Narrative:

A CRJ900 checked on from the north east of boise; descending from 15000 to 13000; I gave a decent to 11000 and described the weather in the area; in relation to thunderstorms and precipitation displayed and previously displayed on the radar scope. I then gave the CRJ900 an initial vector heading 225; and verified the decent to 110; within a minute I observed them descending below 110 in the 11000 ft MVA; I climbed the CRJ900 back to 11;000; initially believing it may be a pilot deviation. After I was relived from position I went to listen to the tapes before calling the aircraft to discuss this. Upon review of the tapes; I found I had issued a turn and a decent to the pilot on the initial vector with a decent to 100; resulting in the decent below the MVA. I reviewed the strip and the markings all indicated that I had only descended the aircraft to 110; then 080 before being cleared for the approach. Further vigilance of what I was saying and what I was hearing back from the pilots would have prevented this along with an alertness to the decent rate of the aircraft.

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Original NASA ASRS Text

Title: BOI Controller described MVA separation event when an incorrect altitude assignment was issued and failed to note the altitude assignment read back.

Narrative: A CRJ900 checked on from the north east of Boise; descending from 15000 to 13000; I gave a decent to 11000 and described the weather in the area; in relation to thunderstorms and precipitation displayed and previously displayed on the RADAR scope. I then gave the CRJ900 an initial vector heading 225; and verified the decent to 110; within a minute I observed them descending below 110 in the 11000 FT MVA; I climbed the CRJ900 back to 11;000; initially believing it may be a pilot deviation. After I was relived from position I went to listen to the tapes before calling the aircraft to discuss this. Upon review of the tapes; I found I had issued a turn and a decent to the pilot on the initial vector with a decent to 100; resulting in the decent below the MVA. I reviewed the strip and the markings all indicated that I had only descended the aircraft to 110; then 080 before being cleared for the approach. Further vigilance of what I was saying and what I was hearing back from the pilots would have prevented this along with an alertness to the decent rate of the aircraft.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.