AFD, TFR's , Notams Local, Distant
It is in the AFD for the NW. In the back of the airport facility directory are special procedures, direction you must circle (CW or CCW), altitude, terrain clearance and freq to monitor. Washington state Gov, aeronautics division states, like Andy said, states 122.75 is required to be monitored to fly around Mt. St. Helen. There's scientific activity and yes even volcanic action involved. Don't forget to check the TFR's and NOTAM's.
4/3131 - WA.. VOLCANIC ACTIVITY FOR MT. SAINT HELENS VOLCANO, WA 461200N/1221048W OR THE BATTLE GROUND /BTG/ VORTAC 011 DEGREE RADIAL 032 NAUTUCAL MILES. CONTINUED VOLCANIC ACTIVITY REPORTED FOR MT. SAINT HELENS VOLCANO, WA. USGS /ALERT LEVEL 2/ AVIATION ALERT COLOR ORANGE IN EFFECT. AIRCRAFT REQUEST TO EXERCISE CAUTION UNTIL FURTHER NOTICE AND MAINTAIN WATCH FOR TEMPORARY FLIGHT RESTRICTIONS NOTAM/SIGMET FOR AREA. UPDATES TO ST. HELENS VOLCANO ALERTS ARE AVAILABLE FROM THE USGS ON THE WORLD WIDE WEB AT
HTTP://VULCAN.WR.USGS.GOV. CONTACT SEATTLE ARTCC 253-351-3529 FOR ADDITIONAL INFORMATION. WIE UNTIL UFN
AND
5/9066 - WA.. FLIGHT RESTRICTIONS MT. ST. HELENS VOLCANO. EFFECTIVE IMMEDIATELY AND UNTIL FURTHER NOTICE. PURSUANT TO 14 CFR SECTION 91.137(A)(2)
TEMPORARY FLIGHT RESTRICTIONS ARE IN EFFECT WITHIN A 1.5 NAUTICAL MILE RADIUS OF 461151N/1221118W OR THE BATTLE GROUND /BTG/ VORTAC 11 DEGREE RADIAL AT 31.8 NAUTICAL MILES AT AND BELOW 9000 FEET MSL TO PROVIDE A SAFE ENVIRONMENT FOR VOLCANIC ACTIVITY. U.S.F.S., TELEPHONE 360-891-5140 OR FREQ 132.125, IS IN CHARGE OF THE OPERATION. SEATTLE /SEA/ THE SYSTEM OPERATIOINS SUPPORT CENTER/SOSC, PHONE 202-267-3333, IS THE FAA COORDINATION FACILITY. WIE UNTIL UFN