter
         described, subject to the condition that the COMMISSION decides their
         execution:

                                                                               3
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         -        The increase of resources and extension of the crossing tunnel
                  equals the amount of US $ 1,810,899.51 Dollars (One Million
                  Eight Hundred and Ten Thousand Eight Hundred and Ninety Nine
                  Dollars 51/100 Currency of the United States; plus VAT;

         -        Pre-deviation by the left bank equals the amount of US $
                  2,969,437.75 Dollars (Two Million Nine Hundred and Sixty Nine
                  Thousand Four Hundred and Thirty Seven Dollars 75/100 Currency
                  of the United States) plus VAT;

         -        In the event the COMMISSION decides not to execute the
                  pre-deviation by the left bank, this shall pay for the
                  "emportalamiento" of said tunnel the amount of $ 338,578.50
                  Dollars (Three Hundred and Thirty Eight Thousand Five Hundred
                  and Seventy Eight Dollars 50/100 Currency of the United
                  States) plus VAT;

         -        Pre-deviation by the right bank equals the amount of US $
                  3,533,182.44 Dollars (Three Million Five Hundred and Thirty
                  Three Thousand One Hundred and Eighty Two Dollars 44/100
                  Currency of the United States), plus VAT;

         -        In the event the COMMISSION decides not to execute the
                  pre-deviation by the right bank, the COMMISSION shall pay for
                  the construction of the access road, the ramp and
                  "emportalamiento" of said tunnel the amount of US $
                  1,662,411.00 Dollars (One Million Six Hundred and Sixty Two
                  Thousand Four Hundred and Eleven Dollars 00/100 Currency of
                  the United States) plus VAT.

I.5      That on September 30, 2004, the PARTIES subscribed the Amendment
         Agreement Number 3 to the Agreement (hereinafter referred to as
         "Amendment Agreement Number 3") according to that established by
         Articles 59 of the Law of Public Works and Services Related to the
         Same, and 69 and 79 of its Regulations, in order to: (i) Modify the
         Execution Schedule of the Amendment Agreement Number 2, according to
         that established in the Third Clause and in the last paragraph of the
         Fourth Clause of the same Amendment Agreement Number 2, as well as that
         contained in Recitals I.6 and II of this Agreement and upon analyzing
         the actual geological conditions found at the deviation tunnel No. 1 in
         the intersection with the crossing tunnel the

                                                                               4
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         activities conducted for the execution of the pre-deviation by the
         right bank and the effect on the construction of the baseboard (plinth)
         in the river bed, because of Calypso's default, the parties agree to a
         new Execution Schedule of the Works that is attached to the Amendment
         Agreement Number 3 as Exhibit 5. (ii) Recognize the real amount of the
         Associated Additional Costs that derived from the execution of
         Additional Works of Deviation, ordered by the commission under the
         modality of unitary prices, for the execution of the deviation tunnels
         and the pre-deviation tunnel by the right bank, as well as the works
         ordered by the commission, for the potential pre-deviation by the left
         bank. (iii) Cancel the amounts of the Additional Deviation Works
         indicated in Clause Sixth of the amendment Agreement number 2, which
         was not necessary to build. (iv) Recognize and pay, if applicable,
         under the modality of unitary prices, the affectations in time and cost
         for the recovering of the program derived from that indicated in
         Recital I.6 and the Recitals of item II of this Agreement. (v) Define
         the new Dates of Critical Events 1.3, 1.5, 1.6, 1.12 and 1.13,
         established in Exhibit Number 3 of the Agreement, derived from the
         modifications to the contractual conditions that prevailed to this
         date, according to Clauses 13.3 and 27.3 second paragraph of the
         Agreement and that are attached to Amendment Agreement Number 3 as
         Exhibit 4, replacing that indicated in Exhibit 3 of the Agreement. (iv)
         Precise the average daily yields that the CONTRACTOR, in accordance
         with the Execution Schedule, shall execute for each of the materials
         that form the rock-fill dam in each of the phases of its construction
         process, to comply with the Critical Event 1.9 related to the "final
         closure of the deviation tunnels to start the filling of the
         reservoir", which date is July 1st., 2006, that are attached to
         Amendment Agreement Number 3 Exhibit 6.

