411 REFERENCE · Wikibooks
Adventist Youth Honors Answer Book/Backpack trip
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Read over the answers in the Backpacking and Hiking honor before setting out. Both have a lot of information that is helpful for a trip like this, and a 15-mile trip will meet the "big" requirement in both.
"Carrying all needed supplies" means that you do not hike from point A to point B while someone else drives an SUV there laden with all your gear.