Exhibit 4.18

                       ASSIGNMENT AND ASSUMPTION AGREEMENT


         This Assignment and Assumption Agreement, dated as of June 25, 1999
(this "Agreement"), is between AES Ironwood, Inc., a Delaware corporation (the
"Assignor"), having its principal office at 829 Cumberland Street, Lebanon,
Pennsylvania 17042, and AES Ironwood, L.L.C., a Delaware limited liability
company (the "Assignee"), having its principal office at 1001 North 19th Street,
Arlington, Virginia 22209.

                              W I T N E S S E T H:

         WHEREAS, the Assignor is party to that certain Agreement for
Engineering, Procurement and Construction Services, dated as of September 23,
1998 (the "EPC Contract"), with Siemens Westinghouse Power Corporation;

         WHEREAS, the Assignor desires to assign to the Assignee, and the
Assignee desires to assume, all of the Assignor's right, title and interest in,
to and under the EPC Contract.

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements contained herein, and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Assignor and the
Assignee hereby act and agree as follows:

         1. Assignment. The Assignor hereby conveys, assigns and transfers to
the Assignee and its successors and assigns all of the Assignor's right, title
and interest in, to and under the EPC Contract.

         2. Assumption. The Assignee hereby accepts the foregoing assignment,
transfer and conveyance of the Assignor's right, title and interest in, to and
under the EPC Contract, and the Assignee hereby agrees and confirms that it
shall be bound by all the terms of, and undertake, assume and accept all of the
rights, obligations and liabilities of, the Assignor under the EPC Contract
whether arising before, on or after the date of this Agreement.

         3. Release and Waiver. The Assignee hereby releases and forever
discharges the Assignor from all claims and liabilities arising out the EPC
Contract, and the Assignee hereby waives any and all claims it may have against
the Assignor now existing or hereafter arising out of the EPC Contract.

         4. Counterparts. This Agreement may be executed in any number of
counterparts, and each counterpart hereof shall be deemed to be an original
instrument, but all such counterparts shall constitute but one assignment.

         5. Further Assurances. The Assignor agrees to take all such further
reasonable actions and execute and deliver all such further documents as are
necessary to effectuate the purposes of this Agreement.



         6. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York except any such laws that
would direct the application of the law of another jurisdiction.

         7. Successors and Assigns. This Agreement shall bind the Assignor and
its respective successors and assigns and inure to the benefit of the Assignee
and its successors and assigns.

         8. Descriptive Headings. The descriptive headings of the several
paragraphs of this Agreement are for convenience only and shall not be deemed to
affect the meaning or construction of any of the provisions hereof.







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         IN WITNESS WHEREOF, the Assignor and the Assignee have executed this
Agreement by their duly authorized representatives as of the date and year first
above written.

                                    ASSIGNOR:


                                    AES IRONWOOD, INC.,


                                    By:  /s/ Patricia L. Rollin
                                         -------------------------------
                                         Name:   Patricia L. Rollin
                                         Title:  Vice President


                                    ASSIGNEE:


                                    AES IRONWOOD, L.L.C.


                                    By:  /s/ Patricia L. Rollin
                                         -------------------------------
                                         Name:   Patricia L. Rollin
                                         Title:  Vice President




                      [ASSIGNMENT AND ASSUMPTION AGREEMENT]



CONSENT, ACKNOWLEDGMENT AND AGREEMENT:

         Siemens Westinghouse Power
Corporation hereby (i) consents to the
assignment contemplated by this
Agreement, (ii) acknowledges the
assumption contemplated by this
Agreement and (iii) agrees that the
Assignor shall have no liability for any
claim now existing or hereafter arising
under the EPC Contract.

SIEMENS WESTINGHOUSE POWER CORPORATION



By:  /s/ James Mackey
     -----------------------------
     Name:  James Mackey
     Title: Director Project Management