ADA-ES (ADES)

7 No right of action shall accrue on this Bond to any person or entity other than the Owner or its heirs, executors, administrators or successors.

8 The Surety hereby waives notice of any change, including changes of time, to the Construction Contract or to related subcontractors, purchase orders and other obligations. Surety hereby stipulates and agrees that no change extension of time, amendment, modification or addition to the terms of the Construction Contract or the work to be performed thereunder shall in any way affect its obligations under this bond.

9 Any proceeding, legal or equitable, under this Bond may be instituted in any court of competent jurisdiction in accordance with the applicable provisions of the Construction Contract and shall be instituted within two (2) years after Contractor Default or within two years after the Contractor ceased working or within two (2) years after the Surety refuses or fails to perform its obligations under this Bond, whichever occurs first. If the provisions of this Paragraph are void or prohibited by law, the minimum period of limitation available to sureties as a defense in the jurisdiction shall be applicable.

7 No right of action shall accrue on this Bond to any person or entity other than the Owner or its heirs, executors, administrators or successors.

8 The Surety hereby waives notice of any change, including changes of time, to the Construction Contract or to related subcontractors, purchase orders and other obligations. Surety hereby stipulates and agrees that no change extension of time, amendment, modification or addition to the terms of the Construction Contract or the work to be performed thereunder shall in any way affect its obligations under this bond.

9 Any proceeding, legal or equitable, under this Bond may be instituted in any court of competent jurisdiction in accordance with the applicable provisions of the Construction Contract and shall be instituted within two (2) years after Contractor Default or within two years after the Contractor ceased working or within two (2) years after the Surety refuses or fails to perform its obligations under this Bond, whichever occurs first. If the provisions of this Paragraph are void or prohibited by law, the minimum period of limitation available to sureties as a defense in the jurisdiction shall be applicable.

7 No right of action shall accrue on this Bond to any person or entity other than the Owner or its heirs, executors, administrators or successors.

8 The Surety hereby waives notice of any change, including changes of time, to the Construction Contract or to related subcontractors, purchase orders and other obligations. Surety hereby stipulates and agrees that no change extension of time, amendment, modification or addition to the terms of the Construction Contract or the work to be performed thereunder shall in any way affect its obligations under this bond.

9 Any proceeding, legal or equitable, under this Bond may be instituted in any court of competent jurisdiction in accordance with the applicable provisions of the Construction Contract and shall be instituted within two (2) years after Contractor Default or within two years after the Contractor ceased working or within two (2) years after the Surety refuses or fails to perform its obligations under this Bond, whichever occurs first. If the provisions of this Paragraph are void or prohibited by law, the minimum period of limitation available to sureties as a defense in the jurisdiction shall be applicable.

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Exhibit 10.50(a) to Form 10-Q for the Quarter Ended September 30, 2008 filed by ADA-ES, Inc. (File No. 000-50216) on November 7, 2008

7 No right of action shall accrue on this Bond to any person or entity other than the Owner or its heirs, executors, administrators or successors.

8 The Surety hereby waives notice of any change, including changes of time, to the Construction Contract or to related subcontractors, purchase orders and other obligations. Surety hereby stipulates and agrees that no change extension of time, amendment, modification or addition to the terms of the Construction Contract or the work to be performed thereunder shall in any way affect its obligations under this bond.

9 Any proceeding, legal or equitable, under this Bond may be instituted in any court of competent jurisdiction in accordance with the applicable provisions of the Construction Contract and shall be instituted within two (2) years after Contractor Default or within two years after the Contractor ceased working or within two (2) years after the Surety refuses or fails to perform its obligations under this Bond, whichever occurs first. If the provisions of this Paragraph are void or prohibited by law, the minimum period of limitation available to sureties as a defense in the jurisdiction shall be applicable.