         According to that provided for in the Third Clause of the Amendment
         Agreement Number 3 the PARTIES agree and acknowledge to increase the
         original amount of the portion of the unitary prices of the agreement
         for the Associated Additional Works that derived from the execution of
         the following Additional Deviation Works ordered by the COMMISSION and
         that were effectively executed:

                                                                               5
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         (i)      Extension of the crossing tunnel from the connection of tunnel
                  1 to tunnel 2 (sic) the amount of this Additional work equals
                  the amount of US$ 261,145.08 (Two Hundred and Sixty One
                  Thousand One Hundred and Forty Five Dollars 08/100 Currency of
                  the United States) plus VAT.

         (ii)     The execution of the pre-deviation by the right bank, the
                  amount of this Additional Deviation Work equals the amount of
                  $ 1,457,047.88 US (One Million Four Hundred and Fifty Seven
                  Thousand Forty Seven Dollars 88/100 Currency of the United
                  States) plus VAT.

         In accordance with the above, an increase is presented with respect to
         the original amount of the Price of the Agreement in the portion
         related to the Catalog of Unitary Prices, in the amount of $
         1,718,192.96 Dollars (One Million Seven Hundred and Eighteen Thousand
         One Hundred and Ninety Two Dollars 96/100 Currency of the United
         States), which represents a 2.61 % (two point sixty one per cent) of
         increase with respect to the original amount of the Price of the
         Agreement in the portion related to Unitary Prices and a 11.43 %
         (eleven point forty three per cent) accumulated with respect to the
         original amount of the Price of the Agreement in the portion related to
         Unitary Prices, as a result the total amount of the portion regarding
         the Unitary Prices of the Agreement, in the amount of US $
         73,292,536.81 Dollars (Seventy Three Million Two Hundred and Ninety Two
         Thousand Five Hundred and Thirty Six Dollars 81/100 Currency of the
         United States) plus VAT.

I.6      That Clause 11 "Adjustment of Costs" of the Agreement provides as
         follows:

         The COMMISSION and the CONTRACTOR acknowledge that the portion of the
         works covered by the Agreement under the modality of payment of unitary
         prices,

                                                                               6
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         this is, the Activities at Unitary Prices, shall not be subject to the
         adjustment of costs established in the Law of Public Works and Services
         Related to the Same and its Regulations because the quotation for such
         works derives from the basic elements of cost valued in Dollars, and
         therefore the CONTRACTOR expressly waives the right to adjustment of
         costs to the price of the aforementioned works. Said works shall only
         be subject to adjustment of costs in accordance with the guidelines
         issued, if applicable, by the Ministry of the Comptrollership and
         Administrative Development, in accordance with that established in
         Article 59 of the Law of Public Works and Services Related to the Same.

         The COMMISSION and the CONTRACTOR acknowledge that portion of the works
         covered by the Agreement under the modality of lump-sum price, this is
         the Lump-sum Activities, shall only be subject to costs adjustments in
         accordance with the guidelines issued, if such is the case, by the
         Ministry of the Comptroller and Administrative Development, in
         accordance with that established in Article 59 of the Law of Public
         Works and Services Related to the Same.

I.7      Article 59 of the Law of Public Works and Services Related to the same
         provides in its third, fourth, fifth and sixth paragraph, as follows:

         The lump-sum agreements or the portion of the mixed ones of this kind
         shall not be modified in their amount or term, nor shall they be
         subject to any adjustment of costs.

         However, in the event that following the awarding of a lump-sum
         agreement or the portion of the mixed ones of this kind, economic
         circumstances of general nature may arise without the responsibility of
         the parties and therefore they could not have been subject matter of
         consideration in the tender that served as basis for the awarding of
         the correspondent agreement; such as, among others: fluctuations in the
         exchange rate or changes in the national or international prices that
         result in the direct increase or reduction in the costs of the raw
         materials necessary for the

                                                                               7
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         works not yet executed in accordance with the originally agreed
         schedule; the agencies and entities shall recognize the increases or
         request reductions.

         The provisions of the above paragraph shall be governed by the
         guidelines issued by the Comptrollership; same that shall consider,
         among other matters, the mechanisms available to the PARTIES to face
         these situations.

         Once the potential modifications to the corresponding agreement are
         determined, the timely execution of the agreements shall be the
         responsibility of the corresponding agency or entity.

