Exhibit








Exhibit 10.51
ELEVENTH AMENDMENT TO OFFICE LEASE
1099 18th Street, Denver, Colorado
For valuable consideration, the receipt and adequacy of which are expressly acknowledged, Landlord and Tenant (as defined below) agree as of the Effective Date that:
1.Definitions. In this Eleventh Amendment, the following terms have the meaning given:
(a)Effective Date: November 9, 2007.
(b)Landlord: Cumberland Office Park, LLC, a Georgia limited liability company.
(c)Tenant: Anadarko Petroleum Corporation, a Delaware corporation.
(d)Lease:  Agreement of Lease, dated July 30, 2002, between Denver-Stellar Associates Limited Partnership,  a Delaware limited partnership ("DSA") and Western Gas Resources, Inc. ("Original Tenant") ("Original Lease"), as amended by:
(1)First Amendment to Lease, dated as of September 10, 2002, between DSA and Original Tenant ("First Amendment");
(2)Second  Amendment  to Lease,  dated  as of July  23,  2004,  between  DSA  and  Original  Tenant ("Second Amendment");
(3)Third Amendment  to  Lease, dated as of November  1, 2004,  between DSA  and Original  Tenant ("Third Amendment");
(4)Fourth Amendment  to Lease, dated as of December  31, 2004, between  DSA and Original Tenant ("Fourth Amendment");
(5)Fifth Amendment  to Lease, dated as of April 20, 2005, between DSA and Original Tenant ("Fifth Amendment");
(6)Sixth Amendment to Lease, dated as of  May 18, 2005, between DSA and Original Tenant ("Sixth Amendment");
(7)Seventh  Amendment  to  Lease,  dated  as of June  15, 2005,  between  DSA  and Original  Tenant ("Seventh Amendment");
(8)Eighth Amendment to Lease, dated as of November 15, 2005 ("Eighth Amendment"), between Landlord, as successor-in-interest to DSA and Original Tenant;
(9)Ninth Amendment between Landlord and Tenant, successor  in interest to Original Tenant, dated as of February 16, 2007 ("Ninth Amendment") adding the Expansion Space (as defined below);
(10)Tenth Amendment dated September 11, 2007, between Landlord and Tenant ("Tenth Amendment"); and
(11)This Eleventh Amendment between Landlord and Tenant.
(e)Existing Space:   Existing Space is comprised of approximately 103,263 rentable square feet more particularly described in the Ninth Amendment and on the Premises Schedule attached as Schedule 1 to the Eleventh Amendment (the "Premises Schedule").
(f)Ninth Amendment Expansion Space:   Expansion Space  added  pursuant  to  the  Ninth  Amendment  is comprised of the floors or portions thereof more particularly described in the Ninth Amendment and on the Premises Schedule.


1







(g)Tenth Amendment Expansion Space:   Additional space added to the Premises and more particularly described in the Tenth Amendment and on the Premises Schedule.
(h)Suites 400 :   Approximately 16,506 rentable square feet being the entire fourth floor of the Building as shown on Exhibit B-1 to this Eleventh Amendment.
(i)Suite 600:   Approximately 4,539 rentable square feet on the sixteenth floor of the Building as shown on Exhibit B-2 to this Eleventh Amendment.
(j)Building Address:    Granite Tower
1099 18th Street
Denver, CO 80202
(k)Extended Expiration Date:   April 30, 2018.
(l)Scheduled Delivery Date of Suite 400:   November 1, 2007, subject to the timely vacation of the existing tenant and subject to Exhibit C of the Ninth Amendment.
(m)Scheduled Delivery Date of Suite 600:   December 1, 2007, subject to the timely vacation of the existing tenant and subject to Exhibit C of the Ninth Amendment.
(n)Delivery Date:   The actual delivery date as determined pursuant to Exhibit C to the Ninth Amendment for the space defined in subparagraph (h) and (i) above. The Delivery Date for such space will be confirmed by a Delivery Date Certificate substantially in the form of Exhibit D attached to the Ninth Amendment.
(o)Capitalized Terms.   Any capitalized term used in this Eleventh Amendment but not defined in this Eleventh Amendment has the meaning set forth for such term in the Ninth Amendment.
2.Controlling Lease Documents.   Except as specifically set forth in paragraph 5 of the Ninth Amendment, as of the Effective Date, the term "Lease" shall mean the Original Lease, the Ninth and Tenth Amendments, and this Eleventh Amendment. The First through Eighth Amendments, inclusive, were terminated and replaced in their entirety by the Ninth Amendment.
3.Suite 400.   As of the Effective Date, Landlord leases to Tenant and Tenant leases from Landlord Suite 400 in accordance with this Eleventh Amendment.
(a)Landlord will deliver Suite 400 to Tenant on or before the Scheduled Delivery Date in the condition required pursuant to a Exhibit C of the Ninth Amendment. Tenant acknowledges and agrees that the Scheduled Delivery Date for Suite 400 may be delayed if the existing tenant fails to timely vacate. Landlord shall use commercially reasonable efforts to cause the existing tenant to vacate Suite 400 on a timely basis. In the event the existing tenant fails to vacate as of the  Scheduled Delivery Date, Landlord will credit the Tenant all rent received in excess of Base Rent and Additional Rent under such existing tenant's lease as a result of any holdover. The actual Delivery Date for Suite 400 will be determined pursuant to Exhibit C to the Ninth Amendment and confirmed as required herein. From and after the Delivery Date for Suite 400, all references in the Lease to the term "Premises" shall include Suite 400.
(b)The Base Rent for Suite 400 is set forth an Schedule 2 herein. Rent will commence for Suite 400 on the later of May l, 2008 or 90 days after the Actual Delivery Date for Suite 400.
(c)Tenant will have the opportunity to inspect Suite 400 after the existing tenant vacates the space and has removed any personal proper1y. Tenant agrees to accept Suite 400 in its current "as-is" condition subject to Landlord's obligation to provide the tenant finish allowance described in the next sentence. The tenant finish allowance for Suite 400 will be $40,00 per square foot
4.Suite 600.   As of the Effective Date, Landlord lenses to Tenant and Tenant leases from Landlord Suite 600 in accordance with this Eleventh Amendment:


