Document:

<PAGE>
                                                                  Exhibit 10.4.2

                                October 20, 1999

Zachry Construction Company
527 Logwood
San Antonio, Texas  78224-0130

Attn:  Robert J. Kalt

RE:      TENASKA GEORGIA GENERATING STATION
         Exercise of Option 5 to Exhibit J - 500 kV switchyard

Dear Mr. Kalt:

Tenaska Georgia Partners, L.P. hereby exercises Option 5 to Exhibit J of the EPC
Contract, 500 kV Switchyard. Please acknowledge receipt of this notice by
signing below and returning the letter to me.

Sincerely,

TENASKA GEORGIA PARTNERS, L.P.
BY:      TENASKA GEORGIA, INC.
         MANAGING GENERAL PARTNER

BY:
         MICHAEL F. LAWLER
         VICE PRESIDENT OF FINANCE            ----------------------------------
         AND TREASURER                        FOR: ZACHRY CONSTRUCTION CO.
                                                   JOHN G. BERRA, VICE PRESIDENT

CC:      HAROLD MOSLEY, ZACHRY CONSTRUCTION CO.
         ANDY JONES<PAGE>

                                                                  EXHIBIT 10.4.3

                     AGREEMENT FOR ASSIGNMENT AND ASSUMPTION

                                       OF

                        EPC AGREEMENT TO TENASKA GEORGIA

         This Agreement for Assignment and Assumption of EPC Agreement (this
"Agreement") entered into by and between Tenaska Georgia I, L.P., a Delaware
limited partnership ("Tenaska") and Tenaska Georgia Partners, L.P., a Delaware
limited partnership ("Tenaska Georgia"), this 10th day of November, 1999.

         WHEREAS, Tenaska and Zachry Construction Corporation, a Delaware
corporation ("Zachry") entered into an Engineering, Procurement and Construction
Agreement dated September 15, 1999, which provides for the design and
construction of a dispatchable electric generating facility on a Plant Premises
located in Heard County in the State of Georgia ("EPC Agreement"); and

         WHEREAS, Article 21 of the EPC Agreement provides that such agreement
may be assigned to an Affiliate of Tenaska or an entity in which an Affiliate of
Tenaska has an ownership interest; and

         WHEREAS, by a First Amendment to Engineering, Procurement and
Assignment Agreement, dated October 8, 1999, Tenaska and Zachry have amended the
EPC Agreement, such reference to the EPC Agreement when made hereinafter
including such amendment; and

         WHEREAS, pursuant to Article 21 of the EPC Agreement, Tenaska desires
to assign the EPC Agreement to Tenaska Georgia.

         NOW, THEREFORE, the parties agree as follows:

1.   In consideration of payments received, Tenaska assigns to Tenaska Georgia
     all of its rights and benefits under the EPC Agreement and Tenaska further
     assigns and delegates all of its duties and obligations under the EPC
     Agreement to Tenaska Georgia.

2.   Tenaska Georgia accepts the assignment from Tenaska of all rights and
     benefits under the EPC Agreement, and assumes all of the duties and
     obligations of Tenaska as contained in the EPC Agreement.

3.   Notwithstanding the assignment and assumptions made in this Agreement,
     Tenaska retains the perpetual right for Tenaska to use any and all Drawings
     (as defined in the EPC Agreement) prepared by Zachry under the EPC
     Agreement, subject to any limitations on such use which may arise under the
     EPC Agreement, and for such purpose Tenaska Georgia grants and confirms
     such perpetual license to Tenaska to use such Drawings for any and all
     purposes which Tenaska may desire, including such other projects as Tenaska
     may determine, subject to any limitations on such use which may arise under
     the EPC Agreement.

4.   Tenaska Georgia hereby releases Tenaska from any and all duties,
     obligations and liabilities under the EPC Agreement.

5.   Notwithstanding this Agreement, Tenaska agrees to (a) continue to be bound
     by the confidentiality provisions applicable to Owner pursuant to Article
     22 of the EPC Agreement (b) remain liable to Zachry under the EPC Agreement
     for its acts and omissions prior to the date of this Agreement and (c) be
     bound by the terms of the EPC Agreement, including all limitations on
     liability with respect to any rights or actions which may have accrued in
     favor of Tenaska prior to the date of this Agreement

6.   This Agreement shall not become effective until a fully executed copy of
     this Agreement, including the Agreement and Consent of Zachry, attached
     hereto, is executed and delivered to Tenaska and Tenaska Georgia.

