Scuba/Altitude

Ascent Rate At Altitude
30 feet per minute at all altitudes above sea level, verses 60 feet per minute at sea level

How To Find Your Pressure Group After Arriving At Altitude
If your starting altitude is less than dive altitude then add 2 pressure groups for each 1000 feet of altitude you increase.

If starting at altitudes of 4000 or higher, add 4 pressure groups for each 1000 feet of altitude increase.

If diving at an altitude of 8000 feet or greater wait 6 hours before diving.

Repetitive Diving
When diving at altitude it is recommended to limit your diving to no more than 2 dives per day.

Safety Stop Requirement
A safety stop is required for all dives at altitude. The depth of the safety stop changes with altitude. Refer to the above chart for correct depth.

Depth Gauges
Your depth gauge or computer must be adjusted for altitude diving. If you gauge cannot be adjusted then use the following formula to convert the closed bourdon tube gauge to get actual depth.

Depth Shown in feet + 1 foot + (1 foot per 1000 feet above sea level) = Actual depth

Source
http://utahscubadiver.com/wp-content/uploads/2012/04/AltitudeTables.pdf