Here is the full list of all 10 Firewatch achievements worth 1,000 gamerscore. It takes around 4-5 hours to unlock all of the achievements on Xbox One.
Completed Day 79
Completed Day 77
Got stung by a bee. It happens.
Completed Day 76
Completed Day 2
Completed Day 1
Fill a disposable camera with photos.
Have a hands-on encounter with the local wildlife.
Adopt a turtle.
Find and hear the recording of the song "Ol' Shoshone."