7.   This Agreement shall inure to and be binding upon the successors and
     assigns of the parties.

8.   This Agreement shall be governed by and construed according to the laws of
     the State of Texas.

                                            TENASKA GEORGIA I, L.P.,
                                            a Delaware limited partnership

                                            By: TENASKA GEORGIA, INC.

                                            Managing General Partner

/S/___________________     By: /S/____________________________
Witness                           Michael F. Lawler

                                            Title: Vice President of Finance
                                                   & Treasurer

                                            TENASKA GEORGIA PARTNERS, L.P.,
                                            a Delaware limited partnership

                                            By: TENASKA GEORGIA, INC.
                                            Managing General Partner

/S/___________________     By: /S/____________________________
Witness                           Michael F. Lawler

                                            Title: Vice President of Finance
                                                   & Treasurer

<PAGE>

                              AGREEMENT AND CONSENT

         Zachry Construction Corporation, a Delaware corporation ("Zachry")
consents to the assignment of the Engineering, Procurement and Construction
Agreement between Zachry and Tenaska Georgia I, L.P., a Delaware limited
partnership ("Tenaska"), dated September 15, 1999, ("EPC Agreement") as
subsequently amended by a First Amendment to Engineering, Procurement and
Assignment Agreement, dated October 8, 1999, between Tenaska and Zachry
(reference to the EPC Agreement hereinafter to include such amendment) to
Tenaska Georgia Partners, L.P., a Delaware limited partnership ("Tenaska
Georgia") and the assumption by Tenaska Georgia of the EPC Agreement as set
forth in the Agreement for Assignment and Assumption of EPC Agreement to Tenaska
Georgia attached hereto.

         Zachry hereby releases Tenaska from any and all duties, obligations and
liabilities under the EPC Agreement except that Tenaska shall (a) continue to be
bound by the confidentiality provisions applicable to Owner pursuant to Article
22 of the EPC Agreement (b) remain liable to Zachry under the EPC Agreement for
it's acts and omissions prior to the date of this Agreement and (c) be bound by
the terms of the EPC Agreement, including all limitations on liability with
respect to any rights or actions which may have accrued in favor of Tenaska
prior to the date of this Agreement.

         Dated this 10th day of November, 1999.

                                            ZACHRY CONSTRUCTION CORPORATION,
                                            a Delaware corporation

/S/_________________________              By: /S/______________________________
Witness                                          Robert J. Kalt
                                                 Vice President<PAGE>
                                                                   EXHIBIT 10.5

                             GUARANTY OF OBLIGATION

This Guaranty is made by Willbros Group, Inc., a Panama corporation,
("Guarantor"), in favor of TENASKA GEORGIA PARTNERS, L.P., a Delaware limited
partnership ("Tenaska"), with respect to that certain Engineering, Procurement
and Construction Agreement dated the 23rd day of September, 1999, between
Tenaska and WILLBROS ENGINEERS, INC., a Delaware corporation ("Contractor"), for
the construction of a natural gas transmission pipeline from the
Transcontinental Gas Pipeline Corporation meter station to the Tenaska Georgia
Generation Station, as amended, supplemented or otherwise modified from time to
time (hereinafter called the "EPC Agreement"), in consideration of the execution
of the EPC Agreement by Tenaska with Contractor.

Guarantor states and represents that Guarantor will derive direct and indirect
benefit from the making of the Guaranty.

NOW, THEREFORE, for good and valuable consideration, Guarantor hereby covenants
and agrees as follows:

