Exhibit 3.15

State of Delaware

Secretary of State

Division of Corporations

Delivered 02:02 PM 10/16/2009

FILED 12:53 PM 10/16/2009

SRV 090941788 — 4742810 FILE

CERTIFICATE OF FORMATION

OF

AURORA MASSACHUSETTS, LLC

     1. The name of the limited liability company is Aurora Massachusetts, LLC.

     2. The address of its registered office in the State of Delaware is: Corporation Trust Center, 1209 Orange Street, in the City of Wilmington, Delaware 19801. The name of its registered agent at such address is The Corporation Trust Company.

     IN WITNESS WHEREOF, the undersigned have executed this Certificate of Formation of Aurora Massachusetts, LLC this 16th day of October, 2009.

By:	/s/ Russell A. Hilton
	Russell A. Hilton
	Organizer