2







(a)Tenant acknowledges that Landlord will deliver Suite 600 to Tenant on or before the Scheduled Delivery Date in the condition required pursuant to Exhibit C of the Ninth Amendment. Tenant acknowledges and agrees that the Scheduled Delivery Date for Suite 600 may be delayed if the existing tenant fails to timely vacate. Landlord shall use commercially reasonable efforts to cause the existing tenant to vacate Suite 600 on a timely basis. In the event the existing tenant fails to vacate as of the Scheduled Delivery Date, Landlord will credit to Tenant all rent received in excess of Base Rent and Additional Rent under such existing tenant's lease as a result of any holdover. The actual Delivery Date for Suite 600 will be determined pursuant to Exhibit C to the Ninth Amendment and confirmed as required therein. From and after the Delivery Date of Suite 600, all references in the Lease to the term "Premises" shall include Suite 600.
(b)The Base Rent for Suite 600 is set forth on Schedule 2 hereto. Rent will commence for Suite 600 on the later of May 1, 2008 or ninety (90) days after the actual Delivery Date for Suite 600.
(c)Tenant will have the opportunity to inspect Suite 600 after the existing tenant vacates the space and has removed any personal property. Tenant agrees to accept Suite 600 in its current "as-is" condition subject to Landlord's obligation to provide the tenant finish allowance described in the next sentence. The tenant finish allowance for Suite 600 will be $12.36 per square foot.
(d)Tenant authorizes Landlord to deduct from the tenant finish allowance described above the sum of $10,000.00, to pay an early termination fee to the existing tenant of Suite 600, which deduction shall be taken after the existing tenant has vacated the space.
5.Tenant's Proportionate Share.   In accordance with the Ninth Amendment Tenant's Proportionate Share of the Premises will be calculated in accordance with Section 4(a)(iv) of the Original Lease and amended as and when additional space is added to the Premises and Base Rent commences for such additional space.
6.Parking.   In accordance with the Ninth Amendment from January 1, 2008, through the Term of the Lease, for all square footage in the Premises in excess of the Original Premises square footage (81,189 rentable square feet), Tenant will have the right, in accordance with Exhibit F to the Ninth Amendment, to lease 1.1 parking spaces in the Building Garage per 1,000 rentable square feet of the Premises in excess of the Original Premises square footage, of which 10% of such spaces may be reserved, at the rates set forth on such Exhibit F to the Ninth Amendment as adjusted from time to time.
7.Termination Options.   The termination options set forth in paragraph 15 of the Ninth Amendment continue in full force and effect for the Premises as increased by this Eleventh Amendment.
8.Broker.   Each of Landlord and Tenant represents and warrants to the other that neither bas dealt with any broker or agent in negotiating this Eleventh Amendment except Frederick Ross Company (Landlord's broker) and Cushman & Wakefield of Texas, Inc. (Tenant's broker) (collectively, the "Brokers"). Landlord will pay any commission owed to the Brokers pursuant to a separate agreement. Each of Landlord and Tenant ,will indemnify and bold the other harmless from all damages paid or incurred by the other resulting from any claims asserted against such party by brokers or agents claiming through the other party.
9.Reaffirmation of Lease Terms.   Tenant and Landlord agree that the terms,  covenants,  and conditions of the Lease  shall remain and continue in full force and effect as amended herein. Tenant confirms that Landlord is in compliance with the Lease provisions and that Tenant does not have any defenses, claims or offsets against Landlord as of the date hereof. As of the date hereof, Tenant waives and releases Landlord and its agents and employees, from any and all claims, demands, damages, actions, causes of action, or suits of any kind or nature whatsoever, known or unknown, arising out of or in connection with the Lease and/or the use or occupancy of the Premises prior to the date hereof. Except as specifically modified  in this Eleventh Amendment the Lease remains in full force and effect. If there is any conflict between the terms and provisions of this Eleventh Amendment and  the terms and provisions of the Lease as amended by the Ninth and Tenth Amendments, the terms and provisions of this Eleventh Amendment shall govern,
10.Authority.   Each of Landlord and Tenant represents and warrants to the other that the person executing this Eleventh Amendment on behalf of such party is duly authorized to do so. As of the Effective Date, Tenant represents and warrants to Landlord that (a) there are no subleases, assignments, or other agreements between Tenant and any third party concerning or affecting the Lease or the Premises or any portion thereof; and (b) Tenant has not assigned, conveyed, pledged, or granted any interest in the Lease or any portion of the Premises to any person or entity.