1.       Guarantor hereby unconditionally guarantees the full and timely
         performance by Contractor of all of its obligations under the EPC
         Agreement, as it from time to time may be amended, and hereby
         undertakes that if Contractor shall in any respect fail to perform and
         observe all of the terms, provisions, conditions, and stipulations of
         the EPC Agreement, Guarantor warrants the faithful performance of all
         of such terms and conditions and will fully indemnify and keep
         indemnified Tenaska against all claims, losses, damages, costs and
         expenses whatsoever which Tenaska may incur by reason of Contractor's
         failure to perform and observe any of the terms, provisions,
         conditions, and stipulations of the EPC Agreement (collectively, the
         "Guaranteed Obligations"). THE OBLIGATIONS OF GUARANTOR HEREUNDER SHALL
         NOT BE REDUCED, LIMITED OR TERMINATED, NOR SHALL GUARANTOR BE
         DISCHARGED FROM ANY THEREOF, FOR ANY REASON WHATSOEVER (other than the
         payment, observance and performance of the Guaranteed Obligations and
         other than as provided in Section 9 of this Guaranty), including (and
         whether or not the same shall have occurred or failed to occur once or
         more than once and whether or not Guarantor shall have received notice
         thereof):

         (a)      (i) any increase in, (ii) any extension of the time of
                  payment, observance or performance of, (iii) any other
                  amendment or modification of any of the other terms and
                  provisions of, (iv) any release, composition or settlement
                  (whether by way of acceptance of a plan of reorganization or
                  otherwise) of, (v) any subordination (whether present or
                  future or contractual or otherwise) of, or (vi) any discharge,
                  disallowance, invalidity, illegality, voidness or other
                  unenforceability of, the Guaranteed Obligations;

<PAGE>

         (b)      (i) any failure to obtain, (ii) any release, composition or
                  settlement of, (iii) any amendment or modification of any of
                  the terms and provisions of, (iv) any subordination of, or (v)
                  any discharge, disallowance, invalidity, illegality, voidness
                  or other enforceability of, any other guaranties of the
                  Guaranteed Obligations;

         (c)      any termination of or change in any relationship between
                  Guarantor and Contractor, including any such termination or
                  change resulting from a change in the ownership of Guarantor
                  or from the cessation of any commercial relationship between
                  Guarantor and Contractor;

         (d)      any exercise of, or any election not or failure to exercise,
                  delay in the exercise of, waiver of, or forbearance or other
                  indulgence with respect to, any right, remedy or power
                  available to Tenaska, including (i) any election not or
                  failure to exercise any right of set-off, recoupment or
                  counterclaim, and (ii) any election of remedies effected by
                  Tenaska, and

         (e)      ANY OTHER ACT OR FAILURE TO ACT OR ANY OTHER EVENT OR
                  CIRCUMSTANCE THAT (i) VARIES THE RISK OF GUARANTOR HEREUNDER
                  OR (ii) BUT FOR THE PROVISIONS HEREOF, WOULD, AS A MATTER OF
                  STATUTE OR RULE OF LAW OR EQUITY, OPERATE TO REDUCE, LIMIT OR
                  TERMINATE THE OBLIGATIONS OF THE GUARANTOR HEREUNDER OR
                  DISCHARGE GUARANTOR FROM ANY THEREOF.

2.       Guarantor represents and warrants to Tenaska and Tenaska's successors
         and assigns that:

         (a)      Guarantor is duly organized and validly existing as a Panama
                  corporation;

         (b)      Guarantor is authorized and has all necessary power and
                  authority, corporate and other, to execute and deliver this
                  Guaranty and to perform the obligations of Guarantor,
                  including all obligations of Contractor pursuant to the EPC
                  Agreement;

         (c)      This Guaranty reasonably may be expected to benefit directly
                  or indirectly, Guarantor;

         (d)      This Guaranty has been duly executed and delivered by
                  Guarantor and is the valid, binding, and enforceable contract
                  of Guarantor;

         (e)      The execution and delivery of this Guaranty by Guarantor and
                  its performance of its obligations under the Guaranty, do not
                  (and, to the best of Guarantor's knowledge, will not) conflict
                  with any law, rule or regulation, or any agreement,
                  instrument, indenture, deed or any other restriction, to which
                  such Guarantor is subject or a party, or accelerate or affect
                  any of its obligations under any thereof.

<PAGE>

3.       Guarantor shall cause Contractor to duly and timely perform all of the
         Guaranteed Obligations including the obligations of Contractor under
         the EPC Agreement, as it may from time to time be amended.

4.       The obligations of Guarantor hereunder include, without limitation, all
         liabilities for liquidated or similar damages and warranty obligations
         of Contractor.

5.       Tenaska may enforce against Guarantor any and all of the rights of
         Tenaska under this Guaranty without having instituted or completed any
         legal, arbitration or other proceedings against Contractor or any
         partner or joint venturer in Contractor.