I.8      On May 21, 2004, the Ministry of Public Office published in the
         Official Gazette of the Federation, the Order that provides the
         guidelines to conduct the review and adjustment of the price of Steel
         in the agreements and orders formalized under the Public Works Laws and
         Services Related to the Same, and the Acquisitions, Leases and Services
         of the Public Sector and its Regulations (hereinafter the
         "Guidelines"), same that became effective on the day following its
         publication and for a term of six months as of the date in which they
         became effective, to be applicable only for purposes of recognizing the
         change in the price of Steel in the relevant participation that
         corresponds to this concept regarding the total amount of the
         agreement. The adjustments shall be calculated as of the month of
         November 2003 regarding works not yet executed, according to the
         current Execution Schedule or, in the event of delay not attributable
         to the CONTRACTOR, with respect to the agreed upon schedule.

         For purposes of the Guidelines it is understood by "Steel" the
         different presentations of the aforementioned metal, among others,
         slabs, rolled-shape, extrusive angles, corrugated bar, rustles, etc.

                                                                               8
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         Said Order in its first three paragraphs of the portion of the
         considerations establishes that as of December 2003 the price of the
         Steel in its several presentations has been increasing constantly and
         unforeseeable in the market ranging such increases from 20 % to 50 %.
         That such event has had an impact on the public works agreements under
         completion in which the raw material of Steel and its different
         presentations represents at least 10 % of the total amount of related
         operations and contracts not being this a limitation because in
         accordance with official communication UNAOPSPF/309/BM/1460/2004 said
         10 % is only enunciatively in the consideration, thus the
         entrepreneurial chambers, suppliers and contractors, as well as the
         governmental agencies and Entities involved in the problematic filed a
         petition to the Ministry of Public Office stressing the need of
         establishing the correspondent guidelines and normative mechanisms to
         face this situation in order to prevent cancellations of projects,
         rescissions or early termination of the corresponding transactions and
         agreements.

I.9      The Ministry of Public Office (SFP), by means of Official Communication
         Number UNAOPSPF/309/BM/0769/2004, dated July 26, 2004, answered the
         doubts set out by the CONTRACTOR, by means of its communication dated
         July 5, 2004, derived from the interpretation and application of the
         Guidelines.

I.10     On August 9, 2004, the CONTRACTOR notified the COMMISSION its request
         for review and adjustment of the price of Steel, to which it attaches
         the valid and unquestionable documentation that identifies the relative
         participation of Steel regarding the total amount of the Agreement, the
         objective elements that were considered for its determination, as well
         as the identification of the executed portion of the Works as of
         November 2003, in accordance with that established in provision
         Eleventh, paragraph 1) of the Guidelines.

I.11     The Ministry of the Public Office, by means of official communication
         Number UNAOPSPF/309/BM/0884/2004 dated September 7, 2004, responded to
         the new

                                                                               9
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         doubts filed by the CONTRACTOR, by official communication dated
         September 1, 2004, which also have an influence in the application and
         interpretation of the Guidelines.

1.12     The Ministry of the Public Office, by means of official communication
         number UNAOPSPF/309/BM/1460 dated December 13, 2004, responded to the
         consultation filed by the COMMISSION, by means of official
         communications numbers DPIF/510/2004 and BGD Number 364/2004 dated
         October 25, 2004 and December 7, 2004, respectively, arising out of the
         interpretation and application of the Guidelines.

I.13     That they (sic) recognize that the Agreement, as it refers to the price
         of Steel is within the assumptions mentioned in item First of the
         guidelines in paragraphs: b) Mixed Agreements in the portion related to
         lump-sum; c) Unitary Prices Agreements formalized in foreign currency.
         These shall include the Mixed Agreements when the portion of unitary
         (sic) has been agreed upon in foreign currency and this includes Steel.

I.14     The Agreement and this Agreement are regulated by the Law of Public
         Works and Services Related to the same, its Regulations and other
         federal laws that result applicable, in accordance with Clauses 11 and
         31.1 of the Agreement.

I.15     That as of the submission of the petition of the CONTRACTOR, the
         PARTIES have met to review and conciliate, as possible, the
         documentation presented and the CONTRACTOR, where applicable, has
         completed the information requested by the COMMISSION.

