FILE - This Monday, Sept. 27, 2010, file photo, shows hikers on the South Kaibab Trail in Grand Canyon National Park, Ariz. One of the most lucrative contracts in the National Park Service is going ... more 
FILE - This Monday, Sept. 27, 2010, file photo, shows hikers on the South Kaibab Trail in Grand Canyon National Park, Ariz. One of the most lucrative contracts in the National Park Service is going out to bid for a third time, after Grand Canyon found the previous bids unacceptable. The successful bidder will provide lodging, food, retail and transportation services as well as mule rides on the South Rim. Those services are expected to bring in nearly $1 billion in gross revenue over 15 years. (AP Photo/Carson Walker, File) less 
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Associated Press | Photo By Carson Walker, File
Tue, Aug 19, 2014 1:18 PM EDT