6.       This Guaranty shall be governed by and construed according to the laws
         of the State of Texas. Guarantor submits to personal jurisdiction in
         the State of Texas and further agrees that the non-exclusive venue for
         any such action may be in the state and federal courts located in
         Dallas County, Texas.

7.       Guarantor waives: (a) any requirement, and any right to require, that
         any right or power be exercised or any action be taken against the
         Contractor, any partner or joint venturer in Contractor, or any other
         guarantor or any collateral for the Guaranteed Obligations; (b) (i)
         notice of acceptance of and intention to rely on this Agreement, and
         (ii) all other notices that may be required by applicable law or
         otherwise to preserve any rights against Guarantor under this
         Agreement, including any notice of default, demand, dishonor,
         presentment and protest; and, (c) diligence.

8.       Guarantor shall not assert any right to set off against claims by
         Tenaska hereunder other than claims which Contractor has a right to set
         off under the EPC Agreement.

9.       Notwithstanding any other provision to the contrary set forth herein,
         Guarantor retains the right to assert any and all claims, defenses and
         limitations of liability possessed by Contractor under the terms of the
         EPC Agreement, (but excluding any defense based upon absence of binding
         effect of the EPC Agreement).

10.      Guarantor's obligations hereunder (a) are absolute and unconditional,
         (b) subject to Section 9 above, are unlimited in amount, except as
         provided in the EPC Agreement, (c) constitute a guaranty of payment and
         performance and not a guaranty of collection, (d) are as primary
         obligor and not as a surety only, (e) shall be a continuing guaranty of
         all present and future Guaranteed Obligations, and (f) shall be
         irrevocable.

<PAGE>

11.      This Guaranty may be assigned by Tenaska to Tenaska's lenders for the
         project and shall inure to the benefit of such assignee(s).

12.      Notice to Guarantor shall be to:
                  Willbros Group, Inc.
                  %Willbros USA, Inc.
                  600 Willbros Place
                  2431 East 61st Street
                  Tulsa, Oklahoma 74136
                  Attn: John Hove

         IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be
executed and delivered to Tenaska in the name and on behalf of Guarantor by one
of its officers who is duly authorized to do so, for the benefit of Tenaska, as
of this 23rd day of Septmber, 1999.

                                  Guarantor
                                  WILLBROS GROUP, INC.

ATTEST:

By: /s/                           By: /s/
   -----------------------           ------------------------
                                            (Name)

Title: Assistant Secretary           Executive Vice President
      --------------------           ------------------------
                                            (Title)

<PAGE>

                            CERTIFICATE OF SECRETARY

                              WILLBROS GROUP, INC.

         I, John N. Hove, being the duly elected and acting Corporate Secretary
of WILLBROS GROUP. INC., a corporation organized and existing under and by
virtue of the laws of the Republic of Panama (hereinafter referred to as the
"Corporation"), do hereby

                                 C E R T I F Y :

1.       THAT the following preambles and resolutions are a true, correct and
complete copy of the same duly adopted by Memorandum of Action signed by all of
the members of the Executive Committee of the Board of Directors of the
Corporation on September 23, 1999, and that such resolutions have not been
rescinded since their adoption and are in full force and effect on the date
hereof:

EXECUTION OF GUARANTEE

              WHEREAS, Willbros Engineers, Inc., a Delaware corporation ("WEI"),
         is an indirect wholly-owned subsidiary of the Corporation; and

              WHEREAS, WEI has entered into an Engineering, Procurement and
         Construction Agreement dated September 23, 1999, with Tenaska Georgia
         Partners, L.P., a Delaware limited partnership ("Tenaska"), with
         respect to the construction of a natural gas transmission pipeline from
         the Transcontinental Gas Pipeline Corporation meter station to the
         Tenaska Georgia Generation Station (the "EPC Agreement"); and

              WHEREAS, WEI has certain obligations to Tenaska under the EPC
         Agreement; and

              WHEREAS, Tenaska has requested the provision of a parent company
         guarantee by the Corporation with respect of the obligations of WEI
         under the EPC Agreement, such guarantee to be substantially in the same
         form attached hereto (the "Guarantee"); and

              WHEREAS, the provision of the Guarantee is deemed to be in the
         best interests of the Corporation;