3







11.Miscellaneous Provisions.
(a)Governing Law.   The governing law of this Eleventh Amendment and all provisions hereunder shall be governed by and construed in accordance with the laws of the State of Colorado.
(b)Complete Agreement.  This Eleventh Amendment contains all agreements, understandings and arrangements between the parties hereto with regard to the matters described herein.
(c)Benefit.   Subject to the limitations on Tenant's assignment and subleasing provided in the Lease, this Eleventh Amendment shall inure to the benefit of and be binding upon the parties hereto and their respective successors and assigns.
(d)Amendment.   This Eleventh Amendment may not be amended except in writing signed by the parties hereto.
(e)Headings.   The paragraph headings of this Eleventh Amendment are for reference only and shall not be deemed to alter or affect the meaning of the terms hereof.
(f)Binding Effect.   This Eleventh Amendment becomes effective only upon the execution and delivery by Landlord and Tenant.
(g)Time.   Time is of the essence hereof.
(h)Survival.  All covenants, agreements, representations and warranties as set forth in this Eleventh Amendment shall survive the termination of the Lease as amended herein.
(i)Counterparts.   This Eleventh Amendment may be executed in two or more counterparts, each of which shall be deemed an original, but all of which shall constitute one and the same agreement.
(j)Exhibits.   The following schedule and exhibits are attached to and incorporated in this Eleventh Amendment.
		
	Schedule 1
	Premises Schedule


		
	Schedule 2
	Monthly Base Rent


		
	Exhibit B-1
	Suite 400


		
	Exhibit B-2
	Suite 600



The undersigned have executed this Eleventh Amendment as of the Effective Date.
	
		
	LANDLORD:
	TENANT:

	 
	 

	Cumberland Office Park, LLC,
a Georgia limited liability company
	Anadarko Petroleum Corporation,
a Delaware corporation

	 
	 

	By: GPI Tower, Ltd.,
a Texas corporation, its sole member
	By: /s/ John A. Frere III
Name: John A. Frere III
Title: Manager, Real Estate & Facilities

	 

	By: SF Realty, Inc.,
a Texas corporation, its general partner
	 

	 
	 

	By: /s/ Stephanie T. Lawrence
Name: Stephanie T. Lawrence
Title: Vice President - Managing Director - Denver
	 

	 
	 








4








SCHEDULE 1-Premises Schedule (11/1/2007)
	
											
	 	Category
	Floor(s)
	Suite#
	Square
Footage
	Base
Year
(after
1/1/08)
	Tenant
Allowance
	

Schedule
Delivery
Date
	

Actual
Delivery
Date
	

Rent
Commencement
Date (after 1/1/08)

	 
	 	 
	 
	 
	 
	 
	 
	 
	 
	 

	 	Existing Space *
	 
	 
	 
	 
	 
	 
	 
	 

	 	through 8th Amendment
	9-12
	All of Floors 9,
10, 11 and 12
	81,189
	

	2008
	$32.00
	N/A
	N/A
	5/1/2008

	 	through 8th Amendment
	16
	1600
	21,080
	

	2008
	$32.00
	N/A
	N/A
	5/1/2008

	 	through 8th Amendment
	20
	2030
	994
	

	2008
	$32.00
	N/A
	N/A
	5/1/2008

	 	Total Existing Space:
	 
	 
	103,263
	

	 
	 
	 
	 
	 

	 	 
	 
	 
	 
	 
	 
	 
	 
	 

	 	Expansion Space
	 
	 
	 
	 
	 
	 
	 
	 