I.16     That in the Third Memorandum of Clarifications to the Agreement, in the
         second paragraphs of item "SOLE" it reads:

                                                                              10
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         "With reference to the first paragraph of Clause 9.3 of the Agreement
         ("Variations in the Works, Additional Works") the PARTIES clarify that
         the increase amount of the Price of the Agreement that is established
         in one or more amendment agreements that result from the application of
         the Guidelines and from the request for the adjustment of the price of
         the Steel, shall be computed as additional work for purposes of the
         maximum amount of increases to the price to which item 10 of the First
         Memorandum of Clarifications refers to.

         The PARTIES also clarify that such one or more amendment agreements,
         shall expressly establish the percentage that represents the agreed
         upon Price increase of the Agreement and that, only for purposes of
         that provided for in item 10 of the First Memorandum of Clarifications,
         such increase shall be allocated to the Price of the Agreement in the
         portion related to Unitary Prices".

I.17     The PARTIES declare that for this Agreement for the portion of the
         Agreement at unitary prices the amount of the Steel was determined in
         accordance with the procedure established in the eleventh guideline,
         paragraph II, subparagraph B) of the Guidelines, determining the
         participation of Steel considering within the price of Steel the direct
         and indirect costs, financing, profit and additional charges, in the
         percentages indicated in Exhibit 12 of the Agreement. For the portion
         of the Agreement at lump-sum the amount of participation of Steel was
         determined in accordance with the procedure established in item
         eleventh of the guidelines, paragraph II, subparagraph A), considering
         only the value of the Steel at direct cost of the raw material plus the
         financing cost, and deflation element "i" considering the one of the
         date of delivery of the work.

I.18     That on February 9 of the current year, the CONTRACTOR filed a writ of
         "complaint" before the Unit for Acquisition Standards, Public Works,
         Services, and Federal Patrimony of the Ministry of the Public Office,
         in order to initiate the administrative procedure of conciliation
         provided for in articles 89, 90 and 91 of the

                                                                              11
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

         Law of Public Works and Services Related to the Same, by being in
         disagreement with the criteria that have been applied to this date in
         order not to recognize the adjustments in the costs of Steel in the
         portion related to lump-sum that is determined from the sale price of
         the Agreement, that is to say, including direct cost, indirect cost,
         financing, profit and additional charges, as well as the application of
         deflactor "i" that may correspond on the date of adjustment.

II.      The COMMISSION declared that:

II.1     It agrees and acknowledges the right of the CONTRACTOR to adjust the
         price of Steel in the Agreement, due to the increases the same was
         subject to, both in the portion related to the lump-sum activities, as
         well as in the portion related to unitary prices activities, following
         the procedure that is outlined in the Guidelines determining the need
         to modify the Agreement, and therefore the execution of the Amendment
         Agreement (hereinafter referred to as the "Amendment Agreement") based
         on the following:

II.2     It has determined the need to recognize the payment to the CONTRACTOR
         due to the increase in the price of the Steel, since the Ministry of
         the Public Office issued the Order that establishes the guidelines to
         carry out the review to and adjustment of the price of Steel in the
         agreements and orders executed under the laws of Public Works and
         Services Related to the Same, and the Acquisitions, Leases and Services
         of the Public Sector and its Regulations, as a consequence of the
         increase in the price of the Steel, and that have affected in a direct
         manner the cost of the Works executed and that shall continue to have
         an impact on the Works pending to be executed.

II.3     Its legal representative has sufficient powers and authority to bind
         the COMMISSION in terms of this Amendment Agreement, being the same
         evidenced according to that provided for in Recital I.F of the
         Agreement.

                                                                              12
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

II.4  It also justifies the execution of this Amendment Agreement, in addition
      to the reasons exposed in the preceding recitals, based on the technical
      opinion that is attached to this Amendment Agreement as Exhibit 1

III.  The CONTRACTOR declares that:

III.1 Its representative has sufficient powers and authority to bind the
      CONTRACTOR under the terms of this Amendment Agreement, as it appears in
      public deed number 158,595 granted before Mister Jesus Castro Figueroa,
      Notary Public Number 38 of the Federal District, dated September 6, 2003,
      recorded with the Public Registry of Commerce of the Federal District
      under commercial folio number 299,934 on February 26, 2003, same powers
      that to this date have not been modified, restricted or revoked in any
      manner whatsoever.

