Supplemental Indenture




 Exhibit 4.9(a) 
 SUPPLEMENTAL INDENTURE 
 dated as of April 17, 2000 
 among 
 LYONDELL CHEMICAL COMPANY, 

as Company, 
 ARCO CHEMICAL TECHNOLOGY,
INC. 
 and 
 ARCO CHEMICAL
TECHNOLOGY, L.P., 
 as Subsidiary Guarantors 
 and 
 THE BANK OF NEW YORK, 
 as Trustee 
  

 10 7/8% Senior Subordinated Notes due 2009 
  








 THIS SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), entered into as of April 17,
2000, among LYONDELL CHEMICAL COMPANY, a Delaware corporation (the “Company”), ARCO Chemical Technology, Inc. and ARCO Chemical Technology, L.P. (collectively, the “Subsidiary Guarantors”) (each an “Undersigned”) and
THE BANK OF NEW YORK, as trustee (the “Trustee”). 
 RECITALS 
 WHEREAS, the Company, the Subsidiary Guarantors party thereto and the Trustee entered into the
Indenture, dated as of May 17, 1999 (the “Indenture”), relating to the Company’s 10 7/8%
Senior Subordinated Notes due 2009 (the “Notes”); 
 WHEREAS, as a condition to the Trustee entering into the Indenture and
the purchase of the Notes by the Holders, the Company agreed, subject to certain exceptions, pursuant to Section 4.21 of the Indenture to cause any Restricted Subsidiary that has guaranteed or secured Indebtedness of the Company or any of its
Restricted Subsidiaries to provide Subsidiary Guarantees. 
 AGREEMENT 
 NOW, THEREFORE, in consideration of the premises and mutual covenants herein contained and intending to be legally bound, the parties hereto hereby agree
as follows: 
 Section 1. Capitalized terms used herein and not otherwise defined herein are used as defined in the Indenture.

 Section 2. Each Undersigned, by its execution of this Supplemental Indenture, agrees to be a Subsidiary Guarantor under the Indenture
and to be bound by the terms of the Indenture applicable to Subsidiary Guarantors, including but not limited to, Article 13 thereof. 
 Section 3. This Supplemental Indenture shall be governed by and construed in accordance with the internal laws of the State of New York. 
 Section 4. This Supplemental Indenture may be signed in various counterparts which together shall constitute one and the same instrument. 
 Section 5. This Supplemental Indenture is an amendment supplemental to the Indenture and said Indenture and this Supplemental Indenture shall
henceforth be read together. 
  

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 IN WITNESS WHEREOF, the parties have duly executed and delivered this Supplemental Indenture or have
caused this Supplemental Indenture to be duly executed on their respective behalf by their respective officers thereunto duly authorized, as of the day and year first above written. 
  

			
	LYONDELL CHEMICAL COMPANY
		
	 By:
	 	/s/ Robert T. Blakely
		 	 
	 Name:
	 	Robert T. Blakely
	 Title:
	 	Executive Vice President and Chief Financial Officer
	
	 ARCO CHEMICAL TECHNOLOGY, INC.

		
	 By:
	 	/s/ Francis P. McGrail
		 	 
	 Name:
	 	Francis P. McGrail
	 Title:
	 	President
	
	 ARCO CHEMICAL TECHNOLOGY, L.P.

		
	 By:
	 	ARCO CHEMICAL TECHNOLOGY MANAGEMENT, INC.
		 	    Sole General Partner
		
	 By:
	 	/s/ Francis P. McGrail
		 	 
	 Name:
	 	Francis P. McGrail
	 Title:
	 	President
	
	 THE BANK OF NEW YORK, as Trustee

		
	 By:
	 	/s/ Van K. Brown
		 	 
	 Name:
	 	Van K. Brown
	 Title:
	 	Assistant Vice President


  

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