	 	9th Amendment
	6
	650
	16,089
	

	2008
	$40.00
	N/A
	2/16/2007
	5/1/2008

	 	9th Amendment
	13
	1300 (all)
	20,740
	

	2008
	$40.00
	N/A
	9/1/2007
	5/1/2008

	 	9th Amendment
	14
	1400 (all)
	20,740
	

	2008
	$40.00
	N/A
	9/1/2007
	5/1/2008

	 	9th Amendment
	15
	1500 (all)
	20,740
	

	2008
	$40.00
	N/A
	9/1/2007
	5/1/2008

	 	9th Amendment
	17
	1700 (all)
	19,688
	

	2008
	$40.00
	N/A
	6/1/2007
	5/1/2008

	 	9th Amendment
	18
	182011840
	6,048
	

	2008
	$40.00
	N/A
	9/1/2007
	5/1/2008

	 	9th Amendment
	18
	Remaining 18th
	14,090
	

	2008
	$40.00
	8/1/2008
	TBD
	**

	 	10th Amendment
	5
	550
	3,075
	

	2008
	$40.00
	12/1/2007
	TBD
	5/1/2008 (est)**

	 	10th Amendment
	5
	570
	2,928
	

	2008
	$40.00
	11/1/2007
	TBD
	5/1/2008 (est)**

	 	10th Amendment
	6
	Core Space
	380
	

	2008
	$40.00
	N/A
	9/1/2007
	5/1/2008

	 	10th Amendment
	22
	2200 (all)
	21,154
	

	2008
	$40.00
	12/1/2007
	TBD
	5/1/2008 (est)**

	 	11th Amendment
	4
	400 (all)
	16,506
	

	2008
	$40.00
	12/1/2007
	TBD
	5/1/2008 (est)**

	 	11th Amendment
	6
	Remaining 6th
	4,539
	

	2008
	$10.98
	12/1/2007
	TBD
	5/1/2008 (est)**

	 	Total Expansion Space:
	 
	 
	166,717
	

	 
	 
	 
	 
	 






		
	*
	Prior to January l, 2008, the Existing Space Base Rent and Bose Year are set forth in the Lease as amended through the 8th Amendment.


		
	*
	Commencing January 1, 2008, Base Rent and Base Year are reset as set forth on this Schedule and Schedule 2. Rent commences ninety (90) days after the Delivery Date for such space, but in no event earlier than May 1, 2008.












Schedule 1








SCHEDULE 2
	
										
	 	Granite Tower

	 	Annual Base Rental Rate Commencing 1/1/2008*

	 	Period
	Existing Space:
13-18 Floors:
Total RSF:
	103,263
102,046
205,309
	4th Floor:
22nd Floor:
Total RSF:
	16,506
21,154
37,660
	6th Floor:
Suite 550:
Suite 570:
Total RSF
	21,008
3,075
2,928
27,011
	Total RSF: 
269,980

	 
	 	From
	To
	 
	 
	 
	 

	 	01/01/08
	04/30/08
	abated
	abated
	abated
	abated

	 	05/01/08**
	12/31/08
	$374,860.02**
	$83,950.42**
	$53,459.27**
	$512,269.70**

	 	01/09/09
	12/31/09
	$379,308.38
	$86,053.10
	$54,787.31
	$520,148.79

	 	01/01/10
	12/31/10
	$383,927.83
	$88,187.17
	$56,160.37
	$528,275.37

	 	01/01/11
	12/31/11
	$437,650.35
	$90,415.38
	$57,578.45
	$585,644.18

	 	01/01/12
	12/31/12
	$448,600.17
	$92,674.98
	$59,019.04
	$600,294.18

	 	01/01/13
	12/31/13
	$459,721.07
	$94,997.35
	$60,482.13
	$615,200.55

	 	01/01/14
	12/31/14
	$471,355.25
	$97,351.10
	$61,990.25
	$630,696.59

	 	01/01/15
	1:2/31/15
	$482,989.42
	$99,799.00
	$63,543.38
	$646,331.80

	 	01/01/16
	12/31/16
	$495,136.87
	$102,278.28
	$65,141.53
	$662,556.68

	 	01/01/17
	12/31/17
	$507,455.41
	$104,851.72
	$66,762.19
	$679,069.32

	 	01/01/18
	04/30/18
	$520,116.13
	$107,456.53
	$68,427.87
	$696,000.53




		
	*
	Prior to January 1, 2008, the Existing Space Base Rent and Base Year are set forth in the Lease as amended through the 8th Amendment.


		
	**
	Commencing January 1, 2008, Base Rent and Base Year are reset as set forth on Schedule 1. Rent commences ninety (90) days after the Delivery Date for such space, but in no event earlier than May 1, 2008. This Schedule is the actual product after the square footage multiplied by the applicable per square foot rental rates.


(Note: Rentable Square Feet, as set forth above, may not yet have been delivered (e.g. 14,090 square feet on ti1e 18th floor have a scheduled delivery date of August 1, 2008).












Schedule 2