III.2 The amount of adjustment of the price of Steel of the lump-sum agreement,
      should be determined as of the sale price of the Agreement, this is,
      including direct cost, indirect cost, financing, profit and additional
      charges, as well as to apply the deflactor "i" of the adjustment date,
      inasmuch as the recognition of the COMMISSION according to official
      communication number UNAOPSPF/309/BM/1460/2004, dated December 13, 2004,
      the adjustment of the costs because of the increase of the price of Steel
      in this agreement in the lump-sum portion is as of the cost plus the
      financing and considering deflactor "i" which corresponds to the date of
      delivery of the works, and therefore the CONTRACTOR will make use of all
      the legal instances available to it in order to obtain the total
      recognition of the concepts that were not subject to recognition and
      payment of this Amendment Agreement.

Therefore, the PARTIES agree to the execution of this Amendment Agreement for
the recognition and payment, by attributing its cost to the portion of the price
of the agreement

                                                                              13
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

at unitary prices, the increase in the cost of Steel, determined for the portion
of lump-sum as of the direct cost of steel and its financing, and in the portion
corresponding to the unitary prices as of the direct cost, plus the indirect
cost, financing, profit and additional charges, abiding to such effects to the
procedures established in the Guidelines published in the Official Gazette of
the Federation on May 21, 2004, as well as in the clarifications that have as
well an effect in the application or interpretation of the guidelines issued by
the Ministry of the Public Office, by means of official communications numbers
UNAOPSPF/309/BM/0769/2004 dated July 26, 2004, Number UNAOPSPF/309/BM/0884/2004
dated December 13, 2004 and the written request that for such purposes was filed
by the CONTRACTOR and that was conciliated as much as possible with the
COMMISSION.

Furthermore, the PARTIES agree to the execution of this Amendment Agreement in
accordance with that provided for in articles 59 of the Law of Public Works and
Services Related to the Same, 69 and 79 of its Regulations and other legal
standards and provisions that are applicable and in the Guidelines and
particularly item fifteenth that establishes that in all applicable cases the
respective amendment agreement to the agreements mentioned in the first item of
the guidelines of the Order, shall be executed in writing, the same (parties)
grant and undertake the following

                                     CLAUSES

FIRST.- Based upon that established in the Recitals of this Amendment Agreement,
the PARTIES agree to modify, assigning its cost to the portion of the price of
the agreement at unitary prices the amount of the Price of the Agreement by the
application of the Guidelines to effect the review and adjustment of the price
of Steel in the Agreement, both for the Lump-Sum Activities as for the Unitary
Prices Activities, resulting in an amount equal to $ 43,061,607.78 Dollars
(Forty Three Million Sixty One Thousand Six Hundred and Seven Dollars 78/100
Currency of the United States of America) plus the Value Added Tax hereinafter
VAT, in accordance with the documents that are detailed in Exhibit 2 of

                                                                              14
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

this Amendment Agreement. Inasmuch as such amount is added as additional work
according to the Third Memorandum of Clarifications to the Agreement, the total
amount of the portion at Unitary Prices of the Agreement equals consequently the
amount of $116,354,144.59 Dollars (One Hundred and Sixteen Million, Three
Hundred and Fifty Four Thousand, One Hundred and Forty Four Dollars 59/100
Currency of the United States of America) plus VAT which represents a 65.47%
(sixty five point forty seven per cent) of increase with respect to the original
amount of the Price of the Agreement in the portion related to Unitary Prices
and an increase of 76.90% (Seventy Six point Ninety per cent) accumulated with
respect to the original amount of the Price of the Contract in the portion
related to Unitary Prices, which represents an increase to the total amount of
the Agreement, of $50,581,072.00 Dollars (Fifty Million Five Hundred and Eighty
One Thousand and Seventy Two Dollars 00/100 Currency of the United States of
America) plus VAT, equivalent to 6.76%.

