Narrative:

The flight was proceeding to pdx via bonul 2 arrival. The WX was clear with excellent visibility. The aircraft was at FL200 on the transition from pendleton when cleared (we thought) to descend to 10000 ft by bonul and to be down to 13000 ft or below by rainr. A slow descent was initiated and the aircraft altitude by rainr was about 11000 ft descending to 10000 ft. There was no query made by the controller about our altitude, but shortly after a clearance was given to another aircraft behind us to cross rainr at or above 13000 ft and cross bonul at 10000 ft. I asked the copilot if we had been given that type of clearance and he said he did not believe so. In retrospect, after noting that the MEA between dufor and rainr is 13000 ft and between rainr and bonul is 10000 ft, I concluded that our clearance probably was to cross rainr at or above 13000 ft and cross bonul at 10000 ft. At no time was our altitude questioned by the controller, but I feel that we had misunderstood the clearance and not been corrected on the readback. A contributing factor was the excellent visibility of the day (unusual in the northwest) with the resultant sightseeing in the vicinity of mt hood. Also contributing was that most crossing restrictions seem to be to cross a fix at or below a certain altitude to maintain a lower altitude.

Related reports:

Google
 

Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT IN ACR LGT FAILING TO MAKE ITS ALT XING RESTRICTION. CLRNC INTERP.

Narrative: THE FLT WAS PROCEEDING TO PDX VIA BONUL 2 ARR. THE WX WAS CLR WITH EXCELLENT VISIBILITY. THE ACFT WAS AT FL200 ON THE TRANSITION FROM PENDLETON WHEN CLRED (WE THOUGHT) TO DSND TO 10000 FT BY BONUL AND TO BE DOWN TO 13000 FT OR BELOW BY RAINR. A SLOW DSCNT WAS INITIATED AND THE ACFT ALT BY RAINR WAS ABOUT 11000 FT DSNDING TO 10000 FT. THERE WAS NO QUERY MADE BY THE CTLR ABOUT OUR ALT, BUT SHORTLY AFTER A CLRNC WAS GIVEN TO ANOTHER ACFT BEHIND US TO CROSS RAINR AT OR ABOVE 13000 FT AND CROSS BONUL AT 10000 FT. I ASKED THE COPLT IF WE HAD BEEN GIVEN THAT TYPE OF CLRNC AND HE SAID HE DID NOT BELIEVE SO. IN RETROSPECT, AFTER NOTING THAT THE MEA BTWN DUFOR AND RAINR IS 13000 FT AND BTWN RAINR AND BONUL IS 10000 FT, I CONCLUDED THAT OUR CLRNC PROBABLY WAS TO CROSS RAINR AT OR ABOVE 13000 FT AND CROSS BONUL AT 10000 FT. AT NO TIME WAS OUR ALT QUESTIONED BY THE CTLR, BUT I FEEL THAT WE HAD MISUNDERSTOOD THE CLRNC AND NOT BEEN CORRECTED ON THE READBACK. A CONTRIBUTING FACTOR WAS THE EXCELLENT VISIBILITY OF THE DAY (UNUSUAL IN THE NW) WITH THE RESULTANT SIGHTSEEING IN THE VICINITY OF MT HOOD. ALSO CONTRIBUTING WAS THAT MOST XING RESTRICTIONS SEEM TO BE TO CROSS A FIX AT OR BELOW A CERTAIN ALT TO MAINTAIN A LOWER ALT.

Data retrieved from NASA's ASRS site as of July 2007 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.