Montana Swims may be Altitude Adjusted as follows :
Times achieved at an altitude of 3, 000 feet or above may be adjusted by the seconds indicated below:
 

Event Distance 3000-4250 feet 4251-6500 feet above 6500 feet
200 0.5 seconds 1.2 seconds 1.6 seconds
400M or 500Y 2.5 seconds 5 seconds 7 seconds
800 Free Relay 2 seconds 4.8 seconds 6.4 seconds
800M or 1000Y 5 seconds 10 seconds 15 seconds
1500M or 1650Y 11 seconds 23 seconds 32.5 seconds
Cities :
Billings
Great Falls
Helena
Kalispell
Missoula
Polson
Whitefish

Bozeman

Butte

 
  1. Subtract the time indicated above from the actual time achieved at altitude. This is the time to be used on the entry form and seeding will be based on that time. Information relative to the adjustment accompanying the entry form must include name of swimmer, event, date of performance, elevation location, actual time, corrected time, and signature of coach.
  2. A swimmer or relay may use the above adjustments to meet the national qualifying time standard and seeding will be based upon that time.


Taken from the 2006 USAS Rules Article 207.10.5 
 
MT City Elevations and Altitude Adjustment Information PDF