SECOND.- According to Exhibit 6 of this Amendment Agreement, the amount
disbursed from December 1, 2003 to March 31, 2005 is equal to $23,269,611.95
Dollars (Twenty Three Million Two Hundred and Sixty Nine Thousand Six Hundred
and Eleven Dollars 95/100 Currency of the United States of America) plus VAT,
and the amount pending to execute from April 1st., 2005 to August, 2007 is
$19,791,995.83 Dollars (Nineteen Million Seven Hundred and Ninety One Thousand
Nine Hundred and Ninety Five Dollars 83/100 Currency of the United States of
America) plus VAT, said amounts are integrated as follows:

From December 1st. 2003 to March 31st. 2005

<TABLE>
<S>                                       <C>
Lump-sum Civil Work and Related           $  7,324,470.74 US Dollars, plus VAT.

Lump-sum Electromechanical Work           $ 10,310,979.95 US Dollars, plus VAT.

Unitary Price Civil Work and Related      $  5,382,526.41 US Dollars, plus VAT.
</TABLE>

Therefore, from April 1st. 2005 to August, 2007.

                                                                              15
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

<TABLE>
<S>                                       <C>
Lump-sum Civil Work and Related           $ 12,697,580.10 US Dollars, plus VAT.

Lump-sum Electromechanical Work           $  5,801,373.74 US Dollars, plus VAT.

Unitary Price Civil Work and Related      $    812,571.16 US Dollars, plus VAT.
</TABLE>

The PARTIES agree that the amounts corresponding to the recognition of the
increase in the cost of Steel, both in the Lump-sum Activities as well as in the
Unitary Prices they shall abide to that established in Clauses 1.1
"Definitions", "Date of Payment of the Agreement" and 6.6 corresponding to
"Payment of Price of the Agreement or of the Value of Termination"

THIRD.- The preparation and review of the adjustment research of the price of
the Steel and the determination of the amounts mentioned in the FIRST Clause,
was made in accordance with that established in the Guidelines issued by the
Ministry of the Public Office, published at the Official Gazette of the
Federation on May 21, 2004 and in its clarifying official communications
UNAOPSPF/309/BM/0769/2004 dated July 26, 2004, Number UNAOPSPF/309/BM/0884/2004
dated September 7, 2004 (sic) AOPSPF/309/BM/1460/2004 dated December 13, 2004.

The amount established in the First Clause of this Agreement was determined for
the value of the work pending of execution as of December, 2003, applying the
prices index published monthly by the Bank of Mexico corresponding to the period
of November 2003 to November 2004, as established by the ELEVENTH Guideline,
section II, paragraph A), item 3.

The PARTIES agree that the Execution Schedule that was taken as grounds for the
determination of the amount for the increase of the price of Steel corresponds
to the Amendment Agreement Number 3.

                                                                              16
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

FOURTH.- The PARTIES agree to leave out as a pending matter to be discussed and
included in a future Agreement, if applicable, the amount of adjustment in the
price of Steel of the portion of the agreement at lump-sum, that is determined
as of the price of sale of the Agreement, this is, including direct and indirect
cost, financing, profit and additional charges, (that) in opinion of the
CONTRACTOR shall be taken into consideration in order to determine the amount of
adjustment of the costs of Steel, considering that mentioned in the Guidelines
and the aforementioned clarifying official communications that were not subject
of recognition and payment of this Amendment Agreement, as well as to apply
deflactor "i" that corresponds to the date of adjustment, inasmuch as the
recognition of the COMMISSION to the adjustment of costs due to the increase in
the price of Steel in this Amendment Agreement in the portion of lump-sum is as
of the direct cost without the cost of transportation mentioned in Exhibit OE -4
plus financing and considering deflactor "i" as the one corresponding to the
delivery date of the work. Therefore, the CONTRACTOR sets out and the COMMISSION
agrees that the execution of this Amendment Agreement does not imply nor it may
be interpreted as a waiver to exercise its rights before the corresponding legal
instances in order to obtain the above mentioned full recognition, regarding the
concepts that were not subject to the adjustment of costs in this Amendment
Agreement.

For this purposes, and in order to conciliate its disputes with the COMMISSION,
the CONTRACTOR filed for the conciliatory administrative procedure as mentioned
in Recital I.18 of the Chapter of Recitals of this Amendment Agreement.