<PAGE>

              NOW, THEREFORE, BE IT

              RESOLVED, that the form of, and the terms and conditions contained
         in, the Guarantee be, and the same hereby are, authorized and approved
         in all respects; and further

              RESOLVED, that the execution, delivery and performance by the
         Corporation of the Guarantee be, and the same hereby are, authorized
         and approved in all respects; and further

              RESOLVED, that the Chairman, the President and each of the Vice
         Presidents of the Corporation be, and each of them individually hereby
         is, authorized and empowered to negotiate and make such changes,
         modifications, additions and deletions to the Guarantee as they, or any
         of them, in their sole discretion, may deem appropriate, and to execute
         and deliver, for and on behalf of the Corporation, the Guarantee, in
         such form as the officer or officers executing the same shall deem
         necessary, advisable or appropriate, as shall be conclusively evidenced
         by his signature affixed thereon; and further

              RESOLVED, that the officers of the Corporation be, and each of
         them individually hereby is, authorized and empowered, for and on
         behalf of the Corporation, to execute and deliver any and all
         additional documents, instruments and papers, and to take or cause to
         be taken such additional actions, as they or any of them, in their sole
         discretion, may deem necessary, convenient or appropriate in connection
         with the negotiation, execution and deliver of the Guarantee and to
         carry out the purposes of the foregoing resolutions, and in this
         connection to take such action and to execute, deliver, acknowledge,
         record, file and certify all such further instruments, certificates,
         letters, agreements, documents, papers and undertakings as the officer
         or officers so acting may consider and determine necessary, advisable
         or convenient, as shall be conclusively evidenced by his signature
         affixed thereon.

2.       THAT the persons identified below are duly elected, qualified and
acting Officers of the Corporation; and that they hold the office or offices set
forth opposite their names on the date hereof:

<TABLE>
<CAPTION>

            NAME                                         TITLE
         <S>                                <C>
         Larry J. Bump                      Chairman of the Board and Chief
                                              Executive Officer

         Paul A. Huber                      President and Chief Operating Officer

</TABLE>

                                       2

<PAGE>

<TABLE>
<CAPTION>

            NAME                                         TITLE
         <S>                                <C>
         Melvin F. Spreitzer                Executive Vice President, Treasurer
                                              And Chief Financial Officer

         Lawrence R. Fisher, Jr.            Senior Vice President

         John N. Hove                       Corporate Secretary

         J.T. Dalton                        Assistant Secretary

         Kathy E. Alexander                 Assistant Secretary

         Thomas B. Reilly                   Assistant Treasurer

         David W. Arneson                   Assistant Treasurer

</TABLE>

3.       AND I FURTHER CERTIFY THAT I am authorized to execute this Certificate
on behalf of the Corporation.

         IN WITNESS WHEREOF, I have hereunto executed this Certificate and
affixed the seal of the Corporation, this 27th day of September, 1999

                                  By: /s/ John N. Hove
                                     ------------------------------------
                                               John N. Hove
                                            Corporate Secretary

         I Paul A. Huber, President of the Corporation, do hereby certify that
John N. Hove is the duly elected, qualified and acting Corporate Secretary of
the Corporation, and that the signature set forth above his name is his true and
genuine signature.

         IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 27th
day of September, 1999.

                                      /s/ Paul A. Huber
                                      -----------------------------------
                                                Paul A. Huber
                                                  President

                                       3

<PAGE>

County of Tulsa                 )
State of Oklahoma               ) Section
United States of America        )

       Before me, the undersigned, a Notary Public in and for the aforementioned
County, State and Country, on this 27th day of September, 1999, personally
appeared Paul A. Huber and John N. Hove, President and Corporate Secretary,
respectively, of WILLBROS GROUP, INC., to me known to be the identical persons
who executed the foregoing instrument, and acknowledged that they executed the
same as their free and voluntary act and deed, and as the free and voluntary act
and deed of said Corporation.

       In Witness Whereof, I have hereunto set my official signature and affixed
my notarial seal the day and year last above written.

                                  /s/ Kathy E. Alexander
                                  -------------------------------------
                                            Kathy E. Alexander
                                              Notary Public

My Commission Expires:
  February 27, 2001
----------------------

                                       4

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00001-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00001-of-00352.parquet"}], [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00001-of-00352.parquet"}]]