FIFTH. - The increase to the amount of the Agreement mentioned in the FIRST
Clause of the Amendment Agreement does not include the eventual adjustments to
the price of Steel of the Electromechanical Equipment in Exhibit 5 of this
Amendment Agreement, of which there is no developed design as to this date. The
corresponding evaluation of the adjustment of the price of Steel in these
equipments shall be made at the moment when these designs are available under
the Guidelines issued by the Ministry of the Public Office published in the
Official Gazette of the Federation on May 21, 2004, its clarifying official

                                                                              17
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

communications and the resolution that may be reached on the matters currently
at issue mentioned in the FOURTH Clause of this Amendment Agreement.

Once the information and resolutions pending to conduct the pending evaluation
mentioned hereunder and in the FOURTH Clause is available, the PARTIES agree to
confront them within a term not to exceed 60 days following its delivery by the
CONTRACTOR, who shall include them in the Monthly Advance Report of the month
following the one in which such conciliation is made.

SIXTH. - The PARTIES recognize that this Amendment Agreement do not include the
additional and extraordinary works related to the Unitary Prices Activities and
that to obtain the adjustment of the price of Steel that may correspond to them,
the resulting updating factor obtained for the portion of Unitary Prices and
included in Exhibit 7 shall be applied to them according to their term of
execution. For such purposes it is agreed that the adjustments referred to in
this Clause shall be made according to the procedures and criteria contained in
this document and the Guidelines issued for such purpose by the S.F.P. and the
later clarifications.

SEVENTH. - The amount mentioned in the FIRST Clause shall have the treatment
referred to in the Third Memorandum of Clarifications to the Agreement, in the
second paragraph of its "SOLE" item:

"With reference to the first paragraph of Clause 9.3 of the Agreement
("Variations in the Works, Additional Works"), the PARTIES hereby clarify that
the amount of increase in the Price of the Agreement that is established in one
or more amendment agreements that may result from the application of the
Guidelines and from the request of adjustment of the price of Steel, shall be
computed as additional work for purposes of the maximum amount of increases to
the price to which reference is made in item 10 of the First Memorandum of
Clarifications.

                                                                              18
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

The PARTIES also clarify that said amendment agreement or agreements, shall
expressly mention the percentage that represents the increase to the Price of
the Agreement agreed upon and that, only for the effects provided for in item 10
of the First Memorandum of Clarifications, such increase shall be attributed to
the Price of the Agreement in the portion related to Unitary Prices".

EIGHT. - The monthly advances of the amount of the increase to the price of
Steel covered by this Amendment Agreement that may correspond to the works
executed and to be executed in accordance with the current Execution Schedule,
shall have the same recognition treatment and form of payment as those
established in the Agreement for the Lump-sum and the Unitary Prices Activities,
according to Clauses 9.2, 10.1 and 13.4. The COMMISSION shall recognize them in
an independent manner according to Exhibit 14 of the Agreement and the First,
Second and Third Memorandum of Clarifications to the Agreement, that is to say,
as if it was an event of recognition of advances in the construction contained
in the economic form OE - 11B.

The Monthly Advances Report to which Clause 13.4 of the Agreement refers to and
item 4 of the First Memorandum of Clarifications due to the adjustment of the
costs of Steel, may be made on a monthly basis through advance reports submitted
every two weeks in an independent manner to the Monthly Advances Report in the
construction, and according to the result of the calculation of Exhibit 2.

NINTH. - The PARTIES agree that the amount of the Compliance Guarantee granted
by the CONTRACTOR for an amount equivalent to ten percent (10%) of the amount
of the authorized investment for the third fiscal year, is sufficient to
guarantee the due, proper and absolute fulfillment by the CONTRACTOR of all its
obligations derived from the Agreement and this Amendment Agreement for the
current fiscal year.

TENTH. - Attached to this Amendment Agreement as exhibit 8 the
documentation identified as follows:

                                                                              19
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

1. Resolution that establishes the guidelines to conduct the review and
adjustment of the price of Steel, published by the Ministry of the Public Office
in the Official Gazette of the Federation on May 21, 2004

2. Official communication of the Ministry of the Public Office Number
UNAOPSPF/309/BM/0769/2004 dated July 26, 2004

3. Official communication of the Ministry of the Public Office Number
UNAOPSPF/309/BM/0884/2004 dated September 7, 2004

4. Official communication of the Ministry of the Public Office Number
AOPSPF/309/BM/1460/2004 dated December 13, 2004

5. Indexes of Banco de Mexico (Mexico's Central Bank) for the considered Steels

6. Exchange rate Peso / Dollar issued by the Banco de Mexico

7. Homologation conciliated for the adjustment of costs

8. Exhibit OT - 7, General Schedule of the Project, of the portion of lump-sum
of the Electromechanical Work of the Agreement 3 (three)

9. Exhibit OT - 14A, calendarized Schedule for the use of the most significant
materials and equipment of permanent installation of the Agreement 3 (three)

10. Exhibit OT - 11A, Schedule of monthly amounts for the portion of Unitary
Prices of the concepts of Civil Works of the Agreement 3 (three)

11. Calendarized Schedule of disbursements of the portion at Unitary Prices of
the monthly usage of the materials and equipments of permanent installation of
the Agreement 3 (three)

12. Weight and Valuation of Steel of the electromechanical equipment included in
the Agreement 4

13. Official communication of the Ministry of the Public Office Number
AOPSPF/309/BM/0799/2004 dated August 9, 2004

14. Writ of complaint before the Standards Unit of Acquisitions, Public Works,
Services, and Federal Patrimony of the Ministry of the Public Office, in order
to initiate the administrative procedure of conciliation provided for in
articles 89, 90 and 91 of the Law of Public Works and Services Related to the
Same

                                                                              20
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

ELEVENTH. - The execution of this Agreement does not represent a waiver to the
rights available to the CONTRACTOR, derived from the execution of the works in
the terms established in the Bidding Rules, in the Agreement, in the First,
Second and Third Memorandum of Clarifications, in the Amendment Agreements
numbers 1, 2 and 3 and the increase of the price of Steel nor of any other
situation prior to the execution of this Amendment Agreement.

TWELFTH. - The PARTIES agree that according to that mentioned in Clause 24.1.c
of the Agreement it shall be reviewed by means of the actualization of the
research of risks made on the account and on behalf of the CONTRACTOR, and if
applicable, it shall modify the minimum Liability limits agreed to by the
CONTRACTOR AS required under Clause 24.1 c, of the Agreement.

THIRTEENTH. - The PARTIES agree that, except for that expressly provided for in
this Amendment Agreement, the rest of the Clauses that are made a part of the
Agreement and its Amendment Agreements are mandatory, and they shall rule in
full force and effect.

The terms used with capital letters in this document shall have the same meaning
as the one given to them in Clause 1.1 of the Agreement and in the First, Second
and Third Amendment Agreements, the Resolution and its clarification official
communications issued by the Ministry of the Public Office, except as otherwise
expressly specified in this Amendment Agreement.

IN WITNESS OF THE ABOVE, the PARTIES execute and grant, through their legally
authorized representatives, this Amendment Agreement, in six counterparts
equally valid, in Mexico City, Federal District, on March 31st., 2005.

      By the "COMMISSION"                       By the "CONTRACTOR"

                                                                              21
<PAGE>
                        FEDERAL COMMISSION OF ELECTRICITY

                                                     AGREEMENT NUM. PIF-005/2003
                                                          CONTRACT NUM. 4 (FOUR)

-----------------------------------         ------------------------------------
MR. EUGENIO LARIS ALANIS                    MR. LUIS HORCASITAS MANJARREZ
MANAGER OF PROJECTS OF                               LEGAL REPRESENTATIVE
FINANCES INVESTMENTS

EXHIBITS:

1.    Technical report

2.    Calculation of the review and adjustment of the price of Steel in
      the Civil Works, Related Works and Electromechanical Works.

3.    Exhibit OE - 11, Program of monthly amounts for the portion of
      lump-sum for Mechanical, Electric, Civil Works and Related Works
      Concepts of Agreement 3 (three)

4.    Exhibit OE - 13, Calendarized Schedule of expenses of the portion of
      Lump-Sum of monthly use of the materials and equipment of permanent
      installation of the Agreement 3 (three)

5.    List of electromechanical equipment pending to be evaluated in its
      content of Steel

6.    Monthly amount derived from the adjustment of the price of Steel
      according to the Execution Schedule

7.    Factors of Adjustment of Costs obtained according to the Guidelines

8.    Documentation related to the Adjustment of costs.

                                                                              22

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